KR20080046486A - Optical plate for surface light source and backlight unit having the same - Google Patents

Abstract

An optical plate for surface light source and a back light unit having the same are provided to improve the brightness, brightness uniformity, concentration and the penetration of light from the surface light source by means of optical element of new structure. An optical plate for surface light source has a first pattern spaced by first pitch on its one side. The first pattern consists of a prism-shaped linear part and a lens-shaped curved part. The inner angle of the linear part is in the range of 40-60 degrees(Theta1). The curved part is formed in the rate of 50-80% of the first pattern height. The pitch of the first pattern is less than 300 micrometer. A second pattern is spaced by second pitch on another side of the optical plate for surface light source. The second pattern consists of a prism-shaped linear part and a lens-shaped curved part on the upside of the linear part. The inner angle of the linear part of the second pattern is in the range of 60-80 degrees. The curved part of the second pattern is formed in the rate less than 30% of the second pattern height. The second pitch of the second pattern is less than 300 micrometer.

Description

Optical plate for surface light source and backlight unit having the same {OPTICAL PLATE FOR SURFACE LIGHT SOURCE AND BACKLIGHT UNIT HAVING THE SAME}

1 is a perspective view showing an example of a flat fluorescent lamp.

2 is a perspective view showing an optical plate according to an embodiment of the present invention.

3 is a perspective view showing an optical plate according to another embodiment of the present invention.

4 is a cross-sectional view taken along line II ′ of FIG. 2.

5 is an enlarged view of a portion A of FIG. 4;

6 is a cross-sectional view showing an optical plate of the present invention.

7 is a schematic view showing a cross-sectional structure of the first pattern of the optical plate of the present invention.

8 is a schematic view showing a cross-sectional structure of a second pattern of the optical plate of the present invention.

9-12 is process drawing which showed an example of the manufacturing method of the optical plate of this invention.

13 is an exploded perspective view of a backlight unit including the optical plate of the present invention.

*** Explanation of symbols for the main parts of the drawing ***

210: optical plate 210a: first pattern

210b: second pattern

The present invention relates to an optical plate for a surface light source and a backlight unit having the same, and to a novel optical member for a surface light source for improving transmittance, luminance and luminance uniformity, and a backlight having the same.

Unlike other light emitting displays, a liquid crystal display does not emit light by itself, and thus requires a separate backlight.

A variety of surface light sources are used for the backlight used in the liquid crystal display, and a cold cathode fluorescent lamp (CCFL) in which a cold cathode is enclosed inside a tubular bulb, a hot cathode fluorescent lamp (HCFL) that employs a hot cathode instead of a cold cathode, and a plurality of tubules An external electrode fluorescent lamp (EEFL) employing a common electrode outside the valve is used. Recently, a flat fluorescent lamp (FFL) has been proposed in which a discharge space is formed of a flat substrate instead of a tubular bulb.

The backlight light source should have low power consumption and excellent luminous efficiency, and should have high brightness and uniform brightness.

1, a flat fluorescent lamp is shown as an example of a surface light source device. The surface light source device 100 includes a light source body 110 and electrodes 160 provided on outer surfaces of both edges of the light source body 110. The light source body 100 includes an upper substrate and a lower substrate disposed to face each other to form the discharge space 150. Partition portions 140 formed by a portion of the upper substrate abutting the lower substrate divide the space between the upper substrate and the lower substrate into a plurality of light emitting regions 120. Discharge gas is injected into the discharge space 150, and discharge is performed by a voltage applied through the electrode 160.

As the liquid crystal display device becomes larger, the luminance required for the rear light source continues to increase. In order to increase the luminance, the tube current supplied to the surface light source device must be increased. However, when the tube current is increased, the lifespan of the surface light source device is reduced, and the driving inverter of the surface light source device has a limit in the available power.

In addition, for example, in the surface light source device including the plurality of discharge regions 120 and the barrier rib portion 140 as illustrated in FIG. 1, light is emitted only in the discharge region, and the barrier portion acts as a dark portion to reduce the overall luminance. There is a problem in that bright lines are generated due to the difference in luminance between the discharge region and the partition wall portion.

Conventionally, an optical member including a diffusion plate and a diffusion sheet is disposed at a predetermined distance from the surface light source device to remove the bright lines and increase the luminance uniformity. However, the optical member including the diffusion plate and the diffusion sheet has a problem of increasing the manufacturing cost of the backlight unit and complicating the manufacturing process. In addition, the diffuser plate is formed in a structure in which fine glass beads are dispersed therein, and scatters light emitted from the surface light source device to achieve uniformity in luminance, but there is a limitation in that the overall luminance decreases.

Therefore, there is a demand for an optical member having a new structure for improving luminance and removing bright lines of the surface light source device.

An object of the present invention is to provide an optical plate for improving the luminance and luminance uniformity of light emitted from a surface light source device.

In addition, another object of the present invention is to provide a novel optical plate that improves the light collecting and transmittance of light emitted from the surface light source device.

Another object of the present invention is to provide an optical member for backlight that is easy to manufacture and advantageous for mass production.

The present invention is a plate having a first pattern spaced apart by a first pitch on one surface, the first pattern is a surface light source consisting of a linear portion of the prism shape and a lens-shaped curved portion of the upper portion of the linear portion It provides an optical plate for.

The inner angle of the linear portion of the first pattern is preferably in the range of 40 ° to 60 °, and the curved portion is preferably formed at a ratio of 50 to 80% of the height of the first pattern.

The optical plate may further include a second pattern spaced apart from the first pitch of the first pattern by a second pitch different from the first plate. In this case, the second pattern may include a prism-shaped linear portion and a lens-shaped curved portion above the linear portion, and the inner angle of the linear portion of the second pattern may be in a range of 60 ° to 80 °. Preferably, the curved portion of the second pattern is formed at a rate of 30% or less of the height of the second pattern.

The present invention also provides a surface light source including at least one discharge space and an electrode unit for applying a voltage to the discharge space; A case accommodating the surface light source; A plate having a first pattern spaced apart from the surface light source at a predetermined interval, the first pattern being spaced at a first pitch on one surface thereof, wherein the first pattern has a prism-shaped linear portion and a lens shape above the linear portion; An optical plate consisting of curved portions of; And an inverter configured to apply a discharge voltage to the electrode to drive the surface light source.

As the surface light source, not only a flat fluorescent lamp in which a plurality of discharge channels are spaced apart from each other by a partition wall portion, but also a cold cathode fluorescent lamp, a hot cathode fluorescent lamp, an external electrode type tubular fluorescent lamp, and a plurality of light emitting diodes may be used. Can be.

According to the present invention, it is possible to improve the optical properties such as the light condensation, light uniformity, etc. of the backlight without using or using an additional optical sheet including a diffusion plate and a diffusion sheet, in particular a plurality of light emitting regions and non-light emitting regions In the surface light source including the bright line due to the non-emitting region can be removed. The backlight unit according to the present invention does not exclude that a separate light collecting or diffusing optical sheet is included in addition to the optical plate.

FIG. 2 illustrates an optical plate 210 according to an embodiment of the present invention. As shown, the optical plate has a first pattern 210a formed on an upper surface of a flat plate, and a second pattern on a lower surface thereof. 210b) is formed.

Unlike shown, the optical plate according to the present invention may have a regular pattern formed only on one surface of the upper surface or the lower surface. In this case, the other surface can maintain a smooth plane.

As described below, the first pattern 210a and the second pattern 210b are formed in a complex structure including a prismatic lower part and a lenticular upper part, so that optical characteristics such as light condensation and transmittance may be obtained. Improve the light distribution, improve the light distribution uniformity of the surface light source device, and reduce the light loss.

In the embodiment illustrated in FIG. 2, the first pattern 210a and the second pattern 210b of the optical plate are formed in a bar shape extending in one direction (X direction). Alternatively, the first pattern 210a and the second pattern 210b may be formed in different directions.

3 illustrates an optical plate 220 according to another embodiment of the present invention. Unlike the above-described embodiment, the first pattern 220a on the upper surface of the optical plate and the second pattern 220b on the lower surface of the optical plate 220 have at least two directions. It is arranged in (X direction, Y direction). This structure is a two-dimensional arrangement of the unit patterns of the first pattern 220a and the second pattern 220b on the surface of the optical plate, and corresponds to changes in the shape of the discharge space of the surface light source device. The optical properties can be further improved.

FIG. 4 is a cross-sectional view taken along line II ′ of FIG. 2, and a portion A of FIG. 4 is enlarged in FIG. 5.

The optical plate 210 according to the present invention includes a first pattern 210a in which a unit pattern composed of a lower prism shape and an upper lens shape is continuous at a first pitch.

The first pattern 210a serves to condense the light L1 emitted from the surface light source device through the optical plate to be uniformly emitted to the front surface. As a result, the luminance unevenness due to the luminance difference between the light emitting area and the non-light emitting area of the surface light source device can be reduced, and in particular, the bright lines caused by the non-light emitting area can be removed.

In addition, the optical plate of the present invention includes a second pattern 210b in which a unit pattern composed of a prism shape lower portion and an upper portion of a lens shape is continuous at a second pitch different from the first pitch on the other surface. The light L2 emitted from the surface light source device is scattered through the second pattern 210b to increase luminance uniformity. In addition, the light reflected from the inner surface of the first pattern is reflected (total reflection) again at the inner surface 210b 'of the second pattern, thereby reducing the light loss and increasing the overall transmittance of the optical plate.

In particular, in the optical plate according to the present invention, the transmittance in the vertical direction is improved by the interaction between the first pattern 210a and the second pattern 210b, and the overall brightness is increased.

The first pitch P1 of the first pattern and the second pitch P2 of the second pattern are preferably 300 μm or less in consideration of light characteristics such as light scattering and luminance, and patterns are formed on both the upper and lower surfaces of the optical plate. In order to prevent the moiré effect caused by the inter-pattern interference, it is preferable that the first pitch of the first pattern and the second pitch of the second pattern are not mutual integer multiples.

7 shows a unit pattern cross-sectional structure of the first pattern of the optical plate of the present invention. The unit pattern includes a prism-shaped linear portion L converging upwardly to the bottom and a lens-shaped curved portion R on the linear portion. In the first pattern, it was confirmed that the inner angle θ1 of the linear portion was preferably in the range of 40 ° to 60 ° in view of light collection, transmittance and luminance. In addition, in the first pattern, the curved portion R is preferably formed at a larger ratio than the linear portion L, and in the ratio of 50 to 80% of the height of the first pattern in terms of light condensation, transmittance and luminance. It was confirmed that it is appropriate to form the curved portion R.

8 illustrates a unit pattern cross-sectional structure of a second pattern of the optical plate of the present invention. Similarly to the first pattern, the second pattern also includes a linear portion L having a prism shape inclined to the upper portion and inclined upward, and a curved portion R having a lens shape on the linear portion. In the second pattern, it was confirmed that the inner angle θ2 of the linear portion was in the range of 60 ° to 80 ° in terms of transmittance, light distribution uniformity, and light loss reduction. In the second pattern, it is preferable that the curved portion R is formed at a smaller ratio than the linear portion L, and the ratio is less than or equal to 30% of the height of the second pattern in terms of transmittance, light distribution uniformity, and light loss reduction. It was confirmed that it is appropriate to form the curved portion R.

The optical plate according to the present invention can be manufactured by various methods. 9 to 12 illustrate one embodiment of manufacturing the optical plate of the present invention. First, a plate body 250 having a predetermined thickness is prepared (step S10). The thickness of the plate body 250 need not be particularly limited but is preferably 1 mm or more.

As the material of the plate body, a transparent polymer may be used. For example, polymethyl methacrylate (PMMA), polycarbonate (PC), polystyrene (PS), and methyl methacrylate-styrene copolymer (MS) , Cycloolefin (COP) and the like, but is not necessarily limited to these materials. In addition, it is preferable that the material used as the plate body has a refractive index in the range of 1.45 to 1.6 for excellent light condensing properties.

The first pattern and the second pattern may be directly formed on the upper surface 250a and the lower surface 250b of the plate body, respectively, but a separate resin layer 255 is formed as in step S20 to form a fine pitch pattern. can do. The material of the resin layer 255 is not particularly limited, but in order to improve the transmittance of the optical plate, it is preferable to use a material having a refractive index n2 smaller than the refractive index n1 of the plate body.

The resin layer 255 is press-molded to form a fine pitch first pattern 255 '(step S30). When using a thermosetting material as the resin layer may further comprise a UV curing step after pressure molding.

Finally, the second pattern 250b 'is formed on the lower surface of the plate body 250 (step S40). The second pattern 250b ′ may be formed by molding a lower surface of the plate body with a roller having a predetermined shape, and may be formed before forming the resin layer 255, as necessary.

Unlike the aforementioned manufacturing method, the optical plate according to the present invention can form both the first pattern and the second pattern by an extrusion process.

13 is an exploded perspective view showing a backlight unit including an optical plate according to the present invention. As shown, the backlight unit includes the optical plate 210, the surface light source device 300, the upper and lower cases 1100 and 1200, and the inverter 1300 according to the above-described embodiment.

The lower case 1200 includes a bottom portion 1210 and a plurality of sidewall portions 1220 extending to form an accommodation space from an edge of the bottom portion 1210 to accommodate the surface light source device 300. The surface light source device 300 is accommodated in the storage space of the lower case 1200. The inverter 1300 is disposed on the rear surface of the lower case 1200 and generates a discharge voltage for driving the surface light source device 300. The discharge voltage generated from the inverter 1300 is applied to the electrodes 360 of the surface light source device 300 through the first and second power lines 1352 and 1354, respectively. The upper case 1100 is coupled to the lower case 1200 to support the light source 300 and the optical sheet 900. The upper case 1100 prevents the light source 300 from being separated from the lower case 1200.

The optical plate 210 is spaced apart from the surface light source device 300 at a predetermined interval, and uniformly condenses the light emitted from the surface light source device. Therefore, the optical characteristics of the backlight unit can be improved, and the overall thickness and volume can also be reduced.

Although not shown, a light collecting or diffusing optical sheet may be further included in addition to the optical plate 210.

In the above, it has been described with reference to preferred embodiments of the present invention, but those skilled in the art or those skilled in the art from the spirit and scope of the invention described in the claims to be described later Various modifications and variations can be made in the present invention without departing from the scope thereof.

According to the present invention, it is possible to improve the light collecting characteristics and transmittance of light generated in the surface light source device to improve the light efficiency of the backlight unit. In particular, it is possible to secure the product reliability by improving the luminance and luminance uniformity of the surface light source device and removing the bright lines. In addition, it is easy to manufacture the optical plate, it is possible to reduce the volume of the backlight unit can extend the application range of the backlight.

Claims (19)

A plate having a first pattern spaced at a first pitch on one surface thereof, wherein the first pattern includes a prism-shaped linear portion and a lens-shaped curved portion above the linear portion Optical plate for surface light source. The optical plate for a surface light source according to claim 1, wherein an inner angle of the linear portion is in a range of 40 ° to 60 °. The optical plate of claim 1, wherein the curved portion is formed at a ratio of 50 to 80% of the height of the first pattern. The optical plate for a surface light source according to claim 1, wherein the first pitch of the first pattern is 300 µm or less. The optical plate for a surface light source according to claim 1, wherein a second pattern spaced apart from the first pitch of the first pattern and the second pitch is formed on the other surface of the optical plate. The optical plate of claim 5, wherein the second pattern comprises a prism-shaped linear portion and a lens-shaped curved portion above the linear portion. The optical plate for a surface light source according to claim 6, wherein an inner angle of the linear part of the second pattern is in a range of 60 ° to 80 °. The optical plate of claim 5, wherein the curved portion of the second pattern is formed at a ratio of 30% or less of the height of the second pattern. The optical plate for a surface light source according to claim 5, wherein the second pitch of the second pattern is 300 µm or less. 10. The optical plate for a surface light source according to claim 9, wherein the second pitch of the second pattern is not an integer multiple of the first pitch. A surface light source including at least one discharge space and an electrode unit applying a voltage to the discharge space; A case accommodating the surface light source; A plate having a first pattern spaced apart from the surface light source at a predetermined interval and spaced at a first pitch on one surface thereof, wherein the first pattern has a shape of a prism-shaped linear portion and an upper portion of the linear portion; An optical plate composed of curved portions; And And an inverter configured to apply a discharge voltage to the electrode to drive the surface light source. The backlight unit of claim 11, wherein an inner angle of the linear portion is in a range of 40 ° to 60 °. The backlight unit of claim 11, wherein the curved portion is formed at a ratio of 50 to 80% of the height of the first pattern. The backlight unit of claim 11, wherein a second pattern spaced apart from the first pitch of the first pattern and the second pitch is formed on the other surface of the optical plate. The backlight unit of claim 14, wherein the second pattern comprises a prism-shaped linear portion and a lens-shaped curved portion above the linear portion. The backlight unit of claim 15, wherein an inner angle of the linear portion of the second pattern is in a range of 60 ° to 80 °. The backlight unit of claim 15, wherein the curved portion of the second pattern is formed at a ratio of 30% or less of the height of the second pattern. 12. The surface light source of claim 11, wherein the surface light source includes a flat fluorescent lamp, a cold cathode fluorescent lamp, a hot cathode fluorescent lamp, an external electrode type capillary fluorescent lamp, and a plurality of light emission, in which a plurality of discharge channels are spaced apart from each other by a partition wall part. The backlight unit, characterized in that any one selected from a flat lamp comprising a diode. 12. The backlight unit of claim 11, further comprising a light converging or diffusing optical sheet.

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