JP2000098355A - Liquid crystal display device and method of manufacturing the same - Google Patents

Abstract

[PROBLEMS] To prevent the occurrence of display unevenness by sufficiently polymerizing a polymer precursor located immediately below a light-shielding portion, to further improve the uniformity of RGB color reproducibility, and to reflect light. It is an object of the present invention to provide a liquid crystal display device and a method for manufacturing the same, which are capable of improving contrast reduction due to scattering at a junction between a pixel electrode and a relay electrode in a contact hole. SOLUTION: A polymer dispersed liquid crystal layer 4 composed of a polymer and a liquid crystal is sandwiched between an array substrate 2 on which a reflective pixel electrode 5 is formed and an opposing substrate 3 on which a light shielding portion 7 is formed. I have. The polymer-dispersed liquid crystal layer 4 irradiates ultraviolet rays from the counter substrate side 3 and then irradiates ultraviolet rays from the array substrate 2 side, thereby forming a mixed solution containing a liquid crystal material and a polymer precursor disposed between the substrates. The polymer precursor is polymerized to phase-separate the liquid crystal and the polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device used for an information portable terminal, a mobile phone, a game machine, a television, a monitor, and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art With the recent miniaturization of information equipment, reduction in weight and power consumption has been desired. In order to achieve weight reduction and low power consumption, in the field of liquid crystal display devices, in particular, research on reflection type liquid crystal display devices that do not use a backlight is being vigorously pursued.

In response to such demands, in recent years, polymer-dispersed liquid crystals have been used and thin film transistors (thin-filtration) have been used.
(M transistor: TFT) A liquid crystal display device having a structure in which a reflective pixel electrode is provided on an array substrate and a color filter is provided on a counter substrate has been proposed. However, such a liquid crystal display element has the following problems.

(1) First problem When the above-mentioned liquid crystal display element is manufactured by a normal manufacturing process, the following problems occur. That is, since a polymer-dispersed liquid crystal is used, an ultraviolet irradiation step for photopolymerizing a polymer precursor is required at the time of production. At the time of this ultraviolet irradiation, since the reflective pixel electrode shields the ultraviolet light,
Irradiation from the FT array substrate side is not possible. Therefore, it is necessary to irradiate ultraviolet rays from the counter substrate side. However, as shown in FIG.
A frame-shaped light shielding portion (usually referred to as a frame) 61 is formed in the outer peripheral portion of the frame. The light-shielding portion 61 is an indispensable structure for preventing the display from floating and obtaining a good display. Therefore, when ultraviolet light is irradiated from the counter substrate side, the polymer precursor located immediately below the light shielding portion 61 remains unpolymerized due to the presence of the light shielding portion 61. Then, during long-term storage, the unpolymerized material seeps into the color filter 60 as shown in FIG. 11 to form a seepage portion 62 having low scattering properties. The oozing portion 62 causes display unevenness, and has a problem that the in-plane uniformity of the panel is impaired.

Further, a thin film transistor (TFT) array is changed from a-Si (amorphous silicon) TFT to p-S
With the shift to i (polysilicon) TFTs, those having a structure in which a driver circuit is built in the array are increasing. Then, such a built-in driver circuit is disposed immediately below the light shielding unit 61. This is to prevent a malfunction due to a change in TFT characteristics due to incident light. Therefore, the width of the light-shielding portion 61 tends to be larger than when there is no built-in driver circuit, and the importance of solving the above problem is increasing.

(2) Second Problem In a conventional liquid crystal display device of an external type with a reflector (a system in which a reflector is attached to the outside of a display panel), irradiation is performed from the back side of the array substrate during manufacturing. Therefore, the irradiation intensity of the ultraviolet light applied to each pixel is uniform, and R (red) G
(Green) B (blue) The particle size of each pixel was uniform. However, the scattering phenomenon in the polymer-dispersed liquid crystal is shown in FIG.
As shown in (1), there is a wavelength dependency, and a difference in scattering property occurs for each color. If the particle size is uniform, red is generally weakly scattered as shown in FIG. Therefore, if the particle size of each of the RGB pixels is uniform, the scattering properties become non-uniform (see Japanese Unexamined Patent Publication No.
184815). Even when ultraviolet rays are irradiated from the color filter side, the same problem occurs if the particle diameters are almost the same.

In view of the above problem, there is an example in which the particle size is adjusted by changing the irradiation intensity of ultraviolet rays for each of the RGB pixels (see Japanese Patent Application Laid-Open No. 8-129163). That is,
In this conventional example, the particle size of RGB is adjusted so that R <G <B, and the scattering characteristics of each pixel are balanced. However, in this conventional example, since ultraviolet irradiation is performed in three times of RGB from the array substrate side, it is necessary to mask other GB pixel portions when polymerizing and phase-separating the R pixel portion. There is. That is,
It is necessary to repeat the process of masking each of RGB and then irradiating ultraviolet rays three times. Further, as the array becomes higher definition, it becomes more difficult to adjust the particle size of each RGB pixel. Also, even if you do masking,
The leakage light of ultraviolet rays may promote polymerization and phase separation of the adjacent pixel portion, and may impair color reproducibility.

(3) Third Problem FIG. 13 is a partial cross-sectional view of a conventional reflection type liquid crystal display element 70 with an active matrix element provided with a flat film. In order to form the reflective pixel electrode 72 on the inner surface of the panel, the following steps are performed. First, a step of forming a TFT [or thin-film diode (TFD)] 74 on a glass substrate 73 and performing wiring required for each element.
Second, a step of forming a planarizing film 75 of an acrylic compound or the like on each TFT 74 on the substrate. Third, TFT
Contact hole 76 for forming a junction with 74
And forming a metal such as Al to form a reflective pixel electrode 72.
Is a step of forming

A problem with the substrate configuration having undergone the above steps will be described with reference to FIG. FIG. 14A is a cross-sectional view of a junction 80 between the reflective pixel electrode 72 and the relay electrode 77 in the contact hole 76. As shown in the figure, the junction 80 between the reflective pixel electrode 72 and the relay electrode 77 has a concave structure. This causes the following problems. That is, in the polymer-dispersed liquid crystal, when no voltage is applied as shown in FIG. 14B, external light incident on the polymer-dispersed liquid crystal layer 81 is scattered by the liquid crystal layer 81, and a white display is provided to the observer. Looks like. When a voltage is applied, as shown in FIG. 14C, the liquid crystal 82 of the polymer-dispersed liquid crystal layer 81 is oriented in the direction in which the voltage is applied. In this state, the external light reaches the reflective pixel electrode 72 and is reflected at the same angle as the incident angle. For this reason, it appears black to the observer. However, since the joint 80 is depressed, a part of the incident angle is specularly reflected, and the observer sees a slightly bright black display. As described above, the regular reflection at the bonding portion 80 lowers the contrast during black display.

[0010]

The above problems are summarized as follows.

(1) Only by irradiating the ultraviolet rays from the counter substrate side, an unpolymerized portion is generated immediately below the light shielding portion 61, and the unpolymerized portion oozes out into the color filter portion and the oozing portion 6.
2 are formed. Due to the seepage portion 62, display unevenness occurs and reliability is reduced.

(2) In the conventional method of finely adjusting the particle size of each of RGB, it is necessary to repeat a process of masking each of RGB and then irradiating ultraviolet rays three times, which makes the manufacturing operation troublesome. Poor. Further, as the array becomes higher definition, it becomes more difficult to adjust the particle size for each RGB pixel. Furthermore, even if the masking is performed, the leakage of ultraviolet light may promote polymerization and phase separation of the adjacent pixel portion, and may impair color reproducibility.

(3) The junction 80 between the reflective pixel electrode 72 and the relay electrode 77 in the contact hole has a concave structure. Due to this, a part of the incident angle is specularly reflected during black display, The observer saw the image as a slightly bright black display, causing a decrease in contrast.

In view of the above problems, the present invention sufficiently polymerizes a polymer precursor located immediately below a light-shielding portion to prevent display unevenness, and further improves the uniformity of RGB color reproducibility. In addition, it is another object of the present invention to provide a liquid crystal display device and a method for manufacturing the same, which are capable of reducing a decrease in contrast due to scattering at a junction between a reflective pixel electrode and a relay electrode in a contact hole.

[0015]

In order to solve the above-mentioned problems, the present invention irradiates ultraviolet rays from a counter substrate side, and then irradiates ultraviolet rays from an array substrate side, and a liquid crystal material and a polymer disposed between the substrates. The liquid crystal and the polymer are phase-separated by polymerizing a polymer precursor in a mixed solution containing the precursor. Alternatively, in order to polymerize the polymer precursor, ultraviolet rays are simultaneously irradiated from both the counter substrate side and the array substrate side.

According to the above configuration, the polymer precursor located immediately below the light-shielding portion is sufficiently polymerized by the irradiation of ultraviolet rays from the array substrate side. Accordingly, a polymer-dispersed liquid crystal layer having no unpolymerized portion can be obtained, and in-plane uniformity and reliability can be improved.

The present invention can be suitably applied not only to a reflection type liquid crystal display device but also to a transmission type liquid crystal display device. For example, in the case of a transmissive liquid crystal display device using a substrate having a low transmittance of ultraviolet rays as an array substrate, irradiation with ultraviolet rays from the array substrate side may cause the reflection type liquid crystal display device to be different from the reflective liquid crystal display device described in the section of the related art. A similar problem (the occurrence of seepage due to the unpolymerized portion) occurs. Therefore, in the case of a transmissive liquid crystal display device having such a configuration, by applying the present invention, a polymer-dispersed liquid crystal layer having no unpolymerized portion can be obtained, and in-plane uniformity and reliability can be improved. Will be done.

Further, according to the present invention, a reflection plate is internally provided.
The present invention can be applied not only to a reflection type liquid crystal display device having a so-called reflection image electrode, but also to an absorption plate type reflection type liquid crystal display device having an absorber provided on an array substrate.

The light-shielding portion may be a frame-shaped light-shielding portion formed around the opposing substrate. Here, the frame-shaped light-shielding portion is provided to prevent floating of the display and obtain a good display, and is generally called a frame.

It is desirable that the width of the frame-shaped light shielding portion is 0.1 mm or more. If the width of the light shielding part is small,
Upon irradiation with ultraviolet rays, the polymer precursor located immediately below the light-shielding portion is sufficiently polymerized due to the wrapping of the ultraviolet rays. Therefore, when the width of the light shielding portion is small, only irradiation from the counter substrate side is sufficient. However, the width of the light-shielding portion cannot be extremely reduced in manufacturing, and usually needs to be 0.1 mm or more. On the other hand, if the width of the light shielding portion is 0.1 mm or more,
Due to the large width, unpolymerized portions are generated. Therefore, not only irradiation from the counter substrate side but also irradiation from the array substrate side is required.

Further, according to the present invention, a color filter corresponding to red, green and blue is formed on the opposite substrate, and the particle size of the liquid crystal for each of the RGB pixels corresponding to the color filter is set to the blue pixel, the green pixel and the red pixel. It is characterized by increasing in order. In addition, a driving voltage value for obtaining the same transmittance decreases in the order of a blue pixel, a green pixel, and a red pixel.

As described above, by making the particle size of the liquid crystal different for each of the RGB pixels, or by making the driving voltage value for obtaining the same transmittance different for each of the RGB pixels, the color of each color is changed. Non-uniform scattering can be prevented, uniform scattering properties can be obtained on the entire display surface, and display characteristics are improved.

Here, the particle size of the liquid crystal refers to a PNL having a structure in which a polymer spreads in a three-dimensional network in a continuous phase of the liquid crystal.
In C (Polymer Network Liquid Crystal), it means the distance between the meshes. PDLC in which spherical or spheroidal liquid crystal droplets are dispersed independently from each other in a polymer matrix.
In the case of (Polymer Dispersed Liquid Crystal) or NCAP (Nematic Curvilinear Aligned Phase) in which a nematic liquid crystal is microencapsulated with polyvinyl alcohol or the like, it means the particle diameter of a liquid crystal droplet.

Further, according to the present invention, a flattening film is formed on an array substrate having an active matrix element, and a reflective pixel electrode is formed on the flattening film. A liquid crystal display element having a structure electrically connected via a relay electrode in a contact hole formed in the flattening film, wherein a junction between the reflective pixel electrode and the relay electrode is depressed, A light shielding portion is formed in the recessed portion. Further, a light-shielding portion is formed on the opposite substrate so as to shield the recessed portion from light.

By providing the light shielding portion in this way, it is possible to prevent a part of the incident angle from being specularly reflected at the time of black display due to the concave portion. Therefore, in black display, a decrease in contrast can be prevented.

[0026]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a simplified sectional view of a reflective liquid crystal display device according to Embodiment 1. The reflective liquid crystal display element 1 includes an array substrate 2 on which TFTs and metal wirings are formed, an opposing substrate 3 disposed opposite the array substrate 2, and a high-positioned substrate disposed between the array substrate 2 and the opposing substrate 3. And a molecular dispersion type liquid crystal layer 4. A reflective pixel electrode 5 made of aluminum (Al) or the like is formed on the inner surface of the array substrate 2. Although only one reflective pixel electrode 5 is illustrated for simplification of the drawing, a plurality of reflective pixel electrodes 5 are actually arranged in a matrix.

The opposite substrate 3 has an RGB color filter 6 formed on the inner surface thereof, and a transparent electrode 10 formed on the inner surface of the color filter 6. As shown in FIG. 2, a frame-shaped light-shielding portion 7 is formed on the outer peripheral portion of the color filter 6. The light-shielding portion 7 is provided to prevent floating of the display and obtain a good display, and is generally called a frame.
Since the light-shielding portion 7 is not a display area, the reflective pixel electrode 5 does not exist below the light-shielding portion 7. That is, the reflection pixel electrode 5 is arranged only in a region facing the color filter 6 (corresponding to a display region). The polymer-dispersed liquid crystal layer 4 includes a polymer 8 in the continuous phase of the liquid crystal 9.
It is a polymer network type liquid crystal (PNLC) layer having a structure spreading in a three-dimensional network. The polymer precursor is sufficiently polymerized not only in the region located below the color filter 6 in the polymer-dispersed liquid crystal layer 4 but also in the region located below the light-shielding portion 7. No unpolymerized parts are present. Therefore, in the liquid crystal display element 1 according to the present invention, the occurrence of the seepage phenomenon due to the unpolymerized portion as in the conventional example is prevented, and the display without display unevenness is possible.

FIG. 3 is a sectional view for explaining a method of manufacturing the reflection type liquid crystal display element according to the first embodiment. The reflection type liquid crystal display element 1 was manufactured by the following method.

(1) Preparation of Empty Panel A TFT was formed as a switching element on an array substrate 2 made of glass. Next, the reflective pixel electrode 5 was formed on the array substrate 2 by evaporating Al. Next, on the array substrate 2, SE-7229 (trade name:
(Nissan Chemical Industry Co., Ltd.) applied with a spinner and then 80 ° C.
, And then main firing at 180 ° C. After the firing, resin spacers were sprayed.

On the other hand, a color filter 6 and a light shielding portion 7 are formed on a counter substrate 3 made of glass, and a transparent electrode 10 is formed so as to cover the color filter 6 and the light shielding portion 7. In this state, S is applied to the opposite substrate 3 in the same manner as the array substrate 2.
E-7992 was applied, and then preliminary firing and main firing were performed. After the main baking, a main seal portion 15 for enclosing the liquid crystal material was formed on the counter substrate 3. At this time, Structbond X which is a thermosetting resin is used as a sealant.
N-21-S (trade name: manufactured by Mitsui Chemicals, Inc.) was used. After pre-baking the main sealant at 85 ° C., the array substrate 2 was bonded to the counter substrate 3. At this time, the gap between the substrates was set to be approximately 5 μm. The main sealant was finally baked at 150 ° C. for 120 minutes while being pressed at a constant pressure. Thus, an empty panel was produced.

(2) Injection of polymer-dispersed liquid crystal material Next, a mixed solution (hereinafter, referred to as a polymer-dispersed liquid crystal material) composed of a photopolymerizable polymer precursor and liquid crystal is filled in the empty panel. , By vacuum injection. The polymer-dispersed liquid crystal material is a polymer network material PNM.
-201 (manufactured by Dainippon Ink and Chemicals, Inc.) was used.

(3) Ultraviolet Irradiation Step Next, in order to phase-separate the liquid crystal and the polymer in the PNM-201, as shown in FIG. went. At this time, an IR cut filter was inserted over the entire irradiation surface in order to suppress heat generation of the panel due to infrared rays from the ultra-high pressure mercury lamp 17. In order to prevent deterioration of the liquid crystal material and the like, a cut filter for cutting light in a low wavelength range not related to polymerization was inserted. In such a state, the ultraviolet irradiation is performed on the opposite substrate 3.
When performed only from the side, since the opposing substrate 3 has the light-shielding portion 7, the polymer precursor in this portion remains partially as an unpolymerized substance 19. If left as it is, a seepage portion with low scattering property is formed, and the in-plane uniformity is impaired. Therefore,
In order to prevent seepage by the unpolymerized substance 19, FIG.
As shown in (b), a step of irradiating ultraviolet rays from the back side of the array substrate 2 was performed. In the present embodiment, since the reflective pixel electrode 5 is not formed in a portion where the unpolymerized substance 19 is present, the unpolymerized substance 19 undergoes polymerization and phase separation by irradiation from the back side of the array substrate 2 and polymer dispersion. The liquid crystal layer 4 was formed.

By the irradiation of ultraviolet rays again from the back side of the array substrate 2, the unpolymerized substance 109 was polymerized and phase-separated, and no seepage into the color filter 6 was observed.

As described above, by irradiating the ultraviolet rays again from the back side of the array substrate 2 after irradiating the ultraviolet rays from the counter substrate 3 side, the in-plane uniformity and reliability were improved.

It should be noted that when the light shielding portion 7 is irradiated with ultraviolet rays,
Heated. The unpolymerized product is less likely to be polymerized due to a rise in temperature due to heating. For this reason, when irradiating with ultraviolet rays, the temperature was kept constant by using a cooling / constant temperature device such as a constant temperature water tank. Thus, cooling is effective in reducing unpolymerized substances 19.

According to the experimental results of the present inventor, when ultraviolet irradiation is performed only from the counter substrate side, if the width d (see FIG. 2) of the light shielding portion 7 is 50 μm or less, almost no seeping-out portion occurs. Without affecting the in-plane uniformity. This is because, if the thickness is 50 μm or less, the ultraviolet rays are radiated to the polymer precursor located immediately below the light-shielding portion 7 and irradiated, and the polymerization of the polymer precursor proceeds. Width d is 0.1mm
Above, slight seepage occurred. Also,
If it is 0.5 mm or more, a large amount of seepage was generated. Therefore, when the width d of the light-shielding portion 7 is 0.5 mm or more, it is essential to perform the two-step ultraviolet irradiation according to the present embodiment, and even when the width d is 0.1 mm or more, the two-step ultraviolet irradiation is performed. It is desirable to perform ultraviolet irradiation.

When an electric field was applied to the liquid crystal display device manufactured by the method according to the present embodiment, uniform display without display unevenness was obtained.

In this embodiment, the first ultraviolet irradiation is performed from the opposite substrate side. However, if the irradiation from the array substrate side is performed first, the ultraviolet rays can be completely cut by the reflective pixel electrode. Instead, ultraviolet rays are partially applied to the polymer-dispersed liquid crystal material. Thereby, the polymerization of the polymer precursor in the polymer-dispersed liquid crystal material slightly proceeds. Then, the polymerization of the polymer precursor progresses slightly, so that the size of the particle size of the liquid crystal is determined, and a phenomenon occurs that the particle size does not increase even if the counter substrate is irradiated with ultraviolet light thereafter. Therefore, if the array substrate side is irradiated first, there is a problem that a liquid crystal having a desired particle size cannot be obtained.
It is necessary to irradiate ultraviolet rays first from the counter substrate side.

(Embodiment 2) FIG. 4 is a sectional view for illustrating a method of manufacturing a liquid crystal display element according to Embodiment 2. The liquid crystal display element 1A according to the second embodiment has a configuration similar to that of the liquid crystal display element 1 according to the first embodiment, and corresponding portions are denoted by the same reference numerals. Reflective liquid crystal display device 1
A was produced by the following method.

First, an empty panel was manufactured by the same method as the manufacturing method in Embodiment 1, and then a polymer-dispersed liquid crystal material was injected. In the ultraviolet irradiation step, unlike the first embodiment, ultraviolet rays were simultaneously irradiated from the array substrate 2 side and the counter substrate 3 side. As described above, the feature of the second embodiment is that the ultraviolet irradiation process is performed twice in the first embodiment, but the ultraviolet irradiation is performed simultaneously from above and below the liquid crystal display panel.

The ultraviolet light irradiated from above the counter substrate 3
In the polymer dispersed liquid crystal material (PNM-201), regions other than the region located below the light-shielding portion 7 are polymerized. On the other hand, the ultraviolet light irradiated from below the array substrate 2 polymerizes the polymer dispersed liquid crystal material in the entire region. Therefore, the polymer-dispersed liquid crystal material in the region located below the light-shielding portion 7 is also polymerized. As a result, the entire liquid crystal display element has no unpolymerized portions,
A polymer dispersed liquid crystal layer 4 having a uniform in-plane is formed. When an electric field was applied to the manufactured liquid crystal display element, a uniform display without display unevenness was obtained. Note that, in this embodiment, since ultraviolet irradiation is performed simultaneously from both the counter substrate and the array substrate, one manufacturing process can be omitted compared to Embodiment 1, and workability can be improved. .

(Embodiment 3) FIG. 5 is a sectional view for illustrating a method of manufacturing a liquid crystal display device according to Embodiment 3. In the second embodiment, the ultra-high pressure mercury lamp 17 is disposed so as to sandwich the liquid crystal display element from above and below. In the third embodiment, as shown in FIG. On the array substrate 2 side, a reflection plate 20 and a light guide 21 were arranged instead of the ultrahigh pressure mercury lamp 17. The light guide 21 is, for example, a glass thermostatic water bath. The light guide 21 has a certain thickness, and is 3 cm in the present embodiment. The light guide 21 is not particularly limited as long as it has a high ultraviolet transmittance, such as a quartz substrate, instead of a glass thermostat.

The ultra-high pressure mercury lamp 17 and the reflection plate 20
The light guide 21 collects the leakage light of the ultraviolet light from the ultrahigh-pressure mercury lamp 17 with the light guide 21 and reflects the reflected ultraviolet light from the reflector 20 below the light-shielding portion 7 with a polymer-dispersed liquid crystal material ( PNM-201) for polymerization and phase separation. Thus, the reflection plate 20 and the light guide 21
A uniform polymer-dispersed liquid crystal layer could be formed by the combination of. When an electric field was applied to the manufactured liquid crystal display element, a uniform display without display unevenness was obtained.

In the above example, the light guide 21 is arranged so as to be in contact with the array substrate 2. However, if there is a gap between the light guide 21 and the array substrate 2, the interface reflection may occur. This makes it impossible to guide the reflected light to the array substrate 2. In the case where a gap is provided between the light guide 21 and the array substrate 2, the gap may be filled with, for example, ethylene glycol or the like, which allows optical coupling between the light guide 21 and the array substrate 2. In the present embodiment,
Since ultraviolet irradiation is performed simultaneously from both the opposing substrate and the array substrate, one manufacturing step can be omitted as compared with the first embodiment, and workability can be improved.

In the first to third embodiments, the reflection type liquid crystal display device provided with a so-called reflection image electrode in which a reflection plate is internally provided, but the present invention is not limited to this. The present invention is also applicable to a reflection type liquid crystal display device of an absorption plate type in which an absorber is provided on a substrate.

In the first to third embodiments, the reflection type liquid crystal display device has been described. However, the present invention is not limited to this, and can be suitably applied to a transmission type liquid crystal display device. For example, in the case of a transmission type liquid crystal display element using a substrate having a low transmittance of ultraviolet rays as an array substrate, when ultraviolet rays are irradiated from the array substrate side, the same problem as in the case of a reflection type liquid crystal display element (due to unpolymerized portions). Leaching). Therefore, by applying the present invention to a transmissive liquid crystal display element having such a configuration, a polymer-dispersed liquid crystal layer having no unpolymerized portion can be obtained, and in-plane uniformity and reliability can be improved. Will be.

Comparative Example 1 A polymer-dispersed liquid crystal material (PNM-201) is filled and sealed in a liquid crystal display element having the panel configuration described in the first and second embodiments by a vacuum injection method. If only the ultraviolet rays are irradiated from the counter substrate side and left for a while, the scattering state changes from the vicinity of the light shielding portion 61 around the color filter as shown in FIG. As it began to spread gradually.

(Embodiment 4) FIG. 6 is a partial cross-sectional view of a reflection type liquid crystal display device of Embodiment 4. Embodiment 4
Has a configuration basically similar to that of the liquid crystal display element 1 of the first embodiment, and corresponding parts are denoted by the same reference numerals. In this liquid crystal display element 1B, the color filter 6A of the polymer dispersed liquid crystal layer 4
Of liquid crystals 9R, 9G, 9B in regions corresponding to R, G, B
Are such that rB <rG <rR. Here, the particle size of the liquid crystal means a mesh interval in a PNLC having a structure in which a polymer spreads in a three-dimensional network in a continuous phase of the liquid crystal as in this embodiment. In the case of PDLC or NCAP in which spherical or spheroidal liquid crystal droplets are dispersed independently of each other, it means the particle diameter of the liquid crystal droplet.

By setting the particle size of the liquid crystal as described above, the scattering can be made uniform. Because, as described in the section of the prior art, the scattering intensity of the polymer-dispersed liquid crystal depends on the wavelength. For this reason, the scattering at R becomes insufficient with the conventional uniform particle size (JP-A-7-3120).
No. 13). On the other hand, as shown in FIG.
For each particle size of B, there is an optimum particle size that maximizes the scattering, and the scattering becomes worse even if it is larger or smaller (see Japanese Patent Application Laid-Open No. Hei 7-312013). Therefore, R is adjusted to an optimum particle size, and B and G are made smaller than the above to achieve uniform scattering. Note that the R pixel,
One pixel is composed of the G pixel and the B pixel.

FIG. 8 is a sectional view for illustrating a method for manufacturing the liquid crystal display element according to the fourth embodiment. The reflection type liquid crystal display element 1B was manufactured by the following method. That is, (1) a process of manufacturing an empty panel and (2) a process of injecting a polymer dispersed liquid crystal material (PNM-201) are performed in the same manner as in the manufacturing method of the first embodiment. Next, as shown in FIG. 8, ultraviolet irradiation was performed from the counter substrate 3 side by the ultrahigh pressure mercury lamp 17. At this time, the color filter 6A was formed as follows. That is, the transmittance of the color filter 6A for each of R, G, and B with respect to the ultraviolet rays is set so that B>G> R.
G and B were formed. As a result, the UV light is
By passing through the G and B color filters 6A, R
Ultraviolet rays could be irradiated such that the particle size at each pixel of GB was in the order of rB <rG <rR. The reason why the particle diameters of R, G, and B can be finely adjusted by changing the UV transmittance of each of R, G, and B of the color filter 6A is as follows. For each color filter,
Ultraviolet light is absorbed for each color of G and B. Further, as the intensity of ultraviolet light increases, the particle size decreases. Therefore, R, G,
This is because the particle size can be adjusted for each color by adjusting the ultraviolet transmittance of the B color filter.

By using the color filter 6A as described above, a reflection type liquid crystal display having the polymer dispersed type liquid crystal layer 4 in which the particle size of R, G and B satisfies rB <rG <rR by one irradiation of ultraviolet rays. Element 1B was produced. Therefore,
The workability is significantly improved as compared with a conventional example (Japanese Unexamined Patent Publication No. 8-129163) in which a mask is used and ultraviolet irradiation is performed three times for each of R, G, and B.

According to the experimental results of the present inventors, regarding the characteristics of the thus-obtained reflection type liquid crystal display element 1B, when the ultraviolet transmittance of B is increased, the particle size becomes smaller than the optimum particle size. The balance with R has improved.
The particle size of B was smaller than that of R by about 0.1 μm.
When the difference between the particle diameters of R and B was in the range of 0.05 μm to 2.0 μm, the effect of uniform display was observed. 0.0
At 5 μm or less, scattering at R was insufficient, and at 2.0 μm or more, B scattering was insufficient.

In the conventional example (Japanese Patent Application Laid-Open No. 8-129163), the display is made uniform by adjusting the particle size in the order of B>G> R. On the other hand, in the present embodiment, the display is made uniform by adjusting the particle size so that B <G <R. This is apparent from the characteristics shown in FIG.
For each particle size of B, there is an optimum particle size that maximizes scattering, and there are two particle sizes having the same scattering intensity. In the conventional example, fine adjustment is made to r'B>r'G> rR, and in the present embodiment, fine adjustment is made to rB <rG <rR. Here, r′B is the particle size of B of the conventional example,
The gain at r'B and the gain at rB are the same. Also, r'G is the particle diameter of G in the conventional example, and the gain at r'G and the gain at rG are the same. Therefore, from the viewpoint of the scattering characteristics, the fine particle size adjustment in the conventional example and the fine particle size adjustment in the present embodiment are essentially the same. However, assuming that the conventional example and the present embodiment are set to have the same scattering characteristics, as shown in FIG.
The particle size difference between G and B is small and there is difficulty in manufacturing.
On the other hand, in the present embodiment, the particle size difference among R, G, and B is large, and manufacturing is easy. Further, since the scattering properties of R are inherently poor, the color purity of R tends to decrease in the order of the conventional example. On the other hand, in the present embodiment, since the particle size is determined centering on R, it is easy to increase the contrast.

In the above example, the reflection type liquid crystal display element has been described, but the present invention is not limited to this.

(Embodiment 5) The liquid crystal display element according to Embodiment 5 has the same configuration as the liquid crystal display element according to Embodiment 4. However, as shown in FIG. 8, the driving voltage value for the same transmittance in each of the R, G, and B pixels is B, respectively.
Embodiment 4 in that the order is>G> R.
And different. Therefore, at the time of manufacturing, the ultraviolet transmittance of each color of the plurality of color filters is set in advance so that the driving voltage value for obtaining the same transmittance is different for each pixel corresponding to each color. As a result, the ultraviolet rays pass through the R, G, and B on the color filter, so that the R, G, and
Polymerization and phase separation of PNM-201 occurred such that the drive voltage values for the same transmittance in each B pixel were in the order of B>G> R. As a result, the particle size of each pixel is basically the same as in the fourth embodiment. However, in contrast to Embodiment 4 where the scattering intensity is adjusted to be equal, Embodiment 5 is characterized in that the voltage is adjusted. As for the uniformity of display, the uniformity in halftone display is most important. Therefore, by lowering the driving voltage of B, which basically has high scattering, the uniformity in the halftone is improved. in this way,
By setting the drive voltage to B>G> R, uniform display of color balance in halftone was seen as an effect.

(Embodiment 6) FIG. 9 is a partial sectional view of a reflective liquid crystal display device according to Embodiment 6. Basically, it is the same as the first embodiment. However, in the reflective liquid crystal display element 1C according to the sixth embodiment, the flattening film 30 is formed on the array substrate 2 having the TFT 29, and the reflective pixel electrode 5 is formed on the flattening film 30. I have. The reflection pixel electrode 5 and the TFT 29 are electrically connected via a relay electrode 32 in a contact hole 31 formed in the flattening film 30. Then, the reflection pixel electrode 5
The junction between the electrode and the relay electrode 32 is depressed, and a light-shielding portion 34 is formed in the depressed portion 33.

Here, the principle of operation of the liquid crystal display device according to the present embodiment will be described. In the polymer-dispersed liquid crystal, the refractive indices of the photopolymerizable polymer compound and the liquid crystal molecules are designed to be the same when a voltage is applied and different when no voltage is applied. When no voltage is applied, the refractive index of the polymer compound is different from that of the liquid crystal molecules, so that light is scattered when passing through the polymer dispersed liquid crystal layer. Next, when a voltage is applied, the refractive index between the liquid crystal molecules and the polymer becomes equal, so that light can travel straight through the polymer-dispersed liquid crystal layer. When the straight light from the outside reaches the reflective pixel electrode 5, the light is originally reflected. For this reason, the observer looks black when viewed from the front. As described above, it is possible to switch the scattering by the transparent application of the voltage and the removal of the voltage. However, if the bonding portion has a concave structure, a part of the reflected light is directed toward the front. As a result, it has been found that the display becomes brighter in the black display state and the contrast is reduced. In order to solve this problem, in the present embodiment, the upper part of the relay electrode 32 is covered with the light shielding part 34 made of resin or a chromium compound.

FIG. 9B is a front view of the reflection pixel electrode pixel 5. The portion indicated by the broken line is the recessed portion 33. A light-shielding portion 34 indicated by a solid line was formed so as to cover the depression 33. The light shielding portion 34 sufficiently covers the recessed portion 33,
It is desirable that the coverage is as small as possible.

By forming the light-shielding portion 34 in this manner, the incidence of external light on the recessed portion 33 can be shielded, and the reduction in contrast can be improved.

The liquid crystal display element 1 according to the present embodiment
When an electric field was applied to C, a uniform display without display unevenness was obtained. In addition, when an external driving circuit such as a driver circuit or a control circuit for color display was connected to display a computer screen or a television screen, and the contrast was measured, a good contrast was obtained.

(Embodiment 7) FIG. 10 shows Embodiment 7 of the present invention.
FIG. 2 is a partial cross-sectional view of the reflective liquid crystal display element of FIG. The difference between the reflection type liquid crystal display element 1D according to the present embodiment and the liquid crystal display element 1C described in the sixth embodiment is that the sixth embodiment is different from the sixth embodiment.
In this embodiment, the light shielding portion 34 is formed on the reflective pixel electrode 5 to eliminate the specular reflection at the junction between the reflective pixel electrode 5 and the relay electrode 32. That is, 34 is formed to eliminate the light incident on the junction. In other words, when the recessed portion 33 is in a bare state, the light is slightly reflected in black display and the contrast is reduced due to regular reflection. In order to solve this problem, in the present embodiment,
When forming the color filter 6 on the opposing substrate 3, the TFT 2
A light-shielding part 34 made of resin or a chromium compound was formed in a normal line passing through the center of the relay electrode 32 joining the pixel electrode 9 and the reflective pixel electrode 5.

FIG. 10B is a back view of the color filter 6.
Shown in If the light-shielding portion 34 is formed in the color filter 6, it is possible to block external light from entering the recessed portion 33. As a result, it is possible to improve a decrease in contrast during black display. Note that it is desirable to have a sufficient area to block the light incident on the recessed portion 33 and to make the coverage range as small as possible.

When an electric field was applied to the liquid crystal display element 1D having the above configuration, a uniform display without display unevenness was obtained.
In addition, connecting an external drive circuit such as a driver circuit or control circuit for color display, displaying a computer screen or TV screen, and measuring the contrast,
Good contrast was obtained.

In the first to seventh embodiments, the polymer network type liquid crystal has been described as the polymer dispersed type liquid crystal. However, NCAP and PDLC can be implemented according to the same principle.

In the first to seventh embodiments, the RGB
Has been described, but color filters composed of cyan, magenta, and yellow can be implemented according to the same principle.

[0067]

As described above, according to the present invention, the following effects can be obtained.

(1) By irradiating ultraviolet rays from the counter substrate side and then irradiating ultraviolet rays from the array substrate side, or simultaneously irradiating ultraviolet rays from both the counter substrate side and the array substrate side, the unpolymerized portion is irradiated. A polymer-dispersed liquid crystal layer having no in-plane uniformity, excellent in-plane uniformity, and a highly reliable polymer-dispersed liquid crystal display device can be realized.

(2) Further, by adjusting the transmittance of the color filter corresponding to RGB to ultraviolet light and irradiating ultraviolet light from above the color filter, the particle size or driving voltage of each pixel of RGB is adjusted, and the scattering property is balanced. By doing so, a polymer-dispersed liquid crystal display element having uniform in-plane color reproducibility can be realized.

(3) Further, a light-shielding portion is formed in a concave portion of a junction between the reflective pixel electrode and the relay electrode in the contact hole, or a light-shielding portion is formed on the opposite substrate so as to cover the concave portion. Thus, a polymer-dispersed liquid crystal display device having good contrast can be realized.

[Brief description of the drawings]

FIG. 1 is a simplified cross-sectional view of a reflective liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a plan view of a color filter according to Embodiment 1 of the present invention.

FIG. 3 is a cross-sectional view for explaining the method for manufacturing the reflective liquid crystal display element in the first embodiment of the present invention.

FIG. 4 is a cross-sectional view for explaining a method for manufacturing a reflective liquid crystal display element in Embodiment 2 of the present invention.

FIG. 5 is a cross-sectional view for explaining a method for manufacturing a reflective liquid crystal display element in Embodiment 3 of the present invention.

FIG. 6 is a partial cross-sectional view of a reflective liquid crystal display device according to a fourth embodiment of the present invention.

FIG. 7 is a diagram illustrating a relationship between a particle size and a gain of each of RGB pixels according to the fourth embodiment of the present invention.

FIG. 8 is a diagram illustrating a relationship between a voltage and a gain of each RGB pixel according to a fifth embodiment of the present invention.

FIG. 9 is a configuration diagram of a reflective liquid crystal display device according to a sixth embodiment of the present invention.

FIG. 10 is a configuration diagram of a reflective liquid crystal display device according to a seventh embodiment of the present invention.

FIG. 11 is a plan view of a color filter of a conventional reflective liquid crystal display device.

FIG. 12 is a diagram illustrating a relationship between an applied voltage and transmittance of each pixel of RGB.

FIG. 13 is a sectional view of a conventional reflective liquid crystal display device.

FIG. 14 is a sectional view showing the vicinity of a reflective pixel electrode of a conventional reflective liquid crystal display device.

[Explanation of symbols]

 1, 1A, 1B, 1C, 1D: reflective liquid crystal display element 2: array substrate 3: counter substrate 4: polymer dispersed liquid crystal layer 5: reflective pixel electrode 6, 6A: color filter 7, 34: light shielding portion 29: TFT 30: Flattening film 31: Contact hole 32: Relay electrode 33: Depressed portion

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Kubota 1006 Kadoma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Terms (reference) 2H089 HA04 KA08 QA16

Claims (29)

[Claims] 1. A polymer dispersed liquid crystal comprising a polymer and a liquid crystal between an array substrate and a counter substrate having a light-shielding portion and an array substrate on which pixel electrodes are formed. A liquid crystal display device having a structure in which layers are sandwiched, wherein the polymer-dispersed liquid crystal layer irradiates ultraviolet rays from the counter substrate side, and then irradiates ultraviolet rays from the array substrate side,
The liquid crystal is formed by polymerizing a polymer precursor of a mixed solution containing a liquid crystal material and a polymer precursor disposed between the substrates to phase-separate the liquid crystal and the polymer. Display element. 2. A polymer-dispersed liquid crystal comprising a polymer and a liquid crystal between an array substrate and an opposing substrate having an array substrate on which pixel electrodes are formed and a light-shielding portion. A liquid crystal display device having a structure in which layers are sandwiched, wherein the polymer-dispersed liquid crystal layer simultaneously irradiates ultraviolet rays from both the counter substrate side and the array substrate side, and a liquid crystal material disposed between the substrates. A liquid crystal display device characterized by being formed by polymerizing a polymer precursor in a mixed solution containing a polymer and a polymer precursor to cause phase separation of a liquid crystal and a polymer. 3. The liquid crystal display device according to claim 1, wherein the light-shielding portion is a frame-shaped light-shielding portion formed around the counter substrate. 4. A color filter is formed on the counter substrate, and the light-shielding portion is a frame-shaped light-shielding portion formed on an outer peripheral portion of the color filter. The liquid crystal display device according to the above. 5. The liquid crystal display device according to claim 3, wherein the width of the frame-shaped light shielding portion is 0.1 mm or more. 6. A mixed solution containing a liquid crystal material and a polymer precursor is arranged between an array substrate on which pixel electrodes are formed and an opposing substrate on which a light-shielding portion is formed. A method for producing a liquid crystal display device comprising a phase separation step of producing a polymer-dispersed liquid crystal layer composed of a polymer and a liquid crystal by polymerizing a precursor to phase-separate the liquid crystal and the polymer, A liquid crystal, wherein the ultraviolet irradiation in the phase separation step includes a first irradiation step of irradiating ultraviolet rays from the counter substrate side, and a second irradiation step of irradiating from the array substrate side after the first irradiation step. A method for manufacturing a display element. 7. A mixed solution containing a liquid crystal material and a polymer precursor is arranged between an array substrate on which pixel electrodes are formed and an opposing substrate on which a light-shielding portion is formed, and the polymer is irradiated with ultraviolet light. A method for producing a liquid crystal display device comprising a phase separation step of producing a polymer-dispersed liquid crystal layer composed of a polymer and a liquid crystal by polymerizing a precursor to phase-separate the liquid crystal and the polymer, A method for manufacturing a liquid crystal display device, wherein the ultraviolet irradiation in the phase separation step is performed by simultaneously irradiating ultraviolet light from both the counter substrate side and the array substrate side. 8. In the phase separation step, ultraviolet rays are radiated from the counter substrate side, and a part of the ultraviolet rays from the counter substrate side is reflected by a reflector provided outside the array substrate. 8. The method according to claim 7, wherein the irradiation is performed from the substrate side. 9. The method according to claim 8, wherein a light guide made of a material capable of transmitting ultraviolet light is provided on a front surface of the reflection plate. 10. The method according to claim 9, wherein the light guide is a water tank. 11. The method according to claim 6, wherein the light-shielding portion is a frame-shaped light-shielding portion formed in a peripheral portion of the counter substrate. 12. A color filter is formed on the counter substrate, and the light-shielding portion is a frame-shaped light-shielding portion formed on an outer peripheral portion of the color filter. The manufacturing method of the liquid crystal display element described in. 13. The method according to claim 11, wherein the width of the frame-shaped light shielding portion is 0.1 mm or more. 14. An array substrate on which a pixel electrode is formed,
A liquid crystal display element having a counter substrate on which a counter electrode is formed, and having a structure in which a polymer-dispersed liquid crystal layer composed of a polymer and a liquid crystal is sandwiched between an array substrate and a counter substrate, A plurality of color filters are formed on the opposite substrate,
A liquid crystal display device characterized in that the particle size of liquid crystal differs for each pixel corresponding to each color of the plurality of color filters. 15. A color filter corresponding to red, green, and blue color filters, wherein the particle size increases in the order of blue pixels, green pixels, and red pixels. 15. The liquid crystal display device according to 14. 16. An array substrate on which pixel electrodes are formed,
A liquid crystal display element having a counter substrate on which a counter electrode is formed, and having a structure in which a polymer-dispersed liquid crystal layer composed of a polymer and a liquid crystal is sandwiched between an array substrate and a counter substrate, A plurality of color filters are formed on the opposite substrate,
A liquid crystal display device characterized in that pixels corresponding to the respective colors of the plurality of color filters have different driving voltage values for obtaining the same transmittance. 17. The color filter for a plurality of colors is a color filter corresponding to red, green, and blue, and the drive voltage value decreases in the order of a blue pixel, a green pixel, and a red pixel. 16. The liquid crystal display device according to item 16. 18. The array substrate according to claim 14, wherein a reflection plate is provided inside or outside the array substrate.
The liquid crystal display element as described in the above. 19. An array substrate on which a pixel electrode is formed,
A liquid crystal display having a structure in which a counter electrode and a counter substrate on which a plurality of color filters are formed, and a polymer dispersed liquid crystal layer composed of a polymer and a liquid crystal interposed between the array substrate and the counter substrate. A method of manufacturing an element, wherein the ultraviolet transmittance of each color of the color filters of the plurality of colors is preset so that the particle size of liquid crystal is different for each pixel corresponding to each color, And irradiating the liquid crystal display device with ultraviolet rays. 20. The color filter for a plurality of colors, wherein the color filters correspond to red, green, and blue, and the color filters are arranged such that the particle size of the liquid crystal increases in the order of blue, green, and red pixels. 20. The method for manufacturing a liquid crystal display device according to claim 19, wherein the ultraviolet transmittance of each of the colors is preset. 21. The color filters of a plurality of colors are color filters corresponding to cyan, magenta, and yellow, and each color of the color filters is such that the particle size increases in the order of yellow pixel, magenta pixel, and cyan. 20. The method according to claim 19, wherein each ultraviolet transmittance is set in advance. 22. An array substrate on which a pixel electrode is formed,
A liquid crystal display having a structure in which a counter electrode and a counter substrate on which a plurality of color filters are formed, and a polymer dispersed liquid crystal layer composed of a polymer and a liquid crystal interposed between the array substrate and the counter substrate. A method of manufacturing an element, wherein the ultraviolet transmittance of each of the colors of the plurality of color filters is set in advance so that a driving voltage value for obtaining the same transmittance is different for each pixel corresponding to each color, A method of manufacturing a liquid crystal display device, comprising a step of irradiating ultraviolet rays through the color filter. 23. The plurality of color filters are color filters corresponding to red, green, and blue colors, and the plurality of color filters are arranged such that the drive voltage value decreases in the order of a blue pixel, a green pixel, and a red pixel. 23. The method according to claim 22, wherein the ultraviolet transmittance of each color of the color filter is set in advance. 24. The color filter of a plurality of colors is a color filter corresponding to cyan, magenta, and yellow, and the drive voltage value is a yellow pixel, a magenta pixel,
23. The method for manufacturing a liquid crystal display device according to claim 22, wherein the ultraviolet transmittance of each color of the plurality of color filters is set in advance so as to decrease in order of cyan. 25. A flattening film is formed on an array substrate having an active matrix element, a reflective pixel electrode is formed on the flattening film, and the reflective pixel electrode and the active matrix element are flattened. It is electrically connected through a relay electrode in a contact hole formed in the film, a counter electrode is formed on a counter substrate facing the array substrate, and between the array substrate and the counter substrate. Is a liquid crystal display element having a structure in which a polymer-dispersed liquid crystal layer composed of a polymer and a liquid crystal is sandwiched, wherein a junction between the reflective pixel electrode and the relay electrode is depressed, and the depressed portion A liquid crystal display device, wherein a light shielding portion is formed on the liquid crystal display device. 26. A flattening film is formed on an array substrate having an active matrix element, a reflective pixel electrode is formed on the flattening film, and the reflective pixel electrode and the active matrix element are flattened. It is electrically connected through a relay electrode in a contact hole formed in the film, a counter electrode is formed on a counter substrate facing the array substrate, and between the array substrate and the counter substrate. Is a liquid crystal display element having a structure in which a polymer-dispersed liquid crystal layer composed of a polymer and a liquid crystal is sandwiched, wherein a junction between the reflective pixel electrode and the relay electrode is depressed, and the depressed portion A light-shielding part is formed on the counter substrate so as to shield light from the liquid crystal display element. 27. The liquid crystal display device according to claim 25, wherein the light shielding portion is made of a resin or a chromium compound. 28. A liquid crystal display device according to claim 25, wherein said active matrix element is a thin film transistor or a thin film diode. 29. The liquid crystal display according to claim 25, wherein a color filter including three types of red, blue and green or three types of cyan, magenta and yellow is formed on the counter substrate. element.