JP6768093B2 - LED package, backlight unit and liquid crystal display device - Google Patents

Description

The present invention relates to an LED package, a backlight unit and a liquid crystal display device.

In recent years, an LED package in which an LED (light emitting diode) is mounted on a frame has been used as a light source for lighting equipment, liquid crystal display devices, and the like.
The LED mounted on the LED package is generally a semiconductor in which a p-type semiconductor and an n-type semiconductor are pn-junctioned, and the wavelength of light emitted can be controlled depending on the type of compound used as the semiconductor.

An LED is suitable as a light source for a liquid crystal display device because it consumes less power than other light sources and is easy to miniaturize. As an LED package for a conventional liquid crystal display device, a package capable of emitting white light has generally been used. For example, an LED package (for example, Patent Document 1) in which a plurality of LEDs having different emission colors are mounted, and an LED package (for example, Patent Document 2) in which an LED and a phosphor are combined are known.
On the other hand, in recent years, with the practical application of organic EL displays, it has become important to improve the color reproducibility of liquid crystal display devices. The color display of the liquid crystal display device is realized by absorbing the light emitted from the white light source with the light in a part of the wavelength region by the color filter. In order to improve the color reproducibility of the liquid crystal display device, it is effective to narrow the wavelength range of the light transmitted through the color filter, but on the other hand, there arises a problem that the light utilization efficiency is lowered. In order to solve this problem, it is necessary to emit light in a narrow wavelength range corresponding to the three primary colors of light from the light source, and to match those wavelength regions with the wavelength regions transmitted by the color filter.
Against the background as described above, recently, it is also known to use quantum dots (QD) as a phosphor to be combined with an LED (for example, Patent Document 3).

Japanese Unexamined Patent Publication No. 2014-154644 Japanese Unexamined Patent Publication No. 2007-067184 Japanese Unexamined Patent Publication No. 2012-191144

Quantum dots use light from an LED as an excitation source and can emit light at a wavelength longer than the wavelength of the excitation source. In addition, the wavelength of the quantum dot can be adjusted by changing the type or size, and the quantum dot has a high quantum efficiency approaching that of a YAG (yttrium aluminum garnet) phosphor. Therefore, by using the quantum dots, it is possible to obtain an LED package having a desired emission color, high brightness, and a narrow half width of the emission spectrum. Further, by using an LED package using quantum dots as a light source for a backlight, a liquid crystal display device having a wide color reproduction range can be obtained.
However, there is a problem that quantum dots deteriorate in a short time when they receive light from an LED in the presence of moisture or oxygen. Further, when the quantum dots are present in the vicinity of the LED of the excitation source, the deterioration of the quantum dots is accelerated in an environment of high light intensity and high temperature.

The present invention has been made to solve the above problems, and is a long-life LED that suppresses the deterioration of quantum dots, has a desired emission color, has high brightness, and has a narrow full width at half maximum of the emission spectrum. The purpose is to provide a package.
Another object of the present invention is to provide a backlight unit and a liquid crystal display device having a significantly improved color reproduction range by providing an LED package having the above-mentioned characteristics.

As a result of diligent research to solve the above problems, the present inventors have effective deterioration of quantum dots by arranging a glass cell containing quantum dots dispersed in a resin or an organic solvent above the LED. We have found that it can be suppressed as a target, and have reached the present invention.
That is, the present invention is characterized by having a frame on which an LED is mounted and a glass cell arranged above the LED and containing quantum dots dispersed in a resin or an organic solvent. It is an LED package.

Further, the present invention is a backlight unit characterized by having the LED package.
Further, the present invention is a liquid crystal display device characterized by having the backlight unit.

According to the present invention, it is possible to provide a long-life LED package that suppresses deterioration of quantum dots, has a desired emission color, has high brightness, and has a narrow full width at half maximum of the emission spectrum.
Further, according to the present invention, it is possible to provide a backlight unit and a liquid crystal display device having a significantly improved color reproduction range by providing an LED package having the above-mentioned characteristics.

It is sectional drawing which shows the LED package of this invention. It is sectional drawing of the glass cell used in the LED package of this invention.

Hereinafter, preferred embodiments of the LED package of the present invention will be described with reference to the drawings.
1 (a) and 1 (b) are schematic cross-sectional views showing the LED package of the present invention. In FIGS. 1A and 1B, the LED package 1 of the present invention has a frame 2, an LED 3 mounted on the frame 2, and a glass cell 4 arranged on the upper portion of the LED 3.

The frame 2 is not particularly limited as long as the LED 3 can be mounted, and a frame known in the art can be used.
The material of the frame 2 is not particularly limited, but in general, resins such as polycarbonate, polyphthalamide, nylon (registered trademark), polyethylene terephthalate, polybutylene terephthalate, and PC (polycarbonate) / ABS alloy can be used.
The shape of the frame 2 is not particularly limited, but it is preferable to have a recess from the viewpoint of packaging and luminous efficiency. In particular, the luminous efficiency can be improved by forming a recess in which the upper diameter is larger than the lower diameter and the side surface is inclined. The frame 2 having such a shape can be manufactured by a method known in the art such as injection molding.

Further, it is preferable that the frame 2 is a reflective frame 2 or that a reflector is provided on the surface of the frame 2 on the side on which the LED 3 is mounted. With such a configuration, the light from the LED 3 can be efficiently introduced into the glass cell 4, so that the luminous efficiency can be improved. The reflective frame 2 is not particularly limited, but can be formed by using a resin material having high reflectance or the like. Further, the reflecting plate arranged on the surface of the frame 2 is not particularly limited, but a metal plate having high reflectance or the like can be used.

The LED 3 mounted on the frame 2 is not particularly limited, and those known in the art such as a blue LED, a green LED, and a red LED can be used. Among them, when white light is realized by combining the light from the LED 3 and the light from the quantum dots 6, the LED 3 is preferably a blue LED. Although not shown, the LED 3 is connected to a lead electrode or the like, and can generate light by applying an electric signal from the lead electrode.

The glass cell 4 arranged above the LED 3 contains the quantum dots 6 dispersed in the resin or the organic solvent 5.
Here, the term "glass cell 4" as used herein means a member made of glass having an internal space capable of being filled with a resin or an organic solvent 5 in which quantum dots 6 are dispersed in a layered manner. Specifically, the glass cell 4 has at least two glass plates and has a structure in which a layered internal space is formed between the two glass plates. For example, the glass cell 4 has a structure in which two glass plates 10 face each other with a gap between the glass walls 11 as shown in FIG. The glass plate 10 is not limited to a flat surface, but may be a curved surface.
Further, in the present specification, the "quantum dot 6" is a nanoscale material having unique optical properties according to quantum mechanics, and has a particle size of generally 1 nm to 100 nm, preferably 1 nm to 50 nm, and more preferably 1 nm to 20 nm. Means very small semiconductor particles. The quantum dot 6 absorbs photons having an energy larger than the band cap (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 6 has a property of absorbing light having a wavelength below a certain level, and can generate light having various wavelengths by controlling the particle size.

Quantum dots 6 generally include one or more semiconductor materials. The semiconductor material is not particularly limited, but is limited to group IV elements, group II-VI compounds, group II-V compounds, group III-VI compounds, group III-V compounds, group IV-VI compounds, and the like. Examples thereof include group I-III-VI compounds, group II-IV-VI compounds, and group II-IV-V compounds. Specifically, 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.

Further, the quantum dot 6 may have a core-shell type structure including a core containing one or more semiconductor materials and a shell containing one or more semiconductor materials. Specifically, quantum dots 6 having CdSe as a core and CdZnS as a shell (red emission), CdZnSe as a core, quantum dots 6 having CdZnS as a shell (green emission), CdS as a core, and quantum dots having CdZnS as a shell. 6 (blue emission) or the like can be used.

Although the examples of the spherical quantum dots 6 are shown in FIGS. 1 (a) and 1 (b), the shape of the quantum dots 6 is not limited to the spherical shape, and may be various shapes such as a rod shape and a plate shape. You may.

The quantum dot 6 having the above-mentioned characteristics is known in the art and can be manufactured according to a known method.

The resin used for the dispersion of the quantum dots 6 is not particularly limited, and those known in the art can be used. Among them, epoxy resins, urea resins and silicone resins having excellent properties such as the dispersibility of the quantum dots 6 and the effect of preventing moisture and oxygen are preferable.
The organic solvent used for the dispersion of the quantum dots 6 is not particularly limited, and those known in the art can be used. The organic solvent is preferably an organic solvent having a high boiling point (preferably 100 ° C. or higher) having good dispersibility of the quantum dots 6. Examples of organic solvents include toluene, styrene, xylene and the like.

The shape of the glass cell 4 containing the quantum dots 6 dispersed in the resin or the organic solvent 5 may be appropriately set according to the shape of the concave portion of the frame 2, and is not particularly limited. Specifically, the glass cell 4 preferably has a structure corresponding to the shape of the recess (opening) of the frame 2.

Further, it is preferable that the glass cell 4 is not in direct contact with the LED 3. Since the surface temperature of the LED 3 becomes considerably high, by arranging the glass cell 4 away from the LED 3, it is possible to suppress a decrease in fluorescence efficiency due to deterioration of the quantum dots 6 due to heat generated from the LED 3.

When the glass cell 4 is arranged away from the LED 3, a space 7 may be provided between the LED 3 and the glass cell 4 as shown in FIGS. 1a) and 1b).
Further, the glass cell 4 may be arranged inside the recess of the frame 2 as shown in FIG. 1a), or may be arranged above the recess of the frame 2 as shown in FIG. 1b).

In the glass cell 4, the quantum dots 6 absorb the light from the LED 3, and as a result of the quantum dots 6 being excited, light having a wavelength longer than that of the light from the LED 3 is generated. Therefore, a desired emission color can be realized by controlling the type and the number of the LED 3 and the quantum dots 6. In particular, when realizing white light, the LED 3 is a blue LED, and the quantum dots 6 are excited by the blue light (absorbing the blue light) to have a peak center wavelength of 510 to 610 nm, preferably 520 nm to 580 nm. It preferably contains a first quantum dot having a peak center wavelength of 600 to 700 nm (absorbing blue light), preferably 610 nm to 680 nm, which is excited by blue light. With such a configuration, white light can be realized by combining the blue light from the blue LED, the green light from the first quantum dot, and the red light from the second quantum dot.

The space 7 formed between the glass cell 4 and the LED 3 may be left as air, but may be filled with an inert gas such as nitrogen or a sealing resin. The sealing resin is not particularly limited, and those known in the art can be used. Further, as the sealing resin, the same resin as that used for dispersing the quantum dots 6 may be used.
Further, the space 7 may be filled with a sealing resin in which particles are dispersed. Since the light from the LED 3 can be dispersed by using the sealing resin in which the fine particles are dispersed, the quantum dots 6 are uniformly irradiated with the light, and uniform light emission from the quantum dots 6 can be realized. .. The particles are not particularly limited, and particles known in the art can be used.

Although not essential, a polarizing plate may be arranged on the glass cell 4. By arranging the polarizing plate, only light in a specific vibration direction can pass through. Therefore, it can be used in applications that require light in a specific vibration direction (for example, a backlight unit).

Further, a reflective frame 2 may be used, or a reflective plate may be provided on the surface of the frame 2 on which the LED 3 is mounted, and a reflective polarizing plate may be used as the polarizing plate. With this configuration, the light reflected by the reflective polarizing plate is reflected by the reflective frame 2 or the reflecting plate to change the polarization state. By repeating this reflection, it is possible to obtain an optical cycle structure capable of passing the reflective polarizing plate with an efficiency close to 100%.

The LED package 1 of the present invention having the above configuration has a desired emission color, has high brightness and has a long life, and can be used for a backlight unit and a liquid crystal display device.

Hereinafter, the details of the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
(Example 1)
An LED package having the structure shown in FIG. 1 (a) was produced. In this LED package, a blue LED is used as an LED, a first quantum dot that is excited by blue light as a quantum dot (absorbs blue light) and emits green light, and a second quantum dot that emits red light are mixed. Was used. Moreover, a silicone resin was used as a resin for dispersing the quantum dots. The first quantum dot and the second quantum dot are white light obtained by combining blue light from a blue LED, green light from the first quantum dot, and red light from the second quantum dot. It is mixed in the ratio that can be obtained.
Next, the reliability test was performed on the obtained LED package. In the reliability test, the LED package was installed in a constant temperature and humidity chamber set to a temperature of 60 ° C. and a relative humidity of 90%, a current of 20 mA was passed through the LED, and the LED was lit for 1026 hours. This was done by measuring changes in total luminous flux and chromaticity. As a result, the change in total luminous flux after 1026 hours with respect to the initial value was + 1%, and the change in chromaticity was -0.012 for Cx and -0.001 for Cy.

Further, the color reproducibility was evaluated in the liquid crystal display device provided with the above-mentioned LED package as the light source of the liquid crystal display device and the comparison LED package using YAG (yttrium aluminum garnet) as the phosphor. The two types of liquid crystal display devices have exactly the same configurations except that the light sources are different. As a result of the measurement, the color reproduction range of the liquid crystal display device provided with the LED package for comparison using the YAG phosphor as the light source was about 72% of the NTSC, whereas the liquid crystal display provided with the above LED package. The color reproduction range of the device was about 96% of the NTSC.

(Comparative Example 1)
An LED package having the same structure as that of Example 1 was produced except that the one excluding the glass plate on the upper part of the closed container 10 was used.
Next, the reliability test was performed on the obtained LED package. In the reliability test, the LED package was installed in a constant temperature and humidity chamber set to a temperature of 60 ° C. and a relative humidity of 90%, a current of 20 mA was passed through the LED, and the LED was lit for 1010 hours, as in Example 1. This was done by measuring the changes in the total luminous flux and chromaticity of the LED at that time. As a result, the change in total luminous flux after 1010 hours with respect to the initial value was −8%, and the change in chromaticity was −0.075 for Cx and −0.117 for Cy.

(Comparative Example 2)
A sheet formed by wrapping quantum dots dispersed in resin between two barrier films having a barrier performance on the order of 10-2 (g / m2 · day) is placed on an edge light type backlight and is reliable. A sex test was performed. In the reliability test, a backlight in which the above sheet was placed was installed in a constant temperature and humidity chamber set to a temperature of 65 ° C. and a relative humidity of 75%, and blue light was emitted to the sheet containing the quantum dots in 1013. This was done by irradiating for a long time. The irradiation amount of blue light was 12,000 cd / m2. As a result of the reliability test, the change in brightness after 1013 hours with respect to the initial value was -68%, and the change in chromaticity was -0.115 for Cx and -0.351 for Cy.

Comparing the results of Example 1 with the results of Comparative Examples 1 and 2, the LED package of Example 1 has a larger change in total luminous flux (luminance) and chromaticity than the LED packages of Comparative Examples 1 and 2. It has been reduced. In addition, the color reproduction range of the liquid crystal display device using the LED package of Example 1 as the light source is significantly expanded as compared with the liquid crystal display device using the conventional LED package using the YAG phosphor as the light source.
As can be seen from the above results, according to the present invention, by using a glass cell containing quantum dots dispersed in a resin or an organic solvent, deterioration of the quantum dots is suppressed and a desired emission color is obtained. It is possible to provide a long-life LED package having high brightness and a narrow half-value width of the emission spectrum. Further, by using the LED package as a backlight source, the color reproduction range can be significantly expanded as compared with the conventional liquid crystal display device.

1 LED package, 2 frames, 3 LEDs, 4 glass cells, 5 resin or organic solvent, 6 quantum dots, 7 spaces, 10 glass plates, 11 glass walls.

Claims (9)

The frame on which the LED is mounted and
A glass cell arranged above the LED, which has a glass cell containing quantum dots dispersed in a resin or an organic solvent.
The space formed by the frame and the glass cell is filled with an inert gas.
The overall glass cell, the top surface of the glass cells are arranged in a recess of the frame so that the top surface and the same surface of the side wall of said frame,
The organic solvent contains styrene and
The resin in which the quantum dots are dispersed contains urea resin.
A reflective polarizing plate is provided on the glass cell,
An LED package characterized in that the frame is a reflective frame, or a reflector is provided on the surface of the frame on the side on which the LED is mounted . The LED package according to claim 1, wherein the glass cell is not in direct contact with the LED. The LED package according to claim 1 or 2, wherein the LED is mounted on the bottom surface of the recess. The lower end of the glass cell is arranged at the connection point of the vertical portion and the inclined portion of the recess of the frame so that the entire lower end of the glass cell is exposed to the space formed by the frame and the glass cell. The LED package according to claim 1. The LED package according to any one of claims 1 to 4 , wherein the quantum dots are two or more types of quantum dots having different emission wavelengths. The LED emits blue light, and the quantum dots are excited by the blue light and have a peak center wavelength of 510 to 610 nm, and are excited by the blue light and peak at 600 to 700 nm. The LED package according to any one of claims 1 to 5 , wherein the LED package includes a second quantum dot having a central wavelength. The glass cell has a structure in which two glass plates are opposed to each other at intervals through a glass wall.
The LED package according to claim 1, wherein the glass plate has a curved surface shape. A backlight unit comprising the LED package according to any one of claims 1 to 7 . A liquid crystal display device comprising the backlight unit according to claim 8 .

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