JP3371545B2 - Inkjet recording paper - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording material, and more particularly to a water-based ink jet recording sheet having characteristics such as excellent color development, dot shape and water resistance.

[0002]

2. Description of the Related Art The performance of ink jet printers using water-based inks, especially the improvement in printing speed, resolution, saturation, etc., enables high-speed absorption even on recording materials,
Higher characteristics such as high absorption capacity and regular ink bleeding are required, and so-called coated paper having an ink-receptive coating layer on the surface has been developed. For example, Japanese Patent Application Laid-Open No. 62-158084 discloses a method for producing an inkjet recording medium having high water-based ink absorbency, color reproducibility and color density, which uses fine particle synthetic silica. That is, in order to meet the above-mentioned required characteristics, it is usually practiced to provide a coating layer containing a white pigment having excellent liquid absorption property such as fine particle synthetic silica as a main component on the surface of a base paper containing cellulose pulp as a main component. Has been done.

Recently, ink jet recording paper has been increasingly used as an office document, and a sheet has been desired more than a continuous paper such as a conventional foam paper, and the running property of the paper when feeding it to a printer is important. It has become a challenge. Also,
Ink jet recording paper is used not only as an office document indoors but also because it can be easily printed, it tends to be used outdoors for posting, and the durability of the paper, especially the water resistance of the base material is required. When the base material is paper, there is a problem that the base material is torn when wet with rain or the like and cannot be used continuously. However, for example, Japanese Patent Laid-Open No.
Japanese Patent Publication No. 82589 discloses a water-resistant inkjet recording paper in which a sheet made of a monoaxially biaxially stretched film having a multilayer structure containing a polyolefin containing an inorganic pigment as a main component is provided with an ink receptive coating layer. .

For example, in order to use such a film (so-called synthetic paper) for outdoor use, when printing with a printer as a sheet, the sheets are fed in an overlapping manner due to static electricity charged on the sheets, There were problems such as not being sent. Further, although such recording paper rarely emits paper dust or the like from the support, it is easy to be charged, so that dust in the atmosphere is easily adsorbed, which is likely to cause a problem when used in a clean room or the like. JP-A-58-177390
Japanese Patent Laid-Open Publication No. 1993-242242 discloses a recording paper of an electric field control type ink jet system in which ink is charged in a strong electric field and is ejected onto a recording paper provided on a surface of a counter electrode, and a quaternary ammonium salt is used for an ink receiving layer or a support. Type conductive agent, 20
Surface resistance of the ink receiving layer at 9 ℃ and 30% RH is 9 × 10
^An inkjet paper having a resistance of ¹¹ Ω or less is disclosed.

Further, Japanese Patent Application Laid-Open No. 62-183379 discloses an upper-medium type recording paper having a Steckigt sizing degree of 10 seconds or less in a non-electric field acceleration type ink jet system.
There is disclosed an ink jet paper having a surface resistance of 1 × 10 ¹² Ω or less at 20 ° C. and 65% RH and 1 × 10 ¹⁴ Ω or less at 20 ° C. and 20% RH. Since all of these recording papers use the paper as a base material or a recording medium, they have no water resistance and have problems such as tearing when used outdoors. Therefore, an inkjet recording paper that solves these problems has been desired.

[0006]

SUMMARY OF THE INVENTION The present invention is capable of printing high-quality images at high speed by using an ink jet printer using water-based ink, and has no running trouble at the time of printing, and further has high water resistance. It is an object of the present invention to provide an aqueous inkjet recording sheet having the same.

[0007]

DISCLOSURE OF THE INVENTION In view of the above situation, the present inventors have earnestly studied the static electricity charged on base paper and recording paper, and as a result, the biaxial stretching containing a mixture of a polyolefin resin and an inorganic pigment as a main component. An ink-receptive coating layer containing an inorganic pigment and a resin as a main component is provided on one surface of a sheet-like support made of a resin film having a multilayer structure, and a back layer containing a conductive agent and a resin as a main component is provided on the opposite surface, The surface electric resistance of the back layer is 9 × 1 under the conditions of 20 ° C. and 65% RH.
By below 0 ¹⁰ Omega, an inkjet
When printing with a printer , a high-quality and highly colored image can be obtained, and further, paper feeding troubles during printing can be eliminated, and the present invention has been completed.

That is, the ink jet recording paper according to the present invention contains a mixture of a polyolefin resin and an inorganic pigment as a main component, and has a multi-layered sheet-like support composed of a plurality of resin films stretched in longitudinal and / or transverse directions. A body and an ink-receptive coating layer formed on one surface of the sheet-shaped support and containing an inorganic pigment and a resin as main components,
The ink-receptive coating layer is made of a fine particle synthetic system as an inorganic pigment.
Comprises Rica, is formed on the opposite surface of said sheet support, and a back layer containing a conductive agent and resin as a main component, the surface electrical resistance of the surface having the back layer, 20
It is characterized in that it is 9 × 10 ¹⁰ Ω or less under conditions of ° C and 65% RH.

To explain the present invention in more detail, a sheet-like support made of a biaxially stretched multi-layered resin film containing a mixture of a polyolefin resin and an inorganic pigment used in the present invention as a main component is generally a synthetic paper. It is a type of film called "40 to 60", not to mention low humidity conditions.
Even under the condition of about% RH, there was a problem that static electricity was easily charged and papers were easily stuck to each other. Further, the inorganic pigments used in the present invention, especially synthetic silica and the like, originally have a strong function as an insulator, and once they are charged, they are difficult to escape,
In particular, the film-based one had a problem of sticking between the paper due to static electricity. However, by providing a conductive layer containing a conductive agent and a resin as a main component on the back surface of the synthetic paper provided with such an ink-receptive coating layer, the back surface charge is reduced, and the printer when used in a single sheet It was found that troubles such as double feeding at the time of paper feeding can be prevented.

Furthermore, by incorporating a conductive agent in the ink-receptive coating layer containing an inorganic pigment and a resin as main components, surface charging is also reduced and the surface electrical resistance is 20 ° C.
By setting it to 9 × 10 ⁹ Ω or less under the condition of 65% RH ,
It has been found that there are further effects even in the case of low humidity.
In the electric field control type inkjet method, both ink and recording paper are charged, so if the surface electric resistance of the ink receptive coating layer is high, the ink droplets ejected from the nozzles may reach a predetermined position when the environmental humidity decreases. Instead, it is known that a so-called splashing phenomenon occurs in which the image is scattered around and the resolution is lowered, or the periphery is soiled.

The present inventors have found that this splashing phenomenon also occurs in the non-electric field control type ink jet system, and the cause is still the charging of the ink and the recording paper.
For example, as a non-electric field control type inkjet system, in a so-called thermal type inkjet system in which ink is heated to expand bubbles in the ink and eject ink droplets by the pressure generated at that time, friction occurs when the ink moves through a thin nozzle. It is considered that the toner is charged by the like and is ejected onto the recording paper.
At that time, if the recording paper is not conductive, its charge is retained,
Since the next ink droplets to be ejected are charged to the same potential,
It will be difficult to get close to the first ink drop and will be scattered around. However, this effect is secondary and
It is not the main effect of the present invention.

The pigment used in the ink-receptive coating layer used in the present invention preferably contains an inorganic pigment as a main component, which is porous, has high ink absorbency, and enables clear color development. As such a pigment, fine particle synthetic silica, zeolite, calcium carbonate, calcium silicate, aluminum hydroxide, calcined clay, kaolin clay, talc, white carbon, organic pigment (plastic pigment), etc. are generally used for paper coating. Examples of such pigments include fine particle synthetic silica. The use ratio of such a pigment is 5 in the total solid content of the coating layer.
It is 0 to 90% by weight. If it is less than 50%, the ink absorbency becomes insufficient, and if it exceeds 90%, the strength of the ink-receptive coating layer may decrease, which is not suitable.

The resin used in the ink-receptive coating layer and back layer of the present invention includes a derivative modified with polyvinyl alcohol and silanol groups, proteins such as casein, starch, and starch derivatives thereof, and styrene-butadiene copolymer. Polymer, conjugated diene polymer latex such as methyl methacrylate-butadiene copolymer, acrylic polymer latex such as polymer or copolymer of acrylic acid ester and methacrylic acid ester, vinyl such as ethylene-vinyl acetate copolymer -Based polymer latex, or modified polymer latex containing functional groups such as carboxyl groups and cationic groups of these various polymers, synthetic resin-based water-based adhesives such as thermosetting resins such as melamine resin and urea resin, maleic anhydride Acid copolymer resin type, polyacrylamide type, polymethylmeta Polymers such as relate type, polyurethane resin type, unsaturated polyester resin type, polyvinyl butyral type, alkyd resin type, and other synthetic resin type adhesives have good adhesion to pigments and good affinity with water-based inks. Therefore, it is preferably used because it improves the liquid absorbing property.

Especially as the resin of the present invention, a polyvinyl alcohol derivative modified with a silanol group is preferable.
Silanolized polyvinyl alcohol is disclosed in JP-A-58-5.
9203 No. urchin I are shown in Japanese, after the vinyl compound containing silicon is copolymerized with vinyl acetate, by saponifying a vinyl acetate unit in the polyvinyl alcohol, silicon-containing monomer units, a silanol group it is obtained by converting each. Since silanolated polyvinyl alcohol specifically and firmly binds to an inorganic pigment such as finely divided synthetic silica, a sufficient coating strength can be realized with a small amount that does not interfere with color development or resolution.

The proportion of the resin used in the ink-receptive coating layer is 10 to 50% by weight, preferably 10 to 40% by weight, based on the total solid content of the coating layer. If it is less than 10%, the adhesive strength will be insufficient, and there is a concern that the strength of the coating layer will decrease. Meanwhile, 5
If it exceeds 0%, the adhesiveness is increased, but the use ratio of the pigment is reduced, and as described above, there is a problem in the ink absorptivity, which is not suitable.

The conductive agent used in the present invention is an inorganic salt such as sodium chloride, lithium chloride, sodium aluminate, sodium phosphate, calcium chloride or magnesium chloride,
Anionic polyelectrolytes such as organic acid salts such as potassium formate and sodium oxalate, polyacrylic acid salts, polymethacrylic acid salts, styrene-maleic acid copolymer salts, polystyrene sulfonic acid salts, phosphoric acid ester salts, and sulfuric acid ester salts. , Poly (vinylbenzyltrimethylammonium chloride), poly (N-methylvinylpyridinium chloride), poly (N, N) dimethyl-3,5-methylenepiperidinium chloride, dimethyldiallylammonium chloride-sulfone-copolymer, etc. Etc. are appropriately selected and used.

The use ratio of these conductive agents in the ink receptive coating layer and the back layer is 10 to 10% of the total solid content of the coating layer.
It is 50% by weight, preferably 10-40% by weight. 10
If it is less than wt%, it is difficult to obtain the effect as a conductive agent, and if it exceeds 50 wt%, it is not worth using and it is not suitable in terms of cost. In addition, pigment dispersants, defoamers, colorants, antioxidants, ultraviolet absorbers, viscosity modifiers, cross-linking agents and the like are appropriately used as additives according to the production conditions, print quality and required performance.

The support film used in the present invention comprises, as a thermoplastic resin, a polyolefin resin such as polyethylene, polypropylene, ethylene-propylene copolymer or ethylene-vinyl acetate copolymer, or one containing them as a main component. To use. As another thermoplastic resin, polystyrene, an acrylic ester copolymer, or the like can be mixed and used. Inorganic fine powder is mixed with this thermoplastic resin to form a film, which is biaxially stretched. In the present invention, it is preferable to use a multilayer film obtained by laminating a plurality of such films as a support. For example, it is effective to use a 2-3 layer film consisting of a base material layer and a double-sided or single-sided paper-like layer, or a 3-5-layer film in which a surface layer is further formed on the paper-like layer on at least one side thereof. .

As the inorganic fine powder to be blended with the thermoplastic resin used in the present invention, calcium carbonate having an average particle size of 20 μm or less, calcined clay, diatomaceous earth, talc, silica and the like are used for the base material layer and the paper-like layer. However, for the surface layer, calcium carbonate, titanium oxide, barium sulfate and the like are preferable. The blending amount of these inorganic fine powders is preferably 8 to 65% by weight. If it is less than 8% by weight, there is not enough paper-like layer,
Absorbency is also insufficient, and on the other hand, when it is 65% by weight or more, the strength is insufficient, which is not preferable. As the biaxially stretched film, a thermoplastic film known as so-called synthetic paper can be used. Such films have a thickness of 1
Generally, a thickness of about 5 to 200 μm is preferable. The basis weight is preferably 10 to 150 g / m ^2, but is not particularly limited.

Known coating equipment such as a bar coater, an air knife coater, a blade coater and a gravure coater is applied to apply the coating material of the present invention. The sheet provided with the ink-receptive coating layer on the base paper can be used as it is as the recording sheet of the present invention, but it can be treated with, for example, a super calendar or a gloss calendar to give the surface smoothness. Is.

The coating amount of the ink absorptive coating layer obtained in the present invention is determined by the end use and does not need to be unnecessarily increased as long as the ink absorptivity, recording characteristics, storability, etc. are satisfied. It is used by appropriately selecting from the range of 10 g / m ² . If the ink-receptive coating layer is less than 3 g / m ² , the ink absorption capacity is insufficient in many cases, and the image runs out, color bleeding occurs, the image becomes blurred, the drying is slow, and the ink adheres to the roll. It gets dirty. In addition, since the amount of ink absorbed by the base paper is large, there is a problem that curling and unevenness are likely to occur. However, when an ink-receptive coating layer having a coating amount of more than 20 g / m ² is provided, the coating layer is too thick to weaken the adhesiveness to paper, which often causes a problem such as clogging of the head nozzle, which further reduces cost. Is also expensive.

[0022]

The present invention will be described in more detail with reference to the following examples, but of course the present invention is not limited thereto. In the following, parts and% mean parts by weight and% by weight.

Example 1 Multi-layered synthetic paper YUPO FPG-110 containing an inorganic pigment
An ink receptive coating layer (hereinafter abbreviated as coating layer) is applied to one side of (thickness 110 μm, made by Oji Oka Synthetic Paper Co., Ltd.) using a test bar coater at a rate of 12 g / m ² and dried. ) Is formed, and 3 g / m ² of paint-2 is similarly formed on the back surface.
Was coated and dried to form a back layer to prepare an inkjet recording sheet. The surface electric resistance of the recording surface was 7 × 10 ⁹ Ω, and the surface electric resistance of the back surface was 4 × 10 ⁹ Ω.

[0024]   Paint-1     Fine particle silica 70 parts       (Trademark: Fine seal, Tokuyama Soda)     Calcium carbonate (Brilliant, Shiraishi Kogyo) 30 parts     Polyvinyl alcohol 30 parts       (Trademark: PVA117, made by Kuraray)   Paint-2     Polyvinyl alcohol 85 parts       (Trademark: K-17, manufactured by Denki Kagaku Kogyo)     Conductive agent       (Trademark: Chemistat 5500, manufactured by Sanyo Chemical Industries) 15 parts

Example 2 An ink jet recording sheet was produced in the same manner as in Example 1 except that the coating material 3 was applied at a rate of 9 g / m ² and dried to form a coating layer. The surface electric resistance of the recording surface was 8 × 10 ¹⁰ Ω and the surface electric resistance of the back surface was 5 × 10 ⁹ Ω.

[0026]   Paint-3     Fine particle silica 100 parts       (Trademark: Fine seal, Tokuyama Soda)     Polyvinyl alcohol 25 parts       (Trademark: PVA117, made by Kuraray)

Example 3 Multi-layer synthetic paper YUPO FPG-95 (thickness: 95 μm, made by Oji Yuka Synthetic Paper) having a multi-layer structure containing an inorganic pigment was coated on one side with a test bar coater at a rate of 15 g / m ² of paint-4. Coating with,
Dry to form a coating layer, and similarly apply coating 5 to the back surface at a rate of ² g / m ² and dry to form a back layer,
An inkjet recording paper was prepared. The surface electric resistance of the recording surface is 3 × 10 ⁸ Ω, and the surface electric resistance of the back surface is 6 × 10 ⁹ Ω.
Met.

[0028]   Paint-4     Fine particle silica 100 parts       (Trademark: Fine seal, Tokuyama Soda)     Polyvinyl alcohol 17 parts       (Trademark: GL-03, made by Japan Synthetic Rubber)     12 parts silanolated polyvinyl alcohol       (Trademark: R-1130, made by Kuraray)     Conductive agent       (Trademark: Chemistat 5500, manufactured by Sanyo Chemical Industries) 20 parts   Paint-5     Oxidized starch 70 parts       (Ace A: made by Prince Corn Starch)     Conductive agent       (Sodium chloride) 30 parts

Comparative Example 1 Paint-1 was applied to one side of the base paper used in Example 1 in a laboratory using a test bar coater at a rate of 10 g / m ² and dried to form a coating layer, and an ink jet was prepared. Recording paper was manufactured. The surface electric resistance of the recording surface was 8 × 10 ¹⁰ Ω, and the surface electric resistance of the back surface was 5 × 10 ¹¹ Ω.

Comparative Example 2 Paint-3 was applied to one side of the base paper used in Example 1 in a laboratory using a test bar coater at a rate of 11 g / m ² and dried to form a coating layer, and an ink jet was prepared. Recording paper was manufactured. The surface electric resistance of the recording surface was 4 × 10 ⁸ Ω, and the surface electric resistance of the back surface was 9 × 10 ¹¹ Ω.

Table 1 shows the evaluation results of these coated papers. The inkjet recording characteristics and the runnability were evaluated by the following methods. Ink jet printer (trademark: Desk Writer-C, HP Co.) was used,
The ink absorption, the vividness of color development, the splashing, and the paper running property were evaluated. In order to evaluate the ink absorbency, the number of seconds until the printed ink dries was measured.
5 seconds or less is indicated by ◯, 6 to 10 seconds is indicated by Δ, and 11 seconds or more is indicated by x. For the vividness of color development, the color development of yellow, magenta and cyan color inks was visually evaluated. Good color development is indicated by O, insufficient color development is indicated by Δ, and defective color is indicated by X. For the splashing, the occurrence of splashing on the printed matter was visually evaluated. Regarding the paper running property, 20 sheets were collectively set in a printer, continuously fed, and the number of running troubles (double feeding, paper jam, etc.) was counted. The surface electric resistance was measured on the basis of the method described in JIS-K-6911 using a high resistance meter manufactured by Hewlett-Packard Co., after moisture conditioning for 24 hours under conditions of 20 ° C. and 65% RH.

[0032]

[Table 1]

As can be seen from Table 1, the ink jet recording sheets obtained in the examples are very excellent in all of ink absorbency, vividness of color development, and paper running property. However, the ink jet recording sheet obtained by the comparative example is inferior in paper running property, although the color development and the ink absorption are the same as those of the example. Further, the ink-receptive coating layer having a small surface electric resistance has less occurrence of splashing.

[0034]

The ink jet recording paper of the present invention is excellent in ink absorbency and color development, and enables ink jet printing with good paper running performance even though synthetic paper is the support. .

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B41M 5/00

Claims (3)

(57) [Claims] 1. A sheet-shaped support having a multi-layered structure, which contains a mixture of a polyolefin resin and an inorganic pigment as a main component and comprises a plurality of resin films stretched in the longitudinal and / or transverse directions, and the sheet-shaped support. And an ink-receptive coating layer containing an inorganic pigment and a resin as a main component , and the ink-receptive coating layer is formed as an inorganic pigment.
Particle synthetic silica, comprising a back layer formed on the opposite surface of the sheet-shaped support, a conductive agent and a resin as a main component, the surface electrical resistance of the surface having the back layer,
An inkjet recording paper, which has a resistance of 9 × 10 ¹⁰ Ω or less under conditions of 20 ° C. and 65% RH. 2. A conductive agent is contained in the ink receptive coating layer.
Surface resistance of the surface having the ink receptive coating layer.
9 × 10 under the conditions of 20 ° C. and 65% RH ⁹ Ω or less
The ink jet recording according to claim 1, wherein
Paper. 3. A resin in the ink-receptive coating layer
Contain silanolated polyvinyl alcohol
The inn according to claim 1 or 2, characterized in that
Cudget recording paper.