JPH06222331A - Projection type liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide projected images which obviates the light leakage from space parts and has a high contrast by forming the spacers for regulating the inter-electrode spacings of a liquid crystal display element as non-light transmissive spacers. CONSTITUTION:A liquid crystal material 9 and a transparent solid material 8 exist dispersedly between transparent glass substrates 1 and 2 having transparent electrodes 3, 4 via spacers having non-light transmissivity. A driving circuit 10 is connected to these transparent electrodes 3, 4. The refractive index of the transparent solid material 8 and the refractive index of the liquid crystal material 9 coincide and collimated beams of light pass these materials to attain a transparent state when the refractive index of the transparent solid material 8 and the ordinary ray refractive index of the liquid crystal material are made to coincide. A difference arises between the refractive index of the transparent solid material 8 and the refractive index of the liquid crystal material 9 and the collimated beams of light are scattered to attain a turbid state when a voltage is not applied. The collimated beams of light arriving at the spacers 7 at this time are shut off or scattered by the spacers 7 and are not displayed as luminescent point on a projection screen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to improve the contrast of a projection type liquid crystal display device by using a transmission-scattering type liquid crystal display element having a non-transparent spacer.

[0002]

2. Description of the Related Art Conventionally, in a projection type liquid crystal display device, a liquid crystal layer is sandwiched between two glass substrates with transparent electrodes, and polarizing plates are arranged on both outer sides of the glass substrates.
The N (twisted nematic) method has been mainly used.

However, since such a liquid crystal display device has a polarizing plate, the brightness of the device is not sufficient.
It had the drawback of reducing the transmittance by about 40%.
Further, in order to obtain sufficient brightness on the projection screen, an extremely strong light source is required, and there are drawbacks such as deterioration of the life of the liquid crystal display element due to heat generation of the light source and change of characteristics.

For such a TN type liquid crystal display element, there has been proposed a method which does not require a polarizing plate and electrically controls the apparent birefringence of the liquid crystal to create a cloudy state or a transparent state.

In the first type of this system, the ordinary refractive index of liquid crystal molecules and the refractive index of the transparent solid substance are matched,
It utilizes the fact that when a voltage is applied and the alignment of the liquid crystal molecules is aligned, the liquid crystal molecules become transparent, and when no voltage is applied, the liquid crystal molecules become disordered and the liquid crystal molecules become clouded and opaque.

A typical example of this method is a method called nematic curve linear aligned face (NCAP), which is a method of dispersing capsule type liquid crystal microdroplets in a polymer. In this method, since the capsule type liquid crystal microdroplets are completely and independently encapsulated in the polymer, they do not flow and can be formed into a film, and the durability is relatively stable. It is easy (described in Japanese Patent Publication No. 58-501631).

The second type is called a polymer network liquid crystal (PNLC) or a polymer disperse liquid crystal (PDLC), which dissolves an uncured resin such as an acrylic or epoxy UV curable resin and a liquid crystal material. The liquid crystal and the resin are phase-separated by irradiating the cured product with ultraviolet rays or heating and curing it (Japanese Patent Laid-Open No. 1198725/1989).

The structure of a conventional transmission-scattering type liquid crystal display element used as a light valve of a projection type liquid crystal display device is shown in FIG. In FIG. 2, thin film transistors and the like are omitted.

The light emitted from the light source which is collimated by the condenser lens is usually split into red (R), green (G) and blue (B) by a dichroic mirror, and is incident on three liquid crystal panels. In a liquid crystal panel, a liquid crystal material 9 and a transparent solid substance (resin, etc.) 8 are dispersed through a spacer 11 between transparent glass substrates 1 and 2 having transparent electrodes 3 and 4, and a liquid crystal layer Sealing materials 5 and 6 are provided in order to shield the external environment from the outside. Further, the drive circuit 10 is the transparent electrode.
Connected to 3, 4.

In FIG. 2, when the refractive index of the transparent solid substance 8 and the ordinary refractive index of the liquid crystal material 9 are matched, liquid crystal molecules are aligned in an electric field when a voltage is applied, so that the transparent solid substance The refractive index and the refractive index of the liquid crystal material match each other, and light passes therethrough to become a transparent state.

On the other hand, when no voltage is applied, since the liquid crystal molecules are arranged along the inner wall surface of the transparent solid substance 8, there is a difference in refractive index between the refractive index of the transparent solid substance and the refractive index of the liquid crystal material. It will occur and will be clouded and scattered.

The diameter of the spacer used is generally in the range of 10 μm to 20 μm in view of the scattering property of visible light and the driving voltage.

[0013]

In the transmission-scattering type liquid crystal display element, the transparent state and the white turbid state are created by the electric field as described above to perform ON-OFF and obtain the contrast. The light should be completely scattered and the brightness on the projection screen should be minimal. However, with conventional spacers, it is impossible to scatter or shield parallel light, so the light leaked from the spacer part forms an image on the projection screen, and this is visually recognized as a bright spot, resulting in a significant decrease in contrast. , The image quality will be degraded.

The present invention is intended to solve the problems of these prior arts, and it is an object of the present invention to obtain a projected image with high contrast without light leakage from the spacer portion.

[0015]

In the projection type liquid crystal display device according to the present invention, the spacer of the liquid crystal display element is made to be light non-transmissive.

This spacer is achieved by using black polymer beads manufactured by Sekisui Fine Chemical Co., Ltd.

[0017]

According to the above-mentioned structure of the present invention, since the spacer is made impermeable to light, it is possible to prevent deterioration of display quality due to deterioration of contrast of the projection type liquid crystal display device due to light leakage from the spacer portion. be able to.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. It should be noted that the following FIG. 1 is only shown schematically for easy understanding of the present invention.
Thin film transistors and the like are omitted.

FIG. 1 is a sectional view of a liquid crystal display panel according to the present invention. Between the transparent glass substrates 1 and 2 having the transparent electrodes 3 and 4, a liquid crystal material 9 and a transparent solid substance 8 are dispersedly present via a spacer 7 having a light non-transmissive property,
Sealing materials 5 and 6 are provided to shield the liquid crystal layer from the outside world. Further, the drive circuit 10 is connected to the transparent electrodes 3 and 4.

In FIG. 1, when the refractive index of the transparent solid substance 8 and the ordinary refractive index of the liquid crystal material 9 are matched, liquid crystal molecules are aligned in an electric field when a voltage is applied, so that the transparent solid substance The refractive index and the refractive index of the liquid crystal material are the same, and parallel light passes through and becomes transparent.

On the other hand, when no voltage is applied, since the liquid crystal molecules are arranged along the inner wall surface of the transparent solid substance 8, there is a difference in refractive index between the refractive index of the transparent solid substance and the refractive index of the liquid crystal material. It occurs and collimated light is scattered.

Next, the parallel light that reaches the above-mentioned spacer 7 is different from the case where a normal spacer such as a commercially available glass fiber is used. It is scattered and does not appear as a bright spot on the projection screen.

FIG. 3 shows the scattering characteristics of the projection type liquid crystal display device according to the present invention. As compared with the conventional scattering characteristic of FIG. 4, it can be seen that there is no light leakage near the light receiving angle of 0 degree.

The liquid crystal display elements used in the measurement of FIGS. 3 and 4 were 2-ethylhexyl acrylate (manufactured by Nacalai Tesque Co., Ltd.) 7.0 wt% as a monomer, and Biscoat # 3700 (Osaka Organic Chemical Industry Co., Ltd.) as an oligomer. )
Made of 11.6 wt% and Darocure 651 (made by Merck) 0.4 wt% as a photo-curing initiator, and a photopolymerizable material having a viscosity of 3 centipoise, and ZLI4792 (NI point 92 degrees, n _e =
1.573, n _o = 1.479) (manufactured by Merck Japan Co., Ltd.) 81.0
wt% composition, UV light (57mW / cm at 60 ℃)
² ) was irradiated for 5 seconds and manufactured.

The cross-sectional structure of the device thus manufactured was observed by a scanning electron microscope (SEM), and it was found that the liquid droplets were 1.5
It was around μm.

In this embodiment, the black polymer beads are used as the light non-transmissive spacer. However, since it is enough to prevent the parallel light irradiated on the spacer portion from leaking to the projection screen as it is, the spacer having the light scattering property is used. Even if it is one, it can exert the same function.

[0027]

Since the projection type liquid crystal display device using the transmission-scattering type liquid crystal display element according to the present invention is constructed by using the non-transparent spacer, the contrast can be improved. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a transmission-scattering type liquid crystal display device for projection showing an embodiment of the present invention.

FIG. 2 is a sectional view of a conventional transmission-scattering type liquid crystal display device for projection.

FIG. 3 is a light scattering characteristic diagram of a transmission-scattering type liquid crystal display device for projection according to an embodiment of the present invention.

FIG. 4 is a light scattering characteristic diagram of a transmission-scattering type liquid crystal display device for projection of a conventional example.

[Explanation of symbols]

 1, 2 Transparent substrate 3, 4 Transparent electrode 5, 6 Sealing material 7 Optical non-transparent spacer material 8 Transparent solid substance (resin) 9 Liquid crystal material 10 Drive circuit 11 Spacer material

Claims (2)

[Claims] 1. A liquid crystal material having two electrode substrates, at least one of which is transparent, and a liquid crystal layer sandwiched therebetween, the liquid crystal layer having a positive dielectric anisotropy, and a transparent solid. A projection type liquid crystal display device having a transparent-scattering type liquid crystal display device made of a substance, characterized in that a spacer for regulating an electrode interval of the liquid crystal display device is impermeable to light. 2. The projection type liquid crystal display device according to claim 1, wherein the liquid crystal display element is an active matrix liquid crystal display element.