Optical laminate for display device and display device using same

Abstract

The present disclosure provides an optical laminate for a display device capable of suppressing a decrease in display quality of a display device when barrier properties are improved using a silicon oxide. An optical laminate for a display device, the optical laminate having a barrier film and a second substrate, the barrier film having an inorganic oxide layer on a first substrate, the first substrate side of the barrier film and the second substrate being laminated with an adhesive layer interposed therebetween, the inorganic oxide layer containing a silicon oxide and having a thickness of 30 nm or more, and the inorganic oxide layer containing a silicon oxide having 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.

Description

Technical Field

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

[0002] E-paper consumes power only when rewriting information, and its display remains active even after power is cut off, thus minimizing power consumption compared to liquid crystal and organic EL displays. Furthermore, e-paper offers excellent properties such as flexibility, thinness, and lightness.

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

[0004] The display medium layer of electronic paper, for example, consists of a pigment dispersed in a filling liquid. Electronic paper uses voltage control to position the desired pigment in the display medium layer toward the viewer, allowing the information displayed on the electronic paper to be rewritten. The display medium layer can easily degrade when the filling liquid evaporates or moisture from the outside air intrudes, degrading the rewriting performance of the information. Furthermore, to achieve thinness, lightness, and flexibility, electronic paper often uses a plastic film for at least one of the back substrate and the transparent substrate. Plastic film has inferior barrier properties to glass. Therefore, plastic films with improved barrier properties are required.

[0005] In display devices other than electronic paper, such as organic EL display devices and liquid crystal display devices using a wavelength conversion sheet, there is sometimes a demand for a plastic film with improved barrier properties.

[0006] Therefore, an optical laminate having a layer with good barrier properties formed on a plastic film has been developed. For example, Patent Documents 1 to 4 have proposed optical laminates for electronic paper.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2019-89311

[0010] Patent Document 2: Japanese Patent Application Publication No. 2018-180212

[0011] Patent Document 3: International Publication No. 2017 / 130617

[0012] Patent Document 4: Japanese Patent Application Laid-Open No. 2014-148584 Summary of the Invention

[0013] Problems to be solved by the invention

[0014] Optical laminates for display devices such as electronic paper are required to have high barrier properties and optical characteristics. In particular, in electronic paper, as colorization has been advanced from the black and white color system, the requirements for optical properties have become increasingly stringent in recent years. As a means of achieving high barrier properties and optical characteristics, the present inventors have studied the use of silicon oxide as a material for the barrier layer of optical laminates for display devices such as electronic paper, and have increased the thickness of the barrier layer containing silicon oxide.

[0015] However, when the thickness of the barrier layer containing silicon oxide is increased, tiny black dots may be visually recognized within the surface of the optical laminate. If these tiny black dots are clearly visible, the display quality of a display device such as electronic paper may be reduced.

[0016] Patent Documents 1 to 4 do not investigate the above-mentioned problems that arise when silicon oxide is used to improve barrier properties.

[0017] The present disclosure aims to provide an optical laminate for display devices that can suppress degradation of display quality of electronic paper and other display devices when silicon oxide is used to improve barrier properties. Another object of the present disclosure is to provide a display device using the optical laminate for display devices.

[0018] Means for solving problems

[0019] The present disclosure provides the following <1> ~ <2> .

[0020] <1> An optical laminate for a display device, wherein:

[0021] The optical layered body for a display device includes a barrier film and a second substrate, wherein the barrier film includes an inorganic oxide layer on a first substrate.

[0022] The first substrate side of the barrier film is laminated with the second substrate via an adhesive layer.

[0023] The inorganic oxide layer comprises silicon oxide and has a thickness of 30 nm or more.

[0024] The haze of the second substrate is less than or equal to the haze of the barrier film,

[0025] The thickness of the barrier film is less than or equal to the thickness of the second substrate.

[0026] <2> A display device including the optical layered body for a display device according to <1> above.

[0027] Effects of the Invention

[0028] The optical layered body for a display device of the present disclosure and a display device using the same can suppress degradation of display quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a cross-sectional view showing one embodiment of the optical layered body for a display device of the present disclosure.

[0030] Figure 2 is a cross-sectional view showing one embodiment of the electronic paper of the present disclosure. DETAILED DESCRIPTION

[0031] Hereinafter, embodiments of the present disclosure will be described.

[0032] In this specification, haze refers to haze according to JIS K7136: 2000. In this specification, the expression "AA to BB" refers to AA or more and BB or less. In this specification, an "optical laminate for a display device" may be simply referred to as an "optical laminate."

[0033] [Optical laminate for display device]

[0034] The optical layered body for a display device disclosed herein comprises a barrier film and a second substrate, wherein the barrier film comprises an inorganic oxide layer on a first substrate.

[0035] The first substrate side of the barrier film is laminated with the second substrate via an adhesive layer.

[0036] The inorganic oxide layer comprises silicon oxide and has a thickness of 30 nm or more.

[0037] The haze of the second substrate is less than or equal to the haze of the barrier film,

[0038] The thickness of the barrier film is less than or equal to the thickness of the second substrate.

[0039] Figure 1 1 is a cross-sectional view showing one embodiment of the optical layered body 100 of the present disclosure. Figure 1 The optical layered body 100 includes a barrier film 10 having an inorganic oxide layer 12 on a first substrate 11 and a second substrate 30 . Figure 1 In the optical laminate 100, the first substrate 11 side of the barrier film 10 and the second substrate 30 are laminated via the adhesive layer 20. Figure 1 In the embodiment, the barrier film 10 includes an inorganic oxide layer 12 on a first substrate 11 , and further includes a coating layer 13 on the inorganic oxide layer 12 .

[0040] Figure 1 is a schematic cross-sectional view. Figure 1 In the figures, the scales of the layers constituting the optical layered body 100 are schematically shown for ease of illustration and are different from the actual scales. Figure 2 The same is true.

[0041] <Features of the Optical Layered Body of the Present Disclosure>

[0042] The main features of the optical layered body disclosed in the present invention are the following structures (1) to (3).

[0043] (1) The inorganic oxide layer contains silicon oxide and has a thickness of 30 nm or more.

[0044] (2) The relationship of haze of the second substrate ≤ haze of the barrier film is satisfied.

[0045] (3) The relationship of the thickness of the barrier film ≤ the thickness of the second substrate is satisfied.

[0046] Hereinafter, the technical concept of suppressing the degradation of the display quality of a display device such as electronic paper by the above-mentioned configurations (1) to (3) will be described.

[0047] As described in (1) above, the inorganic oxide layer of the optical laminate of the present disclosure comprises silicon oxide and has a thickness of 30 nm or greater. By using silicon oxide as the inorganic oxide constituting the inorganic oxide layer, it is possible to suppress price increases in the optical laminate. In addition, by setting the thickness of the inorganic oxide to 30 nm or greater, it is possible to impart high barrier properties to the optical laminate.

[0048] However, if the thickness of the inorganic oxide layer containing silicon oxide is increased, the b* value of the L*a*b* color system of the inorganic oxide layer tends to become higher due to the silicon oxide. In addition, when the inorganic oxide layer is formed by a vacuum evaporation method or the like, black tiny dots are sometimes seen in the inorganic oxide layer. For example, in the inorganic oxide layer formed by the vacuum evaporation method, black tiny dots are formed due to the splashing phenomenon. The black tiny dots are local defects during film formation, so the longer the film forming time, the easier it is to produce black tiny dots in the surface of the optical laminate. In other words, the more the thickness of the inorganic oxide layer increases, the easier it is to produce black tiny dots in the surface of the optical laminate. It is difficult to completely eliminate the black tiny dots. For example, the reduction of the splashing phenomenon of vacuum evaporation has been studied, but the splashing phenomenon cannot be completely eliminated at the time of application of this application.

[0049] On the other hand, even if tiny black dots are generated in the optical laminate, the barrier properties can sometimes be maintained at a qualified level (it is believed that since the thickness of the inorganic oxide layer is more than 30 nm, even if defects are generated in a part of the thickness direction, the prescribed barrier properties can sometimes be maintained. Alternatively, it is believed that by filling the defective parts with a coating layer formed on the inorganic oxide layer, the prescribed barrier properties can sometimes be maintained.). In order to improve the yield rate, it is considered to use an optical laminate with tiny black dots as a qualified product. However, as mentioned above, if the thickness of the inorganic oxide layer containing silicon oxide is thickened, the b* value of the L*a*b* color system becomes higher due to silicon oxide, so the optical laminate has a yellow tint. Moreover, the aforementioned tiny black dots are easy to become obvious relative to the background of the yellow hue of silicon oxide added to the screen of the display device such as electronic paper for white display. In particular, the proportion of white display of electronic paper is high, so it is easy to have the problem of obvious tiny black dots.

[0050] As described above, the configuration (1) is excellent in terms of easily achieving low cost and high barrier properties, but the presence of tiny black dots is a major factor in reducing the display quality of electronic paper and other display devices. However, the optical layered body disclosed herein, through the configurations (2) and (3), suppresses the reduction in display quality of electronic paper and other display devices.

[0051] The following further describes the reason why the reduction in display quality of a display device such as electronic paper can be suppressed by satisfying the above-mentioned (2) and (3).

[0052] In a display device such as electronic paper, a barrier layer such as an inorganic oxide layer is preferably configured near a display element such as an electronic paper display element. That is, the optical laminate of the present invention is preferably configured in a manner such that the barrier film is closer to the display element than the second substrate. If the optical laminate of the present invention is configured as described above, the barrier film is farther away from the visual identifier than the second substrate. The haze of the second substrate and the haze of the barrier film both play a role in making it difficult to visually identify the tiny black dots, but the role of the component at a position far from the visual identifier becomes stronger. Therefore, in order to make the tiny black dots difficult to be visually identified, the composition of the above (2) is important. It should be noted that the values ​​of the haze of the inorganic oxide layer and the coating layer described later are extremely low. Therefore, it can be said that the haze of the barrier film is essentially the haze of the first substrate.

[0053] Light diffused by the haze of the barrier film is further diffused depending on the thickness of the second substrate. Therefore, by satisfying both the configuration (2) and the configuration (3), the black microdots can be made less visible. On the other hand, even if the configuration (2) is satisfied but the configuration (3) is not, the diffusion of light corresponding to the thickness of the second substrate becomes insufficient, making the black microdots more visible.

[0054] As described above, by the configurations of (2) and (3), it is possible to make the black minute dots difficult to be visually recognized, thereby easily suppressing degradation in the display quality of a display device such as electronic paper.

[0055] In order to more easily suppress degradation of display quality of a display device such as electronic paper by the above-mentioned configurations (1) to (3), it is preferable to further include the following configurations (2') and (3').

[0056] (2') The relationship of haze of the second substrate < haze of the barrier film is satisfied.

[0057] (3') The relationship of the thickness of the barrier film < the thickness of the second substrate is satisfied.

[0058] <Barrier Film>

[0059] The barrier film needs to have an inorganic oxide layer on a first substrate. The barrier film preferably further has a coating layer on the inorganic oxide layer. That is, the barrier film preferably has an inorganic oxide layer and a coating layer on the first substrate. In the barrier film, the inorganic oxide layer and the coating layer are preferably each a single layer.

[0060] <<First Base Material>>

[0061] Examples of the first substrate include resin films comprising one or more resins selected from polyester, triacetyl cellulose, cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyethersulfone, polysulfone, polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyetherketone, acrylic acid, polycarbonate, polyurethane, and amorphous olefin.

[0062] 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 the polyester film include polyethylene terephthalate films and polyethylene naphthalate films.

[0063] 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.

[0064] In the components described in this specification, when multiple upper and lower limit options are provided, embodiments of a range formed by combining one selected from the upper limit option with one selected from the lower limit option are described. For example, embodiments of the range of the thickness 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.

[0065] In this specification, measurements of various parameters such as layer thickness, haze, and b* value are performed in an atmosphere of 23°C ± 5°C and a relative humidity of 40% to 65%, unless otherwise specified. Furthermore, prior to measuring various parameters, the sample is exposed to this atmosphere for 30 minutes to 60 minutes.

[0066] To facilitate the relationship of haze of the second substrate ≤ haze of the barrier film, the first substrate preferably has a layer containing a matting agent on at least one side of the resin film. Alternatively, to facilitate the relationship, the first substrate preferably contains an internal diffusing agent in the resin film.

[0067] As the matting agent and the internal diffusing agent, general-purpose inorganic particles and organic particles can be used.

[0068] 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.

[0069] In order to improve adhesion, etc., the surface of the first substrate on the side where the inorganic oxide layer is formed may be subjected to a surface treatment. Examples of surface treatments include corona discharge treatment, ozone treatment, low-temperature plasma treatment, glow discharge treatment, and oxidation treatment. Furthermore, an easy-adhesion layer may be formed on the surface of the first substrate on the side where the inorganic oxide layer is formed.

[0070] <<Inorganic Oxide Layer>>

[0071] The inorganic oxide layer must contain silicon oxide. Furthermore, the thickness of the inorganic oxide layer must be at least 30 nm. Including silicon oxide as the inorganic oxide constituting the inorganic oxide layer can suppress price increases for the optical laminate. By setting the inorganic oxide thickness to at least 30 nm, the optical laminate can be endowed with high barrier properties.

[0072] Silicon oxide is an oxide containing silicon. A representative example of silicon oxide is silicon oxide (SiOx) such as silicon dioxide. That is, the inorganic oxide layer preferably contains silicon oxide.

[0073] 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 within a range that does not inhibit the effects of the present disclosure.

[0074] In order to further 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.

[0075] If the inorganic oxide layer is too thick, cracks are likely to form in the inorganic oxide layer. Furthermore, when the inorganic oxide layer reaches a predetermined thickness, its 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.

[0076] The inorganic oxide layer is preferably a single layer.

[0077] The inorganic oxide layer can be formed, for example, by physical vapor deposition (PVD) methods such as vacuum evaporation, sputtering, and ion plating, or chemical vapor deposition (CVD) methods such as plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition. Of these, vacuum evaporation is preferred due to its high evaporation speed and good productivity. PVD is preferred over CVD because it is difficult for carbon to be mixed into the inorganic oxide layer.

[0078] <<Coating layer>>

[0079] In order to further improve the barrier properties, the barrier film preferably has a coating layer on the inorganic oxide layer.

[0080] The coating layer preferably comprises one or more selected from a water-soluble polymer and a metal alkoxide compound. The coating layer more preferably comprises one or more selected from a water-soluble polymer and a metal alkoxide compound, and further preferably comprises one or more selected from a water-soluble polymer and one or more selected from a metal alkoxide compound.

[0081] Examples of water-soluble polymers include polyvinyl alcohol, polyvinyl pyrrolidone, and ethylene-vinyl alcohol copolymers. Among these, polyvinyl alcohol and ethylene-vinyl alcohol copolymers are preferred due to their barrier properties, with polyvinyl alcohol being more preferred. Specifically, the coating layer preferably comprises one or more selected from polyvinyl alcohol and ethylene-vinyl alcohol copolymers, with polyvinyl alcohol being more preferred.

[0082] When the coating layer contains a water-soluble polymer and a metal alkoxide compound, the content of the water-soluble polymer is preferably from 5 parts by mass to 500 parts by mass, more preferably from 7 parts by mass to 100 parts by mass, and further preferably from 8 parts by mass to 50 parts by mass, relative to 100 parts by mass of the total amount of the metal alkoxide compound.

[0083] Examples of the metal alkoxide compounds include metal alkoxides, metal alkoxide hydrolysates, and metal alkoxide polymers.

[0084] Metal alkoxides are composed of M(OR) n A compound represented by the general formula: wherein 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.

[0085] The coating layer can be formed, for example, by applying a coating solution containing components constituting the coating layer onto the inorganic oxide layer and drying the coating solution. The coating solution may contain additives such as a silane coupling agent, a curing agent, and a dispersant.

[0086] 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.

[0087] 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 further preferably 300 nm or less. By setting the thickness to 600 nm or less, the optical laminate can be made thinner and cracks in the coating layer can be easily suppressed.

[0088] The lower limit of the haze of the barrier film is preferably 0.3% or greater, more preferably 0.5% or greater, and even more preferably 0.8% or greater. 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.

[0089] By setting the haze of the barrier film to 0.3% or more, it is possible to make the tiny black dots less visible, thereby more easily suppressing a decrease in the display quality of a display device such as electronic paper.

[0090] When the haze of the barrier film is too high, the display of display devices such as e-paper sometimes becomes blurred and difficult to see. Therefore, by setting the haze of the barrier film to 8.0% or less, it is possible to more easily suppress the deterioration of the display quality of display devices such as e-paper.

[0091] The total light transmittance of the barrier film according to JIS K7361-1:1997 is preferably 80% or more, more preferably 85% or more, and further preferably 87% or more.

[0092] The thickness of the barrier film is preferably 5.0 μm or more, more preferably 8.0 μm or more, and further 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 further preferably 40.0 μm or less.

[0093] By setting the thickness of the barrier film to 5.0 μm or more, it is possible to easily improve the processability of the barrier film. By setting the thickness of the barrier film to 75.0 μm or less, it is possible to easily thin the display device such as e-paper.

[0094] For the barrier film, preferably, when the first substrate side is the light incident surface, the b* value in the L*a*b* color system based on the reflected light is 0.1 or more and 5.0 or less. The b* value is more preferably 0.2 or more and 3.0 or less, and further preferably 0.3 or more and 2.0 or less.

[0095] The larger the b* value of the barrier film, the greater the tendency for the thickness of the inorganic oxide layer containing silicon oxide to be larger. Therefore, by setting the b* value of the barrier film to 0.1 or more, it is possible to easily achieve good barrier properties. On the other hand, if the b* value of the barrier film is too large, the minute black dots tend to become more obvious. Therefore, by setting the b* value of the barrier film to 5.0 or less, it is possible to make the minute black dots less visually recognizable, and thus it is possible to more easily suppress the deterioration of the display quality of display devices such as e-paper.

[0096] In this specification, the reflected light on which the b* value is calculated is measured in a manner that includes the specular reflection component based on the geometric condition d of JIS Z8722:2009.

[0097] <Geometric condition d of JIS Z8722:2009>

[0098] Irradiate the specimen with a single light beam whose optical axis does not exceed 10° from the normal line of the specimen surface, and collect and receive the light reflected in all directions. In addition, in this case, the irradiation light beam does not include light rays having an inclination of 5° or more with respect to its center line.

[0099] The b* value of the aforementioned barrier film is the b* value of reflected light. Furthermore, light passing through the barrier film is reflected by the display element. For example, in the case of a barrier film for electronic paper, light passing through the barrier film is reflected by the electronic paper display element. Therefore, when measuring the b* value of the barrier film, the reflection from the display element is taken into account. Specifically, a sample is prepared in which a fully diffused standard white reflector is arranged on the surface of the barrier film opposite to the light incident surface, and the b* value of the barrier film is measured using this sample.

[0100] The L*a*b* color system is based on the L*a*b* color system standardized by the International Commission on Illumination (CIE) in 1976 and is adopted in JIS Z8781-4:2013.

[0101] <Second Base Material>

[0102] As the second substrate, there can be mentioned a resin film comprising one or more resins selected from polyester, triacetyl cellulose, cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyethersulfone, polysulfone, polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyetherketone, acrylic acid, polycarbonate, polyurethane and amorphous olefin.

[0103] Among these resin films, stretched polyester films are preferred, and biaxially stretched polyester films are more preferred, from the perspectives of mechanical strength, dimensional stability, and heat resistance. Examples of polyester films include polyethylene terephthalate films and polyethylene naphthalate films. Furthermore, the resin film serving as the second substrate is preferably one that can reduce haze.

[0104] In order to suppress blocking, the second substrate may have an anti-blocking layer containing a matting agent on at least one surface of the resin film. As the matting agent, general-purpose inorganic particles and organic particles can be used.

[0105] If the haze of the second substrate is too high, the display of a display device such as electronic paper may become blurry 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.

[0106] 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.

[0107] The haze of the barrier film / 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.

[0108] By setting the ratio to 1.05 or greater, tiny black dots can be made less visible, thereby more easily suppressing degradation in the display quality of electronic paper or other display devices. By setting the ratio to 5.0 or less, blurring of the display of electronic paper or other display devices can be easily suppressed, thereby more easily suppressing degradation in the display quality of electronic paper or other display devices.

[0109] 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.

[0110] By setting the thickness of the second substrate to 20.0 μm or more, the tiny black dots can be made more difficult to be visually discerned, thereby more easily suppressing the degradation of the display quality of a display device such as electronic paper. By setting the thickness of the second substrate to 120.0 μm or less, it is easier to suppress the blurring of the display of a display device such as electronic paper, thereby more easily suppressing the degradation of the display quality of a display device such as electronic paper. In addition, by setting the thickness of the second substrate to 120.0 μm or less, it is easier to make a display device such as electronic paper thinner.

[0111] The ratio of the thickness of the second substrate to the thickness of the barrier film is preferably 1.2 to 10.0, more preferably 1.5 to 8.0, and even more preferably 2.0 to 5.0.

[0112] By setting the ratio to 1.2 or greater, tiny black dots can be made less visible, thereby more easily suppressing degradation in the display quality of electronic paper or other display devices. By setting the ratio to 10.0 or less, blurring of the display of electronic paper or other display devices can be easily suppressed, thereby more easily suppressing degradation in the display quality of electronic paper or other display devices.

[0113] In this specification, the thickness of the second substrate and the barrier film is defined as the average thickness of 10 arbitrary locations. The thickness of the second substrate and the barrier film can be measured using a film thickness gauge. Examples of such a film thickness gauge include a digital standard outside micrometer (Model: MDC-25SX) manufactured by Mitutoyo.

[0114] <Adhesive Layer>

[0115] The adhesive layer is located between the barrier film and the second substrate, and has the function of integrating the barrier film, the adhesive layer, and the second substrate.

[0116] Examples of the adhesive constituting the adhesive layer include moisture-curing adhesives, heat-curing adhesives, ultraviolet-curing adhesives, heat-sensitive adhesives (eg, hot-melt adhesives), and pressure-sensitive adhesives. For these various adhesives, general-purpose adhesives can be used.

[0117] In order to ensure good adhesion over a long period of time, the adhesive layer is preferably formed from a curing adhesive. Examples of curing adhesives include moisture-curing adhesives, thermosetting adhesives, and UV-curing adhesives. Among these, thermosetting adhesives and UV-curing adhesives are preferred, and thermosetting adhesives are more preferred.

[0118] Examples of thermosetting adhesives include general-purpose one-component curing adhesives and two-component curing adhesives. Of these, two-component curing polyurethane adhesives are preferred. Two-component curing polyurethane adhesives are adhesives containing a polyol compound and an isocyanate compound.

[0119] 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.

[0120] A thickness of 2 μm or greater facilitates good adhesion between the barrier film and the second substrate. A thickness of 30 μm or less facilitates thinning of electronic paper and other display devices, and reduces stress caused by adhesive shrinkage during curing.

[0121] The adhesive layer preferably has a high total light transmittance and a low haze. Therefore, the adhesive layer preferably does not contain an internal scattering agent or a visible light absorber.

[0122] <Physical properties>

[0123] <<Water Vapor Transmission Rate>>

[0124] The water vapor permeability of the optical layered body according to JIS K7129-2:2019 is preferably 0.02 g / m 2 Less than 0.01g / m 2 Less than one day.

[0125] The temperature and humidity conditions for measuring water vapor permeability are 40°C and 90% relative humidity. Prior to measuring water vapor permeability, the sample for measurement is exposed to an atmosphere of 23°C ± 5°C and a relative humidity of 40% to 65% for 30 minutes to 60 minutes.

[0126] The water vapor permeability can be measured using, for example, a MOCON ultra-high-sensitivity water vapor permeability measuring device (trade name: AQUATRAN 3) manufactured by Hitachi High-Tech Science Corporation.

[0127] <<Oxygen Transmission Rate>>

[0128] The value of oxygen permeability of the optical laminate according to JIS K7126-2:2006 is preferably 0.5 cc / m 2 ·day·atm or less.

[0129] The temperature and humidity conditions for measuring oxygen permeability were 23°C and 90% relative humidity. Prior to measuring oxygen permeability, the sample was exposed to an atmosphere of 23°C ± 5°C and a relative humidity of 40% to 65% for 30 minutes to 60 minutes.

[0130] The oxygen permeability can be measured, for example, using an oxygen permeability measuring apparatus manufactured by MOCON (trade name: OX-TRAN) (MOCON method).

[0131] <<Total Light Transmittance>>

[0132] The total light transmittance of the optical layered body according to JIS K7361-1:1997 is preferably 85% or more, more preferably 87% or more, and even more preferably 89% or more.

[0133] <Layered Structure>

[0134] Examples of the laminated structure of the optical layered body of the present disclosure include the following (1) and (2). In the following (1) and (2), " / " refers to the interface between layers.

[0135] (1) Inorganic oxide layer / first substrate / adhesive layer / second substrate

[0136] (2) Coating layer / inorganic oxide layer / first substrate / adhesive layer / second substrate

[0137] The optical layered body of the present disclosure may have layers other than those described above, within a range not hindering the effects of the present disclosure.

[0138] The optical laminate disclosed herein can be used in electronic paper, liquid crystal displays, EL displays such as organic and inorganic EL displays, plasma displays, and LED displays such as miniature LEDs and micro-LEDs. Liquid crystal displays include those using wavelength conversion sheets.

[0139] [Display device]

[0140] The display device of the present disclosure includes the optical laminate for a display device of the present disclosure.

[0141] Examples of display devices include electronic paper, liquid crystal display devices, EL display devices such as organic EL display devices and inorganic EL display devices, plasma display devices, and LED display devices such as miniature LED and micro LED display elements. Liquid crystal display devices include those using a wavelength conversion sheet.

[0142] The display device of the present disclosure may be electronic paper including an electronic paper display element and the optical layered body of the present disclosure, wherein the barrier film side of the optical layered body is arranged to face the electronic paper display element.

[0143] Figure 2 is a cross-sectional view showing one embodiment of the electronic paper 300 of the present disclosure. Figure 2 The electronic paper 300 includes an electronic paper display element 200 and the optical laminate 100 of the present disclosure. Figure 2 The electronic paper 300 is arranged such that the surface of the optical laminate 100 on the barrier film 10 side faces the electronic paper display element 200 side.

[0144] In this specification, "the surface of the optical layered body on the barrier film side" means the surface of the optical layered body on the side having the barrier film when the adhesive layer is used as a reference.

[0145] As the electronic paper display element, a general electronic paper display element can be used. The electronic paper display element includes, for example, a back electrode substrate having a back substrate and a back electrode, a transparent electrode substrate having a transparent substrate and a transparent electrode, and a display medium layer provided between the back electrode substrate and the transparent electrode substrate.

[0146] As the back electrode substrate, the transparent electrode substrate and the display medium layer, general-purpose back electrode substrates, transparent electrode substrates and display medium layers can be used.

[0147] For example, the display medium layer can be appropriately selected according to the display method of the electronic paper, such as electrophoresis, twisting ball, powder transfer, liquid crystal, and electrochromic display.

[0148] The electronic paper display element and the optical laminate of the present disclosure are preferably laminated via an adhesive layer. As the adhesive constituting the adhesive layer, a general-purpose adhesive can be used.

[0149] The electronic paper disclosed herein may include components other than the electronic paper display element and the optical laminate disclosed herein. Components other than the electronic paper display element and the optical laminate disclosed herein include a touch panel, an anti-reflection film, an anti-glare film, and the like. The touch panel is preferably disposed between the electronic paper display element and the optical laminate disclosed herein. The anti-reflection film and the anti-glare film are preferably disposed on the side of the optical laminate disclosed herein opposite to the electronic paper display element.

[0150] In the display device disclosed herein, the display device may be a liquid crystal display device, which includes a backlight source and a liquid crystal display element, and the backlight source includes: at least one light source that emits primary light; an optical plate that is arranged adjacent to the light source and is used for guiding or diffusing light; and a wavelength conversion sheet that is arranged on the light emitting side of the optical plate, and the wavelength conversion sheet includes an optical laminate for the display device.

[0151] The liquid crystal display element and the backlight can use a general-purpose liquid crystal display element and backlight. In addition, the light source and the optical plate constituting the backlight can use a general-purpose light source and optical plate.

[0152] Examples of wavelength conversion sheets constituting backlights include those comprising, in this order, a first quantum dot protective film, a quantum dot-containing layer, and a second quantum dot protective film. In such wavelength conversion sheets, at least one of the first quantum dot protective film and the second quantum dot protective film is preferably an optical laminate for a display device disclosed herein. Preferably, within the wavelength conversion sheet, the optical laminate is arranged such that the barrier film-side surface of the optical laminate faces the quantum dot-containing layer.

[0153] The quantum dot-containing layer may be a general-purpose quantum dot-containing layer. Of the first quantum dot protective film and the second quantum dot protective film, the protective film not using the optical laminate of the present disclosure may be a general-purpose protective film.

[0154] This disclosure includes the following <1> ~ <9> .

[0155] <1> An optical laminate for a display device, wherein:

[0156] The optical layered body for a display device includes a barrier film and a second substrate, wherein the barrier film includes an inorganic oxide layer on a first substrate.

[0157] The first substrate side of the barrier film is laminated with the second substrate via an adhesive layer.

[0158] The inorganic oxide layer comprises silicon oxide and has a thickness of 30 nm or more.

[0159] The haze of the second substrate is less than or equal to the haze of the barrier film,

[0160] The thickness of the barrier film is less than or equal to the thickness of the second substrate.

[0161] <2> according to <1> In the optical laminate for a display device, the barrier film has a haze of 0.3% to 8.0%.

[0162] <3> according to <1> or <2> In the optical layered body for a display device, the haze of the second substrate is 0.1% or more and 5.0% or less.

[0163] <4> according to <1> ~ <3> The optical laminate for a display device according to any one of the preceding claims, wherein the barrier film has a thickness of 5.0 μm to 75.0 μm.

[0164] <5> according to <1> ~ <4> In any one of the optical layered bodies for display devices, the second substrate has a thickness of 20.0 μm to 120.0 μm.

[0165] <6> according to <1> ~ <5> The optical laminate for a display device according to any one of the preceding claims, wherein the barrier film has a coating layer on the inorganic oxide layer.

[0166] <7> according to <1> ~ <6> The optical layered body for a display device according to any one of the preceding claims, wherein the barrier film has a b* value of 0.1 to 5.0 based on L*a*b* colorimetric system based on reflected light when the first substrate side is the light incident surface.

[0167] <8> A display device comprising <1> ~ <7> The optical laminate for a display device described in any one of the preceding claims.

[0168] <9> according to <8> The display device, wherein

[0169] The display device is electronic paper,

[0170] The electronic paper includes an electronic paper display element and the optical stack for a display device, and is arranged so that a surface of the optical stack for a display device on the barrier film side faces the electronic paper display element.

[0171] Example

[0172] Next, the present disclosure will be described in more detail with reference to Examples, but the present disclosure is not limited to these Examples. Unless otherwise specified, "parts" and "%" are based on mass.

[0173] 1. Measurement and evaluation

[0174] The optical layered bodies for display devices of Examples and Comparative Examples, and the barrier films and second substrates constituting the optical layered bodies were subjected to the following measurements and evaluations.

[0175] The evaluation or measurement of 1-1 to 1-4 was performed in an atmosphere with a temperature of 23°C ± 5°C and a relative humidity of 40% to 65%. The sample was exposed to the above atmosphere for 30 minutes to 60 minutes before the evaluation or measurement.

[0176] 1-1. E-paper display quality

[0177] A white film (haze: 30.0%) was prepared as a simulated 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 Examples and Comparative Examples. These black dots were considered to be black dots generated in the inorganic oxide layer.

[0178] An optical layered body having black dots drawn thereon was superimposed on the white film to prepare a sample for evaluation. The optical layered body was arranged so that the barrier film side faced the white film side.

[0179] The samples were visually observed from a distance of 30 cm in a bright room environment to visually evaluate whether the black dots were clearly visible. The evaluators were 20 healthy people aged 20 to 30 years old, and the evaluation was performed according to the following criteria.

[0180] <Level Standards>

[0181] A: Less than 2 people answered that they could clearly visually recognize the black dots.

[0182] B: The number of people who answered that they could clearly visually recognize the black dot was 3 or more and 5 or less.

[0183] C: The number of people who answered that they could clearly visually recognize the black dots was 6 or more and 10 or less.

[0184] D: 11 or more people answered that they could clearly visually recognize the black dots.

[0185] 1-2. Haze

[0186] The haze of the barrier film and the second substrate constituting the optical laminates of Examples and Comparative Examples was measured using a haze meter (Murakami Color Research Laboratory, Model: HM-150). The light incident surface when measuring the haze of the barrier film was the surface on the coating layer side.

[0187] 1-3. b* value

[0188] Samples were prepared in which a fully diffuse standard white reflector was placed on the coating layer side of the barrier films constituting the optical laminates of Examples and Comparative Examples. The first substrate-side surface of these samples served as the light incident surface, and the b* value of the samples based on the L*a*b* colorimetric system was measured for reflected light. A spectrophotometer (trade name: V670) manufactured by JASCO Corporation was used as the measurement apparatus, with the following units used as accessory units.

[0189] Accessory unit: Integrating sphere unit (made by JASCO Corporation, model: ISN-723)

[0190] Light source: Deuterium lamp (190-350nm), halogen lamp (330-2700nm)

[0191] ·Measurement spot diameter: 2mm

[0192] 1-4. Total light transmittance

[0193] The total light transmittance of the optical layered bodies of the Examples and Comparative Examples was measured using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory). The light incident surface was the surface of the optical layered body facing the second substrate. A total light transmittance of 85% or greater was considered acceptable.

[0194] 1-5. Water vapor permeability

[0195] For the optical laminates of the embodiments and comparative examples, the water vapor permeability values ​​based on JIS K7129-2: 2019 were measured. The measuring device used was the MOCON ultra-high sensitivity water vapor permeability measuring device (trade name: AQUATRAN 3) produced by Hitachi High-Tech Science. The temperature and humidity conditions for measuring the water vapor permeability were set to 40°C and a relative humidity of 90%. In addition, before the measurement of the water vapor permeability, the sample for measurement was exposed to an atmosphere with a temperature of 23°C ± 5°C and a relative humidity of 40% to 65% for 30 minutes to 60 minutes. The water vapor permeability was 0.02 g / m 2 ·Those who complete the test for day or less are considered qualified.

[0196] 2. Preparation of optical laminates for display devices

[0197] [Example 1]

[0198] A first substrate was prepared, comprising a biaxially oriented PET film with a matting agent layer formed on one surface. The biaxially oriented PET film had a thickness of 22 μm, the matting agent layer had a thickness of 1 μm, and the total thickness was 23 μm. The haze of the first substrate was 1.5%.

[0199] Silicon oxide (SiO 2 ) was deposited by vacuum deposition on the surface of the first substrate that did not have the layer containing the matting agent, thereby forming an inorganic oxide layer (thickness: 70 nm).

[0200] Next, the following coating liquid for forming a covering layer was applied on the inorganic oxide layer by gravure printing and heat-treated at 180° C. for 60 seconds to form a covering layer having a thickness of 300 nm. This provided the barrier film used in Example 1.

[0201] Next, a two-component curable 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 a 7 μm thick adhesive layer, thereby obtaining a laminate having an adhesive layer on the second substrate. Subsequently, the laminate and the barrier film were dry-laminated, with the adhesive layer side of the laminate facing the first substrate side of the barrier film, to obtain the optical laminate for a display device of Example 1.

[0202] <Preparation of coating liquid for forming covering layer>

[0203] Tetraethoxysilane was added to a solution (pH 2.2) containing water, isopropyl alcohol, and 0.5N hydrochloric acid while cooling it to 10°C to prepare Solution A. Separately, Solution B was prepared by mixing polyvinyl alcohol (with a saponification value of 99% or higher) and isopropyl alcohol. Solutions A and B were mixed to prepare a coating solution for forming a covering layer (solids content: 5% by mass). The mass ratio of tetraethoxysilane to polyvinyl alcohol in the coating solution was 29:4.

[0204] [Comparative Example 1]

[0205] The first substrate was replaced with a biaxially stretched PET film (thickness: 75 μm, haze: 0.8%; the second substrate of Example 1). Furthermore, the second substrate was replaced with a biaxially stretched PET film (thickness: 23 μm, haze: 1.5%; the first substrate of Example 1). Except for the above changes, the same procedures as in Example 1 were followed to obtain an optical laminate for a display device of Comparative Example 1.

[0206] The thicknesses of the inorganic oxide layer and the coating layer of the barrier films of Comparative Examples 1 to 6 were the same as those of the barrier film of Example 1.

[0207] [Example 2]

[0208] As the first substrate, a substrate having a layer containing a matting agent formed on one surface of a biaxially stretched PET film was prepared. In the first substrate, the thickness of the biaxially stretched PET film was 22 μm, the thickness of the layer containing the matting agent was 3 μm, and the total thickness was 25 μm. The haze of the first substrate was 2.6%. Since the surface of the matting layer of the first substrate of Example 2 was large, the haze was greater than that of the first substrate of Example 1. In addition, as the second substrate, a biaxially stretched PET film (thickness: 75 μm, haze: 0.9%) was prepared. Except for using the above materials as the first substrate and the second substrate, the same operation as in Example 1 was carried out to obtain an optical laminate for a display device of Example 2.

[0209] The thicknesses of the inorganic oxide layer and the coating layer in Examples 2 and 3 were the same as those of the barrier film in Example 1.

[0210] [Example 3]

[0211] A biaxially stretched PET film (thickness: 50 μm, haze: 1.0%) was prepared as the first substrate. Furthermore, a biaxially stretched PET film (thickness: 75 μm, haze: 0.9%) was prepared as the second substrate. The same procedures as in Example 1 were followed, except that the above materials were used as the first and second substrates, to obtain an optical layered body for a display device according to Example 3.

[0212] [Example 4]

[0213] The 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. The optical layered body 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.

[0214] [Example 5]

[0215] The 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. Furthermore, a biaxially stretched PET film (thickness: 50 μm, haze: 2.1%) containing particles was prepared as a second substrate. The optical layered body for a display device of Example 5 was obtained in the same manner as in Example 1, except that these materials were used as the barrier film and the second substrate.

[0216] [Example 6]

[0217] As the second substrate, a biaxially stretched PET film (thickness: 50 μm, haze: 1.0%) was prepared. An optical layered body for a display device of Example 6 was obtained in the same manner as in Example 1 except that the above material was used as the second substrate.

[0218] [Example 7]

[0219] As the second substrate, a biaxially stretched PET film (thickness: 100 μm, haze: 1.1%) was prepared. An optical layered body for a display device of Example 7 was obtained in the same manner as in Example 1 except that the above material was used as the second substrate.

[0220] [Comparative Example 2]

[0221] A biaxially stretched PET film (thickness: 23 μm, haze: 0.3%) was prepared as the first substrate. Furthermore, a biaxially stretched PET film (thickness: 75 μm, haze: 1.2%) was prepared as the second substrate. The same procedures as in Example 1 were followed, except that the above materials were used as the first and second substrates, to obtain an optical laminate for a display device according to Comparative Example 2.

[0222] [Comparative Example 3]

[0223] A biaxially stretched PET film (thickness: 23 μm, haze: 0.9%) was prepared as the first substrate. Furthermore, a biaxially stretched PET film (thickness: 50 μm, haze: 1.0%) was prepared as the second substrate. The same procedures as in Example 1 were followed, except that the above materials were used as the first and second substrates, to obtain an optical layered body for a display device according to Comparative Example 3.

[0224] [Comparative Example 4]

[0225] A biaxially stretched PET film (thickness: 23 μm, haze: 0.9%) was prepared as the first substrate. Furthermore, a biaxially stretched PET film containing particles (thickness: 50 μm, haze: 2.8%) was prepared as the second substrate. An optical layered body for a display device according to Comparative Example 4 was obtained in the same manner as in Example 1, except that the above materials were used as the first and second substrates.

[0226] [Comparative Example 5]

[0227] A biaxially stretched PET film (thickness: 50 μm, haze: 1.0%) was prepared as the first substrate. Furthermore, a biaxially stretched PET film (thickness: 23 μm, haze: 1.1%) was prepared as the second substrate. The same procedures as in Example 1 were followed, except that the above materials were used as the first and second substrates, to obtain an optical laminate for a display device according to Comparative Example 5.

[0228] [Comparative Example 6]

[0229] A biaxially stretched PET film (thickness: 23 μm, haze: 0.3%) was prepared as the first substrate. Furthermore, a biaxially stretched PET film (thickness: 23 μm, haze: 1.1%) was prepared as the second substrate. The same procedures as in Example 1 were followed, except that the above materials were used as the first and second substrates, to obtain an optical layered body for a display device according to Comparative Example 6.

[0230] [Comparative Example 7]

[0231] The 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. Furthermore, a biaxially stretched PET film (thickness: 50 μm, haze: 2.8%) containing particles was prepared as a second substrate. The optical layered body for a display device of Comparative Example 7 was obtained in the same manner as in Example 1, except that these materials were used as the barrier film and the second substrate.

[0232] [Table 1]

[0233]

[0234] From the results in Table 1, it was confirmed that the optical layered bodies for display devices of Examples had good barrier properties and could suppress degradation of display quality.

[0235] Explanation of symbols

[0236] 10: Barrier film

[0237] 11: The first base material

[0238] 12: Inorganic oxide layer

[0239] 13: Coating layer

[0240] 20: Adhesive layer

[0241] 30: Second base material

[0242] 100: Optical laminate for display device

[0243] 200: Electronic paper display components

[0244] 300: Electronic paper

Claims

1. An optical laminate for a display device, wherein: The optical layered body for a display device includes a barrier film and a second substrate, wherein the barrier film includes an inorganic oxide layer on a first substrate. The first substrate side of the barrier film is laminated with the second substrate via an adhesive layer. The inorganic oxide layer comprises 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, 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 barrier film has a haze of 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 second substrate has a thickness of 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 optical laminate for a display device according to claim 1, wherein The barrier film has a b* value of 0.1 to 5.0 based on a L*a*b* colorimetric system based on reflected light when the first substrate side is a light incident surface. 8 . A display device comprising the optical layered body for a display device according to claim 1 .

9. The display device according to claim 8, wherein The display device is electronic paper, The electronic paper includes an electronic paper display element and the optical stack for a display device, and is arranged so that a surface of the optical stack for a display device on the barrier film side faces the electronic paper display element.

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