JP3243340B2 - Light modulation element and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light modulation device using a liquid crystal / polymer composite film which has a response to an electric field or heat and can display and record various kinds of information, and a method of manufacturing the same. The light modulation device of the present invention can be widely applied to light control panels, displays, recording media, and the like.

[0002]

2. Description of the Related Art Conventionally, liquid crystal displays have characteristics such as low power consumption, light weight, and thinness, and are widely used as wristwatches, calculators, personal computers, televisions, and the like as display media for characters and images. . In general TN- and STN-liquid crystal displays, liquid crystal is sealed in a liquid crystal cell in which a predetermined seal or the like is provided between glass plates having transparent electrodes, and sandwiched by polarizing plates from both sides. However, (1) a viewing angle is narrow because two polarizing plates are required, and a backlight with high power consumption is required because of insufficient brightness. (2) Dependence on cell thickness. big,
It is difficult to increase the area. (3) Since the structure is complicated and it is difficult to enclose the liquid crystal in the cell, there are problems such as a high manufacturing cost. There are limits to reducing power consumption and cost.

As a liquid crystal display medium which solves such problems, application of a light modulation element based on a light scattering mechanism using a liquid crystal / polymer composite film in which liquid crystal is dispersed in a polymer matrix is expected. Development has been activated. already,
A large number of light modulation elements using a liquid crystal / polymer composite film and a method for manufacturing the same have been disclosed. One of the methods is to prepare a liquid crystal from an emulsion dispersed in an aqueous solution of polyvinyl alcohol (PVA) (Japanese Patent Publication No. Hei 3- No. 52843). The light modulation element manufactured by this method has characteristics such as a contrast ratio that can be improved by adding a dichroic dye and a low transmittance when a voltage is turned off.

[0004]

[Problems to be Solved by the Invention]
The light modulation element made from the VA dispersion aqueous solution has the above-mentioned characteristics, but the liquid crystal PVA dispersion aqueous solution is
It is difficult to form a uniform liquid crystal / polymer composite film that has poor wettability to an electrode substrate and can be used for a light modulation element. As PVA, an appropriate degree of polymerization (300 to
1,200) and a degree of saponification (85% to 50%), the electrode substrate can be formed into a film having a satisfactory level of wettability by blade coating. There are problems such as uneven coating at the end of coating and use of an expensive extra dispersion.

[0005] In addition, since the aqueous solution of PVA has a low viscosity,
The problem that conventional processing methods (such as blade coating) cannot be applied to perform pattern coating in which an emulsion obtained by emulsifying liquid crystal in an aqueous solution and forming a composite film only on a necessary portion on an electrode substrate. There is also a method of applying a pattern on an electrode substrate using a screen printing plate without a mesh and a doctor and drying it, and then bonding the formed patterned liquid crystal / polymer composite film to the counter electrode substrate, or A liquid crystal / polymer composite film formed in a compartment, which is filled with an emulsion only in a plurality of compartments partitioned by a partition made of an electrically insulating material and formed on a base material and which is lower than the height of the partition after drying. Even if the method of filling the space between the counter electrode base material with the conductive material and connecting the conductive material and the electrode is used, since the viscosity is similarly low, the dispersion liquid on the back surface of the plate is also used. There are problems such dents film in the center of the back around and compartment.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, to facilitate pattern coating, and to provide only a plurality of compartments partitioned by partition walls made of an electrically insulating material. An object of the present invention is to provide a light modulation element which can be easily coated and has excellent characteristics as a result, and a method for manufacturing the same.

[0007]

The above object is achieved by the present invention described below. That is, the present invention relates to a light modulation element using a liquid crystal / polymer composite film in which liquid crystal particles are dispersed in a polymer matrix, wherein the composite film comprises liquid crystal particles,
The degree of polymerization is 300 to 1,200 and the degree of saponification is 50% to 85.
% Polyvinyl alcohol (PVA) and a degree of polymerization of 1.5
PVA having a degree of saponification of 50 to 100% and a degree of saponification of 50 to 100%
Using a liquid crystal / polymer composite film having a final mixing ratio (weight ratio) of (PVA + thickener) / liquid crystal of 5/95 to 50/50. An element and a method for manufacturing the same.

[0008]

The dispersibility of the liquid crystal PVA dispersion greatly affects not only processability, especially wettability to the electrode substrate, but also electro-optical characteristics. Therefore, the dispersibility of the liquid crystal is determined by using P having a polymerization degree of 300 to 1,200 and a saponification degree of 50% to 85%.
It is improved by using an aqueous solution of VA, and the flow characteristics of the liquid crystal dispersion are adjusted to a suitable thickener, that is, the degree of polymerization is 1,500 to 3,0.
By using an aqueous solution of PVA having a saponification degree of 50% to 100%, a liquid crystal / polymer composite film excellent in processability and electro-optical characteristics can be produced.

That is, first, the liquid crystal is polymerized at a polymerization degree of 300 to 1,2.
And an aqueous solution of PVA having a saponification degree of 50% to 85%, and a suitable thickener, that is , a polymerization degree of 1,5
PVA having a degree of saponification of 50 to 100% and a degree of saponification of 50 to 100%
A liquid crystal PVA dispersion prepared by adding an aqueous solution of, for example, a metal screen printing plate without a mesh and a doctor apply a pattern on an electrode substrate, and after drying, form a patterned liquid crystal / polymer By laminating the composite film and the counter electrode substrate, or filling the emulsion only in a plurality of compartments partitioned by partitions made of an electrically insulating material formed on the electrode substrate, after drying, from the height of the partitions The space between the liquid crystal / polymer composite film formed in the compartment and the counter electrode base material is filled with a conductive material, and the conductive material and the electrode are connected. / A pattern coat for forming a polymer composite film becomes possible, and as a result, a light modulation element having excellent characteristics can be manufactured.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments. As shown in Table 1 below and FIG. 1, the surface tension of the aqueous solution varies depending on the degree of polymerization and the degree of saponification of PVA. That is, depending on the degree of polymerization and the degree of saponification of PVA, a difference occurs in the ability of PVA to disperse liquid crystals. Thus, the lower the degree of polymerization and the lower the degree of saponification,
The ability of VA to disperse the liquid crystal is increased.

[0011]

[Table 1] Degree of saponification and degree of polymerization of various PVAs

As a result, when the liquid crystal (E-44) was dispersed using aqueous solutions of various PVAs shown in Table 2 below,
The dispersibility of the liquid crystal particles differs depending on A, and the particle size distribution of the liquid crystal particles changes as shown in FIGS.

Table 2 Structure and processability of PVA in liquid crystal (E-44) dispersion of various PVAs

On the other hand, if the degree of saponification of PVA is high, the dispersibility of the liquid crystal particles is deteriorated, the proportion of the liquid crystal present in the aqueous phase is increased, and the particle size distribution is wide and the particle size is large. As a result, when the dispersibility is poor, the wettability to the electrode substrate is poor, the workability is reduced (Table 2), and the particle size distribution of the liquid crystal / polymer composite film is wide and the particle size is large (see FIG. 2). 2-4), and the electro-optical characteristics are also reduced (FIG. 5).
Also, when the degree of polymerization of PVA is large, the dispersibility of the liquid crystal particles is poor, the particle size distribution is wide, the particle size is large, and the electro-optical characteristics are low (FIGS. 2 to 5), but the viscosity is high. The workability is improved (Table 2). Under such circumstances, a suitable degree of polymerization (300-1,200) and a degree of saponification (50%-
If it is 85%), the wettability of the electrode base material reaches a level that does not cause any problem. However, in order to perform pattern coating only where necessary, the conventional processing method should be applied because the PVA has a low viscosity. Can not do.

[0014] While such action, Ru is cod by polymerization degree and molecular weight of the PVA, as described above, in order to pattern coat, only one type of PVA is both processability and electro-optical properties I cannot be satisfied. Therefore, first, a thickener is added to the PVA aqueous solution in which the liquid crystal is dispersed to increase the viscosity of the liquid crystal dispersion, thereby imparting processability. Thickeners are heavy Godo 1,500 to 3,000 and a saponification degree of 50% to 100% of PVA. The aqueous solution of PVA is added to increase the viscosity of the liquid crystal PVA dispersion, and a dispersion having processability is used. For example, a metal screen printing plate without a mesh and a doctor apply a pattern on an electrode substrate, and then dry the pattern. After that, the formed pattern-shaped liquid crystal / polymer composite film and the counter electrode substrate are bonded to each other or only in a plurality of compartments partitioned by partition walls made of an electrically insulating material formed on the electrode base material. After filling the emulsion and drying, the space between the liquid crystal / polymer composite film formed in the compartment, which is lower than the height of the partition walls, and the counter electrode base material is filled with a conductive material to form a conductive material and an electrode. By connecting, it becomes possible to perform a pattern coating for forming a liquid crystal / polymer composite film only where necessary, and as a result, it is possible to manufacture a light modulation element having excellent characteristics. The ability. You.

More specifically, first, PVA for dispersing a liquid crystal that satisfies the electro-optical characteristics includes:
Degree of polymerization 300-1,200 and degree of saponification 50% -100%
Is used. When the degree of polymerization is less than 300, the mechanical strength of PVA as a liquid crystal / polymer composite film is insufficient. If the degree of polymerization exceeds 1,200, the dispersibility of the liquid crystal deteriorates. As the dispersion conditions, a liquid crystal is added to a 1 to 15% by weight aqueous solution of PVA so that PVA / liquid crystal = 2.5 / 97.5 to 15/85, and dispersed by mechanical stirring or ultrasonic waves. Is preferred. If the mixing ratio is less than 2.5 / 97.5,
The liquid crystal cannot be dispersed, and if the mixing ratio exceeds 15/85, the dispersibility of the liquid crystal particles deteriorates.

Next, as a thickener for improving the processability, a polymerization degree of 1,500 to 3,000 and a saponification degree of 50% to
Ru have use 100% of the PVA. At this time, in the case of mechanical dispersion or ultrasonic dispersion, since the particle size distribution of the liquid crystal particles dispersed in the first step is destroyed, it is necessary to form a uniform dispersion aqueous solution under gentle conditions such as shaking. As the final dispersion, the total PVA is PVA / liquid crystal = 5 / 95-50
/ 50. When the ratio is less than 5/95, the strength as a film cannot be maintained, and the light scattering ability of the obtained device is reduced. Further, the total PVA is PVA / liquid crystal = 50/5.
If it exceeds 0, the driving voltage of the device becomes high, and the response becomes poor. The final concentration of total PVA is 10% by weight to 6%.
It is preferable to adjust the amount to be 0% by weight. If it is less than 10% by weight, the viscosity becomes too low, and if it exceeds 60% by weight, the viscosity becomes too high and handling becomes difficult.

The liquid crystal referred to in the present invention is an organic mixture showing a liquid crystal state at around normal temperature, and includes a nematic liquid crystal, a cholesteric liquid crystal, and a smectic liquid crystal. Among them, a nematic liquid crystal or a nematic liquid crystal to which a cholesteric liquid crystal is added is preferable in terms of characteristics. A dye may be incorporated in the liquid crystal to improve contrast or color tone. When a dichroic dye is added, it can be used not only as a scattering-transmission type composite film, but also as a composite film that switches between light absorption (coloring) and a transparent state due to the guest-host effect of the dye. . As a method of dispersing the liquid crystal in the PVA aqueous solution, a mixing method using various stirring devices such as an ultrasonic disperser or a film emulsification method (Tadao Nakajima, Masataka Shimizu, PHARMTECH JAPAN)
Vol. 4, No. 10 (1988)) is effective. The size (diameter) of the liquid crystal emulsion particles depends on the dispersion method used, but is generally preferably in the range of 0.5 to 7 μm, and more preferably in the range of 1 to 4 μm.

The method of the present invention for forming a liquid crystal / polymer composite film from the liquid crystal particle dispersion thus obtained is a method of applying and drying the emulsion on a suitable electrode substrate by a usual coating method. . When a liquid crystal / polymer composite film is formed on the entire surface of the electrode substrate, a normal coating method may be used. However, when a uniform composite film is formed at a predetermined position or only on a predetermined portion of the substrate in a pattern, coating is performed using a metal screen plate without a mesh and a doctor, or an electrically insulating film formed on the electrode substrate is used. It is desirable to use a special method or the like in which a liquid crystal emulsion is filled in a compartment partitioned by a partition made of a material. The thickness of the composite membrane obtained in this manner is 5 to 1
About 5 μm is preferable.

As the metal screen plate having no mesh, any conventionally known metal screen plate can be used. Usually, a metal screen plate having a plate thickness of 20 to 100 μm is used. 0
5 to 0.5 mm, cutting edge thickness 50 to 100 μm, width 20 to
100 mm and a 0.5 to 5 mm edge are used. In this case, the area (pattern) where the composite film is to be formed
Dents of the coating film is a problem that the resulting may occur in the central portion of the raised and the coating film of the edge of the coating film on the inner. In a preferred embodiment of the present invention, the above problem is that the plate thickness of the metal screen plate is 10 to 20 μm,
In addition, the problem is solved by providing an auxiliary plate in the doctor to be used.

FIG. 6 is a view for explaining the shape of a doctor provided with the auxiliary plate. The doctor 1 has a material thickness (T).
0.05-0.5mm, blade edge thickness (t) 50-100μ
m, width (L) 20-100 mm, cutting edge (1) 0.5-5
The auxiliary plate (2) (thickness (D) 5 to 10 mm) is adjusted so that the blade edge of the doctor 1 comes out about 1 to 2 mm. By using the metal screen plate and the doctor with the auxiliary plate as described above, problems such as bulging of the edge of the coating film and dent of the coating film in the center of the coating film occur in the area (pattern) where the composite film is to be formed. Without this, it is possible to provide a light modulation element having a composite film with a high precision thickness.

In another preferred embodiment of the present invention, the liquid crystal emulsion is treated to produce microcapsules containing liquid crystals, and the microcapsule dispersion is prepared as it is or after separation, to prepare a coating liquid again. A liquid crystal / polymer composite film can be produced by the method as described above. As a method for producing microcapsules from an emulsion in which liquid crystals are dispersed, both a chemical production method and a physicochemical production method can be used. As the chemical preparation method, there are an interfacial polymerization method using a synthesis reaction, an in situ polymerization method, and a curing-in-liquid coating method which causes a change in physical properties of a polymer. The interfacial polymerization method is a method in which a water-soluble monomer and an oil-soluble monomer are selected as two kinds of monomers that undergo a polycondensation or polyaddition reaction, and either one is dispersed and reacted at the interface. i
The n situ polymerization method is a method in which a reactant (monomer and initiator) is supplied from one of the inside and the outside of the core material and reacted on the surface of the capsule wall film.

Examples of the physicochemical preparation method include a coacervation method using phase separation, an interfacial precipitation method, a submerged concentration method,
There are a submerged drying method and a secondary emulsion method. A simple coacervation method in which phase separation is caused by a decrease in solubility, and a complex coacervation method in which phase separation is caused by electrical interaction can also be used. The interface precipitation method is a method capable of encapsulation under mild conditions without vigorous reaction or rapid pH change, for example, by dispersing an emulsion in which a liquid crystal core material is dispersed in a solvent solution of a hydrophobic polymer. After that, it is further redispersed in an aqueous protective colloid solution.

[0023]

Next, the present invention will be described more specifically with reference to examples and comparative examples. Example 1 KP-06 (manufactured by Nippon Synthetic Chemical Industry, degree of polymerization: about 600,
Saponification degree: 71.0-75.0)
After ultrasonic dispersion of -44 (manufactured by Merck), KH-17
(Manufactured by Nippon Synthetic Chemical Industry, degree of polymerization: about 1,700, degree of saponification: 78.5 to 81.5), and finally a PVA / liquid crystal = 20/80 (weight ratio) was added. An aqueous PVA dispersion of the liquid crystal was prepared such that The electro-optical properties of the liquid crystal / polymer composite film obtained from this dispersion are
E-44 was added to a 10% by weight aqueous solution of P-06 by adding KP-06 /
E-44 = 20/80 (w / w) was added so as to be obtained, and it was not inferior but rather excellent as compared with that obtained from a dispersion obtained by ultrasonic dispersion (FIG. 7). ). Using this dispersion, a film was formed on the element substrate by metal screen printing without a mesh. As shown in FIG. 8, the viscosity was high and the thixotropic property was slightly increased, and as a result, a good pattern coat was formed.

Example 2 KP-06 (manufactured by Nippon Synthetic Chemical Industry, degree of polymerization: about 800,
Saponification degree: 71.0 to 75.0%) in a 5% by weight aqueous solution,
After BL-010 (manufactured by Merck) was dispersed by a film emulsification method, AH-26 (manufactured by Nippon Synthetic Chemical Industry, polymerization degree: about 2,
600, a 10% by weight aqueous solution having a saponification degree of 97.0 to 98.8), and finally PVA / liquid crystal = 15/85.
(Weight ratio) An aqueous dispersion of PVA of the liquid crystal was prepared so as to have a weight ratio. A liquid crystal / polymer composite film obtained from this dispersion in the same manner as in Example 1 has excellent electro-optical properties and is uniformly formed in a compartment defined by partitions made of an electrically insulating material formed on an electrode substrate. Could be filled.

Example 3 KP-06 (manufactured by Nippon Synthetic Chemical Industry, degree of polymerization: about 600,
Saponification degree: 71.0-75.0)
-44 (manufactured by Merck) at a mixing ratio of PVA / liquid crystal of 5/9.
5 (w / w) and dispersed by a film emulsification method. KH-20 (manufactured by Nippon Synthetic Chemical Industry, degree of polymerization: about 2,000, degree of saponification: 78.5 to 78.5)
81.5) by (KP-06 + KH-20) / E-44 =
17/83 (w / w) was added and stirred. Using this dispersion, a metal screen plate without mesh (manufactured by Sonocom Co., plate thickness 20 μm), a doctor (manufactured by Tokyo Seisakusho, material thickness 0.15 mm, blade edge thickness 85 μm, blade width 60 mm, blade edge 1.4 mm) and an auxiliary plate (85mm thick,
(Width: 58.6 mm), and was printed in a pattern on the element substrate and dried to form a film. As a result, a uniform coating film was formed without ridges on the edges or dents in the film at the center.

Comparative Example 1 E-44 was added to a 10% by weight aqueous solution of KP-06 by adding KP-06.
/ E-44 = 20/80 (w / w)
Using a dispersion obtained by ultrasonic dispersion, pattern coating without a mesh was performed. However, as shown in FIG. 7, since the viscosity was extremely low, set-off of the dispersion to the back of the plate and squeegee There was a problem in the uniformity of the film thickness and the like when printing was performed. Comparative Example 2 E-44 was added to a 10% by weight aqueous solution of KP-06, and KP-0
6 / E-44 = 15/85 (weight ratio), which was dispersed and formed into a film by the film emulsification method, was inferior in electro-optical properties, and was formed by coating in the same manner. The film had uniformity problems.

[0027]

According to the present invention, a liquid crystal / polymer composite film can be formed only on a necessary portion on an element substrate,
It is possible not only to manufacture a patterned light modulation element that has not been conventionally used, but also to achieve a reduction in element manufacturing cost. In addition, it is also possible to reduce the deterioration of visibility due to uneven application of the emulsion and the bonding failure of the counter electrode base material. On the other hand, the combined use of high molecular weight PVA improves the mechanical strength of the liquid crystal / polymer composite film, and is also effective in stabilizing the electro-optical characteristics.

[0028]

[Brief description of the drawings]

FIG. 1 shows the relationship between the degree of saponification and molecular weight of PVA and the surface tension of a PVA aqueous solution (4% PVA aqueous solution, measurement temperature 20
FIG.

FIG. 2 is a diagram illustrating a particle size distribution of liquid crystal particles in various PVAs.

FIG. 3 is a diagram illustrating a particle size distribution of liquid crystal particles in various PVAs.

FIG. 4 is a photograph for explaining the structure of a liquid crystal / various PVA thin films.

FIG. 5 is a diagram illustrating the electric field response of a liquid crystal / various PVA composite film.

FIG. 6 is a view for explaining the shape of a doctor provided with an auxiliary plate.

FIG. 7 is a diagram illustrating the electric field response of a liquid crystal / various PVA composite film.

FIG. 8 illustrates the viscosity of a liquid crystal dispersion.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor: Shin Miyanowaki 1-1-1, Ichigaya-Kaga-cho, Shinjuku-ku, Tokyo Dai Nippon Printing Co., Ltd. (56) References JP-A-2-110520 (JP, A JP-A-4-29218 (JP, A) JP-A-2-4215 (JP, A) JP-A-57-76896 (JP, A) JP-A-62-231930 (JP, A) 56920 (JP, A) JP-A-1-202711 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1334 B41M 1/12

Claims (6)

(57) [Claims] 1. A light modulation device using a liquid crystal / polymer composite film in which liquid crystal particles are dispersed in a polymer matrix, wherein the composite film is formed of a liquid crystal particle and a polymerization degree of 300 to 1,2.
And polyvinyl alcohol (PVA) having a saponification degree of 50% to 85% and a polymerization degree of 1,500 to 3,000
And a final mixing ratio of (PVA + thickener) / liquid crystal (weight ratio).
Using a liquid crystal / polymer composite film having a ratio of 5/95 to 50/50. 2. A method of manufacturing a light modulation element using a liquid crystal / polymer composite film in which liquid crystal particles are dispersed in a polymer matrix, wherein the composite film is formed by mixing a liquid crystal with a degree of polymerization of 300 to 300.
After dispersing in a PVA aqueous solution having a saponification degree of 1,200 and a saponification degree of 50% to 85%, a polymerization degree of 1,500 to 3,000 and
A thickener consisting of PVA having a degree of saponification of 50% to 100% ,
The final mixing ratio (weight ratio) of (PVA + thickener) / liquid crystal is 5
A method for producing a light modulation element, comprising a step of forming a liquid crystal emulsion formed by adding a liquid crystal emulsion so as to have a ratio of / 95 to 50/50. 3. A liquid crystal emulsion is formed by applying a pattern on an electrode substrate using a metal screen plate having no mesh and a doctor and then drying and bonding a counter electrode substrate on which a sealing material is formed. 3. The method for manufacturing a light modulation element according to item 2 . 4. The metal screen plate has a thickness of 10 to 20.
The method for manufacturing a light modulation element according to claim 3 , wherein the thickness is μm. 5. A method of manufacturing an optical modulation element according to claim 3 which doctor the auxiliary plate is provided. 6. A liquid crystal emulsion is filled only in a plurality of compartments partitioned by a partition made of an electrically insulating material formed on an electrode substrate, and after drying, formed in a compartment lower than the height of the partition. a liquid crystal / polymer composite film, which is, the light modulation according to what Re one of claims 2 to 5 connecting the space conductive substance by filling the conductive material and the electrode and the counter electrode substrate Device manufacturing method.