JPH05346578A - Liquid crystal display panel - Google Patents

Abstract

PURPOSE:To obtain improved structure which can suppress the divergence of luminous flux after transmission small as to the liquid crystal display panel which converges and transmits illumination light through the pixel opening part of a liquid crystal part through lenses. CONSTITUTION:On both surfaces (1st surface S1 and 2nd surface S2) of a substrate 11 on an illumination light incident side between two glass substrates 11 and 12 which constitute the liquid crystal display panel 5, microlenses 13, 14 are arrayed and formed corresponding to respective pixel opening parts 16, and on the opposite surface (4th surface S4) of the other substrate 12 from the liquid crystal layer, microlenses 15 are similarly arrayed and formed. Then the panel is so manufactured that f1=t1/n1, f2=t1/(2n1), and f3=t2/n2, where t1 and t2 are the thicknesses of both the substrates 11 and 12, n1 and n2 are the refractive indexes. and f1, f2, and f3 are the focal lengths of the lenses 13, 14, and 15.

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 panel which is 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. The light flux emitted from the metal halide lamp 1 is reflected by the concave mirror 2 or collimated by the condenser lens 3 or directly, and the liquid crystal display panel 5 (hereinafter abbreviated as LCD) is illuminated via the relay lens 4. A television image, a personal computer screen, etc. are displayed on the LCD 5, 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 (thin film 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 of solving this, as shown in FIG. 5, 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
The light is focused on the pixel opening 16 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.

[Mathematical formula-see original document] 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 the 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.
An array of minute lenses was provided on each of the three surfaces (first surface, second surface, and fourth surface) of the glass substrate, and the lens arrays of the first surface and the fourth surface were arranged in an afocal configuration.

[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 that shown in FIG. LCD in FIG.
5 is a liquid crystal layer 15 between the two transparent glass substrates 11 and 12.
Both glass substrates 11 and 1 are formed by sealing the periphery with sandwiching
Of the two, both surfaces of the substrate 11 on the illumination light incident side (first surface S ₁ ,
Microlenses 13 and 14 are formed in an array on the second surface S ₂ ) so as to correspond to the respective pixel openings 16, and the surface of the other substrate 12 opposite to the liquid crystal layer (the fourth surface S ₄ ). Also, the minute lenses 15 are formed in the same arrangement.

The minute lenses 13, 14 and 15 can be manufactured as a gradient index lens on the surface of the substrate 11 made of, for example, soda lime glass by using a known ion exchange method. That is, both sides or one side of the substrate glass is 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 with a predetermined lens array pattern by photolithography. It can be prepared by a method of diffusing ions that enhance the diffusion by exchanging with alkali ions in the glass.
The lens obtained in this way has a refractive index profile in which the refractive index is greatest at the substrate surface and gradually decreases in the radial direction towards the substrate thickness.

Here, the thicknesses of both substrates 11 and 12 are t ₁ ,
When t _{2 is} the refractive index of n ₁ and n ₂ , and the focal lengths of the lenses 13, 14 and 15 are f ₁ , f ₂ and f ₃ , f _{1 to} f ₃ are

## EQU4 ## f ₁ = t ₁ / n ₁ (4)

F ₂ = t ₁ / (2n ₁ ) (5)

## EQU6 ## Fabrication is performed so that f ₃ = t ₂ / n ₂ (6). For example, t ₁ = t ₂ = 1.1 mm,
When n ₁ = n ₂ = 1.53, f ₁ = f ₃ = 719 μm, f ₂
= 359 μm.

In this manner, the three surfaces S ₁ , S ₂ , S ₄ of the substrate are formed.
When an array of minute lenses is formed on each of the
_The parallel rays incident on the _first lens 13 are the first surface S ₁ and the fourth surface
Since the minute lenses on the surface S ₄ are arranged afocal, they propagate in parallel after being emitted from the lens 15 on the fourth surface S ₄ (the solid line in FIG. 1). A ray inclined by an angle θ is also refracted by the lens 14 having the second surface S ₂ , the direction of the principal ray is bent and is incident on the entire pupil surface of the fourth surface lens 15, and after passing through this lens 15, the principal ray is changed. Emit as parallel rays inclined by an angle θ (rays in dotted line in the figure).

Therefore, the divergence angle of the light beam emitted from the LCD 5 can be greatly reduced to ± θ, which is ± (θ + α) in the conventional configuration of FIG. 4, and therefore the aperture of the projection lens 6 is L and θ. If it is the same as equation (1),

(7) 2L tan θ = 42 mm (7) The diameter can be significantly reduced.

Although not shown in FIG. 1, the surfaces S ₁ , S ₂ ,
When the LCD 5 is actually constructed by using the glass substrates 11 and 12 provided with the arrays of the lenses 13, 14 and 15 in S ₄ , a concrete structure as shown in FIG. 2 is given as a representative example. In FIG. 2, an alkali elution preventing film 20 is coated on the surface of the glass substrate 11 facing the liquid crystal layer, and a black matrix 21, a color filter 22, a level coating material 23, and a transparent conductive film 24 are provided thereon.

After the alkali elution preventing film 20 is coated on the surface of the other glass substrate 12 facing the liquid crystal layer, the wiring portion 28, the TFT portion 26, and the pixel electrode 27 are formed.
Is provided, and liquid crystal is sealed between this and the glass substrate 11 to form an LCD. Each array of the minute lenses 13, 14, and 15 has a three-layer afocal arrangement as shown in the figure.

The alkali elution preventing film 20 is made of, for example, SiO.
It is obtained by dipping ₂ in a liquid phase and then baking it to form a film. For the transparent conductive film 24 and the pixel electrode 27, for example, an ITO film or the like is used.

FIG. 3 shows another embodiment of the present invention. In this example, non-alkali glass (eg, Corning # 7059 glass, quartz glass, etc.) is used for the glass substrates 11 and 12, and minute convex lenses 13, 14 and 15 made of a transparent resin material are formed on the surface of the glass substrate. Each array is formed by molding using a Ni stamper and adhering it to the glass surface at the same time. Then, the second surface lens 14
By incorporating pigments corresponding to colors such as red, green, and blue into the resin material, the lens function and the color filter function are provided. The convex lens effect is obtained by making the refractive index of the resin material of the lens 14 higher than that of the level coat material 23.

In the embodiment described above, both glass substrates 1
Although single glass plates are used as the glass plates 1 and 12, one or both substrates may be formed by laminating a plurality of glass plates. That is, the first substrate 11 can be formed by bonding two glass plates, each having a minute lens array formed on one surface side, with the lens surfaces facing outward. In addition, the second substrate 12 can be configured by bonding the above-mentioned single-sided lens array forming glass plate and a glass plate on which no lens is formed.

[0020]

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. Also, even with the improved structure as described in FIG. 6, the light beam inclined with respect to the optical axis becomes the second
Although there is a problem that the brightness is lowered because the light does not enter the surface lens 14 correctly, 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, thereby making the device compact and low. It is extremely effective for cost reduction.

Further, when the microlens array has a three-layer structure as in the present invention, it is not necessary to provide the lens array on the surface on which the TFT is formed, so that high flatness of the glass substrate can be secured and stable operation of the TFT can be ensured. It will be possible.

[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 sectional view showing another embodiment of the present invention.

FIG. 4 is a schematic sectional view of a liquid crystal projector.

FIG. 5 is a sectional view showing a first example of a conventional liquid crystal display panel with a lens.

FIG. 6 is a sectional view showing a second example of a conventional liquid crystal display panel with a lens.

[Explanation of symbols]

1 Light Source Lamp 2 Concave Mirror 3 Condenser Lens 4 Relay Lens 5 Liquid Crystal Display Panel (LCD) 6 Projection Lens 11 Glass Substrate 12 Glass Substrate 13 First Surface Micro Lens 14 Second Surface Micro Lens 15 Fourth Surface Micro Lens 16 Liquid Crystal Aperture 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 100 Available light ray 101 Unavailable light ray S ₁ First surface S ₂ No. 2nd surface S ₃ 3rd surface S ₄ 4th surface

Claims (9)

[Claims] 1. In a liquid crystal display panel having a pair of glass substrates and a liquid crystal layer provided between the substrates, each surface of the substrate is provided with first, second, and
When expressed as three or four surfaces, a large number of microlenses having a positive power are two-dimensionally arrayed and formed on a total of three surfaces of the first surface, the second surface, and the fourth surface, with their axes being common. A liquid crystal display panel, characterized in that the microlenses on the first surface and the microlenses on the third surface are configured and arranged substantially afocal. 2. The second surface of the substrate is provided with at least one of a transparent conductive film, a light-shielding coating layer having a large number of light transmission openings, and a plurality of color filters corresponding to each pixel. The liquid crystal display panel according to claim 1, further comprising a TFT on the third surface. 3. The distance between the first surface and the third surface is t ₁ , the distance between the third surface and the fourth surface is t ₂ , the refractive index of the first substrate is n ₁ , and the second substrate is Has a refractive index of n ₂ , the first surface of the substrate, the second surface of
When the focal lengths of the minute lenses on the first surface and the third surface are f ₁ , f ₂ , and f ₃ , respectively, roughly f ₁ = t ₁ / n ₁ , f ₂ =
The liquid crystal display panel according to claim 1, wherein the relationship of t ₁ / (2n ₁ ), f ₃ = t ₂ / n ₂ is satisfied. 4. At least one of the pair of glass substrates is configured by laminating a glass plate on which an array of microlenses is formed and a glass plate on which a lens array is similarly formed or not formed. The liquid crystal display panel according to claim 1. 5. The lens array of at least one surface of the minute lens array of each surface is composed of an array of minute convex lenses made of a transparent resin material adhered to the surface of the glass plate. The liquid crystal display panel according to any one of 3 and 4. 6. The liquid crystal display panel according to claim 1, wherein at least one surface of the glass substrate is provided with a protective coating for preventing elution of alkali in the glass. .. 7. The transparent conductive film is coated on at least one surface of the glass substrate.
7. The liquid crystal display panel according to any one of 4, 5, and 6. 8. The black matrix is provided on at least one surface of the glass substrate.
4. The liquid crystal display panel according to any one of 4, 5, 6, and 7. 9. The glass substrate according to claim 1, wherein at least one surface of the glass substrate is provided with color filters of a plurality of colors corresponding to respective pixels. LCD display panel.