JP2011116914A - Fluorescent solution, fluorescent film and use thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorescent solution having a uniformly dispersed fluorescent material and further giving a fluorescent film without deteriorating the fluorescent material; to provide a fluorescent film having excellent optical characteristics, film flatness and heat resistance using the solution; and to provide electronic devices such as a light emitting device, an illumination device, and a backlight for a display device, using the fluorescent film. <P>SOLUTION: The fluorescent solution includes: (A) a transparent resin component; (B) a fluorescent component containing at least one fluorescent material which is excited by light of a specific wavelength range and emits light of a different wavelength range; and (C) an organic solvent component containing at least one organic solvent of a specific weight of at least 1.0. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a transparent resin, a phosphor, a fluorescent solution containing an organic solvent, a fluorescent film, and uses thereof. In particular, the present invention relates to a fluorescent solution and a fluorescent film containing a fluorescent substance that is excited by light emitted from a light emitting diode, a semiconductor laser, or the like, and uses thereof, and in particular, a white lighting apparatus using a blue light emitting diode (blue LED) as a light source In addition, the present invention relates to a fluorescent solution, a fluorescent film, and a use thereof that can be suitably used as a backlight for a liquid crystal display device.

  A light emitting device using a light emitting diode (LED) is generally manufactured by sealing an LED element with a transparent resin layer (sealing resin layer) in which phosphors are dispersed. The phosphor contained in the encapsulant absorbs a part of the light emitted from the LED element and is excited to emit fluorescence in a specific wavelength region. As a result, the light emitted from the light emitting diode is a color mixture of the light emitted from the LED element and the light emitted from the phosphor. For example, by using a blue LED element as the LED element and using a phosphor that emits yellow fluorescence as the phosphor, the LED emits white light that is a mixed color of blue and yellow.

  The color that the LED develops is determined by the type of the LED element, the type and concentration of the phosphor dispersed in the sealing resin layer that covers the LED element, the thickness of the sealing material layer, and the like.

  Usually, the sealing resin layer is formed by dripping or potting a liquid sealing resin material and then curing it, but the phosphor content in the sealing resin layer and the thickness of the sealing material layer. There is a problem that the color tone varies among individual LEDs due to variations in (or potting amount).

  Further, since the sealing resin layer is in direct contact with the electrode, the fluorescent material, and sometimes the organic dye system, has a problem that the deterioration due to direct current is significant.

Therefore, a planar light source suitable for a liquid crystal display device using a fluorescent film that is not in direct contact with the electrode has been proposed. (Patent Document 1)
Moreover, in order to make it easy to control the phosphor content and the resin layer thickness, an optical semiconductor manufacturing method using a fluorescent film has been proposed. (Patent Document 2)

Japanese Patent No. 3116727 JP 2009-1441066 A

  Patent Document 1 describes a method for coating a film made of a phosphor, an acrylic resin, and butyl carbitol acetate as a method for producing a fluorescent film. It was a problem that the phosphor deteriorates due to moisture absorption and the luminous efficiency decreases.

  Further, Patent Document 2 exemplifies that methyl ethyl ketone is used as a solvent. However, as in Patent Document 1, deterioration of the phosphor has been a problem.

  The present invention has been accomplished in view of the above circumstances, and an object of the present invention is to obtain a fluorescent solution that can uniformly disperse a phosphor and obtain a phosphor film without deteriorating the phosphor. Furthermore, it aims at providing the fluorescent film excellent in an optical characteristic, film flatness, and heat resistance obtained using the said solution. Another object of the present invention is to provide electronic devices such as a light emitting device, a lighting device, and a backlight for a display device using the fluorescent film of the present invention.

  As a result of intensive studies to solve the above-described problems, the present inventors have produced (A) a transparent resin, (B) a phosphor, and (c) a specific gravity of 1.0 or more when producing a fluorescent film. It has been found that it is effective to use a fluorescent solution containing a solvent. As a result, it is difficult to reduce the dispersibility of the phosphor, and the deterioration of the phosphor during film formation can be reduced. The headline has led to the present invention.

  That is, the present invention has the following configuration.

  (A) a transparent resin component containing at least one transparent resin, and (B) a phosphor component containing at least one phosphor that is excited by light in a specific wavelength region and emits light in a different wavelength region. The fluorescent solution which consists of (C) organic solvent component containing a seed | species organic solvent WHEREIN: The said organic solvent component is related with the fluorescent solution characterized by including the organic solvent whose specific gravity is 1.0 or more.

  Another invention of the present invention relates to a fluorescent film produced using a fluorescent solution.

  Furthermore, the present invention relates to an electronic device using a fluorescent solution or a fluorescent film.

  The fluorescent solution according to the present invention is suitable as a solution for producing a fluorescent film in which the phosphor is uniformly dispersed since it has a good dispersibility of the phosphor. In addition, the fluorescent film according to the present invention has a uniform luminous property because the phosphor is uniformly and finely dispersed, and also has excellent brightness because of its excellent transparency. Therefore, the use as electronic devices, such as a light-emitting device, an illuminating device, a backlight for liquid crystal display devices, is anticipated, for example.

  Hereinafter, embodiments of the present invention will be specifically described.

  An embodiment of the present invention will be described as follows. Note that the present invention is not limited to this.

  The fluorescent solution according to the present invention is used in electronic devices such as a light emitting device, a lighting device, and a backlight for a liquid crystal display device. In particular, it can be used as a solution for film production for converting the color of light in a device using a blue LED element as a light source.

  The fluorescent solution of the present invention comprises (A) a transparent resin component, (B) a fluorescent component, and (C) an organic solvent component as essential components, and (C) the organic solvent component contains an organic solvent having a specific gravity of 1.0 or more. It is a feature.

  Hereinafter, (A) transparent resin component, (B) fluorescent component, (C) organic solvent component, (D) and other components contained in the phosphor solution will be described in detail.

(A) Transparent resin The transparent resin component used in the present invention is not particularly limited as long as it is a resin having good light transmissivity, but acrylic resin, lactone resin, glutarimide resin, polycarbonate resin, silicone resin. Resins, cellulose resins, cycloolefin resins, transparent polyimide resins, polyester resins and the like can be preferably used.

  In particular, a resin having a thickness of 40 μm to 60 μm and a total light transmittance of 80% or more can be preferably used. The total light transmittance can be measured with a general haze meter such as 300A or NDH5000 (both manufactured by Nippon Denshoku Industries Co., Ltd.).

  Among the above-mentioned transparent resins, a transparent resin having a film-like in-plane retardation of 20 nm or less and a thickness direction retardation of 50 nm or less can be preferably used as a good optical property. When the in-plane retardation exceeds 20 nm or the thickness direction retardation exceeds 50 nm, when a fluorescent film manufactured from the fluorescent solution of the present invention is disposed between the light guide plate and the deflection plate of the liquid crystal display device, The contrast in the liquid crystal display device tends to be lowered.

  Among the transparent resins, a transparent resin having a glass transition temperature of 100 ° C. or higher is preferable, and a transparent resin having a glass transition temperature of 150 ° C. or higher can be more preferably used.

  When the glass transition temperature is less than 100 ° C., the resin is softened due to heat generation of the LED element, and color unevenness is likely to occur, or color discoloration tends to occur due to a decrease in fluorescence emission efficiency.

  Examples of the transparent resin having a high glass transition temperature include a polycarbonate resin and a transparent polyimide resin, and a transparent polyimide resin can be more preferably used particularly in terms of a small thermal expansion coefficient.

  Previously, the output was small and heat resistance was not an issue, but as brightness increases and size increases in the future, higher output is required, and heat resistance of the materials used, especially thermal degradation, is an issue It is becoming. Furthermore, in the future, there is a high possibility that color change due to dimensional change due to heat as well as thermal degradation will become a problem. Therefore, a material having a small thermal expansion coefficient is required. Specifically, 100 ppm or less is preferable in the temperature range of 100 ° C. or less, 50 ppm is more preferable, and 20 ppm or less is particularly preferable.

  Said transparent resin can also be used independently, and may mix and use 2 or more types of transparent resin.

(B) Phosphor component The phosphor component used in the present invention is not particularly limited as long as it is a phosphor that is excited by light in a specific wavelength region and emits light in a different wavelength region. In the case of an element, a yellow phosphor can be preferably used as the phosphor. The yellow phosphor is excited by partially absorbing blue light and can emit yellow fluorescence. By this color conversion, white light can be emitted by mixing blue light that is not absorbed by the phosphor and yellow light emitted from the phosphor.

Examples of the yellow phosphor include Y A G such as RE ₃ (Al, Ga) ₅ O ₁₂ : Ce phosphor (R E represents at least one selected from Y 1, G d, and L a). Phosphor, A E ₂ S i O ₄ : Eu phosphor (A E is an alkaline earth element such as S r, B a, C a, etc.) . As such a yellow phosphor, two types of phosphors having different dominant wavelengths can be used.

  As other phosphors, red phosphors and green phosphors can be preferably used in combination with yellow phosphors, particularly for adjusting the white color of blue LED elements.

The red phosphor, for example, L a ₂ O ₂ S: oxysulfide phosphor such as E u phosphor are preferably used, _{further, A E 2 S i 5 N} 8: represented by E u Nitride-based phosphor, Y ₂ Si ₃ O ₃ N ₄ : Oxynitride-based phosphor represented by Ce or A E x (Si, Al) 1 ₂ (N, O) _{1 6} : Eu Sialon phosphors and the like can also be preferably used.

Examples of the green phosphor include SrGa ₂ S ₄ : Eu and CaSrGa ₂ S ₄ : Eu.

  In addition to the inorganic phosphors described above, organic phosphors (dyes or pigments) can also be preferably used.

  The above phosphors can be used alone or in combination of two or more.

  The particle size of the phosphor is not particularly limited, but in the case of an inorganic system, a phosphor having an average primary particle size in the range of 0.5 μm to 100 μm is preferable, 1 μm to 50 μm is more preferable, and 2 μm to 10 μm is more preferable. preferable. If it is 0.5 μm or less, the phosphor is less likely to absorb light, so that the color tends not to be white. If it is 100 μm or more, the total light transmittance tends to decrease and the luminance tends to decrease.

  Further, the phosphor is preferably surface-treated for the purpose of increasing the affinity with the resin composition, or for the purpose of suppressing or controlling the aggregation of the fluorescent component.

  Conventionally, since the LED light source is a point light source, there has been no major problem with respect to dispersibility related to color uniformity. In addition, when the phosphor is mixed in the sealing material, since discoloration occurs due to heat, dispersibility such as segregation is more important than uniform dispersibility. However, in the fluorescent film, discoloration due to heat is less likely to occur than in a sealing material, and a uniform color is required to be developed by increasing the area, and it is necessary to uniformly disperse the phosphor.

  The method of surface treatment of the phosphor is not particularly limited, but may be performed using a known surface treatment agent under known conditions. Specific examples of the compound that can be used as the surface treatment agent include silane coupling agents, silane compounds such as dimethyldichlorosilane, hexamethyldisilazane, and silicone oil, and titanate coupling agents. Titanium compounds, fatty acids such as stearic acid, various surfactants, various resin acids, various phosphate esters, and the like can be used. In particular, from the viewpoints of good dispersibility in the resin composition and easy control of the surface treatment degree of the phosphor, silane compounds and titanium compounds can be used more preferably.

  Aggregates can be suppressed by the surface treatment, and the average particle size in the particle size distribution in the solution or in the film is preferably suppressed to about 3 times or less of the primary particle size.

(C) Organic solvent component The organic solvent used in the present invention is not particularly limited as long as it is an organic solvent capable of dissolving the transparent resin component (A), but an organic solvent having a specific gravity of 1.0 or more is preferable. Can be used.

  In general, a phosphor has a specific gravity of 2 or more. Therefore, when a solvent having a specific gravity of 1.0 or more is used, the phosphor tends not to settle in the solution. In addition, when a fluorescent solution is formed into a film by a solution casting method, that is, when a film is produced by casting (casting) a fluorescent solution on a substrate and drying it in a drying path, the phosphor being dried is also used. There is a tendency to prevent sedimentation.

  Preferred organic solvents include polyhydric alcohol derivatives such as ethylene glycol monomethoxymethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, methylene chloride, chlorobenzene, о-chlorotoluene, p-chlorotoluene, 1,2- Halogenated hydrocarbons such as dichloroethane and 1,1-dichloroethane are exemplified.

  In view of excellent light conversion efficiency of the obtained fluorescent film, a halogenated hydrocarbon system can be particularly preferably used. The reason why light conversion efficiency is excellent is not clear, but halogenated hydrocarbons are solvents that are relatively difficult to absorb moisture. When adjusting fluorescent solutions or manufacturing fluorescent films, phosphors with poor water resistance are deteriorated by moisture. It is speculated that it is suppressing. As the halogenated hydrocarbon, methylene chloride that can be dried at a relatively low temperature can be more preferably used.

(D) Other components The fluorescent solution of the present invention may contain a filler component, a transparent bead component or the like, if necessary. The purpose is to adjust the viscosity of the fluorescent solution or to improve the heat resistance of the fluorescent film. In addition, the filler component may be included, and the inorganic filler component is not particularly limited, but titanium oxide, barium sulfate, barium titanate, finely divided silica, fumed silica, synthetic silica, talc, clay, magnesium carbonate, Examples thereof include calcium carbonate, aluminum oxide, aluminum hydroxide, fumed metal oxide, and mica powder. Inorganic fillers such as finely divided silica, fumed silica, synthetic silica, and fumed metal oxide are more preferably used.

  The inorganic filler is preferably surface-treated in the same manner as the phosphor component (B).

  Moreover, instead of the filler component, silica or titanium oxide, which is a raw material of silica or titanium oxide, may be mixed, and silica or titanium oxide may be generated in the solution by a known sol-gel method.

  In addition, since the filler obtained by the sol-gel method has a particle size of 1 μm or less, there is an advantage that the effect of improving heat resistance is easily obtained as compared with the case where the inorganic filler component is mixed, and the transparency is not easily impaired. .

  The fluorescent solution of the present invention can contain transparent beads for the purpose of diffusing the light transmitted through the fluorescent film. Transparent beads are obtained by grafting (co) polymerizing crosslinked poly (meth) acrylates and monomers containing either aromatic vinyl or (meth) acrylate as an essential component to the crosslinked polymer. Examples thereof include a core-shell type fine particle resin, a silicone resin fine powder, and fine powder silica.

<Fluorescent film>
The fluorescent film of the present invention can be obtained using the fluorescent solution of the present invention. Specifically, the above-described fluorescent solution can be cast or applied to the surface of the support, and the cast or applied fluorescent solution can be dried to form a film. If this fluorescent film is peeled off from the support, a single-layer fluorescent film can be obtained.

  The fluorescent film can be obtained by film formation by the melt extrusion method or the above-described casting method, but since a uniform thickness accuracy is required by increasing the area, it is advantageous to form the film by the casting method.

  The surface of the fluorescent film can be subjected to a surface treatment in order to improve the adhesion with other constituent materials in the electrical equipment. The film surface may be coated with a surface modifier such as a silane coupling agent or a titanate coupling agent, or subjected to a discharge treatment such as a corona treatment or a plasma treatment.

Further, it is preferable to form a light diffusion layer on at least one surface of the film.
The light diffusion layer can be formed by applying a solution containing at least one transparent resin component and at least one transparent bead to the film surface and drying it.

  The transparent resin is not particularly limited, but is the same component as the transparent resin component used for the fluorescent film in order to eliminate the influence of the interface between the film and the layer after forming the light diffusion layer or to reduce the warpage of the film. It is preferable to make it.

  As the transparent bead component, beads similar to the transparent beads listed in the above (D) other components can be preferably used. The particle diameter of the transparent beads is preferably selected in accordance with the required light diffusibility, but is preferably selected in the range of 1 to 20 um.

  Moreover, it is preferable to set the layer thickness of a light-diffusion layer in the range of -1um-+ 3um of the diameter of the bead used for the light-diffusion layer from the point of light diffusivity.

Claims (3)

(A) a transparent resin component containing at least one transparent resin, and (B) a phosphor component containing at least one phosphor that is excited by light in a specific wavelength region and emits light in a different wavelength region. A fluorescent solution comprising an organic solvent component (C) containing a seed organic solvent, wherein the organic solvent component contains an organic solvent having a specific gravity of 1.0 or more. Another invention of the present invention relates to a fluorescent film manufactured using a fluorescent solution. The present invention relates to an electronic device using a fluorescent solution or a fluorescent film.