An infrared light-emitting module and a preparation method thereof

Abstract

The present invention discloses an infrared light-emitting module and a preparation method thereof. The module includes a glue iron. A reflective film, a light guide plate, a diffusion film, a lower brightness enhancement film, and an upper brightness enhancement film are sequentially installed in the assembly groove of the glue iron from bottom to top. An infrared LED point light source with a wavelength of 600 nm to 750 nm is provided between one side of the light guide plate, the reflective film, and the diffusion film. The infrared LED point light source includes a substrate layer, a Bragg optical reflection layer, an N-type confinement layer, an active layer, a P-type confinement layer, and a window layer. The infrared wave emitted by the infrared light-emitting module of the present invention has a stimulating and activating effect on the cone cells in the retina of the human eye, thereby helping with eye training. By setting side point light sources, the light-emitting angle is larger. And through the setting angle cooperation of the upper and lower brightness enhancement films, infrared light perpendicular to the human eye direction can be generated, avoiding light spillage, making it more concentrated and more direct in stimulating and activating the cone cells of the eye retina, and helping the eyes recover visual health.

Description

Technical Field

[0001] The present invention belongs to the technical field of light-emitting modules, and particularly relates to an infrared light-emitting module and a preparation method thereof. Background Art

[0002] Light-emitting modules are widely used in daily life and work. However, the light emitted by traditional light-emitting modules is mostly white light or red light within the visible light wavelength range, and its main purpose is to provide a light-emitting source for various display devices (such as display screens, etc.). However, it cannot generate colored light with a specific wavelength, such as infrared light with a specific wavelength for training human retinal biological cells. Therefore, the existing light-emitting modules cannot be applied to the training of human retinal biological cells. Summary of the Invention

[0003] The purpose of the present invention is to provide an infrared light-emitting module and a preparation method thereof to solve at least one technical problem existing in the prior art.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] In the first aspect, the present invention provides an infrared light-emitting module, including a glue iron. The glue iron includes an assembly groove, and a reflective film, a light guide plate, a diffusion film, a lower brightness enhancement film, and an upper brightness enhancement film are sequentially installed in the assembly groove from bottom to top. An infrared LED point light source is provided between the reflective film and the diffusion film on one side of the light guide plate.

[0006] The infrared LED point light source includes a substrate layer. A Bragg optical reflection layer is provided on the substrate layer. An N-AIGaInPN type confinement layer with a thickness of 1800 nm to 2200 nm is provided on the Bragg optical reflection layer. An I-AIGaInP active layer with a thickness of 0.1 nm to 0.3 um is provided on the N-type confinement layer. A P-AIGaInP P-type confinement layer with a thickness of 34000 nm to 36000 nm is provided on the I-AIGaInP active layer. A p-GaP window layer with a thickness of 47000 nm to 49000 nm is provided on the P-type confinement layer.

[0007] The substrate layer includes a GaAs substrate with a thickness of 220 to 320 nm. A SiO2 protective layer with a thickness of 200 to 220 nm is provided on the surface of the GaAs substrate. An ITO enhancement layer with a thickness of 200 to 250 nm is provided on the surface of the SiO2 protective layer.

[0008] The infrared wavelength emitted by the infrared LED point light source formed by connecting the above layers is 600 nm to 750 nm.

[0009] In a possible design, the module further includes a black glue, and the black glue is installed above the upper brightness enhancement film.

[0010] In a possible design, the light guide plate is made of polymethyl methacrylate (PMMA) material and is manufactured by laser engraving.

[0011] In a possible design, the light guide uniformity of the light guide plate is not less than 90%.

[0012] In a possible design, a light emission control circuit is further included. The light emission control circuit includes a microprocessor chip U4 of model SY7201ABC. One end of an inductor L1 and the positive terminal of the infrared LED point light source are respectively connected to the LX pin of the microprocessor chip U4. The negative terminal of the infrared LED point light source is connected to a first capacitor C3 and then grounded. The ground pin GND of the microprocessor chip U4 is grounded. The FB pin of the microprocessor chip U4 is respectively connected to one end of a first resistor R13, one end of a second resistor R12, and the positive power supply. The other end of the first resistor R13 and the other end of the second resistor are grounded. The IN pin of the microprocessor chip U4 is respectively connected to the other end of the inductor L1, one end of a second capacitor C2, and a 3.3V voltage. The other end of the second capacitor C2 is grounded. The OVP pin of the microprocessor chip U4 is connected in series with a third resistor R9 and is respectively connected to one end of the first capacitor C3 and the negative power supply. The EN / PWM pin of the microprocessor chip U4 is connected in series with a fourth resistor R10 and then connected to the power supply voltage VCC.

[0013] In a possible design, the light emission angle of the infrared LED point light source is not less than 120 degrees. Prisms are provided on both the lower brightness enhancement film and the upper brightness enhancement film, and the installation angle of the prisms is adjustable.

[0014] In a possible design, the total thickness of the infrared light emitting module is not greater than 0.95 mm.

[0015] In a second aspect, the present invention provides a method for manufacturing an infrared light emitting module as described in any one of the possible designs in the first aspect, including:

[0016] Using GaAs as the substrate, AIGaInP as the die bonding material, and the Bragg optical reflection layer as the epitaxial technology, an infrared LED point light source is manufactured by an infrared light emitting module manufacturing process.

[0017] Select a PMMA light guide material plate, and according to a preset graphic size, use a laser device to engrave the light guide material plate into a light guide plate with a uniform dot matrix.

[0018] Install a reflective film, the light guide plate, a diffusion film, a lower brightness enhancement film, and an upper brightness enhancement film in sequence from bottom to top in the assembly groove of the glue iron, and install the infrared LED point light source between the reflective film and the diffusion film on one side of the light guide plate to obtain the infrared light emitting module.

[0019] In a possible design, the Bragg optical reflective layer includes an AIAs optical reflective layer, an AIGa optical reflective layer, or an As optical reflective layer.

[0020] In a possible design, select a PMMA light guide material plate, and according to the preset graphic size, use a laser device to engrave the light guide material plate into a light guide plate with a uniform dot matrix, including:

[0021] Select a PMMA light guide material plate, and according to the preset light guide plate size, light guide dot matrix rectangle, and dot matrix size, use a laser device to perform laser engraving on the light guide material plate to obtain a light guide plate with uniform distribution and neat dot matrix.

[0022] Beneficial effects:

[0023] 1. The present invention prepares an infrared LED point light source with an infrared wavelength of 600nm to 750nm by setting a GaAs substrate layer, a confinement layer and an active layer of AIGaInP material, and an epitaxial reflective layer of Bragg optics, and setting the process parameters of each connection layer. This infrared light wave has a stimulating and activating effect on the cone cells and rod cells in the retina of the human eye, thus helping with eye training; and by installing a reflective film, a light guide plate, a diffusion film, a lower brightness enhancement film, and an upper brightness enhancement film in sequence from bottom to top in the assembly groove of the glue iron, and setting the infrared LED point light source between the reflective film and the diffusion film on one side of the light guide plate. This point light source is a side point light source with a larger emission angle. Through the setting angle cooperation of the upper and lower brightness enhancement films, infrared light perpendicular to the human eye direction can be generated in the optimal state, avoiding light spillage, making it more concentrated and direct in stimulating and activating the cone cells and rod cells of the eye retina, and helping the eyes recover visual health.

[0024] 2. The light guide plate in the present invention uses PMMA material as the light guide plate material, and this material has the advantages of a flat surface and good uniformity. After laser engraving, a uniformly distributed concave dot pattern can be obtained, and the uniformity can reach not less than 90%, so that it has a soft light effect and uniform light emission when conducting and scattering light.

[0025] 3. After the infrared light source prepared by the above process parameters is assembled into an infrared light emitting module, the total thickness of the overall infrared light emitting module is not greater than 0.95mm, making the product thinner and more comfortable to use. Description of the drawings

[0026] Figure 1Schematic structural diagram of the infrared light-emitting module in this embodiment;

[0027] Figure 2 Circuit schematic diagram of the light-emitting control circuit in this embodiment;

[0028] Figure 3 Flowchart of the preparation method of the infrared light-emitting module in this embodiment.

[0029] Wherein, 1 - glue iron; 11 - assembly groove; 2 - reflective film; 3 - light guide plate; 4 - diffusion film; 5 - lower brightness enhancement film; 6 - upper brightness enhancement film; 7 - infrared LED point light source; 8 - black glue. Detailed implementation manners

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this specification clearer, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this specification. Apparently, the described embodiments are some, but not all, of the embodiments of this specification. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this specification without creative efforts shall fall within the scope of protection of the present invention.

[0031] Embodiment

[0032] As Figure 1 and Figure 2 shown, in a first aspect, this embodiment provides an infrared light-emitting module, including a glue iron 1, the glue iron 1 includes an assembly groove 11, and a reflective film 2, a light guide plate 3, a diffusion film 4, a lower brightness enhancement film 5, and an upper brightness enhancement film 6 are sequentially installed in the assembly groove 11 from bottom to top. An infrared LED point light source 7 is provided between one side of the light guide plate 3 and between the reflective film and the diffusion film 4;

[0033] The infrared LED point light source 7 includes a substrate layer, a Bragg optical reflection layer is provided on the substrate layer, an N-AIGaInP (aluminum gallium indium phosphide) N-type confinement layer with a thickness of 1800 nm to 2200 nm is provided on the Bragg optical reflection layer, an I-AIGaInP active layer with a thickness of 0.1 nm to 0.3 um is provided on the N-type confinement layer, a P-AIGaInP P-type confinement layer with a thickness of 34000 nm to 36000 nm is provided on the I-AIGaInP active layer, and a p-GaP (gallium phosphide) window layer with a thickness of 47000 nm to 49000 nm is provided on the P-type confinement layer;

[0034] The substrate layer includes a GaAs (gallium arsenide) substrate with a thickness of 220 - 320 nm. A SiO2 (silicon dioxide) protective layer with a thickness of 200 - 220 nm is provided on the surface of the GaAs substrate, and an ITO (indium tin oxide) enhancement layer with a thickness of 200 - 250 nm is provided on the surface of the SiO2 protective layer; preferably, the SiO2 protective layer with a thickness of 200 - 220 nm is electroplated on the surface of the GaAs substrate, and the ITO enhancement layer with a thickness of 200 - 250 nm is electroplated on the surface of the SiO2 protective layer.

[0035] The infrared wavelength emitted by the infrared LED point light source 7 formed by connecting the above layers is 600 nm - 750 nm.

[0036] Among them, it should be noted that the assembly groove 11 provided in the glue iron 1 is used to provide an assembly space for each component and play a protective role. Preferably, the glue iron 1 is integrally injection-molded.

[0037] Among them, it should be noted that the reflective film is used to reflect the infrared light scattered from the back of the light guide plate 3 back to the light guide plate 3 to increase the luminous brightness and luminous uniformity.

[0038] Among them, it should be noted that the light guide plate 3 is used to convert the point light source emitted by the infrared LED point light source 7 into a surface light source and is used for light conduction and heat dissipation. In order to improve the uniformity of light conduction and scattering of the light guide plate 3, preferably, in this embodiment, polymethyl methacrylate PMMA (polymethyl methacrylate, also known as acrylic or plexiglass) material is used and made by laser engraving. Among them, the light guide plate 3 formed by laser engraving has a V-CUT pattern, so as to obtain a light guide plate 3 with a uniformity of not less than 90%. The uniformity of the existing light guide plate 3 is generally not less than 80%, and the traditional small dot printing method is used. After printing on the light guide plate 3, the flatness and uniformity of the dot pattern obtained will be different, and its light guide uniformity can only reach ≥80%. Therefore, the light guide plate 3 in this embodiment is superior to the traditional light guide plate 3 and can be effectively applied to the stimulation and training of human eye cells.

[0039] Among them, it should be noted that the diffusion film 4 is used to further improve the uniformity of the surface light source by means of the diffusion particles on its surface; the lower brightness enhancement film 5 and the upper brightness enhancement film 6 are respectively used to achieve the concentration and re-diffusion of the infrared light source by means of the micro-patterns on their surfaces, so as to further improve the brightness and uniformity of the module. The emission angle of the infrared LED point light source 7 is not less than 120 degrees. Both the lower brightness enhancement film 5 and the upper brightness enhancement film 6 are provided with prisms, and the installation angles of the prisms can be adjusted, so that the focused light in the direction perpendicular to the human eye can be generated, avoiding the overflow of infrared light, and finally forming the infrared light perpendicular to the human eye at 90°, so as to more intensively and directly stimulate and activate the cone cells and rod cells of the eye retina, which is beneficial to the visual health of the eyes. Compared with the traditional white LED with an emission angle not greater than 100° and the emitted light angle being astigmatic and unable to be focused, this embodiment can better act on the stimulation and training of human eye cells.

[0040] In a possible design, in order to fixedly install the infrared light-emitting module on the device to be used, such as an eye biovision instrument, the module further includes a black glue 8, and the black glue 8 is installed above the upper brightness enhancement film 6.

[0041] In a possible design, the total thickness of the infrared light-emitting module prepared by the above process parameters is not greater than 0.95 mm, making the product thinner and more comfortable to use.

[0042] As Figure 2 shown, in a possible design, in order to control the on-off of the infrared LED point light source, the module further includes a light-emitting control circuit. The light-emitting control circuit includes a microprocessor chip U4 of model SY7201ABC. One end of the LX pin of the microprocessor chip U4 is respectively connected to one end of the inductor L1 and the positive end of the infrared LED point light source. The negative end of the infrared LED point light source is connected to the ground after connecting the first capacitor C3. The ground pin GND of the microprocessor chip U4 is grounded. The FB pin of the microprocessor chip U4 is respectively connected to one end of the first resistor R13, one end of the second resistor R12 and the positive power supply. The other end of the first resistor R13 and the other end of the second resistor are grounded. The IN pin of the microprocessor chip U4 is respectively connected to the other end of the inductor L1, one end of the second capacitor C2 and the 3.3V voltage. The other end of the second capacitor C2 is grounded. The OVP pin of the microprocessor chip U4 is connected in series with the third resistor R9 and then respectively connected to one end of the first capacitor C3 and the negative power supply. The EN / PWM pin of the microprocessor chip U4 is connected in series with the fourth resistor R10 and then connected to the power supply voltage VCC.

[0043] Among them, preferably, the parameter values of each circuit component in the light-emitting control circuit of this embodiment can be: the inductance of inductor L1 is 6.8 uH (microhenry), the capacitance of the first capacitor C3 is 1 uF / 50V, the resistance values of the first resistor R13 and the second resistor R12 are 10 ohms, the capacitance of the second capacitor C2 is 4.7 uF, the resistance values of the third resistor R9 and the fourth resistor R10 are zero. Among them, the output constant current OUT of this light-emitting control circuit is 200 mV, and the inductance of the inductor L1 is not greater than 6.8 uH, otherwise the power supply IC may generate relatively serious heat.

[0044] Based on the above-disclosed content, in this embodiment, an infrared LED point light source 7 with an infrared wavelength of 600 nm to 750 nm is prepared by setting a GaAs substrate layer, a confinement layer and an active layer of AIGaInP material, and an epitaxial reflective layer of Bragg optics, and setting the process parameters of each connection layer. This infrared wave has a stimulating and activating effect on the cone cells and rod cells in the retina of the human eye, thus helping with eye training; and by sequentially installing a reflective film 2, a light guide plate 3, a diffusion film 4, a lower brightness enhancement film 5 and an upper brightness enhancement film 6 from bottom to top in the assembly groove 11 of the glue iron 1, and arranging the infrared LED point light source 7 between one side of the light guide plate 3, the reflective film and the diffusion film 4. This point light source is a side point light source with a larger light-emitting angle. Through the setting angle cooperation of the upper and lower brightness enhancement films, infrared light perpendicular to the human eye direction can be generated in the optimal state, avoiding light spillage and making it more concentrated and direct to stimulate and activate the cone cells of the eye retina, helping the eyes to restore visual health. In addition, the light guide plate 3 of this embodiment uses PMMA material as the material of the light guide plate 3, and this material has the advantages of a flat surface and good uniformity. After laser engraving, a uniformly distributed concave dot pattern can be obtained, and the uniformity can reach not less than 90%, so that it has a soft light effect and uniform light emission when conducting and scattering light.

[0045] As Figure 3 shown, in the second aspect, this embodiment provides a preparation method of an infrared light-emitting module as described in any possible design of the first aspect, including but not limited to being implemented by steps S101 to S103:

[0046] Step S101. Using GaAs as the substrate, AIGaInP as the chip mounting material, and Bragg optical reflective layer as the epitaxial technology, an infrared LED point light source 7 is prepared by using the infrared light-emitting module manufacturing process;

[0047] Among them, the manufacturing process of the infrared light-emitting module in this embodiment adopts the existing manufacturing process, and the specific process includes: making the substrate, sampling inspection, removing the outer packaging, vacuum treatment in the preloading chamber, removing the inner packaging and loading the chip, high-vacuum treatment, loading the chip into the reaction chamber, epitaxial growth, taking out the chip, photolithography, secondary epitaxy, taking out the chip, detecting the epitaxial wafer, and data analysis, etc. Details are not described here.

[0048] Among them, it should be noted that the infrared LED point light source 7 obtained by the above method includes a substrate layer, a Bragg optical reflection layer is provided on the substrate layer, an N-AIGaInP N-type confinement layer with a thickness of 1800 nm to 2200 nm is provided on the Bragg optical reflection layer, an I-AIGaInP active layer with a thickness of 0.1 nm to 0.3 um is provided on the N-type confinement layer, a P-AIGaInP P-type confinement layer with a thickness of 34000 nm to 36000 nm is provided on the I-AIGaInP active layer, and a p-GaP window layer with a thickness of 47000 nm to 49000 nm is provided on the P-type confinement layer; the substrate layer includes a GaAs substrate with a thickness of 220 to 320 nm, a SiO2 protective layer with a thickness of 200 to 220 nm is provided on the surface of the GaAs substrate, and an ITO enhancement layer with a thickness of 200 to 250 nm is provided on the surface of the SiO2 protective layer; the infrared wavelength emitted by the infrared LED point light source 7 formed by connecting the above layers is 600 nm to 750 nm.

[0049] Among them, preferably, the Bragg optical reflection layer includes an AIAs (aluminum arsenide) optical reflection layer, an AIGa (aluminum gallium) optical reflection layer, or an As (arsenic) optical reflection layer.

[0050] Step S102. Select a PMMA light guide material plate, and according to the preset graphic size, use a laser device to engrave the light guide material plate into a light guide plate 3 with a uniform dot matrix.

[0051] In a possible design, selecting a PMMA light guide material plate and engraving the light guide material plate into a light guide plate 3 with a uniform dot matrix according to the preset graphic size by using a laser device includes:

[0052] Select a PMMA light guide material plate, and according to the size of the light guide plate 3, the rectangular dot matrix of the light guide points, and the dot matrix size preset, use a laser device to perform laser engraving on the light guide material plate to obtain a light guide plate 3 with uniform distribution and neat dot matrix.

[0053] Among them, it should be noted that after the light guide plate 3 is manufactured, it can be used to convert the point light source emitted by the infrared LED point light source 7 into a surface light source, and is used for light conduction and heat dissipation. In order to improve the uniformity of light conduction and scattering of the light guide plate 3, preferably, in this embodiment, polymethyl methacrylate (PMMA) (also known as acrylic or plexiglass) material is used and manufactured by laser engraving. Among them, the light guide plate 3 formed by laser engraving has a V-CUT pattern, so as to obtain a light guide plate 3 with a uniformity of not less than 90%. The uniformity of the existing light guide plate 3 is generally not less than 80%, and the traditional small dot printing method is adopted. After printing on the light guide plate 3, the flatness and uniformity of the dot matrix pattern obtained will be different, and its light guiding uniformity can only reach ≥80%.

[0054] Step S103. Install a reflective film, the light guide plate 3, a diffusion film 4, a lower brightness enhancement film 5, and an upper brightness enhancement film 6 in sequence from bottom to top in the assembly groove 11 of the glue iron 1, and install the infrared LED point light source 7 between the light guide plate 3, the reflective film and the diffusion film 4 on one side of the light guide plate 3 to obtain the infrared light emitting module.

[0055] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An infrared light-emitting module, characterized in that, It includes a glue iron (1), and the glue iron (1) includes an assembly groove (11). A reflective film (2), a light guide plate (3), a diffusion film (4), a lower brightness enhancement film (5) and an upper brightness enhancement film (6) are sequentially installed in the assembly groove (11) from bottom to top. An infrared LED point light source (7) is provided on one side of the light guide plate (3) and between the reflective film and the diffusion film (4); The infrared LED point light source (7) includes a substrate layer. A Bragg optical reflection layer is provided on the substrate layer. An N-AIGaInP N-type confinement layer with a thickness of 1800 nm to 2200 nm is provided on the Bragg optical reflection layer. An I-AIGaInP active layer with a thickness of 0.1 nm to 0.3 um is provided on the N-type confinement layer. A P-AIGaInP P-type confinement layer with a thickness of 34000 nm to 36000 nm is provided on the I-AIGaInP active layer. A p-GaP window layer with a thickness of 47000 nm to 49000 nm is provided on the P-type confinement layer; The substrate layer includes a GaAs substrate with a thickness of 220 to 320 nm. A SiO2 protection layer with a thickness of 200 to 220 nm is provided on the surface of the GaAs substrate. An ITO enhancement layer with a thickness of 200 to 250 nm is provided on the surface of the SiO2 protection layer; The infrared wavelength emitted by the infrared LED point light source (7) is 600 nm to 750 nm; The module further includes a black glue (8), and the black glue (8) is installed above the upper brightness enhancement film (6); The light guide plate (3) is made of polymethyl methacrylate PMMA material and is manufactured by laser engraving; The light guide uniformity of the light guide plate (3) is not less than 90%; It also includes a light emission control circuit. The light emission control circuit includes a microprocessor chip U4 of model SY7201ABC. The LX pin of the microprocessor chip U4 is respectively connected to one end of an inductor L1 and the positive end of the infrared LED point light source. The negative end of the infrared LED point light source is connected to the ground after connecting a first capacitor C3. The ground pin GND of the microprocessor chip U4 is grounded. The FB pin of the microprocessor chip U4 is respectively connected to one end of a first resistor R13, one end of a second resistor R12 and the positive power supply. The other end of the first resistor R13 and the other end of the second resistor are grounded. The IN pin of the microprocessor chip U4 is respectively connected to the other end of the inductor L1, one end of a second capacitor C2 and a 3.3V voltage. The other end of the second capacitor C2 is grounded. The OVP pin of the microprocessor chip U4 is connected in series with a third resistor R9 and is respectively connected to one end of the first capacitor C3 and the negative power supply. The EN / PWM pin of the microprocessor chip U4 is connected in series with a fourth resistor R10 and is connected to the power supply voltage VCC; The light emission angle of the infrared LED point light source (7) is not less than 120 degrees. The lower brightness enhancement film (5) and the upper brightness enhancement film (6) are both provided with prisms, and the installation angles of the prisms can be adjusted; The total thickness of the infrared light-emitting module is not greater than 0.95 mm.

2. A method for preparing an infrared light-emitting module as described in claim 1, characterized in that, It includes: An infrared LED point light source (7) is manufactured by using an infrared light-emitting module manufacturing process with GaAs as the substrate, AlGaInP as the mounting material, and a Bragg optical reflection layer as the epitaxial technology; A PMMA light guide material plate is selected, and according to a preset graphic size, the light guide material plate is engraved into a light guide plate (3) with a uniform dot matrix by using a laser device; A reflective film, the light guide plate (3), a diffusion film (4), a lower brightness enhancement film (5), and an upper brightness enhancement film (6) are sequentially installed from bottom to top in an assembly groove (11) of an adhesive iron (1), and the infrared LED point light source (7) is installed between the reflective film and the diffusion film (4) on one side of the light guide plate (3) to obtain the infrared light-emitting module; The Bragg optical reflection layer includes an AlAs optical reflection layer, an AlGa optical reflection layer, or an As optical reflection layer; Selecting a PMMA light guide material plate and engraving the light guide material plate into a light guide plate (3) with a uniform dot matrix according to a preset graphic size by using a laser device, including: Selecting a PMMA light guide material plate, and performing laser engraving on the light guide material plate according to a preset light guide plate size, a dot matrix rectangle of light guide points, and a dot matrix size to obtain a light guide plate (3) with uniform distribution and neat dot matrix.

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