Adhesive sheet and display body

Abstract

The present invention provides an adhesive sheet (1) having an adhesive layer (11) in which the absolute value of a slope (S1) represented by formula (1) is greater than 0.026 and the haze value of the adhesive layer (11) is 10%-100% (inclusive), where H (450) is the haze value (%) of the adhesive layer (11) due to light having a wavelength of 450 nm and H (650) is the haze value (%) due to light having a wavelength of 650 nm. The adhesive force of the adhesive sheet (1) to soda-lime glass is 1 N / 25 mm or more. According to the adhesive sheet (1), the light emission color can be adjusted to a color other than white while exhibiting concealment. S1 = (H (650)-H (450)) / 200... (1)

Description

Technical Field

[0001] This invention relates to adhesive sheets and display bodies. Background Technology

[0002] In recent years, liquid crystal displays (LCDs) have been widely used as display devices (monitors) in electronic devices such as portable phones, smartphones, tablets, and game consoles. Since the display portion formed by the liquid crystal panel itself does not emit light, display devices using this display portion have a backlight to illuminate it.

[0003] Until now, the backlight configuration in display devices as described above has typically been a side-light type, where the light source is positioned on the side of the light guide plate. However, recently, from the perspective of screen brightness and contrast, a direct-lit backlight, where the light source is positioned directly below the display, has been proposed. In direct-lit backlights, to increase the amount of light and to ensure uniform light distribution between the center and edges of the screen during display device fabrication, it has been proposed to provide a large number of light-emitting elements, typically light-emitting diodes (LEDs), on the substrate.

[0004] In displays with direct-lit backlights containing numerous light-emitting elements, concealment is required because the arrangement of the light-emitting elements and electronic circuitry are visible from the display section. Patent Document 1 proposes a solution where an adhesive layer containing light-scattering particles is provided on the light-emitting elements of the backlight. This allows the arrangement of the light-emitting elements and electronic circuitry to be concealed through the light-scattering effect of the light-scattering particles.

[0005] Existing technical documents Patent documents Patent Document 1: Japanese Patent No. 5590582 Summary of the Invention

[0006] (a) Technical problems to be solved Here, when it is desired that the emitted light from the backlight is white, it is generally expected that this emitted light will not be colored by the adhesive layer. However, sometimes it is also desirable to color the emitted light from the backlight into a desired color.

[0007] The present invention was made in view of the actual situation, and its purpose is to provide an adhesive sheet and display body that can adjust the light emission color to a color other than white while exhibiting concealment.

[0008] (II) Technical Solution To achieve the above objectives, firstly, the present invention provides an adhesive sheet having an adhesive layer, characterized in that, when the haze value (%) of the adhesive layer caused by light with a wavelength of 450 nm is set as H(450), and the haze value (%) caused by light with a wavelength of 650 nm is set as H(650), the absolute value of the slope S1 expressed by the following formula (1) is greater than 0.026, the haze value of the adhesive layer is 10% or more and 100% or less, and the adhesion force of the adhesive sheet to soda-lime glass is 1 N / 25 mm or more (Invention 1). S1=(H(650)-H(450)) / 200…(1).

[0009] Second, the present invention provides an adhesive sheet having an adhesive layer, characterized in that, when the haze value (%) of the adhesive layer caused by light with a wavelength of 450 nm is set as H(450), the haze value (%) caused by light with a wavelength of 550 nm is set as H(550), and the haze value (%) caused by light with a wavelength of 650 nm is set as H(650), at least one of the absolute values ​​of the slope S2 expressed by the following formula (2) and the absolute values ​​of the slope S3 expressed by the following formula (3) is 0.032 or more, the haze value of the adhesive layer is 10% or more and 100% or less, and the adhesion force of the adhesive sheet to soda-lime glass is 1 N / 25 mm or more (Invention 2). S2=(H(550)-H(450)) / 100…(2), S3=(H(650)-H(550)) / 100…(3).

[0010] In the aforementioned inventions (Inventions 1 and 2), when at least one of the absolute values ​​of slope S1, or slope S2 and slope S3, is large as described above, the emitted color of the resulting display, particularly a display with blue, green, and red light sources, can be easily adjusted to a color other than white. Furthermore, by keeping the haze value of the adhesive layer within the aforementioned range, excellent concealment can be achieved; for example, the arrangement of light-emitting elements and electronic circuitry in a direct-lit backlight with multiple light-emitting elements can be suppressed from being seen from the display section. Moreover, by setting the adhesive force to the aforementioned value, a suitable adhesive force can be achieved for bonding the display components together, and the desired durability can be obtained.

[0011] In the above invention (Invention 1), the slope S1 can be a negative value (Invention 3).

[0012] In the above invention (Invention 2), the slope S2 and the slope S3 can be negative values ​​(Invention 4).

[0013] In the above inventions (Inventions 1 and 2), when the haze value (%) of the adhesive layer caused by light with a wavelength of 550 nm is set as H (550), the slope S3 expressed by the following formula (3) can be 0 or more and 0.015 or less (Invention 5). S3=(H(650)-H(550)) / 100…(3).

[0014] In the above inventions (Inventions 1 and 2), when the haze value (%) of the adhesive layer caused by light with a wavelength of 550 nm is set as H (550), the slope S3 expressed by the following formula (3) can be greater than 0.015 (Invention 6). S3=(H(650)-H(550)) / 100…(3).

[0015] In the above inventions (Inventions 1 to 6), it is preferable that the gel fraction of the adhesive constituting the adhesive layer is 20% or more and 100% or less (Invention 7).

[0016] In the above inventions (Inventions 1 to 7), it is preferable that the adhesive constituting the adhesive layer contains light-diffusing particles (Invention 8).

[0017] In the above invention (Invention 8), it is preferred that the average particle size of the light-diffusing particles is 0.1 μm or more and 20 μm or less (Invention 9).

[0018] In the above inventions (Inventions 8 and 9), it is preferred that the refractive index of the light-diffusing particles is 1.30 or higher and 2.00 or lower (Invention 10).

[0019] In the above inventions (Inventions 8 to 10), it is preferable that the content of the light-diffusing particles in the adhesive is 1% by mass or more and 70% by mass or less (Invention 11).

[0020] In the above inventions (Inventions 8-11), it is preferred that the light-diffusing particles are light-diffusing particles formed of silicone resin (Invention 12).

[0021] In the above inventions (Inventions 1 to 12), the adhesive constituting the adhesive layer is preferably an acrylic adhesive (Invention 13).

[0022] In the above inventions (Inventions 1 to 13), it is preferred that the thickness of the adhesive layer is 10 μm or more and 2000 μm or less (Invention 14).

[0023] In the above inventions (Inventions 1 to 14), it is preferable that the adhesive sheet has two release sheets, and the adhesive layer is sandwiched between the release sheets in a manner that contacts the release surfaces of the two release sheets (Invention 15).

[0024] In the above inventions (Inventions 1-15), it is preferable that the adhesive sheet is used to attach two display body components having a blue light source, a green light source and a red light source (Invention 16).

[0025] Third, the present invention provides a display body having a backlight having a blue light source, a green light source and a red light source, characterized in that a display body component closer to the display surface than the backlight is attached to another display body component (invention 17) via the adhesive layer of the adhesive sheet (inventions 1-16).

[0026] In the above invention (Invention 17), preferably the blue light source, the green light source and the red light source are light-emitting diodes (Invention 18).

[0027] (III) Beneficial Effects The adhesive sheet and display body of the present invention can adjust the light emission color to a color other than white while exhibiting concealment. Attached Figure Description

[0028] Figure 1 This is a cross-sectional view of an adhesive sheet according to one embodiment of the present invention.

[0029] Figure 2 This is a cross-sectional view of a display body according to one embodiment of the present invention.

[0030] Figure 3 This is a cross-sectional view of a display body according to another embodiment of the present invention. Detailed Implementation

[0031] The embodiments of the present invention will be described below.

[0032] [Adhesive sheet] The adhesive sheet of one embodiment of the present invention has an adhesive layer.

[0033] Regarding the aforementioned adhesive layer, when the haze value (%) caused by light with a wavelength of 450 nm is set as H(450), the haze value (%) caused by light with a wavelength of 550 nm is set as H(550), and the haze value (%) caused by light with a wavelength of 650 nm is set as H(650), it is preferable that the absolute value of the slope S1 is greater than 0.026, or at least one of the absolute values ​​of the slope S2 and the slope S3 is 0.032 or greater. Furthermore, the haze values ​​in this specification are values ​​measured according to JIS K7136:2000.

[0034] S1=(H(650)-H(450)) / 200 …(1) S2=(H(550)-H(450)) / 100 …(2) S3=(H(650)-H(550)) / 100 …(3) As described above, when the absolute value of slope S1, or at least one of the absolute values ​​of slope S2 and slope S3, is large, the emitted color in the resulting display, particularly a display with blue, green, and red light sources (hereinafter sometimes referred to as "RGB light sources"), can be easily adjusted to a color other than white. The reason for this is that when the absolute value of slope S1, or at least one of the absolute values ​​of slope S2 and slope S3, is large, the diffusion of blue, green, and red light becomes uneven, resulting in uneven color mixing and thus producing a color other than white.

[0035] From the above perspective, the absolute value of the slope S1 is more preferably 0.027 or higher, particularly preferably 0.028 or higher. From the perspective of more easily emphasizing colors other than white, the absolute value of the slope S1 is preferably 0.029 or higher, more preferably 0.050 or higher, particularly preferably 0.070 or higher, and even more preferably 0.080 or higher. On the other hand, from the perspective of preventing excessive emphasis on colors other than white, the upper limit of the absolute value of the slope S1 is preferably 0.20 or lower, more preferably 0.15 or lower, particularly preferably 0.10 or lower, and even more preferably 0.09 or lower. Furthermore, from the perspective of giving a light and soft impression to colors other than white, the upper limit of the absolute value of the slope S1 is preferably 0.20 or lower, more preferably 0.12 or lower, particularly preferably 0.08 or lower, and even more preferably 0.04 or lower, wherein it is preferably less than 0.029.

[0036] Similarly, from the above perspective, at least one of the absolute values ​​of slope S2 and slope S3 is preferably 0.034 or more, more preferably 0.040 or more, particularly preferably 0.050 or more, further preferably 0.060 or more, and most preferably 0.070 or more. On the other hand, from the perspective of preventing excessive emphasis on colors other than white, the upper limit of the absolute values ​​of slope S2 and slope S3 is preferably 0.20 or less, more preferably 0.15 or less, and particularly preferably 0.10 or less.

[0037] Here, when adjusting the emitted color of the obtained display body, especially a display body with an RGB light source, to yellow, it is preferable to make the slope S1 negative or to make both slopes S2 and S3 negative. As described above, it is believed that when the absolute value of slope S1, or at least the absolute value of slope S2 and slope S3, is above a predetermined value, and these slopes are negative, blue light will diffuse more easily, and green, yellow, and red light will diffuse more difficultly, resulting in a stronger display of yellow light.

[0038] When adjusting the emitted color of the obtained display body, especially a display body with RGB light source, to a pale yellow, it is preferable to set the slope S3 to 0.000~0.015, more preferably to 0.004~0.014, particularly preferably to 0.008~0.013, and even more preferably to 0.010~0.012. As described above, it is believed that when the absolute value of the slope S1, or at least one of the absolute values ​​of the slope S2 and the slope S3 is above a predetermined value, and the slope S3 is as small as described above, blue~green~yellow light will become difficult to diffuse, and red will become easier to mix with blue~green~yellow, resulting in a pale yellow color.

[0039] As described above, when the luminescence color is adjusted to pale yellow, the slope S2 is preferably 0.038~0.075, more preferably 0.040~0.070, particularly preferably 0.041~0.060, and even more preferably 0.042~0.050.

[0040] When adjusting the emitted color of the obtained display body, especially a display body with RGB light source, to blue, it is preferable to set the slope S3 to be greater than 0.015, more preferably to 0.018 to 0.050, particularly preferably to 0.020 to 0.040, and even more preferably to 0.022 to 0.030. As described above, it is believed that when the absolute value of the slope S1, or at least one of the absolute values ​​of the slope S2 and the slope S3 is greater than a predetermined value, and the slope S3 is larger than described above, blue-green-yellow light will become difficult to diffuse, and red will become difficult to mix with blue-green-yellow, resulting in a stronger display of blue light.

[0041] As described above, when the emission color is adjusted to blue, the slope S2 is preferably 0.010~0.037, more preferably 0.020~0.036, particularly preferably 0.030~0.035, and even more preferably 0.032~0.034.

[0042] In this embodiment, the haze value of the adhesive layer is preferably 10% to 100%. This provides excellent concealment, for example, suppressing the visibility of the arrangement of light-emitting elements and electronic circuitry in a direct-lit backlight with multiple light-emitting elements from the display unit. From this perspective, the lower limit of the haze value is more preferably 30% or more, particularly preferably 50% or more, and even more preferably 60% or more. From the perspective of ensuring the amount of light from the backlight and the clarity of the image, the upper limit of the haze value is more preferably 100% or less, particularly preferably 95% or less, and even more preferably 90% or less.

[0043] The haze value (H(450)) of the adhesive layer caused by light with a wavelength of 450 nm is preferably 10 to 100%, more preferably 30 to 99%, particularly preferably 50 to 95%, and even more preferably 60 to 90%. As a result, it becomes easy to satisfy the above-mentioned slope S1, slope S2 and haze value.

[0044] When the light emission color is adjusted to yellow, the haze value (H(450)) of the adhesive layer caused by light with a wavelength of 450nm is preferably 50~100%, more preferably 70~94%, particularly preferably 80~92%, and even more preferably 84~88%.

[0045] When the luminescence color is adjusted to pale yellow, the haze value (H(450)) of the adhesive layer caused by light with a wavelength of 450 nm is preferably 20 to 100%, more preferably 35 to 88%, particularly preferably 50 to 77%, and even more preferably 60 to 66%.

[0046] When the light emission color is adjusted to blue, the haze value (H(450)) of the adhesive layer caused by light with a wavelength of 450nm is preferably 50~100%, more preferably 60~92%, particularly preferably 70~88%, and even more preferably 79~84%.

[0047] The haze value (H(550)) of the adhesive layer caused by light with a wavelength of 550 nm is preferably 10 to 100%, more preferably 30 to 99%, particularly preferably 50 to 95%, and even more preferably 60 to 90%. As a result, it becomes easy to satisfy the above-mentioned slope S2, slope S3 and haze value.

[0048] When the light emission color is adjusted to yellow, the haze value (H(550)) of the adhesive layer caused by light with a wavelength of 550nm is preferably 40~100%, more preferably 50~92%, particularly preferably 60~85%, and even more preferably 70~80%.

[0049] When the light emission color is adjusted to pale yellow, the haze value (H(550)) of the adhesive layer caused by light with a wavelength of 550nm is preferably 10~100%, more preferably 30~85%, particularly preferably 50~75%, and even more preferably 60~70%.

[0050] When the light emission color is adjusted to blue, the haze value (H(550)) of the adhesive layer caused by light with a wavelength of 550nm is preferably 50~100%, more preferably 70~95%, particularly preferably 80~92%, and even more preferably 85~90%.

[0051] The haze value (H(650)) of the adhesive layer caused by light with a wavelength of 650 nm is preferably 10 to 100%, more preferably 30 to 99%, particularly preferably 50 to 95%, and even more preferably 60 to 90%. As a result, it becomes easy to satisfy the above-mentioned slope S1, slope S3 and haze value.

[0052] When the light emission color is adjusted to yellow, the haze value (H(650)) of the adhesive layer caused by light with a wavelength of 650nm is preferably 30~100%, more preferably 40~85%, particularly preferably 50~75%, and even more preferably 60~69%.

[0053] When the light emission color is adjusted to pale yellow, the haze value (H(650)) of the adhesive layer caused by light with a wavelength of 650nm is preferably 40~100%, more preferably 50~90%, particularly preferably 60~85%, and even more preferably 69~80%.

[0054] When the light emission color is adjusted to blue, the haze value (H(650)) of the adhesive layer caused by light with a wavelength of 650nm is preferably 50~100%, more preferably 65~97%, particularly preferably 70~93%, and even more preferably 80~90%.

[0055] The ratio (H(450) / H(550)) of the haze value of the adhesive layer caused by light with a wavelength of 450 nm to the haze value caused by light with a wavelength of 550 nm is preferably 0.80 to 1.20, more preferably 0.85 to 1.15, particularly preferably 0.90 to 1.12, and even more preferably 0.93 to 1.10. This makes it easier to satisfy the slope S2 described above. Furthermore, from the perspective of more easily emphasizing colors other than white, it is preferable to exclude the range of 0.98 to 1.02 from the above range.

[0056] The ratio (H(450)) of the haze value of the adhesive layer caused by light with a wavelength of 650 nm to the haze value caused by light with a wavelength of 550 nm (H(650) / H(550)) is preferably 0.80 to 1.20, more preferably 0.85 to 1.15, particularly preferably 0.90 to 1.10, and even more preferably 0.95 to 1.05. This makes it easier to satisfy the slope S3 described above. Furthermore, from the perspective of more easily emphasizing colors other than white, it is preferable to exclude the range of 0.99 to 1.01 from the above range.

[0057] In this embodiment, the adhesion strength of the adhesive sheet to the soda-lime glass is preferably 1 N / 25 mm or more. This provides an adhesion strength suitable for bonding the components of the display body together, and achieves the desired durability. From this perspective, the adhesion strength is more preferably 6 N / 25 mm or more, particularly preferably 12 N / 25 mm or more, and even more preferably 18 N / 25 mm or more.

[0058] Furthermore, the upper limit of the aforementioned adhesive force is preferably 60 N / 25 mm or less, more preferably 45 N / 25 mm or less, particularly preferably 30 N / 25 mm or less, and even more preferably 25 N / 25 mm or less. This provides good reworkability, and allows for the reuse of expensive display components in the event of bonding errors.

[0059] Here, the adhesion in this specification basically refers to the adhesion measured by the 180-degree peel method based on JIS Z0237:2022. 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. Then it is placed under normal pressure, 23°C and 50%RH for 24 hours. Then the peel is measured at a peeling speed of 300 mm / min.

[0060] Preferably, the adhesive constituting the adhesive layer in this embodiment contains light-diffusing microparticles. Through the light-diffusing effect of these microparticles, the aforementioned slopes S1, S2, S3, and haze value can be adjusted to the desired values.

[0061] The average particle size (measured by centrifugal sedimentation transmission method) of the aforementioned light-diffusing particles is preferably 0.1 to 20 μm, more preferably 0.5 to 16 μm, particularly preferably 1 to 12 μm, and even more preferably 2 to 10 μm. Through light diffusion based on this particle size, the aforementioned slope S1, slope S2, slope S3, and haze value can be easily adjusted to the desired values.

[0062] In addition, the average particle size measured by the centrifugal sedimentation transmission method was measured using a centrifugal automatic particle size distribution measuring device (manufactured by HORIBA, Ltd., product name "CAPA-700") as the sample obtained by thoroughly stirring 1.2g of light-diffusing microparticles with 98.8g of isopropanol.

[0063] The content of light-diffusing particles in the adhesive is preferably 1 to 70% by mass, more preferably 2 to 55% by mass, particularly preferably 3 to 40% by mass, even more preferably 4 to 30% by mass, and most preferably 4.5 to 25% by mass. Based on this content, the aforementioned slope S1, slope S2, slope S3, and haze value can be easily adjusted to the desired values.

[0064] When the emission color is adjusted to yellow, light-diffusing microparticles with an average particle size preferably of 0.1~20μm, more preferably 0.5~12μm, particularly preferably 1~8μm, and even more preferably 2~4μm are selected. The content of these light-diffusing microparticles in the adhesive is preferably set to 1~20% by mass, more preferably 2~12% by mass, particularly preferably 3~8% by mass, and even more preferably 4~6% by mass. This allows for easy adjustment of the haze slope to a negative value and easy adjustment of the emission color to yellow.

[0065] When the emission color is adjusted to a pale yellow, light-diffusing microparticles with an average particle size preferably of 0.1-20 μm, more preferably 1-12 μm, particularly preferably 2-8 μm, and even more preferably 3-5 μm are selected. The content of these light-diffusing microparticles in the adhesive is preferably set to 0.1-20% by mass, more preferably 1-12% by mass, particularly preferably 2-8% by mass, and even more preferably 4-6% by mass. Therefore, the slope S3 described above can be easily made to a predetermined value, and the emission color can be easily adjusted to a pale yellow.

[0066] When the emission color is adjusted to blue, light-diffusing microparticles with an average particle size preferably of 0.1~20μm, more preferably 1~17μm, particularly preferably 5~14μm, and even more preferably 8~11μm are selected. The content of these light-diffusing microparticles in the adhesive is preferably set to 1~70% by mass, more preferably 8~40% by mass, particularly preferably 16~30% by mass, and even more preferably 20~25% by mass. Therefore, the slope S3 described above can be easily made to a predetermined value, and the emission color can be easily adjusted to blue.

[0067] The type of adhesive used in the adhesive layer constituting the adhesive sheet of this embodiment is not particularly limited, as long as it meets the above-mentioned physical properties. For example, it can be any one of acrylic adhesives, polyester adhesives, polyurethane adhesives, rubber adhesives, silicone adhesives, etc. Furthermore, the adhesive can be any one of emulsion type, solvent type, or solvent-free type, and can be any one of cross-linked type or non-cross-linked type. Among these, acrylic adhesives with excellent adhesive properties and optical properties are preferred. As an acrylic adhesive, a cross-linked acrylic adhesive is preferred, and a thermally cross-linked acrylic adhesive is even more preferred. Furthermore, the adhesive in this embodiment can be an adhesive that is cured by non-reactive energy radiation or an adhesive that is cured by active energy radiation. In addition, from the perspective of the United Nations Sustainable Development Goals (SDGs), materials with high biomass content, renewable or reusable materials, or materials that have already been recycled or reused can be used as the materials constituting the adhesive.

[0068] Specifically, the adhesive in this embodiment is preferably crosslinked from an adhesive composition (hereinafter sometimes referred to as "adhesive composition P") containing a (meth)acrylate polymer (A), a crosslinking agent (B), and light-diffusing microparticles (C). The adhesive obtained by crosslinking adhesive composition P readily satisfies the aforementioned physical properties. Furthermore, in this specification, (meth)acrylate refers to both acrylic acid and methacrylic acid. Other similar terms are also used. In addition, "polymer" also includes the concept of "copolymer".

[0069] (1) Components of adhesive composition P (1-1) (Meth)acrylate polymer (A) The (meth)acrylate polymer (A) in this embodiment preferably comprises a monomer containing a reactive group as a monomer unit constituting the polymer, wherein the monomer containing the reactive group has reactive groups within its molecule that react with the crosslinking agent (B). The reactive groups from the monomer containing the reactive group react with the crosslinking agent (B) to form a crosslinked structure (three-dimensional network structure), thereby obtaining an adhesive with the desired cohesive strength.

[0070] As monomers containing reactive groups, preferred examples include monomers having a hydroxyl group in the molecule (hydroxyl-containing monomers) and monomers having a carboxyl group in the molecule (carboxyl-containing monomers). Among these, hydroxyl-containing monomers or carboxyl-containing monomers with excellent reactivity with the crosslinking agent (B) are preferred, and hydroxyl-containing monomers are particularly preferred.

[0071] Examples of hydroxyl-containing monomers include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxybutyl methacrylate, and 4-hydroxybutyl methacrylate, among other hydroxyalkyl methacrylates. From the perspective of reactivity with the crosslinking agent (B) and copolymerization with other monomers, hydroxyalkyl methacrylates having 1 to 4 carbon atoms are preferred. Specifically, 2-hydroxyethyl methacrylate and 4-hydroxybutyl methacrylate are preferred examples, and 2-hydroxyethyl acrylate or 4-hydroxybutyl acrylate are particularly preferred. These hydroxyl-containing monomers can be used alone or in combination of two or more.

[0072] Examples of carboxyl-containing monomers include acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid, among other olefinic unsaturated carboxylic acids. Among these, acrylic acid is preferred from the perspective of the reactivity of the carboxyl group in the resulting (meth)acrylate polymer (A) with the crosslinking agent (B) and its copolymerization with other monomers. These carboxyl-containing monomers can be used alone or in combination of two or more.

[0073] The (meth)acrylate polymer (A) preferably contains 1-40% by mass, more preferably 6-36% by mass, particularly preferably 12-32% by mass, and even more preferably 18-28% by mass of a monomer containing a reactive group as the monomer unit constituting the polymer, wherein 20-26% by mass of a monomer containing a reactive group is preferred as the monomer unit constituting the polymer. This allows for the formation of a good cross-linked structure in the resulting adhesive, resulting in suitable cohesive strength. Furthermore, the dispersibility of the light-diffusing particles (C) in the resulting adhesive tends to improve.

[0074] Furthermore, it is preferable that the (meth)acrylate polymer (A) does not contain carboxyl-containing monomers as monomer units constituting the polymer. Since carboxyl groups are acidic components, by not containing carboxyl-containing monomers, even if substances that are prone to defects due to acid, such as transparent conductive films or metal films like indium tin oxide (ITO), exist in the adhesive's adherent material, these acid-induced defects (corrosion, changes in resistance, etc.) can be suppressed. However, it is permissible to contain a specified amount of carboxyl-containing monomers to the extent that the aforementioned defects do not occur. Specifically, in the (meth)acrylate polymer (A), it is permissible to contain carboxyl-containing monomers as monomer units 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.

[0075] The (meth)acrylate polymer (A) preferably contains alkyl (meth)acrylate as a monomer unit constituting the polymer. This results in good adhesion. The alkyl group can be linear or branched.

[0076] From the perspective of adhesion, alkyl methacrylates with 1 to 20 carbon atoms in the alkyl group are preferred as (meth)acrylates. Examples of alkyl methacrylates with 1 to 20 carbon atoms in the alkyl group include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, n-decyl methacrylate, n-dodecyl methacrylate, tetradecyl methacrylate, hexadecyl methacrylate, and octadecyl methacrylate. Among these, from the perspective of further improving adhesion and easily satisfying the above-mentioned physical properties, alkyl methacrylates with 4 to 8 carbon atoms in the alkyl group are preferred, particularly n-butyl methacrylate, 2-ethylhexyl methacrylate, or isooctyl methacrylate, and even more preferably n-butyl methacrylate, 2-ethylhexyl methacrylate, or isooctyl methacrylate. In addition, these alkyl (meth)acrylates can be used alone or in combination of two or more.

[0077] The (meth)acrylate polymer (A) preferably contains 30-99% by mass, more preferably 40-90% by mass, particularly preferably 45-80% by mass, and even more preferably 50-70% by mass of alkyl (meth)acrylate as the monomer unit constituting the polymer. Thus, the adhesive formed from the adhesive composition containing the (meth)acrylate polymer (A) can exhibit suitable adhesive properties, and appropriate amounts of other monomer components, such as monomers containing reactive functional groups, can be introduced into the (meth)acrylate polymer (A).

[0078] Preferably, the (meth)acrylate polymer (A) contains monomers with an intramolecular alicyclic structure (alicyclic monomers) as monomer units constituting the polymer. It is speculated that because alicyclic monomers have a large volume, their presence in the polymer widens the spacing between polymers, tending to impart softness and good adhesion to the resulting adhesive. In addition, they tend to reduce the storage modulus, thus improving the followability to steps and unevenness (hereinafter sometimes referred to as "step followability").

[0079] The carbon rings in the alicyclic monomer can be saturated or partially unsaturated. Furthermore, the alicyclic structure can be a monocyclic alicyclic structure or a multicyclic alicyclic structure (bicyclic, tricyclic, or other rings). From the perspective of ensuring appropriate spacing between the resulting (meth)acrylate polymer (A) and reducing the storage modulus, the aforementioned alicyclic structure is preferably a multicyclic structure. Furthermore, considering the compatibility of the (meth)acrylate polymer (A) with other components, the aforementioned multicyclic structure is particularly preferred to be bicyclic to tetracyclic. In addition, from the same perspective as above, the number of carbon atoms in the alicyclic structure (referring to the total number of carbon atoms in the ring-forming portion; when multiple rings exist independently, it refers to their total number of carbon atoms) is generally preferably 5 to 15, and particularly preferably 7 to 10.

[0080] Examples of alicyclic monomers include cyclohexyl methacrylate, dicyclopentyl methacrylate, adamantyl methacrylate, isobornyl methacrylate, dicyclopentenyl methacrylate, and dicyclopentenoxyethyl methacrylate. Among these, dicyclopentyl methacrylate (10 carbon atoms in the alicyclic structure), adamantyl methacrylate (10 carbon atoms in the alicyclic structure), or isobornyl methacrylate (7 carbon atoms in the alicyclic structure) are preferred for their good adhesion and superior step-following properties. Isobornyl methacrylate is particularly preferred, and isobornyl methacrylate is even more preferred. These alicyclic monomers can be used alone or in combination of two or more.

[0081] When the (meth)acrylate polymer (A) contains an alicyclic monomer as a monomer unit constituting the polymer, from the perspective of reducing the storage modulus, it is preferable to contain 1 to 40% by mass, more preferably 4 to 32% by mass, particularly preferably 8 to 24% by mass, and even more preferably 12 to 16% by mass of the alicyclic monomer.

[0082] It is also preferable that the (meth)acrylate polymer (A) contains a nitrogen-containing monomer as a monomeric unit constituting the polymer. By having a nitrogen-containing monomer as a structural unit in the polymer, the adhesive can be given a specified polarity, and excellent affinity can still be achieved for adhesives such as glass, which have a certain degree of polarity. As a nitrogen-containing monomer, from the perspective of giving the (meth)acrylate polymer (A) a suitable rigidity, a monomer having a nitrogen-containing heterocycle is preferred. Furthermore, from the perspective of increasing the degree of freedom of the portion from the aforementioned nitrogen-containing monomer in the higher-order structure of the constructed adhesive, it is preferable that the nitrogen-containing monomer does not contain reactive unsaturated double bond groups other than the polymerizable group used in the polymerization of the (meth)acrylate polymer (A).

[0083] Examples of monomers having nitrogen-containing heterocycles include N-(meth)acryloylmorpholine, N-vinyl-2-pyrrolidone, N-(meth)acryloylpyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylaziridine, aziridinediethyl ester, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimazole, N-vinylcarbazole, and N-vinylphthalimide. Among these, N-(meth)acryloylmorpholine, which exhibits superior adhesive properties, is preferred, and N-acryloylmorpholine is particularly preferred. These monomers having nitrogen-containing heterocycles can be used alone or in combination of two or more.

[0084] When the (meth)acrylate polymer (A) contains a nitrogen-containing monomer as a monomer unit constituting the polymer, it is preferable to contain 1 to 30% by mass, more preferably 2 to 20% by mass, particularly preferably 3 to 12% by mass, and even more preferably 4 to 8% by mass of the nitrogen-containing monomer as a monomer unit constituting the polymer. As a result, the adhesive can fully exert its excellent adhesion to glass.

[0085] (Meth)acrylate polymer (A) may contain other monomers as constituent units of the polymer, as desired. As other monomers, monomers without reactive functional groups are preferred so as not to hinder the aforementioned effects of monomers containing reactive functional groups. Examples of such monomers include methoxyethyl methacrylate, ethoxyethyl methacrylate, alkoxyalkyl methacrylates, vinyl acetate, styrene, etc. These monomers may be used alone or in combination of two or more.

[0086] The (meth)acrylate polymer (A) is preferably a linear polymer. By being a linear polymer, it becomes easier for the molecular chains to become entangled with each other, and an increase in cohesive force can be expected.

[0087] (Meth)acrylate polymer (A) can be obtained by solution polymerization, by polymerization without solvent, or by emulsion polymerization. Solution polymers obtained by solution polymerization are preferred. As solution polymers, high molecular weight polymers are readily obtained, resulting in adhesives with excellent durability.

[0088] The polymerization form of (meth)acrylate polymer (A) can be a random copolymer or a block copolymer.

[0089] The weight-average molecular weight of the (meth)acrylate polymer (A) is preferably 100,000 to 2,000,000, more preferably 200,000 to 1,600,000, particularly preferably 300,000 to 1,200,000, further preferably 400,000 to 900,000, and most preferably 450,000 to 700,000. This allows for the acquisition of an adhesive with suitable storage modulus and tack. Here, the weight-average molecular weight in this specification is a value converted from standard polystyrene determined by gel permeation chromatography (GPC).

[0090] In addition, in the adhesive composition P, the (meth)acrylate polymer (A) can be used alone or in combination of two or more.

[0091] In this embodiment, the content of (meth)acrylate polymer (A) in the adhesive composition P is preferably 50-99% by mass, more preferably 60-98% by mass, particularly preferably 65-97% by mass, even more preferably 70-96% by mass, and even more preferably 75-95% by mass. This results in good adhesion.

[0092] (1-2) Crosslinking agent (B) The crosslinking agent (B) can be any substance that can react with the reactive groups present in the (meth)acrylate polymer (A). Examples of crosslinking agents (B) include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, hydrazine-based crosslinking agents, aldehyde-based crosslinking agents, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, and ammonium salt-based crosslinking agents. Furthermore, the crosslinking agent (B) can be used alone or in combination of two or more.

[0093] When the reactive group of the (meth)acrylate polymer (A) is hydroxyl, it is preferable to use an isocyanate-based crosslinking agent that is highly reactive with the hydroxyl group.

[0094] Isocyanate-based crosslinking agents include at least polyisocyanate compounds. Examples of polyisocyanate compounds include: aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and phenylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate; and their biuret forms, isocyanurate forms, and adducts as reaction products with low-molecular-weight compounds containing active hydrogen, such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. From the perspective of reactivity with hydroxyl groups, trimethylolpropane-modified aromatic polyisocyanates are preferred, and trimethylolpropane-modified toluene diisocyanate is particularly preferred.

[0095] The content of crosslinking agent (B) in the adhesive composition P is preferably 0.01 to 2 parts by mass relative to 100 parts by mass of (meth)acrylate polymer (A), more preferably 0.04 to 1 part by mass, particularly preferably 0.07 to 0.5 parts by mass, and even more preferably 0.1 to 0.2 parts by mass. This readily results in suitable cohesive strength and adhesive force of the obtained adhesive.

[0096] (1-3) Light-diffusing particles (C) The light-diffusing microparticles (C) are any substances that can exhibit the specified light-diffusing properties and enable the resulting adhesive layer and adhesive sheet to satisfy the aforementioned physical properties.

[0097] Examples of light-diffusing microparticles (C) include: inorganic light-diffusing microparticles such as silica, calcium carbonate, aluminum hydroxide, magnesium hydroxide, clay, talc, and titanium dioxide; organic light-diffusing microparticles such as acrylic resins, polystyrene resins, polyethylene resins, epoxy resins, copolymers of these resins, or mixtures thereof; light-diffusing microparticles formed from silicon-containing compounds with an intermediate structure of inorganic and organic components, such as silicone resins (e.g., the Tospearl series manufactured by Momentive Performance Materials Japen LLC); and light-diffusing microparticles mixed with organic resins and silicone resins. Among these, light-diffusing microparticles formed from silicone resins (silicon-containing compounds with an intermediate structure of inorganic and organic components) are preferred. This makes it easier for the resulting adhesive layer to satisfy the aforementioned physical properties. The above-mentioned light-diffusing microparticles (C) can be used alone or in combination of two or more.

[0098] Regarding the shape of the light-diffusing particles (C), spherical light-diffusing particles with uniform light diffusion are preferred, and perfectly spherical light-diffusing particles are particularly preferred, but the shape is not limited thereto. The preferred average particle size of the light-diffusing particles (C) is as described above.

[0099] The refractive index of the light-diffusing microparticles (C) is preferably 1.30 to 2.00, more preferably 1.35 to 1.85, particularly preferably 1.40 to 1.65, even more preferably 1.42 to 1.55, and most preferably 1.43 to 1.45. Through the light diffusion effect generated by the difference between this refractive index and the refractive index of the matrix (especially the matrix of acrylic adhesives), the aforementioned slopes S1, S2, S3, and haze values ​​can be easily adjusted to the desired values. Furthermore, the refractive index of the light-diffusing microparticles can be determined using Method B of JIS K 7142:2008.

[0100] The content of light-diffusing microparticles (C) in the adhesive composition P is the same as the content of light-diffusing microparticles in the adhesive described above, and is preferably 0.1 to 150 parts by weight relative to 100 parts by weight of (meth)acrylate polymer (A), more preferably 1 to 100 parts by weight, particularly preferably 2 to 50 parts by weight, further preferably 3 to 30 parts by weight, and preferably 4 to 26 parts by weight.

[0101] (1-4) Silane coupling agent (D) The preferred adhesive composition P further contains a silane coupling agent (D). Therefore, if the adherend has a glass component, the adhesion between the obtained adhesive and the glass component is improved. Furthermore, even if the adherend is a plastic sheet, the adhesion between the obtained adhesive and the plastic sheet is improved. Thus, the obtained adhesive easily achieves the desired adhesive strength.

[0102] As a silane coupling agent (D), an organosilicon compound having at least one alkoxysilyl group in the molecule, good compatibility with the (meth)acrylate polymer (A), and light transmittance is preferred.

[0103] Examples of silane coupling agents (D) include: vinyltrimethoxysilane, vinyltriethoxysilane, methacryloyloxypropyltrimethoxysilane, and other silicon compounds containing polymerizable unsaturated groups; 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and other silicon compounds with epoxy structures; 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, etc. Thiol-containing silicon compounds such as propyl dimethoxymethylsilane; amino-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane; condensates of 3-chloropropyltrimethoxysilane, 3-isocyanopropyltriethoxysilane, or at least one thereof with alkyl-containing silicon compounds such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. These silane coupling agents can be used alone or in combination of two or more.

[0104] The content of silane coupling agent (D) in the adhesive composition P is preferably 0.01 to 1 part by weight, more preferably 0.1 to 0.7 parts by weight, and particularly preferably 0.2 to 0.5 parts by weight, relative to 100 parts by weight of the (meth)acrylate polymer (A). This results in good compatibility with the (meth)acrylate polymer (A) and other blending materials, and the resulting adhesive readily achieves the desired optical properties described above, while also exhibiting good adhesion to the adhered object.

[0105] (1-5) Various additives Various additives commonly used in acrylic adhesives can be added to the adhesive composition P as needed, such as active energy radiation curing components, photopolymerization initiators, ultraviolet absorbers, infrared absorbers, refractive index modifiers, antistatic agents, colorants, tackifiers, rust inhibitors, antioxidants, light stabilizers, and softeners. Furthermore, the additives constituting the adhesive composition P do not include the polymerization solvents and diluents described later.

[0106] (2) Preparation of adhesive composition P The adhesive composition P can be prepared by manufacturing a (meth)acrylate polymer (A), mixing the obtained (meth)acrylate polymer (A), a crosslinking agent (B), and light-diffusing particles (C), and adding silane coupling agent (D), additives, etc. as needed.

[0107] (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 by solution polymerization. However, the invention is not limited thereto, and polymerization can also be carried out without a solvent. Examples of polymerization solvents include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, etc., and two or more can be used simultaneously.

[0108] Examples of polymerization initiators include azo compounds and organic peroxides, and two or more can be used simultaneously. Furthermore, in the aforementioned polymerization process, the weight-average molecular weight of the resulting polymer can be adjusted by incorporating chain transfer agents such as 2-mercaptoethanol.

[0109] After obtaining (meth)acrylate polymer (A), a crosslinking agent (B), light-diffusing microparticles (C), and, as needed, a silane coupling agent (D), additives, and a diluent are added to a solution of (meth)acrylate polymer (A), and the mixture is thoroughly mixed to obtain an adhesive composition P (coating solution) diluted with a solvent. Furthermore, if any of the above components is used in solid form, or if precipitation occurs when mixed with other components in an undiluted state, this component can be dissolved or diluted separately in a diluent beforehand and then mixed with the other components.

[0110] As diluents for the above-mentioned purposes, for example, the following can be used: 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; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve solvents such as ethyl cellosolve.

[0111] The concentration and viscosity of the coating solution prepared in this way are not particularly limited as long as they are within the range suitable for coating, and can be appropriately selected according to the situation. For example, the adhesive composition P can be diluted to a concentration of 10 to 60% by mass. Furthermore, the addition of a diluent or similar solvent is not necessary when obtaining the coating solution; if the viscosity of the adhesive composition P is a suitable viscosity for coating, a diluent may not be added. In this case, the adhesive composition P becomes a coating solution in which the polymerization solvent of the (meth)acrylate polymer (A) is used directly as the diluent.

[0112] (3) Formation of adhesive layer In this embodiment, the adhesive layer is preferably formed by crosslinking the adhesive composition P (the coating layer). The crosslinking of the adhesive composition P can generally be carried out by heat treatment. Alternatively, the drying process, in which diluents or the like evaporate from the coating layer of the adhesive composition P applied to the desired object, can also be used as the heat treatment.

[0113] The heating temperature for the heat treatment is preferably 50~150℃, and more preferably 70~120℃. Furthermore, the heating time is preferably 10 seconds~10 minutes, and more preferably 50 seconds~2 minutes.

[0114] After heat treatment, a curing period of approximately 1 to 2 weeks can be set at room temperature (e.g., 23°C, 50%RH) as needed. When this curing period is required, an adhesive will form after the curing period; when no curing period is required, the adhesive will form after the heat treatment is completed.

[0115] Through the above-mentioned heat treatment (and aging), the (meth)acrylate polymer (A) is crosslinked by the crosslinking agent (B) to obtain the adhesive.

[0116] (4) Properties of adhesive (adhesive layer) (4-1) Gel fraction In this embodiment, the gel fraction of the adhesive is preferably 20-100%, more preferably 30-85%, particularly preferably 40-70%, further preferably 45-60%, and most preferably 50-56%. This results in good cohesion, and improved adhesion and step-following properties. Furthermore, the method for determining the gel fraction is shown in the experimental examples described later.

[0117] (4-2) Total transmittance The lower limit of the total light transmittance of the adhesive layer of the adhesive sheet in this embodiment is preferably 70% or more, more preferably 80% or more, particularly preferably 90% or more, and even more preferably 99% or more. This results in good visibility for the display. On the other hand, the upper limit of this total light transmittance is not particularly limited and is generally 100% or less. Here, the total light transmittance in this specification is the value measured according to JIS K7136:2000.

[0118] (4-3) Thickness of adhesive layer From the perspective of adhesion and light diffusion, the thickness of the adhesive layer of the adhesive sheet in this embodiment (the value measured according to JIS K7130) is preferably 10~2000μm, more preferably 20~1200μm, particularly preferably 30~600μm, and even more preferably 40~200μm.

[0119] (5) Specific structure of the adhesive sheet The specific structure of the adhesive sheet, as an example of this implementation scheme, is shown below. Figure 1 .

[0120] like Figure 1 As shown, in one embodiment, the adhesive sheet 1 comprises two release sheets 12a and 12b and an adhesive layer 11, wherein the adhesive layer 11 is sandwiched between the two release sheets 12a and 12b in a manner that contacts the release surfaces of the two release sheets 12a and 12b. Furthermore, in this specification, the release surface of a release sheet refers to the surface of the release sheet that exhibits release properties, including both surfaces that have undergone release treatment and surfaces that still exhibit release properties even without release treatment.

[0121] The adhesive layer 11 is the adhesive layer of the adhesive sheet in the above embodiment, and its physical properties and composition are as described above.

[0122] The aforementioned release tabs 12a and 12b protect the adhesive layer 11 until the adhesive sheet 1 is used, at which point it is peeled off. In the adhesive sheet 1 of this embodiment, one or both of the release tabs 12a and 12b are not necessary.

[0123] As release 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, ionomer resin film, ethylene-(meth)acrylate copolymer film, ethylene-(meth)acrylate polymer film, polystyrene film, polycarbonate film, polyimide film, fluoropolymer film, etc. Furthermore, cross-linked films of these films can also be used. Further, laminated films of these films can also be used. Additionally, from the perspective of SDGs, materials constituting the release sheets can be materials with high biomass content, renewable or reusable materials, or materials that have already been recycled or reused.

[0124] Preferably, the peeling surface (particularly the surface in contact with the adhesive layer 11) of the aforementioned release sheets 12a and 12b is subjected to a peeling treatment. Examples of release agents used in the peeling treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents.

[0125] There are no particular restrictions on the thickness of the release strips 12a and 12b, which are usually around 20~150μm.

[0126] For the two peeling sheets 12a and 12b mentioned above, it is preferable that one of the peeling sheets is a heavy-peeling type with high peeling force, and the other peeling sheet is a light-peeling type with low peeling force.

[0127] (6) Manufacturing of adhesive sheets As an example of manufacturing adhesive sheet 1, the use of the above-described adhesive composition P will be described. A coating solution of adhesive composition P is applied to the release surface of a release sheet 12a (or 12b), and then subjected to heat treatment to thermally crosslink the adhesive composition P to form a coating layer. The release surface of another release sheet 12b (or 12a) is then laminated onto this coating layer. When a curing period is required, the coating layer forms an adhesive layer 11 by setting a curing period; when a curing period is not required, the coating layer directly forms the adhesive layer 11. Thus, the above-described adhesive sheet 1 is obtained. The heat treatment and curing conditions are as described above.

[0128] As another manufacturing example of the adhesive sheet 1, a coating liquid of the adhesive composition P is applied to the release surface of a release sheet 12a, and then heated to thermally crosslink the adhesive composition P, forming a coating layer, thus obtaining a release sheet 12a with a coating layer. Furthermore, the same coating liquid of the adhesive composition P is applied to the release surface of another release sheet 12b, and then heated to thermally crosslink the adhesive composition P, forming a coating layer, thus obtaining a release sheet 12b with a coating layer. Then, the release sheet 12a with the coating layer and the release sheet 12b with the coating layer are bonded together such that the two coating layers are in contact with each other. When a curing period is required, the stacked coating layers form an adhesive layer 11 by setting a curing period; when a curing period is not required, the stacked coating layers directly form the adhesive layer 11. Thus, the adhesive sheet 1 is obtained. According to this manufacturing example, even when the adhesive layer 11 is relatively thick, stable manufacturing can be performed.

[0129] The coating method for the coating liquid of the above-mentioned adhesive composition P can be, for example, by rod coating, blade coating, roller coating, squeegee coating, die coating, gravure coating, etc.

[0130] (7) Uses of adhesive sheets The adhesive sheet 1 of this embodiment can be suitably used to bond two display components in a display body with an RGB light source. In this display body, the emission color can be easily adjusted to a color other than white by means of the adhesive layer 11.

[0131] One or both of the two display components bonded to the adhesive layer 11 can be rigid materials that do not bend or hardly bend, or flexible materials such as films. According to the adhesive sheet 1 of this embodiment, even two rigid materials can be bonded well.

[0132] As described below, the adhesive sheet 1 of this embodiment can be suitably used to protect the bonding of the panel to a display module or other optical components equipped with a backlight, or to protect the bonding of the backlight to a display portion or other optical components such as a liquid crystal panel. However, the present invention is not limited thereto, and can also be used to bond desired display components together.

[0133] [Display Body] In one embodiment of the present invention, the display body is a display body having a backlight having a blue light source, a green light source and a red light source, wherein a display body component closer to the display surface than the backlight is attached to another display body component (including the backlight) via an adhesive layer of the adhesive sheet of the above embodiment.

[0134] The aforementioned blue, green, and red light sources are preferably light-emitting diodes (LEDs), and more preferably sub-millimeter light-emitting diodes (mini LEDs) or micro light-emitting diodes (micro LEDs).

[0135] like Figure 2 As shown, a display body 2A in one embodiment includes a first display body component 21 (one display body component), a second display body component 22 (another display body component), and an adhesive layer 11 located therebetween to bond the first display body component 21 and the second display body component 22 together.

[0136] One of the first display body component 21 and the second display body component 22 may have an uneven surface on the side to which the adhesive layer 11 is adhered. Figure 2 In the embodiment shown, the first display body component 21 has unevenness on the surface on the adhesive layer 11 side caused by the printing layer 23.

[0137] The adhesive layer 11 in the above-mentioned display body 2A is the adhesive layer 11 of the above-mentioned adhesive sheet 1.

[0138] As for the display body 2A, examples include liquid crystal (LCD) displays with backlights having RGB light sources and light-emitting diode (LED) displays, or touch panels.

[0139] The first display component 21 is preferably a glass plate, a plastic plate, or the like, and more preferably a protective panel formed by a laminate containing them. In this case, the printed layer 23 is usually formed in a frame shape on the adhesive layer 11 side of the first display component 21.

[0140] The glass plate mentioned above is not particularly limited, and examples include chemically strengthened glass, alkali-free glass, quartz glass, soda-lime glass, barium-strontium glass, aluminosilicate glass, lead glass, borosilicate glass, and barium borosilicate glass. The thickness of the glass plate is not particularly limited, but is typically 0.1 to 5 mm, preferably 0.2 to 2 mm.

[0141] The plastic sheet used is not particularly limited; for example, acrylic sheets and polycarbonate sheets can be included. The thickness of the plastic sheet is not particularly limited, but is typically 0.2 to 5 mm, preferably 0.4 to 3 mm.

[0142] Furthermore, various functional layers (transparent conductive film, metal layer, silicon dioxide layer, hard coating, anti-glare layer, etc.) can be formed on one or both sides of the aforementioned glass or plastic plate, and optical components can also be stacked on one or both sides of the aforementioned glass or plastic plate. In addition, the transparent conductive film and metal layer can be patterned.

[0143] 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 optical component that is part of a display module, or a laminate containing a display module that is to be attached to the first display component 21.

[0144] Examples of the aforementioned optical components include anti-spray films, polarizers, polarizers, retardation plates, viewing angle compensation films, brightness enhancement films, contrast enhancement films, liquid crystal polymer films, diffusion films, semi-transparent reflective films, and transparent conductive films. Examples of anti-spray films include hard coating films formed by forming a hard coating on one side of a substrate film.

[0145] The material constituting the printed layer 23 is not particularly limited, and known materials used for printing can be used. The thickness of the printed layer 3, i.e., the height of the step, is preferably 0.5 to 50 μm, more preferably 1 to 30 μm, and particularly preferably 3 to 20 μm. By keeping the thickness of the printed layer 3 within the above range, the step following ability provided by the adhesive layer 11 can be effectively utilized, and the concealment required for the purpose of the printed layer 3 can be sufficiently ensured. In addition, the printed layer 3 is generally formed in a frame shape on the adhesive layer 11 side of the display body constituent component.

[0146] Regarding the manufacturing of the aforementioned display body 2A, as an example, a release sheet 12a of the adhesive sheet 1 can be peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1 can be attached to the side of the first display body constituent member 21 where the printed layer 3 is present.

[0147] Then, another release 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 body component 22 to obtain the display body. In addition, as another example, the bonding order of the first display body component 21 and the second display body component 22 can be changed.

[0148] like Figure 3 As shown, another embodiment of the display body 2B is constructed by comprising a backlight 30, an adhesive layer 11 stacked on the backlight 30, and a display portion 40 stacked on the adhesive layer 11. In this display body 2B, the backlight 30 corresponds to a second display body component, and the display portion 40 corresponds to a first display body component. The backlight 30 in this display body 2B corresponds to a direct-lit backlight.

[0149] As a type of display 2B, liquid crystal displays (LCDs) are preferably listed, but are not limited to this.

[0150] The adhesive layer 11 in the above-mentioned display body 2B is the adhesive layer 11 of the above-mentioned adhesive sheet 1.

[0151] The backlight 30 is constructed by having one or more substrates 31 and a plurality of light-emitting elements 32 disposed on the substrates 31. The backlight 30 has an uneven surface caused by the plurality of light-emitting elements 32.

[0152] There are no particular limitations on the substrate 31, and any substrate commonly used for backlights can be used. The substrate 31 is typically a printed circuit board (PCB).

[0153] The substrate 31 can be formed as a single unit by mounting multiple light emitters 32 together, or it can be formed separately by mounting one light emitter 32 on each substrate 31. In the case of separate formation, each substrate 31 is typically fixed to a frame, support, housing, etc. In this embodiment, as... Figure 3 As shown, the preferred substrate 31 is formed as a single unit by mounting multiple light emitters 32 together.

[0154] A reflective layer can be formed on the surface of the substrate 31 on the side of the adhesive layer 11, or a reflective member can be provided on the surface of the substrate 31 on the side of the adhesive layer 11. This effectively improves the brightness of the backlight 30. The material of the reflective layer or the reflective member can be a known material.

[0155] Examples of light-emitting elements 32 include light-emitting diodes (LEDs), laser diodes (LDs), organic electroluminescent elements, and inorganic electroluminescent elements. Among these, LEDs are preferred from the perspective of adjusting the emission color using the adhesive layer 11, and sub-millimeter LEDs or micro LEDs are particularly preferred.

[0156] The thickness (height) of the light emitter 32 is preferably 10~300μm, more preferably 30~200μm, particularly preferably 50~150μm, and even more preferably 80~100μm.

[0157] Furthermore, the width of the gap between adjacent light emitters 32 is preferably 0.01 to 10 mm, particularly preferably 0.1 to 4 mm, and even more preferably 0.5 to 2 mm.

[0158] The shape of the light-emitting body 32 is not particularly limited, and it is usually rectangular, hemispherical, etc. The size of the light-emitting body 32 is also not particularly limited. From the perspective of the sealing performance of the light-emitting body, the side length or diameter when viewed from above is preferably 0.01~100mm, more preferably 0.1~10mm, particularly preferably 0.2~5mm, and even more preferably 0.5~2mm.

[0159] Display unit 40 may include, for example, a liquid crystal panel, but is not limited to this. For example, it may be part of the constituent components of the liquid crystal panel, or an optical component used at the same time to add or enhance the function of the liquid crystal panel (e.g., a light diffuser, an ultraviolet absorption filter, etc.). Display unit 40 may be a known display unit.

[0160] Regarding the manufacturing of the display body 2B in this embodiment, for example, a peeling sheet 12a of the adhesive sheet 1 can be peeled off, and the exposed adhesive layer 11 can be attached to the side of the backlight 30 where the light-emitting body 32 is located.

[0161] Then, another release tab 12b is peeled off from the adhesive layer 11 of the adhesive tab 1, and the exposed adhesive layer 11 is attached to the display unit 40. Furthermore, as another example, the attachment order of the backlight 30 and the display unit 40 can be changed.

[0162] Here, a desired optical component can be provided between the adhesive layer 11 and the display portion 40, or on the surface of the display portion 40 opposite to the adhesive layer 11. Examples of such optical components include brightness enhancement films, contrast enhancement films, viewing angle compensation films, transparent conductive films, liquid crystal polymer films, semi-transparent reflective films, anti-scattering films, and light diffusion plates.

[0163] The embodiments described above are provided for ease of understanding of the present invention and are not intended to limit the invention. Therefore, the elements disclosed in the above embodiments are intended to include all design changes and equivalents that fall within the scope of the present invention.

[0164] For example, either of the release tabs 12a and 12b in the adhesive tab 1 can be omitted.

[0165] Furthermore, in this specification, when "X~Y" (where X and Y are arbitrary numbers) is used, unless otherwise stated, it means "X or more and Y or less," and also includes the meaning of "preferably greater than X" or "preferably less than Y." Additionally, when "X or more" (where X is any number) is used, unless otherwise stated, it includes the meaning of "preferably greater than X," and when "Y or less" (where Y is any number) is used, unless otherwise stated, it includes the meaning of "preferably less than Y."

[0166] Example The present invention will be further described in detail below by way of examples, etc., but the scope of the present invention is not limited to these examples, etc.

[0167] [Example 1] 1. Preparation of (meth)acrylate polymers (Meth)acrylate polymer (A) was prepared by solution polymerization of 27.5 parts by weight of n-butyl acrylate, 27.5 parts by weight of 2-ethylhexyl acrylate, 15 parts by weight of isobornyl acrylate, 5 parts by weight of N-acryloylmorpholine, and 25 parts by weight of 2-hydroxyethyl acrylate. The molecular weight of (meth)acrylate polymer (A) was determined by the method described later, and the weight-average molecular weight (Mw) was 500,000.

[0168] 2. Preparation of adhesive compositions 100 parts by mass (conversion value of solid content; the same applies below) of the (meth)acrylate polymer (A) obtained in step (1) above, 0.15 parts by mass of the isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, Inc., product name "TAKENATE D-101E") as crosslinking agent (B), 5 parts by mass of light-diffusing microparticles (C1; manufactured by Momentive Performance Materials Japen LLC, product name "Tospearl 145", average particle size: 4.5 μm, refractive index: 1.43) formed from silicone resin (a silicon-containing compound with an intermediate structure of inorganic and organic) as light-diffusing microparticles (C), and 0.26 parts by mass of 3-glycidyl etheroxypropyltrimethoxysilane as silane coupling agent (D) are mixed, stirred thoroughly, and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition.

[0169] Table 1 shows the proportions (converted to solids) of the adhesive composition when (meth)acrylate polymer (A) is set at 100 parts by weight. Details of the abbreviations, etc., listed in Table 1 are as follows.

[0170] [(Meth)acrylate polymer (A)] BA: n-Butyl acrylate 2EHA: 2-Ethylhexyl acrylate IBXA: Isoborneol Acrylate ACMO: N-Acryloylmorpholine HEA: 2-Hydroxyethyl acrylate [Light-diffusing particles (C)] C1: Light-diffusing microparticles formed from silicone resin (a silicon-containing compound with an intermediate structure of inorganic and organic components) (manufactured by Momentive Performance Materials Japen LLC, product name "Tospearl 145", average particle size: 4.5 μm, refractive index: 1.43). C2: Light-diffusing microparticles formed from silicone resin (a silicon-containing compound with an intermediate structure of inorganic and organic components) (manufactured by Momentive Performance Materials Japen LLC, product name "Tospearl 120", average particle size: 2.0 μm, refractive index: 1.43). C3: Light-diffusing microparticles formed from silicone resin (a silicon-containing compound with an intermediate structure of inorganic and organic components) (manufactured by Momentive Performance Materials Japen LLC, product name "Tospearl 1100", average particle size: 11 μm, refractive index: 1.43). 3. Manufacturing of adhesive sheets Using a doctor blade coater, the coating solution of the obtained adhesive composition is applied to the peeling treatment surface of a heavy-release type release sheet R1, which has been peeled from one side of a polyethylene terephthalate film using an organosilicon-based release agent. The sheet is then heated at 90°C for 1 minute to form a coating layer.

[0171] Then, the coating layer on the release sheet R1 obtained above is bonded to a lightly releaseable release sheet R2, which has been treated to peel one side of the polyethylene terephthalate film using an organosilicon-based release agent, so that the peeled side of the release sheet R2 is in contact with the coating layer, thus creating an adhesive sheet consisting of a release sheet R2 / adhesive layer coating layer (thickness: 50 μm) / release sheet R1.

[0172] Furthermore, the thickness of the adhesive layer mentioned above was measured according to JIS K7130 using a constant pressure thickness gauge (manufactured by Derrick Corporation, product name "PG-02") (the same applies below). In addition, regarding the peel force of the release tabs R1 and R2 in the obtained adhesive sheet, it was confirmed that the peel force of release tab R1 is greater than that of release tab R2.

[0173] [Examples 2-3, Comparative Examples 1-5] Except for changing the type and doping amount of the light-diffusing microparticles (C) 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. In Comparative Example 2, C2 and C3 were mixed and doped as the light-diffusing microparticles (C). In Comparative Example 3, two adhesive layers with a thickness of 50 μm were stacked to form an adhesive layer with a thickness of 100 μm.

[0174] The above weight-average molecular weight (Mw) is the converted weight-average molecular weight of polystyrene determined by gel permeation chromatography (GPC) under the following conditions (GPC determination).

[0175] <Measurement Conditions> • GPC measuring apparatus: Manufactured by TOSOH CORPORATION, HLC-8020 • GPC column (passes through in the following order): Manufactured by TOSOH CORPORATION TSK guard column HXL-H TSK gel GMHXL (×2) TSK gel G2000HXL • Determination of solvent: tetrahydrofuran • Measurement temperature: 40℃ [Experimental Example 1] (Determination of gel fraction) The adhesive sheets manufactured in the examples and comparative examples were cut into 80mm × 80mm sizes. The adhesive layer was wrapped in a polyester mesh (mesh size 200), and its mass was weighed using a precision balance. The mass of the mesh alone was then subtracted to calculate the mass of the adhesive only. This mass is denoted as M1.

[0176] The adhesive encased in the aforementioned polyester mesh was then 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, followed by further drying in an oven at 80°C for 12 hours. After drying, its mass was measured using a precision balance, and the mass of the mesh alone was subtracted to calculate the mass of the adhesive alone. This mass is designated as M2. The gel fraction (%) is expressed as (M2 / M1) × 100. The results are shown in Table 2.

[0177] [Experimental Example 2] (Determination of Haze Value) The adhesive layer of the adhesive sheet manufactured in the examples and comparative examples was bonded to glass and used as the sample for measurement. After performing a background measurement on the glass, the haze values ​​(%; H(450)) caused by light with a wavelength of 450 nm, the haze values ​​(%; H(550)) caused by light with a wavelength of 550 nm, the haze values ​​(%; H(650)) caused by light with a wavelength of 650 nm, and the haze values ​​(%) of all light wavelengths were measured using a haze meter (manufactured by NIPPON DENSHOKU INDUSTRIES Co., Ltd., product name "SH7000") according to JISK 7136:2000. The results are shown in Table 2.

[0178] Furthermore, the slope S1, S2, and S3, expressed by equation (1), are calculated. Further, the ratio of haze value (H(450)) to haze value (H(550)) (H(450) / H(550)) and the ratio of haze value (H(450)) to haze value (H(550)) (H(650) / H(550)) are calculated. The results are presented in Table 2.

[0179] S1=(H(650)-H(450)) / 200 …(1) S2=(H(550)-H(450)) / 100 …(2) S3=(H(650)-H(550)) / 100 …(3) [Experimental Example 3] (Determination of Total Transmittance) The adhesive layer of the adhesive sheet manufactured in the examples and comparative examples was bonded to glass and used as the test sample. After background measurement of the glass, the total transmittance (%) of the test sample was measured using a haze meter (manufactured by NIPPON DENSHOKU INDUSTRIES Co., Ltd., product name "NDH5000") according to JIS K7136:2000. The results are shown in Table 2.

[0180] [Experimental Example 4] (Determination of Adhesion) Peel release sheet R2 from the adhesive sheet manufactured in the examples and comparative examples, and attach the exposed adhesive layer to the easy-adhesive layer of a polyethylene terephthalate (PET) film (manufactured by TOYOBO CO., LTD., product name "COSMOSHINE PET A4360", thickness: 100 μm) to obtain a laminate of release sheet R1 / adhesive layer / PET film. Cut the obtained laminate into pieces 25 mm wide and 100 mm long.

[0181] Under conditions of 23°C and 50%RH, the release sheet R1 was peeled from the aforementioned laminate, and the exposed adhesive layer was attached to soda-lime glass (manufactured by Nippon Sheet Glass Co., Ltd.). Then, a pressure of 0.5 MPa was applied at 50°C for 20 minutes using an autoclave manufactured by Kurihara Seisakusho Co., Ltd. The sample was then left to stand at 23°C and 50%RH for 24 hours. The adhesion (before UV exposure; N / 25 mm) was then measured using a tensile testing machine (manufactured by ORIENTEC CORPORATION, product name "TENSILON") at a peeling speed of 300 mm / min and a peeling angle of 180°. For conditions not described here, measurements were performed according to JIS Z0237:2022. The results are shown in Table 2.

[0182] [Experimental Example 5] (Evaluation of Hue) The adhesive layer of the adhesive sheet manufactured in the examples and comparative examples was bonded to a soda-lime glass plate (manufactured by Nippon SheetGlass Co., Ltd., 70mm long × 70mm wide × 1.1mm thick) and used as a sample (two release sheets had been removed). The sample was positioned 3cm away from a white light source (LED; manufactured by Panasonic Corporation, product name "LDL40SN2225", total luminous flux 2500lm, color temperature 5000K) so that the glass plate was on the white light source side. The hue of the white light source observed through the sample was then visually confirmed. The results are shown in Table 2.

[0183] [Experimental Example 6] (Evaluation of Concealment) The adhesive layer of the adhesive sheet manufactured in the examples and comparative examples was adhered to a soda-lime glass plate (manufactured by Nippon SheetGlass Co., Ltd., 70mm long × 70mm wide × 1.1mm thick) and used as a sample (the two release sheets had been peeled off). On the other hand, the following two sizes of text were printed in black on white paper and used as evaluation benchmarks.

[0184] 1...Font size: 16 points, font: MS Gothic, text column: あいうえお 2...Font size: 8 points, font: MS Gothic, text column: あいうえお The sample was positioned 3 cm away from the evaluation reference object, with the glass plate serving as the evaluation reference object. Then, at a distance of 50 cm from the sample, the text on the evaluation reference object was observed visually through the sample. The visibility of the text was determined based on the following criteria to evaluate its concealment. The results are shown in Table 2.

[0185] A: It can visually recognize 1, but it is difficult to visually recognize 2.

[0186] F: Both 1 and 2 can be easily visually recognized.

[0187] [Table 1] [Table 2] As shown in Table 2, the adhesive sheet manufactured according to the embodiments can adjust the hue of the luminescent color to a color other than white. Furthermore, the adhesive sheet exhibits excellent concealment and adhesion.

[0188] Industrial applicability The adhesive sheet of the present invention is suitable for use in displays with RGB light sources in the backlight, particularly blue LEDs, green LEDs and red LEDs.

[0189] Explanation of reference numerals in the attached figures 1: Adhesive sheet; 11: Adhesive layer; 12a, 12b: Release sheet; 2A, 2B: Display body; 21: First display body component; 22: Second display body component; 23: Printed layer; 30: Backlight; 31: Substrate; 32: Light emitter; 40: Display section.

Claims

1. An adhesive sheet, which is an adhesive sheet having an adhesive layer, characterized in that, When the haze value (%) of the adhesive layer caused by light with a wavelength of 450 nm is set as H(450), and the haze value (%) caused by light with a wavelength of 650 nm is set as H(650), the absolute value of the slope S1 expressed by the following formula (1) is greater than 0.

026. The haze value of the adhesive layer is above 10% and below 100%. The adhesive sheet has an adhesion force of 1 N / 25 mm or more to the soda-lime glass. S1=(H(650)-H(450)) / 200…(1).

2. An adhesive sheet, which is an adhesive sheet having an adhesive layer, characterized in that, When the haze value (%) of the adhesive layer caused by light with a wavelength of 450 nm is set as H(450), the haze value (%) caused by light with a wavelength of 550 nm is set as H(550), and the haze value (%) caused by light with a wavelength of 650 nm is set as H(650), at least one of the absolute values ​​of the slope S2 expressed by the following formula (2) and the absolute values ​​of the slope S3 expressed by the following formula (3) is 0.032 or more. The haze value of the adhesive layer is above 10% and below 100%. The adhesive sheet has an adhesion force of 1 N / 25 mm or more to the soda-lime glass. S2=(H(550)-H(450)) / 100…(2), S3=(H(650)-H(550)) / 100…(3).

3. The adhesive sheet according to claim 1, characterized in that, The slope S1 is negative.

4. The adhesive sheet according to claim 2, characterized in that, The slopes S2 and S3 are negative.

5. The adhesive sheet according to claim 1 or 2, characterized in that, When the haze value (%) of the adhesive layer caused by light with a wavelength of 550 nm is set as H(550), the slope S3 expressed by the following formula (3) is 0 or more and 0.015 or less. S3=(H(650)-H(550)) / 100…(3).

6. The adhesive sheet according to claim 1 or 2, characterized in that, When the haze value (%) of the adhesive layer caused by light with a wavelength of 550 nm is set as H(550), the slope S3 expressed by the following equation (3) is greater than 0.

015. S3=(H(650)-H(550)) / 100…(3).

7. The adhesive sheet according to claim 1 or 2, characterized in that, The adhesive comprising the adhesive layer has a gel content of 20% or more and 100% or less.

8. The adhesive sheet according to claim 1 or 2, characterized in that, The adhesive that constitutes the adhesive layer contains light-diffusing particles.

9. The adhesive sheet according to claim 8, characterized in that, The average particle size of the light-diffusing particles is greater than 0.1 μm and less than 20 μm.

10. The adhesive sheet according to claim 8, characterized in that, The refractive index of the light-diffusing particles is greater than 1.30 and less than 2.

00.

11. The adhesive sheet according to claim 8, characterized in that, The content of the light-diffusing particles in the adhesive is more than 1% by mass and less than 70% by mass.

12. The adhesive sheet according to claim 8, characterized in that, The light-diffusing particles are light-diffusing particles formed from silicone resin.

13. The adhesive sheet according to claim 1 or 2, characterized in that, The adhesive that constitutes the adhesive layer is an acrylic adhesive.

14. The adhesive sheet according to claim 1 or 2, characterized in that, The thickness of the adhesive layer is more than 10 μm and less than 2000 μm.

15. The adhesive sheet according to claim 1 or 2, characterized in that, The adhesive sheet has two release tabs. The adhesive layer is sandwiched between the two release tabs in a manner that contacts the release surfaces of the two release tabs.

16. The adhesive sheet according to claim 1 or 2, characterized in that, The adhesive sheet is used to bond two display components that have blue, green and red light sources together.

17. A display body comprising a backlight having a blue light source, a green light source, and a red light source, characterized in that, A display component closer to the display surface than the backlight is attached to another display component via the adhesive layer of the adhesive sheet as described in claim 1 or 2.

18. The display body according to claim 17, characterized in that, The blue light source, the green light source, and the red light source are all light-emitting diodes (LEDs).

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