JP4293664B2 - Method for forming microlens array and microlens array - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a microlens array and a microlens array.
[0002]
[Prior art]
The microlens array is a microlens having a size of several hundred μm or less arranged in a one-dimensional or two-dimensional array, and is widely known in the field of optoelectronics. For example, when a microlens array corresponding to each pixel of the liquid crystal element is used, light shielded by the black matrix can be condensed on each pixel, and light use efficiency can be improved. (NIKKEI MICRODEVICES, (12) 129, (1991), Tadashi Aoki, National Technical Report, 36, (3) Jun. 116 (1990)). In addition, if a microlens array is used at the coupling portion between the optical fibers and the light receiving elements arranged in an array, the light receiving efficiency can be improved.
[0003]
Such a microlens array is one in which a minute convex lens is formed on a substrate, and a lens effect is generated by a refractive index distribution generated by ion exchange by bringing a substrate containing ions into contact with another ion source. There are proposed a refractive index distribution type microlens array, a structure in which a minute concave shape is formed on a substrate, and a convex lens is formed by filling a filling material having a refractive index higher than that of the substrate in the concave shape.
[0004]
A structure in which a concave lens is formed and a convex lens is formed by filling a concave mold with a filling material having a refractive index higher than that of the substrate, so that the surface of the resulting microlens array itself can be formed flat. Compounding with an optical element such as an interference filter and a pinhole, and bonding with a liquid crystal element are easy, and there is an advantage that it is extremely advantageous in manufacturing.
[0005]
As a method of forming a microlens array in which a minute concave shape is formed on a substrate and a concave lens is filled with a high refractive index material to form a convex lens, a method by wet etching is known. In this method, an etching mask having a minute opening is formed on a substrate such as glass, immersed in an etching solution such as hydrofluoric acid, and isotropic wet etching is performed with the etching solution from the minute opening to form a substrate such as glass. In this method, a hemispherical concave shape is formed, then the etching mask is removed, and the concave forming portion is filled with a filling material having a refractive index higher than that of the substrate. In addition, as this filling substance, organic substances such as polycarbonate and acrylic styrene copolymer resin are generally known.
[0006]
[Problems to be solved by the invention]
However, in the method of forming a microlens array by wet etching, the shape of the microlens that can be formed for isotropic etching is determined by the size of the minute opening, and it is extremely difficult to form a microlens array of any shape. is there. Further, the substrate to be used must be able to be etched with an etching solution, and only a limited material such as quartz glass can be used as the material constituting the substrate.
[0007]
The present invention has been made in view of the problems of the microlens array forming method and the microlens array described above, and a microlens array having an arbitrary shape can be formed, and an arbitrary material is selected as the substrate material to be used. An object of the present invention is to provide a microlens array forming method and a microlens array excellent in optical characteristics.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the first invention
A recessed portion forming step of forming a plurality of minute recessed portions on a transparent substrate;
A lens portion forming step of forming a lens portion by filling the concave portion formed by the concave portion forming step with a filling material having a refractive index higher than the refractive index of the substrate;
The concave portion forming step includes a transfer layer forming step for forming a transfer layer having a plurality of minute transfer concave shapes on the substrate, and a plurality of minute concave shapes on the substrate by transferring the shape of the transfer layer to the substrate. And a transfer process for forming the portion.
[0009]
The second invention is
In the method for forming a microlens array according to the first invention,
In the transfer layer forming step, a transfer material layer constituting the transfer layer is formed on the substrate, and a resist mask is formed on the transfer material layer in which minute openings corresponding to the arrangement of the microlens array are formed, A method of forming a microlens array, comprising a step of forming a plurality of minute transfer concave shapes on the transfer material layer by etching through the resist mask to obtain a transfer layer.
[0010]
The third invention is
In the method for forming a microlens array according to the first invention,
In the transfer layer forming step, a wall-like object is formed on the substrate corresponding to the arrangement of the microlens array, and a liquid material is supplied between the wall-like objects to form a transfer layer having a concave shape for transfer. A method for forming a microlens array.
[0011]
The fourth invention is:
In the method for forming a microlens array according to the first invention,
The transfer layer forming step uses a photomask in which a photosensitive resin layer is formed on the substrate, a pattern corresponding to a microlens array shape is formed on the photosensitive resin layer, and the photomask and the photosensitive layer are formed. A method for forming a microlens array comprising a step of forming a plurality of transfer layers having a concave shape for transfer by exposing and developing at a distance of 20 μm or more from a resin layer.
[0012]
The fifth invention is:
In the method for forming a microlens array according to the first invention,
In the transfer layer forming step, a photosensitive resin layer is formed on the substrate, and the photosensitive resin layer is exposed and developed using a gradation mask in which a pattern corresponding to a microlens array shape is formed. A method for forming a microlens array, comprising the step of forming a transfer layer having a plurality of minute transfer concave shapes.
[0013]
The sixth invention is:
In the method for forming a microlens array according to the fifth invention,
A method of forming a microlens array, wherein the gradation mask is formed of minute dots.
[0014]
The seventh invention
In the method of forming a microlens array according to any one of the first to sixth inventions,
A method for forming a microlens array, wherein a transfer step of transferring the shape of the transfer layer to a substrate is performed by dry etching.
[0015]
The eighth invention
In the method for forming a microlens array according to the seventh invention,
In the method for forming a microlens array, the dry etching rate in the transfer step is different between the dry etching rate of the substrate and the dry etching rate of the transfer layer.
[0016]
The ninth invention
In the method of forming a microlens array according to any one of the first to eighth inventions,
9. The microlens array according to claim 1, wherein the substrate includes a concave portion forming substrate that forms a plurality of minute concave portions, and a support substrate that supports the concave portion forming substrate. It is the formation method.
[0017]
The tenth invention is
A microlens array formed by the microlens array forming method according to any one of the first to tenth aspects of the invention.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an explanatory diagram of a method for forming a microlens array according to an embodiment of the present invention. The microlens array forming method according to this embodiment includes (1) a transfer layer forming step of forming a transfer layer having a plurality of minute concave portions transferred onto the substrate (FIG. 1A). )), (2) a transfer step (see FIG. 1B) for transferring the shape of the transfer layer to the substrate to form a plurality of minute concave portions on the substrate, and (3) formed by this transfer step. A lens portion forming step (see FIGS. 1C and 1D) for forming the lens portion by filling the concave portion with a filling material having a refractive index higher than that of the substrate. A method for forming a microlens array according to the embodiment will be described below with reference to FIG.
[0019]
(1) Transfer layer forming process
This step is a transfer layer forming step in which a transfer layer 20 having a plurality of concave concave spherical or aspherical shapes 30 to be transferred to the substrate 10 is formed on the substrate 10.
[0020]
Here, the substrate 10 must be transparent to the wavelength used for the microlens array, and Al ₂ 0 _Three Substrates made of metal oxides such as substrates and MgO substrates, ceramic substrates such as SiC, SiN and MgF, silicon substrates and GaAs substrates, various glass substrates such as quartz glass and alumina silicate glass, polyethylene terephthalate (PET), polycarbonate and polyurethane Or a plastic substrate such as epoxy resin, or a composite substrate thereof is appropriately selected.
[0021]
The transfer layer 20 is formed by forming a transfer material layer 21 (see FIG. 2) on the substrate 10 and forming a transfer concave shape 30 on the transfer material layer 21. The transfer material layer 21 is formed of an organic polymer such as polyethylene terephthalate (PET), polycarbonate, polyurethane, epoxy resin, polyimide, polyimide precursor, water-soluble polymer such as polypinyl alcohol or hydroxyethyl cellulose that can form the concave shape 30 for transfer. A molecule or a composite material thereof is appropriately selected. Al ₂ 0 _Three It is also possible to use metal oxides such as MgO, ceramics such as SiC and SiN, various glasses such as silicon, quartz glass, and alumina silicate glass.
[0022]
The transfer material layer 21 may be formed on the entire surface of the substrate 10 or may be partially formed at a site where the microlens array is formed. As a method for forming the transfer material layer 21, a known method such as screen printing, spin coating, vacuum deposition, sputtering, or CVD is used. The thickness of the transfer material layer 21 to be formed is appropriately determined depending on the desired shape of the microlens array, but is preferably about 0.05 μm to 100 μm.
[0023]
The method of forming the concave shape 30 for transfer is a method of forming by machining, a method of forming by pressing or heating and pressing on the transfer layer using a press mold having a convex mold, and a photocurable resin on the substrate. A method of forming a photocurable resin by curing using press and light irradiation using a press mold having a convex mold, a method of forming by injection molding using an injection mold having a convex mold, or a minute opening For example, a method of forming by etching using a resist mask having the above is used. In particular, a method of forming by etching using a resist mask having a minute opening is an excellent method capable of efficiently forming a high-definition spherical concave shape for transfer as compared with other methods.
[0024]
FIG. 2 is an explanatory diagram of a method for forming the concave shape 30 for transfer by etching using a resist mask having a minute opening. In this method, first, the transfer material layer 21 is formed on the substrate 10. Next, a resist mask 2 provided with minute openings 3 corresponding to the arrangement of the microlens array is formed on the transfer material layer 21 (see FIG. 2A). Next, wet etching or dry etching is performed using the resist mask 2 as a mask to form a concave shape 30 for transfer (see FIG. 2B). Next, the resist mask 2 is removed to obtain a substrate in which a transfer layer 20 is formed on the substrate 10 (see FIG. 2C).
[0025]
Here, the resist mask 2 is appropriately selected from materials that are not affected by the step of forming a spherical concave shape for transfer on the transfer layer through the minute opening 3, and a metal such as Au, Cr, W, Ta, or the like, ITO, MgO, Al ₂ O _Three Metal oxides such as, organic compounds such as epoxy resins and novolak resins are used. The shape of the minute opening 3 is formed corresponding to the arrangement of the desired microlens array, and the size of the opening needs to be the same as or smaller than the diameter of the desired microlens. .
[0026]
The method of forming the microscopic aperture 3 is a method of forming the resist mask 2 in a portion other than the microscopic aperture 3 by printing such as screen printing or intaglio printing using an ink capable of forming the resist mask 2. A method for forming a resist mask 2 and forming a micro-opening 3 by using a photolithography process, a portion for forming the micro-opening 3 is masked in advance, and a material for forming the resist mask 3 is formed on the entire surface. Then, a method of removing the masked portion and forming the minute opening 3 is used.
[0027]
In the wet etching performed through the minute opening 3, the transfer material layer 21 is etched but the resist mask 2 is not etched. The wet etching is performed by isotropically etching a part of the transfer material layer 21 from the minute opening 3. By doing.
[0028]
Etching solutions in this case include hydrofluoric acid aqueous solution, sulfuric acid aqueous solution, nitric acid aqueous solution, hydrochloric acid aqueous solution or an aqueous solution composed of a mixed solution of these acids, sodium carbonate aqueous solution, potassium hydroxide aqueous solution, sodium hydroxide aqueous solution, hydrazine and amine compounds. Selected from organic solutions such as acetone and butyl acetate.
[0029]
In the dry etching performed through the minute openings 3, the transfer material layer 21 is etched and the resist mask 2 is processed in an air layer containing an etching gas that does not etch, and a part of the transfer layer 21 is removed from the minute openings 3. A process of isotropic etching is performed. The etching gas in the gas layer at this time is CF _Four , CHF _Three , SF ₆ , NF _Three , Cl ₂ A plasma reactive gas containing components such as these is preferred.
[0030]
The method of removing the resist mask 2 is appropriately selected depending on the material constituting the resist mask 2, and dissolution removal of the resist mask 2 with an acid aqueous solution, an alkali solution or an organic solvent, removal of the resist mask 2 by dry etching, or the like is used. Further, the resist mask 2 does not necessarily need to be removed, and the removal process is not necessary when the optical path of the microlens array is not affected.
[0031]
FIG. 3 is an explanatory diagram of another method for forming the transfer layer 20 having a concave shape for transfer. In the method shown in FIG. 3, wall-like objects 5 are formed on the substrate 10 corresponding to the arrangement of the microlens arrays (see FIG. 3A), and at least a liquid material 51 is provided between these wall-like objects 5. The transfer layer 20 having the transfer concave shape 30 is formed by drying the liquid material.
[0032]
3A, the wall-like object 5 is formed corresponding to the arrangement of the microlens array, and the shape thereof is formed and arranged on the substrate 10 in a polygonal shape such as a quadrangular shape, a hexagonal shape or an octagonal shape or a circular shape. .
[0033]
The wall 5 is made of polyethylene terephthalate (PET), polycarbonate, polyurethane, epoxy resin, polyimide, polyimide precursor, organic polymer such as water-soluble polymer such as polypinyl alcohol or hydroxyethyl cellulose, or a composite material thereof. It is selected appropriately. Al ₂ 0 _Three It is also possible to use metal oxides such as MgO, ceramics such as SiC and SiN, various glasses such as silicon, quartz glass, and alumina silicate glass.
[0034]
The method for forming the wall-like object 5 is a method of forming the wall-like object 5 by printing such as screen printing or intaglio printing using an ink capable of forming the wall-like object 5, and forming a material for forming the wall-like object 5 on the entire surface of the substrate 10. , A method of forming the wall-like object 5 using a photolithography process, a portion for forming the wall-like object 5 is masked in advance, a material for forming the wall-like object 5 is formed on the entire surface, and the masked portion is removed to form a wall shape. A method for forming the object 5 is used.
[0035]
The liquid material 5 is obtained by dissolving a non-volatile substance in a volatile solution, and a sol-gel solution or a solution obtained by dissolving an organic polymer in a solvent is effective.
[0036]
Further, as a method of supplying the liquid material 51 into the wall-shaped object 5, a method of applying a liquid material to the upper surface of the substrate 10 can be used. As a method for applying the liquid material on the upper surface of the substrate 10, methods such as screen printing, curtain coating, dipping, and spin coating are preferable. By applying and drying the liquid material, a spherical or aspherical concave shape is formed on the wall surface of the wall-like material 5 due to the surface tension of the liquid material. In this case, some liquid material 51 may remain on the wall-shaped material 5.
[0037]
By forming a wall-like object 5 corresponding to the arrangement of the microlens array on the substrate 10, applying a liquid material 51 to the entire wall-like object and drying it, thereby forming a minute concave shape for transfer. Since the concave shape for transfer 30 can be formed without using a press die having a convex shape or the like, a high-definition concave shape for transfer can be efficiently formed.
[0038]
FIG. 4 is an explanatory view of still another method for forming the transfer layer 20 having a concave shape for transfer. In the method shown in FIG. 4, a photomask 83 in which a fine pattern corresponding to the arrangement and shape of the microlens array is formed on the substrate 10 on which the photosensitive resin layer 7 as a transfer material layer is formed is formed on the substrate 10. The transfer layer 20 having the concave shape 30 for transfer is obtained by placing the substrate at a distance of 20 μm or more from the surface, exposing the surface, and developing the surface.
[0039]
As the photosensitive resin 7, a known photosensitive resin used in a printed circuit board, a semiconductor manufacturing process, or the like can be used, and a known method such as screen printing, curtain coating, dipping, or spin coating is used as a method for forming the photosensitive resin 7. It is done. The photomask 83 is formed by forming a light transmitting portion and a light blocking portion on a transparent support such as glass or plastic. When a photodegradable photosensitive resin is used as the photosensitive resin layer 7, the photomask 83 is used for transfer. When a photomask that transmits light is used for the portion where the concave shape 30 is formed and a photopolymerizable photosensitive resin is used, it is necessary to use a photomask that does not transmit light for the portion where the concave shape 30 for transfer is formed. .
[0040]
Here, when the interval between the photosensitive resin layer 7 and the photomask 83 is set to 20 μm or more, the transmitted light is diffracted, and a difference in light amount occurs between the central portion and the peripheral portion where the microlens is formed. By forming the photosensitive resin layer as described above and developing the exposed photosensitive resin layer 7 with an interval of 20 μm or more with a developer, a transfer concave shape 30 is obtained.
[0041]
Here, the distance between the photosensitive resin layer 7 and the photomask 83 needs to be 20 μm or more. However, if the distance is too wide, the amount of diffracted light increases, and the shape of the concave shape 30 for transfer cannot be formed. This interval depends on the exposure apparatus used, but is preferably 200 μm or less. According to this method, since the concave shape for transfer 30 can be formed without using a press die having a convex shape, a high-definition concave shape for transfer can be efficiently formed.
[0042]
FIG. 5 is an explanatory view of still another method for forming the transfer layer 20 having a concave shape for transfer. In the method shown in FIG. 5, a gradation mask 84 in which a fine pattern corresponding to the arrangement and shape of the microlens array is formed on the substrate 10 on which the photosensitive resin layer 7 as a transfer material layer is formed. The transfer layer 20 having the concave shape 30 for transfer is obtained (see FIG. 5B) by developing after exposure to light (see FIG. 5A), developing after exposure.
[0043]
As the photosensitive resin 7, a known photosensitive resin used in a printed circuit board, a semiconductor manufacturing process, or the like can be used. As a method for forming the photosensitive resin 7 on the substrate 10, known methods such as screen printing, curtain coating, dipping, and spin coating can be used. Used.
[0044]
The gradation mask 84 is formed by forming a light transmitting portion and a light blocking portion on a transparent support such as glass or plastic, and corresponds to each microlens of the microlens array as shown in FIG. The portion has a configuration in which the light transmission amount changes stepwise. Here, the gradation mask that changes the light transmittance stepwise changes the thickness of the material such as Cr that forms the light-shielding portion and changes the amount of transmission stepwise, and the materials that have different light transmission amounts sequentially. It is the structure to form.
[0045]
Further, as a more preferable gradation mask, fine dots having a resolution equal to or less than the resolution of the photosensitive resin 7 are used, and the density for forming the fine dots is sequentially changed to change the light transmission amount step by step. Is effective.
[0046]
Further, when a photodegradable photosensitive resin is used as the photosensitive resin layer 7, the gradation mask 84 uses a photomask through which light is transmitted stepwise in a portion where the transfer spherical concave shape 34 is formed. When a polymerizable photosensitive resin is used, it is necessary to use a gradation mask that does not transmit light stepwise to a portion where the concave shape for transfer 30 is formed.
[0047]
As described above, the photosensitive resin layer 7 is formed, and the photosensitive resin layer 7 exposed using the gradation mask 84 is developed with a developer, whereby the transfer concave shape 30 is obtained.
[0048]
In this case, by using the gradation mask 84, the light transmission amount changes stepwise, the development amount of the photosensitive resin layer 7 changes stepwise, and the transfer concave shape 30 is obtained. Further, by controlling the change in the light transmission amount of the gradation mask 84, the shape of the concave shape for transfer 30 can be spherical or aspherical.
[0049]
The above-described method using the gradation mask has an advantage that the concave shape 30 for transfer can be formed with high accuracy and efficiency without using a press die having a convex shape, and a spherical shape as the concave shape for transfer. In addition to the above, an aspherical shape can be easily and efficiently formed.
[0050]
(2) Transfer process
In this step, the shape of the transfer layer 20 formed in the transfer layer forming step is transferred to the substrate 10 to form a plurality of minute concave portions 31 (see FIG. 1B) on the substrate. Here, as a method for transferring the concave shape 30 for transfer to the substrate 10, an etching method, a sand blast method, a method by ion milling, or the like is possible.
[0051]
As a method used for this transfer process, in particular, if a dry etching method is used, a plurality of minute concave portions 31 can be formed on the substrate 10 with high accuracy and efficiency. Among dry etching, CF _Four , CHF _Three , SF ₆ , NF _Three , Cl ₂ Reactive ion etching using a reactive gas such as is preferable. In this case, when etching is performed under the condition that the dry etching rate of the transfer concave shape 30 and the dry etching rate of the substrate 10 are different, a minute concave portion 31 obtained by amplifying the shape of the transfer concave shape 30 can be formed. It is possible to control the optical properties of the array.
[0052]
More specifically, when the dry etching rate of the substrate 10 is twice as fast as the dry etching rate of the transfer concave shape 30, the depth of the minute concave portion 31 formed on the substrate 10 is It becomes twice the depth of the concave shape 30. Further, when the dry etching rate of the substrate 10 is 0.5 times the dry etching rate of the transfer concave shape 30, the depth of the minute concave portion 31 formed on the substrate 10 is the transfer concave shape 30. 0.5 times the depth of.
[0053]
Further, when the ratio of the dry etching rate of the transfer concave shape 30 to the dry etching rate of the substrate 10 is changed in the dry etching process, a minute concave portion 31 having an aspherical curvature is obtained, and an aspherical microlens array is obtained. It is possible to control the optical characteristics of the microlens array.
[0054]
Here, the dry etching rate of the transfer concave shape 30 and the dry etching rate of the substrate 10 can be changed by a combination of the material of the substrate 10 to be used and the material of the transfer layer 20. Moreover, it can be changed according to dry etching conditions such as a dry etching method and a gas type to be used.
[0055]
(3) Lens part formation process
In this step, a plurality of minute concave portions 31 formed by the concave portion forming step are filled with a filling material having a refractive index higher than the refractive index of the substrate 10 to form the lens portions 32, respectively. Is a step of forming.
[0056]
The filling material having a refractive index higher than that of the substrate 10 needs to be transparent with less scattering with respect to the wavelength used for the microlens array, and may be a plastic such as polyethylene terephthalate (PET), polycarbonate, polyurethane, epoxy resin, or the like. These composite materials are appropriately selected. In particular, organic substances containing S in the molecular chain are effective because of their high refractive index.
[0057]
The method of filling the concave portion 31 with a filling material having a refractive index higher than that of the substrate 10 is selected as appropriate depending on the characteristics of the filling material used, a method of applying and curing a liquid material, a method of melting and bonding, and supplying a monomer. A method of polymerizing with heat or light is used. In addition, after forming the lens part 32, it is also preferable to grind and flatten the formed surface.
[0058]
Further, as a mode of filling the concave portion 31 with the filling material, as shown in FIG. 1C, in addition to the mode of filling the filling material only into the concave portion 31 of the substrate 10, FIG. As shown in FIG. 5, the filling material may be filled into the concave portion 31, and at the same time, the filling material may be applied to the surface of the substrate 10 to form the flat portion 33 made of the filling material.
[0059]
In addition, as shown in FIG. 6, it is also preferable to attach the support substrate 11 to the back surface of the substrate 10 in order to reinforce the mechanical strength of the substrate 10. According to this, since the material of the substrate 10 can be selected considering only the ease of forming the concave portion 31 without being restricted by the mechanical strength, a more appropriate material can be selected. It becomes. In this case, the substrate 10 and the support substrate 11 need to be transparent to the light used, and the substrate 10 is preferably an organic polymer material such as a resin that can easily form the concave portion 31, and the support substrate 11 has high mechanical strength. Ceramics and glass are preferred.
[0060]
The microlens array formed by the above-described microlens array formation method has high accuracy, excellent optical characteristics, can form a flat microlens array, and can be easily integrated with other optical elements. . The method for forming a microlens array and the microlens array of the present invention are not limited to a microlens array formed on a liquid crystal element or a microlens array used in a coupling portion of an optical fiber and a light receiving element. It can also be used in the field of optoelectronics such as a condensing lens for optical pickup such as a disk, a one-dimensional image sensor, and a coupling element of an LED printer.
[0061]
Next, the present invention will be described in more detail with reference to examples.
Example 1
FIG. 7 is an explanatory diagram of a method for forming a microlens array according to the first embodiment of the present invention. Hereinafter, Example 1 will be described with reference to FIG.
[0062]
A polyimide precursor (trade name: Semicofine 811 manufactured by Toray Industries, Inc.) is applied as a transfer layer 20 on a substrate 10 made of alkali-free glass (NA40: manufactured by HOYA Corporation) having a thickness of 1.1 mm, and a resist mask is formed thereon. 2 is applied with a photoresist (trade name: AZ1350; manufactured by Clariant Japan), exposed using a photomask for forming a microscopic aperture, and developed with an alkali developer to form the microscopic aperture 3, A part of the polyimide precursor transfer layer 20 was dissolved with the alkaline developer through the minute openings 3 to form a transfer concave shape 30 in the transfer layer 20 (see FIG. 7A).
[0063]
In this case, the micro openings 3 are arranged in a lattice shape within a 40 mm square at a pitch of 80 μm, and the depth of the formed concave shape 30 for transfer is 1 μm. Next, the resist mask 3 was dissolved and removed using butyl acetate to obtain a substrate 10 having a transfer layer 20 in which a minute transfer concave shape 30 having a depth of 1 μm was formed (see FIG. 7B).
[0064]
Next, the entire surface of the transfer layer 20 from which the concave shape for transfer 30 is formed is ground with a sand blasting apparatus using a SiC abrasive having an average particle diameter of 20 μm, and grinding is performed while preserving the concave shape for transfer 30. Subsequently, this is performed until the transfer layer 20 disappears, whereby the transfer concave shape 30 of the transfer layer 20 is transferred to the substrate 10, and a large number of minute concave portions 31 having a depth of 1.5 μm are formed on the substrate 10 ( (See FIG. 7C).
[0065]
Next, a polysulfone which is a filling material made of a material having a higher refractive index than that of the substrate 10 (for example, UDEL P-1700, trade name of Amoco Performance Products) is applied to the surface of the substrate 10 where the concave portion 31 is formed. Then, it was heat-welded at 200 ° C., and after cooling, the formed surface was polished to obtain a microlens array shown in FIG.
[0066]
The microlens array described above was a very good microlens array with a focal length variation of ± 18%.
[0067]
(Example 2)
FIG. 8 is an explanatory diagram of a method of forming a microlens array according to the second embodiment of the present invention. The second embodiment will be described below with reference to FIG.
[0068]
Photoresist (trade name: AZ1350; manufactured by Clariant Japan) is applied on a substrate 10 made of quartz glass having a thickness of 0.7 mm by spin coating to a thickness of 0.8 μm to form a photosensitive resin layer 7. The photosensitive resin layer 7 was exposed using a photomask 83 through which the array portion of the microlens array transmits light (see FIG. 8A).
[0069]
Next, the photosensitive resin layer 7 was developed with an alkali developer and heated at 200 ° C. for 1 hour to obtain a circular wall 5 having a width of 1 μm, a radius of 24 μm, and a height of 0.7 μm (FIG. 8). (See (B)). Next, an aqueous solution containing 5% by weight of polypinyl alcohol is dip coated on the substrate 10 on which the wall-like object 7 is formed, and dried at 60 ° C. for 2 hours, so that the concave shape 30 for transfer shown in FIG. It was formed on the substrate 10.
[0070]
Next, the substrate 10 is subjected to CHF using a parallel plate type plasma etching apparatus. _Three Etching was performed in plasma gas for 40 minutes, and the shape of the concave shape for transfer 30 was transferred to the substrate 10 to form a large number of minute concave portions 31 (see FIG. 8D). In this case, the etching rate of the substrate 10 was 2.5 times the etching rate of the concave shape 30 for transfer, and the depth of the minute concave portion 31 was 1, 4 μm.
[0071]
Next, a thermosetting Crezohernovolak epoxy resin, which is a filling material having a refractive index higher than that of the substrate, was applied to the surface on which the minute concave portion 31 was formed, thereby obtaining a microlens array (FIG. 8E )reference). This microlens array was very good with a variation in focal length of ± 8%.
[0072]
(Example 3)
FIG. 9 is an explanatory diagram of a method for forming a microlens array according to Example 3 of the present invention. Hereinafter, Example 3 will be described with reference to FIG.
[0073]
A photosensitive resin (trade name: AZ1350; manufactured by Clariant Japan) is applied to a substrate 10 made of quartz glass having a thickness of 0.7 mm by spin coating to a thickness of 1.2 μm, and the array portion of the microlens array transmits light. Using a photomask, the distance between the photomask and the photosensitive resin layer was 22 μm apart, and after exposure, development was performed with an alkaline developer to obtain a concave shape 30 for transfer having a width of 2 μm and a radius of 12 μm (see FIG. 9A). ).
[0074]
Next, the substrate 10 is subjected to CF using a parallel plate type plasma etching apparatus. _Four Etching was performed in plasma gas for 40 minutes to transfer the shape of the concave shape 30 for transfer to the substrate 10 to form a minute concave portion 31 (see FIG. 9B). The etching rate of the substrate 10 was 0.8 times the etching rate of the transfer concave shape 30, and the depth of the minute spherical concave portion 31 was 0.96 μm.
[0075]
Si, which is a filling material having a refractive index higher than that of the substrate 10, is formed on the surface on which the minute concave portion 31 is formed by sputtering, and the formed surface is polished and smoothed to obtain a microlens array (FIG. 9C )reference). This microlens array has a very good microlens array with a variation in focal length of ± 7%.
[0076]
(Example 4)
FIG. 10 is an explanatory diagram of a method for forming a microlens array according to Example 4 of the present invention. Hereinafter, Example 4 will be described with reference to FIG.
[0077]
A substrate 10 made of 100 μm fluororesin is formed on a Si support substrate 11, and a photosensitive resin (trade name: CD-500; manufactured by Asahi Chemical Research Laboratories) is applied on the substrate by screen printing to a thickness of 2.4 μm, The photosensitive resin layer 7 was formed and exposed using a gradation mask 84 in which the light transmittance of the arrangement portion of the microlens array changed in a stepwise manner (see FIG. 10A).
[0078]
Next, this substrate was developed with a developer composed of a 1% aqueous sodium carbonate solution heated to 35 ° C. to form a transfer concave shape 30 having a radius of 63 μm and a depth of 1.8 μm (FIG. 10B). reference). As shown in FIG. 10 (E), the gradation mask 84 has a light transmittance of 0% and a 5 μm outside of the circular portion at the center of the microlens 10 μm with respect to each microlens array portion of the microlens array. The circular portion has a light transmittance of 5%, the outer 5 μm circle portion has a light transmittance of 10%, the outer 5 μm circle portion has a light transmittance of 20%, and the outer 5 μm circle portion has a light transmittance of 30%. %, The outer 5 μm circle part has a light transmittance of 50%, and the outer 2 μm circle part has a gradation mask having a light transmittance of 100%. The gradation 84 mask controls the amount of transmitted light with a dot arrangement density of 2 μm.
[0079]
Next, the substrate 10 is subjected to CH 2 using a parallel plate type plasma etching apparatus. _Four And CF _Four Etching was performed in plasma of mixed gas for 40 minutes, and the shape of the concave shape 30 for transfer was transferred to the substrate 10 to form a minute concave portion 31 (see FIG. 10C). The etching rate of the substrate 10 was 3.8 times the etching rate of the concave shape 30 for transfer, and the depth of the minute concave portion 31 was 6.8 μm.
[0080]
Next, 2,5-dimethylmercapto-1,4-dithiane 1M and bidroxyethyl methacrylate 2M, which are high refractive fillers having a higher refractive index than that of the substrate 10, are applied to the surface on which the minute concave portion 31 is formed. A photo-curing resin consisting of 3 wt% of an agent (trade name Irgacure 184, etc., manufactured by Ciba-Gaigi Co., Ltd.) is applied by spin coating, and is bonded to the counter substrate 12 made of a glass plate. Irradiation gave a microlens array (see FIG. 10D). This microlens array was extremely good with a variation in focal length of ± 7%.
[0081]
【The invention's effect】
As described above in detail, the present invention has a concave portion forming step of forming a plurality of minute concave portions on a transparent substrate, and the concave portion formed by the concave portion forming step has a higher refractive index than the substrate. A lens portion forming step of forming a lens portion by filling a filling material having a refractive index, wherein the concave portion forming step includes transferring a plurality of transfer layers having a minute transfer concave shape to be transferred to the substrate. A transfer layer forming step for forming on the substrate; and a transfer step for transferring the shape of the transfer layer to the substrate to form a plurality of minute concave portions on the substrate. This makes it possible to efficiently form a microlens array having excellent characteristics and arbitrary optical characteristics.
[0082]
In this case, as the transfer layer forming step, a resist mask is formed on the transfer material layer with micro openings corresponding to the arrangement of the microlens array, and the transfer concave shape is formed on the transfer layer material layer through the micro openings. By adopting the method of forming the shape, it is possible to efficiently form the concave shape for transfer.
[0083]
Also, as a transfer layer forming step, after forming a wall-like object corresponding to the arrangement of the microlens array on the substrate, a liquid material is applied to the entire wall-like object and dried to form a minute transfer concave shape. By adopting it, it is possible to efficiently form a concave shape for transfer.
[0084]
Further, as a transfer layer forming step, a photosensitive resin layer is formed on the substrate, and a photomask corresponding to the arrangement of the microlens array and the photosensitive resin layer are exposed and developed at a distance of 20 μm or more to develop a minute size. By adopting the method of forming the concave shape for transfer, it is possible to efficiently form the concave shape for transfer.
[0085]
In addition, the transfer step of transferring the above-described concave shape for transfer to the substrate is performed by dry etching, and the shape of the concave shape for transfer is changed by making the dry etching rate of the transfer layer different from the dry etching rate of the substrate. An extremely fine microlens array can be formed on the substrate, or an aspherical concave can be formed on the substrate, and the optical characteristics of the microlens array can be precisely controlled. Making it possible to get a way.
[0086]
Furthermore, by configuring the substrate with a substrate that forms a minute concave portion and a support substrate that mechanically supports the substrate, the selectivity of the material of the substrate that can form the minute concave portion is greatly expanded. This makes it possible to obtain a higher-performance microlens array.
[0087]
Further, the microlens array formed by the above-described microlens array forming method has excellent optical characteristics.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an embodiment of a method for forming a microlens array according to the present invention.
FIG. 2 is an explanatory diagram of a transfer layer forming step.
FIG. 3 is an explanatory diagram of a transfer layer forming step.
FIG. 4 is an explanatory diagram of a transfer layer forming step.
FIG. 5 is an explanatory diagram of a transfer layer forming step.
FIG. 6 is a diagram showing an example in which a substrate is reinforced with a support substrate.
7 is an explanatory diagram of Example 1. FIG.
8 is an explanatory diagram of Embodiment 2. FIG.
9 is an explanatory diagram of Example 3. FIG.
10 is an explanatory diagram of Example 4. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Board | substrate, 20 ... Transfer layer, 30 ... Concave shape for transfer, 31 ... Fine concave part, 32 ... Lens part, 83 ... Photomask, 84 ... Gradation mask.

Claims (5)

A concave portion forming step for forming a plurality of minute concave portions on a transparent substrate, and a concave portion formed by the concave portion forming step is filled with a filling material having a refractive index higher than the refractive index of the substrate. A lens part forming step for forming a part,
The concave portion forming step includes a transfer layer forming step for forming a transfer layer having a plurality of minute transfer concave shapes on the substrate, and a plurality of minute concave shapes on the substrate by transferring the shape of the transfer layer to the substrate. A transfer step for forming a portion ,
The transfer layer forming step forms a wall-like object on the substrate corresponding to the arrangement of the microlens array, and supplies a liquid material between the wall-like objects to form a transfer layer having a concave shape for transfer. A method for forming a microlens array comprising the step of: 2. The method for forming a microlens array according to claim 1 , wherein the transfer step of transferring the shape of the transfer layer to the substrate is performed by dry etching. 3. The method for forming a microlens array according to claim 2 , wherein the dry etching rate in the transfer step is different between the dry etching rate of the substrate and the dry etching rate of the transfer layer. Method. In the method for forming a microlens array according to any one of claims 1 to 3, wherein the substrate comprises a concave portion substrate for forming a plurality of minute concave portions, and a support substrate for supporting the concave portion-forming substrate A method of forming a microlens array, comprising: A microlens array formed by forming a microlens array according to any one of claims 1 to 4.

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