JP3207634B2 - Process for producing matte coated paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an excellent white paper and a printed surface having low ink gloss, high gloss after printing, high contrast, and extremely low gloss unevenness and ink unevenness despite the low glossiness of the white paper. The present invention relates to a method for producing a matte coated paper having a shape and a small difference between front and back.

[0002]

2. Description of the Related Art In recent years, there has been an increasing need for matte coated papers which are dull but have a smooth surface and excellent ink receptivity, and are mainly used for fine art printing, catalogs, brochures, calendars and commercial publications. Is used for the body text sheet.

[0003] Among matte coated papers, printed matter called matte tone has low gloss on all white paper surfaces, single-color printing surfaces, and multicolor printing surfaces, and gives a flat and moist visual and tactile feeling over the entire surface. On the other hand, there is a case where the glossiness of a blank paper surface is not desired, but a certain glossiness is desired only for a printing surface. In other words, we want to make the text part or non-image area easy to read or be easy on the eyes with a low level of white paper glossiness, and to make the image area brighter with gloss to create a high-quality printed material with rich contrast. Needs. This is what is called the dull tone.
The dull tone is between the matte tone and the gloss tone, and generally, the glossiness of white paper and the gloss after printing are slightly higher than the mat tone, and the gloss after printing is slightly lower than the gloss tone.

[0004] Matte matte coated paper is usually compared with glossy coated paper in order to keep the gloss of white paper low.
The coating composition containing a large amount of calcium carbonate, which is a coarser pigment, is coated with various coaters and commercialized as it is, or commercialized only by mild calendering.
These matte matte coated papers are generally inferior in smoothness and ink adhesion, inferior to dull and glossy coated papers in terms of gloss after printing, and do not give printed matter rich in contrast. .

[0005] Also, dull-tone coated paper is generally commercialized by applying a lighter super calender treatment to a coated paper containing a larger amount of kaolin in order to increase gloss after printing as compared with a matte tone, and to further increase the amount of kaolin. ing. Accordingly, the glossiness of blank paper is increased, not only does not provide a printed matter having high contrast, but also uneven orientation of plate-like kaolin is generated, and uneven gloss and unevenness of ink attachment are increased, resulting in a loss of quality.

In order to solve such a problem, a method of treating coated paper with a metal roll having a specific surface roughness has already been proposed (Japanese Patent Laid-Open No. 4-119192). The surface roughness of each metal roll is specified to be treated with a roll having an Rmax (maximum height) of 8 to 25 μm, and the coating liquid and coating method are not specified.

[0007]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies to solve the above-mentioned problems of the matte coated paper, and as a result, have found that a coated paper containing a specific amount of a specific heavy calcium carbonate is required. The object of the present invention is to apply the liquid by overcoating, undercoating in two separate coats, drying, and then calendering by a specific paper passing method into a super calender of 6 or more stages incorporating two metal rolls, Despite the low glossiness of the white paper, it has high ink adhesion and high gloss after printing, rich in contrast, and has excellent white paper and printing surface condition with extremely low gloss unevenness and uneven ink adhesion, and has little difference between front and back. Matt coated paper was obtained.

[0008]

According to the present invention, the average particle size is
An undercoat coating liquid containing 10 to 90 parts by weight of heavy calcium carbonate of 0.5 to 1.0 μm and 90 to 10 parts by weight of kaolin is applied to base paper, and heavy calcium carbonate having an average particle size of 0.5 to 1.5 μm. Is coated with a topcoat liquid containing 55 to 95 parts by weight of kaolin and 5 to 45 parts by weight of kaolin and dried, and the surface roughness (Rz: ten-point average roughness JIS B0601) of 8 to 14 μm and 3 to
A 6-stage or more super calender incorporating two 7 µm metal rolls. Pass the coated paper so that one side of the coated paper first hits the 8 to 14 µm metal roll and the other side hits the 3 to 7 µm metal roll later. A method for producing a matte coated paper characterized by the following.

Hereinafter, the present invention will be described in detail. The present inventors previously prepared a coated paper obtained by applying a coating liquid containing 50 to 95 parts by weight of heavy calcium carbonate having an average particle diameter of 0.5 to 1.5 μm in one or more layers, to obtain a surface roughened paper. Rmax is 2
It was recognized that a print having high contrast was obtained by treating with a 8 μm metal roll (Japanese Patent Application No. 4-191354). However, according to the subsequent study, when the paper is passed through a vertical type super-calender of 6 or more steps, there is a difference between the front and back sides of the matte coated paper obtained when the surface roughness of the metal roll is the same as in this method. Admitted.

Conventionally, as a numerical value defining the surface roughness of a roll, Rmax (JISB0601: maximum height) has been used.
However, the value of Rmax is not reproducible due to the manufacturing method of the roll surface processing, and differs depending on the measurement position.
We acknowledged that the quality could not be controlled properly with these numbers. Therefore, as a result of re-examination by the present inventors, R
It was recognized that the quality could be controlled with good reproducibility by using z (JIS B0601: ten-point average roughness). By the way,
The conventional value of Rmax tends to be larger than Rz, but since the value of Rmax is not reproducible as described above, there is no fixed correlation between the two values.

Furthermore, as a result of intensive studies on the compositions of the undercoating coating liquid and the topcoating coating liquid used in the present invention, it was found that the average particle diameter of the heavy calcium carbonate in the undercoating coating liquid exceeds 1.0 μm. Or, if the compounding amount exceeds 90 parts by weight, the smoothness after coating the top coating liquid is inferior,
It was recognized that the gloss improvement after the final printing was insufficient. Further, when the amount of the heavy calcium carbonate is less than 10 parts by weight or the average particle size is less than 0.5 μm, the glossiness of the white paper after coating with the top coating liquid is too high,
It was recognized that a printed surface with high contrast could not be obtained. On the other hand, if the average particle size of the heavy calcium carbonate in the overcoating liquid exceeds 1.5 μm, or if the compounding amount exceeds 95 parts by weight, the improvement in gloss after printing becomes insufficient. On the other hand, if the amount of heavy calcium carbonate is less than 55 parts by weight or the average particle size is less than 0.5 μm, the glossiness of white paper becomes too high, and a printed surface with high contrast cannot be obtained.

In the case of treatment with a super calender having six or more stages, if one side of the coated paper is first applied to a metal roll having a surface roughness of less than 8 μm, the opposite side after passing the paper is used. It was recognized that there was a problem that the final blank glossiness was too high. If the roll is first applied to a roll larger than 14 μm, the gloss after final printing is insufficiently improved.

Similarly, the glossiness of the white paper becomes too high when the opposite surface to be applied later is applied to a roll having a surface roughness smaller than 3 μm, and when the opposite surface is applied to a roll having a surface roughness larger than 7 μm.
Insufficient improvement in gloss after printing.

Therefore, when processing with a super calender, the coated paper must be finished so that one side of the coated paper first hits a metal roll of 8 to 14 μm and the other side of the coated paper hits a metal roll of 3 to 7 μm later. There is a problem that a gloss difference occurs after printing.

As described above, according to the present invention , the glossiness (JIS P-8142) is obtained by applying the specific coating liquid twice as described above and finishing the paper passing under the above-mentioned calender conditions.
(75 ° white paper glossiness) is adjusted to be a coated paper of 40% or less .

As the adhesive used in the present invention, various copolymers such as styrene / butadiene, styrene / acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylate, vinyl acetate / butyl acrylate and polyvinyl alcohol; Maleic anhydride copolymer,
Synthetic adhesives such as acrylic acid / methyl methacrylate copolymers, natural adhesives such as oxidized starch, esterified starch, enzyme-modified starch, and cold-water-soluble starch obtained by flash-drying them, casein, soy protein, etc. And generally known adhesives. These adhesives are used in an amount of 5 to 50 parts by weight per 100 parts by weight of the pigment. In the coating liquid of the present invention, various auxiliaries, such as a dispersant, a thickener, a water retention agent, a defoaming agent, and a water-proofing agent, which are blended in a general pigment for coated paper are used.

The coating composition thus prepared is obtained by coating a base coat and a top coat with a blade coater and a blade coater, respectively.
A combination of an air knife coater and a blade coater, a blade coater and an air knife coater, a gate roll coater and a blade coater, and a combination of a gate roll coater and an air knife coater are applied on the base paper by on-machine or off-machine.

As the base paper, a paper-based or board-based base paper having a basis weight of 30 to 400 g / m ² used for general printing coated paper is used. The coating amount of the coating composition on such base paper is 15 to 50 by dry weight in terms of quality.
It is adjusted in the range of g / m ² .

As described above, the present inventors have found that the average particle size is 0.5 to 1.
An undercoat coating solution containing 10 to 90 parts by weight of 0 μm heavy calcium carbonate and 90 to 10 parts by weight of kaolin is coated on base paper, and heavy calcium carbonate having a particle size of 0.5 to 1.5 μm is coated on the base paper.
After coating and drying an overcoating liquid containing 55 to 95 parts by weight and 5 to 45 parts by weight of kaolin, the surface roughness (Rz: ten point average roughness JIS B0601) of 8 to 14 μm and 3 to 7 μm A super calendar with 6 or more stages incorporating two metal rolls.
One side of the coated paper first hits a metal roll of 8 to 14 μm,
Finishing so that the opposite side later hits a metal roll of 3 to 7 μm, so that despite the glossiness of white paper being 40% or less, the ink inking property, the gloss after printing is high, the contrast is rich, the uneven gloss, the ink inking It was confirmed that a matte coated paper having excellent white paper and printed surface state with very little unevenness and having a small difference between front and back can be obtained.

[0020]

【Example】

(Examples 1 to 3 and Comparative Examples 1 to 9) The present invention will be specifically described below with reference to examples, but the present invention is not limited by these.

As shown in Table 1, kaolin [manufactured by Engelhard Co., Ltd., trade name: Ultra White 90] and heavy calcium carbonate [manufactured by Sankyo Seimitsu Co., Ltd., trade name: Escalon # 1500 (average particle diameter) 1.7 μm), trade name: Escalon # 2000 (average particle diameter 1.2 μm), trade name: Escalon # 2200 (average particle diameter 0.9 μm) or manufactured by Yotai Co., Ltd., trade name: Tankal NCC-α-90 (average particle) 0.3 parts by weight of a dispersant (Toa Gosei Co., Ltd., trade name: Aron T-40) is added to 100 parts by weight of the mixed pigment having a diameter of 0.5 μm), and the mixture is dispersed in water using a Cowles disperser. 5 parts by weight of oxidized starch (Oji Cornstarch Co., Ltd., trade name: Oji Ace B) and 10 parts by weight of synthetic adhesive (Asahi Kasei Co., Ltd., trade name: L-1762) as an adhesive, top coat and undercoat Coating composition A solid concentration of 63%)
I got

This was coated on a base paper having a basis weight of 90 g / m ^{2 using} a blade coder so that the dry weight (one side) of the undercoat coating composition shown in Table 1 was 8 g / m ² , and dried. Then, a top coat composition shown in Table 1 was coated with a blade coater such that the dry weight (one side) thereof was 7 g / m ² .
Dried.

As shown in FIG. 1, the obtained coated paper had a surface roughness (Rz: ten-point average roughness JIS B0601) shown in Table 1.
Is a first roughened roll (3-2) using a 12-stage super calender (Minami Senju Seisakusho) consisting of a metal roll (3) incorporating two metal rolls of 5 μm, 11 μm or 18 μm and a cotton roll (1). Is the F side (4-
Treated as in 1). Linear pressure during calendar processing
100kg / cm, metal roll temperature 70 ℃, processing speed 600m / m
in constant.

In Comparative Examples, Comparative Example 8 was not subjected to calendering, and Comparative Example 9 was such that the coating composition had a dry weight (one side) of 15 g / m ^2. Is a coated paper obtained by applying a single layer on the coated paper.

<Quality evaluation method> Average particle size: The average particle size was measured using a light transmission type particle size distribution measuring device SHC5000 manufactured by Seishin Enterprise at the 50% point of the cumulative weight distribution.

White paper gloss: Measured at an angle of 75 degrees according to JIS P-8142.

Smoothness: Measured with a Japan Tappi No5 Oken type smoothness tester.

Gloss after printing: Ink for Sakata Inks offset printing (product name:
(Diatone GSL red) was printed using 0.35 cc, and after leaving it overnight, the glossiness was measured at 75 degrees.

Contrast: Using a two-color offset sheet-fed printing machine (Ryobi: 3302M), printing was performed using one-color indigo and two-color red ink, and the contrast between white paper and the printed surface was visually evaluated. The visual evaluation criteria were the following three levels. ：: Very rich contrast △: Normal contrast ×: Insufficient contrast

・ Surface (irregular gloss, irregular ink coverage): 2
Using a color offset sheet-fed printing machine (Ryobi: 3302M), printing was performed using one-color indigo and two-color red ink, and the gloss unevenness on the blank paper surface and the ink adhesion unevenness on the print surface were visually evaluated. The visual evaluation criteria were the following three levels. ◎: Very good surface condition ○: Relatively good surface condition △: Normal surface condition

Front-back difference: Using a two-color offset sheet-fed printing press (Ryobi: 3302M), printing was performed using one-color indigo and two-color red ink, and the front and back differences between the blank and printed surfaces were visually evaluated. . The visual evaluation criteria were the following two levels. ◎: Those with almost no front and back ×: Those with front and back

[0032]

[Table 1]

[0033]

As is clear from Table 1, Example 1,
2 and 3 have high smoothness despite low blank gloss,
The print finish is very glossy and very rich in contrast after printing, and there is very little gloss unevenness of white paper and unevenness of ink deposition, and there is almost no difference between the front and back sides.

On the other hand, in Comparative Example 1, since the content of kaolin in the undercoat coating liquid was high, the glossiness of white paper was too high and the contrast was poor. In Comparative Example 2, since the particle diameter of the heavy calcium carbonate blended in the undercoat coating liquid was large, the smoothness was low and the gloss after printing was low. In Comparative Example 3, since the amount of kaolin in the topcoat coating solution was high, the glossiness of white paper was too high and the contrast was poor. Comparative Example 4
Has a large particle size of heavy calcium carbonate blended in the overcoating liquid, and therefore has low smoothness and low gloss after printing. In Comparative Example 5, since the surface roughness of the roll that first hits the coated paper is smaller than the surface roughness of the roll that hits later, the smoothness, blank gloss, and gloss after printing of the later hitting surface are higher than the first hitting surface. And the difference between the front and back is too large. In Comparative Example 6, since the surface roughness of the first contacting roll is too large, the smoothness, glossiness of white paper, and gloss after printing of the first contacting surface are lower than that of the later contacting roller, and the front-back difference is too large. In Comparative Example 7, since the surface roughness of the first roll and the second roll is too large, the smoothness is low and the gloss after printing is low. In Comparative Example 8, since no calendar processing was performed, the smoothness was low and the gloss after printing was low. Comparative Example 9 has only one coating layer, and therefore has low smoothness and low gloss after printing.

As can be seen from the above, the matte coated paper produced by the method for producing a matte coated paper according to the present invention gives unprecedented excellent quality, and its product value is extremely large. is there.

[Brief description of the drawings]

FIG. 1 is a super calendering apparatus which is composed of 12 rolls for obtaining a matte coated paper used in an embodiment of the present invention and which is first passed so that a surface corresponding to a roughening roll is an F surface. FIG.

[Explanation of symbols]

 1-1-6 Cotton Roll 2-1-2 Chilled Roll 3-1-2 Roughened Metal Roll 4 Coated Paper 4-1 F-side 4-2 W-side

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-221499 (JP, A) JP-A-2-2344993 (JP, A) JP-A-4-119192 (JP, A) JP-A-4-199 91294 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) D21H 19/00-27/42

Claims (1)

(57) [Claims] (1) In the production of matte coated paper in which a base paper is coated with a coating liquid twice, 10 to 90 parts by weight of heavy calcium carbonate having an average particle size of 0.5 to 1.0 μm and 90 to 10 parts by weight of kaolin are used. Undercoat coating solution containing parts by weight is coated on base paper, and the particle size is
55-95 parts by weight of 0.5-1.5 μm heavy calcium carbonate,
Coating a topcoat coating solution containing 5-45 parts by weight of kaolin,
After drying, the surface roughness of the roll (Rz: ten-point average roughness J)
IS B0601) has two metal rolls of 8 to 14 μm and 3 to 7 μm.
With a super calender of 6 or more stages incorporating this, one side of coated paper hits a metal roll of 8 to 14 μm first, and the other side hits a metal roll of 3 to 7 μm later, and the gloss (JIS
P-8142 A method for producing matte coated paper, characterized in that the paper is calendered so that 75% white paper glossiness is 40% or less.