JP3911149B2 - Photosensitive material and marking method - Google Patents

Description

【００１８】
上表における視認性は、各々のドットパターンを目視観察したとき、ドットパターンが視線の方向によらず明瞭に確認できるものを「○」、その存在が確認できるものの視線の方向によっては確認しにくくなるものを「△」、一瞥ではその存在の確認が困難なものを「×」として評価した結果を表している。また、視認性の良否に大きな関連性をもつと考えられるドットパターン領域の平均表面粗さを測定し、その測定値も合わせて記載してある。なお、平均表面粗さは、ドットパターン領域内の単位面積中に含まれる微小な凹凸の高低差を算術平均した値で表している。
【００１９】
以上の実験結果から、視認性は発振波長を９．１９１８μｍ〜９．７５３４μｍの９μｍ帯に設定する方が有利であることが確認され、この場合の表面粗さがほとんど０．１μｍを越えるようになっていることがわかる。表面粗さが大きくなると光の散乱も増えるから、ドットパターン領域をその周囲から識別しやすくなる。また、レーザービーム照射による熱溶融部分の大きさは、１０μｍ帯よりも９μｍ帯のレーザービームを用いた方が小さくなる。これは、乳剤層２４ｂ及びベース層２４ａは、ともに１０μｍ帯よりも９μｍ帯のレーザービームに対する吸収効率が高いので、直接照射された表層部分での溶融，蒸散が促進され、その周辺や内部への熱エネルギーの伝播が少なくなるためである。そして、このことは表面粗さを大きくすることにも効果的に作用する。
【００２０】
さらに、ドットパターンの大きさと視認性との相関を調べるために、図３の実験装置を用いて様々な直径をもつドットパターンを形成して目視観察を行った。ドットパターンの直径は、印字ヘッド２０とＸレイフイルム２４との間隔を調節することによって変更した。ドットパターンの直径と視認性との相関は表２に示すとおりで、視認性の評価は先の表１と同じ基準による。なお、図２に示すように、レーザービームを走査してＸレイフイルム３に照射したときには、ビームスポットの形状が真円からわずかに偏平な楕円形状となるが、視認性に関しては真円とみなして差し支えない。
【００２１】
【表２】

【００２２】
この実験結果から、ドットパターンの直径が１００μｍ〜５００μｍの範囲であれば、その識別性が十分であることが確認できた。ただし、一文字のサイズを例えば２．５ｍｍ×２．５ｍｍのサイズとし、その一文字を５×５のドットパターンで表そうとするときには、１つのドットパターンの直径が５００μｍを越えてしまうと隣接するドットパターンとの重なりが生じやすくなり、視認性を妨げる大きな原因になるので好ましくない。
【００２３】
【実施例】
以上の実験結果を踏まえ、一文字分のサイズが２．５ｍｍ×２．５ｍｍで、この一文字を５×５ドットで表現する場合のドットパターンとしてどのような形態のものが好適であるかを図３の実験装置を用いてさらに検討したところ、図６〜図１０に示す形態のものが視認性の点で優れ、また不要な光カブリを発生させることがないものとして効果的であることがわかった。なお、図１１のドットパターンは比較例を示すもので、視認性が不十分でその周囲に光カブリ故障が生じたものである。図６〜図１０に示すサンプル１〜５及び、図１１に示す比較例のドットパターンデータ（ドットパターンの直径Ｗ、凹凸量、溶融部の平均表面粗さ）と、そのときのレーザービームの照射条件（発振波長、照射時間Ｔ、ビームプロファイル）は次の表３に示すとおりである。なお、ビームプロファイルは、ビームスポット領域内の照射エネルギーがガウス型分布であるか、スポット領域全域で等しいフラットトップのいずれであるかを表している。
【００２４】
【表３】

【００２５】
サンプル１〜３はいずれも乳剤層２４ｂの厚み以下の範囲内で乳剤層２４ｂを深さＤとなる凹形状に溶融、蒸散させたドットパターンをもつ。そして、サンプル１は、図６に示すように断面において乳剤層２４ｂだけを矩形状に粗く蝕刻したドットパターンとなっている。サンプル２は、ビームスポットの周囲に熱溶融した乳剤層２４ｂがわずかに盛り上がったドットパターンであり、サンプル３は、ビームスポットを１〜２ｍｍに拡大してドットパターンの直径Ｗを大きくし、相対的にエネルギー密度を小さくしたものである。
【００２６】
サンプル４はレーザービームを照射して乳剤層２４ｂが突沸した状態で照射を止め、乳剤層２４ｂが局所的に蒸散する直前に再固化させたもので、表面を凸状に盛り上がらせたドットパターンとなっている。その突出高さＨは、乳剤層２４ｂの厚み以下である。なお、突出高さＨを高くすれば視認性はよくなるが、擦れあったときに損傷，破損しやすくなる。この点、サンプル４ではその突出高さを乳剤層２４ｂの厚み以下に抑えているのでこうした問題はほとんど生じることはなく、しかもその平均表面粗さを０．２μｍ〜１．０μｍにしたこととあいまって、十分な視認性が得られている。
【００２７】
サンプル５は図１０に示すように断面においてレーザービーム照射部分の乳剤層２４ｂを全て溶融、蒸散し、ベース層２４ａの表層部分も１０μｍ溶融、蒸散させたドットパターンとなっている。
【００２８】
これらのサンプル１〜５のもつドットパターンは、その直径Ｗが１００μｍ〜５００μｍで十分な大きさをもち、また各々の表面が０．２μｍ〜１．０μｍの平均表面粗さとなっているため、目視したときにその周囲と明瞭に識別することができる。これに対し、図１１に示す比較例では、ドットパターンの直径Ｗが１００μｍ未満で小さいだけでなく表面粗さも不十分であるため、目視による識別が困難である。また、凹凸量（深さ）Ｄが大きくベース層２４ａに達している。このため、レーザービームがベース層２４ａ内の不純物などに照射され、これらを発光させてしまうので、Ｘレイフイルム２４に光カブリ故障が生じやすく、実用にならない。ベース層内の不純物による光カブリを防止するために、ベース層表面に厚みＳの乳剤層が形成されている感光材料とドットの凹凸量は、Ｓ＋１０μｍ以下になるようにするのが好ましい。
【００２９】
このように、視認性に優れ、Ｘレイフイルムに光カブリ故障を生じさせることがないドットパターンが決まれば、このドットパターン形状が得られるように、例えば表３に挙げたようなレーザービームの照射条件を整えればよい。そして、このように決めた照射条件のもとでドットパターンの印字を行うことにより、Ｘレイフイルムに対して好適な文字やマークの印字を安定して行うことが可能となる。
【００３０】
なお、ドットパターンの直径Ｗの最小値は視認性の上から１００μｍ以上にしておくことが必要であるが、直径Ｗの最大値は一文字のサイズ及び、この一文字を表すドットの数によって大きくすることが可能である。例えば、一文字のサイズを５ｍｍ×５ｍｍとし、これを５×５のドット数で表現する場合には、隣接ドットとの重畳を考慮して一個のドットパターンの直径Ｗを最大で１ｍｍまで大きくすることが可能となる。つまり、一文字のドットパターンが縦にＭ個、横にＮ個配列して縦横サイズがＡ×Ｂの場合、１００μｍ以上かつ、Ａ／Ｍ又はＢ／Ｎのいずれか小さい方以下の直径まで大きくすることができる。また、ドットパターンの識別性を良好に保つためには、やはりドット領域の平均表面粗さについては、０．２μｍ〜１．０μｍの範囲にしておくのがよい。
【００３１】
以上、図示した実施の形態にしたがって説明してきたが、本発明はＸレイフイルムだけでなく、１３５フイルムやブローニーフイルムなどのネガあるいはポジフイルムにも等しく適用が可能である。また、レーザービームの発振波長は感光材料を構成する乳剤層やベース層の素材に応じて適宜に選択すればよい。
【００３２】
【発明の効果】
上述のように、本発明によれば、レーザービームを感光材料の乳剤層に照射して形成される略円形のドットパターンの配列により、縦にＭ個、横にＮ個配列して縦横サイズがＡ×Ｂの文字やマークの印字を行うにあたり、個々のドットパターンの凹凸量を乳剤層の厚み＋１０μｍ以下とし、その直径が１００μｍ以上かつ、Ａ／Ｍ又はＢ／Ｎのいずれか小さい方以下の直径をもつ略円形状とし、平均表面粗さを０．２μｍ〜１．０μｍにしたから、光学的な識別性に優れ、しかも感光材料に不要な光カブリを生じさせることなく、高品位のマーキングを行うことができる。特に、感光材料のベース層にＰＥＴが用いられたＸレイフイルムである場合には、発振波長が９μｍ〜１０μｍのレーザービームを３μ秒〜２０μ秒の範囲で照射してドットパターンを形成するのが効果的である。
【図面の簡単な説明】
【図１】レーザーマーキング装置の概略図である。
【図２】ドットパターンの配列による文字のマーキングの一例を示す説明図である。
【図３】ドットパターン評価用の実験装置の概略図である。
【図４】近赤外領域における乳剤層の透過スペクトルを示すグラフである。
【図５】近赤外領域におけるベース層の透過スペクトルを示すグラフである。
【図６】サンプル１のドットパターンの概略を示す中央断面図である。
【図７】サンプル２のドットパターンの概略を示す中央断面図である。
【図８】サンプル３のドットパターンの概略を示す中央断面図である。
【図９】サンプル４のドットパターンの概略を示す中央断面図である。
【図１０】サンプル５のドットパターンの概略を示す中央断面図である。
【図１１】比較例のドットパターンの概略を示す中央断面図である。
【符号の説明】
３，２４ Ｘレイフイルム
１０，２０ 印字ヘッド
１１，２１ レーザー発振器
１２ レーザー偏向器
２２ 集光レンズ
２４ａ ベース層
２４ｂ 乳剤層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photosensitive material on which characters and marks are printed by laser beam irradiation and a marking method thereof.
[0002]
[Prior art]
As described in Japanese Patent Application Laid-Open No. 10-6549, a laser beam is intermittently irradiated to sequentially form a dot pattern on the surface of the photosensitive material, and visually readable characters and marks are printed by the continuous dot pattern. A marking method is known. Irradiation of the laser beam leaves a partial melt mark on the surface of the photosensitive material, and this melt mark is observed as a dot pattern. Characters and patterns represented by these dot pattern arrays are accurately recognized. In order to be able to do so, it is necessary that each dot pattern is easy to identify.
[0003]
[Problems to be solved by the invention]
In order to form an easily identifiable dot pattern, several conditions are set for the energy density of the laser beam and the irradiation time (pulse width) of the laser beam in the method described in the above publication. However, regardless of the laser beam irradiation time, the energy density of the laser beam is difficult to manage because it is difficult to measure, and the composition of the base layer and emulsion layer changes when the type of photosensitive material changes. Therefore, it is difficult to say that this is a very practical method for forming a dot pattern with stable quality.
[0004]
Also, when the laser beam is irradiated from the emulsion layer side of the photosensitive material, if the laser beam reaches the base layer with a certain intensity, the impurities contained in the base layer emit light upon receiving the irradiation, It has also been confirmed that optical fog is generated in the emulsion layer. When such an optical fog failure occurs, the quality of the photosensitive material is significantly deteriorated.
[0005]
The present invention has been made in consideration of the above-mentioned background, and does not cause unnecessary optical fogging in the photosensitive material when irradiated with a laser beam, and it is possible to print characters and marks by an array of dot patterns that are optically easy to identify. An object of the present invention is to provide a photosensitive material subjected to the above-described process and a marking method thereof.
[0006]
[Means for Solving the Problems]
In achieving the above object, the present invention has focused on the fact that the discriminability of the dot pattern depends on the shape of the dot pattern itself on the surface of the photosensitive material. When a dot or dot pattern formed by irradiating a laser beam from the emulsion surface side of thickness S is arranged vertically M and N horizontally and a character or mark having a vertical and horizontal size of A × B is printed, The pattern has an unevenness of S + 10 μm or less, a substantially circular shape having a diameter of 100 μm or more and A / M or B / N, whichever is smaller, when viewed from the emulsion layer side, and has a surface roughness of 0. It is set in the range of 2 μm to 1.0 μm. By using such a dot pattern, it becomes possible to print easily distinguishable characters and marks without optical fogging failure. The characters and marks printed in this way can be read not only by visual reading with visible light, but also by automatic reading using, for example, infrared rays in a dark room. Further, the dot pattern does not necessarily have a perfect circle shape.
[0007]
If the irradiation time of the laser beam per dot pattern becomes longer, the heat generated in the irradiation area propagates and melts and the diameter of the dot pattern tends to be larger than the target setting value. When the thickness is 3 to 5 μm and the photosensitive material is an X-ray film using PET (polyethylene terephthalate) as a base layer, a laser beam with an oscillation wavelength of 9 μm to 10 μm is irradiated in a range of 3 to 20 μs. preferable.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an outline of a laser marking apparatus that performs printing by irradiating the surface with a laser beam in the process of transporting a long X-ray film. An X-ray film 3 is wound around the winding core 2 with the emulsion surface facing the front side, and the X-ray film 3 is wound around the winding core 6 through an appropriate pass roll, print roll 4, and suction drum 5. The suction drum 5 has a large number of air suction holes formed on the outer peripheral surface thereof, and rotates at a constant speed by a drive signal from the winding control device 7. The winding control device 7 further controls the rotation of the winding core 2 and applies a constant back tension to the X-ray film 3 between the winding drum 2 and the suction drum 5. The winding core 6 is driven so as to wind up the X-ray film 3 sent from the suction drum 5.
[0009]
The suction drum 5 has a large number of air suction holes on its outer peripheral surface, and conveys it at a constant speed without slipping while sucking the base surface side of the X-ray film 3. Accordingly, the transport speed of the X-ray film 3 on the print roll 4 matches the rotational peripheral speed of the suction drum 5. A rotary encoder 8 is combined with the suction drum 5, and the rotary encoder 8 outputs a conveyance pulse corresponding to the rotational speed of the suction drum 5.
[0010]
A print head 10 is provided facing the outer periphery of the print roll 4. The print head 10 includes a laser oscillator 11 and a beam deflector 12 including a condenser lens. The laser oscillator 11 is constituted by a CO ₂ gas laser tube, and emits a laser beam having a constant oscillation wavelength at a constant time width (pulse width) at a timing according to a drive signal from the laser control device 15. The beam deflector 12 is composed of, for example, an AOD (acousto-optic device), and scans the laser beam in a direction orthogonal to the transport direction of the X-ray film 3 by a deflection signal from the laser control device 15.
[0011]
A print pattern signal corresponding to characters and marks to be recorded on the X-ray film 3 is input from the winding control device 7 to the laser control device 15. The laser controller 15 inputs a drive signal to the laser oscillator 11 based on the print pattern signal while monitoring the transport length of the X-ray film 3 based on the transport pulse from the rotary encoder 8, and also to the beam deflector 12. Each of them is operated by inputting a deflection signal. Thus, as shown in FIG. 2, the scanning direction of the laser beam 16 by the beam deflector 12 is the main scanning direction, the transport direction of the X-ray film 3 is the sub-scanning direction, and the character “F” is 5 × 5 dots, for example. It will be printed.
[0012]
When a laser beam is irradiated to the emulsion layer of the X ray film 3, the emulsion layer is locally heated and melted, and the melted trace becomes a dot pattern. In order to print characters and marks represented by such an arrangement of dot patterns with high quality, the individual diameters of the dot patterns are made almost constant, and the position at which the transport speed of the X-ray film 3 is kept constant. It is necessary to irradiate a laser beam. Therefore, as shown in FIG. 2, the X-ray film 3 is wrapped on the print roll 4 so that the distance from the print head 10 is kept constant, and the transport speed of the X-ray film 3 matches the peripheral speed of the suction drum 5. The laser beam 16 is irradiated at the position where Note that printing may be performed by irradiating the X-ray film 3 on the print roll 4 with the laser beam 16.
[0013]
By the way, most of the photosensitive material such as the X-ray film 3 is used for image recording, and the space for printing characters and marks is narrow. For example, the X-ray film 3 is cut into a sheet shape and commercialized, and characters and marks representing manufacturers and types are often printed along the edge of the film sheet. And, since the number of dots used to represent a character within a certain size and to represent a character is naturally limited, what kind of dot pattern is advantageous for improving visibility In order to do this, a laser beam irradiation experiment was conducted using the experimental apparatus shown in FIG.
[0014]
In FIG. 3, the print head 20 includes a laser oscillator 21 and a condenser lens 22, and the laser controller 21 controls the drive of the laser oscillator 21. The laser oscillator 21 uses a CO ₂ gas laser tube whose oscillation wavelength can be varied by a grating using a diffraction grating, and the oscillation wavelength and laser beam irradiation time (in accordance with a control signal from the laser controller 23). (Pulse width) can be adjusted. The condensing lens 22 condenses the laser beam 16 emitted from the laser oscillator 21 with a beam diameter of about 4 mm to a spot diameter of about 0.2 mm at a position 54 mm in front of the condensing lens 22. A sheet-like X-ray film 24 is set as an evaluation sample at this condensing position.
[0015]
As the X-ray film 24, a base layer 24a made of PET (polyethylene terephthalate) having a thickness of about 175 μm and an emulsion layer 24b having a thickness of about 2 to 5 μm coated on the surface thereof was used. The laser oscillator 21 has a variable oscillation wavelength in the near infrared region of about 9 μm to 11 μm. Therefore, when the transmittance spectra in the near-infrared region of the emulsion layer 24b and the base layer 24a were measured in advance, the measurement results were as shown in FIGS. 4 and 5, respectively. Since there is no extreme difference in reflectivity, it can be seen that both the base layer 24a and the emulsion layer 24b have higher absorption in the 9 μm band (9 μm or more and less than 10 μm) than in the 10 μm band (10 μm or more and less than 11 μm).
[0016]
Therefore, an irradiation experiment was performed using the experimental apparatus shown in FIG. 3 while changing the oscillation wavelength of the laser beam 16, and it was first confirmed whether or not the discriminability of the dot pattern depends on the oscillation wavelength of the laser beam. In this experiment, the irradiation time (pulse width) of the laser beam 16 was set to 10 μsec, and the spot diameter of the laser beam 16 on the surface of the emulsion layer 24b was set to 0.2 mm. The experimental results are shown in Table 1.
[0017]
[Table 1]

[0018]
The visibility in the above table is “○” when the dot pattern can be clearly confirmed regardless of the direction of the line of sight when each dot pattern is visually observed, but it is difficult to confirm depending on the direction of the line of sight although its presence can be confirmed. The result is evaluated as “Δ”, and “×” as the one that is difficult to confirm the existence of. Moreover, the average surface roughness of the dot pattern area considered to have a great relevance to the quality of visibility is measured, and the measured value is also described. The average surface roughness is expressed as an arithmetic average value of the height difference of minute unevenness included in the unit area in the dot pattern region.
[0019]
From the above experimental results, it has been confirmed that it is advantageous to set the oscillation wavelength in the 9 μm band of 9.91818 μm to 9.7534 μm, and the surface roughness in this case almost exceeds 0.1 μm. You can see that Since the scattering of light increases as the surface roughness increases, it becomes easier to identify the dot pattern region from its periphery. In addition, the size of the heat-melted portion by laser beam irradiation is smaller when the 9 μm band laser beam is used than when the 10 μm band is used. This is because both the emulsion layer 24b and the base layer 24a have higher absorption efficiency with respect to the laser beam in the 9 μm band than in the 10 μm band, so that melting and transpiration are promoted in the directly irradiated surface layer portion, This is because the propagation of thermal energy is reduced. This also effectively acts to increase the surface roughness.
[0020]
Further, in order to investigate the correlation between the size of the dot pattern and the visibility, dot patterns having various diameters were formed using the experimental apparatus shown in FIG. 3 and visually observed. The diameter of the dot pattern was changed by adjusting the distance between the print head 20 and the X-ray film 24. The correlation between the diameter of the dot pattern and the visibility is as shown in Table 2, and the evaluation of visibility is based on the same criteria as in Table 1 above. As shown in FIG. 2, when the X-ray film 3 is irradiated by scanning with a laser beam, the shape of the beam spot changes from a perfect circle to a slightly flat elliptical shape. It does not matter.
[0021]
[Table 2]

[0022]
From this experimental result, it was confirmed that the discriminability was sufficient when the diameter of the dot pattern was in the range of 100 μm to 500 μm. However, when the size of one character is, for example, 2.5 mm × 2.5 mm and the character is to be represented by a 5 × 5 dot pattern, if the diameter of one dot pattern exceeds 500 μm, adjacent dots Overlap with the pattern is likely to occur, which is not preferable because it is a major cause of hindering visibility.
[0023]
【Example】
Based on the above experimental results, FIG. 3 shows what type of dot pattern is suitable when the size of one character is 2.5 mm × 2.5 mm and this character is expressed by 5 × 5 dots. Further examination using the experimental apparatus shown in FIG. 6 revealed that the configuration shown in FIGS. 6 to 10 is excellent in terms of visibility and is effective as not generating unnecessary optical fog. . The dot pattern in FIG. 11 shows a comparative example, in which the visibility is insufficient and an optical fogging failure occurs around the dot pattern. The dot pattern data (the diameter W of the dot pattern, the unevenness amount, the average surface roughness of the melted portion) of the samples 1 to 5 shown in FIGS. 6 to 10 and the comparative example shown in FIG. 11, and the laser beam irradiation at that time Conditions (oscillation wavelength, irradiation time T, beam profile) are as shown in Table 3 below. The beam profile indicates whether the irradiation energy in the beam spot area is a Gaussian distribution or is an equal flat top over the entire spot area.
[0024]
[Table 3]

[0025]
Samples 1 to 3 each have a dot pattern in which the emulsion layer 24b is melted and evaporated in a concave shape having a depth D within the range of the thickness of the emulsion layer 24b or less. Sample 1 has a dot pattern in which only the emulsion layer 24b is roughly etched into a rectangular shape in the cross section as shown in FIG. Sample 2 is a dot pattern in which an emulsion layer 24b thermally melted around the beam spot is slightly raised. Sample 3 has a beam spot enlarged to 1 to 2 mm to increase the diameter W of the dot pattern. The energy density is reduced.
[0026]
Sample 4 was irradiated with a laser beam and stopped when the emulsion layer 24b bumped, and re-solidified immediately before the emulsion layer 24b evaporated locally. It has become. The protruding height H is equal to or less than the thickness of the emulsion layer 24b. Note that, if the protrusion height H is increased, the visibility is improved, but it is easily damaged or broken when rubbed. In this respect, in Sample 4, since the protruding height is suppressed to be equal to or less than the thickness of the emulsion layer 24b, such a problem hardly occurs, and the average surface roughness is 0.2 μm to 1.0 μm. Thus, sufficient visibility is obtained.
[0027]
As shown in FIG. 10, the sample 5 has a dot pattern in which the emulsion layer 24b in the laser beam irradiated portion is completely melted and evaporated in the cross section, and the surface layer portion of the base layer 24a is also melted and evaporated.
[0028]
The dot patterns of these samples 1 to 5 have a sufficient size with a diameter W of 100 μm to 500 μm, and each surface has an average surface roughness of 0.2 μm to 1.0 μm. Can be clearly distinguished from its surroundings. On the other hand, in the comparative example shown in FIG. 11, since the dot pattern diameter W is less than 100 μm and is small, the surface roughness is insufficient, so that visual identification is difficult. The unevenness (depth) D is large and reaches the base layer 24a. For this reason, the laser beam is irradiated on the impurities in the base layer 24a and emits them, so that an optical fogging failure is likely to occur in the X-ray film 24, which is not practical. In order to prevent optical fogging due to impurities in the base layer, it is preferable that the unevenness of the dots and the photosensitive material in which the emulsion layer having the thickness S is formed on the surface of the base layer is S + 10 μm or less.
[0029]
In this way, when a dot pattern having excellent visibility and causing no optical fogging failure in the X-ray film is determined, for example, laser beam irradiation as shown in Table 3 is obtained so that this dot pattern shape can be obtained. What is necessary is just to prepare conditions. By printing a dot pattern under the irradiation conditions determined in this way, it is possible to stably print characters and marks suitable for the X-ray film.
[0030]
The minimum value of the diameter W of the dot pattern needs to be 100 μm or more from the viewpoint of visibility, but the maximum value of the diameter W should be increased depending on the size of one character and the number of dots representing this one character. Is possible. For example, when the size of one character is 5 mm × 5 mm and this is expressed by the number of dots of 5 × 5, the diameter W of one dot pattern should be increased up to 1 mm in consideration of overlapping with adjacent dots. Is possible. That is, when M dot patterns of one character are arranged vertically and N are arranged horizontally and the vertical and horizontal size is A × B, the diameter is increased to 100 μm or more and smaller than A / M or B / N, whichever is smaller. be able to. In order to maintain good dot pattern discrimination, it is preferable that the average surface roughness of the dot region be in the range of 0.2 μm to 1.0 μm.
[0031]
Although the present invention has been described according to the illustrated embodiment, the present invention is equally applicable not only to an X-ray film but also to a negative or positive film such as a 135 film or a Brownie film. Further, the oscillation wavelength of the laser beam may be appropriately selected according to the material of the emulsion layer and base layer constituting the photosensitive material.
[0032]
【The invention's effect】
As described above, according to the present invention, the vertical and horizontal sizes can be obtained by arranging M in the vertical direction and N in the horizontal direction by arranging the substantially circular dot pattern formed by irradiating the emulsion layer of the photosensitive material with the laser beam. When printing characters and marks of A × B, the unevenness of each dot pattern is the emulsion layer thickness +10 μm or less, the diameter is 100 μm or more, and A / M or B / N, whichever is smaller Because it has a substantially circular shape with a diameter and an average surface roughness of 0.2 μm to 1.0 μm, it has excellent optical discrimination and high-quality marking without causing unnecessary optical fogging in the photosensitive material. It can be performed. In particular, in the case of an X-ray film in which PET is used for the base layer of the photosensitive material, a dot pattern is formed by irradiating a laser beam having an oscillation wavelength of 9 μm to 10 μm in a range of 3 μsec to 20 μsec. It is effective.
[Brief description of the drawings]
FIG. 1 is a schematic view of a laser marking device.
FIG. 2 is an explanatory diagram showing an example of character marking based on an arrangement of dot patterns.
FIG. 3 is a schematic diagram of an experimental apparatus for dot pattern evaluation.
FIG. 4 is a graph showing a transmission spectrum of an emulsion layer in a near infrared region.
FIG. 5 is a graph showing a transmission spectrum of a base layer in a near infrared region.
6 is a central cross-sectional view showing an outline of a dot pattern of Sample 1. FIG.
7 is a central sectional view showing an outline of a dot pattern of Sample 2. FIG.
8 is a central cross-sectional view showing an outline of a dot pattern of Sample 3. FIG.
FIG. 9 is a central sectional view showing an outline of a dot pattern of Sample 4.
10 is a central sectional view showing an outline of a dot pattern of Sample 5. FIG.
FIG. 11 is a central sectional view schematically showing a dot pattern of a comparative example.
[Explanation of symbols]
3,24 X-ray film 10,20 Print head 11, 21 Laser oscillator 12 Laser deflector 22 Condensing lens 24a Base layer 24b Emulsion layer

Claims (5)

The emulsion layer having a thickness S formed on the surface of the base layer of the photosensitive material is irradiated with a laser beam having a substantially circular beam spot shape to form a dot pattern , and this dot pattern is arranged vertically and horizontally to display characters or marks. In marking method to print,
The dot pattern has a less irregularity S + 10 [mu] m with respect to the thickness direction of the photosensitive material, so that the arithmetic average surface roughness becomes 0.2μm~1.0μm, 9μm~10μm the oscillation wavelength of the laser beam, the 2. A marking method , wherein an irradiation time of the laser beam per dot pattern is 3 μs to 20 μs . When the dot pattern is arranged M in the vertical direction and N in the horizontal direction to print characters or marks with the vertical and horizontal sizes of A × B, the shape of the dot pattern is 100 μm when viewed from the emulsion layer side. 2. The marking method according to claim 1 , wherein the marking method has a substantially circular shape having a diameter equal to or smaller than the smaller one of A / M and B / N. 3. The marking method according to claim 1, wherein a beam profile of the laser beam is a Gaussian type or a flat top type. A photosensitive material on which characters or marks are printed by the marking method according to claim 1. 5. The photosensitive material according to claim 4, wherein the photosensitive material is an X-ray film using PET as the base layer .

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