JP4014585B2 - Absorbent articles - Google Patents

Description

  The present invention relates to absorbent articles such as sanitary napkins, panty liners, and incontinence pads.

As a conventional technique related to absorbent articles such as sanitary napkins, Patent Document 1 includes an absorber having an upper layer disposed on the surface material side and a lower layer disposed on the back material side, and the density of the lower layer is defined as the upper layer. Absorbent articles having a higher density than the above are described. In addition, the same document 1 describes the formation of a recess by embossing as a specific means for increasing the density of the lower layer.
Patent Document 2 describes an absorbent article in which an embossed recess having a shape that does not include a straight line and does not have a depression is arranged on the absorbent body of the absorbent article.

JP 2004-121382 A JP 2003-33397 A

However, in the absorbent article described in Patent Document 1, since the upper layer of the absorbent body is not embossed, when the upper layer absorbs the liquid, the upper layer sags and fits to the wearer's excretory part and the like. The property cannot be improved sufficiently.
Moreover, since the absorbent article of patent document 2 does not form the embossed recessed part in the site | part corresponding to an excretion part, like patent document 1, a sag occurs in the absorber in the site | part corresponding to an excretion part, The fit to the excretion part cannot be improved. In addition, in the absorbent article described in Patent Document 2, when the embossed recess is provided in the absorbent body in the part corresponding to the excretion part, the softness in the part is impaired.

  Accordingly, an object of the present invention is to provide an absorbent article that can be softly and satisfactorily fitted to the excretory part and the like, can maintain its fit well even during wearing, and has excellent liquid drawability. There is.

The present invention is an absorbent article having a skin contact surface, a non-skin contact surface, and an absorbent body interposed between both surfaces, wherein the absorbent body is formed by laminating an upper absorbent layer and a lower absorbent layer. It has a laminated portion, the upper absorbent layer is located on the skin contact surface side, the lower absorbent layer is located on the non-skin contact surface side, and the laminated portion of the absorber is 0. Under the load of 5 g / cm ^2, the apparent density of the lower absorbent layer is lower than that of the upper absorbent layer, and under the load of 20 g / cm ² , the apparent density of the lower absorbent layer is the same as the apparent density of the upper absorbent layer or The apparent density of the upper absorbent layer is higher than the apparent density of the upper absorbent layer. In the stacked portion, the contact area between the upper absorbent layer and the lower absorbent layer side surface is equal to the upper absorbent layer side surface pair of the lower absorbent layer. smaller than the planar contact area, in 20 g / cm ² under a load, the lower absorbent layer The density of the contact part in contact with the upper absorbent layer is higher than the density of the non-contact part not in contact with the upper absorbent layer, and the non-contact part is in the thickness direction of the absorber and the upper absorption. The above object is achieved by providing an absorbent article that has entered the upper absorbent layer side beyond the position of the contact interface with the layer .

  The absorbent article of the present invention can be softly and satisfactorily fitted to the excretory part and the like, and the fit is well maintained even during wearing, and the liquid drawability is also excellent.

Hereinafter, the present invention will be described based on preferred embodiments thereof.
A sanitary napkin 1 (hereinafter also referred to as the present napkin 1) as an embodiment of the present invention includes a skin contact surface 2, a non-skin contact surface 3, and a gap between both surfaces as shown in FIGS. It has an intervening liquid-retaining absorber 4. The skin contact surface 2 is a surface directed toward the wearer's skin when worn, and the non-skin contact surface 3 is a surface directed toward the opposite side of the wearer's skin when worn.
The skin contact surface 2 of the napkin 1 is constituted by a liquid-permeable top sheet 21, and the non-skin contact surface 3 is constituted by a liquid-impermeable back sheet 31. The absorber 4 is fixed between the top sheet 21 and the back sheet 31. The napkin 1 has a shape having a longitudinal direction and a width direction. The top sheet 21 is joined to the back sheet 31 with an adhesive or the like in the vicinity of both side edges of the absorber 4. The top sheet 21 and the back sheet 31 are joined to each other at both longitudinal ends of the napkin 1 by heat sealing or the like to form the end seal portion 11.
An adhesive is applied in a predetermined shape on the back sheet 31 that forms the non-skin contact surface 3, and a slip prevention layer (not shown) is formed. The slip prevention layer is for fixing the napkin 1 to a mounting tool such as shorts, and is protected until use by a release paper or a release sheet (not shown).

  As the forming material of each of the top sheet 21 and the back sheet 31 in the napkin 1, those used for absorbent articles such as sanitary napkins, panty liners, incontinence pads and the like can be used without particular limitation. As the sheet, an air-through nonwoven fabric, a spunbond nonwoven fabric or the like subjected to a hydrophilic treatment with a surfactant, or a perforated sheet or a perforated film can be preferably used. As the back sheet, in addition to a non-moisture permeable film sheet or a moisture permeable film sheet, a composite with a nonwoven fabric such as SMS or a moisture permeable film can be used.

  As a material for forming the absorbent body 4, a fiber aggregate or a combination of this and a polymer water-absorbing polymer can be preferably used. As fibers constituting the fiber assembly, hydrophilic fibers such as pulp fibers, synthetic fibers (preferably subjected to hydrophilic treatment), and the like can be used. A fiber aggregate or a combination of this and a polymer water-absorbing polymer may be coated with a water-permeable covering sheet made of tissue paper or a water-permeable nonwoven fabric. The polymer water-absorbing polymer may be present in the form of a layer or may be mixed with pulp fibers or the like. The polymer water-absorbing polymer has a holding performance capable of absorbing and holding a liquid 20 times or more of its own weight, and is preferably in the form of particles having a gelling property. For example, starch-acrylic acid (salt) graft copolymer Preferred examples thereof include saponified polymers, saponified products of starch-acrylonitrile copolymers, crosslinked products of sodium carboxymethyl cellulose, and acrylic acid (salt) polymers.

As shown in FIGS. 1 and 2, the absorbent body 4 in the present napkin 1 has a laminated portion 40 in which an upper absorbent layer 41 and a lower absorbent layer 42 are laminated at the center in the width direction of the napkin 1. Yes. In the laminated portion 40, the upper absorbent layer 41 is located on the skin contact surface 2 side, and the lower absorbent layer 42 is located on the non-skin contact surface 3 side. The laminated portion 40 in the napkin 1 is formed at a position slightly deviated from the front end portion or the rear end portion in the longitudinal direction of the napkin 1.
The layered portion 40 of the napkin 1 is formed in an excretion portion facing portion that is disposed to face the excretion portion of the wearer when worn. The position of the laminated portion 40 can be appropriately determined depending on the position of the site corresponding to the excretion part of the wearer in the napkin 1 or other absorbent article.

Laminated portion 40 of the absorbent core 4 in the napkin 1 is under 0.5 g / cm ² load, but the apparent density of the lower absorbent layer 42 is lower than the apparent density of the upper absorbent layer 41, 20 g / cm ² under a load The apparent density of the lower absorbent layer 42 is the same as the apparent density of the upper absorbent layer 41 or higher than the apparent density of the upper absorbent layer 41. Under a load of 0.5 g / cm ² The pressure is assumed in a state where the napkin (absorbent article) is lightly brought into contact with the skin before or at the start of wearing. Under 20 g / cm ² load, the pressure in a state in which a napkin (absorbent article) is fixed and worn on a wearing tool such as shorts is assumed. Both assume a stationary state.

In the napkin 1, since the apparent density of the lower absorbent layer 42 under a load of 0.5 g / cm ² (hereinafter also referred to as low pressure) is set lower than the apparent density of the upper absorbent layer 41, the napkin 1 is attached. In this case, the lower absorbent layer 42 is pressed flexibly in the thickness direction by being pressed by the upper absorbent layer 41, so that the touch of the laminated portion 40 against the skin of the wearer is soft, and the excretory part due to its good deformability Etc. can be fitted well.
Further, the excreted liquid is smoothly taken into the upper absorbent layer 41, and even if the upper absorbent layer 41 absorbs the liquid, the upper absorbent layer 41 is difficult to sag, and the thickness of the upper absorbent layer 41 or the laminated portion 40 can be reduced. The shape is kept stable during wearing. Therefore, the fitting property with respect to the excretion part etc. of the lamination | stacking part 40 during wear is maintained favorably.

On the other hand, under a load of 20 g / cm ² (hereinafter, also referred to as a mounted state), the apparent density of the lower absorbent layer 42 is the same as the apparent density of the upper absorbent layer 41 or from the apparent density of the upper absorbent layer 41. Therefore, in the mounted state, the liquid is smoothly drawn from the upper absorbent layer 41 to the lower absorbent layer 42 due to the density gradient. Therefore, even in a state where the absorbent body 4 has absorbed a certain amount of liquid, inconvenience such as liquid return (wet back) from the absorbent body 4 to the skin contact surface hardly occurs, and a light and comfortable wearing feeling can be obtained.

From the viewpoint of improving the flexibility and fit when the napkin 1 is worn while preventing the upper absorbent layer 41 from sag after liquid absorption, and the upper absorbent layer 41 and the lower part under low pressure and in a worn state. From the viewpoint of enabling the reversal of the apparent density with the absorption layer 42 (including the case where they are the same) and realizing good drawability of the liquid into the lower absorption layer 42, the upper portion of the stacked portion 40 at a low pressure. apparent density ρA absorbent layer 41 is preferably 0.05~0.25g / cm ^3, more preferably 0.08~0.20g / cm ^3, more preferably 0.10~0.15g / cm ^3, apparent density ρB of the lower absorbent layer 42 is preferably 0.05~0.20g / cm ^3, more preferably 0.05~0.15g / cm ^3, more preferably 0.08~0.12g / cm ³ The ratio (ρA / ρB) of the two is 1. 5 to 5.0, more preferably from 1.1 to 3.0, more preferably 1.2 to 2.0.

The upper absorbent layer 41 in the laminated portion 40 in the mounted state is realized from the viewpoint of realizing excellent liquid pull-in property and liquid return preventing property in the mounted state, and establishing the relationship of ρA> ρB under low pressure. apparent density ρA of 'is preferably 0.05~0.25g / cm ^3, more preferably 0.08~0.20g / cm ^3, more preferably 0.10~0.15g / cm ^3, the lower absorbent apparent density .rho.B 'is layer 42, preferably 0.07~0.3g / cm ^3, more preferably 0.10~0.25g / cm ^3, more preferably 0.12~0.20g / cm ^3, The ratio (ρA ′ / ρB ′) of both is preferably 0.20 to 1.0, particularly 0.3 to 0.90.

  Furthermore, the change in the liquid drawing property under low pressure and in the mounted state is small (that is, the liquid drawing property is stabilized), and from the viewpoint of suppressing the shape change and stabilizing the local fit, the lower pressure in the upper absorbent layer 41 is reduced. The ratio (ρA / ρA ′) of the apparent thickness to the mounting state is preferably 1.0 to 2.0, more preferably 1.05 to 1.5, and still more preferably 1.05 to 1.3. From the viewpoint of good cushioning properties and good liquid mobility from the upper absorbent layer 41 to the lower absorbent layer 42, the ratio of the apparent thickness (ρB / ρB ′) of the lower absorbent layer 42 between the low pressure state and the mounted state is as follows. 1.1 to 3.0, and particularly preferably 1.2 to 2.5.

The method for measuring the apparent density of the upper absorbent layer 41 and the lower absorbent layer 42 is performed as follows.
<Measurement method of apparent density under load>
Using a compression tester (for example, a handy compression tester “KES-G5” manufactured by Kato Tech Co., Ltd.), the laminated portion of the absorber is loaded in the thickness direction at a speed of 0.2 mm / sec with a load of 20 g / cm ^2. Compress until Measure the thickness of the laminated part from the chart when the load reaches 0.5 g / cm ^{2 and} when the load reaches 20 g / cm ² (or set the data of the compression tester so that it can be read by a computer etc.) To do). The measurement is performed three times using three samples, and the average result is defined as the “apparent thickness” at each time point. Next, the laminated portion of the absorber is cut (in this case, using a sharp blade or the like so that the state of the cut surface does not change from that before cutting. Feather Safety Razor Co., Ltd., part number FAS-10 was used), The cut surface is adjusted to the “apparent thickness” at each time point by sandwiching the upper surface / lower surface with an acrylic plate and adjusting the load. This is observed with a microscope (VH8000) manufactured by Keyence, respectively, and the thickness from the upper surface (surface on the skin contact surface side) of the upper absorbent layer to the boundary surface and from the boundary surface of the lower absorbent layer to the non-skin contact surface Was measured respectively. Moreover, the weight of each of the upper absorbent layer and the lower absorbent layer was measured, and the apparent density under each load was determined from the measured weight and the thickness measured as described above.

In this napkin 1, as shown in FIG.2 and FIG.3, the upper absorption layer 41 in the lamination | stacking part 40 is embossed, and, thereby, the density of the upper absorption layer 41 (even other than an embossing part) is carried out. Increased so that the density changes less with increasing load.
Specifically, a large number of pressing recesses 41a having a circular shape in plan view are formed on the surface of the upper absorbent layer 41 in the laminated portion 40 on the lower absorbent layer 42 side by embossing. On the other hand, a portion corresponding to the upper absorbent layer 41 in the lower absorbent layer 42 is not subjected to such embossing, and therefore the lower absorbent layer 42 in the laminated part 40 is pressed by the upper absorbent layer 41. The thickness is easily reduced and the density is greatly increased. The density of the pressing recess 41a is preferably 0.2 to 0.7 g / cm ³ , and more preferably 0.4 to 0.6 g / cm ³ , from the viewpoint of improving the drawability of the liquid.

The pulp basis weight of the upper absorbent layer 41 in the laminated portion 40 is preferably 100 to 500 g / m ² , particularly 200 to 400 g / m ² , and the thickness of the upper absorbent layer 41 under low pressure is 1 to 5 mm, particularly It is preferable that it is 2-4 mm.
The basis weight of the lower absorbent layer 42 in the laminated portion 40 is preferably 50 to 400 g / m ² , particularly 200 to 300 g / m ² , and the thickness of the lower absorbent layer 42 under low pressure is 0.5 to 4 mm, In particular, it is preferably 1 to 3 mm.

  In the napkin 1, as described above, the compressed portion 41 a is formed on the surface of the upper absorbent layer 41 on the lower absorbent layer 42 side in the laminated portion 40, so that the lower absorbent layer 42 of the upper absorbent layer 41 is formed. The surface-to-plane contact area of the side surface (also referred to as the contact area of the upper absorption layer 41) is larger than the surface-to-plane contact area of the surface of the lower absorption layer 42 on the upper absorption layer 41 side (also referred to as the contact area of the lower absorption layer 42). Is also getting smaller. The contact area with the plane is an area of a portion where the upper absorbent layer and the lower absorbent layer press the mating surface (assumed to be a plane) at the boundary between them.

  Since the contact area of the upper absorbent layer 41 is smaller than the contact area of the lower absorbent layer 42, the upper absorbent layer 41 can partially and strongly compress the lower absorbent layer 42 with a small area in the mounted state. This is because when the load applied to the upper absorbent layer and the load transmitted to the lower absorbent layer are considered to be substantially the same, the contact area of the upper absorber is made small at the boundary surface, so the contact area at the actual contact portion is This is because a larger load than the reduced amount is applied (further, the load transmitted to the lower absorbent layer is considered to increase by the upper absorbent layer). Thereby, the density of the contact part in a lower absorption layer becomes large, and the drawing-in property of a liquid improves further combined with the effect of the density increase by being unembossed.

As means for reducing the contact area of the upper absorbent layer 41 (also referred to as contact area reduction means), in addition to embossing, through-hole processing, adhesive impregnation, and the like can be used. It is possible to increase the overall density without reducing the absorption capacity, and the density gradually increases toward the embossed part in the absorber, and a rigid structure (column structure) It is particularly preferable to make it because it has a high drawability of the liquid and does not sag during absorption of the liquid and fits the body.
The contact state of the upper absorbent portion and the lower absorbent portion in the minute region is partially due to a part of the lower absorbent layer forming a lower density than the surrounding area in the compressed recess of the upper absorbent portion, exceeding the boundary (virtual) surface. Although it is thought that the liquid movement from the upper absorbent body to the lower absorbent body is performed at a place other than the compressed recess of the upper absorbent body, there is no particular effect on the absorbability. .

The contact area between the upper absorbent layer 41 and the lower absorbent layer 42 is measured as follows.
<Measuring method of contact area of upper absorbent layer 41>
The contact area of the upper absorbent layer is measured by the following method. A sample is cut out in a size of 60 mm × 100 mm, and the surface of the sample on the lower absorbent layer side on a stamp stand made by Mitsubishi Pencil Co., Ltd. [Unistamp (trade name), red, stamp size 65 mm × 105 mm]. Is placed on the stamp side, and is allowed to stand for 30 seconds in a state of being pressurized with an acrylic plate (80 mm × 120 mm) having a thickness of 5 mm and a weight. At this time, the total weight of the acrylic plate and the weight is adjusted to 1.2 kg (equivalent to 20 g / cm ² ). After removing the stamp base and the weight, an image of the surface of the sample on the lower absorption layer side (surface colored by the stamp) is captured. To capture the image, use the center of the sample, use two [Sunlight SL-230K2; made by LPL Co., Ltd.] as the light source, and use a CCD camera (HV-37; made by Hitachi Electronics Co., Ltd.). ) And a lens (Ai AF Nikol 24 mm F2.8D manufactured by Nikon) were connected by an F mount, and an image was captured and processed using a Nexus NewQube (Ver. 4.22). In the image processing, the area of the portion other than the emboss colored with the stamp by “binarization” is obtained as the “contact area ratio”. (Actually, after “manual binarization”, morphology processing such as “hole filling” and “particle removal” is performed to optimize the colored portion, and “particle shape measurement” obtains the area ratio = “contact area ratio”. (The area ratio was obtained by “the number of pixels in the colored portion” / “all pixels on the screen 640 × 480” × 100.)

<Measuring method of contact area of lower absorbent layer 42>
The lower absorbent layer is the same as the method for measuring the contact area of the upper absorbent layer 41 described above except that the surface on the non-skin contact surface side faces up and the surface on the upper absorbent layer side of the sample is the stamp side. To measure.
The contact area ratio in the upper absorbent layer is preferably 60 to 100%, particularly preferably 70 to 95%, and more preferably 80 to 90%. The contact area ratio in the lower absorption layer is almost 100%.

  The napkin 1 has a shape having a longitudinal direction and a width direction. As shown in FIG. 2, the lower absorbent layer 42 is outward from the laminated portion 40 in each of the longitudinal direction and the width direction of the napkin 1. It is extended. By extending at least one of the upper absorbent layer 41 and the lower absorbent layer 42 in the width direction, a raised portion in which the laminated portion 40 protrudes toward the skin contact surface side can be formed in the center portion in the width direction of the napkin 1. It is possible to improve the fit of the wearer to the excretory part and the like. In the present napkin 1, as described above, a raised portion is formed at a portion corresponding to the excretory portion, but instead of this, or at the same time, a raised portion may be formed at a portion corresponding to the rupture. it can.

  In this napkin 1, as shown in FIG.2 and FIG.3, the part 44 extended outward from the lamination | stacking part 40 in the lower absorption layer 42 is also the same as the pressing recessed part 41a of the upper absorption layer 41 mentioned above. The pressing recess 44a is formed by the same embossing. By forming the pressing recess 41a in the extended portion 44 from the laminated portion 40 by embossing, the diffusibility of the liquid in the direction parallel to the surface of the lower absorbent layer 42 can be improved, and the liquid from the surface can be improved. Can be further improved. Thereby, the smooth feeling of a skin contact surface can be improved further. The same effect can be obtained when the surface contact area of the portion 44 extending outward from the laminated portion 40 is reduced by means other than embossing as described above as the contact area reducing means of the upper absorbent layer 41. Is obtained.

  Since the upper absorbent layer penetrates into the lower absorbent layer in the mounted state, the upper absorbent layer and the lower absorbent layer are not easily displaced, particularly in the case where the upper absorbent layer is smaller as in the form of FIG. It is valid. Furthermore, as shown in FIG. 1, the contact surface with the lower absorption layer is uneven so that it is more difficult to shift.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, instead of extending the lower absorbent layer 42 from the laminated portion 40 as in the napkin 1, the upper absorbent layer 41 can be extended as shown in FIG. 4B. Even in such a case, a raised portion having excellent fit can be formed in a portion corresponding to the excretion portion. Furthermore, the absorber in the present invention, as shown in FIG. 4 (d), but it may also comprise only stacked portion 40.
Further, in place of the lower absorbent layer 42 of the absorbent body 4 in the napkin 1, as shown in FIG. 4A, the thickness of the laminated portion 40 and the thickness of the portion extending from the laminated portion 40 are uniform. Layer 42 can also be used. In addition, about the absorber shown in FIG. 4, the code | symbol same as the code | symbol used for the napkin 1 is attached | subjected to the component similar to the absorber in the napkin 1 mentioned above.

  Moreover, the planar view shape of the compression recessed part 41a, 41b, 44a can be made into arbitrary shapes, such as an ellipse, an egg shape, a triangle, a rectangle, a square, a star shape, a heart shape other than circular. Moreover, each pressing recessed part can be made into the thing of continuous shapes, such as parallel line form or a grid | lattice form, instead of a discontinuous thing. Moreover, in order to improve leak-proof property with these pressing recessed parts, a pressing groove can also be formed along the both sides of the laminated part of a napkin, and its periphery. If a pressing groove is formed, high leakproofness can be imparted while maintaining the drawability of the liquid in the pressing recess.

Moreover, you may extend a surface sheet and coat | cover a back sheet. Further, it is possible to form a flap extending from both sides and rub it to the crotch portion of the underwear or to use it by spreading it on the bottom of the underwear. The lower absorbent layer may be embossed.
The absorbent article of the present invention may be a panty liner, an incontinence pad, a disposable diaper, etc., in addition to a sanitary napkin. The present invention is particularly suitable for those that are fixedly mounted on a mounting tool such as shorts.

FIG. 1 is a plan view showing part of a sanitary napkin according to an embodiment of the present invention. 2A and 2B are schematic cross-sectional views schematically showing a cross section taken along the line XX of FIG. 1, in which FIG. 2A is a view showing a substantially unloaded state, and FIG. 2B is a view showing a mounted state. FIG. 3 is a plan view showing a state in which the absorbent body in the sanitary napkin of FIG. 1 is separated into an upper absorbent layer and a lower absorbent layer, and each is viewed from the non-skin contact surface side. FIG. 4 is a schematic cross-sectional view showing a cross-section in the width direction of an absorbent body according to another embodiment of the present invention.

Explanation of symbols

1 Sanitary napkin (absorbent article)
2 Skin contact surface 21 Top sheet 3 Non-skin contact surface 31 Back sheet 4 Absorbent body 40 Laminated portion 41 Upper absorbent layer 41a Squeezed recess (contact area reducing means)
42 Lower absorption layer 44 A portion extending from the laminated portion

Claims (5)

An absorbent article having a skin contact surface, a non-skin contact surface and an absorbent body interposed between both surfaces,
The absorber has a laminated portion in which an upper absorbent layer and a lower absorbent layer are laminated, the upper absorbent layer is located on the skin contact surface side, and the lower absorbent layer is on the non-skin contact surface side Located in the
In the laminated portion of the absorber, the apparent density of the lower absorbent layer is lower than the apparent density of the upper absorbent layer under a load of 0.5 g / cm ^{2, and} the apparent density of the lower absorbent layer is higher under a load of 20 g / cm ^2. It is made to be the same as the apparent density of the absorbent layer or higher than the apparent density of the upper absorbent layer,
In the laminated portion, the surface-to-plane contact area of the surface of the upper absorption layer on the lower absorption layer side is smaller than the surface-to-plane contact area of the surface of the lower absorption layer on the upper absorption layer side,
Under a load of 20 g / cm ² , in the lower absorbent layer, the density of the contact portion in contact with the upper absorbent layer is higher than the density of the non-contact portion not in contact with the upper absorbent layer, and the non-contact portion is An absorbent article that has entered the upper absorbent layer side beyond the position of the contact boundary surface between the contact portion and the upper absorbent layer in the thickness direction of the absorbent body . The surface of the lower absorbent layer side of the upper absorbent layer in the stacked portions, the absorbent article according to claim 1, wherein the pair of planar contact area by embossing are reduced. The absorbent article according to claim 1, wherein the upper absorbent layer has a flat surface on the skin contact surface side.   The absorbent article has a longitudinal direction and a width direction, and the upper absorbent layer or the lower absorbent layer extends outward from the laminated portion at least in the width direction of the absorbent article. An absorbent article according to any one of the above.   The absorptive article according to claim 4 in which processing which reduces a surface contact area is given to a field by the side of said non-skin contact surface of a portion extended from said lamination part in an upper part absorption layer or a lower part absorption layer. .

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