JP3083617B2 - Transparent sheet heating element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent sheet heating element, and more particularly to a heater for a liquid crystal device.

[0002]

2. Description of the Related Art The operating characteristics of a liquid crystal element are greatly affected by the environmental temperature in which it is installed. When the temperature decreases, for example, when the temperature becomes 0 ° C. or less, the response speed decreases,
If the temperature is lower than -30 ° C, practical problems will be caused.

[0003] For example, it is desired that a device used as various displays of an automobile or the like operates normally even at a low temperature.

Conventionally, a method of heating a liquid crystal element used in such an environment by arranging a grid-like or frame-shaped heating resistor in the periphery has been proposed. In this method, the entire liquid crystal element is made uniform. However, arranging an opaque heating element hinders the display of the liquid crystal element, and also has disadvantages such as a reduction in the display area.

Therefore, the present inventors have proposed a method in which electrodes are provided at both ends of a transparent conductive thin film previously laminated on a transparent substrate, and a voltage is applied between the electrodes.

[0006]

According to the method proposed by the present inventors, heating can be performed uniformly over the entire liquid crystal element, but the following problems occur.

When the applied power applied to the transparent sheet heating element is large, the sheet heating element becomes high temperature and damages the heating element itself, and in some cases, even the liquid crystal element may be damaged. It is conceivable to attach a temperature control mechanism to the sheet heating element or the liquid crystal element, but this is not a preferable method because it causes a cost increase. In addition, if the applied power is reduced, the liquid crystal element itself cannot be sufficiently heated, or a long time is required for heating, which hinders the start of the automobile.

As described above, the applied voltage and the applied power are important for heating the liquid crystal element, and the surface resistance of the transparent conductive thin film is also an important factor in view of the above. The lower the surface resistance is, the more preferable the planar heating element is. However, if the transparent conductive thin film layer is designed to have a low resistance value, the visible light transmittance of the planar heating element is reduced, and the The transmittance is reduced, and therefore, it is necessary to increase the luminance of the backlight, which is not preferable in terms of the life of the backlight, and has a problem such as an increase in power consumption.

[0009]

[Means for Solving the Problems] As a result of intensive research to solve the above problems, electrodes are provided at both ends of a transparent conductive thin film laminated on a transparent substrate, and a voltage is applied to the electrodes. And (A) the transparent conductive thin film laminated on a transparent substrate has a surface resistance of R (Ω / □) and the thickness of the transparent conductive thin film is t (angstrom), log t = −0.011R + 2.065 when 10 ≦ R ≦ 30 Expression (1) log t = −0.011R + 2 .360 (2) expression 1 ≦ R ≦ 10 log t = −0.043R + 2.386 (3) expression log t = −0.043R + 2.643 (4) expression and R = 30 (5) expression R = 1 (1) in the equation (6) , (2), (3), (4), (5), and (6), and the parallel light transmittance T (%) measured at a wavelength of 550 nm is t ≧ − 8T + 690 (7) Expression (7) that satisfies the expression (7), and (B) a voltage V (V) applied to both ends of the transparent conductive thin film by the method defined in the main text and an applied power P The relationship with (W / cm ² · second) is expressed by log P = −0.037V + 2.703 (8) and log P = −0.037V + 0.546 (9). It has been found that a transparent sheet heating element within the range enclosed by the expression (3) may be used.

FIG. 1 is a sectional view of a transparent sheet heating element as an example of the present invention.

For the transparent substrate 1 used in the present invention, a conventionally known polymer resin can be used in addition to a polyester resin, a polynaphthalate resin, a polyamide resin, a polyimide resin, an acrylate resin, and a polycarbonate resin. Any shape may be used. From the viewpoint of the following electrode processing, protective layer processing, further processing such as bonding to a polarizing plate, lightness and impact resistance, a film-like polymer resin having a thickness of 50 to 500 μm is used. Particularly, a thickness of 75 to 180 μm is preferable.

The adhesive layer 3 of the present invention comprises a conventionally known adhesive,
Although any pressure-sensitive adhesive can be used, an acrylate-based pressure-sensitive adhesive is preferably used in view of processability to the transparent substrate, bonding to a polarizing plate 11 described later, and durability.

Although the thickness of the adhesive layer 3 is not particularly limited, it is usually 5 to 100 μm, and usually 10 to 70 μm. The adhesive layer 3 may be processed into the transparent substrate 1 in advance, and then the transparent conductive thin film 2 may be processed. Alternatively, the transparent conductive thin film 2 may be once processed into the transparent substrate 1 and then processed into another surface. it can. Particularly in the latter case, a high quality transparent conductive thin film 2 can be obtained.

After processing the transparent substrate 9, the transparent conductive thin film 2, the transparent insulating layer 4, the electrode and the transparent film 9 having the adhesive layer 8, the adhesive layer 3 may be processed. In particular, in this case, as described above, compared to the case where the adhesive layer 3 has been previously processed, the adhesive is cut into powder during the subsequent processing and handling, and the adhesive is mixed into the respective layers due to the protrusion of the adhesive in the processing step. Can be removed, so that a transparent sheet heater can be obtained with higher yield. When this processing method is employed, it is preferable to appropriately process an anti-occurrence layer on the back surface of the transparent substrate 1 in advance in order to prevent generation of scratches or oligomers on the transparent substrate 1 in the processing step.

It is convenient to use a metal thin film as the transparent conductive thin film 2 in the present invention. The metal thin film is, for example, A
There are g, Au, Cu, Ni, Al, and Cr, and one or an alloy selected from the group of Ag, Au, and Cu is particularly preferably used in terms of transparency and electrical characteristics.

The thickness t (angstrom) of the transparent conductive thin film is log t = −0.011R + 2.065 when 10 ≦ R ≦ 30 in relation to the surface resistance R (Ω / □) of the transparent conductive thin film. Expression (1) log t = −0.011R + 2.360 Expression (2) When 1 ≦ R ≦ 10 log t = −0.043R + 2.386 Expression (3) log t = −0.043R + 2.643 ( 4) Formula and R = 30 Formula (5) Formula R = 1 Formula (6) Formula (1), (2), (3), (4), (5), and the range encompassed by Formula (6) And in a state where the transparent conductive thin film 2 is laminated on the transparent substrate 1, the parallel light transmittance T (%) at a wavelength of 550 nm is selected so as to satisfy t ≧ −8T + 690 (7) .

Usually, in order to satisfy the expression (7), a high-refractive-index dielectric thin film, for example, TiO ₂ , ITO, In ₂ O ₃ , ZnO or the like is laminated on one or both sides of the metal thin film. Often preferred.

If the above formulas (1) to (7) are exceeded, it becomes difficult to develop transparency, electrical characteristics, and the like as a transparent sheet heating element. The performance as a transparent sheet heating element can be provided only within the above range.

These thin films are formed on the transparent substrate 1 by a conventionally known method.

The transparent insulating layer 4 in the present invention may or may not be provided, but is preferably provided. In this case, a conventionally known thermosetting or ultraviolet curing resin is used. Any resin may be used as long as it is transparent. However, from the viewpoint of durability, a resin having a low halogen element content is preferable.
m, particularly preferably 100 ppm or less. Transparent insulating layer 4
Is provided by a conventionally known printing method, coating method, or the like, and has a thickness of 2 to 50 μm, particularly 5 to 30 μm.

The electrodes 10 in the method of the present invention are formed at both ends (both ends in terms of an electric circuit) of the transparent conductive thin film 2.

The (conductive) resin 5 is formed on the transparent conductive thin film 2 by a conventionally known method, for example, a printing method or a coating method. The conductive resin layer 5 is usually made of silver powder, gold powder, carbon powder,
Any mixture of other metal powders and resins such as vinyl, phenol, epoxy and polyamide resins can be used. In particular, a mixture of silver powder and the above-mentioned resin system is preferably used from the viewpoint of conductivity as an electrode. The film thickness is 2 to 20 μm, usually 5 to 20 μm, as a film thickness after firing.

According to the method of the present invention, a conductive metal foil or a conductive metal wire 6 having an (insulating) adhesive layer is provided on the (conductive) resin layer 5. The conductive metal foil or wire 6 is made of copper, silver,
Although any of gold and other metal foils can be used, copper foil is usually sufficient, and a film thickness of 5 to 50 μm is usually used, but the conductive metal foil 6 is processed on the (conductive) resin layer 5. The thickness of the conductive metal foil 6 is set to 15 to 50 μm in order to facilitate the processability of the conductive resin layer 7 and the processability of the transparent film 9 and avoid appearance defects such as entrapment of bubbles.
m is preferably used.

The (insulating) adhesive layer provided on the conductive metal foil 6 usually has a thickness of 5 to 10 in terms of workability.
A pressure-sensitive adhesive having a thickness of 0 μm is provided. In particular, the adhesive strength to the (conductive) resin layer 5 and the overall thickness of the electrode portion 10 and the prevention of air bubble entrapment after processing the transparent film 9, etc.
60 μm is preferably used. The insulating adhesive layer is excellent in workability because the cost can be reduced in comparison with the conductive adhesive, and the thickness of the entire electrode portion can be reduced as described above. .

In a preferred embodiment of the present invention, one or two conductive resin layers 7 are processed on the conductive metal foil 6 so as to cover the entirety of the conductive metal foil 6. The conductive resin layer 7 may use the same material as the above-described conductive resin layer 5 or may use a different material described above. The film thickness per layer is 2 to 20 μm after firing, preferably 5 to 20 μm. In one-layer processing, the conductive resin layer may not be easily mounted on the end of the conductive metal foil.
Layer processing is preferred.

In the present invention, if necessary, a transparent film 9 having an adhesive layer 8 is provided on the above-mentioned structure by a conventionally known method, for example, a method such as lamination. The thickness of the adhesive layer 8 is not particularly limited, and a thickness of 5 to 100 μm, particularly 10 to 70 μm, of the same kind as the adhesive layer 3 is usually used. The transparent film 9 is made of the same kind of material as the transparent substrate 1 described above, and usually has a thickness of 1 to 100 μm, particularly preferably 5 to 50 μm.

The transparent sheet heating element 15 obtained as described above
Are the polarizing plate 11, the liquid crystal element 12, and the polarizing plate 1 in advance.
3 and then used by crimping.

Although the present invention has been described by way of example in which the adhesive layer 3 is laminated on the transparent substrate 1 side, the adhesive layer 3 is laminated on the transparent insulating layer 4 side and pressed against the polarizing plate 11 by pressing. Can also be used.

In the present invention, as described above, the obtained transparent sheet heating element is used by being laminated on the polarizing plate 11, the liquid crystal element 12, and the polarizing plate 13, and the voltage applied to the transparent sheet heating element is determined. The applied power is performed in the following range.

The applied voltage V (V) and applied power P (W / cm ² · second) to the transparent sheet heating element in the method of the present invention are as follows: electrodes are formed on a sheet glass of dimensions 110 × 110 mm square and 3 mm thick; When the transparent surface heating element 15 having an effective conductive surface of 100 × 100 mm square manufactured as described above is pasted through the adhesive layer 3 and is performed under room temperature conditions, log P = −0.037V + 2.703. 8) and log P = −0.037V + 0.546 (9) Equation (8) is selected so as to fall within the range enclosed by the equations (8) and (9). Preferably, log P = −0.037V + 2.590 (10) and log P = −0.037V + 1.532 (11) The range enclosed by the expressions (10) and (11).

The sheet glass having the above-mentioned dimensions and thickness is very similar to the dimensions and thickness of a normal liquid crystal element for a vehicle, and the same is true of the transparent sheet heating element. It is close.

When the value exceeds the expression (8), the surface temperature of the transparent sheet heating element exceeds 100 ° C., and the transparent sheet heating element itself is broken. In particular, when the transparent conductive thin film of the transparent sheet heating element has minute scratches and defects, and when the electrode portion has minute defects, it often occurs. Further, undesired problems such as breakage of the liquid crystal element itself and deterioration of the polarizing plate due to the high temperature occur. The present invention (8)
This is preferable within the range of the formula, since the occurrence is eliminated.

On the other hand, when the value is less than the expression (1) of the present invention, the surface temperature of the transparent sheet-like heating element becomes low, for example, the temperature rise (= surface temperature−room temperature) becomes 10 ° C. or less. For example, when the vehicle temperature is low, the rise of the liquid crystal element is delayed, which causes a problem that it takes time for the liquid crystal element to normally operate.

Therefore, the present invention is set within the scope of the present invention in terms of the constituent materials such as the liquid crystal element, the transparent sheet heating element and the polarizing plate, and the operation of the liquid crystal element.

Next, examples will be shown, but the present invention is not limited to these examples.

[0036]

Example 1 A TiO ₂ thin film was formed on a polyester film 125 μm by sputtering at a vacuum of 1.5 × 10 ⁻³ Torr at 200 Å, and then at a vacuum of 2.0 × 10 ⁻³ Torr, an Ag thin film of 120 Å. And then deposit the TiO ₂ thin film at a vacuum of 1.5
A transparent conductive film was obtained by laminating at 10 ^-3 Torr. The parallel light transmittance is 80% at a wavelength of 550 nm.
And the surface resistance was 10.0 Ω / □.

Next, an acrylate-based pressure-sensitive adhesive of 40 μm was processed on the rear surface of the transparent conductive film to obtain a transparent conductive film with an adhesive.

The above transparent conductive film is 100 mm × 1
Acrylic transparent insulating layer (manufactured by Teikoku Ink Co., Ltd., manufactured by Teikoku Ink Co., Ltd.)
(4440) was screen-printed so as to have a width of 50 mm and a film thickness of 10 μm, and then was solidified by irradiation with ultraviolet light.

Thereafter, an Ag paste was printed on both ends in a width of 5 mm with a thickness of 10 μm (converted to a thickness after drying),
For 30 minutes to obtain a first conductive resin layer. Subsequently, the acrylate-based adhesive layer 20 having a width of 2 mm and a length of 120 mm was used.
A copper foil having a thickness of 30 μm and a thickness of 30 μm was stuck on the conductive resin of the first layer, and an Ag paste was further printed thereon in a width of 5 mm in exactly the same manner as the first layer and dried.

Further, a protective film having a thickness of 25 μm and a polyester film having an acrylate-based pressure-sensitive adhesive (film thickness of 20 μm) was laminated on the above-mentioned structure so as to cover the entire surface to obtain a transparent sheet heater. The visible light transmittance of the heater thus obtained was 81% and 10%.
Ω / □.

This heater is a 3 × 110 mm × 110 mm square.
When bonded to a plate glass having a thickness of mm and energized at a voltage of 24 V for 1.5 hours at a room temperature of 25 ° C., the surface temperature of the heater increased by 80 ° C. as a temperature difference from the measured room temperature. The applied power at that time was 50 W / cm ² · second.

[0042]

Examples 2, 3, and 4 A heater was manufactured in exactly the same manner as in Example 1 except that the thickness of the Ag thin film was changed to 90, 200, and 200 angstroms. 1

[0043]

Comparative Example 1 On a polyester film 125 μm,
The degree of vacuum is 3.0 × 10 ⁻³ To by a sputtering method.
A heater manufactured in exactly the same manner as in Example 1 except that an Au thin film of 150 Å was laminated under rr was used.
Was evaluated in the same way as The results are shown in Table 1.

As for the characteristics of the transparent conductive film on which the Au thin film was laminated, the surface resistance was within the range of the present invention, but the transparency was as low as 60%, which was below the range of the present invention.

[0045]

Comparative Examples 2, 3, and 4 Table 1 shows the results of evaluating heaters manufactured in exactly the same manner as in Examples 3 and 4 in the same manner as in Example 1.

In Comparative Example 2, the heater bonded to the plate glass was broken due to the high temperature and could not be energized. In Comparative Example 3, not only the heater was broken, but also the sheet glass was broken due to heat.

[0047]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a conceptual sectional view of a transparent sheet heater according to the present invention.

FIG. 2 is a conceptual cross-sectional view when used in combination with a liquid crystal element.

FIG. 3 is a conceptual diagram showing a range of a film thickness and a surface resistance of a transparent conductive thin film according to the present invention.

FIG. 4 is a conceptual diagram showing a range of transmittance of a transparent conductive film in which a transparent conductive thin film is laminated according to the present invention.

FIG. 5 is a conceptual diagram showing a range of applied voltage and applied power of a transparent sheet heating element according to the present invention.

[Description of Signs] 1 Transparent substrate 2 Transparent conductive thin film 3,8 Adhesive layer 4 Transparent insulating layer 5,7 Conductive resin layer 6 Conductive metal foil with insulating adhesive layer 9 Transparent film 10 Electrode 11,13 Polarizing plate 12 Liquid crystal element 14 Backlight

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Showa 61-13494 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05B 3/20 G02F 1/133

Claims (1)

(57) [Claims] 1. A transparent surface in which electrodes are provided at both ends of a transparent conductive thin film laminated on a transparent substrate, and a voltage is applied to the electrodes to generate heat in the transparent conductive thin film between the electrodes. (A) The transparent conductive thin film is laminated on a transparent substrate, the surface resistance of the transparent conductive thin film is R (Ω / □), and the thickness of the transparent conductive thin film is t (angstrom). When 10 ≦ R ≦ 30, log t = −0.011R + 2.065 (1) Expression log t = −0.011R + 2.360 (2) Expression 1 ≦ R ≦ 10 log t = − 0.043R + 2.386 (3) Expression log t = −0.043R + 2.643 (4) Expression and R = 30 (5) Expression R = 1 (6) Expressions (1), (2), The range encompassed by equations (3), (4), (5), and (6) And the parallel light transmittance T (%) measured at a wavelength of 550 nm satisfies the expression (7) of t ≧ −8T + 690 (7), and is defined as (B) in the text. The relationship between the voltage V (V) applied to both ends of the transparent conductive thin film by the above method and the applied power P (W / cm ² · second) is expressed by log P = −0.037 V + 2.703 (8) A transparent sheet heating element characterized by the following formula: log P = −0.037V + 0.546 (9) Formula (8) and (9).