JPH03122911A - Pressuresensitive conductive resin composite - Google Patents

Abstract

PURPOSE:To obtain an excellent characteristic as a pressuresensitive conductive film constituent material by composing it of main pigments, control pigments and a binder. CONSTITUTION:A pressuresensitive conductive resin composite is composed of the main pigments 1, control pigments 5 and a binder. The main pigments 1 are the pigments carrying conductivity in the film thickness direction of the pressure sensitive film, while the control pigments 5 are the spherical insulating materials in the surface direction of the film and securing conductivity in the film thickness direction when pressed to a certain extent. A writing condition as a digitizer for handwriting input, thereby, becomes smooth and sensitivity to erroneous touching is lowered while enabling to constitute a digitizer tablet of a large area with a free design for input load.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a pressure-sensitive conductive resin composition.

The pressure-sensitive conductive resin composition according to the present invention is particularly useful as a material constituting a pressure-sensitive conductive film in a pressure-sensitive digitizer that detects a position from a resistance value.

In this specification, "parts" and "%" mean "parts by weight" and "% by weight," respectively.

Prior art and its problems The following pressure-sensitive conductive films for pressure-sensitive digitizers are known.

(a) conductive metal powder in an elastomer such as rubber;
There is a pressure-sensitive conductive film made by crosslinking a material containing metal oxide powder, carbon black powder, etc. (for example, Japanese Patent Laid-Open No. 163945/1983).

However, this pressure-sensitive conductive film has poor handling properties (properties that do not cause erroneous manual force due to the pressure of the hand touching the digitizer during handwriting input), poor hysteresis properties, and furthermore, it is difficult to control the degree of crosslinking. , there is also large variation between production lots. Furthermore, metal fine particles often used as conductive fine particles have a problem in that their conductivity decreases due to oxidation or the like.

(b) There is a method in which patterns such as insulating protrusions are formed on a conductive elastomer layer made by dispersing conductive particles in an elastic polymer material (Japanese Patent Application Laid-Open No. 59-98408, etc.).

However, this pressure-sensitive conductive film has problems such as low resolution, inability to detect continuous lines, and even a small amount of dust may cause failure in conduction.

(C) There is a pressure-sensitive conductive rubber layer coated with an insulating film (Japanese Patent Publication No. 60-9008).

However, this pressure-sensitive conductive film also has problems, such as poor handling characteristics, a large effect of surface irregularities during input, slow restoration of the film after the pressing force is removed, and large hysteresis.

(d) There is a method in which conductive metal fibers are arranged in the thickness direction of an elastomer sheet, and the end portions of the metal fibers exposed on the side surfaces of the sheet in the thickness direction are removed by etching treatment (Japanese Patent Laid-Open No. 58-220307). Public bulletin).

However, like the case (b) above, this pressure-sensitive conductive film also has problems such as low resolution and the inability to detect continuous lines, as well as poor conductivity due to oxidation of the metal fibers and breakage of the metal fibers. There are also problems such as the complexity of the manufacturing process.

(e) There is also a method in which the surface of conductive rubber is processed to form protrusions or ridges (Japanese Utility Model Publication No. 174126/1983).

Even in the case of this method, it is difficult to process a high-resolution film, and the durability is also insufficient.

Means for Solving the Problems As a result of intensive research in view of the current state of the technology as described above, the present inventor has discovered that a composition containing two or more specific pigments and a binder can be used as a pressure-sensitive conductive film. It was discovered that it has excellent properties as a constituent material.

That is, the present invention provides the following composition: (1) A pressure-sensitive conductive resin composition comprising (a) a main pigment, (b) a control pigment, and (d) a binder.

(2) The pressure-sensitive conductive resin composition according to the above item (1), wherein the main pigment is a conductive material and the periphery thereof is covered with another material.

■The above category (1) where the main pigment is spherical carbon fine particles or (
2) The pressure-sensitive conductive resin composition.

■(a) Main pigment, (b) Control pigment (c) binder, and (d) Auxiliary pigment A pressure-sensitive conductive resin composition.

(2) The pressure-sensitive conductive resin composition according to the above item (4), wherein the main pigment is a conductive material and the periphery thereof is covered with another material.

■The above category (4) where the main pigment is spherical carbon fine particles or (
5) The pressure-sensitive conductive resin composition.

In the present invention, the term "main pigment" refers to a pigment that is responsible for the conductivity in the thickness direction of the pressure-sensitive film. Furthermore, the term "control pigment" refers to a spherical insulating material that ensures insulation in the surface direction of the film and conductivity in the film thickness direction due to a constant pressure. moreover,"
"Auxiliary pigment" refers to a material for further improving these properties.

The main pigment (a) used in the present invention includes spherical conductive carbon and spherical conductive carbon coated with thin films of various organic and inorganic materials. Specific examples of spherical conductive carbon include mesocarbon microbeads, glassy carbon microspheres, spherical pitch powder, polymer microspheres, spherical pitch hollow bodies, etc., which are heat-treated at high temperatures to become graphite. . In particular, mesocarbon microbeads are advantageous because graphite particles with excellent sphericity and uniform particle size and good conductivity can be obtained. Examples of inorganic materials that cover such spherical conductive carbon include 5i02, TiO2, and ZnO%AQ203.5.
Metal oxides such as n02, In203; Tic, Si
Metal carbides such as C, AQa C3; MnB, CoB,
NiB, FeB.

Metal borides such as WB; BN, TiN, ZrN.

Metal nitrides such as CrN; Examples of organic materials include synthetic polymer compounds such as ABS resin, polyester, polyether ester, polyolefin, polyamide, polyurethane, butadiene rubber, isoprene rubber, silicone rubber, and polysiloxane. The spherical conductive carbon may be coated with a material by a known method such as an clathration method, a mechanofusion method, a sol-gel method, or a suspension polymerization method. The particle size of the main pigment is usually about 1 to 20 μm, more preferably about 5 to 10 μm.

The (mouth) control pigment used in the present invention includes insulating particles. More specifically, silicone rubber, polyamide, polytetrafluoroethylene, polyurethane,
Examples include particles made of resin such as natural rubber, butadiene rubber, acrylic rubber, nitrile rubber, and NBR, and inorganic particles such as ceramic balloons and porous ceramic particles.

Among these, resin granules having elasticity are more preferred. The particle size of the pigment is usually about 5 to 50 μm, more preferably about 7 to 30 μm.

(2) The binder used in the present invention includes polymers such as silicone rubber, acrylic resin, epoxy resin, vinyl chloride resin, phenol resin, polyester, polyimide, polyamide, polyurethane, neoprene rubber, isoprene rubber, natural rubber, and polyolefin. Examples include materials.

The proportions of the main pigment, control pigment, and binder may vary depending on the properties required for the pressure-sensitive conductive resin composition, but usually 30 to 85 parts of the main pigment and 70 to 70 parts of the control pigment are used.
15 parts and 100 parts in total, binder 50 to 10 parts
It is preferable to set it to about 00 parts. If the amount of the main pigment used is too small, the area in which no current is applied even when pressurized becomes large, resulting in a decrease in resolution. On the other hand, if too much main pigment is used, the main pigments may come into contact with each other in the lateral direction, making it impossible to detect the correct pressurized point, or the main pigments may stack up in the direction of the film thickness, making it difficult to detect when no pressure is applied. It also has conductivity in the film thickness direction. In addition, if the amount of binder is too small, cracks may occur during film formation and firing, and the specific resistance of the film may decrease.
However, the adhesion to the substrate or resistive film may deteriorate, making peeling more likely, resulting in a decrease in the durability of the film. On the other hand, if the amount of binder is too large, the area of the insulating portion becomes large, resulting in a large number of dead points, or a sufficient change in resistance is not exhibited.Furthermore, there is a problem that no current is applied when pressurizing.

In the present invention, in addition to the pigment component consisting of (a) the main pigment and (b) the control pigment, (d) an auxiliary pigment having a particle size of about 1 μm or less, more preferably about 0.01 to 0.04 μm is used in combination. can do. When the auxiliary pigment is electrically conductive, the hysteresis of the pressure-sensitive conductive film is reduced, and the pressure-sensitive conductive properties are not impaired even after long-term use. When the auxiliary pigment is insulating, the lateral insulation of the conductive film is more complete, and the dispersibility of the main pigment and control pigment is improved. Examples of auxiliary pigments include conductive carbon black (for example, commercially available from Akzo, Netherlands under the trade name "Ketchen Black"), silver, and non-conductive ceramic fine particles (SiO2, etc.). Ru. The total amount of auxiliary pigments used varies depending on the materials used, but usually total pigment components 1
00 parts, preferably about 30 to 80 parts of the main pigment, 5 to 40 parts of the control pigment, and 5 to 50 parts of the auxiliary pigment. In this case as well, 5 parts of the binder is added to 100 parts of the total pigment component.
About 0 to 1000 parts are blended.

In addition, it is preferable that the particle size of each pigment component in the composition of the present invention is such that the following pigments are used: control pigment>main pigment>auxiliary pigment.

In the pressure-sensitive conductive composition of the present invention, various additives may be added in order to further improve various properties. For example, lubricants and other components that facilitate the process of forming a film from a composition by methods such as printing, improve the surface smoothness of a sheet or film, and further improve the pressure-sensitive characteristics of a digitizer. A dispersion stabilizer, a plasticizing agent, a deterioration inhibitor, a reinforcing filler, etc. may be used in combination to improve the dispersion stability of the dispersion.

The functions, effects, etc. when the composition of the present invention is used as a pressure-sensitive conductive film will be explained in more detail below with reference to the drawings. In the following, graphitized mesocarbon microbeads (hereinafter referred to as MCMB) will be used to represent the main pigment, but it goes without saying that materials other than MCMB can also be used in the present invention.

As shown in a schematic cross-sectional view in Figure 1, conductive MCMB (1) with a spherical shape and uniform particle size is dispersed in an insulating binder (3) to form a film with a thickness approximately the diameter of the MCMB. When formed, an anisotropic conductive film exhibiting conductivity only in the thickness direction of the film can be obtained.

Furthermore, as shown in Fig. 2, if a film with a thickness slightly larger than the diameter of MCMB (1) is formed in almost the same manner as in Fig. 1, pressure is applied in the thickness direction of the film. Only when added, an anisotropic conductive film exhibiting conductivity in the thickness direction of the film can be obtained.

However, with the binary conductive film of MCMB-binder, problems such as resistance hysteresis when pressurized, lateral conduction due to point contact between adjacent MCMBs when pressurized, and aggregation of MCMB particles occur. It was found that further improvements were required for practical use.

However, as shown in a similar schematic cross-sectional view in FIG. , problems such as lateral conduction due to point contact between adjacent MCMBs when pressurized and aggregation of MCMB particles are substantially eliminated.In addition, in this case, the spherical shape control pigment (5) is By forming the film from a material that has properties such as various elastomers, it is possible to significantly reduce resistance hysteresis when pressure is applied.Furthermore, when used as a pressure-sensitive film for a digitizer tablet, it has a smooth feel. is obtained, which is advantageous in practice.

In the pressure-sensitive conductive film of the type shown in Figure 3, in order to further improve the conductivity during pressure sensing and the long-term stability of the pressure-sensitive characteristics, the particle size must be adjusted as shown in Figure 4. MCMB (
It is preferable to use a conductive auxiliary pigment (7) which is 1/10 or less of 1). In particular, when carbon black is used as the auxiliary pigment (7), MCMB
(1) Since no contact potential difference occurs between the two and no charge transfer occurs even when the two come into contact, the pigment does not deteriorate and the life of the pressure-sensitive conductive film is extended. Carbon black is also more cost-effective than other conductive auxiliary pigments, such as silver.

The mechanism by which the long-term stability of pressure-sensitive properties is improved by using fine conductive auxiliary pigments (7) such as carbon black in the pressure-sensitive conductive film shown in Figure 4 is still not fully understood. Although it has not been done yet, it is assumed that it is as follows.

In the present invention, the main pigment such as MCMB is embedded in the binder forming the film. If the binder is a completely insulating material, the applied pressing force will cause
The binder above or below the main pigment becomes thinner and conducts electricity. This phenomenon is considered to be due to a kind of tunnel effect. However, in the above case, the voltage drop in the film thickness direction becomes extremely large in the binder layer portion. As a result, problems such as peeling at the interface between the main pigment and the binder tend to occur. On the other hand, in a system in which a small amount of carbon black is added, the above-mentioned excessive voltage drop at the binder portion is improved, and breakage due to peeling at the interface between the main pigment and the binder is less likely to occur.

This is thought to be because, unlike the system without carbon black, the current in the binder during pressurization is mainly carried by the conductive film caused by contact with carbon black.

Effects of the Invention When the composition of the present invention is used as a pressure-sensitive conductive film in a digitizer, the following effects are achieved.

(a) The digitizer for handwriting input has a smooth writing feel.

(b) Sensitivity to handling is low and does not cause any practical inconvenience.

(c) It is possible to construct a large-area digitizer tablet with a degree of freedom in designing the input load.

(d) Excellent resolution.

(e) Excellent durability.

(f) There are few manufacturing variations and the accuracy is good.

(g) The manufacturing process is simplified.

(h) Manufacturing costs are reduced.

EXAMPLES Examples and comparative examples are shown below to further clarify the features of the present invention.

The various materials used in the following Examples and Comparative Examples are as follows.

(A) Main pigment: (A)-1・MCMB graphitized material (6μm) (A)-2・
...The surface of (a)-1 above is included in silica (a)-3... Glassy carbon spherules (trademark "C200")
0S", manufactured by Kanebo Co., Ltd.) (a)-4... Glassy carbon small spheres (trademark "GCPI")
O", manufactured by Unitika Co., Ltd.) (B) Control pigment: (B)-1... Silicone rubber sphere (trademark "E-50")
1", manufactured by Toshi Silicone Co., Ltd., 10 μm) (b) -2
...Polytetrafluoroethylene powder (trademark "Luburon L2", manufactured by Daikin Industries, Ltd.).

7 μm) (c) Binder: (c)-1... Phenol resin (trademark "8899",
(manufactured by Kanebo Co., Ltd.) (c)-2... Butadiene rubber solution (trademark "Epol R-15HT", manufactured by Idemitsu Petrochemical Co., Ltd.) (c)-3
... Silicone rubber (trademark "KE-1820", manufactured by Shin-Etsu Chemical Co., Ltd.) (d) Auxiliary pigment: (d)-1 ... Carbon black (trademark "MA-8")
, manufactured by Mitsubishi Kasei Corporation, particle size 24 nm) (d)-2.
・・Conductive carbon black (trademark “Ketchen Black EC600JD”, manufactured by Lion Akzo, particle size 3
0nm) (d)-3... Colloidal silica fine particles (trademark "R9")
72'', manufactured by Nippon Aerosil Co., Ltd., particle size 20 nm) Example 1 265.5 parts of phenol resin ((c'')-1) was dissolved in 265.5 parts of carpitol acetate, and this and the pigments shown in Table 1 were dissolved. Paste A was prepared by mixing 100 parts of the component mixture in a three-roll mill.

Table 1 Pigment components Mixing ratio (a) -1 (b) -1 (d) -1 (d) -2 (d) -3 (parts by weight) 0 5 5 5 On the other hand, Fig. 5 (top view) and As shown in Figure 6 (front view), a polyester film substrate with a film thickness of 125 μm (
11) After screen printing a silver paste (trademark "ED427SS", manufactured by Acheson Japan Co., Ltd.) on top, it was dried to form silver electrodes (13) with a thickness of 8 μm.

On these silver electrodes (13), (13), carbon paste (trademark "MCP2603"
", manufactured by Mitsui Toatsu Co., Ltd.) was further screen printed to form a carbon film (15) with a thickness of 15 μm.

Next, the paste A was screen printed on the carbon film (15) and dried to form a pressure-sensitive conductive film (17) with a thickness of 20 μm. 1mm thick aluminum plate (19
) were laminated together to prepare a pressure-sensitive conductive base material B to be the lower layer of the touch pad.

In addition, the silver electrodes (13), (13) have lead wires (21
) (21) was attached.

Further, as shown in FIG. 7 (top view) and FIG. 8 (right side view), a pressure-sensitive conductive base material C to be the upper layer of the touch pad was prepared by a method substantially similar to that described above. The pressure-sensitive conductive base material C has a structure similar to that of the pressure-sensitive conductive base material B. However, the pressure-sensitive conductive base material C has a protective sheet (
23) is equipped with a 125 μm thick polyester film (manufactured by Dainippon Printing Co., Ltd.), but the pressure-sensitive conductive film (
17) and the aluminum plate (19) are different from pressure-sensitive conductive base material B.

Next, the pressure-sensitive conductive base material C and the pressure-sensitive conductive base material B are stacked so that their silver electrodes (13) and (13) are in contact with each other at right angles, and both are fixed with double-sided adhesive tape (25). As a result, a 3-size pressure-sensitive conductive element (touch pad) was obtained.

The touch pad thus obtained was incorporated into a circuit outlined in FIG. 9, and its characteristics as a position detection element were evaluated.

That is, the touch pad (3) connected to the power supply (31)
3) From the top of the stylus pen (35
), a large resistance change occurs when the load exceeds a certain value (input load).

At this time, the pressure-sensitive conductive film is energized at the point where the pressing force is applied. Therefore, when using a constant current source as the power source (31), determine the current values flowing through the lower layer pressure-sensitive conductive base material B and the upper layer pressure-sensitive conductive base material C, and convert these values to the A/D converter (37). ) to the computer (3
9) and display it graphically, you can draw a figure. In addition, when using a constant potential power source as the power source (31), an A/D converter (37
) by converting the current value and performing simple calculations, the resistance value can be found, and as a result, the position can be known and a figure can be drawn.

Table 13 below summarizes the characteristics of the touch pads obtained in this example and the following examples.

Example 2 Phenol resin ((c)-
1) After dissolving 450 parts and mixing this with 100 parts of the pigment component mixture shown in Table 2 using a three-roll mill to prepare a paste, a touch pad was manufactured in the same manner as in Example 1.

Table 2 Pigment components Mixing ratio (a)-1 (b)-1 (d)-1 (d)-2 (d)-3 (parts by weight) 0 5 0 0 Example 3 Phenol resin in 450 parts of carpitol acetate ((c)-
1) After dissolving 450 parts and mixing this with 100 parts of the pigment component mixture shown in Table 3 using a three-roll mill to prepare a paste, a touch pad was manufactured in the same manner as in Example 1.

Table 3 Pigment components Mixing ratio (parts by weight) (a) -17
0 (b) -115 (d) -18 (d) -22 (d) -35 Example 4 Phenol resin ((c) -
1) After dissolving 220 parts and mixing this with 100 parts of the pigment component mixture shown in Table 4 in a three-roll mill to prepare a paste, a touch pad was manufactured in the same manner as in Example 1.

Table 4 Pigment components Mixing ratio (parts by weight) (a') -1
50 (b) -110 (d) -120 (d) -25 (d) -315 Table 5 Pigment components Mixing ratio (parts by weight) (a) -15
0 (b)-15 (d)-125 (d)-25 (d)-315 Example 5 Phenol resin ((c)-
1) After dissolving 100 parts and mixing this with 100 parts of the pigment component mixture shown in Table 5 in a three-roll mill to prepare a paste, a touch pad was manufactured in the same manner as in Example 1.

Example 6 Phenol resin ((c)-
1) After dissolving 100 parts and mixing this with 100 parts of the pigment component mixture shown in Table 6 using a three-roll mill to prepare a paste, a touch pad was manufactured in the same manner as in Example 1.

Table 6 Pigment components Mixing ratio (parts by weight) (a) -15
0 (b) -130 (d) -110 (d) -25 (d) -35 Table 7 Pigment components Mixing ratio (parts by weight) (a) -25
0 (口') -110 (D) -130 (D)-25 (D)-35 Example 7 Phenol resin ((C)-
1) After dissolving 82 parts and mixing this with 100 parts of the pigment component mixture shown in Table 7 using a three-roll mill to prepare a paste, a touch pad was manufactured in the same manner as in Example 1.

Example 8 262.5 parts of phenolic resin ((c)-1) was dissolved in 262.5 parts of carpitol acetate, and this and 100 parts of the pigment component mixture shown in Table 8 were mixed in a three-roll mill,
After preparing the paste, by the same method as in Example 1,
Manufactured a touchpad.

Table 8 Pigment components Mixing ratio (parts by weight) (A') -3
50 (b)-115 (d)-115 (d)-25 (d)-315 Example 9 400 parts of silicone resin solution ((c)-3) and 100 parts of the pigment component mixture shown in Table 9 were mixed into 3 After mixing with this roll mill to prepare a paste, a touch pad was manufactured by the same method as in Example 1.

Table 9 Pigment components Mixing ratio (parts by weight) (a) -16
0 (b)-115 (2') -120 (d)-25 Example 10 262.5 parts of phenolic resin ((c)-1) was dissolved in 262.5 parts of carpitol acetate, and the 100 parts of the pigment component mixture shown below were mixed in a three-roll mill to prepare a paste, and then a touch pad was manufactured in the same manner as in Example 1.

Table 10 Pigment components Mixing ratio (parts by weight) (a) -450 (b) -115 (d) -115 (d) -25 (d) -315 Table 11 Pigment components Mixing ratio (parts by weight) (a) -15
0 (b) -115 (b) -215 (d) -115 (d) -25 Example 11 262.5 parts of phenolic resin ((c)-1) was dissolved in 262.5 parts of carpitol acetate, and 100 parts of the pigment component mixture shown in Table 11 was mixed in a three-roll mill to prepare a paste, and then a touch pad was manufactured in the same manner as in Example 1.

Example 12 Organic solvent solution of butadiene rubber ((c)-2) 262.
5 parts and 100 parts of the pigment component mixture shown in Table 12 were mixed in a three roll mill to prepare a paste.
A touchpad was manufactured using the same method.

Pigment component (a)-1 (b)-1 (d)-1 (d)-2 (d)-3 Table 12 Mixing ratio (parts by weight) 0 5 5 5 Input load (g) 00 50 30 00 20 60 00 00 00 00 00 00 Table 13 Malfunction load Insulation resistance value (kg) (Ω) 8×109 6X10' X109 X109 X109 1.5X10Il1 X109 8X 109 , is the resistance value of the touch pad when no load is applied.

As is clear from the results shown in Table 13, the human force load applied to the touchpad according to the present invention using a stylus pen with a diameter of 1 mm is 300 g or less, and the input characteristics are excellent. Furthermore, no malfunctions occurred due to manual intervention.

Comparative Example 1 As shown in FIG. 10 (plan view) and FIG. 11 (front view), a polyester film substrate (1
1) After screen printing silver paste (trademark "ED42788", manufactured by Nippon Acheson Co., Ltd.) on top, drying it,
Silver electrodes (13), (13) with a thickness of 8 μm were formed. On these silver electrodes (13), (13), carbon paste (trademark "MCP2603") was applied to obtain a predetermined resistance value.
, manufactured by Mitsui Toatsu Co., Ltd.) was further screen printed to form a carbon film (15) having a thickness of 15 μm and having many projections (41) in the vertical and horizontal directions.

Next, an aluminum plate (19) with a thickness of 1 inch was laminated on the lower surface of the polyester film substrate (11) to prepare a pressure-sensitive conductive base material E to be the lower layer of the touch pad.

In addition, the silver electrodes (13), (13) have lead wires (21
), (21) were attached.

Also, Figure 12 (top view) and Figure 13 (right side view)
As shown in FIG. 2, a pressure-sensitive conductive base material F to be the upper layer of the touch pad was prepared using a method substantially similar to that described above. The pressure-sensitive conductive base material E has a structure similar to that of the pressure-sensitive conductive base material. However, the pressure-sensitive conductive base material F has a 125 μm thick polyester film (manufactured by Oguchi Hon Printing Co., Ltd.) as a protective sheet (23) on the surface, but the aluminum plate (19) and the protrusions (41 ) is different from pressure-sensitive conductive substrates.

Next, the pressure-sensitive conductive base material 1 and the pressure-sensitive conductive base material F are stacked so that their respective silver electrodes (13) and (13) are in contact with each other at right angles, and both are fixed with double-sided adhesive tape (25). As a result, a 3-size pressure-sensitive conductive element (touch pad) was obtained.

However, this type of touch pad with protrusions has low resolution and lacks durability.

Comparative Example 2 In place of paste A in Example 1, pigment (
b) Using a paste using only -1, Example 1
A touchpad was prepared in the same manner.

The resulting touchpad had extremely large variations in resistance depending on the pressed position, and was not practical.

Comparative Example 3 Carpitol acetate 30 was used instead of paste A in Example 1.
Example 1 was prepared using a paste obtained by dissolving 300 parts of phenol resin ((c)-1) in 0 parts and mixing this with 100 parts of the pigment component mixture shown in Table 14 in a three-roll mill. A touchpad was prepared in the same manner.

Table 14 Pigment components Mixing ratio (parts by weight) (d) -15
5 (d)-25 (d)-340 However, the obtained product did not exhibit switching characteristics even when pressed, and was therefore impractical.

Comparative Example 4 Carpitol acetate 12 was used instead of paste A in Example 1.
Example 1 was prepared using a paste obtained by dissolving 120 parts of phenol resin ((c)-1) in 0 parts and mixing this with 100 parts of the pigment component mixture shown in Table 15 using a three-roll mill. A touchpad was prepared in the same manner.

Table 15 Pigment components Mixing ratio (heavy part) (A”) −1
75 (d) -110 (d) -25 (d) -310 However, the obtained touch pad had extremely large variations in resistance value depending on the pressed position (and was not practical).

Reference Example 1 In the combination of the pigment component and the binder in Example 1, pastes were prepared in which the proportions of the pigment component and the binder solid content were varied, and by the same procedure as in Example 1,
A touchpad of the present invention was created.

FIG. 14 shows the resistance of the touch pad when no load is applied and when the load from the stylus pen is 700 g.

The load test was repeated 10,000 times, but almost no variation was observed between tests. Reference Example 2 In the combination of the pigment component and the binder in Comparative Example 4, pastes were prepared in which the proportions of the pigment component and the binder solid content were varied, and by the same procedure as in Example 1,
Created a touchpad.

FIG. 15 shows the resistance of the touch pad when no load is applied and when the load from the stylus pen is 700 g.

The load test was repeated 10,000 times, but the first
As shown by the diagonal lines in Figure 5, the variation between tests is
It was quite large. It is presumed that this is because the control pigment is not contained in the conductive pressure-sensitive film.

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views schematically showing the outline of a binary pressure-sensitive conductive film of MCMB-binder. 3 and 4 are cross-sectional views schematically showing the outline of a pressure-sensitive conductive film using the pressure-sensitive conductive resin composition according to the present invention. 5 to 8 are drawings showing the structure of a touch pad equipped with a pressure-sensitive conductive film using the pressure-sensitive conductive resin composition according to the present invention. FIG. 9 is a circuit diagram used to evaluate the characteristics of the touch pad shown in FIGS. 5 to 8 as a position detection element. 10 to 13 are drawings showing the structure of a touch pad obtained in Comparative Example 1. FIG. 14 is a graph showing the resistance characteristics of a touch pad equipped with a pressure-sensitive conductive film using the pressure-sensitive conductive resin composition according to the present invention. FIG. 15 is a graph showing the resistance characteristics of the touch pad obtained in Comparative Example 4. (1)... MCMB (3)... Insulating binder (5)... Insulating spherical control pigment (7)... Conductive auxiliary pigment (11)... Polyester film substrate (13)・
... Silver electrode (15) ... Carbon film (17) ... Pressure-sensitive conductive film (19) ... Aluminum plate (21) ... Lead wire (23) ... Protective sheet (25) ...Double-sided adhesive tape (31) ...Power supply (33) ...Touch pad (35) ...Stylus pen (37) (39) (41) ...A/D converter ...Computer ...・Protrusion diagram (above) 21°" Figure Figure 9 Figure 5 Figure 12 Figure 13 Figure 14 Figure A page Saito/II Toya Pinet) 1Q Figure 1 Figure 1 Figure 15 Kao Koto/(M1to + Bainta")

Claims (6)

[Claims] (1) (a) Main pigment, (b) control pigment, and (c) Binder A pressure-sensitive conductive resin composition. (2) The pressure-sensitive conductive resin composition according to claim (1), wherein the main pigment is a conductive material, and the periphery thereof is coated with another material. (3) The pressure-sensitive conductive resin composition according to claim (1) or (2), wherein the main pigment is spherical carbon fine particles. (4) (a) Main pigment, (b) Control pigment (c) binder, and (d) Auxiliary pigment A pressure-sensitive conductive resin composition. (5) The pressure-sensitive conductive resin composition according to claim (4), wherein the main pigment is a conductive material, and the periphery thereof is coated with another material. (6) The pressure-sensitive conductive resin composition according to claim (4) or (5), wherein the main pigment is spherical carbon fine particles.