WO2016052625A1

WO2016052625A1 - Backlight unit, liquid crystal display device, wavelength conversion member, and photocurable composition

Info

Publication number: WO2016052625A1
Application number: PCT/JP2015/077754
Authority: WO
Inventors: 達也大場; 直良山田; 啓吾植木; 亮司後藤; 隆米本
Original assignee: 富士フイルム株式会社
Priority date: 2014-09-30
Filing date: 2015-09-30
Publication date: 2016-04-07

Abstract

One embodiment of the present invention relates to a backlight unit which comprises a light source and a wavelength conversion member that is positioned on the optical path of the light discharged from the light source, and wherein: the wavelength conversion member comprises a wavelength conversion layer that contains quantum dots in a matrix, said quantum dots producing fluorescence when excited by excitation light; the wavelength conversion layer is a photocured layer that is obtained by curing a photocurable composition by means of light irradiation; the photocurable composition contains the quantum dots, a polymerizable compound that contains at least an alicyclic epoxy compound, and a photopolymerization initiator; and the loss rate of the light discharged from the light source in the matrix of the wavelength conversion layer is 3% or less in terms of a thickness of 60 μm. Another embodiment of the present invention relates to a liquid crystal display device, a wavelength conversion member or a photocurable composition.

Description

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

The present invention relates to a backlight unit, a liquid crystal display device including the backlight unit, a wavelength conversion member, and a photocurable composition.

Flat panel displays such as liquid crystal display devices (hereinafter also referred to as LCD (Liquid Crystal Display)) consume less power and are increasingly used as space-saving image display devices year by year. The liquid crystal display device is composed of at least a backlight and a liquid crystal cell, and usually further includes members such as a backlight side polarizing plate and a viewing side polarizing plate.

In the flat panel display market, color reproducibility is improving as LCD performance improvement. In this regard, in recent years, quantum dots (also referred to as quantum dots, QDs, or quantum dots) have attracted attention as light emitting materials (see Patent Document 1). For example, when excitation light enters the wavelength conversion member including quantum dots from the backlight, the quantum dots are excited and emit fluorescence. Here, by using quantum dots having different emission characteristics, white light can be realized by emitting red light, green light, and blue light. Since the fluorescence due to the quantum dots has a small half-value width, the white light obtained has high brightness and excellent color reproducibility. With the progress of the three-wavelength light source technology using such quantum dots, the color gamut has been expanded from 72% to 100% in NTSC (National Television System) ratio.

Special table 2013-544018 gazette

The wavelength conversion member usually has a wavelength conversion layer including at least quantum dots in the matrix. For example, Patent Document 1 discloses epoxy as a preferable matrix material (see paragraph 0009 of Patent Document 1). Patent Document 1 describes that the matrix is preferably formed by thermosetting (see paragraph 0091 of Patent Document 1). In the following, a matrix formed by curing a polymerizable compound containing an epoxy compound is referred to as an epoxy matrix.

On the other hand, from the viewpoint of improving the productivity of the wavelength conversion member, photocuring capable of curing the matrix in a short time compared to thermosetting is preferable. Therefore, when the present inventors tried to form the epoxy matrix of the wavelength conversion layer by photocuring in manufacturing the wavelength conversion member, one of the advantages of the wavelength conversion member including quantum dots is a high-intensity white color. In spite of the fact that light can be obtained, in the liquid crystal display device incorporating the manufactured wavelength conversion member, a phenomenon in which the luminance is reduced was observed.

Therefore, an object of the present invention is to achieve an improvement in luminance in a liquid crystal display device having a wavelength conversion member having a wavelength conversion layer containing quantum dots in an epoxy matrix formed by photocuring.

One embodiment of the present invention provides:
A backlight unit including a light source and a wavelength conversion member positioned on an optical path of light emitted from the light source,
The wavelength conversion member has a wavelength conversion layer containing quantum dots in a matrix that are excited by excitation light and emit fluorescence.
The wavelength conversion layer is a photocured layer obtained by curing a photocurable composition by light irradiation,
The photocurable composition includes a quantum dot, a polymerizable compound containing at least an alicyclic epoxy compound, and a photopolymerization initiator,
A backlight unit having a loss rate of light emitted from the light source in the matrix of the wavelength conversion layer of 3% or less in terms of a thickness of 60 μm;
About.

The matrix of the wavelength conversion layer refers to a portion excluding the quantum dots of the wavelength conversion layer, and is a portion that contains at least a polymer of a polymerizable compound and may contain an additive that is optionally added. The loss rate of light emitted from the light source in the matrix is obtained as the light loss rate of the measurement sample prepared by any of the following means 1 to 3. In the present invention, when the value obtained for the measurement sample obtained by at least one of the following means 1 to 3 is 3% or less, the loss rate of light emitted from the light source in the matrix is 3 in terms of a thickness of 60 μm. % Or less.

(Means 1: measured with a model membrane)
A photocurable composition obtained by removing at least a part of a solvent together with quantum dots or quantum dots from a photocurable composition for forming a wavelength conversion layer (photocured layer) is prepared. After applying this photocurable composition to a release film (for example, Lumirror # 50 manufactured by Toray Industries, Inc., 50 μm thick) with a wire bar, another release film is laminated on the release film (at 1200 W / cm in the atmosphere). Using an air-cooled metal halide lamp (for example, manufactured by Eye Graphics Co., Ltd.), ultraviolet rays are irradiated from the coated surface to 2000 mJ / cm ² and cured. The cured film thus obtained is cut into 2 cm square, for example, and then the release films on both sides of the cured film are peeled off to obtain a resin layer single film (model film) having a thickness of 60 μm.
The model film thus obtained is subjected to loss rate measurement by the method described later. The obtained measured value is defined as a loss rate of light emitted from the light source. A model film having a thickness other than 60 μm may be produced as the model film. In this case, when the measured value is converted to a thickness of 60 μm, that is, when the thickness of the model film is T μm, a value calculated by “measured loss rate × (T / 60)” is emitted from the light source. Loss rate of light.

(Means 2: Measured after inactivating quantum dots by exposure to oxygen)
The wavelength conversion layer is exposed in an oxygen atmosphere, for example, in the air until the quantum dots are deactivated. It can be confirmed that the quantum dot has been deactivated by the fact that the quantum dot is not excited even when the excitation light is irradiated, that is, the fluorescence is not detected. In addition, when the wavelength conversion member to be evaluated includes layers and members other than the wavelength conversion layer, the wavelength conversion layer is exposed, for example, by polishing with a commercially available polishing sheet. The wavelength conversion layer sample thus obtained is cut into a 2 cm square, for example, and then subjected to loss rate measurement by a method described later. When the thickness of the sample subjected to the loss rate measurement is 60 μm, the obtained measurement value is set as the loss rate of light emitted from the light source. On the other hand, when the thickness of the sample subjected to the loss rate measurement is other than 60 μm, the value obtained by converting the obtained measurement value to the thickness of 60 μm is set as the loss rate of the light emitted from the light source.

(Means 3: Analyzing the wavelength conversion layer and preparing and measuring a model film having the analyzed composition)
The composition analysis of the wavelength conversion layer can be performed by a composition analysis method using, for example, infrared spectroscopy, NMR (Nuclear Magnetic Resonance), gas chromatography or the like. The composition analysis can be performed using a sample obtained by performing treatment according to the composition analysis method on the wavelength conversion layer. Examples of such a sample include a sample obtained by cutting out a part of the wavelength conversion layer, a solution obtained by dissolving the matrix of the wavelength conversion layer in a solvent capable of dissolving the matrix, and the like. it can. In addition, when the wavelength conversion member to be evaluated includes layers and members other than the wavelength conversion layer, the wavelength conversion layer is exposed, for example, by polishing with a commercially available polishing sheet. And the photocurable composition for forming the matrix of the wavelength conversion layer which became clear by the said composition analysis is prepared. Thereafter, a model membrane is obtained in the same manner as in the first means.

The loss rate of the light emitted from the light source in the measurement sample produced by any one of the above means 1 to 3 is determined by the following method by the absolute luminescence quantum yield measurement method using an integrating sphere.
Measurement light including light having the emission center wavelength of light emitted from the light source is incident on the integrating sphere in which the measurement sample is arranged, and the detected light intensity I at the emission center wavelength is measured. For example, the detection light intensity I at a wavelength of 450 nm is measured for a light source that emits blue light with an emission center wavelength of 450 nm.
The same measurement light is incident on an integrating sphere on which no measurement sample is arranged, and the detected light intensity I ₀ at the emission center wavelength is measured.
The above measured values are obtained, and the loss rate A obtained by the following equation is set as the loss rate of light emitted from the light source.
A = (I ₀ -I) / I ₀
The blue light loss rate is a value obtained by making blue light incident as measurement light and measuring the detection light intensity at a wavelength of 450 nm by the above method. The ultraviolet light loss rate is a value obtained by making ultraviolet light incident as measurement light and measuring the detected light intensity at a wavelength of 400 nm by the above method.
As a measuring apparatus for performing the above measurement, a commercially available apparatus capable of performing an absolute luminescence quantum yield measuring method using an integrating sphere can be used. As an example, an absolute PL (photoluminescence) quantum yield measuring device (C9920-02) manufactured by Hamamatsu Photonics can be mentioned, and this measuring device was used in Examples described later.

In one aspect, the light source is a blue light source. In another aspect, the light source is an ultraviolet light source.

A further aspect of the present invention relates to a liquid crystal display device including the backlight unit and a liquid crystal cell.

A further aspect of the invention provides:
It has a wavelength conversion layer containing quantum dots that are excited by excitation light and emit fluorescence, in a matrix,
The wavelength conversion layer is a photocured layer obtained by curing a photocurable composition by light irradiation,
The photocurable composition includes a quantum dot, a polymerizable compound containing at least an alicyclic epoxy compound, and a photopolymerization initiator,
The wavelength conversion member whose blue light loss rate in the matrix of the wavelength conversion layer is 3% or less in terms of thickness of 60 μm,
About.

A further aspect of the invention provides:
It has a wavelength conversion layer containing quantum dots that are excited by excitation light and emit fluorescence, in a matrix,
The wavelength conversion layer is a photocured layer obtained by curing a photocurable composition by light irradiation,
The photocurable composition includes a quantum dot, a polymerizable compound containing at least an alicyclic epoxy compound, and a photopolymerization initiator,
The wavelength conversion member whose ultraviolet light loss rate in the matrix of the wavelength conversion layer is 3% or less in terms of thickness 60 μm,
About.

A further aspect of the invention provides:
A photocurable composition comprising quantum dots excited by excitation light and emitting fluorescence,
Including a quantum dot, a polymerizable compound containing at least an alicyclic epoxy compound, and a photopolymerization initiator,
A photocurable composition having a blue light loss rate of 3% or less in terms of a thickness of 60 μm, excluding quantum dots of a photocured product obtained by curing the photocurable composition by light irradiation,
About.

For the blue light loss rate for the above photocurable composition,
(1) A measurement sample obtained by means 1 described above,
(2) A measurement sample in which the photocured product obtained by means 1 using a photocurable composition containing quantum dots is deactivated by oxygen exposure according to means 2,
When the value calculated | required by the method described above using at least one is 3% or less, the blue light loss rate of the part except the quantum dot of the said photocuring body is the loss rate of the light radiate | emitted from the light source in a matrix However, it shall be determined that it is 3% or less in terms of thickness 60 μm. This also applies to the ultraviolet light loss rate related to the photocurable composition described later.

A further aspect of the invention provides:
A method for producing a wavelength conversion member having a wavelength conversion layer including quantum dots that are excited by excitation light and emit fluorescence.
The wavelength conversion layer includes quantum dots in the matrix, and the blue light loss rate in the matrix is 3% or less in terms of a thickness of 60 μm,
A method for producing a wavelength conversion member comprising forming a wavelength conversion layer by curing the photocurable composition by light irradiation;
About.

A further aspect of the invention provides:
A photocurable composition comprising quantum dots excited by excitation light and emitting fluorescence,
Including a quantum dot, a polymerizable compound containing at least an alicyclic epoxy compound, and a photopolymerization initiator,
The photocurable composition, wherein the ultraviolet light loss rate of the portion excluding the quantum dots of the photocured product obtained by curing the photocurable composition by light irradiation is 3% or less in terms of thickness of 60 μm,
About.

A further aspect of the invention provides:
A method for producing a wavelength conversion member having a wavelength conversion layer including quantum dots that are excited by excitation light and emit fluorescence.
The wavelength conversion layer includes quantum dots in the matrix, and the ultraviolet light loss rate in the matrix is 3% or less in terms of thickness of 60 μm,
A method for producing a wavelength conversion member comprising forming a wavelength conversion layer by curing the photocurable composition by light irradiation;
About.

Regarding the backlight unit, the wavelength conversion member, and the photocurable composition, in one aspect, the photopolymerization initiator is an iodonium salt compound.

In one embodiment, the iodonium salt compound includes an anion portion having a gas phase acidity in the range of 240 to 290 kcal / mol as the anion portion. Here, “gas phase acidity” is acidity in the gas phase, and is defined as a change in Gibbs energy accompanying acid dissociation by IUPAC (International Union of Pure Pure and Applied Chemistry). The gas phase acidity can be calculated by known calculation software.

In one embodiment, the polymerizable compound contains 1 to 100 parts by mass of the alicyclic epoxy compound with respect to 100 parts by mass of the total amount of the polymerizable compound.

In one aspect, the polymerizable compound further comprises a (meth) acrylate compound.

In one aspect, the (meth) acrylate compound includes monofunctional (meth) acrylate.

In one embodiment, the wavelength conversion layer contains 0.20% by volume or more of light scattering particles.

In one aspect, the photocurable composition contains light scattering particles in an amount of 0.20% by volume or more based on volume with respect to the total solid content. In addition, solid content means the part except a solvent about the composition containing a solvent, and shall mean the whole composition about the composition which does not contain a solvent.

Here, “light scattering particles” refer to particles having a particle size of 0.10 μm or more. Light scattering is caused by optical inhomogeneities within the layer. A particle having a sufficiently small particle size does not significantly reduce the optical uniformity of the layer even if the particle is contained, whereas a particle having a particle size of 0.10 μm or more does not cause the layer to be optically defective. Particles that can be made uniform and thereby cause light scattering.
The particle size in the present invention and the present specification is a value determined by observing with a scanning electron microscope (SEM). Specifically, after photographing a cross section of a photocured material obtained by curing a wavelength conversion layer or a photocurable composition by light irradiation at a magnification of 5000 times, the primary particle diameter is measured from the obtained image. . For particles that are not spherical, the average value of the length of the major axis and the length of the minor axis is determined and used as the primary particle diameter. The primary particle diameter thus obtained is defined as the particle size of the above particles. The average particle size of the light scattering particles is the arithmetic average of the particle sizes of 20 particles randomly extracted from particles having a particle size of 0.10 μm or more in the captured image. The average particle size of the light scattering particles shown in the examples described later is a value obtained by observing and measuring the cross section of the wavelength conversion layer using S-3400N manufactured by Hitachi High-Tech as a scanning electron microscope. .

According to the present invention, there is provided a liquid crystal display device including a wavelength conversion member having a wavelength conversion layer including quantum dots in an epoxy matrix formed by photocuring, and capable of displaying a high-luminance image. Can be provided. Furthermore, according to this invention, the manufacturing method of the wavelength conversion member which enables provision of this liquid crystal display device, a wavelength conversion member, and a backlight unit can also be provided.

FIGS. 1A and 1B are explanatory diagrams of an example of a backlight unit including a wavelength conversion member. FIG. 2 is a schematic configuration diagram of an example of a wavelength conversion member manufacturing apparatus. FIG. 3 is a partially enlarged view of the manufacturing apparatus shown in FIG. FIG. 4 shows an example of a liquid crystal display device.

The following description may be made based on representative embodiments of the present invention, but the present invention is not limited to such embodiments. In the present invention and the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
In the present invention and the present specification, the “half width” of a peak refers to the width of the peak at a peak height of 1/2. The light having the emission center wavelength in the wavelength band of 430 to 480 nm is called blue light, the light having the emission center wavelength in the wavelength band of 520 to 560 nm is called green light, and the emission center wavelength in the wavelength band of 600 to 680 nm. The light having a color is called red light. Ultraviolet light refers to light having an emission center wavelength in the wavelength band of 300 nm to 430 nm. A light source that emits blue light as single peak light is called a blue light source, and a light source that emits ultraviolet light as single peak light is called an ultraviolet light source. Here, to emit light having a single peak means that in the emission spectrum, two or more peaks do not appear as in the case of a white light source, but there is only one peak having the emission center wavelength as an emission maximum. means.
Further, the description relating to an angle such as orthogonal is intended to include a range of errors allowed in the technical field to which the present invention belongs. For example, it means that the angle is within the range of strict angle ± 10 °, and the error from the strict angle is preferably 5 ° or less, and more preferably 3 ° or less.

[Backlight unit, wavelength conversion member, photocurable composition, wavelength conversion member manufacturing method]
The backlight unit of the present invention is a backlight unit including a light source and a wavelength conversion member positioned on an optical path of light emitted from the light source, and the wavelength conversion member emits fluorescence when excited by excitation light. A wavelength conversion layer including a quantum dot in a matrix, the wavelength conversion layer is a photocured layer obtained by curing a photocurable composition by light irradiation, and the photocurable composition includes a quantum dot, a fat The backlight unit includes a polymerizable compound including at least a cyclic epoxy compound and a photopolymerization initiator, and a loss rate of light emitted from a light source in a matrix of the wavelength conversion layer is 3% or less in terms of a thickness of 60 μm. .

As a result of intensive studies to achieve the object described above, the present inventors have found the backlight unit of the present invention. Hereinafter, this point will be further described.
The present inventors consider that the cause is as follows, while repeatedly examining the cause of the luminance decrease in the liquid crystal display device including the wavelength conversion member having the wavelength conversion layer including the epoxy matrix formed by photocuring. It came to.
Examples of the epoxy compound for forming the epoxy matrix include an alicyclic epoxy compound and an aliphatic epoxy compound. In the present invention and this specification, an alicyclic epoxy compound refers to an epoxy compound having a structure in which an epoxy ring and a saturated hydrocarbon ring are condensed, and is an epoxide derived from a cycloalkene, for example. On the other hand, an epoxy compound having a glycidyl group or the like is an aliphatic epoxy compound. Of the above two types of epoxy compounds, alicyclic epoxy compounds are preferred in that the curability by light irradiation is good. However, the present inventors have found that the loss of light due to the absorption of light emitted from the light source by the epoxy matrix formed by photocuring using this alicyclic epoxy compound results in the above-described decrease in luminance. I came to think. Details are as follows.
In a backlight unit including a wavelength conversion member, light emitted from a light source (hereinafter also referred to as “light derived from a light source”) enters the wavelength conversion layer, and at least part of the light strikes the quantum dots. Is excited to emit fluorescence. The backlight unit often includes a reflective member (such as a prism sheet or a brightness enhancement film). After a part of the light from the light source passes through the wavelength conversion layer, it is reflected by a reflective member located on the emission side of the wavelength conversion layer and enters the wavelength conversion layer again (hereinafter, such light is referred to as light). It is also referred to as “return light.”) Fluorescence can also be obtained by excitation of the quantum dots when a part of them hits the quantum dots. Further, a part of the return light may be reflected by a reflective member (for example, a reflector) existing on the light source side after passing through the wavelength conversion layer, and may be incident on the wavelength conversion layer again. As described above, in the backlight unit including the wavelength conversion member, the light derived from the light source repeatedly reflects and enters the wavelength conversion layer, whereby the quantum dots are excited and fluorescence can be obtained. In such a backlight unit, the light derived from the light source is absorbed in the matrix of the wavelength conversion layer, which is considered to reduce the light emission efficiency of the quantum dots even if the absorption is slight. The present inventors consider that the epoxy matrix formed by photocuring using an alicyclic epoxy compound reduces the luminous efficiency of the quantum dots as described above, which is the cause of the above-described decrease in luminance. It came to.
Therefore, the present inventors reduced the loss of light derived from the light source in the epoxy matrix formed by photocuring using an alicyclic epoxy compound by various means described in detail later, for example, and thereby the backlight unit described above. Completed. According to the liquid crystal display device incorporating such a backlight unit, a high-luminance image can be obtained.
However, the above is an inference by the present inventors and does not limit the present invention.

Furthermore, as a wavelength conversion member suitable for a backlight unit using a blue light source as a light source,
It has a wavelength conversion layer containing quantum dots that are excited by excitation light and emit fluorescence, in a matrix,
The wavelength conversion layer is a photocured layer obtained by curing a photocurable composition by light irradiation,
The photocurable composition includes a quantum dot, a polymerizable compound containing at least an alicyclic epoxy compound, and a photopolymerization initiator,
The wavelength conversion member whose blue light loss rate in the matrix of the wavelength conversion layer is 3% or less in terms of thickness of 60 μm,
Are also provided by the present invention.

Furthermore, as a photocurable composition suitable for the production of the wavelength conversion member,
A photocurable composition comprising quantum dots excited by excitation light and emitting fluorescence,
Including a quantum dot, a polymerizable compound containing at least an alicyclic epoxy compound, and a photopolymerization initiator,
A photocurable composition having a blue light loss rate of 3% or less in terms of a thickness of 60 μm, excluding quantum dots of a photocured product obtained by curing the photocurable composition by light irradiation,
Are also provided by the present invention.

Furthermore, as a manufacturing method of the wavelength conversion member,
A method for producing a wavelength conversion member having a wavelength conversion layer including quantum dots that are excited by excitation light and emit fluorescence.
The wavelength conversion layer includes quantum dots in the matrix, and the blue light loss rate in the matrix is 3% or less in terms of a thickness of 60 μm,
A method for producing a wavelength conversion member comprising forming a wavelength conversion layer by curing the photocurable composition by light irradiation;
Are also provided by the present invention.

Furthermore, as a wavelength conversion member suitable for a backlight unit using an ultraviolet light source as a light source,
It has a wavelength conversion layer containing quantum dots that are excited by excitation light and emit fluorescence, in a matrix,
The wavelength conversion layer is a photocured layer obtained by curing a photocurable composition by light irradiation,
The photocurable composition includes a quantum dot, a polymerizable compound containing at least an alicyclic epoxy compound, and a photopolymerization initiator,
The wavelength conversion member whose ultraviolet light loss rate in the matrix of the wavelength conversion layer is 3% or less in terms of thickness 60 μm,
Are also provided by the present invention.

Furthermore, as a photocurable composition suitable for the production of the wavelength conversion member,
A photocurable composition comprising quantum dots excited by excitation light and emitting fluorescence,
Including a quantum dot, a polymerizable compound containing at least an alicyclic epoxy compound, and a photopolymerization initiator,
The photocurable composition, wherein the ultraviolet light loss rate of the portion excluding the quantum dots of the photocured product obtained by curing the photocurable composition by light irradiation is 3% or less in terms of thickness of 60 μm,
Are also provided by the present invention.

Furthermore, as a manufacturing method of the wavelength conversion member,
A method for producing a wavelength conversion member having a wavelength conversion layer including quantum dots that are excited by excitation light and emit fluorescence.
The wavelength conversion layer includes quantum dots in the matrix, and the ultraviolet light loss rate in the matrix is 3% or less in terms of thickness of 60 μm,
A method for producing a wavelength conversion member comprising forming a wavelength conversion layer by curing the photocurable composition by light irradiation;
Are also provided by the present invention.

Hereinafter, the backlight unit, the wavelength conversion member, the photocurable composition, and the method for producing the wavelength conversion member will be described in more detail.

(Configuration of wavelength conversion member, arrangement example)
The wavelength conversion member should just have the function to convert the wavelength of at least one part of incident light, and to radiate | emit the light of a wavelength different from the wavelength of incident light. The shape of the wavelength conversion member is not particularly limited, and may be any shape such as a sheet shape or a bar shape. The wavelength conversion member can be used as a constituent member of the backlight unit of the 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, the backlight unit 1 includes a light source 1A and a light guide plate 1B for making a surface light source. In the example shown in FIG. 1A, the wavelength conversion member is disposed on the path of light emitted from the light guide plate. On the other hand, in the example shown in FIG. 1B, the wavelength conversion member is disposed between the light guide plate and the light source. And in the example shown to Fig.1 (a), the light radiate | emitted from the light-guide plate 1B injects into the wavelength conversion member 1C.
In the example shown in FIG. 1A, the light 2 emitted from the light source 1A disposed at the edge portion of the light guide plate 1B is blue light, and the liquid crystal is applied from the surface on the liquid crystal cell (not shown) side of the light guide plate 1B. It is emitted toward the cell. The wavelength conversion member 1C disposed on the path of the light (blue light 2) emitted from the light guide plate 1B has quantum dots (A) that are excited by the blue light 2 and emit red light 4, and the blue light 2 It includes at least quantum dots (B) that are excited to emit green light 3. In this way, the backlight unit 1 emits the excited green light 3 and red light 4 and the blue light 2 transmitted through the wavelength conversion member 1C. Thus, white light can be realized by emitting red light, green light, and blue light.
The example shown in FIG. 1B is the same as the embodiment shown in FIG. 1A except that the arrangement of the wavelength conversion member and the light guide plate is different. In the example shown in FIG. 1B, the excited green light 3 and red light 4 and the blue light 2 transmitted through the wavelength conversion member 1C are emitted from the wavelength conversion member 1C and enter the light guide plate, and the surface light source is Realized.

(Wavelength conversion layer)
The wavelength conversion member has at least a wavelength conversion layer including quantum dots. The wavelength conversion layer includes quantum dots in the matrix. The matrix includes a polymer, and the wavelength conversion layer can be formed from a photocurable composition including quantum dots and a polymerizable compound. In the wavelength conversion member, the wavelength conversion layer is a photocured layer of a photocurable composition including a quantum dot, one or more polymerizable compounds including at least an alicyclic epoxy compound, and a photopolymerization initiator. The shape of the wavelength conversion layer is not particularly limited, and may be any shape such as a sheet shape or a bar shape.

Quantum dots are excited by excitation light to emit fluorescence. The wavelength conversion layer includes at least one kind of quantum dot and can also include two or more kinds of quantum dots having different light emission characteristics. Known quantum dots include a quantum dot (A) having an emission center wavelength in a wavelength band in the range of 600 nm to 680 nm (A), a quantum dot (B) having an emission center wavelength in a wavelength band in the range of 520 nm to 560 nm, and 400 nm to 500 nm. There is a quantum dot (C) having an emission center wavelength in the wavelength band. The quantum dots (A) are excited by excitation light to emit red light, the quantum dots (B) emit green light, and the quantum dots (C) emit blue light. For example, when blue light is incident as excitation light on a wavelength conversion layer including quantum dots (A) and quantum dots (B), red light emitted from the quantum dots (A) and quantum dots as shown in FIG. White light can be realized by the green light emitted by (B) and the blue light transmitted through the wavelength conversion layer. Alternatively, the red light emitted from the quantum dots (A) and the quantum dots (B) by making ultraviolet light incident on the wavelength conversion layer including the quantum dots (A), (B), and (C) as excitation light. White light can be realized by green light emitted by the blue light and blue light emitted by the quantum dots (C).

The loss rate of light emitted from the light source measured for the matrix of the wavelength conversion layer of the wavelength conversion member included in the backlight unit is 3% or less in terms of thickness of 60 μm. When the loss rate of the matrix of the wavelength conversion layer is 3% or less, the light from the light source can be prevented from being lost by the wavelength conversion layer. The present inventors presume that this point contributes to suppressing luminance reduction in a liquid crystal display device including the backlight unit. The loss rate is preferably less than 3%, more preferably less than 2%, and still more preferably less than 1%. For example, if the loss rate is 0.01% or more, the lower the better, the lower limit is not particularly limited. The method for measuring the loss rate is as described above.

The above loss rate is the loss rate of blue light when the light source included in the backlight unit is a blue light source. Further, when the light source is an ultraviolet light source, it is the loss rate of ultraviolet light. The light loss rate can be controlled, for example, by the formulation of the photocurable composition used to form the wavelength conversion layer. Details will be described later.

(Quantum dot-containing photocurable composition)
The wavelength conversion layer in the said wavelength conversion member is a photocuring layer formed by hardening a quantum dot containing photocurable composition by light irradiation. The quantum dot-containing photocurable composition (also referred to as “photocurable composition”) includes quantum dots, one or more polymerizable compounds including at least an alicyclic epoxy compound, and a photopolymerization initiator. The photocurable composition may contain other components such as an organometallic coupling agent.

(Quantum dot)
A quantum dot is a phosphor that takes discrete energy levels due to the quantum confinement effect. Examples of the shape of the quantum dot include various shapes such as a spherical shape, a rod shape, and a tetrapot type. The bar shape includes anisotropic shapes such as a needle shape, a cylindrical shape, a spheroid shape, and a polygonal column shape. There is no restriction | limiting in particular in the confirmation method of the shape of a quantum dot, For example, it can confirm using a transmission electron microscope. A rod-like quantum dot is also called a quantum rod.

From the viewpoint of expanding the color reproduction range of the liquid crystal display device by narrowing the full width at half maximum (FWHM), from the group consisting of spherical quantum dots and rod-like quantum dots (ie, quantum rods). The quantum dots chosen are preferred.

On the other hand, from the viewpoint of thinning the wavelength conversion layer, it is preferable to increase the concentration of quantum dots in the wavelength conversion layer. From this viewpoint, a quantum dot selected from the group consisting of rod-like quantum dots (that is, quantum rods) and tetrapod type quantum dots is preferable. Details are as follows. Quantum rods and tetrapod-type quantum dots have less reabsorption (also called self-absorption) of emitted light compared to spherical quantum dots, so even if the concentration in the wavelength conversion layer is increased, the emission quantum yield is reduced. There is a small tendency. Therefore, the thickness of the wavelength conversion layer can be reduced by increasing the concentration of quantum dots in the wavelength conversion layer. Thinning the wavelength conversion layer leads to a reduction in the amount of the epoxy matrix formed by photocuring using the alicyclic epoxy compound, thereby further reducing light loss from the light source. Furthermore, it is preferable that the wavelength conversion layer can be made thin because it leads to improvement in curability when photocuring is performed.

The quantum rod that can be used in the wavelength conversion layer is not particularly limited. For example, US Pat. No. 7,303,628, paper (Peng, X. G .; Manna, L .; Yang, W. D .; Wickham, j. Scher, E .; Kadavanich, A .; Alivisatos, A. P. Nature 2000, 404, 59-61), paper (Manna, L .; Scher, E. C .; Alivitas, A. Chem. Soc. 2000, 122, 12700-12706) can be used, and the contents of these documents are incorporated in the present invention.

The average long axis length (average value of the long axis length) of the quantum rod is not particularly limited, but is preferably in the range of 8 to 500 nm from the viewpoint of light emission characteristics, light emission efficiency, and the like, and is in the range of 10 to 160 nm. Is more preferable. The average major axis length is a value obtained by measuring the major axis lengths of 20 or more arbitrarily selected quantum rods with a microscope (for example, a transmission electron microscope) and arithmetically averaging them.
Moreover, the long axis of a quantum rod means the line segment in which the line segment which crosses a quantum rod becomes the longest in the two-dimensional image of the quantum rod obtained by observing with a microscope (for example, transmission electron microscope). The short axis is a line segment that is orthogonal to the long axis and has the longest line segment that crosses the quantum rod.
The average minor axis length (average minor axis length) of the quantum rod is not particularly limited, but is preferably in the range of 0.3 to 20 nm from the viewpoint of light emission characteristics, light emission efficiency, and the like, and in the range of 1 to 10 nm. More preferably. The average minor axis length is a value obtained by measuring the minor axis lengths of 20 or more arbitrarily selected quantum rods with a microscope (for example, a transmission electron microscope) and arithmetically averaging them.
2. The aspect ratio of the quantum rod (the long axis length of the quantum rod / the short axis length of the quantum rod) is preferably 1.5 or more from the viewpoints of better light emission characteristics, suppression of a decrease in light emission efficiency, and the like. 0 or more is more preferable. The upper limit is not particularly limited, but is preferably 20 or less from the viewpoint of ease of handling. The aspect ratio is an average value, and the aspect ratio of 20 or more arbitrarily selected quantum rods is measured with a microscope (for example, a transmission electron microscope), and is an arithmetic average value thereof.
A shape having an aspect ratio of 1.1 or less obtained by the above method is called a spherical shape, and a shape having an aspect ratio of more than 1.1 is called a rod shape.

A ligand having a Lewis basic coordinating group may be coordinated on the surface of the quantum dots of various shapes. Examples of Lewis basic coordinating groups include amino groups, carboxy groups, mercapto groups, phosphine groups, and phosphine oxide groups. Specific examples of the ligand include hexylamine, decylamine, hexadecylamine, octadecylamine, oleylamine, myristylamine, laurylamine, oleic acid, mercaptopropionic acid, trioctylphosphine, and trioctylphosphine oxide. it can. Of these, hexadecylamine, trioctylphosphine, and trioctylphosphine oxide are preferable, and trioctylphosphine oxide is particularly preferable.

Regarding quantum dots, in addition to the above description, for example, JP 2012-169271 A paragraphs 0060 to 0066 can be referred to, but the quantum dots are not limited thereto. As the quantum dots, commercially available products can be used without any limitation. The emission wavelength of the quantum dots can usually be adjusted by the composition and size of the particles, and the composition and size.

As the quantum dots, semiconductor particles having a core-shell structure in which the semiconductor constituting the core is covered with the semiconductor constituting the shell (core-shell type semiconductor particles) are preferable from the viewpoint of light emission efficiency. As the core, for example, multi-component semiconductor particles containing two or more kinds of atoms such as II-VI group semiconductor particles and III-V group semiconductor particles can be used. In one embodiment, these semiconductor particles can be so-called nanoparticles having a particle size of about several nanometers to several tens of nanometers. Specific examples of the semiconductors may constitute a core, CdSe, CdTe, CdS, ZnS , ZnSe, ZnTe, InP, InAs, InGaP, but CuInS _2, etc., without limitation. Among these, CdSe, CdTe, InP, InGaP, and CuInS ₂ are preferable because they can emit visible light with high efficiency. On the other hand, examples of the semiconductor that can constitute the shell include, but are not limited to, CdS, ZnS, ZnO, GaAs, and composites thereof.

Quantum dots may be added to the photocurable composition in the form of particles, or may be added in the form of a dispersion dispersed in a solvent. The addition in the state of a dispersion is preferable from the viewpoint of suppressing the aggregation of the quantum dot particles. The solvent used here is not particularly limited. The quantum dots can be added in an amount of, for example, about 0.01 to 10 parts by mass with respect to 100 parts by mass of the total amount of the photocurable composition.

(Alicyclic epoxy compound)
The photocurable compound contains at least an alicyclic epoxy compound as a polymerizable compound. The alicyclic epoxy compound may be one kind or two or more kinds having different structures. In addition, below, content regarding an alicyclic epoxy compound shall mean these total content, when using 2 or more types of alicyclic epoxy compounds from which a structure differs. This also applies to other components when two or more types having different structures are used. As described above, the alicyclic epoxy compound has better curability by light irradiation than the aliphatic epoxy compound. The use of a polymerizable compound having excellent photocurability is advantageous in that, in addition to improving productivity, a layer having uniform physical properties can be formed on the light irradiation side and the non-irradiation side. As a result, curling of the wavelength conversion layer can be suppressed and a wavelength conversion member with uniform quality can be provided. In general, epoxy compounds also tend to have less cure shrinkage during photocuring. This is advantageous in forming a smooth wavelength conversion layer with little deformation.

The alicyclic epoxy compound has at least one alicyclic epoxy group. Here, the alicyclic epoxy group means a monovalent substituent having a condensed ring of an epoxy ring and a saturated hydrocarbon ring, preferably a monovalent substituent having a condensed ring of an epoxy ring and a cycloalkane ring. It is. As a more preferable alicyclic epoxy compound, the following structure in which an epoxy ring and a cyclohexane ring are condensed:

There may be mentioned those having one or more per molecule. Two or more structures may be contained in one molecule, and preferably one or two in one molecule. In addition, the above structure may have one or more substituents. Examples of the substituent include alkyl groups (for example, alkyl groups having 1 to 6 carbon atoms), hydroxyl groups, alkoxy groups (for example, alkoxy groups having 1 to 6 carbon atoms), halogen atoms (for example, fluorine atoms, chlorine atoms, bromine atoms), cyano Group, amino group, nitro group, acyl group, carboxyl group and the like. The structure is preferably unsubstituted.

The alicyclic epoxy compound may have a polymerizable functional group other than the alicyclic epoxy group. The polymerizable functional group refers to a functional group capable of causing a polymerization reaction by radical polymerization or cationic polymerization, and examples thereof include a (meth) acryloyl group. In addition, the compound which has a (meth) acryloyl group with an alicyclic epoxy group shall calculate content mentioned later as an alicyclic epoxy compound.

Examples of commercially available products that can be suitably used as the alicyclic epoxy compound include Daicel Chemical Industries' Celoxide 2000, Celoxide 2021P, Celoxide 3000, Celoxide 8000, Cyclomer M100, Epolide GT301, Epolide GT401, and 4-vinyl manufactured by Sigma Aldrich. Examples thereof include cyclohexene dioxide, Nippon Terpene Chemical Co., Ltd. D-limonene oxide, Shin Nippon Chemical Co., Ltd. Sunsizer E-PS, and the like. These can be used individually by 1 type or in combination of 2 or more types. Among these, from the viewpoint of improving the adhesion between the wavelength conversion layer and the adjacent layer, the following alicyclic epoxy compounds A and B are particularly preferable. The alicyclic epoxy compound A can be obtained as Daicel Chemical Industries' Celoxide 2021P as a commercial product. The alicyclic epoxy compound B is commercially available as Daicel Chemical Industries, Ltd. Cyclomer M100.

The alicyclic epoxy compound can also be produced by a known synthesis method. The synthesis method does not matter. For example, Maruzen KK Publishing, 4th edition Experimental Chemistry Lecture 20 Organic Synthesis II, 213-, 1992, Ed.by Alfred Hasfner, The chemistry of heterocyclic compounds-Small Ring Heterocycles part3 Oxiranes, John & Wiley and Sons, An Interscience Publication, New York, 1985, Yoshimura, Adhesion, Vol. 29, No. 12, 32, 1985, Yoshimura, Adhesion, Vol. 30, No. 5, 42, 1986, Yoshimura, Adhesion, Vol. 42, 1986, Japanese Patent Application Laid-Open No. 11-1000037, Japanese Patent No. 2926262 and the like.

The alicyclic epoxy compound is a polymerizable compound that is excellent in curability by light irradiation as compared with the aliphatic epoxy compound as described above. However, the present inventors speculate that the alicyclic epoxy compound contributes to the absorption of light derived from the light source. Specifically, the product formed by oxidation of the ring-opened product in which the epoxy ring of the alicyclic epoxy compound is opened by light irradiation contributes to absorption of light derived from a light source such as blue light. I guess. Thus, one means for suppressing the absorption of light derived from the light source is to reduce the content of the alicyclic epoxy compound in the photocurable composition. The content of the alicyclic epoxy compound in the photocurable compound may be 100 parts by mass with respect to 100 parts by mass of the total amount of the polymerizable compound, preferably 90 parts by mass or less, more preferably 80 parts by mass or less, More preferably, it is 70 mass parts or less. Further, the content is, for example, 1 part by mass or more, and preferably 10 parts by mass or more, and 20 parts by mass or more from the viewpoint of obtaining good curability by using an alicyclic epoxy compound. More preferably, it is more preferably 30 parts by mass or more. Some organometallic coupling agents described later contain an alicyclic epoxy group. Such an alicyclic epoxy group-containing organometallic-containing coupling agent is also included in the alicyclic epoxy compound in calculating the content of the alicyclic epoxy compound. The content of such an alicyclic epoxy group-containing organometallic coupling agent in the photocurable composition is 0.1 to 20 parts by mass with respect to 100 parts by mass of the total amount of the alicyclic epoxy compound. Preferably, the content is 0.5 to 20 parts by mass.

(Polymerizable compound that can be used in combination with alicyclic epoxy compounds)
The photocurable compound may contain one or more other polymerizable compounds in addition to one or more alicyclic epoxy compounds as the polymerizable compound. Other polymerizable compounds are preferably (meth) acrylate compounds such as monofunctional (meth) acrylate compounds and polyfunctional (meth) acrylate compounds. Here, in the present invention and the present specification, the (meth) acrylate compound or (meth) acrylate means a compound containing one or more (meth) acryloyl groups in one molecule, and (meth) acryloyl group and Is used to denote one or both of an acryloyl group and a methallyloyl group. In addition, regarding the (meth) acrylate compound, monofunctional means that the number of (meth) acryloyl groups contained in one molecule is one, and polyfunctional means (meth) acryloyl contained in one molecule. It shall be said that the number of groups is two or more. The present inventors presume that the combined use of an alicyclic epoxy compound and a (meth) acrylate compound contributes to suppressing the absorption of light derived from the light source of the wavelength conversion layer matrix. Details are as follows. As described above, the present inventors presume oxidation of a ring-opened product in which an epoxy group of an alicyclic epoxy compound is opened as a cause of absorption of light derived from a light source. On the other hand, the (meth) acrylate compound is a radical polymerizable compound, and it is considered that a part of the radical generated during polymerization is combined with oxygen in the reaction system. As a result of the reduction of oxygen in the reaction system, the present inventors consider that preventing the ring-opened body from being oxidized may contribute to the above-described absorption suppression. However, the above is an inference by the present inventors and does not limit the present invention.

The content of the (meth) acrylate compound in the photocurable composition is preferably 0 to 99 parts by mass, more preferably 30 to 70 parts by mass with respect to 100 parts by mass of the total amount of the polymerizable compounds. Moreover, from the point that there is little cure shrinkage, as a (meth) acrylate compound, a monofunctional (meth) acrylate compound is preferable. The content of the monofunctional (meth) acrylate compound in the photocurable composition is preferably 0 to 99 parts by mass, more preferably 30 to 70 parts by mass with respect to 100 parts by mass of the total amount of the polymerizable compounds. . Some organometallic coupling agents described later include a (meth) acryloyl group. Such a (meth) acryloyl group-containing organometallic-containing coupling agent is also included in the (meth) acrylate compound in calculating the content of the (meth) acrylate compound. In addition, the content of such a (meth) acryloyl group-containing organometallic coupling agent in the photocurable composition may be 0.1 to 20 parts by mass with respect to 100 parts by mass of the total amount of (meth) acrylate compounds. Preferably, the content is 0.5 to 10 parts by mass.

Monofunctional (meth) acrylate compounds include acrylic acid and methacrylic acid, derivatives thereof, and more specifically, compounds having one polymerizable unsaturated bond ((meth) acryloyl group) of (meth) acrylic acid in the molecule Can be mentioned. Specific examples thereof include the following compounds, but the present invention is not limited thereto. In addition, said (meth) acrylic acid shall show one or both of acrylic acid and methacrylic acid.
Methyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, stearyl ( Alkyl (meth) acrylates having an alkyl group such as meth) acrylate having 1 to 30 carbon atoms; aralkyl (meth) acrylates having an aralkyl group such as benzyl (meth) acrylate having 7 to 20 carbon atoms; butoxyethyl (meth) ) An alkoxyalkyl (meth) acrylate having 2 to 30 carbon atoms of an alkoxyalkyl group such as acrylate; the total carbon number of a (monoalkyl or dialkyl) aminoalkyl group such as N, N-dimethylaminoethyl (meth) acrylate; 1-2 An aminoalkyl (meth) acrylate which is: (meth) acrylate of diethylene glycol ethyl ether, (meth) acrylate of triethylene glycol butyl ether, (meth) acrylate of tetraethylene glycol monomethyl ether, (meth) acrylate of hexaethylene glycol monomethyl ether, Octaethylene glycol monomethyl ether (meth) acrylate, nonaethylene glycol monomethyl ether (meth) acrylate, dipropylene glycol monomethyl ether (meth) acrylate, heptapropylene glycol monomethyl ether (meth) acrylate, tetraethylene glycol monoethyl Alkyl chain such as ether (meth) acrylate has 1 to 10 carbon atoms and terminal alkyl (Meth) acrylate of polyalkylene glycol alkyl ether having 1 to 10 carbon atoms in ether; alkylene chain such as (meth) acrylate of hexaethylene glycol phenyl ether having 1 to 30 carbon atoms and terminal aryl ether having 6 carbon atoms (Meth) acrylate of -20 polyalkylene glycol aryl ethers; cycloaliphatic structures such as cyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, isobornyl (meth) acrylate, and methylene oxide-added cyclodecatriene (meth) acrylate (Meth) acrylates having a total carbon number of 4 to 30; fluorinated alkyl (meth) acrylates having a total carbon number of 4 to 30 such as heptadecafluorodecyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, mono (meth) acrylate of triethylene glycol, tetraethylene glycol mono (meth) acrylate, hexaethylene glycol mono (meth) acrylate, octapropylene glycol mono (Meth) acrylate, (meth) acrylate having a hydroxyl group such as mono- or di (meth) acrylate of glycerol; (meth) acrylate having a glycidyl group such as glycidyl (meth) acrylate; tetraethylene glycol mono (meth) acrylate, Polyethylene glycol polymers having 1 to 30 carbon atoms in the alkylene chain such as hexaethylene glycol mono (meth) acrylate and octapropylene glycol mono (meth) acrylate (Meth) acrylate; (meth) acrylamide, N, N- dimethyl (meth) acrylamide, N- isopropyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylamide, acryloyl morpholine (meth) acrylamide and the like. Among these, from the viewpoint of adhesion between the wavelength conversion layer and the adjacent layer, monofunctional (meth) acrylate having a polar functional group is preferable. Preferable polar functional groups include a hydroxy group and a phenyl group. As specific compounds, benzyl acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, 1,4-cyclohexanedimethanol monoacrylate, 2-hydroxy-3-phenoxypropyl acrylate, and 4-hydroxybutyl acrylate are particularly preferable.

(Photopolymerization initiator)
The photocurable composition contains one or more photopolymerization initiators in order to enable curing by light irradiation. A photopolymerization initiator is a compound that can be decomposed by exposure to generate radicals, acids, bases, and other starting species, and can be used to initiate and accelerate the polymerization reaction of a polymerizable compound. is there. Since the alicyclic epoxy compound is a compound capable of cationic polymerization, the photocurable composition preferably contains one or more photocationic polymerization initiators as a photopolymerization initiator. Moreover, since an alicyclic epoxy compound is also an anion polymerizable compound, it is also preferable that the said photocurable composition contains 1 type, or 2 or more types of photo anionic polymerization initiators as a photoinitiator.

Regarding the photocationic polymerization initiator, reference can be made, for example, to paragraphs 0019 to 0024 of Japanese Patent No. 4675719. The photocationic polymerization initiator is preferably contained in an amount of 0.1 mol% or more, more preferably 0.5 to 5 mol% of the total amount of the polymerizable compounds contained in the photocurable composition. Use of an appropriate amount of the polymerization initiator is preferable from the viewpoint of reducing the amount of light irradiation for curing and uniformly curing the entire wavelength conversion layer.

Preferred examples of the cationic photopolymerization initiator include iodonium salt compounds, sulfonium salt compounds, pyridinium salt compounds, and phosphonium salt compounds. Examples of the anion part (counter anion) contained in these salt compounds include CH ₃ SO ₃ ⁻ , C ₆ H ₅ SO ₃ ⁻ , CF ₃ SO ₃ ⁻ , PF ₆ ⁻ , HSbF ₆ ⁻ , HB (C _6). F ₅₎ ₄ ^- can be exemplified. Among these, iodonium salt compounds, sulfonium salt compounds, pyridinium salt compounds, and phosphonium salt compounds having a gas phase acidity in the range of 240 to 290 kcal / mol from the viewpoint of curing speed are preferable. The range of gas phase acidity is more preferably 240 to 280 kcal / mol, and still more preferably 240 to 270 kcal / mol.

Among them, iodonium salt compounds and sulfonium salt compounds are preferable from the viewpoint of excellent thermal stability, and iodonium salt compounds are particularly preferable from the viewpoint of suppressing absorption of light derived from the light source of the wavelength conversion layer. One possible reason why the wavelength conversion layer absorbs light derived from the light source is absorption due to decomposition products of the photopolymerization initiator. However, iodonium salt compounds are difficult to generate decomposition products that contribute to such absorption. The inventors speculate. However, the above is an inference by the present inventors and does not limit the present invention.

The iodonium salt compound is a salt formed by a cation part including I ⁺ in the structure and an anion part having an arbitrary structure, and has three or more electron donating groups. More preferred are diaryliodonium salts, one of which is an alkoxy group. By introducing an alkoxy group, which is an electron donating group, into the diaryliodonium salt in this way, stability is improved due to the ability to suppress decomposition with water and nucleophiles over time and electron transfer due to heat. It is thought that. Specific examples of the iodonium salt compound having such a structure include the following photocationic polymerization initiators (iodonium salt compounds) A and B. Specific examples of the iodonium salt compound having an anion portion having a gas phase acidity in the range of 240 to 290 kcal / mol include the following photocationic polymerization initiator (iodonium salt compound) C.

In addition, absorption of light derived from the light source of the wavelength conversion layer is not performed by using an iodonium salt compound, but by means such as a reduction in the content of an alicyclic epoxy compound or a combined use of a (meth) acrylate compound as described above. Since it can also be reduced, the photocationic polymerization initiator that can be added to the photocurable compound is not limited to the iodonium salt compound. Examples of usable photocationic polymerization initiators include one or a combination of two or more of the following commercially available products: CPI-110P (photocationic polymerization initiator D below), CPI-101A, manufactured by Sun Apro CPI-110P, CPI-200K, WPI-113 manufactured by Wako Pure Chemical Industries, WPI-116, WPI-124, WPI-169, WPI-170, Rhodia PI-2074, BASF Irgacure (registered) Trademark) 250, Irgacure 270, Irgacure 290 (the following photocationic polymerization initiator E).

On the other hand, as for the photoanion polymerization initiator, reference can be made to, for example, paragraphs 0039 to 0053 of JP2013-235216A. The photoanionic polymerization initiator is preferably contained in an amount of 0.5 to 50 mol%, more preferably 1 to 40 mol% of the total amount of the polymerizable compound contained in the photocurable composition.

In addition, when the photocurable composition contains a radical polymerizable compound, the photocurable composition may contain one or more types of photo radical polymerization initiators. As for the photoradical initiator, reference can be made to, for example, paragraphs 0037 and 0042 of JP2013-043382A and paragraphs 0040 to 0042 of JP2011-159924A. The content of the photo radical 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 photocurable composition.

(Organic metal coupling agent)
The photocurable composition may contain an organometallic coupling agent in order to improve the adhesion between the wavelength conversion layer and the adjacent layer. The organometallic coupling agent is an organic compound containing a metal atom such as Si, Ti, Zr, Al, and Sn and having both a hydrolyzable group and a reactive functional group. Examples of hydrolyzable groups include alkoxy groups (RO-) and alkylcarbonyloxy groups (RCOO-). Reactive functional groups include epoxy groups such as alicyclic epoxy groups, and (meth) acryloyl. Group, amino group, vinyl group, mercapto group and the like. In the above, R represents an alkyl group. The organometallic coupling agent is effective because it also has the effect of promoting the thermosetting reaction. As the organometallic coupling agent, for example, various coupling agents such as a silane coupling agent, a titanium coupling agent, a zirconium coupling agent, an aluminum coupling agent, and a tin coupling agent can be used. These organometallic coupling agents are in close contact when the layer adjacent to the wavelength conversion layer is a layer of an inorganic material such as a metal, a metal oxide, or a metal nitride, or a layer containing these inorganic materials in a resin. The improvement effect is large and particularly preferable.

Examples of the silane coupling agent that can be added to the photocurable composition include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3 -Glycidoxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxy Propyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropylto Ethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (Aminoethyl) -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine and its Partial hydrolyzate, 3-trimethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine and its partial hydrolyzate, N-phenyl-3-aminopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane , 3-mercaptopropyltrimethoxysilane, - an isocyanate propyl triethoxysilane and the like. Of these, vinyl, epoxy, (meth) acryloyloxy, amino, and isocyanate-modified silane coupling agents are preferable, and (meth) acryloyloxy-modified silane coupling agents are particularly preferable. These can be used alone or in combination of two or more.

Examples of commercially available silane coupling agents that can be suitably used include those manufactured by Shin-Etsu Chemical Co., Ltd. Examples thereof include KBM-502, KBM-503, KBM-5103, KBE-502, KBE-503, KBM-903, and KBM-9103 manufactured by Shin-Etsu Chemical Co., Ltd.

Further, examples of the silane coupling agent include a silane coupling agent represented by the general formula (1) described in JP2013-43382A. For details, reference can be made to the descriptions in paragraphs 0011 to 0016 of JP2013-43382A.

From the viewpoint of further improving the adhesion between the wavelength conversion layer and the adjacent layer, the organometallic coupling agent is incorporated into the photocurable composition from the total mass of the photocurable composition to the mass of the quantum dots and the solvent. Is preferably contained in the range of 0.1 to 20 parts by weight, more preferably in the range of 0.5 to 10 parts by weight, and in the range of 1 to 5 parts by weight. More preferably it is included.

(Base generator)
In one aspect, a base generator may be blended with the photocurable composition. The base generator means a compound that generates a base by heating or light irradiation. For example, the base can be generated from the base generator by applying heat or irradiating light to the wavelength conversion layer formed by irradiating the photocurable composition containing the base generator. As an example, in the wavelength conversion layer, for example, when sunlight or light from a light source is incident on the wavelength conversion layer, or heat is applied from the outside during a heat resistance test of a wavelength conversion member that can be arbitrarily performed, etc. A base can be generated from the base generator. The base generated here can neutralize the acid when the wavelength conversion layer contains an acid for some reason. It is preferable to neutralize the acid because it can contribute to preventing the change in performance of the wavelength conversion layer over time. In one aspect, the acid generation factor includes a polymerization reaction (curing reaction) in the presence of a photocationic polymerization initiator. Therefore, it is preferable to mix a base generator with a photocurable composition containing a photocationic polymerization initiator.

The base generator is not particularly limited as long as it is a compound that generates a base by heating or light irradiation. For example, 2- (4-biphenyl) -2-propylcarbamate, carbamate derivatives such as 1,1-dimethyl-2-cyanoethylcarbamate, dihydropyridine derivatives such as 1,4-dihydronicotinamide, dicyandiamide, organic salts and inorganic salts A salt composed of an acid and a base is generally known as a base generator, and can be preferably used in the photocurable composition. Among them, a salt composed of an acid and a base is preferable because the composition containing the salt is excellent in stability and relatively inexpensive. Among these, from the viewpoint of compatibility with the polymerizable compound, a salt of an acid and an amine compound is preferable, and an organic salt of an organic acid and an amine compound is more preferable.

The content of the base generator in the photocurable composition is, for example, 0.01 parts by mass or more, preferably 0.1 parts by mass or more, and for example, 20 parts by mass or less with respect to 100 parts by mass of the total amount of the polymerizable compounds. , Preferably 10 parts by mass or less, more preferably 2 parts by mass or less.

(Viscosity modifier)
The photocurable composition may contain a viscosity modifier as necessary. The viscosity modifier is preferably a filler having a particle size of 5 nm to 300 nm. The viscosity modifier is also preferably a thixotropic agent. In the present invention and the present specification, thixotropic property refers to a property of reducing the viscosity with respect to an increase in shear rate in a liquid composition, and a thixotropic agent is a composition obtained by including it in the liquid composition. It refers to a material having a function of imparting thixotropy to an object. Specific examples of thixotropic agents include fumed silica, alumina, silicon nitride, titanium dioxide, calcium carbonate, zinc oxide, talc, mica, feldspar, kaolinite (kaolin clay), pyrophyllite (waxite clay), and sericite. (Sericite), bentonite, smectite vermiculites (montmorillonite, beidellite, nontronite, saponite, etc.), organic bentonite, organic smectite and the like.
In one embodiment, the photocurable composition has a viscosity of 3 to 100 mPa · s when the shear rate is 500 s ⁻¹ , and preferably 300 mPa · s or more when the shear rate is 1 s ⁻¹ . In order to adjust the viscosity in this way, it is preferable to use a thixotropic agent. The reason why the viscosity of the photocurable composition is preferably 3 to 100 mPa · s when the shear rate is 500 s ⁻¹ and preferably 300 mPa · s or more when the shear rate is 1 s ⁻¹ is as follows.
As an example of the manufacturing method of a wavelength conversion member, after apply | coating a photocurable composition to a 1st base material, a 2nd base material is affixed on a photocurable composition so that it may mention later. From the above, a production method including the step of curing the photocurable composition to form the wavelength conversion layer can be mentioned. In the above production method, it is desirable that the coating film is uniformly applied so that no coating stripes are formed when the photocurable composition is applied to the first substrate, and for this purpose, the coating film is made uniform. The viscosity of the coating liquid (photocurable composition) is preferably low from the viewpoints of properties and leveling properties. On the other hand, in order to uniformly bond the second substrate onto the coating solution applied to the first substrate, it is preferable that the resistance to pressure at the time of bonding is high. A coating solution is preferred. The shear rate of 500 s ⁻¹ is a representative value of the shear rate applied to the coating solution applied to the first substrate, and the shear rate of 1 s ⁻¹ is just before the second substrate is bonded to the coating solution. This is a representative value of the shear rate applied to the coating solution. The shear rate 1 s ⁻¹ is merely a representative value. When the second substrate is bonded onto the coating solution applied to the first substrate, the first substrate and the second substrate are bonded to each other while being transported at the same speed. The applied shear rate is approximately ^{0 s −1} , and the shear rate applied to the coating solution in the actual manufacturing process is not limited to 1 s ⁻¹ . Similarly, the shear rate of 500 s ⁻¹ is merely a representative value, and the shear rate applied to the coating solution in the actual manufacturing process is not limited to 500 s ⁻¹ . From the viewpoint of uniform application and bonding, the viscosity of the photocurable composition is 3 to 100 mPa when the representative value of the shear rate applied to the application liquid is 500 s ^-1 when the application liquid is applied to the first substrate. S, so that it is 300 mPa · s or more when the representative value of the shear rate applied to the coating solution is 1 s ⁻¹ immediately before the second substrate is bonded onto the coating solution applied to the first substrate. It is preferable to adjust.

(Light scattering particles)
In one aspect, the wavelength conversion layer may contain light scattering particles. Therefore, light scattering particles may be added to the photocurable composition.

As described above, the particle size of the light scattering particles is 0.10 μm or more. It is preferable from the viewpoint of further improving the brightness that the light scattering particles are contained in the wavelength conversion layer. From the viewpoint of the light scattering effect, the particle size of the light scattering particles is preferably in the range of 0.10 to 15.0 μm, more preferably in the range of 0.10 to 10.0 μm, and 0.20 to 4 More preferably, it is 0.0 μm. Further, in order to further improve the luminance and adjust the luminance distribution with respect to the viewing angle, two or more kinds of light scattering particles having different particle sizes may be mixed and used.

The light scattering particles may be organic particles, inorganic particles, or organic-inorganic composite particles. For example, as the organic particles, synthetic resin particles can be exemplified. Specific examples include silicone resin particles, acrylic resin particles (polymethyl methacrylate (PMMA)), nylon resin particles, styrene resin particles, polyethylene particles, urethane resin particles, benzoguanamine particles, and the like. From the viewpoint of the light scattering effect, it is preferable that the refractive index of the light scattering particles and other parts in the matrix of the wavelength conversion layer is different. From this point of view, the silicone is preferable from the viewpoint of availability of particles having a suitable refractive index. Resin particles and acrylic resin particles are preferred. Also, particles having a hollow structure can be used. Moreover, as inorganic particles, particles such as diamond, titanium oxide, zirconium oxide, lead oxide, lead carbonate, zinc oxide, zinc sulfide, antimony oxide, silicon oxide, and aluminum oxide can be used and have a suitable refractive index. From the viewpoint of availability of particles, titanium oxide and aluminum oxide are preferable.

From the viewpoint of the light scattering effect and the brittleness of the wavelength conversion layer containing this particle, the light scattering particles should be contained in the wavelength conversion layer in an amount of 0.20% by volume or more on a volume basis with the entire wavelength conversion layer being 100% by volume. Preferably 0.20% by volume to 50% by volume, more preferably 0.20% by volume to 30% by volume, and even more preferably 0.20% by volume to 10% by volume. . Therefore, in order to obtain such a wavelength conversion layer, a photocurable composition containing 0.20% by volume or more of light scattering particles on a volume basis with respect to the total solid content of the composition is used as the photocurable composition. preferable. More preferred ranges are the same as above.

Furthermore, in order to adjust the refractive index of the portion excluding the light scattering particles of the matrix, particles having a particle size smaller than that of the light scattering particles can be used as the refractive index adjusting particles. The particle size of the refractive index adjusting particles is less than 0.10 μm.
Examples of the refractive index adjusting particles include particles of diamond, titanium oxide, zirconium oxide, lead oxide, lead carbonate, zinc oxide, zinc sulfide, antimony oxide, silicon oxide, aluminum oxide, and the like. Among them, zirconium oxide and silicon oxide particles are preferable from the viewpoint of little absorption of blue light and ultraviolet light, and zirconium oxide particles are preferable because the refractive index can be adjusted with a small amount. The refractive index adjusting particles may be used in an amount capable of adjusting the refractive index, and the content in the light scattering layer is not particularly limited.

(solvent)
The said photocurable composition may contain the solvent as needed. In this case, the type and amount of the solvent used are not particularly limited. For example, one or a mixture of two or more organic solvents can be used as the solvent.

(Method for forming wavelength conversion layer)
The wavelength conversion layer can be formed by applying a photocurable composition to the surface of a substrate such as a substrate or a barrier film, and then curing the composition by light irradiation.
Application methods include curtain coating, dip coating, spin coating, print coating, spray coating, slot coating, roll coating, slide coating, blade coating, gravure coating, wire bar method, etc. A well-known coating method is mentioned.
Curing conditions can be appropriately set according to the type of polymerizable compound used and the composition of the photocurable composition. Moreover, when a photocurable composition is a composition containing a solvent, before hardening, you may give a drying process for solvent removal.

The photocurable composition may be cured in a state where the photocurable composition is sandwiched between two substrates. One aspect of the manufacturing process of the wavelength conversion member including such a curing process will be described below with reference to the drawings. However, the present invention is not limited to the following embodiments.

FIG. 2 is a schematic configuration diagram of an example of a wavelength conversion member manufacturing apparatus, and FIG. 3 is a partial enlarged view of the manufacturing apparatus shown in FIG. The manufacturing process of the wavelength conversion member using the manufacturing apparatus shown in FIGS. 2 and 3 applies a photocurable composition to the surface of a first substrate (hereinafter referred to as “first film”) that is continuously conveyed. A step of forming a coating film, and a second substrate (hereinafter also referred to as “second film”) that is continuously conveyed are laminated (overlaid) on the coating film, and the first film and the first film In the state where the coating film is sandwiched between the film 2 and the coating film is sandwiched between the first film and the second film, either the first film or the second film is wound around the backup roller. And at least a step of forming a wavelength conversion layer (cured layer) by irradiating with light while continuously transporting and polymerizing and curing the coating film. By using a barrier film having a barrier property against oxygen or moisture as either the first film or the second film, a wavelength conversion member having one surface protected by the barrier film can be obtained. Moreover, the wavelength conversion member by which the both surfaces of the wavelength conversion layer were protected by the barrier film can be obtained by using a barrier film as a 1st film and a 2nd film, respectively.

More specifically, first, the first film 10 is continuously conveyed from the unillustrated transmitter to the coating unit 20. For example, the first film 10 is delivered from the delivery machine at a conveyance speed of 1 to 50 m / min. However, it is not limited to this conveyance speed. When delivered, for example, a tension of 20 to 150 N / m, preferably a tension of 30 to 100 N / m is applied to the first film 10. *

In the coating unit 20, a photocurable composition (hereinafter also referred to as “coating liquid”) is applied to the surface of the first film 10 that is continuously conveyed, and a coating film 22 (see FIG. 3) is formed. . In the coating unit 20, for example, a die coater 24 and a backup roller 26 disposed to face the die coater 24 are installed. The surface opposite to the surface on which the coating film 22 of the first film 10 is formed is wound around the backup roller 26, and the coating liquid is applied from the discharge port of the die coater 24 onto the surface of the first film 10 that is continuously conveyed. As a result, the coating film 22 is formed. Here, the coating film 22 refers to a photocurable composition before curing applied on the first film 10.

In the present embodiment, the die coater 24 to which the extrusion coating method is applied is shown as the coating apparatus, but the present invention is not limited to this. For example, a coating apparatus to which various methods such as a curtain coating method, an extrusion coating method, a rod coating method, or a roll coating method are applied can be used.

The first film 10 having passed through the coating unit 20 and having the coating film 22 formed thereon is continuously conveyed to the laminating unit 30. In the laminating unit 30, the second film 50 that is continuously conveyed is laminated on the coating film 22, and the coating film 22 is sandwiched between the first film 10 and the second film 50.

The laminating unit 30 is provided with a laminating roller 32 and a heating chamber 34 surrounding the laminating roller 32. The heating chamber 34 is provided with an opening 36 for allowing the first film 10 to pass therethrough and an opening 38 for allowing the second film 50 to pass therethrough.

A backup roller 62 is disposed at a position facing the laminating roller 32. The first film 10 on which the coating film 22 is formed is wound around the backup roller 62 on the surface opposite to the surface on which the coating film 22 is formed, and is continuously conveyed to the laminating position P. The laminating position P means a position where the contact between the second film 50 and the coating film 22 starts. The first film 10 is preferably wound around the backup roller 62 before reaching the laminating position P. This is because even if wrinkles occur in the first film 10, the wrinkles are corrected and removed by the backup roller 62 before reaching the laminate position P. Therefore, the position (contact position) where the first film 10 is wound around the backup roller 62 and the distance L1 to the lamination position P are preferably long, for example, 30 mm or more is preferable, and the upper limit is usually It is determined by the diameter of the backup roller 62 and the pass line.

In the present embodiment, the second film 50 is laminated by the backup roller 62 and the laminating roller 32 used in the curing unit 60. That is, the backup roller 62 used in the curing unit 60 is also used as a roller used in the laminating unit 30. However, the present invention is not limited to the above form, and a laminating roller may be installed in the laminating unit 30 in addition to the backup roller 62 so that the backup roller 62 is not used.

By using the backup roller 62 used in the curing unit 60 in the laminating unit 30, the number of rollers can be reduced. The backup roller 62 can also be used as a heat roller for the first film 10.

The second film 50 sent from a sending machine (not shown) is wound around the laminating roller 32 and continuously conveyed between the laminating roller 32 and the backup roller 62. The second film 50 is laminated on the coating film 22 formed on the first film 10 at the laminating position P. Accordingly, the coating film 22 is sandwiched between the first film 10 and the second film 50. Lamination refers to laminating the second film 50 on the coating film 22.

The distance L2 between the laminating roller 32 and the backup roller 62 is a value of the total thickness of the first film 10, the wavelength conversion layer (cured layer) 28 obtained by polymerizing and curing the coating film 22, and the second film 50. The above is preferable. Moreover, it is preferable that L2 is below the length which added 5 mm to the total thickness of the 1st film 10, the coating film 22, and the 2nd film 50. FIG. By setting the distance L2 to be equal to or shorter than the total thickness plus 5 mm, it is possible to prevent bubbles from entering between the second film 50 and the coating film 22. Here, the distance L <b> 2 between the laminating roller 32 and the backup roller 62 refers to the shortest distance between the outer peripheral surface of the laminating roller 32 and the outer peripheral surface of the backup roller 62.

Rotational accuracy of the laminating roller 32 and the backup roller 62 is 0.05 mm or less, preferably 0.01 mm or less in radial runout. The smaller the radial runout, the smaller the thickness distribution of the coating film 22.

Further, 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 backup roller 62 of the curing unit 60 and the temperature of the first film 10. The difference between the temperature of the backup roller 62 and the temperature of the second film 50 is preferably 30 ° C. or less, more preferably 15 ° C. or less, and most preferably the same.

In order to reduce the difference from the temperature of the backup roller 62, when the heating chamber 34 is provided, it is preferable to heat the first film 10 and the second film 50 in the heating chamber 34. For example, hot air is supplied to the heating chamber 34 by a hot air generator (not shown), and the first film 10 and the second film 50 can be heated.

The first film 10 may be heated by the backup roller 62 by being wound around the backup roller 62 whose temperature has been adjusted.

On the other hand, the second film 50 can be heated by the laminating roller 32 by using the laminating roller 32 as a heat roller.
However, the heating chamber 34 and the heat roller are not essential and can be provided as necessary.

Next, the film 22 is continuously conveyed to the curing unit 60 in a state where the coating film 22 is sandwiched between the first film 10 and the second film 50. Curing in the curing unit 60 is performed by light irradiation.

A light irradiation device 64 is provided at a position facing the backup roller 62 and the backup roller 62. The first film 10 and the second film 50 sandwiching the coating film 22 are continuously conveyed between the backup roller 62 and the light irradiation device 64. What is necessary is just to determine the light irradiated by a light irradiation apparatus according to the kind of polymeric compound contained in a photocurable composition, and an ultraviolet-ray is mentioned as an example. As a light source that generates ultraviolet rays, for example, 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, a xenon lamp, or the like can be used. The light irradiation amount may be set within a range in which the polymerization and curing of the coating film can proceed. For example, the coating film 22 can be irradiated with ultraviolet rays having an irradiation amount of 100 to 10,000 mJ / cm ² .

In the curing unit 60, the first film 10 is wound around the backup roller 62 in a state where the coating film 22 is sandwiched between the first film 10 and the second film 50, and is continuously transported from the light irradiation device 64. The wavelength conversion layer (photocured layer) 28 can be formed by performing light irradiation to cure the coating film 22.

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

“Wrapping around the backup roller 62” means a state in which one of the first film 10 and the second film 50 is in contact with the surface of the backup roller 62 at a certain wrap angle. Accordingly, the first film 10 and the second film 50 move in synchronization with the rotation of the backup roller 62 while being continuously conveyed. Winding around the backup roller 62 may be at least during the irradiation of ultraviolet rays.

The backup roller 62 includes a cylindrical main body and rotating shafts arranged at both ends of the main body. The main body of the backup roller 62 has a diameter of φ200 to 1000 mm, for example. There is no restriction on the diameter φ of the backup roller 62. In consideration of curl deformation of the laminated film, equipment cost, and rotational accuracy, the diameter is preferably 300 to 500 mm. The temperature of the backup roller 62 can be adjusted by attaching a temperature controller to the main body of the backup roller 62.

The temperature of the backup roller 62 takes into consideration the heat generation during light irradiation, the curing efficiency of the coating film 22, and the occurrence of wrinkle deformation on the backup roller 62 of the first film 10 and the second film 50. Can be determined. The backup roller 62 is preferably set to a temperature range of 10 to 95 ° C., for example, and more preferably 15 to 85 ° C. Here, the temperature related to the roller refers to the surface temperature of the roller.

The distance L3 between the laminate position P and the light irradiation device 64 can be set to 30 mm or more, for example.

The coating film 22 becomes the 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 conversion member 70 is peeled from the backup roller 62 by the peeling roller 80. The wavelength conversion member 70 is continuously conveyed to a winder (not shown), and then the wavelength conversion member 70 is wound into a roll by the winder.

As mentioned above, although one aspect of the manufacturing process of the wavelength conversion member has been described, the present invention is not limited to the above aspect. For example, a photocurable composition is applied onto a substrate such as a substrate or a barrier film, and a curing is performed after a drying treatment as necessary without laminating a further substrate thereon. The wavelength conversion layer (photocured layer) may be formed by One or more other layers such as an inorganic layer may be laminated on the formed wavelength conversion layer by a known method.

The thickness of the wavelength conversion layer is preferably in the range of 1 to 500 μm, more preferably in the range of 10 to 250 μm, and still more preferably in the range of 30 to 150 μm. A thickness of 1 μm or more is preferable because a high wavelength conversion effect can be obtained. Further, it is preferable that the thickness is 500 μm or less because the backlight unit can be thinned when incorporated in the backlight unit.

(Base material)
The wavelength conversion member may have a base material for strength improvement, film formation ease, and the like. The base material may be included as a layer adjacent to the wavelength conversion layer. One or two or more base materials may be included in the wavelength conversion member, and the wavelength conversion member may have a structure in which the base material, the wavelength conversion layer, and the base material are laminated in this order. Good. When the wavelength conversion member includes two or more base materials, the base materials may be the same or different. The substrate is preferably transparent to visible light. Here, being 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 is measured by measuring the total light transmittance and the amount of scattered light using the method described in JIS-K7105, that is, using an integrating sphere light transmittance measuring device. It can be calculated by subtracting the rate.

The thickness of the substrate is preferably in the range of 10 μm to 500 μm, more preferably in the range of 15 to 400 μm, and particularly in the range of 20 to 300 μm from the viewpoint of gas barrier properties, impact resistance and the like.

Further, the base material can be used as either or both of the first film and the second film described above.

The base material can also be a barrier film. The barrier film is a film having a gas barrier function of blocking oxygen molecules. It is also preferable that the barrier film has a function of blocking water vapor.

The barrier film usually only needs to include at least an inorganic layer, and may be a film including a support film and an inorganic layer. Regarding the support film, for example, refer to paragraphs 0046 to 0052 of JP-A-2007-290369 and paragraphs 0040 to 0055 of JP-A-2005-096108. The barrier film may include a barrier laminate including at least one inorganic layer and at least one organic layer on the support film. As an example, laminated structure of support film / organic layer / inorganic layer, laminated structure of support film / inorganic layer / organic layer, laminated structure of support film / organic layer / inorganic layer / organic layer (here, two layers In the organic layer, one or both of the thickness and the composition may be the same or different). Laminating a plurality of layers in this way can further enhance the barrier property, and on the other hand, the light transmittance of the wavelength conversion member tends to decrease as the number of layers to be laminated increases, which is favorable. It is desirable to increase the number of stacked layers as long as a sufficient light transmittance can be maintained. Specifically, the barrier film preferably has an oxygen permeability of 1 cm ³ / (m ² · day · atm) or less. Here, the oxygen permeability is a value measured using an oxygen gas permeability measuring apparatus (OX-TRAN 2/20: trade name, manufactured by MOCON) under the conditions of a measurement temperature of 23 ° C. and a relative humidity of 90%. is there. The barrier film preferably has a total light transmittance of 80% or more in the visible light region. The visible light region refers to a wavelength region of 380 to 780 nm, and the total light transmittance indicates an average value of light transmittance over the visible light region.
The oxygen permeability of the barrier film is more preferably 0.1 cm ³ / (m ² · day · atm) or less, and more preferably 0.01 cm 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, the better, and the higher the total light transmittance in the visible light region, the better.

―Inorganic layer―
The “inorganic layer” is a layer mainly composed of an inorganic material, and is preferably a layer formed only from an inorganic material. On the other hand, the organic layer is a layer mainly composed of an organic material, and preferably refers to a layer in which the organic material occupies 50% by mass or more, more preferably 80% by mass or more, and particularly 90% by mass or more. To do.
The inorganic material constituting the inorganic layer is not particularly limited, and for example, various inorganic compounds such as metals or inorganic oxides, nitrides, oxynitrides, and the like can be used. As an element constituting the inorganic material, silicon, aluminum, magnesium, titanium, tin, indium and cerium are preferable, and one or two or more of these may be included. Specific examples of the inorganic compound include silicon oxide, silicon oxynitride, aluminum oxide, magnesium oxide, titanium oxide, tin oxide, indium oxide alloy, silicon nitride, aluminum nitride, and titanium nitride. As the inorganic layer, a metal film such as an aluminum film, a silver film, a tin film, a chromium film, a nickel film, or a titanium film may be provided.

Among the above materials, silicon nitride, silicon oxide, or silicon oxynitride is particularly preferable. This is because the inorganic layer made of these materials has a good adhesion to the organic layer, and thus the barrier property can be further enhanced.
A method for forming the inorganic layer is not particularly limited, and various film forming methods that can evaporate or scatter the film forming material and deposit it on the deposition surface can be used.

Examples of the method for forming the inorganic layer include a vacuum evaporation method in which an inorganic material such as an inorganic oxide, an inorganic nitride, an inorganic oxynitride, or a metal is heated and evaporated; an inorganic material is used as a raw material, and oxygen gas is introduced. Oxidation reaction vapor deposition method for oxidizing and vapor deposition; sputtering method using inorganic material as target raw material, introducing argon gas and oxygen gas and performing sputtering; plasma generated on inorganic material with plasma gun Physical vapor deposition method (Physical Vapor Deposition method) such as ion plating method, which is heated by beam, and plasma chemical vapor deposition method using organosilicon compound as raw material when depositing silicon oxide vapor deposition film (Chemical Vapor Deposition method) and the like. Vapor deposition may be performed on the surface of a support film, a wavelength conversion layer, an organic layer or the like as a substrate.

The thickness of the inorganic layer may be 1 nm to 500 nm, preferably 5 nm to 300 nm, particularly preferably 10 nm to 150 nm. Providing a wavelength conversion member that can suppress reflection in the inorganic layer and achieve higher light transmittance while realizing good barrier properties by having the film thickness of the adjacent inorganic layer within the above-described range. Because you can.

In one aspect, the wavelength conversion member preferably has at least one main surface of the wavelength conversion layer in direct contact with the inorganic layer. It is also preferred that the inorganic layer is in direct contact with both main surfaces of the wavelength conversion layer. In one embodiment, it is preferable that at least one main surface of the wavelength conversion layer is in direct contact with the organic layer. It is also preferred that the organic layer is in direct contact with both main surfaces of the wavelength conversion layer. Here, the “main surface” refers to the surface (front surface, back surface) of the wavelength conversion layer disposed on the viewing side or the backlight side when the wavelength conversion member is used. The same applies to the main surfaces of the other layers and members. Further, a known adhesive layer may be used to bond between the inorganic layer and the organic layer, between the two inorganic layers, or between the two organic layers. From the viewpoint of improving light transmittance, it is preferable that the number of adhesive layers is small, and it is more preferable that no adhesive layer is present. In one embodiment, the inorganic layer and the organic layer are preferably in direct contact.

-Organic layer-
Regarding the organic layer, reference can be made to paragraphs 0020 to 0042 of JP-A-2007-290369 and paragraphs 0074 to 0105 of JP-A-2005-096108. In addition, it is preferable that an organic layer contains a cardo polymer in one aspect | mode. Thereby, the adhesiveness between the organic layer and the adjacent layer, particularly the adhesiveness with the inorganic layer is improved, and a further excellent gas barrier property can be realized. For details of the cardo polymer, reference can be made to paragraphs 0085 to 0095 of JP-A-2005-096108 described above. The thickness of the organic layer is preferably in the range of 0.05 μm 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 preferably in the range of 0.5 to 10 μm, and more preferably in the range of 1 to 5 μm. Further, when formed by a dry coating method, it is preferably in the range of 0.05 μm to 5 μm, and more preferably in the range of 0.05 μm to 1 μm. This is because when the film thickness of the organic layer formed by the wet coating method or the dry coating method is within the above-described range, the adhesion with the inorganic layer can be further improved.

In the present invention and the present specification, the polymer means a polymer obtained by polymerizing two or more compounds which are the same or different by a polymerization reaction, and includes an oligomer, and its molecular weight is not particularly limited. Absent. The polymer may be a polymer having a polymerizable group, and may be further polymerized by being subjected to a polymerization treatment according to the type of the polymerizable group such as heating and light irradiation. In addition, polymerizable compounds such as the alicyclic epoxy compounds, monofunctional (meth) acrylate compounds, and polyfunctional (meth) acrylate compounds described above may correspond to the polymer in the above meaning.

The organic layer can also be a cured layer obtained by curing a curable composition containing a (meth) acrylate polymer. The (meth) acrylate polymer is a polymer containing one or more (meth) acryloyl groups in one molecule. As an example of the (meth) acrylate polymer used for forming the organic layer, a (meth) acrylate polymer containing one or more urethane bonds in one molecule can be exemplified. Hereinafter, a (meth) acrylate polymer containing one or more urethane bonds in one molecule is referred to as a urethane bond-containing (meth) acrylate polymer. When the barrier layer includes two or more organic layers, a cured layer obtained by curing a curable composition containing a urethane bond-containing (meth) acrylate polymer and other organic layers may be included. In one aspect, the organic layer in direct contact with one or both main surfaces of the wavelength conversion layer is preferably a cured layer formed by curing a curable composition containing a urethane bond-containing (meth) acrylate polymer.

In the urethane bond-containing (meth) acrylate polymer, in one aspect, it is preferable that a structural unit having a urethane bond is introduced into a side chain of the polymer. Hereinafter, a main chain into which a structural unit having a urethane bond is introduced is referred to as an acrylic main chain.

In addition, it is also preferable that a (meth) acryloyl group is contained in at least one end of the side chain having a urethane bond. It is more preferable that a (meth) acryloyl group is contained in all of the side chains having a urethane bond. Here, the (meth) acryloyl group contained at the terminal is more preferably an acryloyl group.

The urethane bond-containing (meth) acrylate polymer can be generally obtained by graft copolymerization, but is not particularly limited. The acrylic main chain and the structural unit having a urethane bond may be directly bonded or may be bonded via a linking group. Examples of the linking group include an ethylene oxide group, a polyethylene oxide group, a propylene oxide group, and a polypropylene oxide group. The urethane bond-containing (meth) acrylate polymer may contain a plurality of side chains in which structural units having a urethane bond are bonded via different linking groups (including direct bonds).

The urethane bond-containing (meth) acrylate polymer may have a side chain other than the structural unit having a urethane bond. Examples of other side chains include linear or branched alkyl groups. As the linear or branched alkyl group, a linear alkyl group having 1 to 6 carbon atoms is preferable, an n-propyl group, an ethyl group, or a methyl group is more preferable, and a methyl group is further preferable. In addition, other side chains may include different structures. The same applies to structural units having a urethane bond.

The number of urethane bonds and (meth) acryloyl groups contained in one molecule of the urethane bond-containing (meth) acrylate polymer is 1 or more, preferably 2 or more, but is not particularly limited. . The molecular weight of the urethane bond-containing (meth) acrylate polymer is preferably 10,000 or more, more preferably 12,000 or more, and further preferably 15,000 or more. The weight average molecular weight of the urethane bond-containing (meth) acrylate polymer is preferably 1,000,000 or less, more preferably 500,000 or less, and further preferably 300,000 or less. The acrylic equivalent of the urethane bond-containing (meth) acrylate polymer is preferably 500 or more, more preferably 600 or more, further preferably 7,000 or more, and the acrylic equivalent is 5,000 or less. Is preferably 3,000 or less, more preferably 2,000 or less. The weight average molecular weight in the present invention and the present specification refers to a weight average molecular weight obtained by converting a measured value by gel permeation chromatography (GPC) into polystyrene. As measurement conditions by GPC, for example, the following conditions can be employed. The weight average molecular weight described in Examples described later is a value measured under the following conditions.
GPC device: HLC-8120 (manufactured by Tosoh Corporation):
Column: TSK gel Multipore HXL-M (Tosoh Corporation, 7.8 mm ID (inner diameter) × 30.0 cm)
Eluent: Tetrahydrofuran (THF)
The acrylic equivalent is a value obtained by dividing the weight average molecular weight by the number of (meth) acryloyl groups in one molecule.

As the urethane bond-containing (meth) acrylate polymer, one synthesized by a known method may be used, or a commercially available product may be used. Examples of commercially available products include UV curable acrylic urethane polymers (8BR series) manufactured by Taisei Fine Chemical Co., Ltd. The urethane bond-containing (meth) acrylate polymer is preferably contained in an amount of 5 to 90% by mass and preferably 10 to 80% by mass with respect to 100% by mass of the total solid content of the curable composition for forming the organic layer. Is more preferable.

In the curable compound used to form the organic layer, one or more urethane bond-containing (meth) acrylate polymers may be used in combination with one or more other polymerizable compounds. As the other polymerizable compound, a compound having an ethylenically unsaturated bond at a terminal or a side chain is preferable. Examples of compounds having an ethylenically unsaturated bond at the terminal or side chain include (meth) acrylate compounds, acrylamide compounds, styrene compounds, maleic anhydride, etc., (meth) acrylate compounds are preferred, and acrylate compounds Is more preferable.
As the (meth) acrylate compound, (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate and the like are preferable. Specific examples of the (meth) acrylate compound include compounds described in paragraphs 0024 to 0036 of JP2013-43382A or paragraphs 0036 to 0048 of JP2013-43384A.
As the styrene compound, styrene, α-methylstyrene, 4-methylstyrene, divinylbenzene, 4-hydroxystyrene, 4-carboxystyrene and the like are preferable.

The curable composition used for forming the organic layer may contain a known additive together with one or more polymerizable compounds. An example of such an additive is an organometallic coupling agent. For details, the above description can be referred to. The organometallic coupling agent is preferably 0.1 to 30% by mass, and more preferably 1 to 20% by mass, when the total solid content of the curable composition used for forming the organic layer is 100% by mass.

Also, examples of the additive include a polymerization initiator. When a polymerization initiator is used, the content of the polymerization initiator in the curable composition is preferably 0.1 mol% or more, and preferably 0.5 to 5 mol% of the total amount of the polymerizable compounds. More preferred. Examples of photopolymerization initiators include Irgacure series (for example, Irgacure 651, Irgacure 754, Irgacure 184, Irgacure 2959, Irgacure 907, Irgacure 369, Irgacure 379, Irgacure 819, etc.), Darocur, etc., commercially available from BASF. (Darocure) series (for example, Darocur TPO, Darocur 1173, etc.), Quantacure PDO, Ezacure series (for example, Ezacure TZM, Ezacure TZT, Ezacure KTO 46, etc.) commercially available from Lamberti ) And the like.

Curing of the curable composition for forming the organic layer may be performed by treatment (light irradiation, heating, etc.) according to the type of components (polymerizable compound or polymerization initiator) contained in the curable composition. Curing conditions are not particularly limited, and may be set according to the type of components contained in the curable composition, the thickness of the organic layer, and the like.

As for other details of the inorganic layer and the organic layer, reference can be made to the descriptions in the above-mentioned JP-A No. 2007-290369, JP-A No. 2005-096108 and US 2012/0113672 A1.

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

(Emission wavelength of backlight unit)
From the viewpoint of realizing high luminance and high color reproducibility, it is preferable to use a backlight unit that has been converted to a multi-wavelength light source. For example, blue light having an emission center wavelength in a wavelength band of 430 to 480 nm and a peak of emission intensity having a half width of 100 nm or less, and an emission center wavelength in a wavelength band of 520 to 560 nm, and a half width of It is preferable to emit green light having an emission intensity peak that is 100 nm or less and red light having an emission center wavelength in the wavelength band of 600 to 680 nm and having an emission intensity peak that is 100 nm or less. .
From the viewpoint of further improving luminance and color reproducibility, the wavelength band of blue light emitted from the backlight unit is more preferably 440 to 475 nm.
From the same viewpoint, the wavelength band of the green light emitted from the backlight unit is more preferably 520 to 545 nm.
From the same viewpoint, the wavelength band of red light emitted from the backlight unit is more preferably 610 to 640 nm.

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

The backlight unit includes a light source together with at least the wavelength conversion member. In one embodiment, a light source that emits blue light having a light emission center wavelength in a wavelength band of 430 nm to 480 nm (blue light source), for example, a blue light emitting diode that emits blue light can be used. When using a light source that emits blue light, the wavelength conversion layer may include at least quantum dots (A) that are excited by excitation light and emit red light, and quantum dots (B) that emit green light. preferable. Thereby, white light can be embodied 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 aspect, a light source that emits ultraviolet light having an emission center wavelength in a wavelength band of 300 nm to 430 nm (ultraviolet light source), for example, an ultraviolet light emitting diode can be used. In this case, it is preferable that the wavelength conversion layer includes quantum dots (A) and (B) and quantum dots (C) that are excited by excitation light and emit blue light. Thereby, white light can be embodied by red light, green light, and blue light emitted from the wavelength conversion member.
In another embodiment, a laser light source can be used instead of the light emitting diode.

(Configuration of backlight unit)
The backlight unit can be, for example, an edge light type backlight unit including 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. Any known light guide plate can be used without any limitation. However, the backlight unit may be a direct type.

Also, the backlight unit can include a reflecting member at the rear of the light source. There is no restriction | limiting in particular as such a reflecting member, A well-known thing can be used, and it is described in patent 3416302, patent 3363565, patent 4091978, patent 3448626, etc., The content of these gazettes is this Incorporated into the invention.

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

[Liquid Crystal Display]
The above 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 cell.

(Configuration of liquid crystal display device)
The driving mode of the liquid crystal cell is not particularly limited, and is twisted nematic (TN), super twisted nematic (STN), vertical alignment (VA), in-plane switching (IPS), and optically compensated bend cell (OCB). Various modes such as can be used. The liquid crystal cell is preferably VA mode, OCB mode, IPS mode, or TN mode, but is not limited thereto. As an example of the configuration of the VA mode liquid crystal display device, the configuration shown in FIG. 2 of Japanese Patent Application Laid-Open No. 2008-262161 is given as an example. However, the specific configuration of the liquid crystal display device is not particularly limited, and a known configuration can be adopted.

In one embodiment of the liquid crystal display device, a liquid crystal cell having a liquid crystal layer sandwiched between substrates provided with electrodes on at least one of the opposite sides is provided, and the liquid crystal cell is arranged 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 the alignment state of the liquid crystal by applying a voltage. Furthermore, it has an accompanying functional layer such as a polarizing plate protective film, an optical compensation member that performs optical compensation, and an adhesive layer as necessary. Along with (or instead of) a color filter substrate, thin layer transistor substrate, lens film, diffusion sheet, hard coat layer, antireflection layer, low reflection layer, antiglare layer, etc., forward scattering layer, primer layer, antistatic layer Further, a surface layer such as an undercoat layer may be disposed.

FIG. 4 illustrates an example of a liquid crystal display device according to one embodiment of the present invention. The liquid crystal display device 51 shown in FIG. 4 has the backlight side polarizing plate 14 on the surface of the liquid crystal cell 21 on the backlight side. The backlight-side polarizing plate 14 may or may not include the polarizing plate protective film 11 on the backlight-side surface of the backlight-side polarizer 12, but it is preferably included.
The backlight side polarizing plate 14 preferably has a configuration in which the polarizer 12 is sandwiched between two polarizing plate

protective films

11 and 13.
In this specification, the polarizing plate protective film on the side closer to the liquid crystal cell with respect to the polarizer is referred to as the inner side polarizing plate protective film, and the polarizing plate protective film on the side farther from the liquid crystal cell with respect to the polarizer is referred to as the outer side polarizing plate. It is called a protective film. In the example shown in FIG. 4, the polarizing plate protective film 13 is an inner side polarizing plate protective film, and the polarizing plate protective film 11 is an outer side polarizing plate protective film.

The backlight side polarizing plate may have a retardation film as an inner side polarizing plate 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 the surface of the liquid crystal cell 21 opposite to the surface on the backlight side. The display-side polarizing plate 44 has a configuration in which a polarizer 42 is sandwiched between two polarizing plate

protective films

41 and 43. The polarizing plate protective film 43 is an inner side polarizing plate protective film, and the polarizing plate protective film 41 is an outer side polarizing plate protective film.

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

The liquid crystal cell, polarizing plate, polarizing plate protective film and the like constituting the liquid crystal display device are not particularly limited, and those produced by known methods and commercially available products can be used without any limitation. It is of course possible to provide a known intermediate layer such as an adhesive layer between the layers.

Hereinafter, the present invention will be described more specifically based on examples. The materials, amounts used, ratios, processing details, processing procedures, and the like 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 by the specific examples shown below.

(Preparation of barrier film 10)
Using a polyethylene terephthalate film (PET film, manufactured by Toyobo Co., Ltd., trade name: Cosmo Shine (registered trademark) A4300, thickness 50 μm) as a support film, an organic layer and an inorganic layer are formed on one side of the support film by the following procedure. Were sequentially formed.
Trimethylolpropane triacrylate (TMCTA manufactured by Daicel Cytec Co., Ltd.) and a photopolymerization initiator (ESACURE KTO46 manufactured by Lamberti Co., Ltd.) were prepared, weighed so that the mass ratio was 95: 5, dissolved in methyl ethyl ketone, and solid A coating solution having a partial concentration of 15% by mass was obtained. This coating solution was applied onto the PET film with a roll toe roll using a die coater, and passed through a drying zone at 50 ° C. for 3 minutes. Thereafter, the sample was irradiated with ultraviolet rays (integrated irradiation amount: about 600 mJ / cm ² ) in a nitrogen atmosphere, cured by ultraviolet curing, and wound up. The thickness of the first organic layer formed on the support film was 1 μm.

Next, an inorganic layer (silicon nitride layer) was formed on the surface of the organic layer by using a roll-to-roll CVD (Chemical Vapor Deposition) apparatus. 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 source gases. A high frequency power supply having a frequency of 13.56 MHz was used as the power supply. The film forming pressure was 40 Pa, and the reached film thickness was 50 nm.
Thus, the barrier film 10 in which the inorganic layer was laminated on the surface of the first organic layer formed on the support film was produced.

(Preparation of barrier film 11)
A second organic layer was laminated on the surface of the inorganic layer of the barrier film 10.
Urethane bond-containing acrylic polymer (Acrit 8BR500 manufactured by Taisei Fine Chemical Co., Ltd., weight average molecular weight 250,000) and photopolymerization initiator (Irgacure 184 manufactured by BASF Co., Ltd.) are weighed to a mass ratio of 95: 5, and these are converted into methyl ethyl ketone. It was dissolved to prepare a coating solution having a solid content concentration of 15% by mass. The prepared coating solution was applied to the surface of the inorganic layer of the barrier film 10 with a roll toe roll using a die coater, passed through a 100 ° C. drying zone for 3 minutes, and wound up. The thickness of the second organic layer thus formed was 1 μm. Thus, the barrier film 11 in which the inorganic layer was laminated on the surface of the first organic layer and the second organic layer was further laminated was produced.

(Preparation of a photocurable composition containing quantum dots used in Example 1)
The following quantum dot-containing photocurable composition 1 was prepared, filtered through a polypropylene filter having a pore size of 0.2 μm, dried under reduced pressure for 30 minutes, and used as a coating solution.

──────────────────────────────────
Preparation of quantum dot-containing photocurable composition 1 (used in Example 1)
──────────────────────────────────
Quantum dot 1 in toluene dispersion (luminescence maximum: 530 nm) 10 parts by mass Quantum dot 1: INP530-10 (spherical quantum dot) manufactured by NN-labs
Quantum dot 2 in toluene dispersion (emission maximum: 620 nm) 1 part by mass Quantum dot 2: INP620-10 (spherical quantum dot) manufactured by NN-labs
Alicyclic epoxy compound 60 parts by mass Celoxide 2021P (manufactured by Daicel)
Monofunctional acrylate compound 40 parts by mass AMP-10G (manufactured by Shin-Nakamura Chemical Co., Ltd.)
Silane coupling agent 1 2.5 parts by weight KBM-303 (manufactured by Shin-Etsu Chemical Co., Ltd.)
Silane coupling agent 2 2.5 parts by weight KBM-5103 (manufactured by Shin-Etsu Chemical Co., Ltd.)
Photocationic polymerization initiator (iodonium salt compound) A 3 parts by mass Photoradical polymerization initiator Irgacure 819 (manufactured by BASF) 3 parts by mass viscosity modifier (AEROSIL R972 (manufactured by Nippon Aerosil Co., Ltd.)) 3 parts by mass ───── ─────────────────────────────
(In the above, the quantum dot concentration of the toluene dispersion of

quantum dots

1 and 2 is 1% by mass.)

(Production of quantum dot-containing photocurable compositions used in Examples 2 to 12 and Comparative Examples 1 to 6)
A quantum dot-containing photocurable composition was prepared at the composition ratio shown in Table 1 or Table 2, filtered through a polypropylene filter having a pore size of 0.2 μm, dried under reduced pressure for 30 minutes, and used as a coating solution.

(Preparation of photocurable composition containing quantum dots (quantum rods) used in Example 13)
The following quantum dot (quantum rod) -containing photocurable composition 2 was prepared, filtered through a polypropylene filter having a pore size of 0.2 μm, dried under reduced pressure for 30 minutes, and used as a coating solution.
Quantum Rod 1 and Quantum Rod 2 are described in U.S. Pat. No. 7,303,628, paper (Peng, X. G .; Manna, L .; Yang, WD; Wickham, j .; Scher, E .; Kadavanich, A .; Alivisatos, AP Nature 2000, 404, 59-61) and articles (Manna, L .; Scher, EC; Alivisatos, AP J. Am. Chem. Soc. 2000, 122, 12700- 12706). The average major axis length of the quantum rod 1 and the quantum rod 2 confirmed by a transmission electron microscope was 50 nm.

──────────────────────────────────
Preparation of photocurable composition 2 containing quantum dots (used in Example 13)
──────────────────────────────────
10 parts by mass of toluene dispersion of quantum rod 1 Quantum rod 1 (luminescence maximum: 532 nm, half-value width: 30 nm)
1 part by mass of toluene dispersion of quantum rod 2 Quantum rod 2 (luminescence maximum: 626 nm, half-value width 27 nm)
Alicyclic epoxy compound 100 parts by mass Celoxide 2021P (manufactured by Daicel)
Silane coupling agent 1 5 parts by weight KBM-303 (manufactured by Shin-Etsu Chemical Co., Ltd.)
Photocationic polymerization initiator 3 parts by mass CPI-110P (manufactured by San Apro)
Viscosity modifier (AEROSIL R972 (made by Nippon Aerosil Co., Ltd.)) 3 parts by mass ──────────────────────────────────
(In the above, the quantum rod concentration of the toluene dispersion of the

quantum rods

1 and 2 is 1% by mass.)

(Preparation of wavelength conversion member of Example 1)
The barrier film 10 produced by the above-described procedure was used as the first and second films, and a wavelength conversion member was obtained by the manufacturing process described with reference to FIGS. 2 and 3. Specifically, the barrier film 10 is prepared as a first film, and the quantum dot-containing photocurable composition 1 prepared above is formed on the surface of the inorganic layer while continuously transporting at a tension of 1 m / min and 60 N / m. It was applied with a die coater to form a coating film having a thickness of 50 μm. Next, the first film (barrier film 10) on which the coating film is formed is wound around a backup roller, and the second film (barrier film 10) is laminated on the coating film so that the inorganic layer surface is in contact with the coating film. While continuously transporting the coating film sandwiched between the two barrier films 10, the heating zone at 100 ° C. was passed for 3 minutes. Thereafter, using a 160 W / cm air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.), it was cured by irradiation with ultraviolet rays to form a wavelength conversion layer containing quantum dots. The irradiation amount of ultraviolet rays was 2000 mJ / cm ² . L1 was 50 mm, L2 was 1 mm, and L3 was 50 mm.

(Production of wavelength conversion members of Examples 2 to 13 and Comparative Examples 1 to 6)
In Table 1 or Table 2, for the examples and comparative examples described as “barrier film 10” in the column of barrier film, the quantum dot-containing photocurable composition used in each of the examples and comparative examples prepared above ( Using the coating solution, a wavelength conversion member was produced in the same manner as in Example 1.
In Table 1 or Table 2, for the examples described as “barrier film 11” in the column of barrier film, the quantum dot-containing photocurable composition (coating solution) used in each of the examples and comparative examples prepared above. In the same manner as in Example 1, except that the barrier film 10 was used instead of the barrier film 10 as the first film and the second film, and the barrier film 11 was used so that the second organic layer was in contact with the coating film. A wavelength conversion member was produced.

(Measurement of excitation light loss rate of matrix of wavelength conversion layer)
Examples 1 to 12 and Comparative Examples 1 to 6 were used for preparing model films obtained by removing the toluene dispersion of quantum dots 1 and the toluene dispersion of quantum dots 2 from the composition of the photocurable composition containing quantum dots. A composition was prepared, and a model film having a thickness of 60 μm was prepared by means 1 described above. Specifically, a model film was produced by the following method.
About Example 13, the composition for model film preparation which remove | excluded the toluene dispersion liquid of the quantum rod 1 and the toluene dispersion liquid of the quantum rod 2 from the composition of the used quantum rod containing photocurable composition was prepared, and the above-mentioned A model film having a thickness of 60 μm was prepared by means 1. Specifically, a model film was produced by the following method.
After applying the composition for preparing a model film to a release film (Lumirror # 50 manufactured by Toray Industries, Inc., 50 μm thick) with a wire bar, another release film is laminated thereon and air-cooled at 1200 W / cm in the atmosphere. Using a metal halide lamp (manufactured by Eye Graphics Co., Ltd.), ultraviolet rays were irradiated from the coated surface at 2000 mJ / cm ² and cured. The cured film thus obtained was cut into 2 cm square, and then the release films on both sides of the cured film were peeled off to obtain a resin layer single film (model film) having a thickness of 60 μm.
The obtained model membrane was placed in an integrating sphere of an absolute PL quantum yield measuring apparatus (C9920-02) manufactured by Hamamatsu Photonics, and provided in a commercially available tablet terminal (manufactured by Amazon, Kindle Fire HDX 7 ″). The blue light having the emission center wavelength was incident on the wavelength 450 nm which is the emission center wavelength of the blue light source, and the detected light intensity I at the wavelength 450 nm was measured at this time. Then, the transmitted light intensity I ₀ at a wavelength of 450 nm was measured, and the blue light loss rate A of the model film having a thickness of 60 μm was measured by the above-described equation, and the blue color in the matrix of the wavelength conversion layer was determined from the obtained measurement values. The loss rate of light was evaluated according to the following evaluation criteria, and the results are shown in Tables 1 and 2.
A: A <1.0%
B: 1.0 ≦ A <2.0
C: 2.0 ≦ A <3.0
D: 3.0 ≦ A

(Measurement of brightness)
Disassembled a commercially available tablet terminal (Kindle (registered trademark) Fire HDX 7 ″ manufactured by Amazon) with a blue light source in the backlight unit, and took out the backlight unit. Cut out into a rectangle on the light guide plate of the removed backlight unit The wavelength conversion members prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were placed, and two prism sheets with the surface concavo-convex patterns orthogonal to each other were placed on the wavelength conversion member. The luminance Y of the light transmitted through the member and the two prism sheets was measured with a luminance meter (SR3 manufactured by TOPCON) installed at a position of 740 mm in the direction perpendicular to the surface of the light guide plate. The results are shown in the table below.
A +: Y ≧ 11,000 [cd / m ² ]
A: 10,000 ≦ Y <11,000 [cd / m ² ]
B: 9,000 ≦ Y <10,000 [cd / m ² ]
C: 8,000 ≦ Y <9,000 [cd / m ² ]
D: Y <8,000 [cd / m ² ]

(Evaluation of photocurability of wavelength conversion layer)
After preparing the quantum dot containing photocurable composition used by each Example and the comparative example, and apply | coating with the wire bar on the inorganic layer of the barrier film 10, it is 1200W, purging with nitrogen (oxygen concentration 0.5% or less). Using an air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) of / cm, ultraviolet rays were irradiated toward the coated surface at the exposure amount shown in the following table and cured. And sclerosis | hardenability was evaluated as follows by finger touch. The results are shown in the table below.
A: No finger remaining.
B: Some stickiness.
C: Clear tackiness.
D: Clear sticky and uncured.

The components used in the examples and comparative examples described in the above table are as shown in Table 3 below.

From the results of Comparative Examples 3 and 6 in the above table, although the alicyclic epoxy compound has better photocurability than the aliphatic epoxy compound (see Comparative Examples 1, 2, 4, and 5), it is emitted from the light source. It can be seen that this causes a loss of light (excitation light). As a result, in Comparative Examples 3 and 6, a decrease in luminance occurs.
On the other hand, as shown in the above table, in the examples, the luminance improvement is achieved by suppressing the excitation light loss rate to 3% or less in terms of thickness 60 μm while using the alicyclic epoxy compound that contributes to the improvement of photocurability. Could be achieved.

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

Claims

A backlight unit including a light source and a wavelength conversion member positioned on an optical path of light emitted from the light source,
The wavelength conversion member has a wavelength conversion layer including quantum dots in a matrix that are excited by excitation light and emit fluorescence.
The wavelength conversion layer is a photocured layer obtained by curing a photocurable composition by light irradiation,
The photocurable composition includes the quantum dot, a polymerizable compound including at least an alicyclic epoxy compound, and a photopolymerization initiator,
The backlight unit has a loss rate of light emitted from the light source in the wavelength conversion layer matrix of 3% or less in terms of a thickness of 60 μm.
The backlight unit according to claim 1, wherein the photopolymerization initiator is an iodonium salt compound.
The backlight unit according to claim 2, wherein the iodonium salt compound includes, as an anion moiety, an anion moiety having a gas phase acidity in the range of 240 to 290 kcal / mol.
The backlight unit according to any one of claims 1 to 3, wherein the wavelength conversion layer contains 0.20% by volume or more of light scattering particles.
The backlight unit according to any one of claims 1 to 4, wherein the light source is a blue light source.
A liquid crystal display device comprising the backlight unit according to any one of claims 1 to 5 and a liquid crystal cell.
It has a wavelength conversion layer containing quantum dots that are excited by excitation light and emit fluorescence, in a matrix,
The wavelength conversion layer is a photocured layer obtained by curing a photocurable composition by light irradiation,
The photocurable composition includes the quantum dot, a polymerizable compound including at least an alicyclic epoxy compound, and a photopolymerization initiator,
The wavelength conversion member whose blue light loss rate in the matrix of the said wavelength conversion layer is 3% or less in conversion of thickness 60 micrometers.
The wavelength conversion member according to claim 7, wherein the photopolymerization initiator is an iodonium salt compound.
The wavelength conversion member according to claim 8, wherein the iodonium salt compound includes, as an anion moiety, an anion moiety having a gas phase acidity in the range of 240 to 290 kcal / mol.
The wavelength conversion member according to any one of claims 7 to 9, wherein the polymerizable compound further contains a (meth) acrylate compound.
A photocurable composition comprising quantum dots excited by excitation light and emitting fluorescence,
Including the quantum dot, a polymerizable compound containing at least an alicyclic epoxy compound, and a photopolymerization initiator,
A photocurable composition in which a blue light loss rate of a portion excluding quantum dots of a photocured product obtained by curing the photocurable composition by light irradiation is 3% or less in terms of a thickness of 60 μm.
The photocurable composition according to claim 11, wherein the photopolymerization initiator is an iodonium salt compound.
The photocurable composition according to claim 12, wherein the iodonium salt compound includes, as an anion moiety, an anion moiety having a gas phase acidity in the range of 240 to 290 kcal / mol.
The photocurable composition according to any one of claims 11 to 13, wherein the polymerizable compound further comprises a (meth) acrylate compound.
The photocurable composition according to claim 14, wherein the (meth) acrylate compound contains a monofunctional (meth) acrylate.
The photocurable composition according to any one of claims 11 to 15, which contains 0.20% by volume or more of light scattering particles on a volume basis with respect to the total solid content.