JP2004290665A - Absorptive article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an absorptive article whose moisture permeable back sheet is printed with images and the like for improving the design performance, and to keep the high level of the moisture permeability of the back sheet upon broadening the printing area. <P>SOLUTION: In the absorptive article 1, a liquid impermeable and moisture permeable back sheet 3 is formed with a printed part showing letters, shapes, or symbols, and it has 60-100 per inch of the line number of the print dot and 30-80% of print dot concentration in the printed part, and 18% or more ratio of apparent area in the printed part to the back sheet area. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an absorbent article such as a disposable diaper or a sanitary napkin, and more specifically, a large-area printed portion is clearly formed on a liquid-impermeable backsheet without reducing the moisture permeability of the backsheet. It relates to an absorbent article.

  On the back sheet used for absorbent articles such as disposable diapers and sanitary napkins, various patterns or the like may be printed for the purpose of improving the appearance of these absorbent articles. In recent years, as a back sheet on which such a pattern or the like is printed, a moisture-permeable back sheet made of a microporous film has been used (for example, see Patent Document 1). However, when printing is performed on a backsheet made of a microporous film, the fine holes formed in the film are closed by the ink, and the moisture permeability of the backsheet decreases. As a result, the humidity in the clothes increases, and stuffiness and rash are likely to occur. From the viewpoint of improving the design of the product and increasing the added value, it is preferable that the printing area is large. However, when the printing area is widened, the above-mentioned disadvantages become significant. For this reason, conventionally, the printing area cannot be increased, and line drawing, spot printing in which printing is performed only on a very small portion, or the like has been common.

  A printing film obtained by printing a microporous film is also known (see Patent Document 2). The purpose of this printed film is to solve the problem that it is difficult to adjust a dark color when producing a microporous film by mixing a pigment. This patent document describes that even if printing is performed on the entire surface of a microporous film, the film has good air permeability and moisture permeability. The reasons for this are that the thickness of the ink is thin and the degree of the ink closing the micropores is small. As a specific printing condition, it is described that the size of a pixel is 175 lines / inch in gravure printing. However, when printing over a large area using the technique described in this patent document, it is difficult to prevent a decrease in moisture permeability while maintaining the sharpness of printing.

JP 2000-513645 A JP-A-7-278329

  Therefore, the present invention maintains the moisture permeability of the backsheet at a high level even if the printing area is increased in an absorbent article having a design or the like printed on the moisture-permeable backsheet for the purpose of improving the design of the product. It is to provide an absorbent article provided.

  In the printing performed on the back sheet, a large number of minute printing portions, usually called dots, are gathered to form each picture. The present inventors consider that even if the actual printing area (sum of the area of each dot constituting the picture) of this printing picture is the same, the printing area depends on the size of the dot constituting the printing picture. Found that there was a difference in the degree to which the air permeability of the microporous film was inhibited.

  The present invention has been made based on the above-described knowledge, and a printing portion representing a character, a figure, a symbol, or the like is formed on a liquid-impermeable and moisture-permeable back sheet, and the number of lines of printing dots in the printing portion is provided. To provide an absorbent article wherein the ratio of the apparent area of the printed portion to the area of the back sheet is 18% or more, wherein the ratio is 60 to 100 per inch and the dot density of the printed dots is 30 to 80%. Thus, the above object has been achieved.

  In the absorbent article of the present invention, high moisture permeability is maintained even though various patterns are printed on the back sheet. Therefore, in the absorbent article of the present invention, the inside of the dress does not become in a high humidity state, so that stuffiness and fogging are prevented and the added value of the picture is increased.

  Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. FIG. 1 shows an embodiment in which the absorbent article of the present invention is applied to a deployable disposable diaper. In these figures, reference numeral 1 indicates a disposable disposable diaper.

  The diaper 1 includes a liquid-permeable top sheet 2, a liquid-impermeable back sheet 3, and a liquid-retentive absorber 4 interposed between the top sheet 2 and the back sheet 3. I have. Absorbent body 4 is formed in a curved hourglass shape in a region corresponding to the crotch region of diaper 1, and top sheet 2 and back sheet 3 also correspond to the crotch region of diaper 1 according to the shape of absorbent body 4. The region is curved. The absorber 4 is fixedly held between the top sheet 2 and the back sheet 3.

  When the diaper 1 is worn, the waist flaps 5, 5 'are fitted to the wearer's body when the diaper 1 is worn on the back and abdominal waist flaps 5, 5' extending outward from the front and rear of the absorber 4. Elastic members 5a and 5a 'for the belt are arranged in an extended state. Further, on a pair of leg flaps 6, 6 extending laterally from left and right side edges of the absorber 4, three thread-like elastic elastic members 6a, 6a are arranged in an extended state. The waist gathers W and the leg gathers L are formed by the contraction of the elastic members 5a and 6a.

  On the left and right sides of the diaper 1, three-dimensional gather forming sheets 7, 7 are arranged so as to cover side portions of the top sheet 2. Each three-dimensional gather forming sheet 7 has an outer portion and front and rear ends fixed to the top sheet 2 and an inner portion in a free state. And elastic elastic members 7a, 7a are fixed to the side edge of the inner part along the longitudinal direction. When the elastic member 7a is contracted, the inside portion of the three-dimensional gather forming sheet 7 rises, and the three-dimensional gather portion R standing on the body side of the wearer in the diaper 1 is formed.

  A pair of fasteners 8 each made of a tape fastener or the like are attached to both widthwise side edges of the back waist flap 5, and a rectangular waist flap 5 ′ is formed on the back sheet 3 at the waist flap 5 ′. An adherend (not shown) made of a landing tape or the like is attached. Then, when the disposable diaper 1 of the present embodiment is worn, the fasteners 8, 8 are fixed on the adherend. A plurality of waist elastic members 9 are arranged in the diaper width direction in an extended state on the inner side in the diaper width direction at the location of the fastening device 8. When the elastic member contracts, a waist gather portion D is formed.

  Among these members constituting the diaper 1, for example, various nonwoven fabrics or apertured films can be used as the top sheet 2. As the absorber 4, a mixture of pulp fibers and particles of a superabsorbent polymer wrapped with paper such as tissue paper can be used. The back sheet 3 is composed of a laminate of a microporous moisture-permeable film 3a and a nonwoven fabric 3b. In this case, the back sheet 3 is arranged so that the nonwoven fabric 3b constituting the back sheet 3 faces outward of the diaper. The size of the moisture permeable film 3a and the size of the nonwoven fabric 3b are not the same, and the moisture permeable film 3a is almost the same as or larger than the absorber 4, whereas the nonwoven fabric 3b is 3a, the outer shape of the diaper 1. In the present embodiment, a region where the moisture permeable film 3a and the nonwoven fabric 3b overlap is called a back sheet 3.

In the moisture permeable film 3a of the back sheet 3, a printing portion formed of characters, graphics, and / or symbols (hereinafter, collectively referred to as a pattern, etc.) is provided on a surface facing the nonwoven fabric 3b (hereinafter, referred to as a nonwoven fabric facing surface). Is formed. That is, the printing unit is located between the moisture-permeable film 3a and the nonwoven fabric 3b. The printing section is visually recognized from the outside of the diaper through the nonwoven fabric 3b. The printing unit is formed by flexographic printing or gravure printing. In particular, it is preferably formed by flexographic printing from the viewpoint of plate dot control described later. FIG. 2 shows an example of a picture or the like of the printing unit. As shown in FIG. 2, the printing unit P includes a vertical and horizontal lattice pattern and a graphic such as an animal. By forming the printing portion P on the moisture permeable film 3a, the moisture permeability of the moisture permeable film 3a after printing is lower than that before printing. Therefore, the moisture permeability of the back sheet 3 as a whole also decreases. The reduction in the moisture permeability of the back sheet 3 is preferably 30% or less, more preferably 20% or less, and even more preferably 10% or less as compared to before printing. From the viewpoint of suppressing a decrease in the moisture permeability of the entire back sheet 3, the moisture permeability of the printed portion P is preferably 60% or more, and more preferably 80% or more with respect to the printed portion P or the unprinted portion before printing. Is more preferable. Similarly, the difference between the moisture permeability of the entire back sheet 3 and the moisture permeability of the unprinted portion is preferably 0.8 g / (100 cm ² · h) or less, particularly preferably 0.3 g / (100 cm ² · h) or less. . Further, the difference between the moisture permeability of the printed portion P and the moisture permeability of the unprinted portion is preferably 1 g / (100 cm ² · h) or less, particularly preferably 0.5 g / (100 cm ² · h) or less.

  FIG. 3 shows a state where the printed portion of the picture shown in FIG. 2 is enlarged. The printing section is composed of a number of dots printed by the printing method described above. In the figure, black dots are print dots. Generally, the dots are arranged at equal intervals in the width direction and the length direction of the diaper. In the field of printing technology, the number and area of dots are usually represented by the number of lines and the density of a stave. The number of lines represents the number of dots arranged (arranged) in one inch. As the number of lines increases, the distance between adjacent dots decreases, and conversely, when the number of lines decreases, the distance between dots decreases. growing. The halftone dot density is a ratio of the sum of the dot areas per unit area. Therefore, the number of dots increases as the number of lines increases, and if the number of lines is the same (the number of dots is the same), the area of one dot increases as the halftone dot density increases. Generally, the dot density greatly affects the appearance of a picture or the like. The higher the halftone dot density, the more the actual printing area per unit area (the area on which ink is actually applied) increases, so that the picture or the like looks clearer. In the case of the same halftone dot density, the number of dots increases as the number of lines increases, resulting in a finer pattern or the like. However, when the actual printing area increases, the moisture permeability of the back sheet 3 decreases, so that there is a trade-off between the appearance of a picture or the like and the moisture permeability of the back sheet 3. The present inventors set the halftone dot density (actual printing area) and the number of lines to specific ranges, respectively, to maintain the appearance of individual patterns and the like at a high level and to suppress a decrease in the moisture permeability of the back sheet 3. It has been found that even if the number of pictures formed on the back sheet 3 is increased, the moisture permeability can be maintained at a high level.

  Specifically, as a result of the study by the present inventors, the following has been found. As described above, the higher the halftone dot density, the higher the appearance of a pattern or the like, but the actual print area per unit area (the area on which ink is actually applied) increases. The rate at which the micropores of the wet film 3a are closed increases, and the moisture permeability of the back sheet 3 decreases. However, even with the same halftone dot density, it was found that there was a range where the rate of decrease in moisture permeability was relatively low as the shape of the print dot was reduced. Specifically, in the range where the dot area is relatively large, the actual print area and the rate of decrease in moisture permeability are completely correlated, but when the area per dot becomes a certain value or less, the actual print area becomes smaller. It was found that the rate of decrease in moisture permeability was small. Although the reason for this has not been completely elucidated, the present inventors presume the following. When the area per dot is relatively large, it is considered that the coating surface and adhesion of the ink are stable and the micropores in the moisture-permeable film 3a are completely closed. If the area per dot becomes smaller, it is considered that the air permeability is maintained because the ink coating cannot cover the surface roughness of the moisture-permeable film 3a in a completely adhered form. .

  Printing ink generally comprises a colorant and a vehicle (resin, additive, solvent), and the colorant is roughly classified into a pigment and a dye. Pigments are often used as colorants from the viewpoint of light resistance. Pigments are classified into organic pigments and inorganic pigments. Printing inks are classified into solvent-based inks, water-based inks, UV inks, and the like according to the type of vehicle. As the resin, polyvinyl chloride, polyester, polyurethane, cured rosin, chlorinated rubber, petroleum, nitrocellulose, cellulose derivative, ethyl cellulose, polyamide, acrylic resin, maleic acid resin, fumaric acid resin, polyketone, shrack, protein, phenolic resin, Methacrylic acid resin, epoxy resin and the like are used. As the additive, wax, metal soap, surfactant, gelling agent and the like are used. As the solvent, alcohol (methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol), ester (ethyl acetate, isopropyl acetate, n-propyl acetate), aliphatic hydrocarbon (n-hexane, n-heptane, VM & P naphtha) ), Glycol ethers, glycols, aromatic hydrocarbons (toluene, xylene), ketones, water and the like.

  It has also been found that the following advantages can be obtained by representing a pattern or the like by using printed dots. That is, when performing printing of a light color, in order to form it by solid printing, the ratio of the resin component in the ink becomes larger than that of the pigment, and as a result, the light resistance of the printed portion tends to decrease. is there. On the other hand, by expressing a pattern or the like by the print dot, it becomes possible to perform printing of a light color in appearance without lowering the pigment concentration in the ink, and it is possible to prevent the light resistance of the printing portion from lowering. From this viewpoint, the resin component in the ink is preferably 20 to 90% by weight, particularly preferably 30 to 70% by weight based on the total amount excluding the volatile component. Also, it was found that as the amount of the resin component increased, the pores in the ink coating film were filled with the resin, and the moisture permeability tended to decrease. When the ratio of the resin component to the total amount excluding the volatile components in the ink is 70% by weight or less, the reduction in moisture permeability is small, and when it is 60% by weight or less, the reduction is further reduced, which is preferable. However, if the proportion of the resin component is too low, the adhesion strength of the ink coating film may decrease. Therefore, the resin component is preferably 40% by weight or more, particularly preferably 40 to 60% by weight.

  Based on the above findings, in the present invention, the number of lines of printing dots in the printing unit is set to 60 to 100, preferably 70 to 90 per inch. In addition, the halftone dot density of the printing dots in the printing section is set to 30 to 80%, preferably 30 to 70%, and more preferably 30 to 50%. As described above, the number of print dots is the density of print dots, and is represented by the number of lines per inch. The smaller the number of lines, the coarser the dots. As described above, the halftone dot density of the print dot is the ratio of the total area of each print dot to the area of the print portion. The number of lines and halftone dot density of the printed dots are measured by taking a photograph of the printed portion with an optical microscope at a magnification of 20 times, and binarizing the photograph using an image analysis program.

  In the present invention, when the number of lines of the printing dots in the printing section is less than 60 per inch, the ink easily penetrates into the fine holes in the moisture-permeable film 3a, the moisture permeability is reduced, and the sharpness of a pattern or the like is further reduced. I do. If it exceeds 100, the printing plate has poor durability and the dot tip is easily crushed (swelled), so that printing becomes impossible immediately. Further, if the halftone density of the printing dots in the printing section is less than 30%, the color of a picture or the like becomes light and the appearance thereof deteriorates. If it exceeds 80, the actual printing area increases, so that the moisture permeability of the back sheet 3 decreases. It is preferable that the halftone dot density of the printed dots is 70% or less, particularly 50% or less, because the reduction in moisture permeability is further reduced.

  In the present invention, the value of the apparent area ratio on the back sheet is set to 18% or more, preferably 25 or more, in addition to the above-mentioned line number and halftone density of the printed dots. In order to ensure the moisture permeability required for the back sheet 3, it is preferable that the apparent area ratio is small. However, if the apparent area ratio is less than 18%, the value added effect of the product by applying a pattern or the like is low. As a result, there is no point in applying a pattern or the like. The upper limit of the apparent area ratio is not particularly limited, and may be 100%. From the viewpoint of securing sufficient moisture permeability, the upper limit is preferably about 60%. The apparent area ratio (%) is obtained by dividing the sum of the areas within the outermost periphery of each printed portion defined by connecting adjacent print dots having a distance of 1 mm or less (this area is called apparent area) by the area of the back sheet. And multiplied by 100. The picture or the like may be composed of only a halftone dot portion, or may be composed of a solid printing portion and a halftone dot portion. When a picture or the like is composed of a solid printing portion and a halftone dot portion, the apparent printing area ratio on the back sheet in the halftone dot portion can be obtained by subtracting the printing area of the solid printing portion from the entire printing area. Also in this case, the apparent print area ratio on the back sheet in the halftone dot portion is 18% or more.

  Further, in the present invention, the actual print area ratio on the back sheet is preferably 4 to 40%, more preferably 10 to 20%. The actual print area ratio on the back sheet was obtained by dividing the sum of the values obtained by multiplying the dot density and the apparent area for each printed portion (this value is referred to as the actual print area) by the area of the back sheet and multiplying by 100. Value. It is preferable that the actual printing area ratio on the back sheet is within this range, because it is possible to increase the added value of the product while securing necessary moisture permeability.

  With respect to the apparent area ratio and the actual printing area ratio, the area of the printing portion formed in the region of the backsheet 3 facing the absorber 4 (hereinafter, this region is referred to as the absorber facing region) is also important. is there. This is because the absorber-facing area occupies most of the area of the back sheet 3 and most of the vapor is discharged to the outside through the absorber-facing area. From this point of view, in the present invention, the ratio of the sum of the apparent areas of the respective printed portions formed in the absorber facing region is preferably 25 to 100%, more preferably the area of the absorber facing region. 35 to 85% (this value is referred to as an apparent area ratio on the absorber). Further, the ratio of the sum of the actual printing areas of the respective printing portions formed in the absorber-facing region is preferably 6 to 80%, more preferably 15 to 40% with respect to the area of the absorber-facing region. (This value is called the actual printing area ratio on the absorber).

In the moisture-permeable film 3a on which the above-described printing has been performed, the moisture permeability in the printed portion is preferably 0.5 g / (100 cm ² · h) or more, particularly preferably 2 g / (100 cm ² · h) or more. The moisture permeability of a plain region (that is, an unprinted portion) in the moisture-permeable film 3a is preferably 1.5 g / (100 cm ² · h) or more, particularly preferably 2.2 g / (100 cm ² · h) or more. The back sheet 3 in which the nonwoven fabric 3b is laminated on the outer surface of the moisture-permeable film 3a has a moisture permeability of 1.5 g / (100 cm ² · h) or more, particularly 1.8 g / (100 cm ² · h) or more. Preferably, there is. The moisture permeability of the back sheet 3 is determined by measuring the moisture permeability of the printed portion and the moisture permeability of each of the uncoated portions of the back sheet 3. The moisture permeability of the entire back sheet can be obtained by measuring the number of points at which an average value is obtained for the diaper (for example, n = 6 per three diapers) and calculating the average value. The water vapor transmission rate is measured according to JIS Z0208 using a 60 mmφ cup at 30 ° C. and 90% RH. When the back sheet 3 is taken out of the diaper and measured, the absorbent is peeled off with water or the like to make the back sheet 3 alone.

As another method of measuring the moisture permeability of the back sheet, the moisture permeability of the entire back sheet can be determined from the moisture permeability of the printed part and the moisture permeability of the uncoated part by the following method. The apparent area ratio of the printed portion in the following equation means the apparent printed area ratio in the moisture permeability measurement portion (equivalent to 60 mmφ) of the printed portion. Similarly, the apparent moisture permeability of the printed portion means the moisture permeability per unit area of the apparently printed portion of the printed portion.
Apparent printed part moisture permeability = (Printed part moisture permeability-Solid part moisture permeability x (1-Printed part apparent area ratio)) / Printed part apparent area ratio Water vapor permeability of the entire back sheet = Apparent printed part moisture permeability x Back sheet apparent Area ratio + moisture permeability of plain area x (1-apparent area ratio on back sheet)

  As a base material used for the moisture-permeable film 3a, a film is formed by melt-kneading a hydrophobic thermoplastic resin and a fine inorganic filler such as calcium carbonate or an incompatible organic polymer, and the like. A microporous film obtained by uniaxially or biaxially stretching a film is exemplified. Examples of the thermoplastic resin include polyolefin. Examples of the polyolefin include high- to low-density polyethylene, linear low-density polyethylene, polypropylene, and polybutene, and these can be used alone or as a mixture. The pores of the microporous film having a diameter of 0.1 to 10 μm, particularly 0.5 to 5 μm on the surface thereof are hardly closed by the ink while maintaining the mechanical strength of the film, so that the moisture permeability is improved. Is preferable in that can be maintained. Preferred examples of the moisture-permeable film 3a include those described in JP-A-63-146943 filed by the applicant of the present invention.

In the present embodiment, the printed portion is formed on the nonwoven fabric-facing surface of the moisture-permeable film 3a, but instead, the printed portion may be formed on the surface of the moisture-permeable film 3a facing the absorber. In this case, the back sheet 3 preferably has a predetermined light transmittance so that the printed portion can be seen through from the outside of the diaper. From this viewpoint, the light transmittance of the moisture-permeable film 3a used for the back sheet 3 is preferably 30 to 80%, more preferably 35 to 80%, and further preferably 40 to 80%. preferable. The light transmittance is measured by a reflection / transmittance meter (trade name “HR-100” manufactured by Murakami Color Research Laboratory Co., Ltd.). For the measurement, the value of the total light transmittance _Tt is measured using the A light source. Ten points at any point on the sample are measured, and the average value is used as the value of light transmittance (hereinafter, light transmittance refers to the value measured by this method).

Even if the printed portion is formed on any surface of the moisture-permeable film 3a, a nonwoven fabric 3b having a predetermined light transmittance is used so that the printed portion can be seen through from the outside of the diaper. Preferably, it is used. In this respect, the nonwoven fabric 3b preferably has a light transmittance of 50% or more, more preferably 55% or more, and still more preferably 60% or more. From the same viewpoint, it is preferable to use the nonwoven fabric 3b having a basis weight and a thickness at which the light transmittance is obtained. Specifically, the basis weight is preferably 5 to 45 g / m ² , particularly preferably 10 to 40 g / m ² . Further, the thickness is preferably 0.1 to 3.0 mm, particularly preferably 0.2 to 2.0 mm.

  As the nonwoven fabric 3b, for example, a fiber made of a thermoplastic resin alone such as a polyolefin such as polyethylene or polypropylene, a polyester such as polyethylene terephthalate, or a polyamide, or a core-sheath type or side-by-side type using two or more of these resins is used. Non-woven fabrics composed of composite fibers having a structure are exemplified. It is preferable to use a nonwoven fabric manufactured by a general manufacturing method such as an air through method, a melt blown method, a heat sealing method, a spun bonding method, and a suction heat bonding method.

  The nonwoven fabric 3b preferably has a ground color of white or a very pale color, but may be colored in a range that does not impair the sharpness of the printed portion or the appearance of the diaper 1.

  As described above, the present invention has been described based on the preferred embodiments. However, the scope of the present invention is not limited to the above embodiments, and various changes can be made. For example, as described above, the printing portion may be formed on any surface of the moisture-permeable film 3a. In the above-described embodiment, the back sheet 3 is made of a laminate of a moisture-permeable film and a nonwoven fabric. However, the back sheet may be made of a single moisture-permeable film instead. Also in that case, the printing portion may be formed on any surface of the moisture-permeable film.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such an embodiment.

[Example 1]
As the moisture permeable film, a stretched microporous polyethylene film containing particles of calcium carbonate was used. The basis weight of this film was 20 g / m ² , and the moisture permeability was 2.2 g / (100 cm ² · h). This film is used in Kao Corporation's baby disposable diaper "Marys" tape-type. When the surface of this film was observed with an electron microscope, the diameter of the pores on the surface was 0.6 μm on average (1000 times magnification). The picture shown in FIG. 2 was printed on one side of this film using a six-color flexographic printing machine and a flexographic ink containing an organic pigment of each color and a polyurethane resin as the ink. Details of printing are as shown in Table 1. The resin component in the ink was 60 to 85% by mass based on the total amount excluding the volatile components. A spunbond nonwoven fabric having a basis weight of 15 g / m ² was laminated on the printed portion with a hot melt adhesive. The moisture permeability of the obtained back sheet was 2.1 g / (100 cm ² · h) in the unprinted area. The disposable diaper shown in FIG. 1 was obtained using the back sheet thus obtained and other known members.

[Comparative Example 1]
A disposable diaper was obtained in the same manner as in Example 1, except that a picture was printed by solid printing having a halftone dot density of 100%.

[Comparative Example 2]
A commercially available disposable diaper (Printer and Gamble Far East, Inc. disposable diaper Pampers Cotton Care (L size) manufactured by Procter & Gamble Far East, Inc.) having a printed thereon moisture-permeable back sheet was used as Comparative Example 2.

(Performance evaluation)
For the diapers obtained in the examples and comparative examples, various area ratios and moisture permeability were measured. The appearance of the picture was evaluated by the following method. Table 1 shows the results.

[Evaluation of picture appearance]
Three panelists evaluated. The diaper was observed from a distance of about 30 cm, and the quality of the appearance was evaluated on a three-point scale of △, Δ, and ×, using the color density of the pattern, the roughness and clarity of the dots as evaluation points. If the panelers' evaluations were different, they were shown in that range.
：: When the dots of the pattern could not be recognized, and the pattern was clear and had a good appearance.
Δ: When dots are not clear but dots are recognizable, and when sharpness is slightly lacking.
×: When dots can be clearly recognized, and when the color is light and not clear.

  As is clear from the results shown in Table 1, it can be seen that the diaper of Example 1 has a good appearance and has a sufficiently high moisture permeability. On the other hand, it can be seen that the diaper of Comparative Example 1 in which the pattern is formed by solid printing has a good appearance of the pattern, but has a low moisture permeability. Further, it can be seen that the diaper of Comparative Example 2 did not reach a high level in both the moisture permeability and the appearance of the pattern.

[Examples 2 to 10]
A film similar to the moisture-permeable film used in Example 1 (however, the moisture permeability was 2.0 g / (100 cm ² · h)) was prepared using a blue organic pigment-based printing ink with a flexographic printing machine. Printing was performed under the conditions shown. The picture was made with another rabbit pattern by halftone printing. About the obtained back sheet, various area ratios and moisture permeability were measured. The color difference of the pattern was measured by the following method, and the appearance of the pattern was evaluated by the method described above. Table 2 shows the results.

[Example 11]
Using the same film as the moisture-permeable film used in Example 1 (however, the moisture permeability was 2.3 g / (100 cm ² · h)), monochromatic printing was performed on the entire surface. The ink was a green organic pigment-based ink containing the same kind of mainly a polyurethane resin as in Example 1, and the proportion of the resin component in the ink coating film was about 45%. Others were performed similarly to Example 2. About the obtained back sheet, various area ratios and moisture permeability were measured. The color difference of the pattern was measured by the following method, and the appearance of the pattern was evaluated by the method described above. Table 2 shows the results. Even when printing was performed on the entire surface, a resin having a high moisture permeability was obtained in spite of a large actual area ratio on the back sheet because the resin component of the ink was smaller than that in Example 1.

[Comparative Examples 3 to 6]
The same operation as in Example 11 was performed using the same ink as that used in Example 11. About the obtained back sheet, various area ratios and moisture permeability were measured. The color difference of the pattern was measured by the following method, and the appearance of the pattern was evaluated by the method described above. Table 2 shows the results.

[Measurement of color difference of pattern]
Using a color difference meter nR-1 manufactured by Nippon Denshoku Co., a back sheet was placed on white paper, and the difference (ΔEH) between the color difference of the plain portion and the color difference of the printed portion was measured. The greater the ΔEH, the higher the apparent color density. The measurement was performed on the side of the back sheet on which the printing section was formed. When ΔEH is 20 or more, it is slightly clear, and preferably 25 or more.

  As is evident from the results shown in Table 2, the backsheet of each example has a clear pattern and a good appearance, and has a sufficiently high moisture permeability.

It is the top view which looked at the deployment type disposable diaper which concerns on the absorbent article of this invention from the top sheet side. It is a figure showing a picture of a printing part. It is a figure which expands and shows a printing part.

Explanation of reference numerals

1 disposable diapers (absorbent articles)
2 Top sheet 3 Back sheet 3a Moisture permeable film 3b Nonwoven fabric 4 Absorber

Claims (5)

  A printed portion representing characters, graphics or symbols is formed on a liquid-impermeable and moisture-permeable back sheet, and the number of lines of the printed dots in the printed portion is 60 to 100 per inch, and An absorbent article having a dot density of 30 to 80% and a ratio of an apparent area of the printed portion to an area of the back sheet of 18% or more.   2. The absorbent article according to claim 1, wherein the number of lines of the printing dots in the printing unit is 70 to 90 per inch, and the halftone density of the printing dots is 30 to 50%.   The ratio of the apparent area of the printing portion formed in the region facing the liquid-retentive absorber in the region of the back sheet is 25 to 100% with respect to the area of the region facing the absorber. The absorbent article according to claim 1 or 2.   The absorbent article according to any one of claims 1 to 3, wherein the printing unit is formed by flexographic printing. The absorbent article according to any one of claims 1 to 4, wherein the back sheet is made of a microporous film, and a resin component in the ink forming the printing portion is 20 to 90% by mass.

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