Packaging paper having translucent area, envelope with window

Abstract

To provide a packaging paper having a translucent area that provides excellent visibility of the inside.SOLUTION: A packaging paper 1A having a translucent region characteristically includes: a sheet 2 whose main component is cellulose fiber; a transparent material 3 that permeates the inside of the sheet in the entire area or a partial area of the sheet 2; and a cross-hatched printed area 4 in which a light-absorbing substance is attached to the area of the sheet 2 having the transparent material 3.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to wrapping paper. More specifically, it relates to wrapping paper having a translucent region in at least a partial region.

Background Art

[0002] As a method for manufacturing paper with high transparency, for example, a method of papermaking using pulp fibers with increased beating degree or a method of impregnating a resin or the like into the spaces between fibers of a formed base paper is common. The method of papermaking using pulp fibers with increased beating degree is used in the production of glassine paper, tracing paper, etc. These sheets are used for window parts of envelopes, etc. as wrapping paper. However, due to reasons such as the pulp fibers being crushed and cut by high beating, even if pulp fibers with increased beating degree are used for the window of an envelope, they are generally difficult to apply to uses such as packaging bags that require strength.

[0003] On the other hand, the method of impregnating a resin or the like into the spaces between fibers of a formed base paper is used in the production of oil paper, wax paper, etc. For example, various wrapping papers impregnated with a resin or the like have been proposed for the purpose of improving transparency (for example, Patent Documents 1, 2, 3). In Patent Document 1, it is proposed to obtain transparent paper using a clarifying agent in which paraffin wax is blended in an organic solvent solution of a resin. In Patent Document 2, a method of making an opaque paper transparent is proposed, in which a clarifying agent mainly composed of vegetable oil is printed and penetrated onto a specific surface of the opaque paper, and an oil layer protective agent for fixing the clarifying agent is printed and dried on both sides of the clarifying agent penetration layer to form an oil layer protective film. In Patent Document 3, transparent paper in which a specific resin is impregnated into a paper base material is proposed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

[0005] In recent years, envelopes using a plastic film as an envelope with a direct meter or the like, or envelopes in which the address portion of a paper envelope is formed of a plastic film have been used. However, while the elimination of plastics is required, the provision of alternatives to plastic films is desired. Although alternatives using translucent glassine paper for the plastic film portion of envelopes have been provided, there is a problem that information such as the address through the glassine paper is difficult to visually recognize. In addition, when processing envelopes or the like using glassine paper, there are problems with the creases and strength of the glassine paper.

[0006] On the other hand, as described in Patent Documents 1 to 3, a method of partially applying a clarifying agent to reduce opacity has been carried out. Although the method using a clarifying agent is suitable for the strength of packaging paper for uses such as envelopes, the visibility of the address and the like described inside is poor. Therefore, an object of the present invention is to provide a packaging paper having a translucent region excellent in internal visibility. [Means for Solving the Problems]

[0007] As a result of intensive research on packaging paper using a clarifying agent, the present inventor has found that when the paper base material is impregnated with a clarifying agent, although the opacity decreases, light scattering due to the texture of the paper base material occurs and the visibility is impaired. Therefore, the present inventor has found that by performing screen printing of a light-absorbing substance in addition to the application of a clarifying agent, packaging paper excellent in visibility can be obtained, leading to the present invention.

[0008] The present invention has the following aspects. (1) A wrapping paper having a translucent region, comprising: a sheet mainly composed of cellulose fibers; a transparency material penetrating inside the sheet in the entire or partial area of the sheet; and a screen-printed portion with a light-absorbing substance attached to the region of the sheet having the transparency material. (2) The wrapping paper having a translucent region according to (1), wherein the opacity of the region penetrated by the transparency material is 10 to 40%. (3) A packaging bag having a translucent region, formed by making the wrapping paper according to (1) or (2) into a bag shape. (4) An envelope with a window, according to (3), wherein the envelope is the packaging bag, and a window is formed in a part of the envelope by a region penetrated by the transparency material. (5) A method for manufacturing a wrapping paper having a translucent region, characterized by attaching a light-absorbing substance to a sheet mainly composed of cellulose fibers in the entire or partial area of the sheet by screen printing, and then coating and impregnating the region where the screen printing has been performed with a transparency agent. (6) A method for manufacturing a wrapping paper having a translucent region, characterized by coating and impregnating a sheet mainly composed of cellulose fibers with a transparency agent in the entire or partial area of the sheet, then performing screen printing of a light-absorbing substance, and then coating the region where the screen printing has been performed with a transparency agent.

[0009] Furthermore, as a result of repeated studies to improve the visibility of glassine paper and the like, the present inventor has found that by performing screen printing of a light-absorbing substance on a translucent paper made by papermaking using highly beaten pulp such as glassine paper, a wrapping paper with excellent visibility can be obtained, leading to the present invention. That is, the present invention has the following aspects. (7) A sheet mainly composed of cellulose fibers made by papermaking using highly beaten pulp, characterized by having a screen-printed portion with a light-absorbing substance attached to at least a partial area on one side of the sheet, and having a translucent region. (8) An envelope with a window, wherein the window portion of the envelope with a window is the wrapping paper having a translucent region according to (7).

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a wrapping paper having a translucent region with excellent internal visibility.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0012] The wrapping paper having a translucent region of the present invention includes a sheet mainly composed of cellulose fibers, a transparentizing material penetrating inside the sheet in the entire area or a partial area of the sheet, and a screen printing portion in which a light-absorbing substance is attached to the region of the sheet having the transparentizing material. For example, the wrapping paper 1A shown in FIG. 1 includes a transparentizing material 3 penetrating inside the sheet in a partial area of a sheet 2 mainly composed of cellulose fibers; and a screen printing portion 4 in which a light-absorbing substance is attached to the region of one side of the sheet 2 having the transparentizing material 3. Also, for example, the wrapping paper 1B shown in FIG. 2 includes a transparentizing material 3 penetrating inside the sheet 2 in a partial area of the sheet 2 mainly composed of cellulose fibers, a coating layer 5 covering the surface of the region having the transparentizing material 3, and a screen printing portion 4 in which a light-absorbing substance is attached to the region of one side of the sheet 2 having the transparentizing material.

[0013] Figs. 1 and 2 are schematic. The interfaces between the sheet 2 and the transparency material 3, and between the transparency material 3 and the coating layer 5 are generally considered observable using an electron microscope. However, in the cross-sectional views of these interfaces, there may be cases where they do not clearly exist or are difficult to clearly confirm, as schematically illustrated in Figs. 1 and 2. Also, the screen-printed portion 4 has a plurality of dots of a light-absorbing substance attached thereto. Therefore, in the cross-sectional view, the interface of the screen-printed portion 4 (light-absorbing substance) may not necessarily clearly exist as shown in the schematic drawing.

[0014] "Sheet mainly composed of cellulose fibers" "Sheet mainly composed of cellulose fibers" means a sheet in which the content of cellulose fibers is 50% by mass or more based on the entire sheet. The content of cellulose fibers is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 100% by mass based on the entire sheet. Examples of the sheet mainly composed of cellulose fibers include substrates such as paper, paperboard, and non-woven fabric. Among them, a paper substrate is preferable because it is easy to obtain packaging paper having an excellent semi-transparent region.

[0015] The pulp constituting the paper substrate has cellulose fibers as its main component. Examples of the pulp include chemical pulp, mechanical pulp, waste paper pulp, non-wood pulp, etc. However, the pulp in the paper substrate is not limited to these examples.

[0016] Examples of the chemical pulp include pulp derived from softwood (NKP), pulp derived from hardwood (LKP), etc. Examples of the pulp derived from softwood include unbleached softwood kraft pulp (NUKP), bleached softwood kraft pulp (NBKP), semi-bleached softwood kraft pulp (NSBKP), softwood sulfite pulp (NSP), etc. Examples of hardwood pulp include, for example, unbleached hardwood kraft pulp (LUKP), bleached hardwood kraft pulp (LBKP), semi-bleached hardwood kraft pulp (LSBKP), hardwood sulfite pulp (LSP), and the like.

[0017] Examples of mechanical pulp include, for example, stone ground pulp (SGP), pressure ground pulp (PGW), refiner ground pulp (RGP), thermomechanical ground pulp (TGP), chemiground pulp (CGP), groundwood pulp (GP), thermomechanical pulp (TMP), and the like.

[0018] Examples of recycled pulp include, for example, disintegrated recycled pulp, disintegrated and deinked recycled pulp, and disintegrated, deinked, and bleached recycled pulp. Examples of the recycled paper used as the raw material for the recycled pulp include, for example, tea waste paper, kraft envelope waste paper, magazine waste paper, newspaper waste paper, flyer waste paper, office waste paper, cardboard waste paper, high-quality waste paper, Kent waste paper, imitation waste paper, land deed waste paper, and the like. Examples of non-wood pulp include various pulps such as pulp chemically or mechanically produced from non-wood fibers such as kenaf, cotton, hemp, and reed. These pulps may be used alone or in combination of two or more. Among them, chemical pulp is suitable for achieving both the visibility and strength of the sheet, and it is preferably used as the main component.

[0019] When using recycled pulp as the pulp, the content of the recycled pulp is preferably 10% by mass or less, more preferably 5% by mass or less, based on the total mass of the pulp constituting the paper base material. When the content of the recycled pulp is below the above upper limit value, the semi-transparent paper can be suitably applied as a packaging material for food and beverages. The lower limit value of the content of the recycled pulp is 0% by mass.

[0020] The freeness of the pulp constituting the paper base material is preferably 350 ml CSF or more, more preferably 400 to 700 ml CSF, and even more preferably 450 to 600 ml CSF. When the freeness of the pulp in the paper base material is at least the lower limit value of the above numerical range, it is easy to maintain the strength of the packaging paper. When the freeness of the pulp in the paper base material is at most the upper limit value of the above numerical range, it is easy to obtain a packaging paper having a translucent region excellent in transparency and visibility. The freeness (unit: ml CSF) of the pulp in the paper base material is measured according to JIS P8121-2.

[0021] Conventionally, glassine paper generally known as translucent paper uses chemically pulped pulp with a high beating degree, for example, chemically pulped pulp with a freeness of 250 ml CSF or less. However, since the pulp fibers with a high beating degree are crushed and cut, even if they are used for the transparent window part of an envelope, they are not easily applicable to uses such as packaging bags that require strength. On the other hand, in the present invention, since the visibility can be ensured even if the freeness of the paper base material is kept at 350 ml CSF or more, it is easy to maintain the strength of the packaging paper. Further, even a paper base material called glassine paper can be applied as a sheet of packaging paper as long as it can maintain the strength of the package.

[0022] As the paper base material, for example, kraft paper, one-sided kraft paper, one-sided paper, high-quality paper, electrophotographic paper, inkjet recording paper, thermal transfer recording paper, art paper, coated paper, cast coated paper, white cardboard, color board paper, corrugated cardboard liner, etc. can be used. Among them, high-quality paper, electrophotographic paper, kraft paper, and one-sided kraft paper with a low pigment content are preferred because they have excellent visibility in the translucent region.

[0023] Fillers such as talc and calcium carbonate that improve the smoothness and whiteness may be added to the paper base material. However, since the filler can affect the transparency and visibility of the paper, it is preferable to set the filler content within a range that does not impair the visibility, and it is preferable that the paper base material does not contain a filler.

[0024] The basis weight of the paper substrate is preferably 40 to 150 g / cm 2 , more preferably 45 to 100 g / cm 2 , and even more preferably 50 to 85 g / cm 2 . When the basis weight of the paper substrate is below the above upper limit value, it is easy to reduce the opacity of the translucent area of the packaging paper. On the other hand, when the basis weight of the paper substrate is above the above lower limit value, it is easy to obtain good paper strength as packaging paper. The basis weight of the paper substrate is measured according to JIS P8124.

[0025] The density of the paper substrate is preferably 0.5 to 0.8 g / cm 3 , more preferably 0.55 to 0.75 g / cm 3 . When the density of the paper substrate is below the above upper limit value, it is easy to increase the content of the transparentizing material of the packaging paper. When the density of the paper substrate is above the above lower limit value, it is easy to increase the strength of the packaging paper. The density of the paper substrate is measured according to JIS P8118.

[0026] The thickness of the paper substrate is preferably 20 to 120 μm, more preferably 20 to 80 μm, and even more preferably 30 to 70 μm. When the thickness of the paper substrate is above the lower limit value of the above numerical range, it is easy to increase the strength of the packaging paper. When the thickness of the paper substrate is below the upper limit value of the above numerical range, excellent visibility is easily obtained in the translucent area. The thickness of the paper substrate is a value measured by cutting out a cross-section perpendicular to the plane and measuring the maximum value in the thickness direction when observing the cross-section with an electron microscope.

[0027] The manufacturing method of the paper substrate is not particularly limited. For example, a method including a step of beating pulp as a raw material of the paper substrate, a step of papermaking a pulp slurry containing the beaten pulp, and a step of drying the wet sheet obtained by papermaking can be mentioned. In the beating step, it is preferable to beat the raw material pulp until the freeness of the paper substrate reaches a desired range. The beater is not particularly limited. For example, a double disk refiner etc. can be mentioned.

[0028] The paper machine used for papermaking is not particularly limited. For example, a Fourdrinier paper machine, a Duoformer paper machine, a cylinder paper machine, etc. can be mentioned. After papermaking, a smoothing treatment may be applied to the surface of the paper base material obtained through the drying process. By applying the smoothing treatment, the surface strength, printability, etc. can be enhanced. Examples of the smoothing treatment include a method of pressurizing the paper base material between pressable reels. The apparatus for applying the smoothing treatment is not particularly limited. For example, the product is finished by passing the paper through a machine calender, a gloss calender, a soft nip calender, etc. in front of the winder section. A machine calender and a super calender may be used in combination, or a super calender may be used instead of the machine calender.

[0029] "Transparentizing material" The packaging paper of the present invention has a translucent region in which a transparentizing material has penetrated in the entire region or a partial region of a sheet mainly composed of cellulose fibers. When the packaging paper is made into a packaging bag, the contents and the address can be seen through the translucent region from the outside of the packaging bag. The shape and area ratio of the translucent region in plan view are not limited at all. They can be appropriately set or changed according to the use of the packaging paper or the like. In another example, the translucent region may be the entire region in the planar direction of the sheet. Also, the number of translucent regions is not particularly limited and may be one or more. In the case of packaging paper provided with a plurality of translucent regions, the size and shape of each translucent region are also not particularly limited.

[0030] The opacity of the translucent region in which the transparentizing material has penetrated is not particularly limited, but is preferably about 10 to 40%. When it is 10% or more, the visibility due to light scattering inside the sheet tends to decrease, but the absorption of scattered light by the light-absorbing substance functions sufficiently and the visibility effect is enhanced. When the opacity of the translucent region is below the upper limit value of the above numerical range, the transparency of the translucent region is improved. The opacity of the translucent region is measured in accordance with JIS P 8138:1976.

[0031] The haze of the translucent region is preferably 80% or less. When the haze of the translucent region is 80% or less, the transparency of the translucent region is improved. The lower limit value of the haze of the translucent region is not particularly limited, but for example, it is 10% or more, preferably 20% or more. When the haze of the translucent region is equal to or higher than the lower limit value, it is easy to increase the strength of the wrapping paper. The haze of the translucent region is measured in accordance with JIS-K7136.

[0032] The density of the translucent region is 0.7 to 1.2 g / cm 3 is preferable, 0.8 to 1.2 g / cm 3 is more preferable, 0.8 to 1.1 g / cm 3 is even more preferable. When the density of the translucent region is equal to or higher than the lower limit value of the numerical range, it is considered that the air layer between the fibers is sufficiently removed by impregnation with the resin component. When the density of the translucent region is equal to or lower than the upper limit value of the numerical range, the workability when using the wrapping paper 1A as a package or the like is improved. The density of the translucent region is measured in accordance with JIS P8118.

[0033] The transparency-imparting material is not particularly limited. Examples of the transparency-imparting material include transparency-imparting resins such as acrylic resin, polyethylene resin, polyester resin, urethane resin, nitrocellulose, shellac, and rosin; vegetable oils such as tung oil, linseed oil, castor oil, hydrophilic castor oil, coconut oil, soybean oil, and commercially available salad oil; waxes and wax-like substances such as carnauba wax, palm wax, beeswax, whale wax, and wood wax. The transparency-imparting material may be used alone or in combination of two or more.

[0034] Among them, a transparency-imparting resin that is stable over time is preferable, and an acrylic resin is more preferable. Among acrylic resins, in particular, an ultraviolet-curable acrylic resin is preferable because it has excellent surface coating properties and the interface of the region impregnated with the transparency-imparting material 3 is clear in a cross-sectional view. Examples of the ultraviolet-curable acrylic resin include those disclosed in paragraphs 0025 and 0026 of JP-A-2021-91481.

[0035] As the transparency-imparting material, it is preferable to select one having a refractive index in the range of 1.4 to 1.6, preferably 1.45 to 1.58, more preferably 1.48 to 1.58, still more preferably 1.50 to 1.58, and particularly preferably 1.52 to 1.58 from among those exemplified above. This is because the refractive index of cellulose fibers is generally said to be in the range of 1.4 to 1.6. When the refractive index of the transparency-imparting material is within the above numerical range, the difference from the refractive index of cellulose fibers is small, and it is easy to enhance the transparency and visibility of the translucent region. Substances with a high refractive index such as zirconium and titanium may be appropriately blended to adjust the refractive index. The refractive index of the transparency-imparting material 3 is measured in accordance with JIS K7142.

[0036] Since the transparency-imparting material penetrates into cellulose fibers, it is preferably liquid at normal temperature or in a heated state. Also, those that can be dissolved in a liquid medium such as an organic solvent at normal temperature or in a heated state are preferable in terms of permeability. That is, the transparency-imparting material is preferably one that can be impregnated into the sheet as a permeable liquid transparency-imparting agent during production. The translucent region mainly contains the transparency-imparting material, but other components derived from the transparency-imparting agent used during production may be present.

[0037] The transparency-imparting agent is a liquid containing the transparency-imparting material. When the transparency-imparting material is solid at normal temperature, a liquid medium capable of dissolving the transparency-imparting material is used to prepare a liquid transparency-imparting agent. When the transparency-imparting material is liquid at normal temperature, the concentration of the transparency-imparting material may be changed using a liquid medium, or it may be used as it is as the transparency-imparting agent without using a liquid medium.

[0038] The liquid medium is not particularly limited. Either an aqueous solvent or an organic solvent can be used. When the liquid medium contains moisture, the sheet is likely to swell due to the moisture. Also, during subsequent drying, the sheet is likely to shrink. Therefore, curling, warping, and unevenness are likely to occur. Thus, it is preferable that the liquid medium does not contain moisture, and an organic solvent is more preferable.

[0039] The organic solvent may be a polar solvent or a non-polar solvent. Examples of the polar solvent include alcohols, ethers, esters, nonpolar solvents, and the like. Examples of the alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, n-pentanol, and n-hexanol. Examples of ethers include ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monopropyl ether, diethylene glycol monopropyl ether, triethylene glycol monopropyl ether, tetraethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monoisopropyl ether, triethylene glycol monoisopropyl ether, tetraethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, diethylene glycol monoisobutyl ether, triethylene glycol monoisobutyl ether, tetraethylene glycol monoisobutyl ether, ethylene glycol monotertiary butyl ether, diethylene glycol monotertiary butyl ether, triethylene glycol monotertiary butyl ether, tetraethylene glycol monotertiary butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monoethyl ether, tetrapropylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monopropyl ether, tripropylene glycol monopropyl ether, propylene glycol monoisopropyl ether, dipropylene glycol monoisopropyl ether, tripropylene glycol monoisopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether, propylene glycol monoisobutyl ether,Examples of glycol ethers include dipropylene glycol monoisobutyl ether, tripropylene glycol monoisobutyl ether, propylene glycol monotertiary butyl ether, dipropylene glycol monotertiary butyl ether, tripropylene glycol monotertiary butyl ether, etc. Examples of esters include diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, etc. Examples of nonpolar solvents include paraffinic hydrocarbons such as pentane, hexane, heptane, octane, nonane, decane, dodecane; isoparaffinic hydrocarbons such as isohexane, isooctane, isododecane; alkylnaphthalenic hydrocarbons such as liquid paraffin; aromatic hydrocarbons such as benzene, toluene, xylene, alkylbenzene, solvent naphtha; silicone oil, etc.

[0040] The clarifying agent may further contain other components in addition to the clarifying material and the liquid medium. Examples of other components include basic substances such as ammonia, ethylenediamine, and triethylamine; viscosity modifiers such as glycerin and ethylene glycol; high refractive index substances such as zirconium and titanium; defoaming agents; release agents. However, other components are not limited to these examples.

[0041] "Screen printing section" In the packaging paper of the present invention, it is characterized in that there is a screen printing section to which a light-absorbing substance is attached in the region having the clarifying material. The screen printing with the light-absorbing substance functions to absorb the light scattered inside the sheet. Therefore, although the amount of light transmitted through the sheet decreases, the scattered light is suppressed, and the visibility is improved.

[0042] The light-absorbing substance is not particularly limited as long as it has a high absorption coefficient. Since the light-absorbing substance 7 is formed by screen printing, the ink during printing can be prepared and used. For example, black-based components, especially black ink, are preferable in terms of excellent light absorption. The black ink may be a single-color printed black ink or a composite black using multiple colors. However, the color of the light-absorbing substance is not limited to black.

[0043] The screen printing portion is formed by the aggregation of dots. The shape of the dot pattern is not particularly limited. For example, the area may be filled with patterns such as halftone dots, grids, slashes, circles, rings, polygons, etc. The shape of the dot pattern can be appropriately changed according to the setting conditions when performing screen printing.

[0044] The area ratio of the screen printing portion is preferably 20% - 80%, and more preferably 25% - 75%. When the area ratio is equal to or higher than the lower limit value of the numerical range, it is easy for the screen printing portion to absorb scattered light. When the area ratio is equal to or lower than the upper limit value of the numerical range, it is considered that the color tone and color sense of the semi-transparent area are less affected by the screen printing portion. The area ratio referred to here is a value expressed as a percentage of the area of the halftone dots per unit area. In the case of solid printing, the area ratio is 100%, and when there are no dots, the area ratio is 0%. The area ratio can be appropriately changed according to the setting conditions when performing screen printing.

[0045] The size of the dots in screen printing is not particularly limited. For example, 40 - 100 μm is preferable, and 50 - 80 μm is more preferable. When the dot size is equal to or larger than the lower limit value of the numerical range, it is easy for the screen printing portion to absorb scattered light. When the dot size is equal to or smaller than the upper limit value of the numerical range, it is considered that the color tone and color sense of the semi-transparent area are less affected by the screen printing portion. The dot size is a value measured as the diameter or minor axis of the circumscribed circle or circumscribed ellipse with the smallest area among the circumscribed circles or circumscribed ellipses enclosing a single dot. The dot size can be appropriately changed according to the setting conditions when performing screen printing.

[0046] The color of the light-absorbing substance is preferably appropriately changed according to the use of the wrapping paper, the contents when formed into a package, the color tone of the sheet, and the color of the contents. For example, this is because the visibility and color sense can be changed according to the preferences of users and consumers. In commercialization, for example, a light-absorbing substance of the same color system as the color of the contents of the package may be used, or a light-absorbing substance having a complementary color relationship with the color of the contents of the package may be used. Also, regarding the shape of the dot pattern, the size of each dot, and the area ratio of the screen printing portion, it is preferably appropriately changed according to the use of the wrapping paper, the contents when formed into a package, and the color of the contents. This is because the visibility and color sense can be changed according to the preferences of users and consumers.

[0047] "Coating layer" The wrapping paper of the present invention preferably has a coating layer provided on the sheet surface of the translucent region. The visibility of the translucent region is further improved by the coating layer. In an example shown in FIG. 2, that is, in the wrapping paper 1B, the coating layer 5 is provided on the entire surface in the plane direction of the translucent region. However, in other examples, the coating layer may be provided on a part of the plane direction of the translucent region. Also, the number of coating layers may be one or a plurality.

[0048] As the material of the coating layer, a transparent material is preferable from the viewpoint of visibility. Examples of the material of the coating layer include a clarifying material and OP varnish. As the clarifying material, the same materials as those described for the translucent region can be mentioned. When the coating layer contains a clarifying material, the clarifying material of the coating layer and the clarifying material of the translucent region may be of the same type or different types from each other. Also, the material of the coating layer may be used alone as one type, or two or more types may be used in combination.

[0049] OP varnish is sometimes called overprint varnish. The components of OP varnish vary depending on the product, manufacturer, etc., but OP varnish containing at least one or more selected from the group consisting of linseed oil, tung oil, and nitrocellulose is preferred. Examples of commercially available OP varnishes include products of Toyo Ink Co., Ltd., T&K TOKA Co., Ltd., and Fuji Ink Manufacturing Co., Ltd. OP varnish may be used alone or in combination of two or more.

[0050] The thickness of the coating layer is preferably 0.5 to 2.5 μm, more preferably 0.5 to 2.5 μm, and even more preferably 0.7 to 2.0 μm. When the thickness of the coating layer is at least the lower limit value of the above numerical range, it is easy to reduce the unevenness on the surface of the translucent region and improve the smoothness, and excellent visibility can be easily obtained in the translucent region. When the thickness of the coating layer is at most the upper limit value of the above numerical range, the processability when using the packaging paper as a package or the like is improved. The thickness of the coating layer is a value measured by cutting out a cross-section perpendicular to the plane and measuring the maximum value in the thickness direction when observing the cross-section with an electron microscope.

[0051] "Method for manufacturing packaging paper" The method for manufacturing the packaging paper of the present invention is not particularly limited, but for example, (1) A method for manufacturing packaging paper having a translucent region, characterized by performing screen printing of a light-absorbing substance on the entire region or a partial region of a sheet mainly composed of cellulose fibers, and then coating, impregnating, and covering the region where the screen printing has been performed with a clarifying agent. (2) A method for manufacturing packaging paper having a translucent region, characterized by coating and impregnating a clarifying agent on the entire region or a partial region of a sheet mainly composed of cellulose fibers, then performing screen printing of a light-absorbing substance, and then covering the region where the screen printing has been performed with a clarifying agent. etc. can be adopted.

[0052] The transparency agent can penetrate into the interior of the sheet to fill the voids inside the sheet with a transparency agent having a refractive index close to that of cellulose, thereby suppressing refraction inside the sheet. More preferably, by covering up to the sheet surface, refraction due to the unevenness of the sheet surface can be suppressed. The transparency agent may be applied / impregnated onto the sheet at once, or may be applied / impregnated in multiple times. Also, the application / impregnation may be performed from both sides of the sheet. When forming in multiple times, the transparency agents used may be properly selected. For example, it may be impregnated with vegetable oils such as linseed oil and coated with a resin such as an acrylic resin. The method of applying / impregnating the transparency agent onto the sheet is not particularly limited, but a coating machine or a printing machine can be used. Also, since screen printing of a light-absorbing substance is performed on the region to which the transparency agent is applied, it is preferable to use a printing machine for the transparency agent as well.

[0053] For screen printing, known printing methods can be used. For example, offset printing, gravure printing, flexographic printing, screen printing, inkjet printing, electrophotographic printing, etc. can be appropriately used. It may be performed using the same printing machine as for the application / impregnation of the transparency agent. Also, it may be printed on the sheet in advance.

[0054] "Packaging bag and method for manufacturing the same" The packaging paper of the present invention can be made into a bag shape to form a packaging bag. The obtained packaging bag will be a bag having both strength and visibility. Also, in the case of packaging paper provided with a transparency agent in a partial region, the translucent region can be used as a window for checking the contents. When making it into a packaging bag, the packaging paper can be formed into a bag shape by adhering it using a method such as a known adhesive or a heat-sealing agent. Note that the shape of the packaging bag is not particularly limited, such as an envelope, a flat bag, a gusseted bag, a bag with a gusset, a tote bag, etc., and can be appropriately selected.

[0055] (Mechanism of action) The operation mechanism of the present invention will be described with reference to FIGS. 3 to 5. In FIGS. 3 to 5, a transparent resin film F (FIG. 3), a translucent paper 21 (FIG. 4), and wrapping papers 1A (1B) (FIG. 5) are respectively overlaid on the upper side of a packaging object 10 with a target image 11 printed on its upper surface. The direction of the light rays reflected from the target image 11 when the target image 11 is perceived as a visual image 12 from above the translucent area of the wrapping paper is indicated by arrows. In the case of the transparent film F in FIG. 3, the light rays reflected from the target image 11 travel linearly toward the visual position, that is, the position of the visual image, so the contour of the visual image 12A is clear. Therefore, the printed information of the target image 11 can be visually recognized through the film. In the case of the translucent paper 21 in FIG. 4, the light rays reflected from the target image 11 are refracted at the portion of the resin 23 impregnated in the sheet 22, and there is a lot of scattered light. Therefore, the printed information of the target image 11 can be visually recognized through the translucent paper 21. However, due to a lot of light scattering, the visual image 12B is an unclear image with an unclear contour. It is difficult to say that sufficient visibility has been obtained. In the case of the wrapping paper of the present invention in FIG. 5, the scattered light generated inside the sheet is absorbed by the screen printing of the light-absorbing substance. Therefore, among the light rays reflected from the target image 11, the light rays traveling linearly toward the visual position are selectively likely to pass through the translucent area. Therefore, the contour of the visual image 12C is clearer than that of the visual image 12B. The visibility of the contents is improved even through the translucent area.

[0056] So far, the transparent paper impregnated with a transparentizing agent such as resin has been mentioned, but such a technical idea can also be applied to, for example, glassine paper made by papermaking using pulp fibers with a high beating degree. That is, a sheet mainly composed of cellulose fibers made by papermaking using highly beaten pulp, and having a translucent area characterized by having a screen-printed portion of a light-absorbing substance in at least a partial area on one side of the sheet. Since scattering also occurs inside the sheet in the case of glassine paper or the like, when a screen-printed portion of a light-absorbing substance is provided on one side, the visibility through the glassine paper is improved as compared with the case where it is not provided. The action in this case is considered to be the same as the above-described operation mechanism.

[0057] (Use) Examples of the use of the wrapping paper of the present invention include packaging bags, envelopes, window envelopes, as well as packaging materials, clear files, labels, and the like.

Example

[0058] Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited by the following description.

[0059] "Sheet" As a sheet mainly composed of cellulose fibers, a single-sided kraft paper with a basis weight of 45 g / m 2 was prepared. The density of this single-sided kraft paper was 0.75 g / cm 3 and the thickness was 67 μm.

[0060] "Clarifying agent" For Examples 1 to 6, as a clarifying agent, an acrylic paraffin solvent (trade name: Clariten DC, manufactured by Daiwa Chemical Co., Ltd.) was prepared. The refractive index of Clariten DC is 1.50. As a solvent, a paraffin solvent (trade name: Clariten S) was added to prepare a clarifying agent with a clarifying material concentration of 90% by mass. Furthermore, for Example 7, an ultraviolet curable acrylic resin-based OP varnish (trade name: DC Gloss OP Varnish UV-20N) was prepared. The refractive index of DC Gloss OP Varnish UV-20N is 1.53. As a solvent, ethylene glycol monotertiary butyl ether (trade name: UV Fresh Echo II, manufactured by Morita Fine Chemical) was added, and a clarifying agent with a concentration of 95% by mass was used.

[0061] "Light-absorbing substance" Black ink (trade name: NCP Matt Ink, manufactured by DIC Corporation) was used.

[0062] "Manufacture of packaging paper 1: Examples 1 to 7, Comparative Examples 1 to 3" On the glossy surface of the coated craft paper, screening was printed in six patterns shown in Table 1 using black ink with a sheet-fed offset printing press (RYOBI·300ACCD). A micro-meter adjusting type applicator manufactured by Matsuo Sangyo Co., Ltd. was used to apply a transparentizing agent to the screened area so that the coating amount was 1.2 g / m 2 and perform coating and printing. In the case of the acrylic paraffin solvents of Examples 1 to 6, drying was performed for 30 seconds with a hot air dryer at 120°C. In the case of the ultraviolet curable acrylic resin-based OP varnish of Example 7, ultraviolet curing was performed using NPT-453 (4.8 kw, 2 lamps) manufactured by Nippon Bunka Seiko Co., Ltd. In Comparative Example 1, the same operations as in Example 1 were performed except that the transparentizing agent was applied and printed on the area where screening was not performed. In Comparative Example 2, the same operations as in Example 1 were performed except that the transparentizing agent was applied and printed on the area where solid printing was performed instead of screening. In Comparative Example 3, screening was performed, but no transparentizing agent was used.

[0063] <Evaluation method> For the transparent papers of each example, measurement and evaluation were performed by the following methods. The results are shown in Table 1.

[0064] (Opacity of the transparent area) Measured with a colorimeter SC-WT of Suga Test Instruments Co., Ltd. according to JIS P8138:1976.

[0065] (Evaluation of visibility) An A4-sized printed matter with a 10.5-point word document printed on it was placed on a horizontal table, and the packaging paper obtained was placed on it. From a position 30 cm above it, the evaluation of visibility was whether the printed matter could be read through the semi-transparent area of the packaging paper. ◎: Those in which characters can be recognized without omission ○: Those in which characters are partially missing but can be recognized ×: Those in which characters are missing in various places and are difficult to read ××: Those in which characters are missing in various places and are extremely difficult to recognize as characters

[0066]

Table 1

[0067] As shown in Table 1, in the translucent regions of Examples 1 to 7 where screen printing was performed, the visibility was improved compared to Comparative Examples 1 to 3.

[0068] "Manufacture of Wrapping Paper 2: Example 8, Comparative Examples 4 and 5" In Example 8, a transparentizing agent was applied and impregnated onto the glossy surface of single-sided kraft paper using a Matsuo Sangyo micrometer-adjustable applicator so that the coating amount was 1.2 g / m 2 and dried for 30 seconds with a hot air dryer at 120°C to form a translucent region. Thereafter, screen printing was performed with black ink using a sheet-fed offset printing press (RYOBI·300ACCD). Using a Matsuo Sangyo micrometer-adjustable applicator in the screen-printed area, a transparentizing agent was applied and impregnated so that the coating amount was 1.2 g / m 2 and dried for 30 seconds with a hot air dryer at 120°C to form a coating layer with a thickness of 1.0 μm.

[0069] In Comparative Example 4, the same operations as in Example 8 were performed except that the transparentizing agent was applied and printed in the area where screen printing was not performed. In Comparative Example 5, the same operations as in Example 8 were performed except that the transparentizing agent was applied and printed in the area where solid printing was performed instead of screen printing.

[0070] Table 2 shows the evaluation results of the opacity and visibility of each example. The measurement method and evaluation method are the same as those in Examples 1 to 7, etc.

[0071]

Table 2

[0072] As shown in Table 2, excellent visibility was obtained in the translucent region of Example 8.

Explanation of Signs

[0073] 1A, 1B: Wrapping paper having a translucent region 2: Sheet 3: Transparent material 4: Screen printing section 5: Coating layer 10: Packaging 11: Target image 12: Visible image F: Resin film 21: Translucent paper 22: Sheet 23: Transparent material

Claims

1. A sheet mainly composed of cellulose fibers; A transparent material permeating the inside of the sheet in the entire area or a part of the area of ​​the sheet; a halftone printed portion having a light absorbing material attached to an area of ​​the sheet having the transparent material; A wrapping paper having a translucent area,

2. 2. The wrapping paper having a translucent region according to claim 1, wherein the opacity of the region permeated with the transparent material is 10 to 40%.

3. A packaging bag having a translucent region, the packaging paper according to claim 1 or 2 being formed into a bag shape.

4. 4. The packaging bag according to claim 3, wherein the packaging bag is an envelope, and a window is formed in a part of the envelope by an area permeated with a transparent material.

5. A method for producing packaging paper having a translucent region, comprising the steps of: applying a light-absorbing substance to the entire or partial area of ​​a sheet whose main component is cellulose fiber by halftone printing; and then coating and impregnating the halftone-printed area with a clarifying agent.

6. A method for producing packaging paper having a translucent region, comprising the steps of: coating or impregnating a sheet whose main component is cellulose fiber with a transparentizing agent over the entire area or a portion of the sheet; then printing a screen pattern of a light-absorbing material; and then covering the screen-printed area with a transparentizing agent.

7. A sheet mainly composed of cellulose fibers made from highly beaten pulp, A wrapping paper having a translucent region, characterized in that at least a partial area on one side of the sheet has a halftone printed area to which a light absorbing substance is attached.

8. A window envelope, 8. An envelope with a window, the window portion of which is a wrapping paper having a translucent region according to claim 7.

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