JP6780255B2 - Image display device - Google Patents

Description

The present invention relates to an image display device.

Conventionally, as an image display device, a liquid crystal display, a plasma display, an electroluminescence display, a field emission display and the like are known.

The liquid crystal display generally includes a backlight device arranged on the back side of the liquid crystal display panel. The backlight device includes a light source, and the liquid crystal display panel can be illuminated from the back side by emitting light from the light source from the backlight device.

Further, the electroluminescence display (EL display) includes an electroluminescence element (EL element), and when electrical energy is applied to the EL element, the light emitting material contained in the light emitting layer of the EL element emits light.

At present, phosphors, especially quantum dots, are attracting attention because they can improve color reproducibility. Therefore, even in a liquid crystal display, a light wavelength conversion sheet having a light wavelength conversion layer containing a phosphor and a binder resin is incorporated in the backlight device, or in an EL display device, light emission including a phosphor as a light emitting layer of an EL element. The use of layers has been studied (eg, Patent Documents 1 and 2).

JP-A-2015-11518 Japanese Unexamined Patent Publication No. 2014-78380

However, such an optical wavelength conversion sheet or an EL element has a problem that the luminous efficiency of the phosphor is low. Therefore, it is desired to further improve the luminous efficiency of the phosphor.

The present invention has been made to solve the above problems. That is, it is an object of the present invention to provide an image display device capable of improving the luminous efficiency of the phosphor.

According to one aspect of the present invention, the image display device includes a light source and a light wavelength conversion sheet that receives light from the light source, and the light wavelength conversion sheet is dispersed in a host matrix and the host matrix. An image display including an optical wavelength conversion layer including the fluorescent substance and surface plasmon-excited particles having an average particle diameter of 200 nm or less that can excite surface plasmons by light from the light source and dispersed in the host matrix. Equipment is provided.

According to another aspect of the present invention, the image display device includes a light source and a light wavelength conversion sheet that receives light from the light source, and the light wavelength conversion sheet is dispersed in a host matrix and the host matrix. Light transmission including a light wavelength conversion layer containing a phosphor and surface plasmon-excited particles having an average particle diameter of 200 nm or less that are adjacent to the light wavelength conversion layer and capable of exciting surface plasmons by light from the light source. An image display device comprising the surface plasmon excitation particle layer of the above is provided.

According to the image display device of one aspect of the present invention, since the surface plasmon-excited particles are contained in the light wavelength conversion layer, the effect of enhancing the electric field of the surface plasmons excited by the surface plasmon-excited particles causes the phosphor to be of the phosphor. Light absorption and light emission are easily induced, and the light emission efficiency of quantum dots can be improved. Further, according to the image display device of another aspect of the present invention, since the surface plasmon excited particles are contained in the surface plasmon excited particle layer adjacent to the light wavelength conversion layer, the surface excited by the surface plasmon excited particles is contained. Due to the electric field enhancing effect of plasmons, light absorption and light emission of the phosphor are easily induced, and the light emission efficiency of quantum dots can be improved.

It is a schematic block diagram of the image display device which concerns on 1st Embodiment. It is a perspective view of the lens sheet shown in FIG. FIG. 5 is a cross-sectional view taken along the line II of the lens sheet of FIG. It is a schematic block diagram of the light wavelength conversion sheet shown in FIG. It is a figure which shows the operation of the light wavelength conversion sheet shown in FIG. It is a figure which shows typically the manufacturing process of the light wavelength conversion sheet shown in FIG. It is a figure which shows typically the manufacturing process of the light wavelength conversion sheet shown in FIG. It is a schematic block diagram of another image display device which concerns on 1st Embodiment. It is a schematic block diagram of the image display device which concerns on 2nd Embodiment. It is a schematic block diagram of the light wavelength conversion sheet shown in FIG. It is a schematic block diagram of the image display device which concerns on 3rd Embodiment. It is a schematic block diagram of the light wavelength conversion sheet shown in FIG. It is a schematic block diagram of another light wavelength conversion sheet which concerns on 3rd Embodiment. It is a schematic block diagram of the EL element included in the image display device which concerns on 4th Embodiment. It is a schematic block diagram of another EL element included in the image display device which concerns on 4th Embodiment.

[First Embodiment]
Hereinafter, the image display device according to the first embodiment of the present invention will be described with reference to the drawings. In the present specification, terms such as "sheet" and "film" are not distinguished from each other based only on the difference in designation. Therefore, for example, "sheet" is used in the sense of including a member that can also be called a film, and "film" is used in the sense that it also includes a member that can be called a sheet. 1 is a schematic configuration diagram of an image display device according to the present embodiment, FIG. 2 is a perspective view of the lens sheet shown in FIG. 1, and FIG. 3 is a perspective view of the lens sheet of FIG. It is a cross-sectional view, and FIG. 4 is a schematic configuration diagram of an optical wavelength conversion sheet shown in FIG. 5 is a diagram showing the operation of the light wavelength conversion sheet shown in FIG. 4, FIG. 6 is a diagram schematically showing a manufacturing process of the light wavelength conversion sheet shown in FIG. 4, and FIG. 7 is a diagram showing the operation of the light wavelength conversion sheet. It is a figure which shows typically the manufacturing process of the light wavelength conversion sheet shown. FIG. 8 is a schematic configuration diagram of another image display device according to the present embodiment.

[Image display device]
The image display device 10 shown in FIG. 1 includes a backlight device 20 and a display panel 80 arranged on the light emitting side of the backlight device 20. The image display device 10 has a display surface 10A for displaying an image. In the image display device 10 shown in FIG. 1, the surface of the display panel 80 is the display surface 10A.

The backlight device 20 illuminates the display panel 80 in a plane from the back side. The display panel 80 functions as a shutter that controls the transmission or blocking of light from the backlight device 20 for each pixel, and is configured to display an image on the display surface 10A.

<<< Display panel >>
The display panel 80 shown in FIG. 1 has a polarizing plate 81 arranged on the incoming light side, a polarizing plate 82 arranged on the light emitting side, and a display element 83 arranged between the polarizing plate 81 and the polarizing plate 82. And have. The display panel 80 may include the display element 83, and may not include the polarizing plates 81 and 82. The polarizing plates 81 and 82 decompose the incident light into two orthogonal linearly polarized light components (S-polarized light and P-polarized light) and vibrate in one direction (direction parallel to the transmission axis) (for example, P). It has a function of transmitting polarized light (polarized light) and absorbing a linearly polarized light component (for example, S-polarized light) that vibrates in the other direction (direction parallel to the absorption axis) orthogonal to the one direction. The display panel 80 shown in FIG. 1 is a liquid crystal display panel.

When the display element 83 is a liquid crystal display element, the display element 83 is configured so that a voltage can be applied to each region forming one pixel. Then, the orientation direction of the liquid crystal molecules in the display element 83 changes depending on the presence or absence of voltage application. As an example, a linearly polarized light component in a specific direction that has passed through a polarizing plate 81 arranged on the incoming light side rotates its polarization direction by 90 ° when passing through a display element 83 to which a voltage is applied, while rotating the polarization direction by 90 °. When passing through the display element 83 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 display element 83, the linearly polarized light component vibrating in a specific direction transmitted through the polarizing plate 81 may be transmitted through the polarizing plate 82, or absorbed by the polarizing plate 82 and blocked. it can. In this way, the display panel 80 is configured so that the transmission or blocking of light from the backlight device 20 can be controlled for each pixel. The details of the liquid crystal display panel are described in various publicly known documents (for example, "Flat Panel Display Dictionary (supervised by Tatsuo Uchida and Hiraki Uchiike)" published by Kogyo Chosakai in 2001). The detailed description of is omitted.

<<< Backlight device >>>
The backlight device 20 shown in FIG. 1 is configured as an edge light type backlight device, and includes a light source 25, an optical plate 30 as a light guide plate arranged on the side of the light source 25, and a light emitting side of the optical plate 30. The optical wavelength conversion sheet 40 arranged in, the lens sheet 60 arranged on the light source side of the light wavelength conversion sheet 40, the lens sheet 65 arranged on the light source side of the lens sheet 60, and the light source side of the lens sheet 65. It includes a reflective polarizing separation sheet 70 arranged, and a reflective sheet 75 arranged on the side opposite to the light emitting side of the optical plate 30. The backlight device 20 includes an optical plate 30, lens sheets 60 and 65, a reflective polarizing separation sheet 70, and a reflective sheet 75, but these sheets and the like may not be provided. As used herein, the term "light emitting side" means the side of each member where light emitted in the direction emitted from the backlight device is emitted.

The backlight device 20 has a light emitting surface 20A that emits light in a planar shape. In the backlight device 20 shown in FIG. 1, the light emitting surface of the reflective polarizing separation sheet 70 is the light emitting surface 20A of the backlight device 20.

<< Light source >>
The light source 25 may be configured in various forms such as a fluorescent lamp such as a linear cold cathode fluorescent lamp, a point-shaped light emitting diode (LED), or an incandescent lamp. In the present embodiment, the light source 25 is provided by a large number of point-shaped light emitters, specifically, a large number of light emitting diodes (LEDs), which are linearly arranged on the light receiving surface 40C side of the optical plate 40, which will be described later. ,It is configured.

Since the light wavelength conversion sheet 40 is arranged in the backlight device 20, the light source 25 can use only a light emitting body that emits light in a single wavelength range. For example, as the light source, only a blue light emitting diode that emits blue light having high color purity can be used.

<< Optical plate >>
The optical plate 30 as a light guide plate has a rectangular shape in a plan view. The optical plate 30 extends between the light emitting surface 30A formed by one main surface on the display panel 80 side, the back surface 30B composed of the other main surface facing the light emitting surface 30A, and the light emitting surface 30A and the back surface 30B. It has sides and. The side surface of the side surface on the light source 25 side is an incoming light surface 30C that receives light from the light source 25. The light incident on the optical plate 30 from the light entry surface 30C is guided in the optical plate in the direction connecting the light entry surface 30C and the opposite surface facing the light entry surface 30C (light guide direction), and the light exit surface. Emitted from 30A.

As a material constituting the optical plate 30, it is widely used as a material for an optical sheet incorporated in an image display device, has excellent mechanical properties, optical properties, stability, workability, etc., and is inexpensively available. For example, a transparent resin containing one or more of acrylic resin, polystyrene, polycarbonate, polyethylene terephthalate, polyacrylonitrile, etc. as a main component, and epoxy acrylate or urethane acrylate-based reactive resin (ionized radiation curable resin, etc.) are preferably used. Can be done. If necessary, a light diffusing material having a function of diffusing light can be added to the optical plate 30. As the light diffusing material, for example, particles made of a transparent substance such as silica (silicon dioxide), alumina (aluminum oxide), acrylic resin, polycarbonate resin, and silicone resin having an average particle diameter of 0.5 μm or more and 100 μm or less can be used. it can.

<< Lens sheet >>
The lens sheets 60 and 65 have a function of changing the traveling direction of the incident light and emitting the incident light from the light emitting side. In the present embodiment, as shown in FIG. 3, a function of changing the traveling direction of light L1 having a large incident angle and emitting it from the light emitting side to intensively improve the brightness in the front direction (condensing function). At the same time, it has a function (retroreflection function) of reflecting light L2 having a small incident angle and returning it to the light wavelength conversion sheet 40 side. As shown in FIG. 2, the lens sheets 60 and 65 include a light transmitting base material 61 and a lens layer 62 provided on one surface of the light transmitting base material 61.

<Light transmissive base material>
Since the light-transmitting base material 61 is the same as the light-transmitting base materials 50 and 51 described later, the description thereof will be omitted here.

<Lens layer>
As shown in FIGS. 2 and 3, the lens layer 62 includes a sheet-shaped main body 63 and a plurality of unit lenses 64 arranged side by side on the light emitting side of the main body 63.

The main body 63 functions as a sheet-like member that supports the unit lens 64. As shown in FIG. 3, unit lenses 64 are arranged on the light emitting side surface 63A of the main body 63 without leaving a gap. Therefore, the light emitting surfaces 60B and 65B of the lens sheets 60 and 65 are formed by the lens surfaces. On the other hand, as shown in FIG. 3, the light entering side surface 63B of the main body 63 facing the light emitting side surface 63A is a smooth surface forming the light entering side surface of the lens layer 62.

The unit lenses 64 are arranged side by side on the light emitting side surface 63A of the main body 63. As shown in FIG. 2, the unit lens 64 extends linearly in a direction intersecting the arrangement direction AD of the unit lens 64, particularly linearly in the present embodiment. Further, in the present embodiment, a large number of unit lenses 64 included in the lens sheets 60 and 65 extend in parallel with each other. Further, the longitudinal LD of the unit lenses 64 of the lens sheets 60 and 65 is orthogonal to the arrangement direction AD of the unit lenses 64 of the lens sheets 60 and 65.

The unit lens 64 may have a triangular columnar shape, or may have a wavy shape or a bowl shape such as a hemispherical shape. Specifically, examples of the unit lens include a unit prism, a unit cylindrical lens, a unit microlens, and the like. In the present embodiment, as a unit lens, a triangular columnar unit prism whose width becomes narrower toward the light emitting side will be described. The shape of the cross section (also called the main cut surface of the lens sheet) parallel to both the normal direction ND of the sheet surfaces of the lens sheets 60 and 65 and the arrangement direction AD of the unit lens 64 is a triangular shape protruding toward the light emitting side. ing. In particular, from the viewpoint of intensively improving the brightness in the front direction, the cross-sectional shape of the unit lens 64 on the main cutting surface is an isosceles triangle shape, and the apex angle located between the equilateral sides is the light emitting side surface 63A of the main body 63. Each unit lens 64 is configured so as to project from the light emitting side.

From the viewpoint of improving the efficiency of light utilization, the unit lens 64 preferably has an apex angle of 80 ° or more and 100 ° or less, and more preferably about 90 °. However, considering the damage to the tip of the unit lens when winding the optical wavelength conversion sheet, the tip of the unit lens 64 may be curved.

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

As can be understood from FIG. 1, the arrangement direction of the unit lens 64 of the lens sheet 60 and the arrangement direction of the unit lens 64 of the lens sheet 60 intersect, and more specifically, are orthogonal to each other.

<< Reflective Polarized Separation Sheet >>
The reflective polarization separation sheet 70 transmits only the first linearly polarized light component (for example, P-polarized light) among the light emitted from the lens sheet 65, and is a second straight line orthogonal to the first linearly polarized light component. It has a function of reflecting polarized light components (for example, S-polarized light) without absorbing them. The second linearly polarized light component reflected by the reflective polarization separation sheet 70 is reflected again, and the polarized light is eliminated (a state in which both the first linearly polarized light component and the second linearly polarized light component are included). It is incident on the reflective polarizing separation sheet 70 again. Therefore, the reflective polarization separation sheet 70 transmits the first linearly polarized light component of the light incident again, and the second linearly polarized light component orthogonal to the first linearly polarized light component is reflected again. Hereinafter, by repeating the same process, about 70 to 80% of the light emitted from the lens sheet 65 is emitted as the light source light as the first linearly polarized light component. Therefore, by matching the polarization direction of the first linearly polarized light component (transmission axis component) of the reflective polarization separation sheet 70 with the transmission axis direction of the polarizing plate 81 of the display panel 80, the light emitted from the backlight device 20 Can all be used for image formation on the display panel 80. Therefore, even if the light energy input from the light source 25 is the same, it is possible to form a brighter image as compared with the case where the reflective polarizing separation sheet 70 is not arranged, and the energy utilization efficiency of the light source 25 is also improved. improves. In particular, the light reflected by the reflective polarizing separation sheet 70 can be wavelength-converted by the optical wavelength conversion sheet 40. Therefore, by arranging the reflective polarizing separation sheet 70, the wavelength conversion efficiency of the light wavelength conversion sheet 40 can be further increased. Therefore, further improvement in light utilization efficiency can be expected.

As the reflective polarizing separation sheet 70, "DBEF" (registered trademark) available from 3M can be used. In addition to "DBEF", a high-intensity polarizing sheet "WRPS" available from Shinwha Intertek, a wire grid polarizer, or the like can be used as the reflective polarizing separation sheet 70.

<< Reflective sheet >>
The reflective sheet 75 has a function of reflecting the light leaked from the back surface 30B of the optical plate 30 and causing it to enter the optical plate 30 again. The reflective sheet 75 is composed of a white diffuse reflective sheet, a sheet made of a material having a high reflectance such as metal, a sheet containing a thin film made of a material having a high reflectance (for example, a metal thin film) as a surface layer, and the like. obtain. The reflection on the reflective sheet 75 may be regular reflection (specular reflection) or diffuse reflection. When the reflection on the reflective sheet 75 is diffuse reflection, the diffuse reflection may be isotropic diffuse reflection or anisotropic diffuse reflection.

<< Optical wavelength conversion sheet >>
The light wavelength conversion sheet 40 shown in FIG. 4 is a sheet that converts the wavelength of a part of the incident light into another wavelength and emits the other part of the incident light and the wavelength-converted light. is there.

The surface of the optical wavelength conversion sheet 10 on the optical plate 30 side is the light incoming surface 40A, and the surface of the optical wavelength conversion sheet 40 on the lens sheet 60 side is the light emitting surface 40B.

The light wavelength conversion sheet 40 is the side opposite to the surface of the light wavelength conversion layer 41, the barrier films 42 and 43 provided on both sides of the light wavelength conversion layer 41, and the surface of the barrier films 42 and 43 on the light wavelength conversion layer 41 side. It is provided with light diffusion layers 44 and 45 provided on the surface of the above. In the light wavelength conversion sheet 40, the surfaces of the light diffusion layers 44 and 45 form the light incoming surface 40A and the light emitting surface 40B of the light wavelength conversion sheet 40.

The light wavelength conversion sheet 40 has a structure of a light diffusion layer 44 / barrier film 42 / light wavelength conversion layer 41 / barrier film 43 / light diffusion layer 45, but the light wavelength conversion sheet has a light wavelength conversion layer. If so, the structure of the optical wavelength conversion sheet is not particularly limited. For example, the light wavelength conversion sheet includes only a light wavelength conversion layer, a light diffusion layer / barrier film / light wavelength conversion layer / barrier film, a light diffusion layer / barrier film / light wavelength conversion layer, a barrier film / light wavelength conversion layer, or The configuration may be a barrier film / light wavelength conversion layer / barrier film.

In the light wavelength conversion sheet 40, it is preferable that the external haze value of the light wavelength conversion sheet 40 is smaller than the internal haze value of the light wavelength conversion sheet 40. That is, the light wavelength conversion sheet 40 preferably satisfies the relationship of the following formula (1).
Internal haze value> External haze value ... (1)

The internal haze is a haze value caused by the inside of the light wavelength conversion sheet, and does not take into account the uneven shape of the surface of the light wavelength conversion sheet. On the other hand, the external haze value is caused only by the uneven shape of the surface of the light wavelength conversion sheet.

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

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

In the light wavelength conversion sheet 40, in order to make the external haze value of the light wavelength conversion sheet 40 smaller than that of the light wavelength conversion sheet 40, for example, light scattering particles may be added to the inside of the light wavelength conversion sheet 40. .. The light scattering particles may be added to the barrier films 42 and 43 as base materials in addition to the light wavelength conversion layer 41, and may also be added to the light diffusion layers 44 and 45. When the layer to which the light scattering particles are added is the outermost layer, it may be accompanied by an outer haze. Therefore, by controlling the surface unevenness of the outermost layer, the above-mentioned relationship between the inner haze and the outer haze is satisfied. Can be done.

The ratio of the external haze value to the internal haze value (external haze value / internal haze value) in the optical wavelength conversion sheet 40 is preferably 0 or more and 0.1 or less, and more preferably 0 or more and 0.05 or less. .. If this ratio is within this range, the internal haze can sufficiently diffuse the light and excite the quantum dots multiple times.

The external haze value in the optical wavelength conversion sheet 40 is preferably 10% or less (including 0%), and more preferably 5% or less. When the external haze value is 10% or less, retroreflection is likely to occur in a retroreflective sheet such as a lens sheet.

The internal haze value of the light wavelength conversion sheet 40 is preferably 60% or more, and more preferably 80% or more. When the internal haze value is 60% or more, the 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.

The light incoming surface 10A and the light emitting surface 10B of the light wavelength conversion sheet 40 preferably have an uneven shape from the viewpoint of preventing sticking. That is, the light wavelength conversion sheet is in contact with the optical plate or the lens sheet in the backlight device, but if the light wavelength conversion sheet and the optical plate or the lens sheet are stuck to each other, the light wavelength conversion sheet and the optical plate At the interface between the light wavelength conversion sheets and the interface between the optical wavelength conversion sheet and the lens sheet, a pattern called wet-out may be formed as if it were wet with water. On the other hand, when the light entering surface 10A and the light emitting surface 10B have an uneven shape as in the light wavelength conversion sheet 40, the light emitting surface 30A of the optical plate 30 is a part of the light entering surface 40A (for example,). The light coming-in surface 60A of the lens sheet 60 is in close contact with a part of the light-emitting surface 40B (for example, the convex portion), but the light-emitting surface 30A of the optical plate 30 is another part of the light-emitting surface 40A. It is separated from (for example, a recess), and the light entering surface 60A of the lens sheet 60 is separated from another portion (for example, a recess) of the light emitting surface 40B. In this case, the gap between the light emitting surface 30A and the other part of the light entering surface 40A and the gap between the light entering surface 60A and the other part of the light emitting surface 40B are an air layer. Due to the presence of this air layer, the light wavelength conversion sheet 40, the optical plate 30, and the lens sheet 60 are fixed so that the light emitting surface 30A and the light entering surface 40A and the light entering surface 60A and the light emitting surface 40B are in optical contact with each other. Even in this case, it is possible to prevent the light wavelength conversion sheet 40 from sticking to the optical plate 30 and the lens sheet 65, so that the interface between the light wavelength conversion sheet 40 and the optical plate 30 and the light wavelength conversion sheet 40 can be prevented from sticking to each other. It is possible to prevent the formation of wetouts at the interface between the light and the lens sheet 60.

The arithmetic mean roughness (Ra) of the light entering surface 40A and the light emitting surface 40B of the light wavelength conversion sheet 40 is 0.1 μm or more, respectively, in order to further prevent the light wavelength conversion sheet from sticking to the optical plate or the lens sheet. It is preferably 0.5 μm or more, and more preferably 0.5 μm or more.

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

When a light wavelength conversion sheet 40 containing both quantum dots that convert blue light into green light and quantum dots that convert blue light into red light is irradiated using a light source that emits blue light, the transmitted light in the light wavelength conversion sheet. Of these, the ratio of the peak value of green light intensity to the peak value of blue light intensity (peak value of green light intensity / peak value of blue light intensity) is 0.3 or more and 2.0 or less. It is preferably 0.5 or more and 1.5 or less.

The ratio of the peak value of the light intensity of red light to the peak value of the light intensity of blue light (the peak value of the light intensity of red light / the peak value of the light intensity of blue light) in the transmitted light in the light wavelength conversion sheet 40 is , 0.3 or more and 2.0 or less, and more preferably 0.5 or more and 1.5 or less.

In the present 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 Light having a wavelength range of 590 nm or more and 750 nm or less. Further, the light intensity of each of the above lights can be measured using a spectral radiance meter (for example, product name "CS2000", manufactured by Konica Minolta).

When a light wavelength conversion sheet 40 containing both quantum dots that convert blue light into green light and quantum dots that convert blue light into red light is irradiated using a light source that emits blue light, the transmitted light in the light wavelength conversion sheet The chromaticity x and y of are preferably 0.1 or more and 0.35 or less, and more preferably 0.15 or more and 0.25 or less, respectively. When the chromaticity of the transmitted light in the light wavelength conversion sheet is in this range, white light or light having a color close to white can be obtained. The chromaticities x and y are the chromaticities of the CIE1931-XYZ color system. The chromaticities x and y of the transmitted light in the optical wavelength conversion sheet can be measured according to JIS Z8701 using a spectroradiometer (product name "SR-UL2", manufactured by Topcon Co., Ltd.).

The average thickness of the optical wavelength conversion sheet 40 is preferably 10 μm or more and 500 μm or less. When the average thickness of the optical wavelength conversion sheet 40 is within this range, it is suitable for reducing the weight and thinning of the backlight device.

The average thickness of the optical wavelength conversion sheet 40 is calculated using, for example, images of cross sections taken at 20 locations at random 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 optical wavelength conversion sheet 40 is on the order of μm, it is preferable to use SEM. In the case of SEM, the accelerating voltage is preferably 30 kV and the magnification is preferably 1000 to 7000 times, and in the case of TEM or STEM, the accelerating voltage is preferably 30 kV and the magnification is preferably 50,000 to 300,000 times.

<Light wavelength conversion layer>
The optical wavelength conversion layer 41 includes a host matrix 46, quantum dots 47 as phosphors dispersed in the host matrix 46, and surface plasmon excitation particles 48 dispersed in the host matrix 46. The light wavelength conversion layer 41 may further include light scattering particles 49. Since the light wavelength conversion layer 41 contains the light scattering particles 49, the internal haze can be increased.

The average film thickness of the optical wavelength conversion layer 41 is preferably 10 μm or more and 200 μm or less, and more preferably 30 μm or more and 200 μm or less. When the average thickness of the light wavelength conversion layer 41 is within this range, it is suitable for reducing the weight and thinning 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 taken at 20 points at random using a scanning electron microscope (SEM).

In the present embodiment and the embodiments after the present embodiment, quantum dots are used as the phosphor, but the phosphor is not limited to the quantum dots, and the phosphor is not limited to the quantum dots, but instead of the quantum dots or together with the quantum dots. The phosphor of the above may be included in the light wavelength conversion layer. The phosphors other than the quantum dots are not particularly limited, and examples thereof include inorganic phosphors, organic dyes, and / or organometallic complexes. When a light source that emits blue light is used, a phosphor that converts blue light into green light (green emitting phosphor) and a phosphor that converts blue light into red light (red emitting phosphor) can be used. it can.

Examples of the green luminescent phosphor include Y ₃ A _l5 O ₁₂ : Ce ³⁺ , Tb ₃ Al ₅ O ₁₂ : Ce ³⁺ , BaY ₂ SiAl ₄ O ₁₂ : Ce ³⁺ , Ca ₃ Sc ₂ Si ₃ O ₁₂ : Ce ³⁺ , (Ba, Sr) ₂ SiO ₄ : Eu ²⁺ , CaSc ₂ O ₄ : Ce ³⁺ , Ba ₃ Si ₆ O ₁₂ N ₂ : Eu ²⁺ , β-SiAlON: Eu ²⁺ (Si _6-z Al _{z Oz} N _{8- z} : Eu ²⁺ , 0 <z ≦ 4.2), SrGa ₂ S ₄ : Eu ²⁺ , LaSiN: Ce ³⁺ , CaSi ₂ O ₂ N ₂ : Eu ²⁺ , Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ (LAG) or Examples thereof include green luminescent inorganic phosphors such as SrSi ₂ O ₂ N ₂ : Eu ²⁺ , green luminescent organic dyes, and green luminescent organic metal complexes.

Examples of the red light emitting phosphor include CaAlSiN ₃ : Eu ²⁺ , (Sr, Ca) AlSiN ₃ : Eu ²⁺ , Sr ₂ Si ₅ N ₈ : Eu ²⁺ , Sr ₂ (Si, Al) ₅ (N, O) ₈ : Eu ²⁺ , CaS: Eu ²⁺ , La ₂ O ₂ S: Eu ³⁺ , K ₂ SiF ₆ : Mn ^{4+ and} other red luminescent phosphors, red luminescent organic dyes, red luminescent organic metal complexes and the like.

(Host matrix)
The host matrix 46 in the light wavelength conversion layer 41 used in the light wavelength conversion sheet 40 is not particularly limited, and examples thereof include at least one of binder resin, glass such as silica glass, and silica gel. The binder resin is not particularly limited, and examples thereof include a cured product (polymer, crosslinked product) of a curable binder resin precursor. Examples of the curable binder resin precursor include an ionizing radiation polymerizable compound and / or a thermosetting resin. The ionizing radiation polymerizable compound has at least one ionizing radiation polymerizable functional group. As used herein, the "ionizing radiation-polymerizable functional group" is a functional group capable of undergoing a polymerization reaction by irradiation with ionizing radiation. Examples of the ionizing radiation polymerizable functional group include ethylenic double bonds such as a (meth) acryloyl group, a vinyl group, and an allyl group. In addition, "(meth) acryloyl group" means including both "acryloyl group" and "methacryloyl group". In addition, examples of ionizing radiation in the present specification include visible light, ultraviolet rays, X-rays, electron beams, α rays, β rays, and γ rays.

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

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

The ionizing radiation polymerizable oligomer has a weight average molecular weight of more than 1000 and less than 10000. As the ionizing radiation polymerizable oligomer, a polyfunctional oligomer having two or more functional groups is preferable, and a polyfunctional oligomer having three or more (trifunctional) ionizing radiation polymerizable functional groups is preferable. Examples of the polyfunctional oligomer include polyester (meth) acrylate, urethane (meth) acrylate, polyester-urethane (meth) acrylate, polyether (meth) acrylate, polyol (meth) acrylate, melamine (meth) acrylate, and isocyanurate. Examples thereof include (meth) acrylate and epoxy (meth) acrylate.

The ionizing radiation polymerizable prepolymer has a weight average molecular weight of more than 10,000, and the weight average molecular weight is preferably 10,000 or more and 80,000 or less, and more preferably 10,000 or more and 40,000 or less. When the weight average molecular weight exceeds 80,000, the viscosity is high, so that the coating suitability is lowered, and the appearance of the obtained light wavelength conversion layer may be deteriorated. Therefore, when an ionizing radiation-polymerizable prepolymer having a weight average molecular weight of more than 80,000 is used, it is preferable to mix and use the ionizing radiation-polymerizable monomer and the ionizing radiation-polymerizable 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, and 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, and polysiloxane resins. The thermosetting resin may be used alone or in combination of two or more. Among these, epoxy resin and urethane resin are preferable from the viewpoint 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, tetraphenylol ethane type epoxy resin, dicyclopentadienephenol type epoxy resin, hydrogenated bisphenol A type epoxy resin, bisphenol A nucleated polyol type epoxy resin, polypropylene glycol type epoxy resin, glycidyl ester type epoxy resin, A glycidylamine type epoxy resin, a glioxal type epoxy resin, an alicyclic epoxy resin, a heterocyclic epoxy resin and the like can be used.

Examples of the urethane resin include a combination of a polyol compound (main agent) and an isocyanate compound (curing agent). The polyol compound used as the main agent in the urethane resin is not particularly limited, and examples thereof include polyester polyols, polyester polyurethane polyols, polyether polyols, and polyether polyurethane polyols. These polyol compounds may be used alone or in combination of two or more.

The isocyanate-based compound used as a curing agent in the urethane resin is not particularly limited, and for example, polyisocyanate, its adduct, its isocyanurate-modified product, its carbodiimide-modified product, its alohanate-modified product, and its burette. Denatured substances and the like can be mentioned. Specific examples of the polyisethylene include diphenylmethane diisocyanis (MDI), polyphenylmethane diisocyanate (polymeric MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), and bis (4-isocyancylcyclohexyl) methane (H12MDI). , Isophorone diisocyanis (IPDI), 1,5-naphthalenediis diisocyanate (1,5-NDI), 3,3'-dimethyl-4,4'-diphenylenedi isocyanate (TODI), xylene diisocyanate (XDI) and other aromatic diisocyanes. An aliphatic diisocyanate such as tramethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate and isophorone diisocyanate; an alicyclic diisocyanate such as 4,4'-methylenebis (cyclohexyl isocyanate) and isophoron diisocyanate can be mentioned. Specific examples of the adduct body include those obtained by adding trimethylolpropane, glycol, or the like to the polyisocyanate. These isocyanate compounds may be used alone or in combination of two or more.

(Quantum dot)
The quantum dots 47 are nano-sized semiconductor particles having a quantum confinement effect. The particle size and average particle size of the quantum dots 47 are, for example, 1 nm or more and 20 nm or less. When the quantum dot 47 absorbs light from the excitation source and reaches an energy excited state, the quantum dot 47 emits energy corresponding to the energy band gap of the quantum dot 47. Therefore, by adjusting the particle size or the composition of the substance of the quantum dots 47, the energy band gap can be adjusted, and energy in various levels of wavelength bands can be obtained. In particular, the quantum dots 47 can generate strong fluorescence in a narrow wavelength band.

Specifically, the energy band gap of the quantum dots 47 increases as the particle size decreases. That is, as the crystal size becomes smaller, the emission of the quantum dots shifts to the blue side, that is, to the high energy side. Therefore, by changing the particle size of the quantum dot, the emission wavelength can be adjusted over the entire wavelength of the spectrum in the ultraviolet region, the visible region, and the infrared region. For example, when the particle size of the quantum dot is 2.0 nm or more and 3.5 nm or less, it emits blue light, and when the particle size of the quantum dot is 4.0 nm or more and 5.0 nm or less, it emits green light and the quantum dot particle. When the diameter is 5.5 nm or more and 6.5 nm or less, red light is emitted.

As the quantum dots 47, one type of quantum dots may be used, but it is also possible to use two or more types of quantum dots each having an emission band in a single wavelength range due to different particle diameters or materials. is there. As shown in FIG. 4, the optical wavelength conversion sheet 40 has the first quantum dot 47A and the second quantum dot 47B having a light emitting band in a wavelength range different from that of the first quantum dot 47A as the quantum dot 47. And is included.

As shown in FIG. 5, when light is incident from the light input surface 40A of the optical wavelength conversion sheet 40, the light L3 incident on the quantum dots 47 is converted into light L4 having a wavelength different from that of light L3. , Emit from the light emitting surface 40B. On the other hand, even when light is incident from the light entering surface 40A, the light L3 passing between the quantum dots 47 is emitted from the light emitting surface 40B without wavelength conversion.

As described above, some light emitted from the light wavelength conversion sheet 40 is not wavelength-converted. Therefore, a light source that emits blue light is used as the light source, and blue light is converted into green light as the first quantum dot 47A. When a quantum dot is used and a quantum dot that converts blue light into red light is used as the second quantum dot 47B, light that is a mixture of blue light, green light, and red light is emitted from the light wavelength conversion sheet 40. Can be made to.

The quantum dots 47 can generate strong fluorescence in a desired narrow wavelength range. Therefore, the backlight device using the light wavelength conversion sheet 40 can illuminate the display panel with light of the three primary colors having excellent color purity. In this case, the display panel will have excellent color reproducibility.

The quantum dot 47 may have a core-shell type structure mainly having a core made of a semiconductor compound of about 2 nm or more and 10 nm or less and a shell made of a semiconductor compound different from this 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 semiconductor compounds such as AlN, AlP, AlAs, AlSb, GaAs, GaP, GaN, GaSb, InN, InAs, InP, InSb, TiN, TiP, TiAs and III-V semiconductor compounds such as TiSb. , A semiconductor compound such as a group IV semiconductor such as Si, Ge and Pb, or a semiconductor crystal containing a semiconductor. Further, a semiconductor crystal containing a semiconductor compound containing three or more elements such as InGaP can also be used. Among these, semiconductor crystals such as CdS, CdSe, CdTe, InP, and InGaP are preferable from the viewpoints of ease of fabrication, controllability of particle size capable of obtaining light emission in the visible range, and the like.

The shell can improve the luminous efficiency of quantum dots by using a semiconductor compound having a bandgap 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 magnitude relationship include CdSe / ZnS, CdSe / ZnSe, CdSe / CdS, CdTe / CdS, InP / ZnS, Gap / ZnS, Si / ZnS, and the like. Examples thereof 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 47 is not particularly limited, and may be, for example, spherical, rod-shaped, disk-shaped, or other shape. When the shape of the quantum dot 47 is not spherical, the particle diameter of the quantum dot 16 can be a true spherical value having the same volume.

Information such as the particle size, average particle size, shape, and dispersed state of the quantum dots 47 can be obtained by a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM). The average particle size of the quantum dots is determined as the average value of the diameters of the 20 quantum dots measured from the observation image by observing the cross section of the light wavelength conversion layer using a transmission electron microscope or a scanning transmission electron microscope. be able to. Further, since the emission color of the quantum dot changes depending on the particle diameter, it is also possible to obtain the particle diameter of the quantum dot by confirming the emission color of the quantum dot. Further, the crystal structure and crystallite size of the quantum dots can be known by X-ray crystal diffraction (XRD). Furthermore, information on the particle size of quantum dots and the like can be obtained from the ultraviolet-visible (UV-Vis) absorption spectrum.

The content of the quantum dots 47 in the optical wavelength conversion layer 41 is preferably 0.01% by mass or more and 2% by mass or less, and more preferably 0.03% by mass or more and 1% by mass or less. If the content of the quantum dots 47 is less than 0.01% by mass, sufficient emission intensity may not be obtained, and if the content of the quantum dots 47 elements exceeds 2% by mass, sufficient excitation light may be obtained. There is a risk that the transmitted light intensity of will not be obtained. The mass% of the quantum dots, the mass% of the surface plasmon-excited particles, and the mass% of the light-scattering particles described later in the cured light wavelength conversion layer can be roughly calculated by the following methods. 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, after dissolving the host matrix component by acid treatment or the like, the mass of the quantum dot component, the mass of the surface plasmon excitation particle component, and the mass of the light scattering particle component are determined by an induction coupling plasma emission spectroscopic analysis method or the like. Measure each. Then, the ratio of the mass of the quantum dots 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 measured quantum dots. Similarly, the ratio of the mass of the surface plasmon excitation particles contained in at least a part of the sampled light wavelength conversion layer based on the mass of at least a part of the sampled light wavelength conversion layer and the mass of the measured surface plasmon excitation particles. calculate. In addition, 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 measured mass of the light scattering particles. To do.

(Surface plasmon excited particles)
The surface plasmon excitation particles 48 are particles having an average particle diameter of 200 nm or less that can excite surface plasmons by irradiation with light. The light that irradiates the surface plasmon excited particles is not particularly limited, and examples thereof include blue light.

Examples of the surface plasmon excitation particles 48 include at least one of metal particles and oxide semiconductor particles. Among the metal particles, particles composed of one or more noble metals selected from the group consisting of gold, silver, and platinum are particularly preferable, and silver particles are preferable from the viewpoint of cost. Examples of the oxide semiconductor particles include zinc oxide (ZnO), indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ) and the like.

The average particle size of the surface plasmon excitation particles 48 is set to 200 nm or less from the viewpoint of exciting the surface plasmon, but is more preferably 10 nm or more and 150 nm or less. The average particle size of the surface plasmon excited particles can be measured by the same measuring method as the average particle size of the quantum dots.

The average distance from the surface plasmon excitation particle 48 to the nearest quantum dot 47 is preferably 5 nm or more and 1 μm or less. If this average distance is less than 5 nm, the distance from the surface plasmon excited particles to the quantum dots is too close, and the energy obtained by the quantum dots absorbing the light from the light source is transferred to the surface plasmon excited particles. This is because the quantum dots may be deactivated. Further, when this average distance exceeds 1 μm, the distance from the surface plasmon excitation particles to the quantum dots is too long, so that the electric field enhancement effect due to the excitation of the surface plasmons cannot be obtained, and the light emission efficiency is improved. May not be possible. The "distance from the surface plasmon particle to the nearest particle dot" is the shortest distance from the surface of the surface plasmon excitation particle to the surface of the nearest quantum dot from the surface plasmon particle. For the average distance to the quantum dots closest to the surface plasmon excitation particles, observe the cross section of the light wavelength conversion layer using a transmission electron microscope or a scanning transmission electron microscope, and in this observation image, 20 surface plasmon excitation particles. The distances from each to the nearest quantum dot can be measured and calculated as the average value. The lower limit of the average distance between the quantum dots 47 and the surface plasmon excitation particles 48 is more preferably 10 nm or more, and the upper limit of the average distance between the quantum dots 47 and the surface plasmon excitation particles 48 is more preferably 0.5 μm or less. preferable.

The content of the surface plasmon excitation particles 48 in the optical wavelength conversion layer 41 is preferably 0.01% by mass or more and 20% by mass or less, and more preferably 0.1% by mass or more and 10% by mass or less. If the content of the surface plasmon excited particles is less than 0.01% by mass, the emission efficiency may not be improved, and if the content of the surface plasmon excited particles exceeds 20% by mass, the above energy There is a risk of deactivation due to movement.

The shape of the surface plasmon excitation particles 48 is not particularly limited, and is, for example, spherical (true spherical, substantially true spherical, elliptical spherical, etc.), polyhedral, rod-shaped (cylindrical, prismatic, etc.), flat plate, flaky, indefinite. The shape and the like can be mentioned. When the shape of the surface plasmon excitation particles is not spherical, the particle diameter of the surface plasmon excitation particles can be a true spherical value having the same volume.

(Light scattering particles)
The light scattering particles 49 are particles having an action of changing the traveling direction of light by scattering the light that has entered the light wavelength conversion sheet 40.

The content of the light scattering particles 49 in the light wavelength conversion layer 41 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, there is a possibility that the light scattering effect cannot be sufficiently obtained, and further, there is a possibility that the processability is lowered because there are too many light scattering particles.

The average particle size of the light-scattering particles 49 is preferably 20 times or more and 2000 times or less, and more preferably 50 times or more and 1000 times or less of the average particle size of the quantum dots 47. If the average particle size of the light scattering particles is less than 20 times the average particle size of the quantum dots, sufficient light scattering performance may not be obtained in the light wavelength conversion layer, and the average particle size of the light scattering particles becomes If it exceeds 2000 times the average particle size of the quantum dots, the number of light-scattering particles decreases even if the addition amount is the same, so that the number of scattering points decreases and a sufficient light scattering effect cannot be obtained. The average particle size of the light-scattering particles can be measured by the same method as the average particle size of the quantum dots described above.

Further, the average particle diameter of the light scattering particles 49 is preferably 1/300 or more and 1/20 or less, and more preferably 1/200 or more and 1/30 or less of the average film thickness of the light wavelength conversion layer 41. preferable. If the average particle size of the light scattering particles is less than 1/300 of the average thickness of the light wavelength conversion layer, sufficient light scattering performance may not be obtained in the light wavelength conversion layer, and the average of the light scattering particles. If the particle size exceeds 1/20 of the average film thickness of the light wavelength conversion layer, the ratio of light scattering particles to the light wavelength conversion layer decreases even if the amount added is the same, so that the number of scattering points is sufficiently reduced. No light scattering effect can be obtained.

Specifically, the average particle size of the light-scattering particles 49 is, for example, preferably 0.1 μm or more and 10 μm or less, and more preferably 0.3 μm or more and 5 μm or less. If the average particle size of the light scattering particles is less than 0.1 μm, the light wavelength conversion efficiency of the light wavelength conversion sheet may be insufficient, and the light scattering particles must have sufficient light scattering properties. It is necessary to increase the amount added. On the other hand, when the average particle size of the light-scattering particles exceeds 10 μm, the number of light-scattering particles decreases even if the addition amount (mass%) is the same, so that the number of scattering points decreases and a sufficient light-scattering effect is obtained. I can't get it.

The absolute value of the difference in refractive index between the light scattering particles 49 and the host matrix 46 is preferably 0.05 or more, and more preferably 0.10 or more, from the viewpoint of obtaining sufficient light scattering. The refractive index of the light-scattering particles 49 and the refractive index of the host matrix 46 may be larger. Here, as a method for measuring the refractive index of the light scattering particles before being contained in the light wavelength conversion layer, for example, the Becke method, the minimum declination method, the declination analysis, the mode line method, the ellipsometry method and the like are used. can do. As a method for measuring the refractive index of the host matrix (cured product) and the light scattering particles in the light wavelength conversion layer, for example, a fragment of the light scattering particles or a fragment of the host matrix in the cured and produced light wavelength conversion layer can be used. The Becke method can be used for what is taken out in some form. In addition, the difference in refractive index 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 diketric interference microscope manufactured by Mizojiri Optical Co., Ltd.). can do. When the host matrix contains the above-mentioned (meth) acrylate and other resins, the refractive index of the host matrix is a cured product of all the resin components contained except for quantum dots and light-scattering particles. Means the average refractive index of.

The shape of the light-scattering particles 49 is not particularly limited, and for example, spherical (true spherical, substantially true spherical, elliptical spherical, etc.), polyhedral, rod-shaped (cylindrical, prismatic, etc.), flat plate, flaky, indefinite. The shape and the like can be mentioned. When the shape of the light-scattering particles is not spherical, the particle diameter of the light-scattering particles 49 can be a true spherical value having the same volume.

The light-scattering particles 49 are preferably chemically bonded to the host matrix 46 from the viewpoint of firmly fixing the light-scattering particles 49 in the host matrix 46. This chemical bond can be realized by using light scattering particles surface-treated with a silane coupling agent.

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

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

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

Examples of the silane coupling agent having a vinyl group include vinyl trichlorosilane, vinyl trimethoxysilane, vinyl triethoxysilane and the like. 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 xypropylmethyldiethoxysilane 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-aminopropyltrime. Oxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N- (vinylbenzyl)- Examples thereof include a hydrochloride of 2-aminoethyl-3-aminopropyltrimethoxysilane.

As a method of surface-treating the light-scattering particles 49 with a silane coupling agent, a dry method of spraying the silane coupling agent on the light-scattering particles 49 or a silane coupling method after dispersing the light-scattering particles 49 in a solvent. Examples thereof include a wet method in which an agent is added and reacted.

The light scattering particles 49 may be organic particles, but the incident light on the light wavelength conversion sheet 40 can be suitably scattered, and the light wavelength conversion efficiency with respect to the incident light can be preferably improved. Since it can be formed, it is preferably inorganic particles.

Examples of the 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 such as MgO and MgF _2. At least one selected from the group consisting of containing 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. Examples include particles made of a material. Since these inorganic particles can increase the difference in refractive index from the host matrix, they are also preferable from the viewpoint of obtaining a large Mie scattering intensity.

When the light scattering particles 49 are inorganic particles, the incident light on the light wavelength conversion sheet 40 can be suitably scattered, and the light wavelength conversion efficiency with respect to the incident light can be preferably improved. .. In particular, the light scattering particles 49 are preferably particles made of at least one material selected from the group consisting of aluminum-containing compounds, zirconium-containing compounds, titanium-containing compounds, antimony-containing compounds, and silicon-containing compounds.

As the organic particles, particles made of at least one material selected from the group consisting of acrylic resin, styrene resin, melamine resin, and urethane resin are preferable.

Further, since the light wavelength conversion efficiency with respect to the incident light by the light wavelength conversion sheet 40 can be more preferably improved, the light scattering particles 49 may be made of two or more kinds of materials.

<Barrier film>
The barrier films 42 and 43 are films for protecting the quantum dots 47 from water and oxygen. The barrier films 42 and 43 may be only a light-transmitting base material or a barrier layer having a function of protecting the quantum dots 47 from water and oxygen, but as shown in FIG. 4, the quantum dots 47 may be formed of water and oxygen. The light-transmitting base materials 50 and 51 having a function of protecting from the light-transmitting base materials 50 and 51 and the barrier layers 52 and 53 provided on the surfaces of the light-transmitting base materials 50 and 51 and having a function of protecting the quantum dots 47 from moisture and oxygen. A multi-layer structure is preferred.

The oxygen transmission rate (OTR: Oxygen Transmission Rate) of the barrier films 42 and 43 is 1.0 × 10 ^-1 cc / m ² / day / atm or less under the conditions of 23 ° C. and 90% relative humidity. It is preferably 1.0 × 10 ^-2 cc / m ² / day / atm or less. The oxygen permeability can be measured using an oxygen gas permeability measuring device (OX-TRAN 2/21 manufactured by MOCON).

The water vapor transmittance (WVTR: Water Vaper Transmission Rate) of the barrier films 42 and 43 is preferably 1.0 × 10 ^-1 g / m ² / day or less under the conditions of 40 ° C. and 90% relative humidity. , 1.0 × 10 ^-2 g / m ² / day or less, more preferably. The water vapor transmission rate can be measured using a water vapor transmission rate measuring device (DELTAPERM (manufactured by Technolux)).

When light-scattering particles are added to the barrier film, the light-scattering particles can be added to the barrier film by kneading the light-scattering particles into a 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 of the light transmissive substrate opposite to the light wavelength conversion layer side.

(Light transmissive base material)
The thicknesses of the light-transmitting substrates 50 and 51 are not particularly limited, but are preferably 10 μm or more and 500 μm or less. If the thickness of the light-transmitting base materials 50 and 51 is less than 10 μm, the light wavelength conversion sheet may be assembled and wrinkled or broken during handling, and if it exceeds 150 μm, the weight of the display and the thin film may be reduced. It may not be suitable for conversion. The more preferable lower limit of the thickness of the light transmissive substrates 50 and 51 is 50 μm or more, and the more preferable upper limit is 400 μm or less.

The average thickness of the light transmitting substrates 50 and 51 can be calculated using, for example, an image of a cross section taken by a scanning electron microscope (SEM), a transmission electron microscope (TEM), or a scanning transmission electron microscope (STEM). ..

Examples of the constituent raw materials of the light-transmitting base materials 50 and 51 include polyester (for example, polyethylene terephthalate and polyethylene naphthalate), cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyether sulphon, and polysulphon. , Polypropylene, Polymethylpentene, Polyvinyl Chloride, Polypolyacetal, Polyetherketone, Polymethylmethacrylate, Polycarbonate, Polyurethane and other thermoplastics. Preferred examples of the constituent material of the base film include polyester (for example, polyethylene terephthalate and polyethylene naphthalate) and cellulose triacetate.

The light-transmitting base materials 50 and 51 may be composed of a single base material, or may be a laminated base material composed of a plurality of base materials. Such a laminated base material may be composed of a plurality of layers composed of layers of the same type of constituent raw materials, or may be composed of a plurality of layers composed of layers of different types of constituent raw materials, depending on the intended use. Good.

(Barrier layer)
The material for forming the barrier layers 52 and 53 is not particularly limited as long as it can obtain a barrier property, 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 Om} ), titanium oxide (TiO ₂ ), yttrium oxide, boron oxide (B ₂ O ₃ ), and oxidation. Calcium (CaO), silicon oxide nitride (SiO _x N _{yC z} ) and the like can be mentioned, examples of the metal include Ti, Al, Mg, Zr and the like, and examples of the sol-gel material include siloxane. Examples include sol-gel materials. These materials may be used alone or in combination of two or more.

The thicknesses of the barrier layers 52 and 53 are not particularly limited, but are preferably 0.01 μm or more and 1 μm or less. If it is less than 0.01 μm, the barrier performance of the barrier layer may be insufficient, and if it exceeds 1 μm, the barrier performance may be easily deteriorated due to cracks in the barrier layer or the like. The more preferable lower limit of the thickness of the barrier layer is 0.03 μm, and the more preferable upper limit is 0.5 μm.

The thickness of the barrier layer can be determined as an average value of the thickness of the barrier layer measured at 20 points using a transmission electron microscope or a scanning transmission electron microscope. Further, the barrier layers 52 and 53 may be a single layer or may be a stack of a plurality of layers. When a plurality of barrier layers are laminated, each layer constituting the barrier layer may be directly laminated or laminated.

Examples of the method for forming the barrier layers 52 and 53 include a physical vapor deposition (PVD) method such as a sputtering method and an ion plating method, a vapor deposition method such as a chemical vapor deposition (CVD) method, or a roll coating method. The spin coating method and the like can be mentioned. Moreover, you may combine these methods.

The barrier layers 52 and 53 are not particularly limited as long as they have the above-mentioned barrier properties, but from the viewpoint of high barrier properties and the like, a thin-film deposition layer formed by a thin-film deposition method may be used. preferable.

The type of the vapor deposition method is not particularly limited as long as it is a layer formed by the vapor deposition method, and the vapor deposition layer may be a layer formed by the CVD method or by the 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 layer having a high barrier property, but from the viewpoint of manufacturing efficiency and cost, the vapor deposition layer is formed by the PVD method. It is preferable to form.

Examples of the PVD method include a vacuum vapor deposition method, a sputtering method, an ion plating method, and the like. Among them, the vacuum vapor deposition method is preferably used from the viewpoint of its barrier property and the like. Examples of the vacuum vapor deposition method include a vacuum vapor deposition method using an electron beam (EB) heating method, a vacuum vapor deposition method using a high frequency dielectric heating method, and the like.

As the material of the vapor deposition layer, a metal or an inorganic oxide is preferable, and specifically, a metal such as Ti, Al, Mg, Zr, silicon oxide, aluminum oxide, silicon oxide nitride, aluminum oxide nitride, magnesium oxide, and oxidation. zinc, indium oxide, tin oxide, yttrium _oxide, B ₂ O 3, CaO inorganic oxides such like. Among them, silicon oxide and aluminum oxide are preferable from the viewpoint of having high barrier property and transparency.

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

An anchor layer may be formed as a base layer for the barrier layers 52 and 53. Thereby, the barrier property and the weather resistance can be enhanced. Examples of the material for forming the anchor layer include adhesive resins, inorganic oxides, organic oxides, and metals.

Examples of the method for forming the anchor layer include a PVD method such as a sputtering method and an ion plating method, a CVD method, a roll coating method, and a spin coating method. 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 44 and 45 have an uneven shape on the surface, and the uneven shape can diffuse the light incident on the light wavelength conversion sheet 40 and the light emitted from the light wavelength conversion sheet 40. Further, by providing the light diffusion layers 44 and 45, the light wavelength conversion efficiency of the light wavelength conversion sheet 40 can be further improved. The light diffusion layers 44 and 45 contain surface unevenness-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 unevenness-forming particles is preferably 10 times or more and 20,000 times or less, and more preferably 10 to 5000 times, the average particle size of the quantum dots 47 described above. If 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 diffusivity may not be obtained in the light diffusion layer, and the average particle size of the surface unevenness-forming particles is high. If it exceeds 20,000 times the average particle size of the quantum dots, the light diffusion performance of the light diffusion layer becomes excellent, but the light transmission rate of the light diffusion layer tends to be significantly reduced. The average particle size of the surface unevenness-forming particles can be measured by the same method as the average particle size of the quantum dots described above.

Specifically, the average particle size of the surface unevenness-forming particles is, for example, preferably 1 μm or more and 30 μm or less, and more preferably 1 μm or more and 20 μm or less. If the average particle size of the surface unevenness-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 the surface unevenness-forming particles added in order to obtain sufficient light diffusivity. Need to be increased. On the other hand, when the average particle diameter of the surface unevenness-forming particles exceeds 30 μm, the light diffusion performance becomes excellent, but the light transmittance of the light diffusion layer tends to be significantly reduced.

The absolute value of the difference in refractive index 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 diffusivity due to the refractive index of the surface unevenness-forming particles may not be obtained optically, and the improvement of the light wavelength conversion efficiency of the light wavelength conversion sheet may be insufficient. If it exceeds 15, the transmittance of the light diffusing layer may decrease. The more preferable lower limit of the difference in refractive index 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. It should be noted that either the refractive index of the surface unevenness-forming particles or 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 49 and the host matrix.

The shape of the surface unevenness-forming particles is not particularly limited, and for example, spherical (true spherical, substantially true spherical, elliptical spherical, etc.), polyhedral, rod-shaped (cylindrical, prismatic, etc.), flat plate, flaky, and indefinite shape. And so on. When the shape of the surface unevenness-forming particles is not spherical, the particle diameter of the surface unevenness-forming particles can be a true spherical value having the same volume.

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

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

(Binder resin)
The binder resin is not particularly limited, but the same binder resin as the binder resin described in the column of the optical wavelength conversion layer 41 can be used, and thus the description thereof will be omitted here.

<< Manufacturing method of optical wavelength conversion sheet >>
The optical wavelength conversion sheet 40 can be produced, for example, as follows. An example in which the host matrix 46 is a binder resin will be described below. First, as shown in FIG. 6A, a barrier layer 52 is formed on one surface of the light-transmitting base material 50 by a vapor deposition method or the like to form a barrier film 42. Further, in the same manner, the barrier layer 53 is formed on one surface of the light transmissive base material 51 by a vapor deposition method or the like to form the barrier film 43.

Next, a composition for a light diffusing layer containing surface unevenness-forming particles and a curable binder resin precursor is applied to the surface of the barrier film 42 opposite to the surface on the barrier layer 52 side, dried, and the light diffusing layer is dried. A coating film of the composition for use is formed. Similarly, a coating film of the composition for the light diffusion layer is formed on the surface of the barrier film 43 opposite to the surface on the barrier layer 53 side.

Next, the coating film of the composition for the light diffusion layer is cured by ionizing radiation irradiation or the like. As a result, as shown in FIG. 6B, the light diffusion layer 44 is formed on the surface of the barrier film 42 opposite to the surface on the barrier layer 52 side, and the barrier film 42 with the light diffusion layer 44 is formed. Will be done. Further, in the same manner, the barrier film 43 with the light diffusion layer 45 is formed.

After forming the barrier film 42 with the light diffusing layer 44 and the barrier film 43 with the light diffusing layer 45, the surface of the barrier film 43 with the light diffusing layer 45 opposite to the surface on the light diffusing layer 45 side (the surface of the barrier layer 53). ) Is coated with a composition for an optical wavelength conversion layer containing a curable host matrix precursor, quantum dots 47, surface plasmon excited particles 48 and light scattering particles 49, dried, and shown in FIG. 6 (C). As described above, the coating film 54 of the composition for the light wavelength conversion layer is formed. In addition, in order to improve the dispersibility of the surface plasmon excitation particles 48, it is also possible to add a dispersant to the composition for the optical wavelength conversion layer.

The content of the quantum dots 47 in the composition for the optical wavelength conversion layer is preferably 0.01% by mass or more and 2% by mass or less, and more preferably 0.03% by mass or more and 1% by mass or less. If the content of the quantum dots 47 is less than 0.01% by mass, sufficient emission intensity may not be obtained, and if the content of the quantum dots 47 exceeds 2% by mass, sufficient excitation light may be obtained. The transmitted light intensity may not be obtained.

The content of the surface plasmon excitation particles 48 in the composition for the optical wavelength conversion layer is preferably 0.01% by mass or more and 20% by mass or less, and more preferably 0.1% by mass or more and 10% by mass or less. preferable. If the content of the surface plasmon excited particles is less than 0.01% by mass, the emission efficiency may not be improved, and if the content of the surface plasmon excited particles exceeds 20% by mass, the above energy There is a risk of deactivation due to movement.

The content of the light scattering particles 49 in the composition for the light wavelength conversion layer is preferably 1% by mass or more and 50% by mass or less, and 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, there is a possibility that the light scattering effect cannot be sufficiently obtained, and further, there is a possibility that the processability is lowered because there are too many light scattering particles.

It is preferable that the composition for the optical wavelength conversion layer contains a polymerization initiator. A polymerization initiator is a component that is decomposed by light or heat to generate radicals or ionic species to initiate or proceed with the polymerization (crosslinking) of a curable host matrix precursor. The polymerization initiator used in the composition for the optical wavelength conversion layer is a photopolymerization initiator (for example, a photoradical polymerization initiator, a photocationic polymerization initiator, a photoanionic polymerization initiator), a thermal polymerization initiator (for example, a thermal radical). Polymerization initiators, thermal cationic polymerization initiators, thermal anion polymerization initiators), or mixtures thereof.

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

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

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

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

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

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

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

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

The viscosity of the composition for the optical wavelength conversion layer is preferably 10 mPa · s or more and 10000 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 light wavelength conversion layer having a sufficient film thickness, and if it exceeds 10000 mPa · s, the light wavelength When the composition for the conversion layer is applied, it may be difficult to apply the composition or the leveling property may be deteriorated.

After forming the coating film 54 of the composition for the light wavelength conversion layer, as shown in FIG. 7A, the surface of the barrier film 42 with the light diffusion layer 44 opposite to the surface on the light diffusion layer 44 side (barrier layer 52). The barrier film 42 with the light diffusion layer 44 is arranged on the coating film 54 of the composition for the light wavelength conversion layer so that the surface of the composition is in contact with the coating film 54 of the composition for the light wavelength conversion layer. As a result, the coating film 54 of the composition for the light wavelength conversion layer is sandwiched between the barrier films 42 and 43.

Then, as shown in FIG. 7B, the coating film 54 of the composition for the optical wavelength conversion layer is irradiated with ionizing radiation or heated through the barrier film 42 to obtain a curable host matrix precursor. It is cured to form the light wavelength conversion layer 41, and the light wavelength conversion layer 41 is integrated with the barrier film 42 with the light diffusion layer 44 and the barrier film 43 with the light diffusion layer 45. As a result, the optical wavelength conversion sheet 40 shown in FIG. 4 is obtained.

The optical wavelength conversion sheet 40 can be used by incorporating it into another image display device. Hereinafter, an example in which the light wavelength conversion sheet 40 is incorporated into another image display device will be described.

<< Other backlight devices >>
The optical wavelength conversion sheet 40 may be incorporated into an image display device provided with a direct-type backlight device as shown in FIG. The image display device 90 shown in FIG. 8 includes a backlight device 100 and a display panel 80 arranged on the light emitting side of the backlight device 100.

The backlight device 100 includes a light source 25, an optical plate 101 that receives the light of the light source 25 and functions as a light diffusing plate, and an optical wavelength conversion sheet 40 and an optical wavelength conversion sheet 40 arranged on the light emitting side of the optical plate 101. It is provided with a lens sheet 60 arranged on the light emitting side of the lens sheet 60, a lens sheet 65 arranged on the light emitting side of the lens sheet 60, and a reflective polarization separation sheet 70 arranged on the light emitting side of the lens sheet 65. In the present embodiment, the light source 25 is arranged directly below the optical plate 101, not on the side of the optical plate 101. In FIG. 8, the members having the same reference numerals as those in FIG. 1 are the same as the members shown in FIG. 1, and therefore the description thereof will be omitted. The backlight device 100 is not provided with the reflective sheet 75.

<Optical plate>
The optical plate 101 as a light diffusing plate has a rectangular shape in a plan view. The optical plate 101 has an incoming light receiving surface 101A formed by one main surface on the light source 75 side and an outgoing light emitting surface 101B formed by the other main surface on the light wavelength conversion sheet 40 side. The light incident on the optical plate 101 from the light incoming surface 101A is diffused in the optical plate 101 and emitted from the light emitting surface 101B.

The optical plate 101 is not particularly limited as long as it can diffuse the light from the light source 25, and examples thereof include a plate in which light diffusing particles are dispersed in a transparent material. The transparent material is not particularly limited, and examples thereof include transparent resin and inorganic glass. As the transparent resin, a transparent thermoplastic resin is preferably used because it is easy to mold. The transparent thermoplastic resin is not particularly limited, but for example, a polystyrene resin, a styrene-methyl methacrylate copolymer resin, a styrene-methacrylic acid copolymer resin, and a styrene-maleic anhydride copolymer resin. , Methacrylic resin, acrylic resin, polycarbonate resin, ABS resin (acrylonitrile-butadiene-styrene copolymer resin), AS resin (acrylonitrile-styrene copolymer resin), polyolefin resin (polyethylene resin, polypropylene resin, etc.) and the like. .. One of these may be used, or two or more of these may be mixed and used.

<Light diffusing particles>
Examples of the light diffusing particles in the optical plate 101 include light diffusing particles generally used as a diffusing plate.

According to the present embodiment, since the light wavelength conversion layer 41 contains the surface plasmon excitation particles 48 in addition to the quantum dots 47, the luminous efficiency of the quantum dots 47 can be improved. That is, in the surface plasmon excitation particles 48, the surface plasmons are excited by the light from the light source 25. When the surface plasmon is excited by the surface plasmon-excited particles 48, the light absorption and light emission of the quantum dots 47 in the vicinity of the surface plasmon-excited particles 48 are likely to be induced by the electric field enhancing effect of the surface plasmons. As a result, the luminous efficiency of the quantum dots 47 can be improved.

Conventionally, light that has been wavelength-converted by quantum dots emitted from the light wavelength conversion sheet is condensed on the light emitting side of the light wavelength conversion sheet, and light that has not been wavelength-converted by the light wavelength conversion sheet is collected by the light wavelength conversion sheet. It is being studied to improve the light wavelength conversion efficiency by arranging a lens sheet to be returned to the side. However, the light wavelength conversion efficiency is not sufficient only by arranging such a lens sheet, and further improvement of the light wavelength conversion efficiency is desired. According to the present embodiment, when the external haze value of the light wavelength conversion sheet 40 is smaller than the internal haze value of the light wavelength conversion sheet 40, 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 emits the light wavelength conversion sheet without being wavelength-converted by the quantum dots also has straightness. There is. Here, when the external haze value of the optical wavelength conversion sheet is high, the non-wavelength-converted light having straightness on the surface of the optical wavelength conversion sheet is refracted, and in the unconverted wavelength light emitted from the optical wavelength conversion sheet. Has a large number of components with a large emission angle. On the other hand, a lens sheet having a condensing function and a retroreflective function tends to retroreflect the lens sheet as the incident angle on the lens sheet is smaller. That is, the larger the angle of incidence on the lens sheet, the easier it is for the light to pass through the lens sheet. In the present embodiment, in the light wavelength conversion sheet 40, the external haze value is smaller than the internal haze value, so that even if the light that has not been wavelength-converted on the surface of the light wavelength conversion sheet 40 is refracted, it is emitted. It can be emitted in a state where the angle is small, and thus it is possible to increase the number of components having a small emission angle in the unwavelength-converted light emitted from the optical wavelength conversion sheet 40. Therefore, the lens sheet 60 can retroreflect the light emitted from the light wavelength conversion sheet without wavelength conversion and return it to the light wavelength conversion sheet 40 side, so that the opportunity for wavelength conversion increases. Further, since the internal haze value is larger than the external haze value, the optical path length is extended by scattering the light a plurality of times inside the optical wavelength conversion sheet, and the chance of wavelength conversion is further increased. Thereby, the light wavelength conversion efficiency can be improved. Since the quantum dots 47 emit light isotropically, the light wavelength-converted by the quantum dots 47 is oriented in various directions, and when the light reaches the surface of the optical wavelength conversion sheet 40, the light wavelength conversion sheet 40 is further subjected to. Light is refracted on the surface, and the wavelength-converted light becomes light having a large angle and is easily emitted from the light wavelength conversion sheet. Therefore, the wavelength-converted light is relatively easy to pass through the lens sheet 60.

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

According to the present embodiment, since the light wavelength conversion layer 41 contains the light scattering particles 49, 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 25, a quantum dot that converts blue light into green light is used as the first quantum dot 47A, and blue light is converted into red light as the second quantum dot 47B. When a light wavelength conversion sheet containing quantum dots is irradiated with blue light, the chromaticity x and y can be increased as compared with the light wavelength conversion sheet not containing light-scattering particles, and the color is white light or a color close to white. You can get the light of taste.

According to the present embodiment, since the light wavelength conversion sheet 40 contains the light scattering particles 49, the green light emission can be preferentially enhanced over the red light emission. The reason for this is not clear, but light-scattering particles may impede energy transfer from the first QD, which converts blue light to green light, to the second QD, which converts blue light to red light. It is considered that this is because the green light emission that was originally deactivated by the above energy transfer leads to the light emission process without being deactivated, and as a result, the green light emission increases.

[Second Embodiment]
Hereinafter, the image display device according to the second embodiment of the present invention will be described with reference to the drawings. It should be noted that, in the embodiments after the present embodiment, the contents overlapping with the contents of the first embodiment and the drawings used in the embodiments after the present embodiment are the same as the drawings used in the description of the first embodiment. Since the members with the reference numerals are the same as the members shown in the drawings used in the description of the first embodiment, the description thereof will be omitted. FIG. 9 is a schematic configuration diagram of the image display device according to the present embodiment, and FIG. 10 is a schematic configuration diagram of the light wavelength conversion sheet shown in FIG.

[Image display device]
The image display device 110 shown in FIG. 9 has the same configuration as the image display device 10 shown in FIG. 1 except that the light wavelength conversion sheet 120 is provided instead of the light wavelength conversion sheet 40.

<< Optical wavelength conversion sheet >>
As shown in FIG. 10, the light wavelength conversion sheet 120 has a single-layer structure. That is, the light wavelength conversion sheet 120 is composed of only the light wavelength conversion layer 121, and the light wavelength conversion sheet 120 does not include a barrier film. However, when the light-transmitting particles 122 described later do not have a barrier property, it is preferable to provide a barrier film. Further, the light wavelength conversion sheet 120 may further include a light transmissive base material that supports the light wavelength conversion layer 121 in addition to the light wavelength conversion layer 121. By providing the light transmissive base material, the intensity of the light wavelength conversion sheet 120 can be increased. Further, the optical wavelength conversion sheet may be composed of only an optical wavelength conversion layer including a lens unit. Since the light wavelength conversion layer includes a lens portion, the light wavelength conversion sheet has a lens function in addition to the light wavelength conversion function, so that one lens sheet can be omitted, and further reduction in thickness is achieved. be able to.

In the optical wavelength conversion sheet 120, the entire sheet, 40 ° C., water vapor transmission rate at a relative humidity of 90% (WVTR: Water Vaper Transmission Rate) may be a 1g ^/ m 2 · 24h or more. The water vapor permeability is a numerical value obtained by a method based on JIS K7129. The water vapor transmission rate can be measured using a water vapor transmission rate measuring device (DELTAPERM (manufactured by Technolux)). 40 ° C. in the optical wavelength conversion sheet 120, the water vapor permeability at a relative humidity of 90% may constitute a ^{1 × 10 1 g / m 2} · 24h or more.

In the optical wavelength conversion sheet 120, the entire sheet, 23 ° C., the oxygen permeability at a relative humidity of 90% (OTR: Oxygen Transmission Rate ) may be a ^{1cm 3 / m 2 · 24h ·} atm or more. The oxygen permeability is a numerical value obtained by a method based on JIS K7126. The oxygen permeability can be measured using an oxygen gas permeability measuring device (OX-TRAN 2/21 manufactured by MOCON). 23 ° C. in the optical wavelength conversion sheet 120, an oxygen permeability at 90% relative humidity may be a ^{1 × 10 1 cm 3 / m} 2 · 24h · atm or more.

<Light wavelength conversion layer>
The optical wavelength conversion layer 121 includes a host matrix 46, quantum dots 47 dispersed in the host matrix 46, surface plasmon excitation particles 48, and light transmitting particles 122 that enclose the quantum dots 47. The light wavelength conversion layer 121 may further include light scattering particles 49. There is no air layer between the quantum dots 47 and the light-transmitting particles 122, and the surface of the quantum dots 47 is in close contact with the light-transmitting particles 122.

(Light transmissive particles)
The light-transmitting particles 122 may be any particles that enclose the quantum dots 47 and have light transmission properties, but preferably have a barrier property that protects the quantum dots from moisture and oxygen. In the present embodiment, the light-transmitting particles 122 will be described as having a barrier property. By wrapping the quantum dots 48 with the light-transmitting particles 122, the distance between the quantum dots 47 and the surface plasmon excitation particles 48 can be adjusted by the thickness of the light-transmitting particles 122. Further, by wrapping the quantum dots 47 with light-transmitting particles 122 having a barrier property, it is possible to suppress the quantum dots 47 from coming into contact with water or oxygen, so that the quantum dots 47 are prevented from being deteriorated by water or oxygen. it can. As a result, it is possible to suppress a decrease in the luminous efficiency of the quantum dots 47 without providing a barrier film. In the present specification, "light transmission" means having a property of transmitting light, and "light transmission" also includes transparency. Here, in the present embodiment, since the quantum dots are wrapped with light-transmitting particles, if the light emission from the quantum dots emitted from the light wavelength conversion sheet can be confirmed, the light-transmitting particles are light-transmitting. It can be said that it has sex. The emission of quantum dots can be confirmed using a fluorometer. For "barrier property", a durability test was performed on the light wavelength conversion sheet by leaving it in an environment of 40 ° C. and 90% relative humidity for 300 hours, and the reduction rate of the emission peak intensity of the light wavelength conversion sheet before and after the durability test was 10. If it is within%, it can be judged that the light-transmitting particles have a barrier property. However, since the light from the light source transmitted through the light wavelength conversion sheet is not the light generated by the light emission of the light wavelength conversion sheet, the peak intensity of the light from the light source transmitted through the light wavelength conversion sheet is the light emission of the light wavelength conversion sheet. It shall not be included in the peak intensity. Further, when there are a plurality of emission peaks of light emitted from the light wavelength conversion sheet, "the reduction rate of the emission peak intensity is within 10%" means that the reduction rate of the intensity at each emission peak is within 10%. Means that The reduction rate of the emission peak of the light wavelength conversion sheet before and after the durability test is A, the emission peak intensity of the light wavelength conversion sheet before the durability test is B, and the emission peak intensity of the light wavelength conversion sheet after the durability test is C. Then, the reduction rate (A) of the emission peak of the light wavelength conversion sheet before and after the durability test is obtained by the following formula (2).
A = (BC) / B × 100 ... (2)

The material for forming the light-transmitting particles 122 is not particularly limited as long as it has light-transparency, and examples thereof include inorganic oxides. Specifically, examples of the inorganic oxide include silicon oxide (SiO _x ) such as silica, aluminum oxide (Al _{n Om} ) such as alumina, titanium oxide (TiO ₂ ), yttrium oxide, and boron oxide (B). ₂ O ₃ ), calcium oxide (CaO), silicon oxide nitride (SiO _x N _{yC z} ), etc. Among these, silica or alumina such as glass is selected from the viewpoint of low permeability of oxygen and water vapor. preferable. These materials may be used alone or in combination of two or more. It is also possible to use inorganic oxides other than oxide semiconductors.

When the quantum dot 47 contains Cd, the thickness of the light-transmitting particle 122 (distance from the surface of the quantum dot 47 to the outer surface of the light-transmitting particle 122) in order to prevent the elution of Cd contained in the quantum dot 47. Is preferably 2 nm or more, and more preferably 4 nm or more. When the average particle diameter of the light-transmitting particles 122 is about 50 nm, the thickness of the light-transmitting particles 122 can be 10 nm or more. Further, when the average particle diameter of the light-transmitting particles 122 is about 100 nm, the thickness of the light-transmitting particles 122 can be 20 nm or more. The thickness of the light-transmitting particles can be easily measured as an outer portion that does not contain quantum dots in transmission electron microscope observation. When the thickness differs depending on the position of the peripheral edge of the light-transmitting particle, the thickness of the light-transmitting particle is calculated by averaging the entire peripheral edge of the light-transmitting particle.

The light-transmitting particles 122 are preferably chemically bonded to the host matrix 46 from the viewpoint of improving the adhesion to the host matrix 46. This chemical bond can be carried out by the light-transmitting particles 122 surface-modified with a silane coupling agent. As the silane coupling agent, the same silane coupling agent as that described in the section on light scattering particles of the first embodiment can be used, and thus the description thereof will be omitted here.

The light-transmitting particles 122 can be produced, for example, by using the sol-gel method (see Patent No. 5682069). Specifically, first, quantum dots are prepared, an appropriate amount of metal alkoxide (1) is added to the quantum dots, and the surface of the quantum dots is hydrolyzed appropriately by hydrolyzing the metal alkoxide (1). Replace with a thing. Such a liquid is designated as the organic solvent A. On the other hand, the metal alkoxide (2) is dispersed in the aqueous solution and partially hydrolyzed to obtain the aqueous solution B. Here, the metal alkoxide (2) is selected to have a slower hydrolysis rate than the metal alkoxide (1). Then, by mixing the organic solution A and the aqueous solution B, a layer of the metal alkoxide (2) is further formed on the surface of the quantum dots covered with the metal alkoxide (1). Quantum dots that come into contact with water become hydrophilic because the metal alkoxide on the surface is hydrolyzed, and move to the aqueous phase. At this time, the quantum dots form an aggregate. Since the metal alkoxide (2) near the surface is hydrolyzed slower than the metal alkoxide (1), the alkoxide on the surface of the quantum dots is dehydrated and condensed at once when it moves to the aqueous phase, forming a large mass. prevent. An inorganic oxide layer such as a silica glass layer is further deposited on the aggregate in the aqueous phase. This can be done by hydrolyzing a small amount of metal alkoxide (3) in the alkaline region with a large amount of water and alcohol and depositing it on an aggregate of core quantum dots by the usual Stöber process. As a result, the light-transmitting particles 122 that enclose the quantum dots 47 can be obtained.

<< Manufacturing method of optical wavelength conversion sheet >>
The optical wavelength conversion sheet 120 can be produced, for example, as follows. First, a composition for a light wavelength conversion layer containing a curable host matrix precursor, light-transmitting particles 122 wrapping quantum dots 47, surface plasmon-excited particles 48, and light-scattering particles 49 is placed on one surface of a substrate. It is applied and dried to form a coating of the composition for the light wavelength conversion layer. The base material may be a light-transmitting base material, but may not be a light-transmitting base material. It is preferable that the composition for the optical wavelength conversion layer contains a polymerization initiator.

Then, the coating film of the composition for the light wavelength conversion layer is irradiated with ionizing radiation or heat is applied to cure the coating film to form the light wavelength conversion layer 121. Finally, the base material is peeled off from the light wavelength conversion layer 121. As a result, the light wavelength conversion sheet 120 composed of only the light wavelength conversion layer 121 can be obtained.

When the light wavelength conversion sheet includes a light transmissive base material, it is obtained by using a light transmissive base material as the base material and leaving the base material as it is without peeling after forming the light wavelength conversion layer 121. be able to.

According to the present embodiment, since the surface plasmon excitation particles 48 are included in the optical wavelength conversion layer 121 in addition to the quantum dots 47, the luminous efficiency of the quantum dots 47 can be improved for the same reason as in the first embodiment. Can be improved.

According to the present embodiment, since the quantum dots 47 are surrounded by the light-transmitting particles 122, the distance between the quantum dots 47 and the surface plasmon excitation particles 48 can be adjusted by the thickness of the light-transmitting particles 122. As a result, the distance between the quantum dot 47 and the surface plasmon excitation particle 48 does not become too close, and the deactivation of the quantum dot 47 can be suppressed. As a result, the luminous efficiency of the quantum dots 47 can be further improved.

When the quantum dots 47 are wrapped with the light-transmitting particles 122 having a barrier property as in the present embodiment, the quantum dots 47 can be protected from water and oxygen. Thus, 40 ° C. in the optical wavelength conversion sheet 120, even water vapor permeability at a relative humidity of 90% was 1g ^/ m 2 · 24h or more, there is no need to provide a separate barrier film, an optical wavelength conversion sheet 120 It can be used as a single layer.

Normally, since the side surface of the conventional optical wavelength conversion sheet is exposed, the quantum dots at the peripheral edge of the optical wavelength conversion sheet are likely to deteriorate. On the other hand, when the quantum dots 47 are wrapped with the light-transmitting particles 122 having a barrier property as in the present embodiment, the water vapor transmittance of the light wavelength conversion sheet 120 at 40 ° C. and 90% relative humidity is 1 g. / m even had been at 2 ^· 24h or more, the deterioration of the quantum dots 47 existing in the periphery of the optical wavelength conversion sheet 120 can be suppressed.

As described above, since the side surface of the conventional optical wavelength conversion sheet is usually exposed, the quantum dots at the peripheral edge of the optical wavelength conversion sheet are likely to deteriorate. Then, if the quantum dots at the peripheral edge of the optical wavelength conversion sheet are deteriorated, the wavelength conversion efficiency is lowered. This is one of the causes, and when the light from the light source is incident on the light wavelength conversion sheet, the color of the light emitted from the peripheral portion of the light wavelength conversion sheet is the color of the light emitted from the central portion. It may stand out compared to the color. On the other hand, in the present embodiment, when the quantum dots 47 are wrapped with the light-transmitting particles 120 having a barrier property, the deterioration of the quantum dots 47 existing in the peripheral portion of the light wavelength conversion sheet 120 can be suppressed. It is possible to prevent the color of the light emitted from the peripheral portion of the light wavelength conversion sheet 120 from being conspicuous as compared with the color of the central portion.

When the barrier layer of the barrier film is formed by the vapor deposition method, when the optical wavelength conversion sheet is bent, the barrier layer is cracked, and water and oxygen infiltrate into the optical wavelength conversion sheet from there, and the quantum dots are deteriorated. There is a risk. On the other hand, in the present embodiment, since the barrier film is not provided, it is possible to cope with foldable.

According to this embodiment, since it is not necessary to separately provide a barrier film, it is possible to support mobile products (portable computer terminal devices including devices called so-called smartphones) that have strict requirements for thickness.

[Third Embodiment]
Hereinafter, the image display device according to the third embodiment of the present invention will be described with reference to the drawings. FIG. 11 is a schematic configuration diagram of an image display device according to the present embodiment, FIG. 12 is a schematic configuration diagram of an optical wavelength conversion sheet shown in FIG. 11, and FIG. 13 is another optical wavelength conversion according to the present embodiment. It is a schematic block diagram of a sheet.

[Image display device]
The image display device 130 shown in FIG. 11 has the same configuration as the image display device 10 shown in FIG. 1 except that the light wavelength conversion sheet 140 is provided instead of the light wavelength conversion sheet 40.

<< Optical wavelength conversion sheet >>
As shown in FIG. 12, the light wavelength conversion sheet 140 includes the light wavelength conversion layer 141, the light transmissive surface plasmon excitation particle layers 142 and 143 provided on both sides of the light wavelength conversion layer 141, and the surface plasmon excitation. The barrier films 42 and 43 provided on the surface of the particle layers 142 and 143 opposite to the surface of the light wavelength conversion layer 141 and the surfaces of the surface plasmon-excited particle layers 141 and 142 of the barrier films 42 and 43 are It is provided with light diffusion layers 44 and 45 provided on opposite surfaces. That is, in this form, the surface plasmon excited particle layer 142 is adjacent to the light wavelength conversion layer 141, and the light wavelength conversion layer 141 is sandwiched by the surface plasmon excited particle layer 142. Here, since the surface plasmon excitation particle layers 141 and 142 have light transmittance, they are different from the reflective sheets and reflectors conventionally used in liquid crystal display devices. In the present embodiment, the surface plasmon excitation particle layer is arranged on both sides of the light wavelength conversion layer, but it may be arranged on only one side of the light wavelength conversion layer.

<Light wavelength conversion layer>
The light wavelength conversion layer 141 is the same as the light wavelength conversion layer 41 except that it does not contain surface plasmon excitation particles, and thus the description thereof will be omitted. In the present embodiment, the light wavelength conversion layer 141 does not contain surface plasmon excitation particles, but may contain surface plasmon excitation particles.

<Surface plasmon excitation particle layer>
The surface plasmon excitation particle layers 142 and 143 are layers having light transmittance and containing at least surface plasmon excitation particles 48. Since the surface plasmon-excited particles 48 in the surface plasmon-excited particle layers 142 and 143 are the same as the surface plasmon-excited particles 48 described in the first embodiment, the description thereof will be omitted except for the following.

The average distance from the surface plasmon excited particles 48 to the nearest quantum dot 47 in the surface plasmon excited particle layers 142 and 143 is preferably 5 nm or more and 1 μm or less. If this average distance is less than 5 nm, the distance from the surface plasmon excited particles to the quantum dots is too close, and the energy obtained by the quantum dots absorbing the light from the light source is transferred to the surface plasmon excited particles. This is because the quantum dots may be deactivated. Further, when this average distance exceeds 1 μm, the distance from the surface plasmon excitation particles to the quantum dots is too long, so that the electric field enhancement effect due to the excitation of the surface plasmons cannot be obtained, and the light emission efficiency is improved. May not be possible. The lower limit of the average distance between the quantum dots 48 and the surface plasmon excited particles 48 in the surface plasmon excited particle layers 142 and 143 is more preferably 10 nm or more, and the upper limit of this average distance is 0.5 μm or less. More preferred.

The surface plasmon excitation particle layers 142 and 143 have a function of exciting the surface plasmon, but may have other functions. In the present embodiment, the surface plasmon excitation particle layers 142 and 143 have a function as a primer layer for enhancing the adhesion between the optical wavelength conversion layer 141 and the barrier films 42 and 43. In this case, the surface plasmon excitation particle layers 142 and 143 are in close contact with the barrier films 42 and 43 and the optical wavelength conversion layer 141.

When the surface plasmon-excited particle layers 142 and 143 also function as a primer layer, the surface plasmon-excited particle layers 142 and 143 are thermally curable or thermo-curable so as to exert a function as a primer layer in addition to the surface plasmon-excited particles 48. It contains known materials such as thermoplastic polyester resin and polyurethane resin.

The film thickness of the surface plasmon excitation particle layers 142 and 143 is not particularly limited, but is preferably 5 nm or more and 1 μm or less. If the thickness of the surface plasmon excitation particle layer is less than 5 nm, it may be difficult to fix the surface plasmon excitation particles in the layer, and if the thickness of the surface plasmon excitation particle layer exceeds 1 μm, the quantum dots The surface plasmon resonance effect on the surface plasmon resonance may be weakened. The thickness of the surface plasmon excitation particle layer can be determined as an average value of the thickness of the surface plasmon excitation particle layer measured at 20 points using a scanning electron microscope (SEM). The lower limit of the film thickness of the surface plasmon excitation particle layers 142 and 143 is more preferably 10 nm or more, and the upper limit of this film thickness is more preferably 0.5 μm or less.

The content of the surface plasmon excited particles 48 in the surface plasmon excited particle layers 142 and 143 is preferably 0.01% by mass or more and 20% by mass or less, and preferably 0.1% by mass or more and 10% by mass or less. More preferred. If the content of the surface plasmon excited particles is less than 0.01% by mass, the emission efficiency may not be improved, and if the content of the surface plasmon excited particles exceeds 20% by mass, the above energy There is a risk of deactivation due to movement.

<< Other optical wavelength conversion sheets >>
In FIG. 11, light in which the light diffusion layer 44, the barrier film 42, the surface plasmon excitation particle layer 142, the light wavelength conversion layer 141, the surface plasmon excitation particle layer 143, the barrier film 43, and the light diffusion layer 45 are laminated in this order. Although the wavelength conversion sheet 140 is shown, as in the light wavelength conversion sheet 150 shown in FIG. 13, two or more light wavelength conversion layers and two or more surface plasmon excitation particle layers are present, and surface plasmons are present between the optical wavelength conversion layers. Excited particle layers may be arranged. The light wavelength conversion sheet 150 shown in FIG. 13 includes a light diffusion layer 44, a barrier film 42, a surface plasmon excitation particle layer 153, a light wavelength conversion layer 151, a surface plasmon excitation particle layer 154, a light wavelength conversion layer 152, and a surface plasmon excitation. The particle layer 155, the barrier film 43, and the light diffusion layer 45 are laminated in this order.

Since the light wavelength conversion layers 151 and 152 are the same as the light wavelength conversion layer 141, the description thereof will be omitted here. However, when there are two or more light wavelength conversion layers as shown in FIG. 13, the total average film thickness of the light wavelength conversion layers is preferably 30 μm or more and 200 μm or less.

Since the surface plasmon excitation particle layers 153 to 155 are the same as the surface plasmon excitation particle layers 142 and 143, the description thereof will be omitted here.

According to the present embodiment, since the surface plasmon excitation particle layers 142 and 143 are arranged adjacent to the light wavelength conversion layer 141, the surface plasmon excitation particles 48 are excited by the light from the light source 25. Due to the electric field enhancing effect of the surface plasmon, the emission of the quantum dots 47 in the light wavelength conversion layer 141 in the vicinity of the surface plasmon excited particles 48 is likely to be induced. As a result, the luminous efficiency of the quantum dots 47 can be improved.

In the case of the light wavelength conversion sheet 150, the light emission efficiency of the quantum dots 47 can be improved as in the case of the light wavelength conversion sheet 140, but in the case of the light wavelength conversion sheet 150, the light wavelength conversion layers are multi-layered. Therefore, the amount of surface plasmon excited particles 48 existing in the vicinity of the quantum dot 47 increases. As a result, the luminous efficiency of the quantum dots 47 can be further improved as compared with the case of the light wavelength conversion sheet 140.

[Fourth Embodiment]
Hereinafter, the image display device according to the fourth embodiment of the present invention will be described with reference to the drawings. FIG. 14 is a schematic configuration diagram of an image display device according to the present embodiment, and FIG. 15 is a schematic configuration diagram of another EL element included in the image display device according to the present embodiment.

[Image display device]
The image display device 160 shown in FIG. 14 is an electroluminescence display device (hereinafter, this device is referred to as an “EL display device”). The image display device 160 includes an electroluminescence element 170 (hereinafter, this element is referred to as an “EL element”).

<<< EL element >>
As shown in FIG. 14, the EL element 170 includes a support base material 171 and a first electrode layer 172, an electroluminescence layer 173 as a light emitting member (hereinafter, this layer is referred to as an “EL layer”), and a second layer. The electrode layer 174 and the sealing member 175 are laminated in this order. That is, the EL layer 173 is arranged between the first electrode layer 172 and the second electrode layer 174.

<< Supporting base material >>
The support base material 171 may be any as long as it can support the EL layer 173, and those used for a general EL element substrate can be used. Further, in the present invention, since light is extracted from the sealing member 175 side, the support base material 171 may be a light transmissive base material, but may not be a light transmissive base material.

As the support substrate 171, for example, a glass such as quartz glass, a rigid material having no flexibility such as a synthetic quartz plate, or a flexible material having flexibility such as a resin film or an optical resin plate can be used. .. Further, a resin film having a barrier layer formed therein may be used.

<< First electrode layer >>
The first electrode layer 172 is provided so that a voltage is applied between the first electrode layer 172 and the second electrode layer 174 to cause the EL layer 173 to emit light. The first electrode layer 172 may be either an anode or a cathode.

When the first electrode layer 172 is an anode, it is preferable to use a conductive material having a large work function so that holes can be easily injected. Examples of such a conductive material include metals such as Li, Na, Mg, Al, Ca, Ag, and In, or alloys containing one or more of these metals, specifically MgAg, AlLi, AlCa, and the like. Examples include alloys such as AlMg.

<< Second electrode layer >>
The material of the second electrode layer 174 is not particularly limited as long as it is a conductive material having a desired light transmittance, and is, for example, indium tin oxide (ITO), indium zinc oxide (IZO), and tin oxide. , Zinc oxide, indium oxide, zinc aluminum oxide (AZO) and other conductive oxides can be used.

As the light transmittance of the second electrode layer 174, the total light transmittance is preferably 60% or more, and more preferably 70% or more, particularly 80% or more. This is because the light emitted from the light emitting layer can be sufficiently transmitted through the second electrode layer 174. The total light transmittance can be measured by a method conforming to JIS K7361 using a haze meter (manufactured by Murakami Color Technology Laboratory, product number; HM-150).

The second electrode layer 174 is formed in a pattern corresponding to the light emitting layer in the pixel region. The pattern of the transparent electrode layer is set by the pattern of the light emitting layer, and examples thereof include a linear shape and a striped shape.

The film thickness, forming method, and the like of the second electrode layer 174 can be the same as those of a general EL element. Further, although the second electrode layer 174 is formed on the EL layer 173, it may be further formed on the non-light emitting area.

<< EL layer >>
The EL layer 173 includes a light emitting layer 176. Examples of the layer constituting the EL layer 173 other than the light emitting layer 176 include a hole injection layer 177, a hole transport layer 178, an electron injection layer 179, an electron transport layer 180, and the like. In the EL element 170 shown in FIG. 14, the hole injection layer 177 and the hole transport layer 178 are located between the first electrode 172 and the light emitting layer 176, and the hole injection layer 177 transports holes. It is located closer to the first electrode 172 than the layer 178. Further, the electron injection layer 179 and the electron transport layer 180 are located between the second electrode 174 and the light emitting layer 176, and the electron injection layer 179 is located closer to the second electrode 174 than the electron transport layer 180. ing. The hole transport layer is often integrated with the hole injection layer by imparting a hole transport function to the hole injection layer.

As a layer constituting the EL layer, holes or electrons such as a hole block layer and an electron block layer are prevented from penetrating, and excitons are prevented from diffusing and excitons are confined in the light emitting layer. A layer or the like for increasing the recombination efficiency may be further provided.

In addition to the structure shown in FIG. 14, the EL layer has, for example, only the light emitting layer, the hole injection layer / light emitting layer, the hole injection layer / light emitting layer / electron injection layer, and the hole injection layer / hole block. Examples thereof include a layer / light emitting layer / electron injection layer, a hole injection layer / light emitting layer / electron transport layer, and the like.

<Light emitting layer>
The light emitting layer 176 includes a host matrix 181, quantum dots 47 dispersed in the host matrix 181 and surface plasmon excited particles 49. Since the quantum dots 47 and the surface plasmon excitation particles 48 in the light emitting layer 176 are the same as the quantum dots 47 and the surface plasmon excitation particles 48 described in the first embodiment, the description thereof will be omitted here.

Examples of the host matrix 181 include a light emitting material used as a host matrix (host material) in the light emitting layer of the EL element. Specifically, the following dye-based luminescent materials, metal complex-based luminescent materials, and polymer-based luminescent materials can be mentioned. These light emitting materials may be used alone or in combination of two or more.

Examples of the dye-based material include cyclopentadiene derivatives, tetraphenylbutadiene derivatives, triphenylamine derivatives, oxadiazole derivatives, pyrazoloquinoline derivatives, distyrylbenzene derivatives, distyrylarylene derivatives, silol derivatives, thiophene ring compounds, and pyridines. Examples thereof include ring compounds, perinone derivatives, perylene derivatives, oligothiophene derivatives, coumarin derivatives, oxaziazole dimers, pyrazoline dimers and the like.

Examples of the metal complex material include aluminum quinolinol complex, benzoquinolinol berylium complex, benzoxazole zinc complex, benzothiazole zinc complex, azomethylzinc complex, porphyrin zinc complex, europium complex, and Al, Zn, Be as the central metal. Alternatively, a metal complex having a rare earth metal such as Tb, Eu, Dy and having an oxadiazole, thiadiazol, phenylpyridine, phenylbenzimidazole, quinoline structure or the like as a ligand can be mentioned. Specifically, a tris (8-quinolinolato) aluminum complex (Alq3) can be used.

Examples of the polymer-based material include polyparaphenylene vinylene derivatives, polythiophene derivatives, polyparaphenylene derivatives, polysilane derivatives, polyacetylene derivatives, polyvinylcarbazoles, polyfluorenone derivatives, polyfluorene derivatives, polyquinoxaline derivatives, polydialkylfluorene derivatives, and Examples thereof include copolymers thereof. Further, as the polymer-based material, a polymerized material of the above-mentioned pigment-based material and metal complex-based material can also be used.

The film thickness of the light emitting layer 176 is not particularly limited as long as it can provide a field for recombination of electrons and holes and exhibit a function of emitting light, and is, for example, 5 nm or more and 500 nm or less. can do.

The method for forming the light emitting layer 176 can be the same as the method for forming the light emitting layer in a general organic EL element such as a printing method, an inkjet method, and a vacuum vapor deposition method.

<Hole injection layer>
The hole injection layer 177 is a layer having a function of improving the hole injection efficiency from the anode (first electrode layer 172). The hole injection layer 177 can be provided between the anode (first electrode layer 172) and the hole transport layer 178. As a material constituting the hole injection layer 177, a known material can be appropriately used, and there is no particular limitation. For example, phenylamine-based, starburst-type amine-based, phthalocyanine-based, hydrazone derivative, carbazole derivative, triazole derivative, imidazole derivative, oxadiazole derivative having an amino group, vanadium oxide, tantalum oxide, tungsten oxide, molybdenum oxide, ruthenium oxide. , Oxides such as aluminum oxide, amorphous carbon, polyaniline, polythiophene derivatives and the like.

The thickness of the hole injection layer 177 is preferably 5 nm or more and 300 nm or less. If this thickness is less than 5 nm, production tends to be difficult, while if it exceeds 300 nm, the drive voltage and the voltage applied to the hole injection layer tend to increase.

<Hole transport layer>
The hole transport layer 178 is a layer having a function of improving hole injection from a layer closer to the hole injection layer 177 or the first electrode layer 172 (hole transport layer). The material constituting the hole transport layer 178 is not particularly limited, but for example, N, N'-diphenyl-N, N'-di (3-methylphenyl) 4,4'-diaminobiphenyl (TPD), Aromatic amine derivatives such as 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPB), polyvinylcarbazole or its derivatives, polysilanes or its derivatives, side chains or main chains Polysiloxane derivative with amine, pyrazoline derivative, arylamine derivative, stillben derivative, triphenyldiamine derivative, polyaniline or its derivative, polythiophene or its derivative, polyarylamine or its derivative, polypyrrole or its derivative, poly (p-phenylene vinylene) ) Or a derivative thereof, or poly (2,5-thienylene vinylene) or a derivative thereof.

Among these, as the hole transport material used for the hole transport layer 178, polyvinylcarbazole or a derivative thereof, polysilane or a derivative thereof, a polysiloxane derivative having an aromatic amine compound group in the side chain or the main chain, polyaniline or a derivative thereof. , Polythiophene or a derivative thereof, polyarylamine or a derivative thereof, poly (p-phenylene vinylene) or a derivative thereof, or poly (2,5-thienylene vinylene) or a derivative thereof, and the like. It is preferably polyvinylcarbazole or a derivative thereof, polysilane or a derivative thereof, or a polysiloxane derivative having an aromatic amine in the side chain or main chain. In the case of a low-molecular-weight hole transport material, it is preferable to disperse it in a binder resin.

The film thickness of the hole transport layer 178 is not particularly limited, but can be appropriately changed according to the intended design, and is preferably 1 nm or more and 1000 nm or less. If this thickness is less than 1 nm, it tends to be difficult to manufacture, or the effect of hole transport tends to be insufficient, while if it exceeds 1000 nm, it is applied to the drive voltage and the hole transport layer. The voltage tends to increase. Therefore, the thickness of the hole transport layer 178 is more preferably 2 nm or more and 500 nm or less, and further preferably 5 nm or more and 200 nm or less.

<Electron injection layer>
The electron injection layer 179 is a layer having a function of improving the electron injection efficiency from the cathode (second electrode layer 174). The electron injection layer 179 is provided between the electron transport layer 180 and the cathode (second electrode layer 174). Examples of the electron injection layer 179 include alkali metals and alkaline earth metals, alloys containing one or more of the metals, oxides of the metals, halides and carbon oxides, and mixtures of the substances.

Examples of the alkali metals or their oxides, halides and carbon oxides include lithium, sodium, potassium, rubidium, cesium, lithium oxide, lithium fluoride, sodium oxide, sodium fluoride, potassium oxide, potassium fluoride and oxidation. Rubidium, rubidium fluoride, cesium oxide, cesium fluoride, lithium carbonate and the like can be mentioned.

Examples of the alkaline earth metal or its oxides, halides, and carbon oxides include magnesium, calcium, barium, strontium, magnesium oxide, magnesium fluoride, calcium oxide, calcium fluoride, calcium fluoride, barium oxide, and foot. Calcium oxide, strontium oxide, strontium fluoride, magnesium carbonate and the like can be mentioned.

Further, an organometallic compound doped with a metal, a metal oxide, a metal salt, and an organometallic complex compound, or a mixture thereof can also be used as a material for the electron injection layer.

The electron injection layer 179 may have a laminated structure in which two or more layers are laminated. Specific examples thereof include a laminated structure of a Li layer / Ca layer. The film thickness of the electron injection layer 179 is preferably 1 nm or more and 1 μm or less.

<Electronic transport layer>
The electron transport layer 180 is a layer having a function of improving electron injection from a layer (electron transport layer) closer to the electron injection layer 179 or the cathode (second electrode layer 174). As a material for forming the electron transport layer 180, a known material can be used, and an oxadiazole derivative, anthracinodimethane or a derivative thereof, benzoquinone or a derivative thereof, naphthoquinone or a derivative thereof, anthraquinone or a derivative thereof, tetracyanoanthracino. Examples thereof include dimethane or a derivative thereof, fluorenone derivative, diphenyldicyanoethylene or a derivative thereof, a diphenoquinone derivative, or a metal complex of 8-hydroxyquinoline or a derivative thereof, polyquinolin or a derivative thereof, polyquinoxaline or a derivative thereof, polyfluorene or a derivative thereof, and the like. Will be done.

Of these, oxaziazole derivatives, benzoquinone or its derivatives, anthraquinone or its derivatives, or metal complexes of 8-hydroxyquinoline or its derivatives, polyquinoline or its derivatives, polyquinoxalin or its derivatives, polyfluorene or its derivatives are preferable. 2- (4-Biphenylyl) -5- (4-t-butylphenyl) -1,3,4-oxadiazole, benzoquinone, anthraquinone, tris (8-quinolinol) aluminum, and polyquinoline are more preferred.

<< Sealing member >>
The sealing member 175 is for preventing deterioration of the EL layer 173 due to water and oxygen. Examples of the sealing member 175 include a glass plate and the like. Specifically, examples of the glass plate include a soda lime glass plate and a non-alkali glass plate. Since these are relatively inexpensive glass materials, it is possible to reduce the manufacturing cost.

According to the present embodiment, since the light emitting layer 176 contains the surface plasmon excited particles 48, the excitons in the quantum dots 47 excited by the application of the voltage and the surface plasmons excited from the surface plasmon excited particles 48 Coupling facilitates the induction of exciton excitation and emission of quantum dots 47 in the vicinity of the surface plasmon excited particles 48. As a result, the luminous efficiency of the quantum dots 47 can be improved.

<<< Other EL elements >>>
Similar to the second embodiment, in the light emitting layer 176 shown in FIG. 14, the quantum dots 47 may be wrapped with light-transmitting particles. Since the light-transmitting particles are the same as the light-transmitting particles 122 described in the light wavelength conversion layer 121 of the light wavelength conversion sheet 120, the description thereof will be omitted here.

Further, in the EL element 170 shown in FIG. 14, the surface plasmon excitation particles 48 are included in the light emitting layer 176, but the surface plasmon excitation particles 48 are formed in the light emitting layer 191 as in the EL element 190 shown in FIG. Instead of containing it, it may be contained in a layer adjacent to the light emitting layer 191 such as a hole transport layer 192 or an electron transport layer 193. In this case, since the hole transport layer 192 and the electron transport layer 193 adjacent to the quantum dots 191 serve as the surface plasmon excitation particle layer, the light emitting layer 191 is sandwiched by the surface plasmon excitation particle layer.

According to the EL element 190 shown in FIG. 15, since the surface plasmon excitation particles 48 are included in the hole transport layer 192 and the electron transport layer 193 adjacent to the light emitting layer 191, the EL element 170 shown in FIG. For the same reason, the light emission efficiency of the quantum dots 47 can be improved.

In the first to fourth embodiments, quantum dots are used as the phosphor, but even when a phosphor other than the quantum dots is used, the surface plasmon excitation is performed in the same manner as the quantum dots. The effect of enhancing the electric field of the surface plasmon by the particles facilitates the induction of light absorption and light emission of the phosphor in the vicinity of the surface plasmon excited particles. As a result, the luminous efficiency can be improved even when a phosphor other than the quantum dots is used.

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

<Preparation of light wavelength conversion particles>
First, light wavelength conversion particles were obtained by the procedure shown below.
(Light wavelength conversion particle A)
First, 0.2 parts by mass of green emission quantum dots (product name "CdSe / ZnS 530", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle diameter 3.3 nm) and 0.2 parts by mass. Red luminescent quantum dots (product name "CdSe / ZnS 610", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm) were prepared. After preparing the green emission quantum dots and the red emission quantum dots, the surfaces of the green emission quantum dots and the red emission quantum dots are covered with dodecylamine, and these quantum dots are put into a toluene solution (0.4 mL, 1.5 μM / L). Dispersed. Then, tetraethoxysilane (TEOS, 10 μL) was added to this solution, and the mixture was stirred for 3 hours to prepare an organic solution 1.

On the other hand, 3-mercaptopropyltrimethoxysilane (MPS, 1 μL) was mixed with ethanol (25 mL) and aqueous ammonia (4 mL, ammonia concentration 10 wt%) to prepare an aqueous solution 2.

Then, when the organic solution 1 and the aqueous solution 2 were mixed and stirred for 3 hours, the green emission quantum dots and the red emission quantum dots moved to the aqueous phase, and further, an aggregate of the green emission quantum dots and the red emission quantum dots in the aqueous phase. Was formed. The aggregate was removed by centrifugation.

Finally, 0.5 mL of the aqueous solution in which the above aggregates were dispersed was taken out, ethanol (8 mL) and aqueous ammonia (0.1 mL, 25 wt%) were added, and TEOS (14 μL) was further added. As a result, an aggregate composed of green emission quantum dots and red emission quantum dots was wrapped in silica glass to obtain light wavelength conversion particles A having an average particle diameter of 50 nm.

<Preparation of composition for optical wavelength conversion layer>
First, each component was blended so as to have the composition shown below to obtain a composition for an optical wavelength conversion layer.

(Composition for Light Wavelength Conversion Layer 1)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 99 parts by mass-Green emission quantum dots (product name "CdSe / ZnS 530", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS , Average particle size 3.3 nm): 0.20 parts by mass, red emission quantum 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, silver particles (product name "730815", manufactured by SIGMA-ALDRICH): 1 part by mass, alumina particles (product name "DAM-03", manufactured by Denki Kagaku Kogyo, average particle diameter 4 μm): 5 parts by mass, photopolymerization initiator (1-hydroxycyclohexylphenylketone, product name "Irgacure (registered trademark) 184", manufactured by BASF Japan): 1 part by mass

(Composition for Light Wavelength Conversion Layer 2)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 99 parts by mass-Green emission quantum dots (product name "CdSe / ZnS 530", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS , Average particle size 3.3 nm): 0.20 parts by mass, red emission quantum 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, silver particles (product name "730815", manufactured by SIGMA-ALDRICH): 1 part by mass, photopolymerization initiator (1-hydroxycyclohexylphenyl ketone, product name "Irgacure (registered trademark) 184", BASF Japan): 1 part by mass

(Composition for Light Wavelength Conversion Layer 3)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 99 parts by mass-Green emission quantum dots (product name "CdSe / ZnS 530", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS , Average particle size 3.3 nm): 0.20 parts by mass, red emission quantum 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, silver particles (product name "730777", manufactured by SIGMA-ALDRICH): 1 part by mass, photopolymerization initiator (1-hydroxycyclohexylphenyl ketone, product name "Irgacure (registered trademark) 184", BASF Japan): 1 part by mass

(Composition for Light Wavelength Conversion Layer 4)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 99 parts by mass-light wavelength conversion particles A: 5 parts by mass-silver particles (product name "730815", manufactured by SIGMA-ALDRICH): 1 Parts by mass-Photopolymerization initiator (1-hydroxycyclohexylphenylketone, product name "Epoxy® 184", manufactured by BASF Japan): 1 part by mass

(Composition for Light Wavelength Conversion Layer 5)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 99 parts by mass-Green light emitting inorganic phosphor (β-SiAlON: Eu ²⁺ ): 0.20 parts by mass-Red light emitting inorganic phosphor (CaAlSiN) ₃ : Eu ²⁺ ): 0.20 parts by mass, silver particles (product name "730815", manufactured by SIGMA-ALDRICH): 1 part by mass, alumina particles (product name "DAM-03", manufactured by Electrochemical Industry Co., Ltd., average) Particle size 4 μm): 5 parts by mass ・ Photopolymerization initiator (1-hydroxycyclohexylphenylketone, product name “Irgacure® 184”, manufactured by BASF Japan): 1 part by mass

(Composition for Light Wavelength Conversion Layer 6)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 99 parts by mass-Green emission quantum dots (product name "CdSe / ZnS 530", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS , Average particle size 3.3 nm): 0.20 parts by mass, red emission quantum 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-hydroxycyclohexylphenyl ketone, product name "Irgacure (registered trademark) 184", manufactured by BASF Japan): 1 part by mass

(Composition for Light Wavelength Conversion Layer 7)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 99 parts by mass-Green light emitting inorganic phosphor (β-SiAlON: Eu ²⁺ ): 0.20 parts by mass-Red light emitting inorganic phosphor (CaAlSiN) ₃ : Eu ²⁺ ): 0.20 parts by mass, alumina particles (product name "DAM-03", manufactured by Denki Kagaku Kogyo Co., Ltd., average particle diameter 4 μm): 5 parts by mass, photopolymerization initiator (1-hydroxycyclohexylphenylketone) , Product name "Irgacure (registered trademark) 184", manufactured by BASF Japan): 1 part by mass

(Composition for Light Wavelength Conversion Layer 8)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 99 parts by mass-Green emission quantum dots (product name "CdSe / ZnS 530", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS , Average particle size 3.3 nm): 0.20 parts by mass, red emission quantum 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, silver particles: 1 part by mass, photopolymerization initiator (1-hydroxycyclohexylphenyl ketone, product name "Irgacure (registered trademark) 184", manufactured by BASF Japan): 1 part by mass

<Preparation of composition for surface plasmon excitation particle layer>
Each component was blended so as to have the composition shown below to obtain a composition for a surface plasmon excitation particle layer.
(Composition for Surface Plasmon Excited Particle Layer 1)
-Epoxy acrylate (product name "Unidic V-5500", manufactured by DIC): 99 parts by mass-Photopolymerization initiator (1-hydroxycyclohexylphenyl ketone, product name "Irgacure (registered trademark) 184", manufactured by BASF Japan Ltd.) ): 1 part by mass, silver particles (product name "730815", manufactured by SIGMA-ALDRICH): 10 parts by mass

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

<Example 1>
First, two barrier films were prepared by the following method. In a high-frequency sputtering apparatus, by applying a high-frequency power of 13.56 MHz and a power of 5 kW to the electrodes, a discharge is generated in the chamber, and polyethylene terephthalate as a light-transmitting substrate having a size of 7 inches and a thickness of 50 μm is generated. A silica-deposited layer made of a target substance (silica), having a thickness of 50 nm and a refractive index of 1.46, was formed on one side of a film (product name "Lumilar T60", manufactured by Toray Co., Ltd.). As a result, two barrier films having a silica-deposited layer formed on one surface of the polyethylene terephthalate film were formed.

Next, the composition 1 for the light diffusion layer was applied to the surface of both barrier films opposite to the surface on the silica-deposited layer side to form a coating film. Next, the solvent in the coating film was evaporated by passing dry air at 80 ° C. for 30 seconds to dry the formed coating film. Then, an ultraviolet ray was irradiated so that the integrated light amount was 500 mJ / cm ² , and the coating film was cured to form a light diffusing layer having a thickness of 10 μm, and a barrier film with a light diffusing layer was formed.

Next, the composition 1 for a light wavelength conversion layer was applied to the silica-deposited layer side of one of the barrier films with a light diffusion layer and dried at 80 ° C. to form a coating film. Then, the other barrier film with a light diffusing layer was laminated on the surface of the coating film opposite to the surface of the barrier film with a light diffusing layer on the side opposite to the surface on the silica vapor deposition layer side so that the silica vapor deposition layer was in contact with the surface. In this state, by irradiating the coating film with ultraviolet rays so that the integrated light amount is 500 mJ / cm ² , a light wavelength conversion layer having a thickness of 100 μm is formed in close contact with both barrier films with light diffusion layers. did. As a result, the optical wavelength conversion sheet according to Example 1 was obtained. The thickness of the light wavelength conversion layer was obtained from an image of the cross section of the light wavelength conversion sheet taken at 20 points at random using a scanning electron microscope (SEM).

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

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

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

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

<Example 6>
First, two barrier films were prepared by the following method. In a high-frequency sputtering apparatus, by applying a high-frequency power of 13.56 MHz and a power of 5 kW to the electrodes, a discharge is generated in the chamber, and polyethylene terephthalate as a light-transmitting substrate having a size of 7 inches and a thickness of 50 μm is generated. A silica-deposited layer made of a target substance (silica), having a thickness of 50 nm and a refractive index of 1.46, was formed on one side of a film (product name "Lumilar T60", manufactured by Toray Co., Ltd.). As a result, two barrier films having a silica-deposited layer formed on one surface of the polyethylene terephthalate film were formed.

Next, the composition 1 for the light diffusion layer was applied to the surface of both barrier films opposite to the surface on the silica-deposited layer side to form a coating film. Next, the solvent in the coating film was evaporated by passing dry air at 80 ° C. for 30 seconds to dry the formed coating film. Then, an ultraviolet ray was irradiated so that the integrated light amount was 500 mJ / cm ² , and the coating film was cured to form a light diffusing layer having a thickness of 10 μm, and a barrier film with a light diffusing layer was formed.

Next, the composition 1 for surface plasmon excitation particle layer is applied to the silica vapor deposition layer side of both barrier films with light diffusion layers to form a surface plasmon excitation particle layer having a thickness of 100 nm, and the light diffusion layer and surface plasmon excitation are formed. A barrier film with a particle layer was formed. Then, the composition 6 for a light wavelength conversion layer was applied to the surface of one of the light diffusion layers and the surface plasmon excitation particle layer of the barrier film with the surface plasmon excitation particle layer, and dried at 80 ° C. to form a coating film. Then, the other light diffusing layer and the surface plasmon are brought into contact with the surface of the barrier film with the light diffusing layer and the surface plasmon excited particles in the coating film on the side opposite to the surface of the surface plasmon excited particle layer side. A barrier film with an excited particle layer was laminated. In this state, the coating film is cured by irradiating ultraviolet rays so that the integrated light amount is 500 mJ / cm ² , so that the film thickness in close contact with both the light diffusion layer and the barrier film with the surface plasmon excitation particle layer is 100 μm. An optical wavelength conversion layer was formed. As a result, the optical wavelength conversion sheet according to Example 6 was obtained.

<Example 7>
In Example 7, a light wavelength conversion sheet was produced in the same manner as in Example 6 except that a surface plasmon excitation particle layer was formed only on one side of the light wavelength conversion layer.

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

<Comparative example 2>
In Comparative Example 2, an optical wavelength conversion sheet was produced in the same manner as in Example 1 except that the composition 7 for the optical wavelength conversion layer was used instead of the composition 1 for the optical wavelength conversion layer.

<Comparative example 3>
In Comparative Example 3, an optical wavelength conversion sheet was produced in the same manner as in Example 1 except that the composition 8 for the optical wavelength conversion layer was used instead of the composition 1 for the optical wavelength conversion layer.

<Measurement of average particle size of silver particles>
In the light wavelength conversion sheet according to the above Example and Comparative Example 3, the average particle size of the silver particles contained in the light wavelength conversion layer or the surface plasmon excitation particle layer was measured. The average particle size of silver particles is measured by observing the cross section of the optical wavelength conversion sheet at a magnification of 200,000 times using a transmission electron microscope (product name "S-4800", manufactured by Hitachi High-Technologies Corporation). It was calculated as the average value of the diameters of the 20 silver particles obtained.

<Measurement of average distance between silver particles and quantum dots>
In the optical wavelength conversion sheet according to the above Example and Comparative Example 3, the average distance from the silver particle to the nearest quantum dot was obtained. For the average distance from the silver particles to the nearest quantum dot, observe the cross section of the optical wavelength conversion sheet at a magnification of 200,000 times using a transmission electron microscope (product name "S-4800", manufactured by Hitachi High-Technologies Corporation). In this observation image, the distances from the 20 silver particles to the nearest quantum dots were measured and calculated as the average value.

<Brightness measurement>
In the light wavelength conversion sheets according to the above Examples and Comparative Examples, the brightness was measured in a state of being incorporated in the backlight device. Specifically, first, we prepared a backlight device for Kindle Fire (registered trademark) HDX7, and incorporated each optical wavelength conversion sheet into this backlight device. This backlight device includes a blue light emitting diode having a emission peak wavelength of 450 nm, a light diffuser plate, a first prism sheet, and a second prism sheet in this order, and the light according to Examples and Comparative Examples. The wavelength conversion sheet was arranged between the light diffusing plate and the first prism sheet. The first prism sheet and the second prism sheet have a sheet-shaped main body portion and a plurality of triangular columnar unit prisms arranged side by side on the main body portion and each 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, blue light is irradiated to one surface of the light wavelength conversion sheet, and the backlight device is passed through the other surface of the light wavelength conversion sheet. The brightness of the light emitted from the light emitting surface (the surface of the second prism sheet) is measured from the thickness direction of the light wavelength conversion sheet using a spectral emission brightness meter (product name "CS2000", manufactured by Konica Minolta). The measurement was performed under the condition of an angle of 1 °.

The results are shown in Table 1 below.

The results will be described below. The optical wavelength conversion sheet according to Comparative Example 1 does not contain silver particles in the optical wavelength conversion layer or a layer adjacent to the optical wavelength conversion layer, and the optical wavelength conversion sheet according to Comparative Example 3 is an optical wavelength conversion layer. Although silver particles are contained therein, since the average particle size of the silver particles exceeds 200 nm, the electric field enhancing effect of the surface plasmon cannot be obtained, and the brightness of the light emitted from the backlight device is low. On the other hand, the optical wavelength conversion sheets according to Examples 1 to 4, 6 and 7 contained silver particles having an average particle diameter of 200 nm or less in the optical wavelength conversion layer or the surface plasmon-excited particle layer, and thus the surface plasmon. The effect of enhancing the electric field was obtained, and the brightness of the light emitted from the backlight device was higher than the brightness of the light emitted from the backlight device using the optical wavelength conversion sheet according to Comparative Examples 1 and 3. Further, since the light wavelength conversion sheet according to Comparative Example 2 does not contain silver particles in the light wavelength conversion layer or in the layer adjacent to the light wavelength conversion layer, the electric field enhancing effect of surface plasmon cannot be obtained, and the backlight device. The brightness of the light emitted from was low. On the other hand, in the light wavelength conversion sheet according to Example 5, since silver particles having an average particle diameter of 200 nm or less were contained in the light wavelength conversion layer or the surface plasmon excitation particle layer, the electric field enhancing effect of the surface plasmon was obtained. The brightness of the light emitted from the backlight device was higher than the brightness of the light emitted from the backlight device using the optical wavelength conversion sheet according to Comparative Example 2. As a result, it was confirmed that in Examples 1 to 7, the luminous efficiency of the quantum dots could be improved.

10, 90, 110, 130, 160 ... Image display device 25 ... Light source 40, 120, 140, 150 ... Optical wavelength conversion sheet 41, 121, 141, 151 ... Optical wavelength conversion layer 46, 181 ... Host matrix 47 ... Quantum dot 48 ... Surface plasmon-excited particles 49 ... Light-scattering particles 122 ... Light-transmitting particles 142, 153, 154, 155 ... Surface plasmon-excited particle layers 170, 190 ... Electroluminescence element 172 ... First electrode 173 ... Electroluminescence layer 174 ... second electrodes 176, 191 ... light emitting layer

Claims (12)

An image display device including a light source and a light wavelength conversion sheet that receives light from the light source.
The light wavelength conversion sheet has an average particle diameter of 200 nm or less, which is dispersed in the host matrix, the phosphor dispersed in the host matrix, and can excite the surface plasmons by the light from the light source. A light wavelength conversion layer containing surface plasmon excited particles is provided.
The phosphor is a quantum dot,
The content of the surface plasmon excited particles in the light wavelength conversion layer is 0.01% by mass or more and 20% by mass or less.
An image display device in which the average distance from the surface plasmon excited particles to the nearest phosphor is 10 nm or more and 1 μm or less. An image display device including a light source and a light wavelength conversion sheet that receives light from the light source.
The light wavelength conversion sheet is adjacent to a host matrix and a light wavelength conversion layer containing phosphors dispersed in the host matrix, and is adjacent to the light wavelength conversion layer, and 200 nm capable of exciting surface plasmons by light from the light source. It comprises a light-transmitting surface plasmon-excited particle layer containing surface plasmon-excited particles having the following average particle diameters.
The phosphor is a quantum dot,
The content of the surface plasmon excited particles in the surface plasmon excited particle layer is 0.01% by mass or more and 20% by mass or less.
An image display device in which the average distance from the surface plasmon excited particles to the nearest phosphor is 10 nm or more and 1 μm or less. The image display device according to claim 1, wherein the light wavelength conversion layer further includes light-transmitting particles that enclose the phosphor. The image display device according to claim 2, wherein the surface plasmon excitation particle layer is present in two or more layers, and the light wavelength conversion layer is sandwiched between the surface plasmon excitation particle layers. The image display device according to claim 2, wherein the light wavelength conversion layer and the surface plasmon excitation particle layer are each present in two or more layers, and the surface plasmon excitation particle layer is arranged at least between the light wavelength conversion layers. The image display device according to claim 1 or 2, wherein the surface plasmon excitation particles are at least one of metal particles and oxide semiconductor particles. The image display device according to claim 1 or 2, wherein the surface plasmon excitation particles are particles made of one or more precious metals selected from the group consisting of gold, silver, and platinum. The image display device according to claim 1 or 2, wherein the light wavelength conversion layer further includes light scattering particles dispersed in the host matrix. The light-scattering particles are aluminum-containing compounds, zirconium-containing compounds, tin-containing compounds, magnesium-containing compounds, titanium-containing compounds, antimony-containing compounds, silicon-containing compounds, zinc-containing compounds, acrylic resins, styrene trees, melamine resins, and urethanes. The image display device according to claim 8, wherein the particles are particles made of one or more materials selected from the group consisting of resins. The image display device according to claim 1 or 2 , wherein the quantum dots are two or more types of quantum dots having an emission band in a single wavelength range. The image display device according to claim 1 or 2 , wherein the quantum dots include a first quantum dot that converts blue light into green light and a second quantum dot that converts the blue light into red light. The image display device according to claim 1 or 2, further comprising a display panel arranged on the observer side from the light wavelength conversion layer.

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