JP2017057375A - Adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive sheet that has good impact resistance, and inhibits light leakage from its end face in width direction even if it has a narrow width.SOLUTION: There is provided an adhesive sheet comprising a substrate film, and an adhesive layer disposed on at least one surface of the substrate film. The adhesive layer comprises a colorant in the adhesive layer. The adhesive layer has a thickness of higher than 25 μm, and a light transmittance of 5% or less in 0.6 mm of length.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an adhesive sheet. Specifically, for example, the present invention relates to an adhesive sheet suitable for joining a liquid crystal display module unit and a backlight unit in a liquid crystal display device built in a portable electronic device.

  In general, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive; the same shall apply hereinafter) is in the form of a soft solid (viscoelastic body) in a temperature range near room temperature and has a property of easily adhering to an adherend by pressure. Taking advantage of such properties, the pressure-sensitive adhesive is widely used for the purpose of joining, fixing and protecting members in a portable electronic device such as a mobile phone, for example, in the form of a pressure-sensitive adhesive sheet with a substrate. For example, in a liquid crystal display device built in a portable electronic device such as a mobile phone, a liquid crystal display module unit (hereinafter also referred to as “LCD unit”) and a backlight unit (hereinafter also referred to as “BL unit”) are joined. For the purpose, a pressure-sensitive adhesive sheet with a substrate as described above is used. Patent documents 1-3 are mentioned as literature about this kind of technique.

JP 2002-235053 A JP 2007-284551 A JP 2009-197124 A

  If the light from the BL unit leaks through the adhesive sheet, the light may reduce the visibility of the liquid crystal display surface. In order to prevent this, for example, a light-absorbing colored layer (typically a black layer) is provided on the surface of the substrate constituting the pressure-sensitive adhesive sheet from the BL unit side to the LCD unit side. The light transmitted through the light is shielded.

  From the viewpoint of reducing the thickness of a portable electronic device, the adhesive sheet used for joining the LCD unit and the BL unit has also been required to be thin (Patent Document 3, etc.). On the other hand, in recent years, there has been a tendency for portable electronic devices to focus on larger screens (wider display screen area) and designability, in order to suppress portability reduction and increase design flexibility associated with larger screens. In addition, it has been desired to reduce the width of the pressure-sensitive adhesive sheet. In response to such new needs, it is difficult to achieve both narrow width and bonding reliability with a thin adhesive sheet. For example, since the pressure-sensitive adhesive is a viscoelastic body, it can contribute to shock absorption. However, in a thin pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer tends to be thin, and the impact absorption capacity is further reduced by narrowing. For this reason, the thin and narrow pressure-sensitive adhesive sheet tends to lack the impact resistance (the ability to withstand an impact such as a drop impact and maintain the bonding). Since the large-screen LCD unit is heavy, it is particularly difficult to achieve both narrowing and impact resistance.

  The present inventor has studied to increase the thickness of the pressure-sensitive adhesive layer in order to realize a pressure-sensitive adhesive that achieves both narrowing and impact resistance at a higher level. However, if the pressure-sensitive adhesive layer is made thicker to a certain extent in the shape of a pressure-sensitive adhesive sheet different from the previous one (for example, a width of about 0.6 mm or less), the light of the BL unit passes through the pressure-sensitive adhesive layer in the width direction. It has been found that a new problem arises that the leaked light leaks from the end face and causes the uneven brightness of the liquid crystal display surface. In the background, it is considered that the performance of the backlight has been dramatically improved in recent years, and the brightness of the light emitted from the backlight has been improved accordingly.

  Accordingly, an object of the present invention is to provide a pressure-sensitive adhesive sheet that has good impact resistance and has a narrow width and suppressed light leakage from an end face having a width.

  The pressure-sensitive adhesive sheet provided by this specification includes a base film and a pressure-sensitive adhesive layer disposed on at least one surface of the base film. The pressure-sensitive adhesive layer typically contains a colorant in the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer has a thickness greater than 25 μm and a light transmittance of 5% or less at a length of 0.6 mm. Since the pressure-sensitive adhesive sheet configured as described above has a pressure-sensitive adhesive layer thicker than 25 μm, it is suitable for both narrowing and impact resistance. Further, since the light transmittance of the pressure-sensitive adhesive layer at a length of 0.6 mm is limited to 5% or less, in the pressure-sensitive adhesive layer having a thickness advantageous for improving impact resistance, the width and the width direction are reduced. It is possible to suitably achieve both suppression of light leakage to the light source.

  Here, in this specification, “light transmittance at length Amm” means light transmittance measured for a sample having an optical path length of Amm. Hereinafter, the light transmittance at a length of Amm may be referred to as “Amm light transmittance”. A specific method for measuring the Amm light transmittance will be described later. In the following, preventing or suppressing an event in which light is transmitted (penetrated) in the width direction of the pressure-sensitive adhesive sheet and the transmitted light leaks from the end face of the width is sometimes referred to as “horizontal light shielding”.

  The pressure-sensitive adhesive sheet disclosed herein can be preferably implemented in a mode in which the 0.6 mm light transmittance of a layer having a thickness of more than 25 μm among the layers constituting the pressure-sensitive adhesive sheet is 5% or less. According to such an aspect, the light leakage to the width direction of an adhesive sheet can be suppressed more effectively. That is, an adhesive sheet having a more excellent horizontal light shielding property can be realized.

  In the PSA sheet according to a preferred embodiment, the total thickness of the PSA layers contained in the PSA sheet is more than 50% of the total thickness of the PSA sheet. By comprising in this way, the adhesive sheet which exhibits a higher level of impact resistance is realizable.

  The pressure-sensitive adhesive sheet disclosed herein preferably has a vertical light transmittance of 1% or less. According to such an adhesive sheet, vertical light shielding and horizontal light shielding can be suitably realized by a single member.

  The pressure-sensitive adhesive sheet disclosed herein can be suitably implemented in a mode where the vertical light transmittance of the pressure-sensitive adhesive layer is higher than 25%. Such an embodiment is advantageous from the viewpoint of improving the aesthetic appearance of the pressure-sensitive adhesive sheet. For example, poor dispersion due to excessive use of the colorant can be prevented in advance.

  The pressure-sensitive adhesive sheet disclosed herein can be preferably implemented in a shape having a narrow part at least in part. The width of the narrow portion is typically less than 2.0 mm, preferably less than 1.0 mm. The pressure-sensitive adhesive sheet having such a shape tends to cause light leakage in the width direction at the narrow width portion, and the narrow width portion tends to be a starting point of peeling (bonding failure) due to impact. Therefore, it is particularly meaningful to apply the technique disclosed herein to achieve both the impact resistance and the horizontal light shielding property in the narrow portion.

  The pressure-sensitive adhesive sheet disclosed herein can be preferably implemented in a mode in which the width of the pressure-sensitive adhesive layer in the narrow width portion is 50 times or less the thickness of the pressure-sensitive adhesive layer. When the ratio of the thickness to the width of the pressure-sensitive adhesive layer becomes larger, more light is transmitted across the width of the pressure-sensitive adhesive layer constituting the narrow portion diagonally from the bottom to the top with the light source side at the bottom. Inconvenience such as uneven brightness tends to occur. Therefore, it is particularly meaningful to apply the technology disclosed herein to achieve both the impact resistance and the horizontal light shielding property in a suitable manner.

  A pressure-sensitive adhesive sheet according to a preferred embodiment includes a first pressure-sensitive adhesive layer disposed on one surface of the base film and a second pressure-sensitive adhesive layer disposed on the other surface of the base film. It is configured as a sheet. The thicknesses of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are both preferably larger than 25 μm. The pressure-sensitive adhesive sheet having such a configuration is highly useful as a joining member and tends to have good impact resistance even in a narrow width. Both the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer preferably have a 0.6 mm light transmittance of 5% or less. The pressure-sensitive adhesive sheet having such a configuration tends to have good horizontal light-shielding properties and good impact resistance even in a narrow width.

  The pressure-sensitive adhesive sheet disclosed herein utilizes, for example, a liquid crystal display device including an LCD unit and a BL unit, taking advantage of the fact that both impact resistance and horizontal light shielding properties can be suitably achieved even in a narrow width. And can be suitably used for joining the BL unit.

It is sectional drawing which shows one structural example of an adhesive sheet typically. It is sectional drawing which shows the other structural example of an adhesive sheet typically.

  Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention are based on the teachings on the implementation of the invention described in the present specification and the common general technical knowledge at the time of filing. Can be understood by those skilled in the art. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. Further, in the following drawings, members / parts having the same action may be described with the same reference numerals, and overlapping descriptions may be omitted or simplified. In addition, the embodiment described in the drawings is schematically illustrated for clearly explaining the present invention, and does not necessarily accurately represent the size and scale of the pressure-sensitive adhesive sheet of the present invention that is actually provided as a product. .

In the present specification, the “pressure-sensitive adhesive” refers to a material that exhibits a soft solid (viscoelastic body) state in a temperature range near room temperature and has a property of easily adhering to an adherend by pressure as described above. . The adhesive here is generally defined as “CA Dahlquist,“ Adhesion: Fundamental and Practice ”, McLaren & Sons, (1966) P. 143”, and generally has a complex tensile modulus E ^* (1 Hz). It may be a material having a property satisfying <10 ⁷ dyne / cm ² (typically, a material having the above property at 25 ° C.).

  The pressure-sensitive adhesive sheet disclosed herein is a pressure-sensitive adhesive sheet with a base material having a pressure-sensitive adhesive layer on at least one surface of a base film (support). The concept of the pressure-sensitive adhesive sheet herein may include what are called pressure-sensitive adhesive tapes, pressure-sensitive adhesive labels, pressure-sensitive adhesive films and the like. The pressure-sensitive adhesive sheet disclosed herein may be in the form of a roll or a single sheet. Or the adhesive sheet of the form processed into various shapes may be sufficient.

  The pressure-sensitive adhesive sheet disclosed herein may have, for example, a cross-sectional structure schematically shown in FIG. The pressure-sensitive adhesive sheet 1 shown in FIG. 1 includes a base film 10 and a first pressure-sensitive adhesive layer 21 and a second pressure-sensitive adhesive layer 22 supported on the first surface 10A and the second surface 10B of the base film 10, respectively. Prepare. The first surface 10A and the second surface 10B are both non-peelable surfaces (non-peel surfaces). The pressure-sensitive adhesive sheet 1 is used by attaching the surface (first pressure-sensitive adhesive surface) 21A of the first pressure-sensitive adhesive layer 21 and the surface (second pressure-sensitive adhesive surface) 22A of the second pressure-sensitive adhesive layer 22 to an adherend. That is, the pressure-sensitive adhesive sheet 1 is configured as a double-sided pressure-sensitive adhesive sheet (double-sided adhesive pressure-sensitive adhesive sheet). Prior to use, the pressure-sensitive adhesive sheet 1 was protected by release liners 31 and 32 on which the first pressure-sensitive adhesive surface 21A and the second pressure-sensitive adhesive surface 22A had at least a surface (peeling surface) having peelability on the pressure-sensitive adhesive surface side. It has a configuration. Alternatively, the release liner 32 may be omitted, and the release liner 31 having both release surfaces may be used, and the adhesive sheet 1 may be wound to bring the second adhesive surface 22A into contact with the back surface of the release liner 31. Accordingly, the second adhesive surface 22A may also be protected by the release liner 31.

  At least one of the first pressure-sensitive adhesive layer 21 and the second pressure-sensitive adhesive layer 22 is a pressure-sensitive adhesive layer having a thickness of more than 25 μm and a 0.6 mm light transmittance of 5% or less, and in the pressure-sensitive adhesive layer Contains a colorant. Both the first pressure-sensitive adhesive layer 21 and the second pressure-sensitive adhesive layer 22 have a thickness of more than 25 μm, a 0.6 mm light transmittance of 5% or less, and a pressure-sensitive adhesive layer containing a colorant. It may be an agent layer. As the colorant, for example, a black colorant can be preferably used.

  The pressure-sensitive adhesive sheet 1 preferably has a vertical light transmittance of 1% or less. In the base film 10 (preferably a resin film), a colorant may be dispersed (kneaded) for the purpose of adjusting the vertical light transmittance of the pressure-sensitive adhesive sheet 1 and adjusting the reflectance. As the colorant, a black colorant or a white colorant can be preferably employed.

  Moreover, the base film may be colored by the colored layer arrange | positioned on the surface of the base film (preferably resin film). One structural example of an adhesive sheet provided with such a base film is shown in FIG. The base film 10 of the pressure-sensitive adhesive sheet 2 includes a resin film 12 as a base film and a colored layer 14 provided on one surface of the base film. The colored layer 14 can be, for example, a black print layer printed on the surface of the resin film 12. The other structure is the same as that of the adhesive sheet 1 shown in FIG. The resin film 12 may be transparent, and a colorant may be dispersed. Further, the colored layer may be provided only on one surface of the base film as shown in FIG. 2, and the same or different colored layers are provided on one surface and the other surface of the base film, respectively. May be.

  The pressure-sensitive adhesive sheet disclosed herein may be in the form of a single-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer only on one surface of the base film. As an example of the form of the single-sided pressure-sensitive adhesive sheet, the configuration shown in FIG. 1 does not have any one of the first pressure-sensitive adhesive layer 21 and the second pressure-sensitive adhesive layer 22, or the configuration shown in FIG. And a form not having any one of the second pressure-sensitive adhesive layer 22.

<Adhesive layer>
The pressure-sensitive adhesive sheet disclosed herein has a pressure-sensitive adhesive layer thicker than 25 μm on at least one surface of the base film. The pressure-sensitive adhesive sheet configured as described above tends to exhibit good impact resistance even in a narrow width. From the viewpoint of enabling higher impact resistance, the thickness of the pressure-sensitive adhesive layer can be, for example, 27 μm or more, 30 μm or more, or 35 μm or more. The upper limit of the thickness of the pressure-sensitive adhesive layer is not particularly limited. From the viewpoint of ease of processing and the like when preparing the pressure-sensitive adhesive sheet into a narrow shape (a shape including at least a narrow portion), the thickness of the pressure-sensitive adhesive layer is usually suitably 100 μm or less, and 75 μm. The following is preferable, and 60 μm or less (for example, 50 μm or less) is preferable.

  The pressure-sensitive adhesive layer thicker than 25 μm preferably has a 0.6 mm light transmittance of 5% or less. This makes it possible to achieve both narrowing and horizontal light shielding properties. Here, the 0.6 mm light transmittance can be grasped by preparing a sheet-like measurement sample having a thickness of 0.6 mm and measuring the light transmittance in the thickness direction of the measurement sample. The light transmittance is measured by using a commercially available spectrophotometer to irradiate light having a wavelength of 380 to 780 nm perpendicularly to one surface of the measurement sample and measuring the intensity of the light transmitted to the other surface. Desired. As the spectrophotometer, for example, a spectrophotometer manufactured by Hitachi, Ltd. (device name “U4100 type spectrophotometer”) can be used. The same applies to the embodiments described later.

  The 0.6 mm light transmittance of the adhesive layer is measured using a sheet-like adhesive having a thickness of 0.6 mm as a measurement sample. For example, the measurement sample is obtained by holding a container having a flat peelable bottom surface horizontally, pouring the pressure-sensitive adhesive composition into the container, slowly drying or curing, and then sticking a 0.6 mm thick adhesive on the bottom surface. It can be prepared by forming an agent layer. Alternatively, a pressure-sensitive adhesive layer having an appropriate thickness smaller than 0.6 mm (for example, a thickness of about 0.05 mm to 0.2 mm) can be obtained by applying a pressure-sensitive adhesive composition on the release surface of the release liner and drying it. It is also possible to form a measurement sample having a thickness of 0.6 mm by forming and overlapping the pressure-sensitive adhesive layer. It is preferable that the measurement sample obtained by the superposition is then subjected to light transmittance measurement after curing at room temperature for 12 hours or longer (for example, about 24 hours), for example. In the examples described later, the pressure-sensitive adhesive composition is applied to the release surface of the same release liner as that used for the preparation of each pressure-sensitive adhesive sheet, dried at 100 ° C. for 2 minutes, and about 0.1 mm thick on the release surface. A pressure-sensitive adhesive layer was formed, and six pressure-sensitive adhesive layers were stacked to prepare a measurement sample having a thickness of 0.6 mm. After curing the sample at room temperature for 24 hours, light transmittance was measured.

  In general, since the pressure-sensitive adhesive is amorphous and does not show remarkable optical anisotropy, the light transmittance in the thickness direction measured for a pressure-sensitive adhesive having a thickness of 0.6 mm is the same as that of a pressure-sensitive adhesive having a width of 0.6 mm. It can be treated as a characteristic that reflects the light transmittance in the width direction. Therefore, the pressure-sensitive adhesive layer having a lower 0.6 mm light transmittance required by the above measurement method tends to exhibit higher horizontal light shielding properties. By restricting the light transmittance of 0.6 mm to 5% or less, even if the thickness of the pressure-sensitive adhesive layer is larger than 25 mm, light leakage through the pressure-sensitive adhesive layer in the width direction is accurately prevented or suppressed. be able to. From the viewpoint of further improving the horizontal light shielding property or enabling sufficient horizontal light shielding even with a narrower width, the 0.6 mm light transmittance of the pressure-sensitive adhesive layer is preferably 3% or less, more preferably 1% or less, and further preferably. Is 0.5% or less, particularly preferably 0.1% or less. The lower limit of the 0.6 mm light transmittance is not particularly limited, and may be substantially 0%, that is, below the detection limit.

  The method for adjusting the 0.6 mm light transmittance of the pressure-sensitive adhesive layer is not particularly limited, and various known methods can be employed. A typical example of such a technique is a technique in which a colorant is contained in the pressure-sensitive adhesive layer. This method is convenient because the 0.6 mm light transmittance of the pressure-sensitive adhesive layer can be easily adjusted to a desired value depending on the selection and use amount of the colorant. As the colorant, various materials that can be attenuated by reflecting and / or absorbing light traveling in the pressure-sensitive adhesive layer can be used. The color of the colorant is not particularly limited, and may be colored or colorless. Here, “colored” means to include black and metal colors. Further, “colorless” means white. The color of the colorant can be, for example, black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearl, and the like. The colorant can be typically contained in the pressure-sensitive adhesive layer in a dispersed state (can be dissolved) in the constituent material of the pressure-sensitive adhesive layer.

(Base polymer)
In the technology disclosed herein, the type of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited. The above-mentioned pressure-sensitive adhesives are various rubbery polymers such as acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, fluorine polymers and the like known in the field of pressure-sensitive adhesives. 1 type, or 2 types or more may be included as a base polymer. From the viewpoint of adhesive performance and cost, an adhesive containing an acrylic polymer or a rubber polymer as a base polymer can be preferably used. Of these, an adhesive (acrylic adhesive) having an acrylic polymer as a base polymer is preferable. Hereinafter, the pressure-sensitive adhesive layer constituted by the acrylic pressure-sensitive adhesive, that is, the pressure-sensitive adhesive sheet having the acrylic pressure-sensitive adhesive layer will be mainly described. The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet disclosed herein is constituted by the acrylic pressure-sensitive adhesive. It is not intended to be limited.

The “base polymer” of the pressure-sensitive adhesive refers to the main component of the rubbery polymer contained in the pressure-sensitive adhesive. The rubbery polymer refers to a polymer that exhibits rubber elasticity in a temperature range near room temperature. Further, in this specification, “main component” refers to a component contained in an amount exceeding 50% by weight unless otherwise specified.
The “acrylic polymer” refers to a polymer containing monomer units derived from a monomer having at least one (meth) acryloyl group in one molecule as monomer units constituting the polymer. Hereinafter, a monomer having at least one (meth) acryloyl group in one molecule is also referred to as an “acrylic monomer”. Accordingly, the acrylic polymer in this specification is defined as a polymer including monomer units derived from an acrylic monomer. A typical example of the acrylic polymer is an acrylic polymer in which the proportion of the acrylic monomer in all monomer components used for the synthesis of the acrylic polymer is more than 50% by weight.
The term “(meth) acryloyl” means acryloyl and methacryloyl comprehensively. Similarly, “(meth) acrylate” means acrylate and methacrylate, and “(meth) acryl” generically means acrylic and methacryl.

  As the acrylic polymer, for example, a polymer of a monomer raw material that includes alkyl (meth) acrylate as a main monomer and can further include a submonomer copolymerizable with the main monomer is preferable. Here, the main monomer means a component occupying more than 50% by weight of the monomer composition in the monomer raw material.

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. R ² is a chain alkyl group having 1 to 20 carbon atoms. Hereinafter, such a range of the number of carbon atoms may be expressed as “C _1-20 ”. From the viewpoint of the storage elastic modulus of the pressure-sensitive adhesive and the like, an alkyl (meth) acrylate that is a chain alkyl group in which R ² is C _1-14 (eg, C _2-10 , typically C _4-8 ) is used as a main monomer. It is appropriate to do. From the viewpoint of adhesive properties, the main monomer is alkyl acrylate (hereinafter, also simply referred to as C _4-8 alkyl acrylate) in which R ¹ is a hydrogen atom and R ² is a C _4-8 chain alkyl group. Is preferred.

Examples of the alkyl (meth) acrylate in which R ² is a C _1-20 chain alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl. (Meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate , Octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) Acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, And eicosyl (meth) acrylate. These alkyl (meth) acrylates can be used alone or in combination of two or more. Preferred alkyl (meth) acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

The proportion of alkyl (meth) acrylate in the total monomer components used for the synthesis of the acrylic polymer is preferably 70% by weight or more, more preferably 85% by weight or more, and further preferably 90% by weight or more. Although the upper limit of the ratio of alkyl (meth) acrylate is not particularly limited, it is usually preferably 99.5% by weight or less (for example, 99% by weight or less). Alternatively, the acrylic polymer may be obtained by polymerizing substantially only alkyl (meth) acrylate. Moreover, when using _C4-8 alkylacrylate as a monomer component, it is preferable that the ratio of _C4-8 alkylacrylate among the alkyl (meth) acrylate contained in this monomer component is 70 weight% or more, It is more preferably 90% by weight or more, and further preferably 95% by weight or more (typically 99 to 100% by weight). The technique disclosed herein can be preferably implemented in an embodiment in which 50% by weight or more (typically 60% by weight or more) of all monomer components is BA. In a preferred embodiment, the proportion of BA in the total monomer components may be 70% by weight or more, 80% by weight or more, and further 90% by weight or more. All the monomer components may further contain 2EHA in a proportion less than BA.

  Monomers (other monomers) other than those described above may be copolymerized in the acrylic polymer in the technology disclosed herein within a range that does not significantly impair the effects of the present invention. The other monomers can be used for the purpose of adjusting the glass transition temperature (Tg) of the acrylic polymer, adjusting the adhesive performance (for example, peelability), and the like. For example, as a monomer that can improve the cohesive strength and heat resistance of an adhesive, a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, a cyano group-containing monomer, a vinyl ester, an alicyclic (meth) acrylate, an aromatic vinyl compound Etc. Preferred examples of these include vinyl esters. Specific examples of vinyl esters include vinyl acetate (VAc), vinyl propionate, vinyl laurate, and the like. Of these, VAc is preferable. The amount of VAc used can be, for example, about 3.5 to 10% by weight (preferably about 4 to 7% by weight) of all monomer components.

Other monomers that can introduce a functional group that can serve as a cross-linking point to an acrylic polymer or contribute to an improvement in adhesive strength include a hydroxyl group (OH group) -containing monomer, a carboxy group-containing monomer, an acid anhydride group-containing monomer, and an amide. Examples thereof include a group-containing monomer, an amino group-containing monomer, an imide group-containing monomer, an epoxy group-containing monomer, (meth) acryloylmorpholine, and vinyl ethers.
As a preferable example of the acrylic polymer in the technology disclosed herein, an acrylic polymer obtained by copolymerizing a carboxy group-containing monomer as the other monomer may be mentioned. Examples of carboxy group-containing monomers include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. Is done. Of these, AA and MAA are preferable.
As another preferred example, an acrylic polymer obtained by copolymerizing a hydroxyl group-containing monomer as the other monomer may be mentioned. Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meta ) Hydroxyalkyl (meth) acrylates such as acrylate; polypropylene glycol mono (meth) acrylate; N-hydroxyethyl (meth) acrylamide and the like. Among these, a preferred hydroxyl group-containing monomer includes hydroxyalkyl (meth) acrylates in which the alkyl group is a straight chain having 2 to 4 carbon atoms.

The “other monomers” may be used alone or in combination of two or more. The total content of other monomers is preferably about 40% by weight or less (typically 0.001 to 40% by weight) of all monomer components, and is preferably about 30% by weight or less (typically 0.01%). -30% by weight, for example, 0.1-10% by weight) is more preferable.
When a carboxy group-containing monomer is used as the other monomer, the content is about 0.1 to 10% by weight of the total monomer component (for example, 0.2 to 8% by weight, typically 0.5 to 5% by weight). ) Is appropriate. When a hydroxyl group-containing monomer is used as the other monomer, the content is about 0.001 to 10% by weight of the total monomer component (for example, 0.01 to 5% by weight, typically 0.02 to 2% by weight). Is appropriate.

  The copolymer composition of the acrylic polymer is suitably designed such that the glass transition temperature (Tg) of the polymer is −15 ° C. or lower (typically −70 ° C. or higher and −15 ° C. or lower). . The Tg of the acrylic polymer is preferably −25 ° C. or lower (eg, −60 ° C. or higher and −25 ° C. or lower), more preferably −40 ° C. or lower (eg, −60 ° C. or higher and −40 ° C. or lower). Setting the Tg of the acrylic polymer to be equal to or lower than the above-described upper limit value is preferable from the viewpoint of workability for attaching the adhesive sheet.

The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (that is, the type and amount ratio of monomers used for the synthesis of the polymer). Here, the Tg of the acrylic polymer refers to a Tg determined by the Fox formula based on the composition of the monomer component used for the synthesis of the polymer. The formula of Fox is a relational expression between Tg of a copolymer and glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below.
1 / Tg = Σ (Wi / Tgi)
In the above Fox equation, Tg is the glass transition temperature (unit: K) of the copolymer, Wi is the weight fraction of monomer i in the copolymer (copolymerization ratio on a weight basis), 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 the calculation of Tg, the values described in known materials are 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
2-hydroxyethyl acrylate -15 ° C
4-hydroxybutyl acrylate -40 ° C
Vinyl acetate 32 ° C
Styrene 100 ° C
Acrylic acid 106 ℃
Methacrylic acid 228 ° C

  Regarding the glass transition temperature of homopolymers of monomers other than those exemplified above, the values described in “Polymer Handbook” (3rd edition, John Wiley & Sons, Inc., 1989) are used. The highest value is adopted for the monomer whose values are described in this document.

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 is used.
Specifically, a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux condenser is charged with 100 parts by weight of monomer, 0.2 part by weight of 2,2′-azobisisobutyronitrile and acetic acid as a polymerization solvent. 200 parts by weight of ethyl is added and stirred for 1 hour while flowing 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. Next, the mixture is cooled to room temperature to obtain a homopolymer solution having a solid concentration of 33% by weight. Next, this homopolymer solution is cast-coated on a release liner and dried to prepare a test sample (sheet-like 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 shear strain at a frequency of 1 Hz using a viscoelasticity tester (manufactured by TA Instruments Japan, model name “ARES”). Temperature range -70 ° C. to 150 ° C., the viscoelasticity is measured by a shear mode at a heating rate of 5 ° C./min, and the temperature corresponding to the peak top temperature of the shear loss elastic modulus G ″ (G ″ curve is The maximum temperature) is defined as the Tg of the homopolymer.

  The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as synthetic methods for acrylic polymers, such as solution polymerization method, emulsion polymerization method, bulk polymerization method, suspension polymerization method, photopolymerization method, etc. Can be adopted as appropriate. For example, a solution polymerization method can be preferably used. As a monomer supply method when performing solution polymerization, a batch charging method, a continuous supply (dropping) method, a divided supply (dropping) method, or the like that supplies all monomer raw materials at once can be appropriately employed. The polymerization temperature can be appropriately selected according to the type of monomer and solvent to be used, the type of polymerization initiator, and the like, for example, about 20 ° C. to 170 ° C. (typically 40 ° C. to 140 ° C.). it can. In a preferred embodiment, a polymerization temperature of about 75 ° C. or less (more preferably about 65 ° C. or less, for example, about 45 ° C. to 65 ° C.) can be employed.

  The solvent (polymerization solvent) used for the solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds such as toluene (typically aromatic hydrocarbons); acetates such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; 1,2-dichloroethane, etc. Halogenated alkanes; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; Any one kind of solvent or two or more kinds of mixed solvents can be used.

  The initiator used for the polymerization can be appropriately selected from conventionally known polymerization initiators according to the type of the polymerization method. For example, one or more azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be preferably used. Other examples of the polymerization initiator include persulfates such as potassium persulfate; peroxide initiators such as benzoyl peroxide and hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; aromatic carbonyl compounds And the like. Still another example of the polymerization initiator includes a redox initiator based on a combination of a peroxide and a reducing agent. Such a polymerization initiator can be used individually by 1 type or in combination of 2 or more types. 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 monomer components. You can choose from a range.

  According to the solution polymerization, a polymerization reaction liquid in a form in which an acrylic polymer is dissolved in an organic solvent is obtained. The pressure-sensitive adhesive layer in the technology disclosed herein may be formed from a pressure-sensitive adhesive composition containing the above-mentioned polymerization reaction liquid or an acrylic polymer solution obtained by subjecting the reaction liquid to an appropriate post-treatment. As said acrylic polymer solution, what prepared the said polymerization reaction liquid to the appropriate viscosity (concentration) as needed 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 base polymer (preferably acrylic polymer) in the technique disclosed herein is not particularly limited, and may be, for example, in the range of 10 × 10 ^{4 to} 500 × 10 ⁴ . From the viewpoint of adhesive performance, the Mw of the base polymer is in the range of 10 × 10 ^{4 to} 150 × 10 ⁴ (for example, 20 × 10 ⁴ to 75 × 10 ⁴ , typically 35 × 10 ^{4 to} 65 × 10 ⁴ ). Preferably there is. Here, Mw refers to a value in terms of standard polystyrene obtained by GPC (gel permeation chromatography). As the GPC apparatus, for example, a model name “HLC-8320GPC” (column: TSKgelGMH-H (S), manufactured by Tosoh Corporation) can be used.

(Tackifier)
The pressure-sensitive adhesive layer disclosed herein may contain a tackifier. The tackifier is not particularly limited, for example, rosin tackifier resin, terpene tackifier resin, hydrocarbon tackifier resin, epoxy tackifier resin, polyamide tackifier resin, elastomer tackifier resin, Various tackifying resins such as a phenolic tackifying resin and a ketone tackifying resin can be used. Such tackifiers can be used singly or in combination of two or more. When an acrylic polymer is employed as the base polymer, it is preferable to use a rosin-based tackifier resin (for example, a polymerized rosin ester) or a terpene-based tackifier resin (for example, a terpene phenol resin).

  Specific examples of rosin-based tackifying resins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, tall oil rosin; modified rosins modified by hydrogenation, disproportionation, polymerization, etc. Hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosins, etc.); various other rosin derivatives; Examples of the rosin derivatives include those obtained by esterifying unmodified rosin with alcohols (ie, rosin esterified products) and modified rosins (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.) with alcohols. Rosin esters such as modified rosin esterified products (ie, unmodified rosins and modified rosins (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.) modified with unsaturated fatty acids. Unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; Unmodified rosin, modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.), unsaturated fatty acid-modified rosin or unsaturated fatty acid Rosin alcohols obtained by reducing carboxyl groups in modified rosin esters; unmodified rosin, modified rosin Metal salts of rosins (particularly rosin esters) such as various rosin derivatives; rosin phenol obtained by adding phenol to an rosin (unmodified rosin, modified rosin, various rosin derivatives, etc.) with an acid catalyst and thermal polymerization Resin; and the like.

  Examples of terpene-based tackifier resins include terpene resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers; modification of these terpene resins (phenol modification, aromatic modification, hydrogenation modification, hydrocarbons) Modified terpene resin) and the like. 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 tackifying resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic / aromatic petroleum resins (styrene-olefin copolymers, etc. ), Various hydrocarbon resins such as aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, coumarone indene resins, and the like.

  The softening point of the tackifier resin is not particularly limited. In one embodiment, as the tackifying resin, those having a softening point (softening temperature) of about 80 ° C. or higher (preferably about 110 ° C. or higher, more preferably about 135 ° C. or higher) can be preferably used. A terpene tackifying resin (such as a terpene phenol resin) or a rosin tackifying resin (such as an esterified polymerized rosin) having such a softening point can be preferably used. For example, a terpene phenol resin having a softening point of about 135 ° C. or higher (and further about 140 ° C. or higher) can be preferably used. The upper limit of the softening point of the tackifying resin is not particularly limited, and can be, for example, about 200 ° C. or lower (typically about 180 ° C. or lower). In addition, the softening point of tackifying resin can be measured based on the softening point test method (ring ball method) prescribed | regulated to JISK2207.

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

  As an example of a suitable composition of the acrylic pressure-sensitive adhesive disclosed herein, a tackifying resin (for example, terpene phenol resin) having a softening point of 135 ° C. or higher with respect to 100 parts by weight of the acrylic polymer in a ratio of 20 to 60 parts by weight. The composition which contains is mentioned.

  Other examples of suitable compositions for the acrylic pressure-sensitive adhesive disclosed herein include a composition comprising a combination of a rosin-based tackifier resin (for example, a polymerized rosin ester) and a terpene-based tackifier resin (for example, a terpene phenol resin). It is done. According to such a composition, better adhesive properties can be exhibited. The weight ratio of the rosin-based tackifier resin and the terpene-based tackifier resin can be, for example, in the range of 5/95 to 95/5, and may be in the range of 10/90 to 90/10, and 20/80 to The range may be 80/20, or 30/70 to 70/30.

Acrylic pressure-sensitive adhesive disclosed herein hydroxyl value may contain higher tackifier resin T _H1 than 50 mg KOH / g. The hydroxyl value of the tackifier resin _{T H1,} from the viewpoint of adhesive properties improve, for example, it may be at 60 mg KOH / g or more, may be 70 mgKOH / g or more, may be 80 mg KOH / g or more, may be 90 mgKOH / g or more. The hydroxyl value of the tackifier resin _{T H1,} from the viewpoint of compatibility with the acrylic polymer, usually is suitably less 300 mgKOH / g, is preferably from 250 mgKOH / g, 200 mg KOH / g or less (e.g., 150 mgKOH / g or less )

Examples of suitable compositions of the acrylic pressure-sensitive adhesive as disclosed herein, in combination with the tackifier resin T _H1, different tackifying resin T _H2 hydroxyl value 5 mgKOH / g or more, the tackifier as resin T _H1, the The composition which contains. The hydroxyl value of differences between the tackifier resin _{T H1} and the tackifier resin _{T H2} is preferably 10 mgKOH / g or more (e.g. 20 mgKOH / g or higher), may be 30 mgKOH / g or more, it may be 40 mg KOH / g or more. The hydroxyl value of the tackifier resin T _H2 may be higher than the hydroxyl value of the tackifier resin T _H1, may be low. In one embodiment, the hydroxyl value of the tackifier resin T _H2 may be preferably adopted a combination higher than the hydroxyl value of the tackifier resin T _H1. Examples of suitable compositions of the acrylic pressure-sensitive adhesive disclosed herein, the tackifier resin _{T H1} a hydroxyl value of 75 mgKOH / g or less (e.g., 70 mgKOH / g or less), a hydroxyl value of 80 mg KOH / g or more (e.g. 90mgKOH / G or more) and a tackifying resin _TH2 in combination.

Acrylic pressure-sensitive adhesive disclosed herein has an acid value may include high tackifier resin T _A1 than 20 mgKOH / g. The acid value of the tackifying resin T _A1 may be, for example, 30 mgKOH / g or more, or 40 mgKOH / g or more. Further, from the viewpoint of weather resistance of the adhesive, the acid value of the tackifier resin _{T A1} is generally less preferably 150 mgKOH / g, may be below 100 mg KOH / g, or below 70 mgKOH / g.
The hydroxyl value of the tackifier resin T _A1 is not particularly limited. The tackifying resin T _A1 may or may not correspond to the above-described tackifying resin _TH1 or tackifying resin _TH2 . The acid value of the tackifying resin T _A1 may be, for example, 50 mgKOH / g or less, 30 mgKOH / g or less, or 20 mgKOH / g.
An example of a suitable composition of the acrylic pressure-sensitive adhesive disclosed herein includes a composition containing the tackifying resin _TH1 and the tackifying resin _TA1 in combination.

As the tackifying resin T _H1 , the tackifying resin T _H2 , and the tackifying resin T _A1 , those having a desired hydroxyl value or acid value can be selected from the tackifying resins exemplified above. For example, the tackifying resin T _H1 , the tackifying resin T _H2 , and the tackifying resin T _A1 may be independently selected from the group consisting of a rosin-based tackifying resin and a terpene-based tackifying resin (for example, a terpene phenol resin). it can.
The acid value and hydroxyl value of the tackifier resin can be measured by a potentiometric titration method defined in JIS K0070: 1992.

(Coloring agent)
The pressure-sensitive adhesive layer can contain a colorant. Thereby, the light transmittance (light-shielding property) of an adhesive layer can be adjusted. For example, the 0.6 mm light transmittance and the vertical light transmittance of the pressure-sensitive adhesive layer can be adjusted. Adjusting the light transmittance (for example, vertical light transmittance) of the pressure-sensitive adhesive layer can be useful for adjusting the light transmittance of the pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer.

  As the colorant, conventionally known pigments and dyes can be used. Examples of the pigment include zinc carbonate, zinc oxide, zinc sulfide, talc, kaolin, calcium carbonate, titanium oxide, silica, lithium fluoride, calcium fluoride, barium sulfate, alumina, zirconia, iron oxide series, and iron hydroxide series. , Chromium oxide, spinel firing, chromic acid, chromium vermilion, bituminous, aluminum powder, bronze powder, silver powder, calcium phosphate, and other inorganic pigments, phthalocyanine, azo, and condensed azo Organic pigments such as azo lake, anthraquinone, perylene / perinone, indigo, thioindigo, isoindolinone, azomethine, dioxazine, quinacridone, aniline black, triphenylmethane, carbon black It is done. Examples of the dye include azo dyes, anthraquinone, quinone phthalone, styryl, diphenylmethane, triphenylmethane, oxazine, triazine, xanthan, methane, azomethine, acridine, and diazine. A coloring agent can be used individually by 1 type or in combination of 2 or more types as appropriate.

  A black colorant can be preferably used because the light-shielding property can be efficiently adjusted with a small amount of the colorant. Specific examples of black colorants include carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, pine smoke, etc.), graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine. Examples thereof include black, activated carbon, ferrite (nonmagnetic ferrite, magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complex, anthraquinone colorant and the like. Of these, carbon black is preferred.

Since the light-shielding property of the pressure-sensitive adhesive layer can be adjusted efficiently with a small amount of colorant, a particulate colorant (pigment) can be preferably used. In a preferred embodiment, a pigment having an average particle size of 10 nm to 500 nm, more preferably 10 nm to 120 nm (for example, a particulate black colorant such as carbon black) can be used. In this specification, “average particle size” means, unless otherwise specified, a particle size (50% volume) at an integrated value of 50% in a particle size distribution measured based on a particle size distribution measuring apparatus based on a laser scattering / diffraction method. average particle diameter; _hereinafter refers to also) be abbreviated as _{D 50..}

The blending amount of the colorant can be set so that an adhesive layer satisfying a desired 0.6 mm light transmittance is formed, and is not particularly limited. Usually, it is suitable that it is 0.5 parts by weight or more with respect to 100 parts by weight of the base polymer, preferably 1.0 part by weight or more, and more preferably 1.5 parts by weight or more. Moreover, the compounding quantity of a coloring agent can be 15 weight part or less with respect to 100 weight part of base polymers, for example. From the viewpoint of suppressing a decrease in adhesive properties that may occur due to the blending of the colorant, the blending amount of the colorant is usually suitably 10 parts by weight or less with respect to 100 parts by weight of the base polymer, and 5 parts by weight or less Preferably, the amount is 3 parts by weight or less. In a preferred embodiment, the blending amount of the colorant with respect to 100 parts by weight of the base polymer can be 2.5 parts by weight or less (more preferably 2.3 parts by weight or less, for example, 2 parts by weight or less).
The content of the colorant in the pressure-sensitive adhesive layer is usually suitably 0.3% by weight or more of the pressure-sensitive adhesive layer, preferably 0.5% by weight or more, and more preferably 1.0% by weight or more. preferable. The content of the colorant can be, for example, less than 10% by weight, preferably less than 5% by weight, more preferably less than 3.5% by weight, and still more preferably less than 3.0% by weight. In a preferable embodiment, the colorant content of the pressure-sensitive adhesive layer can be less than 2.5% by weight (more preferably less than 2.2% by weight, for example, less than 2.0% by weight).

The pressure-sensitive adhesive composition disclosed herein may contain a component that contributes to improving the dispersibility of the colorant. Such a dispersibility improving component can be, for example, a polymer, an oligomer, a liquid resin, a surfactant, and the like. The dispersibility improving component is preferably dissolved in the pressure-sensitive adhesive composition. The oligomer is, for example, a low molecular weight polymer of a monomer component containing one or more acrylic monomers as exemplified above (for example, Mw is less than about 10 × 10 ⁴ , preferably less than 5 × 10 ⁴ Acrylic oligomer). The liquid resin is, for example, a tackifying resin having a softening point of about 50 ° C. or less, more preferably about 40 ° C. or less (typically rosin-based, terpene-based, hydrocarbon-based tackifying resins such as hydrogenated rosin. Methyl ester, etc.). By such a dispersibility improving component, dispersion unevenness of a colorant (for example, a particulate black colorant such as carbon black) can be suppressed, and consequently, color unevenness of the pressure-sensitive adhesive layer can be suppressed. Therefore, a pressure-sensitive adhesive sheet with better appearance quality can be formed.

  The content of the dispersibility-improving component is not particularly limited, but is usually about 20% by weight or less (preferably about 10% by weight or less) of the entire pressure-sensitive adhesive layer from the viewpoint of suppressing the influence on the adhesive properties (for example, reduction in cohesiveness). More preferably, the content is 7% by weight or less, for example, about 5% by weight or less. In one embodiment, the content of the dispersibility improving component may be about 10 times or less (preferably about 5 times or less, for example, about 3 times or less) of the weight of the colorant. On the other hand, from the viewpoint of suitably exhibiting the effect of the dispersibility-improving component, the content thereof is usually about 0.2% by weight or more of the entire pressure-sensitive adhesive layer (typically about 0.5% by weight or more, preferably About 1% by weight or more is appropriate. In one embodiment, the content of the dispersibility improving component can be about 0.2 times or more (preferably about 0.5 times or more, for example, 1 time or more) of the weight of the colorant.

(Crosslinking agent)
In the technology disclosed herein, the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer may contain a crosslinking agent as necessary. The kind in particular of a crosslinking agent is not restrict | limited, It can select from a conventionally well-known crosslinking agent suitably and can be used. Examples of such crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, peroxide crosslinking agents, urea crosslinking agents, metal alkoxides. Examples of the crosslinking agent include a metal chelate crosslinking agent, a metal salt crosslinking agent, a carbodiimide crosslinking agent, and an amine crosslinking agent. A crosslinking agent can be used individually by 1 type or in combination of 2 or more types. Among these, from the viewpoint of improving cohesive strength, it is preferable to use an isocyanate crosslinking agent and / or an epoxy crosslinking agent, and it is particularly preferable to use an isocyanate crosslinking agent and an epoxy crosslinking agent in combination. The amount of the crosslinking agent used is not particularly limited. For example, the amount can be about 10 parts by weight or less, preferably about 0.005 to 10 parts by weight, more preferably about 0.01 to 5 parts by weight with respect to 100 parts by weight of the base polymer (preferably an acrylic polymer). You can select from a range of parts.

(Other additives)
The pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition such as a leveling agent, a crosslinking aid, a plasticizer, a softening agent, an antistatic agent, an anti-aging agent, an ultraviolet absorber, an antioxidant, or a light stabilizer, if necessary. Various additives generally used in the field of products may be contained. About such various additives, conventionally well-known things can be used by a conventional method, and since it does not characterize this invention in particular, detailed description is abbreviate | omitted.

  The pressure-sensitive adhesive layer (layer made of pressure-sensitive adhesive) disclosed herein is formed from a water-based pressure-sensitive adhesive composition, a solvent-type pressure-sensitive adhesive composition, a hot-melt pressure-sensitive adhesive composition, and an active energy ray-curable pressure-sensitive adhesive composition. It can be an adhesive layer. The water-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition in a form containing a pressure-sensitive adhesive (pressure-sensitive adhesive layer forming component) in a water-based solvent (water-based solvent), and is typically dispersed in water. What is called a type pressure-sensitive adhesive composition (a composition in which at least a part of the pressure-sensitive adhesive is dispersed in water) and the like are included. Moreover, a solvent-type adhesive composition means the adhesive composition of the form which contains an adhesive in an organic solvent. The technique disclosed here can be preferably implemented in an aspect including a pressure-sensitive adhesive layer formed from a solvent-type pressure-sensitive adhesive composition from the viewpoint of pressure-sensitive adhesive properties and the like.

  The pressure-sensitive adhesive layer disclosed herein can be formed by a conventionally known method. For example, a method (direct method) of forming the pressure-sensitive adhesive layer by directly applying (typically applying) the pressure-sensitive adhesive composition to the base film as described above and drying it can be employed. Also, a method (transfer method) in which a pressure-sensitive adhesive composition is applied to a peelable surface (peeling surface) and dried to form a pressure-sensitive adhesive layer on the surface, and the pressure-sensitive adhesive layer is transferred to a base film. ) May be adopted. From the viewpoint of productivity, the transfer method is preferred. As the release surface, the surface of the release liner, the back surface of the substrate film subjected to the release treatment, or the like can be used. The pressure-sensitive adhesive layer disclosed herein is typically formed continuously, but is not limited to such a form, for example, a regular or random pattern such as a dot or stripe. The formed adhesive layer may be sufficient.

The pressure-sensitive adhesive composition can be applied using a conventionally known coater such as a gravure roll coater, a die coater, or a bar coater. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation or curtain coating.
From the viewpoint of promoting the crosslinking reaction and improving the production efficiency, the pressure-sensitive adhesive composition is preferably dried under heating. A drying temperature can be about 40-150 degreeC, for example, and it is preferable to usually be about 60-130 degreeC. After drying the pressure-sensitive adhesive composition, further aging is performed for the purpose of adjusting the component transfer in the pressure-sensitive adhesive layer, progress of the crosslinking reaction, alleviating the distortion that may exist in the base film or the pressure-sensitive adhesive layer, etc. Also good.

<Base film>
As a base film, what contains a resin film as a base film can be used preferably. The base film is typically a member capable of maintaining its shape independently (independent). The base film in the technology disclosed herein can be substantially composed of such a base film. Alternatively, the base film may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include a colored layer, a reflective layer, an undercoat layer, an antistatic layer and the like provided on the surface of the base film.

  The resin film is a film containing a resin material as a main component (for example, a component contained in the resin film in an amount exceeding 50% by weight). Examples of resin films include polyolefin resin films such as polyethylene (PE), polypropylene (PP), and ethylene / propylene copolymers; polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), etc. Polyester resin film; vinyl chloride resin film; vinyl acetate resin film; polyimide resin film; polyamide resin film; fluororesin film; The resin film may be a rubber film such as a natural rubber film or a butyl rubber film. Of these, a polyester film is preferable from the viewpoint of handling properties and processability, and a PET film is particularly preferable. In the present specification, the “resin film” is typically a non-porous sheet and is a concept that is distinguished from a so-called nonwoven fabric or woven fabric (in other words, a concept that excludes nonwoven fabric or woven fabric). is there.

  The resin film can contain a colorant. Thereby, the light transmittance (light-shielding property) of a resin film can be adjusted. For example, the vertical light transmittance and 0.6 mm light transmittance of the resin film can be adjusted. Adjusting the light transmittance (for example, vertical light transmittance) of the resin film is also effective for adjusting the light transmittance of the base film including the resin film and the light transmittance of the pressure-sensitive adhesive sheet including the base film. Can be helpful.

  As the colorant, conventionally known pigments and dyes can be used in the same manner as the colorant that can be contained in the pressure-sensitive adhesive layer. The color of the colorant is not particularly limited, and may be colored or colorless. The color of the colorant can be, for example, black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearl, and the like.

  In one embodiment, the black colorant can be preferably used because the light-shielding property (for example, vertical light transmittance) can be efficiently adjusted with a small amount of the colorant. Specific examples of the black colorant include those exemplified as the colorant that can be contained in the pressure-sensitive adhesive layer. In a preferred embodiment, a pigment having an average particle size of 10 nm to 500 nm, more preferably 10 nm to 120 nm (for example, a particulate black colorant such as carbon black) can be used.

  In another embodiment, the resin film may contain a white colorant. Examples of the white colorant include titanium oxide (titanium dioxide such as rutile titanium dioxide and anatase titanium dioxide), zinc oxide, aluminum oxide, silicon oxide, 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 carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, aluminum silicate, magnesium silicate , Calcium silicate, barium sulfate, calcium sulfate, barium stearate, zinc white, zinc sulfide, talc, silica, alumina, clay, kaolin, titanium phosphate, mica, gypsum, white carbon, diatomaceous earth, bentonite, lithopone Inorganic white colorants such as zeolite, sericite, hydrous halloysite, acrylic resin particles, polystyrene resin particles, polyurethane resin particles, amide resin particles, polycarbonate resin particles, silicone resin particles, urea-formalin Examples thereof include organic white colorants such as resin particles and melamine resin particles.

  The amount of the colorant used in the resin film is not particularly limited, and can be an amount adjusted as appropriate so that desired optical properties can be imparted. The amount of the colorant used is usually suitably about 0.1 to 30% by weight of the resin film, for example 0.1 to 25% by weight (typically 0.1 to 20% by weight). ).

  For the above resin film, fillers (inorganic fillers, organic fillers, etc.), dispersants (surfactants, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents, lubricants as necessary Various additives such as a plasticizer may be blended. The blending ratio of various additives is usually less than 30% by weight (for example, less than 20% by weight, typically less than 10% by weight).

  The resin film may have a single layer structure or may have a multilayer structure of two layers, three layers or more. From the viewpoint of shape stability, the resin film preferably has a single layer structure. In the case of a multilayer structure, at least one layer (preferably all layers) is preferably a layer having a continuous structure of the resin (for example, polyester resin). The method for producing the resin film is not particularly limited as long as a conventionally known method is appropriately employed. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die casting, and calendar roll molding can be appropriately employed.

  The base film may be colored by a colored layer disposed on the surface of the base film (preferably a resin film). Thus, in the base film having the structure including the base film and the colored layer, the base film may or may not contain a colorant. The colored layer may be disposed on one surface of the base film, or may be disposed on both surfaces. In the configuration in which the colored layers are arranged on both surfaces of the base film, the configurations of the colored layers may be the same or different.

  Such a colored layer can be typically formed by applying a colored layer-forming composition containing a colorant and a binder to a base film. As the colorant, conventionally known pigments and dyes can be used in the same manner as the colorant that can be contained in the pressure-sensitive adhesive layer or the resin film. As the binder, a material known in the field of paint or printing can be used without particular limitation. For example, polyurethane, phenol resin, epoxy resin, urea melamine resin, polymethyl methacrylate and the like are exemplified. The colored layer forming composition can be, for example, a solvent type, an ultraviolet curable type, a thermosetting type, or the like. Formation of the colored layer can be carried out without particular limitation by means conventionally employed for forming the colored layer. For example, a method of forming a colored layer (printing layer) by printing such as gravure printing, flexographic printing, and offset printing can be preferably employed.

  The colored layer may have a single-layer structure as a whole, or may have a multilayer structure including two, three, or more sub-colored layers. A colored layer having a multilayer structure including two or more sub-colored layers can be formed, for example, by repeatedly applying (for example, printing) the composition for forming a colored layer. The color and blending amount of the colorant contained in each sub-colored layer may be the same or different. In the colored layer for imparting light-shielding properties, it is particularly meaningful to have a multilayer structure from the viewpoint of preventing the generation of pinholes and improving the reliability of preventing light leakage.

  The thickness of the entire colored layer is usually about 1 μm to 10 μm, preferably about 1 μm to 7 μm, for example, about 1 μm to 5 μm. In a colored layer including two or more sub-colored layers, the thickness of each sub-colored layer is usually preferably about 1 μm to 2 μm.

  The thickness of the base film disclosed here is not particularly limited. From the viewpoint of avoiding an excessively thick adhesive sheet, the thickness of the base film can be, for example, 200 μm or less, preferably 150 μm or less, more preferably 100 μm or less. Depending on the purpose and mode of use of the pressure-sensitive adhesive sheet, the thickness of the base film may be 70 μm or less, 50 μm or less, or 30 μm or less (for example, 25 μm or less). In one embodiment, the thickness of the base film may be 20 μm or less, 15 μm or less, or 10 μm or less (for example, 5 μm or less). By reducing the thickness of the base film, the thickness of the pressure-sensitive adhesive layer can be increased even if the total thickness of the pressure-sensitive adhesive sheet is the same. This can be advantageous from the viewpoint of impact resistance of the pressure-sensitive adhesive sheet. The lower limit of the thickness of the base film is not particularly limited. From the viewpoints of handleability (handling property) and processability of the pressure-sensitive adhesive sheet, the thickness of the base film is usually 0.5 μm or more (for example, 1 μm or more), preferably 2 μm or more, for example, 4 μm or more. In one embodiment, the thickness of the base film may be 6 μm or more, may be 8 μm or more, and may be 10 μm or more (for example, more than 10 μm).

  In the pressure-sensitive adhesive sheet disclosed herein, for example, the 0.6 mm light transmittance of the base film (typically a resin film) is, for example, 15% or less (preferably 10% or less, more preferably 5% or less). Can be implemented. Such a pressure-sensitive adhesive sheet including a base film can exhibit good horizontal light shielding properties. In the base film having a thickness of more than 25 μm, it is particularly significant that the 0.6 mm light transmittance of the base film satisfies the above numerical value. From the viewpoint of obtaining higher horizontal light-shielding properties, the 0.6 mm light transmittance of the base film is preferably 3% or less, more preferably 1% or less, still more preferably 0.5% or less, and particularly preferably 0.8. 1% or less. The lower limit of the 0.6 mm light transmittance of the base film is not particularly limited, and may be substantially 0%, that is, below the detection limit. The 0.6 mm light transmittance of the base film can be measured in the same manner as the 0.6 mm light transmittance of the pressure-sensitive adhesive layer described above using the base film as a measurement sample.

  The pressure-sensitive adhesive sheet disclosed herein can be implemented, for example, in an embodiment in which the base film has a vertical light transmittance of, for example, less than 5%. Thereby, in the adhesive sheet containing the said base film, favorable light-shielding property to a perpendicular direction (thickness direction of an adhesive sheet) can be implement | achieved. From the viewpoint of obtaining a higher level of light shielding properties, the vertical light transmittance of the base film is preferably less than 3%, more preferably less than 1%, even more preferably less than 0.5%, and particularly preferably 0.8. Less than 1%. The lower limit of the vertical light transmittance is not particularly limited, and may be substantially 0%, that is, below the detection limit. The vertical light transmittance of the base film can be measured in the same manner as the 0.6 mm light transmittance of the pressure-sensitive adhesive layer described above, using the base film as a measurement sample.

  The surface of the base film may be subjected to conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and application of a primer. Such a surface treatment may be a treatment for improving the adhesion between the base film and the pressure-sensitive adhesive layer, in other words, the anchoring property of the pressure-sensitive adhesive layer to the base film.

<Release liner>
In the technology disclosed herein, a release liner can be used in forming the pressure-sensitive adhesive layer, preparing the pressure-sensitive adhesive sheet, storing the pressure-sensitive adhesive sheet before use, distributing it, and processing the shape. The release liner is not particularly limited. For example, a release liner having a release treatment layer on the surface of a liner substrate such as a resin film or paper, a fluoropolymer (polytetrafluoroethylene, etc.), a polyolefin resin (polyethylene, A release liner made of a low adhesion material such as polypropylene can be used. The release treatment layer may be formed, for example, by surface-treating the liner base material with a release treatment agent such as silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.

<Adhesive sheet>
The total thickness of the pressure-sensitive adhesive sheet disclosed herein (including the pressure-sensitive adhesive layer and the base film but not including the release liner) is not particularly limited. The total thickness of the pressure-sensitive adhesive sheet can be, for example, about 25.5 μm or more, 30 μm or more, 50 μm or more, or 60 μm or more. The upper limit of the total thickness of the pressure-sensitive adhesive sheet is typically 400 μm or less, preferably 300 μm or less, and may be 250 μm or less (for example, 200 μm or less). In one embodiment, the total thickness of the pressure-sensitive adhesive sheet may be 120 μm or less, and may be 90 μm or less.

  The pressure-sensitive adhesive sheet disclosed herein can be implemented in a mode in which the vertical light transmittance of the pressure-sensitive adhesive sheet is, for example, 5% or less. From the viewpoint of preferably realizing vertical light shielding and horizontal light shielding with a single member, the vertical light transmittance of the pressure-sensitive adhesive sheet is preferably 3% or less, more preferably 1% or less, even more preferably 0.5% or less, particularly Preferably it is 0.1% or less. The lower limit of the vertical light transmittance is not particularly limited, and may be substantially 0%, that is, below the detection limit. The vertical light transmittance of the pressure-sensitive adhesive sheet can be measured in the same manner as the above-described 0.6 mm light transmittance of the pressure-sensitive adhesive layer using the pressure-sensitive adhesive sheet as a measurement sample.

  The pressure-sensitive adhesive sheet disclosed herein comprises a first pressure-sensitive adhesive layer disposed on one surface of a base film and a second pressure-sensitive adhesive layer disposed on the other surface of the base film. It can be suitably implemented in the form of (double-sided adhesive sheet). The pressure-sensitive adhesive sheet having such a configuration is highly useful as a joining member. Moreover, it is easy to increase the ratio of the total thickness of the pressure-sensitive adhesive layer to the total thickness of the pressure-sensitive adhesive sheet (the total thickness of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer), which is suitable for improving impact resistance. ing.

  Here, at least one of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer having a thickness of more than 25 μm and a 0.6 mm light transmittance of 5% or less. The thickness of the other pressure-sensitive adhesive layer is not particularly limited, and may be, for example, 2 μm or more, typically 5 μm or more, preferably 10 μm or more, more preferably 15 μm or more. When the thickness of the other pressure-sensitive adhesive layer is increased, the impact resistance of the pressure-sensitive adhesive sheet tends to be improved. From this point of view, the thickness of the other pressure-sensitive adhesive layer may be 20 μm or more, may be 25 μm or more, and is more than 25 μm (for example, 27 μm or more, further 30 μm or more, or 35 μm or more) in the same manner as one pressure-sensitive adhesive layer. )

  When the thickness of the other pressure-sensitive adhesive layer is larger than 25 μm, the 0.6 mm light transmittance of the other pressure-sensitive adhesive layer is also preferably 5% or less. As a result, it is possible to suitably achieve both impact resistance and horizontal light shielding performance even in a narrow width. On the other hand, when the thickness of the other pressure-sensitive adhesive layer is 25 μm or less, the 0.6 mm light transmittance of the other pressure-sensitive adhesive layer is not particularly limited. The pressure-sensitive adhesive layer disclosed herein is, for example, a pressure-sensitive adhesive layer having a thickness of more than 25 μm and a 0.6 mm light transmittance of 5% or less, and is disposed on the other surface. Further, an embodiment in which the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer having a thickness of 25 μm or less and a light transmittance of more than 5% of 0.6 mm can be preferably implemented.

  As a preferable embodiment of the pressure-sensitive adhesive sheet (single-sided pressure-sensitive adhesive sheet or double-sided pressure-sensitive adhesive sheet) disclosed herein, the 0.6 mm light transmittance of a layer having a thickness of more than 25 μm among the layers contained in the pressure-sensitive adhesive sheet is 5 % Or less (more preferably 3% or less, still more preferably 1% or less, typically 0.1% or less). According to the pressure-sensitive adhesive sheet having such a configuration, good horizontal light shielding properties and impact resistance tend to be realized at the same time even in a narrow width. As a preferred embodiment from the viewpoint of realizing higher horizontal light shielding properties, a layer having a thickness of 20 μm or more (more preferably a layer having a thickness of 15 μm or more, more preferably a layer having a thickness of 10 μm or more) among the layers contained in the pressure-sensitive adhesive sheet. The 0.6 mm light transmittance is 5% or less (more preferably 3% or less, more preferably 1% or less, typically 0.1% or less).

  When the pressure-sensitive adhesive sheet disclosed herein is used for light reflection, the light reflectance of the pressure-sensitive adhesive sheet surface can be, for example, 40% or more, preferably 60% or more, and more preferably 70% or more. More preferred. The upper limit of the light reflectance is ideally 100%, but it may be about 99% or less (for example, 95% or less, typically 92% or less) from the practical aspect.

  The light reflectance (%) of the pressure-sensitive adhesive sheet surface is a surface on which light is irradiated by irradiating one surface of the pressure-sensitive adhesive sheet (light reflectance measurement surface) with light having a wavelength of 550 nm using a commercially available spectrophotometer. It is calculated | required by measuring the intensity | strength of the light reflected by. As the spectrophotometer, for example, a spectrophotometer manufactured by Shimadzu Corporation (device name “MPS-2000”) can be used. The same applies to the embodiments described later.

  The total thickness of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer is not particularly limited. The total thickness of the pressure-sensitive adhesive layer can be, for example, more than 27 μm, typically more than 30 μm, preferably more than 35 μm, more preferably more than 40 μm. When the total thickness of the pressure-sensitive adhesive layer is increased, the impact resistance of the pressure-sensitive adhesive sheet tends to be improved. From this viewpoint, the total thickness of the pressure-sensitive adhesive layer may be more than 40 μm, may be more than 50 μm, may be more than 60 μm, and may be more than 70 μm.

  The ratio of the total thickness of the pressure-sensitive adhesive layer contained in the pressure-sensitive adhesive sheet in the total thickness of the pressure-sensitive adhesive sheet is not particularly limited. Here, the total thickness of the pressure-sensitive adhesive layer contained in the pressure-sensitive adhesive sheet is the total thickness of the pressure-sensitive adhesive layer provided on one surface of the base film and the pressure-sensitive adhesive layer provided on the other surface. Say. In the case of a single-sided pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is provided only on one surface of the base film, the thickness of the pressure-sensitive adhesive layer provided on the other surface is zero, and on the one surface described above The thickness of the provided pressure-sensitive adhesive layer matches the total thickness of the pressure-sensitive adhesive layer. In the pressure-sensitive adhesive sheet disclosed herein, for example, the ratio of the total thickness of the pressure-sensitive adhesive layer to the total thickness of the pressure-sensitive adhesive sheet is 40% or more (preferably 50% or more, typically more than 50%, more preferably 60% or more, more preferably 70% or more). By comprising in this way, compared with the total thickness of an adhesive sheet, it exists in the tendency for a higher level impact resistance to be exhibited also in a narrow width. In one embodiment, the ratio of the total thickness of the pressure-sensitive adhesive layer to the total thickness of the pressure-sensitive adhesive sheet may be 75% or more, and further 80% or more. The upper limit of the ratio of the total thickness of the pressure-sensitive adhesive layer to the total thickness of the pressure-sensitive adhesive sheet is not particularly limited, but is usually 95% or less, preferably 90% or less.

  In the pressure-sensitive adhesive layer included in the pressure-sensitive adhesive sheet disclosed herein having a thickness of more than 25 μm and a light transmittance of 5% or less of 0.6 mm, the vertical light transmittance of the pressure-sensitive adhesive layer is not particularly limited. The vertical light transmittance of the pressure-sensitive adhesive layer may be, for example, 10% or more, 15% or more, or 20% or more. The pressure-sensitive adhesive sheet disclosed herein can be preferably implemented in a mode in which the vertical light transmittance of the pressure-sensitive adhesive layer is more than 25% (more preferably more than 30%). The upper limit of the vertical light transmittance of the pressure-sensitive adhesive layer is not particularly limited as long as the 0.6 mm light transmittance of the pressure-sensitive adhesive layer is 5% or less. As described above, by increasing the allowable limit value of the vertical light transmittance within a range satisfying the 0.6 mm light transmittance of 5% or less, the amount of the colorant necessary for adjusting to the vertical light transmittance is reduced. Can do. This is preferable from the viewpoint of obtaining a pressure-sensitive adhesive sheet having good appearance quality by suppressing the dispersion of the colorant (and hence the color unevenness of the pressure-sensitive adhesive layer). The vertical light transmittance of the pressure-sensitive adhesive layer can be measured in the same manner as the 0.6 mm light transmittance of the pressure-sensitive adhesive layer described above, using the pressure-sensitive adhesive layer as a measurement sample.

  The pressure-sensitive adhesive sheet disclosed herein preferably has a 180-degree peel strength of 3.0 N / 20 mm or more. According to the pressure-sensitive adhesive sheet exhibiting the above characteristics, a highly durable joining structure tends to be realized even in a narrow width. The peel strength is preferably 3.5 N / 20 mm or more, and more preferably 4.0 N / 20 mm or more. The peeling strength here refers to 180 degree peeling strength (180 degree peeling adhesive strength) with respect to a stainless steel plate.

  The 180 degree peel strength can be measured as follows. Specifically, for a measurement sample obtained by cutting the pressure-sensitive adhesive sheet into a size having a width of 20 mm and a length of 100 mm, the adhesion surface of the measurement sample is the surface of a stainless steel plate (SUS304BA plate) in an environment of 23 ° C. and 50% RH. Then, a 2 kg roller is reciprocated once to be pressure-bonded. After leaving this in the same environment for 30 minutes, using a universal tensile compression tester, in accordance with JIS Z 0237: 2000, under conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees, the peel strength (N / 20 mm). As a universal tensile and compression tester, for example, “Tensile and compression tester, TG-1kN” manufactured by Minebea can be used. A similar measurement method is employed in the examples described later.

<Application>
The pressure-sensitive adhesive sheet disclosed herein has good impact resistance even in a narrow width, and is excellent in horizontal light shielding properties. Taking advantage of such characteristics, the pressure-sensitive adhesive sheet can be preferably applied to an electronic apparatus including a liquid crystal display device that requires a predetermined optical characteristic, for example. More specifically, in a liquid crystal display device including an LCD unit and a BL unit, it can be preferably used for joining the LCD unit and the BL unit.

  The pressure-sensitive adhesive sheet disclosed herein can be preferably used for joining, for example, an LCD unit of a portable electronic device and the BL unit. Non-limiting examples of such portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wrist wear devices such as wrist watches, clips, straps, etc. Modular type to be worn on a part of the body, eyewear type (including monocular type and binocular type, including head mounted type), clothing type attached to shirts, socks, hats, etc. in the form of accessories, for example Earphones, earphones, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, electronic books In-vehicle information equipment, portable radio, portable TV, portable printer, portable scanner, portable modem, etc. That. In this specification, “carrying” means that it is not sufficient to be able to carry it alone, but that it has a level of portability that allows an individual (standard adult) to carry it relatively easily. Shall mean.

  The pressure-sensitive adhesive sheet disclosed herein can be used in the form of a joining member processed into various outer shapes, for example, for joining the LCD unit and the BL unit or other joining applications. As a preferable form of such a joining member, a form having a narrow part having a width of less than 2.0 mm (for example, less than 1.0 mm) can be mentioned. Since the pressure-sensitive adhesive sheet disclosed herein includes a pressure-sensitive adhesive layer having a thickness of more than 25 μm and a light transmittance of 0.6 mm or less of 0.6%, the shape including such a narrow portion (for example, a frame shape) Even when used as a joining member, good performance (impact resistance, horizontal shading, etc.) can be exhibited. In one aspect, the width of the narrow portion may be 0.7 mm or less, 0.5 mm or less, or about 0.3 mm or less. Although the minimum of the width | variety of a narrow part is not restrict | limited in particular, Usually, 0.1 mm or more (typically 0.2 mm or more) is suitable from a viewpoint of the handleability of an adhesive sheet.

  The narrow portion is typically linear. Here, the term “linear” is a concept including a linear shape, a curved shape, a bent line shape (for example, an L shape), a ring shape such as a frame shape or a circular shape, or a composite or intermediate shape thereof. . The annular shape is not limited to a curved line, and a part or all of the shape is linearly formed, for example, a shape along the outer periphery of a square (frame shape) or a shape along a fan-shaped outer periphery. It is a concept that includes a ring. The length of the narrow portion is not particularly limited. For example, in the form in which the length of the narrow width 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 pressure-sensitive adhesive sheet disclosed herein can be preferably used in a shape in which the width W of the pressure-sensitive adhesive layer in the narrow width portion is 50 times or less the thickness T of the pressure-sensitive adhesive layer. That is, it can be preferably used in a shape that is attached to the adherend in a shape having a W / T value of 50 or less (more preferably 40 or less, more preferably 30 or less, for example 25 or less). For example, in an annular pressure-sensitive adhesive sheet used for bonding an LCD unit of a liquid crystal display device and the BL unit, when the pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer having a high light transmittance, the light emitted from the BL unit is reduced. The part penetrates the adhesive layer obliquely (to the LCD unit side) from the BL unit side end on the inner periphery of the adhesive layer to the LCD unit side end on the outer periphery of the adhesive layer. Thus, the light that has been transmitted obliquely through the pressure-sensitive adhesive layer to the LDC unit side tends to cause inconveniences such as uneven brightness on the liquid crystal display surface. When the value of W / T decreases, the proportion of light that passes through the pressure-sensitive adhesive layer obliquely toward the LDC unit in the light transmitted through the pressure-sensitive adhesive layer in the width direction tends to increase. Therefore, the significance of preventing or suppressing light leakage in the width direction of the pressure-sensitive adhesive sheet by applying the technology disclosed herein is increased.

The matters disclosed by this specification include the following.
(1) A base film, and a pressure-sensitive adhesive layer disposed on at least one surface of the base film,
The pressure-sensitive adhesive layer contains a colorant in the pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer is a pressure-sensitive adhesive sheet having a thickness greater than 25 μm and a 0.6 mm light transmittance of 5% or less.
(2) The pressure-sensitive adhesive sheet according to (1), wherein any of the layers constituting the pressure-sensitive adhesive sheet has a thickness of more than 25 μm and has a 0.6 mm light transmittance of 5% or less.
(3) The pressure-sensitive adhesive sheet according to (1) or (2), wherein the total thickness of the pressure-sensitive adhesive layers contained in the pressure-sensitive adhesive sheet is more than 50% of the total thickness of the pressure-sensitive adhesive sheet.
(4) The adhesive sheet in any one of said (1)-(3) whose perpendicular light transmittance of the said adhesive sheet is 1% or less.
(5) The pressure-sensitive adhesive sheet according to any one of (1) to (4), wherein the pressure-sensitive adhesive layer has a vertical light transmittance higher than 25%.
(6) The pressure-sensitive adhesive sheet according to any one of (1) to (5), wherein the pressure-sensitive adhesive sheet has a narrow width portion, and the width of the narrow width portion is less than 2.0 mm.
(7) The pressure-sensitive adhesive sheet according to (6), wherein the width of the pressure-sensitive adhesive layer in the narrow width portion is 50 times or less the thickness of the pressure-sensitive adhesive layer.
(8) It is comprised as a double-sided adhesive sheet provided with the 1st adhesive layer arrange | positioned on one surface of the said base film, and the 2nd adhesive layer arrange | positioned on the other surface of this base film. ,
Any of the above (1) to (7), wherein each of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer has a thickness greater than 25 μm and a 0.6 mm light transmittance of 5% or less. The pressure-sensitive adhesive sheet described in 1.
(9) The pressure-sensitive adhesive sheet according to any one of (1) to (8), which is used for joining the LCD unit and the BL unit in a liquid crystal display device including an LCD unit and a BL unit.

(10) The pressure-sensitive adhesive sheet according to any one of (1) to (9), wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer.
(11) The pressure-sensitive adhesive layer contains an acrylic polymer in a proportion exceeding 50% by weight of the polymer component contained in the pressure-sensitive adhesive layer,
The acrylic polymer has the formula (1) as a monomer component:
CH ₂ = C (R ¹ ) COOR ² (1)
(R ¹ in the above formula (1) is a hydrogen atom or a methyl group. R ² is a chain alkyl group having 1 to 20 carbon atoms.) An alkyl (meth) acrylate represented by: The pressure-sensitive adhesive sheet according to any one of (1) to (10), which is contained at a ratio of 70% by weight or more.
(12) The acrylic polymer further includes a functional group-containing monomer as the monomer component,
The functional group-containing monomers are acrylic acid, methacrylic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate and 4 -The adhesive sheet as described in said (11) which is at least 1 sort (s) selected from the group which consists of hydroxybutyl (meth) acrylate.
(13) The pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer includes an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an oxazoline-based crosslinking agent, an aziridine-based crosslinking agent, a melamine-based crosslinking agent, a peroxide-based crosslinking agent, Including at least one kind of crosslinking agent selected from the group consisting of urea crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, carbodiimide crosslinking agents and amine crosslinking agents ( The pressure-sensitive adhesive sheet according to any one of 10) to (12).
(14) The pressure-sensitive adhesive composition according to (13), wherein the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer contains an isocyanate cross-linking agent and an epoxy cross-linking agent in combination.
(15) The pressure-sensitive adhesive layer is composed of a rosin-based tackifier resin, a terpene-based tackifier resin, a hydrocarbon-based tackifier resin, an epoxy-based tackifier resin, a polyamide-based tackifier resin, an elastomer-based tackifier resin, or a phenol-based tackifier. The pressure-sensitive adhesive sheet according to any one of (10) to (14) above, comprising at least one type of tackifying resin selected from the group consisting of a resin and a ketone-based tackifying resin.
(16) The pressure-sensitive adhesive sheet according to (15), wherein the pressure-sensitive adhesive layer contains a rosin-based tackifier resin and a terpene phenol resin in a weight ratio of 5/95 to 95/5.
(17) The pressure-sensitive adhesive layer according to the above (15) or (16), containing 20 to 60 parts by weight of a terpene phenol resin having a softening point of 135 ° C. or higher with respect to 100 parts by weight of the acrylic polymer. Adhesive sheet.
(18) The pressure-sensitive adhesive layer, in combination with a hydroxyl value of 50 mg KOH / g higher than the tackifier resin _{T H1,} the hydroxyl value and the tackifier resin _{T H1} is a 5 mgKOH / g or more different tackifying resin _{T H2} The pressure-sensitive adhesive sheet according to any one of (15) to (17) above.
(19) the pressure-sensitive adhesive layer has a hydroxyl value of 50 mg KOH / g higher than the tackifier resin _{T H1,} including acid value in combination with a 20 mgKOH / g higher than the tackifier resin _{T A1,} the (15) from (18 ) The pressure-sensitive adhesive sheet according to any one of the above.
(20) The pressure-sensitive adhesive sheet according to any one of (1) to (19), wherein the colorant includes carbon black as a black colorant.
(21) The pressure-sensitive adhesive sheet according to (20), wherein the content of the colorant in the pressure-sensitive adhesive layer is 0.3% by weight or more and less than 3.0% by weight.

(22) In a liquid crystal display device comprising an LCD unit and a BL unit, a double-sided adhesive sheet used for joining the LCD unit and the BL unit,
A base film;
A first pressure-sensitive adhesive layer disposed on one surface of the base film;
A second pressure-sensitive adhesive layer disposed on the other surface of the base film,
The base film has a thickness greater than 25 μm and a 0.6 mm light transmittance of 5% or less, or a thickness of 25 μm or less,
Both the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer have a thickness of more than 25 μm and a 0.6 mm light transmittance of 5% or less,
The vertical light transmittance of the pressure-sensitive adhesive sheet is 1% or less,
The total thickness of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer is greater than 50% of the total thickness of the pressure-sensitive adhesive sheet;
At least one of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer in a proportion exceeding 50% by weight of the polymer component contained in the pressure-sensitive adhesive layer,
The acrylic pressure-sensitive adhesive layer is a pressure-sensitive adhesive sheet containing 0.3% by weight or more and less than 3.0% by weight of carbon black.

  Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples. In the following description, “parts” and “%” are based on weight unless otherwise specified.

<Example 1>
In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser and dropping funnel, 92 parts of BA as monomer components, 5 parts of vinyl acetate, 2.9 parts of AA and 0.1 part of 2-hydroxyethyl acrylate Then, 30 parts of ethyl acetate as a polymerization solvent and 120 parts of toluene were charged and stirred for 2 hours while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, 0.2 part of AIBN was added as a polymerization initiator, and solution polymerization was performed at 60 ° C. for 6 hours to obtain an acrylic polymer solution. Mw of this acrylic polymer was about 50 × 10 ⁴ .
For 100 parts of the acrylic polymer contained in the acrylic polymer solution, rosin resin A (polymerized rosin ester, trade name “Pencel D-125”, softening point 120 to 130 ° C., Arakawa Chemical Industries as tackifying resin 10 parts), rosin resin B (disproportionated rosin ester, trade name “Superester A-100”, softening point 95-105 ° C., Arakawa Chemical Industries) and terpene phenol resin (trade name “ “Tamanol 803L”, softening point 145 to 160 ° C., manufactured by Arakawa Chemical Industries, Ltd.), carbon black dispersion (trade name “N-DYM8715 Black” manufactured by Dainichi Seika Kogyo Co., Ltd.), and isocyanate crosslinking agent ( 2 parts of a trade name “Coronate L” (manufactured by Nippon Polyurethane Industry Co., Ltd., solid content: 75%) was added to prepare an adhesive composition A1. This pressure-sensitive adhesive composition A1 contains 2 parts of carbon black as a colorant with respect to 100 parts of the acrylic polymer.

Two release films made of polyester (trade name “Diafoil MRF”, thickness 38 μm, manufactured by Mitsubishi Polyester Co., Ltd.) were prepared as release liners. The pressure-sensitive adhesive composition A1 was applied to the release surfaces of these release liners so that the thickness after drying was 28 μm, and dried at 100 ° C. for 2 minutes. In this way, an adhesive layer was formed on each of the release surfaces of the two release liners.
As a base film, a transparent PET film (trade name “Lumirror”, manufactured by Toray Industries, Inc.) having a thickness of 4.5 μm and a black printed layer (colored layer) provided on the second surface of the PET film (base film); A base film having a total thickness of about 10 μm was prepared. The black print layer was formed by printing using a gravure printing method using an ink composition containing a black colorant. In this example, the pressure-sensitive adhesive layers formed on the two release liners were bonded to the first surface (first surface of the base film) and the second surface (surface of the colored layer) of the base film, respectively. A pressure-sensitive adhesive sheet was produced (transfer method). The release liner was left on the pressure-sensitive adhesive layer as it was and used to protect the surface (adhesive surface) of the pressure-sensitive adhesive layer.

<Example 2>
In this example, a transparent PET film (trade name “Lumirror”, manufactured by Toray Industries, Inc.) having a thickness of 25 μm and a black printed layer (coloring) similar to Example 1 provided on the second surface of the PET film are used as the base film. A base film having a total thickness of about 30 μm was used. The amount of the pressure-sensitive adhesive composition A1 applied to the release film was adjusted so that the thickness after drying was 36 μm. The other points were the same as the production of the pressure-sensitive adhesive sheet according to Example 1, and the pressure-sensitive adhesive sheet according to this example was produced.

<Example 3>
In this example, a PET film (trade name “Lumirror”, manufactured by Toray Industries, Inc.) with a thickness of 38 μm kneaded with a white pigment as a base film and provided on the second surface of the PET film in the order of white, silver and black A base film having a total thickness of about 45 μm composed of the printed layer (colored layer) was used. The amount of the pressure-sensitive adhesive composition A1 applied to the release film was adjusted so that the thickness after drying was 30 μm. The pressure-sensitive adhesive layer formed from this pressure-sensitive adhesive composition A1 was bonded only to the first surface of the base film. The other points were the same as the production of the pressure-sensitive adhesive sheet according to Example 1, and a pressure-sensitive adhesive sheet (single-sided pressure-sensitive adhesive sheet) according to this example was produced.

<Example 4>
A reactor equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser and dropping funnel was charged with 95 parts of BA and 5 parts of AA as monomer components and 150 parts of toluene as a polymerization solvent, and nitrogen gas was introduced. The mixture was stirred for 2 hours. After removing oxygen in the polymerization system in this way, 0.2 part of benzoyl peroxide was added as a polymerization initiator, and solution polymerization was performed at 60 ° C. for 6 hours to obtain an acrylic polymer solution. Mw of this acrylic polymer was about 60 × 10 ⁴ .
A terpene phenol resin as a tackifier resin (trade name “YS Polystar S-145”, softening point of about 145 ° C., manufactured by Yasuhara Chemical Co., Ltd.) with respect to 100 parts of the acrylic polymer contained in the acrylic polymer solution. 10 parts and 30 parts of terpene phenol resin (trade name “Tamanol 803L”, softening point 145 to 160 ° C., manufactured by Arakawa Chemical Industries) and the above carbon black dispersion (including 2 parts of carbon black as a colorant). , 2 parts of an isocyanate-based crosslinking agent (trade name “Coronate L”, Nippon Polyurethane Industry Co., Ltd., solid content 75%) and 0.03 part of an epoxy-based crosslinking agent (trade name “TETRAD-C”, manufactured by Mitsubishi Gas Chemical Co., Ltd.) Were added and stirred and mixed to prepare an adhesive composition A2.
As the substrate film, a 75 μm thick PET film (trade name “Lumirror”, Toray Industries, Inc.) kneaded with a black pigment was used. The amount of the pressure-sensitive adhesive composition A2 applied to the release film was adjusted so that the thickness after drying was 38 μm. The other points were the same as the production of the pressure-sensitive adhesive sheet according to Example 1, and the pressure-sensitive adhesive sheet according to this example was produced.

<Example 5>
A pressure-sensitive adhesive composition A0 containing no colorant was prepared in the same manner as the pressure-sensitive adhesive composition A1, except that the carbon black dispersion was not added.
As the substrate film, a transparent PET film (trade name “Lumirror”, manufactured by Toray Industries, Inc.) having a thickness of 12 μm was used. The amount of the pressure-sensitive adhesive composition A0 applied to the release film was adjusted so that the thickness after drying was 19 μm. The other points were the same as the production of the pressure-sensitive adhesive sheet according to Example 1, and the pressure-sensitive adhesive sheet according to this example was produced.

<Example 6>
In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel, 70 parts of BA as monomer components, 27 parts of EHA, 3 parts of AA and 0.05 parts of 4-hydroxybutyl acrylate, and a polymerization solvent The toluene was charged with 135 parts of toluene and stirred for 2 hours while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, 0.1 part of AIBN as a polymerization initiator was added, and solution polymerization was performed at 60 ° C. for 6 hours to obtain a toluene solution of an acrylic polymer. Mw of this acrylic polymer A was about 40 × 10 ⁴ .
For 100 parts of the acrylic polymer contained in the toluene solution, rosin resin A (polymerized rosin ester, trade name “Pencel D-125”, softening point 120 to 130 ° C., manufactured by Arakawa Chemical Industries, Ltd.) 30 as a tackifier resin Acrylic pressure-sensitive adhesive composition A3 was prepared by adding 2 parts of an isocyanate-based crosslinking agent (trade name “Coronate L”, Nippon Polyurethane Industry Co., Ltd., solid content: 75%).
As the base film, a transparent PET film (trade name “Lumirror”, manufactured by Toray Industries, Inc.) having a thickness of 25 μm was used. The amount of the pressure-sensitive adhesive composition A3 applied to the release film was adjusted so that the thickness after drying was 38 μm. The other points were the same as the production of the pressure-sensitive adhesive sheet according to Example 1, and the pressure-sensitive adhesive sheet according to this example was produced.

<Example 7>
In Example 3, the pressure-sensitive adhesive composition A3 was used in place of the pressure-sensitive adhesive composition A1. The amount of the pressure-sensitive adhesive composition A3 applied to the release film was adjusted so that the thickness after drying was 20 μm. As the base film, a 13 μm thick PET film (trade name “Lumirror”, manufactured by Toray Industries, Inc.) kneaded with a white pigment and printing provided in the order of white, silver and black on the second surface of the PET film A base film having a total thickness of about 20 μm consisting of a layer (colored layer) was used. The other points were the same as the production of the pressure-sensitive adhesive sheet according to Example 3, and a pressure-sensitive adhesive sheet (single-sided pressure-sensitive adhesive sheet) according to this example was produced.

<Example 8>
In this example, a transparent PET film (trade name “Lumirror”, manufactured by Toray Industries, Inc.) having a thickness of 12 μm and a black printed layer (coloring) similar to Example 1 provided on the second surface of the PET film are used as the base film. A base film having a total thickness of about 17 μm was used. The amount of the pressure-sensitive adhesive composition A3 applied to the release film was adjusted so that the thickness after drying was 17 μm. Otherwise in the same manner as in Example 6, a pressure-sensitive adhesive sheet according to this example was produced.

<Example 9>
In Example 2, the pressure-sensitive adhesive composition A3 was used in place of the pressure-sensitive adhesive composition A1. Otherwise in the same manner as in Example 2, a pressure-sensitive adhesive sheet according to this example was produced.

<Example 10>
The pressure-sensitive adhesive layer having a thickness of 20 μm formed from the pressure-sensitive adhesive composition A3 was bonded to the first surface and the second surface of the same base film used in Example 7. Otherwise in the same manner as in Example 6, a pressure-sensitive adhesive sheet according to this example was produced.

[Evaluation]
For the pressure-sensitive adhesive sheet according to each example, 0.6 mm light transmittance (%) of the pressure-sensitive adhesive layer, vertical light transmittance (%) of the pressure-sensitive adhesive sheet, and impact resistance were measured or evaluated. About the adhesive sheet which concerns on Examples 3 and 7, the reflectance (%) of the 2nd surface of an adhesive sheet was also measured.

The impact resistance was evaluated for the pressure-sensitive adhesive sheets according to Examples 1, 2, 4 to 6 and 8 to 10 as follows.
That is, the pressure-sensitive adhesive sheet according to each example was processed into a frame shape having an outer periphery of 40 mm in width, 60 mm in length, and 1 mm in width. The release liner that covers one adhesive surface of the frame-shaped adhesive sheet is peeled off, and the exposed adhesive surface is crimped by reciprocating a 2 kg roller once on a stainless steel plate (SUS304BA plate) 60 mm wide, 80 mm long, and 1 mm thick. did. Immediately after that, the release liner covering the other adhesive surface is peeled off, an acrylic resin plate having a width of 40 mm, a length of 60 mm and a thickness of 2 mm is placed on the exposed adhesive surface, and a load of 50 N is applied from the acrylic plate side for 10 seconds. Crimped. This was cured for 24 hours in an environment of 23 ° C. and 50% RH as an evaluation sample.
The sample for evaluation was dropped freely from a height of 1 m to give an impact to the sample, and the presence or absence of peeling was visually confirmed between the adhesive sheet and the stainless steel plate and between the adhesive sheet and the acrylic resin plate. . When peeling was not recognized, the sample was dropped again from the height of 1 m again, and the presence or absence of peeling was similarly confirmed. This drop test was repeated up to 40 times, and the number of times until peeling occurred was recorded. As a result, E (Excellent) was not observed after 40 drops, G (Good) was observed after 31 to 40 times, and 21 to 30 times. The impact resistance was evaluated by taking A (Acceptable) as the material and P (Poor) as the material where peeling was observed 20 times or less.

  The obtained results are shown in Tables 1 and 2 together with the schematic configuration of the pressure-sensitive adhesive sheet according to each example.

  From the results shown in Tables 1 and 2, it can be seen that each of the pressure-sensitive adhesive sheets of Examples 1, 2, and 4 having a pressure-sensitive adhesive layer thicker than 25 μm exhibits good bonding durability against a drop impact even in a narrow width. . In addition, the pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets of Examples 1 to 4 each have a 0.6 mm light transmittance of 5% or less (specifically less than 0.1%), and have a high horizontal light-shielding property even in a narrow width. You can see that

  In contrast, the pressure-sensitive adhesive sheets of Examples 5, 8, and 10 having a thickness of the pressure-sensitive adhesive layer of 25 μm or less tended to be inferior in impact resistance as compared with the pressure-sensitive adhesive sheets of Examples 1, 2, and 4. Moreover, since the adhesive layer which comprises the adhesive sheet of Examples 5-10 has high 0.6 mm light transmittance, all have a low horizontal light-shielding property compared with the adhesive sheet of Examples 1-4, and especially the thickness of an adhesive layer. It was confirmed that Examples 6 and 9 having a thickness exceeding 25 μm have poor horizontal light-shielding properties.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

DESCRIPTION OF SYMBOLS 1, 2 Adhesive sheet 10 Base film 10A 1st surface 10B 2nd surface 12 Resin film (base film)
14 colored layer 21 first adhesive layer 21A first adhesive surface 22 second adhesive layer 22A second adhesive surface 31, 32 release liner

Claims (9)

A base film, and an adhesive layer disposed on at least one surface of the base film,
The pressure-sensitive adhesive layer contains a colorant in the pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer is a pressure-sensitive adhesive sheet having a thickness greater than 25 μm and a light transmittance of 5% or less at a length of 0.6 mm.   2. The pressure-sensitive adhesive sheet according to claim 1, wherein a layer having a thickness exceeding 25 μm among the layers constituting the pressure-sensitive adhesive sheet has a light transmittance of 5% or less at a length of 0.6 mm.   The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the total thickness of the pressure-sensitive adhesive layers contained in the pressure-sensitive adhesive sheet is more than 50% of the total thickness of the pressure-sensitive adhesive sheet.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive sheet has a vertical light transmittance of 1% or less.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein a vertical light transmittance of the pressure-sensitive adhesive layer is higher than 25%.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive sheet has a narrow width portion, and the width of the narrow width portion is less than 2.0 mm.   The pressure-sensitive adhesive sheet according to claim 6, wherein a width of the pressure-sensitive adhesive layer in the narrow width portion is 50 times or less of a thickness of the pressure-sensitive adhesive layer. It is constituted as a double-sided pressure-sensitive adhesive sheet comprising a first pressure-sensitive adhesive layer disposed on one surface of the base film and a second pressure-sensitive adhesive layer disposed on the other surface of the base film,
Either of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer has a thickness of more than 25 μm and a light transmittance of 5% or less at a length of 0.6 mm. The pressure-sensitive adhesive sheet according to one item.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 8, which is used for joining the liquid crystal display module unit and the backlight unit in a liquid crystal display device including a liquid crystal display module unit and a backlight unit.

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