JP2010241073A - Intermediate transfer body for transfer type inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an intermediate transfer body for transfer type inkjet recording which can be adapted to high-speed and high-density recording. <P>SOLUTION: The intermediate transfer body is used for a transfer type inkjet recording method which includes an intermediate image forming process for forming an intermediate image by applying an aqueous ink containing a color material component with an inkjet recording method on an image forming surface of the intermediate transfer body applied with an aggregation liquid which forms aggregates by contacting with the color material component in the aqueous ink, and a transfer process for transferring the intermediate image to a recording medium from the image forming surface by pressing the recording medium to the image forming surface formed with the intermediate image. The image forming surface is formed with a porous body obtained by biaxially orienting a resin containing a polytetrafluoroethylene, a contact angle of the aggregation liquid on the image forming surface is 90 degrees or more, and a contact angle of the aqueous ink on the image forming surface is less than 90 degrees. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an intermediate transfer member used for a recording method using an inkjet method.

  As a problem of image formation by the ink jet system, there are bleeding that inks applied adjacently are mixed, and beading that ink that has landed first is attracted to ink that has landed later. In order to solve this problem, a transfer type ink jet recording system has been devised in which an intermediate image formed on an intermediate transfer member is transferred to a recording medium.

  In general, an intermediate transfer member used in a transfer type ink jet recording system is required to have a plurality of characteristics. First, it is necessary to make the above-mentioned bleeding and beading hardly occur on the transfer body. In other words, it is difficult to move the ink, and is particularly important when performing high-speed and high-density printing.

  Next, there is transferability. Transferability refers to the ease of movement of an intermediate image formed on an intermediate transfer member to a recording medium. In other words, it is difficult for the ink to remain on the intermediate transfer body after the transfer step, and it is desirable that all the ink that has formed the intermediate image is transferred.

  However, it is not easy to make the above characteristics compatible. This is because if the ink easily moves on the transfer body, the image is disturbed by bleeding or the like, and if it is difficult to move, the transferability is poor.

  Therefore, an intermediate transfer member having a fluororesin porous body on the surface has been proposed for the purpose of satisfying the above characteristics.

  Patent Document 1 exemplifies an intermediate transfer member having a porous intermediate transfer layer made of a fluororesin capable of absorbing dye ink. In this example, since the intermediate transfer layer is configured to temporarily absorb the dye ink applied from the ink jet device, the movement of the ink on the intermediate transfer member is limited, and bleeding and beading are unlikely to occur. Further, it is said that transferability can be improved by using a fluororesin that does not adsorb dye ink to the resin constituting the intermediate transfer member.

  Patent Document 2 exemplifies an intermediate transfer member having a surface of a stretched product of polytetrafluoroethylene as an ink repellent porous material. In this example, the contact angle of the ink on the surface of the intermediate transfer body is at least 90 ° or more, and the intermediate transfer member does not move with a small external force due to the effect of the uneven structure on the surface of the porous body and the meniscus formed by the release agent. It is supposed to be held in. In this state, ink movement and coalescence are suppressed, that is, bleeding and beading are unlikely to occur.

JP 11-291478 A JP 2002-116630 A

  In the conventional technique described above, the following problems may occur.

  In the intermediate transfer body in Patent Document 1, the ink is absorbed inside the porous body, and then the ink is pushed out again by pressure. Therefore, when high-density printing is performed using smaller-sized ink droplets, the transfer is performed. There is a problem that the performance is greatly reduced.

  In the intermediate transfer body in Patent Document 2, the contact angle of the ink on the surface of the intermediate transfer body is at least 90 ° or more. For this reason, the contact area becomes very small with respect to the ink mass, and there is a problem that the image is disturbed due to the ink moving due to inertial force or wind pressure when printing at higher speed. Further, for the same reason, the drawing area with respect to the applied ink amount becomes small, and thus there is a problem that a large number of inks must be applied to fill the recording area of the unit area.

  In short, in an intermediate transfer member having a porous material made of a fluororesin on the surface, if the contact angle of the ink on the surface of the intermediate transfer member is 90 ° or more, the ink on the intermediate transfer member is easily moved by an external force. End up. Conversely, if the contact angle of the ink on the surface of the intermediate transfer member is less than 90 °, there is a problem that the ink easily permeates into the porous body constituting the intermediate transfer member and transferability is poor.

  In the ink jet recording technology that has recently been demanded to increase the speed and density at a dramatic speed, it is extremely important to eliminate this trade-off.

  Furthermore, as a result of detailed examination of these techniques, the present inventors have found that such an "intermediate transfer body having a porous material made of a fluororesin on the surface used for the transfer type ink jet recording system" has a very high drying speed. I found for the first time that there is a problem that it may be late.

  From the viewpoint of productivity, it is also extremely important that the intermediate transfer member has a property that the intermediate image formed on the surface thereof is quickly dried. That is, in the transfer type ink jet recording system, it is necessary to remove excess liquid in the intermediate image between the formation of the intermediate image with ink and the transfer to the recording medium. If this is insufficient, the excess liquid is squeezed out of the image by the pressure at the time of transfer and spreads on the recording medium, causing a significant image disturbance. In particular, when water-based ink is used, the influence of the drying speed on productivity is great. This is due to the low volatility of water which is the main solvent of the water-based ink. Such problems are unlikely to occur because organic solvents such as alcohols and ketones included as the solvent for oil-based inks are highly volatile.

  In the invention of Patent Document 1, since the ink is dried in a state where the ink is absorbed in the porous body, there is a problem that the replacement efficiency of the generated vapor is not good and the drying speed is difficult to increase.

  In the intermediate transfer body in Patent Document 2, since the contact angle of the ink on the surface of the intermediate transfer body is at least 90 ° or more, there is a problem that the surface area per unit volume of the ink becomes small and the drying speed tends to be remarkably slow.

  Accordingly, an object of the present invention is to provide an intermediate transfer body for transfer type ink jet recording which reduces ink bleeding and beading on the surface, is excellent in transferability to a recording medium, and has high drying efficiency even when aqueous ink is used. There is.

  As a result of intensive studies, the present inventor has found that the structure shown below has excellent performance as a transfer-type inkjet recording intermediate transfer member, and has achieved the present invention. .

  That is, according to the present invention, an aqueous ink containing a color material component is subjected to ink jet recording on an image forming surface of an intermediate transfer body provided with an aggregate liquid that forms an aggregate upon contact with the color material component in the aqueous ink. An intermediate image forming step of forming an intermediate image by applying the method, and a transfer in which the recording medium is pressure-bonded to the intermediate transfer body on which the intermediate image is formed, and the intermediate image is transferred from the intermediate transfer body to the recording medium. An intermediate transfer body used in a transfer-type inkjet recording method having a step, wherein an image forming surface of the intermediate transfer body is a porous body obtained by biaxially stretching a resin containing polytetrafluoroethylene Provided is an intermediate transfer member characterized in that the contact angle of the aggregate liquid on the image forming surface is 90 ° or more and the contact angle of the water-based ink on the image forming surface is less than 90 °. By doing so, the above-described problems can be solved.

  According to the present invention, there is provided an intermediate transfer body for transfer type inkjet recording which reduces bleeding and beading of ink on the surface, has excellent transferability to a recording medium, and has high drying efficiency even when aqueous ink is used. be able to.

Schematic diagram showing structure of biaxially stretched porous body (a) Surface (b) Cross section Schematic diagram showing how microdroplets of agglomerated liquid are formed (a) Surface (b) Cross section Schematic diagram showing how the aggregate layer is formed (a) Surface (b) Cross section Schematic diagram showing the schematic configuration of a transfer type inkjet recording apparatus

  The contact angle in this specification refers to an angle formed between the surface of the intermediate transfer body and the tangent of the liquid droplet where the measurement liquid is dropped on the image forming surface of the intermediate transfer body and the liquid droplet is in contact with the intermediate transfer body. That is. There are several types of measurement techniques. In this specification, measurement is performed in accordance with the technique described in “6. Static Method” of JIS R3257.

  In the present specification, the “recording medium” refers not only to paper used in general recording apparatuses but also widely includes cloth, plastic, film and other printing media.

  As an inkjet device applied to the present invention, for example, a mode in which ink is ejected by forming a bubble by causing film boiling in the ink by an electro-thermal converter, a mode in which ink is ejected by an electro-mechanical converter, electrostatic There is a form of discharging ink using Any of various ink jet devices proposed in the ink jet liquid ejection technique can be used. Among these, those using an electro-thermal converter are preferably used from the viewpoint of high-speed and high-density printing.

  In the embodiment of the present invention, the image forming surface of the intermediate transfer member is composed of a porous material obtained by biaxially stretching a resin containing polytetrafluoroethylene. FIG. 1 schematically shows the structure of the image forming surface and its cross section. The porous body forms a specific three-dimensional network structure due to the stretching characteristics of polytetrafluoroethylene, and the surface has a fibrous portion 1 (called a fibril) and a bundling portion 2 (called a node) where the fibers are connected. ).

  The porous body used in the present invention is not particularly limited as long as it is obtained by biaxial stretching. As an example, a method for producing a porous material obtained by biaxially stretching a resin containing polytetrafluoroethylene is exemplified in Japanese Patent No. 1114442.

  There are various levels of the average fibril thickness and the average distance between nodes (≈average fibril length), which can be appropriately selected and used. In particular, the average fibril thickness is preferably 0.5 μm or less, more preferably 0.01 μm or more and 0.4 μm or less. The average node-node distance is preferably 1 μm or more and 10 μm or less, and the average node-node distance is more preferably 2 μm or more and 8 μm or less. If the fibrils are too thick or the average distance between nodes is too short, the air permeability may deteriorate and the drying rate may be slow. If the average distance between the nodes is too far, the ink may get stuck in the gap between the nodes and the transferability may be affected.

  The average fibril thickness referred to here is an average value of the diameters of the thinnest portions of the fibrous fibrils, and can be measured from an electron microscopic image of the surface. Of course, the larger the number of samples for calculating the average value, the better. However, if 100 or more fibrils are used for the calculation, an average value with sufficiently reliable accuracy can be obtained statistically. In order to obtain the average thickness of the fibrils in the present invention, first, an electron microscopic image obtained by photographing a 100 μm × 100 μm region of the surface of the porous body from the vertical direction is obtained. Subsequently, the width of each thinnest part of the fibrils (about 200 to 300) in the region is measured, and the average value is calculated in consideration of the scale of the microscope image.

  Similarly, the average distance between nodes, in other words, the average length of fibrils can be measured from the surface electron microscope image and the like. To do so, it is first necessary to define the boundary between the fibril and the node. In the present invention, the place where the width of the fibril is 1.1 times that of the narrowest part is defined as the boundary between the fibril and the node. Similarly to the above, an electron microscope image obtained by photographing a 100 μm × 100 μm region of the surface of the porous body from the vertical direction is obtained. Next, the boundary between the fibril and the node was defined for the fibrils in the region, the distance between them was measured, and the average value calculated in consideration of the scale of the microscopic image was taken as the average distance between the node and the node.

  Further, there is air permeability as a parameter characterizing the porous body. This means the volume through which a gas of unit pressure can pass through a porous body of unit area per unit time, and the larger the value, the more porous the gas passes through. Among them, the ISO air permeability [μm / Pa · s] is widely used, and is defined and generally used in JIS P8117. The air permeability referred to in this specification is the ISO air permeability.

  A porous body having an ISO air permeability of 4 μm / Pa · s or more can be suitably used in the present invention. If the air permeability is too low, the air permeability may deteriorate and the drying speed may be slow. Preferably it is 6 micrometers / Pa * s or more, More preferably, it is 8 micrometers / Pa * s or more. Moreover, it is preferably 100 μm / Pa · s or less. If it exceeds 100 μm / Pa · s, the strength of the porous body may be insufficient.

  A porous body obtained by biaxially stretching a resin containing polytetrafluoroethylene according to the present invention is extremely simple in production and low in production cost as compared with a foam of the same material. In addition, because of its unique three-dimensional structure, the shape hardly changes even during continuous use compared to the foam, and it has very high reliability even during repeated operation.

  A porous body of resin containing polytetrafluoroethylene can also be obtained by uniaxial stretching. However, in that case, the area of the node portion is large, and a structure in which the fibrils are oriented in substantially the same direction tends to be obtained. In such a structure, a portion having poor drying efficiency is generated in the surface, or the ink is deformed / flows according to the fibril arrangement, causing beading or the like.

  In the present invention, the aggregation liquid 3 is formed on the image forming surface of the intermediate transfer body so as to contact the color material component in the ink to form an aggregate. This state is schematically shown in FIG. At this time, since the contact angle of the aggregated liquid 3 on the image forming surface is 90 ° or more, the aggregated liquid 3 does not spread in a plane but forms a grain shape. Specifically, the microdroplets of the aggregate liquid 3 are formed in the fibril 1 or the node 2 so as to be clumped in a granular form. For this reason, the aggregating liquid 3 does not easily permeate into the porous body forming the image forming surface of the intermediate transfer member, and remains in the vicinity of the porous surface. When the contact angle of the aggregate liquid is less than 90 °, it is difficult to stay near the porous surface. For this reason, the flocculated liquid is likely to penetrate into the porous body, and therefore the flocculated liquid cannot exhibit a sufficient effect.

  The image forming surface refers to all surfaces on which an intermediate image can be formed on the intermediate transfer member.

  In order for the aggregating liquid to exhibit the effect sufficiently, the contact angle on the image forming surface of the intermediate transfer member is preferably 95 ° or more, and more preferably 100 ° or more. Moreover, it is preferable that it is 170 degrees or less, and it is more preferable in it being 150 degrees or less.

  At this time, if the amount of the aggregation liquid applied is too large, problems such as an increase in drying time and an ink moving on the aggregation liquid may disturb the image. For this reason, the application amount of the aggregation liquid is preferably 50% or less, more preferably 20% or less, as a projected coating area occupying the surface. Moreover, it is preferable to set it as 2% or more.

  The aggregation liquid contains a color material aggregation component that aggregates the color material components. Aggregation of the color material component mentioned here means that a color material such as pigment or dye contained in the ink, or a resin adsorbed to the color material reacts chemically with the color material aggregation component or is physically adsorbed. The formation of aggregates. This aggregate formation rate is extremely fast, resulting in a local increase in viscosity.

  The color material aggregation component to be used can be appropriately selected depending on the type of ink used for image formation. For example, a polymer flocculant is preferably used for dye-based inks, and a liquid containing metal ions is preferable for pigment-based inks in which fine particles are dispersed. As another example, a pH adjuster such as an acid buffer may be used, or a compound having a plurality of ionic groups such as a cationic polymer may be used.

Examples of the above-mentioned polymer flocculant include a cationic polymer flocculant, an anionic polymer flocculant, a nonionic polymer flocculant, and an amphoteric polymer flocculant. Specific examples of metal ions include divalent metal ions such as Ca ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg ²⁺ and Zn ^2+, and trivalent metal ions such as Fe ³⁺ and Al ³⁺ . In particular, it is preferable to use a divalent metal. In addition, when using the liquid containing these metal ions, it is desirable to use metal salt aqueous solution. Examples of the anion (counter ion) of the metal salt include Cl ⁻ , NO ₃ ⁻ , SO ₄ ²⁻ , I ⁻ , Br ⁻ , ClO ₃ ⁻ , RCOO ⁻ (R is an alkyl group) and the like.

  The metal salt concentration of the metal salt aqueous solution is preferably 0.01% by mass or more, and more preferably 0.1% by mass or more. Moreover, 20 mass% or less is preferable.

  Moreover, in order to improve the fastness of the finally formed image, the following various resins can be added to the aggregating liquid. By adding a resin, it is possible to increase the mechanical strength of the ink film, and depending on the type, the water resistance of the image can also be improved. For example, polyvinyl alcohol, polyvinyl pyrrolidone and the like are preferably used.

  In addition, the conventionally well-known various methods can be used suitably for the method of providing an aggregating liquid. Examples include die coating, blade coating, gravure roller, and a combination of these with an offset roller. It is also extremely suitable to use an ink jet device as a technique that can be applied at high speed and high accuracy.

  The aggregating liquid can be used by appropriately adjusting the contact angle by adding a surfactant.

  As the surfactant, known substances such as ionic, nonionic, cationic and anionic can be appropriately selected and used as necessary. However, it goes without saying that certain surfactants adversely affect the aggregate liquid and ink and may adversely affect aggregate formation.

  Subsequently, an aqueous ink is applied using an inkjet device onto the intermediate transfer body to which the aggregation liquid has been applied. A state where the water-based ink is applied is schematically shown in FIG.

  As the water-based ink, it is possible to use inks that are widely used as inkjet inks, specifically, various inks in which dyes and pigments are dissolved and / or dispersed. Among them, the pigment ink is particularly suitable because an image having good weather resistance and color developability can be obtained.

  A water-based ink refers to an ink whose main component is water. In particular, an ink containing 45% or more of moisture in the component is preferable, but any ink that forms an aggregate upon contact with the aggregation liquid when applied onto the transfer body can be used.

  Further, the water-based ink preferably has a color material content of 0.1% or more, and more preferably 0.2% or more. Moreover, it is preferable that it is 15.0% or less, and it is more preferable that it is 10.0% or less.

  The coloring material component forming the aggregate includes dyes, pigments, and accompanying resins, and the following can be used.

  Examples of the dye include C.I. I. Direct Blue 6, 8, 22, 34, 70, 71, 76, 78, 86, 142, 199, C.I. I. Acid Blue 9, 22, 40, 59, 93, 102, 104, 117, 120, 167, 229, C.I. I. Direct Red 1, 4, 17, 28, 83, 227, C.I. I. Acid Red 1, 4, 8, 13, 14, 15, 18, 21, 26, 35, 37, 249, 257, 289, C.I. I. Direct Yellow 12, 24, 26, 86, 98, 132, 142, C.I. I. Acid Yellow 1, 3, 4, 7, 11, 12, 13, 14, 19, 23, 25, 34, 44, 71, C.I. I. Food Black 1, 2, C.I. I. Acid Black 2, 7, 24, 26, 31, 52, 112, 118 and the like.

  Examples of the pigment include C.I. I. Pigment blue 1, 2, 3, 15, 16, 22, C.I. I. Pigment red 5, 7, 12, 48, 57, 112, 122, C.I. I. Pigment yellow 1, 2, 3, 13, 16, 83, C.I. I. Pigment Black 1, 6, 7, 8, 9, Channel Black, Furnace Black, MCF88 (manufactured by Mitsubishi Kasei), RAVEN 1255 (manufactured by Colombia), REGAL330R (manufactured by Cabot), ColorBlack FW1, FW18, S170, S150, Printex35 (manufactured by Degussa) Etc.

  These pigments are not limited in form, and for example, any of self-dispersion type, resin dispersion type, microcapsule type and the like can be used. As the pigment dispersant used in this case, a water-soluble dispersion resin having a weight average molecular weight of about 1000 to 15000 can be preferably used. Specific examples include water-soluble vinyl resins, styrene and derivatives thereof, vinyl naphthalene and derivatives thereof, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, acrylic acid and derivatives thereof, maleic acid and derivatives thereof, Examples thereof include itaconic acid and its derivatives, fumaric acid and its block copolymers or random copolymers, and salts thereof.

  In order to improve the fastness of the finally formed image, a water-soluble resin or a water-soluble crosslinking agent can be added. The material used is not limited as long as it can coexist with the ink component. As the water-soluble resin, the dispersion resin exemplified above can be used as it is. As the water-soluble crosslinking agent, oxazoline and carbodiimide are preferably used in terms of ink stability. In addition, reactive oligomers such as polyethylene glycol diacrylate and acryloylmorpholine can also be suitably used.

  An appropriate amount of a non-aqueous solvent can be contained in the aqueous liquid medium constituting the ink together with the above-described color material for the purpose of stabilizing the ejection of the ink jet device and improving the transferability.

  For the ejection stability of the ink jet device, alcohols such as ethyl alcohol and isopropyl alcohol and surfactants are suitable.

  In order to improve transferability, polyethylene glycol, polypropylene glycol, ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, thiodiglycol, hexylene glycol, diethylene glycol, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, glycerin, etc. A water-soluble material having a boiling point and a low vapor pressure is preferred.

  Of course, a mixture of two or more selected from these can also be used.

  The blending ratio of the components constituting the ink is not limited, and can be appropriately prepared within a dischargeable range from the discharge force, nozzle diameter, and the like of the selected inkjet head. In general, it is possible to use an ink in which the color material is 0.1 to 10%, the non-aqueous solvent is 5 to 45%, and the remainder is adjusted with ion-exchanged water on a mass basis.

  When such water-based ink 4 is applied to the image forming surface of the intermediate transfer body to which the aggregate liquid 3 is applied using an inkjet device, the aggregate liquid 3 and the ink 4 are formed on the surface of the fibril 1 or the node 2. Come into contact with each other to form an aggregate 5. This formation rate is extremely higher than the diffusion rate of the color material aggregation component and the flow rate of the ink into the porous body. Therefore, as schematically shown in FIG. 3, the presence of the aggregate 5 makes it difficult for the water-based ink 4 to penetrate into the porous body. Accordingly, as a result, almost all of the color material forming the intermediate image is arranged in the vicinity of the surface of the image forming surface. This is presumed to be one of the causes for the mechanism of expressing excellent transcription.

  On the other hand, the water-based ink 4 as a whole comes in contact with the granular aggregate 3 partially, but also comes into contact with the exposed fibrils 1 and nodes 2, and the ink 4 has a droplet shape with an original contact angle of less than 90 °. Form. Accordingly, the contact area and the surface area are increased, and as a result, the ink is difficult to move even during high-speed printing, leading to a reduction in image disturbance. Further, the increase in the surface area contributes to the improvement of the drying rate, which is a problem found by the inventors.

  By adopting the aspect of the present invention, it is assumed that the surface area of the ink is increased and the outside air with good replacement efficiency can be touched, so that drying can be performed quickly.

  As described above, the present inventor has found for the first time that the ink having a contact angle of less than 90 ° can be formed by taking the embodiment of the present invention and suppressing the penetration of the ink into the porous body. The contact angle on the surface of the intermediate transfer member is preferably 80 ° or less, and more preferably 70 ° or less, in order for the water-based ink to exhibit an appropriate effect. Further, it is preferably 5 ° or more, and more preferably 10 ° or more. This configuration is extremely effective in resolving the contradiction described above.

  Moreover, since the drawing area with respect to the applied ink amount is increased by adopting the aspect of the present invention, the ink consumption amount can be suppressed even when a high-density image is printed. At the same time, since the number of applied inks can be reduced, the load on the ink jet device is reduced.

  Needless to say, when an intermediate image is formed, an image (mirror image) in which a desired image is inverted is formed on the intermediate transfer member.

  It is also preferable to provide a step of reducing moisture by drying from the intermediate image. Insufficient drying of the image may cause excess liquid to overflow or overflow in the subsequent pressure-transfer transfer process, thereby disturbing the image or causing a transfer failure.

  Any of various conventionally used methods can be suitably applied as the drying method. Any of a method by heating, a method of blowing low-humidity air, a method of reducing pressure, and a method of combining these are preferably used. It is also possible to carry out by natural drying.

  In the intermediate transfer member of the present invention, since the inside of the porous body and the outside air communicate with each other through a large number of holes, water vapor generated inside the porous body is likely to diverge to the outside air. This point is also considered to be one of the factors that enable quick drying.

  Thereafter, a recording medium is pressure-bonded to the image, and the image is transferred from the intermediate transfer member to the recording medium, thereby obtaining an image printed matter.

  In this case, it is preferable to apply pressure from both sides of the intermediate transfer member and the recording medium using a pressure roller because an image is efficiently transferred and formed.

  As an additional step, the recording medium on which the post-transfer image recording has been performed may be pressurized with a fixing roller to enhance the surface smoothness. In this case, if the fixing roller is heated, the fastness of the image may be improved, which is also preferable.

  Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples of an intermediate transfer member for transfer type inkjet recording according to the present invention. Of course, the present invention is not limited to the following examples.

  FIG. 4 shows an ink jet recording method in which an aqueous ink containing a color material component is applied to an image forming surface of an intermediate transfer body to which an aggregation liquid that forms an aggregate upon contact with the color material component in the aqueous ink is applied. An intermediate image forming step of forming an intermediate image by applying, and a transfer step of pressing the recording medium onto the image forming surface on which the intermediate image is formed and transferring the intermediate image from the image forming surface to the recording medium It is a schematic diagram of an example of this invention which has these.

  In FIG. 4, the intermediate transfer body 11 is held on a rotatable cylindrical support member 12. The support member 12 is driven to rotate in the direction of the arrow about the shaft 13, and each device arranged in the periphery operates in synchronization with the rotation.

  In this configuration, in addition to rigidity and dimensional accuracy that can withstand pressurization during transfer, characteristics required for reducing rotational inertia and improving control responsiveness, etc., from lightweight metals such as aluminum alloys A cylindrical drum is used as the support member 12 of the intermediate transfer member.

  However, as the support member for the intermediate transfer member, for example, a roller-like or belt-like one can be suitably used according to the form of the recording apparatus to be applied or the transfer to the recording medium.

  In any case, if a drum-like support member or a belt-like endless web-structured support member is used, the same intermediate transfer member can be used continuously and repeatedly. It becomes.

  In addition, although illustration is abbreviate | omitted for simplification of description, various adhesive materials and double-sided tape for holding a transfer body may exist between an intermediate transfer body and a supporting member. Similarly, an elastic body (such as a rubber sheet) for absorbing impact and imparting elasticity may exist between the intermediate transfer member and the support member.

  In this configuration, a roller-type coating device 14 is disposed as a device for applying the aggregation liquid. As a result, the aggregation liquid is continuously applied to the surface of the image forming surface of the intermediate transfer member. In this example, the amount of aggregation liquid applied was adjusted so as to be 10 to 12% as the projected coating area occupied on the surface.

In this example, an aqueous solution of a metal salt, specifically a 10% by mass aqueous solution of calcium chloride (CaCl ₂ · 2H ₂ O) was used as the aggregating liquid. The same applies to the water-based ink described later, but a surfactant was appropriately added to adjust the surface tension. In addition, a metal seed | species and density | concentration can be suitably changed according to conditions.

  Next, ink for image formation is ejected from the inkjet device 15, and an intermediate image (image that is mirror-reversed) is formed on the intermediate transfer body 11. In this configuration, a device of an ink discharge type using an on-demand method using an electro-thermal conversion element is used.

  In addition, as a form of the ink jet device, an ink jet head of a line head form in which ink discharge ports are arranged in the axial direction of the intermediate transfer member (direction orthogonal to the drawing) can also be used.

In this example, a resin-dispersed pigment ink was prepared and used as the ink. The composition is shown below.
("Part" is part by mass)
Pigment coloring material: C.I. I. Pigment Blue 15 3 parts Dispersing resin: Styrene-acrylic acid-ethyl acrylate copolymer (acid value 240, weight average molecular weight 5000) 1 part non-aqueous solvent 1: glycerin 10 parts non-aqueous solvent 2: ethylene glycol 5 parts water ( (Ion-exchanged water): 81 parts In this configuration, the blower 16 is disposed to dry the image on the image forming surface. At the same time, a heater 17 for heating from the back side of the intermediate transfer member is also arranged. Thereby, the moisture of the image is dried, and the disturbance of the image at the time of transfer is suppressed.

  A pressure roller 19 is arranged to bring the recording medium 18 into contact with the dried image on the image forming surface and transfer and form the image. In this configuration, the support member 12 and the pressure roller 19 are pressed so as to sandwich the intermediate transfer body 11 and the recording medium 18, thereby realizing efficient image transfer.

  In this example, a surface hydrophilized pet film (thickness 150 μm) was used as a recording medium. In this example, a long and roll sheet is used as the shape of the recording medium. However, a sheet cut into a prescribed shape may be used.

  Further, in this configuration, the cleaning unit 20 is arranged so that the intermediate transfer body after the intermediate image is transferred to the recording medium is repeatedly used for the next image formation. In the present exemplary apparatus, a Morton roller that is constantly moistened with ion-exchanged water is configured to intermittently contact the surface.

  In the configuration as described above, Examples 1 to 7 and Comparative Examples 1 to 5 according to the present invention were performed. As the intermediate transfer member in each example, an intermediate transfer member having a porous body on the surface obtained by biaxially stretching different polytetrafluoroethylene in each example was used. The porous bodies used in each example show different properties because the conditions during the biaxial stretching process are different. In Example 1, a Temisch porous material manufactured by Nitto Denko Corporation was used as an intermediate transfer material. In other examples, a porous material manufactured by the same company was used as an intermediate transfer member. Contact angle formed between the image forming surface of the intermediate transfer member and the aggregate liquid or ink, the average thickness of the fibrils of the porous body, the average distance between nodes of the porous body, the ISO air permeability of the porous body Are shown in Tables 1 and 2, respectively. The contact angles on the image forming surface of the aggregating liquid in this example and the ink in this example were measured in accordance with JIS R3257 sessile drop method. In the other examples and comparative examples, the contact angles were measured in the same manner. In this example, the same aggregation liquid and ink are used in all the examples and comparative examples. Under the conditions described above, the ease of bleeding and beading on the transfer material, transferability, and drying efficiency were evaluated according to the following criteria. The evaluation was made visually.

<Evaluation criteria>
Ease of occurrence of bleeding beading on the transfer body A: Bleeding beading is not visible B: Bleeding beading is slightly seen C: Bleeding beading is partially seen Less than half D ... Bleeding beading is seen in about half of the area E ... Bleeding beading is seen almost in the whole area Transferability A ... Color on the intermediate transfer body after transfer The remaining of the material cannot be visually observed. B: The color material remains slightly on the intermediate transfer body after transfer. C: The color material remains on the intermediate transfer body after transfer. Not reached D: About half of the color material remains on the intermediate transfer body after transfer E: Most color material remains on the intermediate transfer body after transfer Drying efficiency A: 5 seconds Less than Sufficient moisture is dried B ... Sufficient moisture is dried in 5 seconds to less than 10 seconds C ... Sufficient moisture is dried in 10 seconds to less than 20 seconds D ... Sufficient moisture in 20 seconds to less than 30 seconds E ... Drying of moisture is insufficient even after 30 seconds

  Tables 1 and 2 show the levels of the examples and comparative examples and the evaluation results.

  In Examples 1 to 7, good results were obtained in both transferability and drying efficiency.

  However, in Comparative Example 1 in which a uniaxially stretched porous body was used for the intermediate transfer body, the image quality was lower than that in the case of using a biaxially stretched porous body. Even in Comparative Examples 2 and 3 having a small contact angle of the aggregate liquid, the image quality was not good. Even in Comparative Examples 4 and 5 having a large ink contact angle, the image quality was not good.

  According to the present invention, it is possible to provide an intermediate transfer body for transfer type ink jet recording which reduces bleeding and beading of ink on the surface, has excellent transferability to a recording medium, and has high drying efficiency even when aqueous ink is used. Can do.

Claims (5)

By applying an aqueous ink containing a color material component to an image forming surface of an intermediate transfer body provided with an aggregating liquid in contact with the color material component in the aqueous ink to form an aggregate by an ink jet recording method. A transfer mold having an intermediate image forming step of forming an image, and a transfer step of pressing the recording medium onto the image forming surface on which the intermediate image is formed and transferring the intermediate image from the image forming surface to the recording medium An intermediate transfer member for use in an inkjet recording method,
The image forming surface is formed of a porous body obtained by biaxially stretching a resin containing polytetrafluoroethylene, and the contact angle of the aggregate liquid on the image forming surface is 90 ° or more. An intermediate transfer member for transfer type ink jet recording, wherein the contact angle of the water-based ink on the image forming surface is less than 90 °.   2. The intermediate transfer member for transfer type ink jet recording according to claim 1, wherein an average thickness of fibrils of the porous body is 0.5 μm or less.   The intermediate transfer member for transfer type ink jet recording according to claim 1 or 2, wherein an average distance between nodes of the porous body is 1 µm or more and 10 µm or less.   The transfer type inkjet recording intermediate transfer body according to any one of claims 1 to 3, wherein the porous body has an air permeability of 4 µm / Pa · s or more. An intermediate image is formed by applying an aqueous ink containing a color material component to an image forming surface of an intermediate transfer body to which an aggregate liquid is formed in contact with the color material component in the aqueous ink to form an aggregate. A transfer type ink jet comprising: an intermediate image forming step for forming the intermediate image; and a transfer step for pressing the recording medium onto the image forming surface on which the intermediate image is formed and transferring the intermediate image from the image forming surface to the recording medium. A recording method,
Using a porous body obtained by biaxially stretching a resin containing polytetrafluoroethylene on the image forming surface,
An inkjet recording method, wherein the contact angle of the aggregate liquid on the image forming surface is 90 ° or more, and the contact angle of the water-based ink on the image forming surface is less than 90 °.