JP3653762B2 - Flat lens array and manufacturing method thereof - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a flat lens array and a liquid crystal display element using the same, and more particularly to a flat lens array used for the purpose of improving the light utilization efficiency of the liquid crystal display element.
[0002]
[Prior art]
Conventionally, as a lens array in which a large number of lenses are arranged on a transparent substrate such as glass, a corrosion-resistant protective film (mask film) such as Ti is formed on soda lime glass, and a circular or A flat microlens array that has a refractive index distribution with a substantially semicircular cross section is known by providing a straight slit-like opening and immersing it in molten salt to exchange ions from the opening, so-called ion exchange. (For example, JP-A-57-53702).
[0003]
Further, a liquid crystal element in which a lens array is produced on a soda lime glass substrate, a resin layer is formed thereon with a photocurable resin, and the thickness of the resin layer is controlled by beads is disclosed in Japanese Patent Laid-Open No. Hei 5- No. 273512.
[0004]
Furthermore, there is a method for producing a flat microlens that forms a lens array by forming a substantially hemispherical concave portion on at least one side of a transparent glass substrate and filling the concave portion with a transparent resin material having a refractive index different from that of the glass substrate. (Japanese Patent Laid-Open No. 60-15552). Furthermore, a flat lens formed by bonding another transparent glass substrate to the lens surface side is disclosed (Japanese Patent Laid-Open No. 3-231701).
[0005]
[Problems to be solved by the invention]
In the production of flat microlenses by the ion exchange method, it is essential that the substrate glass contains alkali ions. When the lens is formed using such alkali-containing glass (for example, soda lime glass), polycrystalline silicon is used. (P-Si) Since there is a difference in thermal expansion coefficient with respect to quartz glass or the like which is a cell substrate of a TFT type liquid crystal display element, when the temperature changes, the brightness of the liquid crystal display element is uneven. Further, there is a problem that the alkali ions in the glass substrate are eluted to deteriorate the TFT characteristics. In particular, the problem of this difference in thermal expansion coefficient is serious.
[0006]
In addition, when a lens array is produced on a soda-lime glass substrate, a resin layer is formed on this with a photocurable resin, and the resin lens portion thickness is controlled by the beads, beads having an arbitrary diameter Is not easy to obtain. Further, when this lens array substrate is 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.
[0007]
On the other hand, in the resin-filled lens disclosed in Japanese Patent Application Laid-Open No. 60-15552, the heat resistance of the transparent resin to be filled is often poor, and a resin having a high refractive index does not readily exist. There is a problem that it may be difficult to obtain a lens having lens performance. Furthermore, in the resin-filled lens, in the case of a flat lens formed by bonding another transparent glass substrate to the surface on the concave side, the thickness of the cover glass to be bonded is usually very thin. There are problems such as high polishing costs and the possibility of producing defects in the manufacturing process and not increasing the yield.
[0008]
Therefore, the present invention addresses the problem of the filling material limitation in the resin-filled lens disclosed in JP-A-60-15552 and the problem of the cover glass in the flat lens disclosed in JP-A-3-231701. It is an object of the present invention to provide a solved flat lens array.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, in the present invention, in the glass substrate having a transparent conductive thin film on the surface of a plurality of substantially spherical or substantially cylindrical recesses arranged one-dimensionally or two-dimensionally on the surface thereof, Metal oxide particles are filled as a transparent material having a refractive index higher than that of the glass substrate so that the concave portion is flat on the conductive thin film.
[0010]
As a method of filling the metal oxide particles, the glass substrate is immersed in an electrophoretic electrodeposition bath in which metal oxide particles are dispersed, and a voltage is applied between the substrate and the counter electrode. It can be carried out by electrophoretic deposition of the metal oxide particles.
[0011]
Further, the glass substrate is a low expansion non-alkali glass substrate, and the metal oxide particles have an electrophoretic electrodeposition film of the metal oxide particles having a refractive index higher by 0.05 to 0.8 than the refractive index of the glass substrate. Is a flat lens array.
[0012]
Examples of the glass substrate used in the present invention include quartz glass, soda lime glass, alkali aluminosilicate glass, alkali borosilicate glass, multicomponent non-alkali glass, and low expansion crystallized glass.
[0013]
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, sputtering, or vapor deposition. Among these, the coating film pyrolysis method of a metal organic compound is preferable for mass production because the film formation cost is low. The film thickness is determined from the sheet resistivity and visible light transmittance of the film. The sheet resistivity is preferably 10 ⁴ Ω / □ or less, and the visible light transmittance is preferably 80% or more.
[0014]
Examples of the metal oxide particles for electrophoretic electrodeposition of the present invention include single metal oxides such as TiO ₂ , ZrO ₂ , Al ₂ O ₃ , and Sb ₂ O ₅ , 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 Examples thereof include composite metal oxides such as _2- Sb ₂ O ₅ , Al ₂ O ₃ —Sb ₂ O ₅ , BaTiO ₃ , and PbTiO ₃ . Moreover, each of these metal oxide particles may be used alone, or may be used as a mixture containing at least two kinds of particles of the single metal and composite metal oxide particles.
[0015]
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, a metal oxide aggregate film in which the refractive index is changed by n = 1.6 to 2.2 can be obtained. Furthermore, if the mixing ratio is appropriately selected in combination with SiO ₂ (n = 1.46), the metal oxide aggregate film in which the refractive index is changed between n = 1.46 and 2.2. Can be obtained.
[0016]
These metal oxide particles can be obtained by preparing in the gas phase by a CVD method or the like. It can also be obtained by growing a sol hydrolyzed in the liquid phase and centrifuging it. The composite metal oxide particles are easier to prepare from the liquid phase. The centrifuged particles are fired to control the surface properties as needed. The particles obtained from the gas phase and the liquid phase are used after being dispersed in a solvent by a predetermined method.
[0017]
As the metal oxide particles, it is preferable to select particles having a refractive index higher by about 0.05 to 0.8 than the refractive index of the glass substrate from the viewpoint of the light condensing performance of the obtained flat microlens. As the size of the particles, those having an arbitrary particle size can be used according to the purpose. In general, the average particle size is preferably about 1 to 500 nm.
[0018]
The concentration of the metal oxide particles in the electrophoretic electrodeposition solution is preferably in the range of 0.1% to 15% by weight. Further, about 1% by weight is practically preferable. Further, the electrophoretic electrodeposition solution contains an organic solvent, water, a base, a surfactant, a drying inhibitor, a binder and the like.
[0019]
The organic solvent is used to disperse 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.
[0020]
The base is added to adjust the pH of the electrophoretic electrodeposition solution. As the base to be added, ammonia water is generally used, and the pH of the ammonia water is preferably about pH = 11.7.
[0021]
The drying inhibitor is used in order to prevent the occurrence of cracks by subjecting the aggregate film of electrophoretic electrodeposited metal oxide particles to exposure to air after electrodeposition and drying. Specific examples of the drying inhibitor include organometallic compounds such as 1.4-dioxane and methyltriethoxysilane. Further, the concentration of the drying inhibitor in the electrophoretic electrodeposition solution is preferably in the range of 0.1 wt% to 10 wt%. Further, about 1% by weight is practically preferable.
[0022]
Examples of the binder used in the present invention include organic polymers such as polyacrylic acid.
[0023]
As the counter electrode used in the electrophoresis of the present invention, platinum, stainless steel, graphite, titanium and the like which are not easily eroded by alkali can be used. The polarity is specifically as follows. When metal oxide particles that are negatively charged in a solution such as SiO ₂ , TiO ₂ , or ZrO ₂ are electrophoresed and electrodeposited and filled, an electric field is applied so that the glass substrate side becomes the anode. In addition, when metal oxide particles that are positively charged in a solution such as Al ₂ O ₃ or ITO are electrophoresed and electrodeposited and filled, an electric field is applied so that the glass substrate side becomes a cathode. In either case, the voltage is in the range of 5 to 200 V, and may be either direct current or pulse current.
[0024]
As the corrosion-resistant protective film material used in the production method of the present invention, an appropriate material can be selected depending on the resistance to the etchant to be used, the workability of photolithography patterning, and the film formation cost. 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. For example, 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.
[0025]
The composition of the etchant of the glass substrate used in the production 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. In addition, 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 as required. It is good to add.
[0026]
The thickness of the electrophoretic electrodeposition aggregate film of metal oxide particles in the present invention is not particularly limited. Generally, it is only necessary to have a thickness that can exhibit the light condensing performance of the microlens after film formation and baking.
[0027]
[Action]
According to the present invention, conductivity is imparted to a substrate by forming a transparent conductive thin film on the surface of a plurality of substantially spherical or substantially cylindrical recesses arranged one-dimensionally or two-dimensionally on the surface of the glass substrate. This enables stacking of metal oxide particles by electrophoretic electrodeposition. Furthermore, since a material having a refractive index higher than that of the glass substrate is selected as the metal oxide particles, a flat lens array having a convex or lenticular lens can be obtained.
[0028]
【Example】
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a general cross-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, a concave portion 13 having a substantially spherical or substantially cylindrical curved surface that is arranged one-dimensionally or two-dimensionally is formed by, for example, a chemical etching method described later. This concave portion 13 has a boundary ridge line 16 between adjacent concave portions as shown in FIG. 2 (a), (b), and (c) in a plan view, such as a honeycomb having a square lattice, a hexagonal close-packed lattice, or a stripe, Generally, it is formed so as to be densely packed with polygons having the same shape.
[0029]
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 stacked and filled to each lens of the lens array. Then, an electrophoretic electrodeposition aggregate film 30 of metal oxide particles is provided continuously, and the electrophoretic electrodeposition aggregate film 30 is sintered by firing, and then opposed to the lens surface by polishing or the like. The flat lens array 10 is obtained by making the surface flat and controlling the parallel light rays incident from the substrate to have a thickness that converges near the surface of the electrophoretic electrodeposition aggregate film.
[0030]
FIG. 3 shows a principle diagram of the electrophoretic electrodeposition method. The principle of the electrophoretic electrodeposition method is described in Japanese Patent Laid-Open No. 5-246701 and 1994 Proceedings of the Ceramic Society of Japan 2H08 P.A. 513 is disclosed in detail.
[0031]
FIG. 4 is a schematic view of a liquid crystal display element using the flat lens array of the present invention. By aligning the arrangement pitch of the lenses of the lens array 10 in advance with the pixel pitch of the liquid crystal display element 50, the illumination light is condensed by each lens 12 of the flat lens array 10, and each pixel of the liquid crystal display element is collected. Illumination light that has passed through the transmissive aperture 51 and is blocked by the non-transmissive pixel wiring portion 52 such as electrodes and TFTs in the conventional liquid crystal display element effectively contributes to display, and an image with extremely high definition is obtained. It is done. Thereby, deterioration due to heating of the liquid crystal element can be reduced.
[0032]
(Specific example 1)
FIG. 5 shows an example of a production 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 with a predetermined lens arrangement pattern by photolithography in which a photoresist was applied, exposed, and developed (FIG. 5A). The formed small aperture array is a hexagonal lattice array shown in FIG. 6, whereby a honeycomb type lens array as shown in FIG. 2B is obtained. The diameter of the small opening 41 is desirably sufficiently smaller than the diameter of the lens to be finally obtained.
[0033]
The Cr film-coated substrate having the small opening 41 was immersed in an etchant containing hydrofluoric acid (HF) and sodium dodecylbenzenesulfonate as a surfactant, and chemical etching was performed (FIG. 5B). Here, the concentrations of hydrofluoric acid and sodium dodecylbenzenesulfonate were 10 wt% and 0.1 wt%, respectively. As a result, the surface of the quartz glass substrate is isotropically etched starting from the small opening 41 of the Cr film, and a recess 14 that is substantially a part of a sphere is obtained as shown in FIG. This first-stage etching is stopped in a state where a flat boundary portion 15 having a slight width is left between the adjacent concave portions 14 (see FIG. 5C).
[0034]
Next, after removing the Cr film 40 from the surface of the quartz glass substrate (FIG. 5C), the entire substrate surface was etched by being immersed again in the previous etchant. By this two-stage etching, the etching at the periphery of the recess progressed, and the boundary 15 between the adjacent recesses became a ridgeline 16 with a sharp upper end (FIG. 5D). That is, each of them formed a hexagonal shape that was the same in plan view, and a close-packed array in which adjacent concave portions were in close contact. In addition, the depth of the formed recessed part was about 15 micrometers.
[0035]
After the two-step etching process, an indium tin oxide film 20 was formed as a transparent conductive thin film in the recess 14 by a coating film pyrolysis method. Here, the coating solution contains a metal organic compound of indium and a metal organic compound of tin, which is formed on a substrate by a spin coating method, and then subjected to heat treatment at 500 ° C. for 30 minutes in the air to remove the organic component. Combusted and decomposed to form a metal oxide. The thickness of the coating film after firing was about 100 nm, and the specific resistance was 4 × 10 ⁻² Ωcm.
[0036]
The quartz glass substrate with the transparent conductive thin film was immersed in an electrophoresis electrodeposition bath shown below, and a DC voltage was applied so that the substrate became an anode (see FIG. 3).
[0037]
Here, in the electrophoretic electrodeposition bath, a mixed solution of silica-titania composite metal oxide particles (average particle size 10 nm) prepared by co-hydrolysis-condensation polymerization of metal alkoxide with methyltriethoxysilane, ammonia water, and dimethylacetamide. A surfactant and an organic polymer binder were added to a dispersion medium to which trace amounts were added, and the mixture was uniformly dispersed by stirring for 1 hour at room temperature. The electrophoresis conditions were set to a DC voltage of 50 V to 10 minutes.
[0038]
By the above operation, a quartz glass substrate with an electrophoretic electrodeposition aggregate film made of silica-titania composite metal oxide particles having a film thickness of about 200 μm was obtained. The obtained aggregate film completely fills the concave portion of the quartz glass substrate surface with the transparent conductive film, and the film thickness of 200 μm is sufficiently thick compared to the depth of the concave portion described above, so the surface is 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 varies depending on the firing conditions.
[0039]
The electrophoretic electrodeposited silica-titania aggregate film-coated quartz substrate was baked at 400 ° C. for 1 hour and further at 1000 ° C. for 1 hour to sinter the aggregate film. By the sintering, the thickness was about 100 μm and the refractive index was 1.62. As described above, the silica-titania composite 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 a light-transmitting substrate having a thickness of 100 μm thereon. Therefore, a thin cover glass is not necessary.
[0040]
The film thickness of the electrodeposited aggregate film is such that the light collecting performance of the microlens can be exhibited. Further, in order to improve the flatness of the electrodeposited aggregate film surface, the surface may be polished by about 5 μm. That is, the film thickness of the aggregate film may be controlled so that parallel light incident from the substrate is condensed near the surface of the electrodeposited aggregate film.
[0041]
The curvature radius of the lens convex part of the lens array produced this time is about 20 μm, and the focal length f of the lens is about 120 μm.
[0042]
(Application examples)
A transparent conductive film ITO was formed on the plane side of the flat lens array obtained in Example 1 by a vacuum film forming method to form a counter electrode. Further, this was bonded to a second substrate on which a separate polycrystalline silicon (p-Si) TFT type pixel electrode was formed with a gap, and liquid crystal was injected into the gap to form a liquid crystal display element.
[0043]
Since the arrangement pitch of the lenses of the lens array is matched to the pixel pitch of the liquid crystal display element, the illumination light is condensed by each lens of the flat lens array and transmitted through the liquid crystal layer and the pixel electrode of each pixel of the liquid crystal display element. In addition, the illumination light blocked by the non-light-transmitting portions such as electrodes and TFTs effectively contributed to the display, and an image with extremely high definition was obtained.
[0044]
【The invention's effect】
In the present invention, in the flat lens array obtained by filling the concave portion of the glass substrate with a transparent material having a higher refractive index than that of the glass substrate, the transparent material is filled with metal oxide particles by an electrophoretic electrodeposition method. It is said. As the metal oxide particles, those having a wide range of refractive indexes can be selected, so that lens design restrictions are reduced. In addition, since the metal oxide particles are inorganic, the flat lens array is more reliable.
[0045]
Furthermore, since this metal oxide particle aggregate film can have a role as a cover glass, it is not necessary to use an expensive thin cover glass, and an inexpensive flat lens array can be obtained.
[Brief description of the drawings]
FIG. 1 is a general cross-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 view for explaining the principle of electrophoretic electrodeposition.
FIG. 4 is a schematic view of a liquid crystal display element using the flat lens array of the present invention.
FIGS. 5A and 5B are diagrams illustrating a manufacturing process of a flat lens array according to the invention.
FIG. 6 is a hexagonal array of small openings formed in a Cr film.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Flat type lens array 11 Glass substrate, such as quartz substrate 12 Each lens part 13 of the lens array filled with the electrophoretic electrodeposition aggregate film Recessed part 14 having a substantially spherical or substantially cylindrical curved surface Concave portion 15 that is substantially a part of a sphere 15 Boundary portion 16 between adjacent concave portions Boundary ridge line 20 between adjacent concave portions Transparent conductive thin film 30 Electrophoretic electrodeposition aggregate film 40 Corrosion-resistant protective Cr film 41 formed on Cr film Small opening 50 Liquid crystal display element 51 Pixel opening 52 Pixel wiring part 60 Electrodeposition bath 70 by electrophoresis method Power source 80 Counter electrode 90 Metal oxide particles

Claims (7)

A convex lens obtained by filling the concave portion with a transparent material having a plurality of substantially spherical or substantially cylindrical concave portions arranged one-dimensionally or two-dimensionally on the surface of the glass substrate, and having a higher refractive index than the glass substrate. In a flat lens array with a lenticular lens,
The flat lens array, wherein the transparent material comprises an aggregate film of transparent metal oxide particles obtained by electrophoretic electrodeposition. In the flat lens array according to claim 1,
The glass substrate is a low expansion glass substrate, and the metal oxide particles are metal oxide particles having a refractive index higher by 0.05 to 0.8 than a refractive index of the glass substrate. In the flat lens array according to claim 1 or 2,
The metal oxide particles are single metal oxide particles of TiO ₂ , ZrO ₂ , Al ₂ O ₃ , or Sb ₂ O ₅ , or 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. A flat lens array that is a composite metal oxide particle of any one of Al ₂ O ₃ —Sb ₂ O ₅ , BaTiO ₃ , and PbTiO ₃ . In the flat lens array according to claim 1 or 2,
The flat lens array, wherein the metal oxide particles are a mixture containing at least two or more of the single metal oxide particles and the composite metal oxide particles. The flat lens array according to claim 1,
The concave portion is filled with the metal oxide aggregate film, and the metal oxide aggregate film is further deposited thereon with a predetermined thickness. The glass substrate surface has a plurality of substantially spherical or substantially cylindrical recesses arranged one-dimensionally or two-dimensionally, a transparent conductive thin film is formed on the recess surface, and a transparent material having a higher refractive index than the glass substrate. Filling metal oxide particles by an electrophoretic electrodeposition method to produce a flat lens array having a convex lens or a lenticular lens,
The manufacturing method of the flat lens array characterized by including the following processes.
(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) A step of immersing the glass substrate in an etching solution containing hydrofluoric acid Step (d) Step of forming a transparent conductive thin film on the glass surface on the recess forming side (e) The glass substrate is immersed in an electrophoretic electrodeposition bath in which metal oxide particles are dispersed, and the substrate and the counter electrode Applying a voltage between the metal oxide particles to cause electrophoretic deposition of the metal oxide particles and filling the recesses (f) firing the glass substrate (g) polishing the glass substrate 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 the glass substrate and having a refractive index higher than that of the glass substrate is applied to the recesses by electrophoretic deposition. A liquid crystal display element using a flat lens array provided with a convex lens or a lenticular lens obtained by filling
A transparent electrode of a counter substrate of the liquid crystal display element on the surface of the metal oxide film;
A liquid crystal display element having a structure in which a liquid crystal is sandwiched between a second substrate on which a polycrystalline silicon (p-Si) TFT type pixel electrode is formed and the transparent electrode.

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