JPS6324313B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a planar heating element used in portable hair dyes and other devices that use a storage battery as a power source.

Most conventional hair beauty devices, such as hair curlers, cannot be used where there is no power source.
It was large in size and there was no portable version. Many women experience the need to curl their hair on the go, as the curling effect of their hair diminishes over time. For this reason, there has been an extremely high need for a portable hair curler that is small and lightweight and can be easily curled. The reason why there have been no portable hair curlers is that there were problems with the battery, heater, and structure, and it was not possible to construct a hair curler with an optimal combination.
Under conditions where the power source is a storage battery and only limited power can be extracted, the most important point in product design is the optimal matching of each component, and a design that seeks to optimize this is necessary. .

The biggest problem in constructing a hair curler that uses a storage battery as a power source is how to ensure the usable time per charge of the battery. If you're just doing a simple hairstyle on the go, it will take 30 to 60 seconds to curl each curl, and if you curl 10 spots in total, you'll need at least a battery capacity of 5 to 10 minutes. The power consumed during this time is the sum of the power required for the hair curler's own temperature to reach a curling temperature and the amount of heat radiated from the heater itself, so the heater part has a small heat capacity and the temperature rises quickly. It is necessary to suppress excess heat dissipation due to the rise in the temperature. Furthermore, in order to suppress heat dissipation during curling, it is necessary to configure the hair to the minimum required size and shape, and to configure the heater to be a direct heating type that has good heat transfer efficiency to the hair. From this point of view, it is necessary to combine the best battery with a heater section designed to have an optimal configuration. Nickel-cadmium batteries are common batteries that can withstand large loads, and there are currently no better ones than these, so it is necessary to select and use the one with the optimal size, shape, and electrical capacity. It won't happen. The criteria for selecting batteries is that if space is limited, it is advantageous to use several large batteries in terms of capacity, but since the voltage when connected in series is proportional to the number, As the resistance decreases, the resistance of the heater also needs to be lowered.

The second design issue is temperature control of heater temperature settings. The minimum temperature required for curling is 60℃
The maximum temperature without damaging hair is said to be 80°C, but a technical means is needed to accurately control the temperature of the heater within this temperature range. In terms of ease of use, it reaches 60℃ instantly, and the saturation temperature is
It is required to have the ability to maintain a temperature of 60 to 80°C at 80°C or lower, even during curling, regardless of whether the hair is in contact or not. It is not easy to configure temperature control with a quick response that can be applied to such applications, but if a positive resistance temperature coefficient sheet heating element that has such temperature controllability is used in the heater itself, the above temperature range can be achieved. If so, sufficient performance can be obtained. Positive resistance temperature coefficient sheet heaters can be made from a mixture of crystalline resin and conductive material fine powder, and this principle is based on the rapid expansion of the crystalline resin at its crystal transformation point, which causes the electric current between the conductive material fine powders to increase. It is believed that the bond is lost and the resistance value increases rapidly. The kneaded material itself has insufficient heat soaking effect and rigidity, and fine adjustment of the resistance value during mass production is not easy. Therefore, this kneaded material is made into a paste using an appropriate binder and solvent, and this is made into a paste with a heat soaking effect. A method of coating or printing and drying on a substrate with good quality is required. The crystalline resin is ethylene-vinyl acetate copolymer, which has a crystal transformation point of around 90°C.
A characteristic is obtained in which the resistance value increases rapidly at around 80°C. Note that polyethylene, nylon, etc. can also be used.

The third structural issue is to manufacture a positive resistance temperature coefficient sheet heater that can generate heat using the output voltage of the battery.

Regarding the output voltage of batteries, as mentioned above, it is advantageous in terms of capacity to use large batteries and a small number of batteries.
I want to set the voltage as low as possible. However, as is clear from the principle of the heater, it is necessary to suppress the blending ratio of the conductive material fine powder to a level that can change the resistance to high at high temperatures, so it is impossible to achieve an extremely low resistance. As a result of studying how to reduce the resistance value, we found that by changing the blending ratio of ethylene vinyl acetate copolymer and furnace carbon black to 40:60, 35:65, and 30:70, the temperature coefficient of resistance decreased and the minimum required value was achieved. It was found that 35:65 is the limit for satisfying the temperature coefficient of resistance of 0.05℃ ^-1 at 70 to 80℃. In this case, the lower limit of the resistance value at room temperature was 200Ω/□ even though the coating thickness was 300μ. 200
Ω/□ is a considerably high resistance considering that the output voltage per battery is 1.2V. In order to obtain an output of about 10W immediately after the heater starts energizing, the resistance must be 0.14Ω for 1.2V and 0.58Ω for 2.4V, which is a 3- to 4-digit reduction in resistance compared to the sheet resistance value of the heater material. Is required. In order to achieve a resistance reduction of 3 to 4 orders of magnitude, drastic measures are required, which is impossible within the scope of normal thinking.

As a result of trying to construct ultra-fine comb-shaped electrodes that go beyond common sense in order to achieve low resistance, we found that various relationships were clearly established depending on the sheet resistance of the electrode material itself, the electrode pattern, the dimensions of the heater, etc. Summer. First, regarding the selection of electrode materials, in the process of manufacturing a positive resistance temperature coefficient sheet heater, the substrate must initially be a flat plate because the resistance paste is applied, printed, and dried. Next, there is a step of winding the hair to a diameter of 10-20 mm to directly form the curl part. Therefore, the materials constituting the heater, including the electrodes, must have sufficient flexibility, and in particular, the electrode portions that handle large currents must have sufficient flexibility. As the flexible substrate, a laminate plate of a polyester film and an aluminum plate is used because it has excellent heat uniformity, heat capacity, electrical insulation, heat shrinkage resistance, etc. The electrode material must be able to be constructed on a polyester film, be flexible, have good construction precision, and have low resistance. There are only a few electrode materials that meet this condition, and only a specially formulated epoxy binder silver paste can be used. These silver pastes must be of a type in which the silver content is increased to the limit of printability, and the amount of flexibility imparting agent added is increased to the limit that does not impede curability. As a result of attempts to lower the resistance of the silver paste, it was found that a silver powder content ratio of 80% was the limit for printability, and a coating thickness of 50μ was the limit from the viewpoint of precision and flexibility. Resistance value is 70% silver content
It was 0.3Ω/□ at 75%, 0.1Ω at 80%, and 0.04Ω at 80%. The resistance value of silver paste is limited to 0.04Ω/□, so even wiring with an aspect ratio of 1:10 will reduce the resistance to 0.4Ω.
It was found that even if a heater of the size required for curling was constructed from extremely fine comb-shaped electrodes, low resistance could not be easily obtained due to the resistance value of the electrodes themselves.

Next, regarding the electrode pattern that achieves low resistance, the important dimensions in the design of the ultrafine comb-shaped electrode are:
These are the electrode spacing, the width-to-length ratio of the comb portion of the electrode, and the width-to-length ratio of the comb root portion, which determines the overall length of the heater. The electrode spacing mainly affects the power density of the resistor,
It is thought that the ratio of the width and length of each electrode part mainly affects the resistance value, but if the balance between the two is not properly adjusted, the power density of the resistor is high, but the area ratio occupied by the electrode part is high, making it difficult to use as a heater. There may be cases where the temperature of the electrode does not rise, or where the resistance value of the resistor becomes extremely low relative to the resistance value of the electrode, and a positive temperature coefficient of resistance cannot be obtained as a combined resistance. Additionally, there is a limit to the dimensions of the heater, and if the dimensions are expanded in the comb direction, the resistance of the comb increases and the voltage applied to the resistor decreases.As a countermeasure, the width of the comb is increased. When expanded, the area ratio of the effective heat generating portion of the heater becomes smaller, and in either case, the temperature decreases. Increasing the number of elements in the comb portion increases the resistance at the base of the electrode comb, and as a countermeasure to this, increasing the width of the wiring portion increases the heat dissipation area and lowers the temperature. There seems to be no basic countermeasure other than lowering the resistance value of the electrode material itself, but the lower limit of silver paste that can currently be produced is 0.04Ω/□, so there is currently a limit to the size of the heater.

From the above-mentioned viewpoint, we experimentally investigated the optimum dimensions and shape, and obtained the results shown in FIG. 2 for the heater shown in FIG. 1. As is clear from Figure 2, the voltage
For 2.4V, the electrode width is 1.0mm or less and the electrode spacing is 0.5mm.
If the temperature is below, a heater with a temperature of around 80°C can be obtained by the optimum combination. The dimensions of the effective heat generating part of the heater actually used were 50 mm x 40 mm, and the heater dimensions were 60 mm.
×60 mm, but this was rolled into a 16 mm cylindrical shape and used. The power when saturated at 80℃ is about 3W, so if you use a 600mAh battery at 2.4V, you can use it for about 30 minutes.

As another design issue, we will discuss the relationship with the temperature coefficient of resistance of the heater. The value of the temperature coefficient of positive resistance of a heater is very important as it affects the temperature stability of the heater, but it is important to clarify these relationships because it is closely related to the voltage and electrode pattern of the battery used. It is necessary to Figure 3 shows the results of examining the relationship between the average temperature coefficient of resistance, voltage, and saturation temperature between 70 and 80°C with the electrode pattern fixed. Battery voltage is 1.2V in terms of capacity.
2.4V is most desirable, but if there is sufficient capacity, it is also possible to prioritize the voltage and set it to 3.6V or 4.8V. Including that case, this heater has an average resistance temperature coefficient of 0.05-0.20 at 70-80℃
It is applicable to ℃ ^-1 . The temperature coefficient of resistance is
If it is 0.05℃ ^-1 or more, practically sufficient temperature controllability can be obtained, so it can be said that the necessary range is sufficiently covered.

Next, the embodiment will be explained based on FIGS. 4 to 6.

Figure 4 shows a planar heating element according to an embodiment of the present invention, where 1 is a 0.2 mm aluminum plate, 2 and 2' are 25μ
The electrical insulating layer 3 is made by laminating polyester film on both sides of the aluminum plate 1 with hot melt adhesive, the electrode spacing B is 0.4 mm, and the width A of the comb part
The electrode is 0.6 mm long, the length C of the comb part is 45 mm, the width D of the base of the comb is 5 mm, the length is 50 mm, the number of comb parts is 50, and the dimensions of the aluminum plate 1 are 60 mm x 60 mm. The material for electrode 3 is a binder made of a 1:1 ratio of hardening epoxy and flexible epoxy, and 80% silver powder.
% of low resistance silver paste.

Fig. 5 shows the appearance of a hair curler incorporating a 2.4V positive resistance temperature coefficient sheet heating element, and 4 is the heater shown in Fig. 4, which is wrapped around a base material and has a cylindrical shape. Reference numeral 5 indicates a clip for holding hair between the heater 4, 6 indicates two nickel cadmium batteries provided in the main body 7, 8 indicates a push button for opening and closing the clip 5, and 9 indicates a switch.

Figure 6 shows the silver electrode shown in Figure 4 mixed with a mixture of ethylene vinyl acetate copolymer and furnace carbon black in a ratio of 40:60, ethylene propylene rubber as a binder, and a high boiling point solvent ( FIG. 4 is a diagram showing the positive resistance temperature coefficient of a heater printed and baked with a resistance paste made by grinding it with (for example, tetrahydronaphthalene).
Average resistance temperature coefficient from 70 to 80℃ is 2.4V at 0.08℃ ^-1
A saturation temperature of 80°C can be obtained when applied.

Such a hair curler allows hair to be wrapped directly around the heater 4 and then held between the clips 5 and curled. The battery 6 is charged using a separately provided charger.

As described above, although the present invention has excellent performance, it has a high resistance and was thought to be unsuitable as a battery load. Due to the extreme design of the pattern and temperature coefficient of resistance, it can be applied to voltages as low as 1.2V, and the development of this heater made it possible to create portable hair curlers and other devices for the first time.

[Brief explanation of the drawing]

Figure 1 is a plan view of the comb-shaped electrode, Figure 2 is a characteristic diagram showing the relationship between electrode spacing, width, and heater saturation temperature.
Fig. 3 is a characteristic diagram showing the relationship between heater characteristics, voltage, and saturation temperature, Fig. 4 A and B are plan views and cross-sectional views showing an example of the substrate that constitutes the electrode, and Fig. 5 is a 2.4V
FIG. 6 is a side view showing the appearance of a hair curler incorporating a 2.4V heater, and FIG. 6 is a characteristic diagram showing the relationship between resistance and temperature of an example of a 2.4V heater. 1... Substrate (aluminum plate), 2, 2'... Electric insulating layer, 3... Electrode, 4... Heater.

Claims (1)

[Claims] 1 An aluminum plate with polyester film laminated on both sides is used as a substrate.A comb-shaped electrode is provided on this substrate by applying and drying silver paste, and then conductive carbon black and crystalline resin or its The comb-shaped electrodes are constructed by applying and drying a heating element material made into a paste by adding a binder and a solvent to a mixture kneaded with a copolymer resin.
1.0mm or less, average resistance temperature coefficient of 0.05 from 70 to 80℃
A sheet heating element for hair beauty equipment characterized by a temperature of ~0.2°C ^-1 .