JP6098307B2 - Printing method and heating condition determination method - Google Patents

Description

  The present invention relates to a printing method for applying a cationic photopolymerization ink on a substrate and a method for determining heating conditions. More specifically, the film thickness uniformity of the cationic photopolymerization ink printed on the substrate is The present invention relates to a printing method capable of improving adhesion and a method for determining heating conditions.

  Conventionally, when an image is recorded on various recording media such as paper and cloth using an ink jet recording apparatus, a photocurable ink is used, and the ink that has landed on the recording medium is irradiated with light and cured. It has been known.

  Patent Document 1 describes that when a cationic photopolymerization ink is used as a photocurable ink, the curing reaction is easily influenced by temperature and humidity. To prevent this, the recording medium is heated. Is described.

  Further, in Patent Document 1, in order to prevent the recording medium from being unnecessarily heated during the above heating and causing the distortion or deterioration of the recording medium, 1) the recording medium in the landing area where the ink has landed is heated. In the heating unit that does not discharge ink, an ink jet recording apparatus that reduces the amount of heating of the recording medium compared to when it discharges, or 2) the heating unit on the downstream side and upstream side in the conveyance direction of the recording medium And an inkjet recording apparatus that controls the heating amount of the recording medium by the upstream heating unit based on the heating amount of the recording medium by the downstream heating unit has been proposed.

JP 2007-83574 A

  A member obtained by applying a photocurable ink on a substrate has applicability to various uses such as an optical component such as a lens.

  In applications such as optical parts, dimensional accuracy of the applied coating and adhesion to the substrate are required.

  The technique described in Patent Document 1 can solve the problem that the recording medium itself is distorted or deteriorated by heating when using the photocationic polymerization type ink. There is still room for further improvement in terms of uniformity of the film and adhesion to the substrate.

  In addition, as a photocurable ink, a photo-radical polymerization ink is also known, but it has a strong property of shrinking when cured, and when the substrate is particularly delicate like a lens, the ink shrinks. It has been confirmed by tests that the base material itself is also deformed and causes practical concerns.

  The present inventor has eagerly studied a printing method using a cationic photopolymerization ink, and surprisingly, by setting the temperature of the base material surface at the time of applying the ink and the thermal expansion coefficient of the base material to specific conditions, the base material is unexpectedly changed. The present inventors have found that the photocationic polymerization ink printed on the material is excellent in film thickness uniformity and adhesion, and can satisfy both of these, and have reached the present invention.

  Accordingly, an object of the present invention is to provide a printing method and a heating condition determination method that are excellent in film thickness uniformity and adhesion of a photocationic polymerization ink printed on a substrate, and that can achieve both of them. .

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

1. In a printing method for applying a cationic photopolymerization ink on a three-dimensional substrate, the temperature of the surface of the substrate to which the cationic photopolymerization ink is applied is 30 ° C. or higher, and the environmental temperature is A printing method comprising heating the base material so that the thermal expansion coefficient of the base material is 0.3% or less.

2. In a printing method for applying a cationic photopolymerization ink on a substrate,
An inorganic oxide film is formed on the surface of the substrate to which the cationic photopolymerization ink is applied,
The temperature of the surface of the substrate to which the cationic photopolymerization ink is applied is 30 ° C. or higher, and the coefficient of thermal expansion of the substrate with respect to the environmental temperature is 0.3% or less. A printing method characterized by heating.

3. 3. The printing method according to 1 or 2 , wherein the coefficient of thermal expansion is in a range of 0.1% to 0.3%.

4). 4. The printing method according to 1 , 2, or 3, wherein the substrate is made of plastic.

5. 5. The printing method according to any one of 1 to 4 , wherein the cationic photopolymerization ink contains at least one or both of an oxetane compound and an oxirane compound.

6). 6. The printing method according to 1, 3 , 4 or 5 , wherein an inorganic oxide film is formed on a surface of the substrate to which the photocationic polymerization ink is applied.

7). 3. The printing method according to 2 above, wherein the inorganic oxide film contains at least titanium oxide.

  8). 8. The printing method according to any one of 1 to 7, wherein the substrate is a lens.

  9. The photo-cationic polymerization ink heated so as to be in the range of −10 ° C. or more to + 10 ° C. or less with respect to the heating temperature of the surface of the substrate to which the photo-cationic polymerization-based ink is applied, The printing method according to any one of 1 to 8, wherein the printing is applied to the surface of the substrate.

  10. 10. The printing method according to any one of 1 to 9, wherein the thermal expansion is reversible expansion.

  11. A method for determining a heating condition for determining a heating condition of a base material when applying a cationic photopolymerization ink on a base material, the base material or a base material having substantially the same configuration as the base material An arbitrary heating condition for heating the surface of the substrate to which the photocationic polymerization ink is applied to a temperature of 30 ° C. or higher is set, and in that state, the coefficient of thermal expansion of the substrate with respect to the environmental temperature When the thermal expansion coefficient is 0.3% or less, the heating condition is determined to be acceptable, and when it exceeds 0.3%, the heating condition is determined to be impossible. A method for determining a heating condition, which is applied as the determined heating condition.

  ADVANTAGE OF THE INVENTION According to this invention, it is excellent in the uniformity of the film thickness of the photocationic polymerization type ink printed on the base material, and the adhesive force, and can provide the printing method and the determination method of heating conditions which can make these compatible.

  The printing method according to the present invention is a printing method for applying a cationic photopolymerization ink on a substrate, wherein the temperature of the substrate surface to which the cationic photopolymerization ink is applied is 30 ° C. or higher, and The substrate is heated so that the coefficient of thermal expansion of the substrate with respect to the environmental temperature is 0.3%.

  In the present invention, “the coefficient of thermal expansion of the base material relative to the environmental temperature” means the difference (expansion amount) of the base material at the time of heating to the size of the base material at the environmental temperature. It is expressed as a percentage with respect to the size, and corresponds to the rate of change of the length (linear expansion coefficient). Here, the environmental temperature is usually 20 ° C. The rate of change in length (linear expansion coefficient) can be measured based on, for example, JIS K 7197.

  According to the present invention, the photo-cationic polymerization ink printed on the substrate is surprisingly excellent in the uniformity of the film thickness and the adhesion to the substrate due to the above-described configuration, and both of them can be achieved. An effect is produced.

  The reason why the effect of the present invention is obtained is not necessarily clear, but can be estimated as follows.

  The substrate heated in applying the cationic photopolymerization ink is cooled to the ambient temperature after the ink is applied (or after curing). In this cooling process, the substrate shrinks as a phenomenon opposite to thermal expansion. In the conventional technique, since the shrinkage amount is large, a load is accumulated between the applied surface and the applied cationic photopolymerization ink on the surface of the base material, and the adhesion is reduced.

  On the other hand, in the present invention, by performing thermal expansion so that the thermal expansion coefficient with respect to the environmental temperature is 0.3% or less, preferably 0.1% or more and 0.3% or less, In order to reduce the amount of shrinkage, it is possible to improve the adhesion and maintain for a long time.

  Furthermore, the influence of humidity and temperature on the curing reaction of the cationic photopolymerization ink is also suitably prevented by heating the surface of the substrate to which the cationic photopolymerization ink is applied to 30 ° C. or more, and the film thickness is uniform. Can be improved.

  In the present invention, the thermal expansion of the substrate is preferably reversible expansion. The fact that the thermal expansion of the substrate is a reversible expansion means that shrinkage occurs in the process of cooling the substrate after heating, and in such a case, the present invention is applied. The significance of this is great, and the effects of the invention are remarkably exhibited.

  In the present invention, the substrate to which the cationic photopolymerization ink is applied is not particularly limited as long as it is capable of thermal expansion upon heating, and more preferably can be thermally expanded reversibly.

  Examples of the material for the base material include plastic and glass, and plastic is particularly preferable. Since plastic is relatively easily thermally expanded, the effects of the present invention are more remarkably exhibited.

  Preferred examples of the plastic include polyester, polyolefin, polystyrene, polyvinyl chloride, acrylic resin, epoxy resin, melamine resin, and the like.

In the present invention, an inorganic oxide film is preferably formed on the surface of the substrate to which the photocationic polymerization ink is applied. An inorganic oxide film is a film containing at least an inorganic oxide. As the inorganic oxide, for example, titanium oxide (TiO ₂ ), silicon oxide (SiO ₂ ) and the like can be preferably exemplified, and at least titanium oxide is particularly preferable.

  When utilizing a base material as an optical member, an antireflection coating for preventing light reflection can be provided on the surface of the base material. As such an antireflection coating, the above-described inorganic oxide film exhibits excellent characteristics.

  The present inventor has confirmed by a test that there is a problem that it is difficult to obtain film thickness uniformity by a normal method when applying a photocationic polymerization ink on such an inorganic oxide film. However, when applying the heating conditions of the present invention, the photocationic polymerization ink can be applied on the inorganic oxide film in a state excellent in film thickness uniformity and adhesion. Therefore, in the use as an optical member such as a lens, in addition to the film thickness uniformity and adhesion of the coating film, an effect of achieving both antireflection properties can be obtained.

  In the present invention, the shape of the substrate to which the cationic photopolymerization ink is applied is not particularly limited, and a planar shape and a three-dimensional shape can be preferably exemplified, but a three-dimensional shape is particularly preferable.

  Here, the shape of the base material to which the photocationic polymerization ink is applied is preferably a three-dimensional shape, preferably, the surface to which the photocationic polymerization ink is applied includes a three-dimensional undulation as a whole. Point to. For example, a convex or concave curved surface (for example, a surface formed by part or all of a conical surface or a spherical surface), a surface formed by intersecting two or more planes, and the like can be preferably exemplified.

  Examples of printing on a substrate with a three-dimensional shape include, for example, decoration of a smartphone cover case, marking on a golf ball, printing on a personal computer keyboard, printing of a light-shielding window frame on a 3D-shaped smartphone cover glass, LED Preferred examples include conductive film printing on a three-dimensional device such as OLED, functional film printing such as a semiconductor film (so-called printed electronics field), and formation of light-shielding films for various lenses.

  When the base material has a three-dimensional shape, usually, distortion tends to concentrate locally with shrinkage in the cooling process after heating, and the adhesion of the photocationic polymerization ink is particularly liable to be impaired. This has been confirmed by the inventors' examination. In particular, in the lens, the decrease in adhesion was remarkable. On the other hand, according to the present invention, even if the base material has a three-dimensional shape such as a lens having a convex or concave curved surface, an effect of stably maintaining high adhesion over a long period can be obtained.

  The printing method according to the present invention is particularly preferably used when forming a coating film of a cationic photopolymerization ink on a substrate. The coating film refers to one in which the photocationic polymerization inks applied on the substrate as a plurality of ink droplets are united on the substrate and have a two-dimensional spread. When a relatively large coating film is formed, it is usually easily affected by the distortion caused by the shrinkage of the base material in the cooling process after the heating described above, and the adhesion is easily impaired. In this case, there is an effect that the adhesiveness can be stably maintained.

  Next, the cationic photopolymerization ink used in the present invention will be described.

  The cationic photopolymerization ink used in the present invention is an ink which is polymerized and cured by a cationic reaction with light (active energy rays).

  The cationic photopolymerization ink usually has a great influence of humidity and temperature on the curing reaction. However, according to the present invention, as described above, this influence can be prevented and a uniform film thickness can be suitably achieved.

Furthermore, a characteristic of the photo-cationic polymerization ink is that the curing shrinkage is small. In the present invention, the substrate to which the photocationic polymerization ink is applied is heated so that the coefficient of thermal expansion with respect to the environmental temperature is 0.3% or less, so the shrinkage after heating is small. That is, according to the present invention, since the shrinkage of the photocationic polymerization ink and the shrinkage of the base material are both small, it is difficult for distortion to occur in the bonding surface that couples the two, which also contributes to the improvement in adhesion. It is estimated that
Examples of the cationic polymerizable compound contained in the photo cationic polymerization ink include a compound having an oxetane ring (hereinafter referred to as an oxetane compound), a compound having an oxirane ring (hereinafter referred to as an oxirane compound), and a vinyl ether compound. In particular, it is preferable to include at least one or both of an oxetane compound and an oxirane compound.

<Oxetane compound>
The oxetane compound as a cationically polymerizable compound that can be used in the present invention is a compound having one or more oxetane rings in the molecule. Specifically, 3-ethyl-3-hydroxymethyloxetane (trade name OXT101 manufactured by Toagosei Co., Ltd.), 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene (OXT121 etc.) ), 3-ethyl-3- (phenoxymethyl) oxetane (OXT211 etc.), di (1-ethyl-3-oxetanyl) methyl ether (OXT221 etc.), 3-ethyl-3- (2-ethylhexyloxymethyl) ) Oxetane (OXT212, etc.) can be preferably used, and in particular, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3- (phenoxymethyl) oxetane, di (1-ethyl-3-oxetanyl) methyl Ether can be preferably used. These can be used alone or in combination of two or more.

  The oxetane compound of the present invention is preferably contained in the ink curable with the active energy ray of the present invention in an amount of 5 to 95% by mass, more preferably 20 to 80% by mass.

<Oxirane compounds>
Examples of the oxirane compound include epoxy compounds such as the following aromatic epoxides, alicyclic epoxides, and aliphatic epoxides.

  A preferable aromatic epoxide is a di- or polyglycidyl ether produced by the reaction of a polyhydric phenol having at least one aromatic nucleus or an alkylene oxide adduct thereof and epichlorohydrin, such as bisphenol A or an alkylene oxide thereof. Examples thereof include di- or polyglycidyl ethers of adducts, di- or polyglycidyl ethers of hydrogenated bisphenol A or its alkylene oxide adducts, and novolak-type epoxy resins. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  As the alicyclic epoxide, cyclohexene oxide or cyclopentene obtained by epoxidizing a compound having at least one cycloalkane ring such as cyclohexene or cyclopentene ring with an appropriate oxidizing agent such as hydrogen peroxide or peracid. Oxide-containing compounds are preferred.

  Preferred aliphatic epoxides include di- or polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof, and typical examples thereof include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol or Diglycidyl ether of alkylene glycol such as diglycidyl ether of 1,6-hexanediol, polyglycidyl ether of polyhydric alcohol such as di- or triglycidyl ether of glycerin or its alkylene oxide adduct, polyethylene glycol or its alkylene oxide adduct Diglycidyl ethers of polyalkylene glycols such as diglycidyl ethers, polypropylene glycols or diglycidyl ethers of adducts thereof Tel and the like. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  Among these epoxides, in view of fast curability, aromatic epoxides and alicyclic epoxides are preferable, and alicyclic epoxides are particularly preferable.

  Examples of the most preferred alicyclic epoxide in the present invention include those described in JP-A Nos. 2004-315778 and 2005-28632.

  Specific compounds are described below.

  In the present invention, one of the epoxides may be used alone, or two or more may be used in appropriate combination.

  These oxirane compounds are preferably contained in the ink curable with the active energy ray of the present invention in an amount of 5 to 95% by mass, more preferably 20 to 80% by mass.

<Vinyl ether compound>
Vinyl ether compounds as cationically polymerizable compounds that can be used in the present invention include, for example, ethylene glycol divinyl ether, ethylene glycol monovinyl ether, diethylene glycol divinyl ether, triethylene glycol monovinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, Di- or trivinyl ether compounds such as dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexane dimethanol divinyl ether, hydroxyethyl monovinyl ether, hydroxynonyl monovinyl ether, trimethylolpropane trivinyl ether, ethyl vinyl ether, n- Butyl vinyl ether, Sobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether-o-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, octadecyl Examples thereof include monovinyl ether compounds such as vinyl ether.

<Cationic polymerization initiator>
The cationic photopolymerization ink according to the present invention preferably contains a cationic polymerization initiator as a photopolymerization initiator together with the cationic polymerizable compound.

  Specific examples of the cationic polymerization initiator include a photoacid generator and the like. For example, a chemical amplification type photoresist or a compound used for photocationic polymerization is used (edited by Organic Electronics Materials Research Group, “ Organic materials for imaging ", Bunshin Publishing (1993), see pages 187-192). Examples of compounds suitable for the present invention are listed below.

First, diazonium, ammonium, iodonium, sulfonium, aromatic onium compounds of phosphonium such as ^{_{B (C 6 F 5) 4}} -, PF 6 -, AsF 6 -, SbF 6 -, CF 3 SO 3 - and salts be able to.
Specific examples of onium compounds that can be used in the present invention are shown below.

  Secondly, sulfonated compounds that generate sulfonic acid can be mentioned, and specific compounds thereof are exemplified below.

  Thirdly, halides that generate hydrogen halide can also be used, and specific compounds thereof are exemplified below.

  Fourthly, an iron allene complex can be mentioned.

<Sensitizer>
In the photocationic polymerization ink according to the present invention, it is preferable to use a sensitizer having ultraviolet spectrum absorption at a wavelength longer than 300 nm. For example, a hydroxyl group, an optionally substituted aralkyloxy group or an alkoxy group is used as a substituent. A polycyclic aromatic compound having at least one group, a carbazole derivative, a thioxanthone derivative, and the like can be given.

  As the polycyclic aromatic compound that can be used in the present invention, naphthalene derivatives, anthracene derivatives, chrysene derivatives, and phenanthrene derivatives are preferable. As an alkoxy group which is a substituent, a C1-C18 thing is preferable and a C1-C8 thing is especially preferable. As the aralkyloxy group, those having 7 to 10 carbon atoms are preferable, and benzyloxy groups and phenethyloxy groups having 7 to 8 carbon atoms are particularly preferable.

  Examples of these sensitizers that can be used in the present invention include carbazole derivatives such as carbazole, N-ethylcarbazole, N-vinylcarbazole, N-phenylcarbazole, 1-naphthol, 2-naphthol, 1-methoxynaphthalene, 1-stearyloxynaphthalene, 2-methoxynaphthalene, 2-dodecyloxynaphthalene, 4-methoxy-1-naphthol, glycidyl-1-naphthyl ether, 2- (2-naphthoxy) ethyl vinyl ether, 1,4-dihydroxynaphthalene, 1, , 5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 2,7-dimethoxynaphthalene, 1,1′-thiobis (2-naphthol), 1,1′-bi-2-naphthol, 1,5-naphthyl diglycid Ether, 2,7-di (2-vinyloxyethyl) naphthyl ether, 4-methoxy-1-naphthol, ESN-175 (epoxy resin manufactured by Nippon Steel Chemical Co., Ltd.) or its series, condensate of naphthol derivative and formalin, etc. Naphthalene derivatives, 9,10-dimethoxyanthracene, 2-ethyl-9,10-dimethoxyanthracene, 2-tbutyl-9,10-dimethoxyanthracene, 2,3-dimethyl-9,10-dimethoxyanthracene, 9-methoxy -10-methylanthracene, 9,10-diethoxyanthracene, 2-ethyl-9,10-diethoxyanthracene, 2-tbutyl-9,10-diethoxyanthracene, 2,3-dimethyl-9,10-di Ethoxyanthracene, 9-ethoxy-10-methylanthracene, 9, 0-dipropoxyanthracene, 2-ethyl-9,10-dipropoxyanthracene, 2-tbutyl-9,10-dipropoxyanthracene, 2,3-dimethyl-9,10-dipropoxyanthracene, 9-isopropoxy- 10-methylanthracene, 9,10-dibenzyloxyanthracene, 2-ethyl-9,10-dibenzyloxyanthracene, 2-tbutyl-9,10-dibenzyloxyanthracene, 2,3-dimethyl-9,10 -Dibenzyloxyanthracene, 9-benzyloxy-10-methylanthracene, 9,10-di-α-methylbenzyloxyanthracene, 2-ethyl-9,10-di-α-methylbenzyloxyanthracene, 2-tbutyl -9,10-di-α-methylbenzyloxyanthracene, 2,3- Dimethyl-9,10-di-α-methylbenzyloxyanthracene, 9- (α-methylbenzyloxy) -10-methylanthracene, 9,10-di (2-hydroxyethoxy) anthracene, 2-ethyl-9,10 -Anthracene derivatives such as di (2-carboxyethoxy) anthracene, 1,4-dimethoxychrysene, 1,4-diethoxychrysene, 1,4-dipropoxychrysene, 1,4-dibenzyloxychrysene, 1,4- Examples include chrysene derivatives such as di-α-methylbenzyloxychrysene, phenanthrene derivatives such as 9-hydroxyphenanthrene, 9,10-dimethoxyphenanthrene, and 9,10-diethoxyphenanthrene. Among these derivatives, 9,10-dialkoxyanthracene derivatives which may have an alkyl group having 1 to 4 carbon atoms as a substituent are particularly preferable, and the methoxy group and ethoxy group are preferable as the alkoxy group.

  Examples of the thioxanthone derivative include thioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone 2-chlorothioxanthone, and the like.

<Starting aid>
The cationic photopolymerization ink according to the present invention preferably contains an initiation assistant. Initiation aid is a substance that acts as a sensitizing dye to improve the efficiency of acid generation of the initiator by donating energy to the initiator by light irradiation, electron donation, electron attraction, heat generation, etc. Applied in combination with initiator.

  Examples of the initiator include xanthene, thioxanthone dye, ketocoumarin, thioxanthene dye, cyanine, phthalocyanine, merocyanine, porphyrin, spiro compound, ferrocene, fluorene, fulgide, imidazole, perylene, phenazine, phenothiazine, polyene, azo compound, diphenylmethane , Triphenylmethane, polymethine acridine, coumarin, ketocoumarin, quinacridone, indigo, styryl, pyrylium compound, pyromethene compound, pyrazolotriazole compound, benzothiazole compound, barbituric acid derivative, thiobarbituric acid derivative and the like can be applied.

  In addition to the above-mentioned compounds, it is well known that the initiator acts as a sensitizing dye in documents such as “Development technology of polymer additives” (CMC Publishing Co., Ltd., supervised by Junichi Daikatsu). The substance may be applied. The initiation assistant can also be regarded as a component that forms part of the photopolymerization initiator.

  In addition to these, an accelerator aid may be added to accelerate the photopolymerization (curing) reaction. Examples of these include ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, ethanolamine, diethanolamine, triethanolamine and the like.

<Amine>
The cationic photopolymerization ink according to the present invention may contain an amine compound from the viewpoint of storage stability of the ink. Examples of the amine compound include octylamine, dodecylamine, octadecylamine, naphthylamine, xylenediamine, dibenzylamine, diphenylamine, dibutylamine, dioctylamine, dimethylaniline, dimethyloctadecylamine, dimethylhexadecylamine, diheptylamine, dimethyl Examples include decylamine, quinuclidine, tributylamine, trioctylamine, tetramethylethylenediamine, tetramethyl-1,6-hexamethylenediamine, hexamethylenetetramine, 2-methylaminoethanol, triisopropanolamine, and triethanolamine. Compounds having a nitrogen atom charge of −0.400 or more are triisopropanolamine, diheptylamine, octylamine Dimethyl decyl amine, dimethyl hexadecyl amine, trioctylamine, dimethyl octadecylamine, dodecylamine, there is octadecyl amine.

<Colorant>
The cationic photopolymerization ink according to the present invention may contain a color material. As the color material, a pigment or a dye can be used. From the viewpoint of the weather resistance of the image, it is preferable to use a pigment.

  Various things, such as an organic pigment and / or an inorganic pigment, can be used. Specifically, white pigments such as titanium oxide, zinc white, lead white, litbon, and antimony oxide, black pigments such as aniline black, iron black, and carbon black, yellow lead, yellow iron oxide, Hansa Yellow (100, 50, 30), yellow pigments such as titanium yellow, benzine yellow and permanent yellow, orange pigments such as chrome vermilon, permanent orange, balkan first orange and indanthrene brilliant orange, brown such as iron oxide, permanent brown and para brown Pigment, Bengala, Cadmium Red, Antimony Zhu, Permanent Red, Rhodamine Lake, Alizarin Lake, Thioindigo Red, PV Carmine, Monolite Fast Red, Quinacridone Red Pigment, etc., Cobalt Purple, Manganese Purple, Purple pigments such as violet violet, methyl violet lake, indanthrene brilliant violet, dioxazine violet, ultramarine blue, bitumen, cobalt blue, alkali blue lake, metal free phthalocyanine blue, copper phthalocyanine blue, indanthrene blue and indigo Blue pigments, chrome green, chromium oxide, emerald green, naphthol green, green gold, acid green lake, malachite green lake, phthalocyanine green, and polychlorobrom copper phthalocyanine, as well as various fluorescent pigments, metal powder pigments, Examples include extender pigments.

  The pigments that can be preferably used in the present invention are listed below.

  C. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 81, 83, 87, 93, 95, 97, 98, 109, 114, 120, 128, 129, 138, 150, 151, 154, 180, 185, C.I. I. Pigment Red 5, 7, 12, 22, 38, 48: 1, 48: 2, 48: 4, 49: 1, 53: 1, 57: 1, 63: 1, 101, 112, 122, 123, 144, 146, 168, 184, 185, 202, C.I. I. Pigment Violet 19, 23, C.I. I. Pigment Blue 1, 2, 3, 15: 1, 15: 2, 15: 3, 15: 4, 18, 22, 27, 29, 60, C.I. I. Pigment Green 7, 36, C.I. I. Pigment White 6, 18, 21, C.I. I. Pigment Black 7.

  For the dispersion of the pigment, for example, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, paint shaker, or the like can be used. Further, a dispersing agent can be added when dispersing the pigment. As the dispersant, a polymer dispersant is preferably used, and examples of the polymer dispersant include Avecia's Solsperse series and Ajinomoto Fine-Techno's PB series. Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment. The dispersion medium is used using a solvent or a polymerizable compound. However, the radiation curable ink used in the present invention is preferably solvent-free because it reacts and cures immediately after ink landing. If the solvent remains in the cured image, the solvent resistance deteriorates and the VOC of the remaining solvent arises. Therefore, it is preferable in view of dispersibility that the dispersion medium is not a solvent but a polymerizable compound, and among them, a monomer having the lowest viscosity is selected.

  The pigment is preferably dispersed so that the average particle diameter of the pigment particles is 0.08 to 0.2 μm, and the maximum particle diameter is 0.3 to 10 μm, preferably 0.3 to 3 μm. The selection of the dispersion medium, the dispersion conditions, and the filtration conditions are appropriately set. By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained.

  In the ink according to the present invention, the color material concentration is preferably 1% by mass to 30% by mass of the entire ink. For inks other than white, 1% by mass and 10% by mass are more preferable.

<Additives>
In addition to the above-mentioned components, the following materials can be added to the photocationic polymerization ink according to the present invention in an amount of up to 50% by mass in the ink as necessary.

  Polymer binder, inorganic filler, softener, antioxidant, anti-aging agent, stabilizer, tackifier resin, leveling agent, antifoaming agent, plasticizer, dye, treating agent, viscosity modifier, organic solvent, lubricity Inactive ingredients such as imparting agents and UV blockers can be blended. As the polymer binder, polyester resins, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes are preferable. Examples of inorganic fillers include, for example, zinc oxide, aluminum oxide, antimony oxide, calcium oxide, chromium oxide, tin oxide, titanium oxide, iron oxide, copper oxide, lead oxide, bismuth oxide, magnesium oxide and manganese oxide. Metal / non-metal oxides, hydroxides such as aluminum hydroxide, ferrous hydroxide and calcium hydroxide, salts such as calcium carbonate and calcium sulfate, silicon compounds such as silicon dioxide, kaolin, bentonite, clay and talc Natural pigments, natural zeolite, minerals such as Oya stone, natural mica and ammonite, synthetic inorganic materials such as artificial mica and synthetic zeolite, and various metals such as aluminum, iron and zinc. Some of these may overlap with the pigment, but these may be added to the composition as a filler, if necessary, in addition to the essential pigment. The lubricity-imparting agent is blended for the purpose of improving the lubricity of the resulting coating film. For example, a fatty acid ester wax, silicon wax, fluorine wax, polyolefin, which is an esterified product of a polyol compound and a fatty acid. Mention may be made of waxes such as waxes, animal waxes and plant waxes. Examples of the tackifying resin include rosins such as rosin acid, polymerized rosin acid and rosin acid ester, terpene resin, terpene phenol resin, aromatic hydrocarbon resin, aliphatic saturated hydrocarbon resin, and petroleum resin.

  The method for preparing the cationic photopolymerization ink according to the present invention is not particularly limited as long as the materials constituting them can be sufficiently mixed. Specific examples of the mixing method include a stirring method using a stirring force accompanying the rotation of the propeller, a roll kneading method, and a normal disperser such as a sand mill.

<Ink viscosity>
In the photocationic polymerization ink according to the present invention, the viscosity at 25 ° C. is preferably 5 to 500 mPa · s from the viewpoint of remarkably exhibiting the effects of the present invention.

  In the present invention, the method for applying the cationic photopolymerization ink to the substrate is not particularly limited, and preferably a bar coater coating, roller coating, spin coating, spray coating, blade coating, gravure coating, extrusion coating, ink jet method, or the like. In particular, the inkjet method is preferable.

  In the present invention, the method for heating the substrate surface to which the cationic photopolymerization ink is applied is not particularly limited, and the temperature of the substrate surface at the application of the cationic photopolymerization ink can be heated to 30 ° C. or higher. If it is. The temperature of the substrate surface can be measured by, for example, a thermistor.

  Examples of the heating method include a method of heating the substrate with radiant heat from a light source while irradiating light, a method of heating a stage on which the substrate is mounted with a heater, and the like, one or more of these methods It is also preferable to use in combination.

  In the present invention, the lower limit of the temperature of the substrate surface to which the photocationic polymerization ink is applied is 30 ° C. or higher, preferably 40 ° C. or higher. On the other hand, the upper limit is 0 for the thermal expansion coefficient relative to the environmental temperature of the substrate. Although it will not be limited especially if it is a range which becomes 3% or less, Preferably it is 80 degrees C or less, More preferably, it is 60 degrees C or less.

  In an example of the method for determining the heating condition of the substrate according to the printing method of the present invention, a substrate before being subjected to printing or a substrate having substantially the same structure as this is prepared, and the substrate An arbitrary heating condition for heating the surface to which the photocationic polymerization ink is applied to a temperature of 30 ° C. or higher is set, and in that state, the coefficient of thermal expansion of the substrate with respect to the environmental temperature is measured. If the measured coefficient of thermal expansion is 0.3% or less, the heating condition is determined to be acceptable, and if it exceeds 0.3%, it is determined to be impossible. The heating condition determined to be acceptable is set as the determined heating condition, that is, as the heating condition of the substrate when the photocationic polymerization ink is applied on the substrate.

  In determining the heating conditions in the present invention, it is preferable to confirm that the thermal expansion of the substrate is reversible.

  Furthermore, in the present invention, the cationic photopolymerization ink heated to be in the range of −10 ° C. or higher to + 10 ° C. or lower with respect to the heating temperature of the substrate surface to which the cationic photopolymerization ink is applied, It is preferable to apply to the substrate surface.

  Also from the viewpoint of suitably performing such ink heating, the ink application method used in the present invention is preferably an ink jet method. In the case of using the ink jet method, for example, the above-described ink heating can be suitably performed by heating at least one of the ink flow path and the nozzle in the ink jet head, preferably both, with a heater.

  In the present invention, examples of light (active energy rays) that can be used for curing the cationic photopolymerization ink include ultraviolet rays, electron beams, X-rays, radiation, high frequencies, and the like, and ultraviolet rays are most preferable economically. Examples of the ultraviolet light source include an ultraviolet laser, a mercury lamp, a xenon lamp, a sodium lamp, an alkali metal lamp, and the like, and a laser beam is particularly preferable when a light collecting property is required.

  The irradiation with the active energy ray is performed after the photocationic polymerization ink is applied to the substrate. When applying a plurality of ink droplets, irradiation may be performed every time each ink droplet is applied, or may be irradiated every two or more ink droplets or after all ink droplets are applied.

  Examples of the present invention will be described below, but the present invention is not limited to such examples.

  In addition, in the following description, the description of “part” relating to the blending amount means part by weight unless otherwise specified.

1. Ink Preparation <Ink 1 (Preparation of Photocationic Polymerization Ink (Composition 1)>

"Preparation of pigment dispersion"
A pigment dispersion containing a pigment was prepared according to the following method.
Dispersant (PB824 Ajinomoto Fine Techno Co., Ltd.) 3.5 parts and photopolymerizable compound (Oxetane; Toagosei Co., Ltd. OXT-221) 66.5 parts in a stainless beaker and heated on a 65 ° C. hot plate while heating 1 Dissolve by heating and stirring for hours. Next, after cooling the solution to room temperature, 10 parts of pigment (CI Pigment Black 7) was added thereto, sealed in a glass bottle with 200 g of zirconia beads having a diameter of 0.5 mm, and dispersed with a paint shaker for 2 hours. After that, the zirconia beads were removed to prepare a pigment dispersion.

"Adjusting ink"
The ink composition described below was added to the pigment dispersion, stirred, and filtered through a 0.8 μm membrane filter to prepare ink 1.

Pigment dispersion: 20 parts Oxetane (OXT-221 manufactured by Toagosei Co., Ltd.): 47.5 parts Oxetane (OXT-212 manufactured by Toagosei Co., Ltd.): 10 parts Epoxy compound (Exemplary EP-17): 20 parts Agent (CPI-100P manufactured by San Apro): 2.5 parts

<Preparation of Ink 2 (Photocationic Polymer Ink (Composition 2))>
Ink 2 was prepared in the same manner as ink 1 except that the ink composition was changed as follows and the surface tension was adjusted to 25 mN / m with a surfactant (KF351 manufactured by Shin-Etsu Chemical Co., Ltd.).

Pigment dispersion: 20 parts Oxetane (OXT-221 manufactured by Toagosei Co., Ltd.): 45.5 parts Oxetane (OXT-212 manufactured by Toagosei Co., Ltd.): 10 parts Epoxy compound (Exemplary EP-17): 20 parts Agent (CPI-100P manufactured by San Apro): 2.5 parts Sensitizer (DEA manufactured by Kawasaki Chemical Industries): 2 parts

<Preparation of Ink 3 (Photocationic Polymerization Ink (Composition 3))>

"Preparation of pigment dispersion"
A pigment dispersion was prepared in the same manner as in Ink 1, except that the photopolymerizable compound used in Ink 1 (oxetane; OXT-221 manufactured by Toagosei Co., Ltd.) was changed to an epoxy compound (Celoxide 3000 manufactured by Daicel Chemical Industries).

"Adjusting ink"
The ink composition described below was added to the pigment dispersion, stirred, and filtered through a 0.8 μm membrane filter to prepare ink 3.

Pigment dispersion: 20 parts Epoxy compound (Celoxide 3000 manufactured by Daicel Chemical Industries): 74 parts Triethanolamine: 0.02 parts Photoinitiator (following chemical formula 1): 5 parts Diethylthioxanthone: 1 part chemical formula 1

<Preparation of ink 4 (photo radical polymerization type ink)>

"Preparation of pigment dispersion"
Pigment dispersion similar to ink 1 except that the photopolymerizable compound (OXETAN; OXT-221 manufactured by Toagosei Co., Ltd.) used in ink 1 was replaced with a 1: 1 mixture of tetraethylene glycol diacrylate and lauryl acrylate. Was prepared.

"Adjusting ink"
The ink composition described below was added to the pigment dispersion, stirred, and filtered through a 0.8 μm membrane filter to prepare ink 4.

Pigment dispersion: 20 parts Lauryl acrylate: 22.4 parts Tetraethylene glycol diacrylate: 30 parts Caprolactam-modified dipentaerythritol hexaacrylate:
22.5 parts-Shin-Etsu Silicon KF-352 0.1 part-Photoinitiator (Ciba Specialty Chemicals Irgacure 184):
5 copies

2. Fabrication of base material (lens) <Lens without antireflection film>
A lens (lens without an antireflection film) was molded using the following resin A or resin B in accordance with the shape of the lens indicated by symbol L3 in FIG. 7 of JP2011-209352A.

Resin A: Appell, Mitsui Chemicals Resin B: Iupizeta EP, Mitsubishi Gas Chemical

<Lens with antireflection film>
From the base material side of the lens obtained by using the resin A as described above, a lens (lens with an antireflection film) provided with an antireflection coating in which a TiO ₂ film and an SiO ₂ film were sequentially laminated by a sputtering apparatus was produced.

3. Application of ink to substrate (lens) The ink was filled in a serial type ink jet recording apparatus, and the surface corresponding to the imaging element side of the lens was applied to the outer peripheral portion excluding the effective optical surface. KM512-SHX (nozzle pitch 360 npi (nozzle per inch), droplet size 4 pL) manufactured by Konica Minolta was used as the recording head, and the ink flow path and nozzle were controlled to the temperatures shown in Table 1 by a heater.

  A dot resolution for coating was 1440 dpi, and a coating film was formed by eight scans by an interleave method.

In addition, ultraviolet irradiation was performed by using a Vzero, H bulb manufactured by Integration and installing an ultraviolet lamp in parallel with the head. The integrated light quantity per scan was 30 mJ / cm ² .

  Note that the stage on which the lens was placed during ink jet application was heated using a heater, the temperature of the surface to which ink was applied was measured with a thermistor, and the application was performed while controlling the temperature as shown in Table 1. The environmental temperature at the time of application was 20 ° C., and the relative humidity was 78%.

<Evaluation method>
-Maximum film thickness change The cross section of 10 coated lenses obtained under the same conditions was observed with an optical microscope, and the difference between the maximum and minimum film thicknesses was measured.

  If the difference between the maximum value and the minimum value of the film thickness is less than 2 μm, a stray light suppressing function effective as a lens unit can be obtained, and so-called flare and ghost problems can be reduced. More preferably, it is less than 1 μm.

・ Adhesion 1
The lens with the coating film was stored for 2 months under the conditions of 85 ° C. and 90% RH, visually observed for changes such as peeling of the film, and evaluated according to the following evaluation criteria.

(Evaluation criteria)
A: Good results with no change in appearance for 2 months.
○: No change in appearance after 1 month, but change after 2 months. There is no problem in practical use.
Δ: The film was not lost after storage for 1 month, but there was a bubble-like mark that was partially peeled off, and there was a concern about practical problems.
X: The film was missing after storage for 1 month, so it was not practical.

・ Adhesion 2
At 20 ° C., a cellophane tape (“CT-12” manufactured by Nichiban Co., Ltd.) was used, and was adhered to the coating surface of the lens with a coating film with the belly of the finger and then peeled off. The peeling of the coating film was visually observed and evaluated according to the following evaluation criteria.

(Evaluation criteria)
○: Even if the cellophane tape is peeled off, the coating film is not peeled off.
X: The coating film peeled off with the peeling of the cellophane tape.

-Lens deformation About the lens before and behind application | coating, each shape was measured using the contact-type surface roughness meter, and the following evaluation criteria evaluated.

(Evaluation criteria)
◯: Deformation of height is less than 1 μm.
X: The height is deformed by 1 μm or more (there is a practical concern).

  Table 1 shows the results evaluated by the above evaluation methods.

<Evaluation>
From Table 1, it can be seen that the coating film obtained by the present invention has improved film thickness uniformity, improved adhesion, and can also prevent deformation of the substrate (lens).
Moreover, test No. which is a comparative example. 5 and test no. From the comparison of FIG. 13, it can be seen that by printing on the inorganic oxide film, the uniformity of the film thickness is greatly impaired. However, according to the present invention, the film thickness also on the inorganic oxide film. It can be seen that the uniformity of the can be improved.
Furthermore, test No. which is a comparative example of the present invention. From the comparison of 6, it can be seen that the adhesion is remarkably improved by setting the coefficient of thermal expansion to 0.3% or less in the present invention.

Claims (11)

In a printing method for applying a cationic photopolymerization ink on a three-dimensional substrate,
The temperature of the surface of the substrate to which the cationic photopolymerization ink is applied is 30 ° C. or higher, and the coefficient of thermal expansion of the substrate with respect to the environmental temperature is 0.3% or less. A printing method characterized by heating. In a printing method for applying a cationic photopolymerization ink on a substrate,
An inorganic oxide film is formed on the surface of the substrate to which the cationic photopolymerization ink is applied,
The temperature of the surface of the substrate to which the cationic photopolymerization ink is applied is 30 ° C. or higher, and the coefficient of thermal expansion of the substrate with respect to the environmental temperature is 0.3% or less. A printing method characterized by heating. 3. The printing method according to claim 1, wherein the coefficient of thermal expansion is in a range of 0.1% to 0.3%. The printing method according to claim 1 , wherein the substrate is made of plastic. The optical cationic polymerization based ink, printing method according to any one of claims 1-4, characterized in that it comprises at least one or both of the oxetane compound and an oxirane compound. The printing method according to claim 1, 3 , 4, or 5 , wherein an inorganic oxide film is formed on a surface of the base material to which the photocationic polymerization ink is applied. The printing method according to claim 2, wherein the inorganic oxide film includes at least titanium oxide.   The printing method according to claim 1, wherein the substrate is a lens.   The photo-cationic polymerization ink heated so as to be in the range of −10 ° C. or more to + 10 ° C. or less with respect to the heating temperature of the surface of the substrate to which the photo-cationic polymerization-based ink is applied, The printing method according to claim 1, wherein the printing method is applied to the surface of the base material.   The printing method according to claim 1, wherein the thermal expansion is reversible expansion. A method for determining a heating condition for determining a heating condition of the substrate when applying a cationic photopolymerization ink on the substrate,
Prepare the base material, or a base material having substantially the same configuration as this,
Set an arbitrary heating condition for heating the surface of the substrate to which the photocationic polymerization ink is applied to a temperature of 30 ° C. or higher, and measure the thermal expansion coefficient of the substrate relative to the environmental temperature in that state,
If the coefficient of thermal expansion is 0.3% or less, the heating condition is determined to be acceptable, and if it exceeds 0.3%, it is determined to be impossible.
A heating condition determination method, wherein the heating condition determined to be acceptable is applied as the determined heating condition.