JP3325084B2 - 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 is excellent in ink absorbency, has small ink bleeding unevenness, and has high density and sharpness of a recorded image. The handling relates to a finely coated ink jet recording sheet closer to high quality paper.

[0002]

2. Description of the Related Art In recent years, the use of calcium carbonate to improve whiteness and opacity and to improve the preservability of paper has been increasing the production of paper in the neutral region. When producing paper in the neutral region, a conventional rosin sizing agent that performs in an acidic atmosphere and in the presence of a sulfuric acid band cannot be used, and a neutral sizing agent is used instead.

[0003] As a neutral sizing agent, an alkyl ketene dimer (hereinafter abbreviated as AKD) is used because it is easy to handle, or excellent sizing properties can be obtained by adding a small amount.
Is widely used for coating base paper and woodfree paper. However, paper using AKD also has drawbacks in that the paper becomes slippery and the surface free energy becomes small, causing poor toner fixation in PPC and laser printers.

In recent years, rosin has been improved,
A rosin sizing agent that exhibits a size effect even in a neutral papermaking atmosphere is currently being marketed.

The ink jet recording system records images, characters, and the like on an ink jet recording sheet by flying fine droplets of ink according to various operating principles. However, high speed, low noise, and multicolor printing are easy. Because of this, it is spreading rapidly. Furthermore, images obtained by the multi-color ink jet method are being widely applied to the full-color image recording field because they can obtain a record comparable to multi-color printing by a plate making method and printing by a color photographic method. .

As for the recording sheet, it becomes impossible to sufficiently bring out the performance of a high-speed, high-definition monochrome and full-color ink jet recording apparatus with high-quality paper and coated paper used for ordinary printing and writing. Was. In particular, full-color ink jet recording sheets
Coat types are the mainstream because more stringent quality is required for overstrike.

[0007] In order to satisfy the characteristics required for an ink jet recording sheet, Japanese Patent Publication No. 3-26665 discloses that fine silica particles are coated on a base paper having a basis weight of 60 g / m ² and a Steckigt sizing degree of 4 seconds or less. An example of an ink jet recording sheet provided with a coating layer containing a water-soluble polymer binder is disclosed. JP-A-59-38087 discloses an ink-absorbing layer on a substrate having a size of 0 to 10 seconds. JP-A-59-9 discloses an example of an ink jet recording material provided with
No. 516 discloses an example of an ink jet recording sheet obtained by impregnating a base paper having a Stigget size of 0 to 5 seconds with polyvinylpyrrolidone or the like.

Japanese Patent Application Laid-Open No. 60-63191 discloses an ink jet recording sheet having a high ink absorbency and a good recording dot shape. 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.

Further, as a means for improving the printing quality of an ink jet recording sheet, Japanese Patent Application Laid-Open No. 1-165574 discloses a method in which styrene-acrylic acid copolymer is coated on base paper containing 16% ash in paper. A method of using paper having a human size of 10 seconds or more, JP-A-3-133885
In the official gazette, to increase the resolution and ink absorption speed, such as by coating a large amount of oil-absorbing silica on the paper surface,
The performance as an ink jet recording sheet has been obtained.

[0010] The ink jet recording system is high speed, low noise, easy to multicolor, does not require development-fixing, and can provide a recording comparable to multicolor printing by a plate making system or printing by a color photographic system. Due to the characteristics described above, it is rapidly spreading in various applications such as a recording device for various figures including kanji and full-color images.

The form of the ink jet recording sheet is a plain paper type represented by so-called high-quality paper, PPC paper, bond paper and the like, and ink is received on a support such as paper such as high-quality paper, synthetic paper and synthetic resin film. 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 applications, such as a high-speed, high-definition or full-color apparatus, with respect to the recording sheet, As a result of the demand for higher-level characteristics, coat-type ink-jet recording sheets have become the mainstream.

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,
There is a demand for a low-coating type, which is preferable in terms of handling, and among others, a fine-coating type in which a coating amount closer to plain paper is 0.5 to 5 g / m ² .

However, in the case of color recording, yellow,
In addition to monochromatic recording of magenta, cyan, and black, as well as multicolor recording in which these colors are superimposed, the amount of ink adhesion becomes extremely large. As a result, with the fine coating type, the coating layer (ink receiving layer) cannot absorb the ink completely,
It is becoming necessary to use a relatively low size base paper so that the base paper itself of the support absorbs a part of the attached ink.

[0014]

As described above, when the ink-receiving layer has a low coating amount, a part of the ink adhering to the support is absorbed by using a low-size base paper. However, 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 extremely exposed.
For this reason, the adhered ink permeated into the support, that is, the base paper, along the exposed pulp fiber without forming recording dots of 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 an ink jet recording sheet which is a finely coated type ink jet recording sheet, has no ink bleeding unevenness, has excellent ink absorbability, has 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.

[0016]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above, and as a result, it has been found that the ink is suitable for spreading in the horizontal direction, the periphery of the dots is smooth, and multicolor printing is possible. The invention has led to the invention of a vivid ink jet recording sheet which does not overflow and does not bleed and has a high print density and a bright color tone while having ink absorbency. That is, the inkjet recording sheet of the present invention contains calcium carbonate or kaolin alone or in combination as a filler in an amount of 3 to 15% by weight, and uses a modified rosin for neutral papermaking as an internal sizing agent. JIS P8140
A water absorption of 10 to 15 g / m ² by the Cobb method based on the above, and a coating liquid for an ink receiving layer containing an ultrafine inorganic pigment having a primary particle diameter of 100 nm or less on the surface of the base paper. Is an ink jet recording sheet.

The ink jet recording sheet of the present invention has a coating amount of the ultrafine inorganic pigment of 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 based on the ultrafine inorganic pigment.

Hereinafter, the ink jet recording sheet of the present invention will be described in detail. From the viewpoint of the characteristics of the ink jet recording sheet, the sizing degree of the base paper greatly affects the ink absorption speed and the resolving power. For example, in the case of color printing in which colors are represented by mixed colors, it is necessary that the first color ink is absorbed or hardly remains on the surface before the second color is printed, which is one of the important characteristics. Has become one. The size (water absorption) by the Cobb method is 10 g / m ^2.
The less strongly sized paper has a lower ink absorption speed and better resolution of the first color, but the second color ink overflows and the actual resolution is reduced. Furthermore, printing unevenness also occurs, which is not always satisfactory as an ink jet recording sheet.

On a weak-size paper having a sizing degree (water absorption degree) of more than 15 g / m ² by the Cobb method, the absorption rate of the water-based ink is high and the absorption capacity is increased.
As a result of penetrating into the direction and the inside of the base paper layer, the print density, resolution and chromaticity are reduced.

As described above, although there are portions that can be controlled by the sizing properties of the base paper, it has been found that it is impossible to control the color characteristics and dot shapes (bleeding) in multicolor printing.

It has been found that by subjecting the filler to a protective colloid treatment with an anionic or cationic water-soluble polymer, uneven density caused by uneven absorption can be improved. However, when an anionic water-soluble polymer is used, the inside of the papermaking system is disturbed, and the size hardly develops, which is not preferable.

Further, by applying an ink receiving layer composition mainly composed of ultrafine inorganic pigments having a primary particle diameter of 100 nm or less, not only the optical density and color are improved, but also the absorption of water-soluble ink is improved. In order to control bleeding and concentration, it was found that it was effective to apply a water-soluble polymer such as oxidized starch, PVA or modified PVA in combination with a surface sizing agent, and completed the present invention. 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 fortified rosin with a protective colloid comprising a water-soluble polymer. JP-A-54-11035, JP-A-60-161472, JP-A-63-1201
And sizing agents as disclosed in JP-A-98-98 and the like.

The cationic water-soluble polymer used in the present invention includes a tertiary amine or a quaternary ammonium base.
Vinyltrimethylammonium chloride monomer, 2
Polyacrylamide, sodium polyacrylate, sodium alginate, hydroxymethyl containing 5% by weight or more of a cationic monomer such as methacryloyloxyethyltrimethylammonium chloride monomer, N-acrylamidoethyltrimethylammonium chloride monomer, acrylamide / diallylamine copolymer monomer; Modified products such as cellulose, methylcellulose and polyvinyl alcohol or derivatives thereof can be mentioned.

The filler surface-treated with the cationic water-soluble polymer of the present invention is obtained by adding the cationic water-soluble polymer in an amount of 1 to 5% by weight, based on the pigment, and then performing a surface treatment obtained by stirring. It is. In this case, the stirrer 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 by using a general agitator without pulverization.

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

The following are examples of the ultrafine inorganic pigment used in the present invention. For example, silica (colloidal silica), alumina or alumina hydrate (alumina sol, colloidal alumina, cationic aluminum oxide or its hydrate, pseudoboehmite, etc.), surface-treated cationic colloidal silica, aluminum silicate, magnesium silicate, Magnesium carbonate and the like are preferred, and if the primary particles are porous, it is still more preferable. Is preferably formed. In particular, in the present invention,
It is preferable to coat the pulp fibers themselves with an ultrafine inorganic pigment having an average particle diameter of several hundredths or less of the fiber width on each pulp fiber on the base paper surface.

The water-soluble polymer used in the present invention includes:
For example, polyvinyl alcohol, vinyl acetate, oxidized starch, etherified starch, carboxymethyl cellulose, cellulose derivatives such as hydroxyethyl cellulose, casein, gelatin, soy protein, silyl-modified polyvinyl alcohol, etc .; maleic anhydride resin, styrene-butadiene copolymer, Conjugated diene-based copolymer latex such as methyl methacrylate-butadiene copolymer; a polymer or a copolymer of acrylate and methacrylate;
Acrylic polymer latex such as polymer or copolymer of acrylic acid and methacrylic acid; Vinyl polymer latex such as ethylene-vinyl acetate copolymer; or monomer containing functional group such as carboxyl group 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 resin And the like, and 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 pulp used in the base paper of the present invention includes NBKP, LBKP, NBSP, LBSP, GP,
TMP and waste paper. In use, they are mixed and used at a ratio according to several purposes.

The ink jet recording sheet of the present invention includes
It contains a filler such as talc or titanium oxide, a dye, a sizing agent, a fixing agent, a wet paper strength enhancer, a dry paper strength enhancer, and the like, which are usually used in papermaking, if necessary.

The composition containing the ultrafine inorganic pigment of the present invention contains a commonly used polymer such as styrene-acrylic acid, olefin-maleic acid, acrylic acid, styrene-maleic acid, a surface sizing agent, a dye, It contains a fluorescent whitening agent, a dye fixing agent, a surface strength agent and the like as required.

The ink receiving layer coating liquid containing the ultrafine inorganic pigment of the present invention is typified by a size press, a gaiter coater, a bill blade coater, a blade metering size press, a velvapa coater, a short dwell coater, etc. on the surface of the base paper. Coating can be performed 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 the mechanism is not clearly understood, it is presumed to be expressed by the following actions. That is, the surface of the filler used is formed into a protective colloid with a cationic water-soluble polymer, thereby promoting the penetration of alcohol or polyethylene glycol used as a solvent for the water-soluble ink. As a result,
It is considered that print density unevenness and discoloration of the water-soluble ink do not occur.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. The present invention is not limited to the embodiments.
All parts and percentages in the following are by weight.
The value indicating the amount of smear is the weight after drying unless otherwise specified.

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

Preparation Example 2 Light calcium carbonate added in Preparation Example 1 was replaced with kaolin (trade name: BELITUNG KAOLIN, ALTER)
Pigments surface-treated with a cationic water-soluble polymer were obtained by the same method except that the pigment was changed to ABADI.

Preparation Example 3 An anionic solution was prepared 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 An anionic solution was prepared by the same method except that the cationic water-soluble polymer added in Preparation Example 2 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.

Example 1 Freeness of 380 ml C.I. S. F. LBKP beaten up to 450 ml C.I. S. F. NB beaten up to
Based on the pulp solid content of KP mixed at a weight ratio of 7: 3, the light calcium carbonate of Preparation Example 1 was 10% by solid weight ratio, the sulfate band was 1.0%, and a modified rosin sizing agent (commercially available) Name: NT80, Arakawa Chemical Co., Ltd.), 0.4% as rosin content, amphoteric starch (trade name: Cato3210,
0.8% (Oji National)
/ M ^2, the water absorption degree of Cobb how has papermaking base paper of 13g / m ^2. Then, 100 parts of cationic colloidal silica (trade name: Snowtex-AK (3), manufactured by Nissan Chemical Industries, primary particle diameter 10 to 20 nm) was added to the base paper, and a water-soluble polymer (trade name: PVA117, trade name) was used as an adhesive. 50 parts by Kuraray Co., Ltd., cationic resin as dye fixing agent (trade name: Sumireze Resin 1001, cationic charge amount 3.5)
meq. / G, manufactured by Sumitomo Chemical Co., Ltd.) 30 parts of an ink receiving layer coating solution having a solid content of 10% was applied using a roll coater so as to have a dry solid content of 2 g / m ^2, and dried to obtain a Beck smoothness. A super calender process was performed so as to reach 80 seconds to obtain an ink jet recording sheet.

Example 2 The average primary particle diameter of the ultrafine inorganic pigment used in Example 1 was 65 nm (trade name: Snowtex YL, average particle diameter: 50).
To 80 nm, manufactured by Nissan Chemical Industries, Ltd.), and an ink jet 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 alumina hydrate (Cataloid AS-3, manufactured by Catalyst Chemical Industry Co., Ltd., having a primary particle diameter of about 10 nm). Thus, an ink jet recording sheet was obtained.

Comparative Example 1 Colloidal silica having an average primary particle diameter of 300 nm (trade name: Snowtex PST-3, manufactured by Nissan Chemical Industries, having a primary particle diameter of 300 ± 30) of the ultrafine inorganic pigment used in Example 1
An ink jet recording sheet was obtained in the same manner as in Example 1 except that the thickness was changed to nm).

Comparative Example 2 The ultrafine inorganic pigment used in Example 1 had an average particle size of 1.
Except that the silica was 0 μm (trade name: Nipsil E220A, manufactured by Nippon Silica Industries, average particle size 1.0 μm),
An ink jet recording sheet was obtained in the same manner as in Example 1.

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

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

Example 5 The amount of the ink receiving layer coating solution used in Example 1 was 0.9 g.
An ink jet recording sheet was obtained in the same manner 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 in the same manner 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 mixed.

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

The degree of water absorption (g / m ² ) is JIS P8
The measurement was performed according to the Cobb method according to No. 140, and the immersion time was measured in 10 seconds.

[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 an image analyzer (Luzex 500) is used to evaluate 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 closer to 100 when the circle is closer to a perfect circle, and is a level having no problem if it is 250 or less in practical use.

[Ink Absorption and Coloring] The ink absorption and the sharpness (resolution) of the image are determined by the boundaries between the solid printing portions, such as red printing (magenta + yellow) and green printing (cyan + yellow). The bleeding condition of the ink at the boundary 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. A material having poor ink absorbability significantly impairs image quality (image clarity), so that even if other characteristics, for example, image density and the like are good, it has no meaning. As for the color saturation, the vividness of the color in the above-mentioned heavy-colored portion was visually evaluated. In addition, as an evaluation standard,
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 (trade name: Macbeth RD918, manufactured by Macbeth) at the portion printed solid with black ink. The higher the numerical value is, the higher the image density is and the better the image density is.

[0055]

[Table 1]

In Examples 1 to 8, it was found that the use of an ultrafine inorganic pigment of 100 nm or less can improve the optical density and color chromaticity. On the other hand, Comparative Examples 1 and 2
However, in the case where a pigment having a large particle diameter is used, the optical density and the chromaticity are reduced. Further, in Example 7, when the blending ratio of the water-soluble polymer was less than 5%, there was no problem in characteristics, but it was easy for powder to fall off. In Example 8, although it was more than 95%, there was a tendency that the chromaticity was slightly lowered.

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

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

Example 11 Light calcium carbonate added in Example 1 was replaced with kaolin in Preparation Example 2, the amount added was 10%, the amount added of a rosin sizing agent was 0.3%, and sodium carbonate was used for pH adjustment. 0.
An ink jet 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 15
%, Except that the amount of the rosin sizing agent added was 0.4%.
An ink jet 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, the amount added was 15%, the amount of rosin sizing agent added was 0.4%, and sodium carbonate was used for pH adjustment. 0.
An ink jet recording sheet was obtained in the same manner as in Example 1 except that 5% was added.

Comparative Example 4 Light calcium carbonate added in Example 1 was not added.
An ink jet recording sheet was obtained in the same manner as in Example 1, except that the amount of the rosin sizing agent was changed to 0.3%.

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

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

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

Comparative Example 8 Light calcium carbonate to be added in Example 1 was replaced with kaolin of Preparation Example 2, the amount of addition was 20%, the amount of rosin sizing agent was 0.7%, and sodium carbonate was used for pH adjustment. 0.
An ink jet recording sheet was obtained in the same manner as in Example 1 except that 4% was added.

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

Comparative Example 10 Light calcium carbonate to be added in Example 1 was replaced with kaolin of Preparation Example 2, and the added amount was 10%, the added amount of rosin sizing agent was 1.0%, and sodium carbonate was used for pH adjustment. 0.
An ink jet recording sheet was obtained in the same manner as in Example 1 except that 4% was added.

Comparative Example 11 The amount of light calcium carbonate added in Example 1 was 10
%, Except that the addition amount of the rosin sizing agent was 0.2%.
An ink jet 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 amount added was 10%, the amount added of a rosin sizing agent was 0.2%, and sodium carbonate was used for pH adjustment. 0.
An ink jet recording sheet was obtained in the same manner as in Example 1 except that 4% was added.

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

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

Table 2 summarizes the above results.

[0074]

[Table 2]

From the results in Table 2, it is found that the ink jet recording sheets of Examples 9 to 13 contain 3 to 15% of a filler which has been treated with a cationic water-soluble polymer, and has a water absorbency and a coating liquid for an ink receiving layer. The amounts were all within the range of the present invention, and all were good in ink absorbency, 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, Comparative Example 4 is a base paper containing no filler and has very poor color properties because it is not coated. Comparative Examples 5 and 6 show that as a result of using an untreated filler, uneven absorption occurs. Comparative Examples 7 and 8 contain 20% of the filler and show that absorption unevenness does not occur, but the chromaticity is reduced. In Comparative Examples 9 to 12, the water absorption of the base paper was changed depending on the amount of the sizing agent added. As a result, although uneven absorption does not occur, it indicates that the absorption speed is low in the strong size base paper having a small water absorption, and the chromaticity is poor in the weak size paper having the high water absorption. Comparative Examples 13 and 14
Found that when a filler treated with an anionic polymer was used, the papermaking system was disturbed and it was necessary to add as much as 1.4% of a sizing agent per pulp solid content, which proved to be undesirable in terms of cost. did.

[0077]

The ink jet recording sheet of the present invention is
The base paper containing calcium carbonate and kaolin treated with a cationic water-soluble polymer is coated with an ink receiving layer mainly composed of an ultrafine inorganic pigment having a specific particle size. An ink jet recording sheet which is excellent in ink absorbency, has high image density and sharpness, and can obtain a recording dot shape close to a perfect circle.

Continuation of the front page (56) References JP-A-2-243381 (JP, A) JP-A-4-250091 (JP, A) JP-A-63-256796 (JP, A) JP-A-2-188287 (JP) JP-A-5-59696 (JP, A) JP-A-6-92007 (JP, A) JP-A-6-299500 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) B41M 5/00 D21H 17/67 D21H 27/00

Claims (2)

(57) [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 as a filler, and a modified rosin for neutral papermaking used as an internal sizing agent. An ink containing ultrafine inorganic pigment having a water absorption of 10 to 15 g / m ² by the Cobb method based on JIS P8140 and a primary particle diameter of 100 nm or less on the surface of the base paper. An ink jet recording sheet obtained by applying a receiving layer coating solution. 2. The coating amount of the ultrafine inorganic pigment is from 0.3 to 0.3.
3. The ink receiving layer coating liquid of claim 1, wherein the water-soluble polymer is 3.0 g / m < ² > and the water-soluble polymer is contained in the ink receiving layer coating liquid at a ratio of 10 to 90% by weight based on the ultrafine inorganic pigment. The ink jet recording sheet according to the above.