Patent Application
20120276293
1. Field of the Invention
The present invention relates to the technique of ink jet recording, and more particularly to an ink jet recording method in which an ink image is overcoated with a clear ink.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2005-081754 discloses a technique of applying a clear ink onto an ink image, which is formed on a recording medium in ink jet recording, to thereby overcoat the surface of the ink image with the clear ink. The overcoating can increase glossiness of the image and resistance against scratching (hereinafter referred to as “scratch resistance”).
The state of the surface of the ink image before the overcoating differs depending on the type of ink used to form the ink image and the recording density of the ink. For example, as the recording density increases, dots of an ink having a small surface tension generally tend to easily immingle with one another, and the ink image after being fused and fixed forms a relatively smooth surface. On the other hand, dots of an ink having a great surface tension generally tend to form a surface having relatively noticeable irregularities because those dots are fused and fixed while keeping the dot shape. Color development irrelevant to the image may occur when overcoating the ink image that is formed by using the former ink tending to form the smooth surface. An interference color is generated through a mechanism described below.
A parallel light 1004 (1004a and 1004b) from the sun or a fluorescent lamp, for example, is separated into a reflected light 1005 that is reflected at the surface of the clear ink layer 1003, and a reflected light 1006 that is reflected at the surface of the ink image layer 1002 after passing through the clear ink layer 1003. Interference occurs between the two separated lights due to a difference in optical path therebetween.
Given, for example, that the incident angle is θ, the wavelength of incident light is λ, and the refractive index of the clear ink layer 1003 is n, the intensity of light having the wavelength λ, which satisfies the relationship expressed by the following formula (1), is increased and an interference color of the relevant light is more strongly visually recognized by an observer:
m×λ=n×2d×cos θ+λ/2 (m: natural number) (1)
The wavelength λ satisfying the formula (1) varies depending on a thickness d of the clear ink layer 1003. Therefore, when the thickness of the clear ink layer 1003 is not uniform, the rainbow-colored reflected light may be recognized by the observer in some cases. Such color development irrelevant to an ink image degrades quality of the ink image.
Thus, the ink image having the smooth surface coated with the clear ink is tinted by the interference light having a particular color and is visually recognized as a color tone that has changed from the original color tone of the ink image.
The interference color generated through the above-described mechanism is more conspicuous in a primary color region with a particular ink. In the primary color region, when dots of the same type of ink are applied to the recording medium in closely adjacent relation, those dots tend to easily immingle with one another because of high affinity and to form a smooth ink layer on the surface of the recording medium.
The present invention has been made in view of the above-described problems with the related art. Embodiments of the present invention provide an ink jet recording method and an ink jet recording apparatus, which can suppress generation of an interference color regardless of the type of ink and the recording density by controlling a surface shape of an ink image before the ink image is overcoated with a clear ink.
According to an aspect of the present invention, a recording method includes applying a color ink to a region on a medium, applying a clear ink to the region, and overcoating the applied color ink and the applied clear ink.
According to another aspect of the present invention, a recording apparatus includes a first applying unit configured to apply a color ink to a region on a medium, a second applying unit configured to apply a clear ink to the region, and an overcoating unit configured to overcoat the applied color ink and the applied clear ink.
According to the embodiments of the present invention, in an output print obtained by overcoating the clear ink on an image, light interference at a clear ink layer can be inhibited regardless of the type of the used ink from causing color development irrelevant to the image.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
As mentioned above, when the thickness d of the clear ink layer satisfies the formula (1) at a wavelength of visible light, an interference color is visually recognized with the light having the relevant wavelength. However, when irregularities formed on the surface of an ink image are fairly noticeable as illustrated in
In consideration of such a mechanism, according to an embodiment of the present invention, irregularities are formed on the surface of the ink image before overcoating, to thereby avoid the interference color from being visually recognized with the intensified interference of only light having a particular wavelength.
The embodiment of the present invention will be described in detail below.
When a recording operation command is input from a host apparatus externally connected, one sheet of recording media stacked in paper feed tray 15 is fed to a position where an image can be recorded on the recording medium by the ink jet head mounted to the carriage 11. The carriage motor 12 serves to drive the ink jet head in the main scanning direction. The image is then formed by alternately repeating the main scanning of the ink jet head while the inks are discharged in accordance with recording signals, and an operation of conveying the recording medium through a predetermined distance, thus scanning the ink jet head over a unit region on the recording medium plural times.
A recovering unit 14 for executing a maintenance process of the ink jet head is provided at the end of an area in which the carriage 11 is movable. The recovering unit 14 includes, for example, caps 141 for protecting discharge port surfaces of the ink jet head when the inks are sucked and when the inks are left in the unused state, a discharge receiver 142 for receiving a coating liquid (clear ink) when it is discharged for recovery, and a discharge receiver 143 for receiving the ink when it is discharged for recovery. Wiper blades 144 wipe the discharge port surfaces of the ink jet head, respectively, while moving in a direction denoted by an arrow.
Components and a purification method of an ink set employed in the embodiment will be described below. In the following description, “part” and “%” are each on the basis of mass unless otherwise specified.
10 Parts of a pigment, 30 parts of an anionic high polymer, and 60 parts of pure water, given below, are mixed with one another.
Pigment: [C.I. Pigment Yellow 74 (product name: Hansa Brilliant Yellow 5GX (made by Clariant))
Anionic high polymer P-1: [styrene/butylacrylate/acrylic acid copolymer (copolymerization ratio (ratio by weight)=30/40/30), acid value 202, weight-average molecular weight 6500, aqueous solution with 10% of solid content, and neutralizer: potassium hydroxide]
Then, the foregoing materials are loaded into a batch-type vertical sand mill (made by IMEX Co., Ltd.) and are subjected to dispersion treatment for 12 hours under water cooling with 150 parts of zirconia beads of 0.3-mm diameter put in the sand mill. A resulting dispersion liquid is further subjected to a centrifugal separator to remove coarse particles. A pigment dispersion liquid 1 having a solid content of about 12.5% and a weight-average particle diameter of 120 nm is obtained as a finally prepared substance. By using the pigment dispersion liquid thus obtained, a yellow ink is prepared as follows.
After sufficiently mixing, dissolving and dispersing the following components with one another under agitation, a resulting mixture is filtrated under pressure by using a micro-filter (made by Fujifilm Corporation) having a pore size of 1.0 μm, whereby a yellow ink 1′ is prepared.
Pigment dispersion liquid 1 obtained above: 40 parts
Glycerin: 9 parts
Ethylene glycol: 6 parts
Acetylene glycol ethylene oxide (EO) adduct (product name: Acetylenol EH): 1 part
1,2-Hexanediol: 3 parts
Polyethylene glycol (molecular weight 1000): 4 parts
Water: 37 parts
An AB-type block polymer having an acid value of 300 and a number-average molecular weight of 2500 is prepared with an ordinary method by using benzyl acrylate and methacrylic acid as materials. The AB-type block polymer is neutralized by an aqueous solution of potassium hydroxide and is diluted with ion-exchange water, whereby a homogeneous aqueous solution containing 50% by mass of the above-mentioned polymer is prepared. Further, 100 g of the polymer solution, 100 g of C.I. Pigment Red 122, and 300 g of ion-exchange water are mixed with one another. A resulting mixture is mechanically agitated for 0.5 hour. Next, the mixture is processed by using a micro-fluidizer and by causing the mixture to pass through an interaction chamber five times under liquid pressure of about 70 MPa. A thus-obtained dispersion liquid is subjected to a centrifugal separation process (at 12,000 rpm for 20 minutes) to remove non-dispersed matters including coarse particles, whereby a magenta dispersion liquid is obtained. The magenta dispersion liquid thus obtained has a pigment concentration of 10% by mass and a dispersant concentration of 5% by mass.
A magenta ink is prepared by using the magenta dispersion liquid obtained above. After adding the following components to the magenta dispersion liquid at a predetermined concentration and sufficiently mixing them with one another under agitation, a resulting mixture is filtrated under pressure by using a micro-filter (made by Fujifilm Corporation) having a pore size of 2.5 μm, whereby the magenta ink having a pigment concentration of 4% by mass and a dispersant concentration of 2% by mass is prepared.
Magenta dispersion liquid obtained above: 40 parts
Glycerin: 10 parts
Diethylene glycol: 10 parts
Acetylene glycol EO adduct: 0.5 part
Ion-exchange water (made by Kawaken Fine Chemicals Co., Ltd.): 39.5 parts
An AB-type block polymer having an acid value of 250 and a number-average molecular weight of 3000 is prepared with an ordinary method by using benzyl acrylate and methacrylic acid as materials. The AB-type block polymer is neutralized by an aqueous solution of potassium hydroxide and is diluted with ion-exchange water, whereby a homogeneous aqueous solution containing 50% by mass of the polymer is prepared. Further, 180 g of the polymer solution, 100 g of C.I. Pigment Blue 15:3, and 220 g of ion-exchange water are mixed with one another. A resulting mixture is mechanically agitated for 0.5 hour. Next, the mixture is processed by using a micro-fluidizer and by causing the mixture to pass through an interaction chamber five times under liquid pressure of about 70 MPa. A thus-obtained dispersion liquid is subjected to a centrifugal separation process (at 12,000 rpm for 20 minutes) to remove non-dispersed matters including coarse particles, whereby a cyan dispersion liquid is obtained. The cyan dispersion liquid thus obtained has a pigment concentration of 10% by mass and a dispersant concentration of 10% by mass.
A cyan ink is prepared by using the cyan dispersion liquid obtained above. After adding the following components to the cyan dispersion liquid at a predetermined concentration and sufficiently mixing them with one another under agitation, a resulting mixture is filtrated under pressure by using a micro-filter (made by Fujifilm Corporation) having a pore size of 2.5 μm, whereby the cyan ink having a pigment concentration of 2% by mass and a dispersant concentration of 2% by mass is prepared.
Cyan dispersion liquid obtained above: 20 parts
Glycerin: 10 parts
Diethylene glycol: 10 parts
Acetylene glycol EO adduct: 0.5 part
Ion-exchange water (made by Kawaken Fine Chemicals Co., Ltd.): 53.5 parts
100 G of the polymer solution used in preparing the yellow ink 1′, 100 g of carbon black, and 300 g of ion-exchange water are mixed with one another. A resulting mixture is mechanically agitated for 0.5 hour. Next, the mixture is processed by using a micro-fluidizer and by causing the mixture to pass through an interaction chamber five times under liquid pressure of about 70 MPa. A thus-obtained dispersion liquid is subjected to a centrifugal separation process (at 12,000 rpm for 20 minutes) to remove non-dispersed matters including coarse particles, whereby a black dispersion liquid is obtained. The black dispersion liquid thus obtained has a pigment concentration of 10% by mass and a dispersant concentration of 6% by mass.
A black ink is prepared by using the black dispersion liquid obtained above. After adding the following components to the black dispersion liquid at a predetermined concentration and sufficiently mixing them with one another under agitation, a resulting mixture is filtrated under pressure by using a micro-filter (made by Fujifilm Corporation) having a pore size of 2.5 μm, whereby the black ink having a pigment concentration of 5% by mass and a dispersant concentration of 3% by mass is prepared.
Black dispersion liquid obtained above: 50 parts
Glycerin: 10 parts
Triethylene glycol: 10 parts
Acetylene glycol EO adduct: 0.5 part
Ion-exchange water (made by Kawaken Fine Chemicals Co., Ltd.): 25.5 parts
A resin aqueous solution is obtained as follows. After adding 15.0% by mass of a resin made up of styrene and acrylic acid, one equivalent weight of potassium hydroxide with respect to carboxylic acid constituting the acrylic acid, and water as the rest for adjustment to 100.0% by mass, they are agitated at 80° C. to dissolve the resin. The resin aqueous solution is then obtained by adjusting the composition with water such that the solid content is 15.0% by mass. The resin has a weight-average molecular weight of 7,000.
A clear ink is prepared by sufficiently mixing the following components with one another under agitation. The obtained clear ink is colorless and clear.
Resin aqueous solution: 26.6 parts
Glycerin: 9 parts
Ethylene glycol: 6 parts
Acetylene glycol EO adduct: 1 part
Multi-valued image data in the RGB format is input from the host computer (image input unit) in accordance with a processing flow illustrated in
On the basis of the binary image data obtained in step 102, an image is divided into a plurality of regions, i.e., plural unit regions, and an index (ratio of haze to gloss) for surface smoothness is obtained in relation to an ink image that is to be formed in each unit region. It is then determined whether the obtained haze-to-gloss ratio is not less than a predetermined threshold (0.35 in the embodiment). (Step 103)
Here, the terms “gloss”, “haze”, and “ratio of haze to gloss” used in this specification are defined as follows.
The “gloss” implies a value of gloss (glossiness), which is measured in conformity with the method stipulated in JIS K 5600-4-7, and it provides an index for the intensity of specular reflected light (i.e., light reflected at a reflection angle of (incident angle+0±0.9°)).
The “haze” implies a value of haze, which is measured in conformity with the method stipulated in ISO DIS 13803, and it provides an index for the intensity of diffuse reflected light (i.e., light reflected at a reflection angle of (incident angle+1.8±0.9°)).
The “ratio of haze to gloss” implies a value calculated by division of haze/gloss. The “ratio of haze to gloss” is also generally called “image clarity”. A smaller “ratio of haze to gloss” is equivalent to “higher image clarity”, and it implies a smoother surface. Conversely, a greater “ratio of haze to gloss” is equivalent to “lower image clarity”, and it implies a rougher surface. Therefore, a “high gloss surface” implies a “surface having a small ratio of haze to gloss”, i.e., a “smooth surface”.
The Micro-Haze Plus made by BYK-Gardner is used to separately measure respective values of the gloss and the haze of various color inks. It is to be noted that a measuring device is not limited to the Micro-Haze Plus insofar as it can measure respective values of the gloss and the haze of various color inks.
“Ratio of haze to gloss”=“value of haze”/“value of gloss” (2)
For a region where the “ratio of haze to gloss” obtained in step 103 is estimated to be less than 0.35, the processing flow advances to step 104 in which an amount of clear ink (CL1) applied to form more irregularities is set. The amount of the applied clear ink (CL1) is set on the basis of a graph, depicted in
For example, in Table 1 given later, the “ratio of haze to gloss” in the primary color region of yellow where the recording density is 100% is 0.24, i.e., less than the predetermined threshold of 0.35. Accordingly, the amount of the clear ink applied in a second step (specified in Claim 1) is determined to be 20% (recording density) from the graph of
On the other hand, for a region where the “ratio of haze to gloss” is estimated to be not less than 0.35, the processing flow advances to step 105 in which an amount of clear ink (CL2) applied for overcoating is set.
The amount of the applied clear ink (CL2) is set as appropriate depending on the purpose of use of an ink image. As the thickness of the clear ink increases, a longer wavelength satisfies the formula (1) and the interference color is generally shifted from light of a shorter wavelength to light of a longer wavelength. If the thickness of the clear ink exceeds about 500 nm, the wavelength satisfying the formula (1) is not present in the visible range. Therefore, the interference color is not visually recognized regardless of a degree of smoothness of the surface of the ink image before the overcoating. Also, if the thickness of the clear ink is smaller than about 100 nm, the wavelength satisfying the formula (1) is not present in the visible range and the interference color is not visually recognized. However, a clear ink layer having a certain thickness is required to obtain a proper gloss, whereas a larger thickness of the clear ink layer increases a cost because of consuming the clear ink in a larger amount. For that reason, in one embodiment, the clear ink layer is formed in the range of 100 nm to 400 nm.
After obtaining the amount of each of all the inks applied to form the image, including the clear ink, for each region in steps 104 and 105, the processing flow advances to step 106 in which discharge data for forming the image is produced.
In the embodiment, as described above, the predetermined threshold is set to 0.35 for the “ratio of haze to gloss” in the ink image before the overcoating. Further, because the above-mentioned problem of the interference color is less apt to occur in a region where an image of a secondary or higher-order color is formed, a control process of forming the irregularities by using the clear ink is performed only in the primary color region in the embodiment.
The reason why the secondary or higher-order color region is less apt to form a smooth surface resides in that, even when ink dots having different compositions are present adjacent to each other, inks are not easily immingled and they keep dot shapes, whereby irregularities remain.
While, in the embodiment, the “ratio of haze to gloss” for each unit region is obtained to perform the control process of applying the clear ink, the “ratio of haze to gloss” may be obtained in terms of the type of ink used and the recording density of the ink.
The “ratio of haze to gloss” is substantially uniquely defined corresponding to the type of ink applied to the region where the control process is performed and the recording density of the applied ink. Therefore, the embodiment can be modified in a manner of previously storing, in a memory of the recording apparatus, a table that specifies the “ratio of haze to gloss” corresponding to the type of ink used and the recording density of the ink.
In the embodiment, multi-pass recording of 8 passes is performed by using the ink jet head illustrated in
In the multi-pass recording, an image is completed step by step by obtaining image data, which can be recorded by the ink jet head in one cycle of main scanning, through thinning in accordance with a mask pattern prepared in advance, and by performing the main scanning plural times.
Reference symbols 57a to 57d denote mask patterns assigned respectively to the zone 1 to the zone 4. Each of the mask patterns 57a to 57d has a region of 4 pixels×4 pixels in which recording permissive pixels are defined as indicated by black and non-recording permissive pixels are defined as indicated by white. The recording permissive pixels are completed in a complementary manner by imposing the mask patterns 57a to 57d one above another. When the recording is actually performed, a logical product (AND) operation is executed between image data (recording/non-recording data) assigned to the individual discharge ports and the mask patterns, and a discharge operation is executed on the basis of the logical AND result. While the mask pattern having the region of 4 pixels×4 pixels is used here for the sake of simplicity, an actual mask pattern has a larger number of regions in each of the main scanning direction and the sub-scanning direction.
Reference symbols 58a to 58d illustrate successive steps through which the image is gradually completed on the recording medium by repeating a recording scan. In each recording scan, the zones 1 to 4 of the discharge port row 56 perform recording only on the pixels for which the recording is permitted by the mask patterns 57a to 57d. Whenever each recording scan is finished, the recording medium is conveyed in the sub-scanning direction through a distance corresponding to the width of each region. In such a manner, the image in the unit region of the recording medium (i.e., in a region of the recording medium corresponding to the width of each zone of the discharge port row) is completed with four recording scans. According to the multi-pass recording described above, the image in each unit region of the recording medium is recorded with plural scans by using the plural zones of the discharge port row. Therefore, variations attributable to the discharge ports (nozzles), variations in accuracy of conveying the recording medium are distributed, whereby density variations and striped unevenness can be reduced.
For the sake of simplicity, the above description is made, for example, in connection with the multi-pass recording of 4 passes by referring to
Of the region 164, in the primary color region of yellow with the recording density of 100% (where the amount of the applied clear ink is 20% from
The recording permission rate set for each region (mask pattern) may be not the same for the clear ink that is applied in the second step. For example, when the amount of the applied clear ink is obtained as 50% (recording density), the recording permission rate is set to 6.25% for each of the mask patterns 90a to 90f, 0% for the mask pattern 90g, and 12.5% for the mask pattern 90h. Image data is not present for the clear ink, and one dot of the clear ink is applied to each of all the pixels. Accordingly, it is to be just satisfied that total dots of the clear ink applied to the unit region, in which the “ratio of haze to gloss” is less than the predetermined threshold described above, are completely discharged in 8 passes so as to provide the amount of the applied clear ink (i.e., the recording density), which is obtained from the graph of
When the multi-pass recording of 8 passes is performed by using the above-described mask patterns, the color inks and the clear ink are applied to the unit region by the discharge port rows 4Y to 4K and 4CL1 in the first to eighth passes, and the clear ink is applied to the unit region by the discharge port row 4CL2 in the ninth to sixteenth passes. Stated another way, in the embodiment, the recording in the first to eighth passes corresponds to the first step and the second step of forming an ink image by using the color inks and the clear ink, and the recording in the ninth to sixteenth passes corresponds to a third step of overcoating the ink image with only the clear ink.
As described above, the clear ink is applied to the ink image in the predetermined region of the color ink layer, which forms a smooth flat surface and provides a small value of the “ratio of haze to gloss”, in the same scanning as where the color inks are applied, thereby providing irregularities on the surface of the ink image. Those irregularities cause a variation in a thickness d of the clear ink layer 1607 deposited on the ink image. As a result, there are lights having various wavelengths satisfying the formula (1), which provide a white light by being added to one another. Hence a particular interference color is not generated.
While the above description has been made in connection with the case where the clear ink is applied onto the color ink layer, the image data is not always present in all the regions, and the color inks do not always form the layer over the entire region. On the recording medium, there are not only a blank region where the color inks are not recorded, but also a low-gradation region where the color inks are slightly recorded.
In experimental studies, gloss photo paper made by CANON KABUSHIKI KAISHA (product name “Gloss Photo Paper [light] LFM-GP421R”) was used as the recording medium. The amount of the applied ink was defined 100% when one dot of 4.5 pl was applied to a region of 1/1200 inch square (hereinafter referred to as “1200 dpi square”). The recording operation was performed by first applying the color inks and then applying the clear ink with the multi-pass recording of 8 passes in a state not causing a deviation in each recording region.
Table 1, given below, indicates the “ratio of haze to gloss” for each color at different values of the recording density. Corresponding to the different values of the recording density for each color, Table 1 also indicates, in a column of “Embodiment”, whether an interference color is visually recognized in a primary color image when an ink image is formed through the second step according to the embodiment. Further, Table 1 indicates, in a column of “Comparative Example”, whether an interference color is visually recognized in a primary color image when an ink image is formed according to the related-art method without including the second step. A mark “×” represents the case where the interference color is visually recognized, and a mark “◯” represents the case where the interference color is not visually recognized.
As seen from the results regarding the comparative example in Table 1, in the primary color image of the black ink, the interference color is not visually recognized at the recording density of 100% and 150%, but it is visually recognized at the recording density of 200%. In the primary color image of the cyan ink, the interference color is visually recognized at all the recording densities tested. In the primary color image of the yellow ink, the interference color is visually recognized at the recording density of 100% and 150%, and it is not visually recognized at the recording density of 200%. In the primary color image of the magenta ink, the interference color is not visually recognized at the recording density of 100%, but it is visually recognized at the recording density of 150% and 200%.
As seen from the results regarding the embodiment in Table 1, the interference color is not visually recognized and original color tones are obtained in all the image regions. This is because irregularities are given, by applying the clear ink, to the ink image region where the “ratio of haze to gloss” is less than 0.35.
Further, in the region where the “ratio of haze to gloss” is not less than 0.35, the ink image is formed without applying the clear ink. Therefore, the ink image not generating the interference color can be formed without consuming the clear ink in amount more than necessary, and a cost reduction is realized.
In the embodiment described above, the threshold for the “ratio of haze to gloss” is set to 0.35 such that the clear ink is applied when the “ratio of haze to gloss” is less than 0.35, and the clear ink is not applied when the “ratio of haze to gloss” is not less than 0.35. However, a proper value of the threshold differs depending on the ink and the recording medium used, and it is optionally selected by a user. In general, the threshold may be set to a value in the range of 0.35 to 0.4.
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. 2011-099695 filed Apr. 27, 2011, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-099695 | Apr 2011 | JP | national |
