KR20060059103A - Optical sheet and back light unit using the same - Google Patents

Abstract

The present invention relates to an optical sheet and a backlight unit using the same.

An optical sheet according to an embodiment of the present invention includes a diffusion plate for diffusing light emitted from the outside; A first lens formed on the light incident surface of the diffusion plate; A second lens formed on the light exit surface of the diffusion plate; At least one of the first lens and the second lens is differently formed.

Description

Optical sheet and back light unit using the same             

1 is a view showing a conventional liquid crystal display device.

FIG. 2 is a cross-sectional view illustrating a cross section taken along the line II-II ′ of FIG. 1.

3 is a diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

4 is a cross-sectional view taken along the line IV-IV ′ of FIG. 3.

5A to 5I are views illustrating optical members in various arrangements according to embodiments of the present disclosure.

6A to 6C are diagrams illustrating luminance distributions.

7 is a view showing an optical path of the optical member according to an embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

2, 102: liquid crystal display panels 8, 18, 108, 118: polarizing sheet

10 optical sheet 12 diffuser plate

14, 114: reflector 34, 134: case

36, 136: lamp 120: optical member

122: first lens 124: diffusion layer

126: second lens

The present invention relates to an optical sheet and a backlight unit using the same, and more particularly, to an optical sheet capable of realizing high luminance and a backlight unit using the same.

In general, liquid crystal displays (hereinafter referred to as "LCDs") have tended to be increasingly wider in application due to features such as light weight, thinness, and low power consumption. According to this trend, LCDs are used for office automation equipment, audio / video equipment, and the like. On the other hand, the LCD is controlled to display the desired image on the screen by adjusting the transmission amount of the light beam according to the image signal applied to the plurality of control switches arranged in a matrix form.

Since the LCD is not a self-luminous display device, a light source such as a back light is required. Such LCD backlight has a direct type and an edge type. In the edge type system, a lamp is installed outside the flat plate, and light is incident from the lamp onto the entire surface of the liquid crystal display panel using a transparent light guide plate. The direct type places several lamps in the plane. In addition, a diffusion plate is installed between the lamp and the liquid crystal display panel to maintain a constant space between the liquid crystal display panel and the lamp. Cold Cathode Fluorescent Lamp ("CCFL") method that supplies power by inserting electrodes at both ends of the glass tube of the lamp, and external electrode that supplies power to the electrode part that surrounds both ends of the glass tube of the lamp with metal material Fluorescent lamp (External Electrode Fluorescent Lighting: "EEFL") is a method.

1 and 2 show a conventional LCD.

1 and 2, a conventional LCD includes a liquid crystal display panel 2 for displaying an image and a backlight unit for irradiating uniform light onto the liquid crystal display panel 2.

In the liquid crystal display panel 2, liquid crystal cells are arranged in an active matrix between upper and lower substrates, and pixel electrodes and a common electrode for applying an electric field to each of the liquid crystal cells are provided. Each of these pixel electrodes is connected to a thin film transistor used as a switch element. The pixel electrode drives the liquid crystal cell along with the common electrode according to the data signal supplied through the thin film transistor to display an image corresponding to the video signal. Polarizing plates 8 and 18 having different polarization directions are disposed on the front and rear surfaces of the liquid crystal display panel 2.

The backlight unit includes a case 34, a reflective sheet 14 stacked on the front surface of the case 34, a plurality of lamps 36 positioned on the reflective sheet 14, and a plurality of lamps 36. A diffuser plate 12 and an optical sheet 10 are disposed above.

The case 34 converts a path of light generated from the lamps 36 by reflecting visible light traveling toward the side and the back of the plurality of lamps 36 toward the front side, that is, the diffuser plate 12.

The reflective plate 14 is disposed between the upper surface of the case 34 and the plurality of lamps 36 to reflect the light generated from the lamps 36 and to be irradiated toward the liquid crystal display panel 2 to improve the light efficiency. .

Each of the plurality of lamps 36 includes a glass tube, inert gases inside the glass tube, and a cathode and an anode portion made of metal covering both ends of the glass tube. These multiple lamps 36 are arranged side by side on the case 34. At this time, the plurality of lamps 36 are arranged on the case 34 side by side.

The diffusion plate 12 allows the light emitted from the plurality of lamps 36 to propagate to the liquid crystal display panel and to be incident at a wide range of angles.

The optical sheets 10 may improve the front brightness of the liquid crystal display and reduce power consumption by narrowing the viewing angle of the light emitted from the diffuser plate 12.

The conventional liquid crystal display device having such a structure has many problems in achieving high luminance due to poor light transmittance of the polarizing sheets 8 and 18 and the liquid crystal. Accordingly, there is an urgent need for an optical member capable of scattering light generated from the lamps 36 to increase diffusibility and increase light condensing to improve the overall light efficiency.

Accordingly, it is an object of the present invention to provide an optical sheet capable of achieving high luminance and a backlight unit using the same.

In order to achieve the above object, the optical sheet according to an embodiment of the present invention includes a diffusion plate for diffusing light emitted from the outside; A first lens formed on the light incident surface of the diffusion plate; A second lens formed on the light exit surface of the diffusion plate; At least one of the first lens and the second lens is differently formed.

Each of the first and second lenses includes at least one of a lenticular lens, a broken lenticular lens in which a plurality of lenticular lenses are separated, and a micro lens smaller than the lenticular lens.

The microlens includes at least one of a hemispherical microlens and an elliptical microlens.

The ratio of the diameter and the height of the cross section of the lenticular lens is formed in the range of 0.5: 1 to 3: 1.

The eccentricity of the microlens cross-section ellipse is formed within 0 ~ 0.94, the ratio of the major axis diameter and the minor axis diameter and height of the elliptic sphere formed from the cross section is formed within 2.5 ~ 3.5: 0.5 ~ 3.5: 0.1 ~ 3.0.

The diffusion layer is formed of at least one of a material such as polymethyl methacrylate, polycarbonate, methyl methacrylate-styrene copolymer and the refractive index is formed within 1.2 ~ 1.8.

A backlight unit according to an exemplary embodiment of the present invention includes a backlight unit having a plurality of light sources installed in a liquid crystal display panel, the backlight unit comprising: a diffusion plate formed between the light sources and the liquid crystal display panel; A first lens formed on the light incident surface of the diffusion plate; A second lens formed on the light exit surface of the diffusion plate; At least one of the first lens and the second lens is differently formed.

Other objects and features of the present invention in addition to the above object will be apparent from the description of the embodiments with reference to the accompanying drawings.

2 is a diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

2, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal display panel 102 and a backlight unit for irradiating light onto the liquid crystal display panel 102.

In the liquid crystal display panel 102, liquid crystal cells are arranged in an active matrix form between upper and lower glass substrates, and thin film transistors for switching video signals are provided in each of the liquid crystal cells. It is. The liquid crystal display panel 102 may display an image corresponding to the video signal by changing the refractive index of each of the liquid crystal cells according to the video signal. A tape carrier package (not shown) in which a driver integrated circuit for applying a driving signal to a thin film transistor is mounted on the lower substrate of the liquid crystal display panel 102 is attached. In addition, polarizing sheets 108 and 118 are provided on the front and rear surfaces of the liquid crystal display panel 102, respectively. Here, the polarizing sheets 108 and 118 function to improve the viewing angle of the image displayed by the liquid crystal cells.

The backlight unit receives power from an external power source and includes a plurality of lamps 136 for irradiating light to the liquid crystal display panel 102, a case 134 for storing the plurality of lamps 136, a lamp 136 and Installed between the case 134 to prevent leakage of light generated from the lamp 136 and to diffuse the reflecting plate 114 and the light generated from the lamp 136 to the liquid crystal display panel 102; In addition, the optical member 110 for irradiating the liquid crystal display panel 102 to improve the efficiency of light is provided.

Each of the lamps 136 includes a glass tube, inert gases inside the glass tube, and a cathode and an anode installed at both ends of the glass tube. Inert gas is filled in the glass tube, and phosphor is coated on the inner wall of the glass tube. Each of the plurality of lamps 136, when the AC voltage from the inverter is applied to the high voltage electrode and the low pressure electrode, electrons are emitted from the low pressure electrode collides with the inert gas inside the glass tube to increase the amount of electrons exponentially. . Thereafter, electric current flows inside the glass tube by the increased electrons, and ultraviolet rays are emitted as the inert gas is excited by the electrons. Ultraviolet rays emitted in this manner collide with the luminescent phosphor applied to the inner wall of the glass tube to emit visible light.

The case 134 housing the plurality of lamps 136 is generated in the lamps 136 by reflecting visible light traveling toward the side and the back of the plurality of lamps 136 toward the front, that is, the optical member 110. The path of the light to be converted. In this case 134, a plurality of lamps 136 are arranged at regular intervals.

The reflector plate 114 is disposed between the upper surface of the case 134 and the plurality of lamps 136 to reflect the light generated from the lamps 136 to be irradiated toward the liquid crystal display panel 102, thereby improving light efficiency. Let's do it.

The optical member 120 diffuses and condenses the light generated from the plurality of lamps 136 to improve the efficiency of the light, and converts the exit angle of the light incident on the liquid crystal display panel 102. The optical member 120 includes a diffusion layer 124, a first lens 122 formed on the back of the diffusion layer 124, and a light direction formed on the diffusion layer 124 and different from the light direction of the first lens 122. It has a second lens 126 having a.

The first lens 122 may be formed in a cylindrical or semi-spherical shape at the bottom of the diffusion layer 124, or may be formed in a semi-elliptic shape and a hemispherical shape, respectively, or in combination. The first lens 122 serves to diffuse the light incident from the lamp 136 so as to be directly and evenly distributed on the liquid crystal display panel 102. When the first lens 122 is formed in a cylindrical shape, the diameter and height ratio of the cross section in contact with the diffusion layer 124 is formed within a range of 0.5: 1 to 3: 1.

The diffusion layer 124 contacts one side of the first lens 122 to support the first lens 122 and to diffuse light from the first lens 122 to supply the second lens 126. The diffusion layer 124 has an even and flat shape in the front and rear surfaces so that the first lens 122 is constantly arranged. The diffusion layer 124 is formed of at least one of optical glass such as polymethylmethacrylate (PMMA), polycarbonate, and methyl methacrylate-styrene copolymer (MS resin). The refractive index of the diffusion layer 124 is formed to have a high refractive index, and the same refractive index of the first lens 122, or when the refractive index of the first lens 122 has a range of 1.5 ~ 1.6 refractive index of about 1.2 ~ 1.8 It is preferably formed in the 1.4 to 1.5 in consideration of the refractive index of the first lens (122). In addition, the thickness of the diffusion layer 124 is formed within 0.5mm to 4.0mm in consideration of light refraction from the first lens 122 and thinning of the liquid crystal display device. In addition, a plurality of beads may be formed in the diffusion layer 124 to diffuse light.

The second lens 126 plays a role of generating light, ie, collecting light, so that the light emitted from the diffusion layer 124 through the first lens 122 can be directly and uniformly and evenly directed on the liquid crystal display panel 102 as a whole. do. To this end, the second lens 126 is formed on the upper surface of the diffusion layer 124 as a whole hemispherical, or as a whole semi-elliptical sphere, or a plurality of arrays of cylindrical and small lenses of a combination of hemispherical and semi-elliptic spheres. Can be. Here, in order to maximize the light collecting effect, the second lens 126 has an eccentricity of an elliptical cross section contacting the diffusion layer 124 within 0 to 0.94, and an elliptic spherical shape formed from the cross section has a long axis, a short axis, and a height ratio. It is formed in 2.5-3.5: 0.5-3.5: 0.1-3.0, Preferably it is formed in the ratio of 3: 1: 0.3. Here, the above numerical values are experimental numerical values for irradiating the light irradiated through the diffusion layer 124 to the liquid crystal display panel 102 under optimal conditions.

Optical member 120 according to an embodiment of the present invention having such a structure is formed in various forms such as a micro lens array (MLA) and a lenticular lens array (Lenticular Lens Array). Various forms of this optical member 120 are shown in FIGS. 5A-5I. FIG. 5A is a view illustrating an optical member 120 having a structure in which a first lens 122 is arranged in a semi-spherical micro lens array, and a second lens 126 having a lenticular lens arrangement in the form of a long semicircular cylinder. . FIG. 5B is a view illustrating an optical member 120 having a structure in which the first lens 122 is arranged in a semi-spherical micro lens array, and having a lenticular lens arrangement in which the second lens 126 is broken. FIG. 5C illustrates an optical member 120 in which the first lens 122 has a semi-elliptic spherical micro lens array structure, and the second lens 126 has a lenticular lens array structure in the form of a semi-cylindrical cylinder. FIG. 5D is a view showing an optical member 120 in which the first lens 122 has a semi-elliptic spherical micro lens array structure, and the second lens 126 has a broken lenticular lens array structure in the form of a semi-cylindrical cylinder. FIG. 5E illustrates an optical member 120 having a lenticular lens array structure in which a first lens 122 is cut off, and a second lens 126 having a semi-elliptic spherical micro lens array structure. FIG. 5F illustrates an optical member 120 in which the first lens 122 has a lenticular lens array structure having a semi-cylindrical cylinder shape, and the second lens 126 has a semi-elliptic spherical micro lens array structure. FIG. 5G illustrates an optical member 120 having a lenticular lens array structure having semi-cylindrical cylinders having different sizes from the first lens 122 and the second lens 126. FIG. 5H illustrates an optical member 120 having a lenticular lens structure in which the first lens 122 and the second lens 126 are broken and arranged in different directions. FIG. 5I illustrates an optical member 120 in which the first and second lenses 122 and 126 have different directions and are formed in an array of semi-elliptic spherical micro lens structures.

Optical member 120 according to an embodiment of the present invention can be formed by the various arrangements and arrangements as described above, and the shape of the first and second lenses are reversed, preferably the microlenses of the hemispherical and semi-elliptic spherical Form. When the microlenses are hemispherical and semi-elliptic spherical, the luminance distribution of the optical member 120 according to the exemplary embodiment of the present invention is shown as shown in FIGS. 6B and 6C. 6A is a diagram showing a conventional luminance distribution.

Optical member 120 according to an embodiment of the present invention having such a structure has an optical path as shown in FIG. Referring to FIG. 7, the optical member 120 according to an exemplary embodiment of the present invention diffuses the light generated from the lamp 136 by using the first lens 122 to generate between the lamp 136 arrays. The dark field can be removed, the light efficiency can be increased, the second lens 126 can be used to condense, and the light emission angle of the light can be adjusted to achieve high brightness of the liquid crystal display panel 102. .

As described above, the optical sheet and the backlight unit using the optical sheet according to the embodiment of the present invention improve the efficiency of the light by condensing and diffusing light emitted from the lamp and are formed as a single sheet, thereby simplifying the assembly process of the liquid crystal display device. Can be. Accordingly, the backlight unit according to the embodiment of the present invention can achieve high luminance and reduce production costs.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (7)

A diffusion plate for diffusing light radiated from the outside; A first lens formed on the light incident surface of the diffusion plate; A second lens formed on the light exit surface of the diffusion plate; And the first and second lenses differ in at least one of an arrangement and a shape. The method of claim 1, Each of the first and second lenses, And at least one of a lenticular lens, a broken lenticular lens having a plurality of lenticular lenses separated, and a micro lens smaller than the lenticular lens. The method of claim 2, The micro lens, An optical sheet comprising at least one of a hemispherical microlens and an elliptical microlens. The method of claim 2, The ratio of the diameter and the height of the cross section of the lenticular lens is formed in the range of 0.5: 1 to 3: 1. The method of claim 3, wherein The eccentricity of the microlens cross-section ellipse is formed within 0 ~ 0.94, the ratio of the major axis diameter and the minor axis diameter and height of the elliptic sphere formed from the cross section is formed within 2.5 ~ 3.5: 0.5 ~ 3.5: 0.1 ~ 3.0 Optical sheet made with. The method of claim 1, The diffusion layer is The backlight unit is formed of at least one of a material such as polymethyl methacrylate, polycarbonate, methyl methacrylate-styrene copolymer, the refractive index is formed within 1.2 ~ 1.8. In the backlight unit provided with a plurality of light sources in the liquid crystal display panel, A diffusion plate formed between the light sources and the liquid crystal display panel; A first lens formed on the light incident surface of the diffusion plate; A second lens formed on the light exit surface of the diffusion plate; And the first and second lenses differ in at least one of an arrangement and a shape.

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