Ink coating film and dryness measurement method

Abstract

To provide a liquid ink which contains carbon black and does not contain metal particles, wherein it does not have conductivity, but exhibits conductivity as a dried ink coating film.SOLUTION: An ink coating film laminated on a recording medium contains at least carbon black, does not contain metal particles, and has conductivity.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an ink coating deposited on a recording medium. [Background technology]

[0002] Conventionally, inks containing metal particles, for example, have been known as liquids for forming conductive films (see Patent Documents 1 and 2). These inks are used, for example, to form conductive circuits and electrodes in electronic circuits. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-99275 [Patent Document 2] JP 2022-172874 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, there are no known ink coating films that contain carbon black and no metal particles and have electrical conductivity.

[0005] As a result of extensive research, the present inventors have discovered an ink coating film that contains carbon black and no metal particles and has electrical conductivity, thereby completing the present invention. [Means for solving the problem]

[0006] (1) The present invention relates to an ink coating layer laminated on a recording medium, the ink coating layer containing at least carbon black, not containing metal particles, and having electrical conductivity.

[0007] (2) The ink coating may be solidified by drying on the recording medium.

[0008] (3) The ink coating may be formed by drying an aqueous ink containing at least water on the recording medium and solidifying the ink.

[0009] (4) The water-based ink does not need to be conductive.

[0010] (5) The water-based ink may contain the carbon black, resin particles, a water-soluble organic solvent, and water.

[0011] (6) The resistance of the ink coating is 5.9×10 5 Ω / □ to 3.6×10 11 It may be in the range of Ω / □.

[0012] (7) The resistance of the ink coating is 2.0×10 6 Ω / □ to 3.6×10 11 It may be in the range of Ω / □.

[0013] (8) The resistance of the ink coating is 3.6×10 11 The electrical conductivity of the ink before drying as the ink coating may be lower than 1.0 mS / cm.

[0014] (9) The OD value of the ink coating may be in the range of 0.6 to 2.1.

[0015] (10) The ink coating does not have to include a conductive polymer.

[0016] (11) The carbon black may have an average particle size within a range of 50 nm to 200 nm.

[0017] (12) The carbon black may have an average particle size within a range of 100 nm to 150 nm.

[0018] (13) The recording medium may be non-water absorbing.

[0019] (14) The present invention relates to a method for measuring the dryness of an ink coating film formed when ink on a recording medium is dried, the method comprising measuring the electrical conductivity of the ink coating film and determining the dryness of the ink coating film according to the measured electrical conductivity.

[0020] Ink in a liquid state has no or only slight conductivity, whereas when the ink dries to form an ink film on a recording medium, it has conductivity. Therefore, by measuring the conductivity of the ink film, it is possible to determine whether the ink has dried to form an ink film.

[0021] (15) The resistance of the above ink coating is 3.6×10 11 The electrical conductivity of the ink before drying as an ink coating may be lower than 1.0 mS / cm. Effect of the Invention

[0022] According to the present invention, an ink coating film that contains carbon black and does not contain metal particles and has electrical conductivity is realized. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a perspective view of a printer 10. [Diagram 2] FIG. 2 is a schematic diagram showing the internal configuration of the printer 10. As shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The printer 10, which is an example of an apparatus for forming an ink coating film of the present invention, will be described below. The printer 10 described below is merely an example of an apparatus for forming an ink coating film, and it goes without saying that the ink coating film of the present invention may be formed by other apparatuses. In the following description, the direction is expressed as the progress from the starting point of the arrow to the end point, and the direction is expressed as the movement on the line connecting the starting point and the end point of the arrow. In the following description, the up-down direction 7 is defined based on the state in which the printer 10 is installed so that it can be used (the state in FIG. 1), the front-rear direction 8 is defined with the side where the discharge port 13 is provided as the front side (front), and the left-right direction 9 is defined when the printer 10 is viewed from the front side (front).

[0025] [Appearance of Printer 10] 1, the printer 10 includes a housing 20, a panel unit 21, a cover 22, a paper feed tray 23, and a paper discharge tray 24, which are held by the housing 20. The printer 10 records an image on a sheet 6 (see FIG. 2).

[0026] The sheet 6 is an example of a recording medium. The sheet 6 may be a recording medium cut to a predetermined size, may be a sheet pulled out from a roll wound into a cylindrical shape, or may be a fanfold type. The sheet 6 may be plain paper, or may be a non-water-absorbent medium such as coated paper or film. The term "coated paper" refers to plain paper made of pulp, such as high-grade printing paper or medium-grade printing paper, coated with a coating agent for the purpose of improving smoothness, whiteness, glossiness, etc., and specifically includes high-quality coated paper and medium-quality coated paper. The film is a synthetic resin formed into a sheet. The non-water-absorbent medium refers to a medium that absorbs almost no water within a certain time period until water droplets dry, and refers to, for example, coated paper and plastic substrates such as OPP and PET.

[0027] The panel unit 21 includes a touch panel and a plurality of operation switches and receives operations from a user.

[0028] 2, the paper feed tray 23 is located at the bottom of the housing 20. The paper output tray 24 is located at the bottom of the housing 20, above the paper feed tray 23. The cover 22 is located at the right part of the front surface of the housing 20. The cover 22 is rotatable relative to the housing 20. When the cover 22 is opened, the tank 70 that stores ink is accessible.

[0029] In this embodiment, only one tank 70 is shown, but the tank 70 is not limited to storing one color of ink, such as black, and may have four storage chambers, each of which stores four colors of ink: black, yellow, cyan, and magenta.

[0030] As shown in FIG. 2, the housing 20 holds the print engine 50 therein. The print engine 50 mainly includes a paper feed roller 25, a transport roller 26, a discharge roller 27, a platen 28, and a recording unit 29. The paper feed roller 25 is held by a frame (not shown) provided in the housing 20 so as to be able to abut against the sheet 6 placed on the paper feed tray 23. The paper feed roller 25 is rotated by a motor (not shown). The rotating paper feed roller 25 sends the sheet 6 to a transport path 37. The transport path 37 is a space partitioned by a guide member (not shown). In the illustrated example, the transport path 37 curves and extends from the rear end of the paper feed tray 23 to a position above the paper feed tray 23, and then extends forward.

[0031] The conveying roller 26 is located downstream of the paper feed tray 23 in the conveying direction of the sheet 6. The conveying roller 26 and the driven roller 35 form a roller pair. The conveying roller 26 is rotated by a motor (not shown). The rotating conveying roller 26 and the driven roller 35 convey the sheet 6 sent to the conveying path 37 by the paper feed roller 25 while sandwiching it. The discharge roller 27 is located downstream of the conveying roller 26 in the conveying direction of the sheet 6. The discharge roller 27 and the driven roller 36 form a roller pair. The discharge roller 27 is rotated by a motor (not shown). The rotating discharge roller 27 and the driven roller 36 convey the sheet 6 while sandwiching it, and discharge it to the paper discharge tray 24. The platen 28 is located between the conveying roller 26 and the discharge roller 27 in the front-rear direction 8, downstream of the conveying roller 26 and upstream of the discharge roller 27 in the conveying direction of the sheet 6.

[0032] The conveying roller 26 is provided with a rotary encoder 96. The rotary encoder 96 is an example of a speed sensor. The rotary encoder 96 has an encoder disk 97 and an optical sensor 98. The encoder disk 97 is provided coaxially with the conveying roller 26 and rotates together with the conveying roller 26. The encoder disk 97 has two types of indexes with different transmittances arranged alternately around the entire circumference. The optical sensor 98 can optically read the two types of indexes of the encoder disk 97. The optical sensor reads the two types of indexes of the rotating encoder disk 97, and two types of signals are output from the optical sensor 98 in the form of pulses. The output signal of the optical sensor 98 is received by a controller described later, and the rotation speed of the conveying roller 26 is determined.

[0033] The recording unit 29 has a print head 34 and a heater 39. The print head 34 is located between the transport roller 26 and the discharge roller 27. The print head 34 may be a so-called serial head or a so-called line head. The print head 34 has an internal flow path through which ink flows. The flow path is connected to the tank 70 by a tube 31. That is, ink stored in the tank 70 is supplied to the print head 34 through the tube 31.

[0034] The platen 28 is located below the print head 34. The upper surface of the platen 28 is a support surface for the sheet 6. Although not shown in the figures, an opening through which suction pressure is generated is formed in the upper surface of the platen 28. The sheet 6 is brought into close contact with the upper surface of the platen 28 by the suction pressure generated on the upper surface of the platen 28.

[0035] 2 and 3, a heater 39 is located above the transport path 37, downstream of the print head 34 and upstream of the discharge roller 27. The heater 39 is a so-called halogen heater.

[0036] 2, the heater 39 is located downstream, i.e., in front of the print head 34 in the transport direction. The heater 39 has a halogen lamp 40, which is a heating element that radiates infrared rays, a reflector 41, and a housing 42. The housing 42 is roughly cuboid in shape and opens downward. An opening 43 is located in the bottom wall of the housing 42. Through the opening 43, heat from the halogen lamp 40 and the reflector 41 is radiated to the outside or is blocked.

[0037] A halogen lamp 40 is located in the internal space of the housing 42. The halogen lamp 40 has an elongated cylindrical shape, with the left-right direction 9 being the longitudinal direction. A reflector 41 is located above the halogen lamp 40 in the internal space of the housing 42. The reflector 41 is a metal plate coated with a ceramic film or the like, and is curved in an arc shape with the vicinity of the opening 43 as the central axis. Note that instead of the reflector 41, a halogen lamp 40 coated with a ceramic film or the like may be used.

[0038] The heater 39 heats at least one of the sheet 6 passing under the opening 43 and the ink attached to the sheet 6. In this embodiment, the heater 39 heats both the sheet 6 and the ink. When the ink is heated, the resin particles undergo glass transition, and when the sheet 6 passing under the heater 39 cools, the glass-transitioned resin hardens. This causes the ink to be fixed to the sheet 6.

[0039] The heater 39 is not limited to a halogen heater as long as it can heat the sheet or the ink. For example, the heater 39 may be a carbon heater, a dryer, an oven, a belt conveyor oven, or the like.

[0040] [Water-based ink] The following describes in detail the water-based ink stored in the tank 70. The water-based ink contains carbon black, resin particles, a water-soluble organic solvent, and water. The water-based ink does not contain metal particles or conductive polymers.

[0041] Metal particles include metal materials such as aluminum, silver, gold, platinum, nickel, chromium, tin, zinc, indium, titanium, iron, copper, and alloys thereof. It is sufficient that at least a portion of the metal particles, such as the outer surface, is made of a metal material, and it is not necessary that the entire particle is made of a metal material.

[0042] The conductive polymer may function as a binder or a dispersant. The conductive polymer forms a conductive layer in the ink coating. Examples of the conductive polymer include polythiophenes, polyanilines, and polypyrroles.

[0043] Examples of carbon black include furnace black, lamp black, acetylene black, channel black, etc. The water-based ink may further contain other pigments and dyes in addition to carbon black.

[0044] The solid content of carbon black in the total amount of the water-based ink is, for example, preferably in the range of 1.0% to 10.0% by mass, and more preferably in the range of 3.0% to 5.0% by mass. Carbon black may be used alone or in combination of two or more types.

[0045] The average particle diameter of carbon black is, for example, preferably within the range of 50 nm to 200 nm, more preferably within the range of 100 nm to 150 nm. The average particle diameter can be measured as an arithmetic mean diameter, for example, using a dynamic light scattering particle size distribution measuring device "LB-550" manufactured by Horiba, Ltd.

[0046] As the resin fine particles, for example, those containing at least one of methacrylic acid and acrylic acid as a monomer can be used, and for example, commercially available products may be used. The resin fine particles may further contain, for example, styrene, vinyl chloride, etc. as a monomer. The resin fine particles may be, for example, those contained in a resin emulsion. The resin emulsion is, for example, composed of resin fine particles and a dispersion medium (for example, water, etc.). The resin fine particles are not dissolved in the dispersion medium, but are dispersed within a specific particle size range. Examples of the resin fine particles contained in the resin emulsion include acrylic acid-based resins, maleic acid-based ester resins, vinyl acetate-based resins, carbonate-based resins, polycarbonate-based resins, styrene-based resins, ethylene-based resins, polyethylene-based resins, propylene-based resins, polypropylene-based resins, urethane-based resins, polyurethane-based resins, polyester-based resins, and copolymer resins thereof.

[0047] As the resin emulsion, for example, commercially available products may be used. Examples of commercially available products include "Superflex (registered trademark) 870" (Tg: 71°C) and "Superflex (registered trademark) 150" (Tg: 40°C) manufactured by Daiichi Kogyo Seiyaku Co., Ltd., "Mowinyl (registered trademark) 6969D" (Tg: 77°C) and "Mowinyl (registered trademark) DM774" (Tg: 33°C) manufactured by Japan Coating Resins Co., Ltd., "Polysol (registered trademark) AP-3270N" (Tg: 27°C) manufactured by Showa Denko K.K., "Hi-Loss-X (registered trademark) KE-1062" (Tg: 112°C) and "Hi-Loss-X (registered trademark) QE-1042" (Tg: 69°C) manufactured by Seiko PMC Co., Ltd.

[0048] The content (R) of the resin fine particles in the total amount of the water-based ink is, for example, preferably in the range of 0.1% by mass to 30.0% by mass, more preferably in the range of 0.5% by mass to 20.0% by mass, and particularly preferably in the range of 1.0% by mass to 5.0% by mass. One type of resin fine particles may be used alone, or two or more types may be used in combination.

[0049] The water-soluble organic solvent is an organic solvent that is uniformly mixed when the organic solvent and water are mixed in a ratio of 1:1. Examples of the water-soluble organic solvent include propylene glycol (vapor pressure at 20°C: 0.11 hPa), ethylene glycol (vapor pressure at 20°C: 0.07 hPa), 1,2-butanediol (vapor pressure at 20°C: 0.03 hPa), propylene glycol propyl ether (vapor pressure at 20°C: 2.20 hPa), dipropylene glycol propyl ether (vapor pressure at 20°C: 0.1 hPa), diethylene glycol monobutyl ether (vapor pressure at 20°C: 0.1 hPa), and 1,6-hexanediol (vapor pressure at 20°C: 0.7 hPa).

[0050] The content of the water-soluble organic solvent in the total amount of the ink is, for example, preferably in the range of 10.0% by mass to 40.0% by mass, and more preferably in the range of 20.0% by mass to 40.0% by mass.

[0051] The water is preferably ion-exchanged water or pure water. The water content (W) in the total amount of the ink is, for example, preferably in the range of 10.0% by mass to 90.0% by mass, more preferably in the range of 20.0% by mass to 80.0% by mass. The water content (W) may be, for example, the balance of other components.

[0052] The water-based ink may further contain conventionally known additives as necessary. Examples of additives include surfactants, pH adjusters, viscosity adjusters, surface tension adjusters, and antifungal agents. Examples of viscosity adjusters include polyvinyl alcohol, cellulose, and water-soluble resins.

[0053] The water-based ink can be prepared, for example, by uniformly mixing carbon black, resin fine particles, a water-soluble organic solvent, water, and, if necessary, other additive components, using a conventionally known method, and removing any insoluble matter using a filter or the like.

[0054] The water-based ink may not have electrical conductivity. The electrical conductivity of the water-based ink can be measured, for example, using an electrical conductivity meter F-74 manufactured by Horiba, Ltd. In this specification, "the water-based ink does not have sufficient electrical conductivity" means that the measured electrical conductivity of the water-based ink is lower than 1.0 mS / cm.

[0055] [Ink coating] The ink coating is formed on the recording medium, for example, by ejecting water-based ink onto the recording medium using the print head 34 of the printer 10, and then heating the water-based ink and the recording medium using a heater 39 to dry and solidify the ink.

[0056] The ink coating film thus formed has electrical conductivity. The electrical conductivity of the ink coating film is determined by measuring the resistance of the ink coating film using, for example, a high resistance tester or a tester. The resistance of the ink coating film is, for example, 5.9×10 5 Ω / □ to 3.6×10 11It is preferable that the resistance is within the range of Ω / □, and more preferably, 2.0×10 6 Ω / □ to 3.6×10 11 It is within the range of Ω / □.

[0057] Furthermore, although the water-based ink ejected onto the recording medium is not conductive, once the water-based ink dries and solidifies it becomes conductive. Therefore, by measuring the conductivity of the water-based ink ejected onto the recording medium in the same manner as described above and comparing it with a predetermined threshold value, the dryness of the water-based ink can be determined.

[0058] By being able to determine the degree of dryness of the water-based ink on the recording medium, for example, it is possible to prevent the water-based ink ejected onto roll paper from being wound up into a roll before the ink is dried, and the ink from being transferred to the back side of the roll paper. In addition, since the ink coating is conductive, even if the recording medium becomes electrostatically charged due to friction or the like, it is easy to remove the charge through the ink coating. On the other hand, since the water-based ink is not conductive, the water-based ink is less likely to adhere to the device housing, etc. EXAMPLES

[0059] Examples of the present invention will be described below together with comparative examples. Note that the present invention is not limited or restricted by the following examples and comparative examples.

[0060] [Preparation of water-based ink] A pigment dispersion liquid consisting of carbon black (average particle size 100-150 nm), dispersant, and water, a resin fine particle dispersion consisting of resin fine particles and water, and other components in the composition shown in Table 1 were uniformly mixed to obtain a mixture of 100 mass %. The obtained mixture was filtered through a cellulose acetate type membrane filter (pore size 3.0 μm) manufactured by Toyo Roshi Kaisha, Ltd., to obtain water-based inks A to G. The electrical conductivity of the obtained water-based inks A to G was measured using an electric conductivity meter device F-74 manufactured by Horiba, Ltd. The electrical conductivity of the water-based inks A to G was all lower than 1.0 mS / cm. Wetting agent: Propylene glycol Surfactant: Olfine E1004 manufactured by Nissin Chemical Industry Co., Ltd.

[0061] [Table 1]

[0062] [Ink coating] Water-based inks A to G were applied to an OPP film recording medium using three types of bar coaters (I: film thickness 12.7 μm, II: film thickness 17.8 μm, III: film thickness 22.9 μm). The recording medium with the water-based ink applied was left in a drying oven (temperature 60°C, humidity 40%) for 10 minutes to dry the water-based ink and form an ink coating film. The thickness of the ink coating film formed was calculated from the ratio of the solid content in the water-based ink to the film thickness of the water-based ink applied. The results are shown in Table 2.

[0063] [Table 2]

[0064] [Conductive] The surface resistance was measured by placing a measuring probe in close contact with the ink coating formed on the recording medium and using a high resistivity meter, Hiresta (Hiresta UX MCP-HT800, manufactured by Nitto Seiko Air Analytec Co., Ltd. (formerly Mitsubishi Chemical Corporation)). The results are shown in Table 3.

[0065] [Table 3]

[0066] [Abrasion resistance] An adhesive tape (Nichiban Cellotape) was applied to the ink coating film formed on the recording medium, and the adhesive tape was peeled off to evaluate whether the ink coating film peeled off from the recording medium. The ink coating film was marked with an O when it did not peel off, and marked with an X when it peeled off. The results are shown in Table 4.

[0067] [Table 4]

[0068] [OD value] The optical density (OD value) of the ink coating formed on the recording medium was measured using a spectrophotometer eXact manufactured by X-Rite (light source: D50, viewing angle: 2°, ANSI-T). The results are shown in Table 5.

[0069] [Table 5]

[0070] As shown in Tables 1 and 2, the ink coatings using water-based inks A, B, and C, which contain resin particles, provided ink coatings with a stable thickness depending on the amount of water-based ink applied to the recording medium. Since the thickness of the ink coating is determined by the solid content in the water-based ink, the ink coatings using water-based inks D, E, F, and G, which do not contain resin particles, tended to be thinner than water-based inks A, B, and C, although they tended to be thicker depending on the amount of carbon black, which is a solid content in the water-based ink.

[0071] As shown in Table 3, the conductivity of the ink coating was good for water-based inks D and E, which did not contain resin microparticles and had thin ink coatings, but no consistent trend was observed and conductivity was confirmed for all ink coatings.

[0072] As shown in Table 4, the ink coating film using water-based ink G, which does not contain resin particles and has a high carbon black content, had poor abrasion resistance. In addition, with water-based inks D and F, which do not contain resin particles, there was a tendency for the abrasion resistance to become poor as the ink coating film became thicker.

[0073] As shown in Table 5, there was a tendency for the OD value to be smaller in the ink coating film using water-based ink E, which does not contain resin particles and has a low carbon black content.

Claims

1. An ink coating deposited on a recording medium, comprising: An ink coating film that contains at least carbon black, does not contain metal particles, and has electrical conductivity.

2. The ink coating according to claim 1 , wherein the ink coating is solidified by drying on the recording medium.

3. The ink coating according to claim 2 , wherein the ink coating is formed by drying an aqueous ink containing at least water on the recording medium and solidifying the ink coating.

4. The ink coating film according to claim 3 , wherein the water-based ink is non-conductive.

5. The ink coating according to claim 4 , wherein the water-based ink contains the carbon black, resin particles, a water-soluble organic solvent, and water.

6. The resistance value of the ink coating is 5.9×10 ５ Ω / □ to 3.6 x 10 １１ 2. The ink coating of claim 1, wherein the viscosity is in the range of Ω / □.

7. The resistance value of the ink coating is 2.0×10 ６ Ω / □ to 3.6 x 10 １１ 2. The ink coating of claim 1, wherein the viscosity is in the range of Ω / □.

8. The resistance value of the ink coating is 3.6×10 １１ 2. The ink coating according to claim 1, wherein the electrical conductivity of the ink before drying as the ink coating is lower than 1.0 mS / cm.

9. 2. The ink coating of claim 1, wherein the OD value of the ink coating is in the range of 0.6 to 2.

1.

10. The ink coating of claim 1 , wherein the ink coating does not include a conductive polymer.

11. 2. The ink coating according to claim 1, wherein the carbon black has an average particle size in the range of 50 nm to 200 nm.

12. 2. The ink coating according to claim 1, wherein the carbon black has an average particle size in the range of 100 nm to 150 nm.

13. The ink coating of claim 1 , wherein the recording medium is non-water-absorbent.

14. A method for measuring the dryness of an ink coating film on a recording medium by drying the ink, comprising the steps of: A method for measuring the degree of dryness, comprising measuring the electrical conductivity of the ink coating film and determining the degree of dryness according to the measured electrical conductivity.

15. The resistance value of the ink coating is 3.6×10 １１ 15. The method for measuring the dryness of claim 14, wherein the electrical conductivity of the ink before drying as the ink coating is less than 1.0 mS / cm.

Images