Ink coating film and dryness measurement method

Abstract

According to the present invention, a liquid ink which contains carbon black and does not contain metal particles does not have conductivity but an ink coating film obtained by drying said ink has conductivity. This ink coating film laminated on a recording medium contains at least carbon black, does not contain metal particles, and has conductivity.

Description

Ink film thickness and dryness measurement method

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

[0002] Conventionally, inks containing metal fine particles 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.

[0003] JP 2022-99275 A JP 2022-172874 A

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

[0005] After extensive research, the present inventors have discovered an ink coating film that contains carbon black but no metal particles and has electrical conductivity, thereby completing the present invention.

[0006] (1) The present invention relates to an ink coating film laminated on a recording medium, the ink coating film 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 it.

[0009] (4) The water-based ink may not be electrically 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 value of the ink coating may be within a range of 5.9×10 5 Ω / □ to 3.6×10 11 Ω / □.

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

[0013] (8) The resistance value of the ink coating film may be 3.6×10 Ω / □ or less, and the conductivity of the ink before drying as the ink coating film 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 may not contain a conductive polymer.

[0016] (11) The average particle size of the carbon black may be in the range of 50 nm to 200 nm.

[0017] (12) The average particle size of the carbon black may be in the range of 100 nm to 150 nm.

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

[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 dries. In this measurement method, the conductivity of the ink coating film is measured, and the dryness is determined according to the measured conductivity.

[0020] Ink in a liquid state has no or little conductivity, but when the ink dries and forms an ink film on the recording medium, it becomes conductive. Therefore, by measuring the conductivity of the ink film, it is possible to determine whether the ink has dried and formed an ink film.

[0021] (15) The resistance of the ink coating film may be 3.6×10 Ω / □ or less, and the conductivity of the ink before drying as the ink coating film may be lower than 1.0 mS / cm.

[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.

[0023] Fig. 1 is a perspective view of a printer 10. Fig. 2 is a schematic diagram showing the internal configuration of the printer 10.

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

[0025] 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, a sheet unwound from a cylindrical roll, or a fanfold type. The sheet 6 may be plain paper or a non-water-absorbent medium such as coated paper or film. "Coated paper" refers to plain paper made of pulp, such as high-quality printing paper or medium-quality printing paper, to which a coating agent has been applied to improve smoothness, whiteness, gloss, etc., specifically, high-quality coated paper and medium-quality coated paper. A film is a synthetic resin molded into a sheet. A non-water-absorbent medium refers to a medium that absorbs little water within a certain period of time for water droplets to dry, such as coated paper or a plastic substrate such as OPP or PET.

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

[0028] 2, the paper supply 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 supply tray 23. The cover 22 is located at the right side of the front 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 can be accessed.

[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 storing four colors of ink: black, yellow, cyan, and magenta.

[0030] As shown in FIG. 2 , the housing 20 holds a 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 within the housing 20 so as to be able to contact the sheet 6 placed in 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 defined 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 transport roller 26 is located downstream of the paper feed tray 23 in the transport direction of the sheet 6. The transport roller 26 and the driven roller 35 form a roller pair. The transport roller 26 is rotated by a motor (not shown). The rotating transport roller 26 and the driven roller 35 sandwich and transport the sheet 6 sent out to the transport path 37 by the paper feed roller 25. The discharge roller 27 is located downstream of the transport roller 26 in the transport 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 sandwich and transport the sheet 6, and discharge the sheet 6 to the paper discharge tray 24. The platen 28 is located between the transport roller 26 and the discharge roller 27 in the front-to-rear direction 8, downstream of the transport roller 26 and upstream of the discharge roller 27 in the transport 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 on the encoder disk 97. When the optical sensor reads the two types of indexes on the rotating encoder disk 97, two types of signals are output from the optical sensor 98 in the form of pulses. The output signal from the optical sensor 98 is received by a controller (described later) to determine the rotational speed of the conveying roller 26.

[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. This 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 drawings, an opening through which suction pressure is generated is formed in the upper surface of the platen 28. The suction pressure generated on the upper surface of the platen 28 brings the sheet 6 into close contact with 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] As shown in Figure 2, the heater 39 is located downstream, i.e., forward, 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. Heat from the halogen lamp 40 and reflector 41 is radiated to the outside or is blocked through the opening 43.

[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 its 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 its 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 below 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 passes below the heater 39 cools, the glass-transitioned resin hardens. This fixes the ink to the sheet 6.

[0039] The heater 39 is not limited to a halogen heater as long as it can heat the sheet or 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 water-based ink stored in the tank 70 will be described in detail below. 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, for example, metal materials such as aluminum, silver, gold, platinum, nickel, chromium, tin, zinc, indium, titanium, iron, copper, and alloys thereof. The metal particles need not necessarily be made entirely of a metal material, as long as at least a portion, such as the outer surface, of the metal particles 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, dyes, etc. 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% by mass to 10.0% by mass, and more preferably in the range of 3.0% by mass to 5.0% by mass. One type of carbon black may be used alone, or two or more types may be used in combination.

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

[0046] The resin microparticles may contain, for example, at least one of methacrylic acid and acrylic acid as a monomer, and commercially available products may be used. The resin microparticles may further contain, for example, styrene, vinyl chloride, etc. as a monomer. The resin microparticles may be contained in, for example, a resin emulsion. The resin emulsion is composed of, for example, resin microparticles and a dispersion medium (for example, water, etc.). The resin microparticles are not dissolved in the dispersion medium, but are dispersed within a specific particle size range. Examples of resin microparticles 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., and "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 Corporation.

[0048] The content (R) of the resin 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 particle 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 with water when the organic solvent and water are mixed at 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 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) of the total amount of 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 needed. 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 then removing any insoluble matter using a filter or the like.

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

[0055] [Ink coating film] For example, after the water-based ink is ejected onto the recording medium by the print head 34 of the printer 10, the water-based ink and the recording medium are heated by the heater 39 to dry and solidify, thereby forming an ink coating film on the recording medium.

[0056] The formed ink coating film has conductivity. The conductivity of the ink coating film can be determined by measuring the resistance of the ink coating film using, for example, a Hiresta or a tester. The resistance of the ink coating film is preferably within a range of 5.9×10 Ω / □ to 3.6×10 Ω / □, and more preferably within a range of 2.0×10 Ω / □ to 3.6×10 Ω / □.

[0057] Furthermore, although the water-based ink ejected onto the recording medium is not conductive, it becomes conductive once it dries and solidifies. Therefore, the degree of dryness of the water-based ink can be determined 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.

[0058] By being able to determine the dryness of water-based ink on a recording medium, for example, it is possible to prevent the water-based ink ejected onto roll paper from being transferred to the back surface of the roll paper when the roll paper is wound into a roll before the ink has dried. Furthermore, because the ink coating is conductive, even if static electricity builds up on the recording medium due to friction or other factors, it is easy to remove the charge through the ink coating. On the other hand, because the water-based ink is not conductive, it is less likely to adhere to the device housing, etc.

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

[0060] [Preparation of Water-Based Inks] A pigment dispersion consisting of carbon black (average particle size 100-150 nm), dispersant, and water, with the composition shown in Table 1, a resin microparticle dispersion consisting of resin microparticles and water, and other ingredients were uniformly mixed to obtain a mixture of 100% by mass. The resulting 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 resulting water-based inks A to G was measured using an electrical conductivity meter F-74 manufactured by Horiba, Ltd. The electrical conductivity of each of the water-based inks A to G was lower than 1.0 mS / cm. Wetting agent: propylene glycol Surfactant: Olfine E1004 manufactured by Nissin Chemical Industry Co., Ltd.

[0061]

[0062] [Ink Coating Film] Water-based inks A to G were coated onto 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 coated with the water-based ink 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 formed ink coating film was calculated from the ratio of the solid content in the water-based ink to the film thickness of the coated water-based ink. The results are shown in Table 2.

[0063]

[0064] [Conductivity] A measurement probe was brought into close contact with the ink coating film formed on the recording medium, and the surface resistance was measured 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]

[0066] [Abrasion resistance] An adhesive tape (Cellotape manufactured by Nichiban Co., Ltd.) 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. A mark of ○ was given for cases where the ink coating film did not peel off, and a mark of × was given for cases where the ink coating film peeled off. The results are shown in Table 4.

[0067]

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

[0069]

[0070] As shown in Tables 1 and 2, ink coating films using water-based inks A, B, and C, which contain resin microparticles, provided ink coating films with stable thicknesses depending on the amount of water-based ink applied to the recording medium. Since the thickness of the ink coating film is determined by the solid content in the water-based ink, ink coating films using water-based inks D, E, F, and G, which do not contain resin microparticles, 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, a solid content in the water-based ink.

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

[0072] As shown in Table 4, the ink coating film made using water-based ink G, which does not contain resin microparticles and has a high carbon black content, had poor abrasion resistance. Furthermore, with water-based inks D and F, which do not contain resin microparticles, the abrasion resistance tended to deteriorate as the ink coating film became thicker.

[0073] As shown in Table 5, the ink coating film using water-based ink E, which does not contain resin particles and has a low carbon black content, tended to have a small OD value.

Claims

1. An ink coating layer laminated on a recording medium, the ink coating layer containing at least carbon black and no metal particles, and having 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 according to claim 3, wherein the water-based ink has no electrical conductivity.

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 ink coating according to claim 1, wherein the resistance value of the ink coating is within the range of 5.9×10 5 Ω / □ to 3.6×10 11 Ω / □.

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

8. The ink coating according to claim 1, wherein the resistance value of the ink coating is 3.6 x 1011 Ω / □ or less, and the conductivity of the ink before drying as the ink coating is lower than 1.0 mS / cm.

9. The ink coating according to 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 said ink coating does not include a conductive polymer.

11. 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. The ink coating according to claim 1, wherein the average particle size of the carbon black is within 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 when ink on a recording medium has dried, comprising measuring the electrical conductivity of the ink coating and determining the dryness according to the measured electrical conductivity.

15. A method for measuring the dryness of a liquid according to claim 14, wherein the resistance of the ink coating is 3.6 x 1011 Ω / □ or less, and the conductivity of the ink before drying as the ink coating is lower than 1.0 mS / cm.

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