JP2017076482A - Light wavelength conversion sheet, back-light device and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light wavelength conversion sheet capable of restricting luminance variation before and after moist heat-resistance test, a back-light device with this sheet and an image display device.SOLUTION: In accordance with one preferred embodiment of this invention, this invention relates to a light wavelength conversion sheet 10, and the light wavelength conversion sheet 10 comprises a light wavelength conversion layer 11 including a host matrix 16, quantum dots 17 and light scattering particles 18 dispersed in the host matrix 16, an inner haze value of the light wavelength conversion sheet 10 is 50% or more, light of which wavelength is converted by quantum dots 16 is radiated on one surface 10A of the light wavelength conversion sheet 10 before and after the moist heat resistance test where the light wavelength conversion sheet 10 is left for 500 hours under environment of 60°C and relative humidity of 90%, and when a light luminance injected from the other surface 10B of the light wavelength conversion sheet 10 is measured, a rate of change of the luminance after the moist heat resistance test in respect to the luminance before the moist heat resistance test is ±10% or less.SELECTED DRAWING: Figure 1

Description

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

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

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

JP 2015-1111518 A

  Since the quantum dots absorb light and emit light of different wavelengths as described above, the light wavelength conversion sheet affects the brightness and color tone of the backlight device. For this reason, the light wavelength conversion sheet is adjusted so that the light emitted from the backlight device has a desired brightness and color tone.

  On the other hand, in order to investigate the durability of the light wavelength conversion sheet, various durability tests may be performed on the light wavelength conversion sheet.

  However, quantum dots are easily deteriorated by moisture and heat, so when a moisture and heat resistance test, which is one of durability tests, is performed on the light wavelength conversion sheet, the quantum dots deteriorate due to the moisture and heat resistance test, and the moisture and heat resistance test is performed. Before and after, the luminance of the light emitted from the light wavelength conversion sheet may change significantly. In the light wavelength conversion sheet after the moisture and heat resistance test, even if the light wavelength conversion sheet is adjusted to have the desired brightness and color tone before the moisture and heat resistance test, if the luminance changes before and after the moisture and heat resistance test May not obtain the desired brightness and color tone.

  The present invention has been made to solve the above problems. That is, it aims at providing the light wavelength conversion sheet | seat, backlight apparatus, and image display apparatus which can suppress the luminance change before and behind a heat-and-moisture resistance test.

  According to one aspect of the present invention, there is provided a light wavelength conversion sheet comprising a host matrix, a light wavelength conversion layer including quantum dots and light scattering particles dispersed in the host matrix, and the light wavelength conversion sheet. Before and after the wet heat resistance test in which the internal haze value of the sheet is 50% or more and the light wavelength conversion sheet is left in an environment of 60 ° C. and 90% relative humidity for 500 hours, When the luminance of light emitted from the other surface of the light wavelength conversion sheet is measured by irradiating with a predetermined amount of light that is wavelength-converted by the quantum dots, the moisture and heat resistance with respect to the luminance before the moisture and heat resistance test is measured. An optical wavelength conversion sheet is provided, wherein the luminance change rate after the test is within ± 10%.

  According to another aspect of the present invention, there is provided a light wavelength conversion sheet, comprising a host matrix, a light wavelength conversion layer including quantum dots and light scattering particles dispersed in the host matrix, Before and after a wet heat resistance test in which the ratio of the mass of the light scattering particles to the mass is 0.01 or more and 0.5 or less, and the light wavelength conversion sheet is left in an environment of 60 ° C. and a relative humidity of 90% for 500 hours. Irradiating one surface of the light wavelength conversion sheet with a predetermined amount of light that is wavelength-converted by the quantum dots, and measuring the luminance of the light emitted from the other surface of the light wavelength conversion sheet, There is provided a light wavelength conversion sheet, wherein a change rate of the luminance after the wet heat resistance test with respect to the luminance before the wet heat resistance test is within ± 10%.

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

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

  According to the light wavelength conversion sheet of one embodiment and another embodiment of the present invention, a change in luminance before and after the wet heat resistance test can be suppressed. Moreover, according to the other aspect of this invention, a backlight apparatus and an image display apparatus provided with such a light wavelength conversion sheet can be provided.

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

  Hereinafter, an optical wavelength conversion sheet, a backlight device, and an image display device according to embodiments of the present invention will be described with reference to the drawings. In this specification, terms such as “sheet” and “film” are not distinguished from each other only based on the difference in designation. Thus, for example, “sheet” is used to include a member that may also be referred to as a film, and “film” is used to include a member that may also be referred to as a sheet. FIG. 1 is a schematic configuration diagram of a light wavelength conversion sheet according to the present embodiment, FIG. 2 is a diagram illustrating an operation of the light wavelength conversion sheet according to the present embodiment, and FIGS. 3 and 4 are related to the present embodiment. FIG. 5 is a schematic configuration diagram of another light wavelength conversion sheet, and FIG. 5 and FIG. 6 are diagrams schematically illustrating a manufacturing process of the light wavelength conversion sheet according to the present embodiment.

<<< Light wavelength conversion sheet >>>
The light wavelength conversion sheet 10 shown in FIG. 1 is a sheet that converts the wavelength of some of the incident light to other wavelengths and emits the other part of the incident light and the wavelength-converted light. is there. The light wavelength conversion sheet 10 includes a light wavelength conversion layer 11, barrier films 12 and 13 provided on both surfaces of the light wavelength conversion layer 11, and a side opposite to the light wavelength conversion layer 11 side surface of the barrier films 12 and 13. And light diffusion layers 14 and 15 provided on the surface. In the light wavelength conversion sheet 10, the surfaces of the light diffusion layers 14 and 15 constitute the surface of the light wavelength conversion sheet 10.

  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 light wavelength conversion sheet is not particularly limited. For example, the light wavelength conversion sheet includes only the light wavelength conversion layer, light diffusion layer / barrier film / light wavelength conversion layer / barrier film, light diffusion layer / barrier film / light wavelength conversion layer, barrier film / light wavelength conversion layer, or The configuration may be barrier film / light wavelength conversion layer / barrier film.

  Before and after the wet heat resistance test in which the light wavelength conversion sheet 10 is left in an environment of 60 ° C. and 90% relative humidity for 500 hours, a predetermined amount of light whose wavelength is converted by the quantum dots 17 on one surface 10A of the light wavelength conversion sheet. When the luminance of light emitted from the other surface 10B, which is the surface opposite to the surface 10A of the light wavelength conversion sheet 10, is measured by irradiation with light, the surface 10B of the light wavelength conversion sheet 10 before the wet heat resistance test The change rate of the luminance of the light emitted from the surface 10B of the light wavelength conversion sheet 10 after the wet heat resistance test with respect to the luminance of the light emitted from the light is within ± 10%. The rate of change of the luminance of the light emitted from the surface 10B of the light wavelength conversion sheet 10 after the wet heat resistance test with respect to the luminance of the light emitted from the surface 10B of the light wavelength conversion sheet 10 before the wet heat resistance test is within ± 5%. Is preferred.

  The light applied to one surface of the light wavelength conversion sheet may include light that is not wavelength-converted by the quantum dots as long as it includes light that is wavelength-converted by the quantum dots. When the light wavelength conversion layer includes, for example, both a quantum dot that converts blue light into green light and a quantum dot that converts blue light into red light, the light that is wavelength-converted by the quantum dot is blue light. Can be used. The reason for irradiating the light wavelength conversion sheet with a predetermined amount of light before and after the moisture and heat resistance test is that when the light wavelength conversion sheet is irradiated with different amounts of light before and after the moisture and heat resistance test, an accurate luminance change rate is obtained. Since it was not possible to measure, in order to measure an accurate luminance change rate, the light wavelength conversion sheet was irradiated with a certain amount of light before and after the wet heat resistance test.

The luminance change rate before and after the wet heat resistance test is set to A ₁ , the luminance of light emitted from the surface 10B of the light wavelength conversion sheet 10 before the wet heat resistance test is set to B _1, and the light wavelength after the wet heat resistance test. when the luminance of light emitted from the surface 10B of the conversion sheet 10 was C _1, it can be calculated by the following equation (1).
A ₁ = (C ₁ −B ₁ ) / B ₁ × 100 (1)

  The luminance before and after the wet heat resistance test is determined by using a spectral radiance meter (product name “CS2000”, manufactured by Konica Minolta) from the thickness direction of the light wavelength conversion sheet for light emitted from the other surface of the light wavelength conversion sheet. Thus, measurement is performed under the condition of a measurement angle of 1 °.

  The brightness of light emitted from the other surface of the light wavelength conversion sheet can be obtained by directly or indirectly measuring the brightness of light emitted from the other surface of the light wavelength conversion sheet. In other words, the light wavelength conversion sheet may be obtained by directly measuring the luminance of the light emitted from the other surface, but the light wavelength conversion sheet is incorporated into a backlight device equipped with a light source, a lens sheet, etc. You may obtain by measuring the brightness | luminance of the light radiate | emitted from the light emission surface of a backlight apparatus through the other surface of a sheet | seat. However, it goes without saying that the luminance measurement before the wet heat resistance test and the luminance measurement after the wet heat resistance test are performed under the same conditions.

  The luminance of light emitted from the surface 10B of the light wavelength conversion sheet 10 by irradiating the surface 10A of the light wavelength conversion sheet 10 with a predetermined amount of light when 100 hours and 250 hours have elapsed since the start of the wet heat resistance test. Are measured, the light emitted from the surface 10B of the light wavelength conversion sheet 10 after 100 hours from the start of the wet heat resistance test for the luminance of the light emitted from the surface 10B of the light wavelength conversion sheet 10 before the moisture heat resistance test is measured. Luminance of light emitted from the surface 10B of the light wavelength conversion sheet 10 after 250 hours from the start of the wet heat resistance test with respect to the luminance change rate and the luminance of the light emitted from the surface 10B of the light wavelength conversion sheet 10 before the wet heat resistance test The change rate of each is preferably within ± 10%, and more preferably within ± 5%. In this case, the luminance measurement method, the method of obtaining the luminance change rate, and the like are the same as those before and after the wet heat resistance test.

  Using a light resistance tester (product name “UV Fade Meter U48AU”, manufactured by Suga Test Instruments Co., Ltd.), light from the carbon arc lamp is applied to the light wavelength conversion sheet 10 in an environment of 42 ° C. and 50% relative humidity for 200 hours. When the brightness of the light emitted from the surface 10B of the light wavelength conversion sheet 10 is measured by irradiating the surface 10A of the light wavelength conversion sheet 10 with a predetermined amount of light before and after the light resistance test to be irradiated, the light resistance test The rate of change in the luminance of the light emitted from the surface 10B of the light wavelength conversion sheet 10 after the light resistance test with respect to the luminance of the light emitted from the surface 10B of the previous light wavelength conversion sheet 10 is within ± 10%. Preferably, it is within ± 5%. The reason for irradiating the light wavelength conversion sheet with a predetermined amount of light before and after the light resistance test above is that when the light wavelength conversion sheet is irradiated with different amounts of light before and after the light resistance test, an accurate luminance change rate is obtained. Therefore, in order to measure an accurate luminance change rate, the light wavelength conversion sheet was irradiated with a certain amount of light before and after the light resistance test. The amount of light is not particularly limited.

The luminance change rate before and after the light resistance test is A ₂ , the luminance of light emitted from the surface 10B of the light wavelength conversion sheet 10 before the light resistance test is B _2, and the light wavelength after the light resistance test. when the luminance of light emitted from the surface 10B of the conversion sheet 10 was C _2, can be obtained by the following equation (2).
A ₂ = (C ₂ −B ₂ ) / B ₂ × 100 (2)

  Luminance before and after the light resistance test is performed using a spectral radiance meter (product name “CS2000”, manufactured by Konica Minolta Co., Ltd.) from the thickness direction of the light wavelength conversion sheet for light emitted from the other surface of the light wavelength conversion sheet. Thus, measurement is performed under the condition of a measurement angle of 1 °.

  The brightness of light emitted from the other surface of the light wavelength conversion sheet can be obtained by directly or indirectly measuring the brightness of light emitted from the other surface of the light wavelength conversion sheet. In other words, the light wavelength conversion sheet may be obtained by directly measuring the luminance of the light emitted from the other surface, but the light wavelength conversion sheet is incorporated into a backlight device equipped with a light source, a lens sheet, etc. You may obtain by measuring the brightness | luminance of the light radiate | emitted from the light emission surface of a backlight apparatus through the other surface of a sheet | seat. However, it goes without saying that the luminance measurement before the light resistance test and the luminance measurement after the light resistance test are performed under the same conditions.

  Luminance of light emitted from the surface 10B of the light wavelength conversion sheet 10 by irradiating the surface 10A of the light wavelength conversion sheet 10 with a predetermined amount of light after 50 hours and 100 hours from the start of the light resistance test. Are measured, the light emitted from the surface 10B of the light wavelength conversion sheet 10 after 50 hours from the start of the light resistance test with respect to the luminance of the light emitted from the surface 10B of the light wavelength conversion sheet 10 before the light resistance test is measured. Luminance of light emitted from the surface 10B of the light wavelength conversion sheet 10 after 100 hours from the start of the light resistance test with respect to the rate of change in luminance and the luminance of light emitted from the surface 10B of the light wavelength conversion sheet 10 before the light resistance test The change rate of each is preferably within ± 10%, and more preferably within ± 5%. In this case, the luminance measurement method, the method of obtaining the luminance change rate, and the like are the same as those before and after the light resistance test.

  The internal haze value in the light wavelength conversion sheet 10 is 50% or more. The internal haze is a haze value resulting from the inside of the light wavelength conversion sheet, and does not take into account the uneven shape of the surface of the light wavelength conversion sheet. When the internal haze value of the light wavelength conversion sheet 10 is 50% or more, light can be sufficiently diffused by the internal haze to excite the quantum dots a plurality of times, and the external haze value can be made smaller. Can do. The internal haze value in the light wavelength conversion sheet 10 is preferably 60% or more, more preferably 80% or more, and most preferably 90% or more.

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

In the light wavelength conversion sheet 10, the external haze value of the light wavelength conversion sheet 10 is preferably smaller than the internal haze value of the light wavelength conversion sheet 10. That is, it is preferable that the light wavelength conversion sheet 10 satisfies the relationship of the following formula (3).
Internal haze value> External haze value (3)

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

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

  In the light wavelength conversion sheet 10, in order to make the external haze value of the light wavelength conversion sheet 10 smaller than that of the light wavelength conversion sheet 10, for example, adding light scattering particles inside the light wavelength conversion sheet 10 can be mentioned. . The light scattering particles may be added not only to the light wavelength conversion layer 11 but also to the barrier films 12 and 13 serving as a base material, and may also be added to the light diffusion layers 14 and 15. When the layer to which light scattering particles are added is the outermost layer, it may be accompanied by external haze. Therefore, the relationship between the internal haze and the external haze is satisfied by controlling the surface irregularities of the outermost layer. Can do.

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

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

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

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

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

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

  When a light source that emits blue light is used to irradiate a light wavelength conversion sheet 10 that includes both quantum dots that convert blue light into green light and quantum dots that convert blue light into red light, the transmitted light in the light wavelength conversion sheet The chromaticity x and y are preferably 0.1 or more and 0.35 or less, and more preferably 0.15 or more and 0.25 or less. When the chromaticity of the transmitted light in the light wavelength conversion sheet is within this range, white light or light having a color close to white can be obtained. The chromaticities x and y are chromaticities of the CIE 1931-XYZ color system. The chromaticity x and y of the transmitted light in the light wavelength conversion sheet can be measured in accordance with JIS Z8701 using a spectroradiometer (product name “SR-UL2”, manufactured by Topcon Corporation).

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

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

<< Light wavelength conversion layer >>
The light wavelength conversion layer 11 includes a host matrix 16, quantum dots 17 dispersed in the host matrix 16, and light scattering particles 18. By including the light scattering particles 18, the internal haze can be increased.

  The average film thickness of the light wavelength conversion layer 11 is preferably 10 μm or more and 200 μm or less. If the average thickness of the light wavelength conversion layer is within this range, it is suitable for reducing the weight and thickness of the backlight device. The film thickness of the light wavelength conversion layer can be calculated from an image of the cross section of the light wavelength conversion sheet, which is obtained by randomly shooting 20 sections using a scanning electron microscope (SEM). The lower limit of the average film thickness of the light wavelength conversion layer 11 is more preferably 30 μm or more.

<Host matrix>
The host matrix 16 is not particularly limited, and examples thereof include at least one of binder resin, glass such as silica glass, and silica gel. Although it does not specifically limit as binder resin, The hardened | cured material (polymerized material, crosslinked material) of curable binder resin precursor is mentioned. Examples of the curable binder resin precursor include a photopolymerizable compound and / or a thermosetting resin. The photopolymerizable compound has at least one photopolymerizable functional group. In the present specification, the “photopolymerizable functional group” is a functional group capable of undergoing a polymerization reaction by light irradiation. Examples of the photopolymerizable functional group include ethylenic double bonds such as a (meth) acryloyl group, a vinyl group, and an allyl group. The “(meth) acryloyl group” means to include both “acryloyl group” and “methacryloyl group”. The light irradiated when polymerizing the photopolymerizable compound includes visible light and ionizing radiation such as ultraviolet rays, X-rays, electron beams, α rays, β rays, and γ rays.

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

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

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

  The photopolymerizable prepolymer has a weight average molecular weight exceeding 10,000, and the weight average molecular weight is preferably from 10,000 to 80,000, and more preferably from 10,000 to 40,000. 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. For this reason, when the photopolymerizable prepolymer having a weight average molecular weight exceeding 80,000 is used, it is preferable to mix and use the photopolymerizable monomer and the photopolymerizable oligomer. Examples of the polyfunctional prepolymer include urethane (meth) acrylate, isocyanurate (meth) acrylate, polyester-urethane (meth) acrylate, and epoxy (meth) acrylate.

  The thermosetting resin is not particularly limited. For example, phenol resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, unsaturated polyester resin, polyurethane resin, epoxy resin, aminoalkyd resin, melamine-urea cocondensation Examples thereof include resins, silicon resins, polysiloxane resins, and the like. A thermosetting resin may be used individually by 1 type, and may be used in combination of 2 or more type. Among these, an epoxy resin and a urethane resin are preferable from the viewpoints of curability and heat resistance.

  Examples of the epoxy resin include a combination of an epoxy resin (main agent), an acid anhydride, an amine compound, or an amino resin (curing agent), and a photocationic polymerization initiator. The epoxy resin as the main agent is not particularly limited as long as it has an epoxy group in one molecule. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, brominated bisphenol A type epoxy resin, bisphenol S type Epoxy resin, diphenyl ether type epoxy resin, hydroquinone type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, fluorene type epoxy resin, phenol novolac type epoxy resin, orthocresol novolac type epoxy resin, trishydroxyphenylmethane type epoxy resin, 3 Functional epoxy resin, tetraphenylolethane type epoxy resin, dicyclopentadienephenol type epoxy resin, hydrogenated bisphenol A type epoxy resin, bisphenol A nucleated poly Lumpur type epoxy resins, polypropylene glycol type epoxy resins, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, glyoxal type epoxy resins, alicyclic epoxy resins, and the like heterocyclic epoxy resin.

  Examples of the urethane resin include a combination of a polyol compound (main agent) and an isocyanate compound (curing agent). In the urethane resin, the polyol compound used as the main agent is not particularly limited, and examples thereof include polyester polyol, polyester polyurethane polyol, polyether polyol, polyether polyurethane polyol, and the like. These polyol compounds may be used individually by 1 type, and may be used in combination of 2 or more type.

  In the urethane resin, the isocyanate compound used as a curing agent is not particularly limited. For example, polyisocyanate, its adduct, its isocyanurate modified, its carbodiimide modified, its allophanate modified, its burette, for example. Examples include modified products. Specific examples of the polyisocyanate include diphenylmethane diisocyanate (MDI), polyphenylmethane diisocyanate (polymeric MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), and bis (4-isocyanatocyclohexyl) methane (H12MDI). , Aromatic diisocyanates such as isophorone diisocyanate (IPDI), 1,5-naphthalene diisocyanate (1,5-NDI), 3,3′-dimethyl-4,4′-diphenylene diisocyanate (TODI), xylene diisocyanate (XDI) Aliphatic diisocyanates such as tramethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate DOO; 4,4'-methylenebis (cyclohexyl isocyanate), alicyclic diisocyanates such as isophorone diisocyanate. Specific examples of the adduct include those obtained by adding trimethylolpropane, glycol and the like to the polyisocyanate. These isocyanate compounds may be used individually by 1 type, and may be used in combination of 2 or more type.

<Quantum dots>
The quantum dots 17 are nano-sized semiconductor particles having a quantum confinement effect. The particle diameter and average particle diameter of the quantum dots 17 are, for example, 1 nm or more and 20 nm or less. When the quantum dot 17 absorbs light from the excitation source and reaches an energy excitation state, the quantum dot 17 releases energy corresponding to the energy band gap of the quantum dot 17. Therefore, by adjusting the particle size of the quantum dots 17 or the composition of the substance, the energy band gap can be adjusted, and energy in various levels of wavelength bands can be obtained. In particular, 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 diameter decreases. That is, as the crystal size decreases, the light emission of the quantum dots shifts to the blue side, that is, to the high energy side. Therefore, by changing the particle diameter of the quantum dots, the emission wavelength can be adjusted over the entire wavelength range of the ultraviolet region, the visible region, and the infrared region. For example, when the quantum dot is composed of CdSe / Zn described later, blue light is emitted when the particle diameter of the quantum dot is 2.0 nm or more and 4.0 nm or less, and the particle diameter of the quantum dot is 3.0 nm. When it is 6.0 nm or less, green light is emitted, and when the particle size of the quantum dots is 4.5 nm or more and 10.0 nm or less, red light is emitted. In the above, the particle diameter range of the quantum dot emitting blue light and the particle diameter range of the quantum dot emitting green light partially overlap, and the particle diameter of the quantum dot emitting green light and the red light The range of the particle diameter of the emitted quantum dots partially overlaps, but even if the quantum dots have the same particle diameter, the emission color may vary depending on the thickness of the quantum dot shell, so there is no contradiction. It is not a thing.

  Although one kind of quantum dot may be used as the quantum dot 17, two or more kinds of quantum dots each having an emission band in a single wavelength region can be used depending on the particle diameter or material. is there. As shown in FIG. 1, the optical wavelength conversion sheet 10 includes, as quantum dots 17, first quantum dots 17 </ b> A and second quantum dots 17 </ b> B each having a light emitter in a wavelength region different from that of the first quantum dots 17 </ b> A. Including.

  As shown in FIG. 2, when light is incident from the surface 10 </ b> A of the light wavelength conversion sheet 10, the light L <b> 1 incident on the quantum dots 17 is converted into light L <b> 2 having a wavelength different from that of the light L <b> 1. The light is emitted from 10B. On the other hand, even when light is incident from the surface 10A, the light L1 passing between the quantum dots 17 is emitted from the surface 10B without being wavelength-converted.

  As described above, since there is also light that is not wavelength-converted as light emitted from the light wavelength conversion sheet 10, a light source that emits blue light is used as the light source, and the blue light is converted into green light as the first quantum dots 17A. When a quantum dot is used and a quantum dot that converts blue light into red light is used as the second quantum dot 17B, light that is a mixture of blue light, green light, and red light is emitted from the light wavelength conversion sheet 10. Can be made.

  The quantum dot 17 can generate strong fluorescence in a desired narrow wavelength region. For this reason, the backlight apparatus using the light wavelength conversion sheet 10 can illuminate the display panel with light of three primary colors having excellent color purity. In this case, the display panel has excellent color reproducibility.

  The quantum dots 17 may have a core-shell structure mainly having a core made of a semiconductor compound with a thickness of about 2 nm to 10 nm and a shell made of a semiconductor compound different from the core. The shell functions as a protective layer that protects the core.

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

  The shell can increase the light emission efficiency of the quantum dots by using a semiconductor compound having a band gap higher than that of the semiconductor compound forming the core so that excitons are confined in the core. Examples of the core-shell structure (core / shell) having such a bandgap relationship include CdSe / ZnS, CdSe / ZnSe, CdSe / CdS, CdTe / CdS, InP / ZnS, Gap / ZnS, Si / ZnS, Examples include InN / GaN, InP / CdSSe, InP / ZnSeTe, InGaP / ZnSe, InGaP / ZnS, Si / AlP, InP / ZnSTe, InGaP / ZnSTe, and InGaP / ZnSSe.

  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 other shapes. The particle diameter of the quantum dot 17 can be a true spherical value having the same volume when the shape of the quantum dot 17 is not spherical.

  Information such as the particle diameter, average particle diameter, shape, and dispersion state of the quantum dots 17 can be obtained by a transmission electron microscope or a scanning transmission electron microscope. The average particle diameter of the quantum dots can be determined from the diameters of the 20 quantum dots measured by cross-sectional observation of the light wavelength conversion layer using a transmission electron microscope or a scanning transmission electron microscope. Further, since the emission color of the quantum dots changes depending on the particle diameter, it is possible to determine the particle diameter of the quantum dots by confirming the emission color of the quantum dots. For example, in the case where the quantum dots are made of CdSe / Zn, if green light emission can be confirmed from the quantum dots, the particle diameter of the quantum dots can be considered to be 3.0 nm or more and 6.0 nm or less. The crystal structure and crystal size of the quantum dots can be known by X-ray crystal diffraction (XRD). Furthermore, the information regarding the particle diameter etc. of a quantum dot can also be obtained with an ultraviolet-visible (UV-Vis) absorption spectrum.

  The content of the quantum dots 17 in the light 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 light emission intensity may not be obtained, and if the content of the light wavelength conversion particles exceeds 2% by mass, sufficient excitation will occur. There is a possibility that the transmitted light intensity of light cannot be obtained. In addition, the mass% of the quantum dot in the light wavelength conversion layer which is hardened | cured material, and the mass% of the light-scattering particle mentioned later can be calculated roughly with 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 removing the host matrix components, the quantum dots and the light scattering particles are not removed, and the quantum dot and light scattering particle components have large particle sizes. Separate components of scattering particles. Next, the component mass of the separated quantum dots and the component of the light scattering particles are measured. And the ratio of the mass of the quantum dot contained in at least one part of the sampled light wavelength conversion layer based on the mass of the sampled light wavelength conversion layer and the mass of the quantum dot 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 sheet 10.

  Instead of the internal haze value of the light wavelength conversion sheet 10 being 50% or more, or the internal haze value of the light wavelength conversion sheet 10 is 50% or more, and the mass of the light scattering particles 18 with respect to the mass of the host matrix 16 The ratio (mass of light scattering particles 18 / mass of host matrix 16) may be 0.01 or more and 0.5 or less. If the ratio of the mass of the light-scattering particles to the mass of the host matrix is less than 0.01, the internal haze may be small and the light scattering effect may not be sufficiently obtained, and this ratio exceeds 0.5. Then, since Mie scattering is difficult to occur, the light scattering effect may not be sufficiently obtained, and the workability may be deteriorated because there are too many light scattering particles.

  The ratio of the mass of the light scattering particles 18 (in the case of inorganic particles) to the mass of the host matrix 16 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. As described above, when the components of the host matrix are removed, the quantum dots and the light-scattering particles are not removed. Therefore, the total mass of the components of the quantum dots and the light-scattering particles is measured. Next, the mass of the host matrix is determined by subtracting the total mass of the components of the quantum dots and light-scattering particles contained therein from the mass of at least a part of the sampled light wavelength conversion layer. On the other hand, since the components of quantum dots and light-scattering particles differ greatly in particle size, the components of quantum dots and light-scattering particles are separated from the difference in particle size, and the components of separated light-scattering particles are measured. To do. Then, based on the mass of the host matrix and the mass of the components of the light scattering particles obtained from the above, the ratio of the mass of the light scattering particles to the mass of the host matrix is calculated.

  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, Mie scattering occurs. Since it becomes difficult, the light scattering effect may not be sufficiently obtained, and the processability may be deteriorated because there are too many light scattering particles.

  The average particle size of the light-scattering particles 18 is preferably 20 times or more and 2000 times or less, more preferably 50 times or more and 1000 times or less than the average particle size of the quantum dots 17. 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 is When the average particle diameter exceeds 2000 times the average particle diameter of the quantum dots, the number of light scattering particles decreases even if the addition amount is the same, and therefore the number of scattering points decreases, and a sufficient light scattering effect cannot be obtained. In addition, the average particle diameter of light-scattering particle | grains can be measured by the method similar to the average particle diameter of the quantum dot mentioned above.

  Further, the average particle diameter of the light scattering particles 18 is preferably 1/300 or more and 1/20 or less, more preferably 1/200 or more and 1/30 or less of the average film thickness of the light wavelength conversion layer. . If the average particle diameter of the light scattering particles is less than 1/300 of the average film thickness of the light wavelength conversion layer, sufficient light scattering performance may not be obtained in the light wavelength conversion layer. If the particle diameter 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 addition amount is the same. Light scattering effect cannot be obtained.

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

  From the viewpoint of obtaining sufficient light scattering, 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. Note that either the refractive index of the light scattering particles 18 or 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 included in the light wavelength conversion layer, for example, the Becke method, the minimum deflection angle method, the deflection angle analysis, the mode line method, the ellipsometry method, etc. can do. As a method for measuring the refractive index of the host matrix (cured product) and light scattering particles in the light wavelength conversion layer, for example, a piece of light scattering particles or a piece of host matrix from the cured light wavelength conversion layer is used. The Becke method can be used on something taken out in some form. In addition, the refractive index difference between the host matrix and the light scattering particles is measured using a phase shift laser interference microscope (such as a phase shift laser interference microscope manufactured by FK Optical Laboratory or a two-beam interference microscope manufactured by Mizoji Optical Industry Co., Ltd.). can do. In addition, when the host matrix contains the above-described (meth) acrylate and other resins, the refractive index of the host matrix is a cured product of all the resin components contained excluding quantum dots and light scattering particles. Means the average refractive index.

  The shape of the light-scattering particle 18 is not particularly limited. For example, the shape is spherical (true sphere, approximately true sphere, elliptic sphere, etc.), polyhedral, rod (column, prism, etc.), flat, flake, indefinite. Examples include shape. In addition, the particle diameter of the light-scattering particle | grains 18 can be made into the true spherical value which has the same volume, when the shape of a light-scattering particle | grain is not spherical.

  The light scattering particles 18 are preferably chemically bonded to the host matrix 16 from the viewpoint of firmly fixing the light scattering particles 18 in the host matrix 16. This chemical bond can be realized by using light scattering particles surface-treated with a silane coupling agent.

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

  Examples of the silane coupling agent having a mercapto group include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropyltriethoxysilane.

  Examples of the silane coupling agent having a (meth) acryl group include 3-methacryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, and 3-methacryloyloxypropyltri. Examples include ethoxysilane and 3-acryloyloxypropyltriethoxysilane.

  Examples of the silane coupling agent having a vinyl group include vinyltrichlorosilane, vinyltrimethoxysilane, and vinyltriethoxysilane. Examples of the styryl group-containing silane coupling agent include p-styryltrimethoxysilane.

  Examples of the silane coupling agent having an epoxy group include 3-glycidoxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycid. Examples thereof include xylpropylmethyldiethoxysilane and 3-glycidoxypropyltriethoxysilane.

  Examples of the silane coupling agent having an isocyanate group include 3-isocyanatopropyltrimethoxysilane and 3-isocyanatopropyltriethoxysilane.

  Examples of the silane coupling agent having an amino group include 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, and N-2- (aminoethyl) -3-aminopropyltrimethyl. Oxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N- (vinylbenzyl)- Examples include 2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride.

  Surface treatment of the light-scattering particles 18 with a silane coupling agent includes a dry method in which the light-scattering particles 18 are sprayed with a silane coupling agent, or silane coupling after the light-scattering particles 18 are dispersed in a solvent. The wet method etc. which add an agent and make it react are mentioned.

  The light scattering particles 18 may be organic particles, but the luminance change rate before and after the wet heat resistance test can be reduced, and the incident light to the light wavelength conversion sheet 10 can be suitably scattered. Inorganic particles are preferable because the light wavelength conversion efficiency with respect to the incident light can be suitably improved.

Inorganic particles include aluminum-containing compounds such as Al ₂ O ₃ , zirconium-containing compounds such as ZrO ₂ , tin-containing compounds such as antimony-doped tin oxide (ATO) and indium tin oxide (ITO), and magnesium-containing materials such as MgO and MgF _2. At least one compound selected from the group consisting of compounds, titanium-containing compounds such as TiO ₂ and BaTiO ₃ , antimony-containing compounds such as Sb ₂ O ₅ , silicon-containing compounds such as SiO ₂ , and zinc-containing compounds such as ZnO Particles. These inorganic particles are preferable from the viewpoint of obtaining a large Mie scattering intensity because the difference in refractive index from the host matrix can be increased. Since the light wavelength conversion efficiency with respect to the incident light by the light wavelength conversion sheet 10 can be improved more suitably, the light scattering particles 18 may be made of two or more materials. Among these, at least one selected from the group consisting of an aluminum-containing compound, a zirconium-containing compound, a titanium-containing compound, an antimony-containing compound, and a silicon-containing compound from the viewpoint of further reducing the luminance change rate before and after the heat and humidity resistance test. Compound particles are preferred.

<< Barrier film >>
The barrier films 12 and 13 are films for suppressing the permeation of moisture and oxygen and protecting the quantum dots 17 from moisture and oxygen. The barrier films 12 and 13 may be only a light-transmitting substrate or a barrier layer having a function of protecting the quantum dots 17 from moisture and oxygen. However, as shown in FIG. Light-transmitting base materials 19 and 20 having a function of protecting from light and barrier layers 21 and 22 provided on the surfaces of the light-transmitting base materials 19 and 20 and having a function of protecting the quantum dots 17 from moisture and oxygen A multilayer structure is preferred.

The oxygen transmission rate (OTR: Oxygen Transmission Rate) of the barrier films 12 and 13 is 1.0 × 10 ⁻¹ cc / m ² / day / atm or less at 23 ° C. and a relative humidity of 90%. Preferably, it is 1.0 × 10 ⁻² cc / m ² / day / atm or less. The oxygen permeability can be measured using an oxygen gas permeability measuring device (manufactured by MOCON, OX-TRAN 2/21).

The water vapor transmission rate (WVTR) of the barrier films 12 and 13 is preferably 1.0 × 10 ⁻¹ g / m ² / day or less under conditions of 40 ° C. and 90% relative humidity. 1.0 × 10 ⁻² g / m ² / day or less is more preferable. The water vapor transmission rate can be measured using a water vapor transmission rate measuring device (DELTATAPRM (manufactured by Technolox)).

  In the case of adding light scattering particles to the barrier film, the light scattering particles can be added to the barrier film by kneading the light scattering particles into the light-transmitting substrate. When light scattering particles are added to the barrier film, it is not necessary to provide a light diffusion layer. In this case, an overcoat layer for preventing scratches may be formed on the side opposite to the light wavelength conversion layer side of the light transmissive substrate.

<Light transmissive substrate>
The thickness of the light transmissive substrates 19 and 20 is not particularly limited, but is preferably 10 μm or more and 500 μm or less. If the thickness of the light-transmitting base materials 19 and 20 is less than 10 μm, there is a risk of wrinkling and folding during assembly of the light wavelength conversion sheet and handling, and if it exceeds 150 μm, the weight of the display and the thin film There is a risk that it may not be suitable. The more preferable lower limit of the thickness of the light-transmitting substrates 19 and 20 is 50 μm or more, and the more preferable upper limit is 400 μm or less.

  The average thickness of the light transmissive base materials 19 and 20 can be calculated using, for example, a cross-sectional image taken with a scanning electron microscope (SEM), a transmission electron microscope (TEM), or a scanning transmission electron microscope (STEM). .

  Examples of constituent materials for the light-transmitting substrates 19 and 20 include polyester (for example, polyethylene terephthalate, polyethylene naphthalate), cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyethersulfone, and polysulfone. , Thermoplastic resins such as polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyether ketone, polymethyl methacrylate, polycarbonate, or polyurethane. As a constituent material of the base film, polyester (for example, polyethylene terephthalate, polyethylene naphthalate) and cellulose triacetate are preferably used.

  The light transmissive base materials 19 and 20 may be composed of a single base material, but 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 the same kind of constituent raw material layers, or may be composed of a plurality of layers composed of different kinds of constituent raw material layers, depending on the application. Good.

<Barrier layer>
The material for forming the barrier layers 21 and 22 is not particularly limited as long as barrier properties can be obtained, and examples thereof include inorganic oxides, metals, and sol-gel materials. Specifically, examples of the inorganic oxide include silicon oxide (SiO _x ), aluminum oxide (Al _n O _m ), titanium oxide (TiO ₂ ), yttrium oxide, boron oxide (B ₂ O ₃ ), and oxidation. Examples of the metal include calcium (CaO) and silicon oxynitride carbide (SiO _x N _y C _z ). Examples of the metal include Ti, Al, Mg, and Zr. Examples of the sol-gel material include siloxane. And sol-gel materials. These materials may be used alone or in combination of two or more.

  The thickness of the barrier layers 21 and 22 is not particularly limited, but is preferably 0.01 μm or more and 1 μm or less. When the thickness is less than 0.01 μm, the barrier performance of the barrier layer may be insufficient. When the thickness exceeds 1 μm, the barrier performance may be easily deteriorated due to a crack in the barrier layer. A more preferable lower limit of the thickness of the barrier layer is 0.03 μm, and a more preferable upper limit is 0.5 μm.

  The thickness of the barrier layer can be obtained as an average value of the thickness of the barrier layer measured at 20 locations in the cross-sectional microscope observation. In addition, the barrier layers 12 and 13 may be a single layer or a stack of a plurality of layers. In the case where a plurality of barrier layers are stacked, each layer constituting the barrier layer may be directly stacked or bonded.

  Examples of the method for forming the barrier layers 21 and 22 include a vapor deposition method such as a physical vapor deposition (PVD) method and a chemical vapor deposition (CVD) method such as a sputtering method and an ion plating method, or a roll coating method, Examples include spin coating. Moreover, you may combine these methods.

  The barrier layers 21 and 22 are not particularly limited as long as they have the above-described barrier properties, but from the viewpoint of the high barrier properties, it is possible to use a vapor deposition layer formed by a vapor deposition method. preferable.

  Such a vapor deposition layer is not particularly limited as long as it is a layer formed by a vapor deposition method, and may be a layer formed by a CVD method, or by a PVD method. It may be a formed layer.

  When the vapor deposition layer is formed by a CVD method such as a plasma CVD method, it is possible to form a dense and highly barrier layer. However, from the viewpoint of production efficiency and cost, the vapor deposition layer is formed by the PVD method. Is preferably formed.

  Examples of the PVD method include a vacuum vapor deposition method, a sputtering method, and an ion plating method. Among them, it is preferable to use a vacuum vapor deposition method from the viewpoint of its barrier property. As a vacuum evaporation method, the vacuum evaporation method by an electron beam (EB) heating system, the vacuum evaporation method by a high frequency dielectric heating system, etc. are mentioned, for example.

The material for the vapor deposition layer is preferably a metal or an inorganic oxide, specifically, a metal such as Ti, Al, Mg, Zr, silicon oxide, aluminum oxide, silicon oxynitride, aluminum oxynitride, magnesium oxide, oxidation Examples thereof include inorganic oxides such as zinc, indium oxide, tin oxide, yttrium oxide, B ₂ O ₃ and CaO. Among these, silicon oxide and aluminum oxide are preferable from the viewpoint of high barrier properties and transparency.

  The thickness of the vapor-deposited layer varies depending on the type and configuration of the material used and is appropriately selected, but is preferably 0.01 μm or more and 1 μm or less, and more preferably 200 nm. When the thickness of the vapor deposition layer is thinner than the above range, it may be difficult to obtain a uniform layer, and the barrier property may not be obtained. In addition, when the thickness of the vapor deposition layer is thicker than the above range, the barrier property may be significantly impaired due to a crack in the vapor deposition layer due to external factors such as tension after the deposition layer is formed, In addition, it takes time to form, and productivity may be reduced.

  An anchor layer may be formed as a base layer for the barrier layers 21 and 22. Thereby, barrier property and a weather resistance can be improved. Examples of the material for forming the anchor layer include an adhesive resin, an inorganic oxide, an organic oxide, and a metal.

  Examples of the method for forming the anchor layer include PVD methods such as sputtering and ion plating, CVD, roll coating, and spin coating. Moreover, you may combine these methods. Among them, in-line coating at the time of film formation is preferable because it is excellent in mass productivity and can improve the adhesion of the anchor layer.

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

<Surface unevenness forming particles>
The surface unevenness forming particles are mainly for forming an uneven shape on the surface of the light diffusion layer. However, the surface unevenness forming particles themselves may exhibit light scattering performance.

  The average particle size of the surface irregularity-forming particles is preferably 10 times or more and 20,000 times or less, more preferably 10 to 5000 times the average particle size of the quantum dots 17 described above. When the average particle size of the surface unevenness forming particles is less than 10 times the average particle size of the quantum dots, sufficient light diffusibility may not be obtained in the light diffusion layer, and the surface unevenness forming particles have an average particle size of If it exceeds 20,000 times the average particle diameter of the quantum dots, the light diffusion performance of the light diffusion layer will be excellent, but the light transmittance of the light diffusion layer will be greatly reduced. In addition, the average particle diameter of surface unevenness | corrugation formation particle | grains can be measured by the method similar to the average particle diameter of the quantum dot mentioned above.

  Specifically, the average particle diameter of the surface unevenness forming particles is, for example, preferably from 1 μm to 30 μm, and more preferably from 1 μm to 20 μm. If the average particle diameter of the surface irregularity-forming particles is less than 1 μm, the light wavelength conversion efficiency of the light wavelength conversion sheet may be insufficient, and the amount of addition of the surface irregularity-forming particles is sufficient to provide sufficient light diffusibility. Need to be more. On the other hand, when the average particle diameter of the surface irregularity-forming particles exceeds 30 μm, the light diffusion performance is excellent, but the light transmittance of the light diffusion layer is likely to be greatly reduced.

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

  The shape of the surface irregularity-forming particles is not particularly limited. For example, spherical (true sphere, approximately true sphere, elliptic sphere, etc.), polyhedron, rod (column, prismatic, etc.), flat plate, flake, irregular shape Etc. In addition, when the shape of the surface unevenness forming particles is not spherical, the particle size of the surface unevenness forming particles can be a true spherical value having the same volume.

  The surface irregularity-forming particles are preferably chemically bonded to the binder resin from the viewpoint of firmly fixing the surface irregularity-forming particles in the binder resin. This chemical bond can be realized by using surface irregularity-forming particles whose surface is modified with a silane coupling agent. Since the silane coupling agent is the same as the silane coupling agent described in the column of light scattering particles, the description thereof is omitted here.

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

<Binder resin>
Although it does not specifically limit as binder resin, Since binder resin similar to the binder resin demonstrated in the column of the light wavelength conversion layer can be used, description is abbreviate | omitted here.

<<< Other Light Wavelength Conversion Sheet >>>
In FIG. 1, a light wavelength conversion sheet 10 in which a light diffusion layer 14, a barrier film 12, a light wavelength conversion layer 11, a barrier film 13, and a light diffusion layer 15 are laminated in this order is illustrated. The sheet may have the structure shown in FIG. 3 in order to further improve the adhesion between the wavelength conversion layer 11 and the barrier films 12 and 13, and also shown in FIG. 4 in order to further improve the adhesion. It is good also as a structure.

  In the light wavelength conversion sheet 30 shown in FIG. 3, primer layers 31 and 32 are disposed between the barrier films 12 and 13 and the light wavelength conversion layer 11. 3, members denoted by the same reference numerals as those in FIG. 1 are the same as those shown in FIG.

<< Primer layer >>
The primer layers 31 and 32 are layers that enhance the adhesion between the barrier films 12 and 13 and the light wavelength conversion layer 11, and are in close contact with the barrier films 12 and 13 and the light wavelength conversion layer 11. As a constituent material of the primer layers 31 and 32, known materials may be appropriately selected and used, and examples thereof include thermosetting or thermoplastic polyester resins and polyurethane resins. In addition, you may use a different constituent material for the primer layers 31 and 32, respectively. Moreover, the thickness of the primer layers 31 and 32 is not particularly limited, but can be, for example, 100 nm or more and 3 μm or less.

  In the light wavelength conversion sheet 40 shown in FIG. 4, an adhesive layer in which adhesive layers 41 and 42 and light transmissive base materials 43 and 44 are disposed between the barrier films 12 and 13 and the light wavelength conversion layer 11. 41 and 42 and the light transmissive base materials 43 and 44 are for further improving the adhesion between the barrier films 12 and 13 and the light wavelength conversion layer 11. In FIG. 4, members denoted by the same reference numerals as those in FIG. 1 are the same as the members shown in FIG.

<< Adhesive layer >>
The adhesive layers 41 and 42 are disposed between the barrier films 12 and 13 and the light transmissive base materials 43 and 44, and are in close contact with the barrier films 12 and 13 and the light transmissive base materials 43 and 44. Although it does not specifically limit as a constituent material of the contact bonding layers 41 and 42, For example, a polyurethane resin, a polyester resin, a polyvinyl chloride resin, a polyvinyl acetate resin, a vinyl chloride-vinyl acetate copolymer, an acrylic resin, polyvinyl alcohol Resin, polyvinyl acetal resin, copolymer of ethylene and vinyl acetate or acrylic acid, copolymer of ethylene and styrene and / or butadiene, thermoplastic resin such as olefin resin and / or modified resin thereof, light It is possible to use at least one of a polymer of a polymerizable compound and a thermosetting resin such as an epoxy resin. An acrylic resin, an epoxy resin, or a polyester resin is preferably used as a constituent material of the adhesive layers 41 and 42 from the viewpoint of heat resistance and adhesiveness. Note that different constituent materials may be used for the adhesive layers 41 and 42, respectively. Further, the thickness of the adhesive layers 41 and 42 is not particularly limited, but can be, for example, 100 nm or more and 5 μm or less.

<< light transmissive substrate >>
The light transmissive base materials 43 and 44 are disposed between the adhesive layers 41 and 42 and the light wavelength conversion layer 11, and are in close contact with the adhesive layers 41 and 42 and the light wavelength conversion layer 11. Since the light transmissive base materials 43 and 44 are the same as the light transmissive base materials 19 and 20, the description thereof will be omitted here.

<<< Method for Producing Light Wavelength Conversion Sheet >>>
The light wavelength conversion sheet 10 can be produced as follows, for example. Hereinafter, an example in which the host matrix 16 is a binder resin will be described. First, as shown in FIG. 5A, the barrier layer 21 is formed on one surface of the light-transmitting substrate 19 by vapor deposition or the like, and the barrier film 12 as the second barrier film is formed. Similarly, the barrier layer 22 is formed on one surface of the light transmissive substrate 20 by vapor deposition or the like to form the barrier film 13 as the first barrier film.

  Next, a light diffusing layer composition containing surface irregularity-forming particles and a curable binder resin precursor is applied to the surface of the barrier film 12 opposite to the surface on the barrier layer 21 side, dried, and then the light diffusing layer. A coating film of the composition is formed. Similarly, a coating film of the composition for light diffusion layer is formed on the surface of the barrier film 13 opposite to the surface on the barrier layer 22 side.

  Subsequently, the coating film of the composition for light diffusion layers is hardened by light irradiation etc. Thereby, as shown in FIG. 5B, the light diffusion layer 14 is formed on the surface of the barrier film 12 opposite to the surface on the barrier layer 21 side, and the barrier film 12 with the light diffusion layer 14 is formed. Is done. Similarly, the barrier film 13 with the light diffusion layer 15 is formed.

  After forming the barrier film 12 with the light diffusion layer 14 and the barrier film 13 with the light diffusion layer 15, the surface opposite to the surface on the light diffusion layer 15 side in the barrier film 13 with the light diffusion layer 15 (the surface of the barrier layer 22 ) Is coated with a composition for a light wavelength conversion layer containing a curable host matrix precursor, quantum dots 17 and light scattering particles 18 and dried to convert light wavelength as shown in FIG. A coating film 23 of the layer composition is formed.

  Content of the light-scattering particle | grains 18 in the composition for light wavelength conversion layers is 1 to 50 mass%, and it is preferable that it is 3 to 30 mass%. If the content of the light scattering particles is less than 1% by mass, the light scattering effect may not be sufficiently obtained, and if the content of the light scattering particles exceeds 50% by mass, Mie scattering occurs. Since it becomes difficult, the light scattering effect may not be sufficiently obtained, and the processability may be deteriorated because there are too many light scattering particles.

  It is preferable to include a polymerization initiator in the composition for a light wavelength conversion layer. The polymerization initiator is a component that is decomposed by light or heat to generate radicals or ionic species to initiate or advance polymerization (crosslinking) of the curable host matrix precursor. The polymerization initiator used in the composition for a light wavelength conversion layer is a photopolymerization initiator (for example, a photo radical polymerization initiator, a photo cationic polymerization initiator, a photo anion polymerization initiator), a thermal polymerization initiator (for example, a thermal radical). Polymerization initiator, thermal cationic polymerization initiator, thermal anionic polymerization initiator), or a mixture thereof.

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

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

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

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

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

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

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

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

  The viscosity of the composition for a light wavelength conversion layer is preferably 10 mPa · s or more and 10,000 mPa · s or less. If the viscosity of the composition for the light wavelength conversion layer is less than 10 mPa · s, it may be difficult to form a sufficient film thickness in the light wavelength conversion layer, and if it exceeds 10,000 mPa · s, the light wavelength conversion layer When the layer composition is applied, it may be difficult to apply and the leveling property may be deteriorated.

  After forming the coating film 23 of the composition for the light wavelength conversion layer, as shown in FIG. 6A, the surface opposite to the surface on the light diffusion layer 14 side (barrier layer 21) in the barrier film 12 with the light diffusion layer 14 The barrier film 12 with the light diffusing layer 14 is disposed on the coating film 23 of the composition for light wavelength conversion layer so that the surface thereof is in contact with the coating film 23 of the composition for light wavelength conversion layer. Thereby, the coating film 23 of the composition for optical wavelength conversion layers is pinched between the barrier films 12 and 13.

  Next, as shown in FIG. 6 (B), the coating film 23 of the composition for light wavelength conversion layer is irradiated with light through the barrier film 12 or heat is applied to cure the curable host matrix precursor. Thus, the light wavelength conversion layer 11 is formed, and the light wavelength conversion layer 11, the barrier film 12 with the light diffusion layer 14, and the barrier film 13 with the light diffusion layer 15 are integrated. Thereby, the light wavelength conversion sheet 10 shown in FIG. 1 is obtained.

  The light wavelength conversion sheets 10, 30, and 40 can be used by being incorporated in a backlight device and an image display device. Hereinafter, an example in which the light wavelength conversion sheet 10 is incorporated in a backlight device and an image display device will be described. 7 is a schematic configuration diagram of an image display device including a backlight device according to the present embodiment, FIG. 8 is a perspective view of the lens sheet shown in FIG. 7, and FIG. FIG. 10 is a cross-sectional view taken along line I, and FIG. 10 is a schematic configuration diagram of another backlight device according to the present embodiment.

<<< Image display device >>>
The image display device 60 shown in FIG. 7 includes a backlight device 70 and a display panel 110 disposed on the light output side of the backlight device 70. The image display device 60 has a display surface 60A for displaying an image. In the image display device 60 shown in FIG. 7, the surface of the display panel 110 is the display surface 60A.

  The backlight device 60 illuminates the display panel 110 in a planar shape from the back side. The display panel 110 functions as a shutter that controls transmission or blocking of light from the backlight device 60 for each pixel, and is configured to display an image on the display surface 60A.

<< Display panel >>
A display panel 110 shown in FIG. 7 is a liquid crystal display panel, and is between a polarizing plate 111 disposed on the light incident side, a polarizing plate 112 disposed on the light exit side, and between the polarizing plate 111 and the polarizing plate 112. The liquid crystal cell 113 is provided. Polarizing plates 111 and 112 decompose incident light into two linearly polarized light components (S-polarized light and P-polarized light) orthogonal to each other and vibrate in one direction (a direction parallel to the transmission axis) (for example, P It has a function of transmitting a linearly polarized component (for example, S-polarized light) that transmits polarized light and vibrates in the other direction (direction parallel to the absorption axis) perpendicular to the one direction.

  The liquid crystal cell 113 is configured so that a voltage can be applied to each region where one pixel is formed. Then, the alignment direction of the liquid crystal molecules in the liquid crystal cell 113 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 111 arranged on the light incident side rotates the polarization direction by 90 ° when passing through the liquid crystal cell 113 to which a voltage is applied, When passing through the liquid crystal cell 113 to which no voltage is applied, the polarization direction is maintained. In this case, depending on whether or not a voltage is applied to the liquid crystal cell 113, the linearly polarized light component oscillating in a specific direction transmitted through the polarizing plate 111 is transmitted through the polarizing plate 112 or absorbed and blocked by the polarizing plate 112. it can. In this way, the display panel 110 is configured to control transmission or blocking of light from the backlight device 70 for each pixel. The details of the liquid crystal display panel are described in various known literatures (for example, “Flat Panel Display Dictionary” (published by Tatsuo Uchida, Hiraki Uchiike), 2001, Industrial Research Council). The detailed description of is omitted.

<< Backlight device >>
The backlight device 70 shown in FIG. 7 is configured as an edge light type backlight device, and includes a light source 75, an optical plate 80 as a light guide plate disposed on the side of the light source 75, and a light output side of the optical plate 80. The light wavelength conversion sheet 10 disposed on the lens, the lens sheet 85 disposed on the light output side of the light wavelength conversion sheet 10, the lens sheet 90 disposed on the light output side of the lens sheet 85, and the light output side of the lens sheet 90. The reflection type polarization separation sheet 95 is provided, and the reflection sheet 100 is provided on the side opposite to the light output side of the optical plate 80. The backlight device 70 includes the optical plate 80, the lens sheets 85 and 90, the reflective polarization separation sheet 95, and the reflective sheet 100, but these sheets and the like may not be provided. In the present specification, the “light exit side” means a side from which light is emitted from each member in the direction of exiting the backlight device.

  The backlight device 70 has a light emitting surface 70A that emits light in a planar shape. In the backlight device 70 shown in FIG. 7, the light exit surface of the reflective polarization separation sheet 95 is the light emitting surface 70 </ b> A of the backlight device 70.

  The surface on the optical plate 80 side in the light wavelength conversion sheet 10 is a surface 10A (light incident surface), and the surface on the lens sheet 85 side in the light wavelength conversion sheet 10 is a surface 10B (light exit surface).

<Light source>
The light source 75 may be configured in various modes such as a fluorescent lamp such as a linear cold cathode tube, a point light emitting diode (LED), an incandescent lamp, and the like. In the present embodiment, the light source 75 is constituted by a large number of point-like light emitters, specifically a large number of light emitting diodes (LEDs) arranged in a line on the light incident surface 80C side to be described later of the optical plate 60. ,It is configured.

  As the light wavelength conversion sheet 10 is disposed in the backlight device 70, the light source 75 can use only a light emitter that emits light in a single wavelength region. For example, only a blue light emitting diode that emits blue light with high color purity can be used as the light source.

<Optical plate>
The optical plate 80 as the light guide plate is formed in a square shape in plan view. The optical plate 80 extends between a light exit surface 80A formed by one main surface on the display panel 110 side, a back surface 80B composed of the other main surface facing the light output surface 80A, and the light output surface 80A and the back surface 80B. And a side surface. The side surface on the light source 75 side of the side surfaces is a light incident surface 80 </ b> C that receives light from the light source 75. Light that has entered the optical plate 80 from the light incident surface 80C is guided through the optical plate in a direction (light guide direction) connecting the light incident surface 80C and the opposite surface opposite to the light incident surface 80C. It is emitted from 80A.

  As a material constituting the optical plate 80, a material that is widely used as a material for an optical sheet incorporated in an image display device and has excellent mechanical characteristics, optical characteristics, stability, workability, and the like, and can be obtained at low cost. For example, transparent resins mainly composed of one or more of acrylic resin, polystyrene, polycarbonate, polyethylene terephthalate, polyacrylonitrile, etc., and epoxy acrylate or urethane acrylate reactive resins (ionizing radiation curable resins, etc.) are preferably used. Can be done. If necessary, a light diffusing material having a function of diffusing light can be added into the optical plate 60. As the light diffusing material, for example, particles made of a transparent material such as silica (silicon dioxide), alumina (aluminum oxide), acrylic resin, polycarbonate resin, or silicone resin having an average particle diameter of 0.5 μm to 100 μm are used. it can.

<< Lens sheet >>
The lens sheets 85 and 90 have a function of changing the traveling direction of the incident light and emitting it from the light output side. In the present embodiment, as shown in FIG. 9, the function of concentratingly improving the luminance in the front direction by changing the traveling direction of the light L <b> 3 having a large incident angle and emitting it from the light exit side (condensing function). In addition, it has a function (retroreflection function) of reflecting the light L4 having a small incident angle and returning it to the light wavelength conversion sheet 10 side. The lens sheets 85 and 90 include a light transmissive substrate 86 and a lens layer 87 provided on one surface of the light transmissive substrate 86.

  When the surfaces 10A and 10B of the light wavelength conversion sheet 10 are uneven surfaces, the light exit surface 80A of the optical plate 80 is optically in close contact with a part (for example, a convex portion) of the surface 10A. 10A is preferably separated from other portions (for example, concave portions), and the light incident surface 85A of the lens sheet 85 is optically in close contact with a portion (for example, convex portions) of the surface 10B. It is preferable that it is separated from the other part (for example, recessed part) of 10B. In this case, the gap between the light exit surface 80A and the other part of the surface 10A and the gap between the light incident surface 85A and the other part of the surface 10B form an air layer. By providing this air layer, the light wavelength conversion sheet 10, the optical plate 80, and the lens sheet 85 are fixed so that the light exit surface 80A and the surface 10A and the light entrance surface 85A and the surface 10B are in optical contact. However, since it can suppress sticking of the optical wavelength conversion sheet 10, the optical plate 80, and the lens sheet 85, the interface between the optical wavelength conversion sheet 10 and the optical plate 80, the optical wavelength conversion sheet 10, and the lens sheet 85 can be suppressed. It is possible to suppress the formation of wet-out at the interface between the two.

<Light transmissive substrate>
Since the light transmissive substrate 86 is the same as the light transmissive substrates 19 and 20, the description thereof is omitted here.

<Lens layer>
As shown in FIGS. 8 and 9, the lens layer 87 includes a sheet-like main body 88 and a plurality of unit lenses 89 arranged side by side on the light output side of the main body 88.

  The main body 88 functions as a sheet-like member that supports the unit lens 89. As shown in FIGS. 8 and 9, the unit lenses 89 are arranged on the light exit side surface 88 </ b> A of the main body 88 without leaving a gap. Accordingly, the light exit surfaces 85B and 90B of the lens sheets 85 and 90 are formed by lens surfaces. On the other hand, as shown in FIG. 9, in the present embodiment, the main body 88 has a smooth surface that forms the light incident side surface of the lens layer 87 as the light incident side surface 88B that faces the light output side surface 88A. Yes.

  The unit lenses 89 are arranged side by side on the light exit side surface 88A of the main body 88. As shown in FIG. 8, the unit lenses 89 extend linearly in the direction intersecting the arrangement direction AD of the unit lenses 89, particularly linearly in the present embodiment. In the present embodiment, a large number of unit lenses 89 included in one lens sheet 85, 90 extend in parallel to each other. The longitudinal direction LD of the unit lenses 89 of the lens sheets 85 and 90 is orthogonal to the arrangement direction AD of the unit lenses 89 in the lens sheets 85 and 90.

  The unit lens 89 may have a triangular prism shape, or may have a wave shape or a bowl shape such as a hemisphere. Specifically, examples of the unit lens include a unit prism, a unit cylindrical lens, and a unit microlens. In the present embodiment, a triangular prism-shaped unit prism whose width becomes narrower toward the light output side will be described as a unit lens. The shape of the cross section (also referred to as the main cutting surface of the lens sheet) parallel to both the normal direction ND of the lens surfaces of the lens sheets 85 and 90 and the arrangement direction AD of the unit lenses 89 is a triangular shape protruding to the light output side. ing. In particular, from the viewpoint of intensively improving the luminance in the front direction, the cross-sectional shape of the unit lens 89 at the main cut surface is an isosceles triangle shape, and the apex angle located between the equilateral sides is the light exit side surface 88A of the main body 88. Each unit lens 89 is configured to project from the light to the light exit side.

  The unit lens 89 preferably has an apex angle of 80 ° or more and 100 ° or less, and more preferably an apex angle of about 90 °, from the viewpoint of improving the light utilization efficiency. However, the tip of the unit lens 89 may be a curved surface in consideration of breakage of the tip of the unit lens during winding of the light wavelength conversion sheet.

  The dimensions of the lens sheets 85 and 90 can be set as follows as an example. First, as a specific example of the unit lens 89, the arrangement pitch of the unit lenses 89 (corresponding to the width of the unit lens 94 in the illustrated example) can be set to 10 μm or more and 200 μm or less. However, in recent years, the arrangement of the unit lenses 89 has been highly refined, and the arrangement pitch of the unit lenses 89 is preferably 10 μm or more and 50 μm or less. Further, the protruding height of the unit lens 89 from the main body 88 along the normal direction ND to the sheet surface of the lens sheets 85 and 90 can be set to 5 μm or more and 100 μm or less. Further, the apex angle θ of the unit lens 89 can be set to 60 ° or more and 120 ° or less.

  As can be understood from FIG. 7, the arrangement direction of the unit lenses 89 of the lens sheet 85 and the arrangement direction of the unit lenses 89 of the lens sheet 90 intersect, and more specifically, are orthogonal to each other.

<Reflection-type polarized light separation sheet>
The reflective polarization separation sheet 95 transmits only the first linearly polarized light component (for example, P-polarized light) out of the light emitted from the lens sheet 90, and is a second straight line orthogonal to the first linearly polarized light component. It has a function of reflecting a polarized component (for example, S-polarized light) without absorbing it. In the state where the second linearly polarized light component reflected by the reflective polarization separation sheet 95 is reflected again and the polarization is canceled (including both the first linearly polarized light component and the second linearly polarized light component), The light again enters the reflective polarization separation sheet 95. Therefore, the reflection-type polarization separation sheet 95 transmits the first linearly polarized light component of the incident light again, and the second linearly polarized light component orthogonal to the first linearly polarized light component is reflected again. Hereinafter, by repeating the above process, about 70 to 80% of the light emitted from the lens sheet 90 is emitted as the light source light that has become the first linearly polarized light component. Therefore, by making the polarization direction of the first linearly polarized light component (transmission axis component) of the reflective polarization separation sheet 95 coincide with the transmission axis direction of the polarizing plate 111 of the display panel 110, the emitted light from the backlight device 70 is obtained. All can be used for image formation on the display panel 110. Therefore, even when the light energy input from the light source 75 is the same, it is possible to form an image with higher luminance than in the case where the reflective polarization separation sheet 95 is not disposed, and the energy utilization efficiency of the light source 75 is also improved. improves. In particular, the light reflected by the reflective polarization separation sheet 95 can be wavelength-converted by the light wavelength conversion sheet 10. Therefore, the wavelength conversion efficiency of the light wavelength conversion sheet 10 can be further increased by arranging the reflective polarization separation sheet 95. Therefore, further improvement in light utilization efficiency can be expected.

  As the reflective polarization separation sheet 95, “DBEF” (registered trademark) available from 3M Company can be used. In addition to “DBEF”, a high-intensity polarizing sheet “WRPS”, a wire grid polarizer, and the like available from Shinwha Intertek can be used as the reflective polarization separating sheet 95.

<Reflection sheet>
The reflection sheet 100 has a function of reflecting light leaking from the back surface 80 </ b> B of the optical plate 80 so as to enter the optical plate 80 again. The reflection sheet 100 includes a white scattering reflection sheet, a sheet made of a material having a high reflectance such as metal, a sheet containing a thin film (for example, a metal thin film) made of a material having a high reflectance as a surface layer, and the like. obtain. The reflection on the reflection sheet 100 may be regular reflection (specular reflection) or diffuse reflection. When the reflection on the reflection sheet 100 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 120 shown in FIG. 10 includes a light source 75, an optical plate 121 that receives light from the light source 75 and functions as a light diffusion plate, and a light wavelength conversion sheet 10 that is disposed on the light output side of the optical plate 121. A lens sheet 85 disposed on the light output side of the light wavelength conversion sheet 10 and a reflective polarization separation sheet 95 disposed on the light output side of the lens sheet 85 are provided. In the present embodiment, the light source 75 is disposed not directly on the side of the optical plate 121 but directly below the optical plate 121. 10, members denoted by the same reference numerals as those in FIG. 7 are the same as those shown in FIG. Note that the backlight device 120 does not include the reflective sheet 100.

<Optical plate>
The optical plate 121 as a light diffusing plate is formed in a square shape in plan view. The optical plate 121 has a light incident surface 121A configured by one main surface on the light source 75 side and a light output surface 121B configured by the other main surface on the light wavelength conversion sheet 10 side. The light that enters the optical plate 121 from the light incident surface 121A is diffused in the optical plate 121 and emitted from the light exit surface 121B.

  The optical plate 121 is not particularly limited as long as the light from the light source 75 can be diffused. For example, a plate in which light diffusing particles are dispersed in a transparent material can be used. Although it does not specifically limit as a transparent material, For example, transparent resin, inorganic glass, etc. are mentioned. As the transparent resin, a transparent thermoplastic resin is suitably used because it is easy to mold. The transparent thermoplastic resin is not particularly limited. For example, polystyrene resin, styrene-methyl methacrylate copolymer resin, styrene-methacrylic acid copolymer resin, styrene-maleic anhydride copolymer resin. Methacrylic resin, acrylic resin, polycarbonate resin, ABS resin (acrylonitrile-butadiene-styrene copolymer resin), AS resin (acrylonitrile-styrene copolymer resin), polyolefin resin (polyethylene resin, polypropylene resin, etc.), etc. . One of these may be used, or two or more of these may be mixed and used.

<Light diffusing particles>
Examples of the light diffusing particles in the optical plate 121 include light diffusing particles generally used as a diffusion plate.

  In the present embodiment, an example in which the light wavelength conversion sheet 10 is incorporated in the backlight devices 70 and 120 is described. However, instead of the light wavelength conversion sheet 10, the light wavelength conversion sheets 30 and 40 are replaced by the backlight device 70. , 120 may be incorporated.

  According to this embodiment, the light wavelength conversion layer 11 includes the light scattering particles 18 and the internal haze value of the light wavelength conversion sheet 10 is 50% or more. The light wavelength conversion sheet is irradiated with a predetermined amount of light that is wavelength-converted by the quantum dots 17 on the surface 10A of the light wavelength conversion sheet 10 before and after the wet heat resistance test that is left in an environment of 90% relative humidity for 500 hours. When the luminance of light emitted from the surface 10B of 10 is measured, the change rate of the luminance after the moist heat resistance test with respect to the luminance before the moist heat resistance test can be within ± 10%. Although this reason is not certain, it is considered that the wet heat and heat resistance of the light wavelength conversion layer 11 is improved mainly by containing the light scattering particles 18 in the light wavelength conversion layer 11 in a predetermined amount. Thereby, the brightness | luminance change before and behind a heat-and-moisture resistance test can be suppressed.

  Further, according to the present embodiment, the light wavelength conversion layer 10 includes the light scattering particles 18, and the ratio of the mass of the light scattering particles 18 to the mass of the host matrix 16 is 0.01 or more and 0.5 or less. Therefore, the light of a predetermined light quantity that is wavelength-converted to the surface 10A of the light wavelength conversion sheet 10 before and after the wet heat resistance test in which the light wavelength conversion sheet 10 is left in an environment of 60 ° C. and 90% relative humidity for 500 hours. When the luminance of light emitted from the surface 10B of the light wavelength conversion sheet 10 is measured, the change rate of the luminance after the moist heat resistance test with respect to the luminance before the moist heat resistance test is within ± 10%. Can do. Although this reason is not certain, it is considered that the wet heat and heat resistance of the light wavelength conversion layer 11 is improved mainly by containing the light scattering particles 18 in the light wavelength conversion layer 11 in a predetermined amount. Thereby, the brightness | luminance change before and behind a heat-and-moisture resistance test can be suppressed.

  According to this embodiment, since the light wavelength conversion layer 11 includes the light scattering particles 18 and the internal haze value of the light wavelength conversion sheet 10 is 50% or more, using a light resistance tester, 42 Before and after the light resistance test in which the light wavelength conversion sheet 10 is irradiated with light from the carbon arc lamp in an environment of 50 ° C. and a relative humidity of 50% for 200 hours, light is irradiated on the surface 10A of the light wavelength conversion sheet 10 When the luminance of light emitted from the surface 10B of the wavelength conversion sheet 10 is measured, the surface of the light wavelength conversion sheet 10 after the light resistance test with respect to the luminance of light emitted from the surface 10B of the light wavelength conversion sheet 10 before the light resistance test The change rate of the luminance of light emitted from 10B can be within ± 10%. Although the reason is not clear, it is considered that the light resistance of the light wavelength conversion layer 11 is mainly improved by adding a predetermined amount of the light scattering particles 18 to the light wavelength conversion layer 11. Thereby, the luminance change before and after a light resistance test can also be suppressed.

  Further, according to the present embodiment, the light wavelength conversion layer 10 includes the light scattering particles 18, and the ratio of the mass of the light scattering particles 18 to the mass of the host matrix 16 is 0.01 or more and 0.5 or less. Therefore, the light wavelength conversion sheet is used before and after the light resistance test in which the light wavelength conversion sheet 10 is irradiated with light from the carbon arc lamp for 200 hours in an environment of 42 ° C. and 50% relative humidity using a light resistance tester. When the luminance of the light emitted from the surface 10B of the light wavelength conversion sheet 10 is measured by irradiating the surface 10A of the light 10 with respect to the luminance of the light emitted from the surface 10B of the light wavelength conversion sheet 10 before the light resistance test The change rate of the luminance of the light emitted from the surface 10B of the light wavelength conversion sheet 10 after the light resistance test can be within ± 10%. Although this reason is not certain, it is considered that the light resistance of the light wavelength conversion layer 11 is mainly improved by containing a predetermined amount of the light scattering particles 18 in the light wavelength conversion layer 11. Thereby, the luminance change before and after a light resistance test can also be suppressed.

  Conventionally, light that has been wavelength-converted by quantum dots emitted from the light wavelength conversion sheet is condensed on the light output side of the light wavelength conversion sheet, and light that has not been wavelength-converted by the light wavelength conversion sheet is light wavelength conversion sheet. It has been studied to increase the optical wavelength conversion efficiency by arranging a lens sheet to be returned to the side. However, the optical wavelength conversion efficiency is not sufficient only by arranging such a lens sheet, and further improvement of the optical wavelength conversion efficiency is desired. According to this embodiment, when the external haze value of the light wavelength conversion sheet 10 is smaller than the internal haze value of the light wavelength conversion sheet 10, the light wavelength conversion efficiency can be further improved. That is, since the light emitted from the light source has straightness, the light that enters the light wavelength conversion sheet and is not wavelength-converted by the quantum dots, and the light emitted from the light wavelength conversion sheet also has straightness. Yes. Here, when the external haze value of the light wavelength conversion sheet is high, light that has not been wavelength-converted that has straightness on the surface of the light wavelength conversion sheet is refracted, and light that is not wavelength-converted emitted from the light wavelength conversion sheet In this case, a component having a large emission angle increases. On the other hand, a lens sheet having a condensing function and a retroreflective function tends to make the lens sheet retroreflected more easily as the incident angle to the lens sheet is smaller. That is, there is a tendency that light having a larger incident angle to the lens sheet is more easily transmitted through the lens sheet. In the present embodiment, in the light wavelength conversion sheet 10, the external haze value is smaller than the internal haze value. The light can be emitted in a state where the angle is small. Accordingly, in the light which is emitted from the light wavelength conversion sheet 10 and is not wavelength-converted, a component having a small emission angle can be increased. Therefore, the lens sheet 85 can retroreflect the light emitted from the light wavelength conversion sheet without wavelength conversion and return it to the light wavelength conversion sheet 10 side, so that the opportunities for wavelength conversion increase. Moreover, since the internal haze value is larger than the external haze value, the light path length is increased by scattering light within the light wavelength conversion sheet, and the opportunity for wavelength conversion is further increased. Thereby, the optical wavelength conversion efficiency can be improved. Since the quantum dots 18 emit light isotropically, the light wavelength-converted by the quantum dots 18 is directed in various directions, and when reaching the surface of the light wavelength conversion sheet 10, the surface of the light wavelength conversion sheet is further increased. The light is refracted and wavelength-converted light becomes light with a large angle and is easily emitted from the optical wavelength conversion sheet. For this reason, the wavelength-converted light is relatively easily transmitted through the lens sheet 85.

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

  According to this embodiment, since the light wavelength conversion layer 11 includes the light scattering particles 18, the light wavelength conversion efficiency can be further improved. Therefore, for example, a light source that emits blue light is used as the light source 75, a quantum dot that converts blue light into green light is used as the first quantum dot 17A, and blue light is converted into red light as the second quantum dot 17B. When the light wavelength conversion sheet containing quantum dots is irradiated with blue light, the chromaticity x and y can be increased compared to a light wavelength conversion sheet that does not contain light scattering particles, and white light or a color close to white The light of taste can be obtained.

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

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

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

(Composition 1 for light wavelength conversion layer)
Epoxy acrylate (product name “Unidic V-5500”, manufactured by DIC Corporation): 99 parts by mass Green emitting quantum dot (product name “CdSe / ZnS 530”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS , Average particle size 3.3 nm): 0.20 parts by mass Red-emitting quantum dots (product name “CdSe / ZnS 610”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm) : 0.20 parts by mass / alumina particles (light scattering particles, product name “DAM-03”, manufactured by Denki Kagaku Kogyo Co., Ltd., average particle size 4 μm): 5 parts by mass / photopolymerization initiator (1-hydroxycyclohexyl phenyl ketone) , Product name “Irgacure (registered trademark) 184”, manufactured by BASF Japan Ltd.): 1 part by mass

(Composition 2 for light wavelength conversion layer)
Epoxy acrylate (product name “Unidic V-5500”, manufactured by DIC Corporation): 99 parts by mass Green emitting quantum dot (product name “CdSe / ZnS 530”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS , Average particle size 3.3 nm): 0.20 parts by mass Red-emitting quantum dots (product name “CdSe / ZnS 610”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm) : 0.20 parts by mass / alumina particles (light scattering particles, product name “DAM-03”, manufactured by Denki Kagaku Kogyo Co., Ltd., average particle size 4 μm): 10 parts by mass / photopolymerization initiator (1-hydroxycyclohexyl phenyl ketone) , Product name “Irgacure (registered trademark) 184”, manufactured by BASF Japan Ltd.): 1 part by mass

(Composition 3 for light wavelength conversion layer)
Epoxy acrylate (product name “Unidic V-5500”, manufactured by DIC Corporation): 99 parts by mass Green emitting quantum dot (product name “CdSe / ZnS 530”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS , Average particle size 3.3 nm): 0.20 parts by mass Red-emitting quantum dots (product name “CdSe / ZnS 610”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm) : 0.20 parts by mass / photopolymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name “Irgacure (registered trademark) 184”, manufactured by BASF Japan Ltd.): 1 part by mass

(Composition 4 for light wavelength conversion layer)
Epoxy acrylate (product name “Unidic V-5500”, manufactured by DIC Corporation): 99 parts by mass Green emitting quantum dot (product name “CdSe / ZnS 530”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS , Average particle size 3.3 nm): 0.20 parts by mass Red-emitting quantum dots (product name “CdSe / ZnS 610”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm) : 0.20 parts by mass / alumina particles (light scattering particles, product name “DAM-03”, manufactured by Denki Kagaku Kogyo Co., Ltd., average particle size 4 μm): 0.8 parts by mass / photopolymerization initiator (1-hydroxycyclohexyl) Phenyl ketone, product name “Irgacure (registered trademark) 184”, manufactured by BASF Japan Ltd.): 1 part by mass

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

<Example 1>
First, two barrier films were produced by the following method. Polyethylene terephthalate as a light-transmitting substrate having a size of 7 inches and a thickness of 50 μm is generated in a chamber by applying a high-frequency power with a frequency of 13.56 MHz and a power of 5 kW to an electrode in a high-frequency sputtering apparatus Forming a silica vapor deposition layer as a barrier layer having a thickness of 50 nm and a refractive index of 1.46 made of a target material (silica) on one side of a film (product name “Lumirror T60”, manufactured by Toray Industries, Inc.) Thus, two barrier films each having a silica vapor deposition layer formed on one surface of the polyethylene terephthalate film were formed.

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

Subsequently, the composition 1 for light wavelength conversion layers was apply | coated to the silica vapor deposition layer side of one barrier film with a light-diffusion layer, it was made to dry at 80 degreeC, and the coating film was formed. And the other barrier film with a light-diffusion layer was laminated | stacked so that the silica vapor deposition layer might contact | connect the surface of the silica vapor deposition layer of the barrier film with a light-diffusion layer in a coating film. In this state, the coating film is cured by irradiating ultraviolet rays so that the integrated light quantity becomes 500 mJ / cm ² , thereby forming a light wavelength conversion layer having a thickness of 100 μm adhered to both barrier films with a light diffusion layer. did. As a result, an optical wavelength conversion sheet according to Example 1 was obtained. The average particle diameter of the light-scattering particles in the light wavelength conversion sheet according to Example 1 was 941 times the average particle diameter of the quantum dots and 1/25 of the average film thickness of the light wavelength conversion layer. The average particle diameter of the light scattering particles and the average particle diameter of the quantum dots in the light wavelength conversion sheet were 20 light scattering particles measured by observing a cross section of the light wavelength conversion layer with a transmission electron microscope (TEM). And the diameter of 20 quantum dots. Moreover, the average film thickness of the light wavelength conversion layer was obtained from 20 images of a cross section of the light wavelength conversion sheet randomly using a scanning electron microscope (SEM) and obtained from the image of the cross section.

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

<Example 3>
In Example 3, a light wavelength conversion sheet was produced in the same manner as in Example 1 except that both light diffusion layers were not formed.

<Example 4>
In Example 4, a light wavelength conversion sheet was produced in the same manner as in Example 1 except that the film thickness of the light diffusion layer was 1.5 μm.

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

<Comparative example 2>
In Comparative Example 2, a light wavelength conversion sheet was produced in the same manner as in Example 1 except that the light wavelength conversion layer composition 4 was used instead of the light wavelength conversion layer composition 1.

<Comparative Example 3>
In Comparative Example 3, a light wavelength conversion sheet was produced in the same manner as Comparative Example 1 except that both light diffusion layers were not formed.

<Comparative example 4>
In Comparative Example 4, a light wavelength conversion sheet was produced in the same manner as in Comparative Example 1 except that the thickness of both light diffusion layers was 1.5 μm.

<All haze, internal haze, external haze measurement>
In the light wavelength conversion sheets according to the above examples and comparative examples, total haze, internal haze, and external haze were measured as follows. First, using a haze meter (product name “HM-150”, manufactured by Murakami Color Research Laboratory), all haze values of the light wavelength conversion sheet were measured according to JIS K7136. Thereafter, the surface of both light diffusion layers in the light wavelength conversion sheet is triacetyl cellulose having a thickness of 60 μm via a transparent optical adhesive layer having a film thickness of 25 μm (product name “Panaclean PD-S1”, manufactured by Panac). A base material (product name “TD60UL”, manufactured by FUJIFILM Corporation) was attached. Thereby, the uneven shape of the surface in the light wavelength conversion sheet was crushed, and the surface of the light wavelength conversion sheet became flat. In this state, the haze value was measured according to JIS K7136 using a haze meter (product name “HM-150”, manufactured by Murakami Color Research Laboratory) to determine the internal haze value. And the external haze value was calculated | required by subtracting an internal haze value from all the haze values. Note that the transparent optical adhesive layer and the triacetylcellulose base material may also affect the internal haze value and external haze value of the light wavelength conversion sheet, but when the internal scattering of the light wavelength conversion sheet is extremely large, The influence on the internal haze value and external haze value is extremely small and can be ignored. Further, when the internal scattering of the light wavelength conversion sheet is extremely large, the internal haze value may be the same as the total haze value, so the external haze value may be 0%.

<Arithmetic mean roughness (Ra) measurement>
In the light wavelength conversion sheets according to Examples and Comparative Examples, Ra on the surface of the light wavelength conversion sheet was measured. The definition of Ra shall conform to JIS B0601-1994. Specifically, Ra was measured under the following measurement conditions using a surface roughness measuring device (product name “SE-3400”, manufactured by Kosaka Laboratory Ltd.).
1) Stylus of surface roughness detector (trade name SE2555N (2μ standard) manufactured by Kosaka Laboratory Ltd.)
・ Tip radius of curvature 2μm, apex angle 90 degrees, material diamond 2) Measurement conditions of surface roughness measuring instrument ・ Reference length (cutoff value λc of roughness curve): 2.5 mm
Evaluation length (reference length (cutoff value λc) × 5): 12.5 mm
・ Feeding speed of stylus: 0.5mm / s
・ Preliminary length: (cutoff value λc) × 2
・ Vertical magnification: 2000 times ・ Horizontal magnification: 10 times

<Brightness change in wet heat resistance test>
In the light wavelength conversion sheets according to the above Examples and Comparative Examples, the change in luminance was examined in a heat and humidity resistance test in which the light wavelength conversion sheet was left in an environment of 60 ° C. and 90% relative humidity for 500 hours. Specifically, first, a backlight device for Kindle Fire (registered trademark) HDX7 was prepared, and a light wavelength conversion sheet before the wet heat resistance test was incorporated into the backlight device. This backlight device includes a blue light emitting diode having an emission peak wavelength of 450 nm, a light diffusing plate, a first prism sheet, and a second prism sheet in this order, and the light according to the example and the comparative example. The wavelength conversion sheet was disposed between the light diffusion plate and the first prism sheet. The first prism sheet and the second prism sheet each include a sheet-like main body portion and a plurality of triangular prism-shaped unit prisms arranged side by side on the main body portion and extending in a direction intersecting the arrangement direction. The unit prism had an apex angle of 90 °. The first prism sheet was arranged so that the arrangement direction of the unit prisms was orthogonal to the arrangement direction of the unit prisms of the second prism sheet.

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

  Next, the light wavelength conversion sheet before the moisture and heat resistance test is removed from the backlight device, and a moisture and heat resistance test is performed on the light wavelength conversion sheet by leaving the light wavelength conversion sheet in an environment of 60 ° C. and 90% relative humidity for 500 hours. It was. The light wavelength conversion sheet is disposed between the light diffusion plate of the backlight device and the first prism sheet when 100 hours have passed since the start of the moisture and heat resistance test, 250 hours after the start of the moisture and heat resistance test, and after the moisture and heat resistance test. In the same manner as described above, one surface of the light wavelength conversion sheet is irradiated with blue light, and from the light emitting surface of the backlight device (the surface of the second prism sheet) through the other surface of the light wavelength conversion sheet. The brightness of the emitted light was measured.

  From these measured luminances, the change rate of the luminance after the elapse of 100 hours from the start of the moist heat resistance test, the elapse of 250 hours from the start of the moist heat resistance test, and the luminance after the moist heat resistance test were obtained.

<Brightness change in light resistance test>
In the light wavelength conversion sheets according to the above examples and comparative examples, carbon was used in an environment of 42 ° C. and 50% relative humidity using a light resistance tester (product name “UV Fade Meter U48AU”, manufactured by Suga Test Instruments Co., Ltd.). The change in luminance was examined in a light resistance test in which light from the arc lamp was irradiated on the light wavelength conversion sheet for 200 hours. Specifically, first, the same Kindle Fire (registered trademark) HDX7 backlight device as in the wet heat resistance test was prepared, and the light wavelength conversion sheet was disposed between the light diffusion plate and the first prism sheet.

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

  Next, the light wavelength conversion sheet before the light resistance test is removed from the backlight device, and the light wavelength conversion sheet is relative to the light wavelength conversion sheet using a light resistance tester (product name “ultraviolet fade meter U48AU”, manufactured by Suga Test Instruments Co., Ltd.). A light resistance test was performed in which light from a carbon arc lamp was irradiated for 200 hours in an environment of 60% humidity. After 50 hours from the start of the light resistance test, 100 hours from the start of the light resistance test, and after the light resistance test, the light wavelength conversion sheet according to Example 1 is used as the light diffusion plate and the first prism of the backlight device. In the same manner as described above, one surface of the light wavelength conversion sheet is irradiated with blue light, and the light emitting surface (second prism) of the backlight device passes through the other surface of the light wavelength conversion sheet. The brightness of light emitted from the sheet surface was measured.

  From these measured luminances, the change rate of the luminance after 50 hours from the start of the light resistance test relative to the luminance before the light resistance test, after 100 hours from the start of the light resistance test, and after the light resistance test was obtained.

The results are shown in Tables 1 and 2.

  The results will be described below. The light wavelength conversion sheets according to Comparative Examples 1 to 4 do not contain light-scattering particles or light-scattering particles, but as shown in Table 1, the internal haze value is 50% or more or the host Since the ratio of the mass of the light-scattering particles to the mass of the matrix does not satisfy the requirement of 0.01 or more and 0.5 or less, as shown in Table 2, the luminance after the moisture and heat resistance test with respect to the luminance before the moisture and heat resistance test is shown. The rate of change exceeded the range of ± 10%. On the other hand, the light wavelength conversion sheets according to Examples 1 to 4 include light scattering particles, and as shown in Table 1, the internal haze value is 50% or more or the light scattering with respect to the mass of the host matrix. Since the ratio of the mass of the conductive particles satisfies the requirement of 0.01 or more and 0.5 or less, as shown in Table 2, the rate of change in luminance after the moist heat resistance test with respect to the luminance before the moist heat resistance test is ± 10%. Was within. Thereby, in Examples 1-4, it was confirmed that the luminance change before and behind a heat-and-moisture resistance test can be suppressed.

  The light wavelength conversion sheets according to Comparative Examples 1 to 4 do not contain light-scattering particles or light-scattering particles, but as shown in Table 1, the internal haze value is 50% or more or the host Since the ratio of the mass of the light-scattering particles to the mass of the matrix does not satisfy the requirement of 0.01 or more and 0.5 or less, the luminance after the light resistance test with respect to the luminance before the light resistance test is shown in Table 2. The rate of change exceeded the range of ± 10%. On the other hand, the light wavelength conversion sheets according to Examples 1 to 4 include light scattering particles, and as shown in Table 1, the internal haze value is 50% or more or the light scattering with respect to the mass of the host matrix. Since the ratio of the mass of the luminous particles satisfies the requirement of 0.01 or more and 0.5 or less, as shown in Table 2, the change rate of the luminance after the light resistance test to the luminance before the light resistance test is ± 10%. Was within. Thereby, in Examples 1-4, it was confirmed that the luminance change before and behind a light resistance test can be suppressed.

  Moreover, since the external haze value was larger than the internal haze value, the brightness | luminance of the light radiate | emitted from the backlight apparatus was low before the light wavelength conversion sheet which concerns on Comparative Examples 2-4. On the other hand, the light wavelength conversion sheets according to Examples 1 to 4 had a high luminance of light emitted from the backlight device before the wet heat resistance test because the external haze value was smaller than the internal haze value. Thereby, in Examples 1-4, it was confirmed that the outstanding optical wavelength conversion efficiency is obtained.

  In the above embodiment, CdSe is used as the core material of the green light emitting quantum dot and the red light emitting quantum dot. However, even if a non-Cd material such as InP or InAs is used as the core material, the same as in the above embodiment. Results were obtained.

DESCRIPTION OF SYMBOLS 10, 30, 40 ... Light wavelength conversion sheet | seat 11 ... Light wavelength conversion layer 12, 13 ... Barrier film 14, 15 ... Light diffusion layer 16 ... Host matrix 17 ... Quantum dot 18 ... Light-scattering particle | grains 19, 20 ... Light transmittance Base material 21, 22 ... Barrier layer 23 ... Coating film 60 ... Image display device 70, 120 ... Backlight device 110 ... Display panel

Claims (9)

A light wavelength conversion sheet,
A light wavelength conversion layer comprising a host matrix and quantum dots and light scattering particles dispersed in the host matrix;
The internal haze value of the light wavelength conversion sheet is 50% or more,
Before and after the wet heat resistance test in which the light wavelength conversion sheet is left in an environment of 60 ° C. and 90% relative humidity for 500 hours, a predetermined amount of light that is wavelength-converted by the quantum dots on one surface of the light wavelength conversion sheet. When the luminance of light emitted from the other surface of the light wavelength conversion sheet is measured by irradiating light, the change rate of the luminance after the moist heat resistance test with respect to the luminance before the moist heat resistance test is ± 10%. An optical wavelength conversion sheet characterized by being within the range. A light wavelength conversion sheet,
A light wavelength conversion layer comprising a host matrix and quantum dots and light scattering particles dispersed in the host matrix;
The ratio of the mass of the light scattering particles to the mass of the host matrix is 0.01 or more and 0.5 or less,
Before and after the wet heat resistance test in which the light wavelength conversion sheet is left in an environment of 60 ° C. and 90% relative humidity for 500 hours, a predetermined amount of light that is wavelength-converted by the quantum dots on one surface of the light wavelength conversion sheet. When the luminance of light emitted from the other surface of the light wavelength conversion sheet is measured by irradiating light, the change rate of the luminance after the moist heat resistance test with respect to the luminance before the moist heat resistance test is ± 10%. An optical wavelength conversion sheet characterized by being within the range.   The light wavelength conversion is performed by irradiating one surface of the light wavelength conversion sheet with a predetermined amount of light wavelength-converted by the quantum dots at the time of 100 hours and 250 hours from the start of the wet heat resistance test. When the luminance of the light emitted from the other surface of the sheet was measured, the change rate of the luminance after 100 hours from the start of the moist heat resistance test with respect to the luminance before the moist heat resistance test and before the moist heat resistance test. 3. The light wavelength conversion sheet according to claim 1, wherein a change rate of the luminance after 250 hours from the start of the wet heat resistance test with respect to the luminance is within ± 10%.   The light wavelength conversion sheet according to claim 1 or 2, wherein an external haze value of the light wavelength conversion sheet is smaller than an internal haze value of the light wavelength conversion sheet.   The light wavelength conversion sheet according to claim 4, wherein a ratio of the external haze value to the internal haze value is 0 or more and 0.1 or less.   The light wavelength conversion sheet according to claim 4, wherein the internal haze value is 90% or more and the external haze value is 5% or less.   The light wavelength conversion sheet according to claim 1 or 2, wherein the light scattering particles are inorganic particles. A light source;
A backlight device comprising: the light wavelength conversion sheet according to claim 1, which receives light from the light source. The backlight device according to claim 8;
An image display device comprising: a display panel disposed on a light output side of the backlight device.

Images