JPH07114031A - Supertwisted nematic liquid crystal display element and its production - Google Patents

Abstract

PURPOSE:To lessen a change in cell thickness by external force. CONSTITUTION:A mixture composed of a liquid crystal material, a photopolymerizable compd. and a photopolymerizable initiator is injected between a pair of electrode substrates. The mixture is irradiated with light adjusted in low illuminance regions in the liquid crystal region forming parts of the mixture. As a result, the components included in the photopolymerizable compd. (photosetting liquid crystal compd. and polymerizable compd.) existing in the high illuminance regions first react and the nuclei for high polymer walls are formed. The concn. of the high polymers in the high illuminance regions decreases thereafter and, therefore, the concn. gradient of the high polymer is formed. The unreacted high polymers existing within the low illuminance regions along the concn. gradient are flocculated and polymerizecl and the high-polymer walls 12 are formed in the state adhered to a pair of electrode substrates and the high-polymer walls 11 are formed in the parts formed with the high polymer walls 12. Then, a pair of the electrode substrates 2, 6 and the high polymer walls 12 are in tight contact with each other and, therefore, the thickness of the cell 1 hardly changes even if the external force acts on the electrode substrates 2, 6.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention can be used for flat display devices such as personal computers, liquid crystal televisions, and portable displays (including film substrates). For example, a polymer is used between two opposing substrates. The present invention relates to an STN (Super Twisted Nematic) liquid crystal display element in which a display medium having a liquid crystal region surrounded by a wall is sandwiched and a manufacturing method thereof.

[0002]

2. Description of the Related Art Liquid crystal display devices are available in various display modes. For example, as a liquid crystal display element utilizing the electro-optical effect, a TN (twisted nematic) mode using nematic liquid crystal molecules or an STN (super twisted nematic) mode has been put into practical use. Further, as a STN element aiming at a bright display, a reflection type liquid crystal element having one polarizing plate has been proposed (JP-A-4-97121, JP-A-4-289818).

On the other hand, there is a liquid crystal display element which utilizes a light scattering of liquid crystal without using a polarizing plate and which utilizes a dynamic scattering (DS) mode or a phase transition (PC) mode.

In recent years, as a liquid crystal display element that does not require a polarizing plate and does not require an alignment treatment, there is a method of electrically controlling the transparent or cloudy state by utilizing the birefringence of liquid crystal. This liquid crystal display element is basically
The ordinary refractive index of the liquid crystal molecules and the refractive index of a supporting medium such as a polymer that supports the liquid crystal are matched, and when a voltage is applied and the alignment of the liquid crystal is aligned, a transparent state is obtained. It is displayed by setting the state in which light scattering occurs due to the disorder of the orientation. As the liquid crystal display element of this system, a mixture of a photocurable or thermosetting resin and liquid crystal is used, and only the resin is deposited and cured, and liquid crystal droplets are formed between the cured resins. It has been proposed to manufacture by forming (see Table 6
1-502128).

By the way, as a liquid crystal display device of a non-scattering type different from the one described above, in which a viewing angle characteristic is improved by using a polarizing plate, a mixture of a liquid crystal and a photocurable resin is phase-separated to form a liquid crystal. What is produced by producing a composite material of a polymer material has been proposed (Japanese Patent Laid-Open No. 5-27).
242). In the liquid crystal display device according to this proposal, the orientation of the liquid crystal domains becomes random due to the generated polymer, and the rising directions of the liquid crystal molecules in the individual liquid crystal domains differ when a voltage is applied. Since the upper refractive indexes are the same, the viewing angle characteristics in the halftone state are improved.

Further, as a similar liquid crystal display device, the following has been proposed by the applicant of the present application (Japanese Patent Laid-Open No. 4-2 / 1992).
86487). In this liquid crystal display device, when a mixture of liquid crystal and a photo-curable resin is irradiated with light to be photopolymerized, a light control means such as a photomask is used to make a liquid crystal domain omnidirectional in a pixel region. It is formed in an aligned state, that is, in a radial state, and is configured to operate liquid crystal molecules as if the umbrella were opened or closed by voltage control. With this liquid crystal display device, the viewing angle characteristics can be remarkably improved.

[0007]

However, in the normally used STN liquid crystal display element, the thickness of the liquid crystal layer, that is, the so-called cell thickness changes due to an external force. Therefore, for example, in the case of a liquid crystal display element to which a pen input is made, there is a problem that display unevenness locally occurs due to the pen input.

Further, in a liquid crystal display device having a wide viewing angle by improving the viewing angle characteristics, the electro-optical characteristics are not steep, so that a sufficient duty ratio cannot be obtained, and therefore it is necessary to use an expensive thin film transistor (TFT). However, there is a drawback that the cost becomes high.

The present invention has been made to solve the problems of the prior art, and an object of the present invention is to provide a super twisted nematic liquid crystal display device and a method for manufacturing the same, in which a change in cell thickness due to an external force is small. To do.

[0010]

A super twisted nematic liquid crystal display device according to the present invention comprises a polymer wall between a pair of electrode substrates and a liquid crystal partially or wholly surrounded by the polymer wall. A display medium including a region is provided, and the polymer wall is in close contact with both of the pair of electrode substrates, whereby the above object is achieved.

In this super twisted nematic liquid crystal display device, the material for forming the polymer wall may include a polymer liquid crystal material. The liquid crystal material contained in the liquid crystal region is a nematic liquid crystal having a positive dielectric anisotropy and added with an optical rotatory substance, and the alignment direction in the liquid crystal region in the vicinity of each of the pair of electrode substrates. The angle between them may be 220 ° or more and 290 ° or less.

In the super twisted nematic liquid crystal display element, a polarizer is provided on one of the pair of electrode substrates opposite to the display medium, and a reflector is provided on the other electrode substrate, and The electrode substrate existing between the display medium and the polarizer may have an optical phase compensation function. At this time, it is preferable that the retardation of the liquid crystal region is 500 to 800 nm. The retardation of the electrode substrate having the optical phase compensation function is 150 to 380 nm.
Is preferable.

The super twisted nematic liquid crystal display device may be provided with a color filter. Further, one of the pair of electrode substrates may be provided with a film having a reflection function, and at least a part of the film may have a portion that transmits light. Further, the liquid crystal region may have a smectic phase and a nematic phase.

According to the method of manufacturing a super twisted nematic liquid crystal display device of the present invention, a polymer wall and a part or whole of the polymer wall are surrounded by a pair of electrode substrates, at least one of which is transparent. A method of manufacturing a super twisted nematic liquid crystal display device, wherein a display medium comprising a liquid crystal region and a polymer wall is in close contact with both of the pair of electrode substrates. A step of injecting a mixture with a material between the pair of electrode substrates, and irradiating the mixture with light having an illuminance distribution on the mixture to cause phase separation of a liquid crystal and a polymer material by a photopolymerization reaction. Then, the step of forming the liquid crystal region in the weak illuminance region is included, whereby the above object is achieved.

In this manufacturing method, the illuminance distribution can be formed by a photomask. Further, the mixture is photopolymerized when the liquid crystal material is in an isotropic phase or a nematic phase state, and then the liquid crystal material is in a smectic phase or a nematic phase state. The mixture can be photopolymerized again. Further, when the liquid crystal material is in the isotropic or nematic phase state, the mixture is injected between the pair of electrode substrates and then heated so that the liquid crystal material is in the isotropic phase state. Alternatively, the liquid crystal material may be cooled so as to be in a state of a nematic phase and then irradiated with light. In addition, 35
It is preferable to use light having a wavelength of 0 nm or more.

[0016]

In the present invention, a mixture of a liquid crystal material and a photopolymerizable material is injected between a pair of electrode substrates, and the mixture is irradiated with light in which the liquid crystal region forming portion of the mixture serves as a weak illuminance region.

As a result, first, the components contained in the photopolymerizable material (the photocurable liquid crystal compound and the polymerizable compound) in the high illuminance region react with each other to form a nucleus for the polymer wall, and thereafter,
The concentration gradient of the polymer decreases in the high illuminance region, forming a concentration gradient of the polymer, and unreacted polymers in the low illuminance region gather along the concentration gradient in the high illuminance region and polymerize. Then, the polymer wall is formed so as to be in close contact with the pair of electrode substrates. Further, a liquid crystal region is formed in a portion where the polymer wall is not formed.

Therefore, since the pair of electrode substrates and the polymer wall are in close contact with each other, the cell thickness is unlikely to change even if an external force is applied to the electrode substrates.

[0019]

EXAMPLES The present invention will be specifically described below based on examples.

Example 1 FIG. 1 shows a super twisted nematic liquid crystal display device (hereinafter,
It is simply called a liquid crystal display element. FIG. This liquid crystal display element is a transmissive type and has substrates 2 and 6 having electrodes.
A cell 1 having a display medium 10 sandwiched therebetween is provided, and a polarizing plate 14 is formed on the outer side of an upper substrate 6 forming the cell 1. In the lower substrate 2, a striped lower electrode 4 and an alignment film 5 are formed in this order from the substrate 3 side on the display medium 10 side of an insulating base substrate 3 made of glass or the like. On the other hand, the upper substrate 6 has an insulating base substrate 7 made of glass or the like, and a striped upper electrode 8 and an alignment film 9 formed on the display medium 10 side in this order from the substrate 7 side.

Display medium 1 sandwiched between both substrates 2 and 6
0 has a structure in which the liquid crystal region 11 in the shape of a drop is surrounded by the polymer wall 12. The alignment state of the liquid crystal region 11 is ST
It is N-oriented, and one polymer wall 12 is in close contact with or adheres to the substrates 2 and 6 on both sides.

A method of manufacturing the liquid crystal display device having the above structure will be described below. First, a photocurable liquid crystal compound A (Δε <0) having a polymerizable functional group in the molecule is synthesized.

[0023]

[Chemical 1]

The synthesis is performed as follows. That is,
Esterification of 4'-hydroxy-2,3-difluorobiphenyl is carried out with excess 1,10-dibromodecane in the presence of calcium carbonate. Subsequently, after purification using column chromatography, the purified product is mixed with equimolar amount of tetramethylene ammonium-hydroxypentahydrate and esterified with acrylic acid. Thereby, the photocurable liquid crystal compound A is obtained.

After the preparation is completed, the substrates 2 and 6 are manufactured as follows. For example, a substrate 3 having a thickness of 1.1 mm,
ITO (mixture of indium oxide and tin oxide) is used on 7 to form a striped lower electrode 4 and upper electrode 8 having a thickness of 500 Å, and polyimide (San Ever 150: Nissan) is formed on the substrates 3 and 7. (Manufactured by Kagaku) was applied by spin coating to obtain alignment films 5 and 9, and the alignment films 5 and 9 were rubbed in one direction with a nylon cloth. As a result, the substrates 2 and 6 are manufactured. The lower electrode 4 and the upper electrode 8 are both 1
8 pieces per mm, and the space between adjacent objects is 25μ
m.

Next, the two substrates 2 and 6 which have been subjected to the rubbing treatment are attached to each other so that the orientation treatment directions are 240 ° to each other. At this time, the cell 1 was constructed by keeping the cell thickness with a spacer of 9 μm.

Next, the photomask 20 shown in FIG. 2 is placed on the fabricated cell 1 so that the light shielding portion 20a shields the pixel portion. 20b is a translucent part. Before or after this, the following mixture was injected into the cell 1. The mixture was 0.10 g of R-684 (manufactured by Nippon Kayaku Co., Ltd.),
0.05 g of styrene, 0.10 g of isobornyl acrylate (the above three kinds of materials are polymerizable compounds), 0.75 g of the photocurable liquid crystal compound A,
4 g of liquid crystal material 4427 {a mixture having a twist angle of 240 ° made by S-811 (manufactured by Merck)}, and 0.02
5 g of the photopolymerization initiator Irugacure 651 was uniformly mixed at a homogenizing temperature of 54 ° C. Injection of this mixture was performed by capillary injection. The polymerizable compound and the photocurable liquid crystal compound A are photopolymerizable materials.

Next, the cell 1 in which the mixture was injected was set at 10 mW / cm ² under a high-pressure mercury lamp capable of obtaining parallel rays, and the temperature of the cell 1 was kept at 60 ° C. from the photomask side. It was irradiated with light (ultraviolet light) for 90 seconds. In this state, the ultraviolet light is applied to the cell 1 as a spatially regular pattern.

Next, at 25 ° C. (the liquid crystal is in a nematic state)
Then, the cell 1 was cooled, and ultraviolet rays were continuously irradiated for 3 minutes to cure the resin. Then, the cell 1 was once heated to 100 ° C. and gradually cooled to 25 ° C. over 8 hours. In this process, the liquid crystal molecules are more aligned along the alignment force of the substrate, and the display quality is improved.

Next, the polarizing plate 14 is attached to the cell 1 manufactured as shown in FIG. At this time, the polarization directions of the polarizing plate 14 were adjusted to be 45 ° with respect to the rubbing direction and 105 ° to each other. As a result, a yellow mode transmissive ST without a retardation plate
An N liquid crystal display element is manufactured.

FIG. 3 shows the structure of the display medium 10 when the manufactured cell 1 is observed with a polarization microscope. As shown in the drawing, the liquid crystal region 11 as the photomask is formed, and
The liquid crystal region 11 had the same structure as the conventional STN liquid crystal display element shown in Comparative Example 1 described later. Furthermore, since the photopolymerizable material (resin), that is, the photocurable liquid crystal compound and the polymerizable compound and the photopolymerization initiator are polymerized, the polymer wall 12 contains a liquid crystal polymer. For the liquid crystal display element of Comparative Example 1, the cell prepared in Example 1 was used, and only the liquid crystal material (mixture of the liquid crystal material used in Example 1 and the chiral agent) was injected into the cell to prepare a cell. Then
This is a STN liquid crystal display element in which a polarizing plate was attached to the produced cell as in Example 1.

Table 1 shows the electro-optical characteristics of the cell 1 according to the manufactured example 1. In this table, Comparative Example 1 and Comparative Example 2
The electro-optical characteristics of the cell are also shown.

[0033]

[Table 1]

As can be seen from Table 1, Example 1 of the present invention is comparable in electro-optical characteristics to Comparative Example 1 used conventionally. Although the measurement was performed with the polymer wall 12 included, the contrast was lowered, but when the polymer wall 12 was hidden with a black mask, almost the same contrast was obtained. Furthermore, when cell 1 was pressed with a pen, almost no color change was observed.

Further, in order to check the adhesion between the polymer wall 12 and the substrates 2 and 6, the polymer wall 12 and the liquid crystal region 11 are used.
Only 20 mm square (square with 20 mm on each side)
When it was cut out and one of the substrates was pulled, it did not come off easily. On the other hand, in Comparative Example 1, since there was no polymer wall, the substrate was peeled off while cutting 20 mm square from the cell.

Comparative Example 2 is also shown in Table 1 above. This Comparative Example 2 was obtained by preparing a cell in the same manner as in Example 1, injecting the same mixture as in Example 1 into the cell, and then performing UV irradiation in the same manner as in Example 1 without covering the cell with a photomask. Liquid crystal display device. Comparative Example 2
In the case of the liquid crystal display element, the contrast is lowered. It is considered that the reason is that when such a liquid crystal display element is observed with a polarization microscope, the polymer wall is embedded in the picture element, so that the contrast is lowered.

Therefore, in the liquid crystal display device having such a structure, the polymer wall 12 is in close contact with or adheres to the substrates 2 and 6 on both sides, and therefore, as described in JP-A-4-323616, one side is previously prepared. This is different from the polymer wall in the method for producing a display medium by producing a polymer wall on the substrate, then attaching both substrates, and injecting a liquid crystal material between the substrates in that state. Further, since the polymer wall 12 is in close contact with or adheres to the substrates 2 and 6 on both sides, variation in cell thickness due to external force can be suppressed, and color change and the like seen when pen input is performed can be prevented. Further, the impact resistance when the liquid crystal display element is dropped is remarkably improved. Further, when the liquid crystalline polymer having the same effect as the orientation influence on the substrate is fixed in the polymer wall 12,
Since the alignment control force affects the horizontal direction from the substrate surface and the vertical direction from the polymer wall 12, the alignment state is extremely stabilized. Further, by intentionally producing the majority of the polymer wall 12 outside the picture element, it is possible to prevent the contrast from being lowered by the polymer material as compared with the case where the polymer wall 12 is randomly produced. Further, a polymer thin film may be formed at the interface where the liquid crystal region 11 and the substrate are in contact, but in this case as well, since the alignment regulating force on the substrate is transmitted to the liquid crystal molecules through the polymer, uniform alignment is achieved. Since it is obtained and the liquid crystal region 11 is wrapped three-dimensionally, the liquid crystal region 11 becomes stronger against external force.

Since the polymer wall 12 can be formed almost isotropically, the use of a mode in which two polarizing plates are set to be orthogonal to each other causes the polymer wall existing outside the pixel to be separated. It can also be used as a black mask. Further, a high contrast liquid crystal display mode can be produced by installing a retardation film patterned for each picture element in the mode.

Although the above embodiment is applied to the transmissive liquid crystal display element, the present invention is not limited to this, and can be applied to a reflective STN liquid crystal display element. FIG. 4 shows an example of the case of being used as a reflection type.
In the case of the single polarizing plate method as shown in No. 89818 and No. 4-97121. In this figure, a retardation plate 13 is provided between the cell 1 and the polarizing plate 14. In the substrate 2, a protrusion 17 is formed on the display medium 10 side of the base substrate 3, a smoothing film 16 is formed on almost the entire surface of the substrate 3 so as to cover the protrusion 17, and the smoothing film 16 is formed on the smoothing film 16. The lower electrode 15 in the shape of a stripe made of a reflective metal film is formed.

(Second Embodiment) FIG. 5 is a sectional view showing a liquid crystal display element according to the second embodiment. This liquid crystal display element has, in addition to the liquid crystal display element of FIG. 1, a reflection plate 20 having a reflection region in a portion corresponding to a pixel region on one substrate 2, and a color filter 18 on the other substrate 6. Protective film 19
It is configured to have and. It should be noted that the substrates 2 and 6 in this example were 400 μm in total with an ITO film attached.
A thick acrylic plastic substrate is used.

The liquid crystal display device having such a structure is manufactured as follows. Each of the substrates 2 and 6 having the above-described structure is manufactured, and the same alignment operation as in Example 1 is performed.

Then, as in Example 1, the substrates 2 and 6 were bonded together using a spacer of 5.8 μm, and the following mixture was injected into the cell. The mixture contains 0.10 g R
-684 (Nippon Kayaku Yakuhin), 0.01 g of styrene, and 0.14 g of isobornyl acrylate (the above 3
The type is a polymerizable compound. ), 0.75 g of the photocurable liquid crystal compound A, and 4 g of the liquid crystal material 4427 {S-81.
1 (manufactured by Merck) with a twist angle of 240 °}, and 0.025 g of a photoinitiator Lucirin
It is a mixture of TPO (manufactured by BASF Co., Ltd .: having a light absorption maximum near 400 nm as shown by hatching in FIG. 6). The injection of the mixture was performed by vacuum injection, for example, at 100 Pa and 30 ° C., and immediately after the injection was started, the temperature of the substrate and the injection dish was raised to 60 ° C. The polymerizable compound and the photocurable liquid crystal compound A correspond to the photopolymerizable material.

Next, the cell temperature is set to 80 ° C., and the reflector 2
UV light was continuously irradiated for 3 minutes from the 0 side at the same UV irradiation intensity as in Example 1, and then the cell was cooled to 25 ° C.,
Further, ultraviolet light was irradiated for another 7 minutes. Then, the cell was once heated to 100 ° C. and gradually cooled to 25 ° C. in 8 hours. The retardation (Δ
n ₁ · d ₁ = 650 nm). The substrates 3 and 7 made of acrylic plastic with an ITO film have the absorption curve shown in FIG. 7 and substantially cut light of 350 nm or less.

Next, a single polarizing plate 14 and a retardation plate (Δn ₂ · d ₂ = 350 nm) 13 having an optical phase compensation function were attached to the fabricated cell 1 in the directional relationship shown in FIG. It was As a result, an STN liquid crystal display device of the reflection type single polarizing plate system is manufactured. Note that FIG. 8 will be described later.

The liquid crystal display element manufactured in this manner has the same effects as in Example 1, and the reflector 20 is used.
A region through which light passes is provided so as to correspond to the photomask of the first embodiment, and the photomask is provided inside the cell without installing the photomask outside the cell.
In this method, since the liquid crystal layer and the photomask are closer to each other by the thickness of the substrate than in the case of Example 1, it is possible to prevent the formation of a polymer in the pixel due to the diffraction of light by the photomask, and to achieve a great simplification of the process it can.

Table 2 shows the electro-optical characteristics of the produced liquid crystal display element according to Example 2. This table also shows the electro-optical characteristics of Example 3, Example 4, Comparative Example 3 and Comparative Example 4. The display characteristics were measured by the reflectance of white light in the direction normal to the light incident from the direction inclined by 30 ° from the direction normal to the liquid crystal display device.

[0047]

[Table 2]

Each of the above Examples 3 and 4 and Comparative Examples 3 and 4 is as follows. Example 3 is a reflective cell using the substrate of Example 2 and changing the retardation by changing the cell thickness by changing the spacer diameter from 9 μm to 4.6 μm. Example 4, Comparative Example 3 and Comparative Example 4
Similarly, the spacer diameter is 7.0 μm, 4.0 μm
m, 8.0 μm. However,
The liquid crystal twist angle should be 240 ° S-811.
I adjusted it with.

As can be seen from this table, Comparative Example 3,
In contrast, in Examples 2, 3 and 4, the contrast is improved.

Incidentally, in the case of the liquid crystal display device of the present invention represented by the above-mentioned Examples 1, 2, 3 and 4, the electro-optical characteristics are steep, so that a sufficient duty ratio can be taken. As a result, it is not necessary to use a TFT, so that the cost can be reduced. Furthermore, since the cell has a polymer wall, it is possible to handle external force such as pen input.
Little change in cell thickness and less display unevenness.

The features and modifications of the present invention will be described below.

(Manufacturing Method) In the present invention, it is preferable to make use of the orientation regulating force on the substrate and to form the polymer wall substantially outside the picture element. To do so, a mixture of a liquid crystal material, a photopolymerizable material (that is, a photocurable liquid crystal compound and a polymerizable compound), and a photopolymerization initiator is injected between the substrates subjected to the alignment treatment, and then, substantially. It is preferable to partially radiate the ultraviolet rays so that the pixel portion is not irradiated with the ultraviolet rays. However, the photopolymerization initiator can be omitted.

By the irradiation of ultraviolet rays, a polymer material is polymerized and formed in the area irradiated with ultraviolet rays, and the liquid crystal material is extruded into the area not irradiated with ultraviolet rays.
A liquid crystal region is formed in the non-irradiated region. At this time, in order to make use of the alignment regulating force of the substrate, by using a photocurable resin material having a liquid crystallinity as a part or the whole of the photopolymerizable material, the liquid crystallinity of the mixture of the liquid crystal-photopolymerizable material is improved. Photopolymerization can be carried out without damage.

Further, in the present invention, in order to obtain a more uniform alignment state, the mixture is injected into the cell at a temperature equal to or higher than the homogenizing temperature of the mixture, and the UV irradiation intensity is intentionally made to have a regular intensity. It is preferable to cause photopolymerization to occur regularly, or to lower the cell temperature in a nematic or smectic phase to cause photopolymerization so as to have liquid crystallinity. At this time, it is preferable to use a smectic phase having more excellent crystallinity because the photocurable resin and the like that have entered the liquid crystal can be excluded from the liquid crystal.

(How to give unevenness of illuminance of irradiation UV) In the present invention, how to give the UV irradiation distribution is important, and the light intensity adjusting means such as the above-mentioned photomask, other microlens, and interference plate is used regularly. It is preferable to add a distribution of UV illuminance.

When a photomask is used, the position of the photomask may be either inside or outside the cell, as long as it is possible to form UV light regularly. When it is provided outside the cell, a good UV irradiation distribution cannot be obtained when the photomask is separated from the cell. Therefore, the photomask is preferably provided as close to the liquid crystal-photopolymerizable material mixture as possible. On the other hand, when a substantial photomask that blocks ultraviolet light is provided inside the cell, the photomask comes into contact with the mixture of the liquid crystal and the photopolymerizable material, which is particularly preferable. The following method can be adopted as a specific example provided inside the cell. As the method, in the reflective liquid crystal display element, only the portion of the reflection plate for the picture element is left, and the outside of the picture element is used as the transmissive area, or the reflective type transmissive type is used, and A method in which a film that transmits ultraviolet rays but blocks ultraviolet light, specifically, a color filter, an organic polymer film, or the like is regularly formed while leaving the irradiation region is applicable.

According to the results of the study conducted by the inventors of the present application, a weak illuminance region (to be described later) having a size larger than that of the pixel so that the interface between the liquid crystal region and the polymer wall is extremely reduced in the pixel.
Is preferable, and it is preferable to use a light intensity adjusting means such as a photomask that irradiates only the portion other than the picture element with UV light. The reason for this is an area with low illuminance (weak illuminance area) such as a light area that is blocked by the light-shielding portion of the photomask.
When the pixel size is less than 30% of the size of the pixel, the liquid crystal region to be generated is also less than 30% of the size of the pixel, and as a result, there are many interfaces between the liquid crystal region and the polymer wall in the pixel. The reason for this is that there is a large decrease in contrast due to scattering.

The weak illuminance region may have any shape as long as it covers 30% or more of the size of the picture element and locally reduces the UV intensity.
Squares, trapezoids, rectangles, hexagons, rhombuses, letters, figures separated by curves and straight lines, and some of these figures cut, or figures that combine these figures, or small figures of these figures. An aggregate or the like. In carrying out the present invention, one or more kinds of these figures may be selected and used. Preferably, in order to improve the uniformity of the liquid crystal droplets, it is preferable to limit the shapes to one kind and arrange them as much as possible.

In the present invention, it is important that the liquid crystal regions are regularly arranged in the horizontal direction, that is, in alignment with the picture elements, and the arrangement of the weak illuminance regions becomes a problem. As for the arrangement of the low illuminance area, it is good to match the pitch of the picture element.
It is preferable to arrange one weak illuminance region in the picture element. The weak illuminance region may be arranged over several picture elements, the weak illuminance region may be arranged for each row, or the weak illuminance region may be arranged for each set of several picture elements. Further, the weak illuminance regions do not need to be independent of each other, and may be connected at the end portion, as long as the region that most effectively cuts UV light has the above shape and arrangement. .
Further, when the picture element is large, a polymer wall may be intentionally created in the picture element. In this case, although the contrast is reduced, the supporting force for external pressure is secured.

The UV light source used is preferably parallel rays as much as possible. When the parallelism of light rays is impaired, ultraviolet light enters the non-irradiated area and the polymer material is hardened in the pixel area, so that the contrast is lowered.

(Roughness of display) Due to the difference in refractive index at the interface between the polymer wall and the liquid crystal region, the scattering phenomenon occurs at the interface in the conventional polymer dispersion type liquid crystal element. The same phenomenon occurred in a liquid crystal element surrounded by a non-scattering type (element having a large liquid crystal region and reading the alignment state of liquid crystal molecules by a polarizing plate) polymer. This phenomenon causes the display to be rough, which is a problem. However, in the present invention, even in the polymer material, before and after curing, it is partially in the same alignment state as the liquid crystal state, and since the liquid crystal material and the photopolymerizable material have almost the same refractive index, the roughness is reduced.

(Photocurable Liquid Crystal Compound) In the present invention, the photopolymerizable compound is cured in a liquid crystal state from a homogeneous mixture of a liquid crystal material and a photopolymerizable material between aligned substrates,
Since the liquid crystal and the polymer material are phase-separated, the polymer wall can be formed with the alignment state of the substrate stored in the polymer. As a result, the liquid crystal molecules are subject to the alignment regulating force not only from the plane of the substrate but also from the surface of the polymer wall, and the alignment of the liquid crystal molecules is stable, and at the same time, the alignment of the liquid crystal molecules near the polymer wall is uniform. Can be secured. Conventional method of preparing polymer wall in advance (Special table Sho 61
No. 502128), the alignment was disturbed near the polymer wall, and the display uniformity could not be maintained.

The photo-curable liquid crystal compound used in the present invention has a polymerizable functional group in its molecule, and the liquid crystal compound is a compound represented by the following chemical formula 2.

[0064]

Embedded image A-B-LC ₁ or A-B-LC ₂ -B-A in the chemical formula 1 represents a polymerizable functional group, and CH ₂ ═C
_{H-, CH 2 = CH-COO-} ,

[0065]

[Chemical 3]

A functional group having an unsaturated bond such as CH ₂ —CH—, —N═C═O, or a heterocyclic structure having a strain such as an epoxy group is shown. Moreover, B is a polymerizable functional group and linking group linking the liquid crystalline compound, in particular an alkyl chain _{(- (CH 2) n -} ), an ester bond (-COO-),
Ether bond (-O-), a polyethylene glycol chain (-CH ₂ CH ₂ O-), and a linking group formed by combining these linking groups. LC ₁ represents a liquid crystal compound, and is a compound represented by the following chemical formula 4, a cholesterol ring or a derivative thereof, or the like.

[0067]

Embedded image In the above chemical formula, G is a polar group that causes dielectric anisotropy of liquid crystal and the like, and is —CN, —OCH ₃ , —F, Cl,
-OCF _3, a benzene ring having a functional group such as -OCCl _3, cyclohexane ring, para-diphenyl ring, a phenyl cyclohexane ring, a terphenyl ring, a diphenyl cyclohexane ring. E is a functional group that connects D and G by a single bond,

[0068]

[Chemical 5]

And so on. D is a functional group that binds to B in the chemical formula 2, and is a part that influences the magnitude of dielectric anisotropy and refractive index anisotropy of liquid crystal molecules.
Examples thereof include a paraphenyl ring, a 1,10-diphenyl ring, a 1,4-cyclohexane ring and a 1,10-phenylcyclohexane ring. LC ₂ is a paraphenyl ring, 1,1
0-diphenyl ring, 1,4-cyclohexane ring, 1,1
Including rigid molecules such as 0-phenylcyclohexane ring,
These molecules alone or these molecules are single-bonded

[0070]

[Chemical 6]

Molecules in which a plurality of the above-mentioned molecules are bound by a linking group such as can be used.

When the liquid crystal material used in the liquid crystal display element of the present invention has a positive dielectric anisotropy, the dielectric constant anisotropy Δε is negative as the position of the polar group of G in the above chemical formula. It is located at such a position, and specifically, is a structure containing a 2-substituted product, a 3-substituted product, a 2-3-substituted product of the benzene ring contained in G. When the liquid crystal material used as the liquid crystal material in the device of the present invention has a negative dielectric anisotropy, the polar group of the chemical formula G has a positive dielectric anisotropy Δε. Specifically, it is a structure containing a 4-substituted product, a 3,4,5-substituted product, a 3,4-substituted product, etc., of the benzene ring contained in G. Substituents of these polar substituents need not be the same when a plurality of substituents are present in the same molecule. Furthermore, it is not necessary to use it as a single molecule regardless of whether the dielectric anisotropy Δε is positive or negative.
It may contain a plurality of liquid crystalline polymer materials, and may contain at least one kind of the above compound.

(Polymerizable Compound) As the polymerizable compound which is cured by light, for example, acrylic acid and acrylate having a long-chain alkyl group of C3 or more or a benzene ring, more specifically, isobutyl acrylate, acrylic Acid stearyl, lauryl acrylate, isoamyl acrylate, n-butyl methacrylate, n-lauryl methacrylate, tridecyl methacrylate, 2-ethylhexyl acrylate, n-stearyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 2-phenoxyethyl methacrylate, isobor Nyl acrylate, isobornyl methacrylate and the like can be used. Furthermore, in order to increase the physical strength of the polymer, a polyfunctional resin having two or more functional groups, such as R-684.
(Manufactured by Nippon Kayaku), bisphenol A dimethacrylate,
Bisphenol A diacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, neopentyl diacrylate, and even more preferably , Halogenated, especially chlorinated, and fluorinated resins, eg 2.2.
3.4.4.4-hexafluorobutyl methacrylate,
2.2.3.3.4.4-Hexachlorobutyl methacrylate, 2.2.3.3-Tetrafluoropropyl methacrylate, 2.2.3.3-Tetrafluoropropyl methacrylate, Perfluorooctylethyl methacrylate, Perchloro Octyl ethyl methacrylate, perfluorooctyl ethyl acrylate, and perchlorooctyl ethyl acrylate can be used.

(Liquid Crystal Material) The liquid crystal material is an organic mixture which exhibits a liquid crystal state at around room temperature, and nematic liquid crystal (including dual frequency driving liquid crystal, liquid crystal with Δε <0) or cholesteric liquid crystal is added. A nematic liquid crystal is preferable because of its characteristics. More preferably, a liquid crystal having excellent chemical reaction resistance is preferable because it is accompanied by a photopolymerization reaction during processing. Specifically, it is a liquid crystal having a functional group such as a fluorine atom in the compound, for example, ZLI-4801-000, ZLI.
-4801-001, ZLI-4792, ZLI-44
27 (all manufactured by Merck). In selecting a liquid crystal compound having a polymerizable functional group in the molecule from these liquid crystal materials, it is preferable from the viewpoint of compatibility that the respective portions exhibiting liquid crystallinity are similar. In particular, for F and Cl type liquid crystal materials having a unique chemical environment, F and Cl type liquid crystal compounds having a polymerizable functional group are also used.
A liquid crystal material is preferable.

The refractive index of the liquid crystal material is | ((n _e or n _o ) −n _p ) | <0.1 (n _p is the refractive index of the polymer)
Is preferred. Outside the above range, the refractive index mismatch occurs and the display becomes rough. More preferably, n _p is a value between n _e and n _o . Within this range, even if the liquid crystal molecules are driven by voltage, the difference between the refractive index of the polymer wall and the refractive index of the liquid crystal region is small, and the scattering phenomenon that occurs at the interface between the liquid crystal region and the polymer wall is extremely small. Less. In particular, if it is consistent with the n _o, voltage ON
The black level at the time is improved, which is particularly preferable.

(Mixing ratio of materials) The amount of the photopolymerizable material to be added must be such that the mixture of the liquid crystal material, the photopolymerization initiator and the photopolymerizable material can take a liquid crystal state. The amount by which the liquid crystallinity can be expressed varies depending on the material and is not particularly limited in the present invention, but the amount of the photocurable liquid crystal compound added in the photopolymerizable material is preferably 30% by weight or more and 90% by weight or less. If the content is less than 30%, the temperature range in which the mixture takes a liquid crystal state is reduced, and the STN orientation cannot be sufficiently performed between the substrates. On the other hand, 90
If it exceeds%, the elastic modulus after curing of the photopolymerizable material is low, so that sufficient cell supporting force cannot be obtained.

The weight ratio of mixing the liquid crystal material and the photopolymerizable material is 50:50 to 97: 3 for the liquid crystal material: photopolymerizable material.
Is preferred, and more preferably 70:30 to 90: 1.
It is 0. When the liquid crystal material is less than 50%, the effect of the polymer wall is enhanced, the driving voltage of the cell is significantly increased, and the liquid crystal material is aligned along the alignment control force of the substrate. The liquid crystal area is reduced and the utility is lost. On the other hand, if the content of the liquid crystal material exceeds 97%, the polymer wall is not sufficiently formed, and the physical strength is lowered, so that stable performance cannot be obtained.

(Retardation: d.Δn) In the cell of the present invention, since the liquid crystal region has the same alignment state as that of a normal STN liquid crystal display element, the optimum retardation and the retardation of the retardation plate are the normal STN liquid crystal. It is similar to the display element.

In the case of the reflection type, the product d ₁ · Δn ₁ of the cell thickness d ₁ and the value of Δn ₁ of the liquid crystal is 5 because of problems of contrast and coloring.
It is preferably from 00 nm to 800 nm. But,
The cell alone can be converted into black and white display by installing a substrate having an optical phase compensation function as shown in FIG. For this purpose, the refractive index anisotropy Δn of the substrate having the optical phase compensation function is
The value of the product d ₂ · Δn ₂ of ₂ and the thickness d ₂ is very important.
It is preferably 50 nm to 380 nm, and
(D ₁ · Δn ₁ −d ₂ · Δn ₂ ) = 450 nm to 550 nm
Is preferred.

Furthermore, the optical axis of the substrate having the optical phase compensation function and the orientation direction of the liquid crystal on the substrate are important.
The liquid crystal alignment direction (rubbing direction) n of the upper electrode substrate (corresponding to the upper substrate 7 in FIG. 4) and the optical axis o of the retardation plate (corresponding to 13 in FIG. 4) having an optical phase compensation function shown in FIG.
It is preferable to set the angle β between and the twist angle θ (= 240 °) of the liquid crystal to satisfy β = (θ−180) / 2 ± 10 °. Further, it is preferable that the angle α formed by the alignment direction n of the liquid crystal of the upper electrode substrate and the polarization axis m of the polarizing plate is set within the range of 30 ± 10 °. Also, the twist angle θ
Is an angle between the alignment direction n of the liquid crystal near the upper electrode substrate and the alignment direction 1 (el) of the liquid crystal near the substrate having the reflection function, and is preferably in the range of 220 ° to 290 °. This angle range is similarly applied to the transmission type described later.

FIG. 9 shows a preferred orientation direction of liquid crystal in the case of a transmissive type in which polarizing plates are provided on both sides of the cell. In FIG. 9, t is the alignment direction of the liquid crystal near the lower substrate, u is the alignment direction of the liquid crystal near the upper substrate, v is the polarization direction of the upper polarizing plate, and w is the polarization direction of the lower polarizing plate. Note that the angular relationship in FIG. 9 shows an example of a transmissive type, and is not limited to the illustrated example.

(Photopolymerization Initiator) The photopolymerization initiator may or may not be added, but it is preferably added in order to smoothly proceed the polymerization of the photopolymerizable material. As the photopolymerization initiator (or catalyst), Irugac
ure184, 651, 907, Darocure11
73, 1116, 2959, etc. can be used. The mixing ratio is preferably 0.3% or more and 5% or less with respect to the total amount of the liquid crystal material and the photopolymerizable material. If the content is less than 0.3%, the photopolymerization reaction does not sufficiently occur, while if it exceeds 5%, the phase separation speed between the liquid crystal and the polymer becomes too fast, which makes control difficult and Is smaller and the driving voltage is higher.

When a plastic substrate is used, since ultraviolet rays are absorbed by the substrate and polymerization is less likely to occur, a visible light region is a light absorbing region, and a photopolymerization initiator capable of polymerizing in the visible light region should be used. Is preferred. In particular,
Lucrin TPO (manufactured by BASF), KYACUR
E DETX-S (manufactured by Nippon Kayaku Co., Ltd.) and CGI369 (manufactured by Ciba Geigy).

(Driving Method) The driving method that can be used in the present invention is
The simple matrix drive, active drive of TFT, MIM, etc. are applicable and are not particularly limited. However, in view of the characteristics of the STN liquid crystal display element, simple matrix drive is preferable.

(Substrate Material) As the substrate material, glass or polymer film which is a transparent solid can be used, and as the non-transparent solid, a substrate with a metal thin film aiming at a reflection type, a Si substrate and the like can be used.

As the plastic substrate, a material that does not absorb visible light is preferable, and PET, acrylic polymer, styrene, polycarbonate or the like can be used.

[0087]

As described above in detail, in the case of the present invention, since the polymer wall constituting the display medium is in close contact with both substrates, it is possible to suppress the change in cell thickness due to external pressure, Further, since it can be used without a protective film for inputting with a pen, it is possible to prevent a parallax between the display and the pen position, which is caused by the thickness of the protective film. Furthermore, when a cell is manufactured using a film substrate, it is possible to provide an STN liquid crystal display element that is lightweight, is resistant to display changes due to external deformation, and is resistant to breakage. It can be used as a liquid crystal display device such as an information terminal device.

Further, since the electro-optical characteristics are steep, it is possible to obtain a sufficient duty ratio, it is not necessary to use a TFT, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a liquid crystal display element according to a first embodiment.

2 is a plan view showing a photomask used in Example 1. FIG.

3 is a layout view of a liquid crystal region-polymer wall produced in Example 1. FIG.

FIG. 4 is a cross-sectional view showing a liquid crystal display element to which the present invention is applied to a reflective type.

FIG. 5 is a cross-sectional view showing a liquid crystal display element according to a second embodiment, that is, a self-alignment (having a photomask in a cell) type liquid crystal display element.

FIG. 6 is a graph showing an absorption curve of a photoinitiator used in Example 2.

FIG. 7 is a graph showing an absorption curve of the plastic substrate used in Example 2.

FIG. 8 is a layout view of optical axes (alignment of liquid crystal, polarizing plate, retardation plate) in a reflective liquid crystal display device.

FIG. 9 is a layout view of optical axes (alignment of liquid crystal, polarizing plate, retardation plate) in a transmissive liquid crystal display device.

[Explanation of symbols]

 1 Cell 2 Electrode Substrate 3 Base Substrate 4 Lower Electrode 5 Alignment Film 6 Electrode Substrate 7 Base Substrate 8 Upper Electrode 9 Alignment Film 10 Display Medium 11 Polymer Wall 12 Liquid Crystal Region 13 Phase Difference Plate 14 Polarizing Plate 15 Lower Electrode 16 Smoothing Chemical film 17 Protrusion 20 Photomask 20a Light-shielding portion 20b Light-transmitting portion

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuichi Kanzaki 22-22 Nagaike-cho, Abeno-ku, Osaka City, Osaka Prefecture

Claims (14)

[Claims] 1. A display medium comprising a polymer wall and a liquid crystal region partially or wholly surrounded by the polymer wall is provided between a pair of electrode substrates. A super twisted nematic liquid crystal display element that is in close contact with both a pair of electrode substrates. 2. The super twisted nematic liquid crystal display element according to claim 1, wherein a material for forming the polymer wall contains a polymer liquid crystal material. 3. A liquid crystal material contained in the liquid crystal region is a nematic liquid crystal having a positive dielectric anisotropy and added with an optical rotatory substance, and liquid crystals in the vicinity of both of the pair of electrode substrates. The angle between the orientation directions in the region is 22
3. The super twisted nematic liquid crystal display device according to claim 1, which is 0 ° or more and 290 ° or less. 4. A polarizer is provided on one of the pair of electrode substrates opposite to the display medium on one electrode substrate, and a reflector is provided on the other electrode substrate, and the display medium and the polarizer are provided. The super twisted nematic liquid crystal display element according to claim 1 or 2, wherein the electrode substrate between them has an optical phase compensation function. 5. The retardation of the liquid crystal region is 500.
The super twisted nematic liquid crystal display device according to claim 4, which has a thickness of about 800 nm. 6. The retardation of the electrode substrate having the optical phase compensation function is 150 to 380 nm.
A super twisted nematic liquid crystal display device described in 1. 7. The super twisted nematic liquid crystal display device according to claim 1, further comprising a color filter. 8. The super twisted nematic liquid crystal display element according to claim 1, wherein one of the pair of electrode substrates includes a film having a reflecting function, and at least a part of the film has a portion that transmits light. . 9. The super twisted nematic liquid crystal display element according to claim 1, wherein the liquid crystal region has a smectic phase and a nematic phase. 10. A display medium comprising a polymer wall and a liquid crystal region partially or wholly surrounded by the polymer wall is provided between a pair of electrode substrates, at least one of which is transparent, A method of manufacturing a super twisted nematic liquid crystal display device, wherein the polymer wall is in close contact with both of the pair of electrode substrates, wherein a mixture of a liquid crystal material and a photopolymerizable material is provided between the pair of electrode substrates. And a step of irradiating the mixture with light having an illuminance distribution on the mixture to phase separate the liquid crystal and the polymer material by a photopolymerization reaction to form the liquid crystal region in the weak illuminance region. A method for manufacturing a super twisted nematic liquid crystal display device including: 11. The method for manufacturing a super twisted nematic liquid crystal display device according to claim 10, wherein the illuminance distribution is formed by a photomask. 12. The mixture is photopolymerized when the liquid crystal material is in the isotropic or nematic phase state, and then the liquid crystal material is in the smectic or nematic phase state and The method for producing a super twisted nematic liquid crystal display device according to claim 10, wherein the mixture is photopolymerized again at the time. 13. The mixture is injected between the pair of electrode substrates when the liquid crystal material is in an isotropic phase or a nematic phase, and then heated so that the liquid crystal material is in an isotropic phase state. 11. The method for manufacturing a super twisted nematic liquid crystal display device according to claim 10, wherein the liquid crystal material is cooled so as to be in a nematic phase, and then irradiated with light. 14. The method for manufacturing a super twisted nematic liquid crystal display device according to claim 10, wherein light having a wavelength of 350 nm or more is used as the light.