JPH07128648A - Liquid crystal optical element and its production - Google Patents

Abstract

PURPOSE:To provide the liquid crystal optical element which does not wastefully consume a liquid crystal emulsion, does not contain air bubbles at all in the liquid crystal/high polymer combined film of the liquid crystal optical element and has excellent display characteristics. CONSTITUTION:This liquid crystal optical element is constituted by holding the liquid crystal/high polymer combined film 3 with a pair of conductive substrates 1, 1', at least one which are transparent. At least one of these substrates have a shape building up at the center toward the inner side. This process for production of the liquid crystal optical element comprises forming at least one of the substrates 1 so as to have the shape building up at the center to the inner side and forming the liquid crystal/high polymer combined film 3 on at least one of the substrate surface, then sticking the counter electrode substrate to the substrate. This process for production of the liquid crystal optical element comprises forming the liquid crystal/high polymer combined film 3 on at least one of the substrates, then sticking the counter electrode substrate to the substrate under vacuum deaeration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal optical element,
More specifically, it relates to a liquid crystal optical element using a liquid crystal / polymer composite film in which a liquid crystal is dispersed in a polymer substance.

[0002]

2. Description of the Related Art Conventionally, liquid crystal displays have been widely used as wristwatches, calculators, personal computers, televisions, etc., as a display medium for characters and images because they have characteristics such as low power consumption, light weight and thin shape. . In general TN and STN type liquid crystal displays, liquid crystal is enclosed in a liquid crystal cell in which a predetermined seal is provided between a pair of glass plates having transparent electrodes,
Further, it is sandwiched by polarizing plates from both sides.

However, the above-mentioned conventional liquid crystal display (1) has a narrow viewing angle because it requires two polarizing plates.
In addition, because of insufficient brightness, a backlight with high power consumption is required. (2) Cell thickness dependency is large and it is difficult to increase the area. (3) Formation of alignment film, rubbing treatment There is a problem that the manufacturing cost is high due to the complicated manufacturing process such as encapsulation of liquid crystal in the cell, and there is a limit to the weight reduction, thinning, large area, low power consumption, and cost reduction of the liquid crystal display. is there.

As a liquid crystal display medium for solving such problems, a liquid crystal in which a liquid crystal is dispersed in a polymer matrix /
Applications of polymer composite membranes are expected, and their research and development have been activated. The liquid crystal / polymer composite film manufacturing method can be mainly classified into an emulsion method and a phase separation method. As an emulsion method, polyvinyl alcohol (PVA)
A protective liquid is used as a protective colloid to prepare a liquid crystal from an aqueous solution (JP-A-58-501631), a liquid crystal emulsion is mixed with a latex to prepare an aqueous solution (JP-A-60-252687), and the like. To be

[0005]

Problems to be Solved by the Invention By using the emulsion method, a bright liquid crystal display device having high light utilization efficiency can be obtained by the coating method, and there is a possibility of cost reduction. However, there are various problems in actual manufacturing. In particular, since the coating suitability of the liquid crystal emulsion itself as the coating liquid is not preferable, there is a problem that a uniform liquid crystal / polymer composite film having excellent characteristics cannot be obtained depending on the coating method.

A liquid crystal emulsion obtained by mixing and stirring an aqueous solution of a water-soluble polymer substance and liquid crystal contains 80 parts of a liquid crystal component in order to improve electro-optical characteristics such as reduction of driving voltage.
It is carried out by making the amount of the polymer substance to be 90% by weight or less, but the liquid crystal emulsion has the thixotropic property peculiar to the aqueous solution of the water-soluble polymer substance. Will be difficult. The presence of air bubbles is a fatal problem in products such as display devices.
In particular, air bubbles mixed in at the time of application cannot be removed, and it is extremely difficult to commercialize it. Therefore, it is difficult to satisfy the requirement of uniforming the entire voltage characteristics of the liquid crystal optical element.

Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art and to have excellent display characteristics in which no liquid crystal emulsion is wasted and no bubbles are contained in the liquid crystal / polymer composite film in the liquid crystal optical element. Another object of the present invention is to provide a liquid crystal optical element.

[0008]

The above object can be achieved by the present invention described below. That is, the present invention provides a liquid crystal optical element in which a liquid crystal / polymer composite film is sandwiched between a pair of conductive substrates in which at least one substrate is transparent, and at least one substrate has a shape in which the center is raised inward. A method for producing a liquid crystal optical element comprising a liquid crystal / polymer composite film sandwiched between a pair of conductive substrates, at least one substrate of which is transparent, wherein at least one substrate is a center. And a counter electrode substrate are bonded together after forming a liquid crystal / polymer composite film on at least one substrate surface, and at least one substrate In a method for producing a liquid crystal optical element in which a liquid crystal / polymer composite film is sandwiched between a pair of transparent conductive substrates, after forming a liquid crystal / polymer composite film on at least one substrate, While air-degassed is a manufacturing method of the liquid crystal optical element characterized by bonding the counter electrode substrate.

[0009]

The liquid crystal / polymer composite film formed on the substrate has a raised central portion as in the case of the substrate. When the opposing substrates are bonded together, the opposing substrate first comes into contact with the central portion of the film to form the film. Since they are pasted together in a slightly crushed state, air bubbles do not remain in the liquid crystal / polymer composite film. Further, in another embodiment of the present invention, after the liquid crystal / polymer composite film is formed on at least one of the substrates, the counter electrode substrate is attached while degassing under vacuum. No bubbles remain.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the preferred embodiments. The liquid crystal referred to in the present invention is an organic mixture showing a liquid crystal state at around room temperature, and includes nematic liquid crystal, cholesteric liquid crystal and smectic liquid crystal. Among them, nematic liquid crystal or nematic liquid crystal to which cholesteric liquid crystal is added is preferable in view of characteristics. These liquid crystals may be microencapsulated. The above liquid crystal may be colored with a dichroic dye. The reason for coloring the liquid crystal is also for the purpose of color display by coloring, but also for the purpose of enhancing the contrast of the displayed image by utilizing the difference in light absorption between when voltage is applied and when voltage is not applied.

The dichroic dyes used for coloring are TN and S.
Guest-host type ones generally used in TN type liquid crystal displays may be used, or dyes for liquid crystal / polymer composite film may be used. However, it is preferable that the solubility in the liquid crystal is large, the solubility in the polymer is small, the dichroic ratio is large, and the absorption when a voltage is applied is small, but these characteristics are different depending on the liquid crystal used, and thus are determined for each liquid crystal. There is a need to. When the amount of the dye added is too large, the amount of the dye dissolved in the polymer increases, and color residue occurs when a voltage is applied, which is not preferable. On the other hand, if the amount of the dye is too small, the difference in light absorption between when voltage is applied and when voltage is not applied becomes small, and the effect of improving the contrast is not sufficient. Therefore, it is preferably used in the range of 0.1 to 5% by weight with respect to the liquid crystal used. Furthermore, it is preferable to dissolve it in a concentration of 1 to 3% by weight.

The liquid crystal emulsion used in the present invention may be a conventionally known liquid crystal emulsion method or a phase separation method, and is not particularly limited, but the emulsion method is preferable. The liquid crystal emulsion is obtained by emulsifying and dispersing the above liquid crystal in an aqueous solution containing a suitable matrix resin. As a method of dispersing the above liquid crystal in the Matricex 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)
Dispersion methods such as Volume 4, No. 10, (1988)) are effective. The size of the liquid crystal emulsion particles depends on the dispersion method used, but generally the average particle size is 0.5 to 7 μm.
Is more preferable, and the range of 1-5 μm is still more preferable. PVA is preferably used as the matrix resin used in the preparation of the liquid crystal emulsion, but may be gelatin, acrylic acid copolymer, water-soluble alkyd resin or the like as long as it can be dispersed or dissolved in water.

The amount of liquid crystal and matrix resin used is such that the mixture ratio (weight ratio) of matrix resin / liquid crystal is 5 /.
If the amount of the liquid crystal used is too small, not only the transparency when the voltage is turned on is insufficient, but also a large voltage is required to bring the film into a transparent state. On the other hand, when the amount of the liquid crystal used is too large, not only the scattering (turbidity) when the voltage is off is insufficient, but also the strength of the film is reduced, which is not preferable. As the substrate for forming the liquid crystal optical element of the present invention, at least one of them is a pair such as glass, polymer film or the like to which transparent conductivity such as ITO, SnO ₂ system, ZnO system is provided. It is the substrate of.

Next, a method for manufacturing the liquid crystal optical element of the present invention will be described. FIG. 1 is a diagram schematically illustrating a manufacturing process of a liquid crystal optical element according to a preferred embodiment of the present invention. First, the first
1A, the substrate 1 is formed in a convex shape upward with a gentle curvature, the electrode 2 is formed along the curved surface, and the liquid crystal / polymer composite film 3 is formed on the surface thereof. Are formed. In this state, the electrode 2'is usually formed on the substrate 1 '.
Are attached in parallel as indicated by the arrows, the counter substrate 1 '
The surface of the electrode 2'of is first contacted with the top of the membrane 3 and then the membrane 3 is squeezed together so that even if some bubbles are present on the surface of the membrane 3, the bubbles will be extruded. No bubbles remain in the resulting device.

In the example shown in FIG. 1B, the substrate 1 and the electrode 2 are used.
Both of them are convexly curved upward in the drawing, and have the same effect as the above example. In the example shown in FIG. 1C, both the surface of the substrate 1 and the surface of the electrode 2 are formed in a spherical shape, and the same operational effect as the above example is achieved. In the example shown in FIG. 1D, unlike the above example, a tubular body 4 having the same outer diameter as the substrate 1 is prepared, and a liquid crystal / polymer composite film is formed on the electrode 2 surface formed on the substrate 1. 3 is formed, on the other hand, a counter substrate is made to face the surface of the film 3, vacuum degassing is performed between both substrates, and atmospheric pressure is applied from the outside of both substrates as indicated by an arrow to bring them into close contact with each other.
According to this method, bubbles do not remain in the liquid crystal / polymer composite film of the device obtained in the same manner as in the above embodiment. In the above embodiment, the liquid crystal / polymer composite film is formed on the substrate surface with the center raised, but the liquid crystal / polymer composite film is formed on the flat substrate surface which is the counter electrode. The same action and effect can be obtained by laminating a substrate whose center is raised on the surface.
In the ridge of the substrate, if the ridge is too large, after the substrates are brought into close contact with each other, the film thickness of the liquid crystal / polymer composite film differs between the center and the periphery, and as a result, the transmittance when no voltage is applied is the periphery and the center. However, the appearance of the product is not preferable. In order to prevent such a problem from occurring, when the degree of protrusion of the substrate is a square of 10 cm in length and 10 cm in width, the difference in height between the center of the substrate and the side is 1 to 8 μm.
It is preferably m.

As a method for forming the liquid crystal / polymer composite film on the electrode, any method is adopted. When a liquid crystal emulsion is used, an electrophoresis method, screen printing, stencil printing using a metal mask are used. , Casting, brush coating, spraying, blade coating, doctor coating and the like may be used. In particular, when the electrophoresis method is used, the liquid crystal / polymer composite film 3 can be formed in a pattern by forming the electrode 2 in a pattern or patterning the shape of the counter electrode in the electrodeposition bath. I can. Further, as a method of forming the liquid crystal / polymer composite film in a pattern, a partition wall having an arbitrary pattern is formed on the surface of the electrode substrate by using a thermosetting resin, photoresist, or the like, and the chamber is partitioned by the partition wall. A method of filling and drying a liquid crystal emulsion can also be adopted. Liquid crystal / polymer composite film 3
Can be obtained by applying the liquid crystal emulsion and then drying it at room temperature or at a temperature that does not affect the liquid crystal emulsion.

[0017]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. Example 1 After raising the center of a glass substrate by polishing, an ITO transparent electrode patterned by sputtering was provided. The liquid crystal / polymer composite film was applied to only the necessary portion on the substrate by electrodeposition coating method (current application at 20V for 10 seconds) by immersing the electrodeposition liquid prepared by the following method together with the counter electrode.
It was formed to have a film thickness of 0 μm (when dried). Next, a UV-curable sealant was formed by screen printing so as to have a width of 1 mm on the outer side of 1 mm of the formed liquid crystal / polymer composite film. On the other hand, for the counter electrode, a flat ITO glass substrate that is usually used is prepared, and a pair of these substrates is used as a liquid crystal /
After thermocompression bonding with the polymer composite film sandwiched between them, UV irradiation was performed to cure the sealant, and a liquid crystal optical element of the present invention having a liquid crystal / polymer composite film containing no bubbles was obtained. The liquid crystal optical element was white and opaque when no voltage was applied, but immediately became colorless and transparent when a voltage was applied.

* Preparation of electrodeposition liquid Using a membrane emulsification system manufactured by Ise Chemical Industry Co., Ltd., a liquid crystal emulsion having a continuous phase and dispersed phase weight ratio of 200: 20 was obtained under the following conditions. Dispersed phase: Nematic liquid crystal (E-44, manufactured by Merck) 18 parts Methyl methacrylate 2 parts Azobisisobutyronitrile 0.05 parts Continuous phase: PVA (KP-06, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 5 Weight% aqueous solution Porous glass: MPG with a pore size of 0.27 μm, manufactured by Ise Chemical Industry Co., Ltd. Internal pressure: 2.85 to 2.95 kgf / cm ² Internal flow rate: 0.8 m / sec The obtained liquid crystal emulsion is stirred. Without heating, the mixture was heated at 70 ° C. for 6 hours to obtain microcapsules containing a liquid crystal, which were isolated by centrifugation, and then an electrodeposition solution having the following composition was prepared.

Microcapsules 40 parts Methacrylic acid-butyl methacrylate copolymer 5 parts Triethylamine 1.4 parts Ethanol 30 parts Water 200 parts Methacrylic acid-butyl methacrylate copolymer is 28 parts methacrylic acid and 82 parts butyl methacrylate. Part was dissolved in 170 parts of methyethylsolve, azoisobutyronitrile was added, and the mixture was reacted at 60 ° C. for 6 hours to synthesize. After completion of the reaction, the mixture was poured into a large amount of water / methanol, purified by the reprecipitation method and used.

Example 2 A liquid crystal having a thickness of 10 μm and a size of 20 cm × 20 cm was applied to a flat glass substrate with a transparent electrode by applying the liquid crystal emulsion shown below by a stencil printing method using a metal mask (film thickness 20 μm) and drying. / Polymer composite film was formed.
On the other hand, the counter electrode is an ITO transparent electrode-attached polyethylene terephthalate film (T-COAT, film thickness 125 μm.
m, manufactured by Teijin Ltd., and fixed to a stage for screen printing with a raised central portion capable of vacuum pressure bonding. Then, a UV-curable sealant XNR5493-4A5 (manufactured by Nagase Ciba Co., Ltd.) was screen-printed to have a width of 1 mm and two sides.
It was applied to the periphery of the liquid crystal / polymer composite film so as to form a 0.2 cm square, and pressure-bonded to the above-mentioned glass substrate coated with the liquid crystal / polymer composite film. Then, when the sealant was cured by irradiation with ultraviolet rays, a liquid crystal optical element of the present invention having a liquid crystal / polymer composite film containing no bubbles was obtained.
The liquid crystal optical element was white and opaque when no voltage was applied, but immediately became colorless and transparent when a voltage was applied.

* Preparation of liquid crystal emulsion KP-06 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., degree of polymerization: about 6)
00, saponification degree: 71.0 to 75.0) and 5 wt% aqueous solution of nematic liquid crystal BL-010 (manufactured by Merck) in PV
A / Liquid crystal = 10/90 (w / w)
A liquid crystal emulsion was prepared by ultrasonic dispersion. Then KH
-20 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., degree of polymerization: about 2,0)
00, saponification degree: 78.5 to 81.5) and added 20 wt% aqueous solution so that total PVA / liquid crystal = 20/80 (w / w), and then shaken slowly to give a final stencil. A liquid crystal emulsion suitable for printing was obtained.

Example 3 A thermosetting resin (manufactured by Sonocom Co., Ltd., TC-580) was placed on a flat glass substrate with a transparent electrode (thickness: 1.1 mm, size: 20 cm × 20 cm) at a periphery of 10 mm. −
SN) was applied by a screen printing method and heat-cured at 170 ° C. for 10 minutes to form partition walls having a thickness of 16 μm. This substrate was filled with the liquid crystal emulsion prepared in Example 2 in the partition walls, and squeezed with a gravure coating doctor so that the thickness of the partition walls after drying was obtained. After drying, the partition walls were peeled off to obtain a liquid crystal / polymer composite film having a thickness of 10 μm. The counter electrode substrate is a flat glass substrate with ITO (thickness: 1.1 mm, size: 20 cm × 20 c).
m) is placed on a flat metal plate and subjected to mold release treatment to a depth of 1
A mold in which polymethylmethacrylate (PMMA) was melt-filled in a concave metal plate having the same size as the glass substrate of μm was heated and pressed. As a result, a counter electrode substrate having a 1 .mu.m bulge in the center was obtained, which was pressure-bonded to a substrate on which a liquid crystal / polymer composite film was formed at 80.degree. The device was obtained. The liquid crystal optical element was white and opaque when no voltage was applied, but immediately became colorless and transparent when a voltage was applied.

Example 4 A liquid crystal / polymer composite film was formed from the emulsion prepared in Example 2 on a flat glass substrate with a transparent electrode by the same method as in Example 3. The substrate and the counter substrate are placed in a rectangular tube having an inner mold of the same size as the substrates, with the liquid crystal / polymer composite film inside, and the substrates are vacuum degassed between the substrates. By pressure bonding, it was possible to obtain the liquid crystal optical element of the present invention having a liquid crystal / polymer composite film without bubbles. The liquid crystal optical element was white and opaque when no voltage was applied, but immediately became colorless and transparent when a voltage was applied.

Comparative Example 1 A liquid crystal / polymer composite film was formed on the flat glass substrate with a transparent electrode by the electrodeposition method shown in Example 1. Then, it was heat-pressed with a flat glass substrate with a transparent electrode, but only an optical element containing bubbles was obtained.

[0025]

As described above, according to the present invention, the central portion of the liquid crystal / polymer composite film formed on the substrate is raised like the substrate, and when the counter substrate is bonded, the counter substrate has the above film. Since the films are pasted together in such a state that they first come into contact with the central portion and squeeze the film slightly, air bubbles do not remain in the liquid crystal / polymer composite film. Further, in another embodiment of the present invention, after the liquid crystal / polymer composite film is formed on at least one of the substrates, the counter electrode substrate is attached while degassing under vacuum. No bubbles remain.

[0026]

[Brief description of drawings]

FIG. 1 is a diagram schematically illustrating a manufacturing process of a liquid crystal optical element of the present invention.

[Explanation of symbols]

 1, 1 ': transparent substrate 2, 2': transparent conductive film 3: liquid crystal / polymer composite film 4: cylinder

Claims (4)

[Claims] 1. A liquid crystal optical element in which a liquid crystal / polymer composite film is sandwiched between a pair of conductive substrates, at least one of which is transparent, wherein at least one of the substrates has a shape in which the center is inwardly raised. A liquid crystal optical element characterized by the above. 2. The degree of protrusion determines the size of the substrate by 10c in the vertical direction.
The liquid crystal optical element according to claim 1, wherein the difference in height between the center and the side of the substrate is 1 to 8 μm when the square is m × width 10 cm. 3. A method of manufacturing a liquid crystal optical element comprising a pair of electrically conductive substrates, at least one of which is transparent, sandwiching a liquid crystal / polymer composite film, wherein at least one of the substrates has a center bulged inward. A method for manufacturing a liquid crystal optical element, which has a shape, and after forming a liquid crystal / polymer composite film on at least one substrate surface, bonding a counter electrode substrate. 4. A method of manufacturing a liquid crystal optical element comprising a pair of conductive substrates, at least one of which is transparent, sandwiching a liquid crystal / polymer composite film, wherein at least one of the substrates has a liquid crystal / polymer composite film. A method for manufacturing a liquid crystal optical element, characterized in that the counter electrode substrate is bonded while the pair of substrates is degassed in vacuum after forming.