JPH043020A - Color liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain the color liquid crystal display element having excellent color reproducibility by using a liquid crystalline high-polymer layer having excellent orientability as an optical compensating plate and using a color filter. CONSTITUTION:The optical phase plate 7 consisting of the color filter and the liquid crystalline high polymer essentially consisting of polyester contg. an ortho-substd. arom. unit as a constituting component are provided between at least either of a pair of polarizers 2, 12 and a liquid crystal layer 6. The layer 7 consisting of the liquid crystalline high-polymer layer and the color filter is formed by forming the color filter 18 by a screen printing method, etc., after the formation of the liquid crystalline high-polymer layer 17. The color liquid crystal display element which is improved in optical compensating effect and excellent in the color reproducibility is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color display liquid crystal element using an optical phase plate and a color filter.

[Conventional technology]

Liquid crystals are used in various optoelectronics fields by utilizing the changes in optical properties that occur when the orientation state of liquid crystals changes depending on external fields such as electric fields, magnetic fields, and shear forces. Among these, liquid crystal polymers have higher viscosity in the liquid crystal state than low-molecular liquid crystals, so after aligning them in the liquid crystal state,
It has a feature not seen in low-molecular liquid crystals, in that the orientation state of the liquid crystal state can be fixed by cooling it below the glass transition point. Utilizing this, attempts are being made to apply it to optical electronics fields such as thermal writing optical memory and optical filters.

In order to realize these, it is necessary to highly control the desired molecular orientation. For example, a color compensator for a supertwisted sotonematinok (STN) type liquid crystal display element, which is a type of optical retarder, must function to return light that has become elliptically polarized by the liquid crystal layer back to linearly polarized light. Such functions can only be achieved by aligning liquid crystalline polymers horizontally and in a certain direction with a high degree of order and uniformity.

[Problem to be solved by the invention]

However, it is difficult to achieve highly uniform alignment using conventional liquid crystalline polymer materials and alignment methods, and there has been no material that can be used as an optical sliding plate.

In addition, with conventional optical phase plates made of stretched polymer films, it is not possible to introduce a twisted structure in the orientation.
The optical compensation effect is not good, so there is no problem when displaying black and white, but when using color filters in conjunction with multicolor or full color display, the color reproduction range becomes extremely narrow. Or, the density of the color filter had to be increased, resulting in a significantly darker display.

An object of the present invention is to solve the problems of the prior art and provide a color liquid crystal display element with excellent one-color reproducibility.

[Means and effects for solving the problem] In order to achieve the above object, the present invention provides a pair of substrates, a liquid crystal layer, an electrode for applying a voltage to the liquid crystal layer, and a pair of substrates, a liquid crystal layer, and an electrode for applying a voltage to the liquid crystal layer. In a color liquid crystal display element consisting of a pair of polarizers arranged in a sandwiched manner, a color filter and an optical phase plate made of a liquid crystalline polymer mainly composed of polyester containing ortho-substituted aromatic units as a constituent are combined. - A color liquid crystal display element is provided, characterized in that the color liquid crystal display element is provided between at least one of a pair of polarizers and the liquid crystal layer.

The configuration of the present invention will be explained in detail below.

FIG. 1 is a sectional view showing the structure of a color liquid crystal display element according to the present invention. In the figure, 10 indicates a liquid crystal cell.

The liquid crystal cell 10 is composed of substrates 1, 11, electrodes 4, 14, alignment films 3, 13, liquid crystal 6, and sealing material 5, and polarizing plates 2, 12 are provided on both sides of the liquid crystal cell 0. A layer 7 consisting of a liquid crystal polymer layer and a color filter is provided between the substrate 1 and the upper polarizing plate 2 of the liquid crystal cell IO, thereby configuring a color liquid crystal display element. One of the upper and lower polarizing plates 2 and 12 may be a reflective polarizing plate.

The substrate 1.11 only needs to be transparent, and glass, plastic film, etc. can be used.

Various configurations can be considered for the layer 7 consisting of a liquid crystalline polymer layer and a color filter, and a typical example is shown in FIG. The substrate 15 is made of transparent glass or plastic film, similar to the substrates 1 and 11 of the liquid crystal cell 10.3 The alignment film 16 for aligning the liquid crystal polymer N17 is the same as the alignment films 3 and 13 of the liquid crystal cell 10. Similarly, examples include those that are rubbed after forming a polymer film such as polyimide or polyamideimide, those that are rubbed after forming a coating film such as an organic metal compound or a heat treated film, and an obliquely evaporated film such as SiO. be able to. When the group Fi15 is a plastic film, the substrate can be directly rubbed to align the liquid crystalline polymer.
At this time, the alignment film 16 is not necessary. Furthermore, if the substrate is a plastic film such as polyimide or polyethylene terephthalate that undergoes crystallization by stretching, it can be used without rubbing treatment by using a film that has been stretched in the -axis.

The liquid crystalline polymer layer can be oriented, and rubbing treatment becomes unnecessary.

The liquid crystalline polymer that can be used is a liquid crystalline polymer whose main component is a polyester containing ortho-substituted aromatic units as a constituent, and contains the following catechol units, salicylic acid units, phthalic acid units, and these. Contains a group having a substituent on the benzene ring as a constituent component.

(X represents hydrogen, a halogen such as CQ-Br, an alkyl group or alkoxy group having 1 to 1 carbon atoms, or a phenyl group. Also, k is 0 to 2.) The polyester used in the present invention is In addition to the above structural units, (a) structural units derived from diols (hereinafter referred to as diol component) and structural units derived from dicarboxylic acids (hereinafter referred to as dicarboxylic acid class) and/or (b)
) Composed of structural units derived from oxycarboxylic acids containing both carboxylic acid and hydroxyl groups in one unit (hereinafter referred to as oxycarboxylic acid component).

Among these, the following aromatic and aliphatic diols can be mentioned as diol components.

Y.

(Y is hydrogen, halogen such as CQ, Br, carbon number 1 to 4
represents an alkyl group, an alkoxy group, or a phenyl group, and Q is O-2. ) Examples of dicarboxylic acid components include the following.

It is also preferable to use polymers whose constituent components are aromatic units containing bulky substituents as shown below, or aromatic units containing fluorine or fluorine-containing substituents instead of ortho-substituted aromatic units. .

LII+ (2 is hydrogen, halogen such as CQ, Br, carbon number is 1
4 represents an alkyl group, an alkoxy group, or a phenyl group. The weight is O~2. ) As the oxycarboxylic acid component, the following units can be specifically exemplified.

The liquid crystalline polymer can be applied directly at a temperature above the glass transition point at which the liquid crystalline polymer has fluidity, or by dissolving the liquid crystalline polymer in a solvent. 1! There are methods to apply or print as a liquid. The latter is particularly preferably used in terms of uniformity of film thickness and ease of control. The solvent for the liquid crystalline polymer varies depending on the type of liquid crystalline polymer used, degree of polymerization, etc., but is usually selected from the following.

Chloroform, dichloroethane, dichloroethane,
Halogenated hydrocarbons such as trichlorethylene, dichloroethylene, orthodichlorohenzene, phenyl solvents such as phenol, o-chlorophenol, and cresol, and aprotic polar solvents such as dimethylformamide, dimethylacetamide, and dimethylsulfoxide. , tetrahydrofuran, ether solvents such as dioxane, and mixed solvents thereof.

The solution concentration varies depending on the coating method, the viscosity of the polymer, the desired film thickness, etc. Taking a compensation plate for a liquid crystal display element as an example, the required film thickness is about 2 to 10 tones, so it is usually 2 to 5 tones.
Used in the range of thtZ, preferably ? 30wt%
used within the range. The coating method is spin code method,
Roll coating method, gravure coating method, dipping method,
Screen printing method etc. can be adopted. After coating the liquid crystalline polymer, the solvent is removed by drying, and the liquid crystalline polymer is aligned by heat treatment at a temperature at which the liquid crystalline polymer exhibits liquid crystallinity.

The temperature when aligning the liquid crystalline polymer must be higher than the glass transition point of the liquid crystalline polymer.

It is necessary that the temperature is lower than the transition temperature of the liquid crystalline polymer to an isotropic liquid. The lower the viscosity of the polymer, the better in order to aid the alignment due to the interfacial effect of the alignment film, and therefore the higher the temperature, but if it is too high, it is not preferable as it increases cost and deteriorates workability.

Generally, the temperature range is preferably from 50°C to 300°C.

In order to introduce a twisted structure into the orientation of the liquid crystalline polymer layer 17, a liquid crystalline polymer exhibiting a cholesteric liquid crystal phase may be used. A liquid crystalline polymer exhibiting a cholesteric liquid crystal phase may be obtained by introducing an optically active group into a liquid crystalline polymer exhibiting a nematic phase as described above, or by adding an optically active substance to the liquid crystalline polymer exhibiting a nematic phase.

In this case, the liquid crystalline polymer is aligned in the direction of the alignment treatment on the alignment film surface, and has a helix angle corresponding to the natural pitch in the thickness direction.
In other words, natural pinch is P. , where d is the film thickness and ω is the torsion angle, a torsion angle of ω=360×d/Po(′) is formed.

The configuration example shown in FIG. 2 is a case in which a color filter 18 is provided after the liquid crystalline polymer layer 17 is formed, and the color filter is created using a printing method such as a screen printing method. It is possible to create color patterns such as red, blue, and green necessary for full-color display. It is also possible to dye the liquid crystalline polymer Jli17 after forming it.

When dyes or pigments are added to the liquid crystal polymer, or when a chromophore is introduced into the structure of the liquid crystal polymer to give it color, the liquid crystal polymer layer 17 itself also functions as a color filter. Therefore, the color filter 18 can be omitted.

The substrate 15 for providing the liquid crystal polymer layer 17 can be used in common with the upper substrate 1 of the liquid crystal cell IO in FIG. 1, and in this case, one of the substrates 1 and 15 can be omitted.

If the color filter layer or colored liquid crystal polymer layer is formed to form a color pattern such as a dot pattern or a stripe pattern, the pixels of the liquid crystal cell and the color pattern may appear misaligned when the device is viewed from an oblique direction. In order to avoid this, an arrangement in which the substrate l or 15 is omitted is advantageous.

Also, when placing the layers 15 to 18 in FIG. 2 (corresponding to 7 in FIG. 1) between the substrate 1 and the upper polarizing plate 2 in FIG. is also advantageous.

〔Example〕

Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Example 1) An alignment agent containing polyamic acid as the main ingredient was spin-coded onto a glass substrate, dried in an oven at 100°C for 10 minutes, and then the temperature of the oven was raised to 270°C and maintained for about 1 hour to obtain a polyimide film. Ta. The surface of the polyimide film was rubbed with a nylon flocked cloth to form an alignment film for liquid crystal polymers. Next, a mixed solution of the following polyester-based liquid crystalline polymer was spin-coded onto the surface of this film.

(The book shows that it is an asymmetric carbon) The concentration is 30vtL PLI,! : The weight ratio of PL2 was 0. The solvent used was a mixed solution of phenol and tetrachloroethane (weight ratio 60:40). 90 on the board
The solvent was evaporated by drying in an oven at .degree. C. for 1 hour. Next, the temperature of the oven was raised to 200° C. where the mixture of PLI and PL2 takes a nematic liquid crystal phase, and after 30 minutes, the oven was taken out and rapidly cooled to room temperature. When the substrate with the liquid crystalline polymer film thus obtained was sandwiched between two polarizing plates and visually observed, a uniform birefringence color was observed, indicating that there was no unevenness in the thickness or orientation of the liquid crystalline polymer layer. I found out that there isn't. By polarization analysis, the retardation of this sample was determined to be 840n11, and the twist angle was determined to be 230°.

Next, red, blue, and green color filters were printed on the liquid crystalline polymer layer. This will be referred to as the "substrate Ju."

Next, two glass substrates for liquid crystal cells were prepared, a transparent conductive film was formed by sputtering, and electrodes were patterned by photolithography.

The substrates for these liquid crystal cells can be prepared using the same method as before, and here we apply a polyimide alignment agent by coating →
It was created through the process of drying, firing, and rubbing. These will be referred to as "substrate B" and "substrate C." Substrates B and C were bonded together using an epoxy sealant. The cell gap was controlled to 6.7 microns by scattering plastic beads having an average diameter of 6.6 microns on substrate B in advance. The empty cell thus created was filled with nematic liquid crystal ZLI-2293 manufactured by Merck & Co. and optically active substance S manufactured by Merck & Co.
-811 was added at 7% for 0.72ts. The liquid crystal composition was vacuum-sealed and sealed.

The orientation of the helix induced by s-gti is opposite to that of PL2. The rubbing direction of the alignment films of substrates B and C is
The orientation of S-811 is 230°, and the rubbing direction of the liquid crystal polymer alignment film on the substrate is perpendicular to the rubbing direction of the liquid crystal alignment film on substrate B. Configured. FIG. 3 shows a cross-sectional view after each substrate is bonded together.

A liquid crystal display element was created using the liquid crystal cell created as described above, and each color was displayed.

It was possible to display colorful reds, blues, and greens, and it was also possible to display full colors by mixing these colors.

(Example 2) A mixture of three types of azo dyes exhibiting red, blue, and green was dissolved in a mixed solution of the liquid crystalline polymer PLI used in Example 1 and circle 72, and a three-color liquid crystalline polymer solution was prepared. of! 181g1 9
The concentration of the azo dye mixture was 3% by weight relative to the liquid crystalline polymer. This was printed three times on a substrate with an alignment film prepared in the same manner as in Example 1, and finally 20
It was heated to 0°C and after 30 minutes was rapidly cooled to room temperature. The subsequent steps were performed in the same manner as in Example 1, and substrates A, B, and C were bonded together to create a liquid crystal display element.

Similar to Example 1, this liquid crystal display element also exhibited good color reproducibility.

〔Effect of the invention〕

In the liquid crystal display element of the present invention, by using a liquid crystalline polymer layer with excellent orientation as an optical compensation plate and using a color filter, a color liquid crystal display element with excellent color reproducibility can be provided.

Similarly, excellent color reproducibility can also be achieved by adding dyes or pigments to the liquid crystal polymer layer with excellent orientation, or by using liquid crystal polymers that are originally colored and have excellent orientation. It becomes possible to provide a color liquid crystal display element with

Furthermore, in the color liquid crystal display element of the present invention, since a twisted structure can be introduced into the orientation of the liquid crystal polymer, it is possible to maintain performance equivalent to that of a color liquid crystal display element with two stacked liquid crystal cells. In comparison, the configuration is simpler, and it is possible to reduce weight, thickness, and cost.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a color liquid crystal display element according to the present invention, FIG. 2 is a view showing a typical example of a layer consisting of a liquid crystal polymer layer and a color filter, and FIG. FIG. 3 is a cross-sectional view showing the orientation after bonding the substrates together. 1.11 ・Substrate 2.12 ・Polarizing plate 3.13 ・Alignment film 4.14 ・Transparent electrode 5 Sealant 6 Liquid crystal 7 ・Layer consisting of liquid crystal polymer layer and color filter Patent applicant Rico Co., Ltd. ( 1 other person)

Claims (1)

[Claims] (1) In a color liquid crystal display element consisting of a pair of substrates, a liquid crystal layer, an electrode for applying voltage to the liquid crystal layer, and a pair of polarizers arranged to sandwich the liquid crystal layer, a color filter and , an optical phase plate made of a liquid crystalline polymer mainly composed of polyester containing ortho-substituted aromatic units as a constituent is provided between at least one of the pair of polarizers and the liquid crystal layer. Color liquid crystal display element.