JP2001305518A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize good characteristics, such as high transmissivity and chromaticity, although a spherical lens of good productivity is used as a microlens. SOLUTION: In a display deice which is provided with a light source and a display panel with a transmissivity control layer where a pixel unit to control transmissivity is two-dimensionally placed, controls light intensity of a transmitted light by controlling the transmissvity of the display panel, projects, projects an emitted light from the display panel on a screen or a pupil and performs display by the transmitted light or reflected light of this screen, or a light intensity pattern being made incident from the pupil, a micro lens array formed with a plurality of lenses corresponding to the pixel unit of the display panel is provided between the light source and the display panel, the microlens consists of a high refractive index medium (refractive index n1) consisting of a spherical surface of a light-emitting surface convex, and a low refractive index medium (refractive index n2) formed in the emission surface side, and the refractive index difference is set to 0.25<n1-n2<0.42.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a display device,
For example, the present invention relates to a display device using a liquid crystal panel.

[0002]

2. Description of the Related Art In recent years, a projection type liquid crystal display device has attracted attention as a display device for displaying a large screen. A liquid crystal display device has a transmittance control layer made of liquid crystal. In the case of a projection type, a two-dimensional pattern of transmission / non-transmission is formed on a liquid crystal panel using a laser beam, or a thin film transistor or the like is used as a switch element. There is one that controls the transmittance control layer to form an electrically transparent / non-transparent two-dimensional pattern.

In particular, those using a liquid crystal panel which electrically forms a pattern are expected to be used for large-screen televisions because they can display moving images.

In a projection type liquid crystal device using a display panel which operates as a light valve such as a liquid crystal panel, when focusing attention on a color display, there are a three-panel type and a single-panel type.

[0005] Here, for example, an apparatus using a microlens of a single-plate type will be described. This device is simply as follows. First, each of the RGB of the light from the light source is replaced with one of the RGB.
The three mirrors, each reflecting only one, reflect at different angles. After that, RG is inserted into three openings in one pixel of the liquid crystal panel via the micro lens array.
Each light of B is separated, made incident and transmitted. As a result, a color image is formed.

[0006]

FIG. 6 shows the structure of a general microlens. First, the micro lens
Optical medium 602 having a convex or concave surface (convex surface in the figure)
A substrate 601 supporting the optical medium, an optical medium 603 having another refractive index in contact with the optical medium 602, and a medium 604 for condensing light from the microlens. Normal,
When used in a liquid crystal display device, the medium 604 is a glass substrate forming a liquid crystal panel.

[0007] A spherical surface is conceivable as the shape of the convex or concave surface which is most easily manufactured. This is the same as the case where the shape produced by the simplest movement is a sphere even when an ordinary glass lens is formed by polishing. That is, when the lens array is formed by etching, the most basic shape is a sphere. By adopting this shape, reproducibility in production can be improved. However, there is a problem with a lens using a spherical surface as described below.

[0008] Due to the problems of workability and stability required for optical media, the materials that can be used for these optical media are limited, and the range of refractive indexes that can be used is not very wide. In the configuration of FIG. 6, the focal length f of the lens is such that the radius of curvature of the interface is R, the refractive index of the convex sphere is n1, and
Assuming that the refractive index of 03 is n2 and the refractive index of the working substrate is n3,

(Equation 1) It is.

In order to shorten the focal length, the refractive index difference (n
1-n2) or the radius of curvature R needs to be reduced. As described above, the refractive index difference (n1-n
Since 2) cannot be made too large, the radius of curvature R is reduced. In order to focus on the pixel aperture, it is necessary to shorten the focal length. For this purpose, the microlens is a thick lens having a small radius of curvature R.

However, in a thick spherical lens, spherical aberration remarkably appears. FIG. 7 shows the state of spherical aberration.
In the figure, 701 is a microlens substrate, 702 is a microlens array, 703 is a counter substrate, 704 is a liquid crystal, 7
05 is an array substrate. In the case of a spherical lens, the focal length becomes shorter at the periphery of the lens. At the periphery, the focal length is too short, so that light cannot be sufficiently collected and the performance of the microlens is significantly reduced.

Therefore, the effect of improving the transmittance, which is the effect of the microlens, is reduced, and the image on the transmittance control layer is blurred, so that it is impossible to perform sufficient color separation.

The present invention has been made in view of the above,
It is an object of the present invention to provide a device having high transmittance and good characteristics such as chromaticity while using a microlens array of spherical lenses having good productivity.

[0013]

A first display device according to the present invention comprises a display panel having a transmittance control layer in which pixel units for controlling light transmittance are two-dimensionally arranged, and a pixel of the display panel. A high-refractive-index medium (refractive index n1) comprising a convex spherical surface on the exit surface; and a low-refractive-index medium formed on the exit surface side. (Refractive index n2), and the refractive index difference is set as 0.25 <(n1-n2) <0.42.

A second display device according to the present invention includes a light source and a display panel having a transmittance control layer in which pixel units for controlling the transmittance are arranged two-dimensionally, and the transmittance of the display panel is reduced. By controlling the light intensity of the transmitted light by controlling, the light emitted from the display panel is projected on a screen or a pupil, and the transmitted light or reflected light of the screen or the light intensity pattern incident from the pupil is used. In a display device that performs display, between the light source and the display panel,
A microlens array formed with a plurality of lenses corresponding to pixel units of the display panel, wherein the microlens is a high-refractive-index medium (refractive index: n
1) and a low-refractive index medium (refractive index n2) formed on the exit surface side, and the refractive index difference is set to be 0.25 <(n1-n2) <0.42. Be composed.

Considering the lens characteristics, the lower the refractive index of the low refractive index medium, the better. This is because the larger the refractive index difference (n1-n2), the larger the radius of curvature at the same focal length,
This is because the spherical aberration is reduced. Consider a case where a convex spherical surface is formed and bonded with a material of a low refractive index medium. Optical materials that can be molded include optical resins, glass, and the like, whose refractive index is at most 1.
About 6 is the maximum. Therefore, the lens characteristics are improved by reducing the refractive index on the low refractive index medium side.

The material having the lowest refractive index is gas or vacuum, and its refractive index is almost 1. However, if the refractive index is actually 1, the interface reflection is increased and the characteristics are degraded.

FIG. 8 shows the refractive index n1 = 1.59 of the medium constituting the spherical surface, which was obtained by an experiment independently performed by the inventor.
The refractive index n when the substrate refractive index n3 = 1.52 is used.
2 shows the relationship between 2 and the transmittance. From the original experimental results of the present inventor, the refractive index is 1.2 to 1.2 as compared with the case where the refractive index is 1.
It can be seen that the transmittance is higher in the case of 1.3. The transmittance is low because light is incident on a portion other than the transmission region. In this case, when the temperature of the liquid crystal panel rises or when it is used as a single-panel display device, color mixing or the like is caused. Therefore, the proportion of light that is not transmitted due to spherical aberration should be reduced as much as possible. When the efficiency is reduced by about 10% or less from the maximum efficiency (78% in FIG. 8), the influence of the characteristic deterioration is increased. Therefore,
It can be seen that the maximum allowable refractive index n2 is about 1.34. The refractive index difference at this time is (n1-n2)
= 0.25.

FIG. 9 shows the refractive index n2 and the magnitude of the interface reflection at both ends of the medium (surfaces in contact with n1 and n3) by (theoretical calculation).

As can be seen from this figure, as the refractive index n2 decreases, the reflectance sharply increases. As shown in FIG. 10, the reflection at the microlens portion causes the light reflected at the interface in the liquid crystal panel to be re-reflected at a position close to the light source again, resulting in irregularly-reflected light.
When a single-panel color display is performed, color mixing is caused.
Therefore, we want to keep it below a certain level. Assuming that the minimum condition is equal to or less than the interface reflection (4%) on a normal glass surface, this condition is 1.17 <n2 (refractive index). At this time, the refractive index difference (n1-n2) <0.42.

The inventor of the present invention has uniquely found that if the above conditions are satisfied, a sufficient light-collecting characteristic can be obtained even if a spherical lens is used, and a display device having good characteristics can be realized. In FIG. 10, 1000 is a microlens substrate, 1001 is a convex spherical lens, 1002 is a low refractive index medium, 1003 is a counter substrate, 1004 is a liquid crystal, 1005
Is an array substrate.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, as an embodiment of the present invention, a microlens array 218 and a liquid crystal panel (liquid crystal body) 21 will be described.
FIG. 1 shows the configurations of a lens array 9 formed by molding a resin, a lens array using a fluorine-based inert liquid, and a liquid crystal panel. FIG. 2 shows a single-panel display device as a configuration example of the entire device using the device of FIG.

In FIG. 2, a metal halide lamp 210 is used as a light source. Behind the lamp 210, an elliptical reflector 211 as a reflecting mirror is arranged. A conical lens 212 for adjusting the angle of the light,
3, a filter 214 for cutting off infrared rays and ultraviolet rays, and a condenser lens 215 are provided. Further, a color separation mirror 216 composed of three dichroic mirrors is provided in front of the lens 215. A microlens array 218 and a liquid crystal panel (liquid crystal body) 219 are provided between the pair of polarizing plates 217 and 220 in the traveling direction of the reflected light from the mirror 216. Further, a field lens 221 and a projection lens 222 are provided in front of this.

Next, the optical operation of the display device will be described.

The light of the metal hide lamp 210 is condensed by the spheroidal reflector 211 at a position immediately before the conical lens 212. The conical lens 212 makes it easier to obtain parallel light by bending the exit angle of the collected light toward the optical axis.

The light emitted from the conical lens 212 passes through the stop 2
13 The aperture 213 is used to obtain a predetermined angular distribution, which will be described later, since the angular distribution of light obtained on the exit side of the condenser lens is determined by the area of the exit surface and the focal length of the condenser lens 215. .

Light emitted from the stop 213 is incident on the condenser lens 215 after unnecessary invisible light is removed by the infrared and ultraviolet cut filter 214.

When the condenser lens 215 is made of a normal glass spherical lens, it becomes a thick lens having a large spherical aberration. Therefore, the weight of the Fresnel lens is reduced and the aberration is reduced.

The light which has become substantially parallel light by the condenser lens is converted into three dichroic mirrors 216 (216R, 216R).
216G, 216B). The characteristics of the three dichroic mirrors 216 are as shown in FIG. 4, for example.

That is, each of these three images is 216
R, 216G, and 216B, 216R reflects only red light, that is, R light in visible light, and 216R similarly.
G reflects green light, that is, G light, and 216B reflects only blue light, that is, B light. These three sheets are arranged at different inclinations as shown in FIG. 4 and function to angularly separate the three colors in the horizontal direction of the liquid crystal panel.

The light that has been angle-separated into three colors as described above is polarized by the polarizing plate 217 and then enters the microlens array 218 and the liquid crystal panel 219.

The relationship between the micro lens array 218 and the liquid crystal panel 219 is as shown in FIG. FIG.
In relation to the microlens array 218 and a part of the horizontal cross section of the liquid crystal panel 219, the state of light incident on one microlens 501 is shown. That is, light R, G, and B of three primary colors that are angle-separated into one imaging element in the microlens array 218 that is an imaging element array.
Is incident. Due to this angle difference, one of the liquid crystal panels 219 is interposed via the light incident side substrate 502 constituting the liquid crystal panel.
Light beams are separately incident on three color openings in the pixel.

At this time, the thickness t of the substrate 502 on the light incident side, the refractive index n, the pixel pitch Ppixel and the Plens of the imaging element are approximately as follows with respect to the angle difference Δθ between the three colors of incident light. In a relationship.

[0033]

(Equation 2) In FIG. 5, reference numeral 504 denotes a light-emitting side substrate.

The color-separated light passes through an opening of an appropriate color and passes through the polarizing plate 220 on the emission side to form a color image. The color image is formed on the screen by the field lens 221 and the projection lens 222. Is enlarged and projected, and a large screen is displayed.

Next, the micro lens array and the liquid crystal panel of FIG. 1 will be described.

In the present embodiment, a microlens is used in which convex spherical lenses 102 are arranged in an array on a glass substrate (microlens substrate) 101 using a photocurable epoxy resin. The lens formation pitch is 84 μm in the horizontal direction and 71 μm in the vertical direction on the paper. The radius of curvature of the multiple lenses of the convex spherical lens 102 is about 85 μm. Also, the refractive index n1 of this photocurable epoxy resin
Is n1 = 1.59.

A fluorine-based inert liquid (a medium having a low refractive index) is provided between the microlens and the opposing substrate 104 of the liquid crystal panel.
103 (trade name: Fluorinert FC-70). The refractive index n2 of the inert liquid 103 is n2 =
1.30. As the inert liquid 103, a light or thermosetting liquid can be adopted, and at this time, it also serves as an adhesive. This low refractive index medium 1
03 is not limited to a liquid, but may be a solid, for example.

The opposing substrate 104 of the liquid crystal panel is made of non-alkali glass (trade name: Corning 1739) and has a thickness of 380 μm. The refractive index n3 is
n3 = 1.52. Therefore, the paraxial focal length of the microlens is approximately 450 μm. Therefore, the focal point of the incident light is about 20% of the thickness of the counter substrate 104 on the emission side. This gives the paraxial focal length,
This is because by setting about 20% farther than the pattern surface of the array substrate 106 (that is, the position of the liquid crystal layer 105), the focal length is effectively shortened due to the spherical aberration of the microlens. At this focal length, the best characteristics can be obtained.

When the microlens and the liquid crystal panel shown in FIG. 1 are incorporated in the projection display apparatus shown in FIG. 2 and operated, the transmittance of the liquid crystal panel is 61% despite the use of the spherical lens. High efficiency was obtained. Also, the color separation characteristics are good, and the color mixture between pixels due to leak light is 0.3%.
(Below the measurement limit).

In the present invention, a fluorine-based inert liquid is used as the low refractive index medium. However, as long as the medium has the same refractive index, other liquids or solids may impair the gist of the present invention. is not.

However, since a liquid having a low refractive index can be realized more easily than a solid, and if a liquid is used, it is desirable that the liquid be more inert because of its reliability. Is a very suitable material and is preferred as an optical medium for realizing the present invention. In addition, other materials such as Fomblin (trade name) and Galden (trade name) can be used as the low refractive index medium.

As can be seen from the above description,
The application of the present invention includes, in addition to the above-described display device, another display device, that is, a light source and a display panel having a transmittance control layer in which pixel units for controlling transmittance are arranged two-dimensionally,
Controlling the light intensity of transmitted light by controlling the transmittance of the display panel, projecting the emitted light to the screen or pupil,
The present invention can be applied to a display device that performs display using transmitted light or reflected light from a screen or a light intensity pattern incident from a pupil.

[0043]

As described above, according to the present invention, it is possible to configure a display device having high transmittance and good characteristics such as chromaticity while using a lens array composed of spherical lenses having good productivity. Can be. Therefore, a high-performance display device at low cost can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a micro lens and a liquid crystal panel of a projection type color liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a projection display device that performs color display using a plurality of dichroic mirrors having different arrangement angles from microlenses.

FIG. 3 is a diagram showing reflection characteristics of a dichroic mirror in a projection type color liquid crystal display device.

FIG. 4 is a diagram showing an arrangement of dichroic mirrors in a projection type color liquid crystal display device according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating a relationship between a microlens and a pixel in a projection display device that performs color display using a plurality of dichroic mirrors having different arrangement angles from the microlens.

FIG. 6 is a diagram showing a configuration of a micro lens.

FIG. 7 is a diagram showing spherical aberration in a microlens using a spherical surface.

FIG. 8 is a diagram showing the relationship between transmission efficiency and the refractive index of an optical medium.

FIG. 9 is a diagram showing the relationship between the interface reflectance and the refractive index of the optical medium.

FIG. 10 is a diagram illustrating an optical path of return light based on interface reflectance.

[Explanation of symbols]

Reference Signs List 101 Micro lens substrate 102 Convex spherical lens 103 Low refractive index 104 Opposite substrate 105, 219 Liquid crystal panel 106 Array substrate 210 Metal halide lamp 211 Elliptical reflector 212 Conical lens 213 Aperture 214 Filter for cutting infrared and ultraviolet rays 215 Condenser lens 216 Three dichroic Color separation mirror 217 composed of mirror 217 Incident side polarizing plate 218 Micro lens array 220 Outgoing side polarizing plate 221 Field lens 222 Projection lens

Claims (3)

[Claims] 1. A display panel having a transmittance control layer in which pixel units for controlling light transmittance are two-dimensionally arranged, and a microlens array formed with a plurality of lenses corresponding to the pixel units of the display panel. A high-refractive-index medium (refractive index n1) comprising a spherical surface having a convex exit surface;
Low refractive index medium (refractive index n2) formed on the exit surface side
And a refractive index difference is set to be 0.25 <(n1-n2) <0.42. 2. A light source and a display panel having a transmittance control layer in which pixel units for controlling transmittance are arranged two-dimensionally, and the transmittance of the display panel is controlled by controlling the transmittance of the display panel. A display device that performs intensity control, projects light emitted from the display panel onto a screen or a pupil, and performs display according to a transmitted light or reflected light of the screen, or a light intensity pattern incident from the pupil; A microlens array having a plurality of lenses corresponding to pixel units of the display panel between the light source and the display panel, wherein the microlens is a high-refractive-index medium (refractive index) formed of a spherical surface having a convex exit surface; n1) and a low-refractive index medium (refractive index n2) formed on the exit surface side, and the refractive index difference is set to be 0.25 <(n1-n2) <0.42. Special And the display device. 3. The low-refractive-index medium formed on the exit surface side of the microlens has a refractive index n2 set to 1.17 <n2 <1.37. Display device.