KR20080053767A - Surface light source and backlight unit having the same - Google Patents

Abstract

A surface light source and a back light unit including the same are provided to control an optic profile of a discharge channel cross-section properly and to prevent the dark portion from generating. Plural discharge channels are formed at light source body and have non-plane surfaces to the outside. In the discharge channel, the ratio of the light amount intensity at the center of a light emission area versus the side of a light emission area is 0.8-1.2. The light source body includes the first and second substrates(112,114) and the discharge channel is formed to any one or all between the first and second substrates. The cross-section of the discharge channel is any one among semi-circle, semi-ellipse, circle, ellipse, rectangular, trapezoid. At the center and side of the light emission area of the discharge channel, the surface intensity of illumination differs. At the center and side of the light emission area of the discharge channel, the thickness differs.

Description

Surface light source device and backlight unit including the same {SURFACE LIGHT SOURCE AND BACKLIGHT UNIT HAVING THE SAME}

1 is a perspective view showing a cold cathode fluorescent lamp.

FIG. 2 is a schematic cross-sectional view of the lamp of FIG. 1. FIG.

3 is a cross-sectional view showing an embodiment of a surface light source device according to the present invention.

4 is a sectional view taken along the line X-X 'of FIG.

5 is a cross-sectional view showing a cross-sectional structure of a discharge channel of the surface light source device of FIG.

6 is a cross-sectional view showing another form of the discharge channel of the surface light source device of FIG.

7 is a cross-sectional view schematically showing an optical profile of a discharge channel of the surface light source device according to the present invention.

8 is a cross-sectional view showing a discharge channel in which an optical member is locally formed;

9 is a cross-sectional view showing a discharge channel formed locally with a different thickness.

10 is a cross-sectional view showing a discharge channel including a fluorescent layer having a different thickness.

11 is a sectional view showing a surface light source device according to another embodiment of the present invention.

12 is a partially enlarged view of FIG. 11;

13 is a sectional view showing a surface light source device according to another embodiment of the present invention.

14 is an exploded perspective view of a backlight unit including the surface light source device of the present invention.

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

100: surface light source device 110: light source body

112: first substrate 114: second substrate

120: discharge channel 130: sealing member

140: partition wall 150: discharge space

160: electrode portion 170: optical member

180: fluorescent layer

The present invention relates to a surface light source device, and to a surface light source device having improved luminance uniformity and easy slimming, and a backlight unit including the same.

The liquid crystal display displays an image by using electrical and optical characteristics of the liquid crystal. Liquid crystal displays have the advantages of being very small in volume and light in weight compared to cathode ray tubes (CRTs). As a result, they are widely used in portable computers, communication devices, liquid crystal television receivers, and aerospace industries. .

The liquid crystal display device includes a liquid crystal controller for controlling liquid crystal and a rear light source for supplying light to the liquid crystal. As a rear light source, a cold cathode fluorescent lamp (CCFL), a light emitting diode (LED), a flat fluorescent lamp (FFL) having a rod shape, and the like have been proposed.

In the case of the cold cathode fluorescent lamp 10, as shown in FIG. Since the cross section of the tubular lamp is a circle, as can be seen in the schematic diagram of FIG. 2, the light L ₀ emitted from the light emitting surface is uniform across the entire surface.

On the other hand, in the case of a surface light source device such as a flat fluorescent lamp, a plurality of discharge channels are integrally formed in the light source body, and when the cross section of the exit face of the discharge channel is non-planar, the luminous flux of the emitted light is located at the exit face position. Therefore, it is nonuniform and the brightness uniformity of the whole surface light source falls.

On the other hand, in order to compensate for the luminance uniformity of the surface light source device, the backlight unit requires an optical sheet, and there is a problem in that the thickness of the entire backlight unit is increased by separating the optical sheet and the surface light source device at predetermined intervals.

Improving luminance uniformity and slimming are indispensable conditions for the large area of the backlight unit, and are essential for enhancing the product competitiveness of the liquid crystal display device.

The present invention has been made under such a technical background, and provides a surface light source device having improved luminance uniformity.

In addition, another object of the present invention is to provide a thin backlight unit.

The present invention includes a light source body having a plurality of discharge channels having a non-planar surface with respect to the outside, wherein the discharge channel has a ratio of the intensity of light in the center to the side of the light emitting region in a longitudinal section of 0.8 It provides a surface light source device, characterized in that ~ 1.2.

The light source body may include a first substrate and a second substrate, and the discharge channel may be formed on any one of the first substrate and the second substrate, or both the first substrate and the second substrate.

In addition, the present invention includes a light source body having a plurality of discharge channels having a non-planar surface with respect to the outside, wherein the discharge channel is a ratio of the intensity of the amount of light in the center to the side of the light emitting region when viewed in a longitudinal section. A surface light source device, characterized in that 0.8 to 1.2; A case accommodating the surface light source device; And an inverter for applying a voltage to the light source body.

According to the present invention, in a surface light source device including a plurality of discharge channels, the optical profile of the cross section of the discharge channel is appropriately controlled to improve luminance uniformity and contribute to slimming of the backlight unit.

3 and 4, an example of the surface light source device 100 having a plurality of discharge channels according to the present invention is illustrated. The surface light source device 100 includes a light source body 110 and electrode units 160 provided on outer surfaces of both edges of the light source body 110.

The light source body 110 includes a first substrate 112 and a second substrate 114 disposed to face each other at a predetermined interval. A plurality of partition walls 140 are disposed between the first substrate and the second substrate to divide the space between the first substrate and the second substrate into a plurality of discharge channels 120. The discharge channel 120 and the partition wall part 140 may be formed by, for example, molding the first substrate 112, or may be formed by molding a second substrate instead of the first substrate.

A sealing member 130 is disposed between the edges of the first substrate 112 and the second substrate 114 to isolate the discharge channels 120 from the outside. Alternatively, the first substrate and the second substrate may be sealed by direct fusion.

Discharge gas is injected into the discharge space 150 inside the discharge channel 120. Although not shown, a fluorescent layer and a protective layer may be further included in the discharge channel 120, and a reflective layer may be formed on any one of the first substrate and the second substrate.

In order to drive the surface light source device, a pair of electrodes may be formed on the first substrate 112 and / or the second substrate 114 in the form of a band or island electrode. A pair of electrode portions 160 in the form of a band are formed on the surface of the light source body 110 as shown. The electrode portion may be formed in the same area in each discharge channel, or may be formed in another area according to the position of the discharge channel. When a voltage is applied to the electrode unit 160 using an inverter (not shown), gas injected into the discharge space 150 in the discharge channel is discharged.

The light emitted to the light emitting surface (for example, the first substrate surface) of the discharge channel depends largely on the surface shape of the discharge channel. Referring to FIG. 5, the luminous flux L1 of light emitted vertically from the center portion of the discharge channel is larger than the luminous flux L2 of light emitted from the side portion of the discharge channel, and the difference in the luminous flux distribution is related to the luminance uniformity of the surface light source. It is dropped and visually recognized as a dark part in the partition part located especially between discharge channels.

In order to improve the luminance uniformity, as shown in FIG. 6, the shape of the discharge channel may be formed closer to a spherical shape. However, even in this case, there is still a nonuniformity between the luminous flux L1 of the light emitted from the center portion of the discharge channel and the luminous flux L2 of the light emitted from the side portion of the discharge channel. Therefore, in order to compensate for luminance unevenness in the surface light source device in which the plurality of discharge channels are partitioned by the partition wall portion, the optical sheet (not shown) is spaced apart from the surface light source device at predetermined intervals. However, the optical sheet not only lowers the brightness of the surface light source, but also inevitably increases the thickness of the backlight unit.

In the present invention, in a surface light source having a non-planar discharge channel, the optical profile on the surface of the discharge channel is appropriately controlled to ensure overall luminance uniformity of the surface light source device. Referring to FIG. 7, a cross section of the discharge channel is shown. The intensity of the luminous flux or the light amount in the center portion of the light exit surface (for example, the first substrate) of the discharge channel is referred to as A, and the intensity of the light quantity at the side portion is referred to as B. FIG. At this time, the ratio of A to B is controlled in an appropriate range so that the optical profile at the discharge channel exit surface optimizes the luminance uniformity of the surface light source device.

The inventors found that the ratio of A to B is 0.8 to 1.2, which is most preferable in terms of luminance uniformity. In this case, when defining the intensity of the amount of light at the side portion, the light exit angle θ of the side part can be determined in the range of 20 ° to 50 °, and in the preferred embodiment of the present invention, the side light exit angle θ is It was set to 30 degrees.

In order to control the intensity of the light amount in the side portion and the center portion of the discharge channel at the ratio of the above range, a method such as changing the cross-sectional shape of the discharge channel or additionally forming other members may be applied. In the present invention, the cross section of the discharge channel of the surface light source device may be variously modified, such as a semicircle, a semi-ellipse, a circle, an ellipse, a rectangle, and a trapezoid.

As one method for controlling the optical profile of the discharge channel, the surface roughness of the center portion and the side portion of the light emitting region of the discharge channel may be different. Surface roughness can be locally formed to change the optical profile of the discharge channel. In addition, as illustrated in FIG. 8, the optical profile may be changed by adding the optical member 170 locally in the discharge channel. As the optical member, for example, an optical sheet having a diffusion or scattering function may be used, and the intensity of light may be partially changed by attaching to a central portion or a side portion on the inner surface of the discharge channel.

Alternatively, the transmittance of visible light emitted from the discharge channel may be changed by changing the thickness of the discharge channel. 9, the thickness ts of the side surface portion S is thin and the thickness tc of the central portion C is relatively thick by varying the thickness of the emission surface (eg, the first substrate) of the discharge channel. As a result, light emission is relatively easy in the side part, so that the overall light transmittance of the discharge channel exit surface can be made more uniform. The difference between the thickness ts of the side portion S and the thickness tc of the central portion C may vary depending on the desired optical profile.

Meanwhile, as shown in FIG. 10, the light transmittance of the discharge channel exit surface may be changed by changing the thickness of the fluorescent layer 180 formed in the discharge channel. For example, if the thickness of the fluorescent layer Ps of the discharge channel side portion is formed thicker than the thickness of the fluorescent layer Pc of the center portion, the visible light generation efficiency may be increased at the side portion, thereby increasing the intensity of the light amount of the side portion.

The optical profile of the discharge channel may be controlled by changing the shape of the discharge channel. FIG. 11 illustrates a surface light source device according to another embodiment of the present invention, in which discharge channels are formed on both the first substrate 112 and the second substrate 114. This type of surface light source device is suitable for improving the overall luminance by using, for example, a first substrate corresponding to one surface of the light source body as the main light emitting surface and a second substrate as the auxiliary light emitting surface. When the second substrate is used as the auxiliary light emitting surface, the second substrate may be spaced apart from the second substrate at a predetermined interval, and further include a reflector (not shown).

In this double-sided light emitting surface light source device, as shown in FIG. 12, since the plasma generated inside the discharge channel is nearly spherical, the intensity of light is uniform at the exit surface of the discharge channel, and in particular, the light quantity of the side part can be increased. have.

As shown in FIG. 13, the first substrate and the second substrate may be molded into a shape close to a spherical shape so that the optical profile can be controlled more precisely. The cross-sectional shape or curvature of the discharge channel may vary depending on the desired optical profile.

14 is an exploded perspective view showing a backlight unit including a surface light source according to the present invention. As illustrated, the backlight unit includes a surface light source 300, upper and lower casings 1100 and 1200, an optical sheet 900, and an inverter 1300.

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 300. The surface light source 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 300. The discharge voltage generated from the inverter 1300 is applied to the electrodes 360 of the surface light source 300 through the first and second power lines 1352 and 1354, respectively.

The optical sheet 900 may include a diffusion plate for uniformly diffusing the light emitted from the surface light source 300, and a prism sheet for imparting linearity to the diffused light. The upper case 1100 is coupled to the lower case 1200 to support the surface light source 300 and the optical sheet 900. The upper case 1100 prevents the surface light source 300 from being separated from the lower case 1200. Unlike the illustrated figure, the upper case and the lower case may be formed as one integrated case.

In the surface light source device according to the present invention, luminance uniformity is improved to reduce the distance from the optical sheet when configuring the backlight unit. This is because a sufficient optical effect can be obtained even if the optical sheet is placed close to the surface light source surface. In some cases, all or some layers of the optical sheet may not be used. Therefore, it contributes to thickness reduction of a backlight.

Although described above with reference to the preferred embodiments of the present invention, those skilled in the art or those skilled in the art having ordinary knowledge in the 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, in the surface light source device including the plurality of discharge channels, the optical profile of the cross section of the discharge channel is changed to improve the luminance uniformity. Therefore, in the surface light source device, it is possible to prevent the occurrence of dark portions caused by the decrease in the amount of light on the side of the discharge channel. In addition, the backlight unit can be manufactured slim by not using the optical member used to dilute the dark portion or by reducing the distance between the optical member and the surface light source device.

Claims (9)

A light source body having a plurality of discharge channels having a surface that is non-planar with respect to the outside; The discharge channel is characterized in that the ratio of the intensity of light in the center portion to the side portion of the light emitting region in the longitudinal section is 0.8 ~ 1.2 Surface light source device. The surface light source device of claim 1, wherein the light source body includes a first substrate and a second substrate, and the discharge channel is formed on one of the first substrate and the second substrate. The surface light source device of claim 1, wherein the light source body includes a first substrate and a second substrate, and the discharge channel is formed on both the first substrate and the second substrate. The surface light source device of claim 2, wherein a cross section of the discharge channel is any one of a semicircle, a semi-ellipse, a circle, an ellipse, a rectangle, and a trapezoid. The surface light source device according to claim 1, wherein the center part and the side part of the light emitting area of the discharge channel have different surface roughness. The surface light source device according to claim 1, wherein the center portion and the side portion of the light emitting region of the discharge channel have different thicknesses. The surface light source device of claim 1, wherein an optical member is further formed locally at a central portion or a side portion of the emission region of the discharge channel. The surface light source device of claim 1, wherein a fluorescent layer has a different thickness at a central portion or a side portion of a light emitting region of the discharge channel. And a light source body having a plurality of discharge channels having a non-planar surface relative to the outside, wherein the discharge channel has a ratio of the intensity of light in the center to the side of the light emitting region in a longitudinal section of 0.8 to 1.2. A surface light source device, characterized in that; A case accommodating the surface light source device; And Including an inverter for applying a voltage to the light source body Backlight unit.

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