JP3141946B2 - Color liquid crystal display - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a birefringent color liquid crystal display device using an optical phase plate and a color filter.

[Conventional technology]

Liquid crystals are used in various optoelectronics fields by changing the alignment state due to an external field such as an electric field, a magnetic field, and a shear force, and utilizing the change in optical properties accompanying the change. Of these, liquid crystalline polymers are more viscous in the liquid crystal state than low-molecular liquid crystals, so they can be aligned in the liquid crystal state and then cooled to below the glass transition point to fix the liquid crystal alignment state. Low-molecular liquid crystal. Utilizing this, applications in the field of optoelectronics such as an optical memory for thermal writing and an optical filter have been attempted. To achieve these, it is necessary to control the desired molecular orientation to a high degree.
For example, a color compensator for a super twisted nematic (STN) type liquid crystal display device, which is a kind of optical retarder,
It is necessary to function to return the elliptically polarized light to linearly polarized light by the liquid crystal layer. Such a function has a high degree of order and uniformity in the liquid crystal polymer horizontally and in a certain direction. It can be expressed only by orientation.

In the case of a low-molecular liquid crystal, an alignment control method is almost established, but in the case of a liquid crystalline polymer (polymer liquid crystal), it is not sufficiently established. Examples of liquid crystal polymer alignment control include:
A method of applying an external force such as shear stress, a method of applying an external field such as a magnetic field or an electric field, and the like are known.However, these methods cannot control the orientation of a large area or have a sufficient uniformity. I can't say. When the method of injecting a liquid crystalline polymer into the gap between substrates that has been subjected to alignment treatment in the same way as a low-molecular liquid crystal is applied to the liquid crystalline polymer as it is, the viscosity of the liquid crystalline polymer is high. The liquid crystalline polymer is oriented along the flow, and the desired orientation cannot be obtained, or even if the area is large, it becomes difficult to inject.

The present inventors are able to achieve good alignment over a large area by applying a liquid crystalline polymer to an alignment-treated substrate or a uniaxially stretched plastic substrate and heating the liquid crystal temperature while one side is in contact with air. Was found.
However, in the conventional configuration in which both the substrate for aligning the liquid crystalline polymer and the substrate for the liquid crystal cell are separately required, the number of substrates is increased and the cost is increased. This is inconvenient because the overall weight and thickness increase.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the related art, and an object of the present invention is to provide a high-quality color liquid crystal display element that is lightweight, thin, and has no dot displacement.

[Means and actions for solving the problem]

In order to achieve the above object, according to the present invention, a liquid crystal cell including a pair of substrates, a liquid crystal layer, a liquid crystal polymer layer, an electrode for applying a voltage to the liquid crystal layer, and a color filter is sandwiched. In a color liquid crystal display element consisting of a pair of polarizers arranged on the substrate, via an alignment film layer on the substrate,
A liquid crystal polymer layer and a color filter layer are provided in contact with the liquid crystal polymer layer, and an alignment film layer, a liquid crystal layer and an alignment film layer, an electrode layer and a substrate are sequentially stacked on the liquid crystal polymer layer via an electrode layer, and a pair is formed on both ends of the substrate. And a color liquid crystal display device characterized by comprising a polarizer of: a pair of substrates, a liquid crystal layer, a liquid crystalline polymer layer, an electrode for applying a voltage to the liquid crystal layer, and a color filter. A liquid crystal display device comprising a pair of polarizers arranged so as to sandwich a liquid crystal cell to be formed, a color filter formed by mixing a dye or a pigment with a liquid crystalline polymer layer via an alignment film layer on a substrate. Layer, an alignment film layer, a liquid crystal layer and an alignment film layer, an electrode layer and a substrate are sequentially laminated on this layer via an electrode layer, and a pair of polarizers is provided at both ends of the substrate. Color LCD table An indicator element is provided.

 Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view showing an example of the configuration of a color liquid crystal display device of the present invention. A liquid crystal polymer layer 4 is formed on one surface of an upper substrate 2 with an alignment film 3 interposed therebetween. An electrode 5 and an alignment film 6 are formed. On the other hand, an electrode 9 and an alignment film 8 are formed on one surface of the lower substrate 10. A pair of substrates 2 and 10 on which these various types are formed are separated and opposed so that the electrodes 5 and 9 face inward, and a liquid crystal layer 7 is sandwiched therebetween to form a liquid crystal cell. An upper polarizing plate 1 and a lower polarizing plate 11 are provided so as to sandwich the liquid crystal cell, thereby constituting a liquid crystal display element. In this embodiment, a dye or a pigment is added to the liquid crystalline polymer layer 4 to form a color filter.

Both the upper and lower polarizers 1 and 11 need not be transmissive,
One may be a reflective polarizing plate. Upper and lower substrates 2 and 10
Any transparent material such as glass or plastic may be used. After forming a polymer film such as polyimide, polyether imide, polyamide imide, polyester imide, polyamide, polyester, polyvinyl alcohol, or polyacrylonitrile as the alignment film 3, a rubbing treatment, or an organic metal compound such as alkoxysilane or organic titanate is used. Rubbed coating film or a heat-treated film thereof, or an obliquely deposited film of silicon oxide or the like. The liquid crystal polymer layer 4 can also be oriented by directly rubbing the plastic substrate or using a uniaxially stretched plastic film. In this case, the orientation film 3 becomes unnecessary.

A liquid crystalline polymer layer 4 which is a feature of this configuration example is formed on the alignment film 3 by applying a liquid crystalline polymer. The liquid crystalline polymer that can be used in the present invention is a thermotropic liquid crystalline polymer, the structure is not particularly limited, for example, polyester, polyesteramide, polycarbonate, polyether and the like having a liquid crystal residue in the main chain. Main-chain type liquid crystalline polymer having the following structure: Represents a number. ) Alternatively, a side chain type liquid crystalline polymer having a liquid crystalline residue in a side chain such as a vinyl polymer or polysiloxane having the following structure: ^{M 2: -Ph-Ph-R} 3, -O-Ph-Ph-R 3, -Ph-COO-Ph-
^{R 3, -O-Ph-COO} -Ph-R 3, -Ph-COO-Ph-R 3, -O-P
^{h-OCO-Ph-R 3} , -Ph-Ph-COO-Ph-R 3, -O-Ph-Ph
^{-COO-Ph-R 3, -Ph} -COO-Ph-Ph-R 3, -O-Ph-COO
^{-Ph-Ph-R 3, -Ph} -Ph-OCO-Ph-R 3, -O-Ph-OCO-
^{Ph-Ph-R 3, -Ph} -OCO-Ph-Ph-R 3, -O-Ph-OCO-Ph
-Ph-R ^3, etc. (wherein, R ³ is an alkyl group, an alkoxy group, a halogen atom, a nitro group or a cyano group, n represents. An integer of 0 to 18) can be exemplified. The liquid crystalline polymer is used alone or as a mixture. An optically active group can be introduced into the liquid crystalline polymer, or an optically active compound can be added.

As a coating method, a method in which the liquid crystalline polymer is directly coated at a temperature equal to or higher than a glass transition point having fluidity, or a method in which the liquid crystalline polymer is dissolved in a solvent and applied or printed as a solution is used. The latter method 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 the liquid crystalline polymer used, the degree of polymerization, and the like, but is usually selected from the following.

Chloroform, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, halogenated hydrocarbons such as orthodichlorobenzene, phenol, o-chlorophenol, phenolic solvents such as cresol, dimethylformamide, dimethylacetamide, aprotic polar solvents such as dimethylsulfoxide, Ether solvents such as tetrahydrofuran and dioxane and mixed solvents thereof.

The solution concentration depends on the coating method, the viscosity of the polymer, the desired film thickness, and the like. Taking a compensator for a liquid crystal display device as an example,
Since the required film thickness is about 2 to 10 μm,
It is used in the range of -50 wt%, preferably in the range of 5-30 wt%. As a coating method, a spin coating method, a roll coating method, a gravure coating method, a dipping method, a screen printing method, or the like is employed. After applying the liquid crystalline polymer, the solvent is removed by drying, and the liquid crystalline polymer is heat-treated at a temperature at which the liquid crystalline polymer exhibits liquid crystallinity to orient the liquid crystalline polymer.

The temperature at which the liquid crystalline polymer is oriented needs to be equal to or higher than the glass transition point of the liquid crystalline polymer, and lower than the transition temperature of the liquid crystalline polymer to an isotropic liquid. The lower the viscosity of the polymer is, the better the temperature is, in order to assist the alignment by the interface effect of the alignment film, but the higher the temperature, the higher the temperature. Generally, the range of 50 ° C to 300 ° C is preferable.

In order to introduce a twisted structure into the orientation of the liquid crystalline polymer layer 4, a liquid crystalline polymer exhibiting a cholesteric liquid crystal phase may be used. As described above, the liquid crystalline polymer exhibiting a cholesteric liquid crystal phase may be obtained by introducing an optically active group into the liquid crystalline polymer exhibiting a nematic phase or by adding an optically active substance. In this case, the liquid crystalline polymer is arranged in the orientation direction on the orientation film surface, and the twist angle corresponding to the natural pitch in the thickness direction, that is, the natural pitch is P ₀ , the film thickness is d, and the twist angle is ω. Ω = 360 × d / P ₀ (゜).

The configuration example shown in FIG. 1 is a case in which a dye or a pigment is added to the liquid crystalline polymer layer 4. If a printing method such as a screen printing method is used among the above-mentioned coating methods, a multi-color display or the like can be realized. It can create color patterns such as red, blue, and green necessary for full-color display. Liquid crystalline polymer layer 4
Can be dyed after formation. Further, a color filter layer can be separately provided by a roll coating method, a gravure coating method, a screen printing method, or the like. In this case, another color filter layer is provided between the liquid crystal polymer layer 4 and the electrode 5. . A color filter may be provided on the electrode by electrodeposition after the electrode 5 is provided. However, in this case, the voltage applied to the liquid crystal layer 7 is reduced, so that another electrode is provided on the color filter. Is preferred.

The electrodes 5, 9 are formed by forming a conductive film by a vapor deposition method or a sputtering method and then patterning the conductive film.
According to the film formation method using a mask, patterning can be unnecessary. Alignment film for aligning liquid crystal layer 7
The layers 6 and 8 can be provided in exactly the same manner as the alignment film 3 for aligning the liquid crystalline polymer layer 4, but a method of applying a polymer and performing a rubbing treatment is preferable in terms of productivity.

〔Example〕

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 An orientation agent (PIQ manufactured by Hitachi Chemical Co., Ltd.) as a main component was spin-coated on a glass substrate and dried in an oven at 100 ° C. for 10 minutes.
And kept for about 1 hour to obtain a polyimide film. The film surface was rubbed with a nylon flocking cloth to form an alignment film for a liquid crystalline polymer. Next, a polysiloxane-based liquid crystalline polymer having a repeating unit represented by the following formula a on the film surface and having a glass transition point of 70 ° C .:
A solution was prepared by dissolving a polysiloxane-based liquid crystalline polymer having a repeating unit represented by the following formula b and having an optically active group in a phenol / tetrachloroethane mixed solvent (50:50 wt%) to a concentration of 25 wt%.

After drying this in a 70 ° C oven, the liquid crystalline polymer is heat-treated at 170 ° C for 20 minutes to become a nematic phase,
It was rapidly cooled to room temperature to obtain a liquid crystalline polymer film. The thus obtained substrate with a liquid crystalline polymer film was sandwiched between two polarizing plates and visually observed. As a result, a uniform birefringent color was observed. It turned out that there was no. Ellipsometry showed that this sample had a retardation of 950 nm and a twist angle of orientation of 180 °.

Next, red, blue and green color filters were printed on the liquid crystal polymer layer. Since there is a difference in thickness between the non-pixel portion of the color filter surface and between different color filters, a transparent leveling layer (first layer) is used to fill in these differences.
(Not shown in the figure). Then, a transparent conductive film was formed thereon by sputtering, and the electrodes were patterned by photolithography. The substrate provided with the liquid crystalline polymer film, the color filter, and the patterned electrodes prepared as described above is referred to as “substrate A”.

The other substrate for the liquid crystal cell (referred to as “substrate B”) was prepared in the same manner as in the prior art. That is, a polyimide-based alignment agent was applied to a patterned substrate with electrodes, dried, baked, and rubbed. After similarly providing an alignment film on the substrate A, the substrate A was bonded to the substrate B with an epoxy sealant. The cell gap has an average diameter of 7.4
7.3 μm was controlled by spraying plastic beads of μm on the substrate B in advance. The nematic liquid crystal ZLI manufactured by Merck is placed in the empty cell
A liquid crystal composition in which the company's optically active substance S-811 was added to -2293 was vacuum-sealed and sealed to form a liquid crystal cell. S-81
The direction of the helix induced by 1 was opposite to that of the liquid crystalline polymer b. The rubbing direction of the alignment films on the substrates A and B is
The orientation of S-811 was set to 180 °, and the rubbing direction of the alignment film for liquid crystal on the substrate A was perpendicular to the rubbing direction of the alignment film for liquid crystalline polymer. A pair of polarizers was disposed on both sides of the liquid crystal cell prepared as described above, to obtain a color liquid crystal display device of the present invention.

When each color was displayed using this liquid crystal display element,
Vivid red, blue, and green display were possible, and full color display was also possible by mixing these. Further, even when observed from an oblique direction, no dot shift was observed.

(Example 2) The mixed solution of the liquid crystalline polymers a and b used in Example 1
A mixture of three kinds of azo dyes exhibiting red, blue and green was dissolved to prepare a liquid crystal polymer solution of three colors. The concentration of the azo dye mixture was 3% by weight based on 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, finally heated to 200 ° C., and rapidly cooled to room temperature after 30 minutes. In the subsequent steps, a transparent leveling layer is applied in the same manner as in Example 1, an electrode is patterned to provide an alignment treatment layer, and a substrate A is formed. did. Then, a pair of polarizing plates was disposed on both sides of the liquid crystal cell to obtain a color liquid crystal display device of the present invention.

When each color was displayed using this liquid crystal display element,
As in Example 1, good color reproducibility was exhibited, and there was no dot shift even when viewed from an oblique direction.

〔The invention's effect〕

According to the invention of claim 1, since the optical phase plate made of a liquid crystalline polymer having a color filter is arranged inside the liquid crystal cell, full-color display and multi-color display are possible, and there is no dot shift, Moreover, a light and thin color liquid crystal display device can be provided.

Compared with the prior art, in the present invention, since the liquid crystal cell can be formed from one direction of the manufacturing process, the substrate does not need to be turned upside down and the productivity is improved. Further, even in the case of forming from the same direction, since no adhesive is used, it is possible to avoid such a disadvantage that light loss occurs due to reflection at the interface of the adhesive layer by the adhesive layer and the contrast is reduced.

The same side as the electrode of the liquid crystal cell substrate (outside between the electrodes)
Because there is a polymer liquid crystal layer, and an alignment film is arranged between the electrode and the liquid crystal instead of the polymer liquid crystal layer, the voltage applied to the liquid crystal does not drop, so there is no decrease in contrast,
A high quality color liquid crystal display device is provided.

According to the invention of claim 2, since the optical phase plate made of a colored liquid crystalline polymer is arranged inside the liquid crystal cell,
In addition to the effect of the first aspect, there is an advantage that the process can be simplified.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one configuration example of the color liquid crystal display device of the present invention. 1,11 ... Polarizing plate 2,10 ... Substrate 3,6,8 ... Orientation film 4 ... Liquid crystalline polymer layer 5,9 ... Electrode 7 ... Liquid crystal layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Haruo Iimura 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP 1-282519 (JP, A) JP A 63-149624 (JP, A) Japanese Utility Model 2-51381 (JP, U) Japanese Utility Model 2-45525 (JP, U)

Claims (2)

(57) [Claims] A liquid crystal cell comprising a pair of substrates, a liquid crystal layer, a liquid crystal polymer layer, an electrode for applying a voltage to the liquid crystal layer, and a color filter; In a color liquid crystal display device comprising a liquid crystal polymer layer and a color filter layer in contact with the liquid crystal polymer layer on the substrate via an alignment film layer, the alignment film layer, the liquid crystal layer and the alignment film A color liquid crystal display device comprising: a layer, an electrode layer, and a substrate, sequentially laminated, and a pair of polarizers provided at both ends of the substrate. 2. A pair of polarizers arranged so as to sandwich a liquid crystal cell comprising a pair of substrates, a liquid crystal layer, a liquid crystalline polymer layer, an electrode for applying a voltage to the liquid crystal layer, and a color filter. In a color liquid crystal display device consisting of, a color filter layer formed by mixing a dye or a pigment with a liquid crystalline polymer layer is provided on a substrate via an alignment film layer, and an alignment film layer is A color liquid crystal display device comprising a liquid crystal layer, an alignment film layer, an electrode layer, and a substrate sequentially laminated, and a pair of polarizers provided at both ends of the substrate.