KR101127788B1 - Polarizer with optical compensation film and liquid crystal display device using the same - Google Patents

Abstract

[PROBLEMS] With a simple configuration, a liquid crystal display device having improved front display product is provided.

[Measures] A pair of polarizing plates having electrodes on at least one side and opposed to each other, and a pair of polarizing plates disposed on the outside of the liquid crystal layer formed between the substrates, wherein the polarizing plate is at least a polarizing film and a liquid crystal of the polarizing film. It consists of a protective film formed in the surface of the side attached to a cell, and an optical compensation film (However, the said protective film may be the structure which also functions as the said optical compensation film), The polarization degree of this polarizing plate is 99.5% or more, and the polarization degree of the said board | substrate The retention rate is 90% or more, and the polarization degree retention rate of the said optical compensation film is 90% or more, The polarizing plate characterized by the above-mentioned.

Liquid crystal display, optical compensation film, polarizer

Description

A polarizing plate having an optical compensation film and a liquid crystal display using the same {PLARIZER WITH OPTICAL COMPENSATION FILM AND LIQUID CRYSTAL DISPLAY DEVICE USING THE SAME}

1 is a schematic view showing an example of a liquid crystal display of the present invention.

2 is a schematic side cross-sectional view showing another example of the liquid crystal display device of the present invention.

3 is a schematic side cross-sectional view showing another example of the liquid crystal display device of the present invention.

Fig. 4 is a diagram schematically showing the relationship between the optical axes of the liquid crystal display devices produced in the examples.

※ Description of the main symbols in the drawings

1: upper polarizer outer protective film

2: slow polarizer outer protective film slow axis

3: upper polarizing plate polarizing film

4: upper polarizing plate polarizing film absorption axis

5: Upper polarizing plate liquid crystal cell side protective film (support)

6: Upper polarizer liquid crystal cell side protective film (support) slow axis

7: upper optically anisotropic layer

8: orientation average direction of molecular long axis of upper optically anisotropic layer

9: liquid crystal cell upper substrate

10: rubbing direction for upper substrate liquid crystal alignment

11: liquid crystal molecules (liquid crystal layer)

12: liquid crystal cell lower substrate

13: Rubbing direction for lower substrate liquid crystal alignment

14: lower optically anisotropic layer

15: Orientation average direction of the molecular long axis of the lower optical compensation layer

16: Lower polarizing plate liquid crystal cell side protective film (support)

17: lower polarizer liquid crystal cell side protective film (support) slow axis

18: lower polarizing plate polarizing film

19: Absorption axis of lower polarizing plate polarizing film

20: lower polarizing plate outer protective film

21: slow polarizer outer protective film slow axis

30, 42: polarizer

32, 40: transparent substrate

34: rod-shaped liquid crystalline molecule

36: electric field direction

38: linear electrode

44: insulation layer

46: lower layer electrode

The present invention relates to a liquid crystal display device and a polarizing plate with an optical compensation film used therein.

Liquid crystal display devices are widely used in that display devices used in OA devices such as word processors, notebook computers, PC monitors, portable terminals, televisions, and the like are thin, light in weight, and low in power consumption.

The liquid crystal display device usually has a liquid crystal cell and a polarizing plate. A polarizing plate consists of a protective film and a polarizing film normally, and is obtained by dyeing and extending | stretching the polarizing film which consists of polyvinyl alcohol films with iodine, and laminating | stacking both surfaces with a protective film. In a transmissive liquid crystal display, this polarizing plate is affixed on both sides of a liquid crystal cell, and also one or more optical compensation films may be arrange | positioned. In the reflective liquid crystal display device, the reflecting plate, the liquid crystal cell, one or more optical compensation films, and the polarizing plate are arranged in this order. The liquid crystal cell consists of liquid crystal molecules, two substrates for encapsulating them, and an electrode layer for applying voltage to the liquid crystal molecules. The liquid crystal cell is a twisted nematic (TN), an in-plane switching (IPS), and an OCB (Optically Compensatory Bend), which can display ON and OFF due to differences in the alignment states of liquid crystal molecules and can be applied to both transmissive, reflective and transflective types. ), Display modes such as Vertically Aligned (VA), Electrically Controlled Birefringence (ECB), and Super Twisted Nematic (STN) have been proposed.

Optical compensation films are used in various liquid crystal display devices in order to eliminate image coloring or to enlarge a viewing angle. As the optical compensation film, a stretched birefringent polymer film has been conventionally used. It is proposed to use the optical compensation film which has the optically anisotropic layer formed from the low molecular weight or the polymeric liquid crystalline compound on the transparent support instead of the optical compensation film which consists of a stretched birefringent film. Since a liquid crystal compound has various orientation forms, it became possible to implement | achieve the optical property which cannot be obtained with the conventional stretched birefringent polymer film by using a liquid crystal compound. And it functions also as a protective film of a polarizing plate.

The optical properties of the optical compensation film are determined in accordance with the optical properties of the liquid crystal cell, specifically, the difference in display mode as described above. By using the liquid crystal compound, an optical compensation film having various optical properties corresponding to various display modes of the liquid crystal cell can be produced. In the optical compensation film | membrane using a liquid crystalline compound, what corresponds to various display modes is already proposed. For example, the optical compensation film for a TN mode liquid crystal cell compensates optically in an inclined orientation state on the substrate surface while eliminating the torsion structure of the liquid crystal molecules by applying a voltage, thereby providing contrast visual observation by preventing light leakage in the oblique direction during black display. Improve properties.

The optical compensation film for the TN mode liquid crystal display device compensates optically in the inclined orientation state on the substrate surface while eliminating the torsion structure of the liquid crystal molecules by application of an electric field, thereby providing contrast visual characteristics by preventing light leakage in the oblique direction during black display. Improve. Representative examples of optical compensation include a technique in which a liquid crystal compound is hybridly oriented to form a film, and an example in which a discotic liquid crystalline compound is used for a liquid crystalline compound (see Patent Document 1) or a rugby ball compound is used.

However, it is very difficult to completely optically compensate the liquid crystal cell without any problem even when using an optical compensation film in which the discotic liquid crystal compound is uniformly hybridized. For example, in the TFT type liquid crystal display panel of the TN mode, the front contrast ratio is about 300 to 1, but if the unit cell of the TN mode is produced from the transparent electrode glass substrate, the front contrast ratio can be improved to 600 to 1 or more. This is because there is a polarization canceling effect on the substrate of the TFT display, and leakage light is generated during black display, and the contrast ratio is lowered. There exists an example which controls the scattering characteristic of a color filter substrate as a contrast ratio improvement method of a TFT liquid crystal display device (refer patent document 2).

[Patent Document 1] Japanese Unexamined Patent Publication No. 6-214116

[Patent Document 2] Japanese Unexamined Patent Publication No. 2001-166126

This invention is made | formed in view of all the said troubles, and it is a simple structure, Furthermore, it is a subject to provide the liquid crystal display device with the same viewing angle characteristic, and high contrast conventionally. Moreover, this invention makes it a subject to provide the polarizing plate which can contribute to the contrast improvement of a liquid crystal display device in the state which kept the simple structure and viewing angle characteristic.

Means for solving the above problems are as follows.

(1) A pair of polarizing plates arranged in a liquid crystal display by sandwiching a liquid crystal cell, at least one of which has at least one polarizing film and an optical compensation film, the polarization degree is 99.5% or more, and the polarization degree retention rate of the optical compensation film is 90%. A pair of polarizing plates which are the above.

Since the polarizing plate of (1) has the optical compensation film whose polarization retention is the said range, and polarization degree is the said range, it contributes to the improvement of viewing angle characteristic of a liquid crystal display device, reduction of image coloring, and contributes to high contrast.

(2) The polarizing plate of (1), wherein the transmitted light colors a and b for the vertical incident light of the pair of polarizing plates are both ± 4 or less.

Since the polarizing plate of (2) shows the effect of the polarizing plate of said (1), and the color a, b of the transmitted light of a polarizing plate is ± 4 or less, the liquid crystal display device using this is also favorable that a hue of black display is more achromatic. Is displayed.

(3) A liquid crystal display device having an electrode on at least one side, a pair of opposing substrates, a liquid crystal layer formed between the substrates, and a pair of polarizing plates arranged to sandwich the liquid crystal layer, wherein the pair At least one of the polarizing plates has a polarizing film and an optical compensation film on the side of the polarizing film closer to the liquid crystal layer, the polarization degree of the pair of polarizing plates is 99.5% or more, and the polarization degree of the pair of substrates A liquid crystal display device having a retention rate of 90% or more and a polarization degree retention rate of the optical compensation film of 90% or more.

Since the polarization degree has the optical compensation film of the said range and the polarization retention rate of the said range, since the liquid crystal display device of (3) can display an image of favorable color tone with a wide viewing angle, contrast ratio is remarkably improved.

(4) The liquid crystal display device of (3), wherein both of the pair of polarizing plates have an optical compensation film on the polarizing film and a surface closer to the liquid crystal layer of the polarizing film.

Since the liquid crystal display device of (4) exhibits the effect of (3), and both polarizing plates have an optical compensation film, optical compensation can be made more accurate and a viewing angle and color tone can be improved more.

(5) The liquid crystal display device according to (3) or (4), wherein the polarization degree retention ratio of the optical compensation film is equal to or greater than the polarization degree retention ratio of the pair of substrates.

The liquid crystal display device of (5) is an especially preferable aspect in the transmissive type which arrange | positioned backlight on the board | substrate surface of the back surface of a display surface. Light of the backlight passes through the lower polarizing plate, the lower substrate, the liquid crystal layer, the upper substrate, and the upper polarizing plate and is emitted from the display surface. At this time, high contrast is obtained by making the polarization retention rate of the member closer to a polarizing plate higher. In addition, higher contrast is obtained by increasing the polarization retention ratio of the optical compensation film on the side close to the light source of the pair of substrates sandwiching the liquid crystal layer.

(6) The liquid crystal display device according to any one of (3) to (5), wherein the absorption axes of the pair of polarizing plates are substantially perpendicular to each other.

1.5, 또한 Pb/Pg

1.5 인 (3)～(6) 중 어느 하나의 액정 표시 장치.(7) At least one of said pair of board | substrates is provided with the color filter containing each pattern of red, green, and blue, The polarization degree retention rate of a red pattern, a green pattern, and a blue pattern is respectively Pr, Pg, and Pb. When Pr / Pg

1.5, also Pb / Pg

Liquid crystal display device in any one of (3)-(6) of 1.5 phosphorus.

(8) The electrode comprises a pixel electrode and a counter electrode, and an electric field substantially parallel to the substrate on which the pixel electrode and the counter electrode are arranged is generated by the pixel electrode and the counter electrode. The liquid crystal display device in any one of 7).

(9) The liquid crystal display device according to (8), wherein the electrodes are arranged with different layers, and at least one of the electrodes is made of a transparent electrode.

(10) The liquid crystal display device of (9), wherein the substrate on which the pixel electrode and the counter electrode are disposed is further provided with a conductive layer to which no voltage is applied.

In this specification, "45 degree", "parallel", or "orthogonal" means that it exists in the range of less than an exact angle of +/- 5 degrees. It is preferable that it is less than 4 degrees, and, as for the error with an exact angle, it is more preferable that it is less than 3 degrees. In addition, "+" means counterclockwise with respect to an angle, and "-" means clockwise. In addition, a "ground axis" means the direction in which a refractive index becomes largest. In addition, a "visible light region" means that it is 380 nm-780 nm. The measurement wavelength of the refractive index is a value in the visible region λ = 550 nm unless otherwise specified.

In addition, in this specification, a "polarizing film" and a "polarizing plate" are distinguished, and a "polarizing plate" shall mean the laminated body which has at least one other layer, such as a protective film, on at least one surface among the surfaces of a "polarizing film."

According to the present invention, it is possible to provide a liquid crystal display device, in particular a TN type or IPS type liquid crystal display device, in which the contrast is improved without compromising the viewing angle characteristic with a simple configuration. Moreover, according to this invention, the polarizing plate which contributes also to the contrast improvement of the liquid crystal cell of a TN type or IPS type liquid crystal display device can be provided.

Embodiment of the Invention

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

[Polarizing Plate]

The present invention relates to a pair of polarizing plates arranged by sandwiching a liquid crystal cell in a liquid crystal display device. At least one of the pair of polarizing plates of this invention has at least one polarizing film and an optical compensation film. Moreover, in the polarizing plate of this invention, polarization degree is 99.5% or more, and the polarization degree retention of the said optical compensation film is 90% or more. In the aspect in which both polarizing plates have an optical compensation film, it is preferable that the polarization retention of both optical compensation films is 90% or more. Although TFT type (Thin Film Transistor) type liquid crystal display devices are displays with high contrast and high quality, on the other hand, the contrast ratio is greatly changed depending on the constituent members. In this invention, it is set as the polarizing plate which contributes to raising a liquid crystal display device contrast by setting the polarization degree of a polarizing plate and the polarization retention of the optical compensation film which a polarizing plate has in the said range, respectively.

The polarization degree P of the polarizing plate is

P = ((T? -T⊥) / (T? + T⊥)) ^1/2

 . T? Is the parallel transmittance of a polarizing plate, and is a transmittance obtained when a pair of polarizing plates are arrange | positioned in the state in which the absorption axis was parallel (?). Moreover, T 'is the orthogonal transmittance | permeability of a polarizing plate, and is a transmittance | permeability obtained when arrange | positioning a pair of polarizing plate in the state which an absorption axis orthogonally crosses. The pair of polarizing plates of the present invention has a polarization degree of 99% or more, preferably 99.5% or more, and more preferably 99.9% or more. In addition, polarization retention shows the transmittance | permeability at the time of injecting linearly polarized light into a member. In the present invention, the polarization retention rate of the optical compensation film is 90% or more, preferably 95% or more, and more preferably 99% or more. In addition, the ideal value of the contrast ratio of the display device becomes the ratio T? / T⊥ of the transmittance of the polarization degree, and is approximately 3000 to 1. By using the polarizing plate of this invention whose polarization degree and polarization retention rate of an optical compensation film are the said ranges, the contrast ratio of a liquid crystal display device can be improved and it can become close to an ideal value.

 [Optical compensation film]

At least one of the pair of polarizing plates of this invention has at least one optical compensation film | membrane. The optical compensation film of this invention has 90% or more of polarization retention. In order to improve the polarization retention rate of the optical compensation film to the above range, it is preferable to suppress the diameter of the alignment defect and the foreign matter in the compensation film to 1 micron or less. The optical compensation film contributes to eliminating image coloring or enlarging the viewing angle. Therefore, the polarizing plate of the present invention contributes to the improvement of the contrast ratio of the liquid crystal display device, and also to the improvement of the viewing angle characteristic and the reduction of the image coloring. In the polarizing plate of this invention, all or one part of the optical compensation film may serve as the protective film of a polarizing film. For example, when the optical compensation film is a birefringent polymer film, the optical compensation film itself may be a protective film of the polarizing film, and the optical compensation film is a laminate of a support made of a polymer film or the like and an optically anisotropic layer made of liquid crystal molecules. Can also make the polymer film which is a support body into the protective film of a polarizing film.

There is no restriction | limiting in particular about the material of an optical compensation film, The optically anisotropic layer formed from the stretched birefringent polymer film and liquid crystalline molecule, etc. can be used. Since the liquid crystal molecules have various alignment forms, the optical compensation layer that satisfies the necessary optical characteristics according to the mode of the liquid crystal cell to be compensated by using the liquid crystal molecules can be easily produced. A liquid crystalline compound can be classified into a rod type and a disk type from the shape of the molecule, and both can be used. Although they are classified into low molecular and high polymer types, respectively, they can be used.

Hereinafter, the preferable characteristic, the material which can be used, and a manufacturing method are demonstrated in detail about the optical compensation film which consists of an optically anisotropic layer formed from liquid crystalline molecules.

[Optical Characteristics of Optically Anisotropic Layer]

The retardation (Re) of the optically anisotropic layer formed of the liquid crystalline molecules has a ratio {Re @ 650} / {Re @ 450} of 0.8 to the value Re @ 450 measured at 450 nm and the value Re @ 650 measured at 650 nm. It is preferably between 1.2. By setting it as this range, color taste can be improved remarkably.

In addition, in this specification, the optical characteristic of various members, such as an optically anisotropic layer and a polymer film, shall say the value measured by the following method.

[Retardation]

Re (λ) is measured by injecting light having a wavelength of λnm in the film normal direction in KOBRA 21ADH (manufactured by Ohji Measuring Instruments Co., Ltd.). . Rth (λ) is incident on the Re (λ), the in-plane slow axis (determined by KOBRA 21ADH) as the inclination axis (rotation axis), and enters light having a wavelength of λ nm from a direction inclined at + 40 ° with respect to the film normal direction. Rita measured in three directions of retardation measured by injecting light having a wavelength of λ nm from the direction inclined at -40 ° to the film normal direction using the retardation measured and the in-plane slow axis measured in the plane. KOBRA 21ADH is calculated based on the assumption of the date and average refractive index and the input film thickness. Here, the assumption of the average refractive index may be a polymer handbook (JOHN WILEY & SONS, INC) and catalog values of various optical films. If the value of the average refractive index is not already known, it can be measured by an Abbe refractometer. The value of the average refractive index of a main optical film is illustrated below.

Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethylmethacrylate (1.49), polystyrene (1.59).

KOBRA 21ADH calculates nx, ny, and nz by inputting the assumption value and film thickness of these average refractive indexes. From this calculated nx, ny and nz, Nz = (nx-nz) / (nx-ny) is calculated again.

Molecular orientation axis

Molecular orientation axis is calculated from phase difference when the angle of incidence at vertical incidence is changed by using automatic birefringence meter (KOBRA 21DH, Oji measurement Co., Ltd.) by adjusting humidity of 70mm × 100mm at 25 ℃, 65% RH for 2 hours. do.

(Axis shift)

In addition, the angle of displacement is measured by an automatic birefringence meter (KOBRA-21ADH, Oji measurement equipment Co., Ltd.). 20 points were measured at equal intervals over the entire width in the width direction to obtain an average value of the absolute values. In addition, the range of the slow axis angle (axial deviation) is obtained by measuring 20 points at equal intervals over the entire width direction to obtain the difference between the average of the four points from the larger one and the average of the four points from the smaller one. .

[Optical anisotropic layer]

The preferable aspect of the optically anisotropic layer which consists of a liquid crystalline compound is described in detail.

It is preferable to design an optically anisotropic layer so that the liquid crystal compound in the liquid crystal cell in the black display of a liquid crystal display device may be compensated. The alignment state of the liquid crystal compound in the liquid crystal cell in black display varies depending on the mode of the liquid crystal display device. About the orientation state of the liquid crystal compound in this liquid crystal cell, it describes in IDW'00, FMC7-2, and P411-414. The liquid crystalline molecules used for forming the optically anisotropic layer include rod-like liquid crystalline molecules and disk-like liquid crystalline molecules. The rod-like liquid crystalline molecules and the discotic liquid crystalline molecules may be polymer liquid crystals or low molecular liquid crystals, and also include those in which the low molecular liquid crystals are crosslinked so as not to exhibit liquid crystallinity.

[Bar type liquid crystalline molecule]

Examples of rod-like liquid crystalline molecules that can be used for forming the optically anisotropic layer include azomethines, azoxy compounds, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, and cyanophenylcyclo. Hexanes, cyano substituted phenylpyrimidines, alkoxy substituted phenyl pyrimidines, phenyldioxanes, tolans and alkenylcyclohexyl benzonitriles are preferably used. The rod-like liquid crystalline molecule also includes a metal complex. Moreover, the liquid crystal polymer which contains a rod-shaped liquid crystalline molecule in a repeating unit can also be used as rod-shaped liquid crystalline molecule. In other words, the rod-like liquid crystalline molecules may be combined with the (liquid crystal) polymer. For rod-shaped liquid crystalline molecules, Chapter 4, Chapter 7 and Chapter 11 of the Journal of Chemical Chemistry Vol. 22 Liquid Crystal (1994) Japanese Chemical Society, and Chapter 3 of the Liquid Crystal Devices Handbook Japanese Society for the Promotion of Japan 142 Committee It is described in.

It is preferable that the birefringence of the rod-like liquid crystalline molecules is in the range of 0.001 to 0.7. It is preferable that a rod-shaped liquid crystalline molecule has a polymeric group in order to fix the orientation state. The polymerizable group is preferably a cationic polymerizable group in the radical polymerizable unsaturated group, and specifically, for example, the polymerizable group described in paragraphs [0064] to [0086] of the specification of JP2002-62427A, and the polymerizable group. A liquid crystal compound is mentioned.

Discoid Liquid Crystal Molecules

Examples of discotic (discotic) liquid crystalline molecules that can be used for forming the optically anisotropic layer include C. Destrade et al., Mol. Cryst. Benzene derivatives described in Vol. 71, p. 111 (1981), C. Destrade et al., Mol. Cryst. A report on the truxsen derivatives described in Vol. 122, 141 (1985), Physics lett, A, Vol. 78, 82 (1990), B. Kohne et al., Angew. Chem. 96, page 70 (1984) cyclohexane derivatives and J. M. Lehn et al., J. Chem. Commun., Page 1794 (1985), by J. Zhang et al., J. Am. Chem. Soc. Azacrown-based or phenylacetylene-based chromatographic cycles described in volume 116, page 2655 (1994).

The discotic liquid crystalline molecule also includes a compound showing liquid crystallinity in which a linear alkyl group, an alkoxy group, and a substituted benzoyloxy group are radially substituted as the side chain of the parent nucleus with respect to the mother nucleus at the center of the molecule. It is preferable that a molecule | numerator or an aggregate of molecules is a compound which has rotational symmetry and can give a fixed orientation. In the optically anisotropic layer formed of discotic liquid crystalline molecules, the compound contained in the optically anisotropic layer does not necessarily need to be discotic liquid crystalline molecules, for example, has a group in which low-molecular discotic liquid crystalline molecules react with heat or light. As a result, compounds which have been polymerized or crosslinked by reaction with heat and light, which have become high molecular weight and have lost liquid crystallinity, are also included. Preferred examples of discotic liquid crystalline molecules are described in Japanese Patent Application Laid-Open No. 8-50206. In addition, there exist some described in Unexamined-Japanese-Patent No. 8-27284 about superposition | polymerization of discotic liquid crystalline molecule. 70-300 degreeC is preferable and, as for the discotic nematic liquid crystal phase-solid-state transition temperature of disk-shaped liquid crystalline molecule, 70-170 degreeC is more preferable.

In order to fix a discotic liquid crystalline molecule by superposition | polymerization, it is necessary to couple a polymeric group as a substituent to the disc core of a discotic liquid crystalline molecule. The disk-shaped core and the polymerizable group are preferably a compound bonded through a linking group, thereby maintaining the alignment state even in the polymerization reaction. For example, the compound etc. which were described in Paragraph No. [0151]-[0168] in Unexamined-Japanese-Patent No. 2000-155216 can be mentioned.

Moreover, the preferable aspect also differs in the orientation of the liquid crystalline molecule in an optically anisotropic layer according to the optical characteristic required. The optically anisotropic layer in which the liquid crystalline molecules are fixed in a hybrid alignment state may be used. In the hybrid orientation, the angle formed between the long axis of the liquid crystalline molecules (the disc surface in the discotic liquid crystalline molecules) and the surface of the polarizing film is increased or decreased with the increase in the distance between the optically anisotropic layer and the support interface. The angle is preferably reduced with increasing distance. And as the change of angle is possible, continuous increase, continuous decrease, intermittent increase, intermittent decrease, change including continuous increase and continuous decrease, or intermittent change including increase and decrease. The intermittent change includes a region in which the inclination angle does not change in the middle of the thickness direction. The angle may be increased or decreased as a whole even if it includes an area where the angle does not change. And it is preferable that an angle changes continuously.

The average direction of the discotic liquid crystalline molecule long axis on the support interface side can generally be adjusted by selecting the material of the discotic liquid crystalline molecule or the alignment film or by selecting the rubbing treatment method. In addition, the long-axis (disc surface) direction of the discotic liquid crystalline molecules on the surface side (air side) can generally be adjusted by selecting the type of additive used together with the discotic liquid crystalline molecules or discotic liquid crystalline molecules. Examples of the additive used together with the discotic liquid crystalline molecules include plasticizers, surfactants, polymerizable monomers and polymers. The change degree of the orientation direction of a long axis can also be adjusted by selection of a liquid crystalline molecule and an additive as mentioned above.

[Other composition of optically anisotropic layer]

By using a plasticizer, surfactant, a polymerizable monomer, etc. together with the said liquid crystalline molecule, the uniformity of a coating film, the intensity | strength of a film, the orientation of liquid crystal molecules, etc. can be improved. It is desirable to have compatibility with the liquid crystalline molecules and not to change the inclination angle of the liquid crystalline molecules or to inhibit the orientation.

A radically polymerizable or cationic polymerizable compound is mentioned as a polymerizable monomer. Preferably, it is a polyfunctional radically polymerizable monomer, and it is preferable that it is copolymerizable with the liquid crystal compound containing the said polymeric group. For example, the thing of Paragraph No. [0018]-[0020] is mentioned among Unexamined-Japanese-Patent No. 2002-296423 specification. It is preferable that the addition amount of the said compound exists in the range of 1-50 mass% generally with respect to a disk shaped liquid crystalline molecule, and exists in the range of 5-30 mass%.

Although a conventionally well-known compound is mentioned as surfactant, Especially a fluorine-type compound is preferable. Specifically, the compound of Paragraph No. [0028]-[0056] in Unexamined-Japanese-Patent No. 2001-330725 specification is mentioned, for example.

In the polymer used together with the discotic liquid crystalline molecules, it is preferable that a change in the inclination angle is given to the discotic liquid crystalline molecules.

Examples of the polymer include cellulose esters. As a preferable example of a cellulose ester, the thing of Paragraph No. 001 of Unexamined-Japanese-Patent No. 2000-155216 specification is mentioned. It is preferable to exist in the range of 0.1-10 mass% with respect to liquid crystalline molecule, and, as for the addition amount of the said polymer so that the orientation of liquid crystalline molecules is not impaired, it is more preferable to exist in the range which is 0.1-8 mass%.

[Formation of Optically Anisotropic Layer]

An optically anisotropic layer can be formed by apply | coating the coating liquid containing liquid crystalline molecule and arbitrary additives, such as a polymeric initiator and a polymerizable monomer, to the support surface as needed. It is preferable to use an alignment film.

As a solvent used for preparation of a coating liquid, an organic solvent is used preferably. Examples of organic solvents include amides (eg N, N-dimethylformamide), sulfoxides (eg dimethyl sulfoxide), heterocyclic compounds (eg pyridine), hydrocarbons (eg benzene, hexane), alkyl halides ( Chloroform, dichloromethane, tetrachloroethane), esters (e.g. methyl acetate, butyl acetate), ketones (e.g. acetone, methylethylketone), ethers (e.g. tetrahydrofuran, 1,2-dimethoxyethane) Included. Alkyl halides and ketones are preferred. You may use together 2 or more types of organic solvents.

Application of the coating liquid can be carried out by a known method (eg, wire bar coating method, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).

It is preferable that the thickness of an optically anisotropic layer is 0.1-20 micrometers, It is more preferable that it is 0.5-15 micrometers, It is most preferable that it is 1-10 micrometers.

[Fixing the Orientation State of Liquid Crystal Molecules]

The oriented liquid crystal molecules can be fixed while maintaining the alignment state. It is preferable to perform fixation by a polymerization reaction. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. Photopolymerization reaction is preferred.

Examples of photopolymerization initiators include α-carbonyl compounds (described in the specifications of US Pat. No. 23,684,1, 2367670), acyloinether (described in the specification of US Pat. No. 2448828), compounds of the α-hydrocarbon substituted aromatic acyl ( US Patent No. 2722512, polynuclear quinone compounds (see US Pat. No. 3046127, US Pat. No. 2951758), combinations of triarylimidazole dimers with p-aminophenylketone (US Pat. No. 3549367) ), Acridine and phenazine compounds (Japanese Patent Laid-Open No. 60-105667, described in US Pat. No. 4239850) and Oxadiazole compounds (described in US Pat. No. 4212970).

It is preferable to exist in the range of 0.01-20 mass% of solid content of a coating liquid, and, as for the usage-amount of a photoinitiator, it is more preferable to exist in the range which is 0.5-5 mass%.

It is preferable to use ultraviolet-ray for the light irradiation for superposition | polymerization of a liquid crystalline molecule.

The irradiation energy is preferably in the range of 20 mJ / cm 2 to 50 J / cm 2, more preferably in the range of 20 to 5000 mJ / cm 2, and even more preferably in the range of 100 to 800 mJ / cm 2. Moreover, in order to accelerate | stimulate a photopolymerization reaction, you may irradiate light under heating conditions.

You may form a protective layer on an optically anisotropic layer.

[Alignment Film]

As described above, it is preferable to form an alignment film between the support and the optically anisotropic layer, and to align the liquid crystal molecules on the surface of the alignment film. The alignment film has a function of defining the alignment direction of liquid crystal molecules. The liquid crystal molecules become a predetermined alignment state on the alignment film, and after that, the liquid crystal molecules are fixed in the alignment state, and thus maintain the alignment state even without the alignment film. Therefore, after aligning liquid crystalline molecules on the alignment film surface and forming an optically anisotropic layer, only the optically anisotropic layer may be transferred to the support surface or the polarizing film surface. Therefore, the alignment film is not essential as a component of the optical compensation film.

The alignment film is an organic compound (e.g., ω-trichoic acid) by rubbing treatment of an organic compound (preferably a polymer), evaporation of an inorganic compound, formation of a layer having a micro group, or by a Langmuir-Blodge method (LB film). And dioctadecyl methylammonium chloride, methyl stearate). Moreover, the orientation film | membrane which an orientation function generate | occur | produces by provision of an electric field, provision of a magnetic field, or light irradiation is also known.

It is preferable to form an alignment film by the rubbing process of a polymer. The polymer used for an oriented film has a molecular structure which has a function which orientates a liquid crystalline molecule in principle.

In the present invention, in addition to the function of orienting the liquid crystal molecules, the side chain having a crosslinkable functional group (e.g., a double bond) is bonded to the main chain, or the crosslinkable functional group having the function of orienting the liquid crystal molecules is side chained. It is preferable to introduce in.

As the polymer used for the alignment film, both a polymer crosslinkable by itself or a polymer crosslinked by a crosslinking agent can be used, and a plurality of combinations thereof can be used.

Examples of the polymer include, for example, methacrylate copolymers, styrene copolymers, polyolefins, polyvinyl alcohols and modified polyvinyl alcohols, as described in paragraph [0022] of JP-A-8-338913. Poly (N-methylol acrylamide), polyester, polyimide, vinyl acetate copolymer, carboxymethyl cellulose, polycarbonate and the like. Silane coupling agents can be used as the polymer. Water-soluble polymers (e.g. poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, modified polyvinyl alcohol) are preferred, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are more preferred, and poly Most preferred are vinyl alcohol and modified polyvinyl alcohol. It is especially preferable to use together two types of polyvinyl alcohol or modified polyvinyl alcohol from which a polymerization degree differs.

70-100% is preferable and, as for the saponification degree of polyvinyl alcohol, 80-100% is more preferable. It is preferable that the polymerization degree of polyvinyl alcohol is 100-5000.

The side chain which has the function of orienting liquid crystalline molecules generally has a hydrophobic group as a functional group. The kind of specific functional group is determined according to the kind of liquid crystalline molecule and the orientation state required.

For example, as a modification group of modified polyvinyl alcohol, it can introduce | transduce by copolymerization modification, chain transfer modification, or block polymerization modification. Examples of the modified group include hydrophilic groups (carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, amino groups, ammonium groups, amide groups, thiol groups, etc.), hydrocarbon groups having 10 to 100 carbon atoms, hydrocarbon groups having fluorine atom substitution, thioether groups, and polymerizable groups. (Unsaturated polymerizable group, epoxy group, azirinidyl group, etc.), an alkoxysilyl group (trialkoxy, dialkoxy, monoalkoxy), etc. are mentioned. As a specific example of these modified polyvinyl alcohol compounds, Paragraph Nos. [0022]-[0145] of Unexamined-Japanese-Patent No. 2000-155216, Paragraph No. of [0018]-[0022] ] Etc. are mentioned.

When the side chain having a crosslinkable functional group is bonded to the main chain of the alignment film polymer or the crosslinking functional group is introduced into the side chain having the function of orienting the liquid crystal molecules, the polyfunctional monomer contained in the polymer of the alignment film and the optically anisotropic layer May be copolymerized. As a result, not only between the polyfunctional monomer and the polyfunctional monomer, but also between the alignment film polymer and the alignment film polymer and between the polyfunctional monomer and the alignment film polymer are strongly bonded by covalent bonds. Therefore, by introducing a crosslinkable functional group into the alignment film polymer, the strength of the optical compensation film can be remarkably improved.

It is preferable that the crosslinkable functional group of an oriented film polymer contains a polymeric group similarly to a polyfunctional monomer. Specifically, the thing described in Paragraph No. [0080]-[0100] etc. in Unexamined-Japanese-Patent No. 2000-155216 specification is mentioned, for example.

The alignment film polymer may be crosslinked using a crosslinking agent separately from the above crosslinkable functional groups. Crosslinking agents include aldehydes, N-methylol compounds, dioxane derivatives, compounds acting by activating carboxyl groups, active vinyl compounds, active halogen compounds, isoxazoles and dialdehyde starches. You may use together 2 or more types of crosslinking agents. Specifically, the compound etc. which were described in Paragraph No. [0023]-[0024] of Unexamined-Japanese-Patent No. 2002-62426 specification are mentioned, for example. Aldehydes having high reaction activity, in particular glutaraldehyde, are preferred.

0.1-20 mass% is preferable with respect to a polymer, and, as for the addition amount of a crosslinking agent, 0.5-15 mass% is more preferable. It is preferable that it is 1.0 mass% or less, and, as for the quantity of the unreacted crosslinking agent which remains in an oriented film, it is more preferable that it is 0.5 mass% or less. By adjusting in this way, even if an orientation film is left to be used for a long time in a liquid crystal display device, or it is left to stand in a high temperature, high humidity atmosphere for a long time, sufficient durability without reticulation is obtained.

An orientation film can be formed by apply | coating on the transparent support body containing the said polymer which is an orientation film formation material, and a crosslinking agent fundamentally, and heat-drying (crosslinking), and carrying out a rubbing process. As mentioned above, after apply | coating on a transparent support body, what is necessary is just to perform a crosslinking reaction at arbitrary times. In the case of using a water-soluble polymer such as polyvinyl alcohol as the alignment film forming material, the coating liquid is preferably a mixed solvent of an organic solvent (for example, methanol) having a bubble scavenging effect and water. The ratio is preferably 0: 100 to 99: 1, more preferably 0: 100 to 91: 9, in terms of mass ratio of water: methanol. Thereby, generation | occurrence | production of a bubble is suppressed and the defect of the layer surface of an oriented film, and also an optically anisotropic layer is remarkably reduced.

The coating method of the alignment film is preferably a spin coating method, a dip coating method, a curtain coating method, an extrusion coating method, a rod coating method or a roll coating method. In particular, the rod coating method is preferable. Moreover, as for the film thickness after drying, 0.1-10 micrometers is preferable. Heat drying can be performed at 20 degreeC-110 degreeC. In order to form sufficient crosslinking, 60 to 100 degreeC is preferable, and 80 to 100 degreeC is especially preferable. Although drying time can be performed in 1 minute-36 hours, Preferably they are 1 minute-30 minutes. It is preferable to set pH also to the optimal value for the crosslinking agent to be used, and when glutaraldehyde is used, pH 4.5-5.5, especially 5 are preferable.

An alignment film is formed on a transparent support body or the said undercoat layer. The alignment film can be obtained by crosslinking the polymer layer as described above and then rubbing the surface.

The rubbing process can apply the processing method widely employ | adopted as a liquid-crystal aligning process of LCD. That is, the method of obtaining an orientation by rubbing the surface of an oriented film in a fixed direction using paper, a gauze, a felt, rubber or nylon, polyester fiber, etc. can be used. Generally, it carries out by rubbing about several times using the cloth etc. which averaged the fiber of uniform length and thickness.

Next, the alignment film is functioned, and the liquid crystal molecules of the optically anisotropic layer formed on the alignment film are oriented. Thereafter, if necessary, the alignment film polymer and the polyfunctional monomer contained in the optically anisotropic layer are reacted, or the alignment film polymer is crosslinked using a crosslinking agent.

It is preferable that the film thickness of an oriented film exists in the range of 0.1-10 micrometers.

[Support]

An optically anisotropic layer formed of the above liquid crystal molecules may be formed on the support to form an optical compensation film. The support which comprises an optical compensation film may differ from what was used at the time of preparation of an optically anisotropic layer. For example, the optically anisotropic layer obtained by orienting a liquid crystalline compound and fixing an orientation state can be transferred to a transparent support body, and an optical compensation film can also be manufactured. There is no restriction | limiting in particular about the support body used for the orientation of a liquid crystalline compound, when the support body used for the orientation of a liquid crystalline compound differs from the transparent support body of an optical compensation film | membrane.

It is preferable that it is glass or a transparent polymer film, and, as for the support body of this invention, a polymer film is more preferable. It is preferable that the support has a light transmittance of 80% or more. Examples of the polymer constituting the polymer film include cellulose esters (eg, mono-triallylates of cellulose), norbornene-based polymers, and polymethyl methacrylates. Commercially available polymers (in norbornene-based polymers) may be used, such as Aton and Zeonex (both trade names). Moreover, even if it is a polymer which birefringence is easy to express, such as a polycarbonate and polysulfone which are known conventionally, it can also be used as a support body, if the birefringence expression property is controlled by modifying a molecule | numerator as described in WO00 / 26705 specification.

Especially, a cellulose ester is preferable and the lower fatty acid ester of cellulose is more preferable. Lower fatty acid means a fatty acid having 6 or less carbon atoms. In particular, the cellulose acylate of 2-4 carbon atoms is preferable. Cellulose acetate is particularly preferred. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used.

It is preferable that it is 250 or more, and, as for the viscosity average polymerization degree (DP) of a cellulose acetate, it is more preferable that it is 290 or more. Moreover, it is preferable that cellulose acetate has a narrow molecular weight distribution of Mw / Mn (Mw is mass mean molecular weight, Mn is number average molecular weight) by gel permeation chromatography. As a specific value of Mw / Mn, it is preferable that it is 1.0-1.7, and it is more preferable that it is 1.0-1.65.

As a polymer film, it is preferable to use the cellulose acetate whose acetylation degree is 55.0-62.5%. As for acetylation degree, it is more preferable that it is 57.0-62.0%. The degree of acetylation means the amount of bound acetic acid per cellulose unit mass. Acetylation degree is calculated | required by the measurement and calculation of the acetylation degree in ASTM: D-817-91 (test methods, such as a cellulose acetate).

In cellulose acetate, hydroxyl of 2nd, 3rd, and 6th positions of cellulose is not substituted uniformly, but there exists a tendency for substitution degree of 6th position to become small. In the polymer film used for this invention, substitution degree of 6th position of a cellulose is preferable about the same grade or many compared with 2nd position and 3rd position. The ratio of the substitution degree at the 6th position to the sum of the substitution degree at the 2nd, 3rd, and 6th positions is preferably 30 to 40%, more preferably 31 to 40%, and most preferably 32 to 40%. Do. It is preferable that the substitution degree of 6th is 0.88 or more.

These specific acyl groups and the method for synthesizing cellulose acylate are described in detail on page 9 of the Published Association Publication (Publication No. 2001-1745, published on March 15, 2001).

Although the polymer film retardation value differs in a preferable range according to the liquid crystal cell in which an optical compensation film is used, and its use method, it is preferable that Re retardation value is 0-200 nm, and Rth retardation value is 10-400 nm. It is preferable.

When using two optically anisotropic layers for a liquid crystal display device (that is, when both of a pair of polarizing plate have an optical compensation film), it is preferable that the Rth retardation value of a polymer film exists in the range of 10-250 nm. When using one optically anisotropic layer for a liquid crystal display device (that is, when only one pair of polarizing film has an optical compensation film), it is preferable that the Rth retardation value of a base material exists in the range of 150-400 nm. On the other hand, it is preferable that birefringence ((DELTA) n: nx-ny) of a base film exists in the range of 0.00028-0.020. Moreover, it is preferable that birefringence {(nx + ny) / 2-nz} of the thickness direction of a cellulose acetate film exists in the range of 0.001-0.04.

In order to maintain the polarization degree, when the unitary transmittance of the support constituting the optical compensation film is 90% or more, the absolute value of the retardation value is 20 nm or less, or the retardation value is 20 nm or more, the support slow axis and the polarizing plate absorption axis It is preferable to make the crossing angle with (or transmission axis) less than 10 degrees. Thereby, polarization retention becomes 90% or more.

Here, polarization retention can be measured by a luminance meter (for example, BM-5 manufactured by Topcon Corporation) or a spectrophotometer. A linear polarized light is made to enter a support body, the polarization transmittance of the transmission axis direction parallel to the transmission axis of this linearly polarized light is measured, and the ratio is made into polarization retention. In addition, when retardation exists in media, such as a support body, what is necessary is just to make it the angle which the transmission axis (or absorption axis) of the linearly polarized light to make incident, and the slow axis of a medium make less than 10 degrees.

In order to adjust the retardation of a polymer film, the method of giving external force like extending | stretching is common, but the retardation increasing agent for adjusting optical anisotropy is added as needed. In order to adjust the retardation of a cellulose acylate film, it is preferable to use the aromatic compound which has at least two aromatic rings as a retardation increasing agent. It is preferable to use an aromatic compound in the range of 0.01-20 mass parts with respect to 100 mass parts of cellulose acylates. Moreover, you may use together 2 or more types of aromatic compounds. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring. For example, the compound etc. which were described in EP0911656A2 specification, Unexamined-Japanese-Patent No. 2000-111914, 2000-275434, etc. are mentioned.

Moreover, it is preferable to make the hygroscopic expansion coefficient of the cellulose acetate film used for the optical compensation film of this invention into 30x10 <^-5> /% RH or less. The hygroscopic expansion coefficient is preferably 15 × 10 ⁻⁵ /% RH or less, and more preferably 10 × 10 ⁻⁵ /% RH or less. In addition, although the smaller one is preferable, the hygroscopic expansion coefficient is a value of 1.0x10 <^-5> /% RH or more normally.

The hygroscopic expansion coefficient indicates the amount of change in the length of the sample when the relative humidity is changed under a constant temperature. By adjusting the hygroscopic expansion coefficient, it is possible to prevent the increase in transmittance (light leakage due to deformation) in the frame shape while maintaining the optical compensation function of the optical compensation film.

The measuring method of a hygroscopic expansion coefficient is shown below. Width from a polymer film produced 5㎜, the length was cut out of the sample 20㎜, by fixing the one end hung in an atmosphere of 25 ℃, 20% RH (R 0). A 0.5 g weight was hung on the other end and left for 10 minutes to measure the length (L ⁰ ). Next, the temperature was kept at 25 ° C., and the length (L ¹ ) was measured at a humidity of 80% RH (R ¹ ). The hygroscopic expansion coefficient was calculated by the following equation. The measurement performed 10 samples with respect to the same sample, and employ | adopted the average value.

Hygroscopic expansion coefficient [/% RH] = {(L ¹ -L ⁰ ) / L ⁰ } / (R ¹ -R ⁰ )

In order to reduce the dimensional change by moisture absorption of a polymer film, it is preferable to add the compound, microparticles | fine-particles, etc. which have a hydrophobic group. As a compound which has a hydrophobic group, the raw material corresponding to the plasticizer and deterioration inhibitor which have a hydrophobic group, such as an aliphatic group and an aromatic group, is used especially preferably. It is preferable that the addition amount of these compounds exists in the range of 0.01-10 mass% with respect to the solution (dope) to adjust. Moreover, what is necessary is just to make the free volume in a polymer film small, and the free volume becomes smaller for the quantity of the residual solvent at the time of film formation by the solvent cast method mentioned later specifically ,. It is preferable to dry on the conditions which become the range of 0.01-1.00 mass% of residual solvent amount with respect to a cellulose acetate film.

Additives added to the polymer film or additives that can be added according to various purposes (e.g., sunscreens, release agents, antistatic agents, deterioration agents (e.g. antioxidants, peroxide decomposers, radical inhibitors, metal deactivators) , An acid trapping agent, an amine), an infrared absorber, etc.) may be solid or may be an oily substance. In addition, when a film is formed in multiple layers, the kind and addition amount of the additive of each layer may differ. As for these details, the raw material described in detail on pages 16-22 of the technique of the above described air number 2001-1745 is preferably used. As the usage-amount of these additives, although the addition amount of each raw material is not specifically limited as long as a function is expressed, It is preferable to use suitably in 0.001-25 mass% in the polymer film whole composition.

[Production Method of Polymer Film]

It is preferable to manufacture a polymer film by the solvent cast method. In the solvent cast method, a film is manufactured using the solution (dope) which melt | dissolved the polymer material in the organic solvent.

The dope is flexible on a drum or band and evaporates the solvent to form a film. As for the dope before casting | flow_spread, it is preferable to adjust density | concentration so that solid content may be 18 to 35%. It is preferable to finish the surface of a drum or a band in a mirror surface state.

It is preferable that dope is cast on the drum or band whose surface temperature is 10 degrees C or less. It is preferable to stir and dry for 2 seconds or more after being soft. The obtained film may be peeled off from the drum or the band, and further dried by hot air having gradually changed the temperature to 100 to 160 ° C to evaporate the residual solvent. The above method is described in JP-A-5-17844. According to this method, it is possible to shorten the time from casting to peeling. In order to carry out this method, it is necessary to gel dope at the surface temperature of the drum or band at the time of casting.

In the casting step, one type of cellulose acylate solution may be single-layer casted, or two or more types of cellulose acylate solutions may be simultaneously and / or sequentially hollowed out.

As a method for covalently stacking a plurality of cellulose acylate solutions of two or more layers as described above, for example, a solution containing cellulose acylate may be softened by a plurality of oil studies formed at intervals in the advancing direction of the support. A method of laminating (for example, the method described in JP-A-11-198285), a method of casting a cellulose acylate solution from two oil studies (the method described in JP-A-6-134933), A method of wrapping the flow of a high viscosity cellulose acylate solution with a low viscosity cellulose acylate solution and simultaneously extruding the high and low viscosity cellulose acylate solution (method disclosed in JP-A-56-162617) Can be. This invention is not limited to this.

The manufacturing processes of these solvent cast methods are described in detail in pages 22 to 30 of the above air number 2001-1745, and are dissolved, cast (including covalent smoke), metal supports, drying, peeling, It is classified into extending | stretching etc.

It is preferable that it is 15-120 microns, and, as for the thickness of the film of this invention, 30-80 microns is more preferable.

[Surface Treatment of Polymer Film]

It is preferable to surface-treat a polymer film. Surface treatment includes corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment and ultraviolet irradiation treatment. These are described in detail in pages 30 to 32 of the aforementioned air number 2001-1745. Among these, especially preferably, it is an alkali saponification process, and it is very effective as a surface treatment of a cellulose acylate film.

The alkali saponification treatment may be any method such as immersing in the saponification liquid and applying the saponification liquid, but a coating method is preferable. Examples of the coating method include a dip coating method, curtain coating method, extrusion coating method, bar coating method and E type coating method. Examples of the alkali saponification treatment liquid include potassium hydroxide solution and sodium hydroxide solution, and the prescribed concentration of hydroxide ions is preferably in the range of 0.1 to 3.0N. Moreover, by containing the solvent with favorable wettability with respect to a film (for example, isopropyl alcohol, n-butanol, methanol, ethanol, etc.), surfactant, and a wetting agent (for example, diols, glycerin, etc.) as an alkali treatment liquid, The wettability of the saponified liquid to the transparent support, the stability over time of the saponified liquid, and the like become good. Specifically, the content of Unexamined-Japanese-Patent No. 2002-82226 and WO02 / 46809 is mentioned, for example.

Instead of the surface treatment, in addition to the surface treatment, a single layer method in which only one layer of a resin layer, such as gelatin, containing both a hydrophobic group and a hydrophilic group, or a gelatin layer containing both a hydrophobic group and a hydrophilic group, is applied. As a second layer, a layer that adheres well to the polymer film (hereinafter, referred to as the first layer below) is formed, and a hydrophilic resin layer such as gelatin that adheres well to the alignment layer as the second layer thereon (hereinafter referred to as the second layer below). The so-called middle layer method (for example, described in Unexamined-Japanese-Patent No. 11-248940) which apply | coats is mentioned.

[Polarizing Film]

There is no restriction | limiting in particular about the polarizing film which the polarizing plate of this invention has, Various known polarizing films can be used. In the present invention, the optically anisotropic layer (the first optically anisotropic layer on the side closest to the polarizing film when forming a plurality of optically anisotropic layers) serving as an optical compensation film contains a liquid crystal molecule directly on the polarizing film. May be formed by applying or an alignment film may be formed on the surface of the polarizing film, and the predetermined object may be applied to the alignment film surface. As a result, a thin polarizing plate with small stress (strain x cross-sectional area x elastic modulus) accompanying the dimensional change of the polarizing film is produced without using a polymer film between the polarizing film and the optically anisotropic layer. When the polarizing plate according to the present invention is mounted on a large liquid crystal display device, problems such as light leakage do not occur, and images with high display quality are displayed.

Moreover, when an optical compensation film consists of a support body and the said optically anisotropic layer, you may adhere | attach the back surface (surface of the side in which an optically anisotropic layer is not formed) with the polarizing film surface.

The polarizing film is Optiva Inc. The polarizing film which consists of a coating type polarizing film or a binder represented by an iodine, or a dichroic dye is preferable.

Iodine and a dichroic dye in a polarizing film express polarizing performance by orienting in a binder. It is preferable that iodine and a dichroic dye are oriented according to a binder molecule, or the dichroic dye is oriented in one direction by self-organization such as liquid crystal.

Commercially available polarizers are generally produced by immersing a stretched polymer in a solution of iodine or a dichroic dye in a bath and infiltrating an iodine or a dichroic dye in a binder.

A commercially available polarizing film has an iodine or a dichroic dye distributed at about 4 μm (about 8 μm in both sides) from the polymer surface, and at least 10 μm of thickness is required to obtain sufficient polarization performance. Permeability can be controlled by the solution concentration of an iodine or a dichroic dye, the temperature of the copper bath, and the immersion time.

As mentioned above, it is preferable that the minimum of binder thickness is 10 micrometers. The thinner the upper limit of the thickness, the better the thinner the light leakage point of the liquid crystal display device. It is preferable that it is currently commercially available polarizing plate (about 30 micrometers) or less, 25 micrometers or less are preferable, and 20 micrometers or less are more preferable. If it is 20 micrometers or less, the light leakage phenomenon will not be observed by a 17-inch liquid crystal display device.

The binder of the polarizing film may be crosslinked.

As the binder which is crosslinked, a polymer capable of crosslinking itself can be used. The binder obtained by introducing a functional group into a polymer having a functional group or a polymer can be reacted between the binders by light, heat or pH change to form a polarizing film.

Moreover, you may introduce a crosslinked structure into a polymer with a crosslinking agent. Crosslinking is generally performed by apply | coating the coating liquid containing a polymer or a mixture of a polymer and a crosslinking agent on a transparent support body, and then heating. Since durability should just be ensured at the end of the final product, the crosslinking treatment may be performed at any stage until the final polarizing plate is obtained.

As the binder of the polarizing film, any polymer which can be crosslinked by itself or a polymer crosslinked by a crosslinking agent can be used. Examples of the polymer include the same polymers as those described above for the alignment film.

Most preferred are polyvinyl alcohol and modified polyvinyl alcohol. About modified polyvinyl alcohol, it is described in each Unexamined-Japanese-Patent No. 8-338913, 9-152509, and 9-316127. Polyvinyl alcohol and modified polyvinyl alcohol may use 2 or more types together.

As for the crosslinking agent addition amount of a binder, 0.1-20 mass% is preferable with respect to a binder. The orientation of a polarizing element and the moisture heat resistance of a polarizing film become favorable.

The oriented film contains the crosslinking agent which did not react even after completion | finish of crosslinking reaction to some extent. However, it is preferable that it is 1.0 mass% or less in an alignment film, and, as for the quantity of the remaining crosslinking agent, it is more preferable that it is 0.5 mass% or less. By doing in this way, even if it attaches a polarizing film to a liquid crystal display device and is left for a long time in the atmosphere of long-term use or high temperature, high humidity, a fall of polarization degree does not occur.

Regarding the crosslinking agent, it is described in the specification of US Reissue Patent No. 23297. Boron compounds (eg, boric acid, borax) can also be used as the crosslinking agent.

As the dichroic dye, an azo dye, a stilbene dye, a pyrazolone dye, a triphenylmethane dye, a quinoline dye, an oxazine dye, a thiazine dye or an anthraquinone dye is used. It is preferable that a dichroic dye is water-soluble. The dichroic dye preferably has a hydrophilic substituent (eg, sulfo, amino, hydroxyl).

As an example of a dichroic dye, the compound of Unexamined-Japanese-Patent Method, Air No. 2001-1745, page 58 (issue date March 15, 2001) is mentioned, for example.

It is also possible to arrange | position a polarizing film and an optically anisotropic layer or a polarizing film and an orientation film through an adhesive agent. As the adhesive, a polyvinyl alcohol-based resin (including modified polyvinyl alcohol based on acetacetyl group, sulfonic acid group, carboxyl group and oxyalkylene group) or a boron compound aqueous solution can be used. Polyvinyl alcohol-type resin is preferable. It is preferable to exist in the range of 0.01-10 micrometers after drying, and it is especially preferable to exist in the range which is 0.05-5 micrometers after drying.

 Moreover, in order to raise the contrast ratio of a liquid crystal display device more, it is preferable that the transmittance | permeability of a polarizing plate is higher, and it is preferable that the polarization degree is also higher. The light transmittance of the polarizing plate is preferably in the range of 30 to 50%, more preferably in the range of 35 to 50%, and most preferably in the range of 40 to 60% in light having a wavelength of 550 nm. The degree of polarization is preferably in the range of 90 to 100%, more preferably in the range of 95 to 100%, and most preferably in the range of 99 to 100% for light having a wavelength of 550 nm. As a result, a high contrast ratio is obtained even if the support or the substrate has a polarization canceling effect.

The transmittance is the luminance ratio of the emitted light to the incident light luminance (or the amount of light and the light flux), and the polarization degree is the parallel transmittance when the absorption axes of the two polarizing plates are parallel to each other, and the transmittance when the vertical is T⊥. In this case, P = (T?-T ') / (T? + T').

[Production of Polarizing Plate]

The polarizing film is dyed with iodine or a dichroic dye after stretching the binder at an angle of 10 to 80 degrees with respect to the longitudinal direction (MD direction) of the polarizing film in an inclined manner (stretching method) or rubbing (rubbing method). desirable. It is preferable to extend | stretch so that the inclination-angle may match the angle which the transmission axis of the two polarizing plates joined to the both sides of the liquid crystal cell which comprises LCD, and the longitudinal or horizontal direction of a liquid crystal cell make. Typical inclination angle is 45 degrees. Recently, however, devices other than 45 ° have also been developed in transmissive, reflective and semi-transmissive LCDs, and it is preferable that the stretching direction can be arbitrarily adjusted in accordance with the design of the LCD.

In the stretching method, the stretching ratio is preferably 2.5 to 30.0 times, more preferably 3.0 to 10.0 times. Stretching can be performed by dry stretching in air. In addition, you may perform wet drawing in the state immersed in water. The stretching ratio of dry stretching is preferably 2.5 to 5.0 times, and the stretching drainage of wet stretching is preferably 3.0 to 10.0 times. An extending process may be divided into several times including diagonal stretch. By dividing into several times, it can extend | stretch more uniformly even in high magnification extending | stretching. Before the diagonal stretching, some stretching may be performed horizontally or vertically (to prevent shrinkage in the width direction).

Stretching can be performed by carrying out tenter stretching in biaxial stretching at different stages. The said biaxial stretching is the same as the extending | stretching method performed in normal film film forming. In biaxial stretching, since stretching is performed at different speeds left and right, it is necessary to make the thickness of the binder film different from right to left before stretching. In flexible film forming, a taper is affixed to a die, and the difference of right and left can arise in the flow volume of a binder solution.

As mentioned above, the film 10-80 degree diagonally stretched with respect to MD direction of a polarizing film is manufactured.

In the rubbing method, a rubbing treatment method widely adopted as a liquid crystal alignment treatment step of LCD can be applied. That is, orientation is obtained by rubbing the surface of the film in a predetermined direction using paper, gauze, felt, rubber, nylon, or polyester fiber. Generally, it is performed by rubbing about several times using the cloth which averaged the fiber of uniform length and thickness.

It is preferable to implement using the rubbing roll whose roundness, cylinder degree, and shake (eccentricity) of a roll itself are all 30 micrometers or less. As for the wrap angle of the film with respect to a rubbing roll, 0.1-90 degrees is preferable. However, as described in JP-A-8-160430, it is also possible to obtain stable rubbing treatment by winding 360 degrees or more.

When rubbing a long film, it is preferable to convey a film at a speed | rate of 1-100 m / min in the state of constant tension with a conveying apparatus. It is preferable that the rubbing roll is free to rotate in the horizontal direction with respect to the film traveling direction for setting an arbitrary rubbing angle. It is recommended to select an appropriate rubbing angle in the range of 0 to 60 °. When using for a liquid crystal display device, 40-50 degrees are preferable. 45 ° is particularly preferred.

It is preferable to arrange | position a polymer film (to arrange | position an optically anisotropic layer / polarizing film / polymer film) on the surface on the opposite side to the optically anisotropic layer of a polarizing film. The polymer film arrange | positioned at the surface on the opposite side to the optically anisotropic layer of a polarizing film functions as a polarizing film. It is preferable that the outermost surface has an antireflection film having antifouling properties and scratch resistance.

[Liquid crystal display device]

A pair of polarizing plate of this invention is arrange | positioned by clamping a liquid crystal cell in a liquid crystal display device. Hereinafter, the liquid crystal display device provided with the polarizing plate of this invention is demonstrated.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram of one Embodiment of the liquid crystal display device of this invention. In FIG. 1, the liquid crystal display device has liquid crystal cells 9-13 and a pair of polarizing plates 1-7 and 14-21 arrange | positioned at both sides of a liquid crystal cell. The upper polarizing plate has a polarizing film 3, a pair of transparent protective films 1 and 5 sandwiching it, an upper optical anisotropic layer 7 having optical compensating ability, and the lower polarizing plate includes a polarizing film 18, It has a pair of transparent protective films 16 and 21 which hold | maintain it, and the lower optically anisotropic layer 14 which has optical compensating ability, and are arrange | positioned in a contrasting position centering on a liquid crystal cell, respectively.

The lower protective film 5 of the upper polarizing plate also serves as the support of the upper optical anisotropic layer 7, that is, the upper polarizing plate is attached to the liquid crystal display device as a structure in which the members 1 to 7 are integrally laminated. On the other hand, the upper protective film 16 of the lower polarizing plate also serves as the support of the lower optically anisotropic layer 14, that is, the lower polarizing plate is attached to the liquid crystal display device as a structure in which the members 14 to 20 are integrally laminated. In the liquid crystal display of FIG. 1, a laminate of the upper optical anisotropic layer 7 formed on the transparent support 5 and a laminate of the lower optical anisotropic layer 14 formed on the transparent support 16 are used as the optical compensation film. Function.

Moreover, in this invention, at least one of a polarizing plate should just use the laminated body of a polarizing film and an optically anisotropic layer (for example, the laminated body of 1-7 containing the optically anisotropic layer 7 as an upper polarizing plate), As shown in Fig. 1, both polarizing plates need not be laminates of the above-described configuration. In addition, although the liquid crystal display device of FIG. 1 shows the embodiment using the polarizing plate which laminated | stacked one optically anisotropic layer integrally, the liquid crystal display device of this invention laminates a polarizing plate and at least one optically anisotropic layer integrally. The structure may be used, and the structure is not limited thereto.

In the liquid crystal display of the present invention, since the transparent support of the optical compensation film can serve as a protective film on one side of the polarizing film, an integrated type laminated in the order of a transparent protective film, a polarizing film, a transparent protective film (combining a transparent support) and an optically anisotropic layer. The polarizing plate is used. The polarizing plate not only has a polarizing function but also contributes to enlargement of the viewing angle and reduction of display unevenness. Moreover, since this polarizing plate is provided with the optically anisotropic layer which has optical compensating ability, it can optically compensate a liquid crystal display device accurately with a simple structure.

Moreover, in a liquid crystal display device, it is preferable to laminate | stack from the outer side of the apparatus (side far from a liquid crystal cell) in order of a transparent protective film, a polarizing film, a transparent support body, and an optically anisotropic layer.

Absorption axes 4 and 19 of the polarizing films 3 and 18, transparent protective films 1, 5, 16 and 20, and slow axes 2, 6, 17 and 21 thereof, optically anisotropic layers 7 and 14 And the orientation direction averages (8, 15) of the molecular long axes and the orientation directions (10, 15) of the liquid crystal molecules (11) in an optimum range depending on the material used for each member, the display mode, the laminated structure of the members, and the like. I can adjust it. In order to obtain high contrast, the absorption axes 4 and 19 of the polarizing plates 3 and 18 are disposed so as to be substantially perpendicular to each other. However, the liquid crystal display device of this invention is not limited to this structure.

The liquid crystal cells 9 to 13 consist of an upper substrate 9 and a lower substrate 12 and a liquid crystal layer formed of the liquid crystal molecules 11 sandwiched therebetween. An alignment film (not shown) is formed on the surface (hereinafter may be referred to as an "inner surface") in contact with the liquid crystal molecules 11 of the substrates 9 and 13, and a voltage is obtained by a rubbing process or the like performed on the alignment film. The orientation of the liquid crystal molecules 11 in the unapplied state or the low applied state is controlled. In addition, a transparent electrode (not shown) capable of applying a voltage to the liquid crystal layer made of the liquid crystal molecules 11 is formed on the inner surfaces of the substrates 9 and 12.

[TN mode liquid crystal display]

For example, in the TN mode liquid crystal display device, in the non-driven state in which no driving voltage is applied to the electrode, the liquid crystal molecules 11 in the liquid crystal cell are oriented substantially parallel to the substrate surface, and the alignment direction is between the upper and lower substrates. It is twisted 90 degrees. In the case of a transmissive display device, the light of the backlight is linearly polarized by passing through the lower polarizer. The linearly polarized light propagates along the torsional structure of the liquid crystal layer and passes through the upper polarizing plate as it is by rotating the polarization plane 90 degrees while maintaining the polarization state, and the display device becomes white display.

On the other hand, when the applied voltage is increased, the liquid crystal molecules gradually rise in a direction perpendicular to the substrate surface while eliminating the torsion. In a TN mode liquid crystal display device in an ideal high voltage application state, the twisting of the liquid crystal molecules is almost completely eliminated, and the line alignment state becomes almost perpendicular to the substrate surface. At this time, since the linearly polarized light passing through the lower polarizing plate has no torsion structure in the liquid crystal layer, it propagates without rotating the polarizing plane and is incident at an angle orthogonal to the absorption side of the upper polarizing plate, so that light is blocked and becomes black display. .

Thus, in the TN mode, the polarized light is blocked or transmitted to fulfill the function of the display device. Generally, the ratio of white display brightness and black display brightness is defined as a contrast ratio as a numerical value representing display quality. The higher the contrast ratio, the higher the quality of the display device, and in order to increase the contrast, it is important to maintain and pass the polarization state of the liquid crystal display device.

The operation of the liquid crystal display shown in FIG. 1 will be described taking TN mode as an example. In this embodiment, an example in which active driving is performed using a nematic liquid crystal having positive dielectric anisotropy as a field effect liquid crystal is described.

In the TN mode, the dielectric anisotropy is positive between the upper and lower substrates 9 and 12, and the liquid crystal cell is prepared by rubbing the liquid crystal having refractive index anisotropy Δn = 0.0854 (589 nm, 20 ° C) and Δε = + 8.5. The alignment control of the liquid crystal layer can be controlled by the alignment film and rubbing. It is preferable that the director and so-called tilt angle which show the orientation direction of a liquid crystal molecule shall be about 3 degrees. The rubbing direction is performed in a direction perpendicular to the upper and lower substrates, and the magnitude of the tilt angle can be controlled by the strength, the number of rubbings, and the like. The alignment film can be formed by applying a polyimide film and baking it. The magnitude of the twist angle of the liquid crystal layer is determined by the crossing angle of the rubbing direction of the upper and lower substrates and the chiral agent added to the liquid crystal material. For example, in order to make the twist angle approximately 90 degrees, you may add the chiral agent about 60 micrometers in pitch. Moreover, the thickness d of the liquid crystal layer was set to 5 micrometers.

The liquid crystal material (LC) is not particularly limited as long as it is a nematic liquid crystal. The larger the value of the dielectric anisotropy (Δε), the lower the driving voltage can be. The smaller the refractive index anisotropy (Δn) can make the thickness (gap) of the liquid crystal layer thicker, the sealing time of the liquid crystal can be shortened, and the gap variation can be reduced. The larger Δn is, the smaller the cell gap is, and the faster the response becomes.

In the liquid crystal display device of the TN mode, the absorption axis 4 of the upper polarizing plate and the absorption axis 19 of the lower polarizing plate are roughly orthogonally stacked, and the absorption axis 4 and the upper substrate 9 of the upper polarizing plate of the liquid crystal cell are stacked. The rubbing direction 10 can be laminated | stacked so that it may become roughly parallel, and the absorption axis 19 of the lower polarizing plate, and the rubbing direction 13 of the lower board | substrate 12 will be substantially parallel, respectively. A transparent electrode (not shown) is formed inside each of the alignment films of the upper substrate 9 and the lower substrate 12, but the liquid crystal molecules 11 in the liquid crystal cell in the non-driven state do not apply a driving voltage to the substrate. The polarization state of the light passing through the liquid crystal panel is propagated along the torsional structure of the liquid crystal molecules, and the polarization plane is rotated by 90 ° to be emitted. That is, the liquid crystal display realizes white display in a non-driven state. In contrast, in the driving state, the liquid crystal molecules are oriented in a direction forming a predetermined angle with respect to the substrate surface, and the light passing through the lower polarizing plate is retarded by the optical compensation layers 16, 14, 7, 5. This cancels off, passes through the liquid crystal layer 11 while maintaining the polarization state, and is blocked by the polarizing film 3. In other words, in a liquid crystal display device, an ideal black display is obtained.

In this manner, in the liquid crystal display device, display is performed by controlling transmission of polarized light. Contrast ratio which is a ratio of white display brightness and black display brightness is used for image quality evaluation of a display apparatus. The larger the numerical value is, the more preferable the value is, and a commercially available liquid crystal display device, for example, a value of 300 or more can be obtained. In order to increase the contrast ratio, it is important to increase the white display luminance and decrease the black display luminance. In the display device, in order to increase the white display brightness, it is preferable to emit from the upper polarizing plate without attenuating the transmittance of the polarized light that has passed through the lower polarizing plate from the light source. Similarly, in black display, it is important to completely block outgoing light from the upper polarizer. In the present invention, since a polarizing plate having a polarization degree of 99.5% or more having an optical compensation film having a high polarization retention rate is used, a high contrast image can be displayed. In order to obtain a higher contrast ratio, it is preferable to maintain the polarization state as much as possible when passing through another member, for example, a polarizing plate protective film, a substrate sandwiching the liquid crystal layer, or the like, that is, the polarization degree retention rate of each member. It is preferable to make it high.

As mentioned above, the member which can lower contrast other than a polarizing plate is used for a display apparatus. When the member with a low polarization retention rate is used, the polarization component of the upper polarizing plate absorption axis and the transmission axis direction of a perpendicular | vertical direction may generate | occur | produce, leakage light may arise, black transmittance may rise, and contrast ratio may fall. The polarization retention rate of the member is lowered due to a decrease in the single transmittance of each member, haze (turbidity), scattering degree, birefringence, and the like. In order to improve the polarization retention rate of each member and to make the above range, it is preferable to reduce the diameter of the foreign material in each member. For example, a color filter and a TFT are formed in the board | substrate which clamps a liquid crystal layer, and also become a factor which reduces polarization retention. In order not to reduce the polarization retention rate of a color filter, it is preferable to suppress the planarizing agent at the time of apply | coating a filter to within +/- 0.5 micrometer. Moreover, it is preferable to suppress the particle diameter in a filter binder to 1 micrometer or less. In addition, in order not to lower the polarization retention of the TFT substrate, it is important to increase the transmittance of the substrate, and the TFT wiring width made of metal is set within 3 µm on average, or the cut film is made of epoxy or acrylic resin. It is preferable to set it as an organic insulating film.

In general, in a liquid crystal display device, a transmission type in which a backlight is disposed on a substrate surface on the rear side of the display surface is mainstream, and light of the backlight passes through a lower polarizer, a lower substrate, a liquid crystal layer, an upper substrate, and an upper polarizer. Eject. In such an aspect, high contrast is obtained by increasing the polarization retention rate of the member closer to the polarizing plate. In addition, higher contrast is obtained by increasing the polarization retention ratio of the optical compensation film on the side close to the light source of the pair of substrates sandwiching the liquid crystal layer. Therefore, it is preferable that the polarization degree retention rate of the optical compensation film (14-16 in FIG. 1) of the back side located closer to the backlight side is higher than the board | substrate (9 and 12 in FIG. 1) of a liquid crystal cell.

In addition, the liquid crystal display of the present invention is capable of high contrast display, and in particular, transmittance and luminance at the time of black display are low. Therefore, since the color tone a and b of the transmitted light of a polarizing plate are ± 4 or less, since the hue of a black display becomes more achromatic good display, it is preferable. More preferably, the colors a and b are ± 5 or less, and still more preferably ± 4 or less.

In the liquid crystal display device of the present invention, the contrast ratio T? / T? Is preferably about 3000 to 1 ideally. In general, the display contrast is preferably 2000 to 1 to 100 to 1, and more preferably 1500 to 1 to 300 to 1.

[IPS Mode Liquid Crystal Display]

You may use the polarizing plate of this invention for the liquid crystal display device of IPS mode. As for the liquid crystal display device of the IPS mode using the polarizing plate of this invention, image display of high contrast is possible like embodiment of the liquid crystal display device of the said TN mode.

Fig. 2 is a schematic side cross-sectional view of an embodiment of a liquid crystal display device in IPS mode having a polarizing plate of the present invention. The liquid crystal cell of the IPS mode usually has a plurality of pixels by a matrix electrode, but part of the one pixel is shown in FIG. The liquid crystal display shown in FIG. 2 has a pair of polarizing plates 30 and 42 of this invention. In addition, although the pair of polarizing plates 30 and 42 have a protective film, a polarizing film, and an optical compensation layer, detailed structure is abbreviate | omitted in FIG.

The liquid crystal display of FIG. 2 has a pair of polarizing plates 30 and 42 and a liquid crystal cell in IPS mode. The liquid crystal cell in the IPS mode has a liquid crystal layer containing a pair of transparent substrates 32 and 40 and a rod-shaped liquid crystal molecule 34 sandwiched by the pair of substrates. A linear electrode 38 is formed inside the transparent substrate 40, and an orientation control film (not shown) is formed thereon. The plurality of linear electrodes 38 are spaced apart from each other and constitute a pixel electrode and an opposite electrode so as to be capable of generating an electric field parallel to the substrate 40. The rod-shaped liquid crystalline molecules 34 sandwiched between the substrates 32 and 40 are oriented so as to have a slight angle with respect to the longitudinal direction of the linear electrodes 38 when no electric field is applied (OFF display). Moreover, the dielectric anisotropy of the liquid crystal in this case assumes a positive. When the electric field 36 in the direction indicated by the arrow 36 is applied (ON display), the liquid crystal molecules 34 change the direction in the electric field direction. The light transmittance can be changed by arranging the polarizing plates 30 and 42 at a predetermined angle in the transmission axis. The angle formed by the electric field direction 36 with respect to the surface of the substrate 40 is preferably 20 degrees or less, more preferably 10 degrees or less, that is, substantially parallel. Hereinafter, in this invention, what is 20 degrees or less generically is represented as a parallel electric field. Even if the electrode 38 is divided into upper and lower substrates and formed only on one substrate, the effect is the same.

FIG. 3 shows a schematic side cross-sectional view of another embodiment of a liquid crystal display device in IPS mode. This is a sun that enables faster response and higher transmittance. In addition, about the same member as shown in FIG. 2, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted. Unlike in FIG. 2, the electrode is arranged through the insulating layer 44 (different layers are arranged) to form a two-layer structure of the linear electrode 38 and the lower electrode 46. The lower electrode 46 may be an unpatterned electrode, or may be a linear or the like electrode. It is preferable that the upper electrode 38 is linear, but as long as it can pass through the electric field from the lower electrode 46, any one of a mesh shape, a spiral shape, a point shape, etc. is added, and a floating electrode having a neutral potential is further added. You may also The insulating layer 44 may be an inorganic material such as SiO or a nitride film, or may be an organic material such as acrylic or epoxy.

In the IPS mode, these electrode structures 38, or 38 and 46, and the insulating layer 44 become a factor of lowering the polarization retention, and in order to obtain high contrast, the polarization retention of these electrodes and the insulating layer is adjusted. It is preferable to use 90% or more, more preferably 95% or more, and even more preferably 99% or more. In order to obtain the polarization degree retention rate in the above range, for example, the width and pitch of the linear electrode 38 are set to 2 µm or more which is sufficiently larger than the wavelength of visible light to suppress the diffraction effect; It is effective to suppress the attenuation of the polarization transmittance by setting the transmittance of the insulating layer 44 to 80% or more in the visible light wavelength range.

As the liquid crystal material LC in the IPS mode, a nematic liquid crystal having a constant dielectric anisotropy (Δε) is used. It is preferable to make thickness (gap) of a liquid crystal layer more than 2.8 micrometers and less than 4.5 micrometers. When retardation ((DELTA) n * d) is made into more than 0.25 micrometer and less than 0.32 micrometer, the transmittance | permeability characteristic which has little wavelength dependence in the range of visible light is obtained more easily. By the combination of the predetermined alignment film and the polarizing plate of the present invention, the maximum transmittance is obtained when the liquid crystal molecules rotate 45 degrees in the rubbing direction in the electric field direction. In addition, the thickness (gap) of the liquid crystal layer can be suppressed by polymer beads. Of course, the same gap can also be obtained with glass beads fibers and columnar spacers made of resin. In addition, a liquid crystal material (LC) will not be specifically limited if it is a nematic liquid crystal. The larger the value of the dielectric anisotropy (Δε), the smaller the driving voltage can be, and the smaller the refractive index anisotropy (Δn) can increase the thickness (gap) of the liquid crystal layer, and the sealing time of the liquid crystal is shortened. The gap deviation can be reduced.

[Other mode liquid crystal display device]

Although the display mode of the liquid crystal display device used by this invention is not specifically limited, In addition to the TN mode and IPS mode mentioned above, OCB mode and ECB mode are used preferably. In this invention, the product ((DELTA) n * d) of the thickness d (micrometer) of a liquid crystal layer and refractive index anisotropy ((DELTA) n) shall be 0.2-1.2 micrometer. The optimum value of Δn · d depends on the display mode, and the optimal value of Δn · d of the liquid crystal is 0.2 to 0.5 μm in the TN mode. In OCB mode, the optimum value is 0.4 to 1.2 µm. In ECB mode, the optimum value is 0.2 to 0.5 µm. In addition, the twist (twist angle) of the liquid crystal layer in the TN mode is about 90 ° (85 ° to 95 °) at an optimum value. In these ranges, since the white display brightness is high and the black display brightness is small, a bright and high contrast display device is obtained.

Moreover, these optimum values are the values of a transmission mode, and since the optical path in a liquid crystal cell doubles in a reflection mode, the value of optimal (DELTA) nd is about 1/2 said value. In addition, the twist angle of 30 ° to 70 ° is optimal.

The liquid crystal display device used in the present invention is effective not only in the display mode but also in the VA mode, the ECB mode, and the STN mode.

The liquid crystal display device of this invention is not limited to the structure shown in FIG. 1, and may contain the other member. For example, you may arrange a color filter between a liquid crystal cell and a polarizing film. Moreover, when using as a transmission type, the backlight which uses a cold cathode or a hot cathode fluorescent tube, or a light emitting diode, a field emission element, an electroluminescent element as a light source can be arrange | positioned at the back surface. In addition, the liquid crystal display device of the present invention may be a reflective type, in which case, only one polarizing plate may be disposed on the observation side, and a reflective film is provided on the rear surface of the liquid crystal cell or the lower substrate of the liquid crystal cell. Of course, the front light using the said light source can also be formed in the liquid crystal cell observation side. In addition, the liquid crystal display of the present invention may be a semi-transmissive type in which a reflection portion and a transmission portion are formed in one pixel of the display device in order to achieve both modes of transmission and reflection.

The liquid crystal display of the present invention includes an image direct view type, an image projection type, and a light modulation type. The present invention is particularly effective when applied to an active matrix liquid crystal display device using a three-terminal or two-terminal semiconductor element such as a TFT or a MIM. Of course, the aspect applied to the passive matrix liquid crystal display device represented by STN type called time division drive is also effective.

Hereinafter, the color filter which can be used for the liquid crystal display device of this invention is demonstrated.

[Color filter]

You may form the color filter containing each pattern of red, green, and blue in a pair of board | substrate of the liquid crystal cell of the liquid crystal display device of this invention. A color filter can be produced by the following method, for example. First, the colored pixel according to the objective, such as red, green, blue, is formed on a transparent substrate. As a method of forming colored pixels, such as red, green, and blue, on a transparent substrate, the coloring method of the above-mentioned dyeing, the printing, or the coloring photosensitive resin liquid is apply | coated with a spin coater, etc., and then patterned in a photolithography process, and also a laminate Law and the like can be used as appropriate.

When forming a black mattress using black photosensitive resin, it is preferable to form after the said colored pixel. When the black matrix is first formed, only the surface of the resin is cured in the black photosensitive resin having a high optical density, so that the uncured resin is eluted by the subsequent development treatment, in particular, the development treatment repeated to form colored pixels ( This is because the formed matrix may be peeled off in extreme cases.

In contrast, when the black matrix is formed last, the surroundings of the black matrix are surrounded by colored pixels, and the developer is difficult to penetrate through the cross-section, so that side etch hardly occurs and a black matrix having a high optical density can be formed. There is a big advantage.

In addition, in the case of forming the colored layer for forming colored pixels by the laminating method, when the black matrix is first formed, the place where the colored pixels are formed is closed in a substantially lattice shape with the black matrix, so that bubbles are easily generated during the lamination. there is a problem.

When the light transmittance of the colored pixel with respect to the photosensitive wavelength range of black photosensitive resin exceeds 2%, it is preferable to add a light absorber etc. to a colored pixel beforehand, and to make the transmittance 2% or less. As a light absorber used at this time, a well-known compound can be used. For example, a benzophenone derivative (Mihilers ketone etc.), a merocyanine type compound, a metal oxide, a benzotriazole type compound, a coumarin type compound etc. are mentioned. Among them, it is preferable that the light absorbency is good and the light absorption performance is maintained at 25% or higher even after the heat treatment at 200 ° C. or higher, and specific examples thereof include titanium oxide, zinc oxide, benzotriazole compound, and coumarin compound. In these, a coumarin type compound is especially preferable from a viewpoint of both heat resistance and light absorption. In addition, the above-mentioned heat processing of 200 degreeC or more is performed in order to harden | cure further after forming each pixel.

Next, a black photosensitive resin layer is formed on the entire surface of the transparent substrate by covering the pixel pattern, which is also a method of applying the black photosensitive resin liquid with a spin coater or a roll coater, and also by applying the black photosensitive resin liquid onto the temporary support in advance. The formation material is produced, and the method of transferring this black photosensitive resin layer on a pixel pattern, etc. can be used.

Next, it exposes from the black photosensitive resin layer side through photolithography, and hardens the black photosensitive resin layer of the light shielding part (black matrix) in which a colored pixel does not exist. The colored image is somewhat misaligned due to the alignment error of the exposure machine or the thermal expansion of the substrate, or the thickness or thinness of the pixel itself is not normally arranged at intervals or sizes according to the design dimensions. This tendency becomes especially strong in the board | substrate of a big size. Therefore, when exposing with a photomask at design pixel intervals, a portion in which the black matrix overlaps the pixels or a portion in which a gap is formed between the pixels is generated. The overlapped portions become projections, and the portions in which the gaps are formed are light leakage, which is not preferable.

1.5, 또한 Pb/Pg

1.5 로 하면 백색 표시 및 흑색 표시에 있어서, 액정 표시 장치의 표시색이 무채색으로 되어 양호한 색재현성이 얻어진다. 한편, Pr/Pg 및 Pb/Pg 가 1.5 를 초과하면, 표시가 청색이나 자색으로 착색된다.As the polarization degree retention rate of one pixel color filter, Pr / Pg when the polarization degree retention ratio of the red pattern is Pr, the green pattern is Pg, and the blue pattern is Pb.

1.5, also Pb / Pg

When it is set to 1.5, in the white display and the black display, the display color of the liquid crystal display device becomes achromatic and good color reproducibility is obtained. On the other hand, when Pr / Pg and Pb / Pg exceed 1.5, a display will be colored blue or purple.

Example

 Hereinafter, the present invention will be described in more detail with reference to examples. Materials, reagents, amounts of substances, proportions thereof, operations, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited by the following specific examples.

Example 1

The liquid crystal display device of the structure shown in FIG. 1 was produced. That is, from the observation direction (upper), the upper polarizing plate (1-5), the upper optically anisotropic layer (7), the liquid crystal cell (upper substrate (9), liquid crystal layer (11), lower substrate (12)), lower optically anisotropic layer (14) and lower polarizing plates 16 to 20 were laminated, and a backlight using a cold cathode fluorescent lamp was disposed below the lower polarizing plate.

The manufacturing method of each member used below is demonstrated.

<Production of TN Mode Liquid Crystal Cell>

The liquid crystal cell was made into 4 micrometers of cell gaps (d), and the liquid crystal material which has a positive dielectric constant anisotropic layer was dripped-injected between board | substrates, and Δnd of the liquid crystal layer 11 was 410 nm ((DELTA) n is the refractive index anisotropy of a liquid crystal material. ). The twist angle of the liquid crystal cell is 90 ° counterclockwise by the crossing angle between the rubbing direction 10 of the upper substrate 7 and the rubbing direction 14 of the lower substrate 12 and the addition of a chiral agent. It was. Moreover, when bonding with the up-and-down polarizing plate, it was made so that the up-and-down board | substrate rubbing direction of a liquid crystal cell, and the slow axis (parallel direction and parallel direction; 6, 17) of the support bodies 5 and 16 may become parallel. 4 shows these angles.

<Substrate for liquid crystal cell>

An ITO (oxide of indium tin) film was formed on the transparent electrode of Corning Co., Ltd. transparent glass "7059" by vapor deposition. Both pairs of substrates used this glass, and both substrates had a transmittance of 99.9% and a polarization retention rate of 99%.

<Production of Cellulose Acetate Film>

The following composition was put into the mixing tank, it stirred while heating, and each component was dissolved and the cellulose acetate solution was prepared.

<Cellulose Acetate Solution Composition>

80 parts by mass of cellulose acetate (linter) having an acetylation degree of 60.9%

20 parts by mass of cellulose acetate (linter) having an acetylation degree of 60.8%

Triphenyl phosphate (plasticizer) 7.8 parts by mass

3.9 parts by mass of biphenyldiphenyl phosphate (plasticizer)

300 parts by mass of methylene chloride (first solvent)

54 parts by mass of methanol (second solvent)

11 parts by mass of 1-butanol (third solvent)

4 parts by mass of cellulose acetate (Linter) having an acetylation degree of 60.9%, 16 parts by mass of the following retardation increasing agent, 0.5 parts by mass of silica fine particles (particle diameter: 20 nm, Mohs hardness: about 7), 87 parts by mass of methylene chloride, and the like in another mixing tank 13 mass parts of methanol were thrown in, and it stirred while heating, and prepared the retardation increasing agent solution.

36 mass parts of retardation increasing agent solutions were mixed with 464 mass parts of cellulose acetate solutions, and it fully stirred, and dope was prepared. The addition amount of the retardation increasing agent was 5.0 mass parts with respect to 100 mass parts of cellulose acetate.

[Formula 1]

Retardation synergist

The width | variety of the obtained polymer base material (PK-1) was 1340 nm, and thickness was 92 micrometers. It was 43 nm as a result of measuring the retardation value Re in wavelength 590 nm using the automatic birefringence meter (KOBRA 21DH, an oji measurement Co., Ltd.). Moreover, it was 175 nm when the retardation value (Rth) in wavelength 590nm was measured.

Moreover, the transmittance | permeability of the obtained polymer was 99% and polarization retention was 98%.

Moreover, the moisture absorption expansion coefficient of the produced polymer base material (PK-1) was measured, and it was 12.0x10 <^-5> /% RH.

(Production of the subfloor)

The coating liquid of the following composition was apply | coated and dried to the said cellulose acetate film support body, and the gelatin layer (coating layer) of 0.1 micrometer was formed.

Undercoat Coating Composition

0.542 parts by mass of gelatin

Formaldehyde 0.136 parts by mass

0.160 parts by mass of salicylic acid

Acetone 39.1 parts by mass

15.8 parts by mass of methanol

Methylene chloride 40.6 parts by mass

1.2 parts by mass of water

The alignment film coating liquid of the following composition was apply | coated on this PK-1 with the application amount of 28 mL / m <2> with the # 16 wiper bar coater. The film | membrane was formed by drying for 60 second by 60 degreeC warm air, and 150 second by 90 degreeC warm air. Moreover, the rubbing process was performed to the slow axis (measured at wavelength 632.8 nm) of the polymer base material (PK-1), and the direction of 45 degrees, and it was set as the orientation film.

<Alignment film coating liquid composition>

10 parts by mass of the following modified polyvinyl alcohol

371 parts by mass of water

119 parts by mass of methanol

0.5 mass part of glutaraldehyde (crosslinking agent)

[Formula 2]

Modified polyvinyl alcohol

<Formation of Optically Anisotropic Layer>

46.65 kg of the following discotic liquid crystalline compounds (B), ethylene oxide modified trimethylolpropane triacrylate (V # 360, Osaka Organic Chemical Co., Ltd.) 4.06 kg, cellulose acetate butyrate (CAB551-0.2, Eastman) Chemical Co., Ltd.) 0.90 kg, cellulose acetate butyrate (CAB531-1, Eastman Chemical Co., Ltd.) 0.23 kg, photopolymerization initiator (Irugacure 907, manufactured by Chiba Chemical Co., Ltd.) 1.35 kg, sensitizer (Gayacure DETX, Nippon Chemical Co., Ltd.) NOTE) The solution which melt | dissolved 0.45 kg in 102 kg of methyl ethyl ketone was made into the coating liquid, and this was apply | coated with the wire bar of # 3.4. This was heated for 2 minutes in the constant temperature zone of 130 degreeC, and the discotic liquid crystalline compound was orientated. Next, UV irradiation was performed for 1 minute using a 120 W / cm high-pressure mercury lamp under an atmosphere of 60 ° C to polymerize the discotic liquid crystal compound. Thereafter, it was allowed to cool to room temperature. Thus, the optically anisotropic layer was formed and the optical compensation layer (KH-2) was produced.

Discotic Liquid Crystal Compound (B)

(3)

The Re retardation value of the optically anisotropic layer measured by the wavelength of 546 nm was 40 nm.

In the produced optically anisotropic layer, the disk-shaped liquid crystalline compound had an angle (tilt angle) between the disk surface and the transparent protective film increased from the transparent protective film toward the air interface and hybridly oriented at 11 ° to 66 °. The angle of inclination was measured by using an automatic birefringence meter KOBRA 21ADH (manufactured by Oji Measurement Instruments Co., Ltd.), changing the angle of observation to measure retardation, and assuming that the index of refraction ellipsoid model was `` Design Concepts of the Discotic Negative Birefringence Compensation Films SID98 DIGEST. It calculated by the method described in "."

When the polarizing plate was made into the cross nicol arrangement | positioning, and the nonuniformity of the obtained optical compensation film | membrane was observed, even if it looked in the direction inclined to 60 degrees from the front and a normal line, the nonuniformity could not be detected. Moreover, also in the observation under a polarizing microscope, the orientation defect and the foreign material of diameter 1 micron or more were not observed, and the polarization retention rate was 95%, and was favorable.

<Production of Polarizing Film>

Iodine was adsorbed to the stretched polyvinyl alcohol film to produce a polarizing film, and the produced optical compensation film was attached to one side of the polarizing film on the support surface using a polyvinyl alcohol-based adhesive. In addition, saponification was performed on a cellulose acetate film (TD-80U, manufactured by Fuji Photographic Film Co., Ltd.) having a thickness of 80 µm, and adhered to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. The bonding angle of each film is observed and shown in FIG. 4 from the top. The absorption axis 4 of the upper polarizing film 3 and the slow axis 6 (the flexible direction and the parallel direction) of the support 5 are substantially parallel, and the absorption axis 19 and the support 16 of the lower polarizing film 18 are substantially parallel. The slow axis (17; parallel direction with the casting | flow_spread direction) of was arrange | positioned so that it might become substantially parallel.

Thus, the polarization degree of the pair of polarizing plate produced was 99.95%. Moreover, the colors a and b with respect to the vertical incident light of this polarizing plate were -2 and 3, respectively.

<Optical measurement of the manufactured liquid crystal display device>

The rectangular wave voltage of 60 Hz was applied to the liquid crystal display device thus produced. It was set as the normally white mode of white display 1.5V and black display 5V. The measuring instrument measured the contrast ratio which is the ratio (white display / black display) of a transmittance | permeability using (EZ-Contrast160D, ELDIM make). In the range where the transmittance of the front contrast ratio 3000 to 1 and the adjacent gray scales in the downward direction was not reversed, and the contrast ratio was 10 or more, 80 degrees or more were obtained in the entire upper, lower, left, and right ranges.

Comparative Example 1

In Example 1, the TFT substrate and the color filter substrate which were obtained by disassembling the commercially available liquid crystal panel on the outer side of the transparent glass substrate with ITO were affixed with an adhesive material, and the contrast ratio was measured. The other configuration is the same as that of the first embodiment.

From the display surface, it was set as the upper polarizing plate, the glass substrate with a color filter, the transparent glass with a transparent electrode, the liquid crystal layer, the transparent glass with a transparent electrode, the glass substrate with TFT, the lower polarizing plate, and a backlight. The commercially available liquid crystal panel used the 15-inch television PRIUS made from Hitachi. The liquid crystal television was disassembled, and the glass substrate with a TFT and the glass substrate with a color filter were cut out. Here, the transmittance | permeability of the glass substrate with TFT was 92%, and polarization retention was 87%. The transmittance | permeability of the glass substrate with a color filter was 31%, and the polarization retention was 82%. Moreover, the polarization degree of the vertical polarizing plate was 99.90%.

As a result of measuring the contrast ratio in the same manner as in Example 1, the front contrast was 300: 1.

[Example 2]

In Example 1, the transparator color filter by Fuji Photo Film Co., Ltd. was formed on the transparent glass substrate by the method of Unexamined-Japanese-Patent No. 10-221518, and the transparent electrode substrate with ITO and upper polarizing plate were used for the board | substrate as an adhesive material. It fixed and laminated in between. At this time, the surface unevenness of the transcolor filter was 0.2 micron, and the particle size of the granular material in the binder was 0.1 micron or less in average, and green was 0.15 μm or less in red and blue. The transmittance was 35% and the polarization degree retention 90%. The other configuration is the same as that of the first embodiment.

It was 1500 to 1 as a result of measuring the contrast ratio which made black display voltage 60V square wave voltage 5V and white display voltage 1.5V.

1.3 이었다. 수직입사광에 대한 투과광 색상은 a=2.1, b=2.8 이었다.Moreover, the light transmittance of 1 pixel was microscopically measured by SR-3 of the luminance meter by TOPCON, and the polarization degree retention of each pixel was measured. Pr / Pg = 1.2, also Pb / Pg

Was 1.3. The transmitted light color with respect to the vertical incident light was a = 2.1, b = 2.8.

Example 3

<Production of IPS Mode Liquid Crystal Cell>

On the lower substrate 40 of FIG. 2, a linear electrode was formed by vapor deposition. The copper electrode has a width of 16 µm and is not particularly limited as long as the electrical resistance is low, and may be chromium or copper. By forming the metal electrode of low electrical resistance in this way, the load of the drive LSI can be reduced and power consumption can be reduced. Of course, the linear electrode of ITO may be sufficient. The size of one pixel was 80 占 240 占 퐉 and the distance between the signal electrode and the common electrode was 48 占 퐉. The upper substrate was made of transparent glass without an electrode having a thickness of 0.7 μm.

As liquid crystal material LC, the liquid crystal material used the nematic liquid crystal of dielectric constant anisotropy (DELTA) epsilon, whose value is 13.2, and refractive index anisotropy (DELTA) n 0.085 (589 nm, 20 degree | times) (MLC9100-100 by Merck Co., Ltd.). The thickness (gap) of the liquid crystal layer was 3.5 μm. The same polarizing plate as Example 1 was used.

The transmittance | permeability of this liquid crystal display device was 30%, and the polarization degree retention rate was 85%. At this time, the contrast ratio was 1,200 as 1 when the black display voltage was 60V and the rectangular wave voltage was 2V and the white display voltage was 6V. In the IPS mode liquid crystal display device, the applied electric field direction 36 is approximately parallel to the substrate surface 40 as shown in FIG. 2. Of course, in the vicinity of the linear electrode 38, an electric field in the vertical direction is also generated on the same substrate surface as in the TN mode, but there are many parallel electric field components in the entire apparatus.

Example 4

In Example 3, after forming a beta electrode of ITO on the lower substrate 14 by evaporation, the silicon oxide film (SiO ₂ ) was formed by evaporation equally to 0.5 μm or less so that the polarization degree retention was 99% or more. It was. A linear electrode was formed thereon with ITO 10 micrometers in width, and 5 micrometers in electrode distance. Other configurations are the same as those in the third embodiment.

The transmittance | permeability of the same liquid crystal display device was 30%, and the polarization degree retention rate was 85%. The other configuration is the same as that of the first embodiment. At this time, the contrast ratio was measured using a black display voltage of 60 mA and a rectangular wave voltage of 2 V and a white display voltage of 6 V. As a result, the use of ITO for the linear electrode and the vertical component in the electric field direction 36 in FIG. As a result, the white display transmittance was improved to 1500 to 1.

According to the present invention, it is possible to provide a liquid crystal display device, in particular a TN type or IPS type liquid crystal display device, in which the contrast is improved without compromising the viewing angle characteristic with a simple configuration. Moreover, according to this invention, the polarizing plate which contributes also to the contrast improvement of the liquid crystal cell of a TN type or IPS type liquid crystal display device can be provided.

Claims (11)

delete delete A liquid crystal display device having an electrode on at least one side, a pair of substrates opposed to each other, a liquid crystal layer formed between the substrates, and a pair of polarizing plates arranged to sandwich the liquid crystal layer, At least one of the pair of polarizing plates has a polarizing film and an optical compensation film on a surface closer to the liquid crystal layer of the polarizing film, the polarization degree of the pair of polarizing plates is 99.5% or more, and the pair of substrates The polarization degree retention of is 90% or more, and the polarization degree retention of the optical compensation film is 90% or more, The electrode is composed of a pixel electrode and an opposite electrode, the electrode is arranged with different layers, and at least one of the electrodes is made of a transparent electrode, A liquid crystal display device, wherein the counter electrode is an unpatterned electrode. The method of claim 3, wherein Both of said pair of polarizing plates have a polarizing film and an optical compensation film on the surface of the side closer to the said liquid crystal layer of the said polarizing film. The method according to claim 3 or 4, The liquid crystal display device whose polarization degree retention of the said optical compensation film is more than the polarization degree retention of the said pair of board | substrates. The method according to claim 3 or 4, The absorption axis of the pair of polarizing plates is perpendicular to each other. The method according to claim 3 or 4, At least one of the pair of substrates is provided with a color filter including respective red, green, and blue patterns, and the polarization degree retention ratios of the red pattern, the green pattern, and the blue pattern are respectively Pr, Pg, and Pb. When Pr / Pg

1.5, also Pb / Pg

1.5 person, liquid crystal display. delete delete The method of claim 3, wherein And a conductive layer to which no voltage is applied is disposed on the substrate on which the pixel electrode and the counter electrode are disposed. The method according to claim 3 or 4, The said pixel electrode is a some linear electrode, and the width and pitch of the said pixel electrode are 2 micrometers or more.

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