JP2000098354A - Polymer-dispersed liquid crystal display device and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] To provide a polymer-dispersed liquid crystal display device and a method of manufacturing the same in which scattering characteristics are improved without deteriorating display characteristics. SOLUTION: A liquid crystal droplet 55 is provided between a pair of upper and lower substrates 50, 51 on which electrodes 52, 53 are formed, respectively, by a polymer 54.
The polymer liquid crystal composite 56 dispersed and held therein is disposed, and the liquid crystal droplet 55 has a flat shape in which it is shrunk in a direction perpendicular to the substrate. At the time of manufacture, a mixed composition containing a polymerizable material having a shrinkage rate of 10% or more and 20% or less and a liquid crystal material during the polymerization is injected between the substrates 50 and 51. The polymerizable material in the injected mixed composition is polymerized, whereby the polymer and the liquid crystal are phase-separated to form a polymer liquid crystal composite 56. In the polymerization process, the liquid crystal is contracted due to the contraction of the polymerizable material. The droplet 55 has a flat shape that is contracted in a direction perpendicular to the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer-dispersed liquid crystal display element used for, for example, a projection display and a method for producing the same.

[0002]

2. Description of the Related Art Liquid crystal display elements, which take advantage of the features of thinness, small size, low voltage drive, and low power consumption, display from watches, calculators, etc., to navigation systems, notebook computers, liquid crystal monitors, data projectors, projection liquid crystal televisions. It is widely used everywhere. Among such display modes of the liquid crystal display element, TN (Twisted) is more widely used than before.
Nematic) liquid crystal element having a structure in which liquid crystal molecules are twisted 90 degrees vertically between two opposing substrates.
It is sandwiched between two polarizing plates. Also, an STN (Super Tw) in which the time-division driving characteristics of the TN method are improved.
Liquid crystal display elements of the ised nematic type are also used in Japanese word processors and the like. further,
Recently, an information device using a ferroelectric liquid crystal, which changes the arrangement state of liquid crystal molecules by spontaneous polarization of the liquid crystal molecules and uses an electro-optic effect accompanying the change in the arrangement state for display, has been put to practical use.

However, since these liquid crystal display elements require at least one polarizing plate, there have been problems that the liquid crystal display is dark, that an alignment treatment is required, and that the cell thickness control is not easy.

On the other hand, for such a liquid crystal display device,
There has been proposed a method in which a polarizing plate is unnecessary, and the arrangement of liquid crystal molecules is controlled by an electric field to create a cloudy state or a transparent state. In this method, when a composite of liquid crystal and a transparent polymer is sandwiched between two substrates, and the liquid crystal molecules have a positive dielectric anisotropy, the ordinary refractive index of the liquid crystal molecules and the refractive index of the transparent polymer are used. When the refractive indices are matched, a voltage is applied to align the long axes of the liquid crystal molecules in parallel with the electric field, and when they match the refractive index of the transparent polymer, the interface becomes transparent because there is no light scattering at the interface, On the other hand, when no voltage is applied, the liquid crystal molecules are oriented in various directions, and the refractive index does not match at the interface with the transparent polymer. is there.

A typical example of this method is NCAP (Ne
magic Curvilineear Aligned
Phase is a nematic liquid crystal microencapsulated with polyvinyl alcohol or the like (powder and industrial, VOL.22, NO.8 (199)
0)).

[0006] In addition, PDLC (Polym
er Dispersed Liquid Cryst
al), which is a method of dispersing liquid crystal microdroplets in a polymer matrix (Flat Panel Display '91, Nikkei BP, p. 219).

Further, PNLC (Polymer Net)
There is also a structure called a “Work Liquid Crystal”, which has a structure in which a resin spreads in a three-dimensional network in a continuous phase of a liquid crystal (IEICE technical report, EID89-89, p1).

[0008] These composites of liquid crystal and transparent polymer are collectively called polymer dispersed liquid crystal. Therefore, also in this specification, the term “polymer-dispersed liquid crystal” is used as a generic term including the above-mentioned NCAP, PDLC, PNLC, and the like. That is, in this specification, the term "polymer dispersed liquid crystal" is not limited to liquid crystal droplets dispersed in a polymer matrix in the form of islands, but also those in which liquid crystal droplets are continuously connected, and even resin. Having a structure that spreads like a three-dimensional network in a continuous phase of a liquid crystal.

Conventionally, these methods for producing a composite of a liquid crystal and a polymer involve a mixed composition obtained by dissolving an uncured resin monomer such as an acrylic or epoxy ultraviolet curable resin and a liquid crystal material between two substrates. When the resin is injected and irradiated with ultraviolet rays, the resin monomer is polymerized and the liquid crystal and the resin undergo phase separation. As a result, a structure in which a liquid crystal is dispersed in a polymer or a structure in which a polymer spreads in a network in a liquid crystal is obtained (flat panel display '91, Nikkei B
Company P, p219, IEICE Technical Report, EI
D89-89, p1 etc.).

Incidentally, in such a polymer-dispersed liquid crystal, in order to improve the light scattering property of the composite of the liquid crystal and the polymer, the shape of the liquid crystal droplet is flat (the cross-sectional shape of the liquid crystal droplet is perpendicular to the substrate). Japanese Patent Application Laid-Open No. 5-8030 discloses an example in which the length in the direction is smaller than that in the direction parallel to the substrate.
No. 2 and JP-A-7-181454. That is, Japanese Patent Application Laid-Open No. 5-80302 discloses an example in which liquid crystal droplets are pressed in a heated state to form flat liquid crystal droplets, and the deformation ratio is 1.2 to 5.0 (deformation rate described later). Is equivalent to 20 to 80). Japanese Patent Application Laid-Open No. 7-181454 discloses an example in which a flat liquid crystal droplet is formed by pressing while irradiating ultraviolet rays, and the thickness of the cross section of the liquid crystal droplet is preferably １ ／ of the length, Actually, 1/2 to 1/4 (2 to 4 when converted to a deformation ratio: 50 to 50 to when converted to a deformation ratio described later)
(Corresponding to 75).

It is said that by forming the liquid crystal droplets in a flat shape as described above, there is an advantage that steepness is high and hysteresis is reduced.

[0012]

However, according to our study, when the deformation ratio of the liquid crystal droplet is changed to 1.2 or more (corresponding to 20 when converted into a deformation ratio described later) as described in the above-mentioned example, on the contrary, It has been found that there is a problem in that display characteristics such as a decrease in contrast are deteriorated.

In view of the above problems, it is an object of the present invention to provide a polymer-dispersed liquid crystal display device having improved scattering characteristics without impairing display characteristics, and a method of manufacturing the same.

[0014]

In order to achieve this object, according to the first aspect of the present invention, liquid crystal droplets are dispersed in a polymer between a pair of substrates each having electrodes formed thereon. While the held polymer liquid crystal composite is arranged,
A polymer-dispersed liquid crystal display device having a flat shape in which the liquid crystal droplet is shrunk in a direction perpendicular to a substrate, wherein the length of the axis of the liquid crystal droplet perpendicular to the substrate is L2, and the axis of the liquid crystal droplet is parallel to the substrate. Where L1 is the length and L1 / L2 is the deformation ratio, the deformation ratio of the liquid crystal droplet is 1.2 or less.

According to the above configuration, the object of improving the scattering characteristics is achieved. The reason is described below.

(1) In a general polymer-dispersed liquid crystal display device, liquid crystal droplets are spherical. In this case, the orientation of each liquid crystal droplet is random with respect to the substrate, and is random even in a plane parallel to the substrate. Such an alignment state is obtained because the liquid crystal droplet is spherical and has a symmetric shape, so that the direction in which the pole is generated is not regular. With such a conventional liquid crystal orientation, a sufficient light scattering effect cannot be obtained. Therefore, in order to obtain a sufficient light scattering effect, it is considered effective to treat the liquid crystal molecules in the liquid crystal droplet so as to be arranged in parallel to the substrate. This is because scattering is caused by a mismatch in the refractive index difference between the liquid crystal and the polymer, and a mismatch in the refractive index between the liquid crystal droplets. The effective refractive index anisotropy Δn of
As a result, scattering increases. However, even when the liquid crystal molecules are arranged in parallel to the substrate, scattering is small if the directions of the liquid crystal molecules are aligned in a plane parallel to the substrate. This is because a sufficient difference in the refractive index between the liquid crystal droplets is not obtained, so that a sufficient scattering intensity cannot be obtained. Therefore, the most desirable orientation mode of the liquid crystal molecules for improving the scattering effect is that the liquid crystal molecules in the liquid crystal droplets are arranged in parallel to the substrate and are randomly oriented in a plane parallel to the substrate. On the other hand, by flattening the liquid crystal droplets, the liquid crystal molecules can be arranged in parallel to the substrate. This is because when a liquid crystal droplet is deformed into a flat structure that is shrunk in the cell thickness direction, the length of the liquid crystal droplet in the cell thickness direction becomes shorter than the length of the liquid crystal droplet in the direction parallel to the substrate, resulting in an asymmetry. Become.
In this case, it was found that the liquid crystal molecules in the liquid crystal droplet were oriented in a direction parallel to the substrate. Therefore, the liquid crystal is oriented so that the bipole axis approaches parallel to the substrate. However, even when contracted in the cell thickness direction, the cross-sectional shape of the liquid crystal droplet parallel to the substrate remains circular and is not deformed. Therefore, since the liquid crystal molecules have symmetry in a plane parallel to the substrate, the liquid crystal molecules have no regularity and are randomly aligned. Therefore, by flattening the liquid crystal droplet, the orientation of the liquid crystal molecules in the liquid crystal droplet becomes parallel to the substrate and random in a plane parallel to the substrate, thereby improving the scattering effect. It should be noted here that the improvement of the scattering effect is not a direct effect that the shape of the liquid crystal droplet is deformed, but the deformation makes the orientation of the liquid crystal parallel to the substrate, and random in a plane parallel to the substrate. Because it was. Therefore, regardless of the deformation ratio of the liquid crystal droplet, if the liquid crystal droplet is deformed, the scattering effect is not always improved. In this regard, it has been confirmed by the present inventor that excessive deformation causes deterioration of the characteristics. The reason why excessive deformation causes deterioration of the characteristics is that when the deformation increases, the tendency of the liquid crystal molecules to line up in the cell thickness direction (the short axis direction of the liquid crystal droplet) increases due to the excluded volume effect of the liquid crystal. is there. That is, a phenomenon that the liquid crystal molecules rise in the vertical direction rather occurs due to the excluded volume effect of the liquid crystal. Therefore, by configuring the liquid crystal droplet to be deformed within a range that does not cause a rising force acting on the liquid crystal molecule due to the excluded volume effect of the liquid crystal, the orientation of the liquid crystal molecule in the liquid crystal droplet is relatively parallel to the substrate. Can be close. According to the experimental results of the present inventors, the length of the axis of the liquid crystal droplet perpendicular to the substrate is L2, the length of the axis parallel to the substrate is L1, and L1 / L
By setting the deformation ratio of the liquid crystal droplet to 1.2 or less when the deformation ratio is set to 2, a polymer-dispersed liquid crystal display device capable of improving light scattering characteristics without impairing display characteristics such as contrast is realized. did it.

(2) In addition to the above reasons, the following reason can be considered as a reason for achieving the object of improving the scattering characteristics. That is, the scattering performance of the liquid crystal display element in the absence of an electric field is proportional to the number of times that the incident light is scattered at the polymer / liquid crystal interface due to mismatching of the refractive indexes of the two. Sex will increase. Therefore, when the shape of the liquid crystal droplet is flat, the surface area where the polymer contacts the liquid crystal droplet is increased as compared with when the shape is spherical, and as a result, scattering at the polymer / liquid crystal interface is caused. The number of times increases, and the scattering characteristics of the liquid crystal display element improve.

(3) Regarding the degree of the excessive deformation that deteriorates the above-mentioned scattering characteristics, the following has been found from the experimental results of the present inventors. That is, when the deformation ratio of the liquid crystal droplet was 1.2, almost the same scattering characteristics as those of a non-flat spherical liquid crystal droplet were obtained, and when the deformation ratio exceeded 1.2, the scattering characteristics worsened. Therefore, for the reasons described in the above (1) and (2), the scattering characteristic can be improved by setting the deformation ratio of the liquid crystal droplet to 1.2 or less.

According to a second aspect of the present invention, a polymer liquid crystal composite in which liquid crystal droplets are dispersed and held in a polymer is disposed between a pair of upper and lower substrates on which electrodes are formed, respectively. Is a polymer-dispersed liquid crystal display element having a flat shape contracted in a direction perpendicular to the substrate, wherein the length of the axis of the liquid crystal droplet perpendicular to the substrate is L2, and the length of the axis parallel to the substrate is Is L1 and L1 / L2 is a deformation ratio,
The liquid crystal droplet has a deformation ratio of 1.10 or less.

According to the experimental results of the present inventors, when the deformation ratio of the liquid crystal droplet is 1.10 or less, the scattering characteristics are remarkably improved as compared with the case where the liquid crystal droplet is not deformed. Therefore, it is desirable that the deformation ratio of the liquid crystal droplet is set to 1.10 or less.

According to a third aspect of the present invention, there is provided a polymer liquid crystal composite in which liquid crystal droplets are dispersed and held in a polymer between a pair of upper and lower substrates on which electrodes are formed, respectively. A method for producing a polymer-dispersed liquid crystal display element having a flat shape in which is shrunk in a direction perpendicular to a substrate, comprising: a polymerizable material having a shrinkage rate of 10% or more and 20% or less due to polymerization; And a step of injecting the mixed composition containing the material between the substrates, and polymerizing the polymerizable material in the mixed composition injected between the substrates, thereby causing the polymer and the liquid crystal to phase-separate, thereby increasing the Forming a molecular liquid crystal composite, and in the polymerization process, forming a liquid crystal droplet into a flat shape which is shrunk in a direction perpendicular to the substrate by shrinkage of the polymerizable material.

According to the above configuration, it is possible to realize a polymer-dispersed liquid crystal display device having a flat liquid crystal droplet. Specifically, after a mixed composition comprising a polymerizable material and a liquid crystal material is sealed between a pair of upper and lower substrates and then the polymerizable material is polymerized by light or heat, (1) Two phenomena, ie, precipitation and growth of liquid crystal droplets and (2) shrinkage due to polymerization of the polymerizable material, proceed simultaneously. Then, due to the shrinkage of the polymerizable material, pressure acts in the direction of the thickness of the substrate in the sealed substrate, and at the same time, the liquid crystal droplets (originally spherical) that precipitate and grow are pressed. Therefore, after the completion of the polymerization, a polymer-dispersed liquid crystal having a flattened liquid crystal droplet is formed.

Here, the contraction rate is regulated as described above for the following reason. That is, there is a correspondence between the shrinkage ratio and the deformation ratio of the liquid crystal droplet. In other words, the pressure acting on the liquid crystal droplets during polymerization of the polymerizable material increases as the shrinkage of the polymerizable material increases, and therefore, the deformation ratio of the liquid crystal droplet increases as the shrinkage increases. On the other hand, as described in detail in the operation of the first aspect of the present invention, if the deformation ratio is too large, the scattering characteristics deteriorate rather. Therefore, if the shrinkage ratio is too large, as in the case of the deformation ratio, the scattering characteristics deteriorate rather. On the other hand, if the shrinkage is too small, the pressure acting on the liquid crystal droplet is too small to form a flat liquid crystal droplet,
This is because the scattering characteristics cannot be improved. .

Further, in the present invention, the liquid crystal droplets are flattened due to shrinkage caused by the polymerization of the polymerizable material, so that the liquid crystal droplets are flattened by using a mechanical pressing means. Since the pressing can be performed uniformly, there is no variation in the deformation ratio of the liquid crystal droplet. Therefore, it is possible to realize a liquid crystal display element having high scattering, excellent reproducibility, and without display unevenness.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a polymer dispersed liquid crystal display device according to the third aspect, wherein the polymerizable material is an acrylate or methacrylate material. .

If the polymerizable material is an acrylate or methacrylate material as described above, 10% or more,
A shrinkage of 0% or less can be easily obtained.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a polymer dispersed liquid crystal display device according to the third aspect, wherein the polymerizable material has a monomer having a monofunctional group and a bifunctional group. And a monomer.

As described above, a desired large shrinkage can be obtained by using a monomer having a monofunctional group and a monomer having a bifunctional group as the polymerizable material. In the present invention, in which a monomer having a bifunctional group is used instead of an oligomer generally used as a polymerizable material of a polymer-dispersed liquid crystal, the effect of large volume shrinkage due to polymerization due to small molecular weight is obtained. Play.

[0029]

According to the present inventor, the deformation ratio of the liquid crystal droplet is not increased to 1.2 or more as conventionally proposed, but the deformation ratio of the liquid crystal droplet is changed. It has been found that the characteristics are better when the amount is suppressed.

Embodiment 1 Hereinafter, a liquid crystal display device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of the liquid crystal display device of the present invention, and FIG. 2 is a plan view of the liquid crystal display device of the present invention. In the liquid crystal display element shown in FIG. 1, a transparent electrode 12 is formed inside two substrates 11 facing each other, and a polymer 13 is placed between the transparent electrodes 12.
A liquid crystal element in which liquid crystal droplets 14 are dispersed is disposed. The diameter d0 (see FIG. 2) of the liquid crystal droplet 14 was about 1.2 μm. Note that a dichroic dye may be contained in the liquid crystal. In this case, a guest-host type liquid crystal device that absorbs light with the dichroic dye is obtained.

The present invention is characterized in that the liquid crystal droplet 14 is deformed in the cell thickness direction, and in the case shown in FIG.
The liquid crystal droplet 14 has a flat structure whose length is reduced in the cell thickness direction. That is, the shape of the liquid crystal droplet 14 is a flat shape in which only the length in the cell thickness direction is reduced, and the cross-sectional shape parallel to the substrate remains circular and is not deformed.

Although the arrangement of the liquid crystal molecules is depicted in FIG. 1 as a bipole structure having two poles in the horizontal direction of the drawing, it is intended that the bipole axis exists substantially parallel to the substrate. It is not intended that the bipole axes be aligned in one axial direction. Further, in FIG. 1, in order to facilitate understanding of the drawing, the shapes of the liquid crystal droplets are all drawn as uniform shapes. However, actually, the shapes of the liquid crystal droplets are not uniform as shown in FIG. 1. Note that, as shown in FIG. 2, the bipole axes are randomly present in a plane parallel to the substrate.

A method for manufacturing the above liquid crystal display device will be described below with reference to FIG.

As shown in FIG. 3A, first, two substrates 11 are bonded to face each other. In addition, each substrate 1
A transparent electrode 12 is formed inside 1 and an active matrix substrate on which a TFT transistor is formed is used as one substrate. The distance between the substrates 11 (cell thickness) d
1 can be kept constant by previously spraying spacers 15 which are resin beads having a particle diameter of 12 μm, for example.

Next, as shown in FIG.
In the meantime, a mixture of liquid crystal, polymerizable monomer, oligomer and polymerization initiator is introduced by vacuum injection. At this time, the vacuum injection port (not shown) formed in the seal portion on the side of the liquid crystal panel is not sealed. Thereafter, as shown in FIG. 3C, an ultraviolet ray having a main wavelength of 365 nm is irradiated to polymerize the polymerizable monomer and the oligomer. This allows
As shown in FIG. 3 (d), the polymerizable monomer and the oligomer are polymerized, and a polymer network type liquid crystal element in which spherical liquid crystal droplets 14 as a liquid crystal material are continuously connected and dispersed in a polymer matrix is produced. Is done. It is needless to say that a polymer dispersed liquid crystal element in which liquid crystal droplets are dispersed in a polymer matrix may be structurally used.

Next, as shown in FIG. 3E, the liquid crystal structure is deformed to slightly extrude the liquid crystal inside the liquid crystal panel.

In the step of deforming the liquid crystal structure, a pressing method is used in this embodiment. Specifically, the panel after the UV polymerization was pressed using a jig (apparatus) as shown in FIG. At this stage of the deformation step, the panel is not yet sealed.

Briefly, the procedure of pressing the panel was as follows. A plurality of panels 23 were sandwiched between the bases 21 and 22 of the jig, and a buffer 24 was sandwiched between the panels 23. The platen 21 is configured to move in parallel, and the panel 23 is pressed by tightening a screw attached to the platen 21.

By pressing the panel 23 after the formation of the polymer network structure as described above, the liquid crystal structure was deformed and the liquid crystal inside was slightly extruded as shown in FIG. As a result, as shown in FIG.
4 was able to produce a liquid crystal display device having a flat structure in which the thickness was reduced in the cell thickness direction.

According to the experimental results of the inventor, the cell was left at room temperature in a pressed state, and was deformed by 3% in the cell thickness direction in 5 hours. At this time, the polymer dispersion type liquid crystal element having a liquid crystal droplet structure can be similarly extruded, so that the polymer material is in a gel state and has a property of allowing the liquid crystal material to pass through for a long time. The degree of deformation can be determined from the change in cell thickness, and the amount of deformation can be changed by changing the standing time and the pressing strength.

In order to deform 3% in the cell thickness direction in 5 hours, a pressing force of 0.8 kg / cm ² or more is required, and in order to shorten the extrusion time, 3 kg / cm ² or more is desirable. 1 to push out within 6 hours
0 kg / cm ² or more is desirable.

When the liquid crystal structure is deformed as described above, various characteristics of the liquid crystal display element are largely changed.
Here, in order to quantify the structural change, the deformation rate P
(%) = (Cell thickness before deformation−cell thickness after deformation) / (cell thickness before deformation) × 100. When applied to the case of FIG. 3, since the cell thickness is reduced from d1 to d2 from the state of FIG. 3D to the state of FIG.
(%) = (D1−d2) / (d1) × 100. This indicates the amount of deformation of the liquid crystal structure. In the case of the liquid crystal droplet structure, it corresponds to the oblateness, and indicates that the thickness of the liquid crystal droplet 14 in the cell thickness direction is reduced by P%. Also in the case of the polymer network structure, the thickness similarly decreases by P%, and the ratio of liquid crystal molecules substantially parallel to the glass substrate at the polymer interface increases. Although the liquid crystal droplet is deformed by this manufacturing process, the length of the liquid crystal droplet in the direction parallel to the substrate hardly changes and the length in the thickness direction changes by P% after the deformation process of P%. This is because the liquid crystal has been extruded by the pressing process, and the volume of the liquid crystal in the liquid crystal droplet has changed. Here, the amount of deformation is defined corresponding to the pressing condition P% in the manufacturing process, and this is defined as “the difference between the length of the liquid crystal droplet in the substrate parallel direction and the length in the thickness direction” of “the difference of the liquid crystal droplet in the substrate parallel direction”. Length ”. In this case, the deformation amount is the same as the pressing condition P%. Therefore, unless otherwise specified as a parameter indicating the degree of deformation of the liquid crystal droplet in the pressing process, in the following description, for convenience, the term “deformation rate” is also used to include the term “deformation amount”. I do.

Next, the characteristics of the liquid crystal display device of the present invention formed as described above will be described with reference to the drawings.
The root of the present invention is that the symmetry of the liquid crystal droplet is broken by deforming the structure of the liquid crystal, and the orientation direction of the liquid crystal is relatively close to the substrate.

FIG. 5 illustrates this phenomenon in the case where the liquid crystal droplets are independent of each other and the liquid crystal has a bipolar alignment. When the liquid crystal droplet 14 has a perfect spherical shape as shown in FIG. 5A, the pole (shown by a black circle in the figure) is oriented in an arbitrary direction. This corresponds to a normal polymer dispersion type liquid crystal display element. In this case, since the shape of the liquid crystal droplet 14 is symmetric, there is no anisotropy in the shape, and no regularity occurs in the direction in which the poles are generated. When slightly deformed like 0 to 10% as in the present invention, it becomes a flat shape as shown in FIG. When the liquid crystal droplet 14 is deformed into an asymmetric shape as described above, the liquid crystal is oriented according to the asymmetry. In this embodiment, the structure in which the poles of the bipole structure are generated horizontally is stabilized. Although the poles of the bipole are shown as being arranged in one direction on the left and right in the figure, it is intended that the poles are arranged in a horizontal direction. FIG. 5C is a schematic diagram viewed from above. Since the orientation of the liquid crystal is caused by the asymmetry of the structure of the liquid crystal droplet 14,
Even if the amount of deformation is relatively small, the orientation of the liquid crystal can be made sufficiently close to horizontal.

However, we have found that excessive deformation of more than 10% deteriorates the properties. This is because when the deformation of the liquid crystal droplet becomes 10% or more, the shape of the liquid crystal droplet 14 becomes close to a disk shape. At this time, the liquid crystal molecules are deformed,
There is a tendency to line up in the vertical direction in the figure. This is a liquid crystal drop 14
Is close to a disk shape, liquid crystal molecules are aligned in the short axis direction of the liquid crystal droplet 14 due to the effect of the excluded volume of liquid crystal or the effect of packing. The liquid crystal in this example has a tendency to line up parallel to the polymer interface, but when the deformation increases, the liquid crystal tends to line up vertically due to the excluded volume, rather than the liquid crystal tends to line up parallel to the polymer interface. As a result, the phenomenon that the liquid crystal molecules stand vertically as shown in FIG. 5D was confirmed. FIG. 5E is a schematic view of the liquid crystal droplet 14 of FIG. 5D as viewed from above.

It has been found that the phenomenon that the liquid crystal stands vertically due to the excessive deformation also depends on the size of the liquid crystal droplet 14, and it is difficult to stand vertically when the liquid crystal droplet 14 is large. The size of the liquid crystal droplet 14 here is the longer diameter as observed from above. If it is 10 μm or more, the liquid crystal tends to be relatively hard to stand. The smaller the particle size is, the higher the scattering intensity is. Therefore, when used for a scattering type liquid crystal display element, it is preferable that the particle size is 2 μm or less. . Note that all data described below is for the case where the diameter of the liquid crystal droplet 14 is about 1.2 μm.

The interaction between the polymer interface and the liquid crystal and the dependence of the anchoring strength were also found. It was found that the stronger the anchoring, that is, the more the liquid crystal had a tendency to line up horizontally at the polymer interface, the more difficult it was to stand vertically. Was. If the anchoring strength is high, there is a problem that the driving voltage becomes high,
Although it is difficult to use as a scattering type liquid crystal display device, when a sufficient driving voltage is applied, larger scattering can be obtained.

As described above, by slightly deforming the liquid crystal droplet 14 by about 10% or less, the symmetry of the liquid crystal droplet 14 was broken, and as a result, the liquid crystal molecules could be made nearly parallel to the substrate. By arranging the liquid crystal molecules in this manner, the following device characteristics were obtained.

First, FIG. 6 shows a change in transmittance at the time of scattering according to a change in the deformation rate P described above. Here, the vertical axis of FIG. 6 indicates the transmittance when no electric field is applied. In FIG. 6, a line M1 shows a change when the anchoring strength is normal,
Line M2 indicates a change when the anchoring strength is high. In FIGS. 7, 8 and 10, which will be described later, the line M1 shows a change when the anchoring strength is normal, and the line M2 shows a change when the anchoring strength is strong.

However, methods for evaluating the anchoring strength are not standardized at present. Therefore, the present inventor
The anchoring strength was evaluated using the following evaluation parameters. (Driving voltage V90 when not deformed) / (particle size) In this embodiment, the above evaluation parameter when the anchoring strength is normal is about 6.5, and the above evaluation parameter when the anchoring strength is strong. Was about 11.5. As described later in detail, when the evaluation parameter is 10 or more, 20
%, A scattering state is observed, and deformation up to 20% is effective for improving characteristics.

First, the case where the anchoring strength indicated by the line M1 is normal will be described. Line M1 in FIG.
As shown in the above, the transmittance decreases as the deformation rate increases in the range of the deformation rate P of 0 to 10%. Since the transmittance becomes smaller as the scattering becomes stronger, the scattering intensity, which is the reciprocal of the transmittance, increases as the deformation rate P increases in the range of the deformation rate P of 0% to 10%. To obtain high contrast, high scattering intensity and low transmittance are desired. The reason why the scattering intensity is increased as described above is that the liquid crystal molecules are arranged close to the direction parallel to the substrate. The refractive index anisotropy Δn in the direction parallel to the substrate that contributes to the scattering is effectively increased when the liquid crystal molecules are closer to the horizontal direction, so that the scattering is increased. In order to maximize scattering as a device, a deformation rate of 3
-10% is most desirable.

Also, when a dichroic dye is contained, the dichroic dye molecules are aligned nearly horizontally by arranging the liquid crystal molecules nearly horizontally. As a result, the dichroic ratio of the dichroic dye was improved, so that the absorptance was improved and a high contrast was obtained.

However, as shown by the line M1 in FIG. 6, when the deformation ratio is 10% or more, the scattering intensity rapidly deteriorates,
Actually, there is a problem that the scattering intensity is deteriorated rather than performing the deformation. This is because if the liquid crystal droplets have an excessively flat shape, the liquid crystal molecules have a strong tendency to be arranged vertically to the substrate.

Further, the improvement of the scattering intensity depends on the refractive index anisotropy Δn of the liquid crystal material. The effect was observed when Δn was 0.245 or more, and was remarkable at 0.26 or more.

Next, FIG. 7 shows a change in the drive voltage V90 at the same cell thickness according to the change in the deformation rate P. Where V
90 means the drive voltage when the transmittance is 90%.

As is clear from the results shown in the line M1 in FIG. 7, V90 decreases as the deformation rate P increases. This is also because the effective orientation anisotropy Δε increases as the orientation direction of the liquid crystal molecules approaches the substrate. The dependence of V90 depends on the dielectric anisotropy Δε of the liquid crystal material.
When Δε is 5 or more, a decrease in V90 is observed.
There was an effect that the decrease of 90 was remarkable.

FIG. 8 shows a change in steepness due to the change in the deformation ratio P described above. Here, the index γ indicating the steepness is defined by the ratio between the driving voltage V90 when the transmittance is 90% and the driving voltage V10 when the transmittance is 10%, as shown in FIG. That is, γ is represented by γ = V90 / V10. As is clear from the result shown in line M1 of FIG. 8, the value of γ decreases as the deformation rate P increases. That is,
The steepness increases as the deformation rate P increases.

FIG. 10 shows the change in the response speed with the change in the deformation rate P. Here, the following values were used to evaluate the response speed. That is, V90 shown in FIG.
And V10 are alternately applied to the liquid crystal panel. Then, as shown in FIG. 11A, the transmitted light amount in this case is 10% within a change amount range between 10% and 90%.
(Ie, 80% × 10%) to 90% (ie, 80% × 90)
%) And the rise time T1 required to change to 90%
% (Ie, 80% × 90%) to 10% (ie, 80% × 1)
(0%) was used as an evaluation value of the response speed. As is apparent from the line M1 in FIG. 10, the response speed decreases as the deformation rate P increases.

As described above, the reason why the response speed decreases as the deformation rate P increases includes that the applied voltage V90 decreases, but basically, the orientation direction of the liquid crystal molecules is relatively small. The reason for this is that the momentum required for the molecules to stand by voltage application increases because they become nearly parallel to the substrate.

As described above, the scattering intensity is increased by the deformation ratio P, and V90 is reduced. However, there is a problem that the response speed is reduced. When a TFT substrate is used as in the present embodiment, it is not necessary to sharpen the γ characteristic.
If the characteristics are ignored, it is desirable that the deformation ratio P (%) satisfies the relationship of 10% or less. This corresponds to line M1 in FIG.
According to the results shown in (1) and (2), although the transmittance once decreases with an increase in the deformation rate, when the deformation rate exceeds 10%, the transmittance becomes higher than when no deformation occurs.

From the viewpoint of desirably placing importance on the response speed, it is desirable that the deformation ratio P (%) satisfies the relationship of 5% or less. This is because the response speed suddenly increases at a deformation rate of 5% from the result shown in the line M1 in FIG.

In the above description, the liquid crystal droplet is deformed, but it is essential that the liquid crystal droplet is deformed so that the orientation direction of the liquid crystal molecule is relatively close to the substrate (in other words, the liquid crystal molecule is deformed). To control the effective tilt angle (θp). Here, the effective tilt angle of the liquid crystal molecule is an index indicating how many times the average azimuth of the liquid crystal molecule is tilted from the direction parallel to the substrate when no electric field is applied. On the other hand, when the liquid crystal molecules are made parallel to the substrate as described above, the dielectric constant changes. Therefore, by defining the dielectric constant of the liquid crystal, it is possible to obtain a liquid crystal display element that improves the scattering characteristics without deteriorating the display characteristics, further increases the steepness of the amount of transmitted light with respect to the voltage, and enables simple matrix driving. Can be.

According to the present inventors, it has become possible to experimentally define the permittivity. Specifically, when the dielectric constant is measured by applying a minute voltage of about 0.1 [V], the measured value is the dielectric constant under a minute voltage. It is considered that there is almost no error. Therefore, the experiment was performed by regarding the measured value as the dielectric constant without applying a voltage. More specifically, experiments were performed on liquid crystal droplets having various deformation rates from liquid crystal droplets that were not deformed at all.

As a result, the dielectric ratio E is given by E = (εL−ε⊥)
When defined as / Δε, when E is 0.08 or more and less than 0.345, an improvement in the scattering characteristics and a reduction in voltage can be realized. The above-mentioned εL indicates the permittivity without applying a voltage, ε⊥ indicates the permittivity in the vertical direction of the liquid crystal molecules, and Δε indicates the difference between the permittivity ε‖ in the direction parallel to the liquid crystal molecules and the ε⊥. Further, it is preferable that E is 0.11 or more and less than 0.345. Note that when E is 0.345, the value is a value when the liquid crystal itself is not deformed at all, and when E is 0.08, the deformation ratio P is 10, and when E is 0.11, In some cases, the deformation rate P is 5.

As described above, the desirable dielectric constant of the liquid crystal could be specified experimentally. On the other hand, the relationship between the effective tilt angle (θp) of the liquid crystal molecules and the dielectric constant εL of the liquid crystal was , ΕL = ε⊥ + Δε × sin2θp. Therefore, it is also possible to define the effective tilt angle (θp) of the liquid crystal molecules from the above value of E.

Now, assuming that the absolute value of the angle at which the rod-like liquid crystal molecules are inclined from the direction parallel to the substrate is θ, and that the average value of all the liquid crystal molecules is θp, the condition of E is that the range of θp is 17 Not less than 35.5, more preferably 20
This is less than 35.5. Note that the above θp is 35.5.
Is a value when the liquid crystal itself is not deformed at all.

Table 1 below shows the correspondence between the dielectric ratio E, the average value θp, and the deformation ratio P.

[Table 1]

Next, characteristics when the anchoring strength is high will be described with reference to FIGS. 6, 7, 8, and 10. FIG.
The characteristics in the case where the anchoring strength is high are indicated by a line M2 in FIGS. 6, 7, 8, and 10. When the anchoring is strong, the same phenomenon as in the case where the anchoring strength is normal occurs, but the tendency that the liquid crystal starts to stand in the direction perpendicular to the substrate is weakened. This corresponds to line M in FIGS. 6, 7, 8 and 10.
It is clear from FIG.

The relationship between the transmittance at the time of scattering and the deformation rate shown in FIG. 6 is as shown by the line M2, where the deformation rate is 10%.
To obtain almost the maximum scattering intensity, that is, the minimum transmittance,
When the deformation is further increased, the transmittance increases, and at 20%, the value becomes almost the same as the initial state where no deformation occurs. Therefore, when the deformation is 20% or more, the scattering becomes worse than in the initial state, and the effect of improving the scattering is not seen. In other words, when the anchoring strength is high, the effect of improving the scattering properties is seen at a deformation rate of 20% or less as shown by the line M2.

Further, as shown by the line M2 in FIG. 7, the effect that the drive voltage is also reduced by the deformation rate P is the same as that in the case of the normal line M1 having the anchoring strength. However, if the anchoring strength is high, there is a problem that the drive voltage increases. In the case of this embodiment, almost twice the voltage is required. If the anchoring strength is high, there is a problem that the driving voltage increases. However, if the voltage can be increased by the driving method, this is an effective means.

FIG. 8 shows the relationship of steepness, but there is basically no difference from the case where the anchoring strength is normal. FIG. 10 shows the relationship between the response speeds. The higher the anchoring is, the faster the response speed is. This depends on the applied voltage being high.

(Embodiment 2) In the present embodiment, heat treatment is performed for extrusion. The polymer dispersion type liquid crystal element or the polymer network type liquid crystal element after the polymerization was kept at 120 ° C. for 50 hours without sealing. This treatment also reduced the cell thickness by 3%, and obtained the same characteristics as described above. This is due to volume expansion due to heat treatment.
That is, the liquid crystal material expands with a volume expansion coefficient of about 0.3 × 10 ⁻³ [K ⁻¹ ]. Therefore, at a high temperature of 120 ° C., the liquid crystal material is in an expanded state, and the internal pressure is increased, so that the liquid crystal material is in the same state as when pressed. For this reason, the liquid crystal flows out from the unsealed injection port, and extrusion is realized. Further, by raising the temperature to an isotropic liquid phase at a temperature higher than that of the nematic phase by heating, the fluidity became extremely high, and extrusion was performed effectively.

(Embodiment 3) In this embodiment, both pressurization and heating are used for extrusion. The liquidity of the liquid crystal is not high only by the pressurization as described in Embodiment 1, so that it takes a relatively long time. Here, it was left at a high temperature (120 ° C.) while applying pressure with the jig of the first embodiment. Leaving at a high temperature increases the fluidity and can reduce the time required for extrusion. In this embodiment, a deformation rate of 3% was achieved in 3 hours.

(Embodiment 4) In this embodiment, FIG.
As shown in FIG. 2, a vacuum pack was used for pressurization. In the first and third embodiments, the pressing jig is used. However, uneven pressing may occur due to dust entering between the panels. In the present embodiment, the liquid crystal panel is housed in the pack 30, and the air in the pack 30 is sucked to be in a vacuum state, so that the liquid crystal panel can be pressed uniformly. However, sufficient time is required because atmospheric pressure is applied. Deformation rate 3
It took 30 hours at 120 ° C. to obtain%.

(Embodiment 5) In the present embodiment, hydrostatic pressure application is used for pressurization. The liquid crystal panel described above was subjected to a vacuum packing process, and was immersed in a pressurized water tank to apply pressure to the panel. At this time, the water pressure was 1 kbar. As a result, a deformation rate of 3% was obtained in 8 hours at room temperature.

(Embodiment 6) In this embodiment, a roller press is performed for extrusion. Specifically, as shown in FIG. 13, the liquid crystal was extruded by passing the panel 23 between the roller 71A and the roller 71B having the heating means 73 therein. It was realized in 30 minutes to obtain a deformation rate of 1%.

(Embodiment 7) In this embodiment, extrusion was performed by using the volume expansion of chalcogenide glass. The present embodiment is substantially the same as the first embodiment, except that a chalcogenide glass layer is formed on the inner side of the electrode 12 of the substrate 11. It is a feature of the process to have a step of irradiating light.

In general, chalcogenide glass (for example, As
₂ S ₃₎ to have been known to volume expansion when irradiated with laser light (for example, see Japanese Patent Laid-Open No. 8-86903).
This chalcogenide glass layer is formed in the liquid crystal panel in advance. After a liquid crystal is separated and separated by ultraviolet irradiation to obtain a polymer network structure, the chalcogenide glass layer is irradiated with a laser beam. At this time, the chalcogenide glass was expanded, the internal pressure in the liquid crystal panel was increased, and the liquid crystal was extruded.

(Embodiment 8) Embodiments 1 to 6 above
In this method, the liquid crystal was extruded by pressing or the like after the polymerization, and the liquid crystal was deformed in the cell thickness direction to make the orientation direction of the liquid crystal molecules relatively parallel to the substrate. In contrast, in the present embodiment,
The feature is that the orientation direction of the liquid crystal molecules is close to the substrate parallel without deformation of the liquid crystal. Since liquid crystal molecules have the property of being arranged along a magnetic field, they have succeeded in relatively aligning the liquid crystal molecules in the direction parallel to the substrate by rotating them in a magnetic field.

More specifically, as shown in FIG. 14, a turntable 85 was set in a magnetic field by a magnetic field applying means 84, and the polymerization process described in the first embodiment was performed on the turntable 85. The ultraviolet light from the ultraviolet lamp 81 is
The light is applied to the liquid crystal panel 23 mounted on the turntable 85 via the filter 82. Thereby, the polymerization of the monomer proceeds, and the liquid crystal is deposited. At this time, if a magnetic field is applied, the liquid crystal molecules tend to line up in the direction of the magnetic field. Here, since the turntable 85 is rotating, there is a high probability that the liquid crystal molecules are oriented in the direction parallel to the substrate, and the orientation direction in the direction parallel to the substrate is uniform as shown in FIG. Further, by the rotation of the turntable 85, as shown in FIG. 16, the orientation in the in-plane direction becomes random. Here, FIG. 16 is a conceptual diagram when the element is viewed from above.
In FIGS. 15 and 16, the orientation of the liquid crystal molecules is indicated by arrows.

When the effective tilt angle is reduced by pressing deformation, it is difficult to press uniformly in the cell thickness direction, and shear stress occurs in the direction parallel to the substrate, and the major axes of the liquid crystal droplets are aligned in the shifting direction. There was a tendency. In this regard, by rotating the turntable 85 in a magnetic field as in the present embodiment, the orientation of the liquid crystal molecules is relatively close to the substrate interface and random in the in-plane direction of the substrate. And the scattering intensity could be further improved.

When the effective tilt angle of the liquid crystal is controlled by a magnetic field as in this embodiment, the shape of the liquid crystal droplet is close to a sphere,
It is not particularly deformed. However, the effective tilt angle (θp) of the liquid crystal molecules was 30 ° when the magnetic field strength was 0.3 Tesla, and the ratio in the direction parallel to the substrate was relatively increased. The degree of molecular orientation depends on the magnetic field strength, and an effect was observed at 0.1 Tesla or more. When the magnetic field strength was 3 Tesla or more, the effective tilt angle (θp) of the liquid crystal molecules was almost 0 °.

When the polymer-dispersed liquid crystal element is deformed by pressing, scattering starts to deteriorate at a deformation ratio of 10% or more, and deteriorates rapidly. This is because the larger the deformation, the more the liquid crystal molecules are packed, and the molecules start to stand perpendicular to the substrate, increasing the effective tilt angle. Therefore, there is a limit in reducing the effective tilt angle in the deformation. However, the effective tilt angle could be reduced to 0 degrees by reducing the tilt angle of the molecule without depending on the deformation as in the present embodiment. Thereby, the scattering intensity could be increased without deterioration of the scattering intensity as shown in FIG. That is, according to the present embodiment, θp is 0 or more and 35.5.
Good characteristics can be obtained within the range of less than. In addition,
The conditions are as follows: the dielectric constant of the liquid crystal in the composite is εL, the dielectric constant of the liquid crystal alone in the direction perpendicular to the liquid crystal molecules is ε⊥, the dielectric anisotropy of the liquid crystal alone is Δε, and the dielectric ratio is E = (ΕL −ε
⊥) / Δε, E is 0 or more and 0.
That is, less than 345. In the present embodiment, if the azimuthal angle of the liquid crystal molecules in the direction parallel to the substrate has no anisotropy, scattering is likely to occur, which is convenient.

(Embodiment 9) As shown in FIG. 17, even when polymerization is performed by polarized ultraviolet light during polymerization, the orientation of liquid crystal molecules should be close to the substrate parallel without pressing, as in Embodiment 7. Was completed.

Specifically, when ultraviolet rays were irradiated to polymerize the monomer and precipitate liquid crystal, polarized ultraviolet rays were irradiated. Here, the ultraviolet polarizer 90 was installed between the liquid crystal panel 23 and the ultraviolet lamp 81 and was rotated. Polarized ultraviolet rays hit the panel, and polymerization of the monomer proceeds with anisotropy in the polarization direction. Due to the change of the polarization direction, the direction in the substrate plane is not uniform, but the direction in the direction parallel to the substrate is more likely to be close to parallel.

(Embodiment 10) In this embodiment, a polymer-dispersed liquid crystal element or a polymer network liquid crystal display element which is deformed flat by polymerizing at a high temperature is realized.

As described in Embodiment Mode 1, the liquid crystal panel into which the mixture of the liquid crystal and the monomer has been injected is heated to a high temperature and irradiated with ultraviolet rays at this temperature to separate and separate the liquid crystal. A liquid crystal formed at a high temperature has an isotropic shape at a high temperature, and a spherical shape in a polymer dispersed liquid crystal element. When this is cooled to room temperature, the volume of the liquid crystal shrinks. Here, since the shrinkage ratio of the glass is small, the shrinkage in the substrate surface is small. Therefore, volume shrinkage occurs in the cell thickness direction. When polymerized at 60 ° C. and cooled to 30 ° C., volume shrinkage of as much as 3% occurred in the cell thickness direction. This is equivalent to a deformation rate P (%) of 3%,
Similar properties were obtained.

In order to obtain a deformation ratio P of 0.5%, 35 ° C.
It is preferable that the polymerization be carried out at 40 ° C. or higher to obtain a sufficient effect. In addition, a problem that the size of the polymer matrix becomes large from around 70 ° C.
Above ℃, the problem of volatilization of the monomer material was observed. The polymerization temperature may be 35 ° C or more and 80 ° C or less, and preferably 40 ° C or more and 70 ° C or less.

(Embodiment 11) In this embodiment, TF
It was used for simple matrix driving without using a T substrate. The panel configuration is almost the same as that of the first embodiment, but the substrate used is a substrate that does not use a TFT. Therefore, a selection signal is scanned on one substrate, and a signal corresponding to the presence or absence of display is applied to the other substrate.

The simple matrix is not required as much as the TFT panel even if the response time is relatively slow and the scattering is slightly worse. Rather, there is a merit that the cost is extremely reduced.

As described in the first embodiment, the steepness is increased by increasing the deformation rate. As shown in FIG. 8, when the deformation ratio is 8% or more, γ is 1.3 or less, and simple matrix driving of 10 lines or more is possible. However, the deformation rate is 20
%, There is a problem that the scattering intensity at low temperatures is extremely deteriorated, and it is difficult to use. At 20% or more, since the pressure is considerably reduced, there is a problem that air bubbles are easily generated at a low temperature. In addition, from the viewpoint of relatively emphasizing the response speed, it is desirable to suppress the deformation rate to 15% or less.

At this time, the effective tilt angle (θp) of the liquid crystal molecules is 10 or more and 18 or less, preferably 13 or more and 18 or less.
And the dielectric ratio (E) is 0.03 or more and 0.10 or less, preferably 0.05 or more and 0.10 or less.

(Embodiment 12) FIG. 18 is a sectional view of a liquid crystal display device according to Embodiment 11 of the present invention, and FIG. 19 is a plan view thereof. FIG.
In FIG. 19 and FIG. 19, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. The difference from the first embodiment is that the liquid crystal droplet 14A has a spherical shape instead of a flat structure, and that the orientation of the liquid crystal molecules of the liquid crystal droplet 14A in the substrate plane is made more random.

Although the arrangement of the liquid crystal molecules is illustrated in FIG. 18 as a bipole structure having two poles in the left and right direction in the drawing, this is intended that the bipole axis exists substantially parallel to the substrate. It is not intended that the bipole axes be aligned in one axial direction. As shown in FIG. 19, the bipole axis exists more randomly in the substrate surface than in the first embodiment.

As described above, by making the alignment direction of the liquid crystal molecules nearly horizontal, the refractive index anisotropy Δn in the direction parallel to the substrate which contributes to the scattering is effectively increased, as in the above-described embodiment. The scattering intensity can be increased. Further, since the effective dielectric anisotropy Δε also increases, the driving voltage also decreases. Further, since the arrangement inside the liquid crystal droplets is uniform in most of the liquid crystal droplets 14A, there is an advantage that the γ characteristic of the drive voltage is also sharpened.

Next, a method of manufacturing a liquid crystal display device having the above-described configuration will be described. First, two substrates 11 are attached to each other so as to face each other. A transparent electrode 12 is formed inside each substrate, and a TFT is provided on one substrate.
An active matrix substrate on which a transistor is formed is used. The distance (cell thickness) between the substrates 11 can be kept constant by, for example, spraying resin beads having a particle diameter of 12 μm in advance.

Next, a mixture of a liquid crystal, a polymerizable monomer, an oligomer and a polymerization initiator is introduced between the substrates 11 by vacuum injection. Thereafter, ultraviolet rays having a main wavelength of 365 nm are irradiated to polymerize the polymerizable monomer and oligomer, and a spherical liquid crystal droplet 14 as a liquid crystal material is placed in a polymer matrix.
A polymer network type liquid crystal element in which A is continuously connected and dispersed is prepared. It is needless to say that a polymer dispersed liquid crystal element in which liquid crystal droplets are dispersed in a polymer matrix may be structurally used.

The feature of the present invention is to use a liquid crystal monomer as the polymerizable monomer at this time. Here, the liquid crystal monomer is also called a UV-curable liquid crystal, and is a compound showing a liquid crystal state in a monomer state (for example, Proceedings of the 22nd Liquid Crystal Symposium by Hasebe et al., 39)
See page 1).

When this liquid crystal monomer is used as a polymerizable monomer, the mixture of the liquid crystal, the polymerizable monomer, the oligomer, and the polymerization initiator exhibits a uniform liquid crystal phase at room temperature. When this mixture is injected between the above-mentioned substrates, in this embodiment, the mixture of the liquid crystal and the liquid crystal monomer is arranged in parallel to the substrate. In the case of the present invention, it is not necessary to particularly coat the substrate surface.
A horizontal alignment film used in devices and the like may be applied. However, a rubbing process for arranging in one direction unlike the TN element is not performed.

From the state before the polymerization, the mixture shows a liquid crystal state, and its molecules are arranged in parallel to the substrate. However, since the rubbing process is not performed, they are arranged in a random orientation on the substrate surface. FIG. 20 shows this state. That is, FIG. 20 shows a state before polymerization, and FIG. 20 (a) is an overall view.
0 (b) is a partially enlarged view of FIG. 20 (a). In the figure, the liquid crystal molecules are depicted as being arranged side by side for simplicity, but this is conscious of being arranged horizontally, and is not necessarily arranged in one direction. When viewed from above, the orientation is random. When the mixture in this state is irradiated with ultraviolet light, the liquid crystal monomer 100 is polymerized and the liquid crystal monomers 100 are bonded to each other. Therefore, the molecules of the liquid crystal monomer 100 become larger, and the liquid crystal molecules 101 are eliminated. Therefore, as the polymerization proceeds, the liquid crystal and the polymerized liquid crystal monomer 100 are separated. In this embodiment, the liquid crystal was in the form of drops or a network. FIG. 21 shows this state. FIG. 21A is an overall view, and FIG. 21B is a partially enlarged view of FIG. However, since the liquid crystal was arranged in parallel with the substrate from the initial state, the liquid crystal is affected even after polymerization, and tends to be arranged in parallel with the substrate. According to the invention, after polymerization, the liquid crystal molecules 10
The state in which 1 is arranged almost parallel to the substrate is a liquid crystal monomer 10
0 could be achieved.

It can be said that the present invention is characterized in that the mixture is in a liquid crystal state, and this state is irradiated with ultraviolet rays to be separated. In the conventional example using a polymerizable monomer other than the conventional liquid crystal monomer, the mixture of the liquid crystal, the polymerizable monomer, the oligomer, and the polymerization initiator is a uniform isotropic liquid phase as shown in FIG. When the mixture of the isotropic liquid phases is irradiated with ultraviolet rays, the monomer is polymerized and the liquid crystal precipitates and separates. At this time, the liquid crystal molecules have an orientation orientation that is not as shown in FIG. It will be in a state of being uniformly distributed. In FIG. 22, the alignment direction of the liquid crystal molecules is indicated by arrows.

On the other hand, the mixture in the case where the liquid crystal monomer is used as the polymerizable monomer in the present invention shows a uniform liquid crystal phase from the state before polymerization, as shown in FIG. Then, a polymerization process in which liquid crystal is precipitated from the liquid crystal. Because of this, because of the influence of the initial orientation,
If the initial stage is arranged horizontally on the substrate, the tendency of the liquid crystal molecules to be nearly horizontal even after polymerization becomes stronger.

When a mixture using such a liquid crystal monomer as a polymerizable monomer is injected between a pair of substrates 11 and then irradiated with ultraviolet rays, the liquid crystal monomer and the oligomer are polymerized with a polymerization initiator as a nucleus. As a result, a liquid crystal droplet 14A (or a polymer network) is formed. Here, if the conditions are set so that the molecules are arranged in parallel to the substrate interface in the liquid crystal phase before polymerization, the orientation of the liquid crystal molecules after polymerization is affected by the parallel state before polymerization, as shown in FIG. As shown in b), the tendency to be parallel to the substrate interface becomes closer, and ideally, a structure in which the bipole axes are arranged parallel to the substrate interface is obtained.

Note that the liquid crystal monomer may contain chiral carbon. With this configuration, the liquid crystal molecules have a structure of spiraling in the cell thickness direction, so that the scattering effect can be further improved.

In this embodiment, as an example, a polyimide film (trade name: RN740, manufactured by Nissan Chemical Industries, Ltd.) is applied and baked on the glass substrate 11 so that the alignment of the liquid crystal molecules before polymerization is applied to the substrate interface. It was almost parallel. Here, it is not necessary to perform a rubbing treatment on the polyimide film, and there is also an advantage of simplifying the process. If the rubbing treatment is performed, the orientation directions of the liquid crystal are arranged in a uniaxial direction, which is not suitable for the present invention. Rather, it is desirable that the initial orientation direction is random without performing the orientation process. In this example, the molecules were parallel to the glass interface in the pre-polymerization state without any particular orientation treatment, but were oriented in a random orientation within the substrate plane. Therefore, the orientation of the liquid crystal molecules after the formation of the liquid crystal droplets was also random in the in-plane direction of the substrate, but tended to be aligned parallel to the substrate interface. At this time, the effective tilt angle (θp) of the liquid crystal molecules was small, that is, 20 °.

As described above, in the liquid crystal display device according to the present embodiment, by making the orientation of the liquid crystal molecules parallel to the glass interface, the same effect as in the above embodiment can be obtained, and the liquid crystal molecule substrate can be obtained. Since the orientation in the in-plane direction was made more random than in the above-described embodiment, the scattering characteristics could be further improved.

In this regard, for reference, in the method of performing polymerization in a magnetic field or in the method of performing polymerization with polarized ultraviolet light as in the above-described Embodiments 8 and 9, the rotation speed of the turntable or the rotation speed of the turntable is not considered. Since it is necessary to control the rotation speed of the polarizing plate, it is difficult to completely randomize the orientation in the in-plane direction of the substrate. In the case of this embodiment, there is an advantage that the orientation in the in-plane direction of the substrate can be completely randomized by the simple technique as described above, and the manufacturing is easy.

Next, the characteristics of the liquid crystal display element according to the present embodiment manufactured by the above method and the liquid crystal display element manufactured by the conventional manufacturing method using no liquid crystal monomer as a polymerizable monomer were compared. did. The characteristics of the liquid crystal display element include a scattering gain, a driving voltage, and a γ characteristic. Here, the scattering gain is an index indicating the degree of scattering. When the scattering gain is G, it is represented by G = (panel luminance / panel illuminance) × π. Note that the liquid crystal display device according to the present embodiment was compared for a case where the effective tilt angle (θp) of liquid crystal molecules was 20 °.

As in the present embodiment, the arrangement direction of the liquid crystal molecules is made nearly horizontal, in other words, the effective tilt angle (θp) of the liquid crystal molecules is reduced, or the dielectric ratio E is reduced. As shown in Table 2, the scattering characteristics were improved, the driving voltage was reduced, and the γ characteristics were sharpened.

[Table 2]

According to the experimental results of the present inventor, in order to improve the scattering intensity, the characteristics were improved when θp was less than 35.5, and the contrast was significantly improved when θp was 20 or less. . When expressed by the dielectric ratio E instead of the effective tilt angle θp, the dielectric ratio E is 0 to 0.345.
If it is less than 0.1, the characteristics are improved, and if it is 0.11 or less, the contrast is significantly improved.

Further, with respect to the refractive index anisotropy Δn of the liquid crystal monomer, if Δn is large, there is a problem that the transparency when a voltage is applied is deteriorated. Regarding this point, according to the experiment of the inventor, if Δn is 0.20 or less, there is no practical problem,
If it is 0.15 or less, a transmittance comparable to that of a normal acrylic monomer was obtained.

(Embodiment 13) In this embodiment, one of a pair of substrates 11 is subjected to fine rubbing treatment in a plurality of directions as shown in FIG. 24, fine irregularities were formed.
The other points are the same as in the twelfth embodiment.

Fine rubbing has an uneven pitch of 20 μm.
Was pressed against the surface of the substrate 11 and rubbed a plurality of times in a plurality of directions. At this time, a polyimide film (trade name R manufactured by Nissan Chemical Industries, Ltd.) was used as the alignment film.
N740) was used. On the other substrate 11, irregularities were formed with an acrylic resin, and random irregularities having a pitch of 1 μm and a height of 0.1 μm were formed.

As described above, by the fine rubbing and the formation of the surface irregularities, the direction in which the molecules of the mixture before polymerization are arranged can be made more randomly and finely, and the scattering intensity can be further increased.

In the present embodiment, fine rubbing is performed on one substrate, and fine irregularities are formed on the other substrate. As the substrate, an ordinary substrate may be used without forming fine irregularities. Similarly, fine irregularities may be formed only on one substrate, and the other substrate may be a normal substrate that is not subjected to a rubbing process.

In the twelfth and thirteenth embodiments, the liquid crystal display element driven by the active matrix has been described. However, the present invention using the liquid crystal monomer as the polymerizable monomer is applicable to the liquid crystal display element driven by the simple matrix. Can also be suitably implemented. When the present invention is applied to a liquid crystal display element driven by a simple matrix, the effective tilt angle (θp) of the liquid crystal molecules is set to 10 or more and 18 or less, desirably 13 or more and 18 or less as in the eleventh embodiment. Expressed as (E), the dielectric ratio (E) may be set to be 0.03 or more and 0.10 or less, preferably 0.05 or more and 0.10 or less.

(Embodiment 14) FIG. 25 shows Embodiment 1 of the present invention.
FIG. 26 is a cross-sectional view schematically showing a configuration of the liquid crystal display element according to No. 4, and FIG. 26 is a partial plan view thereof. The fourteenth embodiment is characterized in that a material having a high shrinkage rate is used as a polymerizable material, and the liquid crystal droplet is made flat by shrinkage during polymerization. This is different from the first embodiment in which the liquid crystal droplet is made flat by mechanical pressing. The structure of the liquid crystal display element according to the fourteenth embodiment will be described. Transparent electrodes 52 and 53 made of indium / tin oxide are formed inside two glass substrates 50 and 51 facing each other. A polymer liquid crystal composite layer 56 in which liquid crystal droplets 55 are dispersed in a polymer matrix 54 is disposed between 52 and 53. A sealing resin 57 serving also as a spacer is provided on the periphery of the polymer liquid crystal composite 56.
Are provided, and both substrates 5 are formed by the sealing resin 57.
0 and 51 are bonded together, and the polymer liquid crystal composite layer 56 is sealed. Like the liquid crystal droplet 14 of the first embodiment, the liquid crystal droplet 55 has a flat structure whose length is reduced in the cell thickness direction. The degree of flatness of the liquid crystal droplet 55 is expressed as a deformation ratio of 1.2 or less. The regulation in this way is
If the deformation ratio exceeds 1.2, the scattering characteristics are rather deteriorated. Also, judging from the experimental results described below,
The deformation ratio is desirably 1.10 or less. Here, the deformation ratio means L1 / L2, where L2 is the length of the axis of the liquid crystal droplet perpendicular to the substrate and L1 is the length of the axis parallel to the substrate. The shape of the liquid crystal droplet 55 is the same as the shape of the liquid crystal droplet 14 in the first embodiment, except that the length in the cell thickness direction is reduced, and the cross-sectional shape parallel to the substrate is flat and undeformed. Shape. In FIG. 25, the arrangement of the liquid crystal molecules is depicted as a bipole structure having two poles in the horizontal direction of the drawing, but this is intended that the bipole axis exists substantially parallel to the substrate, and the bipole axis is It is not intended that they are arranged in one axis direction. In addition, as shown in FIG. 26, the bipole axes are randomly present in a plane parallel to the substrate.

The liquid crystal display device according to the fourteenth embodiment can also improve the scattering characteristics according to the same principle as the liquid crystal display device according to the first embodiment.

Next, a method of manufacturing the liquid crystal display device having the above configuration will be described.

(1) Preparation of Empty Cell Glass substrates 50 and 51 on which transparent electrodes 52 and 53 made of indium / tin oxide are formed are prepared.
One of the substrates 0 and 51 (for example, substrate 51)
Sealing resin 57 also serving as a spacer on the surface of transparent electrode 53
An acid anhydride-curable epoxy resin in which glass fiber having a diameter of 13 μm is dispersed, leaving 3 mm as an opening on one side of four sides of the substrate 50 and a width of 2 m on the other side.
m. Next, on the substrate 51, the other glass substrate 50 is placed in a state where the electrode surfaces are opposed to each other, pressurized in this state, heated at 150 ° C. for 2 hours, and cured and bonded to produce an empty cell. .

(2) Measurement of Shrinkage of Polymerizable Material As the polymerizable material, a monomer having a monofunctional group and a monomer having a bifunctional group, which are thermopolymerizable or photopolymerizable, are used. This is based on the idea that it is necessary to select a material having a small molecular weight as a material having a large shrinkage. Therefore, Embodiment 14 of the present invention relates to the polymerizable material.
Is different from a conventional example in which a monomer or oligomer having a monofunctional group is used as a polymerizable material. Incidentally, for reference, in the conventional example, the monomer and the oligomer having a monofunctional group were used as the polymerizable material because the monomer having the monofunctional group alone had sufficient polymerization to form a liquid crystal droplet. Is not obtained. That is, since the wall surface of the liquid crystal droplet is formed by polymerization of the oligomer, the liquid crystal droplet cannot be formed only by the monomer. However, according to experiments performed by the present inventors, it is possible to use a monomer having a bifunctional group instead of an oligomer, that is, using a monomer having a monofunctional group and a monomer having a bifunctional group as a polymerizable material. Thus, it was confirmed that a polymer-dispersed liquid crystal was obtained, and its characteristics were not inferior to those of the polymer-dispersed liquid crystal using an oligomer.

In this embodiment, 78 parts of t-butyl acrylate (Osaka Organic Chemical Industry Co., Ltd.) is used as a monomer having a monofunctional group, and 1,9-nonanediol diacrylate is used as a monomer having a bifunctional group. A mixed composition (hereinafter, referred to as composition A) was prepared which comprised 20 parts of Osaka Organic Chemical Industry Co., Ltd. and 2 parts of Irgacure 651 (manufactured by Ciba Gaiki Co., Ltd.) as a polymerization initiator. After the composition A was sandwiched between the test cells described above and the opening was sealed, polymerization was performed at 40 ° C. using a high-pressure mercury lamp as a light source. At this time,
A light cut filter was arranged on the light irradiation surface to perform polymerization.
As a light cut filter, UV35 (trade name) manufactured by Toshiba Color Glass Co., Ltd. was used. The high-pressure mercury lamp used had a main wavelength of 365 nm and an ultraviolet intensity of 50 mW, and was irradiated for 60 seconds. The thickness between the substrates of the cell thus obtained was measured, and the shrinkage ratio S (%) was calculated as S = (1-D
2 / D1) × 100. The shrinkage of the polymerizable material was 17%.

Here, D1 is the thickness between the substrates before polymerization, D1
2F is the thickness between the substrates after polymerization. In Embodiment 14, t-butyl acrylate was used as the monomer having a monofunctional group, but in addition, isobutyl acrylate, isobutyl acrylate, methyl methacrylate ethyl methacrylate, n-butyl methacrylate, etc. It may be. As the monomer having a bifunctional group, 1,9-nonanediol diacrylate was used.
-Butanediol diacrylate, 1,6-hexanediol diacrylate or the like may be used.

(3) Production of Polymer Dispersion Type Liquid Crystal Display Element In the above-described test cell, the composition A and a liquid crystal material (trade name: TL205, manufactured by Merck Ltd.) were added in a weight ratio of composition A: liquid crystal = 17: After mixing at a rate of 83 and pouring through the opening, sealing the opening, using a high-pressure mercury lamp as a light source,
Polymerization was carried out at 40 ° C. to complete a liquid crystal display device comprising a polymer dispersed liquid crystal. At this time, polymerization was performed by arranging a light cut filter on the light irradiation surface. As a light cut filter, UV35 (trade name) manufactured by Toshiba Color Glass Co., Ltd. was used. The high-pressure mercury lamp has a main wavelength of 36.
Irradiation was carried out for 60 seconds using a material having a UV intensity of 50 mW at 5 nm. (The polymerization conditions are the same as those for the measurement of the shrinkage ratio). Thereby, as the polymerization of the polymerizable material progresses, two phenomena of (1) precipitation and growth of liquid crystal droplets and (2) shrinkage accompanying the polymerization of the polymerizable material simultaneously progress. Then, due to the shrinkage of the polymerizable material, pressure acts in the thickness direction of the substrate in the closed substrate, and at the same time, the liquid crystal droplets (originally spherical) that precipitate and grow are pressed. Therefore, after the completion of the polymerization, a polymer-dispersed liquid crystal having a flattened liquid crystal droplet is formed. Thus, the liquid crystal display device according to Embodiment 14 is manufactured. The liquid crystal display element is destroyed, and the length L1 and the length of the short axis (the axis perpendicular to the substrate of the liquid crystal droplet) of the long axis of the liquid crystal droplet (the axis parallel to the substrate of the liquid crystal droplet) are determined from the sectional shape of the liquid crystal droplet. When L2 was measured and L1 / L2 was determined as the deformation ratio, L1
= 1.2 μm, L2 = 1.1 μm, and the deformation ratio was 1.
09. As described above, in the fourteenth embodiment, since the liquid crystal droplet is deformed by the contraction of the polymerizable material, the liquid crystal droplet can be pressed evenly compared to the case where the liquid crystal droplet is deformed by mechanical pressing. Therefore, there is no variation in the deformation ratio of the liquid crystal droplet, and it is possible to perform display without display unevenness. Further, for the same reason as in the first embodiment, the drive voltage can also be reduced in the fourteenth embodiment.

(Experimental example) Various polymerizable materials having a shrinkage ratio in the range of 10 to 20% were selected, and a liquid crystal display device was manufactured by the above manufacturing method. The scattering property and the driving voltage were measured under the following conditions. Therefore, the results are shown in Table 1. Note that these liquid crystal display elements are referred to as liquid crystal display elements X1, X2, X of the present invention.
3, X4, X5, and X6. Also, the shrinkage rate is 10
Various polymerizable materials outside the range of 20% were selected, and a liquid crystal display device was manufactured by the above manufacturing method. The scattering property and the driving voltage were measured under the following conditions. The results are also shown in Table 1. . Note that these liquid crystal display elements are referred to as comparative liquid crystal display elements Y1, Y2, Y3, Y4, Y5, Y6, and Y7.

[Table 3]

In Table 3, M1200 and M1600
Is a urethane-based oligomer (trade name, manufactured by Toa Gosei Chemical Industry Co., Ltd.).

Experimental conditions Using an LCD 500 manufactured by Otsuka Electronics Co., Ltd., at a measurement temperature of 30
° C and a light receiving angle of 2.8 °. The scattering performance was evaluated by the transmittance T0 (%) in the absence of an electric field. The smaller the transmittance, the better the scattering. The driving voltage was evaluated at a voltage V90 when the transmittance reached 90% of the maximum transmittance. In addition, the deformation ratio destroys the liquid crystal display element and measures the major axis L1 and the minor axis L2 of the liquid crystal droplet from the cross-sectional shape of the liquid crystal droplet.
L1 / L2 was determined as the deformation ratio.

(Results) As is apparent from Table 3, there is a correlation between the shrinkage ratio and the performance of the liquid crystal display element.
%, It is recognized that the scattering property is improved in the case where the polymerizable material is used. However, when the shrinkage ratio exceeds 20%, it is recognized that the scattering property is rather deteriorated.
Further, there is also a correlation between the shrinkage ratio and the deformation ratio of the liquid crystal droplet, and it is recognized that good characteristics can be obtained when the deformation ratio is 1.10 or less. However, when the deformation ratio exceeds 1.2, it is recognized that the scattering property is rather deteriorated. Since the display characteristics were also evaluated at the same time, the results are described below. The liquid crystal display elements X1, X2, X3, X4, X
5 and X6 all showed uniform display without unevenness. On the other hand, comparative liquid crystal display elements Y1, Y2, Y3, Y4
Y5, Y6, and Y7 show uneven display and uneven display.

Further, it is recognized that the drive voltage is reduced in the case where a polymerizable material having a shrinkage of 10% or more is used. However, when the contraction rate exceeds 20%, it is recognized that the driving voltage is rather increased.

(Embodiment 15) FIG. 27A is a schematic sectional view of a liquid crystal display element according to Embodiment 15. In the figure, 114A and 114B are glass substrates, and transparent electrodes (not shown) are formed on mutually opposing surfaces of the glass substrates 114A and 114B. The stacked body 117 is held by the glass substrates 114A and 114B. Laminated body 117
Are a first polymer liquid crystal composite layer 111, a second polymer liquid crystal composite layer 112, and a third polymer liquid crystal composite layer 11.
3 are laminated. The first to third polymer liquid crystal composite layers 111 to 113 are polymer dispersed liquid crystal layers in which liquid crystal droplets 119 are dispersed in a polymer 118.

The first to third polymer liquid crystal composite layers 1
The major axes of the liquid crystal molecules 116 of 11 to 113 are substantially parallel to the substrate. Thereby, the difference in refractive index between the polymer and the liquid crystal can be increased, and a large light scattering effect can be obtained. As a result, high contrast is obtained.
This point is as described in JP-A-8-248398.

Here, the present inventors not only make the liquid crystal molecules parallel to the substrate, but also look at the liquid crystal molecules in the cell thickness direction, the more random the liquid crystal molecules become, the more random they are. , And found that the scattering could be more fully performed. Therefore, in the present invention, as shown in FIG.
The arrangement direction 115 of the liquid crystal molecules 116 is different for each of the liquid crystal molecules 113 to 113. According to such a configuration, the orientation direction 1
It has been found that the refractive index of each of the layers 111 to 113 is different due to the difference in No. 5, and that large scattering can be obtained. In the present invention, the liquid crystal molecules 116 correspond to the substrates 114A,
This state is most desirable if it can be completely randomly oriented in a plane parallel to 114B.

Incidentally, for reference, Japanese Patent Application Laid-Open No.
The liquid crystal display element described in JP-A No. 8398 is a laminate in which polymer dispersed liquid crystal composite layers are laminated, and liquid crystal molecules in each polymer liquid crystal composite layer are fixed in a plane substantially parallel to the electrode surface. And the orientation direction of the liquid crystal molecules between the polymer liquid crystal composite layers is set by an orientation treatment such as rubbing so that they are at 90 degrees to each other. This Japanese Patent Application Laid-Open No. 8-248
In the liquid crystal display device described in Japanese Patent No. 398, an attempt is made to control the alignment of liquid crystal molecules by rubbing.
When rubbing is used, the alignment directions of the liquid crystal molecules in the polymer liquid crystal composite layer are formed so as to intersect with each other by 90 degrees as described above, so that when the liquid crystal molecules are viewed in the cell thickness direction, Basically, liquid crystal molecules are oriented only in two directions, and it is impossible to obtain sufficiently satisfactory scattering. In this regard, the present invention does not require a rubbing treatment and has a structure in which polymer liquid crystal composite layers are laminated, so that liquid crystal molecules can be oriented in different directions for each layer. A remarkably large scattering effect can be obtained as compared with the liquid crystal display element described in the publication.

Further, by adopting a laminated structure, a polymer liquid crystal composite layer having a small layer thickness is required rather than forming a polymer layer having a large layer thickness at a time and controlling the alignment of liquid crystal. The alignment can be performed by performing liquid crystal alignment every time, and as a result, an external force for controlling the alignment of the liquid crystal, for example, an external force required for flattening the liquid crystal droplet can be easily transmitted to the polymer liquid crystal composite layer. Therefore, in the case of the present invention, a more uniform liquid crystal is obtained by controlling the alignment of each layer, compared to a case where a polymer liquid crystal composite layer having a large layer thickness is formed at a time and the alignment of the liquid crystal is controlled. A display element can be realized.

Next, a method of actually performing the alignment treatment of liquid crystal molecules in the present invention will be described.

The first technique is to irradiate a mixture containing a liquid crystal material and a polymerizable material which is a polymer precursor with light, and to irradiate polarized light when obtaining a polymer liquid crystal composite layer by phase separation. Is a method of performing polymer curing in the polarization direction. According to this method, a rod-shaped or rugby ball-shaped liquid crystal droplet shape can be finally obtained, whereby the liquid crystal molecules in the liquid crystal droplet are oriented according to the shape, and the orientation of the liquid crystal in the layer is changed. Can be regulated. By repeating the above operation to change the polarization direction for each layer, it is possible to form a stacked body in which the directions of the liquid crystal molecules are different for each layer.

The second technique is to regulate the orientation of the liquid crystal in each layer by applying a magnetic field or an electric field to each layer during phase separation. Note that the method for manufacturing the stacked body can be performed in the same manner as in the first method. In the second method, not only at the time of phase separation, but also after preparing a polymer liquid crystal composite layer, heating to an isotropic liquid, applying a magnetic field or an electric field in this state, and then lowering the temperature to a liquid crystal state. It is also possible to regulate the arrangement of the liquid crystal for each layer.

Further, as the most desirable mode of the present invention, in order to arrange the liquid crystal molecules of each layer substantially horizontally and randomly on the substrate, after forming each layer, each layer is pressed and disc-shaped or flat-shaped. As shown in FIG.
(B) can be brought into an elastically stable alignment state shown in FIG. 28 (b).
In addition, as a method of forming the liquid crystal droplet 119 into a flat shape at this time, the method described in Embodiment Modes 1 to 13 may be used. Furthermore, a method based on shrinkage during polymerization of the polymerizable material described in Embodiment 14 may be used. According to such a method based on shrinkage, liquid crystal enemies can be pressed uniformly compared to a mechanical pressing method. Therefore, there is no variation in the deformation ratio of the liquid crystal droplets, and display without display unevenness is possible.

In order to obtain a laminate having a uniform thickness as a manufacturing method, the thickness of each layer must be uniform.
Therefore, in the present invention, a composite layer having a uniform thickness can be obtained by using a spacer for each layer.

[0141]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the liquid crystal display device according to the present invention will be described in more detail with reference to embodiments.

Example 1 FIG. 29 is a schematic sectional view of a liquid crystal display device. In this embodiment, two polymer liquid crystal composite layers are laminated. In the figure, 121A,
Reference numeral 121B denotes a glass substrate.
A, 121B, the transparent electrodes 122A, 122B
2B is formed. This glass substrate 121A, 12
The polymer liquid crystal composite layers 123A and 123B are
A stacked body 124 formed by stacking layers is held. Each of the polymer liquid crystal composite layers 123A and 123B is made of a polymer 125
A and 125B constitute polymer-dispersed liquid crystal in which liquid crystal droplets 127A and 127B are dispersed. Liquid crystal droplets 127A and 127B in each of the polymer liquid crystal composite layers 123A and 123B
The long axis of the liquid crystal molecules inside the glass substrates 121A, 121A
1B, and are randomly arranged in a plane substantially parallel to the substrates 121A and 121B. Note that in this specification, the term “liquid crystal molecules are parallel to the substrate” refers to liquid crystal molecules (corresponding to liquid crystal molecules along the bipole axis) that average the inclination angles of all liquid crystal molecules in a liquid crystal droplet. It means parallel to the substrate. In addition, the shape of the liquid crystal droplets 127A and 127B is substantially flat or substantially disc-shaped, that is, circular in cross section when viewed from the cell thickness direction.

Next, a method of manufacturing the liquid crystal display device having the above configuration will be described.

First, a liquid crystal material, a polymerizable material, and a photopolymerization initiator are added, and the mixture is stirred to prepare a uniform mixed solution. Specifically, as a liquid crystal material, E-8
(Merck) was used. Further, as the polymerizable material, a mixture of three kinds of materials, butyl octyl acrylate (BOA), 2-ethylhexyl acrylate (2EHA), and 1,6-hexanediol acrylate (HDDA) is used. I used what was done. In addition, butyl octyl acrylate (BOA) and 2-ethylhexyl acrylate
(2EHA) and 1,6-hexanediol acrylate (HDDA) at a mixing ratio of 1.5: 1.5: 1. Further, as the photopolymerization initiator, Darocure 1173
(Nippon Ciba-Geigy) was used. Darocure 1173
Was 2 wt%. The mixing ratio between the liquid crystal material and the polymerizable monomer was 8: 2.

In this embodiment, the liquid crystal material is E-8
(Manufactured by Merck), but is not limited thereto. Various liquid crystals such as nematic liquid crystal, cholesteric liquid crystal, and smectic liquid crystal which have a positive dielectric anisotropy and show a liquid crystal state at around room temperature. Materials can be used. In addition, one kind of these liquid crystal materials may be used, or two or more kinds may be used in combination. In addition, these liquid crystal materials may contain, for example, a dichroic dye. Further, each polymer liquid crystal composite layer has a different color.
The present invention may be applied to a liquid crystal display element which can contain a color dye and can perform full color display.

In this example, butyl octal acrylate (BOA), 2-ethylhexyl acrylate (2EHA), and 1,6-hexanediol acrylate (HDDA) were used as the polymerizable materials. ) Is used, but the present invention is not limited to this. As the polymerizable material, various polymerizable substances that polymerize by light to produce a polymer compound having transparency can be used, and generally, for example, a monomer or oligomer having a polymerizable functional group such as acrylate, methacrylate, or epoxy is used. May be used. Specifically, as the polymerizable monomer, for example, n-tridecyl acrylate,
2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, monohydroxyethyl phthalate, neopentyl glycol diacrylate, hexanediol diacrylate and the like can be used. As the polymerizable oligomer, polyurethane acrylate, 1,
6-hexanediol diacrylate, pentaerythritol diacrylate monostearate, oligourethane acrylate, polyester acrylate, glycerin diglycidyl ether and the like can be used.

Next, as shown in FIG. 30A, a spacer 131 having a particle size of 2 μm is interposed between the glass substrate 121B and the glass substrate 130 for forming the polymer liquid crystal composite layer.
The substrates 121B and 130 are overlapped so as to keep the distance therebetween constant. The transparent electrode 1 is provided on the glass substrate 121B.
22B is formed, but no transparent electrode is formed on the glass substrate 130. This is because the glass substrate 1
Numeral 30 is used only for forming the polymer liquid crystal composite layer, and as will be described later, the polymer liquid crystal composite layer 1
This is because, after the formation of 23B, it is peeled off from the polymer liquid crystal composite layer 123B and does not become a component of the liquid crystal display element. Therefore, for example, a plastic film or the like may be used instead of the glass substrate 130.

Next, as shown in FIG.
The solution-like mixture is injected between 21B and 130.

Next, as shown in FIG.
The mixture injected between 21B and 130 was irradiated with ultraviolet light. As the conditions for the ultraviolet irradiation, irradiation was performed for 1 minute with an ultraviolet light having a main wavelength of 365 nm and an irradiation intensity of 30 mW. By photopolymerization by this ultraviolet irradiation, the polymer and the liquid crystal phase-separate,
A single-layer polymer liquid crystal composite layer 123B was obtained. In the state shown in FIG. 30C, the polymer liquid crystal composite layer 123
B, each liquid crystal droplet 127B has a spherical shape.
The B liquid crystal molecules are not parallel to the substrate but are oriented in various directions. This was confirmed by the present inventor by observing the polymer liquid crystal composite layer 123B with a polarizing microscope.

Next, as shown in FIG.
A pressure of 5 kg / cm ² was uniformly applied to 21B and 130 by, for example, a press machine, and a part of the liquid crystal in liquid crystal droplet 127B was extruded from between substrates 121B and 130 to the outside. As a result, the liquid crystal droplet 127B was deformed. Observing this deformed state with a polarizing microscope, the liquid crystal droplet 12
It was found that the liquid crystal molecules of 7B were substantially aligned parallel to the substrate 121B, and were randomly arranged in a plane parallel to the substrate 121B as shown in FIG. However, in FIG. 30D, for convenience, the liquid crystal droplet 127B that has been finely deformed is drawn so as to be oriented in a uniform direction, but actually has a deformed shape. But,
Even when the liquid crystal droplet 127B had a deformed shape, the liquid crystal molecules in the liquid crystal droplet 127B were oriented almost parallel to the substrate 121B. When the cross section was observed with a scanning electron microscope, the shape of the liquid crystal droplet 127B was deformed into a flat shape or a disc shape. Note that the deformation of the liquid crystal droplet may be performed by the method of shrinking the polymerizable material during polymerization described in the above-described Embodiment 14 instead of the mechanical pressing by a press machine or the like.

Next, as shown in FIG. 30E, the substrate 130 was peeled off from the single-layered polymer liquid crystal composite layer 123B to form a lower layer for forming a laminate 124.

Next, another single layer of the polymer liquid crystal composite layer 123 is formed by the same steps as those shown in FIGS.
A was prepared and used as the upper layer.

Next, as shown in FIG. 30E, an upper layer and a lower layer were bonded to face each other, and a peripheral portion was sealed, whereby a liquid crystal display element was manufactured.

The inventors of the present invention have conducted experiments on the characteristics of the liquid crystal display device thus manufactured.
%, The contrast was 100: 1, and the driving voltage was 5 V, and a sufficient scattering effect could be obtained.

Further, higher contrast could be realized by increasing the number of layers. For example, a contrast of 300: 1 and a drive voltage of 10 V can be realized with five layers.

(Comparative Example 1) Two single polymer liquid crystal composite layers were formed in the same manner as in Example 1 except that the pressing treatment shown in FIG. Comparative Example 1 was prepared by bonding together in the same manner as in Example 1 to produce a liquid crystal surface element.
And The characteristics of Comparative Example 1 were measured under the same conditions as in Example 1. As a result, the transmittance was 85%, the contrast was 20: 1, and the driving voltage was 7 V, and a sufficient scattering effect could not be obtained.

(Embodiment 2) In this embodiment 2, the laminate 1
The polymer liquid crystal composite layers 123A, 123 constituting
The liquid crystal molecules in the liquid crystal droplets 127A and 127B in B are arranged substantially parallel to the substrates 121A and 121B, and in a plane substantially parallel to the substrates 121A and 121B, the polymer liquid crystal composite layer 123A. , 123B in different directions.

With such a configuration, although the arrangement of the liquid crystal in each layer is random in the plane almost parallel to the substrate and in a plane substantially parallel to the substrate, which is the most preferable mode, the characteristics are slightly inferior to those of the first embodiment. A sufficient scattering effect can be obtained as compared with the conventional example. In this embodiment, an example of two layers will be described. However, by increasing the number of layers, a liquid crystal alignment state closer to an ideal form can be obtained.

The liquid crystal display device having the above structure was manufactured by the following method.

First, FIGS. 30A and 30B of the first embodiment.
The mixture is injected between the substrates 121B and 130 by the steps shown in FIGS. 32A and 32B similar to the steps shown in FIG.
Thereafter, as shown in FIG. 32 (c), the mixture was irradiated with ultraviolet rays through a polarizing element. As the conditions for the ultraviolet irradiation, irradiation was performed for 1 minute with an ultraviolet light having a main wavelength of 365 nm and an irradiation intensity of 30 mW. In addition, the polarization axis direction 132 of the polarizing element at this time is the horizontal direction (the horizontal direction in FIG. 33) of the substrate 121B, as shown in FIG. The polymer and the liquid crystal were phase-separated by the photopolymerization by the irradiation of the polarized ultraviolet light, and a single-layer polymer liquid crystal composite layer 123B in which the liquid crystal droplet 127B was dispersed in the polymer 125B was obtained. Note that the liquid crystal molecules in the liquid crystal droplet 127B at this time have the polarization axis direction 1
It is known that the liquid crystal molecules are deposited along the substrate 121B substantially parallel to the substrate 121B [FIG.
33], and in a plane parallel to the substrate, as shown in FIG.

In this regard, the present inventors observed the polymer liquid crystal composite layer 123B with a polarizing microscope and confirmed that the liquid crystal molecules were substantially parallel to the substrate and aligned in the polarization axis direction 132. are doing. The cross section was observed with a scanning electron microscope, and it was confirmed that the liquid crystal droplet 127B had a rod shape or a rugby ball shape.

Next, as shown in FIG. 33D, the substrate 130 was peeled off from the single-layered polymer liquid crystal composite layer 123 to form a lower layer for forming a laminate 124.

Next, another single-layered polymer liquid crystal composite layer 123A was formed by basically the same steps as those shown in FIGS. 32 (a) to (d), and was used as an upper layer. here,
FIG. 32C is different from the preparation of the polymer liquid crystal composite layer 123B in the preparation of the polymer liquid crystal composite layer 123A.
When irradiating polarized ultraviolet light shown in (1), the polarization direction of the ultraviolet light is different from that in the case of the polymer liquid crystal composite layer 123B. That is, when forming the polymer liquid crystal composite layer 123A, the polarization axis direction 132 of the polarizing element is set to the direction shown in FIG.
Is different from the polarization axis direction 132 shown in FIG. Therefore, the liquid crystal molecules in the liquid crystal droplet 127A of the polymer liquid crystal composite layer 123A are:
It is substantially parallel to the substrate 121A (see FIG. 32 (e)).
In addition, in a plane parallel to the substrate 121A, as shown in FIG.

Next, as shown in FIG. 32 (f), an upper layer and a lower layer were adhered so as to face each other, and the peripheral portion was sealed, whereby a liquid crystal display element was manufactured. This allows
As shown in FIG. 35, a liquid crystal display device in which the orientation direction of liquid crystal molecules differs between the upper layer and the lower layer in a plane parallel to the substrate could be obtained. In FIG. 35, reference numeral A denotes the orientation direction of the upper liquid crystal display element as viewed from above the substrate.
Reference numeral B indicates the orientation direction of the lower liquid crystal display element as viewed from above the substrate. The inventors of the present invention have conducted experiments on the characteristics of the liquid crystal display element thus manufactured, and found that the transmittance was 8%.
5%, contrast 60: 1, and drive voltage 5V.

According to this embodiment, since the alignment of the liquid crystal molecules is performed by polarized light, the liquid crystal molecules cannot be formed completely at random in the direction parallel to the substrate. Because of the difference, a liquid crystal display device having a superior contrast to that of Comparative Example 1 could be obtained, although it was inferior to that of Example 1.

(Embodiment 3) In Embodiment 3, instead of irradiation with polarized ultraviolet rays in Embodiment 2, ordinary unpolarized ultraviolet rays are irradiated, and a magnetic field is applied horizontally to the substrate at that time. It is. The strength of the magnetic field was set to 10K Gauss. The results of microscopic observation and observation with a scanning electron microscope were the same as in Example 2. Further, when the present inventor conducted experiments on the characteristics of the liquid crystal display element thus prepared,
The transmittance was 87%, the contrast was 70: 1, and the driving voltage was 6 V.

Also in this embodiment, although the liquid crystal molecules cannot be formed completely at random in the direction parallel to the substrate, it is inferior to that of the first embodiment because the alignment direction of the liquid crystal is different for each liquid crystal layer. However, a liquid crystal display device having excellent contrast as compared with Comparative Example 1 could be obtained.

Although the liquid crystal display device of the first to third embodiments has a two-layer structure, the liquid crystal display device may have a laminated structure of three or more layers. Can be manufactured. That is, a laminated structure of three or more layers corresponding to the first embodiment will be described.
First, a mixture is injected between a pair of glass substrates for forming a polymer liquid crystal composite layer, and the polymer liquid crystal composite layer for an intermediate layer is formed by the same steps as those shown in FIGS. 30 (c) and 30 (d). To form Thereafter, the pair of glass substrates for forming a polymer liquid crystal composite layer is peeled off from the polymer liquid crystal composite layer for the intermediate layer to produce a single layer of the polymer liquid crystal composite layer for the intermediate layer.
Then, the above steps are performed according to the number of layers to obtain a plurality of polymer liquid crystal composite layers for an intermediate layer. After that, the polymer liquid crystal composite layers are bonded between the upper polymer liquid crystal composite layer 23A and the lower polymer liquid crystal composite layer 23B with the plurality of intermediate polymer liquid crystal composite layers interposed therebetween. Match. Thus,
A liquid crystal display device having a laminated structure of three or more layers is obtained.

Regarding the laminated structure of three or more layers corresponding to the second and third embodiments, except that the liquid crystal molecules in each layer are oriented so as to be different for each layer, the three-layer structure corresponding to the first embodiment is also used. It can be manufactured by a method basically similar to the manufacturing of the above-described laminated structure.

As another manufacturing method, a plurality of polymer liquid crystal composite layers are manufactured in advance, and the plurality of polymer liquid crystal composite layers are interposed between a pair of substrates. The layers and the substrate and the polymer liquid crystal composite layer may be bonded to each other.

Further, in Examples 1 to 3,
A dichroic dye may be added to the liquid crystal. In this case, a guest-host type liquid crystal display device that absorbs light with a dichroic dye is provided.

In Examples 1 to 3,
A different dichroic dye may be added to each layer, and the driving voltage for each layer may be different. In this case, a multi-color display is obtained. Further, the liquid crystal material may be different for each layer.

As described above, in the polymer-dispersed liquid crystal display device in which the polymer liquid crystal composite layers are laminated, the liquid crystal molecules in the liquid crystal droplets in each layer are oriented substantially parallel to the substrate and are aligned with the substrate. Since the layers are oriented in different directions substantially in parallel in the plane, sufficient light scattering can be performed, and as a result, a liquid crystal display device with high contrast can be obtained. In particular, by controlling the alignment direction of the liquid crystal by flattening the liquid crystal droplet by pressing, the direction of the liquid crystal molecules in the substrate surface can be set at random, and scattering can be performed more sufficiently.

[0174]

As described above, according to the present invention, the scattering characteristics can be improved and the driving voltage can be reduced by tilting the liquid crystal molecules in the direction parallel to the substrate within the optimum range. Furthermore, in the present invention, since the liquid crystal droplets are flattened due to shrinkage due to polymerization of the polymerizable material, the liquid crystal droplets are uniformly pressed as compared with a configuration in which the liquid crystal droplets are flattened using mechanical pressing means. Therefore, there is no variation in the deformation ratio of the liquid crystal droplet. Therefore, it is possible to realize a liquid crystal display element having high scattering, excellent reproducibility, and without display unevenness.

[Brief description of the drawings]

FIG. 1 is a sectional view of a liquid crystal display element according to Embodiment 1 of the present invention.

FIG. 2 is a partial plan view of the liquid crystal display device according to the first embodiment of the present invention.

FIG. 3 is a manufacturing process diagram of the liquid crystal display element according to the first embodiment of the present invention.

FIG. 4 is a front view of an apparatus for manufacturing a liquid crystal display element according to Embodiment 1 of the present invention.

FIG. 5 is a diagram for explaining the relationship between the deformation of the liquid crystal and the orientation of the liquid crystal in the liquid crystal display element according to the first embodiment of the present invention.

FIG. 6 is a diagram showing the relationship between the transmittance and the deformation ratio of the liquid crystal display device according to Embodiment 1 of the present invention during scattering.

FIG. 7 is a diagram illustrating a relationship between a driving voltage V90 of the liquid crystal display element and a deformation ratio according to the first embodiment of the present invention.

FIG. 8 is a diagram showing a relationship between a steepness γ and a deformation ratio of the liquid crystal display element according to the first embodiment of the present invention.

FIG. 9 is a diagram showing a relationship between drive voltages V10 and V90 and transmittance.

FIG. 10 is a diagram illustrating a relationship between a response speed and a deformation ratio of the liquid crystal display element according to the first embodiment of the present invention.

FIG. 11 is a diagram showing a change in transmittance with respect to drive voltages V10 and V90.

FIG. 12 is a sectional view of an apparatus for manufacturing a liquid crystal display element according to Embodiment 4 of the present invention.

FIG. 13 is a sectional view of an apparatus for manufacturing a liquid crystal display element according to Embodiment 6 of the present invention.

FIG. 14 is a simplified front view of an apparatus for manufacturing a liquid crystal display element according to Embodiment 8 of the present invention.

FIG. 15 is a sectional view of a liquid crystal display element according to an eighth embodiment of the present invention.

FIG. 16 is a partial plan view of a liquid crystal display element according to Embodiment 8 of the present invention.

FIG. 17 is a perspective view of an apparatus for manufacturing a liquid crystal display element in Embodiment 9 of the present invention.

FIG. 18 is a sectional view of a liquid crystal display element according to Embodiment 12 of the present invention.

FIG. 19 is a partial plan view of a liquid crystal display device according to Embodiment 12 of the present invention.

FIG. 20 is a diagram showing a polymerization process when a liquid crystal monomer is used.

FIG. 21 is a diagram illustrating a polymerization process when a liquid crystal monomer is used.

FIG. 22 is a state diagram before and after polymerization of a conventional example and a twelfth embodiment of the present invention, respectively.

FIG. 23 is a perspective view of one substrate used in Embodiment 13 of the present invention.

FIG. 24 is a perspective view of the other substrate used in Embodiment 13 of the present invention.

FIG. 25 is a sectional view of a liquid crystal display element according to Embodiment 14 of the present invention.

FIG. 26 is a partial plan view of a liquid crystal display device according to Embodiment 14 of the present invention.

FIG. 27 is a schematic diagram of a liquid crystal display element according to Embodiment 15 of the present invention.

FIG. 28 is a schematic diagram showing a liquid crystal alignment direction of a liquid crystal display element according to Embodiment 15 of the present invention.

FIG. 29 is a first example corresponding to the fifteenth embodiment of the present invention;
FIG. 2 is a schematic cross-sectional view of a liquid crystal display device according to the first embodiment.

FIG. 30 is a first example corresponding to the fifteenth embodiment of the present invention;
FIG. 4 is a manufacturing process diagram of the liquid crystal display element according to the first embodiment.

FIG. 31 is a view of the polymer liquid crystal composite layer 123B in the state shown in FIG.

FIG. 32 is a second example corresponding to the fifteenth embodiment of the present invention;
FIG. 4 is a manufacturing process diagram of the liquid crystal display element according to the first embodiment.

FIG. 33 is a view of the polymer liquid crystal composite layer 123B in the state shown in FIG. 32D as viewed from above.

FIG. 34 is a view of the polymer liquid crystal composite layer 123A in the state shown in FIG. 32 (e) as viewed from above.

FIG. 35 is a diagram showing alignment directions of liquid crystal molecules in a polymer liquid crystal composite layer 123A and a polymer liquid crystal composite layer 123B.

[Explanation of symbols]

11, 50, 51, 114A, 114B, 121A, 1
21B: Substrate 12, 52, 53, 122A, 122B: Transparent electrode 13, 54, 118: Polymer 14, 14A, 55, 119, 127A, 127B: Liquid crystal droplet 21, 22: Surface plate 23: Liquid crystal panel 24: Buffer Agent 30: Pack 56: Polymer liquid crystal composite 71A, 71B: Roller 73: Heating means 81: UV lamp 82: Filter 84: Magnetic field applying means 90: Polarizer 111: First polymer liquid crystal composite layer 112: First No. 2 polymer liquid crystal composite layer 113: third polymer liquid crystal composite layer 115, A, B: orientation direction of liquid crystal molecules 116, 125A, 125B: liquid crystal molecules 117, 124: laminate

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tsuyoshi Uemura 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 2H089 HA04 JA04 JA05 KA08 NA25 QA16 TA09

Claims (5)

[Claims] 1. A polymer liquid crystal composite in which liquid crystal droplets are dispersed and held in a polymer is disposed between a pair of substrates on which electrodes are formed, and the liquid crystal droplets shrink in a direction perpendicular to the substrate. And a length of an axis perpendicular to the substrate of the liquid crystal droplet is L2, a length of an axis parallel to the substrate is L1, and L1 / L2 is L1 / L2. A polymer-dispersed liquid crystal display device, wherein the deformation ratio of the liquid crystal droplet is 1.2 or less when the deformation ratio is used. 2. A polymer liquid crystal composite in which liquid crystal droplets are dispersed and held in a polymer is disposed between a pair of substrates on which electrodes are respectively formed, and the liquid crystal droplets shrink in a direction perpendicular to the substrate. And a length of an axis perpendicular to the substrate of the liquid crystal droplet is L2, a length of an axis parallel to the substrate is L1, and L1 / L2 is L1 / L2. A polymer-dispersed liquid crystal display device, wherein the deformation ratio of the liquid crystal droplet is 1.10 or less when the deformation ratio is obtained. 3. A polymer liquid crystal composite in which liquid crystal droplets are dispersed and held in a polymer is disposed between a pair of substrates on which electrodes are formed, and the liquid crystal droplets shrink in a direction perpendicular to the substrate. A method for producing a polymer-dispersed liquid crystal display element having a flattened shape, comprising: mixing a polymerizable material having a shrinkage ratio due to polymerization of 10% or more and 20% or less with a liquid crystal material. Injecting between the substrates, polymerizing the polymerizable material in the mixed composition injected between the substrates, thereby phase-separating the polymer and the liquid crystal to form a polymer-liquid crystal composite. A method of producing a polymer-dispersed liquid crystal display device, comprising: forming a liquid crystal droplet into a flat shape which is shrunk in a direction perpendicular to the substrate due to shrinkage of the polymerizable material in the polymerization process. 4. The method according to claim 3, wherein the polymerizable material is an acrylate-based or methacrylate-based material. 5. The method according to claim 3, wherein the polymerizable material comprises a monomer having a monofunctional group and a monomer having a bifunctional group. Method.