JP2006062170A - Inkjet recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording sheet for forming a print which is free from any defects such as crazing during manufacturing, shows excellent handling properties in the case of bend-cracking and the like and high resistance to light. <P>SOLUTION: This inkjet recording sheet has a porous layer containing (a) a binder containing a polymer compound cross-linked between side chains using a photoinitiator by irradiating a hydrophilic polymer compound, with not less than 300 degree of polymerization, having a plurality of side chains to a main chain, with an ultraviolet light, (b) a chemical compound represented by formula (1) and (c) an inorganic particle. In the formula (1), R<SB>1</SB>, R<SB>2</SB>, R<SB>4</SB>and R<SB>5</SB>are each an alkyl group or a carbonyl group; R<SB>3</SB>is a hydrogen atom, an alkyl group, an alkoxy group, an aryloxy group, an oxy radical group, a hydroxy group or a group which forms an imino group or a hydroxy imino group by hydrolysis; and R<SB>6</SB>, R'<SB>6</SB>are each an optional substituent group. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink jet recording paper, and more particularly to an ink jet recording paper that is free from defects such as cracks during production, has excellent handling properties such as cracks, and forms a print with excellent light resistance. Furthermore, the present invention relates to a method for producing the ink jet recording paper and a recording method using the ink jet recording paper.

  In recent years, in the ink jet recording system, image quality has been improved rapidly and is approaching the image quality of silver halide photographs. As a means for achieving such photographic image quality by ink jet recording, technological improvements are also being attempted rapidly in the recording paper used.

  As for the support used for the ink jet recording paper, a water-absorbing support such as paper and a non-water-absorbing support such as polyester film and resin-coated paper are generally known. The former has the advantage that the support itself can absorb ink, and thus has the advantage of having a high ink absorption ability, but on the other hand, there is a problem that wrinkles are generated after printing due to the water absorption of the support (also called cockling). In addition, there are problems such that it is difficult to obtain high-quality prints, and the print surface is easily rubbed by the head with cockling during printing.

  On the other hand, when a non-water-absorbing support is used, there is an advantage that a high-quality print can be obtained without the above-described problems.

  On the other hand, as the ink receiving layer, for example, an ink jet sheet has been devised in which a hydrophilic binder such as gelatin or PVA is applied as an ink absorbing layer on a highly smooth support to form an ink receiving layer. This type of recording paper absorbs ink by utilizing the swelling property of the binder. Since this ink-receiving layer is a water-soluble resin, it is difficult to dry the ink after printing, the image or film is weak against moisture and not water-resistant, and in recent ink jet printers, the printing speed is high. Because of its rapidity, there was a problem that the absorbability due to the swelling of the binder could not catch up with the discharge amount and discharge speed of the ink, and the ink overflowed and mottled, resulting in loss of adaptability.

  In contrast to the ink jet recording sheet that absorbs ink by utilizing the swellability of the above water-based resin, a recording paper provided with a porous layer having a minute void as an ink absorbing layer has high ink absorption and high speed drying. It is becoming one of the methods that can obtain the closest photo quality.

  This porous layer is mainly formed of a hydrophilic binder and fine particles. As fine particles, inorganic or organic fine particles are known, but in general, inorganic fine particles have a smaller particle size, Since a highly glossy porous layer can be realized, it is preferably used.

  By using a relatively small amount of a hydrophilic binder for such inorganic fine particles, voids are formed between the fine particles, and a porous layer having a high porosity can be obtained.

  By forming the voids, the ink is absorbed by a capillary phenomenon, so that even if the binder is cross-linked using a cross-linking agent or the like to improve the water resistance, the absorption speed is not impaired.

  However, in the case of an inkjet recording paper in which such a porous layer is provided on a non-water-absorbing support such as polyethylene-coated paper, all the ink is temporarily used as an ink receiving layer during inkjet recording. The ink-receiving layer must be a porous layer with a high void volume because it needs to be retained, and therefore it is necessary to form a thick coating film with a high porosity. Usually, a thick layer having a dry film thickness of 25 μm or more, usually 30 μm to 50 μm is formed.

  Since such a porous layer is originally a hard film because the main component is inorganic fine particles, when a thick porous layer is applied on a non-water-absorbing support, it does not crack when dried. Easy to get up. Moreover, it is easy to produce a crack at the time of use.

  Furthermore, light or trace gases in the air, especially ozone, cause discoloration of recorded images over time. Since a recording material having a color material receiving layer having a porous structure has many voids, a recorded image is easily faded by ozone gas in the air.

  As an ink jet recording paper having a porous layer that is less likely to crack during manufacturing and has high resistance to bending after manufacturing, high porosity, high ink absorbability, high water resistance, and high bleeding resistance, it can be used in the main chain. An ink jet having a porous layer containing fine particles and a binder containing a polymer compound crosslinked between the side chains by irradiating ultraviolet rays onto a hydrophilic polymer compound having side chains of 300 or more and having a degree of polymerization Although recording paper (for example, refer to Patent Document 1) is disclosed, light resistance is greatly deteriorated.

  As a method for improving light resistance, a method in which gelatin, an ultraviolet absorber and an antioxidant are contained in the ink receiving layer (for example, see Patent Document 2), a method in which a cationic polymer and a water-soluble ultraviolet absorber are used in combination (for example, a patent). Reference 3), and a method containing a compound that quenches singlet oxygen (see, for example, Patent Document 4) has been disclosed, but was not effective for inkjet recording paper using a photocrosslinking binder.

On the other hand, although a method for improving the light resistance of an ink jet recording paper using a hindered amine compound is disclosed (for example, see Patent Documents 5 and 6), it is impossible to satisfy a sufficiently long light resistance, It was remarkably inferior to a crack.
JP 2004-136644 A (Claims) JP 2000-158802 A (Claims) JP 2000-108500 A (Claims) JP 2000-226544 A (Claims) Japanese Patent Publication No. 4-34512 (Claims) JP 2003-246138 A (Claims)

  An object of the present invention is to provide an ink jet recording paper that does not have defects such as cracks during production, is excellent in handling properties such as cracks, and forms a print excellent in light resistance.

  The above object of the present invention can be achieved by the following configuration.

(Claim 1)
On the support,
(A) a binder containing a polymer compound crosslinked by a photoinitiator between side chains by irradiating a hydrophilic polymer compound having a plurality of side chains in the main chain with a degree of polymerization of 300 or more with ultraviolet rays; (B) a compound represented by the following general formula (1);
(C) An ink jet recording paper comprising a porous layer containing inorganic fine particles.

[Wherein R ₁ , R ₂ , R ₄ , R ₅ represent an alkyl group or a carbonyl group, and R ₃ represents a hydrogen atom, an alkyl group, an alkoxy group, an aryloxy group, an oxy radical group, a hydroxyl group, by hydrolysis. It represents a group which forms an imino group or hydroxy Louis amino group, R _6, R ₆ 'represents any substituent. ]
(Claim 2)
R ₁ , R ₂ , R ₄ and R _{5 in the} general formula (1) are methyl groups, R ₆ is an —OCO—R ₇ group or —NHCO—R ₈ group, and R ₆ ′ is a hydrogen atom. The inkjet recording paper according to claim 1. Here, R ₇ and R ₈ represent an arbitrary substituent.

(Claim 3)
The inkjet recording paper according to claim 2, wherein R _{3 in the} general formula (1) is a hydrogen atom.

(Claim 4)
The inkjet recording paper according to any one of claims 1 to 3, wherein a vapor phase silica having a primary particle size of 20 nm or less is used as the inorganic fine particles.

(Claim 5)
The coating liquid contains a photoinitiator and a compound represented by the general formula (1), and the molar ratio of the piperazine ring unit to the photoinitiator in the compound represented by the general formula (1) is 60 to 1. The inkjet recording paper according to any one of claims 1 to 4, wherein the inkjet recording paper is produced by irradiating ultraviolet rays after coating the coating liquid.

(Claim 6)
After coating the coating liquid containing a photoinitiator, irradiating with ultraviolet rays and drying, the molar ratio of the piperazine ring unit and the photoinitiator in the compound represented by the general formula (1) The inkjet recording paper according to any one of claims 1 to 5, wherein the inkjet recording paper is produced by overcoating the compound represented by the general formula (1) so as to be in a range of 60 to 1.

  According to the present invention, an ink jet recording paper that has no defects such as cracks during production, has excellent handling properties such as cracks, and forms a print excellent in light resistance is obtained.

  The present invention will be described in more detail. A recording material containing a binder obtained by crosslinking a hydrophilic polymer having a crosslinkable group in the side chain in the presence of a photoinitiator is known, but it has excellent cracking resistance and bending resistance, but the light resistance is reduced. I found out that The present inventor has investigated this phenomenon and found that a photoinitiator that can be expected to absorb ultraviolet rays and improve light resistance has a great adverse effect on light resistance. Although the mechanism of deterioration of light resistance due to this photoinitiator has not yet been fully elucidated, radicals are generated during storage from the photoinitiator remaining in the ink receiving layer even after UV irradiation, and this is the initiation reaction. Thus, it is considered that the color material decomposition reaction proceeds in a chained manner.

  On the other hand, various substances that suppress radical decomposition are generally known, but hindered phenol antioxidants, phosphorus antioxidants, sulfur antioxidants, hindered amine light are particularly useful. Stabilizers are known. As light stabilizers, UV absorbers such as benzotriazole, triazine, and benzophenone, hindered amine light stabilizers, and the like are known. Japanese Patent Application Laid-Open No. 2000-158802 describes that the light resistance of ink jet recording paper is greatly improved by using an ultraviolet absorber and a phenolic antioxidant together. It is extremely reasonable to block as much UV rays as possible to initiate color material decomposition reaction as much as possible, and to stop the decomposition reaction with a phenolic antioxidant even if radical decomposition reaction starts from UV rays that could not be blocked. It seems to be a typical technique. In particular, the photoinitiator remaining in the ink receiving layer is expected to be an extremely effective technique for an ink jet recording material that absorbs ultraviolet rays, generates radicals, and accelerates the decomposition reaction of the coloring material.

  However, as a result of diligent study by the present inventor, the recording material containing a binder obtained by crosslinking a hydrophilic polymer having a crosslinkable group in the side chain excellent in cracking resistance and bending resistance in the presence of a photoinitiator is absorbed by ultraviolet rays. Even when using a technique that uses a combination of an agent, a phenolic antioxidant, a phosphorous antioxidant, a sulfurous antioxidant, etc., it is not an effective means for improving light resistance, and it has almost no ultraviolet absorbing ability. It has been found that only the hindered amine light stabilizer represented by the general formula (1) of the invention is an effective means. The effect of the present invention occurs specifically when a hindered amine light stabilizer is contained in a recording material containing a binder obtained by crosslinking a hydrophilic polymer having a crosslinkable group in the side chain in the presence of a photoinitiator. It is a phenomenon.

  In addition, the recording material containing a binder obtained by crosslinking a hydrophilic polymer having a crosslinkable group in a side chain excellent in cracking resistance and bending resistance in the presence of a photoinitiator is represented by the general formula (1) of the present invention. It has been found that when a hindered amine light stabilizer is added, cracking and cracking are also improved. This was also an effect not seen in the hindered phenol radical scavenger. Although the detailed mechanism has not yet been clarified, cracks during manufacturing and cracking after manufacturing are suppressed by appropriately capturing radicals generated from the light stabilizer or shortening the lifetime of the radicals. It is expected that

In the general formula (1) of the present invention, R ₁ , R ₂ , R ₄ and R ₅ represent an alkyl group or a carbonyl group, preferably an alkyl group, and particularly preferably a methyl group.

R ₃ represents a hydrogen atom, an alkyl group, an alkoxy group, an aryloxy group, an oxy radical group, a hydroxyl group, or a group that generates an imino group or a hydroxylimino group by hydrolysis, and is preferably a hydrogen atom or an alkyl group.

When R _{3 in the} general formula (1) represents an aliphatic group, it may have a substituent. Specific examples of R ₃ include hydrogen atom, methyl group, ethyl group, butyl group, octyl group, hydroxy group, methoxy group, ethoxy group, butoxy group, octyloxy group, acetyloxy group, pivaloyloxy group, benzoyloxy group. And acetyl group.

R ₆ and R ₆ ′ represent an arbitrary substituent, and R ₆ represents a hydrogen atom, —OR ₉ (wherein R ₉ represents a hydrogen atom, an aliphatic group, an aromatic group, an alkoxycarbonyl group, an acyl group, an aminocarbonyl group, a _{group), -. NR 10 R 11} ( wherein R ₁₀ and R ₁₁ each independently represent a hydrogen atom, an aliphatic group, an aromatic group, an acyl group, an aminocarbonyl group, or a sulfonyl group), -. COOR ₁₂ (Wherein R ₁₂ represents a hydrogen atom, an aliphatic group or an aromatic group), a halogen atom, an aliphatic group or an aromatic group. R ₆ ′ represents a hydrogen atom, an aliphatic group, an aromatic group, or —OR ₁₃ (wherein R ₁₃ represents a hydrogen atom or an aliphatic group). R ₆ and R ₆ ′ may form a carbonyl group in a form containing a carbon atom substituted by R ₆ and R ₆ ′, or may be linked to each other to form a ring structure. Further, at least one of R ₆ and R ₆ ′ may represent a group that may react with a reactive group contained in a polymer, oligomer, or low molecule to form a bond.

Specific examples of R ₆ include a hydrogen atom, a hydroxy group, a methoxy group, an ethoxy group, a propyloxy group, an octyloxy group, a phenoxyethoxy group, a phenoxy group, an acetyloxy group, a propionyloxy group, a pivaloyloxy group, a benzoyloxy group, Thienyloxy, methoxycarbonyloxy, butylaminocarbonyloxy, phenylaminecarbonyloxy, amino, ethylamino, dibutylamino, dioctylamino, phenylamino, diphenylamino, hydroxyethylamino, bis (Hydroxyethyl) amino group, cyanoethylamino group, carboxyethylamino group, methoxycarbonyloxyethylamino group, chloropropylamino group, methylsulfonylamino group, phenylsulfonylamino group, butyne Aminocarbonylamino group, carboxyl group, methoxycarbonyl group, hydroxyethyloxycarbonyl group, chloro atom, fluorine atom, bromine atom, iodine atom, methyl group, ethyl group, octadecyl group, phenyl group, tolyl group, epoxy group, chloroacetyl An amino group, a chloroacetyloxy group, etc. are mentioned. Specific examples of R ₆ ′ include a hydrogen atom, methyl group, ethyl group, butyl group, octyl group, phenyl group, naphthyl group, hydroxy group, methoxy group, ethoxy group and the like.

R ₆ and R ₆ ′ may form a carbonyl group in a form containing a carbon atom substituted by R ₆ and R ₆ ′, or may be connected to each other to form a 5- to 7-membered ring. Good. In addition, at least one of R ₆ and R ₆ ′ may react with a reactive group contained in the polymer, oligomer or small molecule to form a bond. In this case, the hindered amine compound represents a compound having two or more hindered amine skeletons in one molecule. In this case, at least one of R ₆ and R ₆ ′ includes a hydroxy group, an acyloxy group substituted with a halogen atom or a sulfonate group, an amino group, an acylamino group substituted with a halogen atom or a sulfonate group, a carboxyl group A polymer or oligomer having a reactive group capable of undergoing an addition reaction such as a nucleophilic substitution reaction such as SN1 or SN2 reaction, a salt formation reaction, a Michael reaction or a reaction with an epoxy compound. Alternatively, a low molecular compound can produce a polymer, oligomer or low molecular hindered amine compound having two or more hindered amine skeletons in one molecule.

  In the present invention, it is also preferable to provide at least two ink-receiving layers on the support and to contain more compounds represented by the general formula (1) in the ink-receiving layer far from the support. When three or more ink-receiving layers are provided on the support, it is preferable that the content of the compound represented by the general formula (1) is increased or equivalent in the ink-receiving layer farther from the support. When the ink receiving layer close to the support contains a large amount of the compound represented by the general formula (1), the effect of the present invention decreases, which is not preferable.

  In the present invention, the molar ratio of the piperazine ring of the compound represented by the general formula (1) to the photoinitiator is 1 to 60, more preferably 3 to 40, by weight. When a plurality of ink receiving layers are provided on the support, the molar ratio of the total amount of piperazine rings and the total amount of photoinitiator of the compound represented by the general formula (1) is used. When the molar ratio of the piperazine ring to the photoinitiator of the compound represented by the general formula (1) is 1 or less, cracks and light resistance are liable to deteriorate, and when it is 40 or more, the cracks are deteriorated and broken. It tends to cause deterioration.

  The ink jet recording paper of the present invention is obtained by applying a water-soluble coating liquid that forms a porous layer mainly containing a specific hydrophilic binder and fine particles on a support to form a porous layer having voids.

  The inorganic fine particles used in the present invention are fine inorganic pigments having a large pore volume and a small average particle size. In particular, silica, aluminum hydroxide, boehmite, pseudoboehmite, and fine pigments such as alumina and charcoal cal are used.

  The silica used in the present invention is wet silica or vapor phase silica synthesized by precipitation or gel method using sodium silicate as a raw material.

  For example, fine silica of Tokuyama Co., Ltd. by the precipitation method is commercially available for wet silica, and NIPGEL of Nippon Silica Kogyo Co., Ltd. is commercially available for silica by the gel method. Precipitated silica is generally characterized by 10-60 nm, and gel silica is characterized by silica particles having primary aggregates of approximately 3-10 nm forming secondary aggregates.

  Although there is no restriction | limiting in particular in the lower limit regarding the primary particle diameter of wet silica, it is 3 nm or more from a viewpoint of manufacture stability of a silica particle, and it is preferable that it is 50 nm or less from a viewpoint of the transparency of a film | membrane. In general, wet silica synthesized by the gel method is preferred because the primary particle size tends to be smaller than that of the precipitation method.

  Vapor phase silica is synthesized by combustion using silicon tetrachloride and hydrogen as raw materials. For example, Aerosil series manufactured by Nippon Aerosil Co., Ltd. is commercially available.

In order to obtain an ink absorption layer having a high porosity, the specific surface area measured by the BET method is less than 400 m ² / g, or the isolated silanol group ratio is 0.5 to 2.0. The specific surface area is preferably in the range of 40m ² / g~100m ² / g, the lower limit of the specific surface area of 40 m ² / g from the viewpoint of glossiness is obtained near photographic. The BET method is a method for measuring a specific surface area by a method for obtaining a surface area per 1 g of silica fine particles from a gas phase adsorption isotherm.

  In the vapor phase silica having a specific surface area in this range, it is preferable from the viewpoint of porosity that the coefficient of variation in the primary particle size distribution is 0.01 to 0.4. If the coefficient of variation exceeds 0.4, there is a concern that the porosity is lowered, which is not preferable. In wet silica, the primary particles themselves have a pore size, and this is not the case.

  In the vapor-phase process silica, since the secondary aggregate is formed by relatively weak interaction with wet silica, it has a feature that it can be dispersed with low energy in wet silica.

  The coefficient of variation in the primary particle size distribution of vapor-phase process silica is determined by observing the cross section and surface of the porous layer with an electron microscope, obtaining the particle size of 1000 arbitrary primary particles, and calculating the standard deviation of the particle size distribution. It is obtained as a value divided by the average particle size value. Here, each particle size is represented by a diameter assuming a circle equal to the projected area.

  The average particle size of the primary particles and secondary particles of silica is determined from the particle size of 100 arbitrary particles by observing the cross section and surface of the porous layer with an electron microscope. Here, each particle size is represented by a diameter assuming a circle equal to the projected area. The secondary average particle diameter is preferably 300 nm or less from the viewpoint of ultraviolet light transmission.

  It is also preferable to adjust the water content of the vapor phase silica by storing the vapor phase silica at a humidity of 20 to 60% for 3 days or more.

  In the vapor phase method silica of the present invention, the isolated silanol group ratio is preferably 0.5 to 1.5, more preferably 0.5 to 1.1.

  Alumina used in the present invention refers to aluminum oxide and hydrates thereof, which may be crystalline or amorphous, and have an amorphous, spherical, plate-like or needle-like shape. Is done. In particular, a plate-like alumina hydrate or vapor phase method alumina having an aspect ratio of 2 or more and an average primary particle size of 5 to 30 nm is preferable.

  The content of the inorganic fine particles in the water-soluble coating solution is 5 to 40% by mass, and particularly preferably 7 to 30% by mass.

  Moreover, it is preferable that solid content concentration of the said porous layer containing the hydrophilic resin bridge | crosslinked with an inorganic fine particle and an ultraviolet-ray is 5 to 90% of range.

  The binder used in the porous layer of the present invention is crosslinked by a photoinitiator between side chains by irradiating a hydrophilic polymer compound having a plurality of side chains in the main chain with a polymerization degree of 300 or more with ultraviolet rays. Containing polymer compounds. The hydrophilic polymer compound having a polymerization degree of 300 or more having a plurality of side chains in the main chain is a water-soluble resin that undergoes a reaction and crosslinks upon irradiation with ultraviolet rays, and is water-soluble before the curing reaction. However, it is a resin that becomes substantially water-insoluble after the curing reaction. However, such a resin has a certain degree of hydrophilicity after curing, and maintains a sufficient ink affinity.

  As such a resin, a photo-dimerization type, photodecomposition type, photodepolymerization type, photo-denaturation type, photo-polymerization type or the like is allowed to act on polyvinyl alcohol or the like to cause crosslinking through light via the modification group. A cross-linked group-modified polymer or a polymer directly cross-linked by an electron beam can be used, and examples thereof include nonionic, cationic, and anionic substances. In polymers having a cation or anion moiety in the structure, the surface of the inorganic filler, etc. and the cation or anion moiety may interact or interact with each other to inhibit the crosslinking reaction. Not desirable. This is because a hydrophilic binder that crosslinks with nonionic ultraviolet rays, especially the resin disclosed in Japanese Patent Application Laid-Open No. 2000-181062, has a smaller interaction with inorganic fine particles than cation and anion type substances, and causes a crosslinking reaction efficiently. It is preferable in the invention.

  In addition, as long as the performances intended in the present invention are not deteriorated, the following hydrophilic resin is used in combination with a hydrophilic polymer compound having a degree of polymerization of 300 or more as a binder and having a plurality of side chains in the main chain. And you may make it contain in a porous layer.

  The hydrophilic resin used in combination is not particularly limited, and a hydrophilic resin that can be used as a conventionally known hydrophilic binder can be used. For example, gelatin, polyvinyl pyrrolidone, polyethylene oxide, polyacrylamide, polyvinyl alcohol, etc. Can be used, but polyvinyl alcohol is particularly preferred.

  Polyvinyl alcohol has an interaction with inorganic fine particles, has a particularly high holding power to inorganic fine particles, and is a polymer with relatively small humidity dependency such as hygroscopicity, and has a comparative shrinkage stress during coating and drying. Therefore, the suitability for cracking during coating and drying, which is the subject of the present invention, is excellent. Examples of the polybilyl alcohol preferably used in the present invention include, in addition to ordinary polyvinyl alcohol obtained by hydrolysis of polyvinyl acetate, modified polyvinyl alcohol having a terminal cation modified, anion-modified polyvinyl alcohol having an anionic group, and the like. Polyvinyl alcohol is also included.

  As polyvinyl alcohol obtained by hydrolyzing vinyl acetate, those having an average degree of polymerization of 300 or more are preferably used, and those having an average degree of polymerization of 1000 to 5000 are particularly preferably used. The saponification degree is preferably 70 to 100%, particularly preferably 80 to 99.5%.

  Examples of the cation-modified polyvinyl alcohol have primary to tertiary amino groups and quaternary ammonium groups in the main chain or side chain of the polyvinyl alcohol as described in JP-A-61-110483. Polyvinyl alcohol, which is obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.

  The ratio of the fine particles to the hydrophilic binder of the porous layer according to the present invention is preferably 2 to 50 times in terms of mass ratio. If the mass ratio is 2 times or more, the porosity of the porous layer is good, it is easy to obtain a sufficient void volume, and an excessive hydrophilic binder is prevented from swelling and closing the void during ink jet recording. On the other hand, if this ratio is 50 times or less, it is preferable that cracking hardly occurs when the porous layer is applied as a thick film. A particularly preferable ratio of the fine particles to the hydrophilic binder is 2.5 to 20 times. In particular, from the viewpoint of resistance to breakage of the dried coating film, 5 to 15 times is more preferable.

The porous layer according to the present invention preferably has a capacity of 15 to 40 ml / m ² per unit area of the coating film. This capacity refers to the volume of bubbles generated when a unit volume of the coating film is immersed in water, the volume of water that can be absorbed by the coating film, or the recording paper finally obtained. It is defined by the amount of liquid transfer when the contact time is 2 seconds as measured by the paper and paperboard liquid absorptivity test method (Bristow method) defined in TAPPI 51.

  As the support used in the ink jet recording paper of the present invention, a water-absorbing support (for example, paper) or a non-water-absorbing support can be used. From the viewpoint of obtaining a higher-quality print, non-water-absorbing support. An ionic support is preferred.

  Examples of the non-water-absorbing support preferably used include, for example, polyester film, diacetate film, triatesate film, polyolefin film, acrylic film, polycarbonate film, polyvinyl chloride film, polyimide film, cellophane, A transparent or opaque film made of a material such as celluloid, or a resin-coated paper in which both surfaces of a base paper are coated with a polyolefin resin coating layer, so-called RC paper, or the like is used.

  When applying the water-soluble coating solution on the support, the support is subjected to corona discharge treatment, subbing treatment or the like for the purpose of increasing the adhesive strength between the surface and the coating layer. Is preferred. Furthermore, the inkjet recording paper of the present invention may be a colored support.

  The support preferably used in the present invention is a transparent polyester film, an opaque polyester film, an opaque polyolefin resin film, and a paper support in which both sides of paper are laminated with a polyolefin resin.

  Hereinafter, a paper support laminated with polyethylene, which is the most preferred representative of polyolefin, will be described.

  The base paper used for the paper support is made from wood pulp as a main raw material and, if necessary, paper making using synthetic pulp such as polypropylene or synthetic fibers such as nylon or polyester in addition to wood pulp. As wood pulp, for example, any of LBKP, LBSP, NBKP, NBSP, LDP, NDP, LUKP, NUKP can be used, but more LBKP, NBSP, LBSP, NDP, LDP with more short fibers are used. Is preferred. However, the ratio of LBSP or LDP is preferably 10% by mass or more and 70% by mass or less.

  The pulp is preferably a chemical pulp (sulfate pulp or sulfite pulp) with few impurities, and a pulp having a whiteness improved by bleaching is also useful.

  In the base paper, sizing agents such as higher fatty acids and alkyl ketene dimers, white pigments such as calcium carbonate, talc and titanium oxide, paper strength enhancing agents such as starch, polyacrylamide and polyvinyl alcohol, fluorescent whitening agents, polyethylene glycols A water retaining agent such as a dispersant, a softening agent such as a quaternary ammonium, and the like can be appropriately added.

  The freeness of the pulp used for papermaking is preferably 200 to 500 ml as defined by CSF, and the fiber length after beating is a 24 mesh residual mass% defined by JIS-P-8207, and 42 30-70 mass% of sum with the mass% of a mesh remainder is preferable. In addition, it is preferable that the mass% of 4 mesh remainder is 20 mass% or less.

The basis weight of the base paper is preferably 30 to 250 g, particularly preferably 50 to 200 g. The thickness of the base paper is preferably 40 to 250 μm. The base paper can be given a high smoothness by subjecting it to a calendar process at the paper making stage or after paper making. The density of the base paper is generally 0.7 to 1.2 g / m ³ (according to the method defined in JIS-P-8118). Furthermore, the base paper stiffness is preferably 20 to 200 g under the conditions specified in JIS-P-8143. A surface sizing agent may be applied to the surface of the base paper. As the surface sizing agent, the same sizing agents that can be added to the base paper can be used. The pH of the base paper is preferably 5 to 9 when measured by a hot water extraction method defined in JIS-P-8113.

  The polyethylene covering the front and back surfaces of the base paper is mainly low-density polyethylene (LDPE) or high-density polyethylene (HDPE), but some other LLDPE, polypropylene, etc. can also be used.

  The layer on the coated layer side is preferably one in which rutile or anatase type titanium oxide is added to polyethylene to improve opacity and whiteness, as is widely done in photographic paper. The titanium oxide content is 1 to 20% by mass, preferably 2 to 15% by mass, based on polyethylene.

  The polyethylene-coated paper can be used as glossy paper, or when the polyethylene is melt-extruded and coated on the surface of the base paper, a matte surface or silk-like surface obtained by ordinary photographic photographic paper by performing a so-called molding process Those having a fine grain surface can also be used in the present invention.

  The amount of polyethylene used on the front and back of the base paper is selected so as to optimize the film thickness of the aqueous coating composition and the curl at low and high humidity after providing the back layer, but the aqueous coating according to the present invention The polyethylene layer on the side on which the composition is applied is preferably 20 to 40 μm, and the back layer side is preferably in the range of 10 to 30 μm.

  Furthermore, the polyethylene-coated paper support preferably has the following characteristics.

1) Tensile strength: strength specified by JIS-P-8113, preferably 20-300N in the vertical direction and 10-200N in the horizontal direction 2) Tear strength: as defined by JIS-P-8116 The longitudinal direction is preferably 0.1 to 2N and the lateral direction is preferably 0.2 to 2N. 3) Compression elastic modulus: ≧ 1030 N / cm ²
4) Surface Beck smoothness: 500 seconds or more is preferable as a glossy surface under the conditions specified in JIS-P-8119, but it may be less than this for so-called molded products. 5) Back surface Beck smoothness: JIS- 100 to 800 seconds are preferable under the conditions specified in P-8119. 6) Opacity: Transmittance of light in the visible range is 20% or less, particularly 15% under the measurement conditions of linear light incidence / diffuse light transmission conditions. 7) Whiteness: Hunter whiteness as defined in JIS-P-8123, preferably 90% or more. Further, when measured by JIS-Z-8722 (non-fluorescent) and JIS-Z-8717 (containing fluorescent agent) and displayed by the color display method defined in JIS-Z-8730, L ^* = 90 to 98, a ^* = − 5 to +5, b ^* = − 10 to +5 are preferable.

An undercoat layer is preferably provided on the porous layer side of the support for the purpose of improving the adhesion with the porous layer. The binder for the undercoat layer is preferably a hydrophilic polymer such as gelatin or polyvinyl alcohol, or a latex polymer having a Tg of −30 to 60 ° C. These binders are used in the range of 0.001 to ² g per 1 m ^{2 of} recording paper. In the undercoat layer, a small amount of a conventionally known antistatic agent such as a cationic polymer can be contained for the purpose of antistatic.

  A back layer may be provided on the surface of the support opposite to the porous layer side for the purpose of improving slipperiness and charging characteristics. The binder for the back layer is preferably a hydrophilic polymer such as gelatin or polyvinyl alcohol, a latex polymer having a Tg of −30 to 60 ° C., an antistatic agent such as a cationic polymer, various surfactants, and an average. A matting agent having a particle size of about 0.5 to 20 μm can also be added. The thickness of the back layer is generally 0.1 to 1 μm, but in the case where the back layer is provided for preventing curling, it is generally in the range of 1 to 20 μm. The back layer may be composed of two or more layers.

  In coating the undercoat layer and the back layer, it is preferable to use a surface treatment such as corona treatment or plasma treatment on the surface of the support in combination.

  Various additives can be added to the water-soluble coating liquid for forming the porous layer. Such additives include, for example, cationic mordants, crosslinking agents, surfactants (cations, nonions, anions, amphoterics), white color tone modifiers, fluorescent whitening agents, antifungal agents, viscosity modifiers, low boiling points. Organic solvents, high-boiling organic solvents, latex emulsions, anti-fading agents, UV absorbers, polyvalent metal compounds (water-soluble or water-insoluble), matting agents, silicone oils, etc., among which cationic mordants are used after printing It is preferable in order to improve the water resistance and moisture resistance.

  As the cationic mordant, a polymer mordant having a primary to tertiary amino group and a quaternary ammonium base is used, but there is little discoloration or deterioration of light resistance over time, and the dye mordant has a sufficiently high mordant ability. Therefore, a polymer mordant having a quaternary ammonium base is preferable.

  A preferred polymer mordant is obtained as a homopolymer of a monomer having the quaternary ammonium base, a copolymer with another monomer, or a condensation polymer.

Examples of the polyvalent metal compound include sulfates such as Mg ²⁺ , Ca ²⁺ , Zn ²⁺ , Zr ²⁺ , Ni ²⁺ , and Al ³⁺ , chlorides, nitrates, and acetates. In addition, inorganic polymer compounds such as basic polyaluminum hydroxide and zirconyl acetate are also included as examples of preferable water-soluble polyvalent metal compounds. Many of these water-soluble compounds generally have a function of improving light resistance and improving bleeding and water resistance. These water-soluble polyvalent metal ions are generally used in a range of 0.05 to 20 mmol, preferably 0.1 to 10 mmol, per 1 m ^{2 of} recording paper.

  The coating method of the coating solution can be appropriately selected from known methods, for example, gravure coating method, roll coating method, rod bar coating method, air knife coating method, spray coating method, extrusion coating method, curtain coating. The extrusion coating method using a hopper described in the method or US Pat. No. 2,681,294 is preferably used.

  The porous layer according to the recording paper of the present invention may be a single layer or a multilayer, and in the case of a multilayer structure, it is preferable to apply all the layers simultaneously from the viewpoint of reducing the manufacturing cost.

As the ultraviolet light source used in the present invention, for example, a low pressure, medium pressure, high pressure mercury lamp, metal halide lamp or the like having an operating pressure from several mmHg to 10 atm is used. From the viewpoint of wavelength distribution of the light source, high pressure mercury lamps and metal halide lamps are used. Preferably, a metal halide lamp is more preferable. Moreover, it is preferable to provide a filter that cuts light having a wavelength of 300 nm or less. As the output of the lamp 400W～30kW, as the illuminance ^{10mW / cm 2 ~1kW / cm 2} , preferably from 0.1mJ / cm ² ~150mJ / cm ² as irradiation ^{energy, 1mJ / cm 2 ~50mJ / cm} 2 is More preferred.

When the light source wavelength includes ultraviolet rays of 300 nm or less, or when the irradiation energy exceeds 150 mJ / cm ² , there is a possibility that the mother nucleus of the hydrophilic polymer compound or various coexisting additives may be decomposed by ultraviolet rays. Not only the effect of the present invention cannot be obtained, but also problems such as odor derived from the decomposition products may occur, which is not preferable. When the irradiation energy is less than 0.1 mJ / cm ² , the crosslinking efficiency is insufficient, and the effects of the present invention cannot be obtained sufficiently.

The illuminance upon ultraviolet irradiation is preferably 0.1 mW / cm ² or more and 1 W / cm ² or less. When the illuminance exceeds 1 W / cm ² , the surface curability of the coating is improved, but the deep curability is lowered and a film having only a hard surface is obtained. In that case, the balance of the hardness in the depth direction of the film is lost, and curling or the like occurs, which is not preferable.

When the illuminance is lower than 0.1 mW / cm ^{2, the} crosslinking does not proceed sufficiently due to scattering in the film and the effect of the present invention cannot be obtained, which is not preferable.

When giving the same integrated light quantity (mJ / cm ² ), the preferable range of illuminance is due to the change in the light transmittance. When the concentration distribution of the generated cross-linking reactive species is different due to the transmittance of ultraviolet rays, and the ultraviolet illuminance is high, a high concentration of cross-linking reactive species is generated on the surface layer, and a hard and dense film is formed on the surface of the coating film.

  When the illuminance is in a preferable range, the degree of cross-linking of the surface layer is low and light permeability in the deep direction is high, so that gentle cross-linking is uniformly formed in the deep direction.

  If the illuminance is too low, it takes a long time to give the necessary integrated illuminance, which is not only disadvantageous in terms of equipment introduction, but also because the amount of absolute light due to scattering of ultraviolet rays by the coating film is insufficient. Absent.

  In the present invention, it is also preferable to add a photoinitiator or a sensitizer. These compounds may be dissolved or dispersed in a solvent, or may be chemically bonded to the photosensitive resin.

  There is no restriction | limiting in particular about the photoinitiator and photosensitizer which are applied, A conventionally well-known thing can be used.

  Although there is no restriction | limiting in particular about the photoinitiator and photosensitizer which are applied, A water-soluble thing is preferable from a viewpoint of mixing property and reaction efficiency. In particular, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone (HMPK), thioxanthone ammonium salt (QTX), and benzophenone ammonium salt (ABQ) are preferable from the viewpoint of miscibility with an aqueous solvent. Further, as an example, benzophenones such as benzophenone, hydroxybenzophenone, bis-N, N-dimethylaminobenzophenone, bis-N, N-diethylaminobenzophenone, 4-methoxy-4'-dimethylaminobenzophenone. Thioxanthones such as thioxatone, 2,4-diethylthioxanthone, isopropylthioxanthone, chlorothioxanthone, and isopropoxychlorothioxanthone. Anthraquinones such as ethyl anthraquinone, benzanthraquinone, aminoanthraquinone and chloroanthraquinone. Acetophenones. Benzoin ethers such as benzoin methyl ether. 2,4,6-trihalomethyltriazines, 1-hydroxycyclohexyl phenyl ketone, 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 2- (o-chlorophenyl) -4,5-di ( m-methoxyphenyl) imidazole dimer, 2- (o-fluorophenyl) -4,5-phenylimidazole dimer, 2- (o-methoxyphenyl) -4,5-phenylimidazole dimer, 2- (P-methoxyphenyl) -4,5-diphenylimidazole dimer, 2-di (p-methoxyphenyl) -5-phenylimidazole dimer, 2- (2,4-dimethoxyphenyl) -4,5- Diphenylimidazole dimer 2,4,5-triarylimidazole dimer, benzyldimethyl ketal, 2-benzyl-2-dimethyl Mino-1- (4-morpholinophenyl) -butan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-1-propanone, 2-hydroxy-2-methyl-1- Phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, phenanthrenequinone, 9,10-phenanthrenequinone Benzoins such as methylbenzoin and ethylbenzoin, 9-phenylacridine, acridine derivatives such as 1,7-bis (9,9′-acridinyl) heptane, bisacylphosphine oxide, and mixtures thereof are preferably used. The above may be used alone or in combination.

  In addition to these initiators, accelerators and the like can also be added. Examples of these include ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, ethanolamine, diethanolamine, triethanolamine and the like.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. In the examples, “%” represents mass% unless otherwise specified.

Example 1
<< Preparation of Silica Dispersion S-1 >>
Silica dispersion B1 (pH 2.6, ethanol 0.2%) containing 30% of vapor phase silica (Nippon Aerosil Co., Ltd .; Aerosil 300) having an average primary particle size of about 0.007 μm, which is uniformly dispersed in advance. 5%) and an aqueous solution C-1 (pH 2.5, manufactured by San Nopco, defoamer SN-) containing 1200 g of the cationic polymer dispersant P-1, 12% of n-propanol, and 2% of ethanol. 381 (containing 60 g) was added with stirring at 3000 rpm at room temperature.

Subsequently, it disperse | distributed by the pressure of 3000 N / cm < ² > with the high pressure homogenizer by Sanwa Kogyo Co., Ltd., the whole quantity was finished with the pure water, and the substantially transparent silica dispersion liquid S-1 with a silica content of 25% was obtained.

<< Preparation of Oil Dispersion (B-1) >>
Liquid A and liquid B shown below are dissolved by heating, liquid A and liquid B are mixed at 55 ° C., then emulsified and dispersed with a high-pressure homogenizer, and the total amount is made up to 50 L with pure water, and oil dispersion (B-1 ) Was prepared.

(Liquid A) Compound (a-1) 5 kg
Di-isodecyl-phthalate 7kg
7 kg of ethyl acetate
(Liquid B) Acid-treated gelatin 1kg
22kg of pure water
Cationic polymer (P-1) 20% aqueous solution 4kg
Saponin 20% aqueous solution 3kg
<< Preparation of recording paper 1 >>
UV-crosslinked polyvinyl alcohol derivative aqueous solution (compound-1: polymerization degree of main chain PVA 3000, Slowly add 960 g of saponification degree 88%, crosslinking group modification rate 1 mol%) and 1.94 g of photoinitiator (Irgacure 2959 made by Ciba Specialty Chemicals), then add 208 g of oil dispersion (B-1). And it finished to 6000g with pure water, and obtained coating liquid T-1.

  The obtained coating liquid T-1 was filtered using a TCP-10 type filter manufactured by Advantex Toyo.

Subsequently, the coating liquid T-1 prepared above was coated with polyethylene on both sides of a base paper having a thickness of 170 g / m ² (containing 8% by mass of anatase-type titanium oxide in polyethylene on the porous layer side; porous) gelatin subbing layer of 0.05 g / m ² on the quality layer side, the Tg has the latex polymer of from about 80 ° C. as a back layer 0.2 g / m ²⁾ on the opposite side, 18 g / m in weight per silica ² so as to be applied, then a metal halide lamp having a dominant wavelength 365 nm, using an ultraviolet illuminance is 60 mW / cm ² at a wavelength of 365 nm, the amount of energy in the hot air of 30 mJ / cm irradiated then 80 ° C. the ² UV And dried to obtain inkjet recording paper 1.

<< Preparation of recording sheets 2-7 >>
Inkjet recording papers 2 to 7 were obtained in the same manner except that the compounds shown in Table 1 were used instead of the compound (a-1) in the preparation of the oil dispersion (B-1) during the production of the recording paper 1. It was.

  In the recording material 6, 5 kg of the compound (a-4) and 5 kg of the compound (a-5) were used, and 2 kg of di-isodecyl-phthalate was used. Further, the recording material 7 was not added with an oil dispersion.

<< Preparation of recording paper 8 >>
In the preparation of the coating liquid T-1 during the production of the recording paper 1, 1200 g of an 8% aqueous solution of polyvinyl alcohol having a polymerization degree of 3000 and a saponification degree of 88% was used in place of the ultraviolet crosslinking polyvinyl alcohol derivative aqueous solution. A coating solution T-2 was prepared in the same manner except that 5 g was added.

<< Preparation of recording sheets 9-14 >>
Similarly, instead of the recording paper 1, the preparation of the coating liquid T-1 for the recording paper 2-7 was changed to the method for the recording paper 8, and recording papers 9-14 were produced.

  Incidentally, the recording papers 8 to 14 were not irradiated with ultraviolet rays, and only hot air drying at 80 ° C. was performed.

  The recording paper obtained as described above was further stabilized by storing at 40 ° C. for 3 days.

<Characteristic evaluation of recording paper>
Each recording sheet produced as described above was evaluated by the following method, and the results are shown in Table 1.

(crack)
The presence or absence of cracks generated on the surface of the recording paper and the size thereof were visually observed and evaluated according to the following criteria.
[Standard]
A: No cracks were observed on the surface. B: Cracks having a length of 1 to 2 mm were observed. C: Cracks having a length of 3 mm or more were observed.

(Breaking)
The recording paper cut into 5 mm × 10 cm strips was placed on a paper tube with a core inner diameter of 3 cm, and the cracks of the cracks were visually evaluated in five stages.

A: No breaks B: 6 to less than 20 breaks C: 20 or more breaks In the above evaluation rank, C has no commercial value in practical use.

(Light resistance)
Using an inkjet printer (“PM-900C” manufactured by Seiko Epson Corporation), a solid magenta and cyan image is printed on each inkjet recording sheet, and then passed through a filter that cuts out ultraviolet rays in a wavelength region of 365 nm or less. , “Xenon Weather-ometer Ci65A” (manufactured by ATLAS) was turned on for 3.8 hours under an environmental condition of a temperature of 25 ° C. and a relative humidity of 32%. A cycle of standing for 1 hour under environmental conditions of 91 ° C. and a relative humidity of 91% was performed over 168 hours. Each color image density before and after this test was measured with a reflection densitometer (“Xrite 938” manufactured by Xrite), and the residual ratio of each color density was calculated.

AA: Almost no fading and very good. (Magenta remaining rate: 90% or more)
A: The fading level was small and good. (Magenta remaining rate: more than 70% to less than 90%)
B: Although fading was recognized, it was a level with no practical problem. (Magenta remaining rate: 50-70%)
C: Fading was remarkable, and it was a level causing a problem in practical use.

  From Table 1, it can be seen that the sample of the present invention is an inkjet recording paper that does not have defects such as cracks during production, is excellent in handleability such as cracks, and forms a print excellent in light resistance.

Example 2
<< Preparation of recording sheets 15-20 >>
The recording material 1 photoinitiator (Irgacure 2959, manufactured by Ciba Specialty Chemicals) was changed from 1.94 g to 0.243 g, 0.323 g, 0.485 g, 9.7 g, 19.4 g, and 38.8 g, respectively. Sheets 15 to 20 were produced. The same evaluation as in Example 1 was performed and the results are shown in Table 2.

  From Table 2, it can be seen that the molar ratio of the piperazine ring unit and the photoinitiator in the compound represented by the general formula (1) of the present invention is excellent in the range of 60 to 1.

Example 3
<< Preparation of recording paper 21 >>
The recording paper 21 was prepared by overcoating the ethyl acetate solution of the compound (a-1) to the amount shown in Table 3 after preparing the recording paper 7. The same evaluation as in Example 1 was performed and the results are shown in Table 3.

  From Table 3, since coating is performed again after coating and drying, the effect of suppressing cracking generated during drying cannot be obtained, but a very large light resistance improvement effect can be obtained. Although the detailed mechanism is unknown, it is because the compound is not consumed by the reaction with the photoinitiator radical, or because it exists near the interface with the air inside the void structure, and it is localized and the position of the colorant is close It is estimated to be.

Claims (6)

On the support,
(A) a binder containing a polymer compound crosslinked by a photoinitiator between side chains by irradiating a hydrophilic polymer compound having a plurality of side chains in the main chain with a degree of polymerization of 300 or more with ultraviolet rays; (B) a compound represented by the following general formula (1);
(C) An ink jet recording paper comprising a porous layer containing inorganic fine particles.

[Wherein R ₁ , R ₂ , R ₄ , R ₅ represent an alkyl group or a carbonyl group, and R ₃ represents a hydrogen atom, an alkyl group, an alkoxy group, an aryloxy group, an oxy radical group, a hydroxyl group, by hydrolysis. It represents a group which forms an imino group or hydroxy Louis amino group, R _6, R ₆ 'represents any substituent. ] R ₁ , R ₂ , R ₄ and R _{5 in the} general formula (1) are methyl groups, R ₆ is an —OCO—R ₇ group or —NHCO—R ₈ group, and R ₆ ′ is a hydrogen atom. The inkjet recording paper according to claim 1. Here, R ₇ and R ₈ represent an arbitrary substituent. The inkjet recording paper according to claim 2, wherein R _{3 in the} general formula (1) is a hydrogen atom. The inkjet recording paper according to any one of claims 1 to 3, wherein a vapor phase silica having a primary particle size of 20 nm or less is used as the inorganic fine particles. The coating liquid contains a photoinitiator and a compound represented by the general formula (1), and the molar ratio of the piperazine ring unit to the photoinitiator in the compound represented by the general formula (1) is 60 to 1. The inkjet recording paper according to any one of claims 1 to 4, wherein the inkjet recording paper is produced by irradiating ultraviolet rays after coating the coating liquid. After coating the coating liquid containing a photoinitiator, irradiating with ultraviolet rays and drying, the molar ratio of the piperazine ring unit and the photoinitiator in the compound represented by the general formula (1) The inkjet recording paper according to any one of claims 1 to 5, wherein the inkjet recording paper is produced by overcoating the compound represented by the general formula (1) so as to be in a range of 60 to 1.