JPH05341283A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display element reducing the diameter of a projection lens while holding the availability of a lighting beam high in the case of using it for a liquid projector and miniaturizing a device and reducing its cost. CONSTITUTION:Minute lenses 13 and 14 are arrayed and formed on both surfaces of the substrate 11 of a lighting beam incident side between both glass substrates 11, 12 of a liquid crystal element 5 in one-to-one correspondence in each pixel opening part 15A of a liquid crystal layer 15. Thus, the lighting beam is converged on each pixel opening part 15A of the liquid crystal layer. In such a manner, when the array of the minute lenses are formed on both surfaces of the glass substrate 11, luminous flux, as well inclined by an angle thetais refracted by the minute lens 13 and further refracted by the minute lens 14 of the other surface side at the point of time of converging in the vicinity of the pixel opening part 15A of the liquid crystal layer and the direction of the main beam is bended in parallel to an optical axis.

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 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 reflecting the light flux emitted from the metal halide lamp 1 by the concave mirror 2 or directly collimating it by the condenser lens 3, the liquid crystal display element 5 is passed through the relay lens 4.
(Hereinafter abbreviated as LCD) is illuminated. LCD5 has
A television image, a personal computer screen, etc. are displayed, and this display screen is enlarged and projected on the 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 does not become 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, the light rays shown by the dotted line in the figure reach the position on the projection lens 6 which is away from the optical axis. Therefore, the projection lens 6
It is necessary to increase the caliber of this.

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 =.
If the distance is 200 mm, the spread of the light flux on the projection lens 6 is approximately

## EQU00001 ## 2Ltan .theta. = 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, and generally has a low aperture ratio of about 30% to 40% of the total liquid crystal panel area.
There is a problem that the light incident on the other portions is cut off by the black matrix and cannot be used.

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

[0007]

However, in the above element structure, the luminous flux after passing 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. It will be expanded by ± (θ + α). α is the lens diameter of the minute lens 13, d is the thickness of the glass substrate 11, and n is the refractive index.

[Expression 2] α = tan ⁻¹ [dn / 2t] (2), for example, d = 140 μm, n = 1.53, t
= 1.1 mm, α = 5.6 °, which is about the same as θ. Therefore, when the microlens 13 is inserted to improve the brightness, the aperture of the projection lens 6 should be set to

## EQU00003 ## It is necessary to increase the value to 2 ltan (.theta. +. Alpha.) = 82 mm (3), which causes problems such as difficulty in downsizing the apparatus and increasing cost of the projection lens.

[0008]

In order to solve the problems of the prior art as described above, the present invention comprises an LCD.
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 light flux after passing through the LCD can be suppressed to be smaller than that in the case where an array of minute lenses is provided on only one side of the LCD glass substrate, and the aperture of the projection lens can be made larger than before. Can be made smaller.

[0010]

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.
The arrangement may be the same as in FIG. In FIG. 1, the LCD 5 is
A liquid crystal layer 15 is sandwiched between two transparent glass substrates 11 and 12, and the periphery is sealed, and microlenses 13 and 1 are provided on both surfaces of the glass substrate 11 and 12 on the illumination light incident side.
4 are formed in an array.

The minute lenses 13 and 14 can be manufactured as a gradient index lens on both surfaces of the substrate 11 made of 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 permeation, and openings are formed in this mask film by photolithography in a predetermined lens array pattern to increase the refractive index of the glass through the openings. It can be prepared by a method of diffusing ions by exchanging with alkaline ions in glass. The lenses 13 and 14 obtained by this method have a refractive index distribution in which the refractive index is maximum on the substrate surface and gradually decreases in the radial direction toward the substrate thickness.

The microlenses 13 and 14 on both sides of the substrate are
The pixel openings 15A of the liquid crystal layer 15 are arrayed in a one-to-one correspondence. As a result, 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 the same as that of the substrate 11 within the glass substrate.
To be approximately equal to the thickness. Similarly, the focal length of the minute lens 14 on the other surface side of the substrate is made substantially the same as that of the lens 13.

When an array of minute lenses is formed on both surfaces of the glass substrate 11 in this way, a light beam inclined by an angle θ is also refracted by the minute lens 13 and condensed at the vicinity of the pixel opening 15A of the liquid crystal layer. , The minute lens 14 on the other side
It is refracted at 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 is ± (θ + α) in the configuration of FIG. 4 in the related art, but can be significantly reduced to ± α.

## EQU4 ## The diameter can be significantly 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 array pitch of the minute lenses 13 and 14 is slightly shifted from the pixel pitch of the LCD in accordance with the convergence angle, The light that has converged and propagated after passing 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 constructed using the glass substrate 11 having the arrays of the microlenses 13 and 14 on both sides, a concrete construction as shown in FIG. 2 is typical. Take as an example. In FIG. 2, the surface of the glass substrate 11 facing the liquid crystal layer 25 is coated with a coating film 20 for preventing the elution of alkaline components from the glass, and a black matrix 21,
A color filter 22, a level coat 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 this and the glass substrate 11. To make LCD. Alkali elution prevention film 2
0 is obtained, for example, by dipping SiO ₂ in a liquid phase and then baking it to form a film.
For the pixel electrode 27, for example, an ITO film or the like is used.

In FIGS. 1 and 2, two glass substrates 1 are used.
The microlenses 13 and 14 are formed on only one of the microlenses 1 and 12, but the same glass substrate 11 with microlenses of FIG. 1 is used as the glass substrate 12 on the opposite side to form a four-layer structure of a microlens array. May be In this case, the divergence angle of the light flux after exiting the LCD is not ± α corresponding to the NA of the minute lens, but the parallelism of the illumination light ± θ.

[0018]

In the prior art, when an array of minute lenses is arranged immediately in front of the LCD in order to improve the light utilization efficiency of the LCD, the spread of the light flux 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 made small while keeping the light utilization efficiency of the LCD large, which is extremely effective for downsizing and cost reduction of the device.

[Brief description of drawings]

FIG. 1 is a sectional view showing an 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]

 1 Light Source Lamp 2 Concave Mirror 3 Condenser Lens 4 Relay Lens 5 Liquid Crystal Display Device (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 part

Claims (8)

[Claims] 1. A liquid crystal display device comprising a pair of glass substrates and a liquid crystal layer provided between the substrates, wherein at least one glass substrate of the glass substrates is provided on both sides thereof with respective pixel openings of the liquid crystal layer. A liquid crystal display device, characterized in that minute lenses are formed in an array corresponding to each part. 2. The micro lenses on both sides of the substrate are
The liquid crystal display element according to claim 1, which has optical characteristics such that when parallel light is incident, the light is condensed near the opposite surface of the substrate. 3. The liquid crystal according to claim 1, wherein the microlens has a refractive index distribution in which the substrate surface has a maximum refractive index and gradually decreases in the radial direction toward the inside of the substrate thickness. Display element. 4. The liquid crystal display device according to claim 1, wherein the minute lens is provided only on the glass substrate facing the light source. 5. A transparent coating for preventing elution of alkali ions in glass is coated on at least one surface of the glass substrate on which the minute lenses are formed.
3. The liquid crystal display element according to any one of 3 and 4. 6. The liquid crystal display element according to claim 1, wherein at least one surface of the glass substrate on which the minute lenses are formed is coated with a transparent conductive film. 7. 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 minute lenses are formed. 8. The color filters of a plurality of colors corresponding to the respective pixels are provided on at least one surface of the glass substrate on which the minute lenses are formed, respectively.
5. The liquid crystal display device according to any one of 1.