JP2008010556A - Led light source device and led backlight using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-reliability LED light source device with almost no chromaticity variation between lots, and no chromaticity unevenness that achieves white light having a spectrum distribution including wavelength components corresponding to the light's three primary colors of R (red), G (green), and B (blue) with excellent color reproducibility. <P>SOLUTION: The LED light source device is composed so as to arrange a first color conversion filter 3 formed by dispersing a red phosphor 3a on glass 8, and a second color conversion filter 4 formed by dispersing a green phosphor 4a on the glass 8, in an irradiation direction of a blue LED 2. It is also composed so as to obtain three-wavelength white light of R, G, and B, by B (blue) light emitted from the LED 2 and guided inside the first color conversion filter 3 and inside the second color conversion filter 4, R (red) light guided inside the second color conversion filter 4 after the blue light emitted from the LED 2 is subjected to color conversion with the first color conversion filter 3, and G (green) light that is the light subjected to color conversion with the second color conversion filter 4 after the blue light emitted from the LED 2 is guided inside the first color conversion filter 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an LED light source device and an LED backlight using the same, and more specifically, irradiates an object to be irradiated with white light emitted from an LED light source device using an LED as a light source through a light guide. It relates to an LED backlight.

  Conventionally, a method using a combination of an LED element and a phosphor has been proposed as a method of obtaining light having a chromaticity close to white light using an LED having a steep emission spectrum as a light source. It is coated with a silicone resin in which a yellow phosphor made of YAG: Ce that emits yellow light that is excited by blue light and emits a complementary color of blue is emitted around a blue LED having an emission spectrum peak wavelength of about 450 to 460 nm. In addition, light having a chromaticity close to that of white light is obtained by an additive color mixture of yellow light, in which part of blue light from the blue LED is wavelength-converted by exciting the phosphor, and blue light from the blue LED. .

  The LED having such a structure is used by being incorporated in, for example, a reading light source for a printer, a panel illumination device, a general illumination device, and various indicators, but in the case of a backlight for a color LCD such as a mobile phone or a thin television. An emission spectrum having a wavelength component having a relatively narrow half-value width corresponding to the transmission wavelength region of each color filter of R (red), G (green), and B (blue) is obtained.

To satisfy such requirements, the yellow phosphor _Sr l is excited in the blue light to emit red light in addition to the _- X _Ca X S: Eu and CaAlSiN _3: a red phosphor is added consisting of Eu A part of blue light from the blue LED excites the phosphor to obtain light having a chromaticity close to that of white light by additive color mixing of the yellow light and red light, which are wavelength-converted, and the blue light from the blue LED. A method has been proposed.

  By the way, the method of obtaining light of chromaticity close to white light by sealing the LED element with a resin in which the phosphor is dispersed is difficult to ensure the uniformity of the distribution of the phosphor particles in the sealing resin, Even if the uniformity can be ensured, the emitted light from the light emitting surface of the sealing resin has optical characteristics with uneven color tone due to the optical path length difference until the emitted light of the LED element reaches the light emitting surface of the sealing resin. It will be a thing.

  Therefore, in order to solve such a problem, the semiconductor device is placed in a tank containing suspended particles made of phosphor particles, and a bias voltage is applied to the semiconductor device to thereby suspend the suspended particles on the semiconductor device. Has been disclosed (for example, see Patent Document 1).

  As a light source used for a backlight for a color LCD, the LED having the above configuration has a color purity of a spectrum corresponding to a transmission wavelength region of each color filter of R (red), G (green), and B (blue). It is bad and it is difficult to obtain good color reproducibility.

Therefore, a blue LED element having an emission spectrum peak wavelength of about 460 nm and Sr _1-X Ca _X Ga ₂ S4 that emits light having a sharp spectrum with a small half-value width when excited by the light emitted from the blue LED element: A method of combining a green phosphor made of Eu and a red phosphor made of Sr _1-X Ca _X S: Eu that emits light having a sharp spectrum with a small half-value width has been proposed.

  However, although these sulfide phosphors have high emission luminance, they deteriorate by reacting with water vapor in a high temperature and high humidity environment, and blackening by reacting with the silver film forming the light reflecting surface of the package. There is a lack of reliability.

  The red phosphor emits from the green phosphor, re-absorbs light having a shorter wavelength than the light emitted from the red phosphor, and the red phosphor and the green phosphor have different specific gravities and particle sizes. Therefore, it is difficult to uniformly disperse the two types of phosphors in the sealing resin, and it is also difficult to ensure the mixing ratio of the two types of phosphors with high accuracy and good reproducibility. In order to make the light emitted from the light exit surface of the stop resin to have optical characteristics with good reproducibility and little unevenness in color tone, there is a problem that a great deal of labor and time is spent on production management and the yield is also poor. Yes.

Therefore, in order to solve such a problem, a method of forming a light emitting color conversion member in which phosphor is dispersed in glass by sintering glass powder and phosphor powder is disclosed (for example, (See Patent Document 2).
JP 2005-286327 A JP 2003-258308 A

  However, in the disclosed method, a yellow phosphor that emits yellow light when excited by blue light is dispersed in a glass to form an emission color conversion member, which is effective in reducing variation in optical characteristics among lots. However, it is difficult to use it for a color LCD backlight because the above optical performance is not satisfied.

  Accordingly, the present invention was devised in view of the above problems, and its object is to provide a spectral distribution including wavelength components corresponding to the three primary colors of R (red), G (green), and B (blue) light. It is an object of the present invention to provide a highly reliable LED light source device that realizes white light having a good color reproducibility and has little chromaticity unevenness and lot-to-lot chromaticity variation.

In order to solve the above problem, the invention described in claim 1 of the present invention includes one or a plurality of blue light emitting LEDs having the same emission spectrum,
A first color conversion filter in which a red phosphor is dispersed in glass;
An LED light source device having a second color conversion filter in which a green phosphor is dispersed in glass,
Blue light from the blue light emitting LED is incident on one of the first color conversion filter and the second color conversion filter, and the first color conversion filter and the second color conversion filter. The white light is emitted from the other of the two.

  According to a second aspect of the present invention, in the first aspect, the blue light from the blue light-emitting LED is incident on the first color conversion filter, and the white color from the second color conversion filter is white. The light is emitted.

In the invention described in claim 3 of the present invention, in any one of claims 1 and 2, the red phosphor is Sr _1-X Ca _X S: Eu, and the green phosphor is Sr. _1-X Ca _X Ga ₂ S ₄ : Eu.

  Moreover, the invention described in claim 4 of the present invention includes the LED light source device described in any one of claims 1 to 3 and a light guide, and white light from the LED light source device is guided. The irradiated object is irradiated through a light body.

  The invention described in claim 5 of the present invention is characterized in that, in claim 4, the irradiated object is an LCD.

  The LED light source device of the present invention is applied to one of the first color conversion in which the blue light from the blue light emitting LED is dispersed in the glass and the second color conversion filter in which the green phosphor is dispersed in the glass. By making the light incident, white light is emitted from the other of the first color conversion filter and the second color conversion filter.

  As a result, it has been possible to realize a highly reliable LED light source device that realizes three-wavelength white light with good color reproducibility and has little chromaticity unevenness and chromaticity variation between lots.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. 1 to 6 (the same parts are denoted by the same reference numerals). The embodiments described below are preferable specific examples of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention particularly limits the present invention in the following description. Unless stated to the effect, the present invention is not limited to these embodiments.

  FIG. 1 is a schematic view showing a configuration example of an LED light source device of the present invention. The LED light source device 1 having this configuration includes an LED 2, a first color conversion filter 3, and a second color conversion filter 4.

  The LED 2 is obtained by sealing a LED chip 5 that emits B (blue) light with a sealing resin 6 having translucency. The sealing resin 6 is made of silicone resin, epoxy resin, silicone epoxy resin, and the like, protects the LED chip 5 from the external environment such as moisture, dust, and gas, and applies the external force such as vibration and shock to the aerial wiring wire 7. The light emitting surface of the LED chip 5 and the sealing resin 6 form an interface, so that the refractive index of the member that forms the interface with the light emitting surface of the LED chip 5 is reduced. It also plays a role of improving the light extraction efficiency of the emitted light incident on the sealing resin 6 from the light emitting surface of the LED chip 5 close to the refractive index of the semiconductor material forming the light emitting surface.

  Note that sealing with a low-melting glass instead of the resin sealing 6 is also possible. In this case, glass sealing plays the same role as the resin sealing.

  A first color conversion filter 3 and a second color conversion filter 4 are sequentially arranged from the LED 2 side in the irradiation direction of the LED 2.

The first color conversion filter 3 is a glass 8 having a thickness of 0.3 mm in which a red phosphor 3a is dispersed. The glass powder is a red color composed of Sr _1-X Ca _X S: Eu (0 <X <1). The phosphor powder is formed by mixing 1 wt% of phosphor powder and firing in air at a temperature of about 800 ° C. for several hours.

The second color conversion filter 4 is a glass 8 having a thickness of 0.3 mm in which a green phosphor 4a is dispersed, and Sr _1-X Ca _X Ga ₂ S ₄ : Eu (0 <X <1) with respect to the glass powder. The green phosphor powder is made by mixing 6 wt% and firing in air at a temperature of about 800 ° C. for several hours.

  In such a configuration, the light emitted from the LED 2 enters the first color conversion filter 3 from the light incident surface 3 b of the first color conversion filter 3, and is guided through the first color conversion filter 3. The light reaching the light exit surface 3 c of the first color conversion filter 3 is excited by a part of the B (blue) light from the LED 2 by the red phosphor 3 a dispersed in the first color conversion filter 3. It consists of the converted R (red) light and the B (blue) light from the LED 2 that has passed through the first color conversion filter 3 as it is.

  Then, the light is emitted from the light exit surface 3c of the first color conversion filter 3 and enters the second color conversion filter 4 from the light incident surface 4b of the second color conversion filter 4, and the second color conversion filter. The light that is guided through 4 and reaches the light exit surface 4 c of the second color conversion filter 4 is generated by the red phosphor 3 a dispersed in the first color conversion filter 3 as B (blue) light from the LED 2. R (red) light that has been partially excited, wavelength-converted, and passed through the second color conversion filter 4 as it is, and the green phosphor 4a dispersed in the second color conversion filter 4 are the first color conversion filter. LED 2 that has passed through the first color conversion filter 3 and the second color conversion filter 4 as it is, and G (green) light that has been excited by a part of B (blue) light from the LED 2 that has passed through the LED 3 and has undergone wavelength conversion. From B (blue) light.

  Therefore, the light emitted from the light emitting surface 4c of the second color conversion filter 4 has a spectral distribution including wavelength components corresponding to the three primary colors of R (red), G (green), and B (blue) light. It is recognized by humans as W (white) light by additive color mixture of R (red) light, G (green) light, and B (blue) light.

  FIG. 2 shows the light emitted from the LED and incident on the first color conversion filter, guided through the first color conversion filter and the second color conversion filter, and emitted from the second color conversion filter. The spectral distribution is shown. As can be seen from this spectral distribution, it contains a wavelength component with a relatively narrow half-value width corresponding to the wavelength region indicating the three primary colors of R (red), G (green), and B (blue) light. Three-wavelength white light is formed by additive color mixing.

  The LED light source device described above has a configuration in which each color conversion filter has a phosphor dispersed in glass, so that a substantially uniform phosphor distribution can be obtained over the entire surface of the glass with good reproducibility, and chromaticity variation among lots. And a light source with little chromaticity unevenness on the light exit surface can be realized.

  In addition, a first color conversion filter in which a red phosphor is dispersed is disposed on the side facing the LED, and a second color conversion filter in which a green phosphor is dispersed is sandwiched between the LED and the first color conversion filter. It was arranged on the opposite side. As a result, red light emitted from the red phosphor dispersed in the first color conversion filter is reabsorbed by the green phosphor dispersed in the second color conversion filter and not excited at the wavelength of the red light. There is no. Therefore, it is possible to easily realize an LED light source device that is excellent in separation of R, G, and B wavelength components in the spectrum and excellent in chromaticity reproducibility.

  By the way, the second color conversion filter in which the green phosphor is dispersed is disposed on the side facing the LED, and the first color conversion filter in which the red phosphor is dispersed is sandwiched between the second color conversion filter and the LED. By disposing the light source on the opposite side, it is possible to obtain a light source in which brightness and illuminance are more important than chromaticity reproducibility.

  FIG. 3 shows the spectral distribution when the first color conversion filter is positioned on the side facing the LED and the second color conversion filter positioned on the side facing the LED in the two color conversion filters superimposed on each other. The spectrum distribution when it was made to show is shown.

  In this case, the first color conversion filter is obtained by mixing 2 wt% of the red phosphor powder with respect to the glass powder and firing, and the second color conversion filter is 6 wt% of the green phosphor powder with respect to the glass powder. They are mixed and fired.

  As shown in FIG. 3, when the first color conversion filter in which the red phosphor is dispersed is arranged on the LED side, the three-wavelength white having a spectral distribution in which the output separation of the R, G, and B wavelength components and the output balance are good It can be seen that when a second color conversion filter in which light is obtained and the green phosphor is dispersed is arranged on the LED side, an LED light source device with high brightness can be realized.

  FIG. 4 shows a plurality of types of first color conversion filters having different concentrations of red phosphors and a plurality of types of second color conversion filters having different concentrations of green phosphors. The chromaticity coordinates of the light emitted from each color conversion filter when each of the two color conversion filters is irradiated with light from the blue LED are shown on the chromaticity diagram, and the first color is shown on the same chromaticity diagram. One of the conversion filters and one of the second color conversion filters are overlapped and light from the blue LED is emitted from the first color conversion filter side and emitted from the first color conversion filter. The chromaticity coordinates of three-wavelength white light are shown.

  Samples of the first color conversion filter are three types obtained by mixing 1 wt%, 2 wt%, and 3 wt% of the red phosphor powder (R) with the glass powder and firing, respectively. There are three types of green phosphor powder (G) that are fired by mixing 3 wt%, 6 wt%, and 9 wt%, respectively, with the glass powder.

  As a result, by combining the first color conversion filter obtained by mixing and firing 1 wt% of the red phosphor powder (R) and the second color conversion filter obtained by mixing and firing 6 wt% of the green phosphor powder (G) It was possible to obtain white (W) light having chromaticity coordinates in a target chromaticity coordinate area indicated by a dotted line in the chromaticity diagram.

Incidentally, these _{Sr 1-X Ca X S:} Eu , etc. are deteriorated in several hours in an environment of high temperature and high humidity. However, it is possible to suppress deterioration in a high temperature and high humidity environment by dispersing these phosphors in glass.

FIG. 5 shows a color conversion filter in which a red phosphor made of Sr _1-X Ca _X S: Eu is dispersed in glass and a color conversion in which a green phosphor made of Sr _1-X Ca _X Ga ₂ S ₄ : Eu is dispersed in glass. Shown are the results of measuring the luminous flux of red light and green light emitted from each color conversion filter by leaving the filter in a high-temperature and high-humidity atmosphere at a temperature of 60 ° C. and a humidity of 90% and irradiating excitation light after a certain time. ing.

  FIG. 5 shows that both the color conversion filters maintain the initial luminous flux even after 95 hours even if they are exposed to an atmosphere of temperature 60 ° C. and humidity 90%, and the phosphor is not deteriorated. It could be confirmed.

  As a result, it is clear that even in the high temperature and high humidity environment, even a sulfide phosphor with poor reliability can be drastically improved by dispersing it in glass, and sufficient reliability can be secured. became. Therefore, as a matter of course, this is an effective method for improving the moisture resistance of sulfides such as SrS, CaS, and ZnS and phosphors that are inferior in moisture resistance.

  In addition, by separately providing a color conversion filter in which red phosphor is dispersed in glass and a color conversion filter in which green phosphor is dispersed in glass, the region is excited by blue light and emits red light and excited by blue light. The area that emits green light can be created independently. As a result, it is possible to improve optical characteristics such as color reproducibility, chromaticity unevenness, and chromaticity variation between lots, which are problems when a red phosphor and a green phosphor are mixed.

  FIG. 6 shows an example in which a color LCD is illuminated by an LED backlight using the LED light source device of the present invention.

  A first color conversion filter 3 in which a red phosphor is dispersed in glass and a second color conversion filter 4 in which a green phosphor is dispersed in glass are arranged in an overlapping manner in the irradiation direction of the LED 2. The light exit surface 4 c is attached to the light incident end surface 9 a of the light guide plate 9. A diffusion plate 10 is disposed on the light emitting surface 9b of the light guide plate 9, and an LCD 11 having a color filter (not shown) is disposed thereon.

  Then, the B (blue) light from the LED 2 is guided through the first color conversion filter 3 and the second color conversion filter 4 so that the three-wavelength W (white) light formed on the light guide plate 9 The light is incident on the light guide plate 9 from the light incident end surface 9 a, guided in the light guide plate 9, reaches the diffusion plate 10 from the light emission surface 9 b, and the white diffused light from the diffusion plate 10 irradiates the LCD 11.

  At this time, the mixing concentration of the red phosphor dispersed in the first color conversion filter and the green phosphor dispersed in the second color conversion filter, and / or the first color conversion filter and the second color conversion, respectively. By controlling the thickness of each filter, the mixing ratio of the blue light of the irradiation light and the red light and green light emitted from each phosphor can be changed, so that the spectrum of the three-wavelength white light from the diffusion plate 10 can be changed. The distribution can be optimized to include wavelength components corresponding to the R (red), G (green), and B (blue) transmission wavelength regions of the LCD color filter.

It is the schematic of embodiment concerning this invention. It is a spectrum distribution map of white light formed in an embodiment according to the present invention. It is a spectrum distribution figure when the arrangement | positioning of the color conversion filter which comprises embodiment concerning this invention is changed. It is a chromaticity diagram which shows the chromaticity of the color conversion filter which comprises this invention, and those combination. It is a graph which shows the result of the high temperature, high humidity test of the color conversion filter which comprises embodiment concerning this invention. It is a side view which shows the state which illuminates a color LCD with the LED backlight which uses the LED light source device of this invention.

Explanation of symbols

1 LED light source device 2 LED
Reference Signs List 3 First color conversion filter 3a Red phosphor 3b Light incident surface 3c Light exit surface 4 Second color conversion filter 4a Green phosphor 4b Light entrance surface 4c Light exit surface 5 LED chip 6 Sealing resin 7 Bonding wire 8 Glass 9 Light guide plate 9a Light incident end surface 9b Light exit surface 10 Diffuser plate 11 LCD

Claims (5)

A plurality of blue light emitting LEDs having one or the same emission spectrum;
A first color conversion filter in which a red phosphor is dispersed in glass;
An LED light source device having a second color conversion filter in which a green phosphor is dispersed in glass,
Blue light from the blue light emitting LED is incident on one of the first color conversion filter and the second color conversion filter, and the first color conversion filter and the second color conversion filter. An LED light source device characterized in that white light is emitted from the other side of the LED.   2. The LED light source according to claim 1, wherein blue light from the blue light emitting LED is incident on the first color conversion filter and white light is emitted from the second color conversion filter. 3. apparatus. The red phosphor _{Sr 1-X} Ca _X S: Eu, and the the green phosphor _{Sr 1-X Ca X Ga 2} S 4: any one of claims 1 or 2, characterized in that the Eu LED light source device according to item.   An LED light source device according to any one of claims 1 to 3 and a light guide are provided, and white light from the LED light source device is irradiated to an irradiated object through the light guide. LED backlight.   The LED backlight according to claim 4, wherein the irradiation object is an LCD.

Images