JP2006224494A - Forming method of inkjet image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a forming method of an inkjet image having a feel of gloss approximate to that of a silver salt photographic, without being accompanied by the lowering of ink absorbency and crack resistance at the time of long-period storage. <P>SOLUTION: In the forming method of the inkjet image which records on an inkjet recording medium having an ink absorbing layer on a substrate, the ink absorbing layer contains as a hydrophilic binder a polymeric compound crosslinked by an ionizing radiation, and the ink containing water-dispersible polymer particulates is given at least to a part of the inkjet recording medium. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a novel inkjet image forming method.

  Ink-jet recording is a method in which micro droplets of ink are ejected by various operating principles and deposited on a recording sheet such as paper to record images and characters. Due to the advantages such as being easy to use, it is rapidly spreading in various fields such as various printers, facsimiles, computer terminals and the like.

  In recent years, the ink jet recording system has been rapidly improved in image quality due to various technological innovations in ink jet ink, ink jet recording media, and ink jet printers, and the resulting image quality is approaching that of silver halide photography. However, from the viewpoint of improving ink absorbability, among ink jet recording media having porous ink absorbing layers mainly composed of inorganic fine particles, ink jet recording media using silica fine particles with high cost merit have a low surface gloss and can be obtained. The image quality is still not as good as silver halide photography.

  In response to the above problems, an ink jet recording medium has been proposed in which a glossy expression layer is provided on the surface of the recording medium. For example, Japanese Patent Application Laid-Open Nos. 2001-353957 and 2003-94800 disclose a technique for providing colloidal silica on an ink jet recording medium made of inorganic pigment fine particles. Japanese Patent Application Laid-Open No. 7-117335 discloses an ink jet recording medium in which a glossy expression layer is coated by a wet cast method, wherein the glossy expression layer contains colloidal silica and organic particles. . However, in any of the above proposed methods, the ink absorption speed is decreased by the glossy expression layer, and the image quality is deteriorated when performing high-speed printing.

  Attempts have also been made to form a film with resin on the image surface. For example, a layer made of thermoplastic organic polymer particles is provided on the outermost layer of an ink jet recording medium, and after recording an image, the thermoplastic organic polymer particles are melted to form a film, and as a result, a polymer protective film is formed. As a result, water resistance and weather resistance are improved and glossiness of the image is achieved (for example, see Patent Documents 1 to 4). According to these proposed methods, although a certain degree of effect is recognized for improving image storability, a dedicated ink jet recording medium is required, a dedicated heat fixing device is required, and an ink solvent is used during heat fixing. There are problems such as the occurrence of blistering due to evaporation and the occurrence of film peeling, which are difficult to control. In addition, the outermost layer made of thermoplastic organic polymer particles also has a drawback of hindering ink absorbability.

  On the other hand, a method for improving water resistance and light resistance by adding latex or resin fine particles to ink jet ink has been proposed (see, for example, Patent Document 5). Furthermore, resin addition to ink is disclosed for the purpose of improving ozone gas resistance (see, for example, Patent Documents 6 and 7). In addition, JP-A Nos. 2002-80759, 2002-194253, 2002-264490, 2002-285049, and 2003-55586 disclose techniques for adding latex or resin fine particles to ink. Yes. Also disclosed is a technique for improving gloss uniformity by discharging clear ink containing a resin component after image formation with pigment ink (see, for example, Patent Document 8).

According to these methods, the surface gloss similar to silver salt photography can be obtained, but the following problems are encountered. That is, by adding latex or resin fine particles to the ink, a thin resin layer is formed on the surface of the recording medium after printing. However, if the affinity between the surface of the recording medium and the resin layer is low, there will be a local gap between the surface of the recording medium and the resin layer, causing cracks during storage over time, bleeding due to moisture entering, and print transport. It was found that the resin layer was peeled off at times.
JP-A-4-214446 Japanese Patent Laid-Open No. 10-315448 Japanese Patent Laid-Open No. 11-5362 JP 11-192775 A Japanese Patent Laid-Open No. 11-199808 JP 2001-187852 A JP 2002-240413 A International Patent No. 02/87886 Pamphlet

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its object is to provide a method for forming an inkjet image having glossiness similar to a silver salt photograph without lowering ink absorbability and cracking resistance during long-term storage. There is to do.

  The above object of the present invention is achieved by the following configurations.

(Claim 1)
In an ink jet image forming method for recording on an ink jet recording medium having an ink absorbing layer on a support, the ink absorbing layer contains a polymer compound crosslinked by ionizing radiation as a hydrophilic binder, and contains water-dispersible polymer fine particles An ink jet image forming method comprising applying an ink to be applied to at least a part of the ink jet recording medium.

(Claim 2)
The inkjet image forming method according to claim 1, wherein the ink containing the water-dispersible polymer fine particles is substantially colorless without containing a coloring material.

(Claim 3)
The inkjet image forming method according to claim 1 or 2, wherein the polymer compound crosslinked by ionizing radiation is a saponified polyvinyl acetate having a structural unit represented by the following general formula (1).

[Wherein, R ₁ represents a hydrogen atom or a methyl group, n represents 1 or 2, Y represents an aromatic ring or a single bond, and X represents — (CH ₂ ) _m —COO—, —OCH ₂ —COO -Or -O- is represented, and m is an integer of 0-6. ]
(Claim 4)
The inkjet image forming method according to any one of claims 1 to 3, wherein the ink absorption layer contains inorganic fine particles.

  According to the present invention, it is possible to provide an ink jet image forming method having glossiness similar to that of a silver salt photograph without lowering ink absorbability and cracking resistance during long-term storage.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the present inventors have found that in an ink jet image forming method for recording on an ink jet recording medium having an ink absorbing layer on a support, the ink absorbing layer is used as a hydrophilic binder by ionizing radiation. An ink-jet image forming method characterized by applying an ink containing a crosslinked polymer compound and water-dispersible polymer fine particles to at least a part of the ink-jet recording medium. It has been found that an ink jet image forming method having a glossiness similar to that of a silver salt photograph can be realized without a decrease, and the present invention has been achieved.

  That is, it has been found that, as a constitution of the ink absorbing layer of the ink jet recording medium, the affinity with the ink composed of polymer fine particles is increased by containing a polymer compound cross-linked by ionizing radiation as a hydrophilic binder. As a result, it is possible to obtain glossiness similar to silver salt photography without cracking or blurring of the formed image when stored for a long period of time due to application of ink containing water-dispersible polymer fine particles. It is what I found.

  Details of the present invention will be described below.

  First, the ink jet recording medium according to the present invention will be described.

  The ink jet recording medium according to the present invention (hereinafter also simply referred to as a recording medium) has an ink absorbing layer on a support, and the ink absorbing layer contains a polymer compound crosslinked by ionizing radiation as a hydrophilic binder. It is characterized by that.

  The polymer compound cross-linked by ionizing radiation according to the present invention is a resin that undergoes a cross-linking or polymerization reaction by reacting with ionizing radiation such as ultraviolet rays and electron beams, and is water-soluble before the reaction. A resin that becomes substantially water-insoluble after the reaction is preferable. 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, and other hydrophilic resins, Derivatives and at least one kind selected from the group consisting of these copolymers, or hydrophilic resins thereof, such as photo-dimerization type, photo-decomposition type, photo-polymerization type, photo-denaturation type, photo-depolymerization type, etc. Although it is modified by a group, in the present invention, from the viewpoint of more exerting the object effect of the present invention, it is a polyvinyl acetate saponified product having the structural unit represented by the general formula (1). preferable.

  A resin modified with a photodimerization type or photopolymerization type modification group is preferred 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 styrylquinolium 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, and JP-A-60-252341. A photosensitive resin (composition) described in JP-A-56-67309, JP-A-60-129742, etc., and a group such as an azide group that becomes an amino group and becomes cationic by curing treatment. Examples thereof include photosensitive resins (compositions) described in JP-A-56-67309.

  Next, the saponified polyvinyl acetate having the structural unit represented by the general formula (1) preferably used in the present invention will be described.

  As described above, the saponified polyvinyl acetate according to the present invention is a resin that reacts and crosslinks by irradiation with ionizing rays such as ultraviolet rays and electron beams, and is water-soluble before the curing reaction, but after the curing reaction. Is a resin that is substantially insoluble in water. However, the saponified polyvinyl acetate according to the present invention has a certain degree of hydrophilicity even after curing, and maintains sufficient affinity with ink.

  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. The hydrophilic binder that crosslinks by nonionic ionizing radiation, 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, and causes a crosslinking reaction efficiently. This is preferred in the present invention.

In the general formula (1), R ₁ represents a hydrogen atom or a methyl group, n represents 1 or 2, Y represents an aromatic ring or a single bond, X represents — (CH ₂ ) _m —COO—, — OCH ₂ -COO- or an -O-, m is an integer of 0 to 6.

  Examples of the structural unit represented by the general formula (1) include those shown below.

  The degree of polymerization of the mother nucleus PVA of the saponified polyvinyl acetate according to the present invention is preferably in the range of 400 to 5000, more preferably in the range of 400 to 3500. More preferably, it is the range of 1700-3500. When the degree of polymerization is less than 400, sufficient coating strength cannot be obtained, and when it exceeds 5000, the solution viscosity becomes too high and the coating property is lowered.

  The saponification degree is 60% or more, preferably 70 to less than 100%, more preferably 88% to less than 100%. When the degree of saponification is less than 60%, the effect of suppressing cracking, which is the object of the present invention, is small.

  Synthesis of the saponified polyvinyl acetate represented by the general formula (1) can be performed according to Japanese Patent Application Laid-Open No. 2000-181062.

  Further, the modification rate of the ionizing radiation reactive crosslinking group with respect to the segment is preferably 4 mol% or less, more preferably 0.01 to 1 mol% or less.

  If the degree of polymerization of the segment is less than 400 or the modification rate exceeds 4 mol%, the crosslinking density of the coating film is too high, and the cracking property of the dried coating film is remarkably deteriorated. The balance between the hygroscopic property and the dimensional stability with the material is poor, and the curl resistance is deteriorated, which is not preferable.

  The ratio of fine particles to be described later to the crosslinked hydrophilic resin of the ink absorbing 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 ink absorption layer has a good porosity, it is easy to obtain a sufficient void volume, and an excessive crosslinked hydrophilic resin is prevented from swelling and closing the void during ink jet recording. It is done. On the other hand, if this ratio is 50 times or less, it is preferable that cracks are not likely to occur when the ink absorbing layer is applied as a thick film. A particularly preferable ratio of the fine particles to the crosslinked hydrophilic resin 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 ink absorbing layer according to the present invention preferably contains inorganic fine particles.

  As the inorganic fine particles used in the present invention, fine inorganic fine particles having a large pore volume and a small average particle diameter are used. In particular, silica, aluminum hydroxide, boehmite, pseudoboehmite, and fine inorganic fine particles such as alumina and calcium carbonate 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, Tokuyama fine seal 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 silica is determined by observing the cross section and surface of the ink absorption 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 ink absorption 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 size is preferably 300 nm or less from the viewpoint of transmission of ionizing radiation.

  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, the ratio of isolated silanol groups is preferably 0.5 to 1.5, and 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 form. 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 ink absorbing layer coating liquid containing the inorganic fine particles is 5 to 40% by mass, and particularly preferably 7 to 30% by mass.

  The solid content concentration of the ink absorbing layer containing the inorganic fine particles and the polymer compound cross-linked by the ionizing radiation is preferably in the range of 5 to 90%.

  As the support used in the ink jet recording medium 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 can be used. 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 medium 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 ² (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: ≧ 1.03 kN / 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 ink absorbing layer side of the support for the purpose of improving adhesion to the ink absorbing 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 m ² of the recording medium. 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 ink absorbing 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 forming the ink absorbing 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 an amount of 0.05 to 20 mmol, preferably 0.1 to 10 mmol, per 1 m ² of the recording medium.

  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 ink absorbing layer of the recording medium according to 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.

  In the method for producing an inkjet recording medium according to the present invention, at least one ink absorbing layer containing at least a polymer compound that is crosslinked by ionizing radiation is applied on a support, irradiated with ionizing radiation, and then dried. Manufactured.

  Examples of the ionizing radiation in the present invention include electron beams, ultraviolet rays, α rays, β rays, γ rays, and X-rays. However, they are dangerous to the human body, easy to handle, and can be used industrially. The prevalent UV light is preferred.

For example, low pressure, medium pressure, high pressure mercury lamp, metal halide lamp, etc. having an operating pressure of several hundred Pa to 10 atmospheres are used as the light source. 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 core of the ionizing radiation crosslinkable resin, 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 mixability and reaction efficiency. For example, 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 mixing with an aqueous solvent, In particular, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone (HMPK) is more preferable from the viewpoints of stability and reaction efficiency. 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 -2,4,5-triarylimidazole dimer of diphenylimidazole dimer, benzyldimethyl ketal, 2-benzyl-2-dimethyl Amino-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.

  Next, the ink according to the present invention will be described.

  The inkjet image forming method of the present invention is characterized in that an image is formed by applying ink containing at least water-dispersible polymer fine particles on the above-described inkjet recording medium according to the present invention.

  Hereinafter, the ink containing water-dispersible polymer particles according to the present invention will be described.

  The water-dispersible polymer particles according to the present invention refer to polymer particles that are dispersed in a medium, for example, water, and are also called polymer particles or latex.

  The water-dispersible polymer particles can be used in the form of an aqueous dispersion of various polymers. Specifically, acrylic, styrene-acrylic, acrylonitrile-acrylic, vinyl acetate, vinyl acetate-acrylic, vinyl acetate-vinyl chloride, polyurethane, silicon-acrylic, acrylic silicon, polyester, Epoxy polymers can be mentioned.

  Usually, these water-dispersible polymer fine particles are obtained by an emulsion polymerization method. The surfactants, polymerization initiators, etc. used there may be those used in conventional methods. Regarding the method for synthesizing water-dispersible polymer fine particles, U.S. Pat. Nos. 2,852,368, 2,853,457, 3,411,911, 3,411,912, 4,197, No. 127, Belgian Patent Nos. 688,882, 691,360, 712,823, JP-B 45-5331, JP-A-60-18540, 51-130217, 58-137831, This is described in detail in JP-A-55-50240.

  The water-dispersible polymer fine particles used in the ink according to the present invention preferably have an average particle size of 10 to 200 nm, more preferably 10 to 150 nm, and still more preferably 10 to 100 nm. In this case, by defining the average particle size of the water-dispersible polymer fine particles in the range of 10 nm to 200 nm, the coverage of the polymer fine particles on the recording medium is increased, and it is possible to achieve both the ejection stability of the ink droplets. . That is, when the water-dispersible polymer fine particle diameter is 10 nm or more, the surface of the image after printing is sufficiently covered with the polymer fine particle, and the effect of improving the image storage stability is obtained. On the other hand, when the particle diameter is 200 nm or less, the ejection stability of the ink droplets is improved.

  The average particle size of the water-dispersible polymer fine particles can be easily determined using a commercially available particle size measuring device using a light scattering method or a laser Doppler method, for example, Zetasizer 1000 (manufactured by Malvern).

  In the ink according to the present invention, the content of the water-dispersible polymer particles in the ink is preferably 0.2 to 10% by mass, and more preferably 0.5 to 5% by mass. If the amount of the water-dispersible polymer fine particles added is 0.2% by mass or more, a more sufficient effect on the fading property can be exhibited. Furthermore, the increase in the ink viscosity during storage can be suppressed, which is more preferable.

  In the present invention, the glass transition point (Tg) of the water-dispersible polymer particles in the ink is preferably -30 to 30 ° C, more preferably -20 to 0 ° C. If the glass transition point (Tg) of the water-dispersible polymer fine particles is −30 or more, clogging resistance at the nozzle portion of the recording head can be obtained, and if it is 30 ° C. or less, preferable film forming ability is obtained. be able to.

  The glass transition point (Tg) of the polymer fine particles can be measured by a known method utilizing the fact that the coefficient of thermal expansion and specific heat change discontinuously in the process of changing the temperature. In addition, in J. Brandup, E .; H. Also described in Immersu "Polymer Handbook" 3rd edition (John Wily & Sons) 1989, VI 209-277.

  In the water-dispersible polymer fine particles according to the present invention, the minimum film-forming temperature (MFT) is preferably 0 to 60 ° C. In the present invention, a film-forming aid may be added to control the minimum film-forming temperature of the water-dispersible polymer fine particles. The film-forming aid, also called a plasticizer, is an organic compound (usually an organic solvent) that lowers the minimum film-forming temperature of the polymer latex. For example, “Synthetic Latex Chemistry (Souichi Muroi, published by Kobunshi Shuppankai (1970)” )"It is described in.

  Further, in the inkjet image forming method of the present invention, it is preferable that the ink is a colorless ink containing water-dispersible polymer fine particles and substantially free of a coloring material.

  In the present invention, the colorless ink containing substantially no color material means a state in which the content of the color material is 0.1% or less with respect to the total ink mass, and preferably contains no color material. is there.

  The colorless ink according to the present invention comprises water-dispersible polymer particles and a liquid medium, and preferably contains water-dispersible polymer particles, a water-soluble solvent and water as main components.

  In this invention, the case where a colorless ink and a color material containing ink are mixed is assumed. Therefore, even when the color material-containing ink and the colorless ink are mixed, it is desirable that the color material does not substantially aggregate, and specifically, the change in absorbance of the color material-containing ink is preferably less than 5%.

  One is to mix both inks on a recording medium. Moreover, when supplying colorless ink and color material containing ink from an inkjet nozzle, it may be contaminated by both ink. Furthermore, the same head is used for recording ink for each printing mode or for colorless ink. Even in such a case, there should be no deterioration in image quality or gloss. Assuming such a situation, when the color material-containing ink and the colorless ink are mixed, the absorbance change is 5 with respect to the absorbance immediately after. When it is less than%, it is preferable because image quality and glossiness do not occur.

In addition to the ink containing the water-dispersible polymer particles according to the present invention, an ink containing a coloring material can be used.
As one of the color materials used in the ink of the present invention, it is preferable to use a water-soluble dye such as an acid dye, a direct dye, a reactive dye, or a disperse dye, and it is also preferable to use a pigment.

Examples of water-soluble dyes include acid dyes, basic dyes, and reactive dyes. Particularly preferred is
C. I. Direct Red 2, 26, 31, 62, 63, 72, 75, 76, 79, 80, 81, 83, 84, 89, 92, 95, 111, 173, 184, 207, 211, 212, 214, 218, 221,223,224,225,226,227,232,233,240,241,242,243,247,
C. I. Direct violet 7, 9, 47, 48, 51, 66, 90, 93, 94, 95, 98, 100, 101,
C. I. Direct yellow 8, 9, 11, 12, 27, 28, 29, 33, 35, 39, 41, 44, 50, 53, 58, 59, 68, 86, 87, 93, 95, 96, 98, 100, 106, 108, 109, 110, 130, 132, 142, 144, 161, 163,
C. I. Direct Blue 1, 10, 15, 22, 25, 55, 67, 68, 71, 76, 77, 78, 80, 84, 86, 87, 90, 98, 106, 108, 109, 151, 156, 158, 159, 160, 168, 189, 192, 193, 194, 199, 200, 201, 202, 203, 207, 211, 213, 214, 218, 225, 229, 236, 237, 244, 248, 249, 251, 252, 264, 270, 280, 288, 289, 291,
C. I. Direct Black 9, 17, 19, 22, 32, 51, 56, 62, 69, 77, 80, 91, 94, 97, 108, 112, 113, 114, 117, 118, 121, 122, 125, 132, 146, 154, 166, 168, 173, 199,
C. I. Acid Red 35, 42, 52, 57, 62, 80, 82, 111, 114, 118, 119, 127, 128, 131, 143, 151, 154, 158, 249, 254, 257, 261, 263, 266, 289, 299, 301, 305, 336, 337, 361, 396, 397,
C. I. Acid Violet 5, 34, 43, 47, 48, 90, 103, 126,
C. I. Acid Yellow 17, 19, 23, 25, 39, 40, 42, 44, 49, 50, 61, 64, 76, 79, 110, 127, 135, 143, 151, 159, 169, 174, 190, 195, 196, 197, 199, 218, 219, 222, 227,
C. I. Acid Blue 9, 25, 40, 41, 62, 72, 76, 78, 80, 82, 92, 106, 112, 113, 120, 127: 1, 129, 138, 143, 175, 181, 205, 207, 220, 221, 230, 232, 247, 258, 260, 264, 271, 277, 278, 279, 280, 288, 290, 326,
C. I. Acid Black 7, 24, 29, 48, 52: 1, 172,
C. I. Reactive Red 3, 13, 17, 19, 21, 22, 23, 24, 29, 35, 37, 40, 41, 43, 45, 49, 55,
C. I. Reactive violet 1, 3, 4, 5, 6, 7, 8, 9, 16, 17, 22, 23, 24, 26, 27, 33, 34,
C. I. Reactive Yellow 2, 3, 13, 14, 15, 17, 18, 23, 24, 25, 26, 27, 29, 35, 37, 41, 42,
C. I. Reactive Blue 2, 3, 5, 8, 10, 13, 14, 15, 17, 18, 19, 21, 25, 26, 27, 28, 29, 38,
C. I. Reactive Black 4, 5, 8, 14, 21, 23, 26, 31, 32, 34,
C. I. Basic Red 12, 13, 14, 15, 18, 22, 23, 24, 25, 27, 29, 35, 36, 38, 39, 45, 46,
C. I. Basic violet 1, 2, 3, 7, 10, 15, 16, 20, 21, 25, 27, 28, 35, 37, 39, 40, 48,
C. I. Basic yellow 1, 2, 4, 11, 13, 14, 15, 19, 21, 23, 24, 25, 28, 29, 32, 36, 39, 40,
C. I. Basic Blue 1, 3, 5, 7, 9, 22, 26, 41, 45, 46, 47, 54, 57, 60, 62, 65, 66, 69, 71,
C. I. Basic Black 8
Etc.

As a disperse dye,
Disperse Yellow 3, 4, 42, 71, 79, 114, 180, 199, 227,
Disperse Orange 29, 32, 73, Disperse Red 11, 58, 73, 180, 184, 283,
Disperse Violet 1, 26, 48, Disperse Blue 73, 102, 167, 184
Etc. can be mentioned preferably.

  On the other hand, conventionally known organic and inorganic pigments can be used as the pigment, for example, azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments. , Dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments and other polycyclic pigments, basic dye type lakes, acid dye type lakes and other dye lakes, nitro pigments, nitroso pigments, aniline black, daylight Examples thereof include organic pigments such as fluorescent pigments and inorganic pigments such as carbon black.

  Specific organic pigments are exemplified below.

  Examples of pigments for magenta or red include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the orange or yellow pigment include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 138, pigment yellow 180, and the like.

Examples of pigments for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment Green 7 and the like are used. The color material content in the ink of the present invention is 1 to 20% by mass.

The pigment to be applied in the ink of the present invention is usually dispersed by a known dispersing means using a dispersant, and as an applicable dispersant, an anionic surfactant, a nonionic surfactant, or a water-soluble surfactant is used. A polymeric dispersant can be mentioned.
As the water-soluble polymer dispersant that can be preferably used in the ink of the present invention, the following water-soluble resin is preferably used from the viewpoint of ejection stability.

  As the water-soluble resin, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-maleic acid copolymer, styrene-maleic acid-acrylic acid alkyl ester copolymer are preferably used. Styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer It is a water-soluble resin such as.

  The content of the water-soluble resin with respect to the total amount of the ink is preferably 0.1 to 10% by mass, and more preferably 0.3 to 5% by mass. Two or more of these water-soluble resins can be used in combination.

  Examples of the dispersing means that can be used in the present invention include a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, and a high-pressure homogenizer. Various dispersers can be used. It is also preferable to use a centrifugal separator or a filter for the purpose of removing the coarse particles of the pigment dispersion.

  In the ink of the present invention, the average particle size of the pigment dispersion is preferably 500 nm or less, more preferably 200 nm or less, and particularly preferably 100 nm or less.

  The ink containing the water-dispersible polymer fine particles or the ink containing the coloring material according to the present invention can contain water, an organic solvent, or the like in addition to the constituent elements described above.

  The organic solvent that can be used in the present invention is not particularly limited, but is preferably a water-soluble organic solvent. Specifically, alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, Tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc.), polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexane) Diol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), polyhydric alcohol ethers (eg ethylene glycol) Monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl Ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, dipropylene glycol monopropyl ether, tripropylene glycol dimethyl Ethers), amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethylene Imine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocyclics (eg, 2-pyrrolidone, N-methyl- 2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), sulfoxides (for example, dimethyl sulfoxide) Etc.), sulfones (for example, sulfolane), sulfonates (for example, 1-butanesulfonic acid sodium salt), urea, acetonitrile, acetone and the like.

  Various surfactants can be used in the ink according to the present invention. Each surfactant that can be used in the present invention is not particularly limited, and examples thereof include anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl ethers, and the like. Nonionic surfactants such as oxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. In particular, an anionic surfactant and a nonionic surfactant can be preferably used.

  In the ink of the present invention, a polymer surfactant can also be used. For example, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-maleic acid-acrylic acid. Alkyl ester copolymer, Styrene-maleic acid copolymer, Styrene-methacrylic acid-acrylic acid alkyl ester copolymer, Styrene-methacrylic acid copolymer, Styrene-maleic acid half ester copolymer, Vinyl naphthalene-acrylic acid A copolymer, a vinyl naphthalene-maleic acid copolymer, etc. can be mentioned.

  In addition to the above description, the ink according to the present invention is publicly known depending on the purpose of improving the emission stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances as necessary. Various additives, such as viscosity modifiers, specific resistance regulators, film forming agents, UV absorbers, antioxidants, anti-fading agents, anti-fouling agents, rust inhibitors, etc. can be appropriately selected and used, For example, oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, 57-74192, 57-87989, 60-72785, 61-146591, JP-A-1-95091 and 3-13376, etc. Anti-fading agents, fluorescent whitening agents described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-228771, JP-A-4-219266, etc. Can be mentioned.

  The ink jet head used in the ink jet image forming method of the present invention may be an on-demand system or a continuous system. As the discharge method, an electro-mechanical conversion method (for example, single cavity type, double cavity type, bender type, piston type, shear mode type, shared wall type, etc.), electro-thermal conversion method (for example, thermal ink jet) Specific examples include a mold, a bubble jet (registered trademark) 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). However, 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. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<Production of recording medium>
(Preparation of silica dispersion S1)
Silica dispersion B1 (pH 2.6, ethanol containing 30% of vapor phase silica (Nippon Aerosil Co., Ltd .; Aerosil 300) having an average primary particle size of about 0.007 μm uniformly dispersed in advance. 1%) 400 L of an aqueous solution C1 (pH = 2.5, Sannobuco Antifoam SN381) containing 12% of the cationic polymer (P-1), 10% of n-propanol and 2% of ethanol Was added to 110 L of 2 g) at room temperature with stirring at 3000 rpm. Next, 54 L of a mixed aqueous solution A1 (concentration of 3% each) of boric acid and borax in a 1: 1 mass ratio was gradually added with stirring.

Subsequently, it disperse | distributed by the pressure of ³ kN / cm < ² > with the high-pressure homogenizer by Sanwa Kogyo Co., Ltd., the whole quantity was finished to 630L with pure water, and the almost transparent silica dispersion S1 with a silica content of 19% was obtained.

(Preparation of silica dispersion S2)
In the preparation of the silica dispersion S1, a substantially transparent silica dispersion S2 having a silica content of 19% was prepared in the same manner except that the same amount of pure water was added instead of adding a mixed aqueous solution of boric acid and borax. Prepared.

(Preparation of recording medium A)
To 100 g of the silica dispersion S1 prepared above, 49 g of a 6.5% aqueous solution of polyvinyl alcohol (average polymerization degree: 3500 saponification degree 88%) is gradually added with stirring, and finished to 200 g with pure water. T-1 was obtained.

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

Next, 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 ink absorption layer coating side). back and, also providing a subbing layer containing gelatin of 0.05 g / m ² in the ink absorbing layer coating設面side, on the opposite side of Tg of the latex polymer of from about 80 ° C. containing 0.2 g / m ² The ink jet recording medium A was obtained using a bar coater so that the amount of silica applied was 16 g / m ² and then dried in a hot air oven at 80 ° C.

(Preparation of recording medium B)
A photocrosslinkable polyvinyl alcohol derivative aqueous solution (SPP-SHR, main chain PVA polymerization degree 2300, manufactured by Toyo Gosei Kogyo Co., Ltd.) having a stilbazolium group introduced and adjusted to a concentration of 10% to 100 g of the silica dispersion S2 prepared above. 32 g of a degree of conversion (88%) was gradually added with stirring, and finished to 200 g with pure water to obtain a coating solution T-2.

  The obtained coating liquid T-2 was filtered using a TCP-10 type filter manufactured by Advantex Toyo.

Subsequently, the coating liquid T-2 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 ink absorption layer coating side). and also have a subbing layer containing gelatin of 0.05 g / m ² in the ink absorbing layer coating設面side, Tg is a latex polymer of approximately 80 ° C. containing 0.2 g / m ² on the opposite side It has a back layer) and is applied using a bar coater so that the amount of silica applied is 16 g / m ^2, and then a metal halide lamp having a dominant wavelength at 365 nm and an illuminance at a wavelength of 365 nm of 60 mW / cm using ² UV was irradiated with ultraviolet rays of 30 mJ / cm ² at an energy amount, to obtain an ink jet recording medium B was dried at 80 ° C. in a hot air oven.

(Preparation of recording medium C)
In the production of the recording medium B, a photocrosslinkable polyvinyl alcohol derivative was used as a polyvinyl acetate saponified aqueous solution having a structural unit of the exemplary compound B-2 (main chain PVA polymerization degree 3000, saponification degree 88%, crosslinking group modification rate 1 mol%). The recording medium C was obtained in the same manner except that 0.05 g of Irgacure 2959 manufactured by Ciba Specialty Chemicals was added as a photoinitiator.

(Preparation of recording medium D)
On the recording medium A produced above, a protective layer having the following composition was applied with a bar coater so as to have a solid content of 3 g / m ^2, and dried at 15 ° C. for 30 seconds and at 40 ° C. for 2 minutes to perform inkjet recording. Medium D was obtained.

<Preparation of protective layer coating solution>
Colloidal silica (Nissan Chemical Co., Ltd., Snowtex OL-40, average primary particle size 45 nm) 60 parts Colloidal silica (Nissan Chemical Co., Ltd., Snowtex OZL, average primary particle size 80 nm)
40 parts Polyvinyl alcohol (saponification degree 88%, average polymerization degree 3500) 5.0 parts Boric acid 2.0 parts Surfactant 0.3 parts (Preparation of recording medium E)
In the production of the recording medium D, a recording medium C was used instead of the recording medium A, and a polyvinyl acetate saponified product having a structural unit of exemplary compound B-2 with polyvinyl alcohol and boric acid as a protective layer coating solution ( Main chain PVA polymerization degree 3000, saponification degree 88%, crosslinkable group modification rate 1 mol%) 5 parts and Ciba Specialty Chemicals Irgacure 2959 0.04 part, after coating with a bar coater the main wavelength to 365nm in a metal halide lamp having an illuminance is used ultraviolet 60 mW / cm ² at a wavelength of 365 nm, then irradiated with ultraviolet rays of 30 mJ / cm ² in energy, in the same manner except that dried 2 minutes at 40 ° C., the recording medium E Got.

(Preparation of recording medium F)
A recording medium F was obtained in the same manner as in the production of the recording medium D, except that the two colloidal silicas were removed from the protective layer coating solution and the amount of the solid content was changed to 0.2 g / m ² .

(Preparation of recording medium G)
A recording medium G was obtained in the same manner as in the production of the recording medium E, except that the two colloidal silicas were removed from the protective layer coating solution and the amount of the solid content was changed to 0.2 g / m ² .

  Details of the binder used in each ink absorption layer described in Table 1 with an abbreviation are shown below.

Binder 1: Polyvinyl alcohol (Average polymerization degree: 3500 Saponification degree 88%)
Binder 2: Saponified polyvinyl acetate having a photocrosslinkable polyvinyl alcohol derivative having the structural unit of Exemplified Compound B-2 (main chain PVA polymerization degree 3000, saponification degree 88%, crosslinking group modification rate 1 mol%)
Binder 3: Photocrosslinkable polyvinyl alcohol derivative introduced with a stilbazolium group (Toyo Gosei Kogyo Co., Ltd .: SPP-SHR, main chain PVA polymerization degree 2300, saponification degree 88%)
<Preparation of recording ink>
[Preparation of ink set 1]
Ink set 1 was prepared according to the following procedure. The ink set 1 is composed of six colors, yellow, magenta, cyan, and black dark ink, and magenta and cyan light ink.

<Preparation of dark ink (yellow, magenta, cyan and black)>
Diethylene glycol 10%
Glycerin 10%
Triethylene glycol monobutyl ether 10%
Dye (* 1) 3.0%
Surfinol 465 (manufactured by Air Products) 0.5%
Pure water balance * 1: As for the dye, yellow was direct yellow 86, magenta was direct red 227, cyan was direct blue 199, and black was food black 2.

<Preparation of light ink (magenta and cyan)>
Diethylene glycol 10%
Glycerin 10%
Triethylene glycol monobutyl ether 10%
Dye (* 2) 0.8%
Surfinol 465 0.5%
Pure water balance * 2: The dye used was magenta direct red 227 and cyan was direct blue 199.

[Preparation of ink set 2]
In the preparation of the ink set 1 (6-color ink), Superflex 300 (Daiichi Kogyo Seiyaku, urethane latex) was added to each ink so that the solid content in the ink was 1.0%. Similarly, ink set 2 was prepared.

[Preparation of colorless ink 1]
Diethylene glycol 10%
Glycerin 10%
Triethylene glycol monobutyl ether 10%
SX1105 (Zeon Corporation, styrene-butadiene latex)
1.0% as solid content
Surfinol 465 (manufactured by Air Products) 0.5%
Pure water remaining [Preparation of colorless ink 2]
Diethylene glycol 10%
Glycerin 10%
Triethylene glycol monobutyl ether 10%
Superflex 300 (Daiichi Kogyo Seiyaku, urethane latex)
1.0% as solid content
Surfinol 465 (manufactured by Air Products) 0.5%
Pure water remaining 《Image printing》
Inkjet image recording was performed using a printer equipped with seven recording heads (piezotype: 512 nozzles) on the carriage. Specifically, with the combinations shown in Table 1, each of the six recording heads ejects the prepared six-color ink set onto the recording medium, and the remaining one recording head ejects colorless ink. did. In the case of discharging colorless ink, each ink amount was adjusted so that the ink amount of each colorless ink and the color material-containing ink amount had the relationship shown in FIG. The printed image was a neutral gray image having a reflection density of about 1.0, a black full-color image, and yellow, magenta, cyan, and black fine line images, and each of the obtained images was subjected to the following evaluations. .

<Evaluation of formed image>
[Evaluation of gloss]
The gloss of the black solid image prepared above was visually observed, and the gloss was evaluated according to the following criteria.

◎: Gloss equivalent to or better than silver salt photos ○: Gloss similar to silver salt photos △: Gloss slightly lower than silver salt photos ×: Gloss that is not as good as silver salt photos In the above evaluation rank, if it was ○ or ○, it was judged that the characteristic was excellent in practical use.

[Evaluation of print crack resistance]
Each recording medium on which a black solid image was printed was stored for 2 weeks in an environment of 23 ° C. and 20% RH, and then the state of the black solid image was visually observed, and print crack resistance was evaluated according to the following criteria.

◎: No crack is observed on the print surface. ○: The number of cracks generated on the image surface of 10 cm ² is 1 to ^3. Δ: The number of cracks generated on the image surface of 10 cm ² is 4 to 7 ×: The number of cracks generated on the image surface of 10 cm ² is 8 or more. In the above evaluation rank, if ◎ or ○, it was judged as a practically excellent characteristic.

[Evaluation of ink absorbency]
The neutral gray image created above was visually observed, and ink absorbency was evaluated according to the following criteria.

A: No occurrence of mottled unevenness in the image area. O: Occurrence of mottled unevenness in the image area is slightly observed, but there is no problem with the print quality under visual observation. The occurrence of mottled unevenness can be visually confirmed. X: The occurrence of significant mottled unevenness is recognized in the image portion. In the above evaluation rank, if ◎ or ○, it was judged that the characteristic was practically excellent.

[Evaluation of bleeding resistance during long-term storage]
The yellow, magenta, cyan and black thin line images created above were stored for 1 week in an environment of 40 ° C. and 80% RH, and then visually evaluated, and the bleeding resistance during long-term storage was evaluated according to the following criteria. .

◎: No blurring is observed in all color thin line images. ○: Slight thin line thickening is observed in some images, but is within a practically acceptable range. △: Fine lines appear in some images. Thickness is seen, and this is a quality that is problematic in practice. ×: Obvious thin line thickening is seen in all color thin line images. In the above evaluation rank, if it is ◎ or ○, it is judged that the characteristic is practically excellent. did.

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

  As is apparent from the results shown in Table 1, even when the recording medium having the constitution defined in the present invention is used, the images 1 and 6 prepared with the dye ink not containing the water-dispersible polymer particles are particularly inferior in gloss. As a result. Further, even when an ink containing water-dispersible polymer fine particles is used, if the binder of the recording medium is polyvinyl alcohol having no cross-linking ability due to ionizing radiation, print cracks and long-term as shown in images 2 to 4 can be seen. It can be seen that the effect of the present invention cannot be obtained because the bleeding resistance at the time of storage is deteriorated. Further, when a colloidal silica layer or a single binder layer is provided as the glossy layer, the ink absorption ability is lowered as seen in the images 4 and 5.

  On the other hand, images 8 to 10 formed with a recording medium using photocrosslinkable polyvinyl alcohol as a binder can obtain excellent gloss without providing a special gloss developing layer, and have ink absorbability and long-term storage. It was confirmed that a high effect was obtained with respect to the bleeding resistance of time.

It is a graph which shows the relationship between the ink amount of the colorless ink at the time of image printing, and the color material containing ink amount.

Claims (4)

In an ink jet image forming method for recording on an ink jet recording medium having an ink absorbing layer on a support, the ink absorbing layer contains a polymer compound crosslinked by ionizing radiation as a hydrophilic binder, and contains water-dispersible polymer fine particles An ink jet image forming method comprising applying an ink to be applied to at least a part of the ink jet recording medium. The ink-jet image forming method according to claim 1, wherein the ink containing the water-dispersible polymer fine particles is substantially colorless without containing a coloring material. The inkjet image forming method according to claim 1 or 2, wherein the polymer compound crosslinked by ionizing radiation is a saponified polyvinyl acetate having a structural unit represented by the following general formula (1).

[Wherein, R ₁ represents a hydrogen atom or a methyl group, n represents 1 or 2, Y represents an aromatic ring or a single bond, and X represents — (CH ₂ ) _m —COO—, —OCH ₂ —COO -Or -O- is represented, and m is an integer of 0-6. ] The inkjet image forming method according to claim 1, wherein the ink absorption layer contains inorganic fine particles.

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