JP7069543B2 - Light wavelength conversion composition, light wavelength conversion member, light wavelength conversion sheet, backlight device, and image display device - Google Patents

Description

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

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

Currently, in order to improve color reproducibility, it is being 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 the light emitted by the quantum dots mainly depends on the particle size of the quantum dots. Therefore, in a backlight device incorporating an optical wavelength conversion sheet, various colors can be reproduced while using a light source that projects light in a single wavelength range. For example, when a light source that emits blue light is used, the light wavelength conversion sheet can also absorb blue light and emit green light and red light. Since the backlight device incorporating such an optical wavelength conversion sheet is excellent in color purity, the image display device using this backlight device has excellent color reproducibility.

Japanese Unexamined Patent Publication No. 2015-11518

In the optical wavelength conversion sheet, quantum dots are deteriorated by moisture and oxygen, and the luminous efficiency may decrease. Therefore, barrier members for suppressing the transmission of moisture and oxygen are provided on both sides of the optical wavelength conversion member. It is 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 a reliability test normally performed in a backlight device, a heat resistance test in which the product is left in an environment of 80 ° C. for 500 hours and a heat resistance test in which the product is left in an environment of 60 ° C. and a relative humidity of 90% for 500 hours. Therefore, it is desired that each member of the backlight device meets the criteria for this heat resistance test and moisture heat resistance test. However, when a heat resistance test or a moisture heat resistance test is performed on an optical wavelength conversion sheet having the above structure, there is a problem that the quantum dots are deteriorated and the brightness is lowered.

Further, in the optical wavelength conversion sheet provided with the barrier member, when a heat resistance test or a moisture heat resistance test is performed, pinholes or cracks are likely to occur in the barrier member. When pinholes or cracks occur in the barrier member, moisture or oxygen may enter from there, deteriorating some quantum dots, and causing spot-like reduced brightness (luminance defects) in the optical wavelength conversion sheet. There is. This punctate luminance defect is more easily visible than in the case where the quantum dots are deteriorated as a whole and the luminance is uniformly lowered. Further, at present, it is desired to further reduce the thickness and manufacturing cost of the optical wavelength conversion sheet. For these reasons, it is currently being considered not to use a barrier member. However, since the current optical wavelength conversion member does not have a function of protecting the quantum dots from moisture and oxygen, the quantum dots deteriorate unless the barrier member is used.

The present invention has been made to solve the above problems. That is, it is an object of the present invention to provide a light wavelength conversion composition and a light wavelength conversion member having excellent heat resistance and moisture heat resistance. Further, an optical wavelength conversion sheet having excellent heat resistance and moisture resistance, the barrier member can be omitted, or even when the barrier member is used, the punctate luminance defect can be suppressed, such an optical wavelength conversion member. Alternatively, it is an object of the present invention to provide a backlight device and an image display device provided with an optical wavelength conversion sheet.

As a result of diligent research on the above-mentioned problems, the present inventors have found that the light wavelength conversion composition contains a carboxylic acid and the light wavelength conversion composition has a predetermined acid value, so that the light wavelength conversion composition has excellent heat resistance. And a light wavelength conversion composition and a light wavelength conversion member having moisture heat resistance are obtained, and when a light wavelength conversion sheet is formed using this light wavelength conversion member, it has excellent heat resistance and moisture heat resistance, and also has excellent heat resistance and heat resistance. It has been found that the barrier member can be omitted, or even when the barrier member is used, the point-like brightness defect can be suppressed. The present invention has been completed based on such findings.

According to one aspect of the present invention, the light wavelength conversion composition is a light wavelength conversion composition containing quantum dots and a carboxylic acid, and the acid value of the light wavelength conversion composition exceeds 10 mgKOH / g. Is provided.

In the light wavelength conversion composition, the carboxylic acid may have a polymerizable functional group.

The light wavelength conversion composition may further contain a polymerizable compound.

In the optical wavelength conversion composition, the quantum dots form 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 the shell. It may contain a ligand bound to the surface.

The light wavelength conversion composition may further contain light scattering particles.

According to another aspect of the present invention, there is provided a light wavelength conversion member made of a cured product of the light wavelength conversion composition.

According to another aspect of the present invention, there is provided a light wavelength conversion sheet, which includes the above-mentioned light wavelength conversion member and in which the light wavelength conversion member is formed in a layered manner.

The optical wavelength conversion sheet may further include an optical member arranged on at least one surface side of the optical wavelength conversion member and integrated with the optical wavelength conversion member.

The water vapor transmittance at 40 ° C. and 90% relative humidity in the light wavelength conversion sheet may be 0.1 g / ( ^m 2.24 h) or more.

The oxygen transmittance of the light wavelength conversion sheet at 23 ° C. and 90% relative humidity may be 0.1 cm ³ / ( ^m 2.24 h · atm) or more.

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

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

According to the light wavelength conversion composition of one aspect of the present invention, since the light wavelength conversion composition contains a carboxylic acid and the light wavelength conversion composition exceeds 10 mgKOH / g, the light wavelength conversion composition has excellent heat resistance and moist heat resistance. Objects and light wavelength conversion members can be provided. Further, according to another aspect of the present invention, since the light wavelength conversion sheet is formed by using this light wavelength conversion member, it has excellent heat resistance and moisture heat resistance, and the barrier member can be omitted or a barrier. It is possible to provide an optical wavelength conversion sheet capable of suppressing point-shaped luminance defects even when a member is used. Further, according to another aspect of the present invention, it is possible to provide a backlight device and an image display device including such a light wavelength conversion member and a light wavelength conversion sheet.

It is a schematic block diagram of the light wavelength conversion sheet which concerns on embodiment. It is a figure which shows the operation of the light wavelength conversion sheet which concerns on embodiment. It is a schematic block diagram of another light wavelength conversion sheet which concerns on embodiment. It is a schematic block diagram of another light wavelength conversion sheet which concerns on embodiment. It is a schematic block diagram of another light wavelength conversion sheet which concerns on embodiment. FIG. 5 is a cross-sectional view taken along the line I-I of the optical wavelength conversion sheet of FIG. It is a schematic block diagram of another light wavelength conversion sheet which concerns on embodiment. It is a schematic block diagram of another light wavelength conversion sheet which concerns on embodiment. It is a figure which shows typically the manufacturing process of the optical wavelength conversion sheet which concerns on embodiment. It is a figure which shows typically the manufacturing process of the optical wavelength conversion sheet which concerns on embodiment. It is a schematic block diagram of the image display apparatus including the backlight apparatus which concerns on embodiment. It is a perspective view of the lens sheet shown in FIG. FIG. 2 is a cross-sectional view taken along the line II-II of the lens sheet of FIG. It is a schematic block diagram of the other backlight apparatus which concerns on embodiment. It is a schematic block diagram of the other backlight apparatus which concerns on embodiment. It is a schematic block diagram of the light source shown in FIG. It is a schematic block diagram of the other backlight apparatus which concerns on embodiment. It is an enlarged view near the light entry surface of the optical plate shown in FIG.

Hereinafter, the light wavelength conversion composition, the light wavelength conversion member, the light wavelength conversion sheet, the backlight device, and the image display device according to the embodiment of the present invention will be described with reference to the drawings. In the present specification, terms such as "sheet" and "film" are not distinguished from each other based only on the difference in designation. Therefore, for example, "sheet" is used in the sense of including a member that can also be called a film, and "film" is used in the sense of including a member that can also be called a sheet. FIG. 1 is a schematic configuration diagram of an optical wavelength conversion sheet according to the present embodiment, FIG. 2 is a diagram showing the operation of the optical wavelength conversion sheet according to the present embodiment, and FIGS. 3 to 5, 7, and 8 show the operation of the optical wavelength conversion sheet. Is a schematic configuration diagram of another light wavelength conversion sheet according to the present embodiment, FIG. 6 is a cross-sectional view of the light wavelength conversion sheet of FIG. 5 along the I-I line, and FIGS. 9 and 10 are the present embodiment. It is a figure which shows typically the manufacturing process of the light wavelength conversion sheet which concerns on a form.

<<< Light wavelength conversion composition >>>
The optical wavelength conversion composition is a composition for converting the wavelength of a part of the incident light into another wavelength and emitting the other part of the incident light and the wavelength-converted light. The optical wavelength conversion composition comprises quantum dots and a carboxylic acid. The light wavelength conversion composition may be used in the state of the composition, or may be used in the state of the light wavelength conversion member which is a cured product by curing the light wavelength conversion composition. As used herein, the "light wavelength conversion member" is a member substantially made of a cured product of the light wavelength conversion composition. Here, the above-mentioned "substantially" means that the light wavelength conversion member may contain a little other substance or the like in addition to the cured product of the light wavelength conversion composition. The light wavelength conversion member may be a member made of only a cured product of the light wavelength conversion composition. When forming the 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 also contain additives and solvents.

The light wavelength conversion composition has an acid value of more than 10 mgKOH / g. The lower limit of the acid value of the light wavelength conversion composition is preferably 20 mgKOH / g or more. As used herein, the term "acid value" means the number of mg of potassium hydroxide required to neutralize the acid component contained in 1 g of the light wavelength conversion composition.

The acid value can be measured by an indicator titration method using an alkaline titration solution. Specifically, the acid value can be obtained as follows. The acid value shall be the arithmetic mean value of the values obtained by measuring three times.
(I) Approximately 0.1 to 10 g of the light wavelength conversion composition is precisely weighed and placed in an Erlenmeyer flask, followed by a neutral methanol / acetone solution [a mixture of acetone and methanol in a ratio of 1: 1 (volume ratio)]. In addition, it dissolves.
(Ii) Add a few drops of a phenolphthalein indicator and titrate with a 0.1 mol / L potassium hydroxide titration solution. The end point of neutralization is when the indicator has a slight red color for 30 seconds.
(Iii) Determined using the following equation.
Acid value (mgKOH / g) = (A × f × 5.61) / S
In the formula, A is the mL number of the 0.1 mol / L potassium hydroxide titration solution, f is the titer of the 0.1 mol / L potassium hydroxide titration solution, and S is the sampling of the optical wavelength conversion composition. The amount (g).

The viscosity of the light wavelength conversion composition is preferably 10 mPa · s or more and 10,000 mPa · s or less. If the viscosity of the light wavelength conversion composition is less than 10 mPa · s, it may be difficult to form a sufficient film thickness, and if it exceeds 10,000 mPa · s, when the light wavelength conversion composition is applied, it may be difficult to form a sufficient film thickness. It becomes difficult to apply and the leveling property may deteriorate. 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 10000 mPa · s or less.

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

Specifically, the energy band gap of quantum dots increases as the particle size decreases. That is, as the crystal size becomes smaller, the emission of the quantum dots shifts to the blue side, that is, to the high energy side. Therefore, by changing the particle size of the quantum dot, the emission wavelength can be adjusted over the entire wavelength of the spectrum in the ultraviolet region, the visible region, and the infrared region. For example, when the quantum dot is composed of CdSe / ZnS described later, blue light is emitted when the particle diameter of the quantum dot is 2.0 nm or more and 4.0 nm or less, and the particle diameter of the quantum dot is 3.0 nm. When the particle size is 6.0 nm or less, green light is emitted, and when the particle size of the quantum dots is 4.5 nm or more and 10.0 nm or less, red light is emitted. In the above, the range of the particle size of the quantum dot emitting blue light and the particle size of the quantum dot emitting green light partially overlaps, and the particle size of the quantum dot emitting green light and the red light are overlapped. The range of the particle size of the emitted quantum dots overlaps in part, but even if the quantum dots have the same particle size, the emission color may differ depending on the size of the core of the quantum dots, so there is no contradiction. It's not something to do.

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

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

Quantum dots are 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 done.

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

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

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

The ligand is for stabilizing unstable quantum dots. Examples of the ligand include sulfur compounds such as thiol, phosphorus compounds such as phosphine compounds or phosphine oxides, nitrogen compounds such as amines, and carboxylic acids. A carboxylic acid may be used as the ligand for the quantum dots, but even in this case, the amount of the carboxylic acid as the ligand is extremely small, so that the optical wavelength conversion composition depends only on the carboxylic acid as the ligand. The acid value of the product does not exceed 10 mg / KOH.

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 any other shape. When the shape of the semiconductor nanoparticles is not spherical, the particle diameter of the semiconductor nanoparticles can be a true spherical value having the same volume.

Information such as the particle size, average particle size, shape, and dispersed state of the 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 the average value of the diameters of the 20 quantum dots measured by observation with a transmission electron microscope or a scanning transmission electron microscope. Further, since the emission color of the quantum dot changes depending on the particle diameter, it is also possible to obtain the particle diameter of the quantum dot by confirming the emission color of the quantum dot. Further, the crystal structure and crystallite size of the quantum dots can be known by X-ray crystal diffraction (XRD). Furthermore, information on the particle size of quantum dots and the like can be obtained from the ultraviolet-visible (UV-Vis) absorption spectrum.

The content of the quantum dots with respect to the total solid content mass of the optical 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 the quantum dots is less than 0.01% by mass, sufficient emission intensity may not be obtained, and if the content of the quantum dots exceeds 2% by mass, sufficient transmitted light of excitation light may be obtained. There is a risk that strength will not be obtained.

<< Carboxylic acid >>
The carboxylic acid used in the present invention is a compound containing at least one carboxyl group. The carboxylic acid may contain two or more carboxyl groups, or may contain a functional group other than the carboxyl group.

Examples of the functional group other than the carboxyl group include a polymerizable functional group. Examples of the polymerizable functional group include ethylenically unsaturated groups such as (meth) acryloyl group, vinyl group and allylic group. That is, the carboxylic acid may be an unsaturated carboxylic acid. When the carboxylic acid contains a polymerizable functional group, it can be polymerized with the polymerizable compound and the carboxylic acid can be fixed in the binder resin. When the carboxylic acid contains a polymerizable functional group, the carboxylic acid may contain one or more polymerizable functional groups, but may contain two or more.

The weight average molecular weight of the carboxylic acid is preferably 150 or more and 50,000 or less from the viewpoint of being difficult to volatility, having excellent dispersibility, and being easy to work with. In the present specification, the "weight average molecular weight" is a value obtained by dissolving in a solvent such as tetrahydrofuran (THF) and converting into polystyrene by a conventionally known gel permeation chromatography (GPC) method. The lower limit of the weight average molecular weight of the carboxylic acid is more preferably 300 or more, and the upper limit is more preferably 10,000 or less.

The carboxyl group equivalent (weight average molecular weight / number of carboxyl groups) of the carboxylic acid is preferably 150 or more and 50,000 or less from the viewpoint of facilitating the presence of the carboxylic acid around the quantum dots. The lower limit of the carboxyl group equivalent of the carboxylic acid is more preferably 300 or more, and the upper limit is more preferably 10,000 or less.

Specific examples of the above carboxylic acid include ω-carboxy-polycaprolactone mono (meth) acrylate, monohydroxyethyl phthalate (meth) acrylate, 2-acryloyloxyethyl succinic acid, a reaction product of pentaerythritol and acrylic acid, and anhydrous succinic acid. Acid reactants include 3-buteneic acid, 10-undecenoic acid, n-octanoic acid, stearic acid, adipic acid, dodecanoic acid, 4,4'-dicarboxydiphenyl ether, octadecanoic acid and the like. Among these, ω-carboxy-polycaprolactone mono (meth) acrylate and 2-acryloyloxyethyl succinic acid are preferable from the viewpoint of fixing the carboxylic acid in the binder resin and facilitating the presence of the carboxylic acid around the quantum dots. ..

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

<< Polymerizable compound >>
The polymerizable compound (curable compound) is a polymerizable compound, and examples thereof include an ionizing radiation polymerizable compound (ionizing radiation curable compound) and a thermopolymerizable compound (thermocurable compound). Ionizing radiation as used herein includes visible light, as well as ultraviolet light, X-rays, electron beams, α-rays, β-rays, and γ-rays.

The content of the polymerizable compound with respect to the total solid content mass of the light wavelength conversion composition is preferably 30% by mass or more and 95% by mass or less, and preferably 50% by mass or more and 90% by mass or less. If the content of the polymerizable compound is less than 30% by mass, sufficient curability may not be obtained when forming the optical wavelength conversion member, and the content of the polymerizable compound exceeds 95% by mass. In addition, the effects of improving heat resistance and moisture heat resistance by the above carboxylic acid may not be sufficiently obtained. When the light wavelength conversion composition contains both an ionizing radiation-polymerizable compound and a heat-polymerizable compound described later, the above-mentioned content means the total content of the ionizing radiation-polymerizable compound and the heat-polymerizable compound. It shall be.

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

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

Examples of the ionizing radiation polymerizable monomer include a monomer containing a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate, and ethylene glycol di (meth) acrylate. , Diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, tetramethylene glycol di (meth) acrylate, trimethyl propantri (meth) acrylate, trimethyl ethanetri (meth). ) Acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, glycerol (meth) acrylate (Meta) acrylic acid esters such as, etc. may be mentioned.

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

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

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

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

An epoxy compound is a compound having one or more epoxy groups in the molecule. The epoxy compound is not particularly limited, but for example, bisphenol A type epoxy compound, bisphenol F type epoxy compound, bisphenol S type epoxy compound, biphenyl type epoxy compound, fluorene type epoxy compound, novolak phenol type epoxy compound, cresol novolac type epoxy. Aromatic compounds such as compounds and modified products thereof, or alkylene glycol diglycidyl ethers such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether or 1,6-hexanediol diglycidyl ether, glycerin or an alkylene oxide adduct thereof. Polyglycidyl ether of polyhydric alcohol such as di or triglycidyl ether, diglycidyl ether of polyethylene glycol or its alkylene oxide adduct, polyalkylene glycol diglycidyl ether such as diglycidyl ether of polypropylene glycol or its alkylene oxide adduct, And aliphatic systems such as alkylene oxide. Here, examples of the alkylene oxide include aliphatic epoxy compounds such as ethylene oxide and propylene oxide, 3', 4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, 3,4-epoxycyclohexylmethylmethacrylate and the like. Examples thereof include an alicyclic epoxy compound containing one or more epoxy groups and one or more ester groups in the molecule. Among these, alicyclic epoxy compounds such as 3', 4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate and 3,4-epoxycyclohexylmethylmethacrylate are preferable in terms of adhesive strength and curability. ..

<< Polymerization Initiator >>
A polymerization initiator is a component that is decomposed by light or heat to generate radicals or ionic species to initiate or proceed with the polymerization (crosslinking) of a polymerizable compound. Examples of the polymerization initiator include a photopolymerization initiator (for example, a photoradical polymerization initiator, a photocationic polymerization initiator, a photoanionic polymerization initiator), a thermal polymerization initiator (for example, a thermal radical polymerization initiator, a thermal cationic polymerization initiator). , Thermal anion polymerization initiator), or mixtures thereof.

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

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

Examples of the photocationic polymerization initiator include aromatic diazonium salts, aromatic iodonium salts, and aromatic sulfonium salts. Examples of commercially available photocationic polymerization initiators include ADEKA PTOMER SP-150 and ADEKA PTOMER SP-170 (both manufactured by ADEKA).

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

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

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

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

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

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

<< 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, and more preferably 50 times or more and 1000 times or less the average particle size of the quantum dots. If the average particle size of the light-scattering particles is less than 20 times the average particle size of the quantum dots, sufficient light-scattering performance may not be obtained in the light wavelength conversion member, and the average particle size of the light-scattering particles becomes high. If it exceeds 2000 times the average particle size of the quantum dots, the number of light-scattering particles will decrease even if the amount added is the same, so the number of scattering points may decrease and a sufficient light-scattering effect may not be obtained. .. The average particle size of the light-scattering particles can be measured by the same method as the above-mentioned average particle size of the quantum dots.

Further, the average particle diameter of the light-scattering particles is preferably 1/300 or more and 1/20 or less, and more preferably 1/200 or more and 1/30 or less of the average film thickness of the light wavelength conversion member described later. preferable. If the average particle size of the light-scattering particles is less than 1/300 of the average film thickness of the light-scattering member, sufficient light-scattering performance may not be obtained in the light-scattering member, and the average of the light-scattering particles. If the particle size exceeds 1/20 of the average film thickness of the light wavelength conversion member, the ratio of light scattering particles to the light wavelength conversion member decreases even if the amount added is the same, so that the number of scattering points is sufficiently reduced. No light scattering effect can be obtained.

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

The shape of the light-scattering particles is not particularly limited, and for example, spherical (true spherical, substantially true spherical, elliptical spherical, etc.), polyhedral, rod-shaped (cylindrical, prismatic, etc.), flat plate, flaky, and indefinite shape. And so on. 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.

The silane coupling agent is a group consisting of a vinyl group, an epoxy group, a styryl group, a methacrylic group, an acrylic group, an amino group, a ureido group, a thiol group, a sulfide group and an isocyanate group, although it depends on the type of the polymerizable compound used. It is possible to use one having one or more reactive functional groups selected from. When a compound having a (meth) acryloyl group is used as the polymerizable compound, the coupling agent is at least one reactive 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 functional group. 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 polymerizable compound, the silane coupling agent is an epoxy group, an isocyanate group, a thiol group and an amino. It is preferable to have at least one reactive functional group selected from the group consisting of groups.

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 rate of change in brightness during the heat resistance test and before and after the moisture heat resistance test should be small. Inorganic particles are preferable because they can appropriately scatter the incident light on the light wavelength conversion sheet and can suitably improve the light wavelength conversion efficiency with respect to the incident light.

The inorganic particles include an aluminum-containing compound such as Al ₂ O ₃ , a zirconium-containing compound such as ZrO ₂ , a tin-containing compound such as antimony-doped tin oxide (ATO) and indium tin oxide (ITO), and magnesium such as MgO and MgF ₂ . At least one compound selected from the group consisting of compounds, titanium-containing compounds such as TiO ₂ and BaTiO ₃ , antimony-containing compounds such as Sb ₂ O ₅ , silicon-containing compounds such as SiO ₂ , and zinc-containing compounds such as ZnO. Particles can be mentioned. Since these inorganic particles can increase the difference in refractive index from the binder resin, they are also preferable from the viewpoint of obtaining a large Mie scattering intensity. Since the light wavelength conversion efficiency with respect to the incident light can be more preferably improved by the light wavelength conversion sheet 10, 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 content 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, me scattering occurs. Since it becomes difficult, there is a possibility that the light scattering effect cannot be sufficiently obtained, and further, there is a possibility that the processability is deteriorated because there are too many light scattering particles.

<< Additives >>
The additive is not particularly limited, but a compound that suppresses oxidation and deterioration of quantum dots is preferable. Examples of the compound that suppresses oxidation and deterioration of quantum dots include phenol-based compounds, amine-based compounds, sulfur-based compounds, phosphorus-based compounds, hydrazine-based compounds, amide-based compounds, and hindered amine-based compounds. The additive may have a polymerizable functional group such as an ionizing radiation polymerizable functional group or a thermally polymerizable functional group.

<< Solvent >>
The solvent is not particularly limited, and examples thereof include 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 a part of the incident light into another wavelength and emits the other part of the incident light and the wavelength-converted light. be. The light wavelength conversion sheet 10 shown in FIG. 1 includes a layered light wavelength conversion member 11, light transmissive base materials 12 and 13 provided on both sides of the light wavelength conversion member 11, and light transmissive base materials 12 and 13. It is 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 10A and 10B of the light wavelength conversion sheet 10. The light wavelength conversion sheet 10 includes the light-transmitting base materials 12 and 13, but does not have the barrier layer, and therefore does not have the barrier member composed of the light-transmitting base material and the barrier layer. The light wavelength conversion sheet 10 has a structure of a light diffusion layer 14 / a light transmission base material 12 / a light wavelength conversion member 11 / a light transmission base material 13 / a light diffusion layer 15, but is a light wavelength conversion member. The structure of the optical wavelength conversion sheet is not particularly limited as long as it has.

In the optical wavelength conversion sheet 10, as shown in FIG. 2, when light is incident from the surface 10A of the optical wavelength conversion sheet 10, the light L1 incident on the quantum dots 17 in the optical wavelength conversion member 11 is emitted. It is converted into light L2 having a wavelength different from that of light L1 and emitted from the surface 10B. On the other hand, even when light is incident from the surface 10A, the light L1 passing between the quantum dots 17 in the optical wavelength conversion member 11 is emitted from the surface 10B without being wavelength-converted.

In the optical wavelength conversion sheet 10, the water vapor transmittance (WVTR: Water Vapor Transmission Rate) at 40 ° C. and 90% relative humidity may be 0.1 g / ( ^m 2.24 h) or more in the entire sheet. .. The water vapor permeability is a numerical value obtained by a method based on JIS K7129: 2008. The water vapor permeability can be measured using a water vapor permeability measuring device (product name "PERMATRAN-W3 / 31", manufactured by MOCON). The water vapor transmittance shall be the average value of the values obtained by measuring three times. Since the conventional light wavelength conversion sheet has a barrier member formed therein, the light wavelength conversion sheet 10 has a higher water vapor transmittance than the conventional light wavelength conversion sheet, that is, the light wavelength conversion sheet 10 has a higher water vapor transmittance. Moisture is more easily transmitted than the conventional light wavelength conversion sheet. 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 transmittance is the water vapor transmittance 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 in the entire sheet. May be 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). The oxygen permeability shall be the average value of the values obtained by measuring three times. Since the conventional light wavelength conversion sheet has a barrier member formed therein, the light wavelength conversion sheet 10 has a higher oxygen transmittance than the conventional light wavelength conversion sheet, that is, the light wavelength conversion sheet 10 has a higher oxygen transmittance. Compared to the conventional light wavelength conversion sheet, not only water but also oxygen is easily transmitted. Similar 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.

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

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

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

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

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

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

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

The ratio of the external haze value to the internal haze value (external haze value / internal haze value) in the optical wavelength conversion sheet 10 is preferably 0 or more and 0.1 or less, and more preferably 0 or more and 0.05 or less. .. If this ratio is within this range, the internal haze can sufficiently diffuse the light and excite the quantum dots multiple times.

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

The above definition of "Ra" shall be in accordance with JIS B0601: 1994. Ra can be measured using, for example, a surface roughness measuring instrument (product name "SE-3400", manufactured by Kosaka Laboratory Co., Ltd.). Ra is an arithmetic mean value obtained by randomly measuring 15 points on the surfaces 10A and 10B of the optical wavelength conversion sheet 10 where there is no visual abnormality (where there is no large foreign matter or scratches). ..

When a light wavelength conversion sheet 10 containing both quantum dots that convert blue light into green light and quantum dots that convert blue light into red light is irradiated with a light source that emits blue light, the transmitted light in the light wavelength conversion sheet. Of these, 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 or more and 2.0 or less. It is preferably 0.5 or more and 1.5 or less.

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

As used herein, "blue light" is light having a wavelength range of 380 nm or more and less than 480 nm, "green light" is light having a wavelength range of 480 nm or more and less than 590 nm, and "red light" is Light having a wavelength range of 590 nm or more and 750 nm or less. Further, the light intensity of each of the above lights can be measured using a spectral radiance meter (for example, product name "CS2000", manufactured by Konica Minolta Co., Ltd.).

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

The thickness of the optical wavelength conversion sheet 10 is determined by photographing a cross section of the optical wavelength conversion sheet 10 using a scanning electron microscope (SEM), measuring the thickness of the optical wavelength conversion sheet 10 at 20 points in the image of the cross section, and measuring the thickness thereof. The average value of the thicknesses at 20 points. In the measurement by SEM, it is preferable that the acceleration voltage is 30 kV and the magnification is 1000 to 7000 times.

<< Optical wavelength conversion member >>
The light wavelength conversion member is a cured product of the light wavelength conversion composition, and the light wavelength conversion composition in this case contains quantum dots, the above-mentioned carboxylic acid, and a polymerizable compound. The light wavelength conversion member 11 of the present embodiment is layered, but the shape of the light wavelength conversion member does not have to 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, it contains quantum dots 17, the carboxylic acid, and a binder resin 16 which is a cured product of the polymerizable compound. When the carboxylic acid has a polymerizable functional group, the carboxylic acid and the binder resin may be bonded by the polymerizable functional group of the carboxylic acid.

Whether or not the carboxylic acid is present in the light wavelength conversion member 11 can be confirmed by the same method as the method for confirming whether or not the carboxylic acid 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 range different from that of the first quantum dot 17A. Further, the light wavelength conversion member 11 shown in FIG. 1 further contains light scattering particles 18. By including the light scattering particles 18, the light wavelength conversion efficiency and the internal haze can be improved. The quantum dots 17, the carboxylic acid, and the light-scattering particles 18 included in the light wavelength conversion member 11 are the same as the quantum dots, the carboxylic acid, and the light-scattering particles described above, and thus the description thereof will be omitted here. It shall be.

The light wavelength conversion member 11 preferably has an acid value of more than 10 mgKOH / g. The acid value of the light wavelength conversion member 11 can be measured by composition analysis such as gas chromatography analysis, for example.

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

<Binder resin>
Since the binder resin 16 is a cured product of the above-mentioned 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. 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 Becke method, the minimum declination method, the declination analysis, the mode line method, the ellipsometry method and the like are used. can do. Further, the refractive index of the binder resin 16 in the light wavelength conversion member 11 is determined by, for example, 10 pieces of the binder resin 16 taken out from the light wavelength conversion member 11 by cutting out or the like, and the 10 pieces taken out by the Becke method. The refractive index of the binder resin 16 can be measured and obtained as an average value of 10 of the measured refractive indexes of the binder resin 16. Further, the refractive index of the light-scattering particles 18 is determined by, for example, taking out a fragment from the binder resin 16 in which a part of the surface of the light-scattering particles is exposed by cutting out from the light wavelength conversion member 11 and taking out the fragments. The refractive index of each of the 10 light-scattering particles 18 whose surface is exposed can be measured by the Becke method, and can be obtained as the average value of the 10 measured refractive indices of the light-scattering particles 18. In the Becke method, a refractive index standard solution having a known refractive index is used, the above-mentioned pieces are placed on a slide glass or the like, the refractive index standard solution is dropped onto the sample, and the pieces are immersed in the refractive index standard solution. Is observed by microscopic observation, and the emission line (Becke line) generated on the surface of the binder resin or light-scattering particles cannot be visually observed due to the difference in the refractive index between the surface of the binder resin or light-scattering particles and the refractive index of the refraction standard solution. Refraction index This is a method in which the refractive index of the standard liquid is used as the refractive index of the binder resin or the light-scattering particles. When the surface of the light-scattering particles is not exposed in the removed pieces, the surface of the light-scattering particles is covered with the binder resin, so that the binder resin existing around the light-scattering particles is used. There is no difference in refractive index. Therefore, by measuring the difference in refractive index from the binder resin existing around the light-scattering particles by the Becke method or the like, it is possible to determine whether or not a part of the surface of the light-scattering particles is exposed. .. In addition, the difference in refractive index between the binder resin and the light-scattering particles is measured using a phase-shift laser coherence microscope (phase-shift laser coherence microscope manufactured by FK Optical Research Institute, biluminum coherence microscope manufactured by Mizojiri Optical Co., Ltd., etc.). can do.

<< Light-transmitting substrate >>
The thicknesses of the light-transmitting substrates 12 and 13 are not particularly limited, but are preferably 10 μm or more and 300 μm or less. If the thickness of the light-transmitting base materials 12 and 13 is less than 10 μm, the assembly of the optical wavelength conversion sheet may be wrinkled or broken during handling, and if it exceeds 300 μm, the weight of the display and the thin film may be reduced. It may not be suitable for conversion. The more preferable lower limit of the thickness of the light-transmitting base materials 12 and 13 is 50 μm or more, and the more preferable upper limit is 200 μm or less.

The thickness of the light transmitting base materials 12 and 13 is the cross section of the light transmitting base materials 12 and 13 using a scanning electron microscope (SEM), a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM). Is taken, and the thicknesses of the light-transmitting substrates 12 and 13 are measured at 20 points in the image of the cross section, and the average value of the film thicknesses at the 20 points is used.

Examples of the constituent raw materials of the light-transmitting base materials 12 and 13 include polyester (for example, polyethylene terephthalate and polyethylene naphthalate), cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyether sulphon, and polysulphon. , Polypolymethylpentene, polyvinyl chloride, polyvinylacetal, polyetherketone, polymethylmethacrylate, polycarbonate, or thermoplastic resins such as polyurethane. Preferred examples of the constituent materials of the light-transmitting base materials 12 and 13 include polyester (for example, polyethylene terephthalate and polyethylene naphthalate).

The light-transmitting base materials 12 and 13 may be composed of a single base material, or may be a laminated base material composed of a plurality of base materials. Such a laminated base material may be composed of a plurality of layers composed of layers of the same type of constituent raw material, or may be composed of a plurality of layers composed of layers of different types of constituent raw materials, depending on the intended use. good.

<< Light diffusion layer >>
The light diffusion layers 14 and 15 have an uneven shape on the surface, and the uneven shape can diffuse the light incident on and emitted from the light wavelength conversion sheet 10. By providing the light diffusion layers 14 and 15, the light wavelength conversion efficiency of the light wavelength conversion sheet 10 can be further improved. The light diffusing layers 14 and 15 contain light scattering particles and a binder resin.

<Light scattering particles>
The light-scattering particles in the light-diffusing layers 14 and 15 are mainly for forming an uneven shape on the surface of the light-diffusing layers 14 and 15 and exhibiting a light-scattering function.

The average particle size of the light-scattering particles in the light diffusion layers 14 and 15 is preferably 10 times or more and 20,000 times or less the average particle size of the above-mentioned quantum dots 17, and more preferably 10 to 5000 times. 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-diffusing property may not be obtained in the light-diffusing layer, and the average particle size of the light-scattering particles may not be sufficient. If it exceeds 20,000 times the average particle size of the quantum dots, the light diffusion performance of the light diffusion layer becomes excellent, but the light transmission rate of the light diffusion layer tends to be significantly reduced. The average particle size of the light-scattering particles can be measured by the same method as the above-mentioned average particle size of the quantum dots.

Specifically, the average particle size of the light-scattering particles in the light diffusion layers 14 and 15 is preferably, for example, 1 μm or more and 30 μm or less, and more preferably 1 μm or more and 20 μm or less. If the average particle size of the light-scattering particles is less than 1 μm, the light wavelength conversion efficiency of the light wavelength conversion sheet may be insufficient, and the amount of the light-scattering particles added in order to obtain sufficient light diffusivity. Need to be increased. On the other hand, when the average particle size of the light-scattering particles exceeds 30 μm, the light diffusing performance becomes excellent, but the light transmittance of the light diffusing layer tends to be significantly reduced.

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

Since the shapes of the light-scattering particles in the light-diffusing layers 14 and 15 are the same as the shapes of the light-scattering particles 18 in the light wavelength conversion member 11, the description thereof will be omitted here. The light-scattering particles in the light-diffusing 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 bond can be realized by using light scattering particles surface-modified with a silane coupling agent. Since the silane coupling agent is the same as the silane coupling agent described in the section of light scattering particles in the light wavelength conversion member, the description thereof will be omitted here.

The light-scattering particles may be particles made of an organic material or particles made of an inorganic material. The organic material constituting the light-scattering particles is not particularly limited, and for example, polyester, polystyrene, melamine resin, (meth) acrylic resin, acrylic-styrene copolymer resin, silicone resin, benzoguanamine resin, benzoguanamine / formaldehyde condensation resin. , Polycarbonate, polyethylene, polyolefin and the like. Of these, crosslinked acrylic resin is preferably used. The inorganic material constituting the light diffusing particles is not particularly limited, and examples thereof include inorganic oxides such as silica, alumina, titania, tin oxide, antimony-doped tin oxide (ATO), and zinc oxide fine particles. Among them, silica and / or alumina are preferably used.

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

<< Other optical wavelength conversion sheets >>
As shown in FIG. 3, the optical wavelength conversion sheet may be an optical wavelength conversion sheet 20 having only the optical wavelength conversion member 11 (single-layer structure). Further, as shown in FIG. 4, the light wavelength conversion sheet may be a light wavelength conversion sheet 30 including a light wavelength conversion member 11 and a light transmissive base material 31 that supports the light wavelength conversion member 11. .. By providing the light transmissive base material 31, the intensity of the light wavelength conversion sheet can be increased as compared with the light wavelength conversion sheet 20.

<Light transmissive base material>
As the light-transmitting base material 31 of the light wavelength conversion sheet 30, the same light-transmitting base materials 12 and 13 can be used, so the description thereof will be omitted here.

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

<Optical member>
As used herein, the term "optical member" refers to optical properties (eg, polarization, photorefractiveness, light scattering, light reflectivity, light transmission, light absorption, photodiffraction, diversion, etc.). It means a member having, and is not particularly limited as long as it is a sheet (film) -shaped or plate-shaped member having optical characteristics. Examples of the optical member include an optical plate such as a lens sheet, a light guide plate and a light diffusing plate, a reflective polarizing separation sheet, a polarizing plate and the like. When the optical member sheets are provided on both sides of the optical wavelength conversion sheet, the optical members may be optical members having different optical characteristics. In this 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-transmitting base material 42 and a lens layer 43 provided on one surface of the light-transmitting base material 42. As shown in FIGS. 5 and 6, the lens layer 43 includes a sheet-shaped main body portion 44 and a plurality of unit lenses 45 arranged side by side on the light emitting side of the main body portion 44. The light-transmitting base material 42, the lens layer 43, the main body portion 44, and the unit lens 45 have the same configurations as the light-transmitting base material 101, the lens layer 102, the main body portion 103, and the unit lens 104, which will be described later. Therefore, the description is omitted here.

In the optical wavelength conversion sheet 40, the optical wavelength conversion member 11 and the optical member 41 are integrated by directly applying and curing the optical 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 to each other via an adhesive layer.

<< Other optical wavelength conversion sheets >>
As shown in FIG. 7, the optical wavelength conversion sheet may be an optical wavelength conversion sheet 50 including an optical wavelength conversion member 11 and overcoat layers 51 and 52 covering both sides of the optical wavelength conversion member 11. In the present embodiment, the overcoat layers 51 and 52 are formed on both surfaces of the light wavelength conversion member 11, but if the overcoat layer is formed on at least one surface of the light wavelength conversion member, the light wavelength conversion is performed. It does not have to be formed on both sides of the member 11. When the overcoat layer is provided on only one surface of the light wavelength conversion member, a light transmissive substrate may be provided on the other surface of the light wavelength conversion member.

<Overcoat layer>
The overcoat layers 51 and 52 are layers made of a resin that covers the surface of the light wavelength conversion member 11 and is formed by coating. Other layers such as a light diffusion layer may be formed on the overcoat layers 51 and 52.

The overcoat layers 51 and 52 are provided to prevent the light wavelength conversion member 11 from being directly exposed to the atmosphere. By providing such overcoat layers 51 and 52 on at least one surface of the light wavelength conversion member 11, the quantum dots 15 can be protected from moisture and oxygen, and the light transmissive substrate can be provided on the light wavelength conversion member 11. The thickness of the optical wavelength conversion sheet can be made thinner than that provided on at least one surface of 11.

The overcoat layers 51 and 52 may have some function other than the function of preventing the light wavelength conversion member 11 from being directly exposed to the atmosphere. Specifically, the overcoat layers 51 and 52 may be, for example, a layer having at least one of functions such as antiblocking property, light diffusing property, antistatic property, and antireflection property. When the overcoat layers 51 and 52 are layers having a function of preventing the light wavelength conversion member 11 from being directly exposed to the atmosphere and some other function, the overcoat layers 51 and 52 have some function. The material may be added.

The film thickness of the overcoat layers 51 and 52 is 0.1 μm or more and 100 μm or less from the viewpoint of preventing the light wavelength conversion member 11 from being directly exposed to the atmosphere and reducing the thickness of the light wavelength conversion sheet. Is preferable. The film thickness of the overcoat layer can be measured by the same method as the film thickness of the light wavelength conversion member 11. The lower limit of the film thickness of the overcoat layers 51 and 52 is more preferably 1 μm or more, and the upper limit is more preferably 50 μm or less.

The overcoat layers 51 and 52 preferably have a hardness of 10 μN or more for a vertical force and / or -5 μN or less for a horizontal force in a scratch test. When the overcoat layers 51 and 52 have such hardness, the overcoat layers 51 and 52 become a dense film, so that the ability to prevent the light wavelength conversion member 11 from exposure to the atmosphere is high. The vertical force and horizontal force in the scratch test are indented from the cross section of the overcoat layer to the inside of the overcoat layer using a nanoindentation device (product name "TI950 TriboIndenter", manufactured by HYSITRON). Corner: Ti037_110410 (12)) is pushed in by 50 nm, the depth is kept constant, and the average vertical force (load) and horizontal force measured when this indenter is moved horizontally at a moving speed of 4 μm / min for 30 seconds. The values were obtained respectively, and the average value of the five average values of the vertical force (5 times average value) and the average value of the five average values of the horizontal force (5 times average value) obtained by repeating this scratch test 5 times. And. The larger the value of the normal force and the smaller the value of the horizontal force, the higher the hardness of the overcoat layers 51 and 52. From the viewpoint of enhancing the ability to prevent the light wavelength conversion member 11 from exposure to the atmosphere, the normal force of the overcoat layers 51 and 52 in the scratch test is more preferably 15 μN or more, and the horizontal force is more preferably -8 μN or less. preferable.

The overcoat layers 51 and 52 are not particularly limited as long as they have the above hardness, but for example, a (meth) acrylate compound, an epoxy compound, a combination of isocyanate and a polyol, a metal alkoxide, a silicon-containing resin, a water-soluble polymer, and the like. Alternatively, it can be formed by using a composition for an overcoat layer containing a mixture thereof. Among these, the overcoat layers 51 and 52 are zinc acrylate, a hydrolysis product of alkoxysilane, polyvinyl alcohol, polysilazane, or any of these, from the viewpoint of preventing the light wavelength conversion member 11 from being directly exposed to the atmosphere. It is preferably formed using a composition for an overcoat layer containing a mixture.

In the optical wavelength conversion sheets 20, 30, 40, and 50, the water vapor transmittance at 40 ° C. and 90% relative humidity may be 0.1 g / ( ^m 2.24 h) or more in the entire sheet. In the optical wavelength conversion sheets 20, 30, 40, and 50, even if the oxygen transmittance of the entire sheet at 23 ° C. and 90% relative humidity is 0.1 cm ³ / ( ^m 2.24 h · atm) or more. good. The water vapor transmittance at 40 ° C. and 90% relative humidity in the light wavelength conversion sheets 20, 30, 40, and 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 optical wavelength conversion sheets >>
The optical wavelength conversion sheet may be an optical wavelength conversion sheet 60 as shown in FIG. In this case, the water vapor transmittance and the oxygen transmittance of the light wavelength conversion sheet 60 do not have to be within the above-mentioned range.

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 sides of the light wavelength conversion member 11, and the light wavelength conversion member 11 side of the barrier members 61 and 62. It is provided with light diffusion layers 13 and 14 provided on the side opposite to the surface. In the light wavelength conversion sheet 60, the surfaces of the light diffusion layers 13 and 14 constitute the surfaces 60A and 60B of the light wavelength conversion sheet 60.

<Barrier member>
The barrier members 61 and 62 are members for suppressing the permeation of water and oxygen to protect the quantum dots 17 from water and oxygen. Here, the "barrier member" in the present specification means that the member alone has a water vapor transmittance of less than 0.1 g / ( ^m 2.24 h) at 40 ° C. and a relative humidity of 90%, and is 23 ° C. and a relative humidity. It shall mean a member having an oxygen permeability of less than 0.1 cm ³ / ( ^m 2.24 h · atm) at 90%. The barrier member includes not only a single-layer structure film but also a multi-layer structure film. By installing the barrier members 61 and 62 in a state of sandwiching the optical wavelength conversion member 11, the durability of the quantum dots 17 can be further improved. The 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 permeation of water and oxygen. It includes barrier layers 63 and 64 having a function.

The water vapor transmission rate (WVTR: Water Vapor Transmission Rate) of the barrier members 61 and 62 shall be 1.0 × 10 ⁻² g / ( ^m 2.24 h) or less under the conditions of 40 ° C. and 90% relative humidity. Is more preferable. The water vapor permeability can be measured using a water vapor permeability measuring device (product name "PERMATRAN-W3 / 31", manufactured by MOCON).

The oxygen transmission rate (OTR) of the barrier members 61 and 62 is 1.0 × 10 ⁻² cm ³ / ( ^m 2.24 h · atm) or less under the conditions of 23 ° C. and 90% relative humidity. It is more preferable to have. 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 thin-film vapor deposition layer having a function of suppressing the permeation of water and oxygen. The thin-film deposition layer is a layer formed by a vapor deposition method such as a physical vapor deposition (PVD) method such as a sputtering method or an ion plating method or a chemical vapor deposition (CVD) method. The thin-film deposition layer has the advantage that the barrier property can be enhanced.

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

The film thickness of the thin-film deposition layer is not particularly limited, but is preferably 0.01 μm or more and 1 μm or less. If the film thickness of the thin-film vapor deposition layer is less than 0.01 μm, the barrier performance of the thin-film deposition layer may be insufficient, and if it exceeds 1 μm, the barrier performance may be easily deteriorated due to cracks in the thin-film deposition layer. be. The more preferable lower limit of the thickness of the vapor-filmed layer is 0.03 μm or more, and the more preferable upper limit is 0.5 μm or less.

The film thickness of the thin-film deposition layer is determined by photographing the cross section of the optical wavelength conversion sheet 60 using a scanning electron microscope (SEM), measuring the film thickness of the vapor-film deposition film at 20 points in the image of the cross section, and measuring the film thickness at 20 points. The average value of the thickness. Further, the thin-film deposition layer may be a single layer or may be a stack of a plurality of layers. When a plurality of thin-film deposition layers are laminated, each layer constituting the thin-film deposition layer may be directly laminated or laminated.

<<< Manufacturing method of optical wavelength conversion sheet >>>
The optical wavelength conversion sheet 10 can be manufactured, for example, as follows. First, although not shown, a light-diffusing layer composition containing light-scattering particles and a polymerizable compound is applied to one surface of the light-transmitting base material 12, dried, and then coated with the light-diffusing layer composition. Form a film. Similarly, a coating film of the composition for a light diffusion layer is formed on one surface of the light-transmitting base material 13.

Next, the coating film of the composition for the light diffusion layer is cured by ionizing radiation irradiation or the like. As a result, as shown in FIG. 9A, the light diffusing layer 14 is formed on one surface of the light transmitting base material 12, and the light transmitting base material 12 with the light diffusing layer 14 is formed. Further, although not shown, the light transmissive base material 13 with the light diffusing layer 15 is formed in the same manner.

After forming the light-transmitting base material 13 with the light-diffusing layer 15, as shown in FIG. 9B, the side of the light-transmitting base material 13 with the light-diffusing layer 15 opposite to the surface on the light-diffusing layer 15 side. The light wavelength conversion composition containing quantum dots, the carboxylic acid, and the polymerizable compound and having an acid value of more than 10 mgKOH / g is applied to the surface of the surface, and dried to obtain a coating film 19 of the light wavelength conversion composition. Form.

After forming the coating film 19 of the light wavelength conversion composition, as shown in FIG. 10A, the surface of the light transmissive substrate 12 with the light diffusing layer 14 opposite to the surface on the light diffusing layer 14 side is the light wavelength. The light transmissive base material 12 with the light diffusing layer 14 is arranged on the coating film 19 of the light wavelength conversion composition so as to be in contact with the coating film 19 of the conversion composition. As a result, the coating film 19 of the light wavelength conversion composition is sandwiched between the light-transmitting base materials 12 and 13.

Then, as shown in FIG. 10B, the coating film 19 of the light wavelength conversion composition is irradiated with ionizing radiation or heat is applied to cure the polymerizable compound through the light transmissive substrate 12. The light wavelength conversion member 11 is formed, and the light wavelength conversion member 11 is integrated with the light transmitting base material 12 with the light diffusing layer 14 and the light transmitting base material 13 with the light diffusing layer 15. As a result, the optical wavelength conversion sheet 10 shown in FIG. 1 is obtained.

The optical wavelength conversion sheets 20, 30, and 50 can be manufactured, for example, as follows. First, a light wavelength conversion composition containing quantum dots, the above carboxylic acid, and a polymerizable compound and having an acid value of more than 10 mgKOH / g is applied onto a substrate (not shown), dried, and subjected to light wavelength conversion. Form a coating of the composition. Then, the light wavelength conversion member 11 is formed by irradiating the coating film with ionizing radiation or applying heat to cure the polymerizable compound. After that, the base material is peeled off from the light wavelength conversion member 11. As a result, the optical wavelength conversion sheet 20 shown in FIG. 3 is obtained. On the other hand, when the light transmissive base material 31 is used as the base material, the light wavelength conversion sheet 30 shown in FIG. 4 can be obtained by leaving the base material as it is without peeling it from the light wavelength conversion member 11. can get. In the light wavelength conversion sheet 50 shown in FIG. 7, the composition for the overcoat layer is applied to at least one surface of the light wavelength conversion sheet 20 to form a coating film of the composition for the overcoat layer, and this coating film is formed. Can be formed by curing. The light wavelength conversion sheet 50 can also be formed by the following method. First, the composition for the overcoat layer is applied to one surface of the two substrates to form a coating film of the composition for the overcoat layer. After forming the coating film, the coating film of each overcoat layer composition is irradiated with ionizing radiation or heated to form an overcoat layer. After forming the overcoat layer, the light wavelength conversion composition is applied onto the overcoat layer formed on one of the substrates to form a coating film of the light wavelength conversion composition. Next, the other base material is placed on the coating film of the light wavelength conversion composition so that the overcoat layer formed on the other base material is in contact with the coating film of the light wavelength conversion composition. Next, in this state, the coating film of the light wavelength conversion composition is irradiated with ionizing radiation or heated to form a light wavelength conversion member, and the light wavelength conversion member and the overcoat layer are integrated. Let me. Finally, when both substrates are peeled off, the optical wavelength conversion sheet 50 shown in FIG. 7 is obtained.

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

The light wavelength conversion sheet 60 is a barrier in which the light diffusion layers 14 and 15 are provided with the light transmitting base materials 12 and 13 and the barrier layers 63 and 64 formed on one surface of the light transmitting base materials 12 and 13. If it is formed on the members 61 and 62, it can be formed by the same process as the optical wavelength conversion sheet 10.

The optical wavelength conversion sheets 10, 20, 30, 40, 50, 60 can be used by incorporating them into a backlight device and an image display device. Hereinafter, an example in which the light wavelength conversion sheet 10 is incorporated into 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 the present embodiment, FIG. 12 is a perspective view of the lens sheet shown in FIG. 11, and FIG. 13 is a perspective view of the lens sheet of FIG. It is sectional drawing along the line II. 14, 15, and 17 are schematic configuration diagrams of other backlight devices according to the present embodiment, FIG. 16 is a schematic configuration diagram of a light source shown in FIG. 15, and FIG. 18 is a schematic configuration diagram of a light source. It is an enlarged view near the light source surface of an optical plate.

<<< Image display device >>>
The image display device 70 shown in FIG. 11 includes a backlight device 80 and a display panel 120 arranged on the light emitting 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 the display surface 70A.

The backlight device 80 illuminates the display panel 120 in a plane from the back surface side. The display panel 120 functions as a shutter that controls the 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 >>
The display panel 120 shown in FIG. 11 is a liquid crystal display panel, and is between the polarizing plate 101 arranged on the incoming light side, the polarizing plate 122 arranged on the light emitting side, and the polarizing plate 121 and the polarizing plate 122. It is provided with an arranged liquid crystal cell 103. The polarizing plates 121 and 122 decompose the incident light into two orthogonal linearly polarized light components (S-polarized and P-polarized) and vibrate in one direction (direction parallel to the transmission axis) (for example, P). It has a function of transmitting (polarized light) and absorbing a linearly polarized light component (for example, S-polarized light) that vibrates in the other direction (direction parallel to the absorption axis) orthogonal to the one direction.

The liquid crystal cell 123 is configured so that a voltage can be applied to each region forming one pixel. Then, the orientation 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 arranged on the incoming light side rotates its polarization direction by 90 ° when passing through the liquid crystal cell 123 to which a voltage is applied, while rotating the polarization direction by 90 °. 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 a voltage is applied to the liquid crystal cell 123, the linearly polarized light component vibrating in a specific direction transmitted through the polarizing plate 121 may be transmitted to the polarizing plate 122 or absorbed by the polarizing plate 122 to be blocked. can. In this way, the display panel 120 is configured so that the transmission or blocking of light from the backlight device 80 can be controlled for each pixel. The details of the liquid crystal display panel are described in various publicly known documents (for example, "Flat Panel Display Encyclopedia (supervised by Tatsuo Uchida and Hiraki Uchiike)" published by Kogyo Chosakai in 2001). The detailed explanation of is omitted.

<< Backlight device >>
The backlight device 80 shown in FIG. 11 is configured as an edge light type backlight device, and has a light source 90, an optical plate 95 as a light guide plate arranged on the side of the light source 90, and a light emitting side of the optical plate 95. The optical wavelength conversion sheet 10 arranged in the light wavelength conversion sheet 10, the lens sheet 100 arranged on the light source side of the light wavelength conversion sheet 10, the lens sheet 105 arranged on the light source side of the lens sheet 100, and the light source side of the lens sheet 105. It includes an arranged reflective polarizing separation sheet 110 and a reflective sheet 115 arranged on the side opposite to the light source side of the optical plate 95. The backlight device 80 includes an optical plate 95, lens sheets 100 and 105, a reflective polarizing separation sheet 110, and a reflective sheet 115, but these sheets and the like may not be provided. As used herein, the term "light emitting side" means the side of each member where light emitted in the direction emitted from the backlight device is emitted.

The backlight setting 80 has a light emitting surface 80A that emits light in a planar manner. In the backlight device 80 shown in FIG. 11, the light emitting surface of the reflective polarizing separation sheet 110 is the light emitting surface 80A of the backlight device 80.

The surface of the optical wavelength conversion sheet 10 on the optical plate 95 side is the surface 10A (light entry surface), and the surface of the light wavelength conversion sheet 10 on the lens sheet 100 side is the surface 10B (light emission surface).

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

Since the light wavelength conversion sheet 10 is arranged in the backlight device 80, the light source 90 can use only a light emitting body that emits light in a single wavelength range. For example, as the light source, only a blue light emitting diode that emits blue light having high color purity can be used.

<Optical plate>
The optical plate 95 as a light guide plate has a rectangular shape in a plan view. The optical plate 95 extends between the light emitting surface 95A formed by one main surface on the display panel 120 side, the back surface 95B composed of the other main surface facing the light emitting surface 95A, and the light emitting surface 95A and the back surface 95B. Has sides. The side surface of the side surface on the light source 90 side is an incoming light receiving surface 75C that receives light from the light source 90. The light incident on the optical plate 95 from the light entry surface 95C is guided in the optical plate in the direction connecting the light entry surface 95C and the opposite surface facing the light entry surface 95C (light guide direction), and the light exit surface. Emitted from 95A.

As a material constituting the optical plate 95, it is widely used as a material for an optical sheet incorporated in an image display device, and has excellent mechanical properties, optical properties, stability, processability, etc., and is inexpensively available. For example, a transparent resin containing one or more of acrylic resin, polystyrene, polycarbonate, polyethylene terephthalate, polyacrylonitrile and the like as a main component, and epoxy acrylate and urethane acrylate-based reactive resin (ionized radiation curable resin, 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 substance such as silica (silicon dioxide), alumina (aluminum oxide), acrylic resin, polycarbonate resin, and silicone resin having an average particle diameter of 0.5 μm or more and 100 μm or less can be used. can.

<< Lens sheet >>
The lens sheets 100 and 105 have a function of changing the traveling direction of the incident light and emitting the incident light from the light emitting side. In the present embodiment, as shown in FIG. 13, a function (condensing function) of changing the traveling direction of light L3 having a large incident angle and emitting it from the light emitting side to intensively improve the brightness in the front direction. At the same time, it has a function (retroreflection function) of reflecting light L4 having a small incident angle and returning it to the light wavelength conversion sheet 10 side. The lens sheets 100 and 105 include a light-transmitting base material 101 and a lens layer 102 provided on one surface of the light-transmitting base material 101.

When the surfaces 10A and 10B of the optical wavelength conversion sheet 10 are uneven surfaces, the light emitting surface 95A of the optical plate 95 is optically in close contact with a part (for example, a convex portion) of the surface 10A, and is also a surface. It is preferable that the lens sheet 100 is separated from other parts (for example, concave portions), and the light entering surface 100A of the lens sheet 100 is optically in close contact with a part (for example, convex portions) of the surface 10B and also has a surface. It is preferable that the 10B is separated from other parts (for example, recesses). In this case, the gap between the light emitting surface 95A and the other part of the surface 10A and the gap between the light entering surface 100A and the other part of the surface 10B are 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 emitting surface 95A and the surface 10A and the light entering surface 100A and the surface 10B are in optical contact with each other. However, since it is possible to prevent the light wavelength conversion sheet 10 from sticking to the optical plate 95 and the lens sheet 100, the interface between the light wavelength conversion sheet 10 and the optical plate 95 and the light wavelength conversion sheet 10 and the lens sheet 100 It is possible to suppress the formation of wet-out at the interface between the light and the light.

<Light transmissive base material>
Since the light-transmitting base material 101 is the same as the light-transmitting base materials 12 and 13, the description thereof will be omitted here.

<Lens layer>
As shown in FIGS. 12 and 13, the lens layer 102 includes a sheet-shaped main body 103 and a plurality of unit lenses 104 arranged side by side on the light emitting 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, unit lenses 104 are arranged on the light emitting side surface 103A of the main body 103 without leaving a gap. Therefore, the light emitting surfaces 100B and 105B of the lens sheets 100 and 105 are formed by the lens surfaces. On the other hand, as shown in FIG. 13, the main body 103 has a smooth surface forming the incoming side surface of the lens layer 102 as the incoming light entering side surface 103B facing the light emitting side surface 103A.

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

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

From the viewpoint of improving the efficiency of light utilization, the unit lens 104 preferably has an apex angle of 80 ° or more and 100 ° or less, and more preferably about 90 °. However, considering the damage to the tip of the unit lens when winding the optical wavelength conversion sheet, the tip of the unit lens 104 may be a curved surface.

The dimensions of the lens sheets 100 and 105 can be set as follows, for example. First, as a specific example of the unit lens 104, the arrangement pitch of the unit lens 104 (corresponding to the width of the unit lens 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 lens 104 has been rapidly improved in definition, and it is preferable that the arrangement pitch of the unit lens 104 is 10 μm or more and 50 μm or less. Further, the protruding height of the unit lens 104 from the main body 103 along the normal direction ND of the lens sheets 100 and 105 to the sheet surface can be set to 5 μm or more and 100 μm or less. Further, the apex angle θ of the unit lens 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 lens 104 of the lens sheet 100 and the arrangement direction of the unit lens 104 of the lens sheet 105 intersect, and more specifically, are orthogonal to each other.

<Reflective polarization separation sheet>
The reflective polarization separation sheet 110 transmits only the first linear polarization component (for example, P-polarization) among the light emitted from the lens sheet 105, and is a second straight line orthogonal to the first linear polarization component. It has a function of reflecting a polarizing component (for example, S-polarized light) without absorbing it. The second linear polarization component reflected by the reflective polarization separation sheet 110 is reflected again, and the polarization is eliminated (a state in which both the first linear polarization component and the second linear polarization component are included). It is incident on the reflective polarization separation sheet 110 again. Therefore, the reflective polarization separation sheet 110 transmits the first linear polarization component of the light incident again, and the second linear polarization component orthogonal to the first linear polarization component is reflected again. Hereinafter, by repeating the same process, about 70 to 80% of the light emitted from the lens sheet 105 is emitted as the light source light as the first linearly polarized light component. Therefore, by matching the polarization direction of the first linear polarization component (transmission axis component) of the reflective polarization separation sheet 110 with the transmission axis direction of the polarizing plate 121 of the display panel 120, the light emitted from the backlight device 80 Are all available for image formation on the display panel 120. Therefore, even if the light energy input from the light source 90 is the same, it is possible to form a higher-luminance image as compared with the case where the reflective polarizing separation sheet 110 is not arranged, and the energy utilization efficiency of the light source 90 is also high. improves. In particular, the light reflected by the reflective polarizing separation sheet 110 may be wavelength-converted by the optical wavelength conversion sheet 10. Therefore, by arranging the reflective polarization separation sheet 110, the wavelength conversion efficiency of the optical wavelength conversion sheet 10 can be further increased. Therefore, further improvement in light utilization efficiency can be expected.

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

<Reflective sheet>
The reflective sheet 115 has a function of reflecting the light leaked from the back surface 95B of the optical plate 95 and making it enter the optical plate 90 again. The reflective sheet 115 is composed of a white diffuse reflective sheet, a sheet made of a material having a high reflectance such as metal, a sheet containing a thin film made of a material having a high reflectance (for example, a metal thin film) as a surface layer, and the like. obtain. The reflection on the reflective sheet 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 the light of the light source 90 and functions as a light diffusing plate, and an optical wavelength conversion sheet 10 arranged on the light emitting side of the optical plate 131. The lens sheet 100 arranged on the light source side of the optical wavelength conversion sheet 10, the lens sheet 105 arranged on the light source side of the lens sheet 100, and the reflective polarization separation sheet 110 arranged on the light source side of the lens sheet 105. I have. In the present embodiment, the light source 90 is arranged directly under the optical plate 131, not on the side of the optical plate 131. In FIG. 14, the members having the same reference numerals as those in FIG. 11 are the same as the members shown in FIG. 11, and therefore the description thereof will be omitted. The backlight device 130 is not provided with the reflective sheet 115.

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

The optical plate 131 is not particularly limited as long as it can diffuse the light from the light source 90, and examples thereof include a plate in which light diffusing particles are dispersed in a transparent material. The transparent material is not particularly limited, and examples thereof include transparent resin and inorganic glass. As the transparent resin, a transparent thermoplastic resin is preferably used because it is easy to mold. The transparent thermoplastic resin is not particularly limited, but for example, a polystyrene resin, a styrene-methyl methacrylate copolymer resin, a styrene-methacrylate copolymer resin, and a 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 diffusive particles>
Examples of the light diffusing particles in the optical plate 131 include light diffusing particles generally used as a diffusing plate.

<< Other backlight devices >>
The backlight device 80 shown in FIG. 11 includes a light wavelength conversion sheet 10, but the structure of the backlight device is not particularly limited as long as it includes a light wavelength conversion member. For example, as shown in FIG. 15, 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. 16, the light source 150 has a substrate 151, a reflection member 152 having an opening 152A arranged on the substrate 151, and a light emitting member arranged on the substrate 151 and in the opening 152A of the reflection member 152. It includes a light emitting body 153 such as a diode and a light wavelength conversion member 154 filled in the opening 152A of the reflecting member 152 so as to cover the light emitting body 153. The optical wavelength conversion member 154 is different from the optical wavelength conversion member 11 only in shape and arrangement, 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, so the description thereof is omitted here. And. The light wavelength conversion member 154 can be formed by filling the opening 152A of the reflection member 152 with the light wavelength conversion composition and curing it. When the light source 150 having the light wavelength conversion member 154 is used, the structure is not particularly limited as long as the light wavelength conversion member 154 is arranged so as to cover the light emitting body 153.

<< 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 arranged 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 input surface 95C of the optical plate 95. Since the optical wavelength conversion member 170 has the same configuration and physical properties as the optical wavelength conversion member 11 except that the arrangement location is different from that of the optical wavelength conversion member 11, the 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 input surface 95C of the optical plate 95 and curing it.

It is considered that the reason why quantum dots are easily deteriorated by heat resistance test and moisture heat resistance test is as follows. First, a ligand composed of a sulfur-based compound, a phosphorus-based compound, or the like is coordinated on the surface of the quantum dot, and this ligand is easily desorbed by light or heat. When the ligand is desorbed from the quantum dots, water and oxygen are likely to adhere to the quantum dots, so that the quantum dots are oxidized and deteriorated. As a result, it is considered that the quantum dots are deteriorated by the heat resistance test and the moisture heat resistance test. On the other hand, in the present embodiment, the light wavelength conversion composition and the light wavelength conversion member 11 contain a carboxylic acid and the acid value of the light wavelength conversion composition exceeds 10 mgKOH / g, so that the light wavelength The heat resistance and moisture heat resistance of the conversion composition and the light wavelength conversion member 11 can be improved. This is because the carboxylic acid present in the binder resin assists the role of the ligand even when the ligand is desorbed from the quantum dot (for example, it binds to the quantum dot instead of the ligand and the ligand is used. It is thought that this is because the deterioration of the quantum dots is suppressed because it exerts a function of substituting for. The reason why the acid value of the light wavelength conversion composition exceeds 10 mgKOH / g is that when the acid value of the light wavelength conversion composition is less than 10 mgKOH / g, the heat resistance of the light wavelength conversion composition and the light wavelength conversion member is high. This is because it may not be possible to improve the properties and moisture resistance.

According to the present embodiment, the deterioration of the quantum dot 17 can be suppressed by the optical wavelength conversion member 11 made of a cured product of an optical wavelength conversion composition containing a carboxylic acid and having an acid value of more than 10 mgKOH / g, so that the optical wavelength can be suppressed. In the conversion sheets 10, 20, 30, 40, 50, 60, the barrier member can be omitted, and even when the barrier member is used, the point-shaped brightness defect can be suppressed. That is, in the light wavelength conversion sheets 10, 20, 30, 40, 50, the quantum is formed by the light wavelength conversion member 11 made of a cured product of a light wavelength conversion composition containing a carboxylic acid and having an acid value of more than 10 mgKOH / g. Since the deterioration of the dot 17 can be suppressed, the barrier member can be omitted. Further, in the light wavelength conversion sheet 60 provided with the barrier members 61 and 62, the light wavelength conversion member 11 made of a cured product of the light wavelength conversion composition containing a carboxylic acid and having an acid value of more than 10 mgKOH / g is used. Since the deterioration of the quantum dot 17 can be suppressed, even if pinholes or cracks are generated in the barrier members 61 and 62 and water or oxygen enters through the pinholes or cracks, the point-like brightness defect Can be suppressed. Further, since the deterioration of the quantum dots 17 can be suppressed by the carboxylic acid existing in the optical wavelength conversion member 11, the peripheral portions 10C, 20A, 30A, 40A in the optical wavelength conversion sheets 10, 20, 30, 40, 50, 60A. Deterioration of the quantum dots 17 existing at 50A and 60C can also be suppressed.

In the optical wavelength conversion sheets 10, 20, 30, 40, and 50, the barrier member is not provided because the deterioration of the quantum dots 17 can be suppressed by the carboxylic acid present in the optical wavelength conversion member 11. As a result, the process of the optical wavelength conversion sheet can be simplified, so that the quality can be easily improved and the optical wavelength conversion sheet can be made thinner.

In the optical wavelength conversion sheet 40, since the optical wavelength conversion member 11 and the optical member 41 are integrated, the optical wavelength conversion sheet and the optical member are simplified and thin as compared with the case where the optical wavelength conversion sheet and the optical member are arranged separately and independently. A backlight device can be obtained. That is, when the optical wavelength conversion sheet and the optical member are arranged separately and independently, since an air interface exists between the optical wavelength conversion sheet and the optical member, a relatively large void is created in the backlight device. It takes. On the other hand, in the present 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. This makes it possible to obtain a simplified thin backlight device.

A light emitting body such as a light emitting diode also emits heat when it emits light. Therefore, normally, when the light wavelength conversion member is incorporated in the light source or when the light wavelength conversion member is arranged at a position close to the light source, the light wavelength conversion member is covered in order to suppress the deterioration of the quantum dots. A barrier member is required. On the other hand, in the present embodiment, the carboxylic acid present in the light wavelength conversion members 154 and 170 can improve the heat resistance and the moist heat resistance of the light wavelength conversion members 154 and 170, so that the light wavelength conversion member 154 can be improved. , 170 can suppress deterioration of the quantum dot 17 without covering it with a barrier member. Thereby, the light wavelength conversion member 154 can be incorporated in the light source 150, or the light wavelength conversion member 170 can be arranged at a position close to the light source 90.

Conventionally, the light wavelength-converted by the quantum dots emitted from the optical wavelength conversion sheet is condensed on the light emitting side of the optical wavelength conversion sheet, and the light not wavelength-converted by the optical wavelength conversion sheet is collected by the optical wavelength conversion sheet. It is being studied to improve the light wavelength conversion efficiency by arranging a lens sheet to be returned to the side. However, the optical wavelength conversion efficiency is not sufficient only by arranging such a lens sheet, and further improvement of the optical wavelength conversion efficiency is desired. According to the present embodiment, when the external haze value of the optical wavelength conversion sheet 10 is smaller than the internal haze value of the optical wavelength conversion sheet 10, the optical wavelength conversion efficiency can be further improved. That is, since the light emitted from the light source has straightness, the light that is incident on the light wavelength conversion sheet and is not wavelength-converted by the quantum dots and is emitted from the light wavelength conversion sheet also has straightness. There is. Here, when the external haze value of the optical wavelength conversion sheet is high, the unconverted wavelength light having straightness on the surface of the optical wavelength conversion sheet is refracted, and the unconverted wavelength light emitted from the optical wavelength conversion sheet is emitted. Will have many components with a large emission angle. On the other hand, in a lens sheet having a light collecting function and a retroreflective function, the light incident on the lens sheet at a smaller angle tends to be more likely to be retroreflected. That is, the larger the angle of incidence on the lens sheet, the easier it is for the light to pass through the lens sheet. In the present embodiment, in the light wavelength conversion sheet 10, the external haze value is smaller than the internal haze value, so that even if the light that has not been wavelength-converted on the surface of the light wavelength conversion sheet 10 is refracted, it is emitted. It can be emitted in a state where the angle is small, and thus it is possible to increase the number of components having a small emission angle in the unwavelength-converted light emitted from the optical wavelength conversion sheet 10. 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 opportunity for wavelength conversion increases. Further, since the internal haze value is larger than the external haze value, the optical path length is extended by scattering the light a plurality of times inside the optical wavelength conversion sheet, and the chance of wavelength conversion is further increased. This makes it possible to improve the light wavelength conversion efficiency. Since the quantum dots 17 emit light isotropically, the light wavelength-converted by the quantum dots 17 is oriented in various directions, and when the light reaches the surface of the optical wavelength conversion sheet 10, the surface of the optical wavelength conversion sheet is further reached. The light is refracted at, and the wavelength-converted light becomes light having a large angle and is easily emitted from the light wavelength conversion sheet. Therefore, the wavelength-converted light is relatively easy to pass through the lens sheet 100.

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

According to the present embodiment, since the light wavelength conversion member 11 contains 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 as compared with the light wavelength conversion sheet not containing light-scattering particles, and the color is white light or a color close to white. You can get the light of taste.

According to the present embodiment, since the light wavelength conversion member 11 contains the light scattering particles 18, the green light emission can be preferentially enhanced over the red light emission. The reason for this is not clear, but light-scattering particles may impede energy transfer from the first quantum dot that converts blue light to green light to the second quantum dot that converts blue light to red light. It is considered that this is because the green light emission that was originally deactivated by the above energy transfer leads to the light emission process without being deactivated, and as a result, the green light emission increases.

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

<Preparation of light wavelength conversion composition>
First, each component was blended so as to have the composition shown below to obtain a light wavelength conversion composition.
(Light wavelength conversion composition 1)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 77 parts by mass-ω-carboxy-polycaprolactone mono (meth) acrylate (product name "M-5300", manufactured by Toa Synthetic Co., Ltd., acid value 140-260 mgKOH / g): 23 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): 0.2 Parts by mass, red light emitting quantum dots (product name "CdSe / ZnS 610", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.2 parts by mass, radical polymerization initiator ( 1-Hydroxycyclohexylphenyl ketone, product name "Irgacure (registered trademark) 184", manufactured by BASF Japan, Inc.): 0.2 parts by mass

(Light wavelength conversion composition 2)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 77 parts by mass-ω-carboxy-polycaprolactone mono (meth) acrylate (product name "M-5300", manufactured by Toa Synthetic Co., Ltd., acid value 140-260 mgKOH / g): 23 parts by mass, green emission quantum dots (product name "CdSe / ZnS 530", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.2 Parts by mass ・ Red emission quantum dots (product name “CdSe / ZnS 610”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.2 parts by mass ・ Alumina particles (light scattering) Sex particles, product name "DAM-03", manufactured by Denki Kagaku Kogyo Co., Ltd., average particle diameter 4 μm): 10 parts by mass, radical polymerization initiator (1-hydroxycyclohexylphenylketone, product name "Irgacure (registered trademark) 184", BASF Japan): 0.2 parts by mass

(Light wavelength conversion composition 3)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 62 parts by mass-ω-carboxy-polycaprolactone mono (meth) acrylate (product name "M-5300", manufactured by Toa Synthetic Co., Ltd., acid value 140-260 mgKOH / g): 38 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): 0.2 Parts by mass, red light emitting quantum dots (product name "CdSe / ZnS 610", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.2 parts by mass, radical polymerization initiator ( 1-Hydroxycyclohexylphenyl ketone, product name "Irgacure (registered trademark) 184", manufactured by BASF Japan, Inc.): 0.2 parts by mass

(Light wavelength conversion composition 4)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 88 parts by mass-ω-carboxy-polycaprolactone mono (meth) acrylate (product name "M-5300", manufactured by Toa Synthetic Co., Ltd., acid value 140-260 mgKOH / g): 12 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): 0.2 Parts by mass, red light emitting quantum dots (product name "CdSe / ZnS 610", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.2 parts by mass, radical polymerization initiator ( 1-Hydroxycyclohexylphenyl ketone, product name "Irgacure (registered trademark) 184", manufactured by BASF Japan, Inc.): 0.2 parts by mass

(Light wavelength conversion composition 5)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 77 parts by mass-2-acryloyloxyethyl succinic acid (product name "NK ester A-SA", manufactured by Shin-Nakamura Chemical Industry Co., Ltd., acid value 260mgKOH / g): 23 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): 0.2 parts by mass -Red emission quantum dots (product name "CdSe / ZnS 610", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.2 parts by mass-Radical polymerization initiator (1- Hydroxycyclohexylphenyl ketone, product name "Irgacure (registered trademark) 184", manufactured by BASF Japan, Inc.): 0.2 parts by mass

(Light wavelength conversion composition 6)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 88 parts by mass-2-acryloyloxyethyl succinic acid (product name "NK ester A-SA", manufactured by Shin-Nakamura Chemical Industry Co., Ltd., acid value 260 mgKOH / g): 12 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): 0.2 parts by mass -Red emission quantum dots (product name "CdSe / ZnS 610", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.2 parts by mass-Radical polymerization initiator (1- Hydroxycyclohexylphenyl ketone, product name "Irgacure (registered trademark) 184", manufactured by BASF Japan, Inc.): 0.2 parts by mass

(Light wavelength conversion composition 7)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 77 parts by mass-polybasic acid-modified acrylic oligomer (product name "M-510", manufactured by Toa Synthetic Co., Ltd., acid value 80-120 mgKOH / g ): 23 parts by mass, green emission quantum dots (product name "CdSe / ZnS 530", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.2 parts by mass, red emission Quantum dots (product name "CdSe / ZnS 610", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.2 parts by mass ・ Radical polymerization initiator (1-hydroxycyclohexylphenyl) Ketone, product name "Irgacure (registered trademark) 184", manufactured by BASF Japan, Inc.): 0.2 parts by mass

(Light wavelength conversion composition 8)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 88 parts by mass-polybasic acid-modified acrylic oligomer (product name "M-510", manufactured by Toa Synthetic Co., Ltd., acid value 80-120 mgKOH / g ): 12 parts by mass, green emission quantum dots (product name "CdSe / ZnS 530", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.2 parts by mass, red emission Quantum dots (product name "CdSe / ZnS 610", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.2 parts by mass ・ Radical polymerization initiator (1-hydroxycyclohexylphenyl) Ketone, product name "Irgacure (registered trademark) 184", manufactured by BASF Japan, Inc.): 0.2 parts by mass

(Light wavelength conversion composition 9)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 100 parts by mass-Green emission quantum dots (product name "CdSe / ZnS 530", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS , Average particle size 3.3 nm): 0.2 parts by mass, red emission quantum dots (product name "CdSe / ZnS 610", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm) : 0.2 parts by mass ・ Radical polymerization initiator (1-hydroxycyclohexylphenylketone, product name “Irgacure (registered trademark) 184”, manufactured by BASF Japan): 0.2 parts by mass

(Light wavelength conversion composition 10)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 97 parts by mass-ω-carboxy-polycaprolactone mono (meth) acrylate (product name "M-5300", manufactured by Toa Synthetic Co., Ltd., acid value 140-260 mgKOH / g): 3 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): 0.2 Parts by mass, red light emitting quantum dots (product name "CdSe / ZnS 610", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.2 parts by mass, radical polymerization initiator ( 1-Hydroxycyclohexylphenyl ketone, product name "Irgacure (registered trademark) 184", manufactured by BASF Japan, Inc.): 0.2 parts by mass

(Light wavelength conversion composition 11)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 97 parts by mass-2-acryloyloxyethyl succinic acid (product name "NK ester A-SA", manufactured by Shin-Nakamura Chemical Industry Co., Ltd., acid value 260 mgKOH / g): 3 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): 0.2 parts by mass -Red emission quantum dots (product name "CdSe / ZnS 610", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.2 parts by mass-Radical polymerization initiator (1- Hydroxycyclohexylphenyl ketone, product name "Irgacure (registered trademark) 184", manufactured by BASF Japan, Inc.): 0.2 parts by mass

<Preparation of composition for overcoat layer>
Each component was blended so as to have the composition shown below to obtain a composition for an overcoat layer.
(Composition 1 for overcoat layer)
-Zinc acrylate (product name "ZN-DA" manufactured by Nippon Shokubai Co., Ltd.): 30 parts by mass-Methanol: 70 parts by mass-Photopolymerization initiator (1-hydroxycyclohexylphenylketone, product name "Irgacure (registered trademark) 184," BASF Japan): 1 part by mass

(Composition 2 for overcoat layer)
-A mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate (product name "Aronix (registered trademark) M-403", manufactured by Toagosei Co., Ltd.): 30 parts by mass-Methanol: 70 parts by mass-Photopolymerization initiator (1) -Hydroxycyclohexylphenylketone, product name "Irgacure (registered trademark) 184, manufactured by BASF Japan, Inc.): 1 part by mass

<Preparation of composition for light diffusion layer>
Each component was blended so as to have the composition shown below to obtain a composition 1 for a light diffusion layer.
(Composition 1 for light diffusion layer)
-Pentaerythritol triacrylate: 99 parts by mass-light scattering particles (crosslinked polystyrene resin beads, product name "SBX-4", manufactured by Sekisui Kasei Kogyo Co., Ltd., average particle diameter 4 μm): 158 parts by mass-photopolymerization initiator (1-Hydroxycyclohexylphenylketone, product name "Irgacure (registered trademark) 184, manufactured by BASF Japan, Inc.): 1 part by mass / solvent (methylisobutylketone: cyclohexanone = 1: 1 (mass ratio)): 170 parts by mass

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

Next, the light wavelength conversion composition 1 was applied to a surface of the PET substrate with a light diffusion layer opposite to the surface on the light diffusion layer side and dried at 80 ° C. to form a coating film. Then, the other PET substrate with a light diffusing layer was laminated on the coating film so that the surface of the PET substrate with a light diffusing layer on the other side opposite to the surface on the light diffusing layer side was in contact with the coating film. In this state, the coating film is cured by irradiating ultraviolet rays so that the integrated light amount is 500 mJ / cm ² , to form an optical wavelength conversion member having a film thickness of 100 μm, and the light wavelength conversion member and two pieces of light. It was integrated with a PET substrate with a diffusion layer. As a result, the optical wavelength conversion sheet according to Example 1 was obtained.

<Example 2>
In Example 2, an optical wavelength conversion sheet was produced in the same manner as in Example 1 except that the optical wavelength conversion composition 2 was used instead of the optical 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, an optical wavelength conversion sheet was produced in the same manner as in Example 1 except that the optical wavelength conversion composition 6 was used instead of the optical wavelength conversion composition 1.

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

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

<Example 9>
The light wavelength conversion composition 1 was applied to one surface of a 50 μm-thick polyethylene terephthalate (PET) substrate (product name “Lumilar T60”, manufactured by Toray Industries, Inc.) and dried at 80 ° C. to form a coating film. .. Then, the coating film was cured by irradiating it with ultraviolet rays so that the integrated light amount was 500 mJ / cm ² . Finally, the PET substrate was peeled off to obtain an optical wavelength conversion sheet comprising only an optical wavelength conversion member having a film thickness of 100 μm according to Example 9.

<Example 10>
The composition 1 for the overcoat layer was applied to one surface of the light wavelength conversion sheet (light wavelength conversion member) produced in Example 9 to form a coating film. Then, the coating film was cured by irradiating it with ultraviolet rays so that the integrated light amount was 500 mJ / cm ² , and an overcoat layer having a film thickness of 5 μm was obtained. Next, in the same manner, the composition 1 for the overcoat layer was applied to the other surface of the light wavelength conversion member to form a coating film. Then, the coating film was cured by irradiating it with ultraviolet rays so that the integrated light amount was 500 mJ / cm ² , and an overcoat layer having a film thickness of 5 μm was obtained. As a result, an optical wavelength conversion sheet composed of an optical wavelength conversion member and an overcoat layer formed on both sides of the optical wavelength conversion member was obtained.

<Example 11>
In Example 11, an optical wavelength conversion sheet was produced in the same manner as in Example 10 except that the composition 2 for the overcoat layer was used instead of the composition 1 for the overcoat layer.

<Example 12>
A prism layer composition containing urethane acrylate is uniformly applied to one surface of a 100 μm-thick polyethylene terephthalate (PET) substrate (product name “Lumilar T60”, manufactured by Toray Industries, Inc.) to form a prism layer composition. A coating film was formed, and a laminate for a prism sheet was formed. Then, the traveling speed of the prism sheet laminate is such that the coating film of the lens layer composition is on the molding die side in the rotating molding die having a recess having an inverted shape with respect to the desired unit prism shape. The shape of the unit prism is formed on the coating film of the composition for the prism layer by supplying at 20 m / min using a molding die, and light such as ultraviolet rays is applied to the coating film of the composition for the prism layer via the PET substrate. Irradiation was performed to cure the coating film of the composition for the prism layer. Finally, the cured coating film of the prism layer composition was peeled off from the molding mold together with the PET substrate to obtain a prism sheet having the prism layer formed on one surface of the PET substrate. The prism layer has a sheet-shaped main body and is arranged side by side on the main body, and each extends in a direction intersecting the arrangement direction, has an apex angle of 90 °, a width of 47 μm, and a height. It had a plurality of triangular columnar unit prisms having a size of 30 μm.

Next, the light wavelength conversion composition 1 was applied to the surface of the prism sheet opposite to the surface on the prism layer side of the PET substrate and dried at 80 ° C. to form a coating film. Then, by irradiating the coating film with ultraviolet rays so that the integrated light amount becomes 500 mJ / cm ² , a light wavelength conversion member having a film thickness of 100 μm integrated with the prism sheet was formed. As a result, the optical wavelength conversion sheet according to Example 12 was obtained.

<Example 13>
First, two barrier members were manufactured by the following method. In a high-frequency sputtering device, by applying a high-frequency power of 13.56 MHz and a power of 5 kW to the electrodes, a discharge is generated in the chamber, and polyethylene terephthalate as a light-transmitting substrate having a size of 7 inches and a thickness of 50 μm is generated. A silica vapor-deposited layer made of a target substance (silica) having a thickness of 50 nm and a refractive index of 1.46 was formed on one side of a (PET) base material (product name “Lumilar T60”, manufactured by Toray Co., Ltd.). As a result, two barrier members having a silica-deposited layer formed on one surface of the PET substrate were formed.

Next, the composition 1 for the light diffusion layer was applied to the surface of both barrier members opposite to the surface on the silica vapor deposition layer side to form a coating film. Next, the solvent in the coating film was evaporated by passing dry air at 80 ° C. for 30 seconds through the formed coating film to dry it. Then, the coating film was cured by irradiating it with ultraviolet rays so that the integrated light amount was 500 mJ / cm ² , to form a light diffusing layer having a thickness of 10 μm, and forming a barrier member with a light diffusing layer.

Next, the light wavelength conversion composition 1 was applied to the silica-deposited layer side of one of the barrier members with a light diffusion layer and dried at 80 ° C. to form a coating film. Then, the other barrier member with a light diffusion layer was laminated on the surface of the silica vapor deposition layer of the barrier member with a light diffusion layer in the coating film so that the silica vapor deposition layer was in contact with the surface. In this state, by irradiating the coating film with ultraviolet rays so that the integrated light amount becomes 500 mJ / cm ² , a light wavelength conversion member having a thickness of 100 μm in close contact with both barrier members with a light diffusion layer is formed. bottom. As a result, the optical wavelength conversion sheet according to Example 13 was obtained.

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

<Comparative Example 2>
In Comparative Example 2, an optical wavelength conversion sheet was produced in the same manner as in Example 1 except that the optical wavelength conversion composition 10 was used instead of the optical 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 11 was used instead of the light wavelength conversion composition 1.

<Comparative Example 4>
In Comparative Example 4, an optical wavelength conversion sheet was produced in the same manner as in Example 9 except that the optical wavelength conversion composition 9 was used instead of the optical wavelength conversion composition 1.

<Comparative Example 5>
In Comparative Example 5, an optical wavelength conversion sheet was produced in the same manner as in Example 9 except that the optical wavelength conversion composition 10 was used instead of the optical wavelength conversion composition 1.

<Comparative Example 6>
In Comparative Example 6, an optical wavelength conversion sheet was produced in the same manner as in Example 9 except that the optical wavelength conversion composition 11 was used instead of the optical wavelength conversion composition 1.

<Comparative Example 7>
In Comparative Example 7, an optical wavelength conversion sheet was produced in the same manner as in Example 10 except that the optical wavelength conversion composition 9 was used instead of the optical 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 10 except that the light wavelength conversion composition 10 was used instead of the light wavelength conversion composition 1.

<Comparative Example 9>
In Comparative Example 9, an optical wavelength conversion sheet was produced in the same manner as in Example 10 except that the optical wavelength conversion composition 11 was used instead of the optical 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 12 except that the light wavelength conversion composition 9 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 12 except that the light wavelength conversion composition 10 was used instead of the light wavelength conversion composition 1.

<Comparative Example 12>
In Comparative Example 12, an optical wavelength conversion sheet was produced in the same manner as in Example 12 except that the optical wavelength conversion composition 11 was used instead of the optical wavelength conversion composition 1.

<Comparative Example 13>
In Comparative Example 13, a light wavelength conversion sheet was produced in the same manner as in Example 13 except that the light wavelength conversion composition 9 was used instead of the light wavelength conversion composition 1.

<Comparative Example 14>
In Comparative Example 14, an optical wavelength conversion sheet was produced in the same manner as in Example 13 except that the optical wavelength conversion composition 10 was used instead of the optical wavelength conversion composition 1.

<Comparative Example 15>
In Comparative Example 15, an optical wavelength conversion sheet was produced in the same manner as in Example 13 except that the optical wavelength conversion composition 11 was used instead of the optical wavelength conversion composition 1.

<Measurement of acid value of light wavelength conversion composition>
The acid values of the light wavelength conversion compositions used in the light wavelength conversion sheets according to the above-mentioned Examples and Comparative Examples were measured. The acid value was measured by an indicator titration method using an alkaline titration solution. Specifically, the acid value was determined as follows. The acid value was taken as the arithmetic mean value of the values obtained by measuring three times.
(I) 1 g of the light wavelength conversion composition was precisely weighed and placed in an Erlenmeyer flask, and then a neutral methanol / acetone solution [a mixture of acetone and methanol at a ratio of 1: 1 (volume ratio)] was added and dissolved.
(Ii) Several drops of a phenolphthalein indicator were added, and the solution was titrated with a 0.1 mol / L potassium hydroxide titration solution. The end point of neutralization was when the indicator was slightly crimson for 30 seconds.
(Iii) The acid value was determined using the following formula.
Acid value (mgKOH / g) = (A × f × 5.61) / S
In the formula, A is the mL number of the 0.1 mol / L potassium hydroxide titration solution, f is the titer of the 0.1 mol / L potassium hydroxide titration solution, and S is the sampling of the optical wavelength conversion composition. The amount (g).

<Measurement of water vapor permeability and oxygen permeability>
The water vapor transmittance and the oxygen transmittance were measured in the light wavelength conversion sheets according to the above Examples and Comparative Examples, respectively. The water vapor transmittance of the optical wavelength conversion sheet is 40 ° C. and 90% relative humidity using a water vapor transmittance measuring device (product name "PERMATRAN-W3 / 31", manufactured by MOCON) in accordance with JIS K7129: 2008. It was measured under the conditions of. The oxygen transmittance of the optical wavelength conversion sheet is 23 ° C. relative to 23 ° C. using an oxygen gas transmittance measuring device (product name “OX-TRAN 2/21”, manufactured by MOCON) in accordance with JIS K7126: 2006. It was measured under the condition of 90% humidity. The water vapor permeability and the oxygen permeability were taken as the average value of the values obtained by measuring each three times.

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

In Examples 1 to 11 and 13, and Comparative Examples 1 to 9 and 13 to 15, the light guide plates are arranged so that the blue light emitting diode side is the light entry surface, and the light guide plates are on the light emission surface of the light guide plates. , 13 and the light wavelength conversion sheet, the first prism sheet, and the second prism sheet according to Comparative Examples 1 to 9 and 13 to 15 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 first prism sheet.

In Example 12 and Comparative Examples 10 to 12, the light guide plate is arranged so that the blue light emitting diode side is the light entrance surface, and the prism surface of the prism sheet is on the light emission surface of the light guide plate so as to be the light emission side. The light wavelength conversion sheet and the second prism sheet according to Example 12 and Comparative Examples 10 to 12 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 optical wavelength conversion sheets according to Examples 12 and Comparative Examples 10 to 12. In this way, a backlight device incorporating the optical wavelength conversion sheet according to Example 12 and Comparative Examples 10 to 12 was obtained.

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

Next, the light wavelength conversion sheet before the heat resistance test was removed from the backlight device, and the light wavelength conversion sheet was subjected to a heat resistance test in which the light wavelength conversion sheet was left in an environment of 80 ° C. for 500 hours. Then, the light wavelength conversion sheet after the heat resistance test was incorporated into the backlight device in the same manner as described above. In this state, in the same manner as described above, one surface of the light wavelength conversion sheet is irradiated with blue light, 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 optical wavelength conversion sheet using a spectral emission luminance meter (product name "CS2000", manufactured by Konica Minolta) under the condition of a measurement angle of 1 °.

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

<Measurement of brightness maintenance rate after moisture resistance test>
In the optical wavelength conversion sheet according to the above Examples and Comparative Examples, a moisture resistance test was performed in which the optical wavelength conversion sheet was left in an environment of 60 ° C. and a relative humidity of 90% for 500 hours, and before the heat resistance test in the optical wavelength conversion sheet. The maintenance rate of the brightness after the moisture resistance test for the brightness was investigated. Specifically, first, a Kindle Fire (registered trademark) HDX7 backlight device was prepared, and the optical wavelength conversion sheet before the moisture resistance test was incorporated into this backlight device in the same manner as in the above heat resistance test.

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

Next, the light wavelength conversion sheet before the moisture resistance test was removed from the backlight device, and the light wavelength conversion sheet was subjected to a moisture resistance test in which the light wavelength conversion sheet was left in an environment of 60 ° C. and 90% relative humidity for 500 hours. rice field. Then, the light wavelength conversion sheet after the moisture resistance test was incorporated into the backlight device in the same manner as described above. In this state, in the same manner as described above, one surface of the light wavelength conversion sheet is irradiated with blue light, 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 optical wavelength conversion sheet using a spectral emission luminance meter (product name "CS2000", manufactured by Konica Minolta) under the condition of a measurement angle of 1 °.

From these measured luminances, the maintenance rate of the luminance after the moisture resistance test was determined with respect to the luminance before the moisture resistance test. The brightness retention rate is such that the brightness maintenance rate is D, the brightness of the light emitted from the light emitting surface of the backlight device before the moisture resistance test is E, and the brightness of the light emitted from the light emitting surface of the backlight device after the moisture resistance test is E. Was F, and it was calculated by the following formula. The brightness maintenance rate is preferably close to 100%.
D = F / E × 100

<Evaluation of point-shaped brightness defects>
Using the above-mentioned backlight device incorporating the light wavelength conversion sheet after the heat resistance test according to the above-mentioned Example and the above-mentioned Comparative Example, whether or not 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. Further, by using the above-mentioned backlight device incorporating the light wavelength conversion sheet after the moisture-heat resistance test according to the above-mentioned Example and the above-mentioned Comparative Example, similarly, a dot-like luminance defect on the light emitting surface at the time of light emission in the backlight device. Was visually observed and evaluated. The evaluation criteria are as follows.
◯: No point-shaped luminance defect was confirmed.
Δ: Several point-shaped luminance defects were confirmed.
X: Many dot-shaped luminance defects were confirmed.

<Measurement of deterioration width of the peripheral edge of the optical wavelength conversion sheet>
Using the above-mentioned backlight device incorporating the light wavelength conversion sheet after the heat resistance test according to the examples and the comparative examples, the luminance distribution on the light emitting surface at the time of light emission in the backlight device is measured from the thickness direction of the light wavelength conversion sheet. , 2D color luminance meter (product name "UA-200", manufactured by Topcon Techno House Co., Ltd.) was used for measurement. Then, from the measured luminance distribution of the light emitting surface, the position of the light emitting surface (luminance 80% position) at which the brightness is 80% with respect to the brightness of the central portion of the light emitting surface is obtained, and the position closest to the brightness 80% position on the light emitting surface. The shortest distance from the edge to the position where the brightness is 80% was obtained. Then, the shortest distance was randomly obtained for 20 points, and the average value of the shortest distances at these 20 points was taken as the deterioration width of the peripheral portion of the optical wavelength conversion sheet. Further, using the above-mentioned backlight device incorporating the light wavelength conversion sheet after the moisture resistance test according to the examples and comparative examples, the brightness distribution of the light emitting surface is measured in the same manner, and the brightness of the central portion of the light emitting surface is measured in the same manner. The position of the light emitting surface (luminance 80% position) at which the brightness is 80% was obtained, and the shortest distance from the end closest to the brightness 80% position on the light emitting surface to the brightness 80% position was obtained.

The results are shown in Tables 1 to 3 below.

The results will be described below. As can be seen from Tables 2 and 3, in the light wavelength conversion sheets according to Examples 1 to 12, a carboxylic acid was used and the acid value of the light wavelength conversion composition exceeded 10 mgKOH / g. Comparative Examples 2, 3, 5, which use the optical wavelength conversion sheets and carboxylic acids according to Comparative Examples 1, 4, 7, and 10 which do not use themselves, but have an acid value of 10 mgKOH / g or less in the optical wavelength conversion composition. Compared with the optical wavelength conversion sheets according to 6, 8, 9, 11, and 12, the brightness retention rate after the heat resistance test and after the heat resistance test was higher. Further, in the light wavelength conversion sheet according to Example 13, since the carboxylic acid was used and the acid value of the light wavelength conversion composition exceeded 10 mgKOH / g, the present invention relates to Comparative Example 13 in which the carboxylic acid itself was not used. After the heat resistance test and after the moisture heat resistance test, as compared with the light wavelength conversion sheets according to Comparative Examples 14 and 15 in which the light wavelength conversion sheet or the carboxylic acid is used but the acid value of the light wavelength conversion composition is 10 mgKOH / g or less. It was closer to 100% than the brightness maintenance rate of. This is because the light wavelength conversion compositions 1 to 8 and the cured product thereof have high heat resistance and moisture resistance, and when the acid value of the light wavelength conversion composition exceeds 10 mgKOH / g, the quantum dots It means that the deterioration of the light can be suppressed.

Since the barrier member was not used in the optical wavelength conversion sheets according to Examples 1 to 12 and Comparative Examples 1 to 12, no punctate luminance defect was confirmed. Further, in the light wavelength conversion sheet according to Example 13, a barrier member is used, but a carboxylic acid is used and the acid value of the light wavelength conversion composition exceeds 10 mgKOH / g, so that the luminance is punctate. No shortcomings were identified. On the other hand, in Comparative Examples 14 and 15 in which the optical wavelength conversion sheet according to Comparative Example 13 in which the carboxylic acid itself is not used and Comparative Examples 14 and 15 in which the carboxylic acid is used but the acid value of the optical wavelength conversion composition is 10 mgKOH / g or less, A punctate brightness defect was confirmed. This means that when a carboxylic acid is used and the acid value of the optical wavelength conversion composition exceeds 10 mgKOH / g, the deterioration of the quantum dots can be suppressed.

In the light wavelength conversion sheets according to Examples 1 to 12, a carboxylic acid was used and the acid value of the light wavelength conversion composition exceeded 10 mgKOH / g, so that deterioration of the peripheral portion was suppressed. This means that when a carboxylic acid is used and the acid value of the light wavelength conversion composition exceeds 10 mgKOH / g, it has an effect of suppressing deterioration of quantum dots. On the other hand, the optical wavelength conversion sheet according to Comparative Examples 1, 4, 7, and 10 which does not use the carboxylic acid itself and the comparative example in which the acid value of the optical wavelength conversion composition using the carboxylic acid is 10 mgKOH / g or less. Even in the optical wavelength conversion sheets according to 2, 3, 5, 6, 8, 9, 11, and 12, the result of deterioration of the peripheral portion was 0 mm, but this was because the optical wavelength conversion member was exposed. This is because the quantum dots deteriorated as a whole after the heat resistance test and the moisture heat resistance test, and there was almost no difference in brightness between the peripheral portion and the central portion. Further, in the optical wavelength conversion sheets according to Comparative Examples 13 to 15, the deterioration of the central portion was relatively suppressed by the barrier member, but the deterioration of the peripheral portion was not suppressed.

The total haze value of the optical wavelength conversion sheet according to the first embodiment is 98.9%, the internal haze value is 96.7%, the external haze value is 2.2%, and all the optical wavelength conversion sheets according to the second embodiment. The haze value was 99.3%, the internal haze value was 99.3%, and the external haze value was 0%. Since the external haze value is smaller than the internal haze value in both light wavelength conversion sheets, the brightness is high regardless of before and after the heat resistance test and before and after the moisture heat resistance test, but the light wavelength according to Example 1 Comparing the conversion sheet and the light wavelength conversion sheet according to Example 2, the light wavelength conversion sheet according to Example 2 had higher brightness regardless of before and after the heat resistance test and before and after the moisture heat resistance test. This is because the light wavelength conversion sheet according to Example 2 contains alumina particles as light scattering particles, so that the internal haze value of the light wavelength conversion sheet according to Example 2 is that of the wavelength conversion sheet according to Example 1. This is because it is larger than the internal haze value, and as a result, the external haze value is small. Therefore, it was confirmed that the external haze value can be made smaller by including the light scattering particles in the light wavelength conversion sheet to further increase the internal haze value, and thereby the light wavelength conversion efficiency can be further improved. .. The total haze value, the internal haze value, and the haze value in the optical wavelength conversion sheet were measured as follows. First, using a haze meter (product name "HM-150", manufactured by Murakami Color Technology Laboratory), the total haze value of the optical wavelength conversion sheet was measured according to JIS K7136. After that, a triacetyl cellulose substrate having a thickness of 60 μm (product name “Panaclean PD-S1”, manufactured by Panac Co., Ltd.) is interposed on both sides of the optical wavelength conversion sheet via a transparent optical adhesive layer (product name “Panaclean PD-S1”, manufactured by Panac Co., Ltd.) having a film thickness of 25 μm (product name “Panaclean PD-S1”). TD60UL ", manufactured by Fujifilm Co., Ltd.) was pasted. As a result, the uneven shape of the surface of 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 Technology Laboratory) to obtain the internal haze value. Then, the external haze value was obtained by subtracting the internal haze value from the total haze value. The internal haze value and the external haze value were taken as the arithmetic mean value of the values obtained by measuring each three times. The transparent optical adhesive layer and the triacetyl cellulose substrate may also affect the internal haze value and the external haze value of the optical wavelength conversion sheet, but if the internal scattering of the optical wavelength conversion sheet is extremely large, these may affect the internal haze value and the external haze value. The effect on the internal haze value and the 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 that the external haze value may be 0%.

Further, in the optical wavelength conversion sheets according to Examples 10 and 11, a scratch test was performed on the overcoat layer, and the vertical force and the horizontal force at that time were measured. As a result, the optical wavelength conversion sheet according to Example 10 was found. The vertical force was 21 μN, the horizontal force was -11 μN, and the optical wavelength conversion sheet according to Example 11 had a vertical force of 11 μN and a horizontal force of −6 μN. These overcoat layers became dense films and had the ability to prevent the light wavelength conversion member from exposure to the atmosphere. However, in terms of the ability to prevent the light wavelength conversion layer from exposure to the atmosphere, the light wavelength conversion sheet according to Example 10 It can be said that the overcoat layer is higher than the overcoat layer of the optical wavelength conversion sheet according to the eleventh embodiment. The scratch test was performed using a nanoindentation device (product name "TI950 TriboIndenter", manufactured by HYSITRON) from the cross section of the overcoat layer toward the inside of the overcoat layer (Cube Corner: Ti037_110410 (12)). ) Was pushed in by 50 nm, the depth was kept constant, and the indenter was moved horizontally at a moving speed of 4 μm / min for 30 seconds, and the vertical force (load) and horizontal force at that time were measured and measured. The average value of the vertical force and the horizontal force is obtained, and the average value of the five average values of the vertical force (five times average value) obtained by repeating this scratch test five times is used as the vertical force, and the five horizontal forces are used. The average value of the average values (5 times average value) was used as the horizontal force.

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

10, 20, 30, 40, 50, 60 ... Optical wavelength conversion sheet 11, 154, 170 ... Optical 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 (11)

For forming an optical wavelength conversion member containing quantum dots and binder resin, transmitting a part of excitation light, and converting the excitation light into light having a wavelength different from that of the incident light by the quantum dots. A curable light wavelength conversion composition,
Includes quantum dots, carboxylic acids, and polymerizable compounds ,
The content of the quantum dots with respect to the total solid content mass of the light wavelength conversion composition is 0.01% by mass or more and 2% by mass or less.
A light wavelength conversion composition having an acid value of 30.2 mgKOH / g or more. The light wavelength conversion composition according to claim 1, wherein the carboxylic acid has a polymerizable functional group. The quantum dots include 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 bound to the surface of the shell. , The optical wavelength conversion composition according to claim 1 or 2 . The light wavelength conversion composition according to any one of claims 1 to 3 , further comprising light scattering particles. A light wavelength conversion member made of a cured product of the light wavelength conversion composition according to claim 1 . It is an optical wavelength conversion sheet,
A light wavelength conversion sheet comprising the light wavelength conversion member according to claim 5 , wherein the light wavelength conversion member is formed in a layered manner. The light wavelength conversion sheet according to claim 6 , further comprising an optical member arranged 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 6 or 7 , wherein the light wavelength conversion sheet has a water vapor transmittance of 0.1 g / ( ^m 2.24 h) or more at 40 ° C. and 90% relative humidity. The light according to any one of claims 6 to 8 , wherein the light wavelength conversion sheet has an oxygen transmittance of 0.1 cm ³ / ( ^m 2.24 h · atm) or more at 23 ° C. and 90% relative humidity. Wavelength conversion sheet. Light source and
A backlight device comprising the light wavelength conversion member according to claim 5 for receiving light from the light source or the light wavelength conversion sheet according to any one of claims 6 to 9 . The backlight device according to claim 10,
An image display device including a display panel arranged on the light emitting side of the backlight device.

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