JP4914545B2 - Manufacturing method of liquid crystal display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a liquid crystal display device, and more particularly to a method for manufacturing a polymer dispersed liquid crystal display device.
[0002]
[Prior art]
Liquid crystal display devices generally transmit light by sandwiching a liquid crystal between a pair of transparent electrode substrates, disposing a polarizing plate outside the transparent electrode substrate, and operating the liquid crystal by applying a voltage from the outside to the transparent electrode. This is a display device that realizes display by changing the amount. In order to operate this liquid crystal arbitrarily, it is necessary to perform alignment film processing inside the transparent electrode substrate in a high temperature atmosphere of about 300 ° C. Usually, liquid crystal display devices used for notebook computers, wrist watches, calculators, electronic dictionaries, etc. are called TN (twisted nematic) LCDs and STN (super twisted nematic) LCDs, and polarizing plates or On one side, a reflector integrated with the polarizing plate is attached. By using this polarizing plate, the incident light is reduced to 50% or less, and the display surface becomes dark.
[0003]
In recent years, a polymer-dispersed liquid crystal display device, which is a new display method that does not require a polarizing plate, has been studied because of a demand for realizing a bright display. A typical example is a polymer network liquid crystal (hereinafter referred to as “PN-LC”). This is a display device (hereinafter referred to as “PN-LCD”) using a new composite type liquid crystal material in which a polymer resin that undergoes a cross-linking reaction by ultraviolet rays and a commonly used TN liquid crystal are mixed and dispersed. It is. In addition, a microcapsule type in which liquid crystal is confined in a polymer resin has been studied in advance, but here, PN-LC that can be easily driven at a lower voltage will be described.
[0004]
In PN-LC, when an ultraviolet (UV) polymerizable polymer resin and a TN liquid crystal are mixed and dispersed in an appropriate blend, the polymer forms a network when irradiated with ultraviolet rays, and at the same time, the blended TN liquid crystal is a polymer network. It is uniformly dispersed therein, and has properties that combine the functions of the polymer and the TN liquid crystal. There has been proposed a light scattering mode type display element that uses the difference in refractive index between the polymer network and the TN liquid crystal to scatter incident light to perform display. Compared with conventional TN-LCDs and STN-LCDs, this display element only requires an ultraviolet irradiation device that cures polymer-dispersed liquid crystals, and does not require alignment film processing with high-temperature processing or expensive polarizing plates. Therefore, it is possible to reduce the price of the display device.
[0005]
In general, PN-LC does not cause chromatic dispersion of visible light, and in order to obtain effective scattering characteristics, the particle size of the polymer network is reduced to about 1 micron that is larger than the visible light wavelength. This increases backscattering. The manufacturing factor that determines the particle size of the polymer network is the intensity of ultraviolet irradiation. Although ultraviolet irradiation intensity | strength changes with PN-LC to be used, it is normally 20-30 mw / cm <2> or more at a 365 nm wavelength. In order to realize this irradiation intensity, a metal halide lamp or a high-pressure mercury lamp is used as an ultraviolet light emitting lamp.
[0006]
Further, the ultraviolet irradiation device has a structure that efficiently collects ultraviolet rays from the light source in one direction. In general, since the ultraviolet irradiation work for curing PN-LC is performed at a position in one direction of the lamp, this irradiation apparatus is provided with a reflector that efficiently reflects the ultraviolet light around the lamp. The structure improves the strength and at the same time makes the illuminance of ultraviolet rays uniform.
[0007]
[Problems to be solved by the invention]
However, in the above-described PN-LCD manufacturing method, the conventional ultraviolet irradiation method for curing PN-LC has insufficient uniformity of the particle size of the polymer network formed by the ultraviolet irradiation, and is uniform. There was a problem that backscattering could not be obtained.
[0008]
Further, it has been recognized from experience that the substantial irradiation intensity is high in the central portion and low in the peripheral portion, and therefore display unevenness occurs.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to provide a PN-LCD that does not display unevenness by performing uniform backscattering.
[0010]
[Means for Solving the Problems]
Order to promote the achievement of this object, a process of forming a liquid crystal cell ultraviolet curable polymer material and the liquid crystal of the mixed Go溶 prepared by dispersing, enclosed between a pair of transparent substrates, a center from the periphery the mounting on the plate to ultraviolet reflectance is constructed sequentially different subjected parts, the step of irradiating the steps you placing the liquid crystal cell, an ultraviolet ray to the liquid crystal cell from the surface opposite to the front mounting plate Once, it was decided to include the. At this time, the mounting plate has a low ultraviolet reflectance at a portion where the ultraviolet irradiation is strong, and a high ultraviolet reflectance at a portion where the ultraviolet irradiation is weak. By such a manufacturing method , a PN-LCD having no display unevenness is provided.
[0011]
More preferably, the mounting plate has a lower ultraviolet reflectance stepwise from the peripheral part to the center part. In this way, a PN-LCD having no display unevenness between the peripheral portion and the central portion is provided.
[0012]
The mounting plate described above preferably has a lower ultraviolet reflectance linearly from the periphery to the center. In this way, a PN-LCD having no display unevenness between the periphery and the center is provided.
[0013]
Further preferably, the ultraviolet curable polymer material is a photopolymerizable monomer. If it does in this way, photopolymerization can be performed efficiently.
[0014]
Further, preferably, in the mounting plate, the above-mentioned center portion is black and the above-mentioned peripheral edge portion is white on the mounting surface on which the above-described cell is mounted. In this way, a PN-LCD having no display unevenness between the peripheral portion and the central portion is provided.
[0015]
The mounting plate described above may be gray between the central portion and the peripheral portion. In this case, a PN-LCD having no display unevenness between the peripheral edge portion and the central portion is further provided.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the size, connection relationship, shape, and arrangement relationship of each component are merely schematically shown to the extent that the present invention can be understood. Therefore, the present invention is limited to the illustrated examples. It is not a thing.
[0017]
FIG. 1 is a schematic cross-sectional view of the structure of a polymer dispersion type liquid crystal display device. The principle of the polymer dispersion type liquid crystal display device will be described with reference to FIG.
[0018]
In the structure of the polymer dispersion type liquid crystal display device shown in FIG. 1, electrodes 110a and 110b are first formed on opposing surfaces of two opposing glass substrates 100a and 100b so as to oppose each other. The glass substrate 100a, 100b is sealed after a mixed solution in which the liquid crystal 130 and the ultraviolet curable polymer material, that is, the polymer 140 are dispersed, is injected.
[0019]
The polymer 140 is formed by, for example, irradiating a liquid crystal layer (a layer made of a liquid crystal and a polymer precursor) with ultraviolet rays to deposit the polymer.
[0020]
In this liquid crystal layer, when no electric field is applied, the orientation of the polymer 140 does not vary, whereas the liquid crystal 130 is randomly oriented with respect to the substrates 100a and 100b, so that the refractive indexes of the liquid crystal 130 and the polymer 140 are different. Thus, the incident light is scattered.
[0021]
On the other hand, since the liquid crystal 130 is aligned in the same direction as the polymer 140 when an electric field is applied between the electrodes 110a and 110b, the refractive index of the liquid crystal 130 and the refractive index of the polymer 140 in the direction perpendicular to the substrates 100a and 100b match each other. To do. Accordingly, the incident light is transmitted between the substrates.
[0022]
Next, a method for manufacturing such a polymer dispersion type liquid crystal device will be described with reference to FIGS.
[0023]
According to this method for manufacturing a polymer-dispersed liquid crystal display device, first, a liquid crystal mixture composed of a liquid crystal and an ultraviolet curable resin, that is, a polymer precursor and a chiral agent, between a pair of substrates on which electrodes are formed. Inject material. Further, by irradiating the liquid crystal mixed material with ultraviolet rays (UV), the ultraviolet curable resin is photopolymerized to deposit a polymer matrix. The ultraviolet curable resin described above can be appropriately selected within a range that does not impair the object of the present invention. Preferably, for example, a photopolymerizable monomer is used as the resin. Next, a specific manufacturing method will be described below.
[0024]
(1) First, electrodes having a predetermined pattern are formed on a substrate by using a patterning technique. That is, electrodes 110a and 110b having predetermined patterns are formed on the substrates 100a and 100b, respectively.
[0025]
(2) Subsequently, a sealing material for bonding the substrates 100a and 100b together is printed. That is, a seal printing process for providing a sealant on the substrates 100a and 100b is performed. When forming the sealing material, an injection hole is provided in the sealing material.
[0026]
(3) Next, a pair of substrates 100a and 100b provided with a sealing material are bonded together. That is, both the substrates 100a and 100b are opposed to each other and combined to form a cell between the substrates.
[0027]
(4) Subsequently, a liquid crystal mixed material is injected between a pair of substrates, ie, cells. In other words, the liquid crystal mixed material is injected into the cell through the injection hole provided at the time of forming the sealing material, and the injection hole is sealed.
[0028]
(5) Next, the above-described pair of substrates 100a is placed on the placement plate 250. That is, one glass substrate 100 a is mounted on the mounting plate 250. However, the glass substrate 100a and the mounting plate 250 are substantially brought into contact with each other. Further, the mounting plate 250 is configured such that the central portion 300 has a low ultraviolet reflectance and the peripheral portion 320 has a sequentially increased ultraviolet reflectance.
[0029]
(6) Next, ultraviolet rays are irradiated. That is, the polymer precursor is photopolymerized by irradiating the liquid crystal mixed material with ultraviolet rays to precipitate the polymer. However, UV irradiation is performed from the UV plateau 200 from the other substrate 100b side not in contact with the mounting plate 250.
[0030]
Conventionally, photopolymerization control or the like has been difficult at the peripheral portion and the central portion 300 of the cell, but since the central portion 300 and the peripheral portions 310 and 320 of the mounting plate 250 are different in ultraviolet reflectance, Photopolymerization can be easily controlled.
[0031]
Next, an embodiment of the present invention will be described.
[0032]
<Example 1>
This embodiment will be described with reference to FIG.
[0033]
A pair of transparent or glass substrates patterned with transparent electrodes is used to form a liquid crystal cell having a 10 micron gap. In the cell gap of a heated liquid crystal cell at a temperature of 40 ° C., as a PN-LC, for example, PN-LC15 (PNM157) (trade name) manufactured by Dainippon Ink is kept at 40 ° C. in an isotropic state (isotropic). Inject vacuum.
[0034]
The liquid crystal cell into which the PN-LC 15 has been injected is maintained at a temperature of 20 ° C. using an ultraviolet irradiation device 200 as shown in FIG. 2, and the photopolymerizable monomer is UV cured.
[0035]
Further, a mounting plate 250 having a different ultraviolet reflectance at the central portion 300 and the peripheral portion 320 is provided below the liquid crystal cell. FIG. 3 schematically shows a plan view of the mounting plate 250. With reference to this FIG. 3, the structure and operation | movement of this mounting board are demonstrated.
[0036]
The mounting plate 250 has a central portion 300 that is black and a peripheral portion 320 that is white. Furthermore, the middle part 310 is gray.
[0037]
By doing so, the central portion 300 of the mounting plate 250 does not substantially reflect the ultraviolet light that has passed through the liquid crystal cell. Further, since the peripheral portion 320 of the mounting plate 250 scatters and reflects the ultraviolet light that has passed through the liquid crystal cell, the reflected light is re-irradiated to the peripheral portion 320 of the liquid crystal cell. As a result, the cells of the peripheral edge 320 can be efficiently cured. Further, since the ultraviolet reflectance of the mounting plate 250 is continuously changed, it is empirically possible to perform substantially uniform ultraviolet irradiation on the PN-LC. Can be polymerized. Therefore, a PN-LCD without display unevenness can be manufactured.
[0038]
<Example 2>
The configuration of the mounting plate 250 described above is changed stepwise from black at the central portion 300, gray at the intermediate portion, and white at the peripheral portion 320, but can be modified as appropriate without departing from the object of the present invention. For example, the color change may be provided in more stages, that is, gradations, instead of the three stages of white, black, and gray. That is, black or black intensity may be provided in the gradient.
[0039]
In addition, the color of the mounting plate 250 that has changed from white to black from the peripheral portion 320 to the central portion 300 may naturally be configured to change the color continuously and linearly.
[0040]
Furthermore, the configuration of the mounting plate 250 described above may be changed according to the state of ultraviolet irradiation. For example, when the aforementioned ultraviolet irradiation is set to be strong at the central portion 300 of the liquid crystal cell and weak at the peripheral portion 320 of the liquid crystal cell, conversely, it is weak at the central portion 300 of the liquid crystal cell and strong at the peripheral portion 320 of the liquid crystal cell. Conversely, the configuration of the mounting plate 250 may naturally be changed from black to white from the peripheral portion 320 to the central portion 300.
[0041]
【Effect of the invention】
As is apparent from the above description, according to the present invention, when PN-LC is cured by ultraviolet rays, the particle size of the polymer network at the time of curing PN-LC is obtained by using a mounting plate having a different ultraviolet reflectance. Can be made more uniform. This makes it possible to improve the quality of the PN-LCD. Therefore, the industrial and economic effects are great.
[0042]
Moreover, the ultraviolet irradiation apparatus is not changed, and the particle size of the polymer network at the time of PN-LC curing can be made more uniform with only the mounting plate. Therefore, the economic effect is great from the aspect of capital investment.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of the structure of a polymer dispersed liquid crystal.
FIG. 2 is a diagram illustrating a configuration of an example.
FIG. 3 is a plan view of a mounting plate.
[Explanation of symbols]
100a, 100b Glass substrate 110a, 110b Electrode 130 Liquid crystal 140 Polymer 200 Ultraviolet irradiation device 250 Mounting plate 300 Central part 310 Middle part 320 Peripheral part

Claims (4)

A step of preparing a liquid crystal cell an ultraviolet curable polymer material and mixed Go溶 liquid in which liquid crystal is dispersed, enclosed between a pair of transparent substrates,
On mounting plate to ultraviolet reflectance is constructed sequentially differently toward the center portion from the periphery, the steps placing the liquid crystal cell,
See containing and performing ultraviolet irradiation from the surface opposite to the liquid crystal cell, a is the the mounting plate,
The manufacturing method of a liquid crystal display device , wherein the mounting plate is configured such that the ultraviolet reflectance is low at a portion where the ultraviolet irradiation is strong and the ultraviolet reflectance is high at a portion where the ultraviolet irradiation is weak . 2. The method for manufacturing a liquid crystal display device according to claim 1, wherein the mounting plate is configured such that the ultraviolet reflectance gradually decreases from the peripheral portion to the central portion. The method for manufacturing a liquid crystal display device according to claim 2 , wherein the mounting plate has an ultraviolet reflectance that gradually decreases from a peripheral part to a central part. The method for manufacturing a liquid crystal display device according to claim 2 , wherein the mounting plate has a lower ultraviolet reflectance linearly from the peripheral part to the center part.

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