JPH09216457A - Cast coated paper for ink jet recording and manufacture and recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cast coated paper with superior white paper surface luster and outstanding ink jet recording aptitude. SOLUTION: A liquid of a polymer emulsion containing a monomer with an ethylene unsaturated bond is applied to a paper with an undercoat layer containing pigment and an additive to an coated layer, then this coated layer is pressed against a heated specular drum and is dried to finish the laminate as a cast coated paper for ink jet recording. The polymer has a glass transition point of 40 deg.C or more, and the opacity (measured in compliance with JIS-P-8138) of a test sample of a transparent film on which the polymer is coated in such a manner that the dry weight of the test sample is 20g/m<2> is at most 25%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cast coated paper for ink jet recording, and particularly to a cast coated paper having an excellent white paper surface gloss and excellent ink jet recording (printing) suitability, and a method for producing the same. And recording method.

[0002]

2. Description of the Related Art In recent years, recording by an ink jet printer has been used in various fields because of its low noise, high speed recording, and easy multicoloring. As the ink jet recording paper, high-quality paper designed so as to have high ink absorbability, coated paper having a surface coated with a porous pigment, and the like are applied. By the way, all of these papers are mainly so-called matte ink jet recording papers having low surface gloss.

However, recently, with the expansion of applications such as high-speed ink jet recording, high definition of recorded images, and full-color ink jet recording, an ink jet recording paper having a high surface gloss and an excellent appearance has been desired. Generally, for paper with high surface gloss, apply a plate-like pigment on the surface,
Further, it is obtained by copying the mirror surface of the coated paper having a high gloss, which has been subjected to a calendering treatment, or a wet coating layer, by pressing and drying it on a heating drum surface having a mirror surface, if necessary. Cast coated paper and the like are known.

This cast coated paper has high surface gloss and more excellent surface smoothness as compared with ordinary coated paper which has been subjected to a super calender finish, and since it has an excellent printing effect, it is of high quality. It is mainly used for printed matter and the like, but when it is used for ink jet recording paper, it has various difficulties.

That is, in general, cast coated paper has a high gloss because a film-forming substance such as an adhesive in the pigment composition constituting the coated layer copies the specular drum surface of the cast coater. On the other hand, the presence of this film-forming substance causes the coating layer to lose its porosity, and has problems such as a decrease in ink absorption during inkjet recording and a decrease in print density. Then, in order to improve the ink absorbency, it is necessary to make the cast coating layer more porous, and for that purpose, it is necessary to reduce the amount of the film forming substance. On the other hand, by reducing the amount of film-forming substance,
As a result, the glossiness of white paper is reduced. Furthermore, in order to achieve both white paper gloss and ink absorbency, the coating layer has a two-layer structure, the undercoat layer is a porous layer like conventional inkjet coated paper, and the topcoat layer is a film-forming substance. It may be considered that the glossy layer as a main component is cast-finished and the film-forming substance is distributed only on the surface, but in this case, the printing density was low and the ink absorbability was improved, but it was not at a sufficient level.

As described above, in the present situation, it is extremely difficult to simultaneously satisfy both the higher surface gloss and the excellent ink jet ink absorbability and the printability such as the print density in the cast coated paper for recording.

[0007]

The present inventors have solved the above problems and further improved the high surface smoothness and high gloss originally possessed by the cast coated paper for ink jet recording, and at the same time excellent ink jet recording (printing). A cast coated paper for inkjet recording having suitability is provided.

[0008]

The present invention includes the following aspects. [1] A base paper provided with an undercoating coating layer containing a pigment and an adhesive is coated with a coating solution containing an emulsion of a polymer containing a monomer having an ethylenically unsaturated bond to form a coating layer. Is a cast coated paper for ink jet recording which is pressed against a heated mirror surface drum and dried to finish.
The polymer has a glass transition point of 40 ° C. or higher, and the opacity (measured according to JIS P8138) of a sample obtained by coating the polymer on a transparent film so that the dry weight is 20 g / m ² is 25%. The following are cast coated papers for inkjet recording.

[2] The cast coated paper for ink jet recording according to [1], wherein the polymer emulsion has an average particle diameter of 0.2 μm or less.

[3] A base paper provided with an undercoating coating layer containing a pigment and an adhesive is coated with a coating solution containing an emulsion of a polymer containing a monomer having an ethylenically unsaturated bond to form a coating layer. Is formed, and is pressed against a heated mirror-finished drum and dried to finish, and the polymer has a glass transition point of 4 or less.
Cast coating for ink jet recording at 0 ° C. or higher, and the opacity (measured according to JIS P8138) of a sample obtained by coating a polymer on a transparent film so that the dry weight is 20 g / m ² is 25% or less. Manufacturing method of paper.

[4] The method for producing a cast coated paper for ink jet recording according to [3], wherein the polymer emulsion has an average particle diameter of 0.2 μm or less.

[5] An ink jet recording method for forming an image by ejecting a water-based ink from fine pores onto the cast coated paper for ink jet recording described in [1] or [2].

[6] A coating containing an emulsion of a polymer obtained by polymerizing a monomer containing a monomer having an ethylenically unsaturated bond, on a base paper provided with an undercoat coating layer containing a pigment and an adhesive. Apply the liquid to form a coating layer,
In a cast coated paper for ink jet recording, which is brought into pressure contact with a heated mirror surface drum while the coating layer is in a wet state and dried to finish, the glass transition point of the polymer is 40 ° C. or higher, and Dry weight 2 on the transparent film
It is applied so that it will be 0 g / m ^2, and JIS P8138
A cast coated paper for ink-jet recording, which has a transparency of 25% or less, preferably 20% or less, measured in accordance with.

[7] A coating containing an emulsion of a polymer obtained by polymerizing a monomer containing a monomer having an ethylenically unsaturated bond, on a base paper provided with an undercoat coating layer containing a pigment and an adhesive. Apply the liquid to form a coating layer,
In the method for producing a cast coated paper for ink jet recording, which is brought into pressure contact with a heated mirror drum while the coating layer is in a wet state, and dried to finish, the glass transition point of the polymer is 40 ° C. or higher, Moreover, the polymer was applied onto a transparent film so that the dry weight was 20 g / m ^2, and JIS was used.
The opacity measured in accordance with P8138 is 25% or less,
A method for producing a cast coated paper for inkjet recording, which has a transparency of preferably 20% or less.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The cast coating composition, which is the most important feature of the present invention, will be described. The coating composition for casting contains a polymer emulsion obtained by polymerizing a monomer having an ethylenically unsaturated bond.

Examples of the polymer obtained by polymerizing a monomer having an ethylenically unsaturated bond (hereinafter referred to as an ethylenic monomer) include methyl acrylate, ethyl acrylate butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate and 2-hydroxyethyl acrylate. , Alkyl group such as glycidyl acrylate having 1 to 18 carbon atoms, alkyl methacrylate such as methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycidyl methacrylate having 1 to 18 carbon atoms Methacrylic acid ester, styrene, α
-A polymer obtained by polymerizing ethylenic monomers such as methylstyrene, vinyltoluene, acrylonitrile, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl propionate, acrylamide, N-methylolacrylamide, ethylene and butadiene.

The polymer may be a copolymer in which two or more kinds of ethylenic monomers are used in combination, if necessary, and may be a substituted derivative of these polymers or copolymers. Incidentally, examples of the substituted derivative include a carboxyl group derivative and an alkali derivative thereof. Further, the above-mentioned ethylenic monomer is polymerized in the presence of colloidal silica to obtain Si-
It is also possible to use it in the form of a complex by OR (R: polymer component) bond. In this case, the particle size of the emulsion refers to the composite particle size.

The polymer resin obtained by polymerizing the above-mentioned ethylenic monomer needs to have a glass transition point of 40 ° C. or higher, preferably 50 ° C. or higher. The glass transition point can be adjusted by the monomer composition etc.,
For example, in a styrene-2-methylhexyl acrylate copolymer, increasing the styrene ratio raises the glass transition point. That is, in the conventional production of cast coated paper, in order to obtain an excellent surface gloss, a resin component in the coating composition was sufficiently formed into a film during cast finishing to obtain high gloss. However, in such a conventional method, the porosity of the surface of the cast coating layer is reduced, and as a result, the absorbability of the ink during inkjet recording is lowered, and a cast coated paper having desirable inkjet recording suitability is obtained. I can't. The above polymer is prepared as an emulsion. These are excellent in gloss and ink absorbability as compared with the case of using a water-soluble resin, and have good releasability from a mirror surface.

In the method of the present invention, a polymer having a high glass transition point is used in order not to reduce the absorbability of the ink, and preferably cast finish is performed in a state where the polymer does not completely form a film. As a result, the porosity of the surface of the cast coated paper is effectively maintained, so that it is possible to obtain a cast coated surface that retains ink absorbency and has an excellent glossy surface.

On the other hand, when the glass transition point of the polymer is lower than 40 ° C., the heat of the surface of the cast drum facilitates the film formation of the resin component more than necessary, resulting in the porosity of the surface of the cast coating layer. Property is reduced and the surface has a high gloss value, but the ink absorbency is reduced, which is not preferable.

Further, since the above-mentioned polymers generally have poor fixability of ink jet ink, the ink jet ink usually passes through the cast coating layer and is fixed in the undercoat layer. For this reason, since the ink colored in the undercoat layer is seen through the cast layer, if the transparency of the polymer-containing cast coating layer is poor, problems such as reduction in print density and print unevenness occur.

In order to improve this point, the polymer used for the cast coating layer in the present invention needs to have high transparency. The transparency of the polymer is measured by the method described below.

That is, JIS P8 when coated on a transparent PET film so as to have a dry weight of 20 g / m ^2.
The opacity measured according to 138 is 25% or less, preferably 20% or less (this opacity value is preferably low). When the opacity exceeds 25%, the print density is obviously lowered, and the print unevenness due to the nonuniformity of the cast coating layer is aggravated.
Transparent polyethylene terephthalate film (hereinafter PET)
An opacity of 1.1% is used as the film). Commercially available PET film supplied by Uchida Yoko Co., Ltd. (for transparency dry PPC)
There is.

As a method of increasing the transparency of the above-mentioned polymer, generally, the average particle size of the polymer emulsion may be reduced. The average particle diameter is not necessarily specified because it depends on the type of polymer, but is preferably 0.2 μm or less, more preferably 0.1 μm or less. There is no particular lower limit to the particle size, but with the current technology, it is possible to obtain particles up to about 0.04 μm.

The method of measuring the particle size is not limited, but, for example, Pa
The mass average particle size can be measured by diluting the sample emulsion with deionized water using a sub-micron particle size analyzer NICOMP Model 370 manufactured by Cific Science. In the case of composite particles with colloidal silica or the like, the same measurement is performed. In order to reduce the particle size of the polymer, the amount of seeds that become nuclei at the start of polymerization is adjusted. The larger the amount of seeds that form the core, the smaller the particle size.

Further, in the coating composition for casting, in addition to the above-mentioned polymer, it is used in general coated paper for printing and ink jet paper in order to adjust whiteness, viscosity, fluidity and the like. Various auxiliaries such as pigments, dispersants, thickeners, defoamers, colorants, antistatic agents and preservatives are appropriately added. When the release agent and other substances in the coating composition are pigments or emulsions, those having a small particle size are preferable for improving transparency. When composite particles of a pigment such as colloidal silica and a polymer are used, the particle size of colloidal silica or the like is preferably about 10 to 30 nm. Further, even if a water-soluble resin is contained, the opacity hardly increases, so that it can be added if necessary.

Next, the pigment and adhesive contained in the undercoat layer will be described. That is, as the pigment, for example, kaolin, clay, calcined clay, amorphous silica, zinc oxide,
Aluminum oxide, aluminum hydroxide, calcium carbonate, satin white, aluminum silicate, smectite, magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, styrene plastic pigment,
Urea resin-based plastic pigments, benzoguanamine-based plastic pigments and the like can be used various publicly known pigments in the general coated paper manufacturing field, but amorphous silica excellent in inkjet suitability, aluminum oxide, magnesium carbonate and the like are particularly preferably used. .

Examples of the adhesive include proteins such as casein, soybean protein, and synthetic protein, various starches such as starch and oxidized starch,
Polyvinyl alcohol, cellulose derivatives such as carboxymethyl cellulose and methyl cellulose, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer conjugated diene polymer latex, acrylic polymer latex, ethylene-vinyl acetate copolymer vinyl, etc. Adhesives generally used for coated papers such as a polymer latex are used alone or in combination. The amount of the adhesive compounded is adjusted to 5 to 50% by weight, more preferably 10 to 30% by weight, based on the pigment.

In addition to the above-mentioned pigments and adhesives, cationic resins used in general ink jet paper for the purpose of improving water resistance and printing color density, for example, polyalkylene polyamines such as polyethylene polyamine and polypropylene polyamine, Alternatively, a derivative thereof, an acrylic resin having a tertiary amino group or a quaternary ammonium group, diacrylamine, or the like is used. The addition amount of the cationic resin is 1 to 30 parts by weight with respect to 100 parts by weight of the pigment,
It is more preferably adjusted in the range of 5 to 20 parts by weight. In addition, various auxiliaries such as a dispersant, a thickener, an antifoaming agent, a colorant, an antistatic agent and an antiseptic agent used in the production of general coated paper are appropriately added.

The composition for the undercoat layer comprising the above-mentioned materials is generally adjusted to a solid content concentration of about 1 to 65% by weight, and the base paper has a basis weight of about 20 to 400 g / m ^2. A blade coater so that the dry weight is about ² to 50 g / m ² , and more preferably about 5 to ²⁰ g / m ² .
Coating and drying are carried out by various publicly known coating devices such as an air knife coater, roll coater, brush coater, champlex coater, bar coater and gravure coater. Further, if necessary, smoothing treatment such as super calendering, brushing, and cast finishing can be performed after drying the undercoat layer. The base paper to be the base is not particularly limited, and acid paper or neutral paper used for general coated paper is appropriately used.

On the coated surface of the thus obtained undercoated paper, a cast coating liquid containing the above-mentioned specific polymer was applied to a blade coater, an air knife coater, a roll coater, a brush coater, a chanplex coater, a bar. Coating is performed by various coating devices such as a coater and a gravure coater. As described above, while the coating layer is in a wet state, it is pressed against a heated mirror surface drum and dried to perform cast finishing. In this case, the coating amount of the cast coating liquid is 0.2 to 30 g / m ² , and preferably 1 to 10 g / m ² in terms of dry solid content. When the coating amount of the cast coating layer exceeds 30 g / m ² , the ink absorbency deteriorates,
The print density decreases. If it is 0.2 g / m ² or less, a sufficiently glossy surface cannot be obtained.

[0032]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
Unless otherwise specified, parts and% in the examples represent parts by weight and% by weight, respectively.

Example 1 60 parts of alumina as a pigment, 40 parts of magnesium carbonate,
10 parts of polyvinyl alcohol as an adhesive, 10 parts of dicyandiamide-based resin (trade name: Neofix E-117 / manufactured by Nichika Chemical Co., Ltd.) as a cationic resin,
As a dispersant, 0.5 part of sodium polyphosphate was added to prepare an undercoating coating liquid having a solid content concentration of 15%. This undercoating coating liquid was applied to a base paper of 100 g / m ² of tsubo to a dry weight of 6
Coat with an air knife coater to achieve g / m ² ,
A base paper for undercoating was obtained by drying.

On the other hand, as a cast coating liquid, 60 parts of a styrene-2 methylhexyl acrylate copolymer having a glass transition point of 80 ° C. and an average particle diameter of 0.09 μm, an average particle diameter of 1
A coating liquid for casting comprising 40 parts of 5 nm colloidal silica and 2 parts of calcium stearate as a release agent and having a solid content concentration of 30% was prepared. This coating liquid was coated on the above-mentioned base coating base paper using a roll coater, immediately followed by pressure contact with a mirror surface drum having a surface temperature of 75 ° C., drying and release to obtain a cast coated paper for inkjet recording. It was The coating amount at this time was 5 g / m ² in terms of solid content weight.
The styrene-2 methylhexyl acrylate copolymer, which is a component of the cast coating liquid at this time, was used as a commercially available transparent PET film (supplier: Yoko Uchida Co., Ltd., trade name: for transparent dry PPC, transparent PET film itself). Opacity is 1.1%, thickness is 83μm) and dry weight is 20g
JIS P8138 when applied so that it becomes / m ²
The opacity measured according to the above method was 13%.

Example 2 The glass transition point of the styrene-2 methylhexyl acrylate copolymer in the cast coating liquid in Example 1 was 80 ° C.
A cast coated paper for inkjet recording was obtained in the same manner as in Example 1 except that the temperature was replaced with 45 ° C. At this time, the opacity of the styrene-2 methylhexyl acrylate copolymer in the cast coating liquid was 13%.

Example 3 The glass transition point of the styrene-2 methylhexyl acrylate copolymer in the cast coating liquid in Example 1 was 80 ° C.
A cast coated paper for inkjet recording was obtained in the same manner as in Example 1 except that the temperature was replaced with 65 ° C. At this time, the opacity of the styrene-2 methylhexyl acrylate copolymer in the cast coating liquid was 13%.

Example 4 The average particle size of the styrene-2 methylhexyl acrylate copolymer in the cast coating liquid in Example 1 was 0.09.
A cast coated paper for inkjet recording was obtained in the same manner as in Example 1 except that the thickness was 0.07 μm. At this time, the opacity of the styrene-2 methylhexyl acrylate copolymer in the cast coating liquid was 9%.

Example 5 The average particle size of the styrene-2methylhexyl acrylate copolymer in the cast coating liquid in Example 1 was 0.09.
A cast coated paper for inkjet recording was obtained in the same manner as in Example 1 except that the thickness was 0.13 μm. At this time, the opacity of the styrene-2 methylhexyl acrylate copolymer in the cast coating liquid was 21%.

Example 6 The average particle diameter of the styrene-2 methylhexyl acrylate copolymer in the cast coating liquid in Example 1 was 0.09.
A cast coated paper for inkjet recording was obtained in the same manner as in Example 1 except that the thickness was 0.19 μm. At this time, the opacity of the styrene-2 methylhexyl acrylate copolymer in the cast coating liquid was 24%.

Example 7 Cast coating for ink jet recording was carried out in the same manner as in Example 1 except that the styrene-2 methylhexyl acrylate copolymer in the cast coating liquid was changed to the styrene-methyl acrylate copolymer. Got the paper. At this time, the glass transition point of the styrene-methyl acrylate copolymer in the cast coating liquid was 80 ° C., and the average particle diameter was 0.09 μm.
m, the opacity was 14%.

Example 8 In Example 7, the average particle diameter of 0.09 μm of the styrene-methyl acrylate copolymer in the cast coating liquid was adjusted to 0.
A cast coated paper for inkjet recording was obtained in the same manner as in Example 1 except that the thickness was 13 μm. At this time, the opacity measured in the same manner as in Example 7 was 23%.

Comparative Example 1 The average particle size of the styrene-2methylhexyl acrylate copolymer in the cast coating liquid in Example 1 was 0.09.
A cast coated paper for inkjet recording was obtained in the same manner as in Example 1 except that the thickness was 0.22 μm. At this time, the opacity of the styrene-2 methylhexyl acrylate copolymer in the cast coating liquid was 28%.

Comparative Example 2 The average particle diameter of the styrene-2 methylhexyl acrylate copolymer in the cast coating liquid in Example 1 was 0.09.
A cast coated paper for inkjet recording was obtained in the same manner as in Example 1 except that the thickness was 0.28 μm. At this time, the opacity of the styrene-2 methylhexyl acrylate copolymer in the cast coating liquid was 45%.

Comparative Example 3 The glass transition point of the styrene-2 methylhexyl acrylate copolymer in the cast coating liquid in Example 1 was 80 ° C.
A cast coated paper for inkjet recording was obtained in the same manner as in Example 1 except that the temperature was replaced with 35 ° C. At this time, the opacity of the styrene-2 methylhexyl acrylate copolymer in the cast coating liquid was 15%.

Comparative Example 4 The glass transition point of styrene-2 methylhexyl acrylate copolymer in the cast coating liquid of Example 1 was -25.
A cast coated paper for inkjet recording was obtained in the same manner as in Example 1 except that a styrene-butadiene copolymer having an average particle diameter of 0.15 μm at 0 ° C. was used. At this time, the glass transition point of the styrene-butadiene copolymer in the cast coating liquid was −
The temperature was 25 ° C., the particle size was 0.15 μm, and the opacity was 22%.

The results of the white gloss of the cast coated paper thus obtained and the suitability for ink jet recording (ink absorbency, print density, ink unevenness) are summarized in Table 1. The above evaluation was carried out by the following method.

[Opacity] A copolymer obtained by polymerizing a monomer having an ethylenically unsaturated bond is a commercially available transparent PE.
Dry weight 2 on a T film (supplier: Yoko Uchida Co., Ltd., trade name: for transparency dry PPC, opacity of transparent PET film itself is 1.1%, thickness 83 μm)
It was coated so as to be 0 g / m ² and measured according to JIS P8138. [White paper gloss] The glossiness was measured according to JIS P8142.

[Inkjet Recording Suitability] (Absorbability of Inkjet Recording Ink) Printing was performed with a color printer BJC-600J (inkjet recording apparatus) manufactured by Canon Inc., and the drying property of the ink was visually evaluated. ◯: Slightly soiled when touched with a finger immediately after printing, but almost dry. Δ: The ink portion is slightly shiny immediately after printing, but there is no problem in practical use. X: Due to poor drying of the ink, the ink flows during printing and cannot be used practically.

(Coloring Density of Ink for Inkjet Recording After Recording) Color Printer BJC manufactured by Canon Inc.
Printing was performed with -600J (inkjet recording device), and the ink density was visually evaluated. A: Color density is extremely high. ◯: Color density is good. Δ: Color density is slightly low. X: The color density is low and there is a practical problem.

(Ink absorption unevenness after ink-jet recording ink recording) [Ink absorption unevenness] ⊚: Very good with no absorption unevenness. ◯: Absorption unevenness is slightly observed when observed carefully, but at a good level. Δ: There is uneven absorption, but there is no practical problem. X: Absorption unevenness is clearly recognized.

[0051]

[Table 1]

[0052]

As is clear from the results shown in Table 1, the cast coated paper of the present invention is excellent in surface gloss and ink jet recording suitability.

Claims (5)

[Claims] 1. A base paper provided with an undercoating coating layer containing a pigment and an adhesive is coated with a coating solution containing an emulsion of a polymer containing a monomer having an ethylenically unsaturated bond to form a coating layer. A cast coated paper for ink-jet recording, which is formed by press contact with a heated mirror surface drum and is dried to finish, and the polymer has a glass transition point of 40 ° C. or higher,
Also, the opacity of a sample obtained by applying the polymer on a transparent film so that the dry weight is 20 g / m ² (JIS P813
Cast coated paper for inkjet recording having a content of 25% or less (measured according to 8). 2. The average particle size of the polymer emulsion is 0.
The cast coated paper for inkjet recording according to claim 1, which has a thickness of 2 μm or less. 3. A base paper provided with an undercoating coating layer containing a pigment and an adhesive is coated with a coating solution containing an emulsion of a polymer containing a monomer having an ethylenically unsaturated bond to form a coating layer. A method for producing a cast coated paper for inkjet recording, which comprises forming, press-contacting with a heated mirror surface drum, and finishing by drying, wherein the polymer has a glass transition point of 40 ° C. or higher, and the polymer is on a transparent film. Dry weight 20
Opacity of the sample coated so that it becomes g / m ² (JIS
The method for producing a cast coated paper for inkjet recording, wherein the measurement) is 25% or less according to P8138. 4. The average particle size of the polymer emulsion is 0.
The method for producing a cast coated paper for inkjet recording according to claim 3, which has a thickness of 2 μm or less. 5. An inkjet recording method for forming an image on a cast coated paper for inkjet recording according to claim 1 or 2 by ejecting an aqueous ink from fine pores.