JPH09127488A - Polymer-dispersed liquid crystal display panel and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display panel having strong scattering character and high contrast. SOLUTION: This display panel is constituted of a pair of transparent substrates 1 which have transparent electrodes 2 and at least one of which is transparent. On a surface of the substrate 1, a bifunctional acrylate thin film 3 consisting of polymerizable substances with multifunction such as (metha) acrylate is provided. A polymer-dispersed liquid crystal precursor mixture (premixture) 4 is inserted and held between a pair of substrates which is arranged so that the thin layers 3 are disposed to face each other and then the premixture 4 is converted to a polymer-dispersed liquid crystal 5 by supplying active energy such as ultraviolet ray (UV) and heat to form a polymer-dispersed liquid crystal display panel. The polymer-dispersed liquid crystal display panel is driven by an active matrix and is suitable for using as a projection type optical device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer dispersion type liquid crystal display panel used for a liquid crystal television, a liquid crystal display, a liquid crystal projector and the like, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, a projection type LC capable of obtaining a large screen display
D is being actively developed. Not only the projection type, but also the TN type liquid crystal display panel is widely used in the conventional liquid crystal display panel. However, in the TN type liquid crystal display panel, it has been pointed out that the use efficiency of light is low because the polarizing plate is used, and that the display type is difficult to see especially in a bright room.

As a new display method for solving these problems, a display method with high light utilization efficiency is required. For this reason, a polymer-dispersed liquid crystal display panel capable of performing display without using a polarizing plate has been developed.

FIG. 3 is an explanatory view of the basic structure of a polymer dispersion type liquid crystal display panel, in which (A) is a state in which no voltage is applied,
(B) shows a state in which a voltage is applied. In this figure, 11 and 12 are substrates, 13 is a polymer substance, 14 is liquid crystal molecules, 15 is a power supply, 16 is incident light, 17 is scattered light, 1
8 is transmitted light.

The polymer-dispersed liquid crystal display panel has a structure in which a polymer-liquid crystal composite layer containing liquid crystal molecules 14 in a droplet shape is sandwiched between substrates 11 and 12 between voids existing in a polymer substance 13. have. When the voltage between the electrodes of the substrates 11 and 12 by the power supply 15 is off, the liquid crystal molecules 14 are in a random state, so that there is a difference between the refractive index of the polymer substance 13 and the refractive index of the liquid crystal molecules 14. The incident light 16 is generated and scattered by the liquid crystal molecules 14 to become scattered light 17 (see FIG. 1).
(A)).

When the voltage between the electrodes of the substrates 11 and 12 is turned on, the liquid crystal molecules 14 are aligned in the direction of the electric field, so that the incident light 16 is transmitted without being scattered and becomes transmitted light 18 (FIG. 1).
(B)). As described above, in the polymer-dispersed display panel, since the display can be performed by turning on and off the voltage between the electrodes of the substrates 11 and 12, the polarizing plate which is indispensable in the conventional TN type liquid crystal display panel is unnecessary. Therefore, it is possible to obtain a bright display. Further, regarding the driving of the liquid crystal molecules 14, as in the conventional TN type liquid crystal display panel, the T
The FT method can be used.

FIG. 4 is a conceptual diagram of an evaluation system for measuring the relationship between applied voltage and transmittance in a polymer dispersed liquid crystal display panel. In this figure, 21 is a light source, 22 is a liquid crystal panel, 23 and 24 are transparent substrates, 25 and 26 are transparent electrodes, 2
7 is a polymer dispersed liquid crystal layer, 28 is a variable voltage power source, and 29 is a detector.

The evaluation system for measuring the electro-optical characteristics showing the relationship between the applied voltage and the transmittance in the polymer dispersion type liquid crystal display panel is as follows.
A liquid crystal panel 22 having a structure in which a polymer-dispersed liquid crystal layer 27 is sandwiched in a gap in which transparent substrates 23 and 24 having transparent electrodes 25 and 26 are opposed to each other is provided on the transparent electrodes 25 and 26 of the transparent substrates 23 and 24. The liquid crystal panel 22 has a configuration in which a variable voltage power source 28 for applying a voltage is connected, and one side of the liquid crystal panel 22 is irradiated with light having a constant light intensity to change the voltage applied to the transparent electrodes 25 and 26. The transmitted light is detected by the detector 29. In the case of this figure, the take-in angle θ of the detector 29 is constant.

FIG. 5 is a curve of transmittance versus applied voltage of the polymer dispersed liquid crystal display panel. From this figure, when the applied voltage between the transparent electrodes is increased from 0V, the transmittance of the polymer dispersion type liquid crystal panel gradually increases, has a tendency to sharply increase from about 4V and saturate from about 9V. Is observed. The smaller the transmittance T ₀ when no voltage is applied, the stronger the scattering property.

However, the conventional polymer-dispersed liquid crystal display panel has a problem that it is not possible to obtain a sufficient scattering property in a voltage range that can be driven by the TFT, and a bright and high-contrast display cannot be realized. 2. Description of the Related Art Conventionally, a phase separation method utilizing polymerization is most commonly used in a method for producing a polymer dispersed liquid crystal display panel. In this phase separation method, a polymer-dispersed liquid crystal precursor pair mixture (a mixture of liquid crystal and a monomer, an oligomer, and a polymerization initiator, hereinafter referred to as a premixture) is used in an empty panel that is a liquid crystal display panel.
Is injected, and active energy such as light or heat is applied to cause phase separation in the mixture to produce a polymer dispersion type liquid crystal display panel. At this time, the mixture may be applied on the substrate to have a uniform thickness, and the other substrate may be superposed on the substrate and then activated energy may be applied to produce the layer.

The scattering property and contrast of the polymer dispersion type liquid crystal display panel are determined by the dispersibility of the liquid crystal and the resin. When the dispersibility is uniform and dense, a strong scattering property can be obtained. In addition, the dispersibility depends on the phase separation process between the liquid crystal and the resin when the liquid crystal panel is manufactured. At the substrate interface, the premixture is in contact with a foreign substance, which is the substrate surface. For this reason, the phase separation process is different between the central portion in the thickness direction of the panel and the substrate interface. Since the dispersibility is non-uniform at the substrate interface, the portion that contributes to scattering is reduced, and the scattering property of the panel is reduced.

[0012]

Therefore, even if a polymer-dispersed liquid crystal display panel is manufactured by an ordinary method, a strong scattering property cannot be obtained, and a sufficient contrast ratio cannot be achieved. An object of the present invention is to provide a polymer-dispersed liquid crystal display panel having a strong scattering property and a high contrast.

[0013]

A polymer-dispersed type in which a premixture is sandwiched between a pair of substrates having electrodes and at least one of which is transparent, and active energy is applied to cause the polymer and liquid crystal to phase-separate. In the method of manufacturing a liquid crystal display panel, the present invention is characterized in that a layer made of a polymerizable substance is provided on the surface of the substrate.

The layer provided on the surface of the substrate may be a substance having a polymerizing property, but a substance having an affinity for both the liquid crystal and the resin is desirable for the purpose of uniformly forming a phase-separated structure. . When the polymerizable substance is polyfunctional, a cross-linking structure is formed during polymerization and the phase-separated structure becomes stronger. Therefore, the polymerizable substance is more preferable than the monofunctional substance.

Since (meth) acrylate is generally used as the polymer of the polymer dispersed liquid crystal, it is desirable that the layer provided on the substrate is also (meth) acrylate. The polymerizable substance does not necessarily have to be a resin and may be, for example, a coupling agent or a surfactant.

When a polymer-dispersed liquid crystal is prepared by providing a layer of a substance having polymerizability on the surface of a substrate, a polymerization reaction also takes place between this layer and the polymer-dispersed liquid crystal polymer. Bonding occurs between. As a result, even in the vicinity of the substrate interface, a uniform phase-separated structure that is the same as that in the central portion in the depth direction can be obtained, so that the entire panel can contribute to scattering, and as a result, the scattering property and contrast are improved.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] FIGS. 1A to 1C are explanatory views of a manufacturing process of a polymer dispersion type liquid crystal display panel of a first embodiment.
(A)-(C) has shown each process. In this figure, 1 is a transparent substrate, 2 is a transparent electrode, 3 is a bifunctional acrylate thin film, 4 is a premixture, and 5 is a polymer dispersed liquid crystal.

First Step (See FIG. 1A) A transparent substrate (OA2) on which a transparent electrode 2 made of ITO is formed.
Substrate Nippon Electric Glass Co., Ltd.) 1 was spin-coated with an ethanol solution of a bifunctional acrylate monomer (SR-633 manufactured by Nippon Kayaku Co., Ltd.) and dried at 80 ° C. to prepare a bifunctional acrylate thin film (film thickness 500Å) 3 Was formed.

Second step (see FIG. 1B) Spacer (SP20100 manufactured by Sekisui Fine Chemical Co., Ltd.) on the transparent substrate 1 provided with the bifunctional acrylate thin film 3.
(Not shown), and the transparent substrate 1 and the other transparent substrate 1 provided with the similar thin film 3 are arranged so that the thin films 3 and 3 face each other with a gap of 10 μm, and the periphery thereof is An empty panel was formed by sealing with a thermosetting seal. Then, into this empty panel, a premixture 4 in which a liquid crystal (TL205 manufactured by Merck) and a photocurable resin (PN393 manufactured by Merck) are mixed at a weight ratio of 4: 1 is injected.

Third step (see FIG. 1C) After injecting the premixture 4, ultraviolet rays are irradiated for 3 minutes at 20 ° C. to form a polymer dispersed liquid crystal 5.

[First Comparative Example] Spacers are scattered on a transparent electrode formed on a transparent substrate, and this transparent substrate and another transparent substrate having the same transparent electrode are used as transparent electrodes.
They are arranged facing each other with a gap of μm, and the periphery thereof is sealed with a thermosetting seal to form an empty panel. In this empty panel, a pre-composition having the same composition as that used in the first embodiment is formed. Injected the mixture. That is, a polymer dispersed liquid crystal panel was formed by the same process as in the first embodiment except that the bifunctional acrylate thin film was not provided on the transparent substrate.

[Second Embodiment] On a transparent substrate (OA2 substrate manufactured by Nippon Electric Glass) on which a transparent electrode made of ITO is formed, a trifunctional acrylate monomer (SR-3 is used).
68 Nippon Kayaku Co., Ltd.) was spin-coated in the same manner as in the first embodiment, and dried at 80 ° C. to form a trifunctional acrylate thin film (film thickness 500 Å).

Spacers are scattered on a transparent substrate having a transparent electrode provided with a trifunctional acrylate thin film, and this transparent substrate and another transparent substrate having a similar thin film and transparent electrode are separated by a gap of 10 μm. And place them facing each other,
The periphery was sealed with a thermosetting seal to form an empty panel.

Then, in the empty panel, the liquid crystal (TL2
05 Merck) and a photo-curable resin (photo-curable resin A manufactured by Nippon Kayaku) consisting of an epoxy acrylate were mixed in a weight ratio of 7: 3, and a thermal polymerization initiator (Cadox B-CH50 Kayaku) was further mixed. AKZO) was mixed with the resin at 1%, and the premixture was adjusted and injected. After injecting the premixture, it is left in an oven at 90 ° C. for 1 hour to form a polymer dispersed liquid crystal.

Second Comparative Example A polymer-dispersed type was prepared by the same steps as those of the second embodiment except that a trifunctional acrylate thin film (SR-368 manufactured by Nippon Kayaku Co., Ltd.) was not provided on the transparent substrate. A liquid crystal panel was formed.

FIG. 2 is an explanatory view of the measurement results of the scattering property and the contrast of the present invention and the comparative example. According to this figure, the first
When the polymer dispersion type liquid crystal cell according to the embodiment and the polymer dispersion type liquid crystal cell according to the first comparative example are compared in scattering property and contrast, the polymer dispersion type liquid crystal cell according to the first embodiment is superior. You can see that Also, the second
When the polymer dispersion type liquid crystal cell according to the second embodiment and the polymer dispersion type liquid crystal cell according to the second comparative example are compared in scattering property and contrast, the polymer dispersion type liquid crystal cell according to the second embodiment is superior. You can see that

[0027]

As described above, according to the present invention, a uniform phase-separated structure can be obtained over the entire panel, so that the scattering property and the contrast are improved, and the polymer-dispersed liquid crystal display panel is manufactured. It greatly contributes to the improvement of performance.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a manufacturing process of a polymer-dispersed liquid crystal display panel according to a first embodiment, in which (A) to (C) show each process.

FIG. 2 is an explanatory diagram of measurement results of scattering property and contrast of the present invention and a comparative example.

3A and 3B are explanatory diagrams of a basic configuration of a polymer-dispersed liquid crystal display panel, in which FIG. 3A shows a state in which no voltage is applied and FIG. 3B shows a state in which a voltage is applied.

FIG. 4 is a conceptual diagram of an evaluation system for measuring the relationship between applied voltage and transmittance in a polymer dispersion type liquid crystal display panel.

FIG. 5 is a curve of transmittance versus applied voltage of a polymer-dispersed liquid crystal display panel.

[Explanation of symbols]

 1 Transparent Substrate 2 Transparent Electrode 3 Bifunctional Acrylate Thin Film 4 Premixture 5 Polymer Dispersed Liquid Crystal 11, 12 Substrate 13 Polymeric Material 14 Liquid Crystal Molecule 15 Power Supply 16 Incident Light 17 Scattered Light 18 Transmitted Light 21 Light Source 22 Liquid Crystal Panel 23, 24 Transparent Substrate 25, 26 Transparent Electrode 27 Polymer Dispersed Liquid Crystal Layer 28 Variable Voltage Power Supply 29 Detector

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kimiaki Nakamura 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa, Fujitsu Limited (72) Inventor Hideaki Tsuda 1015 Kamedota, Nakahara-ku, Kawasaki, Kanagawa

Claims (6)

[Claims] 1. A polymer-dispersed liquid crystal display panel comprising a pair of substrates having electrodes, at least one of which is transparent, wherein a layer made of a polymerizable substance is provided on the surface of the substrates, and the layer has the layer. A polymer-dispersed liquid crystal display panel, characterized in that a polymer-dispersed liquid crystal precursor mixture is sandwiched between a pair of substrates and then activated energy is applied to form a polymer-dispersed liquid crystal display panel. 2. A method for producing a polymer dispersion type liquid crystal display panel comprising a pair of substrates having electrodes, at least one of which is transparent, wherein a layer made of a polymerizable substance is provided on the surface of the substrates. A polymer-dispersed liquid crystal display panel, characterized in that a polymer-dispersed liquid crystal display panel is formed by sandwiching a polymer-dispersed liquid crystal precursor mixture between a pair of substrates having the layer and applying activation energy. Production method. 3. The method for producing a polymer dispersed liquid crystal display panel according to claim 2, wherein a polyfunctional substance is used as the polymerizable substance. 4. The method for producing a polymer dispersed liquid crystal display panel according to claim 3, wherein (meth) acrylate is used as the polymerizable resin. 5. An ultraviolet ray is used as active energy, as claimed in any one of claims 5 to 4.
Item 8. A method for producing a polymer-dispersed liquid crystal display panel according to item. 6. The method for producing a polymer dispersion type liquid crystal display panel according to claim 2, wherein heat is used as the active energy.