JP2020140082A - Wavelength conversion sheet and backlight unit - Google Patents

Abstract

To provide a wavelength conversion sheet that is unlikely to generate thermal wrinkles and reduce initial illuminance of a phosphor layer, and can suppress illuminance deterioration.SOLUTION: A wavelength conversion sheet 100 comprises a phosphor layer 4, and a protective film 10 arranged on at least one surface of the phosphor layer. The protective film includes an optical functional layer 1 at least having light diffusion function on one surface of a resin film, and a primer layer 3 for enhancing high adhesion on the other surface, but includes no gas barrier layer. The thickness of the protective film is 60 μm or more and 150 μm or less. The phosphor layer is arranged on a side of the protective film to the primer layer. The primer layer is composed of cured primer composition containing silane coupling agent having amino group, and a ratio E1/E0 of initial illuminance E0 to illuminance E1 after elapse of 500 hours under an environment of 65°C, 95%RH and 85°C is 0.6 or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to a wavelength conversion sheet used for a backlight unit of a liquid crystal display device.

A wavelength conversion sheet that emits white light by irradiating the backlight unit of a liquid crystal display device with a blue light emitting diode as a light source is used. The wavelength conversion sheet is obtained by uniformly dispersing nano-sized fine particles of phosphor (quantum dots) in a transparent resin sheet.

The wavelength conversion sheet is adjusted so that when it is irradiated with blue light, red light is emitted from the red phosphor and green light is emitted from the green phosphor, and the light is combined with the blue light of the blue light emitting diode to become white light. Has been done. Since the quantum dots of such a wavelength conversion sheet have the property of being deteriorated by oxygen and water vapor, it is necessary to protect them with a barrier film that blocks them.

However, the barrier film has a problem that non-uniform heat shrinkage occurs due to the heat treatment received in the manufacturing process, and optical unevenness called heat wrinkles occurs.

For example, in Patent Document 1, in order to provide a wavelength conversion sheet capable of maximizing the performance of quantum dots by using a protective film for a phosphor having excellent barrier properties, a phosphor using quantum dots is provided. A wavelength conversion sheet including a phosphor layer containing the above and one or more protective films for phosphors laminated on at least one surface of the phosphor layer has been proposed. However, since the protective film for the wavelength conversion sheet carries out a step of heating the multilayer film formed on the polyester film at 150 ° C. or higher, it is not possible to eliminate the possibility that appearance defects due to heat wrinkles may occur.

Further, Patent Document 2 has an object of providing a barrier film in which the presence of wrinkles is reduced, and the shrinkage rate in the TD direction before and after heating at 150 ° C. for 30 minutes is −3.0% or more and less than 0%. A barrier film obtained by heating a polyester film and a multilayer film formed on the polyester film at 150 ° C. or higher has been proposed. However, since the barrier film for the wavelength conversion sheet carries out the step of heating the multilayer film formed on the polyester film at 150 ° C. or higher, it is not possible to eliminate the possibility that appearance defects due to heat wrinkles may occur.

Therefore, there has been a demand for a protective film that does not use a barrier film and does not deteriorate the characteristics of the phosphor layer containing quantum dots. As a prior art corresponding to such a technique, for example, Patent Document 3 provides a quantum dot-containing member capable of effectively suppressing a change in emission intensity of a phosphor layer with time without providing a gas barrier layer. With this as an issue, resins having a specific molecular structure have been proposed. Therefore, the phosphor sheet, which is a quantum dot-containing member using this resin, has an advantage that it does not require a barrier film. Further, in order to make the phosphor sheet itself have light diffusivity, in addition to the quantum dots, a dispersant that improves the dispersion state of the light diffusing agent and the light diffusing agent is added. Therefore, it is not necessary to form a matte layer on the phosphor sheet, which simplifies the configuration. Therefore, it is possible to make the backlight unit thinner. However, since the light diffusing agent and the dispersant are added, the density of quantum dots added must be lowered, so that the initial illuminance of the phosphor layer may decrease.

International Publication No. 2015/152396 Japanese Unexamined Patent Publication No. 2016-215579 International Publication No. 2018/092705

In view of the above circumstances, it is an object of the present invention to provide a wavelength conversion sheet capable of suppressing the deterioration of illuminance without the possibility of heat wrinkles and the decrease of the initial illuminance of the phosphor layer. And.

As a means for solving the above problems, the invention according to claim 1 of the present invention is a wavelength conversion sheet including a phosphor layer and a protective film arranged on at least one surface of the phosphor layer. ,
The protective film is provided with an optical functional layer having at least a light diffusing function on one surface of the resin film, a primer layer for enhancing adhesion on the other surface, and a gas barrier layer. No,
The thickness of the protective film is 60 μm or more and 150 μm or less.
The phosphor layer is arranged on the primer layer side of the protective film, and is arranged.
The primer layer is composed of a cured product of a primer composition containing a silane coupling agent having an amino group.
It is a wavelength conversion sheet characterized in that the ratio E1 / E0 of the initial illuminance E0 and the illuminance E1 after 500 hours elapses is 0.6 or more in an environment of 65 ° C. 95% RH 500 hours and 85 ° C. 500 hours. ..

The wavelength conversion according to claim 1, wherein the optical functional layer includes a binder resin and light diffusing particles dispersed in the binder resin. It is a sheet.

The invention according to claim 3 is characterized in that the adhesion of the primer layer adjacent to the phosphor layer is 3 N / 25 mm or more in a peeling test at 300 mm / min according to JIS Z0237. The wavelength conversion sheet according to claim 1 or 2.

The invention according to claim 4 is a backlight unit including an LED light source, a light guide plate, and a wavelength conversion sheet according to any one of claims 1 to 3.

Since the wavelength conversion sheet of the present invention has a layer structure in which a protective film without a gas barrier layer is laminated on a phosphor layer, thermal wrinkles do not occur. Further, it is provided with a phosphor layer in which the ratio E1 / E0 of the initial illuminance E0 and the illuminance E1 after 500 hours elapses is 0.6 or more under the environment of 65 ° C. 95% RH 500 hours and 85 ° C. 500 hours. Moreover, since it is provided with a primer layer having a gas barrier property, it is possible to suppress deterioration of the wavelength conversion sheet.

The cross-sectional view which illustrates the layer structure of the protective film of the wavelength conversion sheet of this invention. The cross-sectional view which illustrates the layer structure of the wavelength conversion sheet of this invention.

<Wavelength conversion sheet>
The wavelength conversion sheet of the present invention will be described with reference to FIGS. 1 and 2.
The wavelength conversion sheet 100 of the present invention has fluorescence in which the ratio E1 / E0 of the initial illuminance E0 and the illuminance E1 after 500 hours is 0.6 or more in an environment of 65 ° C. 95% RH 500 hours and 85 ° C. 500 hours. A wavelength conversion sheet including a body layer 4 and a protective film 10 arranged on at least one surface of the phosphor layer 4.

The protective film 10 of the wavelength conversion sheet 100 of the present invention is provided with an optical functional layer 1 having at least a light diffusion function on one surface of the resin film 2, and the adhesion is enhanced on the other surface. The primer layer 3 having a gas barrier property is provided, and the phosphor layer 4 is arranged on the primer layer 3 side of the protective film 10.
The reason why the primer layer 3 has a gas barrier property is that the primer layer 3 is composed of a cured product of a primer composition containing a silane coupling agent having an amino group.

Examples of the wavelength conversion sheet include, for example, as a binder resin, a thermoplastic resin such as polyester, acrylic, acrylic urethane, polyethylene terephthalate, polyurethane acrylate, urethane, epoxy, polycarbonate, polyamide, polyimide, melamine, and phenol, and a thermosetting resin. , Cadmium selenide (CdSe) as the material of the quantum dots, zinc sulfide (ZnS) as the core shell structure of the quantum dots, and 1 to 20 nm as the average particle diameter of the quantum dots. Quantum dots can be mentioned.

The phosphor layer 4 is a thin film of several tens to several hundreds of μm composed of a binder resin and quantum dots uniformly dispersed therein. As the binder resin, for example, a photosensitive resin can be used. Examples of the photosensitive resin include acrylic urethane-based resin and epoxyamine-based resin.

Inside the binder resin, two kinds of fine particles of a phosphor composed of quantum dots are sealed in a mixed state. As the material of the phosphor, the fluorescent material may be cadmium selenide (CdSe).
Further, the phosphor layer 4 may be a stack of two phosphor layers in which only one type of phosphor is sealed. As those phosphors, those having the same excitation wavelength are selected. The excitation wavelength is selected based on the wavelength of the light emitted by the LED light source. The fluorescent colors of the two types of phosphors are different from each other. Each fluorescent color is red and green. The wavelength of each fluorescence and the wavelength of the light emitted by the LED light source are selected based on the spectral characteristics of the color filter. The peak wavelength of fluorescence is, for example, 610 nm for red and 550 nm for green.

Next, the particle structure of the phosphor will be described. The phosphor has a core as a light emitting portion coated with a shell as a protective film. For example, cadmium selenide (CdSe) can be used for the core, and zinc sulfide (ZnS) can be used for the shell. The quantum yield is improved by covering the surface defects of the CdSe particles with ZnS having a large bandgap. Further, the phosphor may have a core double-coated with a first shell and a second shell. CdSe can be used for the core, zinc selenide (ZnSe) can be used for the first shell, and ZnS can be used for the second shell.

The phosphor layer 4 can be laminated on the protective film 10 by the following procedure, for example. First, the phosphor is mixed with the binder resin. Next, a mixed solution in which the phosphor is mixed with the binder resin is applied to the surface of the protective film 10. Examples of the binder resin include photosensitive resins, thermosetting resins, and chemically curable resins. The binder resin is (UV) cured by ultraviolet irradiation or heating to form the phosphor layer 4. Further, as the binder resin, a photosensitive resin and a thermosetting resin may be used in combination. In this case, the phosphor layer 4 can be formed by heat-curing the binder resin after UV curing. As a result, for example, a phosphor layer 4 having a size of about 50 μm is formed on the protective film 10.

Examples of the photosensitive resin include (meth) acrylate and the like. Further, examples of the thermosetting resin include compounds having an amino group and an epoxy group.

<Protective film>
The protective film 10 is provided with an optical functional layer 1 having at least light diffusivity on one surface of the resin film 2, and a primer layer 3 on the other surface that enhances adhesion to the phosphor layer 4. It has. The protective film 10 used for the wavelength conversion sheet 100 of the present invention does not use a gas barrier layer (a laminated structure composed of a metal oxide thin film formed on a resin film and a coating layer formed on the metal oxide thin film). Therefore, there is no risk of heat wrinkles.

Further, the protective film 10 of the present invention is characterized in that the gas barrier layer is not provided. The gas barrier layer is formed by laminating an inorganic oxide layer such as silicon oxide or aluminum oxide or a barrier coat layer such as polyvinyl alcohol in a single layer or multiple layers. Such a gas barrier layer has a function of providing a gas barrier property as a protective film, but on the other hand, it causes deformation of the film during processing and causes heat wrinkles. Therefore, when the above-mentioned initial luminance difference E1 / E0 of the wavelength conversion film is 0.6 or more, the performance as the wavelength conversion film can be maintained. Therefore, by not providing the gas barrier layer, heat wrinkles are suppressed. The quality of the wavelength conversion film can be improved.

The thickness of the protective film 10 is preferably 60 μm or more and 150 μm or less. When it is 60 μm or more, wrinkles are less likely to occur due to heating or the like when the wavelength conversion film is cured. Further, when it is 150 μm or less, it is possible to suppress a decrease in the light transmittance of the protective film and a decrease in the energy efficiency of the wavelength conversion film due to optical loss and scattering in the base film.

Further, the optical functional layer 1 may be a layer containing a binder resin and particles dispersed in the binder resin.

Further, the adhesion between the phosphor layer 4 and the primer layer 3 is preferably 3N / 25 mm or more in a peeling test at 300 mm / min according to JIS Z0237.

Each component of the wavelength conversion sheet of the present invention will be described below.

(Fluorescent layer)
The phosphor layer 4 used in the wavelength conversion sheet 100 of the present invention has a ratio E1 / E0 of the initial illuminance E0 and the illuminance E1 after 500 hours in an environment of 65 ° C. 95% RH 500 hours and 85 ° C. 500 hours. Use one that is 0.6 or more.

(Resin film)
As the resin film 2, a PET (polyethylene terephthalate) film can be preferably used, but it is not necessary to limit the resin film 2. Any resin film having the same degree of transparency and mechanical strength as PET can be used.

(Optical functional layer)
The optical functional layer 1 has at least an optical function including light diffusivity. Here, the case where the optical functional layer 1 is a light diffusion layer will be described as an example, but it does not mean that the limitation is limited to this. The optical functional layer 1 may have a concave-convex shape as a surface form, or may have a flat surface, for example. Further, as an optical function, it is necessary to have at least a light diffusion function, but other optical functions may be provided.

As the light diffusion layer, a binder resin in which light diffusion particles are uniformly dispersed can be preferably used. For example, a fine uneven shape may be formed on the surface by embedding the light diffusing particles in the binder resin so that a part of the light diffusing particles is exposed from the surface. Since the surface is provided with the uneven shape in this way, it is possible to reliably prevent the occurrence of interference fringes such as the Newton ring.

The binder resin is not particularly limited, but a resin having excellent optical transparency can be used. For example, polyester resin, acrylic resin, acrylic urethane resin, polyester acrylate resin, polyurethane acrylate resin, urethane resin, epoxy resin, polycarbonate resin, polyamide resin, polyimide resin, melamine resin, phenol. Thermoplastic resins such as based resins, thermosetting resins, ionizing radiation curable resins and the like can be used. In addition to the organic resin, a silica binder can also be used. Among these, it is desirable to use an acrylic resin or a urethane resin because of the wide range of materials, and it is more desirable to use an acrylic resin because it is excellent in light resistance and optical characteristics. These are not limited to one type, and a plurality of types can be used in combination.

The light diffusing particles are not particularly limited, but are, for example, inorganic fine particles such as silica, clay, talc, calcium carbonate, calcium sulfate, barium sulfate, titanium oxide, and alumina, as well as styrene resin, urethane resin, and silicone resin. , Acrylic resin, polyamide resin and other organic fine particles can be used. Among these, it is preferable to use fine particles having a refractive index of 1.40 to 1.55 made of silica, acrylic resin, urethane resin, polyamide resin or the like as the light diffusing particles in terms of transmittance. Fine particles with a low refractive index are expensive, while fine particles with an excessively high refractive index tend to impair the transmittance. These are not limited to one type, and a plurality of types can be used in combination.

The average particle size of the fine particles is preferably 0.1 to 30.0 μm, more preferably 0.5 to 10.0 μm, based on the volume of the laser diffraction / scattering method. When the average particle size of the fine particles is 0.1 μm or more, an excellent interference fringe prevention effect tends to be obtained, and when the average particle size is 30.0 μm or less, the transparency tends to be further improved.

The content of the light diffusing particles in the light diffusing layer is preferably 0.5 to 30.0% by mass, more preferably 3.0 to 10.0% by mass, based on the total amount of the light diffusing layer. .. When the content of the light diffusing particles is 0.5% by mass or more, the light diffusing function and the effect of suppressing interference fringes tend to be further improved, and when it is 30.0% by mass or less, the brightness is lowered. There is no.

The light diffusion layer can be formed by applying a coating liquid containing the binder resin and light diffusion particles described above onto the resin film 2 and drying and curing the film. Examples of the coating method include a gravure coater, a dip coater, a reverse coater, a wire bar coater, and a die coater.

(Primer layer)
The primer layer 3 used in the protective film 10 of the wavelength conversion sheet 100 of the present invention was cured by applying a curable resin composition containing a silane coupling agent having an amino acid group to the surface of the resin film 2 and drying it. It is a thing. By laminating the protective film 10 and the phosphor layer 4 via the primer layer 3, excellent adhesion can be obtained.

When the binder resin of the phosphor layer 4 contains an epoxy resin, the excellent adhesion is exhibited by the epoxy resin present in the phosphor layer 4 and the amino present in the primer layer 3. It is considered that the cause is that the group and the group chemically react and bind to each other.

Further, the silane coupling agent having an amino group contributes to the development of excellent adhesion by forming a siloxane bond in the primer layer 3 by hydrolysis condensation, and at the same time, contributes to the improvement of moisture resistance and the suppression of the decrease in gas barrier property. are doing.

The silane coupling agent having an amino group is not particularly limited, and for example, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, and the like. 3-Aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N- (Vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, and the like can be mentioned.

The curable resin composition is not particularly limited, but various ultraviolet curable resin compositions and thermosetting resin compositions can be used.

The UV curable resin composition usually contains a (polymerizable polyfunctional) monomer / oligomer, a photopolymerization initiator, and additives such as fillers, pigments, and UV absorbers.

Examples of the thermosetting resin composition include thermosetting resins such as phenol resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, polyurethane, and thermosetting polyimide, and a curing agent corresponding thereto. And a thermosetting resin compound prepared by mixing additives, diluents, etc. This thermosetting resin compound can be cured by heating it to cause polymerization or cross-linking to form a three-dimensional structure.

<Backlight unit>
Next, a backlight unit using the wavelength conversion sheet 100 of the present invention will be described.
The backlight unit of the present invention includes an LED light source, a light guide plate, and a wavelength conversion sheet 100 of the present invention.

Since the backlight unit of the present invention includes the wavelength conversion sheet 100 of the present invention, thermal wrinkles do not occur. Further, in the phosphor layer 4 using the quantum dots used in the wavelength conversion sheet 100, the ratio of the initial illuminance E0 to the illuminance E1 after 500 hours has passed under the environment of 65 ° C. 95% RH 500 hours and 85 ° C. 500 hours. Since E1 / E0 is 0.6 or more, deterioration of the illuminance of the wavelength conversion sheet 100 can be suppressed.

Next, examples of the wavelength conversion sheet of the present invention will be described.

<Example 1>
(Making a protective film)
First, a protective film as illustrated in FIG. 1 was produced. To prepare a protective film, a PET film having a thickness of x (μm) was first prepared. Here, x = 75.

An acrylic resin is used as a binder resin on one side of the PET film, and silica particles having a volume-based average particle diameter of 1.0 μm by a laser diffraction / scattering method are coated in an amount of 5.0% by mass as a solid content. The liquid was adjusted and applied using a die coater so that the thickness after drying was 3 μm. Then, it dried with warm air to obtain a light diffusing layer (mat layer).

Next, a primer layer was formed on the other surface of the PET film. UV curable containing acrylic resin acrylate containing 0.01% by mass of N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane as a coating liquid for the primer layer and as a silane coupling agent having an amino acid group as a main component. The resin composition was applied and dried using a die coater under the condition that the thickness after drying was 1.0 μm, and then cured by irradiation with ultraviolet rays to form a primer layer. As described above, a protective film was obtained.

Next, a phosphor layer was formed on the primer layer side of the protective film by applying and drying the phosphor layer coating solution with a die coater. As the phosphor layer coating liquid, a binder resin in which quantum dots were uniformly dispersed as a phosphor was used. A coating solution was prepared by mixing acetyl cellulose and a phosphor, adding a solvent for adjusting the viscosity to be suitable for coating, and mixing.

As the binder resin, acetyl cellulose, which is a thermoplastic resin, was used.

Quantum dots were used as the phosphor. As the quantum dots, those in which fine particles of cadmium selenide, which is the core, were coated with zinc sulfide were used. As the phosphor, a phosphor having an average particle diameter of 10 nm on a volume basis by a laser diffraction / scattering method was used. The concentration of the phosphor added to the phosphor layer was set to 5% by mass based on the total amount of the phosphor layer.
The coating liquid was applied and dried by a die coater to form a phosphor layer having a thickness of 100 μm.

In this way, a phosphor layer is formed on the primer layer of the protective film, and then laminated on the phosphor layer with the primer layer side of another protective film facing, and then the front and back sides. By irradiating the primer layer of No. 1 with ultraviolet rays, the primer layer was cured to form a laminated body in which a phosphor layer was sandwiched between two protective films. As described above, five wavelength conversion sheets having a thickness of 100 μm according to Example 1 were prepared.

For the five samples prepared in this way, total light transmittance measurement, appearance (heat wrinkle) inspection of the protective film, initial brightness difference measurement, adhesion between the phosphor layer and the protective film, appearance inspection of the wavelength conversion film, Was carried out.

The total light transmittance was measured using a spectroscopic haze meter SH 7000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.).

The initial luminance difference measurement is the initial luminance difference E1 / E0 which is the ratio of the initial luminance E0 of the wavelength conversion sheet to the luminance E1 after the environmental test (65 ° C., 95% RH, 500 hours and 85 ° C., 500 hours). Was measured and calculated, and the minimum and maximum values were shown.

The adhesion between the phosphor layer and the protective film was measured by a peeling test at 300 mm / min according to JIS Z0237.

The appearance (heat wrinkles) of the protective film is visually inspected, and those without heat wrinkles are 〇 (good), those that are easily visible are × (defective), and slight heat wrinkles are barely visible. Those that are possible are defined as Δ (defective).
The appearance inspection of the wavelength conversion film was also visually carried out, and those in which no appearance defect was observed were evaluated as 〇 (good), and those in which even a slight amount was observed were evaluated as × (defective).

<Example 2>
It was the same as in Example 1 except that x = 100. As a result, the thickness of the wavelength conversion sheet was 104 μm.

<Comparative example 1>
It was the same as in Example 1 except that x = 50. As a result, the thickness of the wavelength conversion sheet was 54 μm.

<Comparative example 2>
It was the same as in Example 1 except that x = 150. As a result, the thickness of the wavelength conversion sheet was 154 μm.

<Comparative example 2>
A wavelength conversion sheet (thickness 106 μm) produced using a protective film provided with a conventional gas barrier layer was evaluated.

The above evaluation results are summarized in Table 1.

The sample of the wavelength conversion sheet produced in Example 1 was good because it had a thickness of 79 μm and a total light transmittance of 88.7% and 88.0% or more (〇), and the protective film had no heat wrinkles and was good. (○), the initial luminance difference was 0.70 and 0.60 or more, which was good, and the appearance inspection as a wavelength conversion film was good (〇) because no wrinkles were observed. In all the samples, the adhesion between the phosphor layer and the protective film was 3.0 to 3.5 N / 25 mm at 85 ° C. after 500 hours and after 65 ° C. and 500 hours, and was 3.0 N / 25 mm or more. It was a good evaluation result. It should be noted that these numerical values are shown as the average value or range of the five samples.

For the sample prepared in Example 2, the thickness was 104 μm, the total light transmittance was 88.4%, which was good (〇), the protective film was good without heat wrinkles (〇), and the initial brightness difference was 0.80. Good (○), the appearance inspection as a wavelength conversion film was good (○) because no wrinkles were found.

Regarding the sample prepared in Comparative Example 1, the thickness was 54 μm, the total light transmittance was 89.6%, which was good (○), the protective film was good without heat wrinkles (○), and the initial brightness difference was 0.65. Good (○), the appearance inspection as a wavelength conversion film was poor (×) due to wrinkles.

The sample prepared in Comparative Example 2 had a thickness of 154 μm, a total light transmittance of 87.5% and was defective (×), the protective film had no heat wrinkles and was good (○), and the initial brightness difference was 0.85. Good (○), the appearance inspection as a wavelength conversion film was good (○) because no wrinkles were found.

Regarding the sample of Comparative Example 3, the thickness was 106 μm, the total light transmittance was 88.5%, which was good (〇), the protective film had thermal wrinkles (×), and the sample in which thermal wrinkles were slightly confirmed (Δ). ) Is also defective, the initial brightness difference is 0.85 to 0.99, which is good (○), and the appearance inspection as a wavelength conversion film shows that wrinkles were not seen (○) and that it was defective (×). )was there. This is because a gas barrier layer is used for the protective film, so that heat wrinkles may occur.

In Example 1, Example 2, Comparative Example 1, and Comparative Example 2, there was no gas barrier layer, and only Comparative Example 3 had a gas barrier layer.

As a result of the above, all the evaluation items were good in Examples 1 and 2 having a thickness of 79 μm to 104 μm, but in Comparative Examples 1 to 3, defects occurred in any of the items. The overall evaluation was poor. Specifically, all of Example 1 having a thickness of 79 μm were good, but in Comparative Example 1 having a thickness of 54 μm, wrinkles were observed in the appearance inspection of the wavelength conversion sheet, which was defective. Therefore, when the thickness of the wavelength conversion sheet is 54 μm or less, wrinkles may occur. Therefore, it is considered that the thickness should be 60 μm or more. Further, in Comparative Example 2 having a thickness of 154 μm, the total light transmittance was slightly less than 88.0%, so that it could not be said to be good. Therefore, it is considered that the thickness should be 150 μm or less.

1 ... Optical functional layer 2 ... Resin film 3 ... Primer layer 4 ... Fluorescent layer 10 ... Protective film 100 ... Wavelength conversion sheet

Claims (4)

A wavelength conversion sheet comprising a phosphor layer and a protective film arranged on at least one surface of the phosphor layer.
The protective film is provided with an optical functional layer having at least a light diffusing function on one surface of the resin film, a primer layer for enhancing adhesion on the other surface, and a gas barrier layer. No,
The thickness of the protective film is 60 μm or more and 150 μm or less.
The phosphor layer is arranged on the primer layer side of the protective film, and is arranged.
The primer layer is composed of a cured product of a primer composition containing a silane coupling agent having an amino group.
A wavelength conversion sheet characterized in that the ratio E1 / E0 of the initial illuminance E0 and the illuminance E1 after 500 hours elapses is 0.6 or more in an environment of 65 ° C. 95% RH 500 hours and 85 ° C. 500 hours. The wavelength conversion sheet according to claim 1, wherein the optical functional layer contains a binder resin and light diffusing particles dispersed in the binder resin. The wavelength conversion sheet according to claim 1 or 2, wherein the adhesion of the primer layer adjacent to the phosphor layer is 3N / 25 mm or more in a peeling test at 300 mm / min according to JIS Z0237. .. A backlight unit including an LED light source, a light guide plate, and a wavelength conversion sheet according to any one of claims 1 to 3.

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