An angle colorshifting type photopolymer hologram film

Abstract

The utility model discloses an angle discoloration type photopolymer hologram film, from top to bottom includes transparent base film layer, photopolymer hologram layer, protection layer, adhesive layer and the angle dependent discoloration film that sticks through adhesive layer in proper order. Among them, angle dependent discoloration film has replaced traditional full black bottom film, provides strong reflection background for photopolymer hologram layer when watching in front, enhances the brightness and contrast of holographic image, and has good covering property simultaneously, avoids the transmission of the information of being pasted object, and when the observation angle deviates, angle dependent discoloration film presents the splendid color effect that changes with angle, replaces the traditional full black bottom when deviating angle and the poor feeling of looking at one's appearance of a piece of black. The utility model solves the problem of the insufficient reflectivity of the translucent bottom, the poor covering property, and overcomes the defect of the poor feeling of looking at one's appearance of the full black bottom deviating angle, and the product's aesthetic degree and decorative property are improved significantly.

Description

Technical Field

[0001] This invention relates to the field of optical thin film technology, and in particular to an angle-changing photopolymer holographic thin film. Background Technology

[0002] Currently, photopolymer hologram products typically use either a semi-transparent or a completely black background as the reflective background, but both have significant drawbacks. Semi-transparent holograms, due to insufficient reflectivity, result in reduced brightness of the holographic image. Furthermore, when applied to products, they lack opacity, allowing the background color or information of the object to show through, interfering with the viewing experience and affecting overall visual quality. While completely black holograms possess sufficient reflectivity and opacity to meet basic holographic display requirements, when the viewing angle deviates from the optimal angle, the holographic image disappears, resulting in a completely black visual effect. This leads to poor aesthetics and a lack of decoration, limiting the product's application in high-end decoration and brand display fields. It also fails to meet market demand for composite functional film products that combine excellent holographic display effects with visually appealing angle variations. Utility Model Content

[0003] In order to overcome the shortcomings of the prior art, this utility model provides a photopolymer holographic film with strong reflective effect, good coverage and angle-changing decorative effect.

[0004] The technical solution adopted by this utility model to solve its technical problem is: An angle-changing photopolymer holographic film comprises, from top to bottom: a transparent base film layer; a photopolymer holographic layer disposed on the transparent base film layer; a protective layer disposed on the photopolymer holographic layer; an adhesive layer disposed on the protective layer; and an angle-dependent color-changing film bonded together by the adhesive layer.

[0005] Furthermore, the angle-dependent color-changing film is selected from liquid crystal color-changing films and optical interference color-changing films.

[0006] Furthermore, the angle-dependent color-changing film is a liquid crystal color-changing film.

[0007] Furthermore, the liquid crystal color-changing film includes cholesteric liquid crystal, and the helical axis of the cholesteric liquid crystal is perpendicular to the film surface.

[0008] Furthermore, the cholesteric liquid crystal comprises at least two liquid crystal layers with different pitches.

[0009] Furthermore, the pitch of the first liquid crystal layer is 330-390 nm, and the pitch of the second liquid crystal layer is 410-500 nm.

[0010] Furthermore, the thickness of the liquid crystal color-changing film is 10-15 μm.

[0011] Furthermore, the cholesteric liquid crystal is a polymer-stabilized cholesteric liquid crystal.

[0012] Furthermore, the transparent base film layer is a PET film.

[0013] Furthermore, the protective layer is a UV-curable coating.

[0014] The beneficial effects of this utility model are: This invention relates to an angle-dependent color-changing photopolymer holographic film. By replacing the traditional all-black base film with an angle-dependent color-changing film, the photopolymer hologram achieves stronger reflectivity and better opacity when viewed from the front, while displaying brilliant color-changing effects when viewed from a different angle. This simultaneously achieves high-brightness display of the holographic image, effective information opacity, and dynamic decorative color changes, significantly improving the product's aesthetics, decorative appeal, and market acceptance. It overcomes the technical shortcomings of traditional semi-transparent holograms, such as insufficient reflectivity and poor opacity, as well as the poor visual appeal of all-black holograms when viewed from a different angle. Attached Figure Description

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0016] Figure 1 This is a schematic diagram of the layered structure of this utility model.

[0017] in, 1. Base film layer; 2. Photopolymer holographic layer; 3. Protective layer; 4. Adhesive layer; 5. Angle-dependent color-changing film. Detailed Implementation

[0018] The following will clearly and completely describe the concept, specific structure, and technical effects of this utility model in conjunction with embodiments and accompanying drawings, so as to fully understand the purpose, features, and effects of this utility model. Obviously, the described embodiments are only a part of the embodiments of this utility model, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are all within the scope of protection of this utility model. Furthermore, all connections / linkages involved in the patent do not simply refer to direct contact between components, but rather to the ability to form a better connection structure by adding or reducing connecting accessories according to specific implementation conditions. The various technical features in this utility model can be combined interactively without contradicting each other.

[0019] Reference Figure 1This invention provides an angle-changing photopolymer holographic film. Through a multi-layered structure, the film achieves enhanced reflection, good opacity, and an angle-changing decorative effect for the holographic image. Specifically, the film comprises, from top to bottom, a transparent base film layer 1, a photopolymer holographic layer 2, a protective layer 3, an adhesive layer 4, and an angle-dependent color-changing film 5 bonded to the adhesive layer 4. This invention solves the problems of insufficient reflectivity and poor opacity in existing semi-transparent holographic images, while also overcoming the defect of completely black holographic images appearing pitch black and having poor visual appeal when viewed from a different angle.

[0020] The transparent base film layer 1 serves as the supporting carrier for the entire thin film structure and has good transparency to ensure that light can fully penetrate and reach the functional layers below.

[0021] In some embodiments, the transparent base film layer 1 can be made of polyethylene terephthalate (PET) film. PET film has excellent mechanical strength, dimensional stability, and optical transparency, and can withstand subsequent processing such as coating, exposure, and curing without significant deformation or deterioration of optical properties. The thickness of the PET film can be selected according to the actual application requirements, ensuring sufficient mechanical support without affecting the overall flexibility and adhesion performance of the film due to excessive thickness.

[0022] A photopolymer holographic layer 2 is set on a transparent base film layer 1. When the photopolymer material is irradiated with light of a specific wavelength, it undergoes a polymerization reaction, forming a periodic change in refractive index, thereby recording holographic interference fringes.

[0023] In the preparation process, a photopolymer is first uniformly coated onto the surface of a transparent base film layer 1 using a coating process to form a photopolymer coating of a certain thickness. Then, using a master template with pre-set holographic images, the holographic information is transferred to the photopolymer coating using optical replication technology. Specifically, the master template is bonded to the base film coated with the photopolymer or kept at a certain distance, and then exposed using a coherent light source (such as a laser). The holographic information on the master template is recorded in the photopolymer layer in the form of interference fringes. After appropriate post-processing (such as heat treatment or ultraviolet curing), the photopolymer layer is cured and formed into a stable holographic image layer.

[0024] The protective layer 3 is placed on top of the photopolymer holographic layer 2, and its main function is to prevent the subsequently applied adhesive layer 4 from eroding or damaging the photopolymer layer. Photopolymer materials are often sensitive to certain chemicals, and direct contact with the adhesive may cause attenuation, blurring, or even complete destruction of the holographic image. As a physical and chemical barrier, the protective layer 3 effectively isolates the photopolymer layer from the adhesive layer 4, ensuring the long-term stability and clarity of the holographic image.

[0025] In some embodiments, the protective layer 3 may be an ultraviolet (UV) curable coating, which is formed by coating the surface of the photopolymer holographic layer 2 with a UV-curable resin and then rapidly curing it under ultraviolet light. The UV-curable coating has advantages such as fast curing speed, uniform film formation, strong adhesion, and good chemical resistance, and can form a dense protective film without damaging the underlying photopolymer.

[0026] The thickness of protective layer 3 is typically controlled between 1 and 10 micrometers, which provides sufficient protection without significantly increasing the overall thickness and hardness of the film.

[0027] An adhesive layer 4 is coated on the surface of the protective layer 3 to firmly bond the angle-dependent color-changing film 5 to the multilayer structure. The adhesive layer 4 needs to possess appropriate bonding strength to ensure that the layers do not peel or misalign under normal use and certain environmental changes. Simultaneously, the adhesive layer 4 should maintain a certain degree of transparency to avoid excessive loss of light transmission. The choice of adhesive can be adjusted according to the properties of the materials being bonded; commonly used adhesives include acrylic adhesives and rubber adhesives. A uniform adhesive layer 4 is formed on the surface of the protective layer 3 through a coating process.

[0028] The angle-dependent color-changing film 5 is bonded to the aforementioned structure via the adhesive layer 4, forming the bottom layer of the entire film. When viewed from the front, it provides a highly reflective background, enhancing the brightness and contrast of the hologram, while also possessing good opacity, preventing the background color or information of the adhered object from showing through. At angles away from the front view, it displays a dazzling color-changing effect, enhancing the product's aesthetics and decorative appeal. The angle-dependent color-changing film 5 can be implemented using different technical approaches, including but not limited to liquid crystal color-changing films and optical interference color-changing films.

[0029] In a preferred embodiment, the angle-dependent color-changing film 5 is a liquid crystal color-changing film.

[0030] Liquid crystal materials possess unique optical anisotropy and self-assembly properties, enabling them to form periodic refractive index distribution structures and selectively reflect light of specific wavelengths. When light is incident on a liquid crystal color-changing film at different angles, the wavelength of the reflected light changes due to variations in Bragg reflection conditions, thus exhibiting different colors. Compared to traditional all-black backing films, liquid crystal color-changing films not only provide sufficient reflectivity and opacity but also display rich color changes with varying angles, significantly enhancing the visual appeal of products.

[0031] Cholesteric liquid crystal materials can be used in liquid crystal color-changing films. Cholesteric liquid crystal molecules are arranged to form a helical structure. When the helical axis is perpendicular to the film surface, the incident light is affected by the periodic refractive index modulation when propagating in the liquid crystal layer. Light of a specific wavelength that satisfies the Bragg reflection condition is selectively reflected, while light of other wavelengths is transmitted or absorbed.

[0032] Furthermore, the wavelength of the reflected light is closely related to the pitch of the liquid crystal and the viewing angle. By adjusting the pitch of the liquid crystal, precise control of the reflected color can be achieved. To achieve richer and more continuous color change effects, the liquid crystal color-changing film can include at least two liquid crystal layers with different pitches. For example, the pitch of the first liquid crystal layer is set to 330-390 nanometers, corresponding to the reflection of blue to blue-green light wavelengths; the pitch of the second liquid crystal layer is set to 410-500 nanometers, corresponding to the reflection of blue-violet to green light wavelengths. When light is incident at different angles, the two liquid crystal layers reflect light of different wavelengths respectively, forming more complex and diverse color change trajectories through superposition, so that the film presents a gradual or abrupt color effect from blue to green, from purple to yellow, etc., at different viewing angles.

[0033] Furthermore, excessive thickness may result in insufficient reflectivity and unsaturated colors; excessive thickness may increase material costs and make the film too rigid, hindering bonding applications. In practical applications, the thickness of liquid crystal color-changing films is typically controlled between 10 and 15 micrometers.

[0034] To further improve the stability and durability of liquid crystal color-changing films, polymer-stabilized cholesteric liquid crystals can be used. A small amount of polymerizable monomers is introduced into the liquid crystal material, and a polymerization reaction is initiated by ultraviolet light to form a polymer network structure in the liquid crystal layer. This network structure can fix the orientation and helical structure of the liquid crystal molecules, preventing rearrangement or pitch changes in the liquid crystal molecules during external forces, temperature changes, or the passage of time, thereby ensuring the long-term stability of the color-changing effect.

[0035] In other embodiments, the angle-dependent color-changing film 5 can also be an optical interference color-changing film. Optical interference color-changing films are typically composed of multiple layers of thin film materials with different refractive indices stacked alternately. When light is incident on this multilayer structure, multiple reflections and interferences occur at the interfaces between layers. Light of a specific wavelength is enhanced by constructive interference, while light of other wavelengths is suppressed by destructive interference. The wavelength of the reflected light also changes with the incident angle, thus achieving an angle-dependent color-changing effect. The advantages of optical interference color-changing films are their relatively stable structure, independence from the orientation state of liquid crystal molecules, and generally good temperature and weather resistance. However, their fabrication process is relatively complex, requiring precise control of the thickness and refractive index of each thin film layer, and the cost is relatively high.

[0036] In some further improved embodiments, in order to enhance the reflective effect of the angle-dependent color-changing film 5, especially to produce brighter and more vivid colors at specific viewing angles, a metal nanoparticle reinforcement layer (not shown) can be added between the adhesive layer 4 and the angle-dependent color-changing film 5.

[0037] When metal nanoparticles are irradiated by light, they exhibit a surface plasmon resonance effect. This means that free electrons on the surface of the metal nanoparticles oscillate collectively under the drive of an optoelectronic field. When the frequency of the incident light matches the plasmon resonance frequency, a strong local electric field enhancement and light absorption or scattering enhancement effect are generated. By selecting metal nanoparticles of appropriate size and material, and matching their surface plasmon resonance wavelength with the reflection wavelength of the angle-dependent color-changing film 5 at a specific angle, enhanced optical coupling between the two can be achieved. Specifically, when light is incident at a specific angle, the plasmon resonance of the metal nanoparticles and the Bragg reflection of the liquid crystal layer overlap in wavelength. The local electric field enhancement effect generated by the plasmon resonance further enhances the intensity of the Bragg reflection, making the reflected light at that angle brighter and more saturated in color, producing a visual effect similar to a metallic luster.

[0038] The metal nanoparticles in the metal nanoparticle reinforcement layer can be selected from gold nanoparticles, silver nanoparticles, copper nanoparticles, aluminum nanoparticles, or combinations thereof. Different metal nanoparticles have different plasmon resonance wavelengths. For example, the plasmon resonance peak of gold nanoparticles is usually around 520-550 nm (green to yellow light band), the resonance peak of silver nanoparticles is around 400-450 nm (blue to violet light band), the resonance peak of copper nanoparticles is around 550-600 nm (yellow to orange light band), and the resonance peak of aluminum nanoparticles can extend to the ultraviolet to visible light range.

[0039] The entire thin film preparation process can be carried out according to the following steps.

[0040] First, the photopolymer material is coated onto the surface of the transparent base film layer 1 (such as PET film) using a coating process, and the coating thickness is controlled according to the desired holographic image effect.

[0041] Secondly, the prepared base film with the photopolymer layer is combined with the holographic master and optically replicated using a laser exposure system. The holographic information on the master is transferred and recorded into the photopolymer layer. After exposure, the film undergoes post-curing treatment to completely solidify the photopolymer and form a stable holographic image.

[0042] The third step involves coating the surface of the cured photopolymer holographic layer 2 with UV-curable resin and then rapidly curing it by UV irradiation to form a protective layer 3. This protective layer 3 has a uniform thickness and is tightly bonded to the photopolymer layer, effectively preventing subsequent adhesives from eroding the photopolymer.

[0043] The fourth step is to apply adhesive to the surface of the protective layer 3 to form the adhesive layer 4. The selection of adhesive should take into account its compatibility with the subsequent bonding materials and the required bonding strength. The surface of the adhesive layer 4 after coating remains sticky, which facilitates the subsequent bonding operation.

[0044] The fifth step is to bond the pre-prepared angle-dependent color-changing film 5 (such as a liquid crystal color-changing film) to the above multilayer structure through the adhesive layer 4. The bonding process requires careful control of pressure and temperature to ensure uniform bonding, no bubbles, and no misalignment, ultimately forming an integrated multilayer thin film structure.

[0045] The sixth step is to cut the laminated film according to the actual product requirements, into the required size and shape, to obtain the final angle-changing photopolymer holographic film.

[0046] The above is a detailed description of the preferred embodiments of the present utility model. However, the present utility model is not limited to the described embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present utility model. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. An angle-changing photopolymer holographic film, characterized in that, From top to bottom, they include: Transparent base film layer; A photopolymer holographic layer disposed on the transparent base film layer; A protective layer is disposed on the photopolymer holographic layer; An adhesive layer disposed on the protective layer; Angle-dependent color-changing film bonded by the adhesive layer.

2. The angle-changing photopolymer holographic film according to claim 1, characterized in that, The angle-dependent color-changing film is selected from either liquid crystal color-changing film or optical interference color-changing film.

3. The angle-changing photopolymer holographic film according to claim 2, characterized in that, The angle-dependent color-changing film is a liquid crystal color-changing film.

4. The angle-changing photopolymer holographic film according to claim 3, characterized in that, The liquid crystal color-changing film includes cholesteric liquid crystal, and the helical axis of the cholesteric liquid crystal is perpendicular to the film surface.

5. The angle-changing photopolymer holographic film according to claim 4, characterized in that, The cholesteric liquid crystal comprises at least two liquid crystal layers with different pitches.

6. The angle-changing photopolymer holographic film according to claim 5, characterized in that, The pitch of the first liquid crystal layer is 330-390 nm, and the pitch of the second liquid crystal layer is 410-500 nm.

7. The angle-changing photopolymer holographic film according to any one of claims 4-6, characterized in that, The thickness of the liquid crystal color-changing film is 10-15 μm.

8. The angle-changing photopolymer holographic film according to any one of claims 4-6, characterized in that, The cholesteric liquid crystal is a polymer-stabilized cholesteric liquid crystal.

9. The angle-changing photopolymer holographic film according to claim 1, characterized in that, The transparent base film layer is a PET film.

10. The angle-changing photopolymer holographic film according to claim 1, characterized in that, The protective layer is a UV-curable coating.

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