A low-light-transmittance composite optical film and its production process

Abstract

The present invention discloses a low-light-transmittance composite optical film and a production process thereof, and relates to the technical field of optical films. A low-light-transmittance composite optical film comprises a substrate layer, a raised layer arranged on both sides of the substrate layer, and a light-shielding layer bonded to the surface of the raised layer, wherein the raised layer is provided with two layers, and the surface of the raised layer away from the substrate layer is wavy; the light-shielding layer is laid on the surface of the raised layer in a wavy shape as a whole, and a filling layer is provided on the surface of the light-shielding layer. A low-light-transmittance composite optical film and a production process thereof proposed by the present invention can reduce the tensile deformation of the light-shielding layer during subsequent stretching by providing a wavy surface on the raised layer, thereby reducing the diameter of the oblate spherical pores, preventing the oblate spherical pores from being stretched too much and being prone to rupture, and the tensile force on the oblate spherical pores is in both the transverse and oblique directions, avoiding excessive unidirectional deformation caused by unidirectional stretching.

Description

Technical Field

[0001] The present invention relates to the technical field of optical films, and in particular to a low-light-transmittance composite optical film and a production process thereof. Background Art

[0002] Chinese patent CN110588119B discloses a high hiding and low light transmittance biaxially oriented nylon film and its preparation method. The film includes a five-layer structure, which is an anti-sticking surface layer, a hiding layer, a rigid support core layer, a hiding layer, and an anti-sticking surface layer from top to bottom; the hiding layer is composed of 60% to 90% nylon 6 and 10% to 40% polyamide elastomer; the hiding layer contains oblate spherical pores, the diameter of the pores parallel to the film plane is 2 to 8um, and the maximum height of the pores perpendicular to the film plane is 0.1 to 0.5um.

[0003] This patent achieves shading to a certain extent without relying on the high hiding power of white ink. However, the bubbles opened in the covering layer of this patent are prone to rupture after the film layer is stretched. The bubbles after stretching are flat and easily sticky after being pressed, thus failing to achieve a shading effect. Summary of the invention

[0004] The object of the present invention is to provide a low-light-transmittance composite optical film and a production process thereof. By arranging a wavy surface on the raised layer, the overall laying area of ​​the shading layer is made larger than the area of ​​the substrate layer. During subsequent stretching, the tensile deformation of the shading layer can be reduced, thereby reducing the diameter of the oblate spherical pores, preventing the oblate spherical pores from being stretched too much and easily cracked. In addition, when the wavy shading layer is stretched, the tensile force on the oblate spherical pores is in both the horizontal and oblique directions, which can cause the oblate spherical pores to deform in multiple directions, avoiding excessive unidirectional deformation caused by unidirectional stretching, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a low-light-transmittance composite optical film, comprising a substrate layer, a raised layer arranged on both sides of the substrate layer, and a shading layer bonded to the surface of the raised layer, wherein the raised layer is provided with two layers, and the surface of the raised layer away from the substrate layer is wavy; the shading layer is laid on the surface of the raised layer in a wavy shape as a whole, a filling layer is provided on the surface of the shading layer, the shading layer contains oblate spherical pores, the diameter of the oblate spherical pores parallel to the film plane is 1-4μm, the maximum height of the oblate spherical pores perpendicular to the film plane is 0.5-0.9μm, and the oblate spherical pores contain solid particles.

[0006] Preferably, the solid particles are one or more combinations of diatomaceous earth, alumina and talc.

[0007] Preferably, the diameter of the solid particles is 10-50 nm.

[0008] Preferably, the manufacturing method of the light-shielding layer is as follows:

[0009] To prepare solid particles, at least one material selected from diatomaceous earth, alumina and talcum powder is subjected to nano-scale pulverization to obtain a solid particle raw material;

[0010] The obtained solid particle raw material is mixed with the carbon dioxide gas material, and the mixture is fully mixed;

[0011] The melt temperature of the extruder is controlled at 260-280°C, and the melt pressure is controlled at 20-25MPa;

[0012] Supercritical carbon dioxide at a pressure of 7-10 MPa and a temperature of 40-50° C. is pumped into the extruder of the covering layer through a metering pump, and the amount of supercritical carbon dioxide injected is 2%-5% of the mass percentage of the covering layer;

[0013] The pressure of the melt in the T-die is controlled at 12-16MPa. At this time, the carbon dioxide begins to gasify to form extremely small pores, and the pores contain solid particles. When the carbon dioxide further expands and grows and stabilizes, spherical pores are formed in the light-shielding layer, and the spherical pores contain solid particles.

[0014] The shading layer is laid in a wave shape along the surface of the raised layer to form a curved shading layer.

[0015] The light-shielding layer is further stretched, and the spherical pores are stretched to form oblate spherical pores, thereby manufacturing the light-shielding layer.

[0016] Preferably, the average thickness of the raised layer is 20-30 um, and the difference in thickness between the thickest position and the thinnest position of the raised layer is less than 5 um.

[0017] Preferably, the raised layer is made of the following materials in parts by weight: 20-30 parts of polyurethane resin, 3-5 parts of polymethyl methacrylate particles, 3-5 parts of titanium dioxide particles and 5-10 parts of silicon dioxide particles.

[0018] Preferably, the surface of the leveling layer is provided with wavy protrusions matching the shading layer, and the leveling layer is made of the following raw materials in parts by weight: 99-99.8 parts of nylon, 0.01-0.05 parts of lubricant, 0.1-0.5 parts of opening agent, 0.01-0.05 parts of heat stabilizer and 0.01-0.05 parts of ultraviolet absorber.

[0019] Preferably, the substrate layer is made of one of PA, PC or PE materials, and the surface of the substrate layer is a rough surface.

[0020] Another technical problem to be solved by the present invention is to provide a production process of a low-light-transmittance composite optical film, comprising the following steps:

[0021] S1: mixing the components of the substrate layer, the protruding layer, the light shielding layer and the filling layer respectively according to the proportion, and dispersing them evenly by a high-speed mixer;

[0022] S2: The raw materials of the substrate layer, the raised layer, the light shielding layer and the filling layer are melted and extruded through their respective extruders, wherein the light shielding layer is foamed into holes, and the raised layer is extruded into a wave shape through an extrusion die, and four extruders are used to divide the flow into a seven-layer structure through an adapter, and the flow flows out through a T-die head and is cooled on a cold roller to form an unstretched sheet;

[0023] S3: Stretching the unstretched sheet step by step or simultaneously under heating at 60-80°C;

[0024] S4: heat-setting the stretched film, wherein the heat-setting temperature is 180-210° C., and the setting time is 10-20 seconds, to obtain a fixed composite optical film.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. By providing a wavy surface on the raised layer, the overall laying area of ​​the light-shielding layer is larger than the area of ​​the substrate layer. During subsequent stretching, the tensile deformation of the light-shielding layer can be reduced, thereby reducing the diameter of the oblate spherical pores, preventing the oblate spherical pores from being stretched too much and easily ruptured. In addition, when the wavy light-shielding layer is stretched, the tensile force on the oblate spherical pores is in the horizontal and oblique directions, which can cause the oblate spherical pores to deform in multiple directions, avoiding excessive unidirectional deformation caused by unidirectional stretching;

[0027] 2. Solid particles are arranged in the oblate spherical pores. By arranging solid particles in the oblate spherical pores, the solid particles can adhere to the inner wall of the oblate spherical pores, thereby increasing the roughness of the inner wall of the oblate spherical pores and preventing the inner wall of the oblate spherical pores from being adhered. At the same time, the solid particles that are not attached to the inner wall of the oblate spherical pores can also form support inside the oblate spherical pores when the oblate spherical pores are under pressure, thereby preventing the oblate spherical pores from rupturing.

[0028] 3. At the same time, the oblate spherical pores and solid particles further realize the diffusion and reflection of light, reducing the light transmittance of the composite optical film. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a cross-sectional view of the composite optical film of the present invention;

[0030] Figure 2 It is an enlarged view of point A of the present invention.

[0031] In the figure: 1, substrate layer; 2, raised layer; 3, shading layer; 31, oblate spherical pores; 32, solid particles; 4, filling layer. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] See also Figure 1-Figure 2 A low-light-transmittance composite optical film comprises a substrate layer 1, a raised layer 2 arranged on both sides of the substrate layer 1, and a shading layer 3 bonded to the surface of the raised layer 2, wherein the raised layer 2 is provided with two layers, and the surface of the raised layer 2 away from the substrate layer 1 is wavy; the shading layer 3 is laid on the surface of the raised layer 2 in a wavy shape as a whole, and by providing a wavy surface on the raised layer 2, the overall laying area of ​​the shading layer 3 is larger than the area of ​​the substrate layer 1, and during subsequent stretching, the tensile deformation of the shading layer 3 can be reduced, thereby reducing the diameter of the oblate spherical pores 31, preventing the oblate spherical pores 31 from being stretched too much and easily cracked, and in addition, when the wavy shading layer 3 is stretched, the tensile force on the oblate spherical pores 31 is in the horizontal and oblique directions, which can cause the oblate spherical pores 31 to deform in multiple directions, avoiding excessive unidirectional deformation caused by unidirectional stretching.

[0034] A filling layer 4 is provided on the surface of the shading layer 3. The shading layer 3 contains oblate spherical pores 31. The diameter of the oblate spherical pores 31 parallel to the film plane is 1-4 μm, and the maximum height of the pores perpendicular to the film plane is 0.5-0.9 μm. The oblate spherical pores 31 contain solid particles 32.

[0035] The solid particles 32 are one or more combinations of diatomaceous earth, alumina and talcum powder. By arranging the solid particles 32 in the oblate spherical pores 31, the solid particles 32 can adhere to the inner wall of the oblate spherical pores 31, thereby increasing the roughness of the inner wall of the oblate spherical pores 31 and avoiding adhesion of the inner wall of the oblate spherical pores 31. At the same time, the solid particles 32 that are not attached to the inner wall of the oblate spherical pores 31 can also form support inside the oblate spherical pores 31 when the oblate spherical pores 31 are under pressure to prevent the oblate spherical pores 31 from breaking.

[0036] The diameter of the solid particles 32 is 10-50 nm.

[0037] The manufacturing method of the light shielding layer 3 is as follows:

[0038] To prepare the solid particles 32, at least one material selected from diatomaceous earth, alumina and talcum powder is subjected to nano-scale pulverization to obtain a raw material of the solid particles 32;

[0039] Mix the obtained solid particle 32 raw material with the carbon dioxide gas material and mix them thoroughly and evenly;

[0040] The melt temperature of the extruder is controlled at 260-280°C, and the melt pressure is controlled at 20-25MPa;

[0041] Supercritical carbon dioxide at a pressure of 7-10 MPa and a temperature of 40-50° C. is pumped into the extruder of the covering layer through a metering pump, and the amount of supercritical carbon dioxide injected is 2%-5% of the mass percentage of the covering layer;

[0042] The pressure of the melt in the T-die is controlled at 12-16 MPa, at which point the carbon dioxide begins to gasify to form extremely tiny pores, and the pores contain solid particles 32. When the carbon dioxide further expands and grows and stabilizes, spherical pores are formed in the light-shielding layer 3, and the spherical pores contain solid particles 32.

[0043] The light shielding layer 3 is laid in a wave shape along the surface of the raised layer 2 to form a curved light shielding layer 3.

[0044] The light-shielding layer 3 is further stretched, and the spherical pores are stretched to form oblate spherical pores 31, thereby manufacturing the light-shielding layer 3.

[0045] The average thickness of the raised layer 2 is 20-30 um, and the thickness difference between the thickest position and the thinnest position of the raised layer 2 is less than 5 um.

[0046] The raised layer 2 is made of the following materials in parts by weight: 20-30 parts of polyurethane resin, 3-5 parts of polymethyl methacrylate particles, 3-5 parts of titanium dioxide particles and 5-10 parts of silicon dioxide particles. The raised layer 2 uses the above materials and has good anti-warping properties, which can ensure a high degree of adhesion between the raised layer 2 and the substrate layer 1 and avoid warping of the optical film. The raised layer 2 has good elasticity and can rebound quickly, further protecting the shading layer 3.

[0047] The surface of the leveling layer 4 is provided with wavy protrusions matching the shading layer 3, and the leveling layer 4 is made of the following raw materials in parts by weight: 99-99.8 parts of nylon, 0.01-0.05 parts of lubricant, 0.1-0.5 parts of opening agent, 0.01-0.05 parts of heat stabilizer and 0.01-0.05 parts of ultraviolet absorber.

[0048] The substrate layer 1 is made of one of PA, PC or PE materials, and the surface of the substrate layer 1 is a rough surface, which can increase the firmness of the bonding between the substrate layer 1 and the protrusion layer 2 .

[0049] Embodiment 1:

[0050] The substrate layer 1 is made of PA material;

[0051] The raised layer 2 is made of the following raw materials in parts by weight:

[0052] 20 parts of polyurethane resin, 3 parts of polymethyl methacrylate particles, 3 parts of titanium dioxide particles and 10 parts of silicon dioxide particles;

[0053] The light shielding layer 3 is made of the following raw materials in parts by weight:

[0054] 70 parts of nylon 6 and 20 parts of polyamide elastomer; solid particles 32 are diatomaceous earth;

[0055] The filling layer 4 adopts the following raw materials by weight:

[0056] 99 parts of nylon, 0.01 parts of lubricant, 0.5 parts of anti-blocking agent, 0.01 parts of heat stabilizer and 0.01 parts of ultraviolet absorber;

[0057] In order to better demonstrate the production process of the low-light-transmittance composite optical film, this embodiment now proposes a production process of the low-light-transmittance composite optical film, including the following steps:

[0058] Step 1: Mix the components of the substrate layer 1, the protruding layer 2, the light shielding layer 3 and the filling layer 4 respectively according to the proportion, and disperse them evenly by a high-speed mixer;

[0059] Step 2: The raw materials of the substrate layer 1, the raised layer 2, the light shielding layer 3 and the filling layer 4 are melted and extruded through their respective extruders, wherein the light shielding layer 3 is foamed into holes, and the raised layer 2 is extruded into a wave shape through an extrusion die, and four extruders are used to divide the flow into a seven-layer structure through an adapter, and the flow flows out through a T-die head and is cooled on a cold roller to form an unstretched sheet;

[0060] Step 3: The unstretched sheet is stretched step by step or simultaneously under heating at 60° C., and the stretching ratio is 3.0×3.0;

[0061] Step 4: heat-setting the stretched film, wherein the heat-setting temperature is 180° C. and the setting time is 10 seconds to obtain a fixed composite optical film.

[0062] Embodiment 2:

[0063] The substrate layer 1 is made of PA material;

[0064] The raised layer 2 is made of the following raw materials in parts by weight:

[0065] 30 parts of polyurethane resin, 5 parts of polymethyl methacrylate particles, 5 parts of titanium dioxide particles and 5 parts of silicon dioxide particles;

[0066] The light shielding layer 3 is made of the following raw materials in parts by weight:

[0067] 70 parts of nylon 6 and 20 parts of polyamide elastomer; solid particles 32 are diatomaceous earth;

[0068] The filling layer 4 adopts the following raw materials by weight:

[0069] 99 parts of nylon, 0.01 parts of lubricant, 0.5 parts of anti-blocking agent, 0.01 parts of heat stabilizer and 0.01 parts of ultraviolet absorber;

[0070] The composite optical film was prepared by the same method as in Example 1.

[0071] Embodiment three:

[0072] The substrate layer 1 is made of PA material;

[0073] The raised layer 2 is made of the following raw materials in parts by weight:

[0074] 30 parts of polyurethane resin, 5 parts of polymethyl methacrylate particles, 5 parts of titanium dioxide particles and 5 parts of silicon dioxide particles;

[0075] The light shielding layer 3 is made of the following raw materials in parts by weight:

[0076] 70 parts of nylon 6 and 20 parts of polyamide elastomer; solid particles 32 are diatomaceous earth;

[0077] The filling layer 4 adopts the following raw materials by weight:

[0078] 99 parts of nylon, 0.01 parts of lubricant, 0.5 parts of anti-blocking agent, 0.01 parts of heat stabilizer and 0.01 parts of ultraviolet absorber;

[0079] The optical film was prepared by the following method:

[0080] Step 1: Mix the components of the substrate layer 1, the protruding layer 2, the light shielding layer 3 and the filling layer 4 respectively according to the proportion, and disperse them evenly by a high-speed mixer;

[0081] Step 2: The raw materials of the substrate layer 1, the raised layer 2, the light shielding layer 3 and the filling layer 4 are melted and extruded through their respective extruders, wherein the light shielding layer 3 is foamed into holes, and the raised layer 2 is extruded into a wave shape through an extrusion die, and four extruders are used to divide the flow into a seven-layer structure through an adapter, and the flow flows out through a T-die head and is cooled on a cold roller to form an unstretched sheet;

[0082] Step 3: The unstretched sheet is stretched step by step or simultaneously under heating at 80°C, and the stretching ratio is 3.5×3.5;

[0083] Step 4: heat-setting the stretched film, wherein the heat-setting temperature is 180° C. and the setting time is 10 seconds to obtain a fixed composite optical film.

[0084] Embodiment 4:

[0085] The substrate layer 1 is made of PA material;

[0086] The raised layer 2 is made of the following raw materials in parts by weight:

[0087] 20 parts of polyurethane resin, 3 parts of polymethyl methacrylate particles, 3 parts of titanium dioxide particles and 10 parts of silicon dioxide particles;

[0088] The light shielding layer 3 is made of the following raw materials in parts by weight:

[0089] 70 parts of nylon 6 and 20 parts of polyamide elastomer; solid particles 32 are diatomaceous earth;

[0090] The filling layer 4 adopts the following raw materials by weight:

[0091] 99 parts of nylon, 0.01 parts of lubricant, 0.5 parts of anti-blocking agent, 0.01 parts of heat stabilizer and 0.01 parts of ultraviolet absorber;

[0092] The optical film was prepared by the following method:

[0093] Step 1: Mix the components of the substrate layer 1, the protruding layer 2, the light shielding layer 3 and the filling layer 4 respectively according to the proportion, and disperse them evenly by a high-speed mixer;

[0094] Step 2: The raw materials of the substrate layer 1, the raised layer 2, the light shielding layer 3 and the filling layer 4 are melted and extruded through their respective extruders, wherein the light shielding layer 3 is foamed into holes, and the raised layer 2 is extruded into a wave shape through an extrusion die, and four extruders are used to divide the flow into a seven-layer structure through an adapter, and the flow flows out through a T-die head and is cooled on a cold roller to form an unstretched sheet;

[0095] Step 3: The unstretched sheet is stretched step by step or simultaneously under heating at 80° C., and the stretching ratio is 4.0×4.0;

[0096] Step 4: heat-setting the stretched film, wherein the heat-setting temperature is 180° C. and the setting time is 10 seconds to obtain a fixed composite optical film.

[0097] Comparative Example 1:

[0098] The substrate layer 1 is made of PA material;

[0099] The raised layer 2 is made of the following raw materials in parts by weight:

[0100] 20 parts of polyurethane resin, 3 parts of polymethyl methacrylate particles, 3 parts of titanium dioxide particles and 10 parts of silicon dioxide particles;

[0101] The light shielding layer 3 is made of the following raw materials in parts by weight:

[0102] 70 parts of nylon 6 and 20 parts of polyamide elastomer;

[0103] The filling layer 4 adopts the following raw materials by weight:

[0104] 99 parts of nylon, 0.01 parts of lubricant, 0.5 parts of anti-blocking agent, 0.01 parts of heat stabilizer and 0.01 parts of ultraviolet absorber;

[0105] The optical film was prepared by the following method:

[0106] Step 1: Mix the components of the substrate layer 1, the protruding layer 2, the light shielding layer 3 and the filling layer 4 respectively according to the proportion, and disperse them evenly by a high-speed mixer;

[0107] Step 2: The raw materials of the substrate layer 1, the raised layer 2, the light shielding layer 3 and the filling layer 4 are melted and extruded through their respective extruders, wherein the light shielding layer 3 is foamed into holes, and the foaming does not contain solid particles 32, and the raised layer 2 is extruded into a wave shape through an extrusion die, and four extruders are used to divide the flow into a seven-layer structure through an adapter, and the flow flows out through a T-die head and is cooled on a cold roller to form an unstretched sheet;

[0108] Step 3: The unstretched sheet is stretched step by step or simultaneously under heating at 60° C., and the stretching ratio is 3.0×3.0;

[0109] Step 4: heat-setting the stretched film, wherein the heat-setting temperature is 180° C. and the setting time is 10 seconds to obtain a fixed composite optical film;

[0110] Comparative Example 2:

[0111] The substrate layer 1 is made of PA material;

[0112] The raised layer 2 is made of the following raw materials in parts by weight:

[0113] 20 parts of polyurethane resin, 3 parts of polymethyl methacrylate particles, 3 parts of titanium dioxide particles and 10 parts of silicon dioxide particles;

[0114] The light shielding layer 3 is made of the following raw materials in parts by weight:

[0115] 70 parts of nylon 6 and 20 parts of polyamide elastomer;

[0116] The filling layer 4 adopts the following raw materials by weight:

[0117] 99 parts of nylon, 0.01 parts of lubricant, 0.5 parts of anti-blocking agent, 0.01 parts of heat stabilizer and 0.01 parts of ultraviolet absorber;

[0118] The optical film was prepared by the following method:

[0119] Step 1: Mix the components of the substrate layer 1, the light shielding layer 3 and the filling layer 4 in proportion, and disperse them evenly by a high-speed mixer;

[0120] Step 2: The raw materials of the substrate layer 1, the light shielding layer 3 and the filling layer 4 are melted and extruded through respective extruders, wherein the light shielding layer 3 is foamed and pore-formed, and three extruders are used to separate the seven-layer structure through an adapter, and the seven-layer structure flows out through a T-die head and is cooled on a cold roller to form an unstretched sheet;

[0121] Step 3: The unstretched sheet is stretched step by step or simultaneously under heating at 60° C., and the stretching ratio is 3.0×3.0;

[0122] Step 4: heat-setting the stretched film, wherein the heat-setting temperature is 180° C. and the setting time is 10 seconds to obtain a fixed composite optical film;

[0123] The composite optical films obtained from Examples 1 to 4, Comparative Examples 1 and 2 were tested to obtain the following data:

[0124]

[0125]

[0126] Among them, transmittance: take a film the size of A4 paper, place it on a haze meter, and test its transmittance value; warping test: place the anti-warping optical film in an environment of 65℃ and 95%RH for 200h, then naturally cool it to room temperature, take out the film and place it on a glass plate, and measure the warping height h; bubble rupture: pore number calculation method: use a scanning electron microscope to observe the cross-section of the film in the MD and TD directions, randomly take a 100um length to observe whether there are bubbles rupture.

[0127] It can be seen from the above table that the composite optical films obtained in Examples 1 to 4 have low paint transmittance and no bubble rupture. Examples 3 and 4 use stretching ratios higher than those in Examples 1 and 2, and no bubble rupture occurs. Compared with Example 1, Comparative Example 1 does not have solid particles 32, and has a higher overall transmittance. Compared with Example 1, Comparative Example 2 lacks the raised layer 2 structure, so that the composite optical film in Comparative Example 2 not only has a high transmittance, but also a high warping value. In Comparative Example 2, no raised layer 2 is provided, and the shading layer 3 is a planar structure. After stretching, bubbles rupture.

[0128] In summary, the present invention proposes a low-light-transmittance composite optical film and a production process thereof. By arranging a wavy surface on the raised layer 2, the overall laying area of ​​the shading layer 3 is made larger than the area of ​​the substrate layer 1. During subsequent stretching, the tensile deformation of the shading layer 3 can be reduced, thereby reducing the diameter of the oblate spherical pores 31, preventing the oblate spherical pores 31 from being stretched too much and easily cracked. In addition, when the wavy shading layer 3 is stretched, the tensile force on the oblate spherical pores 31 is in both the lateral and oblique directions, which can cause the oblate spherical pores 31 to deform in multiple directions, avoiding excessive unidirectional deformation caused by unidirectional stretching. Solid particles 32 are arranged in the oblate spherical pores 31. By arranging the solid particles 32 in the oblate spherical pores 31, the solid particles 32 can adhere to the inner wall of the oblate spherical pores 31, thereby increasing the roughness of the inner wall of the oblate spherical pores 31 and avoiding the inner wall of the oblate spherical pores 31 from sticking. At the same time, the solid particles 32 that are not attached to the inner wall of the oblate spherical pores 31 can also form support inside the oblate spherical pores 31 when the oblate spherical pores 31 are under pressure to prevent the oblate spherical pores 31 from breaking. At the same time, the oblate spherical pores 31 and the solid particles 32 further realize the diffusion and reflection of light, thereby reducing the light transmittance of the composite optical film.

[0129] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A low-light-transmittance composite optical film, comprising a substrate layer (1), a protrusion layer (2) arranged on both sides of the substrate layer (1), and a light-shielding layer (3) bonded to the surface of the protrusion layer (2), characterized in that: The raised layer (2) is provided with two layers, and the surface of the raised layer (2) away from the substrate layer (1) is wavy; the light shielding layer (3) is laid on the surface of the raised layer (2) in a wavy shape as a whole, and a filling layer (4) is provided on the surface of the light shielding layer (3); the light shielding layer (3) contains oblate spherical pores (31); the diameter of the oblate spherical pores (31) parallel to the film plane is 1-4 μm, the maximum height of the oblate spherical pores (31) perpendicular to the film plane is 0.5-0.9 μm, and the oblate spherical pores (31) contain solid particles (32).

2. The low light transmittance composite optical film according to claim 1, characterized in that: The solid particles (32) are one or more combinations of diatomaceous earth, aluminum oxide and talc.

3. The low light transmittance composite optical film according to claim 1, characterized in that: The diameter of the solid particles (32) is 10-50 nm.

4. The low light transmittance composite optical film according to claim 1, wherein: The average thickness of the raised layer (2) is 20-30 μm, and the difference in thickness between the thickest position and the thinnest position of the raised layer (2) is less than 5 μm.

5. The low light transmittance composite optical film according to claim 1, wherein: The raised layer (2) is made of the following materials in parts by weight: 20-30 parts of polyurethane resin, 3-5 parts of polymethyl methacrylate particles, 3-5 parts of titanium dioxide particles and 5-10 parts of silicon dioxide particles.

6. The low light transmittance composite optical film according to claim 1, wherein: The surface of the leveling layer (4) is provided with wavy protrusions matching the light shielding layer (3), and the leveling layer (4) is made of the following raw materials in parts by weight: 99-99.8 parts of nylon, 0.01-0.05 parts of a lubricant, 0.1-0.5 parts of an anti-blocking agent, 0.01-0.05 parts of a heat stabilizer, and 0.01-0.05 parts of an ultraviolet absorber.

7. The low light transmittance composite optical film according to claim 1, characterized in that: The substrate layer (1) is made of one of PA, PC or PE materials.

8. A process for producing a low-transmittance composite optical film according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: mixing the components of the substrate layer (1), the raised layer (2), the light shielding layer (3) and the filling layer (4) in proportion, and dispersing them evenly by a high-speed mixer; S2: The raw materials of the base material layer (1), the raised layer (2), the light shielding layer (3) and the filling layer (4) are melted and extruded through respective extruders, wherein the light shielding layer (3) is foamed to form holes, and the raised layer (2) is extruded into a wave shape through an extrusion die. Four extruders are used to divide the flow into a seven-layer structure through an adapter, and the flow flows out through a T-die head and is cooled on a cold roller to form an unstretched sheet; S3: Stretching the unstretched sheet step by step or simultaneously under heating at 60-80°C; S4: heat-setting the stretched film, wherein the heat-setting temperature is 180-210° C., and the setting time is 10-20 seconds, to obtain a fixed composite optical film.

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