Vehicle-mounted HOE holographic transparent film with edge bevel transition and preparation method thereof

Abstract

This invention discloses a vehicle-mounted HOE holographic transparent film with a beveled edge transition and its preparation method. The transparent film includes a transparent substrate, a holographic functional layer, and a protective layer, with a circumferentially continuous beveled edge at the film's edge. The beveled edge extends obliquely from the glass bonding surface to the non-bonding surface, with an oblique angle α of 3°~15°, a bevel length L of 5 mm~20 mm, and a surface roughness Ra≤0.1 μm. The equivalent transmittance at the edge of the beveled edge smoothly transitions from 70%~85% of the HOE film body to 88%~95% of the vehicle-mounted glass. The preparation method includes HOE substrate preparation, edge positioning, rough polishing, fine polishing correction, cleaning, and optical inspection. This invention eliminates the need for additional functional layers, has a simple and reliable structure, does not affect holographic diffraction function, is resistant to high and low temperatures and impact, is fully adaptable to vehicle-mounted scenarios, has a simple structure, is compatible with existing HOE film manufacturing processes, and effectively improves the overall visibility and safety of the driver.

Description

Technical Field

[0001] This invention relates to the field of automotive holographic display technology, specifically to an automotive HOE holographic transparent film with gradually changing transmittance through edge bevels and its preparation method. Background Technology

[0002] Automotive HOE holographic transparent films are typically applied to the inner surface of the windshield or side windows for HUD or XR displays. Because the HOE film itself needs to perform holographic diffraction imaging, its visible light transmittance is usually lower than that of the automotive glass. When the film edge is a vertically cut surface, abrupt changes in brightness and reflection can easily occur between the film area and the glass area, making the boundary perceptible to the driver.

[0003] Conventional cutting or simple smoothing and polishing can only improve edge burrs, but cannot create a continuous transition of transmittance from the film body area to the glass area. Therefore, an edge transition solution that is simple in structure, compatible with processes, and does not compromise the holographic function is needed. Summary of the Invention

[0004] To address the problems existing in the background technology, and considering the large difference in transmittance between the existing HOE holographic transparent film and automotive glass, as well as the visual abruptness caused by the vertical edge cutting, this invention sets a circumferentially continuous transition slope at the edge of the HOE holographic transparent film. This causes the film thickness and the effective optical path of light passing through the film to gradually decrease along the edge direction. Combined with the low roughness surface after fine polishing, this reduces the abrupt changes in reflection and transmittance caused by the vertical edge.

[0005] The technical solution of the present invention is as follows: I. A type of automotive HOE holographic transparent film with beveled edge transition: The automotive HOE holographic transparent film is used to be bonded to automotive glass and includes a transparent substrate, a holographic functional layer and a protective layer stacked in sequence. The edge of the automotive HOE holographic transparent film is provided with a circumferentially continuous transition slope. The transition slope extends radially from the glass bonding side to the non-bonding side to achieve a gradual transition in transmittance between the automotive HOE holographic transparent film and the automotive glass.

[0006] The inclination angle α of the transition slope is 3°~15°, the slope length L is 5 mm~20 mm, and the surface roughness Ra of the slope is ≤0.1 μm.

[0007] The transparent substrate is polyethylene terephthalate (PET) or polycarbonate (PC) with a thickness of 50 μm to 150 μm; The holographic functional layer is a volumetric holographic grating layer with a thickness of 15 μm to 25 μm; The protective layer is a scratch-resistant and wear-resistant coating with a thickness of 5 μm to 10 μm.

[0008] The vehicle-mounted HOE holographic transparent film has a central region without a transition slope, and a continuous circumferential transition slope is provided around the outer edge of the central region. The transition slope extends radially from the central region to the outer edge, so that the thickness gradually decreases.

[0009] The visible light transmittance of the central area of ​​the automotive HOE holographic transparent film is 70%~85%, and the equivalent visible light transmittance of the outermost edge of the transition slope is 88%~95%, which is consistent with the transmittance of automotive glass.

[0010] II. A method for preparing a vehicle-mounted HOE holographic transparent film: S1. Prepare HOE holographic transparent film substrate; S2. Position and fix the edges of the HOE holographic transparent film substrate; S3. A predetermined transition slope is formed by rough polishing, and the surface roughness of the slope is corrected by fine polishing. S4. Finally, clean and dry the product.

[0011] Step S1 specifically involves preparing a transparent substrate, a holographic functional layer, and a protective layer that are sequentially stacked through coating, exposure, and curing processes to obtain a complete HOE holographic transparent film substrate.

[0012] Step S2 specifically involves fixing the HOE holographic transparent film substrate on the positioning platform and locating the edge processing area according to the preset inclined plane parameters.

[0013] The specific step S3 is as follows: using a diamond grinding wheel or laser polishing equipment, the edge processing area of ​​the HOE holographic transparent film substrate is subjected to gradient polishing. First, rough polishing is used to form a preliminary bevel, and then fine polishing is used to reduce the surface roughness to Ra≤0.1μm, so that the visible light transmittance radially transitions from 70%~85% to 88%~95% from the inside to the outside.

[0014] Step S4 specifically involves ultrasonically cleaning and drying the polished edge processing area to form a vehicle-mounted HOE holographic transparent film.

[0015] This invention utilizes the gradual refraction characteristics of light at an inclined plane to continuously and gradually change the equivalent transmittance of the HOE film from 70%~85% of the original material to 88%~95% to match that of automotive glass, achieving a seamless transition. The manufacturing process employs a gradient polishing technique of "rough polishing + fine polishing," combined with high-precision positioning and cleaning inspection, to ensure accurate inclined plane parameters and stable optical performance.

[0016] The beneficial effects of this invention are as follows: (1) The transition slope weakens the visual boundary between the film area and the glass area, reducing the abruptness in the driver's field of vision. Through the gradual refraction design of the edge slope, the abrupt change in the transmittance of the HOE film and the glass is eliminated, the edge connection is natural, and it does not affect the overall integrity of the driver's field of vision.

[0017] (2) No additional functional layers are required, the structure is reliable, it is compatible with existing coating, exposure, curing and bonding processes, and the cost is low.

[0018] (3) The sloping area is located at the edge, which does not change the holographic imaging area of ​​the HOE film body and can maintain the HUD / XR display function. The sloping parameters (angle, length) match the installation requirements of the vehicle glass and are resistant to high and low temperatures and impact.

[0019] This invention requires no additional functional layer, has a simple and reliable structure, is compatible with existing HOE film preparation processes, does not affect holographic diffraction function, is resistant to high and low temperatures and impact, is fully adaptable to vehicle scenarios, and effectively improves the overall visibility and safety of the driver's field of vision.

[0020] This invention has a simple structure, is compatible with existing HOE film manufacturing processes, and is suitable for automotive HUD / XR transparent display scenarios. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the HOE holographic transparent film for vehicles.

[0022] Figure 2 This is a magnified schematic diagram of a portion of the transition slope.

[0023] Figure 3 This is a schematic diagram illustrating the gradient effect of transmittance.

[0024] Figure 4 This is a flowchart of the preparation process. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0026] like Figure 1 As shown, the automotive HOE holographic transparent film is used to be tightly adhered to the automotive glass, including a transparent substrate 1A, a holographic functional layer 1B and a protective layer 1C stacked in sequence; in specific implementation, the transparent substrate 1A is tightly adhered to the automotive glass.

[0027] like Figure 2 As shown, the overall edge of the vehicle-mounted HOE holographic transparent film is provided with a circumferentially continuous transition slope. The transition slope is formed by the edges of the transparent substrate 1A, the holographic functional layer 1B and the protective layer 1C. The transition slope extends radially from the glass bonding side to the non-bonding side to achieve a gradual transition in transmittance between the vehicle-mounted HOE holographic transparent film and the vehicle glass.

[0028] The transition slope is continuously distributed circumferentially along the HOE holographic transparent film and extends obliquely from the functional surface (the side that adheres to the glass) of the HOE holographic transparent film to the non-functional surface, achieving a seamless transition in transmittance between the HOE holographic transparent film and the glass. The transition slope allows for a continuous change in the effective optical path and interface reflection conditions of the film layer, smoothly transitioning the edge equivalent transmittance from 70%~85% of the HOE film itself to 88%~95% of the automotive glass, reducing the abruptness of the boundary.

[0029] The inclination angle α of the transition slope is 3°~15°, and the slope length L is 5 mm~20 mm. This range provides a sufficiently wide visual transition without excessively occupying the vehicle's glass display or mounting area. The surface roughness of the slope is controlled to Ra≤0.1 μm to avoid edge scattering affecting the driver's field of vision.

[0030] The tilt angle of the transition slope is designed to be 3°~15°. This angle range can ensure the smoothness of the gradual change in transmittance and avoid installation interference caused by excessive slope length. The slope length is 5mm~20mm to match the installation boundary requirements of automotive glass. The surface roughness Ra≤0.1μm ensures uniform light refraction and no scattering interference.

[0031] The transparent substrate 1A is made of polyethylene terephthalate (PET) or polycarbonate (PC) with a thickness of 50 μm to 150 μm; the holographic functional layer 1B is a volumetric holographic grating layer with a thickness of 15 μm to 25 μm; and the protective layer 1C is a scratch-resistant and abrasion-resistant coating with a thickness of 5 μm to 10 μm. The scratch-resistant and abrasion-resistant coating material is a UV-curable acrylate coating, a silicone curing coating, or a polyurethane acrylate curing coating.

[0032] The HOE holographic transparent film for vehicles has a central area without a transition slope. A continuous circumferential transition slope is set around the outer edge of the central area. The transition slope extends radially from the central area to the outer edge, making the thickness gradually decrease.

[0033] Specifically, the transition slope is formed by the edges of the transparent substrate 1A, the holographic functional layer 1B and the protective layer 1C, and extends radially from the central region to the outer peripheral edge, so that the edge thickness of the vehicle-mounted HOE holographic transparent film gradually decreases.

[0034] The visible light transmittance of the central area of ​​the HOE film body of the vehicle-mounted HOE holographic transparent film is 70%~85%, and the equivalent visible light transmittance of the outermost edge of the transition slope is 88%~95%, which is consistent with the transmittance of vehicle-mounted glass (88%~95%).

[0035] The preparation method of this invention includes HOE substrate preparation, edge positioning, rough polishing, fine polishing, cleaning, and optical inspection. Specifically, the method includes: S1. Prepare HOE holographic transparent film substrate; A complete HOE holographic transparent film substrate is obtained by preparing a transparent substrate, a holographic functional layer, and a protective layer in sequence through coating, exposure, and curing processes.

[0036] S2. Position and fix the edges of the HOE holographic transparent film substrate; The HOE holographic transparent film substrate is fixed on a high-precision positioning platform, and the edge processing area is positioned and fixed according to the preset inclined plane parameters (angle, length).

[0037] S3. A predetermined transition slope is formed by rough polishing, and the surface roughness of the slope is corrected by fine polishing. Using diamond grinding wheels or laser polishing equipment, the edge processing area of ​​the HOE holographic transparent film substrate is subjected to gradient polishing, so that the edges of the transparent substrate, holographic functional layer and protective layer together form a predetermined transition slope. First, rough polishing is used to form a preliminary slope, and then fine polishing is used to reduce the surface roughness to Ra≤0.1μm, so that the visible light transmittance radially transitions from 70%~85% to 88%~95% from the inside to the outside.

[0038] S4. Finally, the cleaning and drying processes are carried out. After cleaning, the dimensions of the inclined plane, the transmittance gradient curve, and the holographic diffraction efficiency are tested.

[0039] The edge processing area of ​​the polished HOE holographic transparent film substrate is ultrasonically cleaned and dried. The bevel angle, length and transmittance gradient effect are tested to ensure that they meet the requirements and form the vehicle-mounted HOE holographic transparent film.

[0040] Example 1: like Figure 1 As shown, the automotive HOE holographic transparent film comprises a transparent substrate 1A, a holographic functional layer 1B, and a protective layer 1C stacked sequentially. The transparent substrate 1A provides mechanical support; the holographic functional layer 1B records and reconstructs the holographic grating; and the protective layer 1C improves surface abrasion resistance. A transition slope 1D is formed at the circumferential edge of the automotive HOE holographic transparent film, which is formed by the combined processing of the edges of the transparent substrate 1A, the holographic functional layer 1B, and the protective layer 1C. The film is bonded to the inner surface of the automotive glass 1F using optical adhesive.

[0041] like Figure 2As shown, the tilt angle α of the transition slope 1D is 3°~15°, the slope length L is 5 mm~20 mm, and the surface roughness Ra≤0.1 μm. The transition slope 1D extends laterally from the glass bonding side, so that the overall effective thickness of the film layer at the edge of the automotive HOE holographic transparent film gradually decreases, thereby making the edge equivalent transmittance smoothly transition to the transmittance of the automotive glass.

[0042] During operation, ambient light passes through the complete film layer in the central HOE film body region, and the effective film layer thickness gradually decreases in the transition slope region, resulting in a continuous decrease in absorption, reflection, and diffraction losses. Therefore, as... Figure 3 As shown, the equivalent transmittance can smoothly transition from approximately 78% in the HOE film body area to approximately 92% in the vehicle glass area.

[0043] In use, the HOE holographic transparent film with a transitional bevel is bonded to the inner surface of the vehicle glass using OCA optical adhesive, so that the central holographic functional area corresponds to the HUD / XR projection light path, and the thin end of the transitional bevel faces the surrounding transparent glass area. The HUD / XR projection beam is diffracted from the holographic functional layer to the driver's eye box, while the edge area has a gradual change in transmittance to reduce the sense of the film's boundary.

[0044] like Figure 4 As shown, the preparation method includes substrate preparation, edge positioning, rough polishing, fine polishing correction, and cleaning and inspection. Rough polishing is used to form the basic geometry of the bevel, while fine polishing is used to reduce surface roughness and correct angular errors.

[0045] In the preparation method, a high-precision gradient polishing process is adopted. First, a preliminary inclined surface is formed by rough polishing with a diamond wheel, and then the surface roughness is optimized by laser fine polishing to ensure the angle accuracy and smoothness of the inclined surface. The ultrasonic cleaning step can remove polishing residues and avoid affecting the optical performance.

[0046] In this embodiment, a 100 μm thick PET transparent substrate is selected, a 20 μm thick photopolymer volume holographic functional layer is formed on its surface, and then an 8 μm thick anti-scratch protective layer is formed to obtain a HOE film substrate with a size of 200 mm × 150 mm.

[0047] The preparation process begins with obtaining a complete HOE film substrate. Then, the circumferential edges are rough-polished and fine-polished on a positioning platform. Following this, cleaning, dimensional inspection, surface roughness inspection, transmittance gradient inspection, and diffraction efficiency inspection are performed. Specifically, the substrate is fixed on a five-axis positioning platform with a transition slope angle of 8° and a length of 12 mm. Rough polishing is performed using a diamond grinding wheel, and the surface roughness of the slope after fine polishing is controlled to Ra ≤ 0.05 μm.

[0048] The performance test results are as follows.

[0049] The test data are listed below: (Inclined angle) Test result: 8.1°; Corresponding requirement: 3°~15°.

[0050] (Inclined surface length) test result: 12.05 mm; corresponding requirement: 5 mm~20 mm.

[0051] (Surface roughness) test result: Ra=0.042 μm; corresponding requirement: Ra≤0.1 μm.

[0052] (Diffraction efficiency change) Test results: 88.5% before processing, 87.9% after processing; Corresponding requirement: Maintain the original function.

[0053] (High and low temperature cycling) test results: transmittance change ≤0.5%; corresponding requirement: no cracking after cycling from -40 ℃ to 85 ℃.

[0054] (Adhesion) Test result: Grade 0 in cross-cut adhesion test; Corresponding requirement: No peeling.

[0055] Example 2: A 125 μm thick transparent PC substrate was selected, the holographic functional layer was 20 μm thick, and the protective layer was 8 μm thick. The transition slope angle was set to 5° and the slope length to 18 mm. The remaining processes were the same as in Example 1.

[0056] A smaller bevel angle and a longer bevel length result in a smoother transmittance transition, making it suitable for windshield areas with ample installation space.

[0057] The transmittance test results are as follows.

[0058] The test data are listed below: Distance from membrane body: Transmittance; 0 mm: 76.5%; 3 mm: 77.8%; 6 mm: 79.6%; 9 mm: 82.3%; 12 mm: 85.7%; 15 mm: 89.2%; 18 mm: 92.0%.

[0059] Comparative example: The comparative example used the same HOE film substrate but without the beveled transition surface, and the edges were vertically cut. Observations showed a clear abrupt change in brightness at the film edge; at 550 nm, the transmittance on the film body side was approximately 78%, and the transmittance on the adjacent glass side was approximately 92%, with a transition distance of less than 1 mm and a distinct visual boundary. Compared to this comparative example, Example 1 achieved a continuous transition within a 12 mm width, significantly reducing the abruptness of the edges.

[0060] The above embodiments and performance test results are used to illustrate the technical solution of the present invention and its achievable effects, and are not intended to limit the scope of protection of the present invention. For those skilled in the art, any equivalent substitutions or parameter adjustments made without departing from the concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. A vehicle-mounted HOE holographic transparent film with beveled edge transition, characterized in that, The automotive HOE holographic transparent film is used to be bonded to automotive glass and includes a transparent substrate (1A), a holographic functional layer (1B), and a protective layer (1C) stacked sequentially. The edge of the automotive HOE holographic transparent film is provided with a circumferentially continuous transition slope. The transition slope extends radially from the glass bonding side to the non-bonding side to achieve a gradual transition in transmittance between the automotive HOE holographic transparent film and the automotive glass.

2. The vehicle-mounted HOE holographic transparent film according to claim 1, characterized in that, The inclination angle α of the transition slope is 3°~15°, the slope length L is 5 mm~20 mm, and the surface roughness Ra of the slope is ≤0.1 μm.

3. The vehicle-mounted HOE holographic transparent film according to claim 1, characterized in that, The transparent substrate (1A) is polyethylene terephthalate (PET) or polycarbonate (PC) with a thickness of 50 μm to 150 μm; The holographic functional layer (1B) is a volumetric holographic grating layer with a thickness of 15 μm to 25 μm; The protective layer (1C) is a scratch-resistant and wear-resistant coating with a thickness of 5 μm to 10 μm.

4. The vehicle-mounted HOE holographic transparent film according to claim 1, characterized in that, The vehicle-mounted HOE holographic transparent film has a central region without a transition slope, and a continuous circumferential transition slope is provided around the outer edge of the central region. The transition slope extends radially from the central region to the outer edge, so that the thickness gradually decreases.

5. The vehicle-mounted HOE holographic transparent film according to claim 1, characterized in that, The visible light transmittance of the central area of ​​the automotive HOE holographic transparent film is 70%~85%, and the equivalent visible light transmittance of the outermost edge of the transition slope is 88%~95%, which is consistent with the transmittance of automotive glass.

6. A method for preparing a vehicle-mounted HOE holographic transparent film as described in any one of claims 1 to 4, characterized in that, The method includes: S1. Prepare HOE holographic transparent film substrate; S2. Position and fix the edges of the HOE holographic transparent film substrate; S3. A predetermined transition slope is formed by rough polishing, and the surface roughness of the slope is corrected by fine polishing. S4. Finally, clean and dry the product.

7. The preparation method according to claim 6, characterized in that: Step S1 specifically involves preparing a transparent substrate, a holographic functional layer, and a protective layer that are sequentially stacked through coating, exposure, and curing processes to obtain a complete HOE holographic transparent film substrate.

8. The preparation method according to claim 6, characterized in that: Step S2 specifically involves fixing the HOE holographic transparent film substrate on the positioning platform and locating the edge processing area according to the preset inclined plane parameters.

9. The preparation method according to claim 6, characterized in that: The specific step S3 is as follows: using a diamond grinding wheel or laser polishing equipment, the edge processing area of ​​the HOE holographic transparent film substrate is subjected to gradient polishing. First, rough polishing is used to form a preliminary bevel, and then fine polishing is used to reduce the surface roughness to Ra≤0.1μm, so that the visible light transmittance radially transitions from 70%~85% to 88%~95% from the inside to the outside.

10. The preparation method according to claim 6, characterized in that: Step S4 specifically involves ultrasonically cleaning and drying the polished edge processing area to form a vehicle-mounted HOE holographic transparent film.

Images