KR100727059B1 - Back light unit formed an optical layer laminated with oxide compound - Google Patents

Abstract

A backlight unit is provided to improve the efficiency of light and the purity of color, by using optical resonance induced through an optical layer in which oxide layers are laminated. A plurality of LEDs(Light Emitting Diodes)(40) are distanced from each other on a PCB(Printed Circuit Board)(30). A total reflection layer(50) reflects a light emitted from each of the LEDs toward a space above the LEDs. An optical layer(60) is formed above the LED. The optical layer transmits a portion of the light and reflects another portion of the light toward a space below the PCB. The optical layer is formed of laminated oxide layers. The optical layer induces optical resonance of the light emitted from the LED.

Description

BACK LIGHT UNIT FORMED AN OPTICAL LAYER LAMINATED WITH OXIDE COMPOUND}

       1 is a conceptual diagram of an LCD module according to the prior art,

       2 is a perspective view showing the shape of a general backlight unit;

       3 is a front view of a part of the backlight unit according to the present invention;

       4 is a front view showing an oxide stacked structure according to an embodiment of the present invention;

       5 is a front view illustrating a backlight unit having a side reflector according to an embodiment of the present invention;

       6 is a front view illustrating a backlight unit having a side reflector according to an exemplary embodiment of the present invention;

       7 is a front view showing an oxide laminated structure according to an experimental example of the present invention,

       8 is a graph showing luminance versus light reflectance according to an experimental example of the present invention.

<Explanation of symbols on main parts of the drawings>

1: LCD Module 2: Liquid Crystal Display Panel

4a, 4b: Polarizer 6: Back light unit

8a: Support Main 8b: Top Case

12: light source 14: light guide plate

30: printed circuit board 40: light emitting diode

50: total reflection layer 60: optical layer

70: side reflector 100: back light unit

The present invention relates to a backlight unit, and more particularly, to a backlight unit for increasing luminance by using optical resonance by an optical layer in which oxides are stacked.

CRT (Cathode Ray Tube), which is one of the commonly used display devices, is widely used in televisions and computer monitors, but the weight and volume of the CRT itself do not meet the recent trend of miniaturization and light weight of electronic products.

Accordingly, various technologies have been developed to replace existing CRT displays, and liquid crystal displays (LCDs) using field optical effects, plasma display panels (PDPs), and electric fields using gas discharges. An EL display device (ELD, Electro Luminescence Display) using the light emitting effect and the like.

Among them, LCDs are rapidly expanding their range of application due to improvements in liquid crystal materials and development of micropixel processing technology along with features such as light weight, thinness, and low power consumption. It is widely used in large flat-panel televisions.

However, most liquid crystal display devices require a separate backlight unit as a matting element for displaying an image by controlling an amount of a light source coming from the outside.

As shown in FIG. 1, the LCD module 1 used in a general LCD includes a liquid crystal display panel 2 into which liquid crystal is injected, and a polarizing plate 4a for polarizing light on upper and lower surfaces of the liquid crystal display panel 2. 4b), a backlight unit 6 for supplying a constant light to the liquid crystal display panel 2, a support main 8a and a top case 8b for maintaining the external appearance of the LCD module 1. FIG.

Unlike the CRT or PDP, the liquid crystal display panel 2 mounted on the LCD only changes the arrangement of liquid crystals by applying power, and the liquid crystal display panel 2 itself does not emit light, thereby uniformly irradiating the information display surface. The backlight unit 6 is provided behind the liquid crystal display panel 2.

Here, the backlight unit 6 is divided into an edge type and a direct type according to the position of the light source.

As shown in Figure 2 (a), the light source 12 is provided at the edge of the light guide plate 14 for irradiating light, the direct type is a point light source as shown in Figure 2 (b) 16a is mounted on the printed circuit board 30, or the line light source 16b is mounted on the printed circuit board 30 as shown in FIG. 2 (c). It is distributed throughout.

Here, EL (Electro Luminescence), CCFL (Cold Cathode Fluorescent Lamp), or HCFL (Hot Cathode Fluorescent Lamp), etc. are used as light sources. Light emitting diodes (LEDs) are widely used.

As a method of using a light emitting diode as a light source in a backlight unit, first, a method using a blue light emitting diode and a YAG (Yttrium Aluminum Garnet (YAG) phosphor), and second, a red, green, and blue light emitting diode emitting UV light. Third, a method of using phosphors and a method of mixing light emitted from each light emitting diode using a red light emitting diode, a green light emitting diode, and a blue light emitting diode have been studied.

Here, the method of using a blue light emitting diode and a YAG phosphor has a poor red expression ability and a low luminous efficiency, and the method of using red, green, and blue phosphors in a light emitting diode emitting ultraviolet light is difficult to develop a phosphor and is thermal. The property is not good.

In addition, the method using the red light emitting diode, the green light emitting diode, and the blue light emitting diode has a high intensity of the red light, the green light, and the blue light emitted from each light emitting diode, so that a wide color reproduction range can be designed, but the white surface light source is constituted. There is a problem that a combination of light emitting diodes must be achieved.

In addition, in order to meet the demand for high luminous flux output of backlights, materials for manufacturing lenses, chips, and light emitting diodes for concentrating light emitted from each light emitting diode are required in order to meet the demand for high luminous flux output of a backlight. It is being developed.

The light emitting diode is a type of solid state device that converts electrical energy into light energy. The light emitting diode generally includes a doping layer and an active layer. When a bias is applied across two opposing doping layers, holes and electrons are injected into the active layer. Recombination produces light.

Light generated in the active region is emitted in all directions and escapes out of the semiconductor chip through all exposed surfaces.

The backlight unit including the light emitting diode directs the light escaping from the light emitting diode in the direction of output of the desired light.

However, the light emitting diodes developed to date have not been able to obtain sufficient luminous efficiency due to the light loss due to the degree of transmission in the current diffusion layer and the light loss due to total reflection at the interface where light is emitted.

Therefore, in order to use a light emitting diode in a backlight requiring high luminous flux output, a method of applying a high current to the light emitting diode or increasing the number of light emitting diodes is used.

However, when a high current is applied to the light emitting diode, a large amount of heat is generated in the light emitting diode, so that the light emitting efficiency is reduced, so that a separate heat dissipation design is required on the printed circuit board on which the light emitting diode is mounted. In this case, there is a problem in that the design of the backlight unit becomes difficult and the production cost of the backlight unit increases.

In addition, although a light emitting diode using a nitride semiconductor series or InGaAIP has been developed to increase the light emitting efficiency of the light emitting diode, there is a problem that it is difficult to use the backlight unit because the luminous flux is lower than that of the CCFL.

The present invention has been made to solve the above problems, and provides a backlight unit in which an oxide layered optical layer is formed to improve light efficiency and color purity of the backlight by using optical resonance through an oxide layered optical layer. Its purpose is to.

The backlight unit of the present invention for achieving the above object is a printed circuit board, a plurality of light emitting diodes arranged spaced apart from each other on the printed circuit board, the light formed on the lower side of the printed circuit board and irradiated with the upper side of the printed circuit board A total reflection layer reflecting in a direction and an optical layer formed on an upper side of the printed circuit board to transmit a portion of the irradiated light and reflecting a portion of the irradiated light in a downward direction of the printed circuit board. Induces optical resonance of emitted light.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a front view of a part of a backlight unit according to the present invention, FIG. 4 is a front view showing an oxide stacked structure according to an embodiment of the present invention, and FIG. 5 is a side reflector according to an embodiment of the present invention. FIG. 6 is a front view illustrating a formed backlight unit, and FIG. 6 is a front view illustrating a backlight unit having a side reflector according to an exemplary embodiment.

As shown in FIG. 3, the backlight unit 100 according to the present invention includes a printed circuit board 30, a plurality of light emitting diodes 40 arranged on the printed circuit board 30, and spaced apart from each other, and a light emitting diode ( The total reflection layer 50 reflects the light irradiated from the upper side of the light emitting diode 40 to the upper side of the light emitting diode 40 and a portion of the irradiated light formed on the upper side of the light emitting diode 40 to transmit the light. It includes an optical layer 60 for reflecting in the downward direction of the printed circuit board 30.

The printed circuit board 30 having the pattern supports the light emitting diode 40 and simultaneously emits heat generated from the light emitting diode 40.

A plurality of spaced apart light emitting diodes 40 is mounted on the printed circuit board 30, and a total reflection layer 50 is formed under the light emitting portion 41 of the light emitting diode 40.

The total reflection layer 50 may be bonded to the upper side of the printed circuit board 30 on which the light emitting diode 40 is mounted. The total reflection layer 50 is formed by bonding a reflector film having a high reflectance to an aluminum plate, and reflecting material. The film has a high reflectance such that the reflectance is at least 80% or more, and it is preferable to use one having a low water absorption and a low transmittance.

On the upper side of the light emitting diode 40 and the total reflection layer 50 is formed an optical layer 60 that transmits a portion of the light irradiated at a predetermined optical distance d and reflects a portion of the light. The distance d between the 50 and the optical layer 60 is determined by the following equation so that light passing through the optical layer 60 can achieve constructive interference.

Where n is the refractive index of the total reflection layer 50 or the optical layer 60, t is the geometric thickness of the total reflection layer 50 or the optical layer 60, λ is the peak wavelength of the light emitted from the light emitting diode 40, m is an integer of 0 or more.

In the case where the light emitted from the light emitting diode 40 is red light, green light, or blue light, an integral multiple of the half wavelength of the peak wavelength of each color light is a total reflection layer 50 and an optical layer in order for the red light, green light, or blue light to construct constructive interference. When the sum of the products of the refractive indices and the geometric thicknesses is equal to 60, the light passing through the optical layer 60 is subjected to constructive interference, thereby causing optical resonance.

Accordingly, the luminance of light emitted from the backlight unit 200 is increased, and the half width of the spectral histogram for each color on the emission spectrum is reduced, thereby improving color purity.

Here, of course, the desired spectral peak can be obtained on the emission spectrum by adjusting the thickness of the total reflection layer 50 or the optical layer 60.

The maximum transmission amount Tmax according to the resonance effect generated by adjusting the optical distance d between the total reflection layer 50 and the optical layer 60 is confirmed by the following equation.

Here, T ₁ and R ₁ are the transmittance and reflectance of the optical layer 60, T ₂ and R ₂ are the transmittance and reflectance of the total reflection layer 50, k is the extinction coefficient, t is the geometric thickness, θ is the optical layer (60) ) And the angle of light propagating from the inside to the outside between the total reflection layer 50 and λ are wavelengths of light emitted from the light emitting diode 40.

Therefore, when the maximum transmittance is calculated, it is possible to design an optical layer capable of obtaining a corresponding reflectance.

Light emitted from one light emitting diode 40 mounted on the printed circuit board 30 is partially transmitted through the optical layer 60 in the optical layer 60 to be emitted to the outside of the optical layer 60, and the rest is Reflected by the optical layer 60 and proceeds back to the total reflection layer 50, at this time, the light that is advanced to the total reflection layer 50 is reflected by the total reflection layer 50 to proceed to the optical layer 60 again.

Such transmission and reflection are repeated, and the light emitted from the light emitting diode 40 is amplified by the light emitted through the optical layer 60 and emitted to the outside of the optical layer 60, thereby amplifying the optical layer 60. ) Is dimmed to the outside.

In addition, the light path becomes longer, so that the light mixing is more efficient in the case of irradiating white light by using a red light emitting diode, a green light emitting diode, and a blue light emitting diode and mixing the light emitted from each light emitting diode. Will be done.

Therefore, the higher the reflectance of the light propagated to the total reflection layer 50, the lower the transmittance and the absorbance of the total reflection layer 50.

In this case, the optical layer 60 is formed by stacking oxides to perform both transmission and reflection.

Although the metal layer may be formed in the optical layer 60, except that the structure of the layer is simplified, the thickness of the metal layer is only several tens of nm, so that it is not easy to form the metal crystal layer, and in the case where normal crystal growth is not achieved, Absorption rate is increased, there is a disadvantage that the light absorption rate is increased due to the diffusion between each layer due to the stacking, this is because the increase in light absorption, even if the light resonance induced light loss occurs due to light absorption Since the effects of resonance cannot be sufficiently obtained, it is preferable to form oxides by laminating them.

In the case of stacking oxides, as shown in FIG. 4 (a), a high refractive index oxide of 2.3 or more and a low refractive index oxide or a medium refractive index oxide of less than 2.3 are stacked, or in FIG. 4 (b). As shown, it is possible to laminate oxides of high refractive index, oxides of medium refractive index of 1.5 to less than 2.3, and oxides of low refractive index, and the thickness of the oxide becomes thicker and the absorption rate increases as the number of layers to be laminated increases. This is reduced, which is advantageous for improving the brightness of the backlight.

When the layers having different refractive indices are stacked, reflective characteristics are formed due to the difference in refractive indices between the layers. As the number of stacked layers increases, the light absorption is minimized and the reflective characteristics are improved.

Here, SiO ₂ is mainly used as the low refractive index oxide, Nb ₂ O ₅ is mainly used as the medium refractive index oxide, and TiO ₂ , Ta ₂ O ₃ , or Y ₂ O ₃ is generally used as the high refractive index oxide. However, of course, other oxides may be used in consideration of the refractive index.

In addition, as shown in FIG. 5, in order to prevent light emitted from the light emitting diode 40 from leaking out to the side surface between the total reflection layer 50 and the optical layer 60, the total reflection layer 50 and the optical layer ( 60 may further include a side reflection part 70 included in a side surface of the backlight unit 100.

Like the total reflection layer 50, the side reflector 70 preferably has a higher reflectance, a lower transmittance and an absorptance, and back light emitted from the light emitting diode 40 and irradiated to the side reflector 70. Reflecting the inside of the unit 100 increases the amount of light emitted through the optical layer 60.

Here, as shown in FIG. 6, the side reflection part 70 is preferably formed to face the outside of the backlight unit 200 when viewed in the direction of the optical layer 60 from the total reflection layer 50.

Since light is emitted through the optical layer 60, the light irradiated to the side reflection part 70 is preferably reflected in the direction of the optical layer 60.

As shown in FIG. 6 (a), the side reflection part 70 may be in the shape of a flat plate or a film, but may be formed in a bow shape as shown in FIG. 6 (b).

Referring to the specific experimental example for the formation of the optical layer 60 of the backlight unit 100 according to the present invention.

 7 is a front view illustrating an oxide stacked structure according to an experimental example of the present invention, and FIG. 8 is a graph showing luminance versus light reflectance according to an experimental example of the present invention.

A light emitting diode with a 1W output power is used, with a red light emitting diode having a center wavelength of 627 nm, a green light emitting diode with a center wavelength of 530 nm, and a blue light emitting diode with a wavelength of 455 nm. According to the change in the center wavelength using a light emitting diode within 5%, the drive current is 200 mA.

The light emitting diode is mounted on a printed circuit board, and the mounted light emitting diode maintains an equal interval of 5 to 6 cm, and one light emitting diode set is used by using one red light emitting diode, one green light emitting diode, and one blue light emitting diode. Use

Of course, the combination of the light emitting diodes can be modified in various ways, and the distance between the light emitting diodes can be changed elastically according to the number of light emitting diodes, and two red light emitting diodes, two green light emitting diodes, and one blue light emitting diode are used. One red light emitting diode, two green light emitting diodes, and one blue light emitting diode may be used.

As shown in FIG. 7, using the simulation using the Essential Macleod program, the optical transmittance of the optical layer 60 is 40%, 50%, 60%, 70%, and 80%, respectively, The film including the optical layer 60 manufactured by deriving oxide lamination conditions according to the interfacial properties and coating conditions was manufactured in five forms.

FIG. 7 (a) shows an oxide laminated structure with a light transmittance of 40% of the optical layer 60, FIG. 7 (b) shows an oxide laminated structure with a light transmittance of 50%, and FIG. 7 (c) shows a light transmittance of 60%. 7 (d) is an oxide laminated structure having a light transmittance of 70%, and FIG. 7 (e) is an oxide laminated structure having a light transmittance of 80%.

In order to increase the light reflectance, the number of layers must be large in the oxide laminated structure. Therefore, when the light transmittance is 40%, the oxide layers are laminated 10 times, and the light transmittance is 50%, 60%, and 70%. The oxide layer was laminated eight times, and when the light transmittance was 80%, the oxide layer was laminated six times.

Each of the five types of film is included in the backlight unit and assembled to measure its properties. In order to measure the effects of light resonance, the film is measured in a structure without an optical layer and a reflecting plate to analyze the difference in properties in each case. It was.

Among the oxides, SiO ₂ was used as the low refractive index oxide and TiO ₂ was used as the high refractive index oxide.

FIG. 8 is a graph showing the results of measuring the degree of light emission in a backlight unit in which an optical layer in which oxides are stacked and inducing light resonance and a general backlight unit.

Here, "bare" indicates a state of a backlight unit in which a light emitting diode is mounted in a general backlight unit without light resonance.

As shown in FIG. 8, in the case of a backlight unit having an optical layer in which oxides are laminated to have a light transmittance of 80%, luminance improvement of about 14% is achieved compared to a general backlight unit, and light transmittance is 40% or 50%. It can be seen that even in the case of a backlight unit having an optical layer in which oxides are laminated to be%, 60%, and 70%, the luminance is improved as compared with a general backlight unit.

Although described above with reference to preferred embodiments of the present invention, those skilled in the art will be modified and changed within the scope without departing from the spirit of the invention described in the claims below It should be understood that it can be done.

The backlight unit having the oxide layered optical layer according to the present invention provides a backlight unit that induces optical resonance by the oxide layered optical layer to increase brightness and make light mixing more efficient.

As a result, the power consumption of the backlight unit requiring white light having high luminance is reduced, and the life of the backlight unit is also increased, and optical resonance is induced by the optical layer on which oxides are stacked, thereby resulting in the emission spectrum. The half width of the spectral histogram for each color is reduced to improve color purity, and the desired spectral peak can be realized by adjusting the thickness of the optical layer and the total reflection layer.

Claims (5)

Printed circuit boards, A plurality of light emitting diodes spaced apart from each other on the printed circuit board; A total reflection layer reflecting light emitted from the light emitting diode in an upward direction of the light emitting diode; Including an optical layer formed on the upper side of the light emitting diode to transmit a portion of the irradiated light, the oxide layer is laminated to reflect a portion of the irradiated light in the downward direction of the printed circuit board, Inducing optical resonance of light emitted from the light emitting diode A backlight unit having an optical layer in which oxides are laminated. The method of claim 1, The optical layer is formed by repeatedly stacking oxide layers having different refractive indices at least one or more times. A backlight unit having an optical layer in which oxides are laminated. The method of claim 2, The optical layer is formed by repeatedly stacking a low refractive index oxide or a medium refractive index oxide having a refractive index (n) of 2.3 or less and a high refractive index oxide layer having a refractive index of greater than 2.3 at least one or more times. A backlight unit having an optical layer in which oxides are laminated. The method of claim 2, The optical layer comprises a low refractive index oxide layer having a refractive index of 1.5 or less, a medium refractive index oxide layer having a refractive index of 1.5 or more and 2.3 or less, and a high refractive index oxide layer having a refractive index of 2.3 or more, repeatedly stacked at least one or more times. A backlight unit having an optical layer in which oxides are laminated. The method according to any one of claims 1 to 4, The sum of the products of the refractive index and the thickness of each of the total reflection layer and the optical layer is an integer multiple of half the wavelength of the light emitted from the light emitting diode. The light emitted through the optical layer causes constructive interference Back light unit.

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