JP4239820B2 - INKJET IMAGE FORMING METHOD AND INKJET RECORDED PRODUCT - Google Patents

Description

The present invention relates to an image forming method and an ink-jet recorded matter with Lee inkjet recording medium.

  In recent years, the progress of ink jet technology has been remarkable, and printer technology, ink technology, and dedicated recording medium technology have come together to obtain a quality approaching that of silver halide photography. With such an improvement in image quality, there are many cases where the storability of an inkjet image is compared with a conventional silver salt photograph. However, in many of the dye inks used, the ink-jet image formed is deteriorated due to movement of colorant such as water resistance and weakness of bleeding resistance, light resistance and weakness to oxidizing gas, etc. Deterioration accompanied by chemical reaction peculiar to colorants has been pointed out.

  Many proposals have been made to date to improve the storage stability of dye ink images. As an inkjet recording medium, for example, in Japanese Patent Publication No. 2-31673, a layer composed of thermoplastic organic polymer particles is provided on the outermost layer of the recording medium, and after recording an image, the thermoplastic organic polymer particles are melted and formed into a film. As a result, the formation of a polymer protective film achieves improvement in water resistance and weather resistance and imparting gloss to images.

  Although this technology has been continuously studied and commercialized since then, there are still many points that are insufficient in various characteristics as compared with silver salt photography.

  The first problem is ink absorbability. In recent years, with regard to image quality, due to remarkable progress in printer technology, image quality close to that of silver salt photography has been increasingly gained by the use of small ink droplets, multi-dots, and light ink with low pigment concentration. On the other hand, the printing speed has been increased, the number of nozzles has been increased, the scanning speed has been increased, and further, the adoption of a line head has been promoted. In these cases, the recording medium has a sufficient ink absorption speed and If the ink absorption capacity is not provided, color bleeding and beading are caused and image quality is deteriorated. The color bleed here is a color blur generally referred to, and the beading generally occurs when the ink absorption rate into the ink absorption layer is slow, and visually resembles a small circle. It is recognized as uneven color. This is largely due to the fact that the ink absorption layer (ink permeability) of the ink absorption layer made of thermoplastic organic polymer particles on the surface layer is low. On the other hand, Japanese Patent Application Laid-Open No. 2000-203151 proposes a method for increasing the particle size of the thermoplastic organic polymer particles to be used. As a result, this is a major obstacle to achieving a reduction in the total processing time accompanying an increase in printing speed due to technological improvements. Japanese Patent Laid-Open No. 7-237348 proposes a method of adding silica particles to a layer composed of the thermoplastic organic polymer particles as the outermost layer for the purpose of improving beading. Since some of the silica particles are buried in the voids made of thermoplastic organic polymer particles, the ink absorption rate is rather slow. Even if the particle size distribution is controlled, it is necessary to say that the silica particles are only an additive region and the improvement effect thereof is insufficient. Japanese Patent Laid-Open No. 2000-280603 discloses a method in which the maximum 30% of colloidal silica is added to the outermost thermoplastic organic polymer particles to improve the color, but from the viewpoint of improving ink absorbency. The effect is hardly recognized.

  The second problem is image storability. By melting thermoplastic organic polymer particles, water resistance, bleed resistance, etc. are improved, but even with these technologies, the light resistance is still at a sufficient level compared to silver salt photography. I can't say that. There has been proposed an invention for printing on a recording medium having a layer composed of thermoplastic organic polymer particles on the outermost layer using a pigment ink that can be expected to improve image storability, particularly light resistance. It is not solved at the same time. That is, in Japanese Patent Application Laid-Open No. 11-157207, the ink absorption rate is insufficient, and a drying time of 30 minutes is required after printing, so that the total throughput is greatly reduced. In Japanese Patent Application Laid-Open Nos. 11-192775 and 11-208097, the outermost layer is an ink absorption layer of thermoplastic organic polymer particles, and the ink absorption rate cannot be said to be sufficient. In JP 2000-158803 A, the particle diameter of the thermoplastic organic polymer particles is set to 1 μm or more so that the ink passage (void) is not blocked by the pigment particles in the pigment ink and the ink absorbability is not lowered. However, if the particle size is increased, a great amount of time is required for melting by heat treatment, resulting in an obstacle to shortening the total throughput (conveying time). Japanese Patent Application Laid-Open No. 2000-203152 proposes a method in which an inorganic pigment is added to a lower layer portion of a layer made of thermoplastic organic polymer particles, and the particle size thereof is set to the μm order. However, if an inorganic pigment of the order of μm is used, the transparency of the image is lowered, and it cannot be said that the image quality is equivalent to that of a silver salt photograph.

  The third problem is the total processing speed. The total processing speed is the printing speed and the total time required from the printing until the outermost layer is melted, and includes the drying time and the processing time required for melting and filming. In JP-A-9-104164, a glass fiber having a particularly high aspect ratio is added to the outermost layer made of thermoplastic organic polymer particles to increase heat propagation and to keep energy for film formation low. However, by simply adding glass fiber, a sufficient ink absorption speed cannot be obtained at the same time, it is not suitable for high-speed printing, and cannot contribute to the total throughput.

  Furthermore, in each of the conventional techniques described above, the following further problems arise.

  The first problem is writing on the image. In the case of a recording medium whose outermost layer is mainly composed of thermoplastic organic polymer particles, the writing property with a ballpoint pen, aqueous pen or the like is deteriorated, the ink paste is lowered, and the surface is easily stained due to friction.

  The second problem is a reduction in the surface strength of the image. In the case of a recording medium whose outermost layer is mainly composed of thermoplastic organic polymer particles, there is a drawback that the image is easily scratched and noticeable with a decrease in surface strength.

  The third problem is the weakness of the film after the image recording until the outermost layer is melted. Since the thermoplastic organic polymer particles in the surface layer are easily melted in a later process, the particles are not bound by a strong bond. In many cases, an aqueous latex is used, and the design is relatively low in water resistance before filming. For this reason, in the case of a recording medium whose outermost layer is mainly composed of thermoplastic organic polymer particles, there may be a jagged trace of the conveying system or the surface may be damaged by a roller during the conveying process in the printer after recording. This is particularly noticeable when a high-speed printer is used.

  The fourth problem is image fusion. When storing created images in an album, etc., if they are stored in a high temperature state (for example, in the summer or in a car), the polymer film on the surface of the image and the protective sheet of the album will be fused. There is. For the outermost thermoplastic organic polymer particles, a polymer having a higher Tg is selected so that it does not melt in the daily life. However, after recording, the solvent in the ink, the plasticizer in the album protective sheet, etc. As a result, the apparent Tg is lowered, and fusion may occur in a high temperature state that occurs within the environmental range in daily life.

  In JP-A-7-101142, a small amount of latex is added to the inorganic pigment as the structure of the glossy layer. However, the particle form is changed by calendar treatment in the production process. In addition, there is an example in which an acrylic colloidal silica composite emulsion is used in another configuration, but this is a configuration different from that in which an ink-absorbing void is formed by mixing an inorganic pigment and thermoplastic fine particles. The ink absorptivity derived from the pigment is not sufficiently exhibited, and the gloss expression derived from the polymer component and the image preserving effect are not sufficiently exhibited.

  In order to manufacture a recording medium containing thermoplastic fine particles in the surface layer, a method is generally known in which an ink absorbing layer having high ink absorbability is applied and formed in advance, and then a coating solution containing thermoplastic fine particles is applied. As the thermoplastic fine particles, an aqueous latex is often used from the viewpoint of the environment, and the aqueous latex usually has a relatively low viscosity and is difficult to apply and dry. A binder can be further added to increase the viscosity, but in that case, the ink absorption rate is lowered, which is not preferable.

  Further, a method using silica fine particles and a hydrophilic binder is known as a recording medium having high gloss and a very fast ink absorption speed. In particular, in a production method in which multiple layers are simultaneously coated using the difference in viscosity of the coating solution, the production cost is low, the gloss of the produced recording medium and the ink absorption speed are excellent, and it is well received in the market. Even when a thermoplastic fine particle-containing layer is applied to the surface layer of the silica-based void recording medium, a method in which a silica void layer is formed in advance and a thermoplastic fine particle-containing coating liquid is applied thereon is performed as described above. Has been. This method requires application and drying twice, which is disadvantageous from the viewpoint of production cost.

  On the other hand, when an inkjet recording medium is used under various environmental conditions, it is required to obtain characteristics equivalent to those in a normal environment, for example, 20 ° C. and 50% RH. In particular, when a recording medium containing thermoplastic fine particles in the surface layer is used, the ink absorbability is lowered particularly under high-temperature and high-humidity conditions. It has been found that the range of gloss improvement by melting and forming a film is lowered.

  In particular, it has been found that when a recording medium containing thermoplastic fine particles in the surface layer is used, the recording medium is likely to break and break down in the transport path in the printer under low temperature and low humidity conditions. It has been found that this cracking phenomenon is likely to occur when a recording medium is conveyed at high speed in a printer, particularly when image formation is performed at high speed. In addition, it has been found that when a roll-shaped recording medium is used for continuous printing, the recording medium tends to occur when a large conveying force greater than that of the sheet-shaped recording medium is applied.

Accordingly, a first object of the present invention is to provide an image forming method and an ink jet recorded product capable of obtaining an image with improved image storage stability. The second object is to provide an image forming method and an ink jet recorded product capable of obtaining an image with improved image quality. A third object is to provide an image forming method and an ink jet recorded product capable of obtaining a photographic image quality equivalent to a silver salt photograph. A fourth object is to provide an image forming method and an ink jet recorded product capable of obtaining an image having image storability equivalent to that of a silver salt photograph. A fifth object is an image forming method and an ink jet recorded product that can provide a photographic image quality equivalent to a silver salt photograph at high speed. A sixth object is to enable simultaneous multi-layer coating and to reduce manufacturing costs. A seventh object is to provide an image forming method and an ink jet recorded product that can obtain an image with improved writing property to an image. An eighth object is to provide an image forming method and an ink jet recorded product capable of obtaining an image with improved image surface strength. A ninth object is to provide an image forming method and an ink jet recorded product that can obtain an image that is hardly scratched in a printer. A tenth object is to provide an image forming method and an ink jet recorded product that can obtain an image with improved fusion of images in an album. An eleventh object is to provide an image forming method and an ink jet recorded product that can obtain an image quality equivalent to normal environmental conditions without causing cracks on the surface of the recording medium even under various temperature and humidity environments.

The above object of the present invention can be achieved by the following configurations.
(1) In an ink jet image forming method in which an image is formed on an ink jet recording medium by melting thermoplastic fine particles contained in a surface layer portion to form an image, the ink jet recording medium includes a plurality of ink absorbing layers on a support. have a, all of the plurality of ink absorbing layer contains the following silica having an average primary particle size of 100nm as an inorganic pigment, the surface layer portion containing an inorganic pigment and thermoplastic particles, inorganic pigment and thermoplastic particles the mass ratio is 3/7 or more, 7/3 or less and said surface ratio of the inorganic pigment to the total components in the layer portion 30 mass% or more, of the ink jet image, characterized in that 70 mass% or less Forming method .
(2) The method for forming an inkjet image according to (1), wherein the mass ratio of the inorganic pigment and the thermoplastic fine particles in the surface layer portion of the inkjet recording medium is 4/6 or more and 6/4 or less .
(3) The method for forming an inkjet image according to (1) or (2), wherein the thermoplastic fine particles contained in the surface layer part are melted by a process including heat treatment .
(4) The inkjet image forming method according to any one of (1) to (3), wherein an image is recorded using a pigment ink .
(5) An inkjet recorded product formed by the inkjet image forming method according to any one of (1) to (4) .

According to the present invention, high image quality comparable to a silver salt photograph can be printed at high speed, color bleeding, bronzing, image surface strength, writability have been improved, and light resistance, water resistance, abrasion resistance, and album storage excellent melt contamination resistance, further, it is possible to provide a wide range of film properties (bending crack resistance) even in an environment, color bleeding, images forming method and an ink jet recording material which has excellent image gloss is obtained.

According to the present invention, in an ink jet image forming method in which an image is recorded on an ink jet recording medium and then the thermoplastic fine particles contained in the surface layer portion are melted to form an image, the ink jet recording medium absorbs a plurality of inks on a support. All of the plurality of ink absorbing layers contain silica having an average primary particle size of 100 nm or less as an inorganic pigment, and a surface layer portion contains an inorganic pigment and thermoplastic fine particles, the inorganic pigment and the thermoplastic The mass ratio of the fine particles is 3/7 or more and 7/3 or less, and the ratio of the inorganic pigment to all the components in the surface layer is 30% by mass or more and 70% by mass or less. Preferably they are 30 mass% or more and 60 mass% or less, More preferably, they are 30 mass% or more and 50 mass% or less.

The mass ratio of the inorganic pigment and thermoplastic particles is 3/7 above, it is 7/3 or less is a feature, preferably in particular, 4/6 or more, and 6/4 or less.

  As a support that can be used in the present invention, a support conventionally used for an ink jet recording medium, for example, a paper support such as plain paper, art paper, coated paper, and cast coated paper, a plastic support, and both sides are used. A paper support coated with polyolefin and a composite support obtained by bonding them together can be appropriately selected and used.

  In the recording medium of the present invention, for the purpose of increasing the adhesive strength between the support 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 recording medium of the present invention is not necessarily colorless, and may be a colored recording paper.

  In the recording medium 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 or the like because the recorded image is close to photographic image quality and a high-quality image can be obtained at low cost. A paper support laminated with such 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 is made 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 and / or LDP is preferably 10% by mass or more and 70% by mass or less.

  As the above-mentioned pulp, chemical pulp (sulfate pulp or sulfite pulp) with few impurities is preferably used, and a pulp whose whiteness is improved by performing a bleaching treatment 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 24% by mass as defined in JIS-P-8207, and 42 mesh residue. It is preferable that the sum with the mass% of is 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 / ^{m 2,} especially 50 to 200 g / ^{m 2} is preferred. 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. As the surface sizing agent, a sizing agent similar to the size 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 that covers the front and back of the base paper is mainly low-density polyethylene (LDPE) and / or high-density polyethylene (HDPE), but in addition, some LLDPE (linear low-density polyethylene), polypropylene, etc. should be used. Can do. In particular, the polyethylene layer on the ink absorbing layer side preferably has an improved opacity and whiteness by adding rutile or anatase type titanium oxide to the polyethylene, as widely used 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 and coated on the surface of the base paper, a so-called molding process is performed to provide a matte surface or silky surface as obtained with ordinary photographic printing paper. A surface-formed product 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 curling under low and high humidity after providing a void layer and a back layer. The range is 40 μm and the back layer side is 10 to 30 μm.

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

1. Tensile strength: strength defined by JIS-P-8113, preferably 20 to 300 N in the vertical direction and 10 to 200 N in the horizontal direction. 2. Tear strength: 0.1 to 20 N in the vertical direction and 2 to 20 N in the horizontal direction are preferred by the method specified in JIS-P-8116. Compression modulus ≧ 98.1 MPa
4). Surface Beck smoothness: 20 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 a so-called molded product. Surface roughness: The surface roughness specified in JIS-B-0601 preferably has a maximum height of 10 μm or less per reference length of 2.5 mm. Opacity: when measured by the method defined in JIS-P-8138, 80% or more, particularly 85 to 98% is preferable. Whiteness: L ^* , a ^* , and b ^* defined by JIS-Z-8729 are preferably L ^* = 80 to 95, a ^* = − 3 to +5, and b ^* = − 6 to +2. . 8. Surface glossiness: 60 degree specular glossiness defined in JIS-Z-8741 is preferably 10 to 95%. Clark stiffness: Clark stiffness in the conveying direction of the recording medium 50~300cm ^2/100 in which the support is preferably 10. Water content of middle paper: usually 2 to 100% by weight, preferably 2 to 6% by weight, based on the middle paper
In general, the ink absorbing layer is roughly divided into a swelling type and a void type.

  As the swelling type, a hydrophilic binder is used, for example, gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide or the like is applied alone or in combination, and this is used as an ink absorbing layer.

As the void type, fine particles and a hydrophilic binder are mixed and applied, and particularly glossy ones are preferable. As the fine particles, silica having an average primary particle size of 100 nm or less is used. As the hydrophilic binder, gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide or the like is preferably used alone or in combination.

Of the above two types, in order to adapt to continuous high-speed printing, it is more suitable that the ink absorption speed of the recording medium is faster. In the present invention, a void type is used .

  Hereinafter, the void type ink absorbing layer will be described in detail.

The void layer is formed by soft aggregation of silica having an average primary particle size of 100 nm or less, which is mainly a hydrophilic binder and an inorganic pigment (hereinafter also referred to as 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, a coating liquid containing solid fine particles and a hydrophilic or hydrophobic binder is coated on a support, and after drying, the ink jet recording paper is immersed in water or a liquid containing an appropriate organic solvent, A method for producing voids by dissolving solid fine particles, a method for 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 a drying process, porous A method in which a coating liquid containing solid fine particles and a hydrophilic binder is coated on a support to form voids in or between the porous fine particles. The coating solution containing the solid particles and or particulate oil and a hydrophilic binder having a product coated on a support, and a method of forming an air gap between the solid particles are known. One feature of the present invention is that the void layer is formed by containing silica having an average primary particle size of 100 nm or less.

Examples of silica that is inorganic fine particles used for the above purpose include white inorganic pigments such as synthetic amorphous silica and colloidal silica .

The average primary 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 1,000 arbitrary particle sizes, and calculating the simple average value (number average). As required. Here, the particle diameter of each particle is represented by a diameter assuming a circle equal to the projected area.

  As the silica that can be used in the present invention, silica synthesized by a usual 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.

One feature of silica, which is an inorganic fine particle, is that its average primary particle size is 100 nm or less. For example, in the case of the gas phase method fine particle silica, the average particle size (particle size in the dispersion state before coating) of the inorganic fine particles dispersed in the primary particle state is characterized by being 100 nm or less. There, more preferably 4 to 50 nm, and most preferably from 4 to 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 hydrophilic binders (hereinafter also referred to as water-soluble resins) that can be used in the present invention include polyvinyl alcohol, gelatin, polyethylene oxide, polyvinyl pyrrolidone, polyacrylic acid, polyacrylamide, polyurethane, dextran, dextrin, and color ginane ( κ, ι, λ, etc.), agar, pullulan, water-soluble polyvinyl butyral, hydroxyethyl cellulose, carboxymethyl cellulose and the like. Two or more of these hydrophilic binders can be used in combination.

  The water-soluble resin preferably used in the present invention is polyvinyl alcohol.

  The polyvinyl alcohol preferably used in the present invention includes, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, modified polyvinyl alcohol such as polyvinyl alcohol having a cation-modified terminal and anion-modified polyvinyl alcohol having an anionic group. Alcohol is also included.

  The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 1,000 or more, and particularly preferably has an average degree of polymerization of 1,500 to 5,000. The degree of saponification is preferably 70 to 100%, particularly preferably 80 to 99.5%.

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

  Examples of the ethylenically unsaturated monomer having a cationic group include trimethyl- (2-acrylamido-2,2-dimethylethyl) ammonium chloride and trimethyl- (3-acrylamido-3,3-dimethylpropyl) ammonium chloride. N-vinylimidazole, N-vinyl-2-methylimidazole, N- (3-dimethylaminopropyl) methacrylamide, hydroxylethyltrimethylammonium chloride, trimethyl- (2-methacrylamidopropyl) ammonium chloride, N- (1, 1-dimethyl-3-dimethylaminopropyl) acrylamide and the like.

  The ratio of the cation-modified group-containing monomer of the cation-modified polyvinyl alcohol is 0.1 to 10 mol%, preferably 0.2 to 5 mol%, relative to vinyl acetate.

  Anion-modified polyvinyl alcohol is, for example, polyvinyl alcohol having an anionic group as described in JP-A-1-2060888, as described in JP-A-61-237681 and JP-A-63-330779, Examples thereof include a copolymer of vinyl alcohol and a vinyl compound having a water-soluble group, and modified polyvinyl alcohol having a water-soluble group as described in JP-A-7-285265.

  Nonionic modified polyvinyl alcohol is, for example, a polyvinyl alcohol derivative obtained by adding a polyalkylene oxide group to a part of vinyl alcohol as described in JP-A-7-9758, and described in JP-A-8-25595. And a block copolymer of a vinyl compound having a hydrophobic group and vinyl alcohol. Polyvinyl alcohol can be used in combination of two or more, such as the degree of polymerization and the type of modification.

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

  The ratio of the inorganic fine particles and the water-soluble resin used in the ink absorbing layer is usually 2: 1 to 20: 1 by mass ratio, and particularly preferably 3: 1 to 10: 1.

Further, it may contain a cationic water-soluble polymer having a quaternary ammonium base in the molecule, and is usually used in the range of 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 is deteriorated. 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.

The ink absorption layer composed of a plurality of layers according to the present invention contains silica and thermoplastic fine particles having an average primary particle size of 100 nm or less whose surface layer portion is an inorganic pigment, and the mass ratio of the inorganic pigment to the thermoplastic fine particles is It is 3/7 or more and 7/3 or less, and the ratio of the inorganic pigment with respect to all the components in a surface layer part is 30 mass% or more and 70 mass% or less. The surface layer here is not limited to the case where it is on the outermost surface side of the ink jet recording medium as long as the effect of the present invention is exhibited. The recording medium of the present invention exhibits many of the effects of the present invention by, for example, melting thermoplastic fine particles contained in the surface layer portion by heating after image recording. For example, when printing with dye ink, if light resistance or water resistance is improved by the presence or absence of heat treatment after image recording, the inorganic pigment and the thermoplastic fine particles are included, and the mass ratio of the inorganic pigment and the thermoplastic fine particles 3/7 or more and 7/3 or less, and the ratio of the inorganic pigment to the total components in the layer is 30% by mass or more and 70% by mass or less even if the layer is not the outermost surface side of the inkjet recording medium. Corresponds to the present invention.

In addition, when printing with pigment ink, if the image quality, for example, glossiness is improved, the abrasion resistance is improved, or the degree of bronzing is improved with or without heat treatment after image recording, inorganic pigments and heat Including a plastic fine particle, the mass ratio of the inorganic pigment to the thermoplastic fine particle is 3/7 or more and 7/3 or less, and the ratio of the inorganic pigment to all the components in the layer is 30% by mass or more and 70% by mass or less. Even if the layer is not on the outermost surface side of the ink jet recording medium, the configuration corresponds to the present invention.

  Although the preferable structural example for clarifying the surface layer part said by this invention is enumerated below, the layer structure which concerns on this invention is not limited only to these.

1: Inorganic pigment containing silica having an average primary particle size of 100 nm or less and thermoplastic fine particles, the mass ratio of the inorganic pigment to the thermoplastic fine particles being 3/7 or more and 7/3 or less, and all components in the layer The layer in which the ratio of the inorganic pigment to the ink is 30% by mass or more and 70% by mass or less is the outermost surface side of the ink jet recording medium. 2: Including silica and thermoplastic fine particles whose average primary particle size is 100 nm or less On the layer where the mass ratio of the inorganic pigment to the thermoplastic fine particles is 3/7 or more and 7/3 or less, and the ratio of the inorganic pigment to all the components in the layer is 30 mass% or more and 70 mass% or less. 3. Structure provided with a thin layer for the purpose of improving surface properties 3: Inorganic pigment containing silica having an average primary particle size of 100 nm or less and thermoplastic fine particles, and the mass ratio of inorganic pigment to thermoplastic fine particles being 3/7 more than, A thin layer having an ultraviolet absorbing function for the purpose of cutting harmful light on a layer that is 7/3 or less and the ratio of the inorganic pigment to all components in the layer is 30% by mass or more and 70% by mass or less. 4: Inorganic pigment containing silica having an average primary particle size of 100 nm or less and thermoplastic fine particles, the mass ratio of the inorganic pigment to the thermoplastic fine particles being 3/7 or more and 7/3 or less, and a layer A structure in which a layer containing a matting agent is provided on a layer in which the ratio of the inorganic pigment to all the components in the layer is 30% by mass or more and 70% by mass or less. 5: Including inorganic pigment and thermoplastic fine particles. A peelable layer on a layer in which the mass ratio of the plastic fine particles is 3/7 or more and 7/3 or less, and the ratio of the inorganic pigment to all components in the layer is 30% by mass or more and 70% by mass or less. The configuration provided.

Among the above-described configuration examples, the most preferable configuration is that the content layer of silica and thermoplastic fine particles having an average primary particle size of 100 nm or less, which is an inorganic pigment of one item that can most exert the effects of the present invention, is an ink jet recording medium. This is the case on the outermost surface side.

The surface layer portion of the ink absorbing layer containing silica and thermoplastic fine particles having an average primary particle size of 100 nm or less, which is an inorganic pigment among the plurality of ink absorbing layers in the present invention, refers to one layer in the recording medium manufacturing process. It is preferable to use a coating solution prepared as a single layer in a manufacturing process, and more preferably a single layer.

The surface layer portion containing silica and thermoplastic fine particles having an average primary particle size of 100 nm or less, which is an inorganic pigment according to the present invention, is composed of silica, thermoplastic fine particles and an optional binder component, which are inorganic pigments, having an average primary particle size of 100 nm or less. May be included.

As the silica used in the surface layer portion, silica synthesized by an ordinary wet method, colloidal silica, silica synthesized by a gas phase method, or the like is preferably used, but the fine particle silica particularly preferably used in the present invention is colloidal. Silica or fine particle silica synthesized by a gas phase method is preferable, and among them, fine particle silica synthesized by a gas phase method not only provides a high porosity, but is added to a cationic polymer used for immobilizing a dye. Sometimes coarse aggregates are difficult to form, which is preferable. Alumina or alumina hydrate may be crystalline or amorphous, and any shape such as amorphous particles, spherical particles, and acicular particles can be used. As the inorganic pigment, silica is preferably used in the present invention, and alumina is preferably used in the present invention, and silica is more preferable among them.

  The inorganic pigment is preferably in a state where the fine particle dispersion before mixing with the cationic polymer is dispersed to the primary particles.

  Examples of the thermoplastic fine particles that can be used in the present invention include polycarbonate, polyacrylonitrile, polystyrene, polyacrylic acid, polymethacrylic acid, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyester, polyamide, polyether, These copolymers and their salts are mentioned. Among them, styrene-acrylic acid ester copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-acrylic acid ester copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, SBR latex preferable. The thermoplastic fine particles may be used by mixing a plurality of polymers having different monomer compositions, particle sizes, and polymerization degrees.

  In selecting the thermoplastic fine particles, ink acceptability, glossiness of an image after fixing by heating and pressing, image fastness and releasability should be taken into consideration.

  Regarding the ink receptivity, when the particle diameter of the thermoplastic fine particles is less than 0.05 μm, the separation of the pigment particles and the ink solvent in the pigment ink is slowed, resulting in a decrease in the ink absorption rate. On the other hand, if it exceeds 10 μm, it is not preferable from the viewpoint of film strength and gloss deterioration of the ink jet recording medium after coating and drying. For this reason, the preferable thermoplastic fine particle diameter is preferably 0.05 to 10 μm, more preferably 0.1 to 5 μm. More preferably, it is 0.1-1 micrometer.

  Moreover, a glass transition point (Tg) is mentioned as a reference | standard of selection of a thermoplastic microparticle. When Tg is lower than the coating / drying temperature, for example, the coating / drying temperature at the time of producing the recording medium is already higher than Tg, and the ink solvent permeates, so voids due to the thermoplastic fine particles disappear. Further, when Tg is higher than the temperature at which the support is denatured by heat, in order to melt and form a film after ink jet recording with a pigment ink, a fixing operation at high temperature is required. There is a problem with the thermal stability and the like. The preferable Tg of the thermoplastic fine particles is 50 to 150 ° C.

  Moreover, as minimum film-forming temperature (MFT), the thing of 50-150 degreeC is preferable.

  The thermoplastic fine particles are preferably dispersed in an aqueous system from the viewpoint of environmental suitability, and an aqueous latex obtained by emulsion polymerization is particularly preferable. At this time, the type obtained by emulsion polymerization using a nonionic dispersant as an emulsifier is a form that can be preferably used. The thermoplastic fine particles used are preferably less residual monomer components from the viewpoint of odor and safety, preferably 3% by mass or less, more preferably 1% by mass or less, based on the solid content of the polymer. Preferably it is 0.1 mass% or less.

Surface portion containing an inorganic pigment and thermoplastic particles, as the solid content ^is not particularly limited but preferably in the range of ^{2g / m 2 ~50g / m 2} , the range of 3g / ^{m 2} ~30g / m 2 is more preferable.

In the recording medium of the present invention, the solid content of the thermoplastic fine particles contained in the surface layer portion ^is preferably in the range of ^{0.5g / m 2 ~15g / m 2} , a range of 1g / ^{m 2} ~7g / m 2 is Particularly preferred. When the solid content of the thermoplastic fine particles is too small, a sufficient film cannot be formed, and the pigment cannot be sufficiently dispersed in the film. For this reason, image quality and gloss are not sufficiently improved. On the other hand, when the amount of the solid content of the thermoplastic fine particles is too large, the thermoplastic fine particles cannot be completely formed into a film in a short heating process, and the fine particles remain, and the opacity is increased and the image quality is lowered. In addition, the ink absorption speed is also lowered, causing blurring at the boundary, which becomes a problem.

  The coating solution for the surface layer portion containing the inorganic pigment and the thermoplastic fine particles may be obtained by dispersing the inorganic pigment and the thermoplastic fine particles at the same time, or may be a method of mixing each dispersion prepared when preparing the coating solution.

  The recording medium of the present invention can be used for any of dye ink, pigment ink, water-based ink, oil-based ink, and hot-melt ink, but is particularly suitable for water-based dye ink, water-based pigment ink, and oil-based pigment ink. Ink and water-based pigment ink are more suitable, and water-based pigment ink is most suitable among them.

  In the present invention, the thermoplastic fine particles contained in the surface layer portion are preferably melted by processing after inkjet image recording, which is effective in terms of image quality and image storage. In particular, in the present invention, it is preferable to melt by a heating step.

  Next, the manufacturing method of the inkjet recording medium of this invention is demonstrated.

  As a method for producing an ink jet recording medium, each component layer including a plurality of ink absorbing layers can be produced by individually or simultaneously selecting from a known coating method and coating and drying on a support. it can. Examples of the coating method include a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method, or US Pat. Nos. 2,761,419 and 2,761,791. A slide bead coating method using an hopper, an extrusion coating method, or the like is preferably used.

  In the present invention, in the method for producing an ink jet recording medium having a plurality of ink absorbing layers, the inorganic pigment and the thermoplastic fine particles are contained, and the mass ratio of the inorganic pigment to the thermoplastic fine particles is 3/7 or more, 9/1 or less, In addition, it is preferable that the surface layer portion having a ratio of the inorganic pigment to the total components in the layer of 30% by mass or more and 70% by mass or less and one layer adjacent to the surface layer part are coated simultaneously. The most preferable application mode is to apply all of the plurality of ink absorbing layers simultaneously.

  When the slide bead coating method is used, the viscosity of each coating solution at the time of simultaneous multilayer coating is preferably in the range of 5 to 100 mPa · s, more preferably in the range of 10 to 50 mPa · s. Moreover, when using a curtain application | coating system, the range of 5-1200 mPa * s is preferable, More preferably, it is the range of 25-500 mPa * s.

  Further, the viscosity at 15 ° C. of the coating solution is preferably 100 mPa · s or more, more preferably 100 to 30,000 mPa · s, further preferably 3,000 to 30,000 mPa · s, and most preferably 10 , 30,000 to 30,000 mPa · s.

  As a coating and drying method, the coating liquid is heated to 30 ° C. or more, and after simultaneous multi-layer coating, the temperature of the formed coating film is once cooled to 1 to 15 ° C. and dried at 10 ° C. or more. Is preferred. It is preferable to prepare, apply and dry the coating liquid at a temperature equal to or lower than the Tg of the thermoplastic fine particles so that the thermoplastic fine particles contained in the surface layer portion do not form a film at the time of preparing the coating liquid and at the time of coating and drying. . More preferably, the drying conditions are a wet bulb temperature of 5 to 50 ° C. and a film surface temperature of 10 to 50 ° C. Moreover, as a cooling method immediately after application | coating, it is preferable to carry out by a horizontal set system from a viewpoint of the formed coating-film uniformity.

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

  The ink jet recorded matter of the present invention can be obtained by recording an image on a recording medium with an ink jet printer. In the present invention, as a method for forming an inkjet image, the recorded image is post-processed to melt the thermoplastic fine particles contained in the surface layer portion. Examples of the post-processing method for melting include a method of applying an organic solvent capable of melting thermoplastic fine particles to an image with an inkjet head or the like, a method of melting by heating, and the like. A method of melting by treatment is preferred.

  As the ink used for image recording, a water-based ink composition, an oil-based ink composition, a solid (phase change) ink composition, or the like can be used, but a water-based ink composition (for example, 10% by mass or more per total ink mass) Water-based ink jet recording liquid containing the above water can be used particularly preferably.

  As the colorant used in the ink, a water-soluble dye such as an acid dye, a direct dye, a reactive dye, a disperse dye, or a pigment can be used.

  In the present invention, it is preferable to use a pigment ink as a colorant. This is particularly preferable from the viewpoint of image storage stability. As the pigment used in the pigment ink, insoluble pigments, organic pigments such as lake pigments, carbon black and the like can be preferably used.

  The insoluble pigment is not particularly limited. Dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole and the like are preferable.

  Specific pigments that can be preferably used include the following pigments.

  Examples of the magenta or red pigment 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 pigment for orange or yellow 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. And CI Pigment Yellow 138.

  Examples of the pigment 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. And CI Pigment Green 7.

  For these pigments, a pigment dispersant may be used as necessary. Examples of pigment dispersants that can be used include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates. Acid salt, naphthalene sulfonate, alkyl phosphate, polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine Activators such as oxides, or styrene, styrene derivatives, vinyl naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives Block copolymer comprising a monomer of the above, a random copolymer and can be exemplified salts thereof.

  As a method for dispersing the pigment, for example, various dispersing machines such as 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, and a paint shaker 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.

  The average particle diameter of the pigment particles in the pigment ink is selected in consideration of stability in the ink, image density, glossiness, light resistance, etc. In addition, the image forming method of the present invention improves glossiness, textures. It is preferable to select the particle size as appropriate from the viewpoint of improvement. In the present invention, the reason why glossiness or texture is improved is not clear at this stage, but in the formed image, the pigment is in a desirable state dispersed in the film in which the thermoplastic fine particles are melted. I guess it is related. For the purpose of high-speed processing, the thermoplastic fine particles must be melted and formed into a film in a short time, and the pigment must be sufficiently dispersed in the film. At this time, it is considered that the surface area of the pigment has a great influence, and therefore there is an optimum region for the average particle diameter.

  The water-based ink composition which is a preferable form as the pigment ink preferably uses a water-soluble organic solvent in combination. Examples of the water-soluble organic solvent that can be used in the present invention include alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl). Alcohol), polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol Etc.), polyhydric alcohol ethers (for example, ethylene glycol monomethyl ether, ethylene glycol) Ether monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl 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, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.), amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, mole) Phosphorus, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, 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.), urea, acetonitrile, acetone etc. are mentioned. Preferable water-soluble organic solvents include polyhydric alcohols. Furthermore, it is particularly preferable to use a polyhydric alcohol and a polyhydric alcohol ether in combination.

  The water-soluble organic solvent may be used alone or in combination. The total amount of the water-soluble organic solvent added to the ink is 5 to 60% by mass, preferably 10 to 35% by mass.

  The ink composition may be prepared by adding various known additives such as viscosity according to the purpose of improving ejection stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances as necessary. Adjusting agents, surface tension adjusting agents, specific resistance adjusting agents, film forming agents, dispersants, surfactants, ultraviolet absorbers, antioxidants, anti-fading agents, anti-fouling agents, rust inhibitors, etc. are appropriately selected and used. For example, polystyrene, polyacrylic acid esters, polymethacrylic acid esters, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, or a copolymer thereof, urea resin, melamine resin, etc. Organic latex fine particles, liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil and other oil droplet fine particles, Thion or nonionic surfactants, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, JP-A-57-74192, JP-A-57-87989, 60-72785, 61-146591, anti-fading agents described in JP-A-1-95091 and 3-13376, JP-A-59-42993, 59-52689, 62- 280069, 61-242871, and JP-A-4-219266, etc., optical brighteners, pH adjusters such as sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, etc. Can be mentioned.

  The ink composition has a viscosity at the time of flight of preferably 40 mPa · s or less, and more preferably 30 mPa · s or less. The ink composition has a surface tension during flight of preferably 20 mN / m or more, and more preferably 30 to 45 mN / m.

  A preferred form of the image forming method of the present invention is to melt the thermoplastic fine particles contained in the surface layer portion by heat treatment after image recording. The heat treatment is performed for the purpose of improving image quality such as texture, gloss, bronzing and rubbing by melting thermoplastic fine particles in the recording medium. In the heat treatment, it is desirable to give the amount of heat necessary to almost completely melt the thermoplastic fine particles in the recording medium, while it is desirable to heat-treat in a short time for shortening the treatment time, So long as there is no substantial difference in image quality, the thermoplastic fine particles need not be melted or formed into a film.

  In order to provide the necessary amount of heat in a short period of time, it is desirable to heat using a heat source as high as possible. However, if the temperature is excessively high, the support will be damaged, severe curling will occur, or the image surface will be rough, the roller Contamination may occur, and the range of 100 to 200 ° C is preferable, and the range of 100 to 150 ° C is more preferable.

  The heating method may be performed by a heater built in the printer or by another heater. As the heating means, use of a heating roller is suitable for preventing unevenness and performing continuous processing in a small space. In addition, diverting an electrophotographic heat fixing device is advantageous in terms of cost. For example, the recording medium may be heated and pressurized by passing the recording medium between a heating roller incorporating a heating element and a pressure roller, or the recording medium may be heated between two heating rollers.

  A heating roller consists of a hollow roller, and rotates with a drive means. In the roller, as a heat source, for example, a heating element made of a halogen lamp heater, a ceramic heater, nichrome wire or the like is incorporated. The roller is preferably made of a material having high heat conductivity, and particularly preferably a metal roller. The roller surface is preferably coated with a fluororesin to prevent contamination. In addition, a silicon rubber roller coated with heat-resistant silicon can be used.

When the heating roller is used, the conveyance speed of the recording medium is preferably in the range of 1 to 15 mm / second. This was found to be preferable from the viewpoint of improving the image quality in addition to the viewpoint of high-speed processing. In order to obtain higher texture and gloss, it is preferable to apply pressure at the same time as or immediately after heating. As a pressure to pressurize, the range of 9.8 * 10 < ⁴ > -4.9 * 10 < ⁶ > Pa is preferable. This is because film formation is promoted by pressurization.

  Next, a printer used for ink jet image formation according to the present invention will be described.

  The printer that can be used in the present invention is not particularly limited as long as it has a recording medium storage unit, a transport unit, an ink cartridge, and an inkjet print head, such as a commercially available printer, but at least in a roll shape The recording medium storage unit, the transport unit, the ink jet print head, the cutting unit, and, if necessary, a series of printer sets including a heating unit, a pressure unit, and a recording print storage unit are preferable. The recording head may be any of a piezo method, a thermal method, and a continuous method, but the piezo method is preferable from the viewpoint of stability with pigment ink.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these.

Example 1
<< Preparation of inkjet recording medium >>
An ink jet recording medium was prepared according to the following procedure.

(Preparation of each dispersion)
(Preparation of titanium oxide dispersion-1)
20 kg of titanium oxide having an average particle size of 0.25 μm (Ishihara Sangyo Co., Ltd .: W-10), 150 g of sodium tripolyphosphate having a pH of 7.5, 500 g of polyvinyl alcohol (manufactured by Kuraray Co., Ltd .: PVA235, average polymerization degree 3500), cation After adding to 150 liters of an aqueous solution containing 150 g of the conductive polymer (P-1) and 10 g of the defoaming agent SN381 manufactured by San Nopco Co., Ltd. and dispersing with a high-pressure homogenizer (manufactured by Sanwa Kogyo Co., Ltd.), the total amount is finished to 100 liters. Thus, a uniform titanium oxide dispersion-1 was obtained.

(Preparation of silica dispersion-1)
125 kg of vapor phase method silica (Nippon Aerosil Kogyo Co., Ltd .: A300) having an average primary particle size of 0.007 μm is pH adjusted with nitric acid using a jet stream inductor mixer TDS manufactured by Mitamura Riken Kogyo Co., Ltd. After being sucked and dispersed in 620 liters of pure water adjusted to 2.5 at room temperature, the whole amount was finished to 694 liters with pure water. When this dispersion was diluted and an electron micrograph of silica particles was taken, 85 to 90% by number of all particles had an average particle size of 0.01 μm or less and were dispersed to primary particles. It was confirmed.

(Preparation of silica dispersion-2)
Silica dispersion-1 prepared above in a temperature range of 25-30 ° C. in 18 liters of a solution (pH = 2.3) containing 1.41 kg of cationic polymer (P-2) and 4.2 liters of ethanol Was added over 20 minutes with stirring, and then 7.0 liters of an aqueous solution containing 260 g of boric acid and 230 g of borax (pH = 7.3) was added over about 10 minutes. 1 g of the antifoaming agent SN381 was added. This mixed solution was dispersed twice with a high pressure homogenizer manufactured by Sanwa Kogyo Co., Ltd. at a pressure of 24.5 MPa, and the entire amount was finished to 97 liters with pure water to prepare an almost transparent silica dispersion-2.

(Preparation of silica dispersion-3)
125 kg of gas phase method silica (Tokuyama: QS-20) having an average primary particle size of about 0.012 μm was mixed with nitric acid using a jet stream inductor mixer TDS manufactured by Mitamura Riken Kogyo Co., Ltd. Was dispersed in 620 L of pure water adjusted to 2.5 at room temperature, and then the total amount was finished to 694 L with pure water to prepare silica dispersion-3.

(Preparation of silica dispersion-4)
69.4 L of the silica dispersion-3 prepared above was added to 18 L of an aqueous solution (pH = 2.3) containing 1.14 kg of the cationic polymer (P-1), 2.2 L of ethanol, and 1.5 L of n-propanol. Then, 7.0 L of an aqueous solution containing 260 g of boric acid and 230 g of borax was added, and 1 g of an antifoaming agent SN381 (manufactured by San Nopco) was added. This mixed solution was dispersed with a high-pressure homogenizer manufactured by Sanwa Kogyo Co., Ltd., and the entire amount was finished to 97 L with pure water to prepare silica dispersion-4.

(Preparation of silica dispersion-5)
125 kg of gas phase method silica (Nippon Aerosil Kogyo Co., Ltd .: A50) having an average primary particle size of about 0.03 μm is pH adjusted with nitric acid using a jet stream inductor mixer TDS manufactured by Mitamura Riken Kogyo Co., Ltd. Was dispersed by suction at room temperature in 215 L of pure water adjusted to 2.5, and finished to a dispersion having a solid content concentration of 40 mass / volume% to prepare silica dispersion-5.

(Preparation of silica dispersion-6)
0.56 kg of the cationic polymer (P-1) is dissolved in 27.2 kg of ion exchange water, 63.0 L of the silica dispersion-5 is added with stirring, and then a 6% boric acid aqueous solution ( pH = 6.5) 8.8 L was added, and 1 g of antifoaming agent SN381 (manufactured by San Nopco Co., Ltd.) was added. The mixture was adjusted to pH 4.4 with a 6% nitric acid aqueous solution and then dispersed with a high-pressure homogenizer manufactured by Sanwa Kogyo Co., Ltd., and the whole amount was finished to 99.7 L with pure water, and silica dispersion-6 was prepared. Prepared.

(Preparation of fluorescent brightener dispersion-1)
400 g of oil-soluble fluorescent whitening agent UIVITEX-OB manufactured by Ciba Geigy Co., Ltd. was dissolved by heating in 9.0 kg of diisodecyl phthalate and 12 L of ethyl acetate. This was 3.5 kg of acid-treated gelatin and a cationic polymer (P-2). After adding and mixing with 65 L of an aqueous solution containing 6000 ml of a 50% aqueous solution, the mixture was emulsified and dispersed three times with a high-pressure homogenizer manufactured by Sanwa Industry Co., Ltd. at a pressure of 24.5 MPa, and ethyl acetate was removed under reduced pressure. The total amount was finished to 100 L, and fluorescent brightener dispersion-1 was prepared. The pH of this dispersion was about 5.3.

(Preparation of thermoplastic fine particle coating solution)
(Preparation of thermoplastic fine particle coating solution 1)
A styrene-acrylic latex polymer (Tg 78 ° C., average particle size 250 nm, solid content concentration 40%) emulsion-polymerized using polyvinyl alcohol as an emulsifier is adjusted to pH 4.7 with a 6% nitric acid aqueous solution, and this is a thermoplastic fine particle. It was set as the coating liquid 1.

(Preparation of thermoplastic fine particle coating solution 2)
A vinyl chloride copolymer emulsion Vinibran 602 (manufactured by Nissin Chemical Co., Ltd .: Tg 63 ° C., MFT 130 ° C.) was adjusted to pH 4.7 with a 6% nitric acid aqueous solution, and the viscosity at 43 ° C. was adjusted to 45 cp. A fine particle coating solution 2 was obtained.

(Preparation of thermoplastic fine particle coating solution 3)
Styrene-acrylic latex polymer emulsion-polymerized using polyvinyl alcohol as an emulsifier (Tg 78 ° C., average particle size 170 nm, solid content concentration 38%) is adjusted to pH 4.7 with a 6% nitric acid aqueous solution, and this is a thermoplastic fine particle. It was set as the coating liquid 3.

(Preparation of thermoplastic fine particle coating solution 4)
Styrene-acrylic latex polymer emulsion-polymerized using polyvinyl alcohol as an emulsifier (Tg 65 ° C., average particle size 260 nm, solid content concentration 40%) is adjusted to pH 4.7 with a 6% nitric acid aqueous solution, and this is a thermoplastic fine particle. It was set as the coating liquid 4.

[Preparation of each coating solution]
After preparing each coating solution as described below, each coating solution was filtered using a commercially available filter (TCP10 or TCP30 manufactured by Toyo Roshi Kaisha, Ltd.).

(Preparation of coating solution 1)
While stirring at 40 ° C., the following additives were sequentially mixed in 600 ml of the prepared silica dispersion-2 to prepare coating solution 1.

Polyvinyl alcohol (Kuraray Industries, Ltd .: PVA235
194.6 ml of 7% aqueous solution with an average degree of polymerization of 3500)
Fluorescent brightener dispersion-1 25 ml
Titanium oxide dispersion-1 33ml
Latex emulsion (Daiichi Kogyo Co., Ltd .: AE-803) 18ml
The whole amount was finished to 1000 ml with pure water. The coating solution pH was 4.4.

(Preparation of coating solution 2)
While stirring at 40 ° C., the following additives were sequentially mixed in 650 ml of the prepared silica dispersion-2 to prepare coating solution 2.

Polyvinyl alcohol (Kuraray Industries, Ltd .: PVA235
201.6 ml of 7% solution of average degree of polymerization: 3500)
Optical brightener dispersion-1 35 ml
The whole amount was finished to 1000 ml with pure water. The coating solution pH was 4.4.

(Preparation of coating solution 3)
While stirring at 40 ° C., the following additives were sequentially mixed in 650 ml of the prepared silica dispersion-2 to prepare a coating solution 3.

Polyvinyl alcohol (Kuraray Industries, Ltd .: PVA235
201.6 ml of 7% aqueous solution with an average degree of polymerization of 3500)
Silicon dispersion (Toray Dow Corning Silicone Co., Ltd .:
BY-22-839) 15ml
Saponin 50% aqueous solution 4ml
The whole amount was finished to 1000 ml with pure water. The pH of the coating solution was 4.5.

(Preparation of coating solution 4)
While stirring at 40 ° C., the following additives were sequentially mixed in 600 ml of the prepared silica dispersion-4 to prepare coating solution 4.

Polyvinyl alcohol (Kuraray Industries, Ltd .: PVA203)
6ml of 10% aqueous solution
Polyvinyl alcohol (Kuraray Industrial Co., Ltd .: PVA235)
185ml of 7% aqueous solution
The whole amount was finished to 1000 ml with pure water.

(Preparation of coating solution 5)
After mixing the thermoplastic fine particle coating liquid 1 and the coating liquid 2 prepared so that the mass ratio of thermoplastic fine particles: inorganic pigment is 70:30, the viscosity at 43 ° C. is 45 cp. Water was added to this to make coating solution 5.

(Preparation of coating solution 6)
A coating solution 6 was prepared in the same manner as in the preparation of the coating solution 5 except that the solid content mass ratio of thermoplastic fine particles: inorganic pigment was changed to 45:55.

(Preparation of coating solution 7)
A coating solution 7 was prepared in the same manner as in the preparation of the coating solution 5 except that the solid content mass ratio of thermoplastic fine particles: inorganic pigment was changed to 40:60.

(Preparation of coating solution 8)
A coating solution 8 was prepared in the same manner as in the preparation of the coating solution 5 except that the solid content mass ratio of thermoplastic fine particles: inorganic pigment was changed to 30:70.

(Preparation of coating solution 9)
A coating solution 9 was prepared in the same manner as in the preparation of the coating solution 5 except that the solid content mass ratio of thermoplastic fine particles: inorganic pigment was changed to 20:80.

(Preparation of coating solution 10)
A coating solution 10 was prepared in the same manner as in the preparation of the coating solution 5 except that the solid content mass ratio of thermoplastic fine particles: inorganic pigment was changed to 10:90.

(Preparation of coating solution 11)
The thermoplastic fine particle coating solution 2 and the coating solution 2 are used to mix so that the mass ratio of thermoplastic fine particles: inorganic pigment is 30:70, and then the viscosity at 43 ° C. is 45 cp. Water was added to prepare a coating solution 11.

(Preparation of coating solution 12)
The thermoplastic fine particle coating liquid 3 and the coating liquid 2 are used to mix so that the solid content mass ratio of thermoplastic fine particles: inorganic pigment is 30:70, and then the viscosity at 43 ° C. is 45 cp. Water was added to prepare coating solution 12.

(Preparation of coating solution 13)
The thermoplastic fine particle coating solution 4 and the coating solution 2 are mixed so that the mass ratio of thermoplastic fine particles: inorganic pigment is 30:70, and the viscosity at 43 ° C. is 45 cp. Water was added to prepare a coating solution 13.

(Preparation of coating solution 14)
Using the thermoplastic fine particle coating liquid 1 and the coating liquid 4, after mixing so that the solid content mass ratio of thermoplastic fine particles: inorganic pigment is 30:70, the viscosity at 43 ° C. is 45 cp. Water was added to prepare a coating solution 14.

(Preparation of coating solution 15)
While stirring at 40 ° C., the following additives were sequentially mixed in 710 ml of the silica dispersion-6 prepared above to prepare a coating solution 15.

Polyvinyl alcohol (Kuraray Industries, Ltd .: PVA203)
3ml of 10% aqueous solution
4.8% of polyvinyl alcohol (Kuraray Industrial Co., Ltd .: PVA235) and polyvinyl alcohol (Kuraray Industrial Co., Ltd .: PVA245)
Aqueous solution containing 1.84% of 273 ml
The whole amount was finished to 1000 ml with pure water.

(Preparation of coating solution 16)
A coating liquid 16 was prepared by dispersing 100 parts of alumina hydrate (catalyst AS-3) and 30 parts of polyvinyl alcohol (Kuraray Kogyo Co., Ltd .: PVA117).

(Preparation of coating solution 17)
The thermoplastic fine particle coating solution 1 and the coating solution 16 were mixed so that the mass ratio of thermoplastic fine particles: inorganic pigment was 30:70 to prepare a coating solution 17.

(Preparation of coating solution 18)
A coating liquid 18 was prepared by mixing 100 parts by mass of zinc oxide, 25 parts by mass of polyvinyl alcohol, 5 parts by mass of SBR latex, and 500 parts by mass of water.

(Preparation of coating solution 19)
Chemipearl W-300 (manufactured by Mitsui Chemicals) was used as it was to make coating solution 19.

(Preparation of coating solution 20)
A coating solution 20 was prepared in the same manner as in the preparation of the coating solution 5 except that the solid content mass ratio of thermoplastic fine particles: inorganic pigment was changed to 50:50.

(Preparation of coating solution 21)
In the preparation of the coating liquid 5, a coating liquid 21 was prepared in the same manner except that the solid content mass ratio of thermoplastic fine particles: inorganic pigment was changed to 60:40.

(Preparation of coating solution 22)
A coating solution 22 was prepared in the same manner as in the preparation of the coating solution 5 except that the solid content mass ratio of thermoplastic fine particles: inorganic pigment was changed to 65:35.

(Preparation of coating solution 23)
Using the thermoplastic fine particle coating liquid 1 and the coating liquid 2, after mixing so that the mass ratio of thermoplastic fine particles: inorganic pigment is 50:50, the viscosity at 43 ° C. is 40 mPa · s. Thus, an appropriate amount of water was added to prepare a coating solution 23.

(Preparation of coating solution 24)
The thermoplastic fine particle coating liquid 3 and the coating liquid 2 are used to mix so that the mass ratio of thermoplastic fine particles: inorganic pigment is 50:50, and then the viscosity at 43 ° C. is 40 mPa · s. Thus, an appropriate amount of water was added to prepare a coating solution 24.

(Preparation of coating solution 25)
The thermoplastic fine particle coating solution 4 and the coating solution 2 are used to mix so that the mass ratio of thermoplastic fine particles: inorganic pigment is 50:50, and then the viscosity at 43 ° C. is 40 mPa · s. Thus, an appropriate amount of water was added to prepare a coating solution 25.

[Preparation of inkjet recording medium]
(Preparation of comparative sample 1)
A paper support (also referred to as RC paper, having a thickness of 220 μm and containing 13% by mass of anatase-type titanium oxide based on polyethylene in the polyethylene of the ink absorption layer) coated on both sides with polyethylene is described in the table below. In the same way, three layers are simultaneously applied and dried with a slide hopper so that the coating liquid corresponding to each of the first layer, the second layer, and the third layer in order from the support side becomes the wet film thickness described in the table below. It was. Each coating solution was heated to 40 ° C. and then applied, cooled for 20 seconds in a cooling zone maintained at 0 ° C. immediately after application, and then subjected to 45 ° C. wind (relative humidity 15%) for 60 seconds for 45 seconds. Dry sequentially for 60 seconds with air at ℃ (25% relative humidity) and 60 seconds with wind at 50 ℃ (25% relative humidity) for 2 minutes in an atmosphere of 20 to 25 ° C. and relative humidity of 40 to 60 ° C. After humidity conditioning, the sample was wound up to produce Comparative Sample 1.

(Preparation of comparative sample 2)
Comparative Sample 2 was prepared in the same manner as in Comparative Sample 1 except that the type of coating solution for each layer and the wet film thickness of each layer were changed as described in the table below.

(Preparation of Comparative Sample 3)
On the prepared comparative sample 2, the prepared thermoplastic fine particle coating liquid 1 (abbreviated as L1) is applied using a blade coater so that the solid content of the thermoplastic fine particles is 5 g / m ^2. Comparative sample 3 was prepared by drying under the same conditions as comparative sample 1.

(Preparation of Comparative Sample 4)
Comparative sample 4 was prepared in the same manner as in comparative sample 3, except that thermoplastic fine particle coating liquid 2 (abbreviated as L2) was used instead of thermoplastic fine particle coating liquid 1 (L1).

(Preparation of comparative sample 5)
Except for changing the type of coating solution and wet film thickness of each layer as described in the table below, up to three layers were prepared in the same manner as in Comparative Sample 1, and the fourth layer described in the table below was formed thereon. In the same manner, it was applied and dried to prepare Comparative Sample 5.

(Preparation of samples 1 to 11)
The sample of the present invention was prepared in the same manner as in Comparative Sample 2, except that the coating liquid types and wet film thicknesses of the first to fourth layers were changed as shown in the table below, and all layers were simultaneously coated and dried. 1 to 11 were produced.

(Preparation of sample 12)
On the support used in the comparative sample 1, the coating liquid 16 was applied and dried with an air knife coater so that the dry coating amount was 15 g / m ^2, and then the coating liquid 17 was coated thereon. Similarly, the sample 12 of the present invention was prepared by applying and drying with an air knife coater such that the dry coating amount was 5 g / m ² .

(Preparation of Sample 13)
On the support used in the preparation of the comparative sample 1, the coating liquid 18 was applied and dried by a blade coater so that the dry coating amount was 12 g / m ² . On this, coating liquid 8 was applied so as to have a wet film thickness of 50 μm, and then dried in the same manner as comparative sample 1 to prepare sample 13 of the present invention.

(Preparation of sample 14)
In the preparation of Sample 13, Sample 14 of the present invention was prepared in the same manner except that the coating liquid 19 was used as the coating liquid for the first layer and the dry coating amount was changed to 10 g / m ² .

(Preparation of sample 15)
Sample 15 of the present invention was prepared in the same manner as in Sample 3, except that the support was changed to a water-absorbent paper support (coated paper inner paper thickness: 165 μm).

(Preparation of sample 16)
In the same manner as in Sample 3, except that the support was changed to a white polyethylene terephthalate (thickness: 100 μm) film support, all layers were simultaneously applied and dried to prepare Sample 16 of the present invention.

(Preparation of Samples 17 to 25)
In the comparative sample 2, all layers were simultaneously applied and dried in the same manner except that the types and wet film thicknesses of the first to fourth layers were changed as shown in the table below. 17-25 were produced.

The detailed structure of the upper Symbol samples, shown in Table 1.

The wet film thickness (μm) or solid content mass (g / m ² ) of each coating solution described in the above table is as follows.

Coating solution 1: wet film thickness 50 μm
Coating solution 2: wet film thickness 100 μm
Coating solution 3: wet film thickness 50 μm
Coating solution 4: wet film thickness 65 μm
Coating solutions 5 and 6: wet film thickness 50 μm
Coating solution 6 ′: wet film thickness 55 μm
Coating solutions 7 to 14: wet film thickness 50 μm
Coating solution 15: wet film thickness 65 μm
Coating liquid 16: solid content mass 15 g / m ²
Coating solution 17: solid content mass 5 g / m ²
Coating liquid 18: solid content mass 12 g / m ²
Coating liquid 19: solid content mass 10 g / m ²
Coating solution 20: wet film thickness 40 μm
Coating solution 21: wet film thickness 35 μm
Coating solution 21 ′: wet film thickness 50 μm
Coating solution 22: wet film thickness 30 μm
Coating solutions 23 to 25: wet film thickness 40 μm
Coating solution 24 ′: wet film thickness 45 μm
L1, L2: solid content mass 5 g / m ²
Moreover, * 1 in Table 1 represents the ratio (mass%) of the inorganic pigment with respect to all the components in the outermost layer.

<Production of ink>
A water-based pigment ink was prepared according to the method described below.

(Preparation of pigment dispersion)
(Preparation of yellow dispersion 1)
C. I. Pigment Yellow 74 20% by mass
Styrene-acrylic acid copolymer (molecular weight 10,000, acid value 120)
12% by mass
Diethylene glycol 15% by mass
Ion-exchanged water 53% by mass
After mixing each of the above compositions, the mixture was dispersed using a horizontal bead mill (System Zeta Mini manufactured by Ashizawa Co., Ltd.) filled with 0.3% zirconia beads at a volume ratio of 60% to prepare Yellow Pigment Dispersion 1. The average particle size of the obtained yellow pigment was 112 nm.

(Preparation of magenta dispersion 1)
C. I. Pigment Red 122 25% by mass
Jonkrill 61 (acrylic-styrene resin, manufactured by Johnson)
(Solid content) 18% by mass
Diethylene glycol 15% by mass
Ion-exchanged water 42% by mass
After mixing each of the above compositions, a magenta pigment dispersion 1 was prepared by dispersing using a horizontal bead mill (System Zeta Mini manufactured by Ashizawa Co., Ltd.) filled with 0.3 mm zirconia beads at a volume ratio of 60%. The average particle size of the obtained magenta pigment was 105 nm.

(Preparation of cyan dispersion 1)
C. I. Pigment Blue 15: 3 25% by mass
Jonkrill 61 (acrylic-styrene resin, manufactured by Johnson)
(Solid content) 15% by mass
Glycerin 10% by mass
Ion-exchanged water 50% by mass
Each of the above compositions was mixed, and then dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 0.3 mm zirconia beads at a volume ratio of 60% to prepare Cyan Pigment Dispersion 1. The average particle diameter of the obtained cyan pigment was 87 nm.

(Preparation of Black Dispersion 1)
Carbon black 20% by mass
Styrene-acrylic acid copolymer (molecular weight 7,000, acid value 150)
10% by mass
Glycerin 10% by mass
Ion exchange water 60% by mass
Each of the above compositions was mixed, and then dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 0.3% zirconia beads at a volume ratio of 60% to prepare Black Pigment Dispersion 1. The average particle size of the obtained black pigment was 75 nm.

[Preparation of pigment ink]
(Preparation of dark yellow ink 1)
Yellow dispersion 1 15% by mass
Acrylic emulsion (Yodosol AD53 Tg 80 ° C average particle size 80nm
Japan NCS) 10% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Maltitol 5% by mass
Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 39.9% by mass
Each of the above compositions was mixed and stirred, and then filtered through a 1 μm filter to prepare yellow dark ink 1. The average particle diameter of the pigment contained in the ink was 120 nm, and the surface tension γ was 36 mN / m.

(Preparation of yellow light ink 1)
Yellow dispersion 1 3% by mass
Acrylic emulsion (Yodosol AD53 Tg 80 ° C average particle size 80nm
Japan NCS) 10% by mass
Ethylene glycol 25% by mass
Diethylene glycol 10% by mass
Maltitol 10% by mass
Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 41.9% by mass
The above compositions were mixed and stirred, and then filtered through a 1 μm filter to prepare yellow light ink 1. The average particle size of the pigment contained in the ink was 118 nm, and the surface tension γ was 37 mN / m.

(Preparation of magenta dark ink 1)
Magenta dispersion 1 15% by mass
Styrene-acrylic emulsion (Microgel E-1002
Tg approx. 60 ° C. Average particle size 100 nm Nippon Paint Co., Ltd.) 10% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Maltitol 5% by mass
Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 39.9% by mass
The above compositions were mixed and stirred, and then filtered through a 1 μm filter to prepare magenta dark ink 1. The average particle size of the pigment contained in the ink was 113 nm, and the surface tension γ was 35 mN / m.

(Preparation of magenta light ink 1)
Magenta dispersion 1 3% by mass
Acrylic emulsion (Microgel E-1002 Tg approx. 60 ° C
Average particle size 100 nm Nippon Paint Co., Ltd.) 8% by mass
Ethylene glycol 25% by mass
Diethylene glycol 10% by mass
Maltitol 10% by mass
Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 43.9% by mass
The above compositions were mixed and stirred, and then filtered through a 1 μm filter to prepare magenta light ink 1. The average particle size of the pigment contained in the ink was 110 nm, and the surface tension γ was 37 mN / m.

(Preparation of cyan dark ink 1)
Cyan dispersion 1 10% by mass
Styrene-acrylic emulsion (Yodosol GD86B Tg60 ° C
Average particle size 90nm NCS Japan) 10% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Maltitol 5% by mass
Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 44.9% by mass
The above compositions were mixed and stirred, and then filtered through a 1 μm filter to prepare cyan dark ink 1. The average particle size of the pigment contained in the ink was 95 nm, and the surface tension γ was 36 mN / m.

(Preparation of cyan light ink 1)
Cyan dispersion 1 2% by mass
Acrylic emulsion (Yodosol GD86B Tg60 ° C
Average particle size 90nm NCS Japan) 10% by mass
Ethylene glycol 25% by mass
Diethylene glycol 10% by mass
Maltitol 10% by mass
Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.2% by mass
Ion-exchanged water 42.8% by mass
The above compositions were mixed and stirred, and then filtered through a 1 μm filter to prepare cyan light ink 1. The average particle size of the pigment contained in the ink was 92 nm, and the surface tension γ was 33 mN / m.

(Preparation of black dark ink 1)
Black dispersion 1 10% by mass
Acrylic emulsion (Yodosol GD86B Tg60 ° C
Average particle size 90nm NCS Japan) 8% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Maltitol 5% by mass
Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 46.9% by mass
Each of the above compositions was mixed and stirred, and then filtered through a 1 μm filter to prepare black dark ink 1. The average particle diameter of the pigment contained in the ink was 85 nm, and the surface tension γ was 35 mN / m.

(Preparation of black light ink 1)
Black dispersion 1 2% by mass
Acrylic emulsion (Yodosol GD86B Tg60 ° C
Average particle size 90nm NCS Japan) 8% by mass
Ethylene glycol 25% by mass
Diethylene glycol 10% by mass
Maltitol 10% by mass
Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 44.9% by mass
The above compositions were mixed and stirred, and then filtered through a 1 μm filter to prepare a black light ink 1. The average particle size of the pigment contained in the ink was 89 nm, and the surface tension γ was 36 mN / m.

<Creation of inkjet image>
As described in the table below, inkjet images 1 to 60 were prepared by combining the type of recording medium, the type of each ink, and the presence or absence of heat treatment after image recording.

  Printers and inks used for image output are as follows.

  Images 1 and 2 were output using an ink jet printer PM-770 (manufactured by Seiko Epson Corporation) and a dye ink provided as a standard in the printer.

  Images 3 to 21, 43 to 48, and 55 to 57 are output using an ink jet printer PM-770 (manufactured by Seiko Epson Corporation) and a dye ink that is provided as standard, and then the heating roller portion of FIG. The heat treatment was performed through.

  The images 22 and 23 were output using an inkjet printer MC-2000 (manufactured by Seiko Epson Corporation).

  The images 24 to 42, 49 to 54, and 58 to 60 were filled with the prepared pigment inks in the printer shown in FIG. 1 and printed by the printer shown in FIG.

  The printed image is a wedge test image of yellow, magenta, cyan, and black, a grid-like test chart and a portrait of Y, M, C, B, G, R, and Bk drawn in a width of 1 cm in length and width, respectively. The image was printed.

  FIG. 1 is a schematic configuration diagram showing an ink jet recording apparatus using pigment ink used in Examples.

  In FIG. 1, pigment inks (yellow, magenta, cyan, black, and dark inks) are set on the printer's 8-color head, a roll-shaped recording medium having a roll width of 12.7 cm is set, and yellow, magenta, cyan, Images including black wedge images were printed continuously. The recording medium was cut with a built-in cutter every 8.9 cm. In this way, prints corresponding to the L plate were continuously produced. The recorded print was heat-treated by heating means in the apparatus. The total image forming speed was adjusted by changing the number of head nozzles, scanning speed, head coating frequency, transport speed, fixing roller transport speed, fixing conditions, and recording medium roll width.

  For post-processing after ink jet recording, all images except images 1 and 2 were processed with a heat-fixing roller, and the uppermost thermoplastic fine particles were melted and formed into a film to form an image.

<Evaluation of output image>
The following evaluations were performed on the images 1 to 60 output as described above.
[Evaluation-1: Image quality-related evaluation]
(Visual evaluation of image quality)
Twenty persons were arbitrarily selected as the image quality evaluation panel mainly on the output test chart and person portrait image, and the image quality was visually evaluated. Each sample to be evaluated was evaluated by comparing a similar image with a photographic image reference sample in which a similar image was printed on a conventional color paper (color paper TypeQAA7 gloss type manufactured by Konica).

  In the evaluation, the number of persons judged to be equivalent to the photographic image reference sample among the 20 panelists was totaled, and evaluated according to the ranks 1 to 5 shown below.

5: 17 or more people evaluated to be equivalent to the photographic image reference sample 4: 14 to 16 people evaluated to be equivalent to the photographic image reference sample 3: Evaluated to be equivalent to the photographic image reference sample Number of people: 10 to 13 people 2: 6 to 9 people evaluated as being equivalent to photographic image reference sample 1: Less than 6 people evaluated to be equivalent to photographic image reference sample (Bleed's evaluation)
Bleed related to ink absorption rate was evaluated. For the evaluation, the printed Y, M, C, B, G, R, and Bk strip test charts were visually observed for the occurrence of color bleeding at the boundary between the white background and each color, and evaluated according to the criteria shown below. went.

4: Almost no color blur is observed at the boundary of all colors 3: Slight color blur is observed at the border in one or two colors 2: Color blur at the boundary is observed in several colors 1: Several colors with very intense border color blur (Bronze evaluation)
About the bronzing which is a peculiar phenomenon at the time of using a pigment ink, the following methods evaluated the samples 22-42, 49-54, and 58-60.

  Bronze is evaluated by observing each image from various angles under a fluorescent lamp (observed from 80 °, 60 °, 45 °, and 30 ° when 90 ° is directly above and 0 ° is directly beside). An image in which metallic gloss was recognized was evaluated as 1, and an image in which metal gloss was not observed was evaluated as 2.

(Evaluation of image surface strength)
The image surface strength of each output image surface was measured according to JIS standard K6717. The measurement was performed under a 23 ° C., 55% RH atmosphere using a continuous weighted scratch strength tester (Shinto Kagaku Scratch Meter HEIDON 18 type) with a scratch distance of 100 mm and a load variable from 0 to 100 g. A load value (g) at which the surface was damaged with a 0.5 mm needle (sapphire needle) was measured, and less than 50 g was evaluated as x, and 50 g or more was evaluated as ◯.

Tables 2 and 3 show the image quality-related evaluation results obtained as described above.

[Evaluation-2: Evaluation of abrasion resistance and image storage stability]
(Evaluation of abrasion resistance)
For images printed with pigment ink, the pigment particles are generally on the surface of the image, and the abrasion resistance is weak. Therefore, the abrasion resistance was evaluated. For rubbing resistance, the image was rubbed 5 times with Kimwipe S-200 (manufactured by Crecia), and the degree of image density reduction was graded as follows.

◎: No color fading ○: Some color fading is observed, but I do not care about the image △: Color fading can be confirmed, image quality deteriorates ×: Color fading is large, greatly affecting image quality (Image Evaluation of storage stability 1: light resistance)
The light fastness of each image is determined by irradiating a sample portion having a reflection density of about 1.0 for each of yellow, magenta, cyan, and black single-color wedge images at 70000 Lx for 240 hours using a xenon fade meter, and then reflecting the light. The residual density rate {(reflection density after irradiation with xenon / fadometer / reflection density before irradiation with xenon / fadometer) × 100 (%)} was measured. As a result of the evaluation, since the reflection density remaining rate of the magenta image was the lowest in all samples, the reflection density remaining rate of the magenta image was evaluated according to the following criteria.

5: Reflection density residual ratio is 95% or more 4: Reflection density residual ratio is less than 85 to 95% 3: Reflection density residual ratio is less than 70 to 85% 2: Reflection density residual ratio is less than 50 to 70% 1: Reflection density Residual rate is less than 50% (Evaluation of image storage stability 2: water resistance)
The water resistance was evaluated for the printed images of Samples 1 to 21, 43 to 48, and 55 to 57 using dye ink. Each printed sample was immersed in pure water at 25 ° C. for 1 minute, then taken out, dried, and the residual ratio relative to the untreated sample was determined by the following formula, and the water resistance was evaluated according to the rank described below. .

Water resistance (%) = (main reflection density of the infiltrated sample / main reflection density of the untreated sample) × 100
5: Water resistance (%) is 95% or more 4: Water resistance (%) is less than 85 to 95% 3: Water resistance (%) is less than 70 to 85% 2: Water resistance (%) is less than 50 to 70% 1: Water resistance (%) is less than 50% (Fusibility evaluation during storage of inkjet images)
Each of the formed inkjet image samples is stored in a commercially available album with a protective sheet, stored for 2 months at 50 ° C. and 80% RH, and then the degree of image peeling after the protective sheet is peeled off is visually observed. evaluated.

Tables 4 and 5 show the evaluation results obtained as described above.

  According to the present invention, the following effects can be obtained.

  In images 1 to 21, image 43 to 48, and images 55 to 57 using dye ink, images 3 to 5 printed using comparative recording media 3 to 5 are inferior to silver salt photographs in terms of image quality. In addition, color bleeding (bleed) was deteriorated. This is considered to be caused by the low ink absorption speed of the comparative recording media 3 to 5. In addition to the above images 3 to 5, the image surface strength is also reduced. Further, comparative images 1 and 2 that do not use thermoplastic fine particles in the outermost layer are results that are extremely inferior in light resistance, but also inferior in water resistance, although they are excellent in bleeding. Further, in the images using pigment ink, the image quality obtained is lacking in glossiness and transparency in the comparative images 22 and 23 in which the thermoplastic fine particles are not used in the outermost layer and heat treatment is not performed, and the target photograph It is far from the image quality, and bronzing, which is a unique phenomenon when using pigment ink, is clearly observed, and there is a defect that the image cannot be seen accurately depending on the observation angle. Further, even in the comparative images 24 to 26 subjected to the heat treatment, color bleeding (bleed) occurred, and a satisfactory image could not be obtained. On the other hand, images 6 to 21, images 27 to 42, images 49 to 54, and images 58 to 60 using the recording medium according to the present invention were subjected to heat treatment with respect to each of the above comparative samples. An image close to the quality of salt photographs can be obtained, and it is excellent in bleeding property, abrasion resistance, image surface strength, water resistance, which is a particular problem when using dye ink, and unique property when using pigment ink. The bronzing in question was improved and good results could be obtained across all properties. As for the light resistance, although an improvement in light resistance is recognized with respect to the comparative image even in the image using the dye ink, it cannot be said that the light resistance level is sufficient, but at the level using the pigment ink. Was able to confirm an extremely excellent result.

  In addition, with regard to the writability on each formed image, ink writing was evaluated by writing letters on a white background with a water-based pen, an oil-based ballpoint pen, a fountain pen, and the like. Furthermore, in order to evaluate the durability of a character, evaluation which rubs a character once with Kimwipe S-200 (made by Crecia) and a finger was performed. As a result, the images 3 to 5 and 24 to 26 using the comparative recording medium are poorly ink-stained and faint with respect to any writing instrument, and the characters are rubbed when rubbed. On the other hand, all the images formed using the recording medium according to the present invention showed good writing properties.

  Further, the image 41 recorded on the recording medium 15 with MC2000 was sprayed with ethyl acetate, passed through a pressure roller, and then dried. Like the heat-treated image, the obtained image had improved glossiness, and the effects of the present invention could be confirmed in both image quality and image storage stability.

  Further, although the results are not described in the above table, as a result of evaluating the fusing property at the time of storage of each inkjet image, the sample according to the present invention is an image even if the protective sheet is peeled off after the forced deterioration treatment. It was able to peel off smoothly without causing any defects. On the other hand, each of the images 3 to 5 and the images 24 to 26 adhered to the surface when the protective sheet was peeled off, and when peeled off, the image surface was peeled off at the same time, resulting in an image defect.

Example 2
Using the recording media 1 to 25 of the present invention prepared in Example 1, pigment ink-based continuous high-speed printing and subsequent post-treatment were performed using the apparatus shown in FIG.

As the printing conditions, when the throughput per hour was in the range of 100 L plates (equivalent to 1.13 m ² ) to 1300 L plates (equivalent to 14.69 m ² ), good image quality was obtained. However, when the processing amount per hour was 1400 sheets or more of the L plate, defective conveyance of the recording medium or molten thermoplastic resin adhered to the heat fixing device caused image defects. Although these causes are not clear, it is estimated that as the amount of processing increases, curling occurs in the recording medium due to the influence of moisture that evaporates at the time of heating and fixing, and conveyance failure occurs. Further, when the amount of processing increases, it is necessary to give a necessary amount of heat in a short time during fixing, and therefore the set temperature must be raised. This high temperature processing is presumed to be related to image defects.

As is clear from the results of Example 1, in order to provide a photographic print with an ink jet printer, an image using a pigment ink and a recording medium containing thermoplastic fine particles in the surface layer is used from the viewpoint of image quality and image storage stability. A system that heats and melts the thermoplastic fine particles contained in the surface layer after forming is very suitable. Further, as for the total image forming speed including ink jet image recording and heat fixing, 1 m ² / hour is the minimum required amount, and it is found that the upper limit is 15 m ² / hour in relation to the heating and fixing ability. It was. In addition, when the comparative recording medium 5 is used under the above-described conditions, the image quality is deteriorated due to the conveyance roller. The plastic resin adhered and image defects remarkably occurred, confirming the effectiveness of the continuous high-speed printing of the present invention.

Example 3
[Preparation of Comparative Sample 6]
In the production of the comparative sample 5 described in Example 1, a comparative sample 6 was produced in the same manner except that the following coating liquid 27 was used instead of the coating liquid 5.

(Preparation of coating solution 26 and coating solution 27)
<Preparation of coating liquid 26>
While stirring at 40 ° C., 650 ml of the silica dispersion-2 prepared above was sequentially mixed with the following additives to prepare a coating solution 26.

Polyvinyl alcohol (Kuraray Industries, Ltd .: PVA235
71.4 ml of 7% solution of average polymerization degree: 3500)
Optical brightener dispersion-1 35 ml
The whole amount was finished to 1000 ml with pure water. The coating solution pH was 4.4.

<Preparation of coating liquid 27>
Using the prepared thermoplastic fine particle coating solution 1 and the coating solution 26, after mixing so that the mass ratio of thermoplastic fine particles: inorganic pigment is 10:90, the viscosity at 43 ° C. is 45 cp. Water was added to this to make a coating solution 27.
<Creation of inkjet image>
As described in the table below, in addition to the comparative sample 6 prepared above as a recording medium, the comparative inks 1 to 5 and samples 1 to 25 prepared in Example 1 were used as pigment inks prepared in Example 1 as inks. In accordance with the method described in Example 2, printing and fixing were performed.

<Evaluation of output image>
The following evaluations were performed on the images output as described above.

(Evaluation of fracture resistance under low temperature and low humidity)
According to the method described in Example 2, printing and fixing were performed in an environment of 15 ° C. and 20% RH. The printing conditions were adjusted so that the processing amount per hour was 200 L plates, and the screen breakage was evaluated according to the following criteria. The evaluation was performed on a total of 10 samples by sampling one sample every 20th sample from 200 samples printed in one hour.

3: No cracks are observed on all 10 sheets 2: 2: 1 out of 10 specimens with 1 to 2 cracks per sheet 1: 1 out of 10 sheets per sheet 4 or more specimens that can be broken (evaluation of bleed and gloss under high temperature and high humidity)
According to the method described in Example 2, printing and fixing were performed in an environment of 30 ° C. and 80% RH. The printing conditions were adjusted so that the throughput per hour was 200 L plates, and bleed and gloss were evaluated according to the following criteria. The evaluation was performed on a total of 10 samples by sampling one sample every 20th sample from 200 samples printed in one hour.

<Evaluation of bleed>
It carried out according to the method as described in Example 1.

<Evaluation of gloss: measurement of C value>
The C value at a density of 1.5 of the yellow wedge image was measured, and gloss was evaluated according to the following criteria. The C value referred to in the present invention is a value measured by a reflection method using an optical comb of 2 mm among the image sharpness defined according to JIS-K-7105. In the present invention, a method of applying light to a sample at an angle of 45 degrees is changed to an angle of 60 degrees using an image clarity measuring machine (ICM-1DP) manufactured by Suga Test Instruments Co., Ltd. It was.

5: C value is 85 or more 4: C value is 75 or more, less than 85 3: C value is 65 or more, less than 75 2: C value is 55 or less, less than 65 1: C value is less than 55 Is shown in Table 6 .

  As is clear from the above table, in the recording medium in which the surface layer portion contains inorganic pigments and thermoplastic fine particles, as in Comparative Example 5, when the ratio of the inorganic pigment to all components in the surface layer portion is less than 30%, Bleeding occurs at high temperatures and high humidity, and the image quality is unacceptable for use. Further, as in Comparative Example 6, when the ratio of the inorganic pigment to all components in the surface layer portion exceeded 70%, it was found that there was a cracking failure under low temperature and low humidity, which was a big problem in quality. .

  Further, in the recording medium in which the surface layer portion contains the inorganic pigment and the thermoplastic fine particles, as in Comparative Example 5, if the mass ratio of the inorganic pigment and the thermoplastic fine particles is smaller than 3/7, bleeding at high temperature and high humidity is caused. It has been found that the image quality is high and the image quality is unusable, and the effect of glossiness of the image is significantly reduced.

  Gloss development is considered to be achieved by the thermoplastic fine particles contained in the surface layer portion of the recording medium being processed by a process including heating, etc., so that the thermoplastic fine particles melt or form a film. A higher ratio of the thermoplastic fine particles is expected to have a greater gloss development effect. However, as a result of the study by the present inventors, for example, the gloss development effect is not necessarily greater when the ratio of the thermoplastic fine particles in the surface layer portion is higher so that the gloss is also lower in Comparative Examples 3 and 4. There was found. This is something that cannot normally be predicted.

According to the study in the present invention, in order to obtain an image quality equivalent to a silver salt photograph, thermoplastic fine particles are essential in the surface layer portion, and the mass ratio of the inorganic pigment and the thermoplastic fine particles is 3/7 or more and 9/1 or less In addition, when printing and fixing under high temperature and high humidity, the mass ratio of the inorganic pigment to the thermoplastic fine particles is preferably 3/7 or more and 7/3 or less in the evaluation of glossiness of the image, particularly image clarity. It was found that the ratio is preferably 4/6 or more and 6/4 or less.

  Similarly, the ratio of the inorganic pigment to the total components in the surface layer portion is required to be 30% by mass or more and 70% by mass or less, preferably 30% by mass or more and 60% by mass or less, more preferably 30%. It was found that the content was not less than 50% by mass and not more than 50% by mass.

It is a schematic block diagram which shows an example of the inkjet recording device used by this invention.

Claims (5)

After the image recorded on an ink jet recording medium, in the formation method of the ink-jet images by melting the thermoplastic particles imaging contained in the surface layer portion, the ink jet recording medium is to have a plurality of ink absorbing layer on a support All of the plurality of ink absorbing layers contain silica having an average primary particle size of 100 nm or less as an inorganic pigment, the surface layer portion contains an inorganic pigment and thermoplastic fine particles, and the mass ratio of the inorganic pigment to the thermoplastic fine particles 3-7 or more and 7/3 or less, and the ratio of the said inorganic pigment with respect to all the components in this surface layer part is 30 to 70 mass%, The inkjet image formation method characterized by the above-mentioned . 2. The method of forming an inkjet image according to claim 1, wherein the mass ratio of the inorganic pigment and the thermoplastic fine particles in the surface layer portion of the inkjet recording medium is 4/6 or more and 6/4 or less . The method for forming an inkjet image according to claim 1, wherein the thermoplastic fine particles contained in the surface layer part are melted by a process including a heat treatment . The method of forming an inkjet image according to any one of claims 1 to 3, wherein an image is recorded using a pigment ink . An inkjet recorded product formed by the inkjet image forming method according to claim 1 .

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