TWI904453B - Adhesive sheet and display - Google Patents

Abstract

The present invention addresses the problem of providing an adhesive sheet that enhances the design of a display, and a display with enhanced design. The solution of the present invention is to provide an adhesive sheet 1, which includes an adhesive layer 11 for bonding a display component 21 to other display components 22. The adhesive layer 11 is composed of an adhesive containing a colorant, and has a total light transmittance of 3% or more, and a lightness L₁ of 95 or less according to the CIE 1976 L₁a₁b₁ color system.

Description

Adhesive film and display

This invention relates to an adhesive sheet used for bonding display components, and a display using the adhesive sheet.

In recent years, the use of liquid crystal display devices has increased in various displays, such as in-vehicle displays installed on car dashboards, car navigation systems, and control panels; displays for general user tablet terminals; displays for commercial tablet terminals; displays for digital signage; and displays for outdoor digital signage.

In displays, primarily for automotive applications, as described above, it is required that the display maintain a cohesive look with its surrounding components, such as the frame, when the lights are off, thus enhancing the design. Therefore, it is considered necessary to color the display; for example, patents 1-4 disclose inventions related to display coloring. [Prior Art Documents] [Patent Documents]

[Patent Document 1] Japanese Patent Application Publication No. 2000-313871 [Patent Document 2] Japanese Patent Application Publication No. 2009-188298 [Patent Document 3] Japanese Patent Application Publication No. 2012-234028 [Patent Document 4] Japanese Patent Application Publication No. 2017-57375

The problem to be solved by the invention

However, the coloring purposes of any of the techniques disclosed in the aforementioned patents 1 to 4 are different, so they cannot give the display a sense of unity with the surrounding components to enhance the design.

This invention was made in view of the actual situation described above, and its purpose is to provide an adhesive sheet that enhances the design of a display, and a display with enhanced design. Means for solving the problem

To achieve the above objectives, the first invention provides an adhesive sheet comprising an adhesive layer for bonding a display component to other display components, characterized in that: the adhesive layer is composed of an adhesive containing a colorant, the total light transmittance of the adhesive layer is 3% or more, and the lightness L₽ of the adhesive layer as specified according to the CIE1976 L₁a₂b₂ color system is 95 or less (Invention 1).

According to the invention described above (Invention 1), when applied to a display, the design (appearance harmony, for example) of the display can be improved when the display is turned off. Furthermore, by having a total light transmittance of 3% or more, the visibility of the display can be ensured.

In the above invention (Invention 1), the fog value of the aforementioned adhesive layer is preferably below 80% (Invention 2).

In the above invention (Invention 2), the aforementioned coloring agent is preferably a black pigment or dye (Invention 3).

In the aforementioned inventions (Inventions 1-3), when the content of the aforementioned colorant in the adhesive is set to X% by mass, and the thickness of the adhesive layer is set to Z μm, it is preferable to satisfy the following formula (I) (Invention 4). 5≦X×Z＜250 ‧‧‧(I)

In the above inventions (Inventions 1-4), the aforementioned adhesive is preferably an acrylic adhesive (Invention 5).

In the above inventions (Inventions 1-5), the aforementioned adhesive is preferably a crosslinked adhesive composition containing (meth)acrylate polymer (A), crosslinking agent (B) and colorant (C) (Invention 6).

In the above inventions (Inventions 1 to 6), it is preferable to have two peeling discs and an adhesive layer held by the peeling discs in a manner that contacts the peeling surfaces of the two peeling discs (Invention 7).

The second aspect of this invention is to provide a display body comprising a display body component, other display body components, and an adhesive layer for bonding the aforementioned one display body component and the aforementioned other display body components together, characterized in that the aforementioned adhesive layer is the adhesive layer of the aforementioned adhesive sheet (Invention 1-7) (Invention 8).

In the above invention (Invention 8), at least one of the aforementioned display component and the aforementioned other display component preferably has a step at least on the surface adhered to by the aforementioned adhesive layer (Invention 9).

Of the aforementioned inventions (Inventions 8 and 9), the one with a black frame is preferred (Invention 10). Invention Effect

The adhesive sheet of this invention can improve the design of the display. Furthermore, the display of this invention becomes a product with improved design.

The following describes embodiments of the present invention. [Adhesive Sheet] One embodiment of the present invention provides an adhesive sheet comprising an adhesive layer for bonding a display component to other display components. Preferably, a release liner is deposited on one or both sides of the adhesive layer. The display and display components are described below.

The specific composition of the adhesive sheet, as an example of this embodiment, is shown in Figure 1. As shown in Figure 1, the adhesive sheet 1 consists of two peelable sheets 12a and 12b, and an adhesive layer 11 held by the two peelable sheets 12a and 12b in contact with their peelable surfaces. Furthermore, in this specification, the term "peelable surface" refers to the peelable surface of the sheet, including both surfaces that have undergone peeling treatment and surfaces that are peelable even without peeling treatment.

1. Components 1-1. Adhesive Layer The adhesive layer 11 of the adhesive sheet 1 of this embodiment is composed of an adhesive containing a colorant. Furthermore, the total light transmittance of the adhesive layer 11 (measured according to JIS K7361-1:1997) is 3% or more, and the lightness L✽ of the adhesive layer 11 according to the CIE 1976 L✽a✽b✽ color system is 95 or less. The method for measuring the lightness L✽ in this specification is shown in the test examples described later.

When the adhesive layer 11, which satisfies the aforementioned physical properties, is applied to a display, the display's design (appearance harmony being an example) is enhanced when the lights are off. Specifically, it can give the display a sense of unity with surrounding components, such as a black frame, thereby creating a sense of sophistication. Furthermore, with a total light transmittance of 3% or more, visibility as a display is ensured.

Specifically, examples of such peripheral components include automotive dashboards, which, according to the CIE 1976 L✽a✽b✽ color system, have a lightness L✽ of 23.2, a chromaticity a✽ of -0.5, and a chromaticity b✽ of -1.5. For the color tone of these peripheral components, a lightness L✽ of 5~90, a chromaticity a✽ of -40~40, and a chromaticity b✽ of -40~40 are preferred; a lightness L✽ of 10~80, a chromaticity a✽ of -30~30, and a chromaticity b✽ of -30~30 are particularly good; and a lightness L✽ of 15~70, a chromaticity a✽ of -20~20, and a chromaticity b✽ of -20~20 are even better. The adhesive sheet 1 of this embodiment is suitable for use on displays with peripheral components having the aforementioned color tone.

From the above perspective, the total light transmittance of the adhesive layer 11 is 3% or more, preferably 5% or more, and especially 8% or more. There is no particular upper limit to the total light transmittance, which is usually below 100%. Considering its relationship with the aforementioned lightness L✽, 98% or less is preferred, 95% or less is especially preferred, and 93% or less is even more preferred.

Furthermore, from the perspective of improving design, the lightness L✽ of the adhesive layer 11 is 95 or less, preferably 90 or less, especially 85 or less, and even more preferably 75 or less. On the other hand, from the perspective of improving design and the visibility of the display, the lower limit of this lightness L✽ is preferably 10 or more, especially 20 or more, and even more preferably 25 or more.

Furthermore, according to the CIE1976 L✽a✽b✽ color system, the chromaticity a✽ of the adhesive layer 11 is preferably -40 or higher, better than -30, especially better than -20, further preferably -15 or higher, and best than -10. Also, the chromaticity a✽ is preferably below 40, better than 30, especially better than 20, further preferably below 15, and best below 10. By using the above-mentioned range for chromaticity a✽, the design, especially for automotive displays, is further improved.

Furthermore, according to the CIE1976 L✽a✽b✽ color system, the chromaticity b✽ of the adhesive layer 11 is preferably -40 or higher, better than -30, especially better than -20, further preferably -15 or higher, and best than -10. Also, the chromaticity b✽ is preferably below 40, better than 30, especially better than 20, further preferably below 15, and best below 10. By using the above-mentioned range for chromaticity b✽, the design, especially for automotive displays, is further improved.

The fog value of the adhesive layer 11 is preferably 80% or less, preferably 75% or less, and even more preferably 70% or less. By setting the upper limit of the fog value of the adhesive layer 11 to the above-mentioned value, the total light transmittance is more likely to fall within the above range, and it is easier to give the resulting display a sense of unity with surrounding components (such as the frame). On the other hand, the fog value of the adhesive layer 11 is generally 0% or more. When the colorant in the adhesive layer 11 is a dye, it is preferably 0.01% or more, and especially preferably 0.1% or more. Furthermore, when the colorant in the adhesive layer 11 is a pigment, the fog value of the adhesive layer 11 is preferably 3% or more, better than 10%, and especially preferably 25% or more. By setting the lower limit of the fog value of the adhesive layer 11 as described above, it is easier to give the resulting display a sense of unity with the surrounding components (such as the frame). Furthermore, the fog value in this specification is set to a value measured according to JIS K7136:2000.

The aforementioned total light transmittance and lightness L✽ (as well as chromaticity a✽ and b✽, and haze value) can be achieved by appropriately selecting the type and amount of colorant contained in the adhesive constituting the adhesive layer 11.

The aforementioned colorant can be either a pigment or a dye. The pigment can be either inorganic or organic. From the perspective of the durability of the resulting adhesive, inorganic pigments are preferred. The color of the colorant should be appropriately selected to match the color of the surrounding components to achieve a cohesive look; generally, dark or deep colors such as black, brown, dark blue, purple, and blue are preferred, with black being particularly desirable.

Inorganic pigments include, for example, carbon black, cobalt-based pigments, iron-based pigments, chromium-based pigments, titanium-based pigments, vanadium-based pigments, zirconium-based pigments, molybdenum-based pigments, ruthenium-based pigments, platinum-based pigments, ITO (indium tin oxide) pigments, and ATO (antimony tin oxide) pigments.

Furthermore, examples of organic pigments and dyes include, for instance, amino-based pigments, anthocyanin-based pigments, merocyanine-based pigments, croconium-based pigments, squalium-based pigments, azulenium-based pigments, polymethine-based pigments, naphthoquinone-based pigments, pyranium-based pigments, phthalocyanine-based pigments, naphthalocyanine-based pigments, and naphtholactam. Pigments include: azo dyes, condensed azo dyes, indigo dyes, perinone dyes, perylene dyes, dioxazine dyes, quinacridone dyes, isoindolinone dyes, quinophthalone dyes, pyrrole dyes, thioindigo dyes, metal complex dyes (metal salt dyes), dithiol metal complex dyes, indole phenol dyes, triallylmethane dyes, anthraquinone dyes, naphthol dyes, azomethine dyes, benzimidazolone dyes, pyranthron dyes, and threne dyes, etc.

Examples of black pigments include carbon black, copper oxide, ferric oxide, manganese dioxide, aniline black, and activated carbon. Examples of black dyes include high-concentration plant-based dyes and azo dyes.

The aforementioned pigments or dyes can be appropriately mixed and used in a manner that allows the desired physical properties to be obtained in the adhesive layer 11.

Among the aforementioned colorants, carbon black, nigrosine-based black dyes, and chromate-based black dyes are preferred from the perspective of easily achieving the aforementioned total light transmittance and lightness L✽ (and consequently, haze value) and easily demonstrating the overall appearance with surrounding components. Furthermore, carbon black may or may not undergo a predetermined surface treatment (such as solvent affinity treatment).

When the thickness of the adhesive layer 11 is set to Z μm, the content of the colorant in the adhesive, x by mass % should preferably be a value satisfying the following formula (I): 5 ≦ X × Z < 250 ‧‧‧ (I) By setting the value of X × Z within the above range, the aforementioned total light transmittance and lightness L✽ (and consequently, haze value) can be easily achieved. Furthermore, the thickness of the adhesive layer 11 in this specification is a value measured according to JIS K7130.

From the above perspectives, a lower limit of 7 or above for X×Z is preferable, 10 or above is even better, and 15 or above is even better. Furthermore, an upper limit of 235 or below for X×Z is preferable, 220 or below is even better, and 200 or below is even better.

To ensure that the value of X×Z easily falls within the aforementioned range, the lower limit of the colorant content (X by mass%) in the adhesive is preferably 0.01% by mass or more, particularly preferably 0.05% by mass or more, and further preferably 0.10% by mass or more. Furthermore, the upper limit of the aforementioned colorant content (X by mass%) is preferably 10% by mass or less, particularly preferably 7% by mass or less, and further preferably 4% by mass or less.

The type of adhesive used in the adhesive layer 11 of the adhesive sheet 1 constituting this embodiment is not particularly limited. For example, it can be any of acrylic adhesives, polyester adhesives, polyurethane adhesives, rubber adhesives, polysiloxane adhesives, etc. Furthermore, the adhesive can be any of emulsion type, solvent type, or solvent-free type, and can also be any of cross-linked or non-cross-linked type. Among these, acrylic adhesives with excellent adhesive properties and optical properties are preferred.

Furthermore, acrylic adhesives can be either curable or non-curable. From the perspective of durability and simplification of display manufacturing processes, non-curable acrylic adhesives are preferred. Among non-curable acrylic adhesives, cross-linked types are particularly preferred, and thermally cross-linked types are even better.

The adhesive described above is preferably a crosslinked adhesive composition (hereinafter referred to as "adhesive composition P") containing a (meth)acrylate polymer (A), a crosslinking agent (B), and a colorant (C). The colorant (C) is the aforementioned colorant. The adhesive obtained from this adhesive composition P exhibits excellent optical properties, adhesive strength, and durability (step-following performance under high temperature and humidity conditions). Furthermore, in this specification, the term (meth)acrylate means both acrylic acid and methacrylic acid. Other similar terms are used similarly. Also, "polymer" is intended to include the concept of "copolymer."

(1) Composition of the Adhesive Compound (1-1) (Meth)acrylate Polymer (A) In this embodiment, the (meth)acrylate polymer (A) preferably comprises reactive monomers having reactive groups within the molecule that react with the crosslinker (B). The reactive groups derived from these reactive monomers react with the crosslinker (B) to form a crosslinked structure (three-dimensional network structure), thus yielding an adhesive with the desired cohesive strength.

Examples of reactive monomers include monomers containing hydroxyl groups (hydroxyl-containing monomers), monomers containing carboxyl groups (carboxyl-containing monomers), and monomers containing amino groups (amino-containing monomers). Among these, hydroxyl-containing monomers and carboxyl-containing monomers that exhibit excellent reactivity with crosslinker (B) are preferred, and hydroxyl-containing monomers that cause less adverse effects on the adhered material are particularly preferred.

Examples of hydroxyl-containing monomers include hydroxyalkyl methacrylates such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxybutyl methacrylate, and 4-hydroxybutyl methacrylate. In particular, regarding the reactivity of the hydroxyl group of the obtained (meth)acrylate polymer (A) with the crosslinking agent (B) and its copolymerization with other monomers, 2-hydroxyethyl methacrylate and 4-hydroxybutyl methacrylate are preferred, and 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are especially preferred. These monomers can be used alone or in combination of two or more.

Examples of carboxyl-containing monomers include vinyl unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and leuconic acid. Among these, acrylic acid is preferred in terms of the reactivity of the carboxyl group in the obtained (meth)acrylate polymer (A) with the crosslinker (B) and its copolymerization with other monomers. These monomers can be used alone or in combination of two or more.

Examples of amine-containing monomers include (meth)acrylate aminoethyl ester and (meth)acrylate n-butylaminoethyl ester. These can be used alone or in combination of two or more.

The (meth)acrylate polymer (A) contains reactive monomers as constituent units of the polymer, preferably at least 1% by mass, particularly preferably at least 5% by mass, and even more preferably at least 10% by mass. When the reactive monomer is a hydroxyl-containing monomer, it is particularly preferably at least 15% by mass. Furthermore, the (meth)acrylate polymer (A) contains reactive monomers as constituent units, preferably at least 35% by mass, particularly preferably at least 30% by mass, and even more preferably at least 25% by mass. When the (meth)acrylate polymer (A) contains reactive monomers as constituent units in the above amounts, the resulting adhesive can form a good cross-linked structure and achieve the desired cohesive strength. Furthermore, the colorant (C) in the adhesive exhibits good dispersibility, and the resulting adhesive demonstrates excellent reproducibility and uniformity in terms of total light transmittance, lightness L✽ (and chromaticity a✽ and b✽, as well as haze value), resulting in superior appearance harmony and text visibility. Moreover, when the reactive monomer is a hydroxyl-containing monomer, and its content is 15% by mass or more, a predetermined amount of hydroxyl will remain in the adhesive. The hydroxyl group is a hydrophilic group. When this hydrophilic group is present in a predetermined amount in the adhesive, even when the adhesive is placed under high temperature and high humidity conditions, the water immersed in the adhesive has good compatibility under these conditions. As a result, when it returns to normal temperature and humidity, it can inhibit the whitening of the adhesive (it has excellent resistance to damp heat whitening).

Furthermore, it is preferable that the (meth)acrylate polymer (A) does not contain carboxyl-containing monomers as constituent units of the polymer. Since carboxyl groups are acidic components, the absence of carboxyl-containing monomers can suppress acid-induced adhesion defects to the adhesive substrate. For example, even in the presence of transparent conductive films or metal films such as tin-doped indium oxide (ITO), acid-induced defects (corrosion, resistance changes, etc.) can be suppressed. However, the presence of carboxyl-containing monomers in a predetermined amount is permissible to prevent such defects. Specifically, the (meth)acrylate polymer (A) is permissible to contain carboxyl-containing monomers in an amount of 0.1% by mass or less, preferably 0.01% by mass or less, and more preferably 0.001% by mass or less.

The (meth)acrylate polymer (A) preferably contains alkyl (meth)acrylate as a monomer unit constituting the polymer. This allows for good adhesion. The alkyl group can be linear or branched.

From an adhesive viewpoint, alkyl (meth)acrylates with 1 to 20 carbon atoms in the alkyl group are preferred. Examples of alkyl (meth)acrylates with 1 to 20 carbon atoms in the alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmitate (meth)acrylate, stearyl (meth)acrylate, etc. From the perspective of further enhancing adhesion, (meth)acrylates with 1 to 8 carbon atoms in the alkyl group are preferred, with methyl (meth)acrylate, n-butyl (meth)acrylate, or 2-ethylhexyl (meth)acrylate being particularly preferred, and methyl methacrylate, n-butyl acrylate, or 2-ethylhexyl acrylate being even more preferred. Furthermore, these can be used alone or in combination of two or more.

The (meth)acrylate polymer (A) preferably contains 50% by mass or more of alkyl (meth)acrylate as a monomer unit constituting the polymer, particularly preferably 60% by mass or more, and even more preferably 65% by mass or more. When the lower limit of the alkyl (meth)acrylate content is as described above, the (meth)acrylate polymer (A) can exhibit suitable adhesiveness. Furthermore, the (meth)acrylate polymer (A) preferably contains 99% by mass or less of alkyl (meth)acrylate as a monomer unit constituting the polymer, particularly preferably 95% by mass or less, and even more preferably 90% by mass or less. When the upper limit of the alkyl (meth)acrylate content is as described above, appropriate amounts of other monomer components, such as reactive functional group monomers, can be introduced into the (meth)acrylate polymer (A).

The aforementioned (meth)acrylate polymer (A) preferably contains monomers with an intramolecular alicyclic structure (monomers with an alicyclic structure) as monomer units constituting the polymer. It is presumed that because monomers with an alicyclic structure have a larger volume, their presence in the polymer can increase the spacing between polymer molecules, resulting in an adhesive with excellent flexibility. Consequently, the adhesive exhibits excellent step-following properties.

In monomers containing an alicyclic structure, the carbon rings of the alicyclic structure can be saturated or partially unsaturated. Furthermore, the alicyclic structure can be a monocyclic alicyclic structure or a polycyclic alicyclic structure such as a bicyclic or tricyclic structure. From the viewpoint of achieving an appropriate spacing between the resulting (meth)acrylate polymers (A) and imparting higher stress-relieving properties to the adhesive, the aforementioned alicyclic structure is preferably a polycyclic alicyclic structure. Moreover, considering the compatibility of the (meth)acrylate polymer (A) with other components, the aforementioned polycyclic structure is particularly preferred to have two to four rings. Furthermore, similarly to the above, from the viewpoint of imparting stress mitigation, the carbon number of the alicyclic structure (referring to the total number of carbons in the ring-forming portion, or the total number of carbons when multiple rings exist independently) is generally preferred to be 5 or more, and particularly preferred to be 7 or more. On the other hand, there is no particular upper limit to the carbon number of the alicyclic structure, and similarly to the above, from the viewpoint of miscibility, 15 or less is preferred, and particularly preferred to be 10 or less.

Specifically, examples of monomers containing alicyclic structures include cyclohexyl methacrylate, dicyclopentyl methacrylate, tetraalkyl methacrylate, isocamphenyl methacrylate, dicyclopentenyl methacrylate, and dicyclopentenoxyethyl methacrylate. In particular, dicyclopentyl methacrylate (10 carbons in the alicyclic structure), tetraalkyl methacrylate (10 carbons in the alicyclic structure), or isocamphenyl methacrylate (7 carbons in the alicyclic structure) are preferred, with isocamphenyl methacrylate being particularly preferred, and isocamphenyl methacrylate being even more preferred. These can be used individually or in combination of two or more.

When the (meth)acrylate polymer (A) contains a monomer with an alicyclic structure as a monomer unit constituting the polymer, it is preferable to contain 1% or more of the monomer with an alicyclic structure, particularly preferably 4% or more, and even more preferably 8% or more. Furthermore, it is preferable that the (meth)acrylate polymer (A) contains 30% or less of the monomer with an alicyclic structure as a monomer unit constituting the polymer, particularly preferably 22% or less, and even more preferably 14% or less. By using monomers with an alicyclic structure within the above-mentioned ranges, the resulting adhesive exhibits superior step-following properties and simultaneously becomes a material with superior adhesion to plastics.

Furthermore, it is preferable that the aforementioned (meth)acrylate polymer (A) contains nitrogen-containing monomers as constituent units of the polymer. By including nitrogen-containing monomers as constituent units in the polymer, the adhesive can be endowed with a predetermined polarity, and it can also have excellent affinity for adhesives with a certain degree of polarity, such as glass. As for the aforementioned nitrogen-containing monomers, from the viewpoint of giving the (meth)acrylate polymer (A) suitable rigidity, monomers having nitrogen-containing heterocyclic rings are preferred. Furthermore, from the viewpoint of increasing the degree of freedom of the portion derived from the aforementioned nitrogen-containing monomers in the higher-order structure of the formed adhesive, it is preferable that the nitrogen-containing monomers, apart from the polymerizable group used to form the (meth)acrylate polymer (A), do not contain reactive unsaturated double bonds.

Examples of monomers containing nitrogen-containing heterocyclic rings include N-(meth)acrylamide morpholine, N-vinyl-2-pyrrolidone, N-(meth)acrylamide pyrrolidone, N-(meth)acrylamide piperidine, N-(meth)acrylamide pyrrolidone, N-(meth)acrylamide acrylonitrile propane, acrylonitrile propane ethyl methacrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyridine, 1-vinylimazole, N-vinylcarbazole, and N-vinylphthalimide. N-(meth)acrylamide morpholine, which exhibits superior adhesive strength, is particularly preferred. These monomers can be used alone or in combination of two or more.

When the (meth)acrylate polymer (A) contains nitrogen-containing monomers as constituent units of the polymer, it is preferable that the content of the nitrogen-containing monomers is 1% by mass or more, particularly preferable that it is 4% by mass or more, and even more preferable that it is 8% by mass or more. Furthermore, it is preferable that the (meth)acrylate polymer (A) contains 20% by mass or less of the nitrogen-containing monomers as constituent units of the polymer, particularly preferable that it is 16% by mass or less, and even more preferable that it is 12% by mass or less. When the content of the nitrogen-containing monomers is within the above range, the resulting adhesive can exert excellent adhesion to glass.

(Meth)acrylate polymer (A) may also contain other monomers as constituent units of the polymer, as needed. As other monomers, monomers without reactive functional groups are preferred to avoid hindering the aforementioned effects of monomers containing reactive functional groups. Examples of such monomers include methoxyethyl methacrylate, ethoxyethyl methacrylate, alkoxyalkyl methacrylate, vinyl acetate, styrene, etc. These can be used alone or in combination of two or more.

(Meth)acrylate polymers (A) are preferably linear polymers. Because they are linear polymers, the molecular chains are more likely to become entangled and the cohesive force can be expected to be enhanced, thus making it easier to obtain adhesives with excellent step-following properties under high temperature and high humidity conditions.

Furthermore, the (meth)acrylate polymer (A) is preferably a solution polymer obtained by solution polymerization. Because solution polymers readily produce high molecular weight polymers and can be expected to enhance cohesiveness, it is easy to obtain adhesives with excellent step-following properties under high temperature and high humidity conditions.

The polymerization state of (meth)acrylate polymer (A) can be either a random copolymer or a block copolymer.

The lower limit of the weight average molecular weight of the (meth)acrylate polymer (A) is preferably 200,000 or more, particularly preferably 300,000 or more, and even more preferably 400,000 or more. When the lower limit of the weight average molecular weight of the (meth)acrylate polymer (A) is as described above, the resulting adhesive exhibits superior step-following properties under high temperature and high humidity conditions.

Furthermore, the upper limit of the weight average molecular weight of (meth)acrylate polymer (A) is preferably 2 million or less, particularly preferably 1.5 million or less, and even more preferably 1 million or less. When the upper limit of the weight average molecular weight of (meth)acrylate polymer (A) is as described above or below, the resulting adhesive exhibits superior step-following properties. Also, the weight average molecular weight in this specification is a value converted from standard polystyrene measured using gel osmosis chromatography (GPC).

Furthermore, in the adhesive composition P, the (meth)acrylate polymer (A) can be used alone or in combination with two or more.

(1-2) Crosslinking Agent (B) Crosslinking agent (B) is used to crosslink (meth)acrylate polymer (A) by heating the adhesive component P, and it can form a good three-dimensional network structure. This results in an adhesive with enhanced cohesive strength and excellent step-following properties under high temperature and humidity conditions.

As the aforementioned crosslinking agent (B), it can be any substance that reacts with the reactive groups of the (meth)acrylate polymer (A). Examples include isocyanate crosslinking agents, epoxy crosslinking agents, amine crosslinking agents, melamine crosslinking agents, acrylonitrile crosslinking agents, hydrazine crosslinking agents, aldehyde crosslinking agents, aziroxazoline crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, ammonium salt crosslinking agents, etc. Of the above, when the reactive group of the (meth)acrylate polymer (A) is a hydroxyl group, it is preferable to use an isocyanate-based crosslinker that has excellent reactivity with the hydroxyl group; when the reactive group of the (meth)acrylate polymer (A) is a carboxyl group, it is preferable to use an epoxy-based crosslinker that has excellent reactivity with the carboxyl group. Furthermore, crosslinker (B) can be used alone or in combination with two or more other crosslinkers.

Isocyanate crosslinkers contain at least a polyisocyanate compound. Examples of polyisocyanate compounds include aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate; and biuret and trimer isocyanate forms of these compounds, as well as addition products of reactions with compounds containing low-molecular-weight active hydrogen such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. In particular, from the viewpoint of reactivity with hydroxyl groups, trimethylolpropane-modified aromatic polyisocyanates, especially trimethylolpropane-modified toluene diisocyanate and trimethylolpropane-modified xylene styrene diisocyanate are preferred.

Examples of epoxy crosslinking agents include 1,3-bis(N,N-diepoxypropylaminomethyl)cyclohexane, N,N,N',N'-tetraepoxypropyl-m-phenylenediamine, ethylene glycol diepoxypropyl ether, 1,6-hexanediol diepoxypropyl ether, trihydroxymethylpropane diepoxypropyl ether, diepoxypropylaniline, and diepoxypropylamine. From the perspective of reactivity with carboxyl groups, 1,3-bis(N,N-diepoxypropylaminomethyl)cyclohexane is particularly preferred.

The content of crosslinker (B) in the adhesive composition P is preferably 0.01 parts by weight or more, particularly preferably 0.03 parts by weight or more, and even more preferably 0.05 parts by weight or more, relative to 100 parts by weight of (meth)acrylate polymer (A). Furthermore, this content is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, particularly preferably 1 part by weight or less, and even more preferably 0.4 parts by weight or less. By using the crosslinker (B) content within the above range, the resulting adhesive exhibits good cohesiveness and becomes a material with superior step-following properties under high temperature and high humidity conditions.

(1-3) Colorant (C) Colorant (C) is the aforementioned colorant. Specific types and amounts are as described above.

(1-4) Various Additives The adhesive compound P can be added as needed to various additives commonly used in acrylic adhesives, such as silane coupling agents, rust inhibitors, UV absorbers, antistatic agents, adhesive enhancers, antioxidants, light stabilizers, softeners, refractive index modifiers, etc. Furthermore, the additives constituting the adhesive compound P do not include the polymerization solvents and diluents described later.

Of the above, the adhesive compound P preferably contains a silane coupling agent. This improves adhesion to plastic sheets or glass components and results in superior step-following properties under high temperature and humidity conditions.

As a silane coupling agent, it is preferably an organosilicon compound having at least one alkoxysilyl group in the molecule, and preferably one that has good compatibility with (meth)acrylate polymer (A) and is light-transmitting.

Examples of such silane coupling agents include, for instance, polymerizable unsaturated silica compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane; epoxy-containing silica compounds such as 3-epoxypropoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; and hydroxyl-containing silica compounds such as 3-hydroxypropyltrimethoxysilane, 3-hydroxypropyltriethoxysilane, and 3-hydroxypropyldimethoxymethylsilane. Condensations of silicone compounds, amine-containing silicone compounds such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-isocyanate propyltriethoxysilane, or at least one of these compounds with alkyl-containing silicone compounds such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. These compounds may be used alone or in combination of two or more.

The content of silane coupling agent (D) in the adhesive composition P is preferably 0.01 parts by weight or more, particularly preferably 0.05 parts by weight or more, and even more preferably 0.1 parts by weight or more, relative to 100 parts by weight of (meth)acrylate polymer (A). Furthermore, this content is preferably 1 part by weight or less, particularly preferably 0.5 parts by weight or less, and even more preferably 0.3 parts by weight or less.

The adhesive compound P containing a rust inhibitor is also preferable. Examples of rust inhibitors include azole compounds, triazole compounds, benzotriazole compounds, thiazole compounds, benzothiazole compounds, imidazole compounds, benzimidazole compounds, phosphorus compounds, amine compounds, nitrite compounds, surfactants, and silane coupling agents, with benzotriazole compounds being particularly preferred. When using benzotriazole compounds, the rust-preventive effect on metals is higher, and the compatibility with adhesives is also higher.

The content of the rust inhibitor in the adhesive composition P is preferably 0.01 parts by weight or more, preferably 0.05 parts by weight or more, and more preferably 0.1 parts by weight or more, relative to 100 parts by weight of the (meth)acrylate polymer (A). Furthermore, this content is preferably 3 parts by weight or less, particularly preferably 1 part by weight or less, and more preferably 0.5 parts by weight or less.

(2) Preparation of the Adhesive Compound The adhesive compound P can be prepared by manufacturing a (meth)acrylate polymer (A), mixing the resulting (meth)acrylate polymer (A), a crosslinking agent (B), and a colorant (C), and adding additives as needed.

(Meth)acrylate polymer (A) can be manufactured by polymerizing a mixture of monomers constituting the polymer using conventional free radical polymerization. The polymerization of (meth)acrylate polymer (A) is preferably carried out using a polymerization initiator as needed, and preferably by solution polymerization. Examples of polymerization solvents include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, etc., and two or more types can also be used in combination.

Examples of polymerization initiators include azo compounds and organic peroxides, and two or more types can be used together. Examples of azo compounds include 2,2’-azobisisobutyronitrile, 2,2’-azobis(2-methylbutyronitrile), 1,1’-azobis(cyclohexane-1-carbonitrile), 2,2’-azobis(2,4-dimethylpentanonitrile), 2,2’-azobis(2,4-dimethyl-4-methoxypentanonitrile), dimethyl 2,2’-azobis(2-methylpropionate), 4,4’-azobis(4-cyanovaleric acid), 2,2’-azobis(2-hydroxymethylpropionitrile), and 2,2’-azobis[2-(2-imidazolin-2-yl)propane].

Examples of organic peroxides include benzoyl peroxide, tert-butyl peroxide, cumene hydrogen peroxide, diisopropyl peroxide, di-n-propyl peroxide, di(2-ethoxyethyl) peroxide, tert-butyl peroxynedecanoate, tert-butyl peroxytrimethylacetic acid, (3,5,5-trimethylhexyl peroxide), dipropyl peroxide, and diacetyl peroxide.

Furthermore, in the above polymerization step, the weight-average molecular weight of the obtained polymer can be adjusted by adjusting the chain transfer agent such as 2-hydroxyethanol.

After obtaining (meth)acrylate polymer (A), by adding crosslinking agent (B), colorant (C), and diluents and additives as needed to a solution of (meth)acrylate polymer (A) and mixing thoroughly, a solvent-diluted adhesive compound P (coating solution) can be obtained. Furthermore, in cases where precipitation occurs when any of the above components are used as a solid or mixed with other components in an undiluted state, this component can be dissolved or diluted separately with a diluent beforehand before mixing with other components.

As diluents for the above-mentioned purposes, aliphatic hydrocarbons such as hexane, heptane, and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as dichloromethane and dichloroethane, alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol, acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone, esters such as ethyl acetate and butyl acetate, and celusol solvents such as ethyl celusol are all suitable solvents.

Regarding the concentration and viscosity of the coating solution prepared in this manner, there are no particular restrictions as long as it is within a coatable range, and it can be appropriately selected according to the situation. For example, the adhesive compound P can be diluted to a concentration of 10-60% by mass. Furthermore, when obtaining the coating solution, the addition of diluents is not a necessary condition; if the adhesive compound P has a coatable viscosity, diluents may not be added. In this case, the adhesive compound P becomes a coating solution in which the polymerization solvent of (meth)acrylate polymer (A) is used directly as a diluent.

(3) Formation of the Adhesive Layer In this embodiment, the adhesive layer 11 is preferably composed of an adhesive formed by cross-linking the adhesive composition P (the coating layer). The cross-linking of the adhesive composition P is usually carried out by heat treatment. Furthermore, the drying process, which allows the diluent or the like to evaporate from the coating layer of the adhesive composition P after it is applied to the desired object, can also serve as the heat treatment.

The heating temperature for the heating treatment is preferably 50~150℃, and preferably 70~120℃. In addition, the heating time is preferably 10 seconds to 10 minutes, and preferably 50 seconds to 2 minutes.

After heat treatment, a curing period of approximately 1 to 2 weeks at room temperature (e.g., 23°C, 50%RH) can be set as needed. If the curing period is necessary, an adhesive can be formed after the curing period has elapsed; if the curing period is not necessary, an adhesive can be formed after the heat treatment is completed.

Through the aforementioned heat treatment (and curing), the (meth)acrylate polymer (A) can be fully crosslinked by the crosslinking agent (B). The resulting adhesive is a material with excellent step-following properties under high temperature and high humidity conditions.

(4) Properties of the Adhesive The adhesive of this embodiment preferably possesses the following properties: (4-1) Gel Content The lower limit of the gel content of the adhesive of this embodiment is preferably 20% or more, more preferably 25% or more, and especially preferably 30% or more. When the lower limit of the gel content of the adhesive is as described above, the cohesive strength of the adhesive increases, and it becomes a material with better step-following properties under high temperature and high humidity conditions. Furthermore, the upper limit of the gel content of the adhesive of this embodiment is preferably 95% or less, more preferably 90% or less, especially preferably 80% or less, and further preferably 70% or less. When the upper limit of the gel content of the adhesive is as described above, the adhesive does not become too hard and exhibits excellent step followability both initially and after durability. Furthermore, it demonstrates good adhesion and superior bonding with the substrate. The method for determining the gel content of the adhesive is shown in the test examples described later.

(4-2) Storage Modulus The lower limit of the storage modulus of the adhesive of this embodiment at 23°C is preferably 0.01 MPa or higher, particularly preferably 0.03 MPa or higher, and even more preferably 0.05 MPa or higher. By achieving the aforementioned lower limit of the storage modulus, it becomes an adhesive with excellent step-following properties under high temperature and high humidity conditions. Furthermore, the upper limit of the aforementioned storage modulus is preferably 0.5 MPa or lower, particularly preferably 0.3 MPa or lower, and even more preferably 0.2 MPa or lower. By achieving the aforementioned upper limit of the storage modulus, it becomes an adhesive with excellent initial step-following properties. Furthermore, the storage module in this manual is set to a value measured according to JIS K7244-6 at a measurement frequency of 1 Hz using the torsional shear method. Specifically, as shown in the experimental examples described later.

(5) Thickness of the adhesive layer In this embodiment, the thickness (Z μm) of the adhesive layer 11 of the adhesive sheet 1 is preferably such that it satisfies the value of the aforementioned X×Z formula (I).

Specifically, the thickness of the adhesive layer 11 is preferably 1 μm or more, preferably 2 μm or more, and especially preferably 4 μm or more. When the thickness of the adhesive layer 11 is at the above-mentioned lower limit, it is easy to meet the aforementioned requirements for total light transmittance and lightness L✽ (and consequently chromaticity a✽ and b✽, and haze value) in relation to the content of colorant (C), and it is also easy to achieve the required adhesive force. Furthermore, from the viewpoint of easily achieving excellent step followability, the lower limit is preferably 10 μm or more, preferably 15 μm or more, especially preferably 20 μm or more, and even more preferably 45 μm or more.

Furthermore, the upper limit of the thickness of the adhesive layer 11 is preferably 500 μm or less, preferably 300 μm or less, especially preferably 200 μm or less, and further preferably 150 μm or less. When the upper limit of the thickness of the adhesive layer 11 is as described above, the processability becomes good. Moreover, it is not easy to produce indentations or other appearance defects. Furthermore, in terms of the content of colorant (C), it is easy to meet the aforementioned requirements for total light transmittance and lightness L✽ (and further, chromaticity a✽ and b✽, and haze value). In addition, the adhesive layer 11 can be formed as a single layer or by stacking multiple layers.

1-2. Peel-off Sheets The peel-off sheets 12a and 12b protect the adhesive layer 11 until the adhesive sheet 1 is used. They are peeled off when the adhesive sheet 1 (adhesive layer 11) is used. In this embodiment of the adhesive sheet 1, one or both of the peel-off sheets 12a and 12b may not be necessary.

As peeling sheets 12a and 12b, for example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionic polymer resin film, ethylene-(meth)acrylate copolymer film, ethylene-(meth)acrylate copolymer film, polystyrene film, polycarbonate film, polyimide film, fluororesin film, etc., can also be used. Furthermore, laminated films of these types can also be used.

It is preferable that the peeling surfaces (especially the surfaces in contact with the adhesive layer 11) of the aforementioned peeling sheets 12a and 12b have undergone a peeling treatment. Examples of peeling agents used in the peeling treatment include alkyd-based, polysiloxane-based, fluorinated, unsaturated polyester-based, polyolefin-based, and wax-based peeling agents. Furthermore, it is preferable that one of the peeling sheets 12a and 12b is a heavy-release type with greater peeling force, and the other is a light-release type with less peeling force.

There are no particular restrictions on the thickness of the peeling sheets 12a and 12b, which are usually around 20~150μm.

2. Physical Properties (Adhesive Strength) The lower limit of the adhesive strength of the adhesive sheet 1 of this embodiment to sodium-calcium glass is preferably 1 N/25 mm or more, preferably 5 N/25 mm or more, preferably 10 N/25 mm or more, especially preferably 20 N/25 mm or more, and even more preferably 27 N/25 mm or more. When the lower limit of the adhesive strength is as described above, it becomes a material with superior step-following performance under high temperature and high humidity conditions. Furthermore, the upper limit of the adhesive strength of the adhesive sheet 1 of this embodiment to sodium-calcium glass is preferably 100 N/25 mm or less, especially preferably 80 N/25 mm or less, and particularly preferably 50 N/25 mm or less. When the upper limit of the adhesive force is as described above, good reprocessability can be achieved, and in the event of bonding failure, display components, especially expensive display components, can be reused.

Here, the adhesive force in this instruction manual refers to the adhesive force measured basically using the 180-degree peeling method according to JIS Z0237:2009. The test sample is set to be 25 mm wide and 100 mm long. The test sample is attached to the object to be adhered and pressurized at 0.5 MPa and 50°C for 20 minutes. After being placed under normal pressure, 23°C and 50%RH conditions for 24 hours, the test force is measured at a peeling speed of 300 mm/min.

3. Manufacturing of the Adhesive Sheet As an example of manufacturing the adhesive sheet 1, a coating solution of the aforementioned adhesive compound P is applied to the peeling surface of one peeling sheet 12a (or 12b), and then heated to thermally cross-link the adhesive compound P to form a coating layer. Afterward, the peeling surface of another peeling sheet 12b (or 12a) is superimposed on the coating layer. If a curing period is necessary, it is allowed to mature; otherwise, the coating layer directly becomes the adhesive layer 11. Through the above steps, the adhesive sheet 1 can be obtained. The conditions for the heat treatment and curing are as described above.

Furthermore, as another manufacturing example of the adhesive sheet 1, a coating solution of the aforementioned adhesive composition P is applied to the peeling surface of one peel sheet 12a, and then heated to thermally crosslink the adhesive composition P to form a coating layer, thereby obtaining a peel sheet 12a with a coating layer. Also, a coating solution of the aforementioned adhesive composition P is applied to the peeling surface of another peel sheet 12b, and then heated to thermally crosslink the adhesive composition P to form a coating layer, thereby obtaining a peel sheet 12b with a coating layer. Furthermore, the release sheets 12a and 12b of the coating layer are bonded together in a manner where the two coating layers are in contact with each other. Alternatively, multiple release sheets of the coating layer can be produced, and only the desired number of coating layers can be bonded. A curing period is allowed if necessary; otherwise, the aforementioned layered coating layer directly becomes the adhesive layer 11. Through the above steps, the aforementioned adhesive sheet 1 can be obtained. According to this manufacturing example, even when the adhesive layer 11 is relatively thick, it can be manufactured stably.

Methods for applying the coating liquid to the above-mentioned adhesive composition P include, for example, rod coating, scraper coating, roller coating, squeegee coating, mold coating, gravure coating, etc.

[Display] The types of displays (shown devices) in this embodiment include, for example, in-vehicle displays installed on various devices such as dashboards, navigation systems, and control panels in automobiles; displays for general-use tablet terminals; displays for commercial tablet terminals and digital signage; and displays for outdoor digital signage. These displays are sometimes required to have aesthetic harmony with surrounding components and a premium feel. However, the display of this invention is not limited to these limitations.

As shown in Figure 2, the display body 2 of this embodiment is configured to have the following: a first display body component 21 (a display body component); a second display body component 22 (another display body component); and an adhesive layer 11 located between the first display body component 21 and the second display body component 22 to adhere to each other.

At least one of the first display component 21 and the second display component 22 may also have a step on the surface at least on the side to which the adhesive layer 11 is adhered. In the embodiment shown in Figure 2, the first display component 21 has a step such as a printed layer 3 on the surface on the side of the adhesive layer 11.

The adhesive layer 11 in the aforementioned display 2 is the adhesive layer 11 of the aforementioned adhesive sheet 1.

As a display body 2, examples include liquid crystal display (LCD), light-emitting diode display (LED), organic electroluminescent (OLED) display, electronic paper, etc., and it can also be a touch panel.

The first display component 21 is preferably a protective panel made of laminates containing glass plates, plastic plates, etc. In this case, the printed layer 3 is usually formed in a frame shape on the adhesive layer 11 side of the first display component 21.

The glass sheet mentioned above is not particularly limited; examples include chemically strengthened glass, alkali-free glass, quartz glass, sodium-calcium glass, barium-strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, and barium-borosilicate glass. The thickness of the glass sheet is not particularly limited, typically ranging from 0.1 to 5 mm, preferably from 0.2 to 2 mm.

There are no particular limitations on the plastic sheets mentioned above; for example, acrylic sheets and polycarbonate sheets can be used. The thickness of the plastic sheets is not particularly limited, but is typically 0.2~5mm, preferably 0.4~3mm.

Furthermore, various functional layers (transparent conductive film, metal layer, silicon oxide layer, hard coating layer, anti-glare layer, etc.) can be provided on one or both sides of the aforementioned glass plate and plastic plate, and optical components can also be laminated. Additionally, the transparent conductive film and metal layer can also be chemically treated.

The second display component 22 is preferably an optical component, a display module (e.g., a liquid crystal (LCD) module, a light-emitting diode (LED) module, an organic electroluminescent (OLED) module, etc.) that is pre-attached to the first display component 21, an optical component that is part of the display module, or a laminate containing the display module.

Examples of such optical components include anti-spray films, polarizing plates (polarizing films), polarizers, retardation plates (retardation films), field-of-view compensation films, brightness enhancement films, contrast enhancement films, liquid crystal polymer films, diffusion films, semi-transparent reflective films, and transparent conductive films. For example, an anti-spray film can be a hard coating formed on one side of a substrate film.

The material constituting the printed layer 3 is not particularly limited, and commonly used printing materials can be used. The thickness of the printed layer 3, i.e., the lower limit of the step height, is preferably 3 μm or more, preferably 5 μm or more, especially preferably 7 μm or more, and ideally 10 μm or more. By setting the lower limit as described above, sufficient concealment of electrical wiring, etc., can be ensured from the viewer's side. Furthermore, the upper limit is preferably 50 μm or less, especially preferably 35 μm or less, particularly preferably 25 μm or less, and even more preferably 20 μm or less. By setting the upper limit as described above or less, the adhesion of the adhesive layer 11 to the step height of the printed layer 3 can be prevented from deteriorating.

As an example, the above-mentioned display 2 is manufactured by peeling off the peeling sheet 12a of the adhesive sheet 1 and attaching the adhesive layer 11 exposed on the side where the printed layer 3 of the first display component 21 exists.

Subsequently, another peeling sheet 12b is peeled off from the adhesive layer 11 of the adhesive sheet 1, and the exposed adhesive layer 11 of the adhesive sheet 1 is bonded to the second display component 22. Alternatively, as another example, the bonding order of the first display component 21 and the second display component 22 may be changed.

Here, as shown in Figure 3, the display body 2 of this embodiment preferably has a frame 4 at its periphery. The frame 4 is preferably black. Furthermore, the preferred range of lightness L✽, chromaticity a✽, and chromaticity b✽ as defined by the CIE1976 L✽a✽b✽ color system for the frame 4 is as described above for peripheral components. By having this color, the frame 4 is easily perceived by the human eye as having a high-end feel. Furthermore, the adhesive layer 11 of this embodiment, by having the aforementioned color of the frame 4, enhances its overall integration with the frame 4 and improves its harmony.

In the aforementioned display body 2, the adhesive layer 11, through its physical properties, gives it an overall feel with the black frame 4 and excellent aesthetic harmony. Furthermore, the aforementioned display body 2 ensures its visibility as a display body.

Furthermore, in the aforementioned display 2, when the adhesive layer 11 is formed by the adhesive composition P, because the adhesive layer 11 has excellent step tracking under high temperature and high humidity conditions, the display 2 can suppress floating and peeling near the step even when placed under conditions such as high temperature and high humidity (e.g., 85°C, 85%RH).

The embodiments described above are for the purpose of facilitating understanding of the present invention and are not intended to limit the present invention. Therefore, the elements disclosed in the above embodiments also include all design variations and equivalents that fall within the scope of the present invention.

For example, either or both of the peeling sheets 12a and 12b of the adhesive sheet 1 can be omitted. Alternatively, optical components required for lamination can be used instead of peeling sheets 12a and/or 12b. Furthermore, the first display component 21 can also be without steps. Moreover, not only the first display component 21, but also the second display component 22 can be a component with steps on the adhesive layer 11 side. [Example]

The invention will now be described in more detail by way of examples, but the scope of the invention is not limited by these examples.

[Example 1] 1. Preparation of (Meth)acrylate Polymer 65 parts by weight of 2-ethylhexyl acrylate, 10 parts by weight of isoborneol acrylate, 10 parts by weight of N-acryloylmorpholine, and 15 parts by weight of 2-hydroxyethyl acrylate were copolymerized by solution polymerization to prepare (meth)acrylate polymer (A). The molecular weight of the (meth)acrylate polymer (A) was determined using the method described later to be 500,000 by weight average (Mw).

2. Preparation of the Adhesive Compound 100 parts by weight (solid content conversion value; the same applies below) of the (meth)acrylate polymer (A) obtained in step 1 above, 0.2 parts by weight of trihydroxymethylpropane-modified toluene diisocyanate (manufactured by TOYOCHEM, product name "BHS8515") as crosslinking agent (B), 1.0 part by weight of carbon black pigment (manufactured by TOYOCOLOR, "Multilac black") as colorant (C), and 0.1 parts by weight of 3-epoxypropoxypropyltrimethoxysilane as silane coupling agent were mixed and stirred thoroughly. The mixture was then diluted with methyl ethyl ketone to obtain a coating solution of the adhesive compound.

Table 1 shows the formulations (converted to solids) of the adhesive composition when (meth)acrylate polymer (A) is set at 100 parts by weight (solids conversion value). The details of the abbreviations, etc., recorded in Table 1 are as follows. [(Meth)acrylate polymer (A)] 2EHA: 2-Ethylhexyl acrylate IBXA: Isocamphene acrylate ACMO: N-Acryloylmorpholine HEA: 2-Hydroethyl acrylate MMA: Methyl methacrylate BA: n-Butyl acrylate AA: Acrylic acid [Crosslinker (B)] TDI: Trimethylolpropane-modified toluene diisocyanate (manufactured by TOYOCHEM, product name "BHS8515") XDI: Trimethylolpropane-modified xylene styrene diisocyanate (manufactured by Aekken Chemical Co., Ltd., product name "TD-75") Epoxy: 1,3-Bis(N,N-diepoxypropylaminomethyl)cyclohexane (manufactured by Mitsubishi GAS Chemical Co., Ltd., product name "TETRAD-C") [Colorant (C)] Pigment: Carbon black pigment (manufactured by TOYOCOLOR, "Multilac black") Dye: Aniline black dye (manufactured by Orient Chemical Industry Co., Ltd., product name "NUBIAN BLACK PA-2802")

3. Fabrication of the Adhesive Sheet The coating solution of the adhesive composition obtained in step 2 above is applied to the peeling surface of a heavy-release peel sheet (manufactured by LINTEC, product name "SP-PET752150"), which has been peeled from one side of a polyethylene terephthalate film using a polysiloxane-based release agent, using a doctor blade applicator. The sheet is then heated at 90°C for 1 minute to form a coating layer (thickness: 50 μm). An adhesive sheet consisting of a heavy-release sheet, an adhesive layer (thickness: 50 μm), and a light-release sheet (manufactured by LINTEC, product name "SP-PET381130"), which has undergone release treatment on one side of a polyethylene terephthalate film treated with a polysiloxane release agent, is bonded together. The bond is then cured for 7 days at 23°C and 50% RH.

Furthermore, the thickness of the adhesive layer was measured according to JIS K7130 using a constant pressure thickness gauge (manufactured by Teclock, product name "PG-02").

[Examples 2-14, Comparative Examples 1-4] Except for changes to the types and proportions of the monomers constituting the (meth)acrylate polymer (A), the weight average molecular weight (Mw) of the (meth)acrylate polymer (A), the type and amount of crosslinking agent (B), the type and amount of colorant (C), the amount of silane coupling agent, the amount of rust inhibitor (N,N-bis(2-ethylhexyl)-4-methyl-1H-benzotriazole-1-methylamine) as other additives, and the thickness of the adhesive layer, as shown in Table 1, the adhesive sheet was manufactured in the same manner as in Example 1.

Furthermore, the adhesive sheet of Example 8 was manufactured as follows: A coating solution of the adhesive composition, prepared in the same manner as in Example 1, was applied using a scraper applicator to the peel-treated surface of a heavy-release peel sheet (manufactured by LINTEC Corporation, product name "SP-PET752150"), which had been peeled from one side of a polyethylene terephthalate film using a polysiloxane-based release agent. The coating was then heated at 90°C for 1 minute to form a coating layer (thickness: 50 μm). Furthermore, a coating solution of the adhesive composition, prepared in the same manner as in Example 1, was applied using a scraper applicator to the surface of a light-peel release sheet (manufactured by LINTEC, product name "SP-PET382120") that had undergone a peeling treatment on one side of a polyethylene terephthalate film using a polysiloxane-based release agent. The surface was then heated at 90°C for 1 minute to form a coating layer (thickness: 50 μm).

Next, the heavy-release peel sheet with the coating layer obtained above and the light-release peel sheet with the coating layer obtained above are bonded together with the two coating layers in contact with each other. The adhesive sheet is then cured for 7 days at 23°C and 50%RH to produce an adhesive sheet consisting of a heavy-release peel sheet, an adhesive layer (thickness: 100μm), and a light-release peel sheet.

Here, X×Z is calculated when the content of colorant in the adhesive layer (adhesive composition) obtained in the embodiments and comparative examples is set to X mass% and the thickness of the adhesive layer is set to Z μm. The results are shown in Table 1.

The aforementioned weight-average molecular weight (Mw) is the weight-average molecular weight converted from polystyrene, determined using gel osmosis chromatography (GPC) under the following conditions (GPC determination). <Determination Conditions> • Measuring apparatus: TOSOH, HLC-8020 • GPC columns (passing in the following order): TOSOH TSK guard column HXL-H TSK gel GMHXL (×2) TSK gel G2000HXL • Solvent: Tetrahydrofuran • Measurement temperature: 40℃

[Experimental Example 1] (Determination of Gel Content) (Determination of Gel Content) The adhesive sheets obtained in the Examples and Comparative Examples were cut into 80mm × 80mm pieces. The adhesive layer was then wrapped in a polyester mesh (mesh size 200) and its mass was weighed using a precision balance. The mass of the adhesive alone was calculated by subtracting the mass of the mesh. This mass is designated as M1.

Next, the adhesive encased in the aforementioned polyester mesh was immersed in ethyl acetate at room temperature (23°C) for 24 hours. The adhesive was then removed and air-dried at 23°C and 50% relative humidity for 24 hours, and then dried in an oven at 80°C for 12 hours. After drying, its mass was measured using a precision balance, and the mass of the adhesive alone was calculated by subtracting the mass of the aforementioned mesh. This mass is designated as M2. The gel fraction (%) is expressed as (M2/M1) × 100. The results are shown in Table 2.

[Experimental Example 2] (Determination of Total Light Transmittance) The adhesive layer of the adhesive sheet obtained in the Embodiments and Comparative Examples was adhered to glass and used as the test sample. After background measurement on the glass, the total light transmittance (%) of the test sample was measured according to JIS K7361-1:1997 using a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., product name "NDH-5000"). The results are shown in Table 2.

[Experimental Example 3] (Determination of L✽a✽b✽) The lightness L✽, chromaticity a✽, and chromaticity b✽ of the adhesive layers of the adhesive sheets obtained in the Examples and Comparative Examples were measured using a simultaneous spectrophotometer (manufactured by Nippon Denshoku Kogyo Co., Ltd., product name "SQ2000") according to the CIE 1976 L✽a✽b✽ color system. The results are shown in Table 2.

[Experimental Example 4] (Determination of Fog Value) The fog value (%) of the adhesive layer of the adhesive sheets obtained in the exemplary and comparative examples was measured according to JIS K7136:2000 using a fog meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., product name "NDH-5000"). The results are shown in Table 2.

[Experimental Example 5] (Determination of Storage Modulus) The adhesive sheets obtained from the Embodiments and Comparative Examples were peeled off, and the adhesive layers were stacked in multiple layers to a thickness of 3 mm. From the resulting adhesive layer stacks, a cylinder with a diameter of 8 mm (height 3 mm) was punched and used as a sample.

For the above samples, the storage modulus (MPa) was measured under the following conditions using the torsional shear method with a viscoelasticity measuring apparatus (manufactured by Physica, product name "MCR300") according to JIS K7244-6. The results are shown in Table 2. Measurement frequency: 1Hz Measurement temperature: 23℃.

[Experimental Example 6] (Determination of Adhesion) The adhesive sheets obtained from the Examples and Comparative Examples were peeled off using a light-peel type release sheet. The exposed adhesive layer was then adhered to the easy-adhesion layer of a polyethylene terephthalate (PET) film (manufactured by Toyoshoku Corporation, product name "PET A4300", thickness: 100μm), resulting in a laminate of release sheet/adhesive layer/PET film. The resulting laminate was cut into pieces 25mm wide and 100mm long and used as samples.

Under conditions of 23°C and 50%RH, a re-peeling sheet was peeled from the above-mentioned sample, and the exposed adhesive layer was attached to a sodium-calcium glass (manufactured by Nippon Sheet Glass Co., Ltd.). The sample was then pressurized for 20 minutes at 0.5 MPa and 50°C using a high-pressure autoclave manufactured by Kurihara Seisakusho Co., Ltd. Subsequently, after being placed at 23°C and 50%RH for 24 hours, the adhesive force (N/25 mm) was measured using a tensile testing machine (manufactured by ORIENTEC Co., Ltd., product name TENSILON) at a peeling speed of 300 mm/min and a peeling angle of 180 degrees. Unless otherwise described herein, measurements were performed according to JIS Z0237:2009. The results are shown in Table 2.

[Experimental Example 7] (Appearance Harmony Evaluation) The adhesive sheets obtained from the Embodiments and Comparative Examples were cut into 70mm x 70mm pieces. The adhesive layer of these sheets was then bonded together using two pieces of sodium calcium glass (manufactured by Nippon Sheet Glass Co., Ltd., 70mm x 70mm x 1.1mm thick) and used as a sample.

The obtained samples were placed on black-printed paper (L✽: 29.8, a✽: -0.7, b✽: 0.6) as a background. Furthermore, under a 3-wavelength fluorescent lamp (distance from the lamp: 200cm), the similarity (integration) of the sample with the background was visually assessed, and the appearance harmony was evaluated based on the following criteria. The results are shown in Table 2. ◎: The sample is very similar to the background. ○: The sample has some degree of similarity to the background. ×: The sample is clearly dissimilar to the background.

Furthermore, the hue of the paper printed as black (according to the CIE1976 L✽a✽b color system) was measured using a spectrophotometer (manufactured by BYK Corporation, product name "Spectro guide").

[Experiment Example 8] (Text Visuality Evaluation) On a 15.6-inch monitor with a resolution of 1366×768 (manufactured by Fujitsu, product name "LITEBOOK A574/H"), black text (font: MS PGothic) on a white background was displayed at 100% magnification, ranging in size from 5 to 20 dots (1-dot spacing).

The sample, manufactured in the same manner as in Test Example 7, was placed on the aforementioned display. Furthermore, the size of the legible text was visually confirmed at a position 50 cm from the display, and text legibility was evaluated based on the following criteria. The results are shown in Table 2. ◎: 8-point characters can be seen. ○: While 8-point characters cannot be fully seen, 15-point characters can be seen. ×: 15-point characters cannot be seen.

[Experimental Example 9] (Evaluation of Step Follow-up) (a) Evaluation of the sample fabrication: On the surface of a glass plate (manufactured by NSG PRECISION, product name "Corning Glass EAGLE XG", 90mm x 50mm x 0.5mm), UV-curable ink (manufactured by Teikoku INK, product name "POS-911 ink") was screen-printed into a frame shape (outer dimensions: 90mm x 50mm, width 5mm). Next, the UV-curable ink was irradiated with ultraviolet light (80W/ ^cm² , 2 metal halogen lamps, lamp height 15cm, conveyor belt speed 10~15m/min) to harden the printed UV-curable ink, thereby creating a glass plate with step-induced step (step height: 5μm, 10μm).

The light-release peeling sheet was peeled off from the adhesive sheet manufactured in the embodiments and comparative examples, and the exposed adhesive layer was bonded to the easy-adhesion layer of a polyethylene terephthalate (PET) film (manufactured by Toyosho Co., Ltd., product name "PET A4300", thickness: 100μm) having an easy-adhesion layer. Next, the heavy-release peeling sheet was peeled off to expose the adhesive layer, and the frame-shaped printing was fully covered by the adhesive layer using a laminator (manufactured by Fujipla Co., Ltd., product name "LPD3214") and used as an evaluation sample.

(b) Initial Step Follow-through Evaluation The obtained evaluation results were used to evaluate the initial step follow-through by subjecting the samples to a high-pressure autoclave treatment at 50°C and 0.5 MPa for 30 minutes, based on the following criteria. Furthermore, when the printing steps caused by the adhesive layer were completely buried, the step follow-through was considered good. When floating or peeling was observed at the interface between the printing steps and the adhesive layer, the printing steps could not be followed. The results are shown in Table 2. ◎: Good at a printing step of 10 μm ○: Good at a printing step of 5 μm ×: Floating and peeling occurred at a printing step of 5 μm

(c) Evaluation of Step Follow-through After Duration For samples exhibiting good initial step follow-through, after the aforementioned autoclave treatment, they were placed at atmospheric pressure, 23°C, and 50% RH for 24 hours. Next, they were stored under humid and hot conditions at 85°C and 85% RH for 72 hours (durability test). Subsequently, the step follow-through after durability was evaluated based on the same criteria as above. The results are shown in Table 2.

[Table 1] (Meth)acrylate polymer (A) Crosslinking agent (B) Colorant (C) Silane coupling agent [parts by mass] Rust inhibitor [parts by weight] Adhesive layer thickness (Z) [μm] X (mass%) × Z (μm) Composition Mw Kind mass Kind mass Mass % (X) Implementation Example 1 2EHA/IBXA/ACMO/HEA =65/10/10/15 500,000 TDI 0.2 paint 1.0 0.99 0.1 - 50 49.5 Implementation Example 2 TDI 0.2 paint 0.1 0.10 0.1 - 50 5.0 Implementation Example 3 TDI 0.2 paint 3.0 2.90 0.1 - 50 145.0 Implementation Example 4 TDI 0.2 paint 4.0 3.84 0.1 - 50 192.0 Implementation Example 5 TDI 0.2 paint 2.0 1.96 0.1 - 25 49.0 Implementation Example 6 XDI 0.2 paint 1.0 0.99 0.1 - 50 49.5 Implementation Example 7 TDI 0.2 paint 1.0 0.99 - - 50 49.5 Implementation Example 8 TDI 0.2 paint 1.0 0.99 0.1 - 100 99.0 Implementation Example 9 TDI 0.2 dye 0.3 0.30 0.1 - 50 15.0 Implementation Example 10 TDI 0.2 dye 1.0 0.99 0.1 - 50 49.5 Implementation Example 11 TDI 0.2 paint 5.0 4.75 0.1 - 5 23.8 Implementation Example 12 2EHA/MMA/HEA = 60/20/20 700,000 TDI 0.3 paint 1.0 0.99 0.1 - 50 49.5 Implementation Example 13 TDI 0.6 paint 1.0 0.98 0.1 0.3 50 49.5 Implementation Example 14 BA/AA = 90/10 500,000 Epoxy 0.05 paint 1.0 0.99 - - 50 49.5 Comparative example 1 2EHA/IBXA/ACMO/HEA =65/10/10/15 500,000 TDI 0.2 - - - 0.1 - 50 - Comparative example 2 TDI 0.2 paint 5.0 4.75 0.1 - 50 237.5 Comparative example 3 TDI 0.2 dye 3.0 2.90 0.1 - 50 145.0 Comparative example 4 BA/AA = 90/10 500,000 Epoxy 0.05 - - - - - 50 -

[Table 2] Gel fraction (%) Total light transmittance (%) Color scheme Fog level (%) Storage modulus (MPa) Adhesion force (N/25mm) Appearance Harmony Text visibility Step follower L✽ a✽ b✽ Early stage After durability Implementation Example 1 59 42.8 68.6 0.1 1.1 32.7 0.08 38 ◎ ◎ ◎ ◎ Implementation Example 2 60 92.9 94.1 -0.3 0.3 3.5 0.08 35 ○ ◎ ◎ ◎ Implementation Example 3 56 8.9 33.5 0.5 1.7 65.0 0.08 39 ◎ ◎ ◎ ◎ Implementation Example 4 53 3.6 20.3 0.6 1.6 76.0 0.08 41 ◎ ○ ◎ ◎ Implementation Example 5 57 45.0 69.0 0.1 1.1 29.3 0.08 26 ◎ ◎ ◎ ○ Implementation Example 6 58 43.0 68.8 0.1 1.0 32.2 0.08 37 ◎ ◎ ◎ ◎ Implementation Example 7 59 42.8 68.5 0.1 1.2 32.6 0.08 37 ◎ ◎ ◎ ◎ Implementation Example 8 58 21.3 51.2 0.4 1.4 49.0 0.08 45 ◎ ◎ ◎ ◎ Implementation Example 9 48 47.8 72.1 0.9 -0.3 0.1 0.08 44 ◎ ◎ ◎ ◎ Implementation Example 10 30 10.9 37.4 2.8 -0.8 0.2 0.08 42 ◎ ◎ ◎ ◎ Implementation Example 11 57 52.3 72.4 0.1 0.9 26.4 0.08 7 ◎ ◎ × — Implementation Example 12 73 20.1 69.5 0.2 1.2 51.1 0.13 twenty one ◎ ◎ ◎ ○ Implementation Example 13 71 20.5 69.0 0.2 1.5 50.0 0.13 20 ◎ ◎ ◎ ○ Implementation Example 14 64 44.7 70.1 0.1 1.0 31.6 0.16 31 ◎ ◎ ◎ ◎ Comparative example 1 61 99≦ 96.9 -0.3 0.3 0.3 0.08 36 × ◎ ◎ ◎ Comparative example 2 51 1.8 12.9 0.6 1.6 81.9 0.08 42 ◎ × ◎ ◎ Comparative example 3 55 0.3 0.5 7.1 -5.0 0.0 0.08 42 ◎ × ◎ ◎ Comparative example 4 63 99≦ 96.5 -0.2 0.2 0.3 0.16 28 × ◎ ◎ ◎

As shown in Table 2, the adhesive sheets obtained using the embodiments possess excellent visual harmony and text legibility. Furthermore, the adhesive sheets obtained in Examples 1-10 and 12-14 also exhibit excellent step tracking performance. Industrial Applicability

The adhesive sheet of this invention is suitable for bonding display components, such as those with a black frame, to each other, especially for bonding a protective panel with a step to the desired display component.

1: Adhesive sheet 2: Display body 3: Printed layer 4: Frame material 11: Adhesive layer 12a, 12b: Peel-off sheet 21: First display body component 22: Second display body component

Figure 1 is a cross-sectional view of the adhesive sheet of one embodiment of the invention. Figure 2 is a cross-sectional view of the display body of one embodiment of the invention. Figure 3 is a plan view of the display body with a frame of one embodiment of the invention.

1: Adhesive sheet 11: Adhesive layer 12a, 12b: Peel-off sheet

Claims (6)

An adhesive sheet comprising a colored adhesive layer for bonding one display component to other display components, characterized in that: The aforementioned display has a frame, The aforementioned frame, according to the CIE 1976 L✽a✽b✽ color system, has a lightness L✽ of 5 to 90, a chromaticity a✽ of -40 to 40, and a chromaticity b✽ of -40 to 40, The aforementioned adhesive layer is composed of an adhesive containing a colored agent, The aforementioned colored agent is dark or deep-colored, The aforementioned adhesive is an acrylic adhesive, The adhesive constituting the aforementioned adhesive layer has a storage modulus at 23°C of 0.01 MPa or higher and 0.5 MPa or lower, The aforementioned adhesive layer has a fog value of 80% or less, measured according to JIS K7136:2000, and its lightness L✽, as specified by the CIE 1976 L✽a✽b✽ color system, is 95 or less. The adhesive sheet as described in claim 1, wherein the aforementioned adhesive contains a rust inhibitor. The adhesive sheet as described in claim 1 has two peelable sheets and is held by the peelable sheets in a manner that contacts the peelable surfaces of the two peelable sheets, holding the aforementioned adhesive layer. A display comprising a display component, other display components, and an adhesive layer for bonding the one display component to the other display components, characterized in that: the display has a frame, the frame has a lightness L₁ of 5 to 90, a chromaticity a₁ of -40 to 40, and a chromaticity b₁ of -40 to 40 according to the CIE 1976 L✽a✽b✽ color system, the adhesive layer is an adhesive layer of an adhesive sheet as described in any one of claims 1 to 3 of the patent application. The display as described in claim 4, wherein at least one of the aforementioned display component and the aforementioned other display component has a step formed by a frame-shaped printed layer with a thickness of 3 to 50 μm, at least on the side adhered to by the aforementioned adhesive layer. The display as described in claim 4, wherein the aforementioned frame is black.