JP5169501B2 - Electrode paste for electrodes and transparent touch panel - Google Patents

Description

  The present invention relates to a transparent conductive paste used as an electrode material for a transparent conductive substrate, and a transparent touch panel using the same.

In recent years, functions of various electronic devices are switched using a transparent touch panel on the front surface of a display element such as an LCD. For example, it is manufactured from a constituent material in which an indium tin oxide (hereinafter referred to as ITO) layer is formed on a transparent plastic film, and an electrode layer made of a conductive paste using silver fine powder is formed in an appropriate position on the layer. Has been. However, it has been pointed out that the electrode has a high contact resistance. Therefore, Patent Document 1 has been proposed as a technique for improving such problems. That is, in the light transmissive touch panel, the affinity between indium tin oxide, which is the material of the upper and lower conductive layers, and silver, which is the upper and lower electrodes, is not so good. There was a problem that the connection resistance was large. Therefore, as a conductive paste having a low connection resistance at the interface between the conductive layer and the electrode, an alloy of silver and indium or indium attached to silver in a synthetic resin By using a conductive paste in which the ratio of indium to silver is 1 to 50% by weight, the electrode of this conductive paste has a good interface affinity with the conductive layer of indium tin oxide and has a connection resistance. It is described that the resistance value of the entire electrode can be reduced. However, although the contact resistance can be improved with this conductive paste, it is necessary to prepare an alloy of silver and indium and to make a fine powder, and such a case where indium is adhered to the fine silver powder. Since a process is required, it led to an increase in cost and was not very practical.
JP 2003-217348 A

  Therefore, the problem to be solved by the present invention is that the conductive fine powder has a small contact resistance when used as an electrode layer of a transparent conductive coating film, even without performing a special treatment step as described above. The object of the present invention is to provide a stable conductive paste for electrodes which is 1/4 to 1/10 of the conductive paste using fine silver powder. Another object of the present invention is to provide a transparent touch panel excellent in electrical characteristics such as contact resistance by forming such an electrode conductive paste as an electrode layer.

  The problem to be solved is a conductive paste used for an electrode of a transparent conductive film as described in claim 1, and includes a binder resin, conductive fine powder and a solvent as essential components, The conductive fine powder can be solved by forming a conductive paste for an electrode composed of 0.2 to 20% by mass of tin oxide fine powder and 99.8 to 80% by mass of silver fine powder.

  Preferably, the tin oxide fine powder is an antimony-doped tin oxide fine powder as described in claim 2, and the tin oxide fine powder has a particle size as described in claim 3. It is 5 nm-30 micrometers, Preferably it is solved by setting it as the electrically conductive paste for electrodes in any one of Claim 1 or 2.

  And, as described in claim 4, by using a conductive paste for an electrode according to any one of claims 1 to 3, a transparent touch panel in which an electrode layer is formed on a transparent conductive film is solved. Is done.

The conductive paste used for the electrode of the transparent conductive film of the present invention contains a binder resin, conductive fine powder and a solvent as essential components, and the conductive fine powder is 0.2 to 20% by mass of tin oxide fine powder. Since it is a conductive paste for electrodes composed of 99.8 to 80% by mass of silver fine powder, there is no need for special treatment of the conductive fine powder, and it can be used as an electrode for a transparent conductive coating film. This is a stable conductive paste for electrodes with low contact resistance. That is, the specific resistance is on the order of 10 × 10 ⁻⁵ Ω · cm, the value after the heat resistance test and after the moisture resistance test is stable with little change within 50% of the initial contact resistance value, and A typical contact resistance value is in the range of 1/4 to 1/10 of the conductive paste using silver fine powder.

Further, as the conductive fine powder, preferably, the tin oxide fine powder is an antimony-doped tin oxide fine powder, thereby maintaining conductivity and adhesiveness as a conductive paste for an electrode and a specific resistance. Is about 10 × 10 ⁻⁵ Ω · cm, and the value after the heat resistance test and after the moisture resistance test does not change much within 50% of the initial contact resistance value. It is the range of 1 / 4-1 / 10 of the conductive paste using fine powder, and is preferable as a conductive paste used as an electrode for a transparent conductive coating film. Furthermore, since the particle size of the tin oxide fine powder is 5 nm to 30 μm, the obtained conductive paste for electrodes is easy to handle when forming the electrode layer and has a specific resistance of about 10 × 10 ^−5. It is in the Ω · cm range, and after heat resistance test, the value after moisture resistance test does not change much less than 50% of the initial contact resistance value. It is the range of 1/4 to 1/10 of a paste, and is preferable as a conductive paste used as an electrode for a transparent conductive coating film.

  And as described in Claim 4, the transparent touch panel which formed the electrode layer using the electrically conductive paste for electrodes as described in any one of Claims 1-3 has all the characteristics mentioned above, and is an electrode. It is a transparent touch panel with excellent layer formability.

  The invention described in claim 1 relates to a conductive paste used as an electrode for a transparent conductive film, and the conductive fine powder used is 0.2 to 20% by mass of tin oxide fine powder, silver fine powder. Is a conductive paste for electrodes composed of 99.8 to 80% by mass, and the conductive fine powder does not need to be subjected to a special processing step, and can be simply mixed so that a small contact resistance can be obtained relatively easily. It is the conductive paste for electrodes.

  This will be described in more detail. This type of conductive paste for electrodes is made of transparent and light-transmitting glass, polyethylene terephthalate (hereinafter referred to as PET), acrylic resin, polycarbonate, and other ITO coatings formed on plastic substrates. It is used as a material for forming an electrode layer on the transparent conductive film. That is, as the conductive paced conductive fine powder containing binder resin, conductive fine powder and solvent as essential components, tin oxide fine powder (spherical or flake shaped) and silver fine powder (spherical or flake shaped etc.) ) To use a mixture. More specifically, the conductive fine powder is composed of a mixture of 0.2 to 20% by mass of tin oxide fine powder and 99.8 to 80% by mass of silver fine powder. And, such a mixing ratio is because the contact resistance is insufficient when the addition amount of the tin oxide fine powder is less than 0.2% by mass, and the conductivity deteriorates when it exceeds 20% by mass. is there. By setting it as the said mixing range, the target contact resistance is obtained and the electroconductive paste for electrodes which has sufficient electroconductivity is obtained. Specifically, the contact resistance value is in the range of 1/4 to 1/10 of the conductive paste using fine silver powder, and after the heat resistance test, the contact resistance value after the moisture resistance test is the initial contact resistance value. It does not change much (within 50%). And preferably, the mixing ratio of the tin oxide fine powder and the silver fine powder is 1 to 15% by mass of the tin oxide fine powder and 99 to 85% by mass of the silver fine powder. Further, the amount of the conductive fine powder added is preferably 70 to 95 parts by mass with respect to 100 parts by mass of the solid content of the electrode conductive paste. In addition, as the binder resin, which is an essential component of the conductive paste, polyester resin, acrylic resin, phenol resin, vinyl chloride vinyl acetate copolymer resin, urethane resin, epoxy resin, and the like can be used. It is added in a range of 5 to 30 parts by mass with respect to 100 parts by mass of the solid content of the adhesive paste. Furthermore, as a solvent as an essential component, ethyl diglycol acetate, butyl glycol acetate, butyl diglycol acetate, benzyl alcohol, isophorone and the like can be used. This conductive paste for electrodes requires silver-plated metal fine powder such as silver-plated copper fine powder, silver-plated nickel fine powder, titanium oxide fine powder, carbon fine powder, nickel fine powder, silica fine powder, etc. Can be added. The conductive paste for electrodes of the present invention as described above has a low contact resistance and is stable even when used as an electrode layer of a transparent conductive coating film, and the conductive fine powder contains silver at a specific ratio. Since only the fine powder and the tin oxide fine powder need to be mixed, it is not necessary to perform a special processing step as in the technique described in Patent Document 1.

  Moreover, as tin oxide fine powder, a 5 nm-30 micrometer thing is used as described in Claim 2. However, if it is less than 5 nm, it is difficult to produce, and fine powders exceeding 30 μm are clogged by screen printing or dispenser application. Therefore, it is preferable to select particles having a particle diameter of 10 nm to 10 μm. Further, the tin oxide fine powder is preferably an antimony-doped tin oxide fine powder as described in claim 3. This is because doping with antimony is preferable because conductivity is increased. Usually, the thing doped to about 0.1-20 mass parts with respect to 100 mass parts of tin oxide fine powder is preferable. As described above, the electrode conductive paste in which the conductive fine particles are specified has a low contact resistance and becomes a stable conductive paste even when used as an electrode layer of a transparent conductive coating film. Specifically, after the heat resistance test, the contact resistance value after the moisture resistance test is stable and does not change much from the initial contact resistance value. That is, the contact resistance value is in the range of 1/4 to 1/10 of the conductive paste using fine silver powder. Furthermore, since the conductive fine particles to be used do not need to be subjected to a special processing step, they are practical without increasing the manufacturing cost.

And as described in Claim 4, the transparent touch panel which formed the electrode layer on the transparent conductive film using the conductive paste for electrodes described in any one of Claims 1-3 has a specific resistance. It is about 10 × 10 ⁻⁵ Ω · cm, and the contact resistance value after the heat resistance test and after the moisture resistance test is ¼ to 1/10 of the conductive paste using silver fine powder with respect to the initial contact resistance value. The range is stable and excellent in electrical characteristics and in the formability of the electrode layer.

  An example of a transparent touch panel provided by the present applicant will be described with reference to FIG. Reference numeral 1 denotes a transparent touch panel. The lower base plate 2 or the upper base plate 2 'is made of a plastic base material such as glass or polyethylene terephthalate (hereinafter referred to as PET), acrylic resin, or polycarbonate. A light-transmissive lower conductive layer 3 or upper conductive layer 3 ′ such as ITO is formed on the lower base plate 2 or the upper base plate 2 ′. The conductive paste of the present invention (for example, 0.2 to 20% by mass of tin oxide fine powder and 99.8 to 80% by mass of silver fine powder) is formed at both ends of the lower conductive layer 3 of the lower base plate 2. % Electrode) is used to form the lower electrodes 4 and 4. Similarly, the upper electrodes 4 ′ and 4 ′ are formed on the upper conductive layer 3 ′ of the upper base plate 2 ′ so as to face the lower electrodes 4 and 4 using the conductive paste. The upper electrodes 4 ′, 4 ′ and the lower electrodes 4, 4 facing each other are arranged with resist layers 6, 6 and 6 ′, 6 ′ formed through adhesive materials 5, 5. And the spacer 7 is provided in the appropriate place on the lower conductive layer 3, and it is set as the transparent touch panel 1. FIG. Such a transparent touch panel can be stably used as a component for switching the functions of various electronic devices over a long period of time and has excellent electrical characteristics.

  The effects of the conductive paste of the present invention will be described by the following examples. The electrode paste having the composition shown in Table 1 is cured on a base film (product number: 300RM-4) of Toyobo Co., Ltd. having an ITO conductive layer at 120 ° C. for 10 minutes to form an electrode layer. The specific resistance, initial contact resistance, heat resistance test, moisture resistance test, and adhesion were measured. The binder resin used is Byron 500, which is a polyester resin from Toyobo Co., Ltd. As phosphorous-doped tin oxide fine powder (hereinafter referred to as Sn (P) oxide fine powder), Mitsubishi Materials Corporation S-2000, and as antimony-doped tin oxide fine powder (hereinafter referred to as Sn (Sb) oxide fine powder), Mitsubishi Materials Corporation. Transparent conductive powder TZ-1 (particle size: 10 nm) and Elecom TL-20 (particle size: 7 μm) manufactured by Catalyst Kasei. Furthermore, as a tin oxide fine powder (hereinafter referred to as Sn oxide), TIPEVI (particle size: 1 μm) manufactured by Mitsui Kinzoku Co., Ltd., and as a silver fine powder (hereinafter referred to as Ag fine powder), a flaky silver fine powder manufactured by Fellow's Silver Flake # 65. These conductive fine powders are dispersed in a solvent (Ethyl Glycol Acetate from Daicel Chemical Industries) together with the binder resin so as to have a solid content of 75% by mass to obtain a conductive paste for electrodes. For comparison, Ketjen Black EC, which is a titanium oxide fine powder (hereinafter referred to as Ti oxide fine powder) ET-500W manufactured by Ishihara Sangyo Co., Ltd., and a carbon black (hereinafter referred to as CB fine powder) manufactured by Lion, is used instead of tin oxide fine powder. In addition, a conductive paste for electrodes to which nickel powder 210, which is nickel fine powder (hereinafter referred to as Ni fine powder), manufactured by Inco Limited was added.

  Next, the test items will be described. The specific resistance is obtained by curing a conductive paste on a glass plate at 120 ° C. for 10 minutes to form an electrode layer, measuring the resistance value using a digital multimeter (R6581D) manufactured by ADVANTEST, and further measuring the film thickness and interelectrode distance. Was measured and calculated. The contact resistance is obtained by curing the conductive paste on a substrate film having an ITO conductive layer at 120 ° C. for 10 minutes to form an electrode layer, and a four-terminal four-deep needle method high-precision low resistivity meter (manufactured by Dia Instruments) ( Measured using Lorester GP). The heat resistance test is a measurement of the contact resistance after the sample used for the initial contact resistance measurement is left at 85 ° C. for 500 hours. Further, the moisture resistance test is a measurement of the contact resistance after the sample used for the initial contact resistance measurement is left at 65 ° C. × 95% humidity × 500 hours. In addition, as an adhesive property, an electrode layer is formed, and the conductive paste is cured on a substrate film having an ITO conductive layer at 120 ° C. for 10 minutes to form an electrode layer. A cellophane tape test was conducted with a cutter, and those that did not peel off at all were marked as “O”. The results are as shown in Table 1.

As described in Table 1, those using the conductive paste for electrodes shown in Examples 1 to 16 can be used as the electrode layer of the transparent conductive coating film without performing a special treatment step for the conductive fine powder. When used, it is a conductive paste for electrodes with a contact resistance of 1/4 to 1/10 that of a conductive paste using fine silver powder, and a transparent touch panel using the same has similar characteristics. It was. That is, as described in Examples 1 to 4, a conductive fine powder obtained by mixing 99 to 85% by mass of Ag fine powder and 1 to 15% by mass of oxidized Sn (Sb) fine powder having a particle diameter of 10 nm. The electrode conductive paste used has a specific resistance value of about 10 × 10 ⁻⁵ units, a contact resistance value of 7.2 to 3.6Ω after the heat resistance test, and a contact resistance value of 7.5 after the moisture resistance test. It can be seen that it is a conductive paste for an electrode having an excellent conductivity of ˜4.0Ω and ¼ to 1/10 of the conductive paste using silver fine powder. In addition, the adhesiveness was acceptable without any peeling in the cellophane tape test. Further, as described in Examples 5 to 8, an electrode using conductive fine powder having the same composition as in Examples 1 to 4 except that oxidized Sn (Sb) fine powder having a particle size of 70 μm was used. The conductive paste also has a specific resistance value of about 10 × 10 ⁻⁵ units, a contact resistance value after the heat resistance test of 7.3 to 4.0Ω, and a contact resistance value after the moisture resistance test of 7.7 to 4. It can be seen that the conductive paste for electrodes is excellent as 4Ω and ¼ to 1/10 of the conductive paste using silver fine powder. In addition, the adhesiveness was acceptable without any peeling in the cellophane tape test. Furthermore, as described in Examples 9 to 12, a conductive fine powder obtained by mixing 99 to 85% by mass of Ag fine powder and 1 to 15% by mass of oxidized Sn (P) fine powder having a particle size of 10 nm. The electrode conductive paste used has a specific resistance value of about 10 × 10 ⁻⁵ units, a contact resistance value of 7.1 to 3.3Ω after the heat resistance test, and a contact resistance value of 8.3 after the moisture resistance test. It can be seen that this is an excellent conductive paste for electrodes, ˜4.7Ω, ¼ to 1/10 of the conductive paste using silver fine powder. In addition, the adhesiveness was acceptable without any peeling in the cellophane tape test. Moreover, as described in Examples 13 to 16, an electrode using conductive fine powder in which 99 to 85% by mass of Ag fine powder and 1 to 15% by mass of oxidized Sn fine powder having a particle size of 1 μm were mixed. The conductive paste also has a specific resistance value of about 10 × 10 ⁻⁵ units, a contact resistance value after the heat resistance test of 7.4 to 4.1Ω, and a contact resistance value after the moisture resistance test of 9.1 to 5. It can be seen that the conductive paste for electrodes is 6Ω and ¼ to 1/10 of the conductive paste using silver fine powder. In addition, the adhesiveness was acceptable without any peeling in the cellophane tape test.

On the other hand, when the Ag fine powder shown in Comparative Example 1 is 100% by mass, it can be seen that the initial contact resistance value itself is 30.0Ω, which is higher than that of the example. Further, as in Comparative Example 2, in the case of the conductive paste using the conductive fine powder in which the Ag fine powder is 70% by mass and the oxidized Sn (Sb) fine powder having a particle size of 10 nm is 30%, the specific resistance It becomes a middle value of 10 ⁻⁴ , which is larger than that shown in the example. This seems to be because the added amount of fine powder of oxidized Sn (Sb), which is inferior in conductivity to fine Ag powder, is large. In the case of a conductive paste in which 5% by mass of fine Ti oxide powder is added to 95% by mass of Ag fine powder as in Comparative Example 3, the initial contact resistance value is 100% by mass of Ag fine powder. There is not much change, and the effect of improving the contact resistance is not seen. Also, in the case of the conductive paste in which 5% by mass of CB powder is added to 95% by mass of Ag fine powder as in Comparative Example 4, the initial contact resistance value is much different from that of 100% by mass of Ag fine powder. In addition, the effect of improving the contact resistance was not observed. Further, as in Comparative Example 5, in the case of a conductive paste in which 5% by mass of Ni fine powder was added to 95% by mass of Ag fine powder, the initial contact resistance value was similarly 100% by mass of Ag fine powder. The value was larger than the above, and no effect of improving the contact resistance was found.

  The conductive paste for electrodes of the present invention has an effect of greatly reducing the contact resistance value as compared with the conventional conductive paste using only Ag fine powder, and is used for a long time in various environments. Since it is stable with little change in the contact resistance value, it is useful as an electrode material for a transparent touch panel. Furthermore, since the handling at the time of formation of an electrode layer is easy, a transparent touch panel advantageous from the manufacturing cost and the like can be obtained.

It is a schematic sectional drawing which shows one example of the transparent touch panel of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent touch panel 2, Lower base plate 2 'Upper base plate 3, Lower conductive layer 3' Upper conductive layer 4, Lower electrode layer 4 'Upper electrode layer 5 Adhesive material 6, 6' Resist layer 7 Spacer

Claims (4)

A conductive paste used for an electrode of a transparent conductive film, comprising a binder resin, conductive fine powder and a solvent as essential components, wherein the conductive fine powder is 0.2 to 20% by mass of tin oxide fine powder, silver powder 99.8 to 80 wt% Tona is,
The binder resin is at least one selected from the group consisting of polyester resin, acrylic resin, phenol resin, vinyl chloride vinyl acetate copolymer resin, urethane resin, epoxy resin,
It said solvent is ethyl diglycol acetate, butyl glycol acetate, butyl diglycol acetate, benzyl alcohol, electrode conductive paste consisting at least one Der wherein Rukoto selected from the group consisting of isophorone.   The conductive paste for an electrode according to claim 1, wherein the tin oxide fine powder is an antimony-doped tin oxide fine powder.   3. The conductive paste for an electrode according to claim 1, wherein the tin oxide fine powder has a particle size of 5 nm to 30 μm.   A transparent touch panel, wherein an electrode layer is formed on a transparent conductive film using the electrode conductive paste according to claim 1.

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