JP2010083915A - Peeling sheet for forming unevenness on adhesive layer surface of adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a peeling sheet for producing an adhesive sheet which is excellent in a property for preventing the holding of bubbles and in a readhering property and does not cause the deterioration of adhesiveness. <P>SOLUTION: There is provided the peeling sheet for forming unevenness on the adhesive layer surface of the adhesive sheet, characterized by two-dimensionally continuously forming protections upward projected from an upside horizontal standard surface contacting with the adhesive layer, two-dimensionally repeatedly forming dents having prescribed shapes surrounded with the projections, and forming many fine dents downward sunk from the standard surface on the bottom surfaces of the dents, wherein on the upper side of the peeling sheet, an area occupied by the dents on the standard surface per the total area of the area occupied by the projections and the area occupied by the dents is 40 to 60%; the heights of the projections are 7 to 35 μm; the fine dents are formed at a rate of 5 to 1,000 fine dents per dent on the average; the depths of the fine dents are 3 to 15 μm; and the major axis of the cross section of the fine dent is 3 to 15 μm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention can be re-applied a plurality of times, and is used to obtain a pressure-sensitive adhesive sheet that can be stuck to an adherend without involving air on the sticking surface. The present invention relates to a release sheet capable of forming a structure.
Furthermore, this invention relates to the adhesive sheet provided with this peeling sheet.

The pressure-sensitive adhesive sheet is generally a method such as a method in which a pressure-sensitive adhesive is applied to a substrate and dried, and then a release sheet is bonded, or a method in which a pressure-sensitive adhesive is applied to a release sheet and then dried, and then a method in which the substrate sheet is bonded It is produced by.
This pressure-sensitive adhesive sheet has a smooth surface of the pressure-sensitive adhesive layer, and since there is no air escape when affixed to an adherend, it is easy to entrain air, that is, air bubbles are easily formed. Problems of poor quality and poor appearance.

As a method for improving this problem, various types of pressure-sensitive adhesive films have been proposed in which unevenness is provided on the surface of the pressure-sensitive adhesive layer, and the surface of the release sheet is non-smoothed so as to form air passages when being stuck.
For example, a pressure-sensitive adhesive sheet having an adhesive layer having a large number of independent small convex portions has been proposed as a technique for preventing the so-called “blowing” of fine bubbles at the time of sticking (Patent Document 1). And 2).
In addition to preventing the above-mentioned “blowing”, the pressure-sensitive adhesive sheet has a small contact area because only the tip of the small convex portion of the pressure-sensitive adhesive layer is in close contact with another object when lightly applied. For this reason, it is said that re-sticking is possible. And if it presses strongly against an object, it will not come off unexpectedly, or if a predetermined time passes after sticking, a small convex part will carry out plastic deformation, an adhesion area will increase, and strong adhesive force will generate | occur | produce.

Moreover, in the adhesive processing film comprised from an adhesive film main body and a peeling film, what provided the narrow groove continuous with the predetermined pattern of a grid | lattice form etc. in the adhesive surface side of the adhesive film main body is proposed (patent document 3). .
Furthermore, a release liner having a fine embossing pattern composed of a large number of interconnected linear ridges for forming fine grooves on the adhesive surface for allowing fluid to flow out at the adhesive interface has been proposed ( Patent Document 4).
Noto 2503717 Noto 2587198 gazette JP-A-7-138541 JP 2006-70273 A

  Moreover, the pressure-sensitive adhesive processing sheet described in Patent Document 1 or 2 not only prevents “blowing” at the time of sticking, but also causes “blowing” due to gas generated from plastic, which can occur when sticking to a certain kind of plastic, for example. It can also be prevented. That is, even if the predetermined time has elapsed, a communication gap for eliminating “blowing” is generated, and the entire adhesive surface is not in close contact with the adherend, leading to a decrease in adhesive strength. Has the problem.

The adhesive-processed film described in Patent Document 3 has a relatively large mutual space between the narrow grooves, 3 mm to 20 mm, and a width dimension W of the narrow grooves of 0.1 mm to 2.0 mm. Set to dimensions. For this reason, the re-sticking property of the pressure-sensitive adhesive processed film is not good, and fine bubbles may be included. Furthermore, even after the adhesive film is pasted, the fine groove is visible without being smoothed, and the contact area with the adherend is reduced, leading to a decrease in adhesive strength. Have a problem.

  Moreover, the release liner described in Patent Document 4 has a specific numerical range (60 to 97) with respect to the total area of the release liner surface and the area ratio of the land portion defined by the linear protrusion provided on the liner surface. %), It is intended to improve the ability to remove air and the like, but there is room for improvement, particularly in terms of facilitating multiple reattachments immediately after application.

  In this way, by providing a groove or small convex part on the surface of the pressure-sensitive adhesive layer, it is possible to prevent entrainment of bubbles when sticking the pressure-sensitive adhesive sheet, or to re-apply a plurality of times immediately after sticking, after a predetermined time Has been proposed as a method for improving the so-called “re-stickability”, which exhibits strong adhesive strength, but there are some which are difficult to remove if there are fine bubbles when sticking an adhesive sheet. In addition, there are problems that the appearance of the adhesive surface after application is impaired, or that the adhesive strength itself is reduced.

  The present invention has been made in view of the above-mentioned problems, and is a peel for providing a pressure-sensitive adhesive sheet that is excellent in bubble entrapment prevention property (bubble removal property) and reattachability, and does not cause a decrease in adhesiveness. Provide a sheet. In detail, even when the adhesive sheet is applied to a location that is off the target position, it can be easily applied again, without causing air bubbles to be embraced at the time of application and forming a “bulge”. It is related with the peeling sheet which has an unevenness | corrugation in the surface which contacts the adhesive layer for forming the adhesive layer with favorable adhesiveness with respect to a to-be-adhered body in the adhesive sheet.

  In the release sheet having irregularities on the surface, the present inventors form convex portions so that the concave portions are repeatedly formed in a predetermined shape two-dimensionally, and a large number of bottom surfaces of the concave portions surrounded by the convex portions. It has been found that the structure of providing the minute recesses can improve air entrapment when the release sheet is stacked on the surface of the pressure-sensitive adhesive layer provided on the upper surface of the pressure-sensitive adhesive sheet and pressure-bonded. Furthermore, when the release sheet is pressure-bonded to the surface of the pressure-sensitive adhesive layer, the release sheet convex portions, concave portions and minute concave portions are transferred to the pressure-sensitive adhesive layer surface, and a pressure-sensitive adhesive layer having concave portions, convex portions and fine convex portions is formed on the surface. It is found that the problem of air entrainment that occurs when the pressure-sensitive adhesive sheet is stuck to the adherend surface, the improvement of reattachability to the adherend surface of the pressure-sensitive adhesive sheet, and the decrease in pressure-sensitive adhesive force can be solved. Completed the invention.

  That is, the present invention is a release sheet for forming irregularities on the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheet, and the upper surface of the release sheet is located above the upper horizontal reference surface in contact with the pressure-sensitive adhesive layer. Protruding convex portions are continuously provided two-dimensionally, and a predetermined-shaped concave portion surrounded by the convex portions is repeatedly formed two-dimensionally, and a bottom surface of the concave portion is formed with respect to the reference surface. In the upper surface of the release sheet, the area occupied by the convex portion on the reference surface is the total area of the area occupied by the convex portion and the area occupied by the concave portion. 40 to 60%, the height of the convex part is 7 to 35 μm, the average number of the minute concave parts is 5 to 1000 per concave part, and the depth is 3 to 15 μm, Long diameter of cross section Relates to a release sheet, which is 3 to 15 μm.

In the release sheet, it is preferable that the minute concave portion has a depth of 3 μm to 10 μm and a major axis of the transverse section thereof is 3 to 10 μm.
Moreover, it is preferable that the width | variety of the convex part between the said recessed part and the adjacent recessed part is 10 micrometers-500 micrometers.

And when the said convex part is continuously formed in a grid | lattice form two-dimensionally, it is preferable that the substantially rectangular recessed part enclosed by this convex part has a long side with a length of 17.2 micrometers-1720 micrometers. .
Or when the said recessed part makes round shape, it is preferable that the space | interval of this recessed part and an adjacent recessed part is 80 micrometers-1400 micrometers.

In the present invention, the surface of the pressure-sensitive adhesive layer formed on the base sheet is laminated and pressure-bonded to the surface of the pressure-sensitive adhesive layer, whereby the shape of the convex portion, the concave portion and the minute concave portion of the release sheet is changed to the surface of the pressure-sensitive adhesive layer. The present invention relates to a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer that is transferred to the surface and formed with concave portions, convex portions, and minute convex portions.
The pressure-sensitive adhesive sheet is provided with a pressure-sensitive adhesive layer having an elastic modulus such that the micro-projections disappear with time in a state in which the release sheet is peeled and pasted, and is deformed into a smooth surface, in particular 2 × It is preferable to have a storage elastic modulus of 10 ⁴ Pa to 2 × 10 ⁵ Pa.
Moreover, it is preferable that the said adhesive layer is formed with the adhesive which does not contain a crosslinking agent.

The release sheet of the present invention includes a convex portion formed two-dimensionally continuously on the upper surface of the release sheet, a concave portion surrounded by the convex portion and repeatedly formed two-dimensionally in a predetermined shape, and the concave portion By pressing the concaves and convexes formed by a large number of concave portions provided on the bottom surface of the adhesive sheet onto the adhesive surface of the adhesive sheet, concave portions, convex portions and minute convex portions having a predetermined shape can be easily formed (transferred) on the adhesive surface. )can do.
Further, the release sheet of the present invention has an air interface at the interface when pressing the release sheet and the pressure-sensitive adhesive layer provided on the upper surface of the adhesive sheet base material by the concave and convex portions formed on the base material of the release sheet. In comparison with the prior art, the air can be easily pushed out by pressing even when air is held.

The pressure-sensitive adhesive sheet of the present invention is adhered to the adhesive surface without entrapment of bubbles when the pressure-sensitive adhesive sheet is applied to the adherend by the concave and convex portions formed on the pressure-sensitive adhesive layer by being transferred from the release sheet. In addition, even when bubbles are involved, the bubbles can be easily removed and pasted.
In other words, the concave portion of the pressure-sensitive adhesive layer is formed by the convex portion of the release sheet, and on the upper surface of the convex portion of the pressure-sensitive adhesive layer surrounded by the concave portion, a micro-projection (micro-convex portion) formed by the micro concave portion of the release sheet ) Is formed. This comes into contact with the adherend and is flattened over time due to the flow of the pressure-sensitive adhesive, but the bubbles generated at this time move with the flow of the pressure-sensitive adhesive and escape to the surrounding recesses, so that the generation of bubbles as a whole can be prevented. .
Furthermore, after the adhesive sheet is attached to the adherend by the minute convex portions formed on the adhesive layer, it can be easily attached to the target location.

  The pressure-sensitive adhesive sheet of the present invention includes a pressure-sensitive adhesive layer having an elastic modulus such that the minute convex portion disappears with time and is deformed into a smooth surface while the release sheet is peeled and pasted. As time elapses, the minute projections are plastically deformed to increase the contact area, and a strong adhesive force can be expressed.

As described above, various methods have been proposed so far in which concave grooves and small convex portions are provided on the surface of the pressure-sensitive adhesive layer to prevent entrainment of bubbles when sticking the pressure-sensitive adhesive sheet and to improve re-stickability. However, conventional methods cannot sufficiently overcome these problems, such as the prevention of entrainment when the bubbles are fine, or the decrease in the adhesive strength of the pressure-sensitive adhesive layer. That left a problem.

First of all, the inventors of the present invention have a pressure-sensitive adhesive that does not impair the adhesive force and has good bubble detachability in forming a groove or the like serving as a void hole for preventing bubble entrainment in the pressure-sensitive adhesive layer. The adhesion area of the layer to the adherend was examined. That is, in order to improve the adhesive strength, it is desired that the adhesive area is large, and preferably the entire surface of the pressure-sensitive adhesive layer is in close contact with the adherend (there is no groove or the like in the pressure-sensitive adhesive layer). For this, it is preferable to increase the proportion of grooves and the like formed in the pressure-sensitive adhesive layer to reduce the bonding area.
And in order to make these adhesive force and securing of bubble detachability compatible, the present inventors set the adhesion area with the adherend within a range of 40 to 60% with respect to the total area of the pressure-sensitive adhesive layer surface. The most preferable point is found, and the present invention has been completed. Therefore, this configuration is one of the main features of the present invention.

Moreover, in order to improve the reattachability of an adhesive sheet, it is preferable that the contact | adherence area with the to-be-adhered body per location is small, ie, it is a shape which has a microprotrusion. However, when the shape of such a “microprojection” is increased, the total adhesion area becomes very small as the number of projections is increased, and a decrease in adhesive strength cannot be denied.
The inventors of the present invention have an elastic modulus, specifically 2 × 10 ⁴ Pa to 2 × 2 such that the fine protrusions disappear with time when the adhesive layer is applied to the adhesive sheet and deform into a smooth surface. It has been found that by having a storage elastic modulus of × 10 ⁵ Pa, it adheres to the entire surface after a lapse of a considerable time, and a strong adhesive force can be realized. Therefore, the present invention has such a configuration as another feature.

  Furthermore, the detailed structure regarding the peeling sheet and adhesive sheet of this invention is demonstrated below.

[Peeling sheet]
As a material for the release sheet used in the present invention, a film such as a PET (polyethylene terephthalate) film or an OPP (biaxially stretched polypropylene) film, a polyethylene laminated paper obtained by laminating polyethylene on paper, or the like can be used.
In addition, polyethylene such as PET film and OPP film can be laminated and embossed on the polyethylene part.

In the release sheet of the present invention, the upper surface of the release sheet is provided with a convex portion that protrudes upward with respect to the upper horizontal reference surface that is in contact with the pressure-sensitive adhesive layer. A recess having a predetermined shape surrounded by the two-dimensionally is repeatedly formed in two dimensions, and a number of minute recesses recessed downward with respect to the reference plane are formed on the bottom surface of the recess.
And in the said peeling sheet upper surface, the area which the said convex part occupies in the said reference surface is 40 to 60% with respect to the total area of the area which the said convex part occupies, and the area which the said recessed part occupies.

  The upper horizontal reference plane in contact with the above-mentioned pressure-sensitive adhesive layer protrudes upward and is formed two-dimensionally continuously, and is surrounded by the convex portions and is two-dimensionally formed in a predetermined shape. 1 to 8 will be described in detail with respect to the recesses repeatedly formed and a number of minute recesses formed on the bottom surface of the recesses. However, the convex portions and concave portions shown in FIGS. 1 to 8 are merely examples, and are not limited to the size and shape shown in the drawings.

Fig.1 (a) shows the figure which expanded a part when the state projected on the reference plane of the peeling sheet 1 in which the convex part 2 was continuously formed two-dimensionally in a lattice shape was seen from above. Is. The vertical direction in the figure indicates the length direction of the release sheet. FIG. 1B is a view showing a cross section (cross section (transverse section) orthogonal to the longitudinal direction) orthogonal to the AA ′ plane in FIG.
As shown in FIGS. 1 (a) and 1 (b), the upper surface of the release sheet 1 has a convex portion 2 protruding upward with respect to the upper horizontal reference plane XX ′ in contact with the adhesive layer, A concave portion 3 surrounded by the convex portion 2 is formed, and a number of minute concave portions 4 that are recessed downward with respect to the reference plane XX ′ are formed on the bottom surface of the concave portion 3.

  For the total area of the area occupied by the convex portion and the area occupied by the concave portion with respect to the reference surface, the area occupied by the convex portion is, for example, the convex portion and the concave portion of FIGS. In the case of the release sheet having, it is calculated as follows. 2 and 3 both show a partially enlarged view of the release sheet 1 as viewed from above, and the vertical direction of the figure shows the length direction of the release sheet.

For example, as shown in FIG. 2, when the state projected onto the reference surface of the release sheet 1 is viewed from above, the convex portion 2 having a width a and formed in a lattice shape is surrounded by the convex portion 2. In the case of a release sheet in which a substantially rectangular (square) concave portion 3 having a long side x is repeatedly formed as the region, the area of the upper surface of the release sheet, that is, the total area of the convex portion 2 and the concave portion 3 is [(x + a) ² ]. Converted to The area of the convex portion 2 is converted to [2ax + a ² ], and the area of the concave portion 3 is converted to [x ² ].
Therefore, when the release sheet of the present invention has the shape shown in FIG. 2, the release sheet has a rectangular lattice-like unevenness that satisfies 40 <[2ax + a ² ] / [(x + a) ² ] × 100 <60. The Rukoto. Here, paying attention to the convex portion of the pressure-sensitive adhesive layer (the concave portion 3 of the release sheet), 40 <[x ² ] / [(x + a) ² ] × 100 <60, and the above formula is 1.72a <x <3.44a. Converted to

As shown in FIG. 3, when the state projected onto the reference surface of the release sheet is viewed from above, in the release sheet in which the round-shaped (circular) recesses 3 having a radius b are formed at intervals y, The area of the upper surface of the release sheet, that is, the total area of the convex part 2 and the concave part 3 is [y ² ], the area of the convex part 2 is [y ² −b ² π], and the area of the concave part 3 is [b ² π ].
Therefore, when the release sheet of the present invention has the shape shown in FIG. 3, the release sheet has a circular recess that satisfies 40 <[y ² −b ² π] / [y ² ] × 100 <60. Concavities and convexities are formed, and the above equation is converted to 2.29b <y <2.8b (assuming π = 3.14).

Here, the width a of the convex portion 2 in FIG. 2 or the width of the convex portion 2 in FIG. 3, that is, the width y-2b of the concave portion 3 and the adjacent concave portion 3 is the bubble size when transferred to the adhesive layer. Considering only ease of removal, it is preferably approximately 10 μm to 1000 μm.
However, it is not preferable that the recess formed by being transferred to the pressure-sensitive adhesive layer is clearly visible from the back side after being applied.
For this reason, as a result of these considerations, the width of the concave portion provided in the pressure-sensitive adhesive layer (that is, the width of the convex portion between the concave portion of the release sheet and the adjacent concave portion) is 10 μm to 500 μm, preferably 10 μm to 200 μm. It is preferable.

Considering the width of the convex portion of the release sheet, for example, x in FIG. 2 and y in FIG. 3 are calculated as follows.
That is, in FIG. 2, the width “a” of the convex portion of the release sheet is 10 μm to 500 μm. If the width “a” is 10 μm, x becomes a value of 17.2 μm to 34.4 μm.
In FIG. 3, since y-2b is 10 μm to 500 μm, if y-2b is 10 μm, b is 35 μm or more, and the possible value of y at this time is about 80 μm to 98 μm.

As described above, when the convex portion 2 is formed in a lattice shape two-dimensionally (eg, FIG. 2), the substantially rectangular concave portion surrounded by the convex portion has a long side of 17.2 μm to 1720 μm. In addition, when the recess 3 has a round shape (for example, FIG. 3), the interval between the recess 3 and the adjacent recess 3 is preferably 80 μm to 1400 μm.

  In addition, the shape of the convex part provided in the peeling sheet of this invention and the recessed part which has the predetermined shape enclosed by this convex part is convex part: grid | lattice form-concave part: rhombus (FIG. 4), convex part: lattice form- The concave portion may be various, such as a parallelogram (FIG. 5), or the concave portion: an ellipse (FIG. 6) (note that FIGS. 4 to 6 are all projected onto the reference plane of the release sheet 1). The figure which expanded the one part when a state is seen from upper direction is shown, and the up-down direction of a figure has shown the length direction of the peeling sheet.

As shown in FIG. 7, the convex portion has a quadrangular shape (FIG. 7A), a trapezoid shape (FIG. 7B), a triangular shape (FIG. 7C), and a semicircular shape (see FIG. 7). 7 (d)), and can have various shapes such as a dome shape such as a combination of a quadrangle and a semicircle (FIG. 7 (e)) or an ellipse (FIG. 7 (f)). It is desirable to have a cross section.
The height of the convex portion from the reference surface is 7 to 35 μm, more preferably 7 to 25 μm.

The bottom surface of the recess 3 is provided with a number of minute recesses 4 that are recessed downward with respect to the upper horizontal reference plane XX ′ in contact with the pressure-sensitive adhesive layer (see FIG. 1B).
The minute concave portion 4 becomes a minute convex portion when transferred to the pressure-sensitive adhesive layer, and has a function of improving the reattachability of the pressure-sensitive adhesive sheet.
From this point of view, the depth of the minute recess 4 is 3 μm to 15 μm, preferably 3 μm to 10 μm, and the major axis of the transverse section is 3 to 15 μm, preferably 3 μm to 10 μm.

Further, the shape of the minute recesses 4 viewed from above the release sheet may be various such as a circle, an ellipse, a quadrangle (square, rectangle, rhombus, parallelogram, trapezoid, etc.), a triangle, and the like.
Furthermore, as shown in FIG. 8, the cross section (transverse cross section) orthogonal to the longitudinal direction of the minute recesses 4 is a quadrangle (FIG. 8 (a)), a trapezoid (FIG. 8 (b)), an inverted triangle ( 8C), semicircular shape (FIG. 8D), dome shape such as a combination of a square and a semicircle (FIG. 8E) and an ellipse (FIG. 8F), and so on. be able to.

  5 to 1000, preferably 10 to 250, of the minute recesses 4 are provided on the bottom surface of the recess 3 surrounded by the protrusions 2.

The provision of the concavo-convex portion on the release sheet is achieved by passing the release sheet between the embossing roll engraved under the predetermined condition described above and the pressure roll under the predetermined condition.
Note that the release treatment of the release sheet can be performed before or after the embossing treatment, and the release treatment does not have to be performed.

[Adhesive sheet]
Various substrates such as PET film, OPP film, paper, Japanese paper, cloth, nonwoven fabric, and composite substrates thereof can be used as the substrate used in the pressure-sensitive adhesive sheet of the present invention.
The pressure-sensitive adhesive sheet is formed by applying a pressure-sensitive adhesive to the substrate and drying it.

[Adhesive layer]
As described above, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention has the convex part, concave part, and minute concave part of the release sheet transferred by pressure-bonding the release sheet to the surface thereof. A part will be formed.
Here, the fine convex part of the pressure-sensitive adhesive layer has a function of improving the reattachability of the pressure-sensitive adhesive sheet as described above.
However, if only the minute protrusions are in close contact with the adherend, the adhesive force is weak and peeling occurs.
Therefore, by adopting an adhesive layer having an elastic modulus that disappears over time with the minute projections applied and deforms into a smooth surface as the adhesive layer, the adhesive layer is minute in about 30 minutes immediately after application. The shape of the convex part does not change and it is possible to reapply a plurality of times by maintaining a weak adhesive force. Thereafter, the adhesive layer is deformed and the fine convex part disappears, and the adhesion area with the adherend increases. As a result, it was possible to develop a strong adhesive force.

As such an adhesive layer, the storage elastic modulus of the adhesive layer is preferably 2 × 10 ⁴ Pa to 2 × 10 ⁵ Pa, more preferably 5 × 10 ⁴ Pa to 1 × 10 ⁵ Pa. .
When a storage elastic modulus lower than the above numerical range is adopted as the adhesive layer, the cohesive force of the adhesive layer is weak and the adhesive layer may remain on the adherend, while the storage elasticity higher than the above numerical range. When the rate is adopted, the pressure-sensitive adhesive layer does not change with time (i.e., the fine protrusions do not disappear), and a strong adhesive force cannot be expressed.
In addition, the storage elastic modulus employ | adopted the numerical value measured using Nippon Siber hegner company MCR301.

If the storage elastic modulus of the said adhesive layer is satisfy | filled, the kind and usage-amount of the adhesive to be used and the various additives normally used for an adhesive sheet will not be restrict | limited.
For example, various adhesives such as rubbers and acrylics can be used as the pressure-sensitive adhesive, and the form thereof is not particularly limited and can be used without limitation, such as a solvent type, an emulsion type, and a hot melt type. Moreover, it is not particularly necessary to add a crosslinking agent, but when it is added, it is necessary to adjust the addition amount so as to be in the range of the storage elastic modulus.

[Method of forming recess in adhesive layer]
The pressure-sensitive adhesive sheet formed with the above-mentioned pressure-sensitive adhesive layer and the release sheet in which convex portions, concave portions, and minute concave portions are formed in a predetermined shape are peeled off with the pressure-sensitive adhesive layer surface and convex portions, concave portions, and minute concave portions formed. The sheet surface can be pasted together and passed through two pressure-bonding rolls with adjusted gaps for pressure bonding.
At this time, the pressure-sensitive adhesive is softened and bubbles are easily removed by heating to such an extent that the convex portions and concave portions formed on the release sheet are not crushed. For example, when a release sheet in which convex portions, concave portions, and minute concave portions are formed on polyethylene is used, it is desirable to perform pressure bonding while heating at a temperature of 60 ° C to 80 ° C.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these Examples.

[Production of adhesive sheet with release sheet]
A polyethylene terephthalate (PET # 50) film was adopted as the substrate of the release sheet, and polyethylene was melted and applied to a thickness of 25 μm. After performing a silicone-based release treatment on the polyethylene surface of the obtained film, the sheet is heated to 100 ° C. just before being pressed with an embossing roll, and passed through an embossing roll that can form an embossing pattern of a predetermined shape described later. Pressure was applied to prepare a release sheet having an embossed surface (see Examples 1-4 and Comparative Examples 1-4 below).
Next, a polyethylene terephthalate (PET # 125) film was used as the base material of the pressure-sensitive adhesive sheet, and a rubber-based pressure-sensitive adhesive (storage modulus at 25 ° C .: 5.8 × 10 ⁴ P) was applied at a thickness of 25 μm after drying. Application was made to produce an adhesive sheet.
The release sheet having the embossed surface and the pressure-sensitive adhesive sheet were bonded together through a pressure roll while heating the pressure-sensitive adhesive sheet to 40 ° C. to obtain a pressure-sensitive adhesive sheet with a release sheet.

[Evaluation]
The adhesive sheet with a release sheet was prepared, and after 5 days, the presence or absence of air bubbles present on the adhesive surfaces of both the bonded sheets was magnified 150 times with a video microscope and observed (Evaluation 1).
Further, the embossability after the release sheet was peeled off from the adhesive sheet was similarly observed with a video microscope with a magnification of 150 times (Evaluation 2).
Further, after peeling off the release sheet, macroscopically confirming the reattachability (assessment 3) when the adhesive sheet is attached to the acrylic plate and the disappearance of the minute protrusions (smoothness of the applied surface) after 1 day of application. (Evaluation 4)

[Embossed pattern of release sheet]
Example 1.
When the state projected onto the reference surface of the release sheet is viewed from above, as shown in FIG. 2, the release sheet is such that the convex portion 2 has a square with a width a = 10 μm and the concave portion 3 has a long side x = 30 μm. A grid-like convex portion was formed on the surface. At this time, the height of the convex portion 2 from the reference surface was 20 μm.
The bottom surface of the recess 3 was formed with 16 micro-recesses 4 each having a square shape when the release sheet was viewed from above and having a longitudinal cross section as shown in FIG. 8B. The minute recesses 4 were formed to have a square with an area of 4 μm × 4 μm at the bottom of the recess 3, a depth of 3 μm, and a square with an area of 3 μm × 3 μm at the bottom of the minute recess.

Example 2
In Example 1, the convex part and the concave part were formed in the same manner as in Example 1 except that the width a of the convex part 2 in FIG. 2 was 25 μm and the long side x of the concave part 3 was 65 μm.
In addition, 100 micro concave portions having the same shape as in Example 1 were formed on the bottom surface of the concave portion.

Comparative Examples 1 and 2
By using an acrylic adhesive (isocyanate-based crosslinking agent added, storage elastic modulus at 25 ° C .: 6 × 10 ⁵ Pa) instead of the rubber adhesive, the same protrusions, recesses, and minute as in Example 1 or Example 2 were used. The adhesive layer which has a recessed part was formed, and it was set as the comparative example 1 and the comparative example 2.

Example 3 FIG.
When the state projected onto the reference surface of the release sheet was viewed from above, circular recesses as shown in FIG. 3 were repeatedly formed. Here, the convex portion and the concave portion were formed on the release sheet so that the radius b of the concave portion 2 in FIG. 3 was 35 μm, the interval y was 90 μm, and the height of the convex portion was 20 μm.
In addition, 49 minute recesses having the same shape as in Example 1 were formed on the bottom surface of the recess.

In Example 3, convex portions and concave portions were formed in the same manner as in Example 3 except that the radius b of the concave portion 2 in FIG. 3 was set to 50 μm and the interval y was set to 135 m.
In addition, 100 micro concave portions having the same shape as in Example 1 were formed on the bottom surface of the concave portion.

Comparative Examples 3 and 4
By using an acrylic pressure-sensitive adhesive (isocyanate-based cross-linking agent added, storage elastic modulus at 25 ° C .: 6 × 10 ⁵ Pa) instead of the rubber-based pressure-sensitive adhesive, the same convexity, concave part and minute as in Example 3 or Example 4 were used. The adhesive layer which has a recessed part was formed, and it was set as the comparative example 3 and the comparative example 4.

[Test results]

As shown in Table 1, in the release sheets having the embossed patterns of Examples 1 to 4, bubbles were not generated on the adhesive surface after being bonded to the adhesive sheet, and the embossing property was also good.
Furthermore, the re-sticking property at the time of sticking was excellent, and the fine protrusions disappeared one day after sticking, and a smooth surface could be obtained.

On the other hand, any of Comparative Examples 1 to 4 using an acrylic pressure-sensitive adhesive (storage elastic modulus at 25 ° C .: 6 × 10 ⁵ Pa), in which the storage elastic modulus of the pressure-sensitive adhesive is outside the range defined in the present invention, is attached. After 1 day, the microprojections did not disappear and the surface remained uneven. This suggested that strong adhesive force could not be expressed over time and there was a risk of peeling off.

FIG. 1A is a partially enlarged view of the state projected on the reference surface of the release sheet as viewed from above, and FIG. 1B is an AA ′ plane in FIG. It is a figure which shows the orthogonal cross section. FIG. 2 shows a schematic view when the state projected from the upper side of the reference sheet of the release sheet of the first embodiment of the present invention (form in which convex portions are continuously formed two-dimensionally in a lattice shape) is shown. It is a thing. FIG. 3 shows a schematic view when the state projected from the upper side of the reference surface of the release sheet of the second embodiment of the present invention (form in which the concave portion forms a round shape) is shown. FIG. 4 shows the state projected from the upper side of the reference sheet of the release sheet of the third embodiment of the present invention (form in which convex portions are two-dimensionally continuously formed in a lattice shape and rhombic concave portions are formed). A schematic diagram is shown. FIG. 5 is a schematic diagram when the release sheet of the fourth form of the present invention (form in which convex parts are formed two-dimensionally continuously in a lattice shape and parallelogram-shaped concave parts are formed) is viewed from above. It is shown. FIG. 6 shows a schematic view when the state projected from the upper side of the reference surface of the release sheet of the fifth embodiment of the present invention (the recess has an elliptical shape) is shown. FIG. 7 is a view showing various shapes of the cross section of the convex portion orthogonal to the longitudinal direction of the release sheet. FIG. 8 is a diagram showing various shapes of cross sections perpendicular to the longitudinal direction of the release sheet of the minute recesses.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Release sheet 2 ... Convex part 3 ... Concave part 4 ... Micro recessed part AA '... Cross section XX' orthogonal to the longitudinal direction of a release sheet Adhesive The upper horizontal reference plane x in contact with the layer is a length of a substantially rectangular recess surrounded by a projection formed two-dimensionally in a lattice shape, and is two-dimensional in a lattice shape. Width y of the convex portion formed continuously to the distance b between the concave portion formed in a circular shape and the concave portion adjacent to the circular concave portion b Radius of the concave portion formed in a circular shape

Claims (9)

A release sheet for forming irregularities on the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheet,
On the upper surface of the release sheet, a convex portion protruding upward with respect to the upper horizontal reference surface in contact with the pressure-sensitive adhesive layer is continuously provided in two dimensions,
A concave portion having a predetermined shape surrounded by the convex portion is repeatedly formed two-dimensionally; and
The bottom surface of the recess is formed with a number of minute recesses recessed downward with respect to the reference surface, and the area occupied by the protrusions on the reference surface on the top surface of the release sheet is the area occupied by the protrusions. And 40 to 60% of the total area occupied by the recesses,
The height of the convex part is 7 to 35 μm,
The release sheet according to claim 1, wherein the average number of the minute recesses is 5 to 1000 per recess, the depth is 3 to 15 μm, and the major axis of the transverse section is 3 to 15 μm. 2. The release sheet according to claim 1, wherein the minute recess has a depth of 3 μm to 10 μm, and a major axis of a transverse section thereof is 3 to 10 μm. The release sheet according to claim 1 or 2, wherein the width of the convex portion between the concave portion and the adjacent concave portion is 10 µm to 500 µm. The convex portions are continuously formed in a two-dimensional lattice pattern,
4. The release sheet according to claim 1, wherein the substantially rectangular recess surrounded by the protrusion has a long side having a length of 17.2 μm to 1720 μm. The release sheet according to any one of claims 1 to 3, wherein the recess has a round shape, and an interval between the recess and the adjacent recess is 80 µm to 1400 µm. By applying the release sheet according to any one of claims 1 to 5 to the surface of the pressure-sensitive adhesive layer formed on the substrate sheet, the protrusions, the recesses, and the minute recesses of the release sheet are bonded. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer in which each shape is transferred to the surface of the pressure-sensitive adhesive layer to form concave portions, convex portions, and minute convex portions. The pressure-sensitive adhesive sheet includes a pressure-sensitive adhesive layer having an elastic modulus such that the minute convex portion disappears with time in a state where the release sheet is peeled and pasted, and deforms into a smooth surface. The pressure-sensitive adhesive sheet according to claim 6. The pressure-sensitive adhesive sheet according to claim 7, wherein the elastic modulus of the pressure-sensitive adhesive layer is a storage elastic modulus of 2 × 10 ⁴ Pa to 2 × 10 ⁵ Pa. The pressure-sensitive adhesive sheet according to any one of claims 6 to 8, wherein the pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive not containing a crosslinking agent.

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