JPS62174725A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To produce a liquid crystal display device which makes stable orientation and has a large twist angle with good productivity by constituting said device of the oriented films consisting of a straight chain high polymer having a fluoroalkyl chain at the side chain and liquid crystal having soft skeleton and <5 deg. tilt angle in the non-electrolysis stage. CONSTITUTION:Transparent electrodes 11 and the oriented films 12 which make homogeneous orientation of liquid crystal molecules are respectively formed on a pair of substrates 1 and the nematic liquid crystal which is spirally twisted at 180-360 deg. is sandwiched between the substrates. The oriented films 12 are formed of the straight chain high polymer having the fluoroalkyl chain (CnHmF2n+1-m: n is natural number, m is 0 or <=2n natural number) at the side chain and the liquid crystal 2 has the soft skeleton and is oriented to <5 deg. tilt angle in the non-electrolysis state. Productivity is, therefore, improved by the simple process for production such as printing and coating. The tilt angle is increased by a weak electric field and the responsiveness of the display is im proved.

Description

DETAILED DESCRIPTION OF THE INVENTION A) Industrial Application Field The present invention relates to a liquid crystal display in which liquid crystal molecules have a helical structure. More specifically, the present invention relates to a liquid crystal display in which the helical twist angle is large and the liquid crystal molecules are oriented stably and can be driven at high speed.

(Example) Conventional technology In order to drive liquid crystals by electric field effect, there are conventional technologies in which liquid crystal molecules are oriented in a 90 degree spiral structure (
Special Publication No. 51-13666》. However, a display device with a 90-degree twisted orientation has a large viewing angle dependence and is not suitable for high time division driving. For example, in a matrix display, the display contrast decreases as the number of time divisions increases, but in 1/100 duty drive, the display contrast becomes 3 to 5, reaching the limit of being able to read the displayed content. In addition, the display angle is limited to when viewed from a specific viewing direction, and the viewing direction has a margin of only about 20 degrees with respect to the display surface. This means that they cannot be applied to large screen displays (particularly dot matrix displays with high pixel density).

Therefore, the twist angle of liquid crystals was reconsidered, and
Other display modes have been proposed, such as in Publication No. 0-107020 and Japanese Patent Application Laid-Open No. 60-50511. These devices have a twist angle of liquid crystal as large as 160 to 360 degrees and utilize the birefringence of liquid crystal molecules, and can provide a practical contrast even in 1/too to 1/200 duty driving.

However, in this display mode, there is a problem that must be solved to ensure stable alignment of liquid crystal molecules (drain countermeasures and tilt angle countermeasures).Domain countermeasures refer to non-uniformity of alignment due to increased twist angle. . For example, even if liquid crystal molecules are forced to have a dextrorotatory orientation, a levorotary orientation or an orientation with a different twist angle will occur partially. When this phenomenon occurs, it appears as a difference in display color when not driven and responsiveness when driven, resulting in a significant deterioration in display quality. On the other hand, measures against tilt angle are the angle that liquid crystal molecules make with the substrate surface (
If the tilt angle) is not large, the response will be slow, resulting in
The polymer alignment film used for 0 degree twist orientation has a chill [・
Although the angle is 0 to 2 degrees, it is said that this display mode requires an angle of 5 degrees or more, preferably 10 to 30 degrees.

Regarding these points, the above-mentioned prior document uses an alignment film obtained by obliquely vapor-depositing an inorganic substance onto a substrate,
Orientation stability has been obtained. However, since the deposition angle is an important factor in this alignment film, the area of a uniform alignment film is limited, and the limit is a flat plate with a width of about 10 cIT1 at most. In addition, this display mode has a small tolerance for the thickness of the liquid crystal layer, so it cannot be used if the thickness of the alignment layer is uneven. For these reasons, such an oblique vapor deposition method is not suitable for producing large-area displays or for mass-producing displays regardless of area size.

C) Problems to be Solved by the Invention The present invention has been made in consideration of the above-mentioned points, and provides a liquid crystal display device having a large twist angle that can perform stable alignment with high productivity. be.

2) Means for solving the problem The present invention was made by focusing on the compatibility between liquid crystal molecules and the side chains of the alignment film, and the alignment film is made of polyamide or polyimide having fluoroalkyl chains in the side chains. Using a high-chain polymer film, liquid crystal molecules with a flexible skeleton (having a structure in which the body 1I! (molecular volume) occupied by the molecule increases due to the rotation of the bonds between the return atoms in the liquid crystal molecules) This method uses liquid crystal molecules containing liquid crystal molecules.

E) Effect: This facilitates the production of the alignment film, and the tilt angle is low when no electric field is applied, but increases when the electric field is applied, resulting in good response characteristics.

f) Embodiment FIG. 1 is a sectional view of a liquid crystal display device according to an embodiment of the present invention.
) (1) are substrates arranged facing each other, and transparent electrodes (11) (11) are provided on the opposing inner surfaces for applying an electric field to the liquid crystal.
...and an alignment film (1) that homogeneously aligns liquid crystal molecules.
2) It has <12>. (2) is this board (1) (
1) The sandwiched liquid crystal exhibits a nematic phase and has a chiral nematic display mode having a helical structure twisted by 180 to 360 degrees as shown in the prior art. (3) (3) is a sealant for forming a liquid crystal container to hold liquid crystal (2) between substrates (1) (1). (4) (4) is a polarizing plate placed on the outside of each substrate (1) (1) so as to be located outside the layer of liquid crystal (2), and has a polarizing effect on the substrate (1) (1) itself. It may also be provided on one side only.

For example, the liquid crystal 2) mentioned above has a thickness of 7 μm and Δn is 01
2 to 0.13, and the optically active substance facilitates the formation of a helical structure. More preferable conditions for the liquid crystal (2) will be described later.

Regarding alignment film (12) (12) JP-A-55-1635
No. 13, JP-A-58-91430, JP-A-Sho 6
Application examples to the present invention will be shown based on the alignment agents listed in Publication No. 0-104129, etc. However, as will be detailed later, depending on how these alignment agents are used, homeotropic alignment may occur and the present invention may not be possible. Since it becomes impossible to obtain a display mode in which the torsion angle is increased by 1-homogeneous orientation and the birefringence effect of the liquid crystal is utilized, which is the objective of the above, consideration must be given to this point.

Example (A-1> When one hydrogen atom of ε-caprolactam was replaced with CF, ring-closing copolymerization with ε-caprolactam was performed at various ratios, resulting in an average molecular weight of approximately 100 OOJX child units.

This was dissolved in N-methyl-2-pyrrolidone to make an 8% solution. Then, this solution was applied and dried on a soda glass substrate having a base layer and an electrode film to form a coating of about 1,000 people. This film was rubbed in one direction with a cotton cloth to obtain an alignment film (12).

Then, the gap was adjusted so that the layer thickness of the liquid crystal (2) was 10 μm, and a liquid crystal display was formed.
Filled with 1840 (nematic phase). At this time, the rubbing directions of the substrates (1) and (1) are arranged so that they are opposite to each other with the aim of achieving the minimum twist angle of 180 degrees in order to analyze the characteristics. -〇The relationship between the tilt angle of the substituted liquid crystal molecules (measured by magnetic field method) is as shown in Figure 2, and the tilt angle suitable for this display mode is 5.
Substituted caprolactam to reduce the temperature to 40 degrees or more is 2
It is 0% or more and 60% or less. Although it is difficult to control a delicate range such as 1 displacement position of tilt angle or 0.5 variable potential, 4 to 5 degree single variable displacement control (for example, 15 degrees ± 2 degrees)
is the mixing amount of substituted caprolactam (substitution rate of -CFs)
I confirmed that it can be controlled.

Example (A-2> In the above (A-t), the substitution rate of the fluoroalkyl chain was set to 50%, and n of -CnF□1 was successively changed to form a similar liquid crystal cell. The results are shown in Figure 3. As shown, the tilt angle increased by increasing n.In order to make the tilt angle greater than or equal to 5 degrees and less than 40 degrees, n should be selected as 1 or 2, and this fluoroalkyl chain is one of the factors in orientation. Hydrogen was introduced because it has the strongest effect on the volume exclusion effect (nHFta can also be used).

In this case, n corresponding to the tilt angle could be selected from 1.2.3.

Example (A-3) The indicators in (A-1) and (A-2) above were reclassified based on the molar ratio of substituted caprolactam and were continuously energized.
The figure shows 15 VO-F, 100 μsec, 30 Hz alternating positive and negative pulses applied for 100 hours at room temperature, and then 180
This shows the total area of defective orientations (domains) that occur within the effective display area of 220ml. This shows that the stability of monodomains is related to the amount of fluoroalkyl chains present per unit atom number, but this is also related to liquid crystal molecules, which will be discussed later, so as a guide, 50
It is only necessary to recognize that one or more fluoroalkyl chains are required per 00 atoms.

Example (A-4) Even when polyamide is formed using an amine, the same effect as when using caprolactam can be expected, so only one example will be shown here.

/＼CF s at one location in the main chain of xamethylenediamine
is substituted with adipic acid, and about too
It was taken as the average molecular weight of oo@child unit. This is described above (A-1
In the same manner as above, it was applied onto a glass substrate, dried, and then rubbed to sandwich a liquid crystal exhibiting a nematic phase. The tilt angle at this time was about 15 degrees.

The examples above are polyamide bonds represented by the general formula % (n is a natural number, X, Y are single or multiple linear bonding groups such as methylene group, methylene ether group, phenylene group, phenylene ether group). It is a polymer resin with These resins have an advantage in handling compared to polymer resins having polyimide bonds, which will be exemplified below, in that they are soluble in solvents and can be used in polymerized form.

However, as shown in the prior art of alignment agents mentioned above,
Although polymeric resins have to be polymerized on the substrate, polymeric resins having polyimide bonds are also effective for orientation in the same way as polyamide resins.

For example, [B-0] In the present invention, the polyimide resin represented by the general formula was able to obtain more stable orientation. An example of a material having a polyimide bond will be given below.

Example [B-1 A process in which cocyamine has a fluoroalkyl chain (n, m are natural numbers) and is condensed with carboxylic acid to form a polyimide resin is to print and apply such a resin agent on a substrate and bake it. , then rub in one direction. The rubbing directions were orthogonal to achieve a twist angle of 270 degrees. At this time, the tilt angle could be controlled within the range of 5 to 30 degrees depending on the amount of fluoroalkyl chains when measured using the magnetic field method.

Now, in the above example, the measurement of the tilt angle was explained using the magnetic field method, but there are two reasons for this. Normally, the optical method is used to measure the tilt angle of a liquid crystal display, but it is extremely difficult to measure in the present invention. However, according to the comprehensive analysis results using the optical method, the tilt angle in the absence of an electric field is 3 to 4. degree. "On the other hand, the magnetic field method utilizes the fact that when a magnetic field above a threshold value is applied, liquid crystals that exhibit positive attraction t'A orientation rearrange their molecules with their long axes (optical axes) aligned in the direction of the magnetic field. This is detected as electric capacitance.The conditions for measuring the tilt angle described above are a magnetic field of 30 to 60
Gauss, capacitance side constant voltage IE 0.5 V rms, capacitance measurement frequency 1 kHz. From these facts, it can be analyzed that in the present invention, the tilt angle is low when no electric field is applied, but the tilt angle sharply increases when even a small electric field is applied.

Now, although the above example has been explained with a focus on the tilt angle and the alignment film, the selection of the material for the liquid crystal is also essential for achieving good display. For example, the first group used liquid crystals, and the second group used liquid crystals called RA-N. This group can be said to be liquid crystals with relatively flexible bonds.These groups have the following differences in characteristics.

However, the uniformity of orientation is also affected. Regarding the uniformity of orientation, in addition to the question of whether there are monodomains or defective domains, there is also the question of whether a predetermined alignment state is reproducible even when electrolysis is applied at a threshold voltage or higher.

FIG. 5 is a characteristic diagram in which the occurrence of domains due to liquid crystal materials was investigated from this viewpoint. The liquid crystal with a flexible skeleton here refers to a liquid crystal molecule with a structure in which the volume occupied by the molecule increases due to the rotation of the bonds between carbon atoms.In addition to the liquid crystals belonging to the second group mentioned above, the following can give.

(Here, R is an alkyl group, X is a cyano group, an alkyl group,
Bond X selected from an alkoxy group> And when the amount of liquid crystal molecules having such a flexible skeleton exceeds 30 mol.%, monodomains are rapidly formed even in the wide surface 1 (for example, 100 a x 150 mm or more). But sometimes it's expensive! When pressure is applied, photopastic domains are generated,
After that, even if the voltage is increased to the saturation voltage, the contrast cannot be obtained. Such symptoms do not occur when the amount of liquid crystal molecules having a flexible skeleton exceeds 50 mol.%. (In the above-mentioned first group of liquid crystals, the amount of liquid crystal molecules having a flexible skeleton is 20 mol.%).

FIGS. 6 and 7 show the characteristics of a liquid crystal display when the above-mentioned example [B-0] is used as the main ingredient as the alignment film and the second group is used as the liquid crystal. This display mode is used in two types of display forms determined by the arrangement of the polarizing plates, and these are called blue mode and yellow mode due to their coloring. The blue mode is a deep purple in the unselected state, and the background color is in the selected state, and the characteristic curve in the figure is marked with the symbol (BL).The yellow mode is bright yellow in the unselected state, and dark in the selective layer. It exhibits an indigo color and is marked with the symbol (YE) in the figure. ((TN) in Figure 7 is the characteristic curve of the conventional 90 degree twisted orientation.) 6th rM+:
The response speed to the selection signal at a bias of 1/200 du'-r41/15 and a frame frequency of 128 Hz is shown, indicating that the response is satisfactory for practical use at about room temperature.

Figure 7 shows the size of the display capacity that can provide good contrast, and the viewing angle is 20J with a reflective display.
I! The case of : is shown. The viewing angle dependence is not shown, but it is 1/1o as shown in the conventional example.

When the duty is 20 degrees with a 90 degree twisted orientation, the good viewing angle is approximately 60 degrees in the present invention.

Further, the twist angle of the liquid crystal can be expressed by the steepness of the rise of the shielding effect of transmitted light with respect to the applied tJE (ratio of the voltage to reach 80% of the saturation amount and that of 20%). From this point of view, the display device of the present invention is particularly superior to a display with a twist orientation of 90 degrees at a twist angle of 250 degrees or more, and has a steepness of about 1.06. However, even with such a combination of alignment film and liquid crystal, if the twist angle is large, the orientation will be in the opposite direction, so in order to obtain stable alignment, the twist angle is preferably 290 degrees or less.

In the embodiments described above, it was said that color display could not be performed because both the blue mode and the yellow mode had a unique coloration. However, when 2.0 weight percent of cholesteryl nonanonate is added to Merck's ZLI3093 (a mixture of three types of dichroic dyes in a total of 1.0 to 3.1 weight percent) in a liquid crystal, blue color is produced. mode and can appear black in a non-selected state. Therefore, as shown in FIG. 8, three color filter layers (13R) are provided outside the liquid crystal layer (21).
If 13G>(13B>... is arranged and used in a transmissive display mode, color display can be performed.

g) Effects of the invention As described above, since a linear polymer alignment film can be used, simple manufacturing methods such as printing and coating can be applied, resulting in good productivity. Although it is low at less than 5 degrees, since sufficient consideration is given to van der Waals forces and volume exclusion effects that affect orientation, the tilt angle becomes high in weak electric fields or residual electric fields, resulting in good responsiveness in display driving.

Furthermore, by selecting liquid crystal molecules, stable alignment can be obtained even over a wide display area. From these facts, it is possible to obtain a liquid crystal display having a large display surface with good productivity without compromising the advantages of this display mode having a large twist angle, such as high time-division driving capability and low viewing angle dependence.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal display according to an embodiment of the present invention, and FIGS. 2 to 5 are orientation characteristic diagrams according to an embodiment of the present invention.
6 and 7 are characteristic diagrams of a liquid crystal display according to the present invention, and FIG. 8 is a sectional view of a liquid crystal display to which the present invention is applied. (1)...Substrate, (H) (11)...Transparent electrode, (
12) (12>... alignment film, (13R) (13G) (
13B)...Color filter layer (2) (21)...
Liquid crystal, (3) (3)... sealant, (4) (4)...
・Polarizing plate applicant Sanyo Electric Co., Ltd. 1 other agent Patent attorney Takashi Nishino #A (1 other person) Figure 1 5 N: ni: ()shi-1, )chuPcF3n] Kei Figure 5 12 Figure 7 Procedural amendment (spontaneous) 1. Shigeru of the case 1985 Patent application No. 14766 Voice Z Name of the invention Liquid crystal display 3. Person making the amendment Relationship to the case Name of patent applicant (18B) Sanyo Electric Co., Ltd. 1 other person contact information: Telephone @ (Tokyo) 835-1111 Stationed at Patent Center Simultaneously with the request for examination in the middle of the year 5, counter for amendments 1) Scope of claims in the specification 11) Claims of the invention in the specification Detailed Explanation 4, Part 6, Contents of Amendment 1) The scope of claims will be amended as shown in the attached sheet. 11) B) On page 6, line 14 of the specification, "high chain polymer membrane" should be corrected to "linear polymer membrane." (Example) In line 19 of No. 8 of the specification, the phrase ``ring closed'' will be corrected to ``open ring.'' c) Correct the line containing the general formula of the molecule on the bottom line of page 11 of Specification 4 to include a bond as shown below. or 2) The molecular formula described in the 15th line of the 12th column of Specification 4 is corrected by adding nt- to indicate that it is a linear combination. e) Is the cyclohexane ring in the molecular formula of the liquid crystal in the 1st to 5th lines of the 17th page of the Book of Meisei in the form of a camphorax? In line with the industry reality that liquid crystal compositions with stable characteristics have not yet been put to practical use, we have made it clear that the liquid crystal composition is a transformer type. Rbeta〉(pressure to X RbetatoC-0betato
-0+ORJ means "R-Pen-8X R-Ben-Ben-X R-Pen-C-O+ ) Be/-X" will be corrected. Claims 1) A substrate having an alignment film for homogeneously arranging liquid crystal molecules, and in contact with the alignment film of the substrate, the liquid crystal molecules are arranged at a selected constant angle of 180 degrees or more and 360 degrees or less when in an uncircumcised state. In a liquid crystal display device comprising a nematic liquid crystal twisted and sandwiched in a ring shape, and at least 10,000 polarizers arranged outside the liquid crystal layer, the alignment film has 1 to 11 chains of fluoroalkyl fi. (Cn
Hm F 2 n +1-J'n: nu natural number,
1. A liquid crystal display comprising a linear polymer having a molecular weight of mHO or a natural number equal to or less than H2n), the liquid crystal containing liquid crystal molecules having a flexible skeleton. 2) A patented display device characterized in that the liquid crystal molecules of the liquid crystal in contact with the alignment film are oriented so that the angle (tilt angle) between the surface of the substrate and the liquid crystal molecules is less than 5 degrees in the absence of electrolysis. . 6) The liquid crystal display according to claim 2, wherein the liquid crystal contains liquid crystal molecules having a flexible skeleton in an amount of 307 or more and is a liquid crystal. 4) The liquid crystal display according to item 3, wherein the liquid crystal molecules having a flexible skeleton are trans. 5) The alignment film has polyamide bonds or polyimide bonds.
The liquid crystal display according to claim 2, characterized in that it is made of a polymer compound of -W. 6) The alignment film has the general formula %) (X%Y is a single or multiple linear bonding groups), and the fluoroalkyl chain is attached to the linear bonding group (X or/and Y). It is a provision. Patent featuring joy

Claims (1)

[Scope of Claims] 1) A substrate having an alignment film that homogeneously aligns liquid crystal molecules, and a substrate that is in contact with the alignment film of the substrate, and in the absence of an electric field, the liquid crystal molecules form a spiral shape at a selected angle of 180 degrees or more and 360 degrees or less. In a liquid crystal display device comprising a nematic liquid crystal twisted and held by a nematic liquid crystal and a polarizer disposed on at least one of the outer sides of the liquid crystal layer, the alignment film has a fluoroalkyl chain (CnHmF_
2_n_+_1_-_m: n is a natural number, m is 0 or 2n
1. A liquid crystal display comprising a linear polymer having the following natural numbers), wherein the liquid crystal contains liquid crystal molecules having a flexible skeleton. 2) The liquid crystal molecules of the liquid crystal in contact with the alignment film are oriented so that the angle (Mold angle) between the surface of the substrate and the liquid crystal molecules is less than 5 degrees in the absence of an electric field. A liquid crystal display according to item 1 in the range of . 3) The liquid crystal display according to claim 2, wherein the liquid crystal is a liquid crystal containing 30 mol percent or more of liquid crystal molecules having a flexible skeleton. 4) The liquid crystal molecule having a flexible skeleton is a liquid crystal molecule having a large molecular volume selected from the group of nematic phase liquid crystal having a trans-cyclohexyl group and nematic phase liquid crystal having an alkylcyclohexane group. The liquid crystal display device according to item 3 in the range. 5) The liquid crystal display according to claim 2, wherein the alignment film is made of a polymer compound having a polyamide bond or a polyimide bond. 6) The alignment film has a general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ / and Y). The liquid crystal display according to claim 5. 7) The helical twist angle of the liquid crystal molecules is 250 degrees or more29
The second claim is characterized in that the temperature is 0 degrees or less.
Item LCD display.