Base paper for translucent paper, translucent paper, and method for producing translucent paper

Abstract

The purpose of the present invention is to provide: a base paper used for translucent paper obtained by impregnation with a transparent resin; a translucent paper using the base paper; and a method for producing translucent paper. The raw paper for the translucent paper takes coniferous tree chemical paper pulp and broad-leaved tree chemical paper pulp as main components, the ratio of the coniferous tree chemical paper pulp to the broad-leaved tree chemical paper pulp is 75: 25-51: 49, the gram weight of the raw paper for the translucent paper is 40g / m < 2 >-100g / m < 2 >, and the air permeability of the raw paper for the translucent paper is 10-40 seconds.

Description

Technical Field

[0001] The present invention relates to a base paper for translucent paper, translucent paper, and a method for producing translucent paper. More specifically, the present invention relates to a translucent paper which can be used for packaging paper, printing paper, publication paper, information paper, etc., and in which a partial area or the entire area is translucent, a base paper for translucent paper used for the translucent paper, and a method for producing the translucent paper. Background Art

[0002] Paper packaging such as envelopes and product packages sometimes have a window that allows the recipient's name, address, and contents to be visually confirmed from the outside. A transparent resin film or cellophane is pasted on the window. From the perspective of resource reuse, the latter cellophane is preferably used.

[0003] It has long been known that cellophane is a translucent paper obtained by subjecting paper obtained by finely beating pulp and making paper to a high-pressure calendering process. Since cellophane is not strong enough when used as a packaging body such as an envelope, it is only pasted on the window portion of an envelope, and its use is limited. As a substitute for translucent paper, for example, a method of impregnating the fibers of paper with a transparent resin has been proposed (for example, Patent Documents 1 to 4). By impregnating the spaces between the cellulose fibers of the paper with a transparent resin, the transparency of the translucent area impregnated with the transparent resin can be increased. Compared with cellophane, translucent paper has superior strength, so it can also be used as a packaging body such as an envelope. Prior art literature Patent Literature Patent Document 1: Japanese Patent Application Laid-Open No. 61-132698 Patent Document 2: Japanese Patent Application Laid-Open No. 61-132699 Patent Document 3: Japanese Patent Application Publication No. 2018-9047 Patent Document 4: Japanese Patent Application Publication No. 2021-91481 Summary of the invention Technical problem to be solved by the invention

[0005] However, it has been found that sufficient quality cannot be achieved by simply impregnating with a transparent resin, and the base paper used affects the quality. The present invention provides base paper for translucent paper obtained by impregnating with a transparent resin, translucent paper using the base paper, and a method for producing translucent paper. Solutions for solving technical problems

[0006] The present invention has the following aspects. [1] A base paper for translucent paper, wherein the base paper is impregnated with a transparent material so that the impregnated area becomes translucent, characterized in that: The base paper for the semi-transparent paper is mainly composed of coniferous chemical pulp and broadleaf chemical pulp. The ratio of coniferous chemical pulp to broadleaf chemical pulp is 75:25 to 51:49. The base paper for the semi-transparent paper has a grammage of 40 g / m 2 ~100g / m 2 , The air permeability of the base paper for the translucent paper is 10 seconds to 40 seconds. [2] The base paper for translucent paper according to [1], characterized in that: The base paper for the semi-transparent paper has a grammage of 40 g / m 2 ~75g / m 2 . [3] The base paper for translucent paper according to [1] or [2], characterized in that: The Canadian standard freeness of the coniferous chemical pulp is 400mL to 700mL. The Canadian standard freeness of the hardwood chemical pulp is 350 mL to 650 mL. [4] The base paper for translucent paper according to [1] or [2], characterized in that: The Parker printing surface smoothness of at least one side of the base paper for translucent paper is 5 μm or less.

[0007] [5] A translucent paper, characterized in that: The translucent paper has a translucent region formed by impregnating a transparent material in at least a portion of a base paper for the translucent paper. The base paper for the semi-transparent paper is mainly composed of coniferous chemical pulp and broadleaf chemical pulp. The ratio of coniferous chemical pulp to broadleaf chemical pulp is 80:20 to 51:49. Weight: 40g / m 2 ~100g / m 2 , The air permeability is 10 seconds to 40 seconds. [6] The translucent paper according to [5], characterized in that: The density of the translucent area of ​​the translucent paper is 0.7 g / cm 3 ~2.5g / cm 3 . [7] The translucent paper according to [5] or [6], characterized in that: The base paper for the semi-transparent paper has a grammage of 40 g / m 2 ~75g / m 2 . [8] The translucent paper according to [5] or [6], characterized in that: The light transmittance (T50) of the semi-transparent region under the following measurement condition 1 is 20% or more, "Measurement Condition 1" A light transmittance measuring device having a distance of at least 50 mm between the light projecting part and the light receiving part is used, and the semi-transparent area of ​​the semi-transparent paper is used as a sample for measurement. The light transmittance (T50) when the sample is arranged so that one surface is in contact with the light projecting unit is measured. [9] The translucent paper according to [5] or [6], characterized in that: The light transmittance ratio of the semi-transparent region under the following measurement condition 2 is 44 or more, "Measurement Condition 2" A light transmittance measuring device having a distance of at least 50 mm between the light projecting part and the light receiving part is used, and the semi-transparent area of ​​the paper is used as a sample for measurement. The light transmittance (T50) when the sample is arranged so that one surface is in contact with the light projecting part and the light transmittance (T0) when the sample is arranged so that the other surface is in contact with the light receiving part are measured. The transmittance ratio is calculated using the following mathematical formula 1: Mathematical formula 1: Transmittance ratio = (T50 / T0)×100.

[0008]

[10] A method for manufacturing translucent paper, characterized in that: At least a portion of the base paper for semi-transparent paper is impregnated with a transparent material. The base paper for semi-transparent paper is mainly composed of coniferous chemical pulp and broadleaf chemical pulp. The ratio of coniferous chemical pulp to broadleaf chemical pulp is 80:20 to 51:49. Weight: 40g / m 2 ~100g / m 2 , The air permeability is 10 seconds to 40 seconds.

[11] The method for producing translucent paper according to

[10] , characterized in that: The weight of the semi-transparent base paper is 40 g / m 2 ~75g / m 2 .

[12] The method for producing translucent paper according to

[10] or

[11] , characterized in that: The base paper for the semi-transparent paper has a Parker printing surface smoothness of 5 μm or less on one side, and a transparent material is dip-coated on the other side.

[13] The method for producing translucent paper according to

[10] or

[11] , characterized in that: The Canadian standard freeness of the coniferous chemical pulp is 400mL to 700mL. The Canadian standard freeness of the hardwood chemical pulp is 350 mL to 650 mL. Effects of the Invention

[0009] According to the present invention, there are provided a translucent paper base paper obtained by impregnating a transparent resin to obtain a translucent paper having excellent transparency, visual confirmation and recyclability, a translucent paper obtained by impregnating a transparent resin to obtain a translucent paper having excellent transparency, visual confirmation and recyclability, and a method for producing the translucent paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a top view schematically showing an example of translucent paper. Figure 2 It is schematically indicated Figure 1 Figure 2. Diagram of section II of the translucent paper. Figure 3 It is schematically indicated Figure 1 FIG. 2 is a diagram of section II of another method of translucentizing paper. Figure 4 This is an explanatory diagram schematically showing that a transparent resin film has excellent visibility. Figure 5 This is an explanatory diagram schematically showing that the visual recognition of conventional translucent paper and the like is insufficient. Figure 6 This is an explanatory diagram schematically showing an example of a method for measuring light transmittance. Figure 7 It is an explanatory diagram schematically showing an example of a method for measuring a light transmittance ratio. DETAILED DESCRIPTION

[0011] (Base paper for translucent paper) The base paper for semi-transparent paper of the present invention is impregnated with a transparent material so that the area after the impregnation is semi-transparent. The impregnation of the transparent material can be performed on the entire area of ​​the base paper for semi-transparent paper when viewed from above, or on a local area. The shape and number of the area are not particularly limited. In the area impregnated with the transparent material, since the transparent material penetrates along the thickness direction of the base paper for semi-transparent paper, the gaps inside the paper are filled with the transparent material as much as possible, so that the paper becomes semi-transparent. Furthermore, the term "translucent" means that the opacity of the paper after treatment is lower than that of the paper before treatment, and is not particularly limited, but "translucent" means that the opacity of the treated area is 4% to 25%.

[0012] Base paper for translucent paper is paper mainly composed of coniferous chemical pulp and broadleaf chemical pulp. Examples of coniferous chemical pulp include coniferous unbleached kraft pulp (NUKP), coniferous bleached kraft pulp (NBKP), coniferous semi-bleached kraft pulp (NSBKP), coniferous unbleached sulfite pulp (NUSP), coniferous bleached sulfite pulp (NBSP), and coniferous semi-bleached sulfite pulp (NSBSP). Examples of the broadleaf chemical pulp include broadleaf unbleached kraft pulp (LUKP), broadleaf bleached kraft pulp (LBKP), broadleaf semi-bleached kraft pulp (LBKP), broadleaf unbleached sulfite pulp (LUSP), broadleaf bleached sulfite pulp (LBSP), and broadleaf semi-bleached sulfite pulp (LBSP). Among them, a combination of coniferous tree bleached kraft pulp (NBKP) and broadleaved tree bleached kraft pulp (LBKP) is preferred.

[0013] In the base paper for translucent paper of the present invention, the addition ratio of coniferous chemical pulp to broadleaf chemical pulp is 80:20 to 51:49. The preferred addition ratio is 75:25 to 55:45, and the more preferred addition ratio is 70:30 to 60:40. By specifying the ratio of coniferous chemical pulp to broadleaf chemical pulp, a translucent paper having a balance between transparency and recyclability can be obtained.

[0014] Coniferous chemical pulp has a longer and thicker fiber structure than broadleaf chemical pulp, so if a large amount of coniferous chemical pulp is added, it will become a base paper with a higher porosity, which can effectively impregnate the transparent material. On the other hand, broadleaf chemical pulp has a thin and short fiber structure, so the texture of the paper is good. Therefore, by setting the above addition ratio, the porosity of the base paper and the texture of the paper can be taken into account. In addition, broadleaf chemical pulp has a thin and short fiber structure, so it is easy to be coated with the resin contained in the transparent material. Therefore, considering the ease of defibration when recycling as waste paper, it is preferred to adjust the addition amount of broadleaf chemical pulp.

[0015] The Canadian standard freeness of the coniferous chemical pulp is preferably 400 mL to 700 mL. The Canadian standard freeness is more preferably 420 mL CSF to 650 mL CSF, and further preferably 450 mL CSF to 600 mL CSF. When the Canadian standard freeness is above the lower limit of the above numerical range, the voids of the base paper for translucent paper can be maintained, so the impregnation of the transparent material is excellent. When the Canadian standard freeness is below the upper limit of the above numerical range, the texture of the base paper for translucent paper can be improved, and it is easy to obtain a translucent paper having a translucent area with excellent transparency and visual confirmation.

[0016] The Canadian standard freeness of the hardwood chemical pulp is preferably 350 mL to 650 mL. The Canadian standard freeness is more preferably 370 mL CSF to 630 mL CSF, and further preferably 400 mL CSF to 600 mL CSF. When the Canadian standard freeness is above the lower limit of the above numerical range, the strength of the base paper for translucent paper can be improved. When the Canadian standard freeness is below the upper limit of the above numerical range, the texture of the base paper for translucent paper can be improved, and it is easy to obtain a translucent paper having a translucent area with excellent transparency and visual confirmation.

[0017] In addition, when the Canadian standard freeness of coniferous chemical pulp is higher than that of hardwood chemical pulp, the strength and transparency of the paper are excellent, so it is preferred. In addition, the Canadian standard freeness of pulp is measured in accordance with JIS P8121-2: 2012. In addition, in glass paper, which has been known as translucent paper, chemical pulp with increased beating degree, for example, chemical pulp with a Canadian standard freeness of 250 mL CSF or less is used. However, since the pulp fibers with increased beating degree have been ground or cut, even if it can be used for transparent windows of envelopes, it is difficult to apply it to applications such as packaging bags that require strength.

[0018] Pulps other than coniferous chemical pulp and broadleaved chemical pulp may be used in combination as long as the effects of the present invention are not impaired, such as mechanical pulp, thermomechanical pulp, deinked pulp, non-wood pulp, synthetic pulp, and the like.

[0019] The base paper weight for translucent paper is 40g / m 2 ~100g / m 2 The preferred weight is 40g / m 2 ~80g / m 2 , and preferably 40g / m 2 ~75g / m 2 , and preferably 43g / m 2 ~70g / m 2 , more preferably 45g / m2 ~65g / m 2 . When the gram weight is above the lower limit of the above numerical range, the strength of the paper can be obtained, and the paper can be made into a translucent paper suitable for use as packaging paper, printing paper, etc. When the gram weight is below the upper limit of the above numerical range, the transparency of the translucent paper can be improved. The gram weight is measured according to JIS P8124.

[0020] In the present invention, the air permeability of the base paper for translucent paper is 10 seconds to 40 seconds. The air permeability is preferably 12 seconds to 35 seconds, and more preferably 15 seconds to 33 seconds. When the air permeability is above the lower limit of the above numerical range, the strength of the paper can be obtained, and the paper becomes a translucent paper suitable for use as packaging paper, printing paper, etc. When the air permeability is below the upper limit of the above numerical range, the permeability of the transparent material is excellent, and the transparency of the translucent paper can be improved. The air permeability is measured according to the Wang Yan type air permeability measured based on J.TAPPI-5:2000.

[0021] The density of the base paper for translucent paper is preferably 0.5 g / cm 3 ~0.85g / cm 3 , more preferably 0.6 g / cm 3 ~0.8g / cm 3 When the density is above the lower limit of the above numerical range, the strength of the paper can be obtained, and the paper can be made into a translucent paper suitable for use as packaging paper, printing paper, etc. When the density is below the upper limit of the above numerical range, the permeability of the transparent material is excellent, and the transparency of the translucent paper can be improved. The density is measured in accordance with JIS P8118.

[0022] The porosity of the base paper for translucent paper is preferably 30% to 80%, more preferably 40% to 70%, and further preferably 50% to 70%. When the porosity of the base paper for translucent paper is above the lower limit of the above numerical range, it is easy to improve the transparency of the translucent area. When 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 difficult to decrease. The porosity of the paper substrate is calculated based on the value obtained by dividing the density measured in accordance with JIS P8118 by the true density of cellulose 1.50.

[0023] The Parker printing surface smoothness of at least one side of the base paper for translucent paper is preferably 7 μm or less, more preferably 5 μm or less. The lower limit is not particularly limited. It can be said that the smaller the value, the smoother it is. The Parker printing surface smoothness can evaluate the smoothness of fine parts. The smaller the value, the less scattering of light on the paper surface can be achieved, thereby improving the visual confirmation of the translucent part. The Parker printing surface smoothness is the Parker printing surface smoothness calculated based on ISO8791-4:1992 (soft backing / clamping pressure 500 kPa).

[0024] In addition to pulp, known papermaking auxiliaries such as paper strength enhancers, sizing agents, fillers, and colorants may be appropriately added to the base paper for translucent paper. In addition, since the addition of fillers plays a role in improving the concealing property of paper, it is preferably added within a range that does not impair transparency and visual confirmation, and it is more preferable that no filler is added to the base paper for translucent paper.

[0025] The method for producing the base paper for translucent paper is not particularly limited. For example, there is a method including the steps of beating pulp as a raw material for the base paper for translucent paper, making paper from a pulp slurry containing the beaten pulp, and drying the wet sheet obtained by papermaking.

[0026] In the beating step, the raw material pulp is preferably beaten to achieve the above-mentioned Canadian standard freeness. The beating machine is not particularly limited. For example, a well-known beating machine such as a double disc refiner is exemplified. The papermaking machine used for papermaking is not particularly limited, and examples thereof include a Fourdrinier papermaking machine, a short-wire papermaking machine, and a cylinder papermaking machine. The drying process is not particularly limited, and for example, a drying machine attached to a papermaking machine may be used.

[0027] The base paper for translucent paper can also be subjected to a smoothing treatment. By implementing a smoothing treatment, the scattering of light on the surface of the paper can be reduced, thereby improving the visual confirmation of the translucent part. As a smoothing treatment, for example, tightness pressing, mechanical calendering, gloss calendering, soft calendering, super calendering, etc. can be exemplified, but since these devices increase the density of the paper, it is necessary to pay attention to reducing the line pressure so that the density does not become too high. On the other hand, the transfer method in which the paper is pasted on a smooth surface when it is wet and the smooth surface is removed by drying is preferred because it does not increase the density of the paper. For example, technologies such as Yankee cylinder, casting drum, and film transfer can be used. Among them, the Yankee dryer using a Yankee cylinder is preferred because it is attached to a papermaking machine and has excellent productivity.

[0028] (Translucent paper) The translucent paper of the present invention is a paper obtained by impregnating the above-mentioned base paper for translucent paper with a transparentizing material so that the impregnated area becomes translucent. Figure 1 , Figure 2 The translucent paper 1A exemplified in FIG. 1 includes a base paper 2 for translucent paper and a translucent region 4 in which a transparent material 3 is impregnated in the base paper 2 for translucent paper. Figure 1 , Figure 3 The translucent paper 1B exemplified in the figure has: a base paper 2 for translucent paper, a translucent region 4 obtained by impregnating the base paper 2 for translucent paper with a transparent material 3, and a coating layer 5 covering the translucent region 4. Figure 1 As shown, the translucent region 4 is formed in a local region when viewed from above of the translucent paper base paper 2. For example, when the translucent paper 1A is used as a package, the contents can be seen from the outside of the package through the translucent region 4, or through the translucent region 4 and the coating layer 5.

[0029] The transparent material is not particularly limited as long as it is a material that can be impregnated into the base paper for semi-transparent paper to make the impregnated part semi-transparent. For example, the transparent material includes resins such as acrylic resin, polyethylene resin, polyester resin, polyurethane resin, nitrocellulose, shellac, rosin, etc.; vegetable oils such as tung oil, linseed oil, castor oil, hydrophilic castor oil, coconut oil, soybean oil, and commercial salad oil; wax oils and waxes such as carnauba wax, palm wax, beeswax, spermaceti, and wood wax. The transparent material can be used alone or in combination of two or more.

[0030] Among them, a resin that is stable over time is preferred, and an acrylic resin is more preferred. Among acrylic resins, ultraviolet-curable acrylic resins are particularly excellent in surface coverage, and the interface of the area impregnated with the transparent material becomes clear when viewed in section, so they are preferred. For example, as ultraviolet-curable acrylic resins, there are acrylic resins disclosed in paragraphs 0025 and 0026 of Japanese Patent Publication No. 2021-91481.

[0031] As the transparent material, it is preferred to select a material having a refractive index in the range of 1.4 to 1.6, preferably 1.45 to 1.58, more preferably 1.50 to 1.58, and further preferably 1.52 to 1.58 from the materials exemplified above. The reason is that the refractive index of cellulose fiber is usually in the range of 1.4 to 1.6. If the refractive index of the transparent material is in the above numerical range, the difference with the refractive index of cellulose fiber is small, and it is easy to improve the transparency and visual confirmation of the semi-transparent area. The refractive index of the transparent material is measured in accordance with JIS K7142.

[0032] By impregnating the base paper for translucent paper with a transparent material having a refractive index close to that of the cellulose fibers to fill the gaps between the cellulose fibers inside the paper, the refraction of light caused by the transparent material in the base paper for translucent paper can be reduced. Thus, it is easy to obtain a translucent area with excellent transparency and visual confirmation. In order to adjust the refractive index, high refractive index materials such as zirconium and titanium can be used as needed.

[0033] Since the base paper for translucent paper is impregnated with the transparent material, it is preferably a material that is liquid at room temperature or in a heated state. In addition, from the perspective of permeability, it is also preferred that the transparent material can be dissolved in a liquid medium such as an organic solvent at room temperature or in a heated state. That is, the transparent material is preferably a material that can be impregnated in the base paper for translucent paper as a liquid transparentizing agent having permeability during production.

[0034] In order to reduce the diffuse reflection of light caused by the surface unevenness of the semi-transparent area of ​​the semi-transparent paper, a coating can be provided on at least a portion of the surface of the semi-transparent area. Utilizing this coating, the smoothness of the surface of the semi-transparent area can be improved, the diffuse reflection of light on the surface of the semi-transparent area can be prevented, and the visual confirmation of the semi-transparent area can be improved. As the material of the coating, for example, transparent materials and OP varnish are listed. As transparent materials, the same materials as those exemplified in the item of the semi-transparent area are listed. When the coating contains a transparent material, the transparent material of the coating and the transparent material of the semi-transparent area can be the same as each other, or they can be different types. In addition, the material of the coating can be used alone, or two or more can be used in combination.

[0035] OP varnish is sometimes referred to as overprint varnish. The ingredients of OP varnish vary depending on the product, manufacturer, etc., and preferably contain at least one OP varnish selected from the group consisting of linseed oil, tung oil, and nitrocellulose. Commercially available products of OP varnish include, for example, products of Toyo Ink Co., Ltd., T&K TOKA Co., Ltd., and Fuji Ink Manufacturing Co., Ltd. OP varnishes may be used alone or in combination of two or more. The drying method may be a drying method based on oxidative polymerization, a drying method based on UV effect, or the like.

[0036] As the material of the coating, it is preferred to select a material having a refractive index in the range of 1.4 to 1.6, preferably 1.45 to 1.60, more preferably 1.48 to 1.60, further preferably 1.50 to 1.60, and particularly preferably 1.50 to 1.58 from these materials. The reason is that the refractive index of cellulose fiber is usually in the range of 1.4 to 1.6. By setting the refractive index of the coating to a value close to the refractive index of cellulose fiber, the refraction of light at the interface between the coating and the base paper for translucent paper can be reduced. Thus, it is easy to obtain a translucent area with excellent visual confirmation. The refractive index of the coating is measured in accordance with JIS K7142.

[0037] The opacity of the semi-transparent region is preferably 4% to 25%, more preferably 4% to 20%, and even more preferably 4% to 15%. The opacity of the semi-transparent region is measured in accordance with JIS P8138: 1976. The smaller the opacity value, the more transparent it is.

[0038] The haze of the semi-transparent region is preferably 80% or less. When the haze of the semi-transparent region is 80% or less, the transparency of the semi-transparent region is improved. The lower limit of the haze of the semi-transparent region is not particularly limited, and is, for example, 10% or more, preferably 20% or more. The haze of the semi-transparent region is measured in accordance with JIS-K7136. The smaller the haze value, the smaller the blur.

[0039] To date, haze and opacity have been used to evaluate the visual recognition of a semi-transparent area. However, according to the research of the present inventors, the numerical trends of haze and opacity are often inconsistent with the quality of visual recognition by human eyes. For example, when the whiteness of a sample is high, the transmittance of visible light becomes high, but the visual recognition and visual surface feeling are not necessarily excellent.

[0040] The reason why the numerical tendency of the haze and the quality of the visual recognition are considered to be inconsistent is as follows. Haze is calculated as the ratio of diffuse transmittance to the total transmittance of light passing through the sample. Diffuse transmittance is the transmittance of diffuse light after removing the parallel component of light that passes through the sample when straight light is incident on the sample. Figure 4 , Figure 5 As shown, the human eye tends to preferentially recognize light that travels in a straight line or light with a narrow diffusion angle, compared to diffused light or scattered light with a wide diffusion angle. Thus, in the calculation of haze, the parallel component light that is easily recognized by the human eye is removed from the measurement object, and the diffuse light that is difficult for the human eye to recognize is included in the measurement object to obtain the diffuse transmittance. Since haze is calculated based on the diffuse transmittance, it is not suitable for evaluating the visual perception of the human eye or the quality of visual recognition in the depth direction. Similarly, opacity is obtained by including diffuse light that is difficult for human eyes to recognize in the measurement object, and therefore is not suitable for evaluation of human visual perception of surface and evaluation of visual recognition in the depth direction.

[0041] As a result of the inventor's in-depth research, he came up with the idea of ​​evaluating the visual confirmation of a semi-transparent area based on the degree of blur of the contents seen through the semi-transparent area. The degree of blur depends on the diffusion pattern of the light passing through the semi-transparent area. In the case of a semi-transparent area with a large degree of blur, the diffused light with a wide diffusion angle is relatively more included in the transmitted light, so the visual confirmation of the contents is reduced. In contrast, in the case of a semi-transparent area with a small degree of blur, the light that travels straight and the light with a narrow diffusion angle are relatively more included in the transmitted light, so the visual confirmation of the contents is good. The present inventors devised a method and an index for quantitatively evaluating the blur degree, and found that when the blur degree index is equal to or greater than a specific value, the visibility of the content visually recognized through the semi-transparent region is excellent. The indicators are light transmittance and light transmittance ratio.

[0042] "Determination of light transmittance" In the measurement of transmittance, a transmittance meter is used. The transmittance meter has a light-projecting part that projects light from a light source onto a sample, a light-receiving part that receives light that has passed through the sample, and a sensor that measures the received light. The distance between the light-projecting part and the light-receiving part is greater than 50 mm. Furthermore, when the measurement is performed without a sample, the light-receiving sensitivity characteristics are roughly consistent with the standard spectral luminous efficiency of bright vision. Transmittance measuring instruments are widely available in the market for measuring spectacle lenses, filter glasses, transparent conductive film glasses, etc., and can be measured using an instrument that meets the above measurement conditions. In addition, any instrument that meets the above measurement conditions, such as a spectrophotometer, can be used as a transmittance measuring instrument.

[0043] "Light transmittance (T50)" In the present invention, the light transmittance (T50) under the following measurement condition 1 is preferably 20% or more. "Measurement Condition 1" The light transmittance is measured by using a light transmittance measuring device having a distance of at least 50 mm between the light projecting part and the light receiving part, and placing the semi-transparent area of ​​the paper as a sample to be measured so that one surface of the sample contacts the light projecting part.

[0044] Figure 6: is an explanatory diagram for explaining the measurement. By configuring so that one side S1 of the sample S is in contact with the light-projecting part 101 of the light-transmittance measuring device 100, the light transmittance (T50) can be measured. In the present invention, TLV-304-LC of Asahi Spectroscopy Co., Ltd., which is commercially available as a light transmittance measuring device, is used. The distance between the light-projecting part and the light-receiving part of the device is 51.5 mm. By setting the light transmittance (T50) at least 50 mm apart to 20% or more, a paper having a transparent area with excellent visual confirmation is obtained. The larger the value, the better the visual confirmation, preferably 23% or more. The transmittance (T50) is not measured immediately from the sample, but is measured at a distance of 50 mm, so the light that is scattered within 50 mm and does not reach the light receiving part is eliminated, which is consistent with visual confirmation. Since light is not scattered in the air, the cause of scattering depends on the internal and surface conditions of the sample.

[0045] "Transmittance ratio" In the present invention, it is preferred to have a semi-transparent region having a light transmittance ratio of 44 or more under the following measurement condition 2. "Measurement Condition 2" A transmittance measuring device having a spacing of at least 50 mm between the light-emitting part and the light-receiving part is used, and the semi-transparent area of ​​the paper is used as a sample for measurement. The transmittance (T50) when the sample is configured and measured in a manner that one side is in contact with the light-emitting part, and the transmittance (T0) when the sample is configured and measured in a manner that the other side is in contact with the light-receiving part are measured, are measured, and the transmittance ratio is calculated using the following mathematical formula. Mathematical formula 1: Transmittance ratio = (T50 / T0) × 100

[0046] Figure 7 (a) and (b) are explanatory diagrams for explaining the measurement. like Figure 7 As shown in (a) of FIG. 1 , by arranging the sample S so that one surface S1 is in contact with the light projecting unit 101 of the light transmittance measuring device 100 , the light transmittance ( T50 ) can be measured. like Figure 7 As shown in (b) of FIG. 1 , by arranging the other surface S2 of the sample S to be in contact with the light receiving unit 102 , the light transmittance ( T0 ) can be measured. When measuring the light transmittance (T0), the sample may be pressed with a ring-shaped jig or the like so as to prevent the sample from being bent due to its own weight. In the present invention, TLV-304-LC of Asahi Spectroscopy Co., Ltd., which is commercially available as a transmittance meter, is used. The distance between the light-emitting part and the light-receiving part of the device is 51.5 mm. According to the transmittance (T50) and the transmittance (T0) of two points at least 50 mm apart, the transmittance ratio = (T50 / T0) × 100 is calculated. As long as the value is 44 or more, the paper becomes a transparent area with excellent visual confirmation. The larger the value, the better the visual confirmation, preferably 48 or more, more preferably 50 or more. The transmittance ratio indicates how much the light emitted from the sample (T0) is reduced compared to (T50) measured at a distance of 50 mm. Since (T50) removes the light that is scattered within 50 mm and does not reach the light receiving part, it is consistent with visual confirmation. Since light is not scattered in the air, the cause of scattering depends on the internal and surface conditions of the sample.

[0047] Furthermore, it is more preferable to satisfy both the above-mentioned light transmittance (T50) and light transmittance ratio.

[0048] In order to make the above-mentioned transmittance (T50) of the transparent area above 20% and the above-mentioned transmittance ratio above 44, the refraction and scattering of light on the surface of the paper where the light is incident, the interior of the paper after the light is incident, and the surface of the paper that transmits the light can be controlled.

[0049] The density of the translucent area of ​​the translucent paper is preferably 0.7 g / cm 3 ~2.5g / cm 3 , more preferably 0.7 g / cm 3 ~2.0g / cm 3 , more preferably 0.8 g / cm 3 ~2.0g / cm 3 When the density of the translucent region is above the lower limit of the above numerical range, it is considered that the air layer between the cellulose fibers is fully eliminated by the impregnation of the resin component. When the density of the translucent region is below the upper limit of the above numerical range, the processability of the translucent paper when it is made into a packaging body is improved. The density of the translucent region is measured in accordance with JIS P8118.

[0050] The translucent paper of the present invention can be recycled without distinction. Usually, for paper recycling, the collected waste paper is dissociated at a paper / pulp concentration of about 1% using a large-scale defibrator called a pulper, and the undispersed matter is removed using a coarse fiber machine of about 9 mmφ, and then further dispersed, and fine undispersed matter is removed by a cleaner and a screen of about 1.6 mmφ. In the case of excessive resin, the dissociation and dispersibility become poor, and sometimes these screens are blocked, or the undispersed matter generates dust in the papermaking process and is brought into the paper, causing dust spots. Therefore, it is necessary that there are no undispersed matter such as fragments after re-dissociation. In the translucent paper of the present invention, since the base paper for the translucent paper with controlled pulp addition has a moderate porosity, it is possible to take into account both the improvement of transparency based on the transparent material and the suppression of the reduction of recycling adaptability based on the impregnation of the transparent material.

[0051] (Method for producing translucent paper) The method for producing translucent paper of the present invention is characterized in that the paper comprises coniferous chemical pulp and broadleaf chemical pulp as main components, the ratio of coniferous chemical pulp to broadleaf chemical pulp is 80:20 to 51:49, and the grammage is 40 g / m 2 ~100g / m 2 , at least a portion of the base paper for semi-transparent paper having an air permeability of 10 seconds to 40 seconds is impregnated with a transparentizing material.

[0052] As for the base paper for semi-transparent paper, as described above, a base paper containing a large amount of coniferous chemical pulp and having a specific weight and air permeability is used to form a large number of voids inside the paper, and the transparency can be improved by impregnating the voids with a transparent material. The impregnation of the transparent material can be performed by dip coating.

[0053] The impregnation of the transparent material is carried out by impregnating the base paper for translucent paper with the liquid transparent material. The impregnation and coating can be carried out on any side of the base paper for translucent paper. In the case where the Parker printing surface smoothness of one side of the base paper for translucent paper is less than 5μm, if the transparent material is impregnated and coated on the other side, it will penetrate effectively, so it is preferred. In the case where the Parker printing surface smoothness of both the front and back sides is less than 5μm, the impregnation and coating can be carried out on the side with the larger value. Since the smoothness of the side with a smaller value of the Parker printing surface smoothness is higher, the density of the cellulose fibers is higher as it is closer to the surface. Thus, the impregnation of the transparent material is carried out by impregnation and coating on the side with a smaller cellulose density. On the other hand, since the Parker printing surface smoothness is smooth with a value of less than 5μm, it is possible to suppress the light scattering on the paper surface, so the visual confirmation is excellent, so it is preferred.

[0054] When the transparent material is solid at room temperature, a liquid medium capable of dissolving the transparent material is used to prepare the dip coating solution. When the transparent material is liquid at room temperature, the liquid medium can be used to change the concentration of the transparent material, or the transparent material can be used directly as the dip coating solution without using a liquid medium.

[0055] The liquid medium is not particularly limited. Both aqueous solvents and organic solvents can be used. If the liquid medium contains water, the base paper for translucent paper is easily swollen by the water. In addition, during subsequent drying, the base paper for translucent paper is easily shrunk. Therefore, curling, voids, and unevenness are easily generated. Therefore, the liquid medium is preferably free of water, and an organic solvent is more preferred.

[0056] The organic solvent can be either a polar solvent or a non-polar solvent. Examples of the polar solvent include alcohols, ethers, esters, and nonpolar solvents. Examples of the alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, n-pentanol, and n-hexanol. Examples of the 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 monoisobutyl ether, Tert-butyl ether, diethylene glycol mono-tert-butyl ether, triethylene glycol mono-tert-butyl ether, tetraethylene glycol mono-tert-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, dipropylene glycol monoisobutyl ether, tripropylene glycol monoisobutyl ether, propylene glycol mono-tert-butyl ether, dipropylene glycol mono-tert-butyl ether, tripropylene glycol mono-tert-butyl ether and other glycol ethers. Examples of the esters include diethylene glycol monoethyl acetate and diethylene glycol monobutyl acetate. Examples of the non-polar solvent include paraffin hydrocarbons such as pentane, hexane, heptane, octane, nonane, decane, and dodecane; isoparaffin hydrocarbons such as isohexane, isooctane, and isododecane; alkylcycloparaffin hydrocarbons such as liquid paraffin; aromatic hydrocarbons such as benzene, toluene, xylene, alkylbenzenes, and solvent naphtha; silicone oil, and the like.

[0057] The dip coating liquid may further contain other components besides the transparent material and the liquid medium. Examples of other components include alkaline substances such as ammonia, ethylenediamine, and triethylamine; viscosity modifiers such as glycerol and ethylene glycol; high refractive index substances such as zirconium and titanium; defoamers; mold release agents; and colorants. However, other components are not limited to these examples.

[0058] During the dip coating, a local portion of the surface opposite to the dip-coated surface where the transparentizing material does not reach may be formed in the cross section of the base paper for translucent paper. The reason for this is that in this portion, the surface state of the surface with relatively high smoothness can be maintained in the state before the dip coating of the transparentizing material. During the immersion coating, the transparent material can be impregnated from both sides of the base paper for semi-transparent paper. The reason is to fully impregnate the transparent material inside the paper and reduce the voids where the transparent material is not impregnated.

[0059] The coating amount per unit area of ​​the dip coating liquid is preferably 10 g / m 2 ~70g / m 2 , more preferably 20g / m 2 ~60g / m 2 , more preferably 30g / m 2 ~60g / m 2 When the coating amount per unit area of ​​the immersion coating liquid is greater than the lower limit of the above numerical range, the transparency of the semi-transparent region can be easily improved. When the coating amount per unit area of ​​the immersion coating liquid is less than the upper limit of the above numerical range, the recycling adaptability can be improved.

[0060] The viscosity of the immersion coating liquid is preferably 50Pa·s to 5000mPa·s, more preferably 50Pa·s to 4000mPa·s, and further preferably 50Pa·s to 3000mPa·s. When the viscosity is below the upper limit of the above numerical range, the immersion coating liquid is impregnated into the inside of the paper, and the transparency of the translucent area is easily improved. When the viscosity is above the lower limit of the above numerical range, the boundary between the translucent area and the non-translucent area is clear. The viscosity is measured using a Blookfield type viscometer at 30°C and 60rpm.

[0061] The coating method of the dipping coating liquid is not particularly limited. Examples of the coating method of the transparentizing agent include flexographic printing, inkjet printing, gravure printing, offset printing, gravure offset printing, screen printing, roller coating, bar coating, and blade coating.

[0062] By impregnating the base paper for translucent paper with an impregnation coating liquid containing a transparent material, the spaces between cellulose fibers in the translucent paper can be filled with the transparent material. When an impregnation coating liquid containing a transparent material having a refractive index in the range of 1.4 to 1.6 is used, the spaces in the translucent paper can be filled with a transparent material having a refractive index close to that of cellulose. Therefore, the refraction of light caused by the spaces in the translucent paper can be reduced.

[0063] The dip coating of the base paper for translucent paper with the dip coating liquid may be performed once or in multiple times. When the dip coating is performed in multiple times, the constituent components and compositions of the transparentizing materials used in each of the multiple times may be the same or different.

[0064] When using an ultraviolet curing transparent agent, various light sources such as a high pressure mercury lamp, a metal halide lamp, a xenon lamp, and an electrodeless discharge lamp can be used. The accumulated light quantity is not particularly limited and can be appropriately changed according to the amount of transparent agent used and the type of transparent resin.

[0065] (Translucent Area) The semi-transparent area is formed in a local area of ​​the semi-transparent paper when viewed from above. When the semi-transparent paper is used as a package, the contents and the name of the letter can be seen from the outside of the package through the semi-transparent area. The shape and area ratio of the semi-transparent area when viewed from above are not limited in any way. They can be appropriately set or changed according to the purpose of the packaging paper, the packaging body, or the printing paper. In addition, in other examples, the semi-transparent area can also be the entire area of ​​the semi-transparent paper in the direction of viewing from above. In addition, the number of semi-transparent areas is not particularly limited, and can be one or more. In the case of a semi-transparent paper with multiple semi-transparent areas, the size and shape of each semi-transparent area are not particularly limited.

[0066] (use) The paper according to the present invention has a grammage of 40 g / m 2 The above-mentioned paper can obtain unprecedented transparency and visual confirmation, so it can be used not only for packaging paper, but also for various purposes such as printing paper, book paper, copy paper, information paper, label paper, etc., for visually confirming the image (text, symbols, images, objects, etc.) on the other side of the paper through the paper substrate. [Example]

[0067] Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the following description.

[0068] (Chemical Pulp Preparation) NBKP1: bleached kraft pulp with Canadian standard freeness of 550mL from coniferous trees NBKP2: bleached kraft pulp with Canadian standard freeness of 350 mL LBKP1: Hardwood bleached kraft pulp with Canadian standard freeness of 500mL LBKP2: Hardwood bleached kraft pulp with Canadian standard freeness of 300 mL

[0069] (Manufacturing equipment) M1: Produced using a Fourdrinier paper machine with a Yankee dryer. M2: Produced using a Fourdrinier paper machine with a multi-drum dryer. M3: Paper is made using a Fourdrinier paper machine equipped with a multi-drum dryer and then subjected to super calendering.

[0070] (Manufacture of base paper for translucent paper) The base paper for translucent paper was manufactured by adding chemical pulp and combining the manufacturing apparatus shown in Tables 1 and 2. The measured values ​​of the basis weight, Wangyan air permeability (air permeability) and Parker printing surface smoothness (smoothness) of the obtained base paper for translucent paper are also recorded.

[0071] [Table 1] Production Example 1 Production Example 2 Production Example 3 Production Example 4 Production Example 5 Production Example 6 NBKP1 60 servings 60 servings 60 servings 45 servings 70 servings 20 servings NBKP2 0 copies 0 copies 0 copies 0 copies 0 copies 0 copies LBKP1 40 servings 40 servings 40 servings 55 servings 30 servings 80 servings LBKP2 0 copies 0 copies 0 copies 0 copies 0 copies 0 copies Manufacturing equipment M1 Use M1 Use M1 Use M1 Use M1 Use M1 Use Weight(g / m2) 50.3 60.6 70.4 80.2 50.5 50.4 Air permeability (seconds) 20 23 26 50 18 46 Smoothness(μm) 2.70 2.82 3.01 3.18 2.85 2.34

[0072] [Table 2] Production Example 7 Production Example 8 Production Example 9 Production Example 10 Production Example 11 NBKP1 40 servings 60 servings 60 servings 60 servings 0 copies NBKP2 0 copies 0 copies 0 copies 0 copies 55 servings LBKP1 60 servings 40 servings 40 servings 0 copies 45 servings LBKP2 0 copies 0 copies 0 copies 40 servings 0 copies Manufacturing equipment M1 Use M2 Use M3 Use M1 Use M1 Use <![CDATA[Grammage (g / m 2 )]]> 50.8 69.8 69.8 50.4 50.7 Air permeability (seconds) 25 17 60 24 35 Smoothness(μm) 2.66 8.18 1.94 2.34 2.15

[0073] (Preparation of Dip Coating Solution) Dip coating liquid 1: As a transparent material, an acrylic paraffin solvent (trade name: CLARITEN DC, manufactured by Yamato Chemical Industry Co., Ltd.) was prepared. The refractive index of this transparent material was 1.50. The refractive index was measured using an Abbe refractometer manufactured by ATAGO Co., Ltd. An aromatic paraffin solvent (trade name: CLARITEN S, manufactured by Yamato Chemical Industry Co., Ltd.) was prepared as a solvent, and the transparentizing materials were mixed with the solvent to prepare a dip coating solution having a transparentizing material concentration of 75% by mass. The viscosity of the dip coating solution at 30° C. and 60 rpm was 1800 mPa·s.

[0074] Dip coating solution 2: 40% shellac (manufactured by Koyo Chemical Co., Ltd.) was diluted with anhydrous ethanol from Jianrong Pharmaceutical to prepare an alcohol dilution of shellac having a solid content of 25.0% by mass. The refractive index is 1.46. The refractive index is measured using an Abbe refractometer from ATAGO Co., Ltd. Navy 2G gran solution (blue) of Sumifix HF manufactured by Sumika Chemtex Co., Ltd. was added dropwise to a total mass of 0.2% by mass, and the mixture was dispersed using a rotation / revolution mixer degassing Rentaro ARE310 manufactured by Thinky Co., Ltd. to prepare a dip coating solution. The viscosity of the dip coating solution at 30°C and 60 rpm was 1200 mPa·s.

[0075] (Manufacture of translucent paper) Examples 1 to 7 and Comparative Examples 1 to 4 The surface of the base paper for translucent paper obtained in Manufacturing Examples 1 to 11 opposite to the surface with higher smoothness was coated and impregnated with the impregnation coating liquid 1 using a micrometer-adjustable applicator manufactured by Matsuo Sangyo Co., Ltd., and dried at 100° C. for 5 minutes using a hot air circulation dryer manufactured by Heatech Co., Ltd. The base paper for translucent paper, the type of the impregnation coating liquid, and the impregnation amount are shown in Tables 3 and 4.

[0076] Example 8 The surface of the base paper for semi-transparent paper obtained in Production Example 1 opposite to the surface with a higher smoothness was dip-coated with the dip coating solution 2 using an engraved roll (100 / 18 specification) of Hand K Rocks manufactured by ROLAN Co., Ltd. Specifically, a rubber roll transfer method was used so that the amount of shellac was 18 g / m 2 The immersion coating liquid 2 is repeatedly applied in a manner of , and dried at room temperature to obtain a translucent paper.

[0077] (evaluate) The translucent papers obtained in Examples 1 to 8 and Comparative Examples 1 to 4 and a transparent polyester resin film ("COSMOSHINEA 4160" manufactured by Toyobo Co., Ltd.) as Reference Example 1 were prepared. The evaluation results are shown in Tables 3 and 4.

[0078] "Light transmittance (T50)" As a light transmittance measuring instrument, TLV-304-LC manufactured by Asahi Spectroscopy Corporation was used. Figure 6 The light transmittance (T50) was measured as shown.

[0079] "Transmittance ratio" As a transmittance measuring instrument, TLV-304-LC manufactured by Asahi Spectroscopy Corporation was used. Figure 7As shown, the light transmittance (T50) and the light transmittance (T0) were measured, and the light transmittance ratio was calculated using the following mathematical formula. Mathematical formula 1: Transmittance ratio = (T50 / T0) × 100

[0080] [Haze, Opacity] The haze was measured using "HZ-V3" (manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS-K7136. The opacity was measured using "SC-WT" (manufactured by Suga Test Instruments Co., Ltd.) in accordance with JISP8149.

[0081] [Evaluation of visual confirmation in the depth direction] An A4-size printed material with 10.5-point text was placed on a horizontal table, and each example of packaging paper was placed 5.0 cm above it. Furthermore, the visual recognition of the text of the printed material when viewed through the semi-transparent area of ​​the packaging paper from 30 cm above the packaging paper was evaluated based on the following criteria. A: There is no missing text and it can be clearly identified. B: There are few missing characters, but the characters can be clearly recognized. C: Some characters are missing, but the characters can be recognized. D: There are multiple missing parts, making it difficult to read the text. E: Text is missing in places and it is clearly difficult to discern text.

[0082] “Recycling Adaptability” As an evaluation of recycling suitability, the following re-dissociation evaluation was performed. The obtained translucent paper was torn into 10 mm square pieces by hand, and 500 mL of 3% concentration was stirred for 30 seconds using a household mixer, Tescom mixer TM856-W, and sieved using a 12-mesh sieve of HOGA. ◎: Able to screen ○: Unable to be sieved, but the weight after drying was 0.5 g or less. ×: Unable to be sieved, but the weight after drying exceeded 0.5 g.

[0083] [Table 3] Example 1 Example 2 Example 3 Comparative Example 1 Example 4 Comparative Example 2 Comparative Example 3 Use original paper Production Example 1 Production Example 22 Production Example 3 Production Example 4 Production Example 5 Production Example 6 Production Example 7 Dip coating liquid Liquid 1 Liquid 1 Liquid 1 Liquid 1 Liquid 1 Liquid 1 Liquid 1 <![CDATA[Base paper grammage (g / m 2 )]]> 50.3 60.6 70.4 80.2 50.5 50.4 50.8 <![CDATA[Impregnation amount (g / m 2 )]]> 33.3 39.8 42.2 45.0 34.9 40.3 39.0 Transmittance T50) 28.1 26.7 16.7 13.2 29.7 22.1 24.3 Transmittance (T0) 54.3 53.9 36.7 33.9 55.0 52.9 56.5 Transmittance ratio 51.7 49.5 45.5 38.9 53.0 41.8 43.0 Opacity 17.5 18.0 19.2 22.3 17.0 18.3 20.0 Haze 74.7 76.9 79.9 83.2 66.8 77.6 79.0 Visual confirmation B C C E B D D Redissociation O O O O O × ×

[0084] [Table 4] Example 5 Comparative Example 4 Example 6 Example 7 Example 8 Reference Example 1 Use original paper Production Example 8 Production Example 9 Production Example 10 Production Example 111 Production Example 12 membrane Dip coating liquid Liquid 1 Liquid 1 Liquid 1 Liquid 1 Liquid 2 - <![CDATA[Base paper weight (g / m 2 )]]> 69.8 69.8 50.4 50.7 50.3 21.0 Impregnation amount (g / m2) 41.5 25.8 33.2 29.8 33.5 Light transmittance (T50) 15.9 13.2 27.2 28.6 24.5 88.2 Transmittance (T0) 35.0 32.2 53.9 55.0 52.1 95.5 Transmittance ratio 45.4 41.0 50.4 52.0 47.0 92.4 Opacity 18.3 21.2 18.3 18.2 19.9 0.6 Haze 75.8 81.1 74.2 75.2 77.6 1.0 Visual confirmation C D B B C A Redissociation O 〇 〇 〇 〇 ×

[0085] The packaging paper of the example has excellent visibility in the depth direction. In contrast, the packaging paper of the comparative example having a semi-transparent region whose light transmittance (T50) and light transmittance ratio do not meet the prescribed requirements has poor evaluation results for visibility. In addition, the numerical trends of light transmittance (T50) and light transmittance ratio are roughly consistent with the trends of the quality of visual visibility by human eyes. [Industrial Applicability]

[0086] According to the present invention, it is possible to provide a translucent paper having excellent visibility when observed through a translucent region. Description of Reference Numerals

[0087] 1 (1A, 1B), translucent paper; 2, base paper for translucent paper; 3, transparent material; 4, translucent area; 5, coating; 10, packaging; 11, object image; 12, visual confirmation image; F, resin film; 100, light transmittance measuring device; 101, light projecting part; 102, light receiving part; S, sample; S1, one side of the sample; S2, the other side of the sample.

Claims

1. A base paper for semi-transparent paper, wherein the paper is impregnated with a transparent material so that the impregnated area becomes semi-transparent, characterized in that: The base paper for the semi-transparent paper is mainly composed of coniferous chemical pulp and broadleaf chemical pulp. The ratio of coniferous chemical pulp to broadleaf chemical pulp is 75:25 to 51:

49. The base paper for the semi-transparent paper has a grammage of 40 g / m 2 ~100g / m 2 , The air permeability of the base paper for the translucent paper is 10 seconds to 40 seconds.

2. The base paper for translucent paper according to claim 1, characterized in that: The base paper for the semi-transparent paper has a grammage of 40 g / m 2 ~75g / m 2 .

3. The base paper for translucent paper according to claim 1 or 2, characterized in that: The Canadian standard freeness of the coniferous chemical pulp is 400mL to 700mL. The Canadian standard freeness of the hardwood chemical pulp is 350 mL to 650 mL.

4. The base paper for translucent paper according to claim 1 or 2, characterized in that: The Parker printing surface smoothness of at least one side of the base paper for translucent paper is 5 μm or less.

5. A translucent paper, characterized in that: The translucent paper has a translucent region formed by impregnating a transparent material in at least a portion of a base paper for the translucent paper. The base paper for the semi-transparent paper is mainly composed of coniferous chemical pulp and broad-leaved chemical pulp. The ratio of coniferous chemical pulp to broadleaf chemical pulp is 80:20 to 51:

49. Weight: 40g / m 2 ~100g / m 2 , The air permeability is 10 seconds to 40 seconds.

6. The translucent paper according to claim 5, characterized in that: The density of the translucent area of ​​the translucent paper is 0.7 g / cm 3 ~2.5g / cm 3 .

7. The translucent paper according to claim 5 or 6, characterized in that: The base paper for the semi-transparent paper has a grammage of 40 g / m 2 ~75g / m 2 .

8. The translucent paper according to claim 5 or 6, characterized in that: The light transmittance (T50) of the semi-transparent region under the following measurement condition 1 is 20% or more, "measurement condition 1" A light transmittance measuring device having a distance of at least 50 mm between the light projecting part and the light receiving part is used, and the semi-transparent area of ​​the semi-transparent paper is used as a sample for measurement. The light transmittance (T50) when the sample is arranged so that one surface is in contact with the light projecting unit is measured.

9. The translucent paper according to claim 5 or 6, characterized in that: The light transmittance ratio of the semi-transparent region under the following measurement condition 2 is 44 or more, "Measurement Condition 2" A light transmittance measuring device having a distance of at least 50 mm between the light projecting part and the light receiving part is used, and the semi-transparent area of ​​the paper is used as a sample for measurement. The light transmittance (T50) when the sample is arranged so that one surface is in contact with the light projecting part and the light transmittance (T0) when the sample is arranged so that the other surface is in contact with the light receiving part are measured. The transmittance ratio is calculated using the following mathematical formula: Mathematical formula 1: Transmittance ratio = (T50 / T0)×100.

10. A method for manufacturing translucent paper, characterized in that: At least a portion of the base paper for semi-transparent paper is impregnated with a transparent material. The base paper for the semi-transparent paper is mainly composed of coniferous chemical pulp and broadleaf chemical pulp. The ratio of coniferous chemical pulp to broadleaf chemical pulp is 80:20 to 51:

49. Weight: 40g / m 2 ~100g / m 2 , The air permeability is 10 seconds to 40 seconds.

11. The method for manufacturing translucent paper according to claim 10, characterized in that: The weight of the semi-transparent base paper is 40 g / m 2 ~75g / m 2 .

12. The method for producing translucent paper according to claim 10 or 11, characterized in that: The base paper for the semi-transparent paper has a Parker printing surface smoothness of 5 μm or less on one side, and a transparent material is dip-coated on the other side.

13. The method for producing translucent paper according to claim 10 or 11, characterized in that: The Canadian standard freeness of the coniferous chemical pulp is 400mL to 700mL. The Canadian standard freeness of the hardwood chemical pulp is 350 mL to 650 mL.

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