JP7005916B2 - Light wavelength conversion composition, light wavelength conversion member, light emitting device, backlight device, and image display device - Google Patents

Description

The present invention relates to a light wavelength conversion composition, a light wavelength conversion member, a light emitting device, a backlight device, and an image display device.

A transmissive image display device such as a liquid crystal display device is generally arranged on the back side of a display panel such as a liquid crystal display panel and includes a backlight device that illuminates the display panel.

Currently, in order to improve color reproducibility, it is being studied to incorporate an optical wavelength conversion member containing quantum dots and a binder resin into a backlight device (see, for example, Patent Document 1). Quantum dots can absorb light (primary light) and emit light of different wavelengths (secondary light), and the wavelength of light emitted by quantum dots mainly depends on the particle size of the quantum dots. Therefore, in a backlight device incorporating an optical wavelength conversion member, various colors can be reproduced while using a light emitting element that projects light in a single wavelength range. For example, when a light source that emits blue light is used, the light wavelength conversion member can absorb the blue light and emit green light and red light. Since the backlight device incorporating such a light wavelength conversion member is excellent in color purity, it is possible to improve the color reproducibility in the image display device using this backlight device.

Japanese Unexamined Patent Publication No. 2013-218953

As a method of incorporating the light wavelength conversion member into the backlight device, there is an on-chip method of incorporating the light wavelength conversion member into the light source. However, in the on-chip method, if the light wavelength conversion member is incorporated in the light source, the quantum dots in the light wavelength conversion member may be deteriorated by the heat generated from the light emitting element such as the LED element.

The present invention has been made to solve the above problems. That is, a light wavelength conversion composition having excellent heat resistance, a light wavelength conversion member made of a cured product of such a light wavelength conversion composition, a light emitting device provided with such a light wavelength conversion member, a backlight device, and an image. It is intended to provide a display device.

As a result of diligent research on the above-mentioned problems, the present inventors have found that the optical wavelength conversion composition contains a specific silicone resin in addition to the quantum dots to suppress deterioration of the quantum dots due to heat. It has been found that a conversion composition can be obtained. The present invention has been completed based on such findings.

According to one aspect of the present invention, there is provided an optical wavelength conversion composition comprising quantum dots and a curable silicone resin containing a nitrogen atom.

In the light wavelength conversion composition, the silicone resin may have at least one of a polyimide structure, a polyamide structure, and a polyamide-imide structure.

According to another aspect of the present invention, there is provided a light wavelength conversion member made of a cured product of the light wavelength conversion composition.

According to another aspect of the present invention, there is provided a light emitting device including a light emitting element and the light wavelength conversion member that receives light from the light emitting element.

In the light emitting device, the light emitting element may be an LED element.

In the light emitting device, the light wavelength conversion member may cover the light emitting element.

In the light emitting device, the light emitting device may further include a sealing member provided between the light emitting element and the light wavelength conversion member and sealing the light emitting element.

In the light emitting device, the surface of the light wavelength conversion member on the light emitting side may be a lens surface.

According to another aspect of the present invention, a backlight device including the above light emitting device is provided.

According to another aspect of the present invention, there is provided an image display device including the backlight device and a display panel arranged on the light emitting side of the backlight device.

According to one aspect of the present invention, since the curable silicone resin containing a nitrogen atom is contained, it is possible to provide a light wavelength conversion composition having excellent heat resistance. According to another aspect of the present invention, it is possible to provide a light wavelength changing member having excellent heat resistance, and a light emitting device, a backlight device, and an image display device provided with such a light wavelength converting member.

It is a schematic block diagram of the light emitting device which concerns on embodiment. It is a schematic block diagram of the other light emitting device which concerns on embodiment. It is a schematic block diagram of the image display device which concerns on embodiment. It is a perspective view of the lens sheet shown in FIG. It is a schematic block diagram of the other backlight apparatus which concerns on embodiment.

Hereinafter, the light wavelength conversion composition, the light wavelength conversion member, the light emitting device, the backlight device, and the image display device according to the embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a light emitting device according to the present embodiment, and FIG. 2 is a schematic configuration diagram of another light emitting device according to the present embodiment.

<<< Light wavelength conversion composition >>>
The light wavelength conversion composition is a composition for converting incident light into light of another wavelength. The optical wavelength conversion composition contains quantum dots and a silicone resin containing a nitrogen atom (hereinafter, this silicone resin is referred to as "specific silicone resin"). The light wavelength conversion composition may contain a solvent, a light scattering particle, a phosphor and the like, in addition to the quantum dots and the silicone resin. For example, when the light wavelength conversion composition is used as a light wavelength conversion sheet, the light wavelength conversion composition preferably contains light scattering particles. In addition, in this specification, a "sheet" is a concept including a member which is also called a film.

The light wavelength conversion composition may be used in the state of the composition, or may be used in the state of the light wavelength conversion member described later which is a cured product by curing the light wavelength conversion composition.

The viscosity of the light wavelength conversion composition is preferably 100 mPa · s or more and 10,000 mPa · s or less. When the viscosity of the light wavelength conversion composition is 100 mPa · s or more, the shape after coating can be easily maintained, and when the viscosity is 10,000 mPa · s or less, the light wavelength conversion composition can be easily applied. And good leveling property can be obtained.

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

Specifically, the energy band gap of quantum dots increases as the particle size decreases. That is, as the crystal size becomes smaller, the emission of the quantum dots shifts to the blue side, that is, to the high energy side. Therefore, by changing the particle size of the quantum dot, the emission wavelength can be adjusted over the entire wavelength of the spectrum in the ultraviolet region, the visible region, and the infrared region. For example, when the quantum dot is composed of CdSe / ZnS described later, blue light is emitted when the particle diameter of the quantum dot is 2.0 nm or more and 4.0 nm or less, and the particle diameter of the quantum dot is 3.0 nm. When the particle size is 6.0 nm or less, green light is emitted, and when the particle size of the quantum dots is 4.5 nm or more and 10.0 nm or less, red light is emitted. As used herein, "blue light" is light having a wavelength range of 380 nm or more and less than 480 nm, "green light" is light having a wavelength range of 480 nm or more and less than 590 nm, and "red light" is Light having a wavelength range of 590 nm or more and 750 nm or less. In the above, the range of the particle size of the quantum dot emitting blue light and the particle size of the quantum dot emitting green light partially overlaps, and the particle size of the quantum dot emitting green light and the red light are overlapped. The range of the particle size of the emitted quantum dots overlaps in part, but even if the quantum dots have the same particle size, the emission color may differ depending on the size of the core of the quantum dots, so there is no contradiction. It's not something to do. The average particle size of the quantum dots 18 can be obtained by measuring the particle size of 20 quantum dots in the cross-sectional observation of the light wavelength conversion particle with a transmission electron microscope or a scanning transmission electron microscope and calculating the average value thereof. can.

As the quantum dots, one type of quantum dots may be used, but it is also possible to use two or more types of quantum dots each having a light emitting band in a single wavelength range due to different particle diameters or materials. .. Specifically, the optical wavelength conversion composition may include a first quantum dot and a second quantum dot having an emission band in a wavelength range different from that of the first quantum dot.

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

Quantum dots are composed of, for example, a core made of a first semiconductor compound, a shell made of a second semiconductor compound that covers the core and is different from the first semiconductor compound, and a ligand bonded to the surface of the shell. Has been done.

Examples of the first semiconductor compound constituting the core include MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, and the like. II-VI group semiconductor compounds such as HgS, 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. Further, a semiconductor crystal containing a semiconductor compound containing three or more elements such as InGaP can also be used. Among these, semiconductor crystals such as CdS, CdSe, CdTe, InP, and InGaP are preferable from the viewpoints of ease of production, controllability of particle size capable of obtaining light emission in the visible range, and the like.

As the second semiconductor compound constituting the shell, it is preferable to use a semiconductor compound having a bandgap higher than that of the first semiconductor compound constituting the core so that excitons are confined in the core. This makes it possible to increase the luminous efficiency of the quantum dots. Examples of the second semiconductor compound constituting the shell include ZnS, ZnSe, CdS, GaN, CdSSe, ZnSeTe, AlP, ZnSTe, ZnSSe and the like.

Specific combinations of the core-shell structure (core / shell) consisting of the core and the shell include, for example, CdSe / ZnS, CdSe / ZnSe, CdSe / CdS, CdTe / CdS, InP / ZnS, Gap / ZnS, Si / ZnS, and the like. InN / GaN, InP / CdSSe, InP / ZnSeTe, InGaP / ZnSe, InGaP / ZnS, Si / AlP, InP / ZnSTe, InP / ZnSSe, InGaP / ZnSTe, InGaP / ZnSSe and the like can be mentioned.

The ligand is for stabilizing unstable quantum dots. Examples of the ligand include a sulfur-based compound such as thiol, a phosphorus-based compound such as a phosphine-based compound or a phosphine oxide, a nitrogen-based compound such as an amine, and a carboxylic acid.

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 any other shape. When the shape of the quantum dot is not spherical, the particle diameter of the quantum dot can be a true spherical value having the same volume.

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

The content of the quantum dots with respect to the total solid content mass of the optical wavelength conversion composition is preferably 0.01% by mass or more and 2% by mass or less, and more preferably 0.03% by mass or more and 1% by mass or less. .. When the content of quantum dots is 0.01% by mass or more, sufficient emission intensity can be obtained, and when the content of quantum dots is 2% by mass or less, sufficient transmitted light intensity of excitation light can be obtained. Can be obtained.

<< Specific Silicone Resin >>
Certain silicone resins contain nitrogen atoms. The specific silicone resin is not particularly limited as long as it is a silicone resin containing a nitrogen atom, but for example, a silicone resin having at least one of a polyimide structure, a polyamide structure, and a polyamide-imide structure is preferable. Hereinafter, the silicone resin having a polyimide structure is referred to as a polyimide silicone resin, the silicone resin having a polyamide structure is referred to as a polyamide silicone resin, and the silicone resin having a polyamide-imide structure is referred to as a polyamide-imide silicone resin. As used herein, the term "polyamide" is a concept including an aromatic polyamide (aramid). The specific silicone resin is preferably a polyimide silicone resin from the viewpoint of heat resistance, mechanical properties, and solvent resistance.

Whether or not the specific silicone resin is contained in the optical wavelength conversion composition is determined by (1) infrared spectroscopic analysis (IR), (2) gas chromatography analysis (GCMS), and (3) gel permeation chromatography. It can be confirmed by using analysis (GPC) and nuclear magnetic resonance spectroscopy (NMR spectroscopy) in combination. Specifically, in infrared spectroscopic analysis, the compound contained in the light wavelength conversion composition can be roughly specified, and in gas chromatography analysis, the molecular weight of the compound contained in the light wavelength conversion composition can be specified, and the gel can be specified. In permeation chromatography analysis, the compounds contained in the light wavelength conversion composition can be separated, and in nuclear magnetic resonance spectroscopy, the structural formulas of the compounds contained in the light wavelength conversion composition can be specified. By using it, it can be confirmed whether or not the above-mentioned specific silicone resin is contained in the optical wavelength conversion composition.

The specific silicone resin preferably has a thermosetting group from the viewpoint of obtaining a light wavelength conversion member. As the thermosetting group, a carboxyl group, an amino group, an epoxy group, a hydroxyl group and the like are generally used, but a carboxyl group or a phenol group is preferable because it does not easily react with the amino group in consideration of the polyimide manufacturing process. ..

<Polyimide silicone resin>
The polyimide silicone resin has a polyimide structure (site) and a silicone structure (site). The ratio of the polyimide structure to the silicone structure is not particularly limited, but the mass ratio is preferably 5:95 to 80:20, more preferably 10:90 to 60:40.

The weight average molecular weight of the polyimide silicone resin is preferably 800 or more and 300,000 or less. If the weight average molecular weight of the polyimide silicone resin is 800 or more, the flexibility is excellent, and if it is 300,000 or less, the tack feeling is lost, so that dust is less likely to adhere. In the present specification, the "weight average molecular weight" is a value obtained by dissolving in a solvent such as tetrahydrofuran (THF) and converting into polystyrene by a conventionally known gel permeation chromatography (GPC) method. The lower limit of the weight average molecular weight of the polyimide silicone resin is more preferably 3000 or more, and the upper limit is more preferably 200,000 or less.

The polyimide silicone resin can be obtained, for example, by reacting a tetracarboxylic acid with a diamine having a siloxane bond. The polyimide silicone resin can be produced by a one-step polymerization method in which tetracarboxylic acid and diamine are used in almost equal numbers of moles in the presence of a solvent and polymerized only at a high temperature. In addition, an amic acid is first synthesized at a low temperature and then at a high temperature. It can also be produced by a two-step polymerization method that is imidized with. The molecular weight of the polyimide silicone resin, the ratio of the polyimide structure to the silicone structure, and the like can be appropriately adjusted by controlling the types and reaction conditions of the tetracarboxylic acid and the diamine, which are the raw materials.

Examples of commercially available polyimide silicone resins include SCR-1012 and SCR-1016 (both manufactured by Shin-Etsu Chemical Co., Ltd.).

When the polyimide silicone resin is cured, it is heated at a temperature of, for example, 80 ° C. or higher and 300 ° C. or lower, preferably 100 ° C. or higher and 250 ° C. or lower. At the time of curing, when heated at 80 ° C. or higher, the thermosetting does not take too long, and when heated at 300 ° C. or lower, there is no risk of deterioration of the polyimide silicone resin.

<Polyamide silicone resin>
The polyamide silicone resin has a polyamide structure (site) and a silicone structure (site). The ratio of the polyamide structure to the silicone structure is not particularly limited, but the mass ratio is preferably 5:95 to 80:20, more preferably 10:90 to 60:40.

The weight average molecular weight of the polyamide silicone resin is preferably 800 or more and 300,000 or less. If the weight average molecular weight of the polyamide silicone resin is 800 or more, the flexibility is excellent, and if it is 300,000 or less, the tack feeling is lost, so that dust is less likely to adhere.

The polyamide silicone resin can be obtained, for example, by polycondensation of an aliphatic or aromatic dicarboxylic acid or a reactive derivative thereof with a bi-terminal amino group-modified diorganopolysiloxane, or an aliphatic or aromatic diamine. The molecular weight of the polyamide silicone resin and the ratio of the polyamide structure to the silicone structure can be appropriately adjusted by controlling the types and reaction conditions of the above-mentioned raw materials, dicarboxylic acid and diamine.

<Polyamide-imide silicone resin>
The polyamide-imide silicone resin has a polyamide structure (site), a polyimide structure (site), and a silicone structure (site).

The weight average molecular weight of the polyamide-imide silicone resin is preferably 800 or more and 300,000 or less. If the weight average molecular weight of the polyamide silicone resin is 800 or more, the flexibility is excellent, and if it is 300,000 or less, the tack feeling is lost, so that dust is less likely to adhere.

The polyamide-imide silicone resin can be obtained, for example, by copolymerizing the polyamide-imide resin with a polyfunctional silicone compound, or by modifying the polyamide-imide resin with silicone. The polyamide-imide silicone resin can also be obtained by polycondensing an aromatic tricarboxylic acid or a reactive acid derivative thereof with an aromatic diamine and a diaminosiloxane.

<< Solvent >>
The solvent is not particularly limited, and examples thereof include alcohols such as methanol, ethanol, propanol and isopropyl alcohol; ketones such as methyl ethyl ketone and methyl isobutyl ketone, toluene and cyclohexane.

<< Light-scattering particles >>
The light scattering particles are particles having an action of changing the traveling direction of light by scattering the light that has entered the light wavelength conversion composition or the light wavelength conversion member.

The average particle size of the light-scattering particles is preferably 20 times or more and 2000 times or less, and more preferably 50 times or more and 1000 times or less the average particle size of the quantum dots. If the average particle size of the light-scattering particles is less than 20 times the average particle size of the quantum dots, sufficient light-scattering performance may not be obtained in the light wavelength conversion member, and the average particle size of the light-scattering particles becomes high. If it exceeds 2000 times the average particle size of the quantum dots, the number of light-scattering particles will decrease even if the amount added is the same, so the number of scattering points may decrease and a sufficient light-scattering effect may not be obtained. .. The average particle size of the light-scattering particles can be measured by the same method as the above-mentioned average particle size of the quantum dots.

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

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

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

The light-scattering particles may be organic particles such as acrylic resin particles, styrene resin particles, melamine resin particles, and urethane resin particles, but the rate of change in brightness before and after the energization heat resistance test can be reduced, and the rate of change in brightness can be reduced. Inorganic particles are preferable because the incident light on the light wavelength conversion sheet can be suitably scattered and the light wavelength conversion efficiency with respect to the incident light can be preferably improved.

The inorganic particles include an aluminum-containing compound such as Al ₂ O ₃ , a zirconium-containing compound such as ZrO ₂ , a tin-containing compound such as antimony-doped tin oxide (ATO) and indium tin oxide (ITO), and magnesium such as MgO and MgF ₂ . At least one compound selected from the group consisting of compounds, titanium-containing compounds such as TiO ₂ and BaTiO ₃ , antimony-containing compounds such as Sb ₂ O ₅ , silicon-containing compounds such as SiO ₂ , and zinc-containing compounds such as ZnO. Particles can be mentioned. Since these inorganic particles can increase the difference in refractive index from the binder resin, they are also preferable from the viewpoint of obtaining a large Mie scattering intensity. Since the light wavelength conversion efficiency with respect to the incident light by the light emitting device 10 can be more preferably improved, the light scattering particles may be made of two or more kinds of materials.

The content of the light-scattering particles with respect to the total solid content mass of the light wavelength conversion composition is preferably 1% by mass or more and 50% by mass or less, and more preferably 3% by mass or more and 30% by mass or less. If the content of the light scattering particles is less than 1% by mass, the light scattering effect may not be sufficiently obtained, and if the content of the light scattering particles exceeds 50% by mass, me scattering occurs. Since it becomes difficult, there is a possibility that the light scattering effect cannot be sufficiently obtained, and further, there is a possibility that the processability is deteriorated because there are too many light scattering particles.

<< Fluorescent material >>
The phosphor is appropriately selected and used in order to obtain light having a desired color. As the fluorescent substance, a generally known fluorescent substance can be used.

<<< Optical wavelength conversion member >>>
The light wavelength conversion member is a member made of a cured product of the light wavelength conversion composition. The shape of the optical wavelength conversion member can be appropriately changed depending on the location or the like in which the optical wavelength conversion member is incorporated. The optical wavelength conversion member can be obtained by using a specific curable silicone resin, that is, a specific silicone resin having a thermosetting group.

<<< Light emitting device >>
The light emitting device 10 shown in FIG. 1 is a light emitting element package, and receives light from a package main body 11 having a recess 11A, a light emitting element 12 arranged in the recess 11A of the package main body 11, and a light emitting element 12. It includes a wavelength conversion member 13, an electrode layer 14, and a wire 15. The light emitting device 10 may include a light emitting element 12 and a light wavelength conversion member 13, and may not include other members. Further, although the light emitting device 10 is a display-mounted light emitting device, it may be, for example, a cannonball type light emitting device. The light emitting device may be provided with one or more light emitting elements, and may be provided with a plurality of light emitting elements.

<< Package body >>
The package main body 11 includes a substrate 11B and a reflective member 11C arranged on the surface side of the substrate 11B on the light emitting element 12 side and arranged so as to surround the light emitting element 12. The reflective member 11C has high reflectivity mainly for light in the visible light wavelength range having a wavelength of 380 nm or more and 780 nm or less. The reflective member 11C is not particularly limited as long as it is a member having a reflective surface for reflecting light from the light emitting element 12 and guiding it in a predetermined direction, but is not particularly limited, but is a foam type white polyester, a white polyethylene resin, a silver-deposited polyester, or the like. It is possible to form from.

<< Light emitting element >>
Examples of the light emitting element 12 include a light emitting diode element (LED element), a laser diode element (LD element), and the like. As the light emitting element, a light emitting element that emits light in a single wavelength range can be used. For example, as the light emitting element 12, a blue light emitting diode (blue LED) that emits blue light having high color purity can be used. The light emitting element 12 is electrically connected to the electrode layer 14 via the wire 15.

<< Optical wavelength conversion member >>
The light wavelength conversion member 13 is a cured product of the light wavelength conversion composition. Therefore, the light wavelength conversion member 13 includes the quantum dots 18 and the binder resin 19 made of the cured product of the specific silicone resin. The quantum dot 18 shown in FIG. 1 includes a first quantum dot 18A and a second quantum dot 18B having an emission band in a wavelength range different from that of the first quantum dot 18A. For example, when a blue light emitting diode is used as the light emitting element 12, a quantum dot that converts blue light into green light is used as the first quantum dot 18A from the viewpoint of widening the color range, and the second quantum dot 18B is used. It is preferable to use quantum dots that convert blue light into red light. Since the quantum dots 18 and the specific silicone resin are the same as the quantum dots and the specific silicone resin described in the section of the optical wavelength conversion composition, the description thereof will be omitted here.

The light wavelength conversion member 13 is filled in the recess 11A and covers the light emitting element 12 to seal the light emitting element 12. That is, the light wavelength conversion member 13 also functions as a sealing member for sealing the light emitting element 12.

The thickness of the light wavelength conversion member 13 is preferably 0.1 mm or more and 10 mm or less. When the thickness of the light wavelength conversion member 13 is 0.1 mm or more, the wavelength conversion of the light from the light emitting element 12 can be reliably performed, and the light emitting element 12 can be reliably sealed. The thickness of the light wavelength conversion member 13 is such that the cross section of the light wavelength conversion member 13 is photographed with an optical microscope such as a macroscope having a length measuring function, and the thickness of the light wavelength conversion member 13 is 20 in the image of the cross section. Measure the points and use the average value of the film thickness at the 20 points.

Since the light wavelength conversion member 13 covers the light emitting element 12, it is in contact with the light emitting element 12, but it does not have to be in contact with the light emitting element as long as it is at a position where the light from the light emitting element is received in the light emitting device. Further, although the surface 13A on the light emitting side of the light wavelength conversion member 13 shown in FIG. 1 is a flat surface, it may be a lens surface as described later.

<<< Other light emitting device >>>
The light emitting device includes a light emitting element 12 as shown in FIG. 2, a light wavelength conversion member 21 that receives light from the light emitting element 12, and a sealing member 22 located between the light emitting element 12 and the light wavelength conversion member 21. The light emitting device 20 may be provided with. By interposing the sealing member 22 between the light emitting element 12 and the light wavelength conversion member 21, the light wavelength conversion member 21 can be separated from the light emitting element 12, so that deterioration of the quantum dots 18 due to heat is further suppressed. be able to. In FIG. 2, the members having the same reference numerals as those in FIG. 1 are the same as the members shown in FIG. 1, and therefore the description thereof will be omitted.

The distance from the surface 12A of the light emitting element 12 to the light wavelength conversion member 21 is preferably 0.1 mm or more and 10 mm or less. When this distance is 0.1 mm or more, the quantum dot 18 can be kept away from the light emitting element 12, so that the influence of heat from the light emitting element 12 is small, deterioration of the quantum dot 18 can be suppressed, and the distance is 10 mm or less. If there is, the light emitting device 20 can be made thinner. As used herein, the "distance from the surface of the light emitting element to the light wavelength conversion member" means the distance from the surface of the light emitting element to the surface of the light wavelength conversion member on the light emitting element side.

<< Optical wavelength conversion member >>
The light wavelength conversion member 21 is a cured product of the light wavelength conversion composition. The surface 21A on the light emitting side of the light wavelength conversion member 21 is a lens surface. As used herein, the term "lens surface" means a surface that acts as a lens. The lens surface may be either a lens surface having a light collecting function or a lens surface having a light diffusing function. By making the surface 21A of the light wavelength conversion member 21 a lens surface having a light collecting function, it is possible to improve the light extraction efficiency to the front surface. Further, in the case of a direct type backlight device, it is desired to improve the light diffusivity of the light emitting device in order to reduce the uneven brightness, but the surface 21A of the light wavelength conversion member 21 is a lens having a light diffusing function. Since the light diffusivity can be improved by using a surface, it is particularly suitable for a direct type backlight device.

The surface 21A of the light wavelength conversion member 21 may have a bowl shape such as a hemispherical shape. In this case, the light wavelength conversion member 21 functions as a microlens or the like.

<< Sealing member >>
Since the heat of the light emitting element 12 is applied to the sealing member 22, it is preferable that the sealing member 22 is made of a resin having excellent heat resistance. The resin is not particularly limited, but a silicone resin is preferable. The sealing member 22 may use the above-mentioned specific silicone resin, but may be another silicone resin.

The thickness of the sealing member 22 is preferably 0.1 mm or more and 10 mm or less. When the thickness of the sealing member 22 is 0.1 mm or more, the quantum dots 18 can be kept away from the light emitting element 12, so that the influence of heat from the light emitting element 12 is reduced and the deterioration of the quantum dots 18 is further suppressed. If it is 10 mm or less, the light emitting device 20 can be made thinner.

The light emitting devices 10 and 20 can be used as a light source by incorporating them into a backlight device and an image display device. Hereinafter, an example in which the light emitting device 10 is incorporated into the backlight device and the image display device will be described. FIG. 3 is a schematic configuration diagram of an image display device including a backlight device according to the present embodiment, FIG. 4 is a perspective view of the lens sheet shown in FIG. 1, and FIG. 5 is another back according to the present embodiment. It is a schematic block diagram of a light device.

<<< Image display device >>>
The image display device 30 shown in FIG. 3 includes a backlight device 40 and a display panel 100 arranged on the light emitting side of the backlight device 40. The image display device 30 has a display surface 30A for displaying an image. In the image display device 30 shown in FIG. 3, the surface of the display panel 100 is the display surface 30A.

The backlight device 40 illuminates the display panel 100 from the back side in a plane shape. The display panel 120 functions as a shutter that controls the transmission or blocking of light from the backlight device 40 for each pixel, and is configured to display an image on the display surface 30A.

<< Display panel >>
The display panel 100 shown in FIG. 3 is a liquid crystal display panel, and is between the polarizing plate 101 arranged on the incoming light side, the polarizing plate 102 arranged on the light emitting side, and the polarizing plate 101 and the polarizing plate 102. It is provided with an arranged liquid crystal cell 103. The polarizing plates 101 and 102 decompose the incident light into two orthogonal linearly polarized light components (S-polarized and P-polarized) and vibrate in one direction (direction parallel to the transmission axis) (for example, P). It has a function of transmitting (polarized light) and absorbing a linearly polarized light component (for example, S-polarized light) that vibrates in the other direction (direction parallel to the absorption axis) orthogonal to the one direction.

<< Backlight device >>
The backlight device 40 shown in FIG. 3 is configured as an edge light type backlight device, and includes a light emitting device 10, an optical plate 50 as a light guide plate arranged on the side of the light emitting device 10, and an optical plate 50. The lens sheet 60 arranged on the light emitting side, the lens sheet 65 arranged on the light emitting side of the lens sheet 60, the reflective polarizing separation sheet 70 arranged on the light emitting side of the lens sheet 65, and the light emitting side of the optical plate 50. It is provided with a reflective sheet 80 arranged on the opposite side of the lens. The backlight device 40 includes an optical plate 50, lens sheets 60 and 65, a reflective polarizing separation sheet 70, and a reflective sheet 80, but these sheets and the like may not be provided. As used herein, the term "light emitting side" means the side of each member where light emitted in the direction emitted from the backlight device is emitted.

The backlight device 40 has a light emitting surface 40A that emits light in a planar manner. In the backlight device 40 shown in FIG. 3, the light emitting surface of the reflective polarizing separation sheet 70 is the light emitting surface 40A of the backlight device 40.

<Light emitting device>
The light emitting device 10 is arranged so that the surface 13A of the light wavelength conversion member 13 is on the light input surface 50C side of the optical plate 50, which will be described later. A plurality of light emitting devices 10 are provided linearly along the light entering surface 50C described later of the optical plate 50.

<Optical plate>
The optical plate 50 as a light guide plate has a rectangular shape in a plan view. The optical plate 50 extends between the light emitting surface 50A formed by one main surface on the display panel 100 side, the back surface 50B composed of the other main surface facing the light emitting surface 50A, and the light emitting surface 50A and the back surface 50B. Has sides. The side surface of the side surface on the light emitting device 10 side is an incoming light receiving surface 50C that receives light from the light emitting device 10. The light incident on the optical plate 50 from the light entry surface 50C is guided in the optical plate in the direction connecting the light entry surface 50C and the opposite surface facing the light entry surface 50C (light guide direction), and is guided through the optical plate. Emitted from 50A.

As a material constituting the optical plate 50, it is widely used as a material for an optical sheet incorporated in an image display device, and has excellent mechanical properties, optical properties, stability, processability, etc., and is inexpensively available. For example, a transparent resin containing one or more of acrylic resin, polystyrene, polycarbonate, polyethylene terephthalate, polyacrylonitrile, etc. as a main component, and epoxy acrylate or urethane acrylate-based reactive resin (ionized radiation curable resin, etc.) are preferably used. Can be done. If necessary, a light diffusing material having a function of diffusing light can be added to the optical plate 50. As the light diffusing material, for example, particles made of a transparent substance such as silica (silicon dioxide), alumina (aluminum oxide), acrylic resin, polycarbonate resin, and silicone resin having an average particle diameter of 0.5 μm or more and 100 μm or less can be used. can.

<< Lens sheet >>
The lens sheets 60 and 65 have a function of changing the traveling direction of the incident light and emitting the incident light from the light emitting side. In the present embodiment, the light with a small incident angle is reflected together with the function (condensing function) of changing the traveling direction of the light having a large incident angle and emitting it from the light emitting side to intensively improve the brightness in the front direction. It has a function of returning to the optical plate 50 side (retroreflection function). The lens sheets 60 and 65 include a light-transmitting base material 61 and a lens layer 62 provided on one surface of the light-transmitting base material 61.

<Light transmissive base material>
Examples of the constituent raw materials of the light-transmitting base material 61 include polyester (for example, polyethylene terephthalate and polyethylene naphthalate), cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyethersulfone, polysulfone, and polypropylene. , Polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyether ketone, polymethyl methacrylate, polycarbonate, or thermoplastic resins such as polyurethane.

<Lens layer>
As shown in FIG. 4, the lens layer 62 includes a sheet-shaped main body portion 63 and a plurality of unit lenses 64 arranged side by side on the light emitting side of the main body portion 63.

The unit lenses 64 are arranged side by side on the light emitting side surface 63A of the main body portion 63. As shown in FIG. 4, the unit lens 64 extends linearly in a direction intersecting the arrangement direction AD of the unit lens 64, particularly linearly in the present embodiment. Further, in the present embodiment, a large number of unit lenses 64 included in one lens sheet 60, 65 extend in parallel with each other. Further, the longitudinal LD of the unit lens 64 of the lens sheets 60 and 65 is orthogonal to the arrangement direction AD of the unit lens 64 of the lens sheets 60 and 65.

The unit lens 64 may have a triangular columnar shape, or may have a wavy shape or a bowl shape such as a hemispherical shape. Specifically, examples of the unit lens include a unit prism, a unit cylindrical lens, a unit microlens and the like. Examples of the lens sheet having such a unit lens shape include a prism sheet, a lenticular lens sheet, and a micro lens sheet. The unit lens 64 is a triangular columnar unit prism whose width narrows toward the light emitting side.

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

As can be understood from FIG. 3, the arrangement direction of the unit lens 64 of the lens sheet 60 and the arrangement direction of the unit lens 64 of the lens sheet 65 intersect, and more specifically, are orthogonal to each other.

<Reflective polarization separation sheet>
The reflective polarization separation sheet 70 transmits only the first linear polarization component (for example, P-polarization) among the light emitted from the lens sheet 65, and is a second straight line orthogonal to the first linear polarization component. It has a function of reflecting a polarizing component (for example, S-polarized light) without absorbing it. The second linear polarization component reflected by the reflective polarization separation sheet 70 is reflected again, and the polarization is eliminated (a state in which both the first linear polarization component and the second linear polarization component are included). It is incident on the reflective polarizing separation sheet 70 again. Therefore, the reflective polarization separation sheet 70 transmits the first linear polarization component of the light incident again, and the second linear polarization component orthogonal to the first linear polarization component is reflected again. Hereinafter, by repeating the same process, about 70 to 80% of the light emitted from the lens sheet 65 is emitted as the light source light as the first linearly polarized light component. Therefore, by matching the polarization direction of the first linear polarization component (transmission axis component) of the reflective polarization separation sheet 70 with the transmission axis direction of the polarizing plate 101 of the display panel 100, the light emitted from the backlight device 40 Can all be used for image formation on the display panel 100. Therefore, even if the light energy input from the light emitting device 10 is the same, it is possible to form a brighter image as compared with the case where the reflective polarizing separation sheet 70 is not arranged, and the energy of the light emitting device 10 is used. Efficiency is also improved.

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

<Reflective sheet>
The reflective sheet 80 has a function of reflecting the light leaked from the back surface 50B of the optical plate 50 and causing it to enter the optical plate 50 again. The reflective sheet 80 is composed of a white diffuse reflective sheet, a sheet made of a material having a high reflectance such as metal, a sheet containing a thin film made of a material having a high reflectance (for example, a metal thin film) as a surface layer, and the like. obtain. The reflection on the reflective sheet 80 may be normal reflection (specular reflection) or diffuse reflection. When the reflection on the reflective sheet 80 is diffuse reflection, the diffuse reflection may be isotropic diffuse reflection or anisotropic diffuse reflection.

<< Other backlight devices >>
The backlight device incorporating the light emitting device 10 may be a direct type backlight device as shown in FIG. The backlight device 110 shown in FIG. 5 includes a light emitting device 10, an optical plate 111 that receives the light of the light emitting device 10 and functions as a light diffusing plate, and a lens sheet 60 arranged on the light emitting side of the optical plate 111. The lens sheet 65 arranged on the light emitting side of the lens sheet 65 and the reflective polarization separation sheet 70 arranged on the light emitting side of the lens sheet 65 are provided. In the present embodiment, the light emitting device 10 is arranged directly under the optical plate 111, not on the side of the optical plate 111. In FIG. 5, the members having the same reference numerals as those in FIG. 3 are the same as the members shown in FIG. 5, and therefore the description thereof will be omitted. The backlight device 110 is not provided with the reflective sheet 80.

It is considered that the reason why quantum dots are easily deteriorated by heat is as follows. First, as described above, a ligand composed of a sulfur-based compound, a phosphorus-based compound, or the like is coordinated on the surface of the quantum dot, and this ligand is easily desorbed by light or heat. When the ligand is desorbed from the quantum dots, water and oxygen are likely to adhere to the quantum dots, so that the quantum dots are oxidized and deteriorated. As a result, it is considered that the quantum dots are deteriorated by heat. On the other hand, in the present embodiment, since the optical wavelength conversion composition contains a silicone resin containing a nitrogen atom in addition to the quantum dots, a nitrogen component can be present in the vicinity of the quantum dots. Therefore, a light wavelength conversion composition having excellent heat resistance can be obtained. This is a function that the nitrogen component present in the binder resin assists the role of the ligand even when the ligand is desorbed from the quantum dot (for example, it binds to the quantum dot instead of the ligand and the ligand is used. It is considered that this is because the deterioration of the quantum dot is suppressed because it exerts at least one of the function of substituting the function and the function of capturing oxygen).

Further, since the silicone resin having at least one of the polyimide structure, the polyamide structure, and the polyamide-imide structure has a nitrogen atom, the nitrogen atom is coordinated to the quantum dot, and the silicone resin having these structures is Since it is bulky, it has a function of suppressing the permeation of water and oxygen as compared with a silicone resin having no of these structures. That is, the specific silicone resin has a barrier property. As a result, when the above-mentioned specific silicone resin is used as the silicone resin containing a nitrogen atom, the permeation of water and oxygen can be suppressed, so that the deterioration of the quantum dots can be further suppressed.

In the above embodiment, the light wavelength conversion member 13 is incorporated in the light emitting device 10, but the position of the light wavelength conversion member is not particularly limited as long as it is a position to receive the light from the light emitting device. For example, an optical wavelength conversion sheet provided with a layered optical wavelength conversion member may be incorporated at a position closer to the observer than the optical plate.

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

<Preparation of light wavelength conversion composition>
First, each component was blended so as to have the composition shown below to obtain a light wavelength conversion composition.
<Example 1>
(Light wavelength conversion composition 1)
-Polygonyl silicone resin (product name "SCR-1012", manufactured by Shin-Etsu Chemical Industry Co., Ltd.): 100 parts by mass-Green emission quantum dots (product name "CdSe / ZnS 530", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.2 parts by mass, red emission quantum dots (product name "CdSe / ZnS 610", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm ): 0.2 parts by mass

<Example 2>
(Light wavelength conversion composition 2)
-Polygonyl silicone resin (product name "SCR-1016", manufactured by Shin-Etsu Chemical Industry Co., Ltd.): 100 parts by mass-Green emission quantum dots (product name "CdSe / ZnS 530", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.2 parts by mass, red emission quantum dots (product name "CdSe / ZnS 610", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm ): 0.2 parts by mass

<Comparative Example 1>
(Light wavelength conversion composition 3)
-Dimethyl silicone resin (product name "KER-2500", manufactured by Shin-Etsu Chemical Industry Co., Ltd.): 100 parts by mass-Green emission quantum dots (product name "CdSe / ZnS 530", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.2 parts by mass, red emission quantum dots (product name "CdSe / ZnS 610", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm ): 0.2 parts by mass

<Comparative Example 2>
(Light wavelength conversion composition 4)
-Phenyl silicone resin (product name "KER-6000", manufactured by Shin-Etsu Chemical Industry Co., Ltd.): 100 parts by mass-Green emission quantum dots (product name "CdSe / ZnS 530", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.2 parts by mass, red emission quantum dots (product name "CdSe / ZnS 610", manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 5.2 nm ): 0.2 parts by mass

<Example 3>
The light wavelength conversion composition 1 was filled in the opening (recessed portion of the package body) of the reflective member of a light emitting device (product name "B2020", manufactured by Generites) provided with a blue light emitting diode chip having a light emitting peak wavelength of 450 nm. Then, by heating at 100 ° C. for 5 hours, the light wavelength conversion composition is cured, and the light emission according to the third embodiment is provided with the light wavelength conversion member which is filled in the opening of the reflection member and covers the blue light emitting diode. Obtained the device.

<Example 4>
In Example 4, a light emitting device was obtained in the same manner as in Example 3 except that the light wavelength conversion composition 2 was used instead of the light wavelength conversion composition 1.

<Comparative Example 3>
In Comparative 3, a light emitting device was obtained in the same manner as in Example 3 except that the light wavelength conversion composition 3 was used instead of the light wavelength conversion composition 1.

<Comparative Example 4>
In Comparative Example 4, a light emitting device was obtained in the same manner as in Example 3 except that the light wavelength conversion composition 4 was used instead of the light wavelength conversion composition 1.

<Measurement of brightness maintenance rate after energization heat resistance test>
In the light emitting device according to the above embodiment and the comparative example, an energization heat resistance test was performed in which the light emitting device was energized so that the applied power to the blue light emitting diode was 0.5 W and continuously lit for 500 hours in an environment of 80 ° C. The maintenance rate of the brightness after the energization heat resistance test was investigated with respect to the brightness before the energization heat resistance test. Specifically, first, we prepared a backlight device for Kindle Fire (registered trademark) HDX7. Then, by replacing the light emitting device of this backlight device with the light emitting device before the energization heat resistance test according to the examples and the comparative examples, the light emitting device was incorporated into the examples and the comparative examples in the backlight device.

Then, in the backlight device incorporating the light emitting device according to the examples and the comparative examples, the blue light emitting diode is turned on by energizing so that the applied power to the blue light emitting diode is 0.5 W, and the backlight device is used. The brightness of the light emitted from the light emitting surface (the surface of the second prism sheet) is measured at a position 400 mm away from the light emitting surface (surface) of the backlight device in the thickness direction of the backlight device. CS2000 ”, manufactured by Konica Minolta Co., Ltd.) was used for measurement under the condition of a measurement angle of 1 °.

Next, in this state, an energization heat resistance test was conducted in which the blue light emitting diode was continuously lit for 500 hours in an environment of 80 ° C. Then, the brightness of the light emitted from the light emitting surface of the backlight device (the surface of the second prism sheet) after the energization heat resistance test is set to the light emitting surface of the backlight device in the thickness direction of the backlight device (as described above). Measurement was performed at a position 400 mm away from the surface) using a spectral radiance meter (product name “CS2000”, manufactured by Konica Minolta) under the condition of a measurement angle of 1 °.

From these measured luminances, the maintenance rate of the luminance after the energization heat resistance test with respect to the luminance before the energization heat resistance test was obtained. As for the brightness maintenance rate, the brightness maintenance rate is A, the brightness of the light emitted from the light emitting surface of the backlight device before the energization heat resistance test is B, and the brightness of the light emitted from the light emitting surface of the backlight device after the energization heat resistance test. Was C, and it was calculated by the following formula.
A = C / B × 100

The results are shown in Table 1 below.

The results will be described below. As can be seen from Table 1, since the light emitting device according to Examples 3 and 4 uses a specific silicone resin, the light emitting device according to Comparative Examples 3 and 4 that does not use the specific silicone resin also has heat resistance to energization. The brightness maintenance rate after the test was high.

In the above embodiment, CdSe is used as the core material of the green emission quantum dots and the red emission quantum dots, but even if a non-Cd material such as InP or InAs is used as the core material, the same result as in the above embodiment is obtained. was gotten.

10 ... Light emitting device 12 ... Light emitting element 13 ... Light wavelength conversion member 18 ... Quantum dot 19 ... Binder resin 30 ... Image display device 40 ... Backlight device 100 ... Display panel

Claims (7)

Light emitting element and
A light wavelength conversion member made of a cured product of a light wavelength conversion composition containing quantum dots and a silicone resin containing a nitrogen atom, which receives light from the light emitting element, is provided .
The silicone resin is in contact with the quantum dots,
A light emitting device in which the light wavelength conversion member covers the light emitting element . The light emitting device according to claim 1, wherein the silicone resin has at least one of a polyimide structure, a polyamide structure, and a polyamide-imide structure. The light emitting device according to claim 1 or 2 , wherein the light emitting element is an LED element. The light emitting device according to any one of claims 1 to 3 , further comprising a sealing member provided between the light emitting element and the light wavelength conversion member and sealing the light emitting element. The light emitting device according to any one of claims 1 to 4, wherein the surface of the light wavelength conversion member on the light emitting side is a lens surface. A backlight device comprising the light emitting device according to any one of claims 1 to 5 . The backlight device according to claim 6 and
A display panel arranged on the light emitting side of the backlight device and
An image display device.

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