1. Field of the Invention
The present invention relates to an ink jet printing apparatus and an ink jet printing method that form an image on a print medium using color ink for printing an image and clear ink for protecting the image.
2. Description of the Related Art
Ink jet printing apparatuses have a variety of advantages such as performing high density, high speed printing operations, low running costs and quiet printing, and are commercialized in a variety of forms as output devices for devices of all types and as portable printers, for example.
There has been an increasing demand for ink jet printing apparatuses that output images with improved visual quality and weather resistance, and many apparatuses that print images using pigment ink have been provided recently. A technique for increasing image glossiness and resistance to scratching (hereinafter, “scratch resistance”) by applying clear ink on top of an image formed by color ink, such as pigment ink for example, that is, by overcoating the image surface, is disclosed in Japanese Patent Laid-Open No. 2005-081754.
Nevertheless, in printed objects obtained after overcoating clear ink on an image, colors unrelated to the image are generated by light interference at the clear ink layer, which often deteriorates image quality.
Parallel light from, for example, sunlight or a fluorescent lamp, is split into reflected light 1005, which is reflected at the top of the clear ink layer 1003, and light 1006 which has passed through the clear ink layer 1003 and is reflected at the surface of the pigment layer 1002, and light interference is produced according to the optical path difference between them. When the intensity of light having a wavelength satisfying the equation m×λ=n×2d×cos θ+λ/2 (m is an integer) (equation 1), where θ is angle of incidence, λ is the wavelength of the incident light and n is the index of refraction of the clear ink layer 1003, is increased, the interference color of that light becomes strongly perceptible in comparison to other colors. Also, because the wavelength λ satisfying the above equation changes according to the thickness d of the clear ink layer 1003, when the thickness of the ink layer 1003 is not uniform there are also cases where rainbow-colored reflected light is recognizable. This type of generation of colors that are unrelated to the image degrade the quality of the printed object.
In general it is thought that the following three methods can be used to suppress damage caused by the above described interference. (1) Making the thickness d of the clear ink layer extremely thin. (2) Making the thickness d of the clear ink layer thick to the extent where interference is caused at many visible wavelengths. (3) Forming portions where the clear ink layer is thick and portions where the clear ink layer is thin, generating various interference wavelengths.
However, concerning (1), when the clear ink layer is made extremely thin the original purposes of applying a clear ink layer, that is, glossiness and scratch resistance on the image surface, are not obtained. Also, concerning (1), a thickness on the order of 1 μm is necessary for the clear ink layer to be thick enough that a particular interference color does not stand out, but in this case a large volume of clear ink is consumed in comparison to the color ink. It is not preferable to invite an increase size or cost of apparatus because of clear ink, which does not have a direct relation to the image.
On the other hand, concerning (3), it is necessary to change the application amount of clear ink according to location, in order to form portions where the thickness of the clear ink is thick and portions where the thickness of the clear ink is thin. In this case, if the clear ink printing ratios are biased according to location, as in
The present invention was formed in light of the problems caused by the aforementioned techniques of the prior art. Accordingly it is an object to provide an ink jet printing apparatus and ink jet printing method that are capable of implementing an overcoating in which an interference color of a particular wavelength is not generated, without consuming more clear ink than necessary to overcoat the image.
In a first aspect of the present invention, there is provided an ink jet printing method comprising: a printing step wherein an image is printed on a unit area of the print medium by application of color ink containing color material from an application unit; a first application step wherein clear ink not containing color material is applied by the application unit onto the unit area during the printing step or after the printing step is completed; and a second application step which is performed after the first application step has been completed, wherein the clear ink is applied at the unit area by the application unit, after taking time for the fixation of the clear ink applied at the first application step.
In a second aspect of the present invention, there is provided an ink jet printing apparatus comprising: an application unit capable of applying color ink containing color material and clear ink not containing color material; a control unit configured to control the application unit; wherein the control unit controls the application unit such that an image is printed on a unit area of the print medium by the application of the color ink from the application unit, the clear ink is applied on the unit area during the application of the color ink or after the completion of the application of the color ink by the application unit, and after the application of clear ink has been completed and after taking fixation time for the fixation of the applied clear ink, the clear ink is applied at the unit area again.
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
Embodiments of the present invention will be described in detail below.
When a print operation command is input by the externally connected host computer, one sheet of the print media stacked in the feed tray 15 is fed to a position where printing by the print head mounted on the carriage 11 is possible. Subsequently, an image is formed gradually on the print medium by alternately repeating main print scans of the print head while ejecting ink, according to print signals, and fixed-distance conveyances of the print medium in a direction different than the main scan direction.
A recovery device 14 for executing print head maintenance operations is provided at the end of the region in which the carriage 11 moves. The recovery device 14 is provided, for example, with caps 141 for protecting the ejection port surface of the print head during suction or nonuse, an ejection receptacle 142 for catching clear ink during ejection recovery, and an ejection receptacle 143 for catching color ink ejected during ejection recovery. The wiper blade 144 wipes the ejection port surface of the print head while moving in the direction of the arrow.
306 is an externally connected host computer that forwards image information to be printed, to the ink jet printing apparatus of the present embodiment. The form of the host computer 306 may take the shape of a computer serving as an information processing apparatus or the shape of an image reader. 307 is a reception buffer that temporarily stores data from the host computer 306, and accumulates received data until it is read by the system controller 303.
308 is frame memory for developing data to be printed into image data, and has a memory size, for each ink color, of a capacity sufficient for printing. 309 is a buffer for temporarily storing respective data of each ink color to be printed, and its printing capacity varies in accordance with the number of print head ejection ports.
310 is a printing control unit that, for example, appropriately controls the print head 17 according to commands from the system controller 301 and controls, for example, print speed and the amount of print data. 311 is a print head driver that is controlled by signals from the printing control unit 310 and drives the print head 17, causing ink to be ejected.
In the above configuration, image data supplied from the host computer 306 is forwarded to the reception buffer 307 where it is temporarily stored, and developed into a frame memory 308 provided for each ink color by the system controller 301. Next, the developed image data is read out by the system controller 301, and after prescribed image processing is applied, developed into the buffer 309, for each color. The printing control unit 310 controls the actions of the print head 17 based on image data within each buffer.
The composition of the ink set and the purification method applied in the present embodiment will now be explained. In the present embodiment 4 colors of pigment ink, which contain pigment, are used as the color ink.
First, 10 parts of the pigment shown below, 30 parts of an anionic macromolecule and 60 parts purified water are mixed.
Next, the materials shown above are stocked into a batch type vertical sand-mill (manufactured by Imex), 150 parts of 0.3 mm diameter zirconia beads are filled in, and a dispersion process is carried out while water cooling. Additionally the dispersed liquid is centrifuged and coarse particles are removed. Next, a pigment dispersion element with a solid content of roughly 12.5% and a weighted average grain diameter of 120 nm are obtained as the final manufactured good. Using the obtained pigment dispersion element, ink is manufactured in the manner described below.
The materials below are mixed, sufficiently agitated, and after dissolution and dispersion, pressure filtered in a micro-filter having a pore size of 1.0 μm (manufactured by Fuji Film), and ink 1 is prepared.
First, with benzyl acrylate and methacrylic acid as raw materials, an AB type block polymer, with an acid value of 300 and a number average molecular weight of 2500, is made by the usual method, neutralized by a potassium hydrate aqueous solution, diluted by ion-exchanged water, and a homogenous 50% mass polymer aqueous solution is produced. Also, 100 g of the above polymer solution is mixed with 100 g C.I. pigment red 122 and 300 g of ion-exchanged water, and mechanically agitated for 0.5 hours. Next, using a micro-fluidizer, this mixture is processed by passing it into an interaction chamber at a liquid pressure below roughly 70 MPa for five times. Additionally, the above obtained dispersed liquid is centrifuged (at 12,000 rpm for 20 minutes), removing the undispersed material containing coarse particles, and magenta dispersion fluid is obtained. The pigment density of the obtained magenta dispersion fluid is 10% by weight and the dispersant density is 5% by weight.
The above magenta dispersion fluid is used in the manufacture of ink. The materials below are added making it a prescribed density, and after these materials are sufficiently mixed and agitated, they are pressure filtered in a micro-filter having a pore size of 2.5 μm (manufactured by Fuji Film), and pigment ink is prepared, having a pigment density of 4% by weight and a dispersant density of 2% by weight.
<Cyan Ink>
First, with benzyl acrylate and methacrylic acid as raw materials, an AB type block polymer, with an acid value of 250 and a number average molecular weight of 3000, is made by the usual method, neutralized by a potassium hydrate aqueous solution, diluted by ion-exchanged water, and a homogenous 50% mass polymer aqueous solution is produced. Also, 180 g of the above polymer solution is mixed with 100 g C.I. pigment blue 15:3 and 220 g of ion-exchanged water, and mechanically agitated for 0.5 hours. Next, using a micro-fluidizer, this mixture is processed by passing it into an interaction chamber at a liquid pressure below roughly 70 MPa for five times. Additionally, the above obtained dispersed liquid is centrifuged (at 12,000 rpm for 20 minutes), removing the undispersed material containing coarse particles, and cyan dispersion fluid is obtained. The pigment density of the obtained cyan dispersion fluid is 10% by weight and the dispersant density is 10% by weight.
The above cyan dispersion fluid is used in the manufacture of ink. The materials below are added making it a prescribed density, and after these materials are sufficiently mixed and agitated, they are pressure filtered in a micro-filter having a pore size of 2.5 μm (manufactured by Fuji Film), and pigment ink is prepared, having a pigment density of 2% by weight and a dispersant density of 2% by weight.
100 g of the polymer solution used in the yellow ink is mixed with 100 g of carbon black and 300 g of ion-exchanged water, and mechanically agitated for 0.5 hours. Next, using a micro-fluidizer, this mixture is processed by passing it into an interaction chamber at a liquid pressure below roughly 70 Mpa for five times. Additionally, the above obtained dispersed liquid is centrifuged (at 12,000 rpm for 20 minutes), removing the undispersed material containing coarse particles, and black dispersion fluid is obtained. The pigment density of the obtained black dispersion fluid is 10% by weight and the dispersant density is 6% by weight.
The above black dispersion fluid is used in the manufacture of ink. The materials below are added, making it a prescribed density, and after these materials are sufficiently mixed and agitated, they are pressure filtered in a micro-filter having a pore size of 2.5 μm (manufactured by Fuji Film), and pigment ink is prepared, having a pigment density of 5% by weight and a dispersant density of 3% by weight.
<Clear Ink>
First, resin aqueous solution is obtained in the following manner. 15% by weight of a resin composed of styrene and acrylic acid, and an amount of potassium hydrate chemically equivalent to the carbolic acid composing the acrylic acid are added, and after the remainder is adjusted to 100% by weight by water, it is agitated at 80° C. and the resin is dissolved. After that, it is adjusted with water such that the contained amount of solid contents becomes 15% by weight, and the resin aqueous solution is obtained. The resin has a weight-average molecular weight of 7000.
Each of the components shown below are mixed, and after sufficient agitation, ink is manufactured. The obtained clear ink was colorless and transparent.
Because the surface tension of the clear ink of the present embodiment, manufactured as above, is low, it spreads easily on a print medium. Also, even 2 liquid drops that are printed at spaced positions will become mutually connected if they touch before fixing, and has a characteristic wherein a uniform layer is formed easily.
As can be understood from the figure, in the case where the printing ratio of clear ink is low (lower than 10%), the interference color can not be seen. This is because the uniform layer is not formed, because the dots are dispersed. Or conceivably, this is because, even where the layer has been formed, the wavelength region satisfying equation 1 does not reside in the visible region because it is an ultrathin layer.
When the printing ratio turns to the order of 25% the stabilized clear ink layer is formed and the interfering light can be perceived. Thus, as the clear ink printing ratio, that is, the thickness of the clear ink layer, gradually increases, the long wavelength (λ) interference color becomes perceivable.
Therefore, based on the above result, the present inventors draw attention to the fact that, if the thickness of the clear ink layer is not held and unevenness is made on the image surface, light of various wavelengths (colors) will be included in the reflected light, and a particular interference color can not be easy to notice. In order to accomplish this it has been found that regulation of the timing of the application of the clear ink is effective.
In the present embodiment, a period of time is taken after the uniform clear ink layer (liquid layer) 144 is formed by this first application step. Next, after the clear ink layer 144 has fixed to a degree, a second application step is newly executed, as shown in
The thickness of the clear ink layer shown in
In the present embodiment, 8-pass multi-pass printing is performed by the print head shown in
In a multi-pass printing, image data that the print head can print in 1 main scan is culled according to a mask pattern that has been prepared in advance, and an image is completed in phases by multiple main scans.
57
a to 57d illustrate the mask patterns respectively allocated to regions 1 to 4. Each of the mask patterns 57a to 57d have 4 pixel by 4 pixel areas with determined print-permitted pixels shown in black and non print-permitted pixels shown in white, and when these mask patterns 57a to 57d are superimposed the print-permitted pixels complemented each other. When printing is carried out in practice, a logical AND operation is carried out between the image data (print/non-print data) accorded to the individual ejection ports and the mask pattern, and an ejection operation is executed based on the result thereof. It should be noted that even though, for the sake of simplicity, mask patterns having a 4 pixel×4 pixel area have been illustrated, actual mask patterns have a considerably larger area in both the main scanning direction and the sub-scanning direction.
58
a to 58d illustrate the case where an image is completed on a print medium by repeating print scans. In each print scan, regions 1 to 4 of the ejection port array 56 carry about printing only with respect to pixels that are print-permitted according to the mask patterns 57a to 57d, and when each print scan is completed the print medium is conveyed a distance corresponding to the width of each of the regions in the sub-scanning direction. By this configuration an image of unit area of the print medium (an area of the print medium corresponding to the width of each region of the ejection port array) is completed by 4 print scans.
If this type of multi-pass printing is carried out, variation particular to a nozzle (ejection port) and variance due to imprecision in the conveyance of the print medium are dispersed because each unit area of the print medium is printed by multiple scans and multiple regions of the ejection port array, and it is thus possible to reduce density unevenness and stripes.
In
On the other hand,
With respect to the clear ink, the print permission ratios at each of the regions are not the same, rather, regions 90a to 90f are 6.25%, region 90g is 0% and region h is 12.5%. However, there is no image data for clear ink and any print permitted pixel will be printed of one drop of clear ink. Therefore, printing of clear ink is carried out with respect to all of the print-permitted pixels shown in black, that is, printing is carried out at a printing ratio of 50% in respect to the entire image area.
In the case of carrying out 8-pass multi-pass printing using the above described mask patterns, at a unit area, color ink is printed at passes 1 to 8 at a rate of 12.5%, and clear ink is printed at passes 9 to 14 at a rate of 6.25 percent. After that, at pass 15 no ink is printed, and 12.5% of clear ink is printed at pass 16. Accordingly, in the case of the present embodiment, the printing at passes 9 to 14 becomes the 1st clear ink application step, and the printing of the 16th pass coming after the 15th pass, where the printing of clear ink is not carried out, becomes the 2nd application step.
Above, a case was explained where clear ink was printed on top of the color ink layer 173, but it is not the case that image data exists at every area, and it is not the case that that color ink forms a layer at every area. White paper areas where color ink is not printed on the print medium and low gradation areas where only a small amount of color ink is printed both exist.
On the other hand,
As explained above, according to the present invention it is possible to divide the clear ink overcoat into a 1st application step and a second application step, by way of making one region of the print head of the multi-pass printing a non-printing region (region 7). That is, when performing multi-pass printing at a unit area on a print medium, at least one pass or more where clear ink is not applied is provided between the passes where clear ink is provided. Herewith, because time is provided where clear ink is not applied at the unit area, clear ink is applied at the second application step after the clear ink applied at the first application step has fixed. By way of employing such a configuration, at both image areas, where color ink is printed and white paper areas where color ink is not printed, it is possible to cause various wavelengths (colors) of light to be included in the reflected light in the same way, and it is possible to output printed matter wherein a particular interference color can not be visually perceived when viewed.
As is the case with the 1st embodiment, the printing apparatus shown in
In the present embodiment in order to establish a 1st clear ink application step and a 2nd clear ink application step, the regions of the color ink ejection port array that are used for printing are limited. Concretely, only the ejection ports included in region 242 are used to carry out printing, and ejection ports included in regions other than this are not used to carry out printing. Once again referring to
In the case of the present embodiment, clear ink of the 1st application step is printed at the same print scans as the color ink. In other words, the 1st clear ink application step is performed during the color ink printing step. Therefore, in the multi-pass printing, portions where clear ink is printed after color ink has been printed and portions where color ink is printed after clear ink has been printed are mixed on the print medium. However, because an amount of the low surface tension clear ink drops sufficient for them to connect to each other and form a layer are printed, at the first application step it is possible to form a smooth layer of clear ink similar to that of the 1st embodiment. Thus, it is possible to output printed matter wherein particular interference colors are not visually perceived upon observation, due to the raised portions of clear ink that are formed by the 2nd application step which is performed after the clear ink layer formed in that way has fixed.
As is the case with the 1st embodiment, the printing apparatus shown in
In the present embodiment in order to establish a 1st clear ink application step and a 2nd clear ink application step, after completing color ink multi-pass printing, the clear ink application step is executed after the print medium is fed back.
When the printing has been completed in accordance with the image data, the system controller 301 rotates the conveyance motor in the reverse direction and feeds the print medium back. Next, at step 233, an 8-pass multi-pass printing of clear ink is performed. Because the clear ink ejection port array uses the mask patterns shown in
In the embodiment explained above, in an 8-pass multi-pass printing only the 7th pass (region 7), that is, only 1 scan (region) was a scan in which clear ink was not printed, however, the present invention is not limited as such. In the case where a longer time is needed for fixation, the clear ink non-printing scan may be made N (N is an integer equal to or greater to 1) scans, of 2 or more consecutive scans, suited to this time. Also, print scans for the 2nd application step are also not limited to 1 scan units. For example, referring again to
Also, the present invention is not limited to the construction performing multi-pass printing. The present invention can be applied to the 1-pass printing. Even if the 1-pass printing, the first application step and the second application step for applying the clear ink may be prepared. Additionally, a fixation time for fixing the clear ink applied in the first application step may be prepared between them. In this case it is not necessary to provide print scans without application of ink. That is, a configuration is also acceptable wherein the print head is made to wait without scanning. In this case, it is necessary to provide amount of non ink application time that is at least as long as, or longer, than the amount of time necessary for the print head to make 1 printing pass. For example, if the time necessary for 1 printing pass is taken to be approximately 3 seconds in the present embodiment, a waiting time of at least 3 seconds or more may be provided. Furthermore, in order to improve throughput, it is preferable not to provide more than an amount of time equivalent to 5 passes; for example, in the present embodiment it would be preferable to provide 15 seconds or less.
It is also possible that the fixation time of the clear ink applied by the first application step is set to a time until a flowability of the clear ink is come down to a extent. In other ward, the fixation time may be a time until the clear ink applied by the first application step is fixed enough that the clear ink applied by the second application step is not mixed with the clear ink applied by the first application step and the surface does not become flat.
Furthermore, in the above embodiments, an example of a serial type ink jet printing apparatus that forms images by alternating print head scans and print medium conveyance operations was explained, however, the present invention is not limited to this configuration. The present invention is characterized in that the printing of clear ink to overcoat the printed matter is split into a 1st application step for forming a clear ink layer and a 2nd application step for forming raised portions on the formed clear ink layer. Therefore the present invention can also be advantageously applied to a so-called full-line type printing apparatus in which the print medium is conveyed at a set speed with respect to a fixed print head having an ejection port array corresponding to the width of the print medium. In the case of a full-line type printing apparatus, for example, after carrying out the 1st application step by a clear ink ejection port array, the print medium may be fed back and a 2nd application step may be executed.
Furthermore, in the above embodiments a clear n amount for forming a sufficiently thick layer is printed, and there is no need to use larger amount of clear ink than necessary. Therefore it is desirable that the clear ink print ratio is adjusted to an appropriate value in accordance with the amount of ink drops ejected from the individual ejection ports (ejection volume), the printing resolution of the printing apparatus and the type of print medium, regardless of whether it is equal to or greater than 50% or lower than 50%.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2010-042704, filed Feb. 26, 2010, which is hereby incorporated by reference herein in its entirety.
Number | Date | Country | Kind |
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2010-042704 | Feb 2010 | JP | national |