CN110398801B - Light guide plate scattering mesh point design method based on scattering efficiency - Google Patents

Abstract

The present invention discloses a method for designing scattering dots of a light guide plate based on scattering efficiency, and belongs to the technical field of liquid crystal display and lighting. The method determines the structural type of the scattering dots of the light guide plate by the size of the scattering efficiency. After the scattering dot structural type is determined, the density of the dots is set as an optimization variable, the minimum interval between the dots is a constraint condition, and the uniformity of the light output illumination is an evaluation function. The density of the dots is optimized to obtain the density arrangement of the scattering dots of the light guide plate, which solves the problem that the production cost of the light guide plate is high and it cannot be further optimized due to the adjustment and arrangement of the dot structure and the dot density based on experience at present, so that the optimal dot structure can be quickly selected in the design process of the dot structure of the light guide plate, and the dot structure determined according to the scattering efficiency reduces the number of dots by about 60% under the premise of meeting the same light output uniformity requirements, and the processing time and cost of the light guide plate are greatly reduced.

Description

A Design Method of Scattering Dots of Light Guide Plate Based on Scattering Efficiency

technical field

The invention relates to a method for designing scattering dots of a light guide plate based on scattering efficiency, and belongs to the technical field of liquid crystal display and lighting.

Background technique

Liquid crystal displays (LCDs) have been widely used in various electronic devices such as TVs, computers, and mobile phones. As a passive light-emitting display device, LCDs require backlight modules (BLMs) to provide illumination, so the brightness and uniformity of BLMs Optical properties such as optical properties directly affect the display quality of the LCD, and the Light Guide Plate (LGP) is the most important part of the BLM. At present, the mainstream side-entry LGP in the market mainly uses the scattering dots distributed on the bottom surface to destroy the total reflection of light in the LGP, and exports the light incident from the side from the upper surface. The light energy utilization rate and light uniformity of the LGP become the key indicators and Research hotspots.

A large number of studies have shown that the density distribution (density level) and structure of scattering dots will directly affect the light energy utilization and uniformity of LGP. At present, the optimization design research for LGP mainly focuses on two aspects: one is to achieve the optimization purpose by changing the structure of the network point, such as using a hemisphere, a cone, etc., and changing the radius, height, angle, etc. of the network point. Although this optimization method can be There are many parameters to adjust, but it is cumbersome and difficult to process; the other is to determine the network structure and optimize the density distribution of the network. The advantages are that the optimization parameters are single, easy to master, and convenient for industrial processing.

In fact, regardless of the structure of the dots, the LGP can be uniformly luminous by optimizing the dot density distribution, but the light energy utilization rate may vary greatly, and the light energy utilization rate of the dots with high scattering efficiency will also be higher. At present, the technicians of the light guide plate enterprises mainly rely on experience to select different network point structures to adjust and arrange the network point density, and then process them, and finally make further adjustments according to the actual test results. Even experienced technicians have to repeat the whole process many times, which is time-consuming, labor-intensive and material-intensive, which greatly increases the production cost of the light guide plate. On the basis of the utilization rate of light energy and the uniformity of light output that can be achieved in the prior art, it is impossible to further optimize the dot structure and density distribution of the light guide plate.

SUMMARY OF THE INVENTION

In order to solve the problems of high production cost and cumbersome process of the light guide plate caused by adjusting and arranging the dot structure and dot density based on experience in the existing light guide plate design process, the present invention provides a light guide plate scattering dots based on scattering efficiency. design method.

A method for designing scattering dots of a light guide plate, the method comprising:

The structure type of scattering dots of the light guide plate is determined according to the difference of scattering efficiency P, the scattering efficiency P is the ability of dots to derive light through scattering, and the scattering efficiency P of dots is:

where e _o is the light energy scattered by the mesh point and emitted from the surface of the light guide plate, and e _i is all the light energy incident on a single mesh point on the bottom surface of the light guide plate;

After determining the structure type of scattering dots, the density of dots is set as the optimization variable, the minimum interval between dots is the constraint condition, and the uniformity of illuminance is the evaluation function. arrange;

The light guide plate is designed according to the determined structure type and density of scattering dots of the light guide plate.

的不同确定导光板的散射网点结构类型，其中，平均散射效率

为：Optionally, the determination of the scattering dot structure type of the light guide plate according to the difference in scattering efficiency P is based on the average scattering efficiency of the dots.

The difference determines the type of scattering dot structure of the light guide plate, where the average scattering efficiency

for:

E is the luminous flux of the light-emitting surface, and N is the number of dots in the effective light-emitting area of the light guide plate.

的不同确定导光板的散射网点结构类型，包括：Optionally, the average scattering efficiency according to the dots

The difference determines the type of scattering dot structure of the light guide plate, including:

Determine the size relationship of the effective luminous area of different dot structures under the condition that the luminous flux E of the light-emitting surface and the dot density distribution are the same;

The type of scattering dot structure of the light guide plate is determined according to the size relationship of the effective light emitting area.

Optionally, determining the type of scattering dot structure of the light guide plate according to the size relationship of the effective light emitting area is to select the dot structure with the smallest effective light emitting area under the same condition of the luminous flux E of the light exit surface as the scattering dot structure of the light guide plate.

Optionally, according to the size relationship of the light-emitting area, the structure type of the scattering dots of the light guide plate is determined and/or the density of the dots is optimized to obtain the density arrangement of the scattering dots of the light guide plate, and the Lighttools software tool or the Tracepro software tool is used.

The second object of the present invention is to provide a light guide plate, the structure type and density of scattering dots of the light guide plate are obtained by the above method.

Optionally, the type of scattering dot structure of the light guide plate is a triangular prism dot structure.

Optionally, the inclination angle of the scattering dots of the light guide plate is 60±2°, and the inclination angle is the angle between the scattering surface of the dots and the bottom surface of the light guide plate.

The third object of the present invention is to provide a backlight module, wherein the light guide plate in the backlight module is the above-mentioned light guide plate.

The fourth object of the present invention is to provide a method for designing the scattering dots of the above-mentioned light guide plate and/or the application of the above-mentioned light guide plate in the technical field of liquid crystal display and lighting.

The beneficial effects of the present invention are:

The light guide plate scattering dot design method based on the scattering efficiency proposed by the present invention determines the structure type of the scattering dots of the light guide plate by the size of the scattering efficiency. The minimum interval of the light guide plate is the constraint condition, and the uniformity of the illuminance is the evaluation function. The density of the dots is optimized to obtain the density arrangement of the scattering dots of the light guide plate, which solves the problem that the current design process of the light guide plate relies on experience to adjust the dot structure and dot density. The problems of high production cost and cumbersome process of the light guide plate caused by the arrangement make it possible to quickly select the optimal dot structure in the process of designing the dot structure of the light guide plate, and the dot structure determined according to the scattering efficiency can achieve the same light output. Under the premise of uniformity and brightness requirements and the current limit value of light energy utilization, the number of dots is greatly reduced, and the number of dots is reduced by about 60%, which greatly reduces the processing time and cost of the light guide plate; Compared with the hot-pressed dot structure adopted in the prior art, the triangular prism light guide plate scattering dot structure designed by the method proposed by the invention has the advantages of simpler structure, easier demoulding and more accurate processing.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort.

FIG. 1 is a structural diagram of a backlight module.

Figure 2(a) is the surface microstructure diagram of the LGP dots formed by laser processing and hot pressing;

Figure 2(b) is a diagram of the internal microstructure of the LGP dots formed by laser processing and hot pressing;

Figure 2(c) is the actual luminous effect of the BLM of the hot-pressed LGP.

3 is a graph showing the comparison results of the ratio T% of the area of the light emitting area to the upper surface area of the LGP and the light energy utilization ratio η under the same condition of setting the luminous flux E of the smooth surface for different dot structures.

FIG. 4 is a structural diagram of a triangular prism dot structure adopted in the present invention.

Fig. 5 is a graph showing the simulation result of the "ring mountain" shaped dot structure shown in Fig. 2(a).

FIG. 6 is a diagram showing a simulation result of the triangular prismatic dot structure shown in FIG. 4 .

Figure 7 is the illuminance distribution diagram corresponding to different γ obtained by ray tracing in Lighttools software.

FIG. 8 is a graph showing the effect of γ on the utilization rate of light energy.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

In the prior art, the design of the dot structure and density arrangement in the light guide plate is based on the requirements of light energy utilization rate and light emitting uniformity. The better the design scheme, the better; but the utilization rate of light energy cannot be improved without restrictions. If the utilization rate of light energy is no longer improved, the dot structure and density arrangement of the light guide plate cannot be further optimized, or only relying on Experience and infinite attempts can lead to a more optimized method.

The present application just breaks through this bottleneck problem in the design process of the light guide plate, and proposes a scheme to further optimize the dot structure and density arrangement of the light guide plate with scattering efficiency, so as to achieve the existing light energy utilization rate and light output. Under the premise of the requirement of uniformity, the dot structure and density arrangement of the light guide plate are optimized by taking the scattering efficiency as the standard. The cost is greatly reduced, and at the same time, compared with the existing optimization method relying on experience and infinite attempts, the present invention greatly saves the design time and further reduces the design cost of the light guide plate.

The scheme of the present invention is described in detail below:

Considering that when designing the Light Guide Plate (LGP), the enterprise usually assembles it into a Backlight Module (BLM) for actual luminescence detection, so all the simulation and experimental results of the present invention are derived from the BLM, and its structure is shown in Figure 1. shown. The LGP specification is 173mm 296mm 0.55mm, the material is polymethyl methacrylate (PMMA), and the refractive index is 1.49. The light source is an LED strip, which consists of 46 LEDs arranged at equal intervals, the exit angle is 120°, and the luminous flux of each LED is 22lm. The reflectivity of the bottom reflective film is set to 50%, the optical property of the diffuser film is set to 25° Gaussian scattering, the properties of the prism film are consistent with the BEF II produced by 3M Company in the United States, and the microprisms of the two films are perpendicular to each other.

Example 1:

This embodiment provides a method for designing scattering dots on a light guide plate, the method comprising:

Determine the type of scattering dot structure of the light guide plate according to the different scattering efficiency;

After determining the structure type of scattering dots, the density of dots is set as the optimization variable, the minimum interval between dots is the constraint condition, and the uniformity of illuminance is the evaluation function. arrange;

The light guide plate is designed according to the determined structure type and density of scattering dots of the light guide plate.

Different dots have different ability to derive light through scattering. Let the energy of all light incident on a single dot on the bottom of LGP be e _i , and the energy of light scattered by dots and exiting from the upper surface of LGP is e _o , and the scattering efficiency P of this dot is defined as :

即：But in fact, P is not only related to the structure of the dot, but also to the angle of light incident on the dot; therefore, when dots with the same structure in LGP are located at different positions, the scattering efficiency of dots may be different, especially in LGP Edge dots. Since the e _o of a single dot is difficult to detect, and the luminous flux E of the light-emitting surface can be directly detected, the average scattering efficiency of the dot is considered in this application.

which is:

In the formula, N is the number of dots in the effective light-emitting area of the light guide plate. It is also known that E=ηE ₀ , η is the utilization rate of light energy, and E ₀ is the total luminous flux of the light source, so substitute the above formula (2) to get:

a is the bottom area of a single dot, then e _i ∝aE ₀ , we know that

是网点平均密度，故导光板有效发光区域的网点数量N可表示为：S is the area of the effective light-emitting area; ρ is the dot density, that is, the ratio of the bottom area of a single dot to the area of the grid where it is located;

is the average density of dots, so the number of dots N in the effective light-emitting area of the light guide plate can be expressed as:

Combining the above formulas (4) and (5), the following formula (6) is obtained

与η成正相关性，与

和S成负相关性。It can be seen from (6) that,

has a positive correlation with η, and

negatively correlated with S.

The dot structure of the "ring mountain" structure shown in Figure 2(a) is the dot structure commonly used in the prior art. The LGP dot structure is formed by laser spotting and hot pressing, that is, the microstructure is processed on the surface of the steel plate with a laser, and then The microstructure is transferred to the LGP by the hot pressing process, and the microstructure shown in Fig. 2(a) is formed on its surface, and the structure shown in Fig. 2(b) is formed inside, which is the scattering dots of the hot-pressed LGP. . It can be seen that the structure of the dots is very complex, with an irregular "ring mountain" on the surface and a spherical cap with a small curvature inside. The entire dot runs through the bottom of the LGP, the dot is about 2μm above the bottom, and the depth of the bottom is about 3μm. Figure 2(c) shows the actual luminous effect of the BLM, and the uniformity measured by the 13-point measurement method is 84%.

In order to determine the dot structure with higher scattering efficiency, the present application for three different dot structures of triangular prism shape, hemispherical shape and conical shape, set the luminous flux E of the light-emitting surface under the same conditions to compare the area of the light-emitting area and the area of the upper surface of the LGP. The ratio T% and the light energy utilization rate η, the comparison results are shown in Figure 3, considering T% and η comprehensively, determine the same conditions of luminous flux E, the effective luminous area of the triangular prismatic dot structure is the smallest, so it is determined that the dot structure is triangular prism .

It should be noted that, for the convenience of comparison, in the above process, the three different dot structures are set to have the same bottom area and the same height; The size relationship between the effective light-emitting areas of different dot structures can also be set in other ways, such as the same bottom area but different heights, or other ways, which are not limited in the present invention.

After determining the triangular prismatic dot structure (as shown in Figure 4), continue to use the Lighttools software tool for ray tracing, set the density of the dots as the optimization variable, the minimum interval between the dots as the constraint condition, and the uniformity of the illuminance is The evaluation function is used to optimize the density of the dots to obtain the density arrangement of the scattering dots of the light guide plate;

For the convenience of comparison, the present application compares the network structure shown in Figure 2 and Figure 4:

Both of them are set to achieve 84% uniformity of light output. The simulation results of the "ring mountain"-shaped dot structure shown in Figure 2(a) are shown in Figure 5, and the simulation results of the triangular prism-shaped dot structure shown in Figure 4 are shown in Figure 6 The simulation results show that in order to achieve 84% uniformity of light output, the number of dots required for the "ring mountain"-shaped dot structure shown in Figure 2 is 1,269,957, and its light energy utilization rate is 35%; while the triangular prism shown in Figure 4 The number of dots required for the shape dot structure is only 489,914, and its light energy utilization rate is 43%.

It can be seen that in the embodiment of the present invention, the dot scattering efficiency is used as the judgment condition for determining the scattering dot structure of the light guide plate, which does not need to be repeated many times for comparison, and under the premise of satisfying the uniformity of light output, the density of the dots is further set as the optimization Variable, the minimum interval between the dots is the constraint condition, and the uniformity of the illuminance is the evaluation function. The density of the dots is optimized to obtain the density of the scattering dots of the light guide plate, which reduces the required number of dots by about 60%, making The processing time and cost of the light guide plate have been greatly reduced.

Embodiment 2

This embodiment provides a light guide plate, and the dot structure of the light guide plate is determined by the design method for scattering dots of the light guide plate described in the first embodiment. As shown in FIG. 4 , the dot structure of the light guide plate provided by this embodiment is a triangular prism. , the inclination angle γ of the scattering dots is 60±2°, and the inclination angle γ is the angle between the scattering surface of the dots and the bottom surface of the light guide plate.

It should be noted that when the triangular prism-shaped dot structure is set on the light guide plate, one side of the triangular prism is set on the plane of the light guide plate, and the other two sides are used as the dot scattering surface, so the other two sides of the triangular prism are The bottom angle of is the dot inclination angle.

In order to determine the relationship between the inclination angle γ of the scattering dots and the utilization rate of light energy η, the inclination angle γ is set to take a value in the range of 5° to 90°, and the value interval is 5°. Perform ray tracing in Lighttools software, and the result is shown in Figure 7. Figure 7 is the illuminance map obtained from the incident light source from below the light guide plate. It can be seen from the figure that when γ≤20°, the illuminance value on the low beam side is low, indicating that the dots on the low beam side do not effectively scatter the incident light, and most of the light propagates to the other end and is reflected back, while the high beam side is reflected. The dot density is high, so the illuminance value is relatively high. When γ>20°, the illuminance value on the near-beam side gradually increases, indicating that the dots on the low-beam side gradually scatter most of the light, while the illuminance value on the far-beam side also decreases gradually, even to 0, because there is not much remaining light energy.

之间的关系，图8给出了η随γ的变化曲线。显然，当γ在0～20°时，η与γ呈正相关。γ达到25°～60°时，η几乎达到饱和，在41％左右，这时η与γ几乎无相关性，而有效发光区域面积S变小，即发光的网点变少，说明

变大，两者呈负相关，与理论推导一致，当γ＝60°时，

达到最高。当γ>60°时，η开始下降，有效发光区域更小，η却与γ呈负相关。For further analysis of BLM's η and

The relationship between η and γ is shown in Fig. 8. Obviously, when γ is between 0 and 20°, η is positively correlated with γ. When γ reaches 25° to 60°, η almost reaches saturation and is about 41%. At this time, there is almost no correlation between η and γ, and the area S of the effective light-emitting area becomes smaller, that is, the number of light-emitting dots decreases.

becomes larger, the two are negatively correlated, which is consistent with the theoretical derivation. When γ=60°,

reach the highest. When γ>60°, η begins to decrease, and the effective light-emitting area is smaller, but η is negatively correlated with γ.

对BLM优化设计的影响，用γ＝55°,60°,65°时的网点结构对BLM重新进行均匀性优化设计。将网点的密度设置为优化变量，网点之间的最小间隔作为约束条件，出光面照度均匀度作为评价函数，利用Lighttools中的背光图案优化功能(BPO)进行自动优化，结果列于表1。可见，三者的均匀度U都可达到83％以上，而且网点数量M均减少60％以上，而η仅下降2％，其中γ＝60°的三棱柱网点所用网点数量最少，η最大，说明

最高，可见用较少的网点达到使BLM均匀优化的目的。For the analysis of dot scattering efficiency

Influence on BLM optimization design, the uniformity optimization design of BLM is re-designed with the dot structure when γ=55°, 60°, 65°. The density of the dots is set as the optimization variable, the minimum interval between dots is used as the constraint condition, the illuminance uniformity of the light-emitting surface is used as the evaluation function, and the backlight pattern optimization function (BPO) in Lighttools is used for automatic optimization. The results are listed in Table 1. It can be seen that the uniformity U of the three can reach more than 83%, and the number of dots M is reduced by more than 60%, while η is only decreased by 2%. Among them, the triangular prism with γ=60° uses the least number of dots and η is the largest.

The highest, it can be seen that the goal of uniform optimization of BLM can be achieved with fewer dots.

In the actual production of the LGP master, the reduction in the number of dots will reduce the processing time of the LGP, and also reduce the energy consumption, thereby saving the production cost and improving the production efficiency. The analysis found that the main reasons for the slight decrease of η in Table 1 are: one is that the amount of light transmitted farther and absorbed increases, and the other is that the boundary area of light emission increases, and the amount of boundary loss increases.

Table 1 Comparison of results before and after BLM optimization

It can be seen from Table 1 that when γ=55°, 60°, and 65°, the three uniformities all reach more than 83%, and the number of dots M is reduced by more than 60%. It can be seen that the light guide plate based on the scattering efficiency provided by this application is used The scattering mesh point design method greatly reduces the number of mesh points on the premise of meeting the user's requirements for light uniformity, which greatly reduces the processing time and cost of the light guide plate.

Some steps in the embodiments of the present invention may be implemented by software, and corresponding software programs may be stored in a readable storage medium, such as an optical disc or a hard disk.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (9)

1. A design method for light guide plate scattering dots, characterized in that the method comprises: The structure type of scattering dots of the light guide plate is determined according to the difference of scattering efficiency P, the scattering efficiency P is the ability of dots to derive light through scattering, and the scattering efficiency P of dots is:

where e _o is the light energy scattered by the mesh point and emitted from the surface of the light guide plate, and e _i is all the light energy incident on a single mesh point on the bottom surface of the light guide plate; After determining the structure type of scattering dots, the density of dots is set as the optimization variable, the minimum interval between dots is the constraint condition, and the uniformity of illuminance is the evaluation function. arrange; Design the light guide plate according to the determined structure type and density of scattering dots of the light guide plate; The determination of the structure type of the scattering dots of the light guide plate according to the difference of the scattering efficiency P is based on the average scattering efficiency of the dots

The difference determines the type of scattering dot structure of the light guide plate, where the average scattering efficiency

for:

E is the luminous flux of the light-emitting surface, and N is the number of dots in the effective light-emitting area of the light guide plate. 2. The method according to claim 1, wherein the average scattering efficiency according to the dots

The difference determines the type of scattering dot structure of the light guide plate, including: Determine the size relationship of the effective luminous area of different dot structures under the condition that the luminous flux E of the light-emitting surface and the dot density distribution are the same; The type of scattering dot structure of the light guide plate is determined according to the size relationship of the effective light emitting area. 3. The method according to claim 2, wherein, determining the type of scattering dot structure of the light guide plate according to the size relationship of the effective light emitting area is to select the dot structure with the smallest effective light emitting area under the same luminous flux E as the guide. The scattering dot structure of the light panel. 4 . The method according to claim 3 , wherein the structure type of the scattering dots of the light guide plate is determined according to the size relationship of the light-emitting area and/or the density of the dots is optimized to obtain the density arrangement of the scattering dots of the light guide plate. 5 . cloth, using Lighttools software tool or Tracepro software tool. 5 . A light guide plate, characterized in that the structure type and density arrangement of the scattering dots of the light guide plate are obtained by the method of any one of claims 1-4 . 6 . The light guide plate according to claim 5 , wherein the type of scattering dot structure of the light guide plate is a triangular prism dot structure. 7 . 7 . The light guide plate according to claim 5 , wherein the inclination angle of the scattering dots of the light guide plate is 60±2°, and the inclination angle is the angle between the scattering surface of the dots and the bottom surface of the light guide plate. 8 . 8. A backlight module, wherein the light guide plate in the backlight module is the light guide plate according to any one of claims 5-7. 9. The design method of the scattering dots of the light guide plate according to any one of claims 1-4 and/or the application of the light guide plate according to any one of claims 5-7 in the field of liquid crystal display and lighting technology.

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