JP2003191468A - Image recording method and ink-jet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image recording method and an ink-jet printer capable of imaging with the same image quality and storage property as those of a photograph, and improving the printing speed. <P>SOLUTION: An image is recorded on a recording medium F having an ink absorbing layer on a supporting member and containing a thermoplastic resin in the surface layer by jetting a pigment ink from a line head 11 in a recording part 10. By heating and pressuring latex particles in the recording medium F in a fixing part 50 so as to melt and transparentize the same, image quality with glossiness can be provided, and by taking in the pigment ink in the recording medium F, a long term image quality storage property can be realized. The heating temperature, the pressuring force and the heating time of the fixing part 50 are controlled such that the ink is jetted from the line head 11 by a 6-10 m/s droplet speed and a 2 pl maximum droplet amount, the pixels on the recording medium F are formed by jetting the ink by a 10 ms or less time interval with respect to the adjacent pixels, and the imaging performance ratio of the recording medium F is 60%-95%. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording method and an ink jet printer capable of forming an image having image quality and storability comparable to those of a photograph.

[0002]

2. Description of the Related Art In recent years, image processing technology using an inkjet printer has improved the sharpness and granularity of pixels by reducing the size of ink droplets to be printed, head scanning, and higher accuracy of recording paper conveyance. Efforts are being made to approach image quality. For example, by recording an image with dye ink using resin-coated paper used for photographic printing paper and provided with an ink absorption layer, it has become possible to obtain image quality comparable to silver halide photography. .

However, when an image is recorded with dye ink, the storability of the image, which is an important function of photography, is sometimes deteriorated. Further, when an image is recorded with a pigment ink, the storability of the image is good, but the image quality comparable to that of a silver salt photograph may not be obtained. Image quality is an important performance for photographs that have been traditionally used as a means of expressing images, but the texture of an image cannot be expressed by evaluation scales such as sharpness, graininess, and glossiness. Also, the texture was different from that of the silver salt photograph, and it was different in appearance. Also,
A photograph is also a means of recording an image, and image storability is also an important performance.

Therefore, in order to achieve both high image quality of photographs and storability of images, an image is formed with a pigment ink on a recording paper containing latex as an upper layer of the image receiving layer, and then the image is heated and pressed. There is a printing method to fix the. According to this method, an image close to that of a silver salt photograph was obtained in terms of image storability, sharpness, glossiness, etc., but the color reproducibility and graininess were inferior, and the texture sometimes changed. Further, in the ink jet printer, improvement of printing speed is also an important issue.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention provides an image recording method which has image storability, can obtain image quality comparable to that of a photograph, and can improve printing speed. It is an object to provide an inkjet printer.

[0006]

In order to achieve the above object, an image recording method according to the present invention has a recording medium having an ink absorbing layer on a support and a thermoplastic resin on the surface layer so that the amount of droplets is small. Pigment ink of 2 pl at maximum, droplet speed 6-10m
10m to each adjacent pixel while jetting at / s
Image recording is performed by heating and pressurizing the recording medium so that the image clarity value of the image formed on the recording medium is 60% or more and 95% or less. Characterize.

According to this image recording method, since the recording medium containing the thermoplastic resin in the surface layer is used, it is possible to improve the image clarity value by heating and pressurizing after ejecting the ink. Although the image clarity value of the surface of the recording medium on which the image is formed with the pigment ink is likely to decrease, the thermoplastic resin is melted by heating and pressing to cover the surface of the recording medium, so that the image clarity value is improved.

Further, when the drop velocity of the ink is 6 m / s or less, the time from ejection to landing becomes long, and the fluctuation of the drop velocity causes a large change in the landing position of the drop, which deteriorates the image quality. When the ink drop velocity is 10 m / s or more, the ink is scattered on the surface of the recording medium and the image quality is deteriorated. From the above, the ink drop velocity is 6 to 10 m / s.
By so doing, the color reproduction range is widened and an image with good image quality can be formed.

In addition, the maximum droplet amount of the ejected ink is 2
When it is pl, the graininess is improved and the image quality can be improved. Further, even if the landed ink droplets coalesce and the pigments agglomerate and appear as if they were printed with large droplets, if the ink droplet volume is 2 pl or less, there is no visual effect and the image quality is reduced. A good image can be formed.

Further, when each pixel is formed, the ink is landed on the recording medium so that the time interval of the ink landing on the adjacent pixel is 10 ms at maximum, and the image is formed, thereby improving the printing speed. You can In addition,
Even if the ink of adjacent pixels lands and the pigment agglomerates before the ink is absorbed by the recording medium, the maximum amount of droplets is 2 pl as described above, so there is no adverse effect on image quality.

By heating and pressurizing the recording medium so that the image clarity value becomes 60% to 95%, the glossiness of the image quality is similar to that of a photograph, and a photograph-like texture can be obtained. The image clarity value is, for example, the constitution of the recording medium, the type and content of the thermoplastic resin particles, the heating temperature, the pressurizing pressure, the heating and pressurizing time, the heating and pressurizing method, and the surface which comes into contact with the medium at the time of heating and pressurizing. Can be controlled by the smoothness of

Further, since each pixel is formed with a shift of about half the pixel pitch (about half a pixel) for each line, the ink landing interval of each pixel for each line becomes wider than that of a conventional image. As a result, the number of adjacent pixels on the recording medium is reduced, the ink droplets coalesce, the pigment agglomerates and the granularity is reduced, and the image quality can be improved. Further, the coverage of the recording medium with the ink droplets is improved, and the color reproduction area is widened.

The pigment ink used as the ink is
Compared with dye ink, it is possible to realize long-term image quality preservability of a photographic level without fading due to light or oxygen in a recording medium after image recording. In addition, the pigment ink has a larger diameter than the dye ink and is hard to be absorbed in the recording medium, so that it may not be possible to stably obtain a high image quality comparable to that of a silver salt photograph. By applying pressure, the thermoplastic resin particle layer is melted and becomes transparent, so that a glossy high-quality image can be formed. Further, the pigment ink is covered with the thermoplastic resin particles by the melting of the thermoplastic resin particle layer and is easily absorbed by the recording medium, so that an image having high storability can be formed.

It is preferable that the surface layer of the recording medium further contains an inorganic pigment.

Further, the ink jet printer according to the present invention comprises an ink head for ejecting ink onto the recording medium, and a heating and pressurizing means for heating and pressurizing the recording medium after the ink is ejected. An inkjet printer for recording an image on a recording medium having an ink absorption layer on a support and a thermoplastic resin on the surface layer, wherein each pixel is formed at a time interval of 10 ms or less with respect to an adjacent pixel. Pigment ink having a droplet amount of 2 pl or less is ejected from the ink head at a droplet velocity of 6 to 10 m / s, and the image clarity value of an image formed on the recording medium is 60% or more 95
The heating and pressurizing means heats and pressurizes the recording medium so as to be not more than%.

According to this ink jet printer, the image recording method according to the present invention can be executed. In this case, the ink head is preferably composed of a line head. Further, it is preferable that the heating / pressurizing unit is configured to control at least one of a heating temperature, a pressing force, and a heating / pressurizing time when the recording medium is heated and pressed.
Further, it is preferable that the surface layer of the recording medium further contains an inorganic pigment.

The image clarity is an important factor that determines the aesthetic factor of an image as an index of how sharply an object is projected on the surface of a coating film and without distortion. It is a characteristic value. As a method for measuring the image clarity value, for example, there is a method defined in JIS H8686, in which an optical device is used, and the image clarity is obtained as the image clarity from the waveform of the light quantity obtained through the optical comb. There are various types of optical combs having a dark / light ratio of 1: 1 and widths of 0.125, 0.5, 1.0 and 2.0 mm. For the measurement, the optical comb is moved, the maximum waveform (M) and the minimum waveform (m) on the recording paper are read, and the image definition is obtained by the following formula.

C = (M−m) / (M + m) × 100 where C is the image definition (%), M is the highest waveform, and m is the lowest waveform.

The image sharpness C is an index showing that the larger the value, the better the image clarity, and the smaller the value, the "blur" or "distortion". If the "blur" or "distortion" of this image is small, Even if the gloss values on the gloss meter are the same, the glossiness by appearance becomes strong.

The ink head of the above-mentioned ink jet printer may be of the on-demand type or the continuous type. Further, as a discharge (injection) method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electric-heat conversion method ( Specific examples include a thermal inkjet type, a bubble jet (registered trademark) type, an electrostatic suction type (for example, an electric field control type, a slit jet type, etc.), and a discharge type (for example, a spark jet type). However, any ejection method may be used.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 is a conceptual diagram of an inkjet printer according to an embodiment of the present invention, FIG. 2 is a perspective view schematically showing the ink head of FIG. 1, and FIG. 3 is a partial view of a nozzle of the line head of FIG. (A), a front view (b), (c) for explaining the operation of the electrodes of the nozzle, and a front view (d) for explaining the driving states of the nozzle for jetting and non-jetting. (E),
FIG. 4F is a diagram showing drive waveforms of the nozzles of FIG.

As shown in FIG. 1, the ink jet printer of the present embodiment has a roll body 9 in which a long sheet-shaped recording medium F is wound in a roll shape, and is pulled out from the roll body 9 in a transport direction S. A recording unit 10 having a line head 11 that ejects YMCK four color inks onto the recording medium F to write an image, and a platen 12 that is arranged so as to face the line head 11 via the recording medium F, and an image is recorded. A cutting unit 40 that cuts the written recording medium F into a predetermined size, a fixing unit 50 that fixes the image by heating and pressing the cut recording medium F, and a recording medium F on which the image is fixed are provided. A discharge storage unit 60 for discharging and storing,
Are arranged from the upstream side in the transport direction S.

An accumulation unit 18 is provided between the recording unit 10 and the cutting unit 40 so as to adjust the cutting timing in the cutting unit 40, and the recording medium F is conveyed upstream and downstream of the accumulation unit 18. A pair of conveying rollers 15a and 15b for arranging the conveying rollers are arranged. The accumulation unit 18 has a sensor 1 for detecting the accumulation amount of the recording medium F.
9 is provided. Further, the pair of transport rollers 16 a and 16 b for transporting the cut recording medium F is provided in the fixing unit 50.
Are arranged on the upstream side and the downstream side.

The cutting unit 40 moves the recording medium F at a predetermined position in a direction B indicated by an arrow in order to detect the leading end of the conveyed recording medium F and a detection sensor 41 arranged upstream thereof. And a cutting member 42 that cuts to the size. The cutting member 42 is driven in the direction B and the opposite direction by the cutting portion drive mechanism 25 (FIG. 6).

Next, the line head 11 of FIG. 1 will be described. As shown in FIGS. 1 and 2, the line head 11
Are arranged so that the nozzle surface 61 faces the recording medium F, and the nozzle surface 61 of FIG. 2 extends in a direction orthogonal to the transport direction S of the recording medium F of FIG.

On the nozzle surface 61 of the line head 11 shown in FIG. 2, a large number of nozzles 1a for respectively ejecting ink extend in a line to form a nozzle line 62. A large number of nozzles 1a of the nozzle row 62 are composed of piezo elements that are shear-deformed by the application of a drive signal, and are shear-deformed according to the voltage level of the input drive signal to eject ink onto the recording medium. Images can be written. The recording unit 10 is provided with the line head 11 of FIG. 2 for each color of YMCK, each line head 11 is independently driven, and each pigment ink is ejected from each line head 11 from a total of four nozzle rows to the recording medium F. By ejecting the ink onto the recording medium F, a color image can be formed.

The structure of a large number of nozzles 1a formed on the nozzle surface 61 of the line head 11 of FIG. 2 will be described with reference to FIG. As shown in FIG. 3 (a), the nozzles 1a are arranged in the vertical direction of the drawing, and the piezoelectric elements 31, 32 and 33,
Is formed on the nozzle surface 61 so as to form a pressure chamber by being surrounded by. The piezo element 31 is shown in FIG.
Like the pair of electrodes 31 provided on both wall surfaces of the pressure chamber.
a and 31b, and the other piezoelectric elements 32 to 34 also have the same electrodes. When the drive voltage of the drive signal as shown in FIG. 4 is applied to the electrodes 31a and 31b from the head drive circuit 23, the piezo element 31 is changed from the undeformed state of FIG. 3B to that of FIG. 3C, for example. Shear deformation. The mode of this shear deformation changes depending on the positive / negative polarities applied to the electrodes 31a and 31b, and the degree of deformation also changes depending on the voltage level.

Piezo elements 31 to 34 in the nozzle 1a
When the positive drive voltage V1 of FIG. 4 is applied to each electrode, the pressure chamber as a whole expands from the undeformed state of FIG. 3 (f) where the drive signal is zero, as shown by the solid line in FIG. 3 (d). Then, when the negative drive voltage V2 of each electrode is applied, the shear deformation is performed as a whole as shown by the solid line in FIG. 3 (e). Ink is sucked from an ink tank (not shown) by expanding the pressure chamber as a whole as shown in FIG. 3D, and ink is drawn from the pressure chamber by contracting the pressure chamber as a whole as shown in FIG. 3E. Can be ejected, and ink can be ejected continuously by repeating such an operation.

When a positive drive voltage V1 'smaller than the drive voltage V1 is applied as shown in FIG. 4, the expansion amount of the pressure chamber is smaller than that at the drive voltage V1 as shown by the broken line in FIG. 3 (d). Similarly, when a negative drive voltage V2 ′ whose absolute value is smaller than the drive voltage V2 is added, the contraction amount of the pressure chamber becomes smaller than that at the drive voltage V2 as indicated by the broken line in FIG. 3 (e). . Therefore, the droplet amount of ink ejected from the nozzle 1a changes depending on the ratio (V1 / V2) of the positive drive voltage V1 and the negative drive voltage V2 in FIG.
And the absolute value of the negative drive voltage V2 (V1 + | V2 |)
Since the droplet amount of the ink and the droplet velocity of the ink ejected from the nozzle 1a change, the droplet amount and the droplet velocity of the ink ejected from each nozzle 1a can be adjusted by controlling them appropriately. In addition, when the adjustment range of the ink droplet amount is increased, it can be dealt with by changing the nozzle diameter.

Next, the fixing section 50 of FIG. 1 will be described with reference to FIGS. 1 and 5. FIG. 5 is a front view showing the fixing unit of FIG. 1 in detail. The fixing unit 50 in FIGS. 1 and 5 includes a heating roller 51 that heats the recording medium F, a pressure roller 52 that can press the recording medium F between the heating roller 51, and a surface of the heating roller 51. And a temperature sensor 55 arranged in the vicinity.

The heating roller 51 has a heating element 53 such as a halogen lamp heater, which is a heat source, built-in along the axial direction in a hollow roller, and the controller 20 (based on the temperature detected by the temperature sensor 55). By controlling the heat generation amount of the heating element 53 in FIG. 6), the temperature of the heating roller 51 can be adjusted so as to be maintained within a predetermined temperature range, and the heating temperature of the recording medium F can be adjusted appropriately.

Further, the heating roller 51 has a gear (not shown) provided at the end thereof in the fixing portion drive mechanism 26 (FIG. 6).
The driving force of the drive motor is transmitted by meshing with the gear of the drive motor included in, and is rotationally driven in the rotation direction R.
Further, the heating roller 51 is preferably formed of a material having high thermal conductivity, whereby the recording medium F can be efficiently heated by the heat from the heating element 53, and for example, a metal roller is preferable. It is preferable that the surface of the heating roller 51 has a fluororesin layer, which can prevent ink contamination when the recording medium F is heated and pressed.

The pressure roller 52 is composed of a metal roller such as stainless steel having a rubber coating layer 52c having elasticity on the outer circumference, and roller shafts 52b at both ends thereof are rotatably attached to the support member 58 via bearings 52a. Supported. The supporting member 58 is urged by the pressing members 52 and 57 such as coil springs so that the pressure roller 52 presses the recording medium F against the heating roller 51 with a predetermined pressure to form the nip portion 59. It is biased upward with a substantially constant biasing force. The pressure sensor 27 is arranged so as to come into contact with the upper surface of the support member 58 in the figure, and the pressure sensor 27 measures the pressure applied to the recording medium F between the heating roller 51 and the pressure bonding roller 52.

The longitudinal elastic modulus (Young's modulus) of the rubber coating layer 52c of the pressure roller 52 is preferably in the range of 10 ⁶ to 10 ⁷ Pa, more preferably 1.0 × 10 ^{6 to} 4.0 × 10 ⁶ Pa. . Thereby, the heating roller 51 and the pressure roller 5
The pressure applied to the recording medium F between the recording medium F and the recording medium F is controlled within a predetermined range as described below, so that the width of the nip portion 59 causes the heating roller 51 and the pressure roller 52 to make a large contact with the recording medium F. The size can be set to an appropriate size that allows pressure contact in the area, and the pressing force and the pressing time can be obtained with a simple configuration.

The rubber coating layer 52c of the pressure roller 52
Instead, the outer circumference of the heating roller 51 may be covered with heat-resistant silicone rubber or the like so as to have a longitudinal elastic modulus within the above range.
Both of the two may have a longitudinal elastic modulus in the above range.

Further, the fixing member drive mechanism 2 is arranged so that the support member 58 of the pressure roller 52 pressurizes the heating roller 51 in the direction A shown in FIG. 5 and releases the pressure in the opposite direction A '.
6 (FIG. 6). The pressing force of the pressure roller 52 in the direction of arrow A is applied to the urging member 5.
The pressure applied to the recording medium F between the heating roller 51 and the pressure bonding roller 52 is obtained by applying a substantially constant urging force of the pressure sensors 6 and 57. However, the control unit 20 calculates the pressure based on the measurement result of the pressure sensor 27. The pressure applied to the recording medium F can be adjusted by controlling the pressure applied to the pressure roller 52 in the directions of arrows A and A ′ via the fixing unit drive mechanism 26. In this case, the pressure applied to the recording medium F is 9.8 × 10 ^{4 to} 4.9 × 1.
The range of 0 ⁶ Pa is preferable. As a result, it is possible to obtain a pressing force necessary and sufficient to make the ink receiving layer of the recording medium F, which will be described later, excellently transparent.

The control unit 20 controls the number of rotations of the heating roller 51 and the number of conveyance rollers 16a and 16b.
By controlling the moving speed of the recording medium F in the transport direction S, the heating and pressurizing time of the recording medium F in the fixing unit 50 can be appropriately adjusted.

Next, the control system of the ink jet printer of FIG. 1 will be described with reference to FIG. FIG. 6 is a block diagram showing a control system of the inkjet printer of FIG.
As shown in FIG. 6, the inkjet printer of FIG.
As its control system, a control unit 2 for controlling the entire device
0, an image memory 21 that stores image data signals input from an external device such as a personal computer, an operation panel 22 that allows the user to input various control information, and a drive signal to the line head 11. And a cut portion drive mechanism 25 for driving the cut portion 40, and a fixing portion drive mechanism 26 for driving the fixing portion 50.

The controller 20 controls each nozzle array 6 of the line head 11 based on the image data signal from the image memory 21.
The head drive circuit 23 is caused to generate a drive signal for driving the line head 11 so as to eject ink from each of the nozzles 2 to 6d, and the application timing of the drive signal from the head drive circuit 23 to each nozzle is controlled. .

The control unit 20 also controls the cutting unit drive mechanism 2 based on the position information of the recording medium F from the detection sensor 41.
5, the movement of the cutting member 42 is controlled, and the temperature sensor 55
The temperature of the heating roller 51 is controlled by adjusting the amount of heat generated by the heating element 53 on the basis of the temperature information from the temperature information, and the rotation of the heating roller 51, etc. by the fixing unit drive mechanism 26 and the movement in the directions A and A '. By controlling, the heating temperature, the pressure, and the heating / pressurizing time to the recording medium F can be adjusted.

Next, the recording medium F will be described. Figure 7
FIG. 3 is a sectional view schematically showing a sectional configuration of a recording medium F.
As shown in FIG. 7, the recording medium F includes a support 71 and a surface layer 73 containing thermoplastic resin particles (latex particles).
And a surface layer 73 having a void layer in which the ink solvent component is absorbed after the coloring material and the ink solvent component are separated on the surface of the surface layer 73.
And an ink absorption layer 72 formed between the support 71 and
And used as an inkjet recording sheet.

Further, the ink absorption capacity of the recording medium F
Is 22-60 ml / m^TwoAnd preferably 25 to 6
0 ml / m^TwoAnd more preferably 25-35 ml
/ M ^TwoIs.

Here, the above-mentioned ink absorption capacity can be obtained as follows. That is, a recording medium having a constant area is conditioned under an atmosphere of 25 ° C. and 50% RH for 24 hours or more, and then the recording medium is immersed in pure water for 10 seconds. At this time, as the water is absorbed, the air in the voids of the recording medium adheres to the surface as bubbles to prevent water absorption. Therefore, the recording medium is appropriately vibrated to remove the bubbles. After 10 seconds, the recording medium is pulled out of water, the water content on the surface is quickly removed with a water absorbing material such as filter paper, and then the ink absorption amount can be determined from the change in mass before and after the immersion.

Next, the ink absorbing layer 72 of the recording medium F will be described. Generally, the ink absorbing layer is roughly classified into a swelling type and a void type. As the swelling type, a water-soluble binder is used, and for example, gelatin, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide or the like is applied alone or in combination, and this is used as an ink absorbing layer.

As the void type, fine particles and a water-soluble binder are mixed and applied, and those having a gloss are particularly preferable. As fine particles, alumina or silica is preferable, and silica having a particle diameter of 0.1 μm or less is particularly preferable. As the water-soluble binder, gelatin, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide and the like are preferably used alone or in combination.

Of the two types described above, a faster ink absorption speed on the recording medium is more suitable for continuous high-speed printing. From this point, the void type is particularly preferably used in the present embodiment. You can

The void type ink absorbing layer will be described in more detail below. The void layer is mainly formed by soft aggregation of the hydrophilic binder and the inorganic fine particles. Conventionally, various methods for forming voids in a film are known,
For example, a method in which a uniform coating solution containing two or more kinds of polymers is applied on a support, and these polymers are phase-separated from each other in a drying process to form voids, solid fine particles and a hydrophilic or hydrophobic resin are used. After coating the coating liquid containing it on a support and drying it, the ink jet recording paper is immersed in water or a liquid containing an appropriate organic solvent to dissolve solid fine particles to form voids, and foaming is performed during film formation. After applying a coating solution containing a compound having properties, a method of foaming this compound in the drying process to form voids in the film, and a coating solution containing porous solid fine particles and a hydrophilic binder is applied on a support. Then, a method of forming voids in the porous fine particles or between the fine particles, and containing solid fine particles and / or fine particle oil droplets and a hydrophilic binder having a volume substantially equal to or more than that of the hydrophilic binder. Coating a coating solution on a support, and a method of forming an air gap between the solid particles are known. In the present embodiment, it is particularly preferable that the void layer is formed by containing various inorganic solid fine particles having an average particle diameter of 100 nm or less.

Examples of the inorganic fine particles used for the above purpose include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide. , Zinc sulfide, zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudo-boehmite, aluminum hydroxide, lithopone, zeolite, hydroxylation Examples thereof include white inorganic pigments such as magnesium.

The average particle size of the inorganic fine particles is a simple average value obtained by observing the particles themselves or particles appearing on the cross section or surface of the void layer with an electron microscope and measuring the particle size of 1,000 arbitrary particles. It is calculated as (number average). Here, the particle size of each particle is represented by the diameter assuming a circle equal to the projected area.

As the inorganic fine particles, solid fine particles selected from silica and alumina or alumina hydrate are preferably used.

As silica which can be used in the present embodiment, silica synthesized by an ordinary wet method, colloidal silica, silica synthesized by a vapor phase method, or the like is preferably used, and particularly in the present embodiment. As the fine particle silica used preferably, colloidal silica or fine particle silica synthesized by a vapor phase method is preferable, and among them, fine particle silica synthesized by a vapor phase method not only obtains a high porosity but also fixes a dye. Coarse aggregates are less likely to be formed when added to the cationic polymer used for the purpose, which is preferable. Further, the alumina or the alumina hydrate may be crystalline or amorphous,
In addition, irregular-shaped particles, spherical particles, needle-shaped particles, or any other shape can be used.

The inorganic fine particles are preferably in a state in which the fine particle dispersion liquid before mixing with the cationic polymer is dispersed up to the primary particles.

The particle size of the inorganic fine particles is preferably 100 nm or less. For example, in the case of the gas phase method fine particle silica, the average particle diameter of the primary particles of the inorganic fine particles dispersed in the state of primary particles (particle diameter in the dispersion state before coating) is
It is preferably 100 nm or less, more preferably 4 to
50 nm, most preferably 4 to 20 nm.

As the most preferably used silica synthesized by the vapor phase method having an average primary particle size of 4 to 20 nm, for example, Aerosil manufactured by Nippon Aerosil Co., Ltd. is commercially available. The fine particles of the vapor phase method silica can be relatively easily dispersed even in water by suction with a jet stream inductor mixer manufactured by Mitamura Riken Kogyo Co., Ltd.

The ink absorbing layer preferably contains a water-soluble binder. Examples of the water-soluble binder include polyvinyl alcohol, gelatin, polyethylene oxide, polyvinylpyrrolidone, polyacrylic acid, polyacrylamide, polyurethane, Dextran, dextrin, color genin (κ, ι, λ, etc.),
Examples include agar, pullulan, water-soluble polyvinyl butyral, hydroxyethyl cellulose, carboxymethyl cellulose and the like. It is also possible to use two or more of these water-soluble binders in combination.

The water-soluble binder preferably used in this embodiment is polyvinyl alcohol. The polyvinyl alcohol includes not only ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, but also modified polyvinyl alcohol such as cation-modified polyvinyl alcohol at the terminal and anion-modified polyvinyl alcohol having an anionic group.

The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 1,000 or more, and particularly preferably an average degree of polymerization of 1,500 to.
Those of 5,000 are preferably used. Further, the saponification degree is preferably 70 to 100%, and 80 to 99.
5% is particularly preferable.

As the cation-modified polyvinyl alcohol, for example, primary to tertiary amino groups or quaternary ammonium groups as described in JP-A-61-10483 can be used as the main chain or side chain of the polyvinyl alcohol. The polyvinyl alcohol contained therein is obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.

Examples of the ethylenically unsaturated monomer having a cationic group include trimethyl- (2-acrylamido-2,2-dimethylethyl) ammonium chloride and trimethyl- (3-acrylamido-3,3-dimethylpropyl). ) Ammonium chloride, N-vinylimidazole, N-vinyl-2-methylimidazole, N
-(3-dimethylaminopropyl) methacrylamide,
Hydroxylethyltrimethylammonium chloride, trimethyl- (2-methacrylamidopropyl) ammonium chloride, N- (1,1-dimethyl-3-)
Examples include dimethylaminopropyl) acrylamide.

The proportion of the cation-modified group-containing monomer in the cation-modified polyvinyl alcohol is 0.1 to 10 mol%, preferably 0.2 to 5 mol%, based on vinyl acetate.

The anion-modified polyvinyl alcohol is described in, for example, polyvinyl alcohol having an anionic group as described in JP-A-1-206088 and JP-A-61-237681 and 63-307979. Such a copolymer of vinyl alcohol and a vinyl compound having a water-soluble group, and JP-A-7-285.
The modified polyvinyl alcohol which has a water-soluble group as described in No. 265 is mentioned.

As the nonion-modified polyvinyl alcohol, for example, a polyvinyl alcohol derivative obtained by adding a polyalkylene oxide group to a part of vinyl alcohol as described in JP-A-7-9758, JP-A-8-25795. And a block copolymer of a vinyl compound having a hydrophobic group and vinyl alcohol as described in 1. Polyvinyl alcohol can be used in combination of two or more kinds such as different degree of polymerization and modification.

The amount of the inorganic fine particles used in the ink absorbing layer depends on the required ink absorbing capacity, the porosity of the void layer,
Generally depends on the type of inorganic pigment and the type of water-soluble binder, but generally 5 to 30 per 1 m ^{2 of} recording paper.
g, preferably 10 to 25 g.

The ratio of the inorganic fine particles used in the ink absorbing layer to the water-soluble binder is usually 2: 1 to 2 in terms of mass ratio.
It is preferably 0: 1, and particularly preferably 3: 1 to 10: 1.

Further, a cationic water-soluble polymer having a quaternary ammonium salt group in the molecule may be contained, and usually 0.1 to 10 per 1 m ^{2 of} ink jet recording paper.
g, preferably in the range of 0.2-5 g.

In the void layer, the total amount of voids (void volume)
Is preferably 20 ml or more per 1 m ² of recording paper. When the void volume is less than 20 ml / m ² , the ink absorbability is good when the ink amount during printing is small, but when the ink amount is large, the ink is not completely absorbed, and the image quality is deteriorated. Problems such as delayed drying tend to occur.

In the void layer having an ink holding ability, the void volume with respect to the solid content volume is called the porosity. In the present embodiment, it is preferable that the porosity is 50% or more because the voids can be efficiently formed without unnecessarily increasing the film thickness.

As another type of void type, a polyurethane resin emulsion, a water-soluble epoxy compound and /
Or in combination with acetoacetylated polyvinyl alcohol,
Further, the ink absorbing layer may be formed by using a coating liquid in which epichlorohydrin polyamide resin is used in combination. The polyurethane resin emulsion in this case is preferably a polyurethane resin emulsion having a polycarbonate chain, a polycarbonate chain and a polyester chain and having a particle diameter of 3.0 μm, and the polyurethane resin of the polyurethane resin emulsion is a polycarbonate polyol, a polyol having a polycarbonate polyol and a polyester polyol. Polyurethane resin obtained by reacting with an aliphatic isocyanate compound has a sulfonic acid group in the molecule, and further has an epichlorohydrin polyamide resin and a water-soluble epoxy compound and / or acetoacetylated vinyl alcohol. preferable. It is presumed that in the ink absorbing layer using the polyurethane resin, weak cations and anions are formed, and along with this, voids having an ink dissolving and absorbing ability are formed, so that an image can be formed.

In the present embodiment, it is preferable to use a curing agent. The curing agent can be added at any time during the production of the ink jet recording medium, and for example, it may be added to the coating liquid for forming the ink absorbing layer, but after the ink absorbing layer is formed, the above water-soluble binder is cured. It is preferable to supply the agent.

In the present embodiment, the method of supplying the curing agent for the water-soluble binder after the formation of the ink absorbing layer may be used alone, but preferably the above-mentioned curing agent is applied for forming the ink absorbing layer. It is to be used in combination with the method of adding to the liquid.

The curing agent that can be used in the present embodiment is not particularly limited as long as it causes a curing reaction with a water-soluble binder, but boric acid and salts thereof are preferable, but other known agents are also usable. Can be used, generally is a compound having a group capable of reacting with the water-soluble binder or a compound that promotes the reaction between different groups of the water-soluble binder, and is appropriately selected according to the type of the water-soluble binder. Used. Specific examples of the curing agent include, for example,
Epoxy curing agent (diglycidyl ethyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidyl cyclohexane, N, N-diglycidyl-4-glycidyloxyaniline, sorbitol polyglycidyl ether , Glycerol polyglycidyl ether, etc.), aldehyde curing agents (formaldehyde, glyoxal, etc.), active halogen curing agents (2,4-dichloro-4-)
Hydroxy-1,3,5, -s-triazine etc.), active vinyl compounds (1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonylmethyl ether etc.), aluminum alum and the like.

The boric acid or a salt thereof means an oxyacid having a boron atom as a central atom and a salt thereof, and specifically, orthoboric acid, diboric acid, metaboric acid, tetraboric acid,
Pentaboric acid and octaboric acid and their salts are mentioned.

The boric acid having a boron atom and its salt as a curing agent may be used as a single aqueous solution or as a mixture of two or more kinds. Particularly preferred is a mixed aqueous solution of boric acid and borax.

The aqueous solutions of boric acid and borax can be added only in relatively dilute aqueous solutions, but by mixing them, a concentrated aqueous solution can be obtained and the coating solution can be concentrated. . Further, there is an advantage that the pH of the aqueous solution to be added can be controlled relatively freely.

The total amount of the curing agent used is preferably 1 to 600 mg per 1 g of the water-soluble binder. In addition, the supply amount is 100 to 6 per 1 g of the water-soluble binder.
00 mg is preferred.

The surface layer 73 of the recording medium F according to the present embodiment contains a thermoplastic resin, and preferably contains an inorganic pigment together with the thermoplastic resin.

The surface layer in the present embodiment is not limited to the outermost surface layer, and is not particularly limited as long as it has a structure in which the effects of the present embodiment are exhibited. The recording medium of the present embodiment, after image recording, for example, by melting the thermoplastic resin contained in the surface layer by heating, to form a film,
Many of the effects of this embodiment are exhibited. For example, if a pigment ink is printed and image quality is improved with or without heat treatment after image recording, for example, glossiness is improved, abrasion resistance is improved, or the degree of bronzing is improved, a thermoplastic resin, or Even if the layer containing the inorganic pigment and the thermoplastic resin is not the outermost layer, the structure thereof corresponds to this embodiment.

Preferred constitutional examples for clearly indicating the surface layer in the present embodiment are listed below, but the layer constitution of the recording medium according to the present invention is not limited to these. 1: A structure in which a void-type ink absorbing layer 72 is provided on a support 71, and a layer 73 containing a thermoplastic resin or an inorganic pigment and a thermoplastic resin thereon is the outermost layer. 2: A layer-type ink absorbing layer 72 was formed on a support 71, and a thermoplastic resin, or an inorganic pigment and a thermoplastic resin was contained on the layer 73, for the purpose of improving surface properties. Structure with a thin layer. 3: A layer-type ink absorption layer 72 is provided on a support 71, and a thermoplastic resin, or an inorganic pigment and a thermoplastic resin is included on the layer 73, for the purpose of cutting harmful light. A structure provided with a thin layer having an ultraviolet absorbing function. 4: A layer containing a matting agent was provided on a layer 73 having a void-type ink absorbing layer 72 on a support 71, on which a thermoplastic resin or an inorganic pigment and a thermoplastic resin was contained. Constitution. 5: A structure in which a void-type ink absorbing layer 72 is provided on a support 71, and a peelable layer is provided on a layer 73 containing a thermoplastic resin or an inorganic pigment and a thermoplastic resin on the void type ink absorbing layer 72. .

The most preferable constitution among the constitution examples described above is the case where the layer containing the inorganic pigment and the thermoplastic resin is the outermost layer. The surface layer containing the thermoplastic resin or the inorganic pigment and the thermoplastic resin may contain the inorganic pigment, the thermoplastic resin and, if necessary, the binder component.

The inorganic pigment can be selected from the inorganic fine particles that can be used in the above-mentioned void layer. For example, light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous Examples thereof include earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudo-boehmite, aluminum hydroxide, lithopone, zeolite, and white inorganic pigments such as magnesium hydroxide.

As the preferred inorganic pigment, solid fine particles selected from silica and alumina or alumina hydrate are preferably used, and silica is more preferred.

As the silica, silica synthesized by a usual wet method, colloidal silica, silica synthesized by a vapor phase method or the like is preferably used, and particularly preferably used fine particle silica is colloidal silica or a vapor phase method. The fine particle silica synthesized in 1. is preferable. Among them, the fine particle silica synthesized by the gas phase method not only provides a high porosity, but also a coarse aggregate when added to the cationic polymer used for the purpose of immobilizing the dye. Are less likely to be formed, which is preferable. Further, the alumina or alumina hydrate may be crystalline or amorphous, and those having any shape such as amorphous particles, spherical particles and acicular particles can be used.

The inorganic pigment is preferably in a state in which the fine particle dispersion liquid before mixing with the cationic polymer is dispersed to the primary particles. The particle size of the inorganic pigment is 100n.
It is preferably m or less. For example, in the case of gas phase method fine particle silica, the average particle diameter of the primary particles of the inorganic pigment dispersed in the state of primary particles (particle diameter in the dispersion liquid state before coating) is
It is preferably 100 nm or less, more preferably 4 to
50 nm, most preferably 4 to 20 nm.

Examples of the thermoplastic resin which can be used in the present embodiment include polycarbonate, polyacrylonitrile, polystyrene, polyacrylic acid, polymethacrylic acid, polyvinyl chloride, polyvinylidene chloride,
Examples thereof include polyvinyl acetate, polyester, polyamide, polyether, copolymers thereof and salts thereof.
Among them, styrene-acrylic acid ester copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-acrylic acid ester copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, SBR latex preferable. In addition, the thermoplastic resin may be used by mixing a plurality of polymers having different monomer compositions, particle sizes, and degrees of polymerization.

In selecting the thermoplastic resin, consideration should be given to the ink receptivity of the recording medium, the glossiness of the image after fixing by heating and pressure, the image fastness and the releasability.

Regarding the ink receptivity, when the particle size of the thermoplastic resin is less than 0.05 μm, the separation of the pigment particles and the ink solvent in the pigment ink becomes slow, and the ink absorption speed is lowered. On the other hand, if it exceeds 10 μm, it is not preferable from the viewpoint of film strength and gloss deterioration of the inkjet recording medium after coating and drying. For this reason, the preferable thermoplastic resin diameter is preferably 0.05 to 10 μm,
More preferably, it is 0.1 to 5 μm. More preferably, it is 0.1 to 1 μm.

The glass transition point (Tg) can be mentioned as a criterion for selecting the thermoplastic resin. When Tg is lower than the coating drying temperature, for example, the coating drying temperature at the time of manufacturing the recording medium is already higher than Tg, the ink solvent permeates, and the voids due to the thermoplastic resin disappear. See also T
If g is higher than the temperature at which the support is denatured by heat, a fixing operation at a high temperature is required in order to melt and form a film after ink jet recording with a pigment ink. Thermal stability etc. becomes a problem. The preferable Tg of the thermoplastic resin is 50 to 150 ° C. Also,
The minimum film forming temperature (MFT) is preferably 50 to 150 ° C.

From the viewpoint of environmental suitability, the thermoplastic resin is preferably one dispersed in an aqueous system, and particularly preferably an aqueous latex obtained by emulsion polymerization. At this time, the type of emulsion polymerization using a nonionic dispersant as an emulsifier is
This is a form that can be preferably used. From the viewpoint of odor and safety, the thermoplastic resin used preferably has a small amount of residual monomer components, and is preferably 3% by mass or less, more preferably 1% by mass or less, based on the solid content of the polymer. It is preferably 0.1% by mass or less.

In the case of a surface layer containing an inorganic pigment and a thermoplastic resin, the solid content mass ratio of thermoplastic resin / inorganic pigment can be selected from the range of 90/10 to 10/90, preferably 70/30 to 30 /. The range is 70, more preferably 60/40 to 40/60.

The solid content of the thermoplastic resin contained in the surface layer 73 is 2 g / m ² or more and 20 g / m ² or less, preferably ^{2 to} 15 g / m ^2, more preferably ² g / m 2. It is in the range of 0.5 to 10 g / m ² . If the solid content of the thermoplastic resin is too small, a sufficient film cannot be formed and the pigment cannot be sufficiently dispersed in the film. Therefore, the image quality and gloss are not sufficiently improved. Also,
When the solid content of the thermoplastic resin is too large, the thermoplastic resin cannot be completely formed into a film in a short heating step, and the fine particles remain as opaqueness, which deteriorates the image quality. In addition, the ink absorption speed is also reduced, causing bleeding at the boundary, which is a problem.

The surface layer coating solution containing the inorganic pigment and the thermoplastic resin may be prepared by dispersing the inorganic pigment and the thermoplastic resin at the same time, or may be prepared by dispersing them and mixing them at the time of preparing the coating solution.

The support 71 of the recording medium F is a support conventionally used in ink jet recording media, for example, a paper support such as plain paper, art paper, coated paper and cast coated paper, a plastic support, A paper support having both surfaces coated with a polyolefin, a composite support obtained by laminating these together, and the like can be appropriately selected and used.

Further, in the recording medium F, for the purpose of increasing the adhesive strength between the support 71 and the ink absorbing layer 72, prior to coating the ink absorbing layer 72, the support is subjected to corona discharge treatment or undercoating treatment. Is preferably performed. Furthermore, the recording medium F does not necessarily have to be colorless and may be colored recording paper.

For the recording medium F, a paper support obtained by laminating both sides of a base paper support with polyethylene or the like is used.
It is particularly preferable because the recorded image is close to photographic quality and a high quality image can be obtained at low cost. A paper support laminated with such polyethylene will be described below.

The base paper used for the paper support is made of wood pulp as a main raw material, and if necessary, synthetic paper such as polypropylene or synthetic fibers such as nylon or polyester is used in addition to wood pulp. As wood pulp, LBKP, LBSP, NBKP, NBSP,
Any of LDP, NDP, LUKP, and NUKP can be used, but LBKP, NBSP, which has a large amount of short fibers,
It is preferable to use more LBSP, NDP, and LDP. However, the ratio of LBSP and / or LDP is 1
0 mass% or more and 70 mass% or less are preferable.

As the above-mentioned pulp, a chemical pulp containing few impurities (sulfate pulp or sulfite pulp) is preferably used, and a pulp whose whiteness is improved by bleaching is also useful. The base paper contains sizing agents such as higher fatty acids and alkyl ketene dimers, white pigments such as calcium carbonate, talc and titanium oxide, paper strength enhancers such as starch, polyacrylamide and polyvinyl alcohol, optical brighteners and polyethylene glycols. A water retention agent such as, a dispersant, and a softening agent such as quaternary ammonium can be appropriately added.

The freeness of pulp used for papermaking is CSF.
Is preferably 200 to 500 ml, and the fiber length after beating is 30 to 70% of the sum of the mass% of the 24 mesh residue and the mass% of the 42 mesh residue defined in JIS-P-8207. preferable. The mass% of the 4-mesh residue is preferably 20 mass% or less. The basis weight of the base paper is preferably 30 to 250 g / m ² , and particularly 50 to ²
00 g / m ² is preferred. The thickness of the base paper is 40-250μ
m is preferred. The base paper can be given a high smoothness by calendering at the papermaking stage or after the papermaking. Base paper density is 0.7 to 1.2 g / m ² (JIS-P-8118)
Is common. Furthermore, the stiffness of base paper is JIS-P-814.
20 to 200 g is preferable under the conditions specified in 3. A surface sizing agent may be applied to the surface of the base paper, and as the surface sizing agent, the same sizing agent as that which can be added to the base paper can be used. The pH of the base paper is preferably 5 to 9 when measured by the hot water extraction method specified in JIS-P-8113.

Polyethylene for covering the front and back surfaces of the base paper is mainly low-density polyethylene (LDPE) and / or high-density polyethylene (HDPE), but in addition, LLDPE (linear rhodity polyethylene), polypropylene and the like are partially used. Can be used. In particular, the polyethylene layer on the ink absorption layer side is preferably one in which rutile or anatase type titanium oxide is added to polyethylene to improve opacity and whiteness, as is widely used in photographic printing paper. The titanium oxide content is usually 3 to 20 mass% with respect to polyethylene,
It is preferably 4 to 13% by mass.

The polyethylene-coated paper can be used as a glossy paper, or when a polyethylene is melt-extruded on the surface of a base paper for coating, a so-called embossing treatment is carried out to obtain a matte surface which can be obtained by ordinary photographic printing paper. Those with a silky surface can also be used.

The amount of polyethylene used on the front and back sides of the base paper is selected so as to optimize curling under low and high humidity after providing the void layer and the back layer, but usually the polyethylene layer on the void layer side is used. Is 20 to 40 μm, and the back layer side is 10
It is in the range of 30 μm.

Furthermore, it is preferable that the polyethylene-coated paper support has the following characteristics. 1. Tensile strength: Strength specified by JIS-P-8113, 20 to 300 N in the vertical direction and 10 to 20 in the horizontal direction.
It is preferably 0N. 2. Tear strength: A method defined in JIS-P-8116, 0.1 to 20 N in the longitudinal direction and 2 to 20 N in the lateral direction.
Is preferred. 3. Compression modulus ≧ 98.1 MPa 4. Surface Beck smoothness: 20 seconds or more is preferable as a glossy surface under the conditions specified in JIS-P-8119,
It may be less than this for so-called molded products. 5. Surface roughness: The surface roughness defined by JIS-B-0601 has a maximum height of 10 μ per reference length of 2.5 mm.
It is preferably m or less. 6. Opacity: When measured by the method specified in JIS-P-8138, 80% or more, particularly 85 to 98% is preferable. 7. Whiteness: L *, a defined by JIS-Z-8729
* And b * are L * = 80 to 95, a * = − 3 to +5, b * =
It is preferably -6 to +2. 8. Surface gloss: 6 specified in JIS-Z-8741
The 0 degree specular gloss is preferably 10 to 95%. 9. Clark stiffness: Clark stiffness in the conveying direction S of the recording medium, the support is 50~300cm ^2/100 is preferred. 10. Water content of middle paper: usually 2 to 100% by mass, preferably 2 to 6% by mass based on the middle paper

Any of dye inks, pigment inks, water-based inks, oil-based inks, and hot-melt inks can be used as the recording medium F, but water-based pigment inks and oil-based pigment inks are suitable and water-based pigment inks. Is the most suitable.

Next, a method of manufacturing the recording medium F will be described. As a method for producing this recording medium, each of the constituent layers including the ink absorbing layer can be produced individually or simultaneously by appropriately selecting from known coating methods, coating on a support and drying. As the coating method, for example, roll coating method, rod bar coating method, air knife coating method, spray coating method, curtain coating method, or U.S. Pat.
A slide bead coating method using a hopper described in JP-A-2,761,791 and an extrusion coating method are preferably used.

The viscosity of each coating solution at the time of simultaneous multi-layer coating is 5 when the slide bead coating method is used.
The range is preferably from 100 to 100 mPa · s, more preferably from 10 to 50 mPa · s. When using the curtain coating method, the range of 5 to 1200 mPa · s is preferable, and the range of 25 to 500 mPa is more preferable.
・ S range.

The viscosity of the coating solution at 15 ° C. is preferably 100 mPa · s or more, and 100 to 30,
000 mPa · s is more preferable, still more preferably 3,000 to 30,000 mPa · s, and most preferably 10,000 to 30,000 mPa · s.

As a coating and drying method, the coating liquid is 3 times.
It is preferable that after the simultaneous multilayer coating is performed by heating to 0 ° C. or higher, the temperature of the formed coating film is once cooled to 1 to 15 ° C. and dried at 10 ° C. or higher. During preparation of the coating solution, during coating and during drying, it is preferable to prepare, coat and dry the coating solution at a temperature not higher than Tg of the thermoplastic resin so that the thermoplastic resin contained in the surface layer does not form a film. More preferably,
As the drying conditions, a wet bulb temperature of 5 to 50 ° C. and a film surface temperature of 10
It is carried out under the condition of a temperature range of 50 ° C. In addition, as a cooling method immediately after coating, it is preferable to use a horizontal setting method from the viewpoint of uniformity of the formed coating film.

Further, it is preferable that the step of manufacturing the recording medium has a step of supplying a curing agent for the water-soluble binder after the ink absorbing layer is formed. The method of supplying the curing agent is not particularly limited, and for example, a method of applying a solution containing the curing agent after forming the ink absorbing layer, a method of spraying the solution containing the curing agent onto the surface of the recording medium on which the ink absorbing layer has been formed. Etc. can be appropriately selected and used.

In the manufacturing process, the temperature is 35 ° C. or higher and 70 ° C.
It is preferable to have a step of storing for 24 hours or more and 60 days or less under the following conditions. This heating condition is 35 ° C or higher,
There is no particular limitation as long as it is stored at 70 ° C. or lower for 24 hours or longer and 60 days or shorter, but preferable examples include:
For example, 36 ° C. for 3 days to 4 weeks, 40 ° C. for 2 days to 2 weeks, or 55 ° C. for 1 to 7 days. By performing this heat treatment, it is possible to accelerate the curing reaction of the water-soluble binder or accelerate the crystallization of the water-soluble binder,
As a result, preferable ink absorbency can be achieved.

An image is written and recorded by jetting pigment ink from the line head 11 of FIGS. 1 and 2 onto the recording medium F having the above-described structure. As the ink, a water-based ink composition, An oil-based ink composition, a solid (phase change) ink composition, or the like can be used, but an aqueous ink composition (for example, an aqueous inkjet recording liquid containing 10% by mass or more of water based on the total mass of the ink) is preferable. .

From the viewpoint of image storability, it is preferable to use a pigment ink as the colorant used in the ink. As the pigment used in the pigment ink, an insoluble pigment, an organic pigment such as a lake pigment, and carbon black can be preferably used.

The insoluble pigment is not particularly limited, but for example, azo, azomethine, methine, diphenylmethane, triphenylmethane, quinacridone, anthraquinone, perylene, indigo, quinophthalone, isoindolinone, isoindoline, azine, oxazine. ,
Thiazine, dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole and the like are preferable.

Specific pigments that can be preferably used include the following pigments. Examples of magenta or red pigments include C.I. I. Pigment Red 2, C.I. I. Pigment Red 3, C.I. I. Pigment Red 5, C.I. I. Pigment Red 6, C.I.
I. Pigment Red 7, C.I. I. Pigment Red 1
5, C.I. I. Pigment Red 16, C.I. I. Pigment Red 48: 1, C.I. I. Pigment Red 53:
1, C.I. I. Pigment Red 57: 1, C.I. I. Pigment Red 122, C.I. I. Pigment Red 12
3, C.I. I. Pigment Red 139, C.I. I. Pigment Red 144, C.I. I. Pigment Red 149,
C. I. Pigment Red 166, C.I. I. Pigment Red 177, C.I. I. Pigment Red 178, C.I.
I. Pigment Red 222 and the like.

Examples of orange or yellow pigments include C.I. I. Pigment Orange 31, C.I.
I. Pigment Orange 43, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I.
Pigment Yellow 14, C.I. I. Pigment Yellow 15, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 9
4, C.I. I. Pigment Yellow 138 and the like.

As a pigment for green or cyan,
For example, C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 2, C.I. I. Pigment Blue 1
5: 3, C.I. I. Pigment Blue 16, C.I. I. Pigment Blue 60, C.I. I. Pigment Green 7 and the like.

A pigment dispersant may be used for these pigments if necessary, and examples of the pigment dispersant that can be used include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonic acids. Salt, sulfosuccinate, naphthalene sulfonate, alkyl phosphate,
Activator such as polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine oxide, or styrene, styrene derivative, vinyl Block copolymers of two or more monomers selected from naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, random copolymers Mention may be made of polymers and their salts.

As a method for dispersing the pigment, for example, various dispersing machines such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill and a paint shaker can be used. it can. Also,
It is also preferable to use a centrifugal separator and a filter for the purpose of removing coarse particles of the pigment dispersion.

The average particle size of the pigment particles in the pigment ink is selected in consideration of stability in the ink, image density, gloss feeling, light resistance, etc. In addition, from the viewpoint of improving gloss and improving texture. Also, it is preferable to appropriately select the particle size. The reason why the glossiness or texture is improved is not clear at this stage, but in the formed image, the pigment is related to the state in which the pigment is preferably dispersed in the film in which the thermoplastic resin is melted. It is speculated that For high-speed processing, the thermoplastic resin must be melted in a short time to form a film, and the pigment must be sufficiently dispersed in the film. At this time, it is considered that the surface area of the pigment has a great influence, and therefore the average particle size has an optimum region.

The water-based ink composition, which is a preferred form of the pigment ink, is preferably used in combination with a water-soluble organic solvent. Examples of water-soluble organic solvents that can be used include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc.). , Polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol,
Polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol), polyhydric alcohol ethers (eg ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether) , Diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, ethylene Recall monophenyl ether, propylene glycol monophenyl ether), amines (e.g., ethanolamine, diethanolamine,
Triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-
Ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc., amides (eg, formamide, N, N-dimethylformamide, N, N-dimethyl) Acetamide, etc., heterocycles (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone,
1,3-dimethyl-2-imidazolidinone etc.), sulfoxides (eg dimethyl sulfoxide etc.), sulfones (eg sulfolane etc.), urea, acetonitrile, acetone and the like. Examples of preferable water-soluble organic solvent include polyhydric alcohols. Furthermore, it is particularly preferable to use a polyhydric alcohol and a polyhydric alcohol ether together.

The water-soluble organic solvent may be used alone or in combination of two or more. The total amount of the water-soluble organic solvent added to the ink is 5 to 60% by mass, preferably 10 to
It is 35 mass%.

The ink composition may contain various known additives according to the purpose of improving ejection stability, compatibility with print heads and ink cartridges, storage stability, image storability, and other properties. For example, a viscosity modifier, a surface tension modifier, a specific resistance modifier, a film-forming agent, a dispersant, a surfactant, a UV absorber, an antioxidant, an anti-fading agent, an anti-fouling agent, an anticorrosive agent, etc. are appropriately selected. Can be used as, for example, polystyrene, polyacrylic acid esters, polymethacrylic acid esters, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, or a copolymer thereof, a urea resin, or Organic latex fine particles such as melamine resin, liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, etc. Droplet particles, various surfactants of cationic or nonionic, JP 57-74193,
UV absorbers described in JP-A-57-87988 and JP-A-62-261476, JP-A-57-74192 and 57.
-87989, 60-72785, 61-14.
6591, JP-A-1-95091 and 3-133.
No. 76, etc., anti-fading agent, JP-A-59-4
2993, 59-52689, 62-2800.
69, 61-242871, and JP-A-4-21.
Examples thereof include fluorescent whitening agents, pH adjusting agents such as sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate and the like described in No. 9266.

The ink composition has a flying viscosity of preferably 40 mPa · s or less, more preferably 2 to 20 mPa · s. The surface tension of the ink composition during flight is preferably 20 mN / m or more,
More preferably, it is 30 to 45 mN / m.

Next, the operation of recording an image on the recording medium F by the ink jet printer of FIG. 1 will be described. First, ink is ejected from the line head 11 in the recording unit 10 onto the recording medium F conveyed from the roll body 9 of FIG. 1 to perform image recording. At this time, each nozzle of the line head 11 of each color is recorded on the recording medium F. Ink is ejected almost simultaneously from the
Lines are formed respectively, and the recording medium F is sub-scanned to form lines one after another. In this case, since the drive frequency of the line head 11 can be set to 100 Hz or more, the ink landing time interval in each dot of each line is 10 m.
s or less, and each pixel (dot) is formed with a time interval of 10 ms or less for all adjacent pixels.

Further, as described above, the ink droplet velocity when ejecting ink from each nozzle of the ink head 11 is 6
It is desirable that it is not less than m / s and not more than 10 m / s, and the amount of ink droplets is at most 2.0 pl. The droplet speed and the droplet amount are calculated by the control unit 20 of FIG.
As described above, the ratio (V1 / V) of the positive and negative drive voltages V1 and V2 applied to the piezo elements forming each nozzle.
2) and the sum (V1 + | V2 |) are controlled to adjust to a desired value.

When the droplet speed of the ink ejected from each nozzle of the line head 11 is 6 m / s or less, the time from the ejection of the ink to the landing is long, and the fluctuation of the droplet speed causes a large fluctuation in the landing position. When the edge of the image formed on the recording medium F becomes unclear or the fine line is bent, the image quality is likely to deteriorate, and the droplet velocity is 1
When it is 0 m / s or more, the pigment ink is scattered on the surface of the recording medium F, the recording medium F is easily soiled, and the image quality is deteriorated. Therefore, the ink droplet speed is 6 m / s.
As described above, high-quality printing can be performed by controlling to 10 m / s or less. That is, when the droplet velocity is less than 6 m / s, the dots forming the image are not evenly distributed and are sparsely and densely, resulting in unevenness in the image, rough feeling, straight lines and jagged shapes. While the image quality is deteriorated due to the distortion of the image such as the above, the image quality is not deteriorated when the liquid drop velocity is 6 m / s or more,
Good image quality can be obtained.

Further, when the pigment ink is used as described above, if the ink absorption in the recording medium F is not made in time, the pigment may agglomerate and the image quality may be deteriorated. It is necessary to configure the ink landing time interval to exceed 10 ms as shown in FIG. That is, as shown in FIG. 10, a large number of nozzles 1a for respectively ejecting ink are formed on the nozzle surface 6 of the line head 111 of the recording section, and four nozzle rows 6a, 6b, 6 are formed.
c and 6d are formed so as to extend in one row. The recording unit is provided with such line heads 111 for each color of YMCK, and ink is ejected onto the recording medium F from a total of 16 nozzle rows of each line head 111. That is, as shown in FIG. 11A, each nozzle row 6 of the line head 111 of FIG.
a to 6d are arranged in a line in this order at a constant interval L.
Each nozzle of the set of nozzle rows 6a and 6b is at the same position in the nozzle extending direction, and each nozzle of another set of the nozzle rows 6c and 6d is at the same position between the nozzles of the nozzle rows 6a and 6b. is there. That is, assuming that the nozzle interval between the nozzle and the nozzle next to it is X, each nozzle of the group of nozzle rows 6a and 6b and each nozzle of another group of nozzle rows 6c and 6d are the nozzle and the nozzle next to it. The nozzle spacing X is offset by half so that another dot is formed between the nozzle and the nozzle. The distance L between the nozzle rows 6a to 6d is wider than the dot distance n formed on the recording medium F shown in the lower part of FIG. 11B, and the nozzle rows 6a and 6b and the nozzle rows 6c and 6d are respectively The dots are separated from each other by an odd multiple of the dot interval n, and lines are formed so as to form lines of 50 rows of dots, for example. The nozzle rows 6a and 6c are separated from the nozzle rows 6b and 6d by an even multiple of the dot interval n, and are separated so that, for example, lines of 101 rows of dots are formed therebetween. In FIGS. 11A and 11B, the vertical direction of the drawing is shortened.

Nozzle rows 6a to 6d of the line head 111
Ink is ejected from each of the nozzles of FIG.
Image recording is performed while repeating conveyance below (b). As shown in FIG. 11B, the ink on the recording medium F is ejected from each nozzle of the nozzle rows 6a to 6d to form each dot ◯ (circle in the figure, the same applies hereinafter) at the nozzle row 6a. At the same time, each dot in the nozzle row 6b is a double circle (double circle in the figure, the same applies hereinafter), each dot in the nozzle row 6c is a black circle (in the figure, the same applies below), and each dot is the nozzle row 6d. Form x (penalty mark in the figure, the same applies hereinafter).
In this case, the lines 60a and 60b are formed in the nozzle rows 6a and 6b.
While each dot is formed by the nozzle rows 6c and 6d, each dot ● and each dot x are formed between each dot of the previously formed dots ○ and dots ◎ to form the lines 60c and 60d, respectively. . Next, after the recording medium F is conveyed to the lower part of the drawing by a distance of one line (twice the dot interval n), each nozzle of the nozzle rows 6a to 6d forms a line of each dot.
As shown in FIG. 11B, each line of dots ∘∘∘∘ is formed with a space of one line. That is, FIG.
In FIG. 1 (b), the line 60a of dot ◯ is the line 61a.
It is formed one line after the formation of a, and is formed after forming 25 lines temporally for the line 62a of dot ◯. The line 60b indicated by the dot ◎ is the line 60a as the line next to the line 62a indicated by the dot ◯.
Since it is formed at the same time, it is formed after forming 25 lines from the line 62a. Similarly, since the ink landing time interval between each line and the adjacent line is the time for forming 25 lines, ink is ejected every 0.4 ms (= driving frequency 2.5 kHz). It will be 10 ms. As described above, an image can be formed by forming a plurality of lines 60e composed of each pixel on the recording medium F as shown in FIG. 11B. At this time, the time interval of ink ejection is set. For example, even if it is controlled to 10 ms or less such as 0.4 ms, each pixel of each line can be controlled to be formed at a time interval of 10 ms or more for all the adjacent pixels. In this way, it is possible to increase only the ink landing time interval without increasing the ejection time interval, that is, without decreasing the printing speed.

If the ink landing time interval exceeds 10 ms and the print speed is not slowed down as shown in FIGS. 10 and 11, the apparatus configuration tends to be complicated. However, as in the present embodiment. , The landing time interval is 10
Even if it is less than ms, the maximum drop amount of ink ejected is 2p.
By controlling to 1, the graininess can be improved and the image quality can be improved.
A problem such as printing with large droplets does not occur, the resolution of the image can be prevented from lowering, and the line heads 11 in one row as shown in FIG. 2 can be provided for each color, so that the apparatus configuration is simplified. Also, the printing speed can be improved.

Next, the recording medium F has a pair of conveying rollers 15.
a, 15b are conveyed in the conveying direction S through the accumulation portion 18, cut by the cutting portion 40 to a predetermined size at an appropriate position, and then conveyed to the fixing portion 50 by the conveying roller pair 16a, and the fixing portion 50. It enters between the heating roller 51 and the pressure roller 52. Then, under the control of the control unit 20, the heating roller 51 is heated to a predetermined temperature and driven in the direction A so as to have a predetermined pressure, whereby the recording medium F on which the image is written is heated on the heating roller 51 and the pressure roller 5.
The nip portion 59 formed between the first and second portions is heated / pressurized at the predetermined temperature and the predetermined pressure as described above, and the time for passing through the nip portion 59 is controlled.

As described above, the recording medium F is transferred to the fixing unit 50.
By heating and pressurizing, the latex particles contained in the uppermost surface layer 73 of the recording medium F of FIG. 7 are melted, smoothed and made transparent, and the pigment ink is absorbed in the ink absorption layer 72 to record. The image is fixed on the medium F, and the image clarity value of the image formed on the recording medium F is 60% to 95% of at least one of the heating temperature, the pressing force, and the heating / pressurizing time of the recording medium F at this time. It is controlled to be within the range of%.

That is, the heating temperature T of the recording medium F is T = Tg
± ΔT = 50 to 150 ° C. ± 10 ° C.
The pressure applied to the recording medium F by the heating roller 51 is set to 9.
It is included in the surface layer 73 of the recording medium F of FIG. 7 by controlling the image clarity value of the image within 60% to 95% by controlling so as to be 8 × 10 ^{4 to} 4.9 × 10 ⁶ Pa. When the latex particles are melted and the surface layer 73 is smoothed to be transparent, the appearance is excellent and a glossiness similar to that of a photograph can be obtained to form a high quality image.
It is possible to form an image having excellent storability by being incorporated into No. 2.

If the image clarity value is 60% or less, the gloss peculiar to the photograph is reduced to deteriorate the image quality, and if it is 95% or more, the image is abnormally shiny and the image quality is deteriorated. Since it is easy to get it, the range of 60% to 95% is preferable.

Next, a modification in which the ink landing position on the recording medium F is changed will be described with reference to FIG.
FIG. 8 is a plan view showing the ink landing positions on the recording medium F in this modification.

As shown in FIG. 8, an image is formed such that each pixel formed on the recording medium F is shifted by half a pixel pitch p (about half a pixel) p / 2 for each line. That is, each pixel position on line bb is shifted by about half the pixel pitch p from each pixel position on line aa.
form dd. By forming the lines aa to dd in this way, the shortest distance d between the pixel and the adjacent pixel between the lines aa to dd is larger than the shortest distance d ′ when the pixel is not displaced, and the ink landing interval is large. Since the image is wider than the image in the case where the ink is not displaced, the number of adjacent pixels on the recording medium F is small, and the decrease in the decrease in the granularity due to the aggregation of the ink droplets, the aggregation of the pigments, and the decrease in the amount of the ink droplets is combined as compared with the case where the image is not displaced. The image quality is improved.

As described above, in order to form the lines aa to dd by shifting by approximately half of the pixel pitch p, the nozzle row 62 of the line head 11 is alternately shifted in a staggered manner by p / 2 for each line head. This can be realized by a configuration in which the recording unit 10 is arranged, and the nozzles may be configured so that the ink ejection positions of the nozzles are changed and the ink landing positions are staggered as shown in FIG.

Next, another configuration example of the fixing unit 50 of FIG. 1 will be described with reference to FIG. FIG. 9 is a side view showing the endless belt type fixing unit in detail.

The fixing unit in FIG. 9 is constructed so as to pressurize and heat the recording medium F while being conveyed by the endless belt, and as shown in the figure, the heating roller 410 and the recording medium F.
And a pressure roller 44 for sandwiching the heat roller 410 with the heating roller 410.
0, a driven roller 420 disposed on the downstream side, an endless heating belt 430 stretched between the heating roller 410 and the driven roller 420, and a recording medium F heating belt 4.
A pressing unit 470 for pressing the heating belt 30 and a temperature sensor 480 for detecting the surface temperature of the heating belt 430.
A transport sensor 490 that detects the recording medium F on the upstream side of the heating roller 410 and the pressure roller 440, and a cleaning unit 600 that removes ink stains adhering to the surface of the heating belt 430.

The heating roller 410 is composed of a hollow roller and has a heating element 450 such as a halogen heater as a heat source built therein along the axial direction thereof. The heating element 450 heats the heating roller 410, and the heating roller 410 is suspended on it. Heating belt 4
By heating 30 as well, the recording medium F pressed by the heating belt 430 is heated, and the thermoplastic resin particles on the surface layer thereof are melted. The heating roller 410 is a heating element 45.
The recording medium F is preferably formed of a material having a high thermal conductivity so that the recording medium F can be efficiently heated by the heat generated from 0, and it is preferably formed of a metal roller.

The temperature sensor 480 is arranged close to the heating roller 410, detects the surface temperature of the heating belt 430, and the control unit 20 of FIG. 6 causes the heating element 450 inside the heating roller 410 to detect the surface temperature of the heating belt 430. Of the heating belt 430 is controlled to maintain the surface temperature of the heating belt 430 within a predetermined temperature range. The heating element 450 is the heating roller 41.
It may be provided near the outside of 0.

The heating belt 430 is suspended between the heating roller 410 and the driven roller 420, and after being heated to a predetermined temperature range by the heating element 450, the recording medium F on which an image is formed is pressed to perform recording. The thermoplastic resin particles contained in the surface layer of the medium F are melted, and the surface roughness of the recording medium F becomes approximately the same as the surface roughness of the heating belt 430.

Therefore, the outer surface (recording medium side) of the heating belt 430 is required to have a small surface roughness. Specifically, Ra = 0.5 μm or less and 0.01 μm or more (preferably, Ra). Ra = 0.1 μm or less) is required. Here, to describe the incidental effect of reducing the surface roughness of the belt, generally, for the same material, the smaller the surface roughness, the higher the abrasion resistance and the higher the durability. Are known. Further, it is known that the smaller the surface roughness is, the more excellent the antistatic property and the prevention of offset are. Therefore, such an effect can be obtained in FIG. 9.

The heating belt 430 is basically a metal belt or resin belt coated on the surface thereof. Considering the releasability from the recording medium F and the surface roughness when coated, The following materials are preferred.・ Nickel Belt + Silicon Rubber + PFA ・ Nickel Belt + PFA ・ Nickel Belt + Silicon Rubber ・ Nickel Belt + Fluorine Coat ・ Nickel Belt + Silicon Rubber + Hardened Silicon ・ Nickel Belt + Hardened Silicon ・ Stainless Steel Belt + Silicon Rubber + PFA ・ Stainless Steel Steel Belt + PFA-Stainless Steel Belt + Silicon Rubber-Stainless Steel Belt + Fluorine Coated-Stainless Steel Belt + Silicon Rubber + Hardened Silicon-Stainless Steel Belt + Hardened Silicon-Polyimide Belt + Silicon Rubber + PFA-Polyimide Belt + PFA-Polyimide Belt + Silicon Rubber / Polyimide Belt + Fluorine Coated / Polyimide Belt + Silicon Rubber + Curing Silicon / Polyimide Belt + Curing Silicon

The pressure roller 440 is composed of a metal roller of stainless steel or the like or a metal roller of stainless steel or the like having an elastic coating on the outer periphery, and is heated by the biasing means (not shown) to the heating roller 410 side. Is constantly pressed. When the conveyance sensor 490 provided on the upstream side of the heating roller 410 and the pressure roller 440 detects the conveyance of the recording medium F, the urging means pushes the pressure roller 440 against the heating roller 410 in the control unit 20 of FIG. Control such as weakening the pressure is performed. This prevents the end surfaces of the recording medium F from damaging the surfaces of the heating belt 430 and the pressure roller 440.

The pressing means 470 is a plate-shaped member 471 in contact with the lower surface of the recording medium F in the figure, and a biasing means 47 for biasing the plate-shaped member 471 and the recording medium F toward the heating belt 430.
2 and. The plate-shaped member 471 is preferably made of metal, and its surface roughness is required to be as small as that of the heating belt. Specifically, Ra = 0.5 μ.
m or less and 0.01 μm or more (preferably Ra =
0.1 μm or less) is required. Urging means 4
72 is composed of a spring or the like, and a plurality of them may be provided, and it is possible to adjust the pressing force (pressing force) against the recording medium F. It is preferable to dispose a pressure sensor as in FIG. 5 for detecting the applied pressure.

Further, the heating roller 410 and the driven roller 42
By arranging the auxiliary heating element 451 and the temperature sensor 452 therefor inside the heating belt 430 between 0 and 0, the heating temperature for the recording medium F can be controlled more accurately.

In FIG. 9, when the recording medium F on which an image is recorded with ink is conveyed in the conveying direction S,
The conveyance sensor 490 detects the recording medium F, and the pressure roller 4
After weakening the pressing force of the heating roller 410 of 40,
The recording medium F enters between the heating belt 430 and the pressure roller 440 and moves in the transport direction S.
0 and the plate-shaped member 471 are conveyed. During this conveyance, the recording medium F is heated by the heating belt 430, and the spring 47 of the biasing means 470 is passed through the plate member 471.
It receives pressure from 2. The image clarity value of the image formed on the recording medium F by the control unit 20 of FIG. 6 is 60% to 95% for at least one of the heating temperature and the pressing force.
It is controlled to be within the range. Further, the endless belt system of FIG. 9 is preferable in this respect because it can secure a longer heating time and pressurizing time than the rotary roller system of FIG.

[0146]

EXAMPLES The present invention will be further described with reference to Examples and Comparative Examples.

<< Preparation of Recording Medium >> Samples F1 and F2 of recording media as ink jet recording paper were prepared by the following procedure.

[Preparation of Inorganic Fine Particle Dispersion]

(Preparation of Silica Dispersion Liquid 1) 125 kg of vapor-phase process silica (QS-20 manufactured by Tokuyama Corp.) having an average primary particle size of about 0.012 μm was mixed with a jet stream manufactured by Mitamura Riken Kogyo Co., Ltd. Inductor mixer TD
After S was dispersed by suction in 620 L of pure water whose pH was adjusted to 2.5 with nitric acid at room temperature, the total amount was 694 L with pure water.
After that, a silica dispersion liquid 1 was prepared.

(Preparation of Silica Dispersion Liquid 2) [Chemical Formula 1]
69.4 L of the silica dispersion liquid 1 prepared above is added to 18 L of an aqueous solution (pH = 2.3) containing 1.14 kg of the cationic polymer (P-1), 2.2 L of ethanol, and 1.5 L of n-propanol. The mixture was added with stirring, then 7.0 L of an aqueous solution containing 260 g of boric acid and 230 g of borax was added, and 1 g of an antifoaming agent SN381 (manufactured by San Nopco Ltd.) was added. This mixed solution was dispersed with a high pressure homogenizer manufactured by Sanwa Kogyo Co., Ltd., and the total amount was adjusted to 97 L with pure water to prepare a silica dispersion 2.

[0151]

[Chemical 1]

[Preparation of Thermoplastic Resin Coating Liquid 1] A styrene-acrylic latex polymer (Tg 78 ° C., average particle size 0.3 μm, solid content concentration 40%) emulsion-polymerized using a nonionic surfactant as an emulsifier % Nitric acid aqueous solution to adjust the pH to 4.7, and this was used as a thermoplastic resin coating liquid 1.

[Preparation of coating liquid]

After preparing the coating liquid as described below, the coating liquid was applied to a commercially available filter (TC manufactured by Toyo Roshi Kaisha, Ltd.).
It filtered using P10 or TCP30).

(Preparation of Lower Layer Coating Liquid 1) While stirring at 40 ° C., 710 ml of the silica dispersion 2 prepared above was sequentially mixed with the following additives to prepare a lower layer coating liquid 1.

[0156]   10% water-soluble polyvinyl alcohol (Kuraray Industry Co., Ltd .: PVA203) Liquid: 3 ml Polyvinyl alcohol (Kuraray Industry Co., Ltd .: PVA235) 4.8% and 1.84% of polyvinyl alcohol (PVA245 manufactured by Kuraray Industries Co., Ltd.) Aqueous solution containing ... 273 ml The total volume was adjusted to 1000 ml with pure water.

(Preparation of Upper Layer Coating Liquid 1) The thermoplastic resin coating liquid 1 and the lower layer coating liquid 1 prepared above were mixed so that the solid content ratio of the thermoplastic resin and the inorganic pigment was 40:60. Thereafter, water was added so that the viscosity at 43 ° C. was 45 mPa · s, and this was used as upper layer coating liquid 1.

(Preparation of Upper Layer Coating Liquid 2) Above Upper Layer Coating Liquid 1
In the preparation of, the upper layer coating liquid 2 was prepared in the same manner except that the solid content ratio of the thermoplastic resin and the inorganic pigment was changed to 50:50.

[Preparation of Recording Medium]

A paper support having both sides coated with polyethylene (also referred to as RC paper, having a thickness of 220 μm, and polyethylene in the polyethylene of the ink absorbing layer surface is 13 to polyethylene).
1% by weight of the anatase-type titanium oxide) from the support side to the lower layer coating solution 1 as a first layer.
72 μm, the upper layer coating liquid 1 (average particle diameter of the thermoplastic resin: 0.3 μm) as the second layer, under the condition that the wet film thickness is 60 μm and the solid content of the thermoplastic resin is 3.0 g / m ² ,
Two layers were simultaneously coated and dried using a slide hopper. Each coating solution was heated to 40 ° C. for coating, and immediately after coating, it was cooled for 20 seconds in a cooling zone kept at 0 ° C.
Sequentially dry for 60 seconds with 25 ° C wind (15% relative humidity), 45 seconds with 45 ° C wind (25% relative humidity), and 60 seconds with 50 ° C wind (25% relative humidity), and then 20-25 After conditioned for 2 minutes in an atmosphere of 40 ° C and 60 ° C relative humidity,
The sample was wound to prepare a sample F1. Then, the sample F1 was enclosed in a polyethylene bag and subjected to aging treatment at 55 ° C. for 3 days.

The wet film thickness of the first layer is 184 mμm, the upper layer coating solution 2 is used in the second layer, and the wet film thickness is 40 μm.
m, a sample F2 was prepared in the same manner as the above-described sample F1 except that the solid content rate of the thermoplastic resin was changed to 2.5 g / m ^2, and then the same aging treatment was performed.

<< Preparation of Ink >> A water-based pigment ink was prepared by the following procedure.

[Preparation of Water-based Pigment Ink]

(Preparation of Pigment Dispersion) <Preparation of Yellow Pigment Dispersion 1> C.I. I. Pigment Yellow 74 ... 20% by mass Styrene-acrylic acid copolymer (molecular weight 10,000, acid value 120) ... 12% by mass Diethylene glycol ... 15% by mass Ion-exchanged water ... 53% by mass The additives were mixed and dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 0.3 mm zirconia beads at a volume ratio of 60% to obtain a yellow pigment dispersion 1. The average particle size of the obtained yellow pigment was 112 nm.

<Preparation of Magenta Pigment Dispersion 1> C.I. I. Pigment Red 122 ... 25% by mass John Kryl 61 (acrylic-styrene resin, manufactured by Johnson Co.) ... 18% by mass in solid content Diethylene glycol ... 15% by mass Ion-exchanged water ... 42% by mass The additives were mixed and dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 0.3 mm zirconia beads at a volume ratio of 60% to obtain Magenta pigment dispersion 1. The average particle size of the obtained magenta pigment was 105 nm.

<Preparation of Cyan Pigment Dispersion 1> C.I. I. Pigment Blue 15: 3 ... 25% by mass John Cryl 61 (acrylic-styrene resin, manufactured by Johnson) ... 15% by mass as solid content Glycerin ... 10% by mass Ion-exchanged water ... 50% by mass The above additives were mixed and dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 0.3 mm zirconia beads at a volume ratio of 60% to obtain Syn Pigment Dispersion 1. The average particle size of the obtained cyan pigment is 87n.
It was m.

<Preparation of Black Pigment Dispersion 1> Carbon black ... 20% by mass Styrene-acrylic acid copolymer (molecular weight 7,000, acid value 150) ... 10% by mass Glycerin ... 10% by mass Ion-exchanged water: 60% by mass Disperse the above additives with a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 0.3 mm zirconia beads at a volume ratio of 60% to disperse a black pigment. I got body 1. The average particle size of the obtained black pigment was 75 nm.

(Preparation of Pigment Ink)

<Preparation of Yellow Ink> Yellow Pigment Dispersion 1 ... 15% by mass Ethylene glycol ... 20% by mass Diethylene glycol ... 10% by mass Surfactant (Surfynol 465, Nissin Chemical Industry Co., Ltd.) -0.1% by mass Ion-exchanged water ... 54.9% by mass The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare a yellow ink which is a water-based pigment ink. The average particle size of the pigment in the ink was 120 nm, and the surface tension γ was 36 mN / m.

<Preparation of Magenta Ink> Magenta Pigment Dispersion 1 ... 15% by mass Ethylene glycol ... 20% by mass Diethylene glycol ... 10% by mass Surfactant (Surfynol 465 Nissin Chemical Co., Ltd.) -0.1% by mass Ion-exchanged water ... 54.9% by mass The above compositions were mixed, stirred, and filtered through a 1 µm filter to prepare a magenta ink that is an aqueous pigment ink. The average particle size of the pigment in the ink was 113 nm, and the surface tension γ was 35 mN / m.

<Preparation of Cyan Ink> Cyan Pigment Dispersion 1 ... 10% by mass Ethylene glycol ... 20% by mass Diethylene glycol ... 10% by mass Surfactant (Surfynol 465, Nissin Chemical Industry Co., Ltd.) -0.1% by mass Ion-exchanged water ... 59.9% by mass The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare a cyan ink that is an aqueous pigment ink.
The average particle diameter of the pigment in the ink was 95 nm, and the surface tension γ was 36 mN / m.

<Preparation of Black Ink> Black Pigment Dispersion 1 ... 10% by mass Ethylene glycol ... 20% by mass Diethylene glycol ... 10% by mass Surfactant (Surfynol 465, Nissin Chemical Industry Co., Ltd.) -0.1% by mass Ion-exchanged water ... 59.9% by mass The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare a black ink that was an aqueous pigment ink. The average particle size of the pigment in the ink was 85 nm, and the surface tension γ was 35 mN / m.

Next, each of the samples F1 and F of the above-mentioned recording medium
With respect to No. 2, an image was formed under the following conditions using the ink jet printer of FIG. 1 as an example and a comparative example using the above-described water-based pigment inks. The fixing unit is shown in FIG.
The belt system of FIG. 10 was used as the line head.

The landing time interval of the ejected ink was variously changed as follows. In FIGS. 1, 10 and 11, when the moving speed of the recording medium is V, the time T from when the nozzle row 6a forms a dot to when the nozzle row 6b forms the preceding dot in FIG. 11B. Can be expressed by the following equation (1).

T = (L−n) / V (1) However, L: interval between nozzle rows (FIG. 10), n: dot interval (FIG. 11)

Normal moving speed V (0.1 to 1) of the recording medium
Since L >> n at m / s), the time T can be expressed by the following approximate expression (2).

T = L / V (2)

Here, for example, V ≦ 0.1 m / s, L ≧
With a combination of 1 mm, the ink landing time interval is 10 m
s or more, for example, V ≧ 0.1 m / s, L =
With a combination of 1 mm, the landing time interval can be 10 ms or less. As described above, the ink landing time interval can be changed by changing the moving speed V of the recording medium and / or the interval L between the nozzle rows. In this case, the drive frequency of the line head is also changed so as to have the same landing position interval.

In the present embodiment and the comparative example, the line head nozzle row interval L is set to 1 mm, and the moving speed V of the recording medium is changed in five ways within the range of 1 m / s to 0.05 m / s, whereby the ink The landing time interval is 1.0, 2.0,
The images were formed at 5.0, 10.0, and 20.0 ms, and the quality of the roughness of each image was measured. The amount of each ink droplet was 1 to 5 pl. The droplet amount was adjusted by changing the driving voltage for the nozzle and the nozzle diameter as shown in FIGS. The results are shown in Table 1 below.

An image was formed by forming each line by shifting the ink landing time interval by 10 ms and shifting by half a pixel as shown in FIG.

[0181]

[Table 1]

As can be seen from Table 1, when the landing time interval between adjacent pixels is as short as 10 ms or less, in the comparative example in which the droplet amount of the ejected ink is 3 pl or more, the rough feeling increases as the droplet amount increases. However, in the examples in which the landing time interval is 10 ms or less and the droplet amount is 2 pl or less, the rough feeling is good or good.
On the other hand, in the comparative example in which the landing time interval is 20 ms, the roughness is good when the droplet amount of the ejected ink is in the range of 1.0 to 5.0 pl, but the printing speed is not reduced. Since four line heads as shown in FIG. 10 are required, the device configuration and control become complicated.

As described above, when the pigment ink is used,
If the ink absorption in the recording medium cannot be made in time, the pigment ink droplets of the adjacent pixels will aggregate after landing, resulting in deterioration of image quality. However, in this embodiment, the ink landing time interval is set to 10.
By setting the maximum amount of ink droplets to 2 pl even if it is less than or equal to ms, the roughness is reduced, good image quality is obtained, the device configuration is simplified, and there is no problem of reduction in printing speed.

Further, in the embodiment in which each line is formed by shifting by half a pixel as shown in FIG. 8, the feeling of roughness is reduced and the image quality is improved as compared with the case where the lines are not shifted, and an image is formed with the ink of the same droplet amount. The image quality was improved compared to the image in the case where the density was not low, and in particular, the image quality of the highest density part such as hair and shadow part was improved.

The present invention has been described above with reference to the embodiments and examples, but the present invention is not limited to these, and various modifications can be made within the scope of the technical idea of the present invention. . For example, the configuration of the head in the recording unit is
The present invention is not limited to the line head, and may be a serial head. In this case, it is preferable that the serial head has a nozzle density equal to the dot density.

[0186]

According to the present invention, it is possible to provide an image recording method and an ink jet printer capable of forming an image having the same image quality and storability as a photograph and improving the printing speed.

[Brief description of drawings]

FIG. 1 is a side view schematically showing an inkjet printer according to an embodiment.

FIG. 2 is a perspective view showing a schematic configuration of the line head of FIG.

3 is a perspective view (a) partially showing the nozzle of the line head of FIG. 2, front views (b) and (c) for explaining the operation of the electrode of the nozzle, and the ejection / non-ejection of the nozzle. It is a front view (d), (e), (f) for explaining each drive state.

4 is a diagram showing a drive waveform of each nozzle in FIG.

5 is a side view showing the fixing unit of the inkjet printer of FIG. 1 in more detail.

6 is a block diagram showing a control system of the inkjet printer of FIG. 1. FIG.

FIG. 7 is a cross-sectional view showing a laminated structure of a recording medium according to the present embodiment.

8 is a plan view showing ink landing positions in a modified example of the inkjet printer of FIG.

FIG. 9 is a side view showing another configuration example of the fixing unit of FIG.

FIG. 10 is a diagram for comparison with the present embodiment,
It is a perspective view showing a line head 111 used in an example.

FIG. 11 is a diagram for comparison with the present embodiment,
11A is a plan view showing the arrangement of the nozzle rows 6a to 6d of the line head 111 and FIG. 11A shows ink landing positions on the recording medium when printing is performed using the four line heads of FIG. It is a top view (b) shown corresponding to each nozzle position of a nozzle row.

[Explanation of symbols]

9 rolls 10 Recording section 11 line head 62 nozzle rows 1a nozzle 20 Control unit 23 Head drive circuit 26 Fixing unit drive mechanism 40 cut section 50 fixing unit 51 heating roller 52 Crimping roller 53 heating element 55 Temperature sensor 72 Ink absorption layer of recording medium F 73 surface of recording medium F 410 heating roller 450 heating element 440 pressure roller 430 heating belt 470 biasing means F recording medium S transport direction p pixel pitch

Continued front page    F-term (reference) 2C056 EA01 EA04 EA07 EA11 EA13                       EB14 EB30 EB34 EC07 EC14                       EC29 EC31 EC32 EC36 EC72                       ED01 EE08 FA04 FA13 FC02                       FC06 HA45 HA46                 2C057 AF02 AF29 AG15 AG45 AH20                       AM13 AM15 AM16 AM17 AN05                       BA03 BA14                 2H086 BA03 BA05 BA12 BA15 BA33

Claims (9)

[Claims] 1. A recording medium having an ink-absorbing layer on a support and a thermoplastic resin on the surface has a maximum droplet volume of 2 pl.
Each pixel is formed at a time interval of 10 ms or less with respect to an adjacent pixel while ejecting the pigment ink of No. 6 at a droplet velocity of 6 to 10 m / s, and thereafter, the image clarity value of the image formed on the recording medium is 6
An image recording method characterized in that an image is recorded by heating and pressurizing the recording medium so as to be 0% or more and 95% or less. 2. The image recording method according to claim 1, wherein the pixels are formed so as to be shifted line by line by about half the pixel pitch. 3. The image clarity value is set to 60% or more and 95% or less by controlling at least one of a heating temperature, a pressing force, and a heating / pressurizing time when the recording medium is heated and pressed. The image recording method according to claim 1 or 2. 4. The image recording method according to claim 1, wherein the surface layer of the recording medium further contains an inorganic pigment. 5. An ink jet printer, comprising: an ink head for ejecting ink onto a recording medium; and a heating / pressurizing means for heating and pressurizing the recording medium after the ink has been ejected, for performing image recording on the recording medium. In addition, a recording medium having an ink absorption layer on a support and a thermoplastic resin on the surface layer has a pixel of 10 ms for each adjacent pixel.
Pigment ink having a droplet volume of 2 pl or less is ejected from the ink head at a droplet velocity of 6 to 10 m / so as to be formed at the following time intervals.
Ink jet printer, characterized in that the recording medium is heated and pressed by the heating and pressurizing means so that the image clarity value of the image formed on the recording medium is 60% or more and 95% or less. 6. The ink jet printer according to claim 5, wherein the respective pixels are formed so as to be shifted line by line by approximately half the pixel pitch. 7. The inkjet printer according to claim 5, wherein the ink head is a line head. 8. The heating / pressurizing means is configured to control at least one of a heating temperature, a pressing force, and a heating / pressurizing time at the time of heating and pressurizing the recording medium. Item 8. The inkjet printer according to any one of items 5 to 7. 9. The ink jet printer according to claim 5, wherein the surface layer of the recording medium further contains an inorganic pigment.