JP3198196B2 - Inkjet recording sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink-jet recording sheet, and more particularly, to an ink-jet recording sheet which has no ink bleeding unevenness, has excellent ink absorbency, has high density and sharpness of a recorded image, and has a perfect circular shape. The present invention relates to a finely coated ink jet recording sheet capable of obtaining recording dots close to.

[0002] Ink jet recording is a method in which minute droplets of ink are made to fly and adhere to a recording sheet such as paper by various operating principles 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, and is rapidly spreading in various applications as a recording device for various figures including Chinese characters and color images. Further, an image formed by the multi-color ink jet system can obtain a record comparable to multi-color printing by a plate making system or printing by a color photographic system. Further, in applications requiring a small number of copies, it is being widely applied to the field of full-color image recording because it is cheaper than by photographic technology.

As recording sheets used in the ink jet recording system, efforts have been made in terms of apparatuses and ink compositions in order to use high-quality paper and coated paper used for ordinary printing and writing. However, as the performance of the inkjet recording apparatus has been improved and the use thereof has been expanded, such as by increasing the speed and increasing the definition of the apparatus or by increasing the color, the recording sheet has been required to have higher properties. That is, the recording sheet has a high density of print dots, a bright and vivid color tone, quick absorption of ink, so that ink does not flow or bleed even when print dots overlap, It is required that the diffusion in the direction is not excessively large and that the periphery is smooth and not blurred.

[0004] The form of the ink jet recording sheet is a so-called plain paper type such as so-called high quality paper or bond paper, and an ink receiving layer provided on a support such as paper such as high quality paper, synthetic paper or synthetic resin film. Coating type.

The coating type includes a low coating type of about 1 to 10 / m ^{2, a} medium coating type of about 10 to 20 g / m ² ,
There is a high coating type ink jet recording sheet of 20 g / m ² or more. In particular, in recent years, even with a low coating type, a fine coating type having a lower coating amount of 0.5 to 5 g / m ² is closer to plain paper, and is preferable in appearance and handling. Coating type is desired. However, in the case of color recording, not only single-color recording of yellow, magenta, cyan, and black, but also these colors are superimposed and recorded in multiple colors, and the amount of ink adhesion becomes extremely large.
In the case of the fine coating type, since the ink cannot be completely absorbed by the coating layer, use a relatively low-size base paper.
It is necessary to absorb a part of the attached ink by the base paper itself of the support.

To solve these problems, Japanese Patent Publication No.
JP-A-26665 discloses an example of an ink jet recording paper in which a coating layer containing fine silica and a water-soluble polymer binder is provided on a base paper having a basis weight of 60 g / m ² and a Stockigt size of 4 seconds or less. And JP-A-59-3808.
Japanese Patent Application Laid-Open No. 7-9516 discloses an example of an ink jet recording material in which an ink absorbing layer is provided on a substrate having a sizing degree of 0 to 10 seconds. There is disclosed an example of an ink jet recording paper in which a base paper of up to 5 seconds is impregnated with polyvinylpyrrolidone or the like.

Further, as an ink jet recording sheet having a high ink absorbency and a good recording dot shape,
There is JP-A-60-63191. This publication is characterized in that the surface layer of a recording material (inkjet recording sheet) is a mixture of a filler and a fibrous material. Here, it is described that the material has a substrate made of a fibrous material and filler particles adhered to the surface of the substrate so as to be scattered very thinly. However, this publication does not mention the state where the filler and the fibrous material of the surface layer are mixed and the fibrous material forming the base material is exposed on the surface layer.

[0008]

As described above, when the ink receiving layer has a low coating amount, a part of the adhered ink is absorbed by the support itself using a base paper having a relatively low size. In particular, since the ink receiving layer applied on the support is not uniformly coated on the surface of the ink receiving layer with the entangled irregularities of the pulp fibers, the pulp fibers are in an extremely exposed state. For this reason, the adhered ink penetrates into the support, that is, the inside of the base paper, along the exposed pulp fiber without forming recording dots of a desired shape on the surface of the ink receiving layer,
The recording dots have a spread and spread shape.
In other words, the recorded image lacks sharpness.

An object of the present invention is to provide an ink jet recording sheet which is a finely coated ink jet recording sheet, has no ink bleed unevenness, has excellent ink absorbability, has a high density and sharpness of a recorded image, and has a high quality. It is an object of the present invention to obtain an ink jet recording sheet capable of obtaining recording dots close to a circle.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above, and as a result, have found that there is no ink bleeding, excellent ink absorbency, high density of recorded images, and recording dots close to a perfect circle. The inventors have invented the obtained ink jet recording sheet. That is, the ink jet recording sheet of the present invention, in the ink jet recording sheet, the recording surface of the recording sheet is surface-coated with a composition mainly composed of an ultrafine inorganic pigment along the surface of the pulp fiber in a tangled state of the base paper surface. The pulp fiber shape coated on the recording surface can be visually recognized by a scanning electron microscope on the recording surface, and the surface coverage of the pulp fiber on the recording surface is 70% or more. It is.

Hereinafter, the ink jet recording sheet of the present invention will be described in detail. The ink jet recording sheet of the present invention has a surface coated so that the shape of the pulp fiber on the support, that is, the recording surface on the base paper surface, can be sufficiently identified. The surface coating of the recording surface is uniformly covered with the ultrafine inorganic pigment along the surface of the pulp fiber, and is thinly covered according to the shape of the pulp fiber surface. The surface coverage of the recording surface covers 70% or more of the surface of the pulp fiber on the recording surface, whereby the characteristics intended by the present invention can be sufficiently exhibited. Preferably, 80% or more,
More preferably, it is 90% or more. As a reason,
When the recording surface is evenly covered with the surface, when the ink is applied to the recording surface using an ink jet printer, the recording surface is uniformly covered, so that the ink does not spread in the recording surface direction. This is because recording dots close to a perfect circle can be expressed, and surplus ink permeates from the surface coating surface in the thickness direction of the base paper. On the other hand, if the surface coverage of the recording surface covering the pulp fibers is less than 70%, the ratio of the ink spreading in the recording surface direction increases, and as a result, the recording dots are out of a perfect circle. Further, the penetration into the base paper becomes irregular, and ink bleeding appears.

In the ink jet recording sheet of the present invention, the surface coated surface is a surface uniformly covered along the pulp fiber of the base paper surface, and is coated using a composition mainly composed of ultrafine inorganic pigment. . The primary particle size of the ultrafine inorganic pigment is 100 nm or less, preferably 5
0 nm or less. The finer the particle size, the more uniform the surface coating on the pulp fiber, which is preferable. These ultrafine inorganic pigments usually use colloidal dispersions in water while maintaining the primary particle diameter.

In the ink jet recording sheet of the present invention, a scanning electron microscope can be used as a means for measuring the surface coverage of the pulp fiber surface on the recording surface. Is calculated.

The following can be exemplified as the ultrafine inorganic pigment. For example, silica (colloidal silica), alumina or alumina hydrate (alumina sol,
Colloidal alumina, cationic aluminum oxide or its hydrate, pseudo-boehmite, etc.), surface-treated cationic colloidal silica, aluminum silicate, magnesium silicate, magnesium carbonate, and the like. If the primary particles are porous, it is more preferable. However, even if it is non-porous, it is preferred that it coagulates at the time of preparation of the coating solution or coagulates at the time of coating and drying to form a porous surface coating surface on the pulp fiber surface. In particular, in the present invention, it is preferred that the pulp fibers themselves are coated on each pulp fiber on the base paper surface with an ultrafine inorganic pigment having an average particle size of several hundredths or less of the fiber width.

Further, as the inorganic pigment which can be used in combination with the ultrafine inorganic pigment, any conventionally known inorganic pigment can be used. For example, light calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth,
Examples thereof include calcium silicate, synthetic amorphous silica, aluminum hydroxide, lithopone, zeolite, hydrohaloysite, and magnesium hydroxide. Among these inorganic pigments, porous inorganic pigments are preferable, and porous synthetic amorphous silica, porous magnesium carbonate, porous alumina, and the like can be mentioned. Particularly, porous synthetic amorphous silica having a large pore volume is preferable. . Further, organic pigments such as styrene-based plastic pigment, acrylic-based plastic pigment, polyethylene, microcapsules, urea resin, melamine resin and the like can be used together with the ultrafine inorganic pigment.

As a binder to be used together with the ultrafine inorganic pigment for surface coating, for example, polyvinyl alcohol, vinyl acetate, oxidized starch, etherified starch, cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, casein, gelatin, soybean Protein, silyl-modified polyvinyl alcohol, etc .; conjugated diene copolymer latex such as maleic anhydride resin, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer; polymer or copolymer of acrylate and methacrylate Acrylic polymer latex such as a polymer or a copolymer of acrylic acid and methacrylic acid; vinyl polymer latex such as ethylene-vinyl acetate copolymer; or functional groups such as carboxyl groups of these various polymers Functional group-modified polymer latex; aqueous binder such as thermosetting synthetic resin such as melamine resin and urea resin; polymethyl methacrylate, polyurethane resin, unsaturated polyester resin, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, alkyd Synthetic resin binders such as resins can be mentioned,
At least one kind can be used. Further, a cationic resin added for the purpose of fixing a conventionally known dye can also be used in combination.

The total amount of the binder can be appropriately adjusted in accordance with the characteristics of the target ink jet recording sheet.
６０60% by weight. Further, as other additives, a pigment dispersant, a thickener, a fluidity improver, an antifoaming agent, a foam inhibitor, a release agent, a foaming agent, a penetrant, a coloring dye, a coloring pigment, a fluorescent brightening agent, An ultraviolet absorber, an antioxidant, an antiseptic, an antibacterial agent, a waterproofing agent, a wet paper strength enhancer, a dry paper strength enhancer, and the like can be appropriately blended.

In the present invention, the method of coating the surface includes a method of coating or impregnation, but the amount of coating on the surface-coated surface is not particularly limited. Usually, when the orientation is like plain paper, the amount is preferably 0.5 to 5 g / m ^2, but may be further coated.

The base paper according to the present invention includes LBKP, NBK
Chemical pulp such as P, GP, PGWRMP, TMP, CT
Mechanical pulp such as MP, CMP, CGP and the like, wood pulp such as waste paper pulp such as DIP, and conventionally known pigments as main components, binders and sizing agents, fixing agents, retention improvers, cationizing agents, paper strength agents And the like. Mixing using one or more kinds of additives such as base paper manufactured by various apparatuses such as fourdrinier paper machine, round paper machine, twin wire paper machine, and further, the base paper is further modified with starch, polyvinyl alcohol, etc. Also includes size-pressed base paper. Such a base paper may be coated as it is, or for the purpose of controlling flattening,
A calendar device such as a machine calendar, a TG calendar, or a soft calendar may be used.

In the case of surface coating, coating and impregnating methods include various blade coaters, roll coaters, air knife coaters, bar coaters, rod coaters, gate roll coaters, curtain coaters, short dwell coaters,
Various devices such as a gravure coater, a flexographic gravure coater, and a size press can be used on-machine or off-machine. However, in the present invention, a rod coater or a gate roll coater is preferred. After coating or impregnation, finishing may be performed using a calendar such as a machine calendar, a TG calendar, a super calendar, or a soft calendar.

The aqueous ink referred to in the present invention is a recording liquid comprising the following colorant, liquid medium, and other additives.
Examples of the coloring agent include a direct dye, an acid dye, a basic dye, a reactive dye, and a water-soluble dye such as a food colorant.

Examples of the solvent for the aqueous ink include water and various water-soluble organic solvents such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, Alkyl alcohols having 1 to 4 carbon atoms such as isobutyl alcohol; amides such as dimethylformamide and dimethylacetamide; ketones or ketone alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyethylene glycol and polypropylene glycol Polyalkylene glycols such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexyl Alkylene glycols having 2 to 6 alkylene groups such as lene glycol and diethylene glycol; lower alkyl ethers of polyhydric alcohols such as glycerin, ethylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol and monomethyl ether; Is mentioned. 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. As other additives, for example, a pH adjuster, a sequestering agent, a fungicide, a viscosity adjuster,
Examples include a surface tension adjuster, a wetting agent, a surfactant, and a rust inhibitor.

The ink-jet recording sheet of the present invention can be used not only as an ink-jet recording sheet but also as any recording sheet using a liquid ink during recording. For example, a heat-fusible substance, a heat-fusible ink containing a dye or pigment as a main component is coated on a thin support such as a resin film, high-density paper, or synthetic paper. Heat transfer recording image-receiving sheet for melting and transferring the ink, heat-fusible ink is heated and melted to form fine droplets, ink jet recording sheet for flight recording, ink jet recording sheet using ink in which oil-soluble dye is dissolved in solvent, light An image-receiving sheet corresponding to a photosensitive pressure-sensitive donor sheet using microcapsules containing a polymerizable monomer and a colorless or colored dye or pigment is included.

A common feature of these recording sheets is that the ink is in a liquid state at the time of recording. The liquid ink permeates or spreads in the depth direction or the horizontal direction of the ink receiving layer of the recording sheet until it hardens, solidifies or fixes. The above-mentioned various recording sheets require absorptivity according to each system, and there is no limitation even if the inkjet recording sheet of the present invention is used as the above-mentioned various recording sheets. Furthermore, the ink jet recording sheet of the present invention can be used as a recording sheet for heating and fixing an electrophotographic recording toner widely used in a copying machine, a printer, and the like.

[0025]

The ink jet recording sheet of the present invention is a finely coated ink jet recording sheet, the recording surface of which is coated on the pulp fiber surface along the pulp fiber in the entangled state of the base paper. The shape of the pulp fiber coated on the recording surface can be visually observed with a scanning electron microscope, and the surface coverage of the pulp fiber surface on the recording surface is 7%.
It is characterized by being at least 0%, has no ink bleeding unevenness, and has excellent ink absorbability. This is because when ink is applied to the recording surface of the recording sheet, the ink does not spread in the recording surface direction,
This is because the ink penetrates into the surface coating surface and the excess ink penetrates in the thickness direction of the base paper, so that a recording dot shape close to a perfect circle can be obtained. Further, an ink jet recording sheet having high density and sharpness of a recorded image can be obtained.

[0026]

EXAMPLES The present invention will be described below with reference to examples of the present invention, but the present invention is not limited to these examples.
Further, “parts” and “%” shown in Examples are parts by weight and% by weight unless otherwise specified. In addition, about the ultrafine particle inorganic pigment, although it was used as an aqueous dispersion, all were shown by the solid content.

Example 1 [Preparation of base paper] LBKP83 having a freeness of 450 mlcfs
Pulp slurry consisting of 8 parts of NBKP having a freeness of 480 mlcsf, 0.8 part of cationic starch, 0.4 part of sulfuric acid band, 9 parts of kaolin, and 0.1 part of alkyl ketene dimer.
One part was added to adjust the pH of the pulp slurry to 8.2, paper-dried with a Fourdrinier paper machine, and machine calendered to produce a base paper having a basis weight of 85 g / m ² . Note that the prepared paper had a Steckigt sizing degree of 25 seconds.

[Preparation of Inkjet Recording Sheet] On the base paper prepared as described above, colloidal silica (Snowtex-YL, manufactured by Nissan Chemical Co., Ltd.
100 parts of primary particle diameter (50 to 80 nm), polyvinyl alcohol (PVA117, manufactured by Kuraray) 30 as an adhesive
Parts, an aqueous dispersion having a solid content concentration of 10% and containing 30 parts of a cationic resin (polyfix 601; cation charge amount: 6.9 meq./g, manufactured by Showa Polymer Co., Ltd.) as a dye fixing agent as a main component by a rod coater. It was applied to a dry solid content of 1 g / m ² , dried, and calendered to produce an ink jet recording sheet.

Example 2 100 parts of cationic colloidal silica (Snowtex-AK (3), manufactured by Nissan Chemical Industries, primary particle size 10 to 20 nm) were added to the base paper prepared in Example 1, and polyvinyl alcohol (PVA117) was used as an adhesive. Kuraray) 30 parts,
Cationic resin (SUMIREZ Resin 1
001, cation charge 3.5 meq. / G, manufactured by Sumitomo Chemical Co., Ltd.) An aqueous dispersion containing 30 parts as a main component and having a solid content of 10% is applied using a rod coater to a dry solid content of 2 g / m ² , dried and calendered. Thus, an ink jet recording sheet was prepared.

Example 3 The base paper prepared in Example 1 was coated with alumina hydrate (Cataloid AS-3, manufactured by Sekiyu Kasei Kogyo Co., Ltd., having a primary particle diameter of about 10 n).
m) 100 parts, polyvinyl alcohol (P
VA117, manufactured by Kuraray Co., Ltd.) and 30 parts of a cationic resin (Polyfix 601; cation charge amount: 6.9 meq./g, manufactured by Showa Polymer Co., Ltd.) as a dye fixing agent The aqueous dispersion is coated using an air knife coater so as to have a dry solid content of 5 g / m ² ,
After drying and calendering, an ink jet recording sheet was prepared.

Example 4 The solid concentration of the aqueous dispersion used in Example 3 was adjusted to 10%, and the dry solid content of the base paper of Example 1 was adjusted to 0.5 g / m ² using a size press. Coating, drying and calendering were performed to prepare an ink jet recording sheet.

Example 5 The solid content of the aqueous dispersion used in Example 3 was set to 10%, and the base paper of Example 1 was used to obtain a dry solid content of 2 g / m ² using a gate roll coater. Coated, dried and calendered as described above to produce an ink jet recording sheet.

Comparative Example 1 The base paper prepared in Example 1 was provided with colloidal silica (Snowtex PST-3, manufactured by Nissan Chemical Industries, having a primary particle size of 300).
100 parts, 30 parts of polyvinyl alcohol (PVA117, manufactured by Kuraray Co., Ltd.) as an adhesive, and a cationic resin (Polyx601, cation charge amount of 6.9 meq./g, manufactured by Showa Polymer Co., Ltd.) as a dye fixing agent 30 An aqueous dispersion containing 10 parts by weight as a main component and having a solid content of 10% was applied using a rod coater to a dry solid content of 2 g / m ² , dried, and calendered to prepare an ink jet recording sheet.

Comparative Example 2 Silica (Nipsil E22) was added to the base paper prepared in Example 1.
0A, manufactured by Nippon Silica Industry, average particle size 1.0 μm) 10
0 parts, polyvinyl alcohol (PVA11) as an adhesive
7, Kuraray Co., Ltd.) 30 parts, cationic resin (polyfix 601, cationic charge amount 6.9 m) as a dye fixing agent
eq. / G, manufactured by Showa Polymer Co., Ltd.) An aqueous dispersion containing 30 parts as a main component and having a solid content of 10% was applied using a gate roll coater to a dry solid content of 2 g / m ² and dried.
An ink jet recording sheet was prepared by calendar finishing.

Comparative Example 3 The aqueous dispersion used in Comparative Example 2 was adjusted to have a solid content of 15%, and the base paper of Example 1 was used to apply a dry solid content of 5 g / m ² using an air knife coater. Work, dry,
An ink jet recording sheet was prepared by calendar finishing.

Comparative Example 4 The base paper produced in Example 1 was directly used as an ink jet recording sheet of Comparative Example 3.

The ink jet recording sheets prepared in Examples 1 to 5 and Comparative Examples 1 to 4 were evaluated based on the following methods. The results are shown in Table 1.

[Ink Absorption] The ink absorption and the sharpness of the image are determined by the boundaries between the solid printing portions, for example, red printing (magenta + yellow) and green printing (cyan + yellow).
The degree of bleeding of the ink at the boundary portion was visually determined. The case where the red printed portion and the green printed portion did not overlap and were separated was regarded as good characteristics, and the case where the overlap became large and became a black line was regarded as poor characteristics. Those with poor ink absorption are
Since image quality (image clarity) is significantly impaired, even if other characteristics, for example, image density and the like are good, it has no meaning. As evaluation criteria, A shows good characteristics, B shows good results in practically acceptable range, C shows practical problems, and D shows poor characteristics.

[Image Density] The image density was measured by using a reflection densitometer (Macbeth RD91)
8; manufactured by Macbeth Corporation). The higher the numerical value is, the higher the image density is and the better the image density is.

[Surface Coverage of Recording Surface] The surface coverage of the recording surface (%) was determined by taking an X-ray image of the metal element of the material used on the pulp fiber surface of the ink jet recording sheet using a scanning electron microscope. The surface coverage of the pulp fiber surface was measured as an area ratio using an image analyzer.

[Dot Shape Factor] Using an ink-jet printer (IO-720: manufactured by Sharp Corporation), a single color dot made of black ink is printed, and the dot length A and the dot area A are printed by an image analyzer. Was measured, and a dot shape coefficient C defined by the following equation 1 was calculated. In the case where the dot shape coefficient C is 1.0, the larger the distance from the 1.0 as a perfect circle, the more irregular the dot shape due to dot bleeding or the like.

[0042]

C = L ² / (4π × A) where C is the dot shape factor, L is the perimeter of the dot, A
Represents the area of the dot.

[0043]

[Table 1]

From the results shown in Table 1, the ink jet recording sheets of Examples 1 to 5 and Comparative Examples 1 to 4 have a small particle diameter of the ultrafine inorganic pigment used and a low surface coverage. The results were all within the range of the present invention, and all were good in ink absorption, sharpness, and image density. Further, the dot shape coefficient was small, indicating a recording dot shape close to a perfect circle. On the other hand, in Comparative Examples 1 to 3,
Due to the large particle size used, the surface coverage was low, the image density was low, the dot shape factor was large, and the results were poor.
In Comparative Example 3, although the coating amount was as large as 5 g / m ² , the surface coverage was low due to the large particle size of the inorganic pigment used. In particular, comparing Example 2, Example 5, Comparative Example 1, and Comparative Example 2, it was found that
Although the coating amount was the same as g / m ² , it was shown that the covering ratio to the pulp fiber was poor depending on the particle size of the inorganic pigment used.

[0045]

The ink jet recording sheet of the present invention is
It has a recording surface formed by surface coating the pulp fiber surface of the base paper surface with a composition mainly composed of ultrafine inorganic pigment, and the pulp fiber shape coated on the recording surface can be visually recognized by an electron microscope,
In addition, when the surface coverage is 70% or more, the ink jet recording sheet is free from ink bleeding unevenness, has excellent ink absorbability, has high image density and sharpness, and has a recording dot shape close to a perfect circle.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-27976 (JP, A) JP-A-2-188287 (JP, A) JP-A-63-13776 (JP, A) JP-A-60-1985 63191 (JP, A) JP-A-2-274587 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/00 B41J 2/01 D21H 19/38

Claims (1)

(57) [Claims] In an ink jet recording sheet, a recording surface of the recording sheet is formed along a surface of a pulp fiber in a state of being entangled with a base paper surface, and has a primary particle diameter of 100 nm or less.
Surface with composition mainly composed of ultra-fine inorganic pigment
The recording surface having a coating amount of 0.5 to 5 g / m ² on the coated surface, wherein the shape of the pulp fiber coated on the recording surface can be visually recognized by a scanning electron microscope; An ink jet recording sheet, characterized in that the surface coverage of the pulp fiber coated with is 70% or more.