CN115291434A

CN115291434A - Backlight unit, liquid crystal display device, and wavelength conversion member

Info

Publication number: CN115291434A
Application number: CN202211006169.9A
Authority: CN
Inventors: 米本隆; 岩濑英二郎; 佐藤宏一
Original assignee: Fujifilm Corp
Current assignee: Fujifilm Corp
Priority date: 2014-09-30
Filing date: 2015-09-30
Publication date: 2022-11-04
Also published as: CN115268141A; WO2016052626A1

Abstract

An aspect of the present invention relates to a backlight unit, a liquid crystal display device, and a wavelength conversion member, the backlight unit including: a light source that emits light having a light emission center wavelength λ nm; and a wavelength conversion member located on an optical path of light emitted from the light source, the wavelength conversion member including: a wavelength conversion layer containing a phosphor that is excited by excitation light and emits fluorescence; and a light scattering layer containing particles having a particle size of 0.1 [ mu ] m or more in the matrix, wherein the average refractive index n1 of the wavelength conversion layer and the average refractive index n2 of the matrix of the light scattering layer satisfy the relationship of n1 < n2, and the light absorption rate of the light scattering layer at a wavelength [ lambda ] nm is 8.0% or less.

Description

Backlight unit, liquid crystal display device, and wavelength conversion member

The present application is a divisional application of the Chinese patent application No.201580053006.8 (International application No. PCT/JP2015/077755, title of the invention: backlight unit, liquid crystal display device and wavelength conversion member) filed on 3, 30/2017.

Technical Field

The invention relates to a backlight unit, a liquid crystal display device and a wavelength conversion member.

Background

Flat panel displays such as Liquid Crystal displays (hereinafter also referred to as LCDs) have been used for image Display devices with low power consumption and space saving. The liquid crystal display device is constituted by at least a backlight unit and a liquid crystal unit.

As the backlight unit, a backlight unit including a white Light source such as a white LED (Light-Emitting Diode) as a Light source is widely used. In contrast, in recent years, a new backlight unit has been proposed which embodies white light from light emitted from, for example, a blue LED light source instead of a white light source and light emitted from a wavelength conversion member which includes a fluorescent material excited by the light emitted from the light source and emits fluorescent light and which is disposed as a member separate from the light source (see patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent application laid-open No. 2013-544018

Disclosure of Invention

Technical problem to be solved by the invention

However, patent document 1 proposes to dispose particles (described as scattering particles in patent document 1) in order to provide a function of scattering light to a portion different from a layer (wavelength conversion layer) including a phosphor (see, for example, paragraphs 0162 and 0163 of patent document 1). The present inventors have made the following predictions and studies: the portion different from the wavelength conversion layer has a function of scattering light, which is related to increase in the amount of excitation light incident on the wavelength conversion layer or the amount of light emitted from the wavelength conversion layer and incident on the liquid crystal cell, thereby making it possible to improve the luminance of the liquid crystal display device. As a result of research, it has been found that the provision of the above-described portion can improve the luminance as compared with the case where the portion is not present, but if the luminance can be further improved, it is expected that a clear image with high luminance is displayed by the liquid crystal display device, the cost reduction due to the reduction in the amount of the phosphor used for realizing a constant luminance, and the thinning of the backlight unit due to the thinning of the wavelength conversion layer can be achieved.

Accordingly, an object of the present invention is to further improve luminance in a liquid crystal display device including a backlight unit including a wavelength conversion member.

Means for solving the technical problems

One aspect of the present invention is a backlight unit including: a light source that emits light having a light emission center wavelength λ nm; and a wavelength conversion member located on an optical path of light emitted from the light source,

the wavelength conversion member includes: a wavelength conversion layer containing a phosphor that is excited by excitation light and emits fluorescence; and a light scattering layer containing particles having a particle size of 0.1 μm or more in the matrix,

the average refractive index n1 of the wavelength conversion layer and the average refractive index n2 of the matrix of the light scattering layer satisfy the relationship of n1 < n2, and

the light scattering layer has an absorbance at a wavelength of λ nm of 8.0% or less.

The particle size of the particles was determined by observing the cross section of the light scattering layer with a Scanning Electron Microscope (SEM), and then taking the arithmetic average of the particle sizes of 20 particles randomly. Specifically, a cross section of the light scattering layer was photographed at a magnification of 5000 times, and then primary particle diameters of 20 particles randomly extracted in the obtained image were measured. For the non-spherical particles, the average of the length of the major axis and the length of the minor axis was determined and used as the primary particle diameter. Thus, the arithmetic mean of the primary particle diameters obtained for 20 randomly extracted particles was defined as the particle size of the particles. The particle size shown in examples described later was measured by using S-3400N manufactured by Hitachi High-Tech Co., ltd. As a scanning electron microscope.

The matrix of the light-scattering layer is a portion excluding particles having a particle size of 0.1 μm or more in the light-scattering layer. Light scattering in the light scattering layer is caused by optical unevenness within the layer. Particles having a sufficiently small particle size do not significantly reduce the optical uniformity of the layer even if they are included, whereas particles having a particle size of 0.1 μm or more cause the layer to be optically non-uniform, and therefore are particles that can cause light scattering. Hereinafter, particles having a particle size of 0.1 μm or more are referred to as light scattering particles. The layer containing light scattering particles is used as the light scattering layer in the present invention. The average refractive index n2 of the matrix of the light-scattering layer is a value determined for the measurement matrix prepared by removing the light-scattering particles from the material for forming the light-scattering layer. The matrix composition of the light scattering layer can be determined by a known composition analysis method such as infrared spectroscopy, NMR (Nuclear Magnetic Resonance) measurement, and gas chromatography measurement of a solution obtained by dissolving the matrix of the light scattering layer in an arbitrary solvent that can be dissolved.

The average refractive index in the present invention means an average value of a refractive index nx in the slow axis direction in a plane, a refractive index ny in the fast axis direction in a plane which is a direction orthogonal to the slow axis direction, and a refractive index nz in a direction orthogonal to the slow axis direction and the fast axis direction.

The refractive indices nx and ny can be measured by a known refractive index measuring apparatus. An example of the refractive index measuring device is a multi-wavelength abbe refractometer DR-M2 manufactured by ATAGO co. On the other hand, the refractive index nz can be calculated from the thickness of the layer, retardation in the in-plane direction, and the values of the refractive indices nx and ny as will be described later.

On the other hand, in the case of no slow axis, the average of the in-plane refractive index, the thickness-direction refractive index, and the refractive index in the direction orthogonal to the in-plane direction and the thickness direction is defined as the average refractive index. In this case, the average refractive index in each direction can be obtained by a known refractive index measuring device, for example, a multi-wavelength abbe refractometer DR-M2 manufactured by atagoco.

Then, the absorbance of the light scattering layer at the wavelength λ nm was determined by an optical system using an integrating sphere. By using the integrating sphere, incident light is transmitted through the sample a plurality of times, and thus the amount of absorption can be quantified in a small amount. For example, a commercially available device capable of performing an absolute luminescence quantum yield measurement method using an integrating sphere can be used as the measurement device. As an example, there is an absolute PL (photoluminescence) quantum yield measuring device (C9920-02) manufactured by Hamamatsu Photonics k.k., which is used in the examples described later.

In one embodiment, the light scattering layer is disposed closer to the light emission side (i.e., the liquid crystal cell side in a state of being disposed in the liquid crystal display device) than the wavelength conversion layer.

In one embodiment, the phosphor is a quantum dot.

In one embodiment, the average refractive index n2 of the matrix of the light scattering layer is in the range of 1.45 to 2.00, where n1 < n2.

In one embodiment, the average refractive index n1 of the wavelength conversion layer is in the range of 1.43 to 1.60, where n1 < n2.

In one embodiment, the wavelength conversion layer and the light scattering layer are laminated with a barrier film interposed therebetween.

In one embodiment, the barrier film comprises at least an inorganic layer.

In one embodiment, the inorganic layer is an inorganic layer containing at least one substance selected from the group consisting of silicon oxide, silicon nitride, silicon carbide, and aluminum oxide.

In one embodiment, an inorganic layer, an organic layer, and a base material film are disposed adjacent to each other in this order on the barrier film from the wavelength conversion layer side toward the light scattering layer side. Here, "adjacent" means directly contacting without interposing another layer therebetween.

In one embodiment, the wavelength λ nm is in the wavelength band of blue light.

Another embodiment of the present invention relates to a liquid crystal display device including the backlight unit and a liquid crystal cell.

Another aspect of the present invention relates to a wavelength conversion member including:

a wavelength conversion layer containing a phosphor that is excited by excitation light and emits fluorescence; and a light scattering layer containing particles having a particle size of 0.1 μm or more in the matrix,

the average refractive index n1 of the wavelength conversion layer and the average refractive index n2 of the matrix of the light scattering layer satisfy the relationship of n1 < n2,

and the light scattering layer has an absorbance of 8.0% or less at a wavelength of 450nm.

Effects of the invention

According to the present invention, a liquid crystal display device capable of displaying a high-luminance image can be provided. In addition, according to the present invention, a wavelength conversion member and a backlight unit which can provide such a liquid crystal display device can be provided.

Drawings

Fig. 1 (a) and 1 (b) are explanatory views of an example of a backlight unit including a wavelength conversion member.

Fig. 2 shows a specific example of the layer structure of the wavelength conversion member.

Fig. 3 is a schematic configuration diagram of an example of the apparatus for manufacturing the wavelength conversion member.

Fig. 4 is a partially enlarged view of the manufacturing apparatus shown in fig. 3.

Fig. 5 shows an example of a liquid crystal display device.

Detailed Description

The following description is made based on exemplary embodiments of the present invention, but the present invention is not limited to such embodiments. In the present invention and the present specification, the numerical range expressed by the term "to" means a range including numerical values before and after the term "to" as a lower limit value and an upper limit value.

In the present invention and the present specification, the "half-value width" of a peak means the width of the peak at 1/2 of the peak height. Light having an emission center wavelength in a wavelength band of 430 to 480nm is referred to as blue light, light having an emission center wavelength in a wavelength band of 520 to 560nm is referred to as green light, and light having an emission center wavelength in a wavelength band of 600 to 680nm is referred to as red light. The ultraviolet light is light having a light emission center wavelength in a wavelength band of 300nm to 430 nm. A light source that emits blue light as light having a single peak is referred to as a blue light source, and a light source that emits ultraviolet light as light having a single peak is referred to as an ultraviolet light source. Here, the light emitting a single peak means that only one peak having the emission center wavelength as the absorption maximum value exists in the emission spectrum, and two or more peaks do not appear as in the case of a white light source.

[ backlight Unit, wavelength conversion Member ]

The backlight unit of the present invention includes a light source emitting light having a light emission center wavelength λ nm, and a wavelength conversion member located on an optical path of the light emitted from the light source, the wavelength conversion member including: a wavelength conversion layer containing a phosphor that is excited by excitation light and emits fluorescence; and a light scattering layer containing particles having a particle size of 0.1 [ mu ] m or more in the matrix, wherein the average refractive index n1 of the wavelength conversion layer and the average refractive index n2 of the matrix of the light scattering layer satisfy the relationship of n1 < n2, and the light absorption rate of the light scattering layer at a wavelength [ lambda ] nm is 8.0% or less.

The present inventors have repeatedly conducted intensive studies in order to achieve the aforementioned object, and as a result, have found the backlight unit of the present invention. This point will be further explained below.

As described above, the present inventors considered that providing a portion different from the wavelength conversion layer with a function of scattering light is an effective means for improving luminance. Therefore, the above-described backlight unit has a light scattering layer. The present inventors speculate that the reason why the luminance can be improved by the light scattering layer is that one or both of (1) improvement in the light emission efficiency of the phosphor in the wavelength conversion layer and (2) efficient emission of the fluorescence emitted from the phosphor from the backlight unit can be achieved. The details are as follows.

The light scattering layer may be disposed on at least one of the emission side and the light source side of the wavelength conversion layer. The light scattering layer disposed on the emission side can scatter light emitted from the wavelength conversion layer in various directions. In general, a part of light emitted from the light source (hereinafter, also referred to as "light from the light source") is absorbed by the phosphor in the wavelength conversion layer and excites the phosphor, and another part passes through the wavelength conversion layer and is emitted from the wavelength conversion layer. The light from the light source thus emitted is again incident on the wavelength conversion layer, which is associated with an increase in the light emission efficiency of the phosphor by increasing the amount of excitation light incident on the wavelength conversion layer. In this regard, it is considered that the light scattering layer disposed on the emission side of the wavelength conversion layer as described above scatters light emitted from the wavelength conversion layer from the light source to change the direction of the traveling direction, thereby functioning to return a part of the light to the wavelength conversion layer side. It is presumed that the light from the light source thus returned to the wavelength conversion layer excites the phosphor in the wavelength conversion layer, whereby the amount of light emitted by the phosphor can be increased. In addition, the light scattering layer disposed on the light source side of the wavelength conversion layer can also function to return light transmitted through the wavelength conversion layer to the wavelength conversion layer side again among light from the light source reflected by a reflective member such as a prism sheet disposed on the emission side of the wavelength conversion layer in the backlight unit, and thus it is estimated that the amount of emitted light can be increased by the phosphor.

Since the fluorescent material emits fluorescent light in an isotropic manner, part of the fluorescent light emitted in the layer of the wavelength conversion layer (hereinafter, also referred to as "light from the wavelength conversion layer") is totally reflected at the refractive index interface, and is not led out to the emission side, and is guided into the wavelength conversion member. The light scattering layer disposed on the emission side or the light source side of the wavelength conversion layer can function to change the traveling direction of the waveguide light that repeats the total reflection and to guide the waveguide light to the outside of the wavelength conversion member. Further, it is thus presumed that the amount of light from the wavelength conversion layer emitted from the backlight unit can be increased.

Accordingly, the present inventors considered that the light scattering layer contributes to the improvement of luminance according to the above items (1) and (2).

However, as an aspect of disposing the light-scattering particles in a portion different from the wavelength conversion layer, it is also possible to disperse only the particles as shown in fig. 29 to 31 of patent document 1, but it is preferable to dispose the light-scattering particles as a member (light-scattering layer) including the light-scattering particles in the matrix in order to provide a uniform scattering effect from light emitted from the entire emission-side surface of the wavelength conversion layer. However, in the case where the refractive index n2 of the base of the light scattering layer is smaller than the refractive index n1 of the wavelength conversion layer (n 1 > n 2), when the light scattering layer and the wavelength conversion layer are in contact, total reflection occurs at the interface of these two layers, and light is prevented from being incident on the light scattering layer, and when a layer having a different refractive index, such as a base material, is present between the light scattering layer and the wavelength conversion layer, total reflection occurs at least one interface among the interfaces of two layers having different refractive indices, which are present between the wavelength conversion layer and the light scattering layer, and light is prevented from being incident on the light scattering layer. Thus, the present inventors have provided a light scattering layer satisfying the relationship of n1 < n2 in order to suppress total reflection.

In order to achieve the above (1) (increase in the light emission efficiency of the phosphor in the wavelength conversion layer), the present inventors set the light scattering layer to have an absorbance of 8.0% or less at the emission center wavelength λ nm of the light from the light source, so as to reduce the loss caused by absorption of the excitation light (light from the light source) by the light scattering layer.

As a result of the above-described intensive studies by the present inventors, a liquid crystal display device incorporating the backlight unit can obtain an image with high luminance.

However, the above includes the presumption by the present inventors and the like, and the present invention is not limited at all.

In addition, as a wavelength conversion member of a backlight unit adapted to use a blue light source as a light source, there is also provided according to the present invention a wavelength conversion member including: a wavelength conversion layer containing a phosphor that is excited by excitation light and emits fluorescence; and a light scattering layer containing particles having a particle size of 0.1 [ mu ] m or more in the matrix, wherein the average refractive index n1 of the wavelength conversion layer and the average refractive index n2 of the matrix of the light scattering layer satisfy the relationship of n1 < n2, and the light absorption of the light scattering layer at a wavelength of 450nm is 8.0% or less. The wavelength of 450nm is shown as a representative value of the central emission wavelength of the blue light source, and it is not intended to limit the central emission wavelength of the blue light source to 450nm in the present invention.

Hereinafter, the backlight unit and the wavelength conversion member will be described in further detail.

< absorbance of light-scattering layer at wavelength lambda nm >

As described above, the wavelength conversion member includes, as the light scattering layer, the light scattering layer having an absorbance of 8.0% or less at the emission center wavelength λ nm of the light source, so as to reduce the loss of light from the light source. The absorbance is preferably 7.0% or less, more preferably 5.0% or less, further preferably 3.0% or less, further preferably 2.5% or less, and further preferably 2.0% or less. The absorbance is, for example, 0.01% or more, but the lower the absorbance, the lower the absorbance is not particularly limited. The method of measuring the absorbance is as described above.

In the case where the light source included in the backlight unit is a blue light source, the wavelength λ nm is in the wavelength band of blue light. When the light source is an ultraviolet light source, the wavelength λ nm is in the wavelength band of ultraviolet light. The above-mentioned absorbance of the matrix of the light-scattering layer can be controlled depending on, for example, the formulation of the composition used for forming the light-scattering layer.

< average refractive index n1, n2 >)

For the above-described reason, in the wavelength conversion member, the average refractive index n1 of the wavelength conversion layer and the average refractive index n2 of the base material of the light scattering layer satisfy the relationship of n1 < n2. For example, if the difference between n1 and n2 is Δ n = n2-n1, Δ n may be 0.001 or more, or may be 0.010 or more. However, since n1 < n2 can effectively suppress the total reflection as described above, Δ n is not limited as long as the relationship of n1 < n2 is satisfied.

The average refractive index n2 of the matrix of the light scattering layer may satisfy the relationship n1 < n2. For example, n2 is in the range of 1.45 to 2.00, preferably 1.48 to 1.85, and more preferably 1.50 to 1.80.

On the other hand, the average refractive index n1 of the wavelength conversion layer is, for example, in the range of 1.43 to 1.60, but is not limited to the above range as long as n1 < n2 is satisfied.

The above n1 and n2 can be adjusted according to the formulation of the composition used for forming the wavelength conversion layer and the composition used for forming the light scattering layer.

As described above, the average refractive index is an average value of the refractive index nx in the slow axis direction in the plane, the refractive index ny in the fast axis direction in the plane, which is a direction orthogonal to the slow axis direction, and the refractive index nz in the direction orthogonal to the slow axis direction and the fast axis direction. The slow axis is determined by a known phase difference measuring device. As the phase difference measuring device, for example, KOBRACCD series, KOBRA21ADH, or WR series, which are phase difference measuring devices manufactured by Oji Scientific Instruments co. As described above, nx and ny can be measured by a known refractive index measuring apparatus.

On the other hand, the refractive index nz can be determined from the retardation Re in the in-plane direction, the layer thickness, nx and ny. The retardation Re in the in-plane direction is a retardation measured by causing light having a wavelength λ nm to enter the surface of the layer in the normal direction using a known retardation measuring apparatus. In the present invention, 589nm is used as the wavelength λ nm. When the measurement wavelength λ nm is selected, the measurement can be performed by manually replacing the wavelength selective film or replacing the measurement value with a program or the like. The refractive index also refers to the refractive index of light having a wavelength of 589nm.

The refractive index nz in the direction orthogonal to the slow axis direction and the fast axis direction in the plane can be calculated from the values of the retardation Re in the plane direction, the layer thickness d, the refractive index nx in the slow axis direction in the plane, and the refractive index ny in the fast axis direction in the plane. The layer thickness can be determined by cross-sectional observation using a microscope such as an optical microscope or a Scanning Electron Microscope (SEM).

[ mathematical formula 1]

Formula (1)

Re (θ) represents a retardation value in a direction inclined at an angle of θ ° from a normal direction of the layer to be measured. Thus, the retardation in the in-plane direction is θ =0 °.

In the present invention and the present specification, the description about the angle such as the orthogonality includes an allowable error range in the technical field to which the present invention belongs. For example, it means that the error from the precise angle is preferably 5 ° or less, more preferably 3 ° or less, in a range of less than the precise angle ± 10 °.

< Structure and arrangement example of wavelength converting Member

The wavelength conversion member may have a function of converting at least a part of the wavelength of the incident light to emit light having a wavelength different from the wavelength of the incident light. The shape of the wavelength conversion member is not particularly limited, and may be any shape such as a sheet or a rod. The wavelength conversion member can be used as a constituent of a backlight unit of a liquid crystal display device.

Fig. 1 is an explanatory diagram of an example of a backlight unit 1 including a wavelength conversion member. In fig. 1, a backlight unit 1 includes a light source 1A and a light guide plate 1B serving as a surface light source. In the example shown in fig. 1 (a), the wavelength conversion member is disposed in the path of light emitted from the light guide plate. On the other hand, in the example shown in fig. 1 (b), the wavelength conversion member is disposed between the light guide plate and the light source. In the example shown in fig. 1 (a), light emitted from the light guide plate 1B enters the wavelength conversion member 1C.

In the example shown in fig. 1A, light 2 emitted from the light source 1A disposed at the edge of the light guide plate 1B is blue light, and is emitted from the surface of the light guide plate 1B on the liquid crystal cell (not shown) side toward the liquid crystal cell. The wavelength conversion member 1C disposed on the path of the light (blue light 2) emitted from the light guide plate 1B includes at least quantum dots (a) that are excited by the blue light 2 and emit red light 4, and quantum dots (B) that are excited by the blue light 2 and emit green light 3. Thereby, the green light 3 and the red light 4 excited and the blue light 2 transmitted through the wavelength conversion member 1C are emitted from the backlight unit 1. In this way, white light can be represented by emitting red light, green light, and blue light.

The example shown in fig. 1 (b) is the same as that shown in fig. 1 (a) except that the wavelength conversion member and the light guide plate are arranged differently. In the example shown in fig. 1 (b), the green light 3 and the red light 4 excited by the wavelength conversion member 1C and the blue light 2 transmitted through the wavelength conversion member 1C are emitted from the wavelength conversion member 1C and incident on the light guide plate, whereby a surface light source can be realized.

< light scattering layer >

(light-scattering particles)

The light scattering layer is a layer containing light scattering particles in a matrix. The particle size of the light-scattering particles is 0.1 μm or more, and from the viewpoint of scattering effect, the range of 0.5 to 15.0 μm is preferable, and the range of 0.7 to 12.0 μm is more preferable.

In addition, in order to further improve the luminance or to adjust the distribution of the luminance with respect to the viewing angle, two or more kinds of light scattering particles having different particle sizes may be mixed and used. When particles having a large particle size are referred to as large-diameter particles and particles having a smaller particle size than the large-diameter particles are referred to as small-diameter particles, the particle size of the large-diameter particles is preferably in the range of 5.0 to 15.0 μm, more preferably 6.0 to 12.0 μm, from the viewpoint of imparting external scattering properties and anti-newton ring properties. From the viewpoint of imparting internal scattering properties, the particle size of the small-particle-diameter particles is preferably in the range of 0.5 to 5.0. Mu.m, and more preferably in the range of 0.7 to 3.0. Mu.m.

The light scattering particles may be organic particles, inorganic particles, or organic-inorganic composite particles. For example, synthetic resin particles can be used as the organic particles. Specific examples thereof include silicone resin particles, acrylic resin particles (polymethyl methacrylate (PMMA)), nylon resin particles, styrene resin particles, polyethylene particles, polyurethane resin particles, and benzoguanamine particles, and silicone resin particles and acrylic resin particles are preferable from the viewpoint of easy availability of particles having an appropriate refractive index. Also, particles having a hollow structure may be used.

From the viewpoint of the scattering effect, it is preferable that the difference in refractive index between the light-scattering particles and the matrix of the light-scattering layer is large. From this viewpoint, the refractive index difference Δ n between the light-scattering particles and the matrix is preferably 0.02 or more, more preferably 0.10 or more, and still more preferably 0.20 or more. The refractive index of the light scattering particles is, for example, in the range of 1.40 to 1.45, preferably in the range of 1.42 to 1.45. Here, the refractive index also refers to the average refractive index. The "refractive index" described below is also the same.

From the viewpoint of light-scattering properties of the light-scattering layer and brittleness of the light-scattering layer, the light-scattering particles are contained in the light-scattering layer in a volume fraction of preferably 10 volume% (vol%) to 70vol%, more preferably 20vol% to 60vol%.

(substrate for light scattering layer)

The method for forming the light-scattering layer is not particularly limited, but from the viewpoint of productivity and the like, it is preferable to form the light-scattering layer as a cured layer of a polymerizable composition (curable composition) containing the light-scattering particles and the polymerizable compound. The polymerizable compound may be selected from commercially available polymerizable compounds or polymerizable compounds synthesized by a known method, and used in consideration of the refractive index of the material for forming the wavelength conversion layer so as to satisfy n1 < n2. Examples of the preferable polymerizable compound include a compound having an ethylenically unsaturated bond at least one of a terminal and a side chain and/or a compound having an epoxy group or an oxetane group at least one of a terminal and a side chain, and more preferably a compound having an ethylenically unsaturated bond at least one of a terminal and a side chain. Specific examples of the compound having an ethylenically unsaturated bond at least one of the terminal and the side chain include (meth) acrylate compounds, acrylamide compounds, styrene compounds, maleic anhydride, and the like, with (meth) acrylate compounds being preferred, and acrylate compounds being more preferred. As the (meth) acrylate compound, preferred are (meth) acrylate, urethane (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, and the like. As the styrene compound, styrene, α -methylstyrene, 4-methylstyrene, divinylbenzene, 4-hydroxystyrene, 4-carboxystyrene and the like are preferable.

In the present invention and the present specification, "(meth) acrylate" is used in the meaning of one or both of acrylate and methacrylate, and "(meth) acrylic acid" is used in the meaning of one or both of acrylic acid and methacrylic acid. "(meth) acryloyl group" and the like are also the same.

Among the (meth) acrylate compounds, preferable compounds for further reducing the absorbance of the light scattering layer at the emission center wavelength λ nm of the light source include esters of polyhydric alcohols and polyfunctional (meth) acrylic acids, i.e., polyfunctional (meth) acrylates having 2 or more functions.

Preferable examples of the 2-functional (meth) acrylate include neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, tripropylene glycol di (meth) acrylate, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, and dicyclopentanyl di (meth) acrylate.

Examples of the (meth) acrylate having 3 or more functional groups include ECH (epichlorohydrin) -modified glycerol tri (meth) acrylate, EO (ethylene oxide) -modified glycerol tri (meth) acrylate, PO (propylene oxide) -modified glycerol tri (meth) acrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, EO-modified phosphoric triacrylate, trimethylolpropane tri (meth) acrylate, caprolactone-modified trimethylolpropane tri (meth) acrylate, EO-modified trimethylolpropane tri (meth) acrylate, PO-modified trimethylolpropane tri (meth) acrylate, tris (acryloyloxyethyl) isocyanurate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, caprolactone-modified dipentaerythritol hexa (meth) acrylate, dipentaerythritol hydroxypenta (meth) acrylate, alkyl-modified dipentaerythritol penta (meth) acrylate, dipentaerythritol poly (meth) acrylate, alkyl-modified dipentaerythritol tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, and pentaerythritol ethoxy tetra (meth) acrylate.

From the viewpoint of improving the hardness of the light-scattering layer and the adhesion to an adjacent layer or member, the (meth) acrylate compound is preferably used in combination with the following (1) and (2).

(1) At least one (meth) acrylate selected from the group consisting of 2-functional (meth) acrylates in which the (meth) acrylates are connected to each other by an alkyl group having 5 to 9 carbon atoms, and 2-functional or 3-functional or more (meth) acrylates in which the (meth) acrylates are connected to each other by an alkylene oxide;

(2) At least one of 3 or more functional (meth) acrylates that do not contain alkylene oxide.

Examples of the urethane (meth) acrylate include a urethane acrylate obtained by reacting a diisocyanate such as TDI (toluene diisocyanate), MDI (xylene diisocyanate), HDI (hexamethylene diisocyanate), IPDI (isophorone diisocyanate), HMDI (hexamethylene diisocyanate); polyols such as poly (propylene oxide) diol, poly (tetramethylene oxide) diol, ethoxylated bisphenol a, ethoxylated bisphenol S spiroglycol, caprolactone-modified diol, and carbonate diol; and (urethane) methacrylate obtained by reacting a hydroxy acrylate such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, glycidol di (meth) acrylate, or pentaerythritol triacrylate. Specific examples thereof include polyfunctional urethane (meth) acrylates described in Japanese patent application laid-open Nos. 2002-265650, 2002-355936, and 2002-067238. Further, as other specific examples, there may be mentioned an adduct of TDI and hydroxyethyl acrylate, an adduct of IPDI and hydroxyethyl acrylate, an adduct of HDI and pentaerythritol triacrylate (PETA), a compound obtained by reacting isocyanate remaining after the production of an adduct of TDI and PETA with dodecyloxypropyl acrylate, an adduct of 6,6 nylon and TDI, and an adduct of pentaerythritol, TDI and hydroxyethyl acrylate. Among them, in order to further reduce the absorbance of the light scattering layer in the light emission center wavelength λ nm of the light source, (urethane) methacrylate generated by condensation of a compound having a hydroxyl group and an aliphatic isocyanate is preferable.

In addition, after the long-term use of the wavelength conversion member, in order to keep the absorbance of the light scattering layer low at the emission center wavelength λ nm of the light source, it is preferable to use at least one compound selected from the group consisting of urethane (meth) acrylates, phenol compounds, phosphite triester compounds, sulfur compounds, and hindered amine compounds in combination. If the absorbance of the light scattering layer at the emission center wavelength λ nm of the light source can be kept low even after long-term use of the wavelength conversion member, the decrease in luminance (i.e., the improvement in durability) due to long-term use is suppressed, which is preferable.

As the phenol-based compound, there is used, examples thereof include 2,6-di-tert-butyl-p-cresol, 2,6-diphenyl-4-octadecyloxyphenol, stearyl (3,5-di-tert-butyl-4-hydroxyphenyl) -propionate, distearyl (3,5-di-tert-butyl-4-hydroxybenzyl) phosphate, thiodiglycol bis [ (3,5-di-tert-butyl-4-hydroxyphenyl) propionate ], 1,6-hexamethylenebis [ (3272-di-tert-butyl-4-hydroxyphenyl) propionate ], 1,6-hexamethylenebis [ (3535-zxft-butyl-4-hydroxyphenyl) propionamide ], 4,4 '-thiobis (6-tert-butyl-m-cresol) ], 3584 zxft 3424-hexamethylenebis (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide ] 2,2' -methylenebis (4-methyl-6-tert-butylphenol), 2,2 '-methylenebis (4-ethyl-6-tert-butylphenol), ethylene glycol bis [3,3-bis (4-hydroxy-3-tert-butylphenyl) butyrate ], 4,4' -butylidenebis (6-tert-butyl-m-cresol), 2,2 '-ethylenebis (4,6-di-tert-butylphenol), 2,2' -ethylenebis (4-sec-butyl-6-tert-butylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, bis [ 2-tert-butyl-4-methyl-6- (2-hydroxy-3-tert-butyl-6-tert-butylphenol) Phenyl-5-methylbenzyl) terephthalate, 1,3,5-tris (2,6-dimethyl-3-hydroxy-4-t-butylbenzyl) isocyanurate, 1,3,5-tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-tris (3,5-di-t-butyl-4-hydroxybenzyl) -2,4,6-trimethylbenzene, 1,3,5-tris [ (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxyethyl ] isocyanurate, tetrakis [ methylene-3- (3 ',5' -di-t-butyl-4 ' -hydroxyphenyl) propionate ] methane, 2-tert-butyl-4-methyl-6- (2-acryloyloxy-3-tert-butyl-5-methylbenzyl) phenol, 3,9-bis [1,1-dimethyl-2- { (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy } ethyl ] -2,4,8,10-tetraoxaspiro [ 5.5 ] undecane, tetrakis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate) methane, triethylene glycol bis [ (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate ], 2- [1- (2-hydroxy-3,5-di-tert-pentylphenyl) ethyl ] -4,6-di-tert-pentylphenyl acrylate, and the like.

The phosphite triester compound may include, for example, triphenyl phosphite, trisnonylphenyl phosphite, tricresyl phosphite, tris (2-ethylhexyl) phosphite, tridecyl phosphite, trilauryl phosphite, tris (tridecyl) phosphite, trioleyl phosphite, diphenyl mono (2-ethylhexyl) phosphite, diphenyl mono decyl phosphite, diphenyl mono (tridecyl) phosphite, trilauryl trithiophosphite, tetraphenyl dipropylene glycol diphosphite, tetraphenyl tetra (tridecyl) pentaerythritol tetraphosphite, tetra (C12-C15 alkyl) -4,4' -isopropylidenediphenyl phosphite, bis (tridecyl) pentaerythritol diphosphite and bis (nonylphenyl) pentaerythritol diphosphite in a mixture, bis (decyl) pentaerythritol diphosphite, bis (tridecyl) pentaerythritol diphosphite, tristearyl phosphite, distearyl pentaerythritol diphosphite, tris (2,4-butylphenyl) phosphite, hydrogenated bisphenol A pentaerythritol phosphite polymer, hydrogenated bisphenol A phenyl phosphite polymer, 3963 zxft Methylene bis (4325-bis (tert-butylphenyl) -3525 di-tert-butylphenyl) pentaerythritol diphosphite, pentaerythritol bis (tert-butyl-3536-butyl-ethyl-3536-bis (tert-butyl) pentaerythritol-3526, pentaerythritol bis (tert-butyl-3525) bis (tert-butyl-phenyl) diphosphite, pentaerythritol, 6-tert-butyl-4- [3- (2,4,8,10-tetra-tert-butyldibenzo [ d, f ] [1,3,2] dioxaphosphonite-6-yloxy) propyl ] -o-cresol and the like.

Examples of the sulfur-based compound include dilauryl thiodipropionate, dialkyl thiodipropionates such as myristyl group and distearyl group, and β -alkylmercaptopropionic acid esters of polyhydric alcohols such as pentaerythritol tetrakis (. Beta. -dodecylmercaptopropionate).

Examples of the hindered amine-based compound include 2,2,6,6-tetramethyl-4-piperidinebenzoic acid, N- (2,2,6,6-tetramethyl-4-piperidyl) dodecylsuccinimide, 1- [ (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxyethyl ] -2,2,6,6-tetramethyl-4-piperidyl- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) -2-butyl-2- (3,5-t-butyl-4-hydroxybenzyl) malonate, N, N' -bis (2,2,6,6-tetramethyl-4-piperidyl) hexamethylenediamine, tetrakis (2,2,6,6-tetramethyl-4-piperidyl) butane tetracarboxylate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) butane tetracarboxylate, bis (2,2,6,6-tetramethyl-4-piperidyl) -ditridecyl butane tetracarboxylate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) -ditridecyl butane tetracarboxylate, 3,9-bis [1,1-dimethyl-2- { tris (2,2,6,6-tetramethyl-4-piperidinyloxycarbonyloxy) butylcarbonyloxy } ethyl ] -2,4,8,10-tetraoxy Heterospiro [ 5.5 ] undecane, 3,9-bis [1,1-dimethyl-2- { tris (1,2,2,6,6-pentamethyl-4-piperidinyloxycarbonyloxy) butylcarbonyloxy } ethyl ] -2,4,8,10-tetraoxaspiro [ 5.5 ] undecane, 1,5,8,12-tetrakis [ 4,6-bis { N- (2,2,6,6-tetramethyl-4-piperidinyl) butylamino } -1,3,5-triazin-2-yl ] -1,5,8,12-tetraazadodecane, 1- (2-hydroxyethyl) -2,2,6,6-tetramethyl-4-piperidinol/dimethyl succinate condensate, 2-tert-octylamino-4,6-diclorotriazine/N, N '-bis (2,2,6,6-tetramethyl-4-piperidinyl) hexamethylenediamine, N' -bis (4924 zxft 3724-tetramethyl-4-piperidinyl) hexamethylenediamine condensate, and the like.

Among the above stabilizers, phenol compounds or hindered amine compounds are preferable, and phenol compounds are more preferable. The content of the stabilizer in the light scattering layer is preferably 0.02 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, and still more preferably 0.1 to 3 parts by mass, based on 100 parts by mass of the substrate of the light scattering layer. Two or more kinds of the stabilizers may be used in combination, and when used in combination, the content of each stabilizer may be set to the above range. The content of the stabilizer is preferably within the above range from the viewpoint that the light absorption of the light scattering layer at the emission center wavelength λ nm of the light source can be kept low even after the wavelength conversion member is used for a long period of time, the curability of the light scattering layer, the adhesion to an adjacent layer or member, and the like.

Further, as the acrylate-based compound, a compound having a fluorene skeleton is also preferably used. Specific examples of such a compound include a compound represented by the formula (2) described in WO2013/047524 A1.

In addition, in order to adjust the refractive index of the matrix, particles having a smaller particle size than the light scattering particles can be used as the refractive index adjusting particles. The refractive index adjusting particles have a particle size of less than 0.1 μm.

Examples of the refractive index adjusting particles include particles of diamond, titanium oxide, zirconium oxide, lead carbonate, zinc oxide, zinc sulfide, antimony oxide, silicon oxide, aluminum oxide, and the like. Among them, zirconia or silica particles are preferable from the viewpoint of less absorption of blue light or ultraviolet light, and zirconia particles are preferable from the viewpoint of being able to adjust the refractive index by a small amount. The refractive index adjusting particles may be used in an amount capable of adjusting the refractive index, and the content of the light scattering layer is not particularly limited.

In addition, one or more known additives such as a polymerization initiator and a surfactant, or one or more solvents for adjusting viscosity may be added to the polymerizable composition for forming the light scattering layer in an arbitrary amount. As the additive and the solvent, known additives and solvents can be used without any limitation.

By adjusting the kinds or addition amounts of the above-mentioned various components, the refractive index n2 of the base of the light-scattering layer and the absorbance of the light-scattering layer at the wavelength λ nm can be controlled.

(arrangement position, thickness, and formation method of light scattering layer)

The light scattering layer may be provided on the light emitting side of the wavelength conversion member, on the light source side, on either side, or on both sides. The light scattering layer may be provided as a layer directly contacting the wavelength conversion layer, or may be laminated with the wavelength conversion layer through one or more other layers. Examples of such another layer include an organic layer, an inorganic layer, and a base film included in a barrier film described later. Fig. 2 shows a specific example of the layer structure of the wavelength conversion layer. In fig. 2, the upper side is the light emission side, the lower side is the light source side, reference numerals 10, 10a, and 10b denote light scattering layers, reference numerals 11a and 11b denote barrier films, and reference numeral 12 denotes a wavelength conversion layer. In addition, the layer structure of the barrier film is not shown for simplicity, but the barrier film may be a laminated structure of two or more layers as described later, and is preferably a laminated structure. Fig. 2 is a diagram showing only the layer structure for illustration, and the thickness or the ratio of the thicknesses of the respective layers does not limit the present invention at all, and one or more layers not shown may be included in the wavelength conversion member. In the wavelength conversion member, it is preferable to dispose the light scattering layer at least on the light emission side of the wavelength conversion layer from the viewpoint of further improving the luminance.

The thickness of the light scattering layer can be set to any thickness, and can be set to 1 to 20 μm as an example. From the viewpoint of achieving both light scattering properties and thinning of the light scattering layer, the thickness is preferably in the range of 1 to 10 μm, and more preferably in the range of 1 to 5 μm.

From the viewpoint of improving the in-plane uniformity of light emitted from the backlight unit, the haze of the light scattering layer is desirably high, and is preferably 50% or more, more preferably 70% or more, and further preferably 80% or more.

The light scattering layer may be included in the wavelength conversion member as a layer adjacent to a barrier film described later in detail. In this case, the haze of the laminate of the light scattering layer and the barrier film is preferably in the above range.

The haze of the light scattering layer and the laminate of the light scattering layer and the barrier film was measured according to JISK 7136. An example of the measuring apparatus is a haze meter NDH2000 manufactured by NIPPON DENSHOKU indtrials co.

The total light transmittance of the light scattering layer is preferably 50% or more, more preferably 70% or more, from the viewpoint of improving the in-plane uniformity of light emitted from the backlight unit and from the viewpoint of improving the luminance. The total light transmittance of the light scattering layer was set to a value measured according to jis k 7136. An example of the measuring apparatus is a haze meter NDH2000 manufactured by NIPPON DENS lens HOKU indtrials co.

For example, the light-scattering layer can be formed by applying the polymerizable composition to an appropriate substrate, drying the composition and removing the solvent as needed, and then polymerizing and curing the composition by light irradiation, heating, or the like. For example, a substrate on which a wavelength conversion layer has been formed, or a substrate on which a wavelength conversion layer is formed after a light scattering layer is formed can be used as the substrate. Thus, a wavelength conversion member having a wavelength conversion layer and a light scattering layer can be obtained through or on the substrate. Examples of the coating method include various known coating methods described below for forming the wavelength conversion layer. The curing conditions may be appropriately set depending on the kind of the polymerizable compound to be used and the composition of the polymerizable composition.

< wavelength conversion layer >

(phosphor)

The wavelength conversion layer contains at least a phosphor. The shape of the wavelength conversion layer is not particularly limited, and may be any shape such as a sheet shape or a rod shape.

Among the known phosphors are: a phosphor (A) having an emission center wavelength in a wavelength band ranging from 600nm to 680 nm; a phosphor (B) having an emission center wavelength in a wavelength band ranging from 520nm to 560 nm; and a phosphor (C) having an emission center wavelength in a wavelength band of 400 to 500 nm. The phosphor (a) is excited by the excitation light and emits red light, the phosphor (B) emits green light, and the phosphor (C) emits blue light. For example, when blue light is incident on a wavelength conversion layer including the phosphor (a) and the phosphor (B) as excitation light, white light can be represented by red light emitted from the phosphor (a), green light emitted from the phosphor (B), and blue light transmitted through the wavelength conversion layer as shown in fig. 1. Alternatively, by making ultraviolet light incident on the wavelength conversion layer including the phosphors (a), (B), and (C) as excitation light, white light can be represented by red light emitted from the phosphor (a), green light emitted from the phosphor (B), and blue light emitted from the phosphor (C).

One form of phosphor is a quantum dot. Particularly, in the case where the phosphor contained in the wavelength conversion layer is a quantum dot, in order to obtain white from the backlight unit with a smaller phosphor (quantum dot) content, wavelength conversion of a sufficient amount of light is performed in the wavelength conversion layer, and the backlight unit is preferably designed such that more light passes through the wavelength conversion layer. As the amount of light passing through the light scattering layer increases, the loss (light absorption) in the light scattering layer tends to be reduced, and the brightness tends to be improved more significantly.

Examples of the Quantum dots include Quantum Dots (QDs) which are phosphors having discrete energy levels due to the Quantum confinement effect. Since the half-value width of fluorescence emitted from the quantum dot is smaller than that of fluorescence emitted from another phosphor, the white light obtained by light emission from the quantum dot is preferably a phosphor in terms of excellent color reproducibility. The half-value width of fluorescence emitted from the quantum dot is preferably 100nm or less, more preferably 80nm or less, even more preferably 50nm or less, even more preferably 45nm or less, and even more preferably 40nm or less.

As for the quantum dots, for example, japanese patent laid-open No. 2012-16971 0060 to 0066 can be referred to in addition to the above description, but the present invention is not limited to the description thereof. As the quantum dot, a commercially available product can be used without any limitation. In general, the emission wavelength of a quantum dot can be adjusted by the composition, size, composition and size of the particle.

Further, the phosphor may be a ceramic phosphor. Examples of the ceramic phosphor include a ceramic phosphor obtained by adding a metal element as an activator to an inorganic crystal such as yttrium-aluminum-garnet (YAG), a metal oxide, or a metal sulfide. Specific examples thereof include the following ceramic phosphors. The following, in ": "the metal species to be labeled later as a cation is a metal element added as an activator. Cerium activated yttrium-aluminum-garnet (YAG: ce) ³⁺ ) Phosphor (YAG phosphor), (Ca, sr, ba) ₂ SiO ₄ ：Eu ²⁺ 、SrGa ₂ S ₄ ：Eu ²⁺ 、α-SiAlON：Eu ²⁺ 、Ca ₃ Sc ₂ Si ₃ O ₁₂ ：Ce ³⁺ 、SrGa ₂ S ₄ ：Eu ²⁺ 、(Ca、Sr、Ba)S：Eu ²⁺ 、(Ca、Sr、Ba) ₂ Si ₅ N ₈ ：Eu ²⁺ 、CaAlSiN ₃ ：Eu ²⁺ And the like. In the YAG phosphor, for example, a part or all of yttrium (Y) may be substituted with at least one element selected from the group consisting of Lu, sc, la, gd, and Sm, and a part or all of aluminum (Al) may be substituted with at least one or both of Ga and In. The YAG phosphor can adjust the emission wavelength of the phosphor by changing the composition. For example, by replacing a part or all of Y of the YAG phosphor with Gd, the emission wavelength can be shifted to the longer wavelength side. Further, the substitution amount of Gd is increased to shift the emission wavelength to the longer wavelength side. For example, by substituting Ga for a part of Al in the YAG phosphor, the emission wavelength can be shifted to a short wavelength side. In other words, in this case, a phosphor that emits yellow (green) light having a strong blue color can be used. Other ceramic phosphors can also be adjusted in emission wavelength by adjusting the composition.

The phosphor such as a quantum dot or a ceramic phosphor may be added in the form of particles to the polymerizable composition for forming a wavelength conversion layer (polymerizable composition containing a phosphor), or may be added in the form of a dispersion liquid dispersed in a solvent. From the viewpoint of suppressing aggregation of the phosphor particles, it is preferable to add the phosphor particles in the form of a dispersion. The solvent used herein is not particularly limited. The phosphor may be added, for example, in an amount of about 0.01 to 10 parts by mass based on 100 parts by mass of the total amount of the polymerizable composition.

(method for producing wavelength conversion layer)

The phosphor described above is usually contained in a matrix in the wavelength conversion layer. The matrix is usually a polymer (organic matrix) that polymerizes the polymerizable composition by light irradiation, heat curing, or the like. The shape of the wavelength conversion member is not particularly limited. For example, the wavelength conversion layer may be included in the backlight unit as it is, or may be included in the backlight unit as a laminate (wavelength conversion member) with one or more other layers such as a barrier film described later. Specifically, a wavelength conversion layer can be obtained by applying a polymerizable composition (curable composition) containing a phosphor onto an appropriate substrate and then performing a curing treatment by light irradiation or the like.

The polymerizable compound used for the preparation of the polymerizable composition is not particularly limited. One kind of the polymerizable compound may be used, or two or more kinds may be used in combination. The content of all polymerizable compounds in the total amount of the polymerizable composition is preferably about 10 to 99.99 mass%. Examples of preferable polymerizable compounds include monofunctional or polyfunctional (meth) acrylate compounds such as monofunctional or polyfunctional (meth) acrylate monomers, polymers thereof, and prepolymers thereof, from the viewpoint of transparency, adhesion, and the like of the cured coating film after curing.

Examples of the monofunctional (meth) acrylate monomer include acrylic acid, methacrylic acid, and derivatives thereof, and more specifically, a monomer having one polymerizable unsaturated bond ((meth) acryloyl group) of (meth) acrylic acid in the molecule. For these specific examples, reference may be made to paragraph 0022 of WO2012/077807 A1.

A monomer having one polymerizable unsaturated bond ((meth) acryloyl group) of the above (meth) acrylic acid in one molecule and a polyfunctional (meth) acrylate monomer having two or more (meth) acryloyl groups in one molecule may be used in combination. For details thereof, reference may be made to paragraph 0024 of WO2012/077807 A1. Further, as the polyfunctional (meth) acrylate compound, compounds described in paragraphs 0023 to 0036 of Japanese patent application laid-open No. 2013-043382 can be used. Furthermore, the alkyl chain-containing (meth) acrylate monomers represented by the general formulae (4) to (6) described in the paragraphs 0014 to 0017 of Japanese patent No. 5129458 can also be used.

The amount of the polyfunctional (meth) acrylate monomer used is preferably 5 parts by mass or more per 100 parts by mass of the total amount of the polymerizable compounds contained in the polymerizable composition from the viewpoint of coating film strength, and is preferably 95 parts by mass or less from the viewpoint of suppressing gelation of the composition. From the same viewpoint, the amount of the monofunctional (meth) acrylate monomer used is preferably 5 parts by mass or more and 95 parts by mass or less with respect to 100 parts by mass of the total amount of the polymerizable compounds contained in the polymerizable composition.

Preferable polymerizable compounds include compounds having a cyclic group such as a ring-opening polymerizable cyclic ether group such as an epoxy group or an oxetane group. More preferable examples of such a compound include compounds having an epoxy group (epoxy compounds). As for the epoxy compound, paragraphs 0029 to 0033 of japanese patent application laid-open No. 2011-159924 can be referred to.

The polymerizable composition may contain a known radical polymerization initiator or cationic polymerization initiator as a polymerization initiator. As the polymerization initiator, for example, the paragraph of JP-A2013-043382 No. 0037 and the paragraph of JP-A2011-159924 No. 0040 to 0042 can be referred to. The polymerization initiator is preferably 0.1 mol% or more, more preferably 0.5 to 5 mol% of the total amount of the polymerizable compounds contained in the polymerizable composition.

The wavelength conversion layer is not particularly limited in its formation method as long as it contains the above-described components and a known additive that can be optionally added. A wavelength conversion layer containing a phosphor in a matrix can be formed by applying a composition prepared by mixing the above-described components and, if necessary, one or more known additives, to a suitable substrate, and then performing polymerization treatment such as light irradiation or heating to polymerize and cure the composition. The amount of the additive to be used is not particularly limited, and may be appropriately set. Further, a solvent may be added as necessary for the viscosity of the composition and the like. In this case, the kind and amount of the solvent used are not particularly limited. For example, one kind of organic solvent may be used as the solvent, or two or more kinds may be used in combination.

The wavelength conversion layer can be obtained by applying the polymerizable composition to an appropriate substrate, drying the composition as needed, removing the solvent, and then polymerizing and curing the composition by light irradiation or the like. Examples of the coating method include known coating methods such as a curtain coating method, a dip coating method, a spin coating method, a print coating method, a spray coating method, a slit coating method, a roll coating method, a slide coating method, a blade coating method, a gravure coating method, and a wire bar coating method. The curing conditions can be appropriately set depending on the kind of the polymerizable compound to be used and the composition of the polymerizable composition.

The polymerization treatment of the polymerizable composition may be carried out by any method, and as one method, the polymerization treatment may be carried out in a state where the polymerizable composition is sandwiched between two substrates. An embodiment of a manufacturing process of the wavelength conversion member including such polymerization treatment is described below with reference to the drawings. However, the present invention is not limited to the following embodiments.

Fig. 3 is a schematic configuration diagram of an example of the manufacturing apparatus 100 for a wavelength conversion member, and fig. 4 is a partial enlarged view of the manufacturing apparatus shown in fig. 3. The steps of manufacturing a wavelength conversion member using the manufacturing apparatus 100 shown in fig. 3 and 4 include at least: a step of applying a polymerizable composition containing a fluorescent material to the surface of a continuously conveyed first base material (hereinafter also referred to as a "first film") to form a coating film; a step of laminating (superposing) a continuously conveyed second substrate (hereinafter, also referred to as a "second film") on the coating film, and sandwiching the coating film between the first film and the second film; and a step of forming a wavelength conversion layer (cured layer) by polymerizing and curing the coating film by continuously feeding any one of the first film and the second film around a support roller while sandwiching the coating film between the first film and the second film and by irradiating with light. By using a barrier film having a barrier property against oxygen or moisture as either the first substrate or the second substrate, a wavelength conversion member having one surface protected by the barrier film can be obtained. By using a barrier film as each of the first base material and the second base material, a wavelength conversion member in which both surfaces of the wavelength conversion layer are protected by the barrier film can be obtained. Further, a wavelength conversion member having a wavelength conversion layer, a barrier film, and a light scattering layer can be obtained by using a barrier film in which light scattering layers are laminated. The light scattering layer is provided on one surface of the barrier film, and the wavelength conversion layer is provided on the other surface, but it is preferable from the viewpoint of protecting the wavelength conversion layer by the barrier film. Alternatively, the light-scattering layer may be formed by applying a polymerizable composition for forming the light-scattering layer to the barrier film after the wavelength conversion layer is laminated, and performing polymerization treatment.

More specifically, first, the first film 10 is continuously conveyed from a not-shown conveyor to the coating section 20. For example, the first film 10 is fed from the conveyor at a conveying speed of 1 to 50 m/min. However, the conveying speed is not limited to this. At the time of feeding, for example, a tension of 20 to 150N/m, preferably 30 to 100N/m, is applied to the first film 10.

In the coating section 20, a polymerizable composition containing a fluorescent material (hereinafter, also referred to as "coating liquid") is applied to the surface of the continuously conveyed first film 10 to form a coating film 22 (see fig. 4). The coating section 20 is provided with, for example, a die coater 24 and a backup roll 26 disposed opposite to the die coater 24. The surface opposite to the surface of the first film 10 on which the coating film 22 is formed is wound around the backup roll 26, and the coating liquid is applied from the discharge port of the die coater 24 to the surface of the continuously conveyed first film 10, thereby forming the coating film 22. Here, the coating film 22 refers to a coating liquid before polymerization treatment applied to the first film 10.

In the present embodiment, the die coater 24 to which the extrusion coating method is applied is shown as a coating apparatus, but is not limited thereto. A coating apparatus to which various methods such as a curtain coating method, an extrusion coating method, a bar coating method, a roll coating method, or the like are applied can be used.

The first film 10 passing through the coating section 20 and having the coating film 22 formed thereon is continuously conveyed to the laminating section 30. In the laminating section 30, the continuously conveyed second film 50 is laminated on the coating film 22, and the coating film 22 is sandwiched by the first film 10 and the second film 50.

In the laminating section 30, a laminating roller 32 and a heating chamber 34 surrounding the laminating roller 32 are provided. The heating chamber 34 is provided with an opening 36 through which the first thin film 10 passes and an opening 38 through which the second thin film 50 passes.

A support roller 62 is disposed at a position opposite to the laminating roller 32. The surface of the first film 10 on which the coating film 22 is formed, which is opposite to the surface on which the coating film 22 is formed, is wound around the support roller 62 and continuously conveyed toward the laminating position P. The lamination position P refers to a position where the second film 50 comes into contact with the coating film 22. It is preferable that the first film 10 is wound around the support roller 62 before reaching the lamination position P. This is because even if wrinkles are generated in the first film 10, the wrinkles can be corrected and removed by the support roller 62 until the lamination position P is reached. Therefore, the distance L1 from the position (contact position) where the first film 10 is wound around the support roller 62 to the lamination position P is preferably long, for example, 30mm or more, and the upper limit value thereof is generally determined by the diameter and the trace of the support roller 62.

In the present embodiment, the lamination of the second film 50 is performed by the support roller 62 and the lamination roller 32 used in the polymerization processing section 60. That is, the support roller 62 used in the polymerization processing section 60 is also used as a roller used in the laminating section 30. However, the present invention is not limited to the above embodiment, and the laminating roller may be provided separately from the support roller 62 in the laminating portion 30 so as not to serve as the support roller 62.

The number of rollers can be reduced by using the support roller 62 used in the polymerization treatment section 60 in the laminating section 30. The support roller 62 may be used as a heat roller for the first film 10.

The second film 50 fed from a not-shown conveyor is wound around the laminating roller 32, and is continuously conveyed between the laminating roller 32 and the support roller 62. The second film 50 is laminated on the coating film 22 formed on the first film 10 at the lamination position P. Thereby, the coating film 22 is sandwiched by the first film 10 and the second film 50. The lamination means that the second film 50 is stacked and laminated on the coating film 22.

The distance L2 between the laminating roller 32 and the support roller 62 is preferably equal to or greater than the total thickness of the first film 10, the wavelength conversion layer (cured layer) 28 for polymerizing and curing the coating film 22, and the second film 50. Preferably, L2 is a length of 5mm or less added to the total thickness of the first film 10, the coating film 22, and the second film 50. By setting the distance L2 to a length of 5mm or less added to the total thickness, air bubbles can be prevented from entering between the second film 50 and the coating film 22. Here, the distance L2 between the laminating roller 32 and the support roller 62 is the shortest distance between the outer peripheral surface of the laminating roller 32 and the outer peripheral surface of the support roller 62.

The rotational accuracy of the laminating roller 32 and the support roller 62 is 0.05mm or less, preferably 0.01mm or less in terms of radial vibration. The smaller the radial vibration is, the smaller the thickness distribution of the coating film 22 can be made.

In order to suppress thermal deformation after the coating film 22 is sandwiched between the first film 10 and the second film 50, the difference between the temperature of the support roller 62 and the temperature of the first film 10 in the polymerization processing section 60 and the difference between the temperature of the support roller 62 and the temperature of the second film 50 are preferably 30 ℃ or less, more preferably 15 ℃ or less, and most preferably the same.

In the case where the heating chamber 34 is provided to reduce the temperature difference with the support roller 62, it is preferable to heat the first film 10 and the second film 50 in the heating chamber 34. For example, in the heating chamber 34, hot air is supplied from a hot air generator not shown, and the first film 10 and the second film 50 can be heated.

The first film 10 is wound around the temperature-adjusted support roller 62, and the first film 10 can be heated by the support roller 62.

On the other hand, in the second film 50, the laminating roller 32 is used as a heating roller, and the second film 50 can be heated by the laminating roller 32.

However, the heating chamber 34 and the heating roller are not essential and may be provided as needed.

Subsequently, the coating film 22 is continuously conveyed to the polymerization treatment section 60 while being sandwiched between the first film 10 and the second film 50. In the embodiment shown in the drawing, the polymerization treatment in the polymerization treatment section 60 is performed by light irradiation, but in the case where the polymerizable compound contained in the coating liquid is polymerized by heating, the polymerization treatment may be performed by heating such as blowing of warm air.

A light irradiation device 64 is provided at a position opposite to the support roller 62. The first film 10 and the second film 50 sandwiching the coating film 22 are continuously conveyed between the support roller 62 and the light irradiation device 64. The light irradiated by the light irradiation device is determined by the photopolymerization property contained in the coating liquidThe kind of the compound may be determined, and ultraviolet rays may be used as an example. Examples of the light source for generating ultraviolet rays include a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a carbon arc lamp, a metal halide lamp, and a xenon lamp. The amount of light irradiation may be set within a range in which polymerization curing of the coating film can be performed, and for example, 100 to 10000mJ/cm may be used ² The ultraviolet rays of the irradiation amount are irradiated toward the coating film 22.

In the polymerization processing section 60, the first film 10 is wound around the support roller 62 in a state where the coating film 22 is sandwiched between the first film 10 and the second film 50, and while continuously being conveyed, the coating film 22 is cured by light irradiation from the light irradiation device 64, whereby the wavelength conversion layer (cured layer) 28 can be formed.

In the present embodiment, the first film 10 side is wound around the support roller 62 and continuously conveyed, but the second film 50 may be wound around the support roller 62 and continuously conveyed.

The winding around the support roller 62 means a state in which any of the first film 10 and the second film 50 is in contact with the surface of the support roller 62 at a certain wrap angle. Thus, during the continuous conveyance, the first film 10 and the second film 50 move in synchronization with the rotation of the support roller 62. It is sufficient that the ultraviolet ray is wound around the support roller 62 at least during the irradiation.

The support rollers 62 include a cylindrical body and rotating shafts disposed at both ends of the body. The body of the support roller 62 has a diameter of, for example, 200 to 1000 mm. There is no limitation on the diameter phi of the support roller 62. The diameter is preferably 300 to 500mm in consideration of the crimping deformation, the equipment cost and the rotational accuracy. The temperature of the support roller 62 can be adjusted by mounting a temperature adjuster on the main body of the support roller 62.

The temperature of the support roller 62 may be determined in consideration of heat generation during light irradiation, curing efficiency of the coating film 22, and wrinkle deformation of the first film 10 and the second film 50 generated on the support roller 62. The support roller 62 is preferably set at a temperature in the range of, for example, 10 to 95 deg.C, more preferably 15 to 85 deg.C. Here, the temperature of the roller refers to the surface temperature of the roller.

The distance L3 between the lamination position P and the light irradiation device 64 may be 30mm or more, for example.

The coating film 22 becomes a cured layer 28 by light irradiation, and the wavelength conversion member 70 including the first film 10, the cured layer 28, and the second film 50 is manufactured. The wavelength converting member 70 is peeled from the support roller 62 by the peeling roller 80. The wavelength conversion member 70 is continuously fed to a winding machine, not shown, and then the wavelength conversion member 70 is wound into a roll by the winding machine.

Although the above description has been made on one embodiment of the manufacturing process of the wavelength conversion member, the present invention is not limited to the above embodiment. For example, the wavelength conversion layer (cured layer) may be produced by applying a polymerizable composition containing a phosphor onto a substrate, and performing a polymerization treatment after drying treatment as necessary, without further laminating a substrate thereon. One or more other layers may be stacked on the produced wavelength conversion layer by a known method.

The thickness of the wavelength conversion layer is preferably in the range of 1 to 500. Mu.m, more preferably in the range of 10 to 250. Mu.m, and still more preferably in the range of 30 to 150. Mu.m. When the thickness is 1 μm or more, an excellent wavelength conversion effect can be obtained, and it is preferable. When the thickness is 500 μm or less, the backlight unit can be made thinner and is preferable when the backlight unit is incorporated.

< support body >

The wavelength conversion member may have a support for improving strength, ease of film formation, and the like. The support may be included as a layer adjacent to the wavelength conversion layer, or may be included as a base film of a barrier film described later. In the wavelength converting member, the support may be included in the order of the inorganic layer and the support, or may be included in the order of the wavelength converting layer, the inorganic layer, the organic layer, and the support. The support may be disposed between the organic layer and the inorganic layer, between two organic layers, or between two inorganic layers. The wavelength conversion member may include one or more supports, and the wavelength conversion member may have a structure in which the supports, the wavelength conversion layer, and the supports are stacked in this order. As the support, a transparent support which is transparent to visible light is preferable. Here, the term "transparent to visible light" means that the light transmittance in the visible light region is 80% or more, preferably 85% or more. The light transmittance used as a measure of transparency can be calculated by measuring the total light transmittance and the amount of scattered light by a method described in JIS-K7105, that is, by an integrating-sphere-type light transmittance measuring apparatus and subtracting the water vapor by diffusion from the total light transmittance. As the support, reference is made to Japanese patent application laid-open No. 2007-290369, paragraphs 0046 to 0052, and Japanese patent application laid-open No. 2005-096108, paragraphs 0040 to 0055. The thickness of the support is preferably in the range of 10 to 500. Mu.m, more preferably 15 to 400. Mu.m, particularly preferably 20 to 300. Mu.m, from the viewpoint of gas barrier properties, impact resistance and the like.

The support may be used as a base material of a barrier film described later. The support may be used for either one or both of the first film and the second film. When the support is used for both the first film and the second film, the same support may be used, or different supports may be used.

< Barrier film >

The wavelength converting member preferably comprises a barrier film. The barrier film is a thin film having a gas barrier function of blocking oxygen. The barrier film also preferably has a function of blocking water vapor.

The barrier film is preferably included in the wavelength conversion member as a layer in direct contact with the wavelength conversion layer. Further, one or more barrier films may be included in the wavelength conversion member. The wavelength conversion member preferably has a structure in which a barrier film, a wavelength conversion layer, and a barrier film are laminated in this order.

In the wavelength conversion member, the wavelength conversion layer may be formed using a barrier film as a base material. In addition, either one or both of the first film and the second film may be used as the barrier film. When both the first film and the second film are barrier films, the barrier films used as the first film and the second film may be the same or different.

The barrier film may be any known barrier film, and may be, for example, a barrier film described below.

The barrier film is generally only required to include at least an inorganic layer, and may be a base film or a film including an inorganic layer. As for the base film, reference can be made to the description of the above support. The barrier film may comprise a barrier laminate comprising at least one of the above-described inorganic layers and at least one of the organic layers on a substrate film. Such lamination of several layers is preferable because the barrier property can be further improved. On the other hand, the light transmittance of the wavelength conversion member tends to decrease as the number of stacked layers increases, and therefore it is expected that the number of stacked layers increases within a range in which good light transmittance can be maintained. Specifically, the total light transmittance of the barrier film in the visible light region is preferably 80% or more, and the oxygen permeability is preferably 1.00cm ³ /(m ² Day atm) or less. The oxygen permeability is a value measured by using an oxygen permeability measuring apparatus (OX-TRAN 2/20 manufactured by MOCON INC., trade name) under the conditions of a measurement temperature of 23 ℃ and a relative humidity of 90%. The visible light region is a wavelength region of 380 to 780nm, and the total light transmittance is an average value of light transmittances in the visible light region.

The oxygen permeability of the barrier film is more preferably 0.10cm ³ /(m ² Day atm) or less, and more preferably 0.01cm ³ /(m ² Day atm) or less. The total light transmittance in the visible light region is more preferably 90% or more. The lower the oxygen permeability is, the more preferable is the higher is the total light transmittance in the visible light region.

(inorganic layer)

The "inorganic layer" is a layer containing an inorganic material as a main component, and is preferably a layer formed only of an inorganic material. The organic layer is a layer containing an organic material as a main component, and preferably contains 50 mass% or more of the organic material, more preferably 80 mass% or more of the organic material, and particularly preferably 90 mass% or more of the organic material.

The inorganic material constituting the inorganic layer is not particularly limited, and for example, a metal, or various inorganic compounds such as inorganic oxides, nitrides, and nitride oxides can be used. As the element constituting the inorganic material, silicon, aluminum, magnesium, titanium, tin, indium, and cerium are preferable, and these elements may include one or two or more kinds. Specific examples of the inorganic compound include silicon oxide, silicon carbide, silicon oxynitride, magnesium oxide, titanium oxide, tin oxide, indium oxide alloy, aluminum oxide, silicon nitride, aluminum nitride, and titanium nitride. Further, as the inorganic layer, a metal film such as an aluminum film, a silver film, a tin film, a chromium film, a nickel film, and a titanium film may be provided.

Among the above materials, silicon oxide, silicon nitride, silicon carbide and aluminum oxide are particularly preferable. This is because the inorganic layer including these materials has good adhesion to the organic layer, and therefore, barrier properties can be further improved.

The method for forming the inorganic layer is not particularly limited, and various film forming methods can be used, for example, which can evaporate or scatter a film forming material and can deposit the film forming material on a surface to be evaporated.

Examples of the method for forming the inorganic layer include a physical vapor deposition method (physical vapor deposition method) including: a vacuum evaporation method in which an inorganic material such as an inorganic oxide, an inorganic nitride oxide, or a metal is heated and evaporated; an oxidation reaction vapor deposition method in which an inorganic material is used as a raw material, and oxygen is introduced to oxidize the inorganic material for vapor deposition; a sputtering method in which an inorganic material is used as a target material, argon gas and oxygen gas are introduced, and sputtering is performed to deposit an inorganic material; and an ion plating method in which an inorganic material is heated and evaporated by a plasma beam generated in a plasma gun; and the plasma chemical vapor deposition method uses an organic silicon compound as a raw material in forming a deposited film of silicon oxide. The substrate may be a support, a base film, a wavelength conversion layer, an organic layer, or the like, and vapor deposition may be performed on the surface of the substrate.

The thickness of the inorganic layer may be 1nm to 500nm, preferably 5nm to 300nm, and particularly preferably 10nm to 150nm. This is because the film thickness of the adjacent inorganic layer is within the above range, and therefore a wavelength conversion member that can achieve a good barrier property, suppress reflection in the inorganic layer, and have a higher light transmittance can be provided.

In the wavelength converting member, it is preferable that at least one main surface of the wavelength converting layer is in direct contact with the inorganic layer. It is also preferred that the inorganic layer is in direct contact with both major surfaces of the wavelength converting layer. Here, the "main surface" refers to a surface (front surface, back surface) of the wavelength conversion layer disposed on the recognition side or the backlight side when the wavelength conversion member is used. The same is true with respect to the main surfaces of the other layers or components. Further, the inorganic layer and the organic layer, the two inorganic layers, or the two organic layers may be bonded to each other through a known adhesive layer. From the viewpoint of improving light transmittance, the smaller the number of adhesive layers, the more preferable the absence of adhesive layers. In one embodiment, the inorganic layer is preferably in direct contact with the organic layer.

(organic layer)

As for the organic layer, reference can be made to paragraphs 0020 to 0042 of japanese patent application laid-open No. 2007-290369 and paragraphs 0074 to 0105 of japanese patent application laid-open No. 2005-096108. In addition, the organic layer preferably contains a cardo polymer (cardo polymer). This is because the organic layer can be favorably adhered to the adjacent layer, and particularly, the inorganic layer can be favorably adhered to the organic layer, thereby realizing further excellent gas barrier properties. For details of the cado polymer, reference is made to paragraphs 0085 to 0095 of the above-mentioned Japanese patent application laid-open No. 2005-096108. The film thickness of the organic layer is preferably in the range of 0.05 to 10 μm, and more preferably in the range of 0.5 to 10 μm. When the organic layer is formed by a wet coating method, the thickness of the organic layer is in the range of 0.5 to 10 μm, preferably 1 to 5 μm. When the organic layer is formed by the dry coating method, the thickness of the organic layer is in the range of 0.05 to 5 μm, preferably 0.05 to 1 μm. This is because the film thickness of the organic layer formed by the wet coating method or the dry coating method is in the above range, and thus the adhesiveness with the inorganic layer can be improved.

For other details of the inorganic layer and the organic layer, reference may be made to the descriptions of the above-mentioned japanese patent application laid-open nos. 2007-290369, 2005-096108, and US2012/0113672 A1.

The refractive index of each layer and the base film that can be included in the barrier film is not particularly limited, but for example, the refractive index of the inorganic layer is 1.60 to 1.82, the refractive index of the organic layer is 1.42 to 1.62, and the refractive index of the base film is 1.45 to 1.65. These refractive indices are independent of the magnitude relationship between the refractive index n1 of the wavelength conversion layer and the refractive index n2 of the light scattering layer. May be the same as or different from n1 and n2, and may be larger or smaller. From the viewpoint of suppressing reflection at the interface with the adjacent layer, the difference in refractive index with the adjacent layer is preferably small, and for example, the difference in refractive index with the adjacent layer is preferably less than 5.00, and more preferably less than 3.00. This also applies to the case where a layer other than the barrier film is included.

[ backlight Unit ]

The wavelength conversion member may be used as a constituent member of the backlight unit. The backlight unit includes at least a wavelength conversion member and a light source.

(wavelength of light emitted from backlight Unit)

From the viewpoint of achieving high luminance and high color reproducibility, it is preferable to use a backlight unit that is subjected to multi-wavelength light source. For example, it is preferable to emit: a blue light having an emission center wavelength in a wavelength band of 430 to 480nm and having a peak of emission intensity with a half-value width of 100nm or less; green light having a central emission wavelength in a wavelength band of 520 to 560nm and having a peak of emission intensity with a half-value width of 100nm or less; and red light having an emission center wavelength in a wavelength band of 600 to 680nm and having a peak of emission intensity with a half-value width of 100nm or less.

From the viewpoint of further improving the luminance and color reproducibility, the wavelength band of blue light emitted from the backlight unit is more preferably 440 to 475nm.

From the same viewpoint, the wavelength band of green light emitted from the backlight unit is more preferably 520 to 545nm.

From the same viewpoint, the wavelength band of red light emitted from the backlight unit is more preferably 610 to 640nm.

From the same viewpoint, the half-value widths of the emission intensities of the blue light, the green light, and the red light emitted from the backlight unit are preferably 80nm or less, more preferably 50nm or less, even more preferably 40nm or less, and even more preferably 30nm or less. Among them, the half-value width of the emission intensity of blue light is particularly preferably 25nm or less.

The backlight unit includes at least the wavelength conversion member and the light source. In one embodiment, a light source (blue light source) that emits blue light having an emission center wavelength in a wavelength band of 430nm to 480nm, for example, a blue light emitting diode that emits blue light, can be used as the light source. In the case of using a light source that emits blue light, the wavelength conversion layer preferably contains at least a phosphor that is excited by excitation light and emits red light and a phosphor that emits green light. Accordingly, white light can be represented by blue light emitted from the light source and transmitted through the wavelength conversion member and red light and green light emitted from the wavelength conversion member.

Alternatively, in another embodiment, a light source (ultraviolet light source) that emits ultraviolet light having an emission center wavelength in a wavelength band of 300nm to 430nm, for example, an ultraviolet light emitting diode, may be used as the light source. In this case, the wavelength conversion layer preferably contains a phosphor that emits red light and a phosphor that emits green light, and contains a phosphor that is excited by excitation light and emits blue light. Thus, white light can be represented by red light, green light, and blue light emitted from the wavelength conversion member.

In another embodiment, a laser light source may be used instead of the light emitting diode.

(Structure of backlight Unit)

The backlight unit may be an edge-light type backlight unit having a light guide plate, a reflection plate, or the like as a constituent member. Fig. 1 shows an example of an edge-light type backlight unit. As the light guide plate, a known light guide plate can be used without any limitation. However, the backlight unit may be a direct type.

The backlight unit may further include a reflective member in a rear portion of the light source. Such a reflective member is not particularly limited, and known reflective members can be used, and are described in japanese patent No. 3416302, japanese patent No. 3363565, japanese patent No. 4091978, and japanese patent No. 3448626, and the contents of these publications are cited in the present invention.

The backlight unit also preferably includes a known diffusion plate or diffusion sheet, prism sheet (e.g., BEF series manufactured by Sumitomo 3M Limited), and light guide. Other members are also described in japanese patent No. 3416302, japanese patent No. 3363565, japanese patent No. 4091978, japanese patent No. 3448626, etc., and the contents of these publications are incorporated in the present invention.

[ liquid Crystal display device ]

The backlight unit can be applied to a liquid crystal display device. The liquid crystal display device may include at least the backlight unit and the liquid crystal unit.

(Structure of liquid Crystal display device)

The driving mode of the liquid crystal cell is not particularly limited, and various modes such as Twisted Nematic (TN), super Twisted Nematic (STN), vertical Alignment (VA), in-plane switching (IPS), and Optically Compensated Bend (OCB) can be used. The liquid crystal cell is preferably a VA mode, an OCB mode, an IPS mode, or a TN mode, but is not limited to these modes. An example of a structure of a VA-mode liquid crystal display device is shown in fig. 3 of japanese patent application laid-open No. 2008-262161. However, the specific structure of the liquid crystal display device is not particularly limited, and a known structure can be employed.

In one embodiment of the liquid crystal display device, a liquid crystal cell is provided in which a liquid crystal layer is sandwiched between substrates at least one of which is provided with an electrode facing each other, and the liquid crystal cell is configured to be disposed between two polarizing plates. The liquid crystal display device includes a liquid crystal cell in which liquid crystal is sealed between upper and lower substrates, and displays an image by changing an alignment state of the liquid crystal by applying a voltage. If necessary, the polarizing plate may have additional functional layers such as a polarizer protective film, an optical compensation member for performing optical compensation, and an adhesive layer. Further, a color filter substrate, a thin-layer transistor substrate, a lens film, a diffusion sheet, a hard coat layer, an antireflection layer, a low reflection layer, an antiglare layer, or the like may be disposed, and (or instead of) a surface layer such as a forward scattering layer, a primer layer, an antistatic layer, an undercoat layer, or the like may be disposed.

Fig. 5 shows an example of a liquid crystal display device according to an embodiment of the present invention. The liquid crystal display device 51 shown in fig. 5 has a backlight-side polarizing plate 14 on the surface of the liquid crystal cell 21 on the backlight side. The surface of the backlight-side polarizer 14 on the backlight side of the backlight-side polarizer 12 may or may not contain the polarizer protective film 11, but is preferably included.

The backlight-side polarizing plate 14 is preferably configured such that the polarizer 12 is sandwiched between two polarizer

protective films

11 and 13.

In this specification, a polarizer protective film on a side close to the liquid crystal cell with respect to the polarizer is referred to as an inner polarizer protective film, and a polarizer protective film on a side far from the liquid crystal cell with respect to the polarizer is referred to as an outer polarizer protective film. In the example shown in fig. 5, the polarizer protection film 13 is an inner polarizer protection film, and the polarizer protection film 11 is an outer polarizer protection film.

The backlight-side polarizer may have a retardation film as an inner polarizer protective film on the liquid crystal cell side. As such a retardation film, a known cellulose acylate film or the like can be used.

The liquid crystal display device 51 has a display-side polarizing plate 44 on a surface opposite to the backlight-side surface of the liquid crystal cell 21. The display-side polarizing plate 44 has a structure in which the polarizer 42 is sandwiched between two polarizer

protective films

41 and 43. The polarizer protective film 43 is an inner polarizer protective film, and the polarizer protective film 41 is an outer polarizer protective film.

The backlight unit 1 included in the liquid crystal display device 51 is as described above.

The liquid crystal cell, the polarizing plate protective film, and the like constituting the liquid crystal display device are not particularly limited, and those manufactured by a known method or commercially available products can be used without any limitation. Further, a known intermediate layer such as an adhesive layer may be provided between the layers.

Examples

Hereinafter, the present invention will be described in further detail with reference to examples. The materials, the amounts used, the ratios, the contents of the processes, the process order, and the like, which are shown in the following examples, can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited to the specific examples shown below.

< manufacture of wavelength converting Member >

(preparation of Barrier film 11)

As the support, a polyethylene terephthalate film (PET film, TOYOBO co., ltd., trade name: COSMOSHINE (registered trademark) a4300, 50 μm thick) was used, and an organic layer and an inorganic layer were formed in this order on one surface of the support.

Trimethylolpropane triacrylate (TMPTA manufactured by DAICEL-ALLNEX ltd., ltd.) and a photopolymerization initiator (ESACUREKTO 46 manufactured by Lamberti co., ltd., were weighed so that the mass ratio was 95. The coating liquid was applied to the PET film in a roll-to-roll manner using a die coater, and passed through a drying zone at 50 ℃ for 3 minutes. Thereafter, irradiation was carried out under a nitrogen atmosphere (cumulative dose of irradiation: about 600 mJ/cm) ² ) Ultraviolet rays are cured by means of ultraviolet curing and taken up. The thickness of the first organic layer formed on the support was 1 μm.

Next, an inorganic layer (silicon nitride layer) was formed on the surface of the organic layer using a roll-to-roll CVD (Chemical Vapor Deposition) apparatus. As the source gas, silane gas (flow rate 160 sccm), ammonia gas (flow rate 370 sccm), hydrogen gas (flow rate 590 sccm), and nitrogen gas (flow rate 240 sccm) were used. As the power source, a high-frequency power source having a frequency of 13.56MHz was used. The film forming pressure was 40Pa, and the film thickness was 50nm.

In this manner, the barrier film 11 in which the inorganic layer is laminated on the surface of the first organic layer formed on the support was produced.

(production of light-scattering layer-attached Barrier film (laminated film 13))

After a protective film (PAC 2-30-T manufactured by Sun a. Kaken co., ltd.) was attached to the inorganic layer surface of the barrier film 11 for protection, a light scattering layer was formed on the PET film surface on the back surface in the following manner.

Preparation of the polymerizable composition for Forming the light-scattering layer

As the light-scattering particles, 150g of silicone resin particles (TOSPEARL 120, particle size 2.0 μm, manufactured by Momentive Performance Materials inc., and) and 40g of polymethyl methacrylate (PMMA) particles (teger polymer (Techpolymer), manufactured by SEKISUI CHEMICAL co., ltd., particle size 8 μm), were first stirred with 550g of methyl isobutyl ketone (MIBK) for about 1 hour to be dispersed, thereby obtaining a dispersion.

To the obtained dispersion liquid were added 50g of an acrylate compound (Viscoat 700HV manufactured by Osaka Synthetic chemical laboratories, inc.) and 40g of an acrylate compound (TAISEIFINE CHEMICAL co., 8BR500 (urethane (meth) acrylate) manufactured by ltd.) and further stirred. A coating solution (polymerizable composition for forming a light-scattering layer) was prepared by adding 1.5g of a photopolymerization initiator (IRGACURE (registered trademark) 819 manufactured by BASF Corporation) and 0.5g of a fluorine-based surfactant (FC 4430 manufactured by 3M Corporation).

Coating and curing of the polymerizable composition for forming the light-scattering layer

The PET film surface of the barrier film 11 was disposed and sent out so as to be a coated surface, and was conveyed to a die coater and coated. The amount of Wet (Wet) coating was adjusted to 25cm by a liquid feed pump ³ /m ² The coating was performed (the thickness was adjusted to about 12 μm by using a dry film). After passing through a drying zone at 60 ℃ for 3 minutes, the sheet was wound on a backup roll adjusted to 30 ℃ and dried at 600mJ/cm ² The ultraviolet rays of (3) are cured and then taken up. This gave a laminated film 13 of the barrier film 11 and the light scattering layer.

The haze of the obtained laminated film 13 was measured using a haze meter NDH2000 manufactured by NIPPON DENSHOKU INDUSTRIES co., ltd. according to jis 7136, and was 90%.

(production of wavelength conversion member in example 1)

The following polymerizable composition a containing quantum dots was prepared, filtered through a polypropylene filter having a pore size of 0.2 μm, and dried under reduced pressure for 30 minutes to be used as a coating liquid. The quantum dot concentration in the toluene dispersion was 1 mass% as follows.

As the toluene dispersion of the quantum dot 1 used in example 1, a dispersion of quantum dots having a maximum emission wavelength of 535nm (CZ 520-100 manufactured by NN-LABS, LLC.) was used. As the toluene dispersion of the quantum dots 2, a dispersion of quantum dots (CZ 620-100 manufactured by NN-LABS, LLC.) having a maximum emission wavelength of 630nm was used. The quantum dots contained in these dispersions were dispersed in toluene at a concentration of 3 mass% using CdSe as a core portion, znS as a shell portion, and octadecylamine as a ligand.

The wavelength conversion member was obtained by the manufacturing process described with reference to fig. 3 and 4 using the laminated film 13 produced in the above-described order as the first film and the barrier film 11 as the second film. Specifically, the laminated film 13 was prepared as the first film, and the prepared polymerizable composition A containing quantum dots was applied to the inorganic layer surface by a die coater while continuously conveying the film at a tension of 60N/m at 1 m/min to form a coating film having a thickness of 50 μm. Next, the first film (laminated film 13) having the coating film formed thereon was wound around a support roll, the second film (barrier film 11) was laminated on the coating film in such a direction that the inorganic layer was in contact with the coating film, and the coating film was passed through a heating zone at 100 ℃ for 3 minutes while being continuously conveyed in a state where the first film and the second film sandwiched therebetween. Then, the resultant was cured by irradiation with ultraviolet light using a 160W/cm air-cooled metal halide lamp (EYE GRAPHICS co., ltd.) to form a wavelength conversion layer containing quantum dots. The dose of ultraviolet irradiation was 2000mJ/cm ² . L1 was 50mm, L2 was 1mm, and L3 was 50mm.

The coating film is cured by the irradiation of the ultraviolet rays to form a cured layer (wavelength conversion layer), thereby producing a wavelength conversion member. The thickness of the cured layer of the wavelength converting member was about 50 μm. Thus, a wavelength converting member of example 1 was obtained, which had the laminated film 13 and the barrier film 11 on both surfaces of the wavelength converting layer, respectively, and both main surfaces of the wavelength converting layer were in direct contact with the inorganic layers of the two thin films, and a light scattering layer was formed on one surface.

(production of wavelength conversion member in example 2)

A wavelength conversion member was produced in the same manner as in example 1, except that 50g of a zirconia dispersion (AX-ZP manufactured by Nippon Shokubai co., ltd.) as a dispersion containing refractive index adjusting particles was added to the polymerizable composition for forming a light scattering layer, and the thickness of the resultant was adjusted to about 6 μm with a dry film, and the polymerizable composition for forming a light scattering layer was applied.

The haze of the laminated film included in the wavelength converting member of example 2 (the laminated film of the barrier film 11 and the light scattering layer) was measured to be 95% in the same manner as in example 1.

(production of wavelength conversion member in example 3)

A wavelength converting member was produced in the same manner as in example 1, except that 70g of an acrylate compound having a fluorene skeleton (OSAKA GAS co., ltd. Manufactured ogzoruea 200) was used instead of 50g of the acrylate compound (OSAKA Synthetic Chemical Laboratories, inc., viscoat700 HV) and 40g of the acrylate compound (TAISEI FINE CHEMICAL co., ltd. Manufactured 8BR 500) as the polymerizable compound added to the polymerizable composition for forming the light scattering layer, and the thickness was adjusted to about 8 μm with a dry film and the polymerizable composition for forming the light scattering layer was applied.

The haze of the laminated film included in the wavelength converting member of example 3 (the laminated film of the barrier film 11 and the light scattering layer) was measured to be 95% in the same manner as in example 1.

(production of wavelength conversion member in example 4)

A wavelength converting member was produced in the same manner as in example 1, except that 150g of Polytetrafluoroethylene (PTFE) particles (microdisperss-3000 manufactured by Polysciences, inc., particle size 3.0 μm) was used instead of 150g of silicone resin particles (TOSPEARL 120 manufactured by Momentive Performance Materials inc., particle size 2.0 μm) and that the thickness was adjusted to about 8 μm with a dry film and the polymerizable composition for forming a light scattering layer was applied.

The haze of the laminated film included in the wavelength converting member of example 4 (the laminated film of the barrier film 11 and the light scattering layer) was measured to be 95% in the same manner as in example 1.

(preparation of wavelength conversion member in comparative example 1)

TiO as refractive index adjusting particles is added to a polymerizable composition for forming a light scattering layer ₂ A wavelength converting member was produced in the same manner as in example 1, except that 20g (HTD 760 manufactured by TAYCA CORPORATION) of the polymerizable composition for forming a light scattering layer was applied onto the dried film in such a thickness that the thickness thereof was adjusted to about 6 μm.

The haze of the laminated film (laminated film of the barrier film 11 and the light scattering layer) included in the wavelength converting member of comparative example 1 was measured to be 98% in the same manner as in example 1.

(preparation of wavelength conversion member in comparative example 2)

A wavelength conversion member was produced in the same manner as in example 1, except that 150g of styrene resin particles (SX-130 manufactured by Soken Chemical & Engineering co., ltd., particle size 1.3 μm) was used instead of 150g of silicone resin particles (TOSPEARL 120 manufactured by Momentive performance materials inc., particle size 2.0 μm), and 90g of DPHA (dipentaerythritol hexaacrylate, shin-Nakamura Chemical co., ltd., manufactured) was used instead of 90g of acrylate compound (Viscoat 700HV manufactured by osa Synthetic Chemical Laboratories, inc., usa) and 40g of acrylate compound (8978 zft 8978 co., ltd., 8BR500 manufactured by ltd.) were used as the polymerizable compound added to the polymerizable composition for light scattering layer formation, and that the thickness was adjusted to about 8 μm with a dry film and the polymerizable composition for layer formation was coated.

The haze of the laminated film (the laminated film of the barrier film 11 and the light scattering layer) included in the wavelength converting member of comparative example 2 was measured to be 95% in the same manner as in example 1.

< evaluation method >

(measurement of average refractive indices n1 and n 2)

The refractive index measurement sample for the wavelength conversion layer was produced by the following method.

A wavelength conversion member was produced in the same manner as described above except that the first film and the second film were changed to a PET film (TOYOBO co., ltd.: a 4300). The thickness of the cured layer of the obtained wavelength converting member was 150 μm. A single layer of the wavelength conversion layer was obtained by peeling the double-sided PET film from the obtained wavelength conversion member, and the average refractive index n1 was measured using the single layer as the wavelength conversion layer for refractive index measurement.

The sample for measuring the refractive index of the substrate of the light-scattering layer was produced by the following method.

A polymerizable composition was produced in the same manner as described above except that the light-scattering particles were not added. The polymerizable composition thus prepared was applied to the surface of a PET film (TOYOBO co., ltd. Product: a 4100) in the same manner as in the formation of the light-scattering layer in each of the examples and comparative examples, and after curing in the same manner, the PET film was peeled to obtain a cured layer of a single film having a thickness of 12 μm, and the cured layer was used as a substrate of the light-scattering layer for refractive index measurement to measure the average refractive index n2.

The refractive index nx in the slow axis direction and the refractive index ny in the fast axis direction in the plane were obtained using a multi-wavelength abbe refractometer DR-M2 manufactured by ATAGO co. The refractive index nz as described above is calculated from these values and the retardation Re and the layer thickness in the in-plane direction measured by the above-described method, and the average refractive indices n1 and n2 are determined as the average values of nx, ny, and nz.

The thin film was cut in cross section, and the thickness of the layer was measured using a scanning electron microscope (SEM; S-3400N manufactured by Hitachi High-Tech Co., ltd.).

(measurement of blue light absorbance of light scattering layer)

The laminated film (barrier film with a light scattering layer) 13 produced in each of examples and comparative examples was cut at an angle of 2cm, and then placed in an integrating sphere of an absolute PL quantum yield measuring device (C9920-02) manufactured by Hamamatsu Photonics k.k., and a detected light intensity I at a wavelength of 450nm was measured by allowing blue light having an emission center wavelength at a wavelength of 450nm, which is an emission center wavelength of a blue light source provided in a commercially available flat panel terminal (manufactured by amazon.com, inc., of kindlefilefere hdx7 ") used for the luminance measurement described later to enter. Similarly, the light transmission intensity I at a wavelength of 450nm was measured with respect to a blank in which the thin film was not disposed in the integrating sphere ₀ The blue light absorbance A1 of the laminate film 13 was calculated from the following equation.

(formula) A1= (I) ₀ -I)/I ₀

Similarly, the blue light absorbance A2 of the barrier film 11 on which the light scattering layer is not formed is measured, and the difference from the blue light absorbance A1 of the laminated film 13 is obtained from the following equation, whereby the blue light absorbance a of the single light scattering layer is calculated.

(formula) A = A2-A1

(measurement of luminance)

A commercially available flat panel terminal (manufactured by amazon, inc., kindlef irehdx7 ") provided with a blue light source in the backlight unit was disassembled to take out the backlight unit, the wavelength conversion members of the respective examples and comparative examples cut in a rectangular shape were placed on the light guide plate, and two prism sheets taken out from the kindlef irehdx7 ″ were placed on the wavelength conversion members in a manner that the directions of the surface concave-convex patterns were orthogonal to each other. The backlight unit was lit, and the luminance was measured using a luminance meter (SR 3 manufactured by TOPCON CORPORATION) disposed at a distance of 740mm in the vertical direction from the surface of the backlight unit. If the measured luminance is 15300cd/m ² As described above, it can be determined that the liquid crystal display device incorporating the backlight unit can display an image with high luminance.

The above results are shown in table 1.

[ Table 1]

From the results shown in table 1, it was confirmed that the luminance was improved in examples 1 to 4.

(production of wavelength conversion member in example 5)

A wavelength converting member was produced in the same manner as in example 1, except that 0.45g of 3,9-bis [1,1-dimethyl-2- { (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy } ethyl ] -2,4,8,10-tetraoxaspiro [ 5.5 ] undecane (Sumitomo Chemical co., sumilizer ga-80 manufactured by ltd.) was added to the polymerizable composition for forming a light scattering layer.

The haze of the laminated film included in the wavelength converting member of example 5 (the laminated film of the barrier film 11 and the light scattering layer) was measured to be 91% in the same manner as in example 1.

(production of wavelength conversion member in example 6)

A wavelength conversion member was produced in the same manner as in example 1, except that 0.45g of tetrakis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate) methane (IRGANOX 1010 manufactured by BASF Corporation) was added to the polymerizable composition for forming the light scattering layer.

The haze of the laminated film included in the wavelength converting member of example 6 (the laminated film of the barrier film 11 and the light scattering layer) was measured in the same manner as in example 1 to be 86%.

(production of wavelength conversion member in example 7)

As the polymerizable compound to be added to the polymerizable composition for forming the light scattering layer, trimethylolpropane tri (meth) acrylate (Kyoeisha Chemical co., ltd. LIGHT ACRYLATETMP-a) 50g, ethoxylated pentaerythritol tetra (meth) acrylate (shift-nakamura Chemical co., ltd. ATM-35E) 30g, 1,9-nonanediol di (meth) acrylate (Kyoeisha Chemical co., ltd. LIGHT ACRYLATE, 9 ND-a) 10g were used instead of acrylate compound (Osaka Synthetic Chemical Laboratories, inc. Viscoat700 HV) 50g, acrylate compound (TAISEI FINE CHEMICAL co., ltd. 8) 500 g, ltd. BR) 40g, and a wavelength conversion member was produced in the same manner as in example 1 except that this point.

The haze of the laminated film included in the wavelength converting member of example 7 (the laminated film of the barrier film 11 and the light scattering layer) was measured to be 84% in the same manner as in example 1.

With respect to the wavelength conversion members of examples 5 to 7, various evaluations were performed in the same manner as in example 1. The blue light absorbance and the luminance were measured by the same method as in example 1 (hereinafter, referred to as "measurement before durability test") and the measurement after the durability test. The wavelength conversion member of example 1 was also subjected to the measurement after the durability test.

(measurement after durability test)

The wavelength conversion member was left to stand at 85 ℃ for 150 hours, and the absorbance and brightness of blue light after that were measured in the same manner as the measurement before the durability test.

The above results are shown in table 2.

[ Table 2]

From the results shown in table 2, it was confirmed that in examples 5 to 7, the luminance was improved by the same amount as in example 1, and the durability was improved by the same amount as in example 1.

Industrial applicability

The present invention is useful in the field of manufacturing liquid crystal display devices.

Claims

1. A backlight unit, comprising: a light source that emits light having a light emission center wavelength of λ nm; and a wavelength conversion member located on an optical path of light emitted from the light source,

the wavelength conversion member includes: a wavelength conversion layer containing a phosphor that is excited by excitation light and emits fluorescence; and a light scattering layer containing particles having a particle size of 0.1 μm or more in a matrix,

the light-scattering layer has an absorbance at a wavelength of λ nm of 8.0% or less.

2. The backlight unit according to claim 1,

the average refractive index n1 of the wavelength conversion layer is in the range of 1.43 to 1.60,

the average refractive index n2 of the matrix of the light scattering layer is in the range of 1.45 to 2.00.

3. The backlight unit according to claim 1 or 2,

the light scattering layer includes two or more light scattering particles having different particle sizes.

4. A liquid crystal display device comprising the backlight unit according to any one of claims 1 to 3, and a liquid crystal cell.

5. A wavelength converting member, comprising: a wavelength conversion layer containing a phosphor that is excited by excitation light and emits fluorescence; and a light scattering layer containing particles having a particle size of 0.1 μm or more in a matrix,

the light scattering layer has an absorbance of 8.0% or less at a wavelength of 450nm.

6. The wavelength converting member according to claim 5,

7. The wavelength converting member according to claim 5 or 6,