JPH0922008A - Liquid crystal projection type display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a display which is less deteriorated in performance by rays and heat even if a strong light source is used by arranging dye-based polarizing plates having specific properties on both sides of a light source side and screen side of liquid crystals. SOLUTION: The light emitted from a high-luminance light source 1, such as metal halide lamp, passes an optical system 3 for executing color sepn. of the light to red, green and blue and images are formed in three sets of liquid crystal image forming parts composed of two sheets of polarizing plates 5, 7 and liquid crystal cells 6. The three sets of the images are integrated by a color synthesis system 8 and are further magnified by a projecting lens 9. These images are displayed on a screen 10. In such a case, the dye-based polarizing plates having single transmittance of >=36% and an average polarization rate of >=99.0% are used as the polarizing plates 5, 7 on both sides of the light source side and screen side of the single or plural liquid crystal image forming parts to be used. As a result, the high-reliability display which is not degraded in contrast in spite of long-term irradiation with a strong light source is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal emission type display. More specifically, the present invention relates to a highly reliable liquid crystal projection display having excellent light resistance and heat resistance.

[0002]

2. Description of the Related Art In the field of projection television, which has been constructed exclusively by a CRT (cathode ray tube) system, a system using a liquid crystal projection display has recently been developed due to the development of high-density pixel format technology for liquid crystal displays. It has come to be adopted.

In the case of a liquid crystal projection display, since a polarizing plate and a color filter are used in the liquid crystal image forming section, light is largely absorbed by them, and an image with a small area of 1 to 6 inches is produced. 10 inches to 100
It is inevitable to reduce the brightness by enlarging it to a few inches, so that a light source with high brightness is used. On the other hand, there is a strong demand for further improvement in the brightness of the current production televisions, and as a result, the intensity of the light source used is becoming stronger and stronger.

By the way, a polarizing plate generally used in a liquid crystal image forming portion of a liquid crystal projection type display is an iodine type polarizing plate. However, since this type of polarizing plate uses iodine as a polarizer, it has light resistance and heat resistance. However, the moisture and heat resistance is not sufficient, and various problems occur in actual use.

That is, in addition to the chemical decomposition of the polarizer by intense light, the absorbed light energy is converted into heat energy, which raises the temperature of the polarizing plate, and the heat also deteriorates the polarizer. As a result, the polarization rate of the polarizing plate is lowered, the contrast due to the ON-OFF of the voltage of the liquid crystal display is lowered, or the hue of the polarizing plate is changed from neutral gray to brown or red, and In many cases, the clear hue of the liquid crystal display is impaired.

FIG. 1 shows the basic structure of a general liquid crystal projection type display, and Tables 1 and 2 show the transmittance or reflectance when light is transmitted through or reflected by each element. That is, in FIG. 1, light emitted from a high-intensity light source such as a metal halide lamp is passed through an optical system that performs color separation into red, green, and blue, and three sets each including two polarizing plates and a liquid crystal cell are provided. An image is formed by the liquid crystal image forming section of the above, and the three sets of images are integrated by a color synthesizing system, further enlarged by a projection lens, and an image is displayed on the screen.

[0007]

[Table 1]

[0008]

[Table 2]

Among the optical systems, the optical element having a large loss due to absorption of light is the incident (light source) side polarizing plate and the liquid crystal cell.
It is a point. That is, 60% of the high-energy light that has entered the incident-side polarization plate is absorbed by the polarizer of the polarization plate and not only induces the photochemical decomposition reaction of the polarizer, but is also converted into heat energy to increase the temperature. Therefore, the decomposition of the polarizer is also promoted by the high temperature and the thermal action.

Since most light is absorbed by the incident side polarizing plate and the liquid crystal cell, the emitting side (screen side) polarizing plate receives less light than the incident side polarizing plate, and is not deteriorated by light energy and heat energy. Relatively few. In this way, the polarizing plate used for the liquid crystal projection display is on the incident side,
A polarizing plate provided on either side of the exit side is required to have excellent light resistance and heat resistance, but at least for the polarizing plate on the entrance side, improvement of these durability is an essential requirement.

On the other hand, in addition to the necessity of improving the durability,
The characteristics required in the liquid crystal projection type display are brightness and contrast, and thus it is necessary for the polarizing plate to have a high transmittance and a high transmittance.

[0012]

There is a demand for the development of a liquid crystal projection display in which the performance is less deteriorated by light and heat even when a strong light source is used.

[0013]

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that one or a plurality of liquid crystal image forming units used in a liquid crystal projection display have a light source side and a screen side. As a polarizing plate on both sides, single transmittance 3
It was found that the above-mentioned problems can be solved by employing a dye-based polarizing plate having an average polarization rate of 99.0% or more and 6% or more, and the present invention has been completed.

That is, according to the present invention, in a liquid crystal projection type display including one or a plurality of liquid crystal image forming portions, the single transmittance is 36% or more and the average polarization ratio is 99.0 on both the light source side and the screen side of the liquid crystal. A liquid crystal projection type display comprising a dye-based polarizing plate in an amount of at least 50% is provided.

The present invention will be described in detail. In the present invention, the single transmittance is 36% or more and the average polarization rate is 99.0%.
The dye-based polarizing plate (dye-based high-contrast polarizing plate) described above is manufactured, for example, as follows. After immersing the polyvinyl alcohol film in a dye bath containing a blended composition of yellow, red, blue, and green dyes having a particularly high dichroism at the maximum absorption wavelength, uniaxially 4 to 4 in an aqueous solution containing boric acid. A polarizing film is obtained by uniaxially stretching 5 times the free width, washing with water and drying. Although it has a polarizing function only with a polarizing film, it supports triacetyl cellulose, etc. containing an ultraviolet absorber in order to impart sufficiently high durability to intense light irradiation, high temperature or high temperature and high humidity severe environmental conditions. It is preferred that the films are laminated and adhered from both sides to form a polarizing plate.

Examples of dye-based polarizing plates (dye-based high-contrast polarizing plates) having a single transmittance of 36% or more and an average polarization of 99.0% or more are SG-9 and KPL-T.
-13U, KPL-T-14U, SG-9-38 (all manufactured by Kaya Polar Co., Ltd.), etc.
The optical characteristics and durability of the examples are shown in Table 3 in comparison with a commercially available iodine-based high-contrast polarizing plate A and a commercially available conventional dye-based polarizing plate B.

[0017]

[Table 3] * 1 Durability test (1) Irradiation at 63 ° C carbon arc for 1000 hours (2) Dry heat at 100 ° C for 1000 hours

Here, X, Y, and Z represent the single element, the parallel position, and the orthogonal position transmittance of the visual sensation correction with the C light source, respectively, and ρ is

[0019]

[Equation 1] (P) and (C) represent the hue changes in the parallel position and the orthogonal position, respectively.

Since the conventional dye-based polarizing plate has a low polarization rate and a low transmittance, it cannot be used in a liquid crystal projection display at all. However, the dye-based polarizing plate and the high-contrast polarizing plate have high transmittances. The realization of polarization characteristics has made it a level that can be used in the display field.

The optical performance of the polarizing plate usable for the liquid crystal projection display of the present invention is that the single transmittance has a brightness of 36% or more and the average polarization of 99.0% or more. Is required, the display screen becomes dark when the unit polarization rate is lower than 36%, and the image contrast is deteriorated when the average polarization rate is lower than 99.0%. Preferably, the single transmittance is 38% or more and the average polarization rate is 99.9%.
The above performance is required, and more preferably, the single transmittance is 39% or more and the average polarization rate is 99.96% or more.

[0022]

【Example】

Reference Example 1 A dye-based high-contrast polarizing plate SG-9-38 manufactured by Kaya Polar Co., Ltd. and a commercially available iodine-based high-contrast polarizing plate A (the performance and durability of which are shown in Table 3) are attached to each other to form a test piece. Created. The optical characteristics of this product are shown in Table 4. (Column A) The incident side (light source side) of this test piece is a dye-based high-contrast polarizing plate (SG-9-
38), and a super light resistance test (condition: carbon arc,
Discharge voltage, 2160W, distance from discharge point 140mm,
The surface temperature of the test piece was 95 ° C., and the test piece was exposed for 100 hours. Table 5 shows the results. (Column B)

The transmittance and polarization characteristics are comparable to those when two iodine type polarizing plates are used (Comparative Example 1 described later), and the average polarization rate is lowered and the hue is changed even in the super light resistance test. There was almost no performance deterioration such as.

SG-9 is provided on the light source side (incident side) of the liquid crystal cell.
Three liquid crystal panels for R, G, and B in which -38 was attached with an iodine-based high-contrast polarizing plate on the screen side (outgoing side) were prepared to form a liquid crystal projection display. Although a 250 W metal halide lamp was used as a light source for a long period of time, it was confirmed that the liquid crystal projection display was a highly reliable liquid crystal display with little change in brightness and reduction in contrast.

Example 2 As a polarizing plate, a dye-based high contrast polarizing plate SG-9-
Measurement of optical properties and super light resistance test were carried out in the same manner as in Reference Example 1 when 38 two sheets were combined, and the results are shown in Tables 4 and 5. The brightness and contrast were slightly inferior to the case where two iodine-based high-contrast polarizing plates were used, but in the super-lightfastness test, there was almost no decrease in polarization rate and no change in hue. In addition, the liquid crystal projection display composed of a liquid crystal panel in which the polarizing plate is attached to both sides of a liquid crystal cell showed high reliability even when irradiated by a strong metal highland lamp for a long time.

Comparative Example 1 Measurement of optical characteristics and super lightfastness test when two iodine-based high-contrast polarizing plates A were combined as a polarizing plate were carried out by the same method as in Reference Example 1, and the results are shown in Table 4. , As shown in Table 5. Although the optical characteristics are excellent, the incident-side polarizing plate after the ultralightfastness test was partially browned significantly, and the crossed Nicols color of the two polarizing plates was changed from neutral gray to red.

Further, the reliability of the liquid crystal projection type display using this polarizing plate under the irradiation of a metal halide lamp is considerably inferior to that of Reference Example 1 and Example 2, and the portion irradiated with a strong light source is browned in a patchy manner. The contrast and sharpness of the color tone of this portion were lost.

[0028]

[Table 4]

[0029]

[Table 5] * 1 X: parallel transmittance, Y: orthogonal transmittance, ρ: average polarization * 2 CR is a contrast ratio of a polarizing plate and is calculated by X / Y. * 3 Conditions for ultra-lightfastness test Carbon arc, 2160W discharge / 140mm point 95 ° C, 100 hours irradiation

[0030]

EFFECT OF THE INVENTION It has been possible to manufacture a highly reliable liquid crystal projection type display in which the contrast is not deteriorated even when an intense light source is irradiated for a long time.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of a liquid crystal projection display.

[Explanation of symbols]

 1. Light source 2. Condensing lens 3. Color separation optical system (dichroic mirror) 4. Liquid crystal panel (consisting of 3 sets of R, G, B) 5. Incident side polarizing plate 6. Liquid crystal cell 7. Emitting side polarizing plate 8. Color combining optical system (dichroic prism) 9. Projection lens 10. screen

Claims (1)

[Claims] 1. A liquid crystal projection type display including one or more liquid crystal image forming portions, wherein a single transmittance is 36% or more and an average polarization rate is 99.0% or more on both the light source side and the screen side of the liquid crystal. A liquid crystal projection display with a dye-based polarizing plate placed on it.