toilet paper rolls

Abstract

The problem to be solved by the present invention is to provide a roll of toilet paper that, even in long rolls, has a distinctive and well-designed pattern, with fewer wrinkles and creases, and a smooth surface. To solve the above problems, the toilet paper of the present invention is a roll of toilet paper with a diameter of 90 to 120 mm, wherein the toilet paper has a basis weight of 11.0 to 14.0 g / m², a paper thickness of 60 to 90 μm, and has raised and recessed surfaces created by embossing. One of the surfaces has a pattern formed by solid printing. The pattern has a first solid portion and a second solid portion of different colors. The pattern portion accounts for 8 to 20% of the total area, the first solid portion accounts for 2.0 to 4.0% of the total area, and the second solid portion accounts for 6.0% or more of the total area. Furthermore, the toilet paper is wound on a paper tube with a length of 65 to 90 m and a winding density of 0.83 to 2.05, with the side with the printed pattern as the outer layer.

Description

Technical Field

[0001] This invention relates to a type of toilet paper roll that is rolled into a tube shape. Prior Technology

[0002] Toilet paper rolls are everyday consumer goods. Given the limited space in toilets, a longer roll length is an important factor for consumers when deciding to purchase them.

[0003] In general household products, the roll length of toilet paper is typically around 25m for double-ply toilet paper and around 50m for single-ply toilet paper. However, in recent years, longer rolls, which are 1.5 to 3 times the length of these rolls, have become increasingly common (see Patent Document 1 below).

[0004] In order to make this type of long-sized toilet paper roll with a roll diameter that can be used with a regular household toilet paper holder, the toilet paper needs to be made with a low basis weight, thinner paper, and tightly wound.

[0005] Furthermore, conventional double-layer toilet paper rolls of approximately 25m or single-layer toilet paper of approximately 50m often had patterns or designs printed on them using ink (see Patent Document 2 below). This toilet paper roll boasts an excellent design.

[0006] [Previous Technical Documents] (Patent Documents) Patent Document 1: Japanese Patent Application Publication No. 2018-064664 Patent Document 2: Japanese Patent Application Publication No. 2008-188070 Summary of the Invention

[0007] [The problem the invention aims to solve] However, as mentioned above, long-sized rolls of toilet paper require a low basis weight and thinner paper while being tightly wound. Therefore, if patterns are printed, ink will strike through, resulting in unnecessary ink bleeding on the back.

[0008] Furthermore, because the ink is applied to the thinner paper and the winding is made tighter, paper breaks are more likely to occur during manufacturing, and wrinkles and creases are more likely to form.

[0009] Furthermore, since the ink is applied to the thinner paper, the area where the ink is applied has a noticeable hard texture, making it difficult to feel smooth.

[0010] Furthermore, toilet paper rolls are made of multiple layers of toilet paper. In the case of long-sized products, the patterns on the lower layers of toilet paper will be overly visible, making it impossible to achieve the desired design through patterns.

[0011] Therefore, the main problem that this invention aims to solve is to provide a type of toilet paper that is easy to manufacture, free from wrinkles and creases, and features well-designed patterns, and further makes the surface feel smooth.

[0012] [Technical means used to solve the problem] The first solution to the above problem is a type of toilet paper roll, which is made by winding double-layered toilet paper into a roll with a diameter of 90-120mm, characterized by: The aforementioned toilet paper has a single-layer basis weight of 11.0-14.0 g / m², a paper thickness of 60-90 μm, and features raised or recessed areas created through embossing. One of the surfaces has a pattern formed by solid printing. The aforementioned pattern has a first solid portion and a second solid portion of different colors. The pattern portion occupies 8-20% of the total area. The aforementioned first actual area accounts for 2.0% to 4.0% of the total area. The aforementioned second actual area accounts for more than 6.0% of the total area. Furthermore, the toilet paper roll is wound onto a paper tube with the side printed with the aforementioned pattern as the outer layer side, and has a length of 65 to 90 m and a winding density of 0.83 to 2.05.

[0013] The second method concerns the toilet paper roll of the first method mentioned above, wherein the ten-point average roughness [RzJIS] of the outer layer side of the toilet paper is 0.025~0.320 mm.

[0014] The third method relates to the first or second method of the above-mentioned roll toilet paper, wherein the toilet paper is a double-layered double-embossed toilet paper formed by laminating two thin sheets, one of which has a concave portion and the other has a convex portion, with the concave portion forming surface of these thin sheets being the outer side.

[0015] The fourth method concerns the toilet paper rolls of the first to third methods mentioned above, wherein the roll density is 0.1 to 0.3 g / cm³.

[0016] The fifth method concerns the toilet paper rolls described in the first to fourth methods above, wherein the porosity is 3 to 20%.

[0017] [effect] According to the present invention, a roll of toilet paper can be provided that is easy to manufacture even in long rolls, is free of wrinkles and creases, has a well-designed pattern that is recognizable, and has a smooth surface. Simple Explanation of the Diagram

[0018] Figure 1 is a perspective view of a roll of toilet paper according to an embodiment of the present invention. Figure 2 is a schematic diagram illustrating the measurement sequence of whiteness and color difference in relation to the present invention. Figure 3 is a diagram illustrating the pattern printing of the present invention. Figure 4 is a diagram illustrating an example of an embossed pattern related to the present invention. Implementation

[0019] Next, the toilet paper roll of the present invention will be described with reference to the drawings. As shown in FIG1, the toilet paper roll 1 of the present invention is formed by rolling a double-layered strip toilet paper 10 into a paper tube (also referred to as a core) 20.

[0020] The roll diameter L2 of the toilet paper roll 1 of the present invention is 90-125 mm, preferably 110-125 mm. A roll diameter of 90-125 mm facilitates placement on a standard toilet paper holder. Here, the roll diameter L2 is a value measured using a Diameter Ruler manufactured by Muratec-KDS Co., Ltd., or an equivalent tool. The measured value is set as the average value obtained by measuring at three locations where the width direction changes. Furthermore, the width L1 of the toilet paper roll in this embodiment is not limited, but is preferably 100-130 mm. Also, the outer diameter L3 of the paper tube is not limited, but is preferably 34-42 mmφ.

[0021] The toilet paper roll of the present invention is characterized in that: the toilet paper has a basis weight of 11.0 to 14.0 g / m², a paper thickness of 60 to 90 μm, and has raised and recessed surfaces produced by embossing. On one side, there is a pattern formed by solid-printing. The pattern has a first solid portion and a second solid portion of different colors. The pattern portion accounts for 8 to 20% of the total area, the first solid portion accounts for 2.0 to 4.0% of the total area, and the second solid portion accounts for 6.0% or more of the total area. Furthermore, the toilet paper is wound on a paper tube with a length of 65 to 90 m and a winding density of 0.83 to 2.05, with the side with the pattern printed on it as the outer layer side.

[0022] Regarding the toilet paper roll of the present invention, due to these structures, ink bleed-through is less likely to occur when printing patterns, thus preventing unnecessary ink seepage on the back and making paper breaks less likely during manufacturing. Furthermore, it can be made without wrinkles or creases, and furthermore, the pattern of the underlying toilet paper is not overly discernible, resulting in a toilet paper roll with distinctive design features. Also, the hardness of the ink-bearing area is not obvious, making it feel smooth.

[0023] Regarding the toilet paper roll of the present invention, the thickness of the toilet paper wound on it in a single-layer state is 60-90 μm. Preferably, it is 60-85 μm. If the thickness of the single layer is 60-90 μm, the toilet paper can have sufficient strength and softness, and when the toilet paper with a length of 65-90 m is wound on the paper tube, it is easy to make the roll diameter L2 (diameter) within the range of 90-120 mm. Furthermore, under the conditions of the pattern printing of the present invention, it is easy to form a toilet paper roll that does not have ink see-through, does not have unnecessary ink bleeding on the back, and is less prone to paper breakage during manufacturing.

[0024] The method for measuring paper thickness is as follows: Under the conditions of Japanese Industrial Standard JIS P 8111 (1998), the test piece is conditioned for at least 8 hours, and then, under the same conditions, a single-layer thickness gauge (PEACOCK G type) is used (manufactured by Ozaki Corporation). Specifically, after ensuring there is no debris or dust between the plunger and the measuring stage, the plunger is placed on the measuring stage, and the scale of the aforementioned needle-type thickness gauge is moved to zero. Next, the plunger is pre-lifted, and the test piece is placed on the measuring stage. Then, the plunger is slowly lowered, and the gauge reading is taken. During measurement, the plunger is only placed, not pressed. The plunger terminal is made of metal, and a circular plane with a diameter of 10 mm is perpendicular to the paper surface. The load for this paper thickness measurement is approximately 70 gf. Furthermore, the paper thickness is set as the average value obtained from 10 measurements. Even if the toilet paper has embossed texture, the measurement is performed in the same way. In this case, the measurement is performed with a recess that can be fully inserted into the measuring platform. Any disruption caused by the concave or convex shape during measurement can be ignored. In this paper thickness measurement, the thickness difference caused by the disruption of the concave portion can be disregarded.

[0025] Regarding the toilet paper of the present invention, the basis weight of a single layer is 11.0 to 14.0 g / m². Preferably, it is 11.5 to 13.5 g / m². More preferably, it is 12.0 to 13.0 g / m². If it is within the range of 11.5 to 14.0 g / m², the winding density and porosity of the toilet paper roll of the present invention can be easily adjusted. Furthermore, in the toilet paper roll of the present invention, the dry tensile strength and wet tensile strength, etc., can be appropriately adjusted using well-known methods, within a range that does not impair the effect of the present invention.

[0026] The toilet paper of the present invention has an embossed texture. Embossing makes the toilet paper soft and improves its wiping properties by creating surface irregularities. Furthermore, since embossing creates irregularities on the paper surface, it becomes difficult to discern the patterns on the underlying layers, thus enhancing design flexibility.

[0027] In particular, regarding the toilet paper of the present invention, although it is also possible to create a single-embossed toilet paper by embossing in a double-layered state, it is desirable to create a double-embossed toilet paper by laminating two sheets, one with a recess and the other with a protrusion, with the recessed surfaces of these sheets facing outwards. Double-embossed toilet paper is easier to manufacture in terms of the winding density and winding stiffness of the present invention. Furthermore, double-embossed toilet paper easily forms gaps between layers, making it more difficult to discern the pattern of the underlying layer through the paper surface, thus improving design flexibility. Also, since double-embossed toilet paper has recesses on both sides, the front and back surfaces of the laminated sheets are largely indistinguishable. Furthermore, when both sides are concave, the user touches the gently sloping arched portion between the concave areas with their fingertips, and then touches the back of the paper with multiple fingers. Because of the arched portion formed on the back of the paper, the fingertips feel soft. Moreover, due to the soft pulp material and the gently sloping arched portion, the surface texture is smooth to the touch. Therefore, even if the pattern is formed using solid printing, the patterned area is unlikely to become stiff. Also, double-embossed toilet paper is particularly prone to wrinkles and creases caused by manufacturing processes because it easily stretches when stretched in the direction of the sheet's extension.

[0028] The specific pattern of relief created by embossing is not necessarily limited. Embossing patterns can be set as micro-embossing, dot embossing, creative embossing, and other appropriate embossing patterns. However, it is desirable that the relief created by embossing be configured in a way that does not degrade the recognizability of the printed pattern. For example, it is desirable for the pattern to be a pattern consisting only of neatly arranged recesses on a base that would be perceived as unrelated to the pattern. As a more concrete example, it is desirable for the pattern to be a pattern consisting of squares, triangles, polygons, circles, ellipses, and quadrangular stars formed by extending the four corners of a square, arranged neatly in both the vertical and horizontal directions. Such a pattern will not cause the design formed by the relief created by embossing to interfere with the design of the printed pattern, but will instead create a sense of complementary design.

[0029] A particularly suitable pattern for recesses (convexities) produced by embossing is shown in Figure 4. Recesses 51 (Figure 4A) are squares with a bottom surface of L5 × L5 = 1.0–1.5 × 1.0–1.5 mm, or approximately squares (Figure 4B) formed by the four corners of these squares extending outwards from the diagonals. These recesses 51 are arranged in a grid pattern with a center interval L6 of 4.5–5.5 mm and an angle of 45° relative to the width direction. Valley lines 53 extending from the four corners of each recess 51 are located between the recesses. Furthermore, the valley lines 53 are preferably arranged in an arc-shaped cross-section, with the deepest point at the four corners of the recesses and the shallowest point in the middle between the recesses. This embossing pattern does not reduce the design flexibility of a printed pattern and further enhances softness, flexibility, and thus, the wiping properties of feces. By means of the valley line portion 53 which faces a direction at an angle of 45° to the width direction, the tension during winding is dispersed. Regarding the winding length of the toilet paper roll of the present invention, the embossing process produces a very clear texture and makes it difficult for wrinkles to occur.

[0030] Here, the desired embossing density for this invention is 3 to 25 embossings / cm², preferably 4 to 20 embossings / cm². With an embossing density of 3 to 25 embossings / cm², the design quality generated by embossing and the design quality formed by the pattern produced by printing according to this invention complement each other. Therefore, even if the pattern portion occupies less than 10% of the total area and the second solid portion occupies 6.0% of the total area, the printed pattern is less likely to give a cheap impression and the design quality is significantly enhanced. Embossing density is measured using a ONE-SHOT3D measuring macroscope VR-3200 (model) manufactured by KEYENCE Corporation or equivalent instrument and image analysis software "VR-H2A" or equivalent software. The measurement is performed at 12x magnification and a field of view of 24mm × 18mm. First, the area of ​​the region comprising multiple embossed units constituting the embossed pattern is measured, and the number of embossed elements within that region is calculated. The term "area containing multiple units of embossing" refers to the smallest unit that constitutes the entire embossed pattern that divides the surface of toilet paper into equal areas, or a closed area multiple of the smallest unit. Embossing density (units / cm²) = (number of embossings containing multiple units of embossing) ÷ (area of ​​the area containing multiple units of embossing). This formula can be used to calculate the density. However, the magnification and viewing area can be adjusted appropriately based on the size of the embossing (recesses).

[0031] On the other hand, regarding the toilet paper of the present invention, the ten-point average roughness [RzJIS] of its outer layer side is preferably 0.025 to 0.320 mm. More preferably, it is 0.025 to 0.315 mm. If this range of ten-point average roughness [RzJIS] is set, printing scratches become less likely to occur, printing brightness becomes better, and design is easier to achieve. The ten-point average roughness [RzJIS] is measured using a ONE-SHOT3D measuring macroscope VR-3200 (model) manufactured by KEYENCE Corporation or a similar instrument and image analysis software "VR-H2A" or similar software. The measurement is performed at a magnification of 12x and a field of view area of ​​24 mm × 18 mm. However, the magnification and field of view area can be appropriately changed according to the size of the embossing (recess). The ten-point average roughness [RzJIS] is measured by taking a 3D image of the location, avoiding the areas where ink is applied, and taking any location without embossing, or avoiding the recesses created by embossing, especially the middle part of the recesses when they are arranged neatly. The data is then analyzed. The contour line used for line roughness measurement is measured and analyzed in the paper transport direction. The measurement parameter is the "composite parameter RzJIS". Furthermore, since the outermost surface of toilet paper reflects the smoothness of the toilet paper surface but with low accuracy, the measurement location on the toilet paper roll is set to any location within the range of 29% to 31% from the outermost point of use. The measurement value is set as a 10-point average, and the test sample can be fixed on the measurement stage using a method that does not affect the measurement value.

[0032] Furthermore, regarding the toilet paper of the present invention, the number of creases is preferably 35 to 50 per 10 mm. More preferably, it is 37 to 48 creases per 10 mm, and even more preferably 39 to 45 creases per 10 mm. If the number of creases is set within this range, the surface becomes smoother, and especially in the printing of the pattern according to the present invention, the hardness imparted to the ink area is less noticeable, resulting in an overall smooth feel. This number of creases can be adjusted by the wrinkling rate during the manufacturing of the base paper and the presence or absence of calendering and the calendering pressure. Furthermore, the number of creases is measured using a ONE-SHOT3D measuring macroscope VR-3200 (model) manufactured by KEYENCE Corporation or a comparable instrument and image analysis software "VR-H2A" or comparable software. The measurement is performed at 12x magnification and a field of view of 24 mm × 18 mm. However, the magnification and field of view area can be appropriately changed according to the size of the embossing (recesses). The number of wrinkles is measured by taking 3D photographs of the area where the pattern has been inked, avoiding any location without embossing, and avoiding locations in areas with recesses created by embossing, especially the middle portion of the recesses when they are neatly arranged. The data is then analyzed for measurement. The contour line measured using line roughness is specified, measured, and analyzed perpendicular to the paper's transport direction. The measurement parameter used is "line roughness." The number of ridges within a 10mm measurement distance of the obtained measurement profile curve is defined as the number of wrinkles. Furthermore, since the outermost surface of the toilet paper roll reflects its surface smoothness but has low accuracy, the measurement location on the toilet paper roll is set to any position within the range of 29-31% from the outermost point of use. The measurement value is set as a 10-point average, and the test sample can be fixed on the measurement stage using a method that does not affect the measurement value.

[0033] Regarding the toilet paper roll of the present invention, a pattern is printed on one side of the toilet paper, and it is wound onto a paper tube with the patterned side as the outer layer. In other words, the toilet paper roll of the present invention has a pattern only on the outer layer. By printing the pattern on the outer layer, the pattern can be clearly identified directly from the outside.

[0034] Furthermore, since toilet paper rolls consist of several layers, if the pattern on the bottom of one or more layers is visible, the pattern on that bottom layer may be mixed with the pattern on the outer surface and thus become identifiable. However, the toilet paper of this invention is double-layered, with an unprinted layer on the inner side. Therefore, if the basis weight and paper thickness are set within the range specified in this invention (as described above) and the pattern is formed only on the outer layer, the pattern on the outer surface can be clearly identified, while the pattern on the bottom layer is difficult to identify. In particular, when double embossing is used and gaps are created between the layers, the pattern on the bottom layer becomes even more difficult to identify. Moreover, to ensure that the pattern exists only on the outer side, it is sufficient to roll the paper with the printed side facing outwards.

[0035] The patterns of this invention are formed by printing and do not include cases where the paper is colored during the papermaking stage by supplying dye to the papermaking raw materials. The specific design of the pattern is not particularly limited. Examples include patterns of one or more appropriately selected from plants such as flowers, trees, and grass; living organisms such as people, animals, fish, shellfish, and insects; natural elements such as mountains, rivers, seas, clouds, forests, and woodlands; planets / satellites such as the moon, sun, and stars; and man-made objects such as cars, airplanes, and trams. While the area of ​​a pattern is not necessarily limited, it is desirable to have an area of ​​10.0 mm² to 918 mm². The pattern is easily recognizable, its excellent design is readily apparent, and the amount of ink printed on a single pattern area is not excessive, making it less prone to bleed-through, thus easily demonstrating the effects of this invention.

[0036] The pattern of this invention is formed solely by solid printing. Furthermore, the proportion of the patterned portion to the total area is 8-20%, preferably 8-10%. The proportion of the total area refers to the ratio of the patterned portion of the toilet paper to the area of ​​one of its surfaces. Moreover, since the patterned toilet paper is repeatedly printed at a predetermined pitch during the manufacturing process, the method for calculating the proportion of the patterned portion to the total area is to cut 10 samples every 50cm from the front end of the toilet paper after removing the end cap, then calculate the ratio of the area of ​​the patterned portion in each sample to the area of ​​one of its surfaces (toilet paper width × 50cm), and calculate the average value of the 10 samples. The area of ​​the patterned portion in the sample is measured by optically scanning the sample and then measuring it using well-known software.

[0037] If the patterned portion occupies 8-20% of the total area, the toilet paper will not feel hard when used due to the ink being applied. In particular, when manufactured with the tension required to create other roll structures such as the winding length and roll diameter of the present invention, wrinkles and creases can be prevented.

[0038] Furthermore, regarding the pattern of the toilet paper of the present invention, it particularly has a first solid area and a second solid area of ​​different colors, that is, it has solid printing areas with two or more colors. Moreover, the first solid area can be multiple locations. Also, the second solid area can be multiple locations. In the present invention, the first solid area is one or more areas that have been solidly printed using a single ink, and the entire area of ​​the first solid area is formed using a single printing plate. In the present invention, the second solid area is one or more areas that have been solidly printed using a different ink than the first solid area, and the entire area is formed using a different printing plate than the first solid area. Having solid printing areas with two or more colors makes it easier to improve design flexibility.

[0039] Regarding the pattern of the toilet paper of the present invention, the first solid portion occupies 2.0 to 4.0% of the total area, and the second solid portion occupies 6.0% or more of the total area. By setting the proportion of the first solid portion to 2.0 to 4.0% of the total area and the proportion of the second solid portion to 6.0% or more of the total area, the pattern is clearly identifiable, making it difficult for ink to show through and ensuring design integrity. Furthermore, the toilet paper as a whole does not become rigid, and wrinkles and creases are less likely to occur during the manufacturing process. Moreover, when combined with other structures of the present invention to form a roll of toilet paper, the solid portion is not overly identifiable through the non-patterned portion of the toilet paper located on the outer side, resulting in a roll of toilet paper where the intended design is easily identifiable.

[0040] Here, regarding the toilet paper of the present invention, the thickness of a single layer is 60-90 μm. Thus, with such a thin single layer, especially a low basis weight, if halftone printing is performed within a range of 2.0-4.0% of the total area, insufficient pressure is applied to the sheet during printing, resulting in ink not adhering to the sheet and thus unclear printed areas. Furthermore, this phenomenon is more likely to occur when the area of ​​a pattern is within the aforementioned range of 10.0 mm² to 918 mm². To improve ink adhesion, simply increasing the pressure is sufficient; however, increasing the pressure between the toilet paper and the printing plate leads to a deterioration in operability, such as a slower operating speed. Also, the thickness of the toilet paper may be reduced. Furthermore, if the pressure is too high, ink may penetrate to the layer opposite to the printed surface, resulting in ink bleeding through. Regarding the toilet paper of the present invention, while forming the pattern using only solid printing, the proportion of the first solid area to the total area is set to 2.0% to 4.0%, and the proportion of the second solid area to the total area is set to 6.0% or more. This improves the stability of operability and reduces the problem of back seepage. Furthermore, due to the aforementioned relationship between double embossing and basis weight, it lacks a stiff feel and is less prone to wrinkles and creases.

[0041] Regarding the pattern on the toilet paper of this invention, it is desirable to print it using flexographic printing (letterpress printing) with water-based ink. However, gravure printing such as photogravure printing and offset printing can also be used. In particular, if the ink is water-based, and it is set to a water-based ink with a viscosity of 10 to 50 cps, a developing agent of 30 to 60% by mass, and a water content of 70 to 40% by mass, the pattern can be made sufficiently vivid and wrinkles and creases are less likely to occur even if the paper is soaked with water. Furthermore, the viscosity is a value measured by a type B viscometer.

[0042] While the line count of the anilox roller used when printing patterns related to the present invention is not necessarily limited, it is desirable to set it to 250-600 lines per inch, and more preferably 250-500 lines per inch. This condition is suitable for forming patterns related to the present invention.

[0043] Regarding the toilet paper roll of the present invention, the toilet paper having the above-described pattern is wound onto a paper tube with a winding density of 0.83 to 2.05, resulting in a winding length of 65 to 90 meters. This winding length is more than twice that of a typical household double-layer toilet paper roll of approximately 25 meters. Furthermore, the winding length is measured while unwinding the toilet paper roll without applying tension. For example, it can also be measured while folding the roll back in a zigzag pattern every 5 meters from the start of unwinding.

[0044] Furthermore, the toilet paper roll of the present invention has the aforementioned winding length and a winding density of 0.83 to 2.05. Preferably, it is 0.95 to 1.45, and particularly preferably 1.00 to 1.30. The winding density of the present invention is a value calculated by dividing the actual cross-sectional area by the theoretical cross-sectional area. The actual cross-sectional area is a value calculated by multiplying the winding length by the paper thickness. On the other hand, the theoretical cross-sectional area is a value calculated by subtracting the area of ​​the paper tube opening from the area of ​​the end face. With the aforementioned winding length, especially toilet paper rolls with a winding density in the range of 0.83 to 2.05, it is easy to manufacture and has very few wrinkles and creases. Furthermore, when holding the outer periphery of the toilet paper roll in hand, it feels moderately compact and has a solid winding length without feeling too soft or too hard. If the thickness exceeds 2.05, the toilet paper will feel harder than the actual roll length. On the other hand, if it is less than 0.83, the toilet paper will feel too soft relative to the roll length, and it will often be difficult to feel a firm texture.

[0045] Regarding the toilet paper roll of the present invention, its winding density is as described above, and the roll density is preferably 0.10 to 0.30 g / cm³, more preferably 0.10 to 0.25 g / cm³. The roll density is expressed as (roll mass) ÷ (roll volume). The roll mass is the mass of the toilet paper roll per 114 mm of roll width. The roll volume is expressed as [{cross-sectional area of ​​the roll diameter L2 portion} - (cross-sectional area of ​​the paper tube outer diameter L3 portion)] × roll width (converted to 114 mm). The roll density is also an indicator for toilet paper rolls, indicating the degree of density, whether it is tightly wound or loosely wound. Moreover, if it is too loose, the toilet paper is prone to excessive deformation and flying out (loosening) near the paper tube; and if it is too tight, the toilet paper will feel stiff when held in the hand.

[0046] Furthermore, in the toilet paper rolls of the present invention, the toilet paper rolls are double-embossed and have a predetermined basis weight as described above. The proportion of the patterned portion to the total area is set to 8-20%, the proportion of the first solid portion to the total area is set to 2.0-4.0%, and the proportion of the second solid portion to the total area is set to 6.0% or more. This allows the pattern to be clearly identified, and although see-through is achieved using only solid printing, it is difficult for wrinkles and creases to occur. In other words, when increasing the winding length and winding density, it is necessary to increase the tension to wind the toilet paper rolls onto the paper tube when forming the toilet paper rolls. On patterned toilet paper, the stretching of the printed portion and the unprinted portion becomes different. Therefore, if the tension is increased, wrinkles and creases are more likely to occur on the toilet paper rolls when they are formed. However, this problem is solved in the toilet paper rolls of the present invention. In other words, a roll of toilet paper with excellent pattern recognition and no back seepage can be provided. When held in the hand, it feels sufficiently soft as a product without wrinkles or creases.

[0047] Furthermore, regarding the toilet paper roll of the present invention, a porosity of 3-20% is desired. The porosity (%) of the present invention is a value calculated by (actual porosity volume of the entire roll) / (theoretical roll volume) × 100 (actual porosity of the entire roll). The actual porosity volume of the toilet paper roll is calculated by (actual cross-sectional area (cm²)) × (roll width (cm)), and the theoretical roll volume is calculated by (winding length (cm) × 2 × paper thickness (single layer, cm)) × (roll width (cm)). The porosity (actual porosity of the entire roll, %) is calculated by ((theoretical roll volume (cm³)) - (actual roll volume (cm³)) / (theoretical toilet paper roll volume (cm³)). Calculated by multiplying 3) by 100 (%). The roll width (width of the toilet paper roll) L1 can be set to approximately 100-130 mm. The porosity is an indicator showing the extent of space within the toilet paper roll, representing the degree of spatial bundling. This indicator can be adjusted by embossing, paper thickness, and winding tightness. Thicker paper thickness includes cases where the porosity is higher but the embossing is excessively deep and strong, making it difficult to break, and cases where the paper layer itself is thicker; in either case, a stiff feeling will be felt. Regarding the porosity of this invention, a higher porosity tends to result in a stiffer roll, while a lower porosity tends to result in a softer roll. Furthermore, if the porosity exceeds 20%, the pattern will show through, making the roll design difficult to discern; if it is below 3%, the pattern will appear less vivid due to printing scratches.

[0048] Furthermore, regarding the toilet paper of the present invention, the whiteness (whiteness) of the unprinted portion is 80% or more, and the color difference ΔE between the Lab value obtained by directly measuring the printed portion of the lower layer and the Lab value obtained by measuring the printed portion through the unprinted white portion of the upper layer of toilet paper (ΔL) = (Δa)² + (Δb)² + (ΔL)²)¹ / ² is preferably within the range of 2.20 or less. More preferably, it is less than 2.00. Further, the color difference ΔE' between the Lab value obtained by measuring the printed portion through the unprinted white portion of the upper layer of toilet paper and the Lab value of the unprinted white portion of the upper layer of toilet paper is preferably 6.0 or less. If the whiteness, ΔE, and ΔE' are such, then as shown in FIG3, the pattern 40 of the lower layer seen through the unprinted white portion of the upper layer of toilet paper will not be excessively and clearly discernible, but will become vaguely and slightly discernible. At the same time, the patterns on the upper layer, which would otherwise be directly identifiable, become clearly distinguishable. Therefore, the contrast between the directly identifiable patterns 41 and 42 and the lower layer pattern 40, which is identifiable through the white portion of the toilet paper, creates a unique and distinctive design. In particular, when the pattern printing coverage is 8-20%, the pattern area is not too wide, and the effect created by the contrast between the directly identifiable printed portion, the white portion, and the printed portion identifiable through the upper layer feels appropriate.

[0049] Here, regarding the measurement sequence of whiteness and color difference ΔE, ΔE' of the present invention, as shown in FIG2, five sheets of white cardboard 31 are stacked on a horizontal measuring stage, and then the sample 33 to be measured is stacked on top of them. Further, the unpatterned portion of toilet paper 34 taken from the same roll of toilet paper as the sample 33 is stacked so as to cover the patterned portion 32 of the sample 33 to be measured. Further, a sheet of white cardboard 35 having a 20mmφ windowed portion 36 is stacked on top of it so that the patterned portion 32 to be measured can be located within the windowed portion 36.

[0050] Furthermore, through the windowed portion 36 and across the toilet paper 34, the whiteness and Lab value of the patterned portion being measured are determined using a spectrophotometer / colorimeter (the Lab value obtained by measuring the unpatterned white portion of the upper layer of toilet paper is measured). Next, without moving the measurement location, the toilet paper 34 overlapping the patterned portion 32 is removed, and the whiteness and Lab value of the patterned portion being measured are determined using a spectrophotometer / colorimeter (the Lab value obtained by directly measuring the patterned portion of the lower layer is measured). Then, the sample is further removed, and the whiteness and Lab value of the top layer of the five overlapping white cardboard sheets 31 (the Lab value of the unpatterned white portion of the upper layer of toilet paper) (blank value) are determined using a spectrophotometer / colorimeter. Furthermore, the spectrophotometer / colorimeter used is a PF7000 spectrophotometer / colorimeter manufactured by Nippon Denshoku Kogyo Co., Ltd., or an equivalent instrument. The color difference ΔE and ΔE' are calculated using the measured Lab values.

[0051] The number of colors constituting the pattern on the toilet paper according to the present invention is not particularly limited as long as it is two or more. However, considering the cost, equipment, and the fact that toilet paper is low-density and prone to leakage, two to three colors are desirable. Most preferably, it is desirable that the pattern is composed of two colors, a first solid portion and a second solid portion. Furthermore, when measuring the Lab value of the pattern, in the case of a pattern having multiple colors, it is desirable to measure all portions where the colors differ, and all measured values ​​should be within the aforementioned numerical range.

[0052] The fibers in the toilet paper of this invention are not limited, but it is desirable to use 70-100% by weight of virgin wood pulp and 0-30% by weight of recycled pulp. Blending in recycled pulp allows for cheaper production compared to toilet paper composed of 100% by weight of virgin wood pulp. Furthermore, in the process of regenerating pulp from recycled paper, the fibers tend to become finer compared to the unrecycled pulp fibers. These fibers tend to be denser and have higher paper strength without increasing paper thickness. On the other hand, excessive blending of recycled pulp reduces softness and other texture qualities. Therefore, considering the characteristics of recycled pulp, a blending ratio of 0-30% by weight is preferable. Moreover, the type of recycled pulp is not necessarily limited, but recycled pulp made from milky white cardboard recycled paper or high-quality recycled paper is particularly desirable. These recycled papers incorporate a significant amount of softwood kraft pulp (NBKP) derived from the raw materials, thus easily exhibiting high paper strength.

[0053] For the pulp used, softwood kraft pulp (NBKP) and hardwood kraft pulp (LBKP) are preferred. The desired blending ratio of these pulps is NBKP:LBKP of 20:80 to 50:50. NBKP can also be derived from off-white paperboard pulp. Furthermore, toilet paper manufactured using this virgin wood pulp and the aforementioned high-quality recycled pulp has a mechanical pulp content of less than 5% by mass from recycled paper, an ash content of less than 3% by mass, and a brightness of approximately 80-85%.

[0054] [Elongation at Winding Length (%)] On the other hand, regarding the toilet paper roll of the present invention, a winding length elongation of 1.0 to 3.6% is desirable. More preferably, it is 1.6 to 3.3%, and especially preferably, it is 2.0 to 3.0%. The winding length elongation represents the elongation of the sheet that is stretched and wound within the roll.

[0055] The elongation of the winding length is determined by the winding length L0 and the length of the sheet L1 (m) inside the roll, using the formula (1) for the elongation of the winding length (%) = (L1-L0) / L0…. Here, the winding length L0 (m) is obtained using the following method. The number of sheets is counted by dividing the sheet into units based on the number of holes. The winding length is defined as the first group, from the second sheet to the sixth sheet. The second sheet is the sheet following the outermost rolled sheet (first sheet) of the roll, including the tail seal. Every 5 sheets thereafter, the sheet is cut with scissors or the like and the sheet size is actually measured. The last group of the innermost roll is taken in such a way that it does not contain a pick-up section of 2 sheets. This last group is defined as the nth group. When actually measuring the sheet size, the 5 consecutive sheets (groups) placed on a flat surface are actually measured using a JIS 1 grade metal ruler. First, the average group length is obtained. The average group length is obtained by formula (6) = average group length (m) = {length of the first group + length of the second group + ... + length of the nth group} ÷ n. The winding length L0 is obtained by formula (7) = L0(m) = (average group length) × n + (average group length / 5) × {1 + (number of innermost rolled sheets including the pickup section that cannot form a group)}. In addition, the sheet lengths of the tail seal and pickup section are covered with adhesive and have wrinkles, making it impossible to measure the accurate sheet length. Therefore, it is converted to (average group length / 5) for calculation.

[0056] The length L1 (m) of the sheet inside the roll represents the winding length of the sheet inside the roll, and is obtained in the following order. (1) Use a magic pen or similar tool to draw a straight line on the side of the roll, from the outermost part of the roll to the paper tube and through the central axis of the paper tube. The mark on the outermost part of the roll (the mark of the magic pen) should be aligned with the outermost end of the sheet. (2) Count the number of markings with a special pen at the end of the sheet width of the unwound roll, and set it as the number of overlapping layers (double layer) of the sheet in the roll. For the sheet weight including the pick-up part that cannot form a group, calculate the number of layers by (number of sheets that cannot form a group × average sheet length ÷ [(outer diameter of paper tube r) × π]) and sum them up, and set it as the number of sheet layers P. (3) The cross-sectional area of ​​the roll S (cm 2) = π / 4 × [(roll diameter R) 2 - (paper tube outer diameter r) 2]... Formula (2), S is expressed in cm 2, and the roll diameter R and the paper tube outer diameter r are expressed in cm. (4) Furthermore, when the thickness of the sheet inside the roll in the roll state is set as T (mm), the area formed by rolling the sheet into a roll and stacking it is the cross-sectional area of ​​the roll, which is obtained by formula (3) T (mm) = 1 / 2 × (Rr) / (P × 10). (5) Furthermore, S(cm 2) = length of the sheet inside the roll L1(m) × T(mm) × 10… Formula (4), where T(mm) is the thickness of the sheet inside the roll. (6) Therefore, the length of the thin sheet inside the roll L1(m) = S(cm 2) / (T(mm)×10)... Formula (5) Therefore, substituting into equations (2) and (3), we obtain L1 = π / 2 × (R + r) × P ÷ 100… equation (6). Thus, the elongation (%) of the winding length in formula (1) represents the elongation (%) of the sheet that is stretched and wound inside the roll. The larger the elongation (%), the more it is stretched inside the roll.

[0057] If the elongation rate (%) of the winding length is less than 1.0%, the sheet has high tensile rigidity, making it difficult to stretch and resulting in a paper that feels hard. Furthermore, its high tensile rigidity necessitates deeper embossing to strengthen the embossing and prevent it from crumbling, resulting in a rough surface texture. If the elongation rate (%) of the winding length exceeds 3.6%, the sheet has too low tensile rigidity. The sheet easily stretches, becoming an overly soft paper that loses its weight and solidity. The low tensile rigidity also causes the embossing to stretch, leading to its crumbling and reduced clarity, thus deteriorating the appearance.

[0058] [Example] Next, regarding the embodiments and comparative examples of the toilet paper rolls of the present invention, the following aspects were examined: "smoothness of the sheet," "smoothness of the roll surface," "prevention of back-to-back seepage," "design quality," and "print clarity (including the absence of printing scratches)." The structure, physical properties, composition, and test results of the toilet paper rolls in each example are shown in Table 1 below. Comparative Example 5 and Example 6 were formed by rolling single-embossed toilet paper. Other embodiments and comparative examples were formed by rolling double-layered double-embossed toilet paper, consisting of two sheets with concave portions on one side and convex portions on the other side formed by embossing, with the concave portions facing outwards. The embossing pattern in each example was the arrangement of the concave portions as shown in Figure 4(B). The pattern was based on the combination of flowers and leaves shown in Figure 3, with the area of ​​each pattern adjusted according to the proportion of the total area.

[0059] The smoothness of the toilet paper was evaluated as follows: From a roll of toilet paper, a two-pitch section was taken, with the distance between the perforations of adjacent sheets considered as one pitch. The subject then physically touched a portion of toilet paper at this two-pitch interval. The smoothness of the sheet surface was evaluated on a scale of 1 to 5. The evaluation criteria were: 5 points for "Satisfactory," 4 points for "Slightly Satisfactory," 3 points for "Neither," 2 points for "Slightly Unsatisfactory," and 1 point for "Unsatisfactory." The values ​​in Table 1 are rounded to one decimal place. The number of subjects was 30.

[0060] The smoothness of the toilet paper roll surface was evaluated as follows: Participants physically touched the outer circumference of the roll and rated it on a scale of 1 to 5. The evaluation criteria for smoothness were: 5 points for "Satisfactory", 4 points for "Slightly Satisfactory", 3 points for "Neither", 2 points for "Slightly Unsatisfactory", and 1 point for "Unsatisfactory". The values ​​in Table 1 are rounded to one decimal place. There were 30 participants.

[0061] The prevention of ink seepage was evaluated as follows: Participants visually observed the back side (non-printed side) of the printed portion of the toilet paper roll. Regarding ink seepage into the back side (non-printed side), a score was given as follows: "Completely no ink seepage" - 5 points; "No ink seepage" - 4 points; "Neither" - 3 points; "Slight ink seepage" - 2 points; "Ink seepage" - 1 point. The scores in Table 1 are rounded to one decimal place. The number of participants was 30.

[0062] Design quality was evaluated as follows: Participants visually observed the pattern on the outer circumference of the toilet paper roll, judging the balance between the patterned and white areas, the transparency of the underlying pattern, and other external appearance factors. Scores were assigned based on the following criteria: "Excellent" 5 points, "Excellent" 4 points, "Neither" 3 points, "Somewhat cheap" 2 points, and "Very cheap" 1 point. Table 1 shows values ​​rounded to one decimal place. Thirty participants were tested.

[0063] Print clarity was evaluated as follows: Participants visually observed the back side (non-printed area) of the printed portion of the toilet paper roll. Regarding the printed portion (the area where the ink was transferred), scores were assigned as follows: "No scratches and clear" 5 points; "Slight scratches but generally clear" 4 points; "Scratches present but generally clear" 3 points; "Partially scratched and slightly less clear" 2 points; "Overall printing scratches and not clear" 1 point. Table 1 shows values ​​rounded to one decimal place. The number of participants was 30.

[0064] [Table 1]

[0065] Examples 1 to 6, although the paper thickness was reduced to achieve a longer size, still achieved a design quality of over 8% of the total area of ​​the pattern, and prevented bleed-through despite being solid printing. In particular, the evaluation was higher in the case of double embossing. In contrast, Comparative Example 1, with a solid print of only one color and a total area of ​​7%, had a very low evaluation of design quality. Furthermore, the evaluation of print sharpness was also low. Comparative Example 3 also had a low evaluation of design quality. Comparative Example 4 also had a low evaluation of design quality. This low evaluation is related to the fact that the pattern was formed using only solid printing of one color. It is also believed that printing the flowers and leaves in the same color would affect this evaluation result. Furthermore, the evaluation of print sharpness (printing scratches) was low. Since the printed area reached 21% of the total area and printing scratches were confirmed, the evaluation was low. Bleed-through was also confirmed. Comparative Example 2, whose pattern occupied a proportion of the total area was within the scope of the present invention, but the second solid portion was replaced with halftone printing and the pattern occupied a slightly wider proportion of the total area, but bleed-through occurred and the evaluation of print sharpness was low. Furthermore, Comparative Examples 2-4 have high basis weight and low evaluation of the flexibility of the sheet and roll. Comparative Example 6 uses halftone printing instead of the second solid portion and reduces the proportion of the pattern to the total area, but it exhibits bleed-through and has a low evaluation of print sharpness. Operability is poor.

[0066] On the other hand, Comparative Example 5 is a single-embossed toilet paper with a high basis weight. The smoothness of the sheet and the smoothness of the roll surface were rated poorly, as were the print clarity and back-to-back visibility. This poor rating was attributed to surface roughness.

[0067] Furthermore, especially when observing print clarity, good results can be obtained for toilet paper with a ten-point average roughness [RzJIS] within the range of this invention and with double embossing.

[0068] As described above, the toilet paper rolls of the present invention are easy to manufacture even in long sizes, free from wrinkles and creases, and feature well-designed patterns, making the surface smooth to the touch.

[0069] 1: Toilet paper rolls 10,34: Toilet paper 20: Paper tube (core) L1: Width of toilet paper roll L2: Dimensions of toilet paper roll L3: Outer diameter of paper tube 31, 35: Whiteboard paper 32: Pattern section 33: Sample 36: Window opening section 40: Pattern on the lower layer 41: The first solid part of the upper level 42: The second solid part of the upper level 51: concave part 53: Valley Line Section

[0070] Domestic storage information (please note in order of storage institution, date, and number) none Overseas storage information (please note in the order of storage country, institution, date, and number) none

Claims

1. A type of toilet paper roll, comprising two layers of toilet paper wound into a roll diameter of 90-120 mm, characterized in that: the toilet paper has a basis weight of 11.0-14.0 g / m², a paper thickness of 60-90 μm, and has raised or recessed areas created by embossing; one side of the toilet paper has a pattern formed by solid printing; the pattern has a first solid area and a second solid area of ​​different colors; the pattern area accounts for 8-20% of the total area; the first solid area accounts for 2.0-4.0% of the total area; and the second solid area accounts for 6.0% or more of the total area; and the toilet paper roll is wound onto a paper tube with a length of 65-90 m and a winding density of 0.83-2.05, with the side of the toilet paper with the printed pattern as the outer layer.

2. The toilet paper roll as described in claim 1, wherein, The ten-point average roughness [RzJIS] of the outer layer of the aforementioned toilet paper is 0.025 mm to 0.320 mm.

3. The toilet paper roll as described in claim 1, wherein, The aforementioned toilet paper is a double-layered, double-embossed toilet paper made by laminating two thin sheets, one with a concave portion and the other with a convex portion, with the concave portion of these sheets forming the outer side.

4. The toilet paper roll as described in claim 2, wherein, The aforementioned toilet paper is a double-layered, double-embossed toilet paper made by laminating two thin sheets, one with a concave portion and the other with a convex portion, with the concave portion of these sheets forming the outer side.

5. The toilet paper roll as described in any one of claims 1 to 4, wherein, The density of the roll is 0.1~0.3 g / cm3.

6. The toilet paper roll as described in any one of claims 1 to 4, wherein, The porosity is 3-20%.

7. The toilet paper roll as described in claim 5, wherein, The porosity is 3-20%.

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