JP4289746B2 - Recording medium and image forming method using the recording medium - Google Patents

Description

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【発明の効果】
本発明は、以下に示す顕著な効果を有する。
（１）繊維状物質にアルミナ水和物を添加したため、普通紙の風合いを残した状態でインク吸収性や発色性を良くすることができる。
（２）アルミナ水和物を表面層のみに添加したことで添加効果が大きくなり、少ない添加量でも画像を良くすることができる。
（３）表面層でインク中の色材の吸収を行って、基層でインク中の溶媒成分の吸収を行うため、フルラインヘッドを持ったラインプリンターのような超高速機で印字を行っても溢れやにじみ、ビーディングなどの発生を防ぐことができる。
（４）基層をサイズ処理などを行うことなく裏抜けを防止することができる。
（５）温湿度の変化によるカールや表面を擦った時の粉落ちやケバ立ちを防止することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a recording medium suitable for recording using an ink, and relates to an inkjet recording medium having a high surface density, a clear color tone, and excellent ink absorption capability, while the paper surface has a texture of plain paper. The present invention relates to a recording medium, an image forming method using the recording medium, and a printed matter obtained by the method.
[0002]
[Prior art]
In recent years, an ink jet recording method is a method in which fine droplets of ink are ejected by various operating principles and adhered to a recording medium such as paper to record images, characters, and the like. It has features such as easy colorization, great flexibility in recording patterns, and no need for development / fixing. It is rapidly spreading in various applications including information equipment as a recording device for various images. Furthermore, it is possible to obtain images that are comparable to multi-color printing by the plate-making method and prints by the color photographic method, and images that are formed by the multi-color ink-jet method. Since it is less expensive than multi-color printing or printing, it is being widely applied to the field of full-color image recording.
[0003]
In the ink jet recording system, the recording apparatus and the recording method have been improved along with the improvement of the recording characteristics such as high-speed recording, high definition, full color, etc. It has come to be required. In order to solve such problems, various types of recording media have been proposed. For example, Japanese Patent Application Laid-Open No. 55-5830 proposes an ink jet recording paper provided with an ink-absorbing coating layer on the surface of a support, and Japanese Patent Application Laid-Open No. 55-51583 discloses an amorphous material as a pigment in the coating layer. An example using porous silica has been proposed. In addition, US Pat. Nos. 4,879,166, 5,104,730, and JP-A-2-276670, 5-32413, and 5-32414 have an ink receiving layer using an alumina hydrate having a pseudoboehmite structure. A recording sheet has been proposed. These are forms in which an ink receiving layer containing a pigment such as alumina or silica is formed on a substrate. Since the ink receiving layer is formed, the texture of plain paper is not obtained even if a paper substrate is used. In order to obtain a plain paper-like recording medium, for example, in JP-A-6-312572, 7-25131, and 7-25132, a recording surface in which a very small amount of ultrafine particles are coated on a paper substrate is a fiber of pulp. A medium that retains its shape and has an ultrafine pigment coverage of 70% or more is proposed.
[0004]
On the other hand, a medium in which a filler is internally added to paper has also been proposed. For example, Japanese Patent Application Laid-Open No. 53-49113 proposes a recording paper in which a water-soluble polymer is coated and impregnated on a sheet in which urea formalin resin powder is internally added. Japanese Laid-Open Patent Publication No. 58-8865 proposes a recording paper in which a sheet containing synthetic silicate and glass fiber is coated and impregnated with a water-soluble polymer. These are inks whose ink absorbability is improved by adding a specific fine powder to non-size paper. There are other proposals that give the sheet a fine size. For example, Japanese Examined Patent Publication No. 60-27588 proposes a recording paper having a wet sizing degree of 3 seconds or less and a sheet coated with a wet paper strength enhancer and coated with a surface coating. Japanese Patent Publication No. 61-50795 (Japanese Patent Laid-Open No. 56-57117) proposes a recording paper in which a saponification type sizing agent is coated on the paper surface. These perform size processing to suppress the ink absorbability and control the dot diameter. Further, JP-A-7-232473, JP-A-7-232474, and JP-A-7-232475 propose a recording paper internally containing amorphous alumina hydrate.
[0005]
As another form of the internal paper, a multi-layer paper has been proposed. For example, Japanese Patent Application Laid-Open Nos. Sho 63-118287 and US Pat. No. 4,734,336 propose uncoated paper in which a support layer made of pulp fiber, a filler such as silica and a surface layer made of fiber are superimposed. JP-A-1-78877, JP-A-2-243811, JP-A-2-243382, and JP-A-5-106197 disclose a recording paper in which the base layer or the mating surface of the base layer and the surface layer is processed with a multi-layer paper by combining. Has been proposed. Furthermore, Japanese Patent Application Laid-Open No. 6-219043 proposes a multilayer paper carrying a hardly soluble or water insoluble inorganic substance on the surface layer. JP-A-6-287886, JP-A-7-5430, and JP-A-8-258400 propose multilayer papers using specific pulps such as bulky cellulose, mercerized pulp, hardwood bleached sulfite pulp and the like. Japanese Patent Application Laid-Open No. 9-170190 proposes a multilayer paper whose surface layer is mainly composed of hydrophilic fibers and hydrophobic fibers and whose base layer is mainly composed of cellulose fibers.
[0006]
However, the conventional recording medium has the following problems.
(1) In the recording medium having the structure in which the ink receiving layer is formed on the base material, when paper is used as the base material, the paper texture does not remain because paper or the like is thickly coated on the paper. There is a problem. Although the texture of the paper can be obtained by reducing the coating amount, there is a problem that ink absorbability and color developability are impaired.
(2) The recording medium in which the specific fine powder is internally added to the above-mentioned non-size paper has good ink absorbability, but the back-through occurs when performing multicolor printing. For this reason, there are problems that the printing dots spread and the optical density is not sufficient. On the other hand, the recording medium with a fine size on the sheet can prevent the show-through, but the ink absorbency is not sufficient, causing overflow and blurring in multicolor printing, and the optical density of the printing part does not increase. There is.
(3) In a recording medium having a multi-layer structure, the ink can be prevented from seeping through or see-through from the back surface by applying an internal size to the base layer or by performing a size process on the mating surface of the surface layer and the base layer. . However, since this method limits the penetration of ink into the base layer, ink overflow may occur when multicolor printing or high-speed printing is performed. In addition, calcium carbonate, clay, kaolin, acidic clay, talc, synthetic silica, titanium dioxide and the like are used as internally added pigments, but ink absorption, color development and resolution cannot be satisfied. Multilayer paper using specific pulp such as bulky cellulose, mercerized pulp, hardwood bleached sulfite pulp, etc. has good liquid absorbency and diffusibility, but coloring material does not fix well when recorded by inkjet. However, there is also a problem that the print dot diameter is widened and bleeding is likely to occur, and the optical density is difficult to be obtained. JP-A-8-258400 improves the absorbability by changing the sizing degree of each layer, and silica, calcium carbonate and titanium dioxide are internally added. However, since the filler is internally added to the base layer, resolution and optical properties are improved. There is a problem that the density is not good. A recording medium combining a hydrophilic fiber and a hydrophobic fiber has electrophotographic characteristics and inkjet suitability. However, since it contains a hydrophobic fiber such as polyester, bleeding and repelling may occur in high-speed multicolor printing. .
[0007]
[Problems to be solved by the invention]
The present invention has been made for the purpose of solving the above-mentioned problems. The paper surface has the texture of plain paper and has good ink absorbability, and the optical density of the printing portion is high. It is an object of the present invention to provide a recording medium with less recording material, an image forming method using the recording medium, and a printed matter obtained by the method.
[0008]
[Means for Solving the Problems]
  The above object is achieved by the present invention described below. That is, the present invention,Base layer andTheHaving a surface layer provided on at least one side of the base layerA recording medium, wherein the base layer and the surface layer are mainly composed of fibers obtained from cellulose pulp, andAlumina hydrate with boehmite structure is internally added only to the surface layer.The cellulose pulp of the base layer has a lower beating degree than the cellulose pulp of the surface layer, the base layer has a higher liquid absorbency than the surface layer,
Size processing is not performedThis is a recording medium.
[0010]
  Furthermore, the present invention providesContains coloring materials and solvent componentsIn an image forming method in which a small droplet of ink is ejected from a fine hole and applied to a recording medium for printing, the above-mentioned recording medium is used as the recording mediumThe coloring material in the applied ink is adsorbed on the surface layer of the recording medium, and the solvent component in the applied ink is adsorbed on the base layer of the recording medium.The image forming method is characterized by including ejecting ink droplets by applying thermal energy to the ink.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
By using the recording medium of the present invention, the paper surface has the texture of plain paper, and the ink solvent has good absorbability, the optical density of the printed part is high, the powder fall and curl are small, and the water resistance is high. An excellent recording medium can be obtained.
[0012]
The present inventors have proposed a recording medium in which amorphous alumina hydrate is internally added to a fibrous material (Japanese Patent Nos. 2714350 to 2714352, Japanese Patent Laid-Open No. 9-99627). The present application is an improvement thereof, and is a paper medium having a multilayer structure composed of a surface layer and a base layer, and a recording medium in which alumina hydrate having a boehmite structure is added only to the surface layer. The inventors of the present invention have a recording paper containing alumina hydrate in a multi-layer structure, and the alumina hydrate is added only to the surface layer, and the base layer is made of a material having good liquid absorbency. It has been found that even when printing is performed at high speed, the color development and resolution of the printed image are excellent and the ink absorption speed is fast and overflow does not occur. This is especially effective when printing with an ultra-high speed machine using a full line head. Even when printing at the speed of the present invention is performed, there are advantages that the color developability and resolution of the printed image are remarkably improved, the ink absorbability is good, and the back-through does not occur.
[0013]
By adding alumina hydrate to the surface layer, there is an advantage that color development can be improved even if the amount of alumina hydrate added to the whole is small. Furthermore, boehmite-structured alumina hydrate also has an advantage of high productivity because of its high yield rate with respect to cellulose fibers.
[0014]
Alumina hydrate has a positive charge, so it can fix the coloring materials such as dyes in the ink, and an image with excellent color development can be obtained. In addition, problems such as brown discoloration and light resistance of black ink occur. Therefore, it is preferable as a material used for an inkjet recording medium.
[0015]
As the alumina hydrate present in the recording medium of the present invention, alumina hydrate having a boehmite structure by X-ray diffraction is most preferable because of its good ink absorbability, colorant adsorbability, and color developability. .
[0016]
Alumina hydrate is defined by the following general formula.
[0017]
Al₂O_3-n(OH)_2n・ MH₂O
In the formula, n represents one of integers of 0 to 3, and m represents a value of 0 to 10, preferably 0 to 5. mH₂ The expression O represents a detachable aqueous phase that in many cases does not participate in the formation of the crystal lattice, so that m can also take non-integer values. However, m and n are not zero at the same time.
[0018]
In general, an alumina hydrate crystal having a boehmite structure is a layered compound having a (020) plane forming a giant plane, and exhibits a diffraction peak peculiar to an X-ray diffraction pattern. As the boehmite structure, in addition to perfect boehmite, a structure called excess boehmite and containing excess water between layers of the (020) plane can be taken. The pseudo-boehmite X-ray diffraction pattern shows a broader diffraction peak than that of perfect boehmite. Since complete boehmite and pseudoboehmite are not clearly distinguishable, unless otherwise specified in the present invention, they are referred to as alumina hydrate showing a boehmite structure (hereinafter referred to as alumina hydrate).
[0019]
As the boehmite-structured alumina hydrate used in the present invention, those showing a boehmite structure by X-ray diffraction are preferable because of good color density, resolution, and ink absorbability. Furthermore, alumina hydrate containing a metal oxide such as titanium dioxide or silica can be used as long as it is an alumina hydrate having a boehmite structure.
[0020]
The method for producing the alumina hydrate used in the present invention is not particularly limited, but any method capable of producing an alumina hydrate having a boehmite structure, for example, hydrolysis of aluminum alkoxide, sodium aluminate It can be produced by a known method such as hydrolysis. Further, as disclosed in JP-A-56-120508, amorphous alumina hydrate by X-ray diffraction is subjected to a heat treatment at 50 ° C. or higher in the presence of water, thereby changing to a boehmite structure. Can be used.
[0021]
The present invention is a recording medium comprising a surface layer and a base layer, and the surface layer and the base layer are mainly composed of cellulose fibers. In this structure, only the surface layer contains alumina hydrate. In the present invention, the color material in the printed ink is adsorbed by the surface layer, and the solvent component in the ink passes through the surface layer and is absorbed by the base layer. The texture of the recording medium surface is preferably plain paper. Here, the plain paper style means that the cellulose fibers are exposed on the surface and there is no feeling that fine particles are coated on the touch.
[0022]
Further, the present invention includes a configuration capable of double-sided printing in which surface layers are provided on both sides of the base layer, and further a configuration in which a back layer is provided on the opposite side of the surface layer of the base layer as necessary. Similar to the base layer, the back layer is mainly composed of cellulose fibers and does not contain alumina hydrate.
[0023]
The amount of boehmite-structured alumina hydrate in the present invention is preferably 50% by weight or less of the total weight of the surface layer. Within this range, a good color can be obtained without impairing the texture of the paper on the surface layer. A more preferable addition amount is 2 to 30% by weight, and even when the surface of the recording medium is rubbed, powder falling and flaking are less likely to occur. The most preferable range is 5 to 20% by weight, and it becomes difficult for tears and wrinkles to occur due to a decrease in paper strength in a wet state after printing. The addition amount with respect to the entire recording medium is preferably in the range of 1 to 20% by weight. Within this range, the color density of the printed image is increased and the color of the mixed color portion is improved.
[0024]
  In the present invention, alumina hydrateOn the surface layerAs a method for internal addition, a method of papermaking or coating by mixing an aqueous dispersion of alumina hydrate with a cellulose pulp dispersion can be used.
[0025]
  There is no restriction | limiting in particular as a cellulose pulp used for the surface layer of this invention, a base layer, and a back surface layer. For example, chemical pulp such as sulfite pulp (SP), alkali pulp (AP), kraft pulp (KP), etc. obtained from hardwood and softwood, and deinked two Secondary fiberOldPaper pulp can be used. Further, the pulp can be used without distinction between unbleached pulp, bleached pulp and beating, and unbeaten. In addition, as the cellulose pulp, non-wood pulp fibers such as grass, leaves, bast, and seed hair, for example, pulp such as straw, bamboo, hemp, bagasse, kenaf, honey, and cotton linter can be used. Furthermore, as long as it is a hydrophilic fiber, regenerated fibers such as rayon, and hydrophilic synthetic polymer fibers such as cellulose derivative fibers, polyvinyl alcohol, and polyacrylamide can be used. It is also possible to add general fillers as necessary.
[0026]
The basis weight of the entire recording medium is not particularly limited as long as the basis weight is small and the recording medium is not extremely thin, but 40 to 300 g / m²Is preferable in terms of transportability when printing with a printer or the like. A more preferable range is 60 to 200 g / m.²The opacity can be increased without increasing the bending strength of the paper. Furthermore, sticking does not easily occur when a large number of printed samples are stacked.
[0027]
In the present invention, the basis weight of the surface layer is 5 g / m.²A range of 40% by weight or less of the whole recording medium is preferable. Within this range, even if high-speed printing is performed, the printed color material can be adsorbed in the surface layer, and the optical density of the printing portion can be increased to prevent the occurrence of beading or bleeding. A more preferable range is 10 g / m.²This is the range of 30% by weight or less of the recording medium, and can prevent curling due to humidity during storage or printing environment, and also prevent curling and undulation after printing.
[0028]
Here, the term “brightening” as used in the present invention means that when solid printing is performed on a certain area, a portion colored by a coloring material such as a dye is wider (larger) than the printed area. A phenomenon in which granular density unevenness due to agglomeration of ink droplets generated in a printing portion appears, and repellency means that a non-colored portion occurs in a solid printing portion.
[0029]
There are the following three methods for further preferred embodiments of the surface layer of the present invention, which can be selected and used as necessary.
[0030]
The first method is to add fine fibrillated cellulose in addition to the above as cellulose pulp used for the surface layer. As the fine fibrillated cellulose, for example, those described in JP-A Nos. 7-3691 and 8-284090 can be used. Here, finely fibrillated cellulose is divided into fibrils of structural units that form cell membranes by refining cellulose fibers such as wood pulp, and are many branches while maintaining the fiber form. . The addition amount of the fine fibrillated cellulose is preferably 1 to 50% by weight based on the whole cellulose in the surface layer, and the color of the printed image is improved and the color of the mixed color portion is particularly clear. Further preferable addition amount is 1 to 30% by weight of the whole cellulose in the surface layer, and color depth appears on the printed image, and even if the surface layer is rubbed, fluffing off or powdered off of the internally added alumina hydrate It becomes difficult to rub. The most preferable range is 3 to 20% by weight, the smoothness of the surface of the recording medium is improved, and tackiness of the surface of the recording medium is eliminated even immediately after printing.
[0031]
The second method is a method in which sulfate pulp, sulfite pulp, soda pulp or the like made from hardwood or conifer is added to the cellulose pulp used for the surface layer in addition to the above. For example, those described in JP-A-7-54300 can be used as pulps made from these hardwoods or conifers. Among them, sulfate pulp made from hardwood pulp with a thin fiber wall as described in JP-A-8-258400 and JP-A-8-267907 is most preferred. The added amount of these pulps is preferably 50% by weight or more, and the swelling and curling of the surface layer after printing are reduced. A more preferable range is that the roundness of dots printed at 70% by weight or more is high.
[0032]
The third method is a method in which, in addition to the above-mentioned cellulose pulp used for the surface layer, bulky or interstitial cellulose fibers are added. Examples of the cellulose fibers that are bulky or have many gaps include bulky cellulose fibers described in JP-A-6-287886, mercerized cellulose described in JP-A-7-54300, and JP-A-8-667. There are fluffed celluloses described in the issue. A preferable addition amount is 1 to 30% by weight, and the ink absorption speed is increased and bleeding and beading are less likely to occur. A more preferable range is 1 to 10% by weight, and the fixing of the color material after printing is accelerated.
[0033]
Furthermore, a pulp treated with an enzyme or the like can be added as necessary to improve the smoothness of the surface layer. The pulp to be used is not particularly limited. For example, a method of adding a hemicellulase to an unbeaten pulp described in JP-A-6-158575 and then a beating process, after a beating process described in JP-A-10-259588 There are chemical pulps that have been treated with enzymes having cellulolytic activity.
[0034]
In the present invention, the base layer needs to have higher ink absorbability than the surface layer. In general, the method for measuring the ink absorption speed of each layer or recording medium is a method for determining the Steecht sizing degree, or a method for determining the passage time of the ink from the contact surface to the opposite surface as described in JP-A-6-143793. is there. However, since the ink absorption speed of the recording medium of the present invention is extremely fast, it is difficult to measure by these known methods. In the present invention, the ink absorption speed of each layer or recording medium is measured by a dynamic scanning absorption meter described in JP-A-10-131091. The liquid absorption rate of each layer or recording medium is expressed by the wetting time and the absorption coefficient. It is determined by measuring with pure water and a water-based ink containing a surfactant. In the present invention, if the liquid absorption rate of the base layer is greater than the liquid absorption rate of the surface layer, or if the liquid absorption rate when the surface layer and the base layer are combined is larger than the liquid absorption rate of the surface layer alone, The ink absorption is higher than that of the surface layer.
[0035]
The recording medium of the present invention preferably has a wetting time of 15 milliseconds or less with respect to various liquids. Within this range, there is an effect that the occurrence of beading can be prevented regardless of the ink composition. Furthermore, the absorption coefficient is 5 ml / m for various liquids.²s^-1/2The above is preferable. Within this range, bleeding, repelling and beading can be prevented even when multiple printing is performed at high speed.
[0036]
As a method of making the ink absorbability of the base layer higher than that of the surface layer, one or more methods can be selected and used from the following three methods.
[0037]
In the first method, the beating degree of cellulose pulp used for the base layer is made lower than the beating degree of cellulose pulp used for the surface layer. Here, the beating degree is C.I. S. F. (CANADIAN STANDARD FREEESS). C. of cellulose pulp used for the base layer and the surface layer S. F. A difference of 10 or more is preferable because the solvent component of the ink absorbed by the surface layer can be absorbed quickly. A value of 50 or more is more preferable because it can be absorbed quickly even when multiple printing is performed. The base layer cellulose pulp is more preferably crosslinked cellulose because cockling can be prevented.
[0038]
The second method is to add a superabsorbent material such as an absorbent resin to the base layer. As an absorptive material to be used, a material having an absorption amount three times or more than its own weight is preferable, and there is no particular limitation. Examples include starch-based, cellulose-based, and synthetic polymer-based systems. Specifically, starch-acrylic acid (salt) graft copolymer, saponified starch-acrylonitrile copolymer, starch-ethyl acrylate graft copolymer Saponified product of starch-methyl methacrylate graft copolymer, saponified starch-acrylonitrile graft copolymer, saponified starch-acrylamide graft copolymer, starch-acrylonitrile-2-acrylamido-2-methyl Examples include saponified propane sulfonic acid graft copolymer, acrylic acid (salt) polymer, polyethylene oxide crosslinked with acrylic acid, crosslinked product of sodium carboxymethyl cellulose, crosslinked product of polyvinyl alcohol-maleic anhydride reactant, and the like. . It is preferable to use a fiber-shaped one such as fibrous carboxyl cellulose described in JP-A-9-239903 because the absorption rate can be improved and the shape does not change due to swelling. A highly absorbent material is more preferably a cross-linked product because cockling can be prevented. The amount of the superabsorbent material added is preferably in the range of 1 to 30% by weight of the cellulose fiber because the absorbency is good and the stickiness is low. The range of 1 to 10% by weight is more preferable from the viewpoint of the feel of paper and the bending strength.
[0039]
In the third method, in addition to the cellulose fibers used for the base layer, bulky or gapy cellulose fibers are added. Preferred bulky or interstitial cellulose fibers include, for example, bulky cellulose fibers described in JP-A-6-287886, mercerized cellulose described in JP-A-7-54300, and JP-A-8- And fluffed cellulose described in No. 667.
[0040]
In addition, materials used for general low density paper can also be used. For example, a method using a mechanical pulp such as a pine-based thermomechanical pulp described in JP-A-5-98593, a softwood pulp having a specified range of water retention and a specified range of water retention described in JP-A-6-158579 A method of using a mixture of hardwood pulps at a specific ratio, a modified product of bacterial cellulose described in JP-A-6-248594, JP-A-8-3892, and JP-A-11-200222, and a water retention of bacterial cellulose and water A method of using a mixture of hardwood pulp in a specific range at a specific ratio, a mixture of bacterial cellulose and foaming resin, and a pulp produced from a tree material containing southern hardwood described in JP-A-8-291494, an aqueous solution of sodium hydroxide Using a pulp having a freeness of 400 mCFS or more by treatment with A, A method using LBKP of 500 ml CFS or more including pulp of dipterocarp as described in 04790, fine fiber having a bond reinforcement factor of 0.15 or more and a wet curl factor of 0.4 described in JP-A-10-212690 There is a method of using a curled fiber in the range of -1.0, and one type or two or more types can be used in combination as required.
[0041]
There are no particular restrictions on the amount of cellulose that is bulky or has many gaps. The addition amount is preferably in the range of 10 to 90% by weight. Within this range, the printed ink migrates quickly from the surface layer, and bleeding in multiple printing is less likely to occur. A more preferable range is 30 to 70% by weight, since the surface of the base layer becomes smooth and cockling, wrinkling, and undulation after printing of the base layer can be prevented.
[0042]
In the present invention, since the ink is absorbed by the base layer, the base layer is preferably non-sized or very close to no size. As described in JP-A-1-78877, JP-A-2-243811, JP-A-2-243382, JP-A-3-180599, and JP-A-6-219043, the ink absorption of the base layer is suppressed by size processing or the like. It is different from what prevents omission.
[0043]
In the present invention, a back layer can be formed as necessary. The back layer contains cellulose fibers as a main component and does not contain alumina hydrate. Cellulose fibers can be freely selected from the above, and are not particularly limited. The basis weight is preferably 30% or less of the entire recording medium.
[0044]
As a method for producing a recording medium having a multilayer structure according to the present invention, a method of making paper after making a pulp mixture of a surface layer and a base layer, and a method of applying a pulp mixture of a surface layer after forming the base layer and drying There is a method of forming.
[0045]
As a method for producing in the papermaking process, a generally used multilayer papermaking method can be used. A method using sheeting is preferable because peeling between layers such as the surface layer and the base layer hardly occurs. As the paper machine, a conventionally used long paper machine, round paper machine, circular cylinder, twin wire, and the like can be used. Using a single headbox for making multi-layer paper, the material that forms each layer is allowed to flow in parallel from the stock inlet to form a layered paper layer. The paper material is mixed appropriately at the boundary of each paper layer. This is more preferable because the strength in the Z direction increases. As the single head box, for example, Atrata-Flo from Beloit, Contro-Flo from Tampera, HTB-3L from KMW, or the like can be used.
[0046]
As a method for coating the surface layer, a general coating method can be used. A pulp composition containing alumina hydrate is applied onto the base layer and then dried to form a surface layer. As a method for applying the surface layer pulp composition on the base layer, a gate roll coater, a size press, a bar coater, a blade coater, an air knife coater, a roll coater brush coater, a curtain coater, a gravure coater, a spray device, etc. Can be adopted.
[0047]
In the present invention, a paper strength improver, a yield improver, and a colorant can be added and used as necessary. As the yield improver, a cationic yield improver such as cationized starch or dicyandiamide formalin condensate or an anionic yield improver such as anionic polyacrylamide or anionic colloidal silica may be selected or used in combination. it can. Further, if necessary, the surface smoothness can be improved by size pressing the starch or the like using a calendar roll or the like.
[0048]
In the present invention, it is preferable that the rate of change in the MD direction and the CD direction of the ultrasonic wave propagation speed after rewetting and free drying of the recording medium is 7% or less, respectively. Within this range, deformation, wrinkles, cockling, etc. when multiple printing is performed at high speed can be prevented. Furthermore, it is more preferable that the aspect ratio (ratio between the CD direction and the MD direction) of the change rate is 1.4 or less because curling after printing can be prevented. The rate of change in ultrasonic wave propagation speed after rewetting and free drying, and the same aspect ratio can be achieved by reducing shrinkage due to drying during production of the medium. Specifically, there are methods of using a Yankee dryer, increasing the tension of the dryer canvas, using bulky pulp or crosslinked pulp as the raw material pulp, and increasing the temperature gradient in the initial drying zone. Here, rewetting and free-drying are those in which a measurement sample is immersed in pure water at 20 ° C. for 3 hours and then air-dried in an environment of 20 ° C. and 60% RH for 24 hours as described in JP-A-2-251967. It is.
[0049]
In the present invention, a watermark pattern or printing can be applied to the back surface, which is the opposite surface of the surface layer of the recording medium. By using this watermark pattern or printing, information such as identification of the front and back of the recording medium, display of the product number, printing conditions, and the like can be recorded in advance on the recording medium. For watermarking and printing, symbols such as barcodes, characters and figures such as logos and product names can be used. In addition, watermarks and prints include those that can be identified by visible light, those that can be identified only under specific conditions that cannot be normally identified, such as ultraviolet light, infrared light, and special polarized light, and those that can be identified under magnetic or magnetic fields. . A publicly known method can be used for watermarking and printing on the back side of the recording medium.
[0050]
The alumina hydrate used in the present invention is an alumina hydrate having a boehmite structure, but any alumina hydrate containing a metal oxide such as titanium dioxide or silica can be used as long as it exhibits a boehmite structure by an X-ray diffraction method. Things can also be used. The content of titanium dioxide is preferably in the range of 0.01 to 1.00% by weight of the entire alumina hydrate because the adsorbability of the coloring material can be improved without impairing the affinity with water. As the alumina hydrate having a boehmite structure containing titanium dioxide, for example, those described in Japanese Patent No. 2714351 can be used. The content of silica is preferably 0.1 to 30% by weight of the entire alumina hydrate because both the color developability and the solvent affinity can be satisfied. As the alumina borate of boehmite structure containing silica, for example, those described in Japanese Patent Application No. 10-174778 can be used. Other forms include magnesium, calcium, strontium, barium, zinc, boron, silicon, germanium, tin, lead, zirconium, indium, phosphorus, vanadium, niobium, tantalum, chromium, molybdenum, tungsten instead of titanium dioxide and silica, It can also be used by containing an oxide such as manganese, iron, cobalt, nickel, ruthenium.
[0051]
The shape of the alumina hydrate can be determined by dispersing the alumina hydrate in water, alcohol or the like and dropping it on the collodion film to prepare a measurement sample and observing it with a transmission electron microscope. Among the alumina hydrates, pseudoboehmite has ciliary and other shapes as described in the above-mentioned document (Rocek J., et al, Applied Catalysis, 74, 29-36, 1991). It is generally known that there is. In the present invention, alumina hydrate having any shape of cilia or flat plate can be used. The shape of the alumina hydrate (particle shape, particle size, aspect ratio) was prepared by dispersing alumina hydrate in ion-exchanged water and dropping it onto the collodion membrane to make a measurement sample. It can be measured by observing.
[0052]
According to the knowledge of the present inventor, the flat plate shape has better water dispersibility than the hair bundle (ciliform), and the orientation of the alumina hydrate particles is random when the ink receiving layer is formed. Therefore, it is more preferable because the pore volume is large and the pore radius distribution is wide. Here, the hair bundle shape refers to a state in which the needle-shaped alumina hydrate is gathered like a hair bundle in contact with the side surfaces.
[0053]
The aspect ratio of tabular grains can be determined by the method defined in Japanese Patent Publication No. 5-16015. Aspect ratio refers to the ratio of diameter to particle thickness. Here, the diameter indicates the diameter of a circle having an area equal to the projected area of the particles when the alumina hydrate is observed with a microscope or an electron microscope. The aspect ratio is the ratio between the diameter indicating the minimum value and the diameter indicating the maximum value of the flat plate surface, as observed in the same manner as the aspect ratio. In the case of a hair bundle shape, the method for obtaining the aspect ratio is to determine the diameter and length of the upper and lower circles using the individual acicular particles of alumina hydrate forming the hair bundle as a cylinder. It can be obtained by taking the ratio of the length to. The most preferable shape of the alumina hydrate is a flat shape with an average aspect ratio in the range of 3 to 10, an average particle diameter in the range of 1 to 50 nm, and a hair bundle with an average aspect ratio in the range of 3 to 10. The average particle length is preferably in the range of 1 to 50 nm. If the average aspect ratio is within the above range, gaps are formed between the particles when the ink receiving layer is formed or internally added to the fibrous material, so that a porous structure having a wide pore radius distribution can be easily formed. be able to. If the average particle diameter or the average particle length is in the above range, a porous structure having a large pore volume can be produced.
[0054]
The BET specific surface area of the alumina hydrate of the present invention is 70 to 300 m.²A range of / g is preferred. When the BET specific surface area is smaller than the above range, the printed white turbidity or the water resistance of the image becomes insufficient. When the BET specific surface area is larger than the above range, powder falling easily occurs. The BET specific surface area, pore radius distribution, and pore volume of alumina hydrate can be determined by a nitrogen adsorption / desorption method.
[0055]
The crystal structure of alumina hydrate in the recording medium can be measured by a general X-ray diffraction method. A recording medium containing alumina hydrate was attached to the measurement cell, the peak of the (020) plane where the diffraction angle 2θ appeared at 14 to 15 ° was measured, and the peak diffraction angle 2θ and the half-value width B were The plane spacing of the (020) plane can be obtained by using the Bragg equation, and the crystal thickness in the direction perpendicular to the (010) plane can be obtained by using the Scherrer equation.
[0056]
In the present invention, the plane spacing of the (020) plane of the alumina hydrate in the recording medium is preferably in the range of more than 0.617 nm and not more than 0.620 nm. In this range, the selection range of coloring materials such as dyes to be used is wide, and even if printing is performed using either hydrophobic or hydrophilic coloring materials, the optical density of the printed portion is increased, and blemishes, beading, Occurrence of repelling is reduced. Further, even when printing is performed using hydrophobic and hydrophilic color materials in combination, the optical density and the print dot diameter are uniform regardless of the type of color material. Even if the ink contains a hydrophilic or hydrophobic material, there is no change in the optical density and dot diameter of the printed portion, and the occurrence of blemishes, beading, and repellency is reduced. The crystal thickness in the direction perpendicular to the (010) plane is preferably in the range of 6.0 to 10.0 nm. In this range, the ink absorbability of the recording medium and the adsorbability of the color material are good, and the powder fall is reduced. A method for setting the crystal spacing in the direction perpendicular to the (010) plane of the (020) plane of alumina hydrate in the recording medium is, for example, the method described in JP-A-9-99627. Can be used.
[0057]
The crystallinity of the alumina hydrate in the recording medium can be similarly determined by the X-ray diffraction method. The recording medium containing alumina hydrate was pulverized and attached to a measurement cell. The intensity at a diffraction angle 2θ of 10 ° and the peak of the (020) plane where 2θ appears at 14 to 15 ° were measured, and 2θ = The crystallinity can be obtained from the peak intensity of the (020) plane with respect to the peak intensity of 10 °. The crystallinity of the alumina hydrate in the recording medium is preferably in the range of 15-80. Within this range, the ink absorbency is improved and the water resistance of the printed image is improved. As a method for bringing the crystallinity of alumina hydrate in the recording medium into the above range, for example, a method described in JP-A-8-132931 can be used.
[0058]
The preferable pore structure of the alumina hydrate to be used has the following three types, and one or more types can be selected and used as necessary.
[0059]
In the first pore structure of the present invention, the average pore radius of the alumina hydrate is 2.0 to 20.0 nm, and the half width of the pore radius distribution is 2.0 to 15.0 nm. . Here, the average pore radius is as shown in JP-A-51-38298 and JP-A-4-201011. The half width of the pore radius distribution indicates the width of the pore radius that is half the frequency of the average pore radius.
[0060]
As described in JP-A-4-267180 and JP-A-5-16517, the dye in the ink is selectively adsorbed to pores having a specific radius. If the width is half-maximum, the selection range of usable color materials is widened, and even if hydrophobic or hydrophilic color materials are used, almost no blurring, beading or repellency occurs, and the optical density and dot diameter are uniform. . The alumina hydrate having the pore structure can be prepared by the method described in, for example, Japanese Patent No. 2714352.
[0061]
The second pore structure in the present invention is one in which the alumina hydrate has a maximum in the range of radius 10.0 nm or less and radius 10.0-20.0 nm in the pore radius distribution. The relatively large pores having a radius of 10.0 to 20.0 nm absorb the solvent component in the ink, and the relatively small pores having a radius of 10.0 nm or less adsorb the color material component such as the color material in the ink. . Therefore, both the adsorption of the coloring material and the absorption of the solvent are accelerated. The maximum of a radius of 10.0 nm or less is more preferably within a radius of 1.0 to 6.0 nm, and the adsorption of the coloring material is accelerated within this range. The maximum pore volume ratio (volume ratio of maximum 2) with a pore radius of 10.0 nm or less is 0.1 to 10% of the total pore volume, which satisfies both ink absorptivity and color material fixability. Therefore, it is preferably in the range of 1 to 5%, and in this range, the ink absorption speed and the color material adsorption speed are increased. The alumina hydrate having the pore structure can be prepared by the method described in Japanese Patent No. 2714350, for example. As other methods, it is possible to use a method in which alumina hydrate having a peak at a radius of 10.0 nm and alumina hydrate having a peak between radius 10.0 and 20.0 are used in combination.
[0062]
In the third pore structure of the present invention, the alumina hydrate has a maximum peak in the radius range of 2.0 to 20.0 nm in the pore radius distribution. When the peak is in this range, both ink absorbency and color material adsorption are satisfied, and the transparency of the alumina hydrate is improved, thereby preventing image turbidity. The maximum peak is more preferably in the range of 6.0 to 20.0 nm, and within this range, any of inks using pigments as colorants, inks using dyes, combined inks of dye inks and pigment inks, and mixed inks Even if printing is performed with ink, it is possible to prevent bleeding, repelling, and color unevenness. The most preferable range is a radius of 6.0 to 16.0 nm. Within this range, even when three or more types of inks having different color material concentrations are used, the difference in color due to the concentration is eliminated. The alumina hydrate having the pore structure can be prepared by the method described in, for example, JP-A-9-6664.
[0063]
The total pore volume of alumina hydrate is 0.4 to 1.0 cm.^ThreeA range of / g is preferred. Within this range, ink absorptivity is good and color is not impaired even when multicolor printing is performed. A more preferable range is 0.4 to 0.6 cm.^Three/ G is preferable because it is less likely to cause powder falling or image blurring. Further, it is more preferable that the pore volume of the alumina hydrate in the radius range of 2.0 to 20.0 nm is 80% or more of the total pore volume because white turbidity does not occur in the printed image. As another form, it is also possible to aggregate and use alumina hydrate. The particle diameter is 0.5 to 50 μm and the BET specific surface area / pore volume value is 50 to 500 m.²A range of / ml is preferred. Within this range, a large number of adsorption points of alumina particles are exposed, and therefore beading can be prevented regardless of the printing environment (temperature, humidity). For the agglomerated particles having the pore structure, for example, the method described in JP-A-8-174993 can be used.
[0064]
Additives can be added to the alumina hydrate used in the present invention. As the additive, various metal oxides, divalent or higher metal salts, and cationic organic substances can be freely selected and used as necessary. Examples of the metal oxide include silica, silica alumina, boria, silica boria, magnesia, silica magnesia, titania, zirconia, zinc oxide and other oxides, hydroxides, and divalent or higher metal salts such as calcium carbonate and barium sulfate. Salts such as magnesium chloride, calcium bromide, calcium nitrate, calcium iodide, zinc chloride, zinc bromide, zinc iodide and other halide salts, kaolin, talc and the like are preferable. As the cationic organic substance, quaternary ammonium salts, polyamines, alkylamines and the like are preferable. The addition amount of the additive is preferably 20% by weight or less of the alumina hydrate.
[0065]
In the present invention, the alumina hydrate may be treated with a coupling agent. As the coupling agent to be used, one or more types selected from silane-based, titanate-based, aluminum-based, and zirconium-based coupling agents can be used. It is preferable that the alumina hydrate is hydrophobized by a coupling agent because the color density of the image is high and a clear image can be obtained. When the coupling agent treatment is performed in the range of 0.1 to 30% in terms of the surface area of the entire alumina hydrate, the color developability can be improved without impairing the ink absorbability. The coupling agent treatment method can be carried out, for example, by the method described in JP-A-9-76628.
[0066]
In the present invention, in addition to the alumina hydrate, if necessary, a pigment dispersant, a thickener, a pH adjuster, a lubricant, a fluidity modifier, a surfactant, an antifoaming agent, a water-resistant agent, and a foam inhibitor. It is also possible to add an agent, a release agent, a foaming agent, a penetrating agent, a coloring dye, a fluorescent brightening agent, an ultraviolet absorber, an antioxidant, an antiseptic and an antifungal agent. As the water-proofing agent, a known material such as a halogenated quaternary ammonium salt or a quaternary ammonium salt polymer can be freely selected and used.
[0067]
Alternatively, in the present invention, it is also possible to add a metal alkoxide or a substance capable of crosslinking a hydroxyl group to a dispersion of alumina hydrate. In the production method using this dispersion, bleeding and beading can be prevented even when printing is performed using ink with good permeability to which a large amount of surfactant is added.
[0068]
As a dispersion treatment method for the dispersion liquid containing alumina hydrate, it can be selected from methods generally used for dispersion. As a method and apparatus to be used, gentle stirring such as a homomixer or a rotating blade is preferable to a grinding type disperser such as a ball mill or a sand mill. The applied shear stress varies depending on the viscosity, amount, and volume of the dispersion, but is 0.1 to 100.0 N / m.²(1-1000 dyne / cm²) Is preferred. Within the above range, the viscosity of the alumina hydrate dispersion can be lowered without changing the crystal structure of the alumina hydrate. Furthermore, since the particle diameter of the alumina hydrate can be made sufficiently small, the binding point between the alumina hydrate and the fibrous substance increases. Therefore, the occurrence of powder falling can be suppressed. A more preferable range of the above range is 0.1 to 50.0 N / m.²Within this range, the pore volume of the alumina hydrate cannot be reduced, and the aggregated particles of the alumina hydrate can be broken into fine particles. In addition to preventing the generation of pores having a large radius, peeling and cracking when bent can be prevented, and haze caused by large particles in the recording medium can be reduced. The most preferable range is 0.1 to 20.0 N / m.²In this range, the mixing ratio of the alumina hydrate and the binder in the recording medium can be made constant, so that powder falling and cracking can be prevented, and the optical density of the printed dots is And the dot diameter can be made uniform.
[0069]
The dispersion time varies depending on the amount of the dispersion, the size of the container, the temperature of the dispersion, etc., but is preferably 30 hours or less from the viewpoint of preventing changes in the crystal structure, and if it is 10 hours or less, the pore structure Can be adjusted within the above range. During the dispersion treatment, the temperature of the dispersion liquid may be kept in a certain temperature range by cooling or keeping warm. The preferred temperature range is 10 to 100 ° C. although it varies depending on the dispersion treatment method, material and viscosity. If it is lower than the above range, the dispersion treatment is insufficient or aggregation occurs. If it is higher than the above range, it will gel or its crystal structure will change to amorphous.
[0070]
The ink used in the image forming method of the present invention mainly contains a colorant (dye or pigment), a water-soluble organic solvent, and water. As the dye, for example, a water-soluble dye represented by a direct dye, an acid dye, a basic dye, a reactive dye, an edible pigment, and the like are preferable, and in combination with the above recording medium, fixability, color developability, sharpness, Any one that provides an image satisfying the required performance such as stability, light resistance and the like may be used. As the pigment, carbon black or the like is preferable. A method of using a pigment and a dispersant in combination, a method of using a self-dispersing pigment, and a method of microencapsulation are also possible.
[0071]
The water-soluble dye is generally used by being dissolved in water or a solvent composed of water and a water-soluble organic solvent. As these solvent components, a mixture of water and various water-soluble organic solvents is preferably used. Although used, it is preferable to adjust the water content in the ink to be in the range of 20 to 90% by weight.
[0072]
Examples of the water-soluble organic solvent include alkyl alcohols having 1 to 4 carbon atoms such as methyl alcohol, amides such as dimethylformamide, ketones or ketone alcohols such as acetone, ethers such as tetrahydrofuran, and polyethylene glycol. Examples include polyalkylene glycols, alkylene glycols such as ethylene glycol having 2 to 6 carbon atoms, and lower alkyl ethers of polyhydric alcohols such as glycerin and ethylene glycol methyl ether. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol, and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether and triethylene glycol monoethyl ether are preferred. Polyhydric alcohols are particularly preferred because they have a great effect as a lubricant for preventing clogging reduction of nozzles based on evaporation of water in ink and precipitation of water-soluble dyes.
[0073]
A solubilizer can also be added to the ink. Typical solubilizers are nitrogen-containing heterocyclic ketones, and their intended action is to dramatically improve the solubility of water-soluble dyes in solvents. For example, N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone are preferably used. Furthermore, additives such as a viscosity modifier, a surfactant, a surface tension modifier, a pH adjuster, and a specific resistance adjuster can be added to improve the properties.
[0074]
A method of forming an image by applying the ink to the recording medium is an inkjet recording method, and the recording method is a method in which the ink is effectively detached from a nozzle and ink can be applied to the recording medium. Any method is acceptable. In particular, an ink jet method in which ink subjected to the action of thermal energy undergoes a sudden volume change by the method described in Japanese Patent Application Laid-Open No. 54-59936, and the ink is ejected from the nozzle by the action force due to this state change. It can be used effectively.
[0075]
【Example】
EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated concretely, this invention is not limited to these specific examples.
[0076]
Various physical properties used in the present invention were measured as follows.
[0077]
1. Crystal structure
The X-ray diffraction of the recording medium is measured, the (020) plane spacing is Bragg's formula, the crystal thickness perpendicular to the (010) plane is Scherrer's formula, and the crystallinity is (020) peak intensity. It calculated | required from ratio of 2 (theta) = 10 degrees.
[0078]
2. BET specific surface area, pore radius distribution, pore volume
Measurement was performed using a nitrogen adsorption / desorption method.
Measuring apparatus: Cantachrome, Autosorb 1
[0079]
3. Content of titanium dioxide and silica
The content in the alumina hydrate was examined by ICP method (SPS4000 manufactured by Seiko Denshi Co., Ltd.) after melting the alumina hydrate in borate.
[0080]
4). Particle shape
Alumina hydrate is dispersed in ion-exchanged water and dropped onto a collodion membrane to make a measurement sample. This sample is observed with a transmission electron microscope (H-500, manufactured by Hitachi, Ltd.), and the aspect ratio and particle diameter are measured. The particle shape was determined.
[0081]
5). Changes after rewetting and free drying
The sample was dipped in pure water at 20 ° C. for 3 hours, and then air-dried in an environment of 20 ° C. and 60% RH for 24 hours, whereby the sample was re-wet and free-dried. Details are described on page 161 of 1987 TAPPI “Paper Properties Conference Proceedings” or page 67 of April 1982 issue of Tappi magazine.
[0082]
The ultrasonic propagation velocity of the sample was measured using a sonic sheet tester (trade name, manufactured by Nomura Shoji Co., Ltd.), which is an apparatus defined in ASTM F89-68. Details of the measurement are described in page 40 of the July 1986 issue of the Paper and Pulp Technology Association.
[0083]
The ultrasonic propagation speeds in the CD direction and MD direction of the sample before rewetting and the sample after redrying are measured, respectively, and the ratio between the two is determined from the rate of change in the CD direction and MD direction.
[0084]
6). Liquid absorption rate
The liquid is brought into contact with the sample using a dynamic scanning absorption meter (KM350-D1, trade name, manufactured by Kyowa Seiko Co., Ltd.) to determine the amount of liquid absorption. The liquid absorption amount in the range from about 2 milliseconds to 10 seconds of contact time is measured, and the liquid absorption curve is obtained by taking the square root of the contact time on the horizontal axis and the liquid transfer amount on the vertical axis. From the time when the liquid absorption curve rises, the contact time is determined as the wetting time, and the absorption coefficient is determined from the slope when the liquid is absorbed. As the liquid to be measured, ion exchange water and water-based ink having the following composition were used. In addition to the sample, the liquid absorption coefficients of the surface layer and the base layer were determined to obtain the ratio (base layer / surface layer).
[0085]
Aqueous ink composition (100 parts in total)
Dye (CI Food Black 2) 3 parts
Surfactant (Surfinol 465, manufactured by Nissin Chemical) 1 part
Diethylene glycol 5 parts
Polyethylene glycol 10 parts
Ion exchange water balance
[0086]
7. Standing
The surface of the sample was rubbed 10 times with a nail and the occurrence of fluffing was examined. A sample with no flaking was marked with ◯, a sample with a little rough surface was marked with △, and a sample with obvious flaking on the surface was marked with ×.
[0087]
8). Cutting powder
The sample was cut into a square with a side of 10 mm, and the powder fall off at the periphery was examined. If there was no powder fall, it was rated as “◯”, and if powder fall was occurring, it was marked as “X”.
[0088]
9. Bending powder fall
The sample was folded back in half at the center, and the occurrence of powder falling was examined. A sample that did not fall off even after being bent five times was marked as ◯, a sample that did not fall off until 3 times was marked as Δ, and a sample that had fallen off was marked as ×.
[0089]
10. curl
A sample is cut into a size of 297 × 210 mm and left in 3 environments of 30 ° C./80% RH, 20 ° C./45% RH, 5 ° C./10% RH for 24 hours, and then a flat table is placed in that environment. It left still and measured the amount of curvature with a height gauge. Warpage of 1 mm or less was evaluated as ◯, 3 mm or less as Δ, and 3 mm or more as x.
[0090]
11. tack
The measurement was carried out in the environment of 30 ° C / 80% RH, 20 ° C / 45% RH, 5 ° C / 10% RH for 24 hours. If the surface of the recording medium did not adhere by touching with a finger, it was rated as ◯, and if it adhered, it was marked as x.
[0091]
12 Printing characteristics
Printing was performed using the following three types of printers. The size of the sample to be printed was a size of 297 × 210 mm for printers (a) and (b), and a size of 99 × 150 mm for printer (C) because it was a card printer.
(A) DJ720C (manufactured by HP) with small droplet printing, black is pigment ink, and YMC is dye ink
(B) BJC250 (using a photo cartridge) with light ink printing and a large amount of ink applied (manufactured by Canon Inc.)
(C) Card printer P-400CII (manufactured by Canon Aptex) that performs ultra-high-speed printing using a line head
[0092]
1) Ink absorbability
Solid printing from single to four colors was performed using the above three types of printers. The ink dried state on the surface of the recording medium after printing was examined by touching the recording portion with a finger to check the ink absorbability. The ink amount in single color solid printing was set to 100%. Ink that does not adhere to the finger when the ink amount is 300% (mixed 3 colors), ○ that the ink amount does not adhere to the finger when the ink amount is 200% (mixed 2 colors), and ink that adheres to the finger when the ink amount is 100% If the ink does not adhere to the finger at 100%, it was marked as x.
[0093]
2) Image density
Using a Macbeth reflection densitometer RD-918, the image density of a solid image printed in Y, M, C, and Bk inks with a single color using a printer (c) with an ink amount of 100% was evaluated.
[0094]
3) Solid uniformity, blemishes, beading, repellency, back-through
The solid uniformity, blemishes, beading, and repellency on the surface of the recording medium after the solid printing was performed in a single color or multiple colors with the above three types of printers were visually evaluated. If the density of the solid portion was uniform, it was marked as ◯, and if there was a white spot or uneven density, it was marked as x. If there was no smearing of the color material from the solid print portion, it was rated as “◯”, and if the smear of the color material was visible, it was marked “x”. Similarly, if there was no beading or repelling in the solid printed part, it was marked as ◯. The back side of the recording medium was observed to visually check the color material. If no see-through was observed, it was marked as ◯, and if observed, it was marked as x.
[0095]
4) Color difference between pigment ink and dye ink
The color difference was evaluated by visually observing the portion where solid printing of 100% black was performed using the above three types of printers. If there is no difference in color among the three types, it is indicated as ◯, if there is no difference in color between the printer (a) and one type of printer, Δ, and if there is a difference in color, it is indicated as x.
[0096]
5) Fixability
Using the printer (a), the portion on which black 100% printing was performed was rubbed with a finger to evaluate the fixing property of the color material. If there was no detachment of the coloring material, it was rated as ◯. Y, M, C, and Bk inks were printed in a single color, and one dot was printed with the printer. The diameter of the dot was observed with a microscope.
[0097]
6) Print density and color change
Using the above three types of printers, a pattern was printed with a density change in 128 steps from 0% to 100% for each color, and the color at each print density was visually observed for each color. If the colors of the four colors are the same regardless of the density, ◎ if the colors of the three colors are the same, ◯ if the colors of the two colors are the same, and Δ if the colors of each color change due to the density.
[0098]
7) Curling after printing
The sample was cut into a size of 297 × 210 mm, and 100% solid printing was performed on the entire surface using printers (a) and (b). The amount of warpage was measured with a height gauge after standing on a flat table. Warpage of 1 mm or less was evaluated as ◯, 3 mm or less as Δ, and 3 mm or more as x.
[0099]
8) Tack after printing
Using the above three types of printers, 100% solid printing was performed on the entire surface. If the surface of the recording medium did not adhere by touching with a finger, it was rated as ◯, and if it adhered, it was marked as x.
[0100]
9) Powder fall after printing
Ten samples were stacked and sequentially conveyed by three types of printers, and each of the 10 samples was visually observed. Each sample was marked as ◯ if there was no powder fall, and x if powder fall occurred.
[0101]
10) Sticking after printing
Ten samples were continuously printed with the above three types of printers, and the print samples were superimposed. Each sample was marked as “O” if there was no sticking, and “X” if sticking occurred.
[0102]
11) Surface change after printing
The sample was printed with the above three types of printers, and the printed surface was visually observed. When there was no change on the printed surface, it was marked with ○, and when a change such as swelling was observed on the printed surface, it was marked with ×.
[0103]
12) Cock ring, wrinkle, deformation
The sample was printed with the above three types of printers, and the deformation of the sample was visually observed. If no deformation or the like was observed, it was marked as ◯.
[0104]
Example 1
Commercially available LBKP as a base material pulp was beaten with a double disc refiner to obtain 300 ml of Canadian Standard Freeness (CSF) beating raw material (A).
[0105]
The same commercially available LBKP as the base layer was beaten with the same apparatus as the base layer to obtain 450 ml of the same raw material (B). Boehmite-structured alumina hydrate (alumina hydrate (A)) described in Example 1 of JP-A-9-99627 is added to this beating raw material (B) in an amount of 10% by weight of the raw pulp in terms of dry solid content. The raw material pulp of the surface layer was obtained by adding.
[0106]
The basis weight of the surface layer is 20 g / m in a multilayer paper machine having a multilayer head box.²The basis weight of the base layer is 60 g / m²Two-layer papermaking was performed so that After drying, the calendering is performed so that the linear pressure is 20 kg / cm, and the basis weight is 80 g / m.²Of alumina-added multilayer paper was obtained. The touch was the same as plain paper. The physical properties of the recording medium were measured by the above methods. The results are shown in Table 2.
[0107]
(Example 2)
According to the method described in Example 1 of JP-A-8-284090, C.I. S. F. 300 ml of beating pulp slurry was refined with an abrasive plate rubbing apparatus. Next, an ultrafine treatment was performed with a high-pressure homogenizer to obtain a beating raw material (C) made of fibrillated cellulose.
[0108]
This beating raw material (C) and the beating raw material (B) were mixed at a ratio of 80:20 in terms of dry solid content. Into this, alumina hydrate (A) was mixed in an amount of 10% by weight of the raw material pulp weight in terms of dry solid content to obtain a raw material pulp of the surface layer.
[0109]
Using the beating raw material (A) as the raw material pulp for the base layer, the basis weight of the surface layer is 20 g / m in the same apparatus and method as in Example 1.²The basis weight of the base layer is 60 g / m²A multilayer paper having a two-layer structure was obtained. Further, the surface was calendered in the same manner as in Example 1, and the basis weight was 80 g / m.²Of alumina-added multilayer paper was obtained. The touch was the same as plain paper. The physical properties of the recording medium were measured by the above methods. The results are shown in Table 2.
[0110]
(Example 3)
Using a commercially available hardwood bleached sulfite pulp, 450 ml of Canadian Standard Freeness (CSF) beating raw material (D) was obtained using the same apparatus as in Example 1.
[0111]
This beating raw material (D) and the beating raw material (B) were mixed at a ratio of 60:40 in terms of dry solid content. Into this, alumina hydrate (A) was mixed in an amount of 10% by weight of the raw material pulp weight in terms of dry solid content to obtain a raw material pulp of the surface layer.
[0112]
Using the beating raw material (A) as the raw material pulp for the base layer, the basis weight of the surface layer is 20 g / m in the same apparatus and method as in Example 1.²The basis weight of the base layer is 60 g / m²A multilayer paper having a two-layer structure was obtained. Further, the surface was calendered in the same manner as in Example 1, and the basis weight was 80 g / m.²Of alumina-added multilayer paper was obtained. The touch was the same as plain paper. The physical properties of the recording medium were measured by the above methods. The results are shown in Table 2.
[0113]
(Example 4)
A beaten raw material (E) was obtained by adjusting a cross-linked pulp having a twisted structure as a bulky cellulose fiber (High Bulk Additive, trade name, manufactured by Wafer User Paper).
[0114]
This beating raw material (E) was mixed with the beating raw material (B) at 3% by weight in terms of dry solid content. Into this, alumina hydrate (A) was mixed in an amount of 10% by weight of the raw material pulp weight in terms of dry solid content to obtain a raw material pulp of the surface layer.
[0115]
Using the beating raw material (A) as the raw material pulp for the base layer, the basis weight of the surface layer is 20 g / m in the same apparatus and method as in Example 1.²The basis weight of the base layer is 60 g / m²A multilayer paper having a two-layer structure was obtained. Further, the surface was calendered in the same manner as in Example 1, and the basis weight was 80 g / m.²Of alumina-added multilayer paper was obtained. The touch was the same as plain paper. The physical properties of the recording medium were measured by the above methods. The results are shown in Table 2.
[0116]
(Example 5)
Polyamine resin (Smilease Resin FR-2P, trade name), in an aqueous dispersion having a solid content concentration of 1.5% by weight of a fibrous carboxymethylcellulose sodium salt (Nichirin Chemical) having a degree of etherification of 0.43 and a base saturation of 82%. Sumitomo Chemical Co., Ltd.) was added at a ratio of 2.0% by weight to the fibrous carboxymethylcellulose sodium salt and stirred to obtain a superabsorbent resin.
[0117]
The beating raw material (A) and the superabsorbent resin were mixed at a ratio of 95: 5 in terms of dry solid content to obtain a raw material pulp of the base layer.
[0118]
The raw material pulp of the same surface layer as Example 1 was used as the raw material pulp of the surface layer. The basis weight of the surface layer is 20 g / m by the same apparatus and the same method as in Example 1.²The basis weight of the base layer is 60 g / m²A multilayer paper having a two-layer structure was obtained. Further, the surface was calendered in the same manner as in Example 1, and the basis weight was 80 g / m.²Of alumina-added multilayer paper was obtained. The touch was the same as plain paper. The physical properties of the recording medium were measured by the above methods. The results are shown in Table 2.
[0119]
(Example 6)
The beating raw material (A) and the same beating raw material (E) as in Example 4 were mixed at a ratio of 65:35 in terms of dry solid content to obtain a raw material pulp of the base layer.
[0120]
The raw material pulp of the same surface layer as Example 1 was used as the raw material pulp of the surface layer. The basis weight of the surface layer is 20 g / m by the same apparatus and the same method as in Example 1.²The basis weight of the base layer is 60 g / m²A multilayer paper having a two-layer structure was obtained. Further, the surface was calendered in the same manner as in Example 1, and the basis weight was 80 g / m.²Of alumina-added multilayer paper was obtained. The touch was the same as plain paper. The physical properties of the recording medium were measured by the above methods. The results are shown in Table 2.
[0121]
(Example 7)
According to the method described in Example 1 of JP-A-8-667, an ozone-containing gas was introduced into an aqueous dispersion of commercially available softwood bleached kraft pulp. After dehydration, loosening, and heat drying, the mixture was placed in a blender, and the pulp mass was dissociated into fine fibers to obtain a beating raw material (F) made of fluffed cellulose.
[0122]
The beating raw material (A) and the beating raw material (F) were mixed at a ratio of 65:35 in terms of dry solid content to obtain a raw material pulp of the base layer.
[0123]
The raw material pulp of the same surface layer as Example 1 was used as the raw material pulp of the surface layer. The basis weight of the surface layer is 20 g / m by the same apparatus and the same method as in Example 1.²The basis weight of the base layer is 60 g / m²A multilayer paper having a two-layer structure was obtained. Further, the surface was calendered in the same manner as in Example 1, and the basis weight was 80 g / m.²Of alumina-added multilayer paper was obtained. The touch was the same as plain paper. The physical properties of the recording medium were measured by the above methods. The results are shown in Table 2.
[0124]
(Example 8)
Using a commercially available mercerized kraft pulp, the same apparatus as in Example 1 was used to obtain 740 ml of Canadian Standard Freeness (C.S.F.) beating raw material (G). The beating raw material (A) and the beating raw material (G) were mixed at a ratio of 65:35 in terms of dry solid content to obtain a raw material pulp of the base layer.
[0125]
The raw material pulp of the same surface layer as Example 1 was used as the raw material pulp of the surface layer. The basis weight of the surface layer is 20 g / m by the same apparatus and the same method as in Example 1.²The basis weight of the base layer is 60 g / m²A multilayer paper having a two-layer structure was obtained. Further, the surface was calendered in the same manner as in Example 1, and the basis weight was 80 g / m.²Of alumina-added multilayer paper was obtained. The touch was the same as plain paper. The physical properties of the recording medium were measured by the above methods. The results are shown in Table 2.
[0126]
Example 9
A boehmite-structured alumina hydrate (alumina hydrate (B)) of Example 2 of JP-A-9-99627 was added to the beating raw material (B) in an amount of 10% by weight in terms of dry solids, and the surface layer Raw material pulp was obtained.
[0127]
Using the beating raw material (A) as the raw material pulp for the base layer, the basis weight of the surface layer is 20 g / m in the same apparatus and method as in Example 1.²The basis weight of the base layer is 60 g / m²A multilayer paper having a two-layer structure was obtained. Further, the surface was calendered in the same manner as in Example 1, and the basis weight was 80 g / m.²Of alumina-added multilayer paper was obtained. The touch was the same as plain paper. The physical properties of the recording medium were measured by the above methods. The results are shown in Table 2.
[0128]
(Example 10)
Boehmite-structured alumina hydrate (alumina hydrate (alumina hydrate) described in Example 1 of JP-A-9-66664) having a pore volume of radius 2.0 to 20.0 of 80% or more of the total pore volume. C)) was added to the beating raw material (B) in an amount of 10% by weight in terms of dry solid content to obtain a raw material pulp for the surface layer.
[0129]
Using the beating raw material (A) as the raw material pulp for the base layer, the basis weight of the surface layer is 20 g / m in the same apparatus and method as in Example 1.²The basis weight of the base layer is 60 g / m²A multilayer paper having a two-layer structure was obtained. Further, the surface was calendered in the same manner as in Example 1, and the basis weight was 80 g / m.²Of alumina-added multilayer paper was obtained. The touch was the same as plain paper. The physical properties of the recording medium were measured by the above methods. The results are shown in Table 2.
[0130]
(Example 11)
Add 10 wt% of boehmite-structured alumina hydrate (alumina hydrate (D)) containing titanium dioxide of Example 3 of JP-A-9-99627 to the beating raw material (B) in terms of dry solid content. Thus, raw material pulp of the surface layer was obtained.
[0131]
Using the beating raw material (A) as the raw material pulp for the base layer, the basis weight of the surface layer is 20 g / m in the same apparatus and method as in Example 1.²The basis weight of the base layer is 60 g / m²A multilayer paper having a two-layer structure was obtained. Further, the surface was calendered in the same manner as in Example 1, and the basis weight was 80 g / m.²Of alumina-added multilayer paper was obtained. The touch was the same as plain paper. The physical properties of the recording medium were measured by the above methods. The results are shown in Table 2.
[0132]
Example 12
Aluminum doxide was produced according to the method described in US Pat. No. 4,242,271. The obtained aluminum dodexide, ion exchange water, and orthosilicic acid were mixed. The aluminum dodexide was hydrolyzed while stirring this mixed solution in a reaction vessel. The hydrolysis conditions and the mixing ratio of aluminum dodexide and orthosilicic acid are as follows. In addition, the same weight as the aluminum dodexide in ion-exchange water was used.
Hydrolysis temperature: 110 ° C
Hydrolysis time: 30 minutes
Mixing ratio: 8.45
(The mixing ratio is the amount of silicic acid added to 100 parts by weight of alkoxide: parts by weight)
[0133]
The obtained alumina hydrate suspension was spray dried at an inlet temperature of 280 ° C. to obtain silica-containing alumina hydrate powder. The crystal structure of the alumina hydrate was boehmite, and the particle shape was tabular. The physical properties are as follows.
Silica content: 1.0% by weight
Average particle diameter: 27.1 nm
Aspect ratio: 6.1
Crystallinity: 53
[0134]
This silica is contained in an amount of 1.0% by weight, and a boehmite-structured alumina hydrate (alumina hydrate (E)) having a crystallinity of 53 is 10% by weight in terms of dry solid content with respect to the beating raw material (B). The raw material pulp of the surface layer was obtained by adding.
[0135]
Using the beating raw material (A) as the raw material pulp for the base layer, the basis weight of the surface layer is 20 g / m in the same apparatus and method as in Example 1.²The basis weight of the base layer is 60 g / m²A multilayer paper having a two-layer structure was obtained. Further, the surface was calendered in the same manner as in Example 1, and the basis weight was 80 g / m.²Of alumina-added multilayer paper was obtained. The touch was the same as plain paper. The physical properties of the recording medium were measured by the above methods. The results are shown in Table 2.
[0136]
(Example 13)
10 wt. Of a boehmite-structured alumina hydrate (alumina hydrate (F)) having a crystallinity of 32.2 in Example 2 of JP-A-8-132731 relative to the beating raw material (B) in terms of dry solid content. % To obtain a raw material pulp for the surface layer.
[0137]
Using the beating raw material (A) as the raw material pulp for the base layer, the basis weight of the surface layer is 20 g / m in the same apparatus and method as in Example 1.²The basis weight of the base layer is 60 g / m²A multilayer paper having a two-layer structure was obtained. Further, the surface was calendered in the same manner as in Example 1, and the basis weight was 80 g / m.²Of alumina-added multilayer paper was obtained. The touch was the same as plain paper. The physical properties of the recording medium were measured by the above methods. The results are shown in Table 2.
[0138]
(Example 14)
Alumina hydrate pigment B described in the example of JP-A-8-174993 is agglomerated using aqueous ammonia in the same manner as in Example 2 to obtain aggregated particles of alumina hydrate (alumina hydrate ( G)) was formed.
[0139]
Alumina hydrate (G) was added to the beating raw material (B) in an amount of 10% by weight in terms of dry solids to obtain a raw material pulp for the surface layer.
[0140]
Using the beating raw material (A) as the raw material pulp for the base layer, the basis weight of the surface layer is 20 g / m in the same apparatus and method as in Example 1.²The basis weight of the base layer is 60 g / m²A multilayer paper having a two-layer structure was obtained. Further, the surface was calendered in the same manner as in Example 1, and the basis weight was 80 g / m.²Of alumina-added multilayer paper was obtained. The touch was the same as plain paper. The physical properties of the recording medium were measured by the above methods. The results are shown in Table 2.
[0141]
(Example 15)
Alumina hydrate (alumina hydrate (H)) treated with a coupling agent was prepared according to the method described in Example 1 of JP-A-9-76628.
[0142]
Alumina hydrate (H) was added to the beating raw material (B) in an amount of 10% by weight in terms of dry solids to obtain a raw material pulp for the surface layer.
[0143]
Using the beating raw material (A) as the raw material pulp for the base layer, the basis weight of the surface layer is 20 g / m in the same apparatus and method as in Example 1.²The basis weight of the base layer is 60 g / m²A multilayer paper having a two-layer structure was obtained. Further, the surface was calendered in the same manner as in Example 1, and the basis weight was 80 g / m.²Of alumina-added multilayer paper was obtained. The touch was the same as plain paper. The physical properties of the recording medium were measured by the above methods. The results are shown in Table 2.
[0144]
(Example 16)
Commercially available LBKP was beaten as the raw material pulp of the back layer using the same apparatus and method as in Example 1 to obtain 350 ml of Canadian Standard Freeness (CSF) raw material (H).
[0145]
The basis weight of the surface layer of the surface layer is 20 g / m using the same multilayer paper machine as in Example 1 using the same surface layer raw material pulp and base layer raw material pulp as in Example 1.²The basis weight of the base layer is 60 g / m²The basis weight of the back layer is 20 g / m²Three-layer papermaking was performed so that Calendering is performed so that the linear pressure is 20 kg / cm after drying, and the basis weight is 100 g / m.²Of alumina-added multilayer paper was obtained. The touch was the same as plain paper. The physical properties of the recording medium were measured by the above methods. The results are shown in Table 2.
[0146]
  (Example 17)
  Using the same surface layer raw material pulp and base layer raw material pulp as in Example 1, using the same multilayer paper machine as in Example 1Surface layerBasis weight is 20g / m²The basis weight of the base layer is 60 g / m²Two-layer papermaking was performed so that A screen with a watermark pattern was placed on the wire of the paper machine, and the paper was made so that the wire portion was the back of the recording medium. After drying, the calendering is performed so that the linear pressure is 20 kg / cm, and the basis weight is 80 g / m.²Of alumina-added multilayer paper was obtained. Further, the surface was calendered in the same manner as in Example 1, and the basis weight was 80 g / m.²Of alumina-added multilayer paper was obtained. There was a watermark on the back that could be visually observed. The touch was the same as plain paper. The physical properties of the recording medium were not different from those in Examples 1-16.
[0147]
(Example 18)
Using an offset printer and printing ink (F gloss ink # 85, trade name, manufactured by Dainippon Ink Co., Ltd.) manufactured by AB Dick, USA on the back surface of the recording medium of Example 1 (surface layer non-forming surface of the base layer) A barcode pattern was printed. The printed pattern could be observed visually. There was no change in the surface layer, and the feel and physical properties were the same as in Examples 1-16.
[0148]
Example 19
A barcode pattern was printed on the back surface of the recording medium of Example 1 (the surface layer-unformed surface of the base layer) using an offset printing machine manufactured by AB Dick, USA and a commercially available magnetic ink. The magnetic print pattern could be observed with a reader. There was no change in the surface layer, and the feel and physical properties were the same as in Examples 1-16.
[0149]
(Example 20)
A barcode pattern was printed on the back surface of the recording medium of Example 1 (the surface layer-unformed surface of the base layer) using an offset printer manufactured by AB Dick, USA and a commercially available infrared ink. The printed pattern could not be observed visually but could be observed with an infrared reader. There was no change in the surface layer, and the feel and physical properties were the same as in Examples 1-16.
[0150]
(Example 21)
Using the same beating raw material (A) as in Example 1, a basis weight of 60 g / m using a TAPPI standard sheet former²The base layer of paper was made. The basis weight of the surface layer is 20 g / m on the base layer using the same beating raw material (B) as in Example 1.²It was bar-coated so that Thereafter, it was dried by heating in an oven (Yamato Scientific) at 100 ° C. for 10 minutes. Further, calendaring is performed in the same manner as in Example 1 to obtain a basis weight of 80 g / m.²Of alumina-added multilayer paper was obtained. The touch was the same as plain paper. The physical properties of the recording medium were measured by the above methods. The results are shown in Table 2.
[0151]
[Table 1]

[0152]
[Table 2]

[0153]
[Table 3]

[0154]
[Table 4]

[0155]
[Table 5]

[0156]
【The invention's effect】
The present invention has the following remarkable effects.
(1) Since the alumina hydrate is added to the fibrous material, the ink absorbability and the color developability can be improved while leaving the texture of plain paper.
(2) Addition of alumina hydrate only to the surface layer increases the effect of addition, and the image can be improved even with a small addition amount.
(3) Since the surface layer absorbs the coloring material in the ink and the base layer absorbs the solvent component in the ink, even if printing is performed with an ultra-high speed machine such as a line printer having a full line head. Overflow, bleeding, and beading can be prevented.
(4) Through-holes can be prevented without sizing the base layer.
(5) It can prevent curling and flaking when rubbing the curl or surface due to changes in temperature and humidity.

Claims (10)

A recording medium having a surface layer at least provided on one surface of the base layer and the substrate,
The base layer and the surface layer are mainly composed of fibers obtained from cellulose pulp,
Alumina hydrate having a boehmite structure only on the surface layer are internally added,
The cellulose pulp of the base layer has a lower beating degree than the cellulose pulp of the surface layer,
The base layer has a higher liquid absorbency than the surface layer,
A recording medium that is not subjected to size processing .   The recording medium according to claim 1, wherein the base layer and the surface layer of the recording medium are formed by combining.   3. The recording medium according to claim 1, wherein the amount of boehmite-structured alumina hydrate added to the recording medium is 2 to 30% by weight of the surface layer. The recording medium according to any one of claims 1 to 3 wherein the surface layer is characterized by containing a microfibrillated cellulose. The surface layer is the recording medium according to any one of claims 1 to 4, characterized in that it contains sulfate pulp to hardwood or softwood as raw material, sulfite pulp, soda pulp. The recording medium according to any one of claims 1 to 5 wherein the base layer is characterized by containing an absorbent material 1 or more. The recording medium according to any one of claims 1 to 6 , wherein the base layer contains one or more types selected from Munsellated cellulose, fluffed cellulose, and bulky cellulose. The wetting time obtained from an absorption curve of the recording medium by a dynamic scanning absorption meter is 15 milliseconds or less, and an absorption coefficient is 5 ml / m ² s ^−1/2 or more. The recording medium according to any one of 1 to 7 . In an image forming method in which ink droplets containing a coloring material and a solvent component are ejected from fine holes and applied to a recording medium for printing,
The recording medium according to any one of claims 1 to 8 is used as a recording medium ,
An image forming method comprising adsorbing a coloring material in an applied ink on a surface layer of the recording medium and adsorbing a solvent component in the applied ink on a base layer of the recording medium . When an ink containing a color material and a solvent component is applied to the surface layer of the multilayer paper, the color material in the applied ink is adsorbed by the surface layer of the recording medium, and the solvent component in the applied ink is The recording medium according to claim 1, wherein the recording medium is adsorbed by a base layer of the recording medium.