Adhesive film for OLED display device

Abstract

Provided is an adhesive film that provides high impact resistance to an OLED display device that does not use a polarizing plate.　This adhesive film for an OLED display device is used in an OLED display device in which only optical elements having a degree of polarization of 95% or less are laminated on the viewing side of OLED elements, the adhesive film being characterized by having an adhesive layer that has a storage modulus of 1.0 × 104 to 2.0 × 107 Pa at 25°C, having a thickness of 300 μm or less, and having an impact force in a ball drop test of 800 N or less.

Description

Adhesive film for OLED display devices

[0001] This invention relates to an adhesive film for OLED display devices. More specifically, it relates to an adhesive film used in OLED display devices that do not use polarizing plates.

[0002] OLED (Organic Light Emitting Diode) displays offer several advantages over liquid crystal displays, including higher visibility, less dependence on viewing angle, and faster response times. Furthermore, because OLED displays do not use backlights, they are more suitable for thinner designs and can be used as flexible, curved, or foldable devices.

[0003] OLED display devices typically have an OLED element in which an anode, an OLED layer including a light-emitting layer, and a cathode are stacked in this order. Because the electrodes (anode or cathode) of the OLED element are made of transparent conductive materials with a high refractive index such as ITO or metal materials with high reflectivity, ambient light is reflected by the electrodes, which can lead to problems such as reduced contrast and reflections due to internal reflection, potentially degrading the display performance of the OLED display device.

[0004] To suppress the adverse effects of external light reflection, it has been proposed to place a polarizing plate and a circular polarizing plate, such as a λ / 4 plate, on the viewing side of the OLED display device (for example, Patent Document 1). Such a circular polarizing plate also has the function of blocking ultraviolet rays contained in ambient light and preventing the degradation of OLED elements due to ultraviolet rays. Furthermore, due to the mechanical properties of the circular polarizing plate itself, it also has the function of absorbing external shocks and preventing damage to the OLED display device.

[0005] However, using circular polarizers results in poor light utilization efficiency (i.e., light collection rate) due to absorption by the polarizer, leading to low brightness. Increasing the light emission intensity of the OLED element to obtain the desired brightness increases power consumption and shortens the lifespan of the OLED element. Furthermore, including the adhesive layer used to attach the polarizer, it becomes about 0.15 mm thick, which is disadvantageous for making OLED display devices thinner. In addition, circular polarizers are expensive, which increases manufacturing costs.

[0006] As an alternative to circular polarizers, a method has been proposed to improve the luminous intensity of an OLED element while preventing external light reflection by placing a color filter on the viewing side of the OLED element and aligning it so that the color filter is the same color as the OLED layer's emitted color. (For example, Patent Document 2).

[0007] One form of OLED display device is known to be an OLED display device having a microcavity structure (also called multiple reflection interference, optical resonator, or micro-resonator). According to OLED display devices having a microcavity structure, the spectrum of light extracted to the outside becomes steep and high intensity, which is said to improve brightness and color purity (for example, Patent Document 3).

[0008] In OLED display devices, various optical element layers, such as an adhesive layer, a substrate like plastic or thin glass, and a hard coat layer, are laminated on the viewing side of the OLED element to provide functions such as surface protection and flexibility.

[0009] Japanese Patent Publication No. 2003-332068, Japanese Patent Publication No. 2018-112715, Japanese Patent Publication No. 2015-207377

[0010] However, while polarizing plates offer excellent impact resistance and can provide sufficient impact resistance to OLED display devices, the problem was that without polarizing plates, the impact resistance to OLED display devices was insufficient.

[0011] Therefore, the object of the present invention is to provide an adhesive film that can impart high impact resistance to OLED display devices that do not use polarizing plates.

[0012] As a result of diligent research to achieve the above objective, the inventors of the present invention have found that an OLED display device using an adhesive film for OLED display devices having a specific configuration can exhibit sufficient impact resistance even when the OLED display device does not use a polarizing plate, and have completed the present invention.

[0013] In other words, the present invention provides an adhesive film for use in an OLED display device in which only optical elements with a polarization degree of 95% or less are laminated on the viewing side of the OLED element, wherein the adhesive layer has an adhesive layer, and the storage modulus of the adhesive layer at 25°C is 1.0 × 10⁻⁶ ４ ~2.0 x 10 ７ The present invention provides an adhesive film for OLED display devices characterized by being Pa, having a thickness of 300 μm or less, and having an impact force of 800 N or less in a ball drop test.

[0014] The thickness of the adhesive layer is preferably 250 μm or less.

[0015] In the aforementioned adhesive film, it is preferable that the impact force in the ball drop test before and after the reliability test described below satisfies the following equation (1): • Reliability test: Performed by storing the adhesive film at 85°C for 240 hours. 0.7 ≤ [Impact force after reliability test (N)] / [Impact force before reliability test (N)] ≤ 1.2 (1)

[0016] Preferably, the adhesive film has a first adhesive layer, a second adhesive layer, and an intermediate layer located between the first and second adhesive layers.

[0017] The adhesive layer is at a frequency of 10 at 25°C. ３ Preferably, the loss coefficient (tanδ) has a peak in the range of Hz or higher, and the value of the peak top is 1.5 or higher.

[0018] The present invention also provides an OLED display device in which only optical elements with a polarization degree of 95% or less are laminated on the viewing side of the OLED element, including the adhesive film.

[0019] The adhesive film of the present invention can provide high impact resistance to OLED display devices that do not use polarizing plates.

[0020] Figure 3(b) is a schematic cross-sectional view showing one embodiment of an OLED display panel used in the OLED display device of the present invention. Figure 3(b) is a schematic cross-sectional view showing one embodiment of the OLED display device of the present invention. Figures (a) and (b) are schematic cross-sectional views showing one embodiment of the adhesive film of the present invention. Figure 3(b) is a schematic cross-sectional view showing one embodiment of an OLED display device using the adhesive film of the present invention. Figures (a) and (b) are schematic cross-sectional views showing other embodiments of the adhesive film of the present invention. Figure 3(b) is a partially enlarged cross-sectional view of the adhesive film shown. Figure 3(b) is a schematic diagram of the apparatus used for the ball drop test in the embodiment of the present application.

[0021] The present invention provides an adhesive film for an OLED display device. The adhesive film for an OLED display device of the present invention may be referred to as "the adhesive film of the present invention." The present invention also provides an OLED display device comprising an optical laminate including the adhesive film. The optical laminate is a laminate obtained by removing the OLED display panel from the OLED display device of the present invention, and includes the adhesive film of the present invention. The optical laminate is composed of optical elements.

[0022] The OLED display device of the present invention has an OLED display panel in which only optical elements with a polarization degree of 95% or less are laminated on the viewing side of the OLED elements. "Only optical elements with a polarization degree of 95% or less are laminated on the viewing side of the OLED elements" means that the optical elements on the viewing side of the OLED elements do not include optical elements with a polarization degree exceeding 95%. "Optical elements with a polarization degree exceeding 95%" are not particularly limited, but include polarizers such as linear polarizers, quarter phase difference plates, half phase difference plates, circular polarizers, and reflective polarizers. In other words, the OLED display device of the present invention is an OLED display device that does not include polarizers on the viewing side of the OLED elements.

[0023] The degree of polarization is determined using the following formula, based on the parallel transmittance Tp and orthogonal transmittance Tc, which are measured using a UV-Vis spectrophotometer and corrected for luminous sensitivity: Degree of polarization (%) = {(Tp - Tc) / (Tp + Tc)} １／２ ×100

[0024] Since the OLED display device of the present invention does not include a polarizing plate on the viewing side of the OLED element, absorption of light emitted from the OLED element by the polarizing plate is suppressed, the light transmittance is improved, power consumption can be saved, and this contributes to extending the service life of the OLED element. Furthermore, eliminating the use of a polarizing plate enables a reduction in thickness and reduces manufacturing costs.

[0025] The pressure-sensitive adhesive film of the present invention is a pressure-sensitive adhesive film used for an OLED display device in which only an optical element having a polarization degree of 95% or less is laminated on the viewing side of an OLED element, the pressure-sensitive adhesive film has a pressure-sensitive adhesive layer, and the storage elastic modulus of the pressure-sensitive adhesive layer at 25°C is 1.0×10 ４ to 2.0×10 ７ Pa, has a thickness of 300 µm or less, and has an impact force of 800 N or less in a ball drop test. The pressure-sensitive adhesive film of the present invention having the above characteristics is preferable in that it can impart excellent impact resistance to an OLED display device despite the small thickness of the pressure-sensitive adhesive film. Accordingly, the pressure-sensitive adhesive film of the present invention can also be used for smartphones and the like.

[0026] The pressure-sensitive adhesive film of the present invention may have two or more pressure-sensitive adhesive layers. When the pressure-sensitive adhesive film of the present invention has two or more pressure-sensitive adhesive layers, it may or may not include a first pressure-sensitive adhesive layer, a second pressure-sensitive adhesive layer, and an intermediate layer positioned between the first and second pressure-sensitive adhesive layers. The intermediate layer is not particularly limited, and examples thereof include layers such as a resin layer, an adhesive layer, a glass layer, a hard coat layer, an antireflection layer, an antiglare layer, a compatible layer, an impact absorption layer, and an antistatic layer described later. Among these, the intermediate layer is preferably a resin layer described later.

[0027] From the viewpoint of improving impact resistance, the pressure-sensitive adhesive film of the present invention preferably has a resin layer. Furthermore, the pressure-sensitive adhesive film of the present invention may include, as a constituent of the pressure-sensitive adhesive film, an optical element other than the pressure-sensitive adhesive layer and the resin layer laminated in the OLED display device of the present invention.

[0028] In the pressure-sensitive adhesive film of the present invention, the impact force (N) in a ball drop test is not particularly limited as long as it is 800 N or less. For example, it is preferably 760 N or less, more preferably 730 N or less. Although the lower limit of the impact force (N) is not particularly limited, it is preferably 100 N, more preferably 400 N. The method for measuring the impact force (N) by the ball drop test is not particularly limited, and for example, the measurement can be performed by the method described in the examples mentioned later.

[0029] In the pressure-sensitive adhesive film of the present invention, it is preferable that the impact force in the ball drop test before and after the reliability test shown below satisfies the following formula (1). ・Reliability test: Conducted by storing the pressure-sensitive adhesive film at 85°C for 240 hours 0.7≦[impact force after reliability test (N)] / [impact force before reliability test (N)]≦1.2 (1)

[0030] In the above formula (1), the lower limit of [impact force after reliability test (N)] / [impact force before reliability test (N)] is more preferably 0.8, and particularly preferably 0.9. Further, the upper limit is more preferably 1.1, and particularly preferably 1.0.

[0031] The thickness of the pressure-sensitive adhesive film of the present invention is not particularly limited as long as it is 300 µm or less. For example, it is preferably 40 µm to 250 µm, more preferably 80 µm to 200 µm.

[0032] In the present specification, the term "pressure-sensitive adhesive film" is intended to include the meanings of "pressure-sensitive adhesive sheet" and "pressure-sensitive adhesive tape". That is, the pressure-sensitive adhesive film of the present invention may be a pressure-sensitive adhesive sheet or pressure-sensitive adhesive tape in the form of a sheet or a tape. The pressure-sensitive adhesive film of the present invention is a component for forming an optical laminate, and may include the above-mentioned high-refractive-index pressure-sensitive adhesive layer.

[0033] The adhesive film of the present invention may be a so-called "substrate-less type" adhesive film that does not have a substrate (corresponding to the "resin layer" described later), or it may be an adhesive film that has a substrate. In this specification, the "substrate-less type" adhesive film may be referred to as a "substrate-less adhesive film," and the adhesive film that has a substrate may be referred to as a "substrate-attached adhesive film." An example of the substrate-less adhesive film is a double-sided adhesive sheet consisting only of an adhesive layer. The adhesive layer in the double-sided adhesive sheet may consist of a single layer, or it may have a multi-layer structure of two or more layers. An example of the substrate-attached adhesive film is a single-sided adhesive film having an adhesive layer on one side of the substrate, or a double-sided adhesive film having adhesive layers on both sides of the substrate. The adhesive layer in the single-sided adhesive film may consist of a single layer, or it may have a multi-layer structure of two or more layers. Furthermore, the two adhesive layers may be formed continuously, or they may be formed independently (i.e., via other layers). One of the adhesive layers in the double-sided adhesive film may consist of a single layer, or it may have a multi-layer structure of two or more layers. Furthermore, the two adhesive layers may be formed continuously or independently (i.e., via other layers). Also, the other adhesive layer may consist of a single layer or may be a multi-layer structure of two or more layers. Furthermore, the two adhesive layers may be formed continuously or independently (i.e., via other layers). The "substrate" mentioned above refers to the support, which is the part that is attached to the adherend together with the adhesive layer when the adhesive film of the present invention is used (applied) to the adherend. The release liner that is peeled off when the adhesive film is used (applied) is not included in the substrate.

[0034] The various components of the adhesive film of the present invention will be described below.

[0035] (OLED Display Panel) The OLED display panel used in the OLED display device of the present invention includes, as an essential component, an OLED element in which an anode, an OLED layer including a light-emitting layer, and a cathode are stacked in this order. An optical laminate is stacked on the viewing side of the OLED element of the OLED display panel.

[0036] An embodiment of the OLED display panel constituting the OLED display device of the present invention will be described below with reference to the drawings, but the present invention is not limited to this embodiment. Figure 1 is a schematic cross-sectional view showing an embodiment of the OLED display panel.

[0037] As shown in Figure 1, the OLED display panel 100 has a red OLED element 12R in which a transparent electrode 11a, a red OLED layer 10R that emits red light, and a back electrode 11b are stacked in this order; a green OLED element 12G in which a transparent electrode 11a, a green OLED layer 10G that emits green light, and a back electrode 11b are stacked in this order; and a blue OLED element 12B in which a transparent electrode 11a, a blue OLED layer 10B that emits blue light, and a back electrode 11b are stacked in this order. Each of the OLED elements 12R, 12G, and 12B of multiple colors is arranged sequentially on the substrate 13. A TFT (Thin Film Transistor) layer 14 is formed on the surface of the substrate 13 where each OLED element is arranged, and is connected to the back electrode 11b of each of the OLED elements 12R, 12G, and 12B of multiple colors.

[0038] In the OLED display panel 100 shown in Figure 1, a color filter 15 is positioned on the viewing side (upper side in Figure 1) of each of the multiple-color OLED elements 12R, 12G, and 12B. The color filter 15 includes a red colored layer 15R, a green colored layer 15G, and a blue colored layer 15B, with a black matrix layer 16 provided between each colored layer.

[0039] In Figure 1, the color filter 15 has a red colored layer 15R, a green colored layer 15G, and a blue colored layer 15B, which are arranged to face the red OLED element 12R, the green OLED element 12G, and the blue OLED element 12B, respectively.

[0040] The transparent electrode 11a is either a cathode or an anode, but is generally provided as a cathode. Transparent conductive materials such as ITO (indium tin oxide), indium oxide, IZO (indium zinc oxide), SnO2, and ZnO are used as the material for forming the transparent electrode 11a.

[0041] The back electrode 11b functions as the counter electrode to the transparent electrode 11a. The back electrode 11b can be either an anode or a cathode, but is generally provided on the substrate 13 as an anode. Examples of forming materials include metals such as gold, silver, and chromium. Therefore, the back electrode 11b is capable of reflecting light.

[0042] A bonding layer 17 is provided between the substrate 13 and the color filter 15. The bonding layer 17 is light-transmitting. The material of the bonding layer 17 can be any material commonly used in OLED display devices, such as a photocurable resin like a photosensitive polyimide resin, or a thermosetting resin.

[0043] In addition to the configuration shown in Figure 1, the OLED display panel 100 may also have other configurations that an OLED display panel may have, such as a hole injection layer, a hole transport layer, an electron transport layer, a sealing layer, a touch sensor panel, etc. (not shown).

[0044] A feature of the OLED display panel in Figure 1 is that a color filter 15 is arranged on each of the multiple-color OLED elements 12R, 12G, and 12B such that the same colored layers 15R, 15G, and 15B face each other. As shown in Figure 1, white ambient light W passes, for example, through the red colored layer 15R, then through the transparent electrode 11a and the red OLED layer 10R that emits red light, is reflected by the back electrode 11b, and then passes through the red OLED layer 10R, the transparent electrode 11a, and the red colored layer 15R again, and the reflected light G enters the observer's eye.

[0045] When ambient light W is incident on the red colored layer 15R, the green and blue light is absorbed, reducing the light intensity to 1 / 3. Furthermore, the reflected light G passes through the red colored layer 15R and the red OLED layer 10R again, causing attenuation. Also, since the reflected light G is red, it can enhance the red light emitted from the OLED layer 10R. Similarly, when ambient light W is incident on the green colored layer 15G and the blue colored layer 15B, the green and blue light can be enhanced, respectively. Therefore, by using a color filter in conjunction with the OLED display panel, it is possible to significantly suppress the reflection of ambient light and improve the luminous intensity of the OLED element, even without using a polarizing plate for anti-reflection.

[0046] However, color filters generally suffer from interference inconsistencies due to their regular two-dimensional structure. Furthermore, color filters are prone to reflection at their interfaces, reducing the light collection efficiency from the OLED element. Additionally, color filters do not offer sufficient UV absorption compared to polarizers, leading to OLED elements being more susceptible to degradation over time due to UV radiation (i.e., poor weather resistance). Finally, color filters do not offer sufficient shock absorption compared to polarizers.

[0047] Furthermore, the OLED display panel 100 of this embodiment has a microcavity structure. Light generated from the OLED layers 10R, 10G, and 10B passes through the transparent electrode 11a and is emitted to the outside. Here, the emitted light includes both components: "direct light" emitted directly from the OLED layers 10R, 10G, and 10B toward the transparent electrode 11a, and "reflected light" emitted from the OLED layers 10R, 10G, and 10B toward the back electrode 11b, which is reflected by the back electrode 11b before being directed toward the transparent electrode 11a. Specifically, a first optical path C1 is formed in which a portion of the light emitted from the OLED layers 10R, 10G, and 10B proceeds to the transparent electrode 11a side without proceeding to the back electrode 11b side and is emitted to the outside through the transparent electrode 11a, and a second optical path C2 is formed in which the remaining portion of the light emitted from the OLED layers 10R, 10G, and 10B proceeds to the back electrode 11b side, is reflected by the back electrode 11b, and is then emitted to the outside through the OLED layers 10R, 10G, 10B and the transparent electrode 11a. The thicknesses of the OLED layers 10R, 10G, and 10B are different so that the light components corresponding to each color reinforce each other through the interference of this direct light and reflected light. Specifically, the thicknesses of the OLED layers 10R, 10G, and 10B are different so that the optical path length between the back electrode (positive electrode) 11b and the transparent electrode (negative electrode) 11a is matched to the respective EL spectral peak wavelengths of red, green, and blue, and the thicknesses of the OLED layers 10R, 10G, and 10B are different so that the strongest light is extracted from each color. Specifically, the short-wavelength blue OLED layer 10B is designed to be thin, while the long-wavelength red OLED layer 10R is designed to be thick. The light generated in the OLED layer is repeatedly reflected between the positive and negative electrodes. By resonating and emphasizing only the light of wavelengths that match the optical path length, and weakening the light of other wavelengths that do not match the optical path length, the spectrum of the light extracted to the outside becomes steep and high-intensity, improving brightness and color purity.

[0048] While OLED display panels with a microcavity structure offer excellent benefits such as improved brightness and color purity, their steep spectral profile can lead to problems with strong viewing angle dependence (narrow viewing angle). Therefore, when viewing an image from an oblique angle, a color shift may occur, causing the image to appear in a different color than intended.

[0049] (Optical element) The optical element is an optical element laminated on the viewing side of the OLED display device and includes at least an adhesive layer. The optical element may further include at least one layer selected from adhesive layers, resin layers, glass layers, hard coat layers, anti-reflective layers, anti-glare layers, compatible layers, shock-absorbing layers, anti-static layers, etc. However, the optical element does not include polarizers or other elements with a polarization degree exceeding 95%.

[0050] (Adhesive layer) The adhesive layer is a layer that has adhesive properties at room temperature and adheres to the substrate with light pressure. Even when the substrate attached to the adhesive layer is peeled off, the adhesive layer retains practical adhesive strength.

[0051] The adhesive layer constituting the optical element preferably has a high refractive index, from the viewpoint of preventing interfacial reflection and improving the light collection efficiency of the light emitted from the OLED element. The refractive index of the adhesive layer is preferably 1.57 or higher, more preferably 1.575 or higher, even more preferably 1.580 or higher, particularly preferably 1.585 or higher, even more preferably 1.590 or higher, and may also be 1.595 or higher.

[0052] The refractive index of the adhesive layer can be adjusted, for example, by the type and content of aromatic ring-containing monomers, high refractive index organic materials, and high refractive index inorganic materials.

[0053] The adhesive layer is not particularly limited, but it is preferable that it has light scattering properties (the function of scattering light) from the viewpoint of efficiently reducing color shift and interference unevenness in the OLED display device.

[0054] When an OLED display device includes a color filter on the viewing side and the adhesive layer has light scattering properties, it is preferable that the distance between the adhesive layer having light scattering properties and the color filter is 700 μm or less, from the viewpoint of reducing color shift and interference unevenness of the OLED display device and suppressing image blurring of the OLED display device caused by light scattering. From the viewpoint of suppressing image blurring of the OLED display device caused by light scattering, it is more preferable that the distance between the adhesive layer having light scattering properties and the color filter is 600 μm or less, even more preferable that it is 500 μm or less, and most preferable that it is 0 μm, i.e., the adhesive layer having light scattering properties and the color filter are in direct contact.

[0055] The distance between the light-scattering adhesive layer and the color filter refers to the distance (μm) between the surface of the adhesive layer in the color filter direction and the surface of the color filter in the adhesive layer direction. If other layers are laminated between the adhesive layer and the color filter, this distance corresponds to the thickness (μm) of those other layers (or their sum if there are two or more layers).

[0056] The haze value of the adhesive layer is not particularly limited, but from the viewpoint of efficiently reducing color shift and interference unevenness in the OLED display device, it is preferably 20% or more, more preferably 30% or more, even more preferably 40% or more, and particularly preferably 50% or more. Furthermore, from the viewpoint of suppressing image blurring in the OLED display device and displaying high-definition images, the haze value of the adhesive layer is preferably 90% or less, more preferably 80% or less, and even more preferably 70% or less.

[0057] The total light transmittance of the adhesive layer is not particularly limited, but from the viewpoint of ensuring the brightness of the OLED display device, it is preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, and particularly preferably 90% or more. Furthermore, the upper limit of the total light transmittance of the adhesive layer is not particularly limited, but it may be less than 100%, 99.9% or less, or 99% or less.

[0058] The haze value and total light transmittance of the pressure-sensitive adhesive layer can each be measured by the methods defined in JIS K7136 and JIS K7361, and can be controlled by the type and thickness of the pressure-sensitive adhesive layer, the type and blending amount of the light-scattering fine particles described later, and the like.

[0059] The pressure-sensitive adhesive layer has a frequency of 10 at 25°C ３ Hz or higher, it has a peak of loss factor (tanδ), and the peak top value is preferably 1.5 or more, more preferably 1.55 or more, still more preferably 1.6 or more, and particularly preferably 1.7 or more. When the pressure-sensitive adhesive layer is a multi-layered pressure-sensitive adhesive layer of two or more layers, the loss factor (tanδ) of the pressure-sensitive adhesive layer is measured by regarding the two or more pressure-sensitive adhesive layers as one pressure-sensitive adhesive layer. When the loss factor of the pressure-sensitive adhesive layer is within the above range, impact resistance tends to be improved.

[0060] The pressure-sensitive adhesive layer has a frequency of 10 at 25°C ３ to 10 ７ Hz range, it preferably has a peak top of the loss factor (tanδ). When the pressure-sensitive adhesive layer has the peak top of the loss factor (tanδ) within the above range, impact resistance tends to be improved.

[0061] The thickness of the pressure-sensitive adhesive layer is not particularly limited, but from the viewpoint of improving thickness and impact resistance, it is preferably 250 µm or less, more preferably 15 to 200 µm, still more preferably 20 to 150 µm. Impact resistance tends to improve as the thickness (total thickness) of the pressure-sensitive adhesive layer increases. When the pressure-sensitive adhesive layer consists of two or more pressure-sensitive adhesive layers in contact with each other, the thickness of the pressure-sensitive adhesive layer is the total thickness of the two or more pressure-sensitive adhesive layers.

[0062] The storage modulus and loss factor (tanδ) can be calculated, for example, by performing dynamic viscoelasticity measurements as described in the examples below, and can be adjusted by adjusting the type and composition of the adhesive constituting the adhesive layer, the type and amount of crosslinking agent used, etc. In particular, when the adhesive layer is composed of an acrylic adhesive, the storage modulus and loss factor (tanδ) can be adjusted by increasing the proportion of alkyl (meth)acrylate in the acrylic polymer as the base polymer to a certain extent, or by using a specific type of alkyl (meth)acrylate, for example, an alkyl (meth)acrylate having a relatively long alkyl group. Furthermore, the storage modulus and loss factor (tanδ) can also be adjusted by adding a specific plasticizer to the adhesive layer.

[0063] The light-scattering fine particles have an appropriate refractive index difference with respect to the adhesive layer (the adhesive in the adhesive layer) and impart light-scattering properties to the adhesive layer. It is preferable for the adhesive layer to contain light-scattering fine particles in that it is given light-scattering performance. Examples of light-scattering fine particles include inorganic fine particles and polymer fine particles. Examples of inorganic fine particles include silica, calcium carbonate, aluminum hydroxide, magnesium hydroxide, clay, talc, and titanium dioxide. Examples of polymer fine particles include silicone resin, acrylic resin, methacrylic resin (e.g., polymethyl methacrylate), polystyrene resin, polyurethane resin, melamine resin, polyethylene resin, and epoxy resin. The light-scattering fine particles are preferably polymer fine particles, and in particular, fine particles composed of silicone resin (for example, the Tospearl series manufactured by Momentive Performance Materials Japan Co., Ltd.) are preferable because they have excellent dispersibility and stability with respect to the adhesive layer, and an appropriate refractive index difference with the adhesive layer (the adhesive in the adhesive layer), resulting in an adhesive layer with excellent scattering performance that exhibits uniform haze in the plane, thus reducing color shift and interference unevenness in OLED display devices. The shape of the light-scattering fine particles may be, for example, perfectly spherical, flattened, or irregularly shaped. The light-scattering fine particles may be used alone or in combination of two or more types.

[0064] The ratio of the change in refractive index before and after humidification of the adhesive layer is not particularly limited, but from the viewpoint of preventing interfacial reflection and stably improving the light collection rate of light emitted from the OLED element even in a high temperature and high humidity environment, it is preferably 0.05 or less, preferably 0.04 or less, more preferably 0.02 or less, and particularly preferably 0.01 or less.

[0065] The ratio of the change in refractive index before and after humidification of the adhesive layer can be calculated using the following formula: Ratio of change in refractive index before and after humidification = |Initial refractive index - Refractive index after humidification| / (Initial refractive index)

[0066] The "refractive index after humidification" mentioned above refers to the refractive index of the adhesive layer after it has been stored for 120 hours in a humidified environment at a temperature of 85°C and a relative humidity of 85%.

[0067] The ratio of the change in refractive index before and after humidification can be adjusted by the type and content of aromatic ring-containing monomers, high refractive index organic materials, and high refractive index inorganic materials, as well as the type of adhesive constituting the adhesive layer, monomer composition, degree of crosslinking, thickness, etc.

[0068] The adhesive constituting the adhesive layer is not particularly limited, but examples include acrylic adhesives, rubber adhesives, vinyl alkyl ether adhesives, silicone adhesives, polyester adhesives, polyamide adhesives, urethane adhesives, fluorine adhesives, epoxy adhesives, and the like. Among these, acrylic adhesives are preferred as the adhesive constituting the adhesive layer in terms of transparency, tackiness, weather resistance, cost, and ease of designing the adhesive. In other words, the adhesive layer is preferably an acrylic adhesive layer composed of acrylic adhesives. The adhesive can be used alone or in combination of two or more types.

[0069] The acrylic adhesive layer contains an acrylic polymer as a base polymer. The acrylic polymer is a polymer that contains an acrylic monomer (a monomer having a (meth)acryloyl group in its molecule) as a monomer component constituting the polymer. Preferably, the acrylic polymer is a polymer that contains an alkyl (meth)acrylate as a monomer component constituting the polymer. The acrylic polymer can be used alone or in combination of two or more types.

[0070] The adhesive composition forming the adhesive layer may be in any form. For example, the adhesive composition may be an emulsion type, a solvent type (solution type), an active energy ray curing type, a hot melt type, etc. Among these, solvent type and active energy ray curing type adhesive compositions are preferred in terms of productivity and ease of obtaining an adhesive layer with excellent optical properties and appearance characteristics.

[0071] In other words, the adhesive layer is an acrylic adhesive layer containing an acrylic polymer as the base polymer, and is preferably formed by a solvent-type or active energy ray-curable acrylic adhesive composition.

[0072] Examples of the adhesive composition for forming the acrylic adhesive layer (acrylic adhesive composition) include an acrylic adhesive composition in which an acrylic polymer is an essential component, or an acrylic adhesive composition in which a mixture of monomers constituting the acrylic polymer (sometimes referred to as a "monomer mixture") or a partially polymer thereof is an essential component. An example of the former is a so-called solvent-type acrylic adhesive composition. An example of the latter is a so-called active energy ray-curable acrylic adhesive composition. The "monomer mixture" means a mixture containing monomer components that constitute a polymer. The "partial polymer" may also be referred to as a "prepolymer," and means a composition in which one or more monomer components of the monomer mixture are partially polymerized.

[0073] The acrylic polymer is a polymer composed (formed) using acrylic monomers as essential monomer components. Preferably, the acrylic polymer is a polymer composed (formed) using alkyl (meth)acrylate as an essential monomer component. That is, it is preferable that the acrylic polymer contains alkyl (meth)acrylate as a constituent unit. In this specification, "(meth)acrylic" means "acrylic" and / or "methacrylic" (either one or both of "acrylic" and "methacrylic"), and the same applies to other terms. The acrylic polymer is composed of one or more monomer components.

[0074] As the essential monomer component, the alkyl (meth)acrylate ester is preferably one having a linear or branched alkyl group. The alkyl (meth)acrylate ester can be used alone or in combination of two or more types.

[0075] The alkyl (meth)acrylate ester having a linear or branched alkyl group is not particularly limited, but examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate (lauryl (meth)acrylate), and n-octyl (meth)acrylate, which have 1 to 20 linear or branched alkyl groups. Among these, alkyl (meth)acrylate esters having a linear or branched alkyl group having 4 to 18 carbon atoms are preferred. Furthermore, the alkyl (meth)acrylate esters having linear or branched alkyl groups can be used alone or in combination of two or more.

[0076] The proportion of the alkyl (meth)acrylate in the total monomer components (100% by weight) constituting the acrylic polymer is not particularly limited, but is preferably 50% by weight or more (for example, 50 to 100% by weight), more preferably 60 to 99.5% by weight, even more preferably 70 to 99% by weight, and particularly preferably 80 to 98% by weight.

[0077] The acrylic polymer may contain copolymerizable monomers as monomer components constituting the polymer, together with the alkyl (meth)acrylate ester. That is, the acrylic polymer may contain copolymerizable monomers as constituent units. The copolymerizable monomers can be used alone or in combination of two or more types.

[0078] While the copolymerizable monomers are not particularly limited, monomers having nitrogen atoms in their molecules and monomers having hydroxyl groups in their molecules are preferred in terms of suppressing turbidity in high humidity environments, improving durability, compatibility with various additives, and transparency.

[0079] The monomer having a nitrogen atom in its molecule is a monomer (monomer) that has at least one nitrogen atom in its molecule (one molecule). In this specification, the "monomer having a nitrogen atom in its molecule" may be referred to as a "nitrogen atom-containing monomer." The nitrogen atom-containing monomer is not particularly limited, but cyclic nitrogen-containing monomers, (meth)acrylamides, etc., are preferred. The nitrogen atom-containing monomer can be used alone or in combination of two or more types.

[0080] The cyclic nitrogen-containing monomer is not particularly limited as long as it has a polymerizable functional group having an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group, and has a cyclic nitrogen structure. The cyclic nitrogen structure is preferably one in which a nitrogen atom is contained within the cyclic structure.

[0081] Examples of the cyclic nitrogen-containing monomers include N-vinyl cyclic amides (lactam-based vinyl monomers) such as N-vinyl-2-pyrrolidone, and vinyl monomers having a nitrogen-containing heterocycle.

[0082] The monomer having a hydroxyl group in its molecule is a monomer having at least one hydroxyl group in its molecule (one molecule), and preferably has a polymerizable functional group having an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group, and also has a hydroxyl group. However, the monomer having a hydroxyl group in its molecule does not include the nitrogen atom-containing monomer. That is, in this specification, monomers having both a nitrogen atom and a hydroxyl group in their molecule are included in the "nitrogen atom-containing monomer". In this specification, the "monomer having a hydroxyl group in its molecule" may be referred to as a "hydroxyl group-containing monomer". The hydroxyl group-containing monomer can be used alone or in combination of two or more types.

[0083] Examples of the hydroxyl group-containing monomers include hydroxyl group-containing (meth)acrylic acid esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; vinyl alcohol; and allyl alcohol. Among these, hydroxyl group-containing (meth)acrylic acid esters are preferred as the hydroxyl group-containing monomer, and more preferably 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA).

[0084] When the acrylic polymer contains the hydroxyl group-containing monomer as a monomer component constituting the polymer, the proportion of the hydroxyl group-containing monomer in the total monomer components (100% by weight) constituting the acrylic polymer is not particularly limited, but is preferably 10% by weight or less, more preferably 5% by weight or less, and even more preferably 3% by weight or less.

[0085] Examples of copolymerizable monomers other than nitrogen atom-containing monomers and hydroxyl group-containing monomers include alicyclic structure-containing monomers, polyfunctional monomers, (meth)acrylate alkoxyalkyl esters, carboxyl group-containing monomers, epoxy group-containing monomers, and the like. Examples of the carboxyl group-containing monomers include (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, and acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride.

[0086] The content of the base polymer (especially acrylic polymer) in the adhesive layer is not particularly limited, but is preferably 40% by weight or more (e.g., 40 to 100% by weight) based on 100% by weight of the total weight of the adhesive layer, more preferably 50% by weight or more (e.g., 50 to 100% by weight), and even more preferably 60% by weight or more (e.g., 60 to 100% by weight).

[0087] The base polymer, such as the acrylic polymer contained in the adhesive layer, is obtained by polymerizing monomer components. The polymerization method is not particularly limited, but examples include solution polymerization, emulsion polymerization, bulk polymerization, and polymerization by active energy ray irradiation (active energy ray polymerization).

[0088] When polymerizing the monomer components mentioned above, polymerization initiators such as solvents, thermal polymerization initiators, and photopolymerization initiators (photoinitiators) may be used depending on the type of polymerization reaction. Polymerization initiators can be used individually or in combination of two or more types.

[0089] The thermal polymerization initiator is not particularly limited, but examples include azo polymerization initiators, peroxide polymerization initiators (e.g., dibenzoyl peroxide, tert-butyl permaleate, etc.), and redox polymerization initiators. Among these, the azo polymerization initiator disclosed in Japanese Patent Application Publication No. 2002-69411 is preferred. Examples of the azo polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionic acid)dimethyl, and 4,4'-azobis-4-cyanovaleric acid. The thermal polymerization initiator can be used alone or in combination of two or more.

[0090] When the azo polymerization initiator is used during the polymerization of the acrylic polymer, the amount of the azo polymerization initiator used is not particularly limited, but for example, it is preferably 0.05 parts by weight or more, more preferably 0.1 parts by weight or more, and also preferably 0.5 parts by weight or less, and more preferably 0.3 parts by weight or less, based on 100 parts by weight of the total monomer components constituting the acrylic polymer.

[0091] The aforementioned photopolymerization initiator is not particularly limited, but examples include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, and the like. The photopolymerization initiator can be used alone or in combination of two or more types.

[0092] When the photopolymerization initiator is used during the polymerization of the acrylic polymer, the amount of the photopolymerization initiator used is not particularly limited, but for example, it is preferably 0.01 parts by weight or more, more preferably 0.1 parts by weight or more, and preferably 3 parts by weight or less, and more preferably 1.5 parts by weight or less, based on 100 parts by weight of the total monomer components constituting the acrylic polymer.

[0093] A crosslinking agent may be used to form the adhesive layer. For example, the acrylic polymer in the acrylic adhesive layer can be crosslinked to control the gel fraction. The crosslinking agent can be used alone or in combination of two or more types.

[0094] The aforementioned crosslinking agent is not particularly limited, but examples include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, and urea-based crosslinking agents. Among these, isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferred.

[0095] When a crosslinking agent is used to form the adhesive layer, the amount of the crosslinking agent used is not particularly limited, but from the standpoint of obtaining sufficient adhesive reliability, it is preferably 0.001 parts by weight or more, and more preferably 0.01 parts by weight or more, per 100 parts by weight of the base polymer. Furthermore, from the standpoint of obtaining appropriate flexibility in the adhesive layer and improving adhesive strength, the upper limit of the amount used is preferably 10 parts by weight or less, and more preferably 5 parts by weight or less, per 100 parts by weight of the base polymer.

[0096] The adhesive layer (particularly the acrylic adhesive layer) may contain a silane coupling agent to improve adhesive reliability under humid conditions, and especially to improve adhesive reliability to glass. The silane coupling agent can be used alone or in combination of two or more types. When the adhesive layer contains a silane coupling agent, the adhesion under humid conditions, particularly to glass, can be improved.

[0097] The silane coupling agent is not particularly limited, but examples include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and N-phenyl-aminopropyltrimethoxysilane. Furthermore, commercially available silane coupling agents such as the trade name "KBM-403" (manufactured by Shin-Etsu Chemical Co., Ltd.) are also available. Among these, γ-glycidoxypropyltrimethoxysilane is preferred as the silane coupling agent.

[0098] When the adhesive layer contains a silane coupling agent, the content of the silane coupling agent in the adhesive layer (particularly the acrylic adhesive layer) is not particularly limited, but is preferably 0.01 parts by weight or more, and more preferably 0.02 parts by weight or more, per 100 parts by weight of the base polymer. Furthermore, the upper limit of the silane coupling agent content is preferably 10 parts by weight or less, and more preferably 1 part by weight or less, per 100 parts by weight of the base polymer.

[0099] The adhesive layer may, if necessary, further contain additives such as crosslinking accelerators, tackifying resins (rosin derivatives, polyterpene resins, petroleum resins, oil-soluble phenols, etc.), degradation inhibitors, fillers, colorants (pigments, dyes, etc.), antioxidants, chain transfer agents, plasticizers, softeners, surfactants, and antistatic agents, to the extent that they do not impair the effects of the present invention. Such additives can be used individually or in combination of two or more.

[0100] The method for producing the adhesive layer (especially the acrylic adhesive layer) is not particularly limited, but examples include applying the adhesive composition onto a substrate (including the resin layer and glass layer described later) or a release liner and drying and curing the resulting adhesive composition layer, or applying the adhesive composition onto a substrate (including the resin layer and glass layer described later) or a release liner and curing the resulting adhesive composition layer by irradiating it with active energy rays. Furthermore, if necessary, it may be further heated and dried.

[0101] Examples of the active energy rays include ionizing radiation such as alpha rays, beta rays, gamma rays, neutron rays, and electron beams, as well as ultraviolet rays, with ultraviolet rays being particularly preferred. Furthermore, the irradiation energy, irradiation time, and irradiation method of the active energy rays are not particularly limited.

[0102] The adhesive composition can be prepared by known or conventional methods. For example, a solvent-type acrylic adhesive composition can be prepared by mixing an additive as needed with a solution containing the acrylic polymer. For example, an active energy ray-curable acrylic adhesive composition can be prepared by mixing an additive as needed with a mixture of the acrylic monomers or a partial polymer thereof.

[0103] Furthermore, known coating methods may be used for applying (coating) the adhesive composition. For example, coaters such as gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, bar coaters, knife coaters, spray coaters, comma coaters, and direct coaters may be used.

[0104] In particular, when forming an adhesive layer using an active energy ray-curable adhesive composition, it is preferable that the active energy ray-curable adhesive composition contains a photopolymerization initiator.

[0105] The storage modulus of the adhesive layer at 25°C is 1.0 × 10⁻⁶. ４ ~2.0 x 10 ７ Pa is not particularly limited, but for example, 3.0 × 10 ４ ~2.0 x 10 ７ Pa is preferred, and more preferably 5.0 × 10 ４ ~2.0 x 10 ７ Pa, more preferably 1.0 × 10 ５ ~2.0 x 10 ７ The storage modulus of the adhesive layer is within the above range, which has the advantage that the adhesive layer absorbs impact, improving the impact resistance of the OLED display device. Furthermore, a synergistic effect with the above-mentioned adhesive layer thickness may also be achieved.

[0106] (Adhesive layer) An adhesive layer is a layer that can bond substances together by being interposed between the adherends. When the adherends bonded with the adhesive layer are peeled off, the adhesive layer no longer possesses practical adhesive strength.

[0107] Various adhesives can be used to form the adhesive layer constituting the optical element. Examples include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl latex, and aqueous polyester. These adhesives are usually used as aqueous solutions (aqueous adhesives) and contain 0.5 to 60% by weight of solids. Among these, polyvinyl alcohol-based adhesives are preferred, and acetoacetyl group-containing polyvinyl alcohol-based adhesives are more preferred.

[0108] The water-based adhesive may contain a crosslinking agent. Typically, the crosslinking agent is a compound having at least two functional groups in one molecule that are reactive with the polymer and other components constituting the adhesive. Examples include alkylenediamines; isocyanates; epoxys; aldehydes; amino-formaldehydes such as methylolurea and methylolmelamine. The amount of crosslinking agent in the adhesive is typically about 10 to 60 parts by weight per 100 parts by weight of the polymer and other components constituting the adhesive.

[0109] The adhesive may contain additives. Examples of such additives include coupling agents such as silane coupling agents and titanium coupling agents, adhesion promoters such as ethylene oxide, ultraviolet absorbers, degradation inhibitors, dyes, processing aids, ion trapping agents, antioxidants, tackifiers, fillers, plasticizers, leveling agents, foam inhibitors, antistatic agents, heat stabilizers, hydrolysis stabilizers, and the like.

[0110] The adhesive may be applied to one or both of the two adherends to be bonded. After bonding, a drying process can be performed to form an adhesive layer consisting of a coated and dried layer. After the drying process, ultraviolet light or electron beams may be irradiated as needed. The thickness of the adhesive layer is not particularly limited, but when using a water-based adhesive, it is preferably about 30 to 5000 nm, more preferably about 100 to 1000 nm, and when using an ultraviolet-curing adhesive, electron beam-curing adhesive, etc., it is preferably about 0.1 to 100 μm, more preferably about 0.5 to 10 μm.

[0111] (Resin Layer) The resin layer constituting the optical element is not particularly limited, but an example is a plastic film. Preferred materials for the plastic film, etc., include polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), which have excellent dimensional stability and are resistant to shrinkage, cyclic olefin polymers (COP), polycarbonate (PC), polyetheretherketone (PEEK), and transparent polyimide (CPI). These plastic materials can be used individually or in combination of two or more. The release liner that is peeled off when the optical element is used (attached) is not included in the "resin layer".

[0112] The resin layer is preferably transparent. The total light transmittance of the resin layer in the visible light wavelength range (according to JIS K 7361-1) is not particularly limited, but is preferably 85% or more, and more preferably 88% or more.

[0113] In the present invention, the refractive index difference between the adhesive layer and the resin layer (the absolute value of "refractive index of the adhesive layer" - "refractive index of the resin layer") is not particularly limited, but from the viewpoint of improving interfacial anti-reflective properties and improving the light collection rate from the OLED element, it is preferably 2 or less, more preferably 1 or less, even more preferably 0.5 or less, and particularly preferably 0.3 or less. When the resin layer consists of a multilayer structure of two or more continuous layers, the refractive index difference is measured by considering the two or more layers as a single resin layer.

[0114] The thickness of the resin layer is not particularly limited, but is preferably 5 to 150 μm, more preferably 10 to 120 μm, even more preferably 15 to 100 μm, and most preferably 20 to 80 μm. The resin layer may be in the form of a single layer or a multi-layer structure. Furthermore, the surface of the resin layer may be appropriately subjected to known and conventional surface treatments, such as physical treatments like corona discharge treatment or plasma treatment, or chemical treatments like undercoating. When the resin layer consists of a multi-layer structure of two or more continuous layers, the thickness is measured by considering the two or more layers as a single resin layer.

[0115] (Glass layer) The glass layer constituting the optical element is not particularly limited, and an appropriate one can be used depending on the purpose. Examples of glass layers, classified by composition, include soda-lime glass, borate glass, aluminosilicate glass, and quartz glass. Furthermore, classifications based on alkali content include alkali-free glass and low-alkali glass. The alkali metal component of the glass (e.g., Na) ２ O, K ２ O, Li ２ The content of O) is preferably 15% by weight or less, and more preferably 10% by weight or less.

[0116] The thickness of the glass layer is not particularly limited, but considering the surface hardness, airtightness, and corrosion resistance of the glass, it is preferably 20 μm or more. Furthermore, it is desirable that the glass layer has flexibility and bendability like a film, and a thickness of 60 μm or less is preferable in order to suppress double image projection and enable the projection of a clear image. The thickness of the glass layer is more preferably 30 μm to 55 μm, and particularly preferably 40 μm to 50 μm.

[0117] The light transmittance of the glass layer at a wavelength of 550 nm is preferably 85% or higher. The refractive index of the glass layer at a wavelength of 550 nm is preferably 1.4 to 1.65. The density of the glass layer is preferably 2.3 g / cm³. ３ ~3.0 g / cm ３ And more preferably 2.3 g / cm³ ３ ~2.7 g / cm ３ That is the case.

[0118] There are no particular limitations on the method for forming the glass layer, and an appropriate method can be adopted depending on the purpose. Typically, the glass layer can be produced by melting a mixture containing main raw materials such as silica and alumina, an antifoaming agent such as Glauber's salt or antimony oxide, and a reducing agent such as carbon at a temperature of about 1400°C to 1600°C, forming it into a thin sheet, and then cooling it. Examples of glass layer forming methods include the slot-down draw method, the fusion method, and the float method. The glass layer formed into a sheet by these methods may be chemically polished with a solvent such as hydrofluoric acid as needed to thin it or improve its smoothness.

[0119] (Hard Coat Layer) The hard coat layer constituting the optical element can be formed from any suitable resin, as long as it has sufficient surface hardness, excellent mechanical strength, and excellent light transmittance. Specific examples of resins include thermosetting resins, thermoplastic resins, UV-curing resins, electron beam-curing resins, and two-component mixed resins. Among these, UV-curing resins are preferred because they allow for the formation of the hard coat layer with simple operation and high efficiency.

[0120] Examples of UV-curable resins include polyester-based, acrylic-based, urethane-based, amide-based, silicone-based, and epoxy-based UV-curable resins. UV-curable resins include UV-curable monomers, oligomers, and polymers. Preferred UV-curable resins include resin compositions containing acrylic monomer or oligomer components having preferably two or more, more preferably three to six, UV-polymerizable functional groups. Typically, UV-curable resins contain photopolymerization initiators.

[0121] The hard coat layer can be formed by any suitable method. For example, the hard coat layer can be formed by applying a resin composition for forming a hard coat layer onto a substrate (including the resin layer and the glass layer), drying it, and curing the dried coating film by irradiating it with ultraviolet light.

[0122] The thickness of the hard coat layer is not particularly limited, but is, for example, 2 μm to 20 μm, preferably 4 μm to 15 μm.

[0123] (Anti-reflective layer) Any suitable configuration can be used as the anti-reflective layer constituting the optical element. For example, (i) a single layer of low refractive index layer with an optical film thickness of 120 nm to 140 nm and a refractive index of 1.35 to 1.55, (ii) a laminate having a medium refractive index layer, a high refractive index layer and a low refractive index layer in that order, and (iii) an alternating multilayer laminate of high refractive index layer and low refractive index layer.

[0124] Examples of materials that can form a low refractive index layer include silicon dioxide (SiO₂). ２ ), magnesium fluoride (MgF ２) are examples. The refractive index of the low refractive index layer is typically around 1.35 to 1.55.

[0125] Examples of materials that can form a high refractive index layer include titanium oxide (TiO2). ２ ), niobium oxide (Nb ２ O ３ or Nb ２ O ５ Examples include tin-doped indium oxide (ITO). The refractive index of the high refractive index layer is typically around 1.60 to 2.20.

[0126] Examples of materials that can form an intermediate refractive index layer include titanium oxide (TiO2). ２ Examples include a mixture of a material capable of forming a low refractive index layer and a material capable of forming a high refractive index layer (for example, a mixture of titanium oxide and silicon oxide). The refractive index of the medium refractive index layer is typically around 1.50 to 1.85. The thicknesses of the low refractive index layer, medium refractive index layer, and high refractive index layer can be set to achieve an appropriate optical film thickness according to the layer structure of the anti-reflective layer, the desired anti-reflective performance, etc.

[0127] The anti-reflective layer may be formed by a dry process (e.g., sputtering), a wet process (e.g., coating), or a combination of both dry and wet processes.

[0128] The thickness of the anti-reflective layer is not particularly limited, but is typically around 20 to 300 nm.

[0129] (Anti-glare layer) Any known anti-glare layer can be used without limitation as a component of the optical element, and is generally formed as a layer in which inorganic or organic particles are dispersed in a resin as an anti-glare agent.

[0130] The anti-glare layer is not particularly limited, but for example, it is formed using an anti-glare layer forming material containing a resin, particles, and a thixotropy imparting agent, and the particles and the thixotropy imparting agent aggregate to form convex portions on the surface of the anti-glare layer. With this configuration, the anti-glare layer has excellent display characteristics that achieve both anti-glare properties and prevention of white blurring, and despite being formed by utilizing particle aggregation, it is possible to prevent the occurrence of protrusions on the surface of the anti-glare layer that would be appearance defects, thereby improving the product yield.

[0131] Examples of the aforementioned resins include thermosetting resins and ionizing radiation-curable resins that harden with ultraviolet light or other light. Commercially available thermosetting resins or UV-curable resins can also be used as the aforementioned resin.

[0132] The particles for forming the anti-glare layer primarily function to provide anti-glare properties by creating an uneven surface on the formed anti-glare layer, and to control the haze value of the anti-glare layer. The haze value of the anti-glare layer can be designed by controlling the refractive index difference between the particles and the resin.

[0133] The weight-average particle size (D) of the particles is preferably within the range of 2.5 to 10 μm. By setting the weight-average particle size of the particles within this range, for example, better anti-glare properties and prevention of white blurring can be achieved. The weight-average particle size of the particles is more preferably within the range of 3 to 7 μm. The weight-average particle size of the particles can be measured, for example, by the Coulter count method. For example, using a particle size distribution analyzer that utilizes the pore electrical resistance method (product name: Coulter Multisizer, manufactured by Beckman Coulter, Inc.), the number and volume of the particles are measured by measuring the electrical resistance of the electrolyte corresponding to the volume of the particles as the particles pass through the pores, and the weight-average particle size is calculated.

[0134] The shape of the particles is not particularly limited; for example, they may be bead-like or roughly spherical, or they may be irregular in shape, such as powder. However, roughly spherical particles are preferred, more preferably roughly spherical particles with an aspect ratio of 1.5 or less, and most preferably spherical particles.

[0135] The thickness (d) of the anti-glare layer is not particularly limited, but it is preferably in the range of 3 to 12 μm. By setting the thickness (d) of the anti-glare layer within this range, for example, curling of the optical laminate can be prevented, and problems such as poor transportability and reduced productivity can be avoided.

[0136] The method for manufacturing the anti-glare layer is not particularly limited and may be manufactured by any method. For example, it can be manufactured by preparing an anti-glare layer forming material (coating liquid) containing the resin, the particles, the thixotropy imparting agent, and the solvent, applying the anti-glare layer forming material (coating liquid) to form a coating film, and curing the coating film to form the anti-glare layer. Methods such as a transfer method using a mold, or a method for imparting uneven shapes using sandblasting, embossing rolls, etc., can also be used in combination.

[0137] For example, coating methods such as the fountain coating method, die coating method, spin coating method, spray coating method, gravure coating method, roll coating method, and bar coating method can be used to apply the anti-glare layer forming material.

[0138] The anti-glare layer may have a multi-layer structure with two or more layers stacked on top of it. The anti-reflective layer described above may be placed on top of the anti-glare layer. For example, one of the factors that reduces the visibility of an OLED display device is the reflection of light at the interface between the air and the anti-glare layer. The anti-reflective layer reduces this surface reflection. Note that the anti-glare layer and the anti-reflective layer may each have a multi-layer structure with two or more layers stacked on top of each other.

[0139] (Compatibility layer) The compatibility layer constituting the optical element is formed between the resin layer and the hard coat layer, anti-reflective layer, or anti-glare layer. The formation of this compatibility layer improves the adhesion between the resin layer and the hard coat layer, anti-reflective layer, or anti-glare layer.

[0140] The mechanism by which the compatible layer (also called the penetration layer) is formed is not particularly limited, but for example, in the formation of the hard coat layer, anti-reflective layer, or anti-glare layer, it is formed in the process of applying, penetrating, and drying the coating liquid for forming the hard coat layer, anti-reflective layer, or anti-glare layer to the resin layer. In the drying step, for example, the coating liquid for forming the hard coat layer, the coating liquid for forming the anti-reflective layer, or the coating liquid for forming the anti-glare layer penetrates the resin layer, and the compatible layer is formed, which includes the resin derived from the resin layer and the resin derived from the hard coat layer, anti-reflective layer, or anti-glare layer. The resin contained in the compatible layer is not particularly limited, and for example, it may be simply a mixture (compatible) of the resin contained in the resin layer and the resin contained in the hard coat layer, anti-reflective layer, or anti-glare layer. Furthermore, the resin contained in the compatible layer may be such that at least one of the resin contained in the resin layer and the resin contained in the hard coat layer, anti-reflective layer, or anti-glare layer undergoes a chemical change due to heating, light irradiation, etc.

[0141] (Shock-absorbing layer) The shock-absorbing layer constituting the optical element may be composed of any suitable resin layer capable of achieving a desired shock absorption rate. The resin layer may be composed of a resin film or an adhesive. The shock-absorbing layer typically includes epoxy resin, urethane resin, or acrylic resin. These resins may be used alone or in combination.

[0142] (Antistatic layer) The antistatic layer constituting the optical element is not particularly limited, but for example, it is an antistatic layer formed by coating with a conductive coating liquid containing a conductive polymer. Specific coating methods include the roll coating method, the bar coating method, the gravure coating method, etc.

[0143] (Manufacturing Method for Optical Laminates) The manufacturing method for optical laminates is not particularly limited, and they can be manufactured by sequentially laminating adhesive layers, bonding layers, resin layers, glass layers, hard coat layers, anti-reflective layers, anti-glare layers, compatible layers, shock-absorbing layers, etc., that constitute the optical elements, on the viewing side of the OLED display panel. Alternatively, the laminates that constitute the optical laminate can be manufactured in advance and then laminated on the viewing side of the OLED display panel. When laminations that constitute the optical laminate are manufactured in advance, they may be the entire laminate that constitutes the optical laminate, or they may be a portion of the laminate that constitutes the optical laminate, divided and laminated on the viewing side of the OLED display panel.

[0144] The layers constituting the optical element, or the laminate thereof, may be protected by a release liner or surface protective film until use.

[0145] (Release Liner) The adhesive layer may have a release liner on its surface (adhesive side) until use. The release liner is used as a protective material for the adhesive layer and is peeled off when it is attached to the substrate. Note that the release liner is not part of the optical element and is not necessarily required.

[0146] (Surface Protection Film) The outermost surface of the optical laminate (the outermost surface on the viewing side) may be protected by a surface protection film. The surface protection film may be applied by the consumer. The surface protection film is not part of the optical elements and is not necessarily required. The surface protection film can be a known or conventional surface protection film and is not particularly limited, but for example, a plastic film with an adhesive layer on its surface can be used.

[0147] (OLED Display Device of the Present Invention) Below, an embodiment of an OLED display device in which an optical laminate is stacked on the viewing side of an OLED display panel will be described with reference to the drawings, but the present invention is not limited to this embodiment. Figure 2 is a schematic cross-sectional view showing an embodiment of the basic configuration of an OLED display device in which an optical laminate is stacked.

[0148] As shown in Figure 2, the OLED display device 200 has layers constituting the optical laminate 20 laminated on the viewing side (upper side in Figure 2) of the OLED display panel 100. The OLED display panel 100 is not particularly limited, but for example, it may have the same configuration as the OLED display panel 100 shown in Figure 1.

[0149] In the OLED display device 200 shown in Figure 2, 21 to 29 are layers constituting the optical laminate 20, where 21 is an adhesive layer or bonding layer, 22 is a resin layer, glass layer or shock-absorbing layer, 23 is a hard coat layer or anti-glare layer, 24 is an adhesive layer or bonding layer, 25 is a resin layer, glass layer or shock-absorbing layer, 26 is an adhesive layer or bonding layer, 27 is a resin layer, glass layer or shock-absorbing layer, 28 is a hard coat layer or anti-glare layer, and 29 is an anti-reflective layer, with any one of 21, 24, or 26 being an adhesive layer. The laminated structure of the optical laminate 20 shown in Figure 2 is not limited to this embodiment, and other layers constituting optical elements may be inserted between any layers of the laminated structure of the optical laminate 20 shown in Figure 2, and any layer of the laminated structure of the optical laminate 20 shown in Figure 2 may not be present.

[0150] In Figures 3(a) to 3(c), 300 and 301 are adhesive films, 31 is an adhesive layer, 32 is a substrate (resin layer), 33 is a release liner, 302 is an OLED display device, and 100 is an OLED display panel.

[0151] In Figure 3(a), the adhesive film 300 is configured such that an adhesive layer 31 and a base material 32 are laminated in that order on top of a release liner 33. The base material 32 is not an essential component (see Figure 3(b)), but its presence is preferable from the viewpoint of improving impact resistance. The release liner 33 is temporarily attached to the surface of the adhesive layer 31. The release liner 33 is not particularly limited, but for example, it is preferable to use one that is configured such that a release layer is provided on one side of a sheet-like base material using a release agent, so that one side becomes the release surface. Before bonding to the OLED display panel 100 as the adherend, the release liner 33 is peeled off from the surface of the adhesive layer 31, and the exposed surface of the adhesive layer 31 is bonded to the surface of the OLED display panel 100, thereby temporarily attaching the adhesive film to the OLED display panel 100. The thickness of the release liner 33 is not particularly limited, but for example, it is 3 to 200 μm, preferably 10 to 100 μm.

[0152] Figure 3(c) shows the form in which the adhesive film obtained by the above operation is temporarily attached to the OLED display panel 100. In Figure 3(c), the adhesive layer 31 of the adhesive film is in contact with the viewing side (upper side) of the OLED display panel 100, forming the OLED display device 302.

[0153] If the adhesive film has a base material 32, an adhesive film without a release liner 33 can also be used. The adhesive film may be wound so that the adhesive surface of the adhesive layer 31 that does not face the base material 32 is in contact with and protected from the surface of the base material 32 where the adhesive layer 31 is not present (roll form). In the case of an adhesive film in roll form, before bonding to the OLED display panel 100, the surface of the adhesive layer 31 is exposed and the exposed surface of the adhesive layer 31 is bonded to the surface of the OLED display panel 100, thereby temporarily attaching the adhesive film to the OLED display panel 100.

[0154] By applying an adhesive strength-enhancing treatment to the adhesive layer 31 of the adhesive film temporarily attached to the adherend, the adhesive strength of the adhesive layer 31 is increased, and the adherend and the substrate 32 are fixed together via the adhesive layer 31.

[0155] In Figures 4(a) to 4(c), 303 and 304 are adhesive films, 31 is an adhesive layer, 32 is a substrate (resin layer), 33 is a release liner, 305 is an OLED display device, and 100 is an OLED display panel.

[0156] In Figure 4(a), the adhesive film 303 is configured such that adhesive layers 31 are provided on both sides of a substrate 32. In Figure 4(b), adhesive layers 31 are provided on both sides of the substrate 32, and release liners 33 are further provided on both sides, with the release liners 33 temporarily attached to the surface of the adhesive layers 31. The release liners 33 are not particularly limited, but for example, a sheet-like substrate can be preferably used, configured such that a release layer is provided on one side using a release agent, making that side the release surface. Before bonding to the OLED display panel 100 as the adherend, the release liner 33 is peeled off from the surface of one of the adhesive layers 31, and the exposed surface of the adhesive layer 31 is bonded to the surface of the OLED display panel 100, thereby temporarily attaching the adhesive film to the OLED display panel 100. The thickness of the release liner 33 is not particularly limited, but for example, it is 3 to 200 μm, preferably 10 to 100 μm.

[0157] Figure 4(c) shows the form in which the adhesive film obtained by the above operation is temporarily attached to the OLED display panel 100. In Figure 4(c), the adhesive film has an adhesive layer 31 in contact with the viewing side (upper side) of the OLED display panel 100, forming the OLED display device 305.

[0158] When the adhesive film has a release liner 33 on one side and the adhesive layer 31 exposed on the other side, it may be made into a roll by winding it. In the case of an adhesive film in a roll form, before bonding it to the OLED display panel 100, the surface of the adhesive layer 31 is exposed and the exposed surface of the adhesive layer 31 is bonded to the surface of the OLED display panel 100, thereby temporarily attaching the adhesive film to the OLED display panel 100.

[0159] By applying an adhesive strength-enhancing treatment to the adhesive layer 31 of the adhesive film temporarily attached to the adherend, the adhesive strength of the adhesive layer 31 is increased, and the adherend and the substrate 32 are fixed together via the adhesive layer 31.

[0160] In this specification, "adhered" refers to a state in which two laminated layers are firmly bonded together, making separation at their interface impossible or difficult. "Temporarily bonded" refers to a state in which the adhesive force between two laminated layers is weak, allowing for easy separation at their interface.

[0161] In Figure 5, X1 is an adhesive film, X11 is an adhesive layer, and L1 is a substrate (resin layer). A portion or all of the outer peripheral edge X11a of the adhesive layer X11 in the adhesive film X1 is located away from the outer peripheral edge L1a of the substrate L1 in the in-plane direction of the film. The in-plane direction of the film refers to the in-plane direction perpendicular to the thickness direction of the adhesive film X1 (adhesive layer X11). Specifically in this embodiment, a portion or all of the outer peripheral edge X11a of the adhesive layer X11 is located at a distance of 5 to 2000 μm inward from the nearest outer peripheral edge L1a of the substrate L1 in the in-plane direction of the film. The separation distance D in the in-plane direction between the outer peripheral edge X11a of the adhesive layer X11 located away from the outer peripheral edge L1a of the substrate L1 in the in-plane direction of the film and said outer peripheral edge L1a is preferably 10 μm or more, more preferably 30 μm or more, more preferably 40 μm or more, and more preferably 50 μm or more. Furthermore, the separation distance D between the outer peripheral ends X11a and L1a is preferably 1500 μm or less, more preferably 1000 μm or less, more preferably 500 μm or less, and more preferably 300 μm or less.

[0162] An adhesive film X1 having the above configuration can be manufactured, for example, as follows. First, a raw material for an adhesive film with a release liner is prepared for producing the adhesive film X1 through cutting processes such as full-back processing. For example, a raw material for an adhesive film with a release liner can be produced by applying an adhesive composition for forming an adhesive layer X11 onto a predetermined substrate to form an adhesive composition layer, laminating a release liner on the adhesive composition layer, and curing the adhesive composition. Next, while the raw material for the adhesive film with a release liner is subjected to pressure in the thickness direction, it is processed so that an adhesive film X1 having the desired outer dimensions is formed on the raw material. When the raw material for the adhesive film with a release liner is subjected to pressure in the thickness direction, the adhesive layer of the raw material can elastically deform in response to the pressure, and elastically stretch and spread in the in-plane direction of the raw material with an elongation rate corresponding to the pressure, and the outer edge of the raw material can elastically bulge out from between the release liner and the substrate. In this type of processing, a cutting process such as full-back processing is performed on the adhesive film material with a release liner, which is under pressure in the thickness direction, so that a part or all of the outer edge of the adhesive film X1 is newly shaped to obtain an adhesive film X1 with the desired outer dimensions, and the elastically bulging adhesive layer is cut off. Then, in the adhesive film X1 obtained after the pressure is released, the adhesive layer X11 returns from an elastically deformed state to an undeformed state and takes a state where it is retracted inward between the base material L1 and the outer edge of the adhesive film X1 newly created in the processing process. That is, in the manufactured adhesive film X1, as shown in Figure 5 for example, a part or all of the area of ​​the outer edge X11a of the adhesive layer X11 is located inward in the film plane direction from the outer edge L1a of the base material L1.

[0163] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0164] [Example 1-1: Preparation of Adhesive Film 1-1] Preparation of (meth)acrylic polymer A In a four-necked flask equipped with a stirring bar, thermometer, nitrogen gas inlet tube, and condenser, 46 parts by weight of 2-ethylhexyl acrylate (2EHA), 40 parts by weight of lauryl acrylate (LA), 5 parts by weight of n-octyl acrylate (NOAA), 7 parts by weight of 4-hydroxybutyl acrylate (4HBA), 2 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 0.05 parts by weight of Irgacure 819 (trade name, manufactured by BASF Corporation) and Irgacure 184 (trade name, manufactured by BASF Corporation), which are photopolymerization initiators, were added. Then, nitrogen gas was introduced and nitrogen purging was performed for about 1 hour while stirring at 28°C. After that, 5 mW / cm² was added. ２ The polymer was polymerized by irradiation with UVA, and the solid content was adjusted to 10% by mass to obtain a (meth)acrylic polymer A solution.

[0165] Preparation of Acrylic Adhesive Composition A: To 100 parts by weight of the obtained (meth)acrylic polymer A solution, 0.1 parts by weight of the crosslinking agent dipentaerythritol hexaacrylate (DPHA), 1 part by weight of the acrylic oligomer (ODM, DCPMA (dicyclopentanyl methacrylate) / MMA (methyl methacrylic acid) (mass ratio) = 60 / 40), and 0.3 parts by weight of the silane coupling agent (product name: KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.) were blended and mixed to prepare Acrylic Adhesive Composition A.

[0166] - Preparation of adhesive film 1-1: Acrylic adhesive composition A is uniformly applied to the surface of a 75 μm thick PET film (transparent substrate, release liner) treated with a silicone release agent, and an illuminance of 5 mW / cm is applied using a black light (manufactured by Toshiba Corporation, product name "FL15BL"). ２ , cumulative light intensity 1300 mJ / cm ２ An adhesive layer was obtained by irradiating with ultraviolet light under the specified conditions. Next, the obtained adhesive layer was peeled off the PET film to obtain adhesive film 1-1. Adhesive film 1-1 corresponds to a "substrate-less adhesive film".

[0167] [Example 1-2: Preparation of Adhesive Film 1-2] Preparation of (meth)acrylic polymer B In a four-necked flask equipped with a stirrer, thermometer, nitrogen gas inlet tube, and condenser, 10 parts by weight of 2-ethylhexyl acrylate (2EHA), 20 parts by weight of butyl acrylate (BA), 60 parts by weight of n-octyl acrylate (NOAA), 8 parts by weight of 4-hydroxybutyl acrylate (4HBA), 2 parts by weight of N-vinyl-2-pyrrolidone (NVP), 0.05 parts by weight of photopolymerization initiators Irgacure 819 (trade name, manufactured by BASF Corporation) and 0.05 parts by weight of Irgacure 184 (trade name, manufactured by BASF Corporation) were added. Then, nitrogen gas was introduced and nitrogen purging was performed for about 1 hour while stirring at 28°C. After that, 5 mW / cm² was added. ２ The polymer was polymerized by UVA irradiation, and the solid content was adjusted to 10% by mass to obtain (meth)acrylic polymer B solution.

[0168] Preparation of Acrylic Adhesive Composition B: To 100 parts by weight of the obtained (meth)acrylic polymer B solution, 0.1 parts by weight of the crosslinking agent dipentaerythritol hexaacrylate (DPHA), 1.5 parts by weight of acrylic oligomer (ODM, DCPMA (dicyclopentanyl methacrylate) / MMA (methyl methacrylic acid) (mass ratio) = 60 / 40), 0.3 parts by weight of silane coupling agent (trade name: KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.02 parts by weight of Irgacure 819 (trade name, manufactured by BASF Corporation) were blended and mixed to prepare Acrylic Adhesive Composition B.

[0169] - Preparation of adhesive film 1-2: Adhesive film 1-2 (substrate-less adhesive film) was prepared in the same manner as in Example 1-1, except that acrylic adhesive composition B was used.

[0170] [Example 1-3: Preparation of Adhesive Film 1-3] Preparation of (meth)acrylic polymer C A four-necked flask equipped with a stirrer, thermometer, nitrogen gas inlet tube, and condenser was charged with 99 parts by weight of butyl acrylate (BA), 1 part by weight of 4-hydroxybutyl acrylate (4HBA), 0.1 parts by weight of 2,2'-azobisisobutyronitrile (AIBN), and 140 parts by weight of toluene. After introducing nitrogen gas while gently stirring and thoroughly purging with nitrogen, the polymerization reaction was carried out for 8 hours while maintaining the liquid temperature in the flask at around 70°C to prepare a (meth)acrylic polymer C solution.

[0171] Preparation of Acrylic Adhesive Composition C: To 100 parts by weight of the obtained (meth)acrylic polymer C solution, 1.2 parts by weight of the crosslinking agent Niper (trade name: Niper BMT, manufactured by NOF Corporation), 0.01 parts by weight of Takenate D110N (trade name: trimethylolpropane / xylylene diisocyanate adduct, manufactured by Mitsui Chemicals, Inc.), 30 parts by weight of oligomer (B-13L), and 0.3 parts by weight of silane coupling agent (trade name: KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.) were blended and mixed to prepare Acrylic Adhesive Composition C.

[0172] The oligomer (B-13L) was prepared as follows: In a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser, 95 parts by weight of butyl acrylate (BA), 2 parts by weight of acrylic acid (AA), 3 parts by weight of methyl acrylate (MA), 0.1 parts by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and 140 parts by weight of toluene were charged. After introducing nitrogen gas while gently stirring and thoroughly purging with nitrogen, the polymerization reaction was carried out for 8 hours while maintaining the temperature of the liquid in the flask at around 70°C to prepare an acrylic oligomer (oligomer B-13L) solution. The weight-average molecular weight of oligomer B-13L was 4500.

[0173] - Preparation of adhesive films 1-3: Acrylic adhesive composition C was uniformly applied to the surface of a 75 μm thick PET film (transparent substrate, release liner) treated with a silicone release agent using a fountain coater. The film was then dried in a 155°C air-circulating constant temperature oven for 2 minutes to form an adhesive layer with a thickness of 150 μm on the surface of the substrate. Next, the obtained adhesive layer was peeled off the PET film to obtain adhesive film 1-3. Adhesive film 1-3 corresponds to a "substrate-less adhesive film".

[0174] [Comparative Example 1: Preparation of Adhesive Films 1-4] Preparation of (meth)acrylic polymer D In a four-necked flask equipped with a stirrer, thermometer, nitrogen gas inlet tube, and condenser, 67 parts by weight of 2-ethylhexyl acrylate (2EHA), 13 parts by weight of N-vinyl-2-pyrrolidone (NVP), 20 parts by weight of hydroxyethyl acrylate (HEA), 0.05 parts by weight of Irgacure 819 (trade name, manufactured by BASF Corporation) and 0.05 parts by weight of Irgacure 184 (trade name, manufactured by BASF Corporation), which are photopolymerization initiators, were added. Then, nitrogen gas was introduced and nitrogen purging was performed for about 1 hour while stirring at 28°C. After that, 5 mW / cm² was added. ２ The polymer was polymerized by UVA irradiation, and the solid content was adjusted to 10% by mass to obtain a (meth)acrylic polymer D solution.

[0175] Preparation of Acrylic Adhesive Composition D: To 100 parts by weight of the obtained (meth)acrylic polymer D solution, 0.3 parts by weight of the crosslinking agent dipentaerythritol hexaacrylate (DPHA), 5.9 parts by weight of the acrylic oligomer (ODM, DCPMA (dicyclopentanyl methacrylate) / MMA (methyl methacrylic acid) (mass ratio) = 60 / 40), and 0.3 parts by weight of the silane coupling agent (product name: KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.) were blended and mixed to prepare Acrylic Adhesive Composition D.

[0176] - Preparation of adhesive film 1-4: Adhesive film 1-4 (substrate-less adhesive film) was prepared in the same manner as in Example 1-1, except that acrylic adhesive composition D was used.

[0177] [Example 2-1: Preparation of Adhesive Film 2-1] Acrylic adhesive composition A was uniformly applied to the surface of a 75 μm thick PET film (transparent substrate, release liner) treated with a silicone release agent using a fountain coater, and dried in a 155°C air-circulating constant temperature oven for 2 minutes to form an adhesive layer with a thickness of 75 μm on the surface of the substrate. Next, the obtained adhesive layer was peeled off from the PET film and attached to both sides of a substrate (product name "RV20", acrylic film, 20 μm thick, manufactured by Toyo Kohan Co., Ltd.) to prepare adhesive film 2-1. Adhesive film 2-1 corresponds to a double-sided adhesive film with a substrate.

[0178] [Example 2-2: Preparation of Adhesive Film 2-2] Adhesive film 2-2 was prepared in the same manner as in Example 2-1, except that the base material was changed to (product name "S10 (25)", PET film, thickness 20 μm, manufactured by Toray Industries, Inc.).

[0179] [Example 2-3: Preparation of Adhesive Film 2-3] Adhesive film 2-3 was prepared in the same manner as in Example 2-1, except that the base material was changed to (product name "TAC (25)", TAC film, thickness 25 μm, manufactured by Toray Industries, Inc.).

[0180] [Evaluation] The adhesive films obtained in the examples and comparative examples were evaluated as follows.

[0181] (Measurement of Storage Modulus G' and Loss Factor (tanδ)) A 1 mm thick test specimen was prepared by taking only the adhesive layer from the adhesive film described in the Examples and Comparative Examples and stacking multiple sheets. A measurement sample, punched out of this test specimen into an 8.0 mm diameter disc, was sandwiched and fixed between parallel plates, and dynamic viscoelasticity measurements were performed using a dynamic viscoelasticity measuring device (ARES-G2) under the following conditions to determine the storage modulus G' at 25°C, the value of the loss factor (tanδ) peak top, and the frequency (Hz) of the loss factor (tanδ) peak top. The results are shown in Tables 1 and 3. - Temperature range: -50 to 150°C - Resolution per digit of frequency: 5 - Angular frequency: ω = 0.1 to 100 rad / sec - Parallel plate: 7.9 mmφ - Distortion: 0.3% A master curve was created using ARES-G2 with 25°C as the reference temperature, and the frequency f value was calculated from f (Hz) = ω / (2π). The storage modulus G' and tanδ at 25°C were then read.

[0182] (Evaluation of impact force) The impact force (N) of the adhesive films obtained in the examples and comparative examples was evaluated by a ball drop test. The results are shown in Tables 1 and 3.

[0183] - Preparation of evaluation samples: For the adhesive films described in the examples and comparative examples, pressure-sensitive paper (manufactured by Fujifilm Corporation, pressure measurement film Prescale for ultra-low pressure) was attached to either (1) one side of the adhesive layer or (2) the side of the adhesive layer opposite to the side to which the substrate was attached, and samples were obtained by laminating the substrate, adhesive layer, and pressure-sensitive paper in that order. The obtained samples were autoclaved (50°C, 0.5 MPa, 15 minutes) to be used as evaluation samples. Note that (1) above corresponds to adhesive films 1-1 and 1-4 of Example 1-1 and Comparative Example 1, and (2) above corresponds to other examples and their adhesive films.

[0184] ・Test Method 1: Set the evaluation samples according to the examples and comparative examples on the stand of the ball drop impact tester (Y in Figure 6). Note that Y1 in Figure 6 is the base material, Y2 is the adhesive layer, and Y3 is the pressure-sensitive paper. In the evaluation samples according to Example 1 and Comparative Example 1, Y1 is not present. 2: Set a 10g steel ball (Y4 in Figure 6) at a height of 30cm (Y5 in Figure 6). 3: Drop the steel ball and measure the impact force with a sensor located below the stand.

[0185] (Evaluation of Reliability) The adhesive films obtained in the examples and comparative examples were stored at 85°C for 240 hours, and the impact force in the ball drop test was measured in the same manner as in the "Evaluation of Impact Force" described above. The impact force before the reliability test (N), the impact force after the reliability test (N), and the value obtained by the following formula (1) are shown in Table 2. [Impact force after reliability test (N)] / [Impact force before reliability test (N)] (1)

[0186]

[0187]

[0188]

[0189] 100 OLED display panel 10R Red OLED layer 10G Green OLED layer 10B Blue OLED layer 11a Transparent electrode (cathode) 11b Back electrode (anode) 12R Red OLED element 12G Green OLED element 12B Blue OLED element 13 Substrate 14 TFT layer 15 Color filter 15R Red colored layer 15G Green colored layer 15B Blue colored layer 16 Black matrix layer W Ambient light G Reflected light C1 First optical path (direct light) C2 Second optical path (reflected light) 17 Bonding layer 200 OLED display device 20 Optical laminate 21 Adhesive layer or adhesive layer 22 Resin layer, glass layer or shock-absorbing layer 23 Hard coat layer or anti-glare layer 24 Adhesive layer or adhesive layer 25 Resin layer, glass layer or shock-absorbing layer 26 Adhesive layer or adhesive layer 27 Resin layer, glass layer or shock-absorbing layer 28 Hard coat layer or anti-glare layer 29 Anti-reflective layer 300 Adhesive film with substrate 301 Adhesive film 302 OLED display device 303 Adhesive film 304 Adhesive film 305 OLED display device 31 Adhesive layer 32 Substrate (resin layer) 33 Release liner X1 Adhesive film X11 Adhesive layer X11a Outer edge of adhesive layer L1 Substrate (resin layer) L1a Outer edge of substrate (resin layer) Y Ball drop impact tester Y1 Substrate Y2 Adhesive layer Y3 Pressure-sensitive paper Y4 Steel ball Y5 Height of steel ball

Claims

1. An adhesive film for use in an OLED display device in which only optical elements with a polarization degree of 95% or less are laminated on the viewing side of the OLED element, the adhesive film having an adhesive layer, wherein the storage modulus of the adhesive layer at 25°C is 1.0 × 10⁻⁶ ４ ~2.0 x 10 ７ An adhesive film for OLED display devices, characterized by being Pa, having a thickness of 300 μm or less, and having an impact force of 800 N or less in a ball drop test.

2. The adhesive film for an OLED display device according to claim 1, wherein the thickness of the adhesive layer is 250 μm or less.

3. The adhesive film for an OLED display device according to claim 1 or 2, wherein the impact force in the ball drop test before and after the reliability test shown below satisfies the following formula (1). • Reliability test: Performed by storing the adhesive film at 85°C for 240 hours. 0.7 ≤ [Impact force after reliability test (N)] / [Impact force before reliability test (N)] ≤ 1.2 (1) 4. The adhesive film for an OLED display device according to claim 1 or 2, comprising a first adhesive layer, a second adhesive layer, and an intermediate layer located between the first and second adhesive layers.

5. The adhesive layer has a frequency of 10 at 25°C. ３ The adhesive film for an OLED display device according to claim 1 or 2, wherein the loss coefficient (tanδ) has a peak in the range of Hz or higher, and the value of the peak top is 1.5 or higher.

6. An OLED display device comprising the adhesive film described in claim 1 or 2, wherein only optical elements with a polarization degree of 95% or less are laminated on the viewing side of the OLED element.

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