JP2001279600A - Light-shielding paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide light-shielding paper having a low basis weight and exhibiting a very high light-shielding property in spite of the high brightness of the paper, and difficultly causing a curling phenomenon and also enabling the recycling of fiber from waste paper. SOLUTION: This light-shielding paper has a basic constitution where deeply- colored paper 3 having light-shielding performance is laminated on the underside of white 1 through an adhesive layer 2. A second white may be laminated on the underside of the deeply-colored paper through a second adhesive layer, and a white pigment-coated layer having both of high capacity and high brightness may be set up on the underside of the deeply-colored paper. When performing ink-jet recording, an ink-receiving layer may be set up on the surface of the white. Light-shielding paper having forgery-preventing effect can be formed by including fibrous matter and/or particulate matter both emitting fluorescence under exposure to ultraviolet light in the white because the fibrous matter and/or the particulate matter are/is invisible under an ordinary (visible) light-irradiated condition but emit(s) fluorescence under exposure to ultraviolet light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light shielding paper having a high whiteness on the surface, a low basis weight, an extremely large opacity, and substantially shielding light.

[0002]

2. Description of the Related Art Paper has a three-dimensional sheet-like structure in which cellulose fibers, which are the main material, are intertwined in a complex manner, so that light incident on the paper repeats complicated reflection and refraction, and is the same as paper. It is characterized by much greater opacity than a polymer film which is a sheet-like material. Opacity is a particularly important characteristic of paper used for printing on both sides because if the opacity is small, characters printed on the surface can be seen through the back side.

[0003] Light shielding paper having extremely high opacity and substantially shielding light is used for applications such as concealing labels to be attached to scratch lottery and postcards, and light shielding building materials. In the present invention, a scratch lot paper will be described as a typical example. "Scratch lottery"
It is also called “instant lottery”, and has a structure in which the lottery is displayed in advance on the surface of the lottery and a peelable coating layer is formed on the surface of the display unit with an aluminum paste ink having excellent concealing properties. The lottery purchaser determines whether or not the lottery has come off by scraping off the coating layer with the tip of a nail or a coin.

Accordingly, in the case of "scratch lottery paper", it is necessary to apply strong light from the back side of the surface displaying the hit / miss to prevent the hit / miss from being detected. The performance is required to be extremely large, and the ability to substantially block light is required.

In order to increase the opacity of paper, the basis weight of the paper must be increased, a pigment having a high refractive index, such as titanium dioxide powder, must be used together (internal addition) during papermaking, and kaolin must be added to the paper surface. Means such as applying a coating mainly composed of an inorganic powder having a large refractive index, such as calcium carbonate and titanium dioxide powder, and a binder have been adopted. This technique is often used when white or near white color is required for paper.

The opacity can also be increased by absorbing the light incident on the paper. To achieve this, black dyes and pigments with excellent light absorption are internally added to the paper, and a paint containing black dyes and a binder as main components is applied to the surface of the paper. I have. Light-shielding paper used to prevent exposure of photographic films and X-ray films is manufactured in this manner.

On the other hand, in order to increase the whiteness of paper, bleached pulp having high whiteness is used for pulp used as a raw material for paper, and clay having high whiteness, calcium carbonate,
Means such as internally adding pigments such as kaolin, talc, and titanium dioxide powder, and coating the surface of paper with a paint consisting of a high-whiteness inorganic powder such as kaolin, calcium carbonate, and titanium dioxide powder and a binder. Has been adopted.

Heretofore, it was not possible to produce a paper having a very low opacity and a high whiteness with a low basis weight paper without using a special technique. As one example of realizing this, opaque paper in which high whiteness paper is laminated on both sides of an aluminum foil or an aluminum vapor-deposited film has been manufactured. In this example, the aluminum foil or the aluminum vapor-deposited layer functions as a light blocking layer and a reflection layer, maintains a high whiteness at a low basis weight, and achieves extremely large opacity.

In Japanese Patent Application Laid-Open No. Hei 7-242086, a pigment having excellent opacity, such as carbon black, aluminum flake, or pearl pigment, is applied to the surface of a base paper to form a scratch lot paper that is opaque to transmitted light. A proposal has been made.

[0010]

In the case of opaque paper in which paper and aluminum foil are bonded as described above, aluminum foil is expensive, and it is not possible to recover papermaking fibers from waste paper. It is necessary to perform an incineration process, and there is an environmental problem such that the aluminum foil remains without being incinerated during the incineration process. In the case of opaque paper in which paper and an aluminum vapor-deposited film are bonded, there are problems such as damaging the furnace during incineration and generating harmful gas.

Further, in the conventional scratch lot paper proposed in the above-mentioned Japanese Patent Application Laid-Open No. 7-242086, it is necessary to increase the coating amount of the pigment having excellent opacity in order to enhance the light-shielding property. Since it is necessary to impart printability, a white pigment is further applied on the coating layer of the pigment having excellent opacity. As is well known, the curl phenomenon in which the processed paper curves and curls is caused by a difference in moisture absorption and desorption between the front and back of the base paper, resulting in a difference in expansion and contraction on the front and back of the base paper. Since the conventional scratch lot paper having the above configuration has to have a configuration having a double coating layer on one side of the base paper, a difference in moisture absorption and desorption easily occurs on the front and back of the base paper, and the curl is curled. It always had a fatal problem of being easy.

An object of the present invention is to solve these problems. That is, despite having high whiteness, a light-shielding paper exhibiting extremely large light-shielding properties at a low basis weight, hardly curling, and capable of recovering fibers from waste paper is provided. Make it an issue.

[0013]

Means for Solving the Problems The present inventors have made intensive studies with the aim of solving the above problems and completed the present invention. The basic structure of the light shielding paper according to the present invention is as follows. It is characterized in that dark-colored paper having the property of shielding light is laminated on the back surface of white paper via an adhesive layer.

According to the light-shielding paper having the above-mentioned basic structure, even if a strong light is applied from the back side of the paper on the dark-colored paper side, the light is not transmitted, and the light-shielding property is excellent. Further, since the surface of the white paper has high whiteness due to the white paper, desired printing can be performed. Since the back surface of this paper has a dark color of dark paper, printing on the back surface is performed with white or a color close to white.

In the light-shielding paper of the present invention, in order to be able to perform desired printing on both the front and back sides, the first
A dark paper having the ability to block light is laminated on the back surface of the white paper via a first adhesive layer, and a second white paper is laminated on the back surface of the dark paper via a second adhesive layer. A stacked configuration can be adopted.

Further, the light shielding effect is further improved by providing a white pigment coating layer having high opacity and high whiteness on the front surface, the back surface, or both the front and back surfaces of the dark paper in the light shielding paper having the above-mentioned basic structure. In addition, the whiteness of both the front surface of the white paper and the back surface of the dark paper can be further improved. Therefore, when desired printing is performed on the surface of the white paper, the value of the printed matter such as print finish, appearance, and sense of quality can be further enhanced. In addition, when a white pigment coating layer is provided on the back surface of the dark paper, when the desired printing is performed on this white pigment coating layer, the value of the printed matter such as print finish, appearance, and luxury is similarly increased. Can be enhanced.

As the above-mentioned dark paper, a paper made by fixing a dark pigment which does not elute in water can be preferably used.

As the above-mentioned white paper, a paper in which a white pigment coating layer is provided on the front surface, the back surface or both the front and back surfaces of the base paper can be preferably used.

Further, the white paper of the light-shielding paper of the present invention can be made to be a forgery-preventing paper by containing fibrous materials and / or granular materials which emit fluorescence when irradiated with ultraviolet rays. In other words, such fibrous materials and granular materials cannot or cannot be visually recognized under ordinary light (natural light, incandescent light, fluorescent light, etc.). When the paper or the granular material emits various fluorescent colors, the authenticity of the paper can be easily and reliably determined.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments shown in the drawings. FIG. 1 schematically shows the basic structure of the light shielding paper of the present invention. A dark paper 2 having a light shielding performance is laminated on the back surface of a white paper 1 via an adhesive layer 3. I have.

When producing the white paper 1 used in the present invention, softwood bleached kraft pulp (NB
Mainly wood pulp such as KP), hardwood bleached kraft pulp (LBKP), softwood bleached sulphite pulp (NBSP), and if necessary, non-wood pulp such as hemp, bamboo, straw and kenaf Can be. If necessary, pigments such as clay, kaolin, talc, titanium dioxide, calcium carbonate, and aluminum hydroxide powder are added to these raw material pulp, and sizing agents such as rosin sizing agents, and dry paper strength such as polyacrylamide are added. A paper stock is prepared by appropriately adding a papermaking auxiliary material such as a wet paper strength enhancer such as a polyamide, polyamine, epichlorohydrin or a melamine resin, and a fixing agent such as a sulfuric acid band. . S. F. According to a conventional method, the paper is made to have a basis weight of 40 to 100 g / m ² by using a paper machine such as a round paper machine, a fourdrinier machine, and a twin wire machine.

If necessary, a styrene-based resin, a styrene-acrylic resin, a styrene-maleic acid resin, an alkyl Chemicals such as ketene dimer, starch, oxidized starch, hydroxyethylated starch, carboxymethylated cellulose, carboxymethylated guar gum, phosphorylated guar gum, oxidized guar gum, polyvinyl alcohol, and polyacrylamide may be applied to the surface. It is also possible to apply a coating of several g / m ² with a coating material used for the finely coated paper using a bill blade coater or the like.

As described above, it is necessary that the light-shielding paper does not substantially transmit light even when strong light is applied from the back side of the paper. A dark paper having the ability to block light is attached to the back surface. As such dark paper, in addition to black paper,
Colored paper having a dark color, such as black-gray paper, black-brown paper, black-red paper, black-blue paper, etc., can be used, and only enough light to substantially shield light after bonding with white paper. What is necessary is just a shielding ability.

When making a dark paper, except that a dark dye or pigment is added to the stock and fixed on the pulp fiber,
Papermaking and similar way white paper described above can be employed, usually papermaking so that the basis weight of 40 to 100 g / m ^2.

As the dark color dye used for making the dark paper, known dyes such as direct dyes having low lightness such as black, black gray, black blue and black brown, acid dyes, basic dyes and disperse dyes can be used. . In addition, as the dark color pigments, organic pigments such as lake pigments, toner pigments, etc.,
Inorganic pigments such as red iron and carbon black can be used. Those having the greatest effect are black dyes and pigments, and black dyes, aniline black and carbon black can be preferably used. In the production of dark paper, these dark dyes and pigments can be used alone or in combination of two or more.
To 30% by weight.

It is preferable to use a pigment that does not elute in water, for example, carbon black, as a dark pigment used in the production of dark paper. If a pigment that does not dissolve in water is used, even if a postcard with a scratch lot or a concealment label is placed in a shirt pocket or the like and washed, the pigment in the dark paper elutes and contaminates the surroundings. This is because such an adverse effect can be prevented.

As the adhesive used for laminating the white paper and the dark paper, any well-known water-based or solvent-based adhesive can be used. For example, examples of the water-based adhesive include a starch-based adhesive, a polyvinyl alcohol-based adhesive, a synthetic resin emulsion adhesive, and a synthetic rubber latex adhesive. As the solvent-based adhesive, polyurethane-based dry laminating adhesive, synthetic rubber adhesive,
Any of hot melt adhesives such as EVA can be used.

Particularly, in light shielding paper used for scratch lot paper, it is desirable to use a water-resistant adhesive. When using light-shielding paper as a scratch lot paper where white paper and dark paper are bonded with a non-water-resistant adhesive, immerse the paper in water to peel off the white paper and dark paper, and irradiate light from the back of the white paper. It is possible to see through the appearance of hits and whites printed on the white paper surface, and then paste the dark paper on the back of the white paper again, without peeling the aluminum paste ink coating layer on the surface of the lottery paper There is a danger that the hit or miss of the lottery will be visible. By using a water-resistant adhesive for laminating white paper and dark paper,
Such a danger can be reliably prevented.

In order to further enhance the light shielding effect of the light shielding paper, a coloring agent having a light shielding property, such as a coloring dye, a coloring pigment, or a white pigment, may be added to the adhesive.
As the coloring dye or pigment having excellent light-shielding properties to be added to the adhesive, the same kind of coloring dye or pigment as used in the production of the above-described dark paper can be used. These coloring dyes and pigments can be used alone or as a mixture of two or more kinds. The amount added to the adhesive is usually from several weight% to 30 weight%.
And

In particular, when the light-shielding paper of the present invention is used as a concealing label sheet to be attached to a scratch lot paper or a postcard, the light-shielding colorant added to the adhesive does not elute in water. For example, it is desirable to use a dark colored pigment such as carbon black or a dark colored dye that does not elute in water. If a coloring agent that does not dissolve in water is added to the adhesive, the coloring agent in the adhesive will be eluted even if the postcard with a scratch lot or concealment label is washed in a shirt pocket, etc. This can prevent the adverse effect of contaminating the surroundings.

FIG. 2 shows another embodiment of the light shielding paper of the present invention. The dark paper 2 having the light shielding performance is provided on the back surface of the first white paper 1a by the first adhesive layer 3a. The second white paper 1b is laminated via a second adhesive layer 3b on the back surface of the dark paper. According to the light shielding paper having the configuration shown in FIG. 2, since the front and back surfaces of the paper are formed of white paper, desired printing can be performed on the front and back white paper.

FIG. 3 shows still another embodiment of the light-shielding paper of the present invention. A dark-colored paper 2 having a light-shielding property is laminated on the back surface of a white paper 1 via an adhesive layer 3. A white pigment coating layer 4 having high opacity and high whiteness is provided on the back surface of the dark paper. Since the white pigment coating layer 4 is highly opaque, it also has a function of shielding light emitted from the back surface of the light shielding paper, so that the light shielding effect can be further improved. In addition, this white pigment coating layer 4
Due to the high opacity, the color of dark paper is not seen through, and the coating layer 4 itself has a high degree of whiteness. Can be printed on both sides.

The white pigment coating layer 4 in FIG. 3 is formed by applying a coating liquid containing a highly opaque and high whiteness white pigment and a binder as main components using a well-known coating machine. Can be formed. As a coating liquid for forming the white pigment coating layer 4, the same coating liquid as that used for forming the white pigment coating layers 5a and 5b shown in FIG. 4 described later can be used. When it is necessary to particularly increase opacity, it is desirable to use a coating liquid containing a large amount of a pigment such as titanium dioxide or kaolin as a white pigment. In order to form the white pigment coating layer 4, instead of applying the above-described coating solution, a highly opaque and high whiteness ink containing a white pigment and a binder as main components is used. It can also be formed by solid printing using a printing machine.

When the white paper 1 used in the present invention has high whiteness and high opacity by itself, it can be used as it is as the white paper in the light shielding paper of the present invention. As shown in FIG.
White pigment coating layers 5a, 5a,
The paper on which b is formed can also be used as the white paper 1.

The white pigment coating layer 5a is a layer that appears on the surface side of the white paper 1 and has a function of concealing the color of the dark paper 2 so that it cannot be seen through from the white paper side. It has a function of imparting high whiteness to the surface and improving printability in multicolor printing and the like. The coating liquid for forming the white pigment coating layer 5a is kaolin, calcium carbonate,
One or a mixture of two or more kinds of white pigments such as titanium dioxide and aluminum hydroxide powder and a mixture of one or more kinds of binders such as styrene / butadiene latex, methyl methacrylate / butadiene latex, starch and polyvinyl alcohol. The main component is prepared by appropriately mixing conventionally used auxiliary materials for coating such as a dispersant, a waterproofing agent, a preservative, and a fungicide. Considering the recovery of papermaking fibers from waste paper, it is particularly preferable to use a water-soluble binder such as starch or polyvinyl alcohol as the binder. The mixing ratio of the binder in the coating solution is usually 10 to 30 with respect to 100 parts by weight of the white pigment.
Parts by weight. The white pigment coating layer 5a can be formed by applying the coating liquid thus prepared to the surface of the base paper A using a known coater such as an air knife coater, a blade coater, or a roll coater. it can.
The coating amount of the coating layer 5a is usually 5 to 25 g / m ² . When the white pigment coating layer 5a has high whiteness of the base paper A and high opacity,
It is not necessarily required.

The purpose of providing the white pigment coating layer 5b on the back surface of the base paper A is to conceal the color of the dark paper 2 so that it cannot be seen through from the white paper side. In order to form such a coating layer 5b, basically the same coating liquid as that used for forming the white pigment coating layer 5a may be used, but from the viewpoint of the above-mentioned hiding function. It is particularly preferable to use titanium dioxide having a large effect of imparting opacity as a white pigment.

When the white paper 1 and the dark paper 2 are bonded with an adhesive, when a solvent-based adhesive is applied to the back surface of the white paper 1 and bonded to the dark paper 2, the white paper 1 It is desirable that the white pigment coating layer 5b serving as the back surface has a solvent penetration resistance that does not allow the solvent of the solvent-based adhesive to penetrate. In order to impart solvent penetration resistance to the white pigment coating layer 5b, use a binder having excellent solvent penetration resistance as a binder used in the white pigment coating layer, and increase the ratio of the binder to the white pigment. Means such as providing a coating layer for preventing the penetration of a solvent on the white pigment coating layer may be appropriately applied.

On the other hand, an ink jet printer is sometimes used for printing and printing, such as a hit or a scratch of a scratch lot. When ink-jet recording is performed on the light-shielding paper of the present invention, as shown in FIG. 5, an ink receiving layer 6 for well-known ink-jet recording can be provided on the surface of the white paper 1. In particular, if the recording surface is required to have water resistance (the property that the ink in the recording portion of characters and images does not ooze out due to the effect of water droplets, etc.), coat the surface of the white paper 1 with a cationic substance. It is preferable to form the ink receiving layer 6 by applying a coating liquid containing a cationic substance. This is because the anionic ink jet recording ink is hardly dissolved in water by the cationic substance in the ink receiving layer 6, and can impart water resistance.

As the cationic substance, for example, polyethyleneimine, a water-soluble salt of metal, polyvinylpyridium bromide, polyethyleneimine, dimethyldiallylammonium chloride, polyethyleneimine organic acid salt,
Cationic colloidal silica, polyalkylene polyamine dicyandiamide ammonium salt condensate, polyethyleneimine quaternary ammonium compound, dialkanolamino-modified alkylene glycol derivative, acrylamide / diallyldimethylammonium chloride copolymer containing acrylamide and diallyldimethylammonium chloride as main monomers Well-known cationic substances such as coalescence can be used.

When the light-shielding paper of the present invention is used as a scratch lot paper, it is desirable to apply forgery prevention means to the paper. As forgery prevention means, for example, it is preferable to include, for example, a fibrous material or a granular material that emits fluorescent light in various hues upon irradiation with ultraviolet light in the white paper 1, or a mixture of both. These fibrous or granular materials are not visible under normal light, but emit various fluorescent colors when irradiated with ultraviolet light, and fibrous or granular materials that emit fluorescent light when paper is irradiated with ultraviolet light. If is not visible, it can be easily and reliably determined that the sheet is a forged sheet.

Fibrous materials and particles that emit fluorescence when irradiated with ultraviolet light
Various types of state-of-the-art materials have been proposed in the past, and in the present invention,
These well-known ones can be used. For example, Japanese Patent Application Laid-Open
Stilbene-based fireflies proposed in -122100
Fibers fixed with light dye, disclosed in JP-A-6-128807
Proposed Sr_Five(PO_Four)_ThreeCl: Eu, Zn_Two G
eO_Two: Mn, Y_TwoO_TwoS: Metal oxide-based fireflies such as Eu
Fiber into which optical pigment has been kneaded, JP-A-10-164273
Self-adhesion by physical or chemical action proposed in
Fluorescent coloring particles with fluorescent pigment fixed to the surface of the developing particles
Water, proposed in Japanese Patent Application No. 11-347237.
Mixing powdery substances with insoluble fluorescent dyes and / or pigments
Fluorescent particles consisting of granulated material or powdery material
Granules and water-insoluble fluorescent dye formed on the outside of the granules
And / or fluorescent coloring particles comprising a pigment coating layer
Can be used.

In the case where the white paper 1 is a white paper in which a white pigment coating layer 5a is provided on the surface of a base paper A as shown in FIG. Can be contained in the base paper A. In this case, if the base paper A or the white pigment coating layer 5a contains a pigment such as titanium dioxide or kaolin having a property of absorbing ultraviolet light, the ultraviolet light is irradiated to determine the authenticity of the paper. Ultraviolet rays are absorbed by such a pigment, making it difficult for the fibrous or granular material in the base paper A to emit fluorescent color. Therefore,
It is desirable that the base paper A and the white pigment coating layer 5a do not substantially contain a pigment that absorbs ultraviolet rays. For example, a pigment that does not absorb ultraviolet rays, such as aluminum hydroxide or plastic pigment, may be contained.

[0043]

The present invention will be further described below with reference to examples and comparative examples. Note that “parts by weight” and “% by weight” shown in Examples and Comparative Examples are values in terms of dry weight.

[Example 1] <Production of base paper> 30 parts by weight of NBKP and 70 parts by weight of LBKP were subjected to a freeness of 430 ml C.I. S. F. 1 part by weight of titanium dioxide powder, 3 parts by weight of kaolin, 0.4 parts by weight of a paper strength enhancer (trade name "Polyaclon", manufactured by Misawa Ceramics Co., Ltd.), and a sizing agent (trade name "Size Pine") E ", manufactured by Arakawa Chemical Industry Co., Ltd.) 0.8 parts by weight,
A stock was prepared by adding 5 parts by weight of a sulfuric acid band, and a base paper having a basis weight of 70 g / m ² (base paper A in FIG. 4) was formed using a fourdrinier paper machine.

<Preparation and Coating of White Pigment Coating Layer> 250 parts by weight of titanium dioxide powder, 5 parts by weight of a dispersant, and 360 parts by weight of water were treated with a disperser, and SB was used as a binder.
R latex (trade name “Smartex 750”, manufactured by A & L Japan Co., Ltd.) was added in an amount of 50 parts by weight to prepare a white pigment coating liquid. This coating liquid was applied to the back surface of the base paper obtained above using an air knife coater so as to be 15 g / m ^2, and a white pigment coating layer (the coating film of FIG. 4) was applied to the back surface of the base paper. A white paper having a basis weight of 85 g / cm ² having a layer 5b) was produced. Since the surface of the base paper had high whiteness, a white pigment coating layer (coating layer 5a in FIG. 4) was formed on the base paper surface.
Was not provided.

<Production of dark paper> 25 parts by weight of NBKP, L
BKP (75 parts by weight) is freeness 280 ml C.I. S. F.
And 10 parts by weight of carbon black, 0.4 parts by weight of a paper strength agent ("Polyaclon"), 0.8 parts by weight of a sizing agent ("Size Pine E"), and 5 parts by weight of a sulfuric acid band were added thereto. A stock was prepared, and a dark paper with a basis weight of 70 g / m ² was formed using a Fourdrinier paper machine.

<Preparation of adhesive> Urethane resin (trade name "Takelac A-975", manufactured by Takeda Pharmaceutical Co., Ltd.)
To 40 parts by weight, 3.5 parts by weight of an isocyanate curing agent (trade name "Takenate A3", manufactured by Takeda Pharmaceutical Co., Ltd.) and 140 parts by weight of ethyl acetate were added to prepare a dry laminating adhesive coating liquid.

<Bonding of white paper and dark paper> 4 g / m ² of an adhesive coating solution was applied on the white pigment coating layer on the back surface of the white paper using a gravure coater laminator and bonded in a drying zone. After the solvent in the agent coating layer was volatilized, it was bonded to dark paper at the combiner roll, and the basis weight was 159 g / m2.
^Two light-shielding papers were produced.

Example 2 <Manufacture of base paper> 30 parts by weight of NBKP and 70 parts by weight of LBKP were used with a freeness of 430 ml C.I. S. F. 4 parts by weight of kaolin, 0.05 parts by weight of fluorescent particles which emit red light upon irradiation with ultraviolet rays for the purpose of preventing forgery, 0.4 parts by weight of a paper strength enhancer (trade name "Polyaclon"), 0.8 parts by weight of a sizing agent (trade name “Size Pine E”) and 5 parts by weight of a sulfuric acid band were added to prepare a stock, and a base paper having a basis weight of 70 g / m ² was prepared using a fourdrinier paper machine (see FIG. 4 was prepared.

<Preparation and Coating of White Pigment Coating Layer> After 250 parts by weight of kaolin, 5 parts by weight of a dispersant, and 360 parts by weight of water were treated with a dispersing machine, SBR latex (trade name: “Smartex”) was used as a binder. 750 ") was added to prepare a white pigment coating liquid. This coating solution was applied to the surface of the base paper obtained above using an air knife coater.
g / cm ² to form a white pigment coating layer (coating layer 5a in FIG. 4) on the surface of the base paper.

Further, on the back surface of the base paper, a white pigment coating layer (coating layer 5b in FIG. 4) of 15 g / m ² similar to that provided in Example 1 was provided. / M ² of white paper was produced. This white paper was subjected to a smoothing treatment using a super calender.

<Lamination of White Paper and Dark Colored Paper>
In the same manner as in Example 1, the same dark-colored paper as used in Example 1 was bonded to the double-sided coated white paper obtained above to prepare a light-shielding paper having a basis weight of 164 g / m ² , which was provided with a forgery prevention means. . When this light-shielding paper is irradiated with ultraviolet rays (light of a commercially available black light) from the double-side coated white paper side, particles whose presence could not be visually recognized under normal illumination are colored red,
Its presence was clearly visible.

[Comparative Example 1] (Light-shielding paper having a configuration of coated paper / aluminum foil / coated paper) A dry laminating adhesive coating liquid similar to that used in Example 1 was applied to both surfaces of an aluminum foil having a thickness of 15 μm. 3 g / m ^{2 on} one side
After applying and evaporating the solvent, the basis weight is 50 g.
/ M ² coated paper on both sides of aluminum foil, weighing 146
g / m ² of light-shielding paper was produced.

Comparative Example 2 (Light-shielding paper having a structure in which a dark-colored coating layer is provided on the surface of coated paper) Coated paper having a basis weight of 128 g / m ² (trade name “Silver Diamond”, manufactured by Mitsubishi Paper Mills, Ltd.) )), A black coating liquid composed of 100 parts by weight of carbon black and 20 parts by weight of SBR latex (trade name “Smartex 750”)
It was applied so that the 0 g / m ^2, was produced light-shielding paper having a basis weight of 168 g / m ^2.

[Evaluation of Performance of Light Shielding Paper] With respect to the light shielding papers obtained in the above Examples and Comparative Examples, the basis weight, thickness, and whiteness are shown in Table 1, and various performances are evaluated together. Also shown. The measuring method and the evaluation method are as follows.

<Measurement of Whiteness> The whiteness of the surface of the light-shielding paper sample was measured according to the method specified in JIS P8123.

<Evaluation of Light Shielding Property> A white light lamp (trade name “LAMP HOUSE MOL”) integrated with a projector
EL 15HLE "manufactured by Senner Co., Ltd.) and a transformer (trade name" POWER SUPLY MODEL 151 ").
5D "(manufactured by Senner Co., Ltd.) to adjust the voltage so that the illuminance of the lamp can be adjusted.
The sample mounting table is arranged at a distance of 50 mm. A hole having a diameter of 80 mm is formed in the sample mounting table, and the sample of the light shielding paper is placed on the sample mounting table so as to close the hole.

This apparatus was installed in a dark room, and the illuminance at the center of the hole of the sample mounting table where no sample was placed was 100.
The voltage was adjusted with a transformer so that the output became 10,000 lux. The illuminance was measured using an illuminometer (trade name "Digital Illuminometer TIH" manufactured by Minolta Co., Ltd.). In this state, the light-shielding paper sample was placed on the sample mounting table so that the light hit from the back side, and light transmitted through the hole of the sample mounting table was visually observed from the front side of the light-shielding paper. The light shielding property was evaluated in the following four stages. A: The outline of the hole is not visible at all from the light shielding paper surface side. ：: The outline of the hole looks extremely faint from the light shielding paper surface side. Δ: The outline of the hole is slightly visible from the light shielding paper surface side. ×: The outline of the hole is clearly visible from the light shielding paper surface side.

<Evaluation of curl>
After being left in an air-conditioned room at 0% RH and an air-conditioned room at 30 ° C.-80% RH for 5 hours, the state of the curl was visually observed. The evaluation was performed in the following four stages. ：: No or very slight occurrence. ：: Slightly generated, but not practically a problem. Δ: A level that is considerably generated and poses a practical problem. X: A level that is severely generated and cannot be used practically.

<Evaluation of Recoverability of Fiber from Waste Paper> A light-shielding paper sample was cut into a square of 1 cm, and 5 g of the sample was placed in 700 mL.
(Milliliter) of water was placed in a household mixer and treated for 1 minute to disintegrate the light shielding paper. Using the obtained processed product, a hand-made sheet was manufactured using a 25-cm square hand-made sheet device, and the presence or absence of binding fibers and undisintegrated material in the sheet was visually observed. The evaluation was performed in the following four stages. ◎: No binding fiber or undisintegrated material at all. ：: A state in which there are some binding fibers and undisintegrated material, but it can be sufficiently used for the inner layer paper of paperboard. B: Bundling fibers and undisintegrated material remain, and cannot be used for the inner layer paper of paperboard without long-time disintegration treatment. ×: A state in which a large amount of bound fibers and undisintegrated matter remain even after long-time disaggregation treatment.

<Evaluation of suitability for incineration treatment> The light shielding paper sample was evaluated by the amount of residue generated when it was incinerated in an incinerator. The evaluation was performed in the following four stages. ：: Completely incinerated, the residue is incinerated ash only, in the same state as when high quality paper was incinerated. ：: Incineration, but some residue is generated. Δ: Incineration occurs, but considerable residue is generated. X: A state in which a large amount of unburned residue is generated.

[0062]

Table 1 shows the following. 1) Compared to Comparative Example 1 (laminating aluminum foil), which is a conventional example of light shielding paper, the light shielding paper according to the embodiment of the present invention can recover fibers from waste paper and is suitable for incineration treatment. It turns out that it is excellent.

2) Also in comparison with Comparative Example 2, it is understood that the light-shielding paper of the example of the present invention has excellent light-shielding properties. When the light-shielding property of only the dark-colored paper used in the examples was measured in the same manner as the light-shielding paper, the evaluation was ◎. The amount of carbon black contained in this dark paper was calculated to be 6.3 g / m ² , whereas the amount of carbon black used in Comparative Example 2 was 33.3 g / m ² .
The amount of carbon black in the examples was about 1 /
5, the reason why the light shielding property is much better is that the light incident on the dark paper is complicated because the carbon black particles are dispersed and distributed throughout the thickness direction of the dark paper in the present invention. This is probably because the light is repeatedly reflected and absorbed until it reaches the opposite surface. On the other hand, in Comparative Example 1, since carbon black is contained in the coating layer and the carbon black particles are densely distributed in the coating layer, the effect of repeated light reflection and absorption is obtained. Is thought to be less.

[0065]

As can be seen from the above description, the light shielding paper according to the present invention has the following effects. 1) A light shielding paper having high whiteness and extremely high opacity can be obtained without increasing the basis weight.

2) Compared with a conventional light shielding paper to which an aluminum foil or an aluminum vapor-deposited film is pasted, the aluminum foil does not remain without burning during the incineration treatment, and no harmful gas is generated. Also, incineration is easy. Further, the papermaking fibers can be easily recovered from the waste paper.

3) Since a plurality of coating layers are not formed on only one side of the base paper, curling hardly occurs.

4) If necessary, a coating layer for improving printability and a water-resistant ink-receiving layer for ink jet recording can be easily provided on the surface of white paper.

5) By incorporating fibrous or particulate matter which emits fluorescent light upon irradiation with ultraviolet light into white paper, a light shielding paper for preventing forgery can be easily manufactured.

6) By including a light-shielding dye or pigment in the adhesive layer, the light-shielding property can be further improved.

7) When a coloring pigment which does not dissolve in water is used as a coloring agent to be added to the adhesive layer or the dark pigment used in the production of the dark paper, the light shielding paper is put in the pocket of clothing. Even when washing is performed as it is, the coloring dye and pigment are not eluted and the surroundings are not contaminated.

8) When light-shielding paper in which dark paper is exposed on the back side is used as a scratch lot paper, the coating layer of the aluminum paste ink on the front side of the paper is not peeled off, and the back side of the paper is strongly seen in order to see the appearance of hitting / losing. When light is applied, the dark paper on the back side absorbs the light and generates heat and burns in a few seconds, so that such an action can be prevented beforehand.

9) By taking advantage of such features, the light shielding paper of the present invention is a light shielding paper, a food packaging material, a food container, a concealing label to be attached to a scratch lot, a postcard, etc. For example, it can be suitably used as paper for wallpaper or blinds).

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a basic configuration of a light shielding paper of the present invention.

FIG. 2 is a sectional view showing an embodiment of the light shielding paper of the present invention.

FIG. 3 is a sectional view showing another embodiment of the light shielding paper of the present invention.

FIG. 4 is a cross-sectional view illustrating an example of white paper used in the present invention.

FIG. 5 is a cross-sectional view showing a preferred embodiment used for ink jet recording in the light shielding paper of the present invention.

[Explanation of symbols]

 1, 1a, 1b: white paper 2: dark paper having light shielding performance 3, 3a, 3b: adhesive layer 4: white pigment coating layer having high opacity and high whiteness 5a, 5b: white Pigment coating layer 6: Ink receiving layer in ink jet recording A: Base paper

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shinichi Akahori, 501, Honjuku, Nagaizumi-cho, Sunto-gun, Shizuoka Prefecture Inside (72) Inventor Tomoki Hirasawa 501, Honjuku, Nagaizumi-cho, Sunto-gun, Shizuoka Prefecture Special paper Co., Ltd. (72) Inventor Yoshihiko Fukumuro 501, Honjuku, Nagaizumi-cho, Sunto-gun, Shizuoka Prefecture Intra-specialty Paper Co., Ltd. In-house (72) Inventor Shotaro Okamura 4--14-12 Koishikawa, Bunkyo-ku, Tokyo Kyodo Printing Co., Ltd. (72) Inventor Hideo Nagasawa 4-14-12 Koishikawa, Bunkyo-ku, Tokyo Kyodo Printing Co. Inventor Hirofumi Tezuka 4-14-12 Koishikawa, Bunishi-ku, Tokyo Kyodo Printing Co., Ltd. F-term (reference) 4F100 AR00E BA02 BA03 BA04 BA05 BA06 BA07 BA14 BA26 CA13B CA13E DE01A DE01C DG01A DG01C DG07A DG07B DG07C DG07D DG07E EH41B EH411 EH46E EH462 GB07 GB90 JA13 JA13B JA13D JL10A JL10B JL10C JL10E JL11E JN02 JN02E JN13A JN13C JN30 JN30A JN30C 4L055 AC06 AG02 AG08 AG19 AG27 AG63 AG75 AG85 AG97 AH02 AH03 AH11 AH16 AH33 AH37 AJ03 BE08 EA05 EA08 EA14 FA12 GA21 GA50

Claims (11)

[Claims] 1. A light-shielding paper characterized in that dark paper having a light-shielding property is laminated on the back surface of a white paper via an adhesive layer. 2. A dark paper having a light shielding property is laminated on a back surface of the first white paper via a first adhesive layer, and a second white paper is formed on a back surface of the second white paper by a second adhesive layer. Light-shielding paper, wherein the light-shielding paper is laminated via an adhesive layer. 3. A dark paper having a light shielding property is laminated on the back surface of the white paper via an adhesive layer, and a highly opaque and high whiteness white is printed on the front surface, the back surface, or both the front and back surfaces of the dark paper. A light shielding paper comprising a pigment coating layer. 4. The light-shielding paper according to claim 1, wherein the dark-colored paper is formed by fixing a dark-colored pigment that does not elute in water. 5. The light shield according to claim 1, wherein the white paper has a configuration in which a white pigment coating layer is provided on the front surface, the back surface, or both the front and back surfaces of the base paper. paper. 6. The light-shielding paper according to claim 1, wherein the white paper contains a fibrous material and / or a granular material that emits fluorescence when irradiated with ultraviolet light. . 7. The white paper has a configuration in which a white pigment coating layer is provided on the surface of a base paper, and the fibrous material and / or granular material that emits fluorescence when irradiated with ultraviolet light is contained in the base paper. The light-shielding paper according to claim 6, wherein the base paper and the white pigment coating layer do not substantially contain a pigment that absorbs ultraviolet light. 8. The base paper having a basis weight of 40 to 100 g /
m^TwoThe coating amount of the white pigment coating layer is 5 to 25 g on one side.
/ M^TwoThe basis weight of the dark paper is 40 to 100 g / m ^TwoIn
The method according to any one of claims 5 to 7, wherein
Light shielding paper. 9. The light-shielding paper according to claim 1, wherein the adhesive layer contains a dye and / or a pigment excellent in light-shielding properties. 10. The light shielding paper according to claim 9, wherein a coloring dye and / or pigment which does not elute in water is used as the dye and / or pigment having excellent light shielding properties. 11. The whiteness of the surface of the white paper is JIS
The light shielding paper according to any one of claims 1 to 10, wherein the whiteness specified by P-8123 is 60% or more.