JP3033929B2 - Transparent paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent paper, and in particular, has excellent printability, especially an effect of preventing set-off of ink, and has excellent ink setting properties and drying despite having a flat and uniform transparency. It relates to a transparent paper having excellent properties.

[0002]

2. Description of the Related Art Conventionally, various methods for producing transparent paper have been known.
Typical methods are to treat paper with concentrated sulfuric acid to make it transparent, to make beaten chemical pulp to make paper, to impregnate base paper with a clarifying agent such as wax or synthetic resin, to make synthetic fiber or synthetic pulp. There is a method in which the mixed paper is made transparent by heating and pressing.

[0003] Printing on these transparent papers is also used for various purposes. In general, in offset printing, the vehicle in the ink penetrates into the paper layer immediately after printing, whereby the viscosity of the ink film transferred to the paper surface increases, and the ink film rapidly loses fluidity and solidifies. This is called a set,
As the setting progresses, the ink does not adhere to the finger to the extent that it is held down with the finger. If this set is delayed for any reason,
In the case of sheet-fed printing, pressure is applied when the paper is stacked on the output tray of the printing press, and in the case of rotary printing, the pressure is applied when the paper is wound, so that the ink adheres to the back side of the paper on it . This phenomenon is called “set-off”, and when set-off occurs, it becomes a major problem in quality.

[0004] All of the above-mentioned transparent papers have a flat and uniform transparency without causing any irregularities on the surface because the internal voids are significantly reduced and the surface of the paper is smooth. On the other hand, on the other hand, there is a problem in that the permeation of the ink into the paper layer is inevitably hindered, the setting of the ink is slowed, and set-off occurs when the printed matter is stacked. In the case of oxidation polymerization type ink,
Since the drying of the ink proceeds by the supply of oxygen in the air after printing, the above-mentioned transparent paper, which has excellent surface smoothness and extremely small internal voids, has another problem that the ink drying property is poor. ing.

[0005] Therefore, when printing such transparent paper, the printing speed is set to 50% or less of that of ordinary paper, or the setting and drying properties are reduced in order to prevent set-off and to promote the setting and drying of ink. Do not use fast drying special ink for excellent synthetic paper, add compound or drying accelerator to ink for preventing set-off, sprinkle powder on the printing surface, or do not pile up at the paper output section. Measures were taken, which required very complicated labor and cost.

[0006]

SUMMARY OF THE INVENTION The main object of the present invention is to solve such problems. Specifically, as with conventional transparent paper as described above, despite having a flat and uniform transparency without causing the surface to feel uneven, ink transfer during printing can be performed. It is an object of the present invention to provide a transparent paper which has an excellent effect of preventing ink, has a quick setting and drying of ink, and is compatible with various printing methods such as high quality paper.

[0007]

SUMMARY OF THE INVENTION The present inventors have previously disclosed in Japanese Patent Application No. 2-258652 a method of forming a convex and a non-pattern portion on a base paper having a substantially uniform fiber amount in the thickness direction. Imparted, a transparentizing agent dissolved in an organic solvent, and dried after coating the void volume occupied by the non-pattern portion or less, the design paper characterized by increasing the difference in transparency between the convex pattern and the non-pattern portion Filed. An object of the present application is to obtain a design paper having excellent transparency between a pattern portion and a non-pattern portion and having a transparent feeling.

[0008] The present inventors have continued to study the production of transparent paper by using a flat base paper without a pattern and infiltrating it with a clarifying agent dissolved in an organic solvent. It was found that a uniform transparent feeling could not be obtained, and a problem of ink set-off during printing and a problem of poor ink setting and drying occurred. In order for the clarifying agent dissolved in the organic solvent to be able to penetrate into the base paper, the density of the base paper must be reduced, but for that purpose, it is necessary to suppress beating during preparation of the stock, and inevitably The formation of the base paper becomes worse. When the clarifying agent is impregnated into base paper having poor formation, poor formation is emphasized, and a flat and uniform transparency cannot be obtained at all. The clarifying agent also suppresses the penetration of the vehicle in the ink into the paper, delays the setting of the ink, and tends to cause set-off.

On the contrary, even if the same clarifying agent is used,
Japanese Patent Application No. 2-258652 described above in which a pattern is provided on a base paper.
It was found that these problems hardly occurred in the transparent paper proposed by No. As a result of studying this phenomenon in detail by the present inventors,
It has been found that the reason for this is that the uneven portion provided on the base paper has an effect of preventing the ink surface from adhering to the back surface of the paper in a wide area.

The present inventors have further studied and obtained a transparent paper having a flat, uniform transparency and excellent printability by forming a specific fine uneven portion on the surface. And found that the present invention was completed. The present invention provides a transparent agent is, are substantially uniform fiber quantity is filled into the base paper having a substantially uniform fine irregularities on at least one surface of the entire surface formed to the thickness direction
In the transparent paper, the fine irregularities have a center line average roughness of 5 to 50 μm, a maximum height of 60 μm or less, and a pitch of 0.5 μm or less.
The transparent paper is 1 mm to 1.5 mm.

The base paper used in the present invention needs to have a substantially uniform fiber amount in the thickness direction. One object of the present invention is to obtain a transparent paper having a flat and uniform transparency over the entire surface of the paper. Therefore, a base paper having an uneven fiber amount in the thickness direction, for example, Japanese Patent Publication No. 37-1
No. 5405, Japanese Patent Publication No. 50-32564, Japanese Patent Publication No. 51-
A base paper whose formation is intentionally broken or a base paper having a see-through pattern, such as a design paper described in No. 44206, is not suitable for the present invention.

The transparent paper of the present invention can be prepared by a method of filling a base paper having fine irregularities on its surface with a clarifying agent or a method of filling a base paper having a flat surface with a clarifying agent and then subjecting it to a shaping treatment. Obtainable.

First, a method of filling a base paper having a surface with fine irregularities with a clarifying agent will be described. Base paper is softwood bleached kraft pulp (NBKP), hardwood bleached kraft pulp (LBKP), softwood bleached sulphite pulp (N
Wood pulp such as BSP), thermomechanical pulp (TMP), etc., or hemp,
Non-wood pulp such as bamboo, straw, kenaf pulp and the like, synthetic pulp such as polyolefin, rayon, vinylon, nylon, polyester and the like may be used alone or in combination as appropriate, and various fillers, coloring agents, A sizing agent, a wet paper strength enhancer, a dry paper strength enhancer and the like are appropriately used in combination, and usually have a freeness of 100 to 500 ml. S. F. ,
Preferably 250-300 ml C.I. S. F. Beaten
It is usually produced using a fourdrinier paper machine or a circular net paper machine at a basis weight of 40 to 250 g / m ² (basis weight in terms of absolute dryness, the same applies hereinafter), preferably 50 to 150 g / m ² .

A method in which fine irregularities formed on the base paper are pressed on a paper machine or on wet paper having a water content of about 30 to 50% added to a formed paper with an embossing roll of rubber, metal, synthetic resin or the like. Alternatively, it is formed on one side or both sides of the base paper by a method such as pressing a wet paper having a water content of about 60% on a paper machine with a knitted felt or the like.

The fine irregularities of the present invention, when filled with a clearing agent and measured with a stylus type surface roughness measuring instrument specified in JIS B-0651, are JIS B-06.
The center line average roughness defined by 01 is 5 to 50 μm, preferably 15 to 35 μm, the maximum height is 60 μm or less, preferably 40 μm or less, and the pitch (average interval between peaks of the uneven portion) is 0. 0.1 to 1.5 mm, preferably 0.1 to 1.5 mm.
It needs to be formed to have a thickness of 25 to 0.5 mm. These values focus on only the fine irregularities formed by the shaping treatment and the like, and exclude the surface roughness derived from the pulp fibers that the base paper originally has.

The center line average roughness is an effective index for indicating the height of the peaks and the depths of the valleys of the irregularities on the surface of the paper. In the present invention, when this value is smaller than 5 μm, the transferability of the ink is reduced. Although the print quality after printing is improved, the effect of preventing set-off is not obtained, and the ink drying property is also deteriorated. Also 6
If it is larger than 0 μm, the effect of preventing set-off increases,
Although drying of the ink is quicker, uneven portions are visually recognized, and it is difficult to obtain a uniform transparency. In addition, reproducibility of halftone dots at the time of printing is deteriorated, resulting in poor printing. In consideration of the balance between the two, it is particularly preferable to form fine uneven portions so that the center line average roughness is 15 to 35 μm.

Further, even when the center line average roughness is in the range of 5 to 50 μm, since the paper has “undulations” peculiar to the fibers forming the sheet, the contrast is increased when the height of the projections (mountains) is increased. Is emphasized, and a uniform transparent feeling cannot be obtained. Therefore, the maximum height from the center line needs to be 60 μm or less, preferably 40 μm or less.

Even if the center line average roughness and the maximum height of the fine irregularities are in the above range, if the number of irregularities present per unit area of the transparent paper is small, the printing surface comes into contact with the back surface of the paper. The area becomes large, set-off occurs, and the ink setting property deteriorates. Therefore, in the present invention, the pitch of the concave and convex portions (average interval between peaks) needs to be 0.1 to 1.5 mm, preferably 0.25 to 0.5 mm.

Fine irregularities are formed almost uniformly on the front surface of one or both sides of the base paper, but in the present invention, it is particularly preferable to form them on both surfaces. By doing so, the same printing effect can be obtained regardless of which side of the paper is printed. In addition, when the uneven portions are provided on both surfaces, the effect of obtaining a uniform transparency is also enhanced.

As described above, when the paper is generally made with a low freeness (in a state where the beating is advanced), the formation of the paper is improved, and the homogeneity is improved. According to the results of studies by the present inventors, even a base paper that has been beaten to the limit that can be used in the present invention, if fine rugged portions are not formed on the surface, poor paper formation will be caused when filled with a clarifying agent. It was emphasized that it was not possible to obtain a uniform transparent feeling as much as conventionally known transparent paper.

It is considered that the reason why the flat and uniform transparency is obtained by providing the fine uneven portions is that light is scattered by the uneven portions formed on the surface, thereby canceling the poor formation of the base paper. . This effect is further emphasized when fine irregularities are provided on both surfaces.

In the present invention, the fine irregularities on the surface reduce the magnitude of secondary bonds between molecules between the ink and the paper to be set off. That is, it is said that this uneven portion suppresses the distance of the secondary binding force, and the size is weakened in inverse proportion to the third or sixth power of the distance between the molecules,
At a slight distance, the adhesion energy of each other is significantly reduced. Therefore, the fine irregularities have a great effect on the printability of transparent paper having a small porosity, especially on the prevention of set-off.

In the present invention, any known clarifying agent can be used. For example, waxes such as paraffin, higher fatty acid, fatty acid amide, fatty acid alcohol ester, phenol resin, urea resin, epoxy resin, melamine resin, Alkyd resin or the like, or thermosetting resin modified from them, polyacrylate, polymethacrylate, polyvinyl chloride, polyvinyl acetate, polystyrene, polybutene, polyester, polyurethane, polyamide, nitrocellulose, cellulose acetate, cellulose acetate Butyrate, hydroxyethyl cellulose, cellulose or polysaccharide derivatives such as sucrose acetate isobutyrate, rosin, rosin ester,
Ultraviolet light consisting of dammar resin, shellac, or a resin modified from these, or a prepolymer having a radical polymerizable unsaturated group in the molecule, a liquid vinyl monomer such as styrene or methyl methacrylate, and a photosensitizer. Curable resin (cured by UV lamp etc.), prepolymer having radically polymerizable unsaturated group in the molecule, styrene, liquid vinyl monomer such as methyl methacrylate and unsaturated polyester, diacryl phthalate, modified acrylic, Radiation-polymerizable resin such as electron beam composed of modified epoxy, modified urethane, polyfunctional monomer and the like (cured by an electron beam generator or the like) or the like, and these may be used alone or in combination of several kinds. In the present invention, a curing agent, an optional coloring agent, a surfactant, a plasticizer, and the like can be appropriately mixed and used in addition to the clarifying agent.

In the present invention, the clarifying agent-containing solution prepared as described above is filled in a base paper. As a filling method, a method of filling using a known coating machine such as a gravure coater or a roll coater, a method of filling using an impregnating machine, and the like can be adopted.

As described above, fine irregularities may be formed by forming a base paper having no irregularities by filling the transparency with a transparentizing agent, in addition to the method of filling the base paper with the irregularities beforehand. After that, it may be provided based on a method of shaping using an embossing machine. Also in this case, the center line average roughness, the maximum height, and the pitch need to be the numerical values described above, and it has been confirmed that the object of the present invention can be achieved by any method.

[0026]

EXAMPLE 1 30 parts by weight of papermaking NBKP and 70 parts by weight of LBKP of base paper were blended.
Freeness 430 ml C.I. S. F. Was beaten. Then, a sizing agent (trade name "Size Pine E", manufactured by Arakawa Hayashi Sanyaku Co., Ltd.) and pulp solids 1% and a starch (trade name "Amicol 602", Niseki Co., Ltd.) to pulp solids 1% was added, and the pH was adjusted to 4.5 with aluminum sulfate. This slurry is formed by a fourdrinier paper machine, dewatered and then pre-dried, and when the water content is 15%, a press mold is applied between the embossing roll and the counter roll having a flat surface at a linear pressure of 100 kg / cm. Then, it was dried to obtain a base paper having a basis weight of 100 g / cm ² . 62 parts by weight of a transparency-treated polyacrylate resin (trade name "TESFINE 404", manufactured by Hitachi Chemical Co., Ltd.)
A gravure roll coater was used to apply a coating consisting of 5 parts by weight of polyethylene glycol, 28 parts by weight of toluene, and 5 parts by weight of methyl ethyl ketone to a dry solid weight of 10 g / m ² on a gravure roll coater. The back side (smooth side) was coated and dried to obtain a transparent paper. When the obtained transparent paper was measured with a surface roughness measuring device, the center line average roughness of the surface (embossed surface) was 5 μm and the maximum height was 5 μm.
m, and the pitch was 1.5 mm.

EXAMPLE 2 The center line average roughness of the surface was changed by changing the embossing roll.
The same transparent paper as in Example 1 was manufactured except that a surface having a thickness of 0.1 μm, a maximum height of 60 μm, and a pitch of 0.1 mm was obtained.

Example 3 The same transparent paper as in Example 1 was produced except that the embossing roll was changed to obtain a surface having a center line average roughness of 25 μm, a maximum height of 20 μm, and a pitch of 0.4 mm.

Example 4 The embossing roll was changed and the same shaping treatment was performed on the front and back sides, and the center line average roughness on one side was 5 μm, the maximum height was 5 μm, and the pitch was 1.5.
The same transparent paper as in Example 1 was produced except that the sides of mm were obtained.

Example 5 Two embossing rolls identical to those in Example 1 were manufactured and subjected to the same shaping treatment on the front and back, and a surface having a center line average roughness of 50 μm, a maximum height of 60 μm, and a pitch of 0.1 mm on one side was obtained. A transparent paper identical to that of Example 1 was manufactured except for the above.

Comparative Example 1 The same transparent paper as in Example 1 was produced except that the base paper was not subjected to the shaping treatment, and a flat surface having a center line average roughness of 3 μm and a maximum height of 4.5 μm was obtained. did.

Comparative Example 2 Example 1 was repeated except that the embossing roll was changed and the same molding treatment was applied to the front and back sides, and a surface having a center line average roughness of one side of 60 μm, a maximum height of 70 μm, and a pitch of 6 mm was obtained. The same transparent paper was produced.

Comparative Example 3 A transparent paper manufactured by a conventional method is described as a comparative example. Commercially available tracing paper (made by bleaching bleached chemical pulp for a long time and making it extremely viscous and papermaking), (trade name “Classico Tracing”, manufactured by Mitsubishi Paper Mills, basis weight 75 g / m ² ) When measured using a needle meter, the center line average roughness was 0.2 μm and the maximum height was 0.1 μm.

Table 1 shows the evaluation results of the transparent paper obtained in each of the examples and comparative examples. The evaluation was performed by the following method. 1) Center line average roughness, and maximum height, and pitch:
In accordance with JIS B-0651 and JIS B-0601, a surface roughness measuring device (trade name "Surfcoder SE-3")
0C "(manufactured by Kosaka Laboratory Co., Ltd.). 2) Opacity: Measured according to JIS P-8138. The smaller the value, the better the transparency. 3) Transparency homogeneity: Flat and uniform transparency was visually determined. Evaluation was made by a five-point method, where one point was the worst and five points were the best. Three or more points are levels that can satisfy the object of the present invention. 4) Effect of preventing set-off of ink: Printing was performed using an offset printing machine to evaluate sheet-fed printing. The evaluation was carried out visually and evaluated by a five-point method. One point indicates the worst (severe set-off) and 5 points indicates the best (no set-off). Three or more points are levels that can satisfy the object of the present invention. 5) Ink setting property: Solid printing was performed using a standard offset printing ink using an RI tester (manufactured by Akira Seisakusho Co., Ltd.), and the state of the ink setting was evaluated with a finger.
One point indicates the worst, and five points indicate the best. Three or more points are levels that can satisfy the object of the present invention. 6) Ink drying property: Solid printing was performed using a standard offset printing ink using an RI tester (manufactured by Akira Seisakusho Co., Ltd.). (Interval) was evaluated for ink transferability to the white paper side. The evaluation was carried out visually and evaluated by a five-point method. One point indicates the worst (severe set-off) and 5 points indicates the best (no set-off). Three or more points are levels that can satisfy the object of the present invention.

[0035]

[Table 1]

As is clear from Table 1, in Example 1 in which the values of the center line average roughness and the maximum height are small and the pitch is large, the set-off and settability of the ink are at levels that can be satisfied at last. It can be seen that Examples 2 and 3 of the above have extremely excellent performances. In Comparative Example 2 where these values are very large, it can be seen that the ink has an effect of preventing set-off of the ink, the setting property and the drying property, but has no uniformity of transparency. In a comparison between a case where the same shaping treatment was applied only to the surface and a case where the same shaping treatment was applied to both surfaces (comparison between Example 1 and Example 4), it was better to apply the same shaping treatment to both surfaces to prevent ink set-off. It can be seen that the effect is excellent, and the ink setting property and the drying property are also improved. It can be seen that in Comparative Example 1 in which a flat base paper was filled with a clarifying agent, the ink set-off prevention effect, the ink setting property, and the drying property were significantly inferior. The transparent paper obtained by the conventional method, in which bleached chemical pulp is beaten for a long time and extremely viscous and made into paper (Comparative Example 3), is excellent in homogeneity of transparency, but has an ink set-off preventing effect and an ink setting. It can be seen that the properties and drying properties are significantly inferior.

[0037]

The present invention is configured as described above,
As with conventional transparent paper, despite having a flat, uniform transparency that does not cause unevenness on the surface, it has an excellent effect of preventing ink set-off during printing. It is quick to set and dry, making it possible to manufacture transparent paper that can be used in various printing methods such as high-quality paper. Taking advantage of such characteristics, the transparent paper of the present invention can be suitably used for book return, covers, envelopes, handbags, stationery paper, and the like.

Claims (1)

(57) [Claims] 1. A clarifying agent which is filled in a base paper having a substantially uniform amount of fibers in a thickness direction, and in which a substantially uniform fine uneven portion is formed on at least one entire surface .
In Akirashi; center line average roughness of the minute uneven portion is 5 to 50 [mu] m, the maximum height is 60μm or less, transparent paper, characterized in that the pitch is 0.1 to 1.5 mm.