JP2022058459A - Light wavelength conversion sheet, backlight device, and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for evaluating degradation of a light wavelength conversion sheet capable of quantitative degradation evaluation with high correlation with visual evaluation.

SOLUTION: A method for evaluating degradation of a light wavelength conversion sheet 10 equipped with a host matrix and quantum dots dispersed in the host matrix. This method comprises the steps of: measuring, while one surface 10A of the light wavelength conversion sheet 10 is irradiated with light having a wavelength convertible by the quantum dots, a luminance distribution of at least part of the other surface 10B on a reverse side of one surface 10A of the light wavelength conversion sheet 10; obtaining a luminance change amount distribution on the basis of the measured luminance distribution; detecting a maximum value from the obtained luminance change amount distribution and a minimum value adjacent to the maximum value; and determining a width between a position where the maximum value is obtained and a position where the minimum value is obtained and evaluating the degradation of the light wavelength conversion sheet on the basis of the width.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a method for evaluating deterioration of an optical wavelength conversion sheet, an optical wavelength conversion sheet, a backlight device, and the like.
And the 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 considered to incorporate an optical wavelength conversion sheet including an optical wavelength conversion layer containing quantum dots and a binder resin into a backlight device (for example,).
See 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 films for suppressing the transmission of moisture and oxygen are provided on both sides of the optical wavelength conversion layer. It is provided. Since the barrier film is provided so as to sandwich the light wavelength conversion layer, the light wavelength conversion sheet usually has a structure in which the barrier film, the light wavelength conversion layer, and the barrier film are laminated in this order.

However, even an optical wavelength conversion sheet having the above structure is usually cut because the optical wavelength conversion sheet is cut to a desired size with barrier films provided on both sides of the optical wavelength conversion layer. There is no barrier film on the side surface of the light wavelength conversion sheet, and the light wavelength conversion layer is exposed. Therefore, the quantum dots at the edges of the optical wavelength conversion sheet are more likely to deteriorate than those at the center of the optical wavelength conversion sheet. When the quantum dots at the edges of the optical wavelength conversion sheet are deteriorated, the edges have a color different from that at the center when emitting light.

Currently, the deterioration evaluation of the optical wavelength conversion sheet is performed visually, but in order to visually evaluate the deterioration of the optical wavelength conversion sheet with a certain objectivity, a skilled technique is required. Therefore, there is a demand for a deterioration evaluation method for an optical wavelength conversion sheet that has a high correlation with visual evaluation and can be quantified. A quantitative deterioration evaluation method for the optical wavelength conversion sheet has not yet been established.

The present invention has been made to solve the above problems. It is an object of the present invention to provide a deterioration evaluation method for an optical wavelength conversion sheet capable of quantitative deterioration evaluation having a high correlation with visual evaluation. Another object of the present invention is to provide an optical wavelength conversion sheet in which it is difficult to confirm a change in color due to deterioration of quantum dots when visually evaluated at the time of light emission, and a backlight device and an image display device provided with such an optical wavelength conversion sheet. do.

According to one aspect of the present invention, there is a deterioration evaluation method for an optical wavelength conversion sheet including an optical wavelength conversion layer including a host matrix and quantum dots dispersed in the host matrix.
In a state where one surface of the optical wavelength conversion sheet is irradiated with light that can be wavelength-converted by the quantum dots, the brightness distribution of at least a part of the other surface of the optical wavelength conversion sheet opposite to the one surface. A step of obtaining a brightness change amount distribution based on the measured brightness distribution, and a step of detecting a maximum value and a minimum value adjacent to the maximum value from the obtained brightness change amount distribution. Deterioration evaluation of the optical wavelength conversion sheet, comprising a step of obtaining a width from a position where the maximum value is obtained to a position where the minimum value is obtained and evaluating deterioration of the optical wavelength conversion sheet based on the width. The method is provided.

In the deterioration evaluation method of the light wavelength conversion sheet, the step of measuring the luminance distribution is at least the step of measuring the luminance of the end portion of the luminance conversion sheet, and the step of obtaining the luminance change amount distribution is the step of obtaining the light. It may be a step of obtaining the luminance change amount of the end portion of the wavelength conversion sheet.

In the deterioration evaluation method of the light wavelength conversion sheet, a step of arranging the light wavelength conversion sheet on the light emitting surface of the direct type backlight device is further provided before the step of measuring the luminance distribution.
The size of the light wavelength conversion sheet may be smaller than the size of the light emitting surface, and the light emitted in the step of measuring the luminance distribution may be the light emitted from the backlight device.

In the deterioration evaluation method of the light wavelength conversion sheet, a barrier film that suppresses the transmission of water or oxygen may be further provided on at least one surface of the light wavelength conversion layer.

In the deterioration evaluation method of the optical wavelength conversion sheet, the light whose wavelength can be converted by the quantum dots is blue light, and the quantum dots convert the blue light into green light and the blue light. It may include a second quantum dot that converts it into red light.

According to another aspect of the present invention, it is an optical wavelength conversion sheet including an optical wavelength conversion layer including a host matrix and quantum dots dispersed in the host matrix, and has a temperature of 60 ° C. with respect to the optical wavelength conversion sheet. After the durability test, the width is 5 mm or less when the deterioration of the optical wavelength conversion sheet is evaluated by the deterioration evaluation method. An optical wavelength conversion sheet is provided.

In the light wavelength conversion sheet, a barrier film that suppresses the transmission of water and oxygen may be further provided on at least one surface of the light wavelength conversion layer.

In the light wavelength conversion sheet, the first quantum dot converts the blue light into green light.
Quantum dots and a second quantum dot that converts the blue light into red light may be included.

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 deterioration evaluation method of the optical wavelength conversion sheet according to one aspect of the present invention, quantitative deterioration evaluation having a high correlation with visual evaluation is possible. Further, according to another aspect of the present invention, an optical wavelength conversion sheet in which color change due to deterioration of quantum dots is less likely to be confirmed when visually evaluated at the time of light emission, and a backlight device and an image provided with such an optical wavelength conversion sheet. A display device can be provided.

It is a figure for demonstrating the deterioration evaluation method of the optical wavelength conversion sheet which concerns on embodiment. It is a figure at the time of measuring the luminance distribution of the light wavelength conversion sheet which concerns on embodiment. 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 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. 5 is a cross-sectional view taken along the line I-I of the lens sheet of FIG. It is a schematic block diagram of the other backlight apparatus which concerns on embodiment. It is a graph which showed the luminance distribution of the light wavelength conversion sheet which concerns on a sample 2. It is a graph which showed the luminance change amount distribution of the light wavelength conversion sheet which concerns on a sample 2. It is a graph which enlarged a part of the luminance change amount distribution of FIG.

Hereinafter, a method for evaluating deterioration of an optical wavelength conversion sheet according to an embodiment of the present invention, an optical wavelength conversion sheet,
The backlight device and the image display device 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 diagram for explaining a deterioration evaluation method of the optical wavelength conversion sheet according to the embodiment, FIG. 2 is a diagram for measuring the luminance distribution of the optical wavelength conversion sheet according to the embodiment, and FIG. 3 is a diagram. It is a schematic block diagram of the light wavelength conversion sheet which concerns on this embodiment, and FIG. 4 is a figure which shows the operation of the light wavelength conversion sheet which concerns on this embodiment.

<<< Deterioration evaluation method for optical wavelength conversion sheet >>>
When evaluating the deterioration of the optical wavelength conversion sheet, first, as shown in FIG. 1, a deterioration evaluation device 1 and an optical wavelength conversion sheet 10 to be measured are prepared. The deterioration evaluation device 1 is arranged above the direct type backlight device 2 and the backlight device 2, and is an optical wavelength conversion sheet 1.
It includes a luminance meter 3 that measures the luminance of 0, and a processing device 4 that is electrically connected to the luminance meter 3.

<< Backlight device >>
The backlight device 2 includes a light source 5 and a light diffusing plate 6 arranged on the light source 5 and having a function of diffusing the light from the light source 5. In addition to the light source 5 and the light diffusing plate 6, the backlight device 2 may include a lens sheet and a reflective polarizing separation sheet on the light diffusing plate 6. Figure 1
The light emitting surface 2A of the backlight device 2 shown in the above is composed of a light emitting surface of a light diffusing plate.

<Light source>
The light source 5 irradiates light whose wavelength is converted by the quantum dots 17, which will be described later.
The light source 5 is not particularly limited as long as it irradiates light whose wavelength is converted by the quantum dots 17, but is, for example, a fluorescent lamp such as a linear cold cathode fluorescent lamp or a point-shaped light emitting diode (LE).
D) and incandescent light bulbs can be mentioned. When the quantum dot 17 includes a first quantum dot that converts blue light into green light and a second quantum dot that converts blue light into red light, the light source 2 is a light source that emits blue light. A blue light emitting diode is particularly preferable. As used herein, "blue light" is light having a wavelength range of 380 nm or more and less than 480 nm, and "green light" is defined as "green light".
Light having a wavelength range of 480 nm or more and less than 590 nm, and "red light" is 590 nm.
Light having a wavelength range of 750 nm or less.

<Light diffuser>
The light diffusing plate 6 has an incoming light surface 6A formed by one surface on the light source 5 side and an outgoing light surface 6B formed by the other surface on the light wavelength conversion sheet 10. The light incident on the light diffusing plate 6 from the light entering surface 6A is diffused in the light diffusing plate 6 and emitted from the light emitting surface 6B.

The light diffusing plate 6 is not particularly limited as long as it can diffuse the light from the light source 5, 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, polystyrene resin, styrene-.
Methyl methacrylate copolymer resin, styrene-methacrylic acid copolymer resin, styrene-maleic anhydride copolymer resin, methacrylic resin, acrylic resin, polycarbonate resin, A
Examples thereof include BS resin (acrylonitrile-butadiene-styrene copolymer resin), AS resin (acrylonitrile-styrene copolymer resin), and polyolefin resin (polyethylene resin, polypropylene resin, etc.). One of these may be used, or two or more of these may be mixed and used. Examples of the light diffusing particles in the light diffusing plate 6 include light diffusing particles generally used as a light diffusing plate.

<< Luminance meter >>
The luminance meter 3 measures the luminance distribution of the other surface 10B on the opposite side of the backlight device 2 side of the optical wavelength conversion sheet 10 from the one surface 10A. The luminance meter may be a surface luminance meter that measures the luminance distribution of the entire surface. The luminance meter 3 is not particularly limited, and a commercially available product can be used. Examples of commercially available luminance meters include UA-200 (manufactured by Topcon Techno House). The distance (focal length) from the surface 10B of the optical wavelength conversion sheet 10 to the luminance meter 3 can be appropriately adjusted.

<< Processing equipment >>
The processing device 4 has a function of capturing the luminance distribution measured by the luminance meter 3 as data and obtaining the luminance change amount distribution based on the captured luminance distribution. Further, the processing device 4 may have a function of extracting a luminance distribution in a designated portion (for example, a linear portion from any one end edge to the other end edge of the optical wavelength conversion sheet).

<< Optical wavelength conversion sheet >>
The light wavelength conversion sheet 10 to be measured is a sheet 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. be.
The size of the light wavelength conversion sheet 10 is preferably smaller than the size of the light emitting surface 2A of the backlight device 2. By using the optical wavelength conversion sheet 10 having such a size, it is possible to evaluate not only the deterioration of the central portion of the optical wavelength conversion sheet 10 with respect to the end portion but also the deterioration of the end portion of the optical wavelength conversion sheet 10. can. As used herein, the term "deterioration of the end portion" means that the quantum dots existing at the end portion of the optical wavelength conversion sheet are deteriorated.

As shown in FIG. 3, the optical wavelength conversion sheet 10 includes an optical wavelength conversion layer 11, barrier films 12 and 13 provided on both sides of the optical wavelength conversion layer 11, and optical wavelength conversion layers in the barrier films 12 and 13. It is provided with light diffusion layers 14 and 15 provided on a surface opposite to the surface on the 11 side. In the light wavelength conversion sheet 10, the surface of the light diffusion layers 14 and 15 is the light wavelength conversion sheet 1.
It constitutes the surface of 0.

The light wavelength conversion sheet 10 has a structure of a light diffusion layer 14 / barrier film 12 / light wavelength conversion layer 11 / barrier film 13 / light diffusion layer 15, but the light wavelength conversion sheet has a light wavelength conversion layer. If so, the structure of the optical wavelength conversion sheet is not particularly limited. For example, the light wavelength conversion sheet is a light diffusion layer / barrier film / light wavelength conversion layer / barrier film, barrier film /
Light wavelength conversion layer / barrier film, light transmission base material / light wavelength conversion layer / light transmission base material, light diffusion layer / overcoat layer / light wavelength conversion layer / overcoat layer / light diffusion layer, or overcoat layer It may be configured as a / optical wavelength conversion layer / overcoat layer.

In the optical wavelength conversion sheet 10, as shown in FIG. 4, 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 layer 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 layer 11 is emitted from the surface 10B without being wavelength-converted.

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 light wavelength conversion sheet 10 is in this range, it is suitable for weight reduction and thinning of the backlight device in which the light wavelength conversion sheet 10 is incorporated.

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. Among these, the optical wavelength conversion sheet 10
Considering that the film thickness is on the order of μm, it is preferable to use SEM. SEM
When measuring in, it is preferable that the acceleration voltage is 30 kV and the magnification is 1000 to 7000 times.

Since the light wavelength conversion sheet 10 includes the barrier films 12 and 13, the entire sheet has a water vapor transmittance (WVTR: Water Vapor Transmission) at 40 ° C. and a relative humidity of 90%.
Rate) is preferably less than 0.1 g / ( ^m 2.24 h). 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 optical wavelength conversion sheet 10 includes the barrier films 12 and 13, the oxygen transmission rate (OTR: Oxygen Transmission Rate) at 23 ° C. and 90% relative humidity is provided for the entire sheet.
Is preferably less than 0.1 cm ³ / ( ^m 2.24 h · atm). 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.

The water vapor transmittance of the light wavelength conversion sheet 10 at 40 ° C. and 90% relative humidity is 1.0 × 1.
It is preferably 0-2 g / ( ^{m 2.24} h) or less, and the optical wavelength conversion sheet 1
Oxygen permeability at 23 ° C at 0 and 90% relative humidity is 1.0 × 10 ^-2 cm ³ / (m ² ·.
It is preferably 24 h · atm) or less.

<Light wavelength conversion layer>
The optical wavelength conversion layer 11 includes a host matrix 16 and quantum dots 17 dispersed in the host matrix 16. The light wavelength conversion layer 11 preferably contains light scattering particles 18 in order to increase the wavelength efficiency. Further, the optical wavelength conversion layer 11 preferably contains an additive for suppressing deterioration of the quantum dots 17. Both sides of the light wavelength conversion layer 11 are covered with the barrier fluids 12 and 13, but the side surfaces of the light wavelength conversion layer 11 are exposed.

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

(Host matrix)
The host matrix 16 is not particularly limited, and examples thereof include at least one of a binder resin, glass such as silica glass, and silica gel. The binder resin is not particularly limited, and examples thereof include polymers of polymerizable compounds. The polymerizable compound (curable compound) is a polymerizable compound, and examples thereof include an ionizing radiation polymerizable compound (ionizing radiation curable compound) and a thermopolymerizable compound (thermocurable compound). Examples of ionizing radiation in the present specification include visible light and ultraviolet rays, X-rays, electron beams, α rays, β rays, and γ rays.

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 Etc. (meta)
Acrylic acid esters can 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, and polyether (meth).
Examples thereof include acrylates, polyol (meth) acrylates, melamine (meth) acrylates, isocyanurate (meth) acrylates, and epoxy (meth) acrylates.

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 layer 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.

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 novolak type epoxy. Compounds, aromatics such as modified products thereof, or ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether or 1
, 6-Hexanediol Diglycidyl ether such as alkylene glycol diglycidyl ether, Polyglycidyl ether of polyhydric alcohol such as di or triglycidyl ether of glycerin or its alkylene oxide adduct, diglycidyl of polyethylene glycol or its alkylene oxide adduct Examples thereof include polyalkylene glycol diglycidyl ethers such as ethers, polypropylene glycols or diglycidyl ethers of alkylene oxide adducts thereof, and aliphatic systems such as alkylene oxides. 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, 3', 4'-in terms of adhesive strength and curability
Epoxy Cyclohexyl Methyl 3,4-Epoxy Cyclohexane Carboxylate, 3,4
-Alicyclic epoxy compounds such as epoxycyclohexylmethylmethacrylate are preferred.

(Quantum dot)
The quantum dots 17 are nano-sized semiconductor particles having a quantum confinement effect. The particle size and average particle size of the quantum dots 17 are, for example, 1 nm.
It is 20 nm or less. When the quantum dot 17 absorbs light from an excitation source and reaches an energy excited state, the quantum dot 17 emits energy corresponding to the energy band gap of the quantum dot. Therefore, by adjusting the particle size or the composition of the substance of the quantum dots 17, the energy band gap can be adjusted, and energy in various levels of wavelength bands can be obtained. In particular, the quantum dots 17 can generate strong fluorescence in a narrow wavelength band.

Specifically, the energy band gap of the quantum dots 17 increases as the particle size decreases. That is, as the crystal size becomes smaller, the emission of the quantum dots 17 shifts to the blue side, that is, to the high energy side. Therefore, by changing the particle size of the quantum dot 17, 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, the quantum dot 17 is CdSe described later.
When composed of / ZnS, the particle size of the quantum dot 17 is 2.0 nm or more and 4.0.
When it is nm or less, it emits blue light, when the particle size of the quantum dot 17 is 3.0 nm or more and 6.0 nm or less, it emits green light, and when the particle size of the quantum dot 17 is 4.5 nm or more and 10.0 nm or less. Emits red light. 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 17, 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. be. Specifically, the optical wavelength conversion layer 11 is the first quantum dot 17A.
And the second quantum dot 17B having an emission band in a wavelength range different from that of the first quantum dot 17A.
And may be included.

The quantum dots 17 can generate strong fluorescence in a desired narrow wavelength range. For this reason,
A backlight device using an optical wavelength conversion sheet can illuminate a display panel with light of three primary colors having excellent color purity. In this case, the display panel will have excellent color reproducibility.

The quantum dots 17 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. It is configured.

Examples of the first semiconductor compound constituting the core include MgS, MgSe, MgTe, and the like.
CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaT
II-VI group semiconductor compounds such as e, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe and HgTe, AlN, AlP, AlAs, AlSb, G
aAs, GaP, GaN, GaSb, InN, InAs, InP, InSb, TiN, T
Examples thereof include semiconductor compounds such as group III-V semiconductor compounds such as iP, TiAs and TiSb, 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, and Cd.
Examples thereof include SSe, 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, and CdTe / Cd.
S, InP / ZnS, Gap / ZnS, Si / ZnS, InN / GaN, InP / CdS
Se, InP / ZnSeTe, InGaP / ZnSe, InGaP / ZnS, Si / Al
P, 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.

The shape of the quantum dot 17 is not particularly limited, and may be, for example, a spherical shape, a rod shape, a disk shape, or any other shape. The particle size of the semiconductor nanoparticles is determined when the shape of the semiconductor nanoparticles is not spherical.
It can be a spherical value having the same volume.

Information such as the particle size, average particle size, shape, and dispersed state of the quantum dots 17 can be obtained by a transmission electron microscope or a scanning transmission electron microscope. The average particle size 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 17 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 17. Regarding the crystal structure and crystallite size of the quantum dots 17,
It can be known by X-ray crystal diffraction (XRD). Furthermore, UV-Vis
) Information on the particle size of quantum dots can be obtained from the absorption spectrum.

The content of the quantum dots 17 in the optical wavelength conversion layer 11 is preferably 0.01% by mass or more and 2% by mass or less, and more preferably 0.03% by mass or more and 1% by mass or less. If the content of the light wavelength conversion particles is less than 0.01% by mass, sufficient emission intensity may not be obtained, and if the content of the light wavelength conversion particles exceeds 2% by mass, sufficient excitation may be obtained. There is a possibility that the transmitted light intensity of light cannot be obtained. The mass% of the quantum dots in the optical wavelength conversion layer which is a cured product.
And the mass% of the light-scattering particles described later can be roughly calculated by the following method. First, at least a part of the light wavelength conversion layer is sampled from the light wavelength conversion sheet, and its mass is measured. Next, the host matrix contained in the sampled portion is dissolved in a solvent or incinerated by combustion to remove the components of the host matrix. When the components of the host matrix are removed, the quantum dots and light-scattering particles are not removed, and since the particle sizes of the quantum dots and the light-scattering particles are significantly different, the quantum dot components and light are different due to the difference in particle size. Separate the components of the scattering particles. Then, the mass of the separated quantum dot component and the component of the light-scattering particle are measured, respectively. Then, the ratio of the mass of the quantum dots contained in at least a part of the sampled light wavelength conversion layer based on the mass of at least a part of the sampled light wavelength conversion layer and the mass of the quantum dots is calculated. Further, the ratio of the mass of the light scattering particles contained in at least a part of the sampled light wavelength conversion layer is calculated based on the mass of at least a part of the sampled light wavelength conversion layer and the mass of the light scattering particles.

(Light scattering particles)
The light scattering particles 18 are particles having an action of changing the traveling direction of light by scattering the light that has entered the light wavelength conversion layer 11.

The average particle size of the light-scattering particles 18 is 20 times or more the average particle size of the quantum dots 17 2000.
It is preferably fold or less, and more preferably 50 times or more and 1000 times or less. If the average particle size of the light-scattering particles is less than 20 times the average particle size of the quantum dots, sufficient light-scattering performance may not be obtained in the light wavelength conversion layer, and the average particle size of the light-scattering particles becomes If it exceeds 2000 times the average particle size of the quantum dots, the number of light-scattering particles will decrease even if the amount added is the same, so the number of scattering points will decrease and a sufficient light-scattering effect may not be obtained. .. note that,
The average particle size of the light-scattering particles 18 can be measured by the same method as the average particle size of the quantum dots 17 described above.

The average particle size of the light-scattering particles 18 is 1 / of the average film thickness of the light wavelength conversion layer 11 described later.
It is preferably 300 or more and 1/20 or less, and more preferably 1/200 or more and 1/30 or less. If the average particle size of the light scattering particles is less than 1/300 of the average film thickness of the light wavelength conversion layer, sufficient light scattering performance may not be obtained in the light wavelength conversion layer, and the average of the light scattering particles. If the particle size exceeds 1/20 of the average film thickness of the light wavelength conversion layer, the ratio of light scattering particles to the light wavelength conversion layer decreases even if the amount added is the same, so that the number of scattering points is sufficiently reduced. No light scattering effect can be obtained.

Specifically, the average particle diameter of the light-scattering particles 18 is preferably, for example, 0.1 μm or more and 10 μm or less, and more preferably 0.3 μm or more and 5 μm or less. If the average particle size of the light scattering particles is less than 0.1 μm, the light wavelength conversion efficiency of the light wavelength conversion sheet may be insufficient, and in order to obtain sufficient light scattering properties, the light scattering particles may have insufficient light scattering properties. It is necessary to increase the amount added. On the other hand, when the average particle size of the light-scattering particles exceeds 10 μm, the number of light-scattering particles is reduced even if the addition amount (% by mass) is the same, so that the number of scattering points is reduced and a sufficient light-scattering effect is obtained. I can't get it.

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

The light-scattering particles 18 are preferably surface-treated with a silane coupling agent from the viewpoint of firmly fixing the light-scattering particles 18 in the host matrix 16. By surface-treating with a silane coupling agent, it can be chemically bonded to the host matrix 16.

The light-scattering particles 18 may be organic particles such as acrylic resin particles, styrene resin particles, melamine resin particles, and urethane resin particles, but the rate of change in brightness before and after the moisture resistance test can be reduced. Further, inorganic particles are preferable because the incident light on the light wavelength conversion sheet can be suitably scattered and the light wavelength conversion efficiency with respect to the incident light can be preferably improved.

The inorganic particles include an aluminum-containing compound such as Al ₂ O ₃ , a zirconium-containing compound such as ZrO ₂ , a tin-containing compound such as antimony-doped tin oxide (ATO) and indium tin oxide (ITO), and magnesium such as MgO and MgF ₂ . At least one compound selected from the group consisting of compounds, titanium-containing compounds such as TiO ₂ and BaTiO ₃ , antimony-containing compounds such as Sb ₂ O ₅ , silicon-containing compounds such as SiO ₂ , and zinc-containing compounds such as ZnO. Particles can be mentioned. Since these inorganic particles can increase the difference in refractive index from the binder resin, they are also preferable from the viewpoint of obtaining a large Mie scattering intensity. The light scattering particles 18 may be made of two or more kinds of materials because the light wavelength conversion efficiency with respect to the incident light can be more preferably improved by the light wavelength conversion sheet 10.

The content of the light scattering particles 18 in the light wavelength conversion layer 11 is preferably 1% by mass or more and 50% by mass or less, and more preferably 3% by mass or more and 30% by mass or less. If the content of the light scattering particles is less than 1% by mass, the light scattering effect may not be sufficiently obtained, and if the content of the light scattering particles exceeds 50% by mass, me scattering occurs. Since it becomes difficult, there is a possibility that the light scattering effect cannot be sufficiently obtained, and further, there is a possibility that the processability is deteriorated because there are too many light scattering particles.

The absolute value of the difference in refractive index between the light-scattering particles 18 and the host matrix 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 host matrix 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 layer, for example, the Becke method, the minimum declination method, the declination analysis, the mode line method, the ellipsometry method and the like are used. can do. Further, the refractive index of the host matrix 16 in the optical wavelength conversion layer 11 is determined by, for example, 10 pieces of the host matrix 16 taken out from the light wavelength conversion layer 11 by cutting out or the like, and the 10 pieces taken out by the Becke method. The refractive index of the host matrix 16 was measured, and the measured refractive index of the host matrix 16 was 1.
It can be obtained as an average value of 0 pieces. The refractive index of the light-scattering particles 18 is, for example,
Fragments whose surface is partially exposed from the host matrix 16 are taken out from the light wavelength conversion layer 11 by cutting out, etc., and 10 light scattering particles whose surface is exposed by the Becke method in the taken out fragments. The light scattering particles 1 measured by measuring the refractive index of each of the 18
It can be obtained as an average value of 10 refractive indexes of 8. In the Becke method, a refractive index standard solution having a known refractive index is used, the above-mentioned pieces are placed on a slide glass or the like, the refractive index standard solution is dropped onto the sample, and the pieces are immersed in the refractive index standard solution. Is observed by microscopic observation, and the emission line (Becke line) generated on the surface of the binder resin or light-scattering particles cannot be visually observed due to the difference in the refractive index between the surface of the binder resin or light-scattering particles and the refraction index standard solution. Refraction index This is a method in which the refractive index of a standard solution is used as the refractive index of a host matrix or light-scattering particles. When the surface of the light-scattering particles is not exposed in the removed fragments, the surface of the light-scattering particles is covered with the host matrix, so that the surface of the light-scattering particles is covered with the host matrix existing around the light-scattering particles. There is no difference in refractive index. Therefore, by measuring the difference in refractive index from the host matrix existing around the light-scattering particles by the Becke method or the like, it is possible to determine whether or not a part of the surface of the light-scattering particles is exposed. .. In addition, the difference in refractive index between the binder resin and the light-scattering particles is measured using a phase-shift laser interference microscope (such as a phase-shift laser interference microscope manufactured by FK Optical Research Institute or a two-beam interference microscope manufactured by Mizojiri Optical Co., Ltd.). can do.

(Additive)
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 be bound to the host matrix.

<Barrier film>
The barrier films 12 and 13 are films for suppressing the permeation of water and oxygen to protect the quantum dots 17 from water and oxygen. Here, the "barrier film" in the present specification.
Is a single member with a water vapor permeability of 0.1 g / ( ^m 2.24) at 40 ° C and 90% relative humidity.
H) or less, and the oxygen permeability at 23 ° C. and 90% relative humidity is 0.1 cm ³ / (m ² ·.
It shall mean a film having less than 24h · atm). The barrier film includes not only a single-layer structure film but also a multi-layer structure film. By installing the barrier films 12 and 13 in a state of sandwiching the optical wavelength conversion layer 11, the durability of the quantum dots 17 can be further improved. The barrier films 12 and 13 shown in FIG. 3 are light-transmitting base materials 19.
, 20 and barrier layers 21 and 22 provided on the light wavelength conversion layer 11 side of the light transmissive base materials 19 and 20 and having a function of suppressing the transmission of water and oxygen.

Water vapor transmission rate (WVTR) of barrier films 12 and 13
Is 1.0 × 10 ^-2 g / (m ^2.24h ) under the conditions of 40 ° C. and 90% relative humidity.
The following 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 water vapor transmittance shall be the average value of the values obtained by measuring three times.

The oxygen transmission rate (OTR: Oxygen Transmission Rate) of the barrier films 12 and 13 is 23.
1.0 × 10 ^-2 cm ³ / ( ^m 2.24 h ・ at) under conditions of ° C and relative humidity of 90%
m) It is more preferable that it is less than or equal to m). 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.

(Light transmissive base material)
The thickness of the light-transmitting base materials 19 and 20 is not particularly limited, but is preferably 10 μm or more and 300 μm or less. If the thickness of the light-transmitting base materials 19 and 20 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 19 and 20 is 50 μm or more, and the more preferable upper limit is 2.
It is 00 μm or less.

The thickness of the light-transmitting base materials 19 and 20 includes a scanning electron microscope (SEM) and a transmission electron microscope (SEM).
Using a TEM) or a scanning transmission electron microscope (STEM), a cross section of the light transmissive substrate 19 or 20 is photographed, and the thickness of the light transmissive substrate 19 or 20 is measured at 20 points in the image of the cross section.
The average value of the film thicknesses at the 20 locations is used.

Examples of the constituent raw materials of the light-transmitting base materials 19 and 20 include polyester (for example, polyethylene terephthalate and polyethylene naphthalate), cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyethersulfone, and polysulfone. , Polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyether ketone, polymethyl methacrylate, polycarbonate, or thermoplastic resins such as polyurethane. Light-transmitting substrate 12, 1
The constituent material of 3 is preferably polyester (for example, polyethylene terephthalate, polyethylene naphthalate).

The light-transmitting base materials 19 and 20 may be composed of a single base material, or may be a laminated base material composed of a plurality of base materials. Such a laminated base material may be composed of a plurality of layers composed of layers of the same type of constituent raw materials, or may be composed of a plurality of layers composed of layers of different types of constituent raw materials, depending on the intended use. good.

(Barrier layer)
The barrier layers 21 and 22 are composed of a thin-film 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 is
It may be directly laminated or laminated.

<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 the light wavelength conversion sheet 10 and the light emitted from the light wavelength conversion sheet 10. Light diffusion layer 14,
By providing 15, the optical wavelength conversion efficiency of the optical 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-diffusivity may not be obtained in the light-diffusing layer, and the average particle size of the light-scattering particles may not be sufficient. If it exceeds 20,000 times the average particle size of the quantum dots, the light diffusion performance of the light diffusion layer becomes excellent, but the light transmission rate of the light diffusion layer tends to be significantly reduced. The average particle size of the light-scattering particles can be measured by the same method as the average particle size of the quantum dots 17 described above.

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 0.0.
It is preferably 2 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. A more preferable lower limit of the difference in refractive index between the light-scattering particles and the binder resin is 0.03 or more.
A 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.

The shape of the light-scattering particles in the light-diffusing layers 14 and 15 is the light-scattering particles 18 in the light wavelength conversion layer 11.
Since it is the same as the shape of, 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.

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. ,
Examples thereof include polycarbonate, polyethylene and polyolefin. 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, antimonated tin oxide (ATO), and zinc oxide fine particles. Among them, silica and / or alumina are preferably used.

(Binder resin)
As the binder resin, a polymer of a polymerizable compound can be used. As the polymerizable compound, the same polymerizable compound as that described in the column of the light wavelength conversion layer can be used, and therefore the description thereof will be omitted here.

After preparing the deterioration evaluation device 1 and the light wavelength conversion sheet 10, the light wavelength conversion sheet 10 is placed on the light emitting surface 2A (light emitting surface 3B of the light diffusing plate 6) of the backlight device 2. Next, the light source 5 of the backlight device 2 irradiates the surface 10A of the light wavelength conversion sheet 10 with light whose wavelength can be converted by the quantum dots 17. Then, in this state, the surface 10B of the optical wavelength conversion sheet 10
The luminance distribution of at least a part of the above is measured by the luminance meter 3. When a surface luminance meter is used as the luminance meter 3, the luminance of the entire surface 10B of the optical wavelength conversion sheet 10 is measured.

The luminance distribution measured by the luminance meter 3 is taken into the processing apparatus 4 as data. In the processing apparatus 4, the luminance change amount distribution is obtained based on the luminance distribution captured as data. Specifically, for example, in the luminance distribution, the luminance distribution is standardized so that the maximum luminance is 100%, the unit is converted to%, and then the luminance change amount distribution is obtained from the luminance distribution. The amount of change in brightness is the difference in brightness for each measurement interval when measuring brightness. The measurement interval is preferably 0.5 mm or less, more preferably 0.2 mm or less. When a surface luminance meter is used as the luminance meter 3, when the size of the light wavelength conversion sheet 10 is smaller than the size of the light emitting surface 2A, not only the brightness of the entire surface 10B of the light wavelength conversion sheet 10 but also the luminance Since the brightness of the light emitting surface 2A outside the light wavelength conversion sheet 10 can also be measured, in the processing apparatus 4, any point A on the light emitting surface 2A outside the light wavelength conversion sheet 10 as shown in FIG. By crossing the light wavelength conversion sheet 10 along one side of the light wavelength conversion sheet 10 and designating a straight portion to another arbitrary point B on the light emitting surface 2A outside the light wavelength conversion sheet 10, this designation is made. The brightness distribution in the specified part is extracted, and the brightness change amount distribution in the specified part is obtained. In this way, the light wavelength conversion sheet 10 is crossed along one side of the light wavelength conversion sheet 10 from an arbitrary point A on the light emitting surface 2A outside the light wavelength conversion sheet 10, and is outside the light wavelength conversion sheet 10. Since the end portions 10C and 10D of the light wavelength conversion sheet 10 can be accurately evaluated by obtaining the brightness change amount distribution up to another arbitrary point B on the light emitting surface 2A, the end portion 1 of the light wavelength conversion sheet 10 can be accurately evaluated.
Not only the deterioration of the part inside 0C and 10D, but also the end portion 10C of the optical wavelength conversion sheet 10.
The deterioration of 10D can be evaluated.

Then, the maximum value and the minimum value adjacent to the maximum value are detected from the obtained luminance change amount distribution. The "maximum value" in the present specification means a point where the amount of change in luminance changes from an increase to a decrease, and the amount of change in luminance is 1.5% or more. Further, the “minimum value” in the present specification means a point where the amount of change in luminance changes from a decrease to an increase, and the amount of change in luminance is −1.5% or less. If the maximum value or the minimum value is not detected, it is determined that there is no deterioration of the optical wavelength conversion sheet in this portion.

When the maximum value and the minimum value are detected, the width from the position where the maximum value is obtained to the position where the minimum value is obtained (hereinafter, this width is referred to as "deterioration width") is obtained and based on this deterioration width. And evaluate the deterioration of the optical wavelength conversion sheet. Specifically, for example, the deterioration of the optical wavelength conversion sheet can be evaluated depending on whether or not the deterioration width is within a predetermined range. For example, when this deterioration width is 5 mm or less, even if the color change of the light wavelength conversion sheet is visually evaluated, the color change is not noticed, so that the deterioration width of the light wavelength conversion sheet is 5 mm or less. In that case, it can be determined that the deterioration of the optical wavelength conversion sheet is not deteriorated in the evaluated portion. Therefore, this deterioration width is 5.
Deterioration of the optical wavelength conversion sheet can be evaluated depending on whether or not it is mm or less.

The deterioration width indicates how wide the deterioration of the quantum dots is, and the larger the deterioration width is, the wider the region where the quantum dots are deteriorated. Here, the human eye tends to detect deterioration of the optical wavelength conversion sheet when the local brightness change is large, but cannot detect deterioration of the optical wavelength conversion sheet when the deteriorated region is narrow. be. Therefore, with the human eye, when the change in brightness is large locally and the area where the light wavelength conversion sheet is deteriorated is wide, the deterioration of the light wavelength conversion sheet can be detected, but the change in brightness is locally caused. Even if it is large, if the deteriorated region of the optical wavelength conversion sheet is narrow, the deterioration of the optical wavelength conversion sheet cannot be detected. On the other hand, in the present embodiment, since the deterioration of the optical wavelength conversion sheet is evaluated by the deterioration width, it is possible to perform a quantitative deterioration evaluation having a high correlation with the visual evaluation.

The deterioration evaluation method of the present embodiment is particularly effective in an optical wavelength conversion sheet having barrier films on both sides of the optical wavelength conversion layer such as the optical wavelength conversion sheet 10. That is, when the barrier films are provided on both sides of the light wavelength conversion layer, both sides of the light wavelength conversion layer are covered with the barrier film, but the edges of the light wavelength conversion layer are exposed. Therefore, the end portion (the portion including the edge) of the optical wavelength conversion layer is liable to deteriorate. Here, in the light wavelength conversion sheet, when the end portion of the light wavelength conversion sheet is deteriorated, the light from the light source of the backlight device (for example, blue light) is absorbed and lost, so that the end portion of the light wavelength conversion sheet is lost. The brightness drops sharply in the part. Therefore, when the size of the light wavelength conversion sheet is smaller than the light emitting surface of the backlight device, it can be placed on one side of the light wavelength conversion sheet from any point on the light emitting surface of the backlight device outside the light wavelength conversion sheet. When the brightness change distribution is measured along the light wavelength conversion sheet to another arbitrary point on the light emitting surface outside the light wavelength conversion sheet, this of the light wavelength conversion sheet from the above arbitrary point. Since there is a light diffuser that does not absorb the light from the light source of the backlight device up to the edge of the light wavelength conversion sheet on the point side, the amount of change in brightness is almost constant, but it enters the edge of the light wavelength conversion sheet. Since the brightness drops sharply, a minimum value appears in the brightness change amount distribution. Then, when it passes through the deteriorated end portion, it enters the non-deteriorated portion of the optical wavelength conversion sheet, so that the luminance increases sharply and a maximum value appears in the luminance change amount distribution. Further, in the non-deteriorated portion of the optical wavelength conversion sheet, the amount of change in brightness is almost constant, but when it enters the end on the opposite side of the deterioration, the brightness drops sharply, so that the amount of change in brightness is distributed. The minimum value appears again in. Then, when the light wavelength conversion sheet passes through the edge opposite to the edge, it enters the light diffusing plate, so that the maximum value appears again in the luminance change amount distribution. Therefore, at the end of the optical wavelength conversion sheet, by measuring the deterioration width, it is possible to easily grasp how much the deterioration is from the edge of the optical wavelength conversion sheet toward the center.

In the above, a light wavelength conversion sheet smaller than the light emitting surface of the backlight device is used, but for example, the quantum dots may deteriorate in a spot shape in a portion other than the end portion of the light wavelength conversion sheet, and the quantum dots may be deteriorated. The size of the light wavelength conversion sheet does not necessarily have to be smaller than the light emitting surface of the backlight device in order to grasp how large the spot is deteriorated.

When the deterioration of the light wavelength conversion sheet 10 is evaluated by the deterioration evaluation method of the present embodiment, if the deterioration width of the light wavelength conversion sheet 10 is 5 mm or less, the visual evaluation at the time of light emission is performed for the above reason. It is difficult to confirm the change in color due to the deterioration of the quantum dots 17. In particular, a durability test was performed on the light wavelength conversion sheet 10 in an environment of 60 ° C. and a relative humidity of 90% for 500 hours, and the deterioration width of the light wavelength conversion sheet 10 after the durability test was 5 mm or less. Therefore, even after the durability test, it is difficult to confirm the change in color due to the deterioration of the quantum dots 17 by visual evaluation at the time of light emission. This makes it possible to provide the optical wavelength conversion sheet 10 in which it is difficult to confirm the change in color due to the deterioration of the quantum dots 17 at the time of light emission. An optical wavelength conversion sheet having a deterioration width of 5 mm or less can be achieved, for example, by adding the above-mentioned additive or the like for suppressing the deterioration of quantum dots to the optical wavelength conversion layer.

The optical wavelength conversion sheet 10 can be used by incorporating it 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. 5 is a schematic configuration diagram of an image display device including a backlight device according to the present embodiment, FIG. 6 is a perspective view of the lens sheet shown in FIG. 5, and FIG. 7 is an I- of the lens sheet of FIG. It is a cross-sectional view along the line I, and FIG. 8 is a schematic configuration diagram of another backlight device according to the present embodiment.

<<< Image display device >>>
The image display device 30 shown in FIG. 4 includes a backlight device 40 and a backlight device 40.
It is provided with a display panel 80 arranged on the light emitting side of the above. The image display device 30 has a display surface 30A for displaying an image. In the image display device 30 shown in FIG. 5, the surface of the display panel 80 is the display surface 30A.

The backlight device 40 illuminates the display panel 80 in a plane from the back surface side. The display panel 80 functions as a shutter that controls the transmission or blocking of light from the backlight device 40 for each pixel, and is configured to display an image on the display surface 70A.

<< Display panel >>
The display panel 80 shown in FIG. 5 is a liquid crystal display panel, and is between the polarizing plate 81 arranged on the incoming light side, the polarizing plate 82 arranged on the light emitting side, and the polarizing plate 81 and the polarizing plate 82. It is provided with an arranged liquid crystal cell 83. The polarizing plates 81 and 82 decompose the incident light into two orthogonal linear polarization components (S-polarization and P-polarization) 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 83 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 83 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 81 arranged on the incoming light side has a polarization direction of 90 ° when passing through the liquid crystal cell 83 to which a voltage is applied.
It is rotated while maintaining its polarization direction as it passes through the liquid crystal cell 83 to which no voltage is applied. In this case, depending on whether or not a voltage is applied to the liquid crystal cell 83, the linearly polarized light component vibrating in a specific direction transmitted through the polarizing plate 81 is transmitted through the polarizing plate 82, or the polarizing plate 8 is used.
It can be absorbed and blocked at 2. In this way, the display panel 80 is configured so that the transmission or blocking of light from the backlight device 40 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 40 shown in FIG. 5 is configured as an edge light type backlight device, and has a light source 50, an optical plate 55 as a light guide plate arranged on the side of the light source 50, and a light emitting side of the optical plate 55. The optical wavelength conversion sheet 10 arranged in the light wavelength conversion sheet 10, the lens sheet 60 arranged on the light source side of the light wavelength conversion sheet 10, and the lens sheet 65 arranged on the light source side of the lens sheet 60.
A reflective polarizing separation sheet 70 arranged on the light emitting side of the lens sheet 65, and a reflective sheet 75 arranged on the side opposite to the light emitting side of the optical plate 55 are provided. The backlight device 40 includes an optical plate 55, lens sheets 60 and 65, a reflective polarizing separation sheet 70, and a reflective sheet 75, 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 40 has a light emitting surface 40A that emits light in a planar manner. In the backlight device 40 shown in FIG. 5, the light emitting surface of the reflective polarizing separation sheet 70 is the light emitting surface 40A of the backlight device 40.

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 60 side is the surface 10B (light emission surface).

<Light source>
Since the light source 50 is the same as the above light source, the description thereof will be omitted here.

<Optical plate>
The optical plate 65 as a light guide plate has a rectangular shape in a plan view. Optical plate 65
Refers to a back surface 65A composed of one main surface on the display panel 80 side, a back surface 65B composed of the other main surface facing the light emitting surface 65A, and a side surface extending between the light emitting surface 65A and the back surface 65B. Have. The side surface of the side surface on the light source 50 side is an incoming light receiving surface 55C that receives light from the light source 50. The light incident on the optical plate 55 from the light entering surface 55C is the light entering surface 55.
The inside of the optical plate is guided in the direction (light guide direction) connecting C and the opposite surface facing the incoming light surface 55C.
It is emitted from the light emitting surface 55A.

As a material constituting the optical plate 55, 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, acrylic resin, polystyrene, polycarbonate,
A transparent resin containing one or more of polyethylene terephthalate, polyacrylonitrile or the like as a main component, or an epoxy acrylate or urethane acrylate-based reactive resin (ionizing radiation curable resin or the like) can be preferably used. If necessary, a light diffusing material having a function of diffusing light can be added to the optical plate 55. As a light diffusing material, for example, the average particle size is 0.
.. Silica (silicon dioxide), alumina (aluminum oxide), 5 μm or more and 100 μm or less,
Particles made of a transparent substance such as an acrylic resin, a polycarbonate resin, and a silicone resin can be used.

<< Lens sheet >>
The lens sheets 60 and 65 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. 7, the light L3 having a large incident angle
The light wavelength conversion sheet 10 reflects light L4 having a small incident angle, as well as a function (condensing function) of changing the traveling direction of the light and emitting it from the light emitting side to intensively improve the brightness in the front direction.
It has a function to return to the side (retroreflection function). The lens sheets 60 and 65 include a light transmitting base material 61 and a lens layer 62 provided on one surface of the light transmitting base material 61.

<Light transmissive base material>
Since the light-transmitting base material 61 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. 6 and 7, the lens layer 62 includes a sheet-shaped main body portion 63 and a plurality of unit lenses 64 arranged side by side on the light emitting side of the main body portion 63.

The main body 63 functions as a sheet-like member that supports the unit lens 64. As shown in FIGS. 6 and 7, unit lenses 64 are arranged on the light emitting side surface 63A of the main body 63 without leaving a gap. Therefore, the light emitting surfaces 60B, 65 of the lens sheets 60, 65.
B is formed by the lens surface. On the other hand, as shown in FIG. 7, the main body portion 63 has a smooth surface forming the light entering side surface of the lens layer 62 as the light entering side surface 63B facing the light emitting side surface 63A.

The unit lenses 64 are arranged side by side on the light emitting side surface 63A of the main body portion 63. As shown in FIG. 6, the unit lens 64 is linear in a direction intersecting the arrangement direction AD of the unit lens 64.
In particular, in the present embodiment, it extends linearly. Further, in the present embodiment, a large number of unit lenses 64 included in one lens sheet 60, 65 extend in parallel with each other. Further, the longitudinal LD of the unit lens 64 of the lens sheets 60 and 65 is the lens sheet 6.
It is orthogonal to the arrangement direction AD of the unit lens 64 at 0 and 65.

The unit lens 64 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 60 and 65 and the arrangement direction AD of the unit lens 64 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 64 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 63 of the main body portion 63.
Each unit lens 64 is configured so as to project from A to the light emitting side.

From the viewpoint of improving the efficiency of light utilization, the unit lens 64 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 64 may be a curved surface.

The dimensions of the lens sheets 60 and 65 can be set as follows, for example. First, as a specific example of the unit lens 64, the arrangement pitch of the unit lens 64 (corresponding to the width of the unit lens 64 in the illustrated example) can be set to 10 μm or more and 200 μm or less. However, in recent years, the arrangement of the unit lens 64 has been rapidly improved in definition, and it is preferable that the arrangement pitch of the unit lens 64 is 10 μm or more and 50 μm or less. In addition, the lens sheet 60,
The protruding height of the unit lens 64 from the main body 63 along the normal direction ND to the seat surface of 65 can be 5 μm or more and 100 μm or less. Further, the apex angle θ of the unit lens 64 is set to 60.
It can be ° or more and 120 ° or less.

As can be understood from FIG. 5, the arrangement direction of the unit lens 64 of the lens sheet 60 and the arrangement direction of the unit lens 64 of the lens sheet 65 intersect, and more specifically, are orthogonal to each other.

<Reflective polarization separation sheet>
The reflective polarization separation sheet 70 transmits only the first linear polarization component (for example, P-polarization) among the light emitted from the lens sheet 65, 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 70 is reflected again, and the polarization is eliminated (a state in which both the first linear polarization component and the second linear polarization component are included). It is incident on the reflective polarizing separation sheet 70 again. Therefore, the reflective polarization separation sheet 70 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, 70 to 8 of the light emitted from the lens sheet 65
About 0% is emitted as the light source light which is 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 70 with the transmission axis direction of the polarizing plate 121 of the display panel 80, the light emitted from the backlight device 40 Are all available for image formation on the display panel 80. Therefore, even if the light energy input from the light source 50 is the same, as compared with the case where the reflective polarizing separation sheet 70 is not arranged,
It is possible to form an image with higher brightness, and the energy utilization efficiency of the light source 50 is also improved. In particular, the light reflected by the reflective polarizing separation sheet 70 may be wavelength-converted by the optical wavelength conversion sheet 10. Therefore, by arranging the reflective polarization separation sheet 70, 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.

The reflective polarization separation sheet 70 is "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 75 has a function of reflecting the light leaked from the back surface 55B of the optical plate 55 and making it enter the optical plate 90 again. The reflective sheet 75 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 75 may be normal reflection (specular reflection) or diffuse reflection. When the reflection on the reflection sheet 75 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 90 shown in FIG. 8 includes a light source 50, an optical plate 100 that receives the light of the light source 50 and functions as a light diffusing plate, and an optical wavelength conversion sheet 10 arranged on the light emitting side of the optical plate 100. The lens sheet 60 arranged on the light emitting side of the optical wavelength conversion sheet 10, the lens sheet 65 arranged on the light emitting side of the lens sheet 60, and the reflection type polarization separation sheet 70 arranged on the light emitting side of the lens sheet 65. I have. In the present embodiment, the light source 50 is arranged directly under the optical plate 100, not on the side of the optical plate 100. In FIG. 8, the members having the same reference numerals as those in FIG. 5 are the same as the members shown in FIG. 5, and therefore the description thereof will be omitted. In the backlight device 90, it should be noted.
The reflective sheet 75 is not provided.

<Optical plate>
Since the optical plate 100 as the light diffusing plate is the same as the light diffusing plate 3, the description thereof will be omitted here.

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

<Preparation of composition for optical wavelength conversion layer>
First, each component was blended so as to have the composition shown below to obtain a composition for an optical wavelength conversion layer.
(Composition for Light Wavelength Conversion Layer 1)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC Corporation): 92.
5 parts by mass, triphenylphosphine (phosphine compound, product name "JC-263", manufactured by Johoku Chemical Industry Co., Ltd.): 7.5 parts by mass, green emission quantum dots (product name "CdSe / ZnS 530", SIGMA-ALDRI)
Made by CH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.2 parts by mass, red emission quantum dots (product name "CdSe / ZnS 610", SIGMA-ALDRI
Made by CH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.2 parts by mass ・ Radical polymerization initiator (1-hydroxycyclohexylphenyl ketone, product name “Irg”
acure (registered trademark) 184 ", manufactured by BASF Japan Ltd.): 0.2 parts by mass

(Composition for Light Wavelength Conversion Layer 2)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 95 parts by mass-Triphenylphosphine (phosphine compound, product name "JC-263", manufactured by Johoku Chemical Industry Co., Ltd.): 5.0 mass Part ・ Green emission quantum dots (product name “CdSe / ZnS 530”, SIGMA-ALDRI
Made by CH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.2 parts by mass, red emission quantum dots (product name "CdSe / ZnS 610", SIGMA-ALDRI
Made by CH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.2 parts by mass ・ Radical polymerization initiator (1-hydroxycyclohexylphenyl ketone, product name “Irg”
acure (registered trademark) 184 ", manufactured by BASF Japan Ltd.): 0.2 parts by mass

(Composition for Light Wavelength Conversion Layer 3)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC Corporation): 50 parts by mass-trimethylolpropane tris (3-mercaptobutyrate) (product name "TPMB",
Showa Denko Corporation): 50 parts by mass, green emission quantum dots (product name "CdSe / ZnS 530", SIGMA-ALDRI)
Made by CH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.2 parts by mass, red emission quantum dots (product name "CdSe / ZnS 610", SIGMA-ALDRI
Made by CH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.2 parts by mass ・ Radical polymerization initiator (1-hydroxycyclohexylphenyl ketone, product name “Irg”
acure (registered trademark) 184 ", manufactured by BASF Japan Ltd.): 0.2 parts by mass

(Composition for Light Wavelength Conversion Layer 4)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC Corporation): 70 parts by mass-trimethylolpropane tris (3-mercaptobutyrate) (product name "TPMB",
Showa Denko Corporation): 30 parts by mass, green emission quantum dots (product name "CdSe / ZnS 530", SIGMA-ALDRI)
Made by CH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.2 parts by mass, red emission quantum dots (product name "CdSe / ZnS 610", SIGMA-ALDRI
Made by CH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.2 parts by mass ・ Radical polymerization initiator (1-hydroxycyclohexylphenyl ketone, product name “Irg”
acure (registered trademark) 184 ", manufactured by BASF Japan Ltd.): 0.2 parts by mass

(Composition for Light Wavelength Conversion Layer 5)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC Corporation): 100
Mass part, green emission quantum dots (product name "CdSe / ZnS 530", SIGMA-ALDRI
Made by CH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.2 parts by mass, red emission quantum dots (product name "CdSe / ZnS 610", SIGMA-ALDRI
Made by CH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.2 parts by mass ・ Radical polymerization initiator (1-hydroxycyclohexylphenyl ketone, product name “Irg”
acure (registered trademark) 184 ", manufactured by BASF Japan Ltd.): 0.2 parts by mass

(Composition for Light Wavelength Conversion Layer 6)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC Corporation): 99.
8 parts by mass, triphenylphosphine (phosphine compound, product name "JC-263", manufactured by Johoku Chemical Industry Co., Ltd.): 0.2 parts by mass, green emission quantum dots (product name "CdSe / ZnS 530", SIGMA-ALDRI)
Made by CH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.2 parts by mass, red emission quantum dots (product name "CdSe / ZnS 610", SIGMA-ALDRI
Made by CH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.2 parts by mass ・ Radical polymerization initiator (1-hydroxycyclohexylphenyl ketone, product name “Irg”
acure (registered trademark) 184 ", manufactured by BASF Japan Ltd.): 0.2 parts by mass

(Composition for Light Wavelength Conversion Layer 7)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC Corporation): 97 parts by mass-trimethylolpropane tris (3-mercaptobutyrate) (product name "TPMB",
Showa Denko Corporation): 3 parts by mass, green emission quantum dots (product name "CdSe / ZnS 530", SIGMA-ALDRI)
Made by CH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.2 parts by mass, red emission quantum dots (product name "CdSe / ZnS 610", SIGMA-ALDRI
Made by CH, core: CdSe, shell: ZnS, average particle size 5.2 nm): 0.2 parts by mass ・ Radical polymerization initiator (1-hydroxycyclohexylphenyl ketone, product name “Irg”
acure (registered trademark) 184 ", manufactured by BASF Japan Ltd.): 0.2 parts by mass

<Preparation of composition for light diffusion layer>
Each component was blended so as to have the composition shown below to obtain a composition 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 "Irgacu"
re (registered trademark) 184, manufactured by BASF Japan Ltd.): 1 part by mass, solvent (methyl isobutyl ketone: cyclohexanone = 1: 1 (mass ratio)): 170 parts by mass

<Sample 1>
First, two barrier films were prepared by the following method. In a high-frequency sputtering apparatus, 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-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 film (product name "Lumirror T60", manufactured by Toray Industries, Inc.). As a result, two barrier films having a silica-deposited layer formed on one surface of the polyethylene terephthalate film were formed.

Next, the composition for the light diffusion layer was applied to the surface of both barrier films opposite to the surface on the silica-deposited 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. afterwards,
A light diffusing layer having a film thickness of 10 μm was formed by irradiating ultraviolet rays so that the integrated light amount was 500 mJ / cm ² to cure the coating film, and a barrier film with a light diffusing layer was formed.

Next, the composition 1 for a light wavelength conversion layer was applied to the silica-deposited layer side of one of the barrier films with a light diffusion layer and dried at 80 ° C. to form a coating film. Then, the other barrier film with a light diffusion layer was laminated on the surface of the silica-deposited layer of the barrier film 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 layer having a thickness of 100 μm in close contact with both barrier films with a light diffusion layer is formed. bottom. As a result, length 10 cm x width 10 cm
The optical wavelength conversion sheet according to the sample 1 of the above was obtained.

<Samples 2-7>
In Samples 2 to 7, an optical wavelength conversion sheet was prepared in the same manner as in Sample 1 except that each optical wavelength conversion composition shown in Table 1 was used instead of the optical wavelength conversion composition 1.

<Evaluation of deterioration of optical wavelength conversion sheet by deterioration width>
In the optical wavelength conversion sheet according to the above samples 1 to 7, a durability 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 the optical wavelength conversion sheet after the durability test deteriorated. It was evaluated whether there was a part that was doing.

Specifically, first, a backlight device including 21 blue light emitting diodes having a emission peak wavelength of 450 nm and a light diffusing plate arranged on the blue light emitting diodes was prepared. The blue light emitting diodes were arranged in a plane at equal intervals of 7 in length and 3 in width, and the size of the light diffusing plate was 25 cm in length × 15 cm in width. The light emitting surface of the backlight device was composed of the light emitting surface of the light diffusing plate.

On the other hand, in the optical wavelength conversion sheet according to the above samples 1 to 7, 4 optical wavelength conversion sheets are used.
A durability test was conducted in which the product was left in an environment of 0 ° C. and a relative humidity of 90% for 300 hours. Then, the light wavelength conversion sheet after the durability test was placed on the light emitting surface of the backlight device (the light emitting surface of the light diffusing plate). Then, with the blue light emitting diode of the backlight turned on, a 2D color luminance meter (product name "UA-200", manufactured by Topcon Techno House Co., Ltd.) from above the optical wavelength conversion sheet.
Was used to measure the brightness distribution of the entire surface of the 2D color luminance meter side of the light wavelength conversion sheet and the light emitting surface outside the light wavelength conversion sheet.

After measuring the brightness distribution, the measured brightness distribution is imported into a personal computer as data, and the captured brightness distribution data is converted into light wavelength from any point on the light emitting surface outside the light wavelength conversion sheet. The light wavelength conversion sheet was crossed along one side of the sheet, and the luminance distribution of the linear portion was extracted to another arbitrary point on the light emitting surface outside the light wavelength conversion sheet (see FIG. 9). Next, in this extracted luminance distribution, the luminance distribution is standardized so that the maximum luminance is 100%, the unit is converted to%, the luminance change amount distribution is obtained from the luminance distribution, and the maximum luminance is obtained from the luminance distribution. A value and a minimum value adjacent to the maximum value were detected (see FIGS. 10 and 11). The luminance measurement interval was 0.12 mm.
Then, the deterioration width, which is the width from the detected maximum value to the minimum value, was obtained. Since it passes through the two ends of the optical wavelength conversion sheet, the maximum value and the minimum value may appear at one end and the maximum value and the minimum value may appear at the other end in the luminance change amount distribution. However, in that case, the deterioration width was obtained for each, and the larger deterioration width was used as the deterioration width. In FIGS. 10 and 11, since the horizontal axis is the number of pixels, it is deteriorated by multiplying the absolute value of the difference between the pixel in which the maximum value appears and the pixel in which the minimum value appears by 0.12 mm, which is the size of one pixel. The width dw was calculated.

<Visual deterioration evaluation of optical wavelength conversion sheet>
In the optical wavelength conversion sheet according to Samples 1 to 7 after the durability test, it was visually evaluated whether or not there was a deteriorated portion. Specifically, the optical wavelength conversion sheet after the durability test was placed on a light diffusing plate on a blue light emitting diode having an emission peak wavelength of 450 nm. Then, the surface of the light wavelength conversion sheet was visually evaluated with the blue light emitting diode turned on. The evaluation criteria are as follows.
◯: Since the color of the edge was equivalent to that of the center, no deterioration of the edge was confirmed.
X: Since the color of the edge was different from the color of the center, deterioration of the edge was confirmed.

The results are shown in Table 1 below.

The results will be described below. As shown in Table 1, since the deterioration width of the optical wavelength conversion sheet according to Samples 4 to 7 exceeded 5 mm, deterioration of the end portion was confirmed by visual evaluation. On the other hand, in the optical wavelength conversion sheets according to Samples 1 to 4, the deterioration width was 5 mm or less, so that the deterioration of the end portion was not confirmed by visual evaluation.

1 ... Deterioration evaluation device 2 ... Backlight device 2A ... Light emitting surface 3 ... Brightness meter 4 ... Processing device 5 ... Light source 6 ... Light diffusion plate 10 ... Light wavelength conversion sheet 11 ... Light wavelength conversion layer 16 ... Binder resin 17 ... Quantum dots 30 ... Image display device 40, 90 ... Backlight device 80 ... Display panel

Claims (6)

An optical wavelength conversion sheet including a host matrix and an optical wavelength conversion layer containing quantum dots and additives dispersed in the host matrix.
The quantum dots consist of 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. Configured
The additive is at least one of a phosphine compound and trimethylolpropane tris (3-mercaptobutyrate).
The side surface of the light wavelength conversion layer is exposed, and a durability test is performed on the light wavelength conversion sheet in an environment of 60 ° C. and 90% relative humidity for 500 hours, and the light wavelength conversion after the durability test is performed. At least a part of the other surface of the light wavelength conversion sheet opposite to the one surface in a state where one surface of the light wavelength conversion sheet is irradiated with light whose wavelength can be converted by the quantum dots. A step of measuring the brightness distribution of the light, and a step of obtaining a brightness change amount distribution which is a distribution of the difference in brightness for each measurement interval when measuring the brightness distribution based on the measured brightness distribution. The step of detecting the maximum value and the minimum value adjacent to the maximum value from the brightness change amount distribution, and the width from the position where the maximum value is obtained to the position where the minimum value is obtained are obtained, and the width is 5 mm or less. The width when the deterioration of the optical wavelength conversion sheet is evaluated by the deterioration evaluation method of the optical wavelength conversion sheet including the step of evaluating the deterioration of the optical wavelength conversion sheet depending on whether or not the light is 5 mm or less. Wave conversion sheet. The light wavelength conversion sheet according to claim 1, further comprising a barrier film that suppresses the transmission of water and oxygen on at least one surface of the light wavelength conversion layer. The optical wavelength conversion sheet according to claim 1 or 2, wherein the quantum dots include a first quantum dot that converts the blue light into green light and a second quantum dot that converts the blue light into red light. .. The optical wavelength conversion sheet according to any one of claims 1 to 3, wherein the phosphine-based compound is triphenylphosphine. Light source and
A backlight device comprising the light wavelength conversion sheet according to any one of claims 1 to 4, which receives light from the light source. The backlight device according to claim 5 and
An image display device including a display panel arranged on the light emitting side of the backlight device.

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