JP4269381B2 - Microlens substrate for liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a microlens substrate having a plurality of microlenses formed on a transparent substrate, and more particularly to a microlens substrate for a liquid crystal display device used in a liquid crystal display device such as a liquid crystal projection device.
[0002]
[Prior art]
In general, a liquid crystal display device mainly includes a pair of opposing substrates on which a polarizing film and a transparent electrode are respectively disposed, and a liquid crystal substance sealed between the substrates. In a color liquid crystal display device for displaying a color image, a color filter layer for coloring polarized light is provided on one of the pair of substrates.
[0003]
When performing screen display, by changing the alignment state of the liquid crystal substance sealed between the electrode substrates by applying a voltage between the opposing transparent electrodes, and controlling the polarization plane of the light transmitted through the liquid crystal substance, The transmission and non-transmission are controlled by the polarizing film. In the following description, the pixel portion is a portion that changes the alignment state of the liquid crystal by applying a voltage to the sandwiched liquid crystal (that is, a portion where transmission and non-transmission of light are controlled. A region where the electrodes overlap in plan view), and a non-pixel portion indicates a region between the pixel portions.
[0004]
Further, at least one of the pair of substrates is generally provided with a light shielding layer called a black matrix, in which a light transmitting opening is formed at a portion facing each pixel portion. ing. The black matrix improves the contrast of screen display by blocking unnecessary light in the outer peripheral area of the pixel portion, and further, the wiring to the liquid crystal display element, the electrodes for driving the liquid crystal, etc. are provided at the light blocking portion. Sometimes it has a protective role.
[0005]
As types of liquid crystal display devices, there are known a projection television for enlarging and projecting a liquid crystal display image on a screen, and a liquid crystal projection device such as a data projection. In a liquid crystal projection apparatus, a system in which a built-in light source (light) is arranged and a light beam emitted from the built-in light source is incident on a liquid crystal panel (a pair of substrates sandwiching the liquid crystal) to obtain a display screen is widely spread. is doing.
[0006]
In recent years, there has been an increasing demand for high-definition display images in image display apparatuses, and this demand is also increasing in liquid crystal display apparatuses. As is well known, in order to obtain a high-definition image, it is necessary to increase the number of pixels.
However, when the number of pixels of the liquid crystal projection device is increased in order to obtain a high-definition image, the display image becomes dark and the quality of the displayed image is deteriorated.
[0007]
This is because the size of the pair of substrates constituting the liquid crystal projection apparatus is generally about 0.9 to 1.3 inches diagonal from the output efficiency of the built-in light source. Since the size of the substrate is determined, when the number of pixels formed on the substrate is increased, the pitch between the pixels is narrowed.
Furthermore, the wiring of the liquid crystal display element and the electrodes for driving the liquid crystal require a certain amount of area. Therefore, the size of the light blocking area of the black matrix formed to protect them is assumed even if the number of pixels increases. However, it cannot be reduced, and must be as large as the conventional one.
[0008]
Therefore, as the number of pixels increases and the pitch between pixels decreases, the area of each opening formed in the black matrix must be reduced. That is, it can be said that the aperture ratio of the black matrix must be reduced.
When the number of pixels of the liquid crystal projection device is increased and the aperture ratio of the black matrix is reduced, the amount of light passing through the aperture is reduced, the display image becomes dark, and the quality of the displayed image is degraded.
[0009]
As a means for preventing such a reduction in image quality caused by a reduction in the aperture ratio of the black matrix, it is known that a microlens is provided on one side of a pair of substrates sandwiching the liquid crystal. By arranging the microlens, it becomes possible to condense the light that has been blocked by the light blocking portion of the black matrix in the pixel area (opening area of the black matrix) by the microlens, increasing the light utilization efficiency, Bright image display can be achieved.
[0010]
As a method for forming a microlens, the following methods are known. That is, the glass substrate is covered with a metal mask having a predetermined opening pattern, and the glass substrate is immersed in a specific processing solution, and the refractive index of the glass substrate portion exposed from the metal mask is changed to a lens shape to form a lens pattern. A glass diffusion method, and a wet etching method in which a glass substrate is directly etched to obtain a lens pattern. Also, after a resist pattern or metal film pattern having a predetermined shape is formed on glass and a glass pattern is formed by directly dry etching the glass to obtain a lens pattern, or after a resist pattern having a predetermined shape is formed on the glass. A heat flow method in which a resist pattern is formed into a lens by the surface tension of the melted resist pattern by heating, a stamper method in which a transparent resin is formed on glass and then pressure-bonded with a mold or the like and further thermally cured to form a lens Are known.
[0011]
Here, the light condensing property of the lens is determined by the curvature of the lens. As shown in FIG. 3, when the microlens 33 is formed on the transparent substrate 32, a transparent thin plate 35 made of glass or the like is pasted on the microlens 33 via the adhesive layer 34, and flattened. Thereafter, it is common to form a black matrix 37 and a conductive film 38. In other words, by flattening the uneven surface generated by the formation of the microlens, a gap defect with the opposing substrate is prevented, and the accuracy in forming the black matrix and the conductive film is improved. Because.
When the transparent thin plate 35 is attached on the microlens 33 via the adhesive layer 34, the refractive index difference between the microlens 33 and the adhesive layer 34 is also related to the light collecting property. However, the curvature of the microlens 33 is determined by the pitch between the microlenses 33 and the height of the lens. Even if an attempt is made to increase the curvature of the lens in order to increase the light condensing property of the microlens 33, the liquid crystal panel It can be said that there is a limit to the increase in curvature, such as the limitation of the thickness of the pair of substrates). On the other hand, it can be said that the greater the difference in refractive index between the lens and the adhesive, the higher the light collecting property of the lens. For this reason, when it is desired to increase the light condensing performance of the lens, but there is a limit to the increase in the curvature of the lens, it is easy to increase the refractive index difference between the microlens 33 and the adhesive layer 34 in order to improve the light condensing performance. I can say that.
[0012]
A resin having a refractive index of about 1.65 is commercially available as a material for the microlens, and a material having a refractive index of about 1.35 is commercially available as a material for the adhesive layer. However, if an adhesive having a lower refractive index is used to increase the difference in refractive index between the microlens and the adhesive layer in order to improve the light condensing property, there arises a problem that the reliability of the liquid crystal display device is lowered. Is.
[0013]
That is, many low-refractive index adhesives having a refractive index of 1.5 or less contain a lot of fluorine, and generally, the lower the refractive index adhesive, the higher the fluorine content. As the fluorine content increases, the adhesiveness of the adhesive (particularly, the adhesiveness with a transparent thin plate made of glass) decreases. For this reason, when a low refractive index adhesive with a high fluorine content is used, heat treatment (for example, about 200 ° C.) performed in the manufacturing process of the liquid crystal display device or heat generated from a light source incorporated in the liquid crystal display device Then, the adhesiveness of the adhesive is lowered by light, and the microlens substrate is distorted due to peeling of the transparent thin plate at the adhesive interface, and the reliability of the liquid crystal display device is lowered.
[0014]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described problems, and the problem is that the heat treatment is performed in the manufacturing process of the liquid crystal display device and the light and heat emitted from the light source are exposed. However, it is an object of the present invention to provide a highly reliable microlens substrate for a liquid crystal display device that does not cause distortion or peeling at the adhesive interface.
[0015]
[Means for Solving the Problems]
The present inventors have intensively studied to solve the above-mentioned problems and have arrived at the present invention. That is, the present invention provides a liquid crystal in which at least a plurality of microlenses, an adhesive layer, and a transparent thin plate are sequentially disposed on a transparent substrate, and a liquid crystal material is sandwiched between a counter substrate having a predetermined electrode pattern that is separately prepared. In the microlens substrate for a display device, a transparent resin layer containing a solvent formed flat between the adhesive layer and the transparent thin plate is disposed, and the transparent resin layer and the adhesive layer contain fluorine, The refractive index of the adhesive layer is lower than that of the microlens, the adhesive layer has a higher fluorine content than the transparent resin layer, and the refractive index of the adhesive layer is lower than the refractive index of the transparent resin layer. The difference in refractive index with the microlens is increased, the adhesive layer is coated with a microlens, and the interface with the transparent resin layer is flattened. Les It is obtained by the board's.
[0016]
Generally, the refractive index of an adhesive (adhesive layer) used for attaching a transparent thin plate on a microlens for planarization is desirably 1.5 or less. However, as described above, the lower the refractive index of the adhesive layer, the higher the fluorine content, and the lower the adhesiveness between the adhesive layer and the transparent thin plate. When using an adhesive layer with low adhesiveness, it is considered to roughen the surface of the transparent thin plate in contact with the adhesive layer as a means of improving the adhesion between the transparent thin plate made of glass and the adhesive layer. It is done. However, in that case, the transparent thin plate causes light scattering, which causes a problem of reducing the light use efficiency, which is not preferable.
[0017]
Therefore, the present inventors have conceived of disposing a transparent resin layer between the transparent thin plate and the adhesive layer as described above.
That is, the transparent resin layer has a role as an adhesive layer (or adhesive layer) that increases the adhesion between the transparent thin plate and the adhesive layer.
[0018]
Here, it may be considered that the microlens and the transparent thin plate are attached only by the transparent resin layer. However, a solvent is contained in the transparent resin layer for reasons such as providing fluidity, and bubbles are generated by the solvent in the transparent resin layer during curing. Generally, no solvent is contained in the adhesive, and no bubbles are generated even when the adhesive is cured. For this reason, in order to prevent the generation of bubbles, the adhesion between the adhesive layer and the transparent thin plate should be increased through the transparent resin layer having a small fluorine content when the microlens is attached to the transparent thin plate. Is desirable.
[0019]
The material of the transparent resin layer disposed on the microlens substrate of the present invention includes a thermosetting resin, a UV (ultraviolet) curable resin, and the like. The adhesive layer is not particularly limited as long as it has high adhesiveness, and may be appropriately selected according to the material of the adhesive layer, the heating temperature in the manufacturing process of the liquid crystal display device, and the like.
That is, the transparent resin layer mainly composed of a resin and the adhesive layer have good adhesion, and the transparent resin layer with a low fluorine content also has good adhesion to a transparent substrate such as glass. By interposing the layer, the adhesiveness between the adhesive layer and the transparent thin plate is improved.
[0020]
Further, the present invention is that the refractive index of the transparent resin layer, equal to the refractive index of the transparent thin plate or is also of the less refractive index of the transparent thin plate. As a result, the incident light loss that the light incident on the interface between the transparent resin layer and the transparent thin plate is reflected and the light transmitted through the liquid crystal panel is reduced is reduced, and the amount of light passing through the liquid crystal panel is reduced. Therefore, a bright image display can be realized.
[0021]
Further, the present invention, the a micro lens is glass, the between the micro lens and the adhesive layer, providing the thin-film transparency resin layer having a curved surface to fit the curved surface of the microlenses This is a microlens substrate for a liquid crystal display device as described above.
[0022]
The resin used as the main material of the adhesive layer generally includes acrylic resin, epoxy resin, etc., but the material of the transparent resin layer provided between the adhesive layer and the transparent thin plate is the main material of the adhesive layer. If it is close to the resin used as the material (for example, when the adhesive layer was an acrylic adhesive, an acrylic resin was used as the transparent resin layer, and the adhesive layer was an epoxy adhesive) In the case of using an epoxy resin as a transparent resin layer), the adhesiveness and adhesion between the adhesive layer and the transparent thin plate can be improved, and the physical properties (for example, thermal expansion coefficient) between the adhesive layer and the transparent resin layer , Stretching rate, chemical bond, etc.) are substantially the same. In this case, the expansion and contraction of the two (adhesive layer and transparent resin layer) generated during the heat treatment performed in the manufacturing process of the liquid crystal display device is substantially the same, and there is an effect that distortion generated by the heat treatment can be suppressed to be small. It becomes.
[0023]
The microlens formed on the microlens substrate of the present invention may use the same formation method as the conventional one, such as the method described in the above (conventional technology).
For this reason, depending on the method of forming the microlens, the microlens is made of resin or the microlens is made of glass (etching is performed on the glass substrate as a support, and microlens-like irregularities are formed on the surface of the glass substrate. If formed).
[0024]
When the microlens is made of resin, since the microlens and the adhesive layer are made of resin, it can be said that the microlens and the adhesive layer have a degree of adhesion that has no practical problem. It can be said that a transparent resin layer may be provided between the adhesive layer. However, as shown in FIG. 2, when the microlens 23 is made of glass, since the degree of adhesion between the glass and the adhesive layer is insufficient, a transparent thin plate (thin plate glass 25 shown in the example of FIG. 2). Transparent resin between the microlens 23 and the adhesive layer 24 in order to prevent a decrease in the adhesion between the microlens 23 made of glass and the adhesive layer 24. The layer 26 may be provided.
[0025]
As described above, according to the present invention, even if a low refractive index adhesive having a large fluorine content is used, there is no distortion due to a decrease in adhesiveness, peeling at the adhesive interface, etc., and high reliability. A microlens substrate is obtained.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described.
[0027]
Nippon Electric Glass Co., Ltd., trade name “Neoceram Glass” is used as the transparent substrate 2, and a positive resist manufactured by GS (JSR) is used as a microlens base material on the transparent substrate 2, and the trade name “MFR-352”. (Viscosity 80 cp) was spin-coated at 1800 rpm for 60 seconds. Next, the transparent substrate 2 was pre-baked at 90 ° C. for 3 minutes, and then the resist was subjected to pattern exposure using a stepper manufactured by Nikon Corporation.
[0028]
Next, the transparent substrate 2 was subjected to dip development (liquid temperature: 23 ° C., development time: about 40 seconds) using a developer (trade name “PD523AD”, 1.2% liquid) manufactured by JSR (JSR). After the development, the transparent substrate 2 was washed with sufficient water and then rinsed.
[0029]
Next, the microlens base material remaining on the transparent substrate 2 is irradiated with ultraviolet light having a main wavelength of 365 nm of about 600 mJ / cm ² to perform bleaching processing for erasing the photosensitive group of the photosensitive resist in the microlens base material. gave. As a result, a transparent microlens that prevents light absorption by the photosensitive group can be obtained.
[0030]
Next, the transparent substrate 2 was heated stepwise from 90 ° C. to 190 ° C. with a hot plate to obtain a microlens 3 made of a plurality of resins having a convex cross section as shown in FIG.
[0031]
Next, in this example, a thin glass was used as the transparent thin plate 5, and an acrylic thermosetting transparent resin (manufactured by Nippon Kayaku Co., Ltd., trade name) on the surface of the transparent thin plate 5 facing the microlens 3. “AR7468-410N”, refractive index n = 1.44) was spin-coated to a thickness of 0.4 μm. Next, the transparent thin plate 5 was heated on a hot plate at 100 ° C. for 5 minutes and then heated at 200 ° C. for 5 minutes to perform a two-stage baking process, whereby a transparent resin layer 6 was formed on the transparent thin plate 5.
[0032]
Next, the resins (that is, the microlens 3 and the transparent resin layer 6) face each other between the transparent substrate 2 on which the plurality of microlenses 3 formed of the resin are disposed and the transparent thin plate 5 on which the transparent resin layer 6 is formed. The adhesive layer 4 was bonded together. For the adhesive layer 4, the same acrylic adhesive as the transparent resin (Adel UV curable adhesive, trade name “L-102” (refractive index n = 1.42)) was used. In this example, when the adhesive layer 4 was cured, ultraviolet light having a dominant wavelength of 365 nm was irradiated at about 15000 mJ / cm ² .
[0033]
Next, after the bonding was completed, a metal chromium film (film thickness of about 1500 mm) was formed on the transparent thin plate 5, and then a black matrix 7 was formed by a known photoetching method.
After the formation of the black matrix 7, a transparent conductive film 8 made of ITO (mixed oxide of tin oxide and indium oxide) was formed by a known sputtering film formation, and the microlens substrate 1 shown in FIG. 1 was obtained.
[0034]
The microlens substrate 1 obtained in this example was heated at a temperature of 200 ° C. for 3 hours assuming a manufacturing process of a liquid crystal display device. For evaluation of reliability, the microlens substrate 1 was left for 1000 hours in an atmosphere at a temperature of 60 ° C. and a humidity of 95%.
In both cases after heating and after standing, peeling of the transparent thin plate 5 was not observed, and no change such as waviness occurred on the surface of the transparent thin plate 5, and the microlens substrate 1 according to this example was not distorted. It was a small microlens substrate.
[0035]
As mentioned above, although an example of the embodiment of the present invention has been described, the embodiment of the present invention is not limited to the above description and drawings, and various modifications may be made based on the gist of the present invention. Needless to say. For example, in the above description, the black matrix is formed on the microlens substrate side, but it may be provided on the opposite substrate side. Furthermore, a color filter may be formed on either the microlens substrate or the counter substrate.
Moreover, as shown in FIG. 2, the microlens may be made of glass.
[0036]
【The invention's effect】
As described above, in the microlens substrate of the present invention, a transparent resin having a structure close to the resin that is the main material of the adhesive layer is disposed as an adhesive layer between the adhesive layer and the transparent thin plate. Thereby, a heat treatment (for example, about 200 ° C.) performed in the manufacturing process of the liquid crystal display device, or a highly reliable microlens substrate that is free from distortion and peeling due to heat, light emitted from a light source incorporated in the liquid crystal display device. It can be.
Further, in the microlens substrate of the present invention, the reflection when the light enters the microlens substrate is suppressed by making the refractive index of the transparent resin layer smaller than the refractive index of the transparent thin plate. Furthermore, since there is no problem of adhesiveness between the adhesive layer and the transparent thin plate, it is possible to use an adhesive having a lower refractive index than that having a large fluorine content, and the difference in refractive index between the lens and the adhesive can be greatly increased. It becomes possible to improve the light condensing property of the microlens substrate. That is, the microlens substrate of the present invention can collect light incident on the substrate at a predetermined portion (for example, a pixel region) without causing loss due to reflection. Therefore, by using the microlens substrate of the present invention, it is possible to obtain a liquid crystal panel with high light utilization efficiency, and thus to provide a highly reliable liquid crystal display device that enables bright screen display.
[0037]
[Brief description of the drawings]
FIG. 1 is a cross-sectional explanatory view showing a main part of an embodiment of a microlens substrate for a liquid crystal display device of the present invention.
FIG. 2 is a cross-sectional explanatory view showing the main part of another embodiment of the microlens substrate for a liquid crystal display device of the present invention.
FIG. 3 is a cross-sectional explanatory view showing a main part of an example of a conventional microlens substrate for a liquid crystal display device.
[Explanation of symbols]
1, 21, 31 Micro lens substrate 2, 22, 32 Transparent substrate 3, 23, 33 Micro lens 4, 24, 34 Adhesive layer 5, 25, 35 Transparent thin plate 6, 26 Transparent resin layer 7, 27, 37 Black matrix 8, 28, 38 conductive film

Claims (2)

  A microlens substrate for a liquid crystal display device, in which at least a plurality of microlenses, an adhesive layer, and a transparent thin plate are sequentially arranged on a transparent substrate, and a liquid crystal substance is sandwiched between a counter substrate having a predetermined electrode pattern that is separately prepared A transparent resin layer containing a solvent formed flat between the adhesive layer and the transparent thin plate, wherein the transparent resin layer and the adhesive layer contain fluorine, and the refractive index of the adhesive layer The adhesive layer has a higher fluorine content than the transparent resin layer, and the refractive index of the adhesive layer is lower than the refractive index of the transparent resin layer. A microlens substrate for a liquid crystal display device, wherein the difference in refractive index is increased, the adhesive layer is covered with a microlens, and the interface with the transparent resin layer is flattened. Wherein a micro lens is glass, the between the micro lens and the adhesive layer, according to claim 1, characterized in that a thin-film transparency resin layer having a curved surface to fit the curved surface of the microlenses 2. A microlens substrate for a liquid crystal display device according to 1.

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