JPH0717127A - Ink jet recording sheet - Google Patents

Abstract

PURPOSE:To provide a thinly coated type ink jet recording sheet excellent in ink absorbency, imparting high image density or sharpness and obtaining a recording dot having an almost circular shape. CONSTITUTION:An ink jet recording sheet is obtained by applying a coating soln. for an ink receiving layer containing ultrafine granular inorg. pigment with a primary particle size of 100nm or smaller to raw paper containing 3-15% of a filler whose surface has been treated with a cationic water-soluble polymer, using modified rosin for neutral paper and having water absorption due to a Cobb method of 10-15g/m<2>.

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 specifically, it has excellent ink absorbency, little ink bleeding unevenness, and high density and sharpness of recorded images. The handling relates to an ink jet recording sheet of a slightly coated type, which is closer to high quality paper.

[0002]

2. Description of the Related Art In recent years, the number of cases in which paper is manufactured in a neutral region has been increasing for the purpose of improving whiteness and opacity by using calcium carbonate, and improving storage stability of paper. When producing paper in the neutral range, conventional rosin sizing agents that perform well in an acidic atmosphere and in the presence of a sulfuric acid band cannot be used, and instead, neutral sizing agents are used.

Here, as a neutral sizing agent, an alkyl ketene dimer (hereinafter abbreviated as AKD) is used because it is easy to handle or excellent sizing property can be obtained by adding a small amount.
The aqueous dispersion of is widely used for coated base paper and fine paper. However, the paper using AKD also has drawbacks that it becomes slippery, the surface free energy becomes small, and the toner fixing failure of PPC and laser printer is caused.

Furthermore, in recent years, rosin has been improved,
Rosin sizing agents are commercially available that exhibit sizing effects even in a neutral papermaking atmosphere.

The ink jet recording system is one in which minute droplets of ink are ejected according to various operating principles to record images, characters and the like on an ink jet recording sheet, but it is easy to achieve high speed, low noise and multicolor. Therefore, it is rapidly spreading. Further, an image obtained by a multicolor ink jet system is being widely applied to the full-color image recording field because it can obtain a recording comparable to that of the multicolor printing by the plate making system or the printing by the color photographic system. .

As the recording sheet, it is impossible to sufficiently bring out the performance of high-speed and high-definition monochrome and full-color ink jet recording apparatus with high-quality paper or coated paper used for ordinary printing or writing. It was In particular, full-color inkjet recording sheets
Coated type is predominant because more stringent quality is required for repeated striking.

In order to satisfy the characteristics required as an ink jet recording sheet, Japanese Examined Patent Publication (Kokoku) No. 3-26665 discloses a base paper having a Steckigt sizing degree of 4 seconds or less based on a basis weight of 60 g / m ² and fine silica particles. An example of an inkjet recording sheet provided with a coating layer containing a water-soluble polymer binder is disclosed, and JP-A-59-38087 discloses an ink absorption layer on a substrate having a size degree of 0 to 10 seconds. An example of an ink jet recording material provided with is disclosed in JP-A-59-9.
Japanese Patent No. 516 discloses an example of an ink jet recording sheet in which a base paper having a Steckigt size degree of 0 to 5 seconds is impregnated with polyvinyl pyrrolidone or the like.

Further, as an ink jet recording sheet having high ink absorbency and capable of obtaining a good recording dot shape, there is JP-A-60-63191. The publication is characterized in that the recording material (inkjet recording sheet) has a surface layer in which a filler and a fibrous material are mixed.

Further, as a means for improving the printing quality of an ink jet recording sheet, Japanese Patent Laid-Open No. 165574/1989 discloses that a styrene / acrylic acid copolymer is coated on a base paper containing 16% ash content. A method for producing paper having a human sizing degree of 10 seconds or more, JP-A-3-133685
In the publication, in order to increase the resolving power and the ink absorption speed, a method of coating silica with a large oil absorption amount on the surface of paper,
It has acquired the performance of an inkjet recording sheet.

The ink jet recording system has high speed, low noise, easy multicoloring, no development-fixing is required, and a recording comparable to multicolor printing by plate making system or printing by color photographic system can be obtained. Due to the characteristics of the above, it is rapidly spreading in various applications such as recording devices for various figures including Chinese characters and full-color images.

As the form of the ink jet recording sheet, a plain paper type represented by so-called high-quality paper, PPC paper, bond paper and the like and paper such as high-quality paper, synthetic paper, synthetic resin film and the like are used to receive ink. It is roughly classified into a coating type provided with a layer, but with the improvement of the performance of the ink jet recording apparatus and the expansion of the application such as high speed / high definition or full color of the apparatus, the recording sheet is also As a result of the demand for higher performance, the color type ink jet recording sheet is mainly the coat 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 are high coating type inkjet recording sheets of 20 g / m ² or more. Especially in recent years,
There is a demand for a low coating type which is preferable for handling, and a fine coating type which has a coating amount of 0.5 to 5 g / m ² which is closer to that of plain paper.

However, in the case of color recording, yellow,
Not only single-color recording of magenta, cyan, and black but also double-color recording in which these colors are overlapped, an extremely large amount of ink adheres. As a result, in the slightly coated type, the coating layer (ink receiving layer) cannot absorb the ink completely,
It has become necessary to use a relatively low size base paper to absorb some of the deposited ink on the support base paper itself.

[0014]

As described above, when the ink receiving layer has a low coating amount, a base paper having a low size is used to absorb a part of the adhered ink in the support. However, since the ink receiving layer coated on the support is not uniformly coated on the indented concavities and convexities of the pulp fiber on the surface, the exposure of the pulp fiber is in a serious state.
Therefore, the deposited ink penetrates into the support, that is, the base paper along the exposed pulp fibers without forming recording dots having a desired shape on the surface of the ink receiving layer, and the recording dots spread and spread. It will take on a shape. In other words, the recorded image lacks sharpness.

An object of the present invention is to provide a fine coating type ink jet recording sheet even with an ink jet recording sheet, which has excellent ink absorbency without uneven bleeding of ink, high density and sharpness of recorded image, and true The purpose of the present invention is to obtain an inkjet recording sheet from which recording dots close to a circle can be obtained.

[0016]

As a result of intensive studies in view of the above, the inventors of the present invention have found that the lateral diffusion of ink is appropriate, the periphery of dots is smooth, and multicolor printing is performed. The present invention has led to the invention of an ink jet recording sheet that does not overflow and bleed, has high ink absorption, high printing density, and bright and vivid color. That is, the ink jet recording sheet of the present invention contains 3 to 15 wt% of calcium carbonate or kaolin alone or in combination as a filler, and uses a modified rosin for neutral papermaking as an internal sizing agent for papermaking. In accordance with JIS P8140
Water absorption by the Cobb method of 10 to 15 g / m ² and a surface of the base paper coated with an ink receiving layer coating liquid containing an ultrafine inorganic pigment having a primary particle diameter of 100 nm or less. And an inkjet recording sheet.

In the ink jet recording sheet of the present invention, the coating amount of the ultrafine particle inorganic pigment is 0.3 to 3.0 g / m.
² , wherein the water-soluble polymer is contained in the ink receiving layer coating liquid in a ratio of 10 to 90% by weight with respect to the ultrafine particle inorganic pigment.

The ink jet recording sheet of the present invention will be described in detail below. From the characteristics of the inkjet recording sheet, the sizing degree of the base paper has a great influence on the ink absorption speed and the resolution. For example, in the case of color printing in which colors are expressed by mixed colors, it is necessary that the first color ink be absorbed or hardly remain on the surface before the second color is printed, which is one of the important characteristics. It has become one. Size degree (water absorption) by Cobb method is 10 g / m ²
If the size of the paper is smaller than the above, the absorption speed of the ink will be slow and the resolution of the first color will be good, but the ink of the second color will overflow and bleed, and the substantial resolution will be reduced. Further, printing unevenness occurs, which is not always satisfactory as an inkjet recording sheet.

In the case of weak size paper having a sizing degree (water absorption) of more than 15 g / m ² by the Cobb method, the absorption speed of the water-based ink is high and the absorption capacity is increased, but the ink is XY.
As a result of penetrating in the direction and inside the base paper layer, the print density, resolution and chromaticity decrease.

As described above, although it is possible to control some parts depending on the size of the base paper, it has been found that it is impossible to control the color properties and dot shape (bleeding) in multicolor printing.

It has been found that the concentration unevenness caused by the absorption unevenness can be improved by subjecting the filler to a protective colloid treatment with an anionic or cationic water-soluble polymer. However, the use of an anionic water-soluble polymer is not preferable because the inside of the papermaking system is disturbed and the size is hard to develop.

Further, by coating an ink receiving layer composition mainly composed of ultrafine particle inorganic pigments having a primary particle diameter of 100 nm or less, the optical density and chromaticity are improved and, in addition, absorption of water-soluble ink is achieved. In order to control the bleeding and the concentration, it was found that it is effective to apply a water-soluble polymer such as oxidized starch, PVA or modified PVA and a surface sizing agent together, and the present invention was completed. It was

The modified rosin for neutral papermaking used in the present invention is an emulsion-type sizing agent obtained by emulsifying a conventionally used rosin or reinforced rosin with a protective colloid consisting of a water-soluble polymer. 54-11035, 60-161472, 63-1201.
Examples thereof include sizing agents as disclosed in Japanese Patent Publication No. 98 and the like.

The cationic water-soluble polymer used in the present invention is a tertiary amine or a quaternary ammonium base,
Vinyl trimethyl ammonium chloride monomer, 2
-Polyacrylamide containing 5% by weight or more of a cationic monomer such as methacryloyloxyethyltrimethylammonium chloride monomer, N-acrylamidoethyltrimethylammonium chloride monomer, acrylamide / diallylamine copolymer monomer, sodium polyacrylate, sodium alginate, hydroxymethyl Examples thereof include modified products such as cellulose, methyl cellulose and polyvinyl alcohol, or derivatives thereof.

The filler surface-treated with the cationic water-soluble polymer of the present invention is a surface-treated filler obtained by adding 1 to 5% by weight of the cationic water-soluble polymer to the pigment and then stirring the mixture. Is. The stirrer in that case may be a pulverizer such as a turbine type disperser having a high shearing force, a sand mill, a colloid mill, or a ball mill, but a sufficient effect can be obtained even if a general agitator without pulverization is used.

The ink jet recording sheet according to the present invention is an ink jet recording sheet used in a drop-on-demand type or continuous type printer, a facsimile and a copying machine using a water-soluble ink.

As the ultrafine particle inorganic pigment used in the present invention, the following can be exemplified. 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 can be mentioned, and it is more preferable if the primary particles are porous, but even if they are non-porous, they agglomerate at the time of preparing the coating solution or further agglomerate at the time of drying the coating, and the pulp fiber surface is porous It is preferable that the surface coated surface of is formed. In particular, in the present invention,
It is preferable to coat the pulp fiber itself with an ultrafine particle inorganic pigment having an average particle diameter of several hundredths of the width of the fiber on each pulp fiber on the surface of the raw paper.

As the water-soluble polymer used in the present invention,
For example, polyvinyl alcohol, vinyl acetate, oxidized starch, etherified starch, carboxymethyl cellulose, cellulose derivatives such as hydroxyethyl cellulose, casein, gelatin, soybean protein, silyl modified polyvinyl alcohol, etc .; maleic anhydride resin, styrene-butadiene copolymer, Conjugated diene copolymer latex such as methyl methacrylate-butadiene copolymer; polymer or copolymer of acrylic acid ester and methacrylic acid ester,
Acrylic polymer latex such as polymer or copolymer of acrylic acid and methacrylic acid; vinyl polymer latex such as ethylene vinyl acetate copolymer; or functional group-containing unit such as carboxyl group of these various polymers Polymer latex modified with functional groups; water-based binder such as thermosetting synthetic resin such as melamine resin, urea resin; polymethylmethacrylate, polyurethane resin, unsaturated polyester resin, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, alkyd resin Examples of the binder include synthetic resin binders such as the above, and at least one kind can be used. Also, a cationic resin added for the purpose of fixing a conventionally known dye can be used together.

The pulp used in the base paper of the present invention includes NBKP, LBKP, NBSP, LBSP, GP,
Examples include TMP and waste paper. In use, they are used by mixing several kinds in a ratio according to the purpose.

The ink jet recording sheet of the present invention comprises
It optionally contains fillers such as talc and titanium oxide, dyes, sizing agents, fixing agents, wet paper strength enhancers, dry paper strength enhancers and the like, which are usually used in papermaking.

The composition liquid containing the ultrafine inorganic pigment of the present invention contains a surface sizing agent, a dye, which is a commonly used polymer such as styrene-acrylic acid, olefin-maleic acid, acrylic acid, styrene-maleic acid, etc. A fluorescent whitening agent, a dye fixing agent, a surface strength agent and the like are contained as necessary.

The ink receiving layer coating liquid containing the ultrafine particle inorganic pigment of the present invention is represented by a size press, gaiter coater, bill blade coater, blade metalling size press, bell vapa coater, short dwell coater, etc. on the surface of the base paper. It is possible to coat using various blades, rods, air knives, curtain coaters and the like.

[0033]

The ink jet recording sheet of the present invention exhibits effective characteristics. Although its mechanism is not clearly understood, it is presumed that it is expressed by the following actions. That is, by making the surface of the filler used as a protective colloid with a cationic water-soluble polymer, it promotes the penetration of alcohol and polyethylene glycol used in the solvent of the water-soluble ink.
It is considered that uneven printing density and discoloration of the water-soluble ink do not occur.

[0034]

EXAMPLES The present invention will be described in detail below with reference to examples. The present invention is not limited to the examples.
All parts and% in the following are by weight.
The value indicating the smear amount is the weight after drying unless otherwise specified.

Preparation Example 1 Light calcium carbonate with a solid content of 10% (trade name: TP
121, manufactured by Okutama Kogyo Co., Ltd.) 3 parts of a cationic water-soluble polymer (trimethylammonium chloride methacrylate monomer: vinyl alcohol = copolymer having a composition of 30:70) was added to 100 parts of a solid content of the slurry under stirring,
After continuing stirring until uniform, a pigment surface-treated with a cationic water-soluble polymer was obtained.

Preparation Example 2 The light calcium carbonate added in Preparation Example 1 was converted to kaolin (BELITUNG KAOLIN, ALTER
A pigment surface-treated with a cationic water-soluble polymer was obtained by the same method except that the pigment was changed to ABADI.

Preparation Example 3 Anionic properties were obtained by the same method except that the cationic water-soluble polymer added in Preparation Example 1 was changed to an anionic water-soluble polymer (trade name: Aron T40, manufactured by Toagosei Co., Ltd.). A pigment surface-treated with a water-soluble polymer was obtained.

Preparation Example 4 Anionic water-soluble polymer added in Preparation Example 2 was changed to anionic water-soluble polymer (trade name: Aron T40, manufactured by Toagosei Co., Ltd.) except that the same procedure was followed. A pigment surface-treated with a water-soluble polymer was obtained.

Example 1 Freeness of 380 ml C.I. S. F. LBKP beaten up to 450 ml C. S. F. NB beat up to
10% by weight of light calcium carbonate of Preparation Example 1 by weight of solid content, 1.0% by weight of sulfuric acid band, and modified rosin sizing agent (commercial rosin sizing agent) with respect to pulp solids in which KP was mixed in a weight ratio of 7: 3. Name: NT80, Arakawa Chemical Co., Ltd.) rosin content 0.4%, amphoteric starch (trade name: Cato3210,
0.8% of Oji National Co., Ltd. is added, and the basis weight is 80g.
/ M ² and a water absorption of 13 g / m ² according to the Cobb method were made into paper. Then, 100 parts of cationic colloidal silica (trade name: Snowtex-AK (3), manufactured by Nissan Kagaku Co., Ltd., primary particle size 10 to 20 nm) is added to the paper thus produced, and a water-soluble polymer (trade name: PVA117, as an adhesive). 50 parts by Kuraray Co., Ltd., a cationic resin as a dye fixing agent (trade name: Sumirez Resin 1001, cationic charge amount 3.5)
meq. / G, manufactured by Sumitomo Chemical Co., Ltd.) and coated with an ink receiving layer coating liquid having a solid content concentration of 10% to a dry solid content of 2 g / m ² using a roll coater, and dried to obtain a Beck smoothness. Super calendar processing was performed for 80 seconds to obtain an ink jet recording sheet.

Example 2 The ultrafine inorganic pigment used in Example 1 has an average primary particle size of 65 nm (trade name: Snowtex YL, average particle size 50).
˜80 nm, manufactured by Nissan Kagaku Co., Ltd.), and an inkjet recording sheet was obtained in the same manner as in Example 1.

Example 3 The same method as in Example 1 except that the ultrafine inorganic pigment used in Example 1 was changed to alumina hydrate (Cataloid AS-3, manufactured by Catalysts & Chemicals Industries Co., Ltd., primary particle size: about 10 nm). Thus, an inkjet recording sheet was obtained.

Comparative Example 1 Colloidal silica having an average primary particle diameter of 300 nm of the ultrafine particle inorganic pigment used in Example 1 (trade name: Snowtex PST-3, manufactured by Nissan Kagaku Co., Ltd., primary particle diameter 300 ± 30)
nm) was used to obtain an inkjet recording sheet in the same manner as in Example 1.

Comparative Example 2 The ultrafine inorganic pigment used in Example 1 had an average particle size of 1.
Other than 0 μm silica (trade name: Nipsil E220A, manufactured by Nippon Silica Industry Co., Ltd., average particle size 1.0 μm)
An inkjet recording sheet was obtained in the same manner as in Example 1.

Comparative Example 3 The base paper prepared in Example 1 was used as it is as an ink jet recording sheet of Comparative Example 3.

Example 4 The coating amount of the ink receiving layer coating liquid used in Example 1 was 0.5 g.
An ink jet recording sheet was obtained by the same method as in Example 1 except that / m ² was used.

Example 5 The coating amount of the ink receiving layer coating liquid used in Example 1 was 0.9 g.
An ink jet recording sheet was obtained by the same method as in Example 1 except that / m ² was used.

Example 6 The coating amount of the ink receiving layer coating liquid used in Example 1 was 5.4 g.
An ink jet recording sheet was obtained by the same method as in Example 1 except that / m ² was used.

Example 7 An ink jet recording sheet was obtained in the same manner as in Example 1 except that 5 parts of the water-soluble polymer in the ink receiving layer coating liquid used in Example 1 was blended.

Example 8 An ink jet recording sheet was obtained in the same manner as in Example 1 except that 95 parts of the water-soluble polymer in the coating liquid for the ink receiving layer used in Example 1 was blended.

The ink jet recording sheets prepared in the above Examples and Comparative Examples were evaluated according to the following methods, and the results are shown in Table 1. The water absorption of each of the base papers used was 13 g / m ² .

Further, the water absorption (g / m ² ) is JIS P8.
The measurement was performed according to the Cobb method according to 140, but the immersion time was 10 seconds.

[Dot shape factor] An ink jet printer (IO-720: manufactured by Sharp Corporation) is used to print a single color dot of black ink, and an image analyzer (Luzex 500 is used as an evaluation of ink bleeding.
0, manufactured by Nireco Co., Ltd.), the perimeter of the dot and the area of the dot were measured, and the shape factor SF2 was calculated. Shape factor SF
2 is an index that is closer to 100 as it is closer to a perfect circle, and is practically no problem if it is 250 or less.

[Ink Absorption and Chromaticity] Ink absorption and image sharpness (resolution) are determined by the boundary between solid color solid printing portions, for example, red printing (magenta + yellow) and green printing (cyan + yellow). The degree of ink bleeding at the boundary was visually determined. When the red printed portion and the green printed portion did not overlap and were separated, the characteristics were good, and when the overlapping was large and a black line was formed, the characteristics were bad. A substance having poor ink absorbability remarkably impairs image quality (image sharpness), so that it does not make any sense even if other properties such as image density are good. As for the color property, the vividness of the color in the above-mentioned heavy color portion was visually evaluated. In addition, as an evaluation standard,
A is good in characteristics, B is good in a practically acceptable range, C is practically problematic, and D is poor in characteristics.

[Image Density] The image density was measured by using a reflection densitometer (trade name: Macbeth RD918, manufactured by Macbeth Co., Ltd.) on a portion solidly printed with black ink. The higher the value, the higher the image density and the better, but normally, 1.20 or more is good.

[0055]

[Table 1]

In Examples 1 to 8, it was found that the optical density and color chromaticity can be improved by using an ultrafine particle inorganic pigment of 100 nm or less. On the other hand, Comparative Examples 1 and 2
In the case of using a pigment having a large particle size, the optical density and chromaticity deteriorate. Further, in Example 7, when the blending ratio of the water-soluble polymer was less than 5%, there was no problem in characteristics, but powder drop was likely to occur. In Example 8, although it was more than 95%, the chromaticity tended to deteriorate slightly.

Example 9 The amount of light calcium carbonate added in Example 1 was 3
%, Except that the amount of rosin sizing agent added was 0.4%,
An inkjet recording sheet was obtained in the same manner as in Example 1.

Example 10 The light calcium carbonate added in Example 1 was replaced with kaolin in Preparation Example 2, the amount added was 3%, the amount of rosin sizing agent was 0.3%, and sodium carbonate was added for pH adjustment. 0.4
An ink jet recording sheet was obtained in the same manner as in Example 1 except that the addition amount was 0.1%.

Example 11 The light calcium carbonate added in Example 1 was replaced with kaolin in Preparation Example 2, the addition amount was 10%, the addition amount of rosin sizing agent was 0.3%, and sodium carbonate was added for pH adjustment. 0.
An inkjet recording sheet was obtained in the same manner as in Example 1 except that 4% was added.

Example 12 The amount of light calcium carbonate added in Example 1 was changed to 15
%, Except that the amount of rosin sizing agent added was 0.4%,
An inkjet recording sheet was obtained in the same manner as in Example 1.

Example 13 The light calcium carbonate added in Example 1 was replaced with kaolin in Preparation Example 2 in an amount of 15%, a rosin sizing agent was added in an amount of 0.4%, and sodium carbonate was added for pH adjustment. 0.
An inkjet recording sheet was obtained in the same manner as in Example 1 except that 5% was added.

Comparative Example 4 The light calcium carbonate added in Example 1 was not added,
An inkjet recording sheet was obtained in the same manner as in Example 1 except that the amount of rosin sizing agent added was 0.3%.

Comparative Example 5 The procedure was carried out except that the light calcium carbonate added in Example 1 was replaced with untreated light calcium carbonate, the addition amount was 10%, and the addition amount of the rosin sizing agent was 0.4%. An inkjet recording sheet was obtained in the same manner as in Example 1.

Comparative Example 6 The light calcium carbonate added in Example 1 was replaced with untreated kaolin, the addition amount was 10%, the addition amount of the rosin sizing agent was 0.4%, and sodium carbonate was used for pH adjustment. An inkjet recording sheet was obtained in the same manner as in Example 1 except that 0.4% was added.

Comparative Example 7 The amount of the light calcium carbonate added in Example 1 was 20.
%, Except that the amount of rosin sizing agent added was 0.7%,
An inkjet recording sheet was obtained in the same manner as in Example 1.

Comparative Example 8 The light calcium carbonate added in Example 1 was replaced by kaolin in Preparation Example 2, the addition amount was 20%, the rosin sizing agent was 0.7%, and sodium carbonate was used for pH adjustment. 0.
An inkjet recording sheet was obtained in the same manner as in Example 1 except that 4% was added.

Comparative Example 9 The addition amount of the light calcium carbonate added in Example 1 was 10
%, Except that the amount of rosin sizing agent added was 1.0%,
An inkjet recording sheet was obtained in the same manner as in Example 1.

Comparative Example 10 The light calcium carbonate added in Example 1 was replaced with kaolin in Preparation Example 2 in an amount of 10%, a rosin sizing agent in an amount of 1.0%, and sodium carbonate for pH adjustment. 0.
An inkjet recording sheet was obtained in the same manner as in Example 1 except that 4% was added.

Comparative Example 11 Light calcium carbonate added in Example 1 was added in an amount of 10
%, Except that the amount of rosin sizing agent added was 0.2%,
An inkjet recording sheet was obtained in the same manner as in Example 1.

Comparative Example 12 The light calcium carbonate added in Example 1 was replaced with kaolin in Preparation Example 2, the addition amount was 10%, the addition amount of rosin sizing agent was 0.2%, and sodium carbonate was used for pH adjustment. 0.
An inkjet recording sheet was obtained in the same manner as in Example 1 except that 4% was added.

Comparative Example 13 Example 1 except that the light calcium carbonate added in Example 1 was replaced with the light calcium carbonate of Preparation Example 3 and the addition amount was 10% and the addition amount of the rosin sizing agent was 1.4%. An ink jet recording sheet was obtained by the same method as described above.

Comparative Example 14 The light calcium carbonate added in Example 1 was replaced with kaolin in Preparation Example 4, the amount added was 10%, the amount of rosin sizing agent was 1.4%, and sodium carbonate was added for pH adjustment. 0.
An inkjet recording sheet was obtained in the same manner as in Example 1 except that 4% was added.

The above results are summarized and the results are shown in Table 2.

[0074]

[Table 2]

From the results shown in Table 2, in the ink jet recording sheets of Examples 9 to 13, 3 to 15% of the filler treated with the cationic water-soluble polymer was internally added, the water absorption and the coating liquid of the ink receiving layer were applied. Both the amounts were within the range of the present invention, and all were good in ink absorbency, sharpness and image density.
Also, the dot shape coefficient was small and the recording dot shape was close to a perfect circle. On the other hand, Comparative Example 4 is a base paper containing no filler, and since it is not coated, the colorability is very poor. Comparative Examples 5 and 6 show that uneven absorption occurs as a result of using the untreated filler. In Comparative Examples 7 and 8, 20% of the filler was internally added, and it is shown that the unevenness of absorption does not occur but the chromaticity is deteriorated. In Comparative Examples 9 to 12, the water absorption of the base paper is changed depending on the addition amount of the sizing agent. As a result, it is shown that the uneven absorption does not occur, but the absorption speed is low in the strong size base paper having a low water absorption, and the color property is poor in the weak size paper having a high water absorption. Comparative Examples 13 and 14
When using a filler treated with an anionic polymer, the papermaking system was disturbed, and it was necessary to add a sizing agent as much as 1.4% based on the solid content of pulp, which was not preferable in terms of cost. did.

[0077]

The ink jet recording sheet of the present invention is
It consists of a base paper containing calcium carbonate and kaolin treated with a cationic water-soluble polymer, and an ink-receiving layer mainly composed of ultrafine inorganic pigments having a specific particle size. It is an inkjet recording sheet which has no ink absorption, is excellent in ink absorption, has high image density and sharpness, and has a recording dot shape close to a perfect circle.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroo Kaiji 3-4-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Paper Mills Co., Ltd.

Claims (2)

[Claims] 1. A filler containing 3 to 15% by weight of calcium carbonate or kaolin surface-treated with a cationic water-soluble polymer, alone or in combination, and using a modified rosin for neutral papermaking as an internal sizing agent. An ink containing a superfine inorganic pigment having a water absorption of 10 to 15 g / m ² according to the Cobb method based on JIS P8140 and having a primary particle diameter of 100 nm or less on the surface of the base paper. An inkjet recording sheet characterized by being coated with a receiving layer coating liquid. 2. The coating amount of ultrafine inorganic pigment is 0.3 to
^{3. The amount} of water-soluble polymer is 3.0 g / m ² , and the water-soluble polymer is contained in the ink receiving layer coating liquid in a ratio of 10 to 90% by weight with respect to the ultrafine inorganic pigment. The inkjet recording sheet described.