JP2017137451A - Light wavelength conversion composition, wavelength conversion member, light wavelength conversion sheet, backlight device and picture display unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light wavelength conversion composition and a light wavelength conversion member having excellent thermostability, and also to provide a light wavelength conversion sheet having excellent thermostability where a barrier member can be omitted, or a dot-like luminescence failure can be suppressed even if a barrier member is used, and a backlight device and a picture display unit equipped with such a light wavelength conversion member or a light wavelength conversion sheet.SOLUTION: A light wavelength conversion composition includes a quantum dot and a monofunctional thiol compound having one thiol group in a molecule.SELECTED DRAWING: Figure 1

Description

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

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

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

JP 2015-1111518 A

  In the light wavelength conversion sheet, the quantum dots are deteriorated by moisture and oxygen, and the light emission efficiency may be lowered. Therefore, barrier members for suppressing the transmission of moisture and oxygen are provided on both surfaces of the light wavelength conversion member. Provided. Since the barrier member is provided so as to sandwich the light wavelength conversion member, the conventional light wavelength conversion sheet has a structure in which the barrier member, the light wavelength conversion member, and the barrier member are laminated in this order.

  On the other hand, as one of the reliability tests that are usually performed in a backlight device, there is a heat resistance test that is left in an environment of 80 ° C. for 500 hours, and each member of the backlight device satisfies the standard of the heat resistance test. It is necessary to satisfy. However, when a heat resistance test is performed on the light wavelength conversion sheet having the above structure, there is a problem that the quantum dots deteriorate and the luminance decreases.

  Moreover, in a light wavelength conversion sheet provided with a barrier member, when a heat resistance test is performed, pinholes and cracks are likely to occur in the barrier member. When pinholes or cracks occur in the barrier member, moisture or oxygen enters from it, and some quantum dots deteriorate, and there is a risk that a portion where the luminance is reduced in a dot shape (luminance defect) will occur in the light wavelength conversion sheet There is. This dot-like luminance defect is more visible than the case where the quantum dots deteriorate as a whole and the luminance decreases uniformly. At present, further reduction in the thickness of the light wavelength conversion sheet and reduction in manufacturing cost are desired. From these facts, it is currently studied not to use a barrier member. However, since the present light wavelength conversion member does not have a function of protecting the quantum dots from moisture and oxygen, the quantum dots are deteriorated unless a barrier member is used.

  The present invention has been made to solve the above problems. That is, it aims at providing the light wavelength conversion composition and light wavelength conversion member which have the outstanding heat resistance. Moreover, while having excellent heat resistance, a barrier member can be omitted, or even when a barrier member is used, a light wavelength conversion sheet that can suppress point-like luminance defects, such a light wavelength conversion member or light wavelength An object of the present invention is to provide a backlight device and an image display device provided with a conversion sheet.

  As a result of intensive studies on the above problems, the present inventors have made a light wavelength conversion composition and a light wavelength conversion member having excellent heat resistance by including a specific thiol compound in the light wavelength conversion composition. In addition, when the light wavelength conversion sheet is formed using this light wavelength conversion member, it has excellent heat resistance, the barrier member can be omitted, or even when the barrier member is used. It has been found that the luminance defect of can be suppressed. The present invention has been completed based on such findings.

  According to one aspect of the present invention, there is provided a light wavelength conversion composition comprising a quantum dot and a compound having one thiol group in the molecule.

  According to the other aspect of this invention, the light wavelength conversion member which consists of hardened | cured material of said light wavelength conversion composition is provided.

  According to the other aspect of this invention, it is a light wavelength conversion sheet | seat, Comprising: The light wavelength conversion sheet | seat provided with said light wavelength conversion member and the said light wavelength conversion member is formed in layer form is provided.

  According to the other aspect of this invention, a backlight apparatus provided with a light source and said light wavelength conversion sheet which receives the light from the said light source is provided.

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

  According to the light wavelength conversion composition of one embodiment of the present invention and the light wavelength conversion member of another embodiment, the light wavelength conversion having excellent heat resistance is included because the compound includes one thiol group in the molecule. A composition and a light wavelength conversion member can be provided. Moreover, according to the other aspect of this invention, since the light wavelength conversion sheet is formed using this light wavelength conversion member, while having the outstanding heat resistance, a barrier member can be abbreviate | omitted or a barrier member is used. Even if it is a case, the light wavelength conversion sheet which can suppress a dotted | punctate brightness | luminance defect can be provided. Moreover, according to the other aspect of this invention, a backlight apparatus and an image display apparatus provided with such a light wavelength conversion member and a light wavelength conversion sheet can be provided.

It is a schematic block diagram of the light wavelength conversion sheet which concerns on embodiment. It is a figure which shows the effect | action of the light wavelength conversion sheet which concerns on embodiment. It is a schematic block diagram of the other light wavelength conversion sheet which concerns on embodiment. It is a schematic block diagram of the other light wavelength conversion sheet which concerns on embodiment. It is a schematic block diagram of the other light wavelength conversion sheet which concerns on embodiment. It is sectional drawing along the II line of the light wavelength conversion sheet | seat of FIG. It is a schematic block diagram of the other light wavelength conversion sheet which concerns on embodiment. It is a schematic block diagram of the other light wavelength conversion sheet which concerns on embodiment. It is a figure which shows typically the manufacturing process of the light wavelength conversion sheet which concerns on embodiment. It is a figure which shows typically the manufacturing process of the light wavelength conversion sheet which concerns on embodiment. 1 is a schematic configuration diagram of an image display device including a backlight device according to an embodiment. It is a perspective view of the lens sheet shown by FIG. It is sectional drawing along the II-II line of the lens sheet of FIG. It is a schematic block diagram of the other backlight apparatus which concerns on embodiment. It is a schematic block diagram of the other backlight apparatus which concerns on embodiment. It is a schematic block diagram of the light source shown by FIG. It is a schematic block diagram of the other backlight apparatus which concerns on embodiment. FIG. 18 is an enlarged view of the vicinity of a light incident surface of the optical plate shown in FIG. 17.

  Hereinafter, a light wavelength conversion composition, a light wavelength conversion member, a light wavelength conversion sheet, a backlight device, and an image display device according to embodiments of the present invention will be described with reference to the drawings. In this specification, terms such as “sheet” and “film” are not distinguished from each other only based on the difference in designation. Thus, for example, “sheet” is used to include a member that may also be referred to as a film, and “film” is used to include a member that may also be referred to as a sheet. FIG. 1 is a schematic configuration diagram of a light wavelength conversion sheet according to the present embodiment, and FIG. 2 is a diagram illustrating an operation of the light wavelength conversion sheet according to the present embodiment. FIG. 6 is a schematic configuration diagram of another optical wavelength conversion sheet according to the present embodiment, FIG. 6 is a cross-sectional view taken along line II of the optical wavelength conversion sheet in FIG. 5, and FIGS. It is a figure which shows typically the manufacturing process of the optical wavelength conversion sheet which concerns on a form.

<<< Light wavelength conversion composition >>>
The light wavelength conversion composition is a composition for converting the wavelength of a part of incident light into another wavelength and emitting the other part of the incident light and the wavelength-converted light. The light wavelength conversion composition includes quantum dots and a compound having one thiol group in the molecule (hereinafter, this compound is referred to as “monofunctional thiol compound”). The light wavelength conversion composition may be used in the state of a composition, or the light wavelength conversion composition may be cured and used in the state of a light wavelength conversion member that is a cured product. In the present specification, the “light wavelength conversion member” is a member substantially made of a cured product of the light wavelength conversion composition. Here, the term “substantially” means that the light wavelength conversion member may contain some other substance in addition to the cured product of the light wavelength conversion composition. In addition, the member which consists only of hardened | cured material of a light wavelength conversion composition may be sufficient as a light wavelength conversion member. When forming a light wavelength conversion member, the light wavelength conversion composition further contains a polymerizable compound, and may further contain a polymerization initiator in addition to the polymerizable compound. The light wavelength conversion composition preferably further contains light scattering particles, and may contain an additive or a solvent.

  The viscosity of the light wavelength conversion composition is preferably 10 mPa · s or more and 10,000 mPa · s or less. When the viscosity of the light wavelength conversion composition is less than 10 mPa · s, it may be difficult to form a sufficient film thickness. When the viscosity exceeds 10,000 mPa · s, the light wavelength conversion composition may be applied. Coating may be difficult and leveling properties may be deteriorated. The lower limit of the viscosity of the light wavelength conversion composition is preferably 10 mPa · s or more, and the upper limit of the viscosity of the light wavelength conversion composition is preferably 10,000 mPa · s or less.

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

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

  As the quantum dot, one kind of quantum dot may be used, but it is also possible to use two or more kinds of quantum dots each having an emission band in a single wavelength region by different particle diameters or materials. . Specifically, the light wavelength conversion composition may include a first quantum dot and a second quantum dot having an emission band in a wavelength region different from that of the first quantum dot.

  Quantum dots can generate strong fluorescence in a desired narrow wavelength range. For this reason, the backlight device using the light wavelength conversion sheet can illuminate the display panel with light of three primary colors having excellent color purity. In this case, the display panel has excellent color reproducibility.

  The quantum dot is composed of, for example, a core made of a first semiconductor compound, a shell made of a second semiconductor compound that covers the core and is different from the first semiconductor compound, and a ligand bonded to the surface of the shell. Has been.

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

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

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

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

  The shape of the quantum dot is not particularly limited, and may be, for example, a spherical shape, a rod shape, a disk shape, 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 diameter, average particle diameter, shape, and dispersion state of the quantum dots can be obtained by a transmission electron microscope or a scanning transmission electron microscope. The average particle diameter of the quantum dots can be obtained as an average value of the diameters of 20 quantum dots measured by observation with a transmission electron microscope or a scanning transmission electron microscope. In addition, since the emission color of the quantum dot changes depending on the particle diameter, the particle diameter of the quantum dot can be obtained from confirmation of the emission color of the quantum dot. In addition, the crystal structure and crystallite size of the quantum dots can be known by X-ray crystal diffraction (XRD). Furthermore, the information regarding the particle diameter etc. of a quantum dot can also be obtained with an ultraviolet-visible (UV-Vis) absorption spectrum.

  The content of the quantum dots with respect to the total solid content of the light wavelength conversion composition is preferably 0.01% by mass or more and 2% by mass or less, and more preferably 0.03% by mass or more and 1% by mass or less. . If the content of quantum dots is less than 0.01% by mass, sufficient emission intensity may not be obtained. If the content of quantum dots exceeds 2% by mass, sufficient transmitted light of excitation light is transmitted. There is a risk that strength cannot be obtained.

<< Monofunctional thiol compound >>
As described above, the monofunctional thiol compound is a compound having one thiol group in the molecule, but “monofunctional” in the monofunctional thiol compound means that there is one thiol group in the molecule. . Therefore, the monofunctional thiol compound may contain other functional groups in addition to the thiol group, but preferably does not contain a group (crosslinkable group) capable of crosslinking with a polymerizable compound such as an ethylenically unsaturated group. .

  Whether or not a monofunctional thiol compound is contained in the light wavelength conversion composition is determined by (1) infrared spectroscopic analysis (IR), (2) gas chromatography analysis (GCMS), (3) gel permeation chromatography analysis. (GPC) and nuclear magnetic resonance spectroscopy (NMR spectroscopy) can be used in combination. Specifically, in infrared spectroscopic analysis, the compounds contained in the light wavelength conversion composition can be roughly specified, and in gas chromatography analysis, the molecular weight of the compound contained in the light wavelength conversion composition can be specified. In permeation chromatography analysis, compounds contained in the light wavelength conversion composition can be separated, and in nuclear magnetic resonance spectroscopy, the structural formula of the compound contained in the light wavelength conversion composition can be specified. By using, it can be confirmed whether the monofunctional thiol compound is contained in the light wavelength conversion composition.

  The monofunctional thiol compound is not particularly limited as long as it is a compound having one thiol group in the molecule, and examples thereof include a monofunctional primary thiol compound, a monofunctional secondary thiol compound, and a monofunctional tertiary thiol compound. Among these, the monofunctional primary thiol compound and the monofunctional secondary thiol compound have little steric hindrance in the vicinity of the thiol group, specifically, the α position with respect to the thiol group, and are easily present around the surface of the quantum dot. Monofunctional primary thiol compounds and monofunctional secondary thiol compounds are preferred.

  The monofunctional primary thiol compound has one thiol group in the molecule and no hydrocarbon group is bonded to the carbon to which the thiol group is bonded, or one hydrocarbon group is bonded. A monofunctional secondary thiol compound means a compound having one thiol group in the molecule and two hydrocarbon groups bonded to the carbon to which the thiol group is bonded. The monofunctional tertiary thiol compound means a compound having one thiol group in the molecule and three hydrocarbon groups bonded to the carbon to which the thiol group is bonded.

  Since the monofunctional secondary thiol compound is less likely to react with the polymerizable compound than the monofunctional primary thiol compound, the monofunctional secondary thiol compound is less likely to be incorporated into the binder resin than the monofunctional primary thiol compound. For this reason, the monofunctional secondary thiol compound is easier to reach the surface of the quantum dot than the monofunctional primary thiol compound. Further, when the monofunctional primary thiol compound is used, there is a problem that the odor is strong. However, when the monofunctional secondary thiol compound is used, the problem of odor can be solved. For this reason, the monofunctional secondary thiol compound is more preferable than the monofunctional primary thiol compound.

Although it does not specifically limit as a monofunctional thiol compound, From the viewpoint of sclerosis | hardenability in the case of formation of a light wavelength conversion member, or the heat resistant improvement of a quantum dot, the compound shown by following General formula (1) is preferable.

In the formula, R ^{1 to} R ³ are each independently a hydrogen atom or an optionally substituted alkyl group having 1 to 20 carbon atoms. When at least one of R ^{1 to} R ³ is an alkyl group, the alkyl group may be linear or branched, but when the alkyl group is bulky, it is difficult to reach the surface of the quantum dot due to steric hindrance, A linear alkyl group is preferred.

When at least one of R ^{1 to} R ³ is an alkyl group, examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, tert-butyl group, n-pentyl group, neopentyl group, tert-pentyl group, isopentyl group, 2-methylbutyl group, 1-ethylpropyl group, hexyl group, isohexyl group, 4-methylpentyl group, 3-methylpentyl group, 2-methylpentyl group, 1-methylpentyl group, 3,3-dimethylbutyl group, 2,2-dimethylbutyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 1,3-dimethylbutyl Group, 2,3-dimethylbutyl group, 1-ethylbutyl group, 2-ethylbutyl group, heptyl group, octyl group, nonyl group, decyl Etc. The.

When at least one of R ^{1 to} R ³ is an alkyl group, one methylene group or two or more non-adjacent methylene groups in the alkyl group are —O—, —S—, —SO ₂ —, —CO—. Substituted with at least one group selected from the group consisting of: —COO—, —OCO—, —NR ⁴ —, —CONR ⁴ —, —NR ⁴ CO—, —N═CH— and —CH═CH—. (Wherein R ⁴ independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms).

As the monofunctional primary thiol compound, the handling property of the thiol compound itself, the compatibility with the polymerizable compound, and the viscosity of the light wavelength conversion composition containing the thiol compound and the polymerizable compound are 10 mPa · s or more and 10,000 mPa · s or less. From the viewpoint, a compound represented by the following general formula (2) is preferable.
^{_{HS-CH 2 -R 5 (2}} )
In the formula, R ⁵ is an optionally substituted alkyl group having 1 to 20 carbon atoms. R ⁵ may be linear or branched, but if R ⁵ is bulky, it is difficult to exist around the surface of the quantum dot due to steric hindrance, and therefore a linear alkyl group is preferable.

R ⁵ is an alkyl group similar to the alkyl group described for R ^{1 to} R ³ , and one methylene group or two or more non-adjacent methylene groups in the alkyl group are —O—, —S—, — Selected from the group consisting of SO ₂ —, —CO—, —COO—, —OCO—, —NR ⁴ —, —CONR ⁴ —, —NR ⁴ CO—, —N═CH— and —CH═CH—. It may be substituted with at least one group (in the formula, each R ⁴ independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms).

  The weight average molecular weight or thiol group equivalent (weight average molecular weight / number of thiol groups) of the monofunctional thiol compound is preferably 50 or more and 700 or less. When the weight average molecular weight or thiol group equivalent of the monofunctional thiol compound is less than 50, the dispersibility of the monofunctional thiol compound in the light wavelength conversion composition may be deteriorated. As such, it begins to solidify (gel form), and during the preparation of the composition, work load such as weighing and dispersion increases. In this specification, the “weight average molecular weight” is a value obtained by dissolving in a solvent such as tetrahydrofuran (THF) and converting to polystyrene by a conventionally known gel permeation chromatography (GPC) method. The lower limit of the weight average molecular weight or thiol group equivalent of the monofunctional thiol compound is more preferably 100 or more, and the upper limit is more preferably 500 or less.

  Specific examples of the monofunctional primary thiol compound include octyl mercaptopropionate, stearyl-3-mercaptopropionate, 1-octadecanethiol, 1-hexadecanethiol and the like. Specific examples of the monofunctional secondary thiol compound include 3-methyl-2-butanethiol, 2-butanethiol, cyclohexyl mercaptan, and the like. Specific examples of the monofunctional tertiary thiol compound include tert-butyl mercaptan.

  The content of the monofunctional thiol compound with respect to the total solid mass of the light wavelength conversion composition is preferably 5% by mass or more. When the content of the monofunctional thiol compound is less than 5% by mass, the deterioration of the quantum dots may not be suppressed during the heat resistance test. The content of the monofunctional thiol compound can be confirmed by the same method as the method for confirming whether or not the monofunctional thiol compound is present in the light wavelength conversion composition. Specifically, for example, the monofunctional thiol compound contained in the light wavelength conversion composition is identified (identified) by nuclear magnetic resonance spectroscopy, and then gas chromatography analysis or gel permeation chromatography corresponding to the monofunctional thiol compound is performed. The content of the monofunctional thiol compound in the light wavelength conversion composition can be determined from the peak area ratio obtained by the graphic analysis. In addition, when multiple types of monofunctional thiol compounds are used, the said content shall mean the total content of multiple types of monofunctional thiol compounds. The lower limit of the content of the monofunctional thiol compound with respect to the total solid mass of the light wavelength conversion composition is more preferably 10% by mass or more, and the upper limit of the content of the monofunctional thiol compound is 50% by mass or less. Is preferable, and it is more preferable that it is 40 mass% or less. If the content of the monofunctional thiol compound with respect to the total solid content of the light wavelength conversion composition exceeds 50% by mass, sufficient curability may not be obtained when forming the light wavelength conversion member.

<< 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 (thermosetting compound). Examples of the ionizing radiation in this specification include visible light, ultraviolet rays, X-rays, electron beams, α rays, β rays, and γ rays.

  The content of the polymerizable compound relative to the total solid mass of the light wavelength conversion composition is preferably 30% by mass to 95% by mass, and more preferably 50% by mass to 90% by mass. If the content of the polymerizable compound is less than 30% by mass, sufficient curability may not be obtained when forming the light wavelength conversion member, and the content of the polymerizable compound exceeds 95% by mass. And there exists a possibility that the effect of the heat resistance improvement by a monofunctional thiol compound may not fully be acquired. When the light wavelength conversion composition contains both an ionizing radiation polymerizable compound and a thermopolymerizable compound described later, the above content means the total content of the ionizing radiation polymerizable compound and the thermopolymerizable compound. Shall.

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

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

  The ionizing radiation polymerizable monomer has a weight average molecular weight of 1000 or less. Examples of the ionizing radiation polymerizable monomer include monomers containing a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and ethylene glycol di (meth) acrylate. , Diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, tetramethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylol ethanetri (meth) ) Acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaeryth Ritorutetora (meth) acrylate, dipentaerythritol hexa (meth) acrylate, glycerol (meth) (meth) acrylic acid esters such as acrylate.

  The ionizing radiation polymerizable oligomer has a weight average molecular weight of more than 1000 and 10,000 or less. As the radical polymerizable oligomer, a polyfunctional oligomer having 2 or more functional groups is preferable, and a polyfunctional oligomer having 3 (trifunctional) or more radical polymerizable functional groups is preferable. Examples of the polyfunctional oligomer include polyester (meth) acrylate, urethane (meth) acrylate, polyester-urethane (meth) acrylate, polyether (meth) acrylate, polyol (meth) acrylate, melamine (meth) acrylate, and isocyanurate. (Meth) acrylate, epoxy (meth) acrylate, etc. are mentioned.

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

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

  Examples of the thermopolymerizable compound include cyclic ether compounds having at least one cyclic ether group in the molecule such as epoxy compounds and oxetane compounds, and vinyl ether compounds. As the cationically polymerizable compound, from the viewpoint of further suppressing the occurrence of tunneling, a cyclic ether compound is preferable, and among the cyclic ether compounds, an epoxy compound is preferable.

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

<< Polymerization initiator >>
The polymerization initiator is a component that is decomposed by light or heat to generate radicals or ionic species to initiate or advance polymerization (crosslinking) of the polymerizable compound. Examples of the polymerization initiator include a photopolymerization initiator (for example, a photo radical polymerization initiator, a photo cation polymerization initiator, a photo anion polymerization initiator), a thermal polymerization initiator (for example, a thermal radical polymerization initiator, a thermal cation polymerization initiator). , Thermal anionic polymerization initiator), or a mixture thereof.

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

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

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

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

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

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

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

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

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

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

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

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

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

  The shape of the light-scattering particles is not particularly limited. For example, the shape is spherical (true sphere, approximately true sphere, elliptical sphere, etc.), polyhedral, rod (column, prism, etc.), flat plate, flake, irregular shape. Etc. In addition, when the shape of the light scattering particles is not spherical, the particle diameter of the light scattering particles can be a true spherical value having the same volume.

  The light scattering particles are preferably surface-treated with a silane coupling agent from the viewpoint of firmly fixing the light scattering particles in the binder resin. By surface-treating with a silane coupling agent, it can be chemically bonded to a binder resin described later.

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

  The light-scattering particles may be organic particles such as acrylic resin particles, styrene resin particles, melamine resin particles, and urethane resin particles, but the luminance change rate before and after the heat resistance test can be reduced, and light Inorganic particles are preferable because incident light on the wavelength conversion sheet can be suitably scattered, and light wavelength conversion efficiency for the incident light can be suitably improved.

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

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

<< Additives >>
Although it does not specifically limit as an additive, The compound which suppresses the oxidation and deterioration of a quantum dot is preferable. Examples of the compound that suppresses the oxidation and deterioration of quantum dots include phenolic compounds, amine compounds, phosphorus-containing compounds, sulfur-containing compounds, carboxy group-containing compounds, hydrazine compounds, amide compounds, and hindered amine compounds. . The additive may have a polymerizable functional group such as an ionizing radiation polymerizable functional group or a heat polymerizable functional group.

<< Solvent >>
Examples of the solvent include, but are not limited to, alcohols such as methanol, ethanol, propanol, and isopropyl alcohol; ketones such as methyl ethyl ketone and methyl isobutyl ketone, toluene, and cyclohexane.

<<< Light Wavelength Conversion Member and Light Wavelength Conversion Sheet >>>
The light wavelength conversion sheet 10 shown in FIG. 1 is a sheet that converts the wavelength of some of the incident light to other wavelengths and emits the other part of the incident light and the wavelength-converted light. is there. The light wavelength conversion sheet 10 shown in FIG. 1 includes a layered light wavelength conversion member 11, light transmissive substrates 12 and 13 provided on both surfaces of the light wavelength conversion member 11, and light transmissive substrates 12 and 13. Are provided with light diffusion layers 14 and 15 provided on the side opposite to the surface on the light wavelength conversion member 11 side. In the light wavelength conversion sheet 10, the surfaces of the light diffusion layers 14 and 15 constitute the surfaces 10 </ b> A and 10 </ b> B of the light wavelength conversion sheet 10. The light wavelength conversion sheet 10 includes the light transmissive substrates 12 and 13, but does not include the barrier layer, and thus does not include the barrier member including the light transmissive substrate and the barrier layer. The light wavelength conversion sheet 10 has a structure of light diffusion layer 14 / light transmissive base material 12 / light wavelength conversion member 11 / light transmissive base material 13 / light diffusion layer 15; If it has, the structure of a light wavelength conversion sheet will not be specifically limited.

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

In the optical wavelength conversion sheet 10, the oxygen transmission rate (OTR: Oxygen Transmission Rate) at 23 ° C. and 90% relative humidity is 0.1 cm ³ / (m ² · 24 h · atm) or more. Also good. The 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 2/21”, manufactured by MOCON). Since the conventional light wavelength conversion sheet is formed with a barrier member, the light wavelength conversion sheet 10 has a higher oxygen transmission rate than the conventional light wavelength conversion sheet, that is, the light wavelength conversion sheet 10 is Compared with the conventional light wavelength conversion sheet, not only moisture but also oxygen is easily transmitted. Similarly to the above, when the light wavelength conversion sheet includes an optical member in addition to the light wavelength conversion member, the oxygen transmittance is the oxygen transmittance of the entire light wavelength conversion sheet including the optical member.

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

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

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

In the light wavelength conversion sheet 10, the external haze value of the light wavelength conversion sheet 10 is preferably smaller than the internal haze value of the light wavelength conversion sheet 10. That is, the light wavelength conversion sheet 10 preferably satisfies the relationship of the following formula.
Internal haze value> External haze value

  The internal haze value and the external haze value can be determined using a haze meter (product name “HM-150”, manufactured by Murakami Color Research Laboratory). Specifically, first, the total haze value of the light wavelength conversion sheet is measured according to JIS K7136: 2000 using a haze meter. Thereafter, a triacetylcellulose base material (product name “Panaclean PD-S1”, manufactured by Panac Co., Ltd.) having a thickness of 25 μm is formed on both surfaces of the light wavelength conversion sheet via a transparent optical adhesive layer (product name “Panaclean PD-S1”, manufactured by Panac Corporation). TD60UL "(manufactured by FUJIFILM Corporation) is pasted. Thereby, the uneven shape on the surface of the light wavelength conversion sheet is crushed, and the surface of the light wavelength conversion sheet is flattened. And in this state, an internal haze value is calculated | required by measuring a haze value according to JISK7136 using a haze meter (product name "HM-150", Murakami Color Research Laboratory make). The external haze value is obtained by subtracting the internal haze from the total haze. The “external haze value” in the present specification means the external haze value of the entire light wavelength conversion sheet. That is, the external haze value in this specification means the sum of the external haze value on one surface of the light wavelength conversion sheet and the external haze value on the other surface of the light wavelength conversion sheet.

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

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

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

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

  The definition of “Ra” is based on JIS B0601: 1994. Ra can be measured using, for example, a surface roughness measuring instrument (product name “SE-3400”, manufactured by Kosaka Laboratory Ltd.).

  When a light source that emits blue light is used to irradiate a light wavelength conversion sheet 10 that includes both quantum dots that convert blue light into green light and quantum dots that convert blue light into red light, the transmitted light in the light wavelength conversion sheet The ratio of the peak value of green light intensity to the peak value of blue light intensity (peak value of green light intensity / peak value of blue light intensity) is 0.3 to 2.0 It is preferable that it is 0.5 or more and 1.5 or less.

  The ratio of the peak value of the light intensity of the red light to the peak value of the light intensity of the blue light in the transmitted light in the light wavelength conversion sheet 10 (the peak value of the light intensity of the red light / the peak value of the light intensity of the blue light) is 0.3 or more and 2.0 or less, and more preferably 0.5 or more and 1.5 or less.

  In this specification, “blue light” is light having a wavelength range of 380 nm or more and less than 480 nm, “green light” is light having a wavelength range of 480 nm or more and less than 590 nm, and “red light” is It is light having a wavelength range of 590 nm to 750 nm. The light intensity of each light can be measured using a spectral radiance meter (for example, product name “CS2000”, manufactured by Konica Minolta).

  The average thickness of the light wavelength conversion sheet 10 is preferably 10 μm or more and 500 μm or less. If the average thickness of the light wavelength conversion sheet 10 is within this range, it is suitable for reducing the weight and thickness of the backlight device.

  The average thickness of the light wavelength conversion sheet 10 is calculated using, for example, cross-sectional images taken at 20 random locations with a scanning electron microscope (SEM), a transmission electron microscope (TEM), or a scanning transmission electron microscope (STEM). it can. Among these, considering that the film thickness of the light wavelength conversion sheet 10 is on the order of μm, it is preferable to use SEM. In the case of SEM, the acceleration voltage is preferably 30 kV and the magnification is preferably 1000 to 7000 times. In the case of TEM or STEM, the acceleration voltage is preferably 30 kV and the magnification is preferably 50,000 to 300,000 times.

<< Light wavelength conversion member >>
The light wavelength conversion member is a cured product of the light wavelength conversion composition. In this case, the light wavelength conversion composition contains a polymerizable compound and a polymerization initiator in addition to quantum dots and monofunctional thiols. Although the light wavelength conversion member 11 of this embodiment is layered, the shape of the light wavelength conversion member may not be layered. That is, the shape of the light wavelength conversion member can be appropriately changed depending on the location where the light wavelength conversion member is used.

  Since the light wavelength conversion member 11 is a cured product of the light wavelength conversion composition, the light wavelength conversion member 11 includes quantum dots 17, a monofunctional thiol compound, and a binder resin 16 that is a cured product of a polymerizable compound. Whether or not the monofunctional thiol compound is present in the light wavelength conversion member 11 can be confirmed by a method similar to the method for confirming whether or not the monofunctional thiol compound is present in the light wavelength conversion composition. . The quantum dot 17 shown in FIG. 1 includes a first quantum dot 17A and a second quantum dot 17B having an emission band in a wavelength region different from that of the first quantum dot 17A. The light wavelength conversion member 11 shown in FIG. 1 further includes light scattering particles 18. By including the light scattering particles 18, the light wavelength conversion efficiency and the internal haze can be increased. The quantum dots 17, monofunctional thiols, and light scattering particles 18 included in the light wavelength conversion member 11 are the same as the quantum dots, monofunctional thiols, and light scattering particles described above. Shall be omitted.

  In the light wavelength conversion member 11, it is preferable that content of the sulfur element in the light wavelength conversion member 11 measured by a fluorescent X ray analysis is 0.5 mass% or more. If the content of elemental sulfur is less than 0.5% by mass, the deterioration of the quantum dots may not be suppressed during the heat resistance test. The content of the elemental sulfur in the light wavelength conversion member can be measured by using a fluorescent X-ray analyzer (product name “EDX-800HS”, manufactured by Shimadzu Corporation). The lower limit of the content of sulfur element in the light wavelength conversion member 11 is preferably 1% by mass or more, and the upper limit of the content of sulfur element is preferably 20% by mass or less, and is 10% by mass or less. It is more preferable. If the content of the elemental sulfur exceeds 20% by mass, sufficient curing may not be performed during the formation of the light wavelength conversion member.

  The elemental sulfur is present around the quantum dots and in the binder resin 16, but may contain a thiol compound as a ligand for the quantum dots. In this case, the light wavelength conversion member does not contain quantum dots. By performing elemental analysis using an energy dispersive X-ray spectrometer (EDX) attached to an electron microscope in the region, it is possible to determine the presence or absence of sulfur element in the binder resin.

  In the light wavelength conversion member 11, the content of the monofunctional thiol compound in the light wavelength conversion member 11 is preferably 0.5% by mass or more. When the content of the monofunctional thiol compound is less than 0.5% by mass, deterioration of the quantum dots may not be suppressed during the heat resistance test. The content of the monofunctional thiol compound in the light wavelength conversion member 11 can be measured by the same method as the method for measuring the content of the monofunctional thiol compound in the light wavelength conversion composition. The lower limit of the content of the monofunctional thiol in the light wavelength conversion member 11 is preferably 1% by mass or more, and the upper limit of the content of the monofunctional thiol compound is preferably 20% by mass or less, preferably 10% by mass. The following is more preferable. When the content of the monofunctional thiol compound exceeds 20% by mass, sufficient curing may not be performed at the time of forming the light wavelength conversion member.

  The average film thickness of the light wavelength conversion member 11 is preferably 10 μm or more and 200 μm or less. If the average thickness of the light wavelength conversion member 11 is within this range, it is suitable for reducing the weight and thickness of the backlight device. The film thickness of the light wavelength conversion member 11 can be calculated from 20 images of a cross section of the light wavelength conversion sheet 10 randomly using a scanning electron microscope (SEM) and from the image of the cross section. The upper limit of the average film thickness of the light wavelength conversion member 11 is more preferably less than 170 μm.

<Binder resin>
Since the binder resin 16 is a cured product of the polymerizable compound, it is omitted here.

  The absolute value of the difference in refractive index between the light-scattering particles 18 and the binder resin 16 is preferably 0.05 or more, and more preferably 0.10 or more, from the viewpoint of obtaining sufficient light scattering. Note that either of the refractive index of the light scattering particles 18 and the refractive index of the binder resin 16 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 member, for example, the measurement is performed by the Becke method, the minimum deflection angle method, the deflection angle analysis, the mode line method, the ellipsometry method, etc. can do. As a method for measuring the refractive index of the binder resin and light scattering particles in the light wavelength conversion member, for example, a piece of light scattering particles or a host matrix fragment is taken out from the cured light wavelength conversion member in some form. The Becke method can be used on In addition, the refractive index difference between the binder resin and the light scattering particles is measured using a phase shift laser interference microscope (such as a phase shift laser interference microscope manufactured by FK Optical Laboratory or a two-beam interference microscope manufactured by Mizoji Optical Industry Co., Ltd.). can do.

<< light transmissive substrate >>
The thickness of the light-transmitting substrates 12 and 13 is not particularly limited, but is preferably 10 μm or more and 300 μm or less. If the thickness of the light-transmitting substrates 12 and 13 is less than 10 μm, there is a risk of wrinkling or folding during assembly of the light wavelength conversion sheet and handling, and if it exceeds 300 μm, the weight of the display and the thin film There is a risk that it may not be suitable. The more preferable lower limit of the thickness of the light-transmitting substrates 12 and 13 is 50 μm or more, and the more preferable upper limit is 200 μm or less.

  The average thickness of the light transmissive substrates 12 and 13 can be calculated using, for example, a cross-sectional image taken with a scanning electron microscope (SEM), a transmission electron microscope (TEM), or a scanning transmission electron microscope (STEM). .

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

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

<< light diffusion layer >>
The light diffusion layers 14 and 15 have a concavo-convex shape on the surface, and the light that enters and exits the light wavelength conversion sheet 10 can be diffused by the concavo-convex shape. By providing the light diffusion layers 14 and 15, the light wavelength conversion efficiency in the light wavelength conversion sheet 10 can be further increased. The light diffusion layers 14 and 15 contain light scattering particles and a binder resin.

<Light scattering particles>
The light-scattering particles in the light diffusion layers 14 and 15 are mainly for forming a concavo-convex shape on the surfaces of the light diffusion layers 14 and 15 and exhibiting a light-scattering function.

  The average particle diameter of the light-scattering particles in the light diffusion layers 14 and 15 is preferably 10 to 20,000 times, more preferably 10 to 5000 times the average particle diameter of the quantum dots 17 described above. preferable. If the average particle size of the light-scattering particles is less than 10 times the average particle size of the quantum dots, sufficient light diffusibility may not be obtained in the light diffusion layer, and the average particle size of the light-scattering particles may be If it exceeds 20,000 times the average particle diameter of the quantum dots, the light diffusion performance of the light diffusion layer will be excellent, but the light transmittance of the light diffusion layer will be greatly reduced. In addition, the average particle diameter of light-scattering particle | grains can be measured by the method similar to the average particle diameter of the quantum dot mentioned above.

  Specifically, the average particle diameter of the light scattering particles in the light diffusion layers 14 and 15 is, for example, preferably 1 μm to 30 μm, and more preferably 1 μm to 20 μm. If the average particle diameter of the light scattering particles is less than 1 μm, the light wavelength conversion efficiency of the light wavelength conversion sheet may be insufficient, and the amount of light scattering particles added to provide sufficient light diffusibility. Need to be more. On the other hand, when the average particle diameter of the light scattering particles exceeds 30 μm, the light diffusion performance is excellent, but the light transmittance of the light diffusion layer is likely to be greatly reduced.

  The absolute value of the difference in refractive index between the light-scattering particles and the binder resin in the light diffusion layers 14 and 15 is preferably 0.02 or more and 0.15 or less. If it is less than 0.02, the light diffusibility due to the refractive index of the light scattering particles cannot be obtained optically, and the improvement of the light wavelength conversion efficiency of the light wavelength conversion sheet may be insufficient. If it exceeds 15, the transmittance of the light diffusion layer may be lowered. The more preferable lower limit of the difference in refractive index between the light-scattering particles and the binder resin is 0.03 or more, and the more preferable upper limit is 0.12. Note that either of the refractive index of the light-scattering particles and the refractive index of the binder resin may be larger. The refractive indexes of the light scattering particles and the binder resin can be measured by the same method as the refractive indexes of the light scattering particles 18 and the first binder resin.

  Since the shape of the light-scattering particles in the light diffusion layers 14 and 15 is the same as the shape of the light-scattering particles 18 in the light wavelength conversion member 11, description thereof will be omitted here. The light scattering particles in the light diffusion layers 14 and 15 are preferably chemically bonded to the binder resin from the viewpoint of firmly fixing the light scattering particles in the binder resin. This chemical bonding can be realized by using light scattering particles whose surface is modified with a silane coupling agent. Since the silane coupling agent is the same as the silane coupling agent described in the column of the light scattering particles in the light wavelength conversion member, the description thereof is omitted here.

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

<Binder resin>
As the binder resin, a cured product of a polymerizable compound can be used. As the polymerizable compound, since the same compound as the polymerizable compound contained in the light wavelength conversion composition can be used, the description thereof is omitted here.

<< Other light wavelength conversion sheet >>
As shown in FIG. 3, the light wavelength conversion sheet may be the light wavelength conversion sheet 20 having only the light wavelength conversion member 11 (single layer structure). The light wavelength conversion sheet may be a light wavelength conversion sheet 30 including a light wavelength conversion member 11 and a light-transmitting base material 31 that supports the light wavelength conversion member 11, as shown in FIG. . By providing the light transmissive substrate 31, the strength of the light wavelength conversion sheet can be increased more than that of the light wavelength conversion sheet 20.

<Light transmissive substrate>
As the light transmissive substrate 31 of the light wavelength conversion sheet 30, the same material as the light transmissive substrates 12, 13 can be used, and the description thereof will be omitted here.

<< Other light wavelength conversion sheet >>
As shown in FIGS. 5 and 6, the light wavelength conversion sheet is disposed on at least one surface side of the light wavelength conversion member 11 and the light wavelength conversion member 11 and integrated with the light wavelength conversion member 11. The optical wavelength conversion sheet 40 provided with the optical member 41 may be sufficient.

<Optical member>
In this specification, the “optical member” means optical properties (for example, polarization, light refraction, light scattering, light reflectivity, light transmission, light absorption, light diffraction, optical rotation, etc.). It is not particularly limited as long as it is a sheet (film) -like or plate-like member having optical characteristics. Examples of the optical member include a lens sheet, an optical plate such as a light guide plate and a light diffusing plate, a reflective polarization separation sheet, and a polarizing plate. When the optical member sheet is provided on both sides of the light wavelength conversion sheet, the optical member may be an optical member having different optical characteristics. In the present embodiment, an example in which the optical member is a lens sheet will be described.

  As shown in FIGS. 5 and 6, the optical member 41 includes a light transmissive substrate 42 and a lens layer 43 provided on one surface of the light transmissive substrate 42. As shown in FIGS. 5 and 6, the lens layer 43 includes a sheet-like main body 44 and a plurality of unit lenses 45 arranged side by side on the light output side of the main body 44. The light transmissive substrate 42, the lens layer 43, the main body 44, and the unit lens 45 have the same configuration as the light transmissive substrate 101, the lens layer 102, the main body 103, and the unit lens 104 described later. Therefore, the description is omitted here.

  In the light wavelength conversion sheet 40, the light wavelength conversion member 11 and the optical member 41 are integrated by directly applying and curing the light wavelength conversion composition on one surface of the optical member 41. The light wavelength conversion member 11 and the optical member 41 may be bonded together via an adhesive layer.

<< Other light wavelength conversion sheet >>
As shown in FIG. 7, the light wavelength conversion sheet is a light wavelength sheet 50 including a light wavelength conversion member 11 and overcoat layers 51 and 52 arranged on at least one surface side of the light wavelength conversion member 11. There may be. In the present embodiment, the overcoat layers 51 and 52 are formed on both surfaces of the light wavelength conversion member 11.

<Overcoat layer>
The overcoat layers 51 and 52 are layers made of a cured product (polymerized product, cross-linked product) of a polymerizable compound. Unlike the light-transmitting substrate, the overcoat layer composition is applied to the surface of the light wavelength conversion member. , Dried and cured. As the polymerizable compound for forming the overcoat layers 51 and 52, the cured product (polymerized product, crosslinked product) of the polymerizable compound described in the column of the light wavelength conversion composition can be used, and therefore it is described here. Shall be omitted.

  The overcoat layers 51 and 52 may be a layer that only exhibits the function of covering the surface of the light wavelength conversion member, or may be a layer that is intended to exhibit some other function. Specifically, the overcoat layers 51 and 52 have at least a function of covering the surface of the light wavelength conversion member 11, for example, at least antiblocking property, light diffusion property, antistatic property, barrier property, antireflection property, and the like. It may be a layer that exhibits any function. When the overcoat layers 51 and 52 are layers that exhibit the function of covering the surface of the light wavelength conversion member 11 and some other function, the overcoat layers 51 and 52 exhibit a cured product of the polymerizable compound and some function. And a material for doing so.

In the light wavelength conversion sheets 20, 30, 40, and 50, the water vapor transmission rate at 40 ° C. and a relative humidity of 90% may be 0.1 g / (m ² · 24 h) or more in the entire sheet. In the light wavelength conversion sheets 20, 30, 40, 50, even if the entire sheet has an oxygen permeability of 0.1 cm ³ / (m ² · 24 h · atm) at 23 ° C. and a relative humidity of 90%. Good. The water vapor transmission rate at 40 ° C. and 90% relative humidity in the light wavelength conversion sheets 20, 30, 40, 50 may be 1 g / (m ² · 24 h) or more, and the light wavelength conversion sheets 20, 30, The oxygen permeability at 23 ° C. and 90% relative humidity at 40 and 50 may be 1 cm ³ / (m ² · 24 h · atm) or more.

<< Other light wavelength conversion sheet >>
The light wavelength conversion sheet may be a light wavelength conversion sheet 60 as shown in FIG. In this case, the water vapor transmission rate and the oxygen transmission rate of the light wavelength conversion sheet 60 may not be within the above-described ranges.

  The light wavelength conversion sheet 60 shown in FIG. 8 includes a light wavelength conversion member 11, barrier members 61 and 62 provided on both surfaces of the light wavelength conversion member 11, and the light wavelength conversion member 11 side of the barrier members 61 and 62. Light diffusion layers 13 and 14 provided on the side opposite to the surface are provided. In the light wavelength conversion sheet 60, the surfaces of the light diffusion layers 13 and 14 constitute the surfaces 60 </ b> A and 60 </ b> B of the light wavelength conversion sheet 60.

<Barrier member>
The barrier members 61 and 62 are members for suppressing the permeation of moisture and oxygen and protecting the quantum dots 17 from moisture and oxygen. Here, the “barrier member” in the present specification is a single member having a water vapor transmission rate of less than 0.1 g / (m ² · 24 h) at 40 ° C. and a relative humidity of 90%, and at 23 ° C. and a relative humidity. A member whose oxygen permeability at 90% is less than 0.1 cm ³ / (m ² · 24 h · atm) is meant. The barrier member includes not only a single layer structure film but also a multilayer structure film. The durability of the quantum dots 17 can be further improved by installing the barrier members 61 and 62 in a state where the light wavelength conversion member 11 is sandwiched. Barrier members 61 and 62 shown in FIG. 8 are provided on the light transmissive base materials 12 and 13 and the light wavelength conversion member 11 side of the light transmissive base materials 12 and 13 and suppress the transmission of moisture and oxygen. Barrier layers 63 and 64 having functions.

The water vapor transmission rate (WVTR) of the barrier members 61 and 62 is 1.0 × 10 ⁻² g / (m ² · 24 h) or less at 40 ° C. and a relative humidity of 90%. Is more preferable. The water vapor transmission rate can be measured using a water vapor transmission rate measuring device (product name “PERMATRAN-W3 / 31”, manufactured by MOCON).

The oxygen transmission rate (OTR: Oxygen Transmission Rate) of the barrier members 61 and 62 is 1.0 × 10 ⁻² cm ³ / (m ² · 24 h · atm) or less at 23 ° C. and a relative humidity of 90%. More preferably it is. The oxygen permeability can be measured using an oxygen gas permeability measuring device (product name “OX-TRAN 2/21”, manufactured by MOCON).

(Barrier layer)
The barrier layers 63 and 64 are composed of a vapor deposition layer having a function of suppressing permeation of moisture and oxygen. A vapor deposition layer is a layer formed by vapor deposition methods, such as physical vapor deposition (PVD) methods, such as sputtering method and an ion plating method, and chemical vapor deposition (CVD) method, for example. A vapor deposition layer has the advantage that barrier property can be improved.

  The material for forming the vapor deposition layer is not particularly limited as long as it can be vapor-deposited by a vapor deposition method and has barrier properties, and examples thereof include inorganic oxides such as silicon oxide and aluminum oxide, metals, and the like.

  Although the film thickness of a vapor deposition layer is not specifically limited, It is preferable that they are 0.01 micrometer or more and 1 micrometer or less. If the thickness of the deposited layer is less than 0.01 μm, the barrier performance of the deposited layer may be insufficient, and if it exceeds 1 μm, the barrier performance may be easily deteriorated due to cracks in the deposited layer. is there. The minimum with more preferable thickness of a vapor deposition layer is 0.03 micrometer or more, and a more preferable upper limit is 0.5 micrometer or less.

  The film thickness of the vapor deposition layer can be calculated from 20 images of a cross section of the light wavelength conversion sheet 60 randomly using a scanning electron microscope (SEM) and from the image of the cross section. Moreover, a single layer may be sufficient as a vapor deposition layer, and what laminated | stacked the several layer may be sufficient as it. When a plurality of vapor deposition layers are laminated, each layer constituting the vapor deposition layer may be directly laminated or bonded.

<<< Method for Producing Light Wavelength Conversion Sheet >>>
The light wavelength conversion sheet 10 can be produced as follows, for example. First, although not shown, a light diffusing layer composition containing light scattering particles and a polymerizable compound is applied to one surface of the light transmissive substrate 12 and dried to apply the light diffusing layer composition. A film is formed. Similarly, a coating film of the composition for light diffusion layer is formed on one surface of the light transmissive substrate 13.

  Subsequently, the coating film of the composition for light diffusion layers is hardened by light irradiation etc. Thereby, as shown in FIG. 9A, the light diffusion layer 14 is formed on one surface of the light transmissive substrate 12, and the light transmissive substrate 12 with the light diffusion layer 14 is formed. Although not shown, the light transmissive substrate 13 with the light diffusion layer 15 is formed in the same manner.

  After forming the light transmissive substrate 13 with the light diffusing layer 15, as shown in FIG. 9B, the side opposite to the surface on the light diffusing layer 15 side of the light transmissive substrate 13 with the light diffusing layer 15. The light wavelength conversion composition is applied to the surface of the film and dried to form a coating film 19 of the light wavelength conversion composition.

  After forming the coating film 19 of the light wavelength conversion composition, the surface opposite to the surface on the light diffusion layer 14 side in the light transmissive substrate 12 with the light diffusion layer 14 is the light wavelength as shown in FIG. The light-transmitting substrate 12 with the light diffusion layer 14 is disposed on the coating film 19 of the light wavelength conversion composition so as to contact the coating film 19 of the conversion composition. Thereby, the coating film 19 of the light wavelength conversion composition is sandwiched between the light-transmitting substrates 12 and 13.

  Next, as shown in FIG. 10 (B), the coating compound 19 of the light wavelength conversion composition is irradiated with ionizing radiation through the light-transmitting substrate 12, or heat is applied to cure the polymerizable compound. Thus, the light wavelength conversion member 11 is formed, and the light wavelength conversion member 11 is integrated with the light transmissive substrate 12 with the light diffusion layer 14 and the light transmissive substrate 13 with the light diffusion layer 15. Thereby, the light wavelength conversion sheet 10 shown in FIG. 1 is obtained.

  The light wavelength conversion sheets 20, 30, 50 can be produced, for example, as follows. First, a light wavelength conversion composition containing quantum dots, a monofunctional thiol compound, a polymerizable compound and a polymerization initiator is applied onto a substrate (not shown), dried, and then a coating film of the light wavelength conversion composition Form. And the light wavelength conversion member 11 is formed by irradiating this coating film with ionizing radiation or applying heat to cure the polymerizable compound. Thereafter, the substrate is peeled from the light wavelength conversion member 11. Thereby, the light wavelength conversion sheet 20 shown in FIG. 3 is obtained. On the other hand, when the light-transmitting base material 31 is used as the base material, the base material is left as it is without peeling from the light wavelength conversion member 11, so that the light wavelength conversion sheet 30 shown in FIG. can get. Moreover, the composition for overcoat layers is apply | coated to both surfaces of the light wavelength conversion sheet 20, and it is made to dry, and the coating film of a light wavelength conversion composition is formed. Then, the overcoat layers 51 and 52 are formed by irradiating the coating film with ionizing radiation or applying heat to cure the polymerizable compound. Thereby, the light wavelength conversion sheet 50 shown in FIG. 7 is obtained.

  The light wavelength conversion sheet 40 is formed by applying the light wavelength conversion composition on one surface side of the optical member 41 and drying it to form a coating film of the light wavelength conversion composition. And the light wavelength conversion member 11 is formed by irradiating this coating film with ionizing radiation or applying heat to cure the polymerizable compound. Thereby, the light wavelength conversion sheet 40 shown in FIG. 5 is obtained.

  The light wavelength conversion sheet 60 includes a light diffusing layer 14, 15, a light transmissive base material 12, 13, and a barrier layer 63, 64 formed on one surface of the light transmissive base material 12, 13. If it forms in the members 61 and 62, it can be formed by the same process as the optical wavelength conversion sheet 10 later.

  The light wavelength conversion sheets 10, 20, 30, 40, 50, 60 can be used by being incorporated in a backlight device and an image display device. Hereinafter, an example in which the light wavelength conversion sheet 10 is incorporated in a backlight device and an image display device will be described. 11 is a schematic configuration diagram of an image display device including a backlight device according to this embodiment, FIG. 12 is a perspective view of the lens sheet shown in FIG. 11, and FIG. It is sectional drawing along the II line. 14, 15 and 17 are schematic configuration diagrams of another backlight device according to the present embodiment, FIG. 16 is a schematic configuration diagram of the light source shown in FIG. 15, and FIG. 18 is shown in FIG. It is an enlarged view near the light incident surface of the optical plate.

<<< Image display device >>>
An image display device 70 shown in FIG. 11 includes a backlight device 80 and a display panel 120 disposed on the light output side of the backlight device 80. The image display device 70 has a display surface 70A for displaying an image. In the image display device 70 shown in FIG. 11, the surface of the display panel 120 is a display surface 70A.

  The backlight device 80 illuminates the display panel 120 in a planar shape from the back side. The display panel 120 functions as a shutter that controls transmission or blocking of light from the backlight device 80 for each pixel, and is configured to display an image on the display surface 70A.

<< Display panel >>
A display panel 120 shown in FIG. 11 is a liquid crystal display panel, and is between a polarizing plate 101 disposed on the light incident side, a polarizing plate 122 disposed on the light exit side, and between the polarizing plate 121 and the polarizing plate 122. The liquid crystal cell 103 is provided. The polarizing plates 121 and 122 decompose incident light into two linearly polarized light components (S-polarized light and P-polarized light) orthogonal to each other and vibrate in one direction (direction parallel to the transmission axis) (for example, P It has a function of transmitting a linearly polarized component (for example, S-polarized light) that transmits polarized light and vibrates in the other direction (direction parallel to the absorption axis) perpendicular to the one direction.

  The liquid crystal cell 123 is configured such that a voltage can be applied to each region where one pixel is formed. Then, the alignment direction of the liquid crystal molecules in the liquid crystal cell 123 changes depending on the presence or absence of voltage application. As an example, the linearly polarized light component in a specific direction transmitted through the polarizing plate 121 disposed on the light incident side rotates the polarization direction by 90 ° when passing through the liquid crystal cell 123 to which a voltage is applied, When passing through the liquid crystal cell 123 to which no voltage is applied, the polarization direction is maintained. In this case, depending on whether or not a voltage is applied to the liquid crystal cell 123, the linearly polarized light component oscillating in a specific direction transmitted through the polarizing plate 121 is transmitted through the polarizing plate 122 or absorbed and blocked by the polarizing plate 122. it can. In this way, the display panel 120 is configured to control transmission or blocking of light from the backlight device 80 for each pixel. The details of the liquid crystal display panel are described in various known literatures (for example, “Flat Panel Display Dictionary” (published by Tatsuo Uchida, Hiraki Uchiike), 2001, Industrial Research Council). The detailed description of is omitted.

<< Backlight device >>
A backlight device 80 shown in FIG. 11 is configured as an edge-light type backlight device, and includes a light source 90, an optical plate 95 as a light guide plate disposed on the side of the light source 90, and a light output side of the optical plate 95. The light wavelength conversion sheet 10 disposed on the lens, the lens sheet 100 disposed on the light output side of the light wavelength conversion sheet 10, the lens sheet 105 disposed on the light output side of the lens sheet 100, and the light output side of the lens sheet 105. The reflection-type polarization separation sheet 110 disposed and the reflection sheet 115 disposed on the side opposite to the light output side of the optical plate 95 are provided. The backlight device 80 includes the optical plate 95, the lens sheets 100 and 105, the reflective polarization separation sheet 110, and the reflective sheet 115, but these sheets and the like may not be provided. In the present specification, the “light exit side” means a side from which light is emitted from each member in the direction of exiting the backlight device.

  The backlight unit 80 has a light emitting surface 80A that emits light in a planar shape. In the backlight device 80 shown in FIG. 11, the light exit surface of the reflective polarization separation sheet 110 is the light emitting surface 80 </ b> A of the backlight device 80.

  The surface on the optical plate 95 side in the light wavelength conversion sheet 10 is a surface 10A (light incident surface), and the surface on the lens sheet 100 side in the light wavelength conversion sheet 10 is a surface 10B (light exit surface).

<Light source>
The light source 90 includes, for example, a fluorescent lamp such as a linear cold cathode tube, or a light emitter such as a point light emitting diode (LED) or an incandescent lamp. In the present embodiment, the light source 90 is composed of a large number of point-like light emitters, specifically, a large number of light emitting diodes (LEDs) arranged in a line on the light incident surface 95C side to be described later of the optical plate 95. ,It is configured.

  As the light wavelength conversion sheet 10 is disposed in the backlight device 80, the light source 90 can use only a light emitter that emits light in a single wavelength region. For example, only a blue light emitting diode that emits blue light with high color purity can be used as the light source.

<Optical plate>
The optical plate 95 as the light guide plate has a quadrangular shape in plan view. The optical plate 95 extends between the light output surface 95A formed by one main surface on the display panel 120 side, the back surface 95B formed of the other main surface facing the light output surface 95A, and the light output surface 95A and the back surface 95B. And have side faces. Of the side surfaces, the side surface on the light source 90 side is a light incident surface 75 </ b> C that receives light from the light source 90. Light entering the optical plate 95 from the light incident surface 95C is guided through the optical plate in a direction (light guide direction) connecting the light incident surface 95C and the opposite surface opposite to the light incident surface 95C. It is emitted from 95A.

  As a material constituting the optical plate 95, a material that is widely used as a material for an optical sheet incorporated in an image display device and has excellent mechanical characteristics, optical characteristics, stability, workability, and the like, and can be obtained at low cost. For example, transparent resins mainly composed of one or more of acrylic resin, polystyrene, polycarbonate, polyethylene terephthalate, polyacrylonitrile, etc., and epoxy acrylate or urethane acrylate reactive resins (ionizing radiation curable resins, etc.) are preferably used. Can be done. If necessary, a light diffusing material having a function of diffusing light can be added to the optical plate 75. As the light diffusing material, for example, particles made of a transparent material such as silica (silicon dioxide), alumina (aluminum oxide), acrylic resin, polycarbonate resin, or silicone resin having an average particle diameter of 0.5 μm to 100 μm are used. it can.

<< Lens sheet >>
The lens sheets 100 and 105 have a function of changing the traveling direction of incident light and emitting it from the light exit side. In the present embodiment, as shown in FIG. 13, the function of concentratingly improving the luminance in the front direction by changing the traveling direction of the light L <b> 3 having a large incident angle and emitting it from the light exit side (condensing function). In addition, it has a function (retroreflection function) of reflecting the light L4 having a small incident angle and returning it to the light wavelength conversion sheet 10 side. The lens sheets 100 and 105 include a light transmissive substrate 101 and a lens layer 102 provided on one surface of the light transmissive substrate 101.

  When the surfaces 10A and 10B of the light wavelength conversion sheet 10 are uneven surfaces, the light exit surface 95A of the optical plate 95 is optically in close contact with a part (for example, a convex portion) of the surface 10A. 10A is preferably separated from other portions (for example, concave portions), and the light incident surface 100A of the lens sheet 100 is optically in close contact with a portion (for example, convex portions) of the surface 10B. It is preferable that it is separated from the other part (for example, recessed part) of 10B. In this case, the gap between the light exit surface 95A and the other part of the surface 10A and the gap between the light incident surface 100A and the other part of the surface 10B form an air layer. By providing this air layer, the light wavelength conversion sheet 10, the optical plate 95, and the lens sheet 100 are fixed so that the light exit surface 95A and the surface 10A and the light entrance surface 100A and the surface 10B are in optical contact. However, since it can suppress sticking of the optical wavelength conversion sheet 10, the optical plate 95, and the lens sheet 100, the interface between the optical wavelength conversion sheet 10 and the optical plate 95 and the optical wavelength conversion sheet 10 and the lens sheet 100 can be suppressed. It is possible to suppress the formation of wet-out at the interface between the two.

<Light transmissive substrate>
Since the light transmissive substrate 101 is the same as the light transmissive substrates 12 and 13, the description thereof will be omitted here.

<Lens layer>
As shown in FIGS. 12 and 13, the lens layer 102 includes a sheet-like main body 103 and a plurality of unit lenses 104 arranged side by side on the light output side of the main body 103.

  The main body 103 functions as a sheet-like member that supports the unit lens 104. As shown in FIGS. 12 and 13, the unit lenses 104 are arranged on the light exit side surface 103 </ b> A of the main body 103 without leaving a gap. Therefore, the light exit surfaces 100B and 105B of the lens sheets 100 and 105 are formed by lens surfaces. On the other hand, as shown in FIG. 13, the main body 103 has a smooth surface that forms the light incident side surface of the lens layer 102 as the light incident side surface 103B that faces the light output side surface 103A.

  The unit lenses 104 are arranged side by side on the light exit side surface 103 </ b> A of the main body 103. As shown in FIG. 12, the unit lenses 104 extend linearly in the direction intersecting the arrangement direction AD of the unit lenses 104, in particular, linear in this embodiment. In the present embodiment, a large number of unit lenses 104 included in one lens sheet 100, 105 extend in parallel to each other. Further, the longitudinal direction LD of the unit lenses 104 of the lens sheets 100 and 105 is orthogonal to the arrangement direction AD of the unit lenses 104 in the lens sheets 100 and 105.

  The unit lens 104 may have a triangular prism shape, or may have a wave shape or a bowl shape such as a hemisphere. Specifically, examples of the unit lens include a unit prism, a unit cylindrical lens, and a unit microlens. Examples of the lens sheet having such a unit lens shape include a prism sheet, a lenticular lens sheet, and a microlens sheet. In the present embodiment, a triangular prism-shaped unit prism whose width becomes narrower toward the light output side will be described as a unit lens. The shape of the cross section (also referred to as the main cutting surface of the lens sheet) parallel to both the normal direction ND of the lens surfaces of the lens sheets 100 and 105 and the arrangement direction AD of the unit lenses 104 is a triangular shape protruding to the light output side. ing. In particular, from the viewpoint of intensively improving the luminance in the front direction, the cross-sectional shape of the unit lens 104 at the main cut surface is an isosceles triangle shape, and the apex angle located between the equilateral sides is the light exit side surface 103A of the main body 103. Each unit lens 104 is configured to project from the light to the light exit side.

  The unit lens 104 preferably has an apex angle of 80 ° to 100 °, more preferably an apex angle of about 90 °, from the viewpoint of improving the light utilization efficiency. However, considering the breakage of the tip of the unit lens during winding of the light wavelength conversion sheet, the tip of the unit lens 104 may be a curved surface.

  The dimensions of the lens sheets 100 and 105 can be set as follows as an example. First, as a specific example of the unit lenses 104, the arrangement pitch of the unit lenses 104 (corresponding to the width of the unit lenses 104 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 lenses 104 has been highly refined, and the arrangement pitch of the unit lenses 104 is preferably 10 μm or more and 50 μm or less. Further, the projection height of the unit lens 104 from the main body 103 along the normal direction ND to the sheet surface of the lens sheets 100 and 105 can be set to 5 μm or more and 100 μm or less. Furthermore, the apex angle θ of the unit lens 104 can be set to 60 ° or more and 120 ° or less.

  As can be understood from FIG. 11, the arrangement direction of the unit lenses 104 of the lens sheet 100 and the arrangement direction of the unit lenses 104 of the lens sheet 105 intersect, and more specifically, are orthogonal to each other.

<Reflection-type polarized light separation sheet>
The reflection-type polarization separation sheet 110 transmits only a first linearly polarized light component (for example, P-polarized light) out of the light emitted from the lens sheet 105, and is a second straight line orthogonal to the first linearly polarized light component. It has a function of reflecting a polarized light component (for example, S-polarized light) without absorbing it. In the state where the second linearly polarized light component reflected by the reflective polarization separation sheet 110 is reflected again and depolarized (including both the first linearly polarized light component and the second linearly polarized light component), The light again enters the reflective polarization separation sheet 110. Therefore, the reflective polarization separation sheet 110 transmits the first linearly polarized light component of the incident light again, and the second linearly polarized light component orthogonal to the first linearly polarized light component is reflected again. Hereinafter, by repeating the above process, about 70 to 80% of the light emitted from the lens sheet 105 is emitted as the light source light that has become the first linearly polarized light component. Accordingly, by making the polarization direction of the first linearly polarized light component (transmission axis component) of the reflective polarization separation sheet 110 coincide with the transmission axis direction of the polarizing plate 121 of the display panel 120, the emitted light from the backlight device 80. Can be used for image formation on the display panel 120. Therefore, even when the light energy input from the light source 90 is the same, it is possible to form an image with higher brightness than in the case where the reflective polarization separation sheet 110 is not disposed, and the energy utilization efficiency of the light source 90 is also improved. improves. In particular, the light reflected by the reflective polarization separation sheet 110 can be wavelength-converted by the light wavelength conversion sheet 10. Therefore, the wavelength conversion efficiency of the light wavelength conversion sheet 10 can be further increased by arranging the reflective polarization separation sheet 110. Therefore, further improvement in light utilization efficiency can be expected.

  As the reflective polarization separation sheet 110, “DBEF” (registered trademark) available from 3M Company can be used. In addition to “DBEF”, a high-intensity polarizing sheet “WRPS” available from Shinwha Intertek, a wire grid polarizer, or the like can be used as the reflective polarization separating sheet 90.

<Reflection sheet>
The reflection sheet 115 has a function of reflecting light leaking from the back surface 95 </ b> B of the optical plate 95 so as to enter the optical plate 90 again. The reflection sheet 115 is composed of a white scattering reflection sheet, a sheet made of a material having a high reflectance such as metal, a sheet containing a thin film (for example, a metal thin film) made of a material having a high reflectance as a surface layer, and the like. obtain. The reflection on the reflection sheet 115 may be regular reflection (specular reflection) or diffuse reflection. When the reflection on the reflection sheet 115 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 sheet 10 may be a direct type backlight device as shown in FIG. The backlight device 130 shown in FIG. 14 includes a light source 90, an optical plate 131 that receives light from the light source 90 and functions as a light diffusing plate, and a light wavelength conversion sheet 10 that is disposed on the light output side of the optical plate 131. A lens sheet 100 disposed on the light output side of the light wavelength conversion sheet 10, a lens sheet 105 disposed on the light output side of the lens sheet 100, and a reflective polarization separation sheet 110 disposed on the light output side of the lens sheet 105. I have. In the present embodiment, the light source 90 is disposed not directly on the side of the optical plate 131 but directly below the optical plate 131. 14, members denoted by the same reference numerals as those in FIG. 11 are the same as the members shown in FIG. Note that the backlight device 130 is not provided with the reflection sheet 115.

<Optical plate>
The optical plate 131 as a light diffusing plate has a square shape in plan view. The optical plate 131 has a light incident surface 131A constituted by one main surface on the light source 95 side and a light outgoing surface 131B constituted by the other main surface on the light wavelength conversion sheet 10 side. Light incident on the optical plate 131 from the light incident surface 131A is diffused in the optical plate 131 and emitted from the light exit surface 131B.

  The optical plate 131 is not particularly limited as long as the light from the light source 90 can be diffused, and examples thereof include a plate in which light diffusing particles are dispersed in a transparent material. Although it does not specifically limit as a transparent material, For example, transparent resin, inorganic glass, etc. are mentioned. As the transparent resin, a transparent thermoplastic resin is suitably used because it is easy to mold. The transparent thermoplastic resin is not particularly limited. For example, polystyrene resin, styrene-methyl methacrylate copolymer resin, styrene-methacrylic acid copolymer resin, styrene-maleic anhydride copolymer resin. Methacrylic resin, acrylic resin, polycarbonate resin, ABS resin (acrylonitrile-butadiene-styrene copolymer resin), AS resin (acrylonitrile-styrene copolymer resin), polyolefin resin (polyethylene resin, polypropylene resin, etc.) and the like. . One of these may be used, or two or more of these may be mixed and used.

<Light diffusing particles>
Examples of the light diffusing particles in the optical plate 131 include light diffusing particles generally used as a diffusion plate.

<< Other backlight devices >>
The backlight device 80 shown in FIG. 11 includes the light wavelength conversion sheet 10, but the structure of the backlight device is not particularly limited as long as the light wavelength conversion member is included. For example, the backlight device may be a backlight device 140 including a light source 150 instead of the light wavelength conversion sheet 10 and the light source 90, as shown in FIG. As shown in FIG. 16, the light source 150 includes a substrate 151, a reflection member 152 having an opening 152 </ b> A disposed on the substrate 151, and a light emission disposed on the substrate 151 and in the opening 152 </ b> A of the reflection member 152. A light emitter 153 such as a diode, and a light wavelength conversion member 154 filled in the opening 152A of the reflection member 152 so as to cover the light emitter 153 are provided. The optical wavelength conversion member 154 is different from the optical wavelength conversion member 11 only in shape and location, and the configuration and physical properties of the optical wavelength conversion member 154 are the same as those of the optical wavelength conversion member 11, and therefore the description thereof is omitted here. And The light wavelength conversion member 154 can be formed by filling the light wavelength conversion composition into the opening 152A of the reflection member 152 and curing it. In addition, when using the light source 150 which has the light wavelength conversion member 154, if the light wavelength conversion member 154 is arrange | positioned so that the light-emitting body 153 may be covered, a structure will not be specifically limited.

<< Other backlight devices >>
The backlight device may be the backlight device 160 shown in FIG. Specifically, the backlight device 160 shown in FIG. 17 includes a layered light wavelength conversion member 170 disposed between the light source 90 and the optical plate 95 instead of the light wavelength conversion sheet 10. The light wavelength conversion member 170 shown in FIG. 17 is provided on the light incident surface 95 </ b> C of the optical plate 95. The optical wavelength conversion member 170 is different from the optical wavelength conversion member 11 only in the arrangement location, and the configuration and physical properties of the optical wavelength conversion member 170 are the same as those of the optical wavelength conversion member 11, and thus description thereof will be omitted here. . The light wavelength conversion member 170 can be formed by applying the above light wavelength conversion composition to the light incident surface 95C of the optical plate 95 and curing it.

  It is considered that the reason why the quantum dots are easily deteriorated by the heat resistance test is as follows. First, a ligand made of thiol, phosphine, or the like is coordinated on the surface of the quantum dot, but the surface of the quantum dot is not entirely covered with the ligand, and there are places where the ligand does not exist. And it is thought that a water | moisture content or oxygen adheres to the location where this ligand does not exist in the surface of a quantum dot, a quantum dot will be oxidized and a quantum dot will deteriorate. Such deterioration of the quantum dots proceeds at an accelerated rate when heat is applied to the quantum dots. For this reason, it is thought that a quantum dot will deteriorate by a heat resistance test. On the other hand, it is known that a thiol compound forms a copolymer by a thiol-ene reaction with a polymerizable compound. When the thiol compound is copolymerized with the polymerizable compound by a thiol-ene reaction, the thiol compound may not reach a location where the ligand on the surface of the quantum dot does not exist. In thiol compounds, the greater the number of thiol groups present in the molecule, the greater the chance of a thiol-ene reaction with the polymerizable compound. It can be said that there are few opportunities which produce a thiol-ene reaction with a polymeric compound compared with a compound. In this embodiment, since the light wavelength conversion composition or the light wavelength conversion member 11 contains a monofunctional thiol compound, the monofunctional thiol compound has a ligand on the surface of the quantum dot 17 as compared with the polyfunctional thiol compound. Since it is easy to reach the periphery of the part which is not, the monofunctional thiol compound can exist around the part where the ligand on the surface of the quantum dot 17 does not exist. Thereby, deterioration of the quantum dot 17 at the time of a heat test can be suppressed, As a result, the heat resistance of the light wavelength conversion composition and the light wavelength conversion member 11 can be improved.

  According to this embodiment, since the deterioration of the quantum dots 17 can be suppressed by the monofunctional thiol compound present in the light wavelength conversion member 11, in the light wavelength conversion sheets 10, 20, 30, 40, 50, 60, the heat resistance In addition, the barrier member can be omitted, and even when the barrier member is used, dot-like luminance defects can be suppressed. That is, in the light wavelength conversion sheets 10, 20, 30, 40, and 50, deterioration of the quantum dots 17 can be suppressed by the monofunctional thiol compound present in the light wavelength conversion member 11, so that the barrier member can be omitted. . Moreover, in the light wavelength conversion sheet 60 provided with the barrier members 61 and 62, since the deterioration of the quantum dot 17 can be suppressed by the monofunctional thiol compound present in the light wavelength conversion member 11, for example, the barrier members 61 and 62 Even when pinholes or cracks are generated in the water and moisture or oxygen enters from the pinholes or cracks, the point-like luminance defect can be suppressed. Moreover, since the deterioration of the quantum dot 17 can be suppressed by the monofunctional thiol compound present in the light wavelength conversion member 11, the peripheral portions 10C, 20A, 30A in the light wavelength conversion sheets 10, 20, 30, 40, 50, 60 , 40A, 50A, and 60C, the deterioration of the quantum dots 17 can also be suppressed.

  In the light wavelength conversion sheets 10, 20, 30, 40, and 50, since the deterioration of the quantum dots 17 can be suppressed by the monofunctional thiol compound present in the light wavelength conversion member 11, no barrier member is provided. Thereby, while being able to simplify the process of a light wavelength conversion sheet, it becomes easy to improve quality, and thickness reduction of a light wavelength conversion sheet can be achieved.

  In the light wavelength conversion sheet 40, the light wavelength conversion member 11 and the optical member 41 are integrated. Therefore, the light wavelength conversion sheet 40 is simplified and thin compared to the case where the light wavelength conversion sheet and the optical member are separately disposed. A backlight device can be obtained. That is, when the light wavelength conversion sheet and the optical member are separately arranged, there is an air interface between the light wavelength conversion sheet and the optical member, so that a relatively large gap is formed in the backlight device. Cost. On the other hand, in this embodiment, since the light wavelength conversion member 11 and the optical member 41 are integrated, there is no air interface between the light wavelength conversion member 11 and the optical member 41. Thereby, a simplified thin backlight device can be obtained.

  Light emitters such as light emitting diodes also generate heat during light emission. For this reason, normally, when the light wavelength conversion member is incorporated in the light source or when the light wavelength conversion member is disposed at a position close to the light source, the light wavelength conversion member is covered to suppress the deterioration of the quantum dots. A barrier member is required. On the other hand, in this embodiment, since the heat resistance in the light wavelength conversion members 154 and 170 can be improved by the monofunctional thiol compound present in the light wavelength conversion members 154 and 170, the light wavelength conversion members 154, Even if 170 is not covered with a barrier member, deterioration of the quantum dots 17 can be suppressed. Thereby, the light wavelength conversion member 154 can be incorporated in the light source 150, or the light wavelength conversion member 170 can be disposed at a position close to the light source 90.

  Conventionally, light that has been wavelength-converted by the quantum dots emitted from the light wavelength conversion sheet is condensed on the light output side of the light wavelength conversion sheet, and light that has not been wavelength-converted by the light wavelength conversion sheet is converted to the light wavelength conversion sheet. It has been studied to increase the optical wavelength conversion efficiency by arranging a lens sheet to be returned to the side. However, the optical wavelength conversion efficiency is not sufficient only by arranging such a lens sheet, and further improvement of the optical wavelength conversion efficiency is desired. According to this embodiment, when the external haze value of the light wavelength conversion sheet 10 is smaller than the internal haze value of the light wavelength conversion sheet 10, the light wavelength conversion efficiency can be further improved. That is, since the light emitted from the light source has straightness, the light that enters the light wavelength conversion sheet and is not wavelength-converted by the quantum dots, and the light emitted from the light wavelength conversion sheet also has straightness. Yes. Here, when the external haze value of the light wavelength conversion sheet is high, light that has not been wavelength-converted that has straightness on the surface of the light wavelength conversion sheet is refracted, and light that is not wavelength-converted emitted from the light wavelength conversion sheet In this case, a component having a large emission angle increases. On the other hand, a lens sheet having a condensing function and a retroreflective function tends to make the lens sheet retroreflected more easily as the incident angle to the lens sheet is smaller. That is, there is a tendency that light having a larger incident angle to the lens sheet is more easily transmitted through the lens sheet. In the present embodiment, since the external haze value is smaller than the internal haze value in the light wavelength conversion sheet 10, even if light that has not undergone wavelength conversion is refracted on the surface of the light wavelength conversion sheet 10, it is emitted. The light can be emitted in a state where the angle is small. Accordingly, in the light which is emitted from the light wavelength conversion sheet 10 and is not wavelength-converted, a component having a small emission angle can be increased. Therefore, the lens sheet 100 can retroreflect the light emitted from the light wavelength conversion sheet without wavelength conversion and return it to the light wavelength conversion sheet 10 side, so that the opportunities for wavelength conversion increase. Moreover, since the internal haze value is larger than the external haze value, the light path length is increased by scattering light within the light wavelength conversion sheet, and the opportunity for wavelength conversion is further increased. Thereby, the optical wavelength conversion efficiency can be improved. Since the quantum dots 17 emit light isotropically, the light wavelength-converted by the quantum dots 17 is directed in various directions, and when reaching the surface of the light wavelength conversion sheet 10, the surface of the light wavelength conversion sheet is further increased. The light is refracted and wavelength-converted light becomes light with a large angle and is easily emitted from the optical wavelength conversion sheet. For this reason, the wavelength-converted light is relatively easily transmitted through the lens sheet 100.

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

  According to this embodiment, since the light wavelength conversion member 11 includes the light scattering particles 18, the light wavelength conversion efficiency can be further improved. Therefore, for example, a light source that emits blue light is used as the light source 90, a quantum dot that converts blue light into green light is used as the first quantum dot 17A, and blue light is converted into red light as the second quantum dot 17B. When the light wavelength conversion sheet containing quantum dots is irradiated with blue light, the chromaticity x and y can be increased compared to a light wavelength conversion sheet that does not contain light scattering particles, and white light or a color close to white The light of taste can be obtained.

  According to this embodiment, since the light wavelength conversion member sheet 11 includes the light scattering particles 18, green light emission can be preferentially enhanced over red light emission. The reason for this is not clear, but the light-scattering particles appear to inhibit energy transfer from the first quantum dot that converts blue light to green light to the second quantum dot that converts blue light to red light. This is probably because the green light emission that was originally deactivated by the above-described energy transfer does not deactivate, and thus reaches the light emission process, and as a result, the green light emission increases.

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

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

(Light wavelength conversion composition 1)
Epoxy acrylate (product name “Unidic V-5500”, manufactured by DIC Corporation): 79.4 parts by mass • Octyl mercaptopropionate (monofunctional primary thiol compound, product name “BMPA-2EH”, manufactured by Sakai Chemical Co., Ltd.) : 20 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): 0.20 parts by mass red emission quantum Dot (product name “CdSe / ZnS 610”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.20 parts by mass / radical polymerization initiator (1-hydroxycyclohexyl phenyl ketone) , Product name “Irgacure (registered trademark) 184”, manufactured by BASF Japan Ltd.): 0.2 parts by mass

(Light wavelength conversion composition 2)
Epoxy acrylate (product name “Unidic V-5500”, manufactured by DIC Corporation): 69.4 parts by mass • Octyl mercaptopropionate (monofunctional primary thiol compound, product name “BMPA-2EH”, manufactured by Sakai Chemical Co., Ltd.) : 20 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): 0.20 parts by mass red emission quantum Dot (product name “CdSe / ZnS 610”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.20 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-hydroxycyclohexyl Nyl ketone, product name “Irgacure (registered trademark) 184”, manufactured by BASF Japan Ltd.): 0.2 parts by mass

(Light wavelength conversion composition 3)
Epoxy acrylate (product name “Unidic V-5500”, manufactured by DIC Corporation): 59.4 parts by mass • Octyl mercaptopropionate (monofunctional primary thiol compound, product name “BMPA-2EH”, manufactured by Sakai Chemical Co., Ltd.) : 40 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): 0.20 parts by mass red emission quantum Dot (product name “CdSe / ZnS 610”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.20 parts by mass / radical polymerization initiator (1-hydroxycyclohexyl phenyl ketone) , Product name “Irgacure (registered trademark) 184”, manufactured by BASF Japan Ltd.): 0.2 parts by mass

(Light wavelength conversion composition 4)
Epoxy acrylate (product name “Unidic V-5500”, manufactured by DIC Corporation): 94.4 parts by mass • Octyl mercaptopropionate (monofunctional primary thiol compound, product name “BMPA-2EH”, manufactured by Sakai Chemical Co., Ltd.) : 5 parts by mass green emitting quantum dots (product name “CdSe / ZnS 530”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.20 parts by mass red emitting quantum Dot (product name “CdSe / ZnS 610”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.20 parts by mass / radical polymerization initiator (1-hydroxycyclohexyl phenyl ketone) , Product name “Irgacure (registered trademark) 184”, manufactured by BASF Japan Ltd.): 0.2 parts by mass

(Light wavelength conversion composition 5)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC Corporation): 79.4 parts by mass-Stearyl-3-mercaptopropionate (monofunctional primary thiol compound, product name "STMP", SC organic chemistry 20 parts by mass, green light emitting quantum dots (product name “CdSe / ZnS 530”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.20 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): 0.20 part by mass / radical polymerization initiator (1-hydroxy Cyclohexyl phenyl ketone, product name “Irgacure (registered trademark) 184” manufactured by BASF Japan Ltd.): 0.2 quality Part

(Light wavelength conversion composition 6)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC Corporation): 79.4 parts by mass-3-methyl-2-butanethiol (monofunctional secondary thiol compound, manufactured by Tokyo Chemical Industry Co., Ltd.): 20 Mass parts / green light emitting quantum dots (product name “CdSe / ZnS 530”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.20 parts by mass / red light emitting quantum dots ( Product name “CdSe / ZnS 610”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.20 parts by mass / radical polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product Name “Irgacure (registered trademark) 184” (manufactured by BASF Japan): 0.2 parts by mass

(Light wavelength conversion composition 7)
・ Epoxy acrylate (product name “Unidic V-5500”, manufactured by DIC Corporation): 79.4 mass parts ・ tert-butyl mercaptan (monofunctional tertiary thiol compound, manufactured by Tokyo Chemical Industry Co., Ltd.): 20 mass parts ・ Green Luminescent quantum dots (product name “CdSe / ZnS 530”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.20 parts by mass / red luminescent quantum dot (product name “CdSe / ZnS 610 ”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.20 parts by mass / radical polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name“ Irgacure ( Registered trademark) 184 ", manufactured by BASF Japan Ltd.): 0.2 parts by mass

(Light wavelength conversion composition 8)
Epoxy acrylate (product name “Unidick V-5500”, manufactured by DIC): 100 parts by mass Green emitting quantum dot (product name “CdSe / ZnS 530”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS , Average particle size 3.3 nm): 0.20 parts by mass Red-emitting quantum dots (product name “CdSe / ZnS 610”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm) : 0.20 parts by mass. Radical polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name “Irgacure (registered trademark) 184”, manufactured by BASF Japan Ltd.): 0.2 parts by mass

(Light wavelength conversion composition 9)
Epoxy acrylate (product name “Unidic V-5500”, manufactured by DIC Corporation): 79.4 parts by mass Tetraethylene glycol bis (3-mercaptopropionate) (bifunctional thiol compound, product name “EGMP-4” , Manufactured by SC Organic Chemical Co., Ltd.): 20 parts by mass, green light emitting quantum dots (product name “CdSe / ZnS 530”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size: 3.3 nm): 0.0. 20 parts by mass / red light emitting quantum dots (product name “CdSe / ZnS 610”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.20 parts by mass / radical polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name “Irgacure (registered trademark) 184”, BASF Made emissions Co., Ltd.): 0.2 parts by weight

(Light wavelength conversion composition 10)
・ Epoxy acrylate (product name “Unidic V-5500”, manufactured by DIC Corporation): 79.4 parts by mass ・ Trimethylolpropane tristhiopropionate (trifunctional thiol compound, product name “TMTP”, manufactured by Sakai Chemical Co., Ltd.) : 20 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): 0.20 parts by mass red emission quantum Dot (product name “CdSe / ZnS 610”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.20 parts by mass / radical polymerization initiator (1-hydroxycyclohexyl phenyl ketone) , Product name “Irgacure (registered trademark) 184”, manufactured by BASF Japan Ltd.): 0.2 parts by mass

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

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

Subsequently, the light wavelength conversion composition 1 was apply | coated to the surface on the opposite side to the surface by the side of the light-diffusion layer in one PET base material with a light-diffusion layer, and it was made to dry at 80 degreeC, and the coating film was formed. And the other PET base material with a light-diffusion layer was laminated | stacked on the coating film so that the surface on the opposite side to the surface by the side of the light-diffusion layer in the other PET base material with a light-diffusion layer may contact | connect. In this state, the coating film is cured by irradiating ultraviolet rays so that the integrated light quantity becomes 500 mJ / cm ² to form a light wavelength conversion member having a film thickness of 100 μm, and the light wavelength conversion member and two light beams A PET substrate with a diffusion layer was integrated. As a result, an optical wavelength conversion sheet according to Example 1 was obtained.

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

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

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

<Example 5>
In Example 5, a light wavelength conversion sheet was produced in the same manner as in Example 1 except that the light wavelength conversion composition 5 was used instead of the light wavelength conversion composition 1.

<Example 6>
In Example 6, a light wavelength conversion sheet was prepared in the same manner as in Example 1 except that the light wavelength conversion composition 6 was used instead of the light wavelength conversion composition 1.

<Example 7>
In Example 7, a light wavelength conversion sheet was produced in the same manner as in Example 1 except that the light wavelength conversion composition 7 was used instead of the light wavelength conversion composition 1.

<Example 8>
The optical wavelength conversion composition 1 was applied to one surface of a polyethylene terephthalate (PET) base material (product name “Lumirror T60”, manufactured by Toray Industries, Inc.) having a thickness of 50 μm, and dried at 80 ° C. to form a coating film. . And the ultraviolet-ray was irradiated so that the integrated light quantity might be 500 mJ / cm < ² >, and the coating film was hardened. Finally, the PET substrate was peeled off to obtain a light wavelength conversion sheet consisting only of a light wavelength conversion member having a film thickness of 100 μm according to Example 6.

<Example 9>
A prism layer composition containing urethane acrylate was uniformly applied to one surface of a polyethylene terephthalate (PET) base material (product name “Lumirror T60”, manufactured by Toray Industries, Inc.) having a thickness of 100 μm. A coating film was formed to form a prism sheet laminate. Then, the prism sheet laminate is traveled at a running speed so that the coating layer of the lens layer composition is on the molding die side and has a concave portion having a reverse shape with respect to the shape of the desired unit prism. The shape of the unit prism is formed on the coating film of the prism layer composition by a molding die by supplying at 20 m / min, and light such as ultraviolet rays is applied to the coating film of the prism layer composition through the PET substrate. Irradiation was performed to cure the coating film of the prism layer composition. Finally, the cured coating film of the prism layer composition was peeled off from the molding die together with the PET base material to obtain a prism sheet having a prism layer formed on one surface of the PET base material. The prism layer has a sheet-like main body, and is arranged side by side on the main body. Each prism layer extends in a direction intersecting the arrangement direction, has an apex angle of 90 °, a width of 47 μm, and a height. Had a plurality of triangular prism unit prisms.

Next, the light wavelength conversion composition 1 was applied to the surface of the prism sheet opposite to the surface on the side of the prism layer of the PET substrate, and dried at 80 ° C. to form a coating film. Then, the light wavelength conversion member having a thickness of 100 μm integrated with the prism sheet was formed by irradiating the ultraviolet ray with an integrated light amount of 500 mJ / cm ² to cure the coating film. As a result, an optical wavelength conversion sheet according to Example 9 was obtained.

<Example 10>
First, two barrier members were produced by the following method. Polyethylene terephthalate as a light-transmitting substrate having a size of 7 inches and a thickness of 50 μm is generated in a chamber by applying a high-frequency power with a frequency of 13.56 MHz and a power of 5 kW to an electrode in a high-frequency sputtering apparatus. A silica vapor deposition layer having a thickness of 50 nm and a refractive index of 1.46 made of a target material (silica) was formed on one side of a (PET) substrate (product name “Lumirror T60”, manufactured by Toray Industries, Inc.). As a result, two barrier members each having a silica vapor deposition layer formed on one surface of the PET substrate were formed.

Next, the composition for light diffusion layer was applied to the surface opposite to the surface on the silica vapor deposition layer side of both barrier members to form a coating film. Next, the solvent in the coating film was evaporated by allowing the formed coating film to dry by passing dry air at 80 ° C. for 30 seconds. Then, the light diffusion layer with a film thickness of 10 μm was formed by irradiating the ultraviolet ray so that the integrated light amount was 500 mJ / cm ² to cure the coating film, thereby forming a barrier member with a light diffusion layer.

Subsequently, the light wavelength conversion composition 1 was apply | coated to the silica vapor deposition layer side of one barrier member with a light-diffusion layer, it was made to dry at 80 degreeC, and the coating film was formed. And the other barrier member with a light-diffusion layer was laminated | stacked so that the silica vapor deposition layer might contact | connect the surface of the silica vapor deposition layer of the barrier member with a light-diffusion layer in a coating film. In this state, the coating film is cured by irradiating ultraviolet rays so that the integrated light quantity becomes 500 mJ / cm ² , thereby forming a light wavelength conversion member having a thickness of 100 μm adhered to both barrier members with a light diffusion layer. did. As a result, an optical wavelength conversion sheet according to Example 10 was obtained.

<Comparative Example 1>
In Comparative Example 1, a light wavelength conversion sheet was produced in the same manner as in Example 1 except that the light wavelength conversion composition 8 was used instead of the light wavelength conversion composition 1.

<Comparative example 2>
In Comparative Example 2, a light wavelength conversion sheet was produced in the same manner as in Example 1 except that the light wavelength conversion composition 9 was used instead of the light wavelength conversion composition 1.

<Comparative Example 3>
In Comparative Example 3, a light wavelength conversion sheet was produced in the same manner as in Example 1 except that the light wavelength conversion composition 10 was used instead of the light wavelength conversion composition 1.

<Comparative Example 4>
In Comparative Example 4, a light wavelength conversion sheet was produced in the same manner as in Example 8 except that the light wavelength conversion composition 8 was used instead of the light wavelength conversion composition 1.

<Comparative Example 5>
In Comparative Example 5, a light wavelength conversion sheet was produced in the same manner as in Example 8 except that the light wavelength conversion composition 9 was used instead of the light wavelength conversion composition 1.

<Comparative Example 6>
In Comparative Example 6, a light wavelength conversion sheet was produced in the same manner as in Example 8 except that the light wavelength conversion composition 10 was used instead of the light wavelength conversion composition 1.

<Comparative Example 7>
In Comparative Example 7, a light wavelength conversion sheet was produced in the same manner as in Example 9 except that the light wavelength conversion composition 8 was used instead of the light wavelength conversion composition 1.

<Comparative Example 8>
In Comparative Example 8, a light wavelength conversion sheet was produced in the same manner as in Example 9 except that the light wavelength conversion composition 9 was used instead of the light wavelength conversion composition 1.

<Comparative Example 9>
In Comparative Example 9, a light wavelength conversion sheet was produced in the same manner as in Example 9 except that the light wavelength conversion composition 10 was used instead of the light wavelength conversion composition 1.

<Comparative Example 10>
In Comparative Example 10, a light wavelength conversion sheet was produced in the same manner as in Example 10 except that the light wavelength conversion composition 8 was used instead of the light wavelength conversion composition 1.

<Comparative Example 11>
In Comparative Example 11, a light wavelength conversion sheet was produced in the same manner as in Example 10 except that the light wavelength conversion composition 9 was used instead of the light wavelength conversion composition 1.

<Comparative Example 12>
In Comparative Example 12, a light wavelength conversion sheet was produced in the same manner as in Example 10 except that the light wavelength conversion composition 10 was used instead of the light wavelength conversion composition 1.

<Measurement of content of monofunctional thiol compound>
In the light wavelength conversion sheet according to the above examples and comparative examples, the content of the sulfur element contained in the light wavelength conversion member is measured using a fluorescent X-ray analyzer (product name “EDX-800HS”, manufactured by Shimadzu Corporation). Measured.

<Measurement of water vapor transmission rate and oxygen transmission rate>
In the light wavelength conversion sheets according to the above examples and comparative examples, the water vapor transmission rate and the oxygen transmission rate were measured, respectively. The water wavelength transmission sheet has a water vapor transmission rate of 40 ° C. and a relative humidity of 90% using a water vapor transmission rate measuring device (product name “PERMATRAN-W3 / 31”, manufactured by MOCON) in accordance with JIS K7129: 2008. The measurement was performed under the following conditions. In addition, the oxygen transmission rate of the light wavelength conversion sheet is 23 ° C. relative to an oxygen gas transmission rate measurement device (product name “OX-TRAN 2/21”, manufactured by MOCON) according to JIS K7126: 2006. Measurement was performed under the condition of 90% humidity.

<Measurement of luminance maintenance ratio after heat resistance test>
In the light wavelength conversion sheet according to the above examples and comparative examples, a heat resistance test is performed in which the light wavelength conversion sheet is left in an environment of 80 ° C. for 500 hours, and a heat resistance test for luminance before the heat resistance test in the light wavelength conversion sheet. Later, the maintenance ratio of luminance was examined. Specifically, first, a backlight device of Kindle Fire (registered trademark) HDX7 was prepared, and a light wavelength conversion sheet before a heat resistance test was incorporated into the backlight device. This backlight device includes a blue light emitting diode having an emission peak wavelength of 450 nm, a light guide plate, a first prism sheet, and a second prism sheet in this order.

  In Examples 1-8 and Comparative Examples 1-6, 10-12, the light guide plate is disposed so that the blue light emitting diode side is the light incident surface, and Examples 1-8 are provided on the light exit surface of the light guide plate. 10 and Comparative Examples 1 to 6 and 10 to 12, the light wavelength conversion sheet, the first prism sheet, and the second prism sheet were arranged in this order to obtain a backlight device. Note that the second prism sheet was disposed so that the arrangement direction of the unit prisms was orthogonal to the arrangement direction of the unit prisms of the first prism sheet.

  In Example 9 and Comparative Examples 7 to 9, the light guide plate is disposed so that the blue light emitting diode side is the light incident surface, and the prism surface of the prism sheet is on the light output side of the light guide plate. The light wavelength conversion sheet and the second prism sheet according to Example 9 and Comparative Examples 7 to 9 were arranged in this order to obtain a backlight device. The second prism sheet was arranged so that the arrangement direction of the unit prisms was orthogonal to the arrangement direction of the unit prisms of the prism sheets in the light wavelength conversion sheets according to Example 9 and Comparative Examples 7 to 9. Thus, the backlight apparatus with which the light wavelength conversion sheet | seat which concerns on Example 9 and Comparative Examples 7-9 was integrated was obtained.

  Then, the blue light emitting diode of the backlight device incorporating the light wavelength conversion sheet is turned on, the blue light is irradiated on one surface of the light wavelength conversion sheet, and the backlight device is passed through the other surface of the light wavelength conversion sheet. The luminance of light emitted from the light emitting surface (surface of the second prism sheet) is measured from the thickness direction of the light wavelength conversion sheet using a spectral radiance meter (product name “CS2000”, manufactured by Konica Minolta). The measurement was performed at an angle of 1 °.

  Subsequently, the light wavelength conversion sheet before the heat resistance test was removed from the backlight device, and a heat resistance test was performed on the light wavelength conversion sheet by leaving the light wavelength conversion sheet in an environment of 80 ° C. for 500 hours. And the light wavelength conversion sheet | seat after a heat resistance test was integrated in the said backlight apparatus similarly to the above. In this state, as described above, blue light is irradiated on one surface of the light wavelength conversion sheet, and the light emitting surface of the backlight device (the surface of the second prism sheet) is passed through the other surface of the light wavelength conversion sheet. ) Was measured from the thickness direction of the light wavelength conversion sheet using a spectral radiance meter (product name “CS2000”, manufactured by Konica Minolta) at a measurement angle of 1 °.

From these measured luminances, the maintenance ratio of the luminance after the heat resistance test with respect to the luminance before the heat resistance test was determined. The luminance maintenance factor is A, the luminance maintenance factor is A, the luminance of light emitted from the light emitting surface of the backlight device before the heat resistance test is B, and the luminance of light emitted from the light emitting surface of the backlight device after the heat resistance test. Was determined by the following formula.
A = C / B × 100

<Spot-like luminance defect evaluation>
Using the above backlight device incorporating the light wavelength conversion sheet after the heat resistance test according to the above examples and comparative examples, whether there is a point-like luminance defect on the light emitting surface at the time of light emission in the backlight device. It was visually observed and evaluated. The evaluation criteria were as follows.
○: No dot-like luminance defect was confirmed.
Δ: Several point-like luminance defects were confirmed.
X: Many point-like brightness | luminance defects were confirmed.

<Measurement of degradation width of peripheral edge of optical wavelength conversion sheet>
Using the above backlight device incorporating the light wavelength conversion sheet after the heat resistance test according to the examples and comparative examples, the luminance distribution on the light emitting surface at the time of light emission in the backlight device is determined from the thickness direction of the light wavelength conversion sheet. Measurement was performed using a 2D color luminance meter (product name “UA-200”, manufactured by Topcon Technohouse Co., Ltd.). Then, from the measured luminance distribution of the light emitting surface, the position of the light emitting surface where the luminance is 80% with respect to the luminance of the central portion of the light emitting surface (luminance 80% position) is obtained, and is closest to the luminance 80% position on the light emitting surface. The shortest distance from the edge to the 80% luminance position was determined. And this shortest distance was calculated | required about 20 places at random, and the average value of these 20 shortest distances was made into the degradation width of the peripheral part of a light wavelength conversion sheet.

The results are shown in Tables 1 and 2.

  The results will be described below. As can be seen from Table 1 and Table 2, in the light wavelength conversion sheets according to Examples 1 to 9, since monofunctional thiol compounds are used, the light according to Comparative Examples 1, 4, and 7 not using thiol compounds. Compared to the light wavelength conversion sheets according to Comparative Examples 2, 3, 5, 6, 8, and 9 using the wavelength conversion sheet and the polyfunctional thiol compound, the luminance maintenance rate was high. Moreover, in the light wavelength conversion sheet | seat which concerns on Example 10, since the monofunctional thiol compound is used, the light wavelength conversion sheet | seat which concerns on the comparative example 10 which does not use the thiol compound, and the comparative example 11 which used the polyfunctional thiol compound Compared with the light wavelength conversion sheet according to, 12, the luminance maintenance rate was high. This is because the heat resistance of the light wavelength conversion compositions 1 to 7 and the cured product thereof is high, and the monofunctional thiol compound can suppress the deterioration of the quantum dot, and moreover, the deterioration suppression effect of the quantum dot than the polyfunctional thiol compound. Means high.

  In the light wavelength conversion sheets according to Examples 1 to 9 and Comparative Examples 1 to 9, since no barrier member was used, no dotted luminance defect was confirmed. Moreover, in the light wavelength conversion sheet | seat which concerns on Example 10, although the barrier member was used, since the monofunctional thiol compound was used, the dotted | punctate brightness | luminance defect was not confirmed. On the other hand, the point-like brightness | luminance defect was confirmed in the comparative examples 11 and 12 using the light wavelength conversion sheet | seat and the polyfunctional thiol compound which concern on the comparative example 10 which does not use the thiol compound. This means that the monofunctional thiol compound can suppress the deterioration of the quantum dots and has a higher effect of suppressing the deterioration of the quantum dots than the polyfunctional thiol compound.

  In the light wavelength conversion sheets according to Examples 1 to 10, a monofunctional thiol compound is used, and in the light wavelength conversion sheets according to Comparative Examples 2, 3, 5, 6, 8, 9, 11, and 12, Since the functional thiol compound was used, the deterioration of the peripheral portion was suppressed. This means that the monofunctional thiol compound and the polyfunctional thiol compound have an effect of suppressing deterioration of the quantum dots. On the other hand, even in the light wavelength conversion sheets according to Comparative Examples 1, 4, and 7 that did not use the monofunctional thiol compound or the polyfunctional thiol compound, the result of the deterioration of the peripheral portion was 0 mm. Because the wavelength conversion layer was exposed, the quantum dots deteriorated overall after the heat resistance test, and there was almost no difference in luminance between the peripheral portion and the central portion. In the light wavelength conversion sheet according to Comparative Example 10, deterioration of the central portion was relatively suppressed by the barrier member, but deterioration of the peripheral portion was not suppressed.

  The total haze value of the light wavelength conversion sheet according to Example 1 is 98.9%, the internal haze value is 96.7%, and the external haze value is 2.2%. The haze value was 99.3%, the internal haze value was 99.3%, and the external haze value was 0%. In both light wavelength conversion sheets, the external haze value is smaller than the internal haze value, so both have high brightness regardless of before and after the durability test, but the light wavelength conversion sheet according to Example 1 and Example When the light wavelength conversion sheet according to 2 was compared, the light wavelength conversion sheet according to Example 2 had higher brightness regardless of before and after the heat resistance test. This is because the light wavelength conversion sheet according to Example 2 contains alumina particles as light scattering particles, and therefore the internal haze value of the light wavelength conversion sheet according to Example 2 is the same as that of the wavelength conversion sheet according to Example 1. This is because it is larger than the internal haze value, thereby reducing the external haze value. Therefore, it was confirmed that by adding light scattering particles to the light wavelength conversion sheet and further increasing the internal haze value, the external haze value can be further reduced, thereby further improving the light wavelength conversion efficiency. . In addition, the total haze value, internal haze value, and haze value in the light wavelength conversion sheet were measured as follows. First, using a haze meter (product name “HM-150”, manufactured by Murakami Color Research Laboratory), all haze values of the light wavelength conversion sheet were measured according to JIS K7136. Thereafter, a triacetylcellulose base material (product name “Panaclean PD-S1”, manufactured by Panac Co., Ltd.) having a thickness of 25 μm is formed on both surfaces of the light wavelength conversion sheet via a transparent optical adhesive layer (product name “Panaclean PD-S1”, manufactured by Panac Corporation). TD60UL "(manufactured by FUJIFILM Corporation) was pasted. Thereby, the uneven shape of the surface in the light wavelength conversion sheet was crushed, and the surface of the light wavelength conversion sheet became flat. In this state, the haze value was measured according to JIS K7136 using a haze meter (product name “HM-150”, manufactured by Murakami Color Research Laboratory) to determine the internal haze value. And the external haze value was calculated | required by subtracting an internal haze value from all the haze values. Note that the transparent optical adhesive layer and the triacetylcellulose base material may also affect the internal haze value and external haze value of the light wavelength conversion sheet, but when the internal scattering of the light wavelength conversion sheet is extremely large, The influence on the internal haze value and external haze value is extremely small and can be ignored. Further, when the internal scattering of the light wavelength conversion sheet is extremely large, the internal haze value may be the same as the total haze value, so the external haze value may be 0%.

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

10, 20, 30, 40, 50, 60 ... light wavelength conversion sheets 11, 154, 170 ... light wavelength conversion member 16 ... binder resin 17 ... quantum dots 18 ... light scattering particles 19 ... coating film 70 ... image display device 80 , 130, 140, 160 ... Backlight device 120 ... Display panel

Claims (13)

A light wavelength conversion composition comprising:
A light wavelength conversion composition comprising a quantum dot and a compound having one thiol group in the molecule.   The light wavelength conversion composition of Claim 1 whose content of the said compound is 5 mass% or more with respect to the total solid content mass of the said light wavelength conversion composition.   The light wavelength conversion composition according to claim 1, further comprising a polymerizable compound.   The quantum dot includes a core made of a first semiconductor compound, a shell covering the core and made of a second semiconductor compound different from the first semiconductor compound, and a ligand bonded to the surface of the shell. The light wavelength conversion composition according to claim 1.   The light wavelength conversion composition according to claim 1, further comprising light scattering particles.   The light wavelength conversion member which consists of hardened | cured material of the light wavelength conversion composition of Claim 3.   The light wavelength conversion member according to claim 6 whose content of sulfur element in said light wavelength conversion member measured by fluorescent X-ray analysis is 0.5 mass% or more. A light wavelength conversion sheet,
An optical wavelength conversion sheet comprising the optical wavelength conversion member according to claim 6, wherein the optical wavelength conversion member is formed in a layer shape.   The light wavelength conversion sheet according to claim 8, further comprising an optical member disposed on at least one surface side of the light wavelength conversion member and integrated with the light wavelength conversion member. The light wavelength conversion sheet according to claim 8, wherein the light wavelength conversion sheet has a water vapor transmission rate of 0.1 g / (m ² · 24 h) or more at 40 ° C. and a relative humidity of 90%. The light wavelength conversion according to claim 8, wherein the light wavelength conversion sheet has an oxygen permeability of 0.1 cm ³ / (m ² · 24h · atm) or more at 23 ° C and a relative humidity of 90%. Sheet. A light source;
A backlight device comprising: the light wavelength conversion member according to claim 3 or the light wavelength conversion sheet according to claim 8 that receives light from the light source. The backlight device according to claim 12,
An image display device comprising: a display panel disposed on a light output side of the backlight device.

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