JP5250218B2 - Coated paper - Google Patents

Description

  The present invention relates to a coated paper excellent in gloss, smoothness and surface strength. More specifically, the present invention relates to a coated paper excellent in printability in offset printing, gravure printing, ink-jet printing, etc. with excellent glossiness, surface smoothness, excellent appearance, strong surface strength and no white spots due to peeling of the coating layer. Is.

In offset printing and gravure printing, printing problems such as white spots (misdots) and paper dust have still occurred, and drastic measures have been taken to improve printing efficiency, printing quality and printing work. There is a need to improve performance. On the other hand, with regard to printed materials, in recent years, in commercial printing applications such as magazines, flyers, brochures, catalogs, etc., there has been a demand for improved printing quality such as white paper gloss and printing gloss so as to improve the appearance of products.
In particular, offset printing has made great progress such as high-speed mass printing and automation. Accordingly, various physical properties have been demanded for paper from the viewpoint of workability and printability. Such offset printing is a printing method in which information such as characters and images is printed from a plate on a rubber roll called a blanket and transferred from the blanket to the paper. However, when the paper is peeled off from the blanket during printing due to the high-speed printing of the printing press. In addition, it is easy to cause a white-out problem in which a part of the paper is peeled off together with the ink, and the demand for printing paper having higher surface strength is increasing. Also, as the grade of paper used, general coated paper (A2, A3 grade coated paper) is often used in commercial printing, but these printed materials are required to have white paper gloss and printing gloss equivalent to high-quality printed materials. Therefore, there is a need for white paper gloss and printing gloss comparable to art paper (A0, A1 coated paper) and cast coated paper of higher grade.
In addition, gravure printing is excellent in gradation reproducibility, and is often used in commercial printing such as magazines, catalogs, pamphlets and the like that require better appearance. Such gravure printing is a metal roll whose plate is harder than offset printing, and the printing surface is difficult to adhere completely to the substrate during printing. The phenomenon that the phenomenon of not being transferred) is likely to occur. In order to deal with this problem, coated paper for gravure printing is required to have particularly good smoothness and cushioning properties.

On the other hand, recording by an ink-jet printer is used in many fields because it is low in noise and can be recorded at high speed, and it is easy to increase the number of colors. Ink used for ink-jet recording contains a large amount of solvent, so it must be quickly penetrated into the paper. Originally, it was mainly used for ink-jet recording paper such as high-quality paper or matte-coated paper. As images close to photographs are demanded, high gloss inkjet recording papers such as so-called cast coated papers are also increasing.
In recent years, digital cameras and ink-jet printers have been rapidly spreading, and there are applications such as printing images from digital cameras with ink-jet printers and creating New Year's postcards, etc. In order to perform offset printing on postal codes and stamps, paper with no printing unevenness is required.
In addition, with regard to glossiness, a technology to measure so-called image clarity has been developed, which is based on how clear and undistorted the image is displayed when an object appears on the surface of the coating film, rather than the conventional glossiness. This is one of the required qualities.

In Patent Document 1, in order to provide excellent gloss and image clarity, a wet coating layer coated with a gloss layer coating material is gelled by a coagulation treatment such as a coagulation liquid, and is pressed onto a mirror-finished heating drum and dried. In other words, an ink jet recording paper using a so-called gelling cast method (coagulation method) and containing an alumina hydrate in the gloss layer is disclosed. It is also described that the shape of the alumina hydrate is preferably a flat plate shape with good ink absorbability. In addition, Patent Document 2 is an ink jet recording medium (paper) that has excellent ink absorptivity, has image quality comparable to silver salt photographic printing paper, and has high scratch resistance, coating layer strength, and even high print density. The recording layer manufactured by the cast coating method and subjected to the cast treatment contains a colloidal silica having an average particle diameter of 10 to 90 nm or less and a colloidal silica having an average particle diameter of 100 to 300 nm. The document states that the casting process is preferably a solidification method.
However, as the resolution of inkjet printers increases, a higher level of image clarity has been demanded.
JP-A-2005-246806 JP 2005-280147 A

  The main problems to be solved by the present invention are gloss, surface smoothness, excellent appearance, high surface strength, no white spots due to peeling of the coating layer, printing in offset printing, gravure printing, inkjet printing, etc. The object is to obtain a coated paper with excellent suitability.

The present invention that has solved this problem is as follows.
[Invention of Claim 1]
A coated paper having a base paper and at least one coating layer mainly composed of a pigment and a binder on the base paper,
A coated paper characterized by containing, as the binder, at least a lower alkyl-silanol-modified polyvinyl alcohol having 6 or less carbon atoms .

[Invention of Claim 2]
The coated paper according to claim 1, wherein the alkyl group is a methyl group.

[Invention of Claim 3]
The coated paper according to claim 1 or 2, wherein acicular alumina hydrate is contained as the pigment.

[Invention of Claim 4]
The coated paper according to any one of claims 1 to 3, wherein at least an acrylic ester resin or a derivative thereof and a urethane resin or a derivative thereof are contained as the binder.

[Invention of Claim 5]
The coating layer is two or more layers,
As a binder of the coating layer in contact with the surface of the base paper, at least a lower alkyl-silanol-modified polyvinyl alcohol having 6 or less carbon atoms is contained,
As a pigment of the outermost layer of the coating layer, at least acicular alumina hydrate is contained, and at least an acrylic ester resin or a derivative thereof, and a urethane resin or a derivative thereof are contained as a binder,
The acrylic ester resin is contained in an amount of 5 to 40 parts by mass based on the active ingredient based on 100 parts by mass of the pigment, and the urethane resin is contained in an amount of 1 to 20 parts by mass based on the active ingredient based on 100 parts by mass of the pigment. The
The coated paper of any one of Claims 1-4.

[Invention of Claim 6]
The coated paper according to any one of claims 1 to 5, wherein an outermost layer of the coating layer is provided by a rewet cast method.
[Invention of Claim 7]
The pigment contains colloidal silica together with the acicular alumina hydrate,
The mixing ratio of the acicular alumina hydrate and colloidal silica was 30 to 70:70 to 30 on a mass basis.
The coated paper of any one of Claims 1-6.

  By using alkyl-silanol-modified polyvinyl alcohol as a binder for the coating layer, the coating layer can be uniformly formed, and a coated paper excellent in gloss, surface smoothness, and surface strength was obtained.

Next, an embodiment of the present invention will be described.
As shown in FIG. 1, the coated paper of the present embodiment has at least one layer on a base paper 4. In the illustrated example, the coated paper has two layers consisting of a lower layer 2 and a surface layer 3 formed on the lower layer 2. Has a coating layer.

  In the present embodiment, the pulp used for the base paper 4 is not particularly limited. For example, softwood unbleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), and hardwood bleached kraft pulp. Chemical pulp such as (LBKP); thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), refiner mechanical pulp (RMP), refiner ground pulp (RGP), chemiground pulp (CGP), thermoground pulp (TGP) , Machine pulp such as groundwood pulp (GP), stone grand pulp (SGP), pressurized stone grand pulp (PGW); waste paper pulp derived from chemical pulp and mechanical pulp such as deinking pulp (DIP) and waist pulp (WP) Etc., and this It can be selected and used one or more kinds from among.

  In this Embodiment, it is preferable that the base paper 4 contains a filler so that the ash content according to JIS P8251 may be 1 to 20% by mass. The filler improves the unevenness in printing by improving the smoothness, improves the opacity to prevent the back-through of the printed image, and further suppresses the interfiber bonding of the pulp and creates a void in the base paper. Printing unevenness is reduced by improving the cushioning properties during printing. When the ash content is less than 1% by mass, uneven printing tends to occur, and when it exceeds 20% by mass, the interfiber bonding of the pulp is excessively reduced, and part of the base paper drops off during printing, and the cuts are cut. Sometimes paper dust tends to be generated.

  In this Embodiment, the kind of the above filler is not specifically limited, Titanium oxide, clay, talc, calcium carbonate, etc. are mentioned.

From the viewpoint of improving the surface strength and reducing paper dust during offset printing, the base paper 4 is composed of oxidized starch, acetylated starch, esterified starch, etherified starch, cationized starch, hydroxylethyl etherified starch (HES), and self-modification. It is preferable to contain various starches such as starch (APS starch), enzyme-modified starch, urea phosphate esterified starch by internal addition and / or surface coating. The content in the base paper 4 is preferably 1 to ²⁰ g / m ² .

  The base paper 4 can contain other known chemicals such as a paper strength enhancer, an internal additive sizing agent, an external additive sizing agent, and a yield improving agent as other additive chemicals. In addition, the base paper 4 can include one provided with a coating layer containing a pigment and a binder for the purpose of improving the smoothness and whiteness of the surface. The coating pigment and binder are not particularly limited, and examples of the pigment include inorganic pigments such as amorphous silica, colloidal silica, alumina, clay, calcium carbonate, talc, magnesium carbonate, barium persulfate, and magnesium silicate. Examples of the binder include silanol-modified polyvinyl alcohol, ethylene vinyl acetate copolymer (EVA), styrene butadiene copolymer, vinyl acetate, polyvinyl acetal, oxidized starch, etherified starch, acrylate resin, and acrylamide resin. , Polyester resins, urethane resins, and the like. Among these, at least one kind or two or more kinds can be selected and used.

  Furthermore, the base paper 4 can be subjected to a flattening process using a calendar for the purpose of improving the glossiness and smoothness of the surface. A method for flattening is not particularly limited, and examples thereof include a super calendar, a soft calendar, a machine calendar, and the like, and at least one type or two or more types can be selected and used.

  On this base paper 4, at least one coating layer (2, 3) containing a pigment and a binder is provided. Although it does not specifically limit as a pigment of this coating layer (2,3), For example, inorganic pigments, such as amorphous silica, colloidal silica, alumina, clay, calcium carbonate, talc, magnesium carbonate, barium persulfate, magnesium silicate Is mentioned.

  The particle diameter of the above pigment is not particularly limited, but the average secondary particle diameter by the Cole counter method is preferably in the range of 1 to 10 μm. If the thickness is less than 1 μm, there is no void in the layer and the ink setting property (drying property after printing) tends to decrease. If the thickness exceeds 10 μm, the void in the layer is large and printing unevenness tends to occur.

  The binder for adhering the pigment to the base paper 4 preferably contains alkyl-silanol-modified polyvinyl alcohol (PVA). The alkyl group of the alkyl-silanol-modified polyvinyl alcohol is a lower alkyl group, preferably a branched lower alkyl group having 6 or less carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, n-pentyl group, isopentyl group, 2-methylpentyl group, neopentyl group, n-hexyl group, 4-methylpentyl group, 3-methylpentyl Group, 2-methylpentyl group, 3,3-dimethylbutyl group, 2,2-dimethylbutyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2, 3-dimethylbutyl group etc. are mentioned, A methyl group is more preferable. When alkyl-silanol-modified polyvinyl alcohol is used, the solid content of the paint can be increased, so that a uniform coating layer (2, 3) can be formed. As a result, the coating layer (2, 3) can be formed uniformly, and gloss and smoothness are improved. Also, by increasing the solid content of the paint, it is difficult for the paint to sink into the base paper 4 immediately after coating, and the binder stays in the coating layer (2, 3). It is possible to prevent white spots from being peeled off from the work layer, and to reduce the amount of paper dust generated during cutting of the guillotine, thereby preventing white spots from being caused by paper dust.

  However, other binders can be included as the binder. The type of other binders is not particularly limited. For example, silanol-modified polyvinyl alcohol, ethylene vinyl acetate copolymer (EVA), styrene butadiene copolymer, vinyl acetate, polyvinyl acetal, oxidized starch, etherified starch, acrylate ester Resin, acrylamide resin, polyester resin, urethane resin, and the like. Among these, at least one kind or two or more kinds can be selected and used.

However, even when other binder is included, the alkyl-silanol-modified polyvinyl alcohol is 1 to 50 parts by weight, preferably 5 to 30 parts by weight, based on the active ingredient based on 100 parts by weight of the pigment. It is desirable to satisfy both smoothness and print quality. The coating amount itself is not particularly limited and is, for example, 5 to 30 g / m ² in terms of dry mass. Moreover, the coating layer (2, 3) can be made into the structure which provided the surface layer 3 containing a pigment and a binder on the lower layer 2. FIG. Although it does not specifically limit as the said pigment and a binder, It is preferable to contain an acicular ester-type resin and a urethane resin as a needle-like alumina hydrate as a pigment and a binder.

  As a result of intensive studies to solve the above problems, the present inventors have found that in all of the offset printing paper, gravure printing paper, and inkjet recording paper, the coating layer contains an alkyl-silanol-modified PVA inside the coating layer. It has been found that the glossiness, smoothness and surface strength of the ink can be improved, and the printing quality can also be improved. Furthermore, it discovered that image clarity can be improved by using a needle-shaped thing as the alumina hydrate which the surface layer 3 contains. However, in this case, the improvement of the coating layer strength and the improvement of the bleeding of the printing were not complete. Although the coating layer strength and surface strength can be adjusted by increasing or decreasing the amount of binder used, for example, increasing the binder reduces white spots due to peeling of the coating layer, but the ink absorbability deteriorates and the fine printability decreases. It was a conflict and it was difficult to achieve both. Therefore, as a result of further diligent research, the present inventors have found that by using an acrylic ester resin or a derivative thereof and / or a urethane resin or a derivative thereof as the binder of the surface layer 3, the ink absorbability and the peeling of the coating layer are reduced. I found out that both the problems of white spots can be solved.

  Here, the acrylic ester resin refers to a polymer obtained by polymerizing an acrylic ester and / or a methacrylic ester as a main monomer, and includes those obtained by copolymerizing vinyl chloride, vinyl acetate, butadiene and the like. The urethane resin is a urethane bond-containing polymer obtained by reacting diisocyanate and dialcohol, and includes those having a network structure by reacting polyol or polyisocyanate.

In this embodiment, the alumina hydrate is a compound represented by the formula Al ₂ O ₃ .nH ₂ O (n is an integer of 1 or more). Depending on the difference in composition and crystal form, it is classified into gypsite, vialite, norstrandite, boehmite, boehmite gel (pseudoboehmite), diaspore, amorphous amorphous, etc., but boehmite is preferable because of less ink bleeding. The needle shape means a shape having a major axis / minor axis ratio of 5 to 50, preferably 10 to 30, as observed by a microscope. The size of the acicular alumina hydrate is not particularly limited, and the major axis is, for example, 100 to 200 nm.

  As the pigment other than the acicular alumina hydrate, the same pigments as in the lower layer 2 can be used, but among them, colloidal silica is preferably used. In the case of using a combination of acicular alumina hydrate and colloidal silica, the blending ratio (mass basis) of the both is acicular alumina hydrate: colloidal silica = 30 to 70:70 to 30. It is preferable that ink absorbency and gloss / image clarity can be satisfied.

  In this embodiment, the number of blending parts of the acrylic ester resin and the urethane resin is not particularly limited, but the acrylic ester resin is preferably 5 to 40 parts by weight, and 10 to 40 parts by weight based on the active ingredient with respect to 100 parts by weight of the pigment. Part is more preferred. If the amount of the acrylate ester resin is too small, the strength inside the coating layer may decrease and a lot of white spots may occur. If the amount of the acrylate ester resin is excessive, the surface of the surface layer 3 is formed into a film, and the ink absorbency is increased. May be inferior. On the other hand, the urethane resin is preferably 1 to 20 parts by mass and more preferably 2 to 10 parts by mass based on the active ingredient based on 100 parts by mass of the pigment. If the amount of the urethane resin is too small, the strength inside the coating layer may be reduced and white spots may be generated, and the ink absorbability due to acicular alumina hydrate is likely to be reduced. On the other hand, if the amount is too large, the surface of the surface layer 3 is formed into a film, and the ink absorptivity may be inferior.

  When the lower layer 2 contains the alkyl-silanol-modified polyvinyl alcohol, the content is 1 to 50 parts by weight, preferably 5 to 30 parts by weight based on the active ingredient with respect to 100 parts by weight of the pigment. When it is contained in the surface layer 3, it is 1 to 30 parts by mass, preferably 2 to 20 parts by mass based on the active ingredient based on 100 parts by mass of the pigment. If the amount of alkyl-silanol-modified polyvinyl alcohol is too small, the concentration of the coating solution cannot be increased, and glossiness, smoothness, and surface strength are reduced. On the other hand, if the amount is too large, the coating layer (2, 3) containing the alkyl-silanol-modified polyvinyl alcohol may be formed into a film, resulting in poor ink absorbability. However, when at least one of the lower layer (coating layer) 2 and the surface layer (coating layer) 3 contains alkyl-silanol-modified polyvinyl alcohol, the coated paper 1 has a high level of gloss and image clarity.

  In addition, in the lower layer 2 and the surface layer 3, you may contain binders other than an acrylic ester resin, a urethane resin, and alkyl-silanol modified polyvinyl alcohol.

The coating amount of the surface layer 3 is not specifically limited, For example, it is 5-159 / m < ² > by dry mass.

  It does not specifically limit as a coating method of the coating liquid of the coating layer 2 and the coating layer 3, For example, using well-known coating machines, such as an air knife coater, a roll coater, a bar coater, a comma coater, a blade coater. Can be applied.

  The coated paper 1 of this embodiment may be flattened to improve glossiness and smoothness. A method for flattening is not particularly limited, and examples thereof include a super calendar, a soft calendar, a machine calendar, and the like, and at least one type or two or more types can be selected and used.

Further, in order to have a gloss as high as that of a silver salt photograph, a surface finish may be performed. As the method, a so-called cast coating is performed in which, while the surface of the coating layer 3 to which the coating material for the coating layer 3 is applied is in a wet state, the coating layer 3 is pressed against a heated mirror surface and then dried. It is preferable to use the method. In general, the cast coating method includes (1) a wet casting method (direct method) in which a coating layer is in a wet state and is dried by pressure bonding (pressure contact) to a mirror-finished heating drum, and (2) a wet coating method. Re-wet casting method (re-wetting method) in which the work layer is once (semi-) dried and then swelled and plasticized (wet) with a re-wetting liquid, and then pressed onto a mirror-finished heating drum (drying method). (3) Wet coating The layer can be divided into three types, that is, a gelation cast method (coagulation method) in which the layer is made into a gel state by a coagulation treatment such as a coagulation liquid, and then pressed onto a mirror-finished heating drum and dried. In this embodiment, the rewet cast method is preferable because the coating layer 3 can be formed without lowering the gloss of the white paper. In addition, according to the gelation cast method (coagulation method), the coating layer 3 becomes porous, so that the glossiness of blank paper is reduced regardless of the thickness of the coating layer, and the amount of paper dust generated when cutting guillotine is reduced. To do.

  The coated paper 1 of this embodiment can achieve a blank paper glossiness of 70% or more and image clarity of 50% or more, and is excellent in glossiness, smoothness, and ink absorption. Also, the surface strength is good, no paper dust is generated by guillotine cutting, and part of the paper is not peeled off together with the ink during printing, so there is no white spot trouble. The surface property is less deteriorated due to the surface being rubbed against other paper or a roll or bar inside the printer.

  Examples The effects of the present invention will be clarified with examples, but the present invention is not limited to these examples.

(Base paper)
100% hardwood bleached kraft pulp was used as a raw material, and the freeness was 370 ml. A paper strength agent and a sizing agent were each internally added in an amount of 5 kg based on the active ingredient standard to 1 t of the absolutely dry pulp, and talc was internally added as a filler so as to have an ash content of 13%. After papermaking and drying with a long paper machine, the oxidized starch was coated to a dry mass of 3.0 g / m ² using a size press to obtain a base paper having a rice basis weight of 157 g / m ² .

(Coating layer (lower layer))
Methyl-silanol modified PVA (WACKER, product number: 2907) or silanol modified PVA (WACKER, product number: P6060) is used as a binder for 100 parts by mass of amorphous silica (Grace, product number: ED5). The coating liquid containing as described in Table 1 was prepared, and this was coated on the surface of the base paper with an air knife coater so as to have a dry weight of 10 g / m ² . Each number is a number based on the active ingredient (the same applies to the following).

(Coating layer (surface layer))
60 parts by mass of acicular alumina hydrate (produced by Grace, product number: EM5075, major axis / minor axis ratio = 15, major axis 150 nm), colloidal silica (produced by Grace Japan Co., Ltd., product number: Ludox CL-P) 20 parts by mass And colloidal silica (manufactured by Catalyst Kasei Kogyo Co., Ltd., product number: Fine Cataloid C-125) with respect to 130 parts by mass of pigment, an acrylic ester resin (manufactured by NSC Japan, product number: A coating solution containing Yodozol KE35), urethane resin (manufactured by Nikka Chemical Co., Ltd., product number: Neofix IJ-170) and methyl-silanol modified PVA (manufactured by WACKER, product number: 2907) in the number of parts shown in Table 1 was prepared. , which, under the coating and drying the surface after, so that the dry mass 12 g / m ² by air knife coater And Engineering, were mirror-finished by re-wet casting method (re-wet method).
However, in Example 34 and Comparative Example 8, mirror finishing was performed by gelation cast method, and in Examples 6, 11, 16, 17 and Comparative Examples 2 and 5, flat alumina hydrated instead of acicular alumina hydrate. A product (manufactured by Sasol, product number: Disperal HP14, major axis / minor axis ratio = 1.2) was used. Further, the blending amount was appropriately changed as shown in Table 1.

(Measurement and evaluation method)
The inkjet recording paper produced as described above was measured and evaluated as follows. The results are shown in Table 1.

1) White paper gloss The 75 ° white paper gloss was measured according to JIS P 8142.

2) Beck smoothness Measured according to JIS P 8119.

3) Regular reflection smoothness Using a total reflection type printing smoothness meter (Microtopograph manufactured by Toyo Seiki Co., Ltd.), the measurement was performed under the condition of a set pressure of 25 kg / cm ² .

4) PPS smoothness Using a smoothness tester (Parker Print Surf, Lorentzen & Wettre) due to air leakage, measurement was performed at a clamp pressure of 490 Kpa and an air pressure of 1 MPa.

5) Image clarity Measured according to JIS H 8686-2.

6) Ink absorbability Solid printing was performed, and after 10 seconds from the completion, it was bonded to a high-quality paper and evaluated for transfer to the high-quality paper. The printing method and evaluation criteria were as follows.
(Printing method)
(1) Inkjet paper (Examples 1 to 34, Comparative Examples 1 to 9)
It printed with the inkjet printer (the Epson company make, PM-820).
(2) Coated paper (Examples 35 to 44, Comparative Examples 10 to 11)
Printing was performed using an oxidation polymerization type process ink (model number: Fusion G, manufactured by Dainippon Ink & Chemicals, Inc.) on an offset sheet-fed printing machine (model number: RVK3B, manufactured by MAN ROLAND).
(Evaluation criteria)
A: Transfer to fine paper was not observed.
○: Transfer to fine paper was slight.
(Triangle | delta): The transfer to quality paper was seen clearly.
X: Transfer to fine paper was remarkably observed.
Of the above evaluation criteria, the cases of ○ and ○ are judged to be actually usable.

7) Surface strength (coating layer peeling)
Using an RI printing aptitude tester (manufactured by Meisei Seisakusho), single color printing was performed on the paper surface with printing ink (product number: FINEINK, manufactured by Dainippon Ink & Chemicals, Inc.). The number of white spots per 25 cm ² was measured and evaluated based on the following evaluation criteria.
(Evaluation criteria)
A: No white spots occur and the printability is very good.
○: There are 1 to 2 white spots and excellent printability.
(Triangle | delta): There are 3-5 white areas, and it is a little inferior to printability.
X: The number of white spots exceeds 6, and the printability is very poor.
Of the above evaluation criteria, the cases of ○ and ○ are judged to be actually usable.

8) Printability (fine printability)
Characters and images were printed with an inkjet printer (manufactured by Epson, PM-820), and evaluated visually and with a magnifying glass (magnification 10 times) based on the following evaluation criteria.
A: No blurring of characters / images.
○: Slight blurring of characters / images occurs, but it cannot be visually confirmed.
Δ: Some blurring of characters and images occurs and can be visually confirmed.
×: The characters and images are noticeably blurred.
Of the above evaluation criteria, the cases of ○ and ○ are judged to be actually usable.

  As shown in Table 1, in Examples 1 to 34, the white gloss, Beck smoothness and image clarity are high, the coating layer strength is strong and the white spots are small, and the ink absorptivity and fine printability are good. It was. On the other hand, when flat alumina hydrate was used for the pigment of the coating layer, the image clarity was lowered. In addition, even when acicular alumina hydrate is used for the coating layer pigment, the surface strength and the fine printability are deteriorated when an acrylic ester resin or a urethane resin is used alone as a binder. In addition, the surface strength of Examples 1 to 34 was improved as compared with commercially available inkjet paper (Comparative Example 9, product number: glossy paper for digital camera WP2827, manufactured by Apica Corporation).

  The present invention is applicable as a coated paper having good white paper gloss, smoothness, and surface strength.

It is a fragmentary sectional view of the coated paper of this form.

  DESCRIPTION OF SYMBOLS 1 ... Coated paper, 2 ... Coating layer (lower layer), 3 ... Coating layer (surface layer), 4 ... Base paper.

Claims (7)

A coated paper having a base paper and at least one coating layer mainly composed of a pigment and a binder on the base paper,
A coated paper characterized by containing, as the binder, at least a lower alkyl-silanol-modified polyvinyl alcohol having 6 or less carbon atoms .   The coated paper according to claim 1, wherein the alkyl group is a methyl group.   The coated paper according to claim 1 or 2, wherein acicular alumina hydrate is contained as the pigment.   The coated paper according to any one of claims 1 to 3, wherein at least an acrylic ester resin or a derivative thereof and a urethane resin or a derivative thereof are contained as the binder. The coating layer is two or more layers,
As a binder of the coating layer in contact with the surface of the base paper, at least a lower alkyl-silanol-modified polyvinyl alcohol having 6 or less carbon atoms is contained,
As a pigment of the outermost layer of the coating layer, at least acicular alumina hydrate is contained, and at least an acrylic ester resin or a derivative thereof, and a urethane resin or a derivative thereof are contained as a binder,
The acrylic ester resin is contained in an amount of 5 to 40 parts by mass based on the active ingredient based on 100 parts by mass of the pigment, and the urethane resin is contained in an amount of 1 to 20 parts by mass based on the active ingredient based on 100 parts by mass of the pigment. The
The coated paper of any one of Claims 1-4.   The coated paper according to any one of claims 1 to 5, wherein an outermost layer of the coating layer is provided by a rewet cast method. The pigment contains colloidal silica together with the acicular alumina hydrate,
The mixing ratio of the acicular alumina hydrate and colloidal silica was 30 to 70:70 to 30 on a mass basis.
The coated paper of any one of Claims 1-6.

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