JP2005144677A - Inkjet recording paper and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a void type inkjet recording paper having excellent discoloring and fading resistance and improved productivity and coating stability, and a production method for the same. <P>SOLUTION: The inkjet recording paper, which has on a support a surface layer containing a hydrophilic binder containing organic fine particles A or B and a polymer compound cross-linked or polymerized by the ionizing radiation and a porous layer, is produced by irradiating the ionizing radiation on the surface layer coating liquid and applying simultaneous multilevel coating to the surface layer and the porous layer. The organic fine particles A are organic fine particles insoluble in a water which is soluble or swollen in a water soluble organic solvent having an SP value of 18.414 to 30.69 (MPa)<SP>1/2</SP>and a boiling point of not lower than 120°C. The organic fine particles B have a polymer containing 5 mass % or more of a repetition unit as a copolymerizable component represented by formula (1), and has a mean particle diameter of 100 nm or less under each glass transfer temperature (Tg) of 70 °C or higher. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink jet recording paper (hereinafter also simply referred to as a recording paper) and a method for producing the same, and more particularly to an ink jet recording paper having excellent ink absorbability and little image deterioration due to harmful gases and a method for producing the same.

  Inkjet recording is a method in which minute ink droplets are ejected by various operating principles and adhered to recording paper such as paper to record images, characters, etc., but with relatively high speed, low noise, and multiple colors. It has advantages such as being easy to make. The clogging and maintenance of the nozzles, which has been a problem in the inkjet recording method, has been improved from both sides of the ink and the device, and is now rapidly spreading to various fields such as various printers, facsimiles, and computer terminals. ing. In particular, since the image quality of printers has recently improved and has reached photographic quality, photographic quality has been achieved on recording paper, and the texture of silver halide photography (glossiness, smoothness, stiffness, etc.) has been reproduced. It is requested to do. As one of the methods for reproducing the texture of a silver salt photograph, a so-called swelling type ink jet recording paper is known in which a hydrophilic binder such as gelatin or polyvinyl alcohol is coated on a support as a recording paper. However, there are disadvantages such as a slow ink absorption speed, a sticky surface after printing, and an image that tends to bleed due to the influence of humidity during storage. In particular, since the ink absorption speed is slow, the ink droplets mix before being absorbed, tend to cause bleeding (bleeding) between different colors and uneven color (beading) within the same color, Achievement is very difficult.

  Instead of the above-mentioned swelling type ink jet recording paper, what is now becoming the mainstream is the so-called gap type ink jet recording paper, which is characterized by its high absorption speed because it absorbs ink in fine gaps. Examples of recording papers that simultaneously achieve silver salt photographic image quality and silver salt photographic texture are disclosed in JP-A-10-119423, JP-A-10-119424, JP-A-10-175364, JP-A-10-19376, 10-193676, 10-217601, 11-20300, 11-106694, 11-321079, 11-348410, 10-178126, 11-348409, JP 2000-27093, 2000-94830, 2000-158807, 2000-211121, and the like.

  On the other hand, in addition to image quality and texture, demands for durability and image storability have become higher, and many attempts have been made to reach the silver salt photography level in terms of light resistance, discoloration resistance, moisture resistance, water resistance, and the like. Examples of the improvement in light resistance include JP-A-57-74192, JP-A-57-87989, JP-A-57-74193, JP-A-58-152072, JP-A-1-95091, JP-A-1-95091 and JP-A-1-95091. No. 115677, No. 3-13376, No. 4-7189, No. 7-195824, No. 8-25796, No. 11-321090, No. 11-277893, and JP 2000-37951 A A number of techniques have been disclosed.

In the case of void type ink jet recording paper, there is a problem that not only light resistance but also discoloration due to harmful gas is likely to occur due to the void structure. In particular, it tends to occur with phthalocyanine-based aqueous dyes used in general color inkjet printers. Although the mechanism of this discoloration has not yet been clarified, since the fine void structure has a high surface area and the inorganic fine particles used have an active surface, ozone, oxidant, SO _x , trace amounts of active harmful gases in the air such as NO _x is inferred to be decomposed dye. With regard to techniques for improving the phenomenon of discoloration, for example, JP-A-63-252780, JP-A-64-11877, JP-A-1-108083, JP-A1-216881, JP-A-1-218882, JP-A-1-258980 No. 2-188287, No. 7-237348, No. 7-266689, No. 8-164664, etc. Because of the characteristics that are more likely to deteriorate, the conventional improvement technology is insufficient in its improvement effect, and a more drastic improvement is desired.

  As one of the countermeasures against the above problems, the improvement can be made by using the swollen type recording paper. However, it is very difficult to improve the slow ink absorption speed, which is an essential problem.

  In addition, the ink-jet recording method using pigment ink can solve a certain degree of discoloration color problem, but the characteristics such as glare (bronzing) on the recording paper have not reached a level that gives sufficient image quality. Currently. As another method, a gas barrier method such as laminating the print or putting it in a frame, or after printing on a recording paper containing thermoplastic fine particles on the surface, the gas barrier layer is heated or pressurized. Is disclosed (for example, see Patent Documents 1 to 5). Certainly, according to the proposed method, it is very effective for resistance to discoloration, but both require post-processing and load individual processes. In particular, in large-format ink jet recording with a width of 60 cm or more, not only laminating and heat roll processing are troublesome, but the dedicated equipment is also large-sized, expensive, and generally not widely used.

  In addition, an ink jet recording paper having a void layer having organic fine particles and inorganic fine particles is disclosed (for example, see Patent Document 6). However, since these organic fine particles are dissolved only in a special solvent and not in an organic solvent used in general ink for ink jet printers, they cannot be used for normal ink jet recording. is there.

  The inventors of the present invention have previously found out that it is very effective in preventing discoloration by containing specific organic fine particles in the coating layer of the recording paper. In particular, it is effective to contain the organic fine particles in the surface layer at a high concentration. These specific organic fine particles are dissolved or swollen by an organic solvent contained in the ink of the ink jet printer, and form a surface layer of the ink landing portion. As a result, harmful gases are blocked and discoloration can be prevented.

In order to provide the surface layer on the porous layer, it is advantageous in terms of productivity to apply the porous layer and the surface layer in a simultaneous multi-layer, but the surface layer coating solution is more advantageous than the porous layer coating solution. If the viscosity is low and simultaneous layering, both liquids are mixed at the interface between the porous layer and the surface layer, resulting in a problem that the surface of the finished coating film is disturbed. Moreover, since the viscosity of the surface layer is low, there is also a problem that unevenness is likely to occur due to hot air for drying during drying.
JP 59-222381 A Japanese Patent Laid-Open No. 62-271781 JP 11-157207 A JP-A-11-245507 JP 2000-71608 A Japanese Unexamined Patent Publication No. 63-60784

  The present invention has been made in view of the above-mentioned problems, and its object is a void-type that has excellent resistance to discoloration, enables simultaneous multilayer coating of a porous layer and a surface layer, and has improved productivity and coating stability. An inkjet recording sheet and a method for manufacturing the inkjet recording sheet are provided.

The above object of the present invention is achieved by the following configurations.
(Claim 1)
An ink jet having a surface layer containing organic fine particles A or organic fine particles B defined below, and a hydrophilic binder containing a polymer compound crosslinked or polymerized by ionizing radiation, and one or more porous layers on a support. An ink jet recording paper produced by irradiating the surface layer coating solution with ionizing radiation and then simultaneously coating the porous layer with the porous layer.

Organic fine particles A: Organic fine particles insoluble in water that have an SP value of 18.414 to 30.69 (MPa) ^1/2 and a boiling point of 120 ° C. or higher and are dissolved or swelled by a water-soluble organic solvent, and have a glass transition temperature ( Organic fine particles having a Tg) of 70 ° C. or more and an average particle diameter of 100 nm or less.

  Organic fine particles B: a polymer containing 5% by mass or more of a repeating unit represented by the following general formula (1) as a copolymerization component, a glass transition temperature (Tg) of 70 ° C. or higher, and an average particle size of 100 nm The following organic fine particles.

[Wherein, X represents —O— or —N (R ₂ ) —, R ₁ represents a hydrogen atom or a methyl group, R ₂ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, Is —O—, J is an alkylene group having 2 to 8 carbon atoms which may have an ether structure or a thioether structure, Y represents a hydroxyl group, an alkoxyl group or a carbamoyl group, and X represents In the case of —N (R ₂ ) —, J is a single bond or an alkylene group having 2 to 8 carbon atoms, which may have an ether structure or a thioether structure, and Y is a hydrogen atom, a hydroxyl group, an amino group Represents a group, an alkoxyl group or a carbamoyl group. ]
(Claim 2)
2. The ink jet recording paper according to claim 1, wherein the polymer compound crosslinked or polymerized by ionizing radiation is an ultraviolet dimerization polymer compound or an electron beam curable polymer compound.
(Claim 3)
The high molecular compound that is crosslinked or polymerized by ionizing radiation is an ultraviolet-crosslinked modified polyvinyl alcohol having a degree of polymerization of 300 or more and an ionizing radiation reaction modification rate of 4 mol% or less. 2. Inkjet recording paper described in 1.
(Claim 4)
Inkjet having organic fine particle A or organic fine particle B as defined above and a surface layer containing a hydrophilic binder containing a polymer compound crosslinked or polymerized by ionizing radiation and one or more porous layers on a support A method for producing an ink jet recording paper, characterized in that the surface layer coating solution is irradiated with ionizing radiation and then simultaneously coated with the porous layer to produce the recording paper.
(Claim 5)
5. The method for producing an ink jet recording paper according to claim 4, wherein the polymer compound crosslinked or polymerized by ionizing radiation is an ultraviolet dimerization polymer compound or an electron beam curable polymer compound.
(Claim 6)
5. The polymer compound that is crosslinked or polymerized by ionizing radiation is an ultraviolet-crosslinked modified polyvinyl alcohol having a degree of polymerization of 300 or more and an ionizing radiation reaction modification rate of 4 mol% or less. A method for producing an inkjet recording paper as described in 1 above.

  According to the present invention, there are provided a void-type ink jet recording paper having excellent resistance to discoloration, simultaneous multi-layer coating of a porous layer and a surface layer, and improved productivity and coating stability, and a method for producing the ink jet recording paper can do.

  Hereinafter, the best mode for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

  As a result of diligent investigations in view of the above-mentioned object, the present inventor contains a hydrophilic binder containing organic fine particles A or organic fine particles B as defined above on a support and a polymer compound that is crosslinked or polymerized by ionizing radiation. In an inkjet recording paper having a surface layer and one or more porous layers, it is excellent in resistance to discoloration due to harmful gases, etc. by simultaneously applying multilayer coating with the porous layer after irradiating the surface coating liquid with ionizing radiation In addition, the present inventors have found that an ink jet recording sheet with improved productivity can be realized and have reached the present invention.

  With respect to the mechanism for achieving the object effect of the present invention by the configuration defined in the present invention, all are not clarified at present, but are presumed as follows.

  By irradiating the surface layer coating liquid containing the organic fine particles A or the organic fine particles B defined in the present invention and a hydrophilic binder containing a polymer compound cross-linked or polymerized by ionizing radiation in advance before application, By making the surface coating solution highly viscous, even when simultaneously layered with a highly viscous porous layer, liquid mixing at the interface does not occur, and a good film surface is obtained without being blown by drying air and causing unevenness. It is what Further, by simultaneously applying the surface layer and one or more porous layers, productivity is remarkably improved with a decrease in the number of times of application, leading to a reduction in production cost.

  The layer located in the lower part of the surface layer is a void-type ink absorbing layer having a porous structure, so that the ink absorption is excellent, and the surface layer containing the organic fine particles A or the organic fine particles B as defined above allows the harmful gas to be absorbed. By forming the blocking layer, high discoloration resistance can be achieved.

  Details of the present invention will be described below.

  First, the details of the organic fine particles A and the organic fine particles B according to the present invention will be described.

The organic fine particle A according to the present invention is an organic fine particle insoluble in water that has an SP value of 18.414 to 30.69 (MPa) ^1/2 and is dissolved or swelled by a water-soluble organic solvent having a boiling point of 120 ° C. or higher. Thus, it is defined as organic fine particles having a glass transition temperature (Tg) of 70 ° C. or more and an average particle diameter of 100 nm or less. The SP (Solubility Parameter) value referred to in the present invention is a solubility parameter and is one useful measure for predicting the solubility of a substance. The unit of SP value is represented by (MPa) ^1/2 and refers to the value at 25 ° C. The SP value of the organic solvent is described in, for example, “POLYMER HANDBOOK” (J. Brandrup et al., A Wiley-interscience Publication), page IV-337, and various publications.

  Examples of water-soluble organic solvents that can be used in the present invention (representing typical SP values in parentheses) include alcohols (eg, butanol (23.3), isobutanol (21.5) secondary butanol). (22.1), tertiary butanol (21.7), pentanol, hexanol, cyclohexanol (23.3), benzyl alcohol (24.8), etc.), polyhydric alcohols (for example, ethylene glycol (29. 9), diethylene glycol (24.8), triethylene glycol (21.9), polyethylene glycol, propylene glycol (25.8), dipropylene glycol (20.5), polypropylene glycol, butylene glycol, hexanediol (21. 1), pentanediol, glycerin (33.8) Hexanetriol, thiodiglycol, etc.), alkyl ales of polyhydric alcohol (for example, ethylene glycol monomethyl ether (23.3), ethylene glycol monoethyl ether (21.5), ethylene glycol monobutyl ether, ethylene glycol dimethyl ether (17 .6), diethylene glycol monomethyl ether (23.3), diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol monoethyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, triethylene Glycol diethyl ether, triethylene glycol Dimethyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol monobutyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, etc.), amines (eg, ethanolamine, diethanolamine, triethanolamine, N- Methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine (25.2), diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides ( For example, formamide, N, N-dimethylformamide, N , N-dimethylacetamide, etc.), heterocyclic rings (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), sulfoxides ( For example, dimethyl sulfoxide etc.), sulfones (for example, sulfolane etc.) etc. are mentioned.

  In the present invention, particularly preferred water-soluble organic solvents are polyhydric alcohols, alkyl ethers of polyhydric alcohols, and heterocyclic rings, and it is preferable to select 2 to 3 kinds thereof.

  Examples of the water-soluble organic solvent having an SP value in the range of 18.414 to 30.69 according to the present invention include ethylene glycol, diethylene glycol, triethylene glycol, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, triethanolamine, and 2-pyrrolidone. Are preferably used, but diethylene glycol monobutyl ether (SP value 19.437, boiling point 230 ° C.) is particularly preferably used.

  As the water-soluble organic solvent according to the present invention, one having a boiling point of 120 ° C. or higher is selected. The upper limit of the boiling point is not particularly limited, but those having a melting point of 30 ° C. or lower are preferable.

The organic fine particles A according to the present invention have an SP value of 18.414 to 30.69 (MPa) ^1/2 and have a boiling point of 120 ° C. or higher and dissolve or swell in the water-soluble organic fine particles. And having a glass transition temperature (Tg) of 70 ° C. or higher and an average particle diameter of 100 nm or less, a polymer having a weight average molecular weight of 5,000 or more is preferable. Polyvinyl chloride, polyvinylidene chloride, polyacrylate, polymethacrylate, elastomer, ethylene-vinyl acetate copolymer, styrene- (meth) acrylic copolymer, polyester, polyvinyl ether, polyvinyl acetal, polyamide, polyurethane, polyolefin, SBR, NBR, polytetrafluoroethylene, chloroprene, protein, polysaccharide , Rosin ester, shellac resin, and the like. Particularly preferred materials for the organic fine particles A are polyvinyl acetal resins, polyurethane resins, rosin ester resins, (meth) acrylate resins, SBR, and the like, and resins comprising two or more monomers by modification or copolymerization. Are preferably used, and those obtained by adding a specific modifying group to the resin or excluding the leaving group may be used, or two or more kinds of materials may be mixed to form organic fine particles. You may mix and use the above organic fine particles.

  In the present invention, “dissolved by an organic solvent” means that the organic fine particles A and the water-soluble organic solvent in the ink form a single phase in an equilibrium state, and “swells by the organic solvent” means the organic fine particles. It means that A increases the volume by absorbing the water-soluble organic solvent. The preferred volume increase rate when swollen is 2 to 8 times.

  The organic fine particles A according to the present invention must be insoluble in water in order to not dissolve in ink jet recording. However, it is allowed to absorb water as long as the ink absorption speed is not hindered. Water up to 20% by mass of the organic fine particles A may be absorbed. Further, the organic fine particles A according to the present invention need only be contained in such an amount that the organic fine particle A-containing layer is softened after printing, but is preferably 50% or more by mass ratio with respect to the solid content in the layer, More preferably, it is 75% or more.

  Moreover, you may use a crosslinking agent for the organic fine particle A which concerns on this invention in the range which does not have trouble in the melt | dissolution with respect to a water-soluble organic solvent, or swelling. In the present invention, a conventionally known crosslinking agent can be appropriately selected and used as the crosslinking agent regardless of whether it is organic or inorganic.

  The average particle diameter of the organic fine particles A according to the present invention greatly affects the surface gloss of the recording paper. In this invention, although it is one characteristic that it is 100 nm or less, a preferable average particle diameter is 1-100 nm, More preferably, it is 5-100 nm. When the average particle diameter of the organic fine particles A is 5 to 100 nm, an effect of reducing the difference in gloss between the printed portion and the non-printed portion is preferable. The average particle size is measured by observing the cross section and surface of the organic fine particle-containing layer with an electron microscope, obtaining the particle size of a large number of arbitrary organic fine particles A, and obtaining the simple average value (number average). In addition, each particle size is represented by the diameter when a circle equal to the projected area is assumed. The shape of the organic fine particles A according to the present invention does not need to be a true sphere, and may be a needle shape or a plate shape. The particle size is obtained from the volume in terms of a sphere.

  Next, the organic fine particles B according to the present invention will be described.

  The organic fine particles B referred to in the present invention has a polymer containing 5% by mass or more of the repeating unit represented by the general formula (1) as a copolymerization component, and has a glass transition temperature (Tg) of 70 ° C. or higher. And it defines as an organic fine particle with an average particle diameter of 100 nm or less.

  Details of the repeating unit represented by the general formula (1) will be described below.

  From the viewpoint of preferably exhibiting the object effect of the present invention, the repeating unit represented by the general formula (1) is preferably hydrophilic as the organic fine particles B. Specifically, the acrylic monomer shown below is used. Body, acrylamide monomer and / or methacrylamide monomer can be obtained by polymerizing, but the present invention is not limited thereto.

  What imparts hydrophilicity to the repeating unit represented by the general formula (1) is each partial structure such as X, J and substituent Y, which forms the general formula (1). In the present invention, it is preferable that hydrophilicity is imparted by the substituent Y. In addition, as a substituent used for imparting hydrophilicity to the repeating unit represented by the general formula (1), “structure-activity relationship of drug (guideline to drug design and action mechanism)” (chemical (Regional Special Issue No. 122) Substituents having a negative hydrophobicity parameter (π) can be used, as described in the Structure-Activity Relationship Social Report, Nanedo (1980), p96-103.

  The organic fine particles B according to the present invention are required to have a specific repeating unit represented by the general formula (1) as a copolymerization component in an amount of 5% by mass or more, but may contain 10% by mass or more. preferable. Further, the organic fine particle B itself is preferably hydrophilic but not water-soluble, and therefore it is preferably adjusted to a content of 10 to less than 50% by mass.

  Hereinafter, although the specific example of the polymer which contains 5 mass% or more of repeating units represented by the said General formula (1) as a copolymerization component used as a structural component of the fine particulate B based on this invention is shown, this invention is shown. Is not limited to these.

  On the other hand, as the other monomer component of the polymer constituting the organic fine particles B, any conventionally known one having an ethylenically unsaturated group is selected. These may be a single type or a plurality of types. Examples of such monomers are alkyl esters or alkyl amides of acrylic acid or methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, i -Butyl acrylate, i-butyl methacrylate, t-butyl acrylate, t-butyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, styrene, vinyl toluene, α-methyl styrene , Vinyl acetate, acrylonitrile, methacrylonitrile, or acrylic acid, methacrylic acid, fumaric acid, itaconic acid, Rain acid or dimethylaminomethyl acrylate, diethylaminomethyl acrylate, dibutylaminomethyl acrylate, dihexylaminomethyl acrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, (t-butyl) aminoethyl acrylate, diisohexylaminoethyl acrylate, dihexyl Examples include aminopropyl acrylate and di (t-butyl) aminohexyl acrylate. Of these, styrene, methyl methacrylate, and n-butyl acrylate are preferably used.

  The organic fine particles B according to the present invention are preferably prepared as a water-based emulsion to constitute a coating liquid, and the ionicity of the emulsion particles in that case is preferably equal to the coating liquid or nonionic. Moreover, it is preferable that the ionicity of the coating liquid of the layer containing the organic fine particle B is equal to the ionicity of the coating liquid of the other layer or nonionic. Further, it is most preferable that the ionicity of all of the organic fine particles B and the coating liquid is cationic or nonionic.

  Normally, ink jet recording paper is used at room temperature, but the storage state before use is not necessarily room temperature, and particularly in a sealed car in the summer, the environment is very high. It is desirable that it can be used without any trouble even after passing through. For this reason, the glass transition temperature (Tg) of the organic fine particles B needs to be 70 ° C. or higher, preferably 80 ° C. or higher, and more preferably 90 ° C. to 120 ° C.

  When the glass transition temperature (Tg) of the organic fine particles A and B is less than 70 ° C., the organic fine particles are likely to be fused by heating, and as a result, the voids on the surface of the recording paper are reduced or reduced. In addition, the ink absorption speed is likely to decrease.

  Here, the Tg of the polymer, which is a constituent component of the organic fine particles according to the present invention, can be calculated by mass fraction from the Tg of the monomer homopolymer as a copolymerization component and the monomer composition ratio. is there. For example, Tg of a polymer having a composition of styrene (homopolymer Tg = 100 ° C. = 373 K): n-butyl acrylate (homopolymer Tg = −54 ° C. = 219 K) of 4: 1 (mass ratio) is 1 / ((1 / 373K) × 4/5 + (1 / 219K) × 1/5) = 327K (= 54 ° C.). Regarding the Tg of the monomer homopolymer, many measured values are published in POLYMER HANDBOOK (A WILEY-INTERSCIENCE PUBLICATION).

  The average particle size of the organic fine particles B needs to be 100 nm or less, preferably 60 nm or less, more preferably 20 to 40 nm. The organic fine particles B according to the present invention are conventionally known. It is preferably synthesized in water by an emulsion polymerization method or the like. The particle size can be adjusted to be in the range from about 20 nm to about 100 nm by a conventionally known method such as adjusting the type and amount of the emulsifier and the monomer component.

  In order to exhibit the effect of the present invention remarkably, the content of the organic fine particles A or B as the surface layer disposed on the surface of the ink absorbing layer is preferably 50 to 90% by mass. From the viewpoint of effectively preventing mutual fusion and further increasing the ink absorption rate, the same inorganic fine particles as those used in the ink absorbing layer described later may be contained, and the content of the inorganic fine particles is 10-50. It is preferable that it is mass%.

  The ink jet recording paper of the present invention is characterized by having a surface layer containing the organic fine particles A or the organic fine particles B, but the surface layer as used in the present invention is limited to the outermost surface layer. There is no particular limitation as long as the effect of the present invention is exhibited.

  One feature of the surface layer according to the present invention is that it contains a hydrophilic binder containing a polymer compound that is crosslinked or polymerized by ionizing radiation together with the organic fine particles A or B.

  The water-soluble polymer compound that is cross-linked or polymerized by ionizing radiation in the present invention is a water-soluble resin that undergoes a cross-linking or polymerization reaction by reacting with ionizing radiation such as ultraviolet rays and electron beams. A resin that is water-soluble before but becomes substantially water-insoluble after the reaction. Such a resin has hydrophilicity after the reaction and maintains sufficient affinity with ink.

  Examples of such resins include saponified polyvinyl acetate, polyvinyl acetal, polyethylene oxide, polyalkylene oxide, polyvinyl pyrrolidone, polyacrylamide, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, or derivatives of the above hydrophilic resins, and these It is at least one selected from the group consisting of copolymers, or a hydrophilic resin modified with a modifying group such as a photodimerization type, a photodecomposition type, a photopolymerization type, a photomodification type, or a photodepolymerization type It is. Among these, a resin modified with a photodimerization type or photopolymerization type modification group is preferable from the viewpoint of sensitivity or stability of the resin itself. As the photodimerization-type modifying group, those having a diazo group, a cinnamoyl group, a styrylpyridinium group, or a stilquinolium group introduced are preferable, and a resin dyed with a water-soluble dye such as an anionic dye after photodimerization is preferable. Examples of such a resin include resins having a cationic group such as a primary amino group or a quaternary ammonium group, such as JP-A-62-283339, JP-A-1-198615, JP-A-60-252341, Photosensitive resins (compositions) described in JP-A-56-67309, JP-A-60-129742, etc., resins that become cationic after curing, such as azide groups that become amino groups by curing treatment, For example, photosensitive resins (compositions) described in JP-A-56-67309 and the like can be mentioned.

  The photosensitive resin described in JP-A-56-67309 contains a polyvinyl alcohol structure,

2-azido-5-nitrophenylcarbonyloxyethylene structure represented by:

It is a resin composition which has 4-azido-3-nitrophenyl carbonyloxyethylene structure represented by these.

  Specific examples of the photosensitive resin are described in Examples 1 and 2 in the official gazette, and the constituent components and usage ratio of the photosensitive resin are described on page 2 of the official gazette.

  JP-A-60-129742 discloses a polyvinyl alcohol structure as a photosensitive resin.

The resin composition which has the following structure is mentioned.

  In the present invention, among the hydrophilic polymer compounds that are cross-linked by ionizing radiation, the photopolymerizable modifying group is represented by, for example, the general formula (1) disclosed in JP-A No. 2000-181062. A saponified polyvinyl acetate having a structural unit is preferred from the viewpoint of reactivity.

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

  The photopolymerization initiator and the photosensitizer to be applied are not particularly limited, and conventionally known ones can be used. For example, benzophenones (for example, benzophenone, hydroxybenzophenone, bis-N, N-dimethylaminobenzophenone, Bis-N, N-diethylaminobenzophenone, 4-methoxy-4'-dimethylaminobenzophenone, etc.), thioxanthones (for example, thioxatone, 2,4-diethylthioxanthone, isopropylthioxanthone, chlorothioxanthone, isopropoxychlorothioxanthone, etc.), anthraquinone (For example, ethyl anthraquinone, benzanthraquinone, aminoanthraquinone, chloroanthraquinone, etc.), acetophenones, benzoin ethers such as benzoin methyl ether, 2,4,6- Rehalomethyltriazines, 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-dimethylamino-1 (4-morpholinophenyl) -butan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-1-propanone, 2-hydroxy-2-methyl-1-phenyl-propane- 1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, phenanthrenequinone, 9,10-phenanthrenequinone, methylbenzoin, Examples include benzoins such as ethylbenzoin, 9-phenylacridine, acridine derivatives such as 1,7-bis (9,9'-acridinyl) heptane, bisacylphosphine oxide, and mixtures thereof. They can be used or mixed. In particular, water-soluble 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 4- (2-hydroxyethoxy) -phenyl- (2- Water-soluble initiators such as hydroxy-2-propyl) ketone, thioxanthone ammonium salt, and benzophenone ammonium salt are preferred from the viewpoint of excellent mixing properties and crosslinking efficiency.

  In addition to these photopolymerization 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.

  The degree of polymerization of the hydrophilic resin modified with the ionizing radiation reaction-modifying group is preferably 300 or more, more preferably 1700 or more, from the viewpoint of resistance to cracking of the dried coating film.

  The ratio of the ionizing radiation reaction-modifying group (modification rate or crosslinking group modification rate) is preferably 4 mol% or less, more preferably 2 mol% or less, from the viewpoint of resistance to cracking of the dried coating film.

  This folding resistance is related to the crosslinking density of the crosslinking by the ionizing radiation reaction-modifying group, and if the crosslinking density is too high, the cracking becomes worse. The crosslink density is related to the modification rate and the degree of polymerization of the hydrophilic resin to be modified.

  The addition amount of the polymer compound that is crosslinked or polymerized by ionizing radiation is 1/20 to 1/5 in terms of mass ratio with respect to the organic fine particles A or organic fine particles B. If the amount added is large, the ink absorbability deteriorates, and if the amount added is small, cracks deteriorate.

  Examples of the ionizing radiation in the present invention include electron beams, ultraviolet rays, α rays, β rays, γ rays, X-rays, etc., but there are dangers to the human body, easy handling, and industrial use thereof. The electron beam and the ultraviolet ray that are widely used are particularly preferable.

  Examples of the electron beam irradiation method include a scanning method, a curtain beam method, and a broad beam method. The curtain beam method is preferable from the viewpoint of processing capability. The acceleration voltage of the electron beam can be changed as appropriate depending on the specific gravity and film pressure of the coating film, but 20 to 300 kV is appropriate. The irradiation amount of the electron beam is preferably in the range of 0.1 to 20 Mrad.

As the ultraviolet light source, for example, a low pressure, medium pressure, high pressure mercury lamp, metal halide lamp or the like having an operating pressure of several hundred Pa to 1 MPa is used, but a high pressure mercury lamp or metal halide lamp is preferable from the viewpoint of wavelength distribution of the light source. 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. The output of the lamp ^{400W~30kW, 10mW / cm 2 ~10kW /} cm 2 as illuminance, preferably 0.1~500mJ / cm ² as irradiation energy, 1 to 100 mJ / cm ² is more preferable.

When the light source wavelength includes ultraviolet rays of 300 nm or less, or when the irradiation energy exceeds 500 mJ / cm ² , the base of the ionizing radiation crosslinkable resin or various coexisting additives is decomposed by ionizing radiation, and this Not only the effects of the 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 to 1} W / cm ² . When the illuminance exceeds 1 W / cm ² , the viscosity of the irradiated coating liquid surface is increased, but the thickening at the deep portion is reduced. In addition, when the illuminance is lower than 0.1 mW / cm ^{2, the} reaction does not proceed sufficiently due to scattering or the like in the coating solution, and the coating solution does not thicken, 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 depending on the transmittance of ultraviolet rays and the ultraviolet illuminance is high, high concentration cross-linking reactive species are generated on the surface of the coating liquid, and only the surface becomes a liquid with a large viscosity increase.

  In the present invention, before the simultaneous multilayer coating, the surface layer coating solution is irradiated with ionizing radiation by the above-described method. The term “before coating” as used in the present invention is defined as before the surface layer and one or more porous layer coating liquids are laminated on the support. The irradiation method of ionizing radiation can be performed by various methods. For example, the irradiation may be performed from the upper part of the adjustment pot of the coating solution, or from the side surface if it is a transparent pot. Alternatively, before the one or more porous layer coating liquids are laminated, the surface coating liquid feeding pipe to the coater may be irradiated from the side surface using a transparent material.

  In the present invention, in the surface layer according to the present invention, in addition to the polymer compound that is crosslinked or polymerized by the ionizing radiation according to the present invention, other hydrophilic binders and hydrophobic emulsions can be mixed and used.

  In order to clearly indicate the surface layer in the present invention, preferable configuration examples are listed below, but the layer configuration according to the present invention is not limited thereto.

1: A layer having a void-type ink absorbing layer on a support, and a layer containing a hydrophilic binder containing organic fine particles A or organic fine particles B and a polymer compound that is crosslinked or polymerized by ionizing radiation is the first. Structure 2 that is a surface layer: a hydrophilic ink binder having a void-type ink absorbing layer on a support, and containing an organic fine particle A or an organic fine particle B and a polymer compound that is crosslinked or polymerized by ionizing radiation. A layer provided with a thin layer for the purpose of improving the surface physical properties 3: a void-type ink absorbing layer on the support, and organic fine particles A or organic fine particles B; And a layer containing a hydrophilic binder containing a polymer compound that is cross-linked or polymerized by ionizing radiation, and a thin layer having an ultraviolet absorbing function for the purpose of cutting harmful light. 4: A void-type ink absorption layer is provided on a support, and a layer containing a hydrophilic binder containing organic fine particles A or organic fine particles B and a polymer compound that is crosslinked or polymerized by ionizing radiation is provided thereon. Furthermore, a structure in which a layer containing a matting agent is further provided thereon: 5: a void-type ink absorbing layer on a support, on which organic fine particles A or organic fine particles B, and high molecular weight that is crosslinked or polymerized by ionizing radiation The structure which provided the layer in which the hydrophilic binder containing a molecular compound was provided, and also provided the peelable layer on it.

  The most preferable configuration among the above configuration examples includes the organic fine particle A or the organic fine particle B according to the item 1 that can most effectively exert the effect of the present invention, and a hydrophilic binder containing a polymer compound that is crosslinked or polymerized by ionizing radiation. This is the case when the layer is the outermost layer.

  Next, a porous layer (also referred to as an ink absorbing layer) formed below the surface layer will be described.

  The ink jet recording paper of the present invention has one or more porous layers, so-called ink absorbing layers.

  In general, the ink absorbing layer is roughly divided into a swelling type and a void type. As the swelling type, a water-soluble binder such as gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide or the like is applied alone or in combination to form an ink absorbing layer. As the void type, a mixture of fine particles and a water-soluble binder is applied and particularly glossy is preferable. As the fine particles, alumina or silica is preferable, and those using silica having a particle size of 0.1 μm or less are particularly preferable. As the water-soluble binder, gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide or the like is preferably used alone or in combination.

  In order to adapt to continuous high-speed printing in the above-mentioned swollen type and gap type recording paper, it is suitable that the ink absorption speed of the recording paper is faster.From this point, in the present invention, the gap type recording paper is It can be particularly preferably used.

  Hereinafter, the void-type ink absorbing layer (hereinafter also referred to as void layer) will be described in more detail.

  The void layer is mainly formed by soft aggregation of a hydrophilic binder and inorganic fine particles. Conventionally, various methods for forming voids in a film are known. For example, a uniform coating solution containing two or more kinds of polymers is coated on a support, and these polymers are phase-separated from each other in the drying process. A method of forming voids by applying a coating liquid containing solid fine particles and a hydrophilic or hydrophobic resin on a support, and after drying, the inkjet recording paper is immersed in water or a liquid containing an appropriate organic solvent. , A method of creating voids by dissolving solid fine particles, a method of forming voids in a film by applying a coating liquid containing a compound having a property of foaming during film formation, and then foaming this compound in the drying process, porous A coating liquid containing porous solid fine particles and a hydrophilic binder on a support to form voids in or between the porous fine particles, a volume approximately equal to or larger than the hydrophilic binder Solid particles and or a coating solution containing a particulate oil and a hydrophilic binder is coated on a support, and a method of forming an air gap between the solid particles are known having.

  In the present invention, it is particularly preferable that the void layer is formed by containing various inorganic solid fine particles having an average particle diameter of 4 to 400 nm. If it exceeds 400 nm, the surface gloss of the coating film deteriorates, which is not preferable.

  Examples of the inorganic fine particles used for the above purpose include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide. , Zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, magnesium hydroxide, etc. A white inorganic pigment etc. can be mentioned.

  The average particle size of the inorganic fine particles is determined by observing the particles themselves or the particles appearing on the cross section or surface of the void layer with an electron microscope, measuring the particle size of 1,000 arbitrary particles, and calculating the simple average value (number average). ). Here, the particle diameter of each particle is represented by a diameter assuming a circle equal to the projected area. As the inorganic fine particles, it is preferable to use silica and solid fine particles selected from alumina or alumina hydrate.

  As silica that can be used in the present invention, silica synthesized by an ordinary wet method, colloidal silica, silica synthesized by a gas phase method, or the like is preferably used. Colloidal silica or fine particle silica synthesized by a gas phase method is preferable. Among them, fine particle silica synthesized by a gas phase method not only provides a high porosity but also a cationic polymer used for the purpose of immobilizing a dye. When added to, it is preferable because coarse aggregates are hardly formed. Alumina or alumina hydrate may be crystalline or amorphous, and any shape such as amorphous particles, spherical particles, and acicular particles can be used. The inorganic fine particles are preferably in a state where the fine particle dispersion before mixing with the cationic polymer is dispersed to the primary particles. The inorganic fine particles preferably have a particle size of 4 to 400 nm or less. For example, in the case of the above vapor phase method fine particle silica, the average particle size of primary particles of inorganic fine particles dispersed in a primary particle state (particle size in a dispersion state before coating) is preferably 100 nm or less, More preferably, it is 4-50 nm, Most preferably, it is 4-20 nm. As the silica synthesized by the vapor phase method in which the average particle diameter of primary particles is 4 to 20 nm, which is most preferably used, for example, Aerosil manufactured by Nippon Aerosil Co., Ltd. is commercially available. The vapor phase fine particle silica can be dispersed to primary particles relatively easily by being sucked and dispersed in water, for example, by a jet stream inductor mixer manufactured by Mitamura Riken Kogyo Co., Ltd.

  Examples of the hydrophilic binder that can be used in the void layer according to the present invention include polyvinyl alcohol, gelatin, polyethylene oxide, polyvinyl pyrrolidone, polyacrylic acid, polyacrylamide, polyurethane, dextran, dextrin, color ginnan (κ, ι, λ Etc.), agar, pullulan, water-soluble polyvinyl butyral, hydroxyethyl cellulose, carboxymethyl cellulose and the like. Two or more of these water-soluble binders can be used in combination.

The amount of inorganic fine particles used in the void layer largely depends on the required ink absorption capacity, the void ratio of the void layer, the type of inorganic fine particles, and the type of water-soluble binder, but in general, per 1 m ^{2 of} recording paper, Usually 5 to 30 g, preferably 10 to 25 g.

  In the ink jet recording paper of the present invention, a cationic polymer is preferably used for the purpose of preventing bleeding of an image due to storage after recording. Examples of cationic polymers include polyethyleneimine, polyallylamine, polyvinylamine, dicyandiamide polyalkylene polyamine condensate, polyalkylene polyamine dicyandiamide ammonium salt condensate, dicyandiamide formalin condensate, epichlorohydrin-dialkylamine addition polymer, diallyldimethylammonium chloride Polymer, diallyldimethylammonium chloride / SO2 copolymer, polyvinylimidazole, vinylpyrrolidone / vinylimidazole copolymer, polyvinylpyridine, polyamidine, chitosan, cationized starch, vinylbenzyltrimethylammonium chloride polymer, (2-methacryloyloxy) Ethyl) trimethylammonium chloride polymer, dimethylaminoethyl methacrylate Over preparative polymer, and the like. Examples include the cationic polymers described in Chemical Industry Times, August 15 and 25, 1998, and polymer dye fixing agents described in “Introduction to Polymer Drugs” issued by Sanyo Chemical Industries, Ltd. The addition amount of the cationic water-soluble polymer is usually 0.1 to 10 g, preferably 0.2 to 5 g, per 1 m 2 of the ink jet recording paper.

In the void layer, the total amount of voids (void volume) is preferably 20 ml or more per 1 m ^{2 of} recording paper. When the void volume is less than 20 ml / m ² , the ink absorbency is good when the amount of ink at the time of printing is small, but when the amount of ink increases, the ink is not completely absorbed and the image quality deteriorates, Problems such as delay in drying are likely to occur.

  In the void layer having ink retention ability, the void volume relative to the solid content volume is referred to as a void ratio. In the present invention, it is preferable to set the porosity to 50% or more because the voids can be efficiently formed without unnecessarily increasing the film thickness.

  As another type of void type, in addition to forming an ink absorbing layer using inorganic fine particles, a polyurethane resin emulsion, a water-soluble epoxy compound and / or an acetoacetylated polyvinyl alcohol, and an epichlorohydrin polyamide resin are used in combination. The ink absorbing layer may be formed using the applied coating liquid. The polyurethane resin emulsion in this case is preferably a polyurethane resin emulsion having a polycarbonate chain, a polycarbonate chain and a polyester chain and a particle diameter of 3.0 μm, and the polyurethane resin of the polyurethane resin emulsion is a polyol having a polycarbonate polyol, a polycarbonate polyol and a polyester polyol. And the polyurethane resin obtained by reacting the aliphatic isocyanate compound with a sulfonic acid group in the molecule, and further having an epichlorohydrin polyamide resin, a water-soluble epoxy compound and / or an acetoacetylated vinyl alcohol. preferable. In the ink absorption layer using the polyurethane resin, it is estimated that a weak aggregation of a cation and an anion is formed, and accordingly, a void having an ink solvent absorption ability is formed, so that an image can be formed.

  Various additives other than those described above can be used in the ink absorbing layer of the ink jet recording paper of the present invention and other layers provided as necessary. For example, organic latex fine particles such as polystyrene, polyacrylic acid esters, polymethacrylic acid esters, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, or a copolymer thereof, urea resin, or melamine resin , Anionic, cationic, nonionic and amphoteric surfactants, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988 and JP-A-62-261476, JP-A-57-74192, 57-87989, 60-72785, 61-146591, JP-A-1-95091 and JP-A-3-13376, etc., JP-A-59-42993, 59- Nos. 52689, 62-280069, 61-242871, and JP-A-4-2192. Optical brighteners described in No. 6 etc., pH adjusters such as sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, antifoaming agents, preservatives, thickeners, antistatic Various known additives such as an agent and a matting agent can also be contained.

  The ink absorbing layer may be composed of two or more layers. In this case, the structures of the ink absorbing layers may be the same or different from each other.

  As the support that can be used in the present invention, those conventionally known for ink jet recording paper can be used as appropriate, and may be a water-absorbing support or a non-water-absorbing support. Preferably there is. That is, in the case of the non-water-absorbing support, a larger amount of the water-soluble organic solvent in the ink remains in the recording paper than in the case of the water-absorbing support, and thus acts more effectively on the dissolution of organic fine particles. Therefore, it is estimated that the effects of the present invention can be remarkably exhibited. To be precise, it is preferable to use “a support that does not absorb the water-soluble organic solvent in the ink”, but here, even if a non-water-absorbing support is used, the effect of the present invention is remarkably exhibited. I think we can.

  Examples of the water-absorbing support that can be used in the present invention include sheets and plates having general paper, cloth, wood, and the like. In particular, paper is excellent in water absorption of the substrate itself and It is most preferable because of its excellent cost. As the paper support, the main raw materials are chemical pulps such as LBKP and NBKP, mechanical pulps such as GP, CGP, RMP, TMP, CTMP, CMP, and PGW, and wood pulp such as waste paper pulp such as DIP. It is. In addition, various fibrous materials such as synthetic pulp, synthetic fiber, and inorganic fiber can be appropriately used as a raw material as necessary. If necessary, various conventionally known additives such as sizing agents, pigments, paper strength enhancers, fixing agents, fluorescent whitening agents, wet paper strength agents, cationizing agents and the like are added to the paper support. be able to. The paper support can be produced with various paper machines such as a long net paper machine, a circular net paper machine, and a twin wire paper machine by mixing the above-mentioned fibrous material such as wood pulp and various additives. Further, if necessary, the paper can be subjected to size press treatment with starch, polyvinyl alcohol or the like, various coating treatments, or calendar treatment on a paper making stage or a paper machine. Non-water-absorbing supports that can be preferably used in the present invention include transparent supports and opaque supports. Examples of the transparent support include films having materials such as polyester resins, diacetate resins, triatesate resins, acrylic resins, polycarbonate resins, polyvinyl chloride resins, polyimide resins, cellophane, and celluloid. Among them, those having a property of resisting radiant heat when used for overhead projectors (OHP) are preferable, and polyethylene terephthalate is particularly preferable. The thickness of such a transparent support is preferably 50 to 200 μm. Further, as the opaque support, for example, resin-coated paper (so-called RC paper) having a polyolefin resin coating layer in which white pigment or the like is added to at least one of the base paper, white pigment such as barium sulfate is added to polyethylene terephthalate. A so-called white pet is preferable. For the purpose of increasing the adhesive strength between the various supports and the ink absorbing layer, the support is preferably subjected to corona discharge treatment, subbing treatment or the like prior to application of the ink absorbing layer. Furthermore, the inkjet recording paper of the present invention is not necessarily colorless, and may be a colored recording sheet.

  In the ink jet recording paper of the present invention, it is particularly preferable to use a paper support obtained by laminating both sides of a base paper support with polyethylene because the recorded image is close to photographic image quality and a high-quality image can be obtained at low cost.

  Such a paper support laminated with polyethylene will be described below.

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, any of LBKP, LBSP, NBKP, NBSP, LDP, NDP, LUKP, and NUKP can be used, but it is preferable to use more LBKP, NBSP, LBSP, NDP, and LDP with a large amount of short fibers. . However, the ratio of LBSP or LDP is preferably 10 to 70% by mass. 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 the mass% of the 24 mesh residue defined by JIS-P-8207 and the 42 mesh residue. The sum of the mass% of the minute is preferably 30 to 70%. 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 calendering at the paper making stage or after paper making. The density of the base paper is generally 0.7 to 1.2 g / cm ³ (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. 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 that covers the front and back surfaces of the base paper is mainly low-density polyethylene (LDPE) and / or high-density polyethylene (HDPE), but some other LLDPE, polypropylene, and the like can also be used. In particular, the polyethylene layer on the ink absorbing 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 usually 3 to 20% by mass, preferably 4 to 13% by mass, based on polyethylene. Polyethylene-coated paper can be used as glossy paper, or when the polyethylene is melt-extruded onto the surface of the base paper and coated, a so-called molding process is performed to form a matte or silky surface that can be obtained with ordinary photographic paper These can also be used in the present invention. In the polyethylene-coated paper, the water content in the paper is particularly preferably maintained at 3 to 10% by mass.

  The surface layer containing the organic fine particle A or the organic fine particle B as defined above of the recording paper of the present invention and a hydrophilic binder containing a polymer compound that is crosslinked or polymerized by ionizing radiation and one or more porous layers are simultaneously used. The method of applying the multilayer can be appropriately selected from known methods. As the coating method, for example, an extrusion coating method or an extrusion coating method using a hopper described in US Pat. No. 2,681,294 is preferably used.

  A layer such as an undercoat layer that is appropriately provided as necessary can be appropriately selected from known methods. As the coating method, for example, a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method, or an extrusion coating method using a hopper described in US Pat. No. 2,681,294 is preferable. Used.

  The film thickness of the surface layer according to the present invention is preferably 0.5 to 5 μm as a dry film thickness. If the thickness is less than 0.5 μm, interference fringes are generated due to the difference in the refractive index of the coating film, and the surface of the recording paper is glaring. More preferably, it is 1-5 micrometers. On the other hand, if the surface layer is too thick, cracks are likely to occur, and problems such as deterioration in ink absorbency and reduction in print density are caused.

  In image recording using the ink jet recording paper of the present invention, a recording method using water-based ink is preferable. The water-based ink as used in the present invention means a recording liquid comprising the following colorant, liquid medium, and other additives.

  As the colorant that can be used in the present invention, water-soluble dyes or water-dispersible pigments such as direct dyes, acid dyes, basic dyes, reactive dyes, food dyes, and the like known in ink jet can be used. Among them, a particularly preferable colorant is an ink using a phthalocyanine dye as a cyan dye. Phthalocyanine dyes are particularly widely used and used among cyan dyes.

  Examples of the solvent for the water-based ink include water and various water-soluble organic solvents, for example, alcohols such as methyl alcohol, i-propyl alcohol, butyl alcohol, t-butyl alcohol, and i-butyl alcohol; dimethylformamide, dimethylacetamide, and the like. Amides; Ketones or ketone alcohols such as acetone and diacetone alcohol; Ethers such as tetrahydrofuran and dioxane; Polyalkylene glycols such as polyethylene glycol and polypropylene glycol; Ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1 Polyhydric alcohols such as 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol, glycerin and triethanolamine; Glycol methyl ether, diethylene glycol methyl (or ethyl) ether, lower alkyl ethers of polyhydric alcohols such as triethylene glycol monobutyl ether. Among these water-soluble organic solvents, polyhydric alcohols such as diethylene glycol, triethanolamine and glycerin, and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monobutyl ether are preferable.

  Examples of other water-based ink additives include pH adjusters, metal sequestering agents, antifungal agents, viscosity modifiers, surface tension adjusters, wetting agents, surfactants, and rust inhibitors.

  The aqueous ink liquid preferably has a surface tension in the range of 25 to 60 mN / m, preferably 30 to 50 mN / m at 20 ° C. in order to improve the wettability with respect to the recording paper.

  The printer that can be used in the present invention is not particularly limited as long as it has a commercially available printer, for example, a recording medium storage unit, a transport unit, an ink cartridge, and an ink jet print head, but at least a roll-shaped recording medium A series of printer sets including a storage unit, a transport unit, an inkjet print head, a cutting unit, and, if necessary, a heating unit, a pressure unit, and a recording print storage unit are preferable. The ink jet print head to be used may be an on-demand system or a continuous system. In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method (for example, a thermal type) Examples thereof include an ink jet type, a bubble jet (R) type, an electrostatic attraction method (for example, an electric field control type, a slit jet type, etc.), and a discharge method (for example, a spark jet type). The electro-mechanical conversion method is preferable, but any discharge method may be used.

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

<< Preparation of each coating solution >>
(Preparation of porous coating solution)
While stirring at 40 ° C., the following additives were sequentially mixed with 500 g of the following silica dispersion S-1, and finally the total amount was adjusted to 1000 g with pure water to prepare a porous layer coating solution.

8% by mass aqueous solution of polyvinyl alcohol having a polymerization degree of 3500 (PVA235 manufactured by Kuraray Co., Ltd.)
160g
8% by mass aqueous solution of polyvinyl alcohol having a polymerization degree of 4500 (PVA245 manufactured by Kuraray Co., Ltd.)
50g
(Preparation of silica dispersion S-1)
The average particle diameter of primary particles uniformly dispersed in advance in 120 g of an aqueous solution of 10% by weight of cationic polymer P-1 (containing 10% by weight of n-propanol and 2% by weight of ethanol) is about 7 nm. 400 g of silica dispersion (pH 2.6, containing 0.5% by mass of ethanol) containing 30% by mass of phase method silica (produced by Nippon Aerosil Co., Ltd .; Aerosil 300), 3.6 g of boric acid, and 0.8 g of borax The mixture was added with stirring at 3000 rpm at room temperature. Subsequently, it disperse | distributed by the pressure of ³ kN / cm < ² > with the high-pressure homogenizer by Sanwa Kogyo Co., Ltd., and the whole quantity was finished with a pure water so that the silica content might be 20 mass%, and silica dispersion liquid S-1 was obtained. The obtained silica dispersion S-1 was filtered using a TCP-10 type filter manufactured by Advantex Toyo. It was 36 nm when the average secondary particle diameter of the silica was measured.

  The average secondary particle size was measured by diluting the silica dispersion 50 times and using a dynamic light scattering type particle size measuring device Zeta Sizer 1000HS (Malvern).

[Preparation of surface coating solution]
(Preparation of surface coating solution 1)
Organic fine particle emulsion LI 500g
50 g of fine particle silica (Rokuro Seal QS-20, manufactured by Tokuyama Corporation)
8% by mass aqueous solution of polyvinyl alcohol having a polymerization degree of 3500 (PVA235 manufactured by Kuraray Co., Ltd.)
125g
After the above additives were mixed, the surface coating solution 1 was prepared by finishing 1000 g with pure water.

<Preparation of organic fine particle emulsion LI>
n-Butyl acrylate: styrene: 2-hydroxyethyl methacrylate: t-butyl methacrylate = 10: 50: 20: 20 (mass ratio) monomers are used for emulsion polymerization according to a known method to obtain an organic compound having a solid content concentration of 20%. A fine particle emulsion (LI) was prepared. The surfactant used in the preparation was stearyltrimethylammonium chloride, which is a cationic surfactant, and 3% by mass was added as a solid content with respect to the total monomer amount. The average particle size of the organic fine particles contained in the organic fine particle emulsion (LI) prepared as described above is determined by coating the organic fine particle emulsion on a polyester film and drying it at a temperature of Tg or less. The film surface was observed and measured with an electron microscope and found to be 30 nm. The glass transition temperature (Tg) determined from the Tg of each constituent monomer by the above-described method was 76 ° C.

(Preparation of surface coating solution 2)
Organic fine particle emulsion LI (supra) 500g
50 g of fine particle silica (Rokuro Seal QS-20, manufactured by Tokuyama Corporation)
90 g of photocrosslinkable polyvinyl alcohol derivative aqueous solution into which a stilbazonium group was introduced (SPP-SHR manufactured by Toyo Gosei Kogyo Co., Ltd., solid content concentration 11 mass%, main chain PVA polymerization degree 2300, saponification degree 88%)
After mixing each of the above additives, the surface coating solution 2 was prepared by finishing to 1000 g with pure water.

(Preparation of surface coating solution 3)
Organic fine particle emulsion LI (supra) 500g
50 g of fine particle silica (Rokuro Seal QS-20, manufactured by Tokuyama Corporation)
UV-polymerized polyvinyl alcohol derivative aqueous solution 1 125g
Photoinitiator (Nippon Kayaku Kayacure QTW) 1.8g
After mixing the above additives, the surface coating solution 3 was prepared by finishing 1000 g with pure water.

<Preparation of UV polymerization type polyvinyl alcohol derivative aqueous solution 1>
With reference to the method described in JP-A No. 2000-181062, p- (3-methacryloxy-2-hydroxypropyloxy) benzaldehyde is reacted with polyvinyl alcohol having a polymerization degree of 3500 and a saponification degree of 88%, and the following formula (6 An ultraviolet-curing polyvinyl alcohol derivative aqueous solution 1 having a crosslinking group modification rate of 2 mol% and a solid content concentration of 8 mass% was prepared.

(Preparation of surface coating solution 4)
In the preparation of the surface layer coating solution 3, a surface layer coating solution 4 was prepared in the same manner except that the following UV polymerization type polyvinyl alcohol derivative aqueous solution 2 was used instead of the UV polymerization type polyvinyl alcohol derivative aqueous solution 1.

<Preparation of UV polymerization type polyvinyl alcohol derivative aqueous solution 2>
In the same manner as the UV-polymerizable polyvinyl alcohol derivative aqueous solution 1, an UV-polymerizable polyvinyl alcohol derivative aqueous solution 2 having a crosslinking group modification rate of 3.5 mol% and a solid content concentration of 8% by mass was prepared.

(Preparation of surface coating solution 5)
In the preparation of the surface coating solution 3, the surface coating solution 5 was prepared in the same manner except that the following ultraviolet polymerization polyvinyl alcohol derivative aqueous solution 3 was used instead of the ultraviolet polymerization polyvinyl alcohol derivative aqueous solution 1.

<Preparation of UV polymerization type polyvinyl alcohol derivative aqueous solution 3>
In the same manner as the UV-polymerizable polyvinyl alcohol derivative aqueous solution 1, an UV-polymerizable polyvinyl alcohol derivative aqueous solution 3 having a crosslinking group modification rate of 4.5 mol% and a solid content concentration of 8% by mass was prepared.

(Preparation of surface coating solution 6)
In the preparation of the surface coating solution 3, the surface coating solution 6 was prepared in the same manner except that the following ultraviolet polymerization polyvinyl alcohol derivative aqueous solution 4 was used instead of the ultraviolet polymerization polyvinyl alcohol derivative aqueous solution 1.

<Preparation of UV polymerization type polyvinyl alcohol derivative aqueous solution 4>
A UV-polymerizable polyvinyl alcohol derivative aqueous solution 4 was prepared in the same manner except that the polymerization degree was changed to 300 in the preparation of the UV-polymerizable polyvinyl alcohol derivative aqueous solution 1.

(Preparation of surface coating solution 7)
A surface coating solution 7 was prepared in the same manner as in the preparation of the surface coating solution 3, except that the following UV polymerization type polyvinyl alcohol derivative aqueous solution 5 was used instead of the UV polymerization type polyvinyl alcohol derivative aqueous solution 1.

<Preparation of UV polymerization type polyvinyl alcohol derivative aqueous solution 5>
A UV-polymerizable polyvinyl alcohol derivative aqueous solution 5 was prepared in the same manner as in the preparation of the UV-polymerizable polyvinyl alcohol derivative aqueous solution 1 except that the polymerization degree was changed to 1000.

<Production of inkjet recording paper>
[Preparation of inkjet recording paper 1]
Polyethylene-coated paper both sides of thick 170 g / m ² base paper coated with polyethylene (containing anatase type titanium oxide 8% by weight in polyethylene of the ink absorbing layer side, the ink absorbing layer side of the 0.05 g / m ² On the support 1 which has a gelatin subbing layer and a latex polymer having a Tg of about 80 ° C. on the opposite side and a back layer of 0.2 g / m ² , the prepared porous layer coating solution is placed on a slide hopper. The ink-jet recording paper 1 was prepared by coating with a wet film thickness of 180 μm, followed by drying with warm air and storing for 12 hours in an environment of 40 ° C. and 80% RH.

[Preparation of inkjet recording paper 2]
On the support 1, the prepared porous layer coating solution and the surface layer coating solution 1 are simultaneously coated using a slide hopper under the conditions that the wet film thicknesses are 180 μm and 10 μm. After drying, it was stored in an environment of 40 ° C. and 80% RH for 12 hours to produce inkjet recording paper 2.

[Preparation of inkjet recording paper 3]
The prepared surface layer coating solution 1 is put in a 1 L transparent container and irradiated with an electron beam with an acceleration voltage of 175 kV and an irradiation dose of 5 Mrad from the side of the container, and then the porous layer coating solution and the electron beam irradiated on the support 1 The surface coating solution 1 is applied simultaneously with a slide hopper under the conditions that the wet film thicknesses are 180 μm and 10 μm, and then dried with warm air, and then in an environment of 40 ° C. and 80% RH for 12 hours. The ink-jet recording paper 3 was prepared by storage.

[Preparation of inkjet recording paper 4]
The surface layer coating solution 2 prepared above was placed in a transparent container 1L, metal halide lamp having a dominant wavelength 365 nm, illuminance using the ultraviolet 60 mW / cm ² at a wavelength of 365 nm, the side surface with ultraviolet rays at 30 mJ / cm ² at an energy amount After that, the porous layer coating solution and the UV-irradiated surface layer coating solution 2 are applied simultaneously on the support 1 under the conditions that the wet film thicknesses are 180 μm and 10 μm using a slide hopper. Then, after drying with warm air, the ink-jet recording paper 4 was produced by storing in an environment of 40 ° C. and 80% RH for 12 hours.

[Preparation of inkjet recording paper 5-9]
In the production of the ink jet recording paper 4, ink jet recording papers 5 to 9 were produced in the same manner except that the surface layer coating liquids 3 to 7 were used in place of the surface layer coating liquid 2, respectively.

<< Characteristic test of organic fine particles >>
[Solubility test of organic fine particles]
The organic fine particle emulsion (LI) used for the production of the recording sheets 2 to 9 was dissolved as a result of mixing with diethylene glycol monobutyl ether [SP value 19.437 (MPa) ^1/2 , boiling point 230 ° C.] at room temperature. .

[Electron microscope observation of surface and cross section of recording paper after treatment A]
As a result of observing the surface and cross section of the recording papers 1 to 9 with the electron microscope, the recording papers 2 to 9 are fused to each other as the organic fine particles are dissolved or swollen. The condition was observed.

<Process A>
A 20% aqueous solution of diethylene glycol monobutyl ether [SP value 19.437 (MPa) ^1/2 , boiling point 230 ° C.] was uniformly spray-coated on the surfaces of recording papers 1-9. The coating amount was 20 ml / m ² . Then, this part was dried for 1 hour in an environment of 23 ° C. and 55% RH.

<< Preparation of cyan ink liquid >>
A cyan ink liquid having the following composition was prepared.

Water 68.5 parts Diethylene glycol monobutyl ether 12 parts Diethylene glycol 10 parts Glycerin 8 parts C.I. I. Direct Blue 86 1 part Surfactant (Surfinol 465 manufactured by Shin-Etsu Chemical Co., Ltd.) 0.5 part << Inkjet image printing and evaluation >>
(Image printing)
The cyan ink liquid was mounted on an ink jet printer PM-800C (manufactured by Seiko Epson Corporation), and a cyan solid image was printed on the recording sheets 1 to 9 produced above. The ink discharge amount was 12 ml / m ^2, and this solid image was dried for 1 hour in an environment of 23 ° C. and 55% RH.

[Evaluation of recording paper and printed images]
(Evaluation of discoloration resistance)
After the solid image formed according to the above method was stored at 23 ° C. for 1 day, each solid image portion was pasted on the window in the office room and left for 6 months in an environment exposed to external airflow but not exposed to direct sunlight. The reflection density of the printed part before and after being left was measured with a red monochromatic light using a reflection densitometer, and the density residual rate was determined according to the following formula, which was used as a measure for the resistance to discoloration.

Concentration residual ratio = (Concentration after standing for 6 months / Concentration before standing) × 100 (%)
[Evaluation of coating film uniformity]
The surface of each of the produced recording papers was visually observed to confirm the presence or absence of coating failure such as blown unevenness, and coating uniformity was evaluated according to the following criteria.

○: Application failure such as spraying unevenness does not occur at all △: Application failure such as spraying unevenness can be confirmed slightly, but is within a practically acceptable range ×: Application failure such as spraying unevenness is conspicuous It is a quality that poses a practical problem [Evaluation of resistance to cracking]
Each recording sheet was cut into a 5 × 10 cm strip, and this was applied to a paper tube with a core inner diameter of 3 cm so that the ink absorbing layer coating surface was on the outside. The number was measured.

  The results obtained as described above are shown in Table 1.

  As is clear from Table 1, the surface layer and the porous layer containing the organic fine particles A or the organic fine particles B according to the present invention on the support and a hydrophilic binder containing a polymer compound that is crosslinked or polymerized by ionizing radiation. The recording paper of the present invention produced by irradiating the surface layer coating solution with ionizing radiation and then simultaneously coating with the porous layer has improved resistance to discoloration of the image due to air oxidation, and is porous. It can be seen that even when the quality layer and the surface layer are applied simultaneously, there is no occurrence of unevenness of the coating surface, and the formed coating film is excellent in resistance to breakage.

Claims (6)

An ink jet having a surface layer containing organic fine particles A or organic fine particles B defined below, and a hydrophilic binder containing a polymer compound crosslinked or polymerized by ionizing radiation, and one or more porous layers on a support. An ink jet recording paper produced by irradiating the surface layer coating solution with ionizing radiation and then simultaneously coating the porous layer with the porous layer.
Organic fine particles A: Organic fine particles insoluble in water that have an SP value of 18.414 to 30.69 (MPa) ^1/2 and a boiling point of 120 ° C. or higher and are dissolved or swelled by a water-soluble organic solvent, and have a glass transition temperature ( Organic fine particles having a Tg) of 70 ° C. or more and an average particle diameter of 100 nm or less.
Organic fine particles B: a polymer containing 5% by mass or more of a repeating unit represented by the following general formula (1) as a copolymerization component, a glass transition temperature (Tg) of 70 ° C. or higher, and an average particle size of 100 nm The following organic fine particles.

[Wherein, X represents —O— or —N (R ₂ ) —, R ₁ represents a hydrogen atom or a methyl group, R ₂ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, Is —O—, J is an alkylene group having 2 to 8 carbon atoms which may have an ether structure or a thioether structure, Y represents a hydroxyl group, an alkoxyl group or a carbamoyl group, and X represents In the case of —N (R ₂ ) —, J is a single bond or an alkylene group having 2 to 8 carbon atoms, which may have an ether structure or a thioether structure, and Y is a hydrogen atom, a hydroxyl group, an amino group Represents a group, an alkoxyl group or a carbamoyl group. ] 2. The ink jet recording paper according to claim 1, wherein the polymer compound crosslinked or polymerized by ionizing radiation is an ultraviolet dimerization polymer compound or an electron beam curable polymer compound. The high molecular compound that is crosslinked or polymerized by ionizing radiation is an ultraviolet-crosslinked modified polyvinyl alcohol having a degree of polymerization of 300 or more and an ionizing radiation reaction modification rate of 4 mol% or less. 2. Inkjet recording paper described in 1. Inkjet having organic fine particle A or organic fine particle B as defined above and a surface layer containing a hydrophilic binder containing a polymer compound crosslinked or polymerized by ionizing radiation and one or more porous layers on a support A method for producing an ink jet recording paper, characterized in that the surface layer coating solution is irradiated with ionizing radiation and then simultaneously coated with the porous layer to produce the recording paper. 5. The method for producing an ink jet recording paper according to claim 4, wherein the polymer compound crosslinked or polymerized by ionizing radiation is an ultraviolet dimerization polymer compound or an electron beam curable polymer compound. 5. The polymer compound that is crosslinked or polymerized by ionizing radiation is an ultraviolet-crosslinked modified polyvinyl alcohol having a degree of polymerization of 300 or more and an ionizing radiation reaction modification rate of 4 mol% or less. A method for producing an inkjet recording paper as described in 1 above.