Process method for preventing internal engraving line diffusion, light control film and light control glass

Abstract

The application discloses a process method for preventing internal engraving line diffusion, a dimming film and dimming glass, and aims to overcome the technical problem of dye PDLC dimming film internal engraving line diffusion and blur caused by resin heat flow during high-temperature and high-pressure laminating. The method comprises the following steps: firstly, pre-curing is performed, low-intensity ultraviolet light is used for irradiation, the crosslinking degree of the film reaches 40-60%, the Shore hardness reaches 30-40HA, and a stable semi-cured matrix is formed; then, laser internal engraving is performed to complete the internal engraving line with clear profile and regular appearance; finally, complete curing is performed, high-intensity ultraviolet irradiation is used to increase the crosslinking degree to more than 90%, and the final shaping of the film is realized. The process controls the curing state in stages, effectively inhibits the line diameter diffusion phenomenon in the process of heat pressing and laminating, improves the internal engraving pattern sharpness, product yield and overall visual effect.

Description

Technical Field

[0001] This invention relates to the field of dimming liquid crystal film technology, and particularly to a process method for preventing the diffusion of internal engraving lines, a dimming film, and dimming glass. Background Technology

[0002] Polymer-dispersed liquid crystal (PDLC) dimming film is a functional thin film that can switch between transparent and opaque states under the control of an electric field. To meet the market's demand for personalized colors, dye-based PDLC dimming films have emerged. These films incorporate specific organic dyes into traditional PDLC formulations, resulting in neutral tones ranging from dark gray to black after curing. To further achieve zonal control and graphic display functions, the industry commonly uses laser engraving technology to etch the conductive layer of the dimming film to form precise insulating patterns.

[0003] In the manufacturing of automotive dimming sunroofs, lamination is a key packaging process: a dye-based PDLC dimming film with an internally engraved pattern is placed between two pieces of glass, with polyvinyl butyral (PVB) film as the intermediate layer, to construct a sandwich structure of "glass-PVB-dimming film-PVB-glass". Then, the PVB is melted and flowed through a high-temperature and high-pressure autoclave, ultimately achieving a strong composite structure.

[0004] However, when using dye-based PDLC dimming films, the lamination process can cause quality issues such as abnormal diffusion of the laser engraving linewidth. Because the high energy of the laser etching process can cause physical damage and even localized carbonization to the dye within the film, the initial linewidth is 5–20 μm, which is invisible to the human eye. However, in the high-temperature and high-pressure environment of subsequent lamination, these damaged areas become structural weak points, and due to thermal stress and interface migration effects, the linewidth can significantly expand to 60–100 μm.

[0005] This diffusion phenomenon leads to blurred edges and loss of precision in the internally engraved pattern, weakening the electrical isolation reliability of the zone control and creating a noticeable visual defect due to the visible linewidth after diffusion. This severely impacts product appearance quality and production yield. Therefore, effectively suppressing the diffusion of laser-engraved line diameters in dye-based PDLC dimming films during the lamination process has become a pressing technical challenge in this field. Summary of the Invention

[0006] This invention addresses the technical problem of diffusion and blurring of engraved lines caused by resin heat flow during the high-temperature, high-pressure lamination of dye-based PDLC dimming films. It proposes a staged curing process. This method involves three synergistic steps: pre-curing to construct a semi-cured stable matrix with specific cross-linking degree and hardness; precise control of laser engraving process parameters; and final high-intensity complete curing. These steps achieve precise fixation of the laser-engraved pattern, effectively suppressing the macroscopic flow of the resin-liquid mixture and solving the line diameter diffusion problem during lamination. The final engraved linewidth deviation is stably controlled within ±5μm, improving pattern processing accuracy, product yield, and visual consistency. The technical solution provided by this invention is as follows:

[0007] In a first aspect, the present invention provides a process method for preventing the diffusion of internal engraving lines, the process method being used to solve the problem of internal engraving line diffusion after dye PDLC lamination; comprising the following steps:

[0008] Pre-curing step: Use a light source with a wavelength of 320~420nm and a power of 25~60mW / cm². 2 The dye PDLC film is irradiated with light intensity for 5-10 minutes to make its crosslinking degree reach 40%-60% and its Shore hardness reach 30-40HA, and it is in a semi-cured state.

[0009] Laser internal engraving step: Laser internal engraving is performed on the dye PDLC film that has undergone the pre-curing step;

[0010] Complete curing step: The dye PDLC film treated by the laser engraving step is irradiated with a light source to make its crosslinking degree reach more than 90%.

[0011] Optionally, in the pre-curing step, the corresponding light source wavelength and process parameters are matched according to the type of photoinitiator selected:

[0012] When using benzoin-based photoinitiators, the light source wavelength is controlled at 320–340 nm, and the light intensity at 25–45 mW / cm². 2 The pre-curing time is 8~15 min;

[0013] When using diphenylphosphine oxide photoinitiator, the light source wavelength is controlled at 350~370 nm and the light intensity at 40~50 mW / cm². 2 The pre-curing time is 5~10 min;

[0014] When using acylphosphine oxide photoinitiators, the light source wavelength is controlled at 380~400 nm and the light intensity at 35~55 mW / cm². 2 The pre-curing time is 7~12 min;

[0015] When using α-aminoketone photoinitiators, the light source wavelength is controlled at 400-420 nm, and the light intensity at 40-60 mW / cm². 2 The pre-curing time is 15~20 min.

[0016] Optionally, in the pre-curing step, the adhesion between the dye PDLC film and the conductive substrate is controlled at 30~50gf.

[0017] Optionally, in the laser engraving step, the laser energy is set according to the degree of crosslinking of the pre-cured dye PDLC film; wherein: the laser energy is 20~40 mJ / cm 2 The engraving speed is 200~250mm / s, the laser frequency is 20~30kHz, and the laser focus is located at a depth of 190~200 μm below the upper surface of the dye PDLC film.

[0018] When the degree of crosslinking is 40%~50%, the laser energy is 20~30 mJ / cm. 2 ;

[0019] When the degree of crosslinking is 50%~60%, the laser energy is 30~40 mJ / cm. 2 .

[0020] Optionally, in the laser engraving step, the engraving speed is set according to the adhesion between the pre-cured dye PDLC film and the conductive substrate; when the adhesion increases by 10 gf, the engraving speed is increased by 30~50 mm / s accordingly.

[0021] Optionally, in the laser engraving step, the laser frequency is set according to the Shore hardness of the dye PDLC film after pre-curing; when the Shore hardness increases by 10 HA, the laser frequency is increased by 5~10 kHz accordingly.

[0022] Optionally, in the complete curing step, a light source with a wavelength of 365nm, 395nm, or 405nm is used to irradiate the dye PDLC film treated by the laser engraving step for 30 to 60 seconds with a light intensity of 130 to 150mW / cm², so that its crosslinking degree reaches more than 90%.

[0023] Optionally, the method further includes an electrical repair step:

[0024] A stepped voltage program is applied to the fully cured dye PDLC membrane. The initial voltage of the stepped voltage program is 30-50% of the rated driving voltage of the membrane, and the voltage is increased stepwise by 10%-15% for 3-5 cycles.

[0025] Secondly, the present invention also provides a dye PDLC dimming film, which is prepared by the method described above.

[0026] Thirdly, the present invention also provides a dimming glass, comprising two layers of glass and a dimming film laminated therebetween, wherein the dimming film is the aforementioned dye PDLC dimming film.

[0027] By adopting the above technical solution, the process method, dimming film, and dimming glass for preventing the diffusion of internal engraving lines provided by the present invention have the following beneficial effects:

[0028] 1. This invention uses a pre-curing step to form a semi-cured stable matrix with a cross-linking degree of 40%~60% and a Shore hardness of 30~40HA on the dye PDLC film. This matrix effectively inhibits material flow during laser engraving and ensures compatibility with low-energy laser processing, thereby preventing line diameter expansion. In the laser engraving step, by precisely controlling the laser energy, scanning speed, pulse frequency, and focal position, the engraved lines are made into regular rectangles with no burrs or tails at the edges, fundamentally eliminating the risk of flow diffusion due to material redundancy in subsequent high-temperature and high-pressure processing. After low-energy laser cutting, the liquid crystal-polymer system in the engraved area has neat molecular chain breakage without local loose structure, making it less prone to collapse under high-temperature conditions. At the same time, in a high-pressure environment, the softer surrounding materials preferentially undergo slight deformation, while the engraved lines, due to the high rigidity of the matrix, maintain morphological stability and do not undergo compression deformation or diffusion. Finally, the complete curing step uses high-intensity ultraviolet light irradiation to increase the cross-linking degree of the film to over 90%, achieving optimized film performance and permanent fixation of the engraved morphology, avoiding pattern distortion. This technical solution, through the synergistic process of low-intensity pre-curing and low-energy laser engraving, provides a stable material basis for the engraved lines to resist deformation and diffusion in the subsequent high-temperature and high-pressure lamination process, achieving line diameter accuracy control within ±5μm, and improving the sharpness of pattern edges, product visual quality and production yield.

[0029] 2. Optionally, the present invention adopts a closed-loop process of physical shaping-chemical fixation-electrical repair. Through the synergistic effect of pre-curing, complete curing and staged electrical treatment, the residual conductive impurities (such as ITO conductive film residue) and micro-stress concentration areas inside the film layer are effectively eliminated, thereby improving the long-term working reliability and environmental stability of the dye PDLC dimming film. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the dye PDLC dimming film provided in an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of a dye-based automotive dimming sunroof assembly provided in an embodiment of the present invention.

[0033] The following is supplementary explanation of the attached figures:

[0034] 11-Transparent flexible substrate; 12-Transparent conductive layer; 13-Liquid crystal-dye composite functional layer;

[0035] 21-Dye PDLC dimming film; 22-Glass; 23-Intermediate layer adhesive. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. In the description of the invention, it should be understood that the terms "upper," "lower," "top," "bottom," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein.

[0038] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included. For example, a specified range from “1 to 10” should be considered to include any and all subranges between the minimum value 1 and the maximum value 10. Exemplary subranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0039] This invention provides a process method for preventing the diffusion of internal engraving lines, which is used to solve the problem of internal engraving line diffusion after dye PDLC lamination; the method includes the following steps:

[0040] Pre-curing step: Use a light source with a wavelength of 320~420nm and a power of 25~60mW / cm². 2 (far below the 150mW / cm required for complete curing) 2 Irradiating the dye-coated PDLC film with UV light intensity for 5-10 minutes allows its crosslinking degree to reach 40%-60% (≥90% for complete curing) and its Shore hardness to reach 30-40 HA (≥80 HA for complete curing), forming a semi-cured stable state. This low-intensity UV pre-curing process solves the technical problem of excessive film fluidity preventing laser engraving without pre-curing. Simultaneously, due to the moderate pre-curing degree and low crosslinking degree, lower laser energy can be used for effective engraving, avoiding the drawback of high-intensity pre-curing causing the film's crosslinking degree to instantly rise above 80%, requiring a significant increase in laser energy. This pre-curing process induces partial physical reactions between the liquid crystal and the polymer, forming a semi-cured film with both moderate flexibility (preventing film cracking during subsequent engraving) and sufficient structural strength (inhibiting thermal flow and diffusion of materials during engraving). By precisely controlling the pre-curing light intensity and irradiation time, the film's crosslinking degree and hardness are ensured to be within an appropriate range, providing a guarantee for controlling the engraving line diameter from the material basis. The coordinated control of light intensity and time keeps the membrane in a semi-crosslinked equilibrium state, which resists material flow during the internal engraving process while being compatible with low-energy laser cutting, thus avoiding wire diameter expansion. In addition, this process ensures uniform crosslinking of the membrane in the thickness direction, avoiding the gradient structure formed by "over-crosslinking of the surface layer and under-crosslinking of the bottom layer," which would lead to inconsistent or diffused wire diameters during internal engraving.

[0041] Laser internal engraving step: Laser internal engraving is performed on the dye PDLC film, which is in a semi-cured, medium-viscosity, and low-hardness state after pre-curing treatment. The laser energy is set according to the degree of cross-linking of the pre-cured dye PDLC film; preferably, the laser energy is precisely controlled between 20 and 40 mJ / cm². 2 (significantly lower than the 80~120mJ / cm required for complete curing) 2This method effectively avoids the melting and diffusion problems caused by high energy. During high-energy laser cutting, the temperature of the engraved area instantly rises to 160~180℃, leading to polymer network damage and a decrease in the interaction force between the liquid crystal and the polymer. Under the combined action of laser impact and material surface tension, significant diffusion occurs around the engraved line, resulting in a visible diameter exceeding 50μm. Low-energy laser precision cutting achieves ordered molecular chain breakage and a regular interface, preventing the formation of local loose structural domains, thus ensuring the structural stability of the engraved area. Under high-temperature conditions, its regular molecular arrangement effectively suppresses the risk of structural collapse. Simultaneously, under high pressure, when the surrounding softer matrix material preferentially undergoes slight plastic deformation, the engraved line area, due to its high cross-linking density and rigidity, can maintain geometric stability without being squeezed, deformed, or experiencing outward diffusion of material, thereby ensuring the precise positioning and functional integrity of the engraved pattern in the lamination process. Furthermore, the engraving speed is increased to 200~250mm / s. The laser frequency is set to 20-30 kHz (significantly higher than the full curing speed of 130-150 mm / s). By shortening the laser-film contact time, the heat-affected zone (i.e., the visible area around the laser-cut area where the temperature rises due to heat absorption, material properties change, and diffuses after high-temperature lamination) is reduced, thereby improving the wire diameter after lamination. Simultaneously, the laser frequency is adjusted to 20-30 kHz (higher than the full curing frequency of 10-15 kHz), utilizing high-frequency pulses to achieve precise cutting and effectively suppressing the formation of edge burrs on the inner engraving lines (referring to filamentous / granular excess material remaining on the edge of the inner engraving lines after laser engraving, connected to the main body but exceeding the design boundary; this is caused by tailing residue due to excessively low material viscosity or semi-molten accumulation of material due to an excessively wide heat-affected zone). Excessive edge burrs can lead to blurred and distorted patterns, reduced product yield, and additionally increased inner engraving line width, failing to meet the fine wire diameter requirements. Furthermore, the laser focus is located 190° below the upper surface of the dye PDLC film. Within a depth range of ~200 μm (unlike the process where the laser needs to be focused on the surface during full curing), the laser focus is preferably located at 1 / 2 of the thickness of the dye PDLC film to ensure uniformity of the engraving depth. For dye PDLC films in a semi-cured state, due to the lower energy and faster speed of the engraving, the focus position needs to be rematched to ensure that the laser energy is accurately applied to the conductive layer: if the focus is too high, the cross-section of the engraved line will be wider at the top and narrower at the bottom; if it is too low, it will be wider at the bottom and narrower at the top. Both morphologies are not conducive to the stability of the engraved line and the width of the heat-affected zone will be too large. When the focus is located at 190 ~ 200 μm (i.e., close to the middle of the dye PDLC film), the cutting cross-section is rectangular, achieving synergistic optimization of cutting width, cross-sectional shape, heat-affected zone and burrs. This ensures that the overall width of the engraved line is controlled within 5~20 μm and the burr width is limited to 5~10 μm. The actual line diameter meets the requirements of precision small line diameter design and effectively suppresses the line diameter diffusion effect during the lamination process.By optimizing and precisely matching the engraving parameters of the low-crosslinked dye PDLC film, the engraved line morphology is ensured to be a regular rectangle with no burrs or tails at the edges, fundamentally eliminating the possibility of "redundant material" that can flow and diffuse under high temperature and pressure. Finally, through a synergistic process of low-intensity pre-curing and low-energy laser engraving, a stable engraved line morphology is formed, providing a core structural foundation and technical guarantee for resisting line diameter diffusion during subsequent high-temperature and high-pressure lamination.

[0042] Complete curing step: The dye PDLC film treated in the laser engraving step is irradiated with a light source to achieve a crosslinking degree of over 90%. Preferably, a light source with a wavelength of 365nm, 395nm, or 405nm is used at a concentration of 130~150mW / cm². 2 High-intensity ultraviolet light irradiation of the dye PDLC film for 30-60 seconds achieves a cross-linking degree of over 90%, ensuring complete curing of the PDLC film and guaranteeing its optimal performance. Simultaneously, it completely fixes the morphology of the engraved lines without pattern distortion. High-energy ultraviolet light irradiation reintegrates and fixes the structure of the surrounding area affected by the laser engraving energy, enhancing the strong adhesion between the polymer system and the conductive layer. This ensures the engraved pattern remains stable during subsequent high-temperature, high-pressure lamination, preventing lateral or longitudinal displacement. Compared to traditional methods that involve complete curing before engraving, this method avoids the technical defect of irreparable damage to the area around the engraved lines caused by strong laser energy. The step-by-step process of first forming a semi-cured stable structure, then performing precise engraving, and finally complete curing effectively maintains the integrity and functionality of the engraved pattern.

[0043] Optionally, in the pre-curing step, the corresponding light source wavelength and process parameters are matched according to the type of photoinitiator selected:

[0044] When using benzoin-based photoinitiators, the light source wavelength is controlled at 320–340 nm, and the light intensity at 25–45 mW / cm². 2 The pre-curing time is 8~15 min;

[0045] When using diphenylphosphine oxide photoinitiator, the light source wavelength is controlled at 350~370 nm and the light intensity at 40~50 mW / cm². 2 The pre-curing time is 5~10 min;

[0046] When using acylphosphine oxide photoinitiators, the light source wavelength is controlled at 380~400 nm and the light intensity at 35~55 mW / cm². 2 The pre-curing time is 7~12 min;

[0047] When using α-aminoketone photoinitiators, the light source wavelength is controlled at 400-420 nm, and the light intensity at 40-60 mW / cm². 2 The pre-curing time is 15-20 minutes. Photoinitiators are the core of photocuring technology. After absorbing light energy of a specific wavelength, they generate active intermediates such as free radicals or cations. These active substances can initiate polymerization and cross-linking reactions of monomers, thereby achieving rapid curing of the material. Different photoinitiators correspond to different wavelengths. The key to control during pre-curing is the degree of curing, which should be kept at a low level of 40-60%. The wavelengths corresponding to these initiators are all different, and the parameter ranges and times are all designed to ensure that the degree of pre-curing is within this range.

[0048] Optionally, in the pre-curing step, the adhesion between the dye PDLC film and the conductive substrate is controlled at 30~50 gf. Dye molecules achieve coordinated rotation with liquid crystal molecules by attaching to them. If the adhesion between the liquid crystal and the polymer network is insufficient, some liquid crystal molecules will detach from the polymer network and be stretched under stress during laser cutting, forming a tailing defect, directly causing abnormal thickening of the engraved line diameter. Simultaneously, if the adhesion between the liquid crystal-polymer composite system and the conductive layer substrate is insufficient, it can easily cause overall or local displacement deformation of the circuit under the high pressure of the lamination process, leading to excess dye overflowing from the edge of the engraved line, also resulting in increased line diameter. By controlling the adhesion between the dye PDLC film and the conductive substrate within the range of 30~50 gf, the interface bonding between the two is ensured to be stable, providing reliable substrate support for the laser engraving process, effectively suppressing abnormal line diameter caused by tailing and displacement, and ensuring the accurate forming and dimensional stability of the engraved pattern.

[0049] Optionally, when the degree of crosslinking is 40%~50%, the laser energy is 20~30 mJ / cm. 2 When the degree of crosslinking is 50%~60%, the laser energy is 30~40 mJ / cm. 2 The degree of crosslinking of pre-cured dye PDLC films is positively correlated with their hardness. Increased crosslinking (e.g., from 40% to 50%) promotes the formation of a denser three-dimensional network structure between polymer molecular chains, leading to increased film hardness and enhanced resistance to laser penetration. This necessitates a corresponding increase in laser energy (e.g., an increase of 5-10 mJ / cm²). 2 This ensures that the laser effectively penetrates and thoroughly etches the conductive layer, forming a clear and complete internal engraving pattern. Conversely, when the cross-linking degree is low (the network structure is relatively loose), the film's hardness and laser resistance are weaker, and the laser energy can be appropriately reduced to avoid excessive damage. By precisely controlling the laser energy based on the pre-curing cross-linking degree, the accuracy and integrity of internal engraving processing under different pre-curing degrees can be achieved.

[0050] Optionally, in the laser engraving step, the engraving speed is set according to the adhesion between the pre-cured dye PDLC film and the conductive substrate; when the adhesion increases by 10 gf (for example, from 30 gf to 40 gf), the engraving speed is increased by 30~50 mm / s accordingly to reduce the adhesion effect of the material under the laser action, thereby effectively suppressing the trailing phenomenon caused by material adhesion at the edge of the engraved line.

[0051] Optionally, in the laser engraving step, the laser frequency is set according to the Shore hardness of the pre-cured dye PDLC film; when the Shore hardness increases by 10 HA (e.g., from 30 HA to 40 HA), the laser frequency is correspondingly increased by 5~10 kHz. Increasing the laser frequency shortens the interval between laser pulses, allowing adjacent laser action points to form continuous, overlapping cutting trajectories at the microscale, thereby effectively avoiding edge burrs caused by discontinuous cutting and improving the sharpness and smoothness of the engraved lines.

[0052] Optionally, the method may also include an electrorepair step:

[0053] A stepped voltage program is applied to the fully cured dye PDLC membrane. The initial voltage of the stepped voltage program is 30-50% (preferably 50%) of the membrane's rated driving voltage, and the voltage is increased stepwise in increments of 10% to 15%, and the cycle is performed for 3 to 5 cycles.

[0054] Taking a rated voltage of 60V as an example, the specific steps include:

[0055] Pretreatment cycle: Apply 30V voltage (50% of rated drive voltage), power on / off interval 3s, last for 60s, gently activate the material and initially remove impurities from the partition line surface;

[0056] First cycle: Apply 36V voltage (60% of the rated drive voltage), switch on and off at 3s intervals, last for 30s, to further ablate residual contaminants on the partition lines;

[0057] Second cycle: Apply 48V voltage (80% of the rated drive voltage), switch on and off at 3s intervals, and continue for 30s to eliminate conductive film residues and local micro-connections.

[0058] Third cycle: Apply 60V voltage (100% of the rated drive voltage), switch on and off at 3s intervals, for a total of 120s, to repair the excessively thin wire diameter and establish a stable conductive path.

[0059] Explosion point detection cycle: Apply 90V voltage (150% of rated drive voltage), switch on and off at 3s intervals, for a total of 60s, to perform final quality verification and screening of potential breakdown points.

[0060] To achieve stable internally engraved wire structure and optimized electrical performance, a gentle electric field guides liquid crystal molecules to align in an orderly manner during the low-voltage startup phase, preventing secondary diffusion caused by violent molecular migration due to excessive electric field strength. During the gradual voltage ramp-up phase, a slow increase in voltage ensures uniform current density distribution, effectively suppressing material softening caused by localized overheating. At the rated voltage stage, a stable electric field promotes the formation of an oriented anchoring structure between liquid crystal molecules and the polymer network, strengthening interfacial bonding and establishing a stable conductive path. In the high-voltage testing phase, applying 150% of the rated voltage verifies the structural stability of the fine internally engraved wire, ensuring reliable zone isolation performance and breakdown resistance. This progressive electrical intervention method based on material properties effectively compensates for deficiencies in structural control, enabling the internally engraved wire to simultaneously possess stable dimensional appearance, excellent electrical performance, and long-term operational reliability after lamination. It serves as a key supplementary means to suppress wire diameter diffusion and improve product yield.

[0061] This invention also provides a dye-based PDLC dimming film, which is prepared by the aforementioned method. Please refer to... Figure 1 The dye-based PDLC dimming film has a multilayer composite structure, comprising, from top to bottom, a transparent flexible substrate 11, a transparent conductive layer 12, and a liquid crystal-dye composite functional layer 13. The transparent flexible substrate 11 is preferably polyethylene terephthalate (PET), and the transparent conductive layer 12 is an indium tin oxide (ITO) layer. During laser engraving, the laser beam penetrates the transparent flexible substrate 11 and is precisely focused on the transparent conductive layer 12. By controlling the laser energy, an engraved pattern with insulating properties is formed, thereby constructing a zoned control circuit. The linewidth of the dye-based PDLC dimming film after laser engraving is 10~20 μm, and the linewidth diffusion is controlled within ±5 μm in subsequent lamination processes.

[0062] This invention also provides a dimming glass, comprising two layers of glass and a dimming film laminated therebetween, wherein the dimming film is the aforementioned dye PDLC dimming film.

[0063] In a specific application example, please refer to Figure 2 This dimming glass can be used as an automotive dimming sunroof assembly. Its preparation method includes a lamination process: a dye-modified PDLC dimming film 21 is sandwiched between two layers of glass 22, with PVB adhesive used as an interlayer adhesive 23; subsequently, the assembled structure is placed in an autoclave and subjected to high temperature and high pressure treatment in a sealed environment. Preferred process parameters are: temperature 130~150℃, pressure 1~1.5 MPa, and holding time 1~2 h. Under these conditions, the PVB adhesive fully melts, achieving a strong bond between the two glass layers and completely encapsulating the dye-modified PDLC dimming film, ultimately forming the automotive dimming sunroof assembly.

[0064] The following detailed description of examples of the present invention is exemplary and is used only to explain the present invention, and should not be construed as limiting the present invention.

[0065] Example 1

[0066] This embodiment provides a process method for preventing the diffusion of inner engraving lines. The specific implementation process is as follows: First, a pre-curing treatment is performed, using a diphenylphosphine oxide-based photoinitiator and an ultraviolet light source with a wavelength of 365 nm at 45 mW / cm². 2 The dye-modified PDLC film was irradiated with light intensity for 8 minutes to achieve a crosslinking degree of 48% and a Shore hardness of 32 HA, while controlling the adhesion between the film and the conductive substrate at 38 gf. Subsequently, laser engraving was performed, and the laser energy was set to 28 mJ / cm² based on the pre-cured film's state parameters. 2 The engraving speed was 235 mm / s, the laser frequency was 23 kHz, and the laser focus was precisely located at 1 / 2 of the film thickness; then, a complete curing process was performed using a 365 nm ultraviolet light source at 140 mW / cm². 2 After irradiating the film with light intensity for 45 seconds, the cross-linking degree of the film was increased to 92%. Finally, an electrical repair step was performed, in which a stepped voltage treatment was applied to the fully cured film. Based on the rated voltage of 60V, voltages of 30V (60s), 36V (30s), 48V (30s), 60V (120s) and 90V (60s) were applied sequentially. Each stage used a pulse mode with a 3s on-off interval to obtain the dye PDLC dimming film. The treated dye PDLC dimming film and PVB film were sandwiched together between two layers of glass and kept at 135℃ and 1.0MPa for 1.5h in an autoclave to form an integrated automotive dimming sunroof assembly.

[0067] Example 2

[0068] The process method is the same as in Example 1, except that a benzoin-based photoinitiator is used for pre-curing, and a 380nm wavelength light source at 30mW / cm² is used. 2 Irradiate with light intensity for 10 minutes.

[0069] Example 3

[0070] The process method is the same as in Example 1, except that the adhesion between the dye PDLC film and the conductive substrate is 18 gf.

[0071] Example 4

[0072] The process method is the same as in Example 1, except that the crosslinking degree of the dye PDLC film after pre-curing reaches 55%, and 28 mJ / cm is still used. 2 Laser energy.

[0073] Example 5

[0074] Referring to the process method of Example 1, the difference is that when the adhesion between the dye PDLC film and the conductive substrate is 38 gf, the engraving speed is maintained at 235 mm / s.

[0075] Example 6

[0076] The process method is the same as in Example 1, except that the laser frequency is still 23kHz when the Shore hardness is 38HA.

[0077] Example 7

[0078] The process method is the same as in Example 1, except that the initial voltage in the electrical repair is set to 70% of the rated voltage.

[0079] Example 8

[0080] Referring to the process method of Example 1, the difference is that in the laser engraving step, the laser focus is located at a depth of 205 μm below the upper surface of the dye PDLC film.

[0081] Example 9

[0082] Referring to the process method of Example 1, the difference is that the engraving speed is set to 180 mm / s in the laser internal engraving step.

[0083] Example 10

[0084] The process method is the same as in Example 1, except that the light intensity is set to 100 mW / cm² during the complete curing step. 2 The irradiation time is 60 seconds.

[0085] Comparative Example 1

[0086] The process method is the same as in Example 1, except that no pre-curing step is performed; the laser engraving is performed directly after complete curing.

[0087] Comparative Example 2

[0088] Referring to the process method of Example 1, the difference is that the pre-curing step uses a light source with a wavelength of 280nm and a power of 45mW / cm². 2 Irradiate with light intensity for 8 minutes.

[0089] Comparative Example 3

[0090] Referring to the process method of Example 1, the difference is that the pre-curing step is: using a light source with a wavelength of 365nm, 395nm or 405nm, irradiated with a light intensity of 15mW / cm² for 8 minutes.

[0091] Comparative Example 4

[0092] Referring to the process method of Example 1, the difference is that the pre-curing step uses a light source with a wavelength of 365nm, 395nm, or 405nm at a power of 45mW / cm². 2 Irradiate with light intensity for 3 minutes.

[0093] Test case

[0094] Systematic testing was conducted on the dye-based PDLC dimming films and finished automotive dimming sunroof components (300mm×300mm) prepared in Examples 1-10 and Comparative Examples 1-4. The width of the engraved lines was measured immediately after laser engraving using an optical microscope or confocal microscope to assess initial processing accuracy. After lamination, the same location was re-measured to obtain the final finished linewidth and calculate the line diameter deviation to evaluate line diameter stability and dimensional accuracy. Product yield was assessed by statistically analyzing the proportion of Grade A products out of 100 samples that simultaneously met linewidth tolerance (±5μm), had no electrical breakdown, and had no optical defects. Long-term reliability testing involved 1000 hours of accelerated aging at 100℃ to examine linewidth stability and insulation performance degradation. Insulation performance degradation was determined by testing the optical performance on both sides of the engraved lines. If the haze difference between the two sides was greater than 1%, insulation performance degradation was considered unacceptable; if the haze difference was greater than 0.5% but less than 1%, it was considered slight and acceptable; and if the haze difference was less than 0.5%, it was considered negligible. Adhesion was assessed using the cross-cut adhesion test combined with tape peel testing; Shore hardness was measured using a Shore A hardness tester according to ASTM D2240 standard; the degree of cross-linking was calculated by solvent extraction to determine the insoluble content, supplemented by Fourier transform infrared spectroscopy (FTIR) to quantitatively analyze characteristic functional groups and verify the degree of curing. The structural characterizations are shown in Tables 1 to 3.

[0095] Table 1. Crosslinking Degree, Shore Hardness, and Adhesion

[0096]

[0097] Table 2 Initial machining accuracy and finished product dimensional stability

[0098]

[0099] Table 3 Long-term reliability test results

[0100]

[0101] Analysis of the test results above shows that the complete combination of process parameters established in Example 1 exhibits optimal performance in suppressing wire diameter diffusion, ensuring product yield, and long-term reliability. Specifically, by precisely controlling the cross-linking degree and hardness of the film through pre-curing, it provides an ideal semi-cured substrate state for subsequent laser engraving. Based on this, the optimized laser parameters and focal position are matched to achieve the minimum initial processing linewidth (11 μm) and the optimal finished product linewidth control (21 μm), with a wire diameter deviation of only 10 μm. Compared to other examples, when the pre-curing parameters deviate from this optimized range (such as the change in initiator and wavelength in Example 2 leading to a decrease in cross-linking degree, the weak adhesion in Example 3, and the excessive cross-linking in Example 4), or when the laser processing parameters are not adjusted accordingly (such as the focal position deviation in Example 8 and the reduction in engraving speed in Example 9), it will lead to an increase in the finished product linewidth (26-30 μm), an increase in the linewidth change rate (100%-145.5%), and a further expansion of the linewidth after long-term aging (37-44 μm), resulting in a decrease in product yield to 75.1%-80.7%. Especially when the film condition is poorly controlled (such as abnormal adhesion or excessive hardness without adjusting the laser frequency), the line diameter diffusion phenomenon is aggravated. In contrast, the control group (without pre-curing, or with inappropriate pre-curing wavelength / insufficient energy / too short time) cannot form an effective semi-cured structure, resulting in a large initial linewidth (15-17μm). Under the high temperature and pressure of lamination, severe molecular flow and line diameter diffusion occur, and the finished product linewidth increases sharply to 58-69μm, with a linewidth change rate as high as 282.4%-331.3%. Moreover, the linewidth continues to deteriorate after long-term aging (79-97μm), and the insulation performance becomes completely unacceptable, resulting in a product yield of zero. In summary, the specific film state formed by pre-curing is the structural basis for suppressing the flow of polymer materials and the diffusion of line diameter in subsequent processes, while the precisely matched laser energy, speed, frequency and focal position are the key to ensuring the precision of micro-scale processing. The two work together to ensure that after complete curing and electrical repair, the final product maintains the best linewidth stability, insulation performance and a product yield of up to 99.5% during the lamination and long-term aging process.

Claims

1. A process for preventing the diffusion of internal engraving lines, the process being used to solve the problem of internal engraving line diffusion after dye PDLC lamination; characterized in that, Includes the following steps: Pre-curing step: Use a light source with a wavelength of 320~420nm and a power of 25~60mW / cm². 2 The dye PDLC film is irradiated with light intensity for 5-10 minutes to make its crosslinking degree reach 40%-60% and its Shore hardness reach 30-40HA, and it is in a semi-cured state. Laser internal engraving step: Laser internal engraving is performed on the dye PDLC film that has undergone the pre-curing step; Complete curing step: The dye PDLC film treated by the laser engraving step is irradiated with a light source to make its crosslinking degree reach more than 90%.

2. The method according to claim 1, characterized in that, In the pre-curing step, the corresponding light source wavelength and process parameters are matched according to the type of photoinitiator selected: When using benzoin-based photoinitiators, the light source wavelength is controlled at 320–340 nm, and the light intensity at 25–45 mW / cm². 2 The pre-curing time is 8~15 min; When using diphenylphosphine oxide photoinitiator, the light source wavelength is controlled at 350~370 nm and the light intensity at 40~50 mW / cm². 2 The pre-curing time is 5~10 min; When using acylphosphine oxide photoinitiators, the light source wavelength is controlled at 380~400 nm and the light intensity at 35~55 mW / cm². 2 The pre-curing time is 7~12 min; When using α-aminoketone photoinitiators, the light source wavelength is controlled at 400-420 nm, and the light intensity at 40-60 mW / cm². 2 The pre-curing time is 15~20 min.

3. The method according to claim 1, characterized in that, In the pre-curing step, the adhesion between the dye PDLC film and the conductive substrate is controlled at 30~50gf.

4. The method according to claim 1, characterized in that, In the laser engraving step, the laser energy is set according to the degree of crosslinking of the pre-cured dye PDLC film; wherein: the laser energy is 20~40mJ / cm 2 The engraving speed is 200~250mm / s, the laser frequency is 20~30kHz, and the laser focus is located at a depth of 190~200 μm below the upper surface of the dye PDLC film. When the degree of crosslinking is 40%~50%, the laser energy is 20~30 mJ / cm. 2 ; When the degree of crosslinking is 50%~60%, the laser energy is 30~40 mJ / cm. 2 .

5. The method according to claim 3, characterized in that, In the laser engraving step, the engraving speed is set according to the adhesion between the pre-cured dye PDLC film and the conductive substrate; when the adhesion increases by 10 gf, the engraving speed is increased by 30~50 mm / s accordingly.

6. The method according to claim 1, characterized in that, In the laser engraving step, the laser frequency is set according to the Shore hardness of the dye PDLC film after pre-curing; when the Shore hardness increases by 10 HA, the laser frequency is increased by 5~10kHz accordingly.

7. The method according to claim 1, characterized in that, In the complete curing step, a light source with a wavelength of 365nm, 395nm or 405nm is used to irradiate the dye PDLC film treated by the laser engraving step for 30 to 60 seconds with a light intensity of 130~150mW / cm², so that its crosslinking degree reaches more than 90%.

8. The method according to claim 1, characterized in that, The method also includes an electrical repair step: A stepped voltage program is applied to the fully cured dye PDLC membrane. The initial voltage of the stepped voltage program is 30-50% of the rated driving voltage of the membrane, and the voltage is increased stepwise by 10%-15% for 3-5 cycles.

9. A dye-based PDLC dimming film, characterized in that, It is prepared by the method according to any one of claims 1 to 8.

10. A type of dimming glass, characterized in that, It includes two layers of glass and a dimming film laminated therebetween, wherein the dimming film is the dye PDLC dimming film as described in claim 9.

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