JP6586805B2 - Edge light type backlight and liquid crystal display device - Google Patents

Description

  The present invention relates to a quantum dot laminate, a backlight, and a liquid crystal display device.

  Developments for improving the light emission efficiency and color rendering of liquid crystal display backlights and lighting devices are advancing. In recent years, in order to realize such a light emitting device, a combination of a light source that generates primary light (such as a blue LED that emits blue light) and a quantum dot phosphor made of semiconductor fine particles (hereinafter referred to as “quantum dots”). Light emitting devices are being developed.

The quantum dots are, for example, nano-sized compound semiconductor fine particles composed of semiconductor fine particles composed of a core made of CdSe and a shell made of ZnS and a ligand covering the periphery of the shell. The quantum dot has a quantum confinement effect because its particle size is smaller than the Bohr radius of the exciton of the compound semiconductor. Therefore, the luminous efficiency of the quantum dots is higher than that of a phosphor (rare earth phosphor) that uses a rare earth ion as a conventional activator, and a high luminous efficiency of 90% or more can be realized.
In addition, since the emission wavelength of the quantum dot is determined by the band gap energy of the compound semiconductor fine particles quantized in this way, an arbitrary emission wavelength, that is, an arbitrary emission spectrum can be obtained by changing the particle size of the quantum dot. Can do. By combining these quantum dots with a blue LED or the like, it is possible to realize a backlight with high luminous efficiency and high color rendering (see, for example, Patent Documents 1 to 3).

As a method of incorporating quantum dots into a backlight device, an on-chip method of incorporating quantum dots in a light source, an on-edge method of arranging a transparent tube containing quantum dots between a light source and a light guide plate, and a light output side of the light guide plate In addition, an on-surface method is known in which a sheet containing quantum dots (quantum dot sheet) is disposed on a light source.
However, in the on-chip method, since the quantum dots are incorporated in the light source, the quantum dots are exposed to a high temperature, and the conversion efficiency of the quantum dots is inferior. In the on-edge method, the transparent tube containing the quantum dots is disposed between the light source and the light guide plate, so that the size increases. In particular, in mobile devices, miniaturization is required, so it is difficult to cope with the on-edge method.
On the other hand, the on-surface method does not have the above-mentioned problem, and it is also possible to use a conventionally used backlight device. For these reasons, it is currently being studied to incorporate quantum dots into a backlight device by an on-surface method.

  However, an on-surface type backlight using a quantum dot sheet sometimes has insufficient front luminance, which is a general required performance of the backlight.

International Publication No. 2012/132239 Japanese Patent Laid-Open No. 2015-18131 Japanese Patent Laying-Open No. 2015-28139

  An object of this invention is to provide the quantum dot laminated body, backlight, and liquid crystal display device with favorable front luminance in view of the said problem.

The present invention provides the following quantum dot sheet, backlight and liquid crystal display device of [1] to [9].
[1] A quantum dot laminate for a backlight having a prism sheet on a quantum dot sheet, wherein the quantum dot sheet includes a quantum dot that absorbs primary light and emits secondary light and a binder resin. It has a dot-containing layer, and the surface of any one of the quantum dot sheets is vertically irradiated with visible light having a light source as a halogen lamp (12V, 48W), and the intensity of transmitted light is −85 degrees to +85 A quantum dot laminate that satisfies the following condition (1) when measured every 1 degree within a range up to 5 degrees.
<Condition (1)>
The sum of the intensities of −5 ° to + 5 ° is P ₁ , the sum of the intensities of −70 ° to −85 ° and + 70 ° to + 85 ° is P ₂ , and the intensities of −15 ° to −45 ° and + 15 ° to + 45 ° sum of the upon the _{P 3, (P 1 + P} 2) / P 3 is 0.65 or less.
[2] The quantum dot laminate according to [1], wherein the quantum dot sheet satisfies the following condition (2).
<Condition (2)>
_{P 2} / P ₁ is 0.15 or more.
[3] The quantum dot laminate according to [1] or [2], wherein the quantum dot-containing layer contains internal diffusion particles.
[4] The above [3], wherein n _B / n _A is 1.02 or more or 0.98 or less when the refractive index of the binder resin is n _A and the refractive index of the internal diffusion particles is n _B. 2. A quantum dot laminate according to 1.

[5] The quantum dot laminate according to any one of [1] to [4], wherein the quantum dot sheet is formed by sandwiching both surfaces of the quantum dot-containing layer with a light-transmitting substrate.
[6] The quantum dot laminate according to any one of [1] to [5], wherein the quantum dot sheet further includes a light diffusion layer.
[7] At least one surface of the quantum dot sheet has the arithmetic average roughness Ra having a cutoff value of 0.8 mm in accordance with JIS B0601: 2001 of 0.1 to 10 μm according to the above [1] to [6]. The quantum dot laminate according to any one of the above.
[8] comprising at least one light source that emits primary light, an optical plate disposed adjacent to the light source for light guide or diffusion, and an optical member disposed on a light emitting side of the optical plate. A backlight in which the optical member is the quantum dot laminate according to any one of [1] to [7].
[9] A liquid crystal display device including a backlight and a liquid crystal panel, wherein the backlight is the backlight according to [8].

  The quantum dot laminate, the backlight, and the liquid crystal display device of the present invention can improve the front luminance.

It is sectional drawing which shows one Embodiment of the quantum dot laminated body of this invention. It is sectional drawing which shows one Embodiment of the quantum dot sheet | seat which comprises the quantum dot laminated body of this invention. It is sectional drawing which shows other embodiment of the quantum dot sheet | seat which comprises the quantum dot laminated body of this invention. It is sectional drawing which shows other embodiment of the quantum dot sheet | seat which comprises the quantum dot laminated body of this invention. It is sectional drawing which shows one Embodiment of the backlight of this invention. It is sectional drawing which shows other embodiment of the backlight of this invention. It is sectional drawing which shows one Embodiment of the liquid crystal display device of this invention.

Embodiments of the present invention will be described below.
[Quantum dot stack]
The quantum dot laminate of the present invention is a quantum dot laminate for backlight having a prism sheet on a quantum dot sheet, and the quantum dot sheet absorbs primary light and emits secondary light. And a quantum dot-containing layer containing a binder resin, and the surface of any one of the quantum dot sheets is irradiated vertically with visible light using a halogen lamp (12 V, 48 W) as a light source, and the intensity of transmitted light The following condition (1) is satisfied when measured at a time in the range of −85 degrees to +85 degrees.
<Condition (1)>
The sum of the intensities of −5 ° to + 5 ° is P ₁ , the sum of the intensities of −70 ° to −85 ° and + 70 ° to + 85 ° is P ₂ , and the intensities of −15 ° to −45 ° and + 15 ° to + 45 ° sum of the upon the _{P 3, (P 1 + P} 2) / P 3 is 0.65 or less.
Hereinafter, “−70 degrees to −85 degrees and +70 degrees to +85 degrees” is referred to as “± 70 degrees to ± 85 degrees” and “−15 degrees to −45 degrees and +15 degrees to +45 degrees”. It may be “± 15 degrees to ± 45 degrees”.

FIG. 1 is a cross-sectional view showing an embodiment of a quantum dot laminate 100z of the present invention. As shown in FIG. 1, the quantum dot laminated body 100z of this invention has the prism sheet 100y on the quantum dot sheet 100x.
As shown in FIG. 1, it is preferable to interpose an air layer between the quantum dot sheet 100x and the prism sheet 100y without bringing the quantum dot sheet and the prism sheet into close contact with each other with an adhesive or the like.

Quantum dot sheet A quantum dot sheet has a quantum dot content layer, and satisfies the above-mentioned conditions (1).
The fact that the quantum dot sheet satisfies the condition (1) means that the light emitted from the quantum dot sheet is emitted at a low angle of −5 degrees to +5 degrees with respect to the emitted light of ± 15 degrees to ± 45 degrees, and This means that there is not too much outgoing light with a high angle of ± 70 ° to ± 85 °. The prism sheet having an apex angle of approximately 90 degrees has a strong action of collecting light incident at ± 15 degrees to 45 degrees in the front direction, while incident light with a low angle of −5 degrees to +5 degrees and ± 70 degrees to Incident light with a high angle of 85 degrees cannot be collected in the front direction. Specifically, in a prism sheet having an apex angle of approximately 90 degrees, incident light at a low angle of −5 degrees to +5 degrees is totally reflected or emitted at an angle slightly away from the front direction, and ± 70 degrees to Incident light at a high angle of 85 degrees is either totally reflected or emitted at a high angle.
Therefore, when the quantum dot sheet satisfies the condition (1), the emitted light from the quantum dot sheet is efficiently collected in the front direction by the prism sheet, and the front luminance of the quantum dot stack can be improved.
On the other hand, when the quantum dot sheet does not satisfy the condition (1), the light emitted from the quantum dot sheet is not efficiently collected in the front direction by the prism sheet, and the front luminance of the quantum dot laminate cannot be improved. .

(P ₁ + P ₂ ) / P ₃ is preferably 0.40 or less, more preferably 0.36 or less, and even more preferably 0.34 or less. Note that if (P ₁ + P ₂ ) / P ₃ is too small, too much light gathers in the front direction and the viewing angle becomes extremely narrow. For this reason, (P ₁ + P ₂ ) / P ₃ is preferably 0.25 or more, and more preferably 0.30 or more.

  When the condition (1) is satisfied even if light is incident from any of the upper and lower surfaces of the quantum dot sheet, the direction in which the quantum dot sheet is installed with respect to the prism sheet is not particularly limited. On the other hand, when the condition (1) is satisfied only when light is incident from one of the upper and lower surfaces of the quantum dot sheet, the light incident surface when the condition is satisfied is directed to the prism sheet side, A quantum dot sheet shall be installed.

The quantum dot sheet preferably satisfies the following condition (2).
<Condition (2)>
_{P 2} / P ₁ is 0.15 or more.

Of the light emitted from the quantum dot sheet, the primary light is mostly low-angle light and is diffusive light having directivity, while the secondary light converted by the quantum dots is uniform diffused light. The secondary light, which is evenly diffused, diffuses a large proportion of light up to a high angle, and light tends to leak from the edge region of the quantum dot sheet, while the primary light has a small proportion of diffused light at a high angle, Light does not leak easily. For this reason, the ratio of the primary light is increased in the edge region of the quantum dot sheet, and the primary light is likely to be colored (blue if the primary light is blue).
The large P ₂ / P ₁ means that the primary light is sufficiently diffused by the quantum dot sheet, and the difference in the ratio between the primary light and the secondary light at a high angle can be reduced. _Therefore, the P 2 / _{P 1} by 0.15 or more, it is possible to suppress the color of the edge region.
P ₂ / P ₁ is more preferably 0.25 or more, further preferably 0.35 or more, still more preferably 0.40 or more, and most preferably 0.50 or more. . If P ₂ / P ₁ is too large, diffusion becomes too strong and it becomes difficult to satisfy the condition (1). _Therefore, it is preferable that P 2 / _{P 1} is 0.65 or less, more preferably 0.60 or less.

Method of measuring transmitted light intensity The intensity of transmitted light can be measured as follows.
First, the visible light which makes a light source a halogen lamp (12V, 48W) is irradiated as a parallel light with respect to any one surface of a quantum dot sheet. In measuring the intensity of transmitted light, the surface that irradiates the quantum dot sheet with light is the light incident surface when the quantum dot sheet is used as a backlight (the surface on the side facing the optical plate for light guide or diffusion). It is preferable that
After irradiating the light, the transmitted light is scanned by the light receiver at every angle in a certain angle range, and the intensity (luminance) at each angle is measured. The measurement range is a measurement in a range of ± 85 degrees, where the vertical direction is 0 degrees (regular transmission direction). When measuring the intensity, the brightness of the light source is constant. When measuring the intensity (luminous intensity), the aperture angle of the light receiver detected by the diaphragm of the light receiver is set to 1 degree. For this reason, for example, a range of ± 0.5 degrees is measured for measurement of 0 degree (regular transmission direction), a range of 0.5 to 1.5 degrees is measured for measurement of 1 degree, and a measurement of -1 degree is performed. Then, the range of -0.5 to -1.5 degrees is measured. There is no restriction | limiting in particular about the apparatus which measures intensity | strength, A general purpose goniophotometer (goniophotometer) can be used. In the present invention, a trade name GC5000L manufactured by Nippon Denshoku Industries Co., Ltd. (light beam diameter: about 3 mm, tilt angle within the light beam: within 0.8 degrees, receiver opening angle: 1 degree) is used as the goniophotometer. did. Moreover, let the value of conditions (1) and (2) be the average value at the time of measuring 20 times.

Transmittance The total light transmittance of JIS K7361-1: 1997 of the quantum dot sheet of the present invention is not particularly limited, but is usually about 40% or more.
In the measurement of total light transmittance, the surface that irradiates the quantum dot sheet with light is the surface opposite to the prism sheet when the quantum dot laminate is used (the quantum dot sheet laminate is a constituent member of the backlight). It is preferable that the light incident surface be used as a light incident surface.

Surface Roughness In the quantum dot sheet of the present invention, the arithmetic average roughness Ra of at least one surface is preferably 0.1 to 10 μm, more preferably 0.2 to 8 μm, and 0.5 to 5 μm. More preferably. Moreover, it is preferable that both surfaces of a quantum dot sheet satisfy | fill the range of said Ra.
By setting Ra to 0.1 μm or more, it is possible to prevent adhesion with a member in contact with the quantum dot sheet. Examples of the member in contact with the quantum dot sheet include a prism sheet located on the light emitting side of the quantum dot sheet and an optical plate for light guide or diffusion located on the light incident side of the quantum dot sheet. Moreover, the light leakage of a polarizing plate and the fall of front luminance can be suppressed by Ra being 10 micrometers or less.
Moreover, Ra is 0.5-10 micrometers from a viewpoint of aiming at the balance of favorable front luminance, the suppression of the color of an edge area | region, and the light leakage of a polarizing plate by controlling the intensity | strength of a spreading | diffusion. Preferably, it is 1-5 micrometers. Further, by setting the Ra on the light incident surface side to 1 μm or more, retroreflectivity is imparted, the light recycling rate is increased, and the quantum dot content can be reduced.
In addition, Ra and Rz _{JIS mentioned} later are based on JIS B0601: 2001, and are average values when measured 20 times with a cutoff value of 0.8 mm.

In the quantum dot sheet of the present invention, the ten-point average roughness Rz _{JIS of} at least one surface is preferably 0.120 μm, more preferably 0.2 to 10 μm, and more preferably 0.5 to 8 μm. Is more preferable. Moreover, it is preferable that both surfaces of a quantum dot sheet satisfy | fill the range of the said Rz _JIS .
Rz _JIS satisfying the above range indicates that the surface roughness of the quantum dot sheet has a certain randomness and that there is no extreme bias in the roughness. Therefore, when Rz _JIS satisfies the above range, it is possible to reduce the unevenness of diffusion and to prevent local adhesion.
Further, from the viewpoint of balancing the balance between the good front luminance, the suppression of the color of the edge region, and the light leakage of the polarizing plate by controlling the intensity of diffusion, Rz _JIS is preferably 1 to 10 μm. 2 to 8 μm is more preferable.
In order to make Ra and Rz _JIS within the above ranges, a light diffusion layer described later may be positioned on the outermost surface of the quantum dot sheet.

Configuration of Quantum Dot Sheet The quantum dot sheet of the present invention has a quantum dot-containing layer including a quantum dot that absorbs primary light and emits secondary light and a binder resin.
As quantum dots, the first quantum dots that absorb primary light having a wavelength corresponding to blue and emit secondary light having a wavelength corresponding to red, and the primary light that absorbs primary light having a wavelength corresponding to blue correspond to green It is preferable that at least one second quantum dot that emits secondary light having a wavelength to be emitted is included, and it is more preferable that both the first quantum dot and the second quantum dot are included.
The primary light having a wavelength corresponding to blue preferably has a peak wavelength in the range of 380 to 480 nm, and more preferably has a peak wavelength of 450 nm. The secondary light having a wavelength corresponding to green preferably has a peak wavelength in the range of 495 to 570 nm, and more preferably has a peak wavelength of 528 nm. The secondary light having a wavelength corresponding to red preferably has a peak wavelength in the range of 620 to 750 nm, and more preferably has a peak wavelength of 637 nm.

2-4 is sectional drawing which shows embodiment of the quantum dot sheet | seat which comprises the quantum dot laminated body of this invention. The quantum dot sheet 100x in FIG. 2 has light transmissive base materials 21a and 21b and light diffusion layers 42a and 42b on the upper and lower surfaces of the quantum dot-containing layer 10. The quantum dot sheet 100x of FIG. 3 has barrier layers 32a and 32b, light-transmitting substrates 21a and 21b, and light diffusion layers 42a and 42b on the upper and lower surfaces of the quantum dot-containing layer 10. The quantum dot sheet 100x of FIG. 4 has light-transmitting base materials 21a and 21b on the upper and lower surfaces of the quantum dot-containing layer 10, and the barrier film 30a via the adhesive layers 51a and 51b on the light-transmitting base material. , 30b, and light diffusion films 40a, 40b on the barrier film via adhesive layers 52a, 52b.
The quantum dot sheet of FIGS. 2 to 4 has a configuration (light transmissive substrate, barrier layer, light diffusion layer, etc.) other than the quantum dot-containing layer, but the quantum that constitutes the quantum dot laminate of the present invention. The dot sheet only needs to have at least a quantum dot-containing layer and satisfy the above condition (1), and a configuration other than the quantum dot-containing layer (light transmissive substrate, barrier layer, light diffusion layer, etc.) is necessary. It may be provided according to.
Moreover, although the quantum dot sheet | seat of FIGS. 2-4 has only one quantum dot content layer, the quantum dot sheet may have two or more quantum dot content layers.

The quantum dot sheet preferably has a vertically symmetric configuration with the quantum dot-containing layer as the center, as shown in FIGS. By having this configuration, strain can be evenly distributed, the flatness of the quantum dot sheet can be improved, and the adhesion at the interface of the quantum dot sheet can be improved. When the flatness of the quantum dot sheet is improved, it is preferable in that in-plane luminance unevenness can be suppressed.
Note that a layer configuration that is vertically symmetrical in the thickness direction means that the number of layers and the type of layers are the same up and down, and the thicknesses of the layers are substantially the same. In order to say that the thicknesses are substantially the same, the ratio of the thicknesses of the upper and lower layers in the relationship of interest is preferably in the range of 0.95 to 1.05, and in the range of 0.97 to 1.03. Is more preferable.
Further, it is preferable that the layers having a symmetrical relationship have substantially the same composition. In order to say that the compositions are substantially the same, 90% by mass or more of the constituent components of the layer are preferably the same, more preferably 95% by mass or more are the same, and 99% by mass or more are the same. Further preferred.

Quantum dot-containing layer The quantum dots (first quantum dot and second quantum dot) will be described below.
Quantum dots are nanometer-sized fine particles of semiconductors that have specific optical and electrical properties due to the quantum confinement effect (quantum size effect) in which electrons and excitons are confined in small crystals of nanometer size. It exhibits properties and is also called semiconductor nanoparticles or semiconductor nanocrystals.
The quantum dot is a semiconductor nanometer-sized fine particle and is not particularly limited as long as it is a material that produces a quantum confinement effect (quantum size effect). For example, as described above, there are semiconductor fine particles whose emission color is regulated by their own particle size and semiconductor fine particles having a dopant. As the quantum dots in the present invention, both semiconductor fine particles whose emission color is regulated by their own particle diameter and semiconductor fine particles having a dopant can be used, and excellent color purity can be obtained.

Quantum dots have different emission colors depending on their particle diameters. For example, in the case of quantum dots composed only of a core made of CdSe, the particle diameters are 2.3 nm, 3.0 nm, 3.8 nm, 4 nm, The peak wavelengths of the fluorescence spectrum at .6 nm are 528 nm, 570 nm, 592 nm, and 637 nm. That is, the particle size of the quantum dot that emits secondary light having a peak wavelength of 637 nm is 4.6 nm, and the particle size of the quantum dot that emits secondary light having a peak wavelength of 528 nm is 2.3 nm.
The quantum dot-containing layer may contain quantum dots that emit secondary light having a wavelength corresponding to red and quantum dots other than quantum dots that emit secondary light having a wavelength corresponding to green.
The content of the quantum dots is appropriately adjusted according to the thickness of the quantum dot-containing layer, the light recycling rate in the backlight, the target color, and the like. If the thickness of a quantum dot content layer is the range mentioned below, the content of a quantum dot is about 0.01-1.0 mass part to 100 mass parts of binder resin of a quantum dot content layer. If the content of the quantum dots is about this level, the above conditions (1) and (2) are hardly affected.

Specifically, the core material of the quantum dot includes MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS II-VI group semiconductor compounds such as HgSe and HgTe, III- such as AlN, AlP, AlAs, AlSb, GaAs, GaP, GaN, GaSb, InN, InAs, InP, InSb, TiN, TiP, TiAs and TiSb Examples thereof include semiconductor compounds such as Group V semiconductor compounds, Group IV semiconductors such as Si, Ge and Pb, or semiconductor crystals containing semiconductors. Alternatively, a semiconductor crystal including a semiconductor compound containing three or more elements such as InGaP can be used.
Further, as a quantum dot composed of semiconductor fine particles having a dopant, a semiconductor crystal obtained by doping the semiconductor compound with a cation of a rare earth metal such as Eu ³⁺ , Tb ³⁺ , Ag ⁺ , or Cu ⁺ or a cation of a transition metal is used. It can also be used.
As a material for the core of the quantum dot, a semiconductor crystal such as CdS, CdSe, CdTe, InP, InGaP is used from the viewpoint of ease of fabrication, controllability of the particle diameter to obtain light emission in the visible range, and fluorescence quantum yield. Is preferred.

The quantum dot may be composed of one kind of semiconductor compound or may be composed of two or more kinds of semiconductor compounds, for example, a core made of a semiconductor compound and a shell made of a semiconductor compound different from the core. It may have a core-shell type structure.
When a core-shell quantum dot is used, the semiconductor that constitutes the shell uses a material with a higher band gap than the semiconductor compound that forms the core so that excitons are confined in the core. Can be increased.
Examples of the core-shell structure (core / shell) having such a bandgap relationship include CdSe / ZnS, CdSe / ZnSe, CdSe / CdS, CdTe / CdS, InP / ZnS, Gap / ZnS, Si / ZnS, Examples include InN / GaN, InP / CdSSe, InP / ZnSeTe, InGaP / ZnSe, InGaP / ZnS, Si / AlP, InP / ZnSTe, InGaP / ZnSTe, and InGaP / ZnSSe.

The size of the quantum dot may be appropriately controlled depending on the material constituting the quantum dot so that light having a desired wavelength can be obtained. As the particle size of the quantum dot decreases, the energy band gap increases. That is, as the crystal size decreases, the light emission of the quantum dots shifts to the blue side, that is, to the high energy side. Therefore, by changing the size of the quantum dot, the emission wavelength can be adjusted over the entire wavelength range of the ultraviolet region, the visible region, and the infrared region.
In general, the particle size (diameter) of the quantum dots is preferably in the range of 0.5 to 20 nm, and particularly preferably in the range of 1 to 10 nm. The narrower the quantum dot size distribution, the clearer the emission color.
The shape of the quantum dot is not particularly limited, and may be, for example, a spherical shape, a rod shape, a disk shape, or other shapes. When the particle dot is not spherical, the particle size of the quantum dot can be a true spherical value having the same volume.
The quantum dot may be coated with a resin. Further, the refractive index of the binder resin of the quantum dot containing layer and n _A, the refractive index of the resin (coating resin) for covering the quantum dots upon the n _B, n _{B /} n _A is 1.02 or more, or 0 It is preferable to satisfy a relationship of .98 or less. A quantum dot coated with a resin can improve the durability of the quantum dot. Moreover, when the refractive index of binder resin and the refractive index of coating resin satisfy | fill the said relationship, the quantum dot coated with resin has an effect | action of the internal diffusion particle mentioned later.
In the present invention, the refractive index is determined by light having a wavelength of 450 nm.

  Information such as the particle size, shape, and dispersion state of the quantum dots can be obtained by a transmission electron microscope (TEM). The crystal structure and particle size of the quantum dots can be obtained by X-ray crystal diffraction (XRD). Furthermore, the information regarding the particle size and surface of a quantum dot can also be obtained by an ultraviolet-visible (UV-Vis) absorption spectrum.

  Examples of the binder resin for the quantum dot-containing layer include thermoplastic resins, cured products of thermosetting resin compositions, and cured products of ionizing radiation curable resin compositions. Among these, from the viewpoint of durability, a cured product of the thermosetting resin composition and a cured product of the ionizing radiation curable resin composition are preferable, and a cured product of the ionizing radiation curable resin composition is more preferable.

The thermosetting resin composition is a composition containing at least a thermosetting resin, and is a resin composition that is cured by heating.
Examples of the thermosetting resin include acrylic resin, urethane resin, phenol resin, urea melamine resin, epoxy resin, unsaturated polyester resin, and silicone resin. In the thermosetting resin composition, a curing agent is added to these curable resins as necessary.

The ionizing radiation curable resin composition is a composition containing a compound having an ionizing radiation curable functional group (hereinafter also referred to as “ionizing radiation curable compound”). Examples of the ionizing radiation curable functional group include an ethylenically unsaturated bond group such as a (meth) acryloyl group, a vinyl group, and an allyl group, and an epoxy group and an oxetanyl group. Among them, an ethylenically unsaturated bond group is preferable. . Of the ethylenically unsaturated bond groups, a (meth) acrylate group is preferred. Hereinafter, an ionizing radiation curable compound having a (meth) acryloyl group is referred to as a (meth) acrylate compound.
In the present specification, “(meth) acrylate” refers to methacrylate and acrylate. In the present specification, “ionizing radiation” means an electromagnetic wave or charged particle beam having an energy quantum capable of polymerizing or cross-linking molecules, and usually ultraviolet (UV) or electron beam (EB) is used. In addition, electromagnetic waves such as X-rays and γ-rays, and charged particle beams such as α-rays and ion beams can also be used.

The ionizing radiation curable compound may be a monofunctional ionizing radiation curable compound having only one of the above functional groups, or may be a polyfunctional ionizing radiation curable compound having two or more of the above functional groups. Or a mixture thereof.
The ionizing radiation curable compound may be a monomer, an oligomer, a low molecular weight polymer, or a mixture thereof.
Among the ionizing radiation curable compounds, the monofunctional monomer is preferable in terms of improving adhesion between the quantum dot-containing layer and the light-transmitting substrate and suppressing polymerization shrinkage. In particular, when the thickness of the quantum dot-containing layer is thick, the above-described effect is remarkable when a monofunctional monomer is used.
Moreover, when the adhesiveness of a quantum dot content layer improves using a monofunctional monomer, it will become possible to adhere members, such as a light-transmitting base material, to a quantum dot content layer, without going through an adhesive bond layer. That is, by using a monofunctional monomer to improve the adhesion of the quantum dot-containing layer, the configuration of the quantum dot sheet can be easily symmetric with respect to the thickness direction about the quantum dot-containing layer. Moreover, the moisture resistance and oxygen resistance of a quantum dot can be improved by sticking a quantum dot content layer to members, such as a translucent base material, without passing through an adhesive bond layer.
The proportion of the monofunctional monomer in the total ionizing radiation curable compound is preferably 40% by mass or more, more preferably 60% by mass or more, further preferably 80% by mass or more, and 90% by mass. More preferably, it is more preferably 100% by mass.

  In addition, since the quantum dots are vulnerable to humidity, it is preferable to use as the main component an ionizing radiation curable compound that does not have a hydroxyl group in the molecule. Specifically, the ratio of the ionizing radiation curable compound having no hydroxyl group in the molecule to the total ionizing radiation curable compound is preferably 80% by mass or more, more preferably 90% by mass or more, and 100 More preferably, it is mass%.

  Examples of ionizing radiation curable compounds that do not contain a hydroxyl group in the molecule include ethyl (meth) acrylate, butyl (meth) acrylate, ethylhexyl (meth) acrylate, phenoxyethyl (meth) acrylate, octyl (meth) acrylate, dicyclopentenyl ( Monofunctional (meth) acrylate compounds such as (meth) acrylate, pentaerythritol tetra (meth) acrylate, 1,6-hexanediol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) Acrylate, tricyclodecane dimethanol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane ethoxytri (meth) acrylate, dipentaerythritol hex (Meth) acrylate, pentaerythritol ethoxy tetra (meth) acrylate, polyfunctional (meth) acrylate compounds such as ditrimethylolpropane tetra (meth) acrylate.

  The ionizing radiation curable compound preferably has a total carbon number of 8 or more from the viewpoint of improving hydrophobicity and improving the moisture resistance of the quantum dots. In consideration of the adhesion of the quantum dot-containing layer in addition to the moisture resistance, the total number of carbon atoms of the ionizing radiation curable compound is more preferably 8-20. For example, examples of the monofunctional (meth) acrylate monomer having a total carbon number of 8 or more include ethylhexyl (meth) acrylate and octyl (meth) acrylate.

The molecular weight of the ionizing radiation curable compound is preferably 100 to 2000, more preferably 120 to 1000, and still more preferably 150 to 500. When the molecular weight of the ionizing radiation curable compound is 100 or more, it is possible to easily prevent liquid dripping at the time of production, and when the molecular weight is 2000 or less, the pressure at the time of bonding in the step (d) described later is The thickness of the dot-containing layer can be easily made uniform.
When a monofunctional monomer is used as the ionizing radiation curable compound, the molecular weight of the monofunctional monomer is 100 from the viewpoint of preventing dripping at the time of production, uniforming the thickness of the quantum dot-containing layer, and adhesion of the quantum dot-containing layer. It is preferable that it is -500, It is more preferable that it is 120-400, It is further more preferable that it is 150-250.

When the ionizing radiation curable compound is an ultraviolet curable compound, the ionizing radiation curable composition preferably contains additives such as a photopolymerization initiator and a photopolymerization accelerator.
Examples of the photopolymerization initiator include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler's ketone, benzoin, benzylmethyl ketal, benzoylbenzoate, α-acyloxime ester, thioxanthones, and the like.
These photopolymerization initiators preferably have a melting point of 20 ° C. or lower. This is because when the melting point is 20 ° C. or lower, it can be easily dissolved at room temperature when added to the ionizing radiation curable compound at the time of production.
The photopolymerization accelerator can reduce polymerization inhibition by air during curing and increase the curing speed. For example, p-dimethylaminobenzoic acid isoamyl ester, p-dimethylaminobenzoic acid ethyl ester, etc. One or more selected may be mentioned.

Internal diffusion particles The quantum dot-containing layer preferably contains internal diffusion particles. By including the internal diffusion particles, light can be diffused to a high angle, and the above-described conditions (1) and (2) can be easily satisfied.

As the internal diffusion particles, both organic particles and inorganic particles can be used. Examples of the organic particles include particles made of polymethyl methacrylate, acrylic-styrene copolymer, melamine resin, polycarbonate, polystyrene, polyvinyl chloride, benzoguanamine-melamine-formaldehyde condensate, silicone resin, fluorine resin, polyester, and the like. . Examples of the inorganic fine particles include fine particles made of silica, alumina, zirconia, titania and the like.
Examples of the shape of the internal diffusion particles include a spherical shape, a disk shape, a rugby ball shape, and an indefinite shape.
The internal diffusion particles may be hollow particles, porous particles, or solid particles.

Further, as the internal diffusion particles, those in which n _B / n _A is 1.02 or more or 0.98 or less when the refractive index of the binder resin is n _A and the refractive index of the internal diffusion particles is n _B are used. It is preferable. n _B / n _A is a relative refractive index between the binder resin and the internal diffusion particles, and diffusion (particularly diffusion to a high angle) by setting n _B / n _A to 1.02 or more or 0.98 or less. And the conditions (1) and (2) described above can be easily satisfied. Further, by setting n _B / n _A to 1.02 or more or 0.98 or less, the probability that the primary light collides with the quantum dots increases, and the amount of quantum dots used can be reduced.
n _B / n _A is more preferably 1.10 or more and 0.95 or less, or 1.15 or more and 0.90 or less from the viewpoint of a balance between strong diffusibility and suppression of light leakage of the polarizing plate.
The refractive index of the internal diffusion particles can be measured by the Becke method, and the refractive index of the binder resin can be measured by the Abbe method.

  The content of the internal diffusion particles is preferably 1 to 40 parts by mass and more preferably 3 to 30 parts by mass with respect to 100 parts by mass of the binder resin. By setting the content of the internal diffusing particles in the above range, light can be diffused to a high angle while light leakage from the polarizing plate can be prevented.

  The average particle size of the internal diffusion particles is preferably 10 μm or less, and more preferably 3 μm or less, from the viewpoint of increasing the number of particles per content and achieving diffusion uniformity. Note that the lower limit of the average particle size of the internal diffusion particles is about 0.1 μm.

The average particle diameter of the internal diffusion particles can be calculated by the following operations (1) to (3).
(1) The transmission observation image of a quantum dot content layer is imaged with an optical microscope. The magnification is preferably 500 to 2000 times.
(2) Ten arbitrary particles are extracted from the observed image, the major axis and minor axis of each particle are measured, and the particle diameter of each particle is calculated from the average of the major axis and minor axis. The major axis is the longest diameter on the screen of individual particles. The minor axis is a distance between two points where a line segment perpendicular to the midpoint of the line segment constituting the major axis is drawn and the perpendicular line segment intersects the particle.
(3) The same operation is performed five times on the observation image of another screen of the same sample, and the value obtained from the number average of the particle diameters for a total of 50 particles is taken as the average particle diameter of the internal diffusion particles.
The average particle diameter of the diffusing particles in the light diffusing layer to be described later can also be calculated according to the above work.

The thickness of the quantum dot-containing layer is preferably 10 to 200 μm, more preferably 20 to 150 μm, and still more preferably 30 to 130 μm. When the thickness of the quantum dot-containing layer is within this range, it is suitable for reducing the weight and thickness of the display device, and color unevenness due to fluctuation (manufacturing tolerance) of the thickness of the quantum dot-containing layer can be suppressed.
The thickness of the quantum dot-containing layer can be calculated, for example, by measuring the thickness at 20 locations from a cross-sectional image taken using a scanning transmission electron microscope (STEM) and calculating the average value of the 20 locations. The STEM acceleration voltage is preferably 10 kv to 30 kV, and the magnification is preferably 1000 to 7000 times.
The thicknesses of the other layers constituting the quantum dot sheet can also be measured by the same method as described above. When the thickness is nano-order, the STEM magnification is preferably 50,000 to 300,000 times.

Light transmissive substrate The quantum dot sheet of the present invention preferably has a light transmissive substrate from the viewpoint of mechanical strength and stiffness. From this point of view, it is preferable that the light-transmitting substrate has one or more sheets above and below the quantum dot-containing layer.
Moreover, it is preferable that a quantum dot sheet | seat is the structure formed by pinching both surfaces of a quantum dot content layer with a transparent base material. According to this configuration, the quantum dot-containing layer can be protected, and the oxygen resistance and moisture resistance of the quantum dots can be improved.

The light-transmitting substrate is not particularly limited, but preferably has a light-transmitting property, smoothness, heat resistance, and excellent mechanical strength. Examples of such a light-transmitting substrate include polyester, triacetyl cellulose (TAC), cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyether sulfone, polysulfone, polypropylene, polymethylpentene, polyvinyl chloride, Examples thereof include plastic films such as polyvinyl acetal, polyether ketone, acrylic, polycarbonate, polyurethane, and amorphous olefin (Cyclo-Olefin-Polymer: COP).
Among these, from the viewpoint of mechanical strength, dimensional stability, and heat resistance, polyester (polyethylene terephthalate, polyethylene naphthalate) that has been stretched, particularly biaxially stretched, is preferable.

The thickness of the light-transmitting substrate is preferably 10 to 200 μm, more preferably 20 to 150 μm, and even more preferably 30 to 100 μm, from the viewpoint of the balance between weather resistance, mechanical strength, handleability, and thinning.
In addition to physical treatment such as corona discharge treatment and oxidation treatment, a coating called an anchor agent or a primer may be applied to the surface of the light transmissive substrate in advance in order to improve adhesion.

Barrier layer The quantum dot sheet of the present invention preferably has a barrier layer in order to improve the moisture resistance and oxygen resistance of the quantum dots. The barrier layer may be provided only on one side of the quantum dot-containing layer, but is preferably provided on both sides of the quantum dot-containing layer.
The barrier layer may be provided on a light-transmitting base material that sandwiches the quantum dot-containing layer as shown in FIG. 3, or may be provided on another light-transmitting base material as shown in FIG.
The barrier layer is preferably provided on the side close to the quantum dot-containing layer. For example, when it has a light-diffusion layer mentioned later, it is preferable to provide a barrier layer in the quantum dot content layer side rather than a light-diffusion layer.

The barrier layer is preferably made of an inorganic substance or an inorganic oxide, and examples thereof include a vapor deposition film of an inorganic substance or an inorganic oxide and a hydrolyzed film of an inorganic alkoxide.
The barrier layer can be formed by a known method using a known inorganic substance, inorganic oxide, inorganic alkoxide, and the like, and the composition and formation method are not particularly limited. The barrier layer may be a single layer or may have two or more layers. When two or more barrier layers are provided, each may have the same composition or a different composition.

The material of the deposited film is silicon (Si), aluminum (Al), magnesium (Mg), calcium (Ca), potassium (K), tin (Sn), sodium (Na), boron (B), titanium (Ti). , Lead (Pb), zirconium (Zr), yttrium (Y), and the like, oxides thereof, and those in which an organic substance is blended.
The inorganic alkoxide that is a material of the hydrolyzed membrane is also called a metal alkoxide, and examples thereof include silicon alkoxide such as tetraalkoxysilane, titanium alkoxide, and aluminum alkoxide.

The thickness of the barrier layer is preferably 5 to 1000 nm, more preferably 7 to 700 nm, and more preferably 10 to 500 nm, from the viewpoint of the balance between moisture resistance, oxygen resistance, cracking suppression, and light transmittance. Further preferred. When the barrier layer is a deposited film, the thickness of the barrier layer is preferably 5 to 30 nm, more preferably 7 to 25 nm, and still more preferably 10 to 20 nm.
As a method for forming a vapor deposition film as a barrier layer, for example, a physical vapor deposition method (PVD method) such as a vacuum vapor deposition method, a sputtering method and an ion plating method, a plasma chemical vapor deposition method, a thermal chemical vapor deposition method, or the like. Examples thereof include a chemical vapor deposition method (CVD method) such as a growth method and a photochemical vapor deposition method.

Light Diffusion Layer The quantum dot sheet of the present invention preferably has a light diffusion layer in order to enhance the diffusion and easily satisfy the conditions (1) and (2).
The light diffusion layer may be provided only on one side of the quantum dot-containing layer, but is preferably provided on both sides of the quantum dot-containing layer. Moreover, it is preferable to arrange | position a light-diffusion layer in the position which can be identified with the outermost layer of a quantum dot sheet, or the outermost layer. When the light diffusing layer is provided only on one side of the quantum dot-containing layer, the light diffusing layer is preferably disposed at the outermost layer on the light emitting surface side or a position where it can be identified with the outermost layer.
The position that can be identified with the outermost layer is the light diffusion when a thin film (thickness of 100 nm or less) that does not substantially affect the surface unevenness of the light diffusion layer is formed on the light diffusion layer. Refers to the position of the layer.
The light diffusion layer may be provided on a light-transmitting base material that sandwiches the quantum dot-containing layer as shown in FIGS. 2 and 3, or may be provided on another light-transmitting base material as shown in FIG. Good.

The light diffusion layer preferably has external diffusion due to surface irregularities. By disposing such a light diffusion layer at a position where it can be identified with the outermost layer or the outermost layer, it is possible to prevent adhesion with a member (such as a brightness enhancement sheet) that comes into contact with the quantum dot sheet. Moreover, low to medium angle diffusion is enhanced by external diffusion, and conditions (1) and (2) can be easily satisfied.
The light diffusion layer can be formed from, for example, a binder resin and diffusion particles.

Examples of the binder resin of the light diffusion layer include thermoplastic resins, cured products of thermosetting resin compositions, and cured products of ionizing radiation curable resin compositions. Among these, from the viewpoint of scratch resistance, a cured product of a thermosetting resin composition and a cured product of an ionizing radiation curable resin composition are preferable, and a cured product of an ionizing radiation curable resin composition is more preferable.
As the thermosetting resin composition and the ionizing radiation curable resin composition, those similar to those exemplified for the quantum dot-containing layer can be used.

The ratio of the average particle diameter of the diffusion particles to the thickness of the light diffusion layer (average particle diameter of diffusion particles / thickness of the light diffusion layer) is preferably 0.10 to 2.00, preferably 0.15 to 1 .50 is more preferable, and 0.20 to 1.00 is more preferable.
By setting the ratio of the average particle diameter of the diffusion particles of the light diffusion layer on the light exit surface side to the thickness of the light diffusion layer to be 0.10 or more, strong external diffusion can be imparted. Further, by setting the ratio of the average particle diameter of the light diffusion layer of the light diffusion layer on the light incident surface side to the thickness of the light diffusion layer to be 0.10 or more, retroreflectivity is imparted and the light recycling rate is increased. It is possible to reduce the content of quantum dots. Further, by setting the ratio of the average particle diameter of the diffusion particles and the thickness of the light diffusion layer to 2.00 or less, the diffusion particles can be sufficiently retained in the light diffusion layer.
Moreover, from the viewpoint of easily obtaining the effect based on the above ratio, the average particle diameter of the diffusion particles of the light diffusion layer is preferably 1 to 20 μm, and more preferably 1 to 10 μm.

  As the diffusion particles, both organic particles and inorganic particles can be used, and the same particles as those exemplified as the internal diffusion particles of the quantum dot-containing layer can be used.

The thickness of the light diffusion layer is preferably 1 to 30 μm, and more preferably 3 to 20 μm, from the viewpoints of the retention of diffusing particles and external diffusibility.
The diffusing particles of the light diffusion layer are preferably 10 to 200 parts by mass and more preferably 30 to 170 parts by mass with respect to 100 parts by mass of the binder resin from the viewpoint of the balance between diffusibility and coating film strength. Preferably, it is 50-150 mass parts.

Adhesive layer In order to laminate the layers constituting the quantum dot sheet, an adhesive layer may be interposed between the layers. For example, in FIG. 4, an adhesive layer is provided between the light transmissive substrate and the barrier film, and between the barrier film and the diffusion film.
The adhesive layer can be formed from a general-purpose pressure-sensitive adhesive (pressure-sensitive adhesive), a thermosetting adhesive, or an ionizing radiation curable adhesive.
The thickness of the adhesive layer is preferably 0.5 to 20 μm and more preferably 1 to 10 μm from the viewpoint of adhesive strength and thinning.

  The quantum dot sheet may have functional layers other than the above, such as an antireflection layer and an antistatic layer.

Although the manufacturing method of a quantum dot sheet is not specifically limited, For example, it can manufacture in order of the following (a)-(d).
(A) The process of obtaining the laminated body A by laminating | stacking the transparent base material and layer which are located on one surface of a quantum dot content layer on the basis of a quantum dot content layer.
(B) The process of obtaining the laminated body B by laminating | stacking the transparent base material and layer which are located on the other surface of a quantum dot content layer on the basis of a quantum dot content layer.
(C) A quantum dot-containing layer coating solution containing a quantum dot that absorbs primary light and emits secondary light and a binder resin component on one surface of any one of the laminates A and B The process of apply | coating and forming a quantum dot content layer.
(D) The process of bonding the laminated body in which the quantum dot containing layer is not formed in the step (c) and the surface on the quantum dot containing layer side of the laminated body in which the quantum dot containing layer is formed in the process (c).

  In the step (d), an adhesive layer may be used. However, by bonding without using the adhesive layer, a vertically symmetric configuration is possible with the quantum dot-containing layer as the center as shown in FIGS. Therefore, it is preferable.

In the case where the binder resin of the quantum dot-containing layer is a cured product of an ionizing radiation curable resin composition, in order to bond the laminate A and the laminate B without using an adhesive layer in the step (d), It is preferable to adopt this method.
First, it is preferable that the ionizing radiation curable resin composition contains a monofunctional monomer (in other words, the quantum dot-containing layer coating solution contains a monofunctional monomer).
Second, when forming the quantum dot-containing layer in the step (c), the ionizing radiation is not irradiated, or the ionizing radiation dose is suppressed and an uncured portion is left in the ionizing radiation curable resin composition. It is preferable that ionizing radiation is irradiated after step (d) to advance the curing of the ionizing radiation curable resin composition.
Combining the first method and the second method is preferable in that the workability of bonding the two laminates without using an adhesive layer is improved in step (d).

Prism sheet A prism sheet is a structure in which a plurality of structural rows having a triangular cross-sectional shape are formed substantially in parallel. The apex angle of the triangle in the cross section is preferably 85 to 95 degrees, and more preferably 88 to 92 degrees. By setting the apex angle to 85 to 95 degrees, the front luminance can be improved. The cross-sectional shape is preferably an isosceles triangle.

  As the prism sheet, either a repeated arrangement in which individual triangles in cross section have the same shape or a different shape array is preferably used. In addition, the height in the thickness direction of the structure row formed on the sheet surface may be constant or may vary as viewed in the longitudinal direction of the structure row. Furthermore, in the sheet surface, the top line of the structural row may be linear or may be changed into a wave shape.

  It is preferable to have the support part which supports a structure row below the structure row. The height of the structure row is about 5 to 50 μm, and the thickness of the support portion is about 25 to 300 μm. The structure rows may be arranged without a gap as shown in FIG. 1, or may be arranged with a gap. The pitch of the structure rows (the pitch of the apex angles of the triangles in the cross section) is substantially the same as the height of the structure rows when the structure rows are arranged without gaps.

In addition, the prism sheet may have a base material instead of a single layer structure. For example, the structure which has a support part and a structure row | line | column on a base material is mentioned. When a prism sheet has a base material, the thickness of a support part can be made thinner than the said thickness.
Further, in FIG. 1, only one prism sheet is provided on the quantum dot sheet, but two prism sheets may be provided. When two prism sheets are provided, it is preferable to arrange the structure rows so that the direction of the structure row is perpendicular to the lower one and the upper one.

Examples of the method for producing the prism sheet include transfer shaping techniques such as the 2P method, the 2T method, and the embossing method. For example, a mold having a shape complementary to the surface shape of the prism sheet is prepared, and the mold is filled with a polymer resin, and after the shape pattern is transferred and shaped, the polymer resin is cured, A prism sheet is obtained by peeling from the mold. On the other hand, in the case of using a base material, the polymer resin or the like is filled in the mold, the base material is overlaid thereon, the polymer resin or the like is cured, and the base material is peeled off from the mold. A prism sheet having a support portion and a structure row thereon is obtained.
As the polymer resin of the prism sheet, for example, the resin exemplified in the quantum dot-containing layer can be used.

In the quantum dot laminate, the prism sheet is preferably arranged so that the unstructured surface of the prism sheet faces the quantum dot sheet side.
Further, in the quantum dot laminate, it is preferable that the prism sheet and the quantum dot sheet are not bonded, and an air layer is interposed between the prism sheet and the quantum dot sheet.

[Backlight]
The backlight of the present invention includes at least one light source that emits primary light, an optical plate that is disposed adjacent to the light source, and that guides or diffuses light, and an optical device that is disposed on the light output side of the optical plate. In the backlight including the member, the optical member is the above-described quantum dot sheet of the present invention.

  As an example of the backlight of the present invention, an edge light type backlight as shown in FIG. 5 or a direct type backlight as shown in FIG. 6 can be adopted.

  The optical plate 120 used in the edge light type backlight of FIG. 5 is an optical member for guiding the primary light emitted from the light source 110, and is a so-called light guide plate. The light guide plate has, for example, a substantially flat shape formed such that at least one surface is a light incident surface and one surface substantially orthogonal to the light incident surface is a light emitting surface.

  The light guide plate is mainly made of a matrix resin selected from highly transparent resins such as polymethyl methacrylate. The light guide plate may be added with resin particles having a refractive index different from that of the matrix resin as required. Each surface of the light guide plate may have a complicated surface shape instead of a uniform plane, and may be provided with a dot pattern or the like.

  The optical plate 120 used in the direct type backlight of FIG. 6 is an optical member (light diffusing material) having light diffusibility for making the pattern of the light source 110 difficult to see. Examples of the light diffusing material include a milky white resin plate having a thickness of about 1 to 3 mm.

  In addition to the light source, optical plate, and quantum dot sheet described above, the edge light type and direct type backlights include a reflection plate, a light diffusion film, a prism sheet, a brightness enhancement film (BEF), and a reflection type depending on the purpose. One or more members selected from a polarizing film (DBEF) and the like may be provided. The reflecting plate is disposed on the side opposite to the light emitting surface side of the optical plate. The light diffusion film, the prism sheet, the brightness enhancement film, and the reflective polarizing film are disposed on the light exit surface side of the optical plate. By having a configuration including one or more members selected from a reflector, a light diffusion film, a prism sheet, a brightness enhancement film, a reflective polarizing film, etc., a backlight having excellent balance of front luminance, viewing angle, etc. Can do.

In the edge light type and direct type backlights, the light source 110 is a light emitter that emits primary light, and it is preferable to use a light emitter that emits primary light having a wavelength corresponding to blue. The primary light having a wavelength corresponding to blue preferably has a peak wavelength in the range of 380 to 480 nm, and more preferably has a peak wavelength of 450 nm. The light source 110 is preferably an LED light source, more preferably a blue single-color LED light source, from the viewpoint that a device for installing a backlight can be simplified and miniaturized. The number of the light sources 110 is at least one, and a plurality of light sources 110 are preferable from the viewpoint of emitting sufficient primary light.
In addition, when only one of the first quantum dots and the second quantum dots is contained in the quantum dot-containing layer of the quantum dot sheet, in addition to the primary light source composed of a light emitter that emits primary light having a wavelength corresponding to blue. It is preferable to have an auxiliary light source. Specifically, when only the first quantum dot is contained in the quantum dot-containing layer, it is preferable to use a light emitter that emits light having a wavelength corresponding to green as an auxiliary light source. Moreover, when only the 2nd quantum dot is contained in a quantum dot content layer, it is preferable to use the light-emitting body which emits the light of the wavelength equivalent to red as an auxiliary light source.

  Since the backlight of the present invention uses the above-described quantum dot sheet of the present invention, the color of the edge region of the backlight and the angle dependency of the color can be improved.

[Liquid Crystal Display]
The liquid crystal display device of the present invention is a liquid crystal display device including a backlight and a liquid crystal panel, and the backlight is the above-described backlight of the present invention.

  FIG. 7 is a cross-sectional view showing an embodiment of the liquid crystal display device of the present invention. The liquid crystal display device 300 in FIG. 7 includes a backlight 200 and a liquid crystal panel 210. Further, the backlight 200 and the liquid crystal panel 210 are incorporated and fixed in the holder 220.

  The liquid crystal panel includes a polarizing plate (not shown) and a color filter (not shown). The liquid crystal panel is not particularly limited, and generally known liquid crystal panels for liquid crystal display devices can be used. For example, a liquid crystal panel having a general structure in which the upper and lower sides of the liquid crystal layer are sandwiched between glass plates, specifically, display types such as TN, STN, VA, IPS and OCB can be used.

  The polarizing plate is not particularly limited as long as it has desired polarization characteristics, and generally known polarizing plates can be used as a polarizing plate for a liquid crystal display device. Specifically, for example, a polyvinyl alcohol film is stretched, and a polarizing plate containing iodine is preferably used.

The color filter is not particularly limited. For example, a color filter that is generally known as a color filter of a liquid crystal display device can be used. The color filter is usually composed of transparent colored patterns of each color of red, green and blue, and each transparent colored pattern is composed of a resin composition in which a colorant is dissolved or dispersed, preferably pigment fine particles are dispersed. .
The color filter is formed by adjusting the ink composition colored in a predetermined color and printing it for each colored pattern, or a paint type photosensitive resin composition containing a colorant of a predetermined color The method of forming by a photolithographic method using a thing is mentioned.

  The display image of the liquid crystal display device is displayed in color as white light emitted from the backlight passes through the color filter. A liquid crystal display device can realize a display that is excellent in brightness and efficiency and generates a very clear color by using a color filter that matches a backlight spectrum of quantum dots.

  The liquid crystal panel may have a configuration in which an arbitrary layer is formed as a single layer or multiple layers on a color filter. The optional layer is not particularly limited. For example, the sensor layer for touch panel, hard coat layer, antistatic layer, low refractive index layer, high refractive index layer, antiglare layer, antifouling layer, antireflection layer, high dielectric Examples thereof include a body layer, an electromagnetic wave shielding layer, and an adhesive layer.

  Since the liquid crystal display device of the present invention uses the above-described backlight of the present invention, the color of the edge region of the display image and the angle dependency of the color can be improved.

  EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited at all by these examples. “Part” and “%” are based on mass unless otherwise specified. The refractive index is a refractive index with a wavelength of 450 nm unless otherwise specified.

1. Measurement and Evaluation of Physical Properties of Quantum Dot Sheets Physical property measurements and evaluations of quantum dot sheets of Examples and Comparative Examples were performed as follows. The results are shown in Table 1.

1-1. Intensity of transmitted light A light source angle of 0 was measured by transmission measurement using a goniophotometer (GC-5000L, manufactured by Nippon Denshoku Industries Co., Ltd., light source: halogen lamp (12V, 48W)) by the method described in the specification text. The intensity and the sensitivity setting were set to 1000 times, the intensity of the transmitted light of the quantum dot sheet was measured every degree, and P ₁ , P ₂ and P ₃ were calculated. The average value when measured 20 times is shown in Table 1. The intensity was measured in a range of ± 85 degrees in the normal transmission direction (0 degrees).

1-2. Surface roughness Ra and Rz on the surface of the quantum dot sheet using a surface roughness measuring instrument (model number: SE-3400 / manufactured by Kosaka Laboratory Ltd.) according to JIS B0601: 2001 under the following measurement conditions. _JIS was measured. The average value when measured 20 times is shown in Table 1.
[Surface probe for surface roughness detection]
Product name SE2555N manufactured by Kosaka Laboratory Ltd. (tip radius of curvature: 2 μm, apex angle: 90 degrees, material: diamond)
[Measurement conditions of surface roughness measuring instrument]
Reference length (roughness curve cut-off value λc): 0.8 mm
Evaluation length (reference length (cutoff value λc) × 5): 4.0 mm
・ Feeding speed of stylus: 0.5mm / s
・ Preliminary length: (cutoff value λc) × 2
・ Vertical magnification: 2000 times ・ Horizontal magnification: 10 times

1-3. Front luminance The backlights of the examples and comparative examples were turned on, and the front luminance was visually evaluated. Twenty subjects evaluated and calculated the average score based on the evaluation criteria of one point that felt bright enough, two points that could be said to be neither, and three points that felt dark. Those with an average score of less than 1.25 points are “AA”, those with an average score of 1.25 or more and less than 1.50 points are “A”, and those with an average score of 1.50 or more and less than 1.75 points Is “B”, those having an average score of 1.75 or more and less than 2.00 are “B ⁻ ”, and those having an average score of 2.00 or more are “C”.

1-4. Color of edge region The backlights of the examples and comparative examples were turned on, and the color of the edge region of the backlight was visually evaluated from the front direction. 1 point for those who do not care about bluishness at all, 2 points for those with a slight bluishness level, but no problem for practical use, and 3 points for those with strong blueness and practically problematic level Based on the criteria, 20 subjects evaluated and calculated the average score. Those with an average score of 1.25 or less are “AAA”, those with an average score of more than 1.25 and less than 1.50 are “AA”, and those with an average score of more than 1.50 and less than 1.75 "a", having an average point of less than 2.00 points 1.75 points than "B", the average point is the following: 2.00 points than 2.25 points "B ^-", the average score is 2 . A score exceeding 25 points was designated as “C”.

2. Fabrication of Quantum Dot Refer to the method described in the technical document “Journal of American Chemical Society. 2007, 129, 15432-15433”, and an InP / ZnS core-shell quantum dot (quantum dot A having a peak wavelength of 637 nm in the fluorescence spectrum). ), And InP / ZnS core-shell quantum dots (quantum dots B) having a fluorescence spectrum peak wavelength of 528 nm.
Next, quantum dots A are added to a mixed solution of aminopolystyrene (manufactured by SMA, trade name: SMA EF80) and epoxy resin (manufactured by Loctite, trade name: E-30CL) in a solvent. A polystyrene mixture was prepared. After the solvent of the mixed solution is evaporated and the mixture is further cured to obtain a cured product, the cured product is pulverized with a ball mill to obtain quantum dots C in which quantum dots A are coated with aminopolystyrene and epoxy resin. Obtained. The same operation was performed on the quantum dots B, and quantum dots D obtained by coating the quantum dots B with aminopolystyrene and epoxy resin were obtained.

3. Production of Quantum Dot Sheet and Quantum Dot Laminate [Example 1]
A barrier layer having a thickness of 20 nm made of silicon oxide was formed on one surface of a biaxially stretched PET film having a thickness of 12 μm by a PVD method to obtain a barrier film. Next, on one surface of a 50 μm thick biaxially stretched PET film, a light diffusing layer coating solution a1 having the following formulation was applied and dried so that the thickness after drying was 11 μm, and then irradiated with ultraviolet rays to irradiate the light diffusing layer. And a light diffusion film was obtained. Next, a light diffusion film, a barrier film, and a biaxially stretched PET film having a thickness of 50 μm were laminated in the order described above via an adhesive layer having a thickness of 3 μm to obtain a laminate A (see FIG. 4). The barrier film and the light diffusing film were bonded together so that the surfaces on the biaxially stretched PET film side of both faces each other. Subsequently, the laminated body B was obtained by the operation | work similar to the above.
Next, the quantum dot-containing layer coating liquid b1 having the following prescription is applied to the surface of the laminate A on the biaxially stretched PET film side, dried so that the thickness after drying becomes 100 μm, and contains the quantum dots not irradiated with ionizing radiation. A layer was formed.
Next, the quantum dot-containing layer that has not been irradiated with ionizing radiation is laminated with the biaxially stretched PET film side surface of the laminate B facing each other, and ultraviolet rays are irradiated from the light diffusion layer side of the laminate A to obtain ionizing radiation. Curing of the curable resin composition was advanced to obtain a quantum dot sheet 1.
Next, a prism sheet (manufactured by 3M Japan, trade name: BEF2-T-155N) was placed on the quantum dot sheet 1 to obtain a quantum dot laminate of Example 1.

<Light diffusion layer coating solution a1>
・ Pentaerythritol triacrylate 30 parts (manufactured by Nippon Kayaku Co., Ltd., KAYARAD-PET-30)
・ 70 parts of urethane acrylate (manufactured by Nippon Synthetic Chemical Co., Ltd., UV1700B)
-Photopolymerization initiator 5 parts (BASF, Irgacure 184)
・ Silicon-based leveling agent 0.1 part (Momentive Performance Materials, TSF4460)
・ 100 parts of urethane resin diffusion particles (average particle size 3μm)
・ 500 parts of diluted solvent

<Quantum dot content layer coating liquid b1>
-100 parts of isononyl acrylate (monofunctional monomer, refractive index 1.45)
-Photopolymerization initiator 5 parts (BASF, Irgacure 184)
・ Quantum dot A 0.2 part ・ Quantum dot B 0.2 part ・ Inner scattering particle 20 parts (true spherical alumina, average particle diameter 1.5 μm, refractive index 1.76)
・ Diluted solvent 5 parts

[Example 2]
Laminates A and B were obtained in the same manner as in Example 1 except that the light diffusion layer coating solution a1 was changed to the following light diffusion layer coating solution a2 and the thickness of the light diffusion layer was changed to 2 μm. Next, on the light diffusion layers of the laminate A1 and the laminate B1, the following overcoat layer coating liquid c1 is applied so that the thickness after drying is 120 nm, dried, and irradiated with ultraviolet rays to form an overcoat layer. Laminated body A1 and laminated body B1 were obtained. Next, on the surface on the biaxially stretched PET film side of the laminate A1, the quantum dot-containing layer coating solution b2 having the following formulation is applied and dried so that the thickness after drying is 100 μm, and the acrylic polyol and isocyanate are completely removed. An unreacted quantum dot-containing layer was formed.
Next, the quantum dot-containing layer and the biaxially stretched PET film side surface of the laminate B1 are laminated facing each other, and aged at 50 ° C. for one week to allow the reaction between acrylic polyol and isocyanate to proceed. Sheet 2 was obtained.
Next, a prism sheet (manufactured by 3M Japan, trade name: BEF2-T-155N) was placed on the quantum dot sheet 2 to obtain a quantum dot laminate of Example 2.

<Light diffusion layer coating solution a2>
・ Pentaerythritol triacrylate 30 parts (manufactured by Nippon Kayaku Co., Ltd., KAYARAD-PET-30)
・ 70 parts of urethane acrylate (manufactured by Nippon Synthetic Chemical Co., Ltd., UV1700B)
-Photopolymerization initiator 5 parts (BASF, Irgacure 184)
・ Silicon-based leveling agent 0.1 part (Momentive Performance Materials, TSF4460)
・ 5 parts of urethane resin diffusion particles (average particle size 3μm)
・ 500 parts of diluted solvent

<Quantum dot content layer coating liquid b2>
-Acrylic polyol 162 parts (manufactured by DIC, Acrydic A-807, solid content 50%)
・ Isocyanate 32 parts (Mitsui Chemicals, Takenate D110N, solid content 60%)
・ Quantum dot C 0.4 part ・ Quantum dot D 0.4 part ・ Diluent 400 parts

<Overcoat layer coating solution c1>
・ 1 part of UV curable resin (manufactured by Nippon Kayaku Co., Ltd., KAYARAD-PET-30)
-Photopolymerization initiator 0.2 part (manufactured by BASF, Irgacure 127)
・ Leveling agent 0.1 parts (manufactured by Dainichi Seika Kogyo Co., Ltd., Seika Beam 10-28 (MB))
・ Diluted solvent 90 parts

[Example 3]
A quantum dot sheet 3 was obtained in the same manner as in Example 1 except that the internal scattering particles of the quantum dot-containing layer coating liquid b1 were changed to true spherical zirconia (average particle diameter 0.1 μm, refractive index 2.2). . Next, a prism sheet (manufactured by 3M Japan, trade name: BEF2-T-155N) was placed on the quantum dot sheet 3 to obtain a quantum dot laminate of Example 3.

[Example 4]
The quantum dot sheet 4 was formed in the same manner as in Example 1 except that the internal scattering particles of the quantum dot-containing layer coating solution b1 were changed to true spherical styrene beads (average particle diameter 3.0 μm, refractive index 1.59). Obtained. Next, a prism sheet (manufactured by 3M Japan, trade name: BEF2-T-155N) was placed on the quantum dot sheet 4 to obtain a quantum dot laminate of Example 4.

[Example 5]
A quantum dot sheet 5 was obtained in the same manner as in Example 1 except that the internal scattering particles were removed from the quantum dot-containing layer coating solution 1a. Next, a prism sheet (manufactured by 3M Japan, trade name: BEF2-T-155N) was placed on the quantum dot sheet 5 to obtain a quantum dot laminate of Example 5.

[Example 6]
The quantum dot sheet 6 was obtained in the same manner as in Example 1 except that the addition amount of the urethane resin-based diffusion particles in the light diffusion layer coating liquid a1 was changed to 5 parts and the thickness of the light diffusion layer was changed to 3 μm. . Next, a prism sheet (manufactured by 3M Japan, trade name: BEF2-T-155N) was placed on the quantum dot sheet 6 to obtain a quantum dot laminate of Example 6.

[Comparative Example 1]
A quantum dot sheet 7 was obtained in the same manner as in Example 1 except that the addition amount of the urethane resin diffusion particles in the light diffusion layer coating liquid a1 was changed to 3 parts and the thickness of the light diffusion layer was changed to 3 μm. . Next, a prism sheet (manufactured by 3M Japan, trade name: BEF2-T-155N) was placed on the quantum dot sheet 7 to obtain a quantum dot laminate of Comparative Example 1.

[Comparative Example 2]
A quantum dot sheet 8 was obtained in the same manner as in Example 1 except that the addition amount of the urethane resin-based diffusing particles in the light diffusion layer coating liquid a1 was changed to 0 part. Next, a prism sheet (manufactured by 3M Japan, trade name: BEF2-T-155N) was placed on the quantum dot sheet 8 to obtain a quantum dot laminate of Comparative Example 2.

4). Production of Backlight and Liquid Crystal Display Device A commercially available liquid crystal display device (7 inches diagonal) using a blue LED as a light source was disassembled, and the backlight was taken out. The backlight was an edge light type, and had a reflecting plate below the light guide plate and a light diffusion film and a prism sheet above the light guide plate.
The light diffusion film and the prism sheet are removed from the backlight, and the quantum dot laminates of Examples 1 to 6 and Comparative Examples 1 and 2 are disposed on the light guide plate, and Examples 1 to 6 and Comparative Examples 1 to 2 are arranged. Got the backlight.
Next, the backlights of Examples 1 to 6 and Comparative Examples 1 and 2 were returned to the places where the backlights of the disassembled liquid crystal display devices were installed, and the liquid crystal display devices of Examples 1 to 6 and Comparative Examples 1 to 2 were returned. Got.

As is clear from the results in Table 1, the quantum dot laminates, backlights and liquid crystal display devices of Examples 1 to 6 are compared with the quantum dot laminates, backlights and liquid crystal display devices of Comparative Examples 1 and 2, It was confirmed that the front luminance was good.
Furthermore, the quantum dot laminates, backlights, and liquid crystal display devices of Examples 1 to 6 can improve the color of the edge region as compared with the quantum dot laminates and backlights of Comparative Examples 1-2. .

10: Quantum dot-containing layers 21a, 21b, 31a, 31b, 41a, 41b: light-transmitting substrate 30a, 30b: barrier film 32a, 32b: barrier layer 40a, 40b: light diffusion film 42a, 42b: light diffusion layer 51a , 51b, 52a, 52b: Adhesive layer 61: Laminate A
62: Laminate B
100x: quantum dot sheet 100y: prism sheet 100z: quantum dot stack 110: light source 120: optical plate 130: reflector 200: backlight 210: liquid crystal panel 220: holder 300: liquid crystal display device

Claims (8)

Edge light type comprising: at least one light source that emits primary light; an optical plate disposed adjacent to the light source for guiding light; and an optical member disposed on a light emitting surface side of the optical plate. Backlight,
The optical member includes a quantum dot sheet and a prism sheet positioned on the light exit surface side of the quantum dot sheet,
The light source is disposed adjacent to a surface substantially orthogonal to the light exit surface of the optical plate;
The quantum dot sheet has a quantum dot-containing layer including a quantum dot that absorbs primary light and emits secondary light and a binder resin,
Visible light having a halogen lamp (12V, 48W) as a light source is irradiated perpendicularly to one of the surfaces of the quantum dot sheet, and the intensity of transmitted light is 1 degree within a range of -85 degrees to +85 degrees. An edge light type backlight that satisfies the following condition (1) when measured for each.
<Condition (1)>
The sum of the intensities of −5 ° to + 5 ° is P ₁ , the sum of the intensities of −70 ° to −85 ° and + 70 ° to + 85 ° is P ₂ , and the intensities of −15 ° to −45 ° and + 15 ° to + 45 ° sum of the upon the _{P 3, (P 1 + P} 2) / P 3 is 0.65 or less. The edge light type backlight according to claim 1, wherein the quantum dot sheet satisfies the following condition (2).
<Condition (2)>
_{P 2} / P ₁ is 0.15 or more. The edge light type backlight according to claim 1, wherein the quantum dot-containing layer contains internal diffusion particles. The refractive index _{n A} of the binder resin, when the refractive index of the inner diffusion particles was _{n B,} n B / _{n A} is the edge of Claim 3 is 1.02 or more, or 0.98 or less Light type backlight . The edge light type backlight according to any one of claims 1 to 4, wherein the quantum dot sheet is formed by sandwiching both surfaces of the quantum dot-containing layer with a light-transmitting substrate. The edge light type backlight according to claim 1, wherein the quantum dot sheet further has a light diffusion layer. At least one surface of the quantum dot sheet has an arithmetic average roughness Ra with a cutoff value of 0.8 mm in accordance with JIS B0601: 2001 of 0.1 to 10 µm. Edge light type backlight . A liquid crystal display device comprising a backlight and a liquid crystal panel, wherein the backlight is the backlight according to any one of claims 1 to 7 .