JPH10170908A - Optical element and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the contrast ratio and to widen the visual field angle, by laminating a first polymer liquid crystal layer (polarizing plate) and a second polymer liquid crystal layer (perpendicularly oriented layer) on a light- transmissible substrate, and varying the liquid crystal phase development temps. of this first polymer liquid crystal layer and this second polymer liquid crystal layer by a specific value or above. SOLUTION: An STN liquid crystal cell 2 is oriented by a right-hand twist from 0 deg. to -240 deg. and a film having the perpendicularly oriented layer 3 is stuck onto the substrate of this STN liquid crystal cell 2. A film having a twisted nematic oriented layer 4 is stuck onto the perpendicularly oriented layer 3. The liquid crystalline high polymer of the twisted nematic oriented layer 4 is deflected by a left-hand twist from 30 deg. to 270 deg.. The polarizing plate 5 is stuck onto the twisted nematic oriented layer 4. The polarizing plate 1 is stuck to the side opposite to the side of the STN liquid crystal cell 2 where the perpendicularly oriented layers 3 are disposed. The liquid crystal phase development temps. of the polarizing plate 1 and the perpendicularly oriented layers 3 are varied by >=10 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element suitable for use in, for example, compensating a phase difference in a liquid crystal display device and a method of manufacturing the same. The present invention relates to an optical element formed by laminating molecular liquid crystal layers and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, in various OA devices such as personal computers, opportunities to handle images having a large amount of information have been increasing. For this reason, demands for high resolution and full color display are increasing in display devices, and the same is true for liquid crystal displays.

However, since the STN (Super Twisted Nematic) liquid crystal display device is a display system using a birefringent mode, color compensation must be performed by compensating for a phase difference. In addition, since liquid crystal is used, there is a strong demand for an increase in the viewing angle.

By the way, the above-mentioned phase difference compensation method includes:
A method has been proposed in which a film obtained by uniaxially stretching a resin film is used in combination with an STN liquid crystal display device (JP-A-63-149624).

However, in a retardation compensation film using a uniaxially stretched film, the retardation of a liquid crystal display cell having a twisted nematic orientation cannot be completely compensated, and color compensation cannot be performed to a satisfactory level. Was.
In addition, the problem that the viewing angle is narrow could not be solved.

[0006] As another phase difference compensation method, a W cell system in which a phase difference compensation cell using a liquid crystal cell is stacked on a liquid crystal display cell, or a liquid crystal display element similar to the W cell system is used. In order to compensate for a phase difference using a liquid crystal, there is known a method using a phase difference compensation film in which a liquid crystal polymer is twisted and nematically aligned (Japanese Patent Laid-Open No. 3-8772).
No. 0). In these phase difference compensation methods, STN
Since the phase difference caused by the birefringence of the liquid crystal display device is similarly compensated by using liquid crystal, the phase difference can be effectively compensated as compared with the case where a uniaxially stretched film is used. However, even with these phase difference compensation methods, the viewing angle cannot be expanded to a satisfactory level.

In order to increase the viewing angle, compensation is performed by controlling the refractive index anisotropy of the stretched film so that the refractive index in the thickness direction becomes a value between two refractive indices in the film plane. A method using a film is known (Japanese Unexamined Patent Publication No.
157911).

[0008] However, even if the refractive index anisotropy of the stretched film is controlled as described above, the viewing angle cannot be sufficiently widened. In recent years, attempts have been made to increase the viewing angle using a microlens sheet. However, when the microlens sheet is disposed inside the polarizing plate, there is a problem that the color compensation performance is deteriorated due to the phase difference of the microlens sheet.
On the other hand, when the micro lens sheet is arranged outside the polarizing plate, the distance between the pixel and the lens sheet is large,
There is a problem that the displayed image blurs.

[0009]

As described above, the ST
Various methods are known for color compensation of an N liquid crystal display device, and depending on the method, it has become possible to perform color compensation to a satisfactory degree. However, further improvement in contrast and expansion of the viewing angle is required.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical device such as a liquid crystal display device which can not only compensate for a phase difference but also enlarge a contrast and a viewing angle, and a method of manufacturing the same.

[0011]

According to the first aspect of the present invention, there is provided an optical element comprising: a first polymer liquid crystal layer having a twisted nematic alignment fixed on a translucent substrate; and a second polymer liquid crystal layer having a vertical alignment fixed. Wherein the first polymer liquid crystal layer and the second polymer liquid crystal layer have a liquid crystal phase onset temperature different by 10 ° C. or more.

The invention according to claim 2 is a method for manufacturing an optical element, wherein a first polymer liquid crystal layer having a twisted nematic alignment fixed on a light transmitting substrate and a second polymer liquid crystal layer having a vertical alignment fixed thereon. When laminating the first and second polymer liquid crystal layers,
The method is characterized in that a difference of 10 ° C. or more is provided in the liquid crystal phase onset temperature of the polymer liquid crystal layer, and the polymer liquid crystal layer having the higher liquid crystal phase onset temperature is laminated and aligned first.

According to a third aspect of the present invention, there is provided a method for manufacturing an optical element, wherein a first polymer liquid crystal layer having a twisted nematic alignment fixed and a second polymer liquid crystal layer having a vertical alignment fixed on a light transmitting substrate.
After one of the polymer liquid crystal layers is formed, the other polymer liquid crystal layer formed on another substrate is laminated.

The optical element according to the present invention is obtained by combining a first polymer liquid crystal layer having a fixed twisted nematic orientation and a second polymer liquid crystal layer having a fixed vertical orientation on a translucent substrate. ON / OF of STN liquid crystal display
It is possible to reduce the luminance inversion caused by the viewing angle of F, and further, by making the liquid crystal phase onset temperature of the first polymer liquid crystal layer and the second polymer liquid crystal layer different by 10 ° C. or more, In order to suppress the disorder of the alignment that occurs when the second polymer liquid crystal phases are sequentially laminated, and even when the liquid crystal phase development temperatures are close to each other, they are separately formed on the liquid crystal layer in which one alignment is fixed. The feature is that the contrast and the viewing angle characteristics are improved by laminating the other alignment fixed liquid crystal layer.

Hereinafter, the present invention will be described in detail. Polymer Liquid Crystal Material The polymer liquid crystal material used in the first and second polymer liquid crystal layers may be either a main chain type or a side chain type, and specific examples of the liquid crystalline polymer include: For example, main-chain liquid crystal polymers such as polyester, polyamide, polycarbonate, and polyesterimide, and side-chain liquid crystal polymers such as polyacrylate, polymethacrylate, polymalonate, and polysiloxane can be exemplified. It is in a glassy state at a temperature lower than the onset temperature of the liquid crystal phase, and a liquid crystal in a wide temperature range is preferable.

The liquid crystal phase onset temperature of the polymer liquid crystal material is preferably in the range of not less than the upper limit temperature of use of the liquid crystal display device used in combination with the optical element according to the present invention and not more than the deformation temperature of the translucent substrate. . Since the main-chain type polymer liquid crystal material has a relatively high liquid crystal phase onset temperature, the liquid crystal is formed by bonding between mesogens (segments that exhibit liquid crystallinity) with bent segments or highly flexible siloxane-based segments. It is preferred to lower the phase onset temperature. If the liquid crystal phase onset temperature is too high, it may not be possible to orient when laminated on a light-transmitting substrate having a low deformation temperature.

First Polymer Liquid Crystal Layer The first polymer liquid crystal layer is a polymer liquid crystal layer having a fixed twisted orientation. In this case, the twist angle of the polymer liquid crystal layer in the twist orientation is the same as the twist angle of the liquid crystal display device used in combination with the optical element according to the present invention, and the twist direction is reversed.

In order to align the liquid crystal in a twisted nematic orientation,
What is necessary is just to introduce the substituent which shows optical activity in a liquid crystal molecule,
As such a substituent, those represented by the following structural formulas 1 and 2 can be exemplified.

[0019]

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[0020]

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A low-molecular compound having optical activity and having excellent compatibility with a high-molecular liquid crystal material may be mixed in the liquid crystal material layer. , 2 can be exemplified.

[0022]

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[0023]

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Second Polymer Liquid Crystal Layer In the optical element according to the present invention, a second polymer liquid crystal layer having a fixed vertical alignment is laminated in addition to the first polymer liquid crystal layer. Regarding the method of vertically aligning the molecular liquid crystal material, a method of applying lecithin, stearic acid, a monobasic chromium carboxylate complex or the like to the base material surface can be used, and generally known vertical alignment treatment of low molecular liquid crystal is performed. Can be applied. Further, when the liquid crystal is heated and a liquid crystal state is applied, an electric field or a magnetic field is applied and the liquid crystal is aligned by an external force, and then the liquid crystal material is rapidly cooled to fix the vertical alignment.

Light- Transmissive Substrate As the light-transmissive substrate, a glass film; a glass plate; a plastic film or plate having a low residual retardation such as polycarbonate, polyarylate or triacetyl cellulose can be used. The residual retardation is desirably 10 nm or less, and more desirably 5 nm or less. When the residual retardation is larger than 10 nm, the color compensation ability is reduced, and when used as an optical element, particularly an optical compensation film of a liquid crystal display device, sufficient performance may not be exhibited.

Manufacturing Method As a method of forming a first polymer liquid crystal layer having a twisted nematic orientation on a light-transmitting substrate, for example, generally known methods such as polyimide and polyvinyl alcohol are used on a light-transmitting substrate. After forming the alignment film, a method of rubbing the surface of the alignment film, or obliquely depositing an oxide such as SiO on the surface of the substrate, and then coating a polymer liquid crystal material may be mentioned. it can. When the substrate is formed of a plastic film, the polymer liquid crystal material to be coated can be twisted and nematically aligned by directly rubbing the film surface.

With respect to the method of forming the first polymer liquid crystal layer, a polymer liquid crystal material is dissolved in an appropriate solvent, and a spin coater, a roll coater, a microgravure coater,
After applying by a known coating method such as an offset gravure coater, drying may be performed by a known drying means such as hot air heating or infrared heating to remove the solvent.

As for the formation of the second polymer liquid crystal layer, similarly to the first polymer liquid crystal layer, a polymer liquid crystal material is coated by a known coating method and dried by a known drying means. This can be done by removing the solvent.

The first polymer liquid crystal layer and the second polymer liquid crystal layer may be sequentially laminated on one side of a light-transmitting substrate, or the first and second polymer liquid crystal layers may be laminated on the substrate. May be separately laminated on both sides. When the first and second polymer liquid crystal layers are stacked on one side of the substrate,
Any of the second polymer liquid crystal layers may be formed on the substrate side.

According to the second aspect of the present invention, when laminating the first polymer liquid crystal layer and the second polymer liquid crystal layer,
A difference of 10 ° C. or more is provided between the liquid crystal phase onset temperatures of the first and second polymer liquid crystal layers, and the polymer liquid crystal layer having the higher liquid crystal phase onset temperature is first laminated on a light transmitting substrate and aligned. In this way,
The optical element according to the first aspect of the present invention can be obtained. In this case, since the polymer liquid crystal layer having the higher liquid crystal phase manifestation temperature is laminated and aligned first, the liquid crystal phase laminated later is obtained. In the orientation of the polymer liquid crystal layer having the lower expression temperature, the orientation of the polymer liquid crystal layer having the relatively higher liquid crystal phase expression temperature which has been oriented earlier is less likely to be disturbed. When the difference in the liquid crystal phase onset temperature is less than 10 ° C., when the polymer liquid crystal layer to be stacked second is oriented under an environment of a desired temperature, the polymer liquid crystal layer stacked first is The orientation is disturbed, and when it is used as a retardation plate for an STN liquid crystal display device, the contrast is lowered and the viewing angle characteristics are deteriorated.

It should be noted that in the second aspect of the present invention,
The first and second polymer liquid crystal layers may be laminated on one surface of the light-transmitting substrate, or may be dispersed and laminated on both surfaces of the light-transmitting substrate.

According to the third aspect of the present invention, in laminating the first and second polymer liquid crystal layers, first, the first or second polymer liquid crystal layer is formed on a light-transmitting substrate. By laminating the second or first polymer liquid crystal layer formed on another base material, the first and second polymer liquid crystal layers are laminated.

In the manufacturing method according to the third aspect of the present invention, the first and second polymer liquid crystal layers may be laminated on one side of the transparent substrate. They may be dispersed and laminated on both sides.

As a method of lamination, any of a method of laminating from the surface of the polymer liquid crystal layer formed on the substrate and a method of laminating from the surface of the substrate may be employed, and the method of laminating from the surface of the polymer liquid crystal layer may be employed. In the method, a transfer method in which the substrate is peeled off after lamination may be used.

The substrate for peeling is formed so that the polymer liquid crystal layer can be formed in a state of twisted nematic alignment or vertical alignment, and can be peeled off without difficulty during lamination. The material is not particularly limited as long as it is a material, and examples thereof include a glass film, a glass plate, a plastic film or a plate exemplified as the above-described transparent substrate material, and a material having no such transparency. be able to.

When the substrate is not peeled off, a transparent material exemplified in the above-mentioned substrate for peeling and having a small peeling property is preferably used. In the case where the second or first polymer liquid crystal layer is laminated on one of the first and second polymer liquid crystal layers, an adhesive is interposed between the polymer liquid crystal layers to be laminated,
Thereby, the first and second polymer liquid crystal layers may be adhered to each other, or may be adhered to each other by means such as heating without interposing an adhesive or the like.

According to the third aspect of the present invention, the first polymer liquid crystal layer having the twisted nematic alignment fixed is provided;
The second polymer liquid crystal layer having a fixed vertical alignment is not particularly limited by the liquid crystal phase onset temperature, and can be suitably used when the difference in the liquid crystal phase onset temperature is less than 10 ° C. Is the way.

[0038] In the optical element according to the invention described in the action claim 1, on a transparent substrate, since the first, second liquid crystal polymer layer are combined as described above, for example, STN liquid crystal display It is possible to suppress the luminance inversion due to the ON / OFF viewing angle of the device. In addition, the first polymer liquid crystal layer having the twisted nematic alignment fixed and the liquid crystal phase onset temperature of the second polymer liquid crystal layer having the vertical alignment fixed are different from each other by 10 ° C. or more. Even in such a case, the disorder of the alignment of the polymer liquid crystal layer stacked first is unlikely to occur.

In the method of manufacturing an optical element according to the second aspect of the present invention, when the first polymer liquid crystal layer and the second polymer liquid crystal layer are laminated on a light-transmitting substrate, a liquid crystal phase of both layers is developed. In order to orient the polymer liquid crystal layer having the higher liquid crystal phase manifestation temperature first by making the temperature different by 10 ° C. or more, the polymer liquid crystal layer which has been firstly aligned when the polymer liquid crystal layer to be laminated later is to be aligned. In the above, the disorder of the orientation hardly occurs.

In the method for manufacturing an optical element according to the third aspect of the present invention, after laminating one polymer liquid crystal layer on a light-transmitting substrate, the other polymer liquid crystal layer is formed on another substrate. Are formed, the respective alignments are maintained even when the liquid crystal phase development temperatures are close to each other.

[0041]

The present invention will be clarified by the following non-limiting examples.

Example 1 A polyimide-based alignment film was formed on the surface of a light-transmitting substrate made of a polyethersulfone film, rubbed, and then subjected to a rubbing treatment, followed by a polymer having a structure represented by the following chemical formula (1). Liquid crystal material (weight average molecular weight 8
A 23% by weight anisole solution of a mixture obtained by adding 6% by weight of a chiral agent for left twisting (trade name: CB-15, manufactured by Roddick Co., Ltd.) to a liquid crystal phase developing temperature of 120 ° C.) was dried by a microgravure coater. Later thickness is 5μ
m, kept in a hot-air drying oven at 125 ° C. for 10 minutes, quenched, and formed a first polymer liquid crystal layer fixed in a 240 ° left-handed twisted nematic orientation.

A lecithin is applied to the surface opposite to the substrate on which the first polymer liquid crystal layer is formed, and a polymer liquid crystal material having a structure represented by the following chemical formula (2) (weight average molecular weight: 10 15% by weight of the liquid crystal phase onset temperature of 95 ° C)
A methyl ethyl ketone solution is applied by a micro gravure coater so that the thickness after drying becomes 2 μm, and 70 ° C.
After being kept in a hot air drying furnace for 10 minutes and further in an infrared heating furnace at 100 ° C. for 5 minutes, it was rapidly cooled to form a second polymer liquid crystal layer having a fixed vertical alignment. Thus, the first polymer liquid crystal layer is provided on one side of the translucent substrate, and the second polymer liquid crystal layer is provided on the other side.
An optical element having a polymer liquid crystal layer laminated thereon was obtained.

[0044]

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[0045]

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Example 2 One side of a translucent substrate made of a polysulfone film was coated with a chromium mystinate complex,
A 25% by weight methyl ethyl ketone solution of a polymer liquid crystal material (weight average molecular weight of 80,000, liquid crystal phase onset temperature of 120 ° C.) having a structure represented by the above chemical formula (1) is dried by an offset gravure coater to have a thickness of 2 μm. Then, the mixture was retained in a hot-air drying oven at 70 ° C. for 10 minutes and in an infrared heating oven at 125 ° C. for 5 minutes, and then rapidly cooled to form a second polymer liquid crystal layer fixed in a vertical alignment.

On the surface of the polysulfone film opposite to the surface on which the second polymer liquid crystal layer was formed, a polyimide-based alignment film was formed, and rubbing treatment was performed. 20% by weight of a mixture obtained by adding 6% by weight of a left-handed chiral agent (trade name: CB-15, manufactured by Roddick Co.) to a molecular liquid crystal material (weight average molecular weight: 60,000, liquid crystal phase onset temperature: 101 ° C.) The thickness of the methyl ethyl ketone solution after drying with an offset gravure coater is 5
μm, retained in a hot air drying furnace at 70 ° C. for 10 minutes, retained in an infrared heating furnace at 105 ° C. for 5 minutes, quenched, and fixed to a 240 ° left-handed twisted nematic orientation. Thus, one polymer liquid crystal layer was formed.

As described above, an optical element was obtained in which the first polymer liquid crystal layer was formed on one side of the substrate made of the polysulfone film and the second polymer liquid crystal layer was formed on the other side.

[0049]

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Example 3 A polycarbonate film was used as a light-transmitting substrate, and after forming a polyimide-based alignment film on one surface of the polycarbonate film, a high-molecular liquid crystal material (weight average molecular weight 8 Ten thousand,
6% by weight of a chiral agent for left-hand twist (trade name: CB-15, manufactured by Roddick Co., Ltd.) based on a liquid crystal phase development temperature of 120 ° C.)
A 20% by weight methyl ethyl ketone solution of the added mixture is spin-coated so as to have a thickness of 5 μm after drying, dried in a gear oven set at 80 ° C. for 10 minutes, and further increased the set temperature to 120 ° C. After heating for 5 minutes, the mixture is rapidly cooled to room temperature to fix a twisted nematic orientation having a film thickness of 5 μm with a 240 ° left-handed twist and a first twisted nematic orientation.
Was formed.

On the other hand, a polyethylene terephthalate (PET) film which has been subjected to a release treatment is prepared as a substrate,
After forming a lecithin layer on the treated surface of the polyethylene terephthalate film, a polymer liquid crystal material represented by the chemical formula (1) (weight average molecular weight 80,000, liquid crystal phase onset temperature 120 ° C.)
Was spin-coated with a 20% by weight methyl ethyl ketone solution and dried in a gear oven set at 80 ° C. for 10 minutes.
The temperature was further increased to 120 ° C., heated for 5 minutes, and then rapidly cooled to room temperature to form a second polymer liquid crystal layer having a thickness of 2 μm and having a fixed vertical alignment on the substrate.

An acrylic pressure-sensitive adhesive layer having a thickness of 4 μm was formed on the first polymer liquid crystal layer having a structure in which the first polymer liquid crystal layer was formed on a light-transmitting substrate, and was formed on the pressure-sensitive adhesive layer. Then, the second polymer liquid crystal layer supported by the PET film is attached so as to be laminated, and then the PET film is peeled off, and the first and second polymer liquid crystal layers are laminated on the light transmitting substrate. The obtained optical element was obtained.

Example 4 A saponified triacetylcellulose film was used as a light-transmitting substrate, the surface of the saponified triacetylcellulose film was subjected to a rubbing treatment, and thereafter, a polymer liquid crystal represented by the above chemical formula (1) Chiral agent for left-hand twisting (trade name: CB, manufactured by Roddick Co., Ltd.) against the material (weight average molecular weight 100,000, liquid crystal phase onset temperature 120 ° C.)
Anisole solution of 33% by weight of a mixture obtained by adding 5% by weight of -15) is spin-coated so that the thickness after drying becomes 6 μm, and dried in a gear oven set at 120 ° C. for 20 minutes. ° A first polymer liquid crystal layer formed by fixing a twisted nematic alignment with a left twist was formed.

A PET film, the surface of which has been release-treated, and which has been treated by applying a chromium mysinate complex, is separately prepared as a substrate, and the treated surface of the substrate is subjected to the above chemical formula (3)
A 33% by weight anisole solution of the polymer liquid crystal material (weight average molecular weight of 60,000, liquid crystal phase onset temperature of 101 ° C.) shown in (1) is spin-coated so that the thickness after drying becomes 2 μm.
It was dried in a gear oven set at 0 ° C. for 20 minutes to form a second polymer liquid crystal layer having a thickness of 2 μm and having a fixed vertical alignment.

The second polymer liquid crystal layer was laminated on the first polymer liquid crystal layer via an acrylic adhesive (thickness: 5 μm), the PET film was peeled off, and the saponified triacetyl cellulose film was removed. On one side of a substrate made of
An optical element having a polymer liquid crystal layer laminated thereon was obtained.

Comparative Example 1 A polyimide-based alignment film was formed on the surface of a polyether sulfone film, subjected to rubbing treatment, and the treated surface was treated with a polymer liquid crystal material represented by the above formula (1) (weight average molecular weight). 80,000, liquid crystal phase onset temperature 12
0 ° C.), a 23% by weight anisole solution of a mixture obtained by adding 6% by weight of a chiral agent for left-hand twisting (trade name: CB-15, manufactured by Roddick Co., Ltd.) was dried by a microgravure coater to a thickness of 5 μm. After being kept in a hot-air drying oven at 150 ° C. for 10 minutes, the mixture was rapidly cooled to form a first polymer liquid crystal layer in which a twisted nematic orientation of 240 ° left twist was fixed.

[0057] Lecithin is applied to the substrate surface opposite to the surface on which the first polymer liquid crystal layer is formed, and the chemical formula (1)
Of a 25% by weight methyl ethyl ketone solution of the polymer liquid crystal material (weight average molecular weight of 80,000, liquid crystal phase onset temperature of 120 ° C.) shown by the above was dried by a microgravure coater to have a thickness of 2%.
μm, and put in a hot-air drying oven at 125 ° C. for 10 minutes.
After quenching after drying for 2 minutes, the second
Was formed. In this way, an optical element having the first and second polymer liquid crystal layers having the same liquid crystal phase onset temperature on both surfaces made of a polyether sulfone film was obtained.

(Comparative Example 2) An optically transparent substrate was prepared by coating a chromium mysinate complex on the surface of a polysulfone film. A 20% by weight methyl ethyl ketone solution of a molecular liquid crystal material (weight average molecular weight: 60,000, liquid crystal phase onset temperature: 101 ° C.) is applied by an offset gravure coater so that the thickness after drying becomes 2 μm, and is applied at 70 ° C.
A substrate having a second polymer liquid crystal layer having a vertical orientation fixed after being retained in a hot air drying furnace for 10 minutes, then retained in an infrared heating furnace at 105 ° C. for 5 minutes, and then rapidly cooled to room temperature. I got

On the surface of the substrate opposite to the surface on which the polymer liquid crystal layer was formed, a polyimide-based alignment film was formed, rubbed, and subjected to a rubbing treatment to obtain a polymer liquid crystal material represented by the chemical formula (2) (weight average). A mixture obtained by adding 6% by weight of a chiral agent for left-hand twisting (trade name: CB-15) to a molecular weight of 100,000 and a liquid crystal phase onset temperature of 95 ° C.)
A weight-% methyl ethyl ketone solution was applied by an offset gravure coater so that the thickness after drying was 5 μm, and was retained in a hot-air drying oven at 70 ° C. for 10 minutes.
The mixture was allowed to stay in an infrared heating furnace at 0 ° C. for 5 minutes, and then cooled rapidly to form a first polymer liquid crystal layer having a 240 ° left-handed twisted nematic orientation fixed. As described above, the first and second surfaces of the substrate made of polysulfone film
An optical element on which a second polymer liquid crystal layer (difference in liquid crystal phase development temperature was 6 ° C.) was formed.

(Comparative Example 3) A polycarbonate film was prepared as a substrate, a polyimide-based alignment film was formed on one surface thereof, and a polymer liquid crystal material represented by the chemical formula (3) (weight average) was formed on the surface on which the alignment film was formed. A 20 wt% methyl ethyl ketone solution of a mixture obtained by adding 5 wt% of a chiral agent for left-hand twisting (trade name: CB-15, manufactured by Roddick Co., Ltd.) to a molecular weight of 90,000 and a liquid crystal phase onset temperature of 101 ° C. is dried. After spin coating to a thickness of 5 μm, dry in a gear oven set at 80 ° C. for 10 minutes, further raise the set temperature to 120 ° C., heat for 5 minutes, quench at room temperature, and twist 240 ° left twist A polymer liquid crystal layer formed by fixing the twisted nematic alignment was formed to obtain an optical element.

(Comparative Example 4) A saponified triacetylcellulose film having a rubbed surface was prepared as a substrate, and a polymer liquid crystal material represented by the above formula (3) (weight average molecular weight: about 100,000, liquid crystal phase onset temperature) 101 ° C) and a chiral agent for left-hand twisting (Rodick, trade name: CB-1)
A 5% by weight of 5) is added to a 33% by weight anisole solution of the mixture, spin-coated so that the thickness after drying becomes 6 μm, dried in a gear oven set at 120 ° C. for 20 minutes, and twisted 240 ° left. A polymer liquid crystal layer formed by fixing the twisted nematic alignment was formed.

As described above, an optical element was prepared in which a polymer liquid crystal layer having a twisted nematic orientation fixed on one surface of a saponified triacetyl cellulose substrate was prepared.

(Evaluation of Examples and Comparative Examples) In Examples 1 to 4 and Comparative Examples 1 and 2, evaluation was performed in the following arrangement. FIG. 1 is a perspective view showing a stacking order and a relative positional relationship of a liquid crystal cell and an optical element in a manufactured STN liquid crystal display element. As shown in FIG.
The N liquid crystal cell 2 is oriented with a right twist of 0 ° to −240 °, and a film having a vertical alignment layer 3 is attached on the substrate of the STN liquid crystal cell 2. A film having a twisted nematic alignment layer 4 is stuck on the vertical alignment layer 3. In the twisted nematic alignment layer 4, the liquid crystalline polymer is oriented with a left twist of 30 ° → 270 °. A polarizing plate 5 is attached on the twisted nematic alignment layer 4. The polarization direction of the polarizing plate 5 is 135 °. The polarizing plate 1 is attached to the STN liquid crystal cell 2 on the side opposite to the side on which the vertical alignment layer 3 is provided. The polarization direction of the polarizing plate 1 is 45 °.

In Comparative Examples 3 and 4, as shown schematically in FIG. 2, a 135 ° polarizing plate 12 was attached to the polymer liquid crystal layer 11 of 30 ° → 270 ° left twist of the obtained optical element, and an ellipse was formed. A polarizing plate is formed, and then the elliptically polarizing plate is adhered to one side of the STN liquid crystal display cell 13 having a right twist of 0 ° -−240 ° via an adhesive (not shown). A 45 ° polarizing plate 14 was attached to the other surface of the liquid crystal display to form an STN liquid crystal display device.

Evaluation of STN liquid crystal display device: For the STN liquid crystal display device prepared as described above, the contrast ratio of the front when an image signal is input, and ON / OFF.
Were evaluated for visual characteristics (with or without gradation inversion area). At the time of evaluation, as shown in FIG.
The measurement was carried out over the entire region inclined 70 ° from the front of the liquid crystal display device 23. The results are shown in Table 1 below.

[0066]

[Table 1]

As is clear from Table 1, in Comparative Examples 1 and 2, since the difference between the liquid crystal phase onset temperatures of the first and second polymer liquid crystal layers was less than 10 ° C., the front contrast ratio was low, and There was a grayscale inversion area.

Also, in Comparative Examples 3 and 4, since only a single polymer liquid crystal layer was used, although the surface contrast ratio was high, a gradation inversion region was recognized. On the contrary,
In the optical elements according to Examples 1 to 4, there is no gradation inversion area of ON / OFF, and therefore, even when the observation point is inclined, an image can be clearly recognized, and the viewing angle is large. I was assured. In addition, the front contrast ratio also kept a high value.

[0069]

According to the first aspect of the present invention, the first polymer liquid crystal layer in which the twisted nematic alignment is fixed to the translucent substrate and the second high-molecular liquid crystal layer in which the vertical alignment is fixed are provided. Since the liquid crystal phase development temperature of both polymer liquid crystal layers is different by 10 ° C. or more, for example, S
When combined to perform color compensation on a TN liquid crystal display device, it is possible to suppress the luminance inversion due to the ON / OFF viewing angle, to effectively enlarge the viewing angle of the liquid crystal display device, and to increase the contrast ratio. Can be increased.

According to a second aspect of the present invention, in the method of manufacturing an optical element, the first polymer liquid crystal layer having the twisted nematic alignment fixed on the translucent substrate and the second polymer liquid crystal layer having the vertical alignment fixed thereon. When laminating the polymer liquid crystal layer of the above, a difference of 10 ° C. or more is provided for each liquid crystal phase onset temperature, and the polymer liquid crystal layer on which the liquid crystal phase onset is higher is first laminated and oriented. When the polymer liquid crystal layer to be laminated later is oriented, disorder of the orientation of the polymer liquid crystal layer laminated earlier is less likely to occur. Therefore, it is possible to reliably provide the optical element according to the first and second aspects of the present invention.

Similarly, according to the third aspect of the present invention,
After forming one of a first polymer liquid crystal layer having a twisted nematic orientation fixed on a translucent substrate and a second polymer liquid crystal layer having a fixed vertical orientation, another substrate is formed. By laminating the other polymer liquid crystal layer formed in the above, in order to obtain an optical element, without disturbing the orientation of the polymer liquid crystal layer formed on the translucent substrate before lamination, the other Since the polymer liquid crystal layers can be laminated, even if a polymer liquid crystal having a liquid crystal phase development temperature close to each other is used, it is possible to reliably provide an optical element.

[Brief description of the drawings]

FIG. 1 shows a stacking relationship between first and second polymer liquid crystal layers, a polarizing plate, and an STN liquid crystal display cell in an STN liquid crystal display device configured in Examples 1 to 4 and Comparative Examples 1 and 2 of the present invention. FIG.

FIG. 2 is a schematic cross-sectional view of an STN liquid crystal display device according to Comparative Examples 3 and 4;
FIG. 2 is a schematic perspective view for explaining a lamination relationship between a liquid crystal display cell and a polarizing plate.

FIG. 3 is a schematic perspective view for explaining a configuration of a method for measuring the presence or absence of a grayscale inversion region in the STN liquid crystal display device configured in the example and the comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... First polymer liquid crystal layer 2, 5 ... Polarizer 3 ... Second polymer liquid crystal layer 4 ... STN liquid crystal display cell

Claims (3)

[Claims] 1. A first polymer liquid crystal layer having a twisted nematic alignment fixed on a light transmitting substrate and a second polymer liquid crystal layer having a vertical alignment fixed thereon.
Wherein the first polymer liquid crystal layer and the second polymer liquid crystal layer have different liquid crystal phase onset temperatures by 10 ° C. or more. 2. When laminating a first polymer liquid crystal layer having a fixed twisted nematic orientation and a second polymer liquid crystal layer having a fixed vertical orientation on a light-transmitting substrate, A difference of 10 ° C. or more in the liquid crystal phase onset temperature of the polymer liquid crystal layer is provided, a polymer liquid crystal layer having a higher liquid crystal phase onset temperature is laminated on a substrate and aligned, and then a polymer liquid crystal having a lower liquid crystal phase onset temperature is obtained. A method for producing an optical element, comprising laminating and orienting layers. 3. After forming one of a first polymer liquid crystal layer having a fixed twisted nematic orientation and a second polymer liquid crystal layer having a fixed vertical orientation on a translucent substrate, the substrate is formed on another substrate. A method for manufacturing an optical element, comprising laminating another formed polymer liquid crystal layer.