JPH08171003A - Plate-like lens array and its production - Google Patents

Abstract

PURPOSE: To provide a plate-like lens array solved in the problem of restriction of a filling material or the problem of a cover glass in a lens formed by filling a resin in the recessed part of a base plate. CONSTITUTION: In the plate-like lens array 10 formed by having plural spherical or cylindrical recessed parts 13 linearly or two dimensionally arrayed on the surface of the glass base plate 11 and filling a transparent material having higher refractive index than that of the glass base plate 11 into the recessed parts 13 to make a concave or lenticular lens, the transparent material is composed of an aggregated film 30 of transparent metal oxide particles by electrophoresis electrodeposition method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat plate type lens array and a liquid crystal display device using the same, and more particularly to a flat plate type lens array used for the purpose of improving the light utilization efficiency of the liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, as a lens array in which a large number of lenses are arranged on a transparent substrate such as glass, a well-known photolithography technique is formed by forming a corrosion-resistant protective film (mask film) such as Ti on soda lime glass. A flat plate having a refractive index distribution whose cross section is substantially semicircular by a so-called ion exchange method, in which a circular or linear slit-shaped opening is provided, and this is immersed in molten salt to perform ion exchange from the opening. A microlens array is known (for example, Japanese Laid-Open Patent Publication No.
7-53702).

A liquid crystal element is characterized in that a lens array is formed on a soda lime glass substrate, a resin layer is formed on this with a photocurable resin, and the thickness of the resin layer is controlled by beads. It is disclosed in Kaihei 5-273512.

Furthermore, a flat glass microlens is formed on at least one side of a transparent glass substrate by forming a substantially hemispherical recess, and filling the recess with a transparent resin material having a refractive index different from that of the glass substrate to form a lens array. A manufacturing method is disclosed (Japanese Patent Laid-Open No. 60-15552). Further, there is disclosed a flat lens in which another transparent glass substrate is bonded to the lens surface side (Japanese Patent Laid-Open No. 3-231701).

[0005]

In the production of a flat plate microlens by the ion exchange method, it is essential that the substrate glass contains alkali ions, and such an alkali-containing glass (for example, soda lime glass) is used. When a lens is constructed, polycrystalline silicon (p-Si) T
Since the coefficient of thermal expansion is different from that of quartz glass, which is the cell substrate of the FT type liquid crystal display element, the brightness of the liquid crystal display element becomes uneven when the temperature changes, and There is a problem that the alkali ions are eluted to deteriorate the characteristics of the TFT. Especially, the problem of the difference in the coefficient of thermal expansion is significant.

When a lens array is formed on a soda lime glass substrate, a resin layer is formed on the resin array with a photo-curable resin, and the thickness of the resin lens portion is controlled by beads, an arbitrary diameter is used. Is not easy to obtain. Further, when this lens array substrate is built in and used as a counter substrate of a liquid crystal display element, there is a problem that it is difficult to ensure reliability because the resin directly contacts the liquid crystal.

On the other hand, in the resin-filled type lens disclosed in Japanese Patent Laid-Open No. 60-15552, the transparent resin to be filled is often poor in heat resistance, and a resin having a high refractive index is often present. However, there is a problem in that it may be difficult to obtain a lens having desired lens performance. Further, in the resin-filled lens, in the case of a flat plate lens in which another transparent glass substrate is joined to the surface on the concave side, the thickness of the cover glass to be joined is usually very thin, so There are problems that the polishing cost is high, that defects are likely to occur in the manufacturing process, and the yield does not increase.

Therefore, the present invention is disclosed in JP-A-60-15552.
To provide a flat lens array that solves the problem of the restriction of the filling material in the resin-filled lens shown in Japanese Patent No. 3187, etc. and the problem of the cover glass in the flat lens shown in JP-A-3-231701. To aim.

[0009]

In order to solve the above-mentioned problems, in the present invention, a transparent conductive thin film is formed on the surface of a plurality of substantially spherical or cylindrical recesses which are one-dimensionally or two-dimensionally arranged on the surface thereof. In the glass substrate having, the metal oxide particles are filled as a transparent material having a refractive index higher than that of the glass substrate so that the recess is flat on the transparent conductive thin film.

As a method for filling the metal oxide particles, the glass substrate is immersed in an electrophoretic electrodeposition bath in which the metal oxide particles are dispersed, and a voltage is applied between the substrate and the counter electrode. By doing so, the metal oxide particles can be electrophoresed and electrodeposited.

Further, the glass substrate is a low expansion non-alkali glass substrate, and the electrophoretic electrodeposition film of the metal oxide particles has a refractive index of 0.05 to 0.8 higher than that of the glass substrate. The flat lens array made of oxide particles is used.

Examples of the glass substrate used in the present invention include quartz glass, soda lime glass, alkali aluminosilicate glass, alkali borosilicate glass, multi-component non-alkali glass, and low expansion crystallized glass.

Examples of the transparent conductive thin film used in the present invention include indium tin oxide and tin oxide thin films. The thin film can be formed by thermal decomposition of a coating film of a metal organic compound, a sputtering method, or a vapor deposition method. Of these, the metal organic compound coating film thermal decomposition method is preferable for mass production because the film formation cost is low. The film thickness is determined from the sheet resistivity of the film and the visible light transmittance. Sheet resistivity is 10 ⁴ Ω
It is preferable that the visible light transmittance is 80% or more.

The metal oxide particles for electrophoretic electrodeposition according to the present invention include single metal oxides such as TiO ₂ , ZrO ₂ , Al ₂ O ₃ and Sb ₂ O ₅ , and SiO ₂ --TiO ₂ . SiO _{2
-ZrO 2, SiO 2 -Al 2 O} 3, SiO 2 -Sb 2 O 5,
_{TiO 2 -ZrO 2, TiO 2 -Al} 2 O 3, TiO 2 -Sb
_{2 O 5, ZrO 2 -Al 2} O 3, ZrO 2 -Sb 2 O 5, Al 2
Examples thereof include complex metal oxides such as O ₃ —Sb ₂ O ₅ , BaTiO ₃ , and PbTiO ₃ . Further, the metal oxide particles may be used alone, or may be used as a mixture containing at least two kinds of particles among the single metal and the composite metal oxide particles.

The refractive index of each metal oxide particle will be described. TiO ₂ , ZrO ₂ , Al ₂ O ₃ , and Sb ₂ O ₅ have refractive indexes of about n = 2.2, 2.0, 1.6, and 1.9, respectively. Furthermore, in these combinations, if the mixing ratio is appropriately selected, the refractive index is n = 1.6 to 2.2.
It is possible to obtain a metal oxide aggregate film that has been changed by.
Furthermore, in combination with SiO ₂ (n = 1.46),
If the mixing ratio is appropriately selected, the refractive index is n = 1.
It is possible to obtain a metal oxide aggregate film changed in 46 to 2.2.

These metal oxide particles can be obtained by preparing in the gas phase by the CVD method or the like. It can also be obtained by growing a hydrolyzed sol in the liquid phase and centrifuging it. The particles of the composite metal oxide are easier to prepare from the liquid phase. The centrifuged particles are optionally calcined to control surface properties. The particles obtained from the gas phase and the liquid phase are used by being dispersed in a solvent by a predetermined method.

The metal oxide particles are selected to have a refractive index higher than that of the glass substrate by about 0.05 to 0.8.
It is preferable from the viewpoint of the light collecting performance of the obtained flat plate microlens. Regarding the particle size, any particle size can be used according to the purpose. Generally, it is preferable that the average particle diameter is about 1 to 500 nm.

The concentration of the metal oxide particles in the electrophoretic electrodeposition solution is preferably in the range of 0.1% by weight to 15% by weight. Further, about 1% by weight is practically preferable. Further, this electrophoretic electrodeposition solution contains an organic solvent, water, a base, a surfactant, a drying inhibitor, a binder and the like.

The organic solvent is for dispersing the metal oxide particles, and is not particularly limited as long as it is compatible with the organic metal compound, water and base. Specifically, alcohols such as methanol, ethanol, propanol and butanol, and ketones such as acetone and methyl ethyl ketone are used.

The base is added to adjust the pH of the electrophoretic electrodeposition solution. Ammonia water is generally used as a base to be added, and the pH of the ammonia water is pH = 1.
About 1.7 is preferable.

The drying inhibitor is used to prevent the generation of cracks by exposing the aggregate film of metal oxide particles electrophoretically electrodeposited to air after the electrodeposition and drying. Specific drying inhibitors include organic metal compounds such as 1.4-dioxane and methyltriethoxysilane. Furthermore, the concentration of the drying inhibitor in the electrophoretic electrodeposition solution is
It is preferably in the range of 0.1% by weight to 10% by weight. Further, about 1% by weight is practically preferable.

Examples of the binder used in the present invention include organic polymers such as polyacrylic acid.

As the counter electrode used in the electrophoresis of the present invention, platinum, stainless steel, graphite, titanium or the like which is not easily corroded by alkali can be used. The polarity is specifically as follows. SiO ₂ , TiO ₂ ,
When metal oxide particles that are negatively charged in a solution such as ZrO ₂ are electrophoresed and filled by electrodeposition, an electric field is applied so that the glass substrate side serves as an anode. When metal oxide particles that are positively charged in a solution of Al ₂ O ₃ , ITO or the like are electrophoresed and filled by electrodeposition, an electric field is applied so that the glass substrate side serves as the cathode. In either case, the voltage is 5
The range is 200 V, and either direct current or pulse current may be used.

The corrosion-resistant protective film material used in the manufacturing method of the present invention can be appropriately selected depending on the resistance to the etchant used, the workability of photolithographic patterning and the film formation cost. Further, the film thickness to be formed can be arbitrarily selected according to the purpose, and film materials having different compositions can be stacked and filled in multiple layers. Examples of the corrosion-resistant protective film material include metals such as chromium, nickel, tantalum, silicon and gold, and oxides or nitrides thereof. These corrosion-resistant protective films can be formed by a sputtering method, a vapor deposition method, or the like.

The composition of the etchant of the glass substrate used in the manufacturing method of the present invention is selected according to the composition of the glass substrate to be etched. For example, when etching a quartz glass substrate, an aqueous solution containing hydrogen fluoride and a surfactant such as sodium dodecylbenzenesulfonate is used as an etchant. Further, when etching a soda lime glass substrate, a mineral acid such as sulfuric acid or an organic acid such as acetic acid is often added in addition to hydrogen fluoride, and a surfactant such as sodium dodecylbenzenesulfonate may be added as necessary. Should be added.

The thickness of the electrophoretic electrodeposition aggregate film of metal oxide particles in the present invention is not particularly limited. Generally,
It suffices that the microlenses have a thickness capable of exhibiting the condensing performance after the film formation and firing.

[0027]

According to the present invention, conductivity is imparted to a substrate by forming transparent conductive thin films on the surfaces of a plurality of substantially spherical or columnar recesses arranged in a one-dimensional or two-dimensional manner on the surface of a glass substrate. In this way, it is possible to stack and fill the metal oxide particles by the electrophoretic electrodeposition method. Furthermore, since a material having a higher refractive index than the glass substrate is selected as the metal oxide particles, a flat lens array having convex or lenticular lenses can be obtained.

[0028]

The present invention will be described in detail below with reference to the drawings. FIG. 1 shows a general sectional structure of a flat lens array according to the present invention. On one side of a glass substrate 11 such as a quartz substrate, one-dimensionally or two-dimensionally arranged concave portions 13 having a smooth curved surface of a substantially spherical shape or a substantially cylindrical shape are formed by, for example, a chemical etching method described later. This recess 13
Generally has a boundary ridge line 16 between adjacent concave portions, such as a honeycomb or a stripe, which is a square lattice, a hexagonal close-packed lattice, as shown in (a), (b) and (c) of FIG. It is formed so as to be a dense packing of polygons of the same shape.

Next, a transparent conductive thin film 20 is formed on the surface of each of the recesses 13, and an electrophoretic electrodeposition aggregate film 30 of metal oxide particles having a refractive index larger than that of the substrate 11 is laminated and filled to form a lens array. Each of the lens parts 12 and further provided with an electrophoretic electrodeposition aggregate film 30 of metal oxide particles continuously, and after the electrophoretic electrodeposition aggregate film 30 is sintered by firing, the lens surface is polished or the like. The flat lens array 10 is obtained by flattening the surface opposite to and controlling so that the parallel light rays incident from the substrate have a thickness to be condensed near the surface of the electrophoretic electrodeposition aggregate film.

FIG. 3 shows the principle of the electrophoretic electrodeposition method. The principle of the electrophoretic electrodeposition method is described in JP-A-5-24.
6701 and the 1994 Annual Meeting of the Ceramic Society of Japan, 2H08 P. 513.

FIG. 4 is a schematic view of a liquid crystal display device using the flat lens array of the present invention. By adjusting the arrangement pitch of the lenses of the lens array 10 in advance to the pixel pitch of the liquid crystal display element 50, the illumination light is condensed by each lens 12 of the flat plate type lens array 10, and the illumination light of each pixel of the liquid crystal display element is condensed. Through the transparent opening 51,
In the conventional liquid crystal display element, the illumination light blocked by the non-transparent pixel wiring portion 52 such as the electrodes and the TFTs effectively contributes to the display, and an image with extremely high definition can be obtained. Further, this can reduce deterioration of the liquid crystal element due to heating.

(Specific Example 1) FIG. 5 shows an example of a manufacturing process of a flat lens array according to the present invention. A Cr film 40 was formed on the surface of the quartz glass substrate 11 as a hydrofluoric acid-resistant protective film by a sputtering method. Next, small openings 41 were formed in the Cr film 40 in a predetermined lens array pattern by photolithography in which a photoresist was applied, exposed, and developed (FIG. 5A). The formed small aperture array is the hexagonal lattice array shown in FIG.
A honeycomb lens array as shown in (b) is obtained. It is desirable that the diameter of the small opening 41 be sufficiently smaller than the diameter of the lens to be finally obtained.

The Cr film-coated substrate having the small openings 41 was immersed in an etchant containing hydrofluoric acid (HF) and sodium dodecylbenzenesulfonate as a surfactant to carry out chemical etching (FIG. 5B). . Here, the concentrations of hydrofluoric acid and sodium dodecylbenzenesulfonate were 10% by weight and 0.1% by weight, respectively. As a result, starting from the small opening 41 of the Cr film,
The surface of the quartz glass substrate is isotropically etched, as shown in FIG.
As shown in (b), the recess 14 which is a part of a sphere is obtained. This first stage etching is performed by
It is stopped while leaving a flat boundary portion 15 having a slight width between the four (see FIG. 5C).

Next, the Cr film 4 is formed from the surface of the quartz glass substrate.
After removing 0 (FIG. 5C), it was immersed again in the above etchant to etch the entire surface of the substrate. By this two-step etching, the etching in the peripheral portion of the recess proceeds, and the boundary 15 between the adjacent recesses has a ridge line 16 with a sharp upper end.
(Fig. 5 (d)). That is, in a plan view, each has the same hexagonal shape, and the adjacent recesses are in a close-packed arrangement in which the adjacent recesses are in close contact with each other. The depth of the formed recess was about 15 μm.

After the two-step etching process, the recess 14 is formed.
Then, an indium tin oxide film 20 was formed as a transparent conductive thin film by a thermal decomposition method of the coating film. Here, the coating solution contains a metal organic compound of indium and a metal organic compound of tin, which is formed on the substrate by spin coating and then 5
By heat-treating at 00 ° C. for 30 minutes in the air, organic components are burnt and decomposed to form metal oxides. The film thickness after baking is about 100 nm and the specific resistance is 4 × 10.
^{It was -2} Ωcm.

The quartz glass substrate with the transparent conductive thin film was immersed in an electrophoretic electrodeposition bath shown below, and a DC voltage was applied so that the substrate became an anode (see FIG. 3).

In the electrophoretic electrodeposition bath, silica-titania composite metal oxide particles (average particle size 10 nm) prepared by cohydrolysis-condensation polymerization of metal alkoxide were added to methyltriethoxysilane, aqueous ammonia and dimethylacetamide. The dispersion medium containing a trace amount of a surfactant and an organic polymer binder was added to the mixed solution, and the mixture was uniformly dispersed by stirring at room temperature for 1 hour. The electrophoresis condition was a DC voltage of 50V-10 minutes. did.

By the above operation, a quartz glass substrate with an electrophoretic electrodeposition aggregate film made of silica-titania composite metal oxide particles having a thickness of about 200 μm was obtained. The obtained aggregate film completely fills the concave portion on the surface of the quartz glass substrate through the transparent conductive film, and the film thickness of 200 μm is sufficiently thicker than the depth of the concave portion described above. It was almost flat (Fig. 5 (e)). Further, this thickness may be set in consideration of the shrinkage of the aggregate film due to firing described later. Needless to say, the shrinkage due to firing changes depending on the firing conditions.

The electrophoretic electrodeposited silica-titania aggregate film-attached quartz substrate was further heated at 400 ° C. for 1 hour and further at 1000 ° C.
Then, the aggregate film was sintered by firing for 1 hour. The sintering resulted in a thickness of about 100 μm and a refractive index of 1.62. As described above, the silica-titania mixed metal oxide particles completely fill the concave portion having a depth of about 15 μm on the surface of the quartz glass substrate, and further have the function of the transparent substrate having a thickness of 100 μm thereon. Therefore, a thin cover glass is unnecessary.

The film thickness of the electrodeposited aggregate film is such that the condensing performance of the microlens can be exhibited. Further, in order to improve the flatness of the surface of the electrodeposited aggregate film, the surface may be polished by about 5 μm. That is, the film thickness of the aggregate film may be controlled so that the parallel light rays incident from the substrate are condensed near the surface of the electrodeposition aggregate film.

The radius of curvature of the convex portion of the lens of the lens array manufactured this time is about 20 μm, and the focal length f of the lens is
Is about 120 μm, which shows good light condensing characteristics.

Application Example A transparent conductive film ITO was formed on the flat surface side of the flat plate type lens array obtained in Example 1 by a vacuum film forming method to form a counter electrode. Further, this was attached to a second substrate on which a polycrystalline silicon (p-Si) TFT type pixel electrode was separately formed with a gap,
Liquid crystal was injected into the gap to form a liquid crystal display device.

Since the arrangement pitch of the lenses of the lens array is matched with the pixel pitch of the liquid crystal display element, the illumination light is condensed by the respective lenses of the flat plate type lens array and the pixels of the liquid crystal layer and the respective pixels of the liquid crystal display element. Penetrates the electrode, and the electrode, TFT
Illumination light that was blocked by the non-translucent portion effectively contributed to the display, and an image with extremely high definition was obtained.

[0044]

According to the present invention, in a flat lens array obtained by filling a concave portion of a glass substrate with a transparent material having a higher refractive index than that of the glass substrate, the transparent material contains metal oxide particles by an electrophoretic electrodeposition method. Filled to form an aggregate film. As the metal oxide particles, those having a wide range of refractive indexes can be selected, so that there are less restrictions on the lens design. Further, since the metal oxide particles are inorganic substances, this flat plate type lens array becomes more reliable.

Further, since the metal oxide particle aggregate film can have a role as a cover glass, it is not necessary to use an expensive thin cover glass,
An inexpensive flat plate lens array can be obtained.

[Brief description of drawings]

FIG. 1 is a general sectional structure of a flat lens array according to the present invention.

FIG. 2 is an example of a plan view of a flat lens array.

FIG. 3 is a diagram illustrating the principle of an electrophoretic electrodeposition method.

FIG. 4 is a schematic view of a liquid crystal display element using the flat lens array of the present invention.

5A to 5D are views for explaining a manufacturing process of a flat lens array according to the present invention.

FIG. 6 is a hexagonal array of small openings formed in a Cr film.

[Explanation of symbols]

10 Flat Lens Array 11 Glass Substrate such as Quartz Substrate 12 Each Lens Part of Lens Array Filled with Electrophoretic Electrodeposition Aggregate Film 13 Recess with a Approximately Spherical or Cylindrical Curved Surface 14 Obtained by First Stage Recessed part which is almost a part of a sphere 15 Boundary between adjacent recesses 16 Border line between adjacent recesses 20 Transparent conductive thin film 30 Electrophoretic electrodeposition aggregate film 40 Corrosion resistance protection Cr film against etchant 41 Formed on Cr film Small opening 50 Liquid crystal display element 51 Pixel opening 52 Pixel wiring 60 Electrophoresis bath 70 by electrophoretic method 70 Power supply 80 Counter electrode 90 Metal oxide particles

Front Page Continuation (72) Inventor Tsutomu Minami 2-7-1 Onodai, Osaka Sayama City, Osaka Prefecture (72) Inventor Masahiro Tatsumi Sand, 445-31 Jokuro, Sakai City, Osaka Prefecture

Claims (7)

[Claims] 1. A glass substrate having a plurality of substantially spherical or substantially cylindrical recesses arranged one-dimensionally or two-dimensionally, and filling the recesses with a transparent material having a higher refractive index than that of the glass substrate. In the flat plate lens array provided with the convex lens or the lenticular lens obtained by the above, the transparent material is composed of an aggregate film of transparent metal oxide particles by an electrophoretic electrodeposition method. 2. The flat plate lens array according to claim 1, wherein the glass substrate is a low expansion glass substrate, and the metal oxide particles have a refractive index of 0.05 to 0.05 as compared with a refractive index of the glass substrate.
0.8 A flat lens array which is a metal oxide particle having a high refractive index. 3. The flat plate lens array according to claim 1, wherein the metal oxide particles are TiO ₂ , ZrO ₂ , Al ₂ O ₃ ,
Alternatively, a single metal oxide particle of either Sb ₂ O ₅ or
Alternatively, SiO ₂ —TiO ₂ , SiO ₂ —ZrO ₂ , SiO
_{2 -Al 2 O 3, SiO 2} -Sb 2 O 5, TiO 2 -ZrO 2,
_{TiO 2 -Al 2 O 3, TiO} 2 -Sb 2 O 5, ZrO 2 -A
_{l 2 O 3, ZrO 2 -Sb} 2 O 5, Al 2 O 3 -Sb 2 O 5, B
A flat lens array which is a composite metal oxide particle of either aTiO ₃ or PbTiO ₃ . 4. The flat lens array according to claim 1, wherein the metal oxide particles are a mixture containing at least two kinds of the single metal oxide particles and the composite metal oxide particles. Flat lens array. 5. The flat plate lens array according to claim 1, wherein the recess is filled with the metal oxide aggregate film,
Further, a flat plate type lens array in which the metal oxide aggregate film is further deposited thereon with a predetermined thickness. 6. A glass substrate surface having a plurality of substantially spherical or substantially columnar recesses arranged one-dimensionally or two-dimensionally, a transparent conductive thin film being formed on the surface of the recesses. A method for producing a flat-plate lens array having a convex lens or a lenticular lens by filling transparent metal oxide particles having a high refractive index by an electrophoretic electrodeposition method, which comprises the following steps: Manufacturing method of flat lens array. (A) A step of forming a hydrofluoric acid-resistant protective film on the glass substrate (b) A step of forming a desired opening pattern in the protective film (c) The glass substrate is immersed in an etching solution containing hydrofluoric acid Step (d) Step of forming a transparent conductive thin film on the glass surface on the side where the recess is formed (e) The glass substrate is immersed in an electrophoretic electrodeposition bath in which metal oxide particles are dispersed, and further the substrate and the counter electrode A voltage is applied between the electrodes to cause the metal oxide particles to electrophoretically and electrodeposit to fill the recesses. (F) A step of firing the glass substrate (g) A step of polishing the glass substrate 7. A transparent metal oxide particle having a plurality of substantially spherical or substantially cylindrical recesses arranged one-dimensionally or two-dimensionally on the surface of a glass substrate, the transparent metal oxide particles having a higher refractive index than that of the glass substrate. A liquid crystal display device using a flat lens array having a convex lens or a lenticular lens obtained by filling by an electrophoretic electrodeposition method, wherein a transparent electrode of a counter substrate of the liquid crystal display device is provided on the surface of the metal oxide film. A liquid crystal display device having a structure in which a liquid crystal is sandwiched between the transparent substrate and a second substrate having a polycrystalline silicon (p-Si) TFT pixel electrode formed thereon.