Gradient color film, gradient color window film, and preparation method and application of gradient color film

Abstract

The invention relates to a gradient color film, a gradient color window film and a preparation method and application of the gradient color film. A thin film in the conveying process is obliquely arranged in the width direction, so that the depths, located in a dyeing solution, of all positions of the thin film in the width direction are different; the retention time of the thin film conveyed at a constant speed in the dyeing liquid in the width direction is different due to the difference of the depths, so that the gradual-change dyeing effect of the thin film from deep to shallow is realized; the dyeing mode can be suitable for dyeing of single-color dye, and the effect that the single color gradually changes from deep to light is achieved; in addition, the dyeing method is simple and easy to implement, continuous production can be achieved, the production cost is low, the dye is immediately dried after being adsorbed on the film through the large surface area, oxidation and color fading are not prone to occurring, and the stability after dyeing is good.

Description

Technical Field

[0001] The present invention relates to the technical field of film dyeing, and in particular to a gradient color film, a gradient color window film, and a preparation method and application of the gradient color film. Background Art

[0002] At present, various types of films are widely used in the market. Among them are gradient color films. At present, such films generally adopt magnetron sputtering coating technology to produce the effect of gradient from one color to another or more colors. For example, Chinese patent CN113403593B "Gradient color film and its preparation method and application" magnetron sputters a film layer with gradient thickness on the film substrate, and obtains a gradient color effect according to the principle of optical interference. Chinese patent application CN112048699A "A method for preparing a gradient PET film" coats a material layer with a refractive index on the PET film, and the material layer is composed of alternating high refractive index and low refractive index material layers, thereby producing a gradient color effect on the refraction of light.

[0003] The gradient color window film prepared by the above-mentioned prior art not only has a complex preparation process and huge equipment investment, but also the gradient color effect is formed by refraction of light under the premise that the film itself has a special structure, and cannot be formed only by dyeing.

[0004] Therefore, the structure and preparation method of the gradient color film need to be improved. Summary of the invention

[0005] The first technical problem to be solved by the present invention is to provide a gradient color film with a simple structure and capable of presenting a gradient color effect in view of the current status of the prior art.

[0006] The second technical problem to be solved by the present invention is to provide a window film having the above-mentioned gradient color film applied thereto in view of the current status of the prior art.

[0007] The third technical problem to be solved by the present invention is to provide a method for preparing a gradient color film with a simple preparation method, easy to realize continuous production, low production cost and good dyeing stability in view of the current status of the prior art.

[0008] The fourth technical problem to be solved by the present invention is to provide an application of the above-mentioned gradient color film in view of the current status of the prior art.

[0009] The technical solution adopted by the present invention to solve at least one of the above technical problems is:

[0010] A gradient color film includes a substrate layer, wherein two opposite edges of the substrate layer are defined as a first width edge and a second width edge, and the color of the substrate layer gradually deepens from the first width edge to the second width edge to form a gradient color, and the gradient color is obtained by dyeing the substrate layer with a dyeing liquid.

[0011] The gradient color effect formed by the gradient color film of the present invention does not rely on the special structure of the film and the corresponding light refraction, but directly obtains the gradient color effect by dyeing with dyeing liquid. Not only is the structure of the film simple, but the gradient color effect is also more stable.

[0012] Preferably, the substrate layer is subjected to corona treatment, and the corona treatment process occurs before dyeing. Corona treatment of the substrate layer before dyeing can increase the adhesion of the dye on the substrate layer and improve the dyeing effect.

[0013] As an improvement, the corona value of the corona treatment gradually increases from the first width edge to the second width edge. This treatment method can achieve or enhance the gradient color dyeing effect by changing the adsorption effect of the dye at various locations of the substrate layer.

[0014] A gradient color window film includes the above-mentioned substrate layer, and also includes a hardening layer, an installation glue layer and a protective film coated on the side of the substrate layer. Preferably, the first side of the substrate layer is coated with the hardening layer, and the second side of the substrate layer is coated with the installation glue and the protective film.

[0015] The gradient color window film of the present invention can be attached to various light-transmitting windows for use, so as to achieve a good gradient shading effect.

[0016] A method for preparing a gradient color film comprises the following steps:

[0017] (1) Prepare staining solution;

[0018] (2) placing the film on a support that can be transported transversely (along the length of the film) and partially arched downward, the support being located above the dyeing liquid;

[0019] Before dyeing, the film is adjusted to be tilted in a direction perpendicular to the conveying direction, that is, the first width edge of the film is at the top and the second width edge is at the bottom; the support is lowered until the arch of the film is at least partially immersed in the dyeing liquid, the film is conveyed, and dyeing begins;

[0020] (3) The dyed film is dried in an oven and stored to obtain the gradient color film.

[0021] In the present invention, it is particularly important that: during the dyeing process, the depth of the film inserted into the dyeing liquid gradually increases from the first width edge to the second width edge, and when the film is transported along its length, the residence time of the film in the dyeing liquid gradually increases from top to bottom. According to the length of time the film stays in the dyeing liquid, the color of the film is darker or lighter. The lowest part of the film stays in the dyeing liquid for the longest time and the color dyed is relatively darker. The part closer to the liquid surface has a shorter residence time and the color dyed is lighter, thereby producing a gradient color.

[0022] Preferably, the film has a width direction with respect to a horizontal plane with an inclination angle of 30° to 60°. By controlling the inclination direction, the residence time of different parts of the film in the dye solution can be controlled, thereby adjusting the gradient dyeing effect.

[0023] Preferably, the film is subjected to corona treatment before dyeing. The corona treatment increases the roughness of the film surface, which can increase the specific surface area, increase the contact and adsorption of the dye, and thus improve the dyeing fastness and stability.

[0024] As an improvement, the corona treatment is a single-sided or double-sided gradient corona treatment in the same direction, that is, when the film is tilted, the corona treatment value of the film increases from top to bottom. The above treatment method has two effects: (1) through the gradient corona treatment, the roughness of the film surface presents a gradient change in the width direction, and the gradient change cooperates with the adsorption force of the dyeing liquid and the residence time of each part of the film in the dyeing liquid, which can greatly improve the gradient coloring effect of the film; when the film is corona treated by the present invention, the power of the working end of the corona generating device can be controlled to make the working power present a gradient distribution, or the gap distance between the working end of the corona generating device and the film can be controlled to change in a gradient, so that the corona value of the film in the transverse direction changes in a gradient, and the specific surface area on the width of the film changes in sequence, which can be combined with the dyeing method of non-equal time dyeing in the width direction of the film, and can effectively enhance the gradient color effect of the film in the width direction; (2) the film is subjected to a gradient corona treatment on its width, and a good visual effect can be maintained at all parts of the film under the premise of realizing the gradual color change of the film.

[0025] In the present invention, the selected film raw material can be a transparent film made of PET material, or can be other transparent plastic films.

[0026] Preferably, the corona treatment value is 15-80 dyn / cm, more preferably 30-70 dyn / cm. The gradient corona value can be changed in a gradient within a range of less than 80 dyn / cm to meet product requirements.

[0027] Preferably, the temperature of the dyeing liquid is 80-160° C. The drying temperature of the oven is 100-140° C.

[0028] Preferably, during the dyeing process, the film is uniformly conveyed at a speed of 0.5 to 3.5 m / min. The conveying speed can be adjusted according to actual production requirements, and can also be fine-tuned in accordance with the dyeing solution temperature, concentration, film tilt angle, etc., to achieve the best dyeing effect.

[0029] Preferably, the film is arranged so that the downwardly arched portion is in a V-shaped, U-shaped or S-shaped structure. Changing the structure can control the length of the film passing through the dyeing liquid.

[0030] Preferably, the dyeing solution comprises a medium, a dye, a leveling agent and a fixing agent, the medium is decamethylcyclopentasiloxane (D5), the dye is a disperse dye, and the leveling agent is selected from leveling agent GS and β-cyclodextrin.

[0031] An application of a gradient color film is used on the front windshield of a car, wherein the color of the gradient color film gradually becomes lighter from top to bottom in the middle and upper part of the front windshield of the car. For car drivers, this application can reduce the stimulation of strong light to the eyes, which not only improves driving comfort, but also reduces the cost of using the car.

[0032] Compared with the prior art, the advantages of the present invention are: the present invention arranges the film in the conveying process obliquely in the width direction, so that the film is located at different depths in the dyeing liquid at different locations in the width direction. The different depths make the conveyed film stay in the dyeing liquid for different times in the width direction, thereby achieving a gradual dyeing effect of the film from dark to light; the dyeing method of the present invention can be applied to dyeing with a single color dye to obtain a gradual effect from dark to light with a single color, which is impossible to achieve with the prior art; in addition, the dyeing method of the present invention is simple and easy to implement, can realize continuous production, and has low production cost. After the dye is adsorbed on the film, it is immediately dried and is not easy to oxidize or fade, and has good stability after dyeing. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the structure of an embodiment of the present invention (state before dyeing);

[0034] Figure 2 It is a structural schematic diagram of an embodiment of the present invention (during dyeing process);

[0035] Figure 3 The conveying tracks at various locations in the width direction of the film in the embodiment of the present invention;

[0036] Figure 4 A diagram showing the connection structure between the guide roller and the support arm in an embodiment of the present invention;

[0037] Figure 5 Schematic diagram of the structure of the window film in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below with reference to the accompanying drawings.

[0039] In the embodiment of the present invention, the film material is a PET film with a visible light transmittance of 89%, a dielectric decamethylcyclopentasiloxane (D5) [purchased from Zhejiang PuKa Chemical Co., Ltd.], a disperse blue 79 [purchased from Hubei Hengjingrui Chemical Co., Ltd. Model: Disperse Blue HGL], a leveling agent GS [purchased from Nantong Runfeng Petrochemical Co., Ltd.], and a fixing agent JV-603 [purchased from Dongguan Jiewei Industrial Co., Ltd.].

[0040] Embodiment 1:

[0041] like Figure 5 As shown, the gradient color film of this embodiment includes a substrate layer A, and the two opposite edges of the substrate layer A are defined as a first width edge and a second width edge. The color of the substrate layer A gradually deepens from the first width edge to the second width edge to form a gradient color, and the gradient color is obtained by dyeing the substrate layer A with a dyeing liquid. The gradient color effect formed by the gradient color film in this embodiment does not rely on the special structure of the film and the corresponding light refraction, but directly obtains the gradient color effect by dyeing with a dyeing liquid. Not only is the structure of the film simple, but the gradient color effect is more stable.

[0042] The gradient color window film of this embodiment includes the above-mentioned substrate layer A, and also includes a hardening layer B, a mounting adhesive layer C and a protective film D coated on the side of the substrate layer A. The first side of the substrate layer A is coated with the hardening layer B, and the second side of the substrate layer A is coated with the mounting adhesive layer C and the protective film D. The gradient color window film can be attached to various light-transmitting windows for use to achieve a good light-shielding effect.

[0043] The method for preparing the gradient color film in this embodiment comprises the following steps:

[0044] (1) preparing a dyeing solution, comprising a medium decamethylcyclopentasiloxane (D5), disperse blue 79, leveling agent GS and fixing agent JV-603, wherein the weight proportions of disperse blue 79, leveling agent GS and fixing agent JV-603 are 8.6%, 0.9% and 0.5% respectively, and the remaining 90% is the medium, and the temperature of the dyeing solution is controlled at 135° C.;

[0045] (2) placing the film on a support that can be transported laterally and partially arched downward (in a V shape), the support being located above the dyeing solution;

[0046] Before dyeing, adjust the direction of the film so that it is tilted and arranged perpendicular to the conveying direction, that is, the first width edge of the film is at the top and the second width edge is at the bottom, so that the width direction of the film is arranged at 45 degrees to the surface of the dyeing liquid; lower the bracket until 1 / 2 of the width of the film is immersed in the dyeing liquid at the arched part, and start dyeing the film slowly and evenly at a speed of 1 m / min;

[0047] During the dyeing process, the depth of the film penetrating into the dyeing liquid gradually increases from the first width edge to the second width edge. When the film is transported at a uniform speed, the residence time of the film in the dyeing liquid gradually increases from top to bottom. Figure 3 As shown, the stay time of AA', BB', and CC' on the film in the dye solution is extended successively, and the film presents light and dark colors according to the length of time it stays in the dye solution. The lowest part of the film stays in the dye solution for the longest time, and the color it dyes is relatively the darkest. The part closer to the liquid surface has a shorter stay time and a lighter color, thus producing a gradient color.

[0048] (3) The dyed film is washed with water, dried with a coloring agent, and dried in an oven with the oven temperature controlled at 120° C., and then stored to obtain a gradient color window film substrate.

[0049] It should be noted that, since the film itself has a certain elasticity, the change in film surface area caused by corona treatment will gradually weaken over time until it disappears, but this does not affect the strengthening effect of corona treatment on improving the adsorption of dye molecules on the film surface during the dyeing production process.

[0050] like Figure 1 , 2 As shown in Figures 4 and 5, the production equipment of the gradient color film of this embodiment includes a dye vat 1 and a bracket 2. The dye vat 1 is used to hold the dyeing liquid, and the dye vat 1 has an open top. The bracket 2 is arranged above the dye vat 1 so as to be movable up and down, and the bracket 2 is provided with a support arm 21 extending downward, and the lower end of the support arm 21 is connected to a guide roller for supporting and laterally transmitting the film 100, and the guide roller is arranged transversely perpendicular to the transmission direction of the film 100 and includes at least a first guide roller 01 and a second guide roller 02 of different heights, and the first guide roller 01 and the second guide roller 02 can be constrained on the support arm 21 in an inclined manner up and down along their axes.

[0051] The first guide roller 01 and the second guide roller 02 are restrained to form a dyeing support area as the support 2 is lowered, and the film 100 is transferred to the dyeing support area and is located in the dyeing vat 1. With such a structure, it is convenient to control the dyeing position and size of the film. For example, by controlling the height of the support descent, the size of the film immersed in the dyeing liquid can be controlled in the vertical film transmission length direction, that is, the width direction of the film, so as to obtain a film with a set dyeing size.

[0052] The inclination angle a of the first guide roller 01 and the second guide roller 02 is 30° to 60°. By setting this angle, the vertical distance of each part of the film intruding into the dye solution in the width direction can be controlled to be different, thereby controlling the dyeing time in each part of the film in the width direction to obtain a better gradient dyeing effect.

[0053] An adjusting member capable of adjusting the inclination angle of the first guide roller 01, the second guide roller 02 and the corresponding support arm 21 is provided at the connection point. The adjusting member may be a connecting block 211 capable of swinging up and down relative to the support arm 21, and the rotating shaft matched with the guide roller is constrained on the side of the connecting block 211. The connecting block 211 may be locked and fixed by a bolt 212 after adjusting the swing position relative to the support arm 21. The above structure facilitates the adjustment of the inclination angle of the first guide roller 01 and the second guide roller 02 to match the corresponding dyeing time and dyeing temperature to obtain the best gradient dyeing effect.

[0054] From a side view, the dyeing support area is constrained to be a V-shaped, U-shaped or S-shaped structure, and this embodiment shows a V-shaped structure. Such a structure is used to facilitate immersing a specific part of the film in the dyeing liquid and to facilitate controlling the dyeing size.

[0055] This embodiment also includes a third guide roller 03, the lower end of the first guide roller 01 is located at the lowest point, the second guide roller 02 and the third guide roller 03 are respectively arranged on both sides of the first guide roller 01, and the lower ends of the second guide roller 02 and the third guide roller 03 are higher than the lower end of the first guide roller 01. In this embodiment, the second guide roller 02 and the third guide roller 03 are at the same height. The above structure facilitates the guiding and conveying of the film at different heights in a symmetrical manner with respect to the first guide roller 01 as the center, thereby improving the stability and reliability of the film conveying.

[0056] This embodiment also includes an unwinding roller 3, a drying mechanism 4 and a winding roller 5. The unwinding roller 3 is arranged upstream of the dyeing vat 1 and is used to unwind the film to be dyed. The drying mechanism 4 is arranged downstream of the dyeing vat 1 and is used to wash and dry the dyed film. The winding roller 5 is arranged downstream of the drying mechanism 4 and is used to wind and store the dyed and dried film. The above structure is convenient for realizing continuous automated production.

[0057] The guide rollers of this embodiment further include a first guide roller 001 and a second guide roller 002. The first guide roller 001 is arranged downstream of the unwinding roller 3 to guide the film output by the unwinding roller 3, and the second guide roller 002 is arranged upstream of the drying mechanism 4 to guide the film about to enter the drying mechanism 4. The above structure is adopted to further improve the transmission stability and reliability of the film and avoid the deviation of the dyeing effect due to local misalignment of the film.

[0058] The bracket 2 of this embodiment has a transversely arranged main body, and the guide roller, the unwinding roller 2, and the winding roller 5 are all restrained under the main body by the support arm 21. With the above structure, it is convenient to control the entire film height and tilt angle adjustment structure through the bracket 2, making the overall structure of the equipment more compact and convenient to operate.

[0059] Embodiment 2:

[0060] The difference between this embodiment and embodiment 1 is that:

[0061] The substrate layer A in this embodiment is subjected to corona treatment, and the corona treatment process occurs before dyeing. The corona treatment of the substrate layer A before dyeing can increase the adhesion of the dye on the substrate layer and improve the dyeing effect. The corona value of the corona treatment in this embodiment gradually increases from the first width edge to the second width edge. This treatment method can achieve or strengthen the gradient color dyeing effect by changing the adsorption effect of the dye at various locations of the substrate layer A.

[0062] The method for preparing the gradient color film in this embodiment adds a corona treatment process to the film to be dyed.

[0063] The film subjected to single-sided gradient corona treatment has a corona value range of 30-70dyn / cm. In this embodiment, the film material used is PET film, and the gap distance between the working end of the corona generating device and the film is controlled to achieve gradient change, and the angle between the working end face of the corona generating device and the width direction of the film is adjusted. The smaller the gap distance between the two, the greater the corona dyne value, and vice versa, so that the change of the corona dyne value in the width direction of the film meets the set requirements. After continuous operation, a film to be dyed with transverse and longitudinal corona values ​​that meet the required range is obtained.

[0064] In this embodiment, the power of the corona generating device during the corona treatment of the PET film is 9KW, the angle between the working end face and the width direction of the film is 0.09°, the maximum distance between the working end face and the film gap within the effective width of 1 meter of the film is 2.5mm, and the minimum distance is 0.5mm. After the corona treatment, the corona dyne value is tested to change gradually from 30 to 70dyn / cm.

[0065] Comparative Example 1:

[0066] The difference between this comparative example and Example 1 is that after the film is immersed in the dyeing liquid, the film in this comparative example is arranged parallel to the liquid surface of the dyeing liquid in the width direction.

[0067] Comparative Example 2:

[0068] The difference between this comparative example and Example 2 is that the film in this comparative example is treated with single-sided corona instead of gradient corona, and the single-sided corona value is 70 dyn / cm.

[0069] Comparative Example 3:

[0070] The only difference between this comparative example and Example 2 is that after the film is immersed in the dyeing liquid, the film in this comparative example is arranged parallel to the liquid surface of the dyeing liquid in the width direction.

[0071] The films prepared in Examples 1 and 2 and Comparative Examples 1, 2 and 3 were subjected to subsequent processes such as coating a hard layer, installing glue, and laminating a release protective film to obtain a finished film with a gradient color effect. The LS110H (split transmittance measuring instrument) of Linshang Technology was used to test the visible light transmittance at five points of equal distance in the horizontal direction of the film in the immersion area. The results are as follows:

[0072] 5cm from the edge 15cm from the edge 25cm from the edge 35cm from the edge 45cm from the edge Example 1 85％ 85.7％ 86.6％ 87.7％ 88％ Comparative Example 1 85.2％ 85.1％ 85％ 85.2％ 85.2％ Example 2 78.3％ 80.2％ 82.3％ 84.8％ 87.8％ Comparative Example 2 78.2％ 78.8％ 79.8％ 80.9％ 81.8％ Comparative Example 3 78.3％ 78.9％ 81.3％ 83.3％ 84.1％

[0073] From the appearance of the finished product and the visible light transmittance data listed in the table, it can be seen that:

[0074] Example 1 enters the dyeing liquid with an inclined surface to dye, and can obtain a clear gradient color effect. Comparative Example 1 enters the dyeing liquid with a uniform height in the width direction to dye, and basically cannot produce a gradient color effect.

[0075] In Example 2, a PET film treated with a gradient corona is dipped into the dye solution in an inclined manner, and a large range of light transmittance variation can be obtained (this is because the interval width of the dyeing depth is increased), and there is an obvious level gradient effect, and the depth variation range of the gradient color is larger than that of Example 1. In Comparative Example 2, a PET film treated with a non-gradient corona is dipped into the dye solution in an inclined manner, and an obvious level gradient effect can be obtained, and the range of light transmittance variation is not large, and the depth variation range of the gradient color is equivalent to that of Example 1, but due to the enhanced adsorption effect of the dye after corona treatment, the light transmittance is reduced.

[0076] Comparative Example 3 uses a PET film treated with gradient corona, but enters the dyeing liquid in a manner of equal height in the width direction, and can also obtain a more obvious gradient color effect, but the overall light transmittance will be less than that of Example 1. From the effect reflected by this group of data, when the film is not dyed in an inclined transmission mode, but only gradient corona dyeing is used, a relatively good gradient color effect can also be obtained. In addition, when only the film is dyed in an inclined transmission mode without corona treatment, the gradient color range of the obtained gradient color film is slightly smaller; when only the film is dyed after gradient corona treatment, the gradient color range of the obtained gradient color film is slightly larger; when the film is dyed in an inclined transmission mode and corona treatment is combined, the gradient color range of the obtained gradient color film is the largest.

[0077] It should be noted that the main features of the product prepared in Example 1 are: obvious gradient color effect, good light transmittance, but small range of dyeing depth variation; the main features of the product prepared in Example 2 are: obvious gradient color effect, large range of dyeing depth variation, but light transmittance will be reduced accordingly. Considering factors such as different user habits and needs, different usage scenarios, etc., it is not required that the gradient color range is as large as possible, and the preparation method of Example 1 or Example 2 can be selected to produce a gradient color film according to actual needs.

[0078] In addition, it should be noted that the solution of the present invention can obtain a gradient effect from dark to light in a single color, but is not limited to obtaining a gradient effect from dark to light in a single color. The solution of the present invention can also obtain a color gradient film, which can be achieved by controlling the dyeing depth on the width of the film, the transmission speed, the up and down movement of the bracket, the corona control, the direction of the inclined surface, and passing through more than one color dye vat in sequence.

[0079] In the specification and claims of the present invention, terms indicating directions, such as "front", "rear", "up", "down", "left", "right", "side", "top", "bottom", etc., are used to describe various exemplary structural parts and elements of the present invention, but these terms are used here only for the purpose of convenience of description and are determined based on the exemplary orientations shown in the accompanying drawings. Since the embodiments disclosed in the present invention can be arranged in different directions, these terms indicating directions are only used as explanations and should not be regarded as limitations. For example, "up" and "down" are not necessarily limited to directions opposite to or consistent with the direction of gravity.

Claims

1. A gradient color film, comprising a substrate layer, characterized in that: The two opposite edges of the substrate layer are defined as a first width edge and a second width edge, and the color of the substrate layer gradually deepens from the first width edge to the second width edge to form a gradient color, which is obtained by dyeing the substrate layer with a dyeing liquid.

2. The gradient color window film according to claim 1, characterized in that: The substrate layer is subjected to corona treatment, and the corona treatment process occurs before dyeing.

3. The gradient color window film according to claim 2, characterized in that: The corona value of the corona treatment gradually increases from the first width edge to the second width edge.

4. A gradient color window film, characterized in that: The invention comprises the base material layer according to any one of claims 1 to 3, and further comprises a hardening layer and a protective film located on the side of the base material layer.

5. The gradient color window film according to claim 4, characterized in that: A hardening layer is disposed on the first side of the substrate layer, and a protective film is disposed on the second side of the substrate layer.

6. A method for preparing the gradient color film according to claim 1, characterized in that The following steps are involved: (1) Prepare staining solution; (2) placing the film on a support that can be transported laterally and partially arched downward, the support being located above the dyeing liquid; Before dyeing, the film is adjusted to be tilted in a direction perpendicular to the conveying direction, that is, the first width edge of the film is at the top and the second width edge is at the bottom; the support is lowered until the arch of the film is at least partially immersed in the dyeing liquid, and the film is conveyed in the length direction to start dyeing; (3) The dyed film is dried in an oven and stored to obtain the gradient color film.

7. The method for preparing a gradient color film according to claim 6, characterized in that: During the dyeing process, the depth of the film penetrating into the dyeing liquid gradually increases from the first width edge to the second width edge, and when the film is conveyed along its length direction, the residence time of the film in the dyeing liquid gradually increases from top to bottom.

8. The method for preparing a gradient color film according to claim 7, characterized in that: The inclination angle of the width direction of the film relative to the horizontal plane is 30° to 60°.

9. The method for preparing a gradient color film according to claim 6, characterized in that: During the dyeing process, the film is transported at a uniform speed, and the speed of the uniform transport is 0.5 to 3.5 m / min.

10. The method for preparing a gradient color film according to claim 6, characterized in that: Prior to dyeing, the film was corona treated.

11. The method for preparing a gradient color film according to claim 10, characterized in that: The corona treatment is a single-sided or double-sided same-direction gradient corona treatment, that is, when the film is arranged in an inclined state, the corona treatment value of the film increases from top to bottom.

12. The method for preparing a gradient color film according to claim 11, characterized in that: The corona treatment value is 15-80 dyn / cm.

13. The method for preparing a gradient color window film substrate according to claim 12, characterized in that: The corona treatment value is 30-70 dyn / cm.

14. The method for preparing a gradient color film according to any one of claims 6 to 13, characterized in that: The temperature of the dyeing solution is 80-160°C.

15. The method for preparing a gradient color film according to any one of claims 6 to 13, characterized in that: The drying temperature of the oven is 100-140°C.

16. The method for preparing a gradient color window film substrate according to any one of claims 6 to 13, characterized in that: The film is arranged so that the downwardly arched portion is in a V-shaped, U-shaped or S-shaped structure.

17. An application of the gradient color film according to claim 1 or 6, characterized in that: When used on the front windshield of a car, the color of the gradient color film gradually becomes lighter from top to bottom in the middle and upper part of the front windshield of the car.

Images