Patent Publication Number: US-2013229714-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. 2012-048146, filed Mar. 5, 2012; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a lens array having a light-blocking film provided between a plurality of lenses, an image forming device, and a method for manufacturing a lens array. 
     BACKGROUND 
     A light-blocking film for preventing stray light has been included in 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, confocal laser microscopes, or, in the field of optical communications, optical disks, image displays, image transmission and coupling, optical metrology, optical sensing, optical processing, and the like. 
     However, lens arrays having a light-blocking film made of ultraviolet curable ink (that cures using ultraviolet light) suffer drawbacks. As examples, the UV curable ink blocks ultraviolet light from the lens array, and the UV curable ink is unable to cure sufficiently. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating a first embodiment of an image forming device. 
         FIG. 2  is a schematic diagram illustrating a black (K) image formation section 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 diagram illustrating a lens array according to the first embodiment. 
         FIG. 5  is a schematic illustration of a lens array seen from the line d-d′ in  FIG. 4 . 
         FIG. 6  is a schematic diagram of a light-shield film forming device according to the first embodiment. 
         FIG. 7  is a schematic diagram of an apparatus for the irradiation of ultraviolet light according to the first embodiment. 
         FIG. 8  is a schematic diagram of a substrate on a conveyance stage according to a method for manufacturing the light-blocking film according to the first embodiment. 
         FIG. 9  and  FIG. 10  are schematic diagrams for explaining the ejection of ultraviolet curable ink according to embodiments of a method for manufacturing the light-blocking film according to the first embodiment blocking 
         FIG. 11  is a schematic diagram illustrating the completion of forming the light-blocking film in the method for manufacturing the light-blocking film according to the first embodiment. 
         FIG. 12  is a schematic diagram of a portion of a light-blocking film forming device according to a second embodiment. 
         FIG. 13  is a schematic diagram of the irradiation of ultraviolet light onto an ultraviolet curable ink according to the second embodiment. 
         FIG. 14  is a schematic diagram of the irradiation of ultraviolet light onto the ultraviolet curable ink according to the second embodiment. 
         FIG. 15  is a schematic diagram of the irradiation of ultraviolet light onto the ultraviolet curable ink according to a third embodiment. 
         FIG. 16  is a perspective view of a portion of a lens array according to the third embodiment. 
         FIG. 17  is a schematic diagram of an alternative embodiment for the irradiation of ultraviolet light onto an ultraviolet curable ink according to the third embodiment. 
         FIG. 18  is a schematic diagram of another alternative embodiment for the irradiation of ultraviolet light onto an ultraviolet curable ink on the first lens surface according to the third embodiment. 
         FIG. 19  is a schematic diagram of another alternative embodiment for the irradiation of ultraviolet light onto an ultraviolet curable ink on the second lens surface according to the third embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments disclosed herein provide a lens array and an image forming device, and a method for manufacturing the lens array, which lens array irradiates ultraviolet light onto an ultraviolet curable ink sufficiently to completely cure the ultraviolet curable ink. 
     In general, according to one embodiment, a lens array that achieves the effects of the embodiments will be explained referring the drawings. Identical references will be used for identical parts in each drawing and for brevity; the explanation for the elements will not be repeated. 
     According to one embodiment, a lens array includes: a substrate including a lens surface having a plurality of lenses; a protruding plane that protrudes from an end portion of the lens surface; and a light-blocking film arranged between the plurality of lenses on the lens surface. 
     First Embodiment 
     A first embodiment will be explained referring to  FIG. 1  to  FIG. 11 .  FIG. 1  illustrates a color MFP (Multi-Function Peripheral)  10  as an image forming device in the first embodiment. A platen  12  made with transparent glass is provided on top of a main body  11  of the MFP  10 , and an auto document feeder (ADF)  13  on the platen  12  can be freely opened or closed. An operating panel  14  is provided at the upper portion of the main body  11 . The operating panel  14  has a variety of keys and a touch-panel display. 
     A scanner unit  15 , which is an image reading device, is provided below the lower portion of the ADF  13  inside the main body  11 . The scanner unit  15  scans a document G 1  fed by the ADF  13 , or a document G 2  placed on the platen  12 , and generates image data. A contact image sensor  16   a  is incorporated in an image reading unit  16 . The image sensor  16   a  is arranged in a main scanning direction (into the paper in  FIG. 1 ). The image-scanning device  16  includes a light source. Light from the light source is irradiated onto the document G 2  placed on the platen. The light is reflected by the document G 2  and passes a lens array before reaching the image sensor  16   a . The image sensor  16   a  is at a fixed position shown in  FIG. 1 , when scanning a document fed by the ADF  13 . 
     A printer unit  17  is provided at the center portion inside the main body  11 . A plurality of cassettes  18  that contain various sizes of paper are provided at the lower portion of the main body  11 . The printer unit  17  has a photosensitive drum and a scanning bed  19  including a LED as an exposure device, and generates an image by scanning the photosensitive drum using a light beam from the scanning head  19 . 
     The printer unit  17  generates images on a paper by processing image data that is scanned by the scanner unit  15 , or the image data that is generated by a PC (Personal Computer) or the like. The printer unit  17  can be a tandem color laser printer, for example, including image forming units  20 Y (yellow),  20 M (magenta),  20 C (cyan) and  20 K (black). The image forming units  20 Y,  20 M,  20 C and  20 K are provided below an intermediate transfer belt  21  in a parallel arrangement from the upstream side to the downstream side of the intermediate transfer belt  21 . The scanning bed  19  also has multiple scan heads  19 Y (yellow),  19 M (magenta),  19 C (cyan) and  19 K (black) corresponding to the image forming units  20 Y,  20 M,  20 C and  20 K. 
       FIG. 2  illustrates the black (K) image forming unit  20 K out of the image forming units  20 Y,  20 M,  20 C and  20 K shown in  FIG. 1 . Hereafter, the image forming unit  20 K will be explained as a representative, because each of the image forming units  20 Y,  20 M,  20 C and  20 K has the same configuration with the exception of the color configuration. 
     The image forming unit  20 K has a photosensitive drum  22 K as an image-carrying member. An electrostatic charging unit  23 K, a developing unit  24 K, a primary transferring roller  25 K, and a cleaner  26 K having a blade  27 K are arranged around the photosensitive drum  22 K in the direction of rotation t. The scan head  19 K irradiates a light to an exposure spot on the photosensitive drum  22 K and forms an electrostatic latent image on the photosensitive drum  22 K. 
     The electrostatic charging unit  23 K of the image forming unit  20 K charges the surface of the photosensitive drum  22 K. The developing unit  24 K supplies a black toner to the photosensitive drum  22 K by a developing roller  24   a  to which a developing bias is applied. The cleaner  26 K cleans up the residual toner on the surface of the photosensitive drum  22 K using the blade  27 K. 
     As illustrated in  FIG. 1 , toner cartridges  28 Y (yellow),  28 M (magenta),  28 C (cyan) and  28 K (black) that supply toner to the image forming units  20 Y,  20 M,  20 C and  20 K are provided at the top of the image forming units  20 Y,  20 M,  20 C and  20 K. 
     The intermediate transfer belt  21  is extended through a drive roller  31 , a driven roller  32  and a tension roller  30 , and circulates in the direction of the arrow y. Also, a portion of the intermediate transfer belt  21  is faces and touches the photosensitive drums  22 Y (yellow),  22 M (magenta),  22 C (cyan) and  22 K (black) of the image forming units  20 Y,  20 M,  20 C and  20 K. By the coupling or contact of the intermediate transfer belt  21  with the primary transferring roller  25 K (shown in  FIG. 2 ), a primary transfer voltage is applied to the position on the intermediate transfer belt  21  that is facing the photosensitive drum  22 K. A toner image on the photosensitive drum  22 K is then transferred to the intermediate transfer belt  21 . 
     A secondary transferring roller  33  is provided to face the driving roller  31  that provides motion to the intermediate transfer belt  21 . When a paper or other printing medium sheet S passes between the driving roller  31  and the secondary transferring roller  33 , a secondary transfer voltage is applied to the paper sheet S by the secondary transferring roller  33 , and toner images on the intermediate transfer belt  21  are thereby transferred to the paper sheet S. A belt cleaner  34  is provided adjacent the driven roller  32  of the intermediate transfer belt  21 , in a position relative to the transfer of the belt such that the remnants of a latent image on the intermediate belt  21  which were transferred to the sheet S are removed from the intermediate belt  21  before that portion of the intermediate belt reaches the latent image writing position of the first photosensitive drum and a scanning bed  19 Y of the printing unit  17 . 
     As illustrated in  FIG. 1 , conveying rollers  35 , which convey the paper sheet S taken from a paper feed cassette  18 , and a resist roller  35   a , are provided between the paper feed cassette  18  and the secondary transferring roller  33 . In addition, a fixing unit  36  is provided downstream of the secondary transferring roller  33  to fix an image on the sheet. Paper discharge rollers  37  are provided downstream of the fixing device  36 . The paper discharge rollers  37  eject the paper sheet S to a discharge section  38 . 
     A reverse conveying path  39  is provided downstream of the fixing unit  36 . The reverse conveying path  39  reverses the paper sheet S and guides the paper sheet S towards the secondary transferring roller  33  when performing duplex, i.e., two sided, printing. 
     The scan head  19 K illustrated in  FIG. 2  faces the photosensitive drum  22 K. The photosensitive drum  22 K rotates at a predetermined speed and stores an electrical charge on its surface. Alight 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 . A support  42  is provided at the bottom of the holding member  41 . The support  42  has a plurality of LED elements  43  as a light source (only one is shown in the side view of  FIG. 2 ). The LED elements  43  are provided in the main scanning direction (toward the paper) and are equally spaced in a linear fashion in the direction of belt motion past the scan head  19 K. A control substrate  43   a  including a driver IC to control emission of the LED  43  is provided on the support  42 . 
     The control substrate  43   a  generates control signals for the scan head  19 K based on image data to cause light to be emitted from the LED element  43  at a certain light intensity based on the control signals. The light emitted from the LED element  43  passes through the lens array  50  and forms an electrostatic latent image on the photosensitive drum  22 K. The scan head  19 K has a cover glass  44  at the top portion of the holding member  41  (the irradiating side). 
     Referring to  FIGS. 1 and 3 , as an image on a document, such as a sheet of paper, passes the image reading unit  16 , the image sensor  16   a  thereof scans images of the document G 2  (shown in  FIG. 1 ) placed on the platen  12 , or the document G 1  fed by the ADF  13  (shown in  FIG. 1 ), in accordance with an operation of the operating panel  14  (shown in  FIG. 1 ). The image sensor  16   a  is a one-dimensional sensor arranged in the main scanning direction (into the paper). Two LED line lighting systems  47  and  48 , which illuminate towards the documents, are arranged in the main scanning direction (into the paper) on the top surface of a chassis  45 , that is provided on a substrate  46  below the platen  12 , to illuminate any image on the document. The light source for illuminating documents is not restricted to an LED, and a fluorescent tube, a xenon tube, a cold-cathode tube, or an organic EL can be also used. 
     A lens array  50  is supported in between the LED line lighting systems  47  and  48  at the upper portion of the chassis  45 . An image sensor  49 , comprised of CCD and CMOS, is mounted on the substrate  46  located at the bottom of the chassis  45 . The LED line lighting systems  47  and  48  illuminate the image scanning position of a document on the platen  12 , and the light reflected at the image scanning position enters the lens array  50 . The lens array  50  functions as an erecting equal-magnification lens. Light that enters the lens array  50  is passed from the plane of the lens array  50  and forms an image on the image sensor  49 . The light that forms an image is converted to electric signals by the image sensor  49  and is transferred to a memory unit (not shown) of the substrate  46 . 
     As an image forming device, an MFP (Multi-Function Peripheral) is used as an example and explained in this embodiment, although an image forming device is not restricted to an MFP. A stand-alone printer, or a stand-alone scanner, can also be an image forming device. 
     The lens array  50  will be explained in detail next. As illustrated in  FIG. 4  and  FIG. 5 , the lens array  50  includes a transparent substrate  51  having a plurality of lenses  52  on a lens surface  51   a , and a light-blocking film  53 , in this example 24 μm thick, which is formed on the lens surface  51   a  between each lens  52 . The substrate  51  having the lenses  52  can be formed by molding a transparent material into the shape of a generally flat substrate  51  having individual lenses  52  protruding from a surface thereof. The light-blocking film  53  is formed on the substrate  51 , between the individual lens elements  53 , using a light-blocking film forming device  60 , illustrated in  FIG. 6 . The light-blocking film forming device  60  forms the light-blocking film  53  by ultraviolet curing of ink applied by an inkjet method. The light-blocking film forming device  60  includes an inkjet printing unit  62 , ultraviolet irradiating device  63 , a conveyor bed  64  and a control unit  66 . 
     The conveyor bed  64  supports the substrate  51  having the plurality of lenses  52  thereon, and moves in the direction shown by the arrow r, and conveys the substrate  51  relative to the inkjet printing unit  62  and the ultraviolet irradiating device  63  (shown schematically in  FIG. 6 ). The inkjet printing unit  62  ejects an ultraviolet curable ink  61  from above of the substrate  51  toward the space between each lens  52  on the lens surface  51   a . The ultraviolet irradiating device  63  includes: a first irradiating section  63   a  that irradiates ultraviolet  67  from above of the lens surface  51   a , and a second irradiating section  63   b  that irradiates ultraviolet  68  from a side plane  51   b  (shown in  FIG. 7 ) of the substrate  51 , which is perpendicular to the lens surface  51   a . Ultraviolet curable ink  61  is ejected onto the lens surface  51   a  as illustrated in  FIG. 7 . The control unit  66  controls the inkjet printing unit  62 , the ultraviolet irradiating device  63  and the conveyor bed  64 . The control unit  66  controls the speed of the conveyor bed  64  and a timing of the conveyor. The control unit  66  controls an amount of ink ejected from the inkjet printing unit  62  for example. Control of an amount of ink ejected can be implemented by adjusting the voltage for ink ejection to change the drop size, for example, or by adjusting the number of droplets in a multi-drop method. 
     For the light-blocking film forming device  60 , the ultraviolet curable ink  61  can be applied to the lens surface  51   a  by an ink-applying device instead of the inkjet method. Also, in order to form the light-blocking film  53 , the inkjet printing unit  62  and the ultraviolet irradiating device  63  can move relative to the conveyor bed  64  and the substrate  51 , instead of moving the conveyor bed  64  relative to the inkjet printing unit  62  and the ultraviolet irradiating device  63 . 
     The ultraviolet curable ink will be explained. Example light-blocking materials for the ultraviolet curable ink will are listed below. 
     Light-Blocking Material 
     As light-blocking material in order to form a light-blocking film between the plurality of lenses, optical insulating properties and reflecting properties are required to be considered. Consideration of flying capability (drop flight behavior), or dispersing stability, of the ink is required as an inkjet ultraviolet curable ink property; and light-absorbing pigments can be used as such a material. For example, carbon-based pigments, such as carbon black, refined carbon and carbon nanotubes; metallic oxide pigments such as iron black, zinc oxide, titanium oxide, chromium oxide and the iron oxide; sulfide pigments such as zinc sulfide; phthalocyanine pigments; salt pigments such as sulfate metal, carbonate, silicate and phosphate; metallic powder such as aluminum powder, bronze powder and zinc powder can be used. 
     Reactive Material 
     A base material for the light-blocking film is a light curing material including: photopolymerizing reactive materials such as reactive monomers and oligomers having polymerizable functional groups, and a photo initiator that initiates polymerization thereof. Reactive materials can be categorized into radical types and cationic types, though various types are currently used for various purposes. 
     An acryl monomer or oligomer having an acryloyl functional group is representative of the radical type of reactive material which may be used; polymerization is accelerated by radicals, which are generated from a photo initiator after it is irradiated by energy such as light. Coating, ink, optical material, and resist can be used for its application. However, drawbacks associated with these materials, such as enzyme inhibition at the time of polymerization, and relatively larger volume contraction following curing, are issues that need to be controlled if these materials are used. 
     A cyclic ether compound represented by epoxy and an oxetane compound, or a vinyl ether compound having a vinyl ether group are representative of the cationic type of material which may be used. As a photo initiator, polymerization is initiated using electrons generated by irradiation to form an acid to react with the cyclic compound to form a polymer. A cyclic ether compound has minimal volume contraction during polymerization, which leads to superior adhesiveness to a base material. Polymerization can be implemented without enzyme inhibition; superior formability of a thin layer is also a different point compared to the radical type. 
     As a light-blocking film of a lens array, a material that satisfies the property of being capable of being formulated into ink ultraviolet curable ink in light of characteristics described above, and dispensed by inkjet printing, can be properly selected and used. An ink material for this embodiment has no particular limitation as long as the material has an insulating property, a reflecting or non-light transmissive property, suitable strength when cured, and may be cured using ultraviolet light blocking. The ink material should include physical properties, such as viscosity and surface tension, such that it may be used as an inkjet ultraviolet curable ink, as well as dispersion stability for use as light blocking materials, and compatibility with a head member in the inkjet printer. Tangible examples will be listed hereafter. 
     Radical type materials can be represented by a monomer such as monofunctional acrylate, difunctional acrylate, polyfunctional acrylate with three or more functional groups, and an oligomer such as polyester acrylate, urethane acrylate, epoxy acrylate, depending on the number of acryloyl groups in the molecule. Monofunctional monomer among these is often used as a reactive diluent, and plays an important role as viscosity adjusting material as an inkjet ink. 
     As a concrete example, isobornyl acrylate, acryloyl morpholine, dicyclopentadienyl acrylate, an acrylic acid adduct of phenyl glycidyl ether, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 2-hydroxyhexyl acrylate, ethyl carbitol acrylate, tetrahydrofurfuryl acrylate, 2-acryloyloxyethyl phthalate, benzyl acrylate, and methacryl acrylate such as a 2-hydroxyhexyl metacrylate, allyl metacrylate, a benzyl metacrylate, cyclohexyl metacrylate, may be used. 
     As a difunctional acrylate, neopentyl glycol diacrylate, nonanediol diacrylate, tripropylene glycol diacrylate, tricyclodecane dimethanol diacrylate, EO adduct acrylate of the bisphenol A; as a polyfunctional acrylate, trimethylol propane triacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, triacrylate of the isocyanuric acid EO adduct, can be listed. Other than acrylate system, N-vinyl pyrrolidone and N-vinyl caprolactam can be useful as a diluent. 
     Epoxy compound, oxetane compound and vinyl ether compound can be used as cationic type materials. 
     A hydrocarbon group having an aliphatic backbone of 2 values or an alicyclic backbone, and the compound which has an epoxy group or an alicyclic epoxy group in one or both of the basis of 2 values to have an aliphatic chain or an alicyclic backbone can be used as epoxy compounds. For example, alicyclic epoxy represented by CELLOXIDE 2021, CELLOXIDE 2021A, CELLOXIDE 2021P, CELLOXIDE 2081, CELLOXIDE 2000, CELLOXIDE 3000 from DAICEL CORPORATION, (meta)acrylate compound having epoxy group such as CYCLOMER A200, CYCLOMER M100, metacrylate having methyl glycidyl group such as MGMA, low molecular epoxy compound such as glycidol, β-methylepichlorohydrin, α-Pinene oxide, α-olefin monoepoxide of C12 to C14, α-olefin monoepoxide of C16 to C18, epoxidized soybean oil such as DAIMAC S-300K, epoxidized linseed oil such as DAIMAC L-500, polyfunctional epoxy such as EPOLEAD GT301 and EPOLEAD GT40, can be used. 
     In addition, alicyclic epoxy from the Dow Chemical Company in the U.S. such as CYRACURE; a compound, of which the hydroxyl group end of low molecule phenolic compounds which are hydrogenated and made aliphatic is substituted with a group having epoxy; polyvalent aliphatic alcohol such as ethylene glycol, glycerin, neopentyl alcohol, hexanediol, and trimethylolpropane; glycidyl ether compound such as alicyclic alcohol; glycidyl ester such as hexahydrophthalic acid and polyvalent carboxylic acid of hydrogenated aromatic series; can be used. 
     As an oxetane compound, for example, di[1-ethyl(3-oxetanyl)]methyl ether, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, [(1-ethyl-3-oxetanyl)methoxy]cyclohexane, bis[(1-ethyl-3-oxetanyl)methoxy]cyclohexane, compound in which one or more groups containing oxetane are introduced to an alicyclic ring such as bis[(1-ethyl-3-oxetanyl)methoxy]norbornane, an ether compound which dehydration synthesize alcohol including oxetane such as 3-ethyl-3-hydroxymethyl oxetane to aliphatic polyvalent alcohol such as ethylene glycol, propylene glycol and neopentyl alcohol, can be listed. Also, as an oxetane compound including aromatic backbone, for example, 1,4-bis((1-ethyl-3-oxetanyl)methoxy)benzene, 1,3-bis((1-ethyl-3-oxetanyl)methoxy)benzene, 4,4′-bis((3-ethyl-3-oxetanyl)methoxy)biphenyl, phenol novolac oxetane, can be listed. 
     As a vinyl ether compound, 2-ethylhexyl vinyl ether, buntanediol vinyl ether, cyclohexanedimethanol divinyl ether, cyclohexanedimethanol monovinyl ether, dithylene glycol monovinyl ether, dithylene glycol divinyl ether, hexanediol divinyl ether, triethyleneglycol divinyl ether, 4-hydroxybutyl vinyl ether can be listed. It may be preferable to combine a vinyl ether compound with an oxetane compound or epoxy compound, which may be represented in the formula (1) below, solely or in combination into a liquid ink, in case improvement of curing hardness and further decrease in viscosity in addition to an improvement of curing speed are required. 
     Vinyl ether compounds bound to methylene group, such as aliphatic glycol derivatives and cyclohexane dimethanol, are inappropriate for use as inkjet dispersible materials due to a severe inhibition of polymerization by a pigment. However, a compound that is shown in formula (1) below has vinyl ether group directly on an alicyclic backbone, terpenoid backbone, or aromatic backbone and has superior curing properties even if combined together with a pigment. The blending quantity of these compounds is provided in a ratio of 50 parts by weight or less in order to maintain heat plasticity. However, the quantity can be up to a total amount of solvent that cures by acid, when higher solvent resistance and hardness are required, even if losing heat plasticity. 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 (1) above, one of the R13 is at least a vinyl ether group; having a substituent group selected from a vinyl ether group and a hydroxyl group. R14 is a (p+1)-valent group selected from alicyclic backbone, or a backbone having an aromatic ring, where p is a positive integer including 0. When R14 is cyclohexane backbone and also p is 0, at least one of the carbons on the nucleus has ketone structure. As an organic group R14 of (p+1)-valent, for example, (p+1)-valent group including a benzene ring, a naphthalene ring, and a biphenyl ring; and induced (p+1)-valent group including a cycloalkane backbone, norbornane backbone, adamantane backbone, tricyclodecane backbone, tetracyclo dodecane backbone, terpenoid backbone, and cholesterol backbone, can be listed. 
     More specifically, alicyclic polyols such as cyclohexane(poly)ol, norbornane(poly)ol, tricyclodecane (poly) ol, adamantane (poly) ol, benzene (poly) ol, naphthalene(poly)ol, anthracene(poly)ol, and biphenyl(poly)ol, or compounds in which hydrogen atoms of the hydroxyl group in phenol derivatives are substituted to vinyl group can be listed. In addition, compounds in which hydrogen atoms of the hydroxyl group in polyphenol compound such as polyvinyl phenol and phenol novolac are substituted with vinyl group. The compounds above can be used extensively due to a reduction of volatility, even if a part of hydroxyl group remains, or a part of methylene atom of alicyclic backbone is substituted to ketone group. Particularly, a cyclohexane ring that is at least oxidized to cyclohexanone ring when a cyclohexyl monovinyl ether compound is used, because cyclohexyl monovinyl ether compounds have a high volatility. 
     Next, example of a photo initiator can be categorized into a radical system and a cationic system. Common examples are listed. 
     A radical system can be a benzoin ether system, a acetophenone system, and a phosphine oxide system; cleavage type such as 1-hydroxycyclohexyl phenyl ketone, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1; hydrogen atom abstraction type such as benzophenone, 2,4-diethyl thioxanthone, isopropyl thioxanthone, can be listed. 
     A cationic system can be an onium salt, a diazonium salt, a quinone diazide compound, an organohalide, an aromatic sulfonate compound, a bisulphone compound, a sulfonyl compound, a sulfonate compound, a sulfonium compound, a sulfamide compound, an iodonium compound, a sulfonyl diazomethane compound and mixtures thereof. 
     More specifically, triphenylsulfonium triflate, diphenyliodonium triflate, 2,3,4,4-tetrahydroxybenzophenone-4-naphthoquinone diazido sulfonate, 4-N-phenylamino-2-methoxy phenyl diazonium sulfate, 4-N-phenylamino-2-methoxy phenyl diazonium p-ethylphenyl sulfate, 4-N-phenylamino-2-methoxy phenyl diazonium 2-naphthyl sulfate, 4-N-phenylamino-2-methoxy phenyl diazonium phenyl sulfate, 2,5-diethoxy-4-N-4′-methoxyphenyl carbonyl phenyl diazonium-3-carboxy-4-hydroxyphenyl sulfate, 2-methoxy-4-N-phenyl phenyldiazonium-3-carboxy-4-hydroxyphenyl sulfate, diphenylsulfonyl methane, diphenylsulfonyl diazomethane, diphenyl disulfone, α-methylbenzoin tosylate, pyrogallol trimethylate, benzoin tosylate, can be listed. 
     The ultraviolet curable ink  61  is made using these materials and by steps including a step dispersing a (light-blocking material) to monomers (reactive monomer) and a step of adding and mixing obtained dispersed liquid with an appropriate monomer, oligomer and photo initiator, and polymerization inhibitor as necessary, and a final purification step of filtration or centrifugation to remove coarse particles and unnecessary solid contents. 
     The polymerization inhibitor can be cationic system or radical system. Cationic system can be n-hexylamine, dodecylamine, aniline, dimethyl aniline, diphenylamine, triphenyl amine, diazabicyclooctane, diazabicyclo undecane, 3-phenylpyridine, 4-phenylpyridine, lutidine, 2,6-di-t-butyl pyridine. Radical system can be DPPH(1,1-diphenyl-2-picrylhydrazyl), TEMPO(2,2,6,6-tetramethylpiperidinyl-1-oxyl). p-benzoquinone, chloranil, nitrobenzene, hydroquinone (HQ), methyl hydroquinone (MEHQ), t-butyl catechol, dimethyl aniline. 
     As for a material property of the ultraviolet curable ink  61 , there is no effect on the flying capability by the inkjet printing section  62 , if an average particle diameter of insulating material is less than 300 nm. Viscosity values of the ultraviolet curable ink are provided in a range of 5 to 30 mPa·s at 25° C. Surface tension is set within a range of 22 to 40 mN/m. The viscosity value and the surface tension value of the ultraviolet curable ink  61  can be adjusted by a blend of monomer, oligomer or surfactant agent. 
     In order to distribute ink by itself to a narrow part between the lens surface  51   a  and each lens  52 , a contact angle of the lens surface  51   a  of the substrate  51  and the ultraviolet curable ink is less than 20 degree at 25° C. 
     A method for forming the light-blocking film  53  using the ultraviolet curable ink  61  to form a light blocking film on the surface of the substrate  51  and between each lens  52  of the lens surface  51   a  is described referring  FIG. 7  through  FIG. 11 . As a light blocking material or component in the ultraviolet curable ink  61  that is used for the light-blocking film  53 , a light-blocking material can be carbon black, for example. Content of carbon black of the ultraviolet curable ink  61  is set to 3.5 wt %; the light-blocking film  53  is formed to be 24 μm thick. For the ultraviolet lights  67  and  68  (shown in  FIG. 7 ) irradiated from the first irradiating section  63   a  and the second irradiating section  63   b , respectively, of the ultraviolet irradiating unit  63 , illumination intensity is set to 2000 mW/cm 2 , integrated light quantity is set to 400 mJ/cm 2 , and wave length is 365 nm. 
     Regarding the light-blocking film  53  of the lens array  50 , the higher the light-blocking property is, the more stray light can be prevented, which is advantageous for the characteristics of the lens array  50 . The light-blocking property of the light-blocking film  53  can be obtained by measuring optical density (transmission density). Measurement of optical density can be implemented using a 361T Densitometer from X-rite, for example. The light-blocking film  53  can block transmitted light nearly completely when the optical density is 6 or higher. (Optical density is a decadic logarithm of opacity; a larger extinction amount gives a larger value. Where optical density is 6, light penetration efficiency is 0.000001%.) 
     When carbon black is used as a light-blocking material of the light-blocking film  53 , and the content of carbon black is 3.5 wt %, 24 μm thick or more of the light-blocking film  53  is required to have sufficient light-blocking property. When the content of carbon black is 7.5 wt %, 12 μm thick or more of the light-blocking film  53  is required to have sufficient light-blocking property. In order to obtain the light-blocking film  53  having sufficient light-blocking property, there are other ways of making the light-blocking film  53  thicker, or increasing the ratio by weight of a light-blocking material in the ultraviolet curable ink  61 . 
     As illustrated in  FIG. 8 , the substrate  51  is fixed to the conveyor bed  64  and the conveyor bed  64  moves in a direction of the arrow r. When the substrate  51  reaches the inkjet printing unit  62 , as illustrated in  FIG. 9 , the inkjet printing unit  62  ejects the ultraviolet curable ink  61  to the space between lenses  52  from above of the substrate  51  that is moving in the direction of the arrow r. As illustrated in  FIG. 10 , when the substrate  51  reaches the ultraviolet irradiating unit  63  as the conveyor bed  64  moves, the first irradiating section  63   a  irradiates ultraviolet light  67  onto the ultraviolet curable ink  61  from above the lens surface  51   a , and the second irradiating device  63   b  irradiates ultraviolet light  68  to the inside of the substrate  51  from the side plane  51   b  of the substrate  51 . 
     The ultraviolet light  67  from the first irradiating section  63   a  cures the ultraviolet curable ink  61 , which is ejected onto the lens surface  51   a , from the surface side. As illustrated  FIG. 7 , the ultraviolet light  68  from the second irradiating section  63   b  irradiates the ultraviolet curable ink  61  from the inside of the substrate  51  and cures the ultraviolet curable ink  61  from the side of lens surface  51   a  toward the surface of the ultraviolet curable ink  61 . Even if the ultraviolet light  67  from the first irradiating section  63   a  is blocked by the ultraviolet curable ink  61  itself, and the ultraviolet light  67  is unable to reach the lens surface  51   a  sufficiently, the ultraviolet curable ink  61  can be cured sufficiently from the side of the lens surface  51   a  on the back surface of the ultraviolet curable ink  61 , by the ultraviolet light  68  irradiated from the second irradiating section  63   b  irradiated inside of the substrate  51 . 
     Accordingly, after the substrate  51  moves past the ultraviolet irradiating unit  63 , the ultraviolet curable ink  61  is sufficiently cured by the ultraviolet light  67  and the ultraviolet light  68 , and then the lens array  50  having the light-blocking film  53  formed between the lenses  52  with sufficient hardness is produced ( FIG. 11 ). When the property of the light-blocking film  53  that is formed at the lens surface  51   a  was tested by pencil hardness (2B), a scratch was not formed. Thus, the light-blocking film  53  was proven to have sufficient hardness. 
     In contrast to this, as a comparison, when the ultraviolet light  67  was irradiated onto the ultraviolet curable ink  61  discharged on the substrate  51  only from the top surface from the first irradiating section  63   a  in order to attempt curing, an ultraviolet curable ink film for comparison of about 24 μm thick had a scratch formed by a (2B) pencil and proved not to have sufficient hardness. 
     The incidence angle of the ultraviolet light  68  by the second irradiating section  63   b  toward the inside of the substrate  51  from the side plane  51   b  ( FIG. 12 ) of the substrate  51  is not restricted, as long as the ultraviolet light  68  can irradiate the ultraviolet curable ink  61  from the backside of the lens surface  51   a  side. Also, the lens array  50  has the lens surface  51   a  as one major side of the substrate  51  with a plurality of lenses  52 , a lens array can have a lens surface at both major sides of a substrate. Ultraviolet curable ink can be cured sufficiently by irradiating ultraviolet light from the side plane  51   b  of a substrate, even if a lens surface is provided at both major sides. 
     According to the first embodiment, the ultraviolet light  68  is irradiated by the second irradiating section  63   b  from the side plane  51   b  of the substrate  51 . The ultraviolet curable ink  61  on the lens surface  51   a  is cured from both sides by the ultraviolet light  67  from above and the ultraviolet light  68  from the side plane  51   b  directed to the lower side of the ultraviolet curable ink  61 . Even if the ultraviolet light  67  from the first irradiating section  63   a  is blocked from reaching the entire volume of the light curable material by the ultraviolet curable ink  61  itself, it is possible to cure the ultraviolet curable ink  61  by irradiating the ultraviolet light  68  from the side plane  51   b  of the substrate  51  and thus irradiate the side of the up curable layer in contact with the underlying substrate  51 . 
     Second Embodiment 
     A second embodiment will be explained next. In the second embodiment, ultraviolet light irradiated from an ultraviolet irradiating unit is reflected toward the side plane of a substrate and then ultraviolet light irradiates ultraviolet curable ink from the side surface of a substrate. In the second embodiment, identical references will be used for identical configurations described in the first embodiment. 
     As illustrated in  FIG. 12 , an ultraviolet irradiating unit  70  in the second embodiment irradiates ultraviolet light  71  from above the lens surface  51   a  to the ultraviolet curable ink  61  that is ejected onto the lens surface  51   a  of the substrate  51 . The conveyor bed  64  provides a mirror  72  adjacent to the substrate  51 . The irradiating area of the ultraviolet irradiating unit  70  covers the areas of the ultraviolet curable ink  61  and the mirror  72 . The mirror  72  reflects the ultraviolet light  71  irradiated from the ultraviolet irradiating unit device  70  towards the side plane  51   b  of the substrate  51 . 
     When the substrate  51 , having the ultraviolet curable ink  61  formed on the lens surface  51   a  and in the spaces between lenses  52  of the lens surface  51   a  (as described above), reaches the ultraviolet irradiating unit  70 , the ultraviolet irradiating unit  70  irradiates the ultraviolet light  71  from above the lens surface  51   a  while moving in a direction of the arrow r. The ultraviolet light  71  from above the substrate  51  travels toward the surface of the ultraviolet curable ink  61  (toward the lens surface  51   a ) and cures the ultraviolet curable ink  61  from the surface side. Ultraviolet light  73  that is reflected, by the mirror  72  positioned adjacent a side of the substrate  51 , toward the side plane  51   b  of the substrate  51  enters from the side plane  51   b  into the body of the substrate  51 . 
     After being reflected by the mirror  72 , the ultraviolet light  73  enters from the side plane  51   b  of the substrate  51  into the body of the substrate  51 , is reflected toward the backside of the lens surface  51   a  by internal reflection within the body of the substrate  51  to thereby cure the ultraviolet curable ink  61  from the backside of the lens surface  51   a , as illustrated in  FIG. 13 . Even if the ultraviolet light  71  cannot sufficiently reach the lens surface  51   a  from above due to a blockage of ultraviolet light  71  by the ultraviolet curable ink  61  itself, the ultraviolet curable ink  61  can be cured sufficiently from the backside of the lens surface  51   a  side by the ultraviolet light  73  that is reflected back and enters from the side plane  51   b  of the substrate  51 . 
     The ultraviolet curable ink  61  cures sufficiently by the ultraviolet light  71  and the ultraviolet light  73  that is reflected back, and successfully forms a 24 μm thick light-blocking film  74  on the substrate  51  surface and between the lenses  52  with sufficient hardness. The thickness of 24 μm for the light-blocking film  74  is an example and the thickness may be greater than or less than 24 μm. The light-blocking film  74  cured by the ultraviolet light  71  and the ultraviolet light  73  that is reflected back, has sufficient hardness without generation of a scratch by a (2B) pencil, similar to the light-blocking film  53  of the first embodiment. 
     Mirrors can be arranged adjacent to both minor sides of the substrate  51  as illustrated in another example in  FIG. 14 . In this example, a mirror  76  is provided on the conveyor bed  64  on a side of the substrate  51  opposing the side facing the mirror  72  with the substrate between them. The mirror  72  and the mirror  76  each reflect the ultraviolet light  71  toward the side planes  51   b  of the substrate. The ultraviolet curable ink  61  on the substrate  51  is irradiated by the ultraviolet light  71  from above of the lens surface  51   a , and also irradiated by an ultraviolet light  77  reflected by the mirror  72  and an ultraviolet light  78  reflected by the mirror  76  from the side plane  51   b  side. The ultraviolet curable ink  61  is cured by ultraviolet light  71  from the top surface toward the lens surface  51   a , and the reflected ultraviolet lights  77  and  78  from the lens surface  51   a  side toward the top surface, and then is able to form a light-blocking film  79  between the lenses  52  with sufficient hardness. 
     According to the second embodiment, the ultraviolet light  73  reflected by the mirror  72  is irradiated from the side plane  51   b  of the substrate  51 . The ultraviolet curable ink  61  on the lens surface  51   a  is cured from both side of the upper surface and the lens surface  51   a  side, by the ultraviolet light  71  and ultraviolet light  73 . The ultraviolet curable ink  61  can be sufficiently cured by irradiating the ultraviolet lights  77  and  78  from the side plane  51   b  of the substrate  51 , even in the case the ultraviolet lights  71  from above of the lens surface  51   a  is blocked by the ultraviolet curable ink  61  itself. 
     Third Embodiment 
     A third embodiment will be explained next. In the third embodiment, ultraviolet light irradiated from an ultraviolet irradiating unit is reflected toward the side plane of a substrate by a protruding plane of a substrate and then the ultraviolet light irradiates the ultraviolet curable ink from the side of a substrate. In the third embodiment, identical references will be used for identical configurations described in the first and second embodiments. 
     As illustrated in  FIG. 15  and  FIG. 16 , a lens array  80  of the third embodiment has an extended side, such that an inclined reflector may be formed integrally therewith, the inclined plane providing the reflector to reflect the uv light used to cure the light blocking film from the interior of the substrate  51 . The inclined reflector  84  is formed as a declining plane  84  extending from an edge of the extended portion of the substrate into the body of the substrate from the lens surface  83  and in the direction of the individual lenses  82  on the surface  83 . The declining plane terminates in an emend portion  83   a  extending generally perpendicularly from the lens surface  83  inwardly of the lens adjacent to the lenses  82 . The lens surface  83  includes a plurality of lenses  82  disposed on a transparent substrate  81 . The lens array  80  has a light-blocking film  90  formed on the surface thereof between lenses  82  on the lens surface  83 . A declining plane is not restricted to a planar inclination, and it can be spherical or corrugated. 
     The substrate  81  having the declining plane  84  and a plurality of lenses  82  are formed by molding, for example. Upon forming a light-blocking film as described above, and depositing the film between the lenses  82  on the lens surface  83 , an ultraviolet irradiating unit (not shown-similar to the ultraviolet irradiating unit  70  described in  FIG. 12 ) irradiates an ultraviolet light  88  from above the lens surface  83  to the ultraviolet curable ink  61 . An area of ultraviolet irradiation by the ultraviolet irradiating unit covers areas of the ultraviolet curable ink  61  ejected on the substrate  81  as well as the declining plane  84  of the substrate  81 . The declining plane  84  reflects the ultraviolet light  88  irradiated from the ultraviolet irradiating unit toward a side plane  81   b  of the substrate  81 . Ultraviolet light  89  reflected by the declining plane  84  irradiates inside the body of the substrate  81  from the side plane  81   b  of the substrate  81 . 
     While moving the substrate  81  relative to the ultraviolet irradiating unit as described in  FIGS. 6-11 , but excluding the second illumination device  63   b , directs ultraviolet light  88  from above the lens surface  83  to the ultraviolet curable ink  61  on the lens surface  83 , and cures the ultraviolet curable ink  61  from the upper surface side. The ultraviolet light  89  that is reflected back by the declining plane  84  of the substrate  81  toward the side plane  81   b  of the substrate  81  enters from the side plane  81   b  into the body of the substrate  81 . 
     After entering from the side plane  81   b  of the substrate  81  into the body of the substrate  81 , the ultraviolet light  89  reflected by the declining plane  84  is reflected toward the lens surface  83  and cures the ultraviolet curable ink  61  from the lens surface  83  backside within the body and toward the surface. Even if the ultraviolet light  88  from above the lens surface  83  cannot sufficiently reach the lens surface  83  due to a blockage of the ultraviolet light  88  by the ultraviolet curable ink  61  itself, the ultraviolet curable ink  61  can be cured sufficiently from the lens surface  83  backside to the surface by the ultraviolet light  89  that is reflected by the declining plane  84  of the substrate  81  to the inside of the body of the substrate  81 . 
     The ultraviolet curable ink  61  cures sufficiently by the ultraviolet light  88  and the ultraviolet light  89  that is internally reflected on the back side thereof, and successfully forms the light-blocking film  90  between the lenses  82  with sufficient hardness. The light-blocking film  90  cured by the ultraviolet light  88  and the ultraviolet light  89  that is internally reflected, is sufficiently hard to not be scratched by a (2B) pencil, which is similar to the light-blocking film  53  of the first embodiment. 
     The declining plane can comprise declining planes  94  and  96  that extend inwardly of the lens surface from both end portions  93   a  and  93   b , respectively, of the lens surface  93  of a substrate  92  of a lens array  91  as illustrated as an example in  FIG. 17 . The declining planes  94  and  96  reflect ultraviolet light  97  and  98 , which are each reflected ultraviolet light  88  from above a substrate  92 . The reflected ultraviolet light  88  is provided toward a side plane  92   b  of the substrate  92 , and then enters from the side plane  92   b  to inside of the substrate  92 . After entering the body of the substrate  92  from the side plane  92   b , each ultraviolet light  97  and  98  is reflected toward the lens surface  93  and cures the ultraviolet curable ink  61  from the lens surface  93  backside toward the surface. The ultraviolet curable ink  61  is cured by the ultraviolet light  88  from the lens surface  93  side toward the top surface and the reflected ultraviolet lights  97  and  98  from the lens surface  93  backside toward the top surface, and successfully forms a light-blocking film  101  between a plurality of lenses  100  with sufficient hardness. 
     As illustrated as another example in  FIG. 18  and  FIG. 19 , a lens surface can be a substrate  111 , which has a first lens surface  112  and a second lens surface  113  on both major sides of the substrate  111  to form a lens array  110 . The lens array  110  has a protruding plane  116  that protrudes from an end portion  112   a  of the first lens surface  112 . 
     For the lens array  110 , a light-blocking film  118  on the side of the first lens surface  112  having a plurality of lenses  117  is produced first. As illustrated in  FIG. 18 , the ultraviolet curable ink  61  that has been deposited in the spaces between the lenses  117  of the first lens surface  112  while moving as described in  FIGS. 6-11 , is moved relative to a light irradiating unit (not shown). The ultraviolet light  88  is irradiated to the side of the first lens surface  112  by an ultraviolet irradiating unit similar to the light irradiating unit  70  shown in  FIG. 12 . A declining plane  114  of the substrate  111  redirects ultraviolet light  120  (reflected ultraviolet light  88 ) in a direction of a side plane  111   b  of the substrate  111 , and from the side plane  111   b  to the inside of the body of the substrate  111 . After entering from the side plane  111   b , the ultraviolet light  120  is reflected onto the backside of the first lens surface  112  and cures the ultraviolet curable ink  61  from the backside of the first lens surface  112  toward the surface. The ultraviolet curable ink  61  is cured from the upper surface toward the first lens surface  112  by the ultraviolet light  88  from above and also from the backside of the first lens surface  112  utilizing the reflected ultraviolet light  120 , and then successfully forms the light-blocking film  118  between the lenses  117  with sufficient hardness. 
     After forming the light-blocking film  118 , the substrate  111  is inversed (flipped) in order to produce a second insulating film  124  on the side of the second lens surface  113  having a plurality of lenses  123 . As illustrated in  FIG. 19 , the substrate  111  having the ultraviolet curable ink  61  that has been deposited in the spaces between the lenses  123  of the second lens surface  113  as described in  FIGS. 6-11 , is moved relative to the light irradiating unit (not shown-similar to the light irradiating unit  70  shown in  FIG. 12 ), and the ultraviolet light  88  is irradiated onto the side of the lens surface  113 . The declining plane  116  redirects ultraviolet light  126  (reflected ultraviolet light  88 ) in a direction of a side plane  111   b  of the substrate  111 , and enters from the side plane  111   b  to inside of the substrate  111 . After entering the side plane  111   b , the ultraviolet light  126  is reflected on the backside of the second lens surface  113  and cures the ultraviolet curable ink  61  from the backside of the second lens surface  113  toward the surface. The ultraviolet curable ink  61  is cured from the upper surface toward the second lens surface  113  by the ultraviolet light  88  from above and also from the backside of the second lens surface  113  toward the upper surface using the reflected ultraviolet light  126 , and then successfully forms the light-blocking film  124  between the lenses  123  with sufficient hardness. 
     According to the third embodiment and the examples of the third embodiment, ultraviolet light  89 ,  120 ,  126  reflected by the declining plane  84 ,  114 ,  116  is irradiated from the side plane  81   b ,  111   b  of the substrate  81 ,  111 . The ultraviolet curable ink  61  on the lens surface  83 ,  112 ,  113  is cured from both sides of the upper surface side and the side surface of the lens surface  83 ,  112 ,  113 , by the ultraviolet light  88  and ultraviolet light  89 ,  120 ,  126 . The ultraviolet curable ink  61  can be sufficiently cured by irradiating the ultraviolet light  89 ,  120 ,  126  from the side plane  81   b ,  111  of the substrate  81 ,  111 , even when the ultraviolet light  88  from above the lens surface  83  is blocked by the ultraviolet curable ink  61  itself. 
     According to at least one of above embodiments, an ultraviolet curable ink, which is supplied to the space between a plurality of lenses of a lens array, can be cured sufficiently by ultraviolet light irradiated from a side plane of a substrate. 
     The present disclosure is not restricted to the above embodiments and may be embodied in a variety of other forms. Placement configuration and others of a plurality of lenses is optional, for example. 
     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.