Optical laminate for display device and display device using same

Abstract

The present invention provides an optical laminate for a display device, which is capable of suppressing deterioration in display quality of the display device due to barrier property enhancement using silicon oxide. Provided is an optical laminate for a display device with an inorganic oxide layer on a first base material, and a second base material. The first base material side of the barrier film and the second base material are laminated via an adhesive layer. The inorganic oxide layer contains silicon oxide and has a thickness of 30 nm or more. The following conditions are satisfied: the haze of the second base material ≤ the haze of the barrier film; and the thickness of the barrier film ≤ the thickness of the second base material.

Description

Optical laminate for display device and display device using the same

[0001] The present disclosure relates to an optical laminate for a display device and a display device using the same.

[0002] Electronic paper consumes power only when information is rewritten and can maintain display even after power supply is stopped, so it consumes less power than liquid crystal display devices and organic EL display devices. Electronic paper also has excellent properties such as being "excellent in flexibility" and "thin and light."

[0003] Electronic paper is composed of, for example, a rear electrode substrate having a rear substrate and a rear electrode, a transparent electrode substrate having a transparent substrate and a transparent electrode, and a display medium layer disposed between the rear electrode substrate and the transparent electrode substrate.

[0004] The display medium layer of electronic paper is configured, for example, by dispersing a pigment in a filler liquid. Electronic paper allows information displayed on the electronic paper to be rewritten by placing a desired pigment in the display medium layer on the viewer side through voltage control. The display medium layer's information rewriting performance is easily degraded when the filler liquid evaporates or moisture from the outside air invades. Furthermore, electronic paper often uses a plastic film for at least one of the rear substrate and the transparent substrate to achieve thinner, lighter, and more flexible electronic paper. Plastic films have inferior barrier properties compared to glass. Therefore, plastic films with enhanced barrier properties are required. Plastic films with enhanced barrier properties may also be required for display devices other than electronic paper, such as organic electroluminescence (EL) display devices and liquid crystal display devices using wavelength conversion sheets.

[0005] For this reason, optical laminates have been developed in which a layer with good barrier properties is formed on a plastic film. Optical laminates for electronic paper have been proposed in, for example, Patent Documents 1 to 4.

[0006] JP 2019-89311 A JP 2018-180212 A International Publication No. 2017 / 130617 JP 2014-148584 A

[0007] Optical laminates for display devices such as electronic paper are required to have high barrier properties and optical properties. In particular, as electronic paper has progressed from a two-color system of black and white to color, the requirements for optical properties have become stricter in recent years. As a means for achieving high barrier properties and optical properties, the present inventors have investigated using silicon oxide as a material for the barrier layer of optical laminates for display devices such as electronic paper, and increasing the thickness of the barrier layer containing silicon oxide.

[0008] However, when the thickness of the barrier layer containing silicon oxide is increased, minute black dots may be visible within the surface of the optical laminate. If the minute black dots are clearly visible, the display quality of display devices such as electronic paper may be reduced. Patent Documents 1 to 4 do not consider at all the above problems that arise when barrier properties are improved using silicon oxide.

[0009] The present disclosure aims to provide an optical laminate for a display device that can suppress deterioration in the display quality of a display device such as electronic paper when the barrier property is improved by using a silicon oxide, and also aims to provide a display device using the optical laminate for a display device.

[0010] The present disclosure provides the following <1> and <2>: <1> An optical laminate for a display device, comprising: a barrier film having an inorganic oxide layer on a first substrate; and a second substrate, wherein the first substrate side of the barrier film and the second substrate are laminated via an adhesive layer, the inorganic oxide layer contains silicon oxide and has a thickness of 30 nm or more, the haze of the second substrate is equal to or less than the haze of the barrier film, and the thickness of the barrier film is equal to or less than the thickness of the second substrate. <2> A display device, comprising the optical laminate for a display device according to <1>.

[0011] The optical laminate for a display device according to the present disclosure and a display device using the same can suppress deterioration in display quality.

[0012] 1 is a cross-sectional view showing an embodiment of an optical laminate for a display device according to the present disclosure; 2 is a cross-sectional view showing an embodiment of electronic paper according to the present disclosure;

[0013] Hereinafter, embodiments of the present disclosure will be described. In this specification, haze refers to the haze defined in JIS K7136:2000. In this specification, the notation "AA to BB" means AA or more and BB or less. In this specification, the "optical laminate for a display device" may be abbreviated as "optical laminate."

[0014] [Optical Laminate for Display Device] The optical laminate for a display device of the present disclosure comprises a barrier film having an inorganic oxide layer on a first substrate, and a second substrate, wherein the first substrate side of the barrier film and the second substrate are laminated via an adhesive layer, the inorganic oxide layer contains silicon oxide and has a thickness of 30 nm or more, the haze of the second substrate is equal to or less than the haze of the barrier film, and the thickness of the barrier film is equal to or less than the thickness of the second substrate.

[0015] FIG. 1 is a cross-sectional view showing one embodiment of an optical laminate 100 according to the present disclosure. The optical laminate 100 of FIG. 1 includes a barrier film 10 having an inorganic oxide layer 12 on a first substrate 11, and a second substrate 30. In the optical laminate 100 of FIG. 1, the first substrate 11 side of the barrier film 10 and the second substrate 30 are laminated via an adhesive layer 20. In FIG. 1, the barrier film 10 includes an inorganic oxide layer 12 on the first substrate 11, and further includes a coating layer 13 on the inorganic oxide layer 12. FIG. 1 is a schematic cross-sectional view. That is, in FIG. 1, the scale and the like of each layer constituting the optical laminate 100 are simplified for ease of illustration and differ from the actual scale and the like. The same is true for FIG. 2.

[0016] <Characteristics of the Optical Laminate of the Present Disclosure> The optical laminate of the present disclosure is mainly characterized by having the following configurations (1) to (3): (1) The inorganic oxide layer contains silicon oxide and has a thickness of 30 nm or more. (2) The relationship of haze of the second substrate≦haze of the barrier film is satisfied. (3) The relationship of thickness of the barrier film≦thickness of the second substrate is satisfied.

[0017] Hereinafter, the technical concept that the above configurations (1) to (3) can suppress a decrease in the display quality of display devices such as electronic paper will be described. As described in (1) above, the inorganic oxide layer of the optical laminate of the present disclosure contains silicon oxide and has a thickness of 30 nm or more. By using silicon oxide as the inorganic oxide constituting the inorganic oxide layer, it is possible to suppress an increase in the price of the optical laminate. Furthermore, by making the thickness of the inorganic oxide 30 nm or more, it is possible to impart high barrier properties to the optical laminate. However, when the thickness of the inorganic oxide layer containing silicon oxide is increased, the L of the inorganic oxide layer originating from the silicon oxide is increased. ＊ a ＊ b ＊ Color system b ＊ The value tends to be high. Furthermore, when the inorganic oxide layer is formed by a vacuum deposition method or the like, minute black dots may be visible on the inorganic oxide layer. For example, in an inorganic oxide layer formed by a vacuum deposition method, minute black dots are formed due to a splash phenomenon. Since the minute black dots are partial defects during film formation, they are more likely to occur within the surface of the optical laminate as the film formation time increases. In other words, the thicker the inorganic oxide layer, the more likely they are to occur within the surface of the optical laminate. It is difficult to completely eliminate minute black dots. For example, although efforts to reduce the splash phenomenon during vacuum deposition have been made, even at the time of filing this application, it is not possible to completely eliminate the splash phenomenon. On the other hand, even if minute black dots occur in the optical laminate, the barrier property may be able to maintain an acceptable level (since the inorganic oxide layer has a thickness of 30 nm or more, it is believed that the desired barrier property may be maintained even if defects occur in a portion of the thickness direction. Alternatively, it is believed that the desired barrier property may be maintained by filling the defective areas with a coating layer formed on the inorganic oxide layer). In order to improve the yield, it is conceivable to use the optical laminate having minute black dots as a non-defective product. However, as described above, when the thickness of the inorganic oxide layer containing silicon oxide is increased, the L ＊ a ＊ b ＊ Color system b ＊Since the value is high, the optical laminate takes on a yellowish tinge. Furthermore, the aforementioned tiny black dots are easily noticeable against the background of a white display screen of a display device such as electronic paper, which is tinted yellow by the addition of silicon oxide. In particular, since electronic paper has a high proportion of white display, the problem of the tiny black dots being noticeable is likely to occur. As described above, the above-mentioned configuration (1) is excellent in that it easily achieves low cost and high barrier properties, but the presence of the tiny black dots is a factor that reduces the display quality of display devices such as electronic paper. However, the optical laminate of the present disclosure suppresses the degradation of the display quality of display devices such as electronic paper by virtue of the above-mentioned configurations (2) and (3). Below, we will further explain why the above-mentioned configurations (2) and (3) can suppress the degradation of the display quality of display devices such as electronic paper.

[0018] In a display device such as electronic paper, a barrier layer such as an inorganic oxide layer is preferably disposed near a display element such as an electronic paper display element. That is, the optical laminate of the present disclosure is preferably disposed so that the barrier film is closer to the display element than the second substrate. When the optical laminate of the present disclosure is disposed as described above, the barrier film is farther from the viewer than the second substrate. The haze of the second substrate and the haze of the barrier film both have the effect of making minute black dots less visible, but this effect is stronger in components located farther from the viewer. Therefore, the above-mentioned configuration (2) is important for making minute black dots less visible. The inorganic oxide layer and the coating layer described below have extremely low haze values. Therefore, the haze of the barrier film can be said to be essentially the haze of the first substrate. Light diffused by the haze of the barrier film is further diffused depending on the thickness of the second substrate. Therefore, by satisfying the above-mentioned configuration (2) and the above-mentioned configuration (3), minute black dots can be made even less visible. On the other hand, even if the above-mentioned configuration (2) is satisfied, if the above-mentioned configuration (3) is not satisfied, light diffusion according to the thickness of the second substrate will be insufficient, making the tiny black dots more visible. As described above, the above-mentioned configurations (2) and (3) can make the tiny black dots less visible, thereby making it easier to suppress a decrease in the display quality of display devices such as electronic paper. In order to make it easier to suppress a decrease in the display quality of display devices such as electronic paper using the above-mentioned configurations (1) to (3), it is preferable to further include the following configurations (2') and (3'). (2') The relationship of haze of the second substrate < haze of the barrier film is satisfied. (3') The relationship of thickness of the barrier film < thickness of the second substrate is satisfied.

[0019] <Barrier Film> The barrier film must have an inorganic oxide layer on a first substrate. It is preferable that the barrier film further has a coating layer on the inorganic oxide layer. That is, it is preferable that the barrier film has an inorganic oxide layer and a coating layer on a first substrate. In the barrier film, it is preferable that the inorganic oxide layer and the coating layer each be a single layer.

[0020] <<First Substrate>> The first substrate may be a resin film containing one or more resins selected from polyester, triacetyl cellulose, cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyethersulfone, polysulfone, polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyether ketone, acrylic, polycarbonate, polyurethane, amorphous olefin, etc. Among these resin films, stretched polyester films are preferred, and biaxially stretched polyester films are more preferred, from the viewpoints of mechanical strength, dimensional stability, and heat resistance. Examples of polyester films include polyethylene terephthalate films and polyethylene naphthalate films.

[0021] The thickness of the first substrate is preferably 5.0 μm or more, more preferably 8.0 μm or more, and even more preferably 12.0 μm or more. The thickness of the first substrate is preferably 75.0 μm or less, more preferably 50.0 μm or less, and even more preferably 40.0 μm or less.

[0022] In the configuration requirements described herein, when multiple upper limit and lower limit options are shown, it is assumed that the range described is a combination of one selected from the upper limit options and one selected from the lower limit options. For example, embodiments of the thickness range of the first substrate described above include 5.0 μm to 75.0 μm, 5.0 μm to 50.0 μm, 5.0 μm to 40.0 μm, 8.0 μm to 75.0 μm, 8.0 μm to 50.0 μm, 8.0 μm to 40.0 μm, 12.0 μm to 75.0 μm, 12.0 μm to 50.0 μm, and 12.0 μm to 40.0 μm.

[0023] In this specification, the layer thickness, haze, b ＊Unless otherwise specified, the measurement of various parameters such as the value is carried out in an atmosphere at a temperature of 23°C ± 5°C and a relative humidity of 40% to 65%. Furthermore, before measuring the various parameters, the sample is exposed to the atmosphere for 30 minutes to 60 minutes.

[0024] The first substrate preferably has a layer containing a matting agent on at least one surface of the resin film to facilitate satisfying the relationship of haze of the second substrate≦haze of the barrier film. Alternatively, the first substrate preferably contains an internal diffusing agent in the resin film to facilitate satisfying the relationship. General-purpose inorganic particles and organic particles can be used as the matting agent and internal diffusing agent. The haze of the barrier film can be increased by increasing the content of the matting agent or internal diffusing agent, increasing the refractive index difference between the matting agent or internal diffusing agent and the binder resin, or increasing the thickness of the layer containing the matting agent or internal diffusing agent.

[0025] The surface of the first substrate on which the inorganic oxide layer is formed may be subjected to a surface treatment to improve adhesion, etc. Examples of surface treatments include corona discharge treatment, ozone treatment, low-temperature plasma treatment, glow discharge treatment, and oxidation treatment. In addition, an easy-adhesion layer may be formed on the surface of the first substrate on which the inorganic oxide layer is formed.

[0026] <Inorganic Oxide Layer> The inorganic oxide layer must contain silicon oxide. Furthermore, the inorganic oxide layer must have a thickness of 30 nm or more. By containing silicon oxide as the inorganic oxide constituting the inorganic oxide layer, it is possible to suppress an increase in the price of the optical laminate. By making the thickness of the inorganic oxide 30 nm or more, it is possible to impart high barrier properties to the optical laminate. Silicon oxide is an oxide containing silicon. A typical example of silicon oxide is silicon oxide (SiOx) such as silicon dioxide. That is, it is preferable that the inorganic oxide layer contains silicon oxide.

[0027] The total content of silicon and oxygen in the inorganic oxide layer is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more. The inorganic oxide layer may contain elements other than silicon and oxygen as long as the effects of the present disclosure are not impaired.

[0028] To improve the barrier properties, the thickness of the inorganic oxide is preferably 40 nm or more, more preferably 50 nm or more, and even more preferably 55 nm or more. If the thickness of the inorganic oxide layer is too thick, cracks tend to occur in the inorganic oxide layer. Furthermore, when the thickness of the inorganic oxide layer reaches a predetermined thickness, the barrier properties tend to saturate. Therefore, the thickness of the inorganic oxide layer is preferably 200 nm or less, more preferably 150 nm or less, and even more preferably 120 nm or less. The inorganic oxide layer is preferably a single layer.

[0029] The inorganic oxide layer can be formed by, for example, a physical vapor deposition (PVD) method such as vacuum deposition, sputtering, or ion plating, or a chemical vapor deposition (CVD) method such as plasma enhanced chemical vapor deposition, thermal chemical vapor deposition, or photochemical vapor deposition. Among these, the vacuum deposition method is preferred because it has a high deposition rate and good productivity. The PVD method is preferred because it is less likely to introduce carbon into the inorganic oxide layer than the CVD method.

[0030] <<Coating Layer>> The barrier film preferably has a coating layer on the inorganic oxide layer to improve the barrier properties.

[0031] The coating layer preferably contains one or more selected from a water-soluble polymer and a metal alkoxide compound. Of the water-soluble polymer and the metal alkoxide compound, the coating layer more preferably contains one or more selected from the water-soluble polymer, and even more preferably contains one or more selected from the water-soluble polymer and one or more selected from the metal alkoxide compound.

[0032] Examples of water-soluble polymers include polyvinyl alcohol, polyvinylpyrrolidone, and ethylene-vinyl alcohol copolymers, and among these, polyvinyl alcohol and ethylene-vinyl alcohol copolymers are preferred for their barrier properties, with polyvinyl alcohol being more preferred. That is, the coating layer preferably contains one or more selected from polyvinyl alcohol and ethylene-vinyl alcohol copolymers, and more preferably contains polyvinyl alcohol.

[0033] When the coating layer contains a water-soluble polymer and a metal alkoxide-based compound, the content of the water-soluble polymer relative to 100 parts by mass of the total amount of the metal alkoxide-based compounds is preferably 5 parts by mass or more and 500 parts by mass or less, more preferably 7 parts by mass or more and 100 parts by mass or less, and even more preferably 8 parts by mass or more and 50 parts by mass or less.

[0034] Examples of the metal alkoxide-based compound include metal alkoxides, metal alkoxide hydrolysates, and metal alkoxide polymers. The metal alkoxides are M(OR) ｎ In the formula, M represents a metal such as Si, Ti, Al, or Zr, and R represents an alkyl group such as a methyl group or an ethyl group. Specific examples of metal alkoxides include tetramethoxysilane, tetraethoxysilane, and isopropoxyaluminum.

[0035] The coating layer can be formed, for example, by applying a coating liquid containing components constituting the coating layer onto the inorganic oxide layer and drying the coating liquid. The coating liquid may contain additives such as a silane coupling agent, a curing agent, and a dispersant.

[0036] In order to improve the barrier properties, the thickness of the coating layer is preferably 70 nm or more, more preferably 100 nm or more, and even more preferably 150 nm or more. Furthermore, the thickness of the coating layer is preferably 600 nm or less, more preferably 480 nm or less, more preferably 370 nm or less, and even more preferably 300 nm or less. By setting the thickness to 600 nm or less, the optical laminate can be made thinner, and the occurrence of cracks in the coating layer can be easily suppressed.

[0037] The lower limit of the haze of the barrier film is preferably 0.3% or more, more preferably 0.5% or more, and even more preferably 0.8% or more, and the upper limit is preferably 8.0% or less, more preferably 5.0% or less, and even more preferably 3.0% or less. When measuring the haze of the barrier film, the light incident surface is the surface having the inorganic oxide layer relative to the first substrate. By setting the haze of the barrier film to 0.3% or more, minute black dots can be made less visible, which makes it easier to suppress deterioration in the display quality of display devices such as electronic paper. If the haze of the barrier film is too high, the display of the display device such as electronic paper may become blurred and difficult to see. Therefore, by setting the haze of the barrier film to 8.0% or less, it is easier to suppress deterioration in the display quality of display devices such as electronic paper.

[0038] The barrier film preferably has a total light transmittance according to JIS K7361-1:1997 of 80% or more, more preferably 85% or more, and even more preferably 87% or more.

[0039] The thickness of the barrier film is preferably 5.0 μm or more, more preferably 8.0 μm or more, and even more preferably 12.0 μm or more. The thickness of the barrier film is preferably 75.0 μm or less, more preferably 50.0 μm or less, and even more preferably 40.0 μm or less. By making the thickness of the barrier film 5.0 μm or more, the handleability of the barrier film can be easily improved. By making the thickness of the barrier film 75.0 μm or less, it is easy to make display devices such as electronic paper thinner.

[0040] The barrier film is a barrier film that reduces the L based on reflected light when the first substrate side is the light incident surface. ＊ a ＊ b ＊ Color system b ＊ It is preferable that the value is 0.1 or more and 5.0 or less. ＊ The value is more preferably 0.2 or more and 3.0 or less, and even more preferably 0.3 or more and 2.0 or less. ＊ The larger the value, the thicker the inorganic oxide layer containing silicon oxide tends to be. ＊ By making the value 0.1 or more, it is possible to easily improve the barrier properties. ＊ If the value is too large, tiny black dots will be more noticeable. ＊ By setting the value to 5.0 or less, minute black dots can be made less visible, and therefore, deterioration in the display quality of display devices such as electronic paper can be more easily suppressed. ＊ The reflected light used to calculate the value is measured based on geometric condition d of JIS Z8722:2009, including a specular reflection component. <Geometric condition d of JIS Z8722:2009> The sample is irradiated with a single beam of light whose optical axis is angled no more than 10° relative to the normal to the sample surface, and the light reflected in all directions is collected and received. In this case, the irradiated beam of light must not include any rays inclined at an angle of 5° or more relative to its center line.

[0041] The above-mentioned barrier film b＊ The value is the b ＊ In addition, light transmitted through the barrier film is reflected by the display element. For example, in the case of a barrier film for electronic paper, light transmitted through the barrier film is reflected by the electronic paper display element. Therefore, the b ＊ When measuring the value, the reflection of the display element is taken into consideration. Specifically, a sample is prepared by placing a perfectly diffusing standard white reflector on the surface of the barrier film opposite to the light incident surface, and the b value of the barrier film is measured using the sample. ＊ Measure the value. ＊ a ＊ b ＊ The color system is the L color system standardized by the International Commission on Illumination (CIE) in 1976. ＊ a ＊ b ＊ It is based on the color system and is adopted in JIS Z8781-4:2013.

[0042] <Second substrate> The second substrate may be a resin film containing one or more resins selected from polyester, triacetyl cellulose, cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyethersulfone, polysulfone, polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyether ketone, acrylic, polycarbonate, polyurethane, and amorphous olefin. Among these resin films, stretched polyester films are preferred, and biaxially stretched polyester films are more preferred, from the viewpoints of mechanical strength, dimensional stability, and heat resistance. Examples of polyester films include polyethylene terephthalate films and polyethylene naphthalate films. Furthermore, the resin film used as the second substrate is preferably one that can reduce haze.

[0043] The second substrate may have an anti-blocking layer containing a matting agent on at least one surface of the resin film to suppress blocking. As the matting agent, general-purpose inorganic particles and organic particles can be used.

[0044] If the haze of the second substrate is too high, the display of a display device such as electronic paper may become blurred and difficult to see. Therefore, the haze of the second substrate is preferably 5.0% or less, more preferably 3.0% or less, and even more preferably 2.5% or less. The lower limit of the haze of the second substrate is not particularly limited. In order to use a general-purpose resin film as the second substrate, the haze of the second substrate is preferably 0.1% or more, more preferably 0.2% or more, and even more preferably 0.3% or more.

[0045] The ratio of the haze of the barrier film to the haze of the second substrate is preferably 1.05 or more and 5.0 or less, and more preferably 1.10 or more and 3.0 or less. By setting the ratio to 1.05 or more, minute black dots can be made less visible, which makes it easier to suppress deterioration in the display quality of display devices such as electronic paper. By setting the ratio to 5.0 or less, it makes it easier to suppress blurring of the display of display devices such as electronic paper, which makes it easier to suppress deterioration in the display quality of display devices such as electronic paper.

[0046] The thickness of the second substrate is preferably 20.0 μm or more, more preferably 30.0 μm or more, and even more preferably 45.0 μm or more. The thickness of the second substrate is preferably 120.0 μm or less, more preferably 100.0 μm or less, and even more preferably 80.0 μm or less. By making the thickness of the second substrate 20.0 μm or more, it is possible to make the black minute dots less visible, thereby making it easier to suppress deterioration in the display quality of display devices such as electronic paper. By making the thickness of the second substrate 120.0 μm or less, it is easier to suppress blurring of the display of display devices such as electronic paper, thereby making it easier to suppress deterioration in the display quality of display devices such as electronic paper. Furthermore, by making the thickness of the second substrate 120.0 μm or less, it is easier to make display devices such as electronic paper thinner.

[0047] The ratio (thickness of the second substrate) / (thickness of the barrier film) is preferably 1.2 or more and 10.0 or less, more preferably 1.5 or more and 8.0 or less, and even more preferably 2.0 or more and 5.0 or less. By setting the ratio to 1.2 or more, it is possible to make minute black dots less visible, thereby making it easier to suppress deterioration in the display quality of display devices such as electronic paper. By setting the ratio to 10.0 or less, it is easier to suppress blurring of the display of display devices such as electronic paper, thereby making it easier to suppress deterioration in the display quality of display devices such as electronic paper.

[0048] In this specification, the thickness of the second substrate and the barrier film is the average value of the thicknesses measured at any 10 points. The thickness of the second substrate and the barrier film can be measured using a film thickness measuring device. Examples of film thickness measuring devices include Mitutoyo's Digimatic Standard Outside Micrometer (product number: MDC-25SX).

[0049] <Adhesive Layer> The adhesive layer is located between the barrier film and the second substrate, and serves to integrate the barrier film, adhesive layer, and second substrate.

[0050] Examples of adhesives that constitute the adhesive layer include moisture-curing adhesives, heat-curing adhesives, ultraviolet-curing adhesives, heat-sensitive adhesives (for example, hot-melt adhesives), pressure-sensitive adhesives, etc. General-purpose adhesives can be used as these various adhesives.

[0051] The adhesive layer is preferably a layer formed from a curable adhesive to maintain good adhesion over a long period of time. Examples of the curable adhesive include moisture-curable adhesives, heat-curable adhesives, and ultraviolet-curable adhesives. Of these, heat-curable adhesives and ultraviolet-curable adhesives are preferred, and heat-curable adhesives are more preferred.

[0052] Examples of thermosetting adhesives include general-purpose one-component curing adhesives and two-component curing adhesives. Among these, two-component curing polyurethane adhesives are preferred. Two-component curing polyurethane adhesives are adhesives containing a polyol compound and an isocyanate compound.

[0053] The thickness of the adhesive layer is preferably 2 μm or more and 30 μm or less, more preferably 3 μm or more and 20 μm or less, and even more preferably 4 μm or more and 10 μm or less. By making the thickness 2 μm or more, it is possible to easily improve the adhesion between the barrier film and the second substrate. By making the thickness 30 μm or less, it is possible to easily reduce the thickness of display devices such as electronic paper and to easily suppress the generation of stress due to cure shrinkage of the adhesive.

[0054] The adhesive layer preferably has a high total light transmittance and a low haze, and therefore preferably does not contain an internal scattering agent or a visible light absorbing agent.

[0055] <Physical Properties> <Water Vapor Permeability> The optical laminate has a water vapor permeability of 0.02 g / m according to JIS K7129-2:2019. ２ It is preferable that the density is 0.01 g / m or less. ２ It is more preferable that the water vapor permeability is measured at a temperature and humidity of 40°C and a relative humidity of 90%. Furthermore, before measuring the water vapor permeability, the sample to be measured is exposed to an atmosphere at a temperature of 23°C ± 5°C and a relative humidity of 40% to 65% for 30 to 60 minutes. The water vapor permeability can be measured, for example, using a MOCON ultra-high sensitivity water vapor permeability measuring device (product name: AQUATRAN 3) manufactured by Hitachi High-Tech Science Corporation.

[0056] <<Oxygen Permeability>> The optical laminate has an oxygen permeability value according to JIS K7126-2:2006 of 0.5 cc / m ２ The oxygen permeability is preferably 1 / 4 day·atm or less. The temperature and humidity conditions for measuring the oxygen permeability are 23°C and 90% relative humidity. Prior to measuring the oxygen permeability, the sample to be measured is exposed to an atmosphere at a temperature of 23°C±5°C and a relative humidity of 40% to 65% for 30 to 60 minutes. The oxygen permeability can be measured, for example, using an oxygen permeability measuring device (product name: OX-TRAN) manufactured by MOCON Corporation (MOCON method).

[0057] <<Total Light Transmittance>> The optical laminate preferably has a total light transmittance according to JIS K7361-1:1997 of 85% or more, more preferably 87% or more, and even more preferably 89% or more.

[0058] <Layer structure> Examples of the layer structure of the optical laminate of the present disclosure include the following (1) and (2). In the following (1) and (2), " / " means the interface of the layers. (1) Inorganic oxide layer / first substrate / adhesive layer / second substrate (2) Coating layer / inorganic oxide layer / first substrate / adhesive layer / second substrate

[0059] The optical laminate of the present disclosure may have layers other than those described above, as long as the effects of the present disclosure are not impaired.

[0060] The optical laminate of the present disclosure can be used in displays such as electronic paper, liquid crystal displays, EL displays such as organic EL displays and inorganic EL displays, plasma displays, and LED displays such as mini-LED and micro-LED display elements. Liquid crystal displays include liquid crystal displays using a wavelength conversion sheet.

[0061] [Display Device] The display device of the present disclosure includes the above-described optical laminate for a display device of the present disclosure.

[0062] Examples of the display device include electronic paper, liquid crystal display devices, EL display devices such as organic EL display devices and inorganic EL display devices, plasma display devices, LED display devices such as mini LED and micro LED display elements, etc. The liquid crystal display device includes a liquid crystal display device using a wavelength conversion sheet.

[0063] The display device of the present disclosure may be an electronic paper display device, and the electronic paper may include an electronic paper display element and the optical laminate of the present disclosure described above, and the surface of the optical laminate on the barrier film side may be arranged to face the electronic paper display element side.

[0064] Fig. 2 is a cross-sectional view showing one embodiment of electronic paper 300 of the present disclosure. The electronic paper 300 of Fig. 2 includes an electronic paper display element 200 and an optical laminate 100 of the present disclosure. The electronic paper 300 of Fig. 2 is arranged so that the surface of the optical laminate 100 on the barrier film 10 side faces the electronic paper display element 200. In this specification, "the surface of the optical laminate on the barrier film side" means the surface of the optical laminate on the side having the barrier film, when the adhesive layer is used as a reference.

[0065] The electronic paper display element may be a general-purpose electronic paper display element, and may include, for example, a rear electrode substrate having a rear substrate and a rear electrode, a transparent electrode substrate having a transparent substrate and a transparent electrode, and a display medium layer disposed between the rear electrode substrate and the transparent electrode substrate.

[0066] The back electrode substrate, transparent electrode substrate, and display medium layer may be general-purpose back electrode substrate, transparent electrode substrate, and display medium layer. For example, the display medium layer may be appropriately selected depending on the display method of the electronic paper. Examples of display methods for electronic paper include electrophoresis, twist ball, powder migration, liquid crystal display, and electrochromic.

[0067] The electronic paper display element and the optical laminate of the present disclosure are preferably laminated via an adhesive layer, and a general-purpose adhesive can be used as the adhesive constituting the adhesive layer.

[0068] The electronic paper of the present disclosure may have components other than the electronic paper display element and the optical laminate of the present disclosure. Examples of components other than the electronic paper display element and the optical laminate of the present disclosure include a touch panel, an anti-reflection film, an anti-glare film, etc. The touch panel is preferably disposed between the electronic paper display element and the optical laminate of the present disclosure. The anti-reflection film and the anti-glare film are preferably disposed on the opposite side of the optical laminate of the present disclosure from the electronic paper display element.

[0069] The display device of the present disclosure may be a liquid crystal display device, the liquid crystal display device including a backlight and a liquid crystal display element, the backlight including at least one light source that emits primary light, an optical plate that is arranged adjacent to the light source and that guides or diffuses light, and a wavelength conversion sheet that is arranged on the light emission side of the optical plate, and the wavelength conversion sheet includes the optical laminate for a display device.

[0070] The liquid crystal display element and the backlight can be general-purpose ones. Furthermore, the light source and the optical plate constituting the backlight can be general-purpose ones. Examples of wavelength conversion sheets constituting the backlight include those having a first quantum dot protective film, a quantum dot-containing layer, and a second quantum dot protective film in this order. In such wavelength conversion sheets, at least one of the first quantum dot protective film and the second quantum dot protective film is preferably the optical laminate for a display device of the present disclosure. In the wavelength conversion sheet, the optical laminate is preferably arranged so that the surface of the optical laminate facing the barrier film faces the quantum dot-containing layer. A general-purpose quantum dot-containing layer can be used as the quantum dot-containing layer. Of the first quantum dot protective film and the second quantum dot protective film, the protective film that does not use the optical laminate of the present disclosure can be a general-purpose protective film.

[0071] The present disclosure includes the following items <1> to <9>. <1> An optical laminate for a display device, comprising: a barrier film having an inorganic oxide layer on a first substrate; and a second substrate; wherein the first substrate side of the barrier film and the second substrate are laminated via an adhesive layer; the inorganic oxide layer contains silicon oxide and has a thickness of 30 nm or more; the haze of the second substrate is equal to or less than the haze of the barrier film; and the thickness of the barrier film is equal to or less than the thickness of the second substrate. <2> The optical laminate for a display device according to <1>, wherein the haze of the barrier film is 0.3% or more and 8.0% or less. <3> The optical laminate for a display device according to <1> or <2>, wherein the haze of the second substrate is 0.1% or more and 5.0% or less. <4> The optical laminate for a display device according to any one of <1> to <3>, wherein the thickness of the barrier film is 5.0 μm or more and 75.0 μm or less. <5> The optical laminate for a display device according to any one of <1> to <4>, wherein the thickness of the second substrate is 20.0 μm or more and 120.0 μm or less. <6> The optical laminate for a display device according to any one of <1> to <5>, wherein the barrier film has a coating layer on the inorganic oxide layer. <7> The barrier film is configured to reduce L based on reflected light when the first substrate side is a light incident surface. ＊ a ＊ b ＊ Color system b ＊ <8> A display device comprising the optical laminate for a display device according to any one of <1> to <7>. <9> The display device according to <8>, wherein the display device is electronic paper, the electronic paper comprising an electronic paper display element and the optical laminate for a display device, and the surface of the optical laminate for a display device on the barrier film side is disposed on the electronic paper display element side.

[0072] Next, the present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited to these examples. "Parts" and "%" are based on mass unless otherwise specified.

[0073] 1. Measurement and Evaluation The following measurements and evaluations were carried out on the optical laminates for displays of the Examples and Comparative Examples, and the barrier film and second substrate constituting the optical laminates. The results are shown in Table 1. The evaluations or measurements of 1-1 to 1-4 were carried out in an atmosphere at a temperature of 23°C ± 5°C and a relative humidity of 40% to 65%. Furthermore, before the evaluation or measurement, the samples were exposed to the atmosphere for 30 minutes to 60 minutes.

[0074] 1-1. Display Quality of Electronic Paper A white film (haze: 30.0%) was prepared as a pseudo-electronic paper display element. Black dots with a diameter of approximately 100 μm were drawn with a black pen on the barrier film side of the optical laminates of the Examples and Comparative Examples. The black dots were considered to be black dots occurring in the inorganic oxide layer. A sample for evaluation was prepared by overlaying the optical laminate with the drawn black dots on the white film. The optical laminate was positioned so that the barrier film side faced the white film. The sample was visually observed from a distance of 30 cm in a bright room environment, and evaluated by visual observation as to whether the black dots were clearly visible. Twenty healthy individuals in their 20s and 30s were evaluated and ranked according to the following criteria. <Rank Criteria> A: Two or fewer people answered that the black dots were clearly visible. B: Three to five people answered that the black dots were clearly visible. C: 6 to 10 people answered that the black dots were clearly visible. D: 11 or more people answered that the black dots were clearly visible.

[0075] 1-2. Haze Using a haze meter (manufactured by Murakami Color Research Laboratory, product number: HM-150), the haze of the barrier film and second substrate constituting the optical laminates of the Examples and Comparative Examples was measured. When measuring the haze of the barrier film, the light incident surface was the surface on the coating layer side.

[0076] 1-3.b ＊ Samples were prepared by placing a perfectly diffusing standard white reflector on the surface of the barrier film constituting the optical laminate of each of the examples and comparative examples on the coating layer side. The surface of the sample on the first substrate side was used as the light incident surface, and the L value based on the reflected light of the sample was measured. ＊ a ＊ b ＊ Color system b ＊The measurement device used was a spectrophotometer manufactured by JASCO Corporation (product name: V670), and the following accessory units were used: Accessory unit: integrating sphere unit (manufactured by JASCO Corporation, product number: ISN-723) Light source: deuterium lamp (190 to 350 nm), halogen lamp (330 to 2700 nm) Measurement spot diameter: 2 mm

[0077] 1-4. Total Light Transmittance The total light transmittance was measured for the optical laminates of the Examples and Comparative Examples. A haze meter (HM-150, manufactured by Murakami Color Research Laboratory) was used as the measuring device. The light incident surface was the surface on the second substrate side of the optical laminate. A total light transmittance of 85% or more was considered to be acceptable.

[0078] 1-5. Water Vapor Permeability The water vapor permeability values ​​of the optical laminates of the Examples and Comparative Examples were measured according to JIS K7129-2:2019. The measurement device used was a MOCON ultra-high sensitivity water vapor permeability measuring device (product name: AQUATRAN 3) manufactured by Hitachi High-Tech Science Corporation. The temperature and humidity conditions for measuring the water vapor permeability were 40°C and 90% relative humidity. Furthermore, before measuring the water vapor permeability, the measurement sample was exposed to an atmosphere with a temperature of 23°C ± 5°C and a relative humidity of 40% to 65% for 30 to 60 minutes. When the water vapor permeability was 0.02 g / m ２ ・The passing level is less than 1 day.

[0079] 2. Preparation of an optical laminate for a display device [Example 1] A substrate was prepared as a first substrate, which was a biaxially stretched PET film having a layer containing a matting agent formed on one side thereof. The first substrate had a total thickness of 23 μm, with the biaxially stretched PET film having a thickness of 22 μm and the layer containing the matting agent having a thickness of 1 μm. The haze of the first substrate was 1.5%. Silicon oxide (SiO ) was deposited by vacuum deposition on the side of the first substrate that did not have the layer containing the matting agent. ２) was vapor-deposited to form an inorganic oxide layer (thickness: 70 nm). Next, the following coating layer-forming coating liquid was applied onto the inorganic oxide layer by gravure printing, and the resulting coating layer was heated at 180°C for 60 seconds to form a 300 nm-thick coating layer, thereby obtaining a barrier film used in Example 1. Next, a two-component curing polyurethane adhesive was applied to one surface of a second substrate (material: biaxially oriented PET film, thickness: 75 μm, haze: 0.8%) by gravure printing and dried to form an adhesive layer with a thickness of 7 μm, thereby obtaining a laminate having an adhesive layer on the second substrate. Next, the adhesive layer side of the laminate was opposed to the first substrate side side of the barrier film, and the laminate and the barrier film were dry-laminated to obtain an optical laminate for a display device of Example 1.

[0080] <Preparation of Coating Liquid for Forming Covering Layer> Solution A was prepared by mixing tetraethoxysilane into a solution (pH 2.2) containing water, isopropyl alcohol, and 0.5N hydrochloric acid while cooling to 10°C. Separately, solution B was prepared by mixing polyvinyl alcohol with a saponification value of 99% or more and isopropyl alcohol. Solutions A and B were mixed to prepare a coating liquid for forming a covering layer (solid content: 5% by mass). In the coating liquid for forming a covering layer, the mass ratio of tetraethoxysilane to polyvinyl alcohol was 29:4.

[0081] [Comparative Example 1] The first substrate was changed to a biaxially stretched PET film (thickness: 75 μm, haze: 0.8%; the second substrate in Example 1). In addition, the second substrate was changed to a biaxially stretched PET film (thickness: 23 μm, haze: 1.5%; the first substrate in Example 1). Other than the above-mentioned changes, an optical laminate for a display device in Comparative Example 1 was obtained in the same manner as in Example 1. The thicknesses of the inorganic oxide layer and the coating layer in the barrier films of Comparative Examples 1 to 6 were the same as those of the inorganic oxide layer and the coating layer in the barrier film in Example 1.

[0082] [Example 2] A substrate comprising a biaxially stretched PET film with a layer containing a matting agent formed on one side thereof was prepared as the first substrate. The first substrate had a biaxially stretched PET film thickness of 22 μm and a layer containing a matting agent thickness of 3 μm, for a total thickness of 25 μm. The haze of the first substrate was 2.6%. The first substrate of Example 2 had a higher haze than the first substrate of Example 1 due to the large surface irregularities of the matting layer. Furthermore, a biaxially stretched PET film (thickness: 75 μm, haze: 0.9%) was prepared as the second substrate. An optical laminate for a display device of Example 2 was obtained in the same manner as Example 1, except that the above-described materials were used for the first substrate and the second substrate. The thicknesses of the inorganic oxide layer and coating layer in Examples 2 and 3 were the same as those of the inorganic oxide layer and coating layer of the barrier film of Example 1.

[0083] [Example 3] A biaxially stretched PET film (thickness: 50 μm, haze: 1.0%) was prepared as the first substrate. A biaxially stretched PET film (thickness: 75 μm, haze: 0.9%) was prepared as the second substrate. An optical laminate for a display device of Example 3 was obtained in the same manner as in Example 1, except that the above-mentioned materials were used as the first substrate and the second substrate.

[0084] [Example 4] A barrier film used in Example 4 was obtained in the same manner as in Example 1, except that the thickness of the inorganic oxide layer was changed to 40 nm. An optical laminate for a display device of Example 4 was obtained in the same manner as in Example 1, except that the above-mentioned material was used as the barrier film.

[0085] [Example 5] A barrier film used in Example 5 was obtained in the same manner as in Example 2, except that the thickness of the inorganic oxide layer was changed to 100 nm. In addition, a particle-containing biaxially stretched PET film (thickness: 50 μm, haze: 2.1%) was prepared as the second substrate. An optical laminate for a display device of Example 5 was obtained in the same manner as in Example 1, except that the above-mentioned materials were used for the barrier film and the second substrate.

[0086] [Example 6] A biaxially stretched PET film (thickness: 50 μm, haze: 1.0%) was prepared as the second substrate. An optical laminate for a display device of Example 6 was obtained in the same manner as in Example 1, except that the above-mentioned material was used as the second substrate.

[0087] [Example 7] A biaxially stretched PET film (thickness: 100 μm, haze: 1.1%) was prepared as the second substrate. An optical laminate for a display device of Example 7 was obtained in the same manner as in Example 1, except that the above-mentioned material was used as the second substrate.

[0088] [Comparative Example 2] A biaxially stretched PET film (thickness: 23 μm, haze: 0.3%) was prepared as the first substrate. A biaxially stretched PET film (thickness: 75 μm, haze: 1.2%) was prepared as the second substrate. An optical laminate for a display device of Comparative Example 2 was obtained in the same manner as in Example 1, except that the above-mentioned materials were used as the first substrate and the second substrate.

[0089] [Comparative Example 3] A biaxially stretched PET film (thickness: 23 μm, haze: 0.9%) was prepared as the first substrate. A biaxially stretched PET film (thickness: 50 μm, haze: 1.0%) was prepared as the second substrate. An optical laminate for a display device of Comparative Example 3 was obtained in the same manner as in Example 1, except that the above-mentioned materials were used as the first substrate and the second substrate.

[0090] [Comparative Example 4] A biaxially stretched PET film (thickness: 23 μm, haze: 0.9%) was prepared as the first substrate. A biaxially stretched PET film (thickness: 50 μm, haze: 2.8%) containing particles was prepared as the second substrate. An optical laminate for a display device of Comparative Example 4 was obtained in the same manner as in Example 1, except that the above-mentioned materials were used as the first substrate and the second substrate.

[0091] [Comparative Example 5] A biaxially stretched PET film (thickness: 50 μm, haze: 1.0%) was prepared as the first substrate. A biaxially stretched PET film (thickness: 23 μm, haze: 1.1%) was prepared as the second substrate. An optical laminate for a display device of Comparative Example 5 was obtained in the same manner as in Example 1, except that the above-mentioned materials were used as the first substrate and the second substrate.

[0092] [Comparative Example 6] A biaxially stretched PET film (thickness: 23 μm, haze: 0.3%) was prepared as the first substrate. A biaxially stretched PET film (thickness: 23 μm, haze: 1.1%) was prepared as the second substrate. An optical laminate for a display device of Comparative Example 6 was obtained in the same manner as in Example 1, except that the above-mentioned materials were used as the first substrate and the second substrate.

[0093] [Comparative Example 7] A barrier film used in Comparative Example 7 was obtained in the same manner as in Example 1, except that the thickness of the inorganic oxide layer was changed to 40 nm. In addition, a particle-containing biaxially stretched PET film (thickness: 50 μm, haze: 2.8%) was prepared as the second substrate. An optical laminate for a display device of Comparative Example 7 was obtained in the same manner as in Example 1, except that the above-mentioned materials were used for the barrier film and the second substrate.

[0094]

[0095] From the results in Table 1, it can be confirmed that the optical laminates for a display device of the examples have good barrier properties and can suppress deterioration of display quality.

[0096] 10: Barrier film 11: First substrate 12: Inorganic oxide layer 13: Coating layer 20: Adhesive layer 30: Second substrate 100: Optical laminate for display device 200: Electronic paper display element 300: Electronic paper

Claims

1. An optical laminate for a display device, comprising: a barrier film having an inorganic oxide layer on a first substrate; and a second substrate, wherein the first substrate side of the barrier film and the second substrate are laminated via an adhesive layer, the inorganic oxide layer contains silicon oxide and has a thickness of 30 nm or more, the haze of the second substrate is less than or equal to the haze of the barrier film, and the thickness of the barrier film is less than or equal to the thickness of the second substrate.

2. The optical laminate for a display device according to claim 1, wherein the haze of the barrier film is 0.3% or more and 8.0% or less.

3. The optical laminate for a display device according to claim 1, wherein the haze of the second substrate is 0.1% or more and 5.0% or less.

4. The optical laminate for a display device according to claim 1, wherein the barrier film has a thickness of 5.0 μm or more and 75.0 μm or less.

5. The optical laminate for a display device according to claim 1, wherein the thickness of the second base material is 20.0 μm or more and 120.0 μm or less.

6. The optical laminate for a display device according to claim 1, wherein the barrier film has a coating layer on the inorganic oxide layer.

7. The barrier film has an L based on reflected light when the first substrate side is a light incident surface. ＊ a ＊ b ＊ Color space b ＊ The optical laminate for a display device according to claim 1 , wherein the value is 0.1 or more and 5.0 or less.

8. A display device comprising the optical laminate for a display device according to any one of claims 1 to 7.

9. The display device according to claim 8, wherein the display device is electronic paper, the electronic paper including an electronic paper display element and the optical laminate for the display device, and the surface of the optical laminate for the display device facing the barrier film is disposed on the electronic paper display element side.

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