JP2850697B2 - Method for producing double-sided matte coated paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing double-sided matte coated paper. More specifically, the present invention relates to a method for producing a double-sided matte coated paper having no surface difference and excellent surface properties on both sides.

[0002]

2. Description of the Related Art Matte coated papers are used widely in the fields of monochromatic printing to high-grade multicolor printing, since they provide an elegant and calm printing effect in printing, and the demand is growing further. Matte coated paper is obtained by coating a base paper with a paint mainly composed of a pigment and an adhesive, drying, and then treating the coated paper surface with a roll to impart a matte effect to the paper surface. However, as a method of treating the surface of coated paper, the method of light pressure welding using a metal roll having a smooth surface has recently been changed to a method of pressure welding using a roughened roll.

A method of treating the surface of a coated paper using a roughening roll is intended to transfer the pattern on the surface of the roughening roll to the paper surface by pressing against the paper. This is preferable in that unevenness of gloss on the paper surface, that is, so-called gloss mottle, is eliminated, and the texture of the paper surface is fine.

[0004] However, when the matting treatment is performed, since the treatment by the roughening roll is performed on each side of the coated paper,
The matte surface is likely to have a difference between the front and the back, and the most serious is that the gloss tends to be different. Conversely, even if you try to apply matting treatment on both sides simultaneously, passing the coated paper through the nip consisting of roughening rolls will only damage the paper surface and cause paper breakage,
It must be passed between the roughening roll and the elastic roll and processed on one side. That is, in this case, only the surface that comes into contact with the roughening roll is matted, and eventually both surfaces cannot be simultaneously matted.

[0005] Therefore, for example, when the front and back sides of the coated paper are subjected to a matting process by contacting the front and back surfaces once each with a roughening roll, if the front surface is first brought into contact with the roughening roll, the back surface is elastic. When the back surface is brought into contact with the roughening roll, the front surface is brought into contact with the elastic roll to be processed. The surface of the coated paper obtained in this way is more affected by the roll surface that comes into contact in the final stage, and the surface is flat, so that the reverse side is matted on the back side. , The front surface has a higher gloss than the back surface. The opposite phenomenon can be seen in the first stage of paper passing, but the effect of the roll abutting the coated paper in the last stage is much stronger. So, in order to reduce the effect of the roll, in the final stage, the coated paper is passed through the nip between the elastic rolls to improve the effect of eliminating the difference between the front and back sides to a certain extent. It is not at present.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned situation, the present inventors have attempted to eliminate the difference between the front and back of a double-sided mat coated paper obtained by surface treatment using a calender comprising a roughening roll and an elastic roll. Focusing on the shape and roughness of both the roll surface of the roughened roll when processing one side of the coated paper first and the roughened roll when processing the opposite side thereafter, as a result of earnest research, It has been found that by providing a slight difference between the surface shapes of the two, a double-sided matte coated paper having almost no surface difference and excellent surface properties on both surfaces can be obtained, and the present invention has been completed.

[0007] The reason why such a measure must be taken for the roughening rolls is that, as described above, the double-side matting of the coated paper is performed by applying the matte on both sides simultaneously by passing the coated paper between the roughening rolls. Since it is not possible to perform the treatment, each side of the coated paper is processed by being brought into contact with the roughening roll, but in this case, particularly, in the final stage, the surface in contact with the roughening roll and the surface in contact with the elastic roll This is because there is always a difference between the two sides.

The difference between the front and the back is due to the difference in the surface properties of the roughened roll and the elastic roll. The surface contacting the roughened roll is linearly bonded to the elastic roll contacting the opposite surface. Instead, the pattern of the roughened roll can be transferred because of uniform contact having a certain nip width. Therefore, in the final stage, when the roughened roll and the elastic roll are compared with each other, the coated surface that has been abutted and treated, the surface that abuts on the former roll is naturally matted. However, the surface in contact with the latter roll has a smooth paper surface, is glossy, and has gloss.

That is, regarding the glossiness, the effect is clearly opposite between the two rolls, and the surface in contact with the elastic roll in the final stage has a higher glossiness than the surface in contact with the roughening roll. is there. As described above, the roughened roll and the elastic roll play different roles, and it is meaningless to try to make the surface properties of both surfaces of the coated paper closer by using the combined roll.

However, as a means for eliminating the difference between the front and back sides of the paper, only the amount corresponding to the increase in the gloss imparted to the surface that comes into contact with the elastic roll in the final stage is transferred to the roughening roll in the preceding stage. It is effective to strengthen matting applied in contact, that is, to reduce glossiness. Based on this idea, the surface roughness of the roughening roll when applying a matte treatment to one side of the coated paper is better than that of a roughening roll for later matting the opposite side. Japanese Patent Application Laid-Open No. 4-91294 discloses that it is sufficient to make it larger and coarser. However, this method is not preferable because even if the difference between the front and back sides of the glossiness of the coated paper is reduced, the front and back sides can be seen in the surface texture.

As a result of intensive research based on the above examination results,
First, a roughening roll A for matting one side, and a roughening roll B for matting the opposite side later.
By simply making the surface roughness of A macroscopically greater than that of B, even if the coated paper is pressed and matted with such a roughening roll, the difference between the front and back sides in the glossiness is not significant. Even if it can be eliminated, it is not possible to eliminate the difference between the front and back sides of the paper surface. In addition, the present inventors assume that the surface of the roughening roll has a length.
Large irregularities of 10 to 35 μm randomly within 1 mm 3 to 12
When a plurality of roughening rolls each having a rough surface provided thereon and having a small undulation of 2 to 8 μm formed on the rough surface are simply used in combination, the surface properties of the white paper and the surface properties after printing are extremely reduced. It has been proposed that an excellent double-side coated paper can be obtained (Japanese Patent Application No. 3-351068), but it has not been able to eliminate the difference between the front and back of the texture of the coated paper. That is, it is effective to eliminate the difference between the front and back sides of the paper surface only by providing a difference between the roughening rolls A and B in the finer portion, not the macro-roughness of the roughening roll surface. I understood that.

That is, this is a roughening method in which a large undulation corresponding to a macroscopic surface roughness is provided, and a small undulation corresponding to a microscopic surface roughness is provided on a roughened surface which is a larger undulation. What can be achieved for the first time by using a roll is that a difference between the roughening rolls A and B is provided on a rough surface formed of large undulations provided on the roughening rolls A and B. It has proven to be the most effective.

An object of the present invention is to provide a method for producing a double-sided mat coated paper which has almost no difference in front and back sides in glossiness and texture between white papers and has excellent surface properties on both sides.

[0014]

According to the present invention, a coated paper obtained by coating a base paper with a paint containing a pigment and an adhesive as a main component and drying the coated paper is used to form a roughened roll having a surface length of 1 mm. Between 3 and 12 large undulations of 10 to 35 μm are randomly provided between the roughened surface and the roughened roll and the elastic roll on which the small undulations of 1 to 10 μm are further formed. By passing through the surface, only the surface in contact with the roughening roll is matted, and then the opposite surface is treated so as to be in contact with another roughening roll, so that both surfaces are matted. In the method for producing a coated paper, small undulations of a roughening roll for matting one side of the coated paper _first are x ₁ μm, and peaks and valley peaks of large undulations including small undulations are set. The height difference of y is ₁ μm, and the opposite side of the coated paper is roughened for matting X ₂ small roll undulations
μm, small when the ups and downs of big ups and downs of the mountain, including the difference in height between the peak of the peak and the valley was y ₂ μm, the following formula _{(1) x 2 + 6 ≧} x 1 ≧ x 2 +1 ··· (1) And the following equation (2): 1.1y ₂ > y ₁ > 0.9y ₂ (2) The coated paper after passing at least once between the roughening roll and the elastic roll satisfying the relational expression: The difference between the front and back of the gloss measured at an angle of 75 degrees according to JIS P 8142 is 10 points or less, and the two-dimensional surface roughness (R
A method for producing a double-sided matte coated paper, wherein the difference between the front and back of a) is 0.05 μm or less.

More specifically, the present invention will be described in detail. A small undulation x ₁ provided on a roughening roll A for imparting matting to one side of the present invention, and a peak of a mountain including large and small undulations are provided. The height difference between the peak and the peak of the valley is represented by y _1, and the same x ₂ and y ₂ in the roughening roll B for imparting matting to the opposite surface satisfy the above formulas (1) and (2). Set the surface of the roughening roll within the range, and furthermore, the gloss between the coated paper surface obtained by passing the paper between the rolls combined with such a roughening roll and the elastic roll and processing is different. If the treatment is carried out so as to eliminate the difference, the desired effect can be obtained without any difference in the appearance of the skin.

Thus, between the small undulations x ₁ and x ₂ of the roughening rolls A and B is ₁ to 6 μm, preferably 2 μm.
If a difference in the range of .about.4 .mu.m is given, the glossiness of the coated paper obtained will not change. If the make them beyond 6μm the difference between x ₁ and x _2, towards the surface contacting the elastic rolls in the final stage, that ever is lower gloss than surface contacting the roughened roll and opposite The difference between the front and back sides cannot be compensated for by further processing through the nip between the elastic rolls. the difference between x ₁ and x ₂ is less than 1 [mu] m, it is impossible to eliminate the difference between both sides of the gloss.

On the other hand, regarding the large undulations provided on the roughening roll, the difference between A and B must be provided.
Although not as large as in the case of small undulations, since the glossiness changes and greatly affects the texture of the paper surface, the expression (2) must be satisfied. Within the range of this equation (2), y
₁ may be smaller than y _{2 in} some cases. That small when relief provided the difference between x ₁ and x _2, such as when little difference was seen in the plane of temper, if the y ₁ somewhat smaller than y _2, improving the temper can do.

The roughening roll used in the present invention is a roll made of steel or an alloy which has been roughened by sandblasting, corrosion, or the like, or whose surface is further subjected to chrome plating. 3 to 12 large undulations (differences between peaks and valley peaks on the roll surface) of 10 to 35 μm are randomly provided in a length of 1 mm to form a rough surface. A small undulation of 1 to 10 μm is formed on the top.

Examples of the elastic roll used in combination with the roughening roll include cotton, asbestos, wool, and plastic rolls such as polyurethane and polyether. Good, but usually hardness (ASTM D-2240
A Shore D hardness of 80 mm or more is effective.

The pigments for coated paper used in the present invention include kaolin, calcium carbonate, titanium oxide, aluminum hydroxide, satin white, zinc oxide, barium sulfate, calcium sulfate, calcium sulfite, talc, silica, activated clay, Examples of pigments generally used in paints for coated paper, such as diatomaceous earth and plastic pigment, can be given. In particular, those obtained by combining heavy calcium carbonate as a main component and appropriately selecting and combining these pigments are preferably used.

Further, the adhesive for coating liquid used in the present invention includes a casein, a soybean protein, a yeast protein, a starch, an oxidized starch, an esterified starch, an etherified starch, a cationized starch, an enzyme-modified starch and the like. Starch, natural adhesives such as cellulose derivatives and styrene-butadiene copolymers,
Conjugated diene copolymer latex such as methyl methacrylate-butadiene copolymer, acrylic polymer latex such as acrylate ester, methacrylate polymer or copolymer, acetic acid such as ethylene-vinyl acetate copolymer Examples thereof include a vinyl polymer latex and a synthetic adhesive such as polyvinyl alcohol. One or more of these adhesives are used, and 5 to 30 parts by weight per 100 parts by weight of the pigment is blended.

In the preparation of the coating liquid used for the present invention, various auxiliaries usually used in coating liquids such as dispersants, flow modifiers, defoamers and colorants are appropriately selected as necessary. Used as

The coating liquid prepared as described above is composed of cellulose pulp such as wood pulp or waste paper pulp as a raw material, and is coated on both sides of base paper made by a known paper machine, if necessary, in an amount of 10 to 10 per side. It is coated in the range of 35 g / m ² .

The coating method is not particularly limited, and may be appropriately selected from blade coaters, air knife coaters, bar coaters, roll coaters, champlex coaters and the like used in the production of general coated paper.
Single or multi-layer coated, dried to 3-8% moisture content and wound up.

The coated paper thus obtained is passed between the roughening roll and the elastic roll of the present invention while being pressed against each other, and the nip linear pressure, the temperature, and the coating amount of the paint are adjusted. By this, the difference between the front and back of the blank (before printing) glossiness of the coated paper measured at an angle of 75 degrees according to JIS P 8142 is 10 points or less, preferably 0 to 8 points, and the white paper defined by JIS B 0601 A double-sided matte coated paper having a two-dimensional surface roughness (Ra) difference in front and back of 0.05 μm or less, preferably in the range of 0 to 0.04 μm is obtained. Conversely, if the difference in the glossiness of the white paper exceeds 10 points or if the two-dimensional surface roughness of the white paper has a front and back difference exceeding 0.05 μm, it can no longer be said that both surfaces have excellent surface properties, Not suitable for use.

According to the present invention, by adjusting the size of the small undulations provided on the roughening roll, the glossiness of the coated paper can be adjusted without affecting the texture of the paper surface. Therefore, it is superior to a known method of changing macroscopic surface roughness that affects the texture of the paper surface.

[0027]

The present invention will be described in more detail with reference to the following examples, but it should be understood that the present invention is by no means restricted thereto. Hereinafter, all “parts and%” indicate “parts by weight” and “% by weight”.

Example 1 Hardness bleached kraft pulp (LBKP) with a freeness of 450 ml CSF (Canadian standard freeness) 60%, softwood bleached kraft pulp (NBKP) with a freeness of 400 ml CSF 15% and coated paper broke 2
0.5 part of cationized starch (Kate F, manufactured by Oji National Co., Ltd.), 0.3 part of sulfate band (18 crystal water salt of aluminum sulfate), 0.3 part of alkenyl succinic acid sizing agent (Mitsubishi) Petroleum Co., Ltd., Fibran 81) 0.06 parts, heavy calcium carbonate (manufactured by our company, wet pulverized product) 6 parts, precipitated calcium carbonate (Toyo Denka Kogyo Co., Ltd., T
NC C-10) 6 parts and 0.03 part of a polyacrylamide-based retention aid (Percoll 57, manufactured by Allied Colloids Co., Ltd.) were added in this order to obtain a paper stock, and the paper was made with a known fourdrinier paper machine. A surface sizing agent of the following formulation was applied to both sides by a size press at a rate of 2.0 g / m ² per paper and dried, and then pressed on a machine calender at a roll nip linear pressure of 30 kg / cm and wound up as a base paper for coating. The basis weight of the obtained base paper is 8
At 2.0 g / m ² , the two-dimensional surface roughness of the base paper was 2.4 μm.

Formulation of size press solution Enzyme-modified starch (manufactured by the company) 80% Polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Company, T-330H) 17% Styrene acrylic acid-based sizing agent (Arakawa Chemical Industries, Polymalon 1308S) 3%

A coating liquid having the composition shown below is coated on both sides of the base paper obtained as described above by a 18 g / m ² blade coater per side in the order of front and back, and dried by a known dryer. To produce coated paper with a paper moisture content of 6%.

Composition of coating liquid : 28% kaolin (trade name: Ultra White 90, manufactured by Engelhard Co.), 46% heavy calcium carbonate (manufactured by the company, ground calcium carbonate) having an average particle diameter of 1 μm, and precipitated calcium carbonate ( Shiraishi Industry Co., Ltd., product name: Brilliant 15) 16
% And average particle size 2μm Sachin White (made in-house) 10
% Of a pigment mixture in a mixer, and 4 parts of oxidized starch (manufactured by Oji Cornstarch Co., Ltd., trade name: Oji Ace A) and latex (manufactured by Nippon Synthetic Rubber Co., Ltd.) Name: JSR-0632) 11 parts, sodium polyacrylate 0.3 parts as dispersant, calcium stearate 0.4 parts as lubricant, acrylic resin (BASF, Acrosol C-50L) 0.2 parts as water retention agent, fluorescent dye 0.2 parts Were sequentially added and thoroughly mixed and dispersed, and the pH was adjusted to alkaline with a 5% aqueous sodium hydroxide solution to prepare a coating liquid.

Next, a large unevenness of 17 μm is formed on the surface of the roughening roll, and a further small unevenness of 5 μm is formed on the roughened surface randomly provided in six pieces with a length of 1 mm.
The difference between the peak of the mountain and the peak of the valley including large and small undulations is 22
1 μm hard surface roughening roll A and large undulations of 17
1 μm and the same number as 6, but a small undulation was formed at 4 μm, and the difference between the peak and the valley peak including the large and small undulations was 21 μm.
Two cotton elastic rolls (fill mat, manufactured by Yuri Roll Co., Ltd.) having a Shore D hardness of 85 ° according to the standard D-2240 were arranged, and obtained in the super calender shown in FIG. 1 as described above. One side of the coated paper, that is, the surface (non-wire side in the paper machine) is
After that, the paper was passed so that the opposite surface, that is, the back surface (the wire surface in the paper machine) was in contact with B once.
In the super calender, the surface temperature of the roughening roll is 40
° C, roll nip linear pressure 200Kg / cm, paper passing speed 600m /
Per minute, and the quality of the obtained double-sided matte coated paper was evaluated by the following method.

Quality Evaluation Method (1) Glossiness of White Paper Gloss was measured at an angle of 75 degrees according to JIS P 8142. (2) Two-dimensional surface roughness of blank paper Measured in accordance with JIS B 0601 using a surface roughness measuring instrument (model: SE-3AK) manufactured by Kosaka Laboratory, and the center line average roughness (Ra)
Indicated by

Example 2 The large undulation of the roughening roll is the same as in Example 1, except that the small undulation is 6 μm and the difference between the peak of the hill including the large and small undulation and the peak of the valley is 23 μm. One surface-roughened roll A, similarly one surface-roughened roll B having a small undulation of 4 μm and a difference of 21 μm between a peak peak and a valley peak including large and small undulations, each having a Shore D hardness of 90 ° polyether resin elastic roll (YCR-5500, manufactured by Yamauchi) 5
A book and three chilled rolls are arranged, and the surface of the coated paper obtained in the same manner as in Example 1 with the super calender shown in FIG. The paper was passed twice so as to contact the roll B. In the super calender, the surface of the roughened roll was treated at 40 ° C., the roll nip linear pressure was 160 kg / cm, and the paper passing speed was 600 m / min. I went in.

Example 3 A large undulation of 11 μm was formed on the surface of a roughened roll and the length was 1 mm.
On the rough surface that is randomly provided seven between
The roughened roll A, in which the difference between the peaks of the peaks and the valleys including the large and small undulations is 17 μm, and the large
On each of the roughened surfaces, a small undulation of 3 μm is further formed, and a difference between a peak of a hill and a peak of a valley including a large and small undulation is 17 μm. Two elastic rolls made of polyether resin having a hardness of 85 mm (YCR-5100, manufactured by Yamauchi Co., Ltd.) are arranged, and the surface of coated paper obtained in the same manner as in Example 1 using the super calender shown in FIG. Was once contacted with the roughening roll A, and then the paper was passed so that the back surface once contacted the roughening roll B. Supercalender treatment and evaluation of the quality of the obtained double-sided matte coated paper were performed in the same manner as in Example 1.

Example 4 A large undulation of 13 μm was formed on the surface of a roughening roll and the length was 1 mm.
On the rough surface, which is randomly provided between 6
A roughening roll A in which a small undulation of μm is formed and the difference between a peak of a mountain and a peak of a valley including large and small undulations is 21 μm, and a large undulation of 21 μm is randomly generated between a length of 1 mm and 5 mm
On each of the rough surfaces provided, a small undulation of 2 μm is further formed, and each of the roughening rolls B having a difference of 23 μm between the peak of the hill and the peak of the valley including the large and small undulation is 23 μm. Five cotton elastic rolls (fill mat, manufactured by Yuri Roll Co., Ltd.) having a Shore D hardness of 85 mm and three chilled rolls were arranged, and the coating was obtained in the same manner as in Example 1 using the super calender shown in FIG. The paper was passed so that the surface of the paper came into contact with the roughening roll A twice and the back surface of the coated paper came into contact with the roughening roll B twice. The processing conditions in the super calender were the same as in Example 2, and the quality of the obtained double-sided matte coated paper was evaluated in the same manner as in Example 1.

COMPARATIVE EXAMPLE 1 Large irregularities of 17 μm were formed on the surface of the roughened roll with a length of 1 mm.
On the rough surface that is randomly provided between 6
Two roughened rolls A and B (the specifications are the same for both rolls) in which a small undulation of μm is formed, and the difference between the peak of the peak and the peak of the valley including the large and small undulation is 22 μm. The same elastic roll as used in (Polyether resin, Shore D
(Hardness: 85 °). Two coated papers were passed through the super calender shown in FIG. 1 such that the front and back surfaces of the coated paper obtained in the same manner as in Example 1 were respectively in contact with the roughening roll once. I made a paper. The treatment with a super calender and the quality evaluation of the obtained double-sided matte coated paper were performed in the same manner as in Example 1.

Comparative Example 2 A large undulation of 18 μm was formed on the surface of the roughened roll and the length was 1 mm.
5 μm on the rough surface randomly provided between 6
A large undulation of 16 μm is formed on the surface of the roughened roll A and the roughened roll having a difference of 23 μm between the peaks of the peaks and the valleys including the large and small undulations.
On the rough surface that is randomly provided between 6
One rugged roll B having a difference of 21 μm between a peak of a hill and a peak of a valley including large and small undulations is formed, and two elastic rolls same as those in Example 1 are arranged. The coated paper obtained in the same manner as in Example 1 using the super calender shown in FIG.
The sheet was passed through the sheet so that the back surface once contacted the roughening roll B. The treatment of the super calender and the quality evaluation of the obtained double-sided matte coated paper were performed in the same manner as in Example 1.

Comparative Example 3 A large undulation of 11 μm was formed on the surface of the roughened roll and the length was 1 mm.
8 on the rough surface that is randomly provided between
A large undulation of 17 μm is formed on the surfaces of the roughened roll A and the roughened roll in which the difference between the peak of the peak and the peak of the valley including the large and small undulation is 19 μm.
On the rough surface that is randomly provided six between mm,
Further, one roughened roll B having a small undulation of 1 μm and having a difference of 18 μm between the peak of the hill and the peak of the valley including the large and small undulations, five elastic rolls as in Example 3 and chilled Three rolls are arranged, and the coated paper obtained in the same manner as in Example 1 using the super calendar shown in FIG.
The paper was passed so that the front surface was in contact with the roughening roll A twice and the back surface was in contact with the roughening roll B twice. The treatment of the super calender was performed in the same manner as in Example 2, and the quality evaluation of the obtained double-sided matte coated paper was performed in the same manner as in Example 1.

Comparative Example 4 Large undulations of 15 μm on the surface of the roughened roll were 1 mm in length.
On the rough surface that is randomly provided between 6
A large undulation of 14 μm is formed on the surface of the roughened roll A and the surface of the roughened roll in which the difference between the peak of the peak and the peak of the valley including the large and small undulation is 20 μm.
On the rough surface that is randomly provided six between mm,
Further, a roughening roll of 4 μm is formed, and the difference between the peak of the peak and the peak of the valley including the large and small undulations is 18 μm. Each one of the roughening rolls B is made of polyether resin having a Shore D hardness of 95 mm. Two elastic rolls (YCR-5600, manufactured by Yamauchi Co., Ltd.) are arranged, and the coated paper obtained in the same manner as in Example 1 using the super calender shown in FIG. The paper was passed so that the back surface once contacted the roughening roll B. The treatment of the super calender and the quality evaluation of the obtained double-sided matte coated paper were performed in the same manner as in Example 1.

Table 1 shows the results obtained in Examples 1 to 4, and Table 2 shows the results obtained in Comparative Examples 1 to 4.

[0042]

[Table 1]

[0043]

[Table 2]

As can be seen from the table, the roughened roll is provided on each roughened surface between the roughened roll where the first side of the coated paper comes into contact and the roughened roll which subsequently comes into contact with the opposite side. There is an appropriate difference in the size of the small undulations, and the difference between the peak of the peak and the peak of the valley including the large and small undulation of the surface of the roughening roll is provided within a predetermined range. If the surface is treated with such a super calender, there is almost no difference between the front and back sides in the glossiness and the surface roughness of the double-sided mat coated paper, and good quality can be obtained (Examples). 1-4).

On the other hand, when the surface shapes of the two roughening rolls are the same (Comparative Example 1) and the front and back surfaces of the coated paper are respectively subjected to surface treatment, they are first brought into contact with the roughening rolls and treated. Although the glossiness of the surface is reduced once, the surface immediately contacts the elastic roll, and then contacts the elastic roll again, so that the glossiness is considerably increased. , But the subsequent surface treatment with a roughening roll will reduce the gloss,
The glossiness cannot be recovered by only one surface treatment with the elastic roll in the last stage. That is, when the coated surface is first treated with a roughening roll, the glossiness varies greatly depending on the number of times the surface of the coated paper is abutted by an elastic roll used thereafter, and a super In the calendering process, there is always a difference in the number of times of contact with the elastic roll on the front and back of the coated paper, so if the front and back of the coated paper are abutted with a roughening roll having the same surface roughness shape, There is always a difference in the gloss. If the coated paper is not passed through the nip between the elastic rolls and passed through the nip between the roughening roll and the elastic roll at the final stage of the super calendar treatment of the coated paper, The difference between the front and back of the degree and the texture (surface roughness) becomes even larger.

In order to eliminate the difference between the front and the back of the coated paper in such a super calendar process,
Trying to make a difference in the surface roughness of the roughening roll,
Even if there is a difference between the large undulations of the roughening roll, there is no effect of eliminating the difference between the front and back surfaces unless a small undulation provided on the roughened surface has a difference (Comparative Example 2). However,
Even if a difference is made between such two roughening rolls with a small undulation, if the difference exceeds an appropriate range, the glossiness of the opposite surface is too high, and the difference between the front and back surfaces cannot be eliminated yet ( Comparative example 3).

In the surface shapes of the two roughening rolls, the difference between the peak of the peak and the peak of the valley, including large and small undulations, exceeds 10% between the two roughening rolls. If there is a difference, even if there is no difference between the front and back sides of the glossiness of the obtained coated paper, a difference occurs in the surface roughness, which appears as a difference in texture (Comparative Example 4). In other words, the adjustment of the surface roughness between the roughening rolls used for matting requires a macroscopic surface roughness. It is preferable to provide a difference in microscopic surface roughness without changing as much as possible.

[0048]

According to the present invention, when a coated paper is subjected to a matting treatment using an apparatus in which a roughening roll and an elastic roll are combined, the glossiness and the surface roughness (texture) of both surfaces of the coated paper after the treatment are both front and back. In order to eliminate the difference, the roughened surface of the roughened roll is between a roughened roll for matting one side of the coated paper and a roughened roll for matting the opposite side. It is effective to provide an appropriate difference in the surface roughness indicated by small undulations provided on the surface, and the present invention provides a method for producing a double-side matte coated paper having no surface difference and excellent surface properties on both sides. It has the effect that it can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a super calendering apparatus including various rolls for obtaining a double-side matte coated paper by bringing the front and back surfaces of the coated paper into contact with a roughening roll once. FIG. 3 is a schematic cross-sectional view illustrating a paper state. Introduced with the coated paper surface up.

FIG. 2 shows the flow of coated paper in a super calendering apparatus composed of various rolls for contacting the front and back surfaces of the coated paper twice with a roughening roll to obtain a double-sided matte coated paper. FIG. 3 is a schematic cross-sectional view illustrating a paper state. Introduced with the coated paper back side up.

[Explanation of symbols]

 A: Roughening roll B: Roughening roll 1 ... Elastic roll 2 ... Chilled roll 3 ... Paper roll 4 ... Coated paper

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) D21H 25/08 D21H 19/36-19/64 D21G 1/02

Claims (1)

(57) [Claims] 1. A coated paper obtained by coating a base paper with a paint containing a pigment and an adhesive as a main component and drying the coated paper, randomly forming a coated paper having a surface of a roughening roll of 10 to 35 μm in a length of 1 mm. The rough surface is provided with 3 to 12 large undulations, and the rough surface is formed with a small undulation of 1 to 10 μm on the rough surface. In the method for producing a double-sided matte coated paper in which only the surface in contact with the roughening roll is matted, and then the opposite surface is treated so as to be in contact with another roughening roll, and both surfaces are matted. a small undulation roughening roll for matting the one surface of the coating to be paper x ₁ [mu] m, the height difference between mountain peaks and valleys of the peak of the large undulations, including small undulations and y ₁ [mu] m to A small undulation of a roughening roll for matting the opposite side of the coated paper later x ₂ μm m, the height difference between the peak of the large undulation including the small undulation and the peak of the valley is y
When the ₂ [mu] m, the following formula _{(1) x 2 + 6 ≧} x 1 ≧ x 2 +1 ··· (1) and the following formula _{(2) 1.1y 2> y 1} > 0.9y 2 ··· (2) The difference between front and back glossiness measured at an angle of 75 degrees according to JIS P 8142 of the coated paper after passing at least once between the roughening roll and the elastic roll satisfying the relational expression is 10 points or less, And two-dimensional surface roughness defined by JIS B 0601 (R
a) a method for producing a double-sided matte coated paper, wherein the difference between the front and back sides is 0.05 μm or less.