Water transfer printing-based forming process of composite pattern on bamboo flute paint surface

Abstract

The present application relates to the technical field of national musical instrument manufacturing, and discloses a bamboo flute paint surface composite pattern forming process based on water transfer printing. First, the surface of the bamboo flute base is cleaned and polished. A primer layer is coated and completely cured. The water transfer printing sticker is activated by being placed in water. An adhesive layer is coated on the surface of the cured primer layer. The activated water transfer printing sticker is laid on the surface of the adhesive layer, and after air pressure combination, the pattern layer is adhered to the primer layer. After the pattern layer is stably attached, a varnish layer is coated on the outer side. After drying, curing and post-processing, a composite paint layer structure with a smooth surface and embedded patterns is formed. The present application completely covers the pattern layer in the paint layer through a multi-layer composite structure, forming an embedded decorative effect. The present application avoids the damage to the bamboo flute base caused by traditional carving processes, improves the surface smoothness, wear resistance and moisture resistance of the product, is suitable for standardized and batch production, and improves the modern process characteristics and consistency of the bamboo flute product.

Description

Technical Field

[0001] This invention relates to the field of ethnic musical instrument manufacturing technology, specifically to a water transfer printing process for forming composite patterns on the lacquer surface of bamboo flutes. Background Technology

[0002] As a traditional Chinese musical instrument, the bamboo flute has long employed traditional methods for surface decoration, including hand carving, pyrography, gilding, and partial coloring, with carving being the most common. Carving decoration involves cutting and shaping the bamboo surface to create patterns. Its advantages include a strong sense of tradition and high artistic value, but this technique has the following drawbacks: Existing carving techniques are subtractive processing methods, which weaken the bamboo tube wall and introduce stress concentration points. When the pattern is located near the membrane hole, finger hole, or fundamental tone hole, it can easily cause the bamboo flute to crack or deform, affecting the structural integrity and acoustic stability of the instrument. The carving process relies on the craftsman's experience, and the same pattern is difficult to maintain in terms of line width, depth, and density between different craftsmen and different batches, resulting in large differences in product appearance and making it difficult to meet the requirements of standardized production. Carving complex patterns requires a long time, making it difficult to form a stable production rhythm. At the same time, the rework rate and scrap rate are significantly affected by the craftsman's skill level, which restricts large-scale production. Furthermore, as ethnic musical instruments develop towards industrialization, branding, and modern aesthetics, the market has placed higher demands on the high flatness, strong wear resistance, and long-term preservation of patterns. Traditional carving decoration methods cannot simultaneously meet the process requirements of flatness and durability. In addition, the destructive nature of carving on the flute body structure limits the diversification of decorative forms and makes it difficult to combine with modern materials and manufacturing technologies.

[0003] Therefore, it is necessary to provide a bamboo flute pattern forming technology that is different from the traditional carving subtractive process and reflects the characteristics of modern paint surface composite process in order to solve the above problems. To this end, a bamboo flute paint surface composite pattern forming process based on water transfer printing is proposed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a water transfer printing-based composite pattern forming process for bamboo flute lacquer surfaces, thereby resolving the issues raised in the background.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a water transfer printing-based composite pattern forming process for bamboo flute lacquer surfaces, comprising the following steps: Step 1: Clean and polish the surface of the bamboo flute base; Step 2: Apply a primer layer to the treated bamboo flute surface and allow the primer layer to fully cure; Step 3: Place the water transfer sticker in water for activation treatment; Step 4: Apply an adhesive layer to the fully cured primer layer; Step 5: Lay the activated water transfer sticker on the surface of the adhesive layer, so that the pattern layer adheres to the primer layer, and let it stand after degassing and pressing. Step 6: After the pattern layer has been stably attached, apply a clear varnish layer to its outer side so that the pattern layer is encapsulated within the varnish layer structure. Step 7: After drying, curing, and post-treatment, a composite paint layer structure with a smooth surface and embedded patterns is formed. Preferably, step one further includes a step of controlling the moisture content of the bamboo, wherein the moisture content of the bamboo is controlled at 8% to 12%.

[0006] Preferably, the primer layer in step two is one or a combination of nitrocellulose lacquer, unsaturated polyester lacquer, or polyurethane lacquer.

[0007] Preferably, the base film of the water transfer sticker in step three is a PE silicone protective film, the water temperature for activation treatment is 18℃~30℃, the soaking time is 30~90 seconds, and it is left to stand for defoaming for 10~30 seconds.

[0008] Preferably, the adhesive layer in step four is a glutinous rice glue system or an AB glue system; The mass ratio of glutinous rice glue to water in the glutinous rice glue system is 1:0.8 to 1:2.0; The mass ratio of component A to component B in the AB glue system is 1:0.8 to 1.2, and deionized water can be added to adjust the viscosity.

[0009] Preferably, the amount of adhesive layer applied in step four is sufficient to form a continuous, unexposed, and unaccumulated wet film.

[0010] Preferably, the bonding pressure in step five is 0.02 to 0.05 MPa, the bonding time is 60 to 180 seconds, the number of times of air venting and pressing is 2 to 5 times, and the standing time after bonding is ≥2 hours.

[0011] Preferably, the varnish layer in step six is ​​PU varnish or UV varnish, with a total coating thickness of 40-80 μm, and is applied in 2-4 thin coats.

[0012] Preferably, the drying and curing temperature in step seven is 22℃~35℃, the relative humidity is 40%~75%, and the curing time is 24~72 hours.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses a multi-layer composite structure design of primer-adhesive-pattern-varnish to completely cover the pattern layer inside the paint layer, forming an embedded decorative effect. This avoids the material reduction damage to the bamboo flute base caused by traditional carving techniques, reduces the risk of cracking and deformation of the bamboo flute, and effectively protects the structural integrity and acoustic stability of the instrument.

[0014] 2. This invention uses a pattern transfer method that combines water transfer printing stickers with adhesive layers, along with segmented bonding and air-venting pressing processes, to ensure that the pattern can be tightly bonded to the complex curved surface of the bamboo flute. This solves the problem of wrinkles and air bubbles that are easily generated on curved surfaces in traditional hand-applied decorations, and achieves continuous and smooth coverage of the pattern on the surface of the bamboo flute.

[0015] 3. By clearly defining the material selection range and process parameter window for primer, adhesive layer and varnish, including activation time, coating thickness, bonding pressure and curing conditions, this invention makes the entire process repeatable and verifiable, reduces the reliance on the personal experience of craftsmen, and provides a technical foundation for the standardized and mass production of bamboo flute decorations.

[0016] This invention uses a varnish layer to seal and protect the pattern, forming a wear-resistant, moisture-proof, and stain-resistant surface layer. This makes the pattern less prone to wear, fading, or whitening due to moisture during daily performance and long-term use, significantly improving the durability and environmental adaptability of bamboo flute products and extending the duration of the decorative effect.

[0017] This invention provides various combination schemes of primer systems and adhesive systems, and gives corresponding process adaptation conditions to meet the needs of different production scenarios, including manual rework-friendly, fast-paced production line type, and high hardness requirement type, thereby enhancing the flexibility and industrial adaptability of the process.

[0018] This invention replaces traditional carving with a surface composite paint layer structure, preserving the original thickness and natural texture of the bamboo substrate while achieving a high degree of flatness in the pattern presentation. This significantly reduces the surface roughness of the final product, and reduces the appearance consistency error from ±35% of traditional carving to ±8%, thereby enhancing the modern craftsmanship and brand recognition of bamboo flute products.

[0019] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0020] Figure 1 This is a flowchart of the process for forming composite patterns on the lacquer surface of bamboo flutes based on water transfer printing, as described in this invention. Figure 2 This is a schematic diagram of the overall structure of the bamboo flute of the present invention; Figure 3 This is a schematic cross-sectional view of the paint layer structure of the present invention; Figure 4 This is a schematic diagram illustrating the effect of continuous and flat state surfaces embedded within the pattern layer of the present invention. Detailed Implementation

[0021] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see Figures 1-4 As shown, the water transfer printing-based composite pattern forming process for bamboo flute lacquer surfaces in this invention is described in this section using multiple embodiments to fully demonstrate the technical solution and adaptability of this invention. Three embodiments are provided, each corresponding to a different combination of primer and adhesive systems, to demonstrate the universality and selectivity of the technical solution of this invention.

[0023] Example 1: Polyurethane primer + AB glue + polyurethane clear varnish solution In this embodiment, polyurethane paint is used as the primer and clear coat system, and AB glue is used as the adhesive layer. This solution takes into account adhesion, wear resistance and process stability, and is suitable for most production scenarios.

[0024] Step 1: Matrix Pretreatment Select a pre-processed bamboo flute substrate (with basic processes such as hole drilling and tuning completed; the moisture content of the bamboo is measured using a moisture meter and controlled within the range of 8%–12%; in this embodiment, the moisture content is controlled at 10%). First, perform surface cleaning. Use a non-woven cloth soaked in anhydrous ethanol with a volume fraction ≥95% to thoroughly wipe the outer surface of the bamboo flute, removing residual oil, sweat, and dust from the processing. After cleaning, use sandpaper for graded sanding, in the order of 400 grit → 600 grit → 800 grit, sanding along the flute's axial direction to avoid magnifying transverse scratches after subsequent coating. The purpose of sanding is to increase the surface roughness of the substrate, improving the mechanical bonding and adhesion between the primer and the bamboo.

[0025] Step 2: Applying the primer layer A polyurethane primer is applied to the pre-treated bamboo flute surface. The polyurethane primer possesses excellent adhesion, flexibility, and water resistance, providing a good foundation for subsequent pattern layers. It is applied by spraying, with each wet film thickness controlled at approximately 40 μm, for a total of two coats. After each coat, the flute is allowed to flash-dry for 15 minutes in a clean environment to allow initial solvent evaporation. After coating, the bamboo flute is placed in an environment with a temperature of 20–28℃ and a relative humidity of 50%–65% for 36 hours to cure. Complete curing of the primer is determined by the flute being no longer sticky to the touch, leaving no indentations, and having formed a continuous and uniform paint film. In this step, the primer seals the bamboo surface, preventing excessive penetration of subsequent adhesives and providing a smooth adhesion base for the pattern layers.

[0026] Step 3: Activation of water transfer film Select a pre-printed water transfer sticker with the desired pattern. Its base film is a PE silicone protective film system, and the pattern layer is a solvent-resistant ink. Completely immerse the sticker in a container of clean water at 25℃ for 60 seconds to activate it. During immersion, the adhesive layer between the pattern layer and the base paper absorbs water and dissolves, making the pattern layer detachable. After immersion, remove the sticker from the water and let it stand in the air for 15 seconds to allow excess water to drain and air bubbles to dissipate. The purpose of this activation treatment is to release the pattern layer from the base paper while maintaining a certain degree of flexibility for application to curved surfaces.

[0027] Step 4: Apply adhesive layer AB adhesive was selected as the bonding material, with component A being epoxy resin and component B being a curing agent. It was prepared at a mass ratio of A:B = 1:1, with 10% deionized water added to adjust the viscosity. After stirring evenly, it was allowed to stand for 5 minutes to defoam, at which point the adhesive viscosity was 1100 cps (25℃). The adhesive was then evenly applied to the fully cured primer surface using a scraping method, with the wet film thickness controlled at approximately 15 μm, forming a continuous, unblemished, and unaccumulated adhesive layer. In this invention, AB adhesive serves as an intermediate transition layer, adhering well to the primer and forming a strong bond with the pattern layer, while also possessing a certain degree of flexibility to accommodate the curved surface of the bamboo flute.

[0028] Step 5: Pattern layer application and venting pressing Align the activated water transfer sticker with the predetermined position on the surface of the bamboo flute, and smoothly lay the pattern layer on the adhesive layer. Since the bamboo flute has a slender tubular structure with a large curvature, if the pattern is large, to prevent wrinkles, the sticker can be divided into two sections, each approximately 100mm long. During application, use a silicone roller to repeatedly roll from the center outwards, applying a pressure of approximately 0.03MPa, for three passes to ensure a tight bond between the pattern layer and the adhesive layer, and to remove air bubbles. After application, place the bamboo flute in a clean environment and let it stand for 2 hours to allow the adhesive layer to initially cure and stabilize, ensuring the pattern layer adheres firmly. The segmented application and air-explosion pressing in this step ensure that the pattern is flat, wrinkle-free, and bubble-free on the complex curved surface.

[0029] Step 6: Apply a top coat of clear varnish. After the pattern layer has adhered stably, a sealing clear coat is applied. The clear coat is a polyurethane clear coat with the same system as the primer to ensure interlayer compatibility. It is applied by spraying, with three coats, each with a wet film thickness of approximately 20 μm, for a total thickness of about 60 μm. Each coat is applied 20 minutes apart to allow the previous coat to dry slightly. The purpose of the clear coat is to completely encapsulate the pattern layer within the paint layer, forming an embedded protective structure that prevents the pattern layer from being directly exposed to the external environment and subjected to wear or corrosion, while also providing a continuous and smooth visual effect.

[0030] Step 7: Drying, curing, and post-treatment After the coating is applied, place the bamboo flute in an environment with a temperature of 22-28℃ and a relative humidity of 50%-60% for 48 hours to ensure complete curing of the paint film. After curing, post-treatment can be performed according to the product's gloss requirements: for a high-gloss effect, use 2000-grit sandpaper to lightly sand the fine particles on the surface, and then use a polishing machine with polishing compound for polishing; for a matte effect, use 1500-grit sandpaper to sand evenly; finally, a bamboo flute product with a smooth surface, embedded patterns, and a smooth touch is obtained.

[0031] This embodiment achieves integrated bonding of primer, adhesive layer, and clear coat through the good interlayer compatibility of the polyurethane system. The pattern layer is firmly encapsulated inside the paint layer, resulting in excellent wear resistance and weather resistance.

[0032] Example 2: Nitrocellulose lacquer + rice glue + polyurethane varnish solution In this embodiment, nitrocellulose lacquer is used as the primer, rice glue as the adhesive layer, and polyurethane varnish as the sealing layer. Nitrocellulose lacquer dries quickly and is easy to sand and rework. Rice glue is environmentally friendly, non-toxic, and has a certain degree of flexibility, making it suitable for production scenarios with a lot of manual operation or processes that require partial rework.

[0033] Step 1: Matrix Pretreatment Similar to Example 1, the bamboo flute substrate was cleaned by ethanol wiping and sanded with 400-grit → 600-grit → 800-grit sandpaper, and the moisture content of the bamboo was controlled to be 9%.

[0034] Step 2: Applying the primer layer Nitrocellulose lacquer is applied as a primer. The main components of nitrocellulose lacquer are nitrocellulose, resin, and solvent. It is characterized by rapid drying, good solvent release, and ease of quick application and repair. Spraying is used, with each coat achieving a wet film thickness of approximately 25 μm. Three coats are applied, for a total thickness of approximately 70 μm. Each coat is flash-dried for 10 minutes, and then cured for 24 hours at 20–25°C. The nitrocellulose primer serves to quickly form a sealing layer, and its excellent sanding properties facilitate subsequent localized adjustments.

[0035] Step 3: Activation of water transfer film Same as in Example 1, with water temperature of 25°C, soaking time of 60 seconds, and standing for 15 seconds to defoam.

[0036] Step 4: Apply adhesive layer Food-grade glutinous rice glue was selected as the adhesive material and mixed at a mass ratio of glutinous rice glue to deionized water of 1:1.3. After stirring evenly, the mixture was allowed to stand and expand for 30 minutes, at which point the viscosity of the glue solution was 5000 mPa·s (25℃). The main component of glutinous rice glue is natural glutinous rice starch, which is environmentally friendly, non-toxic, flexible, and washable. The glutinous rice glue was evenly applied to the primer surface using a scraping method, with the wet film thickness controlled at approximately 20 μm to form a continuous adhesive layer. In this step, the role of the glutinous rice glue is to utilize its moderate initial tack and good wetting properties to ensure stable adhesion of the pattern layer, and in case of any deviation in the adhesion position, it can be fine-tuned by wetting with water within a short time.

[0037] Step 5: Pattern layer application and venting pressing The activated water transfer sticker is laid on the surface of the glutinous rice adhesive layer. A soft squeegee is used to scrape and press outwards from the center to remove air, applying a pressure of approximately 0.02 MPa, repeating this process four times. Because glutinous rice adhesive dries slowly, the resting time after bonding is extended to four hours to ensure the adhesive layer is fully dry and the pattern layer adheres stably. Extending the resting time in this step allows the drying characteristics of the glutinous rice adhesive to be accommodated, preventing the pattern layer from shifting later due to an undried adhesive layer.

[0038] Step 6: Apply a top coat of clear varnish. After the pattern layer has stabilized, a polyurethane varnish is sprayed as a sealing layer. The same polyurethane varnish as in Example 1 is used here to provide excellent abrasion resistance and water resistance. Two to three coats are applied, with a total thickness controlled at approximately 50 μm, and each coat is spaced 20 minutes apart. The varnish serves to protect the pattern layer while compensating for the relatively weak water resistance of the rice glue layer.

[0039] Step 7: Drying, curing, and post-treatment The curing conditions were the same as in Example 1, and fine grinding and polishing were performed after curing for 48 hours.

[0040] The advantages of this embodiment are that the nitrocellulose lacquer is easy to sand and rework, the rice glue is environmentally friendly and can be fine-tuned in the early stage, making it suitable for small-batch, multi-variety manual production. If a positional deviation occurs during the bonding process, the incompletely cured rice glue layer can be wiped with a damp cloth, the pattern layer can be removed, and then the layers can be re-bonded, resulting in low rework costs.

[0041] Example 3: Unsaturated polyester primer + AB glue + UV clear coat solution (fast-paced, high-hardness type) In this embodiment, unsaturated polyester paint is used as the primer, AB glue as the adhesive layer, and UV varnish as the sealing layer. Unsaturated polyester paint has high hardness and good fullness, and UV varnish can be cured quickly by ultraviolet light, making it suitable for large-scale production lines equipped with UV curing equipment, which can significantly shorten the production cycle.

[0042] Step 1: Matrix Pretreatment Similar to Example 1, the bamboo flute base was cleaned and polished, and the moisture content of the bamboo was controlled to be 10%.

[0043] Step 2: Applying the primer layer Unsaturated polyester paint is applied as a primer. The main components of unsaturated polyester paint are unsaturated polyester resin and styrene, characterized by high film hardness, good fullness, and strong abrasion resistance. It is applied by spraying, with each coat's wet film thickness controlled at approximately 40 μm, for a total of two coats and a total thickness of approximately 80 μm. Each coat is flash-dried for 15 minutes, and then cured at 22–28°C for 24–36 hours. The unsaturated polyester primer provides a high-hardness load-bearing base, but its shrinkage rate is relatively high, so it is essential to ensure complete curing before proceeding to the next step.

[0044] Step 3: Activation of water transfer film Same as in Example 1, with water temperature of 25°C, soaking time of 60 seconds, and standing for 15 seconds to defoam.

[0045] Step 4: Apply adhesive layer AB adhesive was selected and prepared at a mass ratio of A:B = 1:0.9. 8% deionized water was added to adjust the viscosity to approximately 1000 cps. The adhesive was applied by spraying, with the wet film thickness controlled at 12–15 μm to form a uniform adhesive layer. In this embodiment, the AB adhesive serves to ensure good adhesion to the high-hardness unsaturated polyester primer and to provide a smooth transition interface for the UV clear coat.

[0046] Step 5: Pattern layer application and venting pressing The bonding process is the same as in Example 1, but the bonding is done in segments, each segment is 100mm long, and the silicone roller is used to remove air three times, and then the segments are left to stand for 2 hours.

[0047] Step 6: Apply a top coat of clear varnish. After the pattern layer has stabilized, a UV varnish is sprayed on. The UV varnish is a UV-curable coating characterized by fast curing speed, high hardness, and good scratch resistance. One to two coats are applied by spraying, with a total thickness controlled at 40–60 μm. Immediately after spraying, the bamboo flute is placed in a UV curing device and cured by UV irradiation according to the device's energy parameters. The curing time is only tens of seconds to several minutes. The UV varnish's function is to quickly form a high-hardness surface, significantly shortening the production cycle, while providing excellent surface protection.

[0048] Step 7: Post-processing After UV curing, the paint film is completely dry and can be lightly polished or directly packaged as needed.

[0049] This embodiment utilizes the rapid curing characteristics of UV clear varnish to shorten the overall process time from 48-72 hours in the traditional solution to 24-36 hours (the main time is consumed in the curing of the primer), significantly improving production efficiency and making it suitable for large-scale mass production.

[0050] Comparative Example: Traditional Carving and Decorative Techniques To facilitate comparison and explanation of the beneficial effects of the present invention, a traditional carving process is provided as a comparative example.

[0051] Bamboo flute substrates of the same batch and specifications as in Example 1 were selected, and patterns were decorated using traditional hand-carving methods. The specific process was as follows: experienced craftsmen designed patterns on the surface of the bamboo flute, and then used a carving knife to perform subtractive cutting along the pattern lines, controlling the carving depth between 0.3 and 1.2 mm. After the pattern carving was completed, local coloring and surface coating were applied for protection. The following data were recorded: carving a single bamboo flute took approximately 80 minutes, the wall thickness reduction was approximately 8%–12%, and the surface roughness Ra was approximately 4.5 μm. Fifty bamboo flutes were randomly selected for appearance consistency evaluation; differences in line width, depth, and density resulted in an appearance consistency error of approximately ±35%. Furthermore, a bending resistance test was conducted on bamboo flutes with carving positions close to the finger holes, observing a decrease in axial bending strength of approximately 17.4% and an increase in pitch drift probability of approximately 12%. During subsequent use, some bamboo flutes developed micro-cracks at the carved patterns.

[0052] Summary of process parameters comparison between the examples and comparative examples To clearly illustrate the technical features of the various embodiments of the present invention and their differences from comparative examples, the following table summarizes them:

[0053] This invention, through three representative embodiments, employs three different material combinations: polyurethane primer / AB glue / polyurethane varnish, nitrocellulose lacquer / glutinous rice glue / polyurethane varnish, and unsaturated polyester primer / AB glue / UV varnish. It systematically demonstrates the applicability and adjustability of this technical solution in three typical scenarios: general production, manual rework-friendly, and fast-paced mass production. Each embodiment achieves the core technological effects of the pattern layer being completely embedded within the lacquer layer structure, a smooth and continuous surface, and no damage to the bamboo flute substrate. Comparison with comparative examples proves the advancements of this invention over traditional carving techniques in terms of structural protection, appearance consistency, surface smoothness, and process controllability. This demonstrates that the invention provides multiple selectable process paths, retaining the flexibility of manual operation while meeting the reproducibility requirements of industrial production, thus providing a complete, reliable, and quantifiable modern technical solution for bamboo flute surface decoration.

Claims

1. A water transfer printing-based composite pattern forming process for bamboo flute lacquer surfaces, characterized in that, Includes the following steps: Step 1: Clean and polish the surface of the bamboo flute base; Step 2: Apply a primer layer to the treated bamboo flute surface and allow the primer layer to fully cure; Step 3: Place the water transfer sticker in water for activation treatment; Step 4: Apply an adhesive layer to the fully cured primer layer; Step 5: Lay the activated water transfer sticker on the surface of the adhesive layer, so that the pattern layer adheres to the primer layer, and let it stand after degassing and pressing. Step 6: After the pattern layer has been stably attached, apply a clear varnish layer to its outer side so that the pattern layer is encapsulated within the varnish layer structure. Step 7: After drying, curing and post-treatment, a composite paint layer structure with a smooth surface and embedded patterns is formed.

2. The water transfer printing-based composite pattern forming process for bamboo flute lacquer surfaces according to claim 1, characterized in that, Step one also includes controlling the moisture content of the bamboo, which is controlled at 8% to 12%.

3. The water transfer printing-based composite pattern forming process for bamboo flute lacquer surfaces according to claim 1, characterized in that, The primer layer mentioned in step two is one or a combination of nitrocellulose lacquer, unsaturated polyester lacquer, or polyurethane lacquer.

4. The water transfer printing-based composite pattern forming process for bamboo flute lacquer surfaces according to claim 1, characterized in that, The base film of the water transfer sticker mentioned in step three is a PE silicone protective film. The water temperature for activation treatment is 18℃~30℃, the soaking time is 30~90 seconds, and it is left to stand for 10~30 seconds to defoam.

5. The water transfer printing-based composite pattern forming process for bamboo flute lacquer surfaces according to claim 1, characterized in that, The adhesive layer mentioned in step four is a glutinous rice glue system or an AB glue system; The mass ratio of glutinous rice glue to water in the glutinous rice glue system is 1:0.8 to 1:2.0; The mass ratio of component A to component B in the AB glue system is 1:0.8 to 1.2, and deionized water can be added to adjust the viscosity.

6. The water transfer printing-based composite pattern forming process for bamboo flute lacquer surfaces according to claim 1, characterized in that, The amount of adhesive layer applied in step four is sufficient to form a continuous, unexposed, and unaccumulated wet film.

7. The water transfer printing-based composite pattern forming process for bamboo flute lacquer surfaces according to claim 1, characterized in that, The bonding pressure in step five is 0.02–0.05 MPa, the bonding time is 60–180 seconds, the number of times of air venting and pressing is 2–5, and the standing time after bonding is ≥2 hours.

8. The water transfer printing-based composite pattern forming process for bamboo flute lacquer surfaces according to claim 1, characterized in that, The clear coat layer mentioned in step six is ​​PU clear coat or UV clear coat, with a total coating thickness of 40-80μm, and is applied in 2-4 thin coats.

9. The water transfer printing-based composite pattern forming process for bamboo flute lacquer surfaces according to claim 1, characterized in that, The drying and curing temperature in step seven is 22℃~35℃, the relative humidity is 40%~75%, and the curing time is 24~72 hours.

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