JP2687035B2 - Manufacturing method of compensator for liquid crystal display element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a compensating plate for a liquid crystal display device, and further to a super twisted nematic (hereinafter abbreviated as STN).
The present invention relates to a method for manufacturing a color compensator for a liquid crystal display device.

(Prior Art and Problems to be Solved by the Invention) Liquid crystal displays occupy a large position in the display field because of their features such as low voltage driving, light weight, and low cost. Among them, the STN liquid crystal display can display a large screen by the multiplex drive dot matrix method, and has a high contrast and a wide viewing angle compared to the conventional twisted nematic (TN) type liquid crystal display. Widely used in the field of liquid crystal displays, such as word processors and various data terminals, which require large screen displays. However, in the STN method, since display is performed by the birefringence effect, coloring of yellow or blue was inevitable. Display in this coloring mode is not only unfavorable from the user's point of view, but also has a serious drawback that it cannot cope with colorization. In order to convert the coloring mode to the black and white mode, a so-called two-layer cell for compensating by arranging another compensation liquid crystal cell with the same cell gap and the twist angle reversed on the original STN liquid crystal cell for display. The method has been put to practical use. Although black-and-white display is certainly possible by using this method, on the other hand, the viewing angle is relatively narrow and the color is seen diagonally, and the manufacturing of compensation cells is difficult and the yield is low, and the manufacturing cost is very high. However, the liquid crystal cell is heavy and thick. In order to eliminate the drawbacks of the two-layer cell system, it has been proposed to realize a black-and-white display by replacing the compensating cell with a single film having the same optical performance (Japanese Patent Laid-Open No. 63-163). 149624).
In principle, if it is possible to produce a uniform film having the same birefringence characteristics as the display cell, the same thickness, the same pitch and the opposite twist structure, by laminating the film on the display cell, A black and white display can be realized. However, in reality, the production of such a film is extremely difficult, and in fact, there is no description in the above-cited patents about the structure of the film and the production method, and no examples are provided, demonstrating the difficulty of embodying this principle. There is. As a convenient method for avoiding this difficulty, realization of a compensating film such as a polycarbonate stretched film in which only the birefringence property is adjusted according to the display cell has been studied. However, the compensation effect of these films is insufficient,
Only a pseudo-black-and-white display of bluish white is obtained when no voltage is applied, and the contrast is considerably lower than that of the two-layer system. As described above, there is no example in which the STN liquid crystal display is completely converted to black and white using the film.

(Means for Solving the Problems) In order to overcome the above-mentioned difficulties relating to a STN liquid crystal display color compensation film, the present inventors have focused on a twisted nematic alignment-fixed polymer liquid crystal having a uniform monodomain structure. As a result of intensive studies, the present invention was finally reached. TECHNICAL FIELD The present invention relates to a method for producing a compensator for a liquid crystal display element, particularly, a compensator for an STN liquid crystal display having the following constitution having a film made of an alignment-fixed liquid crystalline polymer.

That is, the present invention provides an alignment film having the ability to align molecules parallel to an interface on a translucent substrate, twists nematic alignment in the liquid crystal state on the alignment film, and forms a glass state below the liquid crystal transition point. A helical structure in which the constituent molecules have a helical axis in the direction perpendicular to the substrate by applying a liquid crystalline polymer that becomes , The twist angle is in the range of 180 to 300 degrees, the product Δn · d of the birefringence (Δn) and the film thickness (d) is in the range of 0.5 μm to 2.0 μm, and the variation of Δn · d is The present invention relates to a method for producing a compensating plate for a liquid crystal display element, which comprises forming a liquid crystal polymer film having a width within a range of ± 2%.

 Hereinafter, the present invention will be described in detail.

The compensating plate of the present invention is a liquid crystal polymer that exhibits uniform and monodomain nematic alignment on an alignment film formed on a translucent substrate, and that the alignment state can be easily fixed to a liquid crystal polymer in a predetermined amount. A composition containing an active compound or a polymer liquid crystal exhibiting a uniform and monodomain twisted nematic alignment and capable of easily fixing the alignment state is applied, dried and heat treated to form a uniform and monodomain twisted nematic structure. After being formed, it is cooled and then fixed without impairing the alignment in the liquid crystal state.

First, the compensator using the former composition of a nematic liquid crystalline polymer and an optically active compound will be explained. A liquid crystallinity which shows a uniform and monodomain nematic alignment as a base and can easily fix the alignment state. It is essential that the polymer has the following properties. In order to stably fix the nematic orientation, it is important that the liquid crystal phase does not have a liquid crystal phase at a temperature lower than that of the nematic phase in view of the liquid crystal phase series. If these phases are present, they will inevitably pass through these phases when cooling for immobilization, resulting in destruction of the nematic orientation once obtained, resulting in unsatisfactory transparency and compensation effects. It becomes something like. Therefore, in order to manufacture the compensator of the present invention, it is essential to use a polymer liquid crystal having a glass phase at a temperature lower than the nematic phase. By adding an optically active compound to these polymers, a twisted nematic orientation is obtained in the liquid crystal state, and a glass phase is taken below the liquid crystal transition point, so that the twisted nematic structure can be easily fixed. As the type of polymer used, any polymer that is nematically aligned in a liquid crystal state and becomes a glass state at a liquid crystal transition point or lower can be used. For example, a main chain type liquid crystal polymer such as polyester, polyamide, polycarbonate, polyesterimide, or polyacrylate. Examples thereof include side-chain liquid crystal polymers such as polymethacrylate, polymalonate, and polysiloxane.
Among them, polyester is preferred from the viewpoint of ease of synthesis, transparency, orientation, glass transition point and the like. As the polyester used, a polymer containing an ortho-substituted aromatic unit as a constituent component is most preferable, but an aromatic having a bulky substituent in place of the ortho-substituted aromatic unit, or an aromatic having a fluorine or fluorine-containing substituent, or the like. Polymers containing as a component can also be used. The ortho-substituted aromatic unit referred to in the present invention means a structural unit in which a bond constituting a main chain is ortho-positioned to each other. Specific examples include the following catechol units, salicylic acid units, phthalic acid units, and those having a substituent on the benzene ring of these groups.

Etc. (X represents hydrogen, halogen such as C1 and Br, an alkyl group or an alkoxy group having 1 to 4 carbon atoms, or a phenyl group. K is 0 to 2.) Among them, particularly preferable examples are as follows. The following can be exemplified.

(Me; methyl group, Et; ethyl group, Bu; butyl group) The polyester used in the present invention includes (a) a structural unit derived from a diol (hereinafter referred to as a diol component) and a dicarboxylic acid. Structural unit (hereinafter referred to as dicarboxylic acid component) and /
Or (b) a structural unit derived from an oxycarboxylic acid containing a carboxylic acid and a hydroxyl group simultaneously in one unit (hereinafter referred to as an oxycarboxylic acid component) as a constituent component, and preferably further contains the ortho-substituted aromatic unit. Examples of the polymer include.

Among these, examples of the diol component include the following aromatic and aliphatic diols.

(Y represents hydrogen, halogen such as CI or Br, an alkyl group having 1 to 4 carbon atoms, or an alkoxy or phenyl group.
Is 0-2. ) —O— (CH ₂ ) _n —O— (n represents an integer of 2 to 12) Especially _{-O-CH 2 CH 2 -O -} , - O (CH 2) 4 O-, -O (CH _{2) 6} O-, etc. are preferably used.

The following can be exemplified as the dicarboxylic acid component.

(Z represents hydrogen, a halogen such as CI or Br, an alkyl group or an alkoxy group having 1 to 4 carbon atoms, or a phenyl group. M is 0 to 2), Above all, Are preferred.

Specific examples of the oxycarboxylic acid component include the following units.

The molar ratio of dicarboxylic acid to diol is approximately 1: 1 as in the case of general polyester (when oxycarboxylic acid is used, the ratio of carboxylic acid groups to hydroxyl groups). The ratio of ortho-substituted aromatic units in the polyester is usually preferably 5 mol% to 40 mol%, more preferably 10 mol% to 30% mol. If the amount is less than 5 mol%, a crystal phase tends to appear below the nematic phase, which is not preferable. If it is more than 40 mol%,
The polymer tends to lose its liquid crystallinity, which is not preferable. The following polymers can be exemplified as typical polyesters.

A polymer composed of structural units of A polymer composed of structural units of A polymer composed of structural units of A polymer composed of structural units of A polymer composed of structural units of A polymer composed of structural units of A polymer composed of structural units of A polymer composed of the structural units of

In place of the ortho-substituted aromatic unit, a polymer containing, as a constituent, an aromatic unit containing a bulky substituent or an aromatic unit containing a fluorine or fluorine-containing substituent as shown below is also preferably used.

The molecular weight of these polymers is such that the logarithmic viscosity measured at 30 ° C. in various solvents such as a phenol / tetrachloroethane (60/40 (weight ratio)) mixed solvent is usually 0.05 to 3.
0, more preferably in the range of 0.07 to 2.0. When the logarithmic viscosity is less than 0.05, the strength of the obtained polymer liquid crystal becomes weak, which is not preferable. On the other hand, if it is larger than 3.0, the viscosity at the time of liquid crystal formation is too high, causing problems such as a decrease in alignment and an increase in the time required for alignment. The glass transition point of these polyesters is also important and affects the stability of orientation after the orientation is fixed. Although it depends on the application, it is generally desirable that the glass transition point is 30 ° C. or higher, especially 50 ° C. or higher, when it is considered to be used near room temperature. When the glass transition point is lower than 30 ° C., the liquid crystal structure once immobilized may change when used near room temperature, and the function derived from the liquid crystal structure may deteriorate, which is not preferable.

The method for synthesizing these polymers is not particularly limited, and is synthesized by a polymerization method known in the art, for example, a melt polymerization method or an acid chloride method using a corresponding acid chloride of dicarboxylic acid. In the case of synthesis by a melt polymerization method, for example, an acetylated product of the corresponding dicarboxylic acid and the corresponding diol can be produced by polymerizing under a high temperature and a high vacuum, and the molecular weight can be easily controlled by controlling the polymerization time or controlling the charged composition. . In order to accelerate the polymerization reaction, a conventionally known metal salt such as sodium acetate can be used. When the solution polymerization method is used, a desired polyester can be easily obtained by dissolving a predetermined amount of dicarboxylic acid dichloride and diol in a melt and heating in the presence of an acid acceptor such as pyridine.

The optically active compound to be mixed to impart a twist to these nematic liquid crystalline polymers will be described. First, a typical example is an optically active low molecular weight compound. Any compound having optical activity can be used in the present invention, but an optically active liquid crystalline compound is desirable from the viewpoint of compatibility with the base polymer. Specifically, the following compounds can be exemplified.

Cholesterol derivatives, etc.

Next, examples of the optically active compound used in the present invention include an optically active polymer compound. Any polymer compound having an optically active group in the molecule can be used, but a polymer compound exhibiting liquid crystallinity is desirable from the viewpoint of compatibility with the base polymer.
Examples thereof include liquid crystal polyacrylates, polymethacrylates, polymalonates, polysiloxanes, polyesters, polyamides, polyesteramides, polymer bonates, or polypeptides and cellulose having an optically active group. Above all, an aromatic-based optically active polyester is most preferable because of its compatibility with the base nematic liquid crystalline polymer. Specifically, the following polymers can be exemplified.

A polymer composed of a structure of A polymer composed of structural units of A polymer composed of structural units of O (CH ₂ ) _n O (n = 2 to 12), A polymer composed of structural units of A polymer composed of structural units of OCH ₂ CH ₂ O, A polymer composed of structural units of A polymer composed of structural units of A polymer composed of structural units of A polymer composed of structural units of A polymer composed of structural units of A polymer composed of structural units of the following formula: The ratio of optically active groups in these polymers is
The amount is usually 0.5 mol% to 80 mol%, preferably 5% mol to 60 mol%.

The molecular weight of these polymers is, for example, phenol /
Logarithmic viscosity measured at 30 ° C in tetrachloroethane is 0.05
To 5.0 is preferred. If the logarithmic viscosity is greater than 5.0, the viscosity is too high, resulting in a decrease in the orientation, which is not preferred. If the logarithmic viscosity is less than 0.05, control of the composition becomes difficult, which is not preferred.

The liquid crystalline polymer composition used in the present invention has a twisted nematic orientation and a glass state at a temperature below the liquid crystal transition point is prepared by mixing a nematic liquid crystalline polyester and an optically active compound at a predetermined ratio by solid mixing. , Solution mixing or melt mixing. 180 degrees ~ 3
The ratio of the optically active compound in the composition required to give a twist angle of 00 degrees is the ratio of the optically active group in the optically active compound, or the twisting force when the nematic liquid crystal of the optically active compound is twisted. Generally, a range of 0.1 to 50 wt% is preferable, but a range of 0.5 to 50% is preferable.
A range of 30 wt% is preferred. If it is less than 0.1 wt%, the nematic liquid crystal cannot be given a twist angle of 180 degrees or more, and if it is more than 50 wt%, the twist angle becomes more than 300 degrees, and the orientation is adversely affected.

The compensator of the present invention can also be manufactured by using a polymer liquid crystal that can form a uniform, monodomain twisted nematic alignment by itself without using other optically active compounds, and that can easily fix the alignment state. . It is essential that these polymers have an optically active group in the structure and are themselves optically active. Specifically, the main chain type liquid crystal polymer such as optically active polyester, polyamide, polycarbonate, polyester imide, or polyacrylate. Examples thereof include side chain type liquid crystal polymers such as polymethacrylate and polysiloxane. Among them, polyester is preferred from the viewpoint of ease of synthesis, orientation, glass transition point and the like. As the polyester used, a polymer containing an ortho-substituted aromatic unit as a constituent component is most preferable, but an aromatic having a bulky substituent in place of the ortho-substituted aromatic unit, or an aromatic having a fluorine or fluorine-containing substituent, or the like. Polymers containing as a component can also be used. These optically active polyesters can be obtained by introducing the following optically active groups into the nematic liquid crystalline polyester described so far using an optically active diol, dicarboxylic acid or oxycarboxylic acid. (In the formula, * indicates optically active carbon) The proportion of the optically active group required to give a twist angle of 180 to 300 degrees in the polymer is 0.1 to 20 mol%.
Is preferable, and a range of 0.5 to 10 mol% is particularly preferable. If the ratio of optically active groups is less than 0.1%, the twist angle of 180 degrees or more required for this compensator cannot be obtained.
When it is more than 0 mol%, the twisting force is too strong, resulting in a twisting angle of more than 300 degrees, which lowers the compensation effect and is not preferable. The molecular weight of these polymers is preferably 0.05 to 3.0, more preferably 0.07 to 2.0, in logarithmic viscosity measured at 30 ° C. in various solvents such as phenol / tetrachloroethane (60/40) mixed solvent.
When the logarithmic viscosity is less than 0.05, the strength of the obtained polymer liquid crystal becomes weak, which is not preferable. On the other hand, if it is larger than 3.0, the viscosity at the time of forming the liquid crystal is too high, causing problems such as a decrease in alignment and an increase in the time required for alignment. The glass transition point of these polyesters is also important and affects the stability of orientation after the orientation is fixed. Depending on the application,
Generally, considering that the glass transition temperature is around room temperature, the glass transition point is preferably 30 ° C. or higher, and particularly preferably 50 ° C. or higher. If the glass transition temperature is lower than 30 ° C,
When used at around room temperature, the liquid crystal structure once fixed may change, and the function derived from the liquid crystal structure is undesirably reduced.

These polymers can be prepared by using the melt polycondensation method or the acid chloride method described above.

A compensator for a liquid crystal display device of the present invention comprises a translucent substrate, an alignment film formed on the translucent substrate, and a liquid crystal polymer film formed on the alignment film. The molecules that make up the liquid crystalline polymer film have a helical structure with a helical axis perpendicular to the substrate, and the twist angle is 180 to 3
00 degrees, preferably 190-280 degrees, more preferably 200-2
The product Δn · d of the birefringence (Δh) and the film pressure (d) of the film made of the liquid crystalline polymer is 0.5 to 2.0 μm, preferably 0.6 to 1.5 μ, more preferably 0.7 to 1.2. Within the range of μ, and the fluctuation range of Δn · d is ± 2%, preferably ±
It is 1.5%, more preferably ± 1.0%. Examples of the type of translucent substrate used include glass, translucent plastic film, and plastic sheet. As the glass, soda glass, silica-coated soda glass, borosilicate glass, or the like is used. The plastic substrate is preferably optically isotropic, and for example, polymethyl methacrylate, polystyrene, polycarbonate, polyether sulfone, polyphenylene sulfide, amorphous polyolefin or epoxy resin can be used. Among them, polymethyl methacrylate, polycarbonate, polyether sulfone, amorphous polyolefin and the like are preferably used. As the alignment film, a rubbed polyimide film is preferably used, but an alignment film known in the art, such as an obliquely deposited silicon oxide film and a rubbed polyvinyl alcohol film, can of course be used.

A compensating plate of the present invention is manufactured by forming a polymer liquid crystal layer having a compensating effect on the alignment film formed on the translucent substrate. When a composition composed of a nematic liquid crystalline polymer and an optically active compound is used, for example, in the case of solution mixing, both components are first dissolved in a solvent at a predetermined ratio to prepare a solution having a predetermined concentration. When an optically active polymer exhibiting twisted nematic orientation is used in place of the liquid crystalline polymer composition, it is dissolved alone in a predetermined solvent at a predetermined concentration to prepare a solution. The solvent at this time varies depending on the type of polymer, but usually chloroform, dichloroethane,
Halogenated hydrocarbons such as tetrachloroethane, trichloroethylene, tetrachloroethylene, orthodichlorobenzene, mixed solvents of these with phenol, dimethylformamide, dimethylacetamide, dimethylsulfoxide and the like can be used. The concentration of the solution varies greatly depending on the viscosity of the polymer, but is usually used in the range of 5 to 50%, preferably in the range of 10 to 30%.
This solution is then applied on a translucent glass plate, plastic plate or plastic film that has been subjected to an orientation treatment. The method of orientation treatment is not particularly limited,
Anything that aligns liquid crystal molecules parallel to the interface,
For example, polyimide rubbing-treated glass or film, which is obtained by applying polyimide on a substrate and rubbing it, is preferably used. As a coating method, a spin coating method, a roll coating method, a printing method, an immersion raising method, or the like can be adopted. After coating, the solvent is removed by drying, and the mixture is treated at a predetermined temperature for a predetermined time to complete a monodomain twisted nematic orientation. The lower the viscosity of the polymer is, the better the temperature is, in order to assist the orientation by the interfacial effect. Therefore, the higher the temperature, the better. However, if the temperature is too high, it increases the cost and deteriorates the workability. Further, depending on the type of the polymer, since the polymer has an isotropic phase at a higher temperature portion than the nematic phase, no orientation can be obtained by heat treatment in this temperature range.
According to the properties of the polymer as described above, it is preferable to perform heat treatment at a temperature equal to or higher than the glass transition point and equal to or lower than the transition point to the isotropic phase, and generally, the temperature is preferably in the range of 50 ° C. to 300 ° C. A range of from 0 to 250 ° C is preferred. The time required to obtain sufficient alignment in the liquid crystal state on the alignment film is different depending on the composition of the polymer and the molecular weight and cannot be generally determined, but is preferably in the range of 10 seconds to 100 minutes, and particularly 30 seconds to 30 minutes. Ranges are preferred. If it is shorter than 10 seconds, the orientation becomes insufficient, and if it is longer than 100 minutes, the transparency of the obtained compensator may be lowered. A similar orientation state can also be obtained by applying a polymer in a molten state on an oriented substrate and then performing a heat treatment. By performing these treatments using the liquid crystalline polymer of the present invention, first, a uniform twisted nematic alignment can be obtained over the entire surface of the alignment film in a liquid crystal state.

The alignment state thus obtained is then cooled to a temperature below the glass transition temperature of the liquid crystalline polymer, whereby the alignment can be fixed without any loss of alignment. Generally, when a polymer having a crystal phase in a lower temperature portion than a liquid crystal phase is used, the orientation in the liquid crystal state is broken by cooling. According to the method of the present invention, since the polymer system having the glass phase below the liquid crystal phase is used, such a phenomenon does not occur, and the twisted nematic alignment can be completely fixed.

There is no particular limitation on the cooling rate, and the cooling rate is fixed only by taking out from the heating atmosphere into an atmosphere below the glass transition point. In order to increase production efficiency, forced cooling such as air cooling or water cooling may be performed. The film thickness after immobilization is 0.1 μm to 100 μm
Is preferable, and a range from 0.5 μm to 50 μm is particularly preferable. Since Δn of the compensation layer is determined by the type of polymer liquid crystal used, the value of Δn · d should be 0.5 μm to 2.0 μm.
In order to control to μm, it is important to select the film thickness d as well as the type of polymer liquid crystal used. Film thickness is 0.1 μm
If it is smaller, the required twist angle and Δn · d cannot be obtained, and if it exceeds 100 μm, the required twist angle and Δn are also required.
Since n · d cannot be obtained, the effect of orientation becomes weak, and it becomes difficult to obtain uniform orientation.

By applying these coating, drying, heat treatment and cooling methods, it is possible to manufacture a compensating plate having a compensating layer in which the fluctuation range of the film thickness value is within ± 2%. The feature of the present invention is that, as described above, only one surface of the film is in contact with the alignment film to control the alignment, and the other surface is in a free state, for example, in the state in which it is in contact with an air phase, and a high degree of alignment control and its fixing are performed. That can be done. That is, in the present invention, the "free state" refers to a state in which there is no solid surface adhered to one surface. In general, liquid crystal alignment is normally controlled by bringing both interfaces into contact with an alignment film. When one surface is in the air phase, the molecular alignment at the air interface is not uniform, and due to the influence, the entire surface in the film thickness direction is affected. Uniform orientation cannot be obtained. In the case of the present invention, the twisted nematic orientation of the monodomain can be achieved by controlling only one side,
Further, it has a great feature that it can be fixed.

In order for the compensator of the present invention to exert a sufficient compensating effect and obtain a high quality black and white display, it is important to strictly control the optical parameters of the layer (compensation layer) composed of the polymer liquid crystal film. The molecules that make up the layer form a helical structure with a helical axis perpendicular to the substrate, and the twist angle is 180 degrees to 3 degrees.
In the range of 00 degrees, the product Δn · d of the birefringence Δn of the film made of the liquid crystalline polymer and the film thickness d is in the range of 0.5 μm to 2.0 μm, and the fluctuation range of the value of Δn · d is ±. It must be in the range of 2%.

If the values of the twist angle and Δn · d are not within this range, the desired color compensation effect is insufficient and satisfactory black and white display cannot be obtained. Further, when the fluctuation range of the value of Δn · d is larger than the range of ± 2%, uneven display is noticeable and unsightly, and only low quality black and white display is obtained.

The molecules constituting the compensation layer have a helical structure having a helical axis in a direction perpendicular to the substrate, and have a required twist angle and Δ
In order to have n · d, a composition obtained by blending a polymer liquid crystal based on the above-mentioned amount of the optically active compound on an alignment film having the ability to orient molecules parallel to the above-mentioned substrate, or the above-mentioned ratio. The polymer liquid crystal having the optically active group of 1) in the molecule may be oriented and fixed by the above method to have a predetermined film thickness.

The compensator thus obtained may be used as it is, or may be provided with a transparent plastic protective layer for surface protection. Further, it may be used in combination with another optical element such as a polarizing plate.

As described above, the display element compensator manufactured by the manufacturing method of the present invention, especially the STN liquid crystal display color compensator, not only enables complete black and white display by one compensator, Contributes to thinner and lighter
It is of great industrial value.

(Examples) Examples will be described below, but the present invention is not limited thereto. In addition, each analysis method used in the Example is as follows.

(1) Determination of polymer composition The polymer was dissolved in deuterated chloroform or deuterated trifluoroacetic acid and subjected to 400 MHz ¹ H-NMR (JEOL J
NM-GX400).

(2) Measurement of logarithmic viscosity Using an Ubbelohde viscometer, the viscosity was measured in a mixed solvent of phenol / tetrachloroethane (60/40 weight ratio) at 30 ° C.

(3) Determination of liquid crystal phase series It was determined by DSC (Dupont Thermal Analizer) measurement and observation with an optical microscope (BH2 polarization microscope manufactured by Olympus Optical Co., Ltd.).

(4) Determination of Twist Angle and Δn · d The twist angle was determined by ellipsometry, and Δn · d was determined by analyzing and processing data measured by an ellipsometer.

Example 1 60 mmol of terephthalic acid, 30 mmol of methylhydroquinone diacetate, 30 mmol of catechol diacetate and 80 mg of sodium acetate were used in a nitrogen atmosphere at 150 ° C. for 1 hour, 200 ° C. for 1 hour, and 250 ° C. for 1 hour in a stepwise manner. Polymerization was performed while raising the temperature. Then, the polymerization was continued at 250 ° C. for 2 hours while flowing a nitrogen gas, and the polymerization was further performed at the same temperature for 1 hour under reduced pressure. Next, the obtained polymer was dissolved in tetrachloroethane and then reprecipitated with methanol to obtain 10.5 g of a purified polymer having the properties shown in Table 1.

A 15 wt% tetrachloroethane solution containing this polyester and the optically active polyester represented by the following formula in a weight ratio of 95: 5 was prepared.

η in h = 0.15 (The numbers outside [] indicate the molar composition ratio.) Using this solution, the size is 15 cm × 23 cm and the thickness is 1.1 m.
On the glass of m, on a glass substrate having a rubbing-treated polyimide layer, the polymer solution was applied by screen printing, dried and then heat treated at 200 ° C. for 20 minutes and cooled,
A compensating plate having a twisted nematic structure and a compensating layer having a thickness of 3.6 μm and a fluctuation range of the film thickness of ± 1% was prepared. The twist angle of this compensator was -230 °, and Δn · d was 0.83 μm. According to the arrangement shown in FIG. 1 using this compensator,
The twist angle was 230 °, Δn · d was 0.87 μm, and the stack was laminated on the upper surface of a multiplex drive STN liquid crystal cell with a duty ratio of 1/200, and a polarizing plate was attached on the cell to fabricate the cell. The directions of the upper and lower polarizing plates, the rubbing direction of the upper and lower electrode substrates, and the orientation directions of the molecules of the compensating plate at this time are as shown in FIG. The angle between the polarization axes of the upper and lower polarizing plates is 90 °, the angle between the rubbing direction of the lower polarizing plate and the lower electrode substrate is 45 °, and the angle between the rubbing direction of the upper electrode substrate and the compensating plate is 90 °. The angle formed by the orientation direction of molecules on the surface in contact with the upper polarizing plate and the transmission axis of the upper polarizing plate is 45 °. The display of this liquid crystal cell was almost complete black and white display, and almost no color unevenness was observed.

Examples 2 to 8 and Examples 11 and 12 Polyesters having the properties shown in Table 1 were synthesized by using the melt polycondensation method or the acid chloride method. Using the polymer, the optically active compound and the composition ratio shown in Table 2 were used to prepare a compensating plate on each substrate in Table 2. The heat treatment conditions for producing the compensator were as shown in Table 3. Table 3 shows the values of the twist angle, Δn · d, and Δn · d fluctuation width of the obtained compensating plate. Using these compensating plates, they were laminated on STN liquid crystal cells suitable for each optical parameter, and the color compensating effect of the compensating plates was observed. All the compensating plates of the examples showed a sufficient compensating effect, and almost perfect black and white display without color unevenness was obtained.

Example 9 35 mmol of terephthalic acid dichloride, 25 mmol of methylhydroquinone, 25 mmol of catechol, (S) -2-methyl-1,
A solution of 1.4 mmol of 4-butadiol and 35 ml of pyridine in 300 ml of orthodichlorobenzene was polymerized at 70 ° C. for 3.0 hours under a nitrogen stream. Next, the reaction solution was passed, and then poured into methanol to precipitate a polymer, followed by drying under reduced pressure to synthesize a polyester having the properties shown in Table 1. The yield was 9.0 g.

Using this optically active polyester, a compensator was prepared in the same manner as in Example 1 and its compensating performance was examined. As a result, a substantially perfect black and white display without unevenness was obtained.

Example 10 4,4'-biphenyldicarboxylic acid dichloride 25mmo
l, methylhydroquinone 18 mmol, catechol 18 mmol,
(S) -3-methyl-1,6-hexanediol 0.68 mmol
A solution of pyridine and 30 ml of pyridine in 250 ml of orthodichlorobenzene was polymerized at 70 ° C. for 3 hours under a nitrogen stream. Next, the reaction solution was passed, and then poured into methanol to precipitate a polymer, followed by drying under reduced pressure to synthesize a polyester having the properties shown in Table 1. The yield was 8.2 g.

Using this optically active polyester, Example 1 and a compensator were prepared. When the liquid crystal cell was set in the same manner as in Example 1 and the performance was examined, almost uniform black and white display without unevenness was obtained.

Comparative Example 1 40 mmol terephthalic acid dichloride, 20 mm hydroquinone
A solution of ol, 2-methyl-1,4-butanediol (20 mmol) and pyridine (25 ml) in 200 ml of orthodichlorobenzene was polymerized at 70 ° C. for 3 hours under a nitrogen stream. Next, the reaction solution was passed, and then poured into methanol to precipitate a polymer, followed by drying under reduced pressure to synthesize a polyester having the properties shown in Table 1. A 20 wt% dimethylacetamide solution was prepared using a composition containing this polyester and the optically active polyester used in Example 8 in a ratio of 97: 3, and the heat treatment was performed at 200 ° C. for 10 minutes, and the same procedure as in Example 1 was performed. Then, a compensator was prepared and the compensating effect was examined by laminating it on a liquid crystal cell. As a result of observation with a polarization microscope, the twisted nematic orientation of the polydomain was fixed. The compensating effect of this compensator was very imperfect, and although there were some black and white parts, the color unevenness was severe and it was not practical.

(Advantages of the Invention) The compensator of the present invention not only provides high-quality black and white display with extremely little color unevenness, but also has a simple structure using only one translucent substrate.
N Helps to make LCDs thinner and lighter, and has extremely high industrial value.

[Brief description of the drawings]

FIG. 1 is a sectional view of a liquid crystal cell used in an embodiment of the present invention. FIG. 2 shows the mutual relationship of each axis of the material constituting the liquid crystal cell used in the embodiment of the present invention. 1 ... Liquid crystal cell with compensation plate of Example 1 ... Upper polarizing plate 3 ... Polymer liquid crystal layer (compensation layer) 4 ... Substrate glass 5 ... Liquid crystal cell 6 ... Lower polarizing plate 7 ... Lower polarized light Plate transmission axis 8 ...... Upper polarizing plate transmission axis 9 ...... Lower electrode substrate rubbing direction 10 ...... Upper electrode substrate rubbing direction 11 …… Compensation plate substrate rubbing direction 12 …… Molecular on the surface of the compensation layer that contacts the upper polarizing plate Orientation direction of 13 ... Liquid crystal cell molecule twist angle 14 ... Compensation layer molecule twist angle 15 ... Angle between 7 and 9 16 ... Angle between 10 and 11 17 ... Angle between 7 and 8

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Ito 8 Chidori-cho, Naka-ku, Yokohama-shi, Kanagawa Japan Central Petroleum Research Institute (72) Inventor Yasuyuki Takiguchi 1-3-6 Nakamagome, Ota-ku, Tokyo No. In stock company Ricoh Co., Ltd. (72) Inventor Akihiko Kanemoto 1-3-6 Nakamagome, Ota-ku, Tokyo In-house company Ricoh Co. (72) Haruo Iimura 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (56) Reference JP-A-3-87720 (JP, A) JP-A 64-519 (JP, A)

Claims (1)

(57) [Claims] 1. An alignment film having the ability to align molecules parallel to an interface is provided on a translucent substrate, and twisted nematic alignment in the liquid crystal state and glass state below the liquid crystal transition point are provided on the alignment film. By applying a liquid crystalline polymer, the surface of which is not in contact with the alignment film is freed, heat treatment is performed to align it, and then cooled to form a helical structure in which the constituent molecule has a helical axis in the direction perpendicular to the substrate. None, its twist angle is 180
Is in the range of 300 to 300 degrees, the product of birefringence (Δn) and film thickness (d) Δn · d is in the range of 0.5μm to 2.0μm, and the fluctuation range of Δn · d is ± 2%. A method of manufacturing a compensator for a liquid crystal display device, which comprises forming a liquid crystal polymer film.