JP2004226607A - Photorefractive element array substrate and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photorefractive element array substrate which is suitable for an image display device having bright and superior display quality. <P>SOLUTION: A photorefractive element array substrate 6 is provided with a first photorefractvie element array 2 which is provided with two dimensionally arranged first photorefractive elements 2a and a second photorefractive element array 4 which is provided with second photorefractive elements 4a that are arranged in a two dimensional manner so as to correspond to the elements 2a in a 1:1 manner and a transparent substrate 5 in the above order from a light beam incident side. The converging position of the light beams which are passed through the elements 2a and 4a is located in the vicinity of the light emitting side surface of the transparent substrate 5. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a photorefractive element array substrate (for example, a microlens array substrate) having two-dimensionally arranged photorefractive elements (for example, lenses and prisms) and an image display device including the same.
[0002]
[Prior art]
In general, a non-light-emitting image display device changes the light transmittance (or reflectivity) of a plurality of pixels by a drive signal, modulates the intensity of light applied to an image display element (display panel), and displays an image. And display characters. Such an image display device has a direct-view mode (direct-view image display device) and a projection mode in which images and characters are enlarged and projected on a screen by a projection optical system (a so-called projector (projection image display device)).
[0003]
2. Description of the Related Art A projector (including a front type and a rear type) has a single-panel system using a color display panel in which red, green, and blue (hereinafter, referred to as R, G, and B) color filters are arranged on an image display element to be used. And a three-panel type using three display panels for monochrome display.
[0004]
Non-luminous image display devices include liquid crystal display devices, electrochromic display devices, and electrophoretic display devices. Among them, liquid crystal display devices are widely used, for example, in monitors, portable information terminals, mobile phones, and projectors. ing.
[0005]
The liquid crystal display element changes the optical characteristics of the liquid crystal layer of the pixel portion by applying a driving voltage corresponding to an image signal to pixel electrodes arranged regularly in a matrix, and displays an image, a character, or the like. It is configured as follows. As a method of applying an independent drive voltage to the pixel electrodes described above, there are a simple matrix method and an active matrix method in which a non-linear two-terminal element or a three-terminal element is provided in a liquid crystal display element.
[0006]
In the case of the latter active matrix system, a switching element such as an MIM (metal-insulator-metal) element or a TFT (thin film transistor) element and a wiring for supplying a driving voltage to a pixel electrode are provided. When strong light is incident on this switching element, the element resistance in the OFF state is reduced, and not only the charge charged when a voltage is applied is discharged, but also the liquid crystal layer existing in the area where the switching element and the wiring are formed has a regular drive. Since no voltage is applied and the original display operation is not performed, for example, there is a problem that light leakage occurs in a black display state and a display contrast ratio is reduced.
[0007]
Therefore, for example, in a transmissive liquid crystal display element, in order to block light incident on the above-described region, the liquid crystal display element is arranged to face the TFT substrate via a liquid crystal layer and a TFT substrate provided with a switching element and a pixel electrode. A light shielding layer called a black matrix is provided on the opposite substrate. Therefore, in the case of a transmissive liquid crystal display element, since the light is also shielded by the black matrix in addition to the light-shielding TFT, gate bus line and source bus line, the effective pixel portion occupying the pixel section , That is, the aperture ratio is reduced.
[0008]
Further, it is difficult to form these switching elements and wiring electrodes in a size smaller than a certain size due to restrictions on electrical performance and manufacturing technology. Therefore, as the resolution of the liquid crystal display element becomes higher and smaller, the aperture ratio further decreases as the pitch of the pixel electrodes becomes smaller.
[0009]
As the aperture ratio decreases, the amount of light transmitted through the liquid crystal display element decreases, so that a liquid crystal projector that enlarges and projects a small panel on a large screen becomes insufficient in brightness. In particular, in a single-panel projector, brightness is significantly reduced due to light absorption by a color filter.
[0010]
As one method for solving this problem, a method has been put to practical use in which light is focused on individual pixel portions of a liquid crystal display element and a microlens for improving an effective aperture ratio of the liquid crystal display element is provided.
[0011]
In Patent Document 1, white light is made incident on a dichroic mirror arranged in a fan shape, divided into R, G, and B color light fluxes, and each color light flux is applied to a microlens arranged on a light source side of a liquid crystal display element. A method is disclosed in which light beams are incident at different angles and light beams of a predetermined color are condensed on pixels corresponding to each color. By employing this method, it is possible to eliminate the light absorption by the color filter in addition to the effect of improving the effective aperture ratio by the microlens.
[0012]
Further, Patent Document 2 discloses that a microlens has a two-layer structure, R, G, and B light is made incident on a corresponding pixel section by a first microlens, and R, G, and B are made by a second microlens array. A method has been disclosed in which the principal ray of the light is collimated to reduce the amount of light kicked by the projection lens, thereby further increasing the brightness.
[0013]
Most of these microlenses are formed in a counter substrate of a liquid crystal display element, and have a structure sandwiched between two glass plates, between a glass plate and a resin layer or between two types of resin layers. The light is refracted in between to obtain a light-collecting effect.
[0014]
With reference to FIGS. 9 (a) and 9 (b), two typical methods for manufacturing a conventional counter substrate having microlenses will be described.
[0015]
In the first manufacturing method, an opposing substrate including a microlens array is manufactured by the steps schematically shown in FIG.
[0016]
(1) Pattern the photoresist layer on the glass substrate. {Circle around (2)} The patterned resist layer is heated to cause heat dripping to form a resist layer having a microlens shape. {Circle over (3)} The microlens array substrate is obtained by dry-etching the glass substrate together with the microlens-shaped resist layer to form the shape of the resist layer on the glass substrate (etchback). (4) A cover glass is adhered to the obtained microlens array substrate via an adhesive layer, and the surface of the cover glass is polished to obtain a counter substrate. Note that an electrode, an alignment film, and the like are formed as necessary.
[0017]
In the second manufacturing method, an opposing substrate provided with a microlens array is manufactured by the steps schematically shown in FIG.
[0018]
(1) The photoresist layer on the glass substrate is patterned by, for example, electron beam exposure to form a resist layer having a shape of a microlens. This is the master (original). (2) Using a master, a metal stamper is produced by, for example, a plating method. (3) The shape of the microlens is transferred to a glass substrate using a metal stamper to obtain a microlens array substrate. (4) A cover glass is adhered to the obtained microlens array substrate via an adhesive layer, and the surface of the cover glass is polished to obtain a counter substrate.
[0019]
[Patent Document 1]
JP-A-4-60538
[Patent Document 2]
JP-A-7-181487
[0020]
[Problems to be solved by the invention]
However, the microlens array substrate having a two-layer structure disclosed in Patent Document 2 has the following problems.
[0021]
As described with reference to FIGS. 9A and 9B, the normal microlens array substrate has a structure in which a microlens is formed on a glass substrate and a cover glass is attached thereto, that is, two microlenses are provided. Has a structure sandwiched between glass substrates. The thickness of this cover glass is about 30 μm for a normal one-layer microlens array substrate.
[0022]
On the other hand, in a microlens array substrate having a two-layer structure as disclosed in Patent Document 2, the thickness of the cover glass (disposed on the light emission side) needs to be much smaller than 30 μm. The reason will be described below.
[0023]
In the microlens array substrate of Patent Document 2, microlenses having the same focal length have a two-layer structure from the viewpoint of brightness. Therefore, in order for the light condensing position (converging position) of the first microlens to be in the vicinity of the liquid crystal layer, it is necessary to configure the liquid crystal layer to come immediately after the second microlens array. It is necessary to extremely reduce the thickness of the cover glass disposed between the microlens array and the liquid crystal layer.
[0024]
However, it is very difficult to make the thickness of the cover glass extremely thin. The thickness of the cover glass is as thin as about 30 μm, even for a conventional one-layered microlens array substrate, so that a glass plate (cover glass) that is sufficiently thick for the desired thickness is usually used for the microlens. It is manufactured by polishing to a desired thickness after bonding to the surface.
[0025]
Even if a high-grade glass plate is used, the thickness of the glass plate has a variation of about ± 5 μm. Further, the polishing of the glass plate is not performed while checking the thickness of the cover glass itself, but the total thickness from the surface of the cover glass to the base glass plate on which the first microlenses are formed is a predetermined thickness. When the thickness of the base glass plate on which the first microlenses are formed varies, the polishing amount of the cover glass varies accordingly.
[0026]
In a two-layer microlens array substrate, an intermediate glass plate is arranged between the first microlens array and the second microlens array. This intermediate glass also has the same variation as the base glass plate, but like the cover glass described above, the intermediate glass plate is also bonded to the substrate on which the first microlens is formed, and then has a total thickness of the desired thickness. Therefore, the variation of the total thickness of the substrate obtained by polishing the intermediate glass plate is only the variation of the base glass plate.
[0027]
When the cover glass of the microlens having a two-layer structure disclosed in Patent Document 2 is extremely thinned by using such a manufacturing method, the cover glass may be entirely removed due to a variation in the thickness of the base glass plate (about ± 5 μm). Polishing may damage the second microlens array. If the thickness of the cover glass is set to 5 μm or more to prevent this, the convergence position of the luminous flux cannot be set near the liquid crystal layer, that is, near the light exit side surface of the cover glass.
[0028]
As a method of thinning the cover glass, a method of etching the glass can be considered. However, even with this method, a variation in an etching amount of about ± 5 μm to 10 μm occurs, and thus the same problem as described above occurs.
[0029]
In order to solve the above problem, it is conceivable to form a transparent electrode or an alignment film directly on the resin layer forming the microlenses without using a transparent substrate such as a cover glass. However, this is not preferable because of the following problems.
[0030]
Transparent electrodes are easy to form on inorganic materials such as glass, but are difficult to form on organic materials such as resin, resulting in deterioration of film quality, uneven film thickness and cracks (phenomenon of cracking in film). May occur. In addition, organic substances and the like are eluted into the liquid crystal layer from the resin layer or decomposed to generate gas, which adversely affects the liquid crystal material, lowering the voltage holding ratio, generating display unevenness, or lowering the reliability. May be invited.
[0031]
Here, the problem of the conventional microlens array substrate having a two-layer structure has been described using a liquid crystal display element as an example. However, the above problem is not limited to the liquid crystal display element. This is a problem common to microlens array substrates used for light-emitting display elements. In addition, the same problem is not limited to the microlens array substrate, but also to other photorefractive element array substrates in which photorefractive elements are two-dimensionally arranged (for example, a microprism array substrate).
[0032]
The present invention has been made in view of the above points, and an object thereof is to provide an image display device which is bright and has excellent display quality, and a photorefractive element array suitably used for such an image display device. It is to provide a substrate.
[0033]
[Means for Solving the Problems]
A photorefractive element array substrate according to the present invention corresponds to a first photorefractive element array having a plurality of first photorefractive elements arranged two-dimensionally, each of which corresponds to the plurality of first photorefractive elements in a 1: 1 relationship. A second light refraction element array having a plurality of second light refraction elements arranged two-dimensionally as described above, and a transparent substrate in this order from the light incident side, wherein the plurality of first light refraction elements and the plurality The convergence position of the light beam that has passed through the second light refraction element is located near the light emission side surface of the transparent substrate, thereby achieving the above object.
[0034]
It is preferable that the relationship of f1> f2 is established between the focal lengths f1 of the plurality of first light refraction elements and the focal lengths f2 of the plurality of second light refraction elements.
[0035]
In one embodiment, each of the plurality of first photorefractive elements is a microlens. Preferably, the micro lens is an aspheric lens.
[0036]
In one embodiment, each of the plurality of second photorefractive elements is a microlens.
[0037]
In one embodiment, each of the plurality of second light refracting elements is a microprism having a plurality of slopes.
[0038]
The thickness of the transparent substrate is preferably 30 μm or less. More preferably, the thickness of the transparent substrate is 5 μm or more and 25 μm or less.
[0039]
In one embodiment, the transparent substrate is a glass substrate.
[0040]
An image display device of the present invention includes any one of the above-described photorefractive element array substrates, a display medium layer provided on the transparent substrate side of the photorefractive element array substrate, and the light refraction via the display medium layer. And a further transparent substrate opposed to the element array substrate. In one embodiment, the image display device is a liquid crystal display device having a liquid crystal layer as the display medium layer.
[0041]
An image display device according to the present invention includes a light source, a color separation element that divides a light beam from the light source into a plurality of color light beams having different wavelength ranges, and a plurality of two-dimensionally arranged by being irradiated with the plurality of color light beams. A display medium layer having a pixel portion, a first light refraction element array provided on the light incident side of the display medium layer, and a first light refraction element array provided between the first light refraction element array and the display medium layer. An image display device comprising a two-light refractive element array, wherein the first light refractive element array has a plurality of first light refractive elements arranged two-dimensionally, and the second light refractive element arrays are Are provided two-dimensionally so as to correspond to the plurality of first light refraction elements in a one-to-one correspondence, and provided between the second light refraction element array and the display medium layer. A plurality of first photorefractive elements and a transparent substrate The convergence position of the plurality of color luminous fluxes that have passed through the plurality of second light refraction elements is located near the surface of the plurality of pixel portions on the side of the second light refraction element. Is achieved.
[0042]
It is preferable that the relationship of f1> f2 is established between the focal lengths f1 of the plurality of first light refraction elements and the focal lengths f2 of the plurality of second light refraction elements.
[0043]
In one embodiment, each of the plurality of first photorefractive elements is a microlens. Preferably, the micro lens is an aspheric lens.
[0044]
In one embodiment, each of the plurality of second photorefractive elements is a microlens.
[0045]
In one embodiment, each of the plurality of second light refracting elements is a microprism having a plurality of inclined surfaces.
[0046]
The thickness of the transparent substrate is preferably 30 μm or less. More preferably, the thickness of the transparent substrate is 5 μm or more and 25 μm or less.
[0047]
In one embodiment, the transparent substrate is a glass substrate.
[0048]
An image display device according to one embodiment is a liquid crystal projector having a liquid crystal layer as the display medium layer, and further including a projection optical system on a light emission side of the display medium layer.
[0049]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the configuration and operation of a photorefractive element array substrate, an image display device including the same, and an image display device according to an embodiment of the present invention will be described with reference to the drawings. In the following description, a liquid crystal display element is exemplified as an image display element, and a liquid crystal projector is exemplified as an image display device, but the present invention is not limited to these.
[0050]
First, the configuration and function of a microlens array substrate 6 having a microlens as a light refracting element according to an embodiment of the present invention will be described with reference to FIGS.
[0051]
The microlens array substrate 6 includes a first microlens array 2 having two-dimensionally arranged first microlenses 2a, and a second microlens array two-dimensionally arranged so as to correspond to the first microlenses 2a in a one-to-one correspondence. A second microlens array 4 having microlenses 4a and a cover glass 5 are provided in this order from the light incident side. The convergence position of the light beam that has passed through the first micro lens 2a and the second micro lens 4a is located near the light emission side surface of the cover glass 5.
[0052]
An intermediate glass plate 3 is provided between the first micro lens array 2 and the second micro lens array, and the first micro lens array 2 is bonded between the base substrate 1 and the intermediate glass substrate 3. The second microlens array 4 is fixed by an adhesive layer 8 between the intermediate glass substrate 3 and the cover glass 5.
[0053]
As shown in FIGS. 1A and 1B, the light beam transmitted through the microlens array substrate 6 is configured to be converged near the surface on the light emission side of the cover glass 5. Unlike the two-layered microlens array substrate disclosed in Document 2, it is not necessary to make the cover glass extremely thin. For example, a cover glass 5 having a thickness d of 5 μm or more can be used. Therefore, when the cover glass 5 is manufactured, even if the method of polishing the glass substrate is employed as described in the section of the related art, it is possible to prevent the second microlens array from being damaged.
[0054]
Such a configuration can be specifically realized as follows, for example.
[0055]
The focal length f1 of the first microlens 2a having the function of condensing the light beam is set to the focal length of the second microlens array 4a having the function of making the principal rays of the light beam from the corresponding first microlens 2a parallel to each other. It is set longer than f2 (f1> f2). More specifically, the focal point of the first microlens 2a is set near the light exit side surface of the cover glass 5, and the focal point of the second microlens 4a is set near the first microlens 2a. By doing so, the convergence position of the light beam can be set near the light emission side surface of the cover glass 5, and the principal ray of the light beam that has passed through the first micro lens 2a can be collimated by the second micro lens 4a. That is, the R, G, and B color light fluxes incident on the first microlens 2a at different angles are condensed by the first microlens 2a (FIG. 1B shows only the principal ray of each color light flux). ), The principal rays of the respective color luminous fluxes incident on the second micro lens 4a at different angles are made substantially parallel to each other.
[0056]
On the other hand, if a microlens array substrate 76 having a two-layer structure as schematically shown in FIGS. 10A and 10B and disclosed in Patent Document 2, the following problem occurs. I do.
[0057]
The microlens array base 76 is two-dimensionally arranged so as to correspond to the base substrate 71, the first microlens array 72 having the first microlenses 72a, the intermediate glass plate 73, and the first microlenses 72a in a one-to-one correspondence. And a cover glass 75 in this order from the light incident side.
[0058]
In the microlens array substrate 76, the focal length of the first microlenses 72a and the focal length of the second microlenses 74a are set to be equal to each other. As shown in ()), the light is converged near the second microlens array 4 when the cover glass 75 is disposed on the surface of the second microlens array 4 since the cover glass 75 is disposed near the second microlens array 4. The light diverges on the light emission side surface of the cover glass 75. That is, since the light collection efficiency of the microlens array substrate 76 is reduced, it is desired that the cover glass 75 be made as thin as possible. However, as described above, it is practically difficult to polish the cover glass to a thickness of less than 5 μm.
[0059]
Further, in order to set the light condensing position near the light emission side surface of the cover glass 75, a microlens array substrate 76 'having an intermediate glass substrate 73' thinner than the intermediate glass plate 73 of the microlens array substrate 76 is configured. Then, as shown in FIG. 10B, the principal rays of the light beam emitted from the second micro lens 74a are not parallel to each other.
[0060]
That is, in the microlens array substrate 6 of the embodiment according to the present invention, the convergence position of the light beam that has passed through the first microlens 2a and the second microlens 4a is close to the light exit side surface of the transparent substrate (cover glass) 5. Therefore, even if the thickness of the transparent substrate 5 is about 30 μm, a higher light-collecting efficiency than before can be obtained, and the principal rays of the emitted light beam can be made parallel to each other. .
[0061]
FIG. 2 shows the shapes of the first micro lens 2a and the second micro lens 4a and the two-dimensional arrangement of the micro lenses 2a and 4a in the arrays 2 and 4, respectively.
[0062]
As shown in FIG. 2, the first microlens 2a and the second microlens 4a are arranged in a one-to-one correspondence with each other, and the center of each of the first microlenses 2a and the second microlens 4a are arranged. They are arranged so that their centers coincide. Here, the centers of the respective microlenses are arranged so as to correspond to so-called delta-arranged pixels. Although a description will be given of a microlens corresponding to a liquid crystal display element having a delta arrangement, it is needless to say that a microlens corresponding to a stripe arrangement can be similarly manufactured.
[0063]
Since the first micro lens 2a has a function of condensing light, it is preferable to use an aspheric lens. When the first microlens 2a has an aberration, not only does the light collection efficiency decrease, but also when used in an image display device, the color mixture due to the aberration of the first microlens 2a increases and the color purity decreases. By making the first microlens 2a aspherical, it is possible to reduce aberrations that cause the reduction in brightness and color purity.
[0064]
The outer shape of the first microlens 2a (the shape viewed from the normal direction of the plane defined by the plurality of two-dimensionally arranged first microlenses 2a (the normal direction of the base substrate 1)) is a hexagon. . The reason why the first microlens 2a is hexagonal is that the size (diameter) of one microlens itself is smaller than the rectangular shape as the second microlens 4a, and the condensing angle by the microlens is smaller. Because it becomes. If the converging angle of the first microlens 2a is large, even if the light passes through the liquid crystal panel, more light is kicked by the projection lens, and the brightness is undesirably lost.
[0065]
Since the second microlenses 4a function to make the principal rays of the light beams from the corresponding first microlenses 2a parallel to each other, the outer shape is a horizontally long rectangle having a shape different from that of the first microlenses 2a. This allows the R, G, and B light beams to pass through the corresponding pixel openings, and efficiently collimates the principal rays of the light beams.
[0066]
Here, an example is shown in which the first microlens 2a and the second microlens 4a are configured by microlenses having different shapes, but the first microlens 2a may have the same shape as the second microlens 4a.
[0067]
The microlens array substrate of the embodiment according to the present invention is suitably used for a liquid crystal display device of a liquid crystal projector. FIG. 3 schematically shows a configuration of a typical liquid crystal projector 300.
[0068]
The liquid crystal projector 300 includes a light source 301, a dichroic mirror 306 as a color separation element that divides a light beam from the light source 301 into a plurality of color light beams having wavelength ranges different from each other, a display medium layer, and a microscopic device according to an embodiment of the present invention. The liquid crystal display device 307 includes a lens array substrate, and a projection lens 308 that projects light transmitted through the liquid crystal display device 307. The liquid crystal display element 307 has a microlens array substrate on the light incident side of the display medium layer.
[0069]
As the light source 301, for example, a UHP lamp (for example, manufactured by Philips) having a power of 120 W and an arc length of 1.4 mm is used. In addition, a halogen lamp, a xenon lamp, a metal halide lamp, or the like can be used.
[0070]
The light from the light source 301 is converted into substantially parallel light by a parabolic mirror 302, passes through a fly-eye lens 303 and field lenses 304 and 305, and then enters three dichroic mirrors 306 arranged in a fan shape. . After the incident light is separated into R, G, and B color light beams by the three dichroic mirrors 306, the respective color light beams are made incident on one liquid crystal display element (panel) 307 at predetermined different angles. As will be described later, each color light beam enters a corresponding pixel (R pixel, G pixel, B pixel) of the liquid crystal display element 307 and is modulated by the display medium layer. An image formed by the color light flux modulated by the liquid crystal display element 307 is projected and displayed on, for example, a screen (not shown) by the projection lens 308. As the liquid crystal display element 307, various types can be used.
[0071]
The configuration of the liquid crystal display element 40 suitably used as the liquid crystal display element 307 will be described with reference to FIGS. 4 and 5A and 5B.
[0072]
The liquid crystal display element 40 has a microlens array substrate 16 arranged on the light incident side, a liquid crystal layer 19, and a substrate (for example, a TFT substrate) 22. On the liquid crystal layer 19 side of the microlens array substrate 16 and / or the substrate 22, an electrode (not shown) for applying a predetermined voltage to each pixel portion 19 a of the liquid crystal layer 19 and, if necessary, an alignment film ( (Not shown). As the liquid crystal display element 40, various modes of liquid crystal display elements can be used, and TN mode, MVA mode, and IPS mode liquid crystal display elements can be suitably used. The liquid crystal display element of these display modes further includes a pair of polarizing plates (typically disposed before and after the panel) and, if necessary, a retardation plate (for example, disposed on the light emission side of the panel). (All not shown).
[0073]
The microlens array substrate 16 includes a first microlens array 12 having two-dimensionally arranged first microlenses 12a, and a second microlens array two-dimensionally arranged so as to correspond to the first microlenses 12a in a one-to-one correspondence. A second microlens array 14 having microlenses 14a and a cover glass 15 are provided in this order from the light incident side. The convergence position of the light beam that has passed through the first micro lens 12a and the second micro lens 14a is located near the light emission side surface of the cover glass 15, as shown in FIG.
[0074]
For example, the liquid crystal display element 40 has, for example, pixels in a delta arrangement with a pixel pitch of 21 μm × 21 μm, and each of the first micro lens 12 a and the second micro lens 14 a has three pixel portions (R, G And B pixel portions) 19a. The R, G, and B color luminous fluxes separated by the dichroic mirror 306 are condensed by the microlenses 12a and 14a, and the principal rays of the respective color luminous fluxes are collimated and enter the corresponding pixel portions 19a. (See FIG. 5A).
[0075]
The thickness of the cover glass 15 is set to, for example, 10 μm. Since the convergence position of the light beams by the microlens arrays 12 and 14 is set in the vicinity of the light emission side surface of the cover glass 15, even if the cover glass 15 has a thickness of 10 μm, the divergence as in the related art (for example, Since high light-collecting efficiency can be obtained without the need of FIG. 10A, sufficient brightness can be obtained. In addition, since the respective color light beams can be sufficiently collimated, a decrease in color purity (for example, FIG. 10B) unlike the related art does not occur.
[0076]
In addition, since the light beams emitted from the microlens array substrate 16 have high parallelism, the principal rays of the respective color light beams enter the liquid crystal layer 19 almost perpendicularly. Therefore, an image can be displayed with a high contrast ratio without being affected by a decrease in the contrast ratio due to the viewing angle dependency (incident angle dependency) of the liquid crystal display element 40. In addition, as described later, the thickness of the cover glass 15 is preferably 25 μm or less from the viewpoint of light-collecting efficiency, and is preferably 5 μm or more from the viewpoint of manufacturing efficiency.
[0077]
The above-described microlens array substrate 16 can be manufactured, for example, by the following method.
[0078]
First, a first microlens array 12 is formed on a base substrate (for example, 700 μm in thickness) 11 made of glass, and a second microlens array 14 is formed via an intermediate glass plate 13.
[0079]
The pitches of the microlens arrays 12 and 14 are both 63 (H) × 21 (V), and the first microlenses 12a and the second microlenses 14a have a 1: 1 correspondence.
[0080]
As a method for forming the first and second microlens arrays 12 and 14, for example, as shown in FIG. 9B, (1) pattern a photoresist, (2) prepare a master, and (2) (3) A metal stamper is manufactured using a master, and (3) a microlens array is transferred onto a glass substrate using the metal stamper. The method is not limited to this method, and known methods such as an ion exchange method, a swelling method, a heat dripping method, a vapor deposition method, a thermal transfer method, and a machining method can be widely used. In particular, recently, a method of exposing a resist using a mask (gray scale mask) having shading corresponding to the shape of a microlens to obtain a pattern having a desired shape has been put to practical use. This method has an advantage that a microlens having an arbitrary shape can be accurately manufactured.
[0081]
The cover glass 15 provided on the light emission side of the second microlens array 14 is formed by bonding to a substrate on which the second microlens array 14 is formed on thick glass (for example, 500 μm), and then polishing to 10 μm. Is done. As the glass substrate for the base substrate 11 and the cover glass 15, it is preferable to use a general glass substrate for a liquid crystal panel having a thickness in the range of 500 μm to 1100 μm.
[0082]
The reason for setting the thickness of the cover glass 15 to 10 μm is that the thickness of the cover glass 15 is in the range of 5 μm to 15 μm even if there is a variation of ± 5 μm because the base substrate plate 11 has a thickness variation of ± 5 μm. Therefore, the cover glass 15 is not damaged by polishing the cover glass 15 so that the cover glass 15 remains on the second micro lens array 14, and at the same time, the thickness of the cover glass 15 is at most 15 μm. Therefore, there is no reduction in effective light use efficiency.
[0083]
Here, the thickness of the cover glass 15 is set to 10 μm. However, if the thickness is in the range of 5 μm or more and 25 μm or less, the second micro lens array 14 is polished or etched by polishing or etching while suppressing a decrease in light use efficiency. It is possible to form a cover glass.
[0084]
The reason why the thickness of the cover glass 15 is preferably 5 μm or more is that, as described above, the cover glass 15 is entirely polished in consideration of the fact that even a grade in which the thickness variation of the glass substrate is high is about ± 5 μm. Alternatively, this is to prevent the second micro lens array 14 from being damaged due to being etched.
[0085]
On the other hand, the reason why the thickness of the cover glass 15 is preferably 25 μm or less will be described below.
[0086]
As shown in FIG. 5B, when the cover glass 15 is made thicker, out of the R, G, and B light beams condensed by the first microlenses 12a, G and B incident on the peripheral portion of the second microlenses 14a. Of the light flux (color light flux obliquely incident on the main surface of the microlens array substrate 16) does not enter the corresponding second microlens 14a but enters the adjacent microlens 14a (FIG. 5 ( b) Light rays shown by the middle dotted line). When one microlens is made to correspond to three pixels as described above, as shown in FIGS. 5A and 5B, the R light beam is made to enter vertically, and the G and B light beams are In many cases, light beams are obliquely incident from both sides.
[0087]
When the cover glass 15 is made thicker, the R light flux perpendicularly incident on the second microlenses 14a does not lose, but the G and B light fluxes gradually increase in loss as the cover glass 15 becomes thicker. Get dark.
[0088]
Usually, a metal halide lamp or a high-pressure mercury lamp used for a liquid crystal projector has an emission line spectrum in the G and B wavelength ranges and does not have an emission line spectrum in the R band. G and B are stronger than R. Therefore, when these lamps are used, a method of cutting excess G and B luminous flux by electrically controlling the liquid crystal display element in order to balance the light intensity of R, G and B is adopted. Can be This cut amount is usually about 20%.
[0089]
FIG. 6 shows an example of the relationship between the thickness d of the cover glass 15 of the microlens array substrate 16 and the light collection efficiency of G (or B) light. This relationship slightly varies depending on the pitch and the shape of the microlenses, but generally shows the same tendency.
[0090]
Here, as can be seen from FIG. 6, the thickness d of the cover glass 15 when the light amount of G (or B) is lost by about 20%, that is, when the light collection efficiency is 80%, is about 30 μm. That is, the loss of the light amount caused by setting the thickness d of the cover glass 15 to 30 μm is an extra light amount that needs to be finally cut by the liquid crystal display element even when the thickness d of the cover glass 15 is small. However, the brightness is not substantially reduced.
[0091]
By taking the upper limit of the thickness d of the cover glass 15 to be 25 μm in consideration of the variation of the base substrate 11 to ± 30 μm, even if the thickness d of the base glass plate 11 fluctuates to −5 μm, Since the thickness d of the cover glass 15 is 30 μm, there is substantially no decrease in brightness.
[0092]
The first microlens array substrate 12 and the intermediate glass plate 13 are bonded with a resin layer 17, and the second microlens array substrate 14 and the cover glass 15 are bonded with a resin layer 18. The refractive index of the resin layers 17 and 18 is, for example, 1.4, the refractive index of the resin forming the microlenses 12a and 14a is, for example, 1.59, and the difference between the refractive indices (1.59-1. 4 = 0.19) to condense the light beam. Here, the focal length f1 of the first microlens 12a is set such that when light is incident from the first microlens 12a side, the incident light flux converges to almost the surface on the light emission side of the cover glass 15. The focal length f2 of the second microlens 14a is such that the principal ray of the light beam emitted from one point on the first microlens 12a is substantially parallel (substantially perpendicular to the principal surface of the microlens array substrate 16 (see FIG. 4)). It is set to be. Typically, it is set so as to satisfy the relationship of f1> f2.
[0093]
The first micro lens 12a is an aspheric lens, and the second micro lens 14a is a spherical lens.
[0094]
The reason why the first microlens 12a is made aspherical is that the first microlens 12a plays a role of condensing a light beam, so that if the lens has an aberration, not only does the condensing efficiency decrease, but also the liquid crystal display element 40 This is because when used, color mixing due to aberration of the first microlenses 12a increases, and color purity decreases. By making the first micro lens 12a aspherical, it is possible to reduce aberrations that cause a decrease in brightness and color purity.
[0095]
In the microlens array substrate 16 described above, a spherical lens having a constant curvature is used as the second microlens 14a. However, as in the microlens array substrate 36 shown in FIG. The four micro lenses 14a) may be a prism 34a divided into three areas. This is because the second micro lens 14a has a function of substantially collimating the light beam from the first micro lens 12a, and even if there is some aberration, it does not cause a serious problem.
[0096]
The microlens array substrate 36 shown in FIG. 7A is two-dimensionally arranged so as to correspond one-to-one with the microlens array 32 having the microlenses 32a arranged two-dimensionally. A microprism array 34 having a microprism 34a and a cover glass 35 are provided in this order from the light incident side. An intermediate glass plate 33 is provided between the micro lens array 32 and the micro prism array 34.
[0097]
The microprism 34a has inclined surfaces a and b and a center portion (a flat portion having a top surface parallel to the main surface of the microprism array substrate 36) c therebetween. The principal surfaces of the light beams incident on the inclined surfaces a and b from the corresponding microlenses 32a are refracted by the corresponding inclined surfaces a and b on both sides, and are made substantially parallel to the principal light beams of the light beam incident on the center portion c.
[0098]
Typically, like the liquid crystal display element 40 shown in FIG. 4, one microprism 34a is arranged so as to correspond to three pixels of the liquid crystal display element. The micro lens 32a has a function of distributing each of the R, G, and B color light beams to the corresponding pixel unit (see the pixel unit 19a in FIG. 4) and a function of condensing the color light beam. , G, and B to collimate the principal ray of each color light beam. For example, by refracting the B light beam on the inclined surface a and refracting the G light beam on the inclined surface b, the principal ray of each color light beam is made substantially parallel to the principal ray of the R light beam perpendicularly incident on the center part c. Here, the focal length (f2) of such a microprism 34a is defined in the same way as the microlens 14a. That is, as shown in FIG. 7B, also in the case of the microprism 34a, the distance of f2 when the light passing through the hypotenuse of the microprism 34a and the center portion is substantially parallel is determined by the focal length of the microprism 34a. (F2) is defined.
[0099]
This focal length f2 is set shorter than the focal length f1 of the microlenses 32a, and, like the liquid crystal display element 40, has a high light-collecting efficiency and a high parallelism of the emitted light beam, so that it is bright and An image with a high contrast ratio can be displayed.
[0100]
The directions of the microlenses (convex lenses) in the first microlens array 12 and the second microlens array 14 of the liquid crystal display element 40 described above are not limited to the example shown in FIG.
[0101]
For example, the first micro lens 52a and the second micro lens 54a may be arranged like the micro lens array substrate 56 of the liquid crystal display element 60 shown in FIG.
[0102]
The liquid crystal display element 60 includes a microlens array substrate 56 disposed on the light incident side, a liquid crystal layer 59 having a pixel portion 59a, and a substrate (for example, a TFT substrate) 62. The microlens array substrate 56 includes a first microlens array 52 having first microlenses 52a arranged two-dimensionally, and a first microlens array 52 two-dimensionally arranged so as to correspond to the first microlenses 52a in a one-to-one correspondence. A second micro lens array 54 having two micro lenses 54a and a cover glass 55 are provided in this order from the light incident side. An intermediate glass plate 53 is provided between the first micro lens 52a and the second micro lens 54a. The convergence position of the light beam that has passed through the first micro lens 52a and the second micro lens 54a is configured to be located near the light emission side surface of the cover glass 55.
[0103]
Unlike the first micro lens 12a and the second micro lens 14a shown in FIG. 4, the first micro lens 52a and the second micro lens 54a are arranged so that the micro lens has a convex surface on the light incident side. Similarly, in the microlens array substrate 36 shown in FIG. 7, the arrangement of the microlenses 32a and the microprisms 34a may be reversed between the light incidence side and the light emission side.
[0104]
In the above-described embodiment, the configuration using the cover glass as the transparent substrate provided on the emission side of the microlens array substrate is exemplified. However, the present invention is not limited to this, and another material (for example, plastic or a composite material thereof) may be used. You may. Further, in the above-described embodiment, the liquid crystal display element having the liquid crystal layer as the display medium layer has been exemplified. However, the present invention is not limited to the liquid crystal display element, and may be an electrochromic display element, an electrophoretic display element, or an electrical device such as a PLZT. The present invention can be widely applied to non-light-emitting display elements having an optical material as a display medium layer.
[0105]
【The invention's effect】
The light refraction element substrate (e.g., microlens array substrate) of the present invention converges a light beam near the light emission side surface of a transparent substrate (e.g., cover glass) disposed on the light emission side and enters the light beam at a different angle. The principal ray of the light beam can be emitted almost in parallel. Therefore, by using such a photorefractive element, an image display device with excellent display quality can be provided.
[Brief description of the drawings]
FIGS. 1A and 1B are cross-sectional views schematically showing a configuration of a microlens array substrate 6 according to an embodiment of the present invention.
FIG. 2 is a plan view schematically showing a two-dimensional arrangement of first and second microlenses on a microlens array substrate 6 according to an embodiment of the present invention.
FIG. 3 is a diagram schematically showing a configuration of a liquid crystal projector 300 according to an embodiment of the present invention.
FIG. 4 is a cross-sectional view schematically showing a configuration of a liquid crystal display element 40 suitably used for the liquid crystal projector 300.
FIGS. 5A and 5B are schematic cross-sectional views illustrating the configuration and functions of a liquid crystal display device 40. FIGS.
FIG. 6 is a graph showing the relationship between the thickness d of the transparent substrate (cover glass) of the microlens array substrate and the light collection efficiency of the embodiment of the present invention.
FIG. 7A is a cross-sectional view schematically illustrating a configuration of a microlens array substrate 36 according to another embodiment of the present invention, and FIG. 7B is a diagram for explaining the definition of the focal length of a microprism. It is.
FIG. 8 is a cross-sectional view schematically showing a configuration of another liquid crystal display element 60 suitably used for the liquid crystal projector 300.
FIGS. 9A and 9B are schematic diagrams for explaining a known method for manufacturing a microlens array substrate.
FIGS. 10A and 10B are schematic cross-sectional views for explaining a problem of a conventional microlens array substrate.
[Explanation of symbols]
1,11 base substrate
2, 12 First micro lens array
2a, 12a First micro lens
3, 13a Intermediate glass plate
4, 14 Second micro lens array
4a, 14a Second micro lens
5, 15 Cover glass (emission side transparent substrate)
6, 16, 36, 56, 76, 76 'microlens array substrate
7, 8, 17, 18 Adhesive layer
19 Display media layer
19a Pixel portion of display medium layer
22 Further transparent substrate (TFT substrate)
40, 60 liquid crystal display element
300 LCD projector
301 light source
302 Parabolic mirror
303 fly eye lens
304 field lens
305 field lens
306 Dichroic mirror
307 Liquid crystal display element (liquid crystal display panel)
308 Projection lens

Claims (19)

A first light refraction element array having a plurality of first light refraction elements arranged two-dimensionally,
A second light refraction element array having a plurality of second light refraction elements two-dimensionally arranged so as to correspond to the plurality of first light refraction elements in a 1: 1 relationship,
Having a transparent substrate in this order from the light incident side,
A light refraction element array substrate, wherein a convergence position of a light beam passing through the plurality of first light refraction elements and the plurality of second light refraction elements is located near a light emission side surface of the transparent substrate. Between the focal length f1 of the plurality of first light refraction elements and the focal length f2 of the plurality of second light refraction elements,
f1> f2
2. The photorefractive element array substrate according to claim 1, wherein the following relationship is satisfied. 3. The photorefractive element array substrate according to claim 1, wherein each of the plurality of first photorefractive elements is a microlens. The photorefractive element array substrate according to claim 3, wherein the microlens is an aspheric lens. 5. The photorefractive element array substrate according to claim 1, wherein each of the plurality of second photorefractive elements is a microlens. 5. The photorefractive element array substrate according to claim 1, wherein each of the plurality of second photorefractive elements is a microprism having a plurality of inclined surfaces. The photorefractive element array substrate according to claim 1, wherein the transparent substrate has a thickness of 30 μm or less. 8. The photorefractive element array substrate according to claim 1, wherein the thickness of the transparent substrate is 5 μm or more and 25 μm or less. The photorefractive element array substrate according to any one of claims 1 to 8, wherein the transparent substrate is a glass substrate. A photorefractive element array substrate according to any one of claims 1 to 9,
A display medium layer provided on the transparent substrate side of the photorefractive element array substrate,
A further transparent substrate facing the photorefractive element array substrate via the display medium layer,
An image display element having: A light source,
A color separation element that divides the light beam from the light source into a plurality of color light beams having different wavelength ranges,
A display medium layer having a plurality of pixel units which are irradiated with the plurality of color light beams and are two-dimensionally arranged;
A first light refraction element array provided on the light incident side of the display medium layer;
A second photorefractive element array provided between the first photorefractive element array and the display medium layer;
An image display device comprising:
The first light refraction element array has a plurality of first light refraction elements arranged two-dimensionally, and the second light refraction element array corresponds to the plurality of first light refraction elements in a one-to-one correspondence. A plurality of second light refracting elements arranged two-dimensionally as described above,
A transparent substrate provided between the second photorefractive element array and the display medium layer,
The convergence position of the plurality of color light beams passing through the plurality of first light refraction elements and the plurality of second light refraction elements is located near the surface of the plurality of pixel units on the side of the second light refraction element. , Image display device. Between the focal length f1 of the plurality of first light refraction elements and the focal length f2 of the plurality of second light refraction elements,
f1> f2
The image display device according to claim 11, wherein the following relationship is satisfied. The image display device according to claim 11, wherein each of the plurality of first light refraction elements is a microlens. The image display device according to claim 13, wherein the micro lens is an aspheric lens. 15. The image display device according to claim 11, wherein each of the plurality of second light refraction elements is a microlens. The image display device according to claim 11, wherein each of the plurality of second light refraction elements is a microprism having a plurality of slopes. The image display device according to claim 11, wherein the thickness of the transparent substrate is 30 μm or less. The image display device according to claim 11, wherein a thickness of the transparent substrate is 5 μm or more and 25 μm or less. The image display device according to any one of claims 11 to 18, wherein the transparent substrate is a glass substrate.

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