JPWO2006049012A1 - Actinic ray curable inkjet ink, image forming method using the same, and inkjet recording apparatus - Google Patents

Abstract

The present invention provides an actinic ray curable inkjet ink excellent in storage stability and curability, an image forming method using the same, and an inkjet recording apparatus. This actinic ray curable ink-jet ink contains at least silica and surface-treated titanium oxide, a dispersant, an oxetane compound as a cationic polymerizable monomer, and a photoacid generator. .

Description

  The present invention relates to an actinic ray curable inkjet ink capable of stably reproducing a high-definition image, an image forming method using the same, and an inkjet recording apparatus.

  In recent years, the inkjet recording method can create images easily and inexpensively, and thus has been applied to various printing fields such as photographs, various printing, marking, and special printing such as color filters. In particular, an inkjet recording device that emits and controls fine ink droplets, as well as inkjet ink and inkjet ink with improved color reproduction range, durability, and ejection suitability, coloring material color development, surface gloss, etc. It is also possible to obtain image quality comparable to silver halide photography using specially improved paper. The improvement in image quality in today's ink jet recording system is mainly achieved only when all of the ink jet recording apparatus, ink jet ink, and special paper are available.

  However, in an inkjet system that requires dedicated paper, the recording medium is limited, and the cost of the recording medium increases. Therefore, many attempts have been made to record on a transfer medium different from dedicated paper by the ink jet method. Specifically, a phase change ink jet method using a wax ink that is solid at room temperature, a solvent ink jet method using an ink mainly composed of a fast-drying organic solvent, or actinic rays such as ultraviolet rays (UV light) after recording. For example, an ultraviolet curable ink jet method for crosslinking.

  Among these, the actinic ray curable inkjet method has a relatively low odor compared to the solvent-based inkjet method, and a method using the ultraviolet curable inkjet ink is disclosed (for example, see Patent Documents 1 and 2).

  However, even if these actinic ray curable ink-jet inks are used, the dot diameter after landing greatly changes depending on the type of recording material and the working environment, and high-definition images can be obtained for various recording materials. It is difficult to form stably.

  In recent years, many ultraviolet curable inkjet inks using cationically polymerizable compounds have been proposed. These ultraviolet curable ink-jet inks do not receive an oxygen-inhibiting action, but have a problem that they are easily affected by moisture (humidity) at the molecular level. In addition, generation of wrinkles due to curing shrinkage becomes a problem depending on the curing environment.

The image formation by the ultraviolet curable ink jet method is characterized in that a high-quality image can be obtained at a low cost, and an image can be formed on a recording material that does not absorb ink. However, there is a problem peculiar to this ultraviolet curable ink jet system. For example, when an image is formed on a recording material that does not absorb ink, image quality deterioration due to mixing of landed dots with adjacent dots is significant. In particular, when high-definition image formation is required, dot mixing between landed colors becomes a serious problem.
In response to the above problems, actinic ray curable inkjet inks using oxirane compounds, vinyl ether compounds, and oxetane compounds as photopolymerizable compounds have been disclosed (see, for example, Patent Documents 3 and 4). In addition, actinic ray curable inkjet inks using alicyclic epoxy compounds and oxetane compounds as photopolymerizable compounds have been disclosed (see, for example, Patent Documents 5 and 6). However, in each of the proposed methods, the current situation is that the dot bleeding has not been sufficiently eliminated.

  In the case of a general water-based ink jet method, an additive having various functions in special paper or ink has been used to improve the ink permeability to the recording material and solve the above problem. However, the present situation is that no solution has yet been found in image formation on a recording material having no ink absorbability. In the case of high-speed printing, the formed image is often wound, and in particular, development of an actinic ray curable inkjet ink composition having a rapid curing characteristic of the formed image is desired.

In recent years, the demand for white ink is also increasing. Proposals have been made with water-based inks (see, for example, Patent Documents 7 to 11), but highly safe cationic polymerizable ink-jet inks satisfy various requirements such as emission properties, dispersion stability, and curability. There is still no thing yet.
JP-A-6-200204 (Claims, Examples) JP 2000-504778 (Claims, Examples) JP 2001-220526 A (Claims, Examples) JP 2002-188025 A (Claims, Examples) JP 2002-317139 A (Claims, Examples) JP 2003-55449 A (Claims, Examples) JP 2003-176430 A (Claims, Examples) JP 2004-124077 A (Claims, Examples) JP-A-2004-59857 (Claims and Examples) JP 2002-348513 A (Claims, Examples) JP 2002-336295 A (Claims, Examples)

  The present invention has been made in view of the above problems, and an object thereof is to provide an actinic ray curable ink jet ink excellent in storage stability and curability, an image forming method and an ink jet recording apparatus using the same. It is in.

  The above object of the present invention has been achieved by the following constitution.

  1. An actinic ray curable ink-jet ink comprising: titanium oxide containing at least silica and having a surface treatment; a dispersant; an oxetane compound as a cationic polymerizable monomer; and a photoacid generator.

  2. 2. The actinic ray curable inkjet ink as described in 1 above, wherein the dispersant is a polymer dispersant having an amine value.

  3. 3. The actinic radiation curable inkjet ink according to 1 or 2, wherein the dispersant has a content of 35% by mass or more and 60% by mass or less with respect to the titanium oxide.

  4). 4. The actinic radiation curable inkjet ink according to any one of 1 to 3, further comprising a compound having an oxirane ring as the cationic polymerizable monomer.

  5. 5. The actinic ray curable inkjet ink according to 4 above, wherein the compound having an oxirane ring is a compound represented by the following general formula (1).

[Wherein, R ₁ represents an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, an unsubstituted or substituted aromatic group, or an acyl group. ]
6). 5. The actinic ray curable inkjet ink according to 4 above, wherein the compound having an oxirane ring is a compound represented by the following general formula (2).

[Wherein Y _{1 to} Y ₈ each represent a hydrogen atom, an unsubstituted or substituted alkyl group, a carbonyl group, or an ether group, which may be different from each other. ]
7). 5. The actinic ray curable inkjet ink as described in 4 above, wherein the compound having an oxirane ring is α-pinene oxide.

  8). 5. The actinic ray curable inkjet ink as described in 4 above, wherein the compound having an oxirane ring is 1,2: 8,9-diepoxylimonene.

  9. 5. The actinic ray curable inkjet ink as described in 4 above, wherein the compound having an oxirane ring is a vegetable oil having an epoxidized unsaturated bond.

  10. 5. The actinic ray curable inkjet ink as described in 4 above, wherein the compound having an oxirane ring is a compound represented by the following general formula (A).

Wherein, R ₁₀₀ represents a substituent, m0 represents 0-2. r0 represents 1-3. L ₀ represents a C 1-15 r 0 + 1 valent linking group or single bond that may contain an oxygen atom or a sulfur atom in the main chain. ]
11. 11. An image forming method in which the actinic radiation curable inkjet ink according to any one of 1 to 10 above is jetted onto a recording material from an inkjet recording head, and printing is performed on the recording material. An image forming method comprising irradiating an actinic ray within 0.001 to 1 second after an inkjet ink has landed on the recording medium.

  12 An image forming method in which the actinic radiation curable inkjet ink according to any one of claims 1 to 10 is jetted onto a recording material from an inkjet recording head, and printing is performed on the recording material. An image forming method, wherein the total film thickness after the ink jet ink is landed on the recording medium and cured by irradiation with actinic rays is 2 to 25 μm.

  13. 11. An image forming method in which the actinic ray curable inkjet ink according to any one of 1 to 10 is jetted onto a recording material from an inkjet recording head, and printing is performed on the recording material. An image forming method, wherein the amount of droplets of the actinic radiation curable inkjet ink ejected from each nozzle is 2 to 20 pl.

  14 14. The image forming method according to any one of 11 to 13, wherein the ink jet recording head is a line head type.

  15. 15. An ink jet recording apparatus for use in the image forming method according to any one of 11 to 14, wherein the actinic ray curable ink is heated to 35 ° C. to 100 ° C. after the actinic ray curable ink jet ink and the ink jet recording head are heated. An ink jet recording apparatus having a mechanism for ejecting ink jet ink.

  According to the present invention, it is possible to provide an actinic ray curable inkjet ink excellent in storage stability and curability, an image forming method using the same, and an inkjet recording apparatus.

It is a front view which shows an example of a structure of the principal part in the inkjet recording device of this invention. It is a top view which shows another example of a structure of the principal part in the inkjet recording device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 2 Head carriage 3 Inkjet recording head 31 Ink ejection port 4 Irradiation means 5 Platen part 6 Guide member 7 Bellows structure P Recording material

  As a result of intensive studies in view of the above problems, the present inventors have found that at least silica and surface-treated titanium oxide, a dispersant, an oxetane compound as a cationic polymerizable monomer, a photoacid generator, The actinic ray curable inkjet ink characterized by containing an actinic ray curable inkjet ink that is excellent in curability, has no color mixing, and can stably record a high-definition image (hereinafter, referred to as “actinic ray curable inkjet ink”). As soon as the present invention has been realized, it has been found that the ink can be realized.

Details of the present invention will be described below.
First, titanium oxide as a pigment will be described.

  As the titanium oxide that can be used in the present invention, known ones can be used, for example, KA-80, KA-90, KR-380, KR-480 manufactured by Titanium Industry Co., Ltd., R-550, R-780 manufactured by Ishihara Sangyo Co., Ltd. , R-850, R-855, CR-80, CR-90, CR-93, CR-85, JR-403, JR-805, JR-806, JR-701, JR-800, etc. manufactured by Teika Co., Ltd. Can be mentioned.

  There are known methods for surface treatment of titanium oxide. In the present invention, one of the features is that the surface treatment includes at least silica.

  The titanium oxide containing at least silica and surface-treated in the present invention refers to a treatment for precipitating at least silica on the surface of titanium oxide particles, and alumina or the like can be used in addition to silica. Silica or alumina also includes hydrates thereof.

  In this way, when the titanium oxide particles are subjected to a surface treatment containing silica, the surface of the titanium oxide particles is uniformly coated (treated), and at least the titanium oxide particles surface-treated with silica are used. The dispersibility of is improved.

  Further, when the titanium oxide particles are subjected to the treatment with silica and the treatment with alumina, the alumina and the silica treatment may be performed at the same time. In particular, the alumina treatment may be performed first, and then the silica treatment may be performed. Further, the amount of treatment of alumina and silica when treating alumina and silica is preferably higher than that of alumina.

  The surface treatment of the titanium oxide with a metal oxide such as alumina or silica can be performed by a wet method. For example, titanium oxide particles subjected to surface treatment of silica or alumina can be produced as follows.

  Titanium oxide particles (number average primary particle size: 50 nm) are dispersed in water at a concentration of 50 to 350 g / L to form an aqueous slurry, and a water-soluble silicate or a water-soluble aluminum compound is added thereto. Thereafter, alkali or acid is added for neutralization, and silica or alumina is precipitated on the surface of the titanium oxide particles. Subsequently, filtration, washing, and drying are performed to obtain the target surface-treated titanium oxide. When sodium silicate is used as the water-soluble silicate, it can be neutralized with an acid such as sulfuric acid, nitric acid or hydrochloric acid. On the other hand, when aluminum sulfate is used as the water-soluble aluminum compound, it can be neutralized with an alkali such as sodium hydroxide or potassium hydroxide.

  For the dispersion of titanium oxide, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker or the like can be used.

  The dispersion of titanium oxide is preferably such that the average particle size of the titanium oxide particles is 0.05 to 0.5 μm, and the maximum particle size is 0.5 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. The titanium oxide concentration is preferably 1% by mass to 35% by mass of the total ink.

  In the present invention, it is preferable to use a polymer dispersant as the dispersant, and it is more preferable to use a polymer dispersant having an amine value. For example, Enomoto Kasei DA-325, DA-234, DA-703-50, DA-725, DA-705, A-7300, Ajinomoto Fine-Techno PB822, PB821, PB711, Fuka Additives EFKA- 4046, EFKA-4330, EFKA-4300, EFKA-7411, EFKA-7462, EFKA-7476, EFKA-7696, EFKA-5244, EFKA-6220, EFKA-6225, EFKA-7544, Disperbyp-16, manufactured by BYK Chemie -163, Disperbyk-164, Disperbyk-166, Disperbyk-171, Disperbyk-180, Disperbyk-109, Disperbyk-116, Disperb k-2000, Disperbyk-2001, Disperbyk-2050, Disperbyk-2150, Kawano Fine Chemical Co., Ltd. Hinoact T-6000, Hinoact T-8000, Avisia Corp. Solspurs 24000GR, Solspurs 32000, Solspurs 26000, Solspurs 139 Solspurs 33500, Solspers 38500, etc. are mentioned.

  The amine value of the polymer dispersant in the present invention can be determined by potentiometric titration. Examples thereof include the method described in Color Material Association Journal 61, [12] 692-698 (1988). As a usage-amount of a dispersing agent, it is preferable that it is 5-80 mass% with respect to the titanium oxide which is a pigment, and it is more preferable that it is 35-60 mass%.

  In general, a cationic polymerizable monomer is a nonpolar solvent, but has a group involved in polymerization by actinic rays. Therefore, both nonpolar interaction and polar interaction work, so that dispersion stability can be maintained. difficult. Although it is conceivable to increase the amount of the dispersant, the titanium oxide and the dispersant are adsorbed by polar interaction such as acid-base, and the increase in the amount of the dispersant is a reaction for curing the polar group caused by such a dispersant. It will increase in the system, and it is thought that the photogenerated acid is trapped and the curability is deteriorated.

  By using a polymer dispersant having an amine value and a surface-treated titanium oxide containing silica in such a system, the basic group that is the basis of the amine value of the polymer dispersant and the silica used for the surface treatment It is presumed that the acidic group exerts an effect of efficiently adsorbing, and as a result, good dispersion stability can be realized without impairing curability.

  One of the characteristics of the actinic ray curable inkjet ink of the present invention is that it contains an oxetane compound as a cationic polymerizable monomer.

  As the compound having an oxetane ring according to the present invention, for example, any known oxetane compound as described in JP-A Nos. 2001-220526 and 2001-310937 can be used. Further, the combined use of a monofunctional oxetane compound containing one oxetane ring and a polyfunctional oxetane compound containing two or more oxetane rings improves the film strength after curing and the adhesion to the recording material. preferable. However, when a compound having 5 or more oxetane rings is used, the viscosity of the ink composition is increased, which makes it difficult to handle and increases the glass transition temperature of the cured product. Will not be enough.

  The compound having an oxetane ring according to the present invention is preferably a compound having 1 to 4 oxetane rings.

  The ink of the present invention preferably further contains a compound having an oxirane ring as a cationic polymerizable monomer.

  Examples of the compound having an oxirane ring include the compound represented by the general formula (1), the compound represented by the general formula (2), α-pinene oxide, 1,2: 8,9 diepoxy limonene, and epoxidation. The vegetable oil having an unsaturated bond and a compound represented by the general formula (A) are preferable.

In the general formula (1), R ₁ is an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms (for example, an optionally substituted methyl group, ethyl group, propyl group, butyl group, isopropyl group, t-butyl group, hexyl group, 2-ethylhexyl group, benzyl group, etc.), unsubstituted or substituted aromatic group (for example, phenyl group, naphthyl group, etc.), unsubstituted or substituted acyl group (for example, , A benzoyl group, a methacryl group, a stearyl group, etc.), among which an alkyl group is preferable.

  Specific examples of the compound represented by the general formula (1) are shown below, but the present invention is not limited thereto.

  Next, the compound having an oxirane ring represented by the general formula (2) will be described.

In the general formula (2), Y _{1 to} Y ₈ may be different from each other, a hydrogen atom, an unsubstituted or substituted alkyl group (for example, a methyl group, an ethyl group, a propyl group, a butyl group, an isopropyl group, t-butyl group, hexyl group, 2-ethylhexyl group, benzyl group, etc.), unsubstituted or substituted carbonyl group (eg, acetyl group, benzoyl group, etc.), or ether group (eg, alkyl ether group, aryl ether) Group).

  Preferable examples of the compound having an oxirane ring represented by the general formula (2) include compounds represented by the following general formulas (III) and (IV).

In the above general formula (III), R ₂₀₀ represents an aliphatic group other than the α and β positions of the oxirane ring, and m3 represents 0 to 2. X ₁ represents — (CH ₂ ) _n0 —, or — (O) _n0 —, and n0 represents 0 or 1. p1 and q1 each represents 0 or 1, and are not 0 at the same time. r3 represents 1-3. L ₃ represents a linking group or a single bond having an r3 + 1 valent branched structure having 1 to 15 carbon atoms, which may contain an oxygen atom or a sulfur atom in the main chain.

In the above general formula (IV), R ₂₀₁ represents an aliphatic group other than the α and β positions of the oxirane ring, and m4 represents 0 to 2. X ₂ represents — (CH ₂ ) _n1 —, or — (O) _n1 —, and n1 represents 0 or 1. p2 and q2 each represent 0 or 1, and are not 0 at the same time. r4 represents 1-3. L ₄ represents a linking group or a single bond having an r4 + 1 valent branched structure having 1 to 15 carbon atoms, which may contain an oxygen atom or a sulfur atom in the main chain.

  Details of the compounds having an oxirane ring represented by the general formulas (III) and (IV) will be described below.

In the general formula (III), R ₂₀₀ represents an aliphatic group other than the α and β positions of the oxirane ring, and the aliphatic group is an alkyl group having 1 to 6 carbon atoms (for example, methyl group, ethyl group, propyl group). Group, isopropyl group, butyl group, etc.), cycloalkyl group having 3 to 6 carbon atoms (for example, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, etc.), alkenyl group having 1 to 6 carbon atoms (for example, Vinyl group, 1-propenyl group, 2-propenyl group, 2-butenyl group, etc.), alkynyl group having 1 to 6 carbon atoms (for example, acetylenyl group, 1-propynyl group, 2-propynyl group, 2-butynyl group, etc.) ). Preferably, it is a C1-C3 alkyl group, and a methyl group and an ethyl group are more preferable.

m3 represents 0 to 2 and is preferably 1 or 2. X ₁ represents — (CH ₂ ) _n0 — or — (O) _n0 —. n0 represents 0 or 1, and when n0 is 0, it represents that X ₁ does not exist, and m3 + n0 is preferably 1 or more. L ₃ represents a linking group or a single bond having an r 3 + 1 valent branched structure having 1 to 15 carbon atoms, which may contain an oxygen atom or a sulfur atom in the main chain. p1 and q1 each represents 0 or 1 and are not 0 at the same time. r3 represents 1-3.

  Next, the compound having an oxirane ring represented by the general formula (IV) will be described.

In the general formula (IV), R ₂₀₁ represents an aliphatic group other than the α and β positions of the oxirane ring, and the aliphatic group includes an alkyl group having 1 to 6 carbon atoms (for example, a methyl group, an ethyl group, Propyl group, isopropyl group, butyl group, etc.), cycloalkyl group having 3 to 6 carbon atoms (for example, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, etc.), alkenyl group having 1 to 6 carbon atoms (for example, , Vinyl group, 1-propenyl group, 2-propenyl group, 2-butenyl group, etc.), alkynyl group having 1 to 6 carbon atoms (for example, acetylenyl group, 1-propynyl group, 2-propynyl group, 2- Butynyl group). Preferably, it is a C1-C3 alkyl group, and a methyl group and an ethyl group are more preferable.

m4 represents 0 to 2 and is preferably 1 or 2. X ₂ represents — (CH ₂ ) _n1 — or — (O) _n1 —. n1 represents 0 or 1, and when n1 is 0, it represents that X ₂ does not exist. m4 + n1 is preferably 1 or more. p2 and q2 each represent 0 or 1, and are not 0 at the same time. r4 represents 1-3.

L ₄ represents a linking group or a single bond having an r4 + 1 valent branched structure having 1 to 15 carbon atoms, which may contain an oxygen atom or a sulfur atom in the main chain.

  Examples of the divalent linking group having 1 to 15 carbon atoms which may contain an oxygen atom or a sulfur atom in the main chain in the general formula (III) or (IV) include the following groups and these groups and —O—: A group formed by combining a plurality of groups, -S- groups, -CO- groups, and -CS- groups can be given.

Ethylidene group:> CHCH ₃ ,
Isopropylidene group:> C (CH ₃ ) ₂ ,
2,2-dimethyl-1,3-propanediyl group: —CH ₂ C (CH ₃ ) ₂ CH ₂ —,
2,2-dimethoxy-1,3-propanediyl group: —CH ₂ C (OCH ₃ ) ₂ CH ₂ —,
2,2-dimethoxymethyl-1,3-propanediyl group: —CH ₂ C (CH ₂ OCH ₃ ) ₂ CH ₂ —,
1-methyl-1,3-propanediyl group: —CH (CH ₃ ) CH ₂ CH ₂ —,
1,4-dimethyl-3-oxa-1,5-pentanediyl group: —CH (CH ₃ ) CH ₂ OCH (CH ₃ ) CH ₂ —,
1,4,7-trimethyl-3,6-dioxa-1,8-octanediyl group: —CH (CH ₃ ) CH ₂ OCH (CH ₃ ) CH ₂ OCH (CH ₃ ) CH ₂ —,
5,5-dimethyl-3,7-dioxa-1,9-nonanediyl group: —CH ₂ CH ₂ OCH ₂ C (CH ₃ ) ₂ CH ₂ OCH ₂ CH ₂ —,
5,5-dimethoxy-3,7-dioxa-1,9-nonanediyl group: —CH ₂ CH ₂ OCH ₂ C (OCH ₃ ) —,
5,5-dimethoxymethyl-3,7-dioxa-1,9-nonanediyl group: —CH ₂ CH ₂ OCH ₂ C (CH ₂ OCH ₃ ) ₂ CH ₂ OCH ₂ CH ₂ —,
Isopropylidenebis -p- phenylene _{group: -p-C 6 H 4 -C} (CH 3) 2 -p-C 6 H 4 -.

  Examples of the trivalent or higher linking group include a group formed by removing a hydrogen atom at any site from the divalent linking group listed above as much as necessary, and an —O— group, —S— group, and —CO— group. , A group formed by combining a plurality of —CS— groups.

L ₃ and L ₄ may each have a substituent. Examples of the substituent include a halogen atom (for example, chlorine atom, bromine atom, fluorine atom, etc.), an alkyl group having 1 to 6 carbon atoms (for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, etc.) ), An alkoxy group having 1 to 6 carbon atoms (for example, methoxy group, ethoxy group, n-propoxy group, iso-propoxy group, n-butoxy group, tert-butoxy group, etc.), acyl group (for example, acetyl group, Propionyl group, trifluoroacetyl group, etc.), acyloxy group (eg, acetoxy group, propionyloxy group, trifluoroacetoxy group, etc.), alkoxycarbonyl group (eg, methoxycarbonyl group, ethoxycarbonyl group, tert-butoxycarbonyl group, etc.) Etc. As the substituent, a halogen atom, an alkyl group, and an alkoxy group are preferable.

  Specific examples of the compound having an epoxy group represented by the general formula (2) are shown below, but the present invention is not limited thereto.

  Examples of vegetable oils having an epoxidized unsaturated bond that can be used in the present invention include epoxidized vegetable oils having unsaturated bonds such as olive oil, safflower oil, sunflower oil, soybean oil, and linseed oil. Can be used. Moreover, commercially available epoxidized vegetable oil can also be used, for example, Nippon Sanka Co., Ltd. Sansosizer E-4030, ATOFINA Chemical Vf7010, Vf9010, Vf9040 etc. are mentioned.

  Next, the compound having an oxirane ring represented by the general formula (A) will be described.

In the general formula (A), R ₁₀₀ represents a substituent, and examples of the substituent include a halogen atom (for example, a chlorine atom, a bromine atom, a fluorine atom, etc.), an alkyl group having 1 to 6 carbon atoms (for example, , Methyl group, ethyl group, propyl group, isopropyl group, butyl group, etc.), alkoxy group having 1 to 6 carbon atoms (for example, methoxy group, ethoxy group, n-propoxy group, iso-propoxy group, n-butoxy group) , Tert-butoxy group etc.), acyl group (eg acetyl group, propionyl group, trifluoroacetyl group etc.), acyloxy group (eg acetoxy group, propionyloxy group, trifluoroacetoxy group etc.), alkoxycarbonyl group (eg Methoxycarbonyl group, ethoxycarbonyl group, tert-butoxycarbonyl group and the like). Preferred as a substituent is an alkyl group, an alkoxy group or an alkoxycarbonyl group. m0 represents 0 to 2, and 0 or 1 is preferable. r0 represents 1-3. L ₀ represents a C 1-15 r 0 + 1 valent linking group or single bond that may contain an oxygen atom or a sulfur atom in the main chain.

  Further, the compound having an oxirane ring represented by the general formula (A) is preferably an alicyclic epoxide compound represented by the following general formula (I) or (II).

In the general formula (I), R ₁₀₁ represents a substituent, m1 represents 0-2. r1 represents 1-3. L ₁ represents a C 1-15 r 1 + 1 valent linking group or single bond that may contain an oxygen atom or a sulfur atom in the main chain.

In the general formula (II), R ₁₀₂ represents a substituent, m2 represents 0-2. r2 represents 1-3. L ₂ represents a C 1-15 r 2 + 1 valent linking group or single bond which may contain an oxygen atom or a sulfur atom in the main chain.

In the compound represented by the general formula (I) or (II), R ₁₀₁ and R ₁₀₂ each represent a substituent, and examples of the substituent include a halogen atom (for example, a chlorine atom, a bromine atom, fluorine Atoms), an alkyl group having 1 to 6 carbon atoms (for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, etc.), an alkoxy group having 1 to 6 carbon atoms (for example, methoxy group, ethoxy group) , N-propoxy group, iso-propoxy group, n-butoxy group, tert-butoxy group etc.), acyl group (eg acetyl group, propionyl group, trifluoroacetyl group etc.), acyloxy group (eg acetoxy group, propionyl group) Oxy group, trifluoroacetoxy group, etc.), alkoxycarbonyl group (for example, methoxycarbonyl group, ethoxycarbonyl group, tert-butyl group) Alkoxycarbonyl group, etc.), and the like. Preferred as a substituent is an alkyl group, an alkoxy group or an alkoxycarbonyl group.

  m1 and m2 each represent 0 to 2, and 0 or 1 is preferable.

L ₁ represents an r1 + 1-valent linking group or a single bond having 1 to 15 carbon atoms which may contain an oxygen atom or a sulfur atom in the main chain, and L ₂ represents 1 to carbon atoms which may contain an oxygen atom or a sulfur atom in the main chain. 15 represents an r2 + 1-valent linking group or a single bond.

2 to 15 having 1 to 15 carbon atoms which may contain an oxygen atom or a sulfur atom in the main chain represented by L ₁ , L ₂ and L ₃ in the general formula (A), general formula (I) and general formula (II) Examples of the valent linking group include the following groups and groups formed by combining these groups with a plurality of —O— groups, —S— groups, —CO— groups, and —CS— groups.

Methylene group: —CH ₂ —,
Ethylidene group:> CHCH ₃ ,
Isopropylidene group:> C (CH ₃ ) ₂ ,
1,2-ethylene group: —CH ₂ CH ₂ —,
1,2-propylene group: —CH (CH ₃ ) CH ₂ —,
1,3-propanediyl group: —CH ₂ CH ₂ CH ₂ —,
2,2-dimethyl-1,3-propanediyl group: —CH ₂ C (CH ₃ ) ₂ CH ₂ —,
2,2-dimethoxy-1,3-propanediyl group: —CH ₂ C (OCH ₃ ) ₂ CH ₂ —,
2,2-dimethoxymethyl-1,3-propanediyl group: —CH ₂ C (CH ₂ OCH ₃ ) ₂ CH ₂ —,
1-methyl-1,3-propanediyl group: —CH (CH ₃ ) CH ₂ CH ₂ —,
1,4-butanediyl group: —CH ₂ CH ₂ CH ₂ CH ₂ —,
1,5-pentanediyl group: —CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ —,
Oxydiethylene group: —CH ₂ CH ₂ OCH ₂ CH ₂ —,
Thiodiethylene group: —CH ₂ CH ₂ SCH ₂ CH ₂ —,
3-oxothiodiethylene group: —CH ₂ CH ₂ SOCH ₂ CH ₂ —,
3,3-dioxothiodiethylene group: —CH ₂ CH ₂ SO ₂ CH ₂ CH ₂ —,
1,4-dimethyl-3-oxa-1,5-pentanediyl group: —CH (CH ₃ ) CH ₂ O—CH (CH ₃ ) CH ₂ —,
3-oxopentanediyl group: —CH ₂ CH ₂ COCH ₂ CH ₂ —,
1,5-dioxo-3-oxapentanediyl group: —COCH ₂ OCH ₂ CO—,
4-oxa-1,7-heptanediyl group: —CH ₂ CH ₂ CH ₂ OCH ₂ CH ₂ CH ₂ —,
3,6-dioxa-1,8-octanediyl group: —CH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂ —,
1,4,7-trimethyl-3,6-dioxa-1,8-octanediyl group: —CH (CH ₃ ) CH ₂ O—CH (CH ₃ ) CH ₂ OCH (CH ₃ ) CH ₂ —,
5,5-dimethyl-3,7-dioxa-1,9-nonanediyl group: —CH ₂ CH ₂ OCH ₂ C (CH ₃ ) ₂ CH ₂ OCH ₂ CH ₂ —,
5,5-dimethoxy-3,7-dioxa-1,9-nonanediyl group: —CH ₂ CH ₂ OCH ₂ C (OCH ₃ ) ₂ CH ₂ OCH ₂ CH ₂ —,
5,5-dimethoxymethyl-3,7-dioxa-1,9-nonanediyl group: —CH ₂ CH ₂ OCH ₂ C (CH ₂ OCH ₃ ) ₂ CH ₂ OCH ₂ CH ₂ —,
4,7-dioxo-3,8-dioxa-1,10-decandiyl group: —CH ₂ CH ₂ O—COCH ₂ CH ₂ CO—OCH ₂ CH ₂ —,
3,8-dioxo-4,7-dioxa-1,10-decandiyl group: —CH ₂ CH ₂ CO—OCH ₂ CH ₂ O—COCH ₂ CH ₂ —,
1,3-cyclopentane-diyl _{group: -1,3-C 5 H 8 -} ,
1,2-cyclohexanediyl group: -1,2-C ₆ H _10- ,
1,3-cyclohexane diyl _{group: -1,3-C 6 H 10 -} ,
1,4-cyclohexanediyl group: -1,4-C ₆ H _10- ,
2,5-tetrahydrofurandiyl group: 2,5-C ₄ H ₆ O—
p- _{phenylene: -p-C 6 H 4 -} ,
m- phenylene _{group: -m-C 6 H 4 -} ,
α, α′-o-xylylene group: —o—CH ₂ —C ₆ H ₄ —CH ₂ —,
α, α′-m-xylylene group: —m—CH ₂ —C ₆ H ₄ —CH ₂ —,
α, α′-p-xylylene group: —p—CH ₂ —C ₆ H ₄ —CH ₂ —,
Furan-2,5-diyl-bismethylene group: 2,5-CH ₂ —C ₄ H ₂ O—CH ₂ —,
Thiophene-2,5-diyl-bismethylene group: 2,5-CH ₂ —C ₄ H ₂ S—CH ₂ —,
Isopropylidenebis -p- phenylene _{group: -p-C 6 H 4 -C} (CH 3) 2 -p-C 6 H 4 -.

  Examples of the trivalent or higher linking group include a group formed by removing a hydrogen atom at any site from the divalent linking group listed above as much as necessary, and an —O— group, —S— group, and —CO— group. , A group formed by combining a plurality of —CS— groups.

L ₀ , L ₁ and L ₂ may each have a substituent. Examples of the substituent include a halogen atom (for example, chlorine atom, bromine atom, fluorine atom, etc.), an alkyl group having 1 to 6 carbon atoms (for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, etc.) , An alkoxy group having 1 to 6 carbon atoms (for example, methoxy group, ethoxy group, n-propoxy group, iso-propoxy group, n-butoxy group, tert-butoxy group, etc.), acyl group (for example, acetyl group, propionyl) Group, trifluoroacetyl group, etc.), acyloxy group (eg, acetoxy group, propionyloxy group, trifluoroacetoxy group, etc.), alkoxycarbonyl group (eg, methoxycarbonyl group, ethoxycarbonyl group, tert-butoxycarbonyl group, etc.), Etc. As the substituent, an alkyl group, an alkoxy group, and an alkoxycarbonyl group are preferable.

L ₀ , L ₁ and L ₂ are preferably divalent linking groups having 1 to 8 carbon atoms which may contain an oxygen atom or a sulfur atom in the main chain, and the main chain having 2 to 1 carbon atoms having only carbon. A valent linking group is more preferred.

  Although the specific example of the alicyclic epoxide compound represented with preferable general formula (A) below is shown, this invention is not limited to these.

  The addition amount of the compound having an oxirane ring is preferably 10 to 80% by mass. If it is less than 10% by mass, the curability is remarkably changed depending on the curing environment (temperature, humidity) and cannot be used. If it exceeds 80% by mass, the film properties after curing are weak and cannot be used. In the present invention, one type of compound having an oxirane ring may be used alone, or two or more types may be used in appropriate combination.

  The compound having these oxirane rings may be produced by any method, for example, see Maruzen KK Publishing, 4th Edition Experimental Chemistry Course 20 Organic Synthesis II, 213, 1992, Ed. by Alfred Hasfner, The Chemistry of Heterocyclic compounds, Vol. 30, Advertisement, Small Ring Heterocycles part3, Oxilanes, John & Wiley and Sons, An Inc. No. 5, 42, 1986, Yoshimura, Adhesion, Vol. 30, No. 7, 42, 1986, Japanese Patent Application Laid-Open No. 11-100308, Japanese Patent No. 2906245, Japanese Patent No. 2926262, and the like.

  The actinic ray curable inkjet ink of the present invention is characterized by containing a photoacid generator, but any known photoacid generator can be used.

  As the photoacid generator, for example, a chemically amplified photoresist or a compound used for photocationic polymerization is used (edited by Organic Electronics Materials Research Group, “Organic Materials for Imaging”, Bunshin Publishing (1993), 187. To page 192). Examples of compounds suitable for the present invention are listed below.

First, B (C ₆ F ₅ ) ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ SO ₃ ⁻ salt of aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium, phosphonium, etc. be able to.

  Specific examples of onium compounds that can be used in the present invention are shown below.

  Secondly, sulfonated substances 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.

Furthermore, in the actinic ray curable inkjet ink of the present invention, sulfonium salt compounds represented by the following general formulas [1] to [4] that do not generate benzene by actinic ray irradiation are preferable, and the benzene ring bonded to S ⁺ is bonded to the benzene ring. If it has a substituent, the above conditions are satisfied.

In the above general formulas [1] to [4], R _{31 to} R ₄₇ each represent a hydrogen atom or a substituent, R _{31 to} R ₃₃ do not simultaneously represent a hydrogen atom, and R _{34 to} R ₃₇ simultaneously represent It does not represent a hydrogen atom, R _{38 to} R ₄₁ do not represent a hydrogen atom at the same time, and R _{42 to} R ₄₇ do not represent a hydrogen atom at the same time.

The substituent represented by R _{31 to} R ₄₇ is preferably an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, or a hexyl group, Alkoxy groups such as methoxy group, ethoxy group, propyl group, butoxy group, hexyloxy group, decyloxy group, dodecyloxy group, acetoxy group, propionyloxy group, decylcarbonyloxy group, dodecylcarbonyloxy group, methoxycarbonyl group, ethoxycarbonyl Group, carbonyl group such as benzoyloxy group, phenylthio group, halogen atom such as fluorine, chlorine, bromine and iodine, cyano group, nitro group and hydroxy group.

X ₃₁ represents a non-nucleophilic anion residue, and examples thereof include halogen atoms such as F, Cl, Br, and I, B (C ₆ F ₅ ) ₄ , R ₁₈ COO, R ₁₉ SO ₃ , SbF ₆ , AsF ₆ , PF ₆ , BF _{4 and the} like can be mentioned. However, R ₁₈ and R ₁₉ are each an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, a halogen atom such as fluorine, chlorine, bromine or iodine, a nitro group, a cyano group, a methoxy group or an ethoxy group. Represents an alkyl group or a phenyl group which may be substituted with an alkoxy group. Among these, B (C ₆ F ₅ ) ₄ and PF ₆ are preferable from the viewpoint of safety.

  The above compounds can be obtained from THE CHEMICAL SOCIETY OF JAPAN Voi. 71 no. 11, 1998, as well as the photoacid generator described in “Organic Materials for Imaging”, edited by Organic Electronics Materials Research Group, Bunshin Publishing (1993), can be easily synthesized by a known method.

In the present invention, it is particularly preferable that the sulfonium salt represented by the general formulas [1] to [4] is at least one sulfonium salt selected from the following general formulas [5] to [13]. X ₃₁ represents a non-nucleophilic anion residue and is the same as described above.

  In addition, in the actinic ray curable ink jet ink of the present invention, any known basic compound can be used for the purpose of improving storage stability. Typical examples include basic alkali metal compounds and basic compounds. Examples include alkaline earth metal compounds and basic organic compounds such as amines.

  Examples of basic alkali metal compounds include alkali metal hydroxides (eg, lithium hydroxide, sodium hydroxide, potassium hydroxide, etc.), alkali metal carbonates (eg, lithium carbonate, sodium carbonate, potassium carbonate, etc.), Examples include alkali metal alcoholates (for example, sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide, etc.).

  Basic alkaline earth metals include alkaline earth metal hydroxides (eg, magnesium hydroxide, calcium hydroxide, etc.), alkali metal carbonates (eg, magnesium carbonate, calcium carbonate, etc.), alkali metal alcoholates. (For example, magnesium methoxide).

  Examples of basic organic compounds include amines and nitrogen-containing heterocyclic compounds such as quinoline and quinolidine, among these, amines are preferred from the viewpoint of compatibility with photopolymerizable monomers, such as octylamine, naphthylamine, Xylenediamine, dibenzylamine, diphenylamine, dibutylamine, dioctylamine, dimethylaniline, quinuclidine, tributylamine, trioctylamine, tetramethylethylenediamine, tetramethyl-1,6-hexamethylenediamine, hexamethylenetetramine, triethanolamine, etc. Is mentioned.

  The concentration when the basic compound is present is preferably in the range of 10 to 1000 ppm by mass, particularly 20 to 500 ppm by mass, based on the total amount of the cationic polymerizable monomer. In addition, a basic compound may be used individually or may be used together.

  Furthermore, water can be added to suppress curing in an ink state such as in an ink tank, piping, or head. The amount of water added is preferably 0.1% by weight or more and less than 8% by weight of the entire composition.

  It is also possible to combine a radically polymerizable monomer and an initiator into a radical / cation hybrid type curable ink.

  In the ink of the present invention, it is preferable that the viscosity at 25 ° C. is 7 to 50 mPa · s in order to stably discharge from the inkjet head regardless of the curing environment (temperature / humidity) and to obtain good curability. .

  Various additives other than those described above can be used in the actinic ray curable inkjet ink of the present invention. For example, surfactants, leveling additives, matting agents, tamenopolyester resins that adjust film properties, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes can be added.

  As the recording material that can be used in the image forming method of the present invention, various non-absorbable plastics and films used for so-called soft packaging can be used in addition to ordinary uncoated paper, coated paper, etc. Examples of the plastic film include polyethylene terephthalate (PET) film, stretched polystyrene (OPS) film, stretched polypropylene (OPP) film, stretched nylon (ONy) film, polyvinyl chloride (PVC) film, polyethylene (PE) film, An acetyl cellulose (TAC) film can be mentioned. As other plastics, polycarbonate, acrylic resin, ABS, polyacetal, PVA, rubbers and the like can be used. Moreover, it is applicable also to metals and glass.

  The surface energy of these various plastic films differs greatly, and it has been a problem in the past that the dot diameter after ink landing varies depending on the recording material. With the configuration of the present invention, a good high-definition image can be formed on a wide range of recording materials having a surface energy of 35 to 60 mN / m, including OPP films having a low surface energy, OPS films, and PET having a relatively large surface energy.

  In the present invention, recording material costs such as packaging costs and production costs, and print production efficiency. It is more advantageous to use a long (web) recording material in that it can be used for printing of various sizes.

  When the actinic ray curable inkjet ink of the present invention is used to form a white inkjet ink, in addition to the white actinic ray curable inkjet ink of the present invention, it can also be used as a set with an ink having a pigment of another color. It is preferably used in an ink set having at least a yellow ink-jet ink, a magenta ink-jet ink, and a black ink-jet ink, that is, an ink set in which a plurality of inks generally used for so-called color ink-jet printing are set.

  After forming an image using the white inkjet ink of the present invention, an image may be formed using an ink having a pigment of another color. After forming an image using another color ink, the image is formed using a white inkjet ink. Alternatively, the print and head arrangements may be arranged so that an image is formed simultaneously with the inks of other colors.

  Furthermore, in order to form a photographic image by inkjet, so-called dark and light inks having different color material contents can be prepared and used.

  Next, the image forming method of the present invention will be described.

  In the image forming method of the present invention, the actinic ray curable inkjet ink of the present invention is ejected and drawn on a recording material by an inkjet recording method, and then the ink is cured by irradiation with an actinic ray such as ultraviolet rays.

(Ink film thickness after ink landing)
In the present invention, the total ink film thickness after the ink has landed on the recording material and cured by irradiation with actinic rays is 2 to 25 μm. In the actinic ray curable ink jet recording in the screen printing field, the total ink film thickness currently exceeds 25 μm, but in the flexible packaging printing field where the recording material is often a thin plastic material, the recording material described above is used. In addition to the problem of curling and wrinkles, there is a problem that the entire printed matter is changed in its texture and texture.

  Here, “total ink film thickness” means the maximum value of the film thickness of the ink drawn on the recording material, and even for a single color, other two colors are superimposed (secondary color), three colors are superimposed, four colors are used. Even when recording is performed by the overlapping (white ink base) ink jet recording method, the meaning of the total ink film thickness is the same.

(Ink ejection conditions)
As the ink ejection conditions, it is preferable from the viewpoint of ejection stability that the recording head and ink are heated to 35 to 100 ° C. and ejected. Actinic radiation curable ink has a large viscosity fluctuation range due to temperature fluctuations, and the viscosity fluctuations directly affect the droplet size and droplet ejection speed, causing image quality degradation. It is necessary to keep. The control range of the ink temperature is set temperature ± 5 ° C., preferably set temperature ± 2 ° C., more preferably set temperature ± 1 ° C.

  In the present invention, the appropriate amount of liquid discharged from each nozzle is 2 to 20 pl. Originally, in order to form a high-definition image, it is necessary for the amount of droplets to be within this range, but when discharging with this amount of droplets, the above-described discharge stability becomes particularly severe. According to the present invention, even when ejection is performed with a small droplet amount such as 2 to 20 pl, the ejection stability is improved and a high-definition image can be stably formed.

(Light irradiation conditions after ink landing)
In the image forming method of the present invention, actinic rays are irradiated between 0.001 second and 1 second after landing of the ink as irradiation conditions of the active light, and more preferably 0.001 seconds to 0.5 seconds. is there. In order to form a high-definition image, it is particularly important that the irradiation timing is as early as possible.

  As a method for irradiating actinic rays, the basic method is disclosed in JP-A-60-132767. According to this, the light source is provided on both sides of the head unit, and the head and the light source are scanned by the shuttle method. Irradiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. In US Pat. No. 6,145,979, as an irradiation method, a method using an optical fiber or a method of applying a collimated light source to a mirror surface provided on the side surface of the head unit and irradiating the recording unit with UV light is disclosed. . Any of these irradiation methods can be used in the image forming method of the present invention.

  In addition, there is a method of irradiating actinic rays in two stages, first irradiating actinic rays by the above-described method within 0.001 to 2 seconds after ink landing, and further irradiating actinic rays after completion of all printing. This is one of the preferred embodiments. By dividing the irradiation of actinic rays into two stages, it is possible to further suppress the shrinkage of the recording material that occurs during ink curing.

  Conventionally, in the UV ink jet system, a light source with high illuminance in which the total power consumption of the light source exceeds 1 kW · hr is usually used in order to suppress dot spreading and bleeding after ink landing. However, when these light sources are used, particularly in printing on shrink labels and the like, the shrinkage of the recording material is so large that it cannot be practically used.

  In the present invention, it is preferable to use an actinic ray having a maximum illuminance in a wavelength region of 254 nm. Even when a light source having a total power consumption of 1 kW · hr or more is used, a high-definition image can be formed and the recording material can be contracted. Practically acceptable level.

  In the present invention, it is preferable that the total power consumption of the light source for irradiating actinic rays is less than 1 kW · hr. Examples of the light source having a total power consumption of less than 1 kW · hr include, but are not limited to, a fluorescent tube, a cold-labeled electrode tube, a hot cathode tube, and an LED.

  The ink jet recording apparatus of the present invention will be described below with reference to the drawings as appropriate. Note that the ink jet recording apparatus of the drawings is only one aspect of the ink jet recording apparatus of the present invention, and the ink jet recording apparatus of the present invention is not limited to this drawing.

  FIG. 1 is a front view showing a configuration of a main part of the ink jet recording apparatus of the present invention. The ink jet recording apparatus 1 includes a head carriage 2, a recording head 3, an irradiation unit 4, a platen unit 5, and the like. In the ink jet recording apparatus 1, a platen unit 5 is installed under a recording material P. The platen unit 5 has a function of absorbing ultraviolet rays, and absorbs excess ultraviolet rays that have passed through the recording material P. As a result, a high-definition image can be reproduced very stably.

  The recording material P is guided by the guide member 6 and moves from the near side to the far side in FIG. 1 by the operation of the conveying means (not shown). A head scanning unit (not shown) scans the recording head 3 held by the head carriage 2 by reciprocating the head carriage 2 in the Y direction in FIG.

  The head carriage 2 is installed on the upper side of the recording material P, and stores a plurality of recording heads 3 to be described later according to the number of colors used for image printing on the recording material P, with the discharge ports arranged on the lower side. The head carriage 2 is installed with respect to the main body of the recording apparatus 1 in such a manner that it can reciprocate in the Y direction in FIG. 1, and reciprocates in the Y direction in FIG. 1 by driving the head scanning means.

  In FIG. 1, the head carriage 2 is illustrated as accommodating the recording head 3, but in actuality, the number of colors of the recording head 3 accommodated in the head carriage 2 can be determined as appropriate.

  The recording head 3 has a discharge port by operating a discharge means (not shown) provided with a plurality of actinic ray effect inks (for example, UV curable ink) supplied by an ink supply means (not shown). To the recording material P. The UV ink ejected by the recording head 3 is composed of a coloring material, a polymerizable monomer, an initiator, and the like. The monomer crosslinks and polymerizes when the initiator acts as a catalyst when irradiated with ultraviolet rays. It has the property of being cured by reaction.

  During the scanning in which the recording head 3 moves from one end of the recording material P to the other end of the recording material P in the Y direction in FIG. 1 by driving the head scanning means, a certain area (landing possible area) in the recording material P On the other hand, UV ink is ejected as ink droplets, and ink droplets are landed on the landable area.

  The above scanning is performed as many times as necessary, and after UV ink is ejected toward one landable area, the recording material P is appropriately moved from the front to the back in FIG. 1, the recording head 3 discharges UV ink to the next landable area adjacent in the depth direction in FIG.

  By repeating the above operation and ejecting the UV ink from the recording head 3 in conjunction with the head scanning means and the conveying means, an image composed of an aggregate of UV ink droplets is formed on the recording material P.

  The irradiation unit 4 includes an ultraviolet lamp that emits ultraviolet light in a specific wavelength region with stable exposure energy and a filter that transmits ultraviolet light of a specific wavelength. Here, as the ultraviolet lamp, a mercury lamp, a metal halide lamp, an excimer laser, an ultraviolet laser, a cold-indicating electrode tube, a hot-indicating electrode tube, a black light, an LED (Light emitting diode), etc. can be applied. A cold cathode tube, a hot cathode tube, a mercury lamp or black light is preferred. In particular, a low-pressure mercury lamp, a hot cathode tube, a cold cathode tube, and a germicidal lamp that emit ultraviolet light having a wavelength of 254 nm are preferable because they can prevent bleeding and control the dot diameter efficiently. By using black light as the radiation source of the irradiation means 4, the irradiation means 4 for curing the UV ink can be produced at low cost.

  The irradiating means 4 has substantially the same shape as the maximum one that can be set by the recording apparatus (UV inkjet printer) 1 among the landable areas in which the recording head 3 ejects UV ink by one scan driven by the head scanning means. , Having a shape larger than the landable area.

  The irradiation means 4 is fixed on both sides of the head carriage 2 so as to be substantially parallel to the recording material P.

  As described above, as a means for adjusting the illuminance of the ink discharge portion, not only the entire recording head 3 is shielded, but in addition, the ink discharge of the recording head 3 is determined from the distance h1 between the irradiation means 4 and the recording material P. It is effective to increase the distance h2 between the portion 31 and the recording material P (h1 <h2), or to increase the distance d between the recording head 3 and the irradiation means 4 (d is increased). Further, it is more preferable to provide a bellows structure 7 between the recording head 3 and the irradiation means 4.

  Here, the wavelength of the ultraviolet rays irradiated by the irradiation unit 4 can be changed as appropriate by exchanging the ultraviolet lamp or the filter provided in the irradiation unit 4.

  The actinic ray curable ink jet ink of the present invention has very excellent ejection stability and is particularly effective when an image is formed using a line head type ink jet recording apparatus.

  FIG. 2 is a top view illustrating another example of the configuration of the main part of the ink jet recording apparatus.

  The ink jet recording apparatus shown in FIG. 2 is called a line head system, and a plurality of ink jet recording heads 3 of each color are fixedly arranged on the head carriage 2 so as to cover the entire width of the recording material P. ing.

  On the other hand, on the downstream side of the head carriage 2, there is provided irradiation means 4 arranged so as to cover the entire width of the recording material P and cover the entire area of the ink printing surface. As the ultraviolet lamp used in the illuminating means 4, the same one as described in FIG. 1 can be used.

  In this line head system, the head carriage 2 and the irradiating means 4 are fixed, and only the recording material P is conveyed, and ink ejection and curing are performed to form an image.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
<Measurement of amine value of dispersant>
The amine value of each dispersant of PB822, Solsperz 24000GR, Solsperz 32000, EFKA-4330, and EFKA-6230 used for the preparation of each pigment dispersant shown below was measured according to the following method.

  Each dispersant was dissolved in methyl isobutyl ketone, and potentiometric titration was performed with a 0.01 mol / L methyl isobutyl ketone perchlorate solution. The value converted to KOH mg / g was used as the amine value of the dispersant. The potentiometric titration was measured using an automatic titrator COM-1500 manufactured by Hiranuma Sangyo Co., Ltd.

<< Preparation of pigment dispersion >>
[Preparation of Pigment Dispersion D-1]
Each of the following compounds was placed in a stainless beaker and dissolved by heating and stirring for 1 hour while heating on a hot plate at 50 ° C.

PB822 (Ajinomoto Fine Techno Co., Ltd. amine value 15.9 mg / g KOH)
120 parts OXT221 (manufactured by Toagosei Co., Ltd., oxetane compound) 580 parts Next, after cooling the above solution to room temperature, the following pigment was added thereto, and 1000 ml of zirconia beads having a diameter of 0.5 mm were used for 5 hours in a batch sand grinder. After the dispersion treatment, zirconia beads were removed to prepare pigment dispersion D-1. The ratio of the dispersant (PB822) to titanium oxide in the pigment dispersion D-1 is 40% by mass.

Typek R-550 (Ishihara Sangyo Titanium oxide Si / Al treatment) 300 parts [Preparation of pigment dispersion D-2]
Each of the following compounds was placed in a stainless beaker and dissolved by heating and stirring for 1 hour while heating on a hot plate at 50 ° C.

Solspers 24000GR (Avisia Co., Ltd., amine value 35.9 mg / g KOH) 120 parts OXT221 (Toagosei Co., Ltd., oxetane compound) 580 parts The above solution was cooled to room temperature, and then the following pigment was added thereto to add a diameter of 0 After dispersing for 5 hours in a batch sand grinder with 1000 ml of 5 mm zirconia beads, the zirconia beads were removed to prepare pigment dispersion D-2. The ratio of the dispersant (Solspers 24000GR) to titanium oxide in the pigment dispersion D-2 is 40% by mass.

Typek R-780 (Ishihara Sangyo Titanium oxide Si / Al treatment) 300 parts [Preparation of pigment dispersion D-3]
The following compounds were placed in a stainless beaker and mixed with stirring for 1 hour.

EFKA-4330 (manufactured by Fuka Additives Co., Ltd., amine value 30.0 mg / g KOH active ingredient 70%) 350 parts OXT221 (manufactured by Toagosei Co., Ltd., oxetane compound) 350 parts Both 1000 ml of zirconia beads were dispersed in a batch sand grinder for 5 hours, and then the zirconia beads were removed to obtain pigment dispersion D-3. The ratio of the dispersant (EFKA-4330) to titanium oxide in this pigment dispersion D-3 is 81.6% by mass.

Typeke R-780 (Ishihara Sangyo Titanium oxide Si / Al treatment) 300 parts [Preparation of pigment dispersion D-4]
The following compounds were placed in a stainless beaker and dissolved by stirring for 1 hour while heating on a hot plate at 50 ° C.

Solspers 32000 (Avicia Co., Ltd., amine value 27.1 mg / g / KOH, acid value 24.8 mg / g / KOH) 90 parts OXT221 (manufactured by Toagosei Co., Ltd., oxetane compound) 610 parts Next, the above solution was cooled to room temperature Then, the following pigment was added to this, and 1000 ml of zirconia beads having a diameter of 0.5 mm were both dispersed in a batch type sand grinder for 5 hours, and then the zirconia beads were removed to obtain pigment dispersion D-4. The ratio of the dispersant (Solspers 32000) to titanium oxide in this pigment dispersion D-4 is 30% by mass.

Typeke R-780 (Ishihara Sangyo Titanium oxide Si / Al treatment) 300 parts [Preparation of pigment dispersion D-5]
Each of the following compounds was placed in a stainless beaker and dissolved by heating and stirring for 1 hour while heating on a hot plate at 50 ° C.

Solspers 24000GR (Avisia Co., Ltd., amine value 35.9 mg / g KOH) 120 parts OXT221 (Toagosei Co., Ltd., oxetane compound) 580 parts The above solution was cooled to room temperature, and then the following pigment was added thereto to add a diameter of 0 After dispersing for 5 hours with a batch type sand grinder together with 1000 ml of 5 mm zirconia beads, the zirconia beads were removed to prepare pigment dispersion D-5. In this pigment dispersion D-5, the ratio of the dispersant (Solspers 24000GR) to titanium oxide is 40% by mass.

Type A-100 (Ishihara Sangyo Titanium Oxide Untreated) 300 parts [Preparation of Pigment Dispersion D-6]
Each of the following compounds was placed in a stainless beaker and dissolved by heating and stirring for 1 hour while heating on a hot plate at 50 ° C.

EFKA-6230 (manufactured by Fuka Additives Co., Ltd., no amine value) 120 parts OXT221 (manufactured by Toagosei Co., Ltd., oxetane compound) 580 parts Then, after cooling the above solution to room temperature, the following pigment was added thereto and the diameter was reduced to 0. After dispersing for 5 hours in a batch sand grinder together with 1000 ml of 5 mm zirconia beads, the zirconia beads were removed to prepare pigment dispersion D-6. The ratio of the dispersant (EFKA-6230) to titanium oxide in the pigment dispersion D-6 is 40% by mass.

Typek R-550 (Ishihara Sangyo Titanium oxide Si / Al treatment) 300 parts [Preparation of pigment dispersion D-7]
Each of the following compounds was placed in a stainless beaker and dissolved by heating and stirring for 1 hour while heating on a hot plate at 50 ° C.

PB822 (Ajinomoto Fine Techno Co., Ltd. amine value 15.9 mg / g KOH)
120 parts EPB-1: Celoxide 2021P (manufactured by Daicel) 580 parts Next, after cooling the above solution to room temperature, the following pigment was added thereto, and 5 ml in a batch sand grinder together with 1000 ml of 0.5 mm diameter zirconia beads. After the time dispersion treatment, zirconia beads were removed to prepare pigment dispersion D-7.

Typek R-780 (Ishihara Sangyo Titanium oxide Si / Al treatment) 300 parts << Preparation of ink composition >>
Ink compositions 1 to 16 were prepared by sequentially mixing the additives described in Table 1 with each of the prepared pigment dispersions and filtering the mixture with a 5 μm membrane filter. In addition, the numerical value described in Table 1 represents mass%.

In addition, the detail of each additive described with the abbreviation in Table 1 is as follows.
[Oxetane compound]
OXT212 (manufactured by Toagosei Co., Ltd.)
[Compound having an oxirane ring]
PO: α-pinene oxide DEP: 1, 2: 8,9 diepoxy limonene E-4030: Sunsosizer E-4030 (epoxylated fatty acid butyl produced by Shin Nippon Rika Co., Ltd.)
[Photoacid generator]
SP-152: Triphenylsulfonium salt (“Adekaoptomer SP-152” manufactured by Asahi Denka Co., Ltd.)
[Surfactant]
F475: Megafax F475 Perfluoroalkyl group-containing acrylic oligomer (Dainippon Ink & Chemicals, Inc.)
<< Inkjet image formation >>
[Image Forming Method-1]
Each of the inks 1 to 18 prepared above is loaded into a carriage-type inkjet recording apparatus having the configuration shown in FIG. 1 having a piezo-type inkjet nozzle, and is a long polyethylene having a thickness of 120 μm, a width of 600 mm, and a length of 500 m. A white solid image was continuously printed on the terephthalate film to obtain each image. The ink supply system was composed of an ink tank, a supply pipe, a front chamber ink tank immediately before the head, a pipe with a filter, and a piezo head. The ink was insulated from the front chamber tank to the head portion and heated at 50 ° C. The piezo head was driven such that 2 to 20 pl multi-size dots could be ejected at a resolution of 720 × 720 dpi, and each ink was ejected continuously. After landing, it is cured instantaneously (less than 0.5 seconds after landing) by the lamp units on both sides of the carriage. After recording, the total ink film thickness was measured and found to be in the range of 2.3 to 13 μm. In the present invention, dpi represents the number of dots per 2.54 cm. Inkjet images were formed in an environment of 25 ° C. and 30% RH according to the above method.
[Image Forming Method-2]
In the image forming method-1, each image was obtained in the same manner except that the line head recording type ink jet recording apparatus shown in FIG. 2 was used as the ink jet recording apparatus and each of the prepared inks 1 to 19 was loaded. It was.

  Details of the irradiation light source used in each of the image forming methods are as follows.

Irradiation light source used in image forming method-1: high pressure mercury lamp VZero085 (manufactured by INTEGRATION TECHNOLOGY, peak wavelength: 254 nm, maximum illuminance: 400 mW / cm ² )
Irradiation light source used in image forming method-2: low-pressure mercury lamp (Iwasaki Electric custom-made product, five linear light sources arranged, irradiation area 120 mm (longitudinal direction) × 620 mm (lateral direction) Peak wavelength: 254 nm Maximum illuminance: 50 mW / cm ² )
In addition, the illumination intensity of each said irradiation light source measured and displayed the integrated illumination intensity of 254 nm using UVPF-A1 by Iwasaki Electric.

<< Evaluation of formed image and ink >>
[Evaluation of curability]
About each image formed according to the said method, the image printing surface immediately after irradiating actinic light was touched with the finger | toe, and sclerosis | hardenability was evaluated according to the following reference | standard. In Table 2, the result of image forming method-1 is shown as sclerosis evaluation 1, and the result of image forming method-2 is shown as curable evaluation 2.

◎: The surface of the formed image has almost no stickiness and is sufficiently cured ○: The surface of the formed image is slightly sticky, but is sufficiently cured △: The surface of the formed image has a feeling of stickiness However, it is almost cured. X: The formed image flows without being cured.

[Evaluation of ink storage stability]
Each of the inks prepared above was put in a glass bottle and sealed, and then allowed to stand in an environment of 60 ° C. for 1 day, and then the sedimentation state of the pigment particles was visually observed, and the ink storage stability was evaluated according to the following criteria.

○: Sedimentation of pigment particles is hardly observed Δ: Sedimentation of pigment particles is not observed in a stationary state, but agglomerated pigment particles are observed on the wall surface of the glass bottle when the ink liquid is shaken ×: Clearly aggregated at the bottom of the glass bottle Table 2 shows the results obtained as described above in which sedimentation of the pigment particles was observed.

  As is apparent from the results in Table 2, the active ray of the present invention contains titanium oxide, a dispersant, an oxetane compound as a cationic polymerizable monomer, and a photoacid generator, and the titanium oxide is surface-treated containing silica. It can be seen that the curable ink-jet ink is excellent in curability even when a carriage-type ink jet recording apparatus or a line head type ink-jet recording apparatus is used as compared with the comparative example. In addition, it can be seen that the ink of the present invention has little aggregation of pigment particles and excellent ink storage stability even when stored at a high temperature for a long period of time compared to the comparative example.

Claims (15)

An actinic ray curable ink-jet ink comprising: titanium oxide containing at least silica and having a surface treatment; a dispersant; an oxetane compound as a cationic polymerizable monomer; and a photoacid generator.   The actinic ray curable inkjet ink according to claim 1, wherein the dispersant is a polymer dispersant having an amine value. The actinic ray curable inkjet ink according to claim 1 or 2, wherein the dispersant has a content of 35% by mass to 60% by mass with respect to the titanium oxide. The actinic ray curable inkjet ink according to any one of claims 1 to 3, further comprising a compound having an oxirane ring as the cationic polymerizable monomer. The actinic ray curable inkjet ink according to claim 4, wherein the compound having an oxirane ring is a compound represented by the following general formula (1).

[Wherein, R ₁ represents an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, an unsubstituted or substituted aromatic group, or an acyl group. ] The actinic ray curable inkjet ink according to claim 4, wherein the compound having an oxirane ring is a compound represented by the following general formula (2).

[Wherein Y _{1 to} Y ₈ each represent a hydrogen atom, an unsubstituted or substituted alkyl group, a carbonyl group, or an ether group, which may be different from each other. ] The actinic ray curable inkjet ink according to claim 4, wherein the compound having an oxirane ring is α-pinene oxide. The actinic ray curable inkjet ink according to claim 4, wherein the compound having an oxirane ring is 1,2: 8,9-diepoxy limonene. The actinic ray curable inkjet ink according to claim 4, wherein the compound having an oxirane ring is a vegetable oil having an epoxidized unsaturated bond. The actinic ray curable inkjet ink according to claim 4, wherein the compound having an oxirane ring is a compound represented by the following general formula (A).

Wherein, R ₁₀₀ represents a substituent, m0 represents 0-2. r0 represents 1-3. L ₀ represents a C 1-15 r 0 + 1 valent linking group or single bond that may contain an oxygen atom or a sulfur atom in the main chain. ] An image forming method in which the actinic radiation curable inkjet ink according to any one of claims 1 to 10 is jetted onto a recording material from an inkjet recording head, and printing is performed on the recording material. An image forming method comprising irradiating actinic rays for 0.001 to 1 second after the actinic ray curable inkjet ink has landed on the recording medium. An image forming method in which the actinic radiation curable inkjet ink according to any one of claims 1 to 10 is jetted onto a recording material from an inkjet recording head, and printing is performed on the recording material. An image forming method, wherein the total film thickness after the actinic ray curable ink jet ink has landed on the recording medium and cured by irradiation with actinic rays is 2 to 25 μm. An image forming method in which the actinic radiation curable inkjet ink according to any one of claims 1 to 10 is jetted onto a recording material from an inkjet recording head, and printing is performed on the recording material. An image forming method, wherein the amount of droplets of the actinic ray curable inkjet ink ejected from each nozzle of the inkjet recording head is 2 to 20 pl. The image forming method according to claim 11, wherein the inkjet recording head is a line head system. 15. An ink jet recording apparatus for use in the image forming method according to any one of claims 11 to 14, wherein the actinic ray curable ink jet ink and the ink jet recording head are heated to 35 ° C. to 100 ° C. An inkjet recording apparatus having a mechanism for discharging the actinic ray curable inkjet ink.