JP2018124410A - Light wavelength conversion member, backlight device and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light wavelength conversion member having excellent color purity when the member emits light, and a backlight device and an image display device including the light wavelength conversion member.SOLUTION: According to one aspect of the present invention, a light wavelength conversion member 10 converts the wavelength of at least part of incident light having a first emission peak wavelength to emit light having a second emission peak wavelength in at least a visible light region. The light wavelength conversion member 10 includes: a first quantum dot 21 that converts the light having the first emission peak wavelength into light having the second emission peak wavelength different from the first emission peak wavelength; and a first light absorbent that absorbs light in a first wavelength region within the visible light region and between the first emission peak wavelength and the second emission peak wavelength.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light wavelength conversion member, a backlight device, and an image display device.

  2. Description of the Related Art A transmissive image display device such as a liquid crystal display device generally includes a backlight device that is disposed on the back side of a transmissive image display panel such as a liquid crystal display panel and illuminates the transmissive image display panel.

  Currently, it has been studied to incorporate an optical wavelength conversion member including quantum dots into an image display device (see, for example, Patent Document 1). Quantum dots can absorb light (primary light) and emit light of different wavelengths (secondary light). The wavelength of light emitted from the quantum dot mainly depends on the particle diameter of the quantum dot. Therefore, in an image display device incorporating a light wavelength conversion member, various colors can be reproduced while using a light source that projects light in a single wavelength region. For example, when a light source that emits blue light is used, the quantum dots in the light wavelength conversion member can absorb part of the blue light and emit green light and red light, so that various colors can be reproduced. .

JP 2015-1111518 A

  In an image display device incorporating such a light wavelength conversion member, it has been studied to expand the color gamut from the viewpoint of further improving color reproducibility, but the color gamut is expanded by the light wavelength conversion member. Therefore, it is necessary to increase the color purity of each light emitted from the light wavelength conversion member.

  The present invention has been made to solve the above problems. That is, an object of the present invention is to provide a light wavelength conversion member having excellent color purity at the time of light emission, a backlight device and an image display device provided with the light wavelength conversion member.

  The inventors of the present invention have made extensive studies on the above problems, and as a result, it is possible to improve color purity by including a light absorber that absorbs light in a specific wavelength region in the light wavelength conversion member. I found it. The present invention has been completed based on such findings.

  According to one aspect of the present invention, at least part of the light having the first emission peak wavelength incident thereon is converted to have the second emission peak wavelength at least in the visible light region. A light wavelength conversion member that emits light, wherein the light having the first emission peak wavelength is converted into light having the second emission peak wavelength different from the first emission peak wavelength. A quantum dot and a first light absorber that absorbs light in a first wavelength range that is in a visible light region and is between the first emission peak wavelength and the second emission peak wavelength. The optical wavelength conversion member characterized by including is provided.

  In the light wavelength conversion member, the first emission peak wavelength is a peak wavelength of the first emission peak and is present in a blue wavelength range, and a half width of the first emission peak is 40 nm or less. Also good.

  In the light wavelength conversion member, the second emission peak wavelength is a peak wavelength of the second emission peak and is present in a green wavelength range, and a half width of the second emission peak is 50 nm or less. Also good.

  In the light wavelength conversion member, the light wavelength conversion member is a member that further emits light having a third emission peak wavelength different from the first emission peak wavelength and the second emission peak wavelength in a visible light region. A second quantum dot that converts light having the first emission peak wavelength into light having a third emission peak wavelength, and the first emission peak wavelength and the second emission peak wavelength. A second light absorber that absorbs light in a second wavelength region between any one of the light emission peak wavelengths located on the third light emission peak wavelength side and the third light emission peak wavelength; Also good.

  In the light wavelength conversion member, the third emission peak wavelength is a peak wavelength of the third emission peak and is present in a red wavelength range, and a half width of the third emission peak is 50 nm or less. May be.

  The light wavelength conversion member further includes a light wavelength conversion layer and a light absorption layer disposed on a light output side of the light wavelength conversion layer, wherein the light wavelength conversion layer includes the first quantum dots, and The light absorption layer may contain the first light absorber.

  The light wavelength conversion member further includes a retroreflective sheet disposed on the light output side of the light wavelength conversion layer, and the light absorption layer is disposed between the light wavelength conversion layer and the retroreflective sheet. May be.

  The light wavelength conversion member may further include a light wavelength conversion layer, and the light wavelength conversion layer may include the first quantum dots and the first light absorber.

  In the light wavelength conversion member, the light wavelength conversion layer may further include light scattering particles.

  According to another aspect of the present invention, there is provided a backlight device including a light source and the above-described optical wavelength conversion member that receives light from the light source.

  According to another aspect of the present invention, there is provided an image display device comprising the above backlight device and a display panel disposed on the light output side of the backlight device.

  According to one aspect of the present invention, since the first light absorber that absorbs light in the first wavelength region between the first emission peak wavelength and the second emission peak wavelength is included, The color purity of light having a light emission peak wavelength of 2 can be improved, thereby providing a light wavelength conversion member having excellent color purity during light emission. Moreover, according to the other aspect of this invention, a backlight apparatus and an image display apparatus provided with such a light wavelength conversion member can be provided.

It is a schematic block diagram of the optical wavelength conversion member which concerns on embodiment. It is a figure which shows the effect | action of the optical wavelength conversion member which concerns on embodiment. It is a schematic block diagram of the other light wavelength conversion member which concerns on embodiment. It is a schematic block diagram of the other light wavelength conversion member which concerns on embodiment. It is a figure which shows typically the manufacturing process of the optical wavelength conversion member which concerns on embodiment. It is a figure which shows typically the manufacturing process of the optical wavelength conversion member which concerns on embodiment. It is a figure which shows typically the manufacturing process of the optical wavelength conversion member which concerns on embodiment. It is a figure which shows typically the manufacturing process of the optical wavelength conversion member which concerns on embodiment. 1 is a schematic configuration diagram of an image display device including a backlight device according to an embodiment. FIG. 10 is a perspective view of the lens sheet shown in FIG. 9. It is sectional drawing along the II line of the lens sheet of FIG. It is a schematic block diagram of the other backlight apparatus which concerns on embodiment. It is a schematic block diagram of the other backlight apparatus which concerns on embodiment. It is a schematic block diagram of the light source shown by FIG. It is a schematic block diagram of the other backlight apparatus which concerns on embodiment. FIG. 16 is an enlarged view of the vicinity of a light incident surface of the optical plate shown in FIG. 15.

  Hereinafter, a light wavelength conversion member, a backlight device, an image display device, and a composition for a light wavelength conversion layer according to embodiments of the present invention will be described with reference to the drawings. In this specification, terms such as “sheet” and “film” are not distinguished from each other only based on the difference in designation. Thus, for example, “sheet” is used to include a member that may also be referred to as a film, and “film” is used to include a member that may also be referred to as a sheet. FIG. 1 is a schematic configuration diagram of an optical wavelength conversion member according to the present embodiment, FIG. 2 is a diagram illustrating an operation of the optical wavelength conversion member according to the present embodiment, and FIGS. 3 and 4 are related to the present embodiment. It is a schematic block diagram of another light wavelength conversion member, and FIGS. 5-8 is a figure which shows typically the manufacturing process of the light wavelength conversion member which concerns on this embodiment.

<<< Light wavelength conversion member >>>
The light wavelength conversion member 10 shown in FIG. 1 converts the wavelength of at least a part of the incident light having the first emission peak wavelength, so that the second emission peak wavelength is at least in the visible light region. It is a member which emits the light which has. The light wavelength conversion member 10 has not only light having the second light emission peak wavelength but also light having the first light emission peak wavelength when light having the first light emission peak wavelength is incident in the visible light region. The member further emits light having a third emission peak wavelength in the light and visible light regions. The light having the first emission peak wavelength may be light having the first emission peak wavelength in the visible light region, but has the first emission peak wavelength outside the visible light region (for example, the ultraviolet light region). It may be light. In the present specification, the “visible light region” means a region having a wavelength of 380 nm to 780 nm, and the “ultraviolet light region” means a region having a wavelength of 10 nm to less than 380 nm.

  The light wavelength conversion member 10 shown in FIG. 1 is a light wavelength conversion sheet, and includes a light wavelength conversion layer 11, light transmissive substrates 12 and 13 provided on both surfaces of the light wavelength conversion layer 11, and light transmittance. The light absorption layer 14 provided on the side opposite to the surface on the light wavelength conversion layer 11 side in the substrate 12 and the adhesion provided on the side opposite to the surface on the light wavelength conversion layer 11 side in the light transmissive substrate 13. A layer 15, a light transmissive substrate 16 provided on the surface opposite to the light transmissive substrate 12 side of the light absorbing layer 14, and a surface of the adhesive layer 15 on the light transmissive substrate 13 side; Is a light transmissive substrate 17 provided on the opposite surface, and a light diffusing layer provided on a surface of the light transmissive substrates 16, 17 opposite to the light transmissive substrate 16, 17 side surface. 18 and 19. In the light wavelength conversion member 10, the surfaces of the light diffusion layers 18 and 19 constitute the surfaces 10 </ b> A and 10 </ b> B of the light wavelength conversion member 10. The light wavelength conversion member 10 includes the light-transmitting base materials 12, 13, 17, and 18, but does not include the barrier layer, and thus does not include the barrier film formed of the light-transmitting base material and the barrier layer. The light wavelength conversion member 10 includes a light diffusion layer 14 / light transmissive substrate 16 / light absorption layer 14 / light transmissive substrate 12 / light wavelength conversion layer 11 / light transmissive substrate 13 / light absorption layer 15. / Light transmissive substrate 17 / light diffusion layer 15 has a structure, but the structure of the light wavelength conversion member is not particularly limited as long as it includes a first quantum dot and a first light absorber described later. .

In the optical wavelength conversion member 10, the water vapor transmission rate (WVTR: Water Vapor Transmission Rate) at 40 ° C. and a relative humidity of 90% may be 0.1 g / (m ² · 24 h) or more. . The water vapor transmission rate is a numerical value obtained by a method based on JIS K7129: 2008. The water vapor transmission rate can be measured using a water vapor transmission rate measuring device (product name “PERMATRAN-W3 / 31”, manufactured by MOCON). The water vapor transmission rate is an average value of values obtained by measuring three times. Since the conventional light wavelength conversion sheet is formed with a barrier film, the light wavelength conversion member 10 has a higher water vapor transmission rate than the conventional light wavelength conversion sheet, that is, the light wavelength conversion member 10 is Moisture permeates more easily than conventional light wavelength conversion sheets.

In the optical wavelength conversion member 10, the oxygen transmission rate (OTR: Oxygen Transmission Rate) at 23 ° C. and 90% relative humidity is 0.1 cm ³ / (m ² · 24 h · atm) or more. Also good. The light wavelength conversion member 10 may satisfy the water vapor transmission rate and the oxygen transmission rate at the same time. The oxygen permeability is a numerical value obtained by a method based on JIS K7126: 2006. The oxygen permeability can be measured using an oxygen gas permeability measuring device (product name “OX-TRAN 2/20”, manufactured by MOCON). The oxygen transmission rate is the average of the values obtained by measuring three times. Since the conventional light wavelength conversion sheet is formed with a barrier film, the light wavelength conversion unit 10 has a higher oxygen transmission rate than the conventional light wavelength conversion sheet, that is, the light wavelength conversion member 10 is Compared with the conventional light wavelength conversion sheet, not only moisture but also oxygen is easily transmitted.

The water vapor transmission rate at 40 ° C. and 90% relative humidity in the light wavelength conversion member 10 may be 1 g / (m ² · 24 h) or more, and at 23 ° C. and 90% relative humidity in the light wavelength conversion member 10. May have an oxygen permeability of 1 cm ³ / (m ² · 24 h · atm) or more.

  The internal haze value in the light wavelength conversion member 10 is preferably 50% or more. The internal haze is a haze value resulting from the inside of the light wavelength conversion member, and does not take into account the uneven shape of the surface of the light wavelength conversion member. When the internal haze value of the light wavelength conversion member 10 is 50% or more, light can be sufficiently diffused by the internal haze to excite the quantum dots a plurality of times, and the external haze value can be further reduced. Can do. The internal haze value in the light wavelength conversion member 10 is preferably 60% or more, and more preferably 80% or more.

  The external haze value in the light wavelength conversion member 10 is preferably 10% or less (including 0%), and more preferably 5% or less. The external haze value is attributed only to the uneven shape on the surface of the light wavelength conversion sheet. When the external haze value of the light wavelength conversion member 10 is 10% or less, retroreflection tends to occur in a retroreflective sheet such as a lens sheet.

In the optical wavelength conversion member 10, the external haze value of the optical wavelength conversion member 10 is preferably smaller than the internal haze value of the optical wavelength conversion member 10. That is, it is preferable that the optical wavelength conversion member 10 satisfies the relationship of the following formula.
Internal haze value> External haze value

  The internal haze value and the external haze value can be determined using a haze meter (product name “HM-150”, manufactured by Murakami Color Research Laboratory). Specifically, first, the total haze value of the light wavelength conversion sheet is measured according to JIS K7136: 2000 using a haze meter. Thereafter, a triacetyl cellulose substrate (product name “Product name“ TD60UL "(manufactured by FUJIFILM Corporation) is pasted. Thereby, the uneven shape on the surface of the light wavelength conversion sheet is crushed, and the surface of the light wavelength conversion sheet is flattened. And in this state, an internal haze value is calculated | required by measuring a haze value according to JISK7136 using a haze meter (product name "HM-150", Murakami Color Research Laboratory make). The external haze value is obtained by subtracting the internal haze from the total haze. The “external haze value” in the present specification means the external haze value of the entire light wavelength conversion sheet. That is, the external haze value in this specification means the sum of the external haze value on one surface of the light wavelength conversion sheet and the external haze value on the other surface of the light wavelength conversion sheet. Each of the internal haze value and the external haze value is an arithmetic average value of values obtained by measuring three times.

  The internal haze value and the external haze value are related. Specifically, when the internal haze value increases, the external haze tends to decrease even when the same surface irregularities are present. This is considered to be due to the following reason. JIS K7136: 2000 stipulates that the haze is the percentage of transmitted light that passes through the test piece and is 0.044 rad (2.5 °) or more away from the incident light due to forward scattering. Yes. That is, in the definition of haze, transmitted light deviated by 2.5 ° or more with respect to incident light is measured as haze, but is not measured as haze if transmitted light is less than 2.5 ° with respect to incident light. On the other hand, in the light wavelength conversion sheet having a large internal haze, the light is more scattered inside the sheet than in the light wavelength conversion sheet having a smaller internal haze. Transmitted light below 2.5 ° is reduced. For this reason, when the light wavelength conversion sheet having a large internal haze and the light wavelength conversion sheet having a small internal haze have the same surface irregularities, the light wavelength conversion sheet having a large internal haze has a higher internal haze than that. Compared with a small light wavelength conversion sheet, the influence of surface irregularities is reduced. Therefore, considering only the effect of surface irregularities present on the sheet surface, even if the light wavelength conversion sheet having a large internal haze and the light wavelength conversion sheet having a smaller internal haze have the same surface irregularities, The light wavelength conversion sheet having a large haze has not only the transmitted light of less than 2.5 ° with respect to the incident light emitted from the surface unevenness, but also the surface unevenness, compared to the light wavelength conversion sheet having a smaller internal haze. Also, the amount of transmitted light deviated by 2.5 ° or more with respect to the incident light emitted from the light source is reduced. Therefore, it is considered that when the internal haze value increases, the external haze decreases even when the same surface irregularities are provided.

  In the light wavelength conversion member 10, in order to make the external haze value of the light wavelength conversion member 10 smaller than that of the light wavelength conversion member 10, for example, adding light scattering particles inside the light wavelength conversion member 10 can be mentioned. . In the case where the light wavelength conversion member includes a barrier film and / or a light diffusion layer, the light scattering particles may be added to the barrier film in addition to the light wavelength conversion layer 11, or the light diffusion layer. It may also be added inside. When the layer to which light scattering particles are added is the outermost layer, it may be accompanied by external haze. Therefore, the relationship between the internal haze and the external haze is satisfied by controlling the surface irregularities of the outermost layer. Can do.

  The ratio of the external haze value to the internal haze value in the light wavelength conversion member 10 (external haze value / internal haze value) is preferably 0 or more and 0.1 or less, and more preferably 0 or more and 0.05 or less. . If this ratio is within this range, the quantum dots can be excited a plurality of times by sufficiently diffusing light by the internal haze.

  The arithmetic average roughness (Ra) of the surfaces 10A and 10B of the light wavelength conversion member 10 is preferably 0.1 μm or more, and more preferably 0.5 μm or more. The reason why the Ra of the surfaces 10A and 10B of the light wavelength conversion member 10 is preferably 0.1 μm is as follows. The light wavelength conversion sheet is in contact with an optical plate or a lens sheet, which will be described later, in the backlight device. There is a risk that a pattern called wet-out, which is wetted with water, may be formed at the interface between the optical wavelength conversion member 10 and the lens sheet. In order to prevent sticking, Ra is more preferably 0.1 μm or more.

  The definition of “Ra” is in accordance with JIS B0601-1994. Ra can be measured using, for example, a surface roughness measuring instrument (product name “SE-3400”, manufactured by Kosaka Laboratory Ltd.). Ra is an average value of values obtained by measuring 15 points at random on the surface 10A, 10B of the light wavelength conversion member where there is no abnormality (a place where there is no large foreign matter, scratch or the like).

  The thickness of the light wavelength conversion member 10 is preferably 10 μm or more and 500 μm or less. If the thickness of the light wavelength conversion member 10 is within this range, it is suitable for reducing the weight and thickness of the backlight device. The thickness of the light wavelength conversion member 10 is obtained by photographing a cross section of the light wavelength conversion member 10 using a scanning electron microscope (SEM), measuring the thickness of the light wavelength conversion member 10 in 20 positions in the image of the cross section, Let it be the average value of the thickness of 20 places. In the SEM measurement, the acceleration voltage is preferably 30 kV and the magnification is 1000 to 7000 times.

<<< Light wavelength conversion layer >>>
The light wavelength conversion layer 11 includes a binder resin 20 and first and second quantum dots 21 and 22 dispersed in the binder resin 20. The light wavelength conversion layer 11 preferably further includes light scattering particles 23. By including the light scattering particles 23, the light wavelength conversion efficiency and the internal haze can be increased.

  The film thickness of the light wavelength conversion layer 11 is preferably 10 μm or more and 200 μm or less. If the thickness of the light wavelength conversion layer 11 is within this range, it is suitable for reducing the weight and thickness of the backlight device. The film thickness of the light wavelength conversion layer 11 is obtained by photographing a cross section of the light wavelength conversion layer 11 using a scanning electron microscope (SEM), and measuring the film thickness of the light wavelength conversion layer 11 in 20 positions in the image of the cross section. , And the average value of the film thickness at the 20 locations. The upper limit of the average film thickness of the light wavelength conversion layer 11 is more preferably less than 170 μm.

<< Binder resin >>
The binder resin 20 is not particularly limited, but is preferably a polymer of a polymerizable compound (cured product, cross-linked product). The polymerizable compound (curable compound) is a polymerizable compound, and examples thereof include an ionizing radiation polymerizable compound (ionizing radiation curable compound) and a thermopolymerizable compound (thermosetting compound). Examples of the ionizing radiation in this specification include visible light, ultraviolet rays, X-rays, electron beams, α rays, β rays, and γ rays.

(Ionizing radiation polymerizable compound)
The ionizing radiation polymerizable compound has at least one ionizing radiation polymerizable functional group in the molecule. Examples of the ionizing radiation polymerizable functional group include ethylenically unsaturated groups such as a (meth) acryloyl group, a vinyl group, and an allyl group. The “(meth) acryloyl group” means to include both “acryloyl group” and “methacryloyl group”.

  Examples of the ionizing radiation polymerizable compound include an ionizing radiation polymerizable monomer, an ionizing radiation polymerizable oligomer, and an ionizing radiation polymerizable prepolymer, and these can be appropriately adjusted and used. As the ionizing radiation polymerizable compound, a combination of an ionizing radiation polymerizable monomer and an ionizing radiation polymerizable oligomer or an ionizing radiation polymerizable prepolymer is preferable.

  Examples of the ionizing radiation polymerizable monomer include monomers containing a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and ethylene glycol di (meth) acrylate. , Diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, tetramethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylol ethanetri (meth) ) Acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaeryth Ritorutetora (meth) acrylate, dipentaerythritol hexa (meth) acrylate, glycerol (meth) (meth) acrylic acid esters such as acrylate.

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

  The ionizing radiation polymerizable prepolymer has a weight average molecular weight exceeding 10,000, and the weight average molecular weight is preferably 10,000 or more and 80,000 or less, and more preferably 10,000 or more and 40,000 or less. When the weight average molecular weight exceeds 80,000, the viscosity is high, so that the coating suitability is lowered, and the appearance of the obtained light wavelength conversion member may be deteriorated. For this reason, when the ionizing radiation polymerizable prepolymer having a weight average molecular weight exceeding 80,000 is used, it is preferable to mix and use the polymerizable monomer and the polymerizable oligomer. Examples of the polyfunctional polymerizable prepolymer include urethane (meth) acrylate, isocyanurate (meth) acrylate, polyester-urethane (meth) acrylate, and epoxy (meth) acrylate.

(Thermopolymerizable compound)
The thermopolymerizable compound has at least one thermopolymerizable functional group in the molecule. Examples of the thermally polymerizable functional group include cyclic ether groups such as epoxy groups and oxetanyl groups, vinyl ether groups, and the like.

  An epoxy compound is a compound having one or more epoxy groups in the molecule. Although it does not specifically limit as an epoxy compound, For example, a bisphenol A type epoxy compound, a bisphenol F type epoxy compound, a bisphenol S type epoxy compound, a biphenyl type epoxy compound, a fluorene type epoxy compound, a novolak phenol type epoxy compound, a cresol novolak type epoxy Compounds, aromatics such as modified products thereof, or alkylene glycol diglycidyl ethers such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether or 1,6-hexanediol diglycidyl ether, glycerin or alkylene oxide adducts thereof Polyglycidyl ethers of polyhydric alcohols such as di- or triglycidyl ethers, polyethylene glycols or alkylene glycols thereof Diglycidyl ether side adduct, polypropylene glycol or polyalkylene glycol diglycidyl ether diglycidyl ether of alkylene oxide adduct thereof, and aliphatic, such as alkylene oxide. Here, as the alkylene oxide, aliphatic epoxy compounds such as ethylene oxide and propylene oxide, 3 ′, 4′-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, 3,4-epoxycyclohexylmethyl methacrylate and the like Examples thereof include alicyclic epoxy compounds containing one or more epoxy groups and one or more ester groups in the molecule.

<< Quantum dots >>
The light wavelength conversion layer 11 includes a first quantum dot 21 and a second quantum dot 22 as quantum dots. However, the light wavelength conversion layer 11 only needs to include the first quantum dots 21, and does not need to include the second quantum dots 22.

  Quantum dots are nano-sized semiconductor particles having a quantum confinement effect. The particle diameter and average particle diameter of the quantum dots are, for example, 1 nm or more and 20 nm or less. When the quantum dot absorbs light from the excitation source and reaches an energy excited state, the quantum dot emits energy corresponding to the energy band gap of the quantum dot. Therefore, by adjusting the particle size of the quantum dots or the composition of the substance, the energy band gap can be adjusted, and energy in various levels of wavelength bands can be obtained. In particular, quantum dots can generate strong fluorescence in a narrow wavelength band.

  Specifically, the energy band gap of the quantum dot increases as the particle size decreases. That is, as the crystal size decreases, the light emission of the quantum dots shifts to the blue side, that is, to the high energy side. Therefore, by changing the particle diameter of the quantum dots, the emission wavelength can be adjusted over the entire wavelength range of the ultraviolet region, the visible region, and the infrared region. For example, when the quantum dot is composed of CdSe / ZnS described later, blue light is emitted when the particle diameter of the quantum dot is 2.0 nm or more and 4.0 nm or less, and the particle diameter of the quantum dot is 3.0 nm. When it is 6.0 nm or less, green light is emitted, and when the particle size of the quantum dots is 4.5 nm or more and 10.0 nm or less, red light is emitted. In the above, the particle diameter range of the quantum dot emitting blue light and the particle diameter range of the quantum dot emitting green light partially overlap, and the particle diameter of the quantum dot emitting green light and the red light Although the range of the particle diameter of the emitted quantum dots partially overlaps, even if the quantum dots have the same particle diameter, the emission color may vary depending on the size of the quantum dot core, so there is no contradiction. Not what you want. In this specification, “blue light” is light having a wavelength range of 380 nm or more and less than 480 nm, “green light” is light having a wavelength range of 480 nm or more and less than 590 nm, and “red light” is It is light having a wavelength range of 590 nm to 750 nm.

  The first quantum dot 21 converts light having the first emission peak wavelength into light having the second emission peak wavelength in the visible light region, and the second quantum dot 22 is the first quantum dot 22. Is converted into light having a third emission peak wavelength in the visible light region. The first emission peak wavelength, the second emission peak wavelength, and the third emission peak wavelength are different wavelengths. The first emission peak wavelength is the peak wavelength of the first emission peak, the second emission peak wavelength is the peak wavelength of the second emission peak, and the third emission peak wavelength is the third emission peak. It is the peak wavelength of the peak. In this specification, “emission peak” means a mountain-shaped portion in the spectral distribution of emitted light, and “emission peak wavelength” means a wavelength at the apex of the mountain-shaped portion. And The first emission peak wavelength, the second emission peak wavelength, and the third emission peak wavelength are obtained from the light wavelength conversion member using a spectral radiance meter (for example, product name “CS2000”, manufactured by Konica Minolta). It can be determined by measuring the spectral distribution of the emitted light.

  It is preferable that the first emission peak wavelength exists in the blue wavelength range, the second emission peak wavelength exists in the green wavelength range, and the third emission peak wavelength exists in the red wavelength range. In this specification, “blue wavelength region” means a wavelength region of 380 nm or more and less than 480 nm, “green wavelength region” means a wavelength region of 480 nm or more and less than 590 nm, and “red wavelength region” It means a wavelength range of 590 nm to 750 nm.

  The first emission peak wavelength is more preferably in the wavelength range of 430 nm or more and 470 nm or less from the viewpoint of improving the color purity of blue light in the blue wavelength range. The second emission peak wavelength is more preferably in the wavelength range of 500 nm or more and 550 nm or less from the viewpoint of improving the color purity of green light in the green wavelength range. The third emission peak wavelength is more preferably present in the wavelength range of 610 nm or more and 660 nm or less from the viewpoint of improving the color purity of red light in the red wavelength range.

  When the second emission peak wavelength exists in the green wavelength range, the half width of the second emission peak is preferably 40 nm or less. When the second emission peak wavelength exists in the green wavelength range and the half width of the second emission peak is in the above range, green light with improved color purity can be emitted from the light wavelength conversion member. . The half width of the second peak is obtained from the spectral distribution of light emitted from the light wavelength conversion member. The half width of the second emission peak is more preferably 20 nm or less.

  When the third emission peak wavelength exists in the red wavelength range, the half width of the third emission peak is preferably 40 nm or less. When the third emission peak wavelength is in the red wavelength range and the half width of the third emission peak is in the above range, red light with improved color purity can be emitted from the light wavelength conversion member. . The half width of the third peak is obtained from the spectral distribution of light emitted from the light wavelength conversion member. The half width of the third emission peak is more preferably 20 nm or less.

  As shown in FIG. 2, when the light L1 having the first emission peak wavelength is incident on the visible light region from the surface 10A of the light wavelength conversion member 10, the first light incident on the first quantum dot 21 is entered. The light L1 having the emission peak wavelength is converted to the light L2 having the second emission peak wavelength by the first quantum dots 21, and is emitted from the surface 10B. Further, the light L1 having the first emission peak incident on the second quantum dot 22 is converted into the light L3 having the third emission peak wavelength by the second quantum dot 22, and is emitted from the surface 10B. On the other hand, even when light having the first emission peak wavelength is incident from the surface 10A, the light L1 passing between the quantum dots is emitted from the surface 10B without being wavelength-converted. Thus, when light having the first emission peak wavelength is incident on the light wavelength conversion member 10, the light having the first emission peak wavelength, the light having the second emission peak wavelength, and the third emission peak wavelength The three types of light having light exit from the light wavelength conversion member.

  As described above, as the light emitted from the light wavelength conversion member 10 also includes light that is not wavelength-converted, the light having the first emission peak wavelength is blue light, and the light having the second emission peak wavelength is When the light is green light and the third emission peak wavelength is red light, the light wavelength conversion member 10 can emit light in which blue light, green light, and red light are mixed.

  The first quantum dots 21 and the second quantum dots 22 include, for example, a core made of a first semiconductor compound, and a shell made of a second semiconductor compound that covers the core and is different from the first semiconductor compound. And a ligand bound to the surface of the shell.

  Examples of the first semiconductor compound constituting the core include MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, II-VI semiconductor compounds such as HgS, HgSe and HgTe, III such as AlN, AlP, AlAs, AlSb, GaAs, GaP, GaN, GaSb, InN, InAs, InP, InSb, TiN, TiP, TiAs and TiSb A semiconductor crystal containing a semiconductor compound or a semiconductor such as a group V semiconductor compound, a group IV semiconductor such as Si, Ge, and Pb can be given. Alternatively, a semiconductor crystal including a semiconductor compound containing three or more elements such as InGaP can be used. Among these, semiconductor crystals such as CdS, CdSe, CdTe, InP, and InGaP are preferable from the viewpoints of ease of production, controllability of the particle diameter capable of obtaining light emission in the visible range, and the like.

  As the second semiconductor compound constituting the shell, a semiconductor compound having a band gap higher than that of the first semiconductor compound constituting the core is preferably used so that excitons are confined in the core. Thereby, the luminous efficiency of a quantum dot can be improved. Examples of the second semiconductor compound constituting the shell include ZnS, ZnSe, CdS, GaN, CdSSe, ZnSeTe, AlP, ZnSTe, and ZnSSe.

  As a specific combination of the core-shell structure (core / shell) composed of a core and a shell, for example, CdSe / ZnS, CdSe / ZnSe, CdSe / CdS, CdTe / CdS, InP / ZnS, Gap / ZnS, Si / ZnS, Examples include InN / GaN, InP / CdSSe, InP / ZnSeTe, InGaP / ZnSe, InGaP / ZnS, Si / AlP, InP / ZnSTe, InGaP / ZnSTe, and InGaP / ZnSSe.

  The ligand is for stabilizing unstable quantum dots. Examples of the ligand include sulfur compounds such as thiol, phosphorus compounds such as phosphine or phosphine oxide, nitrogen compounds such as amines, and carboxylic acids.

  The shape of the 1st quantum dot 21 and the 2nd quantum dot 22 is not specifically limited, For example, spherical shape, rod shape, disk shape, and other shapes may be sufficient. When the shape of the semiconductor nanoparticles is not spherical, the particle diameter of the semiconductor nanoparticles can be a true spherical value having the same volume.

  Information such as the particle diameter, average particle diameter, shape, and dispersion state of the first quantum dots 21 and the second quantum dots 22 can be obtained by a transmission electron microscope or a scanning transmission electron microscope. The average particle diameter of the quantum dots is determined as an average value of the diameters of 20 quantum dots measured by observing a cross section of the light wavelength conversion layer with a transmission electron microscope or a scanning transmission electron microscope. In addition, since the emission color of the quantum dot changes depending on the particle diameter, the particle diameter of the quantum dot can be obtained from confirmation of the emission color of the quantum dot. In addition, the crystal structure and crystallite size of the quantum dots can be known by X-ray crystal diffraction (XRD). Furthermore, the information regarding the particle diameter etc. of a quantum dot can also be obtained with an ultraviolet-visible (UV-Vis) absorption spectrum.

  The content of the quantum dots in the light wavelength conversion layer 11 is preferably 0.01% by mass or more and 2% by mass or less, and more preferably 0.03% by mass or more and 1% by mass or less. If the content of quantum dots is less than 0.01% by mass, sufficient emission intensity may not be obtained. If the content of quantum dots exceeds 2% by mass, sufficient transmitted light of excitation light is transmitted. There is a risk that strength cannot be obtained. When the first quantum dot 21 and the second quantum dot 22 are used as quantum dots, the content of the quantum dots is the total content of the first quantum dots 21 and the second quantum dots 22. Means. In addition, content (mass%) of the quantum dot in the light wavelength conversion layer which is hardened | cured material, and content (mass%) of the light-scattering particle | grains mentioned later can be calculated roughly with the following method. First, at least a part of the light wavelength conversion layer is sampled from the light wavelength conversion member, and its mass is measured. Next, the binder resin contained in the sampled part is dissolved in a solvent or incinerated by combustion to remove the binder resin component. When the binder resin component is removed, the quantum dots and the light scattering particles are not removed, and the quantum dot and light scattering particle components have large particle sizes. Separate components of scattering particles. Next, the component mass of the separated quantum dots and the component of the light scattering particles are measured. And the ratio of the mass of the quantum dot contained in at least one part of the sampled light wavelength conversion layer based on the mass of the sampled light wavelength conversion layer and the mass of the quantum dot is calculated. Further, the ratio of the mass of the light scattering particles contained in at least a part of the sampled light wavelength conversion layer is calculated based on the mass of at least a part of the sampled light wavelength conversion layer and the mass of the light scattering particles.

<< light scattering particles >>
The light scattering particles 23 are particles having an action of changing the traveling direction of light by scattering the light that has entered the light wavelength conversion member 10.

  The content of the light scattering particles 23 in the light wavelength conversion layer 11 is preferably 1% by mass or more and 50% by mass or less, and more preferably 3% by mass or more and 30% by mass or less. If the content of the light scattering particles is less than 1% by mass, the light scattering effect may not be sufficiently obtained, and if the content of the light scattering particles exceeds 50% by mass, Mie scattering occurs. Since it becomes difficult, the light scattering effect may not be sufficiently obtained, and the processability may be deteriorated because there are too many light scattering particles.

  The average particle size of the light-scattering particles 23 is preferably 20 times or more and 2000 times or less, more preferably 50 times or more and 1000 times or less than the average particle size of the quantum dots. If the average particle size of the light scattering particles is less than 20 times the average particle size of the quantum dots, sufficient light scattering performance may not be obtained in the light wavelength conversion layer, and the average particle size of the light scattering particles is If the average particle diameter exceeds 2000 times the average particle diameter of the quantum dots, the number of light-scattering particles decreases even if the addition amount is the same, so that the number of scattering points may decrease and a sufficient light scattering effect may not be obtained. . In addition, the average particle diameter of light-scattering particle | grains can be measured by the method similar to the average particle diameter of the quantum dot mentioned above.

  Further, the average particle diameter of the light scattering particles 23 is preferably 1/300 or more and 1/20 or less, more preferably 1/200 or more and 1/30 or less of the average film thickness of the light wavelength conversion layer 11. preferable. If the average particle diameter of the light scattering particles is less than 1/300 of the average film thickness of the light wavelength conversion layer, sufficient light scattering performance may not be obtained in the light wavelength conversion layer. If the particle diameter exceeds 1/20 of the average film thickness of the light wavelength conversion layer, the ratio of light scattering particles to the light wavelength conversion layer decreases even if the addition amount is the same. Light scattering effect cannot be obtained.

  Specifically, the average particle diameter of the light-scattering particles 23 is preferably 0.1 μm or more and 10 μm or less, and more preferably 0.3 μm or more and 5 μm or less. If the average particle diameter of the light scattering particles is less than 0.1 μm, the light wavelength conversion efficiency of the light wavelength conversion sheet may be insufficient. In order to obtain sufficient light scattering properties, It is necessary to increase the amount of addition. On the other hand, if the average particle diameter of the light-scattering particles exceeds 10 μm, the number of light-scattering particles is reduced even if the addition amount (% by mass) is the same, so that the number of scattering points is reduced and a sufficient light-scattering effect is obtained. I can't get it.

  The absolute value of the difference in refractive index between the light scattering particles 23 and the binder resin 20 is preferably 0.05 or more, and more preferably 0.10 or more, from the viewpoint of obtaining sufficient light scattering. Note that either the refractive index of the light-scattering particles 23 or the refractive index of the binder resin 21 may be larger. Here, as a method for measuring the refractive index of the light-scattering particles before being included in the light wavelength conversion layer, for example, the Becke method, the minimum deflection angle method, the deflection angle analysis, the mode line method, the ellipsometry method, etc. can do. The refractive index of the binder resin 20 in the light wavelength conversion layer 11 is, for example, 10 pieces of the binder resin 20 taken out from the light wavelength conversion layer 11 by cutting or the like, and the 10 pieces taken out are binder resin by the Becke method. The refractive index of 20 can be measured, respectively, and 10 average values of the measured refractive indexes of the binder resin 20 can be obtained. The refractive index of the light scattering particles 23 in the light wavelength conversion layer 11 is determined by, for example, cutting out a piece of the light scattering particles 23 exposed from the binder resin 20 from the light wavelength conversion layer 11. The refractive index of each of the ten light scattering particles 23 whose surface is exposed by the Becke method is measured on each piece taken out, and the average value of the ten refractive indexes of the measured light scattering particles 23 can be obtained. it can. The Becke method uses a refractive index standard solution with a known refractive index. Place the above piece on a glass slide, drop the refractive index standard solution on the sample, and immerse the piece in the refractive index standard solution. When the surface of the binder resin or light-scattering particle is different from the refractive index of the refractive index standard solution, the bright line (Becke line) generated on the surface of the binder resin or light-scattering particle cannot be visually observed. In this method, the refractive index of the refractive index standard solution is used as the refractive index of the binder resin or light scattering particles. In the removed piece, when the surface of the light scattering particles is not exposed, since the surface of the light scattering particles is covered with the binder resin, the binder resin present around the light scattering particles and There is no difference in refractive index. For this reason, it is possible to determine whether a part of the surface of the light-scattering particles is exposed by measuring the refractive index difference with the binder resin existing around the light-scattering particles by the Becke method or the like. . In addition, the refractive index difference between the binder resin and the light scattering particles is measured using a phase shift laser interference microscope (such as a phase shift laser interference microscope manufactured by FK Optical Laboratory or a two-beam interference microscope manufactured by Mizoji Optical Industry Co., Ltd.). can do.

  The shape of the light-scattering particles 23 is not particularly limited. For example, the shape is spherical (true sphere, approximately true sphere, elliptical sphere, etc.), polyhedral, rod-like (cylindrical, prismatic, etc.), flat, flake-like, indefinite Examples include shape. In addition, the particle diameter of the light-scattering particle | grains 18 can be made into the true spherical value which has the same volume, when the shape of a light-scattering particle | grain is not spherical.

  The light scattering particles 23 are preferably chemically bonded to the binder resin 20 from the viewpoint of firmly fixing the light scattering particles 23 in the binder resin 20. This chemical bond can be realized by using light scattering particles surface-treated with a silane coupling agent.

  As the silane coupling agent, depending on the type of curable binder resin precursor to be used, vinyl group, epoxy group, styryl group, methacryl group, acrylic group, amino group, ureido group, thiol group, sulfide group and isocyanate group It is possible to use those having one or more reactive functional groups selected from the group consisting of: When a compound having a (meth) acryloyl group is used as the curable binder resin precursor, the coupling agent is at least one selected from the group consisting of a thiol group, a (meth) acryloyl group, a vinyl group, and a styryl group. It is preferable to have a reactive functional group of When a compound having at least one group selected from the group consisting of an epoxy group, an isocyanate group, and a hydroxyl group is used as the curable binder resin precursor, the silane coupling agent is an epoxy group, an isocyanate group, a thiol It preferably has at least one reactive functional group selected from the group consisting of a group and an amino group.

  The light scattering particles 23 may be organic particles such as acrylic resin particles, styrene resin particles, melamine resin particles, and urethane resin particles, but the luminance change rate before and after the durability test can be reduced. Inorganic particles are preferred because it is possible to suitably scatter incident light on the light wavelength conversion member 10 and to improve the light wavelength conversion efficiency with respect to the incident light.

Inorganic particles include aluminum-containing compounds such as Al ₂ O ₃ , zirconium-containing compounds such as ZrO ₂ , tin-containing compounds such as antimony-doped tin oxide (ATO) and indium tin oxide (ITO), and magnesium-containing materials such as MgO and MgF _2. At least one compound selected from the group consisting of compounds, titanium-containing compounds such as TiO ₂ and BaTiO ₃ , antimony-containing compounds such as Sb ₂ O ₅ , silicon-containing compounds such as SiO ₂ , and zinc-containing compounds such as ZnO Particles. Since these inorganic particles can increase the difference in refractive index with the binder resin, they are also preferable from the viewpoint of obtaining a large Mie scattering intensity. Since the light wavelength conversion efficiency with respect to the incident light by the light wavelength conversion member 10 can be improved more suitably, the light scattering particles 23 may be made of two or more kinds of materials.

<< light transmissive substrate >>
The thickness of the light transmissive substrates 12 and 13 is not particularly limited, but is preferably 10 μm or more and 500 μm or less. If the thickness of the light-transmitting substrates 12 and 13 is less than 10 μm, the light wavelength conversion sheet may be assembled and wrinkled or broken during handling, and if it exceeds 150 μm, the weight of the display and the thin film may be reduced. There is a risk that it may not be suitable. A more preferable lower limit of the thickness of the light-transmitting substrates 12 and 13 is 50 μm or more, and a more preferable upper limit is 400 μm or less.

  The thickness of the light transmissive base materials 12 and 13 is obtained by photographing a cross section of the light transmissive base materials 12 and 13 using a scanning electron microscope (SEM), and in the image of the cross section, the light transmissive base materials 12 and 13. The thickness is measured at 20 locations, and the average value of the film thicknesses at the 20 locations is measured.

  Examples of constituent materials for the light-transmitting substrates 12 and 13 include polyester (for example, polyethylene terephthalate, polyethylene naphthalate), cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyethersulfone, and polysulfone. , Thermoplastic resins such as polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyether ketone, polymethyl methacrylate, polycarbonate, or polyurethane. As a constituent material of the light-transmitting substrates 12 and 13, preferably, polyester (for example, polyethylene terephthalate, polyethylene naphthalate) is used.

  The light-transmitting substrates 12 and 13 may be composed of a single substrate, but may be a laminated substrate composed of a plurality of substrates. Such a laminated base material may be composed of a plurality of layers composed of the same kind of constituent raw material layers, or may be composed of a plurality of layers composed of different kinds of constituent raw material layers, depending on the application. Good.

<< light absorption layer >>
The light absorption layer 14 has a function of absorbing light in a specific wavelength range. The light absorption layer 14 includes a first light absorber (not shown) that absorbs light in a first wavelength range between the first emission peak wavelength and the second emission peak wavelength, and first emission. The second light absorption that absorbs light in the second wavelength region between the emission peak wavelength located on the third emission peak wavelength side and the third emission peak wavelength among the peak wavelength and the second emission peak wavelength. Agent (not shown). However, it is not always necessary to use both the first light absorber and the second light absorber, and even if both the first light absorber and the second light absorber are used, the first light absorber is not necessarily used. Both the light absorber and the second light absorber need not be present in the light absorption layer 14. For example, the first light absorber may be present in the light absorption layer 14 and the second light absorber may be present in the light wavelength conversion layer.

  The light absorption layer 14 may have other functions in addition to the function of absorbing light in a specific wavelength range. The light absorbing layer 14 shown in FIG. 1 has a function of adhering the light transmissive substrate 12 and the light transmissive substrate 16 in addition to the function of absorbing light in a specific wavelength range. For this reason, the light absorption layer 14 contains an adhesive (not shown) in addition to the first light absorber and the second light absorber.

  The film thickness of the light absorption layer 14 is preferably 3 μm or more and 100 μm or less. If the film thickness of the light absorption layer is less than 3 μm, the chromaticity variation due to the film thickness variation may increase. If the film thickness of the light absorption layer exceeds 100 μm, the thickness of the light wavelength conversion member increases. It may become difficult to handle. The film thickness of the light absorption layer 14 is obtained by photographing a cross section of the light absorption layer 14 using a scanning electron microscope (SEM), measuring the film thickness of the light absorption layer 14 in 20 positions in the image of the cross section, It is set as the average value of the film thickness of a location. The lower limit of the thickness of the light absorption layer 14 is more preferably 5 μm or more, and the upper limit is more preferably 50 μm or less.

  The content of the first light absorber in the light absorption layer 14 is preferably 0.01% by mass or more and 10% by mass or less. If the content of the first light absorber is less than 0.01% by mass, the light in the first wavelength region may not be sufficiently absorbed, and the content of the first light absorber is 10% by mass. If it exceeds 1, the light transmittance of the light wavelength conversion member may be significantly reduced. The content of the first light absorber can be determined by measuring the absorbance by ultraviolet-visible spectroscopy.

  The content of the second light absorber in the light absorption layer 14 is preferably 0.01% by mass or more and 10% by mass or less. If the content of the second light absorber is less than 0.01% by mass, the light in the second wavelength region may not be sufficiently absorbed, and the content of the second light absorber is 10% by mass. If it exceeds 1, the light transmittance of the light wavelength conversion member may be significantly reduced. The content of the second light absorber can be obtained by the same method as the content of the first light absorber.

<Light absorber>
The first light absorber absorbs light in a first wavelength range that is in the visible light region and is between the first emission peak wavelength and the second emission peak wavelength. The light absorber is within the second wavelength region between the emission peak wavelength located on the third emission peak wavelength side of the first emission peak wavelength and the second emission peak wavelength and the third emission peak wavelength. It absorbs light. When the first emission peak wavelength is in the blue region, the second emission peak wavelength is in the green region, and the third emission peak wavelength is in the red region, the second emission peak wavelength is Is located closer to the third emission peak wavelength than the first emission peak wavelength, the second wavelength region is a wavelength region between the second emission peak wavelength and the third emission peak wavelength.

  The first light absorber preferably has an absorption peak wavelength in the first wavelength region, and the second light absorber preferably has an absorption peak wavelength in the second wavelength region. When the first light absorber has an absorption peak wavelength in the first wavelength range, more light in the first wavelength range can be absorbed. Further, since the second light absorber has an absorption peak wavelength in the second wavelength range, more light in the second wavelength range can be absorbed. In this specification, “absorption peak wavelength” means the wavelength at the apex of the absorption peak when the absorption spectrum of the light absorbent is measured.

  A pigment | dye is mentioned as a 1st light absorber and a 2nd light absorber. Examples of the pigment include dyes and pigments, and dyes are preferable to pigments from the viewpoint of suppressing a decrease in light transmittance.

  Specific examples of the first light absorber and the second light absorber include porphyrin dyes, phthalocyanine dyes, cyanine dyes, azo dyes, phycobilin dyes, and the like. However, the first light absorber and the second light absorber can be appropriately selected according to the light in the wavelength range to be absorbed. Specifically, when the first emission peak wavelength exists in a wavelength range of 420 nm or more and 480 nm or less, and the second emission peak wavelength exists in a wavelength range of 500 nm or more and 580 nm or less, Examples of the first light absorber that absorbs light include porphyrin dyes and phthalocyanine dyes. In addition, when the third emission peak wavelength is in a wavelength range of 600 nm or more and 680 nm or less, examples of the second light absorbing agent that absorbs light in the second wavelength range include porphyrin dyes and phthalocyanine series. And pigments.

<Adhesive>
It does not specifically limit as an adhesive agent, For example, well-known adhesive agents, such as a urethane type, a polyester type, a polyether type, an epoxy type, a polyethyleneimine type, a polybutadiene type, can be used.

<< light transmissive substrate >>
Since the light-transmitting substrates 16 and 17 are the same as the light-transmitting substrates 12 and 13, the description thereof will be omitted here.

<< light diffusion layer >>
The light diffusion layers 18 and 19 have a concavo-convex shape on the surface, and the light that enters and exits the light wavelength conversion member 10 can be diffused by the concavo-convex shape. By providing the light diffusion layers 18 and 19, the light wavelength conversion efficiency in the light wavelength conversion sheet 10 can be further increased. The light diffusion layers 18 and 19 contain light scattering particles and a binder resin.

<Light scattering particles>
The light-scattering particles in the light diffusion layers 18 and 19 are mainly for forming a concavo-convex shape on the surfaces of the light diffusion layers 18 and 19 and exhibiting a light-scattering function.

  The average particle diameter of the light-scattering particles in the light diffusion layers 18 and 19 is preferably 10 to 20,000 times, more preferably 10 to 5000 times the average particle diameter of the quantum dots described above. . If the average particle size of the light-scattering particles is less than 10 times the average particle size of the quantum dots, sufficient light diffusibility may not be obtained in the light diffusion layer, and the average particle size of the light-scattering particles may be If it exceeds 20,000 times the average particle diameter of the quantum dots, the light diffusion performance of the light diffusion layer will be excellent, but the light transmittance of the light diffusion layer will be greatly reduced. In addition, the average particle diameter of light-scattering particle | grains can be measured by the method similar to the average particle diameter of the quantum dot mentioned above.

  Specifically, the average particle diameter of the light scattering particles in the light diffusion layers 18 and 19 is, for example, preferably 1 μm to 30 μm, and more preferably 1 μm to 20 μm. If the average particle diameter of the light scattering particles is less than 1 μm, the light wavelength conversion efficiency of the light wavelength conversion sheet may be insufficient, and the amount of light scattering particles added to provide sufficient light diffusibility. Need to be more. On the other hand, when the average particle diameter of the light scattering particles exceeds 30 μm, the light diffusion performance is excellent, but the light transmittance of the light diffusion layer is likely to be greatly reduced.

  The absolute value of the difference in refractive index between the light scattering particles and the binder resin in the light diffusion layers 18 and 19 is preferably 0.02 or more and 0.15 or less. If it is less than 0.02, the light diffusibility due to the refractive index of the light scattering particles cannot be obtained optically, and the improvement of the light wavelength conversion efficiency of the light wavelength conversion sheet may be insufficient. If it exceeds 15, the transmittance of the light diffusion layer may be lowered. The more preferable lower limit of the difference in refractive index between the light-scattering particles and the binder resin is 0.03 or more, and the more preferable upper limit is 0.12. Note that either of the refractive index of the light-scattering particles and the refractive index of the binder resin may be larger. The refractive indexes of the light-scattering particles and the binder resin can be measured by the same method as the refractive indexes of the light-scattering particles 18 and the binder resin.

  Since the shape of the light-scattering particles in the light diffusion layers 18 and 19 is the same as the shape of the light-scattering particles 23 in the light wavelength conversion layer 11, description thereof will be omitted here. The light scattering particles in the light diffusion layers 18 and 19 are preferably chemically bonded to the binder resin from the viewpoint of firmly fixing the light scattering particles in the binder resin. This chemical bonding can be realized by using light scattering particles whose surface is modified with a silane coupling agent. Since the silane coupling agent is the same as the silane coupling agent described in the column of the light scattering particles in the light wavelength conversion member, the description thereof is omitted here.

  The light scattering particles may be particles made of an organic material or particles made of an inorganic material. The organic material constituting the light scattering particles is not particularly limited. For example, polyester, polystyrene, melamine resin, (meth) acrylic resin, acrylic-styrene copolymer resin, silicone resin, benzoguanamine resin, benzoguanamine / formaldehyde condensation resin , Polycarbonate, polyethylene, polyolefin and the like. Of these, a crosslinked acrylic resin is preferably used. Moreover, it does not specifically limit as an inorganic material which comprises the said light-diffusion particle | grains, For example, inorganic oxides, such as a silica, an alumina, a titania, a tin oxide, an antimony dope tin oxide (ATO), a zinc oxide fine particle, etc. are mentioned. Of these, silica and / or alumina is preferably used.

<Binder resin>
Although it does not specifically limit as binder resin, Since the polymer (hardened | cured material, crosslinked material) of the polymeric compound demonstrated in the column of binder resin 20 can be used, description shall be abbreviate | omitted here.

<<< Other Light Wavelength Conversion Member >>>
As shown in FIG. 3, the light wavelength conversion member has a structure of light diffusion layer 18 / light transmissive substrate 16 / light wavelength conversion layer 31 / light transmissive substrate 17 / light diffusion layer 19. The member 30 may be used. In this case, the light wavelength conversion layer 31 includes, in addition to the binder resin, the first quantum dots 21, the second quantum dots 22, and the light scattering particles 23, a first light absorber (not shown) and a second light absorber. Light absorber (not shown).

<<< Other Light Wavelength Conversion Member >>>
As shown in FIG. 4, the light wavelength conversion member has a structure of light absorption layer 41 / light diffusion layer 18 / light transmissive substrate 16 / light wavelength conversion layer 11 / light transmissive substrate 17 / light diffusion layer 19. The optical wavelength conversion member 40 which has this may be sufficient. In this case, the light absorption layer 41 includes a first light absorber (not shown) and a second light absorber (not shown). The light incident surface of the light wavelength conversion member 40 is a surface 40A, and the light exit surface is a surface 40B. In the light wavelength conversion member 40, the light absorption layer 41 may be integrated with the light wavelength conversion layer or the like, but may not be integrated.

  The light absorption layer 41 contains a binder resin in addition to the first light absorber and the second light absorber. Although it does not specifically limit as binder resin of the light absorption layer 41, Since the polymer (hardened | cured material, crosslinked material) of the polymeric compound demonstrated in the column of the binder resin 16 can be used, it abbreviate | omits description here. And

<<< Method for Producing Light Wavelength Conversion Member >>>
The light wavelength conversion member 10 can be produced as follows, for example. First, although not shown, a light diffusing layer composition containing light scattering particles and a polymerizable compound is applied to one surface of the light transmissive substrate 16 and dried to apply the light diffusing layer composition. A film is formed. Similarly, a coating film of the light diffusing layer composition is formed on one surface of the light-transmitting substrate 16.

  Subsequently, the coating film of the composition for light diffusion layers is hardened by light irradiation etc. Thereby, as shown in FIG. 5A, the light diffusing layer 18 is formed on one surface of the light transmissive substrate 16, and the light transmissive substrate 16 with the light diffusing layer 18 is formed. Although not shown, the light transmissive substrate 17 with the light diffusion layer 19 is formed in the same manner.

  On the other hand, as shown in FIG. 5 (B), a light-absorbing layer composition containing a first light-absorbing agent, a second light-absorbing agent, and an adhesive is applied to one side of the light-transmitting substrate 12. Then, a coating film 25 was formed. Next, as shown in FIG. 5C, the formed coating film 25 is in contact with the surface opposite to the surface on the light diffusion layer 18 side of the light transmissive substrate 16 with the light diffusion layer 18. The light transmissive substrate 16 with the light diffusion layer 18 is laminated on the coating film 25. In this state, as shown in FIG. 6A, drying is performed at 20 ° C. or higher and 80 ° C. or lower. Thereby, the light absorption layer 14 is formed, and the light transmissive substrate 12 and the light transmissive substrate 16 with the light diffusion layer 18 are integrated via the light absorption layer 14.

  Moreover, as shown in FIG. 6B, the adhesive layer composition containing an adhesive was applied to one side of the light-transmitting substrate 13 to form a coating film 26. Next, as shown in FIG. 6C, the formed coating film 26 is in contact with the surface opposite to the surface on the light diffusion layer 19 side of the light transmissive substrate 17 with the light diffusion layer 19. The light transmissive substrate 17 with the light diffusion layer 19 is laminated on the coating film 26. In this state, as shown in FIG. 7A, drying is performed at 20 ° C. or higher and 80 ° C. or lower. Thereby, the adhesive layer 15 is formed, and the light transmissive substrate 13 and the light transmissive substrate 17 with the light diffusing layer 19 are integrated via the adhesive layer 15.

  Next, as shown in FIG. 7B, what is the surface on the light diffusion layer 19 side in the laminate 28 having the light transmissive substrate 13, the adhesive layer 15, the light transmissive substrate 17, and the light diffusion layer 19? On the opposite surface, a composition for a light wavelength conversion layer containing the first quantum dots 21, the second quantum dots 22, the light scattering particles 23 and a polymerizable compound is applied and dried to form a light wavelength conversion layer. A coating 29 of the composition is formed.

  The content of the quantum dots with respect to the total solid mass of the composition for the light wavelength conversion layer is preferably 0.01% by mass or more and 2% by mass or less, and preferably 0.03% by mass or more and 1% by mass or less. More preferred. If the content of quantum dots is less than 0.01% by mass, sufficient emission intensity may not be obtained. If the content of quantum dots exceeds 2% by mass, sufficient transmitted light of excitation light is transmitted. There is a risk that strength cannot be obtained. When the first quantum dot 21 and the second quantum dot 22 are used as quantum dots, the content of the quantum dots is the total content of the first quantum dots 21 and the second quantum dots 22. Means.

  The content of the polymerizable compound with respect to the total solid mass of the composition for light wavelength conversion layer is preferably 30% by mass to 95% by mass, and more preferably 50% by mass to 90% by mass. If the content of the polymerizable compound is less than 30% by mass, sufficient curability may not be obtained when forming the light wavelength conversion layer, and the content of the polymerizable compound exceeds 95% by mass. And there exists a possibility that a light wavelength conversion layer may become weak. In addition, when the composition for light wavelength conversion layers contains both the photopolymerizable compound and the thermopolymerizable compound, the above content means the total content of the photopolymerizable compound and the thermopolymerizable compound. To do.

  The content of the light scattering particles 23 with respect to the total solid mass of the composition for light wavelength conversion layer is preferably 1% by mass or more and 50% by mass or less, and more preferably 3% by mass or more and 30% by mass or less. preferable. If the content of the light scattering particles is less than 1% by mass, the light scattering effect may not be sufficiently obtained, and if the content of the light scattering particles exceeds 50% by mass, Mie scattering occurs. Since it becomes difficult, the light scattering effect may not be sufficiently obtained, and the processability may be deteriorated because there are too many light scattering particles.

  It is preferable that the composition for light wavelength conversion layers contains the polymerization initiator. The polymerization initiator is a component that is decomposed by light or heat to generate radicals or ionic species to initiate or advance polymerization (crosslinking) of the curable binder resin precursor. Examples of the polymerization initiator used in the composition for the light wavelength conversion layer include a photopolymerization initiator (for example, a radical photopolymerization initiator, a photocationic polymerization initiator, a photoanion polymerization initiator), and a thermal polymerization initiator (for example, heat A radical polymerization initiator, a thermal cationic polymerization initiator, a thermal anionic polymerization initiator), or a mixture thereof.

  Examples of the photo radical polymerization initiator include benzophenone compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, oxime ester compounds, benzoin ether compounds, thioxanthones, and the like.

  Examples of commercially available photo radical polymerization initiators include IRGACURE 184, IRGACURE 369, IRGACURE 379, IRGACURE 651, IRGACURE 819, IRGACURE 907, IRGACURE 2959, IRGACURE OXE01, and Lucillin TPO (all manufactured by BASF Japan 9) ADEKA), SPEEDCURE EMK (Nihon Sebel Hegner), benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether (all manufactured by Tokyo Chemical Industry Co., Ltd.) and the like.

  As said photocationic polymerization initiator, aromatic diazonium salt, aromatic iodonium salt, aromatic sulfonium salt etc. are mentioned, for example. Examples of commercially available photocationic polymerization initiators include Adekaoptomer SP-150 and Adekaoptomer SP-170 (both manufactured by ADEKA).

  Examples of the thermal radical polymerization initiator include peroxides and azo compounds. Among these, a polymer azo initiator composed of a polymer azo compound is preferable. Examples of the polymer azo initiator include those having a structure in which a plurality of units such as polyalkylene oxide and polydimethylsiloxane are bonded via an azo group.

  Examples of the polymer azo initiator having a structure in which a plurality of units such as polyalkylene oxide are bonded via the azo group include, for example, a polycondensate of 4,4′-azobis (4-cyanopentanoic acid) and polyalkylene glycol. And polycondensate of 4,4′-azobis (4-cyanopentanoic acid) and polydimethylsiloxane having a terminal amino group.

  Examples of the peroxide include ketone peroxide, peroxyketal, hydroperoxide, dialkyl peroxide, peroxy ester, diacyl peroxide, and peroxydicarbonate.

  Examples of commercially available thermal radical polymerization initiators include perbutyl O, perhexyl O, perbutyl PV (all manufactured by NOF Corporation), V-30, V-501, V-601, and VPE-0201. , VPE-0401, VPE-0601 (both manufactured by Wako Pure Chemical Industries, Ltd.) and the like.

  Examples of the thermal cationic polymerization initiator include various onium salts such as a quaternary ammonium salt, a phosphonium salt, and a sulfonium salt. Examples of commercially available thermal cationic polymerization initiators include Adeka Opton CP-66, Adeka Opton CP-77 (all manufactured by ADEKA), Sun-Aid SI-60L, Sun-Aid SI-80L, and Sun-Aid SI-100L ( All of them are manufactured by Sanshin Chemical Industry Co., Ltd.) and CI series (manufactured by Nippon Soda Co., Ltd.).

  The content of the polymerization initiator in the composition for light wavelength conversion layer is preferably 0.3 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the polymerizable compound. When the content of the polymerization initiator is less than 0.3 parts by mass, the polymerizable compound is hard to be cured, and when it exceeds 5.0 parts by mass, the light wavelength conversion member may be yellowed. .

  The viscosity of the composition for a light wavelength conversion layer is preferably 10 mPa · s or more and 10,000 mPa · s or less. If the viscosity of the composition for light wavelength conversion layer is less than 10 mPa · s, it may be difficult to form a sufficient film thickness, and if it exceeds 10,000 mPa · s, the composition for light wavelength conversion layer may be reduced. When applying, it may be difficult to apply and the leveling property may be deteriorated. The lower limit of the viscosity of the composition for light wavelength conversion layer is preferably 10 mPa · s or more, and the upper limit of the viscosity of the composition for light wavelength conversion layer is preferably 10,000 mPa · s or less.

  After forming the coating film 29 of the composition for the light wavelength conversion layer, as shown in FIG. 7C, a laminate having the light transmissive substrate 12, the light absorption layer 14, the light transmissive substrate 16, and the light diffusion layer 18. The laminated body 27 is placed on the coating film 29 of the composition for light wavelength conversion layer so that the surface of the body 27 opposite to the surface on the light diffusion layer 19 side is in contact with the coating film 29 of the composition for light wavelength conversion layer. Deploy. Thereby, the coating film 29 of the composition for light wavelength conversion layers is pinched | interposed between the laminated body 27 and the laminated body 28. FIG.

  Next, as shown in FIG. 8, the composition 29 for the light wavelength conversion layer is cured by irradiating the coating film 29 of the composition for the light wavelength conversion layer 29 with the ionizing radiation through the laminate 27 or by applying heat. Thus, the light wavelength conversion layer 11 is formed, and the light wavelength conversion layer 11 and the laminates 27 and 28 are integrated. Thereby, the optical wavelength conversion member 10 shown by FIG. 1 is obtained.

  The light wavelength conversion members 10, 30, and 40 can be used by being incorporated in a backlight device and an image display device. Hereinafter, an example in which the light wavelength conversion member 10 is incorporated in a backlight device and an image display device will be described. 9 is a schematic configuration diagram of an image display device including a backlight device according to the present embodiment, FIG. 10 is a perspective view of the lens sheet shown in FIG. 9, and FIG. It is sectional drawing along I line. 12, FIG. 13 and FIG. 15 are schematic configuration diagrams of another backlight device according to this embodiment, FIG. 14 is a schematic configuration diagram of the light source shown in FIG. 13, and FIG. 16 is shown in FIG. It is an enlarged view near the light incident surface of the optical plate.

<<< Image display device >>>
The image display device 50 shown in FIG. 9 includes a backlight device 60 and a display panel 100 disposed on the light output side of the backlight device 60. The image display device 50 has a display surface 50A for displaying an image. In the image display device 50 shown in FIG. 9, the surface of the display panel 100 is the display surface 50A.

  The backlight device 60 illuminates the display panel 100 in a planar shape from the back side. The display panel 100 functions as a shutter that controls transmission or blocking of light from the backlight device 60 for each pixel, and is configured to display an image on the display surface 50A.

<< Display panel >>
A display panel 100 shown in FIG. 9 is a liquid crystal display panel, and a polarizing plate 101 disposed on the light incident side, a polarizing plate 102 disposed on the light exit side, and between the polarizing plate 101 and the polarizing plate 102. The liquid crystal cell 103 is provided. Polarizing plates 101 and 102 decompose incident light into two linearly polarized light components (S-polarized light and P-polarized light) orthogonal to each other, and vibrate in one direction (direction parallel to the transmission axis) (for example, P It has a function of transmitting a linearly polarized component (for example, S-polarized light) that transmits polarized light and vibrates in the other direction (direction parallel to the absorption axis) perpendicular to the one direction.

<< Backlight device >>
The backlight device 60 shown in FIG. 9 is configured as an edge light type backlight device, and includes a light source 70, an optical plate 75 as a light guide plate disposed on the side of the light source 70, and a light output side of the optical plate 75. The light wavelength conversion member 10 disposed on the lens, the lens sheet 80 disposed on the light output side of the light wavelength conversion member 10, the lens sheet 85 disposed on the light output side of the lens sheet 80, and the light output side of the lens sheet 85. The reflection-type polarization separation sheet 90 disposed and the reflection sheet 95 disposed on the side opposite to the light output side of the optical plate 75 are provided. The backlight device 60 includes the optical plate 75, the lens sheets 80 and 85, the reflective polarization separation sheet 90, and the reflective sheet 95, but these sheets and the like may not be provided. In the present specification, the “light exit side” means a side from which light is emitted from each member in the direction of exiting the backlight device.

  The backlight device 60 has a light emitting surface 60A that emits light in a planar shape. In the backlight device 60 shown in FIG. 9, the light exit surface of the reflective polarization separation sheet 90 is the light emitting surface 60 </ b> A of the backlight device 60.

  Since the light absorption layer 14 is preferably disposed closer to the observer than the light wavelength conversion layer 11 so as not to absorb incident blue light, the surface on the optical plate 75 side of the light wavelength conversion member 10 is the surface. The surface on the lens sheet 80 side of the light wavelength conversion member 10 is a surface 10B (light exit surface).

<Light source>
The light source 70 emits light having a first emission peak wavelength. The light source 70 may be configured in various modes such as a fluorescent lamp such as a linear cold cathode tube, a point light emitting diode (LED), an incandescent lamp, and the like. In the present embodiment, the light source 70 is composed of a large number of point-like light emitters, specifically, a large number of light emitting diodes (LEDs) arranged in a line on the light incident surface 75C side to be described later of the optical plate 55. ,It is configured. For example, only a blue light emitting diode that emits blue light with high color purity can be used as the light source.

<Optical plate>
The optical plate 75 as the light guide plate is formed in a square shape in plan view. The optical plate 75 extends between the light output surface 75A formed by one main surface on the display panel 100 side, the back surface 75B formed of the other main surface facing the light output surface 75A, and the light output surface 75A and the back surface 75B. And have side faces. Of the side surfaces, the side surface on the light source 70 side is a light incident surface 75 </ b> C that receives light from the light source 70. The light that has entered the optical plate 75 from the light incident surface 75C is guided through the optical plate in a direction (light guide direction) connecting the light incident surface 75C and the opposite surface opposite to the light incident surface 75C. It is emitted from 75A.

<< Lens sheet >>
The lens sheets 80 and 85 have a function of changing the traveling direction of the incident light and emitting it from the light output side. In the present embodiment, as shown in FIG. 11, the function of concentratingly improving the brightness in the front direction by changing the traveling direction of the light L3 having a large incident angle and emitting it from the light exit side (condensing function). In addition, it has a function (retroreflection function) of reflecting the light L4 having a small incident angle and returning it to the light wavelength conversion member 10 side. That is, the lens sheets 80 and 85 function as retroreflective sheets. The lens sheets 80 and 85 include a light transmissive substrate 81 and a lens layer 82 provided on one surface of the light transmissive substrate 81.

  When the surfaces 10A and 10B of the light wavelength conversion member 10 are uneven surfaces, the light exit surface 75A of the optical plate 75 is optically in close contact with a part (for example, a convex portion) of the surface 10A. 10A is preferably separated from other portions (for example, concave portions), and the light incident surface 80A of the lens sheet 80 is optically in close contact with a part (for example, convex portions) of the surface 10B. It is preferable that it is separated from the other part (for example, recessed part) of 10B. In this case, the gap between the light exit surface 75A and the other part of the surface 10A and the gap between the light incident surface 80A and the other part of the surface 10B form an air layer. By providing this air layer, the light wavelength conversion member 10, the optical plate 75, and the lens sheet 80 are fixed so that the light exit surface 75A and the surface 10A and the light entrance surface 80A and the surface 10B are in optical contact. However, since it can suppress that optical wavelength conversion member 10, optical plate 75, and lens sheet 80 stick, the interface between optical wavelength conversion member 10 and optical plate 75, and optical wavelength conversion member 10 and lens sheet 80 are also included. It is possible to suppress the formation of wet-out at the interface between the two.

<Light transmissive substrate>
Since the light transmissive substrate 81 is the same as the light transmissive substrates 12 and 13, the description thereof will be omitted here.

<Lens layer>
As shown in FIGS. 10 and 11, the lens layer 82 includes a sheet-like main body 83 and a plurality of unit lenses 84 arranged side by side on the light output side of the main body 83.

  The main body 83 functions as a sheet-like member that supports the unit lens 84. As shown in FIGS. 9 and 10, the unit lenses 84 are arranged on the light output side surface 83 </ b> A of the main body 83 without leaving a gap. Therefore, the light exit surfaces 80B and 85B of the lens sheets 80 and 85 are formed by lens surfaces. On the other hand, as shown in FIG. 11, in the present embodiment, the main body 83 has a smooth surface that forms the light incident side surface of the lens layer 82 as the light incident side surface 83B that faces the light output side surface 83A. Yes.

  The unit lenses 84 are arranged side by side on the light output side surface 83 </ b> A of the main body 83. As shown in FIG. 10, the unit lens 84 extends linearly in the direction intersecting with the arrangement direction AD of the unit lenses 84, particularly in the present embodiment, linearly. In the present embodiment, a large number of unit lenses 84 included in one lens sheet 80 and 85 extend in parallel to each other. Further, the longitudinal direction LD of the unit lenses 84 of the lens sheets 80 and 85 is orthogonal to the arrangement direction AD of the unit lenses 84 in the lens sheets 80 and 85.

  The unit lens 84 may have a triangular prism shape, or may have a wave shape or a bowl shape such as a hemisphere. Specifically, examples of the unit lens include a unit prism, a unit cylindrical lens, and a unit microlens. Examples of the lens sheet having such a unit lens shape include a prism sheet, a lenticular lens sheet, and a microlens sheet. In the present embodiment, a triangular prism-shaped unit prism whose width becomes narrower toward the light output side will be described as a unit lens. The shape of a cross section (also referred to as a main cutting surface of the lens sheet) parallel to both the normal direction ND of the sheet surfaces of the lens sheets 80 and 85 and the arrangement direction AD of the unit lenses 84 is a triangular shape protruding to the light output side. ing. In particular, from the viewpoint of intensively improving the brightness in the front direction, the cross-sectional shape of the unit lens 84 at the main cut surface is an isosceles triangle shape, and the apex angle located between the equilateral sides is the light exit side surface 83A of the main body 83. Each unit lens 84 is configured to protrude from the light to the light exit side.

  The unit lens 84 preferably has an apex angle of 80 ° or more and 100 ° or less, and more preferably an apex angle of about 90 °, from the viewpoint of improving the light utilization efficiency. However, the tip of the unit lens 84 may be a curved surface in consideration of breakage of the tip of the unit lens during winding of the light wavelength conversion sheet.

  The dimensions of the lens sheets 80 and 85 can be set as follows as an example. First, as a specific example of the unit lens 84, the arrangement pitch of the unit lenses 84 (corresponding to the width of the unit lens 64 in the illustrated example) can be set to 10 μm or more and 200 μm or less. However, in recent years, the definition of the arrangement of the unit lenses 64 is rapidly increasing, and the arrangement pitch of the unit lenses 84 is preferably 10 μm or more and 50 μm or less. Further, the protruding height of the unit lens 84 from the main body 83 along the normal direction ND to the sheet surface of the lens sheets 80 and 85 can be set to 5 μm or more and 100 μm or less. Further, the apex angle θ of the unit lens 84 can be set to 60 ° or more and 120 ° or less.

  As can be understood from FIG. 9, the arrangement direction of the unit lenses 84 of the lens sheet 80 and the arrangement direction of the unit lenses 84 of the lens sheet 85 intersect, and more specifically, are orthogonal to each other.

<Reflection-type polarized light separation sheet>
The reflection-type polarization separation sheet 90 transmits only the first linearly polarized light component (for example, P-polarized light) out of the light emitted from the lens sheet 85 and is a second straight line orthogonal to the first linearly polarized light component. It has a function of reflecting a polarized light component (for example, S-polarized light) without absorbing it. In the state where the second linearly polarized light component reflected by the reflective polarization separating sheet 90 is reflected again and the polarized light is canceled (including both the first linearly polarized light component and the second linearly polarized light component), The light again enters the reflective polarization separation sheet 90. Therefore, the reflective polarization separating sheet 90 transmits the first linearly polarized light component of the incident light again, and the second linearly polarized light component orthogonal to the first linearly polarized light component is reflected again. By repeating such a process, about 70 to 80% of the light emitted from the lens sheet 85 is emitted as light source light that has become the first linearly polarized light component. Therefore, the wavelength conversion efficiency of the light wavelength conversion sheet 10 can be further increased by arranging the reflective polarization separation sheet 110. Therefore, further improvement in light utilization efficiency can be expected.

  As the reflective polarization separation sheet 90, “DBEF” (registered trademark) available from 3M Company can be used. In addition to “DBEF”, a high-intensity polarizing sheet “WRPS” available from Shinwha Intertek, a wire grid polarizer, or the like can be used as the reflective polarization separating sheet 90.

<Reflection sheet>
The reflection sheet 95 has a function of reflecting light leaking from the back surface 75 </ b> B of the optical plate 75 so as to enter the optical plate 70 again. The reflection sheet 95 includes a white scattering reflection sheet, a sheet made of a material having a high reflectance such as metal, a sheet containing a thin film (for example, a metal thin film) made of a material having a high reflectance as a surface layer, and the like. obtain. The reflection on the reflection sheet 95 may be regular reflection (specular reflection) or diffuse reflection. When the reflection on the reflection sheet 95 is diffuse reflection, the diffuse reflection may be isotropic diffuse reflection or anisotropic diffuse reflection.

<< Other backlight devices >>
The backlight device incorporating the light wavelength conversion member 10 may be a direct type backlight device as shown in FIG. The backlight device 110 shown in FIG. 12 includes a light source 70, an optical plate 111 that receives light from the light source 70 and functions as a light diffusing plate, and an optical wavelength conversion member 10 disposed on the light output side of the optical plate 111. A lens sheet 80 disposed on the light exit side of the light wavelength conversion member 10, a lens sheet 85 disposed on the light exit side of the lens sheet 80, and a reflective polarization separation sheet 90 disposed on the light exit side of the lens sheet 85. I have. In the present embodiment, the light source 70 is disposed not directly on the side of the optical plate 111 but directly below the optical plate 111. 12, members denoted by the same reference numerals as those in FIG. 9 are the same as the members shown in FIG. Note that the backlight device 110 is not provided with the reflection sheet 95.

<Optical plate>
The optical plate 111 as a light diffusing plate has a quadrangular shape in plan view. The optical plate 111 has a light incident surface 111A formed by one main surface on the light source 75 side and a light output surface 111B formed by the other main surface on the light wavelength conversion member 10 side. The light that enters the optical plate 111 from the light incident surface 111A is diffused in the optical plate 111 and emitted from the light exit surface 111B.

<Light diffusing particles>
Examples of the light diffusing particles in the optical plate 111 include light diffusing particles generally used as a diffusion plate.

<< Other backlight devices >>
Although the backlight device 60 illustrated in FIG. 9 includes the sheet-like light wavelength conversion member 10, the light wavelength conversion member may not be in the form of a sheet. For example, as shown in FIG. 13, the backlight device may be a backlight device 120 including a light source 130 that is one form of a light wavelength conversion member, instead of the light wavelength conversion sheet 10 and the light source 70. As shown in FIG. 14, the light source 130 includes a substrate 131, a reflection member 132 having an opening 132 </ b> A disposed on the substrate 131, and a light emission disposed on the substrate 131 and in the opening 132 </ b> A of the reflection member 132. A light emitter 133 such as a diode, a light wavelength converter 134 filled in the opening 132A of the reflecting member 132 so as to cover the light emitter 133, and a light absorption layer 135 covering the light exit surface of the light wavelength converter 134 are provided. ing. The optical wavelength conversion unit 134 is different from the optical wavelength conversion layer 11 only in shape and location, and the configuration and physical properties of the optical wavelength conversion unit 134 are the same as those of the optical wavelength conversion layer 11, and therefore the description thereof is omitted here. And Similarly, the light absorption layer 135 is different from the light absorption layer 14 only in the arrangement location, and the configuration and physical properties of the light absorption layer 135 are the same as those of the light absorption layer 14, and thus the description thereof is omitted here. To do. Instead of providing the light absorption layer 135 on the light exit surface of the light wavelength conversion unit 134, the light wavelength conversion unit 134 may contain a first light absorber and a second light absorber.

<< Other backlight devices >>
The backlight device may be the backlight device 140 shown in FIG. Specifically, the backlight device 140 illustrated in FIG. 15 includes a light-transmitting capillary 150 disposed between the light source 70 and the optical plate 75 instead of the light wavelength conversion member 10. The capillary 150 is one form of a light wavelength conversion member, and is provided on the light incident surface 75C of the optical plate 75 as shown in FIG. The capillaries 150 are arranged such that the longitudinal direction is along the arrangement direction of the light sources 70.

  In the capillary 150, the light wavelength conversion unit 151 is enclosed in a tube 152 such as a glass tube, and the outer peripheral surface on the light output side of the tube 152 is covered with a light absorption layer 153. The optical wavelength conversion unit 151 is different from the optical wavelength conversion layer 11 only in the arrangement location and shape, and the configuration and physical properties of the optical wavelength conversion unit 151 are the same as those of the optical wavelength conversion layer 11, and therefore the description thereof is omitted here. And Similarly, the light absorption layer 153 differs from the light absorption layer 14 only in the arrangement location, and the configuration and physical properties of the light absorption layer 153 are the same as those of the light absorption layer 14, and thus the description thereof is omitted here. To do. Instead of providing the light absorption layer 135 in the tube 152, the light wavelength conversion unit 151 may contain a first light absorber and a second light absorber.

  According to this embodiment, the first light absorber absorbs light in the first wavelength region that is in the visible light region and is between the first emission peak wavelength and the second emission peak wavelength. Therefore, it is possible to cut light in an unnecessary wavelength region and to narrow the width of the second emission peak. Thereby, the optical wavelength conversion member 10 which has the color purity excellent at the time of light emission can be obtained. In addition, when light having the first emission peak wavelength is incident on the light wavelength conversion member 10 in the visible light region, the light is converted into the visible light region by the first light absorber, and the first Since the light in the first wavelength range between the emission peak wavelength and the second emission peak wavelength is absorbed, the light in the unnecessary wavelength range can be cut, and the first emission peak and the second emission wavelength can be cut off. The width of the emission peak can be reduced. Thereby, the optical wavelength conversion member 10 which has the color purity excellent at the time of light emission can be obtained. Furthermore, when the light wavelength conversion layer 11 includes the first quantum dots 21 and the second quantum dots 22, and the light absorption layer 14 includes the first light absorber and the second light absorber, The first light absorber can absorb light in the first wavelength region and the second light absorber can absorb light in the second wavelength region, so that light in unnecessary wavelength regions is cut. In addition, the width of the first emission peak, the second emission peak, and the third emission peak can be reduced. Thereby, the light wavelength conversion member which has more excellent color purity at the time of light emission can be obtained.

  According to this embodiment, since the color purity can be improved by the first light absorber and the second light absorber, the first emission peak wavelength exists in the blue wavelength region, and the second emission peak. When the wavelength is in the green wavelength range and the third emission peak wavelength is in the red wavelength range, the color gamut can be expanded.

  According to the present embodiment, since the retroreflective sheets such as the lens sheets 80 and 85 are arranged on the observer side of the light absorption layer 14, a part of the light transmitted through the light absorption layer 14 is retroreflective sheet. Is retroreflected and returned to the light absorption layer 14 side again. Thereby, since the opportunity to cut the light of an unnecessary wavelength region more by the light absorption layer 14 increases, more excellent color purity can be obtained at the time of light emission.

  Conventionally, light that has been wavelength-converted by the quantum dots emitted from the light wavelength conversion sheet is condensed on the light output side of the light wavelength conversion sheet, and light that has not been wavelength-converted by the light wavelength conversion sheet is converted to the light wavelength conversion sheet. It has been studied to increase the optical wavelength conversion efficiency by arranging a lens sheet to be returned to the side. However, the optical wavelength conversion efficiency is not sufficient only by arranging such a lens sheet, and further improvement of the optical wavelength conversion efficiency is desired. According to this embodiment, when the external haze value of the light wavelength conversion member 10 is smaller than the internal haze value of the light wavelength conversion member 10, the light wavelength conversion efficiency can be further improved. That is, since the light emitted from the light source has straightness, the light that enters the light wavelength conversion sheet and is not wavelength-converted by the quantum dots, and the light emitted from the light wavelength conversion sheet also has straightness. Yes. Here, when the external haze value of the light wavelength conversion sheet is high, light that has not been wavelength-converted that has straightness on the surface of the light wavelength conversion sheet is refracted, and light that is not wavelength-converted emitted from the light wavelength conversion sheet In this case, a component having a large emission angle increases. On the other hand, a lens sheet having a condensing function and a retroreflective function tends to make the lens sheet retroreflected more easily as the incident angle to the lens sheet is smaller. That is, there is a tendency that light having a larger incident angle to the lens sheet is more easily transmitted through the lens sheet. In the present embodiment, in the light wavelength conversion member 10, the external haze value is smaller than the internal haze value. Therefore, even if light that has not undergone wavelength conversion is refracted on the surface of the light wavelength conversion member 10, it is emitted. The light can be emitted in a state where the angle is small. Accordingly, in the light which is emitted from the light wavelength conversion member 10 and is not wavelength-converted, a component having a small emission angle can be increased. Therefore, the lens sheet 60 can retroreflect the light emitted from the light wavelength conversion sheet without wavelength conversion and return it to the light wavelength conversion member 10 side, so that the opportunities for wavelength conversion increase. Moreover, since the internal haze value is larger than the external haze value, the light path length is increased by scattering light within the light wavelength conversion sheet, and the opportunity for wavelength conversion is further increased. Thereby, the optical wavelength conversion efficiency can be improved. Since the first quantum dots 21 and the second quantum dots 22 emit light isotropically, the light converted in wavelength by the first quantum dots 21 and the second quantum dots 22 is directed in various directions. When the light reaches the surface of the light wavelength conversion member 10, the light is further refracted on the surface of the light wavelength conversion member, and the wavelength-converted light is easily emitted from the light wavelength conversion member as light having a large angle. For this reason, the wavelength-converted light is relatively easily transmitted through the lens sheet 60.

  In the above description, the light diffusion characteristics (external diffusion characteristics) on the surface of the light wavelength conversion sheet are expressed using the external haze value for the following reason. First, the light diffusion characteristics of the light wavelength conversion sheet can be evaluated by measuring the light intensity of the transmitted light for each angle with a known goniophotometer such as a goniophotometer. It is extremely difficult to define the light diffusion characteristics of the light wavelength conversion sheet using the result of the light intensity. On the other hand, as described above, in the definition of haze, transmitted light deviated by 2.5 ° or more with respect to incident light is measured as haze. Not measured. As described above, as the haze, transmitted light of less than 2.5 ° with respect to incident light is not measured. However, as described above, light having a large incident angle on the lens sheet, that is, transmitted light having a large emission angle on the light wavelength conversion sheet, Since this is a problem, it is important how much transmitted light deviates by 2.5 ° or more from incident light by less than 2.5 °. For this reason, the light diffusion characteristic of the light wavelength conversion sheet can be expressed by the magnitude of the haze value of the light wavelength conversion sheet without measuring the light intensity for each angle of transmitted light by a goniophotometer. On the other hand, since it is necessary to consider that light is refracted on the surface of the light wavelength conversion sheet and the emission angle becomes large, an external haze is used to express the light diffusion characteristics on the surface of the light wavelength conversion sheet. Values were used.

  According to this embodiment, since the light wavelength conversion layer 11 includes the light scattering particles 23, the light wavelength conversion efficiency can be further improved. Therefore, for example, a light source that emits light having a first emission peak wavelength in the blue wavelength range is used as the light source 70, and light having the first emission peak wavelength is used as the first quantum dot 21 in the second wavelength range. A quantum dot that converts light having a first emission peak wavelength into light having a third emission peak wavelength in a red wavelength region is used as a second quantum dot 22 using a quantum dot that converts light having an emission peak wavelength. When used, the chromaticity x and y can be increased compared to a light wavelength conversion member that does not contain light scattering particles, and white light or light with a color close to white can be obtained.

  According to this embodiment, since the light wavelength conversion layer 11 includes the light scattering particles 23, the green light emission can be preferentially enhanced over the red light emission. The reason for this is not clear, but the light-scattering particles appear to inhibit energy transfer from the first quantum dot that converts blue light to green light to the second quantum dot that converts blue light to red light. This is probably because the green light emission that was originally deactivated by the above-described energy transfer does not deactivate, and thus reaches the light emission process, and as a result, the green light emission increases.

  In order to describe the present invention in detail, examples will be described below, but the present invention is not limited to these descriptions.

<Preparation of composition for light wavelength conversion layer>
First, each component was mix | blended so that it might become a composition shown below, and the composition for optical wavelength conversion layers was obtained.

(Composition 1 for light wavelength conversion layer)
Epoxy acrylate (product name “Unidick V-5500”, manufactured by DIC): 100 parts by mass Green emitting quantum dot (product name “CdSe / ZnS 530”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS , Average particle size 3.3 nm): 0.2 parts by mass Red light emitting quantum dots (product name “CdSe / ZnS 610”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm) : 0.2 part by mass-radical polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name “Irgacure (registered trademark) 184”, manufactured by BASF Japan Ltd.): 0.2 part by mass

(Composition 2 for light wavelength conversion layer)
Epoxy acrylate (product name “Unidic V-5500”, manufactured by DIC): 90 parts by mass Green emitting quantum dot (product name “CdSe / ZnS 530”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS , Average particle size 3.3 nm): 0.2 parts by mass Red light emitting quantum dots (product name “CdSe / ZnS 610”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm) : 0.2 parts by mass / alumina particles (light scattering particles, product name “DAM-03”, manufactured by Denki Kagaku Kogyo Co., Ltd., average particle size 4 μm): 10 parts by mass / radical polymerization initiator (1-hydroxycyclohexyl phenyl ketone) , Product name “Irgacure (registered trademark) 184”, manufactured by BASF Japan Ltd.): 0.2 parts by mass

(Composition 3 for light wavelength conversion layer)
Epoxy acrylate (product name “Unidick V-5500”, manufactured by DIC): 100 parts by mass Green emitting quantum dot (product name “CdSe / ZnS 530”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS , Average particle size 3.3 nm): 0.2 parts by mass Red light emitting quantum dots (product name “CdSe / ZnS 610”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm) : 0.2 part by mass / light absorber 1 (light absorption dye, product name “FDB-007”, manufactured by Yamada Chemical Industries, Ltd., absorption peak wavelength 496 nm): 0.02 part by mass / light absorber 2 (light absorption dye) , Product name “PD-320”, manufactured by Yamamoto Kasei Co., Ltd., absorption peak wavelength 595 nm): 0.2 part by mass / radical polymerization initiator (1-hydroxycyclohexyl fe) Ketone, product name, Ltd., "Irgacure (registered trademark) 184", BASF Japan Co., Ltd.): 0.2 parts by weight

<Preparation of composition for light absorption layer>
Each component was mix | blended so that it might become a composition shown below, and the composition for light absorption layers was obtained.
(Composition 1 for light absorption layer)
Light absorber 1 (light absorbing dye, product name “FDB-007”, manufactured by Yamada Chemical Co., Ltd., absorption peak wavelength 496 nm): 0.1 part by mass Light absorber 2 (light absorbing dye, product name “PD- 320 ", manufactured by Yamamoto Kasei Co., Ltd., absorption peak wavelength 595 nm): 1.0 part by mass / urethane adhesive main agent (product name“ ADLOCK RU-69 ”, manufactured by Rock Paint): 32 parts by mass / urethane adhesive curing Agent (Product name “Adlock H-9”, manufactured by Rock Paint): 4 parts by mass / ethyl acetate: 75 parts by mass

(Composition 2 for light absorption layer)
Light absorber 3 (light absorbing dye, product name “FDB-007”, manufactured by Yamada Chemical Co., Ltd., absorption peak wavelength 496 nm): 0.1 part by mass Light absorber 4 (light absorbing dye, product name “FDG- 007 ", manufactured by Yamada Chemical Co., Ltd., absorption peak wavelength 594 nm): 1.0 part by mass / urethane-based adhesive (product name" Adlock RU-69 ", manufactured by Rock Paint): 32 parts by mass / urethane-based adhesive Curing agent (Product name “Adlock H-9”, manufactured by Rock Paint): 4 parts by mass / ethyl acetate: 75 parts by mass

<Preparation of composition for adhesive layer>
Each component was mix | blended so that it might become a composition shown below, and the composition for contact bonding layers was obtained.
(Adhesive layer composition 1)
・ Urethane-based adhesive (Product name “Adlock RU-69”, manufactured by Rock Paint): 32 parts by mass ・ Urethane-based adhesive curing agent (Product name “Adlock H-9”, manufactured by Rock Paint): 4 mass Parts / ethyl acetate: 75 parts by mass

<Preparation of composition for light diffusion layer>
Each component was mix | blended so that it might become a composition shown below, and the composition for light-diffusion layers was obtained.
(Composition 1 for light diffusion layer)
Pentaerythritol triacrylate: 99 parts by mass Light scattering particles (crosslinked polystyrene resin beads, product name “SBX-4”, manufactured by Sekisui Plastics Co., Ltd., average particle size 4 μm): 158 parts by mass Photoinitiator (1-hydroxycyclohexyl phenyl ketone, product name “Irgacure (registered trademark) 184, manufactured by BASF Japan Ltd.): 1 part by mass / solvent (methyl isobutyl ketone: cyclohexanone = 1: 1 (mass ratio)): 170 parts by mass

<Example 1>
The light diffusing layer composition 1 is formed on one side of two polyethylene terephthalate (PET) substrates (product name “Lumirror T60”, manufactured by Toray Industries, Inc.) as light transmissive substrates having a size of 7 inches and a thickness of 50 μm. Was applied to form a coating film. Next, the solvent in the coating film was evaporated by allowing the formed coating film to dry by passing dry air at 80 ° C. for 30 seconds. Then, the light diffusion layer having a film thickness of 10 μm was formed by irradiating ultraviolet rays so that the integrated light amount was 500 mJ / cm ² to cure the coating film, and a PET substrate with a light diffusion layer was formed.

  Moreover, the composition 1 for light absorption layers was apply | coated to the single side | surface of another PET base material (product name "Lumirror T60", Toray Industries, Inc.) 7 inches in size and 50 micrometers in thickness, and the coating film was formed. Next, the solvent in the coating film was evaporated by allowing the formed coating film to dry by passing dry air at 80 ° C. for 30 seconds. Then, the PET base material with a light diffusion layer was laminated | stacked on the coating film so that the surface on the opposite side to the surface at the side of the light diffusion layer in the PET base material with a light diffusion layer may contact | connect this coating film. In this state, heating at 60 ° C. to form a light absorption layer having a film thickness of 20 μm, and a laminate in which the PET base material, the light absorption layer, and the PET base material with a light diffusion layer are integrated Formed.

  Moreover, the composition 1 for adhesive layers was apply | coated to the single side | surface of another PET base material (product name "Lumirror T60", Toray Industries, Inc.) 7 inches in size and 50 micrometers in thickness, and the coating film was formed. Subsequently, the PET base material with a light diffusion layer was laminated | stacked on the coating film so that the surface on the opposite side to the surface at the side of the light diffusion layer in a PET base material with a light diffusion layer may contact | connect the formed coating film. In this state, heating was performed at 60 ° C. to form an adhesive layer having a thickness of 20 μm, and a laminate in which the PET base material, the adhesive layer, and the PET base material with a light diffusion layer were integrated was formed. .

Subsequently, the composition 1 for light wavelength conversion layers was apply | coated to the surface on the opposite side to the surface by the side of the light-diffusion layer in the laminated body which has an contact bonding layer, it was made to dry at 80 degreeC, and the coating film was formed. And the other laminated body was laminated | stacked on the coating film so that the surface on the opposite side to the surface by the side of the light-diffusion layer in the other laminated body might contact | connect a coating film. In this state, ultraviolet rays are irradiated so that the integrated light amount is 500 mJ / cm ² to cure the coating film, thereby forming a light wavelength conversion layer with a film thickness of 100 μm, and a light wavelength conversion layer and two laminated layers Integrated with the body. As a result, an optical wavelength conversion sheet according to Example 1 was obtained.

<Example 2>
In Example 2, a light wavelength conversion sheet was produced in the same manner as in Example 1 except that the light wavelength conversion layer composition 2 was used instead of the light wavelength conversion layer composition 1.

<Example 3>
In Example 3, a light wavelength conversion sheet was produced in the same manner as in Example 1 except that the composition 2 for light absorbing layer was used instead of the composition 1 for light absorbing layer.

<Example 4>
The light diffusion layer composition 1 was applied to one side of two PET substrates (product name “Lumirror T60”, manufactured by Toray Industries, Inc.) as light transmissive substrates having a size of 7 inches and a thickness of 50 μm. A coating film was formed. Next, the solvent in the coating film was evaporated by allowing the formed coating film to dry by passing dry air at 80 ° C. for 30 seconds. Then, the light diffusion layer having a film thickness of 10 μm was formed by irradiating ultraviolet rays so that the integrated light amount was 500 mJ / cm ² to cure the coating film, and a PET substrate with a light diffusion layer was formed.

Subsequently, the composition 3 for light wavelength conversion layers was apply | coated to the surface on the opposite side to the surface by the side of the light-diffusion layer in one PET base material with a light-diffusion layer, and it was made to dry at 80 degreeC, and the coating film was formed. And the other laminated body was laminated | stacked on the coating film so that the surface on the opposite side to the surface at the side of the light-diffusion layer in the other PET base material with a light-diffusion layer may contact | connect a coating film. In this state, the coating film is cured by irradiating ultraviolet rays so that the integrated light quantity becomes 500 mJ / cm ² to form a light wavelength conversion layer with a film thickness of 100 μm, and the light wavelength conversion layer and two light beams A PET substrate with a diffusion layer was integrated. As a result, an optical wavelength conversion sheet according to Example 4 was obtained.

<Comparative Example 1>
In Comparative Example 1, a light wavelength conversion sheet was produced in the same manner as in Example 4 except that the light wavelength conversion layer composition 1 was used instead of the light wavelength conversion layer composition 3.

<Emission peak wavelength, half-value width and luminance measurement>
The light wavelength conversion sheets according to the above examples and comparative examples are each incorporated in a backlight device, and in the backlight device incorporating the light wavelength conversion sheets according to the examples and comparative examples, the spectral distribution of light emitted from the backlight device The emission peak wavelength and the half-value width of the emission peak were determined from the spectral distribution.

  When the light wavelength conversion sheets according to Examples and Comparative Examples were incorporated into a backlight device, first, a Kindle Fire (registered trademark) HDX7 backlight unit was prepared. This backlight device includes a blue light emitting diode having an emission peak wavelength of 450 nm, a light guide plate, a first prism sheet, and a second prism sheet in this order. The first prism sheet and the second prism sheet each include a sheet-like main body portion and a plurality of triangular prism-shaped unit prisms arranged side by side on the main body portion and extending in a direction intersecting the arrangement direction. The unit prism had an apex angle of 90 °.

  Then, the light guide plate is arranged so that the backlight side becomes the light incident surface, and the light wavelength conversion sheet, the first prism sheet, and the second prism sheet are arranged in this order on the light exit surface of the light guide plate. A backlight device was obtained. The prism sheet on the observer side was arranged so as to be orthogonal to the arrangement direction of the unit prisms and the arrangement direction of the unit prisms of the prism sheet.

  Then, the blue light emitting diode of the backlight device incorporating the light wavelength conversion sheet is turned on, the blue light is irradiated on one surface of the light wavelength conversion sheet, and the backlight device is passed through the other surface of the light wavelength conversion sheet. Spectral distribution of light emitted from the light emitting surface (surface of the second prism sheet) from the thickness direction of the light wavelength conversion sheet, using a spectral radiance meter (product name "CS2000", manufactured by Konica Minolta) The measurement was performed at a measurement angle of 1 °. Then, the emission peak wavelength and the half-value width of the emission peak were obtained from the obtained spectral distribution.

The results are shown in Table 1.

  The results will be described below. As can be seen from Table 1, in the backlight device incorporating the light wavelength conversion sheet according to Comparative Example 1, the half-value width of each emission peak in the emitted light was wide. On the other hand, in the backlight device incorporating the light wavelength conversion sheets according to Examples 1 to 3, the half-value width of each emission peak of the emitted light was narrow. Therefore, it was confirmed that when the light absorber is included in the light wavelength conversion sheet, the color purity is improved.

  The total haze value of the light wavelength conversion sheet according to Example 1 is 99.2%, the internal haze value is 96.4%, and the external haze value is 2.8%. The haze value was 99.5%, the internal haze value was 99.5%, and the external haze value was 0%. In both light wavelength conversion sheets, the external haze value is smaller than the internal haze value, so the brightness is high, but the light wavelength conversion sheet according to Example 1 and the light wavelength conversion sheet according to Example 2 are compared. The light wavelength conversion sheet according to Example 2 had higher brightness. This is because the light wavelength conversion sheet according to Example 2 contains alumina particles as light scattering particles, and therefore the internal haze value of the light wavelength conversion sheet according to Example 2 is the same as that of the wavelength conversion sheet according to Example 1. This is because it is larger than the internal haze value, thereby reducing the external haze value. Therefore, it was confirmed that by adding light scattering particles to the light wavelength conversion sheet and further increasing the internal haze value, the external haze value can be further reduced, thereby further improving the light wavelength conversion efficiency. .

  In the above embodiment, CdSe is used as the core material of the green light emitting quantum dots and the red light emitting quantum dots. However, even when a non-Cd material such as InP or InAs is used as the core material, the same results as in the above embodiments are obtained. was gotten.

DESCRIPTION OF SYMBOLS 10, 30, 40 ... Light wavelength conversion member 11, 31 ... Light wavelength conversion layer 14, 41, 135, 153 ... Light absorption layer 20 ... Binder resin 21 ... 1st quantum dot 22 ... 2nd quantum dot 23 ... Light Scattering particle 50 ... image display device 60, 110 ... backlight device 100 ... display panel 130 ... optical member

Claims (11)

An optical wavelength conversion member that converts the wavelength of at least a part of the incident light having the first emission peak wavelength and emits light having the second emission peak wavelength in at least the visible light region. And
A first quantum dot that converts light having the first emission peak wavelength into light having the second emission peak wavelength different from the first emission peak wavelength;
A first light absorber that absorbs light in a first wavelength region that is in a visible light region and is between the first emission peak wavelength and the second emission peak wavelength. An optical wavelength conversion member.   2. The light according to claim 1, wherein the first emission peak wavelength is a peak wavelength of the first emission peak, exists in a blue wavelength region, and a half width of the first emission peak is 40 nm or less. Wavelength conversion member.   4. The light according to claim 3, wherein the second emission peak wavelength is a peak wavelength of the second emission peak, exists in a green wavelength region, and a half width of the second emission peak is 50 nm or less. Wavelength conversion member. The light wavelength conversion member is a member that further emits light having a third emission peak wavelength different from the first emission peak wavelength and the second emission peak wavelength in a visible light region,
A second quantum dot that converts light having the first emission peak wavelength into light having a third emission peak wavelength;
Of the first emission peak wavelength and the second emission peak wavelength, in the second wavelength range between any of the emission peak wavelengths located on the third emission peak wavelength side and the third emission peak wavelength. The light wavelength conversion member according to claim 1, further comprising: a second light absorbent that absorbs the light.   5. The third emission peak wavelength according to claim 4, wherein the third emission peak wavelength is a peak wavelength of the third emission peak, exists in a red wavelength region, and a half width of the third emission peak is 50 nm or less. Light wavelength conversion member.   A light wavelength conversion layer; and a light absorption layer disposed on a light output side of the light wavelength conversion layer, wherein the light wavelength conversion layer includes the first quantum dots, and the light absorption layer includes the first light absorption layer. The light wavelength conversion member according to claim 1, comprising a light absorber.   The retroreflective sheet disposed on the light exit side of the light wavelength conversion layer is further provided, and the light absorption layer is disposed between the light wavelength conversion layer and the retroreflective sheet. Optical wavelength conversion member.   The light wavelength conversion member according to claim 1, further comprising a light wavelength conversion layer, wherein the light wavelength conversion layer includes the first quantum dots and the first light absorber.   The light wavelength conversion member according to claim 6 or 8, wherein the light wavelength conversion layer further contains light scattering particles. A light source;
A light wavelength conversion member according to claim 1, which receives light from the light source.   An image display device comprising the light wavelength conversion member according to claim 1 or the backlight device according to claim 10.

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