Patent Publication Number: US-2013235451-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. 2012-053609, filed Mar. 9, 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 
     A light-blocking film for blocking stray light has been provided to many lens arrays used in image forming devices such as printers, copiers, multifunction peripherals (MFP), fax machines, and scanners; or liquid crystal display devices, solid-state imaging devices, multiple image transfer by optical interconnection devices, confocal laser microscopes, or, in the field of optical communications, optical disks, image displays, image transmission and coupling devices, optical metrology devices, optical sensing devices, optical processing devices, and the like. 
     For a lens array having a light-blocking film formed thereon using ultraviolet curable ink, during curing, the ultraviolet curable ink itself blocks the ultraviolet light, attenuating the ultraviolet light in the depth direction of the ultraviolet curable ink, creating a possibility that the ultraviolet curable ink cannot be sufficiently cured through the depth of the light blocking layer so formed. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating an image forming device according to a first embodiment. 
         FIG. 2  is a schematic diagram illustrating a black (K) image forming device according to the first embodiment. 
         FIG. 3  is a schematic diagram illustrating an image sensor according to the first embodiment. 
         FIG. 4  is a schematic top view illustrating a lens array according to the first embodiment. 
         FIG. 5  is a schematic illustration of the lens array according to the first embodiment taken across line d-d′ of  FIG. 4 . 
         FIG. 6  is a schematic illustration showing an enlarged view of a portion of the lens array in  FIG. 5  according to the first embodiment. 
         FIG. 7  is a schematic illustration showing a light-blocking film forming device according to the first embodiment. 
         FIG. 8  is a graph illustrating light-blocking characteristics of the light-blocking film according to the first embodiment. 
         FIG. 9  is a schematic illustration showing fixation of a substrate to a conveying table in a method for manufacturing the light-blocking film according to the first embodiment. 
         FIG. 10  is a schematic illustration showing ejection of an ultraviolet curable ink in the method for manufacturing the light-blocking film according to the first embodiment. 
         FIG. 11  is a schematic illustration showing ultraviolet irradiation in the method for manufacturing the light-blocking film according to the first embodiment. 
         FIG. 12  is a schematic illustration showing completion of formation of a first light-blocking film and a second light-blocking film in the method for manufacturing the light-blocking film according to the first embodiment. 
         FIG. 13  is a schematic illustration showing an enlarged view of a portion of the lens array in an alternative example of the first embodiment. 
         FIG. 14  is a schematic illustration showing an enlarged view of a portion of the lens array in another alternative example of the first embodiment. 
         FIG. 15  is a schematic illustration showing a state in which two layers of light-blocking films are provided on one side of a lens array according to a second embodiment. 
         FIG. 16  is a schematic illustration showing a state in which two layers of light-blocking films are provided on both sides of a lens array according to the second embodiment. 
         FIG. 17  is a schematic illustration showing a state in which two layers of light-blocking films are provided on one side of the lens array according to a third embodiment. 
         FIG. 18  is a schematic illustration showing a state in which two layers of light-blocking films are provided on both sides of the lens array according to the third embodiment. 
         FIG. 19  is a schematic illustration showing diffusion of ultraviolet rays by a second lens according to the third embodiment. 
         FIG. 20  is a schematic illustration showing a state in which two layers of light-blocking films are provided on one side of a lens array according to a fourth embodiment. 
         FIG. 21  is a schematic illustration showing a state in which two layers of light-blocking films are provided on both sides of a lens array according to the fourth embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention provide a lens array, an image reading device having the lens array, an image forming device having the lens array, and a method for manufacturing a lens array, wherein ultraviolet curable ink which is provided between the plurality of lenses of the lens array is completely irradiated by ultraviolet light in the depth direction, to ensure complete curing of the ultraviolet curable ink forming a light blocking layer. 
     In general, according to one embodiment, a lens array according to one embodiment is provided with a plurality of lenses formed on a substrate and a light-blocking film formed by a plurality of layers formed between the lenses formed using an ultraviolet curable ink. 
     The embodiments for carrying out the disclosure will be explained below with reference to the drawings. The same components in each drawing are given the same reference numerals and will not be described repeatedly for brevity. 
     First Embodiment 
     The first embodiment will be explained with reference to  FIG. 1  to  FIG. 12 .  FIG. 1  shows a color MFP (Multi-Function Peripheral)  10 , which is an image forming device according to the first embodiment. A platen  12  made of a transparent glass is provided on top of a main body  11  of the MFP  10 , and an automatic document feeder (ADF)  13  is provided to open and close on top of the platen  12 . In addition, a control panel  14  is provided on top of the main body  11 . The control panel  14  has various of keys on a touch screen and a display unit. 
     A scanner unit  15 , which is an image reading device, is provided below the ADF  13  inside the main body  11 . The scanner unit  15  reads an original document G 1  sent by the ADF  13 , or an original document G 2  placed on top of the platen  12 , and generates the image data, and is equipped with an image sensor  16   a  of a contact type included in an image reading unit  16 . The image sensor  16   a  is arranged under a main scanning direction of the paper or other media being imaged therebyand extends into the plane of the drawing in  FIG. 1 ). 
     In addition, the 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 through the lens array before reaching the image sensor  16   a . When reading the image of the original document sent by the ADF  13 , the image sensor  16   a  is in a fixed location as shown in  FIG. 1 . 
     A printer unit  17  is provided at a central location inside the main body  11 , and a plurality of cassettes  18  for accommodating paper sheets of each type are provided at the bottom portion of the main body  11 . The printer unit  17  has a photosensitive drum and a scan bed  19  including a LED, which is an exposure means, and the printer unit generates images by scanning the photosensitive drum by a light beam from the scan bed  19 . 
     The printer unit  17  processes the image data read by the scanner unit  15 , or the image data created by a PC (Personal Computer), and forms the images on a paper. The printer unit  17  is, for example, a color laser printer of a tandem system, and includes image forming units  20 Y (yellow),  20 M (magenta),  20 C (cyan), and  20 K (black) for each color. At the bottom side of an intermediate transfer belt  21 , the image forming units  20 Y,  20 M,  20 C, and  20 K are arranged in parallel from the upstream side to the downstream side of the intermediate transfer belt  21 . Furthermore, the scan bed  19  further has multiple scan heads  19 Y (yellow),  19 M (magenta),  19 C (cyan), and  19 K (black) that correspond to the image forming units  20 Y,  20 M,  20 C, and  20 K. 
       FIG. 2  shows the black (K) image forming unit  20 K, among the image forming units  20 Y,  20 M,  20 C, and  20 K. Each of the image forming units  20 Y,  20 M,  20 C, and  20 K has the same configuration with the exception of color designation, so the explanation will be given below using the image forming unit  20 K as representative. 
     The image forming unit  20 K has a photosensitive drum  22 K, which is an image bearing member. Arranged surrounding the photosensitive drum  22 K is a cleaner  26 K, or the like, equipped with a charger  23 K along a rotation direction t, a developing unit  24 K, a primary transfer roller  25 K, and a blade  27 K. The scan head  19 K irradiates light to the exposure position of the photosensitive drum  22 K, and forms an electrostatic latent image on the photosensitive drum  22 K. 
     The charger  23 K of the image forming unit  20 K uniformly charges the surface of the photosensitive drum  22 K. The developing unit  24 K supplies to the photosensitive drum  22 K a black toner from a developing roller  24   a  to which the developing bias is applied. The cleaner  26 K removes the residual toner on the surface of the photosensitive drum  22   k  using the blade  27 K. 
     As shown in  FIG. 1 , provided on top of the image forming units  20 Y,  20 M,  20 C, and  20 K are toner cartridges  28 Y (yellow),  28 M (magenta),  28 C (cyan), and  28 K (black) for supplying toner to each of the image forming units  20 Y,  20 M,  20 C, and  20 K. The toner cartridges  28 Y,  28 M,  28 C, and  28 K are toner cartridges for each color. 
     Referring to  FIG. 1 , the intermediate transfer belt  21  rotates in the direction of arrow y and extends between a drive roller  31 , a driven roller  32 , and a tension rollers  30 . Furthermore, the intermediate transfer belt  21  is in contact so as to face photosensitive drums  22 Y (yellow),  22 M (magenta),  22 C (cyan), and  22 K (black). To the location facing the photosensitive drum  22 K of the intermediate transfer belt  21 , a primary transfer voltage is applied from the primary transfer roller  25 K, and the toner image of the photosensitive drum  22 K is primarily transferred to the intermediate transfer belt  21 . 
     The drive roller  31  coupled to the intermediate transfer belt  21  is provided facing a secondary transfer roller  33 . When a paper sheet S passes between the drive roller  31  and the secondary transfer roller  33 , the secondary transfer voltage is applied to the paper sheet S from the secondary transfer roller  33 , and the toner image on the intermediate transfer belt  21  is transferred to the paper sheet S. A belt cleaner  34  is provided in the vicinity of the driven roller  32  of the intermediate transfer belt  21 . 
     As shown in  FIG. 1 , provided from the paper feed cassette  18  to the secondary transfer roller  33  are conveying rollers  35  and resist rollers  35   a  for conveying a paper sheet S taken out from the paper feed cassette  18 . A fixing unit  36  is further disposed downstream of the secondary transfer roller  33 . In addition, paper discharge rollers  37  are provided downstream of the fixing unit  36 . The paper discharge rollers  37  discharge the paper sheet S to the paper discharge section  38 . 
     Furthermore, a reverse conveying path  39  is provided downstream of the fixing unit  36 . The reverse conveying path  39  reverses the paper sheet S, introducing it to the direction of the secondary transfer roller  33 , and the path is used when performing two-sided printing. 
     The scan head  19 K shown in  FIG. 2  is facing the photosensitive drum  22 K. The photosensitive drum  22   k  rotates at a set rotation speed and stores the charge on the surface. The light from the scan head  19 K is irradiated onto the photosensitive drum  22 K, exposing the photosensitive drum  22 K, and forming an electrostatic latent image on the surface of the photosensitive drum  22 K. 
     The scan head  19 K has a lens array  50 , and the lens array  50  is supported by a holding member  41 . In addition, a support  42  is provided at the bottom portion of the holding member  41 , and an LED element  43 , which is the light source, is disposed on the support  42 . The LED element  43  is provided at regular intervals in a straight line in the main scanning direction (into the paper). Furthermore, provided at the support  42  is a control substrate  43   a  containing a driver (integrated circuit—not shown) for controlling the light emission of the LED element  43 . 
     The control substrate  43   a  generates the control signals of the scan head  19 K based on the image data, and emits light from the LED element  43  at an amount according to the control signals. The rays emitted from the LED element  43  pass through a lens array  50  and form an image on the photosensitive drum  22 K. The rays that form an image at the lens array  50  form an electrostatic latent image on the photosensitive drum  22 K. The scan head  19 K is equipped with a cover glass  44  at the top (light emitting side). 
     The image sensor  16   a  ( 49 ), shown in  FIG. 3 , reads the image of the original document G 2  placed on the platen  12  or the image of the original document G 1  fed by ADF  13  according to the operation of the control panel  14 . The image sensor  16   a  is a one-dimensional sensor arranged in the scanning direction. Provided on the top surface of the platen  12  of a chassis  45 , which is provided on top of the substrate  46 , are two LED line lighting systems  47  and  48  so as to extend in the scanning direction (into the paper). The light source for irradiating the original document is not limited to the LED. Fluorescent tubes, xenon tubes, cold-cathode tubes, organic ELs, or the like, may also be used. 
     The lens array  50  is supported between the LED line lighting systems  47  and  48  on top of the chassis  45 , and the image sensor  49 , including a CCD or a CMOS, is installed in the substrate  46  at the bottom of the chassis  45 . The LED line lighting systems  47  and  48  illuminate an image reading position of the original document on top of the platen  12  and the light reflected at the image reading position is incident on the lens array  50 . The lens array  50  functions as an erecting magnifying lens. The light that is incident on the lens array  50  is emitted from the light-emitting surface of the lens array  50  and forms an image on the sensor  49 . The imaged light is converted into an electrical signal by the sensor  49 , and is transferred to a memory unit (not shown in the drawing) of the substrate  46 . 
     Although the multi-function peripheral (MFP) has been explained as an example of an image forming device in this embodiment, the image forming device is not limited to an MFP. The image forming device may also be, for example, a stand-alone printer or a stand-alone scanner. 
     Next, the lens array  50  will be explained. As shown in  FIG. 4  to  FIG. 6 , the lens array  50  is equipped with a plurality of lenses  52  formed on or in, for example, a transparent substrate  51 . The lens array  50  is equipped with a first light-blocking film  56  in a black color having a thickness of 12 μm formed between each lens  52 , and a second light-blocking film  57  in a black color having a thickness of 12 μm laminated on the first light-blocking film  56 . The first light-blocking film  56  and the second light-blocking film  57  are formed, for example, using an ultraviolet curable ink having the same characteristics. The lens  52  and the substrate  51  of the lens array are, for example, formed by a molding process. 
     The first light-blocking film  56  and the second light-blocking film  57  are formed using a light-blocking film forming device  60  shown in  FIG. 7 . The light-blocking film forming device  60  cures, using an ultraviolet light  67 , an ultraviolet curable ink  61  discharged by an ink-jet method, and first, forms the first light-blocking film  56 . The light-blocking film forming device  60  repeats the same formation step as the formation step of the first light-blocking film  56 , and forms the second light-blocking film  57  by overlapping the second light-blocking film  57  on the first light-blocking film  56 . The light-blocking film forming 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 , which secures and supports the substrate  51  provided with a plurality of lenses  52  extending upwards therefrom moves in the direction of arrow r. The conveyor bed  64  transfers the substrate  51  to a position adjacent to the inkjet printing unit  62  and then to a position adjacent to and underlying the ultraviolet irradiation device  63 . The inkjet printing unit  62  discharges the ultraviolet curable ink  61  between each lens  52  from above the substrate  51 . The ultraviolet irradiation device  63  irradiates the ultraviolet light  67  on the ultraviolet curable ink  61  discharged onto the substrate  51 , from above 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  controls, for example, the conveying speed, or the conveying timing of the conveyor bed  64 . The control unit  66  controls the amount of ink discharged by the inkjet printing unit  62 . Control of the amount of ink discharged is, for example, controlled by adjusting the voltage for discharging the ink, or controlled by adjusting the number of droplets in a multi-drop process. The control unit  66  controls the wavelength of the ultraviolet light of, for example, the ultraviolet irradiation device  63 . 
     In the light-blocking film forming device  60 , the supply of the ultraviolet curable ink  61  may be carried out by coating using an ink coating device, instead of an inkjet method. Or, in order to form the light-blocking films  56  and  57 , instead of moving the conveyor bed  64 , the conveyor bed  64  may be secured, and the inkjet printing unit  62  and the ultraviolet irradiation device  63  may be moved relative to the stationary conveyor bed  64 . 
     The ultraviolet curable ink will be explained and examples of materials of the ultraviolet curable ink will be provided. 
     (Light-Blocking Material) 
     Optical light-blocking properties and reflection characteristics are considered in the light-blocking material for forming the light-blocking film between a plurality of lenses. Next, flight performance, dispersion stability, etc. are considered for the inkjet ultraviolet curable ink. A light-absorbing pigment can be exemplified as such material. For example, carbon-based pigments, such as carbon black, refined carbon, carbon nanotubes, etc.; metal oxide pigments, such as iron black, zinc oxide, titanium oxide, chromium oxide, iron oxide, etc.; sulfide pigments, such as zinc sulfide, etc.; phthalocyanine pigments; pigments including metal sulfates, carbonates, silicates, and phosphates; pigments including metal powder such as aluminum powder, bronze powder, and zinc powder, can be used. 
     (Reactive Material) 
     The material that becomes the backbone of the light-blocking film is a light curable material, and it includes a reactive material by the polymerization of the oligomer, the reactive monomer having a polymerizable functional group; and a photoinitiator for initiating the polymerization thereof. A wide variety of reactive materials have been used in various applications, and it can be broadly divided into a radical type and a cationic type. 
     Acrylic monomers and oligomers having an acryloyl functional group are typical in the radical type; polymerization is promoted from the radical generated from the photoinitiator irradiated by the light. Coating, ink, optical material, resist, and so on can also be used. However, there are also disadvantages, such as generation of oxygen inhibition in polymerization and relatively significant contraction in volume after curing. For applications, it is necessary to have the disadvantages under control. 
     Exemplified as the cationic type are a cyclic ether compound represented by an epoxy or oxetane compound, a vinyl ether compound having a vinyl ether group, or the like, and exemplified as the photoinitiator is the one that carries out polymerization using proton generation by light irradiation. Of these, the cyclic ether compound can be exemplified as the feature due to minimal volume shrinkage after curing, accompanied by excellent adhesion to the substrate. In addition, polymerization can be carried out without generating oxygen inhibition, and it has excellent performance in forming a thin film, so these points are different from those in the radical type. 
     As the light-blocking film of the lens array, taking into consideration the characteristic mentioned above, the materials that have compatibility with the ink characteristics as the inkjet ultraviolet curable ink can be appropriately selected and used. As long as the ink material of this embodiment satisfies the requirements of its compatibility with performances such as light blocking properties as a light-blocking film, reflection characteristics, film curing strength, ultraviolet curing conditions, or the like; physical properties such as viscosity, surface tension, etc. as the characteristic of inkjet ultraviolet curable ink; dispersion stability of the light-blocking material; and the head member, it is not particularly limited. Concrete examples will be described below. 
     Exemplified as the material of a radical type are oligomers represented by the following, depending on the number having acryloyl groups in the molecule, monomers such as monofunctional acrylate, bifunctional acrylate, tri- or higher polyfunctional acrylate, etc.; and 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 a concrete example, the following can be exemplified: acrylic acid adduct of isobornyl acrylate, acryloyl morpholine, dicyclopentadienyl acrylate, 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, etc.; methacrylic acrylate such as 2-hydroxyhexyl methacrylate, acryl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, etc. 
     Exemplified as the bifunctional acrylate are neopentyl glycol diacrylate, nonanediol diacrylate, tripropylene glycol diacrylate, tricyclodecane dimethanol diacrylate, EO adduct acrylate of bisphenol A, etc., and exemplified as the polyfunctional acrylate are triacrylates, such as trimethylolpropane triacrylate, pentaerythritoltriacrylate, dipentaerythritol pentaacrylate, isocyanuric acid EO adduct, etc. Other than those of acrylate-base, N-vinylpyrrolidone, N-vinyl caprolactam, etc. are also useful as diluents. 
     An epoxy compound, an oxetane compound, a vinyl ether compound, etc. can be exemplified as the material of a cationic type. 
     The following compounds can be exemplified as the epoxy compound: a compound having a hydrocarbon group that has a divalent aliphatic skeleton or an alicyclic skeleton, or a compound having an epoxy group or an alicyclic epoxy group to one of or both divalent groups partially having an aliphatic skeleton or an alicyclic skeleton. 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 GT301 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-ethylhexylvinyl ether, buntan diol divinyl ether, cyclohexanedimethanol divinyl ether, cyclohexanedimethanol monovinyl ether, dithylene glycol monovinyl ether, dithylene glycol divinyl ether, hexanediol divinyl ether, triethylene glycol divinyl ether, 4-hydroxybutyl vinyl ether, or the like. When a decrease in viscosity and an 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 (1) in a liquid ink. 
     Because of the 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 it as 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 blending amount of these compounds is preferred to be the ratio of equal to, or less than, 50 parts by weight with respect to the entire liquid ink in order to maintain its thermoplasticity; however, when it is desired to further have a higher solvent resistance and a degree of hardness even when the thermoplasticity is lost, it may further be increased to the total amount of solvent to be cured by acid. 
       R13-R14-(R13) p   Formula (1)
 
     In the formula (1) above, for R 13 , at least one represents a 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; and (p+1) valent groups 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 replaced by 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 replaced 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 replaced 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, a radical type and a cationic type will be separated as an example of the photoinitiator, and those used in general will be enumerated. 
     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-dimethylamimo-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, and benzoin tosylate, or the like. 
     The ultraviolet curable ink  61  is prepared by: carrying out a step of dispersing a (light-blocking material) into (the reactive monomer) using these materials; a step of adding to the obtained dispersion liquid an appropriate monomer, oligomer and a photoinitiator, as well as a polymerization inhibitor, if necessary; followed by mixing and stirring it; and finally a step of purification such as filtration or centrifugation for removing coarse particles and unwanted solids. 
     In the polymerization inhibitor, there are the one in the case of a cationic type, and the one in the case of a radical type. In the case of a 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 a 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 for the physical properties of the ultraviolet curable ink  61 , as long as the average particle diameter of the light-blocking material is less than 300 nm, there will be no effect to the flight performance by the inkjet printing unit  62 . In addition, the viscosity value of the ultraviolet curable ink  61  may be provided in the range of 5-30 mPa·s at 25° C., and the surface tension values to the range of 22-40 mN/m. The viscosity value and the surface tension value of the ultraviolet curable ink  61  can be set by the combination of the monomer, the oligomer, or the surfactant. 
     In order for the ink to flow easily to the narrow regions between the plurality of lenses  52 , a contact angle between the substrate  51  and the ultraviolet curable ink  61  is less than 20 degrees at 25° C. 
     The light-blocking film of the lens array generally can block stray lightswitch would otherwise pass through the substrate  51  between the plurality of lenses and thereby affect image quality. The greater the light blocking capability, the more useful it is in the characteristic of the lens array. The light blocking property of the light-blocking film can be obtained by measuring the optical density (transmission density). The measurement of the optical density can be performed using, for example, a 361T densitometer manufactured by X-rite. The light-blocking film can block the transmitted light as long as its optical density is greater than 6. (The optical density is the logarithm that uses the opacity of 10 as the base, so the larger the amount of dimming light, the larger its value will be. When the optical density is 6, the light transmittance will be 1/1 million %. 
       FIG. 8  shows the relationship between the thickness of the light-blocking (shielding) film and the optical density, as the blocking characteristics when carbon black is used as the light-blocking material. The evaluation of the light-blocking properties is performed for the ultraviolet curable ink having 3.5 wt % in carbon black content and the ultraviolet curable ink having 7.5 wt % in carbon black content. Curing of the ultraviolet curable ink is performed using ultraviolet rays having 2000 mW/cm 2  in irradiance, 400 mJ/cm 2  density, and 365 nm in wavelength. 
     From  FIG. 8 , the ultraviolet curable ink having 3.5 wt % of the light blocking material can obtain sufficient light blocking properties with the film thickness of greater than about 24 μm. It can be confirmed that the ultraviolet curable ink having 7.5 wt % of the light blocking material can obtain sufficient light blocking properties with a film thickness of greater than about 12 μm. As a result, it can be confirmed that preparing a thick light-blocking film formed by the ultraviolet curable ink, or elevating the weight ratio of the light blocking material in the ultraviolet curable ink can achieve sufficient light blocking properties as the light-blocking film for the lens array  50 . 
     In the first embodiment, the content of carbon black in the ultraviolet curable ink  61  used in the first light-blocking film  56  and the second light-blocking film  57  is set to, for example, 3.5 wt %. The first light-blocking film  56  and the second light-blocking film  57  are formed so that each has a thickness of 12 μm, and the total of film thickness of the first light-blocking film  56  and the second light-blocking film  57  on top of the lens array  50  is 24 μm. The ultraviolet rays from the ultraviolet irradiation device  63  has, for example, 2000 mW/cm 2  in irradiance, 400 mJ/cm 2  density, and 365 nm in wavelength. 
     The manufacturing method for forming the first light-blocking film  56  and the second light-blocking film  57  between the plurality of lenses  52  will be explained with reference to  FIG. 9  to  FIG. 12 . In order to form the first light-blocking film  56 , as shown in  FIG. 9 , the substrate  51  is fixed to the conveyor bed  64 , and the conveyor bed  64  is moved in the direction of the arrow r. When the substrate  51  arrives at the inkjet printing unit  62 , the inkjet printing unit  62  discharges the ultraviolet curable ink  61  between the plurality of lenses  52  of the substrate  51  from above the substrate  51  as the substrate  51  moves in the direction of the arrow r, as shown in  FIG. 10 . The discharge amount of the ultraviolet curable ink  61  by the inkjet printing unit  62  is set to an amount in which the film thickness of the first light-blocking film  56  becomes at least 12 μm, after curing. 
     Following the movement of the conveyor bed  64 , when the substrate  51  arrives at the ultraviolet irradiation device  63 , as shown in  FIG. 11 , the ultraviolet irradiation device  63  irradiates the ultraviolet light  67  on the ultraviolet curable ink  61  from above the substrate, and cures the ultraviolet curable ink  61 . The time period for irradiation of the ultraviolet curable ink  61  is set to be, for example, longer than 2 seconds. And, the conveyor bed  64  transports the substrate  51  to which the ultraviolet curable ink  61  has been supplied to the position of the ultraviolet irradiation device  63  in the state of being held horizontally. The ultraviolet curable ink  61  supplied to the substrate  51  naturally spreads between the plurality of lenses  52  on the surface of the substrate to form a relatively uniform thickness ink layer before the ultraviolet light  67  is irradiated thereon. 
     The discharge amount of the ultraviolet curable ink  61  by the inkjet printing unit  62  is adjusted so that the film thickness of the first light-blocking film  56  becomes 12 μm where ink having 3.5% carbon black content is employed. Thus even when the ultraviolet light  67  from the ultraviolet irradiation device  63  has been somewhat blocked by the ultraviolet curable ink  61  itself, it can sufficiently reach the full thickness of the ink layer on the substrate  51  and thereby cure the entire thickness of the ultraviolet curable ink  61 . When the substrate  51  passes through the ultraviolet irradiation device  63 , the ultraviolet curable ink  61  on the substrate  51  is sufficiently cured, and the first light-blocking film  56  having a uniform film thickness of 12 μm among the plurality of lenses  52  is obtained. 
     After forming the first light-blocking film  56 , the conveyor bed  64  is moved in the direction of the arrows (shown in  FIG. 11 ), and the substrate  51  is returned to the position as shown in  FIG. 9 . The light-blocking film forming device  60  repeats the same step as the formation step of the first light-blocking film  56  to the substrate  51 , and deposits the second light-blocking film  57  having a uniform film thickness of 12 μm on top of the first light-blocking film  56 . The light-blocking film forming device  60  irradiates the ultraviolet light  67  by the ultraviolet irradiation device  63  after supplying the ultraviolet curable ink  61  among the plurality of lenses  52  of the substrate  51  from the first light-blocking film  56  by the inkjet printing unit  62 , by the movement of the conveyor bed  64  in the direction of the arrow r. 
     The amount of the ultraviolet curable ink  61  supplied to the top of the first light-blocking film  56  from the inkjet printing unit  62  has been adjusted to an amount so that the film thickness of the second light-blocking film  57  becomes 12 μm where ink having 3.5% carbon black content is used. Due to the set thickness, the ultraviolet light  67  from the ultraviolet irradiation device  63  sufficiently reaches the surface of the first light-blocking film  56 , i.e., reaches the entire volume of the second light blocking film  57 , even when it has been somewhat blocked by the partially cured ultraviolet curable ink  61  in the second light blocking layer  57 . When the substrate  51  passes through the ultraviolet irradiation device  63 , the ultraviolet curable ink  61  on the substrate  51  is sufficiently cured in the thickness dimension, and the second light-blocking film  57  having a uniform film thickness of 12 μm is laminated on the first light-blocking film  56 . 
     The manufacture of the lens array  50  onto which the first light-blocking film  56  and the second light-blocking film  57  have been laminated among the plurality of lenses  52  on top of the substrate  51 , that passes through the ultraviolet irradiation device  63 , has been completed ( FIG. 12 ). The lens array  50  having the light-blocking films is provided with superior light blocking property at a film thickness of 24 μm in total for both the first light-blocking film  56  and the second light-blocking film  57 , enabling the lens array  50  to adequately block stray light. After evaluating the performance of the first light-blocking film  56  and the second light-blocking film  57  formed on the lens array  50  with pencil hardness ( 2 B), it is revealed that the first light-blocking film  56  and the second light-blocking film  57  have sufficient hardness with no scratching, indicating full curing of the film layers  56  and  57 . 
     In contrast to this, a first conventional comparative example is described. Using an ultraviolet curable ink having a content of carbon black of 3.5 wt %, when the ink is discharged to the substrate  51  in an amount to provide a film thickness after curing of 24 μm, the light-blocking film of the first comparative example had scratches caused by the pencil ( 2 B), causing it to peel off, so that a sufficient degree of hardness could not be achieved. As a second comparative example, using the ultraviolet curable ink having a content of carbon black of 7.5 wt %, when the ink is discharged to the substrate  51  in an amount to provide a film thickness after curing of 12 μm, the light-blocking film of the second comparative example had scratches by the pencil ( 2 B), causing it to peel off, so that a sufficient degree of hardness could not be achieved. 
     Although the reactive material used for the ultraviolet curable ink  61  is not limited, using acrylic material as the reactive material inhibits the polymerization reaction due to oxygen in the air, making the surface of the ultraviolet curable ink hard to cure. When the surface of the ultraviolet curable ink  61  does not harden due to oxygen inhibition, it is also possible to provide a step of cleaning the lens array  50  after irradiation of the ultraviolet light  67  in order to remove the uncured ultraviolet curable ink  61 . The step of cleaning the uncured ultraviolet curable ink  61  is optional; for example, it may be a step of immersion in an alcohol-based solvent, or a step of ultrasonic cleaning in an organic solvent. 
     And the number of layers of light-blocking films laminated among the plurality of lenses  52  is not limited. As an alternative example, as shown in  FIG. 13 , for example, the light-blocking films may also be formed into three layers. Provided among the plurality of lenses  52  of a lens array  70  in  FIG. 13  are a first light-blocking film  71  in black color with a thickness of 8 μm, a second light-blocking film  72  in black color with a thickness of 8 μm laminated on top of the first light-blocking film  71 , and a third light-blocking film  73  in black color with a thickness of 8 μm laminated on top of the second light-blocking film  72 . The first light-blocking film  71  to the third light-blocking film  73  are formed using the ultraviolet curable ink  61  having the same characteristics. 
     The light-blocking film forming device  60  irradiates an ultraviolet light  67  to the ultraviolet curable ink  61  discharged from the inkjet printing unit  62 , (described in  FIGS. 9-11 ) and forms the first light-blocking film  71  having a film thickness of 8 μm among the plurality of lenses  52 . The light-blocking film forming device  60  repeats the same formation step as that for the first light-blocking film  71 , and sequentially layers the second light-blocking film  72  and the third light-blocking film  73  on top of the first light-blocking film  71 . For the first light-blocking film  71  to the third light-blocking film  73 , the ultraviolet curable ink  61  is sufficiently irradiated by the ultraviolet light  67  in each formation step to ensure curing of each layer. The lens array  70  having the light-blocking films with superior light blocking properties and at a film thickness of 24 μm in total for both the first light-blocking film  71  to the third light-blocking film  73 , and sufficiently blocks stray light. 
     When laminating a light-blocking film among the plurality of lenses  52 , instead of repeating the formation step of the light-blocking film using a pair of the inkjet printing unit  62  of the light-blocking film forming device  60  and the ultraviolet irradiation device  63 , a plurality of light-blocking films may also be sequentially laminated by using a light-blocking film forming device equipped with a plurality of inkjet printing units and the ultraviolet irradiation devices for forming each light-blocking film. 
     The layer thickness of the light-blocking film laminated among the plurality of lenses  52  is optional for each film. For example, the thickness of the first layer of two layers may be formed thicker than the thickness of the second layer on the surface side. When the thickness of the first layer at the lower side is made thicker, the ultraviolet light may be irradiated from the lower side through a transparent conveyor bed, and the ultraviolet light can be irradiated on both sides of the ultraviolet curable ink, which cures the ultraviolet curable ink reliably. 
     The light blocking properties of each light-blocking film laminated among the plurality of lenses  52  is not limited. As in the another alternative example as shown in  FIG. 14 , each light-blocking film can also be formed by using the ultraviolet curable ink  61  having a 3.5 wt % carbon black content and an ultraviolet curable ink  76  having a 7.5 wt % carbon black content. For example, among the plurality of lenses  52  of a lens array  76  of  FIG. 14 , a second light-blocking film  78  having a thickness of 12 μm using the ultraviolet curable ink  61  having 3.5 wt % carbon black content is laminated on top of a first light-blocking film  77  having a thickness of 7 μm using the ultraviolet curable ink  76  having 7.5 wt % carbon black content. The total of the film thickness of the first light-blocking film  77  and the second light-blocking film  78  is 19 μm in this alternative example. The ultraviolet light passes through the second light-blocking film  78  (due to the lower carbon black content) and sufficiently cures both of the first light-blocking film  77  and the second light-blocking film  78 . 
     In order to form the first light-blocking film  77 , the light-blocking film forming device  60  (described in  FIGS. 9-11 ) irradiates the ultraviolet light  67  on the ultraviolet curable ink  76  after discharging the ultraviolet curable ink  76  having 7.5 wt % carbon black content to the substrate  51  by the inkjet printing unit  62  to form the first light-blocking film  77  having a 7 μm film thickness among the plurality of lenses  52 . In order to form the second light-blocking film  78 , the light-blocking film forming device  60  irradiates the ultraviolet light  67  on the ultraviolet curable ink  61  after discharging the ultraviolet curable ink  61  having 3.5 wt % carbon black content to the first light-blocking film  77  by the inkjet printing unit  62  to form the second light-blocking film  78  having a 12 μm film thickness on top of the first light-blocking film  77 . 
     The first light-blocking film  77  and the second light-blocking film  78  are cured in a reliable manner by sufficiently irradiating the ultraviolet light  67  on the ultraviolet curable ink  76  and the ultraviolet curable ink  61  in each formation step. In the lens array  76 , using the ultraviolet curable ink  76  having 7.5 wt % carbon black content, a light-blocking film of an upper layer may be laminated after forming a light-blocking film of a lower layer using the ultraviolet curable ink  61  having 3.5 wt % carbon black content. As in the other alternative example, when forming onto the lower layer the first light-blocking film  77  that has a large amount of carbon black content, the ultraviolet light can be irradiated on both surfaces of the ultraviolet curable ink  76  by, for example, making the conveyor bed transparent. Thus, the ultraviolet curable ink can be cured in a more reliable manner by irradiating the ultraviolet light from the conveyor bed in addition to the ultraviolet light from above. 
     The light blocking material that constitutes the ultraviolet curable ink is not limited to carbon black; each type of the light blocking material listed above can also be used. When using a pigment as the light blocking material, several types of pigments may be mixed. In such cases, changing the mixing ratio can change the light blocking performance of the light-blocking film formed by the ultraviolet curable ink. 
     According to the first embodiment, among the plurality of lenses  52 , the second light-blocking film  57  is formed on top of the first light-blocking film  56 . In order to make the film thickness of the light-blocking film formed at the first formation step thinner, the first light-blocking film  56  and the second light-blocking film  57  are formed separately from each other. So at each formation step, the ultraviolet light  67  sufficiently irradiates the ultraviolet curable ink  61  to ensure curing of the ultraviolet curable ink  61 . The lens array  50  is equipped with light-blocking films with a film thickness of 24 μm in total for both the first light-blocking film  56  having 12 μm in film thickness and the second light-blocking film  57  having 12 μm in film thickness. This enables superior light blocking properties, enabling the lens array  50  to reliably block stray light, and provides a lens of good quality. 
     Second Embodiment 
     Next, a second embodiment will be explained. A lens array according to the second embodiment includes light-blocking films having a plurality of layers on both major sides of the lens array. The plurality of layers are disposed between a plurality of lenses on both major sides of the substrate. In this second embodiment, the same components that are described in the first embodiment will be given the same reference numerals and detailed explanations of the components will be omitted for brevity. 
     A lens array  80  according to the second embodiment as shown in  FIG. 15  and  FIG. 16  is provided with a plurality of first lenses  82  having base dimension α at each of the two surfaces of a transparent substrate  81 , and a plurality of second lenses  83  having an base dimension β. The base dimension α of the first lenses  82  is wider than the opening width β of the second lenses  83 . Layered in between the plurality of the first lenses  82  of the lens array  80  are a first light-blocking film  85  and a second light-blocking film  86 , each having a 12 μm thickness. The total of the film thickness of the first light-blocking film  85  and the second light-blocking film  86  is 24 μm. Laminated in between the plurality of the second lenses  83  of the lens array  80  are a third light-blocking film  87  and a fourth light-blocking film  88 , each having a 12 μm thickness. The total of the film thickness of the third light-blocking film  87  and the fourth light-blocking film  88  is 24 μm. The first to the fourth light-blocking films  85 - 88  are formed using the ultraviolet curable ink  61  having the same characteristics, the ink of which has 3.5 wt % carbon black content. 
     In the lens array  80 , the first light-blocking film  85  at the first lenses  82  side having the wider base dimension α and the second light-blocking film  86  are formed first. The light-blocking film forming device  60  ( FIG. 10 ) forms the first light-blocking film  85  by discharging the ultraviolet curable ink  61  in an amount so that the film thickness of the first light-blocking film  85 , after curing, becomes 12 μm between the plurality of the first lenses  82 . The first light-blocking film  85  is then cured by exposing the ultraviolet curable ink  61  to the ultraviolet light  67  from the ultraviolet irradiation device  63  ( FIG. 11 ). The light-blocking film forming device  60  repeats the same formation step as that of the first light-blocking film  85 , and laminates the second light-blocking film  86  on top of the first light-blocking film  85 . The first light-blocking film  85  and the second light-blocking film  86  are sufficiently cured by the ultraviolet light  67  emitted from the ultraviolet irradiation device  63 . 
     After forming the first light-blocking film  85  and the second light-blocking film  86 , the substrate  81  is reversed (turned over), and the third light-blocking film  87  and the fourth light-blocking film  88  at the second lenses  83  side are formed with the same formation steps as that of the first light-blocking film  85  and the second light-blocking film  86 . The third light-blocking film  87  and the fourth light-blocking film  88  are sufficiently cured by the ultraviolet light  67  from the ultraviolet irradiation device  63 . 
     In the formation of the first to the fourth light-blocking films  85 - 88  of the lens array  80 , the first and the second light-blocking films  85  and  86  on the side of the first lenses  82  having the wider opening width α may be formed first, or the third and the fourth light-blocking films  87  and  88  on the side of the second lenses  83  having the narrower opening width β may be formed first. 
     For the first to the fourth light-blocking films  85 - 88  of the lens array  80 , when forming in advance the first and the second light-blocking films  85  and  86  on the side of the first lenses  82  having the wider base dimension u, the amount of the ultraviolet light that passes through the first lenses  82  having the wider base dimension u becomes significant. Thus, when forming the third light-blocking film  87 , a portion of the ultraviolet light  67  from above the substrate  81  may be blocked by the first and the second light-blocking films  85  and  86 . However, the third light-blocking film  87  may be cured by irradiating ultraviolet light also from a transparent conveyor bed during the formation of the third light-blocking film  87  on the side of the second lenses  83  having the narrower base dimension β. Accordingly, sufficient ultraviolet light can be irradiated on the third light-blocking film  87  formed after the first and the second light-blocking films  85  and  86  with ultraviolet light from the inside of the substrate  81 , enabling it to sufficiently cure the third light-blocking film  87 . 
     When the third and the fourth light-blocking film  87  and  88  on the side of the second lenses  83  having the narrower base dimension β are formed first, there is a great amount of reflection reflected at the first light-blocking film  85  from the third light-blocking film  87  by the ultraviolet light  67  during cure that is incident from the first lenses  82 , during the formation of the first light-blocking film  85  at the first lenses  82  having the wider opening width. Accordingly, sufficient ultraviolet light can be irradiated to the first light-blocking film  85  formed later also from the inside of the substrate  81 , and the first light-blocking film  85  can be sufficiently cured. 
     According to the second embodiment, the second light-blocking film  86  is laminated after forming the first light-blocking film  85  between the plurality of the first lenses  82  of the substrate  81 , and the fourth light-blocking film  88  is laminated after forming the third light-blocking film  87  between the plurality of the second lenses  83  of the substrate  81 . Since it is possible to make thinner the film thickness of the light-blocking film formed at a single formation step, the ultraviolet light  67  can sufficiently irradiate the ultraviolet curable ink  61 , and the ultraviolet curable ink  61  can be cured in a reliable manner. The lens array  80  is equipped with light-blocking films having 24 μm total film thickness for both the first light-blocking film  85  having 12 μm in film thickness and the second light-blocking film  86  having 12 μm film thickness, at the first lenses  82  side. And at the second lenses  83  side, the lens array is equipped with light-blocking films having 24 μm total film thickness for both the third light-blocking film  87  having 12 μm film thickness and the fourth light-blocking film  88  having 12 μm in film thickness. In this way, superior light blocking properties can be achieved, enabling it to reliably block stray light, and a high quality lens can be obtained. 
     Third Embodiment 
     Next, a third embodiment will be explained. In the third embodiment, the lens array is equipped with a plurality of lenses on both major surfaces of the substrate, and the lenses have different curvatures at each surface. In the third embodiment, the same components as described in the first embodiment will be given the same reference numerals and a detailed explanation of the components will be omitted for brevity. 
     A lens array  90  according to the third embodiment as shown in  FIG. 17  to  FIG. 19  is provided with a plurality of first lenses  92 , each having a first radius of curvature γ, and a plurality of second lenses  93 , each having a second radius of curvature δ, on both major surfaces of a transparent substrate  91 . The first radius of curvature γ of the first lenses  92  is smaller than the second radius of curvature δ of the second lenses  93 . A first light-blocking film  95  and a second light-blocking film  96 , each having 12 μm in thickness, are laminated between the plurality of the first lenses  92  of the lens array  90 . The total film thickness for both the first light-blocking film  95  and the second light-blocking film  96  will become 24 μm after curing. A third light-blocking film  97  and a fourth light-blocking film  98 , each having 12 μm in thickness, are laminated between the plurality of the second lenses  93  of the lens array  90 . The total film thickness for both the third light-blocking film  97  and the fourth light-blocking film  98  will become 24 μm after curing. The first to the fourth light-blocking films  95 - 98  are formed by using the ultraviolet curable ink  61  having the same characteristics in which the content of carbon black is set at 3.5 wt %. 
     For the lens array  90 , for example, the first light-blocking film  95  and the second light-blocking film  96  of the first lenses  92  having the smaller radius of curvature are formed first (using a process similar to the process described in  FIGS. 9-11 ). The light-blocking film forming device  60  forms the first light-blocking film  95  by discharging the ultraviolet curable ink  61  in the amount so that the film thickness of the first light-blocking film  95  after curing becomes 12 μm, between the plurality of the first lenses  92 . The first light-blocking film  95  is then cured by the ultraviolet light  67  from the ultraviolet irradiation device  63 . The light-blocking film forming device  60  repeats the same step as the step of forming the first light-blocking film  95 , and laminates the second light-blocking film  96  on top of the first light-blocking film  95 . The first light-blocking film  95  and the second light-blocking film  96  are sufficiently cured by the ultraviolet light  67  from the ultraviolet irradiation device  63 . 
     After forming the first light-blocking film  95  and the second light-blocking film  96 , the substrate  91  is reversed, and the third light-blocking film  97  and the fourth light-blocking film  98  at the second lenses  93  are formed by the same formation steps as that of the first light-blocking film  95  and the second light-blocking film  96 . The third light-blocking film  97  and the fourth light-blocking film  98  are sufficiently cured by the ultraviolet light  67  from the ultraviolet irradiation device  63 . 
     In forming the first to the fourth light-blocking films  95 - 98  of the lens array  90 , the first and the second light-blocking films  95  and  96  of the first lenses  92  having smaller radius of curvature may be formed first, or the third and the fourth light-blocking films  97  and  98  of the second lenses  93  having larger radius of curvature may be formed first. 
     When the first and the second light-blocking films  95  and  96  of the first lenses  92  having smaller radius of curvature are formed first, then during the formation of the third light-blocking film  97  of the second lenses  93  having larger radius of curvature, the ultraviolet light  67  incident from the second lenses  93  have a long focal length due to large radius of curvature as shown by width A in  FIG. 19 . Therefore, the ultraviolet light is dispersed on a wide region within the substrate  91 , such as within the widened reflection area B by reflection off the first light-blocking film  95 . Therefore, sufficient ultraviolet light can be irradiated from above the substrate  91  as well as from inside the substrate  91  over the entire length of the third light-blocking film  97  formed after the first and the second light-blocking films  95  and  96 . Thus, the third light-blocking film  97  is sufficiently cured. 
     According to the third embodiment, the second light-blocking film  96  is laminated after forming the first light-blocking film  95  between the plurality of the first lenses  92  of the substrate  91 , and the fourth light-blocking film  98  is laminated after forming the third light-blocking film  97  between the plurality of the second lenses  93  of the substrate  91 . The film thickness of the light-blocking film formed by a single formation step can be made thinner, so in each formation step, the ultraviolet light  67  can be sufficiently irradiated to the ultraviolet curable ink  61  to ensure curing of the ultraviolet curable ink  61 . The lens array  90  can be provided with the light-blocking films that have 24 μm in total film thickness in between either the first lenses  92  or the second lenses  93 , so superior light blocking properties can be obtained. The light blocking films ensure blocking of stray light, and a high quality lens can be obtained. 
     Fourth Embodiment 
     Next, a fourth embodiment will be explained. In the fourth embodiment, the lens array is equipped with a plurality of lenses on both major sides of the substrate, and the light-blocking films on each surface of the lens array have different thicknesses. In the fourth embodiment, the same components described in the first embodiment and the alternative example of the first embodiment will be given the same reference numerals and a detailed explanation will be omitted for brevity. 
     A lens array  100  of the fourth embodiment, as shown in  FIG. 20  and  FIG. 21 , is equipped with a plurality of first lenses  102  and a plurality of second lenses  103  on both major sides of a transparent substrate  101 . The first lenses  102  and the second lenses  103  have the same shape. Laminated between the plurality of the first lenses  102  of the lens array  100  are a first light-blocking film  105  and a second light-blocking film  106  having 12 μm in thickness, each of which includes the ultraviolet curable ink  61  having a 3.5 wt % carbon black content. The total film thickness for both the first light-blocking film  105  and the second light-blocking film  106  is 24 μm. Laminated between the plurality of the second lenses  103  of the lens array  100  are a third light-blocking film  107  and a fourth light-blocking film  108  having 6 m in thickness, each of which includes the ultraviolet curable ink  76  having a 7.5 wt % carbon black content. The total film thickness for both the third light-blocking film  107  and the fourth light-blocking film  108  is 12 μm. 
     For the lens array  100 , the first light-blocking film  105  and the second light-blocking film  106  at the first lenses  102  are formed first (using a process similar to the process described in  FIGS. 9-11 ). The light-blocking film forming device  60  forms the first light-blocking film  105  by discharging, between a plurality of the first lenses  102  from the inkjet printing unit  62 , the ultraviolet curable ink  61  in an amount so that the film thickness of the first light-blocking film  105  after curing becomes 12 μm. The ultraviolet curable ink  61  is then cured by the ultraviolet light  67  from the ultraviolet irradiation device  63 . The light-blocking film forming device  60  repeats the same step as the step of forming the first light-blocking film  105 , and laminates the second light-blocking film  106  on top of the first light-blocking film  105 . The first light-blocking film  105  and the second light-blocking film  106  are sufficiently cured by the ultraviolet light  67  from the ultraviolet irradiation device  63 . 
     After forming the first light-blocking film  105  and the second light-blocking film  106 , the substrate  101  is reversed, and the third light-blocking film  107  and the fourth light-blocking film  108  at the second lenses  103  are formed (using a process similar to the process described in FIGS.  9 - 11 ). The light-blocking film forming device  60  forms the third light-blocking film  107  by discharging, between a plurality of the second lenses  103  from the inkjet printing unit  62 , the ultraviolet curable ink  76  ( FIG. 14 ) in an amount so that the film thickness of the third light-blocking film  107  after curing becomes 6 μm, and curing the ultraviolet curable ink  76  by the ultraviolet light  67  from the ultraviolet irradiation device  63 . The light-blocking film forming device  60  repeats the same step as the step of forming the third light-blocking film  107 , and laminates the fourth light-blocking film  108  on top of the third light-blocking film  107 . The third light-blocking film  107  and the fourth light-blocking film  108  are sufficiently cured by the ultraviolet light  67  from the ultraviolet irradiation device  63 . 
     In the formation of the first to the fourth light-blocking films  105 - 108  of the lens array  100 , the first and the second light-blocking films  105  and  106  at the first lenses  102  may be formed first, or the third and the fourth light-blocking films  107  and  108  at the second lenses  103  may be formed first. 
     According the fourth embodiment, the first light-blocking film  105  and the second light-blocking film  106  having 24 μm in total film thickness are laminated between the plurality of the first lenses  102  of the substrate  101 , and the third light-blocking film  107  and the fourth light-blocking film  108  having 12 μm in total film thickness are laminated between the plurality of the second lenses  103  of the substrate  101 . The film thickness of the light-blocking films formed can be made thin in a single formation step, so in each formation step of the first and the second light-blocking films  105  and  106 , the ultraviolet light  67  can sufficiently irradiate the ultraviolet curable ink  61 , and the ultraviolet curable ink  61  can be cured in a reliable manner. Similarly, in each formation step of the third and the fourth light-blocking films  107  and  108 , the ultraviolet light  67  can sufficiently irradiate the ultraviolet curable ink  76 , and the ultraviolet curable ink  76  can be cured in a reliable manner. The lens array  100  is equipped with, on the side of the first lenses  102 , light-blocking films having 24 μm in total film thickness. The first and the second light-blocking films  105  and  106  are formed using the ultraviolet curable ink  61  having a 3.5 wt % carbon black content. The lens array  100  is also equipped with, on the side of the second lenses  103 , light-blocking films having 12 μm in total film thickness, of which are formed using the ultraviolet curable ink  76  having 7.5 wt % in carbon black content. By doing so, superior light blocking properties can be obtained, enabling the lens array  100  to ensure blocking of stray light, and a high quality lens can be obtained. 
     According to at least one embodiment described above, provided between the plurality of lenses of the lens array are light-blocking films with a plurality of layers prepared by dividing the application of ultraviolet curable ink into multiple applications, followed by curing. Since the film thickness of the light-blocking film formed in a single step is thinner, in each formation step, the ultraviolet light can sufficiently irradiate the ultraviolet curable ink and the ultraviolet curable ink can be cured in a reliable manner. The lens array has superior light blocking properties with the final total of the light-blocking films having a plurality of layers. 
     This disclosure is not limited to the embodiments described above and various modifications are possible. For example, the shape, or the like, of the array of the plurality of lenses is arbitrary. 
     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.