A vehicle-mounted HOE holographic transparent film with doping modification and gradually changing transmittance and a preparation method thereof

Abstract

The application discloses a kind of doped modified transmittance gradient vehicle HOE holographic transparent film and preparation method thereof.Transparent film includes HOE film body and the doped transition zone being arranged at its edge, and the doped transition zone is continuously distributed along HOE film body circumference, and the thickness is consistent with holographic function layer;Doped material is liquid crystal material, nanometer silicon dioxide particles or PMMA microsphere, and doping concentration gradually changes from HOE film body side to glass side;Preparation method includes substrate preparation, gradient doping slurry configuration, gradient coating, mask holographic exposure, overall curing and performance detection.The application transmittance accurately changes, realizes edge transmittance continuous transition without increasing obvious thickness step, and is visually insensitive;Transition zone optical uniformity is better, does not affect the XR display effect of HOE film, preparation process is compatible, is suitable for mass production, is closely combined, has strong weather resistance, and has no risk of falling off.

Description

Technical Field

[0001] This invention relates to the field of holographic material modification technology, specifically to a vehicle-mounted HOE holographic transparent film with gradually changing transmittance achieved through gradient doping and its preparation method. Background Technology

[0002] Automotive HOE holographic transparent films need to form a HUD / XR display area on the glass. Due to limitations in holographic materials and diffraction efficiency requirements, the transmittance of the HOE film itself is usually lower than that of the automotive glass, and the film boundary is easily perceived by the driver.

[0003] The transmittance of automotive HOE holographic transparent film differs inherently from that of glass, resulting in abrupt edge transitions and impacting the driving experience. Existing technologies can slightly improve transmittance by adjusting the formula of the HOE film's main material; however, due to limitations in holographic diffraction performance, the potential for further transmittance improvement is limited and cannot match the transmittance of glass. Adding an additional transition coating can lead to problems such as poor adhesion between the coating and the HOE film, aging and peeling, and also affects the holographic display effect. Summary of the Invention

[0004] To address the problems existing in the background art, the present invention provides a doped transition region at the edge of the HOE film body. The doped transition region is arranged with the same thickness as the holographic functional layer, and the concentration of the internal transparent functional material continuously decreases along the width direction.

[0005] This invention proposes to create a transmittance gradient region at the edge of the HOE film by gradient doping with transparent functional materials, which not only does not destroy the core holographic function of the HOE film, but also achieves a seamless connection with glass. By performing material gradient modification in the edge region of the HOE film, a transmittance gradient region can be formed in the same functional layer plane, thereby reducing boundary abrupt changes.

[0006] The technical solution adopted in this invention is as follows: I. A type of automotive HOE holographic transparent film with gradually varying transmittance after doping modification: It includes a HOE film body and a doped transition region disposed at its edge. The doped transition region is continuously distributed circumferentially around the HOE film body. The doped transition region contains a transparent functional material, and the transmittance is gradually changed through gradient doping of the transparent functional material.

[0007] The core technology of this invention is to set a doped transition region at the edge of the HOE film body, and to control the transmittance of this region by gradient doping of transparent functional materials, so as to achieve a continuous gradient from the HOE film body to the glass.

[0008] The HOE film body includes a transparent substrate, a holographic functional layer, and a protective layer stacked sequentially from the side of the vehicle glass outwards; the doped transition region is located in the circumferential edge region of the HOE film body and is on the same layer as the holographic functional layer, and the protective layer is located above the holographic functional layer and the doped transition region.

[0009] The width of the doped transition region is 10 mm to 35 mm, and the thickness is consistent with the holographic functional layer of the HOE film body, which is 15 μm to 25 μm.

[0010] The transparent functional material is a liquid crystal material, nano-silica particles, or polymethyl methacrylate (PMMA) microspheres, and its refractive index differs from that of the holographic functional material of the HOE film body by ≤0.03.

[0011] The doping concentration in the doping transition region gradually changes from 5 wt% to 15 wt% on the HOE film body side to 0 wt% on the glass side.

[0012] The doped transition region does not affect the holographic diffraction performance of the HOE film. In the working wavelength range of 460nm~620nm, the diffraction efficiency of the HOE film is ≥85%.

[0013] II. A method for preparing a vehicle-mounted HOE holographic transparent film: S1. Prepare a transparent substrate and a protective layer; S2. Prepare photopolymerization slurries with different doping concentrations; S3. Gradient coating is performed in the edge region to form a doped transition region, and a HOE film body holographic functional layer is formed in the center region. S4. Perform masked holographic exposure; S5. Finally, perform a curing process.

[0014] The specific step S1 is as follows: the HOE film body is prepared sequentially, including a transparent substrate and a protective layer stacked sequentially from the side of the vehicle glass outwards, with a coating area reserved between the holographic functional layer and the doped transition region.

[0015] Step S2 specifically involves mixing the transparent functional material with the photopolymerized holographic material of the holographic functional layer of the HOE film body, and preparing different slurries with different doping concentrations. Step S3 specifically involves: using a gradient coating device, coating different slurries with decreasing doping concentrations sequentially from the inside to the outside of the HOE film body to the glass side in the edge region of the HOE film body to form a doping transition zone; coating an undoped transparent functional material photopolymer holographic material in the central region to form a holographic functional layer of the HOE film body.

[0016] Specifically, step S4 involves: performing holographic exposure on the holographic functional layer and recording the holographic grating information; Step S5 specifically involves: performing an overall curing process to obtain a complete HOE holographic transparent film.

[0017] In this invention, the doping concentration is higher near the HOE film body, making the optical response of this side match that of the HOE film body; the doping concentration is gradually reduced to 0 wt% near the glass side, making the transmittance of this side close to that of automotive glass. The refractive index of the doped material is close to that of the holographic functional layer material, which can reduce scattering and interface reflection.

[0018] During fabrication, a multi-channel gradient coating device continuously outputs slurries of different concentrations. Undoped or lightly doped holographic material is coated in the central region to form the HOE film body, while a transition region with gradually varying doping concentration is formed at the edge. The doped transition region is masked to prevent the recording of the holographic grating, thus not affecting the central holographic imaging function.

[0019] The beneficial effects of this invention are as follows: (1) Precise gradient of transmittance: Achieve continuous transition of edge transmittance without increasing obvious thickness steps; Achieve continuous and non-abrupt transition of transmittance from HOE film body to glass by setting gradient of doping concentration, which is visually imperceptible.

[0020] (2) Compatible with holographic function: The refractive index of the doped material is matched with that of the holographic functional layer material, and the doped transition region does not participate in holographic exposure. The optical uniformity of the transition region is good and does not affect the XR display effect of the HOE film. The gradient coating, exposure and curing process is compatible with the existing HOE film preparation process (coating, exposure and curing), and is suitable for mass production.

[0021] (3) Stable and reliable structure: The doped transition region is integrated with the holographic functional layer of the HOE film body, which is tightly bonded, has strong weather resistance, and has no risk of falling off. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a doped and modified HOE holographic transparent film.

[0023] Figure 2 This is a schematic diagram showing the gradual change in doping concentration in the transition region.

[0024] Figure 3 This is a schematic diagram of the transmittance gradient curve.

[0025] Figure 4 This is a flowchart of the preparation process. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 1As shown, the film includes a HOE film body 3A and a doped transition region 3B disposed at its edge. The doped transition region 3B is continuously distributed circumferentially around the HOE film body 3A. A transparent functional material is disposed within the doped transition region 3B, and the transmittance from the HOE film body to the automotive glass is gradually changed through gradient doping of the transparent functional material. The doped transition region 3B is located in the same material layer as the holographic functional layer 3A-2, and it is formed by mixing the transparent functional dopant material with the photopolymerizable holographic material. The transmittance is adjusted by the doping concentration gradient.

[0028] The HOE film body 3A includes a transparent substrate 3A-1, a holographic functional layer 3A-2, and a protective layer 3A-3, which are stacked sequentially from the side of the vehicle glass outwards. The vehicle HOE holographic transparent film is used to be tightly adhered to the vehicle glass, and the transparent substrate of the HOE film body 3A is adhered to the vehicle glass.

[0029] The doped transition region 3B is located at the circumferential edge of the HOE film body 3A and is co-layered with the holographic functional layer 3A-2. The width of the doped transition region 3B is 10 mm to 35 mm to ensure a sufficient gradient in transmittance; its thickness is consistent with the holographic functional layer of the HOE film body 3A, ranging from 15 μm to 25 μm, to avoid structural steps that could affect adhesion to the glass. The width of the doped transition region 3B refers to the radial width of the doped transition region from the center region of the HOE film body towards the outer peripheral edge.

[0030] The transparent functional materials are liquid crystal materials, nano-silica particles, or polymethyl methacrylate (PMMA) microspheres. These materials have high transparency and good compatibility with photopolymer holographic materials. Furthermore, their refractive index is compatible with that of the holographic functional material in the holographic functional layer of the HOE film body 3A, with a difference of ≤0.03, in order to reduce interface reflection and scattering.

[0031] The doping concentration adopts a gradient design: the doping concentration of the doping transition region 3B gradually changes from 5 wt%~15 wt% on the HOE film body side to 0 wt% on the automotive glass side, corresponding to a transmittance that gradually changes from 70%~85% on the HOE film body 3A to 88%~95% on the automotive glass side.

[0032] The doped transition region 3B does not affect the holographic diffraction performance of the HOE film body 3A. In the working wavelength range of 460nm~620nm, the diffraction efficiency of the HOE film is ≥85%.

[0033] The above-mentioned film preparation method includes substrate preparation, gradient doping slurry preparation, gradient coating, mask holographic exposure, overall curing, and performance testing. Specific methods include: S1. Prepare a transparent substrate and a protective layer; The HOE film body 3A is prepared sequentially, including a transparent substrate 3A-1 and a protective layer 3A-3 stacked sequentially from the side of the vehicle glass outwards, with a coating area reserved between the holographic functional layer 3A-2 and the doped transition region 3B.

[0034] S2. Prepare photopolymerization slurries with different doping concentrations; The transparent functional material is mixed with the photopolymerizable holographic material of the holographic functional layer 3A-2 of the HOE film body 3A to prepare different slurries with different doping concentrations, namely transparent functional doped materials; the concentration can be 0wt%~15wt%.

[0035] S3. Gradient coating is performed in the edge region to form a doped transition region, and a HOE film body holographic functional layer is formed in the center region. Using a gradient coating device, different pastes with decreasing doping concentrations are sequentially coated from the inside to the outside of the HOE film body side to the glass side in the edge region of the HOE film body 3A to form a doped transition region 3B. In the central region, a photopolymerized holographic material with no doping transparent functional material is coated to form the holographic functional layer 3A-2 of the HOE film body.

[0036] The edge region is a radial transition region adjacent to the central holographic imaging region at the outer circumferential edge of the HOE film body. On the transparent substrate 3A-1, corresponding to the circumferential edge of the HOE film body 3A, photopolymer pastes with decreasing doping concentrations are sequentially coated from the side closer to the central region to the outer peripheral edge to form the doped transition region 3B.

[0037] S4. Perform masked holographic exposure; Holographic exposure was performed on the holographic functional layer 3A-2 to record holographic grating information; Holographic exposure is used to record a holographic grating in the holographic functional layer 3A-2 in the central region to form the HOE display function. The doped transition region 3B mainly serves the function of transmittance gradient and is not used as an effective display imaging area. It is preferred to avoid recording a grating for display imaging by masking or controlling the exposure energy.

[0038] S5. Finally, a curing process is performed, and the transmittance gradient curve and holographic diffraction efficiency are detected after curing.

[0039] The entire film was cured to obtain a complete HOE holographic transparent film, and then the transmittance gradient curve, holographic diffraction efficiency and weather resistance were tested.

[0040] In the above preparation process, a gradient coating device is used to achieve precise control of the doping concentration. This device can continuously output slurries of different concentrations to ensure that the transmittance of the doped transition region gradually and smoothly changes. The holographic exposure step only acts on the central holographic functional layer. The doped transition region does not participate in the recording of the holographic grating, so it will not affect the core diffraction performance of the HOE film and ensure that the diffraction efficiency is ≥85% in the working wavelength range.

[0041] Example 1: like Figure 1 As shown, the automotive HOE holographic transparent film includes a HOE film body 3A and a doped transition region 3B located at its edge. The HOE film body 3A includes a transparent substrate 3A-1, a holographic functional layer 3A-2, and a protective layer 3A-3, which are integrally bonded to the inner surface of the automotive glass 3C.

[0042] The doped transition region 3B is arranged in the same plane as the holographic functional layer 3A-2, with a width of 10 mm to 35 mm and a thickness of 15 μm to 25 μm. The doping material can be liquid crystal material, nano-silica particles, or PMMA microspheres, and the difference in refractive index between the doped region and the holographic functional layer material is ≤0.03.

[0043] like Figure 2 As shown, the doping concentration gradually decreases from 5 wt% to 15 wt% on the HOE film bulk side to 0 wt% on the glass side. Through this gradual concentration change, absorption, scattering, and refractive index modulation in the edge region are gradually weakened. Figure 3 As shown, the transmittance gradually increases from about 77% on the HOE membrane body side to about 92% on the glass side.

[0044] In use, the prepared HOE holographic transparent film is bonded to the inner surface of the vehicle glass using OCA optical adhesive. The central HOE film body area receives HUD / XR projection light and performs diffraction imaging, while the edge doped transition area is used to make the display area transition naturally with the surrounding glass area.

[0045] like Figure 4 As shown, the fabrication process includes substrate preparation, gradient slurry preparation, gradient coating, mask exposure, and curing detection. Mask exposure is applied only to the central holographic functional region to avoid recording irrelevant gratings in the doped transition region.

[0046] In this embodiment, a 100 μm thick PET transparent substrate was selected, and an 8 μm thick protective layer was prefabricated. Nano-sized silica particles with an average particle size of about 50 nm and a refractive index of about 1.46 were mixed with a photopolymerizable holographic material with a refractive index of about 1.48 to prepare four slurries at 10 wt%, 7 wt%, 3 wt%, and 0 wt%.

[0047] A multi-channel gradient coating apparatus was used to form a doped transition region with continuously decreasing concentration in a 20 mm wide area at the edge. A 0 wt% paste was then coated in the central region to form a holographic functional layer. The doped transition region was shielded using a mask, and only the central region was subjected to holographic exposure, followed by overall curing.

[0048] The performance test results are as follows.

[0049] The test data are listed below: (Transition zone width) test result: 20 mm; corresponding requirement: 10 mm~35 mm.

[0050] (Functional layer thickness) test result: 20 μm; corresponding requirement: 15 μm~25 μm.

[0051] (Concentration range) Test results: 10 wt%~0 wt%; corresponding requirements: 5 wt%~15 wt% to 0 wt%.

[0052] (Refractive index difference) test result: 0.02; corresponding requirement: ≤0.03.

[0053] (Central diffraction efficiency) test result: 87.6%; Corresponding requirement: Maintain holographic display function.

[0054] (Weather resistance) test results: transmittance change ≤0.5%; corresponding requirements: no stratification after cycling from -40 ℃ to 85 ℃.

[0055] (Adhesion) Test result: Grade 0 in cross-cut adhesion test; Corresponding requirement: No peeling.

[0056] Example 2 Unlike Example 1, the doping material used was PMMA microspheres with an average particle size of approximately 80 nm and a refractive index of approximately 1.49; the width of the doping transition region was 25 mm, and the maximum doping concentration was 12 wt%. The remaining coating, mask exposure, and curing processes were the same.

[0057] The PMMA microspheres and the holographic functional layer material have a small difference in refractive index, resulting in low scattering loss in the transition region.

[0058] The transmittance test results are as follows.

[0059] The test data are listed below: Distance from membrane body: Transmittance; 0 mm: 77.0%; 5 mm: 79.5%; 10 mm: 83.2%; 15 mm: 87.1%; 20 mm: 90.3%; 25 mm: 92.1%.

[0060] Comparative Example Comparative Example: Using the same HOE film body but without a doping transition region, the film edge is directly adjacent to the automotive glass. Observations show a significant brightness change at the film edge, with transmittance abruptly changing from approximately 77% to approximately 92%. Compared to this comparative example, Example 1 achieves continuous transmittance variation within a 20 mm width through a concentration gradient, resulting in reduced boundary visibility.

[0061] 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 doped and modified automotive HOE holographic transparent film with gradient transmittance, characterized in that, It includes a HOE film body (3A) and a doped transition region (3B) disposed at its edge. The doped transition region (3B) is continuously distributed circumferentially around the HOE film body (3A). The doped transition region (3B) contains a transparent functional material and achieves a gradual change in transmittance through gradient doping of the transparent functional material.

2. The vehicle-mounted HOE holographic transparent film according to claim 1, characterized in that, The HOE film body (3A) includes a transparent substrate (3A-1), a holographic functional layer (3A-2), and a protective layer (3A-3) stacked sequentially from the side of the vehicle glass outwards; the doped transition region (3B) is located in the circumferential edge region of the HOE film body (3A) and is in the same layer as the holographic functional layer (3A-2); the protective layer (3A-3) is located on the holographic functional layer (3A-2) and the doped transition region (3B).

3. The vehicle-mounted HOE holographic transparent film according to claim 1, characterized in that, The width of the doped transition region (3B) is 10 mm to 35 mm, and the thickness is consistent with the holographic functional layer of the HOE film body (3A), which is 15 μm to 25 μm.

4. The vehicle-mounted HOE holographic transparent film according to claim 1, characterized in that, The transparent functional material is a liquid crystal material, nano-silica particles, or polymethyl methacrylate (PMMA) microspheres, and its refractive index differs from that of the holographic functional material of the HOE film body (3A) by ≤0.

03.

5. The vehicle-mounted HOE holographic transparent film according to claim 1, characterized in that, The doping concentration of the doped transition region (3B) gradually changes from 5 wt% to 15 wt% on the HOE film body side to 0 wt% on the glass side.

6. The vehicle-mounted HOE holographic transparent film according to claim 1, characterized in that, The doped transition region (3B) does not affect the holographic diffraction performance of the HOE film body (3A). In the working wavelength range of 460nm~620nm, the diffraction efficiency of the HOE film is ≥85%.

7. A method for producing the HOE holographic transparency film for vehicle use according to any one of claims 1 to 6, characterized by The method includes: S1. Prepare a transparent substrate and a protective layer; S2. Prepare photopolymerization slurries with different doping concentrations; S3. Gradient coating is performed in the edge region to form a doped transition region, and a HOE film body holographic functional layer is formed in the center region. S4. Perform masked holographic exposure; S5. Finally, perform a curing process.

8. The preparation method according to claim 7, characterized in that: The specific step S1 is as follows: the HOE film body (3A) is prepared sequentially, including a transparent substrate (3A-1) and a protective layer (3A-3) stacked sequentially from the side of the vehicle glass outwards, with a coating area reserved between the holographic functional layer (3A-2) and the doped transition region (3B).

9. The preparation method according to claim 7, characterized in that: Step S2 specifically involves mixing the transparent functional material with the photopolymerizable holographic material of the holographic functional layer (3A-2) of the HOE film body (3A) to prepare different slurries with different doping concentrations. The specific steps of step S3 are as follows: using a gradient coating device, different pastes with decreasing doping concentrations are sequentially coated on the edge region of the HOE film body (3A) from the inside to the outside and from the HOE film body side to the glass side to form a doped transition region (3B). In the central region, a photopolymerized holographic material with no doping transparent functional material is coated to form a holographic functional layer (3A-2) of the HOE film body.

10. The preparation method according to claim 7, characterized in that: Specifically, step S4 involves: performing holographic exposure on the holographic functional layer (3A-2) and recording the holographic grating information; Step S5 specifically involves: performing an overall curing process to obtain a complete HOE holographic transparent film.

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