JP6797624B2 - Light source device and display device - Google Patents

Description

The present invention relates to a light source device and a display device.

In recent years, in order to provide a liquid crystal display device capable of displaying an image having good color reproducibility, it is required to develop a technique for increasing the color purity of the incident light on the liquid crystal display element. As an example, a technique using quantum dots has been developed. Quantum dots are phosphors, and when excitation light from a light source such as a light emitting diode (LED) is incident, they generate light having a wavelength longer than the wavelength of the excitation light. The wavelength of the light generated by the quantum dots can be adjusted by changing the type and particle size of the quantum dots. For example, blue light from an LED is used as the excitation light, and the quantum dots are configured to generate green light and red light having a narrow half-value width when the blue light is incident. As a result, it is possible to realize a highly efficient light source capable of generating light in a narrow wavelength region corresponding to the three primary colors of light by using quantum dots.

The light produced by the quantum dots is emitted in various directions. In the technique described in Patent Document 1, the inner surface of the recess in which the light emitting element is provided is used as a reflecting wall, and the reflecting wall surrounding the side of the conversion member including the quantum dots is provided. With such a configuration, it is possible to suppress the spread of the light emitted from the light emitting element and the light emitted from the quantum dots, and reduce the luminance unevenness and the color unevenness.

JP-A-2015-216104 JP-A-2015-23307

Since the light generated by the quantum dots is generally used by emitting light in a direction different from that of the light emitting element, the light directed in the direction of the light emitting element (that is, the light directed in the direction in which the excitation light is incident) is used. It will be wasted. However, although the technique described in Patent Document 1 aims to suppress the lateral spread of light generated by quantum dots, it does not consider the light directed from the quantum dots to the light emitting device. In the technique described in Patent Document 1, light directed from a quantum dot to a light emitting element can be reflected on the inner surface of the recess, but since it is far from the quantum dot to the inner surface, the attenuation is large, and multiple reflection of light occurs on the inner surface. Therefore, the utilization efficiency of the light generated by the quantum dots is greatly reduced.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a light source device and a display device capable of realizing high utilization efficiency of light generated by quantum dots.

One aspect of the present invention is a light source device, which is between a light source unit that generates light, a structure including quantum dots excited by light from the light source unit, and the light source unit and the quantum dots. It is characterized by being provided with a wavelength selective reflection film that transmits light from the light source unit and reflects light generated by the quantum dots.

According to the present invention, the wavelength selective reflection film provided between the light source unit and the quantum dots reflects the light generated by the quantum dots while transmitting the light from the light source unit. Therefore, it is possible to suppress the light generated by the quantum dots from returning to the light source unit and being attenuated, and to improve the utilization efficiency of the light.

It is a front view of the display device which concerns on 1st Embodiment. It is sectional drawing of the display device which concerns on 1st Embodiment. It is sectional drawing of the quantum dot structure which concerns on 1st Embodiment. It is a schematic diagram explaining the reflection of light by the wavelength selective reflection film which concerns on 1st Embodiment. It is sectional drawing of the display device which concerns on 2nd Embodiment. It is a front view of the display device which concerns on 3rd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the respective embodiments. In the drawings described below, those having the same function are designated by the same reference numerals, and the repeated description thereof may be omitted.

(First Embodiment)
FIG. 1 is a front view of the display device 10 according to the present embodiment. The display device 10 includes a liquid crystal panel 20, a light source device 100 provided along the back surface of the liquid crystal panel, and a frame 30 that supports the liquid crystal panel 20 and the light source device 100. In FIG. 1, the liquid crystal panel 20 is shown to pass through the light source device 100 on the back side for visibility. The number and size of each part included in the display device 10 shown in FIG. 1 does not reflect the actual configuration, and may be arbitrarily designed according to the actual mounting method.

The light source device 100 is a direct type backlight unit, and irradiates the liquid crystal panel 20 with light from the back side of the liquid crystal panel 20. The detailed configuration of the light source device 100 will be described later with reference to FIGS. 2 and 3. The liquid crystal panel 20 has a well-known configuration including an electric circuit such as a liquid crystal layer, a polarizing plate, a color filter, and a thin film transistor (TFT). The liquid crystal panel 20 displays a desired image by controlling the transmittance of light from the light source device 100 for each pixel through an electric circuit. The frame 30 is made of resin, metal, or the like, and supports the liquid crystal panel 20 and the light source device 100. Inside the frame 30, electrical wiring to the liquid crystal panel 20 and the light source device 100 is arranged. In the present embodiment, the direct type backlight unit is illustrated as the backlight unit method, but the edge light method may be used.

FIG. 2 is a cross-sectional view of the display device 10 as seen from the line AA of FIG. The light source device 100 includes a light source unit 120 that generates light having a predetermined wavelength, and a quantum dot structure 110 that converts the wavelength of light from the light source unit 120.

The light source unit 120 includes a light emitting element 121, a substrate 122, and a frame 123. The light emitting element 121 generates light having a predetermined wavelength and irradiates it toward the liquid crystal panel 20. The light emitting element 121 is electrically connected to an electric wiring (not shown), and uses the electric power applied through the electric wiring to generate light. The wavelength of light generated by the light emitting element 121 is, for example, a wavelength region of blue light or a wavelength region of ultraviolet light. As the light emitting element 121, any light emitting element such as a light emitting diode (LED) or an organic light emitting diode (OLED) may be used. When the light from the light emitting element 121 is incident on the quantum dot structure 110 described later as excitation light, the light source device 100 can generate light in a narrow wavelength region corresponding to the three primary colors of light.

The frame 123 has a concave shape, and the light emitting element 121 is supported on the bottom surface of the shape. The shape of the frame 123 is not limited to this, and any shape may be used. The frame 123 may be constructed by using any material such as resin, metal, and semiconductor. The frame 123 may be omitted, in which case the light emitting element 121 may be supported directly on the substrate 122.

The substrate 122 extends parallel to the surface of the liquid crystal panel 20 and supports the plurality of light emitting elements 121 and the frame 123. In this embodiment, a predetermined number of light emitting elements 121 and frames 123 are arranged on the substrate 122 in a grid pattern and at equal intervals. The number and arrangement of the light emitting elements 121 and the frame 123 may be arbitrarily set according to the configuration of the display device 10. The substrate 122 may be constructed by using any material such as resin, metal, and semiconductor.

The quantum dot structure 110 is located between the back surface of the liquid crystal panel 20 and the light source unit 120, and is interposed in the optical path of the light emitted from the light source unit 120 to the back surface of the liquid crystal panel 20. That is, the light from the light source unit 120 is applied to the back surface of the liquid crystal panel 20 via the quantum dot structure 110. The quantum dot structure 110 is directly fixed on the frame 123 of the light source unit 120 and is integrated with the light source unit 120. In this embodiment, an On-Chip type mounting method in which one quantum dot structure 110 is provided directly above one light emitting element 121 is adopted. The quantum dot structure 110 includes a wavelength selective reflection film 111 described later on the light source unit 120 side.

FIG. 3 is a detailed cross-sectional view of the quantum dot structure 110 as seen from line AA of FIG. The quantum dot structure 110 includes a wavelength selective reflective film 111, a closed container 112, and a quantum dot 113 and a dispersion medium 114 enclosed in the closed container 112. The dispersion medium 114 is a liquid or solid medium that evenly disperses the quantum dots 113, and is composed of any material such as a resin that transmits light in at least the wavelength region of visible light (about 380 nm to 780 nm). .. It may also contain a material that scatters light.

The closed container 112 is a container having an internal space isolated from the external space (that is, the atmosphere), and uses any material such as glass or resin that transmits light in at least the wavelength region of visible light (about 380 nm to 780 nm). It is composed of. In order to suppress the deterioration of the quantum dots 113 due to water and oxygen, it is desirable that the closed container 112 is constructed by using a material having a barrier property against water and oxygen.

In the present embodiment, the closed container 112 is configured as a glass cell formed by using glass having a high barrier property against water and oxygen. Specifically, the closed container 112 has a square columnar structure in which two glass rectangular plates parallel to each other face each other at a predetermined interval via a glass side wall. The light from the light source unit 120 is vertically incident on the two rectangular plates made of glass. The structure of the closed container 112 is not limited to that shown here, and known ones may be used (see, for example, Patent Document 2). The shape of the closed container 112 may be any shape capable of containing quantum dots, such as a columnar shape and a polygonal columnar shape. At least a part of the wall surface constituting the closed container 112 may be curved instead of flat.

Quantum dots 113 (also referred to as colloidal quantum dots) are nanoscale materials having optical properties according to quantum mechanics, and have a particle size of about 1 nm to 100 nm, preferably 1 nm to 50 nm, and more preferably 1 nm to 20 nm. It is a semiconductor particle. The quantum dot 113 absorbs a photon having an energy larger than the band gap (energy difference between the valence band and the conduction band) and emits light having a wavelength corresponding to the particle size thereof. Therefore, the quantum dot 113 has a property of absorbing light having a predetermined wavelength or less, and can generate light having a desired wavelength by adjusting the particle size. In the present embodiment, the quantum dot 113 is spherical as shown in FIG. 3, but is not limited to this and may have any shape.

Quantum dots 113 include at least one semiconductor material. As the semiconductor material of the quantum dot 113, a group IV element, a group II-VI compound, a group II-V compound, a group III-VI compound, a group III-V compound, a group IV-VI compound, and a group I -III-VI group compounds, II-IV-VI group compounds, II-IV-V group compounds and the like may be used. Specifically, as the semiconductor material of the quantum dot 113, ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgS, MgSe, GaAs, GaN, GaP, GaSe, GaSb, HgO, HgS, HgSe, HgTe , InAs, InN, InP, InSb, AlAs, A1N, A1P, AlSb, TiN, TiP, TiAs, TiSb, PbO, PbS, PbSe, PbTe, Ge, Si and the like can be used. The material of the quantum dot 113 is not limited to the one shown here, and any material may be used as long as the function of the quantum dot can be exhibited.

When the light generated by the light source unit 120 is blue light, the first quantum dot 113 having a emission center wavelength in the wavelength region of green light (about 510 nm or more and 610 nm or less, preferably 520 nm or more and 580 nm or less) and red It is used in combination with a second quantum dot 113 having an emission center wavelength in the wavelength region of light (about 600 nm or more and 700 nm or less, preferably 610 nm or more and 680 nm or less). That is, the blue light generated by the light source unit 120 functions as excitation light for the quantum dots 113 and also functions as visible light emitted by the light source device 100. In the present embodiment, a light source having an emission spectrum having three maximums of blue, green, and red is shown, but the combination of the emission center wavelength of the quantum dots and the quantum dots is not limited to this, and any combination can be used. Good.

When the light generated by the light source unit 120 is ultraviolet light, a first quantum dot 113 having an emission center wavelength in the wavelength region of green light and a second quantum having an emission center wavelength in the wavelength region of red light. The dot 113 and the third quantum dot 113 having the emission center wavelength in the wavelength region of blue light are used in combination. That is, the ultraviolet light generated by the light source unit 120 functions as excitation light for the quantum dots 113.

The quantum dot 113 may have a core-shell type structure including a core containing at least one semiconductor material and a shell containing at least one semiconductor material. Specifically, a quantum dot 113 having CdSe as a core and CdZnS as a shell, a quantum dot 113 having CdZnSe as a core, a quantum dot 113 having CdZnS as a shell, a quantum dot 113 having CdS as a core, and a quantum dot 113 having CdZnS as a shell can be used.

The wavelength selective reflection film 111 (also referred to as a wavelength selective transmission film) is a film that selectively reflects light having a predetermined wavelength and transmits light having other wavelengths. In the present embodiment, the wavelength selective reflection film 111 transmits the wavelength of the excitation light generated by the light source unit 120 (light emitting element 121) and reflects the wavelength of the light generated by the quantum dots 113 using the excitation light. It is composed of. More specifically, when the light generated by the light source unit 120 is in the wavelength region of blue light (for example, 380 nm or more and less than 480 nm), the wavelength selective reflection film 111 transmits the wavelength region of blue light, and green light and It is configured to reflect the wavelength region of red light (for example, 480 nm or more and 780 nm or less). Further, when the light generated by the light source unit 120 is in the wavelength region of ultraviolet light (for example, 10 nm or more and less than 380 nm), the wavelength selective reflection film 111 transmits the wavelength region of ultraviolet light, and green light, red light, and blue light are transmitted. It is configured to reflect the wavelength region of light (for example, 380 nm or more and 780 nm or less). Not limited to this, the wavelength region transmitted and reflected by the wavelength selective reflection film 111 is appropriately set according to the wavelength of the light generated by the light source unit 120 and the quantum dot 113.

The wavelength selective reflection film 111 is provided on the side where the excitation light of the closed container 112 (quantum dot structure 110) is incident. Specifically, the wavelength selective reflection film 111 is provided inside the closed container 112 on the wall surface of the closed container 112 facing the light source portion 120. The wavelength selective reflection film 111 may be provided outside the closed container 112 on a wall surface facing the light source portion 120 of the closed container 112. It is desirable that the wavelength selective reflective film 111 and the wall surface of the closed container 112 are in contact with each other, but a gap may be provided between the wavelength selective reflective film 111 and the wall surface of the closed container 112.

As the wavelength selective reflection film 111, an arbitrary configuration capable of selectively reflecting light of a predetermined wavelength and transmitting light of other wavelengths may be used. As the wavelength selective reflection film 111, for example, a dielectric multilayer film may be used. The dielectric multilayer film is a laminate in which a plurality of layers of inorganic materials or organic materials having different refractive indexes are laminated, and reflects light having a predetermined wavelength according to the thickness and refractive index of the layers constituting the laminate. Has the property of As a specific material for forming the dielectric multilayer film, TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₃ , SiO ₂ , MgF ₂ , CaF _{2, and the} like can be used. The thickness of each layer contained in the dielectric multilayer film is adjusted according to the refractive index of the material of each layer and the wavelength to be reflected.

Further, as the wavelength selective reflection film 111, for example, a cholesteric liquid crystal may be used. The cholesteric liquid crystal has a property of reflecting light having a predetermined wavelength and polarized light according to its spiral structure (that is, pitch and winding direction). Specifically, as the wavelength selective reflective film 111, a laminate in which a right-handed cholesteric liquid crystal and a left-handed cholesteric liquid crystal are laminated, a right-handed (left-handed) cholesteric liquid crystal, a half-wave plate, and a cholesteric liquid crystal in the same winding direction are sequentially arranged. A laminated body can be used. The pitch of the spiral structure of the cholesteric liquid crystal is adjusted according to the wavelength to be reflected.

FIG. 4 is a schematic diagram illustrating the reflection of light by the wavelength selective reflection film 111 according to the present embodiment. In the example of FIG. 4, the light source unit 120 (light emitting element 121) is configured to generate blue light, the wavelength selective reflection film 111 transmits the wavelength region of blue light, and the wavelength region of green light and the wavelength of red light. It is configured to reflect the area. In FIG. 4, among the quantum dots 113, those that emit green light are designated by a G, and those that emit red light are designated by the letter R.

The blue light generated by the light source unit 120 passes through the wavelength selective reflection film 111 and is emitted as it is to the side opposite to the light source unit 120 of the quantum dot structure 110. Further, of the green light and red light generated by the quantum dot 113, the light directed to the side opposite to the light source portion 120 of the quantum dot structure 110 is emitted as it is. On the other hand, of the green light and red light generated by the quantum dot 113, the light directed to the light source unit 120 is reflected by the wavelength selective reflection film 111 and emitted to the side opposite to the light source unit 120 of the quantum dot structure 110.

According to the present embodiment, the excitation light from the light source unit 120 is transmitted through the wavelength selective reflection film 111 and is hardly attenuated, and the light from the quantum dots 113 toward the light source unit 120 is reflected by the wavelength selective reflection film 111 and emitted. Go back in direction. With such a configuration, it is possible to improve the utilization efficiency of the light generated by the quantum dots 113. Since the wavelength selective reflection film 111 is arranged in the vicinity of the quantum dots 113, the light from the quantum dots 113 toward the light source unit 120 is reflected at a position close to the quantum dots 113, and the attenuation of the light can be suppressed. Since the wavelength selective reflection film 111 is arranged inside or outside the excitation light incident surface of the closed container 112, a known configuration of the closed container 112 can be used, and the configuration according to the present embodiment can be easily introduced. be able to.

(Example)
As an example, a sample imitating the light source device 100 according to the above-described embodiment was prepared, and the front luminance was measured. Specifically, it is composed of an inorganic dielectric multilayer film in which a blue LED having a center wavelength of 450 nm and a full width at half maximum of 18 nm is placed on a substrate, and a center wavelength of the reflection band is 525 nm and a full width at half maximum is 56 nm on the surface. A glass plate provided with a wavelength-selective reflective film was fixed away from the LED. Further, a closed container containing green quantum dots having a center wavelength of 530 nm and a full width at half maximum of 40 nm and red quantum dots having a center wavelength of 639 nm and a full width at half maximum of 30 nm was placed on the glass plate. In such a configuration, the blue light from the LED excites the quantum dots, and the light generated by the quantum dots and the blue light from the LED are emitted from the closed container. Of the green light generated by the quantum dots, the light directed to the LED is reflected by the wavelength selective reflection film and returns to the emission direction. In addition, as a comparative example, a sample using a glass plate not provided with a wavelength selective reflection film was prepared.

In the examples and comparative examples, the front luminance of the light passing through the closed container containing the quantum dots was measured with the blue LED lit. As the front luminance, the luminance measured at a viewing angle of 2 degrees above 35 cm of the closed container containing the quantum dots was used. The measurement results are shown in Table 1.

As shown in Table 1, in the examples provided with the wavelength selective reflecting film, the front luminance is improved as compared with the comparative example in which the wavelength selective reflecting film is not provided. Therefore, it was confirmed that the utilization efficiency of the light generated by the quantum dots is improved by providing the wavelength selective reflection film.

(Second Embodiment)
In the first embodiment, the On-Chip type mounting method is adopted, but in the present embodiment, the planar (film-like) quantum dot structure 110 is provided above the plurality of light emitting elements 121. -A Surface type mounting method is adopted. It is the same as the first embodiment except for the shape and arrangement of the quantum dot structure 110. The backlight unit system may be a direct type backlight unit or an edge light system, as in the first embodiment.

FIG. 5 is a cross-sectional view of the display device 10 according to the present embodiment. The quantum dot structure 110 is located between the back surface of the liquid crystal panel 20 and the light source unit 120, and is interposed in an optical path of light emitted from the light source unit 120 to the back surface of the liquid crystal panel 20. The quantum dot structure 110 has a planar (film-like) shape, and extends so as to cover above a plurality of light emitting elements 121 (that is, a part or all of the light emitting elements included in the light source unit 120). The quantum dot structure 110 may have a configuration in which the quantum dots 113 and the dispersion medium 114 are enclosed in the closed container 112 as in the first embodiment, or the solid dispersion medium 114 in which the quantum dots 113 are dispersed is formed into a film. The structure may be stretched into a shape. A preferable example of the structure stretched into the film shape is a structure in which a film made of a solid dispersion medium 114 in which quantum dots 113 are dispersed is sandwiched from above and below by a layer having a gas barrier property.

The wavelength selective reflection film 111 is provided on the side where the excitation light of the quantum dot structure 110 is incident. Specifically, the wavelength selective reflection film 111 is provided between the quantum dot structure 110 and the light source unit 120 so as to extend along the quantum dot structure 110. In the present embodiment, a gap is provided between the quantum dot structure 110 and the wavelength selective reflection film 111, but they may be in close contact with each other.

Also in this embodiment, as in the first embodiment, the effect of improving the utilization efficiency of the light generated by the quantum dots 113 can be obtained.

(Third Embodiment)
In the first embodiment, the On-Chip type mounting method is adopted, but in the present embodiment, the On-Endge type mounting method in which the quantum dot structure 110 is provided along the end face of the liquid crystal panel 20 is used. It has been adopted. The backlight unit is an edge light type. The same as in the first embodiment except for the shape and arrangement of the quantum dot structure 110 and the light source unit 120.

FIG. 6 is a front view of the display device 10 according to the present embodiment. In FIG. 6, the frame 30 is shown to pass through the internal light source device 100 for visibility. In the present embodiment, the light source device 100 including the quantum dot structure 110 and the light source unit 120 is provided along the end face of the liquid crystal panel 20. The light from the light source device 100 is applied to the liquid crystal panel 20 through a light guide plate (not shown) provided on the back side of the liquid crystal panel 20. In the present embodiment, the light source device 100 is provided only on the right end surface of the liquid crystal panel 20, but is provided on one, two or more, or all of the upper end surface, the lower end surface, the left end surface, and the right end surface of the liquid crystal panel 20. May be done.

The light source unit 120 includes a plurality of light emitting elements 121 provided on the substrate 122 extending along the end surface of the liquid crystal panel 20. Unlike the first embodiment, the frame 123 is omitted in the present embodiment, but the frame 123 may be provided. The light emitting element 121 irradiates light having a predetermined wavelength toward the end face of the liquid crystal panel 20.

The quantum dot structure 110 is located between the side surface of the liquid crystal panel 20 and the light source unit 120, and is interposed in the optical path of light emitted from the light source unit 120 to the side surface of the liquid crystal panel 20. The quantum dot structure 110 has a rod-like shape (for example, a columnar or square columnar shape). The quantum dot structure 110 may have a configuration in which the quantum dots 113 and the dispersion medium 114 are enclosed in the closed container 112 as in the first embodiment, or the solid dispersion medium 114 in which the quantum dots 113 are dispersed may be rod-shaped. It may be a structure extended to.

The wavelength selective reflection film 111 is provided on the side where the excitation light of the quantum dot structure 110 is incident. Specifically, the wavelength selective reflection film 111 is provided between the quantum dot structure 110 and the light source unit 120 so as to extend along the quantum dot structure 110. In the present embodiment, a gap is provided between the quantum dot structure 110 and the wavelength selective reflection film 111, but they may be in close contact with each other.

Also in this embodiment, as in the first embodiment, the effect of improving the utilization efficiency of the light generated by the quantum dots 113 can be obtained.

The present invention is not limited to the above-described embodiment, and can be appropriately modified without departing from the spirit of the present invention.

100 Display device 110 Quantum dot structure 111 Wavelength selective reflective film 112 Sealed container 113 Quantum dots

Claims (9)

A light source unit that includes a light source that generates light and a frame that supports the light source,
A container containing quantum dots excited by light from the light source unit,
A wavelength-selective reflective film provided between the light source unit and the quantum dots, which transmits light from the light source unit and reflects light generated by the quantum dots.
Equipped with a,
The container is fixed directly on the frame and
It said wavelength-selective reflective layer includes a light source device you characterized in that it is provided with the wall surface of the container facing the interior and the light source portion of the container. The light source device according to claim 1, wherein the light source unit and the container are integrated. The wavelength of the light from the light source unit is 380 nm or more and less than 480 nm.
The light source device according to claim 1 or 2 , wherein the wavelength of light reflected by the wavelength-selective reflective film is 480 nm or more and 780 nm or less. The wavelength of the light from the light source unit is 10 nm or more and less than 380 nm.
The light source device according to claim 1 or 2 , wherein the wavelength of light reflected by the wavelength-selective reflective film is 380 nm or more and 780 nm or less. The light source unit is configured to generate blue light.
The light source device according to claim 1 or 2 , wherein the wavelength-selective reflecting film is configured to transmit the blue light and reflect green light and red light. The light source device according to any one of claims 1 to 5 , wherein the wavelength selective reflection film includes a dielectric multilayer film. The light source device according to any one of claims 1 to 5 , wherein the wavelength selective reflective film includes a cholesteric liquid crystal. The wavelength selective reflection film has a laminated structure in which a right-handed cholesteric liquid crystal and a left-handed cholesteric liquid crystal are laminated, a laminated structure in which the right-handed cholesteric liquid crystal is laminated, and a half-wave plate and the right-handed cholesteric liquid crystal. Alternatively, the light source device according to claim 7, further comprising a laminated structure in which the left-handed cholesteric liquid crystal is laminated, a half-wave plate, and the left-handed cholesteric liquid crystal. A display device including the light source device according to any one of claims 1 to 8 and a liquid crystal panel provided at a position where light from the light source device is irradiated.

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