JP2006128008A - Lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress occurrence of color unevenness. <P>SOLUTION: A lighting system is provided with a light source in which light-emitting elements IR, IG, IB of red color, green color, and blue color have been arranged, and a wavelength selecting means 3 which has a red light reflecting means in which green light and blue light out of the red light, the green light, and the blue light are made to be selectively transmitted, a green light reflecting means in which the red light and the blue light out of the red light, the green light, and the blue light are made to be selectively transmitted, and a blue light reflecting means in which the red light and the green light out of the red light, the green light, and the blue light are made to be selectively transmitted. The red light reflecting means, the green light reflecting means, and the blue light reflecting means are respectively installed upward the light-emitting elements IR, IG, IB of the red color, the green color, and the blue color. By this, transmission of the surplus red right, green light, and blue light can be prevented in a region where the light intensity is strong of the red light, the green light, and the blue light above the light-emitting elements IR, IG, IB of the red color, the green color, and the blue color. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an illumination device that emits white light.

  Conventionally, a fluorescent lamp (FL), an electroluminescence (EL), and a light emitting diode (LED) are used as a backlight light source of a liquid crystal display (LCD). However, in recent years, LEDs are particularly expected to expand the color reproduction range of LCDs due to their color characteristics.

  As a light source using an LED, there are (1) one using a white LED and (2) one using each color LED alone and diffusing the light from the LED with a diffusion plate or the like to produce white light. However, since a long-life white LED has not been realized at present, the latter is widely studied as a light source (see, for example, Patent Document 1).

  By the way, CRT (Cathode-Ray Tube), LCD (Liquid Crystal Display), etc. are the most common display devices using light mixing. These are color-mixed by adjoining micro dots composed of the three primary colors of light to reproduce the color.

  Even when creating a white light source for backlight, color mixing is easier when the point light sources of the respective colors are brought closer to each other than when the high-power LEDs are separated from each other. Further, by distributing the point light sources that are close to each other evenly in the plane, the distribution of the amount of light in the plane can be kept small. For this purpose, it is preferable to arrange small LEDs close to each other. If this is developed, a display using LED pixels becomes possible. However, this method is not practical at present because of the cost of LED and the difficulty of processing.

  When white light is obtained by diffusing LEDs of each color to perform color mixing, if the point light sources of different colors are far apart, the light mixing becomes very difficult. Therefore, it has been proposed to use a light source in which three color LED chips are fixed on one base. However, this light source has a problem that the yield is low, the cost is high, and a high output light source has not yet been obtained.

  In view of this, a method has been proposed in which color mixing is performed by irradiating and diffusing light over a wide range, using an LED that emits light laterally (side emission), that is, a so-called side mission LED.

JP-A-8-212361

  However, this method has a problem that the degree of light mixing is not sufficient and color unevenness occurs. In addition, there is also a problem that after the light is emitted from the LED to the side, the loss of the light amount increases because the light is raised in the surface direction by the diffusion plate and the prism sheet.

  Therefore, a first object of the present invention is to provide an illumination device that can suppress the occurrence of color unevenness.

  A second object of the present invention is to provide an illumination device that can suppress the occurrence of color unevenness and the loss of light quantity.

In order to solve the above-mentioned problem, the invention according to claim 1 includes a light source in which red, green and blue light emitting elements are arranged,
Red light reflecting means for selectively transmitting green light and blue light among red light, green light and blue light, Green light reflecting means for selectively transmitting red light and blue light among red light, green light and blue light, and red Wavelength selective transmission means having blue light reflection means for selectively transmitting red light and green light among light, green light and blue light, and
The illumination device is characterized in that the red light reflecting means, the green light reflecting means, and the blue light reflecting means are provided above the red, green, and blue light emitting elements, respectively.

  According to the first aspect of the present invention, the amount of red light, green light, and blue light can be reduced above each of the red, green, and blue light emitting elements.

  According to a second aspect of the present invention, in the illumination device according to the first aspect, the red light, the green light and the blue light reflected by the red light reflecting means, the green light reflecting means and the blue light reflecting means are directed to the wavelength selective transmitting means. It is further characterized by further comprising reflecting means for reflecting.

  According to a third aspect of the present invention, in the illumination device according to the first aspect, the red light reflecting means, the green light reflecting means, and the blue light reflecting means correspond to red light, green light, and blue light emitted from the light emitting element, respectively. It consists of a photonic crystal having a band gap.

  According to a fourth aspect of the present invention, in the illumination device according to the first aspect, the photonic crystal is in the form of minute dots.

  The invention described in claim 5 is the illuminating device according to claim 1, further comprising a diffusing unit for diffusing the light transmitted through the wavelength selective transmitting unit.

  The invention described in claim 6 is the illuminating device according to claim 1, further comprising prism means for directing the direction of the light transmitted through the wavelength selective transmission means forward.

  According to a seventh aspect of the present invention, in the illuminating device according to the first aspect of the present invention, the illumination device further includes a polarization selection unit that transmits light having a specific polarization direction among the light transmitted through the wavelength selective transmission unit.

  The reflecting means, the diffusing means, the prism means and the polarized light selecting means typically have a plate, sheet or film shape. The photonic crystal is typically formed on a transparent substrate, and a transparent substrate, sheet, or film is typically used as the substrate.

  As described above, according to the first aspect of the present invention, since the red reflecting means, the green reflecting means, and the blue reflecting means are provided above the red, green, and blue light emitting elements, respectively, the red light emission Reduces red light with a large amount of light above the element, reduces green light with a large amount of light above the green light emitting element, and reduces blue light with a large amount of light above the blue light emitting element . That is, the light emitted from the red, green, and blue light emitting elements can be selectively transmitted by the wavelength selective transmission means to adjust the balance of each color. Therefore, white light with no color unevenness can be generated.

  According to the invention of claim 2, the reflecting means reflects the red light, the green light and the blue light reflected by the red reflecting means, the green reflecting means and the blue reflecting means toward the wavelength selective transmitting means. In addition, the occurrence of color unevenness and the loss of light amount can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings of the following embodiments, the same or corresponding parts are denoted by the same reference numerals.

  FIG. 1 is a cross-sectional view showing an example of the configuration of a lighting device according to the first embodiment of the present invention. As shown in FIG. 1, the display device includes a reflecting plate 2 having a red LED 1 </ b> R, a green LED 1 </ b> G, and a blue LED 1 </ b> B provided on one main surface, and a wavelength selective transmission plate 3.

  Features of this lighting device are as follows: 1) “divide one large light source into fine point light sources by three photonic crystal dots having photonic band gaps corresponding to RGB”, 2) “from LED light source The dots of the photonic crystal are adjusted in accordance with the light intensity of each color, and are arranged so that the transmission intensity of each color is averaged. Note that this illumination device is suitable for use as a backlight of a liquid crystal display device or the like.

  The red LED 1R, the green LED 1G, and the blue LED 1B are configured to emit red light, green light, and blue light, respectively. The reflection plate 2 is for reflecting the light reflected by the wavelength selective transmission plate 3 so as to enter the wavelength selective transmission plate 3 again. The red LED 1R, the green LED 1G, and the blue LED 1B are provided on the reflector 2 in a predetermined two-dimensional pattern, for example. Examples of the two-dimensional pattern include a lattice shape, a stripe shape, and a delta (Δ) shape. In the case of a delta shape, each of the red LED 1R, the green LED 1G, and the blue LED 1B is positioned at each vertex of the delta.

  The wavelength selective transmission plate 3 includes a transparent substrate 3a and a photonic crystal layer 3b provided on the transparent substrate 3a. The transparent substrate 3a is made of a material that can transmit light emitted from the red LED 1R, the green LED 1G, and the blue LED 1B. As such a material, for example, glass or plastic can be used.

  The photonic crystal layer 3b includes dots that selectively reflect green light and blue light while selectively reflecting red light, and dots that selectively transmit red light and blue light while selectively reflecting green light. And dots that selectively reflect blue light but selectively transmit red light and green light. These dots are arranged in, for example, a two-dimensional pattern. Specifically, for example, dots that reflect red light are provided above the red LED 1R, dots that reflect green light are provided above the green LED 1G, and blue light Is provided above the blue LED 1B.

  The dot that reflects the red light emitted from the red LED 1R is composed of a photonic crystal having a band gap corresponding to the red light emitted from the red LED 1R, and the dot that reflects the green light emitted from the green LED 1G is A dot that is composed of a photonic crystal having a band gap corresponding to the green light emitted from the green LED 1G and reflects the blue light emitted from the blue LED 1B has a band gap corresponding to the blue light emitted from the blue LED 1B. It consists of a photonic crystal.

  A photonic crystal is a structure having a periodic structure on the order of the wavelength of light, for example, a finely packed fine particle having a uniform particle diameter, for example, several hundred nm, specifically 200 to 400 nm, semiconductor technology And a structure having a periodic structure in two dimensions (layered), and a structure having a periodic structure in three dimensions. Note that an organic material or an inorganic material can be used as the material of the fine particles.

  A feature of the photonic crystal is that it has a photonic band gap in which light of a certain wavelength cannot enter due to its periodic structure, that is, it strongly reflects light corresponding to the photonic band gap. For this reason, the photonic crystal exhibits a color corresponding to its band gap. This photonic band gap can be easily controlled by adjusting the size of the periodic structure of the photonic crystal. For example, in a photonic crystal composed of fine particles, the photonic band gap can be controlled by changing the particle diameter.

  FIG. 2A is an enlarged cross-sectional view showing a configuration example of the wavelength selective transmission plate 3. FIG. 2B is an enlarged plan view showing a configuration example of the wavelength selective transmission plate 3. 2A and 2B, photonic crystals that reflect red light, photonic crystals that reflect green light, and photonic crystals that reflect blue light are arranged in a two-dimensional pattern.

  FIG. 3 is a plan view schematically showing an example of a dot arrangement pattern. In FIG. 3, hatched circles, white circles, and black circles indicate dots that reflect red light, green light, and blue light, respectively, and stars indicate positions immediately above the red LED 1R, green LED 1G, and blue LED 1B, respectively. . In FIG. 3, the photonic crystal layer 3b is configured by two-dimensionally arranging dots that reflect red light, green light, and blue light, and the dot that reflects red light is higher than the other dots above the red LED 1R. The green LED 1G is provided with more dots that reflect green light than other dots, and the blue LED 1B is provided with dots that reflect blue light compared to the other dots. Many are provided.

  That is, many photonic crystals having a band gap corresponding to red light are provided in the region above the red LED 1R where the amount of red light is large, and green is present in the region above the green LED 1G where the amount of green light is large. Many photonic crystals having a band gap corresponding to blue are provided, and many photonic crystals having a band gap corresponding to blue are provided in a region above the blue LED 1B where the amount of blue light is large.

  A photonic crystal having a band gap corresponding to red light selectively reflects red light, selectively transmits green light and blue light, and a photonic crystal having a band gap corresponding to green light selectively reflects green light, A photonic crystal that selectively transmits red light and blue light and has a band gap corresponding to blue light selectively reflects blue light and selectively transmits red light and green light. In regions above the red LED 1R, the green LED 1G, and the blue LED 1B that have a large amount of light, excessive red light, green light, and blue light can be prevented from being transmitted, and color unevenness can be eliminated.

  The dots provided on the red LED 1R, the green LED 1G, and the blue LED 1B for reflecting the red light, the green light, and the blue light are provided, for example, in a substantially circular shape. Moreover, in the area | region corresponding between each LED, for example, the dot which reflects the light from one LED reduces gradually as it goes to the other one from on the other side, whereas it is from one LED. The dots are arranged so that the number of dots that reflect light gradually increases.

  More specifically, for example, in the region corresponding to the area between the red LED 1R and the green LED 1G, the number of dots that reflect light from the red LED 1R gradually decreases as it goes from directly above the red LED 1R to directly above the green LED 1G. On the other hand, the dots are arranged so that the number of dots reflecting the light from the green LED 1G gradually increases.

  FIG. 4 is a schematic diagram illustrating an example of in-plane distribution (one-dimensional display) of dots of a photonic crystal. In FIG. 4, 11R, 11G, and 11B indicate the light intensities of red light, green light, and blue light, respectively. Reference numeral 12 denotes an in-plane distribution of dots that reflect red light, dots that reflect green light, and dots that reflect blue light.

  As shown in FIG. 4, above the red LED 1R, the green LED 1G, and the blue LED 1B, the density of dots that reflect red light, dots that reflect green light, and dots that reflect blue light increases. Specifically, the density of the photonic crystal dots increases according to the light intensity of each color. More specifically, the density of dots that reflect red light increases according to the light intensity of the red LED 1R, the density of dots that reflect green light increases according to the light intensity of the green LED 1G, and the light of the blue LED 1B increases. Depending on the intensity, the density of dots that reflect blue light increases.

  Below, an example of the formation method of the photonic crystal layer 3b by microparticles | fine-particles is demonstrated. The type of photonic crystal is not particularly limited as long as the balance of each color is adjusted and uniform white light can be obtained.

  First, three types of solutions are prepared in which silica fine particles having a particle size corresponding to red light, silica fine particles having a particle size corresponding to green light, and silica fine particles having a particle size corresponding to blue light are monodispersed. . Then, these solutions are applied in the form of dots on the transparent substrate 3a in accordance with the color intensity from the red LED 1R, the green LED 1G, and the blue LED 1B which are light sources. As the coating method, for example, a printing method such as ink jet can be used. In addition, it is preferable to make a dot small as long as the feature as a photonic crystal is not lost. Then, it is naturally dried slowly so that the droplets of silica fine particles are not disturbed. As a result, a photonic crystal dot is formed.

According to the first embodiment of the present invention, the following effects can be obtained.
The light emitted from the red LED 1R, the green LED 1G, and the blue LED 1B is dispersed in the horizontal direction by using the photonic crystal layer 3b as a RGB small area point light source, and the intensity of the light incident on the photonic crystal layer 3b By changing the arrangement in accordance with the above, it is possible to realize an illuminating device such as a backlight for an LCD having uniform light quantity in a plane without color unevenness.

  In addition, when a photonic crystal made of fine particles is used, a printing technique such as inkjet can be used, and the wavelength selective transmission plate 3 having excellent manufacturability and low cost can be provided. Further, since the color unevenness is eliminated on the light source side, it is not necessary to forcibly perform side radiation, and the light from the LED can be used without waste, and the light quantity of an illumination device such as an LCD backlight can be increased.

  Further, since the light reflected by the wavelength selective transmission plate 3 is repeatedly reflected by the reflection plate 2 until it passes through the wavelength selective transmission plate 3, the light that could not be transmitted through the wavelength selective transmission plate 3 at first is finally obtained. Can be used, and a significant reduction in the amount of light can be prevented.

  Next explained is the second embodiment of the invention. FIG. 5 is a cross-sectional view showing an example of the configuration of the illumination device according to the second embodiment of the present invention. As shown in FIG. 5, the illumination device includes a reflector 2 provided with a red LED 1R, a green LED 1G, and a blue LED 1B on one main surface, and red light and green light emitted from the red LED 1R, the green LED 1G, and the blue LED 1B. And a wavelength selective transmission plate 3 that selectively transmits blue light and a diffusion plate 4 that diffuses light transmitted through the wavelength selective transmission plate 3. By providing this diffusing plate 4, color mixing can be further improved and more uniform white light can be generated.

  Next explained is the third embodiment of the invention. The illumination device according to the third embodiment further includes various optical films above the wavelength selective transmission plate 3. As these various optical films, for example, prism sheets such as BEF (Brightness Enhancement Film), polarization selective films such as D-BEF (Dual-Brightness Enhancement Film), and the like can be used.

  For example, when a prism sheet and a polarization selection film are provided as the optical film, the prism sheet and the polarization selection film are provided so that light transmitted through the wavelength selection transmission plate 3 is transmitted in the order of the prism sheet and the polarization selection film. To do.

  In the case where a prism sheet is further provided, the luminance of the liquid crystal display device can be improved by turning the light beam direction forward when the illumination device is used as a backlight of the liquid crystal display device. Further, in the case where a polarization selection film is further provided, when this illumination device is used as a backlight of a liquid crystal display device, the polarization plane of incident light is made to coincide with the polarization plate while repeating reflection. Brightness can be increased by increasing the amount of light passing therethrough.

  Moreover, you may make it further provide the diffusion plate 3 in the illuminating device by this 3rd Embodiment. In this case, for example, the diffusion plate 3 is provided between the wavelength selective transmission plate 3 and various optical films.

  Although the first to third embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications based on the technical idea of the present invention are possible. is there.

  For example, the numerical values given in the above first to third embodiments are merely examples, and different numerical values may be used as necessary.

  In the first to third embodiments described above, it is possible to adjust the balance of each color so as to generate white light with no color unevenness by not providing dots in regions corresponding to the respective LEDs. Good.

It is sectional drawing which shows one structural example of the illuminating device by 1st Embodiment of this invention. FIG. 2A is an enlarged cross-sectional view showing one configuration example of the wavelength selective transmission plate, and FIG. 2B is an enlarged plan view showing one configuration example of the wavelength selective transmission plate. It is a top view which shows typically an example of the arrangement pattern of a dot. It is a basic diagram which shows an example of the in-plane distribution of the dot of a photonic crystal. It is sectional drawing which shows the example of 1 structure of the illuminating device by 2nd Embodiment of this invention.

Explanation of symbols

  1R ... red LED, 1G ... green LED, 1B ... blue LED, 2 ... reflecting plate, 3 ... wavelength selective transmission plate, 3a ... substrate, 3b ... photonic crystal・ ・ ・ Diffusion plate

Claims (7)

A light source in which red, green and blue light emitting elements are arranged;
Red light reflecting means for selectively transmitting green light and blue light among red light, green light and blue light, Green light reflecting means for selectively transmitting red light and blue light among red light, green light and blue light, and red Wavelength selective transmission means having blue light reflection means for selectively transmitting red light and green light among light, green light and blue light, and
An illumination device, wherein the red light reflecting means, the green light reflecting means, and the blue light reflecting means are provided above the red, green, and blue light emitting elements, respectively.   The reflection means for reflecting red light, green light and blue light reflected by the red light reflection means, the green light reflection means and the blue light reflection means toward the wavelength selective transmission means. The lighting device according to 1.   The red light reflecting means, the green light reflecting means, and the blue light reflecting means are each composed of a photonic crystal having band gaps corresponding to red light, green light, and blue light emitted from the light emitting element. The lighting device according to claim 1.   The lighting device according to claim 1, wherein the photonic crystal is in the form of minute dots.   The illuminating device according to claim 1, further comprising a diffusing unit for diffusing the light transmitted through the wavelength selective transmitting unit.   The illumination device according to claim 1, further comprising prism means for directing the direction of light transmitted through the wavelength selective transmission means forward.   The illumination apparatus according to claim 1, further comprising a polarization selection unit that transmits light having a specific polarization direction out of the light transmitted through the wavelength selection transmission unit.