Patent Publication Number: US-2013229703-A1

Title: Lens array, image forming device and method for manufacturing lens array

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-048147, filed Mar. 5, 2012; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a lens array to which a light-blocking film is provided between a plurality of lenses, an image forming device, and a method for manufacturing a lens array. 
     BACKGROUND 
     Some of the lens arrays used in the optical communication field, the optical disk field, the image display field, and the image transmission and combination field, the optical measurement field, the optical sensing field, and optical processing field, are equipped with a light-blocking film to prevent stray light from entering the lens array. Such lens arrays may be installed in image forming devices including a printer, a copy machine, a multi-function peripheral (MFP), and facsimile, as well as image forming devices including a scanner, multi-image transfer by a liquid display device, solid-state image devices, optical inter connection devices and confocal laser microscopes. 
     The lens array may be formed as a transparent molded element, therein individual lenses extend from the surface of the element to form the array. The array is positioned in a generally central region of the element, and a peripheral region extends around the lens array for mounting the element within a device where it is to be used. In the lens array, a light-blocking film is formed with an ultraviolet curable ink to cover the transparent regions of the element which do not function as lenses, which ink is cured by ultraviolet light. The ultraviolet curable ink possesses a sufficiently low viscosity to spread naturally into small spaces between lenses. However, the relatively low viscosity of the ultraviolet curable ink may result in the ink spreading outwardly from the lens area and into surrounding areas of the element on which the lens array is formed, such as at the edge of the element, and as a result the thickness of the cured film in the area of the lenses may not be sufficient to block light effectively. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing an image forming device according to a first embodiment. 
         FIG. 2  is a schematic diagram showing an image formation device for black (K) according to the first embodiment. 
         FIG. 3  is a schematic diagram showing an image sensor according to the first embodiment. 
         FIG. 4  is a schematic top view showing a lens array according to the first embodiment. 
         FIG. 5  is a schematic illustration showing the lens array according to the first embodiment viewed from the line d-d′ of  FIG. 4 . 
         FIG. 6  is a schematic illustration showing a light-blocking film forming device according to the first embodiment. 
         FIG. 7  is a schematic illustration showing a substrate positioned onto a conveyor bed in a formation process of the light-blocking film according to the first embodiment. 
         FIG. 8  is a schematic illustration showing discharge of an ultraviolet curable ink in a production process of the light-blocking film according to the first embodiment. 
         FIG. 9  is a schematic illustration showing irradiation of ultraviolet rays in the production process of the light-blocking film according to the first embodiment. 
         FIG. 10  is a schematic illustration showing a completed form of the lens array in the production process of the light-blocking film according to the first embodiment. 
         FIG. 11  is a schematic top view showing a lens array according to a second embodiment. 
         FIG. 12  is a schematic illustration showing the lens array according to the second embodiment, viewed from the line e-e′ of  FIG. 11 . 
         FIG. 13  is a schematic top view showing a lens array according to a third embodiment. 
         FIG. 14  is a schematic illustration showing the lens array according to the third embodiment, viewed from the line f-f′ of  FIG. 13 . 
         FIG. 15  is a schematic illustration showing an alternative example of the lens array of the third embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention provide a method for manufacturing a lens array, an image reading device, and an image forming device and lens array, in which a blocking film is formed thereon with a uniform thickness and provides a quality over the entire lens array area by adequately blocking stray light. 
     In general, according to one embodiment, a lens array is provided with a plurality of lenses formed on the effective area of a substrate, a dam structure (flow stopper) formed about an outer periphery of the lenses, and a light-blocking film formed using an ultraviolet curable ink which is located between the plurality of lenses, and between the plurality of lenses and the surrounding dam structure. 
     The embodiments will be explained below with reference to the drawings. Here, the same reference numerals are used for the same components in each drawing. 
     First Embodiment 
     A first embodiment will be explained using  FIGS. 1 through 10 .  FIG. 1  shows color MFP (Multi-Function Peripheral)  10 , which is an image forming device according to the first embodiment. There is a platen  12  made of transparent glass on top of a main body  11  of the MFP  10 , and an automated document feeder (ADF)  13 , which can be opened and closed freely, is installed on top of the platen  12 . Also a control panel  14  is installed on the main body  11 . The control panel  14  has various keys and a touch panel-type display unit. 
     A scanner unit  15 , which is an image reading device, is installed at the lower part of the ADF  13  inside the main body  11 . The scanner unit  15  generates image data by reading an original document G 1  sent by the ADF  13 , or an original document G 2 , placed on the platen  12 , and is equipped with a close-coupled type image sensor  16   a , which is included in the image reading unit. The image sensor  16   a  is positioned in the main scanning direction (into the paper in  FIG. 1 ). Also, an image reading unit  16  includes a light source. The light emitted from the light source irradiates the original document G 2  placed on the platen, and the light reflected by the original document G 2  passes the lens array before reaching the image sensor  16   a . Also, when reading the image of the document sent by the ADF  13 , the image sensor  16   a  is at the fixed position shown in  FIG. 1 . 
     Furthermore, a printer unit  17  is placed at the center inside the main body  11 , and at the lower part of the main body  11  are a plurality of cassettes  18  to hold paper of various sizes. The printer unit  17  has a photoreceptor drum and a scanning head  19 , which includes an LED as a photographic exposure device, and generates images by scanning photoreceptors using the light from the scanning head  19 . 
     The printer unit  17  generates images on paper by processing image data read by the scanner unit  15 , and/or the image data produced by a PC (Personal Computer) and other devices. The printer unit  17  is, for example, a color laser printer by a tandem method, and includes image formation units  20 Y (yellow),  20 M (magenta),  20 C (cyan), and  20 K (black) for each color. Image forming units  20 Y,  20 M,  20 C and  20 K are arranged in parallel beneath an intermediate transfer belt  21  from the upper side toward the lower side. Also, the scanning head  19  has multiple scanning heads  19 Y (yellow),  19 M (magenta),  19 C (cyan) and  19 K (black), which correspond to the image forming units  20 Y,  20 M,  20 C and  20 K. 
       FIG. 2  shows the image formation unit  20 K for black (K) among image forming units  20 Y,  20 M,  20 C and  20 K. Here, each image forming unit  20 Y,  20 M  20 C and  20 K has the same configuration except for the color designation, so the following explanation will be provided using image forming unit  20 K as a representative. 
     The image forming unit  20 K has a photoreceptor drum  22 K, which is an image support body. Around the photoreceptor drum  22 , along a rotation direction t, an electric charger  23 K, a developing unit  24 K, a primary transfer roller  25 K, a cleaner  26 K equipped with a blade  27 K and others are provided. The scanning head  19 K irradiates the photoreceptor drum  22 K and forms electrostatic latent images on the photoreceptor drum  22 K. 
     The electric charger  23 K of the image forming unit  20 K charges the surface of the photoreceptor drum  22 K. The developing unit  24 K provides photoreceptor drum  22 K with black toner through a developing roller  24   a  to which the developing bias is applied. The cleaner  26 K removes residual toner on the surface of the photoreceptor drum  22 K using the blade  27 K. 
     As shown in  FIG. 1 , on the upper part of image formation units  20 Y,  20 M,  20 C and  20 K, toner cartridges  28 Y,  28 M,  28 C and  28 K are installed to provide each developing unit  20 Y,  20 M,  20 C and  20 K with toner. Each of toner cartridges  28 Y,  28 M,  28 C and  28 K includes a toner cartridge for its respective color: yellow (Y), magenta (M), cyan (C) and black (K) 
     The intermediate transfer belt  21  is stretched to a drive roller  31 , a driven roller  32 , and a tension roller  30 , and rotates in the direction of arrow y. Also, the intermediate transfer belt  21  is in contact with and faces photoreceptor drums  22 Y,  22 M,  22 C, and  22 K. To the facing position to the photoreceptor drum  22 K of the intermediate transfer belt  21 , a primary transcription voltage is applied by the primary transfer roller  25 K to perform the primary transcription of the toner image on the photoreceptor drum  22 K to the intermediate transfer belt  21 . 
     Facing the drive roller  31 , which supports the intermediate transfer belt  21 , a secondary roller  33  is provided. When sheet S passes between the drive roller  31  and the secondary transfer roller  33 , a secondary transfer voltage is applied to the sheet S through the secondary transfer roller  33 , and the toner image on the intermediate transfer belt  21  is collectively transcribed secondarily onto sheet S. A belt cleaner  34  is installed near the driven roller  32  of the intermediate transfer belt  21  to clean images from the transfer belt  21 . 
     As shown in  FIG. 1 , provided between the supply cassette  18  and the secondary transfer roller  33  are a conveyance roller  35 , which conveys the sheet S taken from the supply cassette  18 , and a resist roller  35   a . Further, downstream of the secondary transfer roller  33 , a fixing unit  36  is installed. Also, downstream of the fixing unit  36 , a sheet ejection roller  37  is installed. The sheet discharge roller  37  ejects the sheet S to a sheet discharge unit  38 . 
     Furthermore, downstream of the fixing unit  36 , a reverse conveyor path  39  is provided. The reverse conveyor path  39  reverses and leads the sheet S to the direction of the secondary transfer roller  33 , which is used for two-sided copies. 
     The scanning head  19 K shown in  FIG. 2  faces the photoreceptor drum  22 K. The photoreceptor drum  22 K rotates at a pre-set speed, and accumulates electric charge at the surface. Electrostatic latent images are formed at the surface of the photoreceptor drum  22 K by irradiating the light from the scanning head  19 K onto the photoreceptor drum  22 K to expose the photoreceptor drum  22 K. 
     As shown in  FIG. 2 , the scanning head  19 K has a lens array  50 , and the lens array  50  is supported by a holding member  41 . Also, at the bottom, the holding member  41  has a support body  42 , and in the support body  42 , an LED element  43  is provided as the light source. The LED element  43  is installed in a straight line at equal intervals in the scanning direction (into the paper). Also, in the support body  42 , a control substrate  43   a  with a driver IC, which controls the irradiation of LED element  43 , is provided. 
     The control substrate  43   a  generates control signals for the scanning head  19 K based on the image data, and causes the LED element  43  to illuminate with a specified intensity according to the control signal. The light emitted from the LED element  43  passes through the lens array  50  and forms images on the photoreceptor drum  22 K. The light ray imaged on the lens array  50  forms an electrostatic latent image on the photoreceptor drum  22 K. The scanning head  19 K is equipped with a cover glass  44  at the upper part (the light emission side). 
     The image sensor  16   a  ( 49 ) shown in  FIG. 3  reads, following the operation of the control panel  14 , the image of the original document G 2  placed on the platen  12  or the image of the original document G 1  supplied by the ADF  13 . The image sensor  16  is a primary sensor provided in the scanning direction (into the paper). On the upper surface on the side of platen  12  of a chassis  45  deployed on a substrate  46 , two LED line illumination devices  47  and  48 , which emit light in the direction of the document, are installed extending in the scanning direction (into the paper). The light source to irradiate the document is not limited to the LED, but can also be a fluorescent tube, a xenon tube, a cold-cathode tube or organic EL and so on. 
     Between the LED line illumination devices  47  and  48  in the upper part of the chassis  45 , the lens array  50  is supported, and on the substrate  46  at the bottom of the chassis  45 , a CCD or a CMOS image sensor  49  is provided. The LED line illumination device  47  and  48  irradiates the reading spot for the document image on the platen  12 , and the light reflected at the image reading spot enters the lens array  50 . The lens array  50  functions as an erecting magnifying lens. The light that enters into the lens array  50  is emitted from the emission side of the lens array  50 , and images on the image sensor  49 . The imaged light is converted into an electrical signal by the image sensor  49 , and is transferred to the memory region of the substrate  46  (not shown in the drawing). 
     In this embodiment, explanations are made using multi-function peripheral (MFP) as an example of the image forming device. However, the image forming device is not limited to an MFP, but it can be such image reading devices as a stand-alone printer or a stand-alone scanner. 
     Next, the lens array  50  will be explained. As shown in  FIG. 4  and  FIG. 5 , the lens array  50  is, for example, provided with a plurality of lenses  52  in an effective area α having a length A and width B of a transparent substrate  51 . The transparent substrate  51  is also provided with a plurality of dummy lenses  53  (shown with hatched lines) surrounding the lenses  52  in the outer periphery of the lenses  52 , which form a dam structure configured to limit flow of ultraviolet curable ink on the transparent substrate  51  prior to the curing thereof. The lens array  50  is provided with, for example, a black light-blocking film  54  with a thickness of 24 μm, formed between lenses  52  and between lenses  52  and the dummy lenses  53 . The dummy lenses  53  are, for example, formed in conjunction with lenses  52  by a by molding when the substrate  51  is formed. Each lens  52  and the dummy lens  53  have the same shape, and the space between lenses  52  and the dummy lens  53  is the same as the space between the plurality of lenses  52  in the effective area α of the substrate  51 . 
     The light-blocking film  54  is formed using a light-blocking film forming device  60  as shown in  FIG. 6 . The light-blocking film forming device  60  forms the light-blocking film  54  by curing with ultraviolet light the ink sprayed by an inkjet method. The light blocking formation device  60  is equipped with an inkjet printing unit  62 , an ultraviolet irradiation device  63 , a conveyor bed  64  and a control unit  66 . 
     The conveyor bed  64  supports the substrate  51 , equipped with the lenses  52  and dummy lenses  53  formed by a metal mold, in a fixed state, and moves the substrate  51  in the direction of arrow r. The conveyor bed  64  transfers the substrate  51  to locations adjacent the inkjet printing unit  62 , and the ultraviolet irradiation device  63 . The inkjet printing unit  62  discharges an ultraviolet curable ink  61  from above the substrate  51  to the areas between the plurality of lenses  52 , surrounded by the dummy lenses  53 , and between the lenses  52  and the dummy lenses  53 . The ultraviolet irradiation device  63  emits ultraviolet light  67  to the ultraviolet curable ink  61  on the substrate  51 . The control unit  66  controls the inkjet printing unit  62 , the ultraviolet irradiation device  63  and the conveyor bed  64 . The control unit  66 , for example, controls the conveyance speed and conveyance timing of the conveyor bed  64 . The control unit  66 , for example, controls the discharge amount of ink from the inkjet printing unit  62 . The control of discharge amount of ink, for example, is conducted by adjusting the voltage used to discharge the ink to adjust the size of the drops, or adjusting the number of drops of the liquid in a multi-drop process. The control unit  66  controls, for example, the wavelength of ultraviolet rays of the ultraviolet irradiation device  63 . 
     Alternatively, the light-blocking film forming device  60  can supply the ultraviolet curable ink  61 , not by the inkjet method but by using an ink spreading device. Also, in forming the light-blocking film  54 , instead of moving the conveyor bed  64 , the inkjet printing unit  62  and the ultraviolet irradiation device  63  can be moved, while the conveyor bed  64  is fixed. 
     The ultraviolet curable ink will be explained and sample materials for ultraviolet curable ink will be described hereinafter. 
     Light Blocking Materials 
     As the light blocking material for forming light-blocking films between a plurality of lenses, consideration of the optical light blocking properties and the reflective qualities are required. Next, considerations of qualities for an inkjet ultraviolet curable ink such as the flight capability and dispersion stability of the ink are required. For these materials, light absorbing pigments can be employed, for example, carbon-based pigments such as carbon black, refined carbon, carbon nanotube; metallic oxide pigments such as iron black, zinc oxide, titanium oxide, chrome oxide, and iron oxide; sulfide pigments such as zinc sulfide; phthalocyanine-based pigments, such pigments made of salt as metallic sulfate, carbonate, silicate, and phosphate; and metallic powder pigments such as aluminum powder, bronze powder, and zinc powder, can be employed for their light blocking properties. 
     Reactive Materials 
     The fundamental materials for the light-blocking film are photocurable materials, made of reactive materials with a polymeric functional group, which is polymerized by light, such as monomer and oligomer, which are combined with a photoinitiator to trigger the polymerization of the reactive materials. The photocurable materials may be divided into a radical-type and a cation-type of material. 
     For the radical-type, acrylic monomers and oligomers with an acryloyl functional group are representative, in which the polymerization is promoted by radicals generated by the irradiated photoinitiator. However, there are problems such as oxygen inhibition occurring during the polymerization of these materials, and the reduction of volume after curing is relatively significant, so it has been sought to use it by controlling these shortcomings. 
     As the cation-type material, there are such cyclic ether compounds exemplified as epoxy and oxetane compounds, and vinyl ether compounds with a vinyl ether group, which initiate the polymerization using electrons generated by the irradiation of the photoinitiator. Among them, cyclic ether compounds have the characteristics of small volume reduction after the polymerization, and therefore have superior adhesion with the underlying base materials once cured. Also, there is a difference from the radical-type in that the polymerization can proceed without causing oxygen inhibition, and the ability to form thin films is superior. 
     As a light-blocking film for the lens array, taking into consideration the above properties, materials compatible with the ink qualities as the inkjet ultraviolet curable ink can be appropriately chosen for use. For the ink materials of this embodiment, there is no limitation as long as the performance as a light-blocking film, such as the light blocking quality, the reflexive quality, the strength of the curing film, and the ultraviolet curing condition; and physical qualities such as viscosity, surface tension, as an inkjet ultraviolet curable ink, the dispersion stability of the light blocking materials and the compatibility with the head part can be satisfied. In the following, specific examples are listed. 
     Exemplified as the material of a radical type are, depending on the number having acryloyl groups in the molecule, monomers such as monofunctional acrylate, bifunctional acrylate, tri- or higher polyfunctional acrylate, etc.; and oligomers such as polyester acrylate, urethane acrylate, epoxy acrylate, etc. Of those, the monofunctional monomer is often used as a reactive diluent, and as the inkjet ink, it plays an important role as the material for adjusting viscosity. 
     As the specific examples, isobornyl acrylate, acryloyl morpholine, dicyclopentadienyl acrylate, acrylic acid adduct of phenyl glycidyl ether; 2-hydroxy ethyl acrylate, 2-hydroxy propyl acrylate, 2-hydroxy butyl acrylate, 2-hydroxy hexyl acrylate, ethyl carbitol acrylate, tetrahydrofurfuryl acrylate, 2-acryloyloxyethyl phthalate, benzyl acrylate; and methacrylic acrylate such as a 2-hydroxyhexyl methacrylate, acryl methacrylate, benzyl methacrylate, and cyclohexyl methacrylate, may be employed. 
     Exemplified as the bifunctional acrylate are neopentyl glycol diacrylate, nonanediol diacrylate, tripropylene glycol diacrylate, tricyclodecane dimethanol diacrylate, EO adduct acrylate of bisphenol A and so on; and exemplified as the polyfunctional acrylates such as trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, triacrylates of isocyanuric acid EO adduct, and so on. Other than those of acrylate-base, N-vinyl pyrrolidone, N-vinyl caprolactam and so on are also useful as diluents. 
     As cation-type materials, epoxy compounds, oxetane compounds, vinyl ether compounds and so on can be used. 
     Examples of the epoxy compounds include the compounds having an epoxy group or an alicyclic epoxy group, which is present on either or both of a hydrocarbon group having a bivalent aliphatic skeleton or an alicyclic skeleton and a bivalent group having an aliphatic chain or an alicyclic skeleton in a portion thereof. For example, it is possible to employ alicyclic epoxy such as Celloxide 2021, Celloxide 2021A, Celloxide 2021P, Celloxide 2081, Celloxide 2000, and Celloxide 3000 manufactured by Daicel Chemical Industries, Ltd.; Cyclomer A200, Cyclomer M100, which are (meth)acrylate compounds having an epoxy group; methacrylate having a glycidyl methyl group such as MGMA; glycidol, which is a low molecular epoxy compound; β-methyl epichlorohydrin; α-pinene oxide, α-olefin monoepoxide having 12 to 14 carbon atoms; α-olefin monoepoxide having 16 to 18 carbon atoms; epoxidized soy bean oil such as Daimac S-300K; epoxidized linseed oil such as Daimac L-500; and polyfunctional epoxy compounds such as Epolead GT 301 and Epolead GT401. 
     Moreover, it is also possible to use alicyclic epoxy, such as Cylacure, product of Dow Chemical Co., Ltd, U.S.; low molecular weight phenol compounds that are hydrogenated and aliphatized with terminal hydroxyl group thereof being substituted by a group having epoxy; glycidyl ether compounds such as polyhydric aliphatic alcohols/alicyclic alcohols such as ethylene glycol and glycerol, neopentyl alcohol and hexanediol, trimethylolpropane; and glycidyl esters of hexahydrophthalic acid or hydrogenated aromatic polyhydric carboxylic acid. 
     Exemplified as the oxetane compounds are, for example, compounds in which more than one oxetane-containing groups are introduced to alicyclic such as (di[1-ethyl(3-oxetanol)]methyl ether, 3-ethyl-3-(2-ethylhexyloxy methyl)oxetane, [(1-ethyl-3-oxyetanol)methoxy]cyclohexane, bis[(1-ethyl-3-oxetanol)methoxy]cyclohexane, bis[(1-ethyl-3-oxetanol)methoxy]norbonane; ether compounds in which oxetane-containing alcohols such as 3-ethyl-3-hydroxymethyl oxetane is dehydrated and condensed to aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, neopentyl alcohols or the like. In addition, exemplified as the oxetane compounds that contain aromatic skeletons are, for example, 1,4-bis((1-ethyl-3 oxetanil)methoxy)benzene, 1,3-bis((1-ethyl-3 oxetanil)methoxy)benzene, 4,4′-bis((3-ethyl-3 oxetanil)methoxy)biphenyl, phenol novolac oxetane, or the like. 
     Exemplified as the vinyl ether compounds are 2-ethylhexylvinylether, butadiol divinyl ether, cyclohexanedimethanol divinyl ether, cyclohexanedimethanol monovinyl ether, diethylene glycol monovinyl ether, diethylene glycol divinyl ether, hexanediol divinyl ether, triethylene glycol divinyl ether, 4-hydroxybutyl vinyl ether, or the like. When decrease in viscosity and improvement in the degree of hardness in terms of curing are required, in addition to the improvement in the curing rate, it is preferred to blend alone or in combination the vinyl ether compounds expressed by the following formula (I) in a liquid ink. 
     Because of noticeable inhibition of polymerization by pigment in the vinyl ether compound bonded with a methylene group such as aliphatic glycol derivatives and cyclohexanedimethanol, it has been difficult to use this combination as an ink to date. However, as shown in the following formula (1), the compound in which a vinyl ether group directly having an alicyclic skeleton, a terpenoid skeleton, or an aromatic skeleton has excellent curing performances even when it has a pigment. The proportion of the compound may be 50 parts by weight, or less, to maintain the thermoplastic property of the liquid ink. When greater solvent resistance and hardness are required, the proportion may be further increased to the entire quantity of the solvent to be cured by acid, even though some degradation in the thermoplastic property may occur. 
       R13-R14-(R13)p  Formula (1)
 
     In the formula (I) above, for R 13 , at least one represents vinyl ether group, and it represents a substituent selected from a vinyl ether group and a hydroxyl group. R 14  is a (p+1) valent group selected from an alicyclic skeleton or a skeleton having an aromatic ring, and p represents a positive integer including 0. However, when R 14  is a cyclohexane ring skeleton and p is 0, at least one carbon on the ring has a ketone structure. Exemplified as the organic group R 14  of (p+1) valent are, for example, (P+1) valent groups containing a benzene ring, a naphthalene ring, a biphenyl ring; (P+1) valent group to be derived from a cycloalkane skeleton, a norbornane skeleton, a adamantane skeleton, a tricyclodecane skeleton, a tetracyclododecane skeleton, a terpenoid skeleton, and a cholesterol skeleton. 
     To be precise, it is also possible to use a compound in which the hydrogen atom of the hydroxyl group in phenol derivatives as well as cycloaliphatic polyol such as cyclohexane (poly)ol, norbornane (poly)ol, tricyclodecane (poly)ol, adamantane (poly)ol, benzene (poly)ol, naphthalene (poly) ol, anthracene (poly) ol, biphenyl (poly) ol, or the like has been substituted with a vinyl group. In addition, exemplified is also a compound in which the hydrogen atom of the hydroxyl group in the polyphenol compound such as polyvinyl phenol, phenol novolac, etc. has been substituted with a vinyl group. The compounds mentioned above are desirable because the volatility will be reduced even when a portion of the hydroxyl group remains, and even when a portion of the methylene atoms of an alicyclic skeleton has been substituted with a ketone group. In particular, since the cyclohexyl monovinyl ether compound is highly volatile, it is preferred to oxidize the cyclohexane ring to at least a cyclohexanone ring when using the cyclohexyl monovinyl ether compound. 
     Next, as examples of the photoinitiator, there are a radical system and a cationic system. General examples will be listed. 
     For radical type, there are benzoin ethers, acetophenones, phosphine oxides; for example, a cleavage type such as 1-hydroxycyclohexylphenylketone, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-on, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, or the like; a hydrogen abstraction type such as benzophenone, 2,4-diethyl thioxanthone, isopropyl thioxanthone, or the like. 
     It is possible to use the following as the cationic type: onium salts, diazonium salts, quinone diazide compounds, organic halide, aromatic sulfonate compounds, bisulphone compounds, sulfonyl compounds, sulfonate compounds, sulfonium compounds, sulfamide compounds, iodonium compounds, sulfonyl diazomethane compound, and mixtures thereof. 
     More specifically, exemplified are triphenyl sulfonium triflate, diphenyl iodonium triflate, 2,3,4,4-tetrahydroxy benzophenone-4-naphthoquinone diazide sulfonate, 4-N-phenyl-amino-2-methoxyphenyl diazonium sulfate, 4-N-phenylamino-2-methoxyphenyl diazonium-p-ethyl phenyl sulfate, 4-N-phenylamino-2-methoxyphenyl diazonium 2-naphthylsulphate, 4-N-phenylamino-2-methoxyphenyl diazonium phenyl-sulfate, 2,5-diethoxy-4-N-4′-methoxyphenyl carbonyl phenyl diazonium-3-carboxy-4-hydroxyphenyl sulfate, 2-methoxy-4-N-phenyl phenyl diazonium-3-carboxy-4-hydroxyphenyl sulfate, diphenyl sulfonyl methane, diphenyl sulfonyl diazomethane, diphenyl sulfone, α-methyl benzoin tosylate, pyrogallol trimesylate, benzoin tosylate, or the like. 
     The ultraviolet curable ink  61  uses these materials, and, after going through processes, in which (light blocking materials) are dispersed into (reactive monomers), and the obtained dispersed liquid, appropriate monomers, oligomers, the photoinitiator, and as necessary, a polymerization inhibitor are stirred in, and the mixture is filtered or centrifuged to separate rough particles and unnecessary solid contents from the mixture. 
     In the polymerization inhibitor, there are the one in case of cationic type, and the one in case of radical type. In the case of cationic type, exemplified are n-hexylamine, dodecylamine, aniline, dimethylaniline, diphenylamine, triphenylamine, diazabicyclooctane, diazabicycloundecane, 3-phenyl-pyridine, 4-phenyl pyridine, lutidine, 2,6-di-t-butyl pyridine, or the like. In the case of radical type, exemplified are DPPH (1,1-diphenyl-2-picrylhydrazyl), TEMPO (2,2,6,6-tetramethylpiperydinyl-1-oxyl), p-benzoquinone, chloranil, nitrobenzene, hydroquinone (HQ), methyl hydroquinone (MEHQ), t-butyl catechol, dimethylaniline, or the like. 
     As the physical property of ultraviolet curable ink  61 , if an average molecule diameter of the light blocking materials is set to be 300 nm or less, the flight ability of the inkjet printing unit  62  is not influenced. Also, it is preferable to set the viscosity of the ultraviolet curable ink  61  to 5-30 mPa·s at 25° C., and the surface tension to be within the range of 22-40 mN/m. The viscosity or the surface tension value of the ultraviolet curable ink  61  can be set by blending monomer, oligomer or a surfactant. 
     Further, in order to let the ink flow naturally into the narrow portion between the substrate  51  and each lens  52 , the contact angle of the substrate  51  and the ultraviolet curable ink  61  may be 20 degrees or less at  250 C. 
     The production method to form the light-blocking film  54 , which uses ultraviolet curable ink  61 , in the area surrounded by the dummy lenses  53  of the substrate  51 , will be explained using  FIGS. 7 through 10 . For the ultraviolet curable ink  61  used for the light-blocking film  54 , for example, carbon black is used as a light blocking material. The content of carbon black in the ultraviolet curable ink  61  is set to be 3.5 wt %, the light-blocking film  54  is formed with a thickness of 24 μm. The ultraviolet rays  67 , irradiated from the ultraviolet irradiation device  63  is set to have, for example, an irradiance of 2000 mW/cm 2 , a density of 400 mJ/cm 2 , and a wavelength of 365 nm. 
     The greater the light blocking property is, the more stray light the light-blocking film  54  of the lens array  50  can shield, so it is more advantageous as the property of lens array  50 . The light blocking property of light-blocking film  54  can be obtained by, for example, measuring the optical density (transmission density). The optical density, for example, can be measured using 361T densitometer manufactured by X-rite. If the optical density is 6 or greater, the light-blocking film  54  can block light almost completely (the optical density is a logarithm with 10 as the most opaque, and the greater the amount of light reduction is, the greater the value becomes. When the optical density is 6, the transmittance of light is 1/1,000,000%.) 
     When carbon black is used as a light blocking material for the light-blocking film  54 , with the carbon black content for 3.5 wt %, a sufficient light blocking capability can be obtained if the thickness of light-blocking film  54  is about 24 μm or greater. With the carbon black content of 7.5 wt %, a sufficient light blocking capability can be obtained if the thickness of the light-blocking film  54  is about 12 μm or greater. In order to obtain the light-blocking film  54  with sufficient light blocking property, the thickness of the light-blocking film  54  can be increased, or the weight ratio of the light blocking material in the ultraviolet curable ink  61  can be increased. 
     As shown in  FIG. 7 , the substrate  51 , having the lenses  52  and  53  disposed thereon, is fixed on the conveyor bed  64 , and the conveyor bed  64  is moved in the direction of arrow r relative to the inkjet printing unit  62  and the ultraviolet irradiation device  63 . As shown in  FIG. 8 , when the substrate  51  reaches the inkjet printing unit  62 , the inkjet printing unit  62  discharges the ultraviolet curable ink  61  from above the substrate  51 . The ultraviolet curable ink  61  flows to the areas between the plurality of lenses  52 , surrounded by dummy lenses  53  of the substrate  51  (shown in  FIG. 4 ), and between the lenses  52  and the dummy lenses  53 . The ultraviolet curable ink  61 , discharged from the inkjet printing unit  62 , spreads in a uniform thickness in the area surrounded by the dummy lenses  53  between the plurality of lenses  52 , and between the lenses  52  and the dummy lenses  53 , before the substrate  51  reaches the ultraviolet irradiation device  63 . 
     As shown in  FIG. 9 , when the substrate  51  reaches the ultraviolet irradiation device  63  as the conveyor bed  64  moves in the direction r, the ultraviolet irradiation device  63  irradiates the ultraviolet curable ink  61  with ultraviolet rays  67  from above the substrate to cure ultraviolet curable ink  61 . After the substrate  51  passes the ultraviolet irradiation device  63 , the ultraviolet curable ink  61  on the substrate  51  is cured. As shown in  FIG. 10 , when the substrate  51  passes the ultraviolet irradiation device  63 , a lens array  50  with the light-blocking film  54  formed between the plurality of lenses  52 , surrounded by the dummy lenses  53 , and between the lenses  52  and the dummy lenses  53 , is produced. 
     By using the dummy lenses  53  formed on the substrate  51 , the same conditions in the effective area α of the substrate (shown in  FIG. 4 ) can be maintained when forming the light-blocking film  54  because the dummy lenses form a dam or weir preventing the ink from spreading over the entire substrate, so that the in finds a natural level within the perimeter of the dummy substrates to a depth based on the volume of ink dispensed. Thus, the area between the lenses  52  and the dummy lenses  53 , and in the area surrounded by the dummy lenses  53  of the substrate  51 , the light-blocking film  54  with a uniform thickness of 24 μm can be obtained. The light blocking property of the light-blocking film  54  of the lens array  50  is the same in the effective area α of the substrate  51  and in the area around lenses  52  at the edge of the effective area α of the substrate  51 , and the light blocking property having an optical density of 6 was obtained. 
     Here, the lens array  50  has a plurality of lenses  52  provided on one major side of the substrate  51 , but the lens array can have a plurality of lenses provided on both major sides of the substrate. 
     According to the first embodiment, the dummy lenses  53  are formed surrounding the lenses  52  of the substrate  52 , and the light-blocking film  54 , formed from the ultraviolet curable ink, is formed in an area surrounded by the dummy lenses  53 . The lens array  50  has the light-blocking film  54  that has a uniform film thickness on the inside the effective area α, and around the lenses  52  of the edge portion of the effective area α, enabling the light-blocking film  54  to block stray light at the edge portion of the effective area α, and produces a high quality lens array  50  having uniform properties across the entire surface. 
     Second Embodiment 
     Next, a second embodiment will be explained. In the second embodiment, the light-blocking film is formed by supplying the ultraviolet ink inside a wall surrounding the lenses of the substrate. In the second embodiment, for the same configuration explained in the first embodiment, similar reference numerals are used and detailed explanations are omitted for brevity. 
     As shown in  FIG. 11  and  FIG. 12 , a lens array  70  according to the second embodiment is provided with, for example, a plurality of lenses  72  are disposed on a transparent substrate  71  in an effective area β with a length C and a width D. A sidewall  73  is formed on the transparent substrate  71  on the outer periphery of the lenses  72 . The sidewall  73  surrounds the lenses  72 , which is a dam structure according to this embodiment. The lens array  70  is provided with, for example, a black light-blocking film  74  with a thickness of 24 μm, formed between the lenses  72 , and between the lenses  72  and the sidewall  73 . The outer periphery of the sidewall  73  extends to the outer periphery of the substrate  71 , and is formed together with the lenses  72  in a mold, for example, when the substrate  71  is formed. A Height H of the sidewall  73  from a lens formation surface of the substrate  71  (bottom surface of the volume formed between the sidewall  73 ) is set to be higher than a height S of the light-blocking film  74 . The Height H of the sidewall  73  is set, for example, to be higher than a height T of the lenses  72 , so it becomes possible to prevent contact between the lenses  72  and an overlying object during handling the lens array  70 . For example, if another lens array is placed on top of the lens array  70 , the lenses  72  will not contact the other lens array, which prevents damage of the lenses  72 . 
     At the time of forming the light-blocking film  74 , the inkjet printing unit  62  (shown in  FIG. 8 ) discharges the ultraviolet curable ink  61  inside the sidewall  73  of the substrate  71 . The ultraviolet curable ink  61 , discharged from the inkjet printing unit  62 , spreads with a uniform thickness between a plurality of lenses  72 , and between the lenses  72  and the sidewall  73 , inside the sidewall  73 , before the substrate  71  reaches the ultraviolet irradiation device  63  (shown in  FIG. 9 ). While the substrate  71  is passing through, the ultraviolet irradiation device  63  irradiates the ultraviolet rays  67  to the inside of the sidewall  73  to cure the ultraviolet curable ink  61 , and forms the light-blocking film  74  inside the sidewall  73 . 
     In the area surrounded by the sidewall  73  of the substrate  71 , a light-blocking film  74  with adequate light blocking properties, for example a light blocking film with a uniform thickness of 24 μm can be obtained. The light blocking property of the light-blocking film  74  of the lens array  70  is the same in the effective area β of the substrate  71  and in the area around the lenses  72  at the edge of the effective area β of the substrate  71 , and the light blocking property having an optical density of 6 is obtained. 
     Here, the height of the sidewall  73  is not restricted as long as the level of the ultraviolet curable ink  61  deposited by the inkjet printing unit  62  can be regulated. 
     In the second embodiment, the sidewall  73  is formed around the lenses  72  of the substrate  71 , and the light-blocking film  74 , made of the ultraviolet curable ink  61 , is formed in the area surrounded by the sidewall  73 . As in the case of the first embodiment, the lens array  70  can obtain the light-blocking film  74  with a uniform thickness in the area around the lenses  72  at the edge of the effective area β as in effective area β, can shield stray light at the edge of the effective area β, and can obtain uniform lens quality over the entire surface. 
     Third Embodiment 
     Next, a third embodiment will be explained. In the third embodiment, the light-blocking film is formed by providing the ultraviolet curable ink inside a sidewall with a specified width surrounding the lenses of the substrate. In the third embodiment, for the same configuration explained in the first embodiment, the same reference numerals are used and detailed explanations are omitted for brevity. 
     As shown in  FIG. 13  and  FIG. 14 , a lens array  80  according to the third embodiment is provided with, for example, a plurality of lenses  82  in an effective area γ of a transparent substrate  81 , with a length E and a width F, and a ridge  83 . The ridge  83  is formed in the outer periphery of the lenses  82 , and surrounds the lenses  82 , and has a width W, which is a dam structure according to this embodiment. The lens array  80  is provided with, for example, a black light-blocking film  84  with a thickness of 24 μm, formed between the lenses  82 , and between the lenses  82  and the ridge  83 . 
     Each lens  82 , for example, is formed together with the substrate  81  by a metallic mold. The ridge  83  is formed, after the formation of the substrate  81 , by discharging ink to the outer periphery of the lens  82  by, for example, the inkjet method. The ink to form the ridge  83  is not limited to the ultraviolet curable ink. Solid ink, liquid ink, and other inks can also be used. Here, the ridge  83  can also be formed with the lens  82  when it is molded in a mold, for example, while the substrate  81  is being formed. 
     At the formation of the light-blocking film  84 , the ultraviolet curable ink  61  is discharged inside the ridge  83  by the inkjet printing unit  62  (shown in  FIG. 8 ), the ultraviolet curable ink  61  is cured by the ultraviolet irradiation device  63  (shown in  FIG. 9 ) irradiating ultraviolet rays  67 , and the light-blocking film  84  with a uniform film thickness of 24 μm is formed inside the ridge  83 . With area in the effective area γ of the substrate  81  and the area around the lens  82  at the edge of the effective area γ of the substrate  81 , the lens array  80 , provided with the light-blocking film  84 , which has the uniform light blocking property having an optical density of 6, is obtained. 
     Here, the shape of the ridge is not restricted, and for example, as shown in another example in  FIG. 15 , the upper part of a sidewall  93  surrounding lenses  92  of a substrate  91  of a lens array  90  can be formed in a taper (an acute angle). The lens array  90  forms a light-blocking film  94  inside the sidewall  93 . Also, the height of the sidewall is not restricted. For example, one is free to set the height of the sidewall to be the same as the thickness of the light-blocking film if the ultraviolet curable ink is to be dispersed inside the sidewall by rotating the substrate using a spin coat method, instead of the inkjet method. 
     In the third embodiment, the light-blocking film  84  made with the ultraviolet curable ink  61  is formed in the area surrounded by the ridge  83  of the lens  82  of the substrate  81 . As in the first embodiment, the lens array  80  can obtain the light-blocking film  84  with the same film thickness around the lens  82  at the edge of the effective area γ as in the effective area γ, making it possible to block stray light at the edge of the effective area γ. A uniform lens quality can be obtained over the entire area of the lens array  80 . 
     According to at least one of the embodiments discussed above, it is possible to obtain light-blocking films that have a uniform film thickness around the lenses, as well as at the edges of the lenses, by forming a dam structure around a plurality of lenses in the lens array and providing the ultraviolet curable ink inside the dam structure. 
     This disclosure is not limited to the above embodiments; various alterations are possible. For example, the alignment and the shape of lenses and so on are optional. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.