Adhesive sheet and adhesive sheet laminate having the same

Abstract

To provide an adhesive sheet which has light transmittance, air permeability and visibility at a high level and in a well-balanced manner, and an adhesive sheet laminate having the sheet.SOLUTION: An adhesive sheet laminate 20 comprises: an adhesive sheet 15 having a transparent resin substrate 7 and an adhesive layer 5 formed on one face of the substrate 7; and a resin release liner 10 having a release surface 6 which directly covers a face of the adhesive layer 5 on the opposite side of the substrate 7. A grating-shaped protruding portions 9 having a width W of 20 μm or more and 50 μm or less, and portions extending in a first direction and portions extending in a second direction crossing the first direction is formed on the release surface 6, where a length L of one side of each recess 19 partitioned by the protruding portions 9 is 200 μm or more and 350 μm or less; a height H of the protruding portions 9 is 10 μm or more and 25 μm or less; and a value of W / L is 0.100 or more and 0.200 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a pressure-sensitive adhesive sheet and a pressure-sensitive adhesive sheet laminate having the same. [Background technology]

[0002] Decorative sheets that are attached to transparent materials such as glass or acrylic panels are required to have high transparency as well as minimal air entrapment during attachment.

[0003] JP 2004-532336 A (Patent Document 1) describes that an adhesive sheet exhibiting high light transmittance and low haze value can be produced by forming an adhesive layer on the release surface of a release liner having lattice-shaped convex portions formed thereon. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2004-532336 Summary of the Invention [Problem to be solved by the invention]

[0005] The adhesive sheet described in Patent Document 1 has grooves transferred to the adhesive layer, which allows air trapped between the sheet and the adherend to escape more easily. However, as the inventors of the present application continued to develop transparent adhesive films, they noticed that even adhesive sheets with high light transmittance and low haze can cause characters or complex shapes to be distorted when viewed through the sheet, making it difficult to fully discern the content. When adhesive sheets are actually used for decorative purposes, high light transmittance is not enough; high visibility is also required, allowing characters, patterns, figures, etc. behind the sheet to be accurately identified.

[0006] An object of the present invention is to provide a pressure-sensitive adhesive sheet that has a high level of light transmittance, ease of air escape, and visibility in a well-balanced manner, and a pressure-sensitive adhesive sheet laminate having the same. [Means for solving the problem]

[0007] The pressure-sensitive adhesive sheet disclosed herein includes a transparent resin substrate and a pressure-sensitive adhesive layer formed on one surface of the substrate. The pressure-sensitive adhesive layer has a grid-like groove formed therein, the grid-like grooves being composed of a plurality of first grooves extending in a first direction and a plurality of second grooves extending in a second direction intersecting the first direction. Each section of the pressure-sensitive adhesive layer defined by the grid-like grooves has a side length La of 200 μm to 350 μm in plan view, a depth Ha of 10 μm to 25 μm, and a width Wa of 20 μm to 50 μm, with a Wa / La ratio of 0.100 to 0.200.

[0008] The pressure-sensitive adhesive sheet laminate includes a pressure-sensitive adhesive sheet having a transparent resin substrate and a pressure-sensitive adhesive layer formed on one side of the substrate, and a resin release liner covering the surface of the pressure-sensitive adhesive layer opposite the substrate and having a release surface in contact with the pressure-sensitive adhesive layer. The release surface is formed with a lattice-shaped convex portion having a width W of 20 μm to 50 μm and including a portion extending in a first direction and a portion extending in a second direction intersecting the first direction, the length L of one side of each concave portion defined by the convex portion being 200 μm to 350 μm, the height H of the convex portion being 10 μm to 25 μm, and the value of W / L being 0.100 to 0.200. [Effects of the Invention]

[0009] The pressure-sensitive adhesive sheet and pressure-sensitive adhesive sheet laminate including the pressure-sensitive adhesive sheet disclosed in the present specification can provide a pressure-sensitive adhesive sheet that has a high level of well-balanced light transmittance, ease of air escape (so-called "air escape property"), and visibility of characters, etc. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing a resin sheet laminate provided with a release sheet that is applied to a method for recycling a release sheet according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a plan view of the release sheet as seen from the side that contacts the pressure-sensitive adhesive layer. [Figure 3] FIG. 3 is a photograph showing the results of a visibility evaluation of the pressure-sensitive adhesive sheets produced as Example 1 and Comparative Examples 1 to 3. DETAILED DESCRIPTION OF THE INVENTION

[0011] (First embodiment) Fig. 1 is a cross-sectional view showing a pressure-sensitive adhesive sheet laminate according to an embodiment of the present disclosure, and Fig. 2 is a plan view of a release sheet seen from the side that contacts the pressure-sensitive adhesive layer. Fig. 1 is a cross-sectional view of the pressure-sensitive adhesive sheet laminate taken along line II shown in Fig. 2.

[0012] 1 and 2, a pressure-sensitive adhesive sheet laminate 20 of this embodiment comprises a transparent resin substrate 7, a pressure-sensitive adhesive sheet 15 having a pressure-sensitive adhesive layer 5 formed on one surface of the substrate 7, and a resin release liner 10 covering the surface of the pressure-sensitive adhesive layer 5 opposite the substrate 7 and having a release surface 6 in contact with the pressure-sensitive adhesive layer 5. The release liner 10 comprises, for example, a resin sheet 1 and a release layer 3 formed on the release surface 6 side of the resin sheet 1 and containing a silicone-based or fluorine-based release agent.

[0013] The release surface 6 of the release liner 10 is formed with a grid-like convex portion 9 having a width W of, for example, 20 μm or more and 50 μm or less, and having a portion extending in a first direction and a portion extending in a second direction intersecting the first direction, and the length L of one side of each recess 19 defined by the convex portion 9 is 200 μm or more and 350 μm or less, and the height H of the convex portion is 10 μm or more and 25 μm or less. The value of W / L is 0.100 or more and 0.200 or less.

[0014] The shape of the release surface of release liner 10 is transferred to the attachment surface of pressure-sensitive adhesive layer 5 when release liner 10 is peeled off from pressure-sensitive adhesive sheet laminate 20 during use of pressure-sensitive adhesive sheet 15. Therefore, lattice-shaped grooves 11 are formed in pressure-sensitive adhesive layer 5, each of which is composed of a plurality of first grooves extending in a first direction and a plurality of second grooves extending in a second direction intersecting the first direction. When viewed from above, each portion 13 of pressure-sensitive adhesive layer 5 defined by lattice-shaped grooves 11 has a side length La of 200 μm or more and 350 μm or less, a depth Ha of 10 μm or more and 25 μm or less, and a width Wa of 20 μm or more and 50 μm or less. The value of Wa / La is 0.100 or more and 0.200 or less.

[0015] With this configuration, the adhesive sheet 15 of this embodiment exhibits high total light transmittance, and even if air becomes trapped during application, it can be easily released through the grid-shaped grooves 11. Furthermore, if the haze value is, for example, about 20% or less, visual distortion is reduced, improving the visibility of characters and the like. A haze value of 10% or more and 20% or less is more preferable.

[0016] If the length La of one side of the portion partitioned by the grid-like grooves is less than 200 μm, the number of grooves increases, resulting in poor visibility, while if it is greater than 350 μm, air bubbles are more likely to become trapped between the pressure-sensitive adhesive layer 5 and the adherend. If the depth Ha of the grooves 11 is less than 10 μm, air release properties are poor, and if it exceeds 25 μm, the grooves become more noticeable after application and visibility is reduced. By setting the width Wa of the grooves 11 to be 20 μm or more and 50 μm or less, it is possible to suppress an increase in haze while improving air release properties.

[0017] The total light transmittance of the pressure-sensitive adhesive sheet 15 measured in accordance with JIS K7361-1 may be 85% or more, and the haze value measured in accordance with JIS K7361-1 may be 20% or less. The haze value may be 10% or more and 20% or less. If the total light transmittance is within the range of 85% and the haze value is within the range of 20% or less, it is possible to set the width and spacing of the grooves 11 to values that ensure good air release properties without reducing the visibility of characters, etc.

[0018] In the example shown in FIG. 2, the crossing angle between the first direction (for example, the vertical direction shown in FIG. 2) and the second direction (the horizontal direction shown in FIG. 2) is approximately 90°, but it may be any angle between 80° and 90°.

[0019] The substrate 7 may be a laminate made of one or more selected from polyester film, thermoplastic elastomer film, polyolefin resin film, polycarbonate resin film, polyvinyl chloride resin film, polyphenylene sulfide resin film, polyether sulfone resin film, polyethylene sulfide resin film, polyphenylene ether resin film, styrene resin film, acrylic resin film, polyamide resin film, polyimide resin film, and cellulose resin film.

[0020] Although not shown, an antistatic layer or an easy-adhesion layer may be provided on at least one surface of the base material 7. When the pressure-sensitive adhesive sheet 15 of this embodiment is used as a decorative sheet, a printed layer may be formed on at least one surface of the base material 7.

[0021] The adhesive used to form the adhesive layer 5 is not particularly limited, and may be, for example, one or a mixture of two or more selected from acrylic adhesives, acrylic-urethane adhesives, urethane adhesives, silicone adhesives, polyester adhesives, and rubber adhesives. Examples of adhesives that can be used include water-based adhesives, solvent-based adhesives, and solventless adhesives. Biomass adhesives containing materials derived from plants may also be used as the adhesive. Furthermore, the adhesive layer 5 may contain from 1% by mass to 100% by mass of a tackifier derived from plants, such as rosin or terpene.

[0022] The storage modulus of the pressure-sensitive adhesive layer 5 at 23°C and a frequency of 1 Hz is 1.0 × 10 3 Pa or more 5.0×10 6 Pa or less, and may be 1.0 × 10 4 Pa or more 5.0×10 5 It is more preferable that the adhesive strength of the adhesive layer 5 to an adherend at 23°C and a relative humidity of 50% (normal adhesive strength) varies depending on the material of the adherend, but may be approximately 0.1 N / 25 mm or more and 15 N / 25 mm or less 20 minutes after application. The thickness of the adhesive layer 5 is sufficient as long as it is equal to or greater than the height of the convex ridge portions 9 of the release liner 10, and may be, for example, 10 μm or more and 100 μm or less, or 15 μm or more and 50 μm or less.

[0023] The shape of the convex portion 9 is not particularly limited, but as shown in FIGS. 1 and 2, the horizontal cross section may be rectangular or trapezoidal.

[0024] Figure 1 shows an example in which the resin sheet 1 of the release liner 10 is formed from a single layer of polyethylene terephthalate (PET) or the like, but it may also be a laminate formed by laminating, for example, a PET layer having a flat upper surface and a polyethylene (PE) layer having a convex portion formed on the upper surface.

[0025] The convex portions 9 of the release liner 10 may be formed by embossing when the resin sheet 1 is formed, or may be formed by embossing after the release layer 3 is formed on the resin sheet 1. [Example]

[0026] The present invention will be described in more detail below based on examples, but these examples are illustrative and are not intended to limit the present invention.

[0027] <Preparation of adhesive sheet laminate> An appropriate amount of a commercially available isocyanate-based curing agent was mixed with a solution of a commercially available solvent-based acrylic removable adhesive A to prepare adhesive composition A. Next, four types of release liners (release liners 1 to 4) were prepared by embossing, each with a different shaped lattice-shaped convex portion formed on the release surface. The shapes of the convex portions of these release liners were measured using a laser microscope, and the results are shown in Table 1.

[0028] [Table 1] The first release liner had a PET substrate on which a PE layer with convex portions was laminated, and a silicone-based release agent layer was provided on the release surface side of the PE layer. In the first release liner, the length of one side of the concave portion (lattice concave portion width) L was 269.0 μm, the width of the convex portion was 36.0 μm, and the height of the convex portion was 13.3 μm. The crossing angle of the lattice was approximately 83°.

[0029] The second release liner had a structure in which a high-quality paper substrate, a PE layer for sealing, and a silicone-based release agent layer were provided in that order. In the second release liner, the length L of one side of the recessed portion was 332.2 μm, the width of the protruding portion was 64.0 μm, and the height of the protruding portion was 15.5 μm. The crossing angle of the lattice was approximately 90°.

[0030] The third release liner had a structure in which a resin sheet made of PET and a silicone-based release agent layer were provided in that order. In the third release liner, the length L of one side of the recessed portion was 208.2 μm, the width of the protruding portion was 217.1 μm, and the height of the protruding portion was 15.6 μm. The crossing angle of the lattice was approximately 90°.

[0031] The fourth release liner had a structure in which a resin sheet made of PET and a silicone-based release agent layer were provided in that order. In the fourth release liner, the length L of one side of the recessed portion was 1488.1 μm, the width of the protruding portion was 223.0 μm, and the height of the protruding portion was 9.6 μm. The crossing angle of the lattice was approximately 90°.

[0032] Next, a comma-type coater was used to apply PSA composition A to the release surface of the first release liner and dry it to form a PSA layer. A 50 μm-thick transparent PET film (substrate) was then attached to the PSA layer to produce a PSA sheet laminate. The PSA layer had a thickness of 30 μm after drying. The laminate was then placed in a 40°C environment for 72 hours to age. This was designated Example 1.

[0033] A pressure-sensitive adhesive sheet laminate was produced using a second release liner in the same manner as in Example 1. This was designated as the first comparative example.

[0034] A pressure-sensitive adhesive sheet laminate was produced using a third release liner in the same manner as in Example 1. This was designated as the second comparative example.

[0035] A pressure-sensitive adhesive sheet laminate was produced using the fourth release liner in the same manner as in Example 1. This was designated as the third comparative example.

[0036] <Measurement of storage modulus G' of adhesive layer> First, a substrate-less tape having a 50 μm thick adhesive layer was produced using the prepared adhesive composition A. This substrate-less tape was then aged at 40°C for 72 hours. Next, the adhesive layer alone was laminated until the total thickness reached 1 mm, and then punched out to a diameter of 8 mm to produce a tablet. This tablet was sandwiched between the plates of a rheometer (product name: AR2000ex), and the storage modulus G' was measured under conditions of a frequency of 1 Hz, strain of 0.05%, and measurement temperature: -40 to 100°C. As a result of the measurement, the storage modulus G' of the adhesive layer at 23°C was 1.1×10 5 It was Pa. <Optical property measurement> The total light transmittance and haze value of the PSA sheets according to Example 1 and Comparative Examples 1 to 3 were measured using an integrating sphere spectrophotometer (JASCO Corporation, V-770 / ILN-925) according to a method conforming to JIS K7361-1. Measurements were performed by removing the release liner from a test piece cut to an appropriate size, attaching the PSA sheet to a 3 mm thick glass, and irradiating light from the glass side.

[0037] <Visibility evaluation> An adhesive sheet was attached to one side of a 5 mm thick transparent glass plate. A camera was placed 110 cm away from the glass plate on the adhesive sheet side, and a sheet with written text was placed 45 cm away from the glass plate on the opposite side to the adhesive sheet, and the sheet was photographed through the glass plate. This evaluation was performed for each of the adhesive sheets according to Example 1 and Comparative Examples 1 to 3.

[0038] If the characters were clearly readable, the result was judged as "excellent" (symbol ◯); if the characters were unclear but readable, the result was judged as "fair" (symbol △); and if the characters were illegible, the result was judged as "poor" (symbol ×).

[0039] <Evaluation of air release> Each adhesive sheet was cut to a size of 21cm x 30cm and attached to a glass plate, and then an attempt was made to use a squeegee to remove any air bubbles trapped between the adhesive sheet and the glass plate. If the air bubbles were removed with a light force, it was judged as "excellent" (◎), if the air was removed with a strong force, it was judged as "good" (◯), if only some of the air was removed with a strong force, it was judged as "semi-acceptable" (△), and if the air could not be removed, it was judged as "unacceptable" (×).

[0040] <Measurement results> The measurement results of the total light transmittance and haze value of each PSA sheet are shown in Table 2. The results of the visibility evaluation of each PSA sheet are shown in Table 3. The results of the air release evaluation of each PSA sheet are shown in Table 4. A photograph of the visibility evaluation results is shown in Figure 3.

[0041] [Table 2]

[0042] [Table 3]

[0043] [Table 4] As shown in Table 2, the adhesive sheet of Example 1 had an average total light transmittance of 88.4% and a haze value of 14.2%. The adhesive sheet of Comparative Example 1 had an average total light transmittance of 88.2% and a haze value of 24.8%, while the adhesive sheet of Comparative Example 2 had an average total light transmittance of 88.9% and a haze value of 4.3%. The adhesive sheet of Comparative Example 3 had an average total light transmittance of 88.4% and a haze value of 3.3%.

[0044] The adhesive sheet of Example 1 exhibited a high total light transmittance equivalent to those of Comparative Examples 2 to 4, but the haze value was 20% or less, which was lower than that of the adhesive sheet of Comparative Example 1 but higher than that of the adhesive sheets of Comparative Examples 2 and 3.

[0045] However, as shown in Tables 3 and 4 and Fig. 3, it was confirmed that the adhesive sheet of Example 1 had good visibility of characters and good air release properties. In contrast, it was confirmed that the adhesive sheet of Comparative Example 1 had a too high haze value, resulting in reduced visibility, and that the adhesive sheet of Comparative Example 2 had good visibility but slightly poor air release properties. It was confirmed that the adhesive sheet of Comparative Example 3 had good air release properties, but the visibility of characters, etc. was insufficient due to the wide groove width of the adhesive layer. [Industrial Applicability]

[0046] The pressure-sensitive adhesive sheet and pressure-sensitive adhesive sheet laminate including the same according to the present disclosure are useful as decorative sheets, protective films, etc. for windows of buildings and various vehicles. [Explanation of symbols]

[0047] 1 Resin sheet 3 Release layer 5. Adhesive layer 6 Release surface 7 Base material 9 Convex part 10 Release Liner 11 Groove 13 parts 15 Adhesive sheet 19 Recess 20. Adhesive sheet laminate

Claims

1. A transparent resin base material and a pressure-sensitive adhesive layer formed on one surface of the substrate; An adhesive sheet comprising: the pressure-sensitive adhesive layer is formed with a grid-like groove including a plurality of first grooves extending in a first direction and a plurality of second grooves extending in a second direction intersecting the first direction; In the pressure-sensitive adhesive layer, each portion partitioned by the lattice-shaped grooves has a side length La of 200 μm or more and 350 μm or less in a plan view, The depth Ha of the grid-like groove is 10 μm or more and 25 μm or less, The width Wa of the grid-like groove is 20 μm or more and 50 μm or less, A pressure-sensitive adhesive sheet having a Wa / La value of 0.100 or more and 0.200 or less.

2. The total light transmittance measured in accordance with JIS K7361-1 is 85% or more, 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the haze value measured in accordance with JIS K7361-1 is 20% or less.

3. The pressure-sensitive adhesive sheet according to claim 1 , wherein the crossing angle between the first direction and the second direction is 80° or more and 90° or less.

4. The storage modulus of the pressure-sensitive adhesive layer at 23°C and a frequency of 1 Hz was 1.0 × 10 ３ Pa or more 5.0×10 ６ The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the surface roughness is 0.05 Pa or less.

5. a pressure-sensitive adhesive sheet having a transparent resin substrate and a pressure-sensitive adhesive layer formed on one surface of the substrate; a resin release liner covering the surface of the pressure-sensitive adhesive layer opposite to the substrate and having a release surface that comes into contact with the pressure-sensitive adhesive layer; Equipped with a lattice-shaped convex portion having a width W of 20 μm or more and 50 μm or less and including a portion extending in a first direction and a portion extending in a second direction intersecting the first direction is formed on the release surface; The length L of one side of each recess defined by the convex portion is 200 μm or more and 350 μm or less, The height H of the convex portion is 10 μm or more and 25 μm or less, A pressure-sensitive adhesive sheet laminate having a W / L value of 0.100 or more and 0.200 or less.

6. The total light transmittance of the pressure-sensitive adhesive sheet measured in accordance with JIS K7361-1 is 85% or more, 6. The pressure-sensitive adhesive sheet laminate according to claim 5, wherein the pressure-sensitive adhesive sheet has a haze value of 20% or less as measured in accordance with JIS K7361-1.

7. The pressure-sensitive adhesive sheet laminate according to claim 5 , wherein the crossing angle between the first direction and the second direction is 80° or more and 90° or less.

8. The storage modulus of the pressure-sensitive adhesive layer at 23°C and a frequency of 1 Hz was 1.0 × 10 ３ Pa or more 5.0×10 ６ The pressure-sensitive adhesive sheet laminate according to any one of claims 5 to 7, wherein the surface roughness is 0.05 Pa or less.

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