JP2005280299A - Sheet for inkjet recording and method for manufacturing sheet for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet for inkjet recording which is successfully free from phenomena such as waviness, especially cockling after recording an image, and a method for manufacturing a sheet for inkjet recording. <P>SOLUTION: In the sheet for inkjet recording with a recording layer formed on at least one surface of a sheet base material, the sheet base material is not less than 80μm thick and contains an inter-fiber binding inhibitor. In addition, the sheet base material is of such a gradient structure that the content of the inhibitor is large near the surface of a side where the recording layer of the sheet base material is formed and decreases toward the center of the thickness direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink jet recording paper having good corrugation of an ink jet recording paper, in particular, good cockling after image recording. In particular, the present invention relates to an ink jet recording paper that has excellent paper passing properties, high gloss, and good appearance of recorded images.

  The ink jet recording method that ejects water-based ink from a fine nozzle toward the ink jet recording paper and forms an image on the surface of the ink jet recording paper has low noise during recording, easy formation of a full color image, high speed It is widely used in terminal printers, facsimiles, plotters, form printing, and the like due to the fact that recording is possible and the recording cost is lower than other printing apparatuses.

  In recent years, due to the rapid spread of printers and higher resolution and higher speed, inkjet recording paper is required to have higher ink absorption speed than before, and further, with the advent of digital cameras, it is comparable to silver salt photography. There is a strong demand for image uniformity. Further, in order to bring the quality of a recorded image closer to that of a photographic image, further improvement in image recording density and glossiness is desired.

  On the other hand, in order to realize images aligned with silver salt photographs, the amount of ink discharged has also increased, and water, which is an ink solvent, has penetrated into the paper base, causing undulations due to the expansion and contraction of the paper base, There is a problem that an image defect is caused by rubbing with the recording head, or the appearance of the image is impaired due to the undulation remaining after image recording. In order to solve these problems, resin-coated paper obtained by extruding and laminating a synthetic resin such as polyethylene on both sides has been commonly used.

However, if the resin-coated paper is collected as waste paper, the resin in the form of a film remains, and there is a possibility of causing trouble when collecting the waste paper. Further, as a method not using resin-coated paper, a method using a base paper containing a low-density chemical that reduces the fiber-fiber bond of pulp and increases the gap of paper has been proposed (for example, Patent Document 1). However, even this ink jet recording paper does not sufficiently prevent cockling after image recording in a photographic image having a large amount of ink.
JP 2002-103791 A

  In view of the situation as described above, the present invention provides an ink jet recording sheet having good cockling.

  As a result of intensive studies on the above problems, the present inventors have found that the content of the interfiber bonding inhibitor is large near the surface of the paper substrate on which the recording layer is provided, and decreases toward the center in the thickness direction. It has been found that cockling can be improved by providing a recording layer on a paper substrate having a structure.

The present invention includes the following inventions.
(1) In an inkjet recording paper provided with a recording layer on at least one surface of a paper substrate, the paper substrate has a thickness of 80 μm or more, contains an interfiber bond inhibitor, and the interfiber bond inhibitor An ink jet recording paper characterized by having an inclined structure in which the content of is increased near the surface of the paper substrate on which the recording layer is provided and decreases toward the center in the thickness direction.
(2) The ink jet recording paper according to (1), wherein the paper substrate is coated with a coating liquid containing an interfiber bond inhibitor, starch and a surface sizing agent.
(3) The inkjet recording paper according to (1) or (2), wherein an undercoat layer is provided on a paper substrate and then a recording layer is provided.
(4) The inkjet according to any one of (1) to (3), wherein the recording layer contains a fine pigment having an average primary particle size of 0.003 to 0.040 μm and an average secondary particle size of 1 μm or less. Recording sheet.
(5) The ink jet recording paper according to any one of (1) to (4), wherein the ink jet recording paper is a gloss type.
(6) The inkjet recording paper according to any one of (1) to (3), wherein the inkjet recording paper is a mat type.
(7) A paper base material containing an interfiber bond inhibitor, and an inclined structure in which the content of the interfiber bond inhibitor is large near the surface of the paper base material and decreases toward the center in the thickness direction. A method for producing an ink jet recording paper, comprising forming a recording layer on a surface of a paper substrate having a large amount of interfiber bond inhibitor.
(8) The method for producing an ink jet recording paper according to (7), wherein the paper base material contains an inter-fiber bond inhibitor by using both an internally added size and an externally added size.
(9) The method for producing an inkjet recording paper according to (7) or (8), wherein the paper substrate is coated with a coating liquid containing an interfiber bond inhibitor, starch and a surface sizing agent.
(10) The method for producing an inkjet recording paper according to (9), wherein the interfiber bond inhibitor and starch have a mass ratio of 1:99 to 20:80.

  The present invention relates to an ink jet recording paper having good corrugation of an ink jet recording paper, in particular, good cockling after image recording. In particular, the present invention relates to an ink jet recording paper that has excellent paper passing properties, high gloss, and good appearance of recorded images.

  The present invention relates to an inkjet recording paper having a recording layer provided on at least one surface of a paper base material, the paper base material having a thickness of 80 μm or more, containing an interfiber bond inhibitor, and inhibiting the interfiber bond. The ink jet recording paper is characterized in that the content of the agent is large near the surface of the paper substrate on which the recording layer is provided and has an inclined structure that decreases toward the center in the thickness direction. Further, the paper base material contains an inter-fiber bond inhibitor, and the content of the inter-fiber bond inhibitor is large near the surface of the paper base material and has an inclined structure that decreases toward the center in the thickness direction. A method for producing an ink jet recording paper, comprising forming a recording layer on a surface of a paper substrate containing a large amount of interfiber bond inhibitor.

  The interfiber bond inhibitor referred to in the present invention may be any substance that inhibits the binding between fibers of the cellulose fiber raw material constituting the paper substrate to some extent. For example, it has a hydrophobic group and a hydrophilic group in the molecule. There are surfactants that are now well known. Examples thereof include long-chain mono- or dialkyl quaternary ammonium salts, higher alcohol sulfates or phosphates, higher alcohols, higher alcohol fatty acid esters and the like, and are also effective for fatty acid polyamidoamine compounds. It is not particularly limited to the surfactant. Currently available interfiber binding inhibitors include BASF's Sulsol VL, Bayer's Bi-Volume P Liquid, Sansho's React Pake (opacity improver), Kao's KB-08T, KB -115 is a chemical.

  In the present invention, cockling is improved by using a paper base material in which the interfiber bonding inhibitor is distributed more near the surface of the surface on which the recording layer is formed than inside the paper base material. The reason for this is not clear, but when ink jet recording is performed, the dyes and pigments that are colorants are retained on the recording layer or the recording layer surface. The ink solvent constituting the ink is not completely retained by the recording layer or the undercoat layer formed as necessary, but penetrates to the paper substrate. In particular, in the case of photographic image quality output with a large amount of ink, excess ink solvent penetrates to the paper substrate. However, the same amount of ink solvent is not supplied throughout the recording paper, but the ink solvent that reaches the paper substrate due to various factors such as the difference in each ink, the order of jetting ink, the difference in density, etc. The amount is different. It is considered that the difference in the arrival of the ink solvent causes the fiber of the paper base material to have a different amount of elongation and cockling. The constitution of the present invention is that many interfiber bonding inhibitors are distributed near the surface of the paper substrate, and interfiber bonding of the cellulose fiber raw material is inhibited, so there are many voids that absorb the ink solvent. Will exist. Since the voids due to the interfiber bonding inhibitor exist in the lateral direction (portion close to the surface) rather than the thickness direction of the paper substrate, the ink solvent does not permeate only in the thickness direction but is distributed relatively evenly on the surface. Therefore, it is considered that cockling can be prevented. However, when the thickness of the paper base material is less than 80 μm, even if the interfiber bonding inhibitor is contained, cockling cannot be sufficiently prevented. Therefore, the thickness of the paper base material needs to be 80 μm or more. is there. When the thickness of the paper substrate exceeds 360 μm, the effect of containing the interfiber bonding inhibitor distribution (more on the surface and less in the center) tends to be saturated. When the thickness of the material is increased, cockling can be prevented only by containing a small amount of interfiber bonding inhibitor in the paper substrate.

  When the recording layer is formed on both sides, a large amount of interfiber bonding inhibitor is contained near the surfaces of both sides, and a recording layer (an undercoat layer may be formed in advance if necessary) is formed on each side. Good. Further, the interfiber bond inhibitor should be contained in a greater amount near the surface than in the central part, and even when the recording layer is provided only on one side, the near surface on the opposite side contains more interfiber bond inhibitor than in the central part. It does not matter. Note that “near the surface” may be determined, for example, as a surface portion and a center portion when the paper base material is equally divided into three in the thickness direction. In general, it is preferable to contain a large amount of interfiber bonding inhibitor in a portion of about 30% of the thickness of the paper substrate.

In the present invention, it is sufficient that the interfiber bond inhibitor is present in the vicinity of the surface of the paper substrate on which the recording layer is formed, and in the center in the thickness direction. For example, if an interfiber bonding inhibitor is blended only by the internal addition method, it cannot be allowed to exist only near the surface efficiently, so an interfiber binding inhibitor can be a combination of the internal addition method and the external addition method, or an external addition method. It is preferably present by the law.
As the external addition method, there are size press, coating and impregnation, which can be adopted as appropriate, but coating is preferable in order to make it exist as close to the surface as possible. As a coating apparatus to be used, apparatuses such as a two roll size press, a blade metering size press, a lot metering size press, a gate roll coater, a blade coater, a bar coater, a rod blade coater, and an air knife coater can be used.

  Moreover, it is preferable to apply | coat the surface treatment agent containing an interfiber bond inhibitor, starch, and a surface sizing agent on the surface of a paper base material. By using starch and a surface sizing agent together, increase the paper strength of the surface, suppress the penetration of the recording layer coating liquid and undercoat layer coating liquid in the manufacturing process, and adjust the permeability of the ink solvent Can do. By applying these to the surface together with an interfiber bond inhibitor, the coating suitability of the recording layer coating solution and the undercoat layer coating solution and cockling at the time of image recording with a printer are improved.

If the starch content is low, the surface strength will be reduced, causing problems such as piling during printing. Conversely, if the starch content is high, the starch will become hard, and the original paper will be flexible. Will be damaged. In order to provide both of these qualities, the mass ratio of starch to the interfiber bond inhibitor is preferably 1:99 to 20:80, and when the interfiber bond inhibitor is less than 1:99 relative to starch, a feeling of texture is felt. If the ratio exceeds 20:80, the paper strength and the surface strength are lowered, which is not preferable. To be 1.0g ^/ m ² ~6.0g / m 2 coating surface treating agent containing an interfiber bonding inhibitor and surface sizing agent and starch in solids in order to preserve the balance of Nakayaka and surface strength it is preferable, and more preferably set to ^{2.0g / m 2 ~4.0g / m 2} .

  Examples of the starch used in the present invention include, but are not limited to, corn starch, potato starch, tapioca starch, wheat starch, rice starch and the like, oxidized starch, phosphate esterified starch and the like. Absent. These starches can be used alone or in combination of two or more. Furthermore, polyvinyl alcohol and modified polyvinyl alcohol can also be used in combination with the above starch.

As the surface sizing agent used in the present invention, for example, alkyl ketene dimer compounds, alkeni succinic anhydride compounds, styrene-acrylic compounds, higher fatty acid compounds, petroleum resin sizing agents and rosin sizing agents can be used. 0.02g ^{/ m 2} ~0.3g ^/ m 2 preferably contains. If it is less than 0.02 g / m ² , there is no size effect, and if it exceeds 0.3 g / m ² , the size development effect reaches its peak, leading to an increase in cost.

  Furthermore, other water-soluble and / or water-dispersible adhesives that do not cause gelation of the solution or the like within a range that does not impair the effects of the present invention, such as carboxymethyl cellulose, styrene-butadiene copolymer, etc. Latexes, polyacrylamide, and the like can be added as appropriate. A chemical such as a water-proofing agent or a crosslinking agent can be added as appropriate to the extent that the effects of the present invention are not impaired or to assist the present invention.

  Cellulose fiber raw materials that are the main components of the paper base include chemical pulps such as kraft pulp (KP), sulfite pulp (SP), soda pulp (AP), semi-chemical pulp (SCP), and chemi-grandwood pulp (CGP). ) And other semi-chemical pulps, groundwood pulp (GP), thermomechanical pulp (TMP, BCTMP), refiner grandwood pulp (RGP), and other non-wood pulp And deinked pulp made from waste paper. These may be used alone or in combination of two or more. Although it does not specifically limit as a filler mix | blended with a paper base material, The filler generally used for printing paper, for example, calcium carbonate, talc, clay, titanium oxide, white carbon, etc. are used individually or in mixture. Also good.

  Further, in the stock, together with the above raw materials, papermaking chemicals used in normal papermaking, for example, sizing agent, size fixing agent, dry paper strength enhancer, wet paper strength enhancer, yield improver, drainage improver An antifoaming agent, a slime control agent, a dye and the like can be added as necessary.

  The paper used in the present invention is produced by a known paper machine, for example, a long-mesh type, a circular net-type, a short-net type, or a twin-wire type paper machine.

The basis weight of the paper of the present invention ^are those of 40g / ^{m 2} ~210g / m 2 is preferred. If it is less than 40 g / m ^2, it is not preferable because it often causes running out of paper in operation. On the other hand, if the bulk exceeds 210 g / m ² , the paper thickness is too large and it is not suitable for inkjet recording paper.

The density of the paper of the present invention is preferably 0.55cm ³ ~0.70g / cm ^3. If it is less than 0.55 g / cm ³ , operational problems such as running out of paper occur, which is not preferable. On the other hand, if it exceeds 0.70 g / cm ³ , cockling tends to occur.

  In the present invention, an undercoat layer is appropriately provided depending on the type of cellulose fiber raw material, the pulp beating degree, the basis weight of the base paper, the amount of sizing agent applied, and the like. The undercoat layer in the present invention has functions such as preventing the ink solvent from penetrating into the paper base material in order to suppress cockling, delaying it, allowing it to penetrate uniformly, and further absorbing the undercoat layer itself. Not only has it, it prevents gas permeation from the back side of the paper substrate, improves whiteness, prevents yellowing due to heat and light, and further to the base paper when recording layer coating is applied It has a function of suppressing the permeation of the resin to form a good coated surface.

  Pigments used for the undercoat layer are titanium oxide, zinc oxide, light calcium carbonate, heavy calcium carbonate, magnesium carbonate, barium sulfate, clay, kaolin, calcined kaolin, satin white and other inorganic pigments, (meth) acrylic acid esters Examples thereof include organic resin particles made of various synthetic resins such as resin, styrene- (meth) acrylic acid ester copolymer resin, styrene resin, urea-formalin resin, benzoguanamine resin, and nylon resin. Among these pigments, titanium oxide, light calcium carbonate, and styrene- (meth) acrylic acid ester copolymer resin particles are preferable, and titanium oxide, styrene- (meth) acrylic acid are particularly preferable in terms of whiteness, hiding properties, and smoothness. Ester copolymer hollow resin particles are preferably used. Moreover, you may use together as needed.

  The shape and particle size of these pigments can be appropriately selected depending on the required quality of the undercoat layer. Incidentally, when using titanium oxide and hollow resin particles, the particle diameter is preferably 0.1 to 5.0 μm, and more preferably 0.3 to 3 μm. If the particle size is small, the strength and color developability tend to be reduced. If the particle size is large, a smooth and uniform surface cannot be obtained.

  The adhesive used for the undercoat layer can be appropriately selected from aqueous emulsions, water-soluble polymers, and solvent-based polymers that are usually used for paper processing. Examples of aqueous emulsions include styrene-butadiene latex, methyl methacrylate-butadiene latex, acrylonitrile-butadiene latex, (meth) acrylic ester emulsion, vinyl acetate emulsion, ethylene-vinyl acetate emulsion, urethane emulsion. Etc. Examples of the water-soluble polymer include polyvinyl alcohol and derivatives thereof, starch and modified products thereof, cellulose derivatives such as carboxymethyl cellulose, and casein. Examples of the solvent polymer include a resin in which an organic solvent such as toluene, ethyl acetate, methyl ethyl ketone or the like is dissolved or dispersed. Among these adhesives, water-based emulsions and water-soluble polymers are preferable from the viewpoint of ease of handling, safety and hygiene, and water-based emulsions are particularly advantageous in the drying process because they can be water-resistant and highly concentrated. It is done. Moreover, when using aqueous | water-based emulsion resin, the thing whose glass transition temperature of this polymer is -30-40 degreeC is preferable. If it is lower, the film strength is not sufficient, and if it is higher, film formation in the drying process is insufficient and the film strength may be lowered.

The ratio of the pigment to the adhesive is about 2 to 30 parts, preferably about 5 to 20 parts, with respect to 100 parts of the pigment. When the amount of the adhesive is small, the strength of the undercoat layer is lowered, and when the amount of the adhesive is too large, the absorption amount is lowered and the color development is deteriorated, and the whiteness tends to be lowered.
Furthermore, for the undercoat layer, a crosslinking agent that improves water resistance and film strength, an ultraviolet absorber, an antioxidant, an antioxidant, a pH adjuster, a chelating agent, various dyes and pigments for coloring, and a fluorescent brightening agent , Preservatives, thickeners for imparting coating suitability, surfactants, antifoaming agents and the like can be appropriately blended.

The coating material thus prepared can be appropriately set according to the purpose in the range of 1 to 30 g / m ² as a dry coating amount, and preferably 5 to 15 g / m ² . If the amount is less than 1 g / m ² , the effect is not sufficient, and if it is more than 30 g / m ² , the interlayer strength tends to be weak, or the drying process is economically disadvantageous.

  Examples of the coating apparatus for forming the undercoat layer include various known coating apparatuses such as a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a rod blade coater, a lip coater, a curtain coater, and a die coater. Can be mentioned. Moreover, it can also coat with the coating apparatus attached to a paper machine. After coating, it may be finished using a calendar such as a machine calendar, a TG calendar, a super calendar, or a soft calendar.

  Inkjet recording paper is a mat type with a low gloss using a pigment with a relatively large particle diameter for the recording layer, a gloss type using a pigment with a small particle diameter for the recording layer, and a gloss type. However, there are various forms such as a cast type in which the outermost layer of the recording layer is pressed against a mirror drum and finished. Ink jet recording paper using a paper base material causes cockling when the ink solvent permeates the paper base material. Therefore, the present invention particularly restricts the form as long as the paper base material is used. is not. However, glossy ink jet recording paper is often required to have high-quality images, in particular, image quality close to that of photographs, and when such images are recorded, the amount of ink increases, so cockling The problem is remarkable. Further, many glossy ink jet recording papers have improved surface smoothness in order to impart gloss, and cockling tends to be noticeable when cockling occurs. The present invention is preferable for glossy ink jet recording paper, which has a large cockling problem, because of its excellent effect.

  Next, the recording layer will be described. The recording layer contains a pigment and a binder, and is used by blending various auxiliary agents such as a cationic dye fixing agent as required.

As the pigment, it is preferable to contain amorphous silica, alumina and zeolite as main components, kaolin, clay, calcined clay, zinc oxide, aluminum hydroxide, calcium carbonate, satin white, aluminum silicate, colloidal silica, sepiolite, One or more of smectite, synthetic smectite, magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, hydrotalcite and the like can be used in combination.
That is, the type and particle size can be selected and used according to the desired quality, such as ink absorptivity, glossiness, smoothness, and whiteness.

Among these pigments, when a pigment having an average particle diameter of 1 μm to 13 μm is used as a main pigment, the recording layer does not have gloss and a mat type ink jet recording paper is obtained.
In order to obtain a glossy ink jet recording paper, it is necessary to provide at least one layer containing a fine pigment having an average particle diameter of 0.01 to 1 μm as a main pigment. When two or more layers are used, if the lower layer is provided with a pigment having a relatively large particle size and the upper layer is provided with a fine pigment having an average particle size of 0.01 to 1 μm, the lower layer absorbs a large amount of ink solvent. Therefore, it is preferable.

  Fine pigments having an average particle size of 0.01 to 1 μm suitable for the gloss type include gas phase method silica, mesoporous silica, colloidal material of wet method silica produced by condensing activated silicic acid, alumina oxide, It is preferable to use at least one selected from alumina hydrate. Among these, gas phase method silica and alumina oxide are preferably selected. Among the alumina oxides, gas phase method (fumed) alumina oxide is preferable.

  Vapor phase silica is also called fumed silica, and is generally made by flame hydrolysis. Specifically, a method of making silicon tetrachloride by burning with hydrogen and oxygen is generally known, but silanes such as methyltrichlorosilane and trichlorosilane can be used alone or silicon tetrachloride instead of silicon tetrachloride. Can be used in a mixed state.

Mesoporous silica is a porous silica material having an average pore diameter of 1.5 to 100 nm. In addition, mesoporous silica into which aluminum, titanium, vanadium, boron, manganese atoms or the like are introduced can also be used. The physical properties of the porous body are not particularly limited, but the BET specific surface area (nitrogen adsorption specific surface area) is preferably 200 to 1500 m ² / g, and the pore volume is preferably 0.5 to 4 cc / g. The method for synthesizing mesoporous silica is not particularly limited, but is described in U.S. Pat. No. 3,556,725, in which a quaternary ammonium salt containing a long-chain alkyl is used as a template. Hydrothermal synthesis method using amorphous silica powder or alkaline silicate aqueous solution described in Table 5-5503499 etc. as a silica source and using a quaternary ammonium salt having a long chain alkyl group or a phosphonium salt as a template, A method of synthesizing a layered silicate such as kanemite as a silica source described in Kaihei 4-238810, etc. by an ion exchange method using a long-chain alkylammonium cation as a template, further dodecylamine, hexadecylamine, etc. Amines, nonionic surfactants, etc. As the template, it is as a source of silica and water glass or the like and a method of synthesis using an active silica obtained by ion exchange. Examples of the method for removing the template from the nanoporous silica precursor include a method of baking at a high temperature and a method of extracting with an organic solvent.

  The wet-process silica colloid produced by condensing activated silicic acid is obtained by adding an alkali to a colloidally dispersed silica seed solution, and at least selected from an aqueous solution of active silicic acid and alkoxysilane. It is a secondary silica dispersion obtained by growing silica fine particles by adding one kind of feed solution little by little, and can be obtained by a method described in, for example, JP-A-2001-354408.

  Alumina oxide is also generally called crystalline alumina oxide having crystallinity. Specific examples include alumina oxide having χ, κ, γ, δ, θ, η, ρ, pseudo γ, and α crystals. In the present invention, gas phase method alumina oxide and alumina oxide having γ, δ, and θ crystals are preferably selected from the viewpoint of gloss and ink absorbability. Vapor phase alumina oxide (fumed alumina) having a sharp particle size distribution and particularly excellent film formability is most preferred.

  Vapor phase alumina oxide is alumina formed by high temperature hydrolysis of gaseous aluminum trichloride, resulting in the formation of high purity alumina particles. The primary particle size of these particles is nano-order, and shows a very narrow particle size distribution (particle size distribution). Such vapor phase alumina oxide has a cationic surface charge. The use of vapor phase alumina oxide in ink jet coating is shown, for example, in US Pat. No. 5,171,626.

  The alumina hydrate is not particularly limited, but boehmite or pseudoboehmite is preferably selected from the viewpoint of ink absorption speed and film formability. The production method of alumina hydrate includes, for example, a method of hydrolyzing aluminum isopropoxide with water (BE Yoldas, Amer. Ceram. Soc. Bull., 54, 289 (1975), etc.) and aluminum alkoxide. And the like (Japanese Patent Laid-Open No. 06-064918).

  As for the form of the fine pigment, an aggregated particle dispersion of the pigment is mainly preferably used for the purpose of obtaining high ink absorbability, coating film forming property, and smoothness. The average particle size needs to be 0.01 to 1 μm. From the viewpoint of the ink absorption rate and the like, an aggregate pigment having an average particle diameter of 0.01 to 0.7 μm formed by aggregating primary particles having an average primary particle diameter of 0.003 to 0.040 μm is more preferable. Average particles formed by agglomeration of primary particles having an average primary particle size of 0.005 to 0.020 μm in order to easily fix dyes and pigments in the ink and to obtain a high ink absorption rate, printing density, and gloss. A pigment having a diameter of 0.5 μm or less is more preferable.

  A pigment having an average particle size of 0.7 μm or less can be obtained by, for example, a strong force by mechanical means, that is, a so-called breaking down method (a method of fragmenting a bulk material). The mechanical means include: ultrasonic homogenizer, pressure homogenizer, liquid collision type homogenizer, high-speed rotary mill, roller mill, container drive medium mill, medium agitation mill, jet mill, mortar, and crusher (coating in a bowl-shaped container). A device for grinding and kneading the pulverized material with a bowl-shaped stirring bar), a sand grinder, and the like. In order to reduce the particle size, classification and repeated pulverization can be performed.

  The average particle diameter referred to in the present invention is, regardless of whether the pigment is powder or slurry, first, 200 g of a 3% pigment aqueous dispersion is prepared, and then stirred and dispersed at 1000 rpm for 30 minutes with a commercially available homomixer. Immediately observed with an electron microscope (SEM and TEM) (taken 10,000-400,000 times electron micrographs, measured and averaged the diameter of a 5 cm square particle, “Particle Handbook”, Asakura Bookstore, p52, 1991). As a result of measurement by the present inventors, when the pigment is powder (most pigments having a particle diameter of 1 μm or more), it almost matches the manufacturer's catalog value, but in the case of slurry (most pigments having a particle diameter of 1 μm or less). Although the particle size varies greatly depending on the state of aggregation of the slurry, almost the same value can be obtained under the above measurement conditions.

  As the binder contained in the recording layer, any binder known for inkjet recording can be used. For example, polyvinyl alcohol, cation-modified polyvinyl alcohol, silyl-modified polyvinyl alcohol, polyvinyl acetal, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, casein, soy protein, synthetic proteins, starch, polypropylene oxide, polyethylene glycol, polyvinyl ether, polyvinyl acrylamide, polyvinyl pyrrolidone Styrene-butadiene copolymer, methyl methacrylate, styrene-vinyl acetate copolymer, and the like. Among these, polyvinyl alcohol is preferably selected particularly from the viewpoint of adhesion to the pigment. Among these, polyvinyl alcohol having a polymerization degree of 2000 or more is preferable from the balance between film formability and ink absorbability, and polyvinyl alcohol having a polymerization degree of 3600 to 5000 is more preferable. In addition, two or more binders (for example, a water-soluble resin and a water-soluble resin, a water-soluble resin and a latex, etc.) may be used in combination in order to improve ink absorbability.

  In the case of a glossy type ink jet recording paper, it is preferable to form a microporous layer obtained by increasing the viscosity or gelation of the recording layer coating liquid at the same time as or after the coating and drying. There is no particular limitation on the method for thickening or gelating the recording layer coating solution simultaneously with or after coating. For example, (a) thickening or gelation by using a crosslinking agent capable of crosslinking reaction with a hydrophilic binder blended in the recording layer, (b) thickening or gelling by supplying energy such as electron beam Examples of the method include (c) a hydrophilic binder, a thermosensitive polymer compound that exhibits hydrophilicity and hydrophobicity depending on temperature conditions, and a method of increasing the viscosity or gelation by changing the temperature.

  (A) As a method of thickening or gelating using a crosslinking agent capable of crosslinking reaction with the hydrophilic binder blended in the recording layer, the exemplified hydrophilic binder and the crosslinking agent capable of crosslinking reaction with the hydrophilic binder. Are used in combination. For example, a recording layer coating solution is prepared by coating and impregnating a substrate with a crosslinking agent in advance and then applying a recording layer coating solution. After the application, it may be produced by a method of applying a cross-linking agent. However, it is preferable to apply the cross-linking agent in advance because a recording layer with uniform thickening or gelation is obtained.

  Examples of the crosslinking agent include a boron compound, an epoxy compound, a glycidyl compound, a zirconium compound, an aluminum compound, a chromium compound, and the like. Among these, a boron compound is particularly preferable because thickening or gelation occurs quickly.

The boron compound is an oxygen acid having a boron atom as a central atom and a salt thereof. Examples include orthoboric acid, metaboric acid, hypoboric acid, tetraboric acid, pentaboric acid, and their sodium, potassium, and ammonium salts. Among these, orthoboric acid and disodium tetraborate are preferably used because they have an effect of moderately thickening the paint.
Although content of a boron compound is based also on the kind of boron compound and a hydrophilic binder, it is preferable to contain 0.01-1.5 g / m < ² > on the single side | surface of a base material. When the amount is more than 1.5 g / m ² , the crosslinking density with the hydrophilic binder increases, the coating film becomes hard and is easily broken. On the other hand, when the amount is less than 0.01 g / m ² , the crosslinking with the hydrophilic binder is weak, the gelation of the paint is weakened, and the coating film is easily cracked.

  (B) As a method of increasing the viscosity or gelation by supplying energy such as an electron beam, the recording layer binder does not have a radical polymerizable unsaturated bond, and the aqueous solution is irradiated with an electron beam. By using a hydrophilic binder that forms a hydrogel, a coating liquid containing 1 to 100 parts by weight of a hydrophilic binder is applied to 100 parts by weight of the fine pigment, and then irradiated with an electron beam. It is preferable to form the recording layer by hydrolyzing the applied coating solution and then drying it.

  Examples of the hydrophilic binder that does not have a radical polymerizable unsaturated bond and forms a hydrogel by irradiating an aqueous solution with an electron beam include, for example, polyvinyl alcohol, polyethylene oxide, polyalkylene oxide, polyvinyl pyrrolidone, water-soluble Polyvinyl acetal, poly-N-vinylacetamide, polyacrylamide, polyacryloylmorpholine, polyhydroxyalkyl acrylate, polyacrylic acid, hydroxyethylcellulose, methylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose, gelatin, casein, and water-soluble derivatives thereof, Moreover, these copolymers etc. can be illustrated and it is good to use these individually or in combination.

  As an electron beam irradiation method, for example, a scanning method, a curtain beam method, a broad beam method, or the like is adopted, and an acceleration voltage at the time of irradiation with an electron beam is suitably about 50 to 300 kV. The amount of electron beam irradiation is preferably adjusted in the range of about 1 to 200 kGy. If it is less than 1 kGy, it is not sufficient to gel the coating layer, and irradiation exceeding 200 kGy is not preferable because it may cause deterioration or discoloration of the substrate or the coating layer.

  (C) As a hydrophilic binder, a temperature-sensitive polymer compound that exhibits hydrophilicity and hydrophobicity depending on temperature conditions is used. As a method of thickening or gelling by changing the temperature, as the binder, It is preferable to use a temperature-sensitive polymer compound that exhibits hydrophilicity in the temperature range and exhibits hydrophobicity in the temperature range higher than the temperature-sensitive point.

  When this thermosensitive polymer compound is used, coating is performed at a temperature higher than the temperature sensitive point, and by cooling to a temperature lower than the temperature sensitive point, the applied layer is thickened or gelled and then dried. A recording layer may be formed. Examples of such temperature-sensitive polymer compounds include those disclosed in JP-A-2003-40916, which are obtained by polymerization in the presence of polyvinyl alcohol and / or polyvinyl alcohol derivatives. it can.

The recording layer preferably contains a cationic compound. Examples of the cationic compound include 1) polyalkylene polyamines such as polyethylene amine and polypropylene polyamine, or derivatives thereof, 2) acrylic resins having secondary amine groups, tertiary amine groups, and quaternary ammonium groups, 3) Polyvinylamine, polyvinylamidine, 5-membered ring amidines, 4) Dicyan cationic resin represented by dicyandiamide-formalin polycondensate, 5) Polyamine cationic resin represented by dicyandiamide-diethylenetriamine polycondensate, 6) Epo chlorohydrin - dimethylamine addition polymers, 7) dimethyldiallylammonium chloride -SO ₂ copolymer, 8) diallylamine -SO ₂ copolymer, 9) dimethyldiallylammonium chloride polymer, 10) polymer of allyl amine salt 1 Generally available products such as aluminum alkyl salts such as polyalkylaluminum chloride, polyaluminum acetate, polyaluminum lactate, and the like. It is done. In addition, as addition amount of a cationic compound, 1-30 mass parts is preferable with respect to 100 mass parts of pigments, and 2-15 mass parts is more preferable. Further, when two or more recording layers are used, it is preferable that at least the upper layer contains a cationic compound.

  When a silica-based pigment is used, the silica-cationic compound aggregate particles obtained by mixing and aggregating silica and a cationic compound are 0.01 to 1 μm, preferably 0.01 to 0.7 μm. Preference is given to fine particles of pulverized silica-cationic compound aggregates. In this case, the cationic compound is appropriately selected from the above cationic compounds. In particular, aluminum salts such as 1) 5-membered ring amidines, 2) polyaluminum chloride, polyaluminum acetate, and polyaluminum lactate are preferred because of the fixability and dispersibility of dyes and pigments in the ink.

  The recording layer coating solution for forming the recording layer is prepared as an aqueous coating solution using water containing the above pigment, a hydrophilic binder, and, if necessary, a cationic compound as a solvent. The ratio of the pigment to the hydrophilic binder is preferably in the range of 100/50 to 100/2 by mass ratio. 100 / 30-100 / 5 are preferable from the balance of ink absorptivity and coating film strength, and 100 / 25-100 / 10 are more preferable. In addition to pigments, hydrophilic binders, and cationic compounds used in combination as needed, the recording layer contains dispersants, thickeners, antifoaming agents, colorants, and antistatic agents used in general coated paper production. Various auxiliary agents such as preservatives and preservatives are appropriately added.

The recording layer coating solution prepared as described above is applied by the following method, for example. Before the recording layer becomes a reduced rate drying part (indicating a reduced rate drying rate), it is formed by thickening or gelling (for example, thickening or gelling the coating liquid with a crosslinking agent such as a boron compound). . This has a great effect of preventing the coating layer from cracking due to hot air during drying by thickening or gelling the coating in the early stage of drying and preventing the coating from penetrating into the substrate.

The coating amount of the recording layer coating solution is not particularly limited, but is about 1 to 40 g / m ² , preferably 5 to 30 g / m ² . If the coating amount is small, the recent high-speed and high-speed printer may have insufficient ink absorption speed, and if it is too large, it is difficult to control cracks in the coating film.
From the balance between the ink absorption speed and the ink absorption capacity, the coating amount of the recording layer is preferably at least three times the outermost layer coating amount described later. 7 times or more is more preferable, and 10 to 60 times is the most preferable range.

  As the coating apparatus for applying the recording layer coating liquid, the coating method of the pre-measurement method is preferable from the viewpoint of the physical properties of the paint and the coating amount. Examples of the pre-measuring method include various known methods such as lip coaters, curtain coaters, slide beads, slide hoppers, and die coaters such as slot dies. Moreover, when applying two or more layers, it is preferable to apply by Wet on Wet (method to apply the upper layer on the lower layer while the lower layer is not dried).

  The method for drying the recording layer of the present invention is not particularly limited. A drying device conventionally used in a coating machine can be used.For example, various heating drying methods such as hot air drying, gas heater drying, high-frequency drying, electric heater drying, infrared heater drying, and laser drying are preferable and used as appropriate. The Of these, hot air drying is preferred because it is advantageous in terms of cost. It is also possible to cast the outermost layer to make it highly glossy.

  The present invention will be specifically described below with reference to examples. Of course, the present invention is not limited to these examples. Moreover, unless otherwise indicated, the part and% in an example show a mass part and mass%, respectively.

Example 1
[Preparation of paper substrate 1]
To a pulp slurry of LBKP 100 parts having a freeness of 350 ml CSF, light calcium carbonate (manufactured by Shiraishi Calcium Co., Ltd., trade name: PC) was added to 25 parts, 0.9 parts starch per pulp, alkenyl succinic anhydride 0.1 parts, 0.7 parts of sulfuric acid band and 0.5 parts of interfiber binding inhibitor (trade name: KB115, manufactured by Kao Co., Ltd.) were added, and paper was made using a long net paper machine, and starch (Oji Corn Starch) was added. Product name: Ace A) 2.5 g / m ² , fiber binding inhibitor (product of Kao Corporation, trade name: KB115) 0.1 g / m ² , surface sizing agent (Arakawa Chemical Industries, (Product name: Polymeron 482S) A size press was applied so as to obtain 0.1 g / m ² to obtain a paper base having a basis weight of 80 g / m ² and a thickness of 123 μm.

[Adjustment of recording layer coating solution 1]
Wet silica (secondary particle size 4.5 μm, manufactured by Tokuyama Corporation, trade name: Fine Seal X-45) as pigment, 100 parts of silyl-modified polyvinyl alcohol (manufactured by Kuraray, trade name: R-1130) as adhesive And 23 parts of an acrylic resin (Rohm and Haas, trade name: Primal P-376), 10 parts of an acrylamide-diallylamine copolymer (trade name: SR1001) as an ink fixing agent, and dicyandiamide-polyethyleneamine 20 parts of a copolymer (manufactured by Nikka Chemical Co., Ltd., trade name: Neofix IJ-117) was dispersed in water to obtain a recording layer coating solution 1.

[Preparation of inkjet recording paper]
On the paper substrate 1, the recording layer coating solution 1 was applied and dried so that the coating amount was 15 g / m ² , thereby producing a mat type inkjet recording paper.

Comparative Example 1
[Preparation of paper substrate 2]
Light calcium carbonate (manufactured by Shiraishi Calcium Co., Ltd., trade name: PC) was added to a pulp slurry of LBKP 100 parts having a freeness of 450 ml CSF, and 1.0 part starch, alkenyl succinic anhydride per pulp. 0.1 parts, 0.6 parts of a sulfuric acid band and 0.5 parts of an interfiber binding inhibitor (trade name: KB115, manufactured by Kao Corporation) were added, and the paper was made using a long net paper machine, and starch (Oji) cornstarch Co., Ltd., trade name: Ace a) a 3.0g / ^{m 2,} surface sizing agent (manufactured by Arakawa chemical Industries, Ltd., product name: Polymaron 482S) was applied by a size press so as to be 0.01g / ^{m 2} A paper substrate having a basis weight of 80 g / m ² and a thickness of 120 μm was obtained.
[Preparation of inkjet recording paper]
A mat type ink jet recording paper was obtained in the same manner as in Example 1 except that the paper substrate 2 was used.

Comparative Example 2
[Preparation of paper substrate 3]
A paper base was obtained in the same manner as in Example 1 except that the basis weight was 50 g / m ² and the thickness was 77 μm in the production of the paper base of Example 1.
[Preparation of inkjet recording paper]
A mat type ink jet recording paper was obtained in the same manner as in Example 1 except that the paper base 3 was used.

Example 2
[Preparation of paper base 4]
A paper substrate was obtained in the same manner as in Example 1, except that the basis weight was 160 g / m ² and the thickness was 228 μm in the production of the paper substrate of Example 1.

[Adjustment of undercoat layer coating solution]
Hollow plastic pigment (styrene-acrylic copolymer particles, average particle size 1 μm, manufactured by Rohm and Haas, trade name: Ropeke HP-91) as pigment, 100 parts of acrylic polymer (emulsion adhesive) , Manufactured by Rohm and Haas Co., Ltd., trade name: Primal P-376) and gelatinized oxidized starch (water-soluble adhesive, manufactured by Oji Cornstarch Co., Ltd., trade name: Ace A) are dispersed in water. An undercoat layer coating solution was obtained.

[Preparation of aqueous dispersion 1 of silica fine particles]
Gas phase method silica having an average particle diameter of 1.0 μm (average primary particle diameter: about 0.008 μm, manufactured by Nippon Aerosil Co., Ltd., trade name: Aerosil A300) was dispersed with a sand grinder and then further dispersed with a pressure type homogenizer. Then, the dispersion operation of the sand grinder and the pressure homogenizer was repeated until the average particle size became 0.07 μm to prepare a 10% aqueous dispersion. After adding 13 parts of a cationic compound having a 5-membered ring amidine structure (trade name: SC-700, molecular weight: 300,000) having a 5-membered ring amidine structure to the 10% aqueous dispersion and dispersing with a sand grinder, a pressure homogenizer Then, the dispersion operation of the sand grinder and the pressure type homogenizer was repeated until the average particle size became 0.15 μm to prepare an aqueous dispersion of 10% silica fine particles.

[Recording layer coating solution 2]
Wet process silica with an average particle size of 1.5 μm (average primary particle size: about 0.009 μm, manufactured by Tokuyama Corporation, trade name: Fine Seal F-80), 100 parts of polyvinyl alcohol (manufactured by Kuraray Co., Ltd., product) Name: PVA-224) 17 parts, silyl modified polyvinyl alcohol (Kuraray Co., Ltd., trade name: R-1130) 23 parts, diallyldimethylammonium chloride-acrylamide copolymer (manufactured by Nittobo Co., Ltd., trade name) : PAS-J-81) 1 part and a dispersant (Toa Gosei Co., Ltd., trade name: Aron SD-10) 0.2 part mixed water dispersion (concentration: 15%) was prepared.

[Recording layer coating solution 3]
To 100 parts of the silica fine particle aqueous dispersion, 20 parts of polyvinyl alcohol having a polymerization degree of 4500 and a saponification degree of 98% and 5 parts of a cation-modified acrylic resin were mixed to prepare a 5% aqueous solution.

[Preparation of inkjet recording paper]
The undercoat layer coating solution was applied to the paper substrate 4 so as to have a coating amount of 7 g / m ² and dried. On the coating layer, the recording layer coating solution 2 is applied and dried so that the coating amount is 7 g / m ² to obtain the first recording layer. Further, the recording layer coating solution 3 is applied at a coating amount of The coating layer was dried to 1.5 g / m ² to obtain a second recording layer, and a glossy ink jet recording paper was prepared.

Example 3
[Preparation of Paper Base Material 5]
Paper was made under the same conditions as in Example 1, and starch (Oji Cornstarch, trade name: Ace C) and polyvinyl alcohol (Electrochemical Industry, trade name: K-17) at a ratio of 70/30 was used. 0 g / m ² , 0.2 g / m ^{2 of} interfiber binding inhibitor (trade name: KB115, manufactured by Kao Corporation), 0.08 g / m of surface sizing agent (trade name: SKS-293, manufactured by Arakawa Chemical Industries, Ltd.) ² to obtain a paper base having a basis weight of 180 g / m ² and a thickness of 275 μm.

[Preparation of aqueous dispersion 2 of silica fine particles]
Gas phase method silica having an average particle size of 1.0 μm (average primary particle size: about 0.008 μm, manufactured by Nippon Aerosil Co., Ltd., trade name: Aerosil A300) was dispersed with a homomixer, and then the average particle size was 0.00. The mixture was pulverized and dispersed with a high-speed collision type homogenizer until the thickness became 08 μm to prepare a 10% aqueous dispersion. To the 10% aqueous dispersion, 10 parts of a cationic compound having a 5-membered ring amidine structure (molecular weight: 300,000, product name: SC-700) was added, and further dispersed with a high-speed collision type homogenizer. An aqueous dispersion of 10% silica fine particles having an average particle diameter of 0.15 μm was prepared.

[Preparation of aqueous dispersion 3 of silica fine particles]
The 10% aqueous dispersion of the silica fine particles was further dispersed with a high-speed collision type homogenizer to prepare a 10% aqueous dispersion having an average particle diameter of 0.1 μm.

[Adjustment of recording layer coating solution 4]
100 parts of the above aqueous dispersion 2 of silica fine particles, 18 parts of polyvinyl alcohol (polymerization degree 3500, saponification degree 88.5%, manufactured by Kuraray Co., Ltd., trade name: PVA-235) as a binder, dispersant (manufactured by Toa Gosei Co., Ltd.) , Trade name: Aron SD-10) 0.05 parts of a mixed water dispersion (concentration: 15%) was prepared.

[Adjustment of coating solution for outermost layer]
100 parts of the above silica fine particle aqueous dispersion 3 is mixed with 18 parts of an emulsion type acrylic resin latex (average particle diameter: 0.03 μm, Tg = −20 ° C.) and 3 parts of a release agent (ammonium oleate) as a binder. A 5% aqueous solution was prepared.

[Preparation of inkjet recording paper]
After 1 g / m ^{2 of} borax is contained in the paper base material 5 (thickness: 232 μm, tension 0.91 g / m ² ), the recording layer coating liquid 4 is applied onto the surface on which the borax is applied. The coating was applied so that the coating amount was 18 g / m ² , and the paint was quickly gelled. The surface temperature of the coating layer at this time was 25 ° C. Thereafter, the coating layer is dried to a reduction rate drying section with hot air at 110 ° C. to obtain a recording layer, and then the coating amount for the outermost layer is applied on the recording layer online at a coating amount of 1 g / m. ^The glossy ink jet recording paper was prepared by applying a pressure to a mirror drum having a surface temperature of 95 ° C., drying and peeling while being wet.

Comparative Example 3
[Preparation of paper substrate 6]
To a pulp slurry of LBKP 100 parts having a freeness of 350 ml CSF, light calcium carbonate (manufactured by Shiraishi Calcium Co., Ltd., trade name: PC) was added to 25 parts, 0.9 parts starch per pulp, alkenyl succinic anhydride 0.1 part, 0.7 part of sulfuric acid band and 0.5 part of interfiber binding inhibitor (trade name: KB115, manufactured by Kao Co., Ltd.) are added, and paper making is performed using a long net paper machine, and the basis weight is 160 g. A paper substrate was obtained in the same manner as in Example 1 except that the thickness was 225 μm / m ² .
[Preparation of inkjet recording paper]
A glossy ink jet recording paper having an undercoat layer, a first recording layer, and a second recording layer was obtained in the same manner as in Example 2 except that the paper substrate 6 was used.

Comparative Example 4
A glossy ink jet recording paper having a first recording layer and a second recording layer was obtained in the same manner as in Example 2 except that the paper base 6 was used and no undercoat layer was provided.

[Evaluation methods]
The print density and glossiness were evaluated by the following methods. Printing was performed with a commercially available inkjet printer (trademark: PM-950C, print mode: PM photo paper clean mode, manufactured by EPSON).

(Print density)
Black solid printing was performed, and measurement was performed with a Macbeth reflection densitometer (Macbeth RD-920).

(Glossy)
An ISO-400 image (“high-definition color digital standard image data ISO / JIS-SCID”, p13, image name: fruit basket) is printed and visually observed from a horizontal angle with respect to the printed portion. evaluated.
A: There is a glossiness similar to that of a silver salt photograph.
○: There is a glossiness slightly inferior to silver halide photographs.
(Triangle | delta): The same level as a general commercial glossy inkjet recording body.
*: Same level as a mat type inkjet recording medium.

(Cockling)
The waving after 1 hour of printing was visually evaluated with PM-950C and PX-G900.
A: There is no cock ring.
○: When looking closely, it can be seen that slight cockling has occurred. No problem level.
Δ: Some cockling has occurred. Problem level.
X: Cockling has occurred.

The inkjet recording paper of the present invention has a wide range of glossiness from matte paper to glossy paper, and can also be applied to high-quality photographic recording, and can provide an inkjet recording paper with good cockling. .

Claims (10)

In an inkjet recording paper provided with a recording layer on at least one surface of a paper base material, the paper base material has a thickness of 80 μm or more, contains an interfiber bond inhibitor, and the content of the interfiber bond inhibitor However, the ink jet recording paper is characterized in that it has an inclined structure that is close to the surface of the paper substrate on which the recording layer is provided and decreases toward the center in the thickness direction. 2. The ink jet recording paper according to claim 1, wherein the paper base is coated with a coating liquid containing an interfiber bond inhibitor, starch and a surface sizing agent. The inkjet recording paper according to claim 1 or 2, wherein a recording layer is provided after an undercoat layer is provided on a paper substrate. The inkjet recording paper according to any one of claims 1 to 3, wherein the recording layer contains a fine pigment having an average primary particle size of 0.003 to 0.040 µm and an average secondary particle size of 1 µm or less. The inkjet recording paper according to any one of claims 1 to 4, wherein the inkjet recording paper is a gloss type. The inkjet recording paper according to any one of claims 1 to 3, wherein the inkjet recording paper is a mat type. A paper base containing a fiber-fiber binding inhibitor, and having a sloped structure in which the content of the fiber-fiber binding inhibitor is large near the surface of the paper base and decreases toward the center in the thickness direction. A method for producing an ink jet recording paper, comprising forming a recording layer on a surface of a material containing a large amount of interfiber bonding inhibitor. 8. The method for producing an ink jet recording paper according to claim 7, wherein the paper substrate contains an interfiber bond inhibitor by using both the internally added size and the externally added size. The method for producing an inkjet recording paper according to claim 7 or 8, wherein the paper substrate is coated with a coating liquid containing an interfiber bond inhibitor, starch, and a surface sizing agent. The method for producing an ink jet recording paper according to claim 9, wherein the interfiber bond inhibitor and starch have a mass ratio of 1:99 to 20:80.