KR20070072753A - Back-light module using blue light source - Google Patents

Abstract

A backlight module using a blue light source is provided to distribute uniformly the light to an LCD(Liquid Crystal Display), to reduce the power consumption and to have the high durability. A blue LED(Light Emitting Diode)(21) generates the light beam with blue color wavelength. A fluorescent member(40) is coated to a side of a light guide panel corresponding to the LED so that the blue light beam emitted from the LED is changed into the white light beam. The thickness of the fluorescent member is about 100 to 200 micrometer. A light source(20) is constructed by a blue LED and a PCB(Printed Circuit Board)(22) for mounting the blue LED. The light source is arranged at a side of a light guide panel(30). The fluorescent member is coated at the side opposite to the light source. The fluorescent member is a yellow fluorescent member. A YAG fluorescent member is used as the fluorescent member.

Description

 Back-light Module using Blue Light Source}

1 is an exploded perspective view schematically showing an LCD display device to which a backlight module according to the present invention is applied;

2 is an exploded view of a backlight module according to the present invention;

3 is a cross-sectional view of the combination of FIG.

4 is a distribution chart showing color coordinate distribution of a blue light source emitted from a blue LED;

5 to 7 is a distribution chart showing the color coordinate distribution according to the coating thickness of the phosphor,

8 is a distribution diagram showing the change in color coordinate values according to the coating thickness of the phosphor.

♣ Explanation of symbols for the main parts of the drawing

                   10: backlight module 20: light source

21: Blue LED 22: PCB

                   30: LGP 40: phosphor

                   50: LCD panel 60: optical sheet

The present invention relates to an LCD backlight module, and more particularly to a light source module that consumes a uniform light distribution and low power of the backlight.

In general, a liquid crystal display device is a display device using modulation of light by liquid crystal, and includes a liquid crystal panel for displaying an image by controlling the amount of light coming from the outside, and a backlight module for supplying light to the liquid crystal panel. .

       Since the liquid crystal is non-luminescent, a separate light source is required. Therefore, a backlight module, which is a light source for irradiating light from the back of the liquid crystal, is required to supply light to the liquid crystal. The backlight module includes a light source for substantially irradiating light, a light guide plate for guiding the light emitted from the light source toward the liquid crystal display panel, and a diffusion sheet for collecting the light in front. Meanwhile, the backlight module is divided into a direct type backlight module that emits light by installing a light source on the rear surface of the light guide plate and an edge type backlight module that emits light by installing a light source on the side of the light guide plate according to a method of attaching a lamp to the light guide plate. do.

In addition, as a light source, conventionally, a small plasma type light source such as Cold Cathode Fluorescent Lamp (CCFL) and Heated Cathode Fluorescent Lamp (FLFL), or FLFL is used. -Luminescence) device was used.

However, most of the light sources used in the backlight module implement white as a light source of a plasma principle, and the conventional light sources have the following problems. First, the loss of light occurs due to the difference between human visibility and emission spectrum. Second, it has a short lifespan in response to changes in plasma gas pressure. Third, power consumption is severe because it has a high voltage operating voltage of several hundred volts necessary for plasma discharge. Fourthly, an inverter required for generating such high power is required.

To solve this problem, as a light source used in the backlight module, an LED that generates white light having long life, low power, small size, low operating voltage, and high durability may be used. It is not adopted as a light source.

In addition, a method of generating white light has been a method of attaching a blue LED chip on the reflective cup, and then coating a mixture of green light emitting phosphor and red light emitting phosphor on a transparent resin on the top of the blue LED chip and operating the blue LED.

However, the method described above has many difficulties in the process of making white LEDs. In particular, there is a problem in that the white light emitting form is greatly changed depending on the shape of the coating as well as the concentration of the green light emitting phosphor and the red light emitting phosphor coated on the blue LED chip.

Accordingly, an object of the present invention is to provide a backlight module having high durability with uniform light distribution and low power consumption.

According to the present invention, there is provided a backlight module in which a light source is irradiated to a side of a light guide plate, the backlight module comprising: an LED for generating a light source having a blue wavelength; And a phosphor coated on a side of the light guide plate corresponding to the LED so as to convert blue light generated from the LED into white light.

Here, the phosphor is preferably coated with a thickness of 100 ~ 200 ㎛ can convert blue light to white light. On the other hand, the phosphor is characterized in that the yellow phosphor.

Hereinafter, an LCD backlight module according to the present invention will be described in detail with reference to the accompanying drawings.

1 is an exploded perspective view schematically showing an LCD display device to which a backlight module according to the present invention is applied, FIG. 2 is an exploded view of a backlight module according to the present invention, and FIG. 3 is a sectional view of FIG. 2. As shown in the figure, the LCD display device to which the backlight module according to the present invention is applied is composed of a backlight module 10, an LCD panel 50, and an optical sheet 60. Since the LCD panel 50 and the optical sheet 60 are well known to those skilled in the art, detailed descriptions thereof will be omitted.

The backlight module 10 is a light guide plate 30 coated with a light source 20 and a phosphor 40 that converts blue light generated from the light source 20 into a white wavelength on a side surface corresponding to the light source 20. It is composed.

The light source 20 is composed of a PCB 22 on which a blue LED 21 and a blue LED 21 can be disposed. The blue LED 21 is a high brightness blue LED of Surface Mounted Type (SMT) or Chip On Board (COB), and emits light having a wavelength of about 400 to 500 nm. Meanwhile, in the following description, the blue LED 21 used in the present invention has a wavelength of about 470 nm as shown in FIG. 4, which shows the color coordinate distribution of the blue light source emitted from the blue LED 21. Experiment. In addition, the PCB 22 is configured with an electrode and a driving circuit for supplying power to the blue LED 21 described above.

The light guide plate 30 is disposed so that the light source is positioned on the side of the light guide plate 30, and the phosphor 40 is coated on the side facing the light source 30. Phosphor 40 is a yellow phosphor, which is a combination of a yttrium aluminum garnet doped with a cerium (aka, 'YAG phosphor', Y ₃ Al ₅ O ₁₂ ; Ce ³⁺ ). The YAG phosphor uses an oxide or a compound which is easily oxidized at high temperature as a raw material of Y, Gd, Ce, Sm, Al, and Ga, and sufficiently mixes them in a predetermined stoichiometric ratio to prepare a mixed raw material, and the prepared mixed raw material Fluoride, such as ammonium fluoride (NH ₄ F), is mixed into the crucible as a flux in a crucible, calcined for 2-5 hours in the temperature range of 1350-1450 ° C in air, and then ball milled to wash, separate, dry and sieve. To make. The mixed raw material may be prepared by mixing co-precipitation oxide obtained by firing a solution obtained by co-precipitating a dissolved solution of Y, Gd, Ce, Sm, dissolved in an acid according to a stoichiometric ratio in an acid, aluminum oxide and gallium oxide. It may be. On the other hand, any of the phosphors capable of converting a blue light source into a white light source in addition to the above-described YAG phosphor may be used. In the following, it was described and tested as using the above-described yag phosphor.

FIG. 5 shows the color coordinate distribution when the thickness of the phosphor is 60 μm to 100 μm, FIG. 6 shows the color coordinate distribution when the thickness of the phosphor is 100 μm to 200 μm, and FIG. 7 shows the thickness of the phosphor. The color coordinate distribution at the time of 200 µm or more is shown. 8 is a distribution chart showing the change in the color coordinate value according to the coating thickness of the phosphor 40. The portion indicated in yellow in the above figure shows the color coordinate distribution. As shown in Figure 6, the thickness of the phosphor 40 is preferably applied to the side of the light guide plate 100㎛ to 200㎛. When the thickness of the phosphor is smaller than 100 μm as shown in FIG. 5, light transmitted through the phosphor 40 is not converted into white. As shown in FIG. 7, when the thickness of the phosphor 40 is larger than 200 μm, the phosphor is transmitted. Because one light is converted to yellow. That is, as shown in Figure 6, the thinner the thickness of the phosphor 40, the less the color conversion, the thicker the phosphor has a feature that too much color conversion. This can also be seen in the table below. The table below shows the numerical values of the color coordinates according to the thickness of the phosphor.

<Table: Color coordinate values according to the thickness of the phosphor>

division Blue LED Phosphor thickness Uncoated 60㎛ 120 μm 200 μm X color coordinate 0.1454 0.2381 0.3050 0.3369 Y color coordinate 0.0446 0.1986 0.2878 0.3158

Therefore, in the backlight module according to the present invention, the blue light source emitted from the blue LED is converted into white light by the yellow phosphor coated on the side of the light guide plate, and the converted white light is supplied to the liquid crystal panel through the light guide plate. In addition, it is possible to obtain a white light having a desired color coordinate value by appropriately adjusting the coating thickness of the yellow phosphor according to the characteristics of the light guide plate.

In the above description, the light source is described as being provided only on one side of the light guide plate. However, when the light source is provided on both sides of one light guide plate, the above-described operating effect can be obtained by coating phosphors on both sides of the light guide plate.

On the other hand, the scope of the present invention is not limited to the above embodiments can be implemented in various forms of embodiments within the appended claims. Without departing from the gist of the invention as claimed in the claims, any person of ordinary skill in the art is considered to be within the scope of the claims described in the present invention to the extent possible to vary.

As described above, according to the present invention, the present invention, by replacing the light source, such as CCFL used as the backlight light source of the LCD with a linear light source using a blue LED and a light guide plate, the LCD thin and light, high uniformity, A low-cost white backlight module capable of maintaining high brightness is provided.

In addition, a low cost and high durability by applying a low power consumption LED, as well as a portable device employing an LCD provides a backlight module that enables long-term portability and use by lowering the power consumption LCD.

In addition, a light guide plate for controlling the coating thickness of the phosphor is used to convert the blue light generated from the blue LED into white light, and a backlight module having an advantage of controlling color conversion efficiency according to the characteristics of the blue LED is provided. Is provided.

Claims (3)

In the backlight module in which light is irradiated to the side of the light guide plate, An LED for generating light having a blue wavelength; And a phosphor coated on a side of the light guide plate corresponding to the LED to convert blue light generated from the LED into white light. The method of claim 1, The phosphor has a thickness of 100 ~ 200 ㎛ coated module. The method according to claim 1 or 2, The phosphor is a yellow phosphor, characterized in that the phosphor.

Images