JP2023168783A - Transfer body, laminate, package, and method for manufacturing transfer body - Google Patents

Abstract

To provide a transfer body capable of suppressing change in image quality between in an image formed immediately after use and an image formed after repeated use of the transfer body used in a recording method in which a layer containing wax is formed on the transfer body.SOLUTION: There is provided a transfer body 20 including: a base layer 22; and a surface layer 21. The surface layer 21 includes a permeation region 24 of a component (A) in wax, and contains the component (A) at least in an outermost surface. There are also provided: a laminate including the transfer body 20 and a cover member covering a surface of a permeation region 24 of the transfer body; a package including the transfer body 20, and a sealable container for housing the transfer body 20; and a package including the laminate, and a sealed container for housing the laminate.SELECTED DRAWING: Figure 2

Description

The present invention relates to a transfer body used in an inkjet recording device, a laminate that protects the transfer surface of the transfer body, a package containing the transfer body or the laminate, and a method for manufacturing the transfer body.

2. Description of the Related Art A transfer type inkjet recording apparatus is known that forms an intermediate image by ejecting ink from an inkjet head onto an image forming surface of a transfer body, and transfers the intermediate image formed on the transfer body to a recording medium. In order to improve the transferability of an intermediate image formed on a transfer body to a recording medium, it has been proposed to apply ink or processing liquid containing a wax component. Patent Document 1 discloses a recording method that further includes a surface treatment liquid application step of applying a surface treatment liquid to a portion of an intermediate transfer member to which ink is to be applied, prior to the ink application step. The surface treatment liquid contains one or more waxes selected from the group consisting of polyolefin wax, ethylene vinyl acetate wax, and carnauba wax.
An intermediate image containing wax exhibits excellent transferability by being heated above the melting point of the wax and transferred to a recording medium.
On the other hand, the transfer body used in an inkjet recording device gradually deteriorates due to contact with the recording medium when transferring an image from the transfer body to the recording medium, and contact with various members included in the inkjet recording device. . For this reason, in many cases, the transfer member is configured to be detachable from the recording apparatus, and is replaced with a new transfer member as appropriate depending on the usage status of the transfer member.

JP 2014-8609 Publication Japanese Patent Application Publication No. 2005-234127

However, according to studies by the present inventors, even when some layer is formed on the transfer body during the recording process as described in Patent Document 1, the recording There may be differences in image quality. (Hereinafter referred to as "change in image quality at the initial stage of use"). On the other hand, even if a surface protective layer as described in Patent Document 2 is provided on the surface of an inkjet transfer body, damage to the surface during storage and transportation can be suppressed, but the above-mentioned change in image quality occurs at the beginning of use. It couldn't be suppressed.

Therefore, an object of the present invention is to provide an inkjet transfer member that can suppress changes in image quality at the initial stage of use, regardless of whether or not it is stored or transported.
Another object of the present invention is to provide a laminate that protects the transfer surface of the transfer body, a package containing the transfer body or the laminate, and a method for manufacturing the transfer body.

According to one aspect of the present invention, there is provided a transfer body that forms an intermediate image on its surface and transfers the intermediate image to a recording medium, wherein the intermediate image includes a layer containing wax formed on the surface of the transfer body. The transfer body has a surface layer on which a layer containing the wax is formed, and the surface layer has a permeation region of the component (A) in the wax before using the transfer body. There is provided a transfer body characterized in that the layer has a layer extending from the surface toward the thickness direction.
According to another aspect of the present invention, there is provided a laminate including the transfer body and a cover member, wherein the cover member covers the surface of the permeation region of the component (A) of the surface layer. Provided is a laminate characterized in that:
According to still another aspect of the present invention, there is provided a package comprising the transfer body or the laminate, and a sealed container that accommodates the transfer body or the laminate.

Further, the transfer body according to the present invention includes a step of heating the surface layer before containing the component (A) and the component (A) to a temperature higher than the melting point of the component (A), and It can be manufactured by a manufacturing method characterized by comprising a step of applying component (A) and a step of infiltrating the component (A) into the surface layer under heating.

According to one aspect of the present invention, it is possible to provide a transfer body for inkjet use that can suppress changes in image quality at the beginning of use. Further, the present invention can provide a laminate including the transfer body, and a package including the transfer body or the laminate, thereby preventing contamination and damage of the transfer body.

FIG. 1 is a schematic diagram showing an embodiment of an inkjet recording apparatus. FIG. 2 is a schematic cross-sectional view in the thickness direction showing one embodiment of a transfer body. FIG. 2 is a schematic cross-sectional view in the thickness direction showing one embodiment of a laminate. FIG. 2 is a schematic cross-sectional view in the thickness direction showing one embodiment of a package.

The present invention will be described in detail below by citing preferred embodiments.
In the present invention, an inkjet recording method, an inkjet recording apparatus, and an inkjet transfer body may be simply referred to as a "recording method," a "recording apparatus," and a "transfer body," respectively. Physical property values are values at room temperature (25° C.) unless otherwise specified. "(meth)acrylic acid" and "(meth)acrylate" mean "acrylic acid, methacrylic acid" and "acrylate, methacrylate," respectively.

The present inventors have confirmed in detail the state of the transfer body immediately after the start of use and after repeated use, regarding changes in image quality in a recording method in which a layer containing wax is formed on the transfer body. As a result, it was found that one of the causes of the change in image quality at the initial stage of use is the penetration of the components contained in the wax into the surface layer of the transfer body. In other words, immediately after the start of use, most of the wax applied to the surface layer of the transfer body permeates into the surface layer, so the amount of wax remaining on the surface layer is small, but after repeated use, the amount of wax applied to the surface layer is reduced. Most of the wax will remain on the surface layer. In other words, even if the same amount of wax is applied, there will be a difference in the thickness of the wax layer formed at the beginning of use and after repeated use. Therefore, the amount of wax on the surface layer changes immediately after the start of use and after repeated use. As a result, the amount of wax (wax layer thickness) on the recording medium after transfer also varies, resulting in changes in image quality such as density and gloss.
A possible solution to this problem is to change the amount of wax applied immediately after use and after repeated use, but it is difficult to maintain a constant amount of wax absorbed immediately after use. Furthermore, it is not easy to make the amount of absorption uniform over the entire surface. Therefore, the amount of wax applied should be constant. Another option is to use a transfer body that does not absorb wax, but it may be difficult to retain the solidified wax, and the ink image may shift or fall off while the transfer body is rotating. Sometimes.
Note that wax has a lower molecular weight than the resin contained in the ink, and often has a lower melting point. On the transfer body, the wax permeates into the surface layer of the transfer body and exerts an anchoring effect to prevent shifting or falling off during image formation.

Therefore, in the present invention, in a transfer body used in a recording method in which a layer containing wax is formed on the transfer body, the surface layer of the transfer body is made to contain the component (A) in the wax in advance. When the transfer body is used, the transfer body is attached to an inkjet recording device. This makes it possible to suppress changes in the amount of wax on the surface layer, even if the amount of wax applied to the surface layer remains constant from the time the transfer body starts to be used until it is repeatedly used. We were able to suppress changes in image quality until later.

<Inkjet recording device>
FIG. 1 is a schematic diagram showing an embodiment of a transfer type inkjet recording apparatus suitable for a recording method using a transfer body according to the present invention.
A transfer type inkjet recording apparatus 100 shown in FIG. 1 is an inkjet recording apparatus that transfers an intermediate image onto a recording medium 108 via a transfer body 101 to produce a recorded matter. For convenience of explanation, in the inkjet recording apparatus (recording apparatus) shown in FIG. There is. The recording medium 108 is conveyed in the X direction.
This recording device 100 includes a transfer body 101, a support member 102, a wax application device 110, a reaction liquid application device 103, an ink application device 104, a heating device 105, and a pressing member 106. The transfer body 101 is supported by a support member 102 and can be attached to and detached from the support member 102. The wax application device 110 is a device that applies wax onto the transfer body 101 to form a wax layer with a predetermined thickness. The reaction liquid applying device 103 is a device that applies a reaction liquid containing a reactant that reacts with ink to the transfer body 101. The ink applying device 104 includes a recording head that applies ink to the transfer body 101 to which the reaction liquid has been applied to form an intermediate image. The liquid removal device 105 is a device that removes liquid components from the intermediate image on the transfer body. The pressing member 106 is a member for transferring the intermediate image from which the liquid component has been removed onto a sheet-like recording medium 108 such as paper. Further, the recording apparatus 100 may include a transfer body cleaning member 109 that cleans the surface of the transfer body 101 after the transfer, if necessary. As a matter of course, the transfer body 101, the reaction liquid application device 103, the inkjet head of the ink application device 104, the liquid removal device 105, the transfer body cleaning member 109, and the wax application device 110 are used for recording, respectively, in the Y direction. It has a length corresponding to the medium 108.

The transfer body 101 rotates in the direction of arrow A in FIG. 1 around the rotation axis 102a of the support member 102. As shown in FIG. This rotation of the support member 102 causes the image forming area of the transfer body 101 to move in the circumferential direction. A reaction liquid is sequentially applied onto the rotating transfer body 101 by a reaction liquid applying device 103 and ink is applied by an ink applying device 104, so that an ink image is formed on the transfer body 101. The ink image formed on the transfer body 101 is moved to the liquid removal device 105 by rotation of the transfer body 101. The ink image passes through a position where the liquid is removed by the liquid removal device 105, thereby removing the liquid and becoming an intermediate image suitable for transfer. The intermediate image from which the liquid component has been removed has more concentrated ink than the ink image before liquid removal, and is further transferred by the transfer body 101 to a transfer section that comes into contact with the recording medium 108 conveyed by the recording medium conveyance device 107. Moved to 111. While the intermediate image after the liquid is removed is in contact with the recording medium 108, the pressing member 106 presses the intermediate image in the direction of the transfer body 101, thereby transferring the intermediate image onto the recording medium 108. The image transferred onto the recording medium 108 (referred to as a transferred image) is an inverted image of the intermediate image before transfer. Since the wax layer is formed on the surface layer of the transfer body, the intermediate image on the transfer body can be transferred onto the recording medium with good releasability.

Each configuration of the recording apparatus 100 will be described below.
<Wax application device>
The recording apparatus 100 of this embodiment includes a wax application device 110 that forms a wax layer on the transfer body 101. The wax application device 110 in FIG. 1 is a gravure offset roller having a wax storage section 110a that stores wax and wax application members 110b and 110c that apply the wax in the wax storage section 110a onto the transfer body 101. .
The wax application device may be any device that can apply wax onto the transfer body, and various conventionally known devices can be used as appropriate. Specifically, in addition to the illustrated gravure offset roller, examples include an inkjet head, a die coating device (die coater), a blade coating device (blade coater), and the like.
It is preferable to apply the wax in a molten state, and the wax is heated to a temperature higher than the melting point of the wax in the wax storage portion 110a to melt it. By setting the temperature of the transfer body at the time of wax application to be lower than the melting point of the wax, it becomes possible to form a thin wax layer while solidifying the wax.

<Wax>
In a strict chemical sense, wax refers to esters of fatty acids and water-insoluble higher monohydric alcohols or dihydric alcohols, but wax in the present invention broadly refers to the following: show.
The type of wax that can be used in this embodiment is not particularly limited. Specific examples of wax include natural waxes such as beeswax, lanolin, carnauba wax, candelilla wax, and montan wax; petroleum waxes such as paraffin wax and microcrystalline wax; Fischer-Tropsch wax, polyethylene wax, and polypropylene. Synthetic waxes such as wax and oxidized wax; modified waxes such as urethane-modified waxes and alcohol-modified waxes; and α-olefin-maleic anhydride copolymer waxes. These waxes may be used alone or in combination of two or more, if necessary.
In this embodiment, by forming wax between the ink layer and the transfer body, transfer performance and blocking resistance can be improved.
The wax contains a component (A) that can permeate into the surface layer of the transfer body, as described below.

<Reaction liquid application device>
The recording apparatus 100 of this embodiment includes a reaction liquid applying device 103 that applies a reaction liquid to the transfer body 101. The reaction liquid application device 103 in FIG. 1 includes a reaction liquid storage section 103a that stores a reaction liquid, and reaction liquid application members 103b and 103c that apply the reaction liquid in the reaction liquid storage section 103a onto the transfer body 101. The case of a roller is shown.
The reaction liquid application device may be any device that can apply the reaction liquid onto the transfer body, and various conventionally known devices can be used as appropriate. Specifically, in addition to the gravure offset roller, examples include an inkjet head, a die coating device (die coater), a blade coating device (blade coater), and the like. Application of the reaction liquid by the reaction liquid application device may be performed before or after application of the ink, as long as it can be mixed (reacted) with the ink on the transfer body. Preferably, the reaction liquid is applied before the ink is applied. By applying the reaction liquid before applying the ink, during image recording using the inkjet method, problems such as bleeding, where adjacently applied inks mix with each other, and ink that lands first being attracted to ink that lands later, can be avoided. It is also possible to suppress dings.

<Reaction solution>
The reaction liquid is a liquid that aggregates components having anionic groups (resin, self-dispersing pigment, etc.) in the ink when it comes into contact with the ink, and contains a reactant. Examples of the reactant include polyvalent metal ions, cationic components such as cationic resins, and organic acids. Among these, the reactant is preferably an organic acid, and more preferably a divalent or higher polycarboxylic acid (which may be a salt or a hydrogen salt).

The reaction solution may contain other components other than the reactant, if necessary. Other components that can be used include water, water-soluble organic solvents, and other additives that can be used in the ink described later.

<Ink application device>
The recording apparatus 100 shown in FIG. 1 includes an ink application device 104 that is an ink application unit that applies ink to the transfer body 101. It is preferable to use an inkjet recording head as the ink applying device to eject and apply ink. As a recording head, for example, a type that ejects ink by causing film boiling in the ink and forming bubbles using an electro-thermal converter; a type that ejects ink using an electro-mechanical converter; and a type that ejects ink using electrostatic electricity. Examples include a form of discharging . Among these, a recording head using an electrothermal converter is preferred because it can record images with higher speed and higher density.
The recording head has an ejection port surface in which ejection ports are opened on its lower surface (transfer body 101 side). The ejection port face faces the surface of the transfer body 101 with a small gap (about several millimeters) therebetween.
The ink applying device 104 may have a plurality of recording heads in order to apply ink of each color such as cyan, magenta, yellow, and black (CMYK) to the transfer body 101. For example, when forming an intermediate image using four types of CMYK inks, the ink applying device has four recording heads that eject each of the four types of CMYK inks. These recording heads are arranged along the X direction.
The recording head can be a full-line head in which ejection ports are arranged in a range that covers the width of the image recording area of the largest usable recording medium in the Y direction.
In addition to inks containing coloring materials such as cyan, magenta, yellow, and black, a liquid (transfer promoting liquid) for promoting the transfer of the ink to the recording medium may be used. The means for applying the transfer accelerator liquid to the transfer body is not particularly limited, but it is preferable to apply the transfer accelerator liquid by discharging it using an inkjet recording head like ink. Therefore, a transfer accelerator liquid application device can be included in the ink application device 104. It is preferable that the area to which the transfer accelerator liquid is applied to the transfer member includes at least the area to which ink is applied. That is, it is preferable to apply the ink and the transfer accelerator liquid in layers.

[ink]
The ink used in the recording method is preferably an aqueous inkjet ink containing a coloring material. Each component used in the ink will be described in detail below.

(color material)
Pigments and dyes can be used as the coloring material contained in the ink. The content (mass%) of the coloring material in the ink is preferably 0.5% by mass or more and 15.0% by mass or less, and 1.0% by mass or more and 10.0% by mass, based on the total mass of the ink. It is more preferable that it is the following.
Specific examples of pigments include inorganic pigments such as carbon black and titanium oxide; organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole, and dioxazine.
As the dye, it is preferable to use one having an anionic group. Specific examples of dyes include dyes such as azo, triphenylmethane, (aza)phthalocyanine, xanthene, and anthrapyridone. The coloring material contained in the ink used in the inkjet recording method is preferably a pigment, and more preferably a resin-dispersed pigment.

(resin)
The ink can contain a resin. The content (mass%) of the resin in the ink is preferably 0.1% by mass or more and 20.0% by mass or less, and 0.5% by mass or more and 15.0% by mass or less, based on the total mass of the ink. It is more preferable that
The resin can be added to the ink in order to (i) stabilize the dispersion state of the pigment, that is, as a resin dispersant or its aid. Further, (ii) it can be added to ink in order to improve various characteristics of the recorded image. Examples of the form of the resin include block copolymers, random copolymers, graft copolymers, and combinations thereof. Further, the resin may be a water-soluble resin that can be dissolved in an aqueous medium, or may be resin particles that are dispersed in an aqueous medium. The resin particles do not need to contain coloring material.
Examples of the resin include acrylic resin, urethane resin, and olefin resin. Among these, acrylic resins and urethane resins are preferred, and acrylic resins composed of units derived from (meth)acrylic acid and (meth)acrylate are more preferred.

The acrylic resin preferably has a hydrophilic unit and a hydrophobic unit as constituent units. Among these, resins having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one of a vinyl monomer having an aromatic ring and a (meth)acrylic acid ester monomer are preferred. Particularly preferred is a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from an aromatic vinyl monomer of at least one of styrene and α-methylstyrene. Since these resins tend to interact with pigments, they can be suitably used as resin dispersants for dispersing pigments.
The hydrophilic unit is a unit having a hydrophilic group such as an anionic group. The hydrophilic unit can be formed, for example, by polymerizing a hydrophilic monomer having a hydrophilic group. Specific examples of hydrophilic monomers having hydrophilic groups include acidic monomers having carboxylic acid groups such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid, and anions such as anhydrides and salts of these acidic monomers. Examples include sexual monomers. Examples of cations constituting the acidic monomer salt include ions such as lithium, sodium, potassium, ammonium, and organic ammonium. A hydrophobic unit is a unit that does not have a hydrophilic group such as an anionic group. The hydrophobic unit can be formed, for example, by polymerizing a hydrophobic monomer that does not have a hydrophilic group such as an anionic group. Specific examples of hydrophobic monomers include monomers having an aromatic ring such as styrene, α-methylstyrene, and benzyl (meth)acrylate; methyl (meth)acrylate, butyl (meth)acrylate, and (meth)acrylic acid 2. - Examples include (meth)acrylic acid ester monomers such as ethylhexyl.

The urethane resin can be obtained, for example, by reacting a polyisocyanate and a polyol, and may also be obtained by further reacting a chain extender. Examples of the olefin resin include polyethylene and polypropylene.

(aqueous medium)
The ink used in the inkjet recording method can contain water alone or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. As water, it is preferable to use deionized water or ion-exchanged water. The water content (mass%) in the ink is preferably 50.0% by mass or more and 95.0% by mass or less, based on the total mass of the ink. Further, the content (mass%) of the water-soluble organic solvent in the ink is preferably 3.0% by mass or more and 50.0% by mass or less, based on the total mass of the ink. As the water-soluble organic solvent, any solvent that can be used in inkjet inks, such as alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing compounds, and sulfur-containing compounds, can be used.

(Other additives)
In addition to the above-mentioned ingredients, the ink may also contain various other ingredients, such as antifoaming agents, surfactants, pH adjusters, viscosity adjusters, rust preventives, preservatives, anti-mold agents, antioxidants, and anti-reduction agents. It may also contain additives. However, it is preferable that the ink does not contain the reactant used in the reaction liquid as described above. When a reactive agent is contained in the ink, the content of the reactive agent in the ink is set to be a very small amount (for example, about 0.05% by mass or less).

<Liquid removal device>
The liquid removal device 105 can remove the liquid by using various conventional methods, such as heating, blowing low-humidity air, and reducing pressure. In addition to the above-mentioned method, a method of absorbing liquid by pressing a liquid absorbing member including a porous body against the liquid absorbing member can also be used.
Examples of the heating method include non-contact heating mechanisms such as a hot air heating mechanism using a dryer, a radiation heating mechanism using a halogen heater or an infrared heater, and a heating mechanism using electromagnetic induction. Further, a contact type heating mechanism such as a thermopressure heating mechanism using an iron press can also be used. Among these, from the viewpoint of heating efficiency, it is preferable to employ a non-contact heating mechanism using radiation using an infrared heater or the like.

In the case of a method in which a liquid absorbing member including a porous body is pressed, the liquid absorbing member that contacts the ink image and reduces the amount of the liquid component of the ink image is included. The liquid absorbing member may be formed on the outer peripheral surface of the roller, or the liquid absorbing member may be formed in the form of an endless sheet and run in a circular manner. In order to protect the image, the moving speed of the liquid absorbing member may be synchronized with the circumferential speed of the transfer body and the speed of the liquid absorbing member.
Note that the liquid component is not particularly limited as long as it does not have a fixed shape, has fluidity, and has a substantially constant volume. Examples of liquid components include water, organic solvents, and the like contained in ink and reaction liquids.

In this way, the liquid component is removed on the transfer body 101, and an intermediate image with reduced liquid component is formed. The intermediate image after this liquid is removed is then transferred onto the recording medium 108 in the transfer section 111. The device configuration and conditions during transfer will be explained.

<Transfer device>
(Press member)
In this embodiment, an intermediate image (hereinafter simply referred to as an intermediate image) after the liquid on the transfer body 101 is removed is transferred onto the recording medium 108 conveyed by the recording medium conveying means 107 by a transfer pressing member 106. Transfer by bringing it into contact with. By removing the liquid component contained in the intermediate image and then transferring it to the recording medium 108, it is possible to obtain a recorded matter with suppressed curling, cockling, and the like. In this embodiment, the pressing member 106 and the recording medium transport means 107 may be collectively referred to as a transfer device.
The pressing member 106 is required to have a certain degree of structural strength from the viewpoint of conveyance accuracy and durability of the recording medium 108. The material of the pressing member 106 is preferably metal, ceramic, resin, or the like. Among these, the following materials are preferably used in order to have rigidity and dimensional accuracy that can withstand pressure during transfer, as well as to reduce inertia during operation and improve control responsiveness. Aluminum, iron, stainless steel, acetal resin, epoxy resin, polyimide, polyethylene, polyethylene terephthalate, nylon, polyurethane, silica ceramics, alumina ceramics, etc. Moreover, you may use these in combination.
In order to transfer the intermediate image on the transfer body 101 to the recording medium 108, the transfer body 101 is pressed by a pressing member 106. At this time, there is no particular restriction on the pressing time, but it is preferably 5 ms or more and 100 ms or less in order to ensure good transfer and not to impair the durability of the transfer body. Note that the pressing time in this embodiment refers to the time during which the recording medium 108 and the transfer body 101 are in contact, and is measured using a surface pressure distribution measuring device ("I-SCAN", manufactured by Nitta Co., Ltd.). The value was calculated by measuring the surface pressure by dividing the length of the pressurized area in the conveyance direction by the conveyance speed.

Further, there is no particular restriction on the pressure with which the pressing member 106 presses the transfer body 101 during transfer, but it should be ensured that the transfer is performed well and that the durability of the transfer body is not impaired. For this reason, the pressure is preferably 9.8 N/cm ² (1 kg/cm ² ) or more and 294.2 N/cm ² (30 kg/cm ² ) or less. Note that the pressure in this embodiment refers to the nip pressure between the recording medium 108 and the transfer body 101, and the surface pressure is measured using a surface pressure distribution measuring device, and the load in the pressure area is divided by the area. This is the calculated value.
There is no particular restriction on the temperature at which the pressing member 106 presses the transfer body 101 during transfer, but it is preferably at least the glass transition point or softening point of the resin component contained in the ink. Further, a preferred embodiment includes a heating means for heating the intermediate image on the transfer body 101, the transfer body 101, and the recording medium 108 for heating.
Although the shape of the pressing member 106 is not particularly limited, it may have a roller shape, for example.

(Recording medium transport device)
Further, in FIG. 1, the recording medium conveying device 107 for conveying the recording medium 108 is composed of a recording medium feeding roller 107a and a recording medium take-up roller 107b, but it is sufficient that the recording medium can be conveyed, and in particular, this configuration It is not limited to.

<Recording medium>
In this embodiment, the recording medium 108 is not particularly limited, and any known recording medium can be used. Examples of the recording medium include a long material wound into a roll or a sheet material cut into a predetermined size. Examples of the material include paper, plastic film, wood board, cardboard, and metal film.

<Transfer body>
Next, the transfer body will be explained.
The transfer body 101 has a surface layer including an image forming surface. As the surface layer member, any material can be used as long as the component (A) in the wax can permeate therein, and various materials such as resins and ceramics can be used as appropriate. From the viewpoint of durability, materials with high compressive elastic modulus are preferable, and specifically, acrylic resins, acrylic silicone resins, fluorine-containing resins, silicone resins, condensates obtained by condensing hydrolyzable organosilicon compounds, etc. Can be mentioned. In addition, various elastomer materials and rubber materials are also preferably used in terms of processing characteristics and the like. Specifically, examples include fluorosilicone rubber, phenyl silicone rubber, fluororubber, chloroprene rubber, urethane rubber, nitrile rubber, ethylene propylene rubber, natural rubber, styrene rubber, isoprene rubber, butadiene rubber, and ethylene/propylene/butadiene copolymer. Examples include rubber, nitrile butadiene rubber, and the like. In particular, silicone rubber, fluorosilicone rubber, and phenyl silicone rubber are preferable in terms of dimensional stability and durability because of their small compression set, and are also preferable in terms of transferability because their elastic modulus changes little with temperature. .
The surface layer may be subjected to surface treatment in order to improve the wettability, transferability, etc. of the reaction solution within a range that does not impede the permeability of component (A) in the wax. Examples of the surface treatment include flame treatment, corona treatment, plasma treatment, polishing treatment, roughening treatment, active energy ray irradiation treatment, ozone treatment, surfactant treatment, silane coupling treatment, and the like. A plurality of these may be combined. Further, the surface layer can also be provided with an arbitrary surface shape.
Further, the transfer body may have a compressed layer that has a function of absorbing pressure fluctuations separately from the surface layer. Providing a compressed layer is preferable because the compressed layer can absorb deformation, disperse local pressure fluctuations, and maintain good transferability even during high-speed printing. Examples of the material for the compression layer include acrylonitrile-butadiene rubber, acrylic rubber, chloroprene rubber, urethane rubber, and silicone rubber. When molding the rubber material, it is preferable that a predetermined amount of a vulcanizing agent, a vulcanization accelerator, etc. be blended therein, and further a blowing agent, a filler such as hollow fine particles or common salt may be blended as needed to make it porous. As a result, the bubble portion is compressed with a change in volume in response to various pressure fluctuations, so deformation in directions other than the compression direction is small, and more stable transferability and durability can be obtained. Porous rubber materials include those with a continuous pore structure where each pore is continuous with each other and those with an independent pore structure where each pore is independent. In the present invention, any structure may be used, and these structures may be used in combination.
Various adhesives or double-sided tapes may be used between the layers (surface layer, compressed layer) constituting the transfer body to fix and hold them. Further, in order to suppress lateral elongation and maintain firmness when attached to a device, a reinforcing layer having a high compressive elastic modulus may be provided on the lower surface side (opposite side to the surface layer). Moreover, a woven fabric may be used as a reinforcing layer. The transfer body can be manufactured by arbitrarily combining layers made of the above-mentioned materials.

FIG. 2 is a schematic cross-sectional view in the thickness direction showing one embodiment of the transfer body. The transfer body 20 shown in FIG. 2 has a surface layer 21 and a base layer 22 serving as a compressed layer, and the surface layer 21 further has a permeation region 23 containing and permeating component (A).

(Component (A))
Component (A) is a component that can permeate into the surface layer among the wax components applied onto the transfer member during image recording. Since the surface layer of the transfer body contains the component (A) in advance, the degree of penetration of the components in the wax into the transfer body is sufficiently stabilized when the transfer body is installed in the recording device and used. It is in a state of being Thereby, it is possible to suppress most of the wax applied to the surface layer of the transfer body immediately after the start of use from penetrating into the surface layer, and it is possible to suppress changes in image quality due to insufficient amount of wax.
Examples of the component (A) include the wax itself used during image recording, and low molecular weight components among the components contained in the wax. Component (A) may be one type of compound or a mixture of two or more types of compounds.
Component (A) is preferably a substance that easily permeates and is easily retained in the material (resin or rubber) constituting the surface layer of the transfer body. For example, when the material constituting the surface layer is silicone rubber, the component (A) (A) is preferably a lipophilic resin component.

Furthermore, component (A) is preferably a compound having a melting point of 70 to 110°C. When the melting point of component (A) is 70°C or higher, component (A) is difficult to seep out from the surface layer even when the transfer body is stored before use, so a sufficient amount of component (A) is stably retained in the surface layer. You can leave it there. On the other hand, when the melting point is 110° C. or lower, the component (A) contained in the surface layer is likely to soften or melt at the beginning of use, and the state of wax penetration into the surface layer can be stabilized more quickly.

Note that the melting point of component (A) can be measured according to the temperature measurement pattern of ASTM D3418. More specifically, the highest melting temperature was measured using a differential scanning calorimeter (manufactured by PerkinElmer, DSC-7 (product name)) at a heating rate of 10°C/min according to the temperature measurement pattern of ASTM D3418. It can be the peak top value of temperature.

The penetration depth (depth from the surface of the penetration region) of the surface layer by component (A) is preferably 10 μm or more, more preferably 50 μm or more. When the penetration depth by component (A) is 10 μm or more, changes in the amount of wax on the surface layer at the beginning of use can be more stabilized. In addition, when the transfer body has a compressed layer under the surface layer, it is preferable to suppress the penetration depth of the component (A) to a depth that does not completely fill the pores of the compressed layer with the component (A). It is more preferable to suppress the depth to a level that does not reach the layer. Thereby, changes in compression characteristics due to penetration of component (A) can be kept within a range that does not affect the image.
To measure the penetration depth into the surface layer, first freeze-cut the surface layer to which component (A) has been applied in units of several μm using a cryomicrotome, and then examine the cut surface using an FT-IR device manufactured by PerkinElmer. Measured using the ATR method. The intensity of the peak characteristic of component (A) was determined by comparing it with the intensity at the peak position of the surface layer before applying component (A). The characteristic peak generally includes a peak at 2918 cm ^-1 (CH stretching), but this characteristic peak can be selected as appropriate depending on the type of component (A) and the material of the surface layer. .

Further, the permeation region 23 of the component (A) in the surface layer 21 may be formed at least in the region where the intermediate image is formed from the surface of the surface layer toward the thickness direction. Specifically, as shown in FIG. 2, the penetration area 23 may not be formed at both ends in the width direction outside the image forming area.

The size of the transfer body can be freely selected according to the desired print image size. The shape of the transfer body is not particularly limited, and specific examples thereof include a sheet shape, a roller shape, a belt shape, an endless web shape, and the like. Furthermore, the transfer body is removable from the support member, and in the case of a sheet, a seam may be formed, but it is sufficient that no image is formed on the seam. In the case of a roller shape, a belt shape, and an endless web shape, they may be formed integrally with a support member that supports them, and the support member can be replaced together with the recording device. In the case of a belt shape or an endless web shape, it is made separate from the support member, and can be attached and detached by loosening the tension of a member such as a tension roller that holds the support member.

<Support member>
The transfer body 101 is supported on a support member 102. Various adhesives or double-sided tapes may be used to support the transfer body. Alternatively, by attaching an installation member made of metal, ceramic, resin, or the like to the transfer body, the transfer body may be supported on the support member 102 using the installation member.
The support member 102 is required to have a certain degree of structural strength from the viewpoint of transportation accuracy and durability. As the material of the supporting member, metal, ceramic, resin, etc. are preferably used. In particular, the following materials are preferably used in order to have rigidity and dimensional accuracy that can withstand pressure during transfer, as well as to reduce inertia during operation and improve control responsiveness. Aluminum, iron, stainless steel, acetal resin, epoxy resin, polyimide, polyethylene, polyethylene terephthalate, nylon, polyurethane, silica ceramics, alumina ceramics, etc. It is also preferable to use these in combination.

<Method for manufacturing transfer body>
Next, a method for manufacturing the transfer body will be explained.
The above transfer body can be manufactured, for example, by the following manufacturing method.
(i) heating the surface layer before containing component (A) and component (A) to a temperature higher than the melting point of component (A);
(ii) applying component (A) to the surface layer;
(iii) a step of infiltrating the component (A) into the surface layer in a heated state. In the above method, either step (i) or step (ii) may be performed first, but from the viewpoint of ease of applying component (A), step (i) may be performed first. It is preferable that the application in step (ii) and the penetration in step (iii) proceed simultaneously.
When impregnating with component (A), the transfer member is held on a dummy support member so as to be in the same form as the transfer member. The depth of the permeation region can be arbitrarily set by adjusting the material of the surface layer, the temperature and time during permeation, etc.

<Laminated body>
Next, the laminate will be explained.
FIG. 3 is a schematic cross-sectional view in the thickness direction showing an embodiment of a laminate 30 according to the present invention. The laminate 30 shown in FIG. 3 includes a transfer body 20 including a surface layer 21 having a permeation region 23 of component (A) and a base layer 22, and a cover member 31 in contact with the surface layer 21.

(Cover member)
The outer surface of the surface layer in which the permeation region 23 is formed is covered with a cover member 31 . This cover member should just cover at least the image forming area of the surface layer. By being covered with the cover member, the penetration state of the component (A) during storage and transportation can be maintained within a certain range, and the occurrence of in-plane unevenness due to movement of the component (A) can be suppressed.
The degree of penetration of the cover member by component (A) is preferably 1.0 g/m ² or less at 50°C. By setting the degree of penetration of the cover member within the above range, it becomes easier to maintain the content of component (A) in the surface layer.
The method for measuring the degree of penetration of a cover member by component (A) is to first apply a sufficient amount of component (A) onto glass at a temperature higher than the melting point of component (A), cool it to 50°C, and form a layer of component (A). form. A cover member having an area of S (m ² ) and a weight of W1 (g) is brought into close contact thereon using a hand roller, and maintained for 1 hour. After that, the cover member was peeled off, the component (A) remaining on the cover member was removed, and the weight W2 (g) of the cover member was measured using an electronic balance. ² ).

Further, the cover member may have a function similar to a normal protective film, such as covering the surface layer with the cover member to suppress scratches and damage caused by external physical factors such as dust and impact.
The material for such a cover member may be any material as long as it can maintain the state in which the component (A) is permeated into the surface layer of the transfer body. Specifically, paper, plastic film, metal plate, metal foil, etc. can be mentioned. Among these, paper or plastic films are preferred from the viewpoint of transportability, polyolefin films that are easily stretchable are preferred from the viewpoints of adhesion to component (A) or the surface layer, and ease of handling, and polyethylene films are particularly preferred. Further, it may have a laminated structure made of two or more types of materials, and may have a structure having an adhesive layer to further improve the adhesion between the layers.

<Package>
Next, the package will be explained.
FIG. 4 is a schematic cross-sectional view in the thickness direction showing one embodiment of the package. The package 40A shown in FIG. 4A is one in which the surface layer 21 of the transfer body 20 shown in FIG. 2 is housed in close contact with one wall surface of a closed container 41A. Moreover, the package 40B shown in FIG. 4(B) includes the laminate 30 shown in FIG. 3 and a sealed container 41B that accommodates the laminate 30.
By housing the transfer body 20 or the laminate 30 in the airtight container 41 and sealing it, contact with the outside air can be cut off, making it possible to further suppress the deterioration of the component (A) described above. Further, for convenience of transaction in production or distribution, the transfer body 20 is individually packaged in units of one to several sheets and stored or transported together with other materials or other products. Therefore, it is preferable to seal the container from the viewpoint of suppressing contamination of the surrounding area due to outflow or adhesion of component (A).

The sealed container 41 is not particularly limited as long as it can hold the transfer body 20 or the laminate 30 in a sealed state, but it is more preferable if it can be opened easily during use. Examples include glass containers or metal containers with packing, zipper-type resin film bags, and heat-sealable resin film bags. Among these, heat-sealable resin film bags are particularly preferred from the viewpoints of sealability, cost, distribution volume, and the like.
Further, the airtight container 41 preferably has an oxygen permeability of 10 g/m ² ·24 h or less, more preferably 1 g/m ² ·24 h. By using a closed container with such characteristics, it becomes possible to further suppress the deterioration of the component (A) described above.
A particularly preferable airtight container is, for example, the above-mentioned heat-sealable resin film bag, and when a polyethylene laminated film is used as the film material, the airtight container can be 10 g/m ² ·24 h or less. Further, examples of the film of 1 g/m ² ·24 h or less include, for example, a laminated film containing an aluminum or silica vapor-deposited layer, or a laminated film containing an aluminum foil layer sealed by heat sealing.
A part of each wall surface of the airtight container may be constructed from a separate member, for example, a structure may be constructed in which an opaque material and a transparent material are combined to allow confirmation of the contents.
In the case of resin film bags, it is preferable to use ones that have been treated with antistatic treatment to prevent dust from sticking due to static electricity when the bag is unpacked.

Note that the measurement of oxygen permeability in the present invention is a value performed in accordance with JIS K 7126-2. Note that the oxygen permeability measurement environment was a temperature of 23° C. and a humidity of 50% RH.
Further, in the case of the configuration shown in FIG. 4A in which the airtight container 41A also serves as the cover member 31, at least the surface in contact with the surface layer 21, like the cover member 31, has a permeability of component (A) of 1 at 50°C. It is preferable that it is .0g/m2 or ^less .

In addition, when transporting or storing, if necessary, the above-mentioned laminates and packages may be individually packaged in cardboard boxes or other packaging, or multiple transfer bodies, laminates, or packages may be packaged together. It may be packed in one collection box.

Hereinafter, this embodiment will be described in more detail using Examples and Comparative Examples. The present invention is not limited in any way by the following examples unless it exceeds the gist thereof. In the following description of Examples, "parts" or "%" are based on mass unless otherwise specified.

An inkjet transfer body, a laminate, and a package used in Examples were produced by the following method.

<Manufacture of transfer body>
A PET (polyethylene terephthalate) film having a thickness of 50 μm as a base layer was coated with silicone rubber having a rubber hardness of 40 degrees to a thickness of 200 μm as a surface layer. Each component (A) is applied to the surface layer of this silicone rubber at the melting point of component (A) +5°C, and the impregnation time is adjusted so that the penetration depth into the surface is as shown in Table 1. (A) was infiltrated to produce a sheet-like transfer body.
<Manufacture of laminate>
The surface layer impregnated with the above component (A) was covered with a cover member to produce a laminate.
<Manufacture of packaging>
The above transfer body or laminate was placed in an airtight container and sealed with a zipper or heat seal to produce a package.
The component (A), cover member, and sealed container used in each example are as listed in Table 1.

Details of the abbreviations in Table 1 are as follows.
Ingredient (A)
a: Paraffin wax 150°F (product name, manufactured by Nippon Seirosha)
b: Microcrystalline wax Hi-Mic-1070 (product name, manufactured by Nippon Seirosha)
c: Microcrystalline wax Hi-Mic-2095 (product name, manufactured by Nippon Seirosha)
d: Licowax PE 520 (product name, manufactured by Nippon Seirosha)

Cover material high quality paper: OK Prince high quality, basis weight 64g/m ² , thickness 79μm (trade name, manufactured by Oji Paper Co., Ltd.)
PE film: Polyethylene film (thickness 70 μm, manufactured by Japan Polyethylene Co., Ltd.)
PP film: Polypropylene film (thickness 75 μm, manufactured by Daicel Polymer Co., Ltd.)

Airtight container zipper bag: Clean poly N zipper type (product name, manufactured by Marui Co., Ltd.)
PE seal bag: Clean poly N three-sided seal type (product name, manufactured by Maruai Co., Ltd.)
AL seal bag: Aluminum moisture-proof bag type C (product name, manufactured by Marui Co., Ltd.)
In Examples 9 and 10, the sealed container was packed in close contact with the permeation region 23 of the surface layer 21, as shown in FIG. 4(A). In the sealed containers used in Examples 9 and 10, the degree of penetration by component (A) in the wax at 50° C. was 0 g/m ² , which is the same as that of the PE film. The difference in oxygen permeability between a zipper bag and a PE seal bag is that the PE seal bag has its remaining opening sealed by thermocompression bonding, whereas the zipper bag's opening is sealed by the zipper.

<Preparation of pigment dispersion>
(Pigment dispersion liquid 1)
A styrene-ethyl acrylate-acrylic acid copolymer (resin 1) having an acid value of 150 mgKOH/g and a weight average molecular weight of 8,000 was prepared. After neutralizing 20.0 parts of Resin 1 with potassium hydroxide in an equimolar amount to its acid value, an appropriate amount of pure water was added to prepare Resin 1 with a content of Resin 1 (solid content) of 20.0%. An aqueous solution was prepared. A mixture was obtained by mixing 10.0 parts of pigment (carbon black), 15.0 parts of an aqueous solution of Resin 1, and 75.0 parts of pure water. The obtained mixture and 200 parts of zirconia beads having a diameter of 0.3 mm were placed in a batch type vertical sand mill (manufactured by Imex) and dispersed for 5 hours while cooling with water. After centrifugation to remove coarse particles, pressure filtration was performed using a cellulose acetate filter (manufactured by Advantech) with a pore size of 3.0 μm to obtain a pigment with a pigment content of 10.0% and a resin dispersant (resin 1). Pigment dispersion 1 having a content of 3.0% was prepared.

<Preparation of resin particles>
(Resin particle 1)
In a four-necked flask equipped with a stirrer, a reflux condenser, and a nitrogen gas introduction tube, 74.0 parts of ion-exchanged water and 0.2 parts of potassium persulfate were mixed. In addition, 24.0 parts of ethyl methacrylate, 1.5 parts of methacrylic acid, and 0.3 parts of a reactive surfactant (trade name "Aqualon KH-05", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were mixed to form an emulsion. Prepared. Under a nitrogen atmosphere, the prepared emulsion was dropped into the four-necked flask described above over 1 hour, and a polymerization reaction was carried out at 80° C. for 2 hours with stirring. After cooling to 25°C, ion-exchanged water and an aqueous solution containing potassium hydroxide in an equimolar amount to the acid value of the resin particles are added to obtain resin particles with a resin particle (solid content) content of 25.0%. An aqueous dispersion of No. 1 was prepared.

<Preparation of ink>
Ink 1 was prepared by mixing each component (unit: %) shown in Table 2, stirring thoroughly, and then performing pressure filtration using a cellulose acetate filter (manufactured by Advantech) with a pore size of 3.0 μm. In Table 2, "aqueous solution of resin 1" is the same as "aqueous solution of resin 1" used for preparing the pigment dispersion. The numerical value attached to polyethylene glycol is the number average molecular weight of polyethylene glycol. "Acetylenol E100" is the trade name of a surfactant manufactured by Kawaken Fine Chemicals.

<Preparation of reaction solution>
After mixing each component (unit: %) shown in Table 3 and stirring thoroughly, pressure filtration was performed using a cellulose acetate filter (manufactured by Advantech) with a pore size of 3.0 μm to prepare reaction solution 1. In Table 3, "Megafac F444" is a brand name of a surfactant manufactured by DIC Corporation.

<Evaluation>
The produced transfer body, laminate, and package were stored for one month in an environment with a temperature of 60° C. and a humidity of 20%. Then, the cover member and the airtight container were removed from the stored laminate and package, and the transfer body was installed as the transfer body 101 of the recording device 100 in FIG. 1. Further, the wax containing the component A that had penetrated into the surface layer was provided in the wax application device 110, and the above-mentioned ink and reaction liquid were also provided in the recording device 100 of FIG. Immediately after the initial operation of the recording device, printing of solid images was started, and the quality of the images was visually evaluated on the first and 100th sheets. In Comparative Example 1, the wax application device 110 was equipped with b: microcrystalline wax Hi-Mic-1070 (trade name, manufactured by Nippon Seiro Co., Ltd.) to apply wax.
As a result, in the transfer bodies of Examples 1 to 5, the wax on the surface layer sometimes scraped or moved in some places, but there was almost no difference in image quality between the 1st sheet and the 100th sheet. ,It was good. Furthermore, in the laminates and packages of Examples 6 to 15, each having a cover member and an airtight container, there was no change in the quality of the transferred image, and good images were obtained.
On the other hand, in Comparative Example 1 in which the surface layer did not contain component (A), a visible change in the quality of the transferred image was observed between the 1st sheet and the 100th sheet.

The present invention includes the following configurations.
[Configuration 1]
A transfer body that forms an intermediate image on a surface and transfers the intermediate image to a recording medium, the intermediate image having a layer containing wax formed on the surface of the transfer body,
The transfer body has a surface layer on which the layer containing the wax is formed,
A transfer body characterized in that the surface layer has a permeation region of the component (A) in the wax in the thickness direction from the surface of the surface layer before the transfer body is used.
[Configuration 2]
The transfer body according to configuration 1, wherein the penetration region of the surface layer has a depth of 10 μm or more from the outermost surface.
[Configuration 3]
The transfer body according to configuration 1 or 2, wherein the component (A) is a component having a melting point of 70 to 110°C.
[Configuration 4]
A laminate comprising the transfer body according to any one of Structures 1 to 3 and a cover member, wherein the cover member is in contact with and covers the surface of the permeation region of the component (A) of the surface layer. A laminate characterized by:
[Configuration 5]
The laminate according to configuration 4, wherein the penetration degree of the component (A) into the cover member is 1.0 g/m ² or less at 50°C.
[Configuration 6]
A package comprising the transfer body according to any one of Structures 1 to 3 and a closed container that houses the transfer body.
[Configuration 7]
The package according to Structure 6, wherein one wall surface of the airtight container contacts and covers the surface of the permeation region of the component (A) of the surface layer.
[Configuration 8]
In configuration 7, the degree of penetration by the component (A) of the wall surface in contact with the penetration area of the surface layer of the transfer body of the sealed container is 1.0 g/m ² or less at 50 ° C. Packaging as described.
[Configuration 9]
A package comprising the laminate according to configuration 4 or 5 and a sealed container that accommodates the laminate.
[Configuration 10]
The package according to any one of configurations 6 to 9, wherein the airtight container has an oxygen permeability of 10 g/m ² ·24 h or less.
[Configuration 11]
A method for manufacturing a transfer body according to any one of configurations 1 to 3, comprising:
heating the surface layer before containing the component (A) and the component (A) above the melting point of the component (A); and applying the component (A) to the surface layer. A method for manufacturing a transfer body, comprising the step of infiltrating the component (A) into the surface layer under heating.

20 Transfer body 21 Surface layer 22 Base layer (compressed layer)
23 Component (A) penetration area 30 Laminated body 31 Cover members 40A, 40B Packing bodies 41A, 41B Airtight container 100 Transfer type inkjet recording device 101 Transfer body 110 Waxing device

Claims (17)

A transfer body that forms an intermediate image on a surface and transfers the intermediate image to a recording medium, the intermediate image having a layer containing wax formed on the surface of the transfer body,
The transfer body has a surface layer,
A transfer body characterized in that the surface layer has a permeation region of the component (A) in the wax in the thickness direction from the surface of the surface layer before the transfer body is used. The transfer body according to claim 1, wherein the depth of the permeation region of the surface layer from the surface of the surface layer is 10 μm or more. The transfer body according to claim 1, wherein the component (A) has a melting point of 70 to 110°C. The transfer body according to claim 2, wherein the component (A) has a melting point of 70 to 110°C. A laminate comprising the transfer body according to any one of claims 1 to 4 and a cover member, wherein the cover member is in contact with the surface of the permeation region of the component (A) of the surface layer. A laminate characterized by covering. The laminate according to claim 5, wherein the degree of penetration of the component (A) into the cover member is 1.0 g/m ² or less at 50°C. A package comprising the transfer body according to any one of claims 1 to 4 and an airtight container that accommodates the transfer body. The package according to claim 7, wherein one wall surface of the airtight container contacts and covers the surface of the permeation region of the surface layer of the transfer body. Claim 8, wherein the degree of penetration of the component (A) into the wall surface of the sealed container that is in contact with the penetration area of the surface layer of the transfer body is 1.0 g/m ² or less at 50°C. The packaging described in. A package comprising the laminate according to claim 5 and a sealed container that accommodates the laminate. A package comprising the laminate according to claim 6 and a sealed container that accommodates the laminate. The package according to claim 7, wherein the airtight container has an oxygen permeability of 10 g/m ² ·24 h or less. The package according to claim 8, wherein the airtight container has an oxygen permeability of 10 g/m ² ·24 h or less. The package according to claim 9, wherein the airtight container has an oxygen permeability of 10 g/m ² ·24 h or less. The package according to claim 10, wherein the airtight container has an oxygen permeability of 10 g/m ² ·24 h or less. The package according to claim 11, wherein the airtight container has an oxygen permeability of 10 g/m ² ·24 h or less. A method for manufacturing a transfer body according to any one of claims 1 to 4, comprising:
heating the surface layer before containing the component (A) and the component (A) above the melting point of the component (A); and applying the component (A) to the surface layer. A method for manufacturing a transfer body, comprising the step of infiltrating the component (A) into the surface layer under heating.

Images