JP2007062258A - Manufacturing method for inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an inkjet recording medium which is superior in banding resistance, and of which the curling property is improved. <P>SOLUTION: This manufacturing method of the inkjet recording medium manufactures the inkjet recording medium by applying and drying at least one layer of an ink-absorbing layer on a supporting body. In the manufacturing method, the inkjet recording medium is cut into a sheet form after the application and the drying, and an aging process at 35°C or higher for 24 hours or longer is applied under a state in which the sheet-form inkjet recording mediums are stacked. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an ink jet recording medium having improved curling characteristics and banding resistance.

  In recent years, ink jet recording materials have been rapidly improved in image quality and approaching photographic image quality. In particular, in order to achieve image quality comparable to photographic image quality by ink jet recording, improvements have been made from the aspect of ink jet recording media (hereinafter also simply referred to as recording paper), and inorganic fine particles are formed on a highly smooth support. A void-type inkjet recording medium provided with a porous layer having a minute void structure formed from a hydrophilic polymer has high gloss, vivid color, and excellent ink absorbability and drying properties Therefore, it is becoming one of the closest to photo quality. In particular, when a non-water-absorbing support is used, there is no occurrence of cockling after printing, as seen on a water-absorbing support, so-called “wrinkles”, and a high smooth surface can be maintained. You can get a print.

  As the ink absorbing layer, for example, a swelling type ink jet recording medium having a swellable ink absorbing layer by applying a hydrophilic binder such as gelatin or polyvinyl alcohol as an ink absorbing layer on a support having high smoothness is known. On the other hand, Japanese Patent Application Laid-Open No. 10-119423 proposes a void-type inkjet recording medium in which a porous layer having a minute void structure is provided as an ink absorption layer, and has high ink absorption and high-speed drying properties. Therefore, it is becoming one of the methods for obtaining the image quality closest to the silver halide photograph quality.

  This porous layer is mainly formed of a hydrophilic binder and fine particles, and inorganic or organic fine particles are widely used as the fine particles. In general, inorganic fine particles have a smaller particle size. And is preferably used because a highly glossy porous layer can be realized. Further, by using a relatively small amount of a hydrophilic binder with respect to the inorganic fine particles, voids are formed between the inorganic fine particles, and a porous layer having a high porosity can be obtained.

  As a method for producing these ink jet recording media, for example, a method for producing a void-type ink jet recording medium generally includes a hydrophilic binder while continuously conveying a long flexible support. After forming an ink absorbing layer by applying an aqueous coating liquid for forming an ink absorbing layer containing inorganic fine particles to the support, the ink absorbing layer is formed, dried through a drying step and a humidity adjusting step, and then wound while being laminated in a roll shape. It is done.

  The coating liquid used for forming the ink absorbing layer of the ink jet recording medium as described above is mainly composed of inorganic fine particles and is originally a hard coating film. Therefore, a thick porous layer is coated on a support. In this case, the film strength is lowered, and it is easy to induce a failure such as a crack during drying. In the formation process of the porous ink absorbing layer, a small amount of hydrophilic binder is adsorbed on the surface of the fine particles and entangled between the hydrophilic binders, or the fine particles are retained and protected by interactions such as hydrogen bonding between the hydrophilic binders. Colloid is made to form a porous layer. Thereafter, it is considered that the coating film undergoes rapid shrinkage during the drying process, and the film surface is cracked by the shrinkage stress. For the above problems, a crosslinking agent for curing the hydrophilic binder is used from the viewpoint of improving the strength of the coating film and preventing coating film destruction such as cracks, for example, boric acid and its salts, Epoxy curing agents, aldehyde curing agents, active halogen curing agents, active vinyl compounds, aluminum alum and the like are known.

  However, these crosslinking agents often fail to complete the crosslinking reaction with the hydrophilic binder only by the coating and drying process. In such a state, the ink absorption ability is lowered if the film is not sufficiently hardened. However, this causes a drawback such as a so-called banding phenomenon in which a streak in the scanning direction becomes clear during ink jet recording.

  As a countermeasure method for such a problem, an aging treatment is performed in which the crosslinking reaction is completed by storing for a certain period of time in a constant temperature and humidity environment in a state of being coated and dried and laminated in a roll shape (for example, (See Patent Documents 1 and 2.)

  By performing this aging treatment, banding associated with a decrease in ink absorption ability is eliminated, but a strong curl is imparted to the ink jet recording medium because it is stored in a roll and in a high temperature environment for a long time.

  In recent years, the performance improvement of inkjet printers has been achieved not only in high image quality but also in terms of printing speed. For example, as the number of nozzles increases, the print head tends to increase in size. is there. This increase in the size of the print head is advantageous from the viewpoint of print speed, but on the other hand, it tends to cause troubles in transporting the inkjet recording medium. Ink jet printers are designed so that the distance between the print head and the ink jet recording medium is kept appropriate and accurate printing is performed. However, when the curl of the ink jet recording medium becomes strong as described above, the ink jet recording medium A conveyance failure due to a collision with the print head or the like is caused, and as a result, the conveyance cannot be normally performed, resulting in a printing failure such as banding.

In view of the above situation, development of a new manufacturing method of an ink jet recording medium that is excellent in curl characteristics and can suppress banding is desired.
Japanese Patent Laid-Open No. 2003-136836 JP 2005-88410 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing an ink jet recording medium having excellent banding resistance and improved curling characteristics.

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

  (1) In a method for producing an ink jet recording medium, wherein at least one ink absorbing layer is coated and dried on a support, the ink jet recording medium is coated and dried, then cut into a sheet, and the sheet A method for producing an ink jet recording medium, comprising subjecting the ink jet recording medium to an aging treatment at 35 ° C. or more for 24 hours or more.

  (2) The inkjet recording medium according to (1), wherein the aging treatment is performed on the top of the laminated inkjet recording medium with a load of 10 Pa or more and 500 Pa or less applied uniformly. Production method.

  (3) The method for producing an inkjet recording medium according to (1) or (2), wherein the aging treatment is performed by combining two or more conditions having different temperatures or treatment times.

  (4) Before performing the aging treatment, the humidity control treatment is performed for 3 days or more in an environment of 18 ° C. or higher, less than 30 ° C., 50% RH or higher, according to the above (1) to (3) The manufacturing method of the inkjet recording medium of any one of Claims 1.

  (5) The inkjet according to any one of (1) to (4), wherein the outermost ink absorbing layer of the inkjet recording medium contains silica fine particles having an average primary particle size of 10 nm or less. A method for manufacturing a recording medium.

  According to the present invention, it is possible to provide a method for manufacturing an ink jet recording medium having excellent banding resistance and improved curling characteristics.

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

  As a result of intensive studies in view of the above problems, the present inventor has applied the inkjet recording medium in a method for producing an inkjet recording medium in which at least one ink absorbing layer is applied on a support and dried. After drying, the sheet is cut into a sheet shape, and the sheet-like inkjet recording medium is laminated, and then subjected to an aging treatment at 35 ° C. or more for 24 hours or more. It was possible to achieve a sufficient coating strength without impairing the thickness of the ink jet recording medium, and to realize a method for manufacturing an ink jet recording medium excellent in banding resistance.

  Details of the present invention will be described below.

  In the method for producing an ink jet recording medium of the present invention (hereinafter, also simply referred to as “manufacturing method”), the ink jet recording medium is applied, dried, cut into a sheet, and the sheet ink jet recording medium is laminated. It is characterized by performing an aging treatment for 24 hours or more at a temperature of 0 ° C. or higher.

  As a result of earnestly examining the conditions satisfying all of the coating film strength, curl characteristics, and banding resistance, the inventor has obtained a state in which a long inkjet recording medium that has been widely used in the past is laminated in a roll shape. For aging treatment, after cutting to the desired size according to the purpose after coating and drying, it is possible to achieve both banding resistance and curl characteristics by performing aging treatment in a state where this sheet is laminated. Is found.

  In the production method of the present invention, after the ink jet recording medium is applied and dried, it is cut into a sheet, and the cutting time is immediately cut to a predetermined size online after application and drying. Alternatively, it may be coated, dried, laminated once in a roll shape, and stored for a certain period in a state where the humidity change is blocked with a moisture-proof sheet or the like, and then cut into a sheet shape.

  The size for cutting the ink jet recording medium according to the present invention into a sheet shape is not particularly limited and can be cut to an appropriate size according to the purpose and application. However, considering the aging efficiency and the like, the length ( Application direction) It is preferable that the rectangular size is 30 cm to 3.0 m and the width is 21 cm to 3.0 m.

  In the production method of the present invention, aging treatment is performed at 35 ° C. or more for 24 hours or more in a state where the sheet-like inkjet recording medium is laminated. More preferable heating conditions are 35 ° C. or more and 80 ° C. The treatment period is preferably 24 hours or more and 10 days or less. Further, if the heating temperature is 50 ° C. or more and 80 ° C. or less, the treatment period is preferably 24 hours or more and within 8 days, and if the heating temperature is 35 ° C. or more and less than 50 ° C., the treatment period is The period is preferably 4 days or more and 10 days or less.

  In addition, the aging process according to the present invention is preferably performed by combining two or more conditions having different temperatures or processing times from the viewpoint that a more stable aging process can be performed. For example, as the first aging treatment, after performing treatment for 12 hours or more and less than 5 days under conditions of 35 ° C. or more and less than 50 ° C., as the second aging treatment, under conditions of 50 ° C. or more and 80 ° C. or less, Process for 12 hours or more and less than 5 days.

  In the aging process according to the present invention performed under the above conditions, there is no particular limitation on the humidity environment condition, but from the viewpoint of performing a stable and uniform aging process, the humidity environment condition for performing the aging process is 55 ± 15%. It is preferably in the range of RH, more preferably in the range of 55 ± 10% RH, and still more preferably in the range of 55 ± 5% RH.

  Further, in the production method of the present invention, after the ink jet recording medium is applied and dried and then subjected to the aging treatment, it is performed for 3 days or more in an environment of 18 ° C. or higher, less than 30 ° C., 50% RH or higher. It is preferable to perform the humidity conditioning treatment from the viewpoint of performing a more stable and uniform aging treatment. In particular, the humidity condition is 50% RH or more and 80% RH or less, and the humidity conditioning treatment days are 3 days or more, 8 It is preferable to make it less than a day.

  In the production method of the present invention, when the laminated inkjet recording medium is subjected to an aging treatment under the conditions according to the present invention, a load of 10 Pa or more and 500 Pa or less is applied to the uppermost portion of the laminated inkjet recording medium. It is preferable to perform the aging treatment in a state in which is uniformly applied, more preferably 10 Pa or more and 100 Pa or less, and it is preferable to change appropriately depending on the number of laminated layers described below.

  In the present invention, when laminating a sheet-like inkjet recording medium, it is preferable that the sheet-like ink jet recording medium is laminated on a horizontal base as much as possible from the viewpoint that a uniform load can be applied to the entire surface of the sheet. The number of laminated sheet-like inkjet recording media during the aging treatment is not particularly limited, but is preferably about 50 or more and 3000 or less in consideration of aging efficiency, uniformity of aging treatment and production efficiency, More preferably, it is 200 or more and 2000 or less.

  In addition, as a method for uniformly applying the load defined by the present invention to the outermost surface portion of the inkjet recording medium, for example, a metal plate that is not easily deformed, such as a stainless steel sheet, is the same as the sheet-like inkjet recording medium to which the load is applied. A flat plate of a size, and a method of applying a desired load by appropriately adjusting the thickness of the flat plate or the number of laminated sheets, or a paper that is not easily deformed by heat or the like, for example, a support (for example, an inkjet recording medium) An RC base paper (details will be described later) may be cut into the same size as a sheet-like inkjet recording medium to which a load is applied, and the number of sheets necessary for applying a desired load may be stacked.

  Note that the uniform application of the load in the present invention means that the variation width of the load applied to the entire area of the sheet-like inkjet recording medium is within ± 10%.

  Next, details of the ink jet recording medium according to the present invention will be described.

  In general, as the ink absorbing layer forming the ink jet recording medium, there are a swelling type ink absorbing layer and a void type ink absorbing layer as described above, but the ink jet recording medium according to the present invention has the object effects of the present invention. An inkjet recording medium having a void-type ink absorbing layer is particularly preferred from the viewpoint that it can be easily exhibited and a high-quality inkjet image can be obtained.

  Hereinafter, the details of the ink jet recording medium having the void-type ink absorbing layer according to the present invention will be described.

  The void-type ink absorbing layer according to the present invention mainly contains inorganic fine particles and a small amount of a hydrophilic binder, and constitutes a void structure.

[Inorganic fine particles]
Examples of the inorganic fine particles applicable to the ink absorbing layer according to the present invention include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, and hydroxide. Zinc, zinc sulfide, zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, water Mention may be made of white inorganic pigments such as magnesium oxide. The inorganic fine particles can be used as primary particles or in a state where secondary agglomerated particles are formed.

  In the present invention, from the viewpoint of obtaining a high-quality print with an inkjet recording medium, silica-based inorganic fine particles are obtained from a viewpoint that a low refractive index and an average particle diameter of about 0.1 μm or less can be obtained relatively inexpensively. Particles or alumina diameter particles are preferred, and alumina, pseudoboehmite, colloidal silica, silica fine particles synthesized by a gas phase method, etc. are preferred, and silica fine particles having an average particle size of 10 nm or less are particularly preferred.

  Generally, silica fine particles are roughly classified into wet method silica fine particles and gas phase method silica fine particles according to the production method. For the former wet method silica fine particles, active silica is produced by acid decomposition of a silicate, and a method in which this is appropriately polymerized and agglomerated and precipitated to obtain hydrous silica is the mainstream. NIPGEL manufactured by Nippon Silica Kogyo Co., Ltd. is commercially available as a fine seal of Tokuyama Co., Ltd .. Precipitated silica is generally characterized by 10-60 nm, and gel silica is characterized by silica particles having primary aggregates of approximately 3-10 nm forming secondary aggregates.

  On the other hand, the gas phase method silica fine particles preferably used in the latter present invention are those synthesized by combustion method using silicon tetrachloride and hydrogen as raw materials, for example, Aerosil series manufactured by Nippon Aerosil Co., Ltd., manufactured by Tokuyama Co., Ltd. The Leolo Seal series is commercially available.

  In the present invention, it is preferable to use gas phase method silica fine particles that can obtain a high porosity and are difficult to form coarse aggregates when producing a cationic fine particle dispersion. In the vapor phase silica, the secondary aggregate is formed by relatively weak interaction with the wet silica, and thus has a characteristic that it can be dispersed with low energy in the wet silica. In addition, the vapor phase silica fine particles have a particularly large specific surface area, so the ink absorbency and retention are high, and the refractive index is low. Therefore, if the fine particles are dispersed to an appropriate particle size, the ink absorption layer is transparent. There is an advantage that a high color density and a good hue can be obtained.

  The vapor-phase process silica fine particles preferably have an average primary particle diameter of 3 to 50 nm. More preferably, it is 10 nm or less. If the average particle diameter of the primary particles is 50 nm or less, high glossiness of the recording medium can be achieved, and a clear image can be obtained by preventing the reduction of the maximum density due to irregular reflection on the surface. The average particle size of the fine particles in the above is the simple average value (number average) by observing the cross section or surface of the particle itself or the porous ink absorbing layer with an electron microscope, and determining the particle size of many arbitrary particles. As required. Here, each particle size is represented by a diameter assuming a circle equal to the projected area.

As a particularly preferred embodiment, when the porous ink absorbing layer is formed by forming particles of secondary particles or more, the average particle diameter is 20 to 200 nm, and the recording medium that achieves high ink absorption and high gloss Further, it is also preferable to adjust the water content of the vapor-phase method silica by storing the vapor-phase method silica fine particles in an environment having a humidity of 20 to 60% for 3 days or more.

The amount of the vapor phase silica fine particles added depends largely on the required ink absorption capacity, the porosity of the porous ink absorption layer, and the type of the hydrophilic binder, but generally 5 to 30 g per 1 m ² of the recording medium. , Preferably 10 to 25 g.

  The ink absorption capacity increases as the amount of the vapor-phase process silica fine particles added increases. However, since there is a collapse such as curling and cracking, a method of increasing the capacity by the porosity is preferable. A preferable porosity is 40 to 75%. The porosity can be adjusted by the vapor phase silica fine particles to be selected, the kind of the binder, the mixing ratio thereof, or the amount of other additives.

  The porosity here refers to the ratio of the total volume of the voids to the volume of the void layer, and is calculated from the total volume of the layer components and the layer thickness. Further, the total volume of the voids can be easily obtained by measuring the water absorption amount.

[Hydrophilic binder]
Next, the hydrophilic binder used in the ink absorbing layer according to the present invention will be described.

  The hydrophilic binder is not particularly limited, and a conventionally known hydrophilic binder can be used. For example, gelatin, polyvinyl pyrrolidone, polyethylene oxide, polyacrylamide, polyvinyl alcohol, and the like can be used. Polyvinyl alcohol is particularly preferred from the viewpoints of the comparatively small size, the curling of the recording medium being small, and the viewpoint that the binder capacity of the inorganic fine particles is high and the cracking and film-forming properties are excellent with a small amount of use.

  As polyvinyl alcohol preferably used in the present invention, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, modified polyvinyl alcohol such as polyvinyl alcohol having a cation-modified terminal or 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 300 or more, particularly preferably an average degree of polymerization of 1,000 to 5,000, and a saponification degree of 70. -100% is preferable, and 80-99.8% is particularly preferable.

  Examples of the cation-modified polyvinyl alcohol include polyvinyl having a primary to tertiary amino group or a quaternary amino group in the main chain or side chain of the polyvinyl alcohol as described in JP-A No. 61-10383. These are alcohols, which are 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-methylvinylimidazole, N- (3-dimethylaminopropyl) methacrylamide, hydroxyethyltrimethylammonium chloride, trimethyl- (3-methacrylamidopropyl) ammonium chloride, 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.

  Examples of the anion-modified polyvinyl alcohol include polyvinyl alcohol having an anionic group described in JP-A-1-206088, vinyl alcohol described in JP-A-61-237681 and JP-A-63-330779, and water-soluble. And a copolymer with a vinyl compound having a functional group, and a modified polyvinyl alcohol having a water-soluble group described in JP-A-7-285265.

  Nonionic modified polyvinyl alcohol is, for example, a polyvinyl alcohol derivative obtained by adding a polyalkylene oxide group described in JP-A-7-9758 to a part of vinyl alcohol, and described in JP-A-8-25795. 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. In particular, when using polyvinyl alcohol having a degree of polymerization of 2,000 or more, the degree of polymerization is from 0.05 to 10% by weight, preferably 0.1 to 5% by weight, based on the inorganic fine particles. Addition of 2,000 or more polyvinyl alcohol is preferred because there is no significant thickening.

  The ratio of the inorganic fine particles to the hydrophilic binder when forming the ink absorbing layer is preferably 2 to 20 by mass ratio. If the mass ratio is 2 times or more, a porous film having a sufficient porosity can be obtained, a sufficient void volume can be easily obtained, and there is no situation where the voids are blocked by swelling during ink jet recording with a hydrophilic binder. This is a factor that can maintain the ink absorption speed. On the other hand, if this ratio is 20 times or less, cracks are less likely to occur when the ink absorbing layer is applied as a thick film. The ratio of the inorganic fine particles to the particularly preferred hydrophilic binder is 2.5 to 12 times, most preferably 3 to 10 times.

[Other additives]
The ink jet recording medium of the present invention preferably contains a water-soluble polyvalent metal compound.

  Water-soluble polyvalent metal compounds applicable to the present invention include metals such as aluminum, calcium, magnesium, zinc, iron, strontium, barium, nickel, copper, scandium, gallium, indium, titanium, zirconium, tin, and lead. Examples include hydrochloride, sulfate, nitrate, acetate, formate, succinate, malonate, chloroacetate and the like. Of these, water-soluble salts composed of aluminum, calcium, magnesium, zinc and zirconium are preferred because their metal ions are colorless. Furthermore, a water-soluble aluminum compound and a water-soluble zirconium compound are particularly preferable in that they are excellent in bleeding resistance during long-term storage.

  Specific examples of water-soluble aluminum compounds include polyaluminum chloride (basic aluminum chloride), aluminum sulfate, basic aluminum sulfate, aluminum potassium sulfate (alum), ammonium aluminum sulfate (ammonium alum), sodium aluminum sulfate, aluminum nitrate, phosphorus Examples thereof include aluminum oxide, aluminum carbonate, polysulfuric acid aluminum silicate, aluminum acetate, and basic aluminum lactate. Here, the water solubility in the water-soluble polyvalent metal compound means that it is dissolved in water at 20 ° C. by 1% by mass or more, more preferably 3% by mass or more.

  The most preferable water-soluble aluminum compound is basic aluminum chloride having a basicity of 80% or more from the viewpoint of ink absorbability, and can be represented by the following molecular formula.

[Al ₂ (OH) _n Cl _6-n ] _m
(However, 0 <n <6, m ≦ 10)
The basicity is represented by n / 6 × 100 (%).

  Specific examples of the water-soluble zirconium compound are preferably zirconyl carbonate, zirconyl ammonium carbonate, zirconyl acetate, zirconyl nitrate, zirconium oxychloride, zirconyl lactate and zirconyl citrate. Zirconyl ammonium carbonate and zirconyl acetate are particularly preferred. In particular, zirconium oxychloride and zirconyl acetate are preferred from the viewpoint of bleeding resistance during long-term storage.

  Moreover, a cationic polymer can be applied to the ink absorption layer according to the present invention.

  The cationic polymer is a polymer having a primary to tertiary amine, a quaternary ammonium base, a quaternary phosphonium base or the like in the polymer main chain or side chain, and a known compound is used in an ink jet recording medium. In view of ease of production, those substantially water-soluble are preferred.

Examples of cationic polymers include polyethyleneimine, polyallylamine, polyvinylamine, dicyandiamide polyalkylene polyamine condensate, polyalkylene polyamine dicyandiamide ammonium salt condensate, dicyandiamide formalin condensate, epichlorohydrin-dialkylamine addition polymer, diallyldimethylammonium chloride. Polymer, diallyldimethylammonium chloride / SO2 copolymer, polyvinylimidazole, vinylpyrrolidone / vinylimidazole copolymer, polyvinylpyridine, polyamidine, chitosan, cationized starch, vinylbenzyltrimethylammonium chloride polymer, (2-methacryloyloxy) Ethyl) trimethylammonium chloride polymer, dimethylaminoethyl methacrylate Over preparative polymer, and the like.
Alternatively, a cationic polymer described in the Chemical Industry Times, August 15 and 25, 1998, “Polymer Drug Introduction” (published by Sanyo Chemical Industries, Ltd., p787, 1992) An example is an agent.

  The average molecular weight of the cationic polymer is preferably in the range of 2000 to 500,000, more preferably in the range of 10,000 to 100,000.

  The average molecular weight is a number average molecular weight and refers to a polyethylene glycol equivalent value obtained from gel permeation chromatography.

  In addition, when the cationic polymer is added to the coating solution in advance, it may be added not only uniformly to the coating solution but also in the form of forming composite particles together with inorganic fine particles. As a method for preparing composite particles by using inorganic fine particles and a cationic polymer, a method in which a cationic polymer is mixed with inorganic fine particles and adsorbed and coated, a method in which the coated particles are aggregated to obtain higher order composite particles, and further a mixing are performed. And a method of making coarse particles obtained in this way into more uniform composite particles using a disperser.

  The cationic polymer generally has a water-soluble group and thus exhibits water solubility, but may not be dissolved in water depending on, for example, the composition of the copolymerization component. Although it is preferable that it is water-soluble from the ease of manufacture, even if it is sparingly soluble in water, it can be dissolved and used using a water-miscible organic solvent.

  Here, the water-miscible organic solvent means alcohols such as methanol, ethanol, isopropanol, and n-propanol, glycols such as ethylene glycol, diethylene glycol, and glycerin, esters such as ethyl acetate and propyl acetate, acetone, and methyl ethyl ketone. An organic solvent that can dissolve approximately 10% or more in water, such as ketones and amides such as N, N-dimethylformamide. In this case, the amount of the organic solvent used is preferably equal to or less than the amount of water used.

The cationic polymer is usually used in an amount of 0.1 to 10 g, preferably 0.2 to 5 g, per 1 m ² of the ink jet recording medium.

  In the present invention, when the ratio of the inorganic fine particles to the cationic polymer is within the above range, the anionic component of the inorganic fine particles is almost completely covered with the cationic component, so that the coarse particles due to the ionic bond between the inorganic fine particles and the cationic polymer. It is preferable because it does not cause formation.

  Examples of other additives include a crosslinking agent (also referred to as a hardening agent).

  The hardener is generally a compound having a group capable of reacting with the hydrophilic binder or a compound that promotes the reaction between different groups of the hydrophilic binder, and is appropriately selected depending on the type of the hydrophilic polymer. Select and use.

  Specific examples of the hardener include, for example, epoxy hardeners (diglycidyl ethyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidyl cyclohexane, N, N- Diglycidyl-4-glycidyloxyaniline, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, etc.), aldehyde hardeners (formaldehyde, glioxal, etc.), active halogen hardeners (2,4-dichloro-4-hydroxy-1) , 3,5-s-triazine, etc.), active vinyl compounds (1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonylmethyl ether, etc.), boric acid, its salts, borax, aluminum alum, etc. Is mentioned.

  When polyvinyl alcohol or cation-modified polyvinyl alcohol is used as the hydrophilic binder, it is preferable to use a hardening agent selected from boric acid, a salt thereof or an epoxy hardening agent.

  Most preferred is a hardener selected from boric acid or a salt thereof.

  As boric acid or a salt thereof, oxygen acid having a boron atom as a central atom and a salt thereof are shown. Specifically, orthoboric acid, diboric acid, metaboric acid, tetraboric acid, pentaboric acid, octaboric acid or a salt thereof is used. Can be mentioned.

  The amount of the hardener used varies depending on the type of hydrophilic polymer, the type of hardener, the type of inorganic fine particles, the ratio to the hydrophilic polymer, etc., but usually 5 to 500 mg, preferably 10 to 10 g per hydrophilic polymer. 300 mg.

  The above hardener may be added to the coating solution for forming the void layer and / or the coating solution for forming another layer adjacent to the void layer when the coating solution for forming the void layer is applied. Alternatively, a coating solution for forming the void layer is applied onto a support on which a coating solution containing a hardener has been previously applied. Further, the hardener can be supplied to the void layer by coating and drying a hardener-free coating solution for forming the void layer, followed by overcoating with a hardener solution. Preferably, from the viewpoint of production efficiency, a hardening agent is added to a coating solution for forming a void layer or a coating solution for forming a layer adjacent thereto to form a void layer at the same time as forming the void layer. It is preferable to supply.

  In a particularly preferred embodiment in which the void layer is formed by ultrafine silica and polyvinyl alcohol synthesized by a gas phase method, a hardening agent is added in advance to the coating solution for forming the void layer, and a certain time ( Preferably, 10 minutes or more, particularly preferably 30 minutes or more), and when applied to the support and dried, a higher porosity can be achieved without deteriorating the brittleness of the film.

  The above hardener can also be added as an additive when preparing the inorganic fine particle dispersion of the present invention in advance.

  In addition, polystyrene, polyacrylates, polymethacrylates, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, or copolymers thereof, organic latex fine particles such as urea resin, melamine resin, Liquid droplets such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, surfactants such as cations and nonions, described in JP-A-57-74193, 57-87988 and 62-261476 UV absorbers described in JP-A-57-74192, JP-A-57-87989, JP-A-60-72785, JP-A-61465991, JP-A-1-95091 and JP-A-3-13376. Anti-fading agent, JP-A-59-42993, 5 Fluorescent whitening agents, sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, and the like described in Nos. -52689, 62-280069, 61-242871, and JP-A-4-219266. Various known additives such as pH adjusters such as potassium carbonate, antifoaming agents, preservatives, thickeners, antistatic agents and matting agents can also be contained.

[Support]
The support of the ink jet recording medium according to the present invention is preferably a non-water-absorbing support from the viewpoint of obtaining a high-quality print.

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

  When applying a coating solution such as an ink absorbing layer according to the present invention on the support, the surface of the support is subjected to corona discharge treatment or the like for the purpose of increasing the adhesive strength between the support surface and the coating layer. It is preferable to perform a subbing treatment or the like. Furthermore, in the ink jet recording medium according to the present invention, a colored support may be used.

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

  Hereinafter, a non-water-absorbing paper support (also referred to as RC base paper) laminated with polyethylene, which is the most preferred polyolefin resin, will be described.

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

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

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

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

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

  The polyethylene that covers the front and back surfaces of the base paper is mainly low-density polyethylene (LDPE) or high-density polyethylene (HDPE), but other LLDPE, polypropylene, and the like can also be used in part.

  In addition, the polyethylene layer on the side where the ink absorbing layer is applied is an improved opacity and whiteness by adding rutile or anatase-type titanium oxide into polyethylene as is widely done in photographic paper. Is preferred. The titanium oxide content is 1 to 20% by mass, preferably 2 to 15% by mass, based on polyethylene.

  Polyethylene-coated paper can be used as glossy paper. Also, when polyethylene is melt-extruded onto the surface of the base paper and coated, so-called typing treatment is used to produce matte surfaces, silks, etc. What formed the fine surface can also be used by this invention.

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

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

1) Tensile strength: strength specified by JIS-P-8113, preferably 20-300N in the vertical direction and 10-200N in the horizontal direction 2) Tear strength: as defined by JIS-P-8116 The longitudinal direction is preferably 0.1 to 2N, and the lateral direction is preferably 0.2 to 2N. 3) Compression modulus: ≧ 9.8 kN / cm ²
4) Surface Beck smoothness: 500 seconds or longer is preferable as a glossy surface under the conditions specified in JIS-P-8119, but it may be less than this for so-called molded products. 5) Back surface Beck smoothness: JIS- 100 to 800 seconds are preferable under the conditions specified in P-8119. 6) Opacity: Transmittance of light in the visible range is 20% or less, particularly 15% under the measurement conditions of linear light incidence / diffuse light transmission conditions. 7) Whiteness: Hunter whiteness as defined in JIS-P-8123, preferably 90% or more. Further, when measured by JIS-Z-8722 (non-fluorescent) and JIS-Z-8717 (containing fluorescent agent) and displayed by the color display method defined in JIS-Z-8730, L ^* = 90 to 98, a ^* = − 5 to +5, b ^* = − 10 to +5 are preferable.

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

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

  In the method for producing an ink jet recording medium of the present invention, the coating method used when the ink absorbing layer coating liquid is coated on the support can be appropriately selected from known methods, for example, a gravure coating method The roll coating method, the rod bar coating method, the air knife coating method, the spray coating method, the extrusion coating method, the curtain coating method or the extrusion coating method using the hopper described in US Pat. No. 2,681,294 is preferable. Used.

  The constituent layer (ink absorption layer) of the ink jet recording medium according to the present invention may be a single layer or two or more layers, and in the case of two or more layers, The configurations may be the same or different from each other. Moreover, when it comprises by two or more layers, it is preferable from a viewpoint of productivity improvement that it is the method of apply | coating all the structural layers simultaneously.

  When the slide bead coating method is used, the viscosity of each coating solution when two or more constituent layers are applied simultaneously is preferably in the range of 5 to 100 mPa · s, more preferably 10 to 50 mPa · s. Range. 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 resin so that the thermoplastic resin contained in the surface layer does not form a film during preparation of the coating liquid, during coating, and during 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.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, “%” represents mass% unless otherwise specified.

Example 1
<Production of recording medium>
[Production of Recording Medium 1]
(Preparation of silica dispersion D-1)
Gas phase method silica (Nippon Aerosil Co., Ltd., Aerosil 200) having an average particle size of primary particles uniformly dispersed in advance of about 0.012 μm, 25%, anionic fluorescent whitening agent (Ciba Specialty Chemicals Co., Ltd.) , 400 L of silica dispersion B-1 (pH = 2.6, containing 0.5% ethanol) containing 0.6 L of UVITEXNFW LIQUID), 12% of the cationic polymer (P-1) and 10 of n-propanol. % And ethanol 2% containing aqueous solution C-1 (pH = 2.5, containing 2 g of antifoam SN381 manufactured by Sannobuco) was added at room temperature with stirring at 3000 rpm. Next, 54 L of a mixed aqueous solution A-1 (concentration of 3% by mass each) of 1: 1 mass ratio of boric acid and borax was gradually added with stirring.

Subsequently, it disperse | distributed with the pressure of ³ kN / cm < ² > with the high-pressure homogenizer by Sanwa Kogyo Co., Ltd., the whole quantity was finished to 630L with pure water, and the substantially transparent silica dispersion liquid D-1 was obtained.

(Preparation of silica dispersion D-2)
A silica dispersion D-2 was prepared in the same manner as in the preparation of the silica dispersion D-1, except that the anionic fluorescent whitening agent was removed.

(Preparation of cationic fine particle dispersion A-1)
7.89 kg of basic aluminum chloride aqueous solution (manufactured by Taki Chemical Co., Ltd .: Takibaine # 1500, containing 23.75% as Al ₂ O ₃ , basicity 83.5%) was added to 31.5 L of an aqueous solution containing 2% ethanol. Then, a uniform dispersion medium was prepared by stirring. Next, 7.5 kg of gas phase method silica (Aerosil 200 manufactured by Nippon Aerosil Co., Ltd.) having an average primary particle size of about 0.012 μm was used using a jet stream inductor mixer TDS manufactured by Mitamura Riken Kogyo Co., Ltd. By suction dispersion (primary dispersion) in the previously prepared dispersion medium, a primary dispersion having a gas phase silica concentration of 18.5% (Al ₂ O ₃ / SiO ₂ = 0.25) was prepared. At this time, the pH of the primary dispersion was 3.48. Next, 100 ml of an aqueous solution in which 0.9 g of boric acid and 7.5 g of borax were dissolved in 865 ml of the primary dispersion was added and dispersed (secondary dispersion) at a pressure of 50 MPa with a high-pressure homogenizer manufactured by Sanwa Industry Co., Ltd. Finished to 1000 ml (silica fine particle concentration 16%), a cationic fine particle dispersion A-1 having a pH of 4.08 was prepared.

(Preparation of ink absorbing layer coating solution)
Using the silica dispersion D-1, the silica dispersion D-2, and the cationic fine particle dispersion A-1 prepared as described above, the following additives are sequentially mixed to prepare each ink for the porous layer. An absorbent layer coating solution was prepared. In addition, each addition amount was displayed by the amount per 1L of coating liquid.

<First layer ink absorbing layer coating solution: lowermost layer>
Silica dispersion D-1 580 ml
8.0% aqueous solution of polyvinyl alcohol (average polymerization degree: 3800 saponification degree 88%)
250ml
2.0 ml of 4% aqueous solution of surfactant (manufactured by Neos; Footage 400S)
Finished with pure water to a total volume of 1000 ml <Second layer ink absorbing layer coating solution>
Silica dispersion D-1 580 ml
8.0% aqueous solution of polyvinyl alcohol (average polymerization degree: 3800 saponification degree 88%)
240ml
Acrylic copolymer emulsion resin (Daido Kasei Kogyo; Vinizol 1083) 30ml
Finished with 1000 ml of pure water <Ink absorbing layer coating solution for third layer>
Silica dispersion D-2 630ml
8.0% aqueous solution of polyvinyl alcohol (average polymerization degree: 3800 saponification degree 88%)
250ml
Finished with pure water to a total volume of 1000 ml <Fourth layer ink absorbing layer coating solution: outermost layer>
Cationic fine particle dispersion A-1 660 ml
8.0% aqueous solution of polyvinyl alcohol (average polymerization degree: 3800 saponification degree 88%)
250ml
3.0ml of 6% aqueous solution of surfactant (Kao; Cotamin 24P)
The total amount was finished to 1000 ml with pure water. Each ink absorption layer coating solution prepared as described above was filtered with a TCPD-30 filter manufactured by Advantech Toyo with 20 μm filtration accuracy, and then filtered with a TCPD-10 filter. did.

(Preparation of recording medium)
Next, a slide hopper type coater is used on the paper support (RC paper) coated with polyethylene on both sides at 40 ° C. so that each of the ink absorbing layer coating solutions prepared above has the wet film thickness described below. 4 layers were simultaneously applied.

<Wet film thickness>
First layer: 42 μm (Amount of SiO _{2 applied} : 4.33 g / m ² )
Second layer: 43 μm (SiO ₂ attached amount: 4.57 g / m ² )
Third layer: 44 μm (SiO ₂ weight: 4.40 g / m ² )
Fourth layer: 44 μm (Amount of SiO ₂ : 2.0 g / m ² , Amount of Al ₂ O ₃ : 0.5 g / m ² )
The RC paper used the following support wound in a roll shape having a width of about 1.52 m and a length of 3400 m.

The RC paper used has a moisture content of 8% and a basis weight of 170 g. The surface of the photographic paper is extruded and melt coated with polyethylene containing 6% anatase-type titanium oxide at a thickness of 35 μm, and the back side is 40 μm thick. Was extruded and melt coated at a thickness of 35 μm. After corona discharge on the front side, polyvinyl alcohol (PVA235 manufactured by Kuraray Co., Ltd.) was coated with an undercoat layer so that the amount was 0.05 g per 1 m ² of RC paper. After corona discharge on the back side, Tg was about 80 ° C. A back layer containing about 0.4 g of a styrene-acrylate ester latex binder, 0.1 g of an antistatic agent (cationic polymer) and 0.1 g of about 2 μm of silica as a matting agent was applied.

  Drying after applying the ink absorbing layer coating liquid is performed by passing through a cooling zone maintained at 5 ° C. for 15 seconds to lower the film surface temperature to 13 ° C., and then setting the temperature of a plurality of drying zones as appropriate. After drying, the whole length (3400 m) was wound around a plastic core having a diameter of 7.62 cm in a roll shape, and then the outer periphery of the roll sample was wrapped with a moisture-proof plastic sheet to obtain a recording medium 1. It was. The total dry film thickness of the ink absorbing layer of the recording medium 1 thus formed was 42.5 μm, and the dry film thickness of the fourth layer (outermost layer) was 4.0 μm.

[Preparation of recording medium 2]
A recording medium 2 was produced in the same manner as in the produced recording medium 1 except that the cationic fine particle dispersion A-1 used for forming the fourth layer was changed to the following cationic fine particle dispersion A-2. did.

(Preparation of cationic fine particle dispersion A-2)
In the preparation of the cationic fine particle dispersion A-1, gas phase method silica (Aerosil 200 manufactured by Nippon Aerosil Co., Ltd.) having an average primary particle size of about 0.012 μm is used, and an average primary particle size of about 0.007 μm is used. A cationic fine particle dispersion A-2 was prepared in the same manner except that the gas phase method silica (Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.) was used.

<Aging processing of recording medium>
[Aging process 1]
The recording medium 1 whose outer periphery was wrapped with a moisture-proof plastic sheet was subjected to aging treatment 1 for 4 days in a room where the temperature was controlled at a temperature and humidity of 36 ° C. and 55% RH.

[Aging process 2]
In the aging process 1, the aging process 2 was performed in the same manner except that the packaged recording medium 2 was used instead of the packaged recording medium 1.

[Aging process 3]
In the above aging treatment 2, this was designated as aging treatment 3 except that the aging conditions were changed to 53 ° C. and 3 days.

[Aging process 4]
After the moisture-proof plastic sheet of the packaged recording medium 2 was removed, the sheet was immediately cut into a sheet having a width of 152 cm and a length of 215 cm in an environment of 23 ° C. and 55% RH, and 1580 sheets of this sheet-like sample were produced. Next, the 1580 sheets were laminated on a horizontally placed plastic plate, and a moisture-proof plastic sheet was wound around the periphery of the plate under conditions such that the load on each sheet did not change. Next, the sample in the laminated state was moved to a room controlled at a temperature and humidity condition of 32 ° C. and 55% RH, and subjected to aging treatment 4 for 4 days.

[Aging process 5]
In the above aging treatment 4, this was designated as aging treatment 5 except that the aging conditions were changed to 36 ° C. and 12 hours.

[Aging process 6]
In the aging process 4, the recording medium 1 was used in place of the recording medium 2, and the aging process was similarly performed except that the aging condition was changed to 36 ° C. and 4 days.

[Aging process 7]
In the aging process 6 described above, the aging process 7 was performed in the same manner except that the recording medium 2 was used instead of the recording medium 1.

[Aging process 8]
In the aging process 7, the aging process 8 was performed in the same manner except that the aging days were changed from 4 days to 3 days.

[Aging process 9]
In the aging process 7, the aging process was performed in the same manner except that the aging condition was changed to 53 ° C. and 24 hours.

[Aging process 10]
In the aging process 9, the aging process 10 was performed in the same manner except that the aging days were changed from 24 hours to 3 days.

[Aging process 11]
In the aging treatment 10 described above, the same procedure was applied except that five sheets of base paper having a width of 152 cm and a length of 215 cm and 0.024 g / m ² were placed on the top of the 1580 sheets of laminate, and the load was uniformly applied. This was designated as aging process 11. In this state, a load of 12 Pa is uniformly applied to the uppermost recording medium 2 over the entire surface.

[Aging process 12]
In the aging process 11, the aging process 12 is performed in the same manner except that the number of base papers to be loaded is changed to 50 and the condition is such that a load of 120 Pa is uniformly applied to the uppermost recording medium 2. It was.

[Aging process 13]
In the aging treatment 6, the first aging was performed at 36 ° C. for 4 days, and then the second aging was performed at 53 ° C. for 3 days.

<< Evaluation of Aged Sample >>
[Sampling of sample for evaluation]
1) Sample subjected to aging treatment in a roll state: The sample produced in aging treatments 1 to 3 is a sample of A4 size (210 × 297 mm) from the center of 5 m from the top after removing the moisture-proof plastic sheet. Collected.

  2) Sample laminated in sheet form and subjected to aging treatment: A4 size (210 × 297 mm) sample was taken from the center of the sample at the position of the fifth sheet from the outermost surface.

[Evaluation of curl characteristics]
When each sample cut to A4 size is placed on a horizontal test stand in an environment of 23 ° C. and 55% RH and the ink absorbing layer surface is used as a reference, in the case of a positive curl (concave curl), the ink absorbing layer surface In the case of minus curl (convex curl), the ink absorbing layer surface was placed on the bottom, and the height from the test table surface at the four corners of the A4 sample was immediately measured, and the average value was obtained. .

[Evaluation of banding resistance]
Using A Seiko Epson Inkjet Printer PM-4000PX, each A4 size sample is printed with a gradation image in which the density is continuously changed from a black image to a white image in a direction perpendicular to the sample transport direction. The stripes of the image were visually observed, and banding resistance was evaluated according to the following criteria.

◎: No banding is observed. ○: Very weak banding is observed in some image areas, but the image is highly uniform. △: Weak banding is observed in some images. The image is in a practically acceptable range. X: The occurrence of strong banding is recognized and the quality is a problem in practical use. The results obtained as described above are shown in Table 1.

As is apparent from the results shown in Table 1, it can be seen that the sample subjected to the aging treatment according to the method defined in the present invention is superior in curl stability and banding resistance to the comparative example. Among them, a sample subjected to aging treatment using an ink jet recording medium using 0.007 μm silica fine particles for the outermost layer ink absorption layer, a sample obtained by dividing the aging treatment conditions into two conditions, or a laminated state on the outermost layer. It can be seen that an excellent effect is exhibited by performing the aging process with the weight added.
Aging process
[Aging process 14]
After the moisture-proof plastic sheet of the packaged recording medium 2 described in Example 1 was removed, the sheet-like sample was immediately cut into a sheet having a width of 152 cm and a length of 215 cm in an environment of 23 ° C. and 55% RH. 1580 sheets were produced. Next, the 1580 sheets were stacked on a horizontally-made plastic plate, and in this state, humidity control was performed for 3 days in an environment of 23 ° C. and 55% RH. Next, a moisture-proof plastic sheet was wound around the periphery of the laminate under conditions such that the load on each sheet-like sample did not change. Next, the sample in the laminated state was moved to a room controlled to a temperature and humidity condition of a temperature of 53 ° C. and 55% RH, and subjected to an aging treatment 14 for 3 days.

[Aging process 15]
In the aging treatment 14, except that the humidity control condition of the laminate was changed from 23 ° C. and 55% RH to 23 ° C. and 35% RH, this was designated as the aging treatment 15.

<< Evaluation of Aged Sample >>
[Sampling of sample for evaluation]
Regarding the aging treatments 14 and 15 performed above and the aging treatment 10 performed in Example 1, among the 1580 stacked sheet-like samples, the fifth sample from the top, the 790th sample from the top, A fifth sample from the bottom was collected.

(Sample evaluation)
About each sample extract | collected as mentioned above, it carried out similarly to the method as described in Example 1, and evaluated the curl characteristic and the banding tolerance.

  The results obtained as described above are shown in Table 2.

  As is apparent from the results shown in Table 2, by performing the humidity adjustment process under the condition of 55% RH before performing the aging process, the variation in the effect of curling characteristics and banding resistance at the stacking position of the stacked body can be obtained. It can be seen that there is little variation in the effect due to the position even in the laminated state.

Claims (5)

In a method for producing an ink jet recording medium, wherein at least one ink absorbing layer is coated on a support and dried to produce the ink jet recording medium, the ink jet recording medium is coated, dried, cut into a sheet, and the sheet shaped ink jet recording A method for producing an ink jet recording medium, wherein the medium is laminated and subjected to aging treatment at 35 ° C. or more for 24 hours or more. The method for producing an ink jet recording medium according to claim 1, wherein the aging treatment is performed in a state where a load of 10 Pa or more and 500 Pa or less is uniformly applied to the uppermost part of the laminated ink jet recording medium. The method for producing an ink jet recording medium according to claim 1, wherein the aging treatment is performed by combining two or more conditions having different temperatures or treatment times. The humidity control treatment for 3 days or more is performed in an environment of 18 ° C. or higher, less than 30 ° C., and 50% RH or higher before performing the aging treatment. Manufacturing method of inkjet recording medium. The method for producing an ink jet recording medium according to any one of claims 1 to 4, wherein the outermost ink absorbing layer of the ink jet recording medium contains silica fine particles having an average primary particle diameter of 10 nm or less.