JP7304680B2 - Light source, white light source device, and display device - Google Patents

Description

The present invention relates to a light source, a white light source device, and a display device.

An LCD (liquid crystal display) uses a backlight source that irradiates the entire liquid crystal panel from behind with white light. When using an LED (light emitting diode) as a light source, three main methods are used.

The first method is to arrange LEDs that emit three colors of light, R (red), G (green), and B (blue), and illuminate them to synthesize the three colors of light. A white light is obtained.

The second technique uses, for example, a structure in which a blue LED is surrounded by a phosphor-containing resin. In this structure, the blue light emitted by the blue LED is mixed with the fluorescence emitted by the phosphor contained in the phosphor-containing resin to be color-converted into white light. This structure is called a white LED. Yellow phosphor YAG:Ce can be given as an example of the phosphor used for the white LED. FIG. 1 shows a configuration example of a light source using white LEDs. In the light source of FIG. 1, blue LED 101 arranged on substrate 103 is sealed with phosphor-containing resin 102 . A diffusion plate 104 is provided on the light emitting surface. In this structure, in the second method, the phosphor-containing resin is arranged in a small area of the LED, and it is difficult to arrange the phosphor evenly and uniformly. Variation is likely to occur.

For this reason, in recent years, as a third method, attention has been paid to a method in which a phosphor-containing resin is sandwiched between sheet base materials, or a method in which a phosphor-containing resin is processed into a sheet shape and color conversion is performed by a blue LED. are collected (see, for example, Patent Literature 1 and Patent Literature 2). FIG. 2 shows a configuration example of a light source using a phosphor-containing resin processed into a sheet shape. In the light source of FIG. 2, blue LED 101 arranged on substrate 103 is sealed with resin (resin containing no phosphor) 105 . A diffusion plate 104 and a phosphor-containing sheet 106 are provided on the light emitting surface.

By the way, in recent years, the image quality of LCDs has been improved. Among these, the most important technologies are high definition by 4K panels, high contrast by local dimming, and wide color gamut by phosphors with narrow fluorescent spectra. The color gamut of the LCD is determined by the emission spectrum of the backlight source and the spectral transmittance of the R, G, and B color filters of the liquid crystal panel. As for the former, it is desirable to employ a backlight having a moderate peak wavelength and a narrow emission spectrum in each wavelength region of R, G, and B in order to widen the color gamut. Commercially available LCDs mainly use a backlight source that employs a white LED, which is a combination of the above-described blue LED chip and a blue-light-excited phosphor. Therefore, in order to realize a wide color gamut, it is important to employ phosphors having appropriate peak wavelengths and narrow fluorescence spectra in each of the R and G wavelength regions.

In the second technique and the third technique, the sulfide phosphors such as the sulfide green phosphor SrGa ₂ S ₄ :Eu and the sulfide red phosphor CaS:Eu have narrow band emission characteristics. Therefore, it is considered to be a very good phosphor for realizing a wide color gamut LCD. FIG. 3 and Table 1 show fluorescence spectra and fluorescence properties of these sulfide phosphors.

ここで、ＦＷＨＭは、半値全幅（ｆｕｌｌ ｗｉｄｔｈ ａｔ ｈａｌｆ ｍａｘｉｍｕｍ）を表す。

Here, FWHM represents full width at half maximum.

Based on the above technology, the color gamut is being expanded by using a sulfide phosphor sheet.

JP-A-2005-108635 JP 2009-283438 A

An object of the present invention is to provide a light source effective for obtaining a wide color gamut, a white light source device using the light source, and a display device.

Means for solving the above problems are as follows. Namely
<1> A light source including a blue LED that emits blue light and a phosphor that is excited by the blue light emitted by the blue LED,
In the emission spectrum of the light source, the ratio [(B)/(F)] of the peak intensity (B) of the blue light to the peak intensity (F) of the light emitted by the phosphor is 3% or less. Characterized light source.
<2> The light source according to <1>, wherein the phosphor contains sulfur as a constituent.
<3> The light source according to any one of <1> to <2>, wherein the phosphor is contained in a resin-containing phosphor sheet.
<4> the phosphor is a green phosphor,
The light source according to any one of <1> to <3>, wherein the light source is a green light source.
<5> The light source according to <4>, wherein the emission peak of the light emitted from the green phosphor has a half width of 46.0 nm or less.
<6> the phosphor is a red phosphor,
The light source according to any one of <1> to <3>, wherein the light source is a red light source.
<7> The light source according to <6>, wherein the light emitted from the red phosphor has an emission peak half width of 61.0 nm or less.
<8> A white light source device comprising the light source according to any one of <1> to <7>.
<9> a blue light source having a blue LED that emits blue light;
a green light source which is the light source according to any one of <4> to <5>;
a red light source;
It is a white light source device characterized by having
<10> a blue light source having a blue LED that emits blue light;
a green light source;
a red light source which is the light source according to any one of <6> to <7>;
It is a white light source device characterized by having
<11> A display device comprising the white light source device according to any one of <8> to <10>.

An object of the present invention is to provide a light source effective for obtaining a wide color gamut, a white light source device using the light source, and a display device.

FIG. 1 is a schematic diagram showing one configuration example of a conventional light source. FIG. 2 is a schematic diagram showing another configuration example of a conventional light source. FIG. 3 shows fluorescence spectrum examples of a sulfide green phosphor SrGa ₂ S ₄ :Eu and a sulfide red phosphor CaS:Eu. FIG. 4 is a schematic diagram of an example of the light source of the present invention. FIG. 5 is a schematic diagram of another example of the light source of the present invention. FIG. 6 is a schematic diagram of another example of the light source of the present invention. FIG. 7 is a schematic diagram of an example of the white light source device of the present invention. 8 is a schematic diagram of the structure of the phosphor sheet used in Comparative Example 1. FIG. FIG. 9 is a schematic diagram of a light source configuration used for evaluation of Examples and Comparative Examples. 10 shows the spectral radiance (luminescence spectrum) of the light source measured in Comparative Example 1. FIG. 11 shows the spectral transmittance of each color of the liquid crystal panel used in Comparative Example 1. FIG. FIG. 12A shows chromaticity points of red, green, and blue of Comparative Example 1 in the CIE1931 chromaticity coordinate system (x, y). FIG. 12B shows chromaticity points of red, green, and blue of Comparative Example 1 in the CIE1976 chromaticity coordinate system (u', v'). FIG. 13 is a schematic diagram of the structure of the phosphor sheet. FIG. 14 shows the measured spectral radiance (spectrum) of the light source when using the sulfide green phosphor. FIG. 15 shows the measured spectral radiance (spectrum) of the light source when using the sulfide red phosphor. FIG. 16 is a graph normalized with the fluorescence intensity peak value set to 1 (when a sulfide green phosphor is used). FIG. 17 is a graph normalized with the fluorescence intensity peak value set to 1 (when a sulfide red phosphor is used). FIG. 18A is a graph showing the relationship between the peak intensity ratio of the light source and the half width of green light measured when a sulfide green phosphor is used. FIG. 18B is a graph showing the relationship between the peak intensity ratio of the light source and the half width of red light measured when a sulfide red phosphor is used. FIG. 19 is a schematic diagram of a white light source that is an embodiment of the present invention. 20 shows the emission spectra of the white light sources of Comparative Examples 1, 3, and 4. FIG. FIG. 21A shows the chromaticity points of red, green, and blue in Comparative Example 1, Example 3, and Comparative Example 4 in the CIE1931 chromaticity coordinate system (x, y). FIG. 21B shows the chromaticity points of red, green, and blue in Comparative Example 1, Example 3, and Comparative Example 4 in the CIE 1976 chromaticity coordinate system (u', v').

(light source)
The light source of the present invention has at least a blue LED and a phosphor, and if necessary, other members.
The light source has a ratio [(B)/(F)] of the peak intensity (B) of the blue light to the peak intensity (F) of the light emitted by the phosphor in the emission spectrum of the light source is 3% or less. is. The lower limit of the ratio is not particularly limited, and can be appropriately selected according to the purpose. , more preferably 0.10% or more.
When the ratio is 3% or less, an emission peak of the phosphor having a narrow half width can be obtained. A light source having an emission peak with a narrow half width is an effective light source for obtaining a wide color gamut. A narrow half-value width is sometimes expressed as high color purity.

The method for reducing the ratio is not particularly limited and can be appropriately selected according to the purpose. such as increasing the number of

<Blue LED>
The blue LED is not particularly limited as long as it is an LED (light emitting diode) that emits blue light, and can be appropriately selected according to the purpose. etc.
Examples of the blue LED include GaN-based, SiC-based, ZnS-based, and ZnSe-based.

<Phosphor>
The phosphor is not particularly limited as long as it is excited by the blue light emitted by the blue LED, and can be appropriately selected according to the purpose. Examples include a green phosphor, a red phosphor, and a yellow phosphor. is mentioned. Among these, green phosphors and red phosphors are preferable in that the half width of the emission peak can be made narrower.

Examples of the emission peak wavelength of the green phosphor include wavelengths of 530 nm to 550 nm.
Examples of the emission peak wavelength of the red phosphor include wavelengths of 620 nm to 670 nm.

When the phosphor is the green phosphor, the light source is a green light source.
In the green light source, the half-value width of the emission peak of the light emitted by the green phosphor is not particularly limited and can be appropriately selected depending on the purpose. more preferred. The lower limit of the half-value width is not particularly limited and can be appropriately selected according to the purpose. may

When the phosphor is the red phosphor, the light source is a red light source.
In the red light source, the half-value width of the emission peak of the light emitted by the red phosphor is not particularly limited and can be appropriately selected depending on the purpose. more preferred. The lower limit of the half-value width is not particularly limited and can be appropriately selected depending on the purpose. may

Examples of the phosphor include sulfide-based phosphors, oxide-based phosphors, nitride-based phosphors, and fluoride-based phosphors. These may be used individually by 1 type, and may use 2 or more types together.
The phosphor is not limited to the above, and it is naturally understood by those skilled in the art that any phosphor can be applied. For example, quantum dot phosphors such as CdSe/ZnS can also be used. can.

It is preferable that the phosphor contains sulfur as a constituent component in that the half width of the emission peak can be further narrowed.

<<Sulfide Phosphor>>
Examples of the sulfide-based phosphor include the following phosphors.
(i) A red sulfide phosphor (CaS:Eu (calcium sulfide (CS) phosphor), SrS:Eu) having a red fluorescence peak at a wavelength of 620 nm to 670 nm when irradiated with blue excitation light
(ii) A green sulfide phosphor (thiogallate (SGS) phosphor (Sr _x M _1-xy ) Ga ₂ S ₄ :Eu _y (M is one of Ca, Mg, and Ba, and satisfies 0≦x<1 and 0<y<0.2.)
(iii) a mixture of the green sulfide phosphor and the red sulfide phosphor (Ca _1-x )S:Eu _x (which satisfies 0<x<0.05). SrGa ₂ S ₄ :Eu is preferred, and CaS:Eu is preferred as the red phosphor. Here, the sulfide phosphor may be coated with a coating film containing silicon dioxide. Also, the coating film containing silicon dioxide may contain zinc oxide powder.

Specific examples of the sulfide _- based phosphor are not particularly limited and can be appropriately selected depending on the intended purpose. ₄ : Eu, _CaGa2S4 : Eu, (Sr, _Ca , Ba, Mg) _Ga2S4 : Eu (thiogallate (SGS ₎ phosphor), ( _Sr , Ca, Ba) S: Eu, _{Y2O2 S} :Eu, _La2O2S :Eu, _Gd2O2S :Eu and the like _. These may be used individually by 1 type, and may use 2 or more types together.

<<Oxide Phosphor>>
Specific examples _of the oxide _{- based} phosphor are not particularly limited and can be appropriately selected depending on the intended purpose _{. Eu} , _{Tb3Al5O12 :} Ce, _{Ca3Sc2Si3O12 :} Ce and _the like _. These may be used individually by 1 type, and may use 2 or more types together.

Examples of the oxide-based phosphors include oxide-based phosphors that emit red fluorescence with a wavelength of 590 _nm to 620 nm when irradiated with blue _excitation light. ) ₂ SiO ₄ :Eu and the like are suitable.

<<Nitride Phosphor>>
Specific examples _of the nitride _- based _phosphor are not particularly limited _and can be appropriately selected depending on the intended purpose. For example, _Ca2Si5N8 :Eu, _Sr2Si5N8 :Eu, _{Ba2 Si5N8} : Eu, ( _{Ca , Sr, Ba)2Si5N8 :} Eu, _Cax (Al _, Si) ₁₂ (O, N) ₁₆ : Eu (0<x≤1.5), _{CaSi2 O2N2} :Eu, _{SrSi2O2N2 :} Eu _{, BaSi2O2N2 : Eu ,} (Ca _, Sr,Ba ₎ Si2O2N2:Eu, _{CaAl2Si4N8 : Eu ,} CaSiN ₂ :Eu, CaAlSiN ₃ :Eu, (Sr, Ca)AlSiN ₃ :Eu and the like. These may be used individually by 1 type, and may use 2 or more types together.

<<fluoride-based phosphor>>
Specific examples of _the fluoride _- based phosphors ^are _not particularly limited and can be appropriately selected depending ^on _{the intended} purpose _. :Mn ⁴⁺ , K ₃ ZrF ₇ :Mn ⁴⁺ , K ₂ SiF ₆ :Mn ⁴⁺ and the like. These may be used individually by 1 type, and may use 2 or more types together.

<<Phosphor sheet>>
In the light source, it is preferable that the phosphor is contained in a resin-containing phosphor sheet.
The phosphor sheet is obtained, for example, by coating a transparent base material with a phosphor-containing resin composition (so-called phosphor paint) containing the phosphor and a resin.
The thickness of the phosphor sheet is not particularly limited and can be appropriately selected according to the purpose.
The content of the phosphor in the phosphor sheet is not particularly limited, and can be appropriately selected according to the purpose.

<<< Resin >>>
The resin is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include thermoplastic resins and photocurable resins.

-Thermoplastic resin-
The thermoplastic resin is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include hydrogenated styrene copolymers and acrylic copolymers.
The hydrogenated styrene copolymer is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include hydrogenated styrene-ethylene-butylene-styrene block copolymers.
The ratio of styrene units in the styrene-ethylene-butylene-styrene block copolymer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 20 mol % to 30 mol %.
Further, the acrylic copolymer is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include block copolymers of methyl methacrylate (MMA) and butyl acrylate (BA). be done. When the phosphor is a sulfide, the thermoplastic resin is preferably a hydrogenated styrene copolymer rather than an acrylic copolymer.

- Photo-curing resin -
The photocurable resin is produced using a photocurable compound.
The photocurable compound is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include photocurable (meth)acrylates such as urethane (meth)acrylate. Here, the urethane (meth)acrylate is, for example, a product containing an isocyanate group obtained by reacting a polyol and a polyisocyanate (e.g., isophorone diisocyanate, etc.) with a hydroxyalkyl (meth)acrylate (e.g., 2- hydroxypropyl acrylate, etc.).
The content of the urethane (meth)acrylate in 100 parts by mass of the photocurable (meth)acrylate is not particularly limited and can be appropriately selected according to the purpose, but is preferably 10 parts by mass or more.

-Resin composition-
The resin composition containing the resin preferably contains either a polyolefin copolymer component or a photocurable (meth)acrylic resin component.
The polyolefin copolymer is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include styrene copolymers and hydrogenated styrene copolymers.
The styrene-based copolymer is not particularly limited and can be appropriately selected depending on the intended purpose. Examples include styrene-ethylene-butylene-styrene block copolymers, styrene-ethylene-propylene block copolymers, and the like. is mentioned. Among these, hydrogenated styrene-ethylene-butylene-styrene block copolymers are preferred from the viewpoint of transparency and gas barrier properties. By containing the polyolefin copolymer component, excellent light resistance and low water absorption can be obtained.
The content of styrene units in the hydrogenated styrene copolymer is preferably 10% by mass to 70% by mass because if it is too low, the mechanical strength tends to decrease, and if it is too high, it tends to become brittle. , 20% by mass to 30% by mass is more preferable. Also, if the hydrogenation rate of the hydrogenated styrene copolymer is too low, the weather resistance tends to be poor, so it is preferably 50% or more, more preferably 95% or more.
The photocurable acrylate resin component is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include urethane (meth)acrylate, polyester (meth)acrylate, and epoxy (meth)acrylate. Among these, urethane (meth)acrylate is preferable from the viewpoint of heat resistance after photocuring. By including such a photocurable (meth)acrylate resin component, excellent light resistance and low water absorption can be obtained.

Particles (diffusion material) such as an inorganic material having very low light absorption may be added to the phosphor sheet, if necessary. When the refractive index of the encapsulant is different from the refractive index of the added particles, the excitation light can be diffused (scattered) by the particles, thereby increasing the absorption of the excitation light into the phosphor. can be reduced. Examples of the particles (diffusing material) include silicone particles, silica particles, resin particles, composite particles of melamine and silica, and the like. Examples of resins for the resin particles include melamine, crosslinked polymethyl methacrylate, and crosslinked polystyrene. Specific examples of the particles (diffusing material) include, for example, silicone powder KMP series manufactured by Shin-Etsu Chemical Co., Ltd., Optobeads manufactured by Nissan Chemical Industries, Ltd., Techpolymer MBX series and SBX manufactured by Sekisui Plastics Co., Ltd. commercial products such as series, and the like.

<<<transparent substrate>>>
The transparent substrate is not particularly limited and can be appropriately selected according to the purpose, and examples thereof include thermoplastic resin films, thermosetting resin films, photocurable resin films, and the like (JP-A-2011-13567). Publications, JP-A-2013-32515, JP-A-2015-967).

The material of the transparent substrate is not particularly limited and can be appropriately selected depending on the purpose. Examples include polyester films such as polyethylene terephthalate (PET) film and polyethylene naphthalate (PEN) film; polyamide film; Polysulfone film; Triacetylcellulose film; Polyolefin film; Polycarbonate (PC) film; Polystyrene (PS) film; Polyethersulfone (PES) film; unsaturated polyester film; epoxy resin film; fluorine resin film such as PVDF, FEP, and PFA; These may be used individually by 1 type, and may use 2 or more types together.

Among these, polyethylene terephthalate (PET) film and polyethylene naphthalate (PEN) film are particularly preferred.

The surface of such a film may be subjected, if necessary, to corona discharge treatment, silane coupling agent treatment, or the like, in order to improve adhesion to the phosphor sheet-forming resin composition.

The thickness of the transparent substrate is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 10 μm to 100 μm.

Moreover, the transparent substrate is preferably a water vapor barrier film in that hydrolysis of the sulfide phosphor can be further reduced.

The water vapor barrier film is a gas barrier film obtained by forming a metal oxide thin film such as aluminum oxide, magnesium oxide, or silicon oxide on the surface of a plastic substrate or film such as PET (polyethylene terephthalate). A multilayer structure such as PET/SiO _x /PET may also be used.

The water vapor transmission rate of ^the barrier film is not particularly limited ^and can be appropriately selected depending on the intended purpose. A relatively low barrier performance of the order of m ² /day) is preferred. Within this range, it is possible to suppress the intrusion of water vapor and protect the phosphor sheet from water vapor.

Here, one example of the light source of the present invention will be described with reference to the drawings.
FIG. 4 is a schematic diagram of an example of the light source of the present invention.
The light source in FIG. 4 has a phosphor sheet 1 and a blue LED package 2 . A phosphor sheet 1 is arranged so as to be in contact with a blue LED package 2 . The phosphor sheet 1 has a sheet-like resin 1B and phosphors 1A dispersed in the resin 1B. The blue LED package 2 has a substrate 2B, a blue LED 2A arranged on the substrate 2B, and a sealing resin 2C for sealing the blue LED 2A.
In the light source of FIG. 4, most of the blue light emitted by the blue LED is It is used to excite fluorophores, which emit strong fluorescence. Then, in the emission spectrum of the light source, the ratio [(B)/(F)] of the peak intensity (B) of the blue light to the peak intensity (F) of the light emitted by the phosphor is 3% or less, and the half width A narrow phosphor emission peak is obtained.

FIG. 5 is a schematic diagram of an example of the light source of the present invention.
The light source in FIG. 5 has a phosphor sheet 1 and a blue LED package 2 . A phosphor sheet 1 is spaced apart from a blue LED package 2 . The phosphor sheet 1 has a sheet-like resin 1B and phosphors 1A dispersed in the resin 1B. The blue LED package 2 has a substrate 2B, a blue LED 2A arranged on the substrate 2B, and a sealing resin 2C for sealing the blue LED 2A.
Since the phosphor sheet 1 is spaced from the blue LED package 2, deterioration of the phosphor 1A due to heat generated by the blue LED 2A can be reduced.
In the light source of FIG. 5, most of the blue light emitted by the blue LED is It is used to excite fluorophores, which emit strong fluorescence. Then, in the emission spectrum of the light source, the ratio [(B)/(F)] of the peak intensity (B) of the blue light to the peak intensity (F) of the light emitted by the phosphor is 3% or less, and the half width A narrow phosphor emission peak is obtained.

FIG. 6 is a schematic diagram of an example of the light source of the present invention.
The light source of FIG. 6 is a mode in which the phosphor is integrated with the blue LED package. That is, the blue LED package 2 as a light source has a substrate 2B, a blue LED 2A arranged on the substrate 2B, and a sealing resin 2C for sealing the blue LED 2A. are distributed.
In the light source of FIG. 6, most of the blue light emitted by the blue LED is is used to excite the fluorophore, which emits strong fluorescence. Then, in the emission spectrum of the light source, the ratio [(B)/(F)] of the peak intensity (B) of the blue light to the peak intensity (F) of the light emitted by the phosphor is 3% or less, and the half width A narrow phosphor emission peak is obtained.

(White light source device)
A first aspect of the white light source device of the present invention has at least the light source of the present invention and, if necessary, other members.
A second aspect of the white light source device of the present invention has at least a blue light source, a green light source which is the light source of the present invention, and a red light source, and further includes other members as necessary.
A third aspect of the white light source device of the present invention has at least a blue light source, a green light source, and a red light source which is the light source of the present invention, and further includes other members as necessary.

Generally, in the white light source device, a plurality of each of the blue light source, the green light source, and the red light source are arranged. Moreover, in the white light source device, it is preferable that the blue light source, the green light source, and the red light source are alternately arranged at regular intervals.

<Blue light source>
The blue light source is not particularly limited as long as it has a blue LED that emits blue light, and can be appropriately selected according to the purpose.
The blue LED is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include the same blue LED as the blue LED of the light source of the present invention.

<Second Aspect>
In a second aspect of the white light source device of the present invention, the green light source is the green light source of the light source of the present invention. On the other hand, the red light source is not particularly limited and can be appropriately selected according to the purpose.

<<Green light source>>
In a second aspect of the white light source device of the present invention, the green light source is the green light source of the light source of the present invention.

<< red light source >>
In the second aspect, the red light source is not particularly limited and can be appropriately selected according to the purpose. For example, it may be a red LED, or a combination of a blue LED and a red phosphor. There may be. Among these, the red light source is preferably the red light source of the present invention.

Examples of the red LED include AlGaAs (aluminum gallium arsenide), GaAsP (gallium arsenide phosphide), and InGaAsP (indium gallium arsenide phosphide).

The blue LED is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include the same blue LED as the blue LED of the light source of the present invention.

The red phosphor is not particularly limited and can be appropriately selected depending on the intended purpose.

<Third Aspect>
In a third aspect of the white light source device of the present invention, the red light source is the red light source of the light source of the present invention. On the other hand, the green light source is not particularly limited and can be appropriately selected according to the purpose.

<<Green light source>>
In the third aspect, the green light source is not particularly limited and can be appropriately selected according to the purpose. For example, it may be a green LED, or a combination of a blue LED and a green phosphor. There may be. Among these, the green light source is preferably the green light source that is the light source of the present invention.

Examples of the green LED include InGaN (indium gallium nitride), GaN (gallium nitride), and AlGaN (aluminum gallium nitride).

The blue LED is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include the same blue LED as the blue LED of the light source of the present invention.

The green phosphor is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include the green phosphors exemplified in the description of the phosphor of the light source of the present invention.

<< red light source >>
In a third aspect of the white light source device of the present invention, the red light source is the red light source of the light source of the present invention.

<Other parts>
A so-called optical film group is mentioned as said other member. The optical film group includes a prism sheet, a light diffusion sheet, and the like.

The white light source device of the present invention may be a so-called direct type light source device or an edge light type light source device. is preferred.

Here, one example of the white light source device of the present invention will be described with reference to the drawings.
In the white light source device 20 of FIG. 7, a red light source 21, a green light source 22, and a blue light source 23 are arranged on the same plane, and a diffusion plate 24 and three optical films 25A and 25B are provided on the light emitting surface. , and 25C are arranged in this order.
The blue light source 23 is a blue LED package 23A having a blue LED 23a.
The green light source 22 is a combination of a blue LED package 22A having a blue LED 22a and a green phosphor sheet 22B, and has a blue light peak intensity/green light peak intensity ratio of 3% or less.
The red light source 21 is a combination of a blue LED package 21A having a blue LED 21a and a red phosphor sheet 21B, and has a blue light peak intensity/red light peak intensity ratio of 3% or less.

In FIG. 7, in the green light source and the red light source, the blue LED package and the phosphor sheet are in contact with each other, but as in the light source shown in FIG. good too.
Moreover, the green light source and the red light source in FIG. 7 may be in a form in which the phosphor is integrated with the blue LED package as shown in FIG.

(Display device)
A display device of the present invention has at least the white light source device of the present invention and, if necessary, other members such as a color filter.

<Color filter>
The transmission spectrum of the color filter consists of the transmission spectrum of the light filter of each color of RGB, which constitutes the three primary colors of light. Since the transmission spectrum of the color filter differs depending on the liquid crystal panel used, the color filter may be appropriately selected depending on the purpose.

Examples of the present invention will be described below, but the present invention is not limited to these examples.

₍ Sulfide green phosphor, _SrGa2S4 :Eu)
A sulfide green phosphor (SrGa ₂ S ₄ :Eu) used in the following examples and comparative examples was produced by the following method.

A powder gallium compound is added to a solution containing a europium compound and a strontium compound, and a salt is added to obtain a powder (specifically, a powder is obtained by adding a salt for precipitating the europium compound and the strontium compound. ), the powder was calcined. That is, a powdery gallium compound is added to a solution containing a europium compound and a strontium compound, and then a salt is added to obtain a powder (powder mixture) consisting of a mixture of the powder containing europium and strontium and the powdery gallium compound. After obtaining, this powder (powder mixture) was calcined. Here, a powdery gallium compound was added to a solution containing a europium compound and a strontium compound, and a sulfite was added dropwise to obtain a powder containing Sr, Eu, and Ga.
Specifically, the following method was implemented.

First, Ga ₂ O ₃ (purity 7N), Sr(NO ₃ ) ₂ (purity 3N), and Eu ₂ O ₃ (purity 3N), which are reagents manufactured by Kojundo Chemical Laboratory Co., Ltd., and Kanto Chemical Co., Ltd. An aqueous solution of nitric acid (20% concentration) and ammonium sulfite monohydrate from the company were prepared.

Then, Eu ₂ O ₃ was added to the aqueous nitric acid solution and stirred at 80° C. to dissolve the Eu ₂ O ₃ in the aqueous nitric acid solution, and then the solvent was evaporated to obtain Eu(NO ₃ ) ₃ .

Next, the europium compound [Eu(NO ₃ ) ₃ ] and the strontium compound [Sr(NO ₃ ) ₂ ] were added to 500 mL of pure water and stirred. Thus, a solution containing a europium compound and a strontium compound was obtained. By changing the ratio of Eu(NO ₃ ) ₃ and Sr(NO ₃ ) ₂ , the value of x can be changed, thereby adjusting the concentration of Eu, which is the luminescence center. Thereafter, a desired proportion of powdered gallium compound (specifically, powdered Ga ₂ O ₃ ) was added to the solution, and sulfite was added dropwise to the solution while stirring. Specifically, while stirring this solution, a solution containing ammonium sulfite in a molar number 1.5 times the total molar number of Sr and Eu was added dropwise to obtain precipitation/precipitate. This deposit/precipitate contains Sr, Eu and Ga, and more specifically is a mixture of europium strontium sulfite powder and gallium oxide powder. Then, the precipitate was washed with pure water until the conductivity became 0.1 mS / cm or less, filtered, and dried at 120 ° C. for 6 hours to obtain powder containing europium, strontium and gallium (europium and strontium and and a powdered gallium compound [more specifically, a mixture of europium strontium sulfite powder [powder composed of (Sr, Eu) _SO3 ] and gallium oxide powder] ).

Then, 20 g of the powder (powder mixture) thus obtained, 200 g of zirconia balls, and 200 mL of ethanol were placed in a 500 mL pot and mixed by rotating at a rotation speed of 90 rpm for 30 minutes. After the mixing was completed, it was filtered and dried at 120° C. for 6 hours. After that, it was passed through a wire mesh with a nominal opening of 100 μm to obtain a powder mixture.

The powder mixture was then fired in an electric furnace. The firing conditions were as follows. That is, the temperature was raised to 925° C. in 1.5 hours, then maintained at 925° C. for 1.5 hours, and then cooled to room temperature in 2 hours. Hydrogen sulfide was flowed into the electric furnace at a rate of 0.5 L/min during firing. Then, it was passed through a mesh with a nominal opening of 25 μm to obtain a sulfide green phosphor (SrGa ₂ S ₄ :Eu) composed of Sr _1−x Ga ₂ S ₄ :Eu _x (where x is about 0.1). The average particle size of the obtained sulfide green phosphor (SrGa ₂ S ₄ :Eu) was about 4 μm.

(Sulfide red phosphor, CaS:Eu)
In the following examples and comparative examples, R660N (average particle size: about 15 μm) manufactured by Mitsui Mining & Smelting Co., Ltd. was used as the red sulfide phosphor (CaS:Eu).

(Comparative example 1)
First, as a conventional example (comparative example), an LCD using a phosphor sheet using sulfide green/red phosphors and a blue LED light source will be described.

<Production of phosphor sheet>
Evaluation results of an LCD using a phosphor sheet in which a sulfide green phosphor (SrGa ₂ S ₄ :Eu) and a sulfide red phosphor (CaS:Eu) are mixed are shown. A mixture of a sulfide green phosphor SrGa ₂ S ₄ : Eu at a ratio of 60% by mass and a sulfide red phosphor CaS:Eu at a ratio of 40% by mass, and a thermoplastic resin [styrene-ethylene-butylene-styrene block (SEBS ) resin, Septon V9827 manufactured by Kuraray Co., Ltd.] and a solvent (toluene) were mixed to prepare a phosphor paste. Using a roll coater, the above phosphor paste was applied onto a 38 μm thick PET film, and the 38 μm thick PET film was thermally laminated onto the phosphor layer from which the solvent had been volatilized. The phosphor amount at this time was 10.1 g/m ² (sulfide green phosphor SrGa ₂ S ₄ :Eu 6.1 g/m ² , sulfide red phosphor CaS:Eu 4.0 mg/m ² ). . The size of the produced sheet was 300 mm×200 mm. FIG. 8 shows a schematic diagram of the structure of the phosphor sheet. In the phosphor sheet 50 of FIG. 8, the phosphor layer 51 is sandwiched between the PET films 52 and 53, and the phosphor layer 51 is formed by dispersing the sulfide green phosphor 51A and the sulfide red phosphor 51B in the thermoplastic resin 51C. It is

<Evaluation of light source and LCD>
The light source configuration used for this evaluation is as shown in FIG. The size of the light source 60 is 300 mm long×200 mm wide×30 mm high, and the blue LED packages 61 are arranged in a square with a pitch of 30 mm. A diffusion plate 62, the phosphor sheet 50, and three optical films 63A, 63B, and 63C are arranged in this order on the light emitting surface side. The peak wavelength of light emitted from the blue LED used was about 449 nm. A power of 5.5 W was applied to the blue LED. A spectral radiance meter (SR-3 manufactured by Topcon Co., Ltd.) was used to measure the emission characteristics. FIG. 10 shows the measured spectral radiance (luminescence spectrum) of the light source. The half-value width of green fluorescence in the spectral radiance shown in FIG. 10 was 55 nm, and the half-value width of red fluorescence was 68 nm. Similarly, using a spectral radiance meter, the light source shown in FIG. 9 was combined with a commercially available liquid crystal panel, and the chromaticity of each color of red, green, and blue was measured to derive the color gamut. FIG. 11 shows the spectral transmittance of each color of the liquid crystal panel used. 12A and 12B show the chromaticity points of each color of red, green, and blue. FIG. 12A shows the CIE1931 chromaticity coordinate system (x, y), and FIG. 12B shows the CIE1976 chromaticity coordinate system (u', v'). The obtained color gamut was 89.0% (NTSC-xy area ratio) and 109.7% (NTSC-u'v' area ratio).

(Examples 1-2 and Comparative Examples 2-3)
The present invention will now be described. First, the matter that forms the basis of the present invention will be described. A specific example of the present invention will now be described.

<Production of phosphor sheet>
A phosphor paste was prepared by mixing a sulfide green phosphor (SrGa ₂ S ₄ :Eu) with a thermoplastic resin and a solvent. Using a roll coater, the above phosphor paste was applied onto a 38 μm thick PET film, and the 38 μm thick PET film was thermally laminated onto the phosphor layer from which the solvent had been volatilized. FIG. 13 shows a schematic diagram of the structure of the phosphor sheet. In the phosphor sheet 10 shown in FIG. 13, a phosphor layer 11 having sulfide green phosphor 11A dispersed in thermoplastic resin 11B is sandwiched between PET films 12 and 13 . By changing the phosphor concentration in the paste and the coating thickness (thickness of the phosphor layer 11), phosphor sheets having various phosphor amounts were produced. Table 2 summarizes the amount of phosphor in each phosphor sheet. A similar work was also carried out for a sulfide red phosphor (CaS:Eu). It is summarized in Table 3. The size of the produced sheet was 300 mm×200 mm.

<Evaluation of Light Source>
A light source with an array of blue LEDs was prepared. The phosphor sheet was placed above the light source, and the light emission characteristics of the light source were evaluated. FIG. 9 shows the light source structure. The size of the light source is 300 mm long×200 mm wide×30 mm high, and the blue LED packages are arranged in a square with a pitch of 30 mm. The peak wavelength of light emitted from the blue LED used was about 449 nm. A power of 5.5 W was applied to the blue LED. A spectral radiance meter (SR-3 manufactured by Topcon Co., Ltd.) was used to measure the emission characteristics. FIG. 14 shows the measured spectral radiance (spectrum) of the light source when using the sulfide green phosphor. FIG. 15 shows the measured spectral radiance (spectrum) of the light source when using the sulfide red phosphor. When the phosphor amount increases, the blue light intensity decreases and the fluorescence intensity increases. The reason is that an increase in the amount of phosphor increases the amount of conversion from blue light to fluorescence. However, when the amount of phosphor is further increased, a decrease in fluorescence intensity is observed. It is considered that if the amount of phosphor is excessively increased, loss due to increased absorption of excitation light occurs inside the phosphor layer in the process of conversion from blue light to fluorescence.

Now, when understanding the width of the fluorescence spectrum, in FIGS. 14 and 15, the fluorescence intensity peak values are various and difficult to understand. 16 and 17 show normalized graphs with the fluorescence intensity peak value set to 1 for easy understanding. It can be seen that in any phosphor, the width of the fluorescence spectrum narrows as the amount of phosphor increases.

The above results are summarized in Tables 4 and 5, and FIGS. 18A and 18B. It is thought that the half-value width of fluorescence can be reduced by reducing the "blue light peak intensity/fluorescence peak intensity" by increasing the blue light absorption/excitation probability of the phosphor by increasing the amount of phosphor. . As can be seen from Tables 4 and 5, when the ratio of "peak intensity of blue light/peak intensity of fluorescence (green or red light)" is several percent or less, the half-value width of fluorescence becomes significantly smaller. 3% or less is considered to be one standard. As a method for increasing the blue light absorption/excitation probability of the phosphor, other than increasing the amount of the phosphor, a method such as adding a light diffusing material can be considered. Reducing the half-value width of the fluorescence by the above-described method increases the color purity of the primary colors obtained through the LCD, that is, greatly contributes to the expansion of the color gamut of the LCD. However, it can be read from Tables 4 and 5 that if the amount of phosphor is excessively increased, the emission intensity of the phosphor decreases, leading to loss of brightness of the LCD.

(Example 3)
<Estimation of color gamut of LCD using white light source combining the above light sources>
The expansion of the LCD color gamut, which is the object of the present invention, will now be described.
First, FIG. 19 shows a white light source device which is an embodiment of the present invention. In the white light source device 20 of FIG. 19, a red light source 21, a green light source 22, and a blue light source 23 are arranged on the same plane, and a diffusion plate 24 and three optical films 25A and 25B are provided on the light emitting surface. , and 25C are arranged in this order.
As the blue light source 23, a blue LED package 23A having a blue LED 23a is used.
As the green light source 22, a combination of a blue LED package 22A having a blue LED 22a and a green phosphor sheet 22B and having a blue light peak intensity/green light peak intensity ratio of 3% or less was used. Here, the one corresponding to G5 in Table 4 was used.
As the red light source 21, a combination of a blue LED package 21A having a blue LED 21a and a red phosphor sheet 21B and having a blue light peak intensity/red light peak intensity ratio of 3% or less was used. Here, the one corresponding to R5 in Table 5 was used.

When deriving the color gamut of the LCD using the white light source in FIG. 19, the various data evaluated above may be combined. That is, a spectrum of white light is created by synthesizing emission spectra of blue light, green light, and red light emitted from a blue light source, a green light source, and a red light source.
・Blue light:
Let I _b (λ) be the spectral radiance (spectrum). λ is the wavelength.
The blue LED light source data of FIG. 9 are used.
・Green light:
Let the spectral radiance be I _g (λ).
Light source data obtained by combining the blue LED light source of FIG. 9 and the sulfide green phosphor (SrGa ₂ S ₄ :Eu) sheet shown in Table 2 is used. Here, G5 in Table 4 is used.
Red light Let the spectral radiance be I _r (λ).
Light source data combining the blue LED light source of FIG. 9 and the sulfide red phosphor (CaS:Eu) sheet shown in Table 3 is used. Here, R5 in Table 5 is used.

The spectral radiance I(λ) of white light obtained by synthesizing the above data is
I(λ)= _kb · _Ib (λ)+ _kg · _Ig (λ)+ _kr · _Ir (λ)
where k _b + _kg +k _r =1
It can be expressed as. k _i (i=b, g, r) is a coefficient indicating the distribution of each color. These coefficients can be determined such that the chromaticity (x,y) of the white light source derived from I(λ) is some white chromaticity value. The chromaticity of the white light source is determined so that the white chromaticity after transmission through the liquid crystal panel, which will be described below, is substantially the same as in the conventional example.

Next, by multiplying the spectral transmittance of the liquid crystal panel by the spectral radiance I(λ) of the white light, the chromaticities of the red, green, blue, and white colors of the LCD were calculated. The color gamut can be derived from the chromaticity of each color. Note that the spectral transmittance of the liquid crystal panel used in this evaluation is as shown in FIG.

Based on the above description, two white light source spectra were synthesized. FIG. 20 shows emission spectra of white light sources using phosphor sheets G5 and R5. 21A and 21B show the derived chromaticity. Table 6 summarizes the derived color gamuts of LCDs. 20, 21A, 21B, and Table 6, Comparative Example 1 is also described. The color gamut of the LCD in the white light source using the phosphor sheets G5 and R5 of the present invention is NTSC-xy area ratio 91.4% (Comparative Example 1: 89.0%), NTSC-u'v' area The ratio was 116.2 (Comparative Example 1: 109.7%), and it was confirmed that the color gamut was expanded as compared with the conventional one. Further, the half widths of red fluorescence and green fluorescence of the white light source using the phosphor sheets G5 and R5 of the present invention are 60 nm (conventional 68 nm) and 45.5 nm (conventional 55 nm), respectively. The price range has been reduced.

(Comparative Example 4)
The color gamut of the LCD was estimated in the same manner as in Example 3, except that the phosphor sheet G5 was replaced with the phosphor sheet G2 and the phosphor sheet R5 was replaced with the phosphor sheet R1. The results are shown in FIGS. 20, 21A, 21B and Table 6.
Looking at the NTSC-xy color gamut and the NTSC-u'v' color gamut comprehensively, Example 3 is the best. Looking at Comparative Example 4, the NTSC-xy color gamut is equivalent to that of Example 3, but the NTSC-u'v' color gamut of Example 3 is superior. Overall, it is determined that Example 3, which has a small half-value width, is superior.

As described above, in a light source including a blue LED that emits blue light and a phosphor that is excited by the blue light emitted by the blue LED, the emission peak intensity of the light emitted by the phosphor in the emission spectrum of the light source By setting the ratio [(B)/(F)] of the peak intensity (B) of the blue light to (F) to 3% or less, an emission peak with a narrow half width could be obtained. Furthermore, by using the light source in a white light source device, a white light source device with a wide color gamut could be obtained.

INDUSTRIAL APPLICABILITY The light source of the present invention can be suitably used as a light source for televisions, business monitors, liquid crystal displays of personal computers, and the like.
INDUSTRIAL APPLICABILITY The white light source device of the present invention can be suitably used as a white light source device used for televisions, business monitors, liquid crystal displays of personal computers, and the like.
INDUSTRIAL APPLICABILITY The display device of the present invention can be suitably used as a television, a liquid crystal display of a personal computer, or the like.

1 phosphor sheet 1A phosphor 1B resin 2 blue LED package 2A blue LED
2B Substrate 2C Sealing resin

Claims (9)

A light source comprising a blue LED emitting blue light and a phosphor sheet containing a green phosphor excited by the blue light emitted by the blue LED,
the green phosphor is SrGa ₂ S ₄ :Eu,
The SrGa ₂ S ₄ :Eu content in the phosphor sheet is 32 g/m ² or more and 159.8 g/m ² or less,
In the emission spectrum of the light source, the ratio [(B)/(F)] of the peak intensity (B) of the blue light to the peak intensity (F) of the light emitted by the phosphor is 3% or less,
A light source , wherein the half width of the emission peak of the light emitted from the green phosphor is 45.0 nm or less . The light source of claim 1, wherein said light source is a green light source. A light source comprising a blue LED emitting blue light and a phosphor sheet containing CaS:Eu as a red phosphor excited by the blue light emitted by the blue LED,
The CaS:Eu content in the phosphor sheet is 66.5 g/m ² or more and 332.5 g/m ² or less,
In the emission spectrum of the light source, the ratio [(B)/(F)] of the peak intensity (B) of the blue light to the peak intensity (F) of the light emitted by the phosphor is 3% or less,
A light source , wherein the half width of the emission peak of the light emitted from the red phosphor is 61.0 nm or less . 4. The light source of claim 3 , wherein said light source is a red light source. 5. The light source according to claim 1, wherein said phosphor sheet contains resin. A white light source device comprising the light source according to claim 1 . a blue light source having a blue LED that emits blue light;
A green light source, which is the light source according to any one of claims 1 and 2 ;
a red light source;
A white light source device comprising: a blue light source having a blue LED that emits blue light;
a green light source;
a red light source, which is the light source according to any one of claims 3 and 4 ;
A white light source device comprising: A display device comprising the white light source device according to claim 6 .

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