JP7089368B2 - Adhesive sheet - Google Patents

Description

The present invention relates to an adhesive sheet provided with a foam substrate.

In general, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive; the same applies hereinafter) exhibits a soft solid state (viscous elastic body) in a temperature range near room temperature, and has a property of easily adhering to an adherend by pressure. Taking advantage of these properties, the pressure-sensitive adhesive is widely used in various fields for purposes such as joining and fixing, for example, in the form of a pressure-sensitive adhesive sheet with a base material having an pressure-sensitive adhesive layer provided on at least one surface of the base material. ing.

An adhesive sheet with a base material using a foam having a bubble structure as a base material (adhesive sheet with a foam base material) has better shock absorption than an adhesive sheet using a plastic film having no bubble structure as a base material. It can be advantageous in terms of unevenness followability and the like. In addition, it can be advantageous in terms of waterproofness, sealing property, and the like, as compared with an adhesive sheet using a non-woven fabric as a base material. Therefore, the pressure-sensitive adhesive sheet with a foam base material can be preferably applied to joining and fixing parts in portable electronic devices. Patent Documents 1 and 2 are listed as technical documents relating to the pressure-sensitive adhesive sheet with a foam base material.

International Publication No. 2013/154137 Japanese Unexamined Patent Publication No. 2013-213104

In recent years, from the viewpoint of reducing the size and weight of products, it has been required to reduce the width of adhesive sheets used for joining parts and the like. For example, in the adhesive sheet used for fixing the display part protection member (for example, cover glass) of a portable electronic device, the adhesive sheet is used from the viewpoint of increasing the screen size of the information display part, improving the design, and improving the degree of freedom in design. It is meaningful to narrow it down.

However, when the adhesive sheet is narrowed, the bonding performance of parts (for example, pressing adhesive force) tends to decrease. Regarding this point, the present inventor has focused on the fact that when the width of the pressure-sensitive adhesive sheet is about 1 mm or less, the bonding performance deteriorates more than expected from the decrease in the adhesive area due to the narrowing. did. The present invention has been made in view of such circumstances, and an object of the present invention is to provide an adhesive sheet with less deterioration in performance due to narrowing.

One pressure-sensitive adhesive sheet provided herein has a pressure-sensitive adhesive layer on at least one surface of the foam substrate, and the 100% modulus M [N / mm ² substrate] of the pressure-sensitive adhesive sheet and the foam. The relationship with the substrate density D [g / cm ³ ] satisfies 9.0 ≦ (M / D). As described above, the adhesive sheet having a high 100% modulus M for the density D can suppress the degree of performance deterioration due to the narrowing. In addition, M in the above formula means that 100% modulus of the pressure-sensitive adhesive sheet is N / mm ² base material (here, "/ mm ² base material" means "per 1 mm ² cross section of foam base material". It is a numerical part expressed in units of.), And M itself is a dimensionless number (the same applies to M in other equations described in the present specification). Further, D in the above formula is a numerical part when the density of the foam base material is expressed in the unit of g / cm ³ , and D itself is a dimensionless number (other than those described in the present specification). The same applies to D in the formula of.). However, when describing the preferred numerical range of M or D in this specification, for readability, these numerical values may be indicated with a confirmatory unit (for other symbols). The same applies).

The other pressure-sensitive adhesive sheet provided herein has a pressure-sensitive adhesive layer on at least one surface of the foam substrate, and is 100% modulus M [N / mm ² substrate] of the pressure-sensitive adhesive sheet and the above-mentioned. The relationship with the thickness Hs [mm] of the foam base material satisfies 0.75 <M × Hs. An adhesive sheet having such characteristics exhibits strong resistance to elongation (tensile deformation). Therefore, even if the width is reduced, damage to the joint portion due to impact (peeling of the adhesive sheet, tearing of the foam base material, etc.) tends to occur, which is preferable.

In another preferred embodiment, the pressure-sensitive adhesive sheet preferably has a 100% modulus M higher than the 4.0 N / mm ² substrate. Such an adhesive sheet exhibiting 100% modulus M is preferable because it tends to be less likely to cause damage to the joint due to impact even if the width is reduced.

The pressure-sensitive adhesive sheet disclosed herein can be preferably carried out in an embodiment in which the thickness Hs of the foam base material is 0.06 mm to 0.30 mm (for example, 0.10 mm to 0.30 mm). According to the pressure-sensitive adhesive sheet provided with the foam base material having such a thickness, it is possible to achieve both a reduction in the thickness of the joint portion and a good impact resistance in a well-balanced manner.

The pressure-sensitive adhesive sheet according to a preferred embodiment has the following relationship between the pressing adhesive force S _1.0 [N] at a width of 1.0 mm and the pressing adhesive force S _0.3 [N] at a width of 0.3 mm: 0.3 ≦ S _0.3 /. S _1.0 ; is satisfied. As described above, the pressure-sensitive adhesive sheet having a small decrease in pressing adhesive force due to the narrowing of the pressure-sensitive adhesive sheet is, for example, a portion having a width of less than 1.0 mm (typically, a linear portion having a width of less than 1.0 mm). ) Can be suitably used in the form of a joining member.

The pressure-sensitive adhesive sheet disclosed herein is typically configured as a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of the foam substrate. The pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet with a foam base material) having such a form has an advantage that workability is good when joining or fixing parts using the pressure-sensitive adhesive sheet.

As described above, the pressure-sensitive adhesive sheet disclosed herein is suitable for use in joining parts of portable electronic devices because the performance deterioration due to narrowing is small. The adhesive sheet disclosed herein is, for example, for liquid-tightly joining a display unit or a display unit protection member of a portable electronic device and a housing to protect the electronic device housed in the housing from water and dust. Can be preferably used as a fixing member of.

It is a schematic sectional drawing which shows the structure of the pressure-sensitive adhesive sheet which concerns on one Embodiment. It is explanatory drawing which shows the evaluation sample used for the measurement of a pressing adhesive force. It is explanatory drawing which shows the measuring method of a pressing adhesive force. It is explanatory drawing which shows the evaluation sample used for the drop durability test. It is an exploded perspective view which shows the schematic structure of the dustproof evaluation test apparatus. It is sectional drawing which shows the schematic structure of the dustproof evaluation test apparatus.

Hereinafter, preferred embodiments of the present invention will be described.
Here, matters other than those specifically mentioned in the present specification and necessary for the implementation of the present invention shall be in accordance with the teaching regarding the implementation of the invention described in the present specification and the common general knowledge at the time of filing. Can be understood by those skilled in the art on the basis. The present invention can be carried out based on the contents disclosed in the present specification and the common general technical knowledge in the art.
In the following drawings, members / parts having the same function may be described with the same reference numerals, and duplicate description may be omitted or simplified. Further, the embodiments described in the drawings are schematically for the purpose of clearly explaining the present invention, and do not accurately represent the size or scale of the pressure-sensitive adhesive sheet of the present invention actually provided as a product.

As described above, the term "adhesive" as used herein refers to a material that exhibits a soft solid state (viscoelastic body) in a temperature range near room temperature and has the property of easily adhering to an adherend by pressure. .. As defined in "CA Dahlquist," Adhesion: Fundamental and Practice ", McLaren & Sons, (1966) P. 143", the pressure-sensitive adhesive here is generally a complex tensile modulus E ^* (1 Hz). ) < ¹⁰⁷ dyne / cm ² can be a material having the property (typically, a material having the above-mentioned property at 25 ° C.). The "base polymer" of the pressure-sensitive adhesive is the main component (that is, 50% by weight of the rubber-like polymer) of the rubber-like polymer (polymer exhibiting rubber elasticity in a temperature range near room temperature) contained in the pressure-sensitive adhesive. Ingredients that occupy the above). In addition, in this specification, a "main component" means a component which occupies 50% by weight or more unless otherwise specified.

<Foam base material>
The foam base material constituting the pressure-sensitive adhesive sheet disclosed herein is a base material having a portion having bubbles (bubble structure), and typically has at least one layered foam (foam layer). It is a base material containing a layer. The foam base material may be a base material composed of one layer or two or more foam layers. The foam base material may be, for example, a base material substantially composed of only one layer or two or more foam layers. Although not particularly limited, a preferable example of the foam base material in the technique disclosed herein is a foam base material composed of a single layer (one layer) of the foam base material.

The thickness Hs of the foam base material is not particularly limited, and can be appropriately set according to the strength and flexibility of the pressure-sensitive adhesive sheet, the purpose of use, and the like. From the viewpoint of thinning the joint portion, the thickness Hs of the foam base material is usually preferably 0.70 mm or less, preferably 0.40 mm or less, and more preferably 0.30 mm or less. The technique disclosed herein has a thickness Hs of a foam substrate of 0.20 mm or less (typically 0.18 mm or less, for example, 0) from the viewpoint of processability when processing an adhesive sheet into a narrow width. It can be preferably carried out in the embodiment of .16 mm or less). Further, from the viewpoint of impact resistance of the pressure-sensitive adhesive sheet, the thickness Hs of the foam base material is preferably 0.05 mm or more, preferably 0.06 mm or more, and 0.07 mm or more (for example, 0.08 mm or more). ) Is more preferable. The technique disclosed herein is preferably carried out in an embodiment in which the thickness Hs of the foam substrate is 0.10 mm or more (typically, more than 0.10 mm, preferably 0.12 mm or more, for example, 0.13 mm or more). Can be done. As the thickness of the foam base material increases, the desired impact resistance tends to be exhibited even in a narrower width. The impact resistance of the adhesive sheet can be evaluated by, for example, a drop durability test or a post-drop waterproof property test, which will be described later.

The density D of the foam base material (referred to as an apparent density; hereinafter the same unless otherwise specified) is not particularly limited and may be, for example, 0.1 to 0.9 g / cm ³ . From the viewpoint of impact resistance, the density D of the foam base material is preferably 0.8 g / cm ³ or less, preferably 0.7 g / cm ³ or less (for example, 0.6 g / cm ³ or less). In one embodiment, the density D of the foam substrate may be less than 0.5 g / cm ³ and may be less than 0.4 g / cm ³ (eg 0.5 g / cm ³ or less). From the viewpoint of impact resistance, the density D of the foam base material is preferably 0.12 g / cm ³ or more, more preferably 0.15 g / cm ³ or more, and 0.2 g / cm ³ or more (for example, 0. 3 g / cm ³ or more) is more preferable. In one embodiment, the density D of the foam substrate may be 0.4 g / cm ³ or more, 0.5 g / cm ³ or more (eg, more than 0.5 g / cm ³ ), and even more. It may be 0.55 g / cm ³ or more. The density D (apparent density) of the foam base material can be measured according to JIS K 6767.

In a preferred embodiment, the foam substrate density D can be 0.3-0.8 g / cm ³ . As the foam base material having a density in the above range, it is easy to obtain one having good shock absorption and a high (M / D) value. Therefore, the pressure-sensitive adhesive sheet provided with such a foam base material can have good impact resistance at the joint portion and can suppress the degree of performance deterioration due to narrowing.

The average bubble diameter of the foam base material is not particularly limited, but is preferably 300 μm or less, more preferably 200 μm or less, still more preferably 150 μm or less, from the viewpoint of suppressing performance deterioration due to narrowing. From the viewpoint of exhibiting higher performance waterproofness and dustproofness, the average bubble diameter of the foam substrate is preferably 120 μm or less, and is 100 μm or less (typically 90 μm or less, for example 80 μm or less, and further. 70 μm or less) is more preferable. In the technique disclosed herein, by reducing the average bubble diameter of the foam base material, it becomes easy to maintain waterproofness and dustproofness even if an impact is applied in a narrow width such as waterproofness after dropping, which will be described later. There is a tendency. Further, reducing the average bubble diameter is preferable because it can be effective as one method for increasing the above-mentioned M / D value. The lower limit of the average bubble diameter is not particularly limited, but from the viewpoint of impact resistance, 10 μm or more is usually suitable, 20 μm or more is preferable, 30 μm or more is more preferable, and 40 μm or more (for example, 50 μm or more) is further preferable. In one embodiment, the average bubble diameter may be 55 μm or more, and may be 60 μm or more. The average bubble diameter referred to here is a true sphere-equivalent average bubble diameter obtained by observing the cross section of the foam substrate with an electron microscope.

The bubbles contained in the foam base material preferably have a shape relatively close to a circle in the plan view of the foam base material. That is, it is preferable that the average bubble diameter in the flow direction (hereinafter, also referred to as “MD”) and the average bubble diameter in the width direction (hereinafter, also referred to as “CD”) of the foam base material are not too different. The degree of separation of the bubble shape from the circular shape is the ratio of the average cell diameter (MD average cell diameter) for MD to the average cell diameter (CD average cell diameter) for CD of the foam substrate, that is, the following. It can be grasped by using the "aspect ratio (MD / CD)" expressed by the formula as an index. If this aspect ratio (MD / CD) is closer to 1, it can be said that the shape of the bubbles contained in the foam base material in a plan view is closer to a circle.
Aspect ratio (MD / CD) = MD average cell diameter / CD average cell diameter

In one aspect of the technique disclosed herein, the aspect ratio (MD / CD) of the bubbles contained in the foam substrate is preferably 0.7 or more, more preferably 0.75 or more, still more preferably 0.8. That is, for example, 0.85 or more. In one aspect, the aspect ratio may be 0.9 or higher and may be 0.95 or higher (eg, approximately 1.0 or higher). The aspect ratio (MD / CD) is preferably 1.3 or less, more preferably 1.25 or less, still more preferably 1.2 or less, and may be, for example, 1.15 or less. When the aspect ratio (MD / CD) is not too small, the handleability of the pressure-sensitive adhesive sheet using the foam base material can be improved. Further, when the aspect ratio (MD / CD) is not too large, the waterproof property (for example, the waterproof property after dropping) and the dust resistance of the adhesive sheet using the foam base material can be improved. As will be described later, the aspect ratio (MD / CD) of the foam base material constituting the pressure-sensitive adhesive sheet that can be used in the form of having a narrow portion (particularly, the form of an annular member having a narrow portion) is close to 1. Is particularly meaningful.

Here, the MD of the foam base material refers to the extrusion direction in the manufacturing process of the foam base material. Although not particularly limited, the MD in a long foam base material such as a tape usually corresponds to the long direction thereof. Further, the CD of the foam base material refers to a direction orthogonal to the MD of the foam base material and along the surface of the foam base material. The thickness direction of the foam base material (hereinafter, also referred to as “VD”) is a direction orthogonal to both the MD and the CD.

The MD average bubble diameter of the foam base material is measured as follows.
That is, the foam base material is cut along a plane parallel to MD and VD (that is, a plane in which the direction of the perpendicular line coincides with the CD) at the substantially central portion of the CD, and the central portion of the cut surface is cut. Is photographed with a scanning electron microscope (SEM). The captured image is printed on A4 size paper, and a straight line with a length of 60 mm parallel to the MD is drawn on the image. At this time, the magnification of the SEM is adjusted so that about 10 to 20 bubbles exist on a straight line of 60 mm. The number of bubbles existing on the straight line is visually counted, and the MD average bubble diameter is calculated by the following formula.
MD average bubble diameter (μm) = 60 (mm) x 10 ³ / (number of bubbles (pieces) x magnification)

The CD average bubble diameter of the foam base material is measured as follows.
That is, the foam base material is cut along a plane parallel to the CD and VD (that is, a plane in which the direction of the perpendicular line coincides with the MD), and the central portion of the cut surface is photographed by SEM. The captured image is printed on A4 size paper, and a straight line with a length of 60 mm parallel to the CD is drawn on the image. At this time, the magnification of the SEM is adjusted so that about 10 to 20 bubbles exist on a straight line of 60 mm. The number of bubbles existing on the straight line is visually counted, and the CD average bubble diameter is calculated by the following formula.
CD average bubble diameter (μm) = 60 (mm) x 10 ³ / (number of bubbles (pieces) x magnification)

When drawing a straight line, make sure that the straight line penetrates the bubble without making point contact. When some bubbles come into point contact in a straight line, these bubbles are counted as one. Further, when both ends of the straight line do not penetrate the bubble and are located inside the bubble, the number of the bubbles is counted as 0.5.

The average cell diameter in each direction of the foam base material is controlled, for example, by adjusting the composition of the foam base material (the amount of the foaming agent used, etc.) and the production conditions (conditions in the foaming step, stretching step, etc.). be able to.

As the foam substrate in the technique disclosed herein, the relationship between the 10% compressive strength C ₁₀ [kPa] and the 30% compressive strength C ₃₀ [kPa] is as follows: (C ₃₀ / C ₁₀ ) ≤ 5. Those satisfying 0; can be preferably adopted. Here, the 10% compressive strength of the foam base material is obtained by sandwiching a measurement sample having a thickness of about 2 mm by stacking the foam base material cut into a square shape of 30 mm square between a pair of flat plates. The load when compressed by the thickness corresponding to 10% of the thickness (load at a compressive strength of 10%). That is, it refers to the load when the measurement sample is compressed to a thickness corresponding to 90% of the initial thickness. Similarly, for the 30% compressive strength C ₃₀ [kPa] and the 25% compressive strength C ₂₅ [kPa] described later, when the measurement sample is compressed by a thickness corresponding to 30% or 25% of the initial thickness. Refers to the load.
The compressive strength of the foam substrate at any compressibility is measured according to JIS K 6767. As a specific measurement procedure, the measurement sample is set in the center of the pair of flat plates, and the flat plates are continuously compressed to an arbitrary compression rate by narrowing the interval between the flat plates, and the flat plates are stopped there for 10 seconds. Measure the load after the lapse. The compressive strength of the foam base material can be controlled, for example, by the degree of cross-linking and density of the material constituting the foam base material, the size and shape of bubbles, and the like.

A small compressive strength ratio (C ₃₀ / C ₁₀ ) means that the effect of different degrees of compression on the compressive strength is small. For example, when the joint surface of the adhesive sheet has irregularities such as steps and scratches, the width of the adhesive sheet is partially different, or a part of the joint part of the adhesive sheet receives a larger stress than other parts. In such cases, a part of the adhesive sheet may be compressed more than the other part. When the adhesive sheet is narrowed, the difference in the degree of compression due to the above-mentioned step or the difference in partial width tends to become more remarkable. If the difference in compressive strength due to the difference in the degree of compression is too large, the strain is concentrated in the portion where the degree of compression changes, and this portion may become the starting point of peeling of the adhesive sheet or damage to the foam base material. .. Adhesive sheets using a foam base material with a small (C ₃₀ / C ₁₀ ) are less likely to peel off or damage the foam base material because the difference in compressive strength due to the difference in the degree of compression is small. .. This can be advantageous from the viewpoint of improving impact resistance. From the viewpoint of obtaining a better effect, (C ₃₀ / C ₁₀ ) is more preferably 4.5 or less, and further preferably 4.0 or less. (C ₃₀ / C ₁₀ ) may be 3.5 or less. The lower limit of (C ₃₀ / C ₁₀ ) is not particularly limited, but for example, 2.5 or more is appropriate, and 3.0 or more may be used.

The 25% compressive strength C ₂₅ of the foam substrate is not particularly limited, and may be, for example, 20 kPa or more (typically 40 kPa or more). Usually, 250 kPa or more is suitable for C ₂₅ , and 300 kPa or more (for example, 400 kPa or more) is preferable. The pressure-sensitive adhesive sheet provided with such a foam base material can exhibit good durability against impacts such as dropping even if it has a narrow width. For example, tearing of the adhesive sheet due to impact can be better prevented. The upper limit of C ₂₅ is not particularly limited, but usually 1300 kPa or less (for example, 1200 kPa or less) is appropriate. In one embodiment, C ₂₅ may be 1000 kPa or less, 800 kPa or less, and may be 600 kPa or less (for example, 500 kPa or less). The relationship between C ₂₅ [kPa] and the apparent density D [g / cm ³ ] is as follows: 150 ≦ C ₂₅ × D ≦ 400 (for example, 200 ≦ C ₂₅ × D ≦ 350, preferably 240 ≦ C ₂₅ × D ≦ A pressure-sensitive adhesive sheet comprising a foam substrate satisfying 300); may provide better results.

In another preferred embodiment, the foam substrate C ₂₅ can be 20 kPa to 200 kPa (typically 30 kPa to 150 kPa, for example 40 kPa to 120 kPa). Since the pressure-sensitive adhesive sheet provided with such a foam base material has low compressive strength for its density, it can be excellent in cushioning property even if it is narrow. For example, the foam base material absorbs the drop impact, so that the peeling of the adhesive sheet can be better prevented. The relationship between C ₂₅ [kPa] and the apparent density D [g / cm ³ ] is as follows: 100 ≦ C ₂₅ / D ≦ 400 (for example, 150 ≦ C ₂₅ / D ≦ 350, preferably 200 ≦ C ₂₅ / D ≦ A pressure-sensitive adhesive sheet comprising a foam substrate satisfying 300); may provide better results.

The tensile elongation of the foam base material is not particularly limited. For example, a foam base material having a tensile elongation in the flow direction (MD) of 200% to 800% (more preferably 400% to 600%) can be preferably adopted. Further, a foam base material having a tensile elongation in the width direction (TD) of 50% to 800% (more preferably 200% to 500%) is preferable. Elongation of the foam substrate is measured according to JIS K 6767. The elongation of the foam base material can be controlled by, for example, the degree of cross-linking, the apparent density (foaming ratio), and the like.

The tensile strength (tensile strength) of the foam base material is not particularly limited. For example, a foam base material having a tensile strength in the flow direction (MD) of 5 MPa to 35 MPa (preferably 10 MPa to 30 MPa) can be preferably adopted. Further, a foam base material having a tensile strength in the width direction (TD) of 1 MPa to 25 MPa (more preferably 5 MPa to 20 MPa) is preferable. The tensile strength of the foam substrate is measured according to JIS K 6767. The tensile strength of the foam base material can be controlled by, for example, the degree of cross-linking, the apparent density (foaming ratio), and the like.

The material of the foam base material is not particularly limited. Usually, a foam base material containing a foam layer formed of a foam (plastic foam) of a plastic material is preferable. The plastic material for forming the plastic foam (meaning including the rubber material) is not particularly limited, and can be appropriately selected from known plastic materials. As the plastic material, one kind may be used alone or two or more kinds may be used in combination as appropriate.

Specific examples of the plastic foam include a polyethylene-based resin foam such as a polyethylene foam and a polypropylene foam; a polyester-based foam such as a polyethylene terephthalate foam, a polyethylene naphthalate foam, and a polybutylene terephthalate foam. Resin foam; Polyvinyl chloride resin foam such as polyvinyl chloride foam; Vinyl acetate resin foam; Polyphenylene sulfide resin foam; aliphatic polyamide (nylon) resin foam, total fragrance Amid resin foam such as group polyamide (aramid) resin foam; polyimide resin foam; polyether ether ketone (PEEK) foam; styrene resin foam such as polystyrene foam; polyurethane Urethane-based resin foams such as resin foams; and the like. Further, as the plastic foam, a rubber-based resin foam such as a polychloroprene rubber foam may be used.

As a preferable foam, a polyolefin-based resin foam (hereinafter, also referred to as “polyolefin-based foam”) is exemplified. As the plastic material (that is, the polyolefin-based resin) constituting the polyolefin-based foam, various known or commonly used polyolefin-based resins can be used without particular limitation. For example, polyethylene such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer and the like can be mentioned. Examples of LLDPE include Ziegler-Natta catalytic linear low density polyethylene, metallocene catalytic linear low density polyethylene and the like. As such a polyolefin resin, one kind may be used alone or two or more kinds may be used in combination as appropriate.

A preferred example of the foam base material in the technique disclosed herein is a polyethylene-based foam base material substantially composed of a polyethylene-based resin foam from the viewpoint of impact resistance, waterproofness, dust resistance, and the like. , Polyolefin-based foam base material such as polypropylene-based foam base material substantially composed of polypropylene-based resin foam. Here, the polyethylene-based resin refers to a resin containing ethylene as a main monomer (that is, the main component of the monomer), and in addition to HDPE, LDPE, LLDPE, etc., ethylene in which the copolymerization ratio of ethylene exceeds 50% by weight- It may include a propylene copolymer, an ethylene-vinyl acetate copolymer and the like. Similarly, the polypropylene-based resin refers to a resin containing propylene as a main monomer. As the foam base material in the technique disclosed herein, a polyethylene-based foam base material can be preferably adopted.

The method for producing the plastic foam (typically, a polyolefin-based foam) is not particularly limited, and various known methods can be appropriately adopted. For example, it can be produced by a method including the above-mentioned plastic material or the above-mentioned plastic foam molding step, cross-linking step and foaming step. In addition, a stretching step may be included if necessary.
Examples of the method for cross-linking the plastic foam include a chemical cross-linking method using an organic peroxide or the like, an ionizing radiation cross-linking method for irradiating ionizing radiation, and the like, and these methods can be used in combination. Examples of the ionizing radiation include electron beams, α rays, β rays, and γ rays. The dose of ionizing radiation is not particularly limited, and an appropriate irradiation dose can be set in consideration of the target physical properties (for example, the degree of cross-linking) of the foam base material.

The foam base material may contain, if necessary, fillers (inorganic fillers, organic fillers, etc.), antioxidants, antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers, flame retardants, etc. Various additives such as a surfactant may be blended.

The foam substrate in the technique disclosed herein is colored in order to exhibit desired designability and optical properties (for example, light shielding property, light reflection property, etc.) in the pressure-sensitive adhesive sheet provided with the foam substrate. You may. For this coloring, known organic or inorganic colorants can be used alone or in combination of two or more.

For example, when the pressure-sensitive adhesive sheet disclosed herein is used for shading, the visible light transmittance of the foam substrate is not particularly limited, but is 0% to 15%, similar to the visible light transmittance of the pressure-sensitive adhesive sheet described later. It is preferably 0% to 10%, more preferably 0% to 10%. Further, when the pressure-sensitive adhesive sheet disclosed herein is used for light reflection, the visible light reflectance of the foam base material is preferably 20% to 100%, more preferably 20% to 100%, similar to the visible light reflectance of the pressure-sensitive adhesive sheet. It is 25% to 100%.

The visible light transmittance of the foam substrate is one of the foam substrates at a wavelength of 550 nm using a spectrophotometer (for example, a spectrophotometer manufactured by Hitachi High-Technologies Co., Ltd., model “U-4100”). It can be obtained by irradiating from the surface side and measuring the intensity of the light transmitted to the other surface side. The visible light reflectance of the foam base material can be determined by measuring the intensity of the light reflected by irradiating one surface of the foam base material at a wavelength of 550 nm using the spectrophotometer. The visible light transmittance and the visible light reflectance of the adhesive sheet can also be obtained by the same method.

When the pressure-sensitive adhesive sheet disclosed here is used for light-shielding applications, it is preferable that the foam base material is colored black. The black color is L * (brightness) defined by the L * a * b * color system, preferably 35 or less (for example, 0 to 35), and more preferably 30 or less (for example, 0 to 30). .. The a * and b * defined in the L * a * b * color system can be appropriately selected according to the value of L *, respectively. The a * and b * are not particularly limited, but both are preferably in the range of −10 to 10 (more preferably −5 to 5, still more preferably −2.5 to 2.5). For example, it is preferable that both a * and b * are 0 or substantially 0.

In the present specification, L *, a *, and b * defined in the L * a * b * color system are color difference meters (for example, a color difference meter manufactured by Minolta, trade name "CR-200". It is obtained by measuring using "). The L * a * b * color system is a color space recommended by the International Commission on Illumination (CIE) in 1976, and is a color space called the CIE1976 (L * a * b *) color system. It means that. The L * a * b * color system is defined in JIS Z 8729 in the Japanese Industrial Standards.

Examples of the black colorant used for coloring the foam base material to black include carbon black (furness black, channel black, acetylene black, thermal black, lamp black, etc.), graphite, copper oxide, manganese dioxide, and aniline. Black, perylene black, titanium black, cyanine black, activated carbon, ferrite (non-magnetic ferrite, magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complex, composite oxide black dye, anthracinone organic black Dyes and the like can be used. Carbon black is exemplified as a preferable black colorant from the viewpoint of cost and availability. The amount of the black colorant used is not particularly limited, and can be appropriately adjusted so as to impart desired optical characteristics.

When the pressure-sensitive adhesive sheet disclosed herein is used for light reflection, it is preferable that the foam base material is colored white. The white color is L * (brightness) defined by the L * a * b * color system, preferably 87 or more (for example, 87 to 100), and more preferably 90 or more (for example, 90 to 100). .. The a * and b * defined in the L * a * b * color system can be appropriately selected according to the value of L *, respectively. As a * and b *, for example, both are preferably in the range of −10 to 10 (more preferably −5 to 5, still more preferably −2.5 to 2.5). For example, it is preferable that both a * and b * are 0 or substantially 0.

Examples of the white colorant used for coloring the foam base material to white include titanium oxide (titanium dioxide such as rutyl-type titanium dioxide and anatase-type titanium dioxide), zinc oxide, aluminum oxide, silicon oxide, and zirconium oxide. , Magnesium oxide, calcium oxide, tin oxide, barium oxide, cesium oxide, yttrium oxide, magnesium carbonate, calcium carbonate (light calcium carbonate, heavy calcium carbonate, etc.), barium carbonate, zinc oxide, aluminum hydroxide, calcium hydroxide, Magnesium hydroxide, zinc hydroxide, aluminum silicate, magnesium silicate, calcium silicate, barium sulfate, calcium sulfate, barium stearate, zinc oxide, zinc sulfide, talc, silica, alumina, clay, kaolin, titanium phosphate, mica, gypsum, Inorganic white colorants such as white carbon, diatomaceous earth, bentonite, lithopon, zeolite, sericite, hydrohaloicite, acrylic resin particles, polystyrene resin particles, polyurethane resin particles, amide resin particles, polycarbonate resin particles, Examples thereof include organic white colorants such as silicone-based resin particles, urea-formalin-based resin particles, and melamine-based resin particles. The amount of the white colorant used is not particularly limited, and can be appropriately adjusted so as to impart desired optical characteristics.

If necessary, the surface of the foam base material may be subjected to an appropriate surface treatment. This surface treatment can be, for example, a chemical or physical treatment to enhance adhesion to adjacent materials (eg, a pressure-sensitive adhesive layer). Examples of such surface treatments include corona discharge treatment, chromic acid treatment, ozone exposure, flame exposure, ultraviolet irradiation treatment, plasma treatment, application of an undercoat agent (primer), and the like.

<Adhesive>
The pressure-sensitive adhesive sheet disclosed herein has a pressure-sensitive adhesive layer on at least one surface of the foam substrate. The type of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited. The above-mentioned adhesive is one or more selected from various polymers (adhesive polymers) such as acrylic, polyester, urethane, polyether, rubber, silicone, polyamide, and fluorine. Can be a pressure-sensitive adhesive formed from a pressure-sensitive adhesive composition containing, as a base polymer (a main component in the polymer component, that is, a component accounting for 50% by weight or more). The techniques disclosed herein may be preferably carried out, for example, in the form of a pressure-sensitive adhesive sheet with an acrylic pressure-sensitive adhesive.

Here, the "acrylic adhesive" refers to an adhesive using an acrylic polymer as a base polymer. The "acrylic polymer" is a monomer having at least one (meth) acryloyl group in one molecule (hereinafter, this may be referred to as "acrylic monomer") as a main constituent monomer component (main of the monomer). It refers to a polymer as a component (that is, a component that accounts for 50% by weight or more of the total amount of monomers constituting an acrylic polymer). Further, in the present specification, the “(meth) acryloyl group” means a comprehensive term for an acryloyl group and a methacryloyl group. Similarly, "(meth) acrylate" is meant to collectively refer to acrylates and methacrylates.

The acrylic polymer is typically a polymer containing an alkyl (meth) acrylate as a main constituent monomer component. As the alkyl (meth) acrylate, for example, a compound represented by the following formula (1) can be preferably used.
CH ₂ = C (R ¹ ) COOR ² (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. ^R2 is an alkyl group having 1 to 20 carbon atoms. Since it is easy to obtain an adhesive having excellent adhesive properties, R ² is an alkyl group having 2 to 14 carbon atoms (hereinafter, such a range of carbon atoms may be referred to as C _2-14 ). Certain alkyl (meth) acrylates are preferred. Specific examples of the alkyl group of C _2-14 include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-pentyl group and an isoamyl group. , Neopentyl group, n-hexyl group, n-heptyl group, n-octyl group, isooctyl group, 2-ethylhexyl group, n-nonyl group, isononyl group, n-decyl group, isodecyl group, n-undecyl group, n- Examples thereof include a dodecyl group, an n-tridecyl group, an n-tetradecyl group, and the like.

In a preferred embodiment, the total amount of monomers used in the synthesis of the acrylic polymer is approximately 50% by weight or more (typically 50 to 99.9% by weight), more preferably 70% by weight or more (typically 70% by weight or more). 70 to 99.9% by weight), for example, about 85% by weight or more (typically 85 to 99.9% by weight), but the alkyl (meth) acrylate in which ^R2 in the above formula (1) is C _2-14 (meth). More preferably, it is occupied by one or more selected from C _4-10 alkyl (meth) acrylates; particularly preferably one or both of n-butyl acrylates and 2-ethylhexyl acrylates). According to the acrylic polymer obtained from such a monomer composition, a pressure-sensitive adhesive exhibiting good pressure-sensitive properties is easily formed, which is preferable.

Although not particularly limited, as the acrylic polymer, one obtained by copolymerizing an acrylic monomer having a hydroxyl group (—OH) (hydroxyl group-containing acrylic monomer) can be preferably used. An acrylic polymer having such a copolymer composition is preferable because it has an excellent balance between adhesive force and cohesive force, and it is easy to obtain a pressure-sensitive adhesive having excellent removability.

As the hydroxyl group-containing acrylic monomer, one type can be used alone or two or more types can be used in combination. Specific examples of the hydroxyl group-containing acrylic monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 4-hydroxy. Butyl (meth) acrylate, 2-hydroxyhexyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) ) Hydroxyalkyl (meth) acrylates such as acrylates may be mentioned. Further, (4-hydroxymethylcyclohexyl) methyl acrylate, polypropylene glycol mono (meth) acrylate, N-hydroxyethyl (meth) acrylamide, N-hydroxypropyl (meth) acrylamide and the like are exemplified. Of these, hydroxyalkyl (meth) acrylates are preferable, and hydroxyalkyl (meth) acrylates in which the alkyl group in the hydroxyalkyl group is linear with 2 to 4 carbon atoms are particularly preferable.

The hydroxyl group-containing acrylic monomer is preferably used in the range of approximately 0.001 to 10% by weight of the total amount of the monomers used in the synthesis of the acrylic polymer. This makes it possible to realize an adhesive sheet in which the adhesive force and the cohesive force are balanced at a higher level. Further better results can be achieved by setting the amount of the hydroxyl group-containing acrylic monomer to be approximately 0.01 to 5% by weight (for example, 0.05 to 2% by weight). Alternatively, the acrylic polymer in the technique disclosed herein may be one in which the hydroxyl group-containing acrylic monomer is not copolymerized.

The acrylic polymer in the technique disclosed herein may be copolymerized with a monomer (other monomer) other than the above as long as the effect of the present invention is not significantly impaired. Such a monomer can be used, for example, for the purpose of adjusting the glass transition temperature of an acrylic polymer, adjusting the adhesive performance (for example, peelability), and the like. For example, examples of the monomer capable of improving the cohesive force and heat resistance of the pressure-sensitive adhesive include a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, a cyano group-containing monomer, vinyl esters, and an aromatic vinyl compound. Further, as a monomer capable of introducing a functional group which can be a cross-linking base point into an acrylic polymer or contributing to improvement of adhesive strength, a carboxyl group-containing monomer, an acid anhydride group-containing monomer, an amide group-containing monomer, an amino group-containing monomer, and the like. Examples thereof include an imide group-containing monomer, an epoxy group-containing monomer, (meth) acryloylmorpholine, and vinyl ethers. For example, as the other monomer, an acrylic polymer copolymerized with a carboxyl group-containing monomer is preferable.

Examples of the sulfonic acid group-containing monomer include styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, and (meth) acryloyloxy. Examples thereof include naphthalene sulfonic acid and sodium vinyl sulfonic acid.
Examples of the phosphoric acid group-containing monomer include 2-hydroxyethylacryloyl phosphate.
Examples of the cyano group-containing monomer include acrylonitrile and methacrylonitrile.
Examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl laurate and the like.
Examples of the aromatic vinyl compound include styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and other substituted styrenes.

Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.
Examples of the acid anhydride group-containing monomer include maleic anhydride, itaconic anhydride, and an acid anhydride substance of the above-mentioned carboxyl group-containing monomer.
Examples of the amide group-containing monomer include acrylamide, methacrylamide, diethylacrylamide, N-vinylpyrrolidone, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N, N-diethylacrylamide, N, N-diethylmethacrylate, and the like. Examples thereof include N, N'-methylenebisacrylamide, N, N-dimethylaminopropylacrylamide, N, N-dimethylaminopropylmethacrylamide, diacetoneacrylamide and the like.
Examples of the amino group-containing monomer include aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate and the like.
Examples of the imide group-containing monomer include cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, and itaconimide.
Examples of the epoxy group-containing monomer include glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, and allyl glycidyl ether.
Examples of vinyl ethers include methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether and the like.

Such "other monomers" may be used alone or in combination of two or more, but the total amount of the other monomers is the total amount of the monomers used for the synthesis of the acrylic polymer. Of this, it is preferably about 40% by weight or less (typically 0.001 to 40% by weight), and preferably about 30% by weight or less (typically 0.01 to 30% by weight, for example 0.1 to 10%). Weight%) is more preferable. When a carboxyl group-containing monomer is used as the other monomer, the content thereof can be, for example, 0.1 to 10% by weight, and usually 0.2 to 8% by weight, for example, 0.5% of the total amount of the monomers. It is appropriate to set it to ~ 5% by weight. When vinyl esters (for example, vinyl acetate) are used as the other monomers, the content thereof can be, for example, 0.1 to 20% by weight, and usually 0.5 to 10% by weight, based on the total amount of the monomers. % Is appropriate.

The copolymer composition of the acrylic polymer is appropriately designed so that the glass transition temperature (Tg) of the acrylic polymer is −15 ° C. or lower (typically −70 ° C. to −15 ° C.). Yes, preferably −25 ° C. or lower (for example, −60 ° C. to −25 ° C.), and more preferably −40 ° C. or lower (for example, −60 ° C. to −40 ° C.). It is preferable that the Tg of the acrylic polymer is not more than the above-mentioned upper limit value from the viewpoint of impact resistance of the pressure-sensitive adhesive sheet and the like. The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (that is, the type and amount ratio of the monomers used in the synthesis of the polymer).

Here, the Tg of the polymer in the present specification means the Tg obtained by the formula of Fox based on the copolymerization composition of the polymer. As shown below, the Fox formula is a relational formula between the Tg of the copolymer and the glass transition temperature Tgi of the homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer.
1 / Tg = Σ (Wi / Tgi)
In the Fox formula, Tg is the glass transition temperature (unit: K) of the copolymer, Wi is the weight fraction of the monomer i in the copolymer (copolymerization ratio based on the weight), and Tgi is the monomer i. Represents the glass transition temperature (unit: K) of the homopolymer.

As the glass transition temperature of the homopolymer used for calculating Tg, the value described in the publicly known material shall be used. For example, for the monomers listed below, the following values are used as the glass transition temperature of the homopolymer of the monomer.
2-Ethylhexyl acrylate -70 ° C
n-Butyl acrylate -55 ° C
Ethyl acrylate-22 ° C
Methyl acrylate 8 ℃
Methyl methacrylate 105 ° C
Cyclohexylmethacrylate 66 ° C
2-Hydroxyethyl acrylate -15 ° C
Vinyl acetate 32 ° C
Styrene 100 ° C
Acrylic acid 106 ℃
Methacrylic acid 228 ° C

For the glass transition temperature of homopolymers of monomers other than those exemplified above, the numerical values described in "Polymer Handbook" (3rd edition, JohnWiley & Sons, Inc., 1989) shall be used. For monomers for which multiple types of values are described in this document, the highest value is adopted.

For monomers for which the glass transition temperature of the homopolymer is not described in the above document, the value obtained by the following measurement method shall be used (see JP-A-2007-51271). Specifically, 100 parts by weight of a monomer, 0.2 parts by weight of azobisisobutyronitrile and 200 parts by weight of ethyl acetate as a polymerization solvent are added to a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux cooling tube. Add and stir for 1 hour while circulating nitrogen gas. After removing oxygen in the polymerization system in this way, the temperature is raised to 63 ° C. and the reaction is carried out for 10 hours. Then, the mixture is cooled to room temperature to obtain a homopolymer solution having a solid content concentration of 33% by weight. This homopolymer solution is cast-coated on a release liner and dried to prepare a test sample (sheet-shaped homopolymer) having a thickness of about 2 mm. This test sample is punched into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to shear strain at a frequency of 1 Hz using a viscoelasticity test device (ARES, manufactured by TA Instruments) in the temperature range. The viscoelasticity is measured in a shear mode at a temperature rise rate of −70 to 150 ° C. and 5 ° C./min, and the peak top temperature of tan δ (loss tangent) is defined as the glass transition temperature.

Although not particularly limited, in the acrylic polymer, the proportion of the monomer having a glass transition temperature of −45 ° C. or lower of the homopolymer in the total amount of the monomers used in the synthesis of the acrylic polymer is 50% by weight or more. (More preferably, it is 70% by weight or more, for example, 85% by weight or more). According to the acrylic polymer having such a copolymer composition, the impact resistance tends to be improved. The upper limit of the above ratio is not particularly limited, and may be 100% by weight of the total amount of the above monomers. From the viewpoint of adhesive cohesiveness and the like, it is usually appropriate that the proportion of the homopolymer having a glass transition temperature of −45 ° C. or lower in the total amount of the monomers is 99% by weight or less, and 97% by weight or less. Is preferable.

In the technique disclosed herein, the method for obtaining an acrylic polymer is not particularly limited, and is known as a method for synthesizing an acrylic polymer, such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, and a suspension polymerization method. Various polymerization methods can be appropriately adopted. For example, a solution polymerization method can be preferably used. As a monomer supply method for solution polymerization, a batch charging method, a continuous supply (drop) method, a split supply (drop) method, or the like in which all the monomer raw materials are supplied at once can be appropriately adopted. The polymerization temperature can be appropriately selected depending on the type of the monomer and solvent used, the type of the polymerization initiator, etc., and may be, for example, about 20 ° C to 170 ° C (typically 40 ° C to 140 ° C). can.

The initiator used for the polymerization can be appropriately selected from known or conventional polymerization initiators depending on the type of the polymerization method. For example, azo-based polymerization of 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylpropionamidine) disulfate, 2,2'-azobis (2-amidinopropane) dihydrochloride, etc. Initiators may be preferably used. Other examples of polymerization initiators include persulfates such as potassium persulfate and ammonium persulfate; peroxide-based initiators such as benzoyl peroxide, t-butyl hydroperoxide and hydrogen peroxide; and phenyl-substituted ethane and the like. Substituted ethane initiators; aromatic carbonyl compounds; and the like. Yet another example of the polymerization initiator is a redox-based initiator in which a peroxide and a reducing agent are combined. Examples of such redox-based initiators include a combination of a peroxide such as hydrogen peroxide solution and ascorbic acid, a combination of a peroxide such as hydrogen peroxide solution and an iron (II) salt, and a persulfate and sulfite. Examples include a combination with sodium hydrogen peroxide. The polymerization initiator may be used alone or in combination of two or more. The amount of the polymerization initiator used may be a normal amount, for example, about 0.005 to 1 part by weight (typically 0.01 to 1 part by weight) with respect to 100 parts by weight of all the monomer components. You can choose from a range.

The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from known or commonly used organic solvents. For example, aromatic compounds such as toluene and xylene (typically aromatic hydrocarbons); acetates such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane, cyclohexane and methylcyclohexane; 1 , 2-Dichloroethane and other halogenated alkanes; lower alcohols such as isopropyl alcohol, 1-butanol, sec-butanol, tert-butanol (eg, monohydric alcohols having 1 to 4 carbon atoms); tert-butylmethyl Any one solvent selected from ethers such as ethers; ketones such as methyl ethyl ketone and acetyl acetone; or a mixed solvent of two or more kinds can be used. For example, a polymerization solvent (which may be a mixed solvent) having a boiling point in the range of 40 ° C. to 150 ° C. (preferably 60 ° C. to 150 ° C., typically 70 ° C. to 130 ° C.) can be used.

Solution polymerization gives a polymerization reaction solution in which the acrylic polymer is dissolved in an organic solvent. The pressure-sensitive adhesive layer in the technique disclosed herein may be formed from a pressure-sensitive adhesive composition containing the above-mentioned polymerization reaction solution or an acrylic polymer solution obtained by subjecting the reaction solution to an appropriate post-treatment. As the acrylic polymer solution, a solution prepared by adjusting the polymerization reaction solution to an appropriate concentration can be used. Alternatively, an acrylic polymer solution prepared by synthesizing an acrylic polymer by a polymerization method other than solution polymerization (for example, emulsion polymerization, photopolymerization, bulk polymerization, etc.) and dissolving the acrylic polymer in an organic solvent may be used. good.

The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited, and may be, for example, in the range of 10 × 10 ⁴ to 500 × 10 ⁴ . The Mw of the acrylic polymer is preferably in the range of 10 × 10 ⁴ to 150 × 10 ⁴ , more preferably in the range of 15 × 10 ⁴ to 100 × 10 ⁴ , and 20 because it is easy to balance the adhesive properties. The range of × 10 ⁴ to 75 × 10 ⁴ is more preferable. The Mw of the acrylic polymer can be obtained as a standard polystyrene-equivalent value by performing GPC (gel permeation chromatography) on the solvent-soluble component (for example, tetrahydrofuran-soluble component) of the acrylic polymer.

The pressure-sensitive adhesive composition (for example, an acrylic pressure-sensitive adhesive composition) in the technique disclosed herein may include a pressure-sensitive adhesive resin. The tackifier resin is not particularly limited, and for example, various tackifier resins such as rosin-based, terpene-based, hydrocarbon-based, epoxy-based, polyamide-based, elastomer-based, phenol-based, and ketone-based resins can be used alone. Alternatively, two or more types can be used in combination.

Specific examples of the rosin-based tackifier resin include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; modified rosins obtained by modifying these unmodified rosins by hydrogenation, disproportionation, polymerization, etc. ( Hydrogenated rosins, disproportionated rosins, polymerized rosins, other chemically modified rosins, etc.); and other various rosin derivatives; etc. Examples of the above rosin derivatives include those in which unmodified rosin is esterified with alcohols (that is, esterified products of rosin) and modified rosins (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.) are esterified with alcohols. Resin esters such as those obtained (that is, esterified products of modified rosin); unsaturated fatty acid-modified rosins obtained by modifying unmodified rosin and modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.) with unsaturated fatty acids. Unsaturated fatty acid-modified rosin esters in which rosin esters are modified with unsaturated fatty acids; unmodified rosins, modified rosins (hydrogenated rosins, disproportionated rosins, polymerized rosins, etc.), unsaturated fatty acid-modified rosins or unsaturated fatty acids Rodin alcohols obtained by reducing the carboxyl group in the modified rosin esters; metal salts of rosins (particularly rosin esters) such as unmodified rosin, modified rosin, and various rosin derivatives; rosins (unmodified rosin, modified rosin, Examples thereof include a rosin phenol resin obtained by adding phenol to various rosin derivatives and the like with an acid catalyst and thermally polymerizing the ester.

Examples of terpene-based tackifier resins are terpene resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers; these terpene resins are modified (phenolic modification, aromatic modification, hydrogenation modification, hydrocarbons). Modified terpene resin (modified, etc.); etc. Examples of the modified terpene resin include terpene phenol resin, styrene modified terpene resin, aromatic modified terpene resin, hydrogenated terpene resin and the like.

Examples of hydrocarbon-based tackifier resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic / aromatic petroleum resins (styrene-olefin copolymers, etc.). ), Various hydrocarbon-based resins such as aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, kumaron-based resins, and kumaron-inden-based resins. Examples of the aliphatic hydrocarbon resin include polymers of one or more aliphatic hydrocarbons selected from olefins having about 4 to 5 carbon atoms and dienes. Examples of the olefin include 1-butene, isobutylene, 1-pentene and the like. Examples of the above-mentioned diene include butadiene, 1,3-pentadiene, isoprene and the like. Examples of the aromatic hydrocarbon resin include polymers of vinyl group-containing aromatic hydrocarbons (styrene, vinyltoluene, α-methylstyrene, inden, methyl inden, etc.) having about 8 to 10 carbon atoms. Be done. As an example of an aliphatic cyclic hydrocarbon resin, an alicyclic hydrocarbon resin obtained by polymerizing a so-called “C4 petroleum distillate” or “C5 petroleum distillate” after cyclization dimerization; a cyclic diene compound (cyclic diene compound). Polymers of cyclopentadiene, dicyclopentadiene, etilidennorbornene, dipentene, etc.) or their hydrogen additives; alicyclic hydrocarbons with hydrogenated aromatic rings of aromatic hydrocarbon resins or aliphatic / aromatic petroleum resins. Resin; etc.

In the technique disclosed herein, as the tackifier resin, a resin having a softening point (softening temperature) of about 100 ° C. or higher (preferably about 120 ° C. or higher, more preferably about 135 ° C. or higher) can be preferably used. According to the pressure-sensitive adhesive containing the pressure-sensitive adhesive resin having a softening point equal to or higher than the above-mentioned lower limit value, a pressure-sensitive adhesive sheet having more excellent repulsion resistance can be realized. Among the tackifier resins exemplified above, a terpene-based tackifier resin having such a softening point (for example, a terpene phenol resin), a rosin-based tackifier resin (for example, an esterified product of a polymerized rosin) and the like can be preferably used. .. The tackifier resin can be preferably used, for example, in an embodiment containing a terpene phenol resin having a softening point of 135 ° C. or higher. Further, a pressure-sensitive adhesive containing a pressure-sensitive adhesive resin having a softening point of 140 ° C. or higher can realize particularly excellent resilience resistance. For example, a terpene phenol resin having a softening point of 140 ° C. or higher can be preferably used. The upper limit of the softening point of the tackifier resin is not particularly limited, and can be, for example, about 200 ° C. or lower (typically, about 180 ° C. or lower). The softening point of the tackifier resin can be measured based on the softening point test method (ring ball method) specified in JIS K2207.

The amount of the tackifying resin used is not particularly limited, and can be appropriately set according to the desired tackling performance (adhesive strength, etc.). For example, based on the solid content, the tackifier resin is used in a ratio of about 10 to 100 parts by weight (more preferably 15 to 80 parts by weight, still more preferably 20 to 60 parts by weight) with respect to 100 parts by weight of the acrylic polymer. It is preferable to do so.

As an example of a suitable composition of the acrylic pressure-sensitive adhesive disclosed herein, an acrylic polymer having a composition containing 20 to 60 parts by weight of a tackifier resin having a softening point of 120 ° C. or higher with respect to 100 parts by weight of the acrylic polymer. Examples thereof include a composition containing 10 to 50 parts by weight of a tackifier resin having a softening point of 135 ° C. or higher with respect to 100 parts by weight. According to the acrylic pressure-sensitive adhesive having such a composition, both repulsion resistance and flexibility tend to be suitably compatible.

A cross-linking agent may be used in the pressure-sensitive adhesive composition, if necessary. The type of the cross-linking agent is not particularly limited, and a known or commonly used cross-linking agent (for example, isocyanate-based cross-linking agent, epoxy-based cross-linking agent, oxazoline-based cross-linking agent, aziridine-based cross-linking agent, melamine-based cross-linking agent, peroxide-based cross-linking agent). , Urea-based cross-linking agent, metal alkoxide-based cross-linking agent, metal chelate-based cross-linking agent, metal salt-based cross-linking agent, carbodiimide-based cross-linking agent, amine-based cross-linking agent, etc.) can be appropriately selected and used. The cross-linking agent may be used alone or in combination of two or more. The amount of the cross-linking agent used is not particularly limited, and is, for example, about 10 parts by weight or less (for example, about 0.005 to 10 parts by weight, preferably about 0.01 to 5 parts by weight) with respect to 100 parts by weight of the acrylic polymer. You can choose from the range of.

The pressure-sensitive adhesive composition may be a leveling agent, a cross-linking aid, a plasticizer, a softening agent, a filler, a colorant (pigment, dye, etc.), an antioxidant, an antioxidant, an ultraviolet absorber, and an antioxidant, if necessary. It may contain various additives that are common in the field of pressure-sensitive adhesive compositions, such as agents and light stabilizers. As for such various additives, conventionally known additives can be used by a conventional method and do not particularly characterize the present invention, and therefore detailed description thereof will be omitted.

<Adhesive sheet>
The pressure-sensitive adhesive sheet disclosed herein (which may be in the form of an elongated tape or the like) includes a foam base material and an adhesive layer arranged on at least one surface of the foam base material. It is composed of. Such an adhesive sheet may be in the form of a single-sided adhesive sheet having an adhesive layer on only one surface of a foam base material and having only one surface as an adhesive surface (adhesive surface). In such a single-sided adhesive sheet, for example, the surface on the side having no adhesive layer is fixed to the adherend by a method other than adhesive (for example, a method using an adhesive, a method of heat-sealing, etc.). It can be used for joining and fixing parts. The pressure-sensitive adhesive sheet disclosed herein is typically preferably carried out in the form of a double-sided pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet with a foam base material) having pressure-sensitive adhesive layers on both sides of the foam base material. Such a double-sided adhesive sheet is advantageous from the viewpoint of, for example, the ease of joining operation of parts and the stability of joining quality.

The pressure-sensitive adhesive sheet disclosed herein may be, for example, a double-sided pressure-sensitive adhesive sheet having a cross-sectional structure schematically shown in FIG. The double-sided pressure-sensitive adhesive sheet 1 includes a sheet-shaped foam base material 15 and a first pressure-sensitive adhesive layer 11 and a second pressure-sensitive adhesive layer 12 supported on both sides of the base material 15, respectively. More specifically, the first surface 15A and the second surface 15B (both non-peelable) of the base material 15 are provided with the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12, respectively. As shown in FIG. 1, the double-sided adhesive sheet 1 before use (before being attached to the adherend) is spirally wound so that the front surface 17A and the back surface 17B are both overlapped with the release liner 17 which is a release surface. Can be in the form of In the double-sided pressure-sensitive adhesive sheet 1 of this form, the surface of the second pressure-sensitive adhesive layer 12 (second pressure-sensitive adhesive surface 12A) is protected by the front surface 17A of the release liner 17, and the surface of the first pressure-sensitive adhesive layer 11 (first pressure-sensitive adhesive surface 11A). ) Is protected by the back surface 17B of the release liner 17. Alternatively, the first adhesive surface 11A and the second adhesive surface 12A may be in a form protected by two independent release liners, respectively.

As the release liner, a conventional release paper or the like can be used, and the release liner is not particularly limited. For example, a peeling liner having a peeling treatment layer on the surface of a liner base material such as a plastic film or paper; from a low adhesive material such as a fluoropolymer (polytetrafluoroethylene etc.) or a polyolefin resin (polyethylene, polypropylene etc.) A peeling liner; etc. can be used. The peeling treatment layer may be formed by surface-treating the liner base material with a peeling treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.

As a method for forming the pressure-sensitive adhesive layer on the foam substrate, various conventionally known methods can be applied. For example, a method of directly applying the pressure-sensitive adhesive composition to a foam substrate (direct method), a method of applying the pressure-sensitive adhesive composition on an appropriate peeling surface to form a pressure-sensitive adhesive layer on the peeling surface, and the pressure-sensitive adhesive. Examples thereof include a method (transfer method) in which a layer is bonded to a foam substrate and transferred. These methods may be used in combination. Further, different methods may be adopted for the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer. The pressure-sensitive adhesive composition can be applied using a known or conventional coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, or a spray coater. When a pressure-sensitive adhesive composition containing a solvent is used, it is preferable to dry the pressure-sensitive adhesive composition under heating from the viewpoint of promoting the cross-linking reaction and improving the production efficiency.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and can be set according to the purpose of use and the target performance of the pressure-sensitive adhesive sheet. For example, the thickness of the pressure-sensitive adhesive layer can be approximately 5 μm to 150 μm. From the viewpoint of balancing the thinning of the adhesive sheet and the adhesive performance at a high level, the thickness of the adhesive layer is usually about 10 μm or more (preferably about 15 μm or more, more preferably about 20 μm or more, for example, about 25 μm or more. ) Is appropriate, and about 100 μm or less (preferably about 90 μm or less, more preferably about 80 μm or less, for example, about 60 μm or less) is appropriate. In one embodiment, the thickness of the pressure-sensitive adhesive layer can be, for example, about 10 μm to 100 μm (preferably about 15 μm to 90 μm, more preferably about 20 μm to 80 μm). From the viewpoint of reducing the thickness of the pressure-sensitive adhesive sheet, the thickness of the pressure-sensitive adhesive layer may be about 50 μm or less, and further may be about 40 μm or less (for example, about 35 μm or less).

The total thickness of the pressure-sensitive adhesive sheet disclosed herein is not particularly limited, but is usually about 0.07 mm or more (typically about 0.08 mm or more, preferably about 0.09 mm or more, more preferably about 0.10 mm. As described above, for example, about 0.12 mm or more) is appropriate, and may be about 0.15 mm or more. Further, the total thickness of the adhesive sheet is usually about 0.80 mm or less (typically about 0.50 mm or less, preferably about 0.40 mm or less, more preferably about 0.35 mm or less), and is generally suitable. It may be 0.30 mm or less (for example, about 0.25 mm or less, further about 0.20 mm or less). By making the total thickness of the adhesive sheet equal to or less than the above-mentioned upper limit value, it may be advantageous in terms of thinning, downsizing, weight reduction, resource saving, and the like of the product. Further, by setting the total thickness of the adhesive sheet to the above-mentioned lower limit value or more, excellent impact resistance, waterproofness, dustproofness and the like can be exhibited. In one embodiment, the total thickness of the pressure-sensitive adhesive sheet may be in the range of about 0.07 mm to 0.80 mm (for example, about 0.08 mm to 0.50 mm), and may be 0.09 mm to 0.40 mm (typically 0). It may be in the range of about 10 mm to 0.35 mm, for example, about 0.12 mm to 0.30 mm, further about 0.12 mm to 0.25 mm), or in the range of about 0.15 mm to 0.35 mm. You may.

In the pressure-sensitive adhesive sheet disclosed herein, the ratio of the thickness Hs [mm] of the foam base material to the total thickness Ht [mm] of the pressure-sensitive adhesive sheet is not particularly limited. From the viewpoint of effectively achieving both impact resistance and adhesive performance, it is usually appropriate to set Hs / Ht to about 20 to 80%, and about 30 to 70% (for example, about 40 to 60%). Is preferable.

In the case of an adhesive sheet whose adhesive surface is protected by a release liner, the total thickness of the adhesive sheet referred to here does not include the thickness of the release liner. Therefore, for example, in the double-sided adhesive sheet as shown in FIG. 1, the thickness Ht from the first adhesive surface 11A to the second adhesive surface 12A (that is, the thickness from one adhesive surface to the other adhesive surface) of the adhesive sheet is set. The total thickness.

The pressure-sensitive adhesive sheet disclosed herein includes layers other than the foam base material and the pressure-sensitive adhesive layer (intermediate layer, undercoat layer, etc., hereinafter also referred to as "other layers") as long as the effects of the present invention are not significantly impaired. Further may be included. For example, the other layer may be provided between the foam base material and the surface (adhesive surface) of the pressure-sensitive adhesive layer. In the pressure-sensitive adhesive sheet having such a structure, the thickness of the other layers is included in the total thickness of the pressure-sensitive adhesive sheet.

The pressure-sensitive adhesive sheet according to a preferred embodiment of the technique disclosed herein is a 100% modulus M [N / mm ² base material] of the pressure-sensitive adhesive sheet and a density D [g / g / of a foam base material constituting the pressure-sensitive adhesive sheet. The relationship with cm ³ ] satisfies 9.0 ≦ (M / D). An adhesive sheet satisfying such a relationship can be one in which the degree of performance deterioration due to narrowing is suppressed. It is not necessary to clarify the reason, but it can be considered as follows, for example. That is, the fact that the M / D of the pressure-sensitive adhesive sheet is large means that the pressure-sensitive adhesive sheet exhibits high resistance to tensile deformation for the density of the foam base material. Here, when the adhesive sheet is deformed by tensile stress, the contact area (adhesive area) between the adhesive sheet and the adherend generally decreases. Since the adhesive area of a narrow adhesive sheet is small from the beginning, the influence of the decrease in the adhesive area due to tensile deformation on the adhesive performance tends to be particularly large. Adhesive sheets with a large M / D are less likely to decrease in adhesive area with respect to tensile stress, which is considered to be beneficially contributing to suppressing the degree of performance deterioration due to narrowing.

In a preferred embodiment, the M / D value may be greater than or equal to 9.5 and may be greater than or equal to 10.0 and even greater than 10.5 (eg, 11.0 or higher). As the value of M / D increases, the degree of performance deterioration due to narrowing tends to be better suppressed. The upper limit of M / D is not particularly limited, but from the viewpoint of ease of manufacture or availability of the foam base material, 50 or less is usually suitable, 40 or less is preferable, and 30 or less (for example, 25 or less) is preferable. More preferred. In a preferred embodiment, the M / D may be 20 or less, or 15 or less.

Here, the 100% modulus M [N / mm ² substrate] of the pressure-sensitive adhesive sheet is measured as follows. That is, a sample (adhesive sheet) to be measured is cut into a size of 10 mm in width and 40 mm in length to prepare a test piece. At this time, the length direction of the test piece is set to coincide with the flow direction (MD) of the sample. This test piece is set vertically on a tensile tester with a test length (length between chucks) of 10 mm under a measurement environment at a temperature of 23 ° C. and 50% RH, and is stretched in the vertical direction at a tensile speed of 50 mm / min. The value [N / mm ² base material] obtained by converting the strength when the rate of change of the test length is 100% (when extended to 20 mm) into the strength per cross-sectional area of the foam base material is the value of the above sample. It is defined as 100% modulus for MD (hereinafter, also referred to as "MD modulus").
The 100% modulus [N / mm ² substrate] for the TD of the sample is applied in the same manner as in the above MD modulus measurement except that the length direction of the test piece is the width direction (TD) orthogonal to the MD of the sample. Obtain (hereinafter, also referred to as "TD modulus").
By averaging the MD modulus and the TD modulus, 100% modulus M [N / mm ² substrate] of the sample is obtained.

From the viewpoint of reducing the directional dependence of impact resistance, it is preferable that the MD modulus and the TD modulus are not extremely different. Although not particularly limited, the ratio of MD modulus [N / mm ² substrate] to TD modulus [N / mm ² substrate] can be, for example, 0.3 to 3, and is usually 0.5. It is preferably in the range of ~ 2, and more preferably in the range of 0.6 to 1.5.

The 100% modulus M of the pressure-sensitive adhesive sheet disclosed herein is not particularly limited and may be, for example, 2.5 N / mm ² base materials or more. When the 100% modulus M of the pressure-sensitive adhesive sheet is high, damage to the foam base material due to an external force such as an impact tends to be better prevented even in a narrow pressure-sensitive adhesive sheet. In addition, it tends to be easier to suppress performance deterioration due to narrowing. From this point of view, 100% modulus M is preferably higher than 4.0 N / mm ² base material, more preferably 4.5 N / mm ² base material or more, still more preferably 5.0 N / mm ² base material or more. (Typically, it is more than 5.0 N / mm ² base materials, for example, 5.5 N / mm ² base materials or more). The 100% modulus M of the pressure-sensitive adhesive sheet according to a preferred embodiment can be 6.0 N / mm ² substrates or more. Further, from the viewpoint of flexibility and the like, the 100% modulus M of the pressure-sensitive adhesive sheet is usually 12.0 N / mm ² base materials or less, preferably 10.0 N / mm ² base materials or less, and 8.0 N / mm. It is more preferably mm ² base material or less. The 100% modulus M of the pressure-sensitive adhesive sheet can be controlled by, for example, the degree of cross-linking and the density (apparent density) of the foam base material, the size and shape of bubbles, and the like.
The reason why 100% modulus M of the pressure-sensitive adhesive sheet is expressed as a numerical value per cross-sectional area of the foam base material (/ mm ² base material) is that the pressure-sensitive adhesive layer occupies 100% stretching strength of the pressure-sensitive adhesive sheet disclosed here. This is because the contribution is usually extremely small, and if the cross-sectional area of the pressure-sensitive adhesive layer is included when converting the stretch strength per cross-sectional area, it becomes rather difficult to grasp the characteristics of the pressure-sensitive adhesive sheet that suits the purpose of the present application.

The pressure-sensitive adhesive sheets disclosed herein include 100% modulus M [N / mm ² substrate], the density D [g / cm ³ ] of the foam substrate, and the average bubble diameter P [μm] of the foam substrate. It is preferable that the relationship with the following equation: 70 ≦ (M / D) / (P × 10 ^-3 ); The adhesive sheet satisfying the above formula has a foam base material having a small decrease in performance (for example, a decrease in pressing adhesive force) due to narrowing and a large number of bubbles for its density. Therefore, for example, it is waterproof after dropping, which will be described later. It can be excellent in performance of maintaining waterproofness and dustproofness even when it receives an impact in a narrow width such as sex. From the viewpoint of obtaining a more preferable effect, the value of (M / D) / (P × 10 ^-3 ) is preferably 90 or more, more preferably 120 or more, further preferably 150 or more, and may be 170 or more. .. The upper limit of the value of (M / D) / (P × 10 ^-3 ) is not particularly limited, but is usually 700 or less, and 500 or less is appropriate from the viewpoint of availability of materials or ease of manufacture. , Typically 300 or less, and may be 250 or less. In addition, P in the above formula is a numerical part when the above-mentioned average bubble diameter in terms of sphere is expressed in the unit of [μm], and P itself is a dimensionless number (described in the present specification). The same applies to P in other equations.)

In the pressure-sensitive adhesive sheet according to a preferred embodiment, the relationship between the 100% modulus M [N / mm ² base material] and the 25% compressive strength C ₂₅ [kPa] of the foam base material is as follows: C ₂₅ × 10 ^-3 ); is satisfied. Such an adhesive sheet exhibits good cushioning property against compressive stress and strong resistance to elongation, so that it has good shock absorption even if it is narrow and has performance due to narrowing. It can be less degraded. Better results can be achieved with an adhesive sheet having an M / (C ₂₅ × 10 ^-3 ) of 40 or more (more preferably 45 or more, even more preferably 50 or more, for example 55 or more). The upper limit of M / (C ₂₅ × 10 ^-3 ) is not particularly limited and may be, for example, 300 or less (preferably 200 or less, more preferably 150 or less, typically 100 or less).

The pressure-sensitive adhesive sheet according to another preferred embodiment includes 100% modulus M [N / mm ² base material], C ₂₅ [kPa] of the foam base material, and the density D [g / cm ³ ] of the foam base material. The relationship with is satisfied by the following equation: 10 ≦ (M × D) / (C ₂₅ × 10 ^-3 ). Since such an adhesive sheet has a high 100% modulus M for its compressive strength and density, it tends to show good cushioning property against compressive stress and strong resistance to elongation. Therefore, even if the width is narrow, the shock absorption is good and the performance deterioration due to the narrow width can be small. Better results can be achieved with an adhesive sheet in which (M × D) / (C ₂₅ × 10 ^-3 ) is 15 or more (eg, 18 or more). The upper limit of (M × D) / (C ₂₅ × 10 ^-3 ) is not particularly limited and may be, for example, 50 or less (preferably 40 or less, typically 30 or less).

The pressure-sensitive adhesive sheet according to another preferred embodiment of the technique disclosed herein is a 100% modulus M [N / mm ² base material] of the pressure-sensitive adhesive sheet and the thickness Hs of the foam base material constituting the pressure-sensitive adhesive sheet. The relationship with [mm] satisfies 0.50 ≦ M × Hs. Such an adhesive sheet tends to exhibit good impact resistance (for example, durability against a drop impact) even if the width is narrowed. It is considered that this is because the pressure-sensitive adhesive sheet having a value of M × Hs of 0.50 or more generally shows high resistance to tensile deformation, and the pressure-sensitive adhesive area is unlikely to decrease due to tensile stress. Although not particularly limited, the value of M × Hs is preferably 0.60 or more, and 0.70 or more (for example, more than 0.75) from the viewpoint of further improving the impact resistance in a narrow width. It is more preferably 0.80 or more (for example, 0.90 or more). The upper limit of the value of M × Hs is not particularly limited, but from the viewpoint of flexibility and the like, usually 10.0 or less is appropriate, 3.0 or less is preferable, and 2.0 or less (for example, 1.5 or less) is preferable. More preferred.

The pressing adhesive force of the pressure-sensitive adhesive sheet disclosed herein is not particularly limited. The pressure-sensitive adhesive sheet according to a preferred embodiment has a pressing adhesive force of 70 N or more (more preferably 100 N or more, still more preferably 130 N or more, for example 170 N or more) at a width of 1.0 mm. Such an adhesive sheet is preferable because it has high adhesive reliability.

The pressing adhesive force is made of stainless steel by a window frame-shaped (also referred to as "frame-shaped" or simply "frame-shaped") adhesive sheet (typically a double-sided adhesive sheet) having a width of 59 cm, a length of 113 cm, and a width of 1.0 mm. An evaluation sample is prepared by pressure-bonding a steel (SUS) plate and a glass plate with a load of 50 N for 10 seconds, and in this evaluation sample, the glass plate is applied from the inside to the outside at a load speed of 10 mm / min. It is defined as the maximum stress observed until the glass plate and the stainless steel plate are separated by pressing toward the thickness of the glass plate. More specifically, the pressing adhesive force can be measured according to the procedure described in Examples described later. As for the pressing adhesive force of the single-sided adhesive sheet, the adhesive surface is attached to the glass plate, and the surface having no adhesive layer is fixed to the SUS plate by a method other than adhesive to obtain sufficient adhesive strength. Just measure.

In the following description, the pressing adhesive force measured by using the window frame-shaped adhesive sheet having a width of 59 mm, a length of 113 mm, and a width of 1.0 mm is referred to as "pressing adhesive force at a width of 1.0 mm" or "pressing". Adhesive strength (1.0 mm width) "may be described. Similarly, the pressing adhesive force measured using a window frame-shaped double-sided adhesive sheet having a width of 59 mm, a length of 113 mm, and a width of A mm is referred to as "pressing adhesive force at a width of A mm" or "pressing adhesive force (A mm width)". May be written in. The pressing adhesive force (A mm width) can be measured in the same manner as the pressing adhesive force (1.0 mm width) except that a window frame-shaped adhesive sheet having a width of 59 mm, a length of 113 mm and a width of A mm is used.

In the pressure-sensitive adhesive sheet according to a preferred embodiment, the pressing adhesive force S _1.0 [N] at a width of 1.0 mm is 100%, and the pressing adhesive force S _0.3 [N] at a width of 0.3 mm is 27% or more of S _1.0 . That is, S _0.3 / S _1.0 is 27% or more. It is more preferable that S _0.3 / S _1.0 is 30% or more (for example, more than 30%). The value of S _0.3 / S _1.0 is preferably closer to 100%, so that the upper limit is not particularly limited, but it is usually 50% or less, typically 40% or less.
Note that S _0.3 is a numerical value expressing the pressing adhesive force in a width of 0.3 mm in units of [N] (Newton), and S _0.3 itself is a dimensionless number. The same applies to S _1.0 and S _0.5 and S _0.7 described later.

In the pressure-sensitive adhesive sheet according to another preferred embodiment, the pressing adhesive force S _1.0 [N] at a width of 1.0 mm is 100%, and the pressing adhesive force S _0.5 [N] at a width of 0.5 mm is 50% or more of S _1.0 . More preferably, it is more than 50% (for example, 52% or more). The value of S _0.5 / S _1.0 is preferably closer to 100%, so that the upper limit is not particularly limited, but it is usually 70% or less, typically 60% or less.

As described above, the pressure-sensitive adhesive sheet has a reduction rate of the pressing adhesive force of the same or less (preferably 1.1 times or less, more preferably 1.0 times or less, for example, less than 1.0 times) in comparison with the reduction rate of the width. Is a joining member having, for example, at least a part having a width of less than 1.0 mm (typically, a linear part having a width of less than 1.0 mm) because the decrease in the pressing adhesive force due to the narrowing is small. Can be suitably used in the form of.

Further, the fact that the decrease in the pressing adhesive force due to the narrowing of the pressure-sensitive adhesive sheet is small means that the variation in the pressing adhesive force with respect to the variation in the width (particularly, the variation in the range of the width of 1 mm or less) is small. Such an adhesive sheet can be suitably used in the form of a joining member having a linear portion at least in a part thereof and having a width of the linear portion different between a part and another portion. In an adhesive sheet having portions having different widths as described above (particularly, a joining member having at least a part of the linear portions having a width of less than 1.0 mm), the adhesive performance (for example, pressing adhesive force) due to the difference in width can be obtained. If the difference is too large, the strain will be concentrated in the portion where the width changes, which may be the starting point for peeling of the adhesive sheet or damage to the foam base material. An adhesive sheet having a small fluctuation in the pressing adhesive force with respect to a fluctuation in the width is unlikely to be peeled off or damaged, and thus can have excellent impact resistance.

Although not particularly limited, the adhesive sheet disclosed herein has the following conditions:
The pressing adhesive force (0.7 mm width) is 50 N or more (more preferably 70 N or more, still more preferably 90 N or more, for example 120 N or more);
The pressing adhesive force (0.5 mm width) is 35 N or more (more preferably 50 N or more, further preferably 65 N or more, for example 85 N or more); and the pressing adhesive force (0.3 mm width) is 20 N or more (more preferably 30 N). Above, more preferably 40 N or more, for example 50 N or more);
It is preferable to satisfy at least one of. Such an adhesive sheet has excellent adhesive reliability and can be suitable for narrowing.

The pressure-sensitive adhesive sheet disclosed herein may have desired optical properties (transmittance, reflectance, etc.). For example, the pressure-sensitive adhesive sheet preferably has a visible light transmittance of 0% or more and 15% or less (more preferably 0% or more and 10% or less). Further, the pressure-sensitive adhesive sheet used for light reflection applications preferably has a visible light reflectance of 20% or more and 100% or less (more preferably 25% or more and 100% or less). The optical properties of the pressure-sensitive adhesive sheet can be adjusted, for example, by coloring the foam base material as described above.

The pressure-sensitive adhesive sheet disclosed herein is preferably halogen-free from the viewpoint of preventing metal corrosion and the like. The halogen-free nature of the pressure-sensitive adhesive sheet can be an advantageous feature, for example, when the pressure-sensitive adhesive sheet can be used for fixing electrical and electronic components. Further, since the generation of halogen-containing gas during combustion can be suppressed, it is preferable from the viewpoint of reducing the environmental load. For halogen-free pressure-sensitive adhesive sheets, do not intentionally use halogen compounds as raw materials for foam base materials and pressure-sensitive adhesives, use foam base materials that do not intentionally contain halogen compounds, and use halogen when additives are used. It can be obtained by adopting means such as not using an additive derived from a compound alone or in combination as appropriate.

The object (adhesive body) to which the adhesive sheet to be attached disclosed here is not particularly limited. The pressure-sensitive adhesive sheet disclosed herein is, for example, a metal material such as stainless steel (SUS) or aluminum; an inorganic material such as glass or ceramics; polycarbonate (PC), polymethylmethacrylate (PMMA), polypropylene, polyethylene terephthalate (PET). , Acrylonitrile butadiene styrene copolymer resin (ABS), impact resistant polystyrene (HIPS), PC-ABS blend resin, PC-HIPS blend resin and other resin materials; natural rubber, butyl rubber and other rubber materials; and composite materials thereof. It can be used in a mode of being attached to an adherend made of the above.

Since the pressure-sensitive adhesive sheet disclosed here has little deterioration in performance due to narrowing, it can be suitable as a pressure-sensitive adhesive sheet used for the purpose of joining, fixing, etc. in a portable device having a strong demand for narrowing. Further, since the pressure-sensitive adhesive sheet disclosed herein contains a foam base material, it can be excellent in shock absorption, waterproofness, dustproofness and the like. Taking advantage of these features, for electronic device applications, for example, for fixing the display unit of portable electronic devices, for fixing the display unit protection member of mobile electronic devices, for fixing the key module member of mobile phones, for fixing the decoration panel of TVs, etc. It can be preferably applied to applications such as fixing a battery pack of a personal computer and waterproofing a lens of a digital video camera. Particularly preferred applications include mobile electronic device applications. In particular, it can be preferably used for a portable electronic device having a liquid crystal display device. For example, in such a portable electronic device, it is suitable for an application of joining a display unit (which may be a display unit of a liquid crystal display device) or a display unit protection member and a housing.

The display unit protection member is typically a member having a region showing light transmission in the thickness direction (hereinafter, also referred to as “light transmission member”), and may be referred to as a lens. .. Here, the term "lens" as used herein is a concept that includes both a lens that exhibits a refraction action of light and a lens that does not show a refraction action of light. That is, the "lens" in the present specification also includes a light transmissive member having no refraction action, for example, a protective panel that simply protects a display unit of a portable electronic device. The protective panel can also be grasped as a display unit protection member or a display unit cover member having light transmission. When the material of the protective panel is glass, the protective panel can also be referred to as "cover glass". However, the material of the protective panel or the lens is not limited to glass, and may be any material that can exhibit light transmission.

Further, in the present specification, the portable electronic device refers to a general electronic device to be carried and used, and is not particularly limited to other devices. Here, "portable" means that it is not enough to be portable, but that an individual (standard adult) has a level of portability that is relatively easy to carry. do. Examples of the "portable electronic device" here include mobile phones, smartphones, tablet PCs, notebook PCs and the like. Such a portable electronic device may be a so-called wearable type terminal (for example, a wristband type such as a wristwatch type, a head mount type such as a glasses type, etc.). The portable electronic devices include, for example, telephones, watches, cameras, glasses, personal computers and other information terminals, health management tools such as sphygmomanometers, pulse meters, and pedometers, music players, video players, recordings, and recordings. It may have the above functions.

The adhesive sheet disclosed herein is in the form of a joining member processed into various outer shapes, and is preferably used for joining or fixing parts constituting a portable electronic device (for example, joining a display unit or a display unit protection member and a housing). Can be used as a light-transmitting display protection member (typically a protective panel) and a joint to a housing). As a preferable form of such a joining member, a narrow portion having a width of less than 2.0 mm is provided, and the average width W [mm] of the narrow portion is less than 1.0 mm (more preferably 0.7 mm or less, still more preferable. Is 0.5 mm or less, for example, 0.3 mm or less). According to the adhesive sheet disclosed herein, good performance (pressing adhesive force, shock absorption, etc.) is exhibited even when used as a joining member having a shape including such a narrow portion (for example, a frame shape). obtain. The average width W [mm] of the narrow portion of the pressure-sensitive adhesive sheet is obtained by dividing the total area of the narrow width portion included in the pressure-sensitive adhesive sheet by the total length. When the width of the narrow portion is constant, the width of the narrow portion and the above average width match.

The narrow portion is typically linear. Here, the linear shape is a concept including a linear shape, a curved line shape, a polygonal line shape (for example, an L-shape), an annular shape such as a frame shape or a circular shape, and a complex or intermediate shape thereof. .. The above-mentioned annular shape is not limited to that formed by a curved line, and is partially or wholly formed in a straight line, for example, a shape along the outer circumference of a quadrangle (frame shape) or a shape along the outer circumference of a fan shape. It is a concept that includes a ring. The length of the narrow portion is not particularly limited. For example, in a form in which the length of the narrow portion is 10 mm or more (typically 20 mm or more, for example, 30 mm or more), the effect of applying the technique disclosed herein can be suitably exhibited. The width of the narrow portion may be constant or may be partially different.

The pressure-sensitive adhesive sheet disclosed herein has an average width W of the narrow portion in relation to the 100% modulus M [N / mm ² base material] of the pressure-sensitive adhesive sheet and the thickness Hs [mm] of the foam base material. It can be preferably used in a shape having [mm] of 0.4 / (M × Hs) or more. According to the adhesive sheet having such a shape, it is possible to form a joint portion having good impact resistance between the narrow portion and the adherend. The average width W [mm] of the narrow portion is 0.5 / (M × Hs) or more (more preferably 0.6 / (M × Hs) or more, for example 0.7 / (M × Hs) or more). According to the adhesive sheet having a shape, better performance (for example, performance capable of forming a joint portion in which waterproofness and dustproofness are not easily impaired even when subjected to a drop impact) can be realized.

The adhesive sheet disclosed here has the above-mentioned annular shape having a narrow portion, taking advantage of the features that good bonding performance, waterproof performance (for example, waterproofness after dropping), dustproof performance, etc. are easily exhibited even if the width is narrowed. In the form of a joining member, for example, a display unit of a portable electronic device or a display unit protection member and a housing are liquid-tightly bonded to protect the electronic equipment housed in the housing from water and dust. It can be suitably used as a member. Accordingly, according to this specification, there is provided a fixing member for fixing a display unit or a display unit protection member of a portable electronic device to a housing, including any of the pressure-sensitive adhesive sheets disclosed herein. The fixing member typically exhibits an annular planar shape. The ring shape of such an annular fixing member is not particularly limited, and may be, for example, a rectangle (frame shape), a circle, a polygon other than a rectangle (for example, a triangle), or any other irregular shape. Further, in the above concept of an annular shape, in addition to a completely closed annular ring (that is, a seamless annular ring) composed of one sheet, one sheet or a plurality of sheets may be overlapped with each other. A shape that can form a closed ring, or one sheet or a plurality of sheets are arranged so as to be close to each other, and the above-mentioned closely arranged portions are sealed by sealing as necessary. It may include a shape that may form a ring. Here, the proximity is a concept including contact (a state where the distance is zero), and for example, the distance between each other is 0 to 10 mm (typically 0.1 to 10 mm), preferably 0 to 5 mm. (Typically 0.1 to 5 mm), more preferably 0 to 2 mm (typically 0.1 to 2 mm), still more preferably 0 to 1 mm (typically 0.1 to 1 mm). To say. As a method of sealing the overlapped portion or the adjacent portion (for example, abutting), a method of closing with a sealing material such as an adhesive, a method of welding the ends to each other (for example, heat welding), or the like is adopted. be able to.

Further, the pressure-sensitive adhesive sheet disclosed here has a first width by taking advantage of the feature that the fluctuation of the adhesive performance (for example, the pressing adhesive force) is small with respect to the fluctuation of the width (particularly, the fluctuation in the range of the width of 1 mm or less). The above-mentioned form in which the W1 portion having the W1 portion and the W2 portion having the second width larger than the first width are continuously formed (typically annular) and the first width is less than 1 mm. (For example, a fixing member for fixing a display unit or a display unit protection member of a portable electronic device to a housing) can be suitably used. In such a joining member, the concentration of strain on the portion where the width changes (the change between the W1 portion and the W2 portion) is alleviated, so that the adhesive sheet peels off or the foam base material starts from the portion. Is less likely to be damaged. Therefore, it can be excellent in impact resistance.

The matters disclosed in this specification include the following.
(1) An adhesive sheet having an adhesive layer on at least one surface of a foam base material.
An adhesive sheet in which the relationship between the 100% modulus M [N / mm ² substrate] of the adhesive sheet and the density D [g / cm ³ ] of the foam substrate satisfies 9.0 ≦ (M / D).
(2) An adhesive sheet having an adhesive layer on at least one surface of a foam base material.
The relationship between the 100% modulus M [N / mm ² base material] of the pressure-sensitive adhesive sheet and the thickness Hs [mm] of the foam base material constituting the pressure-sensitive adhesive sheet satisfies 0.75 <M × Hs. Adhesive sheet.
(3) The pressure-sensitive adhesive sheet according to (1) or (2) above, wherein the 100% modulus M of the pressure-sensitive adhesive sheet is higher than that of the 4.0 N / mm ² substrate.
(4) The pressure-sensitive adhesive sheet according to any one of (1) to (3) above, wherein the thickness Hs of the foam base material is 0.10 mm to 0.30 mm.
(5) The pressure-sensitive adhesive sheet according to any one of (1) to (4) above, wherein the visible light transmittance of the pressure-sensitive adhesive sheet is 0% or more and 15% or less.
(6) The pressure-sensitive adhesive sheet according to any one of (1) to (5) above, wherein the foam base material is colored black.
(7) The pressure-sensitive adhesive sheet according to any one of (1) to (6) above, wherein the foam base material is a polyolefin-based foam base material.
(8) The pressure-sensitive adhesive sheet according to any one of (1) to (7) above, wherein the foam base material is a polyethylene-based foam base material.
(9) The pressure-sensitive adhesive sheet according to any one of (1) to (8) above, which is configured as a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of the foam base material.
(10) The pressure-sensitive adhesive sheet according to any one of (1) to (9) above, wherein the pressure-sensitive adhesive layer has a thickness of 20 μm to 80 μm.
(11) The pressure-sensitive adhesive sheet according to any one of (1) to (10) above, wherein the total thickness Ht of the pressure-sensitive adhesive sheet is 0.10 mm to 0.35 mm (for example, 0.15 mm to 0.35 mm).
(12) The above-mentioned (1) to (11), wherein the ratio of the thickness Hs [mm] of the foam base material to the total thickness Ht [mm] of the pressure-sensitive adhesive sheet is 30 to 70%. Adhesive sheet.
(13) The pressure-sensitive adhesive sheet according to any one of (1) to (12) above, wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer using an acrylic polymer as a base polymer.
(14) The pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer using an acrylic polymer as a base polymer.
The pressure-sensitive adhesive sheet according to any one of (1) to (13) above, wherein the Tg of the acrylic polymer is −40 ° C. or lower.
(15) The pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer using an acrylic polymer as a base polymer.
Of the total amount of the monomers used in the synthesis of the acrylic polymer, the proportion of the monomers having a homopolymer Tg of −45 ° C. or lower is 70% by weight or more (preferably 85% by weight or more). The adhesive sheet according to any one of (14).
(16) The pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer using an acrylic polymer as a base polymer.
The pressure-sensitive adhesive sheet according to any one of (1) to (15) above, wherein 0.2 to 8% by weight of the total amount of the monomers used for synthesizing the acrylic polymer is a carboxyl group-containing monomer.
(17) The pressure-sensitive adhesive sheet according to any one of (1) to (16) above, wherein the pressure-sensitive adhesive layer contains 20 to 80 parts by weight of a tack-imparting resin with respect to 100 parts by weight of the base polymer of the pressure-sensitive adhesive layer. ..
(18) Any of the above (1) to (17), wherein the pressure-sensitive adhesive layer contains 20 to 60 parts by weight of a tackifier resin having a softening point of 120 ° C. or higher with respect to 100 parts by weight of the base polymer of the pressure-sensitive adhesive layer. Adhesive sheet described in Crab.
(19) The pressure-sensitive adhesive sheet according to any one of (1) to (18) above, wherein the pressure-sensitive adhesive layer is crosslinked with an isocyanate-based cross-linking agent.
(20) The relationship between the pressing adhesive force S _1.0 [N] at a width of 1.0 mm and the pressing adhesive force S _0.3 [N] at a width of 0.3 mm satisfies the following equation: 0.3 ≦ S _0.3 / S _1.0 ;. The adhesive sheet according to any one of (1) to (19) above.
(21) An adhesive sheet having an adhesive layer on at least one surface of a foam base material.
It is configured as a double-sided adhesive sheet having adhesive layers on both sides of the foam base material.
The foam base material is a polyethylene-based foam base material, and the foam base material is a polyethylene-based foam base material.
The pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer using an acrylic polymer as a base polymer, and 85% by weight or more of the total amount of monomers used in the synthesis of the acrylic polymer has a homopolymer Tg of −45 ° C. or lower. It is a monomer and
The pressure-sensitive adhesive layer contains 20 to 80 parts by weight of the tackifier resin with respect to 100 parts by weight of the base polymer.
The thickness Hs of the foam base material is 0.06 mm to 0.30 mm (for example, 0.10 mm to 0.30 mm).
The total thickness Ht of the adhesive sheet is 0.10 mm to 0.35 mm (for example, 0.15 mm to 0.35 mm).
An adhesive sheet in which the relationship between the 100% modulus M [N / mm ² substrate] of the adhesive sheet and the density D [g / cm ³ ] of the foam substrate satisfies 9.0 ≦ (M / D).
(22) An adhesive sheet having an adhesive layer on at least one surface of a foam base material.
It is configured as a double-sided adhesive sheet having adhesive layers on both sides of the foam base material.
The foam base material is a polyethylene-based foam base material, and the foam base material is a polyethylene-based foam base material.
The pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer using an acrylic polymer as a base polymer, and 85% by weight or more of the total amount of monomers used in the synthesis of the acrylic polymer has a homopolymer Tg of −45 ° C. or lower. It is a monomer and
The pressure-sensitive adhesive layer contains 20 to 80 parts by weight of the tackifier resin with respect to 100 parts by weight of the base polymer.
The thickness Hs of the foam base material is 0.06 mm to 0.30 mm (for example, 0.10 mm to 0.30 mm).
The total thickness Ht of the adhesive sheet is 0.15 mm to 0.35 mm.
The relationship between the 100% modulus M [N / mm ² base material] of the pressure-sensitive adhesive sheet and the thickness Hs [mm] of the foam base material constituting the pressure-sensitive adhesive sheet satisfies 0.75 <M × Hs. Adhesive sheet.
(23) The adhesive sheet according to any one of (1) to (22) above, which is used for joining parts of a portable electronic device.

Hereinafter, some examples of the present invention will be described, but the present invention is not intended to be limited to those shown in such examples. In the following description, "part" and "%" are based on weight unless otherwise specified.

<Making an adhesive sheet>
(Example 1)
2.9 parts of acrylic acid, 5 parts of vinyl acetate, 92 parts of n-butyl acrylate, 0.1 part of 2-hydroxyethyl acrylate in a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a dropping device and a nitrogen introduction tube. , And 30 parts of ethyl acetate and 120 parts of toluene were added as a polymerization solvent, and the mixture was stirred for 2 hours while introducing nitrogen gas.
After removing oxygen in the polymerization system in this manner, 0.2 part of 2,2'-azobisisobutyronitrile (AIBN) was added, the temperature was raised to 60 ° C., and the polymerization reaction was carried out for 6 hours. A polymer solution containing the polymer was obtained. The solid content of this polymer solution was 40.0%, and the Mw of the polymer was 50 × 10 ⁴ .
To 100 parts of the polymer in the polymer solution, 10 parts of the trade name "Pencel D-125" (rosin-based tackifier resin, 100% solid content) manufactured by Arakawa Chemical Industry Co., Ltd., Arakawa Chemical Industry Co., Ltd. 10 copies of the product name "Super Ester A-100" (rosin-based tackifier resin, solid content 100%) manufactured by Co., Ltd., and the product name "Foralin 8020F" (rosin-based tackifier resin, solid content 100) manufactured by Eastman Chemical Co., Ltd. %) 5 parts and 15 parts of the trade name "Tamanol 803L" (terpenephenol resin, 100% solid content) manufactured by Arakawa Chemical Industry Co., Ltd. were added, and the mixture was sufficiently stirred until it was dissolved. Further, aromatic polyisocyanate as a cross-linking agent (trade name "Coronate L", manufactured by Nippon Polyurethane Industry Co., Ltd., solid content 75%) at a ratio of 2.0 parts to 100 parts of the polymer in the above polymer solution). Was added and the mixture was sufficiently stirred to obtain a solvent-type pressure-sensitive adhesive composition.
Two commercially available release liners (trade name "SLB-80W3D", manufactured by Sumika Kako Paper Co., Ltd.) were prepared. The pressure-sensitive adhesive composition is applied to one surface (peeling surface) of each of the peeling liners so that the thickness after drying is 50 μm, and the two sheets are peeled off by drying at 100 ° C. for 2 minutes. An adhesive layer was formed on the peeled surface of the liner. Polyethylene foam sheet (thickness 0.15 mm, density 0.56 g / cm ³ , 10% compressive strength (C ₁₀ ) 167 kPa, 25% compressive strength) in which these pressure-sensitive adhesive layers are subjected to corona discharge treatment on both sides. (C ₂₅ ) 468 kPa, 30% compressive strength (C ₃₀ ) 627 kPa, average bubble diameter 55 μm; hereinafter referred to as “base material 1A”), respectively. The release liner was left as it was on the pressure-sensitive adhesive layer and used to protect the surface (adhesive surface) of the pressure-sensitive adhesive layer. The obtained structure was passed once through a laminator (0.3 MPa, speed 0.5 m / min) at 80 ° C., and then cured in an oven at 50 ° C. for 1 day. In this way, the double-sided adhesive sheet according to Example 1 was obtained.

(Example 2)
Polyethylene foam sheet with corona discharge treatment on both sides instead of base material 1A (thickness 0.15 mm, density 0.56 g / cm ³ , 10% compressive strength (C ₁₀ ) 100 kPa, 25% compressive strength The double-sided pressure-sensitive adhesive sheet according to Example 2 was prepared in the same manner as in Example 1 except that (C ₂₅ ) 365 kPa, 30% compressive strength (C ₃₀ ) 515 kPa, average bubble diameter 155 μm; hereinafter referred to as “base material 1B”). Obtained.

(Example 3)
Polyethylene foam sheet with corona discharge treatment on both sides instead of base material 1A (thickness 0.15 mm, density 0.37 g / cm ³ , 10% compressive strength (C ₁₀ ) 34 kPa, 25% compressive strength The double-sided adhesive sheet according to Example 3 was prepared in the same manner as in Example 1 except that (C ₂₅ ) 92 kPa, 30% compressive strength (C ₃₀ ) 117 kPa, average bubble diameter 90 μm; hereinafter referred to as “base material 2A”). Obtained.

(Example 4)
Polyethylene foam sheet with corona discharge treatment on both sides instead of base material 1A (thickness 0.20 mm, density 0.20 g / cm ³ , 10% compressive strength (C ₁₀ ) 19 kPa, 25% compressive strength The double-sided adhesive sheet according to Example 4 was prepared in the same manner as in Example 1 except that (C ₂₅ ) 47 kPa, 30% compressive strength (C ₃₀ ) 59 kPa, average bubble diameter 90 μm; hereinafter referred to as “base material 3A”). Obtained.

(Example 5)
Polyethylene foam sheet with corona discharge treatment on both sides instead of base material 1A (thickness 0.08 mm, density 0.56 g / cm ³ , 10% compressive strength (C ₁₀ ) 148 kPa, 25% compressive strength (C ₂₅ ) 448 kPa, 30% compressive strength (C ₃₀ ) 617 kPa, average bubble diameter 55 μm; hereinafter referred to as “base material 4A”), and the thickness of the pressure-sensitive adhesive layer bonded to both sides of the base material 4A. A double-sided pressure-sensitive adhesive sheet according to Example 5 was obtained in the same manner as in Example 1 except that the values were all 35 μm.

When the MD modulus and the TD modulus of the double-sided pressure-sensitive adhesive sheet (the original fabric of the pressure-sensitive adhesive sheet for manufacturing the fixing member) according to each example were measured by the above-mentioned method, the MD modulus of Example 1 was 6.5 N / mm ² base material, TD. The modulus is 6.2 N / mm ² substrate, the MD modulus of Example 2 is 5.6 N / mm ² substrate, the TD modulus is 4.5 N / mm ² substrate, and the MD modulus of Example 3 is 4.5 N / mm ² . The base material, TD modulus is 6.5 N / mm ² base material, MD modulus of Example 4 is 6.1 N / mm ² base material, TD modulus is 3.1 N / mm ² base material, and MD modulus of Example 5 is 6. The 4N / mm ² substrate and the TD modulus were 6.2 N / mm ² substrate. Table 1 shows the results of obtaining 100% modulus M [N / mm ² base material], M / D and M × Hs of the pressure-sensitive adhesive sheet according to each example from these values.

<Measurement of pressing adhesive force>
The double-sided adhesive sheet was cut into a window frame shape (frame shape) having a width of 59 mm, a length of 113 mm, and a width of 1.0 mm as shown in FIG. 2 to obtain a window frame-shaped double-sided adhesive sheet. Using this window frame-shaped double-sided adhesive sheet, a glass plate having a width of 59 mm, a length of 113 mm, and a thickness of 1 mm (Gorilla glass manufactured by Corning Inc. was used. The same applies hereinafter) and stainless steel having a through hole with a diameter of 15 mm in the center. A steel plate (SUS plate) (width 70 mm, length 130 mm, thickness 2 mm) was bonded by crimping with a load of 50 N for 10 seconds to obtain an evaluation sample.
2A and 2B are schematic views of the evaluation sample, where FIG. 2A is a top view and FIG. 2B is a cross-sectional view taken along the line AA'. In FIG. 2, reference numeral 2 indicates a window frame-shaped double-sided adhesive sheet, reference numeral 21 indicates a SUS plate, reference numeral 22 indicates a glass plate, and reference numeral 21A indicates a through hole provided in the SUS plate 21.
These evaluation samples were set in a universal tensile compression tester (device name "tensile compression tester, TG-1kN" manufactured by Minebea Co., Ltd.). Then, the round bar was passed through the through hole of the SUS plate, and the round bar was lowered at a speed of 10 mm / min to press the glass plate away from the SUS plate. Then, the maximum stress observed until the glass plate and the SUS plate were separated was measured as the pressing adhesive force. The measurement was performed in an environment of 23 ° C. and 50% RH.
FIG. 3 is a schematic cross-sectional view showing a method of measuring the pressing adhesive force. Reference numeral 2 is a window frame-shaped double-sided adhesive sheet, reference numeral 21 is a SUS plate, reference numeral 22 is a glass plate, reference numeral 23 is a round bar, and reference numeral 24 is a reference numeral 24. Indicates a support base. The evaluation sample is fixed to the support base 24 of the testing machine as shown in FIG. 3, and the glass plate 22 of the evaluation sample is pressed by the round bar 23 that has passed through the through hole 21A of the SUS plate 21. In the pressing adhesive force measurement, the SUS plate 21 was not bent or damaged by the load applied by the glass plate 22 being pressed by the round bar 23.

An evaluation sample was prepared in the same manner as above except that the widths of the window frame-shaped adhesive sheet were changed to 0.7 mm, 0.5 mm and 0.3 mm, and the pressing adhesive force was measured in the same manner.
The results obtained are shown in Table 2. "-" In the table indicates that it has not been evaluated.

As shown in Table 2, when the pressure-sensitive adhesive sheet of Example 1 using the base material A1 and the pressure-sensitive adhesive sheet of Example 2 using the base material B1 are compared, Example 1 maintains the pressing adhesive force at a width of 0.5 mm. The rate (S _0.5 / S _1.0 ) was high, and the superiority of Example 1 was even more remarkable in the maintenance rate (S _0.3 / S _1.0 ) of the pressing adhesive force at a width of 0.3 mm. As a result, the pressing adhesive force at the width of 1.0 mm was about the same in Example 1 and Example 2, but the pressing adhesive force at the width of 0.5 mm was about 10% higher in the adhesive sheet of Example 1, and the width was 0. The pressing adhesive force of 3 mm was 20% or more higher in Example 1. For a commercially available pressure-sensitive adhesive sheet composed of an acrylic pressure-sensitive adhesive layer and not having a foam base material, the pressing adhesive force at each of the above sample widths was measured in the same manner, and from the results, (S _0.5 / S _1.0 ) and (S). _{When 0.3} / S _1.0 ) was calculated, (S _0.5 / S _1.0 ) was 46% and (S _0.3 / S _1.0 ) was 20%.

<Drop durability test>
The double-sided adhesive sheet was cut into a window frame shape (frame shape) having a width of 59 mm, a length of 113 mm, and a width of 1.0 mm as shown in FIGS. 4 (a) and 4 (b) to obtain a window frame-shaped double-sided adhesive sheet. .. Using this window frame-shaped double-sided adhesive sheet, a polycarbonate plate (width 70 mm, length 130 mm, thickness 2 mm) and a glass plate (width 59 mm, length 113 mm, thickness 0.5 mm) are crimped with a load of 50 N for 10 seconds. By bonding them together, a sample for evaluation was obtained.
4 (a) and 4 (b) are schematic views of the above-mentioned evaluation sample, (a) is a top view, and (b) is a sectional view taken along the line BB'. In FIG. 4, reference numeral 3 indicates a window frame-shaped double-sided adhesive sheet, reference numeral 31 indicates a polycarbonate plate, and reference numeral 32 indicates a glass plate.
A weight of 160 g was attached to the back surface of the polycarbonate plate of the evaluation sample (the surface opposite to the surface bonded to the glass plate). The evaluation sample with a weight was subjected to a drop test in which it was freely dropped from a height of 1.2 m onto a concrete plate 60 times at room temperature (about 23 ° C.). At this time, the direction of the drop was adjusted so that the six surfaces of the evaluation sample were sequentially downward. That is, 10 cycles of one drop pattern for each of the 6 surfaces were performed.
Then, each time the polycarbonate plate is dropped, it is visually confirmed whether or not the bonding between the polycarbonate plate and the glass plate is maintained, and the number of drops until the polycarbonate plate and the glass plate are peeled off (separated) is counted at room temperature. Evaluated as durability. If no peeling was observed even after dropping 60 times, it was evaluated as "more than 60".

An evaluation sample was prepared in the same manner as above except that the width of the window frame-shaped adhesive sheet was changed to 0.7 mm, 0.5 mm and 0.3 mm, and a drop durability test was conducted in the same manner.

<Waterproof test after dropping>
Based on the IPX7 standard (JIS C 0920 / IEC60529), the waterproofness of the evaluation sample after the drop durability test (after being dropped 60 times) was evaluated. That is, the evaluation sample after the drop durability test was submerged in a water tank at a depth of 1 m in a standard state (23 ° C., 50% RH) for 30 minutes, and the presence or absence of inundation into the inside was confirmed.
The results obtained are shown in Table 3.

<Dustproof test>
A dustproof test was performed using the dustproof evaluation test apparatus shown in FIGS. 5 and 6. Here, FIG. 5 is an exploded perspective view showing a schematic configuration of the dustproof evaluation test device, and FIG. 6 is a cross-sectional view of the dustproof evaluation test device. In FIGS. 5 and 6, reference numeral 120 is a dustproof evaluation test device, reference numeral 121 is a ceiling plate, reference numeral 122 is a spacer, reference numeral 123 is a double-sided adhesive sheet punched into a frame shape into a window frame shape, and reference numeral 125 is an evaluation box. A body, reference numeral 127 indicates an opening (a square shape having a side length of 52 mm), and reference numeral 128 indicates a space portion. The dustproof evaluation test apparatus 120 can form a substantially rectangular parallelepiped sealable space 128 inside by screwing a substantially rectangular flat plate-shaped ceiling plate 121 and an evaluation box 125. The opening 127 is an opening of the space 128. Further, the ceiling plate 121 has a notch in a rectangular shape (trapezoid) in a plan view as an opening.

A rectangular flat plate-shaped spacer 122 larger than the opening 127 is attached to the lower surface of the ceiling plate 121 facing the opening 127 so as to face the entire surface of the opening 127. A double-sided adhesive sheet 123 having a window portion having substantially the same size as the opening 127 is attached to a position facing the opening 127 on the lower surface of the spacer 122. Therefore, by screwing the ceiling plate 121, the double-sided adhesive tape 123 is fixed between the spacer 122 and the peripheral edge of the opening 127. Therefore, by screwing the ceiling plate 121 and the evaluation box 125, the space 128 in the evaluation box 125 is sealed by the adhesive tape 123 and the spacer 122. The thickness of the spacer 122 is selected according to the total thickness of the pressure-sensitive adhesive sheet to be evaluated so as to make up for the difference in the total thickness of the pressure-sensitive adhesive sheet according to each example.

0.1 g of corn starch as dust is put into the space 128 from the opening 127 in the evaluation box 125, the spacer 122 is arranged via the window frame-shaped double-sided adhesive tape 123, and the ceiling plate 121 is used for evaluation from above. By screwing to the box body 125, a dustproof evaluation test apparatus 120 in which the above-mentioned dust (not shown) was housed in the space 128 sealed with the window frame-shaped double-sided adhesive tape 123 was produced. The dustproof evaluation test device 120 was placed in a drum type drop tester (rotary drop device) and rotated at a speed of 3 rpm. The device is stopped every 10 rotations, the dustproof evaluation test device 120 is taken out, and the dust contained in the space 128 leaks from the seal by the window frame-shaped double-sided adhesive tape 123 and adheres to the outer surface of the dustproof evaluation test device 120. The presence or absence was visually observed, and the number of rotations until dust adhesion was observed was recorded.

The double-sided adhesive sheet according to each example has a square opening having a side length of 52 mm and a width of 1 mm (that is, a square shape having an outer peripheral shape of 54 mm on a side) or a width of 0.5 mm. The dustproof test was performed using a window frame-shaped double-sided adhesive tape 123 punched out so as to have a frame shape (that is, a square shape having an outer peripheral shape of 53 mm on each side). The results are shown in Table 3.

As shown in Table 3, in the evaluation at a width of 1.0 mm, the adhesive sheets of Examples 1 and 2 showed good drop durability and waterproofness after dropping, and no particular difference in performance was observed. On the other hand, when the width was 0.5 mm and the width was 0.3 mm, the adhesive sheet of Example 1 had clearly higher drop durability. In addition, although there was no difference in drop durability in the evaluation at a width of 0.7 mm, the adhesive sheet according to Example 2 was found to be flooded in the post-drop waterproofness test, and the adhesive sheet was damaged. There was found. On the other hand, the adhesive sheet of Example 1 showed good waterproofness even after the drop durability test at a width of 0.7 mm. Further, the adhesive sheet of Example 5 has a width of 0.5 mm or more and exhibits good drop durability and waterproofness after falling as in the adhesive sheet of Example 1, and even in a width of 0.3 mm, it is compared with the adhesive sheet of Example 2. Showed high drop durability. Further, the dustproof property of the pressure-sensitive adhesive sheet according to Examples 1 and 5 was superior to that of the pressure-sensitive adhesive sheet according to Example 2 in both the width of 1.0 mm and the width of 0.5 mm.

From the above evaluation results, it can be seen that the pressure-sensitive adhesive sheets of Examples 1 and 5 have less performance deterioration due to narrowing than the pressure-sensitive adhesive sheets of Example 2. For the difference in waterproofness after dropping in a width of 0.7 mm, it is advantageous that the adhesive sheet according to Example 1 and Example 5 uses a foam base material having a smaller average bubble diameter than the adhesive sheet according to Example 2. It is thought that it contributes to. The value of (M / D) / (P × 10 ^-3 ) obtained as the ratio of the value of M / D to the average bubble diameter P [μm] is 207.8 in Example 1 and 57.6 in Example 2. In Example 3, it was 165.2, in Example 4, it was 255.6, and in Example 5, it was 2001.3.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples exemplified above.

1 Double-sided adhesive sheet 11 1st adhesive layer 11A 1st adhesive surface 12 2nd adhesive layer 12A 2nd adhesive surface 15 Foam base material 15A 1st surface 15B 2nd surface 17 Peeling liner 17A Front surface of peeling liner 17B Peeling liner Back side 2 Double-sided adhesive sheet 21 Stainless steel plate 21A Through hole 22 Glass plate 23 Round bar 24 Support stand 3 Double-sided adhesive sheet 31 Polycarbonate plate 32 Glass plate 120 Dustproof evaluation test device 121 Ceiling plate 122 Spacer 123 Double-sided adhesive sheet 125 Evaluation box Body 127 Opening 128 Space

Claims (9)

A pressure-sensitive adhesive sheet having an pressure-sensitive adhesive layer on at least one surface of a foam base material.
The foam base material is a polyolefin-based foam base material, and the foam base material is a polyolefin-based foam base material.
The density D of the foam base material is 0.5 to 0.7 g / cm ³ , and the density D is 0.5 to 0.7 g / cm 3.
The 100% modulus M of the pressure-sensitive adhesive sheet is larger than 5.0 N / mm ² base material and 8.0 N / mm ² base material or less, and
Adhesive in which the relationship between the 100% modulus M [N / mm ² base material] of the pressure-sensitive adhesive sheet and the density D [g / cm ³ ] of the foam base material satisfies 10.0 <(M / D) ≦ 15. Sheet. The pressure-sensitive adhesive sheet according to claim 1, wherein the thickness Hs of the foam base material is 0.05 mm to 0.30 mm. Claim 1 that the relationship between the pressing adhesive force S _1.0 [N] at a width of 1.0 mm and the pressing adhesive force S _0.3 [N] at a width of 0.3 mm satisfies the following equation: 0.3 ≦ S _0.3 / S _1.0 ;. Or the adhesive sheet according to 2. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, which is configured as a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of the foam base material. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the total thickness Ht of the pressure-sensitive adhesive sheet is 0.10 mm to 0.35 mm. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the ratio of the thickness Hs [mm] of the foam base material to the total thickness Ht [mm] of the pressure-sensitive adhesive sheet is 30 to 70%. The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the foam base material has an average bubble diameter of 120 μm or less. The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer using an acrylic polymer as a base polymer. The adhesive sheet according to any one of claims 1 to 8, which is used for joining parts of a portable electronic device.

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