JP3032084B2 - Liquid crystal display device - Google Patents

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 useful for a liquid crystal projection device for enlarging and displaying a television screen, a computer output screen, etc., a so-called liquid crystal projector or a liquid crystal projection television.

[0002]

2. Description of the Related Art A typical example of a liquid crystal projector optical system is shown in FIG.
Shown in After the light flux emitted from the metal halide lamp 1 is reflected by the concave mirror 2 or directly collimated by the condenser lens 3, the liquid crystal display element 5 is relayed through the relay lens 4.
(Hereinafter abbreviated as LCD). LCD5 has
A television image, a personal computer screen, and the like are displayed, and this display screen is enlarged and projected on a screen 7 by the projection lens 6.

The relay lens 4 narrows the light illuminating the LCD 5 to the position of the projection lens 6 so that the vignetting of the light is not so large even if the diameter of the projection lens 6 is not large. . Since the actual lamp 1 is not a point light source but has a finite size, a light ray indicated by a dotted line in the figure reaches a position on the projection lens 6 away from the optical axis. Therefore, the projection lens 6
It is necessary to increase the caliber of this.

[0004] For example, the parallelism of the illumination light is about ± θ = ± 6 °, and the distance between the relay lens 4 and the projection lens 6 is L =
Assuming 200 mm, the spread of the light beam on the projection lens 6 is approximately

1 Ltan θ = 42 mm (1) Therefore, the diameter of the projection lens 6 needs to be 42 mm or more.

On the other hand, the LCD 5 has a wiring area and a T for each pixel.
It has a so-called black matrix that cannot transmit light, such as an FT (pixel transistor) region. Generally, the aperture ratio is as low as about 30% to 40% of the entire liquid crystal panel area.
There is a problem that light incident on other portions is cut by the black matrix and cannot be used.

As one method for solving this problem, as shown in FIG. 4, two glass substrates 11 and 12 constituting an LCD are provided.
A microlens 13 is provided on the glass substrate 11 on the side where light is incident so as to face each pixel.
Condensing the light on the pixel opening 15 by the
Conventionally, a method of increasing the amount of light transmitted through the light has been proposed.

[0007]

However, in the above-described element structure, the luminous flux transmitted through the LCD has an angle ± α corresponding to the NA (numerical aperture) of the minute lens 13 in addition to the spread angle ± θ of the illumination light. Then, it spreads by ± (θ + α). α is, if each lens diameter of the microlens 13 is d, the thickness of the glass substrate 11 is t, and the refractive index is n,

Α = tan ⁻¹ [dn / 2t] (2), for example, d = 140 μm, n = 1.53, t
= 1.1 mm, α = 5.6 °, which is almost the same size as θ. Therefore, when the micro lens 13 is inserted to improve the brightness, the diameter of the projection lens 6 is reduced.

## EQU3 ## It is necessary to make it as large as 21 tan (.theta. +. Alpha.) = 82 mm (3), which causes problems such as difficulty in downsizing the apparatus and increase in cost of the projection lens.

[0008]

In order to solve the problems of the prior art as described above, in the present invention, a liquid crystal display (LCD) is constructed.
Microlenses were arrayed on both surfaces of at least one of the glass substrates so as to correspond to the respective pixel openings of the liquid crystal layer.

[0009]

According to the present invention, the spread of the luminous flux after passing through the LCD can be suppressed smaller than in a case where an array of minute lenses is provided only on one side of the LCD glass substrate, and the aperture of the projection lens can be made larger than before. Can be smaller.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. FIG. 1 is an enlarged sectional view of an LCD showing an embodiment of the present invention.
May be the same as in FIG. In FIG. 1, the LCD 5
The liquid crystal layer 15 is sandwiched between the two transparent glass substrates 11 and 12, and the periphery thereof is sealed.
4 are formed in an array.

The microlenses 13 and 14 can be formed as refractive index distribution type lenses on both sides of a substrate 11 made of, for example, soda lime glass by using a known ion exchange method. That is, both surfaces of the substrate glass are covered with a mask film such as a metal film having a function of preventing ion transmission, openings are formed in the mask film by photolithography in a predetermined lens arrangement pattern, and the refractive index of the glass is increased through the openings. It can be produced by a method in which ions are diffused by exchange with alkali ions in glass. The lenses 13, 14 obtained in this way have a refractive index distribution in which the refractive index is greatest at the substrate surface and gradually decreases in the radial direction towards the substrate thickness.

The micro lenses 13 and 14 on both sides of the substrate are
An array is formed in a one-to-one correspondence with each pixel opening 15A of the liquid crystal layer 15. Thereby, the illumination light is focused on each pixel opening 15A of the liquid crystal layer. That is, the focal length of the minute lens 13 is
It is manufactured so as to be approximately equal in thickness to Similarly, the focal length of the microlenses 14 on the other side of the substrate is made substantially the same as the lens 13.

When an array of microlenses is formed on both sides of the glass substrate 11 as described above, a light beam inclined by an angle θ is refracted by the microlenses 13 and converges near the pixel opening 15A of the liquid crystal layer. And the microlenses 14 on the other side
And the direction of the chief ray is bent parallel to the optical axis.
Therefore, the divergence angle of the light beam emitted from the LCD 5 can be significantly reduced to ± α, which was ± (θ + α) in the conventional configuration of FIG.

## EQU4 ## The diameter can be greatly reduced to 2 ltan θ = 39 mm (4).

When the relay lens 4 is inserted in front of the LCD 5 as shown in FIG. 3, the arrangement pitch of the micro lenses 13 and 14 is slightly shifted from the pixel pitch of the LCD in accordance with the convergence angle. Light that converges and propagates through the relay lens 4 is made incident on each pixel opening 15A of the liquid crystal layer by the minute lenses 13 and 14.

Although not shown in FIG. 1, when the LCD 5 is formed using the glass substrate 11 provided with the arrays of the microlenses 13 and 14 on both sides, a specific configuration as shown in FIG. 2 is a representative example. As an example. In FIG. 2, the surface of the glass substrate 11 on the side facing the liquid crystal layer 25 is coated with a coating 20 for preventing elution of the alkali component from the glass.
A color filter 22, a level coating material 23, and a transparent conductive film 24 are provided.

A wiring portion 28, a TFT portion 26, and a pixel electrode 27 are provided on the surface of the other glass substrate 12 facing the liquid crystal layer 25, and liquid crystal is sealed between the wiring portion 28, the glass substrate 11, and the glass substrate 11. To make an LCD. Alkali elution prevention film 2
0 is obtained, for example, by dipping SiO ₂ in a liquid phase and then baking to form a film.
As the pixel electrode 27, for example, an ITO film or the like is used.

1 and 2, two glass substrates 1 are shown.
Although the microlenses 13 and 14 are formed on only one of the microlenses 1 and 12, for example, the same glass substrate 11 with microlenses as shown in FIG. It may be. In this case, the spread angle of the light beam after the emission from the LCD is not ± α corresponding to the NA of the minute lens, but is ± Parallelism of the illumination light.

[0018]

Conventionally, if an array of minute lenses is arranged immediately before the LCD in order to increase the light use efficiency of the LCD, the spread of the light beam on the projection lens becomes large, so that it is necessary to increase the aperture of the projection lens. However, according to the present invention, the aperture of the projection lens can be reduced while keeping the light use efficiency of the LCD large, which is extremely effective in reducing the size and cost of the device.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention.

FIG. 2 is a sectional view showing another embodiment of the present invention.

FIG. 3 is a schematic sectional view of a liquid crystal projector.

FIG. 4 is a sectional view showing a conventional liquid crystal display device with a lens.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source lamp 2 Concave mirror 3 Condenser lens 4 Relay lens 5 Liquid crystal display element (LCD) 6 Projection lens 11 Glass substrate 12 Glass substrate 13 Micro lens 14 Micro lens 15 Liquid crystal layer 15A Pixel opening 20 Alkali elution prevention film 21 Black matrix 22 Color Filter 23 Level coat layer 24 Transparent conductive film 25 Liquid crystal layer 26 TFT (pixel transistor) 27 Pixel transparent electrode 28 Wiring section

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/1335 G02B 3/00

Claims (7)

(57) [Claims] 1. A liquid crystal display device having a pair of glass substrates and a liquid crystal layer provided between the substrates, wherein each pixel opening of the liquid crystal layer is provided on both surfaces of at least one of the glass substrates. Micro lenses are arranged corresponding to each part, and the focal length of these micro lenses is
A liquid crystal display device characterized in that the thickness is substantially equal to the thickness of the glass substrate on which the microlenses are formed . 2. The liquid crystal display element according to claim 1, wherein the microlenses have a refractive index distribution that gradually decreases in a radial direction toward the inside of the substrate thickness with the substrate surface having a maximum refractive index. 3. The liquid crystal display device according to claim 1, wherein the microlenses are provided only on the glass substrate facing the light source. 4. A glass substrate on which said microlenses are formed, wherein at least one surface of said glass substrate is coated with a transparent film for preventing elution of alkali ions in the glass.
4. The liquid crystal display device according to any one of 3. 5. The liquid crystal display device according to claim 1, wherein at least one surface of the glass substrate on which the microlenses are formed is coated with a transparent conductive film. 6. The liquid crystal display device according to claim 1, wherein a black matrix is provided on at least one surface of the glass substrate on which the microlenses are formed. 7. The glass substrate according to claim 1, wherein a plurality of color filters corresponding to respective pixels are provided on at least one surface of the glass substrate on which the microlenses are formed. The liquid crystal display element as described in the above.