JP2592701B2 - Compensator for liquid crystal display element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a compensator for a liquid crystal display device, and more particularly to a color compensator for a super twisted nematic (hereinafter abbreviated as STN) 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 due to their features such as low voltage drive, light weight, and low cost. Large-screen display is possible with a matrix method. It has features such as higher contrast and wider viewing angle than conventional twisted nematic (TN) liquid crystal displays. Are widely used in the field of liquid crystal displays that require 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. The so-called double STN method, in which another compensation liquid crystal cell with the same cell gap and a reversed twist angle is arranged above the original display STN liquid crystal cell to convert the coloring mode to the black and white mode. Has been put to practical use. However, this method has serious drawbacks in that it is difficult to manufacture a compensating cell and the yield is low, and the liquid crystal cell is made thick and heavy. The present inventors have previously found and proposed that this compensating cell can be replaced by a single compensating plate having a layer of a polymer liquid crystal film having a twisted nematic liquid crystal structure fixed on a light-transmitting substrate. 1-150559). Although this compensator realized high-contrast, high-quality black-and-white display with high contrast, even when the optimum voltage for obtaining the optimum display state was applied to the liquid crystal cell, the color tone of white display was not completely achromatic. There was a problem of very slight color change.

(Means for Solving the Problems) The present inventors have paid close attention to the fact that this coloring is caused by the fact that the transmission spectrum of the liquid crystal cell equipped with the polymer liquid crystal compensator when the selection voltage is applied is not flat, and has been diligently studied. Finally, the present invention has been achieved. An object of the present invention is to provide a compensating plate for a liquid crystal display element, which uses a film having a twisted nematic structure fixed thereon, and has remarkably excellent white display properties.

That is, the present invention provides a light-transmitting substrate, an alignment film formed on the substrate, and a liquid crystal material formed on the alignment film, which is twisted nematically aligned in a liquid crystal state and becomes a glassy state at or below a liquid crystal transition point. The present invention relates to a compensator for a liquid crystal display element, which is constituted by a film made of a polymer and has a dye in the film made of a liquid crystalline polymer.

 Next, the present invention will be described in detail.

FIG. 1 shows a twist angle of 230 ° and a Δn · d (Δn: birefringence, d: thickness) of 0.87 μm equipped with a compensator having a twisted nematic structure made of a polymer liquid crystal containing no dye and fixed.
Thus, the transmission spectrum of a 1/200 duty multibrex drive STN liquid crystal cell was shown. The spectrum 1a is when a selection voltage is applied, and the spectrum 1b is when a non-selection voltage is applied.
The spectrum at the time of non-selection application is flat and black, but the spectrum at the time of selection voltage application is not flat, so that the white display has a slightly bluish yellowish color.
The compensator of the present invention is manufactured by fixing a twisted netic structure using a polymer liquid crystal containing a pigment having a complementary color relationship with the color slightly generated during white display. As a result, the spectrum when the selection voltage is applied is flattened, and more complete white display is achieved.

The compensator of the present invention shows a uniform monodomain twisted nematic alignment, and a liquid crystal polymer capable of easily fixing the alignment state, a composition obtained by adding a predetermined amount of a dye to an alignment film. It is manufactured by heat treatment, forming a uniform, monodomain twisted nematic structure, and then cooling, thereby fixing the alignment in the liquid crystal state without impairing it.

It is essential that the liquid crystalline polymer serving as a base has the following properties. In order to stably fix the twisted nematic alignment, it is important that the crystal has no crystal phase in a lower temperature part than the nematic phase when viewed from the liquid crystal phase series. If these phases are present, they will inevitably pass through these phases when cooled for immobilization, resulting in the destruction of the nematic orientation once obtained.
Therefore, the liquid crystalline polymer used for this purpose is
In addition to having good orientation due to the interface effect, it is essential to have a glass phase at a lower temperature than the twisted nematic phase. Twisted nematic liquid crystal polymers include polymers that have optically active groups themselves and polymers that do not have optically active groups themselves and exhibit twisted nematic liquid crystallinity when mixed with other optically active compounds. is there.

As the polymer to be used, all those which are twisted nematic in the liquid crystal state and are in the glass state below the liquid crystal transition point can be used, for example, main chain type liquid crystal polymers such as optically active polyester, polyamide, polycarbonate, and polyesterimide, or Examples thereof include side-chain liquid crystal polymers such as polyacrylate, polymethacrylate, polymatonate, and polysiloxane. In addition, non-optically active main chain type liquid crystal polymers such as polyester polyamide, polycarbonate and polyesterimide, or side chain type liquid crystal polymers such as polyacrylate, polymethacrylate, polymalonate, polysiloxane, etc., and other optically active compounds, etc. Can be exemplified. 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. 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.

(X represents hydrogen, halogen such as Cl or Br, an alkyl group or an alkoxy group having 1 to 4 carbon atoms or a phenyl group, and k is 0 to 2.) Among these, particularly preferred examples are Can be exemplified.

Me; methyl group, Et; ethyl group, Ba; butyl group The polyesters preferably used in the present invention include: (a) a structural unit derived from a diol (hereinafter referred to as a diol component) and a structure derived from a dicarboxylic acid. Units (hereinafter referred to as dicarboxylic acid components) and / or
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 fatty acid 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—, And the like 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 polyesters (when oxycarboxylic acid is used, the ratio of carboxylic acid groups to hydroxyl groups). The proportion of the ortho-substituted aromatic unit in the polyester is usually preferably in the range of 5 mol% to 40 mol%, more preferably in the range of 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 exhibit no 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 fixed may change when used near room temperature, and the function derived from the liquid crystal structure is undesirably reduced.

The method for synthesizing these polyesters is not particularly limited, and they are 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. When synthesized 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 high temperature and high vacuum, and the molecular weight can be easily controlled by controlling the control of the polymerization time or the charge 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.

As the optically active compound used in the present invention, such as a cholesterol derivative, the following optically active polymer compounds can be mentioned. 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 crystalline polyacrylates, polymethacrylates, polymalonates, polysiloxanes, polyesters, polyamides, polyesteramides, polycarbonates, polypeptides, and celluloses 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
Usually 0.5 mol% to 80 mol%, preferably 5 mol%
~ 60 mol% is desirable.

Further, the molecular weight of these polymers is preferably such that the logarithmic viscosity measured at 30 ° C. in phenol / tetrachloroethane is in the range of 0.05 to 5.0. 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, composition control becomes difficult, which is not preferred.

The liquid crystalline polymer of the present invention, which has a twisted nematic alignment in a liquid crystal state and becomes a glassy state at a temperature equal to or lower than a 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 and solution mixing Alternatively, it can be performed by a method such as melt mixing. The proportion of the optically active compound in the composition varies depending on the ratio of the optically active group in the optically active compound or the torsional force of the optically active compound when the nematic liquid crystal is twisted. A range of 50 wt% is preferred, especially 0.5 to 30
A range of wt% is preferred. If the amount is less than 0.1 wt%, sufficient twist cannot be given to the nematic liquid crystal, and
If it is more than 50 wt%, the orientation is adversely affected.

The compensator of the present invention can also be manufactured by using a liquid crystalline polymer 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 can. It is essential that these polymers have an optically active group in the main chain and are themselves optically active.Specifically, optically active polyesters, polyamides, polycarbonates, main chain type liquid crystal polymers such as polyesterimide, or Examples thereof include side-chain type liquid crystal polymers such as polyacrylate, polymethacrylate, and ponosiloxane. 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) Such.

The ratio of these optically active groups in the polymer is 0.
It is preferably in the range of 1 to 20 mol%, especially 0.5 to 10 mol%
Is preferable. If the ratio of the optically active group is less than 0.1%, the twist structure required for the compensator cannot be obtained, and
If the amount is more than 20 mol%, the torsional force is too strong and the compensation effect is lowered, which is not preferable. The molecular weight of these polymers is such that the logarithmic viscosity measured at 30 ° C. in various solvents, for example, in a phenol / tetrachloroethane (60/40) mixed solvent is 0.0
It is preferably from 5 to 3.0, more preferably from 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 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. Although it depends on the application, it is generally considered to be used near room temperature.
The glass transition point is desirably 30 ° C. or higher, especially 50 ° C.
It is desirable that the temperature is not less than ° C. When the glass transition point is lower than 30 ° C., the liquid crystal structure once fixed may change when used near room temperature, and the function derived from the liquid crystal structure is undesirably reduced.

These polyesters can be produced by using the above-mentioned melt polycondensation method or acid chloride method.

As typical examples of the liquid crystalline polymer of the present invention described above, specifically, Ch; a polymer represented by a cholesteryl group (m / n = 99.5 / 0.5
~ 90/10, preferably 99/1 ~ 95/5) (M / n = 99.5 / 0.5 to 90/10, preferably 99/1 to 95/5) (M / n = 99.5 / 0.5 to 90/10, preferably 99/1 to 95/5, p, q; an integer of 2 to 20) (M / n = 99.5 / 0.5 to 90/10, preferably 99/1 to 95/5, p, q; an integer of 2 to 20) (M / n = 99.5 / 0.5 to 90/10, preferably 99/1 to 95/5) (M / n = 0.5 / 99.5 to 10/90, preferably 1/99 to 5/95) (K = 1 + m + n, k / n = 99.5 / 0.5)
~ 90/10, preferably 99/1 ~ 95/5, l / m = 5/95 ~ 95/5) (K ÷ l + m + n, k / n = 99.5 / 0.5)
~ 90/10, preferably 99/1 ~ 95/5, l / m = 5/95 ~ 95/5) (A) / (B) = 99.5 / 0.5
8585/5 (weight ratio), preferably 99/1 to 95/5, k = 1 +
m, 1 / m = 75 / 25-25 / 75, p = q + r, p / q = 80 / 20-2
0/80) (B) a polymer mixture represented by cholesteryl benzoate ((A) / (B) = 99.5 / 0.5)
~ 80/20 (weight ratio), preferably 99/1 ~ 90/10, m = k +
l, k / l = 80/20-20/80) (A) / (B) = 99.5 / 0.5
~ 80/20, preferably 99/1 to 90/10, k = l + m, l / m
= 25/75 to 75/25, p = q + r, q / r = 20/80 to 80/20) (* indicates optically active carbon).

The molecular weight of these polymers is such that the logarithmic viscosity measured at 30 ° C. in various solvents such as tetrahydrofuran, acetone, cyclohexanone, phenol / tatrachloroethane (60/40) mixed solvent is 0.05 to 3.0, more preferably 0.07 to 3.0. 2.0 range. 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.

Further, any dye may be used as long as it can absorb the peak of the spectrum at the time of applying the selection voltage illustrated in FIG. 1 and flatten the spectrum. That is, any colorant having a complementary color relationship with the color of the cell in this state can be used. Generally, dichroic dyes are preferably used, for example, dyes such as dialkylazobenzene, bisazobenzene, phenylazothiazole, phenylazobenzothiazole, azobenzene, nitrothiazole, aminoanthraquinone, and merocyanine dyes. It is preferably used. The amount of these additives is usually preferably in the range of 0.01 to 0.5 wt% with respect to the polymer, and particularly preferably 0.0 to 0.5 wt%.
A range of 3 to 0.2 wt% is preferred. When the addition amount is less than 0.01%, the effect of flattening the spectrum cannot be sufficiently obtained, and when the addition amount is more than 0.5%, the color of the dye itself becomes strong, and the white display tends not to be obtained. There is.

The compensator of the present invention basically has a laminated structure of a light-transmitting substrate, an alignment film formed on the light-transmitting substrate, and a liquid crystalline polymer film formed on the alignment film. As the light-transmitting substrate, glass, a light-transmitting plastic film, a plastic sheet, or the like can be used. Of these, the plastic substrate is preferably optically isotropic,
For example, polymethyl methacrylate, polystyrene, polycarbonate, polyether sulfone, polyphenylene sulfide, polyolefin, epoxy resin, or the like can be used. A rubbed polyimide film is preferably used as the alignment film.
Oriented films known in the art, such as obliquely deposited silicon dioxide films and rubbed films of polyvinyl alcohol, 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.

A solution is prepared by dissolving a twisted nematic liquid crystalline polymer and a dye in a solvent at a predetermined ratio. The solvent at this time varies depending on the type of the polymer and the dye, but usually, ketones such as acetone, methyl ethyl ketone and cyclohexanone, ethers such as tetrahydrofuran and dioxane, and halogens such as chloroform, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene and orthodichlorobenzene. Hydrocarbons, 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 the alignment treatment is not particularly limited, but any method may be used as long as the liquid crystal molecules are aligned in parallel with the interface.For example, a polyimide rubbed glass or film obtained by applying polyimide on a substrate and rubbing is suitable. Used for

As a coating method, a spin coating method, a roll coating method, a printing method, an immersion pulling method and the like can be adopted. After the application, the solvent is removed by drying, and heat treatment is performed at a predetermined temperature for a predetermined time to complete a monodomain twisted nematic alignment. 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. Also, depending on the type of polymer,
Since it has an isotropic phase at a higher temperature part than the nematic phase, no orientation can be obtained even if heat treatment is performed in this temperature range. According to the properties of the polymer as described above, it is preferable to heat-treat at a temperature equal to or higher than the glass transition point and equal to or lower than the transition point to an isotropic phase,
Generally, the range of 50 ° C. to 300 ° C. is preferable, and the range of 100 ° C. to 250 ° C. is particularly preferable. The time required to obtain sufficient alignment in the liquid crystal state on the alignment film is different depending on the composition and molecular weight of the polymer and cannot be unconditionally determined, but is preferably in the range of 10 seconds to 60 minutes, particularly 30 seconds to 30 minutes. A range is preferred. When the time is shorter than 10 seconds, the orientation becomes insufficient, and when the time is longer than 60 minutes, the productivity is lowered, which is not preferable. 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. At this time, the twist angle or the direction of the twist is
It can be adjusted by adjusting the ratio of the optically active units in the polymer or the amount of the optically active compound to be mixed.

By cooling the thus obtained alignment state to a temperature equal to or lower than the glass transition point of the liquid crystalline polymer containing the dye, the alignment state can be fixed without impairing the alignment at all. 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 a polymer system having a glass phase below a 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 thickness of the film after immobilization is preferably up to 100 μm, particularly preferably up to 50 μm. When the film thickness exceeds 100 μm, the effect of the alignment film is weakened, and it is difficult to obtain uniform alignment.

The compensator thus obtained may be used as it is, or may be provided with a transparent plastic protective layer for surface protection. Two or more compensating plates can be used. Further, it may be used in combination with another optical element such as a polarizing plate. As described above, the display element compensator produced by the production method of the present invention, in particular, a color compensator for an STN liquid crystal display not only enables monochrome display with excellent white display quality, but also is light and thin. . Further, since the production cost is low and the productivity is high, it is of great industrial value.

(Examples) Examples will be described below, but the present invention is not limited thereto.

Example 1 General formula (The number in parentheses indicates the molar composition ratio) 97% by weight of polyester represented by the following general formula: 3% by weight of a polyester having an optically active group represented by

For mixed polymer (logarithmic viscosity of base polymer 0.15, logarithmic viscosity of optically active polymer 0.13) and polymer
A 15 wt% phenol / tetrachloroethane (60/40 weight ratio) solution containing 0.1 wt% red dye G202 was prepared. Using this solution, on a glass plate having a rubbed polyimide layer having a size of 15 cm × 23 cm and a thickness of 0.1 cm,
Cast using a screen printing machine, and then dry.
A heat treatment was performed at 0 ° C. for 30 minutes, and then cooled and fixed. The twist angle of this compensator was -230 °, and Δn · d was 0.84 μm.

The compensator thus produced was placed on the top surface of an STN liquid crystal cell having a twist angle of 230 ° and a Δn · d of 0.87 μm for a multiplex drive with a 1/200 duty ratio according to the position shown in FIG. A polarizing plate was pasted on to prepare a liquid crystal cell. At this time, the directions of the upper and lower polarizers, the rubbing directions of the upper and lower electrode substrates, and the orientation directions of the molecules of the compensator are as shown in FIG. The angle between the polarization axes of the upper and lower polarizers is 90
角度, the angle between the rubbing direction of the lower polarizer and the lower electrode substrate is
45 °, the angle between the rubbing direction of the upper electrode substrate and the rubbing direction of the compensator is 90 °, and the angle between the orientation direction of the molecule of the surface in contact with the upper polarizer and the transmission axis of the upper polarizer is 45 °. .

The spectrum when this liquid crystal cell selection voltage is applied is shown in FIG. 4 (18a). The spectrum of the same arrangement of liquid crystal cells using a compensator manufactured in exactly the same manner without adding a dye (18b) As compared with the case, the spectrum when the selection voltage was applied was flat, and the white display which was closer to an achromatic color was obtained in the actual display.

Example 2 General formula Ch; polymer represented by cholesteryl group (numbers in brackets [] indicate molar composition ratio) Spin coating method using dimethylformamide solution containing 20 wt% and 0.08 wt% merocyanine red dye based on polymer , And heat-treated at 100 ° C. for 20 minutes, and then cooled to produce a polymer liquid crystal compensator having a twisted nematic structure fixed. The helix angle is -231 °,
Δn · d was 0.83 μm. Using this compensator, the transmission spectrum was examined in the same STN liquid crystal cell and arrangement as in Example 1. As a result, the spectrum was flattened compared to the case where no dye was used, and the actual display color was also close to achromatic. A white display was obtained.

(Effect of the Invention) The compensator of the present invention can provide a nearly achromatic white display by a simple method of adding a small amount of a dye, and is easy to manufacture with a simple structure using only one translucent substrate. This is useful for reducing the thickness and weight of the liquid crystal display, and is of great industrial value.

[Brief description of the drawings]

FIG. 1 shows a transmission spectrum of a liquid crystal cell equipped with a polymer liquid crystal compensator to which no dye is added. FIG. 2 is a sectional view of a liquid crystal cell used in the embodiment of the present invention. FIG. 3 shows the mutual relationship of each axis of the material constituting the liquid crystal cell used in the embodiment of the present invention. FIG. 4 shows a transmission spectrum of a liquid crystal cell equipped with a polymer liquid crystal compensator to which the dye of the present invention is added. 1b: When a non-selection voltage is applied 2: Upper polarizing plate 3: Polymer liquid crystal layer (compensation layer) 4: Substrate glass 5: Liquid crystal cell 6: Lower polarizing plate 7: Lower polarizing plate transmission axis 8 ... transmission axis of upper polarizing plate 9 ... rubbing direction of lower electrode substrate 10 ... rubbing direction of upper electrode substrate 11 ... rubbing direction of compensator substrate 12 ... orientation direction of molecules on the surface of compensation layer in contact with upper polarizer 13 ... twist angle of liquid crystal cell molecules 14 ... twist angle of molecules of compensation layer 15 ... angle between 7 and 9 16 ... angle between 10 and 11 17 ... angle between 7 and 8 18a ... dye 18b …… When no dye is added.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroyuki Ito 8 Chidori-cho, Naka-ku, Yokohama-shi, Kanagawa Japan Inside the Central Research Laboratory of Petroleum Corporation (72) Inventor Yasuyuki Takiguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Akihiko Kanemoto 1-3-6 Nakamagome, Ota-ku, Tokyo Incorporation Ricoh Co., Ltd. (72) Haruo Iimura 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (56) References JP-A-52-2541 (JP, A) JP-A-62-232409 (JP, A) JP-A-64-519 (JP, A) JP-A-2-47625 ( JP, A)

Claims (1)

(57) [Claims] 1. A translucent substrate, an alignment film formed on the substrate, and a liquid crystal material formed on the alignment film, which is twisted nematic in a liquid crystal state and has a glassy state below a liquid crystal transition point. A compensator for a liquid crystal display element, comprising a film made of molecules, and containing a dye in the film made of the liquid crystalline polymer.