JP2000159376A - Image recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form images well in all of the areas of the display surface of a thick card medium of high rigidity. SOLUTION: An image recording device has a thermal head 11 for recording images on a rewrittable card medium 1 and has a platen roller 12 opposed to the printing surface 11a of the thermal head to press the card medium against the printing surface at predetermined pressure. The platen roller includes an elastic body 12b having an outer peripheral surface generally defined as a cylinder, the elastic body absorbing the deformation of the card medium and having a thickness and hardness such that it can bring the card medium into intimate contact with the printing surface. The elastic body has a thickness (Tr) satisfying 1/2Th<Tr<1/2Tm, wherein Th is the maximum value of the flatness of the printing surface of the thermal head and Tm is the maximum permissible value of deformation permitted to the card medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image recording apparatus for forming an image on a card medium by heating a thermal head or the like.

[0002]

2. Description of the Related Art In recent years, financial settlement without cash transfer has been frequently performed by guaranteeing payment with a magnetic card such as a credit card. Among such cards, IC cards having an electronic memory and wireless cards having a built-in communication antenna have appeared.

[0003] Most of these cards only display a design or a cautionary statement printed at the time of manufacture, and the amount of displayed information is also limited.

[0004] For this reason, there is a demand for a technique for increasing the amount of information displayed on a card, and further rewriting as necessary to always display the latest information.

As such a display technique, there is a technique of providing a display portion on a card surface capable of recording / erasing a visible image by heat, and rewriting the display portion by heating by bringing a thermal head or the like into contact. is there. In addition, as a rewritable material or a rewritable device, for example,
JP-154198 (white turbidity / transparency changing material), JP-A-63-173684 (coloring / decoloring change material), JP-A-4-197647 (rewriting device) and JP-A-5-44447 (rewriting) Device) has already been disclosed.

As an example of a card that actually rewrites display contents, for example, a card reader / writer having a thin card material of 0.2 mm thickness and a thermal head used for a point card or the like for accumulating shopping benefits is used. Has been put to practical use.

[0007]

However, the card material used as a card medium typified by the above-mentioned credit card is often a card material having a thickness of 0.76 mm in accordance with the JIS standard. Most of the materials are resins, which have high rigidity but are easily permanently deformed by an external force, so that it is difficult to uniformly contact the printing surface of the thermal head and the display surface of the card material.

That is, when the card material is undesirably permanently deformed, a gap is partially formed between the display surface of the card medium and the printing surface of the thermal head, and the gap is displayed on the display surface of the card medium. When rewriting the information, for example, the image “ABC012” shown in FIG.
When rewriting the image "XYZ987" shown in (b), as shown in FIG. 8C, the image is partially recorded first in a direction orthogonal to the direction in which the card medium is transported. There is a problem that the image that remains is not erased but remains as it is. In addition, when the printing surface and the display surface of the card medium are partially pressed with a strong pressing force, there is a problem that color unevenness occurs in a recorded (colored) image as shown in FIG. 8D. .

[0009] Today, in response to the above-mentioned problem, by limiting the area in which image information can be rewritten to a predetermined width (area), it is possible to prevent image defects due to rewriting and incompletely erased images. Although there is an example in which the information is suppressed, the area in which the image information can be rewritten becomes small, so that the needs cannot always be satisfied. In addition, the same result is often caused when the card is distorted or deformed during manufacturing, and it is difficult to form a good image.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image recording apparatus capable of forming an image satisfactorily on all areas of a display surface of a card medium having high rigidity and easily causing permanent deformation.

[0011]

SUMMARY OF THE INVENTION The present invention has been made based on the above problems, and has a heating element array including a plurality of heating elements arranged in a row in a direction orthogonal to a direction in which a recording medium is moved. A thermal head that heats the recording medium by an arbitrary heating element to record an image on the recording medium,
A back platen that is disposed to face the thermal head and moves the recording medium while pressing the recording medium toward the thermal head; and wherein the platen roller is configured to record an image on the recording medium. Includes a support member formed of a material having high rigidity, and an elastic body formed on the support member so as to be able to come into contact with the recording medium at a predetermined pressure. Wherein the degree of flatness of the surface defined by the heating element row is not less than １ ／ and not more than の of the deformable amount allowed for the recording medium. Things.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image recording apparatus according to an embodiment of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, an image recording apparatus 100
Is a thermal head 11 for recording image information on a card medium 1 on which image information can be rewritten, the thermal head 11 being opposed to a printing surface 11a of the thermal head 11, and the card medium 1
Roller (back platen) 12 which presses the card medium 1 toward the thermal head 11 along a not-illustrated transfer path.
3, and a timing sensor 14 for detecting the timing of recording an image on the card medium 1 conveyed by the conveying rollers 13.

The thermal head 11 is formed so as to be able to heat a recording (color-forming layer) of a card medium described below with reference to FIG. This is a line thermal head in which a plurality of heating elements are arranged in a direction orthogonal to the direction in which the card medium is transported.

As will be described later with reference to FIG. 4, the platen roller 12 has an elastic body (rubber material) 12b having a predetermined hardness and a predetermined thickness formed on the outer periphery of a metal roller 12a, for example. A card medium 1 at a position where the platen roller 12 comes into contact with the thermal head 11.
Is brought into close contact with the printing section 11a of the thermal head 11, and the card medium 1 is further transported. The thickness of the rubber material (elastic body) 12b is, for example, as shown in FIG.
The roller 12a may be defined so as to be thinner in the longitudinal direction, that is, near the center in the axial direction, as compared with both ends in the coaxial direction. In this case, the diameter of the center of the roller 12a is larger than that of both ends.

FIG. 2 shows the image recording apparatus 100 shown in FIG.
FIG. 1 is a schematic sectional view illustrating the configuration of a card medium 1 on which an already recorded image can be rewritten.

As shown in FIG. 2, the card medium 1 is
For example, it is a plate formed by using a material having high rigidity such as a vinyl chloride resin as a main material. For example, for a well-known credit card, the length is 85.6 mm × width 54 mm × thickness 0.76 mm. A Japanese Industrial Standard (JI
SX6301).

The card medium 1 has a base layer (vinyl chloride layer) 2 having a thickness of about 0.75 mm, an underlayer (interfacial treatment layer) 3 having a thickness of about 3 μm, and a recordable / erasable information having a thickness of about 7 μm. The recording layer 4 and the surface protection layer 5 having a thickness of about 2 μm are sequentially laminated. Since the base layer 2 is a vinyl chloride resin, the rigidity of the card itself is higher than that of the already described thin card having a thickness of about 0.2 mm, and when the card is stored for a long time in a user's wallet or the like. In some cases, permanent deformation may occur in any direction. On the other hand, due to the thickness of the card itself, there is a characteristic that it is hard to be broken or deformed by an external force that may be instantaneously applied in normal use. The recording layer 4 is made of, for example, a rewritable recording material in which an arbitrary color is developed or erased due to a difference in heating energy, a turbid-transparent change type rewritable recording material, a thermal transfer recording, and a write-once type. Any recording material among various recording materials such as a thermosensitive recording material used as a recording material can be used.

FIG. 3 shows the thermal head 11 shown in FIG.
Is a graph showing the relationship between the energy applied to heat the image display portion (recording layer) 4 of the card medium 1 shown in FIG. 2 to record an image (color the recording layer) and the image density. It is. In FIG. 3, the vertical axis indicates the image density (optical reflection density), and the horizontal axis indicates the amount of energy supplied by the thermal head 11 per one dot of a predetermined size on the card medium 1. In FIG. 3, a curve A indicates a change in density when the card medium 1 in an initial state in which no color is developed is heated (energy is supplied), and a curve B is already colored (an image is recorded). To erase (decolor) an image on the card medium 1
2 shows the relationship between the magnitude of energy to be provided and the image density.

That is, as shown in FIG. 3, in the card medium 1 on which image information can be rewritten, the recording layer 4
After providing an arbitrary amount of energy for erasing an already recorded image for rewriting (image), and subsequently supplying a larger amount of energy for erasing for a new recording By doing so, erasing and recording can be achieved in a series of steps. The recording material that can be used for the recording layer 4 includes a coloring material mainly containing a dye called a leuco dye, and reacting with the coloring material by providing thermal energy to produce an arbitrary color or reduce the color. It is composed of a color reducing agent.

FIG. 4 shows the thermal head 11 shown in FIG.
FIG. 3 is a diagram schematically illustrating the vicinity of the printing surface 11a of the thermal head 11 viewed from a direction perpendicular to the direction in which the card medium 1 is conveyed, with the platen roller 12 separated. is there.

As shown in FIG. 4, the thermal head 1
Reference numeral 1 denotes a heating element array (not shown) in which the entire width is, for example, 52 mm, which is slightly smaller than the width of the card medium, and a predetermined number of heating elements are arranged on the printing surface 11a.

The heating element array (and the printing surface 11a of the thermal head) is not perfectly flat due to the influence of manufacturing technology and cost restrictions, but is controlled to, for example, Th ≦ 0.07 (peak-peak) mm. It has undulation and warpage (non-planarity).

On the other hand, the card medium 1 also has, for example, Tm ≦ 2 m
undulation and warpage controlled by m (Japanese Industrial Standards (JIS)
(The maximum horizontal projection height in a flat place is 2 mm). The maximum amount of waviness or warpage (guaranteed that an image can be written by the recording apparatus 100 of the present invention) of the card medium 1 is “2 (JIS standard value) −0.76 (card Thickness) -0.
07 (head undulation) ≒ 1.23 ”mm.

The platen roller 12 has a hardness of, for example, 60 °.
The urethane rubber (elastic body 12b) is integrally formed on the outer periphery of the roller 12a. The thickness Tr of the elastic body (urethane rubber) 12b is defined so that the outer peripheral surface of the elastic body (urethane rubber) 12b is substantially cylindrical when formed on the roller 12a.
Therefore, in the example shown in FIG. 4, the thickness of the urethane rubber 12b is uniform over substantially the entire area in the longitudinal direction of the roller 12a.
The thickness Tr of the urethane rubber 12b is defined such that the center of the roller 12a in the axial direction of the roller 12a having a cross-sectional shape as described below with reference to FIG.

FIG. 5 shows the platen roller 12 shown in FIG.
It is the schematic explaining another embodiment of.

The platen roller 52 shown in FIG. 5 is formed by forming an elastic body (rubber material) 52b having a predetermined hardness to a predetermined thickness on the outer periphery of a metal roller 52a, for example. The diameter at the central portion in the axial direction is formed to be larger than the diameter at both ends. On the other hand, since the outer diameter of the platen roller 52 including the rubber material 52b is substantially cylindrical, as a result, the roller 5
In the longitudinal direction of 2a, that is, near the center in the axial direction, it is formed thinner than both ends.

According to this configuration, when the card medium 1 comes into contact with the outer peripheral surface of the platen roller 52, the pressure applied to the end of the card medium 1 from the rubber material 52b is applied to the center of the card medium 1 from the rubber material 52b. Since the pressure applied to the card medium 1 is reduced as compared with the pressure applied thereto, the pressure provided by the platen roller 52 to the card medium 1 becomes more uniform.

Next, recording of image information on a card medium and erasing of an already recorded image by the image recording apparatus shown in FIG. 1 will be described. Here, the description of the parts common to each of the platen rollers 12 and 52 shown in FIGS. 4 and 5 will be described without special distinction.

When the card medium 1 is inserted into an insertion slot (not shown), a transport motor (not shown) is driven, and the transport roller 13 is rotated.

The rotation of the transport roller 13 causes the card medium 1 to be transferred to the thermal head 11 and the platen roller 12.
It is transported to (52).

Hereinafter, in order to define the position of the card medium 1 conveyed to the thermal head 11 by the conveying rollers 13, that is, the timing at which image information is written by the thermal head 11, the card medium 1 conveyed by the rollers 13 is a timing sensor. 14.

More specifically, when it is detected that the card medium 1 has passed the timing sensor 14, the timing of writing (rewriting) image information by the thermal head 11 is counted by a control device (not shown).

When the card medium 1 is conveyed to the vicinity of the thermal head 11 by the rotation of the conveying roller 13, the platen roller moves the card medium 1 (with the platen roller) to a printing area where the printing surface 11a of the thermal head 11 is in contact. Conveyed.

As shown in FIG. 6, the card medium 1 conveyed between the thermal head 11 and the platen roller is subjected to a) deformation of the urethane rubber (elastic body) by the card medium 1 and b) deformation of the urethane rubber. Due to the generation of a reaction force from the urethane rubber toward the card medium 1 due to the suppression at the outer peripheral portion of the metal roller, the thermal head 11 is pressed against the printing surface 11a with a substantially uniform pressing pressure.

The configuration of a platen roller in which an elastic body is provided on the outer periphery of a metal roller is well known. However, when a large number of rollers are investigated, a force directed toward the metal roller shown in a) is applied. The degree to which the elastic body is deformed is large.
As already described, the reaction force toward the (printing surface 11a of the thermal head 11) cannot reliably eliminate the deformation (undulation or warpage) of the card medium 1.

Here, referring to FIG. 6 again, the result of confirming the thickness and hardness of the elastic body (rubber material) of the platen roller of the card medium 1 in which deformation (undulation or warpage) is recognized will be described.

As shown in FIG. 6, the card medium 1 is placed between the platen roller and the printing surface 11a of the thermal head 11.
Is guided, the elastic body (rubber material) of the outer peripheral surface of the platen roller is deformed toward the metal roller by the pressing force from the printing surface 11a of the thermal head 11.

At this time, if the thickness of the rubber material is larger than a predetermined thickness, the deformation (undulation or warpage) inherent in the card medium 1 due to the deformation of the rubber material directly becomes a gap between the card medium 1 and the printing surface 11a. Alternatively, the pressure between a specific portion of the card medium 1 and the printing surface 11a increases. In addition, the degree of deformation of the rubber material is not only
It is also governed by the properties (hardness) of the rubber material.

Hereinafter, the conditions of the platen roller which can press the card medium 1 against the printing surface 11a with a uniform pressing force, using the hardness and thickness of the rubber material as parameters, will be described.

As described above, the thickness of the card medium 1 is 0.76 mm as a standard value, and the maximum allowable deformation value Tmo of the card medium 1 is 1.13 mm. Note that the print surface 11a of the thermal head 11 also has undulation and warpage represented by Th ≦ 0.07 mm as described above.

Here, the outer diameter of the metal roller of the platen roller is 20 mm, and the thickness Tr of the rubber material is 0.1 mm.
mm, 0.2 mm, 0.3 mm, and 0.5 mm, and two kinds of hardness, 40 ° and 60 °, are prepared and incorporated into the image recording apparatus 100 shown in FIG. When the state of the image recorded on the display surface of the medium 1 was checked, the phenomenon that the previously recorded image remained without being erased as shown in FIG. 8C or FIG. No example was found in which unevenness in the pressing force was provided to the medium 1 and the recorded (color-developed) image caused color unevenness.

On the other hand, the thickness T of the rubber material of the platen roller
If r is 1 mm, which is larger than the standard value of the thickness of the card medium 1, the rubber material absorbs the deformation of the card medium 1 as described above, and is compared with the example shown in FIG. To a lesser degree, it was confirmed that the previously recorded image was not sufficiently erased.

The thickness T of the rubber material of the platen roller
If r is thinner than 0.1 mm, which is close to Th, which is the maximum value of the flatness (non-planarity) of the printing surface 11a of the thermal head 11, the deformation (undulation or warpage) of the card medium 1 cannot be completely absorbed. However, it was recognized that a portion having a strong pressing force caused by the metal roller was generated, and the color unevenness described above was generated.

More specifically, when the amount of deformation of the card medium 1 at the time of non-pressing indicated by the dotted line is Tmo, the deformation is corrected to some extent by being pressed against the platen roller by the thermal head 11 which is a rigid body. Is done. Here, when the thickness of the rubber material of the platen roller is large, the rubber material follows the deformation of the deformed card medium 1 and deforms. On the other hand, if the thickness of the rubber material is too small, the rubber material reaches the deformation limit even if the degree of deformation of the card medium 1 is slight, so that the swelling T
ho becomes unacceptable.

More specifically, to correct the card medium 1 whose deformation amount is Tmo to be substantially flat, the relative value is 1
The card medium 1 must be displaced by about / 2 Tmo. On the other hand, the thickness Tr of the rubber material is ｍ Tmo.
If the thickness is larger than that, the rubber material deforms first following the deformation of the card medium 1, so that the medium 1 cannot be deformed as expected. Therefore, the maximum value of the thickness Tr of the rubber material is の of the maximum value Tm of the allowable value of the deformation amount allowed for the card medium 1.

Similarly, in order to bring the card medium 1 into close contact with the thermal head 11 whose waviness is Th, the card medium 1 must be displaced by 1/2 Tho as a relative value. Also in this case, if the thickness Tr of the rubber material is less than 1/2 Tho, the displacement of the rubber material cannot follow the undulation of the thermal. Therefore, the lower limit of the thickness Tr of the rubber material is defined as １ ／ of the maximum value Th of the undulation of the thermal head 11.

Hereinafter, from the thickness of the card medium 1 already described, the range required for the thickness Tr of the rubber material on the outer peripheral surface of the platen roller is 0.035 mm <Tr <0.565 mm.

As the rubber material, 40 ° to 6 °
Rubber materials having a hardness in the range of 0 ° are available.

The range of the thickness of the rubber material of the platen roller described with reference to FIG. 6 can be applied to the rollers having different axial thicknesses as shown in FIG.
As a result of the experiment, a more uniform image is obtained by setting the thickness Tr of the rubber material at the center in the axial direction of the roller to 0.15 mm and the thickness Tr at both ends to 0.4 mm.

As described above, the thermal head 11
The card medium 1 guided between the printing surface 11a of the thermal head 11 and the platen roller is placed on the printing surface 11a of the thermal head 11.
The entire area is pressed with a uniform pressing force and is brought into close contact with the printing surface 11a of the thermal head 11.

As a result, the card medium 1 is slid and moved while being in close contact with the printing surface 11a of the thermal head 11. Note that the amount of deformation shown here is within the elastic deformation range of the vinyl chloride resin, which is the main material of the card medium 1, and the card medium 1 is deformed by pressure contact between the printing surface 11a of the thermal head 11 and the platen roller 12 ( After the image is recorded on the recording surface 1a by being slid while correcting the undulation or warpage, the image returns to the original state again.

As described above, the thermal head 11
The thickness Tr of the rubber material on the outer peripheral surface of the roller opposed to the printing surface 11a of the thermal head 11 is not more than 1/2 of the maximum value Tm of the allowable deformation of the card medium 1 and the printing surface 11a of the thermal head 11. The card medium 1 mainly made of a material such as a vinyl chloride resin having a large thickness and a high rigidity, and a thermal head by setting the flatness (undulation and warping) of the maximum value Th to at least 1/2 of the allowable value. 11 can be brought into contact with the entire printing surface 11a with a uniform contact pressure. As a result, recording and rewriting of an image without writing failure or unevenness can be achieved over almost the entire area of the card medium 1.

FIG. 7 is a schematic diagram showing another embodiment of the image recording apparatus shown in FIG.

As shown in FIG. 7, the image recording apparatus 200
Are opposed to a thermal head 11 for recording image information on the card medium 1, a printing surface 11a of the thermal head 11,
A platen roller 12 for pressing the card medium 1 toward the printing surface 11a at a predetermined pressure, a conveying roller 13 for conveying the card medium 1 toward the thermal head 11 along a conveying path (not described in detail), and a card conveyed by the conveying roller 13 A timing sensor 14 for detecting a timing of recording an image on the medium 1, and a predetermined direction from the print surface 11 a of the thermal head 11 and the elastic body 12 b of the platen roller 12 to the card medium 1 being conveyed by the conveyance roller 13. The correction device 215 includes a correction device 215 that temporarily corrects deformation occurring in the card medium 1 by providing a pressing force (correction force).

A predetermined number of correction devices 215 are provided along a transport path (not described in detail) and on the upper and lower sides of the card medium 1, respectively. Note that each of the correction devices 215 is positioned above and below the thermal head 11 so that the card medium 1 with a small degree of deformation does not become a load for transporting the card medium 1 or undesirably generate friction. (In the direction toward the printing surface 11a and the direction in the direction toward the elastic body 12b of the platen roller 12) are arranged, for example, at 1.5, and are arranged in various directions that may occur on the card medium 1. It is vertically moved independently by a correction device driving mechanism (not shown) so that the deformation can be corrected.

The straightening device 215 includes a protruding pad 215a, 215b and 215c made of a polyacetal resin having high abrasion resistance and excellent slidability, or a resin containing fluorine for a solid bearing, for example. At least two sets (upstream and downstream sides in the transport direction of the thermal head 11) in a direction parallel to the direction in which the card medium 1 is transported, and a plurality of rows (three rows in this example) arranged in a direction orthogonal to the direction in which the card medium 1 is transported The card medium 1 is surely brought into contact with the printing surface 11a of the thermal head 11 while being slid (moved) at a uniform speed. In addition, each protruding pad 15a, 15
Needless to say, b and 15c may be configured as rollers that can rotate along the direction in which the card medium 1 is transported.

According to the configuration shown in FIG. 7, since the deformation occurring in the card medium 1 is temporarily corrected, a synergistic effect with the platen roller described in detail with reference to FIGS. Thus, the entire area of the card medium 1 and the print surface 11a of the thermal head 11 can be contacted with a more uniform contact pressure, and the recording and rewriting of an image without writing damage or unevenness can be achieved on almost the entire area of the card medium 1. .

As described above, according to the image recording apparatus of the present invention, an image defect such as writing failure or density unevenness does not occur on a highly rigid card medium mainly made of vinyl chloride resin or the like. A good image can be formed.

Further, the image recording apparatus of the present invention can favorably form an image on the entire recording surface of a card formed of a card material having relatively high rigidity. The present invention is also applicable to a card medium in which an electric circuit is sealed.

Further, since the image recording apparatus of the present invention can form an image on a thin recording medium such as paper or film which has been conventionally used without any problem as in the conventional case, the material of the card medium can be used. Accordingly, it is possible to suppress an increase in cost without requiring a different image recording apparatus.

The amount of deformation given to the card medium by the platen roller and the correction mechanism is defined to be within the elastic deformation range of the base material of the card medium when the card medium is flat. The contact state between the thermal head and the card medium can be maintained uniformly without causing damage.

[0063]

As described above, according to the image forming apparatus of the present invention, even when the recording medium has high rigidity or is deformed, the contact state between the thermal head and the entire recording surface of the card medium is uniform. , A uniform pressure distribution is obtained.

Therefore, a good image can be formed even on a curved or warped card medium. As a result, the previously recorded image may not be sufficiently erased,
Part or all of the newly recorded image is prevented from being lost.

Therefore, it is possible to prevent the card medium from being undesirably consumed due to image defects such as writing errors and density unevenness, and to reduce the card issuing cost.

Further, since the image recording apparatus of the present invention can form an image on a thin recording medium such as a paper or a film which has been conventionally used without any problem, the card issuance cost increases. Can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an image recording apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an example of a card medium applicable to the image recording apparatus shown in FIG.

FIG. 3 is a graph showing a relationship between thermal energy supplied to the card medium shown in FIG. 2 and image density exhibited by the card medium.

FIG. 4 is a schematic diagram showing an example of a configuration of a platen roller of the image recording apparatus shown in FIG. 1, and a relationship between a printing surface of a thermal head and a card medium.

FIG. 5 is a schematic view showing another example of the platen roller shown in FIG. 4;

FIG. 6 is a schematic diagram showing a state in which a thermal head of the image recording apparatus shown in FIG. 1 is in contact with a card medium.

FIG. 7 is a schematic view illustrating another embodiment of the present invention.

FIG. 8 is a schematic diagram showing an example of an image rewritten using a known thermal head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Card medium, 1a ... Recording surface 2 ... Base material, 3 ... Underlayer, 4 ... Recording layer, 5 ... Surface protective layer, 11 ... Thermal head, 11a ... Printing surface, 12 ... Platen roller, 13 ... Conveyance roller, 14 ... Timing sensor, 215 ... Correcting device, 215a ... Pad, 215b ... Pad, 215c ... pad.

Claims (7)

[Claims] An image forming apparatus according to claim 1, wherein the recording medium is heated by an arbitrary heating element in a heating element array including a plurality of heating elements arranged in a row in a direction orthogonal to a direction in which the recording medium is moved. An image for recording an image on the recording medium, comprising: a thermal head that records the image on the recording medium; and a back platen that is arranged to face the thermal head and moves the recording medium while pressing the recording medium toward the thermal head. In the recording apparatus, the platen roller includes a support member formed of a material having high rigidity, and an elastic body formed on the support member so as to be able to contact the recording medium at a predetermined pressure. The thickness is not less than １ ／ of the flatness of the surface defined by the heating element row of the thermal head and is not more than の of the deformable amount allowed for the recording medium. An image recording apparatus, comprising: 2. The image recording apparatus according to claim 1, wherein the thickness of the elastic body is substantially uniform along a direction in which the heating element array of the thermal head extends. 3. A thickness of the elastic body is determined by a plane defined by the heating element array of the thermal head at a central portion of the thermal head in a direction parallel to a direction in which the heating element array extends. 2. The image recording apparatus according to claim 1, wherein the magnitude of the degree is not less than 1/2 and not more than 1/2 of a deformable amount allowed for the recording medium. 4. An image recording apparatus according to claim 1, wherein said elastic body is formed so that both ends thereof are thicker than a central part of said thermal head in a direction in which said row of heating elements extends. apparatus. 5. The elastic body has a hardness of 40 ° to 60 °.
The image recording apparatus according to any one of claims 1 to 4, wherein the image recording apparatus includes a rubber material of the following range. 6. The apparatus according to claim 1, further comprising a correction mechanism for correcting deformation of the recording medium, provided upstream of the platen roller in a direction in which the recording medium is conveyed. The image recording apparatus according to claim 1. 7. The recording medium according to claim 1, wherein the correction mechanism is configured to perform a deformation of the recording medium accompanied by a deformation larger than a deformation allowed for the recording medium conveyed toward the thermal head, to a maximum deformation allowed for the recording medium. 7. The image recording apparatus according to claim 6, wherein the correction is performed until the image is reduced.