JP7039833B2 - Light wavelength conversion member, backlight device, and image display device - Google Patents

Description

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

A transmissive image display device such as a liquid crystal display device is generally arranged on the back side of a transmissive image display panel such as a liquid crystal display panel, and includes a backlight device that illuminates the transmissive image display panel.

Currently, consideration is being given to incorporating an optical wavelength conversion member containing 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 the light emitted by the quantum dots mainly depends on the particle size of the quantum dots. Therefore, in an image display device incorporating an optical wavelength conversion member, various colors can be reproduced while using a light source that projects light in a single wavelength range. For example, when a light source that emits blue light is used, various colors can be reproduced because the quantum dots in the light wavelength conversion member can absorb a part of blue light and emit green light and red light. ..

Japanese Unexamined Patent Publication No. 2015-11518

In an image display device incorporating such a light wavelength conversion member, it is considered to expand the color range from the viewpoint of further improving the color reproducibility, but the color range 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, it is an object of the present invention to provide a light wavelength conversion member having excellent color purity at the time of light emission, a backlight device provided with the light wavelength conversion member, and an image display device.

As a result of diligent research on the above-mentioned problems, the present inventors have found that the color purity can be improved by including a light absorber that absorbs light in a specific wavelength range 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, among the incident light having the first emission peak wavelength, at least a part of the light has a second emission peak wavelength in the visible light region by converting the wavelength of the light. A first light wavelength conversion member that emits light and converts light having the first emission peak wavelength into light having the second emission peak wavelength different from the first emission peak wavelength. Quantum dots and a first light absorber that is in the visible light region and absorbs light in the first wavelength range between the first emission peak wavelength and the second emission peak wavelength. Provided is an optical wavelength conversion member comprising.

In the light wavelength conversion member, the first emission peak wavelength is the peak wavelength of the first emission peak and exists in the blue wavelength region, and the half width of the first emission peak is 40 nm or less. May be good.

In the light wavelength conversion member, the second emission peak wavelength is the peak wavelength of the second emission peak and exists in the green wavelength region, and the half width of the second emission peak is 50 nm or less. May be good.

In the light wavelength conversion member, the light wavelength conversion member further emits light having a third emission peak wavelength different from the first emission peak wavelength and the second emission peak wavelength in the visible light region. There is a second quantum dot that converts light having the first emission peak wavelength into light having a third emission peak wavelength, and of the first emission peak wavelength and the second emission peak wavelength. It further contains a second light absorber that absorbs light 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. May be good.

In the light wavelength conversion member, the third emission peak wavelength is the peak wavelength of the third emission peak and exists in the red wavelength region, and the half width of the third emission peak is 50 nm or less. You may.

The light wavelength conversion member further includes a light wavelength conversion layer and a light absorption layer arranged on the light emitting side of the light wavelength conversion layer, and the light wavelength conversion layer includes the first quantum dot and said. The light absorption layer may contain the first light absorber.

The light wavelength conversion member further includes a retroreflective sheet arranged on the light emitting side of the light wavelength conversion layer, and the light absorption layer is arranged between the light wavelength conversion layer and the retroreflective sheet. You may.

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

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

According to another aspect of the present invention, there is provided a backlight device including a light source and the above-mentioned light 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 including the above-mentioned backlight device and a display panel arranged on the light emitting side of the backlight device.

According to one aspect of the present invention, the first light absorber that absorbs light in the first wavelength range between the first emission peak wavelength and the second emission peak wavelength is contained. It is possible to improve the color purity of light having the emission peak wavelength of 2, thereby providing an optical wavelength conversion member having excellent color purity at the time of emission. Further, according to another aspect of the present invention, it is possible to provide a backlight device and an image display device including such a light wavelength conversion member.

It is a schematic block diagram of the light wavelength conversion member which concerns on embodiment. It is a figure which shows the operation of the light wavelength conversion member which concerns on embodiment. It is a schematic block diagram of another light wavelength conversion member which concerns on embodiment. It is a schematic block diagram of another light wavelength conversion member which concerns on embodiment. It is a figure which shows typically the manufacturing process of the light wavelength conversion member which concerns on embodiment. It is a figure which shows typically the manufacturing process of the light wavelength conversion member which concerns on embodiment. It is a figure which shows typically the manufacturing process of the light wavelength conversion member which concerns on embodiment. It is a figure which shows typically the manufacturing process of the light wavelength conversion member which concerns on embodiment. It is a schematic block diagram of the image display apparatus including the backlight apparatus which concerns on embodiment. It is a perspective view of the lens sheet shown in FIG. FIG. 3 is a cross-sectional view taken along the line I-I 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 in FIG. It is a schematic block diagram of the other backlight apparatus which concerns on embodiment. FIG. 15 is an enlarged view of the vicinity of the light entering surface of the optical plate shown in FIG.

Hereinafter, the light wavelength conversion member, the backlight device, the image display device, and the composition for the light wavelength conversion layer according to the embodiment of the present invention will be described with reference to the drawings. In the present specification, terms such as "sheet" and "film" are not distinguished from each other based only on the difference in designation. Therefore, for example, "sheet" is used in the sense of including a member that can also be called a film, and "film" is used in the sense of including a member that can also be called a sheet. FIG. 1 is a schematic configuration diagram of a light wavelength conversion member according to the present embodiment, FIG. 2 is a diagram showing the operation of the light wavelength conversion member according to the present embodiment, and FIGS. 3 and 4 are views according to the present embodiment. It is a schematic block diagram of another light wavelength conversion member, and FIGS. 5 to 8 are diagrams schematically showing the manufacturing process of the light wavelength conversion member according to this embodiment.

<<< Optical 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 to obtain the second emission peak wavelength in at least the visible light region. It is a member that emits the light it has. When the light having the first emission peak wavelength is incident in the visible light region, the light wavelength conversion member 10 has not only the light having the second emission peak wavelength but also the first emission peak wavelength. It is a member that 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. As used herein, the "visible light region" means a region having a wavelength of 380 nm or more and 780 nm or less, and the "ultraviolet light region" means a region having a wavelength of 10 nm or more and a wavelength of 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 sides of the light wavelength conversion layer 11, and light transmissibility. Adhesion provided between the light absorbing layer 14 provided on the side of the base material 12 opposite to the surface on the light wavelength conversion layer 11 side and the surface of the light transmitting base material 13 on the side opposite to the surface on the light wavelength conversion layer 11 side. The layer 15, the light-transmitting base material 16 provided on the surface of the light-absorbing layer 14 opposite to the surface of the light-transmitting base material 12 side, and the surface of the adhesive layer 15 on the light-transmitting base material 13 side. Is a light-transmitting base material 17 provided on the opposite surface and a light-diffusing layer provided on the surface of the light-transmitting base materials 16 and 17 opposite to the light-transmitting base materials 16 and 17 sides. It has 18 and 19. In the light wavelength conversion member 10, the surfaces of the light diffusion layers 18 and 19 constitute the surfaces 10A and 10B of the light wavelength conversion member 10. The light wavelength conversion member 10 includes light-transmitting base materials 12, 13, 17, and 18, but does not have a barrier layer, and therefore does not have a barrier film composed of a light-transmitting base material and a barrier layer. The light wavelength conversion member 10 includes a light diffusion layer 14 / a light transmitting base material 16 / a light absorbing layer 14 / a light transmitting base material 12 / a light wavelength conversion layer 11 / a light transmitting base material 13 / a light absorbing layer 15. / The structure is the light transmissive base material 17 / the light diffusion layer 15, but the structure of the light wavelength conversion member is not particularly limited as long as it contains the first quantum dot and the first light absorber described later. ..

In the light wavelength conversion member 10, the water vapor transmittance (WVTR: Water Vapor Transmission Rate) at 40 ° C. and 90% relative humidity may be 0.1 g / ( ^m 2.24 h) or more in the entire member. .. The water vapor permeability is a numerical value obtained by a method based on JIS K7129: 2008. The water vapor permeability can be measured using a water vapor permeability measuring device (product name "PERMATRAN-W3 / 31", manufactured by MOCON). The water vapor transmittance shall be the average value of the values obtained by measuring three times. Since the barrier film is formed in the conventional light wavelength conversion sheet, 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 has a higher water vapor transmission rate. Moisture is more easily transmitted than the conventional light wavelength conversion sheet.

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 in the entire member. May be good. The light wavelength conversion member 10 may satisfy the water vapor transmittance and the oxygen transmittance 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 permeability shall be the average value of the values obtained by measuring three times. Since the barrier film is formed in the conventional light wavelength conversion sheet, 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 has a higher oxygen transmission rate. Compared to the conventional light wavelength conversion sheet, not only water but also oxygen is easily transmitted.

The water vapor transmittance of the light wavelength conversion member 10 at 40 ° C. and 90% relative humidity may be 1 g / ( ^m 2.24 h) or more, and at 23 ° C. and 90% relative humidity of the light wavelength conversion member 10. The oxygen permeability of the light may be 1 cm ³ / ( ^m 2.24 h · atm) or more.

The internal haze value of the optical wavelength conversion member 10 is preferably 50% or more. The internal haze is a haze value caused by 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 optical wavelength conversion member 10 is 50% or more, the light can be sufficiently diffused by the internal haze to excite the quantum dots multiple times, and the external haze value can be made smaller. Can be done. The internal haze value of the light wavelength conversion member 10 is preferably 60% or more, more preferably 80% or more.

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

In the light wavelength conversion member 10, it is preferable that 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. That is, it is preferable that the light 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 obtained using a haze meter (product name "HM-150", manufactured by Murakami Color Technology Laboratory). Specifically, first, using a haze meter, the total haze value of the optical wavelength conversion sheet is measured according to JIS K7136: 2000. After that, a triacetyl cellulose substrate having a thickness of 60 μm (product name “Panaclean PD-S1”, manufactured by Panac Co., Ltd.) is interposed on both sides of the optical wavelength conversion sheet via a transparent optical adhesive layer (product name “Panaclean PD-S1”, manufactured by Panac Co., Ltd.) having a film thickness of 25 μm (product name “Panaclean PD-S1”). TD60UL ", manufactured by Fujifilm Co., Ltd.) is pasted. As a result, the uneven shape of the surface of the light wavelength conversion sheet is crushed, and the surface of the light wavelength conversion sheet is flattened. Then, in this state, the internal haze value is obtained by measuring the haze value according to JIS K7136 using a haze meter (product name "HM-150", manufactured by Murakami Color Technology Research Institute). The external haze value is obtained by subtracting the internal haze from the total haze. As used herein, the "external haze value" means the external haze value of the entire optical wavelength conversion sheet. That is, the external haze value in the present 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. The internal haze value and the external haze value shall be the arithmetic mean value of the values obtained by measuring each three times.

The internal haze value and the external haze value are related. Specifically, as the internal haze value increases, the external haze tends to decrease even if the surface has the same surface unevenness. This is considered to be due to the following reasons. JIS K7136: 2000 stipulates that the haze is a percentage of the transmitted light passing through the test piece that deviates by 0.044 rad (2.5 °) or more from the incident light due to forward scattering. There is. 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 transmitted light less than 2.5 ° with respect to incident light is not measured as haze. On the other hand, in the light wavelength conversion sheet having a large internal haze, the light is scattered more inside the sheet as compared with the light wavelength conversion sheet having a smaller internal haze, so that the light reaches the sheet surface with respect to the incident light. There is less transmitted light below 2.5 °. Therefore, when the optical wavelength conversion sheet having a large internal haze and the optical wavelength conversion sheet having a smaller internal haze have the same surface unevenness, the optical wavelength conversion sheet having a larger internal haze has a larger internal haze than that. Compared to a small light wavelength conversion sheet, the effect of surface irregularities is reduced. Therefore, when considering only the influence of the surface unevenness existing on the sheet surface, even if the optical wavelength conversion sheet having a large internal haze and the optical wavelength conversion sheet having a smaller internal haze have the same surface unevenness, the inside Compared to the optical wavelength conversion sheet with a larger haze, the optical wavelength conversion sheet with a smaller internal haze has not only transmitted light of less than 2.5 ° to the incident light emitted from the surface unevenness, but also surface unevenness. The transmitted light that deviates by 2.5 ° or more with respect to the incident light emitted from the light source is also reduced. Therefore, it is considered that when the internal haze value becomes large, the external haze becomes small even if the surface irregularities are the same.

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 to the inside of the light wavelength conversion member 10 can be mentioned. .. When 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, and the light diffusion layer may be added. It may also be added therein. When the layer to which the light-scattering particles are added is the outermost layer, it may be accompanied by external haze. Therefore, by controlling the surface unevenness of the outermost layer, the above-mentioned relationship between the internal haze and the external haze is satisfied. Can be done.

The ratio of the external haze value to the internal haze value (external haze value / internal haze value) in the optical wavelength conversion member 10 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 internal haze can sufficiently diffuse the light and excite the quantum dots multiple times.

The arithmetic average roughness (Ra) of the surfaces 10A and 10B of the optical wavelength conversion member 10 is preferably 0.1 μm or more, and more preferably 0.5 μm or more, respectively. The reason why Ra of the surfaces 10A and 10B of the optical wavelength conversion member 10 is preferably 0.1 μm is as follows. The optical wavelength conversion sheet comes into contact with the optical plate or lens sheet described later in the backlight device, but if the optical wavelength conversion sheet and the optical plate or lens sheet stick to each other, it is between the optical wavelength conversion member and the optical plate. Since there is a possibility that a pattern called wet-out may be formed at the interface between the light wavelength conversion member 10 and the interface between the light wavelength conversion member and the lens sheet, the light wavelength conversion member 10 and the optical plate or the lens sheet may be formed. Ra is more preferably 0.1 μm or more in order to prevent sticking.

The above definition of "Ra" shall be 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 Co., Ltd.). Ra is an average value of values obtained by randomly measuring 15 points on the surfaces 10A and 10B of the light wavelength conversion member where there is no visual abnormality (a place where there is no large foreign matter or scratches).

The thickness of the optical wavelength conversion member 10 is preferably 10 μm or more and 500 μm or less. When the thickness of the optical wavelength conversion member 10 is within this range, it is suitable for reducing the weight and thinning of the backlight device. The thickness of the light wavelength conversion member 10 is determined 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 at 20 points in the image of the cross section, and measuring the thickness thereof. The average value of the thicknesses at 20 points. In the measurement by SEM, it is preferable that the acceleration voltage is 30 kV and the magnification is 1000 to 7000 times.

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

The film thickness of the optical wavelength conversion layer 11 is preferably 10 μm or more and 200 μm or less. When the thickness of the light wavelength conversion layer 11 is within this range, it is suitable for reducing the weight and thinning of the backlight device. For the film thickness of the optical wavelength conversion layer 11, a cross section of the optical wavelength conversion layer 11 is photographed using a scanning electron microscope (SEM), and the film thickness of the optical wavelength conversion layer 11 is measured at 20 points in the image of the cross section. , The average value of the film thickness at the 20 points. It is more preferable that the upper limit of the average film thickness of the optical wavelength conversion layer 11 is less than 170 μm.

<< Binder resin >>
The binder resin 20 is not particularly limited, but is preferably a polymer (cured product, crosslinked product) of a polymerizable compound. 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 (thermocurable compound). Examples of ionizing radiation in the present specification include visible light and 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 (meth) acryloyl group, vinyl group and allylic 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, which 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 a monomer containing a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 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, trimethyl propantri (meth) acrylate, trimethyl ethanetri (meth). ) Acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, glycerol (meth) acrylate (Meta) acrylic acid esters such as, etc. may be mentioned.

As the ionizing radiation polymerizable oligomer, a polyfunctional oligomer having two or more functionalities is preferable, and a polyfunctional oligomer having three or more (trifunctional) 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. Examples thereof include (meth) acrylate and epoxy (meth) acrylate.

The ionizing radiation polymerizable prepolymer has a weight average molecular weight of more than 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. Therefore, when an ionizing radiation-polymerizable prepolymer having a weight average molecular weight of more than 80,000 is used, it is preferable to mix and use the above-mentioned polymerizable monomer and the above-mentioned 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 thermopolymerizable functional group include a cyclic ether group such as an epoxy group and an oxetanyl group, a vinyl ether group and the like.

An epoxy compound is a compound having one or more epoxy groups in the molecule. The epoxy compound is not particularly limited, but for example, bisphenol A type epoxy compound, bisphenol F type epoxy compound, bisphenol S type epoxy compound, biphenyl type epoxy compound, fluorene type epoxy compound, novolak phenol type epoxy compound, cresol novolak type epoxy. Aromatic compounds such as compounds and 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 an alkylene oxide adduct thereof. Diglycidyl ether of polyhydric alcohol such as di or triglycidyl ether, diglycidyl ether of polyethylene glycol or its alkylene oxide adduct, polyalkylene glycol diglycidyl ether such as diglycidyl ether of polypropylene glycol or its alkylene oxide adduct, And aliphatic systems such as alkylene oxide. Here, examples of the alkylene oxide include aliphatic epoxy compounds such as ethylene oxide and propylene oxide, 3', 4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, 3,4-epoxycyclohexylmethylmethacrylate and the like. Examples thereof include an alicyclic epoxy compound containing one or more epoxy groups and one or more ester groups in the molecule.

<< Quantum dots >>
The optical wavelength conversion layer 11 includes a first quantum dot 21 and a second quantum dot 22 as quantum dots. However, the optical wavelength conversion layer 11 may include the first quantum dot 21 and may not include the second quantum dot 22.

Quantum dots are nano-sized semiconductor particles that have a quantum confinement effect. The particle diameter and the average particle diameter of the quantum dots are, for example, 1 nm or more and 20 nm or less. When a quantum dot absorbs light from an excitation source and reaches an energy excited state, it 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 quantum dots increases as the particle size decreases. That is, as the crystal size becomes smaller, the emission of the quantum dots shifts to the blue side, that is, to the high energy side. Therefore, by changing the particle size of the quantum dot, the emission wavelength can be adjusted over the entire wavelength of the spectrum in 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 the particle size 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 range of the particle size of the quantum dot emitting blue light and the particle size of the quantum dot emitting green light partially overlaps, and the particle size of the quantum dot emitting green light and the red light are overlapped. The range of the particle size of the emitted quantum dots overlaps in part, but even if the quantum dots have the same particle size, the emission color may differ depending on the size of the core of the quantum dots, so there is no contradiction. It's not something to do. As used herein, "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 Light having a wavelength range of 590 nm or more and 750 nm or less.

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

It is preferable that the first emission peak wavelength exists in the blue wavelength region, the second emission peak wavelength exists in the green wavelength region, and the third emission peak wavelength exists in the red wavelength region. As used herein, the term "blue wavelength range" means a wavelength range of 380 nm or more and less than 480 nm, the "green wavelength range" means a wavelength range of 480 nm or more and less than 590 nm, and the "red wavelength range" means. It means a wavelength range of 590 nm or more and 750 nm or less.

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

When the second emission peak wavelength is present in the green wavelength region, 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 region and the half-value width of the second emission peak is within the above range, green light having improved color purity can be emitted from the optical wavelength conversion member. .. The full width at half maximum of the second peak shall be obtained from the spectral distribution of the light emitted from the light wavelength conversion member. It is more preferable that the half width of the second emission peak is 20 nm or less.

When the third emission peak wavelength is present in the red wavelength region, the half width of the third emission peak is preferably 40 nm or less. When the third emission peak wavelength exists in the red wavelength region and the full width at half maximum of the third emission peak is within the above range, red light with improved color purity can be emitted from the optical wavelength conversion member. .. The full width at half maximum of the third peak shall be obtained from the spectral distribution of the light emitted from the light wavelength conversion member. It is more preferable that the half width of the third emission peak is 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 incident. The light L1 having the emission peak wavelength of is converted into the light L2 having the second emission peak wavelength by the first quantum dot 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. As a result, 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 Three types of light having the above are emitted from the light wavelength conversion member.

As described above, some light emitted from the light wavelength conversion member 10 is not wavelength-converted. Therefore, the light having the first emission peak wavelength is blue light, and the light having the second emission peak wavelength is the light. When the light is green 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 dot 21 and the second quantum dot 22 are, 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. , Consists of 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, and the like. 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. Examples thereof include semiconductor compounds such as group V semiconductor compounds, group IV semiconductors such as Si, Ge and Pb, or semiconductor crystals containing semiconductors. Further, a semiconductor crystal containing a semiconductor compound containing three or more elements such as InGaP can also 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 particle size capable of obtaining light emission in the visible range, and the like.

As the second semiconductor compound constituting the shell, it is preferable to use a semiconductor compound having a bandgap higher than that of the first semiconductor compound constituting the core so that excitons are confined in the core. This makes it possible to increase the luminous efficiency of the quantum dots. Examples of the second semiconductor compound constituting the shell include ZnS, ZnSe, CdS, GaN, CdSSe, ZnSeTe, AlP, ZnSTe, ZnSSe and the like.

Specific combinations of the core-shell structure (core / shell) consisting of the core and the shell include, for example, CdSe / ZnS, CdSe / ZnSe, CdSe / CdS, CdTe / CdS, InP / ZnS, Gap / ZnS, Si / ZnS, and the like. InN / GaN, InP / CdSSe, InP / ZnSeTe, InGaP / ZnSe, InGaP / ZnS, Si / AlP, InP / ZnSTe, InGaP / ZnSTe, InGaP / ZnSSe and the like can be mentioned.

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 shapes of the first quantum dots 21 and the second quantum dots 22 are not particularly limited, and may be, for example, spherical, rod-shaped, disc-shaped, or other shapes. 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 size, average particle size, shape, and dispersed state of the first quantum dot 21 and the second quantum dot 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 the average value of the diameters of the 20 quantum dots measured by observing the cross section of the optical wavelength conversion layer with a transmission electron microscope or a scanning transmission electron microscope. Further, since the emission color of the quantum dot changes depending on the particle diameter, it is also possible to obtain the particle diameter of the quantum dot by confirming the emission color of the quantum dot. Further, the crystal structure and crystallite size of the quantum dots can be known by X-ray crystal diffraction (XRD). Furthermore, information on the particle size of quantum dots and the like can be obtained from the ultraviolet-visible (UV-Vis) absorption spectrum.

The content of the quantum dots in the optical 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 quantum dot content is less than 0.01% by mass, sufficient emission intensity may not be obtained, and if the quantum dot content exceeds 2% by mass, sufficient excitation light is transmitted. There is a risk that strength will not be obtained. The content of the quantum dots is the total content of the first quantum dots 21 and the second quantum dots 22 when the first quantum dots 21 and the second quantum dots 22 are used as the quantum dots. Means. The content (mass%) of quantum dots in the cured light wavelength conversion layer and the content (mass%) of light-scattering particles described later can be roughly calculated by the following methods. 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 portion is dissolved in a solvent or incinerated by combustion to remove the components of the binder resin. When removing the components of the binder resin, the quantum dots and the light-scattering particles are not removed, and since the particle sizes of the quantum dots and the light-scattering particles are significantly different, the quantum dot components and light are different due to the difference in particle size. Separate the components of the scattering particles. Then, the mass of the separated quantum dot component and the component of the light-scattering particle are measured, respectively. Then, the ratio of the mass of the quantum dots contained in at least a part of the sampled light wavelength conversion layer based on the mass of at least a part of the sampled light wavelength conversion layer and the mass of the quantum dots 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, me scattering occurs. Since it becomes difficult, there is a possibility that the light scattering effect cannot be sufficiently obtained, and further, there is a possibility that the processability is 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, and more preferably 50 times or more and 1000 times or less 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 becomes If it exceeds 2000 times the average particle size of the quantum dots, the number of light-scattering particles will decrease even if the amount added is the same, so the number of scattering points will decrease and a sufficient light-scattering effect may not be obtained. .. The average particle size of the light-scattering particles can be measured by the same method as the above-mentioned average particle size of the quantum dots.

Further, the average particle diameter of the light scattering particles 23 is preferably 1/300 or more and 1/20 or less, and 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 size 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, and the average of the light scattering particles. If the particle size 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 amount added is the same, so that the number of scattering points is sufficiently reduced. No light scattering effect can be obtained.

Specifically, the average particle diameter of the light-scattering particles 23 is, for example, 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 size 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, and in order to obtain sufficient light scattering properties, the light scattering particles may have insufficient light scattering properties. It is necessary to increase the amount added. On the other hand, when the average particle size 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. The refractive index of the light-scattering particles 23 and 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 contained in the light wavelength conversion layer, for example, the Becke method, the minimum declination method, the declination analysis, the mode line method, the ellipsometry method and the like are used. can do. Regarding the refractive index of the binder resin 20 in the optical wavelength conversion layer 11, for example, 10 pieces of the binder resin 20 are taken out from the light wavelength conversion layer 11 by cutting out or the like, and the 10 pieces taken out are taken out by the binder method by the Becke method. The refractive index of each of the 20 is measured, and it can be obtained as an average value of 10 of the measured refractive indexes of the binder resin 20. Further, the refractive index of the light scattering particles 23 in the light wavelength conversion layer 11 is determined by, for example, cutting out a fragment obtained by exposing a part of the surface of the light scattering particles 23 from the binder resin 20 from the light wavelength conversion layer 11. The refractive index of the 10 light-scattering particles 23 whose surfaces are exposed by the Becke method is measured in each of the taken-out pieces, and the average value of the measured refractive indices of the light-scattering particles 23 is obtained. can. In the Becke method, a refractive index standard solution having a known refractive index is used, the above-mentioned pieces are placed on a slide glass or the like, the refractive index standard solution is dropped onto the sample, and the pieces are immersed in the refractive index standard solution. Is observed by microscopic observation, and the emission line (Becke line) generated on the surface of the binder resin or light-scattering particles cannot be visually observed due to the difference in the refractive index between the surface of the binder resin or light-scattering particles and the refraction index standard solution. Refraction index This is a method in which the refractive index of the standard liquid is used as the refractive index of the binder resin or the light-scattering particles. When the surface of the light-scattering particles is not exposed in the removed pieces, the surface of the light-scattering particles is covered with the binder resin, so that the binder resin existing around the light-scattering particles is used. There is no difference in refractive index. Therefore, by measuring the difference in refractive index from the binder resin existing around the light-scattering particles by the Becke method or the like, it is possible to determine whether or not a part of the surface of the light-scattering particles is exposed. .. In addition, the difference in refractive index 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 Research Institute or a two-beam interference microscope manufactured by Mizojiri Optical Co., Ltd.). can do.

The shape of the light-scattering particles 23 is not particularly limited, and is, for example, spherical (true spherical, substantially true spherical, elliptical spherical, etc.), polyhedral, rod-shaped (cylindrical, prismatic, etc.), flat plate, flaky, indefinite. The shape and the like can be mentioned. When the shape of the light-scattering particles is not spherical, the particle diameter of the light-scattering particles 18 can be a true spherical value having the same volume.

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.

The silane coupling agent may be a vinyl group, an epoxy group, a styryl group, a methacrylic group, an acrylic group, an amino group, a ureido group, a thiol group, a sulfide group and an isocyanate group, depending on the type of curable binder resin precursor used. It is possible to use one 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, or a thiol. It is preferred to have at least one reactive functional group selected from the group consisting of groups and amino groups.

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 rate of change in brightness before and after the durability test can be reduced, and the rate of change in brightness can be reduced. Inorganic particles are preferable because the incident light to the light wavelength conversion member 10 can be suitably scattered and the light wavelength conversion efficiency with respect to the incident light can be preferably improved.

The inorganic particles include an aluminum-containing compound such as Al ₂ O ₃ , a zirconium-containing compound such as ZrO ₂ , a tin-containing compound such as antimony-doped tin oxide (ATO) and indium tin oxide (ITO), and magnesium 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 can be mentioned. Since these inorganic particles can increase the difference in refractive index from 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 more preferably improved, the light scattering particles 23 may be made of two or more kinds of materials.

<< Light-transmitting substrate >>
The thicknesses of the light-transmitting substrates 12 and 13 are not particularly limited, but are preferably 10 μm or more and 500 μm or less. If the thickness of the light-transmitting base materials 12 and 13 is less than 10 μm, the assembly of the optical wavelength conversion sheet may be wrinkled or broken during handling, and if it exceeds 150 μm, the weight of the display and the thin film may be reduced. It may not be suitable for conversion. The more preferable lower limit of the thickness of the light-transmitting base materials 12 and 13 is 50 μm or more, and the more preferable upper limit is 400 μm or less.

For the thickness of the light-transmitting base materials 12 and 13, a cross section of the light-transmitting base materials 12 and 13 is photographed using a scanning electron microscope (SEM), and the light-transmitting base materials 12 and 13 are imaged in the cross-sectional image. The thickness of the 20 points is measured at 20 points, and the average value of the film thicknesses at the 20 points is used.

Examples of the constituent raw materials of the light-transmitting base materials 12 and 13 include polyester (for example, polyethylene terephthalate and polyethylene naphthalate), cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyethersulfone, and polysulfone. , Polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyether ketone, polymethyl methacrylate, polycarbonate, or thermoplastic resins such as polyurethane. Preferred examples of the constituent materials of the light-transmitting base materials 12 and 13 include polyester (for example, polyethylene terephthalate and polyethylene naphthalate).

The light-transmitting base materials 12 and 13 may be composed of a single base material, or may be a laminated base material composed of a plurality of base materials. Such a laminated base material may be composed of a plurality of layers composed of layers of the same type of constituent raw materials, or may be composed of a plurality of layers composed of layers of different types of constituent raw materials, depending on the intended use. 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 the first wavelength range between the first emission peak wavelength and the second emission peak wavelength, and the first emission. A second light absorption that absorbs light in the second wavelength range between the emission peak wavelength located on the third emission peak wavelength side of the peak wavelength and the second emission peak wavelength and the third emission peak wavelength. Contains agents (not shown). However, it is not always necessary to use both the first light absorber and the second light absorber, and even when both the first light absorber and the second light absorber are used, the first 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 absorption layer 14 shown in FIG. 1 has a function of absorbing light in a specific wavelength range and a function of adhering the light transmissive base material 12 and the light transmissive base material 16. Therefore, the light absorbing layer 14 contains an adhesive (not shown) in addition to the first light absorbing agent and the second light absorbing agent.

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 may vary greatly due to the variation in the film thickness, and if the film thickness of the light absorption layer exceeds 100 μm, the thickness of the light wavelength conversion member becomes large. It may be difficult to handle. The film thickness of the light absorption layer 14 is determined by photographing a cross section of the light absorption layer 14 using a scanning electron microscope (SEM) and measuring the film thickness of the light absorption layer 14 at 20 points in the image of the cross section. The average value of the film thickness at each location. The lower limit of the film 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, it may not be possible to sufficiently absorb the light in the first wavelength range, and the content of the first light absorber is 10% by mass. If it exceeds, the light transmittance of the light wavelength conversion member may be significantly lowered. 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, it may not be possible to sufficiently absorb the light in the second wavelength range, and the content of the second light absorber is 10% by mass. If it exceeds, the light transmittance of the light wavelength conversion member may be significantly lowered. The content of the second light absorber can be determined by the same method as the content of the first light absorber.

<Light absorber>
The first light absorber is in the visible light region and absorbs light in the first wavelength range between the first emission peak wavelength and the second emission peak wavelength, and is a second. The light absorber is within the second wavelength range 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 exists in the blue region, the second emission peak wavelength exists in the green region, and the third emission peak wavelength exists in the red region, the second emission peak wavelength is selected. Is located on the third emission peak wavelength side of the first emission peak wavelength, so that 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 range, and the second light absorber preferably has an absorption peak wavelength in the second wavelength range. Since the first light absorber has an absorption peak wavelength in the first wavelength region, more light in the first wavelength region can be absorbed. Further, since the second light absorber has an absorption peak wavelength in the second wavelength region, more light in the second wavelength region can be absorbed. As used herein, the term "absorption peak wavelength" means the wavelength at the peak of the absorption peak when the absorption spectrum of the light absorber is measured.

Examples of the first light absorber and the second light absorber include dyes. Examples of the dye include dyes and pigments, but 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-based dyes, phthalocyanine-based dyes, cyanine-based dyes, azo-based dyes, phycobilin-based dyes, and the like. However, the first light absorber and the second light absorber can be appropriately selected depending on the light in the wavelength range to be absorbed. Specifically, when the first emission peak wavelength exists in the wavelength range of 420 nm or more and 480 nm or less, and the second emission peak wavelength exists in the wavelength range of 500 nm or more and 580 nm or less, it is within the first wavelength range. Examples of the first light absorber that absorbs light include porphyrin-based dyes and phthalocyanine-based dyes. When the third emission peak wavelength is in the wavelength range of 600 nm or more and 680 nm or less, the second light absorber that absorbs the light in the second wavelength range is, for example, a porphyrin-based dye or a phthalocyanine-based dye. Examples include pigments.

<Adhesive>
The adhesive is not particularly limited, and for example, known adhesives such as urethane-based, polyester-based, polyether-based, epoxy-based, polyethyleneimine-based, and polybutadiene-based can be used.

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

<< Light diffusion layer >>
The light diffusion layers 18 and 19 have an uneven shape on the surface, and the uneven shape can diffuse the light incident on the light wavelength conversion member 10 and the light emitted from the light wavelength conversion member 10. By providing the light diffusion layers 18 and 19, the light wavelength conversion efficiency of the light wavelength conversion sheet 10 can be further improved. The light diffusing layers 18 and 19 contain light scattering particles and a binder resin.

<Light scattering particles>
The light-scattering particles in the light-diffusing layers 18 and 19 are mainly for forming an uneven shape on the surface of the light-diffusing layers 18 and 19 and exhibiting a light-scattering function.

The average particle size of the light-scattering particles in the light diffusion layers 18 and 19 is preferably 10 times or more and 20,000 times or less the average particle size of the above-mentioned quantum dots, and more preferably 10 to 5000 times. .. 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-diffusivity may not be obtained in the light-diffusing layer, and the average particle size of the light-scattering particles may not be sufficient. If it exceeds 20,000 times the average particle size of the quantum dots, the light diffusion performance of the light diffusion layer becomes excellent, but the light transmission rate of the light diffusion layer tends to be significantly reduced. The average particle size of the light-scattering particles can be measured by the same method as the above-mentioned average particle size of the quantum dots.

Specifically, the average particle size of the light-scattering particles in the light diffusion layers 18 and 19 is preferably, for example, 1 μm or more and 30 μm or less, and more preferably 1 μm or more and 20 μm or less. If the average particle size 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 the light-scattering particles added in order to obtain sufficient light diffusivity. Need to be increased. On the other hand, when the average particle size of the light-scattering particles exceeds 30 μm, the light diffusing performance becomes excellent, but the light transmittance of the light diffusing layer tends to be significantly reduced.

The absolute value of the difference in refractive index between the light-scattering particles in the light-diffusing layers 18 and 19 and the binder resin is preferably 0.02 or more and 0.15 or less. If it is less than 0.02, the light diffusivity 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 decrease. 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 or less. It should be noted that either the refractive index of the light-scattering particles or the refractive index of the binder resin may be larger. The refractive index of the light-scattering particles and the binder resin can be measured by the same method as the refractive index of the light-scattering particles 18 and the binder resin.

Since the shapes of the light-scattering particles in the light-diffusing layers 18 and 19 are the same as the shapes of the light-scattering particles 23 in the light wavelength conversion layer 11, the description thereof will be omitted here. The light-scattering particles in the light-diffusing 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 bond can be realized by using light scattering particles surface-modified with a silane coupling agent. Since the silane coupling agent is the same as the silane coupling agent described in the section of light scattering particles in the light wavelength conversion member, the description thereof will be 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, and 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, crosslinked acrylic resin is preferably used. The inorganic material constituting the light diffusing particles is not particularly limited, and examples thereof include inorganic oxides such as silica, alumina, titania, tin oxide, antimony-doped tin oxide (ATO), and zinc oxide fine particles. Among them, silica and / or alumina are preferably used.

<Binder resin>
The binder resin is not particularly limited, but a polymer (cured product, crosslinked product) of the polymerizable compound described in the column of the binder resin 20 can be used, and thus the description thereof will be omitted here.

<<< Other optical wavelength conversion members >>>
As shown in FIG. 3, the light wavelength conversion member has a structure of a light diffusing layer 18 / a light transmitting base material 16 / a light wavelength conversion layer 31 / a light transmitting base material 17 / a light diffusing layer 19. It may be a member 30. In this case, the light wavelength conversion layer 31 includes a binder resin, a first quantum dot 21, a second quantum dot 22, and a light scattering particle 23, as well as a first light absorber (not shown) and a second light absorber. Contains a light absorber (not shown).

<<< Other optical wavelength conversion members >>>
As shown in FIG. 4, the light wavelength conversion member has a structure of a light absorption layer 41 / a light diffusion layer 18 / a light transmission base material 16 / a light wavelength conversion layer 11 / a light transmission base material 17 / a light diffusion layer 19. It may be the light wavelength conversion member 40 having. In this case, the light-absorbing layer 41 contains a first light-absorbing agent (not shown) and a second light-absorbing agent (not shown). The light incoming surface of the light wavelength conversion member 40 is the surface 40A, and the light emitting surface is the surface 40B. In the light wavelength conversion member 40, the light absorption layer 41 may or may not be integrated with the light wavelength conversion layer or the like.

The light absorption layer 41 contains a binder resin in addition to the first light absorber and the second light absorber. The binder resin of the light absorption layer 41 is not particularly limited, but a polymer (cured product, crosslinked product) of the polymerizable compound described in the column of the binder resin 16 can be used, and thus the description thereof is omitted here. And.

<<< Manufacturing method of optical wavelength conversion member >>>
The light wavelength conversion member 10 can be manufactured, for example, as follows. 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-transmitting base material 16, dried, and then coated with the light-diffusing layer composition. Form a film. Similarly, a coating film of the composition for a light diffusion layer is formed on one surface of the light-transmitting base material 16.

Then, the coating film of the composition for the light diffusion layer is cured by light irradiation or the like. As a result, as shown in FIG. 5A, the light diffusing layer 18 is formed on one surface of the light transmitting base material 16, and the light transmitting base material 16 with the light diffusing layer 18 is formed. Further, although not shown, the light transmissive base material 17 with the light diffusing layer 19 is formed in the same manner.

On the other hand, as shown in FIG. 5B, a composition for a light absorbing layer containing a first light absorber, a second light absorber and an adhesive is applied to one side of the light transmitting base material 12. The coating film 25 was formed. Next, as shown in FIG. 5C, the formed coating film 25 is in contact with the surface of the light-transmitting substrate 16 with the light-diffusing layer 18 opposite to the surface on the light-diffusing layer 18 side. The light-transmitting base material 16 with the light-diffusing layer 18 is laminated on the coating film 25. In this state, as shown in FIG. 6 (A), it is dried at 20 ° C. or higher and 80 ° C. or lower. As a result, the light absorbing layer 14 is formed, and the light transmitting base material 12 and the light transmitting base material 16 with the light diffusing layer 18 are integrated via the light absorbing layer 14.

Further, as shown in FIG. 6B, a composition for an adhesive layer containing an adhesive was applied to one side of the light-transmitting base material 13 to form a coating film 26. Next, as shown in FIG. 6C, the formed coating film 26 is in contact with the surface of the light-transmitting substrate 17 with the light-diffusing layer 19 opposite to the surface on the light-diffusing layer 19 side. The light-transmitting base material 17 with the light-diffusing layer 19 is laminated on the coating film 26. In this state, as shown in FIG. 7 (A), it is dried at 20 ° C. or higher and 80 ° C. or lower. As a result, the adhesive layer 15 is formed, and the light-transmitting base material 13 and the light-transmitting base material 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 of the laminate 28 having the light transmission base material 13, the adhesive layer 15, the light transmission base material 17 and the light diffusion layer 19? A composition for an optical wavelength conversion layer containing a first quantum dot 21, a second quantum dot 22, a light scattering particle 23, and a polymerizable compound is applied to the opposite surface, dried, and the optical wavelength conversion layer is applied. A coating film 29 of the composition for use is formed.

The content of the quantum dots with respect to the total solid content mass of the composition for the optical 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 quantum dot content is less than 0.01% by mass, sufficient emission intensity may not be obtained, and if the quantum dot content exceeds 2% by mass, sufficient excitation light is transmitted. There is a risk that strength will not be obtained. The content of the quantum dots is the total content of the first quantum dots 21 and the second quantum dots 22 when the first quantum dots 21 and the second quantum dots 22 are used as the quantum dots. Means.

The content of the polymerizable compound with respect to the total solid content mass of the composition for the optical wavelength conversion layer is preferably 30% by mass or more and 95% by mass or less, and preferably 50% by mass or more and 90% by mass or less. If the content of the polymerizable compound is less than 30% by mass, sufficient curability may not be obtained when forming the optical wavelength conversion layer, and the content of the polymerizable compound exceeds 95% by mass. Then, the light wavelength conversion layer may become brittle. When the composition for the light wavelength conversion layer contains both a photopolymerizable compound and a thermopolymerizable compound, the above-mentioned content means the total content of the photopolymerizable compound and the thermopolymerizable compound. do.

The content of the light scattering particles 23 with respect to the total solid content mass of the composition for the 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, me scattering occurs. Since it becomes difficult, there is a possibility that the light scattering effect cannot be sufficiently obtained, and further, there is a possibility that the processability is deteriorated because there are too many light scattering particles.

The composition for the optical wavelength conversion layer preferably contains a polymerization initiator. The polymerization initiator is a component that is decomposed by light or heat to generate radicals or ionic species to initiate or proceed the polymerization (crosslinking) of the curable binder resin precursor. Examples of the polymerization initiator used in the composition for the optical wavelength conversion layer include a photopolymerization initiator (for example, a photoradical polymerization initiator, a photocationic polymerization initiator, a photoanionic polymerization initiator) and a thermal polymerization initiator (for example, heat). Radical polymerization initiators, thermal cationic polymerization initiators, thermal anionic polymerization initiators), or mixtures thereof.

Examples of the photoradical polymerization initiator include benzophenone compounds, acetophenone compounds, acylphosphine oxide compounds, titanosen compounds, oxime ester compounds, benzoin ether compounds, thioxanthone and the like.

Commercially available photoradical polymerization initiators include, for example, IRGACURE184, IRGACURE369, IRGACURE379, IRGACURE651, IRGACURE819, IRGACURE907, IRGACURE2959, IRGACURE OXE01, and Lucillin TPO (all manufactured by BASF Japan). Examples thereof include ADEKA), SPEEDCURE EMK (manufactured by Sebel Hegner, Japan), benzoine methyl ether, benzoin ethyl ether, and benzoin isopropyl ether (all manufactured by Tokyo Kasei Kogyo Co., Ltd.).

Examples of the photocationic polymerization initiator include aromatic diazonium salts, aromatic iodonium salts, aromatic sulfonium salts and the like. Examples of commercially available photocationic polymerization initiators include ADEKA PTOMER SP-150 and ADEKA PTOMER 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 a polycondensate of 4,4'-azobis (4-cyanopentanoic acid) and polyalkylene glycol. Examples thereof include a polycondensate of 4,4'-azobis (4-cyanopentanoic acid) and a polydimethylsiloxane having a terminal amino group.

Examples of the peroxide include ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, peroxyesters, diacyl peroxides, peroxydicarbonates and the like.

Commercially available thermal radical polymerization initiators include, for example, Perbutyl O, Perhexyl O, Perbutyl PV (all manufactured by NOF CORPORATION), V-30, V-501, V-601, and VPE-0201. , VPE-0401, VPE-0601 (all manufactured by Wako Pure Chemical Industries, Ltd.) and the like.

Examples of the thermal cationic polymerization initiator include various onium salts such as quaternary ammonium salts, phosphonium salts, and sulfonium salts. Commercially available thermal cationic polymerization initiators include, for example, 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 which are manufactured by ADEKA). All of them include Sanshin Chemical Industry Co., Ltd.) and CI series (Nippon Soda Co., Ltd.).

The content of the polymerization initiator in the composition for the optical 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. If the content of the polymerization initiator is less than 0.3 parts by mass, the polymerizable compound is difficult to cure, and if it exceeds 5.0 parts by mass, the optical wavelength conversion member may turn yellow. ..

The viscosity of the composition for the optical wavelength conversion layer is preferably 10 mPa · s or more and 10,000 mPa · s or less. If the viscosity of the composition for the 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 the light wavelength conversion layer is used. When applying, it becomes difficult to apply, and the leveling property may deteriorate. The lower limit of the viscosity of the composition for the light wavelength conversion layer is preferably 10 mPa · s or more, and the upper limit of the viscosity of the composition for the light wavelength conversion layer is preferably 10000 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 a light transmitting base material 12, a light absorbing layer 14, a light transmitting base material 16 and a light diffusing 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 side of the light diffusion layer 19 is in contact with the coating film 29 of the composition for light wavelength conversion layer. Deploy. As a result, the coating film 29 of the composition for the light wavelength conversion layer is sandwiched between the laminated body 27 and the laminated body 28.

Next, as shown in FIG. 8, the coating film 29 of the composition for the light wavelength conversion layer is irradiated with ionizing radiation or heat is applied to cure the composition for the light wavelength conversion layer through the laminate 27. The light wavelength conversion layer 11 is formed, and the light wavelength conversion layer 11 and the laminated bodies 27 and 28 are integrated. As a result, the optical wavelength conversion member 10 shown in FIG. 1 is obtained.

The optical 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 into 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. 11 is an I- of the lens sheet of FIG. It is sectional drawing along the line I. 12, 13, and 15 are schematic configuration diagrams of other backlight devices according to the present embodiment, FIG. 14 is a schematic configuration diagram of a light source shown in FIG. 13, and FIG. 16 is a schematic configuration diagram of a light source. It is an enlarged view near the light source surface of an optical plate.

<<< Image display device >>>
The image display device 50 shown in FIG. 9 includes a backlight device 60 and a display panel 100 arranged on the light emitting 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 from the back surface side in a plane shape. The display panel 100 functions as a shutter that controls the 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 >>
The display panel 100 shown in FIG. 9 is a liquid crystal display panel, and is between the polarizing plate 101 arranged on the incoming light side, the polarizing plate 102 arranged on the light emitting side, and the polarizing plate 101 and the polarizing plate 102. It is provided with an arranged liquid crystal cell 103. The polarizing plates 101 and 102 decompose the incident light into two orthogonal linearly polarized light components (S-polarized and P-polarized) and vibrate in one direction (direction parallel to the transmission axis) (for example, P). It has a function of transmitting (polarized light) and absorbing a linearly polarized light component (for example, S-polarized light) that vibrates in the other direction (direction parallel to the absorption axis) orthogonal to the one direction.

<< Backlight device >>
The backlight device 60 shown in FIG. 9 is configured as an edge light type backlight device, and has a light source 70, an optical plate 75 as a light guide plate arranged on the side of the light source 70, and a light emitting side of the optical plate 75. The optical wavelength conversion member 10 arranged in the light wavelength conversion member 10, the lens sheet 80 arranged on the light source side of the light wavelength conversion member 10, the lens sheet 85 arranged on the light source side of the lens sheet 80, and the light source side of the lens sheet 85. It includes an arranged reflective polarizing separation sheet 90 and a reflective sheet 95 arranged on the side opposite to the light source side of the optical plate 75. The backlight device 60 includes an optical plate 75, lens sheets 80 and 85, a reflective polarizing separation sheet 90, and a reflective sheet 95, but these sheets and the like may not be provided. As used herein, the term "light emitting side" means the side of each member where light emitted in the direction emitted from the backlight device is emitted.

The backlight setting 60 has a light emitting surface 60A that emits light in a planar manner. In the backlight device 60 shown in FIG. 9, the light emitting surface of the reflective polarizing separation sheet 90 is the light emitting surface 60A of the backlight device 60.

Since the light absorption layer 14 is preferably arranged closer to the observer than the light wavelength conversion layer 11 so as not to absorb the incident blue light, the surface of the light wavelength conversion member 10 on the optical plate 75 side is the surface surface. It is 10A (light entry surface), and the surface of the light wavelength conversion member 10 on the lens sheet 80 side is the surface 10B (light emission surface).

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

<Optical plate>
The optical plate 75 as a light guide plate has a rectangular shape in a plan view. The optical plate 75 extends between the light emitting surface 75A formed by one main surface on the display panel 100 side, the back surface 75B composed of the other main surface facing the light emitting surface 75A, and the light emitting surface 75A and the back surface 75B. Has sides. The side surface of the side surface on the light source 70 side is an incoming light receiving surface 75C that receives light from the light source 70. The light incident on the optical plate 75 from the light incoming surface 75C is guided in the optical plate in the direction connecting the light incoming surface 75C and the opposite surface facing the light incoming surface 75C (light guide direction), and the light is guided through the optical plate. 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 the incident light from the light emitting side. In the present embodiment, as shown in FIG. 11, a function (condensing function) of changing the traveling direction of light L3 having a large incident angle and emitting it from the light emitting side to intensively improve the brightness in the front direction. At the same time, it has a function (retroreflection function) of reflecting 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 transmitting base material 81 and a lens layer 82 provided on one surface of the light transmitting base material 81.

When the surfaces 10A and 10B of the optical wavelength conversion member 10 are uneven surfaces, the light emitting surface 75A of the optical plate 75 is optically in close contact with a part (for example, a convex portion) of the surface 10A, and is also a surface. It is preferable that the lens sheet 80 is separated from other parts (for example, concave portions) of 10A, and the light entrance surface 80A of the lens sheet 80 is optically in close contact with a part (for example, convex portions) of the surface 10B and also has a surface. It is preferable that the 10B is separated from other parts (for example, recesses). In this case, the gap between the light emitting surface 75A and the other portion of the surface 10A and the gap between the light entering surface 80A and the other portion of the surface 10B are 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 emitting surface 75A and the surface 10A and the light entering surface 80A and the surface 10B are in optical contact with each other. However, since it is possible to prevent the light wavelength conversion member 10 from sticking to the optical plate 75 and the lens sheet 80, the interface between the light wavelength conversion member 10 and the optical plate 75 and the light wavelength conversion member 10 and the lens sheet 80 It is possible to suppress the formation of wet-out at the interface between the light and the light.

<Light transmissive base material>
Since the light-transmitting base material 81 is the same as the light-transmitting base materials 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-shaped main body portion 83 and a plurality of unit lenses 84 arranged side by side on the light emitting side of the main body portion 83.

The main body 83 functions as a sheet-like member that supports the unit lens 84. As shown in FIGS. 9 and 10, unit lenses 84 are arranged on the light emitting side surface 83A of the main body portion 83 without leaving a gap. Therefore, the light emitting surfaces 80B and 85B of the lens sheets 80 and 85 are formed by the lens surfaces. On the other hand, as shown in FIG. 11, in the present embodiment, the main body portion 83 has a smooth surface forming the incoming side surface of the lens layer 82 as the incoming light entering side surface 83B facing the light emitting side surface 83A. There is.

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

The unit lens 84 may have a triangular columnar shape, or may have a wavy shape or a bowl shape such as a hemispherical shape. Specifically, examples of the unit lens include a unit prism, a unit cylindrical lens, a unit microlens, and the like. Examples of the lens sheet having such a unit lens shape include a prism sheet, a lenticular lens sheet, and a micro lens sheet. In the present embodiment, as a unit lens, a triangular columnar unit prism whose width becomes narrower toward the light emitting side will be described. The shape of the cross section (also called the main cut 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 lens 84 is a triangular shape protruding toward the light emitting 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 on the main cutting surface is an isosceles triangle shape, and the apex angle located between the equilateral sides is the light emitting side surface 83A of the main body 83. Each unit lens 84 is configured so as to project from the light emitting side.

From the viewpoint of improving the efficiency of light utilization, the unit lens 84 preferably has an apex angle of 80 ° or more and 100 ° or less, and more preferably about 90 °. However, considering the damage to the tip of the unit lens when winding the optical wavelength conversion sheet, the tip of the unit lens 84 may be a curved surface.

The dimensions of the lens sheets 80 and 85 can be set as follows, for example. First, as a specific example of the unit lens 84, the arrangement pitch of the unit lens 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 arrangement of the unit lens 64 has been rapidly improved in definition, and it is preferable that the arrangement pitch of the unit lens 84 is 10 μm or more and 50 μm or less. Further, the protruding height of the unit lens 84 from the main body portion 83 along the normal direction ND of the lens sheets 80 and 85 to the sheet surface 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 lens 84 of the lens sheet 80 and the arrangement direction of the unit lens 84 of the lens sheet 85 intersect, and more specifically, are orthogonal to each other.

<Reflective polarization separation sheet>
The reflective polarization separation sheet 90 transmits only the first linear polarization component (for example, P-polarization) among the light emitted from the lens sheet 85, and is a second straight line orthogonal to the first linear polarization component. It has a function of reflecting a polarizing component (for example, S-polarized light) without absorbing it. The second linear polarization component reflected by the reflective polarization separation sheet 90 is reflected again, and the polarization is eliminated (a state in which both the first linear polarization component and the second linear polarization component are included). It is incident on the reflective polarizing separation sheet 90 again. Therefore, the reflective polarization separation sheet 90 transmits the first linear polarization component of the light incident again, and the second linear polarization component orthogonal to the first linear polarization 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 the light source light as the first linearly polarized light component. Therefore, by arranging the reflective polarization separation sheet 110, the wavelength conversion efficiency of the optical wavelength conversion sheet 10 can be further increased. Therefore, further improvement in light utilization efficiency can be expected.

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

<Reflective sheet>
The reflective sheet 95 has a function of reflecting the light leaked from the back surface 75B of the optical plate 75 and causing it to enter the optical plate 70 again. The reflective sheet 95 is composed of a white diffuse reflective sheet, a sheet made of a material having a high reflectance such as metal, a sheet containing a thin film made of a material having a high reflectance (for example, a metal thin film) as a surface layer, and the like. obtain. The reflection on the reflective sheet 95 may be normal 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. 12. The backlight device 110 shown in FIG. 12 includes a light source 70, an optical plate 111 that receives the light of the light source 70 and functions as a light diffusing plate, and an optical wavelength conversion member 10 arranged on the light emitting side of the optical plate 111. The lens sheet 80 arranged on the light emitting side of the optical wavelength conversion member 10, the lens sheet 85 arranged on the light emitting side of the lens sheet 80, and the reflective polarization separation sheet 90 arranged on the light emitting side of the lens sheet 85 are provided. I have. In the present embodiment, the light source 70 is arranged directly under the optical plate 111, not on the side of the optical plate 111. In FIG. 12, the members having the same reference numerals as those in FIG. 9 are the same as the members shown in FIG. 9, and therefore the description thereof will be omitted. The backlight device 110 is not provided with the reflective sheet 95.

<Optical plate>
The optical plate 111 as a light diffusing plate has a rectangular shape in a plan view. The optical plate 111 has an incoming light input surface 111A formed by one main surface on the light source 75 side and an outgoing light surface 111B formed by the other main surface on the light wavelength conversion member 10. The light incident on the optical plate 111 from the light incoming surface 111A is diffused in the optical plate 111 and emitted from the light emitting surface 111B.

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

<< Other backlight devices >>
The backlight device 60 shown in FIG. 9 includes a sheet-shaped light wavelength conversion member 10, but the light wavelength conversion member does not have to be sheet-shaped. For example, as shown in FIG. 13, the backlight device may be a backlight device 120 provided with a light source 130, which is a 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 has a substrate 131, a reflective member 132 having an opening 132A arranged on the substrate 131, and a light emitting member arranged on the substrate 131 and in the opening 132A of the reflective member 132. A light emitting body 133 such as a diode, a light wavelength conversion unit 134 filled in the opening 132A of the reflecting member 132 so as to cover the light emitting body 133, and a light absorption layer 135 covering the light emitting surface of the light wavelength conversion unit 134 are provided. ing. The optical wavelength conversion unit 134 is different in shape and arrangement from the optical wavelength conversion layer 11, 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. 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 structure and physical properties of the light absorption layer 135 are the same as those of the light absorption layer 14, so the description thereof will be omitted here. do. Instead of providing the light absorption layer 135 on the light emitting 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 shown in FIG. 15 includes a light-transmitting capillary 150 arranged between the light source 70 and the optical plate 75 instead of the light wavelength conversion member 10. The capillary 150 is a form of an optical wavelength conversion member, and is provided on the light input surface 75C of the optical plate 75 as shown in FIG. The capillary 150 is arranged so 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 of the tube 152 on the light emitting side 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, so the description thereof is omitted here. And. Similarly, the light absorption layer 153 is different from the light absorption layer 14 only in the arrangement location, and the structure and physical properties of the light absorption layer 153 are the same as those of the light absorption layer 14, so the description thereof will be omitted here. do. Instead of providing the light absorption layer 135 on the tube 152, the light wavelength conversion unit 151 may contain the first light absorber and the second light absorber.

According to the present embodiment, the first light absorber absorbs light in the first wavelength range within the visible light region and between the first emission peak wavelength and the second emission peak wavelength. Therefore, it is possible to cut light in an unnecessary wavelength range and narrow the width of the second emission peak. Thereby, the light wavelength conversion member 10 having excellent color purity at the time of light emission can be obtained. Further, 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 in the visible light region and is in the visible light region by the first light absorber. 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 peak can be cut. The width of the emission peak can be narrowed. Thereby, the light wavelength conversion member 10 having excellent color purity at the time of light emission can be obtained. Further, when the light wavelength conversion layer 11 includes the first quantum dot 21 and the second quantum dot 22, and the light absorbing layer 14 contains the first light absorbing agent and the second light absorbing agent, the light absorbing layer 14 contains the first light absorbing agent and the second light absorbing agent. Since the first light absorber can absorb the light in the first wavelength range and the second light absorber can absorb the light in the second wavelength range, it cuts the light in the unnecessary wavelength range. At the same time, the widths of the first emission peak, the second emission peak, and the third emission peak can be narrowed. This makes it possible to obtain a light wavelength conversion member having more excellent color purity at the time of light emission.

According to the present 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 is present. When the wavelength exists in the green wavelength region and the third emission peak wavelength exists in the red wavelength region, the color region 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 a retroreflective sheet. It is retroreflected at and returned to the light absorption layer 14 side again. As a result, the light absorption layer 14 increases the chances of cutting light in an unnecessary wavelength range, so that more excellent color purity can be obtained at the time of light emission.

Conventionally, the light wavelength-converted by the quantum dots emitted from the optical wavelength conversion sheet is condensed on the light emitting side of the optical wavelength conversion sheet, and the light not wavelength-converted by the optical wavelength conversion sheet is collected by the optical wavelength conversion sheet. It is being studied to improve the light 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 the present 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 is incident on the light wavelength conversion sheet and is not wavelength-converted by the quantum dots and is emitted from the light wavelength conversion sheet also has straightness. There is. Here, when the external haze value of the optical wavelength conversion sheet is high, the unconverted wavelength light having straightness on the surface of the optical wavelength conversion sheet is refracted, and the unconverted wavelength light emitted from the optical wavelength conversion sheet is emitted. Will have many components with a large emission angle. On the other hand, in a lens sheet having a light collecting function and a retroreflective function, the light incident on the lens sheet at a smaller angle tends to be more likely to be retroreflected. That is, the larger the angle of incidence on the lens sheet, the easier it is for the light to pass 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, so that even if the light that has not been wavelength-converted on the surface of the light wavelength conversion member 10 is refracted, it is emitted. It can be emitted in a state where the angle is small, and thus it is possible to increase the number of components having a small emission angle in the unwavelength-converted light emitted from the light wavelength conversion member 10. 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 opportunity for wavelength conversion increases. Further, since the internal haze value is larger than the external haze value, the optical path length is extended by scattering the light a plurality of times inside the optical wavelength conversion sheet, and the chance of wavelength conversion is further increased. This makes it possible to improve the light wavelength conversion efficiency. Since the first quantum dot 21 and the second quantum dot 22 emit light isotropically, the light wavelength-converted by the first quantum dot 21 and the second quantum dot 22 faces 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 becomes light having a large angle and is easily emitted from the light wavelength conversion member. Therefore, the wavelength-converted light is relatively easy to pass through the lens sheet 60.

In the above, the light diffusion characteristic (external diffusion characteristic) on the surface of the light wavelength conversion sheet is expressed by using the external haze value for the following reasons. 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 variable-angle photometer such as a goniophotometer. It is extremely difficult to define the light diffusion characteristics of the light wavelength conversion sheet using the result of 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, but transmitted light less than 2.5 ° with respect to incident light is measured as haze. Not measured. As described above, the transmitted light having a haze of less than 2.5 ° with respect to the incident light is not measured, but as described above, the light having a large incident angle to the lens sheet, that is, the transmitted light having a large emission angle in the optical wavelength conversion sheet is emitted. Since it is a problem, it is important how much transmitted light exists that is 2.5 ° or more deviated from the transmitted light that is less than 2.5 ° with respect to the incident light. Therefore, 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 the transmitted light by the angle change photometer. On the other hand, it is necessary to consider that the light is refracted on the surface of the light wavelength conversion sheet and the emission angle becomes large. Therefore, in order to express the light diffusion characteristics on the surface of the light wavelength conversion sheet, an external haze is required. The value was used.

According to the present embodiment, since the light wavelength conversion layer 11 contains 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 region is used as the light source 70, and light having a first emission peak wavelength is used as the first quantum dot 21 in the green wavelength region. A quantum dot that converts light having a first emission peak wavelength into light having a third emission peak wavelength in the red wavelength region as a second quantum dot 22 by using a quantum dot that converts light having an emission peak wavelength. When used, the chromaticity x and y can be increased as compared with the light wavelength conversion member containing no light-scattering particles, and white light or light having a tint close to white can be obtained.

According to the present embodiment, since the light wavelength conversion layer 11 contains 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 light-scattering particles may impede 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. It is considered that this is because the green light emission that was originally deactivated by the above energy transfer leads to the light emission process without being deactivated, and as a result, the green light emission increases.

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

<Preparation of composition for optical wavelength conversion layer>
First, each component was blended so as to have the composition shown below to obtain a composition for an optical wavelength conversion layer.

(Composition for Light Wavelength Conversion Layer 1)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 100 parts by mass-Green emission quantum dots (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 emission 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 ・ Radical polymerization initiator (1-hydroxycyclohexylphenylketone, product name “Irgacure (registered trademark) 184”, manufactured by BASF Japan): 0.2 parts by mass

(Composition for Light Wavelength Conversion Layer 2)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 90 parts by mass-Green emission quantum dots (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 emission 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 diameter 4 μm): 10 parts by mass ・ Radical polymerization initiator (1-hydroxycyclohexylphenylketone) , Product name "Irgacure (registered trademark) 184", manufactured by BASF Japan): 0.2 parts by mass

(Composition for Light Wavelength Conversion Layer 3)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 100 parts by mass-Green emission quantum dots (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 dot (product name "CdSe / ZnS 610", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm) : 0.2 parts by mass, light absorber 1 (light absorbing dye, product name "FDB-007", manufactured by Yamada Chemical Industry Co., Ltd., absorption peak wavelength 496 nm): 0.02 parts by mass, light absorbing agent 2 (light absorbing dye) , Product name "PD-320", manufactured by Yamamoto Kasei Co., Ltd., absorption peak wavelength 595 nm): 0.2 parts by mass · Radical polymerization initiator (1-hydroxycyclohexylphenylketone, product name "Irgacure (registered trademark) 184", BASF Made by Japan): 0.2 parts by mass

<Preparation of composition for light absorption layer>
Each component was blended so as to have the composition shown below to obtain a composition for a light absorption layer.
(Composition 1 for light absorption layer)
-Light absorber 1 (light-absorbing dye, product name "FDB-007", manufactured by Yamada Chemical Industry Co., Ltd., absorption peak wavelength 496 nm): 0.1 part by mass-Light-absorbing agent 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 Co., Ltd.): 32 parts by mass ・ Cured urethane adhesive Agent (Product name "Adlock H-9", manufactured by Rock Paint Co., Ltd.): 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 Industry Co., Ltd., absorption peak wavelength 496 nm): 0.1 parts by mass-Light-absorbing agent 4 (light-absorbing dye, product name "FDG-" 007 ”, manufactured by Yamada Chemical Industry Co., Ltd., absorption peak wavelength 594 nm): 1.0 part by mass, urethane adhesive main agent (product name“ Adlock RU-69 ”, manufactured by Rock Paint Co., Ltd.): 32 parts by mass, urethane adhesive Hardener (Product name "Adlock H-9", manufactured by Rock Paint Co., Ltd.): 4 parts by mass, ethyl acetate: 75 parts by mass

<Preparation of composition for adhesive layer>
Each component was blended so as to have the composition shown below to obtain a composition for an adhesive layer.
(Composition 1 for Adhesive Layer)
-Urethane adhesive main agent (product name "Adlock RU-69", manufactured by Rock Paint Co., Ltd.): 32 parts by mass-Urethane adhesive curing agent (product name "Adlock H-9", manufactured by Rock Paint Co., Ltd.): 4 mass Part ・ Ethyl acetate: 75 parts by mass

<Preparation of composition for light diffusion layer>
Each component was blended so as to have the composition shown below to obtain a composition for a light diffusion layer.
(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 Kasei Kogyo Co., Ltd., average particle diameter 4 μm): 158 parts by mass-photopolymerization initiator (1-Hydroxycyclohexylphenylketone, product name "Irgacure (registered trademark) 184, manufactured by BASF Japan, Inc.): 1 part by mass / solvent (methylisobutylketone: cyclohexanone = 1: 1 (mass ratio)): 170 parts by mass

<Example 1>
Composition 1 for the above-mentioned light diffusion layer on one side of two polyethylene terephthalate (PET) base materials (product name "Lumirror T60", manufactured by Toray Industries, Inc.) as a light transmissive base material having a size of 7 inches and a thickness of 50 μm, respectively. Was applied to form a coating film. Next, the solvent in the coating film was evaporated by passing dry air at 80 ° C. for 30 seconds through the formed coating film to dry it. Then, the coating film was cured by irradiating it with ultraviolet rays so that the integrated light amount was 500 mJ / cm ² , to form a light diffusing layer having a film thickness of 10 μm, and to form a PET substrate with a light diffusing layer.

Further, the composition 1 for a light absorption layer was applied to one side of another PET substrate (product name "Lumilar T60", manufactured by Toray Industries, Inc.) having a size of 7 inches and a thickness of 50 μm to form a coating film. Next, the solvent in the coating film was evaporated by passing dry air at 80 ° C. for 30 seconds through the formed coating film to dry it. Then, the PET base material with a light diffusing layer was laminated on the coating film so that the surface of the PET base material with a light diffusing layer opposite to the surface on the light diffusing layer side was in contact with the coating film. In this state, it is heated at 60 ° C. to form a light absorption layer having a film thickness of 20 μm, and a laminate in which the PET substrate, the light absorption layer, and the PET substrate with a light diffusion layer are integrated is formed. Formed.

Further, the adhesive layer composition 1 was applied to one side of another PET substrate (product name "Lumilar T60", manufactured by Toray Industries, Inc.) having a size of 7 inches and a thickness of 50 μm to form a coating film. Next, the PET substrate with a light diffusing layer was laminated on the coating film so that the surface of the PET substrate with a light diffusing layer opposite to the surface on the light diffusing layer side was in contact with the formed coating film. In this state, the mixture was heated at 60 ° C. to form an adhesive layer having a film thickness of 20 μm, and a laminated body in which the PET substrate, the adhesive layer, and the PET substrate with a light diffusion layer were integrated was formed. ..

Next, the composition 1 for the light wavelength conversion layer was applied to the surface of the laminate having the adhesive layer opposite to the surface on the light diffusion layer side, and dried at 80 ° C. to form a coating film. Then, the other laminate was laminated on the coating film so that the surface of the other laminate on the side opposite to the surface on the light diffusion layer side was in contact with the coating film. In this state, ultraviolet rays are irradiated so that the integrated light amount becomes 500 mJ / cm ² , and the coating film is cured to form an optical wavelength conversion layer having a film thickness of 100 μm, and the optical wavelength conversion layer and two layers are laminated. Integrated with the body. As a result, the optical wavelength conversion sheet according to Example 1 was obtained.

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

<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 the light absorption layer was used instead of the composition 1 for the light absorption layer.

<Example 4>
The above composition 1 for a light diffusion layer is applied to one side of two PET base materials (product name "Lumilar T60", manufactured by Toray Industries, Inc.) as light transmissive base materials 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 passing dry air at 80 ° C. for 30 seconds through the formed coating film to dry it. Then, the coating film was cured by irradiating it with ultraviolet rays so that the integrated light amount was 500 mJ / cm ² , to form a light diffusing layer having a film thickness of 10 μm, and to form a PET substrate with a light diffusing layer.

Next, the composition 3 for a light wavelength conversion layer was applied to the surface of the PET substrate with a light diffusion layer opposite to the surface on the light diffusion layer side, and dried at 80 ° C. to form a coating film. Then, the other laminate was laminated on the coating film so that the surface of the PET substrate with the other light diffusion layer opposite to the surface on the light diffusion layer side was in contact with the coating film. In this state, ultraviolet rays are irradiated so that the integrated light amount becomes 500 mJ / cm ² , and the coating film is cured to form an optical wavelength conversion layer having a film thickness of 100 μm, and the optical wavelength conversion layer and two pieces of light are formed. It was integrated with a PET substrate with a diffusion layer. As a result, the optical wavelength conversion sheet according to Example 4 was obtained.

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

<Measurement of emission peak wavelength, half width and brightness>
In the backlight device in which the light wavelength conversion sheets according to the above Examples and Comparative Examples are incorporated in the backlight device, respectively, and the light wavelength conversion sheets according to the Examples and Comparative Examples are incorporated, the spectral distribution of the light emitted from the backlight device is incorporated. Was measured, and the emission peak wavelength and the half-value width of the emission peak were obtained from the spectral distribution.

When incorporating the optical wavelength conversion sheet according to the examples and comparative examples into the backlight device, first, a backlight unit of Kindle Fire (registered trademark) HDX7 was prepared. This backlight device includes a blue light emitting diode having a 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 have a sheet-shaped main body portion and a plurality of triangular columnar unit prisms arranged side by side on the main body portion and each 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 incoming surface, and the light wavelength conversion sheet, the first prism sheet, and the second prism sheet are arranged in this order on the light emitting surface of the light guide plate. , Obtained a backlight device. 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, 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. The spectral distribution of the light emitted from the light emitting surface (the surface of the second prism sheet) is measured from the thickness direction of the optical wavelength conversion sheet using a spectral emission luminometer (product name "CS2000", manufactured by Konica Minolta). The measurement was performed under the condition of a measurement angle of 1 °. Then, the emission peak wavelength and the half width of the emission peak were obtained from the obtained spectral distribution.

The results are shown in Table 1 below.

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 width of each emission peak in the emitted light was wide. On the other hand, in the backlight device incorporating the light wavelength conversion sheet according to Examples 1 to 3, the half width of each emission peak of the emitted light was narrow. Therefore, it was confirmed that the color purity was improved by including the light absorber in the light wavelength conversion sheet.

The total haze value of the optical wavelength conversion sheet according to the first embodiment is 99.2%, the internal haze value is 96.4%, the external haze value is 2.8%, and all the optical wavelength conversion sheets according to the second embodiment. The haze value was 99.5%, the internal haze value was 99.5%, and the external haze value was 0%. In both optical wavelength conversion sheets, the external haze value is smaller than the internal haze value, so that the brightness is high, but the optical wavelength conversion sheet according to Example 1 and the optical wavelength conversion sheet according to Example 2 are compared. The brightness of the optical wavelength conversion sheet according to the second embodiment was higher. This is because the light wavelength conversion sheet according to Example 2 contains alumina particles as light scattering particles, so that the internal haze value of the light wavelength conversion sheet according to Example 2 is that of the wavelength conversion sheet according to Example 1. This is because it is larger than the internal haze value, and as a result, the external haze value is small. Therefore, it was confirmed that the external haze value can be made smaller by including the light scattering particles in the light wavelength conversion sheet to further increase the internal haze value, and thereby the light wavelength conversion efficiency can be further improved. ..

In the above embodiment, CdSe is used as the core material of the green emission quantum dots and the red emission quantum dots, but even if a non-Cd material such as InP or InAs is used as the core material, the same result as in the above embodiment is obtained. was gotten.

10, 30, 40 ... Light wavelength conversion member 11, 31 ... Light wavelength conversion layer 14, 41, 135, 153 ... Light absorption layer 20 ... Binder resin 21 ... First quantum dot 22 ... Second quantum dot 23 ... Light Scatterable particles 50 ... Image display device 60, 110 ... Backlight device 100 ... Display panel 130 ... Optical member

Claims (9)

A light wavelength conversion member that converts at least a part of the incident light having a first emission peak wavelength to emit light having a second emission peak wavelength in at least a visible light region. hand,
A laminated structure including a light wavelength conversion layer, a light absorption layer arranged on the light emission side of the light wavelength conversion layer, and a light diffusion layer arranged on the light emission side of the light wavelength conversion layer and having an uneven shape on the surface. And
One surface of the light wavelength conversion member is the surface of the light diffusion layer.
The light wavelength conversion layer comprises 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 has the light absorption layer in the visible light region and absorbs light in the first wavelength range between the first emission peak wavelength and the second emission peak wavelength. Including
Each layer constituting the light wavelength conversion member is integrated.
The film thickness of the light absorption layer is 3 μm or more and 100 μm or less .
A light wavelength conversion member in which the light absorption layer is arranged between the light wavelength conversion layer and the light diffusion layer . The light according to claim 1, wherein the first emission peak wavelength is the peak wavelength of the first emission peak and exists in the blue wavelength region, and the half width of the first emission peak is 40 nm or less. Wavelength conversion member. The light according to claim 2, wherein the second emission peak wavelength is the peak wavelength of the second emission peak, exists in the green wavelength region, and the 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 the visible light region.
A second quantum dot that converts the light having the first emission peak wavelength into the light having the third emission peak wavelength, and
Within the second wavelength range between the first emission peak wavelength and any emission peak wavelength located on the third emission peak wavelength side of the second emission peak wavelength and the third emission peak wavelength. The optical wavelength conversion member according to any one of claims 1 to 3, further comprising a second light absorber that absorbs the light of the above. The fourth aspect of claim 4, wherein the third emission peak wavelength is the peak wavelength of the third emission peak, exists in the red wavelength region, and the half width of the third emission peak is 50 nm or less. Optical wavelength conversion member. The light wavelength conversion member according to any one of claims 1 to 5 , wherein the light wavelength conversion layer further includes light scattering particles. Light source and
A backlight device comprising the light wavelength conversion member according to any one of claims 1 to 6 , which receives light from the light source. The backlight device according to claim 7, further comprising a retroreflective sheet arranged on the light emitting side of the light wavelength conversion member. An image display device comprising the light wavelength conversion member according to any one of claims 1 to 6 or the backlight device according to claim 7 or 8.

Images