JPH0593903A - Panel heater - Google Patents

Abstract

PURPOSE:To lessen the adverse influence of heater mounting on the image quality of a display device and to obtain the desired heat generation distribution by forming band-shaped electrode patterns in parallel in a band shape and selectively executing the connection with electrodes for voltage impression. CONSTITUTION:Plural pieces of the band-shaped electrodes 2 consisting of transparent conductive thin films to constitute heating sources are formed in parallel on a substrate 1 consisting of a transparent insulating material and the low-resistance electrodes 3 for voltage impression are connected to both ends of the band-shaped electrodes 2. The connecting parts of the band-shaped electrodes 2 of the parts where the generation of the heat within the plane of the heater is desired to be relatively lessened and the electrodes 3 for voltage impression are not connected so as not to contact each other. The control of the distribution of generated energy can be adjusted by the number of the patterns which are not connected according to need. Then, the desired heat generation distribution is obtd. by selectively connecting the band-shaped electrodes 2 for heat generation and the electrodes 3 for voltage impression.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Various types of planar heaters are known according to the application. For example, as a heater used for temperature control of a liquid crystal display cell of a liquid crystal display device, an insulating material such as glass is used. A simple method is known in which a transparent conductive thin film is formed on a transparent substrate to uniformly cover the surface of the substrate, and electricity is applied to the transparent conductive thin film to generate heat.

In addition, in order to control the heat generation distribution, a method of making the film thickness of a specific region of the conductive thin film relatively thin and a method of forming a specific pattern are used.

[0004]

However, in the case of a transparent planar heater used for temperature control of a transmissive liquid crystal display device, it is extremely difficult to change the thickness of the heating element due to the problem of visibility in the display area. This leads to a reduction in the uniformity of the displayed screen, and increasing the film thickness has many problems such as a decrease in the transmittance, making it difficult to obtain the desired heat generation distribution.

As one of the methods for solving this problem, there is a method in which the shape of the conductive thin film is made into a specific pattern shape to obtain a desired heat generation distribution. However, when such a method is used, for example, when the pattern width or shape of the conductive transparent electrode of the planar heater is changed in the display screen of the liquid crystal display device,
The light transmittance changes depending on the pattern part and the color changes, or the transparent electrode pattern of the planar heater and the transparent electrode of the liquid crystal panel interfere and a striped pattern is seen. There is a problem that the liquid crystal display becomes unsightly and the shape and size of the pattern are restricted from the viewpoint of image quality, and a desired heat generation distribution cannot be obtained.

Further, in manufacturing this planar heater, for example, ITO (Indium-Tin-Oxide) is used.
It is very difficult to form a transparent conductive film like that on an insulating transparent substrate such as glass so that the sheet resistance value of the transparent conductive film becomes constant. When a pattern is formed, the variation of the total heater resistance value of the finished sheet heater becomes very large (for example ± 50%), and it is not suitable for actual use as it is. For example, it is very difficult to control when forming a transparent conductive film. There has been a problem that the yield value is extremely deteriorated because the resistance value of the finished sheet heater needs to be selected and used strictly.

The present invention solves the above problems of the prior art,
Provide a planar heater that minimizes the adverse effects on the image quality of the display device due to the mounting of a heater, and also provides a sheet heater that produces a desired heat distribution, and the sheet resistance variation during film formation of the conductive film when creating the sheet heater. It provides a means that can be created without paying too much attention to the above, and can make the yield very high.

[0008]

In order to achieve the above-mentioned object, the sheet heater according to claim 1 has a strip-shaped electrode made of a plurality of conductive thin films juxtaposed on a substrate and near both ends of the strip-shaped electrode. And a strip-shaped electrode are selectively connected to each other. Further, the planar heater according to claim 2 has a strip-shaped electrode composed of a plurality of conductive thin films and a voltage applying electrode in a square region on the substrate, and the strip-shaped electrode is at least one of the four sides of the square region. It is connected to at least two voltage-applying electrodes formed on one side or at least two voltage-applying electrodes formed on at least two opposite sides of the rectangular region. ..

[0009]

According to the invention of claim 1, the amount of heat generation is achieved by connecting or disconnecting the voltage application electrode in at least a part of the area without changing the specific pattern shape of the strip electrode on the substrate. It is possible to obtain a planar heater capable of controlling the heat generation and controlling the overall heat generation distribution. In addition, claim 2
According to the invention, the length of the strip electrode can be changed, whereby the amount of heat generation can be controlled and the overall heat generation distribution can be controlled arbitrarily.

Further, according to the present invention, it is possible to adjust the variation in the total resistance value of the sheet heater due to the variation in the sheet resistance value at the time of forming the conductive thin film.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an embodiment of the sheet heater according to the invention of claim 1.

On a substrate 1 made of an insulating transparent material, a plurality of conductive transparent thin films (for example, ITO,
Strip-shaped electrodes 2 made of a thin film of SnO ₂ or the like are formed in parallel, and low-resistance voltage application electrodes 3 are connected to both ends of the strip-shaped electrode 2.

The connection between the strip electrode 2 and the voltage application electrode 3 in the portion where the heat generation within the heater is desired to be relatively small is not connected. Specifically, for example, laser light is used to apply the strip electrode 2 and the voltage application. Cut the area near the connection with the electrode 3 and disconnect the wire 4.
Do not energize by making the disconnection part 4 without forming a conductive transparent thin film from the beginning with a photolithography mask, or by not electrically connecting when forming the voltage application electrode 3. To

The control of the distribution of the heat generation amount can be adjusted by the number of patterns which are not connected, if necessary. For example, in a simple planar heater, the temperature of the peripheral portion of the substrate 1 is likely to decrease due to the heat radiation due to the heat diffusion and heat radiation, and the temperature of the central portion of the substrate 1 is likely to rise. In order to make the in-plane temperature of the planar heater uniform, it can be controlled by reducing the connection between the strip electrode 2 near the center of the substrate 1 and the voltage application electrode 3.

When the sheet heater is used for heating a liquid crystal display device using, for example, a ferroelectric liquid crystal, the heat distribution required for the sheet heater may not be uniform over the entire surface. It may be necessary to relatively increase or decrease heat generation only in a specific area within the surface.
In such a case, a desired heat distribution can be obtained by selectively connecting the strip-shaped electrode 2 for heating and the electrode 3 for voltage application. Moreover, when used in a liquid crystal display device, for example, all the patterns of the strip-shaped electrode 2 of the planar heater of the portion corresponding to the liquid crystal display portion are made to have substantially the same pattern shape, and only the pattern of the strip-shaped electrode 2 of the unnecessary portion is applied for voltage application. Since the heat generation distribution can be controlled by not connecting to the electrode 3, the change in the transmittance of the planar heater in the liquid crystal display section or the interference with the transparent electrode of the liquid crystal panel does not occur, and the image quality of the liquid crystal display device is degraded. It is possible to obtain a desired heat generation distribution. Especially in the case of a liquid crystal display device using a ferroelectric liquid crystal,
Compared with TN liquid crystal and the like, the temperature characteristics of the liquid crystal material are considerable, the response speed at low temperature is slow, and it is necessary to reduce the temperature distribution in the plane of the liquid crystal panel. Good image quality can be obtained by heating and maintaining the temperature in the plane of the liquid crystal panel to a certain constant temperature and making the temperature distribution uniform. Regarding the ferroelectric liquid crystal element (panel, device), for example, USP45484
76 or USP 4655561, and these ferroelectric liquid crystal elements can be used in the present invention.

An embodiment of a method for suppressing the variation in the total resistance value of the sheet heater will be described below.

An example of a specific method for producing this planar heater is shown below. First, ITO (Indium-Tin-Oxide) is deposited to a thickness of 100 nm on one surface of a 320 × 300 × 1.1 mm glass substrate (eg, # 7059 manufactured by Corning Incorporated) by a sputtering method. I at this time
The sheet resistance value of the TO film usually varies by about 15 to 25 Ω / □. If patterning is performed by photolithography using one type of mask as it is, the variation in the sheet resistance value directly causes the variation in the total resistance value of the planar heater, resulting in a large difference between the power consumption and the heat generation amount.

In order to prevent this, for example, several kinds of masks for photolithography are prepared according to the variation of the sheet resistance value when forming the ITO film. As described above, the pattern shape of this mask is provided by arranging strip-shaped electrode patterns of substantially the same shape in parallel at a predetermined interval to obtain a desired surface shape for the sheet resistance value of the ITO film in a specific range. In order to obtain the total resistance value of the heater, the connection portion with the voltage application electrode is formed so that only a predetermined pattern portion is disconnected. At this time, since the strip-shaped electrode patterns are arranged in parallel and are connected to the voltage application electrodes, it is possible to adjust the total resistance value in the higher direction by breaking the predetermined pattern. By appropriately adjusting the positions and the number of the electrode patterns to be disconnected, it is possible to adjust the ITO film sheet resistance value within a specific range so as to be within the desired heater total resistance value range with respect to the ITO film sheet resistance value variation. You can create several types of masks.

The sheet resistance value of the ITO film after the film formation is sorted into a specific range and divided into groups, and photolithography is performed using a mask corresponding to each sheet resistance value range. Even if the values vary, the total resistance of the finished sheet heater can be kept within a desired range.

As an example of a method of forming the voltage applying electrode 3, the resistance value of the voltage applying electrode 3 is compared with that of the band-shaped electrode 2 at both ends of the pattern of the belt-shaped electrodes 2 provided in parallel. 50μ on 35μm thick copper foil to make it sufficiently low
A copper foil tape with a width of about 3 mm coated with an adhesive of m is adhered, and Ag paste is applied onto the copper foil tape with a width of 6 mm and a thickness of 0.1.
The voltage application electrode 3 was formed by printing in contact with the electrode pattern with a size of about mm.

In the above-mentioned preparation example, the disconnection portion of the electrode pattern was formed by forming the disconnection portion 4 at the time of the mask of photolithography. However, as described above, for example, a predetermined electrode pattern is cut by a laser beam. You may choose to do it.

FIG. 2 shows an embodiment of the sheet heater according to the invention of claim 2.

On a substrate 1 made of an insulating transparent material, a plurality of conductive transparent thin films (for example, ITO, Sn) serving as heat sources are formed.
A strip electrode 2 made of a thin film of O ₂ or the like) is formed in a rectangular region, and both ends of the strip electrode 2 are connected with low-resistance voltage applying electrodes 3 on two sides of the square region which do not face each other. It is provided.

As shown in FIG. 2, the strip electrodes 2 have substantially the same line width and are provided from the lower side portion of the substrate 1 toward the left side portion in the left half of the substrate 1, and the lower left corner of the substrate 1 is provided. The length of the strip electrode 2 is shorter as it is closer to, and is longer as it is closer to the central portion. On the right half of the substrate 1, the strip electrode 2 is formed symmetrically to the left half. Here, the heat generation amount of the strip-shaped electrode 2 for heat generation is inversely proportional to the resistance value when the applied voltage is constant, so that if the line width is the same, the heat generation amount is inversely proportional to the length.

Therefore, when a voltage is applied to the plurality of strip-shaped electrodes 2 shown in FIG. 2, the resistance value of each strip-shaped electrode 2 is proportional to its length. As shown in FIG. 3, the shorter the length of the strip electrode 2, the higher the temperature becomes, and the longer the portion becomes, the lower the temperature becomes. Therefore, the temperature at the lower left and right corners is high and the temperature becomes lower toward the center of the upper side. Distribution.

FIG. 4 shows another embodiment of the planar heater according to the invention of claim 2.

A plurality of strip-shaped electrodes 2 serving as heat sources are formed on the substrate 1, and low-resistance voltage applying electrodes 3 are connected to both ends of the strip-shaped electrode 2.

Here, the voltage applying electrode 3 is provided on the lower side of the substrate 1 so as to be substantially divided into two parts, and the strip-shaped electrode 2 has substantially the same line width and connects between the two divided voltage applying electrodes 3. It is formed in the shape of a downward U-shape. Here, the length of the strip electrode 2 is longer as it is closer to the outer periphery of the substrate 1, and is shorter as it is closer to the center of the lower side. Here, the heat generation amount of the strip-shaped electrode 2 for heat generation is inversely proportional to the resistance value when the applied voltage is constant as described above. Therefore, if the line width is the same, the heat generation amount is inversely proportional to the length. Become.

Therefore, when a voltage is applied to the plurality of strip electrodes 2 shown in FIG. 4, the resistance value of each strip electrode 2 is proportional to its length, and therefore the heat distribution of this sheet heater is distributed. As shown in FIG. 5, the shorter the length of the strip-shaped electrode 2, the higher the temperature becomes, and the longer the portion becomes, the lower the temperature becomes. Therefore, the temperature at the center of the lower side is high and the temperature becomes lower toward the left and right corners of the upper side. Distribution.

In the above embodiments, the strip electrode 2 for heat generation is used.
Although the line widths of the above are almost the same, the line width can be changed appropriately. Further, the number, position and shape of the voltage applying electrodes 3 and the position and shape of the strip electrodes 2 are not limited to those in the above-mentioned embodiment, but can be changed arbitrarily, and are planar so as to have an arbitrary heat generation distribution. It is possible to create a heater. Further, the heat generation distribution can be further adjusted by selectively connecting the strip electrode 2 and the voltage applying electrode 3 shown in FIG. 2 or 4.

When this sheet heater is used for heating a liquid crystal display device, the heat distribution required for the sheet heater is, for example, as described below.

Usually, when the liquid crystal display device is used in a low temperature environment, the response speed of the liquid crystal material at a low temperature is slow, so that a method of heating to a proper temperature with a heater and using it is often used. Looking at the temperature distribution on the surface, the temperature on the lower side is decreasing, and in particular, the temperature decreasing at the lower left and right corners is remarkable. Since the response speed of the liquid crystal material is determined by the lowest temperature part, the liquid crystal material can be driven at a higher speed by raising the temperature of this part. Here, if the heat distribution of the planar heater used is formed as in the embodiment described with reference to FIGS. 2 and 3, it is possible to raise the temperature of the lower temperature portion and the temperature lowering portion on the lower left and right corners, and the temperature distribution is corrected. Since the liquid crystal material can be driven at high speed, the display quality of the liquid crystal display device can be improved.

Particularly, in the case of a liquid crystal display device using a ferroelectric liquid crystal as a liquid crystal material, the temperature characteristic of the liquid crystal material is considerably larger than that of TN liquid crystal and the response speed at a low temperature is slow,
In addition, it is necessary to reduce the temperature distribution in the liquid crystal panel surface, and to maintain the temperature in the liquid crystal panel surface at a certain constant temperature by heating and maintaining it using the planar heater of the present invention and to make the temperature distribution uniform within a certain range. By doing so, good image quality could be obtained. As the ferroelectric liquid crystal element, the above-mentioned U
What is shown by SP etc. can be used.

In each of FIGS. 1, 2 and 4, the substrate 1 and the strip electrode 2 do not have to be transparent, but are preferably transparent for easy use in a liquid crystal display device.

[0035]

As described above, according to the sheet heater of the first aspect, the strip-shaped electrode patterns are formed in strips in parallel, and the connection with the voltage application electrode is selectively performed to obtain the desired pattern. It is possible to prepare a planar heater that can obtain the heat generation distribution of. In addition, when making a planar heater, the variation in sheet resistance during the formation of the conductive thin film
It is possible to adjust by selectively connecting the strip-shaped electrode patterns formed in parallel in strips and the voltage application electrodes, and to keep the total resistance value of the finished sheet heater within a desired range.

On the other hand, according to the sheet heater of claim 2,
By connecting the strip electrodes to the voltage applying electrodes formed on the sides other than the two opposite sides, the length of the strip electrodes for heat generation can be freely changed, so that a desired heat distribution can be obtained. A heater can be created.

Further, according to the present invention, the temperature in the plane of the liquid crystal panel of the liquid crystal display device using the ferroelectric liquid crystal or the like can be uniformly heated and maintained, so that the electro-optical response has little unevenness and high speed. Driving can be enabled.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the invention of claim 1;

FIG. 2 is a diagram showing an embodiment of the invention of claim 2;

FIG. 3 is an explanatory diagram of heat generation distribution of the sheet heater shown in FIG.

FIG. 4 is a diagram showing another embodiment of the invention of claim 2;

5 is an explanatory diagram of heat generation distribution of the sheet heater shown in FIG.

[Explanation of symbols]

 1 substrate 2 strip electrode 3 voltage application electrode 4 disconnection

Claims (4)

[Claims] 1. On a substrate, a strip-shaped electrode made of a plurality of conductive thin films arranged in parallel and a voltage applying electrode provided near both ends of the strip-shaped electrode are combined, and the voltage applying electrode and the strip-shaped electrode are provided. A planar heater that is selectively connected. 2. A rectangular area on the substrate has a plurality of strip electrodes made of a plurality of conductive thin films and a voltage application electrode, and the strip electrode is formed on at least one of the four sides of the square area. Or at least two of the voltage applying electrodes or at least two of the rectangular regions which do not face each other.
A planar heater which is connected to at least two voltage applying electrodes formed on the sides. 3. The planar heater according to claim 1, wherein the substrate is made of an insulating transparent material, and the conductive thin film is a transparent conductive film. 4. The planar heater according to claim 1, which is for a liquid crystal display device.