JPH0450802A - Plate lens array and liquid crystal panel element using it - Google Patents

Abstract

PURPOSE:To improve the brightness by arranging and forming many spherical minute hollows on the surface of a transparent substrate, and filling the inside of this hollow with a transparent material whose refractive index is higher than that of the substrate, and also, allowing thickness of the substrate, the refractive index, the radius of curvature of the hollow, and the refractive index of the filling material to satisfy a specific relation. CONSTITUTION:The liquid crystal panel element is constituted by arranging and forming many spherical minute hollows 6 on the surface of a transparent substrate 1, and also, filling the inside of these hollows 6 with a transparent material 7 whose refractive index is higher than that of the substrate 1 in a state that the surface is flat. Also, thickness of the substrate 1, its refractive index, a radius of curvature of the hollow 6, and a filling material 7 in the hollow are denoted as (t), n0, (r) and n1, respectively and each value is selected so as to satisfy a condition of an expression I, and this element is used in a state that its lens array surface is turned to the outside surface side of a liquid crystal panel. In such a way, by condensing to the liquid crystal opening window, the utilization efficiency of Illumination is raised, and a projected image can be brightened.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a liquid crystal panel used in a liquid crystal television, a liquid crystal video projector, etc., and an optical element suitable as a cell substrate for this panel. The present invention relates to a liquid crystal panel useful for a liquid crystal projector that emits light onto a liquid crystal panel and enlarges and projects the light onto a screen using a projection lens.

[Prior art] Liquid crystal panels generally have pixel wiring and pixel transistors (a
-Si TFT, poly-5i TFT) occupies 60 to 70% of the total LCD panel area, and the area of the liquid crystal aperture window through which illumination light can actually pass through for each pixel is 30 to 40%. % is small. That is, 60 to 70% of the illumination light cannot actually be used and is wasted.

One way to solve these conventional problems is to provide a microlens for each pixel and use this to focus light onto the liquid crystal aperture window, thereby improving the efficiency of lighting use and brightening the projected image. A number of laws have been proposed.

[Problems to be solved by the invention] However, published patents and other publicly known documents to date have only described very conceptual aspects, and it is important to know what kind of specifications the lens should actually be manufactured. There was no specific indication as to whether it was necessary for the effect to be obtained.

[Means for solving problems]

Therefore, the present inventors investigated combination configurations of liquid crystal panels and lens arrays that are highly likely to actually be realized, and calculated the brightness improvement effect through simulation. From the results, the thickness and refractive index of each component were determined. We have discovered the numerical relationship between the radius of curvature of the lens surface and the conditions necessary to obtain a large effect. The present invention is based on this knowledge, and in a liquid crystal panel, one of the pair of cell substrates sandwiching the liquid crystal layer (one of the cell substrates, that is, the side to which illumination light is irradiated) is used on a one-to-one basis for each pixel. A planar lens array is used in which microlens groups are arranged so that each lens corresponds to the other.

This flat lens array is constructed by forming a large number of spherical minute depressions on the surface of a transparent substrate such as glass or plastic, and filling these depressions with a transparent material that has a higher refractive index than the substrate so that the surface is flat. do. Then, the thickness of the substrate is t8, its refractive index is nll, the radius of curvature of the recess is r'-<the refractive index of the material filling the recess is nl, and r n.

The above values are selected so as to satisfy the following conditions, and used with the lens arrangement surface facing the outer surface of the liquid crystal panel.

The flat lens array with the above configuration is extremely useful as a cell substrate for a liquid crystal panel, but it is not limited to this, and is generally an array of many highly condensed light spots on one virtual plane (-dimensional or two-dimensional). This is useful when you want to obtain an array).

[For production]

By designing and manufacturing the specifications of each component in the liquid crystal panel as described above, an extremely large brightness improvement effect can be obtained.

〔Example] FIG. 1 shows one embodiment of the present invention.

The liquid crystal panel 1 is composed of two liquid crystal cell substrates 2122 and a liquid crystal layer. The liquid crystal layer has a liquid crystal opening window 3 that can transmit light for each pixel, and the other portions 4 are non-transparent portions such as TPT and pixel wiring.

The liquid crystal cell substrate 21 on the side where the illumination light is incident is a flat lens array. That is, on the surface 5 of this substrate opposite to the liquid crystal layer, substantially spherical depressions 6 are provided to face each liquid crystal pixel one-to-one. Further, each of the depressions 6 is filled with a high refractive index material, and the surface thereof is substantially flat.

The high refractive index material 7 may be a glass material or a resin material as long as it is a transparent material with a refractive index higher than that of the glass substrate 5. For practical purposes, the surface of the high refractive index material 7 may be coated with a moisture-resistant coating. Further, the surface of the substrate 21 that is in contact with the liquid crystal layer may be coated with a film or/and a conductive film for preventing precipitation of alkaline components in the glass.

Furthermore, glass that does not substantially contain an alkali component can also be used as the substrates 21 and 22.

The spherical recess 6 can be formed, for example, by forming a metal mask having a circular opening with a diameter of several μm to several tens of μm on a glass substrate using photolithography, and etching this using a hydrofluoric acid etchant for an appropriate period of time. It can be made by Since glass etching proceeds approximately isotropically from the mask opening, approximately hemispherical recesses are obtained, and the radius of curvature of the recesses can be controlled by the etching time and the like. Furthermore, by dividing the etching process into two stages, it is also possible to produce spherical depressions that are shallower than a hemispherical shape, or a spherical depression array with a so-called close-packed structure in which adjacent spherical depressions are completely connected. Since this etching method is not an essential part of the present invention, a detailed explanation thereof will be omitted, but it is disclosed in detail in Japanese Patent Application No. 2-27712. As the glass substrate, for example, a Corning 7059 substrate, a soda lime substrate, etc. can be selected.

Now, when constructing a liquid crystal panel with a lens array shown in Figure 1 using such a manufacturing method, in order to obtain a large brightness improvement effect, it is necessary to adjust the refractive index, thickness, radius of curvature of the lens, etc. It is necessary to configure the optical system according to the following numerical limitation conditions.

Here, the refractive index of the liquid crystal cell substrate 21 of the flat lens array is n11, the thickness is t, and the radius of curvature of the spherical recess 6 is r.
Let n be the refractive index of the high refractive index filling material 7.

When the substantially parallel incident light ray 8, which is illumination light, enters the liquid crystal cell substrate 21, the light ray is refracted by the spherical depression 6. At this time, if Ho<n, the spherical depression 6 acts as a convex lens. Due to this convex lens effect, it can be said that the use effect of illumination light is maximized when the incident light beam most effectively enters the liquid crystal aperture window 3.

According to paraxial calculation, the focal length f of a lens due to refraction on one spherical surface is expressed as f = r/ (no-no) ... (i) (for example, "Principles of Optics I", Tokai University Press, etc.) ). In order to focus the refracted light beam on the liquid crystal aperture surface, f = t /
n 6, so the relationship between t, n0, r, and no is basically t/n+=r/(n multi-no)... (2
) must be the formula.

However, the refraction effect due to one spherical surface causes a large positive spherical aberration, and as shown in FIG. 2, peripheral rays are focused more closely than paraxial rays. Therefore, the position where the incident light beam is focused on the region where the total energy is the smallest will be closer than the value of the above paraxial calculation.

Therefore, we actually performed ray tracing using the optical system shown in Figure 1.
The size of one pixel is 100 μm square, and the liquid crystal aperture size is 20 μm.
The number of light rays actually incident on the liquid crystal aperture due to refraction of the spherical surface was calculated when the angle was taken as an angle, and the effective focal position was calculated from the maximum position of the number. Figure 3 shows an example of the calculation results. Assuming a Corning 7059 substrate as the liquid crystal cell substrate, no = 1.53, and n+ = 1.56.
It was calculated as

In the figure, the horizontal axis represents the radius of curvature of the spherical recess 6, and the vertical axis represents the focal length in the liquid crystal cell substrate. The solid line is n+=1.6
These are calculation results using paraxial approximation using equations (1) and (2) with 0. On the other hand, the broken line is the effective focal length determined by ray tracing as described above. That is,
In this optical system, the position where the greatest light focusing effect is obtained including spherical aberration is the value indicated by the dotted line in the figure. Comparing this value with the paraxial calculation results, it is about 90% of the paraxial result when the radius of curvature is large, and about 50% of the paraxial result when the radius of curvature is small.

From the above simulation results, the light focusing effect is the strongest (
The effective focal length fe obtained is approximately 0.3r/(n
o-no)≦fe≦r/(no-no)” (3). Therefore, by making this value fe equal to t/nO, the maximum light focusing effect can be achieved at the liquid crystal aperture position. That is, the numerical relationship between t+nO+n1 is obtained as rn.

It becomes necessary to do so.

In the example shown in FIG. 1, only the cell substrate 21 on the illumination side is a flat lens array, but a similar flat lens array may also be used for the other cell substrate 22.

At this time, equation (4) must be satisfied separately for each side.

In addition, in each formula, the focal length is the distance from the apex of the spherical surface, and the thickness of the lens should be taken into consideration in the analysis, but in this application, compared to a focal length of about 400 to 800 μm,
The thickness of the lens is several +8 m or less, and does not need to be considered in practice.

(Effects of the Invention) As explained above, by setting each numerical value to the condition of the above equation (4), the maximum brightness improvement effect can be obtained in the liquid crystal panel configuration of FIG. 1.

By the way, the size of one lens is about 100 μm square, no-1
, 53, with t = 1.1 mm and n+ = 1.60, a lens was fabricated using a depression with a radius of curvature of approximately 75 μm, and the diameter was approximately 40 μm.
The amount of illumination light focused within the am angle is 1/2 compared to without lenses.
I got more than double that.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG.
A schematic diagram showing the refraction state of light rays at the 1/lens portion provided in the cell substrate in the liquid crystal panel shown in the figure. Figure 3 shows the radius of curvature of the recess forming the lens portion, the refractive index of each constituent material, and the lens focal length. FIG. 2 is a diagram showing calculation results. DESCRIPTION OF SYMBOLS 1... Liquid crystal panel, 21... Flat lens array (liquid crystal cell substrate), 22... Liquid crystal cell substrate, 3... Liquid crystal aperture window, 4... Opaque portion, 6... Spherical surface shaped depression (
Lens part), 7... High refractive index filling material, 8... Illumination light: Hega Fig. 1 Fig. j I 2 Fig. Radius of curvature r of spherical depression (1 m)

Claims (1)

[Scope of Claims] (1) A large number of spherical minute depressions are formed in an array on the surface of a transparent substrate, and these depressions are filled with a transparent material having a higher refractive index than the substrate so that the surface is flat, and The thickness of the substrate is t, its refractive index is n_0, the radius of curvature of the recess is r, and the refractive index of the material filling the recess is n_1, and the relationship is 0.3≦t(n_1−n_0)/rn_0≦1. A flat lens array characterized by: (2) In a liquid crystal panel, at least one of a pair of cell substrates sandwiching a liquid crystal layer is configured with a flat lens array having a group of micro lenses arranged in a one-to-one correspondence with each pixel, and the flat lens The array is made by forming a large number of spherical minute depressions on the surface of a transparent substrate, and filling these depressions with a transparent material having a higher refractive index than the substrate so that the surface is flat. The lens array substrate is arranged facing the outer surface of the liquid crystal panel, and the thickness of the lens array substrate is t, its refractive index is n_0, the radius of curvature of the recess is r, and the refractive index of the material filling the recess is n_1, and 0.3≦t. A liquid crystal panel element having a relationship of (n_1-n_0)/rn_0≦1. (3) A liquid crystal panel element according to claim 2, in which a glass material containing almost no alkali is used as a substrate of the flat lens array. (4) The liquid crystal panel element according to claim 2, wherein the surface of the flat lens array opposite to the lens arrangement surface is coated with a coating that prevents alkali precipitation. (5) The liquid crystal panel element according to claim 2, wherein the surface of the flat lens array opposite to the lens arrangement surface is coated with a transparent conductive film.