CN100433380C - White light emitting device with light emitting diode and application thereof - Google Patents

Abstract

A white light emitting device with light emitting diode comprises a first crystal grain and a second crystal grain, wherein the first crystal grain is provided with a semiconductor light emitting layer capable of generating a first primary color light, and the second crystal grain is provided with two semiconductor light emitting layers capable of generating a second primary color light and a third primary color light respectively; the second primary color light and the third primary color light of the second crystal grain are mixed with the first primary color light of the first crystal grain to output white light. The white light emitting device with the light emitting diode has the advantages of good color rendering and low cost.

Description

White light emitting device with light emitting diode and its application

【Technical field】

The present invention relates to a light-emitting diode (Light Emitting Diode; LED for short) light-emitting device, in particular to a light-emitting diode device capable of emitting white light, which can be used in backlight modules (Back Light Module), traffic signs, Lighting equipment, LED color printers, displays and other devices that require white light sources.

【Background technique】

Referring to Figure 1, the backlight module of a general liquid crystal display can be divided into direct type and side light type according to the incident direction of the light source. Regardless of the type of backlight module, the light source commonly used is cold cathode light tube. However, this kind of cold cathode lamp contains toxic mercury, is fragile, consumes power, and when the cold cathode lamp is used as the light source, its color rendering index (CRI) is also limited.

Therefore, in order to improve the above-mentioned shortcomings, a backlight module using light-emitting diodes as a light source has been developed. FIG. 1 and FIG. side 22. Wherein, the liquid crystal module 2 has a front side 21 and the opposite back side 22; and the liquid crystal module 2 has a color filter unit 23, a liquid crystal unit 24 and a Glass substrate unit 25 . In addition, the backlight module 1 includes a casing 11 defining a chamber 12, a printed circuit board 14 located in the chamber 12 and arranged on the bottom wall 111 of the casing 11 as shown in FIG. 1 , and a plurality of The light emitting unit 13 of the printed circuit board 14 is electrically connected.

Each light emitting unit 13 has a first light emitting diode 131 capable of emitting green light, a second light emitting diode 132 capable of emitting blue light, a third light emitting diode 133 capable of emitting red light, and a first light emitting diode 133 capable of emitting green light. Four LEDs 134 . The light emitted by the first light emitting diode 131, the second light emitting diode 132, the third light emitting diode 133 and the fourth light emitting diode 134 of the light emitting unit 13 is mixed in the chamber 12 to become white light, and then emitted from the top of the housing 11. The edge 112 exits the backlight module 1 and enters the liquid crystal module 2 from the backside 22 of the liquid crystal module 2 .

However, the above-mentioned backlight module 1 using light-emitting diodes as the light source needs to have four light-emitting diodes 131, 132, 133, 134 in the same light-emitting unit 13 in order to achieve the required mixing intensity ratio of red, blue, and green primary colors into white light. It consumes space and increases the difficulty of controlling and driving the driving circuit design of the aforementioned four LEDs 131, 132, 133, 134; in addition, a longer distance from the bottom wall 111 to the top edge 112 of the housing 11 is required for light mixing. It is not conducive to the thinning of the backlight module 1 .

【Content of invention】

The main purpose of the present invention is to provide a white light emitting device with good color rendering and low cost with light emitting diodes.

Another object of the present invention is to provide a backlight module with simplified circuit design, low cost and good filtering characteristics, the backlight module includes a plurality of the above-mentioned white light emitting devices.

A white light emitting device of the present invention comprises a first crystal grain, and the first crystal grain has a semiconductor light emitting layer capable of generating light of a first primary color, and is characterized in that the white light emitting device further comprises a first crystal grain which can generate light of a first primary color. A second crystal grain of the semiconductor light-emitting layer of a second primary color light and a third primary color light, the second primary color light and the third primary color light are mixed with the first primary color light of the first crystal grain to output a white light, the first The two crystal grains also have a p-type cladding layer and an n-type cladding layer, the semiconductor light-emitting layer is interposed between the p-type cladding layer and the n-type cladding layer, and the semiconductor light-emitting layer is adjacent to The light-emitting layer of the p-type cladding layer has an upper barrier film, a lower barrier film, and a carrier confinement film sandwiched between the upper barrier film and the lower barrier film, and the carrier confinement film has a A mountain-shaped structure, the mountain-shaped structure is composed of continuous peaks and valleys, the energy barrier of the carrier confinement film is smaller than the energy barriers of the upper barrier film and the lower barrier film.

【Description of drawings】

Below in conjunction with accompanying drawing and embodiment the present invention is described in detail:

FIG. 1 is a partial cross-sectional side view exploded schematic diagram of a backlight module of a conventional liquid crystal display;

Fig. 2 is a schematic top view of the backlight module of the liquid crystal display;

Fig. 3 is a partial cross-sectional side view schematic diagram of the first embodiment of the backlight module of the present invention, illustrating that the backlight module includes a plurality of white light emitting devices, and each white light emitting device has a first package and a first Two packages;

FIG. 4 is a schematic top view of the optical module of the first embodiment;

Fig. 5 is a schematic partial cross-sectional side view of the white light emitting device in the first embodiment;

6 is a schematic cross-sectional view of a second crystal grain in the first embodiment, illustrating a structure in which the second crystal grain has a first light-emitting layer and a second light-emitting layer;

7 is a schematic cross-sectional view of the light-emitting layer in which the second grain has a mountain-shaped structure in the first embodiment, illustrating that the mountain-shaped structure is formed by continuous peaks and valleys;

Fig. 8 is another package form of the second package of the first embodiment;

9 is a partial cross-sectional schematic diagram of a white light emitting device in a backlight module according to a second embodiment of the present invention;

10 is a schematic top view of the backlight module of the second embodiment;

Fig. 11 is a color diagram of the backlight module of the second embodiment;

FIG. 12 is a spectrum diagram illustrating the emission spectrum of the backlight module of the second embodiment;

13 is a partial cross-sectional schematic diagram of a white light emitting device in a backlight module according to a third embodiment of the present invention;

FIG. 14 is a schematic partial cross-sectional view of a backlight module according to a fourth embodiment of the present invention, illustrating a state where a plurality of white light emitting devices are used as light sources;

FIG. 15 is a schematic side view of the white light emitting device viewed from the right side to the left side of FIG. 14 in the backlight module of the fourth embodiment.

【Detailed ways】

For the convenience of description, in the following embodiments, similar elements are denoted by the same reference numerals.

Referring to FIGS. 3 and 4 , the first embodiment of the present invention is a direct-lit backlight module 3 , which is disposed on the back side 42 of a liquid crystal module 4 . The liquid crystal module 4 has a front side 41 and the opposite back side 42; the liquid crystal module 4 has a color filter unit 43, a liquid crystal unit 44 and a glass substrate unit in sequence from the front side 41 to the back side 42 45.

The backlight module 3 includes a casing 31 defining a chamber 32 and a plurality of white light emitting devices 33 disposed in the chamber 32 . The casing 31 has a first side wall 311 which is transparent and adjacent to the back side 42 of the liquid crystal module 4, a second side wall 312 opposite to the first side wall 311, and a The peripheral edge of the wall 311 is tapered toward the third side wall 313 that is tapered to the peripheral edge of the second side wall 312 . The first side wall 311 , the second side wall 312 and the third side wall 313 define the chamber 32 with each other.

4 and 5, each white light emitting device 33 includes a carrier unit 34 arranged on the second side wall 312, and a first package 35 and a second package 36 arranged in pairs on the carrier unit 34 .

The first package 35 includes a first crystal grain 351 capable of generating a first primary color light, a first carrier 352 for carrying the first crystal grain 351, a conductive p-type electrode lead frame 353 and A conductive n-type electrode lead frame 354 . The p-type electrode lead frame 353 passes through the bearing seat 352 and is electrically connected to the first crystal grain 351 and the carrying unit 34 respectively; the n-type electrode lead frame 354 also passes through the first bearing seat 352 and is respectively connected to the bearing unit 34 The first die 351 is electrically connected to the carrying unit 34 . In this embodiment, the first crystal grain 351 is a red light emitting diode, and the first primary color light is a red light with a wavelength range between 575 nm and 700 nm.

The second package 36 includes a second crystal grain 361 capable of generating a second primary color light and a third primary color light, a second carrier 362 for carrying the second crystal grain 361 , a conductive p-type An electrode lead frame 363 and a conductive n-type electrode lead frame 364 . The p-type electrode lead frame 363 is passed through the second bearing seat 362 and electrically connected with the second crystal grain 361 and the carrying unit 34 respectively; the n-type electrode lead frame 364 is also passed through the second bearing seat 362 and are respectively electrically connected to the second die 361 and the carrying unit 34 .

6 and 7, the second grain 361 has a substrate 52, a buffer layer 53, an n-type cladding layer (cladding layer) 54, a first light-emitting layer 55, a first Two light emitting layers 56, a p-type cladding layer 57, a p-side contact layer 58, a p-type electrode 511 formed on the p-side contact layer 58, an n-side contact formed on the n-type cladding layer 54 layer 59 and an n-type electrode 512 formed on the n-side contact layer 59 .

The second light-emitting layer 56 includes a carrier confinement film 562 with a first surface 564 located below and an opposite second surface 565, and two The lower barrier film 561 and the upper barrier film 563 extending in the direction of the carrier confinement film 562 . The second surface 565 has continuous peaks 567 and valleys 568 , and the peaks 567 and valleys 568 form a mountain-shaped structure 569 .

FIG. 7 is a partially enlarged schematic side view of a longitudinal section of the mountain-shaped structure 569 in FIG. 6 . For two adjacent mountain peaks 567 ', 567 ", the shortest distance between the relatively higher top 5671 ' in the mountain peak 567 ' and the higher top 5671 " in the adjacent mountain peak 567 " is defined as the path length D, that is Define the path length D of the valley 568' surrounded by the aforementioned two adjacent peaks 567', 567". In addition, the distance from the bottom of the valley 568 to the first surface 564 is defined as H, and 0≤H≤2nm; it can be seen that the relatively low saddle 5672' in the mountain peak 567' cannot be called a valley. Furthermore, the length of the longitudinal section of the mountain-shaped structure 569 in Fig. 7 is defined as L, therefore, the density of a light-emitting layer with a mountain-shaped structure is defined as: the sum of the diameter lengths of all mountain-shaped structures within the diameter length of the light-emitting layer and the luminescent layer The ratio of layer diameter to length. That is, the density of the second light emitting layer 56 is equal to (D1+D2+D3+D4+D5+D6+D7)/L. The density of the second light emitting layer 56 is preferably between 5% and 75%.

The energy gap of the material used for the carrier confinement film 562 must be smaller than the energy gap of the upper barrier film 563 and the lower barrier film 561 . In this embodiment, the carrier confinement film 562 is made of a material containing indium and having a chemical formula of Al _(1-xy) In _y Ga _x N, where x≥0, y>0, (1-xy) ≥0. The material of the upper barrier film 563 and the lower barrier film 561 is gallium nitride.

Therefore, the second light-emitting layer 56 emits the third primary color light, that is, blue light, whose wavelength range falls between 430 nm and 485 nm by adjusting the ratio of x and y, and uses the density of the mountain-shaped structure 569 to adjust the emission The intensity of the emitted light. In this embodiment, the density of the second light-emitting layer 56 is equal to 38%.

Similarly, the first luminescent layer 55 in FIG. 6 includes a lower barrier film 551 made of the same material as the second luminescent layer 56, a carrier confinement film 552 with a mountain-shaped structure 559, and an upper barrier film 552. barrier film 553 . The second light-emitting layer 55 can emit the second primary color light, that is, green light, whose wavelength range is between 510 nanometers and 560 nanometers, by adjusting the ratio of x and y, and utilize the density adjustment of the mountain-shaped structure 559 The intensity of emitted light. In this embodiment, the density of the first light-emitting layer 55 is equal to 8%.

It is worth mentioning that, in addition to using the densities of the mountain-shaped structures 559 and 569 to adjust the intensity ratios of the third primary color light and the second primary color light respectively generated by the first light-emitting layer 55 and the second light-emitting layer 56, it is also possible to grow A plurality of the first luminescent layer 55 or the second luminescent layer 56 is used to increase the brightness and adjust the ratio. Furthermore, the second light-emitting layer 56 adjacent to the p-type cladding layer 57 must have a mountain-shaped structure 569, but the first light-emitting layer 55 can also be a light-emitting layer with a quantum well structure instead of a mountain-shaped structure. In addition, the second package 36 (see FIG. 5 ) can also be a package 36' in different package forms as disclosed in FIG. The second crystal grain 361 of the three primary colors, a second bearing seat 362' for carrying the second crystal grain 361, a conductive p-type electrode lead frame 363', a conductive n-type electrode lead frame 364' . The p-type electrode lead frame 363 and the n-type electrode lead frame 364 are respectively electrically connected to the second die 361, and the second carrier 362' is a light-transmitting coating such as resin.

Continuing to refer to FIGS. 4 and 5 , the carrying unit 34 is used to provide the power required by the first package 35 and the second package 36 . In this embodiment, the light emitting devices 33 share the same carrying unit 34, and the carrying unit 34 is a printed circuit board, but the carrying unit 34 may also be a conductive wire. Moreover, the number of the bearing unit 34 is not limited to one, and multiple bearing units 34 may also be used.

With reference to FIG. 3 , when the first package 35 and the second package 36 are driven by power, the first primary color light produced by the first package 35 and the second primary color light produced by the second package 36 and the The third primary color light is mixed in the chamber 32 to emit a white light from the first side wall 311 of the backlight module 3 , and enter the liquid crystal module 4 from the back side 42 of the liquid crystal module 4 .

Because the present invention uses the second crystal grain 361 (see FIG. 6 ) that can generate the second primary color light and the third primary color light at the same time, it can reduce the number of light emitting diodes used, thereby reducing the number of the first side of the backlight module 3. The required light mixing distance between the wall 311 and the second side wall 312 also reduces the thickness of the backlight module 3 , which is beneficial to the thinning of the backlight module 3 . Furthermore, for the first crystal grain 351 that has a fixed wavelength of the first primary color light (red light), when adjusting the white balance, the density of the mountain-shaped structures 559, 569 in the second crystal grain 361 can be adjusted, Or adjust the ratio of x and y in the material containing indium and the chemical formula is Al(1-x-y)InyGaxN, or increase and adjust the number of the first light-emitting layer 55 and the second light-emitting layer 56 to achieve a specific second primary color light (green light) and the third primary color light (blue light) according to the intensity and ratio requirements, and then reach the white balance with the first primary color light of the first crystal grain 351 . In terms of practical application, that is, for the first crystal grain 351 of a red light emitting diode with a specific wavelength, the matching second crystal grain 361 can be directly selected to form a white light emitting device 33, which eliminates the need to adjust the three primary colors. The mixing ratio of light simplifies the design of the previous drive control circuit.

As shown in Figures 9 and 10, the second embodiment of the present invention is also a direct-lit backlight module as in the first embodiment, and also includes a housing 31 defining a chamber 32 and a plurality of housings arranged in the chamber. White light emitting device 33' of chamber 32. The difference is that in the white light emitting device 33 of the first comparative embodiment, the first die 351 and the second die 361 are packaged in the first package 35 and the second package 36 respectively, and then placed in the on the carrier unit 34; and the white light emitting device 33' of the second comparative embodiment is to package the first crystal grain 351 and the second crystal grain 361 in a single white light package 39, and then set it on the carrier unit 34 .

The white light emitting device 33' of the second embodiment includes the carrying unit 34 disposed on the second side wall 312 and the white light package 39. The white light package 39 includes a carrier 392 having a groove 391 , a conductive p-type electrode lead frame 393 and a conductive n-type electrode lead frame 394 . Preferably, the white light package 39 further includes a light-transmitting covering (not shown) filled in the groove 391 , such as made of resin or a light-transmitting material. The first crystal grain 351 and the second crystal grain 361 are accommodated in the groove 391 respectively, and are electrically connected to the p-type electrode lead frame 393 and the n-type electrode lead frame 394 respectively. The p-type electrode lead frame 393 and the n-type electrode lead frame 394 are respectively electrically connected to the carrying unit 34 , so that the first die 351 and the second die 361 can be enabled by the direct current of the carrying unit 34 .

FIG. 11 illustrates the CIE color diagram (ChromaticityDiagram) of the above-mentioned white light package 39. In this embodiment, for the first crystal grain 351 whose wavelength of the first primary color light (red light) has been fixed to 635nm, when adjusting the white balance , the second primary color light (green light) with a wavelength of 538nm and the third primary color light (blue light) with a wavelength of 471nm can be emitted by adjusting the second crystal grain 361 as described in the first embodiment. , and further achieve a white balance with the first primary color light of the first crystal grain 351 .

In addition, as shown in the spectrogram in Figure 12, the relatively high-intensity wavelengths in the emission spectrum of this embodiment are concentrated around 471nm, 538nm and 635nm, respectively, as shown by the solid lines in the figure, that is, blue, green, The wavelength range of the red primary color light. Because the filter spectrum of the color filter unit 43 of the liquid crystal module 4 (see FIG. 3 ) allows the wavelength ranges of the blue, green and red primary colors to pass through as shown by the dotted lines in the figure, the backlight module of this embodiment provides good color rendering. The wavelength of the permanent backlight conforms to the filtering range of the color filter unit 43, so the transmittance of the backlight can be improved, and the brightness and saturation of the liquid crystal display can be increased.

Referring to FIG. 13 , the third embodiment of the present invention is also a direct type backlight module as in the first comparative embodiment. The difference is that each white light emitting device 33" of the third embodiment includes a carrying unit 34 disposed on the second side wall 312 (see FIG. 34 on the first crystal grain 351 and the second crystal grain 361, a plurality of conductive spheres 38 electrically connected to the first crystal grain 351 and the second crystal grain 361 respectively, and a covering of the first crystal grain 351 and the second crystal grain 351 The light-transmitting covering 37 of the two dies 361, and in this embodiment, the light-transmitting covering 37 is a resin.

Referring to FIGS. 14 and 15 , the fourth embodiment of the present invention is a side-lit backlight module 6 , which is disposed on the backside 42 of a liquid crystal module 4 . The backlight module 6 includes a light guide plate 61, a reflective light collecting unit 62, and a plurality of white light emitting devices 33' arranged in a straight line.

The light guide plate 61 has a first side 612 parallel to and adjacent to the back side 42 of the liquid crystal module 4, a second side 613 perpendicular to the first side 612, and a side away from the first side from the second side 613. A side edge of the first side 612 gradually shrinks toward the third side 614 of the first side 612 . The reflective light-collecting unit 62 is connected to the second side 613 and cooperates with the second side 613 to define an accommodating space 615 . The reflective light-collecting unit 62 is used for reflecting light incident thereon.

The white light emitting devices 33' are disposed in the accommodating space 615, and each white light emitting device 33' includes a carrying unit 34 and a white light package 39 arranged on the carrying unit 34. It should be noted that, in this embodiment, the white light emitting device 33' shares a carrying unit 34, and the carrying unit 34 is a printed circuit board.

The white light emitted by driving the white light emitting device 33 ′ through the carrying unit 34 will directly enter the light guide plate 61 through the second side 613 or enter the light guide plate 61 after being reflected by the reflective light collecting unit 62 , and then pass through the light guide plate 61 . Reflected by the third side 614 , it exits the light guide plate 61 from the first side 612 , so that the back side 42 of the liquid crystal module 4 provides the light source required by the liquid crystal module 4 .

In view of the above, the structural feature of the present invention is to use the first crystal grain 351 that can generate the first primary color light and the second crystal grain 361 that can simultaneously generate the second primary color light and the third primary color light to form a white light emitting device, so The number of grains of light-emitting diodes used in adjusting white balance is small, it is easy to adjust the ratio of mixed light, and it can also simplify the design of the circuit board. In addition, it can also provide good color rendering, which can indeed provide a practical Low cost white light emitting device.

Claims (9)

1. A white light emitting device, comprising a first crystal grain, the first crystal grain has a semiconductor light-emitting layer that can generate a first primary color light, and it is characterized in that the white light emitting device also includes a semiconductor light emitting layer that can generate a first primary color light. The second primary color light and the second primary color light of the second crystal grain of the semiconductor light-emitting layer of the third primary color light, the second primary color light and the third primary color light are mixed with the first primary color light of the first crystal grain to output a white light, the second The grain also has a p-type cladding layer and an n-type cladding layer, the semiconductor light-emitting layer is interposed between the p-type cladding layer and the n-type cladding layer, and the semiconductor light-emitting layer is adjacent to the The light-emitting layer of the p-type cladding layer has an upper barrier film, a lower barrier film, and a carrier confinement film sandwiched between the upper barrier film and the lower barrier film, and the carrier confinement film has a mountain-shaped structure, the mountain-shaped structure is composed of continuous peaks and valleys, the energy barrier of the carrier confinement film is smaller than the energy barriers of the upper barrier film and the lower barrier film. 2. The white light emitting device according to claim 1, wherein the first primary color light is a red light with a wavelength range between 575 nm and 700 nm, and the second primary color light is a red light with a wavelength range of The green light falling between 510 nm and 560 nm, the third primary color light is blue light with a wavelength range between 430 nm and 485 nm. 3. The white light emitting device according to claim 1, wherein the carrier confinement film is made of a material having a chemical formula of Al _(1-xy) In _y Ga _x N, and x is greater than or equal to zero, y is greater than zero and (1-xy) is greater than or equal to zero. 4. The white light emitting device according to claim 3, characterized in that: the density of the light-emitting layer with the mountain-shaped structure in the second crystal grain is between 5% and 75%, and the density of the light-emitting layer is all valley-shaped structures The ratio of the sum of the path lengths to the path length of the light-emitting layer. 5. The white light emitting device as claimed in claim 1, further comprising a carrier, a conductive p-type electrode lead frame, and a conductive n-type electrode lead frame, the carrier carries the first crystal grain and For the second crystal grain, the p-type electrode lead frame is electrically connected to the first crystal grain and the second crystal grain respectively, and the n-type electrode lead frame is electrically connected to the first crystal grain and the second crystal grain respectively. 6. The white light emitting device according to claim 5, characterized in that: the supporting base of the white light emitting device has a groove for accommodating the first crystal grain and the second crystal grain, and a A light-transmitting coating covering the first crystal grain and the second crystal grain. 7. The white light emitting device according to claim 1, further comprising a carrying unit for carrying and electrically connecting the first die and the second die, and at least one covering the first die and the second die Two-grain light-transmitting coating. 8 . The white light emitting device according to claim 1 , further comprising a first bearing seat for supporting the first die and a second bearing seat for supporting the second die. 9 . 9. A backlight module for providing a backlight source for a liquid crystal module, characterized in that the backlight module comprises a plurality of white light emitting devices as claimed in claim 5.

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