Micro-gap low trace isolation paper for glass substrate and preparation method and application thereof

Abstract

The application discloses a kind of micro-gap low trace isolation paper for glass substrate and its preparation method and application.The plant fiber slurry is dispersed in water, and after being defibrated, screened and desanded, it is formed into a wet paper web by being cast;Then, after the wet paper web is preliminarily pressed and dehydrated, it is shaped by at least one localized micro-pressing shaping nip, and by the local differential compression and pressure release rebound of different areas of the paper web, a micro-protrusion contact area and at least partially interconnected micro-groove channel are formed on the surface of the paper sheet, and finally, after rebound setting, drying and cleaning aftertreatment, a micro-gap low trace isolation paper is obtained.The isolation paper can reduce the risk of paper marks, white mist, adhesion, foreign matter transfer and peeling instability of large-size glass substrates during stacking, storage and transportation.

Description

Technical Field

[0001] This invention belongs to the field of specialty paper technology, and specifically relates to a micro-gap low-mark release paper for glass substrates, its preparation method and application. Background Technology

[0002] The glass substrates used in the manufacturing process of display panels typically undergo cutting, cleaning, inspection, stacking, storage, transportation, and loading. To prevent scratches, indentations, foreign matter transfer, electrostatic adsorption, or surface contamination caused by direct contact between glass substrates, spacer material is usually placed between adjacent glass substrates. Glass spacer paper is a commonly used insulating and protective material during the stacking, storage, and transportation of glass substrates due to its advantages such as being thin, flexible, cuttable, rollable, easy to process in large formats, and relatively inexpensive.

[0003] As the display industry evolves from low-generation to high-generation lines, the size of glass substrates continues to increase. Early display glass substrates were relatively small, resulting in lower weight per sheet during stacking, handling, and isolation. The impact of spacer materials on interface adhesion, localized moisture retention, and large-area paper residue was relatively limited. With the application of 8.5-generation, 10.5-generation, and higher generation display production lines, glass substrate sizes have gradually increased from smaller areas to several square meters. The length and width of 10.5-generation glass substrates are approaching 3 m × 3.4 m. This significant increase in glass substrate area and weight has simultaneously increased the contact area between adjacent glass and spacer paper, the stacking pressure, the interfacial moisture diffusion distance, and the risk of localized adhesion during storage and transportation. This places higher demands on the cleanliness, dimensional stability, surface contact state, and interfacial dissipation capabilities of the glass spacer paper.

[0004] High-generation display glass substrates require extremely high surface cleanliness. Microparticles, paper dust, migratable organic matter, soluble salts, metal ions, and localized moisture retention on the glass surface can all lead to paper marks, white fog, adhesion, cleaning difficulties, coating defects, or decreased yield in subsequent processes. Especially in the case of large-size stacked glass substrates, the issues between the glass and the spacer paper extend beyond particle scratches or surface contamination; they also include large-area adhesion, interfacial moisture retention, and unstable localized peeling. If the spacer paper surface is too dense or the actual contact area is too large, interfacial moisture cannot easily dissipate quickly between the glass and the paper, making localized white fog, paper marks, indentations, or adhesion more likely during storage and transportation. Therefore, spacers for high-generation display glass substrates not only need appropriate tensile strength, folding endurance, dimensional stability, and automatic handling adaptability, but also require comprehensive control over low ash content, low ion migration, low paper dust, low foreign matter, actual contact area, interfacial moisture dissipation, and peeling stability.

[0005] Existing glass spacers typically improve their performance through raw material purification, surface treatment, mildew prevention, antistatic properties, sizing, calendering, embossing, or breathability adjustment. In current technologies, to reduce the risk of glass surface damage and contamination, those skilled in the art often focus on improving paper smoothness, reducing surface roughness, minimizing paper dust, and increasing paper uniformity. However, for large-size display glass substrates of 10.5 generations and higher, excessively smooth or dense paper surfaces do not necessarily reduce the risk of paper marks. On the contrary, under large-area stacking conditions, an excessively large actual contact area can easily create a localized adhesion interface between the glass and the spacer, making it difficult for moisture to dissipate quickly, thus inducing problems such as white fog, paper marks, adhesion, and unstable peeling.

[0006] When using surface coatings, antistatic salts, mildew inhibitors, sizing agents, or other functional additives, migratable components can be easily introduced, increasing the risk of glass surface contamination, cleaning difficulties, or subsequent process defects. While simply increasing calendering strength can improve paper surface smoothness, it also increases the density of the paper and the actual contact area, reducing the ability of interfacial moisture to dissipate, thereby increasing the risk of paper marks, white fog, and adhesion. Conventional embossing or decal treatments usually focus on improving paper appearance, friction properties, or local air permeability. Simply increasing air permeability may cause paper surface roughness, dusting, insufficient strength, and an increase in local micro-protrusions, which is also detrimental to the long-term stacking and isolation of high-cleanliness glass substrates.

[0007] Therefore, with the increasing demands for larger sizes and higher cleanliness in 10.5-generation and higher generation display glass substrates, traditional glass spacers that rely on ordinary calendering, conventional sizing, surface additives, or conventional embossing to adjust performance are no longer sufficient to simultaneously meet requirements such as low paper residue, low white haze, low migration, suitable air permeability, and stable peeling. The technical challenge for display glass substrate spacers is not simply pursuing smoother or denser paper sheets, but rather the need to synergistically control the actual contact state between the glass and the spacer paper, as well as the interface moisture dissipation path, while maintaining high cleanliness, moderate smoothness, and low migration. It is necessary to provide a new type of spacer paper for glass substrates and its preparation method that, while maintaining appropriate smoothness, operational strength, and cleanliness, reduces the risks of paper residue, white haze, foreign matter transfer, adhesion, and peeling instability during the stacking, storage, and transportation of large-size display glass substrates. Summary of the Invention

[0008] The primary objective of this invention is to overcome the problem that existing glass spacers cannot simultaneously achieve high cleanliness, moderate smoothness, low paper marks, low white fog, suitable air permeability, low migration contamination, interfacial moisture dissipation, and stable peeling performance, and to provide a method for preparing micro-gap low-mark spacers for glass substrates.

[0009] Another object of the present invention is to provide a micro-gap low-scratch release paper prepared by the method.

[0010] Another object of the present invention is to provide the application of the micro-gap low-scratch release paper.

[0011] The objective of this invention is achieved through the following technical solution:

[0012] A method for preparing a micro-gap, low-mark release paper for glass substrates includes the following steps:

[0013] (1) Preparation of wet paper web: Disperse plant fiber pulp in water, adjust the pulp mass concentration to 1.5% to 6.0%, and after descaling, beat the pulp to a freeness of 18°SR to 58°SR. Then, after beating, the pulp is screened and sand removed, and then made into wet paper web;

[0014] (2) Localized micro-pressing and shaping: The wet paper web is initially pressed and dehydrated to a moisture content of 18% to 55%, and then passed through at least one localized micro-pressing and shaping zone to obtain a paper web after localized micro-pressing and shaping; wherein, the localized micro-pressing and shaping zone includes a shaping roller with a discontinuous micro-protrusion structure on its surface and an elastic bearing roller that cooperates with it; the height of the discontinuous micro-protrusion structure of the shaping roller is 1 to 80 μm and is less than half of the total thickness of the release paper, and the average nearest neighbor center distance between adjacent micro-protrusion structures is 20 to 1000 μm; the linear pressure of the localized micro-pressing and shaping zone is 5 to 100 kN / m, and the surface temperature of the shaping roller is 20 to 120℃;

[0015] (3) Spring-setting treatment: The paper web after localized micro-pressing and shaping is subjected to spring-setting treatment 1 to 5 times, and then dried to a moisture content of 3% to 10% to obtain the paper web after spring-setting treatment.

[0016] (4) Cleaning and post-treatment: The paper web after the spring-setting treatment is cleaned and post-treated to obtain micro-gap low-scratch release paper for glass substrates.

[0017] Further, the plant fiber pulp mentioned in step (1) is at least one of softwood pulp, hardwood pulp, bamboo pulp, cotton pulp, hemp pulp, grass fiber pulp and microfibrillated cellulose pulp; preferably at least one of chemical pulp, refined pulp or high-purity cellulose pulp that has undergone purification treatment.

[0018] Furthermore, the water mentioned in step (1) is deionized water.

[0019] Furthermore, the mass concentration of the slurry mentioned in step (1) is preferably 3.0%.

[0020] Further, the rotation speed of the transpiration in step (1) is 8000 to 12000 rpm; preferably 10000 rpm.

[0021] Furthermore, the beating degree of the slurry described in step (1) is preferably 28°SR to 32°SR.

[0022] Furthermore, the screening and sand removal in step (1) includes at least one of primary or multi-stage pressure screening, low-concentration sand removal, high-concentration slag removal, and microporous filtration. Screening and sand removal reduce the content of hard particles, fiber bundles, sand particles, metal shavings, and other foreign matter in the slurry that may cause damage or contamination to the glass surface.

[0023] Furthermore, the screening is preferably performed using a pressure screen with a screen gap width of 0.15 mm.

[0024] Furthermore, the sand removal is preferably performed using a two-stage low-concentration sand remover with an inlet pressure of 0.25 MPa.

[0025] Furthermore, the copying process described in step (1) is carried out by using a long wire mesh, a round wire mesh, a sandwiched wire mesh, or a multi-layer forming method.

[0026] Further, the basis weight of the wet paper web in step (1) is 20-90 g / m²; preferably 35-65 g / m²; more preferably 45-65 g / m².

[0027] Furthermore, the linear pressure of the preliminary pressing and dehydration described in step (2) is 80 to 100 kN / m.

[0028] Furthermore, the moisture content of the wet paper web after the initial pressing and dehydration in step (2) is preferably 35% to 40%; more preferably 38%.

[0029] Further, the shaping roller mentioned in step (2) is a metal roller, a ceramic roller, a rubber roller, a polyurethane roller, or a composite roller made of two or more of the following materials: metal, ceramic, rubber, polyurethane, etc.

[0030] Further, the discontinuous micro-protrusions on the surface of the forming roller described in step (2) are discontinuously distributed in the paper web running direction and / or the paper web transverse direction, forming continuous or semi-continuous low-compression regions between adjacent discontinuous micro-protrusions; when the wet paper web passes through the localized micro-press forming zone, different regions of the paper web form compression differences, and after the paper web leaves the pressing zone, a height difference is formed between the high-compression region and the low-compression springback region, thereby obtaining spaced micro-protrusion contact areas and micro-groove channels located between adjacent micro-protrusion contact areas; the micro-protrusion contact areas are used to form dispersed support contact; the micro-groove channels are interconnected along at least one of the longitudinal, transverse, or oblique directions of the paper web, and are used to form a moisture dissipation path between the glass substrate and the release paper. Thus, the micro-gap low-mark release paper does not form an integral surface contact with the glass in the glass substrate stacked state, but forms dispersed support through the micro-protrusion contact areas, and retains interface communication space through the micro-groove channels.

[0031] Furthermore, the localized micro-pressing shaping described in step (2) includes single-sided shaping, double-sided sequential shaping, or front and back differential shaping; wherein, the height, spacing (center distance), linear pressure, or temperature of the micro-convex structure on the front and back sides can be the same or different to adapt to the different usage requirements of the glass contact surface and the pick-up and put-down surface.

[0032] Further, the height of the discontinuous micro-convex structure of the shaping roller in step (2) is preferably 8 to 12 μm, the average nearest neighbor center distance between adjacent micro-convex structures is preferably 150 to 210 μm (more preferably 180 μm); the linear pressure of the localized micro-pressing shaping zone is preferably 12 to 30 kN / m, and the surface temperature of the shaping roller is preferably 35 to 45℃.

[0033] Furthermore, for single-sided forming, the localized micro-press forming area includes a forming roller with a discontinuous micro-convex structure on its surface and an elastic bearing roller that cooperates with it; for double-sided sequential forming (with the same parameters) or front and back differential forming (with different parameters), the localized micro-press forming area includes a first localized micro-press forming area for forming the front side of the wet paper web and a second localized micro-press forming area for forming the back side of the wet paper web; both the first localized micro-press forming area and the second localized micro-press forming area include a forming roller with a random dotted discontinuous micro-convex structure on its surface, and an elastic bearing roller that cooperates with the forming roller.

[0034] Further, the discontinuous micro-protrusion structure on the surface of the shaping roller in step (2) is at least one of random dot-shaped, strip-shaped, island-shaped, mesh-shaped, honeycomb-shaped, and corrugated micro-protrusion structures; preferably, it is a random dot-shaped micro-protrusion structure, and the equivalent diameter of the top surface of each micro-protrusion structure is 60 to 100 μm (preferably 80 μm).

[0035] Further, the conditions for the rebound shaping treatment in step (3) are: treatment at 25-90℃ and relative humidity of 35%-95% for 1-180 min; preferably: treatment at 35-50℃ and relative humidity of 60%-80% for 20-40 min.

[0036] Furthermore, the drying in step (3) is to dry the paper web to a moisture content of 6.5% to 7%.

[0037] Furthermore, the spring-setting treatment in step (3) is preferably performed 1 to 2 times. After each spring-setting treatment, drying or moisture balancing treatment is performed. The stability of the micro-gap structure on the paper surface is controlled by the synergistic regulation of wet-heat spring-setting and confined drying, so as to stabilize the micro-gap structure on the paper surface and the pore structure inside the paper, thereby reducing the collapse or excessive compaction of the microstructure during subsequent storage, cutting and use.

[0038] Furthermore, the post-cleaning treatment described in step (4) includes one or more of the following: low-tension rewinding, non-contact dust removal (air knife dust removal, vacuum dust collection), ion wind electrostatic elimination, edge lint collection, clean cutting, and dust-free packaging, in order to reduce the impact of paper dust, lint, electrostatically adsorbed particles and packaging contaminants on the surface of the glass substrate.

[0039] Furthermore, the tension of the low-tension rewinding is 30–60 N / m.

[0040] Furthermore, in step (4), the surface area of ​​the micro-convex contact area of ​​the micro-gap low-mark release paper accounts for 5% to 65% of the surface area (preferably 10% to 20%; more preferably 16%), and the area of ​​the micro-groove channel accounts for 35% to 95% of the surface area (preferably 80% to 90%; more preferably 84%). At least a portion of the micro-groove channels are interconnected in the paper web plane direction, forming a moisture dissipation channel between the glass substrate and the release paper, thus maintaining partial connectivity at the glass substrate stacking interface. By controlling the area of ​​the micro-convex contact area and the area of ​​the micro-groove channel, the release paper forms limited contact on the glass substrate surface rather than large-area adhesion, thereby reducing the risks of local moisture retention, white fog, paper marks, adhesion, and peeling instability.

[0041] A micro-gap, low-scratch release paper for glass substrates is prepared by any of the preparation methods described above.

[0042] The basis weight of the micro-gap low-scratch release paper is 20–90 g / m². 2 (Preferably 35-65 g / m²; more preferably 45-65 g / m²), thickness 30-160 μm (preferably 75-100 μm), Gurley air permeability resistance 2-60 s (preferably 10-20 s), Bekk smoothness 10-200 s (preferably 50-100 s), pH of water extract 6.0-8.0 (preferably 6.8-7.6), ash content not higher than 1.0% (preferably 0.38-0.45%).

[0043] The application of the micro-gap low-mark release paper in the stacking, transportation and storage of glass plates.

[0044] Furthermore, the glass sheet is a high-cleanliness glass sheet, including display glass substrates (liquid crystal glass substrates, OLED glass substrates or automotive display glass), optoelectronic or photovoltaic glass, ultra-thin glass, optical glass and other glass sheets with high cleanliness requirements.

[0045] Furthermore, the display glass substrate includes large-size display glass substrates, such as large-size display glass substrates of 10.5 generations or above.

[0046] This invention disperses plant fiber pulp in water, and after descaling, screening, and sand removal, obtains clean fiber pulp, which is then formed into wet paper webs. While the wet paper webs have a moisture content of 18%–55% and still possess a certain degree of plasticity, they are passed through at least one localized micro-pressing shaping zone formed by a shaping roller with a discontinuous micro-protrusion structure on its surface and an elastic pressure roller. Through localized differential compression and springback in different areas of the paper web, spaced micro-protrusion contact areas and at least partially interconnected micro-groove channels are formed on the paper surface. Following springback shaping, drying, and cleaning post-treatment, a micro-gap, low-mark release paper is obtained. The micro-protrusion contact areas form limited contact support between the release paper and the glass substrate, reducing large-area adhesion between the paper and the glass surface; the micro-groove channels form pathways for the escape of interfacial gases and moisture. Together, these form a micro-gap interface with discontinuous micro-contact and interconnected escape channels, thereby reducing the risk of paper marks, white fog, adhesion, foreign matter transfer, and peeling instability during the stacking, storage, and transportation of large-size glass substrates. The release paper can be used for display glass substrates, optoelectronic glass, ultra-thin glass, and other high-cleanliness glass sheets.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] 1. This invention constructs a micro-gap structure on the paper surface by localized micro-pressing and spring-loaded shaping in the wet paper web state, combining micro-convex contact areas and micro-groove channels. This reduces the actual contact area between the glass and the paper while forming an interface moisture dissipation path, thereby synergistically reducing the risks of paper marks, white fog, and adhesion.

[0049] 2. This invention does not rely solely on improving the overall smoothness of the paper, enhancing calendering strength, or performing conventional embossing treatment. It can avoid the paper from becoming too dense, which would lead to decreased air permeability and moisture retention at the interface. It also enables the release paper to have appropriate surface smoothness, handling strength, cleanliness, and peel stability.

[0050] 3. This invention can reduce the use of migratory antistatic salts, sizing agents, mildew inhibitors and surface coatings, thereby reducing the risk of migratory components and foreign matter transferring to the glass surface; at the same time, it can control the micro-gap structure of the glass contact surface and the pick-up and drop surface through single-sided shaping, double-sided sequential shaping or front and back differential shaping, so as to take into account the requirements of glass protection, automatic paper picking, stacking stability and clean cutting.

[0051] 4. The preparation method of the present invention is highly compatible with existing paper forming, pressing, drying, calendering, rewinding and cutting equipment, which facilitates continuous production on existing specialty paper production lines, and is especially suitable for the stacking, storage and transportation of 10.5 generation and higher generation large-size display glass substrates. Attached Figure Description

[0052] Figure 1This is a schematic diagram of the preparation process of the micro-gap low-mark release paper of the present invention;

[0053] Figure 2 This is a schematic diagram of the structure of the localized micro-pressing and shaping pressing zone of the present invention;

[0054] Figure 3 This is a schematic diagram of the surface micro-convex contact area and micro-groove channel of the micro-gap low-mark release paper of the present invention; wherein, (a) is a top view; (b) is a schematic diagram of the interface;

[0055] Figure 4 This is a schematic diagram of water vapor escaping when the micro-gap low-trace release paper of the present invention is used for glass substrate stacking isolation (in the figure, the arrows indicate the direction of water vapor escaping).

[0056] Figure 5 These are actual images and detailed magnified images of the micro-gap low-mark release paper prepared in Embodiment 1 of the present invention; wherein, A is an actual image of the micro-gap low-mark release paper; and B is a detailed magnified image of the micro-gap low-mark release paper.

[0057] In the figure: 1 is the upper forming roller, 2 is the lower support roller, 3 is the wet paper web, 4 is the localized micro-press forming area, 5 is the upper glass substrate, 6 is the lower glass substrate; 31 is the micro-convex contact area, 32 is the micro-groove channel. Detailed Implementation

[0058] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited to the following embodiments. Equivalent substitutions, simple transformations, or conventional adjustments made by those skilled in the art based on the present invention without departing from the concept and technical essence of the present invention should all fall within the protection scope of the present invention.

[0059] Unless otherwise stated, the raw materials, reagents, equipment, and testing methods used in this invention are all conventionally used in this technical field. Experiments or tests in the following examples that do not specify specific conditions are generally performed according to conventional conditions in this technical field, relevant standard methods, or conditions recommended by equipment manufacturers. Unless otherwise stated, the raw materials and reagents used in this invention are commercially available.

[0060] The plant fiber pulp used in this invention is commercially available plant fiber pulp, or plant fiber pulp that has undergone screening, sand removal, washing, and other conventional purification treatments. The plant fiber pulp can be softwood pulp, hardwood pulp, bamboo pulp, cotton pulp, hemp pulp, grass fiber pulp, microfibrillated cellulose pulp, or a combination thereof. In the embodiments, the plant fiber pulp used is softwood pulp (Silver Star).

[0061] The localized micro-pressing shaping roller (upper shaping roller) used in this embodiment of the invention has a discontinuous micro-protrusion structure on its surface. The shaping roller can be a metal roller, ceramic roller, rubber roller, polyurethane roller, or a composite roller made of two or more materials; the discontinuous micro-protrusion structure can be formed by machining, laser processing, etching, spraying, engraving, molding, or other suitable methods. An elastic pressure roller used in conjunction with the shaping roller can serve as a lower support roller to jointly form the localized micro-pressing shaping pressure zone.

[0062] In this invention, the localized micro-pressing shaping is not ordinary calendering or decorative embossing. Ordinary calendering usually compresses the entire paper sheet continuously, which can improve the smoothness of the paper surface, but it easily increases the actual contact area between the glass and the paper sheet; conventional embossing or patterning usually focuses on appearance, friction, or macroscopic air permeability adjustment, and it is difficult to stably obtain discontinuous micro-contact and interconnected water vapor dissipation channels suitable for high-cleanliness glass substrate isolation.

[0063] The localized micro-press forming described in this invention involves creating compression differences in different areas of the paper web while the wet paper web still has a certain moisture content and plasticity. This is achieved through the synergistic effect between the discontinuous micro-protrusions on the surface of the forming roller and the elastic bearing roller. After the paper web leaves the localized micro-press forming pressure zone, different compression areas experience varying degrees of rebound, preserving the height differences. This results in spaced micro-protrusion contact areas and micro-groove channels between adjacent micro-protrusion contact areas on the paper web surface. The micro-protrusion contact areas provide limited contact support when glass substrates are stacked. The micro-groove channels are at least partially interconnected in the paper web plane direction, serving as pathways for moisture dissipation at the interface when the glass substrates are stacked, thereby reducing the risks of paper marks, white fog, adhesion, and peeling instability.

[0064] It should be noted that the micro-gap low-scratch release paper of this invention does not reduce adhesion by increasing the roughness of the paper surface. Instead, while maintaining appropriate smoothness and cleanliness of the paper, it controls the actual contact area with the glass substrate through micro-convex contact areas and provides space for moisture dissipation through micro-groove channels. The micro-convex contact areas and micro-groove channels together constitute a moisture-dissipating micro-gap interface, which enables the release paper to avoid the risks of scratches, dusting, or foreign matter transfer caused by excessive paper surface roughness, while also avoiding the risks of large-area adhesion and moisture retention caused by excessively dense and smooth paper surfaces.

[0065] Example 1

[0066] This embodiment provides a method for preparing micro-gap, low-mark release paper. The preparation process is as follows: Figure 1 As shown, the specific steps include the following:

[0067] (1) Preparation of fiber pulp

[0068] Plant fiber pulp was dispersed in deionized water to adjust the pulp concentration to 3.0%. The dispersed pulp was then thoroughly loosened (10,000 rpm) to dissociate and uniformly disperse the fiber bundles. The pulp was then beating to a beating degree of 32°SR. The beating pulp was then subjected to two stages of low-consistency sand removal and pressure screening (the inlet pressure of the low-consistency sand remover was 0.25 MPa, and the pressure screen was equipped with a slotted drum with a slit width of 0.15 mm) to remove sand particles, hard particles, incompletely dissociated fiber bundles, and other foreign matter that could damage or contaminate the glass substrate surface, resulting in clean fiber pulp.

[0069] (2) Constructing a wet paper web

[0070] The clean fiber pulp obtained in step (1) is conveyed to the wire forming device, and paper is formed using the wire forming method. Through flow feeding, wire forming, dewatering, and preliminary forming, a wet paper web with uniform structure is obtained. The basis weight of the wet paper web is controlled at 50 g / m² to ensure that the wet paper web has the basic strength and structural uniformity required for subsequent localized micro-pressing and shaping.

[0071] (3) Perform localized micro-pressing shaping

[0072] The wet paper web obtained in step (2) is subjected to preliminary pressing and dewatering (press line pressure is 80-100 kN / m), and the moisture content of the wet paper web after preliminary pressing is controlled to be 38%.

[0073] Subsequently, the wet paper web with a moisture content of 38% is passed through the localized micro-press shaping zone. For example... Figure 2 As shown, the localized micro-pressing and shaping zone (4) includes a shaping roller (upper shaping roller (1)) with a random dotted discontinuous micro-convex structure on its surface, and an elastic bearing roller (lower support roller (2)) that cooperates with the shaping roller. The height of the random dotted micro-convex structure on the surface of the shaping roller is 12 μm, the nearest neighbor center distance of a single dotted micro-convex structure is 150-210 μm, and the average nearest neighbor center distance is about 180 μm; the equivalent diameter of the top surface of each micro-convex structure unit is 60-100 μm (set to 80 μm in this embodiment), and the actual microstructure of the release paper surface is as follows. Figure 3 As shown, the micro-convex contact area accounts for approximately 16% of the surface area, and the micro-groove channel area accounts for approximately 84%. The linear pressure of the localized micro-pressing and shaping zone is 25 kN / m, and the surface temperature of the shaping roller is 45℃. The nearest neighbor center distance refers to the distance between the geometric center of a point-like micro-convex structure and the geometric center of the nearest other point-like micro-convex structure. The point-like micro-convex structures are randomly and non-periodically misaligned on the surface of the shaping roller, not forming equidistant linear arrangements, regular matrix arrangements, or horizontally and vertically symmetrical arrangements.

[0074] Under the aforementioned linear pressure, temperature, and paper web moisture content conditions, the random, discontinuous micro-protrusions on the surface of the forming roll, together with the elastic bearing roll, act on the wet paper web (3), causing localized differential compression in different areas of the wet paper web. After the wet paper web leaves the localized micro-pressing forming zone, different compression areas experience varying degrees of depressurization rebound, thereby forming spaced micro-protrusion contact areas (31) on the paper web surface, and forming at least partially interconnected micro-groove channels (32) between adjacent micro-protrusion contact areas (31). The resulting micro-protrusion contact areas are used to provide dispersed support during glass substrate stacking, and the resulting micro-groove channels are used to provide a moisture dissipation path between the glass substrate and the release paper.

[0075] (4) Perform springback shaping treatment

[0076] The paper web after localized micro-pressing in step (3) was placed in an environment with a temperature of 45°C and a relative humidity of 75% for 30 minutes. This allowed the microstructure on the surface of the paper web formed during the pressing process to undergo moderate wet-heat rebound, and stabilized the internal pore structure, micro-convex contact areas, and micro-groove channels, thereby improving the micro-gap retention ability during subsequent rewinding, cutting, and glass stacking processes. After completing the above rebound and shaping treatment, the paper web was dried (95°C) to control the final moisture content of the paper web to 6.5%.

[0077] (5) Perform post-cleaning treatment

[0078] The paper web obtained in step (4) is rewound under low tension (tension 30-60 N / m) to reduce secondary compaction or structural damage to the micro-convex contact areas and micro-groove channels on the paper web surface caused by the rewinding tension. During the rewinding process, an air knife and a vacuum dust collection device are used to perform non-contact dust removal on both sides of the paper web to remove free fibers, paper dust and other loose particles from the paper web surface. After cleaning treatment, the paper web is cleanly slit and wound to obtain micro-gap low-scratch release paper ( Figure 5 ).

[0079] Example 2

[0080] This embodiment provides a method for preparing micro-gap low-mark release paper, including the following steps:

[0081] (1) Preparation of fiber pulp

[0082] The method is the same as in Example 1. The plant fiber pulp is dispersed in deionized water, and the pulp concentration is adjusted to 3.0%. After thorough dissolution, it is beaten to control the pulp degree to 32°SR. Then, the beaten pulp is subjected to two stages of low-consistency sand removal and pressure screening to remove sand particles, hard particles, fiber bundles and other foreign matter, to obtain clean fiber pulp.

[0083] (2) Constructing a wet paper web

[0084] The clean fiber pulp obtained in step (1) is formed by long-wire forming. After wire forming, dewatering and preliminary forming, a wet paper web with a basis weight of 50 g / m² is obtained.

[0085] (3) Perform double-sided sequential localized micro-pressing shaping

[0086] The wet paper web obtained in step (2) is subjected to preliminary pressing (press line pressure is 80-100 kN / m), and the moisture content of the wet paper web after preliminary pressing is controlled to be 38%.

[0087] Subsequently, the wet paper web is sequentially shaped on both the front and back sides by passing it through localized micro-pressing shaping zones. In this embodiment, the localized micro-pressing shaping zones include a first localized micro-pressing shaping zone and a second localized micro-pressing shaping zone. Both the first and second localized micro-pressing shaping zones include shaping rollers with randomly dotted discontinuous micro-convex structures on their surfaces, and elastic pressure rollers (same as in Embodiment 1) that cooperate with the shaping rollers. The basic structure of the two localized micro-pressing shaping zones is similar to... Figure 2 The localized micro-pressing forming zones shown are the same; the equivalent diameter of the top surface of each micro-convex structural unit is 80 μm. For double-sided forming, the front and back of the paper are counted separately, and the area ratio of the two sides is approximately 16% and 84% respectively.

[0088] The first localized micro-press forming zone is used for front-side forming of the wet paper web. The forming roll surface of the first localized micro-press forming zone has a random dotted discontinuous micro-protrusion structure, the height of which is 10 μm and the average nearest neighbor center distance between adjacent micro-protrusion structures is 180 μm; the linear pressure of the first localized micro-press forming zone is 20 kN / m, and the surface temperature of the forming roll is 40℃.

[0089] The second localized micro-press forming zone is used for reverse forming of the wet paper web. The surface of the forming roll in the second localized micro-press forming zone also has a random dotted discontinuous micro-protrusion structure. The height of the micro-protrusion structure is 8 μm, and the average nearest neighbor center distance between adjacent micro-protrusion structures is 180 μm. The linear pressure of the second localized micro-press forming zone is 15 kN / m, and the surface temperature of the forming roll is 35℃.

[0090] Through the aforementioned double-sided sequential localized micro-pressing shaping, local differential compression and springback are generated on both sides of the paper web, thereby forming micro-convex contact areas and at least partially interconnected micro-groove channels on both sides of the paper web, and giving the microstructures on the two sides different structural heights and degrees of compaction. As a result, both sides of the paper web can form limited contact support and moisture dissipation paths when in contact with the glass substrate.

[0091] (4) Perform springback shaping treatment

[0092] The paper web after double-sided sequential localized micro-pressing shaping in step (3) was placed in an environment with a temperature of 45°C and a relative humidity of 75% for 30 minutes to allow the micro-convex contact areas and micro-groove channels on both sides of the paper web to rebound moderately and tend to stabilize. After completing the rebound shaping treatment, the paper web was dried (95°C) to control the final moisture content of the paper web to 6.5%.

[0093] (5) Perform post-cleaning treatment

[0094] The paper web obtained in step (4) is rewound under low tension (tension 30-60 N / m), and air knives and vacuum dust collection devices are used to remove dust from both sides of the paper web in a non-contact manner during the rewinding process. After clean slitting and rewinding, double-sided micro-gap low-scratch release paper is obtained.

[0095] Example 3

[0096] This embodiment provides a method for preparing micro-gap low-mark release paper, including the following steps:

[0097] (1) Preparation of fiber pulp

[0098] The method is the same as in Example 1. The plant fiber pulp is dispersed in deionized water, and the pulp concentration is adjusted to 3.0%. After thorough dissolution, it is beaten to control the pulp degree to 32°SR. Then, the beaten pulp is subjected to two stages of low-consistency sand removal and pressure screening to remove sand particles, hard particles, fiber bundles and other foreign matter, to obtain clean fiber pulp.

[0099] (2) Constructing a wet paper web

[0100] The clean fiber pulp obtained in step (1) is formed by long-wire forming. After wire forming, dewatering and preliminary forming, a wet paper web with a basis weight of 50 g / m² is obtained.

[0101] (3) Perform double-sided sequential localized micro-pressing shaping

[0102] The wet paper web obtained in step (2) is subjected to preliminary pressing (press line pressure is 80-100 kN / m), and the moisture content of the wet paper web after preliminary pressing is controlled to be 38%.

[0103] The wet paper web is sequentially passed through the first localized micro-pressing and shaping zone and the second localized micro-pressing and shaping zone to sequentially shape the front and back sides of the paper web, respectively. The first localized micro-pressing and shaping zone and the second localized micro-pressing and shaping zone both include shaping rollers with random dot-like discontinuous micro-protrusion structures on their surfaces, and elastic pressure rollers that cooperate with the shaping rollers, as in Embodiment 2.

[0104] The first localized micro-press forming zone is used for front-side forming of the paper web. The height of the random dotted discontinuous micro-convex structures on the surface of the first forming roll is 10 μm, the average nearest neighbor center distance between adjacent micro-convex structures is 180 μm, the linear pressure of the first localized micro-press forming zone is 20 kN / m, and the surface temperature of the forming roll is 40℃.

[0105] The second localized micro-press forming zone is used for reverse forming of the paper web. The random dotted discontinuous micro-convex structures on the surface of the second forming roll have a height of 8 μm, the average nearest neighbor center distance between adjacent micro-convex structures is 180 μm, the linear pressure of the second localized micro-press forming zone is 15 kN / m, and the surface temperature of the forming roll is 35℃.

[0106] By using double-sided sequential localized micro-pressing and shaping, local differential compression is generated on both sides of the paper web. After the paper web leaves each localized micro-pressing and shaping zone, it undergoes a rebound effect after depressurization, forming discontinuously distributed micro-convex contact areas and at least partially interconnected micro-groove channels on both sides of the paper web.

[0107] (4) Perform two spring-setting treatments.

[0108] The paper web obtained in step (3) is subjected to two spring-load shaping processes:

[0109] The first rebound setting treatment was carried out at a temperature of 50℃ and a relative humidity of 80% for 20 minutes. This allowed the paper web to undergo wet-heat rebound under high temperature and humidity conditions, releasing some of the internal stress generated during the localized micro-pressing process, thereby improving the structural stability of the micro-convex contact area and the micro-groove channel.

[0110] After the first spring-setting treatment is completed, a second spring-setting treatment is performed. The temperature of the second spring-setting treatment is 35℃, the relative humidity is 60%, and the treatment time is 40 minutes. This process further balances and stabilizes the micro-convex contact area, micro-groove channels, and internal pore structure on the paper web surface, thereby improving the ability of the micro-groove channels to retain their shape under subsequent stacking and humid heat contact conditions.

[0111] After two springback and setting processes, the paper web is dried (95°C) to control the final moisture content of the paper web to 7.0%.

[0112] (5) Perform post-cleaning treatment

[0113] The paper web obtained in step (4) is rewound under low tension (tension 30-60 N / m), and air knives and vacuum dust collection devices are used to remove dust from both sides of the paper web in a non-contact manner during the rewinding process. After clean slitting and rewinding, micro-gap low-scratch release paper is obtained.

[0114] Example 4

[0115] This embodiment provides a method for preparing micro-gap low-mark release paper, including the following steps:

[0116] (1) Preparation of fiber pulp

[0117] The method is the same as in Example 1. The plant fiber pulp is dispersed in deionized water, and the pulp concentration is adjusted to 3.0%. After thorough dissolution, it is pulped and the pulp degree is controlled to 28°SR. Then, the pulped pulp is subjected to two stages of low-consistency sand removal and pressure screening to remove sand particles, hard particles, fiber bundles and other foreign matter, to obtain clean fiber pulp.

[0118] (2) Constructing a wet paper web

[0119] The clean fiber pulp obtained in step (1) is used for papermaking by long wire forming. After wire forming, dewatering and preliminary forming, a wet paper web with a basis weight of 45 g / m² is obtained.

[0120] (3) Perform double-sided sequential localized micro-pressing shaping

[0121] The wet paper web obtained in step (2) is subjected to preliminary pressing (press line pressure is 80-100 kN / m), and the moisture content of the wet paper web after preliminary pressing is controlled to be 38%.

[0122] The wet paper web is sequentially passed through a first localized micro-press shaping zone and a second localized micro-press shaping zone to sequentially shape the front and back sides of the paper web, respectively. Both the first and second localized micro-press shaping zones include shaping rollers with randomly dotted, discontinuous micro-protrusions on their surfaces, and elastic pressure rollers that cooperate with the shaping rollers. The specific details are the same as in Embodiment 2.

[0123] The first localized micro-press forming zone is used for front-side forming of the wet paper web. The height of the random dotted discontinuous micro-convex structures on the surface of the first forming roll is 10 μm, and the average nearest neighbor center distance between adjacent micro-convex structures is 180 μm; the linear pressure of the first localized micro-press forming zone is 18 kN / m, and the surface temperature of the forming roll is 40℃.

[0124] The second localized micro-press forming zone is used for reverse forming of the wet paper web. The height of the random dotted discontinuous micro-convex structures on the surface of the second forming roll is 8 μm, and the average nearest neighbor center distance between adjacent micro-convex structures is 180 μm; the linear pressure of the second localized micro-press forming zone is 12 kN / m, and the surface temperature of the forming roll is 35℃.

[0125] Through the above-mentioned double-sided sequential localized micro-pressing shaping, local differential compression and pressure rebound are generated on both sides of the lower basis paper web, thereby forming a micro-convex contact area and at least partially interconnected micro-groove channels, so that the lower basis paper web can still take into account limited contact support and interface moisture dissipation.

[0126] (4) Perform two spring-setting treatments.

[0127] The paper web obtained in step (3) was subjected to two spring-setting treatments: the first spring-setting treatment was carried out at a temperature of 50°C and a relative humidity of 80% for 20 minutes; the second spring-setting treatment was carried out at a temperature of 35°C and a relative humidity of 60% for 40 minutes. After the two spring-setting treatments were completed, the paper web was dried (at 95°C) to control the final moisture content of the paper web to 7.0%.

[0128] (5) Perform post-cleaning treatment

[0129] The paper web obtained in step (4) is rewound under low tension (tension 30-60 N / m), and non-contact dust removal is performed on both sides of the paper web using an air knife and a vacuum dust collection device during the rewinding process. After clean slitting and rewinding, a low basis weight micro-gap low-scratch release paper is obtained.

[0130] Example 5

[0131] This embodiment provides a method for preparing micro-gap low-mark release paper, including the following steps:

[0132] (1) Preparation of fiber pulp

[0133] The method is the same as in Example 1. The plant fiber pulp is dispersed in deionized water, and the pulp concentration is adjusted to 3.0%. After thorough dissolution, it is beaten to control the pulp degree to 36°SR. Then, the beaten pulp is subjected to two stages of low-consistency sand removal and pressure screening to remove sand particles, hard particles, fiber bundles and other foreign matter, to obtain clean fiber pulp.

[0134] (2) Constructing a wet paper web

[0135] The clean fiber pulp obtained in step (1) is used for papermaking by long-wire forming. After wire forming, dewatering and preliminary forming, a wet paper web with a basis weight of 60 g / m² is obtained.

[0136] (3) Perform double-sided sequential localized micro-pressing shaping

[0137] The wet paper web obtained in step (2) is subjected to preliminary pressing (press line pressure is 80-100 kN / m), and the moisture content of the wet paper web after preliminary pressing is controlled to be 38%.

[0138] The wet paper web is sequentially passed through a first localized micro-press shaping zone and a second localized micro-press shaping zone to sequentially shape the front and back sides of the paper web, respectively. Both the first and second localized micro-press shaping zones include shaping rollers with randomly dotted, discontinuous micro-protrusions on their surfaces, and elastic pressure rollers that cooperate with the shaping rollers. The specific details are the same as in Embodiment 2.

[0139] The first localized micro-press forming zone is used for front-side forming of the wet paper web. The height of the random dotted discontinuous micro-convex structures on the surface of the first forming roll is 10 μm, and the average nearest neighbor center distance between adjacent micro-convex structures is 180 μm; the linear pressure of the first localized micro-press forming zone is 30 kN / m, and the surface temperature of the forming roll is 40℃.

[0140] The second localized micro-press forming zone is used for reverse forming of the wet paper web. The height of the random dotted discontinuous micro-convex structures on the surface of the second forming roll is 8 μm, and the average nearest neighbor center distance between adjacent micro-convex structures is 180 μm; the linear pressure of the second localized micro-press forming zone is 22 kN / m, and the surface temperature of the forming roll is 35℃.

[0141] Through the above-mentioned double-sided sequential localized micro-pressing and shaping, local differential compression and pressure rebound are generated on both sides of the higher basis paper web, thereby forming micro-convex contact areas and at least partially interconnected micro-groove channels, so that the higher basis paper web can obtain better thickness and strength while still retaining the interface moisture dissipation path.

[0142] (4) Perform two spring-setting treatments.

[0143] The paper web obtained in step (3) was subjected to two spring-setting treatments: the first spring-setting treatment was carried out at a temperature of 50°C and a relative humidity of 80% for 20 minutes; the second spring-setting treatment was carried out at a temperature of 35°C and a relative humidity of 60% for 40 minutes. After the two spring-setting treatments were completed, the paper web was dried (at 95°C) to control the final moisture content of the paper web to 7.0%.

[0144] (5) Perform post-cleaning treatment

[0145] The paper web obtained in step (4) is rewound under low tension (tension 30-60 N / m), and non-contact dust removal is performed on both sides of the paper web using an air knife and a vacuum dust collection device during the rewinding process. After clean slitting and rewinding, a micro-gap low-scratch release paper with high thickness and good strength is obtained.

[0146] Comparative Example 1

[0147] This comparative example provides a method for preparing glass spacer paper using a conventional hard calendering process. The difference from Example 1 lies in the use of conventional pressing and conventional hard calendering. Specifically, it includes the following steps:

[0148] (1) Preparation of fiber pulp

[0149] The method is the same as in Example 1. The plant fiber pulp is dispersed in deionized water, and the pulp concentration is adjusted to 3.0%. After thorough dissolution, it is beaten to a beating degree of 32°SR. The beaten pulp is then subjected to two stages of low-consistency sand removal and pressure screening to obtain clean fiber pulp.

[0150] (2) Constructing a wet paper web

[0151] The clean fiber slurry obtained in step (1) is formed using a long-wire forming method. After wire forming, dewatering, and preliminary forming, a slurry with a basis weight of 50 g / m³ is obtained. 2 The wet paper.

[0152] (3) Perform conventional pressing and ordinary hard calendering.

[0153] The wet paper web obtained in step (2) was initially pressed and dehydrated (press line pressure was 80-100 kN / m), and the moisture content of the wet paper web after the initial pressing was controlled to be 38%. The paper web was then dried and subjected to overall calendering using ordinary hard calendering rollers: the hard calendering roller pressure was 60 kN / m, the calendering roller surface temperature was 80℃, the paper web running speed was 15 m / min, and the number of calendering cycles was 2.

[0154] (4) Perform humidity conditioning and drying treatment.

[0155] The calendered paper web was placed in an environment with a temperature of 45℃ and a relative humidity of 75% for 30 minutes, and then dried (95℃) to control the final moisture content of the paper web to 6.5%.

[0156] (5) Perform post-cleaning treatment

[0157] The method is the same as in Example 1. The paper web is rewound under low tension, and non-contact dust removal is performed using an air knife and a vacuum dust collection device. After cleaning, slitting and rewinding, the glass spacer paper of Comparative Example 1 is obtained.

[0158] This comparative example does not employ shaping rollers with discontinuous micro-convex structures on their surfaces, nor does it perform localized micro-pressing shaping. Instead, it uses conventional pressing and ordinary hard calendering to improve paper surface smoothness, resulting in continuous overall compaction of the paper sheet surface. While this method can improve paper surface smoothness, it does not create localized differential compression and springback structures in the wet paper web state. It is difficult to form spaced micro-convex contact areas and interconnected micro-groove channels on the paper sheet surface. Therefore, it tends to form a large actual contact area when stacking with glass substrates, which is not conducive to the dissipation of moisture from the interface.

[0159] Comparative Example 2

[0160] This comparative example provides a method for preparing glass spacer paper without springback shaping, which differs from Example 1 in that it does not involve springback shaping. Specifically, it includes the following steps:

[0161] (1) Preparation of fiber pulp

[0162] The method is the same as in Example 1. Plant fiber pulp is dispersed in deionized water, the pulp mass concentration is adjusted to 3.0%, and after sufficient dissolution, it is pulped to 32°SR. Then, it is subjected to two-stage low-concentration sand removal and pressure screening to obtain clean fiber pulp.

[0163] (2) Constructing a wet paper web

[0164] The clean fiber pulp obtained in step (1) is formed by long-wire forming. After wire forming, dewatering and preliminary forming, a wet paper web with a basis weight of 50 g / m² is obtained.

[0165] (3) Perform localized micro-pressing shaping

[0166] The wet paper web obtained in step (2) is subjected to preliminary pressing and dewatering (press line pressure is 80-100 kN / m), and the moisture content of the wet paper web after preliminary pressing is controlled to be 38%.

[0167] The wet paper web is passed through the localized micro-press shaping zone, in the same manner as in Example 1. The surface of the shaping roll has a random dotted discontinuous micro-convex structure with a height of 12 μm and an average nearest neighbor center distance of 180 μm between adjacent micro-convex structures; the linear pressure of the localized micro-press shaping zone is 25 kN / m, and the surface temperature of the shaping roll is 45°C.

[0168] (4) Direct drying

[0169] After the localized micro-pressing shaping in step (3) is completed, the paper web is directly dried (95°C) into paper, and the final moisture content of the paper web is controlled to 6.5%.

[0170] (5) Perform post-cleaning treatment

[0171] The method is the same as in Example 1. The paper web is rewound under low tension, and non-contact dust removal is performed using an air knife and a vacuum dust collection device. After cleaning, slitting and rewinding, the glass spacer paper of Comparative Example 2 is obtained.

[0172] In this comparative example, after localized micropress forming, the paper web was directly dried without undergoing a springback setting process at 45°C, 75% relative humidity, and 30 min. Due to the lack of a springback setting process, the micro-convex contact areas and micro-groove channels formed after localized micropress forming are difficult to stabilize sufficiently, making them more prone to microstructure collapse or insufficient retention of micro-groove channels during subsequent drying, rewinding, and stacking processes.

[0173] Comparative Example 3

[0174] This comparative example provides a method for preparing glass spacer paper using a flat-surface elastic roller for pressing. The difference from Example 1 is that a flat roller is used for pressing, and the method specifically includes the following steps:

[0175] (1) Preparation of fiber pulp

[0176] The method is the same as in Example 1. Plant fiber pulp is dispersed in deionized water, the pulp mass concentration is adjusted to 3.0%, and after sufficient dissolution, it is pulped to 32°SR. Then, it is subjected to two-stage low-concentration sand removal and pressure screening to obtain clean fiber pulp.

[0177] (2) Constructing a wet paper web

[0178] The clean fiber pulp obtained in step (1) is formed by long-wire forming. After wire forming, dewatering and preliminary forming, a wet paper web with a basis weight of 50 g / m² is obtained.

[0179] (3) Perform leveling roller pressing.

[0180] The wet paper web obtained in step (2) is subjected to preliminary pressing (press line pressure is 80-100 kN / m), and the moisture content of the wet paper web after preliminary pressing is controlled to be 38%.

[0181] This comparative example does not use a shaping roll with a discontinuous micro-convex structure on its surface, but instead uses a flat-surfaced elastic roll to press the paper web. The press line pressure is 25 kN / m, and the roll surface temperature is 45℃.

[0182] (4) Perform humidity conditioning and drying treatment.

[0183] The paper web obtained in step (3) was placed in an environment with a temperature of 45°C and a relative humidity of 75% for 30 min, and then dried (95°C) to control the final moisture content of the paper web to 6.5%.

[0184] (5) Perform post-cleaning treatment

[0185] The method is the same as in Example 1. The paper web is rewound under low tension, and non-contact dust removal is performed using an air knife and a vacuum dust collection device. After cleaning, slitting and rewinding, the glass spacer paper of Comparative Example 3 is obtained.

[0186] In this comparative example, because the surface of the press roll does not have a discontinuous micro-protrusion structure, it cannot form a localized differential compression of the wet paper web. Furthermore, it is difficult to form a rebound height difference after the paper web leaves the press zone corresponding to the discontinuous micro-protrusion structure. Therefore, the paper web surface cannot form discontinuously distributed micro-protrusion contact areas and interconnected micro-groove channels as in Example 1.

[0187] Comparative Example 4

[0188] This comparative example provides a method for preparing glass spacer paper using high linear pressure integral calendering. The difference from Example 1 is that high linear pressure integral calendering is used, and the method specifically includes the following steps:

[0189] (1) Preparation of fiber pulp

[0190] The method is the same as in Example 1. Plant fiber pulp is dispersed in deionized water, the pulp mass concentration is adjusted to 3.0%, and after sufficient dissolution, it is pulped to 32°SR. Then, it is subjected to two-stage low-concentration sand removal and pressure screening to obtain clean fiber pulp.

[0191] (2) Constructing a wet paper web

[0192] The clean fiber pulp obtained in step (1) is formed by long-wire forming. After wire forming, dewatering and preliminary forming, a wet paper web with a basis weight of 50 g / m² is obtained.

[0193] (3) Perform high-pressure overall calendering.

[0194] The wet paper web obtained in step (2) is subjected to preliminary pressing (press line pressure of 80-100 kN / m) and drying (95℃) to control the final moisture content of the paper web to 6.5%. The dried paper web is then calendered as a whole using a calendering roller with a flat surface. The calendering roller pressure is 120 kN / m, the surface temperature of the calendering roller is 80℃, the paper web running speed is 15 m / min, and the calendering is performed twice.

[0195] (4) Perform moisture balance treatment

[0196] The paper sheets that have undergone high linear pressure calendering are subjected to moisture balancing treatment to maintain a moisture state suitable for rewinding and subsequent testing.

[0197] (5) Perform post-cleaning treatment

[0198] The method is the same as in Example 1. The paper is rewound under low tension and non-contact dust removal is performed using an air knife and a vacuum dust collection device. After cleaning, slitting and rewinding, the glass spacer paper of Comparative Example 4 is obtained.

[0199] This comparative example does not employ localized micro-pressing shaping. Instead, it uses a smooth-surfaced calendering roller to calender the entire paper sheet, increasing the calendering pressure to 120 kN / m. This subjects the paper sheet to continuous high pressure, resulting in significant densification. Due to the continuous compaction of the entire paper sheet, the actual contact area on the surface increases, making it difficult to retain the interconnecting microchannels for moisture dissipation at the interface. This demonstrates that simply further increasing the calendering intensity and paper surface smoothness cannot effectively solve the problems of paper marks, white haze, and adhesion during the stacking of high-generation glass substrates.

[0200] Comparative Example 5

[0201] This comparative example provides a method for preparing glass spacer paper with a continuous distribution of micro-convex structures on the surface of a shaping roller. The difference from Example 3 is that the shaping roller in this comparative example has a regular grid-like continuous micro-convex structure on its surface, specifically including the following steps:

[0202] (1) Preparation of fiber pulp

[0203] The method is the same as in Example 3. The plant fiber pulp is dispersed in deionized water, and the pulp concentration is adjusted to 3.0%. After thorough dissolution, it is pulped to a beating degree of 32°SR. The pulped pulp is then subjected to two stages of low-concentration sand removal and pressure screening to obtain clean fiber pulp.

[0204] (2) Constructing a wet paper web

[0205] The clean fiber pulp obtained in step (1) is formed by long-wire forming. After wire forming, dewatering and preliminary forming, a wet paper web with a basis weight of 50 g / m² is obtained.

[0206] (3) Perform double-sided sequential pressing and shaping.

[0207] The wet paper web obtained in step (2) is subjected to preliminary pressing (press line pressure is 80-100 kN / m), and the moisture content of the wet paper web after preliminary pressing is controlled to be 38%.

[0208] The wet paper web is sequentially passed through the first and second press shaping zones, where the front and back sides of the paper web are shaped in sequence; the basic structure of the two pressing zones is similar to... Figure 2The pressure zones shown are the same, the difference being that the surface of the shaping roller adopts a regular grid-like continuous micro-convex structure; the continuous micro-convex structure is formed by the intersecting connection of longitudinal ridges extending circumferentially along the shaping roller and transverse ridges extending axially along the shaping roller, with each ridge forming a continuous grid on the surface of the shaping roller. The width of the ridge is 50 μm, and the center distance between adjacent parallel ridges is 180 μm. The ridge height of the first shaping roller is 10 μm, and the ridge height of the second shaping roller is 8 μm.

[0209] The first pressure zone is used for front-side shaping of the paper web, with a linear pressure of 20 kN / m, a surface temperature of 40℃ for the shaping roller, and a micro-convex structure height of 10 μm on the surface of the shaping roller.

[0210] The second pressure zone is used for reverse side shaping of the paper web, with a linear pressure of 15 kN / m, a surface temperature of 35℃ for the shaping roll, and a micro-convex structure height of 8 μm on the surface of the shaping roll.

[0211] (4) Perform two spring-setting treatments.

[0212] The paper web obtained in step (3) was subjected to two spring-setting treatments: the first spring-setting treatment was carried out at a temperature of 50°C and a relative humidity of 80% for 20 minutes; the second spring-setting treatment was carried out at a temperature of 35°C and a relative humidity of 60% for 40 minutes. After the two spring-setting treatments were completed, the paper web was dried to control the final moisture content of the paper web to 7.0%.

[0213] (5) Perform post-cleaning treatment

[0214] The method is the same as in Example 3. The paper web obtained in step (4) is rewound with low tension, and non-contact dust removal is performed using an air knife and a vacuum dust collection device. After cleaning, slitting and rewinding, the glass spacer paper of Comparative Example 5 is obtained.

[0215] Unlike Example 3, which uses a random, discontinuous micro-protrusion structure that is separated from each other, the forming roller used in this comparative example has a continuous, interconnected, regular grid-like micro-protrusion structure on its surface. Because the longitudinal and transverse ridges intersect and connect to form a continuous grid-like working area, after pressing and shaping, the microgroove area on the paper web surface is divided into multiple relatively closed or only partially connected areas. The overall connectivity of the microgroove channels in the longitudinal, transverse, and diagonal directions of the paper web is significantly reduced, making it difficult to form a continuous interface moisture dissipation path extending to the edge of the paper web. This comparative example shows that a surface with only unevenness is insufficient to achieve good interface moisture dissipation and low paper marks; the discontinuous dispersion of the micro-protrusion contact area and the interconnection of the microgroove channels play an important role in constructing a moisture-dissipating micro-gap interface between the glass substrate and the release paper.

[0216] Effect Example

[0217] 1. Performance Testing

[0218] The release papers prepared in Examples 1-5 and Comparative Examples 1-5 were subjected to tests on basis weight, thickness, Gurley air permeability resistance, Bekk smoothness, pH of the water extract, ash content, surface micro-gap retention rate, paper mark grade after wet heat glass contact, and peel stability. Details are as follows:

[0219] Unless otherwise specified, before testing, the samples should be subjected to temperature and humidity equilibration in an environment with a temperature of 23±1℃ and a relative humidity of 50%±2%, in accordance with the provisions of GB / T 10739—2023 "Standard Atmospheric Conditions for the Treatment and Testing of Paper, Paperboard and Pulp Samples", and the relevant performance tests should be completed under the same conditions. At least 3 parallel samples should be set for each test, and the arithmetic mean should be taken.

[0220] (1) Basis weight: The test shall be conducted in accordance with GB / T 451.2—2023 Paper and paperboard Part 2: Determination of basis weight. A sample of a specified area shall be cut, the mass of the sample shall be determined, and the basis weight shall be calculated according to the ratio of the mass of the sample to the area. The test result shall be expressed in g / m².

[0221] (2) Thickness: The test shall be conducted in accordance with GB / T 451.3—2002 "Determination of thickness of paper and paperboard". A paper thickness measuring instrument shall be used to measure no less than 10 points at different positions on the sample. The measurement positions shall avoid the edges of the paper, creases and obvious defects. The arithmetic mean of the measurement results shall be taken and the test results shall be expressed in μm.

[0222] (3) Gurley air permeability resistance: The test was conducted according to the Gurley method in GB / T 458—2008 "Determination of air permeability of paper and paperboard". A Gurley air permeability meter was used, with an effective test area of ​​6.42 cm². 2 Under specified conditions, record the time required for 100 mL of air to pass through the paper under a specified pressure difference. Test at least five locations for each sample, and express the results in seconds per 100 mL. A higher Gurley air resistance value indicates a longer time for air to pass through the paper, and lower paper permeability; a lower value indicates higher paper permeability.

[0223] (4) Bekk smoothness: The test was conducted according to GB / T 456—2002 "Determination of smoothness of paper and paperboard (Bekk method)". The test was performed on both the front and back sides of the paper, with no less than 5 positions on each side. The time required for a specified volume of air to pass through the gap between the paper surface and the standard glass plate was recorded, and the result was expressed in seconds. The higher the Bekk smoothness value, the smoother the paper surface. The test results were recorded as the Bekk smoothness of the front side and the Bekk smoothness of the back side.

[0224] (5) pH of the aqueous extract: The pH of the aqueous extract was determined according to Method B—pH meter method in GB / T 1545—2008 "Determination of Acidity or Alkalinity of Aqueous Extracts from Paper, Paperboard and Pulp", and the aqueous extract was prepared by cold extraction. Specifically:

[0225] ① Cut the sample into pieces with an area of ​​approximately 5–10 mm. 2 Mix the small pieces thoroughly, weigh out a sample equivalent to 2.0 ± 0.1 g of oven-dry mass, place it in a clean, stoppered conical flask, and add 100 mL of distilled or deionized water. The water used should be boiled and cooled in an environment free from acidic gas pollution, and its conductivity should not exceed 0.1 mS / m.

[0226] ② Seal the conical flask and allow it to stand for 1 hour at 20–25°C. Shake the flask at least once during extraction to ensure the sample is fully wetted. After extraction, wait for the fibers to settle and then take the upper aqueous extract for analysis.

[0227] ③ The pH of the aqueous extract was measured using a pH meter calibrated with a pH standard buffer solution at 20–25°C. Each sample was measured twice in parallel, and the arithmetic mean of the two measurements was taken as the pH of the aqueous extract. The pH of the aqueous extract from the glass spacer paper was 5.5–8.5.

[0228] (6) Ash content: Ash content was determined according to GB / T 22877—2023 "Determination of Ash Content (525℃) of Residues from Ignition of Paper, Paperboard, Pulp and Cellulose Nanomaterials". Specifically:

[0229] ① Place the clean crucible in a muffle furnace at 525±25℃ and heat until constant weight. Remove it, cool it to room temperature in a desiccator, and weigh it, recording the weight as m0. Weigh 2–5 g of the sample and simultaneously determine the oven-dry mass of the sample, recording it as m.

[0230] ② Place the sample in a pre-weighed crucible and heat it slowly to ensure complete carbonization, avoiding excessive ash loss due to rapid combustion. Then, place the crucible in a muffle furnace at 525±25℃ and ignite until the carbonaceous material is completely removed. Remove the crucible, cool it to room temperature in a desiccator, and weigh it. Repeat the ignition, cooling, and weighing process until constant weight is achieved. The total mass of the crucible and the ignition residue is recorded as m1.

[0231] ③ The ash content is calculated according to the following formula: X = (m1 - m0) / m × 100%; where, X: ash content of the sample, in percentage (%); m0: mass of the empty crucible, in grams (g); m1: total mass of the crucible and the ignition residue, in grams (g); m: oven-dry mass of the sample, in grams (g).

[0232] Each sample was measured twice in parallel, and the arithmetic mean of the two measurements was taken as the ash content determination result. The ash content of the glass spacer paper was not higher than 1.0%.

[0233] (7) Surface micro-gap retention rate

[0234] Since existing general testing standards for paper and paperboard do not specify a method for determining the surface micro-gap retention rate, this test uses a non-contact three-dimensional surface morphology measurement method for evaluation:

[0235] ① Five representative test areas were selected from each sample, each with an area of ​​5 mm × 5 mm. Three-dimensional height data of the sample surface were obtained using a white-light interferometric 3D profilometer, a laser confocal microscope, or a non-contact 3D topography measurement device with equivalent measurement accuracy. Using the reference plane formed by fitting the top of the micro-convex contact area as a reference, the effective micro-gap volume of the interconnected micro-groove regions located below this reference plane was calculated and denoted as V0.

[0236] ② Subsequently, a 100 mm × 100 mm sample was placed between two clean, flat display glass surfaces, and a uniform normal pressure of 5.0 kPa was applied. The sample was then placed in an environment with a temperature of 50℃ and a relative humidity of 90% for 96 h. After releasing the pressure, the sample was allowed to recover for 2 h in an environment with a temperature of 23±1℃ and a relative humidity of 50%±2%. The effective micro-gap volume at the same location was measured and recorded as V1.

[0237] ③ The surface microgap retention rate is calculated according to the following formula: R=V1 / V0×100%; where, R: surface microgap retention rate, in percentage (%); V0: effective microgap volume before humid heat and pressure treatment; V1: effective microgap volume after humid heat and pressure treatment.

[0238] The higher the surface micro-gap retention rate, the less likely the micro-convex contact area and micro-groove channel are to compact or collapse under humid, hot and pressurized conditions.

[0239] (8) Paper residue level after contact with damp heat glass

[0240] Display glass with dimensions of 200 mm × 200 mm and uniform surface roughness and cleanliness was used as the test glass. Before testing, the glass surface was cleaned sequentially with deionized water and analytical grade isopropanol, and then dried with clean nitrogen gas. The test method is as follows:

[0241] ① Cut a piece of release paper with dimensions of 210 mm × 210 mm, and stack the release paper and test glass alternately to set up a total of 3 sets of glass-release paper contact interfaces, and apply a load of 1 kg on the top. Place the stacked sample in an environment with a temperature of 50℃ and a relative humidity of 90% for 96 h.

[0242] ② After the test, remove the glass and place it in a clean environment with a temperature of 23±1℃ and a relative humidity of 50%±2% for 30 minutes. Against a black background, illuminate the glass with a white light source of 1000±100 lx at an angle of 15° to 30° to the glass surface. Three testers observe the paper marks, white fog, and localized adhesion. The median of the three ratings is taken as the final paper mark grade. The paper mark grade is evaluated according to the following standards:

[0243] Grade 0: No visible paper marks, white fog, or other deposits on the glass surface;

[0244] Level 1: Slight traces are visible only under oblique strong light, and the area of ​​the traces does not exceed 5% of the effective observation area of ​​the glass;

[0245] Level 2: Slight paper marks or white haze are visible, with the area of ​​the marks greater than 5% but not exceeding 20%;

[0246] Level 3: Obvious paper marks, white haze, or localized adhesion are present, with the area of ​​the marks exceeding 20% ​​but not exceeding 50%;

[0247] Level 4: There are severe or continuous paper marks, obvious white fog, adhesion or foreign matter transfer, and the trace area exceeds 50%.

[0248] The lower the paper scratch rating, the better the heat and moisture contact performance of the release paper with glass.

[0249] (9) Peeling stability

[0250] Peel stability was tested according to the 180° peel test principle in GB / T 2792—2014 "Test Method for Peel Strength of Adhesive Tapes", with adaptive adjustments made based on the characteristic that there is no adhesive layer between the glass spacer paper and the glass. The test method is as follows:

[0251] ① Cut a release paper sample with a width of 25 mm and a length of 200 mm, lay it flat on the surface of a cleaned glass plate, and maintain it for 96 h under a uniform normal pressure of 5.0 kPa in an environment with a temperature of 50℃ and a relative humidity of 90%. After the test, fix the glass plate on the horizontal clamp of the tensile testing machine, fold one end of the release paper back 180° and clamp it in the moving clamp, and peel it continuously at a speed of 100 mm / min.

[0252] ② Remove the data from the first and last 20 mm of the peeling section, and record the average peeling force F, the maximum peeling force Fmax, and the coefficient of variation CV of the effective peeling section in the middle. The coefficient of variation of peeling force is calculated according to the following formula: CV=σ / F×100%; where, CV: coefficient of variation of peeling force, in percentage (%); σ: standard deviation of peeling force in the effective peeling section; F: average peeling force in the effective peeling section.

[0253] Peeling stability was evaluated according to the following criteria:

[0254] Advantages: The peeling process is continuous and stable, with no local adhesion, jumping or paper damage, and CV≤10%;

[0255] Good: No obvious adhesion or paper damage during the peeling process, 10% < CV ≤ 20%;

[0256] Medium: Slight intermittent adhesion or peel force fluctuations exist, 20% < CV ≤ 30%;

[0257] Poor: There is obvious adhesion, sudden jumping, paper tearing or peeling interruption, or CV>30%.

[0258] The smaller the average peel force and maximum peel force, and the lower the coefficient of variation of peel force, the easier it is for the release paper and glass to separate stably.

[0259] (10) The damp heat glass contact test shall be conducted as follows:

[0260] Place the isolation paper to be tested between two clean display glass substrates, such as... Figure 4 shown (Note: Figure 4 The diagram is only used to illustrate the dispersive support effect of the micro-convex contact area and the water vapor dissipation function of the micro-groove channels. The shape, number, and arrangement of the micro-convex contact area and micro-groove channels in the diagram are for illustrative purposes only and do not represent the actual proportion or regular arrangement of the microstructure on the surface of the release paper. The two surfaces of the release paper are then in contact with adjacent glass surfaces. The glass is then stacked at 60℃ and 90%RH for 96 hours. After the test, the glass and release paper are separated, and the peeling state of the release paper is observed. The glass surface is checked for paper marks, white fog, or adhesion to evaluate the interfacial water vapor dissipation capacity, surface micro-gap retention capacity, and glass insulation performance under humid and hot conditions.

[0261] 2. Test Results:

[0262] Table 1

[0263]

[0264] As can be seen from the results in Table 1, Examples 1 to 5, through localized micro-pressing and shaping in the wet paper web state and subsequent springback shaping treatment, enable the paper web surface to form and maintain a micro-gap structure composed of micro-convex contact areas and micro-groove channels. This can improve the interfacial moisture dissipation ability while maintaining appropriate smoothness, resulting in a lower paper mark level after contact with humid heat glass and better peel stability.

[0265] It can also be seen that simply improving the smoothness of the paper does not necessarily lead to a better glass isolation effect. Although Comparative Examples 1 and 4 improved the smoothness of the paper surface through ordinary calendering or high-linear calendering, the increased overall density of the paper increased the actual contact area, resulting in a decrease in the micro-gap retention rate. Consequently, they still exhibited a high level of paper marks and a risk of adhesion after contact with humid and hot glass. Comparative Example 2 did not undergo spring-loaded shaping, resulting in insufficient stability of the micro-convex contact area and micro-groove channels, and a decrease in the micro-gap structure retention rate. Comparative Example 3 did not employ a discontinuous micro-convex structure, making it difficult to form a local differential compression and pressure-rebound structure, resulting in insufficient interfacial moisture dissipation capacity. Although Comparative Example 5 underwent press shaping, it did not form interconnected micro-groove channels, indicating that simply forming a micro-convex structure is insufficient to achieve the interfacial moisture dissipation effect of this invention.

[0266] The above results show that the present invention does not simply pursue the flattening of the paper surface, nor does it arbitrarily form surface microstructures. Instead, it achieves a comprehensive improvement in the isolation performance of high-generation large-size glass substrates by controlling the actual contact state of the glass-isolation paper interface and the moisture dissipation path.

[0267] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a micro-gap, low-mark release paper for glass substrates, characterized in that, Includes the following steps: (1) Preparation of wet paper web: Disperse plant fiber pulp in water, adjust the pulp mass concentration to 1.5% to 6.0%, and after descaling, beat the pulp to a freeness of 18°SR to 58°SR. Then, after beating, the pulp is screened and sand removed, and then made into wet paper web; (2) Localized micro-pressing and shaping: The wet paper web is initially pressed and dehydrated to a moisture content of 18% to 55%, and then passed through at least one localized micro-pressing and shaping zone to obtain a paper web after localized micro-pressing and shaping; wherein, the localized micro-pressing and shaping zone includes a shaping roller with a discontinuous micro-protrusion structure on its surface and an elastic bearing roller that cooperates with it; the height of the discontinuous micro-protrusion structure of the shaping roller is 1 to 80 μm and is less than half of the total thickness of the release paper, and the average nearest neighbor center distance between adjacent micro-protrusion structures is 20 to 1000 μm; the linear pressure of the localized micro-pressing and shaping zone is 5 to 100 kN / m, and the surface temperature of the shaping roller is 20 to 120℃; (3) Spring-setting treatment: The paper web after localized micro-pressing and shaping is subjected to spring-setting treatment 1 to 5 times, and then dried to a moisture content of 3% to 10% to obtain the paper web after spring-setting treatment. (4) Cleaning and post-treatment: The paper web after the spring-setting treatment is cleaned and post-treated to obtain micro-gap low-scratch release paper for glass substrates.

2. The preparation method according to claim 1, characterized in that: The plant fiber pulp mentioned in step (1) is at least one of softwood pulp, hardwood pulp, bamboo pulp, cotton pulp, hemp pulp, grass fiber pulp and microfibrillated cellulose pulp; The discontinuous micro-protrusion structure on the surface of the shaping roller mentioned in step (2) is at least one of the following: random dot-like, strip-like, island-like, mesh-like, honeycomb-like, and corrugated micro-protrusion structure.

3. The preparation method according to claim 1, characterized in that: The height of the discontinuous micro-convex structure of the shaping roller in step (2) is 8 to 12 μm, and the average nearest neighbor center distance between adjacent micro-convex structures is 150 to 210 μm; the linear pressure of the localized micro-pressing shaping zone is 12 to 30 kN / m, and the surface temperature of the shaping roller is 35 to 45℃. The conditions for the rebound shaping treatment in step (3) are: treatment at 25-90℃ and relative humidity of 35%-95% for 1-180 min; In step (4), the surface micro-convex contact area of ​​the micro-gap low-mark release paper accounts for 5% to 65% of the surface area, and the micro-groove channel area accounts for 35% to 95% of the surface area.

4. The preparation method according to claim 3, characterized in that: The discontinuous micro-protrusion structure on the surface of the shaping roller mentioned in step (2) is a random dot-shaped micro-protrusion structure, and the equivalent diameter of the top surface of each micro-protrusion structure is 60 to 100 μm; The conditions for the rebound shaping treatment in step (3) are: treatment at 35-50℃ and relative humidity of 60%-80% for 20-40 minutes; In step (4), the surface micro-convex contact area of ​​the micro-gap low-mark release paper accounts for 10% to 20% of the surface area, and the micro-groove channel area accounts for 80% to 90% of the surface area.

5. The preparation method according to claim 1, characterized in that: The rotation speed for the scavenging process described in step (1) is 8000-12000 rpm; The freeness of the slurry mentioned in step (1) is 28°SR~32°SR; The basis weight of the wet paper web mentioned in step (1) is 20–90 g / m²; The linear pressure for the initial pressing and dehydration described in step (2) is 80-100 kN / m; The moisture content of the wet paper web after the initial pressing and dewatering in step (2) is 35%–40%. The springback shaping process described in step (3) is repeated 1 to 2 times.

6. The preparation method according to claim 1, characterized in that: The screening and sand removal described in step (1) includes at least one of the following: primary or multi-stage pressure screening, low-concentration sand removal, high-concentration slag removal, and microfiltration. The copying process described in step (1) is carried out by using long wire mesh, round wire mesh, sandwiched wire mesh or multi-layer forming method.

7. The preparation method according to claim 1, characterized in that: The shaping roller mentioned in step (2) is a metal roller, ceramic roller, rubber roller, polyurethane roller, or a composite roller made of two or more of the following materials: metal, ceramic, rubber, polyurethane, etc. The post-cleaning treatment described in step (4) includes one or more of the following: low-tension rewinding, non-contact dust removal, ion wind static elimination, edge lint collection, clean cutting, and dust-free packaging.

8. A micro-gap, low-mark release paper for glass substrates, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the micro-gap low-mark release paper of claim 8 in the stacking, transportation and storage of glass plates.

10. The application according to claim 9, characterized in that: The glass sheet is a high-cleanliness glass sheet; The high-cleanliness glass sheets include display glass substrates, optoelectronic or photovoltaic glass, ultra-thin glass, and optical glass.

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