JPH0212192A - Projection type liquid crystal display device - Google Patents

Abstract

PURPOSE:To make a sharp display by incorporating a correcting filter which cuts light having wavelength of >=55nm in an optical system for B and cutting excessive light which is not necessary for the optical system for B. CONSTITUTION:Tricolor light of R, G, and B is transmitted through three TN type liquid crystal panels 4, whose images are formed on the same screen 7 through an optical system. In this projection type liquid crystal display device, the color correcting filter 3 which cuts the light having >=550nm wavelength is built in the optical system for B. Namely, an existent light source, a dichroic mirror, a color filter, etc., are used as they are and the color correcting filter 3 which cuts the light having >=550nm wavelength is built in the B optical system to cuts excessive light which is not required for the B optical system, thereby eliminating leak light of black level. Consequently, the contrast is improved and a sharp image is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a projection type liquid crystal display device for full color display.

Conventional technology LCD display devices include LCD TVs, electronic desktop calculators, clocks, and time meters, and most of them are TN.
It is a type liquid crystal display device. Currently, there is a desire to develop a projection type liquid crystal television using a TN type liquid crystal panel and aiming at a larger screen.

In the case of a projection type liquid crystal television, in order to obtain sufficient brightness on the screen, a strong light beam is incident from behind the liquid crystal panel. In order to perform full-color display, a light source is required that has optimal spectral characteristics for each of the R, G, and B color lights and has a large amount of light.

However, in reality, the amount of light for R and 0% B is large,
Moreover, no light source with optimal spectral characteristics has been found. Therefore, a light source with a large amount of light that has spectral characteristics in the entire visible light range is used, divided into each wavelength range using a dichroic mirror color filter or the like.

In the case of a projection type liquid crystal display device, a TN type liquid crystal panel is used depending on the R, G, and B color incident light from a dichroic mirror, color filter, etc. In the case of a TN type liquid crystal panel, its light transmittance is known to be expressed by the following formula by Gooch and Tully (J, Phys-, 08, 15
75 (1975)).

T: (1+u2)-' ・5in2[(rt/2
) ・ (1+u2)”2] Here, U is mouth = 2
It is defined as Δnd/λ, where T is the light transmittance of the 90 degree TN panel, Δn is the refractive index anisotropy of the liquid crystal material, d is the thickness of the liquid crystal layer, and λ is the wavelength of the transmitted light. That is, the light transmittance T of the TN type liquid crystal display device depends on the value of Δnd once the wavelength of the incident light is determined.

For example, if a liquid crystal material with Δn=0.090 is used as the liquid crystal material, and G with spectral characteristics of center wavelength λ=545 nm
When using a conventional light source, the value of light transmittance T becomes the minimum when d = 5.271 m (in the case of normally black mode, the size of T at this time determines the black level), and the contrast (ratio of maximum transmittance to minimum transmittance) becomes maximum.

Problems to be Solved by the Invention However, even if a TN liquid crystal panel is designed to have a panel with an optimal liquid crystal layer thickness for each color of R, G, and B, the TN liquid crystal panel for B is It is not possible to obtain a large contrast compared to a TN liquid crystal panel. The cause of this is ■ Changes in refractive index anisotropy △n and wavelength dispersion (especially at 550
It changes significantly in the wavelength range of nm or less. ), (2) Optimization of the wavelength distribution of the B light source, dichroic mirror, color filter, etc., and (2) leakage of light from the polarizing element.

Even if the wavelength dispersion of the refractive index anisotropy Δn of the liquid crystal material is reduced, there is a limit. In addition, since there is no light source with a large amount of light that has spectral characteristics in a narrow specific wavelength range for B, and the wavelength range for B of the dichroic mirror color filter is broad, the TN liquid crystal panel for B has sufficient contrast. I can't get it.

An object of the present invention is to provide a projection type liquid crystal display device that solves the problems of conventional liquid crystal display devices.

Means for Solving the Problems The present invention provides an optical system that transmits three color lights of R, G, and B through three TN type liquid crystal panels and forms images of the TN type liquid crystal panels on the same screen. The above object is achieved by incorporating a color correction filter that cuts light having a wavelength of 550 nm or more into a daily use optical system in a projection type liquid crystal display device having the present invention.

Function The present invention uses existing light sources, dichroic mirrors, color filters, etc. as they are, and uses 550 nm in everyday optical systems.
It incorporates a color correction filter that cuts out light with wavelengths longer than m, cuts out unnecessary light for daily use optical systems, eliminates light leakage at black level, and improves contrast.

EXAMPLES The present invention will be explained below using drawings showing examples thereof.

In the first place, a light source that has spectral characteristics in a narrow wavelength range of 450 to 480 nm and has a large amount of light may be used as a daily light source. However, there is no optimal light source, and the present invention uses a currently commercially available light source and color correction filter, and uses the color correction filter to cut out light having a wavelength that causes a decrease in contrast. Further, if all light in the wavelength range other than 450 to 480 nm is cut, the contrast will be improved, but sufficient brightness will not be obtained. Suppresses the decrease in brightness,
In order to improve the contrast, light in the wavelength range of 450 ron or less or light with high visibility in the wavelength range of 480 nm or more is cut. Among them, in order to cut the least amount of light and obtain an efficient effect, it is desirable to cut light having a wavelength of at least 550 nm or more.

Therefore, in the present invention, a currently commercially available halogen lamp or metal halide lamp is used as a light source, and a blue filter, a short wavelength transparent deposited film, or the like is used as a color correction filter that cuts light having a wavelength of at least 550 nm or more. The same effect can be obtained whether the color correction filter is installed on either the incident light side or the output light side of the liquid crystal panel.

Next, the present invention will be briefly and specifically explained.

Example 1 In a liquid crystal display device as shown in FIG. 1, light from a daily light source having spectral characteristics as shown in FIG. 2(a) was irradiated from a metal halide lamp used for light fitting and a dichroic mirror 2. do. Chisso Petrochemical (
IA RIXON (LIXON)-9150 (460r
w, Δn==0.089), a panel was created as follows.

Spin-code polyimide resin PIX-5400 manufactured by Hitachi Chemical on a glass substrate having an ITO electrode on the surface,
It was cured at 250°C for 1 hour. The dry film thickness at this time was 100OA. After the rubbing treatment, the two substrates thus obtained were pasted together via 4.4 μm spacer beads to form a TN-type panel (A) with a twist angle of 90 degrees.
It was created.

A liquid crystal material L I

The light from the B lunar light source having the spectral characteristics shown in Fig. 2(a) is input to the liquid crystal panel 4. This was installed on the incident light side of the liquid crystal panel 4. The emitted light was projected onto the screen 7 using the projection lens 6, and the voltage-light transmittance characteristics on the screen 7 were measured according to a conventional method. From this, the contrast (ratio of maximum transmittance to minimum transmittance) was determined, and the results are shown in Table 1.

Further, the color correction filter 3 was installed on the output light side of the liquid crystal panel 4, and the contrast was determined in the same manner and is shown in Table 1.

＼゛As a comparative example, the contrast in the case where no color correction filter was used was also determined and shown in Table 1.

Table 1 From Table 1, the projection type liquid crystal display device using the color correction filter of the present invention obtained a greater contrast than the comparative example that did not use the color correction filter. As is clear from this, the projection type liquid crystal display device of the present invention can obtain a large contrast by cutting out light having a wavelength of 550 nm or more, and is highly practical. Further, the same effect can be obtained even if the color correction filter is installed either before or after the liquid crystal panel.

Example 2 In a liquid crystal display device as shown in FIG. 1, a metal halide lamp used as a light source 1 and a dichroic mirror 2
From there, light from a B lunar light source having spectral characteristics as shown in FIG. 3(a) is irradiated. MT-5014CB (450 nm, Δn=0, manufactured by Chisso Petrochemical Co., Ltd.) was used as the liquid crystal material.
．． 092), a panel was created as follows.

Polyimide resin PIX-1400 manufactured by Hitachi Chemical was spin-coded onto a glass substrate having an ITO electrode on the surface, and
It was cured for 1 hour at 0°C. The dry film thickness at this time was 80
It was 0A. After the rubbing treatment, the two substrates thus obtained were laminated together via 4.2 μm spacer beads to create a TNN type panel B) with a twist angle of 88 degrees. A liquid crystal material MT-5014CB was sealed in the panel, and a polarizing plate 5 was attached to the liquid crystal panel 4 so as to be in normally black mode.

Light was incident on the liquid crystal panel 4 from a B lunar light source having the spectral characteristics shown in FIG. 3(a). A blue filter B-390 manufactured by Hoya Glass Co., Ltd. (having the transmission characteristics shown in FIG. 3(b)) was used as the color correction filter 3, and was placed on the incident light side of the liquid crystal panel 4. The emitted light is projected onto the screen 7 using the projection lens 6, and the voltage on the screen 7 is -
The light transmittance characteristics were measured. From this, the contrast (ratio of maximum transmittance to minimum transmittance) was determined, and the results are shown in Table 2.

As a comparative example, the contrast without using a color correction filter was similarly determined and shown in Table 2.

(The following is a blank space) Table 2 As is clear from Table 2, the projection type liquid crystal display device using the color correction filter of the present invention obtained a greater contrast than the comparative example that did not use the color correction filter. As can be seen from this, the projection type liquid crystal display device of the present invention has 55
By cutting off wavelength light of 0 nm or more, a large contrast can be obtained, and its practicality is high.

Effects of the Invention The projection type liquid crystal display device of the present invention incorporates a color correction filter that cuts light having a wavelength of 550 or more in the B optical system, thereby cutting unnecessary unnecessary light from the B optical system. Also, it should be possible to eliminate light leakage at the black level, improve contrast, and obtain a clear display.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of a liquid crystal display device according to an embodiment of the present invention, FIG. b) is a graph showing the transmittance of the color correction filter of the same device;
3(a) is a graph showing the emission distribution characteristics of the light source used in Example 2 of the same device, and FIG. 3(b) is a graph showing the transmittance of the color correction filter of the same device. l...Light source, 2...Dichroic mirror 3
... Color correction filter, 4 ... TN type liquid crystal panel, 5 ... Polarizing element, 6 ... Projection lens, 7 ...
··screen. Name of agent Patent attorney Toshio Nakao Figure 2 (a) (b) Wavelength (nm)

Claims (1)

[Claims] In a projection type liquid crystal display device that uses three TN type liquid crystal panels as light pulp for each color of R, G, and B light, the B optical system is equipped with a color correction filter that cuts light with a wavelength of 550 nm or more. A projection type liquid crystal display device characterized by a built-in