A flexible heating film, a heating assembly and a heating device

Abstract

The application discloses a flexible heating film, which comprises a film layer body, the film layer body is provided with a slitting seam along a current direction, the slitting seam penetrates two surfaces of the film layer body, and the material of the film layer body is not removed; an insulating packaging structure of the flexible heating film, which uses the above heating film, and places an insulating film between a first insulating layer and a second insulating layer, one of the first insulating layer and the second insulating layer comprises a base material layer and a glue layer arranged on a side of the base material layer facing the above heating film, and the other one is free of the glue layer in a corresponding region of the film layer body; and a heating device using the above flexible heating film and the insulating packaging structure of the heating film. The application can be used in a wet and cold environment, adapts to instantaneous cold and hot changes, rapidly rises and falls in temperature, has the ability of long-time continuous work in a wide temperature range of 'ambient temperature' to 320 DEG C, is not easy to crack and delaminate, and greatly improves product quality, use stability and safety.

Description

Technical Field

[0001] This invention relates to the field of electrothermal technology, specifically to a flexible heating film, a heating component, and a heating device. Background Technology

[0002] Flexible heating film is a type of heating element with good flexibility. It heats up quickly and effectively by supplying electricity. It has advantages such as fast heating speed, high safety factor, convenient and reliable use, and long service life, and is therefore widely promoted and used.

[0003] Before being used to generate heat, flexible heating films need to be effectively encapsulated to form heating components. During manufacturing, insulating films are usually placed on the upper and lower surfaces of the heating film. To ensure better reliability during use, adhesive films are added between the heating film and the upper and lower insulating films to ensure that the heating film and the insulating film do not separate or bubble during use. However, the absence of separation and bubbling is relative. For example, during long-term use at temperatures exceeding 180 degrees Celsius, problems such as bubbles caused by thermal expansion and contraction and film separation are very likely to occur.

[0004] To address the issues of bubbles and delamination, existing solutions involve creating small holes (round, square, or strip-shaped) in the heating film to mitigate bubbles and film layer separation caused by thermal expansion and contraction. However, these methods are unavoidable in applications with large temperature variations (-40℃ to over 300℃), rapid cooling and heating, or humid environments. These issues persist due to differences in temperature between the outer insulating film and the inner heating film, as well as differences in the coefficients of thermal expansion between the heating film and the insulating and adhesive films. Furthermore, separation and bubbles affect the heat transfer of the heating film. The insulation of the bubbles themselves and the separation layer reflect infrared radiation emitted by the heating film at the bubble locations. For heating films that primarily rely on infrared radiation for heating, small bubbles and localized separation can lead to excessively high temperatures, causing burnout. Bubbles and separation at the electrodes can also affect electrode connections, thus impacting product lifespan. Summary of the Invention

[0005] The present invention aims to solve the above-mentioned technical problems and provide a flexible heating film, heating component and heating device that can be used in a humid and cold environment, adapt to instantaneous temperature changes, rapidly increase and decrease temperature, and have the ability to work continuously for a long time in a wide temperature range from "ambient temperature" to 320°C. It is not easy to crack or delaminate, and greatly improves product quality, usage stability and safety.

[0006] To solve the above-mentioned technical problems, the present invention provides a flexible heating film, including a film body, wherein the film body has a plurality of slits along the current direction, and the material of the film body is not removed when the slits are prepared.

[0007] Furthermore, the slit is composed of several strip slits arranged in sequence. In each slit, there is a gap between adjacent strip slits, and multiple slits are arranged in parallel.

[0008] Furthermore, between two adjacent slits, and between three adjacent strip slits, they are arranged in a triangular pattern; in each slit, each strip slit is cut along the same straight line direction.

[0009] Furthermore, the length of the strip slit is a; in each slit, the gap between adjacent strip slits is c; the distance between adjacent slits is b; where a > b, a > c.

[0010] Furthermore, electrodes are provided at both ends of the heating film along the current direction. The electrodes include a silver paste layer and an external conductive layer. The external conductive layer is a copper foil and / or a carbon nanotube film. The silver paste layer is coated on the heating film and cured. The curing conditions can be high temperature curing at 120-200℃ or medium temperature curing at 60-120℃.

[0011] Furthermore, when the external conductive layer is a copper foil, the copper foil and the silver paste layer are connected by high-temperature pressing; when the external conductive layer is a carbon nanotube film, the carbon nanotube film is pressed into the silver paste layer and cured into an integral mesh structure under high temperature (or medium temperature) conditions. This structure reduces the brittleness of the cured silver paste layer and enhances the toughness and strength of the silver paste layer; when the external conductive layer is a copper foil and a carbon nanotube film, the carbon nanotube film is pressed into the silver paste layer and cured into an integral mesh structure under high temperature (or medium temperature) conditions, and the copper foil and the mesh structure are connected by high-temperature pressing.

[0012] Furthermore, the thickness of the copper foil is 5-12 μm, and the thickness of the carbon nanotube film is 5-12 μm; the indentation distance between the copper foil and the edge of the silver paste layer near the heating film is 0.5-5 mm, and the out-of-range distance between the copper foil and the edge of the silver paste layer away from the heating film is 0.5-5 mm.

[0013] A heating element comprising the flexible heating film described in any one of the preceding claims.

[0014] Furthermore, an insulating film is provided on both surfaces of the flexible heating film, an adhesive layer is provided between the flexible heating film and one of the insulating films, and no adhesive layer is provided between the heating area of ​​the flexible heating film and the other insulating film.

[0015] A heating device, employing the heating film described in any one of the above descriptions or the heating component described in the above descriptions.

[0016] The beneficial effects of this invention are:

[0017] 1. Due to the setting of the slits, the overall strength of the heating film itself is reduced, thereby enhancing the conformability of the heating film to the bonded insulating film, making it less likely to separate from the insulating film after integration.

[0018] 2. The slit is opened in the direction of current, which can ensure that the resistance value before and after the slit remains unchanged, thus ensuring the heating efficiency and preventing the power from decreasing due to the slit.

[0019] 3. For the two-layer insulating film, only one layer of the insulating film has an adhesive layer that is bonded to the heating film. Due to the slits set on the heating film, the heating film can generate less tearing force on the adhesive-coated insulating film when the heating film undergoes rapid temperature changes, reducing the chance of cracking. Furthermore, it ensures a good bond between the heating film and the bonded insulating film, making it less prone to cracking. Even under conditions of rapid temperature changes and humidity, the quality can be guaranteed.

[0020] 4. Although the heating film, insulation film, and adhesive layer are made of different materials and have different coefficients of thermal expansion, they are less prone to bubbles and separation between films during long-term use under large temperature differences and in extremely humid environments. This greatly improves the operating temperature of the product and effectively enhances its quality. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the heating film structure with slits of the present invention;

[0022] Figure 2 This is a schematic diagram of the heating film structure of the present invention, which is formed by several strip cuts;

[0023] Figure 3 This is the present invention. Figure 2 Enlarged schematic diagram of the middle section structure;

[0024] Figure 4 This is a schematic diagram of the heating film structure in one embodiment of the present invention;

[0025] Figure 5 This is a schematic diagram of the heating component structure of the present invention;

[0026] Figure 6 This is the invention Figure 5 Enlarged schematic diagram of the middle section structure;

[0027] Figure 7 This is the present invention. Figure 5 A schematic diagram of the explosion structure.

[0028] The labels in the diagram are as follows: 1. Film body; 2. Slit; 3. Strip slit; 4. Lower insulating film; 5. Upper insulating film; 6. Electrode; 7. Silver paste layer; 8. Copper foil. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0030] Reference Figure 1 As shown, one embodiment of the flexible heating film of the present invention includes a film body 1, which is made of PI graphene or aramid graphene film. A slit 2 is formed on the surface of the film body 1 along the current direction, penetrating both surfaces of the film body 1. Since the slit 2 is cut along the current direction, it does not obstruct or minimally obstructs the current flow. Furthermore, when preparing the slit 2, the material of the film body 1 is not removed; only a cutting action is performed. Therefore, the conductivity value is not changed, and the power performance of the structure is maintained or negligible after cutting.

[0031] By setting the slit 2, the overall strength of the heating film itself is reduced, thereby greatly enhancing the conformability of the heating film to the bonded insulating film, making it difficult for the film body 1 and the insulating film to separate at high temperatures and to generate bubbles, thus meeting the requirements for long-term use at working temperatures above 210 degrees Celsius.

[0032] Reference Figure 2 and Figure 3 As shown, the slit 2 is composed of several strip slits 3 arranged in sequence at intervals. The multiple strip slits 3 on the same slit 2 are also consistent with the current direction and are on a straight line, which means that the conduction resistance value will not be changed. After cutting, the power performance of the structure can be guaranteed not to decrease. Furthermore, the adjacent two slits 2 and the three adjacent strip slits 3 are arranged in a triangular shape, that is, the two slits 2 are staggered, which reduces the overall strength of the heating film itself, but does not cause the problem of the whole film being shapeless. It has good integrity, is easy to manufacture, and greatly increases the conformability of the heating film at the bonding position.

[0033] Specifically, in order to better utilize the performance of the strip kerf 3, refer to Figure 2 As shown, the length of the strip slit 3 is defined as 'a'; the distance between adjacent strip slits 3 in each slit 2 is defined as 'c'; the distance between adjacent slits 2 is defined as 'b'. Since the slits 2 are all cut along the current direction, the distance between any position of two adjacent slits is equal; where a > b, a > c, the optimal value range is a: 10-50 mm, b: 2-5 mm, c: 2-5 mm. By using these values, the overall performance of the membrane body 1 after cutting with the strip slits 3 can be guaranteed to be stable, with excellent conformability and good overall strength. Furthermore, it can reduce the number of cuts and improve production efficiency. The position of the aforementioned transverse interval corresponds to the strip slit 3 of the adjacent slits 2 in the longitudinal interval direction.

[0034] In one embodiment, reference is made to Figure 4 As shown, compared with the above embodiment, the flexible heating film has a fan-shaped structure, and the electrode 6 is set on the two arc-shaped sides of the fan-shaped structure. Therefore, the cutting direction of multiple strip cuts 3 on the same cutting slit 2 is consistent, but the orientation of the strip cuts on different cutting slits is inconsistent. The cutting direction of multiple strip cuts 3 on different cutting slits is arranged in the same direction as the current direction, thereby forming a cutting slit. This arrangement can also meet the requirements of improving the conforming performance of the heating film at the bonding position, and will not hinder or greatly hinder the current flow.

[0035] In one embodiment, reference is made to Figures 5 to 7 As shown, a heating component uses the aforementioned flexible heating film as the heating element. The heating film, through its surface slit design, exhibits good deformation-following effect during use, reducing the occurrence of problems such as delamination and bubbles. The heating film is covered by two layers of insulating film to meet the working conditions of the heating element.

[0036] Specifically, to ensure the heating element can withstand long-term use at high power, the design of its two insulating films has been improved. An upper insulating film 5 and a lower insulating film 4 are respectively set on the back and front of the heating film. The upper insulating film 5 and the lower insulating film 4 cover the heating film and are pressed together at high temperature. An adhesive layer is set between the upper insulating film 5 and the heating film or between the lower insulating film 4 and the heating film. That is, only one layer of insulating film is bonded to the heating film, while the other side is attached. This design, combined with the slit design, forms a good means of mitigation. Through single-sided bonding, during the deformation process of thermal expansion and contraction of the insulating film, the heating film is only restrained by a single layer of insulating film, and there is no problem of double-sided force. Therefore, the deformation adaptability of the heating film is improved. In addition, the strip slit 3 of the heating film can further improve the deformation adaptability. And since the strip slit 3 is not a hole, the adhesive will not pass through the strip slit 3 to connect and fix to the other insulating film, thus ensuring that the other insulating film is not connected to the heating element or the corresponding insulating film in the heating area.

[0037] The following results were obtained by comparing existing heating components with the heating component of the present invention through experiments:

[0038]

[0039]

[0040] In the fabrication of the heating element of this invention, the insulating film can be a flexible PI film, and the adhesive used for bonding can be a high-temperature resistant PI adhesive or epoxy adhesive. First, each heating film, insulating film, etc., is cut according to the design dimensions. The outer dimensions of the insulating film are 15mm larger on each side than the heating film. The electrode 6 is made of 7µm thick and 12mm wide copper foil. The silver paste is a high-temperature resistant silver paste, and the adhesive film is a high-temperature resistant silver paste made of thermoplastic material. Of course, the flexible heating film and electrode 6 can be fabricated into independent products or semi-finished products for sale or use. The silver paste layer and external conductive layer of the electrode can be fabricated and connected separately, or they can be fabricated together with the insulating film.

[0041] First, silver paste is printed on the heating film. Then, the heating film and silver paste are sintered together at a temperature above 100 degrees Celsius to form a silver paste layer 7. Subsequently, the heating film is staggered and cut to obtain a heating film with slits 2. Then, the lower insulating film 4, the heating film, the copper foil, and the upper insulating film 5 are positioned and assembled together. Here, the upper insulating film 5 is an adhesive film with only one layer of adhesive. The position of the adhesive film layer is not limited. Here, the lower insulating film 4 with adhesive is used as an example.

[0042] The assembled layered structure is then aligned and placed on the press platform. Under the pressure of the high-temperature press, air is effectively expelled, bonding the adhesive-coated lower insulating film 4 and the heating film together. The non-adhesive-coated upper insulating film 5, foil, and the periphery (non-heating area) of the adhesive-coated lower insulating film 4 are then pressed together. (The overall size of the heating film is smaller than that of the lower insulating film 4 and the upper insulating film 5.) The pressing temperature is above 200 degrees Celsius, and the pressing time is no less than 3 minutes. Lead wires can then be connected: the lead point must be less than 10mm from the edge of the heating film. Once the heating film is manufactured and passes inspection, it can be stored in the warehouse.

[0043] Through the above design improvements, the heating element of the present invention can reach a temperature of about 350 degrees Celsius and can be used for a long time. In order to ensure stability under high temperature working conditions, the electrodes 6 at both ends of the heating film along the current direction have been improved. The electrodes 6 include a silver paste layer 7 and a copper foil 8. The silver paste layer 7 is coated on the heating film and sintered and cured. The copper foil 8 is connected to the silver paste layer 7 by high temperature pressing. During the high temperature pressing process, the air between the copper foil 8 and the silver paste layer 7 is discharged, and the copper foil 8 can be adsorbed with the silver paste layer 7. Under the action of high temperature and pressure, they are combined into one.

[0044] The copper foil 8 here only needs to be 5-12µm thick. This thickness of copper foil 8 meets the conductivity requirements, and because the copper foil is thinner, it has a strong deformation ability, which can improve the bonding effect between the copper foil and the silver paste layer 7.

[0045] Furthermore, in the combined connection design of copper foil 8 and silver paste layer 7, the width of copper foil 8 is f: 3-30mm, and the width of silver paste layer 7 is e: 3-30mm. Both silver paste layer 7 and copper foil 8 are selected with appropriate widths according to the current. The indentation distance between copper foil 8 and the edge of silver paste layer 7 near the heating film is d: 0.5-5mm. Through the indentation design, the edge of copper foil 8 can achieve a better bonding effect with silver paste layer 7 during the pressing process, avoiding problems such as poor power supply or sparks caused by burrs on the edge of copper foil 8. The excess distance between copper foil 8 and the edge of silver paste layer 7 away from the heating film is h: 0.5-5mm. Copper foil 8 can also form an effective connection with upper insulating film 5 and lower insulating film 4, further improving the connection firmness of copper foil 8.

[0046] In one embodiment, the copper foil can be replaced with a carbon nanotube film to achieve the conductive function. Specifically, the carbon nanotube film is disposed in the silver paste layer 7 and solidified into an integral mesh structure, with a thickness of 5-12 mm.

[0047] In one embodiment, a practical carbon nanotube membrane can also be used in conjunction with copper foil. Specifically, the preparation process differs from the above embodiments in that:

[0048] First, silver paste is printed onto the heating film. Then, a carbon nanotube film is placed on the silver paste and pressure is applied to the carbon nanotube film, causing the silver paste to permeate out of the carbon nanotube film. Finally, the heating film, silver paste, and carbon nanotube film are cured together, forming a network structure. This structure improves the toughness and strength of the silver paste layer 7. Since the cured silver paste layer 7 is generally brittle, it is prone to cracking during use, which affects the use of the electrode 6. However, with the carbon nanotube film, firstly, the toughness and strength are improved, and the cracking problem of the silver paste layer 7 is greatly reduced. Secondly, it can also provide a conductive connection after the silver paste layer 7 cracks, ensuring the integrity of the overall structural pathway.

[0049] In one embodiment, the present invention also discloses a heating device that uses any of the above-mentioned heating films or heating components, has a wide operating temperature range, stable and reliable performance, long service life, and good safety performance.

[0050] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A heating element, characterized in that, Including flexible heating films; The flexible heating film includes a film body, and the film body has a plurality of slits along the current direction. When preparing the slits, the material of the film body is not removed. An insulating film is provided on both surfaces of the flexible heating film, and an adhesive layer is provided between the flexible heating film and one of the insulating films. No adhesive layer is provided between the heating area of ​​the flexible heating film and the other insulating film. The operating temperature of the heating element is 210℃-350℃.

2. The heating component as described in claim 1, characterized in that, The slit is composed of several strip slits arranged in sequence. In each slit, there is a gap between adjacent strip slits, and the slits are arranged in the same direction as the current direction.

3. The heating component as described in claim 2, characterized in that, Between two adjacent slits, and three adjacent strip slits are arranged in a triangular pattern; in each slit, each strip slit is cut along the same straight line direction.

4. The heating component as described in claim 3, characterized in that, The length of the strip cut is a; the gap between adjacent strip cuts in each cut is c; the distance between adjacent cuts is b; where a > b, a > c.

5. The heating component as described in claim 1, characterized in that, The heating film has electrodes at both ends along the current direction. Each electrode includes a silver paste layer and an external conductive layer. The external conductive layer is a copper foil and / or a carbon nanotube film. The silver paste layer is coated on the heating film and cured.

6. The heating component as described in claim 5, characterized in that, When the external conductive layer is a copper foil, the copper foil and the silver paste layer are connected by high-temperature pressing; when the external conductive layer is a carbon nanotube film, the carbon nanotube film is pressed into the silver paste layer and solidified into an integral mesh structure; when the external conductive layer is a copper foil and a carbon nanotube film, the carbon nanotube film is pressed into the silver paste layer and solidified into an integral mesh structure, and the copper foil and the mesh structure are connected by high-temperature pressing.

7. The heating component as described in claim 5, characterized in that, The thickness of the copper foil is 5-12 μm, and the thickness of the carbon nanotube film is 5-12 μm; the indentation distance between the copper foil and the edge of the silver paste layer near the heating film is 0.5-5 mm, and the out-of-range distance between the copper foil and the edge of the silver paste layer away from the heating film is 0.5-5 mm.

8. A heating device, characterized in that, The heating element described in any one of claims 1-7 is used.

Images