Translucent paper and method for manufacturing translucent paper

Abstract

To provide translucent paper capable of obtaining a package having excellent visibility even when a space or a gap exists between a translucent area and its content.SOLUTION: Provided is translucent paper having a translucent area at least in a part of paper, the translucent paper having a translucent area wherein the translucent area has a view feeling transmittance ratio of 44 or over in the following measurement condition 2. The measurement condition 2: a view feeling transmittance measuring apparatus having a gap of at least 50 mm between a light projection unit and a light receiving unit is used; a translucent area of the paper is used as a measuring sample; a view feeling transmittance (T50) measured in a manner that one face of the sample is arranged so as to be in contact with the light projection unit and a view feeling transmittance (T0) measured in a manner that the other face of the sample is arranged so as to be in contact with the light receiving unit are measured; and a view feeling transmittance ratio is obtained by the following mathematical formula. The mathematical formula 1: view feeling transmittance ratio=(T50 / T0)×100.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] This invention relates to translucent paper and a method for producing translucent paper. [Background technology]

[0002] Envelopes, product packaging, and other packaging materials sometimes have a transparent area to allow the recipient's address and contents to be visible from the outside. While transparent resin films are often used for these transparent areas, from the perspective of resource recycling, it is preferable to use translucent paper or translucent paper with a translucent area in which at least a portion of the packaging paper is transparent.

[0003] There are several ways to make paper transparent. For example, highly beaten pulp fibers are used in the manufacture of translucent papers such as glassine paper and tracing paper. However, because the pulp fibers are crushed and cut due to the high degree of beatenness, highly beaten pulp fibers are suitable for applications where strength is required, such as packaging bags, although they can be used for envelope windows. On the other hand, a method of impregnating the voids between cellulose fibers with a transparent resin can maintain paper strength and increase the transparency of the translucent areas impregnated with the transparent resin (for example, Patent Documents 1 and 2). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-91481 [Patent Document 2] Japanese Patent Publication No. 132699 / 1983 [Overview of the project] [Problems that the invention aims to solve]

[0005] For example, when the primary use is intended for packaging thin contents such as documents, like an envelope, visibility can be ensured by pressing the translucent area against the contents with your fingers. However, some packaging materials are used for packaging products with depth and a three-dimensional shape. In addition, due to recent demands for environmental compliance, the scope of application of paper packaging materials as an alternative to plastic packaging is expanding.

[0006] However, with conventional translucent paper, it is difficult to clearly see the contents when there is space or gaps between the translucent area and the contents. Therefore, visibility is insufficient when the contents are packaged with depth. The present invention provides translucent paper and a method for manufacturing translucent paper, which enable the production of packaging that offers excellent visibility even when there is space or gaps between the translucent area and the contents. [Means for solving the problem]

[0007] The present invention has the following aspects. [1] A translucent paper having a translucent region in at least a portion of the paper, wherein the translucent region has a luminous transmittance (T50) of 20% or more under the measurement condition 1 below. "Measurement Condition 1" Using a luminous transmittance meter with a gap of at least 50 mm between the light-emitting and light-receiving parts, The sample used to measure the translucent region of the aforementioned translucent paper is: The luminous transmittance (T50) measured when the sample is placed with one side in contact with the light source.

[0008] [2] Translucent paper having a translucent region in at least a portion of the paper, wherein the translucent region has a luminous transmittance ratio of 44 or more under the measurement condition 2 below. "Measurement Condition 2" Using a luminous transmittance meter with a gap of at least 50 mm between the light-emitting and light-receiving parts, The translucent region of the aforementioned paper is used as a sample for measurement. The luminous transmittance (T50) measured when the sample is placed with one side in contact with the light source, The visual transmittance (T0) is measured when the other surface of the sample is placed in contact with the light-receiving part, and the visual transmittance ratio is determined by the following formula. Formula 1: Visual transmittance ratio = (T50 / T0) × 100

[0009] [3] The translucent paper having a translucent region in at least a part of the paper, wherein the visual transmittance ratio under the following measurement condition 2 is 44 or more, is the translucent paper according to [1]. "Measurement condition 2" Using a visual transmittance measuring device having at least a 50 mm gap between the light-projecting part and the light-receiving part, Taking the translucent region of the paper as a sample for measurement, The visual transmittance (T50) when measured by arranging one surface of the sample in contact with the light-projecting part, The visual transmittance (T0) when measured by arranging the other surface of the sample in contact with the light-receiving part, and the visual transmittance ratio is determined by the following formula. Formula 1: Visual transmittance ratio = (T50 / T0) × 100

[0010] [4] The translucent paper according to any one of [1] to [3], wherein the pulp constituting the paper has a ratio of softwood chemical pulp to hardwood chemical pulp of 80:20 to 51:49. [5] The translucent paper according to any one of [1] to [3], which contains a transparency-imparting material in the translucent region Soaking thereof. [6] The translucent paper according to any one of [1] to [3], further having a screen-printed part to which a light-absorbing substance is attached on at least a part of the translucent region.

[0011] [7] A method for producing a translucent paper, wherein at least a part of the base paper for the translucent paper contains a transparency-imparting material so that the visual transmittance (T50) under the following measurement condition 1 is 20% or more. Soaking "Measurement condition 1" Using a visual transmittance measuring device having at least a 50 mm gap between the light-projecting part and the light-receiving part, Taking the translucent region of the translucent paper as a sample for measurement, The luminous transmittance (T50) measured when the sample is placed with one side in contact with the light source.

[0012] [8] A transparent material is included in at least a portion of the base paper for translucent paper such that the visible transmittance ratio under measurement condition 2 below is 44 or higher. Soaking A method for manufacturing translucent paper. "Measurement Condition 2" Using a luminous transmittance meter with a gap of at least 50 mm between the light-emitting and light-receiving parts, The translucent region of the aforementioned paper is used as a sample for measurement. The luminous transmittance (T50) measured when the sample is placed with one side in contact with the light source, The luminous transmittance (T0) is measured when the other side of the sample is placed in contact with the light-receiving part, and the luminous transmittance ratio is calculated using the following formula. Formula 1: Luminous transmittance ratio = (T50 / T0) × 100

[0013] [9] A transparent material is included in at least a portion of the base paper for translucent paper such that the visible transmittance ratio under measurement condition 2 below is 44 or higher. Soaking A method for producing translucent paper as described in [7]. "Measurement Condition 2" Using a luminous transmittance meter with a gap of at least 50 mm between the light-emitting and light-receiving parts, The translucent region of the aforementioned paper is used as a sample for measurement. The luminous transmittance (T50) measured when the sample is placed with one side in contact with the light source, The luminous transmittance (T0) is measured when the other side of the sample is placed in contact with the light-receiving part, and the luminous transmittance ratio is calculated using the following formula. Formula 1: Luminous transmittance ratio = (T50 / T0) × 100 [Effects of the Invention]

[0014] According to one aspect of the present invention, a translucent paper that exhibits excellent visibility even when there is a space or gap between the translucent paper and the display, and a method for manufacturing the translucent paper are provided. Furthermore, packaging paper is provided that allows for the creation of a packaging body that exhibits excellent visibility even when there is a space or gap between the translucent area and the contents, using the translucent paper; and a packaging body equipped with the packaging paper is also provided. [Brief explanation of the drawing]

[0015] [Figure 1] This is an explanatory diagram illustrating the excellent visibility provided by transparent resin film. [Figure 2] This is an explanatory diagram illustrating the insufficient visibility of conventional translucent paper and similar materials. [Figure 3] This is an explanatory diagram illustrating the method for measuring luminous transmittance. [Figure 4] This is an explanatory diagram illustrating the method for measuring the luminous transmittance ratio. [Figure 5] This is a schematic plan view illustrating an example of translucent paper. [Figure 6] This figure schematically shows the VII-VII cross-section of the translucent paper shown in Figure 5. [Figure 7] This is an explanatory diagram illustrating the estimated mechanism by which visibility is improved by the use of halftone printing. [Modes for carrying out the invention]

[0016] In this specification, the "~" symbol indicating a numerical range means that the numbers before and after it are included as the lower and upper limits, respectively. The lower and upper limits of the numerical ranges disclosed herein can be combined in any way to create new numerical ranges.

[0017] Embodiments of the present invention will be described below with reference to the drawings as appropriate. The dimensional ratios in the drawings are for illustrative purposes only and may differ from those of the actual dimensions. In addition, in the following drawings, identical components are indicated by the same reference numerals, and descriptions of redundant components may be omitted.

[0018] [Visibility indicators] When paper with translucent areas is used as packaging material, consumers and users can see the contents of the package through the translucent areas. The superiority or inferiority of the visibility (visual perception) of the translucent areas is judged or determined by how the visible image is perceived by the human eye. As shown in Figure 1, when a transparent resin film F is placed on top of the contents 10 on which the target image 11 is printed, the light rays reflected from the target image 11 travel in a straight line toward the visual position, that is, the position of the visible image. Therefore, the outline of the visible image 12A is sharp, and the information of the target image 11 can be clearly seen through the resin film F. On the other hand, as shown in Figure 2, in the case of paper 21 having a semi-transparent region, the light rays reflected from the target image 11 are easily refracted within the semi-transparent region 22, and there is also a lot of diffused and scattered light. As a result, the visible image 12B becomes an indistinct image with no clear outline.

[0019] Incidentally, haze and opacity have traditionally been used to evaluate the visibility of translucent areas. However, according to the inventor's research, the numerical trends of haze and opacity often do not correspond to the superiority or inferiority of visibility as perceived by the human eye. For example, when the whiteness of a sample is high, the transmittance of visible light is high, but this does not necessarily mean that the visibility or visual surface quality is superior.

[0020] The reason why the numerical trend of haze does not correspond to the superiority or inferiority of visibility is thought to be as follows: Haze is calculated as the ratio of diffuse transmittance to the total transmittance of light rays transmitted through the sample. Diffuse transmittance is the transmittance of diffuse light obtained by ignoring a sample with linear light and removing the parallel component from the light rays that pass through the sample. On the other hand, as shown in Figures 1 and 2, the human eye preferentially recognizes light that travels in a straight line or light with a narrow diffusion angle, rather than diffuse light or scattered light with a wide diffusion angle. In calculating haze, parallel light components that are easily perceived by the human eye are excluded from the measurement target, while diffuse light that is difficult for the human eye to perceive is included in the measurement target to determine the diffuse transmittance. Since haze is calculated from this diffuse transmittance, it is not suitable for evaluating the perceived surface area by the human eye or the superiority or inferiority of visibility in the depth direction. Similarly, opacity is determined by including diffuse light, which is difficult for the human eye to perceive, in the measurement target, making it unsuitable for evaluating human visual perception of a surface or visibility in the depth direction.

[0021] As a result of diligent research, the inventors conceived the idea of ​​evaluating the visibility of a translucent region based on the degree of blurring of the contents visible through the translucent region. The degree of blurring is due to the diffusion pattern of light transmitted through the translucent region. In the case of a translucent region with a high degree of blurring, a relatively large amount of diffused light with a wide diffusion angle is included in the transmitted light, thus reducing the visibility of the contents. Conversely, in the case of a translucent region with little blurring, a relatively large amount of light traveling in a straight line or light with a narrow diffusion angle is included in the transmitted light, resulting in good visibility of the contents. The inventors devised a method and index for quantitatively evaluating the degree of blurring, and found that if the index of blurring is above a certain value, the visibility of the contents viewed through the semi-transparent area is excellent. These indicators are luminous transmittance and luminous transmittance ratio.

[0022] "Measurement of luminous transmittance" For measuring luminous transmittance, a luminous transmittance meter is used that includes a light-emitting unit that projects light from a light source onto the sample, a light-receiving unit that receives the light transmitted through the sample, and a sensor that measures the received light. The distance between the light-emitting and light-receiving units must be 50 mm or more, and when measured without a sample, the light-receiving sensitivity characteristics should closely match those of the photopic standard relative luminous efficiency. Numerous luminous transmittance meters are commercially available for measuring eyeglass lenses, filter glass, transparent conductive film glass, etc., and measurements can be taken using any device that meets the above measurement conditions. In addition, any device that meets the above measurement conditions, such as a spectrophotometer, can be used as a luminous transmittance meter.

[0023] "Luminous transmittance (T50)" The present invention relates to a paper having a translucent region in which the luminous transmittance (T50) under the following measurement conditions is 20% or more. "Measurement Condition 1" Using a luminous transmittance meter with a gap of at least 50 mm between the light-emitting and light-receiving parts, The translucent region of the aforementioned paper is used as a sample for measurement. The luminous transmittance measured when one side of the sample is placed in contact with the light source.

[0024] Figure 3 is an explanatory diagram illustrating the measurement. The luminous transmittance (T50) can be measured by placing one surface S1 of the sample S in contact with the light-emitting section 101 of the luminous transmittance meter 100. In this invention, the TLV-304-LC from Asahi Spectroscopic Co., Ltd., which is sold as a luminous transmittance meter, was used. In this device, the distance between the light-emitting section and the light-receiving section is 51.5 mm. By setting the luminous transmittance (T50) at a distance of at least 50 mm to 20% or more, the paper will have a transparent area with excellent visibility. The larger the value, the better the visibility, preferably 23% or more. Luminous transmittance (T50) is measured at a distance of 50 mm from the sample, rather than immediately after the light is emitted. This measurement excludes light that is scattered over that 50 mm and does not reach the light-receiving area, thus matching the perceived visibility. Since light does not scatter in air, the cause of scattering is due to the internal and surface conditions of the sample.

[0025] "Luminous transmittance ratio" The present invention relates to a paper having a translucent region where the luminous transmittance ratio under the following measurement conditions is 44 or higher. "Measurement Condition 2" Using a luminous transmittance meter with a gap of at least 50 mm between the light-emitting and light-receiving parts, The translucent region of the aforementioned paper is used as a sample for measurement. The luminous transmittance (T50) measured when the sample is placed with one side in contact with the light source, The luminous transmittance (T0) is measured when the other side of the sample is placed in contact with the light-receiving part, and the luminous transmittance ratio is calculated using the following formula. Formula 1: Luminous transmittance ratio = (T50 / T0) × 100

[0026] Figures 4(a) and 4(b) are explanatory diagrams illustrating the measurement. The luminous transmittance (T50) can be measured by placing one surface S1 of the sample S in contact with the light-emitting section 101 of the luminous transmittance meter 100 (a). The luminous transmittance (T0) can be measured by placing the other surface S2 of the sample S in contact with the light-receiving section 102 (b). When measuring the luminous transmittance (T0), it is advisable to hold the sample in place with a ring-shaped jig or similar to prevent it from bending due to its own weight. In this invention, the TLV-304-LC from Asahi Spectroscopic Co., Ltd., which is sold as a luminous transmittance meter, was used. In this device, the distance between the light-emitting section and the light-receiving section is 51.5 mm. The luminous transmittance ratio = (T50 / T0) × 100 is calculated from the luminous transmittance (T50) and luminous transmittance (T0) of two points at least 50 mm apart. By making this value 44 or higher, the paper will have a transparent area with excellent visibility. The higher the value, the better the visibility; preferably it is 48 or higher, and more preferably 50 or higher. The luminous transmittance ratio indicates how much the light transmitted from the sample decreased from (T0), measured immediately after it was emitted, to (T50), measured at a distance of 50 mm. (T50) excludes the light that was scattered over the 50 mm distance and did not reach the light-receiving part, thus corresponding to visibility. Since light does not scatter in air, the cause of scattering is due to the internal and surface conditions of the sample.

[0027] Furthermore, it is more preferable to satisfy both the luminous transmittance and the luminous transmittance ratio mentioned above.

[0028] In order to achieve a luminous transmittance of 20% or more and a luminous transmittance ratio of 44 or more in the transparent region, it is advisable to control the refraction and scattering of light at the surface of the paper into which light is incident, the interior of the paper into which the incident light is seen, and the surface of the paper into which the transmitted light is seen.

[0029] [Translucent paper] The following explains translucent paper. The translucent paper of the present invention has a translucent region in at least a portion of the paper. A transparency material is applied to at least a portion of the paper before the translucent region is formed (hereinafter also referred to as the base paper for translucent paper). Soaking By doing so, application and inclusion Soaking That area becomes semi-transparent, turning it into semi-transparent paper. Application of transparent materials Soaking This can be applied to the entire surface of the translucent paper base when viewed from above, or to only a portion of it. There are no particular limitations on the shape or number of translucent areas. The transparency material is applied / contained... Soaking In the treated area, the transparency material penetrates in the thickness direction of the base paper for translucent paper, filling the voids inside the paper as much as possible with the transparency material, thereby making the paper translucent. Translucency refers to a decrease in the opacity of the paper after treatment compared to the opacity of the paper before treatment. While not particularly limited, translucency generally refers to a state where the opacity of the treated area (JIS P 8138) is approximately 4-25%.

[0030] (Translucent paper base paper) The base paper for translucent paper is not particularly limited, but it is preferably paper mainly composed of coniferous chemical pulp and hardwood chemical pulp. Examples of coniferous chemical pulp include unbleached coniferous kraft pulp (NUKP), bleached coniferous kraft pulp (NBKP), semi-bleached coniferous kraft pulp (NSBKP), unbleached coniferous sulfite pulp (NUSP), bleached coniferous sulfite pulp (NBSP), and semi-bleached coniferous sulfite pulp (NSBSP). Examples of hardwood chemical pulp include unbleached hardwood kraft pulp (LUKP), bleached hardwood kraft pulp (LBKP), semi-bleached hardwood kraft pulp (LSBKP), unbleached hardwood sulfite pulp (LUSP), bleached hardwood sulfite pulp (LBSP), and semi-bleached hardwood sulfite pulp (LSBSP). In particular, a combination of bleached softwood kraft pulp (NBKP) and bleached hardwood kraft pulp (LBKP) is preferred.

[0031] Because softwood chemical pulp has a longer and thicker fiber structure than hardwood chemical pulp, incorporating a large amount of softwood chemical pulp results in a base paper with a high porosity, allowing for efficient incorporation of transparency-enhancing materials. Soaking This is possible. However, if softwood chemical pulp is added in excess, the paper base for translucent paper will deteriorate, and a uniform translucent region cannot be formed. On the other hand, hardwood chemical pulp has a fine and short fiber structure, which improves the paper base, but if the blending ratio is increased, the paper base will have a low porosity, and the penetration of the transparency material will be insufficient. If the penetration of the transparency material is insufficient, voids will form inside the paper where the transparency material has not penetrated, causing incident light to scatter and reflect inside the paper, resulting in a decrease in the luminous transmittance and luminous transmittance ratio.

[0032] The mixing ratio of coniferous chemical pulp to hardwood chemical pulp is preferably 80:20 to 51:49. A more preferable ratio is 75:25 to 55:45, and an even more preferable ratio is 70:30 to 60:40. By specifying the ratio of coniferous chemical pulp to hardwood chemical pulp, the transparency material can penetrate more easily, and the values ​​of luminous transmittance and luminous transmittance ratio can be increased.

[0033] The Canadian standard water content (CSF) of the aforementioned coniferous chemical pulp is preferably 400 to 700 mL. More preferably, the Canadian standard water content is 420 to 650 mL CSF, and even more preferably 450 to 600 mL CSF. If the Canadian standard water content is above the lower limit of the above numerical range, the voids in the base paper for translucent paper can be maintained, resulting in excellent permeability of the transparency material. If the Canadian standard water content is below the upper limit of the above numerical range, the form of the base paper for translucent paper can be improved, making it easier to obtain translucent paper with a translucent region that is excellent in transparency and visibility.

[0034] The Canadian standard water content (CSF) of the hardwood chemical pulp is preferably 350 to 650 mL. More preferably 370 to 630 mL CSF, and even more preferably 400 to 600 mL CSF. If the Canadian standard water content is above the lower limit of the above numerical range, the strength of the base paper for translucent paper can be increased. If the Canadian standard water content is below the upper limit of the above numerical range, the form of the base paper for translucent paper can be improved, making it easier to obtain translucent paper with a translucent area that is excellent in transparency and visibility.

[0035] Furthermore, it is preferable for softwood chemical pulp to have a higher Canadian standard of filtration than hardwood chemical pulp, as this results in superior paper strength and transparency. The Canadian standard of filtration for pulp is measured according to JIS P8121-2:2012. Incidentally, glassine paper, which has been commonly known as a translucent paper, uses chemical pulp with a high degree of beating, for example, chemical pulp with a Canadian standard of filtration of 250 mlCSF or less. However, because the pulp fibers with a high degree of beating are ground and cut, they are difficult to apply to applications where strength is required, such as packaging bags, although they may be suitable for transparent windows on envelopes.

[0036] Other types of pulp besides softwood chemical pulp and hardwood chemical pulp can be used in combination with the pulp, as long as they do not impair the effects of the present invention. Examples include mechanical pulp, thermomechanical pulp, deinked pulp, non-wood pulp, and synthetic pulp.

[0037] The basis weight of the base paper for translucent paper is 30-150 g / m². 2 Preferably, 40-100 g / m² 2 More preferably, 50-85 g / m 2 This is even more preferable. If the basis weight is above the lower limit of the above numerical range, good paper strength is more likely to be obtained. If the basis weight is below the upper limit of the above numerical range, the transparency of the translucent area is more likely to be increased. The basis weight of the base paper for translucent paper is measured in accordance with JIS P8124.

[0038] The air permeability of the base paper for translucent paper is preferably 10 to 40 seconds. Preferably, it is 12 to 35 seconds, and more preferably 15 to 33 seconds. If the air permeability is above the lower limit of the above numerical range, the paper gains sufficient strength, resulting in translucent paper suitable for applications such as packaging paper and printing paper. If the air permeability is below the upper limit of the above numerical range, the permeability of the transparency material is excellent, and the transparency of the translucent paper can be enhanced. Air permeability is measured according to the Wang Research method of air permeability measured in accordance with J.TAPPI-5-2:2000.

[0039] The density of the base paper for translucent paper is 0.5 to 0.85 g / cm³. 3 Preferably, it is 0.6 to 0.8 g / cm³. 3 This is more preferable. If the density is above the lower limit of the above numerical range, the paper strength is obtained, resulting in a translucent paper suitable for applications such as packaging paper and printing paper. If the density is below the upper limit of the above numerical range, the permeability of the transparency material is excellent, and the transparency of the translucent paper can be increased. The density is measured in accordance with JIS P8118.

[0040] The porosity of the base paper for translucent paper is preferably 30-80%, more preferably 40-70%, and even more preferably 50-70%. If the porosity of the base paper for translucent paper is above the lower limit of the above numerical range, the transparency of the translucent region is easily enhanced. If the porosity of the base paper for translucent paper is below the upper limit of the above numerical range, the physical strength of the sheet is less likely to decrease. The porosity of the paper substrate is calculated from the value obtained by dividing the density measured according to JIS P8118 by the true density of cellulose, which is 1.50.

[0041] The ParkerPrintSurf smoothness of at least one side of the base paper for translucent paper is preferably 7 μm or less, and more preferably 5 μm or less. There is no particular lower limit. The smaller the value, the smoother the surface. ParkerPrintSurf smoothness can evaluate the smoothness of fine details, and the smaller this value, the less light scattering on the paper surface can be reduced, thus increasing the luminous transmittance and luminous transmittance ratio. ParkerPrintSurf smoothness is determined in accordance with ISO 8791-4:1992 (soft backing / clamp pressure 500 kPa).

[0042] In addition to pulp, the base paper for translucent paper may contain known papermaking aids such as paper strength enhancers, sizing agents, fillers, and colorants as appropriate. However, since the addition of fillers tends to increase the opacity of the paper, it is preferable to limit the amount to a level that does not impair transparency and visibility, and it is even preferable not to add fillers to the base paper for translucent paper.

[0043] The method for manufacturing base paper for translucent paper is not particularly limited. For example, a method may include a step of beating pulp which will be the raw material for the base paper for translucent paper, a step of papermaking a pulp slurry containing the beated pulp, and a step of drying the wet sheet obtained by papermaking.

[0044] In the beating process, it is preferable to beating the raw pulp so that it achieves the Canadian standard water content. The beating machine is not particularly limited. For example, known beating machines such as double disc refiners can be used. The papermaking machines used are not particularly limited. Examples include screenprint machines, short screenprint machines, and cylinder screenprint machines. The drying process is not particularly limited. For example, a dryer attached to the paper machine can be used.

[0045] The base paper for translucent paper may be subjected to a smoothing treatment. By applying a smoothing treatment, the scattering of light on the paper surface can be reduced, thereby increasing the luminous transmittance and luminous transmittance ratio of the translucent portion. Examples of smoothing treatments include tightness pressing, machine calendering, gloss calendering, soft nip calendering, and supercalendering. However, these devices increase the density of the paper, so care must be taken to reduce the linear pressure to prevent the density from becoming too high. On the other hand, a transfer method in which the paper is attached to a smooth surface while it is still wet and the smooth surface is transferred by drying is preferable because it does not increase the density of the paper. For example, technologies such as Yankee cylinders, cast drums, and film transfers can be used. Among these, a Yankee dryer using a Yankee cylinder is preferable because it is attached to the paper machine and offers excellent productivity.

[0046] Examples of base papers for translucent paper include kraft paper, semi-gloss kraft paper, semi-gloss paper, fine paper, electrophotographic paper, inkjet recording paper, thermal transfer recording paper, art paper, coated paper, cast coated paper, white cardboard, colored cardboard, and corrugated cardboard liner. Among these, fine paper, electrophotographic paper, kraft paper, semi-gloss kraft paper, and semi-gloss paper are preferred, with semi-gloss kraft paper and semi-gloss paper being more preferred, as they have a low pigment content and easily provide excellent visibility in the translucent region.

[0047] (Formation of translucent regions) The translucent region is formed by applying and impregnating at least a portion of the base paper for translucent paper with a translucent material. When the base paper for translucent paper has a glossy surface with relatively high smoothness and a matte surface with relatively low smoothness, such as one-sided glossy kraft paper or one-sided glossy paper, it is preferable to apply and impregnate the translucent material on the matte surface with relatively low smoothness. This allows for excellent penetration of the translucent material and does not impair the smoothness of the glossy surface with relatively high smoothness, thus preventing light scattering on the surface.

[0048] (transparent material) The clarifying material is not particularly limited. Examples of clarifying materials include acrylic resin, polyethylene resin, polyester resin, urethane resin, nitrocellulose, shellac, rosin, and other clarifying resins; vegetable oils such as tung oil, linseed oil, castor oil, hydrophilic castor oil, coconut oil, soybean oil, and commercially available salad oil; and waxes such as kaunaba wax, palm wax, beeswax, whale wax, and wood wax. One type of clarifying material may be used alone, or two or more types may be used in combination.

[0049] Among these, a transparent resin that is stable over time is preferred, and an acrylic resin is more preferred. Among acrylic resins, ultraviolet-curable acrylic resins are particularly preferred because they have excellent surface coverage and the interface of the region impregnated with the transparent material becomes clear in cross-sectional view. Examples of ultraviolet-curable acrylic resins include those disclosed in paragraphs 0025 and 0026 of Japanese Patent Application Publication No. 2021-91481.

[0050] As the transparency material, it is preferable to select one from the above-mentioned materials with a refractive index within the range of 1.4 to 1.6, preferably 1.45 to 1.58, more preferably 1.50 to 1.58, and even more preferably 1.52 to 1.58. This is because the refractive index of the cellulose fibers in the pulp that constitutes the base paper for translucent paper is generally said to be within the range of 1.4 to 1.6. When the refractive index of the transparency material is within the above numerical range, the difference with the refractive index of the cellulose fibers is small, making it easier to improve the transparency and visibility of the translucent region. The refractive index of the transparency material is measured according to JIS K 7142.

[0051] By impregnating a translucent base paper with a refractive index close to that of cellulose fibers and filling the voids between the cellulose fibers, the refraction of light caused by voids within the base paper can be reduced. Therefore, a translucent region with excellent transparency and visibility can be easily obtained. High refractive index materials such as zirconium and titanium may be used as needed to adjust the refractive index.

[0052] When a transparent material is colored, it is preferable to include a coloring agent (pigment, dye) that is complementary to the color of the transparent material within the translucent base paper for translucent paper. It is believed that the complementary coloring agent, which has penetrated between the cellulose fibers, absorbs incident light, thereby suppressing diffuse reflection and scattering of light, and consequently improving visibility. Examples of coloring agents include blue coloring agents, purple coloring agents, and black coloring agents. Here, "complementary colors" refers, for example, to a combination of colors located directly opposite each other on the color wheel. However, within the range in which the effects of the present invention can be obtained, "complementary colors" may not be limited to colors that are strictly located directly opposite each other on the color wheel, but may also be a combination of colors in a continuous area surrounding them.

[0053] For example, transparent resins derived from non-petroleum components, such as shellac and rosin, are colored. In the case of shellac, a colorant that is complementary to its orange color is preferred. In the case of rosin, a colorant that is complementary to its amber color is preferred. When colored transparent materials derived from non-petroleum components are preferred from an environmental perspective, it is useful to use a colorant that is complementary to the color of the transparent material.

[0054] Since the transparency material is impregnated into the base paper for semi-transparent paper, it is preferable that it be a liquid at room temperature or when heated. Furthermore, materials that can dissolve in a liquid medium such as an organic solvent at room temperature or when heated are also preferable in terms of permeability. In other words, it is preferable that the transparency material be a permeable liquid transparency agent that can be impregnated into the base paper for semi-transparent paper during manufacturing. The transparency agent will be described later.

[0055] The density of the translucent region containing the transparent material is 0.7 to 2.5 g / cm³. 3 Preferably, 0.7 to 2.0 g / cm³ 3 More preferably, 0.8-2.0 g / cm³ 3This is even more preferable. If the density of the translucent region is above the lower limit of the numerical range, it is considered that the air layer between the fibers has been sufficiently eliminated by impregnation with resin components. If the density of the translucent region is below the upper limit of the numerical range, the processability of the packaging paper when used as a packaging material is improved. The density of the translucent region is measured in accordance with JIS P 8118.

[0056] (Clearing agent) A clearing agent is a liquid containing a clearing material. If the clearing material is a solid at room temperature, a liquid clearing agent is prepared using a liquid medium capable of dissolving the clearing material. If the clearing material is a liquid at room temperature, the concentration of the clearing material may be changed using a liquid medium, or it may be used as a clearing agent without using a liquid medium.

[0057] The liquid medium is not particularly limited. Either aqueous solvents or organic solvents can be used. If the liquid medium contains water, the base paper for translucent paper tends to swell due to the water. Furthermore, the base paper for translucent paper tends to shrink during subsequent drying. As a result, curling, bumping, and unevenness are likely to occur. Therefore, it is preferable that the liquid medium does not contain water, and organic solvents are more preferable.

[0058] The organic solvent may be a polar solvent or a nonpolar solvent. Examples of polar solvents include alcohols, ethers, esters, and nonpolar solvents. Examples of 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 Polyethylene 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 various 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, and the like. Examples of esters include, for example, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, and the like. Examples of nonpolar solvents include paraffinic hydrocarbons such as pentane, hexane, heptane, octane, nonane, decane, dodecane; isoparaffinic hydrocarbons such as isohexane, isooctane, isododecane; alkyl naphthenic hydrocarbons such as liquid paraffin; aromatic hydrocarbons such as benzene, toluene, xylene, alkylbenzene, solvent naphtha; silicone oil, and the like.

[0059] 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, triethylamine; viscosity modifiers such as glycerin, ethylene glycol; high refractive index substances such as zirconium, titanium; defoaming agents; mold release agents; coloring agents. However, other components are not limited to these examples.

[0060] During impregnation, a portion where the clarifying material does not reach a part of the other surface may be formed in the cross-section within the base paper for semi-transparent paper. This is because a surface state with relatively high smoothness can be maintained as it is before impregnation with the clarifying material in this portion. It is easy to reduce the unevenness on the surface of the semi-transparent region, and the visibility of the semi-transparent region is more likely to be improved.

[0061] The coating amount per unit area of the clarifying agent is preferably 10 to 70 g / m 2 and more preferably 20 to 60 g / m 2 and even more preferably 30 to 60 g / m 2This is even more preferable. If the amount of clearing agent applied per unit area is greater than or equal to the lower limit of the numerical range, the transparency of the translucent region is more easily increased. If the amount of clearing agent applied per unit area is less than or equal to the upper limit of the numerical range, the clearing agent is less likely to reach a part of the interior.

[0062] The viscosity of the clearing agent is preferably 50 to 5000 mPa·s, more preferably 50 to 4000 mPa·s, and even more preferably 50 to 3000 mPa·s. If the viscosity of the clearing agent is above the upper limit of the above numerical range, the clearing agent will have difficulty reaching a part of the inside. If the viscosity of the clearing agent is below the upper limit of the above numerical range, the clearing agent will easily impregnate the base paper for semi-transparent paper. The viscosity of the clearing agent is measured using a Blookfield viscometer under conditions of 30°C and 60 rpm.

[0063] The method of applying the clearing agent is not particularly limited. Examples of methods for applying the clearing agent include flexographic printing, inkjet printing, gravure printing, offset printing, gravure offset printing, screen printing, roll coating, bar coating, and blade coating.

[0064] By impregnating the base paper for translucent paper with a clearing agent, the voids between the fibers in the base paper can be filled with the clearing material. When using a clearing agent containing a clearing material with a refractive index in the range of 1.4 to 1.6, the voids in the base paper can be filled with a clearing agent that has a refractive index close to that of cellulose. Therefore, the refraction of light caused by the clearing material in the base paper can be reduced.

[0065] The application and impregnation of the clearing agent onto the base paper for semi-transparent paper may be performed in a single step or in multiple steps. If performed in multiple steps, the components and composition of the clearing agent used in each step may be the same or different.

[0066] When using an ultraviolet-curing clearing agent, various light sources can be used, such as high-pressure mercury lamps, metal halide lamps, xenon lamps, and electrodeless discharge lamps. The cumulative light intensity is not particularly limited and can be appropriately adjusted depending on the amount of clearing agent used and the type of clearing resin.

[0067] (Coating layer) A coating layer may be provided on the surface of the paper in the translucent region. The coating layer is intended to increase the smoothness of the surface in the translucent region and reduce irregularities. Reducing surface irregularities prevents diffuse reflection of light on the surface of the translucent region. In addition, the coating layer prevents a reduction in the amount of light due to reflection of incident light while maintaining the amount of light in the parallel component. The reduction in the proportion of diffuse light with a wide diffusion angle in the transmitted light of the translucent region due to the action of such a coating layer is considered to be one of the factors that reduces blurring and improves visibility in the depth direction.

[0068] For visibility, the material of the coating layer is preferably a transparent material. Examples of coating layer materials include transparency materials and OP varnish. Specific examples of transparency materials will be described later. When the coating layer includes a transparency material, the transparency material of the coating layer and the transparency material of the translucent region may be the same or of different types. Furthermore, the coating layer material may be used alone or in combination of two or more types.

[0069] OP varnish is sometimes called overprint varnish. The composition of OP varnish varies depending on the product and manufacturer, but it is preferable to use OP varnish that contains at least one selected from the group consisting of linseed oil, tung oil, and nitrated cotton. Examples of commercially available OP varnishes include those from Toyo Ink Co., Ltd., T&K TOKA Corporation, and Fuji Ink Mfg. Co., Ltd. OP varnish may be used alone or in combination of two or more types. Drying methods may include oxidative polymerization or UV drying.

[0070] As the material for the coating layer, it is preferable to select one from among these that has a refractive index within the range of 1.4 to 1.6, preferably 1.45 to 1.60, more preferably 1.48 to 1.60, even more preferably 1.50 to 1.60, and particularly preferably 1.50 to 1.58. This is because the refractive index of cellulose fibers is generally said to be within the range of 1.4 to 1.6. By setting the refractive index of the coating layer to a value close to that of the cellulose fibers, the refraction of light at the interface between the coating layer and the base paper for translucent paper can be reduced. Therefore, it becomes easier to obtain a translucent region with excellent visibility. The refractive index of the coating layer is measured according to JIS K 7142.

[0071] The smoothness of the coating layer is preferably 50 to 1000 sec, more preferably 50 to 500 sec, and even more preferably 100 to 500 sec. When the smoothness of the coating layer is within the above numerical range, visibility tends to improve further. The smoothness of the coating layer is measured according to JAPAN TAPPI Paper and Pulp Test Method No. 5-2 and JIS P8155.

[0072] The thickness of the coating layer is preferably 0.5 to 2.5 μm, more preferably 0.5 to 2.0 μm, and even more preferably 0.7 to 2.0 μm. If the thickness of the coating layer is above the lower limit of the above numerical range, a glossy surface is obtained, and excellent visibility is easily obtained in the translucent region. If the thickness of the coating layer is below the upper limit of the above numerical range, unevenness and curling of the paper sheet due to the difference in shrinkage after drying between the coated and uncoated parts is suppressed. The thickness of the coating layer is the value measured by taking a cross section perpendicular to the plane and observing the cross section with an electron microscope, and measuring the maximum value in the thickness direction.

[0073] It is preferable that the coating layer be applied to the entire surface in the planar direction of the translucent region, but it may also be applied to a part of the translucent region in the planar direction. Furthermore, there may be one or more coating layers. Part of the coating layer material may penetrate near the surface of the base paper for translucent paper. Filling the voids between the fibers of the base paper for translucent paper with the coating layer material makes it easier to increase transparency.

[0074] The method of applying the coating solution containing the coating layer material is not particularly limited. Examples include various coating methods such as roll coating, bar coating, blade coating, dip coating, flexographic printing, gravure printing, offset printing, gravure offset printing, and silkscreen printing. The drying method is also not particularly limited. It may be air-dried or heat-dried.

[0075] (Shaded printing section) A light-absorbing material can be applied as a halftone print to the translucent areas of translucent paper. As shown in Figure 7, the halftone printing area 6 can absorb scattered light generated within the base paper 2 for the translucent paper. Therefore, among the light rays reflected from the target image 11, light that travels linearly toward the viewing position and light with a narrow diffusion angle are more likely to selectively pass through the translucent region. Consequently, the outline of the visible image 12C becomes sharper than that of the visible image 12B (see Figure 2).

[0076] Each dot of the halftone printing section 6 is made of a light-absorbing material that absorbs light scattered within the translucent paper base 2. As a result, the amount of light transmitted through the translucent paper base 2 decreases, which lowers the luminous transmittance values ​​T50 and T0. However, because scattered light is suppressed, the luminous transmittance ratio can be increased.

[0077] The shape of the dot pattern in the halftone printing section 6 is not particularly limited. For example, it may be a halftone dot, grid, diagonal line, circle, ring, or polygon pattern, but the shape is not limited to these examples. The shape of the dot pattern can be changed as appropriate depending on the settings when performing halftone printing.

[0078] The size of each dot in the halftone printing area 6 is not particularly limited. For example, 40 to 100 μm is preferred, and 50 to 80 μm is more preferred. If the size of the dots is greater than or equal to the lower limit of the numerical range, the halftone printing area 6 is likely to absorb scattered light. If the size of the dots is less than or equal to the upper limit of the numerical range, the halftone printing area 6 is less likely to affect the color tone and appearance of the semi-transparent area 4. The size of a dot is measured as the diameter of the circumcircle or the minor axis of the circumellipse that encloses a single dot and has the smallest area. The size of the dot can be changed as appropriate depending on the settings when performing halftone printing.

[0079] The area ratio of the halftone printing area 6 is preferably 20-80%, and more preferably 25-75%. If the area ratio is above the lower limit of the above numerical range, scattered light is easily absorbed by the halftone printing area 6. If the area ratio is below the upper limit of the above numerical range, the color tone and appearance of the semi-transparent area 4 are less likely to be affected by the halftone printing area 6. The area ratio of the halftone printing area is the percentage of the area occupied by dots per unit area. For solid printing, the area ratio is 100%, and if there are no dots, the area ratio is 0%. The area ratio can be adjusted as needed depending on the settings for halftone printing.

[0080] The light-absorbing material 7 is not particularly limited as long as it is a material with a high absorption coefficient. Since the light-absorbing material 7 is formed by halftone printing, the ink used during printing can be prepared and used. For example, black components, especially black inks, are preferred because they have excellent light absorption properties. The black ink may be a single-color black ink or a composite black using multiple colors. However, the color of the light-absorbing material 7 is not limited to black.

[0081] The color of the light-absorbing substance 7 is preferably changed as appropriate depending on the intended use of the packaging paper 1B, the contents of the package, the color of the base paper for the translucent paper, and the color of the contents. For example, this allows for changes in visibility and color perception to suit the preferences of users and consumers. In commercialization, for example, a light-absorbing substance of the same color as the contents of the package may be used, or a light-absorbing substance that is complementary in color to the contents of the package may be used. Furthermore, it is preferable to appropriately change the shape of the dot pattern in the halftone printing section 6, the size of each dot, and the area ratio according to the intended use of the packaging paper, the contents of the package, and the color of the contents. This is because the visibility and color perception can be changed to suit the preferences of users and consumers.

[0082] In one example shown in Figures 5 and 6, the translucent paper 1B has a halftone printed area 6 in which the light-absorbing material 7 is attached to almost the entire surface in the planar direction of the translucent region 4 on the first surface 2a side. However, in other examples, the halftone printed area may be formed by the light-absorbing material 7 being attached to a part of the translucent region 4 on the first surface 2a side. Even if the light-absorbing material 7 is attached to at least a part of the translucent region 4 on the first surface 2a side, the light-absorbing effect of the halftone printed area can still be obtained.

[0083] The method for manufacturing the packaging paper 1B is not particularly limited. The light-absorbing substance 7 can be attached to the surface of the translucent paper base paper 2 by halftone printing. The halftone printing may be performed before impregnation of the translucent paper base paper with the transparency material, or after impregnation of the translucent paper base paper with the transparency material.

[0084] The method of halftone printing is not particularly limited. Various printing methods can be used. Examples include offset printing, gravure printing, flexographic printing, screen printing, inkjet printing, and electrophotographic printing. Furthermore, halftone printing may be performed on the same printing press as the application and impregnation of the clearing agent, or on separate printing presses.

[0085] The diagrams used in the above illustrative explanation are schematic. Therefore, the boundary lines between the translucent base paper 2 and the translucent region 4 in a plan view, and the boundary lines between the translucent base paper 2 and the coating layer 5 in a plan view, may not necessarily exist as clearly as schematically illustrated. Similarly, the interfaces in a cross-sectional view may not necessarily exist as clearly as schematically illustrated.

[0086] (Manufacturing method for semi-transparent paper) The method for producing the translucent paper of the present invention is any of the following (1), (2), or (3).

[0087] (1) A transparent material is included in at least a portion of the base paper for translucent paper such that the visible transmittance (T50) under measurement condition 1 below is 20% or more. Soaking A method for manufacturing translucent paper. "Measurement Condition 1" Using a luminous transmittance meter with a gap of at least 50 mm between the light-emitting and light-receiving parts, The sample used to measure the translucent region of the aforementioned translucent paper is: The luminous transmittance (T50) measured when the sample is placed with one side in contact with the light source.

[0088] (2) A transparent material is included in at least a portion of the base paper for translucent paper such that the visible transmittance ratio under measurement condition 2 below is 44 or higher. Soaking A method for manufacturing translucent paper. "Measurement Condition 2" Using a luminous transmittance meter with a gap of at least 50 mm between the light-emitting and light-receiving parts, The translucent region of the aforementioned paper is used as a sample for measurement. The luminous transmittance (T50) measured when the sample is placed with one side in contact with the light source, The luminous transmittance (T0) is measured when the other side of the sample is placed in contact with the light-receiving part, and the luminous transmittance ratio is calculated using the following formula. Formula 1: Luminous transmittance ratio = (T50 / T0) × 100

[0089] (3) A transparent material is included in at least a portion of the base paper for translucent paper such that the luminous transmittance (T50) under measurement condition 1 is 20% or more and the luminous transmittance ratio under measurement condition 2 is 44 or more. Soaking A method for manufacturing translucent paper.

[0090] The translucent region of translucent paper is due to the inclusion of a transparency material in the base paper for translucent paper. Soaking Although formed in this manner, the manufacturing process satisfies the above-mentioned luminous transmittance and luminous transmittance ratio, including the manufacturing of the base paper for translucent paper, the selection of the base paper for translucent paper, the selection of the transparency material, and the inclusion of the transparency material. Soaking • Preparation of coating liquid, including Soaking This involves adjusting the amount of coating solution impregnation, adopting a coating layer, and incorporating a halftone printing pattern.

[0091] (Application) The translucent paper of the present invention, and the translucent paper obtained by the method of the present invention, offer transparency and visibility, and can therefore be used in various applications such as packaging paper, printing paper, book paper, copy paper, information paper, and label paper, where an image (characters, symbols, pictures, objects, etc.) on the opposite side of the paper can be seen through the paper substrate.

[0092] In the case of packaging paper, the blurring of the contents when viewed through the translucent area is minimal, resulting in excellent visibility of the contents. Furthermore, visibility remains good even when there is space or gaps between the translucent area and the contents. Therefore, a packaging material with good visual clarity in the depth direction is obtained, resulting in excellent visibility even when the contents are packaged within a depth-based space. Examples of such packaging materials include envelopes and packaging for various products. For example, packaging paper can be formed into a bag to create a packaging bag. The translucent area of ​​the packaging paper can be used as a window to check the contents of the packaging bag. When creating a packaging bag, the packaging paper can be bonded together using various adhesives or heat sealants to form a bag. The shape of the packaging bag is not particularly limited. Examples include envelopes, flat bags, square-bottom bags, gusseted bags, and shopping bags, but are not particularly limited. It should be selected appropriately depending on the contents.

[0093] Although several examples of one embodiment have been described above, the present invention is not limited to the embodiments disclosed herein and can be implemented with appropriate modifications without altering the spirit of the invention. The embodiments disclosed herein can be implemented in various other forms, and various omissions, substitutions, and modifications are possible without departing from the spirit of the invention. [Examples]

[0094] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following description.

[0095] [Raw materials] (Translucent paper base paper) In the following example, the basis weight is 50 g / m². 2A single-sided glossy kraft paper (1) was used. The smoothness of the glossy side of the single-sided glossy kraft paper (1) was 120 sec, and the smoothness of the non-glossy side was 10 sec. The density of the single-sided glossy kraft paper (1) was 0.75 g / cm³. 3 It has a thickness of 67 μm and a porosity of 50%.

[0096] (Clearing agent) The following clearing agent (1) was used as a clearing agent to form a translucent region. Clearing agent (1): Acrylic paraffin solvent (product name: Clariten DC, manufactured by Yamato Chemical Industry Co., Ltd., refractive index of the clearing material: 1.50, viscosity at 30℃ and 60rpm: 2000 mPa·s). The refractive index was measured using an Appe refractive index meter manufactured by Atago Co., Ltd.

[0097] (Coating layer) The following coating liquid (1) was used as the coating liquid when forming the coating layer. Coating liquid (1): DC AB OP varnish OJ3 (manufactured by DIC Graphics Co., Ltd.)

[0098] (Light-absorbing substance) Black ink (product name: NCP Matte Sumi, manufactured by DIC Graphics Co., Ltd.) was used.

[0099] [Example 1] Using a Matsuo Sangyo micrometer-adjustable applicator, the application rate was 34 g / m². 2 The transparentizing agent (1) was applied to the non-glossy side of the glossy kraft paper (1) in such a manner. Then, it was dried for 30 seconds using a 120°C hot air dryer to form a translucent region, and the paper of Example 1 was obtained.

[0100] [Example 2] Using a Matsuo Sangyo micrometer-adjustable applicator, the application rate was 34 g / m². 2A transparency agent (1) was applied to the non-glossy side of the glossy kraft paper (1) to form a translucent region. Next, a halftone print was made on the glossy side of the glossy kraft paper (1) using black ink. The halftone print area ratio was 25%, the dot size was 50 μm, and the shape of each dot was circular. After the halftone print, it was dried for 30 seconds with a 120°C hot air dryer to obtain the paper of Example 2.

[0101] [Example 3] Using a Matsuo Sangyo micrometer-adjustable applicator, the application rate was 34 g / m². 2 To achieve this, a translucent area was formed by applying a transparentizing agent (1) to the non-glossy side of the glossy kraft paper (1). No halftone printing was performed, and the transparentizing agent was applied to the glossy side of the glossy kraft paper (1) at a rate of 1.5 g / m². 2 The coating liquid (1) was applied in such a manner. Then, it was cured with ultraviolet light using NPT-453 (4.8kW, 2 lamps) from Nippon Bunka Seikou Co., Ltd. to obtain the paper of Example 3.

[0102] [Example 4] Using a Matsuo Sangyo micrometer-adjustable applicator, the application rate was 34 g / m². 2 A transparency agent (1) was applied to the non-glossy side of the glossy kraft paper (1) to form a translucent area. Next, a halftone print was made on the glossy side of the glossy kraft paper (1) using black ink. The halftone print area ratio was 25%, the dot size was 50 μm, and each dot was circular in shape. After the halftone print, it was dried for 30 seconds with a 120°C hot air dryer, and then the coating amount was 1.5 g / m². 2 The coating liquid (1) was applied in such a manner, and UV curing was performed using NPT-453 (4.8kW, 2 lamps) from Nippon Bunka Seikou Co., Ltd. to form a coating layer with a thickness of 1.0 μm (smoothness 130 sec) on the glossy surface of the single-sided glossy kraft paper (1), thereby obtaining the paper of Example 4.

[0103] [Example 5] Application amount: 25g / m² 2 The paper of Example 5 was obtained in the same manner as in Example 1, except that it was applied to the non-glossy side of a single-sided glossy kraft paper.

[0104] [Comparative Example 1] Bleached packaging paper (Oji Materia product, 60g / m²) 2 The base paper was prepared as 65 g / m². 2 The smoothness of the glossy surface is 90 sec, and the smoothness of the matte surface is 8 sec. The density is 0.78 g / cm³. 3 The thickness is 78 μm and the porosity is 47.8%. Otherwise, a translucent region was formed on the bleached packaging paper using the same method as in Example 1 to obtain the paper of Comparative Example 1.

[0105] [Reference example 1] A transparent polyester resin film (Toyobo Co., Ltd. product "Cosmoshine A4160") was prepared.

[0106] [sample] The paper with translucent regions obtained in Examples 1 to 5 and Comparative Example 1, and the film from Reference Example 1 were used as samples.

[0107] "Luminous transmittance (T50)" The luminous transmittance (T50) was measured using the TLV-304-LC from Asahi Spectroscopic Co., Ltd. as the luminous transmittance meter, as shown in Figure 3.

[0108] "Luminous transmittance ratio" Using the TLV-304-LC from Asahi Spectroscopic Co., Ltd. as a luminous transmittance meter, the luminous transmittance (T50) and luminous transmittance (T0) were measured as shown in Figure 4, and the luminous transmittance ratio was calculated using the following formula.

[0109] [Haze, Opacity] The haze was measured using the "HZ-V3" (a product of Suga Test Instruments Co., Ltd.) which conforms to JIS-K7136. The opacity was measured using the "SC-WT" (a product of Suga Test Instruments Co., Ltd.) which conforms to JIS P8149.

[0110] [Evaluation of visibility in the depth direction] A printed A4-sized Word document with 10.5-point font size was placed on a horizontal surface, and each example of packaging paper was positioned 5.0 cm above it. Furthermore, the visibility of the printed text was evaluated based on the following criteria when viewed from 30 cm above the packaging paper, through the translucent area of ​​the packaging paper. A: The letters are all clearly recognizable with no missing characters. B: There are slight missing letters, but the letters are clearly recognizable. C: Some characters are missing, but the characters are recognizable. D: Multiple characters are missing, making the text difficult to read. E: Characters are missing in many places, making them extremely difficult to recognize as letters.

[0111] [result] The results are shown in Table 1.

[0112] [Table 1]

[0113] The packaging papers of Examples 1 to 5 exhibited excellent visibility in the depth direction. In contrast, the packaging paper of Comparative Example 1, which had a translucent area where neither the luminous transmittance (T50) nor the luminous transmittance ratio met the predetermined requirements, performed poorly in terms of visibility evaluation. Furthermore, the numerical trends of luminous transmittance (T50) and the luminous transmittance ratio generally coincided with the trends in visibility perceived by the human eye. [Industrial applicability]

[0114] According to one aspect of the present invention, a packaging paper is provided that provides excellent visibility even when there is space or gaps between the translucent area and the contents; and a packaging body equipped with the packaging paper is provided. According to a further aspect of the present invention, a basis weight of 30 g / m² is available, which offers excellent visibility when viewed through a translucent area. 2 The above documents will be provided. [Explanation of Symbols]

[0115] 1 (1A, 1B)...Translucent paper, 2...Base paper for translucent paper, 3...Transparency material, 4...Translucent area, 5...Coating layer, 6...Halfed printing area, 7...Light-absorbing substance, 10...Packaging, 11...Target image, 12...Visible image, F...Resin film, 100...Visual transmittance meter, 101...Light emitting part, 102...Light receiving part, S...Sample, S1...One side of the sample, S2...Other side of the sample.

Claims

1. A translucent paper having a translucent region in at least a portion of the paper, wherein the translucent region has a luminous transmittance ratio of 44 or more under the measurement condition 2 described below. "Measurement Condition 2" Using a luminous transmittance measuring instrument with a gap of at least 50 mm between the light-emitting and light-receiving parts, The translucent region of the aforementioned paper is used as a sample for measurement. The luminous transmittance (T50) measured when the sample is placed so that one side is in contact with the light source, The luminous transmittance (T0) is measured when the other side of the sample is placed in contact with the light-receiving part, and the luminous transmittance ratio is calculated using the following formula. Formula 1: Luminous transmittance ratio = (T50 / T0) × 100

2. The translucent paper according to claim 1, wherein the translucent paper has a translucent region in at least a portion of the paper, and the translucent region has a luminous transmittance (T50) of 20% or more under the measurement condition 1 below. "Measurement Condition 1" Using a luminous transmittance measuring instrument with a gap of at least 50 mm between the light-emitting and light-receiving parts, The sample used to measure the translucent region of the aforementioned translucent paper is: The luminous transmittance (T50) measured when the sample is placed with one side in contact with the light source.

3. The translucent paper according to claim 1 or 2, wherein the pulp constituting the paper has a ratio of softwood chemical pulp to hardwood chemical pulp of 80:20 to 51:

49.

4. The translucent paper according to claim 1 or 2, wherein the translucent region is impregnated with a transparency material.

5. The translucent paper according to claim 1 or 2, further comprising a halftone printed area in which a light-absorbing substance is attached to at least a portion of the translucent area.

6. A method for manufacturing translucent paper, comprising impregnating a transparent material into at least a portion of a base paper for translucent paper such that the visible transmittance ratio under the measurement condition 2 below is 44 or higher. "Measurement Condition 2" Using a luminous transmittance measuring instrument with a gap of at least 50 mm between the light-emitting and light-receiving parts, The translucent region of the aforementioned paper is used as a sample for measurement. The luminous transmittance (T50) measured when the sample is placed so that one side is in contact with the light source, The luminous transmittance (T0) is measured when the other side of the sample is placed in contact with the light-receiving part, and the luminous transmittance ratio is calculated using the following formula. Formula 1: Luminous transmittance ratio = (T50 / T0) × 100

7. A method for producing translucent paper according to claim 6, comprising impregnating a transparent material into at least a portion of the base paper for translucent paper such that the visible transmittance (T50) under the measurement condition 1 below is 20% or more. "Measurement Condition 1" Using a luminous transmittance measuring instrument with a gap of at least 50 mm between the light-emitting and light-receiving parts, The sample used to measure the translucent region of the aforementioned translucent paper is: The luminous transmittance (T50) measured when the sample is placed with one side in contact with the light source.

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