KR100897804B1 - Pattern-graved light guide plate of back light unit - Google Patents

Abstract

The present invention relates to a light guide plate for a backlight unit formed by a method of forming a pattern on a surface of a light guide plate using a laser device and forming a curved pattern depth profile, and more particularly, to form a pattern on one surface of the light guide plate. The depth of the pattern is changed according to the distance from the light source, thereby minimizing the reflection of light from the light incident part within the reference and having a pattern formed by a control method of the pattern forming process that can transmit the light source to the light emitting part with minimum loss. It relates to a light guide plate.

Light guide plate, pattern depth, control system, laser device

Description

Light guide plate for patterned backlight unit {PATTERN-GRAVED LIGHT GUIDE PLATE OF BACK LIGHT UNIT}

The present invention relates to a method of forming a pattern on a surface of a light guide plate using a laser device, and to forming a curved pattern depth profile, and a light guide plate for a backlight unit formed by the method. More specifically, a pattern is formed on one surface of the light guide plate. In forming, the light guide plate having a pattern formed by a pattern forming method that can form a pattern deeper away from the light source to minimize the reflection of light from the light incident portion within the reference and to transmit the light source with a minimum loss to the light distribution portion. .

The most widely commercialized and practical liquid crystal display device in the flat panel display field requires a light emitting device called a back light unit because it does not emit light. The performance of the liquid crystal display device is not only its own characteristics, but also the backlight. It depends a lot on the performance of the unit.

The backlight unit is mainly composed of a light guide plate, an optical film, a lamp assembly, and a mold frame. The liquid crystal display is classified into a direct light and an edge light according to the lamp position of the backlight unit.

The direct method is a method in which light generated from a light source is uniformized using a diffuser plate and incident on the liquid crystal panel. The edge method is a method in which light generated from the side of the light guide plate is reflected by the light guide plate and incident on the liquid crystal panel. In recent years, in line with the trend toward thinner and lighter liquid crystal display (LCD) modules, the edge method is more preferred.

In the edge-type backlight unit, the lamp assembly is installed on the side of the light guide plate, and includes a lamp that emits light and a lamp reflection sheet that is formed in a shape surrounding the lamp to reflect the light emitted from the lamp to the light guide plate.

Since the backlight unit employing the edge method preferably scatters the emitted light uniformly to form uniform brightness on the light guide plate, a pattern of a predetermined shape should be formed on one surface of the light guide plate.

Conventional methods for forming a pattern on a light guide plate include a method of forming a mechanical V-notch using diamond, a printing method, and a method of forming a pattern using a laser.

First, the mechanical cutting method by diamond has a disadvantage that its speed is relatively slow, productivity is low, light is not uniformly scattered due to the roughness of the processing surface, and the reproducibility of reproducing the intended pattern shape is inferior.

In addition, the printing method has a problem in that when the corrosion solution is used after performing exposure and development by a mask pattern and a corrosion solution penetrates between the mask and the light guide plate to form a fine pattern, and the light guide plate is a thin plate, reproducibility is achieved. Falling problems and environmental problems due to the use of corrosion solutions occur.

Therefore, in recent years, the method of forming the pattern of a light guide plate using a laser device is increasing.

The conventional method of forming a pattern of a light guide plate using a laser device is to form a pattern on the surface of the light guide plate by oscillating the laser by adjusting three parameters, the X-axis spacing, the Y-axis spacing, and the size of the individual pattern on the light guide plate plane. By way of example, the shape of the thus formed pattern is as shown in Figure 1 below.

1 is a view showing a pattern shape of a light guide plate formed by a conventional laser pattern forming method.

As shown in an enlarged circle in the circle of FIG. 1, the individual patterns of the light guide plate formed by the conventional laser pattern forming method are in the form of bars, and the shape of the individual patterns in the bar form is the X axis interval A and the Y axis. It is formed repeatedly by varying the interval B and the size C.

The light guide plate in which the pattern is formed by the pattern forming method by the conventional laser method has an effect of increasing the brightness by 8 to 10% compared to the printing method, and the corrosion solution as the surface of the light guide plate is negatively processed by the laser. It is an environmentally friendly method that does not cause any environmental problems due to use.

However, in the conventional laser apparatus, when the light guide plate pattern applied to the backlight unit is formed, the laser power is applied equally throughout the pattern forming process to form the same depth and shape of the individual patterns in the same batch, whereas the size and the individual patterns of the individual patterns are different. By adjusting only the X- and Y-axis spacing between patterns, there is a problem in that dark lines of low luminance are generated in the place where the amount of change is large in adjusting the Y-axis displacement.

In addition, a moiré phenomenon in which streaks or spots appear on the screen may occur due to irregular adjustment of the laser duty variation amounts in the X- and Y-axis directions.

 In addition, the factor for adjusting the laser duty is only three of the X-axis spacing, the Y-axis spacing, and the size of the bar, which has a problem in that convenience and efficiency are inferior in adjusting the luminance and pattern appearance.

The present invention is to solve the above problems, the object is to apply a different output amount for each pattern line during the laser processing of the light guide plate for the backlight unit, by forming a profile of the pattern depth, the dark line of the pattern generated during the laser processing of the existing pattern To prevent formation.

In addition, an object of the present invention is to form a dot-shaped individual pattern, and to control the laser duty value including the laser output amount for each dot, thereby improving luminance.

In addition, the present invention is to control the shape and size change of the individual pattern of the dot shape, to reduce the amount of change in the Y-axis displacement, and to regularly change the laser output in the X-axis and Y-axis direction, thereby preventing the occurrence of dark lines, The purpose is to prevent appearance defects.

In addition, an object of the present invention is to enable a more precise and efficient distribution of luminance and pattern appearance by adding a laser output amount, a dot shape, and a dot depth in addition to the adjustment factor of the laser duty according to the conventional method. .

In the light guide plate for a backlight unit having a pattern according to the present invention for solving the above problems, a light source is provided on one side, and the light source plate is formed on the X axis and the Y axis plane with the origin of the Y axis as the origin of the Y axis. Is formed, and the depth of the pattern is changed according to the Y-axis coordinate, and the intaglio intaglio patterns are spaced apart at predetermined intervals.

In the light guide plate for the backlight unit on which the pattern is formed, it is preferable that at least one of the width or the width of the respective individual patterns of the intaglio increases as the Y-axis coordinate is increased in order to prevent luminance improvement and appearance defects.

In addition, the light guide plate for the backlight unit having the above pattern is preferably formed with a pattern by a laser device for efficient pattern formation.

In addition, the pattern formed to change the depth of the pattern according to the Y-axis coordinates, it is preferable that the depth change profile is formed by the B-spline interpolation method in forming a smooth curved pattern depth profile.

According to the present invention, by forming a profile of the pattern depth by applying a laser duty value including a different output amount for each pattern line during laser processing of the light guide plate for the backlight unit, it is possible to prevent the dark line formation of the pattern generated during laser processing of the existing pattern. Can be.

Further, according to the present invention, it is possible to form a dot-shaped individual pattern, to control the laser duty value and the size change for each dot, thereby improving luminance.

In addition, according to the present invention, by controlling the shape and size change of the individual pattern of the dot shape, the amount of change in the Y-axis displacement is reduced, and the laser output in the X-axis and Y-axis directions is changed regularly to prevent the occurrence of dark lines. And prevent appearance defects.

In addition, according to the present invention, in addition to the adjustment factor of the laser duty according to the conventional method, the laser output amount, the dot shape and the depth of the dot are added, thereby enabling more precise and efficient luminance and pattern appearance distribution adjustment.

Hereinafter, a light guide plate for a backlight unit having a pattern according to the present invention will be described in detail with reference to the drawings.

2A is a cross-sectional view of a light guide plate for a backlight unit having a pattern according to the present invention, and FIG. 2B is a graph showing a profile of a pattern depth according to the present invention.

As shown in FIG. 2A, the light guide plate manufactured by the light guide plate pattern forming method for a backlight unit having a pattern according to the present invention has a profile in which the depth of the formed pattern increases as the Y coordinate increases. In this case, the light generated from the light source is reflected to have the same luminance. In addition, the shapes of the individual patterns each represent an intaglio elliptical shape.

As shown in FIG. 2B, the light guide plate of FIG. 2A has a profile of a depth T of a pattern appearing through a cross section of the light guide plate pattern when a light source is provided at both ends of the Y-axis of the light guide plate. Denoted as 'A') should draw a parabola as the Y coordinate increases.

Here, since the pattern formed on one line of the X axis having the same Y coordinate is applied with the same laser duty and focus, the width, width, and X-axis spacing between the individual patterns formed on the same line are the same.

Since the pattern formed on the light guide plate has to vary the depth of the pattern for each X-axis line, it is difficult to manufacture a conventional method using a laser device that applies a uniform laser output amount for each line.

That is, in addition to changing the laser duty to change the size of the individual pattern on the two-dimensional plane by controlling the short circuit of the pulse signal, the depth of the pattern formed for each line must be changed, and thus the output amount of the laser must be changed at once. There is a need for a control system in a laser device that processes a large amount of data.

In addition, when the parabolic profile is not properly formed, light is lost from the light source at the center of the screen without being transmitted, and the luminance of the center part is lowered than that of the peripheral part. The laser duty value and focus, including the output of the laser, must be adjusted appropriately for each pattern line.

In manufacturing a light guide plate for a backlight unit having a pattern according to the present invention, a laser device capable of adjusting a laser duty value including an output amount of a laser may be used. Preferably, the following control is performed to process a pattern quickly and efficiently. Utilize a laser device equipped with the system.

3 is a view showing a laser device used in the pattern forming process of the light guide plate for a backlight unit according to the present invention for solving the above problems.

As shown in FIG. 3, the light guide plate pattern forming laser apparatus 100 for a backlight unit according to the present invention includes a control system 10 for controlling the motion unit 20 and the output unit 30; Preferably, it consists of a servo motor and a servo drive, and is moved by the motion unit 20 and the motion unit 20 to control the movement of the output unit by the operation signal, and outputs a laser according to the output signal to form a pattern on the light guide plate. It comprises an output unit 30 to.

In addition, the control system 10 according to the present invention includes a programming unit 1 for executing a program for the operation of the output unit and the output of the laser; A local bus (2) connected to the programming unit (1) to receive and process pattern data of one line of the X axis corresponding to a specific Y coordinate of the light guide plate; A motion control unit 3 for controlling the motion unit 20 by using the data transmitted from the local bus 2; It includes an output control unit 4 for controlling the output unit 30 by using the data received from the local bus (2).

The programming unit 1 executes various control data and programs, aligns the CAD pattern data designed by the user according to the working order, and converts the CAD pattern data into a pulse signal which is a laser output signal. Is made of CPU.

The motion control section 3 and the output control section 4 are mounted on the same local bus 2, preferably made of a PCI bus (peripheral component interconnect bus), together with the input / output terminals 5 to be controlled in real time. The use of the local bus (2) as a PCI bus is a property that can be connected to any CPU as long as the PCI bus is commercialized as the local bus (2), and a bridge circuit corresponding thereto is provided even if the CPU types are different. This is because compatibility is secured.

As described above, when the control system 10 is constructed by mounting the motion control unit 3 and the output control unit 4 on one local bus 2, the control of the output change, which has been a problem of the prior art described above, is used. Therefore, there is an effect of preventing the processing time delay.

That is, the technical feature of the control system 10 is to provide a separate output change control unit 5 'as in the prior art, and after the pattern forming operation for one line of priority X axis is finished, In order to prevent the processing time delay when performing the output change process of adjusting the focus and the laser duty value including the laser output amount for the subordinated X axis line to perform the work, the output change control unit 5 'is excluded from the configuration. In addition, a motion system 3 and an output controller 4 are mounted on one local bus 2 to implement a control system capable of collectively processing changes in output signals in the local bus 2. .

A manufacturing method using the laser device 100 having the above configuration will be described.

The light guide plate pattern forming method for a backlight unit according to the present invention includes a data operation step (S10); It comprises a pattern forming step (S20).

The data operation step (S10) is performed by recognizing and recalling the pattern data designed and stored by the user in the programming unit 1 and aligning them according to the work order, and converting the pattern data into a pulse signal which is a laser output signal. This is a preliminary step before performing the pattern forming step (S20).

In the pattern forming step (S20), the local bus 2 sequentially receives processing data for each X-axis line corresponding to a specific Y-axis coordinate in the LGP among the pulse signals by a first-in-first-out method, and the motion control unit 3 and By transmitting an operation signal and an output signal to the output control unit 4, respectively, the output unit 30 is moved, and the output unit 30 adjusts the laser duty value and focus to form a pattern sequentially from the upper end to the lower end of the light guide plate. Is performed.

In the pattern forming step S20, in adjusting the duty value of the oscillated laser, the laser output amount is changed according to the coordinates of the Y-axis, so that the depth and the size of the pattern to be formed are deepened as the coordinates of the Y-axis are increased.

In addition, of course, the individual patterns formed in the same manner as the conventional method are performed by adjusting the X-axis and the Y-axis length, the X-axis and the Y-axis spacing.

The depth profile of the pattern thus formed forms a curved shape. As the curved shape is smoothly controlled, a more precise pattern can be formed, and a precise pattern is formed, so that light scattered from the pattern of the light guide plate can exhibit uniform luminance. . Therefore, a curve interpolation method for controlling the curve of the pattern formed in the programming unit 1 in advance so as to form a smooth curve in the depth profile of the pattern should be provided.

The interpolation method of the curve is possible by controlling the laser duty value to be changed for each line.

First, a case in which a progressive curve interpolation method is applied among the curve interpolation methods will be described. In the gradual change method, L1 is the first Y-coordinate value to be changed in the output unit 30, L2 is the second Y-coordinate value to be changed in the output unit 30, laser output amount to change La to the L1 position, and Lb at the L2 position. When the laser output amount to be changed, and the rate of change of the laser output amount when R1 is moved from the position L1 to the position L2, the rate of change of the laser output amount is derived by the formula R1 = (La-Lb) / (L2-L1), and A1. When the current Y-axis coordinate of the output unit, S is the laser output amount to be applied, the laser output amount applied to one X-axis line corresponding to a specific value on the Y-axis is derived by Equation S = R1 * A1. .

4A and 5A are graphs showing the results of changing the laser duty value and the focus (barrel increase value) by the gradual curve interpolation method as the Y-axis coordinates increase.

As shown in FIGS. 4A and 5A, when the gradual curve interpolation method is applied, since the shape of the curve is not smoothly connected, there is a possibility that a boundary line or a stripe or the like is formed on the pattern when the pattern is formed. Therefore, in order to prevent this, it is necessary to control the shape of the curve to be connected more smoothly.

Therefore, the present invention intends to use the B-spline interpolation method as the curve interpolation method.

In the B-spline curve interpolation method, if the coordinate values of a plurality of control points Po, P ₁ , P ₂ .... Pn on the curve, that is, the laser duty value for each line of the pattern are specified, the output control unit 4 By commanding the laser duty value at the time of performing the pattern forming operation of each line, it is applied to correct so that a curve connecting Po, P ₁ , P ₂ .... Pn is formed smoothly.

The equation applied to the B-spline interpolation method is a formula applied to a general B-spline curve, and a B-spline curve approximating each k-th position vector P _k at (n + 1) control points is (d- 1) In the order polynomial, d is an integer arbitrarily selected within the range 2≤d≤n + 1,

U is a parameter defined in a predetermined range u _min ≤ u _≤ u _max , and N _{k, d} (u) is a spline basis function, and is expressed by an equation of an ignition type as follows.

Where u _k is a knot, u ₀ , u ₂ ... u _m are knots in n + d + 1 intervals at m = n + d, and the set of knots is knot form a vector).

The spline basis function N _{k , d} (u) is defined in d intervals between control points in the kth to k + dth intervals, and is a function capable of local control of a curve affecting only the d intervals.

If the formation of the knot vector is non-uniform, an interpolation method using an equation defined by NURBS (Non-Uniform Rational B-Spline) can be used. .

That is, when n + 1 control points are given,

It is expressed as Here, ω _k is defined as the weight of the k-th control point, and the shape of the curve changes according to the weight and the spline basis function.

The results of controlling the laser duty value and the focus by using the B-spline curve interpolation method applying the above equations are as shown in FIGS. 4B and 5B, respectively.

As shown by the solid yellow lines of FIGS. 4B and 5B, when the B-spline curve interpolation method is used, a profile of a soft pattern may be formed without forming a step in a curve connecting each control point, thereby forming a pattern. Precise control can be performed so that no boundary is formed on the phase.

The light guide plate for a backlight unit according to the present invention having a pattern formed by the pattern forming method will be described through preferred embodiments and comparative examples of the present invention.

First, in order to examine the shape and arrangement of patterns formed by the pattern forming method and the size of individual patterns, as shown in FIG. 6, the light source of the light guide plate for the backlight unit (model name LTN154BT02) having a light source installed on one side is closest to the light source. The X-axis and Y-axis length, the arrangement form, and the shape of the individual pattern of the 10 mm portion of the light incident portion, the center portion, and the 10 mm portion of the incident light portion farthest from the light source were measured.

The measurement results are as shown in Table 1.

As shown in Table 1, the shape of the formed individual pattern is an elliptical shape having a long axis in the X-axis direction, the arrangement of which the pitch of the X-axis and Y-axis of the light incident portion is 747 탆, 554 탆 at the central portion, It can be seen that the spacing becomes 414 µm in the incident light portion, and the gap becomes denser from the incident light portion to the incoming light portion.

In addition, looking at the size of the formed individual pattern, the X-axis length is 170㎛ in the incident light, 236㎛ in the incident light, respectively, the length of the Y-axis is 72㎛ in the incident light, 112㎛ in the incident light, the depth of the pattern It can be seen that the size increases to 12 µm in the miner and 47 µm in the incident light section.

Next, this will be described with reference to FIG. 7, which is a graph showing a change curve of the density of the pattern. Figure 7a is a comparative example, a graph showing the pattern density of the X-axis line according to the change in the Y-axis coordinate of the pattern formed by the conventional pattern formation method, Figure 7b is a pattern formation method according to an embodiment of the present invention It is a graph which shows the pattern density of the X-axis line with the change of the Y-axis coordinate of the formed pattern.

7A and 7B, the horizontal axis of the graph indicates coordinates in the Y-axis direction of the light guide plate pattern, and the vertical axis of the graph indicates density for each line.

As shown in FIG. 7A, in the case of forming a pattern by a conventional pattern forming method, only three factors, the size of the two-dimensional image of the individual patterns, the X-axis spacing and the Y-axis spacing between the individual patterns, are used to control the luminance. Since adjustment is possible, there is no choice but to show an irregular pattern density for generating a constant luminance, and there is a possibility of moiré generation or dark line formation in a line with a rapid change in pattern density.

However, as shown in Figure 7b, it can be seen that the pattern density of the light guide plate formed by applying the pattern formation method according to the present invention increases with a constant slope as the Y-axis coordinates increase. In other words, it is possible to obtain a desired luminance distribution by smoothing the density change of the pattern.

The reason for the above phenomenon is that, when the pattern formation method according to the present invention is applied, the laser duty value including the laser output amount can be adjusted for each line, and accordingly, the two-dimensional image size and the individual pattern of the individual pattern for brightness control This is because the depth of individual patterns and the shape of individual patterns can be adjusted in addition to the three factors of the X-axis spacing and the Y-axis spacing therebetween.

8 is a CAD diagram showing the overall shape of a pattern of a light guide plate for a backlight unit according to an embodiment of the present invention and a comparative example. 8A is a CAD drawing of a pattern formed by a conventional pattern forming method as a comparative example, and FIG. 8B is a CAD drawing of a pattern formed by a pattern forming method according to an embodiment of the present invention.

As shown in FIG. 8A and FIG. 8B, the pattern of the light guide plate in which the pattern is formed according to the present invention has a sharp change in luminance due to the X-axis and Y-axis spacing variations as compared with the case in which the pattern is formed by the conventional method. It can be seen that there is no, and in particular, it can be found that stripes are formed in the lower end of Figure 8a, but in the present invention, as shown in Figure 8b, such a phenomenon does not appear.

Finally, the optical measurement evaluation of the light guide plate for a backlight unit having a pattern according to the present invention will be described.

The measurement temperature was measured at 23 ° C., humidity at 55% in a dark room, and in a windless atmosphere. The measuring instrument was measured after heat treatment on a light guide plate for 30 minutes using a TOPCON BM-7 fast at a distance of 500 mm and a 2 ° field. The measurement points were extracted by a 9-point measurement method that extracts 9 points on the pattern and a 25-point measurement method that extracts 25 points. Measurement points of the light incident part by the 25-point measurement method are as shown in FIG. 9.

10 is a view showing the optical measurement results according to the 25 point measurement method according to the embodiment and comparative example of the present invention, Figure 11 is a photo measurement result by the 25 point measurement method according to the embodiment and the comparative example of the present invention. The figure shown.

The average value of the 25 point measurement method shown in FIG. 10 is shown in Table 2 below.

[Table 2] Luminance Unit: Cd / m ²

division Conventional pattern dot Pattern dot of the present invention Luminance improvement 25-point optical measurement average 3,960 4,509 113.9%

 As shown in FIGS. 10, 11 and Table 2, it can be seen that the light guide plate having the pattern formed by the present invention is about 114% improved in brightness compared to the light guide plate having the pattern formed by the conventional method.

It has been described in detail above with reference to preferred embodiments of the present invention. However, the scope of the present invention is not limited to the above embodiments, but may be embodied in various forms of embodiments within the appended claims. Without departing from the gist of the invention as claimed in the claims, any person skilled in the art to which the invention pertains is considered to be within the scope of the claims of the invention to the various possible modifications possible.

1 is a pattern shape of a light guide plate formed by a conventional laser pattern forming method

2A is a cross-sectional view of a light guide plate for a backlight unit having a pattern according to the present invention;

Figure 2b is a graph showing the profile of the pattern depth of the light guide plate for a backlight unit with a pattern according to the present invention

3 is a laser apparatus used in the pattern formation process of the light guide plate for backlight units by this invention.

Figure 4a is a graph showing the result of changing the laser duty value by the gradual curve interpolation method as the Y-axis coordinates increase

4B is a graph showing the result of changing the laser duty value by the B-spline curve interpolation method as the Y-axis coordinates increase.

5A is a graph illustrating a result of changing a laser focus value by a gradual curve interpolation method as the Y-axis coordinates increase

5B is a graph showing the result of changing the laser duty value by the B-spline curve interpolation method as the Y-axis coordinates increase.

6 is a view showing a measurement portion of the light guide plate for a backlight unit according to an embodiment of the present invention.

7 is a graph showing a change curve of a pattern of a light guide plate for a backlight unit according to an embodiment and a comparative example of the present invention;

8 is a CAD drawing showing the overall shape of a pattern of a light guide plate for a backlight unit according to an embodiment of the present invention and a comparative example;

9 is a view showing a measuring point of the light incident part according to the embodiment and the comparative example of the present invention

10 is a view showing the optical measurement results by the 25-point measurement method according to the Examples and Comparative Examples of the present invention

11 is a view showing a light measurement result by the nine-point measurement method according to the embodiment and comparative example of the present invention

<Description of Signs of Major Parts of Drawings>

1: programming unit 2: local bus

3: motion controller 4: output controller

5: input / output terminal 10: control system

20: motion unit 30: output unit

100: laser device

Claims (5)

In a light guide plate for a backlight unit having a light source consisting of a line light source or a point light source is installed on one side, the X light source and the Y axis plane with the side where the light source is installed as the origin of the Y axis, the pattern is formed on one surface, As the Y-axis coordinates increase, the depth of the pattern increases, the X-axis and Y-axis spacing between the individual patterns of the elliptic intaglio decrease, and the lengths of the intaglio individual patterns in the X-axis and Y-axis directions Formed to increase, The change profile of the depth of the pattern in the Y-axis direction, the pattern spacing and the length of the individual pattern in the X- and Y-axis directions is formed by a B-spline or non-uniform vitrified B-spline (NURBS) interpolation method. The light guide plate for a patterned backlight unit, characterized in that as the Y-axis coordinates increase, the density of the pattern is formed smoothly without a step with a constant slope. The method of claim 1, The light sources are installed one by one at both ends of the light guide plate to face each other, and each side of each light source is installed as the origin of the Y axis, and the pattern depth increases as the distance from both light sources increases, thereby connecting the depth of the pattern in the Y axis direction. The light guide plate for a patterned backlight unit, characterized in that the pattern is formed so that one profile forms the most convex parabolic shape at the center of the light guide plate. delete The method according to claim 1 or 2, The light guide plate for a backlight unit having the pattern formed thereon is a pattern formed by a laser device. delete

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