JP7434759B2 - display device - Google Patents

Description

The present invention relates to a display device.

In recent years, the use of image display devices such as liquid crystal displays (LCDs) and organic EL display devices (organic electroluminescence display devices) has expanded, and they are now being used in televisions, monitors, smartphones, car navigation systems, digital cameras, etc. It's being used.

A liquid crystal display device generally includes a color filter, a counter substrate, and a liquid crystal cell portion having a liquid crystal layer sandwiched therebetween (for example, Patent Document 1). Furthermore, since the liquid crystal display device is non-emissive, it requires a light source such as a backlight, and displays are performed using light emitted from the light source.

Further, as an organic EL display device, one in which an organic EL display element substrate having an organic EL display element and a color filter are combined, an RGB coloring method, etc. are known (for example, Patent Document 2). An organic EL display element is based on a laminated structure of an anode/organic EL layer/cathode, and emits light when a current flows through the organic EL display element. This causes the image to be displayed on the display screen.

Japanese Patent Application Publication No. 2015-179219 Japanese Patent Application Publication No. 2006-228705

The above-mentioned organic EL display device has a problem in that the brightness and color tone within the display screen become uneven locally or between the center and the periphery, and the visibility deteriorates due to conspicuous reflected light. are beginning to be reported. Similar reports have also been made when the display device is used in a vehicle or the like.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a display device with excellent visibility.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention found that various performances such as brightness, color, and reflection directionality become uneven in local areas within the display screen. The reason why visibility decreases due to non-uniformity of various performances near the center and near the edges of the screen is that the temperature inside the display device becomes locally non-uniform, or the temperature inside the display device as a whole becomes uneven. They discovered that this is caused by the optical film inside the display device being deformed by heat due to high temperatures, and were able to solve this problem.
The causes of high temperatures inside the display device include heat generated from the light source when displaying images on the display screen, heat generated by the light emission of organic EL display elements, and the display device being exposed to high temperature environments such as inside a car in summer. It is possible that it may be placed.

The present invention provides the following [1] to [2].
[1] A display device comprising a display element, an optical film including a thermally conductive layer disposed on the light emitting surface side of the display element, and a heat dissipating member thermally grounded from a peripheral edge of the thermally conductive layer.
[2] A display device comprising a display element and an optical film including a radiant heat reflecting layer, which is disposed on the light-emitting surface side of the display element.

According to the present invention, a display device with excellent visibility can be provided.

1 is a schematic cross-sectional view showing an example of a display device according to Embodiment A of the present invention. FIG. 3 is a plan view of an example of a thermally conductive layer of Embodiment A. FIG. 2 is a schematic cross-sectional view showing an example of a display device according to Embodiment B of the present invention.

<Embodiment A>
A display device according to Embodiment A of the present invention includes a display element, an optical film including a thermally conductive layer disposed on the light-emitting surface side of the display element, and a heat dissipating layer that is thermally grounded from a peripheral edge of the thermally conductive layer. It is characterized by having a member.
Hereinafter, the optical film including the thermally conductive layer of Embodiment A may be referred to as "optical film A."
Embodiment A mainly suppresses the temperature inside the display device from becoming locally non-uniform or the temperature inside the display device from becoming high as a whole due to the conduction effect of free electrons.

FIG. 1 is a schematic cross-sectional view showing an example of a display device of Embodiment A. In the display device 1 of FIG. 1, an optical film 13 in which a transparent base material 11 and a heat conductive layer 12 are laminated in this order is provided on the light-emitting surface side of the display element 10. The thermally conductive layer 12 is thermally grounded from its peripheral portion 14 to a heat dissipating member 16 via a conductive wire 15 .

[Thermal earth]
For thermal grounding, as shown in FIG. 1, there is a method in which the peripheral portion 14 of the thermally conductive layer 12, which is outside the image display area, is connected to the heat dissipating member 16. At this time, the peripheral portion 14 of the heat conductive layer 12 and the heat radiating member 16 may be connected directly or may be connected via the conductive wire 15. Further, it is preferable that the conductive wire 15 is fixed to the peripheral portion 14 of the heat conductive layer 12 using a conductive adhesive material having conductivity due to free electrons, such as silver paste, carbon tape, or metal tape.
The thermal ground may be located at one location on the peripheral edge portion 14 of the heat conductive layer 12, or may be located at multiple locations.

(heat dissipation member)
The heat radiating member is a member for radiating heat generated inside the display device from the heat conductive layer to the outside of the display device.
The heat dissipating member is not particularly limited as long as it has a conduction effect due to free electrons, and examples include metals such as gold, silver, copper, aluminum, iron, nickel, and chromium, and alloys of these metals (e.g. , nichrome), and composite members containing these metals and metal alloys.

From the viewpoint of more effective thermal earthing, the heat dissipating member preferably has a volume resistivity of 1.0×10 ⁶ Ωm or less, more preferably 1.0×10 ³ Ωm or less, and 1. It is more preferably 0 Ωm or less, and particularly preferably 1.0×10 ⁻³ Ωm or less.
Further, in Embodiment A, it is preferable that the heat dissipation member also serves as a casing (outer frame) of the display device.

(Optical film A)
Optical film A includes at least a thermally conductive layer. It is preferable that the optical film A has a thermally conductive layer on a transparent base material. The optical film A may further have a functional layer described below.

(thermal conductive layer)
The heat conductive layer used in Embodiment A has the function of dissipating heat generated inside the display device to the outside of the display device, and transmitting heat from the high temperature region to the low temperature region in the high temperature region and low temperature region generated inside the display device. This layer has a function of making the temperature uniform, and has visible light transmittance to the extent that the displayed image on the display panel can be viewed.
Examples of the thermally conductive layer include a layer containing a metal material and in which adjacent metal materials have contact points, and in particular, a layer in which adjacent metal nanowires are dispersed in a transparent resin so as to have contact points with each other. A metal nanowire layer or a mesh-like layer formed of a metal material is preferable. As the transparent resin, for example, a cover resin described below can be used.

When the thermal conductive layer is formed as described above, the heat generated inside the display device is efficiently radiated to the outside of the display device due to the movement of free electrons in the thermal conductive layer, and the heat generated inside the display device is efficiently radiated to the outside of the display device. In the high temperature region and low temperature region, heat is efficiently transferred from the high temperature region to the low temperature region, resulting in a uniform temperature and preventing the occurrence of heat unevenness. By preventing the occurrence of thermal unevenness, deformation of the optical film is suppressed. Note that a metal oxide film such as ITO, which is commonly used as a transparent conductive layer, has a low movement of free electrons, and therefore cannot have a high heat conduction function.
In order to improve heat conduction performance, it is preferable that the free electron density is large (high electrical conductivity). Therefore, the surface resistivity of the thermally conductive layer is preferably 250 Ω/□ or less, more preferably 150 Ω/□ or less, and even more preferably 100 Ω/□ or less.
The surface resistivity can be measured according to JIS K7194:1994 (resistivity test method using the 4-point needle method for conductive plastics) using, for example, a resistivity meter Loresta manufactured by Mitsubishi Chemical Corporation.

Examples of the metal material include metals such as gold, silver, copper, iron, nickel, and aluminum, and alloys thereof. From the viewpoint of thermal conductivity, silver, copper, and aluminum are preferred, and silver is more preferred. Further, the shape of the metal material is not particularly limited, but metal nanowires are preferred from the viewpoints of transparency and thermal conductivity. In particular, silver nanowires are preferable because they have high near-infrared reflectance and are easy to suppress heat generation, and also have excellent bending resistance and can be easily applied to foldable displays.

The average diameter of the metal nanowires is preferably 200 nm or less. By setting the average diameter of the metal nanowires to 200 nm or less, it is possible to suppress an increase in haze. A more preferable lower limit of the average diameter of the metal nanowires is 10 nm or more from the viewpoint of thermal conductivity, and a more preferable range of the average diameter of the metal nanowires is 15 nm or more and 180 nm or less.
It is preferable that the length of the metal nanowire is 1 μm or more. By setting the length of the metal nanowire to 1 μm or more, a long heat conduction path can be formed with one metal nanowire. A preferable upper limit of the length of the metal nanowire is 500 μm or less from the viewpoint of optical transparency.
The length of the metal nanowire is more preferably 3 μm or more and 300 μm or less, and even more preferably 10 μm or more and 30 μm or less.

The diameter of the metal nanowire is determined by measuring the diameter of 50 metal nanowires at 1000 to 500,000 times using a transmission electron microscope (TEM), and finding the average value of the diameters of the 50 metal nanowires. shall be. The length of the metal nanowire is determined by, for example, measuring the length of 50 metal nanowires at 1000 to 500,000 times magnification using a scanning electron microscope (SEM), and calculating the average value of the length of the 50 metal nanowires. shall be sought as.

The method for producing metal nanowires may be any known method and is not particularly limited.

The metal nanowire layer may contain other components such as a cover resin in addition to the metal nanowires.
The cover resin covers the metal nanowires to the extent that electrical conduction can be obtained from the surface of the metal nanowire layer, thereby preventing the metal nanowires from detaching from the metal nanowire layer, and improving the durability and scratch resistance of the metal nanowire layer. In order to improve this, it is included in the metal nanowire layer as necessary.

The thickness of the cover resin is preferably 10 nm or more and less than 300 nm, more preferably 50 nm or more and 200 nm or less.
The film thickness of the cover resin is determined by a cross-sectional photograph of the conductive layer taken using a scanning electron microscope (SEM), scanning transmission electron microscope (STEM), or transmission electron microscope (TEM) at a magnification of 1000 to 500,000 times. The thickness is measured at 10 random locations from the beginning, and the average value of the 10 measured thicknesses is taken as the average value.

The cover resin is not particularly limited and can be used as long as it has light transmittance, and includes those containing a polymer (cured product, crosslinked product) of a polymerizable compound. The cover resin may contain a solvent drying resin in addition to the polymer of the polymerizable compound. Examples of the polymerizable compound include ionizing radiation polymerizable compounds and/or thermally polymerizable compounds.

The ionizing radiation polymerizable compound has at least one ionizing radiation polymerizable functional group in one molecule. The term "ionizing radiation polymerizable functional group" as used herein refers to a functional group that can undergo a polymerization reaction upon irradiation with ionizing radiation. Examples of the ionizing radiation polymerizable functional group include ethylenically unsaturated groups such as (meth)acryloyl group, vinyl group, and allyl group. The term "(meth)acryloyl group" includes both "acryloyl group" and "methacryloyl group." Further, examples of the ionizing radiation irradiated when polymerizing the ionizing radiation polymerizable compound include visible light, ultraviolet rays, X-rays, electron beams, α-rays, β-rays, and γ-rays.

Examples of the ionizing radiation polymerizable compound include ionizing radiation polymerizable monomers, ionizing radiation polymerizable oligomers, and ionizing radiation polymerizable prepolymers, and these can be adjusted appropriately and used. The ionizing radiation polymerizable compound is preferably a combination of an ionizing radiation polymerizable monomer and an ionizing radiation polymerizable oligomer or an ionizing radiation polymerizable prepolymer.

Examples of ionizing radiation polymerizable monomers include monomers containing hydroxyl groups such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, and ethylene glycol di(meth)acrylate. , diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, tetramethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate ) acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, glycerol(meth)acrylate (meth)acrylic acid esters such as

As the ionizing radiation polymerizable oligomer, a polyfunctional oligomer having two or more functional groups is preferable, and a polyfunctional oligomer having three (trifunctional) or more ionizing radiation polymerizable functional groups is preferable. Examples of the polyfunctional oligomer include polyester (meth)acrylate, urethane (meth)acrylate, polyester-urethane (meth)acrylate, polyether (meth)acrylate, polyol (meth)acrylate, melamine (meth)acrylate, and isocyanurate. Examples include (meth)acrylate and epoxy (meth)acrylate.

The ionizing radiation polymerizable prepolymer has a weight average molecular weight of more than 10,000, preferably from 10,000 to 80,000, more preferably from 10,000 to 40,000. When the weight average molecular weight exceeds 80,000, the viscosity is high, resulting in decreased coating suitability, and there is a risk that the appearance of the resulting cover resin may deteriorate. Examples of the polyfunctional prepolymer include urethane (meth)acrylate, isocyanurate (meth)acrylate, polyester-urethane (meth)acrylate, and epoxy (meth)acrylate.

A thermally polymerizable compound has at least one thermally polymerizable functional group in one molecule. The term "thermally polymerizable functional group" as used herein refers to a functional group that can undergo a polymerization reaction between the same functional groups or with other functional groups by heating. Examples of the thermally polymerizable functional group include a hydroxyl group, a carboxyl group, an isocyanate group, an amino group, a cyclic ether group, and a mercapto group.

The thermally polymerizable compound is not particularly limited, and examples thereof include epoxy compounds, polyol compounds, isocyanate compounds, melamine compounds, urea compounds, phenol compounds, and the like.

Solvent-drying resins are resins such as thermoplastic resins that form a film simply by drying a solvent added to adjust the solid content during coating. When a solvent-drying resin is added, film defects on the coating surface of the coating liquid can be effectively prevented when forming the cover resin. The solvent-drying resin is not particularly limited, and generally thermoplastic resins can be used.

Examples of thermoplastic resins include styrene resins, (meth)acrylic resins, vinyl acetate resins, vinyl ether resins, halogen-containing resins, alicyclic olefin resins, polycarbonate resins, polyester resins, and polyamide resins. , cellulose derivatives, silicone resins, rubbers or elastomers, and the like.
The thermoplastic resin is preferably non-crystalline and soluble in an organic solvent (especially a common solvent that can dissolve multiple polymers and curable compounds). In particular, from the viewpoint of transparency and weather resistance, styrene resins, (meth)acrylic resins, alicyclic olefin resins, polyester resins, cellulose derivatives (cellulose esters, etc.), and the like are preferred.

Preferably, the metal nanowire layer contains a reaction inhibitor.
After applying the cover resin composition, the reaction inhibitor is used to treat the metal nanowires with substances in the atmosphere (such as sulfur, oxygen, and halogens in the atmosphere. Alternatively, if the conductive layer and adhesive layer are in contact with each other, the adhesive layer is This is to suppress a decrease in conductivity due to a reaction with the constituent materials).
Examples of the reaction inhibitor include nitrogen-containing compounds such as benzazole compounds, triazole compounds, tetrazole compounds, isocyanuric acid compounds, and aniline compounds. Examples of nitrogen-containing compounds used as reaction inhibitors include 1-aminobenzazole, 5-methylbenzotriazole, 1,2,3-benzotriazole, 1-methyl-1H-tetrazol-5-amine, and DL-α. -Tocopherol, 1-octadecanethiol, 2-mercapto-5-(trifluoromethyl)pyridine, diallyl isocyanurate, diallylpropyl isocyanurate, 6-anilino-1,3,5-triazine-2,4-dithiol, thiocyanuric acid , 3,5-dimethyl-1H-1,2,4-triazole, 4-(1,2,4-triazol-1-ylmethyl)aniline, 6-(dibutylamino)-1,3,5-triazine-2 ,4-dithiol, 4-(1,2,4-triazol-1-yl)aniline, 2-methylthio-benzothiazole, 1-phenyl-5-mercapto-1H-tetrazole, 5-mercapto-1-methyltetrazole, 5-(Methylthio)-1H-tetrazole, 5-amino-1H-tetrazole, 1-(2-dimethylaminoethyl)-5-mercaptotetrazole, 1-(2-dimethylaminoethyl)-5-mercaptotetrazole, 1- Examples include (4-hydroxyphenyl)-5-mercapto-1H-tetrazole, 3-amino-5-mercapto-1,2,4-triazole, and 3,5-diamino-1,2,4-triazole.

The content of the reaction inhibitor in the metal nanowire layer is preferably 0.01% by mass or more and 10% by mass or less. By setting the content of the reaction inhibitor to 0.01% by mass or more, it is possible to suppress the metal nanowires from reacting with substances in the atmosphere. In addition, by setting the content of the reaction inhibitor to 10% by mass or less, the reaction between the metal nanowires and the reaction inhibitor can be prevented from proceeding not only on the surface of the metal nanowires but also inside the metal nanowires, thereby suppressing a decrease in thermal conductivity. .

The thickness of the metal nanowire layer is preferably 10 nm or more and less than 300 nm, more preferably 50 nm or more and 200 nm or less.

The method for forming the thermally conductive layer in a mesh shape is not particularly limited, and examples thereof include metal foil, metal vapor deposition film by vapor deposition, sputtering, etc., metal plating film by electrolytic plating, electroless plating, etc., or metal vapor deposition. Examples include a method of patterning a metal layer by etching, such as stacking a metal plating film on a film, a combination of these, and a method of printing an ink or paste containing a metal in a mesh shape. Further, in order to further improve transparency, the metal nanowire layer may be patterned by etching.

Although the mesh shape of the heat conductive layer is arbitrary and not particularly limited, the typical shape of the openings of the mesh is square. The shape of the opening in plan view is, for example, a regular pattern with periodicity such as a triangle such as an equilateral triangle, a square such as a square, a rectangle, a rhombus, a polygon such as a trapezoid, a polygon such as a hexagon, or a random shape of the opening. irregular pattern shapes, etc. The mesh has a plurality of openings having these shapes, and the openings are usually line-shaped with uniform width. To give an example of a specific size, the width of the line portion between the openings is preferably 1 to 100 μm, more preferably 3 to 50 μm, in terms of thermal conductivity and mesh invisibility. In addition, the opening size is [line pitch] - [line width], and this [line pitch] is 100 μm to 500 μm, and the aperture ratio (total area of openings/total area of mesh part) is 50 It is preferable to set it to 97% from the viewpoint of compatibility between light transmittance and thermal conductivity. Further, the line pitch may be random between 100 μm and 500 μm.
Note that the bias angle (the angle formed by the line portion of the mesh and the outer periphery of the thermally conductive layer) may be appropriately set at an angle at which moiré is less likely to occur, taking into consideration the pixel pitch and light emitting characteristics of the display.

As conceptually illustrated in the plan view of FIG. 2, the heat conductive layer 12 is a layer having a grounding area 122 at the periphery other than the transparent heat conductive area 121 at the center in the plane direction. , is preferable in that it is easy to establish a thermal ground. The grounding area is formed on a part or the entire periphery of the image display area so as not to interfere with image display.
Here, the transparent thermally conductive area is an area that can cover the entire image display area of the display to which the thermally conductive layer is applied. Further, the grounding area is an area for grounding.
In addition, the higher the thermal conductivity of the grounding area, the more preferable it is, and transparency is not necessary, but it is preferable to form it from the same material as the transparent heat conductive area for the purpose of preventing warping of the grounding area, etc. .

Note that the thickness of the heat conductive layer is not particularly limited as long as the free electrons of the heat conductive layer and the heat radiating member are shared.

(Transparent base material)
The transparent base material supports the thermally conductive layer.
The transparent base material preferably has light transmittance, smoothness, heat resistance, and excellent mechanical strength. Such transparent substrates include polyester, triacetylcellulose (TAC), cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyethersulfone, polysulfone, polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal. , polyetherketone, polymethyl methacrylate, polycarbonate, polyurethane, and amorphous olefin (Cyclo-Olefin-Polymer: COP). The transparent base material may be made by laminating two or more plastic films together.
Among these plastic films, stretched, especially biaxially stretched polyester (polyethylene terephthalate, polyethylene naphthalate) is preferred because of its excellent mechanical strength and dimensional stability. Furthermore, when the display device is of a foldable type, polyimide, which has excellent flexibility, is preferable as the plastic film.

Furthermore, among plastic films, plastic films with a retardation value of 3000 to 30000 nm or plastic films with a quarter wavelength retardation may cause unevenness of different colors to be observed on the display screen when viewing images through polarized sunglasses. This is preferable in that it can be prevented.

The thickness of the transparent substrate is preferably 5 to 300 μm, more preferably 30 to 200 μm.
Note that the thickness of the transparent base material can be calculated, for example, by measuring the thickness at 10 locations from a cross-sectional image taken using a scanning transmission electron microscope (STEM) and calculating the average value of the values at 10 locations. It is preferable that the accelerating voltage for STEM is 10 kV to 30 kV and the magnification is 100 to 700 times.
Further, the transparent base material may be one whose surface has been subjected to known adhesion-promoting treatments such as corona discharge treatment, primer treatment, and base treatment.

(Other layers)
The optical film A may further have functional layers such as an antiglare layer, an antireflection layer, an antistatic layer, a refractive index adjustment layer, a hard coat layer, an antifouling layer, and a circularly polarizing plate.
The position of the functional layer in the display device is preferably closer to the surface than the thermally conductive layer. Moreover, when the optical film A has a functional layer, it is preferable to have a thermally conductive layer closer to the display element than the transparent base material, and to have the functional layer closer to the surface side than the transparent base material.

(optical properties)
The optical film A preferably has a total light transmittance of 70% or more according to JIS K7361-1:1997, more preferably 80% or more, and even more preferably 90% or more.
Further, the optical film A preferably has a haze of JIS K7136:2000 of 5% or less, more preferably 3% or less, and even more preferably 1% or less.

(Position of optical film A)
In the display device of Embodiment A, it is preferable that the display element and the optical film (optical film A) including the heat conductive layer are in contact with each other directly or via an adhesive layer.
With this configuration, a display element that generates a large amount of heat from the light emitting surface side (for example, a self-luminous organic EL display element, a micro LED display element, a large display element with a diagonal of 50 inches or more) is provided. It is possible to easily suppress the temperature inside the display device from becoming locally non-uniform or the temperature inside the display device from becoming high overall. The adhesive layer in this structure can be used without particular limitation as long as it has light transmittance, but an adhesive layer that has electrical conductivity is preferable. The thickness of the adhesive layer is approximately 5 to 300 μm.

(Position of thermal conductive layer)
When the optical film A has a multilayer structure having the above functional layer, the position of the thermally conductive layer is not particularly limited, but from the viewpoint of facilitating the effects of the present invention, it is preferable to provide it at a position close to the heat generation source. . Specifically, the heat conductive layer is preferably provided at a position adjacent to the display element.
For example, when the display element is a self-luminous organic EL display element, the organic EL display element generates heat when emitting light, as will be described later. Therefore, when using an organic EL display element as a display element, it is preferable to provide the thermally conductive layer at a position adjacent to the organic EL display element. Furthermore, when the display element is a micro LED display element or when the display element is a large display element with a diagonal of 50 inches or more, the heat conductive layer is preferably provided at a position adjacent to the display element.

Note that when another functional layer is provided between a display element such as an organic EL display element and a thermally conductive layer, it is preferable to include conductive fine particles having a conductive action by free electrons in the functional layer. As a result, heat generated in a display element such as an organic EL display element is transferred to the heat conductive layer, and heat is efficiently transferred from the high temperature area to the low temperature area in the high temperature area and low temperature area generated in the functional layer. It is possible to maintain a uniform temperature and prevent uneven heating.
The conductive fine particles are not particularly limited, and, for example, coated fine particles in which a conductive coating layer is formed on the surface of a core fine particle are preferably used.
The core fine particles are not particularly limited, and include, for example, inorganic fine particles such as colloidal silica fine particles and silicon oxide fine particles, polymer fine particles such as fluororesin fine particles, acrylic resin particles, and silicone resin particles, and fine particles such as organic-inorganic composite particles. . Further, examples of the material constituting the conductive coating layer include metals such as Au, Ag, Cu, Al, Fe, Ni, Pd, and Pt, or alloys thereof.

Further, when the display device of Embodiment A is mounted on a vehicle, by providing the above-mentioned heat conductive layer near the outermost surface of the display device, it is also possible to prevent temperature rise due to external light. Thereby, it is possible to suppress the difference in dimensional change in the vertical direction and the horizontal direction due to the difference in the stretching ratio of the transparent base material, and to prevent deformation of the display screen.
Furthermore, by using a plastic film with a retardation value of 3,000 to 30,000 nm or a plastic film with a quarter wavelength retardation as the transparent base material, it is possible to use polarized sunglasses, making it more suitable for use in vehicles.

(Other optical films)
In addition to the optical film A described above, the display device of Embodiment A includes other functional layers such as an antiglare layer, an antireflection layer, an antistatic layer, a refractive index adjustment layer, a hard coat layer, and an antifouling layer. An optical film may further be provided. In this case, the optical film (optical film A) having a heat conductive layer is preferably provided at a position close to the heat generation source. Note that the other optical film A provided in Embodiment A may be an optical film B described later.

(display element)
Examples of the display element used in Embodiment A include a liquid crystal display element, an organic EL display element, and a micro light emitting diode display element (micro LED display element). Examples of liquid crystal display elements include IPS (In Plane Switching) mode liquid crystal display elements and FFS (Fringe Field Switching) mode liquid crystal display elements. Examples of organic EL display elements include, for example, transparent first electrodes ( An example of this is a structure in which an anode), an organic light-emitting layer including a light-emitting layer, and a second electrode (cathode) are laminated in this order on the surface of a transparent substrate.

In an organic EL display element, by applying a current between a cathode and an anode, an organic light emitting layer between the two electrodes emits light. At this time, energy that does not contribute to light emission is generated as heat, and the inside of the display device may become high temperature. In particular, in the case of the RGB coloring method in which a red light emitting layer, a green light emitting layer, and a blue light emitting layer are arranged in a plane as the light emitting layers of an organic EL display element, each color requires different energy to emit light. Since the heat generated by each screen is different, high-temperature areas and low-temperature areas may occur within the display screen, resulting in heat unevenness (particularly when a still image is displayed, heat unevenness tends to be noticeable). Therefore, when the display element is an organic EL display element, the effects of the present invention can be more significantly exhibited.
Furthermore, since the micro LED display element displays images using a large number of LED chips, it inevitably becomes hot. Therefore, when the display element is a micro LED display element, the effects of the present invention can be more significantly exhibited.
Further, even when the display element is a large display element with a diagonal of 50 inches or more, the inside of the display element tends to reach a high temperature, so that the effects of the present invention can be more clearly exhibited.

The display device of Embodiment A dissipates heat generated inside the display device or heat caused by external light to the outside of the display device by providing an optical film having the above-described heat conductive layer on the light emitting surface side of the display element. This makes it possible to make the temperature within the display screen uniform. As a result, there is no local deformation caused by uneven temperature within the display screen, so there is no local unevenness in brightness or color, and in particular, there is no distortion of external images reflected in the screen. It is possible to obtain a display screen that does not give any discomfort. In particular, this effect can be exhibited significantly when the display element is an organic EL display element, a micro LED display element, a diagonal of 50 inches or more, or when the display device is mounted on a vehicle.

The display device of Embodiment A preferably has a general-purpose heat dissipation mechanism on the side opposite to the light output surface of the display element, from the viewpoint of making it easier to exhibit the effects of the present invention. Examples of general-purpose heat dissipation mechanisms include air cooling fans, heat dissipation fins, heat pumps, Peltier elements, and the like.

<Embodiment B>
A display device according to Embodiment B of the present invention is characterized by having a display element and an optical film including a radiant heat reflecting layer, which is disposed on the light-emitting surface side of the display element.
Hereinafter, the optical film including the radiation heat reflective layer of Embodiment B may be referred to as "optical film B."
In Embodiment B, the radiant heat reflecting layer mainly reflects the radiant heat to suppress the optical film B from becoming high temperature due to the radiant heat.

FIG. 3 is a schematic cross-sectional view showing an example of a display device of Embodiment B. The display device 1 in FIG. 3 has an optical film 19 including a radiation heat reflecting layer 17 on the light-emitting surface side of the display element 10. Further, in FIG. 3, the optical film 19 has a radiant heat reflecting layer 17 and a functional layer 18 on the transparent base material 11. Further, the display device 1 in FIG. 3 includes another optical film 20 between the display element 10 and the optical film 19.

(Optical film B)
Optical film B includes at least a radiation heat reflective layer. Optical film B preferably has a radiant heat reflective layer on a transparent substrate. Optical film B may further have a functional layer described below.
Examples of the transparent base material of optical film B include those similar to the transparent base material of optical film A.

(radiant heat reflective layer)
Generally, "radiant heat" refers to heat carried by electromagnetic waves. As used herein, the term "radiant heat reflective layer" refers to a layer whose average spectral reflectance in the wavelength range of 2000 to 2500 nm is 5% or more.
The radiation heat reflecting layer preferably has an average spectral reflectance of 5% or more, more preferably 10% or more, at a wavelength of 2000 to 2500 nm. Note that if the average spectral reflectance in the wavelength range of 2000 to 2500 nm is made too high, the transmittance on the longer wavelength side of visible light tends to decrease. Therefore, it is preferable that the average spectral reflectance in the wavelength range of 2000 to 2500 nm is 30% or less.
In this specification, the average spectral reflectance in the wavelength range of 2000 to 2500 nm is measured at 5 nm intervals in the wavelength range of 2000 to 2500 nm.

The radiation heat reflecting layer preferably contains a metal or metal oxide that has a high reflectance in the wavelength range of 2000 to 2500 nm. Such metals or metal oxides include gold, silver and ITO (indium tin oxide). Further, from the viewpoint of transparency, the metal or metal oxide having high reflectance in the wavelength range of 2000 to 2500 nm is preferably in the form of nanowires or fine particles.
Preferred embodiments of metals or metal oxides with high reflectance in the wavelength range of 2000 to 2500 nm include silver nanowires, ITO particles, Ag particles, and Au particles.

When the radiant heat reflective layer includes silver nanowires, the radiant heat reflective layer is preferably a silver nanowire layer dispersed in a transparent resin such that adjacent silver nanowires have contact points with each other.
The average diameter of the silver nanowires is preferably 200 nm or less. By setting the average diameter of the silver nanowires to 200 nm or less, it is possible to suppress an increase in haze. The average diameter of the silver nanowires is more preferably 10 nm or more and 180 nm or less.
The length of the silver nanowire is preferably 500 μm or less from the viewpoint of visible light transparency. The length of the silver nanowire is more preferably 1 μm or more and 300 μm or less, and even more preferably 10 μm or more and 30 μm or less.
The diameter and length of the silver nanowires can be calculated using the same method as the diameter and length of the metal nanowires included in the thermally conductive layer described above.

In addition to silver nanowires, the silver nanowire layer may contain other components such as a cover resin.
The cover resin can serve as the transparent resin described above. The cover resin may be the same as the cover resin exemplified for the thermally conductive layer.
The overall thickness of the silver nanowire layer is preferably 10 nm or more and less than 300 nm, more preferably 50 nm or more and 200 nm or less.

When the radiant heat reflective layer contains one or more particles selected from ITO particles, Ag particles, and Au particles (hereinafter sometimes referred to as "radiant heat reflective particles"), the radiant heat reflective layer is formed in a transparent resin. Preferably, the radiation heat reflecting particles are densely packed. Specifically, it is preferable to contain 100 to 1500 parts by mass of the radiant heat reflecting particles, more preferably 200 to 1300 parts by mass, and even more preferably 500 to 1200 parts by mass, based on 100 parts by mass of the transparent resin. .

The average particle diameter of the radiation heat reflecting particles is preferably 5 nm or more and 200 nm or less, more preferably 5 nm or more and 100 nm or less, and even more preferably 10 nm or more and 80 nm or less.
In this specification, the average particle diameter of various particles can be calculated by the following operations (1) to (3).
(1) A cross section of a molded body containing particles is imaged using TEM or STEM. It is preferable that the accelerating voltage of TEM or STEM is 10 kV to 30 kV, and the magnification is 50,000 to 300,000 times.
(2) Extract ten arbitrary particles from the observed image and calculate the particle diameter of each particle. The particle diameter is measured as the distance between the two straight lines in a combination such that when the cross section of the particle is sandwiched between two arbitrary parallel straight lines, the distance between the two straight lines becomes the maximum.
(3) Perform the same operation five times on observed images of the same sample on different screens, and use the value obtained from the number average of a total of 50 particles as the average particle diameter of the particles.

When the heat dissipation and reflection layer contains radiation heat reflection particles, the thickness is not particularly limited and is usually 0.1 to 5.0 μm, preferably 0.3 to 2.0 μm.

(Functional layer)
Optical film B may further have functional layers such as an antiglare layer, an antireflection layer, an antistatic layer, a refractive index adjustment layer, a hard coat layer, an antifouling layer, and a circularly polarizing plate. The position of the functional layer relative to the radiation heat reflective layer within the display device may be determined as appropriate depending on the type of the functional layer.

As will be described later, in the display device of Embodiment B, it is preferable that the optical film B (optical film including a radiant heat reflective layer) is disposed on the outermost surface of the display device. For this reason, it is preferable that the optical film B has an antireflection layer as a functional layer. Further, the position of the antireflection layer relative to the radiant heat reflective layer in the display device is preferably closer to the surface than the radiant heat reflective layer.

When the optical film B has a hard coat layer, its position is preferably between the transparent base material and the radiation heat reflective layer.

(Hard coat layer)
The hard coat layer, which is an example of a functional layer, preferably contains a cured product of a curable resin composition such as a thermosetting resin composition or an ionizing radiation-curable resin composition, from the viewpoint of scratch resistance. It is more preferable to include a cured product of a curable resin composition.

The thermosetting resin composition is a composition containing at least a thermosetting resin, and is a resin composition that is cured by heating. Examples of the thermosetting resin include acrylic resin, urethane resin, phenol resin, urea melamine resin, epoxy resin, unsaturated polyester resin, and silicone resin. In the thermosetting resin composition, a curing agent is added to these curable resins as necessary.

The ionizing radiation-curable resin composition is a composition containing a compound having an ionizing radiation-curable functional group (hereinafter also referred to as "ionizing radiation-curable compound"). Examples of the ionizing radiation-curable functional group include ethylenically unsaturated bond groups such as (meth)acryloyl group, vinyl group, and allyl group, as well as epoxy group and oxetanyl group. The ionizing radiation-curable compound is preferably a compound having an ethylenically unsaturated bond group, more preferably a compound having two or more ethylenically unsaturated bond groups, and especially a compound having two or more ethylenically unsaturated bond groups ( More preferred are meth)acrylate compounds. As the (meth)acrylate compound having two or more ethylenically unsaturated bond groups, both monomers and oligomers can be used.
Note that ionizing radiation refers to electromagnetic waves or charged particle beams that have energy quantum that can polymerize or crosslink molecules, and ultraviolet rays (UV) or electron beams (EB) are usually used, but other Electromagnetic waves such as X-rays and γ-rays, and charged particle beams such as α-rays and ion beams can also be used.
In this specification, (meth)acrylate means acrylate or methacrylate, (meth)acrylic acid means acrylic acid or methacrylic acid, and (meth)acryloyl group refers to acryloyl group or methacryloyl group. means.

From the viewpoint of scratch resistance, the thickness of the hard coat layer is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1.0 μm or more, and even more preferably 2.0 μm or more. Further, from the viewpoint of curl suppression, the thickness of the hard coat layer is preferably 100 μm or less, more preferably 50 μm or less, more preferably 30 μm or less, more preferably 20 μm or less, more preferably 15 μm or less, and more preferably 10 μm or less.

(Anti-reflection layer)
Examples of the antireflection layer include a single layer structure of a low refractive index layer and a laminated structure of a high refractive index layer and a low refractive index layer. When the radiant heat reflective layer contains radiant heat reflective particles, it is preferable in that the radiant heat reflective layer can also serve as a high refractive index layer.

The refractive index of the low refractive index layer is preferably 1.10 to 1.48, more preferably 1.20 to 1.45, more preferably 1.26 to 1.40, and more preferably 1.28 to 1.38. Preferably, 1.30 to 1.32 is more preferable.
Further, the thickness of the low refractive index layer is preferably 80 to 120 nm, more preferably 85 to 110 nm, and even more preferably 90 to 105 nm. Further, the thickness of the low refractive index layer is preferably larger than the average particle diameter of the low refractive index particles such as hollow particles.

Methods for forming a low refractive index layer can be broadly classified into wet methods and dry methods. Wet methods include a sol-gel method using metal alkoxide, a method of forming by coating a low refractive index resin such as a fluororesin, and a method of forming by coating a low refractive index resin such as a fluororesin, and a method of forming a low refractive index layer using a resin composition containing low refractive index particles. Examples include a method of forming the refractive index layer by applying a coating liquid for forming the refractive index layer. Examples of the dry method include a method in which particles having a desired refractive index are selected from among low refractive index particles and formed by physical vapor deposition or chemical vapor deposition.
The wet method is superior to the dry method in terms of production efficiency, suppression of diagonal reflection hue, and chemical resistance. In this embodiment, in the wet method, from the viewpoint of adhesion, water resistance, scratch resistance, and low refractive index, a coating solution for forming a low refractive index layer in which a binder resin composition contains low refractive index particles is used. It is preferable to form it by. As the binder resin composition, for example, the curable resin compositions exemplified for the hard coat layer can be used.

It is preferable that the low refractive index particles include one or more types selected from hollow particles and non-hollow particles. Moreover, from the viewpoint of a balance between low reflection and scratch resistance, it is preferable to use one or more types selected from hollow particles in combination with one or more types selected from non-hollow particles.
The material for the hollow particles and the non-hollow particles may be either an inorganic compound such as silica and magnesium fluoride, or an organic compound, but silica is preferable from the viewpoint of low refractive index and strength.

Considering optical properties and mechanical strength, the average particle diameter of the hollow silica particles is preferably 50 nm or more and 100 nm or less, more preferably 60 nm or more and 80 nm or less. Furthermore, in consideration of dispersibility while preventing agglomeration of the non-hollow silica particles, the average particle diameter of the non-hollow silica particles is preferably 5 nm or more and 20 nm or less, more preferably 10 nm or more and 15 nm or less.

As the content of hollow silica particles increases, the filling rate of hollow silica particles in the binder resin increases, and the refractive index of the low refractive index layer decreases. Therefore, the content of the hollow silica particles is preferably 100 parts by mass or more, more preferably 150 parts by mass or more, based on 100 parts by mass of the binder resin.
On the other hand, if the content of hollow silica particles relative to the binder resin is too large, the number of hollow silica particles exposed from the binder resin will increase, and the amount of binder resin binding between particles will decrease. Therefore, the hollow silica particles are easily damaged or fall off, and the mechanical strength such as scratch resistance of the low refractive index layer tends to decrease. Therefore, the content of the hollow silica particles is preferably 400 parts by mass or less, more preferably 300 parts by mass or less, based on 100 parts by mass of the binder resin.

If the content of non-hollow silica particles is small, even if the non-hollow silica particles are present on the surface of the low refractive index layer, they may not affect the increase in hardness. Furthermore, when a large amount of non-hollow silica particles is contained, the influence of uneven shrinkage due to polymerization of the binder resin can be reduced, and the unevenness that occurs on the surface of the low refractive index layer after the resin is cured can be reduced. Therefore, the content of the non-hollow silica particles is preferably 90 parts by mass or more, more preferably 100 parts by mass or more, based on 100 parts by mass of the binder resin.
On the other hand, if the content of non-hollow silica particles is too large, the non-hollow silica tends to aggregate, causing uneven shrinkage of the binder resin and increasing surface irregularities. Therefore, the content of the non-hollow silica particles is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, based on 100 parts by mass of the binder resin.

By containing hollow silica particles and non-hollow silica particles in the binder resin in the above proportions, the barrier properties of the low refractive index layer can be improved. This is presumed to be because the silica particles are uniformly dispersed at a high filling rate, thereby inhibiting the permeation of gas and the like.
Furthermore, various cosmetics such as sunscreens and hand creams may contain low-molecular-weight polymers with low volatility. By improving the barrier properties of the low refractive index layer, it is possible to suppress the penetration of low-molecular polymers into the coating film of the low-refractive index layer. abnormalities) can be suppressed.

The high refractive index layer preferably has a refractive index of 1.53 to 1.85, more preferably 1.54 to 1.80, more preferably 1.55 to 1.75, and more preferably 1.56 to 1.70. preferable.
Further, the thickness of the high refractive index layer is preferably 200 nm or less, more preferably 50 to 180 nm, and even more preferably 70 to 150 nm.

The high refractive index layer can be formed, for example, from a coating liquid for forming a high refractive index layer containing a binder resin composition and high refractive index particles. As the binder resin composition, for example, the curable resin compositions exemplified for the hard coat layer can be used.

High refractive index particles include antimony pentoxide (1.79), zinc oxide (1.90), titanium oxide (2.3 to 2.7), cerium oxide (1.95), and tin-doped indium oxide (1.90). 95 to 2.00), antimony-doped tin oxide (1.75 to 1.85), yttrium oxide (1.87), and zirconium oxide (2.10).

The average particle diameter of the high refractive index particles is preferably 2 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more. Moreover, from the viewpoint of suppressing whitening and transparency, the average particle diameter of the high refractive index particles is preferably 200 nm or less, more preferably 100 nm or less, more preferably 80 nm or less, more preferably 60 nm or less, and more preferably 30 nm or less. The smaller the average particle diameter of the high refractive index particles, the better the transparency. In particular, by setting the average particle diameter to 60 nm or less, the transparency can be extremely improved.

(optical properties)
The optical film B preferably has a total light transmittance of 70% or more according to JIS K7361-1:1997, more preferably 80% or more, and even more preferably 90% or more.
Further, the optical film B preferably has a haze of JIS K7136:2000 of 5% or less, more preferably 3% or less, and even more preferably 1% or less.

(Position of optical film B)
In the display device of Embodiment B, it is preferable that an optical film (optical film B) including a radiant heat reflective layer is disposed on the outermost surface of the display device. With this configuration, the radiant heat generated from the light emitting surface side of the display element can be dispersed over a relatively wide range without being concentrated in a narrow range, and the radiant heat can be dispersed from the outside of the display device into the display device. Since it is possible to suppress the intrusion of the optical film B, it is possible to easily suppress the optical film B from being deformed due to a high temperature.
Therefore, by arranging the optical film B as described above, display elements that generate a large amount of heat from the light emitting surface side (for example, self-luminous organic EL display elements, micro LED display elements, 50-inch diagonal The effects of the present invention can be easily exhibited even in a display device equipped with the above-mentioned large-sized display element.

In Embodiment B, in the display device, the total thickness of the layers located on the opposite side of the display element from the radiation heat reflecting layer is preferably 350 nm or less, more preferably 300 nm or less, and 270 nm or less. It is even more preferable that there be.
The temperature of the layer located on the opposite side of the display element from the radiant heat reflective layer increases due to radiant heat from the outside of the display device and radiant heat generated from the display element and transmitted through the radiant heat reflective layer. There is a tendency that the greater the total thickness of the layer, the greater the degree of temperature rise. Therefore, by setting the total thickness of the layers located on the opposite side of the display element to the radiation heat reflecting layer within the above range, it is possible to easily suppress the optical film B from becoming high temperature.
The layer located on the opposite side of the display element from the radiation heat reflective layer is a layer that the optical film B (19) itself has, like the functional layer 18 in FIG. 3, or a layer located on the surface side of the optical film B. Examples include layers that the member has.

When the optical film B has a low refractive index layer on the side opposite to the display element from the radiation heat reflecting layer, the total thickness is preferably 50 to 200 nm, more preferably 80 to 150 nm.
When the optical film B has a high refractive index layer and a low refractive index layer on the side opposite to the display element from the radiation heat reflecting layer, the total thickness is preferably 80 to 300 nm, and preferably 130 to 250 nm. is more preferable.

(display element)
Examples of the display element used in Embodiment B include a liquid crystal display element, an organic EL display element, and a micro light emitting diode display element (micro LED display element). Examples of liquid crystal display elements include IPS (In Plane Switching) mode liquid crystal display elements and FFS (Fringe Field Switching) mode liquid crystal display elements. Examples of organic EL display elements include, for example, transparent first electrodes ( An example of this is a structure in which an anode), an organic light-emitting layer including a light-emitting layer, and a second electrode (cathode) are laminated in this order on the surface of a transparent substrate.

In an organic EL display element, by applying a current between a cathode and an anode, an organic light emitting layer between the two electrodes emits light. At this time, energy that does not contribute to light emission is generated as heat, and the inside of the display device may become high temperature. In particular, in the case of the RGB coloring method in which a red light emitting layer, a green light emitting layer, and a blue light emitting layer are arranged in a plane as the light emitting layers of an organic EL display element, each color requires different energy to emit light. Since the heat generated by each screen is different, high-temperature areas and low-temperature areas may occur within the display screen, resulting in heat unevenness (particularly when a still image is displayed, heat unevenness tends to be noticeable). Therefore, when the display element is an organic EL display element, the effects of the present invention can be more significantly exhibited.
Furthermore, since the micro LED display element displays images using a large number of LED chips, it inevitably becomes hot. Therefore, when the display element is a micro LED display element, the effects of the present invention can be more significantly exhibited.
Further, even when the display element is a large display element with a diagonal of 50 inches or more, the inside of the display element tends to reach a high temperature, so that the effects of the present invention can be more clearly exhibited.
Moreover, regardless of the type and size of the display element, when the display device of Embodiment B is mounted on a vehicle, the effects of the present invention can be more significantly exhibited.

The display device of Embodiment B preferably has a general-purpose heat dissipation mechanism on the side opposite to the light output surface of the display element, from the viewpoint of making it easier to exhibit the effects of the present invention. Examples of general-purpose heat dissipation mechanisms include air cooling fans, heat dissipation fins, heat pumps, Peltier elements, and the like.

<Embodiment C>
A display device according to Embodiment C of the present invention includes a display element, an optical film including a thermally conductive layer disposed on the light-emitting surface side of the display element, and a heat dissipating layer that is thermally grounded from the peripheral edge of the thermally conductive layer. The device further includes an optical film including a radiant heat reflecting layer on the light exit surface side of the optical film including the heat conductive layer.

In Embodiment C, the "optical film including a thermally conductive layer disposed on the light emitting surface side of the display element" and the "heat dissipating member thermally grounded from the peripheral edge of the thermally conductive layer" are the same as in Embodiment A. Examples include: Further, in Embodiment C, the "optical film including a radiation heat reflecting layer" may be the same as in Embodiment B. Further, in Embodiment C, the "display element" may be the same as in Embodiment A or B.

Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples. Note that the present invention is not limited to the embodiments described in the examples.

<Embodiment A>
[Example A1]
(1) Preparation of optical film A (1-1) Formation of hard coat layer A biaxially stretched polyethylene terephthalate (PET) film (thickness: 100 μm, area: 552 mm x 959 mm) was prepared as a transparent base material. A hard coat layer forming composition shown below was applied onto one surface of the transparent substrate at a coating speed of 10 m/min to form a coating film. The coating was dried at 90° C. for 60 seconds to remove the solvent. Next, the coating film was irradiated with ultraviolet rays at a dose of 100 mJ/cm ² using an ultraviolet irradiation device to cure the coating film to form a hard coat (HC) layer having a thickness of 5 μm after curing.

(Hard coat layer forming composition)
A composition for forming a hard coat layer was prepared by mixing the following components.
・Pentaerythritol triacrylate (manufactured by Nippon Kayaku Co., Ltd., KAYARAD PET-30): 46 parts by mass ・Photopolymerization initiator (manufactured by Ciba Japan Co., Ltd., Irgacure 184): 4 parts by mass ・Methyl ethyl ketone: 50 parts by mass

(1-2) Formation of thermally conductive layer Next, copper foil (thickness: 10 μm) is pasted with an adhesive on the surface of the transparent base opposite to the surface on which the hard coat layer is formed. Next, a mesh pattern was formed by etching using photolithography to obtain optical film A.
The surface resistance value of the thermally conductive layer of the obtained optical film A was measured by the four-terminal method using "Loresta-EP MCP-T360 manufactured by Mitsubishi Chemical Corporation" and was found to be 4.2 × 10 ^-2 Ω/ It was □.
In addition, a conductive wire was fixed at one location on the periphery of the surface of the heat conductive layer using silver paste, and the conductor wire was further connected to a heat dissipating member (nichrome, volume resistance value 1.5 × 10 ^-6 Ωm) to provide thermal grounding. processed. Note that the area of the fixed portion was 2 mm ² .

(2) Fabrication of display device The original optical sheet and glass plate that were bonded to a commercially available RGB color-coding type organic EL display device (product name: XEL-1, manufactured by Sony Corporation) were peeled off, and replaced with The optical film A obtained above and the glass plate were assembled and each member was sandwiched between them to produce a display device.

A still image was displayed on the display screen of the obtained display device for 12 hours, and then the display screen was visually observed. As a result, there was no uneven brightness or color in the display screen due to the deformation of the optical film A, and there was no sense of discomfort due to the bending of the reflected image, and the visibility was good.

[Example A2]
(1) Preparation of coating liquid (1-1) Preparation of silver nanowire-containing composition Ethylene glycol (EG) was used as a reducing agent and polyvinylpyrrolidone (PVP: average molecular weight 1.3 million, Aldrich Co., Ltd.) was used as a shape control agent and protective colloid agent. A silver nanowire-containing composition was prepared by performing particle formation by separating the nucleation step and particle growth step shown below using the following methods.

<Nucleation process>
2.0 mL of a silver nitrate EG solution (silver nitrate concentration: 1.0 mol/L) was added over 1 minute at a constant flow rate while stirring 100 mL of the EG solution maintained at 160° C. in the reaction vessel. Thereafter, silver ions were reduced while maintaining the temperature at 160° C. for 10 minutes to form silver core particles. The reaction solution had a yellow color due to surface plasmon absorption of nano-sized silver particles, confirming that silver ions were reduced and silver particles (core particles) were formed. Subsequently, 10.0 mL of a PVP EG solution (PVP concentration: 3.0×10 ⁻¹ mol/L) was added at a constant flow rate over 10 minutes.

<Particle growth process>
After completing the above nucleation step, the reaction solution containing the core particles was maintained at 160°C with stirring, and 100 mL of EG solution of silver nitrate (silver nitrate concentration: 1.0 × 10 ^-1 mol/L) and PVP were added. 100 mL of EG solution (PVP concentration: 3.0×10 ⁻¹ mol/L) was added at a constant flow rate over 120 minutes using the double jet method. In this particle growth process, the reaction solution was sampled every 30 minutes and confirmed using an electron microscope. As a result, the core particles formed in the nucleation process grew into a wire-like shape over time, and the particle growth No new fine particles were observed to be formed during the process. When the diameter and length of the silver nanowires finally obtained were measured, the diameter of the silver nanowires was 30 nm and the length was 15 μm. The diameter of the silver nanowire was determined by measuring the diameter of 50 conductive fibers using a transmission electron microscope (TEM) at a magnification of 1000 to 500,000 times and as the average value of the diameters of the 50 conductive fibers. . In addition, the length of the silver nanowires was determined by measuring the length of 50 conductive fibers using a scanning electron microscope (SEM) at 1000 to 500,000 times magnification. It was calculated as an average value.

<Demineralization water washing process>
After the reaction solution that had completed the particle growth step was cooled to room temperature, it was subjected to a desalination washing treatment using an ultrafiltration membrane with a molecular weight cutoff of 0.2 μm, and the solvent was replaced with ethanol. Then, the liquid volume was concentrated to 100 mL to obtain a silver nanowire dispersion. Finally, it was diluted with ethanol and anone so that the silver nanowire concentration was 0.1% by mass and the solvent ratio of anone after dilution was 30% by mass to obtain a silver nanowire-containing composition.

(1-2) Preparation of composition for cover resin A composition for cover resin was obtained by blending each component so as to have the composition shown below.
<Composition for cover resin>
・Mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (product name “KAYARAD PET-30”, manufactured by Nippon Kayaku Co., Ltd.): 5 parts by mass ・Polymerization initiator (product name “Irgacure 184”, manufactured by BASF Japan) : 0.25 parts by mass ・Methyl ethyl ketone: 70 parts by mass ・Cyclohexanone: 24.75 parts by mass

(2) Production of optical film A (2-1) Formation of hard coat layer A biaxially stretched polyethylene terephthalate (PET) film (thickness: 100 μm, area: 552 mm x 959 mm) was prepared as a transparent base material. A hard coat layer forming composition shown below was applied onto one surface of the transparent substrate at a coating speed of 10 m/min to form a coating film. The coating was dried at 90° C. for 60 seconds to remove the solvent. Next, the coating film was irradiated with ultraviolet rays at a dose of 100 mJ/cm ² using an ultraviolet irradiation device to cure the coating film to form a hard coat (HC) layer having a thickness of 5 μm after curing.

(Hard coat layer forming composition)
A composition for forming a hard coat layer was prepared by mixing the following components.
・Pentaerythritol triacrylate (manufactured by Nippon Kayaku Co., Ltd., KAYARAD PET-30): 46 parts by mass ・Photopolymerization initiator (manufactured by Ciba Japan Co., Ltd., Irgacure 184): 4 parts by mass ・Methyl ethyl ketone: 50 parts by mass

(2-2) Formation of a thermally conductive layer Next, the silver nanowire-containing composition is deposited on the surface of the transparent substrate opposite to the surface on which the hard coat layer is formed, in an amount of 10 mg/m ² . It was applied directly. Next, dry air at 50°C was passed through the applied silver nanowire-containing composition for 15 seconds at a flow rate of 0.5 m/s, and then dry air at 70°C was further passed through at a flow rate of 10 m/s for 30 seconds. By evaporating the dispersion medium in the silver nanowire-containing composition, silver nanowires were directly placed on the PET film.
Next, the above composition for cover resin was applied to cover the silver nanowires to form a coating film. Then, dry air at 50°C was passed through the formed coating film for 15 seconds at a flow rate of 0.5 m/s, and then dry air at 70°C was passed through it at a flow rate of 10 m/s for 30 seconds to dry it. By doing so, the solvent in the coating film was evaporated, and the coating film was cured by irradiating ultraviolet rays at an integrated light amount of 100 mJ/cm ² to form a cover resin having a film thickness of 100 nm.
As described above, a thermally conductive layer (silver nanowire layer) was formed, and an optical film A was obtained.

The surface resistance value of the thermally conductive layer of the obtained optical film A was 51 Ω/□ when measured by a four-probe method using “Loresta-EP MCP-T360, manufactured by Mitsubishi Chemical Corporation.”
In addition, a conductive wire was fixed at one location on the periphery of the surface of the heat conductive layer using silver paste, and the conductor wire was further connected to a heat dissipating member (nichrome, volume resistance value 1.5 × 10 ^-6 Ωm) to provide thermal grounding. processed. Note that the area of the fixed portion was 2 mm ² .

(3) Fabrication of display device The original optical sheet and glass plate that were bonded to a commercially available RGB color-coating type organic EL display device (product name: XEL-1, manufactured by Sony Corporation) were peeled off, and replaced with The optical film A obtained above and the glass plate were assembled and each member was sandwiched between them to produce a display device.

A still image was displayed on the display screen of the obtained display device for 12 hours, and then the display screen was visually observed. As a result, there was no uneven brightness or color in the display screen due to the deformation of the optical film A, and there was no sense of discomfort due to the bending of the reflected image, and the visibility was good.

[Comparative example A1]
(1) Preparation of optical film A biaxially stretched polyethylene terephthalate (PET) film (thickness: 100 μm, area: 552 mm×959 mm) was prepared as a transparent base material. A hard coat layer forming composition shown below was applied onto one surface of the transparent substrate at a coating speed of 10 m/min to form a coating film. The coating was dried at 90° C. for 60 seconds to remove the solvent. Next, the coating film was irradiated with ultraviolet rays at a dose of 100 mJ/cm ² using an ultraviolet irradiation device to cure the coating film and obtain an optical film having a hard coat (HC) layer with a thickness of 5 μm after curing. Ta.

(Hard coat layer forming composition)
A composition for forming a hard coat layer was prepared by mixing the following components.
・Pentaerythritol triacrylate (manufactured by Nippon Kayaku Co., Ltd., KAYARAD PET-30): 46 parts by mass ・Photopolymerization initiator (manufactured by Ciba Japan Co., Ltd., Irgacure 184): 4 parts by mass ・Methyl ethyl ketone: 50 parts by mass

(2) Fabrication of display device The original optical sheet and glass plate that were bonded to a commercially available RGB color-coding type organic EL display device (product name: XEL-1, manufactured by Sony Corporation) were peeled off, and replaced with A display device was manufactured by incorporating the optical film and glass plate obtained above and sandwiching each member.

A still image was displayed on the display screen of the obtained display device for 12 hours, and then the display screen was visually observed. As a result, there were areas on the display screen where the brightness and color were uneven due to deformation of the optical film, and it was also confirmed that the reflected image had an unnatural feeling of bending.

[Comparative example A2]
(1) Preparation of optical film (1-1) Formation of hard coat layer A biaxially stretched polyethylene terephthalate (PET) film (thickness: 100 μm, area: 552 mm x 959 mm) was prepared as a transparent base material. A hard coat layer forming composition shown below was applied onto one surface of the transparent substrate at a coating speed of 10 m/min to form a coating film. The coating was dried at 90° C. for 60 seconds to remove the solvent. Next, the coating film was irradiated with ultraviolet rays at a dose of 100 mJ/cm ² using an ultraviolet irradiation device to cure the coating film and obtain an optical film having a hard coat (HC) layer with a thickness of 5 μm after curing. Ta.

(Hard coat layer forming composition)
A composition for forming a hard coat layer was prepared by mixing the following components.
・Pentaerythritol triacrylate (manufactured by Nippon Kayaku Co., Ltd., KAYARAD PET-30): 46 parts by mass ・Photopolymerization initiator (manufactured by Ciba Japan Co., Ltd., Irgacure 184): 4 parts by mass ・Methyl ethyl ketone: 50 parts by mass

(1-2) Formation of transparent conductive layer Next, while introducing argon mixed with 5% by volume of oxygen gas, an ITO target [indium: tin = 90:10 (mass ratio)] was used, and the pressure was 0.15 Pa. , pulse sputtering was performed under the conditions of a frequency of 100 kHz, a power density of 0.64 W/cm ² , and an inversion pulse width of 1 μsec, and a thickness of A 5 nm ITO film was formed to obtain an optical film.

(2) Fabrication of display device The original optical sheet and glass plate that were bonded to a commercially available RGB color-coding type organic EL display device (product name: XEL-1, manufactured by Sony Corporation) were peeled off, and replaced with A display device was manufactured by incorporating the optical film and glass plate obtained above and sandwiching each member.

A still image was displayed on the display screen of the obtained display device for 12 hours, and then the display screen was visually observed. As a result, there were areas on the display screen where the brightness and color were uneven due to deformation of the optical film, and it was also confirmed that the reflected image had an unnatural feeling of bending.

(Summary of results)
In Examples A1 and A2, which have an optical film A having a heat conductive layer and a heat dissipation member that is thermally grounded from the peripheral edge of the heat conductive layer of the optical film A, the visual recognition after displaying a still image for a long time is It was of excellent quality. Furthermore, when a biaxially oriented polyethylene terephthalate (PET) film with a retardation value of 3000 nm or more was used as the transparent base material, visibility was good at any angle and compatible with polarized sunglasses.

<Embodiment B>
(I) Preparation of optical film [Example B1]
A triacetyl cellulose film (thickness: 80 μm, area: 225 mm×150 mm) was prepared as a transparent base material.
On one side of the transparent substrate, a composition containing silver nanowires is applied in the same manner as in Example A2, and after adhering the silver nanowires on the triacetyl cellulose film, a composition for cover resin is further applied. , dried and cured to form a cover resin with a film thickness of 100 nm.
In the manner described above, an optical film B used in Example B1, which has a radiation heat reflecting layer (silver nanowire layer) on a transparent substrate, was obtained.

[Example B2]
A triacetyl cellulose film (thickness: 80 μm, area: 225 mm×150 mm) was prepared as a transparent base material.
A composition for forming a radiation heat reflection layer having the following formulation was applied onto one surface of the transparent substrate, dried and cured to form a radiation heat reflection layer containing ITO particles having a thickness of 700 nm.
In the manner described above, an optical film B used in Example B2, which has a radiation heat reflecting layer (ITO particle-containing layer) on a transparent substrate, was obtained.

(Composition for forming radiant heat reflective layer)
A composition for forming a radiation heat reflective layer was prepared by mixing the following components.
・Pentaerythritol triacrylate (manufactured by Nippon Kayaku Co., Ltd., KAYARAD PET-30): 2 parts by mass ・ITO particles (average particle diameter 30 nm): 10 parts by mass ・Photopolymerization initiator (manufactured by Ciba Japan Co., Ltd., Irgacure 184): 2 parts by mass / Methyl isobutyl ketone: 88 parts by mass

[Comparative example B1]
A triacetyl cellulose film (thickness: 80 μm, area: 225 mm×150 mm) was prepared as an optical film used in Comparative Example B1.

[Comparative example B2]
A triacetyl cellulose film (thickness: 80 μm, area: 225 mm×150 mm) was prepared as a transparent base material.
A thermally conductive layer forming composition having the following formulation was applied onto one surface of the transparent substrate, dried and cured to form a thermally conductive layer containing aluminum nitride particles having a thickness of 700 nm.
In the manner described above, an optical film used in Comparative Example B2, which had a thermally conductive layer (aluminum nitride particle-containing layer) on a transparent substrate, was obtained.

(Composition for forming thermally conductive layer of Comparative Example B2)
A composition for forming a thermally conductive layer was prepared by mixing the following components.
・Pentaerythritol triacrylate (manufactured by Nippon Kayaku Co., Ltd., KAYARAD PET-30): 2 parts by mass ・Aluminum nitride particles (average particle size 1.5 μm): 10 parts by mass ・Photopolymerization initiator (Ciba Japan Co., Ltd.) ), Irgacure 184): 2 parts by mass / Methyl isobutyl ketone: 88 parts by mass

[Comparative example B3]
A triacetyl cellulose film (thickness: 80 μm, area: 225 mm×150 mm) was prepared as a transparent base material.
A thermally conductive layer forming composition having the following formulation was applied onto one surface of the transparent substrate, dried and cured to form a thermally conductive layer containing boron nitride particles having a film thickness of 150 nm.
In the manner described above, an optical film used in Comparative Example B3 having a thermally conductive layer (a layer containing boron nitride particles) on a transparent substrate was obtained.

(Composition for forming thermally conductive layer of Comparative Example B3)
A composition for forming a thermally conductive layer was prepared by mixing the following components.
・Pentaerythritol triacrylate (manufactured by Nippon Kayaku Co., Ltd., KAYARAD PET-30): 2 parts by mass ・Boron nitride particles (average particle diameter 200 nm): 10 parts by mass ・Photopolymerization initiator (manufactured by Ciba Japan Co., Ltd.) , Irgacure 184): 2 parts by mass, methyl ethyl ketone: 88 parts by mass

(II) Production of display device The optical film of Example B1 was placed on a commercially available liquid crystal display device (manufactured by Amazon, trade name: Kindle Fire HDX) with the transparent substrate side facing the display device side, and A liquid crystal display device B1 was obtained.
Similarly, the optical films for Example B2 and Comparative Examples B1 to B3 were placed on a commercially available liquid crystal display device (manufactured by Amazon, trade name Kindle Fire HDX) so that the transparent substrate side of the optical film faced the display device side. Then, liquid crystal display devices of Example B2 and Comparative Examples B1 to B3 were obtained.

(III) Thermal Durability Test The following heat durability test was conducted assuming the inside of a car in the summer.
<Temperature>
The liquid crystal display devices of Examples B1 to B2 and Comparative Examples B1 to B3 produced in (II) above were placed in an oven at 80°C, and after 10 minutes had passed, an IR camera (manufactured by FLIR Systems, trade name: FLIR E4) was placed in an oven at 80°C. ) The temperature was measured from the surface side (the distance between the optical film and the IR camera was 30 cm). Table 1 shows the maximum temperature on the optical film. A maximum temperature of 70°C or less is a passing level.
<Visibility>
The liquid crystal display devices of Examples B1 to B2 and Comparative Examples B1 to B3 produced in (II) above were placed in an oven at 80° C. and taken out after 10 minutes. Immediately after taking it out, display the screen of the liquid crystal display device (a solid green screen) and visually check whether there are any areas on the display screen where the brightness and color tone are uneven due to deformation of the optical film. evaluated. As a result, those with no unevenness in brightness and color were rated "A," and those with uneven brightness and color were rated "C."

(IV) Total light transmittance The total light transmittance of the optical films prepared in (I) above for Examples B1 to B2 and Comparative Examples B1 to B3 was measured. The measuring device used was a haze meter (HM-150, manufactured by Murakami Color Research Institute), and the light incident surface was set to the transparent substrate side.

From the results in Table 1, it can be confirmed that the display devices of Examples B1 and B2 can suppress the temperature rise of the optical film in the thermal durability test and suppress the decrease in visibility due to deformation of the optical film.

The display device of the present invention can be used, for example, in office automation equipment such as a personal computer monitor, notebook computer, or copy machine, in portable equipment such as a mobile phone, watch, or personal digital assistant (PDA), or in home appliances such as a video camera, television, or microwave oven. Suitable for use as equipment, back monitors, car navigation system monitors, car audio equipment, and other in-vehicle equipment.

1: Display device 10: Display element 11: Transparent base material 12: Heat conductive layer 121: Transparent heat conductive region 122: Grounding region 13: Optical film A
14: Peripheral portion 15: Conductive wire 16: Heat dissipation member 17: Radiant heat reflective layer 18: Functional layer 19: Optical film B
20: Other optical films

Claims (10)

A display element;
an optical film including a thermally conductive layer disposed on the light emitting surface side of the display element;
a heat dissipation member thermally grounded from the peripheral edge of the heat conductive layer;
has
The heat dissipation member is a member containing metal,
A display device, wherein the thermally conductive layer is a metal nanowire layer containing metal nanowires and a polymer of an ionizing radiation polymerizable compound having at least one ethylenically unsaturated group in one molecule (excluding a siloxane polymer). 2. The display device according to claim 1, wherein the metal nanowire layer is a layer in which the metal nanowires are dispersed in the polymer of the ionizing radiation polymerizable compound so that adjacent metal nanowires have contact points with each other. The display device according to claim 1 or 2, wherein the metal nanowires are silver nanowires. The display device according to claim 1, wherein the thermally conductive layer has a surface resistivity of 250Ω/□ or less. The display device according to any one of claims 1 to 4, wherein the display element is an organic EL display element. The display device according to any one of claims 1 to 5, which is mounted on a vehicle. 7. The display device according to claim 1, wherein the display element and the optical film including the thermally conductive layer are in contact with each other directly or via an adhesive layer. A display element;
an optical film including a radiant heat reflective layer disposed on the light emitting surface side of the display element;
has
For forming a radiation heat reflection layer, the radiation heat reflection layer contains one or more particles selected from ITO particles, Ag particles, and Au particles and an ionizing radiation polymerizable compound having at least one ethylenically unsaturated group in one molecule. A display device that is a layer made of a cured product of a composition . 9. The display device according to claim 8, wherein the optical film including the radiation heat reflective layer is disposed on the outermost surface of the display device. The display device according to claim 8 or 9 , wherein the total thickness of layers located on the opposite side of the display element from the radiation heat reflecting layer in the display device is 350 nm or less.