WO2022049624A1

WO2022049624A1 - Wavelength conversion member, backlight unit, and image display device

Info

Publication number: WO2022049624A1
Application number: PCT/JP2020/033062
Authority: WO
Inventors: 雄麻吉田; 雄毅仙波; 孝博黒田; 紗也香菊池; 唯史奥田; 正人西村
Original assignee: 昭和電工マテリアルズ株式会社
Priority date: 2020-09-01
Filing date: 2020-09-01
Publication date: 2022-03-10
Also published as: WO2022050229A1

Abstract

This wavelength conversion member has a wavelength conversion layer containing light-scattering particles with a refractive index of 2.3 or less and a fluorescent material. The product of the content A (mass%) of the light-scattering particles in the wavelength conversion layer and the thickness B (μm) of the wavelength conversion layer is in the range of 40-1200.

Description

Wavelength conversion member, backlight unit, and image display device

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

Laminates in which a covering material such as a resin sheet is arranged on both sides of the intermediate layer are used in many technical fields. For example, as a means for improving the color reproducibility of a display of an image display device such as a liquid crystal display device, a wavelength conversion member including a layer containing a quantum dot phosphor and a coating material provided on both sides thereof is known ( For example, see Japanese Patent Publication No. 2013-544018 and International Publication No. 2016/0526225).

The wavelength conversion member including the quantum dot phosphor is arranged in the backlight unit of the image display device, for example. When a wavelength conversion member including a quantum dot phosphor that emits red light and a quantum dot phosphor that emits green light is used, when the wavelength conversion member is irradiated with blue light as excitation light, the quantum dot phosphor emits light. White light can be obtained from the red light and green light produced and the blue light transmitted through the wavelength conversion member.

In recent years, there has been an increasing demand for wavelength conversion members used in thin image display devices such as mobile electronic devices. As the image display device becomes thinner, the distance between the wavelength conversion member and the backlight becomes shorter, and the thickness of the wavelength conversion member itself tends to become thinner. As a result, the uneven brightness between the area directly above the light source of the backlight and the surrounding area becomes conspicuous, which may affect the image quality.
In order to eliminate the difference in the brightness of the backlight, it is effective to increase the ratio (haze) of the diffuse transmitted light to the total light transmitted light in the wavelength conversion member. However, if the ratio of diffused transmitted light is increased, the brightness of the image display device may become insufficient.

In view of the above circumstances, one embodiment of the present disclosure provides a wavelength conversion member, a backlight unit, and an image display device capable of achieving both good image quality and sufficient brightness.

Specific means for solving the above problems include the following embodiments.
<1> Having a wavelength conversion layer including a light scattering particle having a refractive index of 2.3 or less and a phosphor, the content of the light scattering particles in the wavelength conversion layer A (mass%) and the wavelength. A wavelength conversion member having a product of the thickness B (μm) of the conversion layer in the range of 40 to 1200.
<2> The wavelength conversion member according to <1>, wherein the content of the light scattering particles in the wavelength conversion layer is 0.5% by mass to 20% by mass.
<3> The wavelength conversion member according to <1> or <2>, wherein the wavelength conversion layer has a thickness of 40 μm to 120 μm.
<4> The wavelength conversion member according to any one of <1> to <3>, wherein the total light transmittance is 65% or more.
<5> The wavelength conversion member according to any one of <1> to <4>, wherein the haze is 90% or more.
<6> The item according to any one of <1> to <5>, wherein the light scattering particles include at least one selected from the group consisting of zirconia, alumina, silica, zinc oxide, acrylic resin and silicone resin. Wavelength conversion member.
<7> The wavelength conversion member according to any one of <1> to <6>, wherein the phosphor includes a quantum dot phosphor.
<8> The wavelength conversion member according to any one of <1> to <7>, wherein the wavelength conversion layer is a cured product of a composition containing a (meth) acrylic compound.
<9> The wavelength conversion member according to any one of <1> to <8>, wherein the wavelength conversion layer is a cured product of a composition containing a thiol compound.
<10> The wavelength conversion member according to any one of <1> to <9>, which has a covering material that covers at least a part of the wavelength conversion layer.
<11> A backlight unit including the wavelength conversion member according to any one of <1> to <10> and a light source.
<12> An image display device including the backlight unit according to <11>.

According to the present disclosure, a wavelength conversion member, a backlight unit, and an image display device capable of achieving both good image quality and sufficient brightness are provided.

It is a schematic cross-sectional view which shows an example of the schematic structure of the wavelength conversion member. It is a figure which shows an example of the schematic structure of the backlight unit. It is a figure which shows an example of the schematic structure of the liquid crystal display device.

Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including element steps and the like) are not essential unless otherwise specified. The same applies to the numerical values and their ranges, and does not limit the present invention.
In the present disclosure, the term "process" includes, in addition to a process independent of other processes, the process as long as the purpose of the process is achieved even if it cannot be clearly distinguished from the other process. ..
In the present disclosure, the numerical range indicated by using "-" includes the numerical values before and after "-" as the minimum value and the maximum value, respectively.
In the numerical range described stepwise in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in another stepwise description. .. Further, in the numerical range described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.
In the present disclosure, each component may contain a plurality of applicable substances. When a plurality of substances corresponding to each component are present in the composition, the content of each component means the total content of the plurality of substances present in the composition unless otherwise specified.
In the present disclosure, a plurality of types of particles corresponding to each component may be contained. When a plurality of particles corresponding to each component are present in the composition, the particle size of each component means a value for a mixture of the plurality of particles present in the composition unless otherwise specified.
In the present disclosure, the term "layer" or "membrane" is used only in a part of the region, in addition to the case where the layer or the membrane is formed in the entire region when the region is observed. The case where it is formed is also included.
In the present disclosure, the term "laminated" refers to stacking layers, and two or more layers may be bonded or the two or more layers may be removable.
In the present disclosure, the average thickness of the laminate or the layers constituting the laminate is an arithmetic mean value of the thicknesses of any three points measured using a micrometer, a multilayer film thickness measuring device, or the like.
In the present disclosure, "(meth) acryloyl group" means at least one of an acryloyl group and a methacryloyl group, "(meth) acrylic" means at least one of acrylic and methacrylic, and "(meth) acrylate" means acrylate. And Methacrylate, and "(meth) allyl" means at least one of allyl and methacrylic.
In the present disclosure, the (meth) allyl compound means a compound having a (meth) allyl group in the molecule, and the (meth) acrylic compound means a compound having a (meth) acryloyl group in the molecule.
In the present disclosure, the "full width at half maximum" of the wavelength spectrum means the "full width at half maximum".

<Wavelength conversion member>
The wavelength conversion member according to the embodiment of the present disclosure has a wavelength conversion layer including a light scattering particle having a refractive index of 2.3 or less and a phosphor, and the wavelength conversion layer of the light scattering particles. It is a wavelength conversion member in which the product of the content rate A (mass%) and the thickness B (μm) of the wavelength conversion layer is in the range of 40 to 1200.

As a result of the studies by the inventors, a wavelength conversion member including light-scattering particles having a refractive index of 2.3 or less and having a wavelength conversion layer in which the content of the light-scattering particles and the thickness of the wavelength conversion layer satisfy the above relationship It was found that both good image quality and sufficient brightness can be achieved. In particular, it was found that good image quality and sufficient brightness can be achieved at the same time even if the thickness of the wavelength conversion layer is reduced.

A wavelength conversion member containing light-scattering particles having a refractive index of 2.3 or less and having a product of the content A (mass%) and the thickness B (μm) of the wavelength conversion layer in the range of 40 to 1200. The reason why both good image quality and sufficient brightness can be achieved is considered as follows, for example.

Light-scattering particles having a refractive index of 2.3 or less are more forward-scattered light (backlight) in the scattered light obtained by scattering light incident from the backlight than light-scattering particles having a refractive index of more than 2.3. The ratio of scattered light directed to the opposite side to the side) is large. Therefore, even if the amount of light-scattering particles is increased in order to increase the haze value of the wavelength conversion layer, a sufficient amount of transmitted light is secured as compared with the case of increasing the amount of light-scattering particles having a refractive index of more than 2.3. It is considered that the brightness of the image display device is maintained.

Furthermore, the content of light-scattering particles that can achieve both good image quality and sufficient brightness varies depending on the thickness of the wavelength conversion layer. Therefore, by setting the product (A × B) of the content A (mass%) of the light-scattering particles and the thickness B (μm) of the wavelength conversion layer within the range of 40 to 1200, good image quality and sufficient brightness are obtained. It is thought that compatibility with the above will be achieved.

The product of the content A (mass%) of the light-scattering particles and the thickness B (μm) of the wavelength conversion layer may be in the range of 100 to 1000, or may be in the range of 200 to 800. It may be in the range of 300 to 600.

The range of the product of the content rate A (mass%) of the light scattering particles and the thickness B (μm) of the wavelength conversion layer is set in consideration of the refractive index of the light scattering particles contained in the wavelength conversion layer in addition to the above range. You may.
When the refractive index of the light-scattering particles is more than 2.0 and 2.3 or less, the product of the content rate A (mass%) of the light-scattering particles and the thickness B (μm) of the wavelength conversion layer is 100 to 500. It may be within the range, or may be within the range of 200 to 400.
When the refractive index of the light-scattering particles is more than 1.7 and 2.0 or less, the product of the content rate A (mass%) of the light-scattering particles and the thickness B (μm) of the wavelength conversion layer is 100 to 1000. It may be within the range, or may be within the range of 300 to 700.
When the refractive index of the light-scattering particles is 1.7 or less, the product of the content A (mass%) of the light-scattering particles and the thickness B (μm) of the wavelength conversion layer is in the range of 100 to 1200. It may be in the range of 300 to 1000.

The refractive index of the light-scattering particles in the present disclosure is a value with respect to the D line (light having a wavelength of 589.3 nm) of sodium.

The content of the light scattering particles contained in the wavelength conversion layer is not particularly limited as long as the product with the thickness of the wavelength conversion layer is in the range of 40 to 1200. From the viewpoint of obtaining a sufficient light scattering effect, the content of the light scattering particles may be 0.5% by mass or more, 1.0% by mass or more, or 2.0% by mass or more. You may. From the viewpoint of ensuring sufficient brightness, the content of the light scattering particles may be 20% by mass or less, 15% by mass or less, or 10% by mass or less.

The thickness of the wavelength conversion layer is not particularly limited as long as the product with the content of the light scattering particles is in the range of 40 to 1200. From the viewpoint of obtaining a sufficient wavelength conversion effect, the thickness of the wavelength conversion layer may be 40 μm or more, 50 μm or more, or 70 μm or more. From the viewpoint of reducing the thickness of the image display device, the thickness of the wavelength conversion layer may be 120 μm or less, 100 μm or less, or 90 μm or less.

From the viewpoint of ensuring sufficient brightness, the total light transmittance of the wavelength conversion member is preferably 65% or more, more preferably 70% or more, and further preferably 75% or more. The total light transmittance of the wavelength conversion member is measured by the method described in the examples.

From the viewpoint of suppressing uneven brightness of the image, the haze of the wavelength conversion member is preferably 90% or more, more preferably 93% or more, and further preferably 95% or more. The haze of the wavelength conversion member is measured by the method described in the examples.

(Light scattering particles)
The light scattering particles contained in the wavelength conversion layer scatter the light incident on the wavelength conversion layer in the wavelength conversion layer, and act to increase the wavelength conversion efficiency of the incident light by the phosphor.

The refractive index of the light scattering particles contained in the wavelength conversion layer having a refractive index of 2.3 or less may be 2.1 or less, 2.0 or less, or 1.9 or less. May be good. The smaller the refractive index of the light-scattering particles, the larger the ratio of the forward scattered light to the obtained scattered light tends to be.
The lower limit of the refractive index of the light scattering particles is not particularly limited. From the viewpoint of obtaining a sufficient light scattering effect, the refractive index may be 1.4 or more, or 1.5 or more.

Specific examples of the light-scattering particles having a refractive index of 2.3 or less include particles such as alumina, zirconia, silica, zinc oxide, acrylic resin, silicone resin, barium sulfate, and calcium carbonate.

The light scattering particles contained in the wavelength conversion layer may be only one type or two or more types. Further, even if the wavelength conversion layer contains only light-scattering particles having a refractive index of 2.3 or less, it contains light-scattering particles having a refractive index of 2.3 or less and light-scattering particles having a refractive index of more than 2.3. But it may be. Specific examples of the light-scattering particles having a refractive index greater than 2.3 include titanium oxide and the like.

When the wavelength conversion layer contains light scattering particles having a refractive index of more than 2.3, the content is preferably less than 5% by mass of the wavelength conversion layer, and 1% by mass, from the viewpoint of ensuring sufficient brightness. It is more preferably less than, and even more preferably less than 0.5% by mass.

When the wavelength conversion layer contains light-scattering particles having a refractive index of more than 2.3, the above-mentioned "light-scattering particle content A (mass%)" is the light-scattering particles having a refractive index of 2.3 or less and the refractive index. Is the total content with light scattering particles larger than 2.3.

From the viewpoint of ease of forming the wavelength conversion layer, the average particle diameter of the light-scattering particles may be 3.5 μm or less, 2.5 μm or less, or 2.0 μm or less. ..
The average particle size of the light-scattering particles may be 0.1 μm or more, 0.5 μm or more, or 1.0 μm or more.

Specifically, the average particle size of the light-scattering particles can be measured as follows.
The filler is dispersed in purified water containing a surfactant to obtain a dispersion liquid. In the volume-based particle size distribution measured by a laser diffraction type particle size distribution measuring device (for example, Shimadzu Corporation, SALD-3000J) using this dispersion, the value when the integration from the small diameter side is 50% (for example). The median diameter (D50)) is defined as the average particle size of the light-scattering particles.
For the average particle size of the light-scattering particles contained in the wavelength conversion layer, the equivalent circle diameter (geometric mean of major axis and minor axis) was calculated for 50 particles by observing the particles using a scanning electron microscope. , May be obtained as the arithmetic mean value.

(Fluorescent material)
The type of the phosphor contained in the wavelength conversion layer is not particularly limited and can be selected according to the intended use. Examples of the fluorescent substance include an organic fluorescent substance and an inorganic fluorescent substance.

Examples of the organic phosphor include naphthalimide compounds and perylene compounds.
Examples of the inorganic phosphor include Y ₃ O ₃ : Eu, YVO ₄ : Eu, Y ₂ O ₂ : Eu, 3.5 MgO / 0.5 MgF ₂ , GeO ₂ : Mn, (Y · Cd) BO ₂ : Eu, etc. Red light emitting inorganic phosphor, ZnS: Cu · Al, (Zn · Cd) S: Cu · Al, ZnS: Cu · Au · Al, Zn ₂ SiO ₄ : Mn, ZnSiO ₄ : Mn, ZnS: Ag · Cu, ( Zn · Cd) S: Cu, ZnS: Cu, GdOS: Tb, LaOS: Tb, YSiO ₄ : Ce · Tb, ZnGeO ₄ : Mn, GeMgAlO: Tb, SrGaS: Eu ²⁺ , ZnS: Cu · Co, MgO · nB ₂ O ₃ : Green light emitting inorganic phosphors such as Ge · Tb, LaOBr: Tb · Tm, La ₂ O ₂ S: Tb, ZnS: Ag, GaWO ₄ , Y ₂ SiO ₆ : Ce, ZnS: Ag · Ga · Cl , Ca ₂ B ₄ OCl: Eu ²⁺ , BaMgAl ₄ O ₃ : Eu ²⁺ and the like, blue light emitting inorganic phosphors, quantum dot phosphors and the like can be mentioned.

From the viewpoint of color reproducibility, it is preferable that the wavelength conversion layer contains a quantum dot phosphor. The quantum dot phosphor is not particularly limited, and examples thereof include particles containing at least one selected from the group consisting of II-VI group compounds, III-V group compounds, IV-VI group compounds, and IV group compounds.

Specific examples of the II-VI group compounds include CdSe, CdTe, CdS, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, ZnS. , CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSne
Specific examples of the III-V group compounds include GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, PLCAP, PLKAs, VMwareSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb. , AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInNSb, GaInPAs, GaInPSb, In
Specific examples of the IV-VI group compounds include SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbSne, SnPbSe, SnPbSn ..
Specific examples of the Group IV compound include Si, Ge, SiC, SiGe and the like.

From the viewpoint of luminous efficiency, the quantum dot phosphor preferably contains at least one of Cd and In. From the viewpoint of compliance with environmental regulations, it is preferable that the quantum dot phosphor does not contain Cd. Therefore, from the viewpoint of luminous efficiency and compliance with environmental regulations, it is preferable that the quantum dot phosphor contains In.
From the viewpoint of reducing the amount of Cd in the entire quantum dot phosphor, a quantum dot phosphor that does not contain Cd and a quantum dot phosphor that contains Cd may be used in combination.

The quantum dot phosphor may have a core-shell structure. By making the band gap of the compound constituting the shell wider than the band gap of the compound constituting the core, it is possible to further improve the quantum efficiency of the quantum dot phosphor. Examples of the combination of core and shell (core / shell) include CdSe / ZnS, InP / ZnS, PbSe / PbS, CdSe / CdS, CdTe / CdS, CdTe / ZnS and the like.

The quantum dot phosphor may have a so-called core multi-shell structure in which the shell has a multi-layer structure. By stacking one layer or two or more shells with a narrow bandgap on a core with a wide bandgap, and further stacking a shell with a wide bandgap on this shell, the quantum efficiency of the quantum dot phosphor can be further improved. Is possible.

When the wavelength conversion layer contains a quantum dot phosphor, two or more kinds of quantum dot phosphors having different components, average particle diameters, layer structures, etc. may be combined. By combining two or more types of quantum dot phosphors, the emission center wavelength of the entire wavelength conversion layer can be adjusted to a desired value.

The phosphor may include a phosphor G having a emission center wavelength in the green wavelength range of 520 nm to 560 nm and a phosphor R having a emission center wavelength in the red wavelength range of 600 nm to 680 nm.

When the wavelength conversion layer containing the phosphor G and the phosphor R is irradiated with excitation light in the blue wavelength range of 430 nm to 480 nm, green light and red light are emitted from the phosphor G and the phosphor R, respectively. As a result, white light can be obtained by the green light and red light emitted from the phosphor G and the phosphor R and the blue light transmitted through the wavelength conversion layer.

The content of the phosphor in the wavelength conversion layer may be, for example, 0.01% by mass or more, 0.05% by mass or more, and 0.1% by mass or more with respect to the entire wavelength conversion layer. May be. Further, it may be 1.0% by mass or less, 0.8% by mass or less, and 0.5% by mass or less. When the content of the phosphor is 0.01% by mass or more, a sufficient wavelength conversion function tends to be obtained, and when the content of the phosphor is 1.0% by mass or less, aggregation of the phosphor is suppressed. Tend to be.

(Resin composition for wavelength conversion)
The wavelength conversion layer may be in the state of a cured product containing a phosphor and light scattering particles. Such a cured product is obtained by curing, for example, a composition (wavelength conversion resin composition) containing at least a phosphor, light scattering particles, a polymerizable compound, and a photopolymerization initiator. May be good.

The polymerizable compound contained in the wavelength conversion resin composition is not particularly limited, and examples thereof include thiol compounds, (meth) allyl compounds, and (meth) acrylic compounds.

When a coating material is provided on the surface of the wavelength conversion layer, the polymerizable compound is a thiol compound, a (meth) allyl compound, and a (meth) acrylic compound from the viewpoint of adhesion between the wavelength conversion layer and the coating material. It is preferable to include at least one selected from the group consisting of.

The wavelength conversion layer obtained by curing a wavelength conversion resin composition containing a thiol compound as a polymerizable compound and at least one selected from the group consisting of a (meth) allyl compound and a (meth) acrylic compound is a wavelength conversion layer. The sulfide structure (RSR', R and R'formed by the progress of the enthiol reaction between the thiol group and the carbon-carbon double bond of the (meth) allyl group or the (meth) acryloyl group is an organic group. Represents). This tends to improve the adhesion between the wavelength conversion layer and the covering material. Further, the optical characteristics of the wavelength conversion layer tend to be further improved.

(1) Thiol compound The thiol compound may be a monofunctional thiol compound having one thiol group in one molecule, or a polyfunctional thiol compound having two or more thiol groups in one molecule. good. The thiol compound contained in the wavelength conversion resin composition may be only one kind or two or more kinds.

The thiol compound may or may not have a polymerizable group other than the thiol group (for example, (meth) acryloyl group, (meth) allyl group) in the molecule.
In the present disclosure, a compound containing a thiol group and a polymerizable group other than the thiol group in the molecule shall be classified as a "thiol compound".

Specific examples of the monofunctional thiol compound include hexanethiol, 1-heptanethiol, 1-octanethiol, 1-nonanthiol, 1-decanethiol, 3-mercaptopropionic acid, methyl mercaptopropionate, methoxybutyl mercaptopropionate, and the like. Examples thereof include octyl mercaptopropionate, tridecyl mercaptopropionate, 2-ethylhexyl-3-mercaptopropionate, n-octyl-3-mercaptopropionate and the like.

Specific examples of the polyfunctional thiol compound include ethylene glycol bis (3-mercaptopropionate), diethylene glycol bis (3-mercaptopropionate), tetraethylene glycol bis (3-mercaptopropionate), 1,2-. Propropylene glycol bis (3-mercaptopropionate), diethylene glycol bis (3-mercaptobutyrate), 1,4-butanediol bis (3-mercaptopropionate), 1,4-butanediol bis (3-mercaptobutyrate) Rate), 1,8-octanediol bis (3-mercaptopropionate), 1,8-octanediol bis (3-mercaptobutyrate), hexanediol bisthioglycolate, trimethylolpropanthris (3-mercaptopro) Pionate), trimethylolpropanetris (3-mercaptobutyrate), trimethylolpropanetris (3-mercaptoisobutyrate), trimethylolpropanetris (2-mercaptoisobutyrate), trimethylolpropanetristhioglycolate, Tris-[(3-mercaptopropionyloxy) -ethyl] -isocyanurate, trimethylolethanetris (3-mercaptobutyrate), pentaerythritol tetrakis (3-mercaptopropionate), pentaerythritol tetrakis (3-mercaptobutyrate) ), Pentaerythritol tetrakis (3-mercaptoisobutyrate), pentaerythritol tetrakis (2-mercaptoisobutyrate), dipentaerythritol hexakiss (3-mercaptopropionate), dipentaerythritol hexakis (2-mercaptopro) Pionate), Dipentaerythritol Hexakis (3-mercaptobutyrate), Dipentaerythritol Hexakis (3-Mercaptoisobutyrate), Dipentaerythritol Hexakis (2-Mercaptoisobutyrate), Pentaerythritol Tetrakissthioglycolate Examples thereof include rate, dipentaerythritol hexakissthioglycolate and the like.

The thiol compound preferably contains a polyfunctional thiol compound from the viewpoint of further improving the adhesion between the wavelength conversion layer and the coating material, heat resistance, and moisture heat resistance. The ratio of the polyfunctional thiol compound to the total amount of the thiol compound is, for example, preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 100% by mass.

The thiol compound may be in the state of a thioether oligomer that has reacted with the (meth) acrylic compound. The thioether oligomer can be obtained by addition polymerization of a thiol compound and a (meth) acrylic compound in the presence of a polymerization initiator.

Among the thioether oligomers, the thioether oligomer obtained by reacting a polyfunctional thiol compound with a polyfunctional (meth) acrylic compound is preferable from the viewpoint of further improving the optical properties, heat resistance, and moist heat resistance of the cured product, and pentaerythritol. A thioether oligomer obtained by addition polymerization of tetrakis (3-mercaptopropionate) and tris (2-acryloyloxyethyl) isocyanurate is more preferable.

The weight average molecular weight of the thioether oligomer is, for example, preferably 3000 to 10000, more preferably 3000 to 8000, and even more preferably 4000 to 6000.
The weight average molecular weight of the thioether oligomer is obtained by converting the molecular weight distribution measured by gel permeation chromatography (GPC) using a standard polystyrene calibration curve, as shown in Examples described later. ..

The thiol equivalent of the thioether oligomer is, for example, preferably 200 g / eq to 400 g / eq, more preferably 250 g / eq to 350 g / eq, and further preferably 250 g / eq to 270 g / eq. preferable.

The thiol equivalent of the thioether oligomer can be measured by the following iodine titration method.
Weigh accurately 0.2 g of the measurement sample, and add 20 mL of chloroform to make a sample solution. As a starch indicator, 0.275 g of soluble starch dissolved in 30 g of pure water is used, 20 mL of pure water, 10 mL of isopropyl alcohol, and 1 mL of starch indicator are added, and the mixture is stirred with a stirrer. The iodine solution is added dropwise, and the point at which the chloroform layer turns green is defined as the end point. At this time, the value given by the following formula is taken as the thiol equivalent of the measurement sample.
Thiol equivalent (g / eq) = mass of measurement sample (g) x 10000 / titration of iodine solution (mL) x factor of iodine solution

When the wavelength conversion resin composition contains a thiol compound, the content of the thiol compound in the wavelength conversion resin composition is, for example, 5% by mass to 80% by mass with respect to the total amount of the wavelength conversion resin composition. It is preferably 15% by mass to 70% by mass, more preferably 20% by mass to 60% by mass.
When the content of the thiol compound is 5% by mass or more, the adhesion to the coating material of the cured product tends to be further improved, and when the content of the thiol compound is 80% by mass or less, the heat resistance of the cured product tends to be improved. And the moisture and heat resistance tends to be further improved.

(2) (Meta) allyl compound The (meth) allyl compound may be a monofunctional (meth) allyl compound having one (meth) allyl group in one molecule, and two or more (meth) allyl compounds in one molecule. It may be a polyfunctional (meth) allyl compound having a (meth) allyl group. The (meth) allyl compound contained in the wavelength conversion resin composition may be only one kind or two or more kinds.

The (meth) allyl compound may or may not have a polymerizable group (for example, (meth) acryloyl group) other than the (meth) allyl group in the molecule.
In the present disclosure, compounds having a polymerizable group other than the (meth) allyl group in the molecule (however, excluding the thiol compound) shall be classified as "(meth) allyl compound".

Specific examples of the monofunctional (meth) allyl compound include (meth) allyl acetate, (meth) allyl n-propionate, (meth) allylbenzoate, (meth) allylphenylacetate, (meth) allylphenoxyacetate, and (meth). Examples thereof include allyl methyl ether and (meth) allyl glycidyl ether.

Specific examples of the polyfunctional (meth) allyl compound include di (meth) allyl benzenedicarboxylate, di (meth) allyl cyclohexanedicarboxylate, di (meth) allyl maleate, di (meth) allyl adipate, and di (meth). Allyl phthalate, di (meth) allyl isophthalate, di (meth) allyl terephthalate, glycerin di (meth) allyl ether, trimethylpropandi (meth) allyl ether, pentaerythritol di (meth) allyl ether, 1,3-di (Meta) Allyl-5-glycidyl isocyanurate, tri (meth) allyl cyanurate, tri (meth) allyl isocyanurate, tri (meth) allyl trimellitate, tetra (meth) allyl pyromeritate, 1, 3, 4 , 6-Tetra (meth) allyl glycol uryl 1,3,4,6-tetra (meth) allyl-3a-methylglycol uryl 1,3,4,6-tetra (meth) allyl-3a, 6a-dimethyl Glycol-uryl and the like can be mentioned.

Examples of the (meth) allyl compound include compounds having an isocyanurate skeleton such as tri (meth) allyl isocyanurate, tri (meth) allyl cyanurate, and benzenedicarboxylic acid di (meth) from the viewpoint of heat resistance and moisture heat resistance of the cured product. ) At least one selected from the group consisting of allyl and di (meth) allyl cyclohexanedicarboxylate is preferable, a compound having a triisocyanurate skeleton is more preferable, and tri (meth) allyl isocyanurate is further preferable.

(3) (Meta) Acrylic Compound The (meth) acrylic compound may be a monofunctional (meth) acrylic compound having one (meth) acryloyl group in one molecule, and two or more (meth) acrylic compounds in one molecule. It may be a polyfunctional (meth) acrylic compound having a (meth) acryloyl group. The (meth) acrylic compound contained in the wavelength conversion resin composition may be one kind or two or more kinds.

Specific examples of the monofunctional (meth) acrylic compound include (meth) acrylic acid; methyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and isononyl (meth). ) Alkyl (meth) acrylate having an alkyl group having 1 to 18 carbon atoms such as acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate; benzyl (meth) acrylate, phenoxyethyl ( A (meth) acrylate compound having an aromatic ring such as a meta) acrylate; an alkoxyalkyl (meth) acrylate such as butoxyethyl (meth) acrylate; an aminoalkyl (meth) acrylate such as N, N-dimethylaminoethyl (meth) acrylate; Diethylene glycol monoethyl ether (meth) acrylate, triethylene glycol monobutyl ether (meth) acrylate, tetraethylene glycol monomethyl ether (meth) acrylate, hexaethylene glycol monomethyl ether (meth) acrylate, octaethylene glycol monomethyl ether (meth) acrylate, nona Polyalkylene glycol monoalkyl ether (meth) such as ethylene glycol monomethyl ether (meth) acrylate, dipropylene glycol monomethyl ether (meth) acrylate, heptapropylene glycol monomethyl ether (meth) acrylate, and tetraethylene glycol monoethyl ether (meth) acrylate. Acrylate; Polyalkylene glycol monoaryl ether (meth) acrylate such as hexaethylene glycol monophenyl ether (meth) acrylate; Cyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, isobornyl (meth) acrylate, methylene oxide-added cyclo (Meta) acrylate compound having an alicyclic structure such as decatorien (meth) acrylate; (meth) acrylate compound having a heterocycle such as (meth) acryloylmorpholine and tetrahydrofurfuryl (meth) acrylate; heptadecafluorodecyl (meth). ) Fluoroalkyl (meth) acrylates such as acrylates; 2-hydroxyethyl (meth) acrylates, 3-hydroxypropyl (meth) acrylates, 4-hydroxybutyl (meth) acrylates, triethires. (Meta) acrylate compound having a hydroxyl group such as Nglycol mono (meth) acrylate, Tetraethylene glycol mono (meth) acrylate, Hexaethylene glycol mono (meth) acrylate, Octapropylene glycol mono (meth) acrylate; (Meta) acrylate compound having a glycidyl group such as 2- (2- (meth) acryloyloxyethyloxy) ethyl isocyanate, 2- (meth) acryloyloxyethyl isocyanate (meth) acrylate compound having an isocyanate group such as tetra. Polyalkylene glycol mono (meth) acrylates such as ethylene glycol mono (meth) acrylate, hexaethylene glycol mono (meth) acrylate, octapropylene glycol mono (meth) acrylate; (meth) acrylamide, N, N-dimethyl (meth) acrylamide. , N-Isopropyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylamide and other (meth) acrylamide compounds; Be done.

Specific examples of the polyfunctional (meth) acrylic compound include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and 1,9-nonanediol di (meth) acrylate. Polyalkylene glycol di (meth) acrylate; Polyalkylene glycol di (meth) acrylate such as polyethylene glycol di (meth) acrylate and polypropylene glycol di (meth) acrylate; Trimethylol propantri (meth) acrylate, Trimethylol propantri with ethylene oxide (meth) Tri (meth) acrylate compounds such as meth) acrylate and tris (2-acryloyloxyethyl) isocyanurate; ethylene oxide-added pentaerythritol tetra (meth) acrylate, trimethylolpropanetetra (meth) acrylate, pentaerythritol tetra (meth) acrylate and the like. Tetra (meth) acrylate compound; tricyclodecanedimethanol di (meth) acrylate, cyclohexanedimethanol di (meth) acrylate, 1,3-adamantan dimethanol di (meth) acrylate, hydrogenated bisphenol A (poly) ethoxydi ( Meta) acrylate, hydrogenated bisphenol A (poly) propoxydi (meth) acrylate, hydrogenated bisphenol F (poly) ethoxydi (meth) acrylate, hydrogenated bisphenol F (poly) propoxydi (meth) acrylate, hydrogenated bisphenol S (poly) Examples thereof include (meth) acrylate compounds having an alicyclic structure such as ethoxydi (meth) acrylate and hydrogenated bisphenol S (poly) propoxydi (meth) acrylate.

The (meth) acrylic compound is preferably a (meth) acrylate compound having an alicyclic structure or an aromatic ring structure from the viewpoint of further improving the heat resistance and moisture heat resistance of the cured product. Examples of the alicyclic structure or aromatic ring structure include an isobornyl skeleton, a tricyclodecane skeleton, and a bisphenol skeleton.

The (meth) acrylic compound may have an alkyleneoxy group or may be a bifunctional (meth) acrylic compound having an alkyleneoxy group.

As the alkyleneoxy group, for example, an alkyleneoxy group having 2 to 4 carbon atoms is preferable, an alkyleneoxy group having 2 or 3 carbon atoms is more preferable, and an alkyleneoxy group having 2 carbon atoms is further preferable.
The alkyleneoxy group contained in the (meth) acrylic compound may be one kind or two or more kinds.

The alkyleneoxy group-containing compound may be a polyalkyleneoxy group-containing compound having a polyalkyleneoxy group containing a plurality of alkyleneoxy groups.

When the (meth) acrylic compound has an alkyleneoxy group, the number of alkyleneoxy groups in one molecule is preferably 2 to 30, more preferably 2 to 20, and 3 to 20. It is more preferably 10 pieces, and particularly preferably 3 to 5 pieces.

When the (meth) acrylic compound has an alkyleneoxy group, it preferably has a bisphenol structure. As a result, the heat resistance tends to be superior. Examples of the bisphenol structure include a bisphenol A structure and a bisphenol F structure, and among them, the bisphenol A structure is preferable.

Specific examples of the (meth) acrylic compound containing an alkyleneoxy group include alkoxyalkyl (meth) acrylates such as butoxyethyl (meth) acrylates; diethylene glycol monoethyl ether (meth) acrylates and triethylene glycol monobutyl ether (meth) acrylates. , Tetraethylene glycol monomethyl ether (meth) acrylate, hexaethylene glycol monomethyl ether (meth) acrylate, octaethylene glycol monomethyl ether (meth) acrylate, nonaethylene glycol monomethyl ether (meth) acrylate, dipropylene glycol monomethyl ether (meth) acrylate , Polyalkylene glycol monoalkyl ether (meth) acrylate such as heptapropylene glycol monomethyl ether (meth) acrylate, tetraethylene glycol monoethyl ether (meth) acrylate; polyalkylene glycol mono such as hexaethylene glycol monophenyl ether (meth) acrylate. Aryl ether (meth) acrylate; (meth) acrylate compound having a heterocycle such as tetrahydrofurfuryl (meth) acrylate; triethylene glycol mono (meth) acrylate, tetraethylene glycol mono (meth) acrylate, hexaethylene glycol mono (meth). ) A (meth) acrylate compound having a hydroxyl group such as acrylate and octapropylene glycol mono (meth) acrylate; a (meth) acrylate compound having a glycidyl group such as glycidyl (meth) acrylate; polyethylene glycol di (meth) acrylate and polypropylene glycol di. Polyalkylene glycol di (meth) acrylates such as (meth) acrylates; Tri (meth) acrylate compounds such as ethylene oxide-added trimethylol propantri (meth) acrylates; Tetra (meth) acrylates such as ethylene oxide-added pentaerythritol tetra (meth) acrylates. Compounds; Bisphenol type di (meth) acrylate compounds such as ethoxylated bisphenol A type di (meth) acrylate, propoxylated bisphenol A type di (meth) acrylate, propoxylated ethoxylated bisphenol A type di (meth) acrylate; and the like. Be done.
Examples of the (meth) acrylic compound containing an alkyleneoxy group include ethoxylated bisphenol A type di (meth) acrylate, propoxylated bisphenol A type di (meth) acrylate and propoxylated ethoxylated bisphenol A type di (meth) acrylate. Is preferable, and ethoxylated bisphenol A type di (meth) acrylate is more preferable.

In some embodiments, the polymerizable compound may include a thioether oligomer as a thiol compound and a (meth) allyl compound (preferably a polyfunctional (meth) allyl compound). In this case, the content of the (meth) allyl compound may be, for example, 10% by mass to 50% by mass, or 15% by mass to 45% by mass, based on the total amount of the resin composition for wavelength conversion. It may be 20% by mass to 40% by mass.

When the polymerizable compound contains a thioether oligomer and a (meth) allyl compound as the thiol compound, the wavelength conversion material used in combination is preferably in the state of a dispersion liquid dispersed in the silicone compound as the dispersion medium.

In one embodiment, the polymerizable compound is a thiol compound that is not in the form of a thioether oligomer and a (meth) acrylic compound (preferably a polyfunctional (meth) acrylic compound, more preferably a bifunctional (meth) acrylic compound). It may be included. In this case, the content of the (meth) acrylic compound may be, for example, 40% by mass to 90% by mass or 60% by mass to 90% by mass with respect to the total amount of the resin composition for wavelength conversion. It may be 75% by mass to 85% by mass.

When the polymerizable compound contains a thiol compound that is not in the state of a thioether oligomer and a (meth) acrylic compound, the wavelength conversion material used in combination is a (meth) acrylic compound as a dispersion medium, preferably a monofunctional (meth) compound. It is preferably in the state of a dispersion liquid dispersed in an acrylic compound, more preferably isobornyl (meth) acrylate.

(Photopolymerization initiator)
The photopolymerization initiator contained in the wavelength conversion resin composition is not particularly limited, and examples thereof include compounds that generate radicals by irradiation with active energy rays such as ultraviolet rays.

Specific examples of the photopolymerization initiator include benzophenone, N, N'-tetraalkyl-4, 4'-diaminobenzophenone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, 2-Methyl-1- [4- (Methylthio) Phenyl] -2-morpholino-companone-1,4,4'-bis (dimethylamino) benzophenone (also referred to as "Michlerketone"), 4,4'-bis (Diethylamino) benzophenone, 4-methoxy-4'-dimethylaminobenzophenone, 1-hydroxycyclohexylphenylketone, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane-1-one, 1- (4- (4-) Aromatic ketone compounds such as (2-hydroxyethoxy) -phenyl) -2-hydroxy-2-methyl-1-propane-1-one, 2-hydroxy-2-methyl-1-phenylpropane-1-one; alkyl Kinone compounds such as anthraquinone and phenanthrenquinone; benzoin compounds such as benzoin and alkylbenzoin; benzoin ether compounds such as benzoin alkyl ether and benzoin phenyl ether; benzyl derivatives such as benzyl dimethyl ketal; 2- (o-chlorophenyl) -4, 5 -Diphenylimidazole dimer, 2- (o-chlorophenyl) -4,5-di (m-methoxyphenyl) imidazole dimer, 2- (o-fluorophenyl) -4,5-diphenylimidazole dimer, 2- (o-Methenylphenyl) -4,5-diphenylimidazole dimer, 2,4-di (p-methoxyphenyl) -5-phenylimidazole dimer, 2- (2,4-dimethoxyphenyl)- 2,4,5-Triarylimidazole dimer such as 4,5-diphenylimidazole dimer; aclysine derivative such as 9,7- (9,9'-acrydinyl) heptane; 1,2 -Octanedione 1- [4- (Phenylthio) -2- (O-benzoyloxime)], Etanone 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazole-3-yl] -1- Oxyme ester compounds such as (O-acetyloxime); coumarin compounds such as 7-diethylamino-4-methylcoumarin; thioxanthone compounds such as 2,4-diethylthioxanthone; 2,4,6-trimethylbenzoyl-diphenyl-phosphinoxide, 2,4,6-trimethylbenzoyl Acylphosphine oxide compounds such as -phenyl-ethoxy-phosphine oxide; and the like. The wavelength conversion resin composition may contain one kind of photopolymerization initiator alone, or may contain two or more kinds of photopolymerization initiators in combination.

As the photopolymerization initiator, at least one selected from the group consisting of an acylphosphine oxide compound, an aromatic ketone compound, and an oxime ester compound is preferable from the viewpoint of curability, and the acylphosphine oxide compound and the aromatic ketone compound are selected. At least one selected from the above group is more preferable, and an acylphosphine oxide compound is further preferable.

The content of the photopolymerization initiator in the wavelength conversion resin composition is preferably, for example, 0.1% by mass to 5% by mass, preferably 0.1% by mass, based on the total amount of the wavelength conversion resin composition. It is more preferably% to 3% by mass, and even more preferably 0.1% by mass to 1.5% by mass. When the content of the photopolymerization initiator is 0.1% by mass or more, the sensitivity of the wavelength conversion resin composition tends to be sufficient, and the content of the photopolymerization initiator is 5% by mass or less. In addition, the influence of the wavelength conversion resin composition on the hue and the decrease in storage stability tend to be suppressed.

(Other ingredients)
The wavelength conversion resin composition may further contain other components such as a liquid medium (organic solvent or the like), a polymerization inhibitor, a silane coupling agent, a surfactant, a adhesion-imparting agent, and an antioxidant. The wavelength conversion resin composition may contain one kind individually or a combination of two or more kinds for each of the other components.

(Dressing material)
The wavelength conversion member may have a covering material arranged on at least one surface of the wavelength conversion layer. By arranging the covering material, the invasion of moisture, oxygen, etc. into the wavelength conversion layer is suppressed, and the deterioration of the wavelength conversion layer is suppressed. In addition, appropriate rigidity is imparted to the wavelength conversion member to improve handleability.

The material of the covering material is not particularly limited, and polyester such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefin such as polyethylene (PE) and polypropylene (PP), polyamide such as nylon, and ethylene-vinyl alcohol co-weight. It may be coalescence (EVOH) or the like. From the viewpoint of availability, polyethylene terephthalate is preferable as the material of the covering material.

The covering material may be one provided with a barrier layer for strengthening the barrier function against water, oxygen, etc. (barrier film). Examples of the barrier layer include an inorganic layer containing an inorganic substance such as alumina and silica. When the covering material has a barrier layer, it is preferable that the barrier layer is arranged on the side in contact with the wavelength conversion layer.

The oxygen permeability of the coating material is, for example, preferably 1.0 mL / ( ^m 2.24 h · atm) or less, more preferably 0.8 mL / ( ^m 2.24 h · atm) or less, and 0. It is more preferably .6 mL / ( ^m 2.24 h · atm) or less. The oxygen permeability of the coating material can be measured using an oxygen permeability measuring device (for example, MOCON, OX-TRAN) under the conditions of a temperature of 23 ° C. and a relative humidity of 90%.

Further, the water vapor permeability of the coating material is preferably, for example, ¹ × 100 g / ( ^m 2.24 h) or less, and more preferably 8 × 10 ^-1 g / ( ^m 2.24 h) or less. It is preferably 6 × 10 ^-1 g / ( ^m 2.24 h) or less, more preferably. The water vapor permeability of the coating material can be measured using a water vapor permeability measuring device (for example, MOCON, AQUATRAN) under the conditions of a temperature of 40 ° C. and a relative humidity of 100%.

The dressing may include a matte layer for scattering light. When the dressing comprises a barrier layer, the matte layer is preferably placed on the surface opposite to the surface on which the barrier layer of the dressing is placed. Further, with the wavelength conversion layer of the coating material arranged on one surface side of the wavelength conversion layer, the surface on the side not facing the wavelength conversion layer, or the coating material arranged on both surface sides of the wavelength conversion layer. At least one of the surfaces on the non-opposing sides may be roughened. When the wavelength conversion member has a covering material, if the covering material is roughened, the handling of the image conversion member is excellent, and interference fringes due to the adjacent member and the wavelength conversion member coming into close contact with each other can be suppressed. There is a tendency.
The surface of the covering material may have, for example, an arithmetic surface roughness Ra of 0.5 μm or more. Arithmetic surface roughness Ra is measured by a method according to JIS B 0601: 2013.

The thickness of the covering material may be, for example, in the range of 10 μm to 150 μm.

(Structure example of wavelength conversion member)
FIG. 1 shows an example of the schematic configuration of the wavelength conversion member. However, the wavelength conversion member of the present disclosure is not limited to the configuration shown in FIG. Further, the sizes of the wavelength conversion layer and the covering material in FIG. 1 are conceptual, and the relative relationship between the sizes is not limited to this. In each drawing, the same member may be designated by the same reference numeral, and duplicate description may be omitted.

The wavelength conversion member 10 shown in FIG. 1 has a wavelength conversion layer 11 and covering materials 12A and 12B provided on both sides of the wavelength conversion layer 11. The types and average thicknesses of the covering material 12A and the covering material 12B may be the same or different.

The wavelength conversion member having the configuration shown in FIG. 1 can be manufactured by, for example, a known manufacturing method as follows.

First, a wavelength conversion resin composition is applied to the surface of a film-like coating material (hereinafter, also referred to as "first coating material") that is continuously conveyed to form a coating film. The method for applying the wavelength conversion resin composition is not particularly limited, and examples thereof include a die coating method, a curtain coating method, an extrusion coating method, a rod coating method, and a roll coating method.

Next, a film-like covering material (hereinafter, also referred to as "second covering material") that is continuously conveyed is bonded onto the coating film of the wavelength conversion resin composition.

Next, the coating film is cured and a cured product layer is formed by irradiating the active energy rays from the side of the coating material that can transmit the active energy rays among the first coating material and the second coating material. Then, by cutting out to a specified size, a wavelength conversion member having the configuration shown in FIG. 1 can be obtained.
The wavelength and irradiation amount of the active energy ray can be set according to the composition of the wavelength conversion resin composition, the thickness of the wavelength conversion layer, and the like. In one embodiment, ultraviolet rays having a wavelength of 280 nm to 400 nm are irradiated with an irradiation amount of 100 mJ / cm ² to 5000 mJ / cm ² . Examples of the ultraviolet source include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, carbon arc lamps, metal halide lamps, xenon lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, and the like.

If neither the first coating material nor the second coating material can transmit the active energy ray, the coating film is irradiated with the active energy ray before the second coating material is bonded, and the cured product layer is formed. May be formed.

<Backlight unit>
The backlight unit of the present disclosure includes a light source and a wavelength conversion member of the present disclosure.

The backlight unit is preferably a multi-wavelength light source from the viewpoint of improving color reproducibility. In a preferred embodiment, blue light having a emission center wavelength in the wavelength range of 430 nm to 480 nm and having an emission intensity peak having a half width of 100 nm or less, and emission center wavelength in the wavelength range of 520 nm to 560 nm. Back that emits green light having an emission intensity peak having a half-value width of 100 nm or less and red light having an emission center wavelength in the wavelength range of 600 nm to 680 nm and having an emission intensity peak having a half-value width of 100 nm or less. The light unit can be mentioned. The half-value width of the emission intensity peak means the peak width at a height of 1/2 of the peak height.

From the viewpoint of further improving the color reproducibility, the emission center wavelength of the blue light emitted by the backlight unit is preferably in the range of 440 nm to 475 nm. From the same viewpoint, the emission center wavelength of the green light emitted by the backlight unit is preferably in the range of 520 nm to 545 nm. From the same viewpoint, the emission center wavelength of the red light emitted by the backlight unit is preferably in the range of 610 nm to 640 nm.

Further, from the viewpoint of further improving the color reproducibility, the half width of each emission intensity peak of the blue light, green light, and red light emitted by the backlight unit is preferably 80 nm or less, preferably 50 nm or less. It is more preferable to have.

As the light source of the backlight unit, for example, a light source that emits blue light having a emission center wavelength in the wavelength range of 430 nm to 480 nm can be used. Examples of the light source include an LED (Light Emitting Diode) and a laser. When a light source that emits blue light is used, it is preferable that the wavelength conversion member includes at least a quantum dot phosphor R that emits red light and a quantum dot phosphor G that emits green light. Thereby, white light can be obtained by the red light and green light emitted from the wavelength conversion member and the blue light transmitted through the wavelength conversion member.

Further, as the light source of the backlight unit, for example, a light source that emits ultraviolet light having a emission center wavelength in the wavelength range of 300 nm to 430 nm can be used. Examples of the light source include LEDs and lasers. When a light source that emits ultraviolet light is used, the wavelength conversion member preferably includes a quantum dot phosphor B that is excited by excitation light and emits blue light, together with the quantum dot phosphor R and the quantum dot phosphor G. As a result, white light can be obtained from the red light, green light, and blue light emitted from the wavelength conversion member.

The backlight unit of the present disclosure may be an edge light type or a direct type. From the viewpoint of reducing the thickness of the backlight unit, the direct type method is preferable.

Figure 2 shows an example of the schematic configuration of the direct type backlight unit. However, the backlight unit of the present disclosure is not limited to the configuration shown in FIG. Further, the size of the members in FIG. 2 is conceptual, and the relative relationship between the sizes of the members is not limited to this.

The backlight unit 20 shown in FIG. 2 has a light source 21 that emits blue light _LB , a wavelength conversion member 10 that is arranged to face the light source 21, and retroreflection that is arranged to face the light source 21 via the wavelength conversion member 10. The sex member 23 is provided. The wavelength conversion member 10 emits red light LR and green light LG using a part of blue light _LB as excitation light, and red light _LR and green light _LG and blue light _L which is not the _excitation light. _B is emitted. White light _L _W is emitted from the _{retroreflective} member 23 by the red light LR, the green light _LG , and the blue light LB.

<Image display device>
The image display device of the present disclosure includes the backlight unit of the present disclosure described above. The image display device is not particularly limited, and examples thereof include a liquid crystal display device.

FIG. 3 shows an example of the schematic configuration of the liquid crystal display device. However, the liquid crystal display device of the present disclosure is not limited to the configuration shown in FIG. Further, the size of the members in FIG. 3 is conceptual, and the relative relationship between the sizes of the members is not limited to this.

The liquid crystal display device 30 shown in FIG. 3 includes a backlight unit 20 and a liquid crystal cell unit 31 arranged to face the backlight unit 20. The liquid crystal cell unit 31 has a configuration in which the liquid crystal cell 32 is arranged between the polarizing plate 33A and the polarizing plate 33B.

The drive method of the liquid crystal cell 32 is not particularly limited, and is a TN (Twisted Nematic) method, an STN (Super Twisted Nematic) method, a VA (Vertical Birefringence) method, an IPS (In-Plane-Switching) method, an OCB (Optical Birefringence) method. The method and the like can be mentioned.

Hereinafter, the present disclosure will be specifically described with reference to Examples, but the present disclosure is not limited to these Examples.

(Preparation of resin composition for wavelength conversion)
A resin composition for wavelength conversion was prepared by blending a mixture containing the following components with light-scattering particles in an amount such that the content in the wavelength conversion layer was the value (mass%) shown in Table 1.
As a polyfunctional (meth) acrylate compound, tricyclodecanedimethanol diacrylate (Shin-Nakamura Chemical Industry Co., Ltd.) 73 parts by mass As a polyfunctional thiol compound, pentaerythritol tetrakis (3-mercaptopropionate) (SC Organic Chemistry Co., Ltd.) , PEMP) 20.5 parts by mass As a photopolymerization initiator, 2,4,6-trimethylbenzoyl-diphenyl-phosphinoxide (BASF, IRGACURE TPO) 0.5 parts by mass Quantum dot phosphor dispersion as a green luminescent phosphor Liquid (Nanosys, InP / ZnS (core / shell) dispersion, Gen3.0 QD Polymer) 5.0 parts by mass Quantum dot phosphor dispersion as a red light emitting phosphor (Nanosys, InP / ZnS (core / shell)) Dispersion, Gen3.0 QD Compound) 1.5 parts by mass

The following light-scattering particles were used.
Light-scattering particles 1: Zirconia particles (refractive index 2.13, average particle diameter 0.4 to 0.7 μm)
Light scattering particles 2: Zirconia particles (refractive index 2.13, average particle diameter 1.5 to 2.5 μm)
Light scattering particles 3: Alumina particles (refractive index 1.77, average particle diameter 1.6 μm)
Light scattering particles 4: Alumina particles (refractive index 1.77, average particle diameter 0.5 μm)
Light scattering particles 5: Alumina particles (refractive index 1.77, average particle diameter 0.27 μm)
Light scattering particles 6: Acrylic resin particles (refractive index 1.45, average particle diameter 2.0 μm)
Light scattering particles 7: Silicone resin particles (refractive index 1.49, average particle diameter 3.0 μm)
Light-scattering particles 8: Titania particles (refractive index 2.50, average particle diameter 0.36 μm)

Isobornyl acrylate was used as the dispersion medium for the InP / ZnS (core / shell) dispersion liquid. The InP / ZnS (core / shell) dispersion contains 90% by mass or more of isobornyl acrylate.

(Manufacturing of wavelength conversion member)
A coating film was formed by applying each wavelength conversion resin composition obtained above to any of the following coating materials. The same coating material as the coating material on which the coating film was formed was bonded onto this coating film, and ultraviolet rays of 1000 mJ / cm ² were irradiated using an ultraviolet irradiation device (Igraphics Co., Ltd.). As a result, a wavelength conversion member containing a cured product of the wavelength conversion resin composition and having a coating material arranged on both sides of the wavelength conversion layer having the thickness shown in Table 1 was obtained.
Coating material 1: Barrier component is vapor-deposited on one side of the PET film and has a matte layer on the other side. Barrier film with an average thickness of 125 μm Coating material 2: Barrier component is vapor-deposited on one side of the PET film and matted on the other side. Barrier film with an average thickness of 12 μm having a layer Coating material 3: Barrier film having an average thickness of 25 μm having a matte layer on one side of the PET film sputtered with a barrier component.

(Measurement of total light transmittance)
The evaluation wavelength conversion member obtained by cutting the wavelength conversion member into dimensions of 100 mm in width and 100 mm in length is based on JIS K 7136: 2000 using a haze meter (Nippon Denki Kogyo Co., Ltd., NDH-7000SPI). The total light transmittance was measured by the above method.

(Measurement of haze)
The evaluation wavelength conversion member obtained by cutting the wavelength conversion member into dimensions of 100 mm in width and 100 mm in length is based on JIS K 7136: 2000 using a haze meter (Nippon Denki Kogyo Co., Ltd., NDH-7000SPI). Haze was measured by the method used.

(Evaluation of brightness)
The wavelength conversion member for evaluation obtained by cutting the wavelength conversion member into dimensions having a width of 100 mm and a length of 100 mm was measured for brightness using a luminance meter (Photo Research Co., Ltd., PR-655) and evaluated according to the following criteria. As a luminance meter, a camera unit that recognizes optical characteristics is installed at the top, and a BEF (luminance increasing film) plate, a diffuser plate, and an LED light source are provided under the lens, and measurement is performed between the BEF plate and the diffuser plate. A sample was set and the one configured to be able to measure the brightness was used.
〇・・・ Luminance is 800 cd / m ² or more × ・・・ Luminance is less than 800 cd / m ² .

(Evaluation of uneven brightness)
The evaluation wavelength conversion member obtained by cutting the wavelength conversion member into dimensions having a width of 100 mm and a length of 100 mm is placed on a substrate in which mini-LEDs are arranged at intervals of 10 mm × 10 mm, and a composite prism film (composite prism film) is placed on the substrate. POP) and a reflective polarizing film (DBEF manufactured by 3M) were arranged. The mini-LED was turned on, and the presence or absence of luminance unevenness around the mini-LED was visually observed from directly above, and evaluated according to the following criteria.
〇・・・ No or inconspicuous brightness unevenness × ・・・ Brightness unevenness is conspicuous

As shown in Table 1, the wavelength conversion member of the embodiment in which the refractive index of the light scattering particles is 2.3 or less and the value of A × B is in the range of 40 to 1200 is the total light transmittance and the haze. Both values were high enough.
As for the wavelength conversion member of the comparative example in which the refractive index of the light scattering particles exceeds 2.3 or the value of A × B is out of the range of 40 to 1200, either the total light transmittance or the haze is compared with the example. Was also inferior.

All documents, patent applications, and technical standards described herein are to the same extent as if the individual documents, patent applications, and technical standards were specifically and individually stated to be incorporated by reference. Incorporated and incorporated herein.

Claims

It has a wavelength conversion layer including a light scattering particle having a refractive index of 2.3 or less and a phosphor, and has a content A (mass%) of the light scattering particles in the wavelength conversion layer and the wavelength conversion layer. A wavelength conversion member having a product of a thickness B (μm) in the range of 40 to 1200.
The wavelength conversion member according to claim 1, wherein the content of the light scattering particles in the wavelength conversion layer is 0.5% by mass to 20% by mass.
The wavelength conversion member according to claim 1 or 2, wherein the wavelength conversion layer has a thickness of 40 μm to 120 μm.
The wavelength conversion member according to any one of claims 1 to 3, wherein the total light transmittance is 65% or more.
The wavelength conversion member according to any one of claims 1 to 4, wherein the haze is 90% or more.
The wavelength conversion member according to any one of claims 1 to 5, wherein the light-scattering particles include at least one selected from the group consisting of zirconia, alumina, silica, zinc oxide, acrylic resin and silicone resin. ..
The wavelength conversion member according to any one of claims 1 to 6, wherein the phosphor includes a quantum dot phosphor.
The wavelength conversion member according to any one of claims 1 to 7, wherein the wavelength conversion layer is a cured product of a composition containing a (meth) acrylic compound.
The wavelength conversion member according to any one of claims 1 to 8, wherein the wavelength conversion layer is a cured product of a composition containing a thiol compound.
The wavelength conversion member according to any one of claims 1 to 9, further comprising a covering material that covers at least a part of the wavelength conversion layer.
A backlight unit including the wavelength conversion member according to any one of claims 1 to 10 and a light source.
An image display device including the backlight unit according to claim 11.