JP4152601B2 - Image forming method for reversible thermosensitive recording medium - Google Patents

Description

【００５３】
〔実施例２〕
エアーの代わりに冷風機による冷風(２３℃)を吹き付けながら印字を行なったこと以外は、実施例1と全く同様に画像形成を行ない、形成された印字について目視による印字の品位および簡易バーコードリーダーによる読みとりを行い、その結果を表１中に示した。
【００５４】
〔比較例１〕
冷却を行わずに、雰囲気温度 ３０℃で印字を行なったこと以外は、実施例1と全く同様に画像形成を行ない、形成された印字について目視による印字の品位および簡易バーコードリーダーによる読みとりを行い、その結果を表１中に示した。
【００５５】
表１の結果からも明らかなように、実施例および比較例共に英数字の印字を行うことができたしかし、バーコードは、冷却しながら印字した実施例は問題ないが、冷却しなかった比較例１は太いバーが太線で印字できず、バーコードとして使用に耐えないものであった。
【００５６】
因みに、冷却速度を色々と変えて発色濃度を調べた結果、実施例１に用いた可逆性感熱記録媒体の印字に必要な冷却速度は、３００℃／ｓｅｃ以上であり、また消去に必要な冷却速度は、５０〜１００℃／ｓｅｃ以下であることが判明している。また、レーザによる印字は瞬間的に中心部が数百度まで上がるが、周辺部も数１０〜１００℃程度まで加熱されることを確認した。そして、明瞭にバーコードまたは太線の印字を確実に行なうために、記録媒体の冷却温度は、概ね０〜３０℃程度まで行ない、好ましくは、室温以下まで冷却した。
【００５７】
【発明の効果】
この発明は、以上説明したように、可逆性感熱記録媒体の画像形成方法において、加熱された区域に隣接する区域を前記加熱直後に加熱する際、先に加熱された区域を強制冷却しながらこれに隣接する区域を加熱して画像を形成するので、先に加熱された区域を強制冷却することによりこの区域にも発色のために所要の冷却速度が得られて、複数の区域に跨って連続した画像を形成できるという利点がある。
【００５８】
加熱の手段が、レーザ光線の照射による加熱であり、かつ前記先に形成された画像の強制冷却手段が、画像への冷風の吹きつけである可逆性感熱記録媒体の画像形成方法では、レーザ光を複数回重ねて照射する場合に、先に加熱された部分の画像が消えず、複数の区域に跨って連続した画像を形成できる。
【００５９】
また、画像がバーコード画像である可逆性感熱記録媒体の画像形成方法の場合には、１本目の線を印字した直後にその線に隣接させて二本目の線を印字できるため、任意の太さの線を備えたバーコードを印字できる利点がある。
【図面の簡単な説明】
【図１】実施形態の可画像形成方法を模式的に示す説明図
【図２】（ａ）実施形態の可画像形成方法で印字したバーコードを示す平面図
（ｂ）図２（ａ）のバーコードの要部を拡大して示す平面図
【図３】（ａ）レーザマーカを用いて印字された文字の平面図
（ｂ）図２（ａ）の要部を拡大して示す平面図
【図４】従来のバーコードの印字状態を説明する要部拡大平面図
【符号の説明】
１ コンベアライン
２ 通い箱
３ 可逆性感熱記録媒体
４ レーザマーカ
５ バーコード
６ 冷風発生機
７ コンピュータ
８、１２ 先に加熱された線状区域
９、１４ 隣接する線状区域
１０ レーザ光線を当てた部分
１１、１３ 周辺部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming method for a reversible thermosensitive recording medium capable of repeatedly displaying and erasing a visible image.
[0002]
[Prior art]
In general, in the logistics industry that transports and transports packages, general-purpose transport containers equipped with labels (tags) that display information such as destinations and contents of packages are used. When a barcode is printed on the label, automatic identification can be performed by using a barcode reader or a scanner, thereby forming an efficient distribution line.
[0003]
In addition, there are two types of labels attached to these containers: a plug-in type with a mounting holder in the container and a seal type that uses an adhesive for the label, but the former may come off during transportation. In the latter case, it takes time and effort to remove the label after use.
[0004]
As a transport container with a rewritable label that does not need to be peeled off, JP-A-9-188332 discloses that printing with a laser marker can be performed for non-contact printing on the transport container. Has been.
[0005]
On the other hand, as one of reversible thermosensitive recording media that can be printed with a laser marker, a recording material that consists of an organic low molecular weight compound and a polymer matrix and forms an image with contrast between a transparent area and a cloudy area is used. There is also known a recording medium in which an image is formed by providing a colored or decolored area using a leuco dye.
[0006]
The latter is a reversible thermosensitive recording material in which a dye precursor that emits electrons to become a dye and an electron accepting compound are combined. Japanese Patent Application Laid-Open Nos. 5-124360 and 6-210954 disclose electron accepting. It is described that a compound having a long-chain alkyl group in the molecular structure as a functional compound has good visibility.
[0007]
A reversible thermosensitive recording material having a long-chain alkyl group becomes a colored state when rapidly cooled after heating, and becomes a decolored state when slowly cooled after heating, and can form an image with a difference in cooling rate. Incidentally, when the cooling rate is high, the degree of color development becomes high and the contrast of the image becomes high. When the cooling rate is low, the degree of color development becomes thin and the contrast becomes low.
[0008]
When non-contact printing is performed on such a reversible thermosensitive recording material by irradiating with an electron beam using various lasers, the portion near the center of the laser beam becomes high at the time of irradiation and goes to the peripheral portion. According to the low temperature.
[0009]
That is, as shown in FIG. 3, for example, when “number 3” is printed on a reversible thermosensitive recording medium using a laser marker, the central portion of the portion 10 irradiated with the laser beam is heated at a high temperature, while the peripheral portion 11. Since the temperature becomes lower than that, heat conduction occurs from the portion 10 irradiated with the laser beam to the peripheral portion 11 due to such a temperature distribution, thereby rapidly cooling and forming a color to form an image.
[0010]
That is, if heating is performed for a very short time using a thermal head, laser light, or the like, cooling starts immediately after the heating is completed, so that a colored state can be developed.
[0011]
On the other hand, when the reversible thermosensitive recording medium is heated for a relatively long time, not only the recording layer but also the support and the like are heated, so that the cooling rate becomes slow and the color becomes decolored.
[0012]
As described above, even when the same heat source is used, if the cooling rate is controlled by the heating time or the heating temperature, a colored state or a decolored state can be arbitrarily developed.
[0013]
In the case of performing heat development by means other than laser light, a thermal head, a heat roll, a heat stamp, high frequency heating, radiant heat from an electric heater, hot air, or the like can be employed.
[0014]
[Problems to be solved by the invention]
By the way, in the case where a compound having a long-chain alkyl group in the molecular structure as an electron-accepting compound is used as a recording material and an image having a thick line and a thin line such as a barcode is formed using a laser marker or the like, Since the thickness of the line that can be formed with the laser irradiation width is limited, it is necessary to employ a technique of printing two lines next to each other in order to form a thick line exceeding the limit.
[0015]
However, as shown in the enlarged view of the bar code in FIG. 4, immediately after printing the previously heated linear area 12, the peripheral portion 13 of this line is also warmed, so that the adjacent linear shape When the area 14 is irradiated with a laser beam to print the area 14, the peripheral portion 13 previously heated cannot obtain a cooling rate necessary for printing, and the peripheral portion 13 is decolored. There is.
[0016]
For this reason, there has been a problem that barcodes cannot be reliably printed on a reversible thermosensitive recording material using an electron-accepting compound having an alkyl group.
[0017]
Even when an image other than a bar code is formed, the same problem as described above also occurs when, for example, a character or other image composed of a straight line or a curve that is larger than the thickness of the laser irradiation line is developed. .
[0018]
Therefore, the object of the present invention is to solve the above-described problems and to irradiate a laser beam a plurality of times when forming a thick line of a barcode, that is, the area adjacent to the heated area is In the case where an image is formed by heating immediately after the heating, a method in which a substantially continuous image can be formed in a plurality of areas without erasing the image of the previously heated portion.
[0019]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, a reversible thermosensitive recording layer is formed from a recording material containing a dye precursor that emits electrons and becomes a dye and an electron-accepting compound having a long-chain alkyl group, In an image forming method for a reversible thermosensitive recording medium in which a predetermined area of the reversible thermosensitive recording layer is heated at a predetermined speed and then cooled to develop or decolor the area to form an image, and adjacent to the heated area. Since the image forming method of the reversible thermosensitive recording medium is characterized in that an area is heated immediately after the heating, and an area adjacent thereto is heated while forcibly cooling the previously heated area to form an image. is there.
[0020]
In the image forming method of the present invention configured as described above, when the area adjacent to the heated area is heated immediately after the heating, the amount of heat from the area is forcibly cooled by forcibly cooling the previously heated area. Forcibly deprived, so that the previously heated area is not heated by the amount of heat applied to the adjacent area later, that is, the color of the area is not slowed down.
[0021]
In this way, in the image forming method of the present invention, a required cooling rate for color development can be obtained even in the previously heated area, and the adjacent (including some overlapping) heated portions also develop color. Continuous images can be formed in a plurality of heated areas.
[0022]
Further, in order to make the above action more reliable, the means for forced cooling of the previously heated area is to bring the air flow at room temperature or lower into contact with the area. And More preferably, the heating means is heating by laser beam irradiation.
[0023]
In this way, when the laser beam is irradiated to the reversible thermosensitive recording medium a plurality of times in a non-contact state, the image of the previously heated portion does not disappear, and a continuous image is formed across a plurality of areas. it can.
[0024]
In the case of an image forming method for a reversible thermosensitive recording medium in which the image is a bar code image, immediately after printing the first line when forming a thick line that is larger than the line that can be formed by a single movement of the laser. This line is forced to cool with an air flow below room temperature. For this reason, if laser light is irradiated on the portion in order to print the second and subsequent lines adjacent to the line, the amount of heat is taken away from the periphery of the previously heated line. Speed can be obtained with certainty, and color can be developed even at the boundary between adjacent lines or between the lines.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
The basic structure of the reversible thermosensitive recording medium of the present invention is that a recording layer in which various compounds are dispersed in a polymer binder is laminated on a synthetic resin substrate sheet such as polyethylene terephthalate, and a protective layer is further laminated. It has a laminated structure.
[0026]
The reversible thermosensitive recording medium used in the present invention may be a recording medium having a predetermined thermosensitive recording layer, and is usually a reversible thermosensitive recording comprising a required support, a binder provided thereon and a composition of a recording material. Layer is adopted.
[0027]
The reversible thermosensitive recording layer is formed of a recording material containing a dye precursor that emits electrons to become a dye and an electron-accepting compound having a long-chain alkyl group.
[0028]
As the electron donating compound (pigment precursor), a leuco dye having a lactone ring portion in the molecular structure is used. Specific examples of the electron donating compound (dye precursor) include crystal violet lactone, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4 -Azaphthalide, phthalide compounds such as 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide, 3-diethylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6- Methyl-7-anilinofluorane, 2- (2-chloroanilino) -6-diethylaminofluorane, 2- (2-chloroanilino) -6-dibutylaminofluorane, 2-anilino-3-methyl-6- (N -Ethylisopentylamino) fluorane, 3-cyclohexylmethylamino-6-methyl-7-anilinofluorane, 3-benzi Ethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-methylpropylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl And fluorane compounds such as -7-xylidinofluorane.
[0029]
The electron-accepting compound having a long-chain alkyl group used in the present invention is an organic phosphate compound, aliphatic carboxylic acid compound or phenol compound having an aliphatic group having 6 or more carbon atoms, preferably 12 or more carbon atoms. It is a phenolic compound having one aliphatic group.
[0030]
Specific examples of the electron accepting compound include dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid, α-hydroxydecanoic acid, α-hydroxytetradecanoic acid, α-hydroxyhexadecanoic acid. , Α-hydroxyoctadecanoic acid, α-hydroxypentadecanoic acid, α-hydroxyeicosanoic acid, α-hydroxydocosanoic acid, α-hydroxytetracosanoic acid, α-hydroxyhexacosanoic acid, α-hydroxyoctacosanoic acid, etc. It is done. Examples of phenolic compounds include 4'-hydroxy-4-octadecylbenzanilide, N-octadecyl-4-hydroxybenzamide, N- (4-hydroxyphenyl) -N'-octadecylurea, 4-hydroxyphenylpropiono-behenyl hydrazide and the like. Can be mentioned.
[0031]
The recording layer made of the recording material as described above can be provided by dispersing a dye precursor and an electron-accepting compound in a polymer binder and coating the support on paper, synthetic paper, plastic film or the like.
[0032]
As the polymer binder, a resin having good transparency and film forming property and high heat resistance is used. For example, polymethacrylic acid ester, polyacrylic acid ester or copolymer thereof, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinyl acetate-alcohol copolymer Polymer, other vinyl acetate compounds, vinyl chloride copolymer, polyvinylidene chloride, vinylidene chloride copolymer, polyvinyl alcohol, polyester, polyamide, polyurethane, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene A copolymer or the like is preferred.
[0033]
A heat crosslinkable resin can also be used as a binder. As the heat crosslinkable resin, any resin having a hydroxyl group, amino group, carboxyl group and the like that can be thermally crosslinked with an isocyanate crosslinking agent may be used, but acrylic polyol, polyester polyol, and polyurethane polyol resin are particularly preferable.
[0034]
As the isocyanate crosslinking agent, hexamethylene diisocyanate and toluene diisocyanate are particularly preferable.
[0035]
The mixing ratio of the recording material is 10 to 100 parts by weight, preferably 20 to 50 parts by weight of the electron-accepting compound, and 10 to 200 parts by weight, preferably 20 to 100 parts by weight of the binder with respect to 10 parts by weight of the leuco dye. It is.
[0036]
In addition, it is preferable to provide a protective layer on the recording layer of the reversible thermosensitive recording medium in order to improve repetition durability and matching with a thermal head. Examples of such protective coating include polyethylene terephthalate, Resins with high heat resistance such as ether imide, polyether ether ketone, polysulfone, polyphenylene sulfide, polyacrylate, polyether sulfone, polycarbonate, polyethylene naphthalate, polyimide, acrylic resin, ultraviolet curable resin, and electron beam curable resin are preferable.
[0037]
In addition, the recording layer may contain stabilizers, sensitizers, ultraviolet absorbers, dispersants, etc. in order to improve the heat-resistant storage stability and thermal stability of the colored state, prevent discoloration / fading due to light, and improve sensitivity. it can.
[0038]
The reversible thermosensitive recording medium in the present invention is usually a laminate in which a reversible thermosensitive recording layer is provided on a film or sheet-like support such as a card or a label, and an adhesive layer is provided on the back surface. It may be one that can be easily attached, or a card or label that can be attached by means such as a holder.
[0039]
As a heating means in the present invention, a known method can be adopted as long as it is a non-contact heating (printing) means capable of heating the medium by irradiating an electron beam or the like. A gas laser, a YAG laser, a semiconductor laser, an infrared laser, etc. are mentioned.
[0040]
The means for forced cooling of the previously heated area employed in the present invention is a means capable of cooling a reversible thermosensitive recording medium such as a reversible thermosensitive label to a temperature required for color development such as printing. The area is brought into contact with an air flow below room temperature.
[0041]
As shown in FIG. 1, in order to forcibly cool a label-like reversible thermosensitive recording medium 3 affixed to the side of a return box 2 transported by a conveyor line 1, a reversible thermosensitive recording medium is used with a laser marker 4. At the same time as printing the barcode 5 on 3, the air flow from a cold air generator (a so-called spot cooler can be used) 6 to room temperature (1 to 35 ° C.) or less is applied to the entire label-like reversible thermosensitive recording medium 3. Or it sprays on the part heated with the laser beam.
[0042]
In addition, the air flow is a variety of gases such as air and nitrogen gas, such as air flow at room temperature by a fan (fan), cold air whose temperature is adjusted below that, or air flow blown out from a gas cylinder containing compressed air. It is also possible to employ a cooling means such as a direct cooling or a forced cooling of the back and surroundings of the reversible thermosensitive recording medium 3 directly or indirectly with cooling water or other refrigerant, or a mediated cooling by a Peltier element. .
[0043]
In order to cool an airflow at room temperature or less in contact with a predetermined area of the reversible thermosensitive recording medium 3, the airflow may be constantly blown into contact, or the airflow may be contacted only during printing. The airflow contact in the present invention is not only a state in which a cooling airflow is blown against the reversible thermosensitive recording medium 3 from the front of the predetermined area, but is also blown obliquely or substantially parallel to the surface of the predetermined area. This includes the case where the film is formed and cooled.
[0044]
In addition, it is possible to provide a nozzle with a narrow outlet for airflow, and cool only a predetermined portion in accordance with the movement of the laser beam. In that case, as shown in FIG. 1, the positioning of the return box 2 on the conveyor line 1 is performed accurately and the timing of the laser beam by the laser marker 4 and the cooling by the cold air generator 6 is adjusted. The computer 7 is provided.
[0045]
As shown in FIGS. 2 (a) and 2 (b), when forming a barcode on the reversible thermosensitive recording layer, the linear area 8 previously heated in accordance with the printing order is flown at an air flow of room temperature or lower. The linear area 9 adjacent to this is heated by laser light irradiation with forced cooling, and the thick linear lines (in the enlarged view of FIG. 2b, the parallel linear areas appear to be slightly separated, but are substantially adjacent to the naked eye. Is a barcode image formed. In this way, the amount of heat is quickly conducted and diffused from the previously heated linear area 8 and its peripheral part, so that the cooling rate necessary for printing can be obtained reliably, and the adjacent linear area 8 and the linear area 8 are lined up. It is possible to develop a color at a boundary with the line-shaped area 9 and a portion where these linear sections overlap each other, and a thick line necessary for the barcode can be printed.
[0046]
Examples and Comparative Examples
<Creation of reversible thermosensitive label>
(A) Dye precursor: Crystal violet lactone 10 parts by weight (b) Electron accepting compound:
Hydroxyphenylpropiono-behenyl hydrazide 20 parts by weight (c) Binder:
Acrylic polyol (LR-1503: manufactured by Mitsubishi Rayon) 50 parts by weight (d) Solvent: 150 parts by weight of toluene After each material is dispersed in a solvent for about 2 hours using a paint shaker, the following isocyanate compound may be added. Stir to adjust the coating solution.
(E) Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.) 5 parts by weight
The coating solution was coated on a white polyester film of 188 μm (W400: manufactured by Mitsubishi Chemical Polyester Film) using a bar coater, dried at 130 ° C., and then aged at 60 ° C. for 48 hours to provide a recording layer having a thickness of 10 μm. It was. An ultraviolet curable resin was applied thereon to a thickness of 2 μm and cured with ultraviolet rays to form a protective layer, thereby producing a reversible thermosensitive recording medium.
[0048]
A heat-resistant adhesive (double-sided tape 5000N: manufactured by Nitto Denko) was attached to the back surface of the obtained reversible thermosensitive recording medium to produce a reversible thermosensitive label. The obtained reversible thermosensitive label attached to a polypropylene container was used in the image forming methods of Examples and Comparative Examples shown below.
[0049]
[Example 1]
Using a laser marker (Keyence CO2 laser: 12W), air and air drawn from an air compressor at an ambient temperature of 30 ° C to a container with a reversible thermosensitive label, alphanumeric characters and barcodes Is printed.
[0050]
The formed prints were visually read and read with a simple barcode reader, and the results were evaluated.
[0051]
The evaluation is based on a two-step evaluation of good (○ mark) and defective (× mark) for the print quality, and a two-step evaluation of reading (reading ○ mark) and bad (× mark) on the reader. The results are shown in Table 1 with symbols.
[0052]
[Table 1]

[0053]
[Example 2]
Except that printing was performed while blowing cold air (23 ° C.) with a cold air machine instead of air, image formation was performed in the same manner as in Example 1, and the quality of the printed print and the simple barcode reader were visually confirmed. The results are shown in Table 1.
[0054]
[Comparative Example 1]
Except that printing was performed at an ambient temperature of 30 ° C. without cooling, image formation was performed in the same manner as in Example 1, and the quality of the printed print was visually confirmed and read by a simple barcode reader. The results are shown in Table 1.
[0055]
As is clear from the results in Table 1, both the examples and the comparative examples were able to print alphanumeric characters, but the barcodes were printed with cooling, but there was no problem, but the comparison was not cooled. In Example 1, a thick bar could not be printed with a thick line, and it could not be used as a barcode.
[0056]
Incidentally, as a result of examining the color density with various cooling rates, the cooling rate required for printing on the reversible thermosensitive recording medium used in Example 1 is 300 ° C./sec or more, and the cooling required for erasing is performed. The speed has been found to be 50-100 ° C./sec or less. In addition, it was confirmed that printing by a laser instantaneously rose to several hundred degrees in the central portion, but the peripheral portion was also heated to several tens to 100 ° C. In order to clearly print barcodes or bold lines, the recording medium was cooled to about 0 to 30 ° C., and preferably cooled to room temperature or lower.
[0057]
【The invention's effect】
As described above, according to the image forming method of the reversible thermosensitive recording medium, when the area adjacent to the heated area is heated immediately after the heating, the previously heated area is forcibly cooled while being forcibly cooled. Since the image is formed by heating the area adjacent to the area, the required cooling rate for color development can be obtained in this area by forcibly cooling the previously heated area. There is an advantage that an image can be formed.
[0058]
In the image forming method of the reversible thermosensitive recording medium, the heating means is heating by laser beam irradiation, and the forced cooling means of the previously formed image is blowing cold air onto the image. In the case of irradiating a plurality of times, the image of the previously heated portion does not disappear, and a continuous image can be formed across a plurality of areas.
[0059]
Further, in the case of the image forming method of the reversible thermosensitive recording medium in which the image is a barcode image, the second line can be printed immediately adjacent to the first line after printing the first line. There is an advantage that a bar code having a line can be printed.
[Brief description of the drawings]
FIG. 1 is an explanatory view schematically showing an image forming method according to an embodiment. FIG. 2 (a) is a plan view showing a barcode printed by the image forming method according to the embodiment. FIG. [FIG. 3] (a) Plan view of characters printed using a laser marker (b) Plan view showing an enlargement of the main part of FIG. 2 (a) 4] Main part enlarged plan view explaining the state of printing of a conventional barcode [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Conveyor line 2 Returning box 3 Reversible thermosensitive recording medium 4 Laser marker 5 Bar code 6 Cold wind generator 7 Computer 8, 12 The linear area 9 and 14 which were heated previously The adjacent linear area 10 The part 11 which irradiated the laser beam , 13 Peripheral part

Claims (2)

A reversible thermosensitive recording layer is formed with a recording material containing a dye precursor that emits electrons and becomes a dye and an electron-accepting compound having a long-chain alkyl group, and a predetermined area of the reversible thermosensitive recording layer is heated and predetermined. In the image forming method of a reversible thermosensitive recording medium in which an image is formed by coloring or decoloring the area by cooling at a speed,
At the same time by heating with a laser beam to form an image, while cooling forced by contacting the following air flow at room temperature in whole or heating the printed surface of the heated portion by the laser beam of the reversible thermosensitive recording medium, heating the previously the image forming method of the reversible thermosensitive recording medium, characterized in that to form a continuous image in these areas the zones adjacent to the heating zone which is heated by a laser beam.   2. The image forming method for a reversible thermosensitive recording medium according to claim 1, wherein the image has a thick line and a thin line, and the thick line is a bar code printed by adjoining two lines.

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