JP6776422B2 - Wavelength conversion member, phosphor sheet, white light source device, and display device - Google Patents

Description

The present invention relates to a wavelength conversion member, a phosphor sheet, a white light source device, and a display device.

In recent years, a light source device that obtains white light by combining a light emitting diode and a phosphor that emits light having a different wavelength by wavelength-converting a part of the light emitted by the light emitting diode has been known. A light source device that obtains white light in a wide color range by using a light emitting diode and a wavelength conversion member containing an appropriately selected phosphor is often used.

Here, as the wavelength conversion member used in the white light source device using the blue light emitting diode, for example, a sulfide-based red phosphor and a green phosphor having a narrow band emission characteristic excellent in a wide color range characteristic are used. Examples thereof include a sheet-like phosphor layer dispersed in a transparent resin. Then, in one example of the white light source device, the entire light emitting surface of the light source unit having the blue light emitting diode is covered with a phosphor sheet including the phosphor layer.

Here, the above-mentioned fluorescent material sheet usually covers the light source unit from a position separated to some extent from the viewpoint of preventing deterioration of the fluorescent material used. Therefore, the above-mentioned fluorescent material sheet often requires a relatively large amount of fluorescent material in order to ensure good optical properties (for example, brightness). In general, a phosphor used in combination with a light emitting diode is expensive, and the proportion of the phosphor is large even in the cost structure of the phosphor sheet. For this reason, in order to promote the use of the fluorescent material sheet, it is important to reduce the amount of the fluorescent material used to reduce the cost, and various attempts have been made to achieve such a purpose. It has been done.

For example, Patent Document 1 uses a polymer composition in which a phosphor and a light diffusing material having two or more kinds of predetermined refractive indexes are dispersed in a polymer binder which is usually a silicone polymer. It is disclosed that the amount of light used can be reduced and the characteristic fluctuation in the production lot can be less likely to occur.

Japanese Unexamined Patent Publication No. 2014-078691

However, as a result of studies by the present inventors, it is said that the chromaticity of the light emitted through the wavelength conversion member obtained by using the polymer composition disclosed in the above patent document can fluctuate with time. It turned out that there was a problem.
Here, with respect to a wavelength conversion member using a phosphor and a light diffusing material, which can also be used for a white light source device, an idea and an attempt to maintain the chromaticity of light for a long period of time have been made so far. There wasn't.

An object of the present invention is to solve the above-mentioned problems in the past and to achieve the following object. That is, the present invention provides a wavelength conversion member and a phosphor sheet that can be manufactured at low cost and can suppress fluctuations in the chromaticity of light over time when used in a light source device. The purpose is. Another object of the present invention is to provide a white light source device and a display device which can be manufactured at low cost and whose chromaticity of light is suppressed with time.

Here, the present inventors have focused for the first time on reducing the time-dependent fluctuation of the chromaticity of light with respect to a wavelength conversion member made of a phosphor and a light diffusing material. Then, as a result of diligent studies to achieve the above object, by appropriately selecting the material used for the wavelength conversion member, the amount of the phosphor used is reduced, the cost is reduced, and the chromaticity of light is reduced. It was found that the above can be maintained for a long period of time, and the present invention was completed.

The present invention is based on the above-mentioned findings by the present inventors, and the means for solving the above-mentioned problems are as follows. That is,
<1> A phosphor that converts at least a part of the wavelength of the incident light and emits an emitted light having a wavelength different from that of the incident light.
A light diffusing element that diffuses at least one of the incident light and the emitted light,
The base material that holds the light diffusing element and
It is a wavelength conversion member having
The light diffusing element is a silicone resin and
The base material is a wavelength conversion member, characterized by containing a hydrogenated styrene-based copolymer.
By using a silicone resin as a light diffusing element in the wavelength conversion member according to <1>, the amount of a phosphor used can be reduced due to the light scattering effect, and further, the silicone resin and the base material can be used as a base material. By using this in combination with the hydrogenated styrene-based copolymer of No. 1, it is possible to surprisingly maintain the time-dependent fluctuation of the chromaticity of the output light.

<2> The wavelength conversion member according to <1>, wherein the hydrogenated styrene-based copolymer is a styrene-ethylene-butylene-styrene block copolymer elastomer.

<3> The wavelength conversion member according to <1> or <2>, wherein the light diffusing element is a silicone resin particle.

<4> The wavelength conversion member according to <3>, wherein the silicone resin particles have a particle size of 2 μm or more.

<5> The wavelength conversion member according to any one of <1> to <4>, which is a sulfide-based phosphor.

<6> The wavelength conversion member according to <5>, wherein the sulfide-based phosphor contains at least one of a red sulfide phosphor and a green sulfide phosphor.

<7> The wavelength conversion member according to <6>, wherein the red sulfide phosphor is a calcium sulfide phosphor, and the green sulfide phosphor is a thiogallate phosphor.

<8> The above-mentioned <1> to <7>, wherein the absolute value of the difference between the refractive index of the hydrogenated styrene-based copolymer and the refractive index of the silicone resin is 0.04 or more. It is a wavelength conversion member of.

<9> The wavelength conversion member according to any one of <1> to <8>, which is in the form of a sheet.

<10> A phosphor sheet comprising the wavelength conversion member according to <9> and a base material sandwiching the wavelength conversion member.

<11> The phosphor sheet according to <10>, wherein the base material is a water vapor barrier film.

<12> The phosphor sheet according to <11>, wherein the water vapor transmittance of the water vapor barrier film is 0.05 to 20 g / m ² / day.

<13> A white light source device including the wavelength conversion member according to any one of <1> to <9>.

<14> A display device including the white light source device according to <13>.

According to the present invention, there is provided a wavelength conversion member and a phosphor sheet that can be manufactured at low cost and can suppress fluctuations in the chromaticity of light over time when used in a light source device. be able to. Further, according to the present invention, it is possible to provide a white light source device and a display device which can be manufactured at low cost and whose chromaticity of light is suppressed with time.

It is a figure which conceptually shows the action brought about by the light diffusing element in the wavelength conversion member which concerns on one Embodiment of this invention. It is a figure which shows typically the fluorescent substance sheet which concerns on one Embodiment of this invention. It is a figure which shows typically the structure of the light source used for evaluation in an Example.

(Wavelength conversion member)
Hereinafter, the wavelength conversion member according to the embodiment of the present invention will be described.
The wavelength conversion member of one embodiment of the present invention (hereinafter, may be simply referred to as "the wavelength conversion member of the present invention") has at least a phosphor, a light diffusing element, and a base material. If necessary, it may have a coloring material or any other element.

<Fluorescent material>
The phosphor of the wavelength conversion member of the present invention has a property of converting at least a part of the wavelength of the incident light and emitting an emitted light having a wavelength different from the incident light. In addition, the phosphor is retained in the base material together with the light diffusing element described later.
The phosphor is not particularly limited as long as it has the above-mentioned properties, and can be appropriately selected according to the purpose, type, absorption band, light emission band, etc. For example, from the viewpoint of the material, it is a sulfide type. Examples thereof include phosphors, oxide-based phosphors, nitride-based phosphors, fluoride-based phosphors, and other phosphors (YAG-based phosphors, sialone-based phosphors), and red fluorescence from the viewpoint of color. Examples include the body, a green fluorescent substance, and a yellow fluorescent substance. These may be used alone or in combination of two or more. Among these, the sulfide-based phosphor is preferable in that it has a sharp emission spectrum and therefore can reproduce a wide color gamut. On the other hand, sulfide-based phosphors are generally easily deteriorated by water vapor in a high-temperature and high-humidity environment, and it is difficult to use them in white LEDs. Therefore, when a sulfide-based phosphor is used, it is desirable to mold the phosphor layer as a wavelength conversion member into a sheet and cover it with a base material that does not allow water vapor to permeate.

In addition, examples of the sulfide-based phosphor that can be used in the present invention include a red sulfide phosphor and a green sulfide phosphor. Specifically, the sulfide phosphor that can be used in the present invention preferably contains at least one of a red sulfide phosphor and a green sulfide phosphor.
If a mixture of a red sulfide phosphor and a green sulfide phosphor is used as the sulfide-based phosphor, the obtained wavelength conversion member can be suitably used for a white light source device including a blue light emitting diode.

Here, the red sulfide phosphor is, for example, a red sulfide phosphor having a red fluorescence peak having a wavelength of 620 to 670 nm when irradiated with blue excitation light, specifically, CaS: Eu (calcium sulfide (CS) fluorescence). Body), SrS: Eu and the like. These may be used alone or in combination of two or more.
The green sulfide phosphor is, for example, a green sulfide phosphor having a green fluorescence peak having a wavelength of 530 to 550 nm when irradiated with blue excitation light, specifically, a thiogallate (SGS) phosphor (Sr _x M _{1). -xy} ) Ga ₂ S ₄ : Eu _y (M is any of Ca, Mg, Ba, and satisfies 0 ≦ x <1, 0 <y <0.2) and the like.
When a mixture of a red sulfide phosphor and a green sulfide phosphor is used as the phosphor, the proportion of the red sulfide phosphor in the entire phosphor is preferably 40% by mass to 60% by mass. As a result, in a white light source device including a blue light emitting diode, white light having a wide color gamut can be obtained.

The amount of the phosphor in the wavelength conversion member per unit area is not particularly limited, and can be appropriately selected according to the specifications of the phosphor, the chromaticity point of the light source, the diffusion characteristics of the light diffusing element of the light source member, and the like. .. Here, the amount of the phosphor in the wavelength conversion member per unit area is derived from the factors of the concentration of the phosphor in the phosphor layer and the thickness of the phosphor layer, and in addition to the above restrictions, light diffusion By using a silicone resin as an element in combination, for example, the concentration can be 4 g / m ² or less.

<Light diffusion element>
The light diffusing element of the wavelength conversion member of the present invention has a property of diffusing light emitted from a light emitting element such as a phosphor and / or a light emitting diode in the wavelength conversion member. Hereinafter, the action brought about by the light diffusing element in the wavelength conversion member will be conceptually described by taking as an example a case where a red phosphor and a green phosphor are used as the phosphor and a blue light emitting diode is used as the light source. The wavelength conversion member 100 shown in FIG. 1A contains three red phosphors 101 and three green phosphors 102, respectively. Here, nine blue lights (which can be considered as photons) 110 are emitted from the blue light emitting diode 104, and six of them are converted into three red lights 111 and three green lights 112. It is assumed that three blue lights are output to the outside through scattering such as reflection. In this process, it can be considered that each blue light 110 and the converted red light 111 and green light 112 are output to the outside while scattering such as reflection as shown in FIG. 1 (b). On the other hand, when the light diffusing element 103 is added to the wavelength conversion member 100, as shown in FIG. 1C, even if the numbers of the red phosphor 101 and the green phosphor 102 are reduced to two, respectively. , Three red lights 111, three green lights 112, and three blue lights 110 are output, and desired color conversion can be performed. This is because the presence of the light diffusing element 103 increases the scattering of the blue light 110 by the wavelength conversion member 100, which increases the chance that the blue light 110 is absorbed by each phosphor. Finally, in this example, it is possible to reduce the amount of phosphor used to two-thirds.

Here, the light diffusing element used in the present invention needs to be a silicone resin. If a silicone resin is used as the light diffusing element, the chromaticity of the output light can be surprisingly maintained over time when used in combination with a hydrogenated styrene-based copolymer as a base material.
The wavelength conversion member of the present invention may have any element other than the silicone resin as the light diffusing element. However, from the viewpoint of obtaining a desired effect, it is preferable that the wavelength conversion member of the present invention has only a silicone resin as a light diffusing element.

The shape of the silicone resin is not particularly limited and may be appropriately selected depending on the intended purpose, but it is preferably in the form of particles. In other words, the light diffusing element of the wavelength conversion member of the present invention is preferably silicone resin particles. If the silicone resin as the light diffusing element is in the form of particles, the light can be diffused more uniformly, and the amount of the phosphor used can be reduced without deteriorating the optical properties.

The particle size of the above-mentioned silicone resin particles is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 2 μm or more, preferably 20 μm or less, and light scattering. From the viewpoint of, it is more preferably 5 μm or less. When the particle size of the silicone resin particles is 2 μm or more, it is possible to suppress the agglomeration of the silicone resin particles in the manufacturing process of the wavelength conversion member, and to more reliably maintain the quality of the wavelength conversion member. Further, since the particle size of the silicone resin particles is 20 μm or less, the quality such as the coated surface quality and surface smoothness of the phosphor layer (usually assumed to have a thickness of about 30 to 70 μm) as a wavelength conversion member can be improved. Can be maintained.
In the present specification, the “particle size” refers to the average particle size calculated based on the particle volume distribution.

The concentration of the light diffusing element in the wavelength conversion member is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 1 to 10 times the concentration of the phosphor. By being 1 times or more the concentration of the phosphor, the amount of the phosphor used can be reduced by effective scattering of light, and by being 10 times or less the concentration of the phosphor, the brightness and the like can be reduced. It is possible to suppress deterioration of optical properties, generation of unevenness when the phosphor is applied, decrease in adhesion strength with a substrate, and the like.

<Base material>
The base material of the wavelength conversion member of the present invention is a material for holding a light diffusing element. Specifically, the base material according to the present invention is formed from a resin composition, and a light diffusing element can be dispersed in the base material.

Here, the base material used in the present invention needs to contain a hydrogenated styrene-based copolymer. If a hydrogenated styrene-based copolymer is used as the base material, the chromaticity of the light output from the wavelength conversion member can be surprisingly maintained over time when used in combination with a silicone resin as a light diffusing element. .. Further, since the hydrogenated styrene-based copolymer has double bonds removed by hydrogenation, the reactivity between the hydrogenated styrene-based copolymer and the phosphor is significantly low, and the base material itself It is considered that discoloration and discoloration of the output light can be effectively suppressed.
Further, the hydrogenated styrene-based copolymer has a property of having a high water vapor barrier property and a low water absorption. Therefore, the hydrogenated styrene-based copolymer can advantageously suppress the deterioration of the phosphor when a sulfide-based phosphor that is weak against water is used as the phosphor.
Since the hydrogenated styrene-based copolymer is thermoplastic, by using the hydrogenated styrene-based copolymer, for example, the curing operation required when an energy ray-curable silicone resin is used is not performed. , A wavelength conversion member can be obtained. Therefore, the wavelength conversion member can be manufactured at low cost.

The hydrogenated styrene-based copolymer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, styrene-ethylene-butylene-styrene block copolymer elastomer (SEBS), styrene-ethylene-propylene block. Examples thereof include a copolymer elastomer (SEP), a styrene-ethylene-propylene-styrene block copolymer elastomer (SEPS), and a styrene-ethylene-ethylene-propylene-styrene block copolymer elastomer (SEEPS). These may be used alone or in combination of two or more. Among these, the styrene-ethylene-butylene-styrene block copolymer elastomer is preferable in that the chromaticity of the output light can be maintained with time.

The ratio of the styrene unit in the hydrogenated styrene-based copolymer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 20 to 40% by mass. When the styrene unit in the hydrogenated styrene copolymer is 20% by mass or more, the mechanical strength of the base material can be improved, while when it is 40% by mass or less, the embrittlement of the base material can be improved. Can be suppressed.

Regarding the refractive index, the absolute value of the difference between the refractive index of the hydrogenated styrene copolymer used and the refractive index of the silicone resin as a light diffusing element is preferably 0.04 or more. It is more preferably 08 or more. When this absolute value is 0.04 or more, it is possible to sufficiently bring about the effect of sufficiently causing light scattering and reducing the amount of the phosphor used. Further, this absolute value is preferably 0.8 or less without any particular limitation.
It should be noted that the value of either the refractive index of the hydrogenated styrene-based copolymer or the refractive index of the silicone resin is not particularly limited.

The base material used in the present invention may contain a resin other than the hydrogenated styrene-based copolymer. Examples of the resin other than the hydrogenated styrene-based copolymer include known thermoplastic resins and photocurable resins.
However, from the viewpoint of more effectively maintaining the chromaticity of the output light over time, the proportion of the hydrogenated styrene-based copolymer in the resin contained in the base material is preferably 60% by mass or more. , 70% by mass or more is more preferable.

<Color material>
The wavelength conversion member of the present invention may have a coloring material as long as the object of the present invention is not impaired. Here, the coloring material is a substance that absorbs light in a desired wavelength region. The coloring material may be either an organic compound or an inorganic compound, or may be a pigment or a dye, but the dye of the organic compound is used in terms of uniform dispersion and dissolution in the resin. preferable.
The coloring material can be dispersed in the base material at an arbitrary concentration without any particular limitation.

<Shape>
The shape of the wavelength conversion member of the present invention is not particularly limited and may be appropriately selected depending on the intended purpose, and examples thereof include a sheet shape, a dome shape, and a cylindrical shape. Among these, the wavelength conversion member of the present invention can be preferably made into a sheet from the viewpoint of being used as a phosphor layer constituting a phosphor sheet in a planar light source device using a light emitting diode.

When the wavelength conversion member of the present invention is in the form of a sheet, the thickness thereof is not particularly limited and may be appropriately selected depending on the intended purpose, but 20 μm to 200 μm is preferable, and 40 μm to 100 μm is more preferable. If the thickness of the sheet-shaped wavelength conversion member is too thin or too thick, it is difficult to form it uniformly.

<Manufacturing method of wavelength conversion member>
Here, the sheet-shaped wavelength conversion member can be formed on an arbitrary base material. Further, when used for a phosphor sheet in a light source device using a sheet-shaped wavelength conversion member and a light emitting diode, the sheet-shaped wavelength conversion member can be directly formed on a base material constituting the phosphor sheet. .. The method for producing the fluorescent material sheet in this case will be described later.

(Fluorescent sheet)
The fluorescent material sheet of the present invention includes a sheet-shaped wavelength conversion member and a pair of base materials, and further includes other members appropriately selected as necessary. Here, the base material is usually transparent and has a flat plate shape, and has a structure that sandwiches the wavelength conversion member of the present invention described above.
Since the phosphor sheet of the present invention includes the wavelength conversion member of the present invention described above, it can be manufactured at low cost and suppresses time-dependent fluctuations in the chromaticity of light when used in a light source device. Is possible.

FIG. 2 is a diagram schematically showing a fluorescent material sheet according to an embodiment of the present invention. The phosphor sheet 1 in FIG. 2 includes a phosphor layer 100 as a wavelength conversion member and a pair of base materials 105 sandwiching the phosphor layer 100. The phosphor layer 100 has a red phosphor 101 and a green phosphor 102 as phosphors, a light diffusing element 103, and a base material 106. Specifically, the base material 106 holds the light diffusing element 103, and also holds the red phosphor 101 and the green phosphor 102.

The phosphor sheet of the present invention is not limited to the above-described embodiment, and for example, an arbitrary other member (for example, a layer containing a coloring material) is laminated on one side or both sides of the phosphor layer, and the laminated body is formed. An arbitrary other member (for example, a layer containing a coloring material) is laminated on one surface or both surfaces of a fluorescent material sheet sandwiching the fluorescent material layer and a pair of base materials sandwiching the phosphor layer. The fluorescent material sheet made of the above is also included in the present invention. Further, the fluorescent material sheet of the present invention may be sealed by heating the ends of a pair of base materials sandwiching the fluorescent material layer and welding them.

<Base material>
The base material is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a thermoplastic resin film, a thermosetting resin film, and a photocurable resin film (Japanese Patent Laid-Open No. 2011-13567). Japanese Patent Application Laid-Open No. 2013-32515, Japanese Patent Application Laid-Open No. 2015-967).
The material of the base material is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a polyester film such as a polyethylene terephthalate (PET) film or a polyethylene naphthalate (PEN) film; a polyamide film; a polyimide film. Polysulfone film; triacetyl cellulose film; polyolefin film; polycarbonate (PC) film; polystyrene (PS) film; polyether sulfone (PES) film; cyclic amorphous polyolefin film; polyfunctional acrylate film; polyfunctional polyolefin film; non-functional Saturated polyester film; epoxy resin film; fluororesin film such as PVDF, FEP, PFA; and the like. These may be used alone or in combination of two or more.
Among these, polyethylene terephthalate (PET) film and polyethylene naphthalate (PEN) film are particularly preferable.
The surfaces of these films may be subjected to a corona discharge treatment, a silane coupling agent treatment, or the like, if necessary, in order to improve the adhesion to the layers to be contacted.
The thickness of the base material is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 10 μm to 100 μm.

Further, this base material is preferably a water vapor barrier film in that deterioration due to hydrolysis of a phosphor (particularly a sulfide-based phosphor) can be further reduced. Here, the water vapor barrier film is a gas barrier film in which a metal oxide thin film such as aluminum oxide, magnesium oxide, or silicon oxide is formed on a plastic substrate such as PET or the surface of the film. For example, PET / SiOx / PET or the like. It may have a multi-layered structure.
The water vapor permeability of the water vapor barrier film is not particularly limited, as appropriate may be selected, 0.05 g / m ² / day to 20 g / m ² / day is preferred in accordance with the purpose, 0.05 g / m ² / day to 5 g / m ² / day and more preferably (e.g., 0.1 g / m ² / day about relatively low barrier performance). Within such a range, the invasion of water vapor can be suppressed and the phosphor layer can be protected from water vapor.
The water vapor transmittance can be, for example, a value measured under the conditions of a temperature of 40 ° C. and a humidity of 90%.

<Other parts>
Further, the fluorescent material sheet of the present invention may be provided with a cover member or the like at the end thereof without particular limitation. Further, the cover member may have a reflective layer such as an aluminum foil.
Here, the water vapor permeability of the cover member is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 1 g / m ² / day or less.

(Manufacturing of fluorescent sheet)
An example of the method for producing the fluorescent substance sheet of the present invention will be described below.
The method includes at least a stirring step (A) and a laminating step (B), and further includes a punching step (C) and a sealing step (D), if necessary.

-Stirring step (A)-
In the stirring step (A), for example, a resin containing a hydrogenated styrene-based copolymer is dissolved in a solvent to prepare a binder, and then the phosphor and the light diffusing element are mixed at a predetermined blending ratio to make a paste. A mixture is obtained. When the phosphor sheet as the wavelength conversion member contains the coloring material, the coloring material may be mixed together with the phosphor and the light diffusing element at a predetermined blending ratio. Here, the solvent is not particularly limited as long as it can dissolve the resin containing the hydrogenated styrene copolymer, and can be appropriately selected depending on the intended purpose. For example, toluene, methyl ethyl ketone, and the like. Mixtures, etc.

If the proportion of the resin in the paste-like mixture is too small, the adhesiveness becomes insufficient, and if it is too large, it becomes insoluble in the solvent. Therefore, 10% by mass to 40% by mass is preferable, and 20% by mass to 30% by mass is more preferable. ..

-Laminating process (B)-
In the laminating step (B), for example, a paste-like mixture is applied onto the first substrate, and a bar coater is used to make the coating thickness uniform. Next, the applied paste-like mixture is dried in an oven to remove the solvent, and a phosphor layer as a wavelength conversion member is formed. Then, using a device such as a thermal laminator, the second base material is bonded onto the phosphor layer, and the phosphor layer is sandwiched between the first base material and the second base material. Can be obtained.
The method for applying the paste-like mixture to the base material is not particularly limited, and a known method can be used.

-Punching process (C)-
In the punching process (C), for example, the raw fabric of the phosphor sheet obtained in the laminating step (B) is punched by a press machine, and a fluorescent substance of a predetermined size is exposed on the side surface of the end portion. Get a sheet.

-Seal step (D)-
In the sealing step (D), for example, using an aluminum foil tape as a cover member, between the first base material and the second base material in the phosphor sheet obtained in the punching process (C). The exposed phosphor layer is sealed.

(White light source device)
The white light source device of the present invention includes at least the wavelength conversion member of the present invention. More specifically, the white light source device of the present invention includes the phosphor sheet of the present invention, and if necessary, other members such as a light emitting diode and a mounting substrate. Since the white light source device of the present invention includes the wavelength conversion member of the present invention described above, it can be manufactured at low cost and the fluctuation of the chromaticity of light with time is suppressed. Examples of the white light source device of the present invention include lighting devices for various purposes such as a backlight of a liquid crystal display device.
Here, the white light source device may be composed of a blue light emitting diode (LED) and the phosphor sheet of the present invention. In this case, the phosphor sheet of the present invention preferably contains at least one of a red sulfide phosphor and a green sulfide phosphor.

(Display device)
The display device of the present invention includes at least the white light source device of the present invention, and further includes an optical film, a liquid crystal panel, and other members for controlling light rays, if necessary.
Since the display device of the present invention includes the white light source device including the wavelength conversion member of the present invention described above, it can be manufactured at low cost and the fluctuation of the chromaticity of light with time is suppressed. Examples of the display device of the present invention include a liquid crystal display device.

Next, the present invention will be described in more detail with reference to Reference Examples, Examples and Comparative Examples, but the present invention is not limited to the following examples.

<Preparation of green sulfide phosphor>
Eu ₂ O ₃ (manufactured by Kanto Chemical Co., Inc., purity 3N) is added to an aqueous nitric acid solution (manufactured by Kanto Chemical Co., Inc., concentration 20%) and stirred at 80 ° C. to add nitric acid to Eu ₂ O ₃ . It was dissolved in an aqueous solution. Then, the solvent was evaporated to obtain Eu (NO ₃ ) ₃ . Next, Eu (NO ₃ ) ₃ and Sr (NO ₃ ) ₂ (manufactured by High Purity Chemical Laboratory Co., Ltd., purity 3N) were added to 500 mL of pure water and stirred to obtain a solution. .. To this solution, a desired proportion of powdered Ga ₂ O ₃ (manufactured by High Purity Chemical Laboratory Co., Ltd., purity 7N) is added, and ammonium sulfite monohydrate (manufactured by Kanto Chemical Co., Ltd.) is added dropwise with stirring. Then, a precipitate was obtained, which was a mixture of europium strontium sulfite and gallium oxide. The amount of ammonium sulfite monohydrate added dropwise was the amount of moles corresponding to 1.5 times the total number of moles of Sr and Eu in the solution. The obtained precipitate is washed with pure water and filtered until the conductivity becomes 0.1 mS / cm or less, dried at 120 ° C. for 6 hours, and oxidized with powder (europium sulfite / strontium powder). A mixture with gallium powder) was obtained. In addition, this method is a so-called wet method (that is, a method of producing a starting material in a liquid phase).
20 g of the obtained powder, 200 g of zirconia balls, and 200 mL of ethanol were placed in a pot having a capacity of 500 mL, rotated at a rotation speed of 90 rpm for 30 minutes to mix, then filtered and dried at 120 ° C. for 6 hours. Next, the dried product was passed through a wire mesh (mesh) having a nominal opening of 100 μm to obtain a powder mixture. Further, this powder mixture is fired in an electric furnace under the condition that the temperature is raised to 925 ° C. in 1.5 hours, then held at 925 ° C. for 1.5 hours, and then lowered to room temperature in 2 hours. did. During firing, hydrogen sulfide was flowed through the electric furnace at a rate of 0.5 L / min. The calcined powder mixture was passed through a mesh having a nominal opening of 25 μm to obtain a green sulfide phosphor (Sr _1-x Ga ₂ S ₄ : Eu _x , x is about 0.1).
By the way, the x value of the above Sr _1-x Ga ₂ S ₄ : Eu _x can be adjusted by appropriately changing the addition amount of Eu (NO ₃ ) ₃ and Sr (NO ₃ ) _2. , The Eu concentration, which is the center of light emission, can be adjusted.

<Preparation of red sulfide phosphor>
A red sulfide phosphor (“R660N”, CaS: Eu) manufactured by Mitsui Mining & Smelting Co., Ltd. was prepared.

(Standard example 1)
<Preparation of fluorescent sheet>
First, a water vapor barrier film as a base material having a three-layer structure of PET / vapor-deposited SiOx / PET and having a thickness of 38 μm (water vapor transmittance at a temperature of 40 ° C. and a humidity of 90%: about 0.2 g / m ² / I prepared two sheets (day).
On the other hand, a binder is prepared by dissolving styrene-ethylene-butylene-styrene block copolymer elastomer (SEBS) (manufactured by Kuraray Co., Ltd., "Septon V9827", ratio of styrene unit: 30% by mass) in toluene as a solvent. did. The concentration of SEBS in this binder was 32% by mass. The above-mentioned green sulfide phosphor and red sulfide phosphor were added to and mixed with this binder to obtain a paste-like mixture. The ratio of the green sulfide phosphor to the total amount of the phosphor was 57.0% by mass. Further, the concentration of the phosphor (green sulfide phosphor + red sulfide phosphor) in the finally obtained phosphor layer was set to 8.81% by weight.
Next, this paste-like mixture was applied to the surface of the above-mentioned water vapor barrier film using a roll coater, and the solvent was volatilized by drying to form a phosphor layer. Then, a similar water vapor barrier film was heat-laminated on the phosphor layer. In this way, a phosphor sheet including a phosphor layer as a wavelength conversion member and a water vapor barrier film as a base material sandwiching the phosphor layer was produced. The thickness of the phosphor layer was 63 μm.

<Light source for evaluating fluorescent material sheet>
The configuration of the light source used for the evaluation is shown in FIG.
This light source has a size of 300 mm in length × 200 mm in width × 30 mm in height, and blue LEDs are squarely arranged at a pitch of 30 mm. The peak wavelength of the blue LED when emitting light was about 449 nm. 5.5W of electric power was applied to the blue LED.
For the light source containing the prepared phosphor sheet, the emission spectrum of the sample was measured using a spectral radiance meter (SR-3, manufactured by Topcon).

<Evaluation of phosphor sheet>
With respect to the obtained phosphor sheet, the (x, y) chromaticity based on the CIE 1931 color system was determined by a spectral radiance meter using the light source. As a result, the x value was 0.277 and the y value was 0.238. Further, when the brightness of the obtained phosphor sheet was determined by a spectral radiance meter, it was 3518 cd / m ² .
Further, the obtained phosphor sheet was left in an environment having a temperature of 60 ° C. and a relative humidity of 85% for 5000 hours. The chromaticity of the phosphor sheet after being left to stand was measured by using the light source. When the chromaticity difference Δu'v'before and after leaving was determined, it was 0.0074. In deriving the chromaticity difference, the (x, y) chromaticity was converted into the (u', v') chromaticity based on the CIE1976 color system. The chromaticity difference Δu'v'is defined as follows.
(U ₀ ', v ₀ ') Initial chromaticity (u', v') Saturation after 5000 hours Chromaticity difference Δu'v'= ((u'-u ₀ ') ² + (v'-v') ₀ ') ² ) ^0.5
u'= 4x / (-2x + 12y + 3)
v'= 9y / (-2x + 12y + 3)
Here, the reason for expressing the chromaticity difference using the CIE1976 color system is that the (u', v') chromaticity in the CIE1976 color system is more than the (x, y) chromaticity in the CIE1931 color system. This is because the linearity with the chromaticity difference perceived by humans is high.

(Example 1-1)
<Preparation of fluorescent sheet>
First, a water vapor barrier film as a base material having a three-layer structure of PET / vapor-deposited SiOx / PET and having a thickness of 38 μm (water vapor transmittance at a temperature of 40 ° C. and a humidity of 90%: about 0.2 g / m ² / I prepared two sheets (day).
On the other hand, a binder was prepared by dissolving "Styrene-ethylene-butylene-styrene block copolymer elastomer (SEBS)" (manufactured by Kuraray Co., Ltd., "Septon V9827") as a base material in toluene as a solvent. The concentration of SEBS in the mixture was 32% by mass. The above-mentioned green sulfide phosphor and red sulfide phosphor were added to and mixed with this binder, and then a silicone resin powder (Shinetsu Kagaku) as a light diffusing element was added. "KMP-590" manufactured by KMP Co., Ltd.) was further added to obtain a paste-like mixture. The concentration of the light diffusing element was 0.67 times the concentration of the phosphor, and the final mixture was obtained. The concentration of the phosphor (green sulfide phosphor + red sulfide phosphor) in the phosphor layer was set to 8.47% by mass.
Next, this paste-like mixture was applied to the surface of the above-mentioned steam barrier film using a roll coater, and the solvent was volatilized by drying to form a phosphor layer. Then, a similar water vapor barrier film was heat-laminated on the phosphor layer. In this way, a phosphor sheet including a phosphor layer as a wavelength conversion member and a water vapor barrier film as a base material sandwiching the phosphor layer was produced.
The proportion of the green sulfide phosphor and the thickness of the phosphor layer in the total amount of the phosphor were appropriately adjusted so that the (x, y) chromaticity of the phosphor sheet was substantially the same as that of Reference Example 1.
For the obtained phosphor sheet, (x, y) chromaticity, brightness, and chromaticity difference Δu'v'before and after leaving were determined in the same manner as in Reference Example 1.

(Example 1-2)
The concentration of the phosphor (green sulfide phosphor + red sulfide phosphor) in the finally obtained phosphor layer is 8.01% by mass, and the concentration of the light diffusing element is 1.67 times the concentration of the phosphor. A phosphor sheet was prepared in the same manner as in Example 1 except for the above.
The proportion of the green sulfide phosphor and the thickness of the phosphor layer in the total amount of the phosphor were appropriately adjusted so that the (x, y) chromaticity of the phosphor sheet was substantially the same as that of Reference Example 1.
For the obtained phosphor sheet, (x, y) chromaticity, brightness, and chromaticity difference Δu'v'before and after leaving were determined in the same manner as in Reference Example 1.

(Example 1-3)
The concentration of the phosphor (green sulfide phosphor + red sulfide phosphor) in the finally obtained phosphor layer is 7.60% by mass, and the concentration of the light diffusing element is 2.67 times the concentration of the phosphor. A phosphor sheet was prepared in the same manner as in Example 1 except for the above.
The proportion of the green sulfide phosphor and the thickness of the phosphor layer in the total amount of the phosphor were appropriately adjusted so that the (x, y) chromaticity of the phosphor sheet was substantially the same as that of Reference Example 1.
For the obtained phosphor sheet, (x, y) chromaticity, brightness, and chromaticity difference Δu'v'before and after leaving were determined in the same manner as in Reference Example 1.

First, the ratio of the amount of phosphor used in Examples 1-1 to 1-3 (relative amount of phosphor) to the amount of phosphor used in Reference Example 1 is set to the material (fluorescent body, resin, light diffusion) to be blended. Each was calculated by taking into account the weight ratio and specific gravity of the element). In addition, the brightness (relative brightness) in Examples 1-1 to 1-3 with respect to the brightness in Reference Example 1 was calculated.
Next, the concentration of the light diffusing element is taken on the horizontal axis (x-axis) and the amount of phosphor is taken on the vertical axis (y-axis), and the measurement results of Reference Example 1 and Examples 1-1 to 1-3 are plotted. I made a graph. Then, the regression value of the relative amount of the phosphor when the concentration of the light diffusing element became twice the concentration of the phosphor as in Example 1 was obtained. Further, by the same method, the regression value of the relative brightness when the concentration of the light diffusing element becomes twice the concentration of the phosphor as in Example 1 was obtained.
Specifically, as a method of obtaining the regression value, the quadratic function y = ax ² + bx + c was regressed, the coefficients a, b, and c were obtained, and x = 2 was substituted to obtain y.

(Comparative Example 1-1)
A phosphor in the same manner as in Example 1-1, except that a melamine resin (silica composite) A (manufactured by Nissan Chemical Industries, Ltd., "Optobeads 2000M") was used as the light diffusing element instead of the silicone resin powder. A sheet was prepared.
The proportion of the green sulfide phosphor and the thickness of the phosphor layer in the total amount of the phosphor were appropriately adjusted so that the (x, y) chromaticity of the phosphor sheet was substantially the same as that of Reference Example 1.
For the obtained phosphor sheet, (x, y) chromaticity, brightness, and chromaticity difference Δu'v'before and after leaving were determined in the same manner as in Reference Example 1.

(Comparative Example 1-2)
The concentration of the phosphor (green sulfide phosphor + red sulfide phosphor) in the finally obtained phosphor layer is 8.01% by mass, and the concentration of the light diffusing element is 1.67 times the concentration of the phosphor. A phosphor sheet was prepared in the same manner as in Comparative Example 1-1 except for the above.
The proportion of the green sulfide phosphor and the thickness of the phosphor layer in the total amount of the phosphor were appropriately adjusted so that the (x, y) chromaticity of the phosphor sheet was substantially the same as that of Reference Example 1.
For the obtained phosphor sheet, (x, y) chromaticity, brightness, and chromaticity difference Δu'v'before and after leaving were determined in the same manner as in Reference Example 1.

Using the results of Comparative Examples 1-1 to 1-2 and the same method as in Examples 1-1 to 1-3, the concentration of the light diffusing element as Comparative Example 1 was twice the concentration of the phosphor. The regression value of the relative phosphor amount at that time was obtained. Further, by the same method, the regression value of the relative brightness when the concentration of the light diffusing element becomes twice the concentration of the phosphor as Comparative Example 1 was obtained.

(Comparative Example 2-1)
Similar to Comparative Example 1-1 except that melamine resin (silica composite) B (manufactured by Nissan Chemical Industries, Ltd., "Optobeads 3500M") was used instead of melamine resin (silica composite) A as the light diffusing element. To prepare a phosphor sheet.
The proportion of the green sulfide phosphor and the thickness of the phosphor layer in the total amount of the phosphor were appropriately adjusted so that the (x, y) chromaticity of the phosphor sheet was substantially the same as that of Reference Example 1.
With respect to the obtained phosphor sheet, (x, y) chromaticity and brightness were determined in the same manner as in Reference Example 1.

(Comparative Example 2-2)
The concentration of the phosphor (green sulfide phosphor + red sulfide phosphor) in the finally obtained phosphor layer is 8.31% by mass, and the concentration of the light diffusing element is 1.00 times the concentration of the phosphor. A phosphor sheet was prepared in the same manner as in Comparative Example 2-1 except for the above.
The proportion of the green sulfide phosphor and the thickness of the phosphor layer in the total amount of the phosphor were appropriately adjusted so that the (x, y) chromaticity of the phosphor sheet was substantially the same as that of Reference Example 1.
With respect to the obtained phosphor sheet, (x, y) chromaticity and brightness were determined in the same manner as in Reference Example 1.

(Comparative Example 2-3)
The concentration of the phosphor (green sulfide phosphor + red sulfide phosphor) in the finally obtained phosphor layer is 8.01% by mass, and the concentration of the light diffusing element is 1.67 times the concentration of the phosphor. A phosphor sheet was prepared in the same manner as in Comparative Example 2-1 except for the above.
The proportion of the green sulfide phosphor and the thickness of the phosphor layer in the total amount of the phosphor were appropriately adjusted so that the (x, y) chromaticity of the phosphor sheet was substantially the same as that of Reference Example 1.
With respect to the obtained phosphor sheet, (x, y) chromaticity and brightness were determined in the same manner as in Reference Example 1.

Using the results of Comparative Examples 2-1 to 2-3 and the same method as in Examples 1-1 to 1-3, the concentration of the light diffusing element as Comparative Example 2 was twice the concentration of the phosphor. The regression value of the relative phosphor amount at that time was obtained. Further, by the same method, the regression value of the relative brightness when the concentration of the light diffusing element becomes twice the concentration of the phosphor as in Comparative Example 2 was obtained.

(Comparative Example 3-1)
A phosphor sheet was produced in the same manner as in Comparative Example 1-1, except that an acrylic copolymer elastomer (manufactured by Kuraray Co., Ltd., “Clarity LA2140e”) was used as the base material instead of SEBS.
The proportion of the green sulfide phosphor and the thickness of the phosphor layer in the total amount of the phosphor were appropriately adjusted so that the (x, y) chromaticity of the phosphor sheet was substantially the same as that of Reference Example 1.
For the obtained phosphor sheet, (x, y) chromaticity, brightness, and chromaticity difference Δu'v'before and after leaving were determined in the same manner as in Reference Example 1.

(Comparative Example 3-2)
The concentration of the phosphor (green sulfide phosphor + red sulfide phosphor) in the finally obtained phosphor layer is 8.01% by mass, and the concentration of the light diffusing element is 1.67 times the concentration of the phosphor. A phosphor sheet was prepared in the same manner as in Comparative Example 3-1 except for the above.
The proportion of the green sulfide phosphor and the thickness of the phosphor layer in the total amount of the phosphor were appropriately adjusted so that the (x, y) chromaticity of the phosphor sheet was substantially the same as that of Reference Example 1.
For the obtained phosphor sheet, (x, y) chromaticity, brightness, and chromaticity difference Δu'v'before and after leaving were determined in the same manner as in Reference Example 1.

(Comparative Example 3-3)
Except that the concentration of the phosphor (green sulfide phosphor + red sulfide phosphor) in the paste-like mixture was 8.81% by mass and the concentration of the light diffusing element was 2.67 times the concentration of the phosphor. A phosphor sheet was prepared in the same manner as in Comparative Example 3-1.
The proportion of the green sulfide phosphor and the thickness of the phosphor layer in the total amount of the phosphor were appropriately adjusted so that the (x, y) chromaticity of the phosphor sheet was substantially the same as that of Reference Example 1.
For the obtained phosphor sheet, (x, y) chromaticity, brightness, and chromaticity difference Δu'v'before and after leaving were determined in the same manner as in Reference Example 1.

Using the results of Comparative Examples 3-1 to 3-3 and the same method as in Examples 1-1 to 1-3, the concentration of the light diffusing element as Comparative Example 3 was twice the concentration of the phosphor. The regression value of the relative phosphor amount at that time was obtained. Further, by the same method, the regression value of the relative brightness when the concentration of the light diffusing element becomes twice the concentration of the phosphor as in Comparative Example 3 was obtained.

(Evaluation of relative phosphor content)
The relative phosphor amount in each example was evaluated based on the following criteria using the regression value of the relative phosphor amount when the concentration of the light diffusing element was twice the concentration of the phosphor.
⊚: less than 0.7 ○: 0.7 or more and less than 0.8 ×: 0.8 or more

(Evaluation of relative brightness)
The relative brightness in each example was evaluated based on the following criteria using the regression value of the relative brightness when the concentration of the light diffusing element was twice the concentration of the phosphor.
⊚: 0.98 or more ○: 0.90 or more and less than 0.98 ×: less than 0.90

(Evaluation of chromaticity difference Δu'v'before and after leaving)
In each example, when the chromaticity difference Δu'v'before and after leaving was less than 0.01, it was evaluated as ◯, and when it was 0.01 or more, it was evaluated as ×.
These results are shown in Table 1.

From the results in Table 1, by using a material containing a hydrogenated styrene-based copolymer as the base material and using a silicone resin as the light diffusing element, for example, while reducing the amount of phosphor, which is generally expensive. It can be seen that a wavelength conversion member in which fluctuations in chromaticity are sufficiently suppressed can be obtained even after use for 5000 hours.

According to the present invention, there is provided a wavelength conversion member and a phosphor sheet that can be manufactured at low cost and can suppress fluctuations in the chromaticity of light over time when used in a light source device. be able to. Further, according to the present invention, it is possible to provide a white light source device and a display device which can be manufactured at low cost and whose chromaticity of light is suppressed with time.

1 Fluorescent sheet 20 Blue LED package 40 Optical film 60 Diffusing plate 100 Wavelength conversion member (fluorescent layer)
101 Red phosphor 102 Green phosphor 103 Light diffusing element 104 Blue light emitting diode 105 Base material 106 Base material 110 Blue light 111 Red light 112 Green light

Claims (12)

A phosphor that converts at least a part of the wavelength of the incident light and emits an emitted light having a wavelength different from that of the incident light.
A light diffusing element that diffuses at least one of the incident light and the emitted light,
The base material that holds the light diffusing element and
It is a wavelength conversion member having
The light diffusing element is a silicone resin and
The base material is seen containing a hydrogenated styrene-based copolymer,
The phosphor is a sulfide-based phosphor and is
A wavelength conversion member, characterized in that the absolute value of the difference between the refractive index of the hydrogenated styrene-based copolymer and the refractive index of the silicone resin is 0.04 or more . The wavelength conversion member according to claim 1, wherein the hydrogenated styrene-based copolymer is a styrene-ethylene-butylene-styrene block copolymer elastomer. The wavelength conversion member according to claim 1 or 2, wherein the light diffusing element is a silicone resin particle. The wavelength conversion member according to claim 3, wherein the silicone resin particles have a particle size of 2 μm or more. The wavelength conversion member according to any one of claims 1 to 4, wherein the sulfide-based phosphor contains at least one of a red sulfide phosphor and a green sulfide phosphor. The wavelength conversion member according to claim 5 , wherein the red sulfide phosphor is a calcium sulfide phosphor, and the green sulfide phosphor is a thiogallate phosphor. The wavelength conversion member according to any one of claims 1 to 6 , which is in the form of a sheet. A phosphor sheet comprising the wavelength conversion member according to claim 7 and a base material sandwiching the wavelength conversion member. The fluorescent material sheet according to claim 8 , wherein the base material is a water vapor barrier film. The phosphor sheet according to claim 9 , wherein the water vapor permeability of the water vapor barrier film is 0.05 to 20 g / m ² / day. A white light source device comprising the wavelength conversion member according to any one of claims 1 to 7 . A display device including the white light source device according to claim 11 .

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