JP2005062810A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device which has an accurately and optically compensated liquid crystal cell and which can be made thin. <P>SOLUTION: The liquid crystal display device comprises two polarizing films with the absorption axes orthogonal to each other, and between the above two polarizing films: a liquid crystal cell having a pair of substrates and a liquid crystal layer comprising liquid-crystalline molecules held between the substrates, the molecules aligned in the direction almost perpendicular to the substrate in a non-operative state in the absence of an applied external electric field; a first optical anisotropic layer consisting of a thermoplastic polymer stretched film having optically positive refractive index anisotropy and having 40 to 150 nm Re (=(nx-ny)×d for visible light, wherein nx denotes a refractive index in the layer plane, ny denotes an in-plane refractive index in the direction orthogonal to the direction of nx, and d denotes the layer thickness); and a second optical anisotropic layer having optically negative refractive index anisotropy, comprising a discotic liquid-crystalline compound and having ≤10 nm Re as defined above for visible light and 60 to 250 nm Rth(=ä(nx+ny)/2-nz}×d, wherein nz denotes the refractive index in the thickness direction of the layer). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device, and more particularly to a vertical alignment nematic liquid crystal display device having excellent viewing angle characteristics.

  The liquid crystal display device includes a liquid crystal cell and a polarizing plate. The polarizing plate has a protective film and a polarizing film. For example, the polarizing film made of a polyvinyl alcohol film is dyed with iodine, stretched, and both surfaces thereof are laminated with a protective film. In the transmissive liquid crystal display device, the polarizing plate is attached to both sides of the liquid crystal cell, and one or more optical compensation sheets may be disposed. In a reflective liquid crystal display device, a reflector, a liquid crystal cell, one or more optical compensation sheets, and a polarizing plate are arranged in this order. The liquid crystal cell includes a liquid crystal molecule, two substrates for encapsulating the liquid crystal molecule, and an electrode layer for applying a voltage to the liquid crystal molecule. The liquid crystal cell performs ON / OFF display depending on the alignment state of liquid crystal molecules, and can be applied to both transmission and reflection types. TN (Twisted Nematic), IPS (In-Plane Switching), OCB (Optically Compensatory Bend) ), VA (Vertically Aligned), and ECB (Electrically Controlled Birefringence) have been proposed.

  Among such LCDs, for applications that require high display quality, a 90 degree twisted nematic liquid crystal display device (hereinafter referred to as a TN mode) that uses nematic liquid crystal molecules having positive dielectric anisotropy and is driven by a thin film transistor. Is mainly used. However, although the TN mode has excellent display characteristics when viewed from the front, the contrast is reduced when viewed from an oblique direction, or gradation inversion that reverses the brightness in gradation display occurs. There is a viewing angle characteristic that the display characteristic is deteriorated, and this improvement is strongly demanded.

  In recent years, as an LCD method for improving the viewing angle characteristics, nematic liquid crystal molecules having negative dielectric anisotropy are used, and the major axis of the liquid crystal molecules is aligned in a direction substantially perpendicular to the substrate without applying a voltage. A vertical alignment nematic liquid crystal display device (hereinafter referred to as VA mode) in which this is driven by a thin film transistor has been proposed (see Patent Document 1). This VA mode not only has excellent display characteristics when viewed from the front, but also exhibits a wide viewing angle characteristic by applying a viewing angle compensation phase difference film. In the VA mode, a wide viewing angle characteristic can be obtained by using two negative uniaxial retardation films having an optical axis in a direction perpendicular to the film surface, above and below the liquid crystal cell. It is also known that a wider viewing angle characteristic can be realized by using a uniaxially oriented retardation film having a positive refractive index anisotropy with a retardation value of 50 nm (see Non-Patent Document 1). .

However, the use of three retardation films (see Non-Patent Document 1) not only causes an increase in production cost, but also causes a decrease in yield due to the bonding of a large number of films, and further uses a plurality of films. For this reason, there is a problem that the thickness is increased, which is disadvantageous for thinning the display device. Moreover, since an adhesive layer is used for lamination | stacking of a stretched film, an adhesive layer shrink | contracts by a temperature / humidity change, and defects, such as peeling and curvature between films, may generate | occur | produce.
As a method for improving these, a method of reducing the number of retardation films (see Patent Document 2) and a method using a cholesteric liquid crystal layer (see Patent Documents 3 and 4) are disclosed. However, even in these methods, it is necessary to bond a plurality of films, which is insufficient in terms of thinning and production cost reduction. Furthermore, there was a problem that light leakage from the oblique direction of the polarizing plate during black display was recognized, and the viewing angle was not sufficiently expanded (to the extent expected theoretically).

Japanese Patent Laid-Open No. 2-176625 JP-A-11-95208 JP 2003-15134 A JP-A-11-95208 SID 97 DIGEST Pages 845-848

  An object of the present invention is to provide a liquid crystal display device, particularly a VA mode liquid crystal display device, in which a liquid crystal cell is accurately optically compensated and has a small number of sheets to be bonded and can be thinned.

[1] having two liquid crystal films whose absorption axes are orthogonal to each other and a liquid crystal layer composed of a pair of substrates and liquid crystal molecules sandwiched between the two polarizing films. A liquid crystal cell in which the liquid crystalline molecules are aligned in a direction substantially perpendicular to the substrate in a non-driving state in which no external electric field is applied; and a thermoplastic polymer having optically positive refractive index anisotropy It is made of a stretched film, has an optically negative refractive index anisotropy, and has a disc shape, with at least one first optically anisotropic layer having a Re defined below with respect to visible light of 40 to 150 nm. A liquid crystal display device comprising a liquid crystal compound and having at least one second optically anisotropic layer having Re defined below with respect to visible light of 10 nm or less and Rth of 60 to 250 nm.
Re = (nx−ny) × d (1)
Rth = {(nx + ny) / 2−nz} × d (2)
(Nx is the refractive index in the slow axis direction in the plane of the layer, ny is the refractive index in the plane perpendicular to nx, nz is the refractive index in the thickness direction of the layer, and d is the thickness of the layer.)

[2] The liquid crystal display device according to [1], wherein the first optical anisotropic layer is made of a stretched polycarbonate copolymer film.
[3] having two polarizing films whose absorption axes are orthogonal to each other and a liquid crystal layer composed of a pair of substrates and liquid crystal molecules sandwiched between the two polarizing films. A liquid crystal cell in which the liquid crystalline molecules are aligned in a direction substantially perpendicular to the substrate in a non-driving state where no external electric field is applied, and cellulose acylate, wherein the hydroxyl groups of the cellulose are acetyl groups and carbon atoms. The substitution degree A of the acetyl group of the cellulose acylate and the substitution degree B of the acyl group of 3 to 22 carbon atoms satisfy the following formula (C), and the visible light In contrast, at least one layer of the first optically anisotropic layer defined by the following formula having Re of 40 to 150 nm, optically negative refractive index anisotropy, and comprising a discotic liquid crystalline compound, Against visible light A liquid crystal display device having at least one second optically anisotropic layer having Re defined below and Rth of 60 to 250 nm.
Re = (nx−ny) × d (1)
Rth = {(nx + ny) / 2−nz} × d (2)
(Nx is the refractive index in the slow axis direction in the plane of the layer, ny is the refractive index in the plane perpendicular to nx, nz is the refractive index in the thickness direction of the layer, and d is the thickness of the layer.)
Formula (C) 2.0 ≦ A + B ≦ 3.0
[4] The liquid crystal display device according to [3], wherein the acyl group having 3 to 22 carbon atoms is a butanoyl group or a propionyl group.
[5] The liquid crystal display device according to any one of [1] to [4], wherein the second optically anisotropic layer is made of a discotic liquid crystalline compound having a polymerizable group.
[6] The liquid crystal display device according to any one of [1] to [5], wherein the discotic liquid crystalline compound of the second optically anisotropic layer is substantially horizontally aligned.
[7] The liquid crystal display device according to any one of [1] to [6], wherein the first optically anisotropic layer also serves as at least one protective film of the two polarizing films.
[8] The liquid crystal display device according to [1] to [7], wherein the absorption axis of the polarizing film close to the first optically anisotropic layer is substantially perpendicular to the longitudinal direction of the transparent protective film of the polarizing film.
[9] The liquid crystal of [1] to [8], wherein at least one of the transparent protective films close to the liquid crystal cell of the two polarizing protective films is made of cellulose acetate, and Re of the transparent protective film is less than 3 nm. Display device.

  In the present specification, “substantially” with respect to an angle means that the angle is within a range of an exact angle of less than ± 5 °. The error from the exact angle is preferably less than 4 °, more preferably less than 3 °. Further, the “slow axis” means a direction in which the refractive index is maximized. Further, the measurement wavelength of the refractive index is a value at λ = 550 nm in the visible light region unless otherwise specified. In this specification, “visible light” means 400 nm to 700 nm, and the measurement wavelength of the refractive index is a value at λ = 550 nm in the visible light region unless otherwise specified. In this specification, “polarizing film” and “polarizing plate” are distinguished from each other, and “polarizing plate” is a laminate having a transparent protective film for protecting the polarizing film on at least one side of the “polarizing film”. Means.

  According to the present invention, a liquid crystal cell can be optically compensated with the same configuration as a conventional liquid crystal display device by using a predetermined optically anisotropic layer. In the liquid crystal display device of the present invention having the optically anisotropic layer, not only the display quality but also the viewing angle is remarkably improved. In addition, in a conventional liquid crystal display device, in order to incorporate an optical compensation sheet, a step of laminating while strictly adjusting the angles of a plurality of retardation films and polarizing plates is necessary. There is no need, and there is a great merit in terms of cost. That is, according to the present invention, it is possible to provide a liquid crystal display device, in particular, a VA mode liquid crystal display device in which the liquid crystal cell is accurately optically compensated and the number of layers to be bonded is small and can be thinned.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be specifically described. First, an embodiment of the liquid crystal display device of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing an example of the configuration of a liquid crystal display device of the present invention, and FIG. 2 is a configuration of a polarizing plate usable in the present invention. In FIG. 1, an example in which active driving is performed using a nematic liquid crystal having negative dielectric anisotropy as a field effect liquid crystal will be described.

[Liquid Crystal Display]
In FIG. 1, the liquid crystal display device includes a liquid crystal cell (5 to 8) and a pair of polarizing plates 1 and 14 disposed on both sides of the liquid crystal cell. A first optically anisotropic layer 3 is provided between the polarizing plate 1 and the liquid crystal cells 5 to 8, and a second optically anisotropic layer 10 is provided between the polarizing plate 14 and the liquid crystal cells 5 to 8. And 12 are arranged. The liquid crystal cell includes an upper electrode substrate 5, a lower electrode substrate 8, and liquid crystal molecules 7 sandwiched between them. The liquid crystal molecules 7 are aligned in a direction substantially perpendicular to the substrate in a non-driven state in which no external electric field is applied, by rubbing treatment directions 6 and 9 applied to the opposing surfaces of the electrode substrates 5 and 8. Is controlled to do. Further, the upper polarizing plate 1 and the lower polarizing plate 14 are arranged so that the absorption axis 2 and the absorption axis 15 are substantially orthogonal to each other.

  As shown in FIG. 2, the polarizing plates 1 and 14 include a polarizing film 103 and protective films 101 and 105 that sandwich the polarizing film 103. The polarizing plates 1 and 14 can be produced by, for example, dyeing a polarizing film made of a polyvinyl alcohol film with iodine and stretching to obtain the polarizing film 103 and laminating the protective films 101 and 105 on both sides thereof. it can. In the case of lamination, it is preferable in terms of productivity to bond a total of three films of a pair of protective film and polarizing film with a roll, a TO, and a roll. In addition, in the lamination of rolls, TOs and rolls, as shown in FIG. 2, the slow axes 102 and 106 of the protective films 101 and 105 and the absorption axis 104 of the polarizing film 103 can be easily laminated. It is preferable because the polarizing plate has a high mechanical stability in which the dimensional change and curling of the polarizing plate hardly occur. The same effect can be obtained if at least two axes of the three films, for example, the slow axis of one protective film and the absorption axis of the polarizing film, or the slow axes of the two protective films are substantially parallel. can get.

In FIG. 1 again, the first optically anisotropic layer 3 is made of a stretched thermoplastic polymer film having optically positive refractive index anisotropy, and Re is 40 to 150 nm with respect to visible light. On the other hand, the second optically anisotropic layers 10 and 12 have an optically negative refractive index anisotropy, are made of a discotic liquid crystalline compound, have Re of 10 nm or less with respect to visible light, and Rth of 60-250 nm. These optically anisotropic layers 3, 10 and 12 eliminate the image coloring of the liquid crystal cell and contribute to the expansion of the viewing angle.
In the liquid crystal display device of FIG. 1, an example in which two second optically anisotropic layers are used has been described. However, the second optically anisotropic layer may be a single layer, or three or more layers. There may be. The same applies to the first optical anisotropic layer.

Assuming that the upper side is the observer side, FIG. 1 shows that the first optically anisotropic layer 3 has a second optical difference between the observer-side polarizing plate 1 and the observer-side liquid crystal cell substrate 5. The configuration in which the isotropic layers 10 and 12 are disposed between the back-side polarizing plate 14 and the back-side liquid crystal cell substrate 8 has been shown, but the first optical anisotropic layer and the second optical anisotropy are shown. The layers may be replaced, and both the first and second optical anisotropic layers are disposed between the polarizing plate 1 on the viewer side and the substrate 5 for the viewer side liquid crystal cell. Or may be disposed between the back-side polarizing plate 14 and the back-side liquid crystal cell substrate 8. In such an embodiment, the first optical anisotropic layer may also serve as a support for the second optical anisotropic layer.
In the configuration example shown in FIG. 1, the first optical anisotropic layer 3 may be integrated with the polarizing plate 1, and is incorporated in the liquid crystal display device in an integrated state with the polarizing plate 1. it can. Since the first optically anisotropic layer is composed of a polymer stretched film, for example, the first optically anisotropic layer may be used as a protective film on one side of the polarizing film. It is preferable that the polarizing plate and the first optically anisotropic layer (also used as a transparent protective film) are laminated in the order as an integrated polarizing plate. When the integrated polarizing plate is incorporated in a liquid crystal display device, the order of the transparent protective film, the polarizing film, and the first optically anisotropic layer (also known as the transparent protective film) is from the outside of the device (the side far from the liquid crystal cell). It is preferable to incorporate so that

  The same applies to the second optically anisotropic layer 12 and can be incorporated in the liquid crystal display device as an integrated polarizing plate integrated with the polarizing plate 14. Since the second optically anisotropic layer 12 is made of a discotic liquid crystalline compound, it is usually formed on a support. For example, the support of the second optically anisotropic layer may function as a protective film on one side of the polarizing film, and the transparent protective film, the polarizing film, the transparent protective film (also used as the transparent support) and the first It is preferable to form an integrated polarizing plate laminated in the order of two optically anisotropic layers. When the integrated polarizing plate is incorporated in a liquid crystal display device, a transparent protective film, a polarizing film, a transparent protective film (also a transparent support), and a second optical anisotropic layer are formed from the outside (the side far from the liquid crystal cell). It is preferable to incorporate them in this order.

  The liquid crystal display device of the present invention is not limited to the above configuration, and may include other members. For example, a color filter may be disposed between the liquid crystal cell and the polarizing film. In the transmissive liquid crystal display device, a backlight using a cold or hot cathode fluorescent tube, a light emitting diode, or an electroluminescent element as a light source can be disposed on the back surface. On the other hand, in the aspect of the reflective liquid crystal display device, only one polarizing plate is required on the observation side, and a reflective film is provided on the back surface of the liquid crystal cell or the inner surface of the lower substrate of the liquid crystal cell. Of course, it is also possible to provide a front light using the light source on the liquid crystal cell observation side. Further, a transflective type in which a transmissive portion and a reflective portion are provided in one pixel of the display device is also possible.

  The type of the liquid crystal display device of the present invention is not particularly limited, and includes any of image direct view type, image projection type, and light modulation type liquid crystal display devices. The present invention is effective for an active matrix liquid crystal display device using three-terminal or two-terminal semiconductor elements such as TFT and MIM. Of course, it is also effective in a passive matrix liquid crystal display device represented by STN type called time-division driving.

[VA mode liquid crystal cell]
In the present invention, the liquid crystal cell is preferably in the VA mode. The VA mode liquid crystal cell is formed by sealing liquid crystal molecules having negative dielectric anisotropy between upper and lower substrates whose opposite surfaces are rubbed. For example, by using liquid crystal molecules having Δn = 0.0813 and Δε = −4.6, a director indicating the alignment direction of the liquid crystal molecules, that is, a liquid crystal cell having a so-called tilt angle of about 89 ° can be manufactured. At this time, the thickness d of the liquid crystal layer can be about 3.5 μm. The brightness at the time of white display changes according to the magnitude of the product Δnd of the thickness d of the liquid crystal layer and the refractive index anisotropy Δn. In order to obtain the maximum brightness, the thickness d of the liquid crystal layer is preferably in the range of 0.2 to 0.5 μm.

  A transparent electrode (not shown) is formed inside each alignment film (not shown) of the substrate 5 and the substrate 8, but the liquid crystal in the liquid crystal layer is in a non-driving state where no driving voltage is applied to the electrodes. The molecules 7 are aligned substantially perpendicular to the substrate surface, and as a result, the polarization state of the light passing through the liquid crystal panel hardly changes. As described above, since the absorption axis 2 of the upper polarizing plate 1 of the liquid crystal cell and the absorption axis 15 of the lower polarizing plate 14 are substantially orthogonal to each other, light does not pass through the polarizing plate, that is, in FIG. In the liquid crystal display device, an ideal black display is realized in a non-driven state. On the other hand, in the driving state, the liquid crystal molecules are inclined in a direction parallel to the substrate surface, and the light passing through the liquid crystal panel changes the polarization state by the inclined liquid crystal molecules and passes through the polarizing plate. In other words, the liquid crystal display device of FIG. 1 can obtain white display in the driving state.

Here, since an electric field is applied between the upper and lower substrates, an example using a liquid crystal material having negative dielectric anisotropy in which liquid crystal molecules respond in a direction perpendicular to the electric field direction is shown. When the electrode is disposed on one substrate and an electric field is applied in a lateral direction parallel to the substrate surface, a liquid crystal material having a positive dielectric anisotropy can be used.
In addition, in the VA mode liquid crystal display device, the addition of a chiral material generally used in the TN mode liquid crystal display device is rarely used to degrade the dynamic response characteristics, but in order to reduce alignment defects. May be added.

  The features of the VA mode are high-speed response and high contrast. However, there is a problem that the contrast is high in the front but decreases in the oblique direction. During black display, the liquid crystal molecules are aligned perpendicular to the substrate surface. When observed from the front, the liquid crystal molecules have almost no birefringence, so the transmittance is low and a high contrast can be obtained. However, when observed obliquely, birefringence occurs in the liquid crystalline molecules. Further, the crossing angle of the upper and lower polarizing plate absorption axes is 90 ° perpendicular to the front, but is larger than 90 ° when viewed from an oblique direction. Because of these two factors, leakage light occurs in the oblique direction, and the contrast is lowered. In the present invention, in order to solve this problem, at least one first and second optically anisotropic layers are arranged.

  In the VA mode, the liquid crystal molecules are tilted during white display, but the birefringence of the liquid crystal molecules when viewed from an oblique direction is different between the tilt direction and the opposite direction, resulting in differences in luminance and color tone. Occurs. In order to solve this, the liquid crystal cell is preferably multi-domain. Multi-domain refers to a structure in which a plurality of regions having different alignment states are formed in one pixel. For example, in a multi-domain VA mode liquid crystal cell, a plurality of regions in which tilt angles of liquid crystal molecules are different from each other when an electric field is applied exist in one pixel. In a multi-domain VA mode liquid crystal cell, the tilt angle of liquid crystal molecules due to application of an electric field can be averaged for each pixel, whereby the viewing angle characteristics can be averaged. In order to divide the orientation within one pixel, the electrode is provided with slits or protrusions, and the electric field direction is changed or the electric field density is biased. In order to obtain a uniform viewing angle in all directions, the number of divisions may be increased, but a substantially uniform viewing angle can be obtained by dividing into four or eight or more. In particular, it is preferable that the polarizing plate absorption axis can be set at an arbitrary angle when dividing into eight.

  Also, the liquid crystal molecules are difficult to respond at the alignment division region boundary. For this reason, in normally black display, since black display is maintained, a reduction in luminance becomes a problem. Adding a chiral agent to the liquid crystal material contributes to reducing the boundary region.

Hereinafter, the first and second optically anisotropic layers used in the liquid crystal display device of the present invention will be described in detail.
In the present invention, the first and second optically anisotropic layers eliminate image coloring of the liquid crystal display device and contribute to the expansion of the viewing angle. In addition, when the support of the optically anisotropic layer also serves as a protective film for the polarizing plate, or the optically anisotropic layer also serves as the protective film for the polarizing plate, the number of constituent members of the liquid crystal display device can be reduced. Therefore, in this aspect, it contributes also to thickness reduction of a liquid crystal display device.

  In the present invention, the first optically anisotropic layer is made of a thermoplastic polymer film, and the second optically anisotropic layer is made of a discotic liquid crystalline compound. A conventional stretched birefringent polymer film cannot be obtained by combining a first optically anisotropic layer made of a thermoplastic polymer film and a second optically anisotropic layer made of a discotic liquid crystalline compound. Optical properties can be realized, and by incorporating this into a liquid crystal display device, the optical characteristics of the liquid crystal display device are significantly improved.

In the present invention, the in-plane retardation (Re) of the first optical anisotropic layer is 40 to 150 nm, the Re of the second optical anisotropic layer is 10 nm or less, and the Rth is 60 to 250 nm. Since the first and second optically anisotropic layers have an optical compensation function as a whole when combined, it is more preferable to adjust the combined overall retardation. As a whole, the first and second optically anisotropic layers are preferably combined so that Re is 30 to 200 nm and Rth is 60 to 500 nm. Here, Re and Rth are respectively defined by the following equations.
Re = (nx−ny) × d (1)
Rth = {(nx + ny) / 2−nz} × d (2)
In the formula, nx represents the refractive index in the slow axis direction in the plane of the layer, ny represents the refractive index in the plane perpendicular to nx, nz represents the refractive index in the thickness direction of the layer, and d represents the thickness of the layer.

[First optically anisotropic layer]
The Re of the first optically anisotropic layer used in the present invention is 40 to 150 nm, preferably 50 to 120 nm.
The stretched thermoplastic polymer film having positive refractive index anisotropy used for the first optically anisotropic layer of the present invention will be described. Examples of the thermoplastic polymer include one kind selected from a polymer group such as polyarylate, polyester, polycarbonate, polyolefin, polyether, polysulfine, polysulfone, and polyethersulfone, or 2 More than types. Among these, a polycarbonate copolymer, a polyester copolymer, a polyester carbonate copolymer, and a polyarylate copolymer are preferable, and a polycarbonate copolymer is more preferable. The polycarbonate copolymer is preferably a polycarbonate copolymer having a fluorene skeleton, and is obtained by reacting bisphenols with a carbonate ester-forming compound such as phosgene or diphenyl carbonate from the viewpoint of transparency, heat resistance, and productivity. Polycarbonate copolymers are particularly preferred. The component having a fluorene skeleton is preferably contained in an amount of 1 to 99 mol%.
The polycarbonate copolymer used in the present invention preferably has a repeating unit represented by general formula (I) and general formula (II) described in International Patent No. 00/26705.

  The thermoplastic polymer film is a film in which a thermoplastic polymer is oriented by stretching. As a method for producing such a film, a known melt extrusion method, solution casting method, or the like is used. From the viewpoint of appearance, thickness unevenness, etc., the solution casting method is more preferably used. As the solvent in the solution casting method, methylene chloride, dioxolane and the like are used. Moreover, although a well-known method can be used also for the extending | stretching method, longitudinal uniaxial stretching is preferable.

In the present invention, the first optically anisotropic layer is preferably made of a cellulose acylate film. Next, cellulose acylate used for the first optically anisotropic layer will be described. The cellulose acylate used in the first optically anisotropic layer of the present invention is a cellulose acylate in which the degree of substitution of cellulose with a hydroxyl group satisfies the following formula (C).
Formula (C) 2.0 ≦ A + B ≦ 3.0
Here, A and B represent the substitution degree of the acyl group in which the hydroxyl group of cellulose is substituted, A is the substitution degree of the acetyl group, and B is the substitution degree of the acyl group having 3 to 22 carbon atoms.

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with acyl groups. The degree of acyl substitution means the proportion of cellulose esterified at each of the 2-position, 3-position and 6-position (100% esterification has a degree of substitution of 1). In the present invention, the sum of the substitution degree A of the hydroxyl group with the acetyl group and the substitution degree B with the acyl group having 3 to 22 carbon atoms is preferably 2.2 to 2.86, particularly preferably 2.40 to 2 .80. The degree of substitution B is preferably 1.50 or more, particularly 1.7 or more. Further, the substitution degree B is preferably 28% or more of the substitution degree of the 6-position hydroxyl group, more preferably 30% or more, still more preferably 31%, and particularly preferably 32% or more. In addition, the total of substitution degrees A and B relating to the 6-position hydroxyl group of cellulose acylate is preferably 0.75 or more, more preferably 0.80 or more, and particularly preferably 0.85 or more. These cellulose acylates can produce a solution having a preferable solubility, and in particular, a non-chlorine organic solvent can be used to produce a good solution. Furthermore, a solution having a low viscosity and good filterability can be prepared. In addition, the measuring method of substitution degree A and B can be implemented according to ASTM D-817-91.

  The cellulose acylate used in the present invention is preferably substituted with an acyl group having 3 to 22 carbon atoms, more preferably substituted with an acyl group having 3 to 15 carbon atoms, and 3 to 9 carbon atoms. More preferably, it is substituted with an acyl group. The acyl group having 3 to 22 carbon atoms may be an aliphatic group or an allyl group, and is not particularly limited. Specifically, for example, it is an alkyl carbonyl ester, alkenyl carbonyl ester, aromatic carbonyl ester, aromatic alkyl carbonyl ester or the like of cellulose, and each may further have a substituted group. These preferred acyl groups include propionyl, butanoyl, keptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, iso-butanoyl, t-butanoyl, cyclohexanecarbonyl, oleoyl, Examples include benzoyl, naphthylcarbonyl, cinnamoyl groups and the like. Among these, propionyl, butanoyl, dodecanoyl, octadecanoyl, t-butanoyl, oleoyl, benzoyl, naphthylcarbonyl, cinnamoyl and the like. Particularly preferred are propionyl and butanoyl.

  A method for synthesizing cellulose acylate used in the first optically anisotropic layer of the present invention will be described. The basic principle of the cellulose acylate synthesis method is described in Mita et al., Wood Chemistry pages 180-190 (Kyoritsu Shuppan, 1968). A typical synthesis method is a liquid phase acetylation method using a carboxylic acid anhydride-acetic acid-sulfuric acid catalyst. Specifically, cellulose raw materials such as cotton linter and wood pulp are pretreated with an appropriate amount of acetic acid, and then put into a pre-cooled carboxylic acid mixture to be esterified to complete cellulose acylate (2nd, 3rd and 6th). The total degree of acyl substitution at the position is approximately 3.00). The carboxylated mixed solution generally contains acetic acid as a solvent, carboxylic anhydride as an esterifying agent, and sulfuric acid as a catalyst. The carboxylic anhydride is usually used in a stoichiometric excess over the sum of the cellulose that reacts with it and the water present in the system. After completion of the acylation reaction, a neutralizing agent (for example, calcium, magnesium, iron, aluminum or zinc) is used for hydrolysis of excess carboxylic anhydride remaining in the system and neutralization of a part of the esterification catalyst. Of carbonate, acetate or oxide). Next, the obtained complete cellulose acylate is saponified and aged by maintaining it at 50 to 90 ° C. in the presence of a small amount of an acetylation reaction catalyst (generally, remaining sulfuric acid) to obtain the desired degree of acyl substitution and polymerization. The cellulose acylate having a degree is changed. When the desired cellulose acylate is obtained, the catalyst remaining in the system is completely neutralized with a neutralizing agent as described above, or in water or dilute sulfuric acid without neutralization. The cellulose acylate solution is added (or water or dilute sulfuric acid is added into the cellulose acylate solution) to separate the cellulose acylate, and the cellulose acylate is obtained by washing and stabilizing treatment.

In the cellulose acylate film that can be used in the present invention, the polymer component constituting the film is preferably substantially composed of the preferred cellulose acylate described above. “Substantially” means 55% by mass or more (preferably 70% by mass or more, more preferably 80% by mass or more) of the polymer component.
Cellulose acylate particles are preferably used as a raw material for film production. 90% by mass or more of the particles to be used preferably have a particle diameter of 0.5 to 5 mm. Moreover, it is preferable that 50 mass% or more of the particle | grains to be used have a particle diameter of 1-4 mm. The cellulose acylate particles preferably have a shape as close to a sphere as possible.
The degree of polymerization of the cellulose acylate preferably used in the present invention is preferably a viscosity average polymerization degree of 200 to 700, more preferably 250 to 550, still more preferably 250 to 400, and particularly preferably a viscosity average polymerization degree of 250 to 400. 350. The average degree of polymerization can be measured by Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Society, Vol. 18, No. 1, pages 105-120, 1962). Further details are described in JP-A-9-95538.

When the low molecular component is removed, the average molecular weight (degree of polymerization) increases, but the viscosity becomes lower than that of normal cellulose acylate, which is useful. Cellulose acylate having a small amount of low molecular components can be obtained by removing low molecular components from cellulose acylate synthesized by a usual method. The removal of the low molecular component can be carried out by washing the cellulose acylate with an appropriate organic solvent. In addition, when manufacturing a cellulose acylate with few low molecular components, it is preferable to adjust the sulfuric acid catalyst amount in an acetylation reaction to 0.5-25 mass parts with respect to 100 weight of celluloses. When the amount of the sulfuric acid catalyst is within the above range, cellulose acylate that is preferable in terms of molecular weight distribution (uniform molecular weight distribution) can be synthesized.
When used in the production of a cellulose acylate film that can be used in the present invention, the moisture content of the cellulose acylate is preferably 2% by mass or less, more preferably 1% by mass or less, and particularly 0 Cellulose acylate having a water content of 0.7% by mass or less is preferred. In general, cellulose acylate contains water and is known to be 2.5 to 5% by mass. In order to obtain the moisture content of the cellulose acylate in the present invention, it is necessary to dry, and the method is not particularly limited as long as the desired moisture content is obtained.
These cellulose acylates that can be used in the present invention, the raw material cotton and the synthesis method thereof are disclosed in the technical report of the Invention Association (Technical No. 2001-1745, published on March 15, 2001, Invention Association), pages 7-12. It is described in detail on the page.

  The thickness of the first optically anisotropic layer is not particularly limited as long as Re is 40 to 150 nm, but is preferably 20 to 200 μm, and preferably 40 μm to 150 μm from the viewpoint of thinning and ease of handling during manufacturing. Is more preferable.

[Second optically anisotropic layer]
In the present invention, the second optically anisotropic layer has negative refractive index anisotropy, Re is 10 nm or less, and Rth is 60 to 250 nm with respect to visible light. As the second optically anisotropic layer of the present invention, it is preferable to use a discotic liquid crystalline compound.
The discotic liquid crystalline compound is preferably aligned substantially horizontally (average inclination angle in the range of 0 to 10 degrees) with respect to the polymer film surface. The discotic liquid crystalline compounds are disclosed in various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); edited by the Chemical Society of Japan, Quarterly Chemical Review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., Page 1794 (1985); J. Zhang et al., J Am.Chem.Soc., Vol.116, page 2655 (1994)). The polymerization of the discotic liquid crystalline compound is described in JP-A-8-27284.

The discotic liquid crystalline compound preferably has a polymerizable group so that it can be fixed by polymerization. For example, a structure in which a polymerizable group is bonded as a substituent to a disk-shaped core of a disk-shaped liquid crystalline compound can be considered. However, when a polymerizable group is directly bonded to the disk-shaped core, the alignment state is maintained in the polymerization reaction. It becomes difficult. Therefore, a structure having a linking group between the discotic core and the polymerizable group is preferable. That is, the discotic liquid crystalline compound having a polymerizable group is preferably a compound represented by the following general formula (III).
General formula (III)
D (-LP) _n
In the formula, D is a discotic core, L is a divalent linking group, P is a polymerizable group, and n is an integer of 4 to 12.

  Preferred specific examples of the discotic core (D), the divalent linking group (L), and the polymerizable group (P) in the formula (III) are (D1) described in JP-A No. 2001-4837, respectively. To (D15), (L1) to (L25), and (P1) to (P18), and the contents described in the publication can be preferably used.

  Also in the case of a discotic liquid crystalline compound having a polymerizable group, it is preferable to substantially align horizontally. Substantially horizontal means that the average angle (average inclination angle) between the disk surface of the discotic liquid crystalline compound and the surface of the optically anisotropic layer is in the range of 0 ° to 10 °. The discotic liquid crystalline compound may be oriented obliquely. Even in the case of oblique alignment, the average inclination angle is preferably 0 ° to 20 °.

[Fixation of alignment state of liquid crystalline compounds]
The aligned discotic liquid crystalline compound is preferably fixed while maintaining the alignment state. The immobilization is preferably carried out by a polymerization reaction of a polymerizable group introduced into the liquid crystal compound. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator, and a photopolymerization reaction is more preferable. Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin. Compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 3,549,367) Acridine and phenazine compounds (JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970).

The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the solid content of the coating solution. Light irradiation for the polymerization of the liquid crystalline compound is preferably performed using ultraviolet rays. The irradiation energy is preferably ^{20mJ / cm 2 ~50J / cm 2} , further preferably 100 to 800 mJ / cm ^2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. The thickness of the optically anisotropic layer is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm.

  The second optically anisotropic layer is preferably formed by applying a coating liquid containing a liquid crystalline compound and the above polymerization initiator and other additives onto the alignment film. As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination. The coating liquid can be applied by a known method (eg, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).

[Alignment film]
In forming the second optical anisotropic layer, it is preferable to use an alignment film in order to align the liquid crystalline compound. The alignment film may be an organic compound (preferably polymer) rubbing treatment, oblique deposition of an inorganic compound, formation of a layer having a microgroup, or an organic compound (eg, ω-triconic acid) by the Langmuir-Blodgett method (LB film) , Dioctadecyldimethylammonium chloride, methyl stearylate, etc.). Furthermore, an alignment film in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known. An alignment film formed by a polymer rubbing treatment is particularly preferred. The rubbing process is carried out by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth.

The type of polymer used for the alignment film can be determined according to the alignment (particularly the average tilt angle) of the liquid crystal compound. For example, in order to align the liquid crystalline compound horizontally, a polymer (ordinary alignment polymer) that does not decrease the surface energy of the alignment film is used. Specific types of polymers are described in various documents about liquid crystal cells or optical compensation sheets. In particular, in the present invention, when the liquid crystalline compound is aligned in a direction orthogonal to the rubbing treatment direction, the modified polyvinyl alcohol described in JP-A No. 2002-62427 and JP-A No. 2002-98836 are described. Acrylic acid-based copolymers, polyimides described in JP-A No. 2002-268068, and polyamic acid can be preferably used. Any of the alignment films preferably has a polymerizable group for the purpose of improving the adhesion between the liquid crystal compound and the transparent support. The polymerizable group can be introduced by introducing a repeating unit having a polymerizable group in the side chain or as a substituent of a cyclic group. It is more preferable to use an alignment film that forms a chemical bond with the liquid crystal compound at the interface. Such an alignment film is described in JP-A-9-152509.
The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm.
In addition, after aligning the liquid crystalline compound using the alignment film, the liquid crystalline compound is fixed in the aligned state to form an optically anisotropic layer, and only the optically anisotropic layer is polymer film (or transparent support) It may be transferred onto the body).

Next, the polarizing film used in the liquid crystal display device of the present invention will be described in detail.
[Polarizing film]
The polarizing film that can be used in the present invention is not particularly limited, and conventionally known polarizing films can be used. For example, films made of hydrophilic polymers such as polyvinyl alcohol, partially formalized polyvinyl alcohol, partially saponified ethylene / vinyl acetate copolymer, dichroic dyes such as iodine and / or azo, anthraquinone and tetrazine A material obtained by adsorbing a dichroic material composed of the above material and subjecting it to stretching and orientation can be used. In the present invention, it is preferable to use the stretching method described in JP-A No. 2002-131548, and in particular, a width direction uniaxial stretching type tenter stretching machine in which the absorption axis of the polarizing film is substantially perpendicular to the longitudinal direction. It is preferable to use it. By using a uniaxial stretching type tenter stretching machine in the width direction, the longitudinal direction (slow axis direction) of the thermoplastic polymer stretched film used for the first optical anisotropic layer is defined as the longitudinal direction (absorption axis) of the polarizing film. Since it is not necessary to bond at right angles and the longitudinal directions can be bonded to each other, it is preferable in terms of cost and difficulty in entering foreign matter at the time of bonding.

The polarizing film is usually used as a polarizing plate having at least one surface protected by a transparent protective film (also referred to as a protective film). The kind of transparent protective film is not particularly limited, and cellulose esters such as cellulose acetate, cellulose acetate butyrate, and cellulose propionate, polycarbonate, polyolefin, polystyrene, polyester, and the like can be used.
The transparent protective film is usually supplied in a roll form, and it is preferable that the transparent protective film is continuously bonded to the long polarizing film so that the longitudinal directions thereof coincide with each other. Here, the orientation axis (slow axis) of the transparent protective film may be any direction, but the orientation axis of the transparent protective film is preferably parallel to the longitudinal direction for ease of operation. Further, the angle between the slow axis (orientation axis) of the transparent protective film and the absorption axis (stretching axis) of the polarizing film is not particularly limited, and can be appropriately set according to the purpose of the polarizing plate.
In addition, when producing a polarizing film using the width direction uniaxial stretching type tenter stretching machine preferably used in the present invention, the slow axis (alignment axis) of the transparent protective film and the absorption axis (stretching) of the polarizing film are used. Axis) will be substantially orthogonal.

  The retardation of the transparent protective film is, for example, preferably 10 nm or less at 632.8 nm, and more preferably 5 nm or less. From the viewpoint of such low retardation, polyolefins such as cellulose triacetate, ZEONEX, ZEONOR (both manufactured by Nippon Zeon Co., Ltd.) and ARTON (manufactured by JSR Co., Ltd.) are preferably used as the transparent protective film. It is done. Other examples include non-birefringent optical resin materials as described in JP-A-8-110402 or JP-A-11-293116. When cellulose acetate is used for the transparent protective film, the retardation is preferably less than 3 nm, and more preferably 2 nm or less, for the purpose of reducing the change in retardation due to environmental temperature and humidity.

  In the present invention, for the purpose of reducing the thickness or the like, one of the protective films of the polarizing film may also serve as the support for the second optically anisotropic layer, or the first optically anisotropic layer itself. It may be. The optically anisotropic layer and the polarizing film are preferably subjected to a fixing treatment from the viewpoint of preventing displacement of the optical axis and preventing entry of foreign matters such as dust. An appropriate method such as an adhesive method through a transparent adhesive layer can be applied to the fixed lamination. There is no particular limitation on the type of the adhesive and the like, and from the viewpoint of preventing changes in the optical properties of the constituent members, those that do not require a high-temperature process during curing or drying are preferable, and a long-time curing process is preferable. And those that do not require drying time. From such a viewpoint, a hydrophilic polymer adhesive or a pressure-sensitive adhesive layer is preferably used.

  For the formation of the pressure-sensitive adhesive layer, for example, a transparent pressure-sensitive adhesive using an appropriate polymer such as an acrylic polymer, a silicone-based polymer, polyester, polyurethane, polyether, or synthetic rubber can be used. Among these, acrylic pressure-sensitive adhesives are preferred from the viewpoints of optical transparency, adhesive properties, weather resistance, and the like. In addition, an adhesion layer can also be provided as needed on one side or both sides of a polarizing plate for the purpose of adhesion to an adherend such as a liquid crystal cell. In that case, when the pressure-sensitive adhesive layer is exposed on the surface, it is preferable to temporarily attach a separator or the like to prevent contamination of the pressure-sensitive adhesive layer surface until it is put to practical use.

Appropriate functions such as a protective film for various purposes such as water resistance in accordance with the above-mentioned transparent protective film, an antireflection layer and / or an antiglare treatment layer for the purpose of preventing surface reflection, etc. on one or both sides of the polarizing film You may use the polarizing plate in which the layer was formed. The antireflection layer can be suitably formed, for example, as a light interference film such as a fluorine polymer coating layer or a multilayer metal vapor deposition film. The antiglare layer is also formed by an appropriate method that diffuses the surface reflected light, for example, by providing a fine uneven structure on the surface by an appropriate method such as a resin coating layer containing fine particles, embossing, sandblasting or etching. can do.
Examples of the fine particles include inorganic materials having an average particle diameter of 0.5 to 20 μm, such as silica, calcium oxide, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, and antimony oxide. One type or two or more types of fine particles, or crosslinked or uncrosslinked organic fine particles made of a suitable polymer such as polymethyl methacrylate or polyurethane can be used. The above-mentioned adhesive layer or pressure-sensitive adhesive layer may contain such fine particles and exhibit light diffusibility.

[Optical performance of polarizing plate]
The optical properties and durability (short-term and long-term storage stability) of a polarizing plate comprising a transparent protective film, a polarizing film and a transparent support related to the present invention are commercially available super high contrast products (for example, Sanritz Corporation). Manufactured by HLC2-5618 and the like) and preferably have equivalent or better performance. Specifically, the visible light transmittance is 42.5% or more, and the degree of polarization ({(Tp−Tc) / (Tp + Tc)} ^1/2 ≧ 0.9995 (where Tp is parallel transmittance and Tc is orthogonal) The change rate of the light transmittance before and after leaving for 500 hours in a 60 ° C., 90% humidity RH atmosphere and 500 ° C. in a dry atmosphere for 500 hours is 3% based on the absolute value. In the following, it is further preferable that the change rate of the polarization degree is 1% or less, further 0.1% or less based on the absolute value.

  The present invention will be described more specifically with reference to the following examples. The materials, reagents, amounts and ratios of substances, operations, and the like shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention is not limited to the following specific examples.

[Example 1]
A liquid crystal display device having the configuration shown in FIG. 1 was produced. However, the second optically anisotropic layer is only one layer (in FIG. 1, the second optically anisotropic layer 12 is not provided). That is, the upper polarizing plate 1, the liquid crystal cell (upper substrate 5, liquid crystal layer 7, lower substrate 8), and lower polarizing plate 14 were laminated from the observation direction (upper layer), and a backlight light source (not shown) was further arranged. A first optical anisotropic layer 3 and a second optical anisotropic layer 10 for improving the optical performance of the liquid crystal display device were disposed between the upper and lower polarizing plates and the liquid crystal cell. As the upper polarizing plate 1 and the lower polarizing plate 14 used, from the configuration shown in FIG. 2, the protective film 101, the polarizing film 103, and the protective film 105 (assuming that the protective film 105 is disposed closer to the liquid crystal cell). What was used. However, the upper polarizing plate 1 was assembled in the liquid crystal display device after the first optically anisotropic layer 3 was attached to the protective film 105 to produce an integrated upper polarizing plate. For the lower polarizing plate 14, the protective film 105 is also used as a transparent support for the second optical anisotropic layer 10 to produce an integrated lower polarizing plate in which the optical anisotropic layer 10 is integrated. After that, it was incorporated into a liquid crystal display device.

Below, the manufacturing method of each used member is demonstrated.
<Production of liquid crystal cell>
The liquid crystal cell was produced by the following procedure. After applying an alignment film (for example, JALS204R manufactured by JSR Corporation) to the substrate surface, the tilt angle with respect to the so-called substrate surface, which is a director indicating the alignment direction of liquid crystalline molecules, was set to about 89 ° by rubbing treatment. The cell gap between the upper and lower substrates is 3.5 μm, and a liquid crystal having a negative dielectric anisotropy and Δn = 0.0813 and Δε = −4.6 (for example, MLC-6608 manufactured by Merck) is dropped. And sealed.

<Production of integrated upper polarizing plate>
(Preparation of upper polarizing plate)
A polarizing film was prepared by adsorbing iodine to a stretched polyvinyl alcohol film.
A commercially available cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) subjected to saponification treatment is used as a protective film for the polarizing film, and is attached to both surfaces using a polyvinyl alcohol adhesive to produce an upper polarizing plate. did. The protective film had an Re value of 3 nm and an Rth value of 50 nm.
When the stacking angle of each film is based on the left and right directions when the display device is viewed from above (0 °), the angle of the upper polarizing plate protective film slow axes 102 and 106 in FIG. The angle of the absorption shaft 104 (2 in FIG. 1) was 90 °.

(Preparation of the first optical anisotropic layer)
A stretched polycarbonate copolymer film was prepared according to Example 3 of WO00 / 26705. This stretched film had a Re of 55.3 nm at a wavelength of 450 nm, a Re of 60.0 nm at a wavelength of 550 nm, and a Re of 60.6 nm at a wavelength of 650 nm. That is, the stretched film was a film that exhibited a positive refractive index anisotropy and functioned as a first optical anisotropic layer having an Re of 56 ± 5 nm in visible light. The retardation was measured using KOBRA 21DH manufactured by Oji Scientific Co., Ltd. The same applies hereinafter.
This stretched film was bonded to the transparent protective film (105 in FIG. 2) on the side close to the liquid crystal cell of the produced upper polarizing plate with an adhesive to produce an integrated upper polarizing plate. The angle formed by the slow axis 4 of the stretched polycarbonate copolymer film and the lower polarizing plate absorption axis 15 was approximately parallel.

<Integrated lower polarizing plate>
(Production of lower polarizing plate)
As the polarizing film of the lower polarizing plate, the same polarizing film as the upper polarizing plate prepared above was prepared. Fujitac TD80UF was attached as a protective film on one surface of the polarizing film (a protective film far from the liquid crystal cell, 101 in FIG. 2).

(Production of second optically anisotropic layer with transparent support)
<Formation of alignment film>
Next, the surface of Fujitac TD80UF (Re = 3 nm, Rth = 50 nm) was saponified. The saponification treatment was performed by immersing the film in a 2.0N potassium hydroxide solution (25 ° C.) for 2 minutes, neutralizing with sulfuric acid, washing with pure water, and then drying. The surface energy of the saponified surface was determined by a contact method and found to be 63 mN / m. On one surface of the saponified film, a coating solution having the following composition was applied at 28 ml / m ² with a # 16 wire bar coater.
Alignment film coating solution composition Modified polyvinyl alcohol 20 parts by weight Water 361 parts by weight Methanol 119 parts by weight Glutaraldehyde (crosslinking agent) 0.5 parts by weight

  Drying was performed at 25 ° C. for 60 seconds, 60 ° C. warm air for 60 seconds, and 90 ° C. warm air for 150 seconds. The alignment film thickness after drying was 1.1 μm. Further, the surface roughness of the alignment film was measured with an atomic force microscope (AFM: Atomic Force Microscope, SPI3800N, manufactured by Seiko Instruments Inc.), and found to be 1.147 nm. The alignment film was rubbed in the same direction as the slow axis of Fujitac TD-80UF.

<< Formation of Second Optically Anisotropic Layer >>
A coating liquid containing a discotic liquid crystal having the following composition was applied on the alignment film subjected to the rubbing treatment.
Composition of coating liquid for discotic liquid crystal layer Discotic liquid crystalline compound (1) * 1 32.6% by mass
Cellulose acetate butyrate 0.7% by mass
Ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 3.2% by mass
Sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 0.4% by mass
Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) 1.1% by mass
Methyl ethyl ketone 62.0% by mass
* 1: As the discotic liquid crystalline compound (1), 1,2,1 ′, 2 ′, 1 ″, 2 ″ -tris [4,5-di (vinylcarbonyloxybutoxybenzoyloxy) phenylene Exemplified compound TE-8 (8), m = 4) described in JP-A-8-50206, paragraph 0044 was used.

Then, it dried by heating for 2 minutes in a 130 degreeC drying zone, and the disk shaped compound was orientated. Next, using a 120 W / cm high pressure mercury lamp at 130 ° C., UV irradiation was performed for 4 seconds to polymerize the discotic compound. Thereafter, it is allowed to cool to room temperature, has a thickness of 2.2 μm, exhibits optically negative refractive index anisotropy, and has negative optical anisotropy of Re = 0 nm and Rth = 216 nm with respect to visible light. A second optically anisotropic layer was formed. The discotic liquid crystalline compound of the second optically anisotropic layer was horizontally aligned within a range of ± 2 °.
Thus, the 2nd optically anisotropic layer with a transparent support body was produced.

The prepared second optically anisotropic layer with a transparent support is the lower polarizing plate produced above with the surface of the transparent support (Fujitac TD80UF) on which the second optically anisotropic layer is not formed. The protective film (Fujitac TD80UF) was attached to the surface of the polarizing film on the side where the protective film (Fujitac TD80UF) was not attached using a polyvinyl alcohol-based adhesive to produce an integrated lower polarizing plate.
In this integrated lower polarizing plate, the lamination angle of each film is based on the horizontal direction when the display device is viewed from above (0 °) as a reference (0 °). Among these, the axis angle of 15) was set to 0 °, and the angles of the protective film slow axes 102 and 106 were set to 0 °.

<Measurement of leakage light of the manufactured liquid crystal display device>
The viewing angle dependence of the transmittance of the liquid crystal display device thus manufactured was measured. The depression angle was measured from the front to the diagonal direction up to 80 ° every 10 °, and the azimuth angle was measured up to 360 ° every 10 ° on the basis of the horizontal right direction (0 °). It has been found that the luminance at the time of black display increases as the suppression angle increases from the front direction, so that the leakage light transmittance increases and takes a maximum value near the suppression angle of 60 °. It was also found that the contrast, which is the ratio between the white display transmittance and the black display transmittance, deteriorates as the black display transmittance increases. Therefore, it was decided to evaluate the viewing angle characteristics with the maximum values of the black display transmittance on the front side and the leaked light transmittance with a suppression angle of 60 °.
In this example, the front transmittance was 0.02%, and the maximum value of the leaked light transmittance at a suppression angle of 60 ° was 0.04% at an azimuth angle of 30 °. That is, the front contrast ratio was 500 to 1, and the contrast ratio at a suppression angle of 60 ° was 250 to 1.

[Example 2]
In Example 1, the upper polarizing plate and the lower polarizing plate are reversed with respect to the liquid crystal cell, that is, the first optical anisotropic layer and the second optical anisotropic layer are reversed with respect to the liquid crystal cell. Even in this case, the measured value of leakage light of the manufactured liquid crystal display device was the same result as in Example 1.

[Example 3]
The same liquid crystal cell and polarizing film as in Example 1 were used.
<Production of integrated upper polarizing plate>
(Preparation of upper polarizing plate)
A cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was used as the protective film on the side farther from the liquid crystal cell of the polarizing film as in Example 1.
(Formation of first optically anisotropic layer)
The first optically anisotropic layer produced in Example 1 was used as a protective film on the side close to the liquid crystal cell. That is, the first optical anisotropic layer was also used as a protective film on the liquid crystal cell side of the upper polarizing plate. The Re value at 550 nm of the first optical anisotropic layer was 63 nm, and the Re value at visible light was 59 ± 5 nm.

(Formation of second optically anisotropic layer)
After the corona discharge treatment was performed on the formed first optically anisotropic layer, a second optically anisotropic layer composed of an alignment film and a discotic liquid crystalline compound was formed in the same manner as in Example 1.
This was incorporated in the liquid crystal display device as an integral-side upper polarizing plate. The second optically anisotropic layer was disposed in contact with the liquid crystal cell. The slow axis (rubbing direction) of the second optical anisotropic layer is the same as the slow axis direction of the first optical anisotropic layer, and the slow axis of the first optical anisotropic layer is It was made to be orthogonal to the upper polarizing plate absorption axis 2.

<Preparation of integrated lower polarizing plate>
An integrated lower polarizing plate was produced in the same manner as the lower polarizing plate of Example 1 except that the alignment film and the second optically anisotropic layer were removed from the lower polarizing plate used in Example 1. This was incorporated in the liquid crystal display device as an integrated lower polarizing plate.

  Instead of the upper polarizing plate and the lower polarizing plate used in Example 1, the integrated polarizing plate prepared above was incorporated into the liquid crystal display device as the upper polarizing plate and the lower polarizing plate, as in Example 1. Thus, a liquid crystal display device was produced. The measured value of leakage light of the manufactured liquid crystal display device was the same as that of Example 1.

[Example 4]
In Example 1, the support for the second optically anisotropic layer was also used as the protective film for the lower polarizing plate, but it was not used for the same purpose. That is, a polarizing plate with Fujitac TD80UF attached as a protective film on the side close to the liquid crystal cell of the lower polarizing film was incorporated into the liquid crystal display device as the lower polarizing film. Further, in the same manner as in Example 1, a second optically anisotropic layer with a support was produced and incorporated between the liquid crystal cell and the lower polarizing film. When the slow axis of the protective film near the liquid crystal cell and the support of the second optical anisotropic layer are in the same direction, the second optical anisotropic layer has a thickness of 1.4 μm, The Re value and Rth value in visible light were required to be Re = 0 nm and Rth = 140 nm. The measured value of leakage light of the liquid crystal display device manufactured at this time was the same result as in Example 1.

[Comparative Example 1]
As the transparent protective film on the side close to the liquid crystal cell (both for the upper polarizing plate and for the lower polarizing plate), a film having an Re value of 3 nm and an Rth value of 120 nm was used as in Example 1. The first optically anisotropic layer was not formed on the transparent protective film. Other configurations were the same as those in Example 1.
<Measurement of leakage light of the manufactured liquid crystal display device>
The viewing angle characteristics of leaked light at the time of black display of the liquid crystal display device thus manufactured were measured by the same method as in Example 1. The front transmittance in this comparative example was 0.02%, and the maximum value of the leaked light transmittance at a suppression angle of 60 ° was 0.35% at an azimuth angle of 45 °.
Compared with Examples 1 to 4 of the present invention, the leakage light is large, and it is clear that the present invention is superior.

[Comparative Example 2]
The Re value of the transparent protective film on the side close to the liquid crystal cell of the upper polarizing plate is 36 nm, the Rth value is 173 nm, the angle of the slow axis of the protective film outside the upper polarizing plate (the side far from the liquid crystal cell) is 0 °, The angle of the film absorption axis 2 was 0 °, and the angle of the liquid crystal cell side protective film slow axis was 90 °.
Similarly, the Re value of the transparent protective film near the liquid crystal cell of the lower polarizing plate 14 is 9 nm, the Rth value is 68 nm, the angle of the protective film slow axis outside the lower polarizing plate is 90 °, and the polarizing film absorption The angle of the axis 15 was set to 90 °, and the angle of the liquid crystal cell side protective film slow axis was set to 0 °.
Further, no optically anisotropic layer other than the protective film was disposed between the upper and lower polarizing plates and the liquid crystal cell. Other configurations were the same as in Example 1, and a liquid crystal display device was produced.
<Measurement of leakage light of the manufactured liquid crystal display device>
The viewing angle characteristics of leaked light at the time of black display of the liquid crystal display device thus manufactured were measured by the same method as in Example 1. The front transmittance in this comparative example was 0.02%, and the maximum value of the leaked light transmittance at a suppression angle of 60 ° was 0.17% at an azimuth angle of 30 °.
Compared with Examples 1 to 4 of the present invention, the leakage light is large, and the effect of the present invention is clear.

[Comparative Example 3]
All of the upper and lower polarizing plate protective films were made of commercially available cellulose acetate films (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd., Re value was 3 nm, Rth value was 50 nm). Further, one retardation film C (3) made of a stretched film between the upper polarizing plate and the liquid crystal cell, and a retardation film D (10, 12) made of the stretched film between the lower polarizing plate and the liquid crystal cell. ) Was placed. The direction of the slow axis and polarizing plate absorption axis of the polarizing plate protective film was the same as in Example 2.
The retardation film C is made of a norbornene-based stretched film, and the average refractive index in the stretching direction of the film surface is Nx (= 1.51), and the average refractive index in the direction perpendicular to the stretching direction of the film surface is Ny (= 1.1. 509), the average refractive index in the thickness direction of the film surface was Nz (= 1.509), and the thickness of the film was 95 μm. The Re value of the film was 95 nm, and the angle of the slow axis 4 was 0 °. On the other hand, both of the retardation films D (10, 12) are made of a norbornene-based stretched film, the average refractive index in the stretching direction of the film surface is Nx (= 1.51), and the direction perpendicular to the stretching direction of the film surface The average refractive index of the film was Ny (= 1.51), the average refractive index in the thickness direction of the film surface was Nz (= 1.5084), and the film thickness was 70 μm. The Re value of the film is 5 nm, the Rth value is 110 nm, the slow axes of the two films are substantially orthogonal, the angle of the slow axis 13 of the film in contact with the lower polarizing plate is 90 °, and the film in contact with the liquid crystal cell The angle of the slow axis 10 was set at 0 °.

<Measurement of leakage light of the manufactured liquid crystal display device>
The viewing angle characteristics of leaked light at the time of black display of the liquid crystal display device thus manufactured were measured by the same method as in Example 1. The front transmittance in this comparative example was 0.02%, and the maximum value of the leaked light transmittance at a suppression angle of 60 ° was 0.17% at an azimuth angle of 30 °.
Compared with Examples 1 to 4 of the present invention, the leakage light is large and three retardation films are required, so the effect of the present invention is clear.

[Comparative Example 4]
In Comparative Example 3, an optically anisotropic layer E made of a coating type cholesteric liquid crystalline compound was used instead of the retardation film D (10, 12), and the other configurations were the same as those in Comparative Example 3. The optically anisotropic layer E is added with optical rotation by adding the following chiral agent D to the rod-like liquid crystalline compound A with reference to the method described in JP-A-2002-311243, and functions as a cholesteric layer. It was. When the thickness of the same layer was 4 μm, the Re value was 3 nm, the Rth value was 250 nm, and the pitch of the cholesteric liquid crystal was 130 nm. This optically anisotropic layer E was prepared, and the angle of the slow axis in contact with the lower polarizing plate was arranged at 0 °.

<Measurement of leakage light of the manufactured liquid crystal display device>
The viewing angle characteristics of leaked light at the time of black display of the liquid crystal display device thus manufactured were measured by the same method as in Example 1. In this example, the front transmittance was 0.05%, and the maximum value of the leaked light transmittance at a suppression angle of 60 ° was 0.17% at an azimuth angle of 30 °.
Compared with Examples 1 to 4 of the present invention, the leakage light is large, and an extra retardation film is required as compared with the present invention. Therefore, the effect of the present invention is clear.

[Example 5]
A liquid crystal display device having the configuration of FIG. 1 was produced in the same manner as in Example 1 except that the polarizing film and the integrated upper polarizing plate were as follows. At this time, the stretched film serving as the first optically anisotropic layer is made the same in the longitudinal direction with an adhesive on the transparent protective film (105 in FIG. 2) on the side near the liquid crystal cell of the produced upper polarizing plate. Pasted together. The slow axis 4 of the stretched polycarbonate copolymer film and the absorption axis 2 of the upper polarizing plate were approximately orthogonal.
The measured value of leakage light of the manufactured liquid crystal display device was the same as that of Example 1.

(Preparation of polarizing film)
A PVA film having an average degree of polymerization of 2400 and a film thickness of 100 μm is washed with ion exchange water at 15 to 17 ° C. for 60 seconds, and the surface moisture is scraped off with a stainless steel blade, and the concentration of the PVA film is kept constant. While being corrected for concentration, it was immersed in an aqueous solution of 0.77 g / l of iodine and 60.0 g / l of potassium iodide at 40 ° C. for 55 seconds, and further, boric acid 42. After immersing in an aqueous solution of 5 g / l and potassium iodide 30 g / l at 40 ° C. for 90 seconds, both surfaces of the film were scraped off with a stainless steel blade to reduce the moisture content distribution in the film to 2% or less. In this state, it was introduced into a tenter stretching machine having the configuration shown in FIG. 2 described in JP-A-2002-131548. The transfer speed was set at 4 m / min, and 100 m was sent out. The film was stretched up to 5 times in an atmosphere of 60 ° C. and 95%, and then the width was kept constant and dried in an atmosphere of 70 ° C. and then detached from the tenter. The moisture content of the PVA film before starting stretching was 32%, and the moisture content after drying was 1.5%. Wrinkles and film deformation at the tenter exit were not observed. The thickness of the film after stretching and drying was 18 μm.

  The above-mentioned stretched polarizing film was trimmed 3 cm from the width direction with a cutter, and then a commercially available cellulose triacetate film (Fujitac) with both sides of PVA (PVA-117H manufactured by Kuraray Co., Ltd.) as a 3% aqueous solution as an adhesive. TD80UF, manufactured by Fuji Photo Film Co., Ltd., Re value is 3 nm, Rth value is 50 nm) and bonded together, and further heated at 70 ° C. for 10 minutes to form a cellulose triacetate protective film on both sides with an effective width of 650 mm The provided polarizing plate was obtained.

  The absorption axis direction of the obtained polarizing film was inclined by 90 ° with respect to the longitudinal direction. In addition, no color omission stripes were observed with the naked eye.

[Example 6]
<Production of integrated upper polarizing plate>
(Preparation of the first optical anisotropic layer)
<< Production of Cellulose Acylate Propionate Film >>
Each component of the following cellulose acetate solution composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate propionate solution.

Cellulose acetate propionate solution composition Cellulose acetate propionate (CAP-482-20, manufactured by Eastman Chemical Co., Ltd.) 100 parts by mass Triphenyl phosphate (plasticizer) 3.9 parts by mass Biphenyl diphenyl phosphate (plasticizer) 1 .9 parts by mass Methylene chloride (first solvent) 317 parts by mass Methanol (second solvent) 28 parts by mass Silica (particle size 0.2 μm) 0.1 parts by mass

Into the mixing tank, 20 parts by mass of the following retardation control agent, 87 parts by mass of methylene chloride and 13 parts by mass of methanol were added and stirred while heating to prepare a retardation control agent solution 01.
45 parts by mass of the retardation controlling agent solution 01 was mixed with 451 parts by mass of the cellulose acetate propionate solution, and the dope was prepared by sufficiently stirring. The addition amount of the retardation adjusting agent was 7.5 parts by mass with respect to 100 parts by mass of cellulose acetate pionate. The cellulose acetate propionate used had a substitution degree A of acetyl group of 0.18 and a substitution degree B of propionyl group (carbon number 3) of 2.47, which satisfied the above formula (C). . These substitution degrees were calculated by the method described above.

  The obtained dope was cast using a band casting machine. A first optical film comprising a cellulose acetate propionate film (thickness: 92 μm) obtained by laterally stretching a film having a residual solvent amount of 25% by mass at a stretching ratio of 30% using a tenter at 130 ° C. An anisotropic layer was produced. The first optically anisotropic layer had a Re of 61 nm and a Rth of 156 nm at a wavelength of 550 nm. This retardation value was measured using KOBRA 21DH manufactured by Oji Scientific Co., Ltd.

(Formation of second optically anisotropic layer)
The surface of the first optically anisotropic layer (cellulose acetate propionate film) was subjected to the same saponification treatment as in Example 1 to form a similar alignment film. A second optically anisotropic layer having a thickness of 0.7 μm, Re = 0 nm at 550 nm, and Rth = 70 nm was formed on the alignment film using the same second optically anisotropic coating solution as in Example 1. The discotic liquid crystal compound of the second optically anisotropic layer was horizontally aligned within a range of ± 2 °.
Using this, an integrated upper polarizing plate was produced in the same manner as in Example 1, and placed in a liquid crystal display device as in Example 3.

<Preparation of integrated lower polarizing plate>
The same integrated lower polarizing plate as in Example 3 was produced and placed in the liquid crystal display device in the same manner as in Example 3.

<Measurement of leakage light of the manufactured liquid crystal display device>
A liquid crystal display device was produced in the same manner as in Example 3, and the leakage light of the produced liquid crystal display device was measured. The maximum value of leakage light transmittance at a front transmittance of 0.02% and an elevation angle of 60 ° was 0.05% at an azimuth angle of 30 °. That is, the front contrast ratio was 500 to 1, and the contrast ratio at an elevation angle of 60 ° was 200 to 1.
[Example 7]
<Production of integrated upper polarizing plate>
(Preparation of the first optical anisotropic layer)
<< Preparation of cellulose acetate butyrate film >>
Each component of the following cellulose acetate butyrate solution composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate butyrate solution.

Cellulose acetate butyrate solution composition Cellulose acetate butyrate (CAB-381-20, manufactured by Eastman Chemical Co., Ltd.) 100 parts by weight Triphenyl phosphate (plasticizer) 2.0 parts by weight Biphenyl diphenyl phosphate (plasticizer) 1.0 Parts by weight methylene chloride (first solvent) 309 parts by weight methanol (second solvent) 27 parts by weight silica (particle size 0.2 μm) 0.1 parts by weight

  44 parts by mass of the retardation control (raising) agent solution 01 was mixed with 439 parts by mass of the prepared cellulose acetate butyrate solution, and the dope was prepared by sufficiently stirring. The addition amount of the retardation adjusting agent was 7.5 parts by mass with respect to 100 parts by mass of cellulose acetate butyrate. The cellulose acetate butyrate used had an acetyl group substitution degree A of 1.00 and a butanoyl group (carbon number 4) substitution degree B of 1.66, satisfying the above formula (C). These substitution degrees were calculated by the method described above.

  Stretching was performed in the same manner as in Example 6 to produce a first optically anisotropic layer made of cellulose acetate butyrate film (thickness: 92 μm). The first optically anisotropic layer had a Re of 60 nm and a Rth of 153 nm at a wavelength of 550 nm. This retardation value was measured using KOBRA 21DH manufactured by Oji Scientific Co., Ltd.

  The second optically anisotropic layer, the upper polarizing plate, and the lower polarizing plate were produced in the same manner as in Example 6, and arranged in the liquid crystal display device in the same manner as in Example 6. The measured value of leakage light of the liquid crystal display device manufactured at this time was the same result as in Example 6.

It is the schematic which shows an example of the liquid crystal display device of this invention. It is the schematic which shows an example of the polarizing plate which can be used for this invention.

Explanation of symbols

1 Upper polarizing plate 2 Upper polarizing plate absorption axis 3 First optical anisotropic layer 4 First optical anisotropic layer slow axis direction 5 Upper electrode substrate of liquid crystal cell 6 Upper substrate alignment control direction 7 Liquid crystalline molecule 8 Liquid crystal cell lower electrode substrate 9 Lower substrate orientation control direction 10 Second optical anisotropic layer 1
11 Second optical anisotropic layer 1 direction of slow axis 12 Second optical anisotropic layer 2
13 Second optically anisotropic layer 2 Slow axis direction 14 Lower polarizing plate 15 Lower polarizing plate absorption axis direction 101 Polarizing plate protective film 102 Polarizing plate protective film slow axis direction 103 Polarizing plate polarizing film 104 Polarization film absorption axis direction 105 Polarizing plate protective film 106 Polarizing plate protective film slow axis direction

Claims (9)

Two polarizing films whose absorption axes are orthogonal to each other, and between the two polarizing films,
A liquid crystal layer composed of a pair of substrates and a liquid crystal molecule sandwiched between the substrates, and in a non-driven state where no external electric field is applied, the liquid crystal molecules are aligned in a direction substantially perpendicular to the substrate. A liquid crystal cell,
At least one first optically anisotropic layer consisting of a stretched thermoplastic polymer film having optically positive refractive index anisotropy and having a Re defined below with respect to visible light of 40 to 150 nm. ,
Second optical anisotropy having an optically negative refractive index anisotropy, comprising a discotic liquid crystalline compound, Re defined below for visible light is 10 nm or less, and Rth is 60 to 250 nm. A liquid crystal display device having at least one of the layers.
Re = (nx−ny) × d (1)
Rth = {(nx + ny) / 2−nz} × d (2)
(Nx is the refractive index in the slow axis direction in the plane of the layer, ny is the refractive index in the plane perpendicular to nx, nz is the refractive index in the thickness direction of the layer, and d is the thickness of the layer.)   The liquid crystal display device according to claim 1, wherein the first optical anisotropic layer is formed of a stretched polycarbonate copolymer film. Two polarizing films whose absorption axes are orthogonal to each other, and between the two polarizing films,
A liquid crystal layer composed of a pair of substrates and a liquid crystal molecule sandwiched between the substrates, and in a non-driven state where no external electric field is applied, the liquid crystal molecules are aligned in a direction substantially perpendicular to the substrate. A liquid crystal cell,
The cellulose acylate has a hydroxyl group substituted with an acetyl group and an acyl group having 3 to 22 carbon atoms, and the cellulose acylate has an acetyl group substitution degree A and an acyl group with 3 to 22 carbon atoms. The substitution degree B of the group satisfies the following formula (C), and Re defined by the following formula for visible light is at least one layer of the first optically anisotropic layer having a thickness of 40 to 150 nm;
Second optical anisotropy having an optically negative refractive index anisotropy, comprising a discotic liquid crystalline compound, Re defined below for visible light is 10 nm or less, and Rth is 60 to 250 nm. A liquid crystal display device having at least one of the layers.
Re = (nx−ny) × d (1)
Rth = {(nx + ny) / 2−nz} × d (2)
(Nx is the refractive index in the slow axis direction in the plane of the layer, ny is the refractive index in the plane perpendicular to nx, nz is the refractive index in the thickness direction of the layer, and d is the thickness of the layer.)
Formula (C) 2.0 ≦ A + B ≦ 3.0   The liquid crystal display device according to claim 3, wherein the acyl group having 3 to 22 carbon atoms is a butanoyl group or a propionyl group.   The liquid crystal display device according to claim 1, wherein the second optically anisotropic layer is made of a discotic liquid crystalline compound having a polymerizable group.   The liquid crystal display device according to claim 1, wherein the discotic liquid crystalline compound of the second optically anisotropic layer is substantially horizontally aligned.   The liquid crystal display device according to claim 1, wherein the first optical anisotropic layer also serves as at least one protective film of the two polarizing films.   The liquid crystal display according to claim 1, wherein the absorption axis of the polarizing film close to the first optical anisotropic layer is substantially orthogonal to the longitudinal direction of the transparent protective film of the polarizing film. apparatus.   9. The transparent protective film according to claim 1, wherein at least one of the transparent protective films close to the liquid crystal cell is made of cellulose acetate, and Re of the transparent protective film is less than 3 nm. Liquid crystal display device.

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