JPH059894A - High-smoothness mat-tone coated paper - Google Patents

Abstract

PURPOSE:To obtain high-smoothness mat-tone coated paper having high smoothness and excellent printability in spite of low glossiness of white paper. CONSTITUTION:Coated paper prepared by forming a coated layer consisting essentially of pigment and an adhesive on base paper wherein the pigment comprising the coated layer is pigment which contains >=20wt.% starch having 2.0-20 micron volume distribution average particle diameter and <=0.6 coefficient of variation of particle diameter and has (a) <=40% glossiness of white paper and (b) >=500 seconds OKEN type smoothness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly smooth matte coated paper, and in particular, it has a high smoothness, an excellent ink receptivity, and a printability even though the white paper has a low glossiness. The present invention relates to a high smooth matte coated paper of good quality.

[0002]

2. Description of the Related Art A conventional matte coated paper gives an elegant and calm feeling to a printed matter as compared with a coated paper having a high white paper glossiness, and since light reflection is small, printed characters are easy to read. It has the feature. Therefore, it is widely used from monochromatic prints such as text papers to multicolor prints such as posters, catalogs and magazine covers.

However, in order to suppress the glossiness of the white paper to a low level, the conventional matte coated paper contains a coating material containing a main pigment such as heavy calcium carbonate or an agglomerate pigment having a larger particle size than the ordinary coated paper. It is produced by coating the base composition with the industrial composition and then very lightly treating it with a super calender or the like, or drying it without applying it. For this reason, the surface of the conventional matte coated paper has remarkably low smoothness and poor printability such as low ink acceptability. Conversely, in order to improve printability, a treatment for increasing smoothness is required. When it is carried out, there is a drawback that the glossiness of the blank paper becomes high at the same time.

On the other hand, the gravure printing which is widely used at present has good reproducibility of photographs and paintings and forms a beautiful printed surface, but if the surface of the printed paper has low smoothness, miss dots and halftone dots are formed. Reproducibility is likely to occur, the printing effect is significantly reduced, and even in the widely used offset printing, if the surface smoothness of the printing paper is low, the ink acceptability deteriorates, and solid printing parts of multicolor printing In this case, the gloss of the ink becomes uneven, resulting in extremely poor quality printing. Therefore,
The conventional matte-coated paper has a drawback in that the smoothness of the paper surface is low and the ink inking property is poor, and thus high-quality printed matter cannot be obtained by gravure printing or offset printing.

For the purpose of solving such problems, Japanese Patent Laid-Open No. 59-199897 and Japanese Patent Publication No. 3-69693 disclose coating with a coating composition containing a specific heavy calcium carbonate. Disclose the paper. However, these coated papers are not yet sufficient in terms of improving the smoothness while keeping the white paper gloss low, and at present, the production of highly smooth matte coated paper suitable for gravure printing and offset printing. Is difficult and has been a major issue for those who manufacture coated paper.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a highly smooth matte coated paper which has a high smoothness and a good printability even if the white paper glossiness is low. And

[0007]

As a result of research for solving the above-mentioned problems, the inventors of the present invention have found that a starch having a specific volume distribution average particle size and a specific particle size variation coefficient is used as a conventional pigment. The inventors have found that a high smooth matte coated paper having a low white paper gloss, a high smoothness, and an excellent printability can be obtained by mixing and using it together, and thus completed the present invention.

The present invention is a coated paper in which a coating layer containing a pigment and an adhesive as a main component is provided on a base paper, and the pigment constituting the coating layer has a volume distribution average particle diameter of 2.0 to 2.0. 20 microns,
It is a pigment containing 20% by weight or more of starch with a coefficient of variation of particle size of 0.6 or less, (a) white paper gloss of 40% or less, and (b) Oken smoothness of 500 seconds or more. The featured coated paper is provided.

The term "volume distribution average particle size of starch" in the present specification refers to a value obtained by dividing the total volume of individual starch particles by the total number of particles. In the present specification, a particle size distribution measuring device (micrometer) is used. A volume distribution average particle size (MV) obtained by measurement using a track particle size analyzer: Nikkiso Co., Ltd. is used. The volume distribution average particle size of this starch can be calculated based on the following formula: Volume distribution average particle size (MV) = Σ (Vi × di) / ΣVi where Vi = volume ratio in each particle size segment di = representative diameter of the particle diameter in each particle size classification The term "coefficient of variation" in the present specification means the standard deviation (SD) of the volume particle diameter distribution in the volume distribution average particle diameter (MV).
Is the coefficient divided by and can be calculated based on the following formula: Coefficient of variation = SD / MV.

This coefficient of variation is a coefficient by which the influence of the average particle size of the volume distribution can be removed and the variation in particle size can be compared. The smaller the value, the more uniform the particle size and the more uneven the particle size. Indicates that there are few. The starch used in the present invention is a starch having a volume distribution average particle size of 2.0 to 20 microns and a variation coefficient of the volume distribution average particle size of 0.6 or less, which can be used in a non-gelatinized state. Is. For example, rice starch, wheat starch, Takapio starch, corn starch,
Although sweet potato starch and the like can be mentioned, rice starch is particularly excellent because it has a property of absorbing a basic dye well and sticking well to unevenness of paper. If necessary, a modified starch obtained by using the above starch as a raw material can be used. Particularly, when the starch is a slurry having a pH of 2 to 11,
And modified starch which is not gelatinized when dispersed in a paint having a pH of 5 to 10.5 and a temperature of 5 to 50 ° C. Furthermore, if necessary, starch crosslinked with a crosslinking agent such as formaldehyde, epichlorohydrin, succinic acid may be used.

The volume distribution average particle size of the starch used in the present invention is limited to 2.0 to 20 microns, because the volume distribution average particle size is 2.0 microns or less. This is because the glossiness of white paper does not fall below 40%, and when the volume average particle size exceeds 20 microns,
This is because the printability of the coated paper deteriorates due to a decrease in ink acceptability, and the thickness of the coating layer increases. The coefficient of variation of the particle size is set to 0.6 or less in order to suppress the variation in the particle size of the starch particles and improve the performance of the high smooth matte coated paper of the present invention.

The coated paper pigment used in combination with the starch satisfying the above-mentioned conditions may be any conventionally used coated paper pigment.
Although not particularly limited, those having a volume distribution average particle diameter of 0.5 to 10 microns and a coefficient of variation of the volume distribution average particle diameter of 0.3 to 1.5 are generally used. Specific examples include clay, kaolin, talc, aluminum hydroxide,
Light calcium carbonate, heavy calcium carbonate, titanium oxide, magnesium carbonate, alumina, activated clay, acid clay, diatomaceous earth, synthetic silica, zinc oxide, barium sulfate, calcium sulfate, satin white, lake, plastic pigment, binder pigment, etc. ..

The pigments of the present invention are prepared by mixing the starch and at least one of the above pigments. At this time, the ratio of the starch is 20% by weight or more, preferably 30%.
The amount is not less than wt% and the rest is the pigment. The reason for defining the proportion of starch in this way is that if the starch content is less than 20% by weight, the white paper glossiness can be kept low and the printability cannot be improved.

Further, the coating amount of this pigment is 5 to 30 g / m.sup.2, preferably 7 to ²⁰ g in terms of dry weight per one side.
/ M ² . This is because when the coating amount is less than 5 g / m ² , the coating effect is not sufficiently obtained, while when it is 30 g / m ² , the coating effect is saturated. By using the pigment thus prepared, the smoothness is high even if the white paper glossiness is low,
A highly smooth matte coated paper with good printability is obtained, and this coated paper has extremely few dot omissions when used for gravure printing and has excellent dot reproducibility, and especially when used for offset printing. Excellent ink receptivity and blister resistance. Such an effect can be obtained by using a pigment containing a predetermined amount of starch having a specific volume distribution average particle diameter and a coefficient of variation to reduce the white paper gloss, while
It is considered that the starch particles having a uniform particle size facilitate the alignment of the pigment particles in the coating layer, and a coating layer having a large volume and large voids can be obtained. Further, if the starch has a particle size larger than the range of the present invention, the surface smoothness after supercalendering or gloss calendering hardly deteriorates.

Conventionally, when pigment particles having a coefficient of variation of 0.6 or more are not uniform, a low white paper gloss can be obtained, but since the constituent particles also include coarse particles, sufficient surface smoothness cannot be obtained. It was not obtained, and the pigment easily filled the voids in the coating layer to form a dense coating layer, so that the glossiness of the white paper was likely to be high, but the specific volume distribution average particle diameter and the coefficient of variation of the present invention were obtained. By mixing a predetermined amount of starch with the pigment, such a decrease in surface smoothness is satisfactorily prevented.

As the adhesive constituting the coating layer of the present invention, known adhesives can be used without particular limitation,
For example, various copolymers such as styrene / butadiene type, styrene / acrylic type, vinyl acetate / acrylic type, ethylene / vinyl acetate type, butadiene / methylmethacryl type, vinyl acetate / butyl acrylate type, and alkali sensitive polyvinyl acetate. Or alkaline non-sensitive adhesive, further polyvinyl alcohol, maleic anhydride / styrene copolymer, isobutene / maleic anhydride copolymer, synthetic adhesive such as acrylic acid / methacrylate copolymer, further, Oxidized starch, etherified starch, esterified starch, enzyme-modified starch and cold water-soluble starch obtained by flash-drying them, casein, soybean protein and the like can be appropriately selected and used.

The ratio of the adhesive used is 100% pigment.
The solid content is 3 to 50 parts by weight, preferably 5 to 20 parts by weight, based on parts by weight. Also, if necessary, a dispersant,
Viscosity modifier, water retention agent, defoaming agent, water resistance agent, lubricant, dye,
Also, various auxiliaries such as a pH adjusting agent can be appropriately mixed. When preparing the coating composition, various mixers,
A mixing stirrer such as a kneader or a ball mill can be appropriately selected and used according to the type of coating composition.

Preparation of the coating composition for forming the coating layer is carried out by mixing the pigment 100 with the mixing stirrer.
Parts by weight, 3 to 30 parts by weight of the adhesive, and if necessary, additives such as a dispersant are sequentially added. The content of the coating solid content is generally selected from the range of 30 to 80% according to the purpose. The coating layer constituting the coated paper of the present invention is applied in a single layer or multiple layers on both sides or one side of the coated base paper. In this case, the composition of the coating composition applied on both surfaces and the composition of the coating composition forming each layer when applying in multiple layers can be appropriately changed according to a general method. The coating method is also not particularly limited, for example,
Air knife coater, roll coater, bar coater,
Various known coating devices such as a rod coater, a bevel or vent type blade coater, various blade coaters such as a bill blade and a twin blade, and a short dwell coater can be appropriately used. After coating, it is generally finished with a finishing device such as a super calendar or a gloss calendar.

The base paper used in the present invention is not particularly limited, and as the base paper, various wood pulps and synthetic pulps may be used alone or in combination to make paper.

[0020]

According to the present invention, even if the white paper glossiness is low,
A highly smooth matte coated paper having high smoothness and good printability was obtained, and this coated paper showed excellent printability for both gravure printing and offset printing.

[0021]

EXAMPLES The contents and effects of the present invention will be described in detail below based on examples, but the present invention is not limited to the scope of these examples. In addition, "parts" and "%" in Examples mean "parts by weight" and "% by weight", respectively, unless otherwise specified.

Example 1 Pigment of Coated Paper Commercially available rice starch (coefficient of variation 0.58, Micropearl, Shimada Chemical Co., Ltd.) was used alone. Base paper of coated paper A medium coated base paper for gravure having a basis weight of 41 g / m ² was used. Preparation of coating liquid Pigment 100 parts Styrene-butadiene type latex 9 parts (Tg = -20 ° C, T2102P, Nippon Synthetic Rubber) Modified starch 2 parts (Neil gum A85-Abebe) Sodium polyacrylate dispersant 0.4 parts (SDA -40P Somal) pH adjuster (sodium hydroxide) 0.1 part A coating solution was prepared using the above components so that the solid content of the coating was 38 to 50%.

On one side of the base paper, a coating amount of 20 g / m ² is applied to one side after drying the coating solution using a Mayer bar.
The coated paper of the present invention was obtained by coating and drying so as to be (both sides 40 g / m ² ), and further surface-treating with a test super calender. [Example 2] As a pigment, wheat starch (coefficient of variation 0.42, AS-22
Coated paper was prepared in the same manner as in Example 1 except that (5, Chiba Flour Milling) was used alone.

Example 3 As a pigment, cationized tapioca starch (coefficient of variation 0.58, Pira-4, Honshu Sangyo) was used alone, and the coating temperature was set to 30 ° C.
A coated paper was prepared in the same manner as in. Example 4 As a pigment, cross-linked starch (coefficient of variation 0.41,
Coated paper was prepared in the same manner as in Example 1 except that the coating temperature was 60 ° C. and the coating was performed.

[Comparative Example 1] A coated paper was prepared in the same manner as in Example 1 except that a commercially available heavy calcium carbonate (FMT-MAT55 Pharmatech) was used alone as a pigment. [Comparative Example 2] As a pigment, wheat starch (coefficient of variation 0.66,
Example 1 except that RS-100, Chiba Flour Milling) was used.
A coated paper was prepared in the same manner as in.

Comparative Example 3 A coated paper was prepared in the same manner as in Example 1 except that commercially available primary kaolin (coefficient of variation 0.66, Rustra-90, Freeport) was used as the pigment. The results of Examples 1 to 4 are shown in Table 1 and Comparative Examples 1 to 3
The results are shown in Table 2. [Table-1] Example 1 2 3 4 Starch Micropal AS-225 Pila-4 SELEX (rice starch) (wheat starch) (cationized tapioca starch) (crosslinked starch) Volume distribution average particle size 4.7 16.0 14.4 16.7 (μm) Coefficient of variation 0.58 0.42 0.58 0.41 Slurry pH 9.4 9.4 9.4 7.6 Coating pH 8.0 8.0 8.0 7.2 Coating temperature (℃) 30 30 30 60 White paper gloss (%) 26.1 13.6 13.3 13.1 Oken smoothness (s) 2100 710 780 740 Oken air permeability (s) 520 440 490 450 Missing halftone dots (pieces) 1 10 11 12 Halftone dot reproducibility ◎ ○ ○ ○ [Table-2] Comparative Example 1 2 3 Starch FMT-MAT55 RS- 100 Rustra-90 (Heavy carbon) (Wheat starch) (Primary kaolin) Volume distribution Average particle size 3.6 11.4 3.3 (μm) Coefficient of variation 0.81 0.66 0.66 Slurry pH 10.1 9.0 9.1 Coating pH 9.0 8.0 7.9 Coating temperature (℃ ) 30 30 30 White paper gloss (%) 22.8 12.9 71.9 Oken smoothness (s) 1310 630 2280 Oken air permeability (s) 2300 540 36000 Missing dots (pieces) 50 45 40 Halftone reproducibility × × ○ [Example 5] Rice starch (micro pearl) was added as a pigment 6
0% by weight and precipitated calcium carbonate (TP-121M
C, Okutama Kogyo Co., Ltd.) was used, and a coated paper was prepared in the same manner as in Example 1. [Example 6] Rice starch (micropearl) was added as a pigment 2
0% by weight and precipitated calcium carbonate (TP-121M
C, Okutama Kogyo Co., Ltd.) was used, and a coated paper was prepared in the same manner as in Example 1. [Comparative Example 4] Rice starch (micropearl) 10
% By weight and precipitated calcium carbonate (TP-121MC,
A coated paper was prepared in the same manner as in Example 1 except that 90% by weight of Okutama Kogyo Co., Ltd. was used.

The results of Examples 5 and 6 and Comparative Example 4 are shown in Table 3. [Table-3] Example 5 Example 6 Comparative Example 4 Starch pigment / Micropole / TP-121MC Micropole / TP-121MC Micropole / TP-121MC Combined pigment weight% 60/40 20/80 10/90 White paper gloss Degree (%) 31.6 38.2 46.6 Oken smoothness (s) 2000 2100 2010 Oken air permeability (s) 900 1000 1200 Missing dots (pieces) 9 15 40 Reproducibility of dots ◎ ○ × Tables 1, 2 and 3 As is clear from the results of the examples shown in Table 1, starch particles having starch particles used as a coating pigment and having a predetermined volume distribution average particle diameter and a coefficient of variation of the average particle diameter of 0.6 or less are used. The paper coated with the coating composition containing 20% by weight or more of all pigments has high smoothness and low white paper gloss, but has few miss dots and has excellent dot reproducibility. It is a coated paper for printing.

Example 7 As a pigment, rice starch (volume distribution average particle size 4.7 μm, coefficient of variation 0.58, micropearl,
Shimada Chemical Co., Ltd.) 60 parts, heavy calcium carbonate (ACE 25, Dowa Calfine) 40 parts, 0.4 parts sodium polyacrylate, 0.1 parts NaOH were added to prepare a pigment slurry, and phosphoric acid was further added. Esterified starch (Neil gum A-
85 Abe) 3 parts, SBR latex (JSR061
(7, gel content 52%) 12 parts, solid content concentration 38%
A paint was prepared. The resulting coating material is applied with a Meyer bar so that the coated amount is 10 g / m ^{2 on} one side.
It was coated on both sides at g / m ² and dried. The coated paper was conditioned at room temperature (20 ° C., 65% RH) for one day and then subjected to super treatment twice using a super calender under a pressure of 100 kg / cm 2.

[Example 8] As a pigment, 20 parts of rice starch (micropearl) and 40 parts of calcium carbonate (ace 25) were used.
Parts and kaolin (node # 2) 40 parts were used to obtain coated paper under the same conditions as in Example 7. [Example 9] As a pigment, 30 parts of cross-linked starch SELEX,
And 70 parts of calcium carbonate (TP-222H),
A coated paper was obtained under the same conditions as in Example 7, except that the coating amount was 20 g / m ² on one side.

[Comparative Example 5] Wheat starch (RS-
A coated paper was obtained under the same conditions as in Example 9, except that 100 and a coefficient of variation of 0.66) were used. [Comparative Example 6] A coated paper was obtained under the same conditions as in Example 7, except that 40 parts of heavy calcium carbonate (Ace 25) and 50 parts of secondary kaolin (Node # 2) were used without using starch. ..

Comparative Example 7 A coated paper was obtained under the same conditions as in Example 7, except that 100 parts of heavy calcium carbonate (Ace 25) was used alone without using starch. Examples 7-9
The results are shown in Table 4, and the results of Comparative Examples 5 to 7 are shown in Table 5. [Table-4] Example 7 89 Starch Micropal 60 parts Micropal 20 parts SELEX 30 parts (rice starch) (crosslinked starch) Volume distribution average particle size 4.7 16.7 (μm) Coefficient of variation 0.58 0.41 Co-pigment calcium carbonate ace 25 40 parts Ace 25 40 parts TP-222H 70 parts Kaolin-Notebook # 2 40 parts-Coating amount (g / m ² ) One side 10 (both sides 20) One side 10 (both sides 20) One side 20 (both sides 40) White paper gloss (%) 20 29 30 Oken smoothness (s) 920 930 720 Oken air permeability (s) 480 1030 790 Printing gloss (%) 46 59 61 Blister generation temperature (° C) 300 260 260 Ink inking ○ ○ ○ [Table-5] Comparative Example 5 6 7 Starch RS-100 30 parts- (Wheat starch) Volume distribution average particle size 11.4 (μm) Coefficient of variation 0.66 Combined pigment Calcium carbonate TP-222H 70 parts Ace 25 40 parts Ace 25 100 parts Kaolin-Notebook # 2 60 parts-Coating amount (g / m ² ) One side 20 (both sides 40) One side 10 (both sides 20) One side 10 (both sides 20) White paper gloss (%) 30 42 2 8 Oken smoothness (s) 590 900 720 Oken air permeability (s) 1000 1200 980 Printing gloss (%) 54 57 61 Blister generation temperature (° C) 240 200 220 Ink adhesion × △ × Shown in Table 4 As is clear from the results of the examples, the base paper coated with a coating material having a predetermined volume distribution average particle size and a starch particle having a particle size variation coefficient of 0.6 or less in an amount of 20% or more of all pigments. Is a rotary offset coated paper with high smoothness and low white paper gloss, yet high ink gloss after printing, excellent ink receptivity, and excellent blister resistance during printing. .. [Evaluation method] The conditions of measurement and evaluation were as follows. (1) White paper glossiness: angle 7 according to JIS-P8142
It was measured at 5 degrees. (2) Smoothness: J. TAPPI No5 Measured according to Oken type smoothness. The larger the value, the higher the surface smoothness and the smoother. (3) Air permeability: J. TAPPI No5 was measured according to Oken type air permeability, and was used as an index of voids in the coating layer. The smaller the value, the higher the air permeability and the more voids. (4) Miss dot: The number of defective ink transfer per 6.5 cm ^{2 in} 20% gradation part was measured after black printing with a gravure printing tester of Ministry of Finance Printing Bureau. The ink (OG-91 ink from Toyo Ink Mfg. Co., Ltd.) was adjusted to a viscosity of 15 seconds with a # 3 Zahn cup. (5) Halftone dot reproducibility: The halftone dot shape of the sample printed by the above method was visually evaluated.

◎ Excellent ○ Good △ Slightly inferior × Inferior (6) Printing glossiness In accordance with JIS K5701, printing was performed with an RI printer (Asahi Seisakusho) with an ink supply amount of 0.5 cc (Toyo Ink TK Mark V New Red M). Day and night (2
It was left at 0 ° C. and 65% RH). The printing glossiness of the sample left to stand was measured again at 75 degrees. (7) Blister generation temperature Similar to the printing glossiness, printing is performed on both sides with an RI printing machine and left in a normal state for one day (20 ° C. 65% RH). The left sample was immersed in a silicone oil bath and the temperature at which blisters were generated was measured. (8) Inking of ink: A sample whose printing glossiness was measured was visually evaluated.

Claims (1)

Claim: What is claimed is: 1. A coated paper comprising a base paper and a coating layer containing a pigment and an adhesive as a main component, wherein the pigment constituting the coating layer has a volume distribution average particle diameter. A pigment containing 20% by weight or more of starch having a particle size variation coefficient of 2.0 to 20 microns and a particle size variation coefficient of 0.6 or less, (a) white paper glossiness of 40% or less, and (b) Oken type smoothness. Is 500 seconds or more, coated paper.