JP3271025B2 - Polymer dispersed liquid crystal display device 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 polymer-dispersed liquid crystal display (hereinafter simply referred to as "liquid crystal display"), and more particularly, to a liquid crystal / polymer composite film in which liquid crystal is dispersed in a polymer substance. The present invention relates to a liquid crystal display device.

[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 type 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, the above-mentioned conventional liquid crystal display requires (1) a narrow viewing angle because two polarizing plates are required, and a backlight with high power consumption because of insufficient brightness. (2)
The cell thickness dependence is large and it is difficult to increase the area. (3) The production cost is high due to the complicated production process, such as formation of an alignment film, rubbing treatment and sealing of liquid crystal in the cell. Therefore, there is a limit in reducing the weight, thickness, area, power consumption, and cost of a liquid crystal display.

As a liquid crystal display medium which solves such problems, a liquid crystal in which liquid crystal is dispersed in a polymer matrix is used.
The application of polymer composite membranes is expected, and research and development has been activated. The following technologies have already been disclosed.
The method for producing a liquid crystal / polymer composite film can be mainly classified into an emulsion method and a phase separation method. The emulsion method includes a method of preparing an aqueous solution in which liquid crystal is emulsified using polyvinyl alcohol (PVA) as a protective colloid (Japanese Patent Publication No. 58-501631), and a method of mixing a liquid crystal emulsion with latex to prepare an aqueous solution (Japanese Unexamined Patent Application Publication No. Showa 60
-252687) and the like.

On the other hand, the phase separation method can be classified into a method of fixing the phase separation state of the liquid crystal and the matrix resin, and a method of separating the liquid crystal from the matrix resin during film formation. As a method of fixing the phase separation state, a method of dispersing a liquid crystal in an epoxy resin and then curing the liquid crystal (Japanese Patent Application Laid-Open No. 61-1986)
No. 502128) and a method of dispersing a liquid crystal in an ultraviolet curable resin and then curing the liquid crystal (Japanese Patent Publication No. 62-2231). As a method of separating a liquid crystal during film formation, a method of separating phases during curing, a method of separating phases during evaporation of a solvent, and a method of separating phases during a cooling process of a thermoplastic resin are disclosed in JP-A-63-501512. Although disclosed in the gazette, various techniques with further improvements have been reported.

As a method of phase separation during curing, a method of phase separation of liquid crystal during curing in a mixed system of liquid crystal and ultraviolet curable resin (JP-A-63-271233, JP-A-1-252689), A method in which a liquid crystal and a thermosetting epoxy resin mixed system are subjected to phase separation during heat curing (JP-A-63-287820, JP-A-1-29-29).
No. 9022). Methods for phase separation during solvent evaporation include a method using an acrylic resin having an active hydroxyl group as a matrix (Japanese Patent Application Laid-Open No. 1-230693), a method using a cellulose acetate as a matrix (Japanese Patent Application Laid-Open No. 63-1224025), Using a matrix made of a resin that is incompatible with liquid crystal (Japanese Patent Laid-Open No. 63-43)
No. 993).

[0006]

Problems to be Solved by the Invention By using a liquid crystal / polymer composite film, a bright liquid crystal display element having high light use efficiency can be obtained, the production method can be used, and the cost can be reduced. Although it seems to be a very advantageous method at first glance, there are various problems in actual production. In particular, because the coating suitability of the coating liquid itself is not preferable,
There is a problem that a liquid crystal / polymer composite film having excellent characteristics cannot be obtained depending on the coating method. A liquid crystal dispersion obtained by mixing and stirring an aqueous solution of a water-soluble polymer substance and a liquid crystal,
In order to improve the electro-optical characteristics such as lowering of the driving voltage, the liquid crystal component is set to 80 to 90% by weight and the amount of the polymer material component is reduced as much as possible. Has a thixotropic property peculiar to the aqueous solution of water, making it difficult to remove air bubbles from the air. In a product such as a display device, the presence of air bubbles is a fatal problem. In particular, air bubbles mixed during application cannot be removed, and it is extremely difficult to commercialize the product. Therefore, it is also difficult to satisfy the uniformity of the entire voltage characteristics required in the liquid crystal display device.

Further, even in the phase separation type, since the polymer matrix component must be reduced as much as possible, the wettability of the liquid to the substrate is poor, and the liquid is repelled, so that it is difficult to form a uniform film. It is. Thus, various coating methods cannot be applied effectively due to poor coating suitability. For example, the blade coating method has problems such as coating film edge, coating unevenness at the beginning and end of coating, and further has a problem that pattern coating is impossible and expensive extra liquid crystal emulsion is used. or,
In the screen printing method, there are problems such as generation of bubbles at the time of passing through the mesh and back-flow of the emulsion on the back surface of the plate. Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, to make the pattern coating extremely easy, without wasting the liquid crystal emulsion, and without any bubbles in the liquid crystal / polymer composite film in the liquid crystal display device. An object of the present invention is to provide a liquid crystal display device having excellent display characteristics.

[0008]

The above object is achieved by the present invention described below. That is, according to the present invention, in a liquid crystal display device in which a liquid crystal / polymer composite film is sandwiched between a pair of transparent electrode substrates, at least one of the liquid crystal / polymer composite films is formed on a surface of the electrode substrate. Polymer dispersion liquid in a plurality of compartments divided by partition walls made of insulating material
And a conductive layer formed on the surface of the liquid crystal / polymer composite film.
Is a liquid crystal display device and a manufacturing method thereof, wherein being.

[0009]

In the liquid crystal display device of the present invention, a partition having a predetermined height is provided on the surface of the transparent substrate, and the liquid crystal emulsion can be filled in the compartment defined by the partition by the squeegee method. The material can be used, and the liquid crystal / polymer composite film having a uniform thickness can be formed very easily by applying a high-precision thickness in the compartment. Further, since the liquid crystal emulsion in the non-pixel region (outside the necessary compartment) is excluded by the partition, there is an advantage that an expensive liquid crystal emulsion can be used only in the display portion, and further, the liquid crystal emulsion can be easily applied. Therefore, a liquid crystal display device can be easily manufactured even with an electrode substrate made of a polymer material or a film, which has not been realized although the possibility has been conventionally discussed, and the cost of the liquid crystal display device can be greatly reduced.

In addition, since it is easy to color the liquid crystal / polymer composite film with a dichroic dye having a different hue in each compartment, an arbitrary color display or multicolor display can be easily performed for each pattern. A reflective type color display panel, which cannot be expressed by the TN type or STN type, can be supplied at low cost. In addition to high-precision display devices such as personal computers and word processors, color televisions, and other large-capacity single-color or active-matrix display devices, as well as static display devices that display simple characters and patterns. Similarly, the present invention can be applied to a display device, and a large-area display device can be manufactured. A wide range of responses, such as being achievable, is possible.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail with reference to the accompanying drawings, which show a preferred embodiment. FIG. 1 is a diagram schematically illustrating a configuration of a liquid crystal display device according to a preferred embodiment of the present invention and a manufacturing process thereof. First, FIG.
As shown in (1), a transparent conductive film 2 such as an ITO film is formed on the surface of the transparent substrate 1, and on the transparent conductive film 2,
An electrically insulating partition 3 for partitioning the film surface into an arbitrary region is provided. As the transparent substrate 1 used in the present invention, for example, a glass plate, a quartz plate, various synthetic resin plates, films or the like are used.

The partition 3 generally has a plurality of parallel lines,
It is formed in a shape suitable for the purpose, such as a quadrilateral, a polygon, a quadrangle, and an ellipse. For example, in the case of displaying characters and patterns of an appropriate size, it is only necessary to form a partition only on the outer periphery in individual display units, or if the partition spacing is too large, the area within the region may be formed. May be further divided arbitrarily or a column-shaped or plate-shaped independent column may be provided, and the shape of the partition is not limited at all. However, it is preferable that any independent partition walls are continuous in the coating operation. As a material for forming the partition, a general liquid photoresist, a dry photoresist, or the like can be used.
For example, when forming a partition having a height of 25 μm or less, it is desirable to use a liquid photoresist. For example, a liquid photoresist is applied in a pattern on a substrate using a spin coating method or a blade coating method. , Curing and developing to form a partition. On the other hand, 25μ
When forming a partition having a height of m or more, it is desirable to use a dry film photoresist.

These partitions may or may not be colored, but should be colored light-opaque so that they are different in color and do not mix with other colors in adjacent compartments. Is preferred. The partition walls may be colored with a dye or paint after the partition walls are formed, or in the case of a liquid photoresist, the dye is previously dissolved in the resist or a pigment or the like is dispersed in the resist. May be used to form a partition wall.
In addition, colored dry films are also available on the market, and colored partition walls can be easily prepared by using them. It is preferable that the heights of the partition walls formed as described above are sequentially set in consideration of a decrease in volume due to drying after application of the liquid crystal emulsion. The thickness of the liquid crystal / polymer composite film used in the liquid crystal display device of the present invention is about 3 to 15 μm.
And the solid content of the liquid crystal emulsion used is about 30 to 50% by weight, so that the height of the partition walls is generally about 6 to 50 μm. Further, the width of the partition wall can be arbitrarily changed depending on the shape of the display unit, but the interval between the partition walls forming the display unit is large, and when the partition wall is provided inside the display unit, it can withstand the squeegee pressure during application of the liquid crystal emulsion. It is necessary to be a width, but if the width is too wide, the partition walls are conspicuous and the appearance is deteriorated.
m.

Next, a liquid crystal emulsion 5 from which bubbles have been sufficiently removed is gently poured onto the substrate surface on which the partition walls 3 are provided.
By flattening and drying the surface with a squeegee 6 made of a soft metal, hard rubber or the like, a liquid crystal / polymer composite film having the same hue is formed in each compartment. When liquid crystal / polymer composite films having different hues are formed in each compartment, as shown in FIG.
A mask 4 made of metal or the like having a plurality of openings synchronized with the partition walls is overlapped, a liquid crystal emulsion 5 from which bubbles are sufficiently removed is gently poured, and the surface is flattened with a squeegee 6 made of a soft metal or hard rubber. By performing this operation for each liquid crystal emulsion having a different hue, a liquid crystal / polymer composite film having a different hue is formed in each compartment.

As the mask, any mask may be used. For example, when a metal mask is used,
The size of the opening of the metal mask is desirably synchronized with the width between the partition walls filled with the emulsion. However, depending on the properties of the partition walls, the edge of the formed liquid crystal / polymer composite film may be raised. In this case, the edge of the opening can be eliminated by making the opening of the mask slightly smaller than the size of the compartment defined by the partition. The liquid crystal emulsion used in the present invention may be a conventionally known liquid crystal emulsion method, or may be a phase separation method, and is not particularly limited, but an emulsion method is preferred. As a matrix resin used in the emulsion method, PVA is preferably used, but any material which can be dispersed or dissolved in water, such as gelatin, an acrylic acid copolymer, or a water-soluble alkyd resin, may be used.

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. These liquid crystals may be microencapsulated. As a reason for coloring the liquid crystal, there is also a purpose of color display by coloring, but also a purpose of enhancing a contrast of a displayed image by utilizing a difference in light absorption between when a voltage is applied and when no voltage is applied. As the dichroic dye used for coloring, a guest-host type generally used in TN and STN type liquid crystal displays may be used, or a dye for a liquid crystal / polymer composite film may be used. Good. However, it is preferable that the solubility in liquid crystal is large, the solubility in polymer is small, the dichroic ratio is large, and the absorption at the time of voltage application is small. However, these characteristics differ depending on the liquid crystal used. There is a need to. If the amount of the dye is too large, the dissolution in the polymer increases, which is not preferable because the color remains when a voltage is applied. On the other hand, if the amount of the dye is too small, sufficient coloring cannot be performed. It is preferable to use 0.1 to 5% by weight of the liquid crystal used for that purpose. More preferably, it is dissolved in a concentration of 1 to 3% by weight.

The amount of the liquid crystal used is such that the mixing ratio (weight ratio) of matrix resin / liquid crystal is 5/95 to 50/50.
If the amount of the liquid crystal is too small, the transparency at the time of turning on the voltage is not only insufficient, but also it is insufficient in that a large voltage is required to make the film transparent. On the other hand, if the amount of the liquid crystal used is too large, not only is the scattering (turbidity) when the voltage is turned off insufficient, but also the strength of the film is undesirably reduced. For example, as a method of dispersing the liquid crystal in an aqueous polyvinyl alcohol solution, a mixing method using various stirring devices such as an ultrasonic disperser, a film emulsification method (Tadao Nakajima and Masataka Shimizu, PHARMTECH JAPAN Vol. 4, No. 10 (19)
88) is effective. The size of the liquid crystal emulsion particles depends on the dispersion method used, but generally, the average particle size is preferably in the range of 0.5 to 7 μm, and more preferably in the range of 1 to 5 μm.

As shown in FIG. 1 (3), when the liquid crystal emulsion filled in the compartment is dried at room temperature or at a temperature that does not affect the emulsion, the liquid crystal / polymer composite film 7 having a reduced volume is obtained. Is obtained. Next, as shown by the arrow (4) in FIG. 1, another pattern of a mask having openings aligned with the compartments not filled in the step (3) and a different color by a dichroic dye. The above operation and the above operation are repeated using the liquid crystal emulsion thus obtained to obtain a liquid crystal colored with a dichroic dye of a plurality of colors.
A polymer composite film is formed on the transparent conductive film surface for each compartment.

By drying the liquid crystal emulsion in a state where the necessary compartments are all filled with the liquid crystal emulsion, a liquid crystal / polymer composite film 7 is formed as shown in FIG. The volume of the polymer / polymer composite film 7 is reduced by drying, and the surface of the liquid crystal / polymer composite film is lower than the top of the partition 3. This portion is filled with a paste-like conductive agent 8 by a squeegee 9 as shown in FIG. As the paste-like conductive agent, a commercially available silver paste or the like may be used, but a paste containing a high content of an organic solvent or a thermosetting type liquid crystal / polymer composite film at the time of drying or curing is used. May be destroyed. Therefore, a paste-type conductive agent of a solventless type or a room temperature curing type is desirable. Next, as shown in FIG. 1 (6), the transparent conductive film surface of the opposing substrate 11 on which the transparent conductive film 10 is formed is brought into close contact with the above-mentioned conductive agent surface, and the liquid crystal display device of the present invention is completed. I do.

[0020]

[0021]

Next, the present invention will be described more specifically with reference to examples. Example 1 Drift film photoresist (manufactured by San Nopco Co., Ltd., F-1025, 25 μm thickness) is laminated on a 100 mm × 100 mm × 1.1 mm glass with ITO using a laminating machine, and a mask pattern is superimposed. Irradiation with ultraviolet rays and development were performed to produce partition walls. Nematic liquid crystals (E-44, E-44) in which dichroic dyes (G-264, manufactured by Japan Photographic Dye Laboratories) are dissolved in the recesses between the obtained partition walls.
An emulsion prepared by dispersing (available from Merck) in an aqueous PVA solution was poured, and the surface was flattened using a squeegee for screen printing. After drying at room temperature for 24 hours, a conductive agent colored white with titanium oxide was filled with a squeegee into a concave portion generated by volume reduction and air-dried to obtain a liquid crystal display device of the present invention. The resulting display device is opaque blue unless a voltage is applied. However, when a voltage is applied, the liquid crystal / polymer film becomes colorless and transparent, and a blue pattern is clearly displayed on a white base in a reflective type. Was.

[0022]

Example 2 A dry life photoresist (F-1025, 25 μm thick, manufactured by San Nopco Co., Ltd.) was laminated on the ITO side of a glass with ITO of 100 mm × 100 mm × 1.1 mm using a laminating machine, and a mask was used. The pattern was superposed and irradiated with ultraviolet rays, and developed to form a partition. A nematic liquid crystal (BL-90, BL-90, in which a dichroic dye (M-137, manufactured by Mitsui Toatsu Dye Co., Ltd.) is dissolved in the recesses between the obtained partition walls.
An emulsion prepared by dispersing (available from Merck) in an aqueous PVA solution was poured over a metal mask, and the surface was flattened using a squeegee for screen printing. After drying at room temperature for several hours, an emulsion colored with a dichroic dye (S-421, manufactured by Mitsui Toatsu Dye Co., Ltd.) was similarly coated on another metal mask. After drying, an emulsion colored with a dichroic dye (S-426, manufactured by Mitsui Toatsu Dye Co., Ltd.) was similarly coated on another metal mask, dried at room temperature for 24 hours, and then reduced in volume. The resulting recess was filled with a conductive agent using a squeegee and then air-dried to obtain a liquid crystal display device of the present invention. The obtained display device is opaque colored red, blue and green unless a voltage is applied, but when a voltage is applied to the entire display, the entire display becomes colorless and transparent, and the voltage is changed for each pattern. When application and non-application were selected, various color patterns could be displayed.

[0024]

[0025]

According to the present invention as described above, pattern coating is extremely easy, liquid crystal emulsion is not wasted, and the liquid crystal / polymer composite film of the liquid crystal display device has excellent display characteristics in which no bubbles are contained in the liquid crystal / polymer composite film. Liquid crystal display device can be provided.

[0026]

[Brief description of the drawings]

FIG. 1 is a view schematically illustrating a configuration of a liquid crystal display device according to a preferred embodiment of the present invention and manufacturing steps thereof.

[Explanation of symbols]

 1: Transparent substrate 2, 10: Transparent conductive film 3: Partition wall 4: Mask 5: Liquid crystal emulsion 6, 9: Squeegee 7: Liquid crystal / polymer composite film 8: Conductive agent paste 11: Counter substrate

Continuation of the front page (72) Inventor Masayuki Ando 1-1-1, Ichigaya-Kaga-cho, Shinjuku-ku, Tokyo Inside Dai Nippon Printing Co., Ltd. (56) References JP-A-4-84121 (JP, A) JP-A-4 JP-A-284418 (JP, A) JP-A-59-15223 (JP, A) JP-A-4-328523 (JP, A) JP-A-62-231930 (JP, A) JP-A-2-90128 (JP, A) JP-A-1-308679 (JP, A) JP-A-5-297382 (JP, A) JP-A-5-289069 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1334 G02F 1/13 101 B41M 1/12

Claims (5)

(57) [Claims] 1. A polymer dispersed liquid crystal display device comprising a liquid crystal / polymer composite film sandwiched between a pair of transparent electrode substrates, at least one of which is formed on a surface of the electrode substrate. Polymer-dispersed liquid crystal emulsion in a plurality of compartments partitioned by a partition made of isolated electrical insulating material
Formed from tio emissions are and colored by dichroic dye,且
A polymer dispersed liquid crystal display device, wherein a conductive layer is formed on the surface of the liquid crystal / polymer composite film . 2. The polymer-dispersed liquid crystal display device according to claim 1, wherein the liquid crystal / polymer composite film is colored with a dichroic dye having a different hue for each compartment. 3. The partition according to claim 1, wherein the partition is light-impermeable.
4. The polymer-dispersed liquid crystal display device according to 1. 4. A method of manufacturing a polymer-dispersed liquid crystal display device comprising a liquid crystal / polymer composite film sandwiched between a pair of transparent electrode substrates, at least one of which is made of an electrically insulating material. To form multiple compartments,
A mask aligned with the plurality of compartments is overlapped, and a polymer-dispersed liquid crystal emulsion colored with a dichroic dye is filled into the selected compartment through an opening of the mask and dried, and a liquid crystal / polymer is filled in the compartments. Forming a composite membrane; and
Conductive layer formed from conductive paste on liquid crystal / polymer composite film
A method for producing a liquid crystal / polymer composite film, comprising: 5. The method according to claim 4 , wherein the size of the opening of the mask is smaller than the size of the compartment.