KR100423952B1 - back light unit having asymmetric light guide pattern - Google Patents

Abstract

A surface light source device having an asymmetric light guide pattern portion is disclosed. The present invention provides a light guide plate having a light guide pattern portion having a plurality of grooves having an asymmetrical cross section patterned by laser beam processing so as to diffuse and scatter light with uniform illuminance at each portion, and at least one sidewall of the light guide plate. And a light emitting means installed above, and a reflecting plate installed under the light guide plate, and adjusting the relative positional relationship between the laser scan mirror portion and the laser oscillation portion to deflect the laser beam to the light guide plate to form the light guide pattern portion. Machining time can be reduced.

Description

Back light unit having asymmetric light guide pattern

The present invention relates to a surface light source device, and more particularly, to a surface light source device having an asymmetric light guide pattern portion having an improved pattern shape of the light guide pattern portion.

In general, surface light source devices used in light-receiving flat panel display devices such as liquid crystal display devices, lighting signs, etc. are disclosed in Japanese Patent Application Laid-Open No. 60-216435, Korean Patent Application Nos. 93-11174, 94-26117, 94-33115, 94-26116.

In the surface light source device disclosed in the above-mentioned patents, partition walls are alternately installed inside a container having a closed space to form a meandering discharge space, and each electrode is provided at both ends of the discharge space. These discharges have a structure in which the phosphor layer formed in the discharge space is excited to emit light, or light emitting means is provided on the sidewall of the light guide plate to guide light and diffuse the light.

Among them, in the surface light source device employing the edge light method, a reflecting plate is provided on the lower surface of the light guide plate, a diffusion plate, a prism sheet, or the like is provided on the upper surface thereof, and at least one light emitting means is provided on the side wall. As the light emitting means, a cold cathode fluorescent lamp (CCFL) or an LED lamp is used.

In the surface light source device configured as described above, the light irradiated from the light emitting means is irradiated to the light guide plate, and the light guided to the light guide plate is reflected upwardly with a relatively uniform illuminance at each part by a reflecting plate, and the light is diffused or a prism. It spreads forward through the sheet.

In this case, a plurality of light guide patterns are formed on the light guide plate to scatter and diffuse light incident from one surface of the transparent acrylic resin. The light guide pattern portion was formed by a printing method using a mask having a corresponding pattern, or a V-shaped scratch was formed by a non-printing method using a scraper on the bottom surface of the light guide plate.

However, the printing method is complicated in the manufacture of the ink and printing process, there is a lot of defect rate, such as severe dropout or staining of the printed pattern portion, the production yield is low, it is impossible to reuse the light guide plate that is not properly printed, It acts as a synergistic factor.

In the non-printing method, since the processing method for forming the scratch is made mechanically, it is difficult to form a fine pattern portion, and uniform diffusion and scattering of light are not achieved. In addition, when the thickness of the light guide plate becomes thin, it is difficult to narrow the gap according to the depth of the scratch and the degree of scattering, and thus the pattern is visible. Since a large number of scratches must be formed in sequence, the unit processing time becomes longer as the light guide plate becomes larger, and the production efficiency decreases. do. In particular, when the processed line width is increased, deformation of the light guide plate occurs due to frictional heat due to an increase in the friction area during processing.

According to the related art, in order to prevent such a phenomenon, the light guide pattern portion is formed on the light guide plate by laser processing. That is, the laser beam oscillated from the laser device is scanned on the light guide plate to form a light guide pattern portion having a predetermined pattern. Accordingly, it is possible to overcome the difficulty of dropping, spotting, thermal deformation, and fine pattern formation in the pattern portion generated during the printing method or the non-printing method.

In this case, the light guide pattern part may exist in various patterns to reflect, diffuse, and scatter the light emitted from the light emitting means. For example, it can be said that it consists of grooves, such as a dot type | mold, a straight type | mold, a mixed type which combined dot type and straight type | mold. In addition, the size of the groove generally increases gradually as the distance from the light emitting means increases the light guide amount.

However, the formation of the light guide pattern portion according to the conventional laser processing method has the following problems.

When using a laser device, the laser beam should be aligned at a position perpendicular to the processing surface of the light guide plate. To this end, the position is changed by performing a linear reciprocating motion of the laser device on the X and Y axes with respect to the light guide plate using the XY stage. Next, a predetermined light guide pattern portion is formed by scanning a laser beam on one surface of the light guide plate.

This method is a method of processing by reciprocating the XY stage, so the processing time becomes longer, the production efficiency is lowered. In particular, in recent years, the light guide plate has become larger in size, and as the processing area increases, the time taken for the reciprocating motion is proportionally longer, thereby increasing the processing time of the light guide pattern portion. In addition, as the XY stage is mechanically driven, there is a problem that the precision is lowered when a fine pattern is required.

The present invention is to solve the above problems, can be improved on the productivity of the light guide pattern is formed on one surface of the light guide plate to cause the scattering and diffusion of light, asymmetric light guide pattern that can maintain the uniformity of brightness It is an object to provide a surface light source device having a portion.

1 is an exploded perspective view of a surface light source device according to a first embodiment of the present invention;

2 is a cross-sectional view showing a part of the surface light source device according to the second embodiment of the present invention;

3 is a cross-sectional view showing a part of the surface light source device according to the third embodiment of the present invention;

4 is a configuration diagram showing a system for manufacturing the light guide pattern portion of the present invention;

5a to 5c are schematic cross-sectional views showing the shape of the light guide pattern portion of the present invention;

6 is a schematic plan view illustrating an area of a light guide plate according to an embodiment of the present invention;

FIG. 7 is a graph showing light guiding efficiency for the light guiding area of FIG. 6. FIG.

<Brief description of symbols for the main parts of the drawings>

10 ... Surface light source device 11 ... Light guide pattern part

12.Light guide plate 13 ... Light emitting means

14 ... Reflector 15 ... Diffuser

21 ... cover member 22 ... light diffuser

32.Prism part 43.Laser scan mirror part

44 Galvanometer 45a, 45b Reflector

47.Lens section

In order to achieve the above object, the surface light source device having an asymmetric light guide pattern of the present invention,

A light guide plate having a light guide pattern portion having a plurality of grooves having an asymmetrical cross section patterned by laser beam processing so as to diffuse and scatter light with uniform illuminance at each portion;

Light emitting means installed on at least one sidewall of the light guide plate; And

And a reflective plate installed under the light guide plate.

In addition, the light guide pattern portion is characterized in that the inclination angle of the groove is formed larger toward the peripheral portion from the central portion of the light guide plate.

In addition, the light guide pattern portion is characterized in that the inclination angle is set in accordance with the deflection angle of the laser beam output in accordance with the relative position change of the laser scan mirror portion and the laser oscillation portion installed perpendicular to the light guide plate.

Further, the light guide pattern portion is characterized in that the line width of 300 to 600 micrometers.

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

1 shows a surface light source device 10 according to an embodiment of the present invention.

Referring to the drawings, the surface light source device 10 is provided with at least one light guide plate 12 having the light guide pattern portion 11 and at least one sidewall of the light guide plate 12 to irradiate light to the light guide plate 12. A light emitting means 13, a reflector 14 disposed below the light guide plate 12 to reflect light upwards, and a diffuser plate disposed above the light guide plate 12 to scatter and diffuse light forward; 15). In this case, as the light emitting means 13, a cold cathode fluorescent lamp or an LED is used.

The light guide pattern portion 11 is formed on a lower surface of the light guide plate 12 in a predetermined pattern by laser beam processing. The light guide pattern portion 11 is processed into a groove having a dot shape, a straight shape, or a combination of dot and straight shapes. In addition, it may be processed into a square or lattice, or a groove by a combination of these. At this time, the cross-sectional shape of the grooves is not asymmetrical to each other, but asymmetrical. This is because it is processed according to the deflection angle of the laser beam according to the relative positioning between the laser system and the light guide plate 12 which will be described later.

Each groove of the light guide pattern portion 11 changes its size as it moves away from the light emitting means 13 to gradually increase the amount of light guide, thereby preventing a decrease in luminance caused by moving away from the light emitting means 13. desirable. At this time, the line width of the groove is determined according to a certain design rule.

2 shows a surface light source device 20 according to a second embodiment of the present invention.

Here, the same reference numerals as in the above-described drawings indicate the same members having the same function.

Referring to the drawings, the surface light source device 20 is provided with a light guide plate 12 having a light guide pattern portion 11 formed of an asymmetric groove by laser beam processing, and at least one side is provided on the side wall of the light guide plate 12. It includes a light emitting means 13, a reflecting plate 14 provided below the light guide plate 12, and a cover member 21 surrounding the light emitting means (13).

In addition, the light diffusion part 22 formed with a fine scratch is formed on the upper surface of the light guide plate 12. The light diffusing portion 22 may have a different density depending on the site so that light (arrow) irradiated from the light emitting means 13 can be uniformly diffused to the entire surface of the light guide plate 12.

3 shows the surface light source device 30 according to the third embodiment of the present invention.

Referring to the drawings, the surface light source device 30 includes at least a light guide plate 12 having a light guide pattern portion 11 in which an asymmetric groove is patterned by laser beam processing on a lower surface thereof, and at least on sidewalls of the light guide plate 12. One or more light emitting means 13 and a cover member 21 having a reflective film formed on an inner surface of the light guide plate 12 so as to surround the light emitting means 13 and to re-enter light irradiated in the opposite direction of the light guide plate 12 to the light guide plate 12. ).

In addition, the light (arrow) irradiated from the light emitting means 13 is guided through the light guide plate 13 on the upper surface of the light guide plate 12, so that scratches are formed at minute intervals so that light is focused forward or within a predetermined angle. The formed prism portion 32 is formed. When the prism portion 32 is formed, it may not be necessary to provide a separate prism sheet for increasing the amount of light incident on the liquid crystal display and increasing the contrast.

As described in the above-described embodiments, one surface of the light guide plate 12 is light guided so as to scatter, reflect and diffuse the light emitted from the light emitting means 13 to enable uniform illumination over the entire area of the light guide plate 12. The pattern portion 11 is formed, and the light guide pattern portion 11 is formed of a plurality of grooves having an asymmetric shape by using a laser system.

Here, the light guide pattern portion 11 is made by scanning the laser beam in the infrared region capable of absorbing heat to the raw material, for example, acrylic resin constituting the light guide plate 12 in the X-axis and Y-axis direction of the light guide plate 12. .

At this time, the laser system does not move the light guide plate 12 by mechanical driving such as XY stage to oscillate the laser beam to form the light guide pattern portion 11, but instead deflect the laser beam output from the laser oscillator. The pattern portion 11 is formed. The deflected beam causes the light guide pattern portion 12 to have an asymmetry in cross section.

Hereinafter, the process of forming the light guide pattern portion 11 will be described in detail.

As shown in FIG. 4, a pattern is formed on the light guide plate 12 that receives data about the pattern of the light guide pattern unit 11 from the pattern design unit 41 and matches the coordinate value of the pattern through the control unit 42. The position signal corresponding to the desired area is sent to the laser scan mirror 43.

The laser scanning mirror portion 43 adjusts the direction of the laser beam by coupling the reflecting mirrors 45a and 45b on the axis of the galvanometer 44 which rotates microscopically to the left and right or up and down, for example. As is known, the galvanometer 44 controls the rotation angle and direction by installing a mechanism such as a coil on the rotating shaft, and when the current is cut off, the rotating shaft is returned to its original position by the restoring force of the coil. come.

Meanwhile, a pulse signal synchronized to the laser scan mirror 43 is transmitted to the laser oscillator 46 through the controller 42 to selectively scan the laser beam to an area where the pattern of the light guide plate 12 is to be formed. do.

Accordingly, the laser beam output from the laser oscillation unit 46 is changed in the traveling direction by at least one reflector 45a, 45b coupled to the axis of the galvanometer 44 in a predetermined direction, the lens unit While passing through 47, the light guide pattern part 11 is formed on one surface of the light guide plate 12.

As such, the light guide pattern portion 11 formed on the light guide plate 12 is not formed on the XY stage by linear reciprocating motion by mechanical driving, but instead of the laser scan mirror portion 43 with respect to the laser oscillation portion 46. The positions of the reflectors 45a and 45b are relatively adjusted to deflect the laser beam in the region where the pattern of the light guide plate 12 is formed.

In the light guide pattern portion 11 processed in this manner, grooves having an asymmetric shape are formed according to the deflection angle of the laser beam.

5A to 5C show a cross section of the light guide pattern portion 11.

Referring to the drawings, when the laser beam is irradiated perpendicularly to the light guide plate 12, a first groove 11a is formed in the light guide plate 12. The first groove 11a has a bilaterally symmetrical shape since the laser beam oscillated from the laser oscillator 46 as described in FIG. 4 is incident perpendicularly to the light guide plate 12 through the laser scan mirror 43. (FIG. 5A)

When the laser beam oscillated from the laser oscillation unit 46 is incident to one side of the light guide plate 12 at a predetermined angle by the laser scan mirror unit 43, a second groove 11b is formed in the light guide plate 12. It is done. Since the second groove 11b is incident on the light guide plate 12 at an angle of inclination from the vertical axis of the laser scan mirror portion 43 and the light guide plate 12, the cross section has an asymmetrical shape (FIG. 5B). )

On the other hand, the laser beam is incident on the region of the light guide plate 12 opposite to the region where the second groove 11b is formed to be inclined by β angle from the vertical axis of the laser scan mirror portion 43 and the light guide plate 12. The third groove 11c is asymmetrically formed in the direction opposite to the inclination direction of the second groove 11b. (FIG. 5C).

As a result, the laser beam oscillated from the laser oscillation unit 46 is incident on the light guide plate 12 through the laser scan mirror unit 43, and the laser beam is moved to the left and right regions with respect to the center of the light guide plate 12. A plurality of grooves having an inclined asymmetrical shape according to the deflection angle of is formed.

At this time, the degree of asymmetry of the grooves increases in response to the increase of the inclination angle as the grooves move away from the optical central axis with respect to the laser beam. Accordingly, the scattering and diffusion of the light is more excellent, and the uniformity of luminance may be adjusted according to the shape of the pattern and the density of formation in the light guide plate 12.

On the other hand, matters to be considered in designing the light guide pattern portion 11 is to improve the brightness and ensure uniformity.

The luminance is determined by optimizing the processing method and the area where the pattern portion is formed from the light guide plate 12. In the case of using a non-contact method such as a laser system, the luminance is slightly improved since the etching degree is larger than that of the contact method. Indicates.

The uniformity should be the highest at the center of the light guide plate 12 and gradually decreases toward the periphery. Generally, the ratio of the peripheral portion to the center portion, or the minimum luminance to the highest luminance, is required to be 70% or more. This uniformity can be controlled by controlling the size of the light guide pattern portion 11 or the spacing between patterns in the processing using a laser system.

As shown in FIG. 6, the light guiding region of the light guide plate 12 is divided into a peripheral portion (I), a central portion (III), and an intermediate portion (II) between the peripheral portion (I) and the central portion (III). It is preferable that the arithmetic mean value of the overall luminance is maintained in the relation of I <II <III.

In the case of the edge type surface light source device, since the intensity of light is the highest at the periphery of the light guide plate 12 adjacent to the light emitting means 13, the size or density of the light guide pattern portion 11 is controlled. Is possible.

As described above, patterning the luminance ratio of the peripheral portion I to the central portion III of the light guide plate 12 to 70% or more can maintain the uniformity characteristic of the luminance. In this case, region I corresponds to 100% of the light guide region, region II corresponds to 36% of the light guide region, and region III corresponds to 4% of the light guide region.

Based on this, the light guiding efficiency according to the line width change of the light guiding pattern part 11 is measured for each area as follows.

FIG. 7 is a graph illustrating light guiding efficiency for each light guiding region according to line width change of the light guiding pattern 11 by cutting along line IV-IV of the light guiding plate 11 of FIG. 6.

At this time, the X-axis is to display each area separately, the Y-axis represents the light guide efficiency. Here, the light guiding efficiency is divided into a plurality of light guiding plates 12 having a processing area of 300 × 300 mm, the luminance of the center point of each divided surface is measured, and then the average when the uniformity of the luminance satisfies 70% or more. With the luminance as the reference I ₀ , the highest luminance corresponding to the line width change of the pattern is shown as the relative luminance I.

Table 1 is a value obtained by numerically guiding the light guide efficiency of each region according to the line width of the light guide pattern portion 11.

Ⅰ Area Area II Ⅲ area Area II Ⅰ Area A 0.78 0.89 One 0.89 0.78 B 0.82 0.88 One 0.88 0.82 C 0.89 0.92 One 0.92 0.89 D 0.98 0.97 One 0.97 0.98 E 1.05 1.02 One 1.02 1.05 F 1.16 1.09 One 1.09 1.16

Referring to FIG. 7 and Table 1, in the case where the line width of the light guide pattern portion 11 is 300 micrometers (curve A), each of I, II, III, II, and I regions in which the light guide plate 12 is cut in IV-IV The light guide efficiencies were 0.78, 0.89, 1, 0.89, 0.78, showing a gentle upward convex curve.

When the line width of the light guide pattern portion 11 is 400, 500 micrometers (B and C curves), the light guide efficiency is 0.82, 0.88, 1, 0.88, 0.82, and 0.89 for each of I, II, III, II, and I regions. , 0.92, 1, 0.92, 0.89, showing a more gentle convex curve than the A curve.

When the line width of the light guide pattern portion 11 is 600 micrometers (D curve), the light guide efficiency is 0.98, 0.97, 1, 0.97, and 0.98 for each of I, II, III, II, and I regions.

On the other hand, when the line width of the light guide pattern portion 11 is 700 and 800 micrometers (E, F curve), the light guide efficiency is 1.05, 1.02, 1, 1.02, 1.05 and 1.16, 1.09, 1, 1.09 for each region. , 1.16, exhibiting a slightly concave curve approximately downward.

As a result, when the line width of the light guide pattern portion 11 becomes 600 micrometers or more, the relative luminance of the peripheral portion I of the light guide plate 12 incident from the light emitting means 13 becomes high, resulting in a uniformity characteristic of the luminance of 70% or more. Is achieved, but it becomes difficult to satisfy the relationship of I <II <III, which hinders the appearance quality.

As described above, the surface light source device having the asymmetric light guide pattern portion according to the present invention adjusts the relative positional relationship between the laser scan mirror portion and the laser oscillation portion of the laser system by deflecting the laser beam to the light guide plate and scanning the light guide plate. As the processing time for forming the light guide pattern portion can be reduced, the production efficiency can be improved, and thus the manufacturing cost is reduced. In addition, while maintaining the line width of the light guide pattern portion at a constant width, it has an asymmetric structure, it is possible to further improve the scattering, reflection and diffusion of light.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (4)

In the surface light source device having a light guide plate for changing the path of light, at least one light emitting means provided on the side of the light guide plate and a reflecting plate provided below the light guide plate, And a plurality of light guide patterns formed with a large inclination angle of an asymmetric groove formed toward the periphery of the light guide plate according to the deflection angle of the laser beam incident on the bottom surface of the light guide plate. delete delete delete