Diffusion plate and preparation method thereof, backlight module and display equipment

Abstract

The invention discloses a diffusion plate and a preparation method thereof, a backlight module and display equipment, and belongs to the technical field of display, the diffusion plate comprises ellipsoidal bubbles and a base material, the base material comprises a lower base material layer, a middle base material layer and an upper base material layer which are stacked, the ellipsoidal bubbles are located in the middle base material layer, and the upper base material layer is located in the middle base material layer. The inclination angle between the long axis of each ellipsoidal bubble and the lower base material layer is larger than 0 degree and smaller than 90 degrees. The diffusion plate is filled with the ellipsoidal bubbles, and the ellipsoidal bubbles are inclined at a certain angle, so that the light mixing effect is improved.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to a diffusion plate and a preparation method thereof, a backlight module, and a display device. Background Art

[0002] In direct-lit backlight modules, the diffuser is a structural component used to improve the image quality. With the rapid development of industry technology, the number of light strips in backlight modules is decreasing, and the spacing between light strips is increasing. In addition, with the decreasing trend of OD (Optical Distance), the uniform light effect of traditional foam diffusers is very limited, and more advanced foam diffuser technology and processes are needed. Summary of the invention

[0003] The main purpose of the present application is to provide a diffusion plate and a preparation method thereof, a backlight module, and a display device, aiming to solve the technical problem that the existing diffusion plate has a poor light mixing effect.

[0004] To achieve the above-mentioned purpose, the present application provides a diffuser plate, comprising ellipsoidal bubbles and a substrate, wherein the substrate comprises a lower substrate layer, an intermediate substrate layer and an upper substrate layer which are stacked, the ellipsoidal bubbles are located in the intermediate substrate layer, and the inclination angle between the long axis of the ellipsoidal bubbles and the lower substrate layer is greater than 0° and less than 90°.

[0005] In some embodiments of the present application, the inclination angle between the major axis of the ellipsoidal bubble and the lower substrate layer is greater than or equal to 30° and less than or equal to 60°.

[0006] In some embodiments of the present application, the major axis length of the ellipsoidal bubble is 15 μm-30 μm, and the minor axis length of the ellipsoidal bubble is 5 μm-10 μm.

[0007] In some embodiments of the present application, the thickness of the intermediate substrate layer accounts for 80%-90% of the total thickness of the diffuser plate.

[0008] In some embodiments of the present application, surfaces of the lower substrate layer and the upper substrate layer away from the middle substrate layer are both provided with an atomization structure.

[0009] In some embodiments of the present application, the lower substrate layer, the middle substrate layer and the upper substrate layer are made of the same material, which is one of PS, PC, MS or PMMA.

[0010] In addition, to achieve the above-mentioned purpose, the present application also provides a method for preparing a diffuser plate, which is used to prepare the diffuser plate as described above, comprising:

[0011] The substrate raw material particles are melted and three-layer co-extruded to obtain a substrate formed of a stacked lower substrate layer, an intermediate substrate layer and an upper substrate layer, and an inert gas is injected into the intermediate substrate layer to form spherical bubbles;

[0012] Rolling the substrate, and controlling the roller to make the flow rate of the upper substrate layer or the flow rate of the lower substrate layer different from the flow rate of the middle substrate layer, so that the spherical bubbles are transformed into ellipsoidal bubbles with an inclined angle;

[0013] The roll-pressed substrate is cooled to obtain a diffusion plate.

[0014] In some embodiments of the present application, the control roller makes the flow rate of the upper substrate layer or the flow rate of the lower substrate layer different from the flow rate of the middle substrate layer, specifically including:

[0015] The driving roller is controlled to stop rotating for a preset second time interval at each preset first time interval, so that the flow rate of the upper substrate layer is greater than the flow rate of the middle substrate layer, and the flow rate of the middle substrate layer is greater than the flow rate of the lower substrate layer.

[0016] In addition, to achieve the above-mentioned purpose, the present application also provides a backlight module, including the diffusion plate as described above.

[0017] In addition, to achieve the above objectives, the present application also provides a display device, including the backlight module as described above.

[0018] The diffuser provided by the embodiment of the present application comprises an ellipsoidal bubble and a substrate, wherein the substrate comprises a lower substrate layer, an intermediate substrate layer and an upper substrate layer arranged in a stacked manner, the ellipsoidal bubble is located in the intermediate substrate layer, and the inclination angle between the major axis of the ellipsoidal bubble and the lower substrate layer is 0°-90°. The light emitted by the light source can be incident from the lower substrate layer, irradiated to the ellipsoidal bubble of the intermediate substrate layer, and different incident angles are formed on the light incident surface of the ellipsoidal bubble. When the incident angle is greater than the critical angle, total reflection will occur. When the incident angle is less than the critical angle, refraction will occur, and the refracted light enters the ellipsoidal bubble and then emerges from the ellipsoidal bubble. Since there is a certain inclination angle between the major axis of the ellipsoidal bubble and the lower substrate layer, compared with the spherical bubble, the proportion of light that undergoes total reflection is greater, so that the degree to which the propagation direction of the light changes is greater, so the light mixing effect is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present drawings or related technologies, the drawings required for use in the embodiments or related technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present drawings. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0020] Figure 1 It is a schematic diagram of the structure of a spherical bubble diffusion plate in the related art;

[0021] Figure 2 A micrograph of a spherical bubble diffuser in the related art;

[0022] Figure 3 This is the light path diagram of light incident on the surface of the spherical bubble;

[0023] Figure 4 This is the optical simulation diagram of a spherical bubble;

[0024] Figure 5 A schematic diagram of the structure of a diffusion plate provided in an embodiment of the present application;

[0025] Figure 6 A schematic diagram of the cross-sectional structure of an ellipsoidal bubble provided in an embodiment of the present application;

[0026] Figure 7 A micrograph of an ellipsoidal bubble provided in an embodiment of the present application;

[0027] Figure 8 A light path diagram of a light beam incident on an ellipsoidal bubble provided in an embodiment of the present application;

[0028] Fig. 9 An optical simulation diagram of an ellipsoidal bubble provided in an embodiment of the present application;

[0029] Fig.10 A process flow chart of the preparation of a diffusion plate provided in an embodiment of the present application;

[0030] Fig.11 A schematic diagram of the bubble shape transformation process provided in an embodiment of the present application;

[0031] Fig.12 A schematic diagram of the structure of a backlight module provided in an embodiment of the present application;

[0032] Fig.13 Schematic diagram of the test point positions for the nine-point brightness test provided in the embodiment of the present application

[0033] Fig.14 This is a subjective image quality test chart of the diffuser plate 1;

[0034] Fig.15This is a subjective image quality test chart of diffuser plate 2.

[0035] Description of reference numerals:

[0036] 100, spherical bubble diffusion plate; 110, spherical bubble; 120, substrate;

[0037] 200, diffuser; 210, ellipsoidal bubbles; 220, substrate; 221, lower substrate layer; 222, middle substrate layer; 223, upper substrate layer;

[0038] 300 , optical film; 400 , light source; 500 , lens; 600 , reflective sheet; 700 , liquid crystal panel.

[0039] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0040] It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0041] Hereinafter, the diffuser plate and its preparation method, backlight module, and display device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0042] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0043] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the technical solution of the present application is further described below in conjunction with the accompanying drawings and embodiments. However, the present application is not limited to the listed embodiments, and should also include any other known changes within the scope of the rights claimed in the present application.

[0044] In the related technology, the traditional foaming diffuser manufacturing process forms a spherical bubble structure inside the diffuser by filling inert gas during the extrusion process of the diffuser. The original intention of such a diffuser design is to increase the number of refractions and reflections of the light energy of the backlight system, thereby achieving a uniform picture quality effect.

[0045] Figure 1 Schematic diagram of a spherical bubble diffusion plate structure in the related art, such as Figure 1 As shown, the spherical bubble diffusion plate 100 includes spherical bubbles 110 and a substrate 120 , and the spherical bubbles 110 are densely distributed in the substrate 120 . Figure 2 This is a micrograph of a spherical bubble diffuser. Figure 2 It can be seen intuitively that the cross-sectional shape of the bubble is circular, the spherical bubbles 110 are densely distributed, and there are certain differences in the sizes of different spherical bubbles 110.

[0046] Taking the PS (Polystyrene) material substrate as an example, the refractive index of the PS substrate is about 1.6, and the refractive index of air is about 1.0. Due to the large difference in refractive index, when the light enters the substrate, it will be refracted and totally reflected at the interface of the bubble. Refraction and total reflection can change the propagation direction of the light, thereby increasing the optical path and enhancing the effect of mixed light. It can be used in direct-type backlight modules to improve the display quality. When the spacing between the light strips is appropriate, it is helpful to improve subjective display problems such as light shadows, dark corners, and bright edges. Figure 3 is the optical path diagram of the light incident on the surface of the spherical bubble, such as Figure 3 As shown, when light is incident on the surface of the spherical bubble 110 from a certain direction, the critical angle of total reflection C = arcsin (1 / 1.6) ≈ 38°, and light with an incident angle less than 38° can be incident on the spherical bubble 110 by refraction, and then exit the spherical bubble 110 by refraction, and the propagation direction and angle change are small, corresponding to Figure 3 The blue arrow indicates the optical path; light with an incident angle greater than 38° undergoes total reflection at the incident interface, and the propagation direction and angle change significantly, corresponding to Figure 3 The pink arrow indicates the light path. Figure 4 This is the optical simulation diagram of a spherical bubble. Figure 4 It can be seen that an obvious small-scale halo can be generated around the spherical bubble 110, which has a certain light mixing effect.

[0047] With the rapid development of the industry, the thin design and energy-saving design of direct-type backlight modules are the mainstream demands of the market. Reduced OD and fewer light bars have become the development trend of direct-type display products. Figure 1 The foam diffuser shown in the figure has limited light mixing effect, and a foam diffuser technology with better light mixing effect is needed.

[0048] Based on this, the embodiment of the present application provides a diffusion plate 200, Figure 5 A structural diagram of the diffusion plate 200 provided in an embodiment of the present application is shown in FIG. Figure 5 As shown, the diffuser plate 200 includes an ellipsoidal bubble 210 and a substrate 220, wherein the substrate 220 includes a lower substrate layer 221, an intermediate substrate layer 222 and an upper substrate layer 223 which are stacked, and the ellipsoidal bubble 210 is located in the intermediate substrate layer 222, and the inclination angle between the long axis of the ellipsoidal bubble 210 and the lower substrate layer 221 is greater than 0° and less than 90°.

[0049] The diffuser plate 200 of the embodiment of the present application has a film structure including a lower substrate layer 221, an intermediate substrate layer 222 and an upper substrate layer 223. Through the control of the manufacturing process, the ellipsoidal bubbles 210 are wrapped in the intermediate substrate layer 222 and have a certain inclination angle. The lower substrate layer 221 and the upper substrate layer 223 on both sides can protect the intermediate substrate layer 222. Both the lower substrate layer 221 and the upper substrate layer 223 can be used as light incident surfaces.

[0050] Figure 6 is a schematic diagram of the cross-sectional structure of an ellipsoidal bubble, such as Figure 6 As shown, the cross-sectional shape of the ellipsoidal bubble 210 can be approximately an ellipse, and its size can be represented by the size of its major axis and minor axis. Figure 6 If the ellipsoidal bubble 210 is approximated as an ellipsoid, the long axis of the ellipsoidal bubble 210 is the axis passing through its center point and having the largest shape, and the short axis is the axis passing through its center point and having the smallest shape.

[0051] The inclination angle between the long axis of the ellipsoidal bubble 210 and the lower substrate layer 221 refers to the smaller angle formed by the intersection of the straight line where the long axis is located and the plane where the lower substrate layer 221 is located, such as Figure 6 The middle angle α is shown, wherein the dotted line b represents a straight line in the plane of the lower substrate layer 221. This tilt angle α is within the range of greater than 0° and less than 90°, for example, it can be 1°, 15°, 30°, 45°, 60°, 75°, 89° or within the range of any of the above values. The size of the tilt angle can be adjusted according to factors such as the critical angle between the substrate medium and the air medium, and the light energy receiving area of ​​the ellipsoidal bubble 210 in the incident direction. Figure 7 is a micrograph of the ellipsoidal bubble 210 in the embodiment of the present application, Figure 7 It can be seen that although the sizes of the bubbles are different, their cross-sectional shapes are basically elliptical and densely distributed in the substrate.

[0052] When the ellipsoidal bubble 210 is tilted, different light propagation conditions such as refraction and total reflection may occur after the light is incident. Figure 8 is the optical path diagram of the light incident on the ellipsoidal bubble, such as Figure 8 As shown, the calculation of the critical angle of total reflection can refer to the above. When the ellipsoidal bubble has a certain degree of inclination, when the light is incident on the surface of the ellipsoidal bubble 210, the incident angle of most of the light is greater than the critical angle 38°, thereby forming total reflection, corresponding to Figure 8 The pink arrow in the figure indicates the light path. A few rays at the edge are refracted, corresponding to Figure 8 The blue arrows indicate the light path. Fig. 9 This is the optical simulation diagram of the ellipsoidal bubble. Fig. 9 It can be clearly seen that the periphery of the ellipsoidal bubble 210 can produce a large-scale halo diffusion effect, which is particularly evident in the long axis direction. Figure 4 The optical simulation effect is better.

[0053] In this embodiment, the diffuser plate 200 includes an ellipsoidal bubble 210 and a substrate 220, the substrate 220 includes a lower substrate layer 221, an intermediate substrate layer 222 and an upper substrate layer 223 which are stacked, the ellipsoidal bubble 210 is located in the intermediate substrate layer 220, and the inclination angle between the long axis of the ellipsoidal bubble 210 and the lower substrate layer 221 is greater than 0° and less than 90°. The light emitted by the light source is incident from the lower substrate layer 221 and irradiates the ellipsoidal bubble 210 of the middle substrate layer 222, forming different incident angles on the light incident surface of the ellipsoidal bubble 210. When the incident angle is greater than the critical angle, total reflection will occur. When the incident angle is less than the critical angle, refraction will occur. The refracted light enters the ellipsoidal bubble 210 and then exits from the ellipsoidal bubble 210. Since there is a certain inclination angle between the long axis of the ellipsoidal bubble 210 and the lower substrate layer 221, the proportion of light that is totally reflected is larger than that of the spherical bubble, which makes the degree of change in the propagation direction of the light greater, and thus the light mixing effect is improved.

[0054] In some embodiments of the present application, the inclination angle between the major axis of the ellipsoidal bubble 210 and the lower substrate layer 221 is greater than or equal to 30° and less than or equal to 60°. For example, the inclination angle between the major axis of the ellipsoidal bubble 210 and the lower substrate layer 221 can be 30°, 40°, 45°, 50°, 60° or within the range composed of any of the above values. It is understandable that if the inclination angle of the ellipsoidal bubble 210 is too small, the proportion of the incident light that undergoes total reflection will be less, which will lead to insufficient total reflection intensity, and if the inclination angle of the ellipsoidal bubble 210 is too large, the light receiving area will be insufficient. A large light receiving area means that the propagation direction of more incident light can be changed, and less light is emitted directly from the substrate 220. By controlling the inclination angle between the major axis of the ellipsoidal bubble 210 and the lower substrate layer 221 to be greater than or equal to 30° and less than or equal to 60°, the light receiving area and the total reflection light energy ratio can be comprehensively considered to obtain a better light mixing effect.

[0055] In some embodiments of the present application, the major axis length of the ellipsoidal bubble 210 is 15 μm-30 μm. For example, the major axis length of the ellipsoidal bubble 210 can be 15 μm, 18 μm, 20 μm, 25 μm, 30 μm or within the range of any of the above values. It is understandable that the major axis length of the ellipsoidal bubble 210 will affect its size and the area receiving light. Under the same inclination angle, the longer the major axis length, the larger the area receiving light, and too long a major axis length may cause the ellipsoidal bubble 210 to be too deformed. By controlling the major axis length of the ellipsoidal bubble within a suitable range, a larger light receiving area can be obtained.

[0056] In some embodiments of the present application, the minor axis length of the ellipsoidal bubble 210 is 5 μm-10 μm. For example, the minor axis length of the ellipsoidal bubble 210 can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or within the range of any of the above values. It is understood that the ellipsoidal bubble 210 can be regarded as transformed from a spherical shape, so its minor axis length can be maintained close to the original spherical radius, thus reducing the degree of deformation of the spherical bubble and facilitating process control.

[0057] In some embodiments of the present application, the thickness of the intermediate substrate layer 222 accounts for 80%-90% of the total thickness of the diffuser plate 200. For example, the thickness of the intermediate substrate layer 222 may account for 80%, 82%, 85%, 88%, 90%, etc. of the total thickness of the diffuser plate 200. Figure 5 , the total thickness of the diffuser plate 200 is H, and the thickness of the intermediate substrate layer 222 is 0.8H-0.9H. It can be understood that the ellipsoidal bubbles 210 in the intermediate substrate layer 222 are the main structures that play a role in the light mixing effect, so the thickness of the intermediate substrate layer 222 can be set to occupy a larger proportion of the entire diffuser plate 200. The smaller the proportion of the intermediate substrate layer 222 to the total thickness of the diffuser plate 200, the fewer the number of ellipsoidal bubbles 210, and the worse the light mixing effect. The larger the proportion of the thickness of the intermediate substrate layer 222, the more ellipsoidal bubbles 210 can be accommodated, and the better the total reflection effect, so the proportion of the intermediate substrate layer 222 is larger. The lower substrate layer 221 and the upper substrate layer 223 on both sides can protect the intermediate substrate layer 222, and in the preparation process, they can also be used as the part where traction is applied to facilitate the formation of ellipsoidal bubbles 210. The thickness of the lower substrate layer 221 and the upper substrate layer 223 can be the same or different, and can be adjusted according to the actual preparation process, and this embodiment does not impose specific restrictions on this.

[0058] In some embodiments of the present application, the surfaces of the lower substrate layer 221 and the upper substrate layer 223 away from the intermediate substrate layer 222 are both provided with an atomized structure. The atomized structure refers to a structure that can enhance the diffuse reflection on the surface of the diffuser plate. The atomized structure may include a plurality of protrusions, the shape of the protrusions may be triangular, conical or convex lens-shaped, and the surface of the protrusions may be provided with a frosted effect to enhance the diffuse reflection. The provision of the atomized structure can reduce the uneven incidence of light between the intermediate substrate layer 222 and the ellipsoidal bubbles 210, and achieve a more uniform light mixing effect.

[0059] In some embodiments of the present application, the lower substrate layer 221, the middle substrate layer 222 and the upper substrate layer 223 are made of the same material, which is one of PS, PC (Polycarbonate), MS (Styrene-methylmethacrylate copolymer) or PMMA (Polymeric Methyl Methacrylate). It is understandable that the above materials used as the substrate 220 can meet the requirements of the light transmittance and mechanical properties of the diffuser. There are certain differences in the refractive index of different types of substrates 220, but most of them are around 1.6. The ellipsoidal bubbles 210 with a certain tilt angle are arranged therein, which can achieve a good light mixing effect. The lower substrate layer 221, the middle substrate layer 222 and the upper substrate layer 223 are made of the same material, so that the expansion coefficients of the three can be the same, avoiding problems such as warping and bulging caused by differences in expansion coefficients under extreme environmental conditions, thereby improving the display quality.

[0060] In one embodiment, assuming that the inclination angle between the major axis of the ellipsoidal bubble 210 and the lower substrate layer 221 is 0°, refer to Figure 6 , angle α = 0°, at this time the light receiving area is the largest, continue to refer to Figure 8 , in this case Figure 8 The blue arrows in the middle account for most of all incident light, resulting in a very weak total reflection intensity. When the tilt angle increases, the proportion of light that undergoes total reflection as shown by the pink arrows increases, accompanied by a decrease in the light receiving area. Figure 8 As shown by the blue arrow in the middle, this part of the light is incident from the left side of the ellipsoidal bubble 210, refracted into the inside of the ellipsoidal bubble 210, and refracted from the ellipsoidal bubble 210 to the middle substrate layer 222. The light with an incident angle greater than or equal to the critical angle is shown in FIG. Figure 8As shown by the pink arrow in the middle, this part of the light is incident from the right side of the ellipsoidal bubble 210, and is totally reflected directly at the incident position and enters the intermediate substrate layer 222. As the tilt angle continues to increase to 90°, the area of ​​the ellipsoidal bubble 210 receiving light decreases to a minimum value. The surface of the ellipsoidal bubble 210 is a curved surface, and the changes in the light receiving area and the proportion of the totally reflected light may be nonlinear. When the tilt angle is in the range of 30° to 60°, both the total reflection intensity and the light receiving area can be taken into account, and a good light mixing effect can be obtained.

[0061] The embodiment of the present application further provides a method for preparing a diffuser plate. In this embodiment, the method for preparing the diffuser plate includes steps S10 to S30:

[0062] Step S10, melting the substrate raw material particles and performing three-layer co-extrusion to obtain a substrate 220 formed by stacking a lower substrate layer 221, an intermediate substrate layer 222 and an upper substrate layer 223, and injecting an inert gas into the intermediate substrate layer 222 to form spherical bubbles;

[0063] This embodiment adopts a three-layer co-extrusion process to prepare the laminated structure of the diffuser plate 200. The substrate raw material particles refer to the raw material particles used to form the substrate 220. The material of the substrate 220 adopts a polymer substance, which is usually used as a raw material in the form of particles. After the raw material particles are melted, they can pass through three hot runners respectively and melt at a temperature of 180°C-220°C, wherein the upper hot runner is extruded to form an upper substrate layer 223, and the lower hot runner is extruded to form a lower substrate layer 221. The middle hot runner can be filled with an inert gas while extruding to form an intermediate substrate layer 222 including spherical bubbles. It can be understood that when the gas is filled into the middle hot runner, under the action of surface tension, if no other interference is applied, the bubbles are spherical. The filled inert gas can be a gas with strong stability such as nitrogen, which is not easy to react chemically with the substrate 220.

[0064] Step S20, rolling the substrate 220, and controlling the roller to make the flow rate of the upper substrate layer 223 or the flow rate of the lower substrate layer 221 different from the flow rate of the middle substrate layer 222, so that the spherical bubbles are transformed into ellipsoidal bubbles 210 with an inclined angle;

[0065] Fig.10 The process flow chart of the diffusion plate preparation provided in this embodiment is shown in FIG. Fig.10 The substrate raw material particles are injected into different hot runners through a funnel, and after melting, they are co-extruded into a laminated substrate 220 structure through three layers. The rollers roll the substrate 220 and transport the substrate 220 to the subsequent process nodes for processing. The subsequent process includes cooling, trimming, antistatic coating, shearing, stacking, etc. The process of this embodiment may include three sets of rollers, namely Fig.10The rollers of group A are composed of A1, A2, and A3, and the rollers of group B and C. The rollers of group A are used to determine the thickness of the substrate 220, and to emboss a pattern structure on the surface of the upper substrate layer 223 and the lower substrate layer 221. The pattern structure can enhance the diffuse reflection of the surface of the diffuser plate 200. The rollers of group B are used to limit the conveying speed. The rollers of group C are used for antistatic coating. The rotation direction of each roller is as follows: Fig.10 By controlling the roller to make the flow rate of the upper substrate layer 223 or the flow rate of the lower substrate layer 221 different from the flow rate of the middle substrate layer 222, a flow rate difference can be formed between the three film layers, changing the shape of the spherical bubble to an ellipsoidal bubble 210 with an inclined angle.

[0066] In some embodiments of the present application, the step of controlling the roller to make the flow rate of the upper substrate layer 223 or the flow rate of the lower substrate layer 221 different from the flow rate of the middle substrate layer 222 may include: controlling the driving roller to stop for a preset second time interval at every preset first time interval, so that the flow rate of the upper substrate layer 223 is greater than the flow rate of the middle substrate layer 222, and the flow rate of the middle substrate layer 222 is greater than the flow rate of the lower substrate layer 221.

[0067] It should be noted that the preset first time interval refers to the time when the transmission roller is running, and the preset second time interval refers to the time when the transmission roller stops, that is, the transmission roller stops suddenly after the running time lasts for the preset first time interval, and the maintenance time of the emergency stop is the preset second time interval. It can be understood that when the transmission roller stops suddenly from the running state, the substrate 220 transmitted by the roller will generate inertia along the original transmission direction under the action of inertia, and the lower substrate layer 221 is in contact with the transmission roller, and there is also friction between the two, resulting in the fastest falling speed of V3. Therefore, the substrate 220 can generate a flow rate difference of V1>V2>V3, V1 is the flow rate of the upper substrate layer 223, V2 is the flow rate of the middle substrate layer 222, and V3 is the flow rate of the lower substrate layer 221. The bubble is stretched and transformed into a rod shape, and the long axis of the bubble is at a certain inclination angle with the lower substrate layer 221. The flow rate of the substrate 220 is about 5-9 m / s. Combined with other relevant influencing factors, the first time interval can be preset to 8-15 seconds, and the second time interval can be preset to 1-3 seconds. In addition, the transmission rollers that are controlled to stop can be A2, A3, B group, and C group rollers, and the A1 group rollers are kept in operation to avoid accumulation of raw materials.

[0068] Fig.11 Schematic diagram of the bubble shape transformation process in this embodiment. Fig.11V1 is the flow rate of the upper substrate layer 223, V2 is the flow rate of the middle substrate layer 222, and V3 is the flow rate of the lower substrate layer 221. It can be understood that, in general, the flow rates of each film layer are the same, and during the rolling process, V1>V2>V3 can be controlled, that is, a certain flow rate difference is formed between the film layers on both sides of the middle substrate layer 222, and this flow rate difference causes the bubbles in the middle substrate layer 222 to be stretched, resulting in a change in shape, from spherical bubbles to ellipsoidal bubbles 210.

[0069] In some embodiments of the present application, the step of controlling the roller to make the flow rate of the upper substrate layer 223 or the flow rate of the lower substrate layer 221 different from the flow rate of the middle substrate layer 222 may also include: applying traction to the upper substrate layer 223. In this embodiment, a traction process can be added, and by applying traction to the upper substrate layer 223, the flow rate of the upper substrate layer 223 is greater than that of the lower substrate layer 221 during the cooling stage, so that in the cooling stage, a flow rate difference is formed when the diffuser plate 200 is not fully formed, causing the internal spherical bubble to be stretched into an ellipsoid shape and form a certain tilt angle. The magnitude of the applied traction force can be adjusted according to the size and weight of the substrate 220, so that the ellipsoidal bubble 210 can be at a suitable tilt angle.

[0070] In step S30 , the rolled substrate 220 is cooled to obtain the diffusion plate 200 .

[0071] Reference Fig.10 The rolling process can be followed by a cooling treatment to reduce the temperature of the substrate 220 and increase its hardness. After trimming and antistatic coating, the diffusion plate 200 with a certain size is obtained and stacked for storage.

[0072] In this embodiment, by controlling the flow rate of different film layers in the substrate 220, a flow rate difference is formed, and the shape of the bubble is changed from a sphere to a rod. There is no need to make many changes to the process, which reduces the process difficulty and the prepared diffuser has an excellent light mixing effect.

[0073] The embodiment of the present application further provides a backlight module, comprising the diffusion plate 200 as described in the above embodiment. Fig.12 A schematic diagram of the structure of a backlight module provided in this embodiment is shown in FIG. Fig.12As shown, the diffuser plate 200 and the optical film 300 are stacked, and the light emitted from the light source 400 is refracted by the lens 500 and then diverges, and reaches the diffuser plate 200 through reflection by the reflector 600, and is processed by the diffuser plate 200 and the optical film 300, and then irradiates the liquid crystal panel 700. When the light propagates to the diffuser plate 200, it is incident from the lower substrate layer 221, irradiates the ellipsoidal bubble 210 of the middle substrate layer 222, and forms different incident angles on the light incident surface of the ellipsoidal bubble 210. When the incident angle is greater than the critical angle, total reflection will occur, and when the incident angle is less than the critical angle, refraction will occur, and the refracted light enters the ellipsoidal bubble 210 and then exits from the ellipsoidal bubble 210. Since there is a certain inclination angle between the long axis of the ellipsoidal bubble 210 and the lower substrate layer 221, compared with the spherical bubble, the proportion of the light that is totally reflected is greater, so that the degree of change in the propagation direction of the light is greater, so the light mixing effect is improved.

[0074] In one embodiment, a 50-inch, OD 35mm, two-light-bar extreme design direct-type backlight module is used to compare the display effects of a traditional diffuser and the diffuser of the present application. The test results are shown in Table 1 below. In Table 1, diffuser plate 1 is a traditional foam diffuser with spherical bubbles. Diffusion plate 2 is a diffuser prepared in the embodiment of the present application with rod-shaped bubbles and a certain tilt angle. Under the extreme design conditions of 50-inch two light bars, the distance between the light bars is about 240mm. Diffusion plate 1 and diffusion plate 2 are respectively assembled into the direct-type backlight module of the same specifications as above, and the nine-point brightness is measured to compare the subjective image quality. Fig.13 Schematic diagram of the test point positions for a nine-point brightness test, where L represents the length of the liquid crystal panel and W represents the width of the liquid crystal panel.

[0075] Table 1

[0076]

[0077]

[0078] Fig.14 This is the subjective image quality test chart of diffuser plate 1. Fig.15 This is a subjective image quality test chart of diffuser plate 2. Fig.14 , Fig.15 As can be seen from the test data in Table 1, the use of diffusion plate 1 cannot achieve uniform light mixing, the center brightness is low, and subjectively it can be clearly observed that the picture has a sense of layering, with a bright band directly above the light bar and a dark band between the light bar, and the picture quality is extremely uneven; while the use of diffusion plate 2 can stretch the light energy in the area directly above the light bar to the center area, achieving more uniform light mixing, and the center brightness can be increased by more than 10%. It is subjectively uniform without a sense of layering, and the picture quality is excellent.

[0079] The embodiment of the present application further provides a display device, comprising the backlight module as described in the above embodiment. The beneficial effects that can be achieved by the display device of the embodiment of the present application can be referred to the description of the above embodiment, and will not be repeated here.

[0080] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A diffuser plate, characterized in that: It includes ellipsoidal bubbles and a substrate, wherein the substrate includes a lower substrate layer, an intermediate substrate layer and an upper substrate layer which are stacked, the ellipsoidal bubbles are located in the intermediate substrate layer, and the inclination angle between the long axis of the ellipsoidal bubbles and the lower substrate layer is greater than 0° and less than 90°.

2. The diffuser plate according to claim 1, wherein: The inclination angle between the major axis of the ellipsoidal bubble and the lower substrate layer is greater than or equal to 30° and less than or equal to 60°.

3. The diffuser plate according to claim 1, wherein: The length of the major axis of the ellipsoidal bubble is 15 μm-30 μm, and the length of the minor axis of the ellipsoidal bubble is 5 μm-10 μm.

4. The diffuser plate according to claim 1, wherein: The thickness of the intermediate substrate layer accounts for 80%-90% of the total thickness of the diffuser plate.

5. The diffuser plate according to claim 1, wherein: The surfaces of the lower substrate layer and the upper substrate layer away from the middle substrate layer are both provided with an atomization structure.

6. The diffuser plate according to any one of claims 1 to 5, characterized in that The lower substrate layer, the middle substrate layer and the upper substrate layer are made of the same material, which is one of PS, PC, MS or PMMA.

7. A method for preparing a diffusion plate, characterized in that: A method for preparing a diffuser plate according to any one of claims 1 to 6, comprising: The substrate raw material particles are melted and three-layer co-extruded to obtain a substrate formed of a stacked lower substrate layer, an intermediate substrate layer and an upper substrate layer, and an inert gas is injected into the intermediate substrate layer to form spherical bubbles; Rolling the substrate, and controlling the roller to make the flow rate of the upper substrate layer or the flow rate of the lower substrate layer different from the flow rate of the middle substrate layer, so that the spherical bubbles are transformed into ellipsoidal bubbles with an inclined angle; The roll-pressed substrate is cooled to obtain a diffusion plate.

8. The method for preparing a diffuser plate according to claim 7, wherein: The control roller makes the flow rate of the upper substrate layer or the flow rate of the lower substrate layer different from the flow rate of the middle substrate layer, specifically comprising: The driving roller is controlled to stop rotating for a preset second time interval at each preset first time interval, so that the flow rate of the upper substrate layer is greater than the flow rate of the middle substrate layer, and the flow rate of the middle substrate layer is greater than the flow rate of the lower substrate layer.

9. A backlight module, characterized in that: The invention comprises a diffuser plate as claimed in any one of claims 1 to 6.

10. A display device, characterized in that: Comprising the backlight module as claimed in claim 9.

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