JP2012187895A - Inkjet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording method which can perform printing on a barely absorbing record medium, or a non-absorbing record medium such as PET with high-definition and at high speed without the color mix of inks landed on the record medium, and in which the burnish of an image is high, the abrasion resistance of an image is excellent, and nozzles are not clogged to enable stabilized ejection.SOLUTION: In the inkjet recording method provided with a recording head 31 that ejects a plurality of different color inks which contain oil gelatification agents and turn into gel states at room temperature in a state that the recording head 31 is heated at a temperature of +1°C or higher than an initial viscosity rise temperature plus 1°C, the momentary temperature at which a droplet of at least one ink in contact with the record medium 10 first is controlled so as to reach a temperature of gelatification one and +1°C or lower than the initial viscosity rise temperature plus 1°C.

Description

  The present invention relates to an ink jet recording method, and more particularly to an ink jet recording method that emits an ink that contains an oil gelling agent and has a property of gelling near room temperature.

  In recent years, using inkjet systems, I want to print on high-definition and high-speed recording on various recording media such as fine paper recording media such as art paper and coated paper, or non-absorbing recording media such as PET, as well as plain paper. There is a growing demand. When a low-viscosity ink that can be ejected by a conventional inkjet method is printed on such a non-absorbent recording medium at a high speed, adjacent dots are landed before the ink dots that have landed on the recording medium are fixed, color mixing, etc. The image quality degradation was a problem. Accordingly, studies have been made to eject high-viscosity ink that does not cause color mixing from the recording head, but it has not been possible to solve the problem of ejection properties such as nozzle clogging.

  Patent Document 1 discloses an ink jet ink containing an oil gelling agent. When the head temperature is heated to a temperature equal to or higher than the gelation temperature of the ink, the ink undergoes phase inversion (sol → gel) due to the temperature difference of the printing environment temperature. By using an oil gelling agent in ink jet ink, the viscosity is low at the time of ejection, but when ink droplets land on the recording medium, solidification of the ink droplets is completed in a short time, and the ink droplet component Diffusion and the like can be suppressed.

  According to Patent Document 1, by using an ink containing an oil gelling agent, it is possible to provide a recording method that prevents back-through of various recording media and is excellent in ejection properties. However, there is no particular description regarding color mixing.

JP 2005-126508 A

  SUMMARY OF THE INVENTION An object of the present invention is an ink jet which can print on a finely absorptive recording medium or a non-absorbent recording medium such as PET at high speed and with high definition and does not cause color mixing of ink landed on the recording medium. It is to provide a recording method. A further object of the present invention is to provide an ink jet recording method in which the sharpness of fine lines of an image is improved and the gloss of the image is increased.

  Specifically, in accordance with Patent Document 1, a method of ejecting an ink containing an oil gelling agent from a recording head having a temperature higher than the gelation temperature of the ink has been studied, but color mixing is prevented and sharp lines are sharp. The improvement was insufficient.

  In addition, when ink droplets land on the recording medium, we examined discharging ink at a temperature as close to the gelation temperature of the ink as possible so as to quickly gel and suppress wetting and spreading. The ink viscosity becomes high, the tail of the droplet extends long, nozzle clogging occurs, and the like, and it has been a problem to achieve both ejection properties and image quality.

  The present inventors have intensively studied an ink jet recording method capable of improving the ejection property of the ink and improving the image quality of the fine line portion of the image.

  This problem has been solved by controlling the amount of flying droplets, the distance between the nozzle surface and the medium (hereinafter also referred to as the gap width), and the temperature of the recording head. By reducing the droplet volume, the specific surface area of the flying droplets increases, thereby reducing the cooling time constant of the flying droplets, and by increasing the gap width, the flight time becomes longer and the liquid at the time of ejection is reduced. The purpose could be achieved by increasing the difference between the droplet temperature and the droplet temperature upon landing.

  Specifically, the problems of the present invention have been solved by the following means.

  1. In an ink jet recording method comprising a recording head that heats a temperature of a recording head to a viscosity rising temperature of + 1 ° C. or higher, includes an oil gelling agent and is in a gel state at room temperature, and discharges a plurality of inks having different colors. An ink jet recording method, wherein the temperature at the moment when one ink droplet first comes into contact with a recording medium is controlled to be a temperature equal to or higher than a gelling temperature and a viscosity rising temperature + 1 ° C. or lower.

  2. The above-described 1 is characterized in that at the moment when all the ink droplets of the plurality of inks having different colors first come into contact with the recording medium, the temperature becomes equal to or higher than the gelling temperature and the viscosity rising temperature is equal to or lower than + 1 ° C. The ink jet recording method described in 1.

  3. 3. The ink jet recording method according to 1 or 2, wherein the temperature of the recording head is a viscosity rising temperature of the ink + 5 ° C. or more and 80 ° C. or less.

  4). 4. The ink jet recording according to any one of 1 to 3, wherein the ink contains an actinic ray curable composition that is cured by actinic rays, and is cured by ultraviolet irradiation after landing on a recording medium. Method.

  5). 5. The ink jet recording method according to any one of 1 to 4, wherein a viscosity rising temperature of the ink is 50 ° C. or more and 65 ° C. or less.

  6). 6. The ink jet recording method according to any one of 1 to 5, wherein the ink contains 0.3 to 15.0% by mass of the oil gelling agent.

  7). The inkjet recording method according to any one of 1 to 6, wherein the recording head is a line head.

  8). 8. The inkjet recording method according to any one of 1 to 7, wherein the recording medium is heated from the back surface during or before printing.

  According to the present invention, it is possible to perform high-definition and high-speed printing on a slightly absorbent recording medium or a non-absorbing recording medium such as PET, and the ink that has landed on the recording medium does not cause color mixing. It is possible to provide an ink jet recording method in which the gloss of an image is high, the rubbing resistance of the image is excellent, nozzles are not clogged, and stable emission is possible.

It is a schematic diagram which shows the structure of a line type inkjet recording device. It is a perspective view which shows the recording state to the recording medium by a line head. FIG. 3 is a layout diagram of recording heads in a line head. (A) The perspective view shown with 1 part sectional drawing of the chip | tip of the recording head by a 3-cycle drive method. (B) A cross-sectional view of the pressure chamber viewed from the channel array direction of the recording head according to the three-cycle driving method. FIGS. 4A to 4C are diagrams illustrating an operation of a recording head during ink ejection by a three-cycle driving method. FIG. 4 is a layout diagram of four color line heads. FIG. 4 is a diagram illustrating a drive signal for a recording head. It is a figure which shows the temperature and viscosity curve of ink.

  Although the form for inventing is demonstrated in detail below, this invention is not limited to these.

(Inkjet recording device)
FIG. 1 is a schematic diagram showing a configuration of a line-type ink jet recording apparatus 1.

  The long recording medium 10 wound in a roll shape is fed out in the direction of arrow X from the unwinding roll 10A by a driving means (not shown) and conveyed.

  The long recording medium 10 is conveyed while being wound around and supported by a back roll 20. Ink is ejected from the line head 30 toward the recording medium 10 to form an image based on the image data. The line head 30 includes a plurality of inkjet heads (recording heads) 31 corresponding to the ejection width in the recording medium width direction.

  The line head 30 has four color line heads Y, M, C, and K. The ink sent from the ink tank 50 to the intermediate tank 41 for adjusting the back pressure of the ink in the recording head is supplied to the line head Y by the ink tube 43 from the ink tank 50 by the pump P and the ink tube 51. The ink tank 50, the pump P, the ink tube 51, the intermediate tank 41, and the ink tube 43 constitute an ink supply unit 40.

  Similarly, another ink supply unit is connected to the line heads M, C, and K to supply ink.

  An ultraviolet irradiation device 4 is disposed downstream of the line head, and irradiates a recording medium on which an image is formed with ink to cure and fix the photocurable ink. The recording medium on which the image has been fixed is dried by the drying unit 100 and taken up by the take-up roll 10B.

  The recording head is scanned relatively in the direction opposite to the conveyance direction of the recording medium. During scanning, a drive signal is selected based on image data for each pixel period, and the ink ejection state changes.

  Each recording head 31 is arranged so that the nozzle surface side faces the recording surface of the recording medium 10, and a drive signal provided with a circuit for generating a drive signal via the flexible cable 6 (see FIG. 4). It is electrically connected to the generating means 100 (see FIG. 5).

  FIG. 2 is an arrangement example of the recording head 31 in the line head 30. Since the ejection width that can be ejected by one recording head 31 is narrower than the outer dimensions of the recording head, a plurality of recording heads 31 are arranged in a staggered manner in the recording medium conveying direction in order to eject without gaps. In the example shown in FIG. 2, a plurality of recording heads corresponding to the ejection width are arranged in two rows in a staggered manner in the recording medium width direction.

  FIG. 3 shows the relationship between the outer shape, ejection width, and staggered arrangement of the recording head 31. The number of the recording heads 31 and the number of rows in the staggered arrangement are appropriately set according to the ejection width of the recording heads 31 and the like, and are not limited to the example of FIG.

  In the present invention, it is more preferable to heat the back surface of the recording medium during printing or before and after printing. As the heating means, there are a method for controlling the temperature of the conveyance table to be a constant temperature, a method for bringing the recording medium into contact with a heating roller, a flat heater, or the like, and it can be selected as appropriate. A preferable heating temperature range is 40 degrees or more and a gelation temperature or less. When heated to 40 ° C or higher, the droplets after landing are cooled slowly, and the gloss of the printed matter is further improved. If the temperature is lower than the gelation temperature, the ink that has landed on the recording medium does not cause color mixing. An image with high sharpness can be obtained.

(Recording head)
4A is a perspective view showing a partial cross section of the head chip portion of the shear mode type recording head 31 driven by three cycles, and FIG. 4B is a view from the channel arrangement direction of the shear mode type recording head 31 driven by three cycles. FIG. 3 is a cross-sectional view of a pressure chamber 28 as seen.

  In the figure, 310 is a head chip, and 22 is a nozzle forming member bonded to the front surface of the head chip 310.

  The front-side opening and the rear-side opening of each pressure chamber 28 face the front and rear surfaces of the head chip 310, respectively. Each pressure chamber 28 is a straight type whose size and shape are not substantially changed in the length direction from the opening on the rear surface side to the opening on the front surface side.

  One end of the pressure chamber 28 (hereinafter sometimes referred to as a nozzle end) is connected to a nozzle 23 formed on the nozzle forming member 22, and the other end (hereinafter also referred to as a manifold end) is connected to a common ink chamber. 77, the ink supply port 25 is connected to the ink tube 43.

(Heating means)
The heating means including a heater and a temperature sensor (not shown) is attached to the outer surfaces of the manifold members 102, 103, and 104 of the recording head 31 shown in FIG. Can be kept warm.

(Pressure generation means)
As shown in FIGS. 4 and 5, an electrode 29 made of a metal film is formed in close contact with the surface of the partition wall 27 that partitions the pressure chambers 28 to constitute the pressure generating means. That is, the electrodes 29 on the partition walls facing each other in each channel are electrically connected. The electrode 29 in the pressure chamber is connected to the drive signal generating means 100 via the connection electrode 300, the anisotropic conductive film 78, and the cable 6.

  FIGS. 5A to 5C are cross-sectional views of the channel rows as seen from the channel extending direction of the shear mode type recording head driven by three cycles.

  Each partition 27 is constituted by two piezoelectric materials 27 a and 27 b having different polarization directions as indicated by arrows in FIG. 5, but the piezoelectric material may be at least part of the partition 27.

  FIG. 5 shows three (28A, 28B, 28C) which are a part of the pressure chamber 28, which are separated by partition walls 27A, 27B, 27C, 27D.

  The front-side opening and the rear-side opening of each pressure chamber 28 face the front and rear surfaces of the head chip 310, respectively. Each pressure chamber 28 is a straight type whose size and shape are not substantially changed in the length direction from the opening on the rear surface side to the opening on the front surface side.

  As shown in FIG. 4, one end of the pressure chamber 28 (hereinafter sometimes referred to as a nozzle end) is connected to a nozzle 23 formed on the nozzle forming member 22, and the other end (hereinafter sometimes referred to as a manifold end). Is connected to the ink tube 43 via the common ink chamber 77 and the ink supply port 25.

  As shown in FIGS. 4 and 5, an electrode 29 made of a metal film is formed in close contact with the entire inner surface of each channel 28. That is, the electrodes 29 on the partition walls facing each other in each channel are electrically connected. The electrode 29 in the pressure chamber is connected to the drive signal generating means 100 through the connection electrode 300 and the anisotropic conductive film 6.

  By applying an expansion voltage to the electrodes 29A, 29B, and 29C from the drive signal generating unit 100, the partition wall changes from the state of FIG. 5A to the state of FIG. 5B, and the pressure chamber 28B. Ink is introduced into the inside. Next, when a contracting voltage is applied to the electrodes 29A, 29B, and 29C from the drive signal generating means 100, the state shown in FIG. 5C is reached, and pressure is applied to the ink in the pressure chamber 28B by the pressure generating means. , Emitted from the nozzle.

  FIG. 6 shows an example of the configuration of the main part of the ink jet recording apparatus. FIG. 6A is a side view thereof, and FIG. 4B is a top view thereof.

  The ink jet recording apparatus shown in FIG. 6 is called a line recording method, and a plurality of recording heads 31 of each color ink are fixedly arranged on the line head 30 so as to cover the entire width of the recording medium 10. The recording medium is conveyed under the fixed head carriage to form an image.

  The number of recording heads used for each color in the transport direction of the recording medium varies depending on the nozzle density of the heads used and the printing resolution. For example, when it is desired to form an image with a resolution of 1440 dpi using a head with a droplet volume of 2 pl and a nozzle density of 360 dpi, four recording heads are used and shifted with respect to the recording medium conveyance direction. A 1440 × 1440 dpi image can be formed. If you want to form an image with a resolution of 720 x 720 dpi using a head with a droplet volume of 6 pl and a nozzle density of 360 dpi, you can form a 720 dpi image by using two recording heads and shifting them. Become. In the present invention, dpi represents the number of dots per 2.54 cm.

  On the downstream side of the line head, an ultraviolet irradiation device 4 such as a metal halide lamp or an LED lamp is arranged so as to cover the entire width of the recording medium, and after the image is formed, the lamp is irradiated with ultraviolet rays and the image is completely fixed. Is done.

  A temperature control device 5 is attached to the lower part of the recording medium so that the temperature of the recording medium can be adjusted as appropriate.

  FIG. 7 is a diagram showing an example of a drive signal for driving the share mode type piezo recording head to stably discharge a fine droplet at a high speed. In FIG. 7, the horizontal axis represents AL time, and the vertical axis represents drive voltage.

t1 is the first expansion pulse width (pulse width of the first expansion pulse) t2 is the contraction pulse width (pulse width of the contraction pulse) t3 is the second expansion pulse width (pulse width of the second expansion pulse) It is.

  Ink is introduced into the pressure chamber by the first expansion pulse, pressure is applied to the ink by the contraction pulse, the ink is ejected, and the pressure wave applied to the ink is quickly converged by the second expansion pulse, thereby driving at a high frequency (high speed). However, it can be emitted stably.

(ink)
The ink used in the inkjet recording method of the present invention is an ink that enables sol-gel transition by adding an oil gelling agent. Furthermore, the sol-gel phase transition temperature (phase transition temperature) can be easily controlled between the ink temperature at the time of ink ejection and the ink temperature after landing on the recording medium or the like.

  That is, the ink of the present invention has a low viscosity and good fluidity when ejected. In addition, the ink is ejected from the recording head and flies, and the temperature of the ink decreases and the transition to the gel state starts or immediately before the start. Ink dots can be prevented from spreading.

  On the other hand, if the temperature of the ink immediately before landing is too high, the landing ink spreads faster than the speed at which the landed ink is transferred to the recording medium and cooled to the gel transition start temperature. It spreads over.

  The gel referred to in the present invention means that the solute has independent mobility due to the interaction such as lamellar structure, polymer network formed by covalent bond or hydrogen bond, polymer network formed by physical aggregation, and aggregate structure of fine particles. It has a structure that has been lost and assembled, and is a solidified or semi-solidified state with a sudden increase in viscosity and a significant increase in elasticity.

(Oil gelling agent)
The oil referred to in the present invention is a general term for compounds other than water, and the oil gelling agent according to the present invention refers to a compound that can form the gel when added to a compound other than water.

  In general, a gel becomes a fluid solution (sometimes called a sol) by heating, a thermoreversible gel that returns to the original gel when cooled, and once gelled, it can be reheated even if heated. There is a heat irreversible gel that does not return. The gel formed by the oil gelling agent according to the present invention is preferably a thermoreversible gel.

  The sol-gel phase transition of the present invention can be recognized by measuring the viscosity of the sol-state ink while lowering the temperature with a rheometer, and changing the slope of the viscosity change with respect to the temperature change at a certain temperature.

  The oil gelling agent used in the ink of the present invention may be a high molecular compound or a low molecular compound, but is preferably a low molecular compound from the viewpoint of use in ink. Moreover, as the gel structure, a compound in which the oil gelling agent itself can form a fibrous aggregate is preferable. Formation of the fibrous aggregate can be easily confirmed by morphological observation with a transmission electron microscope.

  Specific examples of the polymer compound preferably used in the present invention include fatty acid inulins such as inulin stearate, fatty acid dextrins such as dextrin palmitate and dextrin myristate (available from Chiba Flour as the Leopard series), eicosane behenate Examples include glyceryl diacid, eicosane behenate polyglyceryl (available from Nisshin Oilio as Nomcoat series), and the like.

  Specific examples of the low molecular weight compound preferably used in the present invention include, for example, low molecular weight oil gelling agents described in JP-A-2005-126507, JP-A-2005-255821, and JP-A 2010-1111790, N -Lauroyl-L-glutamic acid dibutylamide, amide compounds such as N- (2-ethylhexanoyl) -L-glutamic acid dibutylamide (available from Ajinomoto Fine-Techno), 1,3: 2,4-bis-O- Dibenzylidene sorbitols such as benzylidene-D-glucitol (available from Gelol D Shin Nippon Rika), petroleum waxes such as paraffin wax, microcrystalline wax, petrolactam, candelilla wax, carnauba wax, rice wax, Tree wax, jojoba oil, jojoba Plant waxes such as body wax and jojoba ester, animal waxes such as beeswax, lanolin and whale wax, mineral waxes such as montan wax and hydrogenated wax, hardened castor oil or hardened castor oil derivatives, and montan wax Derivatives, paraffin wax derivatives, modified waxes such as microcrystalline wax derivatives or polyethylene wax derivatives, higher fatty acids such as behenic acid, arachidic acid, stearic acid, palmitic acid, myristic acid, lauric acid, oleic acid, erucic acid, and stearyl Higher alcohols such as alcohol and behenyl alcohol, hydroxystearic acid such as 12-hydroxystearic acid, 12-hydroxystearic acid derivatives, lauric acid amide, stearic acid amide, behenic acid amide, Fatty acid amides such as oleic acid amide, erucic acid amide, ricinoleic acid amide, 12-hydroxystearic acid amide (for example, Nikka Amide series manufactured by Nippon Kasei Co., Ltd., ITOWAX series manufactured by Ito Oil Co., Ltd., FATTYAMID series manufactured by Kao Corporation) N-substituted fatty acid amides such as N-stearyl stearamide, N-oleyl palmitate, N, N'-ethylenebisstearylamide, N, N'-ethylenebis12-hydroxystearylamide, N, N'- Special fatty acid amides such as xylylene bisstearyl amide, higher amines such as dodecylamine, tetradecylamine or octadecylamine, stearyl stearic acid, oleyl palmitic acid, glycerin fatty acid ester, sorbitan fatty acid ester, Fatty acid ester compounds such as pyrene glycol fatty acid ester, ethylene glycol fatty acid ester, polyoxyethylene fatty acid ester (for example, EMALLEX series manufactured by Nihon Emulsion, Rikumar series manufactured by RIKEN VITAMIN, POEM series manufactured by RIKEN VITAMIN), sucrose Synthetic waxes such as stearic acid and sucrose palmitic acid (eg, Ryoto Sugar Ester series manufactured by Mitsubishi Chemical Foods), polyethylene wax, α-olefin maleic anhydride copolymer wax, and polymerizable wax (UNILIN series Baker-Petrolite), dimer acid, dimer diol (PRIPOR series CRODA) and the like. Moreover, said gelling agent may be used independently and may be used in mixture of 2 or more types.

  The compounds preferably used in the oil gelling agent are C20-C24 linear saturated fatty acids and esters thereof. Examples of the fatty acid include arachidic acid, behenic acid, and lignoceric acid. Of these, glyceryl behenate and behenic acid are preferable.

  Among these, C20 to C24 linear saturated fatty acids and esters thereof are preferable because even if the amount contained in the ink is small, a large viscosity change is caused by a temperature change and the physical properties of the cured ink are not deteriorated. In particular, behenic acid and its esters are preferred. Further, since the viscosity rapidly increases as the temperature of the ink decreases, the reproducibility of the fine lines and the effect of preventing color mixing of the present invention are remarkably excellent.

  In the ink of the present invention, the content of the oil gelling agent according to the present invention is preferably 0.3 to 15% by mass, and more preferably 3 to 15% by mass with respect to the total mass of the ink. If the content of the oil gelling agent is in the range of 0.3 to 15% by mass, more stable emission characteristics can be obtained, and the object and effects of the present invention can be further exhibited. In particular, when a pigment is used as the coloring material, the oil gelling agent may impair the dispersion stability of the pigment, and therefore the content of the oil gelling agent is preferably in the range of 0.3 to 10% by mass.

  The amount of the oil gelling agent added is such that the ink exhibits a low viscosity necessary for ejection at the temperature of the recording head and is in a gel state at room temperature (25 ° C.).

  The gel state means that the viscosity is 500 mPa · s or more, and if the gel state is cooled to room temperature, the ink bleeds or color mixes even if the ink is not cured by irradiation with actinic rays. Does not occur.

  The viscosity is measured using a rheometer MCR300 (manufactured by PaarPhysical) at a shear rate of 1000 [1 / second].

(Coloring material)
In the ink of the present invention, a dye or a pigment can be used without limitation as a color material constituting the ink, but a pigment having good dispersion stability with respect to the ink component and excellent weather resistance is used. It is preferable. Although it does not necessarily limit as a pigment, For example, the organic or inorganic pigment of the following number described in a color index can be used for this invention.

  Examples of red or magenta pigments include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48: 1, 48: 2, 48: 3, 48: 4, 48: 5, 49: 1, and 53: 1. 57: 1, 57: 2, 58: 4, 63: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 88, 104, 108, 112, 122, 123, 144, 146 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, Pigment Orange 13 16, 20, 36, blue or cyan pigments include Pigment Blue 1, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 1 7-1, 22, 27, 28, 29, 36, 60, as green pigment, Pigment Green 7, 26, 36, 50, as yellow pigment, Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137, 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, 193, and black pigments such as Pigment Black 7, 28, 26 can be used depending on the purpose.

  Specific product names include, for example, chromo fine yellow 2080, 5900, 5930, AF-1300, 2700L, chromo fine orange 3700L, 6730, chromo fine scarlet 6750, chromo fine magenta 6880, 6886, 6891N, 6790, 6887. , Chromofine Violet RE, Chromofine Red 6820, 6830, Chromofine Blue HS-3, 5187, 5108, 5197, 5085N, SR-5020, 5026, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 4940, 4973, 5205, 5208, 5214, 5221, 5000P, Chromofine Green 2GN, 2GO, 2G-550D, 5310, 5370, 6830, Ku Mofine Black A-1103, Seika Fast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400 (B), 2500, 2600, ZAY-260, 2700 (B), 2770, Seika Fast Red 8040 , C405 (F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016, 3820, 3891, ZA-215, Seika Fast Carmine 6B1476T-7, 1483LT, 3840, 3870 , Seika Fast Bordeaux 10B-430, Seica Light Rose R40, Seika Light Violet B800, 7805, Seika Fast Maroon 460N, Seika Fast Orange 900, 2900, Seika Light Blue C7 18, A612, cyanine blue 4933M, 4933GN-EP, 4940, 4973 (manufactured by Dainichi Seikagaku), KET Yellow 401, 402, 403, 404, 405, 406, 416, 424, KET Orange 501, KET Red 301, 302 , 303, 304, 305, 306, 307, 308, 309, 310, 336, 337, 338, 346, KET Blue 101, 102, 103, 104, 105, 106, 111, 118, 124, KET Green 201 (large Nippon Ink Chemical Co., Ltd.), Colortex Yellow 301, 314, 315, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U263, Finecol Yellow T-13, T-05, Pi gment Yellow 1705, Colortex Orange 202, Colortex Red 101, 103, 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, UGN, UG276, U456, U457, C USN, Colortex Maroon 601, Colortex Brown B610N, Colortex violet 600, Pigment Red 122, Colortex Blue 516, 517, 518, 519, A818, P-908, 510, Colortex Green 402, 403B, Col. , Lionol lue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (manufactured by Toyo Ink), Toner Magenta E02, Permanent RubinF6B, Toner Yellow HG, Permanent Yellow GG-02, Black Bumpy Carbon G2 , # 2400, # 2350, # 2200, # 1000, # 990, # 980, # 970, # 960, # 950, # 850, MCF88, # 750, # 650, MA600, MA7, MA8, MA11, MA100, MA100R , MA77, # 52, # 50, # 47, # 45, # 45L, # 40, # 33, # 32, # 30, # 25, # 20, # 10, # 5, # 44, And the like, such as F9 (manufactured by Mitsubishi Chemical).

  Further, it is also possible to use a dispersion liquid in which the pigment is dispersed in high concentration in advance in water, a solvent, a polymerizable monomer or the like.

  In the ink of the present invention, it is preferable to use a pigment dispersant for dispersing the pigment. Examples of the dispersant that can be used in the present invention include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates, naphthalene sulfonates, alkyl phosphates, and polyoxyalkylene alkyls. Activators such as ether phosphate, polyoxyalkylene alkylphenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine oxide, or styrene, styrene derivatives, vinyl naphthalene derivatives, Block copolymer consisting of two or more monomers selected from acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, random copolymer Body and the like, and salts thereof.

  For the dispersion of the pigment, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, or the like can be used. It is also possible to add a dispersant when dispersing the pigment.

  In the present invention, the addition amount of the pigment dispersant is preferably 10 to 100% by mass with respect to the pigment.

  The dispersion medium is used using a solvent or a polymerizable compound, but the ink of the present invention is preferably solvent-free because it is reacted and cured after printing. If the solvent remains in the cured image, the solvent resistance deteriorates and the VOC of the remaining solvent arises. Therefore, it is preferable in view of dispersibility that the dispersion medium is not a solvent but a polymerizable compound, and among them, a monomer having the lowest viscosity is selected.

  The average dispersed particle size of the pigment obtained by the above method is preferably 50 nm or more and 150 nm or less. If the average dispersed particle size of the pigment is within the range specified above, the dispersion stability of the ink can be improved. As a result, clogging of the head nozzle is suppressed, and the emission stability is further improved. With the improvement of transparency, the curing efficiency of actinic rays when an actinic ray curable composition described later is contained can be increased.

  In the ink of the present invention, the means for adjusting the average dispersed particle size of the pigment to the range specified above is achieved by, for example, appropriately selecting or combining pigment, dispersant, dispersion medium selection, dispersion conditions, and filtration conditions. can do.

  In the ink of the present invention, conventionally known dyes, preferably oil-soluble dyes, can be used as required.

  Specific examples of oil-soluble dyes that can be used in the present invention are given below, but the present invention is not limited to these.

<Magenta dye>
MS Magenta VP, MS Magenta HM-1450, MS Magenta HSo-147 (manufactured by Mitsui Toatsu Co., Ltd.), AIZENSOT Red-1, AIZEN SOT Red-2, AIZEN SOTRed-3, AIZEN SOT Pink-1, SPERON Red GE SPECIAL (above, manufactured by Hodogaya Chemical Co., Ltd.), RESOLIN Red FB 200%, MACROLEX Red Violet R, MACROLEX ROT5B (above, manufactured by Bayer Japan), KAYASET Red B, KAYASET Red 130, KAYASET Red Japan 802 ), PHLOXIN, ROSE BENGAL, ACID Red (above, made by Daiwa Kasei), HSR-31, DIARESIN Red K (below) , Manufactured by Mitsubishi Kasei Co., Ltd.), Oil Red (manufactured by BASF Japan Co., Ltd.).

<Cyan dye>
MS Cyan HM-1238, MS Cyan HSo-16, Cyan HSo-144, MS Cyan VPG (manufactured by Mitsui Toatsu Co., Ltd.), AIZEN SOT Blue-4 (manufactured by Hodogaya Chemical Co., Ltd.), RESOLIN BR. Blue BGLN 200%, MACROLEX Blue RR, CERES Blue GN, SIRIUS SUPRATURQ. Blue Z-BGL, SIRIUS SUTRA TURQ. Blue FB-LL 330% (above, Bayer Japan), KAYASET Blue FR, KAYASET Blue N, KAYASET Blue 814, Turq. Blue GL-5 200, Light Blue BGL-5 200 (above, Nippon Kayaku Co., Ltd.), DAIWA Blue 7000, Oleosol Fast Blue GL (above, Daiwa Kasei), DIARESIN Blue P (Mitsubishi Kasei), SUDAN Blue 670, NEOPEN Blue 808, ZAPON Blue 806 (above, manufactured by BASF Japan).

<Yellow dye>
MS Yellow HSm-41, Yellow KX-7, Yellow EX-27 (Mitsui Toatsu), AIZEN SOT Yellow-1, AIZEN SOT YellowW-3, AIZEN SOT Yellow-6 (above, manufactured by Hodogaya Chemical Co., Ltd.), MACROLEX Yellow 6G, MACROLEX FLUOR. Yellow 10GN (above, manufactured by Bayer Japan), KAYASET Yellow SF-G, KAYASET Yellow 2G, KAYASET Yellow AG, KAYASET Yellow EG (above, manufactured by Nippon Kayaku), DAIWA YELLOW 330H HSY-68 (manufactured by Mitsubishi Kasei Co., Ltd.), SUDAN Yellow 146, NEOPEN Yellow 075 (above, manufactured by BASF Japan).

<Black dye>
MS Black VPC (Mitsui Toatsu Co., Ltd.), AIZEN SOT Black-1, AIZEN SOT Black-5 (above, Hodogaya Chemical Co., Ltd.), RESORIN Black GSN 200%, RESOLIN Black BS (above, Bayer Japan Co., Ltd.), KAYASET Black A-N (manufactured by Nippon Kayaku Co., Ltd.), DAIWA Black MSC (manufactured by Daiwa Kasei Co., Ltd.), HSB-202 (manufactured by Mitsubishi Kasei Co., Ltd.), NEPTUNE Black X60, NEOPEN Black X58 (manufactured by BASF Japan) .

  The amount of pigment or oil-soluble dye added is preferably 0.1 to 20% by mass, more preferably 0.4 to 10% by mass. If it is 0.1% by mass or more, good image quality can be obtained, and if it is 20% by mass or less, an appropriate ink viscosity in ink ejection can be obtained. In addition, two or more kinds of colorants can be mixed as appropriate for color adjustment.

  The ink of the present invention preferably contains an actinic ray curable composition that cures with actinic rays together with an oil gelling agent and a colorant.

(Actinic ray curable composition)
The actinic ray curable composition (hereinafter also referred to as a photopolymerizable compound) used in the present invention will be described.

  In the present invention, the photopolymerizable compound can be used without any particular limitation. Among them, a photocationic polymerizable compound or a radical polymerizable compound is preferably used, and a radical polymerizable compound is particularly preferable.

(Radically polymerizable compound)
Next, the radical polymerizable compound will be described.

  Various known radically polymerizable monomers can be used as the photoradical polymerizable monomer. For example, photocurable materials using photopolymerizable compositions described in JP-A-7-159983, JP-B-7-31399, JP-A-8-224982, and JP-A-10-863 Cationic polymerization type photocurable resins are known, and recently, photocationic polymerization type photocurable resins sensitized to a long wavelength region longer than visible light are disclosed in, for example, JP-A-6-43633. This is disclosed in, for example, Kaihei 8-324137.

  The radical polymerizable compound is a compound having an ethylenically unsaturated bond capable of radical polymerization, and may be any compound as long as it has at least one ethylenically unsaturated bond capable of radical polymerization in the molecule. , Oligomers, polymers and the like having a chemical form. Only one type of radical polymerizable compound may be used, or two or more types may be used in combination at an arbitrary ratio in order to improve the desired properties.

  Examples of compounds having an ethylenically unsaturated bond capable of radical polymerization include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid and their salts, esters, urethanes, amides. And radically polymerizable compounds such as various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides and unsaturated urethanes.

  Any known (meth) acrylate monomer and / or oligomer can be used as the radical polymerizable compound of the present invention. The term “and / or” as used in the present invention means that it may be a monomer, an oligomer, or both. The same applies to the items described below.

  As the compound having a (meth) acrylate group, for example, isoamyl acrylate, stearyl acrylate, lauryl acrylate, octyl acrylate, decyl acrylate, isomyristyl acrylate, isostearyl acrylate, 2-ethylhexyl-diglycol acrylate, 2-hydroxybutyl acrylate 2-acryloyloxyethyl hexahydrophthalic acid, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, methoxydiethylene glycol acrylate, methoxypolyethylene glycol acrylate, methoxypropylene glycol acrylate, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, 2- Hydroxyethyl acrylic 2-hydroxypropyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl-2-hydroxyethyl-phthalate Monofunctional monomers such as acid, lactone-modified flexible acrylate, t-butylcyclohexyl acrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, 1, 4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, neopentyl glycol diacrylate Bifunctional monomers such as dimethylol-tricyclodecane diacrylate, PO adduct diacrylate of bisphenol A, neopentyl glycol diacrylate hydroxypivalate, polytetramethylene glycol diacrylate, trimethylol propane triacrylate, pentaerythritol triacrylate, penta Trifunctional or more polyfunctional such as erythritol tetraacrylate, dipentaerythritol hexaacrylate, ditrimethylolpropane tetraacrylate, glycerin propoxytriacrylate, caprolactone-modified trimethylolpropane triacrylate, pentaerythritol ethoxytetraacrylate, caprolactam-modified dipentaerythritol hexaacrylate Monomer. In addition, polymerizable oligomers can be blended in the same manner as the monomer. Examples of the polymerizable oligomer include epoxy acrylate, aliphatic urethane acrylate, aromatic urethane acrylate, polyester acrylate, and linear acrylic oligomer. More specifically, Yamashita Shinzo, “Cross-linking agent handbook” (1981 Taiseisha); Kato Kiyosumi, “UV / EB curing handbook (raw material)” (185, Polymer publication society); Study Group, “Application and Market of UV / EB Curing Technology”, page 79 (1989, CMC); Eiichiro Takiyama, “Polyester Resin Handbook”, (1988, Nikkan Kogyo Shimbun) Commercially available products or radically polymerizable or crosslinkable monomer oligomers and polymers known in the industry can be used.

  Among the above monomers, isoamyl acrylate, stearyl acrylate, lauryl acrylate, octyl acrylate, decyl acrylate, isomyristyl acrylate are particularly preferred from the viewpoints of sensitization, skin irritation, eye irritation, mutagenicity, toxicity, etc. , Isostearyl acrylate, ethoxydiethylene glycol acrylate, methoxypolyethylene glycol acrylate, methoxypropylene glycol acrylate, isobornyl acrylate, lactone-modified flexible acrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, dipentaerythritol Hexaacrylate, ditrimethylolpropane tetraacrylate, glycerin Po carboxymethyl triacrylate, caprolactone modified trimethylolpropane triacrylate, pentaerythritol tetraacrylate, caprolactam modified dipentaerythritol hexaacrylate preferred.

  Furthermore, among these, stearyl acrylate, lauryl acrylate, isostearyl acrylate, ethoxydiethylene glycol acrylate, isobornyl acrylate, tetraethylene glycol diacrylate, glycerin propoxy triacrylate, cowprolactone-modified trimethylolpropane triacrylate, caprolactam-modified dipenta Erythritol hexaacrylate is particularly preferred.

  In the present invention, a vinyl ether monomer and / or oligomer and a (meth) acrylate monomer and / or oligomer may be used in combination as the polymerizable compound. Examples of the vinyl ether monomer include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, Di- or trivinyl ether compounds such as methylolpropane trivinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexane dimethanol monovinyl ether, n- B pills vinyl ether, isopropyl vinyl ether, isopropenyl ether -o- propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether. When a vinyl ether oligomer is used, a bifunctional vinyl ether compound having a molecular weight of 300 to 1000 and having 2 to 3 ester groups in the molecule is preferable. For example, compounds available as a VEctomer series of ALDRICH, VEctomer 4010, VEctomer 4020, VEctomer 4040 , VEctomer 4060, VEctomer 5015 and the like are preferable, but not limited thereto.

  In the present invention, various vinyl ether compounds and maleimide compounds can be used in combination as the polymerizable compound. Examples of maleimide compounds include N-methylmaleimide, N-propylmaleimide, N-hexylmaleimide, N-laurylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N, N′-methylenebismaleimide, and polypropylene glycol-bis. (3-maleimidopropyl) ether, tetraethylene glycol-bis (3-maleimidopropyl) ether, bis (2-maleimidoethyl) carbonate, N, N ′-(4,4′-diphenylmethane) bismaleimide, N, N ′ -2,4-tolylene bismaleimide or a polyfunctional maleimide compound which is an ester compound of maleimide carboxylic acid and various polyols disclosed in JP-A-11-124403. As far as There.

  The addition amount of the cationically polymerizable compound and the radically polymerizable compound is preferably 1 to 97% by mass, more preferably 30 to 95% by mass.

(Viscosity rise temperature, gelation temperature)
The viscosity rise temperature refers to a temperature at which the temperature / viscosity curve shifts from a liquid state gradient to a higher gradient when the temperature of the ink is decreased from the sol state temperature, -It is defined as the temperature at the intersection of the tangent of the sol state in the viscosity curve and the tangent of the rising portion of the viscosity when the temperature shifts to a lower temperature. FIG. 8 is a temperature / viscosity curve when the temperature of the ink is lowered from the temperature in the sol state at a rate of 5 ° C./min.

  The gel state is defined as a state where the viscosity is 500 mPa · s or more. The gelation temperature is defined as the temperature at which the viscosity reaches 500 mPa · s when the temperature of the ink is lowered from the temperature in the sol state.

  For the measurement, a rheometer MCR300 (manufactured by PaarPhysical) is used and the shear rate is 1000 [1 / second].

  FIG. 8 shows an example of the temperature / viscosity curve of the ink measured under the above conditions, and shows a method for determining the viscosity rise temperature from the temperature / viscosity curve. # 1, # 2, # 3, and # 4 represent ink types.

  As an example, description will be made using the temperature / viscosity curve of ink indicated by # 1.

  In the temperature / viscosity curve of # 1, the low slope portion when the temperature is lowered from 80 ° C. to 60 ° C. is the sol state, and there is a high slope portion that rises almost linearly from around 55 ° C. When the tangent of the sol state and the tangent of the high slope portion are drawn, the intersection is 56 ° C. Therefore, the viscosity rising temperature of ink # 1 is 56 ° C.

  Further, the gelation temperature of 53.6 ° C. is obtained from the intersection of the temperature / viscosity curve of # 1 and the viscosity of 500 mPa · s.

  The viscosity rising temperature is preferably 50 ° C. or higher and 65 ° C. or lower.

  The gelation temperature is preferably 47 ° C. or higher and 55 ° C. or lower.

(Drop temperature T3 just before landing)
The droplet temperature T3 immediately before landing is obtained by the following equation (2).

Formula (2) T3 = T1 + (T2-T1) × exp (−t1 / t2)
T1: Atmospheric temperature T2: Temperature of the recording head T3: Droplet temperature immediately before landing t1: Droplet flying time t2: Cooling time constant The ambient temperature is the temperature between the nozzle surface of the inkjet head where the ink flies and the recording medium. It is the temperature of the air in the space, and when there is a temperature gradient between the nozzle surface and the recording medium, it is defined as the temperature of the intermediate point. The ambient temperature is preferably controlled by an ink jet recording apparatus. Further, when the ink jet recording apparatus does not have means for controlling the atmospheric temperature, a thermistor or the like can be inserted between the nozzle surface and the recording medium for measurement.

  The cooling time constant t2 is obtained by simulation software Flow-3D (manufactured by Terabyte Co., Ltd.) using the droplet amount, the flying speed, the specific heat of the ink, and the thermal conductivity as parameters.

(Measurement method of specific heat and thermal conductivity of ink)
It can be measured by a thermal characteristic meter KD2Pro (manufactured by Decagon Corp.).

  The flight time t1 is obtained by solving the equation of motion of the following equation (3), where the initial velocity is the injection velocity and the flight distance is the gap width. The ejection speed can be measured by shooting the flying droplet with a high-speed camera.

Formula (3) dv / dt = g− (k1 / m) * v ² − (k2 / m) * v
v: Injection speed (> 0)
m: Droplet mass (obtained by receiving the ejected droplets on the absorbent material and dividing the increased mass of the absorbent material by the number of droplets)
g: How gravitational acceleration k1 = 6πaη, a is the radius of the droplet, eta is = air viscosity resistance ^{k2 (π * a 2 * ρ} ) / 4, ρ is adjusted in the scope of the present invention the density of the air (T3 )
The following equation is derived from equation (2), and T1, T2, and T3 are substituted to obtain t1 / t2.

t1 / t2 = -ln (T3-T1) / (T2-T1)
Therefore, t1 and t2 can be adjusted to the target T3 by adjusting t1 and t2 as follows and adjusting to t1 / t2 obtained as described above.

(Adjustment method of t1)
The gap width for obtaining the target t1 can be obtained by adjusting and determining the ejection speed and the droplet mass according to the nozzle diameter and the drive signal, and then solving the equation (3).

  The equation of motion of Equation (3) can be solved as follows using, for example, Excel.

Three columns of time t (A column), moving distance S (B column), and injection speed v (C column) are prepared. Let the time step be t = 1 × 10 ⁻⁶ (sec).

  Hereinafter, (symbol) represents the cell number of Excel, and [symbol] represents data within the cell number of the symbol.

  First, as the initial value, 0 is set to (A2) of t, 0 is set to (B2) of S, and the injection speed measured by the high-speed camera is set to (C2) of v.

On the next line
[A3] = [A2] + Δt,
[B3] = [B2] + Δt * [C2],
[C3] = [C2] + Δt * (g− (k1 / m) * [C2] ² − (k2 / m) * [C2])), the moving distance S and the injection speed at the next time Can be requested. Repeat this calculation. The gap width can be set by obtaining the maximum movement distance S with the time t smaller than the target t1.

(Adjustment method of t2)
Using Flow-3D, it is possible to determine the amount of droplets and the flying speed to obtain the target t2. The droplet amount and the flying speed can be adjusted by the nozzle diameter and the drive signal.

  In the present invention, T3 is equal to or higher than the gelling temperature and equal to or lower than the viscosity rising temperature + 1 ° C. When T3 is equal to or higher than the gelation temperature, the ink is easily flattened when landed, without reducing the gloss, and can be deformed along the recording medium to increase the contact area with the recording medium. Excellent rub resistance. In addition, when T3 is a viscosity rising temperature of + 1 ° C. or less, the viscosity after landing can be increased so as not to cause color mixing with multicolor ink.

Examples of the method for adjusting the droplet temperature T3 immediately before landing include selection of the temperature of the recording head, the droplet amount, the ejection speed, the gap width, and the oil gelling agent.
(Measurement method of T3)
T3 can also be measured using an infrared radiation thermometer. A device having an ink emissivity of 0.95 and an infrared wavelength of about 8 μm is used. Droplets are continuously discharged at 120 kHz, and the temperature at three points from the nozzle surface is measured. The relationship between the distance from the nozzle surface and the droplet temperature can be graphed to determine the droplet temperature at the gap width distance.

(Recording head temperature)
T3 increases as the temperature of the recording head increases. It is a feature of the present invention that the recording head temperature is set to an ink viscosity rising temperature of + 1 ° C. or higher. Thereby, it is possible to inject at an appropriate voltage or less of the head. The temperature of the recording head is preferably an ink viscosity rising temperature + 5 ° C. or more and 80 ° C. or less. If the viscosity rise temperature of the ink is + 5 ° C. or higher, the ink ejection using the oil gelling agent is stable, and it is easy to adjust T3 to be equal to or higher than the gelation temperature. If it is 80 degrees C or less, durability of a piezoelectric element when a piezoelectric element is used for the pressure generation means of a head will improve.

(Droplet amount)
When the amount of the droplets is large, the range in which the temperature of the droplets decreases during flight is small, and when the amount of the droplets is small, the range of decrease in temperature is large.

  The droplet amount is preferably 1.5 pl or more and 7.0 pl or less. If it is 1.5 pl or more, it is possible to land a droplet on a desired position with high accuracy, and if it is 7.0 pl or less, an image with a fine line can be obtained.

  The gap D (mm) between the nozzle surface and the recording surface is preferably 1.0 mm or more and 2.4 mm or less. If it is 1.0 mm or more, it is not affected by the increase in the ambient temperature due to the head heating temperature, and if it is 2.4 mm or less, the droplets can land on the substrate without being affected by the airflow around the head. Is possible.

  When the droplet amount is V (pl), V / D is preferably 1.0 or more and 3.0 or less. If it is 1.0 or more, the droplets are cooled too much during the flight and the droplets upon landing do not become hard, and good glossiness of the image can be obtained. It is possible to obtain a high-definition image quality when cooled well.

(Injection speed)
The faster the ejection speed, the shorter the flight time, so the drop in the temperature of the droplet becomes smaller, and T3 becomes higher if other conditions are the same.

(Gap width)
When the gap width is small, the flight time is shortened and T3 is increased. When the gap width is large, the flight time becomes long and T3 becomes low. The gap width is preferably 0.5 to 2.5 mm.

  EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but “parts” used in the examples means “parts by mass” unless otherwise specified.

Example 1
<Preparation of radical polymerization type ink>
(Preparation of magenta pigment dispersion 1)
The pigment was dispersed with the following composition.

  The following two compounds were placed in a stainless beaker and dissolved by stirring with heating for 1 hour while heating on a hot plate at 65 ° C.

Pigment dispersant: Ajisper PB824 (manufactured by Ajinomoto Fine Techno) 9 parts Polymerizable compound: APG-200 (tripropylene glycol diacrylate, Shin-Nakamura Chemical Co., Ltd.) 70 parts Polymerization inhibitor: Irgastab UV10 (manufactured by BASF Japan) 0 .02 parts After cooling to room temperature, 21 parts of the following magenta pigment 1 was added thereto, sealed in a glass bottle together with 200 g of zirconia beads having a diameter of 0.5 mm, dispersed in a paint shaker for 8 hours, and then treated with zirconia beads. Removal of magenta pigment dispersion 1 was made.

Magenta pigment 1: Pigment Red 122 (manufactured by Dainichi Seika, Chromo Fine Red 6112JC)
(Adjustment of Cyan Pigment Dispersion 1)
The following cyan pigment dispersion 1 was prepared in the same manner as in the preparation of the magenta pigment dispersion 1, except that the cyan pigment 1 was used instead of the magenta pigment 1.

Cyan pigment 1: Pigment Blue 15: 4 (manufactured by Dainichi Seika, Chromofine Blue 6332JC)
(Preparation of magenta ink 1)
The following additives were sequentially mixed, heated to 80 ° C. and stirred, and then the obtained liquid was filtered with a # 3000 metal mesh filter under heating and cooled to prepare magenta ink 1.

Polymerizable compound: SR344 (polyethylene glycol # 400 diacrylate, manufactured by SARTOMER) 35.0 parts Polymerizable compound: Photomer 4172 (5EO modified pentaerythritol tetraacrylate, manufactured by Cognis) 17.0 parts Polymerizable compound: SR499 (6EO modified) Trimethylolpropane triacrylate (manufactured by SARTOMER) 18.9 parts Polymerization inhibitor: TEMPO: 2,2,6,6-tetramethylpiperidine-1-oxyl
0.1 parts Photopolymerization initiator: TPO (phosphine oxide, DAROCURE TPO, manufactured by BASF Japan) 5.0 parts Magenta pigment dispersion 1 19.0 parts Oil gelling agent: behenic acid: LUNAC BA, manufactured by Kao Corporation 5.0 parts (preparation of magenta inks 2, 3 and cyan inks 1-3)
Magenta inks 2 and 3 and cyan inks 1 to 3 were prepared in the same manner as in the preparation of the magenta ink 1 except that the pigment dispersion, the type and amount of each compound were changed as shown in Table 1.

  In addition, the detail of each compound described in Table 1 is as follows.

(Polymerizable monomer)
SR344: polyethylene glycol # 400 diacrylate, manufactured by SARTOMER Photomer 4172: 5EO modified pentaerythritol tetraacrylate, manufactured by Cognis SR499: 6EO modified trimethylolpropane triacrylate, manufactured by SARTOMER (polymerization inhibitor)
TEMPO: 2,2,6,6-tetramethylpiperidine-1-oxyl (photopolymerization initiator)
TPO: Phosphine oxide (DAROCURE TPO, manufactured by BASF Japan)
Glyceryl behenate: Poem B-100, manufactured by Riken Vitamin Co., Ltd. Behenic acid: Lunac BA, manufactured by Kao Corporation

(Inkjet image formation)
The M recording head of the line head type ink jet recording apparatus having the line type ink jet recording head 31 shown in FIG. 6 is filled with magenta ink 1, the C recording head is filled with cyan ink 1, and the temperature of the recording head is set. Was adjusted to 68 ° C., the ambient temperature was adjusted to 20 ° C., and the gap width (interval between the nozzle surface of the recording head and the recording surface of the recording medium) was adjusted to 1.5 mm. Coated printing paper A was used as a recording medium (manufactured by OK TOPCOAT rice basis weight 128 g / m ² Oji Paper Co., Ltd.) was printed is conveyed at a speed of 1 m / sec, to form an image on the recording medium. The ambient temperature between the recording head and the recording medium was adjusted to 20 ° C. and the humidity was adjusted to 50% relative. In the inkjet printing apparatus, a high-pressure mercury lamp 4 was disposed 20 cm downstream from the head, and UV light was irradiated after image formation.

  The ink supply system was composed of an ink tank, a supply pipe, a front chamber ink tank immediately before the print head, a pipe with a filter, and a print head. The ink was insulated from the front chamber tank to the print head portion and heated to 68 ° C. The recording head 31 has a nozzle diameter of 20 μm, the number of nozzles is 512 nozzles (256 nozzles × 2 rows, staggered arrangement, 1 row nozzle pitch 360 dpi), and each droplet has a volume of 2 pl. The ink was ejected at a droplet speed of 6 m / sec and printed at a recording resolution of 1440 dpi × 1440 dpi.

  For driving the recording head, the droplet volume and the droplet velocity were adjusted by adjusting the second expansion pulse t3 and the Von / Voff voltage ratio using the drive signal shown in FIG.

  Under the above conditions, the following image 1 and image 2 were created.

(Create image 1)
An image pattern in which two fine lines of magenta ink 1 are arranged on a recording medium with a blue solid image of 10 cm × 10 cm created using magenta ink 1 and cyan ink 1 as a background was created to create image 1 .

(Create image 2)
In the production of image 1, a blue solid image was output in the same manner except that the recording medium was changed to four-coated paper (manufactured by SA Kinfuji Oji Paper Co., Ltd.) and magenta ink and cyan ink were simultaneously ejected. It was created.

(Evaluation of color mixing of fine lines)
The presence or absence of color mixing of the fine lines in image 1 was visually observed, and the sharpness of the fine lines was evaluated according to the following criteria.

  ◎… No color mixing at all.

  ○: There is a little color mixing, but there is no problem with the image.

  ×… The color mixture is terrible.

(Glossiness evaluation)
As panelists for image quality evaluation, 20 people were arbitrarily selected and the glossiness of image 2 was visually evaluated. An offset print image created by offset printing (Printmaster GTO52 manufactured by Heidelberg) on the same recording medium was compared and evaluated as a reference sample. In the evaluation, the number of persons judged to have the same glossiness as that of the reference sample of the offset print image among the 20 panelists was totaled, and the glossiness was evaluated according to the following criteria.

  A: The number of people evaluated as being equivalent to the reference sample of the offset print image is 16 or more.

  ◯: The number of persons evaluated as being equivalent to the reference sample of the offset print image is 10 to 15, and the number of persons evaluated as having a lower gloss than the reference sample of the offset print image is 5 to 10 persons.

  Δ: 4 to 9 people evaluated as being equivalent to the reference sample of the offset print image, and 11 to 16 people evaluated that the gloss was lower than the reference sample of the offset print image.

  X: The number of persons evaluated as being equivalent to the reference sample of the offset print image is 3 or less, and the number of persons evaluated as having a lower gloss than the reference sample of the offset print image is 17 or more.

(Evaluation of abrasion resistance)
The sample of image 1 was rubbed 20 times with a dry bencott, and the rub resistance of the image was evaluated according to the following criteria.

  ◎… No ink on the bencott.

  ○: A little ink adhered to Bencott.

  X: A large amount of ink adhered to Bencott.

(Evaluation of nozzle clogging)
One of the recording heads 1 embedded in M of the line head 2 shown in FIG. 6 filled with the magenta ink 1 is driven at a driving frequency of 10 kHz in an environment of 20 ° C. and 30% RH, and continuously for 15 seconds. An intermittent operation of discharge → pause for a fixed time → continuous discharge was performed. At this time, since whether or not the discharge direction is disturbed at the beginning after the discharge pause is determined by the length of the pause time, the emission stability is measured by changing the length of the discharge pause time stepwise. The evaluation was based on the following criteria. A performance of △ or higher was regarded as an acceptable level.

  A: Stable ejection from all nozzles even after a pause of 1 minute.

  ◯: All nozzles stably ejected even after 30 seconds of rest, but nozzles that did not eject after one minute were generated.

  Δ: Stable ejection was performed by all nozzles even after a pause of 2 seconds, but some nozzles were not ejected after a pause of 30 seconds.

  X: No-discharge nozzles were generated after a pause of 2 seconds or more.

  The evaluation results are shown in Table 3.

(Viscosity rise temperature of magenta ink 1 and cyan ink 1)
The magenta ink 1 was heated to 80 ° C. to form a sol, and then the viscosity was measured while being lowered at a rate of 5 ° C./min to prepare a temperature / viscosity curve. The measurement was carried out using a rheometer MCR300 (manufactured by PaarPhysical) under the condition of a shear rate of 1000 [1 / second].

  The viscosity rise temperature was determined as the temperature at the intersection of the tangent line in the sol state and the tangent line of the maximum slope part when the slope rises from the lower temperature in the temperature-viscosity curve.

  In FIG. 8, # 1 is the temperature / viscosity curve of magenta ink 1. The viscosity rising temperature of magenta ink 1 was 56 ° C.

  The viscosity rise temperature was similarly determined for cyan ink 1, and it was 56 ° C.

(The gelation temperature of magenta ink 1 and cyan ink 1)
In the temperature-viscosity curve of # 1 in FIG. 8, the gelation temperature of magenta ink 1 determined from the intersection with the straight line of 500 mPa · s was 53.6 ° C.

  For cyan ink 1, the gelation temperature was determined in the same manner, and it was 53.6 ° C.

(Viscosity rise temperature and gelation temperature of magenta ink 2 and cyan ink 2)
In FIG. 8, # 2 is a temperature / viscosity curve of magenta ink 2. Similarly to the magenta ink 1, it was found from the temperature / viscosity curve of the magenta ink 2 shown in FIG. 8 that the viscosity rising temperature was 51 ° C. and the gelation temperature was 47.2 ° C.

  The cyan ink 2 was measured in the same manner, but the viscosity rising temperature was 51 ° C. and the gelation temperature was 47.2 ° C.

(Viscosity rise temperature and gelation temperature of magenta ink 3 and cyan ink 3)
In FIG. 8, # 3 is a temperature / viscosity curve of magenta ink 3. Even when the magenta ink 3 was cooled to 30 ° C., it remained in a sol state, no rise in viscosity was observed, and neither the viscosity rise temperature nor the gelation temperature was observed.

(Flight time of magenta ink 1 and cyan ink 1)
The flight time t1 of the magenta ink 1 was obtained by solving the equation of motion of the following equation (3) with an initial speed of 6 m / s (injection speed) and a flight distance of 1.5 mm (gap width). As a result, the flight time t1 of the magenta ink 1 was 0.32 ms (milliseconds).

Formula (3) dv / dt = g− (k1 / m) * v ² − (k2 / m) * v
v: Droplet velocity (> 0)
m: droplet mass (product of density of magenta ink 1 and 2 pl (droplet volume))
g: gravitational acceleration k1: 6πaη, a is the radius of the droplet, eta is the viscosity resistance ^{k2 = (π * a 2 *} ρ) / 4 of the air (in [rho air density)
The density of magenta ink 1 = 1 g / cm ³
a: The droplet was determined as a spherical shape from the droplet amount.

η = 1.781e ⁻⁴ mPa · s
ρ = 1.225e ⁻³ g / cm ³
The above conditions are the same for cyan ink 1 as well. Accordingly, the flight time t1 of the cyan ink 1 is 0.32 ms.

(Drop temperature T3 immediately before landing of magenta ink 1 and cyan ink 1)
The droplet temperature T3 immediately before the landing of the magenta ink 1 was determined by the following equation (2). As a result, T3 of magenta ink 1 was 54.3 ° C.

Formula (2) T3 = atmosphere temperature T1 + (T2-T1) × exp (−t1 / t2)
T1: Atmospheric temperature T2: Temperature of recording head T3: Droplet temperature immediately before landing t1: Droplet flight time t2: Cooling time constant The cooling time constant t2 of magenta ink 1 is the amount of droplet, the flying speed, and the volume of ink. The specific heat and the thermal conductivity of the ink were used as parameters and were calculated using simulation software Flow3D. Here, the droplet volume is 2 pl, the ejection speed is 6 m / s, the ink volume specific heat is 1.5e ⁷ erg / cm ³ / K, the thermal conductivity of the ink is 2e ⁴ erg / sec / cm / K, and the flight Since the speed was small during the flight, the injection speed was used as the flight speed. As a result of the simulation, the cooling time constant t2 of the magenta ink 1 was 0.95 sec.

  The above conditions are the same for cyan ink 1 as well. Accordingly, the cooling time constant t2 of the cyan ink 1 is 0.95 sec.

  Using the flight time t1 and the cooling time constant t2 obtained as described above, the above equation (2) was solved under the following conditions to obtain T3 of the magenta ink 1 and cyan ink 1. As a result, T3 was 54.3 ° C. for both inks. It was not less than the gelling temperature and the viscosity rising temperature was + 1 ° C. or less.

  T1 was 20 ° C.

  The temperature T2 of the recording head filled with magenta ink 1 and the recording head filled with cyan ink 1 was set to 68 ° C.

  The simulation results are shown in Table 2. The ejection speed, flight time, droplet amount, head temperature, cooling time constant, and T3 of ink 1 shown in Table 2 are the same for magenta ink 1 and cyan ink 1, and represent values common to both.

Examples 2-7
The image formation, evaluation and simulation of Examples 2 to 7 were performed in the same manner as in Example 1 except that the gap width, the droplet amount, and the temperature of the recording head were changed as shown in Table 2.

  The results are shown in Tables 2 and 3.

Examples 8-12
In Example 1, the magenta ink 1 was replaced with the magenta ink 2, the cyan ink 1 was replaced with the cyan ink 2, and the gap width, the droplet amount, and the temperature of the recording head were changed as shown in Table 2. Then, image formation, evaluation and simulation of Examples 8 to 12 were performed.

  The results are shown in Tables 2 and 3.

Example 13
In Example 1, the magenta ink 1 is replaced with the magenta ink 3, the cyan ink 1 is replaced with the cyan ink 3, and the temperature of the recording head is changed as shown in Table 2. Formation, evaluation and simulation were performed.

  The results are shown in Tables 2 and 3.

Examples 14 and 15
In Example 1, the magenta ink 1 was changed to the following magenta ink 4, the cyan ink 1 was changed to the following cyan ink 4, and the gap width, the droplet amount, and the temperature of the recording head were changed as shown in Table 2 in the same manner. Then, image formation, evaluation and simulation of Examples 14 and 15 were performed.

  The results are shown in Tables 2 and 3.

(Adjustment of magenta pigment dispersion 2)
The following two compounds were placed in a stainless beaker and dissolved by stirring with heating for 1 hour while heating on a hot plate at 65 ° C.

Pigment dispersant: Ajisper PB824 (manufactured by Ajinomoto Fine Techno Co., Ltd.) 9 parts Polymerizable compound: OXT221 (Oxetane 221, manufactured by Toagosei Co., Ltd.) 70 parts After cooling to room temperature, 21 parts of the following magenta pigment was added thereto, and the diameter was 0. 200 g of 5 mm zirconia beads were placed in a glass bottle and sealed, and after a dispersion treatment for 8 hours with a paint shaker, the zirconia beads were removed to prepare a magenta pigment dispersion 2.

Magenta pigment: Pigment Red 122 (manufactured by Dainichi Seika, Chromo Fine Red 6112JC)
(Adjustment of Cyan Pigment Dispersion 2)
The cyan pigment dispersion 2 was prepared in the same manner as in the preparation of the magenta pigment dispersion 2, except that the cyan pigment Pigment Blue 15: 4 (manufactured by Dainichi Seika Co., Ltd., Chromofine Blue 6332JC) was used instead of the magenta pigment. Obtained.

(Preparation of magenta ink 4)
The following additives were sequentially mixed, heated to 100 ° C. and stirred, and then the obtained liquid was filtered through a # 3000 metal mesh filter under heating and cooled to prepare magenta ink 4.

Polymerizable compound: OXT221 (oxetane compound, di (1-ethyl-3-oxetanyl) methyl ether, manufactured by Toagosei Co., Ltd.) 38.95 parts Polymerizable compound: Celoxide 2021P (alicyclic epoxy compound, 3,4-epoxycyclohexane) Hexenylmethyl-3 ′, 4′-epoxycyclohexenecarboxylate, manufactured by Daicel Chemical Industries, Ltd.) 30.0 parts Photopolymerization initiator: CPI-100P (50% propylene carbonate solution of triallylsulfonium salt, manufactured by San Apro) 5.0 Part Sensitizer: DEA (diethoxyanthracene, manufactured by Kawasaki Kasei Kogyo Co., Ltd.) 2.0 parts Surfactant: X22-4272 (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.05 part Magenta pigment dispersion 4 19.0 parts Gelation Agent: Paraffin wax (mp68-70 ° C; Wako Pure Chemical Industries, Ltd.) 5.0 parts (Cyanai Adjustment of click 4)
In the adjustment of the magenta ink 4, the cyan ink 4 was prepared in the same manner except that the cyan pigment dispersion liquid 4 was used instead of the magenta pigment dispersion liquid 4.

(Viscosity rise temperature and gelation temperature of magenta ink 4 and cyan ink 4)
In FIG. 8, # 4 is a temperature / viscosity curve of the magenta ink 4. Similarly to the magenta ink 1, it was found from the temperature / viscosity curve of the magenta ink 4 shown in FIG. 8 that the viscosity rising temperature was 64 ° C. and the gelation temperature was 55 ° C.

  The cyan ink 4 was obtained in the same manner, but the viscosity rising temperature was 65 ° C. and the gelation temperature was 55 ° C.

Example 16
In Example 12, image formation, evaluation, and simulation were performed in the same manner except that the image was formed on an aluminum carrier heated to 40 ° C.

  Tables 2 and 3 show the results of image formation, evaluation and simulation.

  From Tables 2 and 3, images recorded with the recording apparatus of the present invention in which T3 is equal to or lower than the gelation temperature and the viscosity rising temperature is + 1 ° C or higher are free from fine line color mixing, excellent gloss, no nozzle clogging, and abrasion resistance. It turns out that it is excellent in property.

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 2 Recording head 4 High pressure mercury lamp 10 Recording medium 10A Rolling-out roll 10B Winding roll 20 Back roll 23 Nozzle 27 Partition 28 Pressure chamber 29 Electrode 30 Inkjet head unit 31 Inkjet head 102 Manifold member 103 Manifold member 104 Manifold member 128 Air channel 310 head chip

Claims (8)

  In an ink jet recording method comprising a recording head that heats a temperature of a recording head to a viscosity rising temperature of + 1 ° C. or higher, includes an oil gelling agent and is in a gel state at room temperature, and discharges a plurality of inks having different colors. An ink jet recording method, wherein the temperature at the moment when one ink droplet first comes into contact with a recording medium is controlled to be a temperature equal to or higher than a gelling temperature and a viscosity rising temperature + 1 ° C. or lower.   The droplets of all of the plurality of inks having different colors have a temperature equal to or higher than a gelling temperature and a viscosity rising temperature + 1 ° C. or less at the moment of first contact with a recording medium. 2. The ink jet recording method according to 1.   3. The ink jet recording method according to claim 1, wherein the temperature of the recording head is a viscosity rising temperature of the ink + 5 ° C. or more and 80 ° C. or less.   The inkjet according to any one of claims 1 to 3, wherein the ink contains an actinic ray curable composition that is cured by actinic rays, and is cured by ultraviolet irradiation after landing on a recording medium. Recording method.   The ink jet recording method according to claim 1, wherein the ink has a viscosity rising temperature of 50 ° C. or more and 65 ° C. or less.   6. The ink jet recording method according to claim 1, wherein the ink contains 0.3 to 15.0% by mass of the oil gelling agent.   The ink jet recording method according to claim 1, wherein the recording head is a line head.   The inkjet recording method according to claim 1, wherein the recording medium is heated from the back side during printing or before and after printing.

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