JP2015054437A - Image recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image recording method which suppresses deterioration of the image quality by suppressing variation in size of a recording medium through simple temperature control without enlargement of the apparatus.SOLUTION: An image recording method includes, in order, a first heating step of heating a recording medium, an image recording step of recording an image on a recording medium and a second heating step of heating the recording medium recorded with the image. The image recording method has a stage in which the recording medium is elongated by the heating in the first heating step and a stage of shrinkage, in order. The heating in the first heating step is carried out until the time change rate of the shrinkage amount of the recording medium decreases to 0.001%/sec or smaller.

Description

  The present invention relates to an image recording method.

  In an image recording apparatus for forming an image by an inkjet method, a method for forming an image by dissolving resin fine particles contained in the ink by heating and fixing it to the recording medium is known as a means for fixing the ink to the recording medium. . In this method, since the recording medium itself expands and contracts due to heating, the size of the printed material may not always be constant. For this reason, when the printed materials are arranged in one large image, the position of the adjacent images may be shifted due to the difference in the amount of expansion / contraction of each printed material, resulting in a problem that the image quality is deteriorated (hereinafter, this problem may be reduced). "Tiling issue").

  In order to suppress such deterioration of image quality due to deformation of the recording medium, a method is known in which the recording medium is contracted before image recording by heating the recording medium in advance (Patent Document 1). In addition, as a method for suppressing deformation of the recording medium itself, a method for preventing shrinkage of the recording medium while promoting drying by applying superheated steam to the recording medium is disclosed (Patent Document 2).

JP-A-6-344629 JP 2010-158861 A

  However, in the method of heating a recording medium in advance before image recording in Patent Document 1, when heating is performed for ink fixing after image recording, the recording medium is further deformed by heating after recording. For this reason, it is not possible to obtain a sufficient effect with respect to suppression of deterioration in image quality.

  Further, in the method of Patent Document 2, since the recording medium is further contracted by the amount that has been expanded by heat after the end of heating, an effective effect cannot be obtained in terms of suppressing deterioration in image quality. Further, in order to apply superheated steam to the recording medium, it is necessary to configure a tank for storing water and a heater for further heating the steam, so that the apparatus becomes large and apparatus control becomes complicated.

  Furthermore, in the methods of Patent Documents 1 and 2, the deformation becomes non-uniform if there is uneven heating temperature or different heating time. When heating a recording medium having a certain recording area, the temperature control must be precisely performed. No longer. For this reason, an apparatus and control will become complicated.

  Therefore, the present invention has been made in view of such a situation. In other words, an object of the present invention is to provide an image recording method that suppresses a reduction in image quality by suppressing size variation between recording media by simple temperature control without increasing the size of the apparatus. It is.

One embodiment is:
An image recording method comprising: a first heating step for heating a recording medium; an image recording step for recording an image on the recording medium; and a second heating step for heating the recording medium on which the image is recorded. There,
The heating in the first heating step has a stage in which the recording medium expands and a stage in which the recording medium contracts in this order;
The present invention relates to the image recording method, wherein the heating in the first heating step is performed until the time change rate of the shrinkage amount of the recording medium becomes 0.001% / second or less.

  It is possible to provide an image recording method that does not cause an increase in the size of the apparatus, suppresses a variation in size between recording media by simple temperature control, and suppresses a decrease in image quality.

It is a figure showing the expansion-contraction characteristic by the heating of PVC media. It is a figure showing the expansion-contraction characteristic at the time of the heating of polyvinyl chloride media, and after completion | finish of a heating. It is a figure showing the expansion-contraction characteristic by heating of plain paper. It is sectional drawing showing the image recording apparatus used for the image recording method of one Embodiment of this invention. It is sectional drawing showing the other image recording apparatus used for the image recording method of one Embodiment of this invention.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. More specifically, the image recording method of the present invention and the recording medium, image recording apparatus, and ink used in this method will be described.

  The image recording method of the present embodiment includes a first heating step for heating the recording medium, an image recording step for recording an image on the recording medium, and a second heating step for heating the recording medium on which the image is recorded. Have in order. By the heating in the first heating step, the recording medium has a stage in which the recording medium expands and a stage in which the recording medium contracts in this order. Further, the heating in the first heating step is performed until the time change rate of the shrinkage amount of the recording medium becomes 0.001% / second or less.

  Even in the case of a recording medium having a large deformation amount that expands and contracts during heating as described above, heating in the first heating step is performed until the temporal change rate of the shrinkage amount of the recording medium becomes 0.001% / second or less. . Thereby, at the end of the first heating step, the deformation speed of the recording medium is slow. As described above, since the recording medium has undergone a heat history until the deformation speed becomes slow in the first heating step, the recording medium is hardly deformed even if the recording medium is heated in the second heating step. Accordingly, it is possible to suppress a variation in size between the final recording media and to suppress a reduction in image quality. In addition, no special device is required to control the time change rate to 0.001% / second or less, and the size of the device is not increased. The rate of change can be controlled. The time change rate of the shrinkage amount of the recording medium is measured by using a texture analyzer (manufactured by Stable Microsystems) and heating the recording medium having a size of 3 cm × 25 cm while pulling it with a load of 5 g.

<Recording medium>
As the recording medium used in the present embodiment, a recording medium having expansion / contraction characteristics of a stage that expands by heating in the first heating step and a stage that contracts by further heating is used. Examples of the recording medium that expands and contracts as described above by heating include a recording medium having a multilayer structure in which a plurality of different materials are laminated in layers. In the case of a recording medium having a plurality of layers having different constituent materials, the thermal expansion coefficient and the thermal contraction ratio of the respective layers are different, so that the above-mentioned expansion / contraction characteristics are exhibited by the heat treatment, which tends to cause a large deformation.

  For example, PVC media (KSM-VS: manufactured by Kimoto Co.) is a recording medium having a multilayer structure in which a polyvinyl chloride sheet is provided on the outermost surface, an adhesive layer is provided on the lower layer, and a release paper is provided on the lowermost layer. is there. The expansion and contraction behavior of this PVC media during heating is shown in FIG. As shown in FIG. 1, the vinyl chloride media has gone through a stage of stretching immediately after heating and then a stage of contracting. Furthermore, after the heating is completed, a part of the recording medium layer that has been expanded by heat contracts, and thus contracts further. FIG. 2 is a diagram showing the expansion stage (part indicated by A), the contraction stage (part indicated by B), and the expansion / contraction rate after the heating of the PVC media. The amount of shrinkage at the end of heating varies depending on the heating time, and when PVC media is used, the amount of shrinkage increases when the heating time is short.

  For the above reasons, in a recording medium that exhibits two-stage behavior of expansion and contraction, such as PVC media, nonuniform deformation due to variations in heating time and heating temperature is increased, and tiling problems are likely to occur. . In addition, since the shrinkage is started after being stretched, and the stretched layer and the shrinkable layer are present, it takes a long heating time until the shrinkage is settled. For this reason, the image recording method of this embodiment is effective when a recording medium having the above-described expansion / contraction behavior is used.

  On the other hand, a tiling problem hardly occurs for a recording medium that shrinks when heated. FIG. 3 shows the expansion and contraction behavior when plain paper (GF500: manufactured by Canon Inc.) is heated. In plain paper, shrinkage starts immediately after heating and no elongation behavior is observed. Further, when the heating is finished, it expands instead of shrinking, and deforms in a direction to return to the original state. For plain paper that only shrinks, it shrinks immediately after heating, so the time until it shrinks to a certain value is short, and the amount of shrinkage is easily made uniform even by heating for a time required for fixing.

In the present embodiment, the recording medium preferably satisfies the following formula.
(formula)
{(Maximum value of expansion amount of recording medium in first heating step) − (maximum value of shrinkage amount of recording medium in first heating step)} / (length of recording medium before first heating step) × 100 ≧ 0.1%.
Such a recording medium having a large amount of deformation generally has a large variation in size between the recording media, resulting in a decrease in image quality and a tiling problem. However, even in such a recording medium, by applying the image recording method of the present embodiment, it is possible to suppress a variation in size between the recording media and prevent a reduction in image quality.

  The recording medium has a multilayer structure, and at least one of the layers constituting the multilayer structure is preferably a layer having an organic polymer. Moreover, it is more preferable that at least one of the layers constituting the multilayer structure is a layer containing cellulose fibers, and the other at least one layer is a layer containing polyvinyl chloride. Since the recording medium having these multi-layer structures has a large amount of deformation due to expansion and contraction in the first heating step, application of the image recording method of the present embodiment effectively reduces the size variation between the recording media. Can be suppressed.

  Examples of the recording medium having a multilayer structure include those in which a plastic is coated on a substrate such as paper, a plastic film, and a fabric bonded. Examples of the plastic here include polyvinyl chloride, acrylic resin, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, and polypropylene. It is good also as a structure which has an adhesive layer which can be peeled again between said base material and a plastic film. Examples of the woven fabric include polyester, cotton, cotton, silk, and non-woven fabric. In addition, the recording medium of the present embodiment includes a configuration in which an ink receiving layer containing porous inorganic particles is provided on a paper base material such as inkjet recording paper. As the porous inorganic particles, porous amorphous silica, porous magnesium carbonate, porous alumina and the like are preferably used, and the content thereof is 40% by mass or more and 90% by mass or less in terms of solid content in the ink receiving layer. Degree. The ink receiving layer usually also contains a binder resin such as polyvinyl alcohol in order to ensure the necessary coating strength. Furthermore, what laminated | stacked the polymer resin film on the textile fabric which uses a filament (long fiber) is also mentioned. For example, a recording medium having a configuration in which polyvinyl chloride, acrylic resin, polyurethane, polyethylene, or the like is laminated on a glass fiber or polyester fiber fabric.

<Inkjet recording apparatus>
Next, an example of a specific configuration of an ink jet recording apparatus suitable for executing the image recording method of the present embodiment using ink described later will be described.

  FIG. 4 is a sectional view of the main configuration of the recording apparatus 100 according to the present embodiment in the transport direction. The recording medium P is conveyed in the direction indicated by the arrow 1 by a paper feed roller (not shown). The recording medium P fed along the direction of the arrow 1 is conveyed so as to be in contact with the preheater 2 immediately above a preheater (sheet heater: sheet heating element) 2 that performs preheating (first heating step). The control device 11 performs control so that the surface temperature of the recording medium P on which the output of the preheater is printed becomes the set temperature. The preheater 2 may be anything as long as the temperature can be controlled, and may be a radiant heating type sheathed heater or an infrared heater, or a contact heating type seat heater. Moreover, you may use combining a radiation type heater and a contact type heater.

  Subsequently, the recording medium P is conveyed directly below the recording head 101 by being held between the LF roller 17 and the pinch roller 16 and rotating these rollers. The recording head 101 is mounted on a carriage (not shown) supported by the aluminum stay 102. Thus, the recording medium P is scanned in the main scanning direction (direction perpendicular to the paper surface in the figure), and ink is ejected during this time to record on the recording medium P (image recording step). At this time, an ink having a composition described later in which the glass transition temperature of the resin is room temperature or higher is used. An encoder (not shown) that rotates coaxially with the LF roller 17 is provided. As a result, the rotation amount of the LF roller 17 is detected with a resolution of 1/2400 inch in terms of the conveyance distance of the recording medium. The platen 19 supports the conveyed recording medium P from below.

  The liquid drying device 15 is disposed on the downstream side in the transport direction of the recording head 101 or directly above the recording head 101. The liquid drying mechanism 15 includes a sheathed heater 31 and an infrared reflecting plate 32. The infrared reflecting plate 32 surrounds the back side of the sheathed heater 31 when viewed from the conveyance path side of the recording medium P, and has an opening formed on the front side (conveyance path side). It is provided so as to reflect the heat to the conveyance path side. The infrared sensor 23 measures the temperature on the recording medium P in the recording area, and controls the output of the sheathed heater via the control device 11. At this time, the ink temperature on the recording medium P is controlled so as not to exceed the glass transition temperature of the resin contained in the ink. The heating device used in the liquid drying mechanism 15 may be anything as long as the temperature can be controlled, and may be a radiation heating type sheathed heater or an infrared heater, or may be used in combination with a contact heating type sheet heater.

  The fixing device 50 includes two sheathed heaters 51 for supplying energy for fixing the ink applied to the recording medium P (in the second heating step). Further, it has a shape that surrounds the back side of the sheathed heater 51 as viewed from the conveyance path side of the recording medium P and has an opening formed on the front side (conveyance path side). A reflection plate 52 that reflects toward the conveyance path is provided. The shape and the like of the reflecting plate 52 are adjusted so that the temperature of the recording medium P becomes substantially uniform over substantially the entire surface of the fixing device 50 when the sheathed heater 51 generates heat. The infrared sensor 24 measures the temperature on the recording medium P immediately below the sheathed heater, and controls the heating temperature via the control device 11. At this time, the ink temperature on the recording medium P is preferably 60 ° C. or higher. This is because if the set temperature of the fixing heater is lower than 60 ° C., the time for fixing the ink on the recording medium P becomes longer and the fixing strength may be lowered. Any heating device can be used for the fixing device 50 as long as it can be controlled to a desired temperature, and a radiant heating type sheathed heater or an infrared heater may be used, or a contact heating type sheet heater may be used. Moreover, you may use combining a radiation type heater and a contact type heater. The temperature variation of the recording medium P in the fixing device 50 is preferably within ± 15 ° C. As the temperature variation in the fixing device is smaller, the tiling problem is less likely to occur. However, in order to make the temperature of the wide heating region completely uniform, the size and cost of the device are significantly increased.

  The fixing platen 20 supports the back surface of the recording medium P conveyed through the fixing device 50. As described above, the ink ejected from the recording head 101 and landed on the recording medium P can dry the liquid in the liquid dryer 15 and can be strongly fixed on the recording medium by the downstream fixing device 50. The recording medium P exiting the fixing device 50 by conveyance is taken up by a take-up device (not shown) through the discharge roller 18.

  The image recording apparatus used in the present embodiment is preferably configured so that the heating temperatures of the preheater 2, the liquid drying device 15, and the fixing device 50 can be independently controlled. In that case, the temperature of the recording medium conveyed on the preheater 2, the temperature of the recording medium being recorded with ink, and the temperature of the recording medium being fixed are adjusted in accordance with the thickness and type of the recording medium used and the printing mode. Can be adjusted accurately.

  In this embodiment, the control of the heating temperature of the preheater 2, the liquid drying device 15, and the fixing device 50 can be changed and adjusted by an operation panel attached to the recording device or a control host computer connected to the recording device. good. In this case, the heating temperature of the preheater 2, the liquid drying device 15 and the fixing device 50 for heating the recording medium P is set to the environment such as the type and thickness of the recording medium P transported on the platen and the ambient temperature where the recording device is placed. The operator can change and adjust according to.

  Another example of a specific configuration of an image recording apparatus suitable for executing the image recording method of the present embodiment will be described. FIG. 5 shows a configuration in which the basic configuration is the same as that in FIG. 4, but the heating devices used in the pre-heater 2, the liquid drying mechanism 15, and the fixing device 50 are all sheet heaters 53. Since the sheet heater 53 is in direct contact with the recording medium P, heat transfer efficiency is good, and the surface temperature of the recording medium P can be easily controlled. Further, the fixing device 50 includes a blower mechanism 40 so that the removal of the ink solvent can be accelerated. The blower mechanism 40 includes a blower fan 41 and a blower duct 42, and a blower direction control panel 43 is provided at the tip of the blower duct 42. At this time, the blower mechanism 44 is also provided in the area of the preheater 2. By providing the preheater unit with the air blowing mechanism 44 having the same configuration, the recording medium P can be heated more quickly and uniformly. Although the reason is not clear, an area where the change rate of deformation of the recording medium P is large can be shortened by blowing air from the preheater section, which is desirable. This is considered to be because the components contained in the recording medium P that volatilize by heating (water, plasticizer, etc.) are easily removed by blowing, so that deformation occurs quickly. Even in such a configuration, the effect of the present embodiment can be obtained.

<Image recording method>
(Preheating; 1st heating process)
An image recording method using the apparatus in FIG. 4 will be described. The preheater 2 in FIG. 4 preliminarily heats the recording medium until the time change rate of the contraction amount at the stage where the recording medium contracts is 0.001% / second or less. In other words, the heating in the first heating step is completed when the rate of time change of the shrinkage amount at the stage where the recording medium shrinks is 0.001% / second or less. The time change rate of the shrinkage amount of the recording medium is the slope of the tangent line at the time of shrinkage of the recording medium at the end of heating in the graph of heating time and expansion / contraction amount described above with reference to FIG. Further, the heating in the first heating step may be terminated immediately when the time change rate of the shrinkage amount is 0.001% / second or less. Further, the heating in the first heating step may be terminated after a certain time has elapsed after the rate of change in shrinkage with time is 0.001% / second or less. However, even in this case, the time change rate of the shrinkage at the end of heating is set to 0.001% / second or less.

  Since the heating temperature and heating time in the first heating process vary depending on the type of recording medium and the recording mode, they are determined by the combination of the type of recording medium and the recording mode. First, the heating time in the first heating process is determined by the recording speed. The recording speed is determined by the length of the fixing area in the transport direction from the heating temperature and time for sufficient fixing in the second heating step. The time during which the preheater 2 can be heated is determined by the determined recording speed and the heater length in the direction in which the recording medium is conveyed. The apparatus has, as a recording table, the heating time of each recording medium and the deformation rate at the heating temperature, and determines the temperature required for preheating from the preheating time determined by the recording mode. Alternatively, the temperature required for preheating is determined by the operator inputting a numerical value.

  The preset temperature of the preheater 2 (first heating step) is desirably set so that the surface of the recording medium is higher than the preset temperature in the fixing device 50 (second heating step). By making the preset temperature of the preheater 2 higher than the preset temperature in the fixing device 50, the length of the preheater 2 can be shortened, which is advantageous in terms of downsizing the apparatus and efficiency of heat transfer. In addition, when the set temperature of the fixing device 50 is higher than the set temperature of the preheater 2, although the expansion amount and the contraction amount are small, the recording medium in the fixing device 50 may cause expansion and contraction again. For this reason, the image size may become slightly uneven.

  The temperature difference between the set temperatures of the fixing device 50 and the preheater 2 is desirably changed depending on the type of the recording medium when the number of passes or the like changes the time for passing the fixing device 50. For example, when vinyl chloride media is used, the preset temperature of the preheater is increased to set a large difference from the fixing temperature during the first to sixth passes in which the time required for recording is short. Since the fixing device 50 heats only for a short time during a low pass, it is possible to avoid a region where the deformation change rate of the recording medium is large by preheating at a high temperature in advance. On the other hand, in the case of 8 to 32 passes, it is desirable to set the preheater set temperature close to the fixing temperature. When the passage time of the fixing device 50 is sufficient, even from the viewpoint of power saving, even if the preheater set temperature is close to the fixing device 50, a region with a large change rate in which the recording medium is deformed is sufficiently avoided. Can do.

  As described above, the set temperature (the temperature of the recording medium) of the preheater 2 may vary depending on the type of the recording medium, the fixing process conditions, other heating conditions, and the like, but the recording medium is heated to 60 ° C. or higher. Is preferred.

(Image recording process)
The image recording apparatus used in the method of one embodiment of the present invention uses a recording head having a nozzle row in which a plurality of nozzles are arranged. Also, there are a plurality of recording modes with different numbers of passes in multi-pass recording, and recording is executed by switching these modes. The recording mode is switched depending on the recording medium and recording quality. The image recording apparatus also performs heating and / or blowing in the area of the recording head. The heating temperature is preferably lower than the minimum film-forming temperature of resin fine particles contained in the ink described later. The minimum film-forming temperature represents the minimum temperature required for the resin fine particles to form a film by heating. Spread a dispersion of resin fine particles on a thermally conductive plate with a temperature gradient to create a dry film. The dried product forms a uniform continuous film, and the minimum temperature when the film is not whitened is the minimum film-forming temperature. It can be measured. This is because if the heating is performed at a temperature higher than the minimum film-forming temperature, resin fine particles may form a film in the nozzles of the recording head or ink adhering to the head face surface may adhere to cause ejection failure. It is desirable to perform the recovery operation of the recording head in order to avoid clogging of the discharge nozzles. The recovery operation includes an operation of wiping the face surface of the recording head and an operation of sucking ink with a pump. This operation may be performed at regular time intervals, or may be performed when the temperature of the recording head exceeds a predetermined temperature.

(Ink fixing; second heating step)
In the second heating step, for example, heat fixing is performed to fix the ink on the recording medium. The higher the heating temperature, the shorter the fixing time. However, if the heating temperature is too high, the recording medium may be slightly deformed. Therefore, the temperature is preferably 60 ° C. or higher and 120 ° C. or lower.

  Note that the recording medium is also heated in the second heating step, but since the recording medium has already undergone expansion and contraction history of expansion and contraction in the first heating step, it is difficult to expand and contract by reheating. . For this reason, since the deformation amount (elongation amount, shrinkage amount) of the recording medium in the second heating step is small, the size variation between the recording media after the second heating step does not increase. Therefore, the heating in the second heating step does not affect the effect of the present invention.

  When the variation in the heating temperature of the recording medium in the second heating step is larger than the set value ± 3 ° C. in the heating region or in the heating time, the deformation amount of the recording medium may vary depending on the location. However, in the image recording method of the present embodiment, even in such a case, the recording medium is not greatly deformed by the heating in the second heating step as described above, so that variation in size between the recording media is suppressed. can do.

  In the second heating step, the heating time may be changed for 10 seconds or more for each recording medium. In this case, since the amount of heat applied in the second heating step is different for each recording medium, the amount of deformation may be different for each recording medium. However, in the image recording method of the present embodiment, even in such a case, since the recording medium is not greatly deformed by the heating in the second heating step as described above, it is possible to suppress deterioration in image quality. .

  The temperature of the recording medium in the first heating step is preferably higher than the temperature of the recording medium in the second heating step. The difference between the temperature of the recording medium in the first heating step and the temperature of the recording medium in the second heating step is preferably 5 ° C. or more. Thereby, the deformation of the recording medium in the second heating step can be further suppressed, and a printed matter with excellent image quality can be obtained.

<Water-based ink>
The ink of this embodiment will be described. The ink of this embodiment is, for example, an aqueous ink containing at least resin fine particles, water, and a colorant, and further containing a water-soluble organic solvent, a surfactant, and other components as necessary. By using water as the main solvent, the ink viscosity does not increase compared to when an organic solvent is used, and the ink jet head can be stably ejected.

  The pH of the water-based ink may be any pH as long as the stability of the composition is maintained, and both are preferably neutral as a region where dispersibility is maintained. Specifically, the pH is preferably 5 or more and 10 or less.

(Resin fine particles)
The water-based ink used in the image recording method of the present embodiment includes resin fine particles. By including resin fine particles in the water-based ink, an image having more excellent abrasion resistance can be formed on the recording medium. In particular, it is preferable to record an image using a water-based ink containing resin fine particles on a non-ink-absorbing or low-ink-absorbing recording medium such as a vinyl chloride film or a polypropylene film. In this case, an image having excellent abrasion resistance can be formed through the heat fixing step. The reason is that in the heat fixing step, the resin fine particles have the effect of solidifying the ink and further fixing the solidified ink on the recording medium, and this effect can be further enhanced by heating. In particular, the water-based ink preferably contains resin fine particles in an emulsion state or a suspension state. By containing the resin in a fine particle state, it is easy to adjust the viscosity of the water-based ink to an appropriate range in the ink jet recording method, and it is easy to ensure storage stability and ejection stability. In addition, by making the resin in a fine particle state, aggregation of the colorant when the ink is landed on the recording medium can be suppressed, which can contribute to suppression of uneven density / bleeding.

  The average particle diameter of the resin fine particles is preferably in the range of 5 nm to 400 nm, more preferably in the range of 50 nm to 300 nm, from the viewpoint of ensuring the storage stability and ejection stability of the water-based ink. The content of the resin fine particles is preferably 15% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less in terms of solid content with respect to the total amount of the aqueous ink. By being within this range, the water-based ink composition can be solidified and fixed firmly on the recording medium, even on a non-ink-absorbing or low-absorbing recording medium, in combination with the steps in the preferred image recording method described above. Can be made. Further, when the content is 15% by mass or less, the storage stability and ejection stability of the water-based ink can be ensured.

(Coloring agent)
As the colorant used in the ink in the present embodiment, any of pigments and dyes can be used, and these can also be used in combination. There is no restriction | limiting in particular in the kind of pigment, According to the objective, it can select suitably, Any of an inorganic pigment and an organic pigment may be sufficient. You may use these pigments in mixture of multiple types. As the dye, those having excellent water resistance and light resistance, which are classified into acid dyes, direct dyes, basic dyes, reactive dyes, and food dyes in the color index, are used. These dyes may be used in combination of a plurality of types, or may be used in combination with other colorants such as pigments as necessary.

(Water-soluble organic solvent)
The aqueous ink preferably includes an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. It is preferable to use deionized water (ion exchange water) as water. These water-soluble organic solvents can be used alone or in combination of two or more.

(Surfactant)
The ink used in this embodiment preferably contains a nonionic surfactant. The nonionic surfactant has an action of spreading the water-based ink uniformly on the recording medium. Therefore, when the water-based ink containing this is used, there is an effect that density unevenness and blurring are reduced and a clear image can be obtained. Nonionic surfactants having such effects include polyoxyethylene alkyl ethers, polyoxypropylene alkyl ethers, polycyclic phenyl ethers, sorbitan derivatives, fluorines, silicones, acetylene glycols and the like. . Among these, the surfactants that are particularly excellent in the above-described effects and that are preferable for water-based inks include fluorine-based surfactants and silicone-based surfactants.

(Other ingredients)
The ink used in this embodiment contains a nitrogen-containing compound such as urea or ethylene urea, a surfactant, an antifoaming agent, a rust preventive, a preservative, and an antifungal agent as necessary, in addition to the above components. be able to. The ink may contain various additives such as an antioxidant, a reduction inhibitor, an evaporation accelerator, and a chelating agent. Further, an infrared absorbing material may be added in order to improve heat absorption characteristics in fixing.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  In order to obtain the relationship between the heating time and the heating temperature of the recording medium, the time change rate of the expansion / contraction amount of the vinyl chloride media (KSM-VS: manufactured by Kimoto Co.) during heating was measured. This PVC media stretched and contracted upon heating as described above with reference to FIGS. The measurement of the amount of expansion and contraction with time was performed by using a texture analyzer (manufactured by Stable Microsystems) and heating each recording medium having a size of 3 cm × 25 cm with a load of 5 g to measure the amount of expansion and contraction. . Table 1 shows the measurement results of the time change rate of the amount of expansion and contraction at various heating temperatures and heating times. In Table 1, the determination when the rate of time change in shrinkage at the end of heating is 0.001% / second or less is “OK”, and the determination when the value is greater than 0.001% / second is “NG”. did.

  From the results of Table 1, it can be seen that the determination is “OK” under the conditions of a temperature of 110 ° C. for a time of 60 to 180 seconds, a temperature of 90 ° C. for a time of 90 to 180 seconds, and a temperature of 70 ° C. for a time of 120 to 240 seconds.

  Subsequently, using the apparatus shown in FIG. 4, five sheets of 1.2 m × 3 m were printed at the set temperature and heating time of each heater shown in Table 2. The heating with the preheater corresponds to the first heating process, and the heating with the fixing device corresponds to the second heating process, which is the same in the following tables. Further, the difference between the average value and the maximum value of the length of the five printed materials, and the difference between the average value and the minimum value were obtained, and each was regarded as a variation in size. Judgment was made as “X” when (size variation) / (length of recording medium before heating) × 100 was 0.1% or more, and “◯” when smaller than 0.1%.

  As shown in Table 2, in Comparative Examples 1 to 4, since the heating condition in Table 1 is the region where the time change rate of the recording medium is NG, the variation in the size of the final printed matter is 0.1% or more. The size of the printed material was different. In Examples 1 to 5, since the time change rate of the recording medium is in the OK region, the size variation is smaller than 0.1%, and there is no difference in the size between the printed materials.

  Subsequently, Table 3 shows the time change rate when each recording medium was heated at 90 ° C. As the recording medium, tarpaulin (LL banner 13 oz mat type: manufactured by Sakurai Co., Ltd.), cloth-based media (SS2020: manufactured by Seiren Shoji Co., Ltd.), and acrylic-based media AF1000 (manufactured by Sumitomo 3M) were used. The determination was “OK” when the time change rate during contraction was 0.001% / second or less, and the determination was “NG” when the value was greater than 0.001% / second.

  Tarpaulin, cloth-based media, and acrylic-based media also stretched in the initial stage of heating and contracted by further heating. From the results in Table 3, it can be seen that the determination is “OK” under the conditions of 180 to 240 seconds for tarpaulin, 240 to 300 seconds for fabric media, and 180 to 240 seconds for acrylic media. Moreover, the deformation amount at the time of heating exceeded 0.1%, and it was found that the deformation amount may be large. Here, the deformation amount at the time of heating represents {(maximum value of the expansion amount of the recording medium) − (maximum value of the shrinkage amount of the recording medium)} / (length of the recording medium before heating) × 100.

  Subsequently, using the apparatus shown in FIG. 4 for each medium, five printed materials of 1.2 m × 3 m were prepared at the set temperatures and heating times of the heaters shown in Table 4. The difference between the average values of the lengths of the five printed materials and the difference between the average value and the minimum value were obtained, and each was regarded as a variation in size. In the judgment, (size variation) / (length of recording medium before heating) × 100 is “x” when 0.1% or more, and “◯” is smaller than 0.1%. .

  As shown in Table 4, even in various recording media, the variation in size between printed materials was small under the condition of performing the preheating heating time in which the time change rate during shrinkage was 0.001% / second or less.

  Next, using vinyl chloride media (KSM-VS: manufactured by Kimoto Co., Ltd.), setting the preheating temperature and the fixing device temperature as shown in Table 5, and using the apparatus shown in FIG. 4, three 1.2 m × 3 m printed matter Created. Further, in consideration of the variation in the fixing temperature, a heater with a heater temperature of 5 ° C. increased similarly. The difference between the length of the printed matter prepared under the conditions of Table 5 and the length of the printed matter obtained by raising the fixing temperature by 5 ° C. is shown in Table 5. In the determination, “×” indicates that the variation in size is 0.1% or more, and “◯” indicates that the variation is less than 0.1%. The variation in size is {(length of the printed material prepared under the conditions in Table 5) − (length of the printed material increased by 5 ° C. fixing temperature)} / (length of the printed material prepared under the conditions of Table 5). X) x100.

  From the results of Table 5, even when the temperature of the fixing device is different, the variation in the size of the printed matter was small if preheating was performed so that the time change rate of the recording medium at the time of shrinkage was 0.001% / second or less. .

  Next, using vinyl chloride media (KSM-VS: manufactured by Kimoto Co., Ltd.), setting the preheating temperature and the fixing device temperature as shown in Table 6, and using the apparatus shown in FIG. 4, three 1.2 m × 3 m printed matter Created. Further, in consideration of the head recovery operation during the recording, the one in which the passage time of the fixing device was set to 30 seconds longer was similarly prepared. The difference between the length of the printed material created under the conditions of Table 6 and the length of the printed material obtained by increasing the passage time of the fixing device by 30 seconds was shown in Table 6. In the determination, “×” indicates that the variation in size is 0.1% or more, and “◯” indicates that the variation is less than 0.1%. The variation in size is {(the length of the printed material created under the conditions in Table 6) − (the length of the printed material obtained by increasing the passage time of the fixing device by 30 seconds)} / (created under the conditions in Table 6). Length of printed matter) × 100.

  From the results shown in Table 6, even when the fixing time was different, the variation in the size of the printed matter was small if preheating was performed so that the time change rate of the recording medium during shrinkage was 0.001% / second or less.

  Next, using vinyl chloride media (KSM-VS: manufactured by Kimoto Co., Ltd.), setting the preheating temperature and the fixing device temperature as shown in Table 7, and using the apparatus shown in FIG. Created. The difference between the average values of the lengths of the five printed materials and the difference between the average value and the minimum value were obtained, and each was regarded as a variation in size. In the judgment, (size variation) / (length of recording medium before heating) × 100 is “x” when 0.1% or more, and “◯” is smaller than 0.1%. .

  As shown in Table 7, even when the preheating temperature and the fixing device temperature are different, there is no variation in size between printed materials under the preheating heating time condition in which the time change rate of the recording medium during shrinkage is 0.001% / second or less. It was getting smaller. Further, when the preheating temperature was higher than the fixing device temperature, the preheating time could be shortened.

DESCRIPTION OF SYMBOLS 100 Recording apparatus 101 Recording head 102 Stay 2 Preheater 11 Control apparatus 15 Liquid drying apparatus 16 Pinch roller 17 LF roller 18 Discharge roller 19 Platen 20 Fixing platen 23 Infrared sensor 24 Infrared sensor 31 Seeds heater 32 Infrared reflector 40 Blow mechanism 41 Blow Fan 42 Blower duct 43 Blower direction adjusting plate 50 Fixing device 51 Seed heater 52 Reflector P Recording medium

Claims (8)

An image recording method comprising: a first heating step for heating a recording medium; an image recording step for recording an image on the recording medium; and a second heating step for heating the recording medium on which the image is recorded. There,
The heating in the first heating step has a stage in which the recording medium expands and a stage in which the recording medium contracts in this order;
An image recording method, wherein the heating in the first heating step is performed until a time change rate of a shrinkage amount of the recording medium becomes 0.001% / second or less. The image recording method according to claim 1, wherein the recording medium satisfies the following expression.
(formula)
{(Maximum value of expansion amount of recording medium in the first heating step) − (maximum value of shrinkage amount of recording medium in the first heating step)} / (of the recording medium before the first heating step) Length) x 100 ≥ 0.1% The recording medium has a multilayer structure;
3. The image recording method according to claim 1, wherein at least one of the layers constituting the multilayer structure is a layer containing an organic polymer.   The layer constituting the multilayer structure, at least one layer is a layer containing cellulose fibers, and at least one other layer is a layer containing polyvinyl chloride. Image recording method.   5. The image recording method according to claim 1, wherein in the first heating step, the recording medium is heated so that a temperature of the recording medium is 60 ° C. or higher.   The variation in the heating temperature of the recording medium in the second heating step is larger than a set value of ± 3 ° C. in the heating region or in the heating time. Image recording method.   The image recording method according to claim 1, wherein the temperature of the recording medium in the first heating step is higher than the temperature of the recording medium in the second heating step. .   The image recording method according to claim 7, wherein a difference between the temperature of the recording medium in the first heating step and the temperature of the recording medium in the second heating step is 5 ° C. or more.