High-transmittance ultrathin liquid crystal display glass explosion-proof film and preparation method thereof

Abstract

The application discloses a high-transmittance ultra-thin liquid crystal display glass explosion-proof film and a preparation method thereof, and belongs to the technical field of liquid crystal display equipment protection films. The explosion-proof film comprises, in sequence from an attaching surface to an outer surface, an OCA high-transmittance optical adhesive layer, a first directional high-brightness film layer, a nano-reinforced layer and a second directional high-brightness film layer. The two directional high-brightness film layers are PET-based composite film layers, are stretched along a first direction and a second direction respectively, and the two directions are perpendicular to each other. The two directional high-brightness film layers contain carbon nanotubes arranged in a directional manner along the stretching direction, form a light guide structure, and together with a vertical intersecting optical axis form an optical grid. Through unique structure and material design, the application realizes an ultra-thin thickness (which can be lower than 180 mu m) and light weight, has high light transmittance (> 95.5%), low haze, excellent impact strength, and can effectively eliminate Newton's rings and Moire patterns, and perfectly solves the technical problems of thick and heavy, low light transmittance and influence on display effect of traditional tempered glass protection films.

Description

Technical Field

[0001] This invention belongs to the field of protective film technology for liquid crystal display devices, specifically relating to a high-transmittance ultra-thin explosion-proof film for liquid crystal display glass and its preparation method. Background Technology

[0002] As LCD technology develops towards larger sizes (such as 65 inches, 75 inches, and even 98 inches and above), the surface area of ​​the screen and its fragility increase simultaneously, making it extremely susceptible to damage from scratches, collisions, or accidental impacts during transportation, installation, and use. Therefore, a protective film is typically applied to the surface of the LCD module to prevent glass shards from flying when the panel breaks and to enhance its impact resistance.

[0003] Most commercially available explosion-proof screen protectors are made of tempered glass. While they provide basic protection, they have significant drawbacks: First, tempered glass is dense and heavy, which significantly increases the overall weight and structural burden when applied to large screens. Second, its thickness is usually quite large (usually exceeding 0.5mm), which is not conducive to the design of thinner and lighter display devices. Furthermore, the inherent light transmittance loss and light reflection issues of glass can lead to a decrease in screen brightness, reduced color saturation, and narrower viewing angles after applying the screen protector, severely impacting the user's visual experience. Summary of the Invention

[0004] The purpose of this application is to provide an impact-resistant protective film and its preparation method to address the shortcomings of current technology. This can effectively solve the problems of thickness, low light transmittance, and impact on display effect in existing protective film technologies, while also possessing good mechanical properties.

[0005] This invention provides a high-transmittance ultra-thin liquid crystal display glass explosion-proof film, which includes, from the attachment surface to the outer surface, the following layers in sequence: an OCA high-transmittance optical adhesive layer, a first oriented high-brightness film layer, a nano-reinforcement layer, and a second oriented high-brightness film layer; wherein the first oriented high-brightness film layer is a PET-based composite film layer stretched along a first direction, and the second oriented high-brightness film layer is a PET-based composite film layer stretched along a second direction, and the second direction is perpendicular to the first direction.

[0006] Furthermore, the preparation process of the first oriented high-brightness film layer and the second oriented high-brightness film layer is as follows:

[0007] S1: PET and carbon nanotubes are mixed evenly at a mass ratio of 90:1 and then added to a twin-screw extruder for melt blending extrusion granulation to prepare PET / carbon nanotube masterbatch.

[0008] S2: Preparation of the first oriented high-brightness film layer: The first matrix resin and PET / carbon nanotube masterbatch are premixed and dried at a mass ratio of 50-90:1. The mixture is then melt-extruded at 270-290℃ using a twin-screw extruder to form a cast sheet with a thickness of 1.0-1.5mm. The cast sheet is then oriented and stretched along the first direction, and heat-set at 200-220℃ for 5-8s before cooling to obtain the first oriented high-brightness film layer. Preparation of the second oriented high-brightness film layer: The second matrix resin and PET / carbon nanotube masterbatch are premixed and dried at a mass ratio of 50-90:1. The mixture is then melt-extruded at 270-290℃ using a twin-screw extruder to form a cast sheet with a thickness of 1.0-1.5mm. The cast sheet is then oriented and stretched along the second direction, and heat-set at 200-220℃ for 5-8s before cooling to obtain the second oriented high-brightness film layer.

[0009] Furthermore, both the first matrix resin and the second matrix resin are PET resins.

[0010] Furthermore, the thickness of the first oriented high-brightness film layer is 30-80 μm, preferably 50 μm.

[0011] Furthermore, the thickness of the second oriented high-brightness film layer is 30-80 μm, preferably 50 μm.

[0012] Furthermore, the carbon nanotubes are single-walled carbon nanotubes with a diameter of 1-2 nm and a length of 5-10 μm.

[0013] Further, the directional stretching process in step S2 is as follows: preheating temperature 80-95℃, stretching temperature 90-110℃, stretching rate 10-15m / min, and stretching ratio 3.0-4.0.

[0014] The first and second oriented high-brightness films are made of PET substrate, with carbon nanotubes introduced through blending and dispersion. During the stretching and orientation process of the PET film, the carbon nanotubes are straightened and oriented synchronously with the polymer chains along the stretching direction, forming a hollow cylindrical light guide structure. This structure not only reduces the absorption and scattering of light by the material through the hollow cavity, but its cylindrical walls also play a role in collecting and laterally confining the incident light, thereby improving the forward transmittance and focusing effect of the light. At the same time, the optical axes (i.e., the orientation direction of the carbon nanotubes) of the first and second oriented high-brightness films are perpendicular to each other, forming an "optical grating" structure. This structure can effectively disrupt the interference conditions of light, avoiding the generation of Newton's rings or moiré patterns due to interference caused by equal film thickness, thereby ensuring the visual uniformity of the displayed image and further synergistically improving the overall transmittance and brightness of the film.

[0015] Furthermore, the OCA high-transmittance optical adhesive layer is an optically transparent adhesive (OCA) with a thickness of 5-15μm, a total light transmittance of greater than 99%, a haze of less than 0.5%, and excellent initial tack, long-term durability, and anti-aging properties.

[0016] Furthermore, the nano-reinforcing layer is a hafnium-doped indium oxide (In2O3:HfO2) transparent conductive film deposited using magnetron sputtering technology, with a thickness of 0.3-1 μm, preferably 0.5 μm.

[0017] This application provides a method for preparing the above-mentioned high transmittance ultrathin liquid crystal display glass explosion-proof film, including the following steps:

[0018] (1) A layer of OCA adhesive is coated on the surface of the liquid crystal glass, and then baked and cured in an oven to obtain an OCA high-transmittance optical adhesive layer;

[0019] (2) A first oriented high-brightness film layer is attached to the surface of the OCA high-transmittance optical adhesive layer;

[0020] (3) A hafnium-doped indium oxide (In2O3:HfO2) nano-reinforcing layer is deposited on the surface of the first oriented high-brightness film using a magnetron sputtering process;

[0021] (4) A second oriented high-brightness film is attached to the surface of the nano-reinforced layer;

[0022] (5) The preliminarily stacked film structure is fed into a high-temperature and high-pressure composite roller for pressing to form the high transmittance ultra-thin liquid crystal display glass explosion-proof film.

[0023] Furthermore, in step (3), the magnetron sputtering process uses a ceramic target doped with 5-15wt% HfO2 in In2O3 as the target material, and is carried out under the conditions of argon-oxygen mixed atmosphere, working pressure 0.3-0.8Pa, substrate temperature 80-150℃, and sputtering power 100-300W.

[0024] Compared with the prior art, the present invention has the following advantages and technical effects:

[0025] The high-transmittance ultra-thin liquid crystal display glass explosion-proof film provided by this invention possesses superior optical performance. By introducing and precisely oriented carbon nanotubes in the first and second oriented high-brightness film layers, the oriented arrangement of carbon nanotubes effectively improves the microstructure of the PET matrix and reduces light scattering. Simultaneously, their unique orientation and the combined effect of the two vertical structures optimize the optical path and suppress interference. In conjunction with the OCA high-transmittance optical adhesive layer and the nano-reinforcing layer, ultra-high total light transmittance and extremely low haze are achieved, thereby maximizing the preservation of the screen's original brightness and color. More importantly, the optical axes of the two films intersect perpendicularly, forming a unique "optical grid" that effectively disrupts light interference conditions, fundamentally eliminating visual defects such as Newton's rings and moiré patterns, ensuring image uniformity.

[0026] The high-transmittance ultra-thin liquid crystal display glass explosion-proof film provided by this invention achieves an excellent balance between mechanical protection and thinness. Through the synergistic effect of a bidirectional cross-reinforced high-brightness film layer and an intermediate nano-reinforcing layer (hafnium-doped indium oxide thin film), the film layer is endowed with extremely high tensile strength, modulus, and impact resistance, ensuring reliable explosion-proof protection. At the same time, the overall structure achieves an ultra-thin thickness (<180μm) and extremely light weight, perfectly matching the development trend of thinner and lighter large-size display devices and solving the application burden caused by excessive thickness and weight of tempered glass films. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the high transmittance ultra-thin liquid crystal display glass explosion-proof film structure provided in Embodiment 1 of the present invention. Detailed Description

[0028] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0029] Example 1

[0030] This embodiment provides a method for preparing a high-transmittance ultra-thin liquid crystal display glass explosion-proof film, the specific steps of which are as follows:

[0031] (1) Preparation of PET / carbon nanotube masterbatch: PET chips and single-walled carbon nanotubes with a diameter of 1-2 nm and a length of 5-10 μm are mixed evenly in a high-speed mixer at a mass ratio of 90:1. Then, the mixture is added to a twin-screw extruder and melt-blended, extruded, and granulated at 280 °C to obtain PET / carbon nanotube masterbatch.

[0032] (2) Preparation of the first oriented high-brightness film layer: The PET matrix resin and the masterbatch obtained in step (1) were premixed at a mass ratio of 80:1 and dried thoroughly. The mixture was fed into a twin-screw extruder and melt-extruded at 280°C. The mixture was then cast onto a cooling roller through a T-die to form a uniform cast sheet with a thickness of approximately 1.2 mm. Subsequently, the cast sheet was stretched longitudinally (in the first direction) with the following stretching process parameters: preheating temperature 90°C, stretching temperature 105°C, stretching rate 12 m / min, and stretching ratio 3.5. The stretched film was heat-set at 210°C for 6 s, cooled, and then wound up to obtain a first oriented high-brightness film layer with a thickness of approximately 50 μm.

[0033] (3) Preparation of the second oriented high-brightness film: Repeat step (2), only change the stretching direction to the transverse direction (second direction), and keep the other process parameters exactly the same as the raw material ratio to obtain a second oriented high-brightness film with a thickness of about 50 μm.

[0034] (4) Preparation of the overall structure of the explosion-proof membrane:

[0035] a. A layer of optically transparent adhesive (OCA) is uniformly coated on the surface of a cleaned liquid crystal glass substrate and baked in an 80°C oven to cure, forming an OCA high-transparency optical adhesive layer with a thickness of about 10μm.

[0036] b. The first oriented high-brightness film layer (with the carbon nanotube orientation direction being longitudinal) obtained in step (2) is flatly attached to the surface of the OCA high-transmittance optical adhesive layer.

[0037] c. Using a magnetron sputtering device, with an In2O3 ceramic target doped with 10 wt% HfO2 as the target material, under the conditions of an argon and oxygen mixed atmosphere (Ar:O2=9:1), a working pressure of 0.5 Pa, a substrate temperature of 120℃, and a sputtering power of 200W, a hafnium-doped indium oxide (In2O3:HfO2) film with a deposition thickness of about 0.5 μm was deposited on the surface of the first oriented high-brightness film layer to form a nano-reinforcement layer.

[0038] d. The second oriented high-brightness film layer (with the carbon nanotube orientation direction being transverse) obtained in step (3) is flatly attached to the surface of the nano-reinforcement layer, ensuring that its optical axis is perpendicular to the first layer.

[0039] e. The above-mentioned laminated structure is fed into a high-temperature and high-pressure composite roller and pressed under the conditions of 100°C and 0.6 MPa to obtain the final explosion-proof film sample.

[0040] Example 2

[0041] The difference between this embodiment and Example 1 is that in the first and second oriented high-brightness film layers, the ratio of PET matrix resin to PET / carbon nanotube masterbatch is adjusted to 50:1, and the thickness of both film layers is controlled at 30 μm. The thickness of the nano-reinforcing layer is adjusted to 0.3 μm. The thickness of the OCA high-transmittance optical adhesive layer is 5 μm. The remaining preparation steps and parameters are the same as in Example 1.

[0042] Example 3

[0043] The difference between this embodiment and Example 1 is that the ratio of PET matrix resin to PET / carbon nanotube masterbatch in the first and second oriented high-brightness films is adjusted to 90:1, and the thickness of both films is controlled at 80 μm. The thickness of the nano-reinforcing layer is adjusted to 1.0 μm. The thickness of the OCA high-transmittance optical adhesive layer is 15 μm. The magnetron sputtering substrate temperature is adjusted to 150℃, and the sputtering power is 300 W. The remaining preparation steps and parameters are the same as in Example 1.

[0044] Comparative Example 1

[0045] Compared to Example 1, pure PET resin was used without the addition of carbon nanotubes. Longitudinal and transversely stretched PET films, each with a thickness of 50 μm, were prepared using the same process as in Example 1. All other steps and process parameters were identical to those in Example 1.

[0046] Comparative Example 2

[0047] Compared to Example 1, the preparation process was the same as in Example 1, but only a single layer of carbon nanotube-containing high-brightness film (100 μm thick) stretched in a single direction (longitudinal) was used. After laminating a 10 μm OCA high-transmittance optical adhesive layer, a 0.5 μm hafnium-doped indium oxide nano-reinforcing layer was deposited on its surface, thus forming the "OCA high-transmittance optical adhesive layer / unidirectional high-brightness film / nano-reinforcing layer" structure. Other steps and process parameters were exactly the same as in Example 1.

[0048] Performance Testing and Results Analysis

[0049] The samples obtained in Examples 1-3 and Comparative Examples 1-2 were subjected to key performance tests, and the test standards and methods are as follows:

[0050] Transmittance and haze: According to standard GB / T 2410-2008, the transmittance and haze of the visible light band (380-780nm) are tested using a haze meter.

[0051] Newton's rings / Moiré pattern observation: Under a standard fluorescent light box, attach the sample to an LCD screen displaying a uniform white image, and visually observe and record the interference fringes from different angles.

[0052] Impact resistance: According to the falling ball impact test method, a steel ball with a diameter of 19mm and a weight of 100g is used to freely fall from different heights to impact the center of the sample, and the maximum impact energy (J) that the sample is not broken is recorded.

[0053] Tensile strength and modulus of elasticity: tested using a universal testing machine in accordance with standard GB / T 1040.3-2006.

[0054] sample Light transmittance (%) Haze (%) Newton's rings / Moiré pattern Maximum impact energy (J) Tensile strength (MPa) Elastic modulus (GPa) Example 1 96.8 0.6 none 5.2 325 8.7 Example 2 95.5 0.8 none 3.8 298 8.1 Example 3 97.1 0.5 none 6.5 350 9.0 Comparative Example 1 91.2 1.5 Slight moiré patterns 1.5 105 3.5 Comparative Example 2 95.0 0.9 There are obvious Newtonian rings 4.0 280 7.2

[0055] As shown in the table above, Examples 1-3 all exhibited excellent transmittance (>95.5%) and low haze (<0.8%), and no Newton's rings or moiré patterns were observed. This verifies the anti-reflective effect of the carbon nanotube light-conducting structure and the interference-eliminating effect of the "optical grating" structure. Comparative Example 1 (without carbon nanotubes) showed significantly reduced transmittance, increased haze, and slight moiré patterns. Comparative Example 2 (one-way film) had acceptable transmittance, but due to the lack of a counteracting effect perpendicular to the optical axis, obvious Newton's rings were produced. The impact strength, tensile strength, and modulus of Examples 1-3 were all much higher than those of Comparative Example 1 (pure PET composite film), demonstrating the synergistic toughening effect of carbon nanotube reinforcement and nano-reinforcing layer. Comparative Example 2, due to only unidirectional reinforcement, showed significant anisotropy in its mechanical properties, and its overall strength was lower than that of the bidirectional reinforced examples. As can be seen, by arranging carbon nanotubes vertically to form an enhanced network and introducing a nano-reinforcing layer, the present invention has successfully achieved excellent optical performance and protective capabilities at an ultra-thin thickness (<180μm), thus resolving the contradiction between the thickness and the impact on display effect of existing technologies.

Claims

1. A high-transmittance ultra-thin explosion-proof film for liquid crystal display glass, characterized in that, The layers, from the attachment surface to the outer surface, sequentially include: an OCA high-transmittance optical adhesive layer, a first oriented high-brightness film layer, a nano-reinforcing layer, and a second oriented high-brightness film layer; the nano-reinforcing layer is a hafnium-doped indium oxide transparent conductive film with a thickness of 0.3-1 μm; wherein the optical axes of the first and second oriented high-brightness films intersect perpendicularly to each other, and the preparation processes of the first and second oriented high-brightness films are as follows: S1: PET and carbon nanotubes are mixed evenly at a mass ratio of 90:1 and then added to a twin-screw extruder for melt blending extrusion granulation to prepare PET / carbon nanotube masterbatch. S2: Preparation of the first oriented high-brightness film layer: The first matrix resin and PET / carbon nanotube masterbatch are premixed and dried at a mass ratio of 50-90:1, melt-extruded to form a cast sheet, the cast sheet is oriented and stretched along the first direction, and then cooled after heat setting to obtain the first oriented high-brightness film layer; Preparation of the second oriented high-brightness film layer: The second matrix resin and PET / carbon nanotube masterbatch are premixed and dried at a mass ratio of 50-90:1, melt-extruded to form a cast sheet, the cast sheet is oriented and stretched along the second direction, and then cooled after heat setting to obtain the second oriented high-brightness film layer; and the second direction is perpendicular to the first direction, and both the first matrix resin and the second matrix resin are PET resin.

2. The high transmittance ultra-thin liquid crystal display glass explosion-proof film according to claim 1, characterized in that, The carbon nanotubes are single-walled carbon nanotubes with a diameter of 1-2 nm and a length of 5-10 μm.

3. The high transmittance ultra-thin liquid crystal display glass explosion-proof film according to claim 1, characterized in that, The thickness of the first oriented high-brightness film layer is 30-80 μm; the thickness of the second oriented high-brightness film layer is 30-80 μm.

4. The high transmittance ultra-thin liquid crystal display glass explosion-proof film according to claim 1, characterized in that, The OCA high-transmittance optical adhesive layer has a thickness of 5-15 μm, a total light transmittance of greater than 99%, and a haze of less than 0.5%.

5. A method for preparing a high-transmittance ultra-thin liquid crystal display glass explosion-proof film according to any one of claims 1-4, characterized in that, Includes the following steps: (1) A layer of OCA adhesive is coated on the surface of the liquid crystal glass and then dried and cured in an oven to obtain an OCA high-transmittance optical adhesive layer; (2) A first oriented high-brightness film layer is attached to the surface of the OCA high-transmittance optical adhesive layer; (3) A hafnium-doped indium oxide nano-reinforcing layer is deposited on the surface of the first oriented high-brightness film layer using a magnetron sputtering process; (4) A second oriented high-brightness film is attached to the surface of the nano-reinforced layer; (5) The preliminarily stacked film structure is fed into a high-temperature and high-pressure composite roller for pressing to form the high transmittance ultra-thin liquid crystal display glass explosion-proof film.

6. The preparation method according to claim 5, characterized in that, In step (3), the nano-reinforced layer is deposited by magnetron sputtering. The target material is a ceramic target doped with 5-15wt% HfO2 in In2O3. The process conditions are: argon-oxygen mixed atmosphere, working pressure 0.3-0.8Pa, substrate temperature 80-150℃, and sputtering power 100-300W.

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