JP7611220B2 - Release liner, pressure sensitive adhesive sheet, and method for producing pressure sensitive adhesive sheet - Google Patents

Description

The present invention relates to a release liner, an adhesive sheet, and a method for producing an adhesive sheet.

Conventionally, to prevent air bubbles from getting in between the adhesive sheet and the adherend, causing swelling, shapes for the adhesive layer in contact with the adherend have been considered for expelling air bubbles. For example, Patent Document 1 discloses forming a plurality of minute convex portions scattered like islands on the adhesive layer. Meanwhile, Patent Document 2 discloses forming grooves on the surface of the adhesive layer, and by attaching the adhesive sheet to the adherend in a predetermined attachment direction relative to the grooves, air bubbles are effectively expelled through the grooves.

The shape of these adhesive layers can be shaped by transferring the shape of a release liner that overlaps the adhesive layer. For example, in Patent Document 3, the adhesive layer is securely attached to the lattice-shaped surface of the release liner, thereby accurately transferring the shape of the release liner to the adhesive layer.

Patent No. 3377439 International Publication No. 2003/025078 Patent No. 5236854

However, when the present inventors formed an adhesive layer on a release liner having a lattice-like surface shape as in Patent Document 3 above, the surface of the adhesive layer was deformed to have irregularities to match the surface shape of the release liner. As a result, when a base layer was placed on the adhesive layer and bonded together while pressing with a roller to produce an adhesive sheet, it became clear that air bubbles could be trapped between the depressions on the surface of the adhesive layer and the base layer, which could result in reduced adhesion between the adhesive layer and the base layer and poor appearance.

The present invention has been made to solve such newly discovered problems, and aims to provide a release liner, an adhesive sheet, and a method for producing an adhesive sheet that can suppress the formation of air bubbles between the adhesive layer and the base layer.

In order to achieve the above object, the release liner of the present invention has a plurality of linearly extending first ridges and a plurality of second ridges on one surface, and is long. The first ridges extend obliquely with respect to the longitudinal direction of the release liner and reach an edge of the release liner in a cross direction perpendicular to the longitudinal direction (machine direction), and the second ridges extend while intersecting with the first ridges and reach an edge of the release liner. The first ridges and the second ridges form a parallelogram-shaped recess when viewed from a direction perpendicular to the surface of the release liner, and each of two opposing corners of the parallelogram in the longitudinal direction is smaller than 90°. The cross-sectional shape of the first ridges and the second ridges in the longitudinal direction is triangular, with the height being greater than the width.

To achieve the above objective, the adhesive sheet of the present invention has the release liner, adhesive layer, and base layer in this order in the stacking direction.

To achieve the above object, the method for manufacturing an adhesive sheet of the present invention involves forming an adhesive layer on the surface of the release liner, overlaying a base layer on the adhesive layer and pressing the base layer against the adhesive layer while bonding the base layer and the adhesive layer together in the longitudinal direction.

According to the invention having the above configuration, when the adhesive layer is formed on the release liner and bonded to the base layer, air bubbles are less likely to be trapped between them, and the formation of air bubbles between the adhesive layer and the base layer can be suppressed.

FIG. 2 is a plan view showing the release liner of the first embodiment. 2A to 2C are schematic diagrams illustrating a method for producing the pressure-sensitive adhesive sheet of the first embodiment. FIG. 2 is a plan view showing the bonding of a pressure-sensitive adhesive layer and a base layer in one comparative example. FIG. 11 is a plan view showing the bonding of a pressure-sensitive adhesive layer and a base layer in another comparative example. 5 is a cross-sectional view taken along line 5-5 in FIG. 3 or FIG. 4. FIG. 6 is a cross-sectional view showing the progress of planarization of the surface of the pressure-sensitive adhesive layer from the state shown in FIG. 5 . FIG. 4 is a plan view showing locations where air is likely to be trapped when flattening of the surface of the adhesive layer progresses from the state shown in FIG. 3 . FIG. 5 is a plan view showing locations where air is likely to be trapped when flattening of the surface of the adhesive layer progresses from the state shown in FIG. 4 . FIG. 2 is a plan view showing the bonding of the pressure-sensitive adhesive layer and the base layer in the first embodiment. FIG. 10 is a plan view showing that when the flattening of the surface of the adhesive layer progresses from the state of FIG. 9, the locations where air is likely to be trapped are suppressed. FIG. 6 is a plan view showing a release liner of a second embodiment. FIG. 6 is a partially enlarged view of a cross section along the longitudinal direction of a release liner of a second embodiment. FIG. 5 is a partially enlarged view showing a cross section along the longitudinal direction of a release liner of a second embodiment and a pressure-sensitive adhesive layer dried on the surface of the release liner.

Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings. Note that the dimensional ratios in the drawings are exaggerated for the convenience of explanation and differ from the actual ratios.

First Embodiment
As shown in FIG. 1, the release liner 100 of the first embodiment has a plurality of first ridges 101 and a plurality of second ridges 102 extending linearly on one surface, and is long.

The material from which the release liner 100 is formed is not particularly limited, and may be, for example, a resin film such as polyethylene terephthalate, or may be a paper coated with a resin such as polyethylene. The first ridge portion 101 and the second ridge portion 102 are formed by, for example, embossing such a resin film or paper.

The first ridge portion 101 extends obliquely with respect to the longitudinal direction D1 of the release liner 100 and reaches an edge 103 of the release liner 100 in a width direction D2 perpendicular to the longitudinal direction D1. The second ridge portion 102 extends while intersecting the first ridge portion 101 and reaches the edge 103.

The multiple first ridges 101 and multiple second ridges 102 form a diamond-shaped (parallelogram) recess 104 when viewed from a direction perpendicular to the surface of the release liner 100. The diamond shape of the recess 104 has two opposing angles θ in the longitudinal direction D1 that are acute angles, and the length L1 of the diagonal line connecting the two angles θ is longer than the length L2 of the diagonal line connecting the other two corners different from the two angles θ (L1>L2).

As shown in Figure 2, the release liner 100 is used to manufacture the adhesive sheet 1000. The adhesive sheet 1000 has the release liner 100, the adhesive layer 110, and the substrate layer 120 in this order in the stacking direction.

After production, the adhesive sheet 1000 is cut into an appropriate shape and used, for example, as a marking film to be attached to the exterior material of a vehicle such as a motorcycle, as stickers for advertising or display, or as a marking film used on a signboard, but there are no particular limitations on the applications for which the adhesive sheet 1000 is used.

When the adhesive sheet 1000 is used, the release liner 100 is peeled off, and the surface of the adhesive layer 110 exposed thereby has grooves formed thereon to which the shapes of the first ridges 101 and the second ridges 102 are transferred. The grooves communicate with the outside at the edge of the adhesive layer 110 because the first ridges 101 and the second ridges 102 reach the edge 103 as shown in FIG. 1. Therefore, when the adhesive sheet 1000 is attached to an adherend via the adhesive layer 110, any air bubbles that may get in between them are effectively expelled from between the adhesive layer 110 and the adherend, preventing the adhesive sheet 1000 from swelling.

In the manufacturing method of the adhesive sheet 1000, first, an adhesive layer 110 is formed on the release liner 100, and then a substrate layer 120 is bonded to the adhesive layer 110.

The adhesive layer 110 is formed by drying the adhesive 111 applied to the release liner 100. The adhesive 111 is not particularly limited, and examples thereof include acrylic adhesives, rubber adhesives, silicone adhesives, urethane adhesives, polyester adhesives, styrene block copolymer adhesives, vinyl alkyl ether adhesives, etc. These may be used alone or in combination of two or more.

The adhesive 111 is applied to the surface of the release liner 100 on which the first ridge portion 101 and the second ridge portion 102 are provided. The adhesive 111 is applied thicker than the height T1 of the first ridge portion 101 and the second ridge portion 102, but there is no particular limitation on how thick it is applied. The height T1 of the first ridge portion 101 and the second ridge portion 102 is, for example, 5 μm to 35 μm. The adhesive 111 is applied to a predetermined thickness, for example, by a knife coater, but there is no particular limitation on the application method. If the adhesive 111 contains a solvent or water, it is dried after application.

The adhesive 111 is transported in the longitudinal direction D1 together with the release liner 100, and is dried while passing through the drying oven H. The release liner 100 is transported, for example, by a roll-to-roll method. The drying oven H dries the adhesive 111, for example, by hot air or radiant heat, but there is no particular limitation on how the adhesive 111 is dried.

Before drying, the surface of the adhesive layer 110 is generally flat, but as the solvent and the like are removed from the adhesive 111 by drying and the thickness of the adhesive layer 110 decreases, the adhesive layer 110 deforms to fit the shapes of the first ridge 101 and the second ridge 102. As a result, as shown by reference numeral 2 in FIG. 2, a depression 112 having a diamond shape generally similar to the diamond shape of the recess 104 formed by the first ridge 101 and the second ridge 102 is formed on the surface of the adhesive layer 110.

After drying, the adhesive layer 110 is further transported together with the release liner 100 with the depressions 112 formed on its surface, and the base layer 120 is laminated. The material for forming the base layer 120 is, for example, polyvinyl chloride or polyurethane, but is not limited thereto.

The base layer 120 is continuously supplied in accordance with the transport of the release liner 100 and the adhesive layer 110, and is superimposed on the surface of the adhesive layer 110. The base layer 120 is pressed by a cylindrical roller R while superimposed on the adhesive layer 110, and the base layer 120 and the adhesive layer 110 are bonded together in the longitudinal direction D1.

By the pressure from the roller R, the depressions 112 on the surface of the adhesive layer 110 are leveled to a substantially uniform thickness T2 of, for example, about 15 μm to 50 μm, and the adhesive layer 110 and the base layer 120 are tightly adhered to each other without any gaps. However, from the experience of the inventors, this is not the case when a release liner with a different surface shape than in this embodiment is used, resulting in an adhesive layer with depressions formed on the surface that differ from those in this embodiment.

For example, as in the comparative example shown in Figure 3, when a rectangular or square depression 112A having two sides perpendicular to the longitudinal direction D1 is formed on the surface of the adhesive layer 110A, air bubbles may be formed between the base layer 120 and the adhesive layer 110A after pressing with the roller R.

Furthermore, even when diamond-shaped depressions 112B are formed on the surface of the adhesive layer 110B as in another comparative example shown in Figure 4, if the shape of the diamond is different from that of the above embodiment, with two opposing corners in the longitudinal direction D1 being obtuse angles and the diagonal in the longitudinal direction D1 being shorter than the diagonal perpendicular thereto, air bubbles may be formed between the base layer 120 and the adhesive layer 110B after pressing with the roller R.

Although these depressions 112A, 112B are both approximately the same size as the depression 112 in the above embodiment, it is believed that the formation of air bubbles is due to their shape.

5 and 6, the surfaces of the adhesive layers 110A and 110B are flattened as they pass through the contact point R1 between the roller R and the base layer 120, and the depressions 112A and 112B are crushed in the opposite direction to the conveying direction of the adhesive layers 110A and 110B. At that time, air is likely to be trapped in the side walls forming the depressions 112A and 112B on the upstream side of the conveying direction.

As shown in Figures 7 and 8, in the comparative example, the points 113A and 113B where such air is likely to be trapped remain widely uncrushed until just before they pass through the contact point R1 between the roller R and the base material layer 120 and are flattened, which is thought to make it easy for air bubbles to form.

Such air bubbles are undesirable because they can reduce adhesion between the base layer 120 and the adhesive layer 110A, or between the base layer 120 and the adhesive layer 110B, or can be visually recognized as blisters, resulting in poor appearance.

On the other hand, in this embodiment, as shown in Figures 9 and 10, the side walls 114 constituting the recess 112 are gradually flattened as the material is transported due to their characteristic shape (which is substantially the same as the diamond shape of the recess 104 of the release liner 100), so that the areas 113 where air is likely to be trapped are small, and it is believed that the formation of air bubbles between the adhesive layer 110 and the base layer 120 is suppressed.

Second Embodiment
11 , the release liner 200 of the second embodiment has a plurality of first ridges 201 and second ridges 202 formed on one surface, similar to the first embodiment. The first ridges 201 and the second ridges 202 intersect with each other to form recesses 104 similar to the first embodiment.

The first protrusion portion 201 has a cross-sectional shape different from the first protrusion portion 101 of the first embodiment, and the second protrusion portion 202 has a cross-sectional shape different from the second protrusion portion 102 of the first embodiment.

As shown in Figure 12, the cross-sectional shapes of the first protrusion portion 201 and the second protrusion portion 202 in the longitudinal direction D1 are triangular. Other than this, the configuration of the release liner 200 is similar to that of the release liner 100 of the first embodiment. In addition, the manufacturing method of the adhesive sheet using the release liner 200 is also similar to the manufacturing method of the first embodiment shown in Figure 2.

As shown in Figure 13, during production, when the adhesive layer 110 dries, since in this embodiment the cross-sectional shapes of the first protrusion portion 201 and the second protrusion portion 202 are triangular, the surface of the adhesive layer 110 also deforms to form protruding portions 213, 214 that are approximately triangular in shape.

Furthermore, when the protruding portions 213, 214 are approximately triangular, the protruding portions 213, 214 are more likely to be crushed toward the depression 112 between them when the pressing force F is applied, compared to when the protruding portions 213, 214 are, for example, trapezoidal or rectangular in shape and receive the pressing force F from the roller R on a surface basis, thereby more effectively eliminating the depression 112 and preventing the formation of air bubbles.

The present invention is not limited to the above-described embodiments and can be modified in various ways within the scope of the claims.

For example, in the first embodiment, the first ridge portion 101 and the second ridge portion 102 have a rectangular cross-sectional shape as shown in Fig. 2, and in the second embodiment, the first ridge portion 201 and the second ridge portion 202 have a triangular cross-sectional shape as shown in Fig. 12, but are not limited to these shapes. For example, the first ridge portion and the second ridge portion having a cross-sectional shape different from the above embodiments, such as a trapezoid or a mountain shape with rounded apexes, are also included in the scope of the present invention.

In addition, the adhesive sheet 1000 of the above embodiment has a release liner 100, an adhesive layer 110, and a substrate layer 120, but adhesive sheets having layers other than these are also included in the scope of the present invention.

100, 200 Release liner,
101, 201 First protrusion portion,
102, 202 second protrusion portion,
103 edge of release liner in width direction;
104 recessed portion,
110 The pressure-sensitive adhesive layer of the embodiment,
110A, 110B Comparative adhesive layer,
111 Adhesives,
112 Depression of the adhesive layer of the embodiment;
112A, 112B Depressions in the adhesive layer of the comparative example;
120 Base material layer,
1000 adhesive sheets,
D1 longitudinal direction,
D2: width direction perpendicular to the longitudinal direction;
H drying oven,
L1: a diagonal line connecting two opposing corners in the longitudinal direction;
L2: A diagonal line connecting the two other angles.
R. Lola,
R1: contact point between the roller and the base layer;
θ Two opposing angles in the longitudinal direction.

Claims (1)

A long release liner having a plurality of linearly extending first ridge portions and a plurality of linearly extending second ridge portions provided on one surface thereof,
the first protrusion extends obliquely with respect to a longitudinal direction of the release liner and reaches an edge of the release liner in a width direction perpendicular to the longitudinal direction,
the second ridge portion extends while intersecting the first ridge portion and reaches an edge of the release liner,
the first protrusions and the second protrusions form a parallelogram-shaped recess when viewed in a direction perpendicular to the surface of the release liner,
The parallelogram has two opposing angles in the longitudinal direction each of which is smaller than 90°,
a pressure-sensitive adhesive layer is formed on the surface of a release liner, the cross-sectional shapes of the first protrusion portion and the second protrusion portion in the longitudinal direction being triangular with a height greater than a width, and a base layer is placed on the pressure-sensitive adhesive layer and pressed against the base layer, while bonding the base layer and the pressure-sensitive adhesive layer together in the longitudinal direction.