JPH0815687A - Liquid crystal display element and liquid crystal display device using element - Google Patents

Abstract

PURPOSE:To improve an aperture ratio using a microlens, to improve the parallelism of a light ray incident on a liquid crystal and to ameliorate the contrast characteristic by forming a microlens having a positive refractive index on the side of an entrance light ray and a microlens having a negative refractive index on the side of an outgoing light ray. CONSTITUTION:A transparent substrate 4 on the side on which a light ray radiated from a light source is made incident is composed of a planar microlens array 1. The planar microlens array 1 is formed so that a microlens 1a having a positive refractive index and a microlens 1b having a negative refractive index are arranged on an optical axis and the respective unit lenses 1a, 1b are arranged as the same arrangement as the pixel arrangement of a liquid crystal 5. Consequently, the incident light ray is effectively introduced to the aperture part, not interrupted by a light shielding part not contributed to display, the incident light ray is converged by the microlens 1a of a positive refractive index, made to be a parallel beam by the microlens 1b of a negative refractive index and made incident on the liquid crystal 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmissive liquid crystal display element for injecting liquid crystal between a pair of transparent substrates and displaying image information by the electro-optical effect of the liquid crystal, and a light source for the transmissive liquid crystal display element. The present invention relates to a liquid crystal display device used as a valve.

[0002]

2. Description of the Related Art The structure of a twisted nematic (TN) type liquid crystal display element, which is a typical example of a liquid crystal display element, has a structure in which liquid crystal is injected between a pair of transparent substrates having transparent electrode coatings before and after a liquid crystal cell. , Each polarization direction is 90 ° to each other
The two polarizing plates are arranged differently, and the amount of incident light transmitted is controlled by combining the action of rotating the plane of polarization by the electro-optical effect of liquid crystal and the action of selecting the polarization component of the polarizing plate. Image information is displayed. The liquid crystal display device is described in detail, for example, in "Basics and Applications of Liquid Crystal Electronics" edited by Sasaki, Ohmsha (1979). In the liquid crystal display element as described above, a portion that does not contribute to display, such as a metal wiring of an electrode in each pixel, a non-linear element or switching element added as means for individually controlling each pixel, a gap around the pixel electrode ( There is a light shield. Therefore, particularly in a transmissive liquid crystal display element, the light emitted from the light source and reaching the light-shielding portion out of the light emitted to the liquid crystal display element does not pass through the liquid crystal display element, so that the light utilization efficiency is reduced. Become. Usually, the light utilization efficiency is expressed by the aperture ratio of the liquid crystal display element, which is a problem. The aperture ratio is defined as follows.

Aperture ratio = effective area contributing to display in 1 pixel / area of 1 pixel whole area Further, when the liquid crystal display element is miniaturized in order to make the display device using the liquid crystal display element compact, If the liquid crystal display element has the same number of pixels, the smaller the liquid crystal display element is, the smaller the area of one pixel is,
The influence of the above-mentioned light-shielding portion becomes large and it becomes difficult to make it bright. Further, in order to increase the definition of the liquid crystal display element with the same size and to increase the resolution of the display device using the liquid crystal display element, the pixel pitch is It is necessary to reduce the size, but in that case, if all the constituent elements of the liquid crystal display element can be reduced in size, the influence of the light-shielding portion does not change and the aperture ratio does not change. The width of the wiring and the size of the additional element cannot be reduced to a certain extent or less, and as a result, the aperture ratio becomes worse as the definition is increased.

The transmission type liquid crystal display element and the liquid crystal display device having the improved aperture ratio are disclosed in, for example, Japanese Patent Laid-Open No.
There are those provided with a microlens array as described in JP-A-2-179283 and JP-A-2-115889.

[0005]

In the above-mentioned prior art, the microlens array having a positive refractive index is formed on the substrate on the light incident side of the liquid crystal display element, and the contrast characteristics of the liquid crystal panel are considered. Was not considered. Therefore, the following problems occur.

7 and 8 are schematic cross-sectional views of a portion corresponding to one pixel of a liquid crystal display element for explaining the problems of the prior art, and the liquid crystal layer and the other transparent substrate are omitted.

In FIG. 7, the light rays 10 incident on the liquid crystal panel are refracted by the individual microlenses of the flat plate microlens array 1 and are incident on the openings, so that the apparent aperture ratio of the liquid crystal panel is improved. However, the light ray 11 emitted from the microlens is larger than the angle of the light ray 10 incident on the liquid crystal panel. The angle of this ray increases as the refractive index of the microlens increases.

FIG. 8 shows the contrast characteristic with respect to the angle of the incident light ray of a normal liquid crystal panel. However, since the light ray incident on the liquid crystal is the light ray 11 emitted from the microlens, the contrast characteristic is deteriorated.

As described above, in the above prior art, the display device using the liquid crystal display element provided with the microlens array and the illumination optical system, or the projection by projecting the image by the display device on the screen by the projection lens is used. The contrast characteristic of the liquid crystal panel was not taken into consideration when constructing the type display device. Therefore, an object of the present invention is to solve the above conventional problems, improve the aperture ratio by using a microlens, and improve the parallelism of light rays incident on the liquid crystal, thereby providing a liquid crystal display with good contrast characteristics. To provide a device.

[0010]

In order to solve the above problems, the present invention provides a transmissive liquid crystal display device in which liquid crystal is injected between a pair of transparent substrates and image information is displayed by the electro-optical effect of the liquid crystals. , A flat plate microlens having a positive refractive index on the incident light side and a microlens having a positive refractive index on the outgoing light side are formed to improve the parallelism of light rays incident on the liquid crystal. .

[0011]

According to the liquid crystal display device having the above-described structure of the present invention, the incident light beam is effectively guided to the opening, and the metal wiring of each electrode and the non-linear element or switching added as means for individually controlling each pixel are provided. A bright image even if the aperture ratio is poor (small) because "vignetting" of the incident light due to being blocked by a portion (light-shielding portion) that does not contribute to display, such as a gap around the element or the pixel electrode, is generated. Information display is obtained. Further, according to the configuration of the present invention, the incident light beam is focused by the microlens having a positive refractive index, and becomes substantially parallel light by the microlens having a negative refractive index and is incident on the liquid crystal, so that a liquid crystal display device having a bright and good contrast is obtained. Is obtained.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiments shown in FIGS. FIG. 1 is a sectional view of a liquid crystal display element 9 according to the first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a pair of flat plate microlens arrays, which are two-dimensionally arranged lens arrays in which a large number of unit lens portions 1a and 1b are adjacently arranged vertically and horizontally corresponding to pixels. Further, the optical axes of the respective lenses are made to coincide between the unit lens portions 1a and 1b of the flat plate microlens array. On the unit lens portion 1b side of the flat plate microlens array 1, a light shielding portion 2 of a metal thin film called a black matrix (the space between the light shielding portions 2 is the opening), a color filter 3 and a transparent electrode 4 are formed. There is. A transparent electrode 4 and a non-linear element or a switching element 7 added as means for individually controlling each pixel are formed on the opposing surface side of one transparent substrate 6, and the flat plate microlens array 1 and the transparent substrate 6 are formed. Liquid crystal 5 is enclosed between them. Reference numerals 8 and 8 denote a pair of polarizing plates. In the figure, the polarizing plate 8, each microlens array 1 and the transparent substrate 6 are in close contact with each other, but they may be separated from each other. Together, these constitute the liquid crystal display element 9.

Next, a method of manufacturing the flat plate microlens array 1 in this embodiment will be described. FIG. 2 is a partial perspective view schematically showing the flat plate microlens array of FIG.

The flat plate microlens array 1 shown in FIG.
Is a transparent parallel flat plate glass substrate having a refractive index N ₀ (for example, a borosilicate optical glass substrate having a thickness t ₁ of about 1 mm is used in this embodiment) on both surfaces, and a refractive index different from the refractive index N _0. This is a so-called gradient index type flat plate microlens array in which the regions N ₁ and N ₂ are formed with periodicity. The gradient index microlens array can be formed by, for example, an ion exchange method. In this ion exchange method, a mask layer having a required pattern is formed on a transparent parallel flat glass substrate by using, for example, a metal, and the mask layer is immersed in a molten salt bath to obtain Na + (sodium ion) and K + (potassium ion) contained in the glass. ) Are exchanged with cations such as Tl + (thallium ion) contained in the molten salt through the exposed surface of the glass. The region thus ion-exchanged has a refractive index different from that of the original glass and becomes a refractive index distribution region having a function of refracting light. Furthermore, by using a different molten salt for each surface when immersing the parallel plate glass substrate in the molten salt,
Microlenses having different refractive indexes can be formed on each surface.

Further, the refractive index N ₀ of the parallel plate glass substrate
On the other hand, when the refractive index N _{2 on} the liquid crystal 5 side and the refractive index N ₁ on the opposite side of the liquid crystal 5 satisfy the following conditional expressions, the liquid crystal 5 side is a microlens having a negative refractive index, and the opposite side of the liquid crystal 5 is positive. It is possible to form a microlens having a refractive index of.

FIG. 3 is a principle explanatory view for explaining the effect of the flat plate microlens array 1 of the present embodiment described above.

FIG. 3A shows the unit lens 1a in the case where the flat plate microlens array 1 of the conventional embodiment has a positive refractive index, and θ _i is the incident angle to the microlens θ _0. Is the exit angle from the microlens. When the height of the light beam incident on the microlens is h and the focal length of the microlens is f, the exit angle θ ₀ from the microlens is expressed by the following equation (2).

Tan θ ₀ = tan θ _i + h / f (2) When the unit lens 1a has a positive refractive index, θ ₀ becomes larger than θ _i as in the above formula. Therefore, when the microlens is used, the incident angle to the liquid crystal becomes large, so that the contrast characteristic deteriorates.

In this embodiment, as shown in FIG. 3B, the flat plate microlens array 1 is composed of microlenses having a positive refractive index and microlenses having a negative refractive index. Ray 1 incident on
1 is focused by a microlens having a positive refractive index,
Since the microlens having a negative refractive index makes almost parallel light and enters the liquid crystal 5, in the present invention, even if the microlens is used, the incident angle to the liquid crystal does not become large, so that the contrast characteristic is not deteriorated.

In FIG. 4, the feature of this embodiment is that it is composed of two flat plate microlenses having a positive refractive index and a flat plate microlens having a negative refractive index.

The manufacturing method of the microlens used in this embodiment is the same as that of the first embodiment, except that only one side surface of the parallel plate glass substrate is dipped in the molten salt to form the microlens having the refractive index. is there.

Next, a liquid crystal display device using the liquid crystal display element of this embodiment as a light valve will be described with reference to embodiments. FIG. 5 is a sectional view showing the principle configuration of a first embodiment of a liquid crystal display device using the liquid crystal display element according to the embodiment of the present invention shown in FIGS. 1 to 4 as a light valve. Figure 5
FIG. 5A is a sectional view showing the principle structure of a liquid crystal display device having an illumination system including a light source, and FIG. 5B is a sectional view showing the principle structure of a projection type liquid crystal display device having an illumination system including a light source and a projection system. It represents.

In FIG. 5A, 12 is a light source (white light source) such as a metal halide lamp or a halogen lamp, 13 is a concave mirror, and 14 is a condenser lens group.
The light valve is composed of the liquid crystal display element 9 shown in FIGS. In the figure, the light emitted from the light source 12 that emits white light is reflected by a reflecting mirror such as a concave mirror 13, or a part of the light is not reflected by the reflecting mirror, and each of them is a condensing lens group. After passing through 14, the light enters the liquid crystal display element 9. In the liquid crystal display element 9, the incident light is effectively guided to the pixel electrode (opening) by the action of the flat plate microlens array described above, and the image on the liquid crystal surface is diffused without causing the loss of light utilization efficiency due to the light shielding portion. As shown in FIG. 39, bright image information can be obtained. In addition, the liquid crystal display element 9
As a drive circuit of, for example, laser disk, VTR
Video chroma processing circuit 1 for video input from
6, and is input to the RGB output circuit 17. R
In the GB output circuit 17, since the video signals corresponding to R, G, and B and the liquid crystal display element 9 are AC-driven, the polarities are inverted every vertical period and are input to the electrodes of the liquid crystal display element 9 via the X driver 18. . The video chroma processing circuit 16, R
GB output circuit 17, X driver 18, and Y driver 1
9 is synchronized by the synchronization processing circuit 20 and the controller 21.

In the projection type liquid crystal display device shown in FIG. 5B, the image information after being emitted from the light source, incident on the liquid crystal display element 9 and passing therethrough is enlarged by the projection lens 22 in the same manner as described above, and is projected on the screen 23. Bright image information can be obtained by enlarging and projecting on.

FIG. 6 is a block diagram showing a second embodiment of a liquid crystal display device using the liquid crystal display element according to the embodiment of the present invention as a light valve.

FIG. 6 shows a liquid crystal display device according to the present invention, which is a so-called three primary color R (red), G (green), B (blue).
The three-plate projection type liquid crystal display device using a total of three sheets is shown for each of the three colors. In the figure, for example, a light beam emitted from a light source 12 using metal halide, xenon, halogen, etc. is reflected directly or by a concave mirror 13,
Infrared cut filter 2 that reflects heat rays and passes visible light
4 and then enters the condenser lens group 14 and then exits so as to be substantially parallel to the optical axis of the ray, and the ray is then arranged at an angle of 45 ° with respect to the optical axis of the ray. B
The (blue) reflection dichroic mirror 25a reflects the B light and transmits the R (red) and G (green) lights.

The reflected B ray has its optical path bent by the total reflection mirror 26 and enters the liquid crystal display element 9. On the other hand, the R and G rays transmitted through the B-reflecting dichroic mirror 25a are incident on the G-reflecting dichroic mirror 25b arranged at an angle of 45 ° with respect to the optical axis of the ray, and the G-rays are changed by the G-reflecting dichroic mirror 25b. It is reflected and the R ray is transmitted. The reflected G ray enters the liquid crystal display element 9 as it is. On the other hand, the R ray that has passed through the G reflection dichroic mirror 25b is incident on the liquid crystal display element 9 with its optical path bent by the total reflection mirror 26.

Further, an image corresponding to each of R, G, and B displayed on the liquid crystal surface of each liquid crystal display element 9 has a B reflecting surface 27 and an R reflecting surface 28, and the reflecting surface has each color. The dichroic prism 29 configured so as to form an angle of 45 ° with respect to the optical axis of the light beam synthesizes the synthesized image with the projection lens 22 to obtain a magnified real image on the screen 23. There is.

Further, as a drive circuit of the liquid crystal display element in the embodiment shown in the figure, there is a circuit shown in the lower part of the figure, for example. That is, a video input from a laser disk, a VTR, etc. is connected to the video / chroma processing circuit 1
Output circuit 1 processed by 6 and corresponding to each color of R, G, B
Type in 7. Since the RGB output circuit 17 AC-drives the video signal and the liquid crystal display element corresponding to each color, the polarities are inverted every vertical period and input to the liquid crystal display element 9 via the X driver 18 corresponding to each color. The video / chroma processing circuit 16, the output circuit 17 corresponding to each color, the X driver 18, and the Y driver 19 are synchronized by the synchronization processing circuit 20 and the controller 21 corresponding to each color. It should be understood that the liquid crystal display element 9 used in this embodiment does not require the color filter 33 in the configuration shown in FIGS.

[0031]

As described above, according to the present invention, even if the aperture ratio, which is one of the main factors that deteriorates the light utilization efficiency of the liquid crystal display device, is poor (small), it is almost affected by the conventional technique. It is possible to provide a liquid crystal display device having a high apparent aperture ratio, that is, a liquid crystal display device having bright image information, and improving the parallelism of incident light rays to a liquid crystal surface to provide a liquid crystal display device having good contrast performance. it can.

[Brief description of drawings]

FIG. 1 is a sectional view of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is an external perspective view schematically showing the flat plate microlens array of FIG.

FIG. 3 is a partial cross-sectional view schematically showing the flat plate microlens array of FIG.

FIG. 4 is a cross-sectional view of an essential part of a liquid crystal display element according to a second embodiment of the present invention.

FIG. 5 is a configuration explanatory diagram of a liquid crystal display device and a projection type liquid crystal display device according to a first embodiment of the present invention using the liquid crystal display elements according to the first and second embodiments of the present invention.

FIG. 6 is a structural explanatory view of a liquid crystal display device according to a second embodiment of the present invention using the liquid crystal display element according to the first and second embodiments of the present invention.

FIG. 7 is a schematic cross-sectional view of a liquid crystal display device for explaining the problems of the prior art.

FIG. 8 is a schematic cross-sectional view of a liquid crystal display element for explaining the problems of the conventional technique.

[Explanation of symbols]

 1, 1 ... Flat plate microlens array, 1a, 1b ... Unit lens part, 2 ... Shading part, 3 ... Color filter, 4 ... Transparent electrode, 5 ... Liquid crystal, 6 ... Transparent substrate, 7 ... Switching element, 8 ... Polarizing plate , 9 ... Liquid crystal display element, 10 ... Incident light beam, 11 ... Outgoing light beam, 12 ... Light source, 13 ... Concave mirror, 14 ... Condenser lens group, 15 ... Diffuser plate, 16 ... Video / chroma processing circuit, 17 ... RGB output circuit , 18 ... X driver, 19 ... Y driver, 20 ... Synchronous processing circuit, 21 ... Controller, 22 ... Projection lens, 23 ... Screen, 24 ... Infrared cut filter, 25 ... Dichroic mirror, 26 ... Total reflection mirror, 27 ... B reflective surface, 28 ... R reflective surface, 29 ... Dichroic prism.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Taishi Yamazaki 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Ltd.

Claims (8)

[Claims] 1. A transmissive liquid crystal display device in which liquid crystal is injected between a pair of transparent substrates and the image information is displayed by the electro-optical effect of the liquid crystal, wherein a transparent substrate on the side on which a light beam emitted from a light source is incident. The flat plate microlens array (1) is formed, and the flat plate microlens array has microlenses having a positive refractive index and microlenses having a negative refractive index arranged on the optical axis, and each unit lens portion (1a) (1
A liquid crystal display device characterized in that b) is arranged in the same arrangement as the liquid crystal pixel arrangement. 2. A transmissive liquid crystal display device in which a liquid crystal is injected between a pair of transparent substrates to display image information by the electro-optical effect of the liquid crystal, wherein the transparent substrate on the side on which a light beam emitted from a light source is incident. The flat plate microlens array (1) is composed of a closely attached substrate, and the flat plate microlens array has a microlens having a positive refractive index and a microlens having a negative refractive index arranged on the optical axis. 2. The liquid crystal display device, wherein the unit lens portions (1a) and (1b) of (1) are arranged in the same arrangement as the liquid crystal pixel arrangement. 3. The flat plate microlens array (1) according to claim 1, wherein a refractive index N ₀ different from the refractive index N ₀ is incident on a side of a substrate having a refractive index N ₀ on which a light beam emitted from a light source is incident. _A binary matrix type refractive index distribution type in which a region ₁ is formed with periodicity and a region with a refractive index N ₂ different from the refractive indices N ₀ and N ₁ is formed on the output side with periodicity. A liquid crystal display device using a flat microlens array. 4. The refractive index N ₀ , N ₁ , N _{2 according to} claim 3.
Satisfying the following conditional expression: a liquid crystal display device. N ₁ ＞ N ₀ ＞ N ₂ ………………………… (1) 5. The flat plate microlens array (1) according to claim 1 or 2, wherein the flat plate microlens array (1) comprises a flat plate microlens array having a positive refractive index and a flat plate microlens array having a negative refractive index. Liquid crystal display device characterized by. 6. The flat microlens array (1) according to claim 5, wherein a region having a refractive index N ₁ different from said refractive index N ₀ is periodically formed in a substrate having a refractive index N _0.
A liquid crystal display device characterized by using a gradient index flat plate microlens array in the form of an original matrix. 7. A liquid crystal display device according to claim 1, which is used as a light valve, and is composed of at least the liquid crystal display device (9) and an illumination optical system. Liquid crystal display device. 8. A liquid crystal display element according to claim 1, which is used as a light valve, and which comprises at least the liquid crystal display element (9), an illumination optical system, and a projection optical system. A liquid crystal display device characterized by the above.