JP2022052029A - Led substrate - Google Patents

Abstract

To provide an LED substrate that makes it possible to provide an LED substrate suitable for thinning.SOLUTION: An LED substrate includes at least a base material, an LED light source, and a reflective material, and the height (H) of the LED light source is 300 μm or less, the thickness (T) of the reflective material is 20 μm or more and 120 μm or less, and the surface roughness Ra of the surface of the reflective material is 10 nm or more and less than 300 nm.SELECTED DRAWING: None

Description

The present invention relates to an LED substrate preferably used for thin liquid crystal display applications.

In recent years, many displays using liquid crystals have been used as display devices for personal computers, televisions, mobile phones and the like. These liquid crystal displays can be displayed by installing a surface light source called a backlight from the back side and irradiating the light.

LEDs have come to be used as a light source for a backlight for a liquid crystal display, and are becoming thinner. In order to reduce the thickness, there is an increasing need for members such as smaller members used, thinner film members, and integrated multiple functions.

Conventionally, the backlight has a reflective plate (sometimes called a reflective film), which is a film to which a white pigment is added or a film containing fine bubbles inside, or these films and a metal plate or plastic. Those made by laminating boards have been used. In particular, a film containing fine bubbles inside is widely used because it has a certain effect on improving the brightness and making the screen brightness uniform (Patent Documents 1 and 2).

Japanese Patent Application Laid-Open No. 2003-160682 Special Fair 8-16175 Gazette

However, as the technology for reducing the size and thickness of the backlight and increasing the definition of the screen advances, the performance and effect of the conventional reflective film are not sufficient. In addition, efforts have been made to improve the performance and effect of the conventional reflective film by combining it with other members, but the effect is not sufficient.

An object of the present invention is to solve the above problems and to provide an LED substrate suitable for thinning.

As a result of diligent studies in view of the above problems, it was found that the above problems can be solved by an LED substrate having the following configuration, and the present invention has been reached.
That is, [I] is an LED substrate having at least a base material, an LED light source, and a reflective material.
The height (H) of the LED light source is 300 μm or less, and the height (H) is 300 μm or less.
The thickness (T) of the reflective material is 20 μm or more and 120 μm or less.
An LED substrate having a three-dimensional surface roughness SRa of the surface of the reflective material of 10 nm or more and less than 300 nm.
[II] The LED substrate according to [I], wherein the ratio (T / H) of the height (H) of the LED light source to the thickness (T) of the reflective material is 0.1 to 1.0.
[III] The LED substrate according to [I] or [II], wherein the glossiness at an incident angle of 85 ° on the surface of the reflective material is 80 or more.
[IV] One of [I] to [III], wherein the reflective material contains titanium oxide, and the content thereof is 0.1% by weight or more and 50% by weight or less with respect to the total weight of the reflective material. The LED substrate described.
[V] The LED substrate according to any one of [I] to [IV], wherein the reflective material contains a polyester resin and the content thereof is 5% by weight or more with respect to the total weight of the reflective material.
[VI] The LED according to any one of [I] to [V], wherein the reflective material contains bubbles and the content thereof is 1% by volume or more and 80% by volume or less with respect to the total volume of the reflective material. substrate.
[VII] Backlight using the LED substrate according to any one of [I] to [VI].

According to the present invention, it is possible to provide an LED substrate suitable for thinning.

As a result of diligent studies on such issues, the present inventors have obtained results.
An LED substrate containing at least a base material, an LED light source, and a reflective material.
The height (H) of the LED light source is 300 μm or less, and the height (H) is 300 μm or less.
The thickness (T) of the reflective material is 20 μm or more and 120 μm or less.
It has been found that if the LED substrate has a surface roughness SRa of 10 nm or more and less than 300 nm on the surface of the reflective material, sufficient performance can be obtained even if the thickness is reduced.

The present invention will be described in detail below.

The LED substrate of the present invention needs to have at least a base material, an LED light source, and a reflective material. Hereinafter, each member will be described.

[Base material]
In the LED substrate of the present invention, the substrate is not particularly limited as long as it is in the shape of a flat plate, and can be appropriately selected depending on the intended purpose. A substrate, a metal substrate, a glass substrate, a glass epoxy substrate, or the like can be used. It is preferable that the substrate has a metal circuit or a terminal for connecting to the LED. The method for forming the metal circuit portion is not particularly limited, and a method by various plating treatments, a mask forming method of masking other than the circuit forming portion, a modification of the substrate surface by laser irradiation, a method of partial removal, and a combination thereof are used. Things can be mentioned.

Examples of the metal type of the circuit portion formed by the above method include gold, silver, copper, platinum, zinc, tin, nickel, cadmium, chromium, and alloys containing them, and gold, copper, and nickel are particularly metal circuits. It is preferable from the viewpoint of formability and adhesion of the portion. Further, from the viewpoint of improving the stability and conductivity of the metal circuit portion, a metal layer made of a different kind of metal may be formed on the metal circuit portion of the molded product by a method such as plating.

The metal circuit portion may be on the surface on the LED side or the surface on the opposite side, or may be formed so that two or more substrates are bonded together and exist in the middle thereof.

[LED light source]
In the LED substrate of the present invention, it is preferable that the LED light source is mounted on the substrate. The height of the LED light source needs to be 300 μm or less. It is more preferably 250 μm or less, still more preferably 200 μm or less. When the height of the LED is larger than 300 μm, the total thickness of the LED substrate cannot be reduced, which is not preferable. Further, when the height of the LED is lower than 20 μm, the brightness may be insufficient. It is more preferably 30 μm or more, still more preferably 50 μm or more.

In the LED light source in the LED substrate of the present invention, it is preferable that the electrode portion drawn from the LED (light emitting diode) element is connected to the metal circuit of the substrate. The electrode portion may extend from the side surface of the LED element, or may be connected to the metal circuit of the substrate from the bottom surface of the LED element. The height of the LED light source in the present application refers to the height with respect to the surface of the substrate, and when connecting to a metal circuit from the electrode on the bottom surface of the LED element, the thickness of the connection portion such as wiring or solder is also the thickness of the LED light source. It shall be included as the height.

[Reflective material]
In the LED substrate of the present invention, it is preferable that the reflective material is provided on the same surface as the LED light source.

The reflective material of the present invention may also serve as a solder resist layer applied for the purpose of protecting and insulating a metal circuit formed on the substrate surface, or a highly reflective layer may be provided as a reflective material separately from the solder resist layer. good. In that case, the solder resist layer and the highly reflective layer are treated as constituting the reflective material. In the present invention, the reflective layer made of resin laminated on the surface on the same side as the LED light source is used as the reflective material. However, those that exist above the sealing resin and LED light source described later and cover the LED are excluded.

The thickness (T) of the reflective material of the present invention needs to be 20 μm or more and 120 μm or less. If the thickness is thinner than 20 μm, the reflection performance may be insufficient, which is not preferable. Originally, the thicker the reflective material, the higher the reflection performance, but if it is thicker than 120 μm, it is not preferable because it may obstruct the light emitted in the lateral direction from the small LED light source having a low height and the brightness may decrease. It is more preferably 40 μm or more and 105 μm or less, and further preferably 60 μm or more and 95 μm or less.

The ratio (T / H) of the height (H) of the LED light source of the present invention to the thickness (T) of the reflective material is preferably 0.1 to 1.0. It is more preferably 0.2 to 0.85, still more preferably 0.3 to 0.75. If the thickness ratio is less than 0.1, the reflective material may be thin and the brightness may decrease. If it is larger than 1.0, the reflective material may obstruct the light emitted from the side surface of the LED light source, and the brightness may decrease.

The surface roughness SRa of the surface of the reflective material of the present invention needs to be 10 nm or more and less than 300 nm. When the surface roughness SRa is 300 nm or more, when the LED substrate is incorporated as a light source of the backlight, it may cause uneven brightness in which only the area directly above the LED becomes brighter than other places. Normally, the larger the surface roughness SRa, the more the light is diffused, so the unevenness of the luminance tends to be suppressed. However, by setting the surface roughness SRa of the surface of the reflective material within the above range, the reflection from the optical film group is performed. It is possible to suppress the occurrence of luminance unevenness due to secondary reflection that occurs because the shape of the LED becomes easy to see due to the diffusion of the reflective material. If the surface roughness SRa is smaller than 10 nm, the cost for processing increases, which is not preferable. It is more preferably 20 nm or more and less than 250 nm, and further preferably 30 nm or more and less than 200 nm.

As the solder resist layer, a known one can be used, but a white solder resist is preferable. The white solder resist is preferably whitened by inorganic particles. Inorganic particles include silica, colloidal silica, calcium carbonate, aluminum silicate, calcium phosphate, alumina, magnesium carbonate, zinc carbonate, titanium dioxide, zinc oxide (zinc white), antimony oxide, cerium oxide, zirconium oxide, tin oxide, lanthanum oxide. , Magnesium oxide, barium carbonate, basic lead carbonate (lead white), barium sulfate, calcium sulfate, lead sulfate, zinc sulfide, mica, mica titanium, talc, clay, kaolin, and the like. Further, they can be used alone or in a mixture of two or more kinds, but barium sulfate particles, titanium dioxide particles and calcium carbonate are preferable because high optical properties can be obtained. More preferably, titanium dioxide particles, especially titanium dioxide particles having a rutile-type crystal structure, are particularly preferable. It is generally said that titanium dioxide can have three types of crystal structures: rutile type, anatase type, and brookite type, but the rutile type has the highest refractive index and excellent reflection efficiency.

The number average particle diameter of the inorganic particles is preferably 30 nm or more and 500 nm or less. It is more preferably 50 nm or more and 450 nm or less, and further preferably 100 nm or more and 400 nm or less. When the number average particle diameter of the inorganic particles is smaller than 30 nm, the particles tend to aggregate and the surface of the solder resist layer may become rough. If it is larger than 500 nm, the surface may become rough due to the unevenness of the particles.

When the reflective material of the present invention has a highly reflective layer, the highly reflective layer may be in contact with the solder resist layer, or may be laminated via a functional layer such as an adhesive layer.

The highly reflective layer of the reflective material in the present invention is a resin layer having a function of reflecting visible light, and is a method of containing a white pigment, a method of containing bubbles inside, and two or more kinds of resins having different refractive indexes. A method of reflecting by interference reflection by alternately stacking the above is preferably used. These methods may be used alone or in combination.

The highly reflective layer of the reflective material in the present invention preferably has an average reflectance of 80% or more in the visible light wavelength region (400 nm to 800 nm). It is more preferably 90% or more, still more preferably 95% or more. If the average reflectance is less than 80%, the reflective performance as a reflective material may be insufficient.

As the resin for the highly reflective layer, a thermoplastic resin is preferable from the viewpoint of handleability and film formation. Examples of the thermoplastic resin include polyethylene, polypropylene, poly (1-butene), poly (4-methylpentene), polyisobutylene, polyisoprene, polybutadiene, polyvinylcyclohexane, polystyrene, poly (α-methylstyrene), and poly (poly (α-methylstyrene)). p-Methylstyrene), Polynorbornen, Polychloride represented by polycyclopentene, etc., Polyamide represented by Nylon 6, Nylon 11, Nylon 12, Nylon 66, etc., Ethylene / propylene copolymer, Ethylene / Vinylcyclohexane copolymer, Ethylene / Vinyl Vinyl monomers represented by cyclohexene copolymers, ethylene / alkyl acrylate copolymers, ethylene / acrylic methacrylate copolymers, ethylene / norbornen copolymers, ethylene / vinyl acetate copolymers, propylene / butadiene copolymers, isobutylene / isoprene copolymers, vinyl chloride / vinyl acetate copolymers, etc. Copolymer resins, polyacrylates, polymethacrylates, polymethylmethacrylates, polyacrylamides, acrylic resins typified by polyacrylonitrile, polyethylene terephthalates, polypropylene terephthalates, polybutylene terephthalates, polyethylene-2,6-naphthalates, etc. Polyester, polyethylene oxide, polypropylene oxide, polyether represented by polyacrylene glycol, diacetyl cellulose, triacetyl cellulose, propionyl cellulose, butyryl cellulose, acetylpropionyl cellulose, cellulose ester resin represented by nitrocellulose, polylactic acid. , Biodegradable polymers such as polybutyl succinate, other, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, polyacetal, polyglucolic acid, polycarbonate, polyketone, polyether sulfone, polyether ether ketone, Modified polyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide, polysiloxane, tetrafluoroethylene resin, trifluoroethylene resin, trifluorochloride ethylene resin, tetrafluoroethylene-6fluoropropylene copolymer, polyfluoride Biniriden and the like can be mentioned.

When it contains a white pigment, it is preferably inorganic particles. Inorganic particles include silica, colloidal silica, calcium carbonate, aluminum silicate, calcium phosphate, alumina, magnesium carbonate, zinc carbonate, titanium dioxide, zinc oxide (zinc white), antimony oxide, cerium oxide, zirconium oxide, tin oxide, lanthanum oxide. , Magnesium oxide, barium carbonate, basic lead carbonate (lead white), barium sulfate, calcium sulfate, lead sulfate, zinc sulfide, mica, mica titanium, talc, clay, kaolin, and the like. Further, they can be used alone or in a mixture of two or more kinds, but among them, barium sulfate particles, titanium dioxide particles and calcium carbonate are preferable because high optical characteristics and film formation stability can be obtained. Further, titanium dioxide particles, particularly titanium dioxide particles having a rutile-type crystal structure, are particularly preferable. It is generally said that titanium dioxide can have three types of crystal structures: rutile type, anatase type, and brookite type, but the rutile type has the highest refractive index and excellent reflection efficiency.

The reflective material of the present invention contains titanium oxide, and the content thereof is preferably 0.1% by weight or more and 50% by weight or less with respect to the total weight of the reflective material. It is more preferably 3% by weight or more and 45% by weight or less, and further preferably 5% by weight or more and 40% by weight or less. It is preferable to contain titanium oxide in such a ratio because the reflectance of the reflective material can be increased. If the amount of titanium oxide is less than 0.1% by weight, the reflectance may be insufficient. If the amount of titanium oxide is more than 50% by weight, the reflective material may become brittle.

As a method of containing bubbles inside, (1) a method of containing a foaming agent in the thermoplastic resin A and foaming by heating at the time of extrusion or film formation, or foaming by chemical decomposition to form bubbles, (2). ) A method of adding a gas or a vaporizable substance at the time of extruding the thermoplastic resin A, (3) Adding inorganic particles and / or a thermoplastic resin B incompatible with the resin to the thermoplastic resin A, and uniaxially or A method of generating fine bubbles by biaxial stretching can be mentioned, but in the present invention, from the comprehensive viewpoints such as film forming property, ease of adjusting the amount of bubbles contained therein, and manufacturing cost. , It is preferable to use the method (3) above.

As the inorganic particles in the above method (3), the same inorganic particles as described above can be preferably used.

When two or more kinds of resins having different refractive coefficients are alternately laminated, the α layer containing the thermoplastic resin α as the main component and the thermoplastic resin β having a different refractive index from the thermoplastic resin α are used as the main components. It is preferable to have a multi-layer laminated structure in which 51 or more layers of β layers are alternately laminated.

Among the above-mentioned thermoplastic resins, at least one of the thermoplastic resin A, the thermoplastic resin α and the thermoplastic resin β may contain polyester as a main component from the viewpoint of strength, heat resistance, transparency and versatility. preferable. Assuming that the total of all the resins constituting the high-reflection layer is 100% by mass, if the polyester is 50% by mass or more and 100% by mass, it can be said to be the main component. If the polyester content is less than 50% by mass, heat resistance and productivity may decrease.

The reflective material of the present invention contains a polyester resin, and the content thereof is preferably 5% by weight or more with respect to the total weight of the reflective material. It is more preferably 10% by weight or more, still more preferably 20% by weight or more. It is preferable that the reflective material has a highly reflective layer containing a polyester resin and is in the above range.

Preferred embodiments of polyester are described below. The polyester refers to a polymer having an ester bond as a main chain, and the polyester used in the present invention is preferably a polyester having a polycondensation structure of a dicarboxylic acid and a glycol (diol).

Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyetanedicarboxylic acid, and 5-sodium sulfone as aromatic dicarboxylic acids. Aromatic dicarboxylic acids such as dicarboxylic acids, oxalic acids, succinic acids, adipic acids, sebacic acids, dimer acids, maleic acids, fumaric acids and other aliphatic dicarboxylic acids, and 1,4-cyclohexanedicarboxylic acids and other alicyclic dicarboxylic acids. , Each component such as an oxycarboxylic acid such as paraoxybenzoic acid can be mentioned. Further, as a dicarboxylic acid ester derivative component, an esterified product of the above dicarboxylic acid compound, for example, dimethyl terephthalate, diethyl terephthalate, 2-hydroxyethylmethyl ester terephthalate, dimethyl 2,6-naphthalenedicarboxylic acid, dimethyl isophthalate, adipic acid. Each component such as dimethyl, diethyl maleate, and dimethyl dimerate can be mentioned.

Examples of the glycol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6. -Hydroxydihydroxy compounds such as hexanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, 1,4 Examples thereof include alicyclic dihydroxy compounds such as cyclohexanedimethanol, spiroglycol, 1,4: 3,6-dianhydro-D-glucitol (isosorbide), and aromatic dihydroxy compounds such as bisphenol A and bisphenol S. Each of these may be used alone or in combination of two or more.

As the polyester used in the present invention, a copolymerized polyester may be used. It is preferable that the copolymerized polyester is copolymerized with two or more of the above-mentioned polyester dicarboxylic acid components and / or two or more of the glycol components listed above. As a method of introducing the copolymerization component, the copolymerization component may be added at the time of polymerization of the polyester pellet as a raw material and used as a pellet in which the copolymerization component is polymerized in advance, or, for example, polyethylene naphthalate may be used. A method may be used in which a mixture of pellets polymerized alone and polyethylene terephthalate pellets is supplied to an extruder and copolymerized by an ester exchange reaction at the time of melting. Further, a film obtained by copolymerizing a small amount of trimellitic acid, pyromellitic acid and an ester derivative thereof may be used as long as the film-forming property is not affected.

When the thermoplastic resin A is polyester, it is preferable that the thermoplastic resin B is a thermoplastic resin incompatible with polyester. Thermoplastic resins that are incompatible with polyester include olefin resins such as polyethylene, polypropylene, polybutene, polymethylpentene, and cyclic olefins, styrene resins, polyacrylate resins, polycarbonate resins, polyacrylonitrile resins, and polyphenylene sulfide resins. Fluoro-based resin etc. are selected. Of these, olefin resins or styrene resins are preferable, and the olefin resins include polyethylene, polypropylene, and poly-4-methylpentene-1 (hereinafter, may be abbreviated as "polymethylpentene" or "PMP"). , Ethylene-propylene copolymer, ethylene-butene-1 copolymer, cyclic olefin, and polystyrene, polymethylpentene, polydimethylstyrene and the like are preferable as the styrene resin. These may be homopolymers or copolymers, and further, two or more kinds of thermoplastic resins may be used in combination. The thermoplastic resin B is preferably contained in an amount of 1 to 50% by mass with respect to the total mass of the highly reflective layer of the present invention. If the amount of the thermoplastic resin B is less than 1% by mass, the reflectance as a reflective layer may be insufficient, and if it is more than 50% by mass, the mechanical strength, heat resistance, and manufacturing cost of the polyester may decrease.

As a method for obtaining the mass ratio of the polyester and the thermoplastic resin B, a method of combining a plurality of analyzes according to the type of each resin can be considered. A method of removing only polyester with a solvent, separating the remaining thermoplastic resin B with a centrifuge, and determining the mass ratio from the mass of the obtained residue, IR (Infrared Spectroscopy), ¹ H-NMR or ¹³ . After identifying each resin by C-NMR, both polyester and thermoplastic resin B are dissolved in a soluble solvent, impurities and inorganic substances are removed by centrifugation, and the mass ratio is determined by determining the concentration by absorbance. The method can be used. As the solvent soluble in polyester, trifluoroacetic acid, 1,1,1,3,3,3-hexafluoro-2-propanol, o-chlorophenol and the like are used.

The highly reflective layer of the present invention preferably reflects visible light by a method containing a white pigment, a method containing bubbles inside, or a method combining these.

The reflective material of the present invention contains bubbles, and the content thereof is preferably 1% by volume or more and 80% by volume or less with respect to the total volume of the reflective material. By setting the content of bubbles in the above range, it is easy to increase the reflectance. If the content of bubbles is less than 1% by volume, the reflectance may be insufficient. Further, if the number of bubbles exceeds 80% by volume, the structure may not be maintained. More preferably, it is 10% by volume or more and 60% by volume or less. More preferably, it is 20% by volume or more and 50% by volume or less.

The reflective material of the present invention preferably has a glossiness of 80 ° or more at an incident angle of 85 ° on the surface of the reflective material. It is more preferably 90 or more, still more preferably 100 or more. The upper limit is not particularly limited, but it is preferable that the upper limit is 150 or less because the production becomes easy. When the glossiness of 85 ° is 80 or more, when the LED substrate is incorporated as a light source of the backlight, it is preferable because it is easy to suppress the luminance unevenness that becomes brighter only directly above the LED as compared with other places. When the glossiness of 85 ° is less than 80, when the LED substrate is incorporated as a light source of the backlight, it may not be possible to suppress the uneven brightness in which only the area directly above the LED becomes brighter than in other places.

The highly reflective layer of the present invention may be laminated with a solder resist layer via an adhesive layer. The adhesive layer is a layer made of a resin having adhesive properties, and can be produced by various methods such as coating using a gravure coater, a die coater, a bar coater, a knife coater, extruded lamination, and transfer. The resin used for the adhesive layer is not particularly limited, but for example, an acrylic resin, a polyether resin, a urethane resin, a silicone resin, or the like is preferably used. As the type of resin, it is preferable to select an appropriate resin depending on the object to be adhered, but a silicone-based resin is most preferable from the viewpoint of heat resistance.

The pressure-sensitive adhesive layer in the present invention preferably has a thickness of 0.1 μm or more and 30 μm or less. It is more preferably 0.5 μm or more and 20 μm or less, and further preferably 1 μm or more and 15 μm or less. If the thickness is less than 0.1 μm, the adhesive strength may be insufficient. Further, if it is larger than 30 μm, the thickness of the reflective material may become too large.

The LED substrate of the present invention may be entirely sealed with a transparent resin including the LED light source and the reflective material. Transparency means that the total light transmittance of a solid measured in accordance with JIS-K7361-1 (1997) is 50% or more. Examples of the transparent resin include a thermoplastic resin, a thermosetting resin, and a photocurable resin. Specifically, methacrylic resin such as polymethylmethacrylate, styrene resin such as polystyrene and styrene-acrylonitrile copolymer, polycarbonate resin, polyester resin, phenoxy resin, polyvinyl alcohol resin, polyester resin, epoxy resin, phenol resin, Examples thereof include silicone resin.

The LED substrate of the present invention is preferably used as a backlight. That is, the LED substrate of the present invention is suitable as an LED substrate for a backlight. In the case of a backlight using the LED substrate of the present invention, it is possible to reduce the thickness and have excellent in-plane brightness uniformity. Is preferable as an LED substrate.

Hereinafter, the present invention will be described in detail with reference to Examples. Each characteristic value was measured by the following method.

(1) Height of LED light source (H), thickness of reflective material (T)
Observation was performed using a surface shape measuring device VertScan 2.0 (manufactured by Ryoka System Co., Ltd.). The height from the surface portion of the base material including the metal circuit portion to the apex portion of the LED light source was defined as the height (H) of the LED light source. Similarly, the height from the surface portion of the base material including the metal circuit portion to the outermost surface of the reflective material was defined as the thickness (T) of the reflective material. When the surface portion of the base material was not exposed, the height (H) and the thickness (T) were calculated by observing the cut surface.

(2) Surface roughness SRa
Measured using a three-dimensional fine surface shape measuring instrument (ET-4000AK manufactured by Kosaka Seisakusho), and from the obtained surface profile curve, according to JIS B 0601 (1994), the arithmetic mean roughness SRa of the outermost surface of the reflective material The value was calculated. When the reflective material had a highly reflective layer, the measurement was performed on the surface of the highly reflective layer, and when only the resist layer was used, the measurement was performed on the surface of the resist layer. The measurement conditions are as follows.

X-direction measurement length: 0.5 mm, X-direction feed rate: 0.1 mm / sec.

Y-direction feed pitch: 5 μm, number of Y-direction lines: 40.

Cutoff: 0.25 mm.

Needle pressure: 0.02mN
Measurement terminal: Made of diamond, R = 0.5 μm, 60 °
(3) Glossiness Using a digital variable angle gloss meter UGV-5B (manufactured by Suga Test Instruments Co., Ltd.), the glossiness of 85 ° was measured according to JIS Z-8741 (1997). The measurement conditions are the values when the 85 ° glossiness is an incident angle = 85 ° and a light receiving angle = 85 °. When the reflective material had a highly reflective layer, the measurement was performed on the surface of the highly reflective layer, and when only the resist layer was used, the measurement was performed on the surface of the resist layer.

(4) Volume Fraction of Bubbles in the Reflective Material Using a microtome, the reflective material is cut perpendicular to the surface direction of the reflective material without crushing the cross section in the thickness direction. The in-plane cutting direction was performed in two directions, an arbitrary direction and a direction perpendicular to the arbitrary direction. Next, the cut cross section is observed using a scanning electron microscope, and an image magnified at 5000 times is obtained. The observation location shall be randomly determined within the layer, but the vertical direction of the image shall be parallel to the thickness direction of the reflective material. In addition, the observation position was moved in the thickness direction to prepare a continuous image from one surface to the other. In the cross-sectional image in each direction, the area (S _v ) of the bubble portion is divided by the total cross-sectional area (S _all ) of the reflective material, and (S _v / S _all ) × 100 is the volume fraction of the bubbles in the image. The volume fraction (%) of bubbles was calculated from the additive average of all images.

(5) Reflectiveness and uneven brightness Place a transparent acrylic plate (thickness 0.6 mm) and a QD sheet taken out from a commercially available TV (Samsung Electronics, Q8) on the LED substrate so that OD = 5 mm, and evaluate. Created a backlight for. The measurement was performed from the front direction, that is, the direction perpendicular to the backlight, using a two-dimensional color luminance meter CA-2000 manufactured by Konica Minolta Sensing Co., Ltd. The luminance meter was installed so that the distance between the camera and the substrate was 50 cm, and the average luminance in an area of 30 mm × 60 mm in the center of the substrate was measured. The resolution was 60 × 120. The voltage was adjusted and measured so that a current of 500 mA would flow through the LED board with a DC power supply device. The brightness in Reference Example 1 was set to 100%, and the reflectivity was evaluated as follows.
A: Relative brightness 120% or more B: Relative brightness 110% or more and less than 120% C: Relative brightness 100% or more and less than 110% D: Relative brightness less than 100%.

Similarly, the ratio of the maximum luminance Lmax and the minimum luminance Lmin in the area was taken, and the luminance unevenness was evaluated as follows.
A: Lmax / Lmin is less than 1.2 B: Lmax / Lmin is 1.2 or more and less than 1.5 C: Lmax / Lmin is 1.5 or more and less than 1.8 D: Lmax / Lmin is 1.8 or more.

[Raw materials used]
(1) Polyester resin (a)
Polymerization of terephthalic acid and ethylene glycol using antimony trioxide as a catalyst was carried out by a conventional method to obtain polyethylene terephthalate (PET). The glass transition temperature of the obtained PET was 77 ° C., the melting point was 255 ° C., the intrinsic viscosity was 0.63 dl / g, and the terminal carboxyl group concentration was 40 eq. It was / t.

(2) Copolymerized polyester resin (b)
A commercially available 1,4-cyclohexanedimethanol copolymerized polyester (GN001 manufactured by Eastman Chemical Company) was used.

(3) Copolymerized polyester resin (c)
A commercially available PBT-PAG (polyalkylene glycol) copolymer "Hytrel 7247" (manufactured by Toray DuPont Co., Ltd.) was used. The resin is a block copolymer of PBT (polybutylene terephthalate) and PAG (mainly polytetramethylene glycol).

(4) Thermoplastic resin (d)
A commercially available cyclic olefin resin "TOPAS 6017" (Nippon Polyplastics Co., Ltd.) was used.

(5) Titanium dioxide master (e)
50 parts by weight of the polyester resin (a) and 50 parts by weight of titanium dioxide particles (number average particle size 0.25 μm) were kneaded with a twin-screw extruder to obtain titanium dioxide master pellets (e).

(6) Titanium dioxide master (f)
To 50 parts by mass of titanium dioxide particles (number average particle size 0.25 μm), 0.25 parts by mass of a silane coupling agent “11-100 Adaptive” (manufactured by Tohredo Corning Co., Ltd.) was added, and the surface was treated by a conventional method. Then, the thermoplastic resin (d) was kneaded with 50 parts by mass by a twin-screw extruder to obtain a titanium dioxide master pellet (f).

(7) Aggregated silica master (g)
Agglomerated silica particles (number average particle diameter 4.0 μm) were kneaded with 10 parts by mass of particle concentration and 90 parts by mass of polyester resin (a) with a twin-screw extruder to obtain silica master (g).

(Reference Example 1, Examples 1 to 9, Comparative Examples 1 to 4)
[Highly reflective layers 1 to 7]
The raw materials having the compositions shown in Table 2 are vacuum-dried at a temperature of 180 ° C. for 6 hours, then the raw materials for the core layer (Y) are supplied to the main extruder, melt-extruded at a temperature of 280 ° C., and then filtered by a 30 μm cut filter. After supplying the raw material for the surface layer (X) to the sub-extruder and filtering it with a 30 μm cut filter after melt extrusion at a temperature of 290 ° C., the surface layer (X) is both the core layer (Y) in the T-die composite mouthpiece. They were merged so as to be laminated (X / Y / X) on the surface layer. The surface layer (X) and the core layer (Y) were laminated so that the mass ratio was 1/8/1.

Then, it was extruded into a sheet to form a molten sheet, and the molten sheet was coagulated and cooled and solidified on a drum maintained at a surface temperature of 25 ° C. by an electrostatic application method to obtain an unstretched film. Subsequently, the unstretched film was preheated with a roll group heated to a temperature of 80 ° C., and then stretched in the longitudinal direction (longitudinal direction) at the magnification shown in Table 2 while irradiating from both sides with an infrared heater to 25 ° C. A uniaxially stretched film was obtained by cooling with a roll group at the same temperature. Then, while grasping both ends of the uniaxially stretched film with clips, the film was guided to a preheating zone at 110 ° C. in the tenter, and then stretched at 120 ° C. in the direction perpendicular to the longitudinal direction (horizontal direction) at the magnification shown in Table 2. Further, subsequently, the heat treatment at the temperature shown in Table 2 was performed in the heat treatment zone in the tenter, and then the film was uniformly slowly cooled and then wound on a roll to obtain a white film having the thickness shown in Table 2. The white film contains 100 parts by mass of a silicone resin adhesive (SH4280PSA, manufactured by Toray Dow Corning Co., Ltd.), 0.15 parts by mass of a benzoyl peroxide catalyst (Niper (R) BMT-K40, manufactured by Nichiyu Co., Ltd.), and A mixture of 50 parts by mass of toluene was applied so that the thickness after drying was 5 μm, and heat-cured at 70 ° C. for 3 minutes and at 180 ° C. for 5 minutes.

[LED board]
An LED substrate was prepared in which 30 × 60 LEDs having the sizes shown in Table 1 were arranged in parallel on a resin substrate at a pitch of 2.54 mm. A resist (white solder resist PSR-4000: manufactured by Taiyo Ink Mfg. Co., Ltd., containing 30% by mass of titanium oxide) and a highly reflective layer were formed on the resin substrate with the configurations and thicknesses shown in Tables 1 and 2.

Claims (7)

An LED substrate having at least a base material, an LED light source, and a reflective material.
The height (H) of the LED light source is 300 μm or less, and the height (H) is 300 μm or less.
The thickness (T) of the reflective material is 20 μm or more and 120 μm or less.
An LED substrate having a three-dimensional surface roughness SRa of the surface of the reflective material of 10 nm or more and less than 300 nm. The LED substrate according to claim 1, wherein the ratio (T / H) of the height (H) of the LED light source to the thickness (T) of the reflective material is 0.1 to 1.0. The LED substrate according to claim 1 or 2, wherein the glossiness at an incident angle of 85 ° on the surface of the reflective material is 80 or more. The LED substrate according to any one of claims 1 to 3, wherein the reflective material contains titanium oxide, and the content thereof is 0.1% by weight or more and 50% by weight or less with respect to the total weight of the reflective material. The LED substrate according to any one of claims 1 to 4, wherein the reflective material contains a polyester resin, and the content thereof is 5% by weight or more with respect to the total weight of the reflective material. The LED substrate according to any one of claims 1 to 5, wherein the reflective material contains bubbles, and the content thereof is 1% by volume or more and 80% by volume or less with respect to the total volume of the reflective material. A backlight using the LED substrate according to any one of claims 1 to 6.