Laser recording medium

Abstract

To provide a laser recording medium including a plurality of color developing layers capable of selectively developing a color with a plurality of kinds of laser beams for recording which can reduce an adverse effect by positional deviation between a focal point of the laser beams for recording and the color developing layers.SOLUTION: A laser recording medium includes a color information recording part 2 capable of recording a color image by irradiation with a laser beam, wherein in the color information recording part 2, a plurality of color developing layers capable of developing a color with chromatic colors having different hues are stacked on a base material layer. Wavelength regions of the laser beam capable of being absorbed by the plurality of color developing layers are made different, in each of the color developing layers, a laser beam of such a wavelength as to be capable of transmitting the color developing layers stacked on the color developing layer, and be capable of being absorbed by the color developing layer is configured as a laser beam for recording, and the plurality of color developing layers are configured so that the wavelength region of the laser beam for recording becomes shorter as the layer exists higher.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a laser recording medium capable of recording a color image using laser light.

Background Art

[0002] There is known a laser recording medium having three color developing layers capable of developing colors with three different primary colors, and mixing images recorded by individually heating and developing each color developing layer with laser light to record image information in full color (for example, Patent Document 1).

[0003] The laser recording medium of Patent Document 1 is configured such that the light absorption characteristics of the three color developing layers are made different, and a plurality of types of recording laser lights can be selectively used to individually heat and develop each color developing layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When heating and developing the color developing layer of the laser recording medium with recording laser light, it is necessary to adjust the position of the focus so that the recording laser light is focused near the height of the target color developing layer. Here, in a configuration in which a plurality of color developing layers are stacked as in the laser recording medium of Patent Document 1, since the distance from the condenser lens is different between the upper color developing layer and the lower color developing layer, a positional deviation between the color developing layer and the focus is likely to occur, and the greater such a positional deviation becomes, the more adverse effects such as the recorded image information becoming unclear occur.

[0006] The present invention has been made in view of such a situation, and relates to a laser recording medium including a plurality of color developing layers that can be selectively colored by recording laser light, and aims to provide a configuration capable of reducing the adverse effects caused by the positional deviation between the focus of the recording laser light and the color developing layers.

Means for Solving the Problems

[0007] The present invention is a laser recording medium including a color information recording unit capable of recording a color image by irradiating laser light, wherein the color information recording unit has a plurality of color developing layers that can be colored with chromatic colors having different hues, laminated on a base material layer. The plurality of color developing layers have different wavelength ranges of laser light that can be absorbed. Each color developing layer is capable of transmitting the color developing layer laminated on the color developing layer, and uses laser light in the wavelength range that can be absorbed by the color developing layer as the recording laser light. The plurality of color developing layers are characterized in that the wavelength range of the recording laser light is shorter for the layers arranged in the upper layer.

[0008] Even when using the same condenser lens for focusing, due to axial chromatic aberration, the longer the wavelength of the recording laser light, the longer the focal length. Therefore, in the present invention, the upper color developing layer close to the condenser lens has a relatively short focal length of the recording laser light, and the lower color developing layer far from the condenser lens has a relatively long focal length of the recording laser light. Due to such a difference in focal length, the positional deviation between each color developing layer and the focus caused by the difference in the distance from the condenser lens to each color developing layer is reduced. Therefore, according to the present invention, the adverse effects caused by the positional deviation between the color developing layer and the focus can be reduced compared to the conventional configuration. Also, generally, when a laser recording apparatus focuses on a laser recording medium, it detects a color developing layer in the upper layer of the laser recording medium with laser light or the like, and adjusts the thicknesses of the respective layers in the design of the laser recording medium by adding or subtracting the thicknesses of the respective layers to the height of the color developing layer so that the focus is positioned near the height of each color developing layer. At this time, since there are errors in the thicknesses of the respective layers constituting the laser recording medium, the actual height of the focus will vary by the amount of the error in the thicknesses of the respective layers. And such variation in the focus height becomes larger as the color developing layer in the lower layer farther from the surface of the laser recording medium is reached. On the other hand, in the present invention, the recording laser light in the lower layer having a longer wavelength has a deeper depth of focus than the recording laser light in the upper layer having a shorter wavelength and is less affected by the deviation of the focus position, so that the adverse effect due to the variation in the focus height caused by such layer thickness error can be reduced.

Advantages of the Invention

[0009] As described above, according to the present invention, in a laser recording medium including a plurality of color developing layers that can be selectively colored with a plurality of types of recording laser light, the adverse effect due to the positional deviation between the focus of the recording laser light and the color developing layer can be reduced as compared with the conventional configuration.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0011] Embodiments of the present invention will be described by the following examples.

Examples

[0012] As shown in FIG. 1(A), the laser recording medium 1 of this example is a certificate paper used for issuing a card-type identity certificate. On the laser recording medium 1, a color information recording unit 2 is provided in a rectangular area on the left side of the front side. The color information recording unit 2 is a white plain area, and when the identity certificate is issued, as shown in FIG. 1(B), the face image F of the person to be certified is recorded as a color image by laser light. Further, a monochrome information recording unit 3 for recording and displaying the attribute information of the person to be certified is provided in a rectangular area on the right side of the front side of the laser recording medium 1. As shown in FIG. 1(A), only the item names of the attribute information are pre-printed in a white plain area in the monochrome information recording unit 3, and when the identity certificate is issued as shown in FIG. 1(B), the attribute information is recorded as black characters by laser light.

[0013] FIG. 2 shows the layer structure of the laser recording medium 1. The laser recording medium 1 includes a substrate layer and a protective layer that covers the front side (the upper side in FIG. 2) of the substrate layer. As shown in FIG. 2(A), in the color information recording section 2, three color developing layers and two heat insulating layers are disposed between the protective layer and the substrate layer. The color developing layer is a layer for recording the face image F in color by laser light. As will be described later, the three color developing layers are configured to be capable of developing in different colors by irradiation with laser light. The heat insulating layer is provided between the color developing layers. On the other hand, as shown in FIG. 2(B), in the monochrome information recording section 3, a black developing layer capable of recording information in black by laser light is disposed between the protective layer and the substrate layer. Although not shown, the pre-printing of the monochrome information recording section 3 is formed between the surface of the substrate layer (the substrate layer and the black developing layer). Also, although not shown, the portions other than the color information recording section 2 and the monochrome information recording section 3 have a two-layer structure of only the substrate layer and the protective layer.

[0014] The substrate layer supports the color developing layer and the black developing layer from the back side. The thickness of the substrate layer is not particularly limited, but is preferably about 50 μm to 1000 μm. The substrate layer may be a single sheet or a laminate of a plurality of sheets. Specific examples of the material of the substrate layer include paper, resin sheets, or combinations thereof. The surface of the substrate layer is preferably a color that does not affect the color of the face image F recorded in the color information recording section 2. Specific examples of the color include white, light colors, and colorless.

[0015] The protective layer is provided for the purpose of preventing damage or deterioration of the color developing layer or black color developing layer, and forgery of the recorded information. The protective layer is composed of a substantially transparent material that transmits the recording laser light used for information recording and enables the recorded information to be visible. Further, the protective layer can be preferably composed of a material that does not transmit water or air. Desirable film materials for constituting the protective layer include polyvinyl chloride (PVC), glycol-modified polyethylene terephthalate (PETG), polyethylene terephthalate (PET), polypropylene (PP), and the like. The thickness of the protective layer is not particularly limited, but is preferably about 1 μm to 100 μm. The protective layer can be composed of one or a plurality of films. When the protective layer is a film, it is proposed to bond it to the base material layer, color developing layer, etc. with an adhesive or the like.

[0016] The three-layer color developing layer is substantially transparent before recording the face image F, and is configured to develop colors in colors with different hues by irradiation with laser light. Each color developing layer contains a photothermal conversion agent that absorbs laser light of a predetermined wavelength and generates heat, a thermosensitive color developing component that develops color when the temperature reaches a predetermined color developing threshold temperature or higher, and a binder resin. That is, each color developing layer generates heat by irradiation with laser light having a wavelength that can be absorbed by the photothermal conversion agent, and develops color when the irradiated portion rises to the color developing threshold temperature. The three-layer color developing layer develops colors in different three primary colors due to differences in the thermosensitive color developing components contained therein. Specifically, as shown in FIG. 2(A), the upper color developing layer in the upper layer (surface side) develops color in yellow (Y), the middle color developing layer in the middle layer develops color in magenta (M), and the lower color developing layer in the lower layer (base material layer side) develops color in cyan (C). That is, in this embodiment, a yellow image, a magenta image, and a cyan image are individually recorded on each color developing layer, and these images are overlapped and mixed to enable the full-color face image F to be recorded and displayed in the color information recording unit 2.

[0017] The thickness of the color developing layer is not particularly limited, but is preferably about 1 μm to 50 μm. As the constituent material of the color developing layer, known materials can be preferably used. For example, as a suitable photothermal conversion agent that absorbs laser light in the near-infrared region and generates heat, cyanine dyes can be mentioned. As the heat-sensitive color developing component, a combination of a leuco dye and a developer can be used. The leuco dye and the developer can be respectively selected from known materials according to the color to be developed. As the binder resin, a colorless resin material such as polyvinyl alcohol can be used.

[0018] The photothermal conversion agents contained in each color developing layer have different wavelength ranges of the laser light to be absorbed. Thereby, the laser recording medium 1 is configured such that by selectively irradiating three types of recording laser lights having different wavelengths from the front side, the three-layer color developing layers can be selectively heated to individually control the color development of each color developing layer. Specifically, the upper color developing layer is configured to absorb the recording laser light of the first wavelength, generate heat and develop color, and transmit the recording laser lights of the second wavelength and the third wavelength. Then, the intermediate color developing layer is configured to absorb the recording laser light of the second wavelength, generate heat and develop color, and transmit the recording laser light of the third wavelength. Then, the lower color developing layer is configured to absorb the recording laser light of the third wavelength and generate heat and develop color.

[0019] The three-wavelength recording laser lights used for recording on the laser recording medium 1 are not particularly limited, but it is desirable that all of them be recording laser lights in the near-infrared region. Specific laser lights include YAG laser light, CO 2 laser light, YVO 4 laser light, fiber laser light, semiconductor laser light, etc. As specific wavelengths, it is proposed to use three types of 785 nm, 860 nm, and 1064 nm. In this embodiment, the absorption characteristics of the laser light of each color developing layer are set such that the first wavelength, which is the shortest wavelength among the three wavelengths, is used as the recording laser light for the upper color developing layer, and the third wavelength, which is the longest wavelength among the three wavelengths, is used as the recording laser light for the lower color developing layer.

[0020] The heat insulation layer is disposed between the color developing layers to suppress heat conduction between the color developing layers. That is, when heating and developing the target color developing layer with the recording laser beam, the heat insulation layer prevents other color developing layers from rising to the color development threshold temperature due to the heat of the color developing layer. The heat insulation layer is made of a substantially transparent material so as to transmit the recording laser beam and not block the information recorded on the color developing layer. Suitable materials for the heat insulation layer include polyvinyl alcohol, polyvinyl acetate, and polyacryl. The thickness of the heat insulation layer is not particularly limited, but a suitable thickness for suppressing heat conduction between the color developing layers is 1 μm to 50 μm.

[0021] The color developing layer and the heat insulation layer constituting the color information recording unit 2 can be formed by applying a paint containing the material of each layer to the front side of the base material layer or the back side of the protective layer and drying and laminating them.

[0022] The black color developing layer is substantially transparent before recording and is configured to develop a black color upon irradiation with a laser beam having a predetermined wavelength. Examples of the black color developing layer include a composition comprising a photothermal conversion agent that absorbs a laser beam having a predetermined wavelength and generates heat, and a resin that is carbonized black by the heat generated by the photothermal conversion agent. As the composition of the black color developing layer, a known composition can be widely adopted. The black color developing layer is made of a material that absorbs all of the three-wavelength recording laser beams used for recording in the color information recording unit 2. The thickness of the black color developing layer is not particularly limited, but is preferably about 1 μm to 200 μm. When the color information recording unit 2 and the monochrome information recording unit 3 are adjacent to each other as in this embodiment, it is preferable to set the thickness of the black color developing layer so that the step difference at the boundary between the color information recording unit 2 and the monochrome information recording unit 3 is reduced. The black color developing layer can be preferably formed by applying a material to the front side of the base material layer or the back side of the protective layer.

[0023] When issuing an identity document using the laser recording medium 1, as shown in FIGS. 1(A)→1(B), a face image F is recorded in the color information recording section 2 and characters indicating attribute information are recorded in the monochrome information recording section 3 using a laser recording apparatus capable of irradiating the recording laser light of the above-described three wavelengths.

[0024] FIG. 3 shows the configuration of a laser recording apparatus 10 capable of recording a face image F and attribute information on the laser recording medium 1 of the present embodiment. The laser recording apparatus 10 includes laser oscillators 11a, 11b, 11c that output recording laser light, a condensing section 12 that condenses the recording laser light onto the laser recording medium 1, an optical fiber 13 that guides the recording laser light from the laser oscillators 11a, 11b, 11c to the condensing section 12, a stage 14 that holds the laser recording medium 1, a stage moving mechanism 15 that moves the stage 14, an output control section 16 that controls the operation of the laser oscillators 11a, 11b, 11c and the condensing section 12, a position control section 17 that controls the operation of the stage moving mechanism 15, and a calculation section 18 that performs overall control of the laser recording apparatus 1.

[0025] Such a laser recording apparatus 10 is capable of recording information with recording laser light of three wavelengths, and one type of each of the laser oscillators 11a, 11b, 11c that output recording laser light of each wavelength is arranged. The condensing section 12 includes a single condensing lens 19, and the three-wavelength recording laser light output by the laser oscillators 11a, 11b, 11c and guided by the optical fiber 13 is condensed by the same condensing lens 19. Further, the condensing section 12 includes a height detection mechanism capable of detecting the height of the laser recording medium 1 with laser light, and a lens moving mechanism that moves the focusing lens 19 up and down to adjust the focal position of the recording laser light. Since the configuration of such a laser recording apparatus 10 is well-known, detailed description thereof is omitted.

[0026] The above-described laser recording apparatus 10 records a face image F and attribute information on the laser recording medium 1 mainly by sequentially executing the following steps (1) to (7). (1) Set the laser recording medium 1 before recording at a predetermined position on the stage 14. (2) Detect the height of the laser recording medium 1 by the height detection mechanism of the light condensing unit 12. (3) Based on the height of the laser recording medium 1, move the condenser lens 19 up and down to adjust the focal position. (4) Input the data of the face image F to be recorded and the attribute information into the calculation unit 18. (5) Record the face image F in the color information recording unit 2. (6) Record the attribute information in the monochrome information recording unit 3. (7) Unload the laser recording medium 1 after recording from the stage 14.

[0027] In the step of recording the face image F in the color information recording unit 2 (step (5) above), the calculation unit 18 color-separates the full-color digital data of the face image F into the three primary colors of CMY. Then, the cyan plate image, the magenta plate image, and the yellow plate image obtained by color separation are respectively recorded on the three-layer color developing layer using three-wavelength laser light. Specifically, the calculation unit 18 cooperatively operates the laser oscillator 11c and the stage moving mechanism 15 via the output control unit 16 and the position control unit 17, and irradiates the required position of the laser recording medium 1 with the recording laser light of the third wavelength under the required conditions (irradiation time · irradiation intensity) to record the cyan plate image on the lower color developing layer. Then, similarly, irradiate the recording laser light of the second wavelength to record the magenta plate image on the intermediate color developing layer, and further irradiate the recording laser light of the first wavelength to record the yellow plate image on the upper color developing layer.

[0028] In this way, the laser recording medium 1 of this embodiment selectively irradiates the recording laser light of three types of wavelengths from the front side of the color information recording unit 2, individually records cyan, magenta, and yellow images on the three-layer color developing layer, and overlaps the images recorded on each color developing layer, so that a full-color face image F can be recorded in the color information recording unit 2.

[0029] In the step of recording the attribute information in the monochrome information recording unit 3 (step (6) above), The calculation unit 18 operates the laser oscillator 11c and the stage movement mechanism 15 in a coordinated manner to irradiate the required position of the monochrome information recording unit 3 with recording laser light from the front side under required conditions, thereby carbonizing the required part of the black color developing layer. At this time, if the energy of the recording laser light irradiated to the monochrome information recording unit 3 is relatively high, not only can the recording part be made to develop black by carbonization, but it can also be raised to the front side by the foaming of the binder resin. Since the black color developing layer can absorb the recording laser light of the above three wavelengths, the recording laser light used for recording by the color information recording unit 2 can be used when recording by the monochrome information recording unit 3.

[0030] Hereinafter, the configuration according to the main part of the present invention will be described. As described above, the laser recording medium 1 of this embodiment includes three color developing layers having different wavelength ranges of laser light that can be absorbed, and is configured to heat and develop each color developing layer using laser light of different wavelength ranges as recording laser light. And in this embodiment, the color developing layer arranged in the upper layer (front side) is configured such that the wavelength range of the recording laser light becomes shorter. The shorter the wavelength of the recording laser light, the shorter the focal length due to axial chromatic aberration, and the longer the wavelength of the recording laser light, the deeper the depth of focus. Therefore, in such a configuration, compared with the conventional configuration, the adverse effect due to the positional deviation between the focal point of the recording laser light and the color developing layer can be reduced.

[0031] Specifically, since the distances from the condenser lens 19 of the laser recording apparatus 10 to the three-layer color developing layers are different, positional deviations are likely to occur between the focal point of the recording laser beam and each color developing layer. In contrast, as shown in FIG. 4, the laser beam of the first wavelength used for coloring the upper color developing layer has the shortest wavelength among the three wavelengths and the shortest focal length, so it is focused closer to the condenser lens 19 than the other recording laser beams. Also, the laser beam of the third wavelength used for coloring the lower color developing layer has the longest wavelength among the three wavelengths and the longest focal length, so it is focused at a position farther from the condenser lens 19 than the other recording laser beams. For this reason, in this embodiment, as shown in FIG. 4, even if the distances from the condenser lens 19 to the respective color developing layers are different, the positional deviation between the focal point of the recording laser beam and each color developing layer can be prevented by the length of the focal length of each recording laser beam. Therefore, in this embodiment, compared with the conventional configuration, the adverse effects due to the positional deviation between the color developing layer and the focal point can be reduced.

[0032] Also, in the above-described laser recording apparatus 10, the height of the upper color developing layer is detected by the height detection mechanism of the condensing unit 12, and the position of the condenser lens 19 is adjusted so that the focal point of the first laser beam coincides with the upper color developing layer. In this embodiment, as described above, the deviation of the focal position due to the difference between the distance to the upper color developing layer and the distances to the other color developing layers is reduced by the length of the focal length of each recording laser beam. However, since there are errors in the thicknesses of the color developing layers and the heat insulating layer, the focal heights of the other color developing layers will vary by the amount of the error in the thickness of each layer. And such variation in the focal height becomes larger for the recording laser beam that is focused on the lower layer side (substrate layer side) away from the upper color developing layer. In contrast, in this embodiment, as shown in FIG. 4, the depth of focus D1, D2, D3 of each recording laser beam becomes deeper for the recording laser beam of the lower layer side color developing layer due to the difference in wavelength, and the lower layer side color developing layer is less affected by the positional deviation of the focal point. Therefore, in this embodiment, the adverse effects due to the variation in the focal height caused by such layer thickness errors can be reduced.

[0033] Examples 2 and 3 will be described below. These examples are obtained by partially modifying the configuration of Example 1 above. The configurations not particularly mentioned are common to Example 1, and the same reference numerals as those in Example 1 are used in the text and drawings for explanation.

Example

[0034] Each color developing layer according to Example 1 above is a homogeneous layer containing a photothermal conversion agent and a thermosensitive color developing component. In contrast, in the color information recording section 2a according to this example, as shown in Fig. 5(A), each color developing layer is composed of two layers: a photothermal conversion layer containing a photothermal conversion agent and not containing a thermosensitive color developing component, and a thermosensitive color developing layer containing a thermosensitive color developing component and not containing a photothermal conversion agent. That is, in the color developing layer according to this example, the photothermal conversion layer absorbs the recording laser light and generates heat, and transfers the heat to the adjacent thermosensitive color developing layer to raise the temperature to the threshold temperature, thereby developing color in a predetermined hue. Thus, the color developing layer according to the present invention may be composed of two layers, namely, a photothermal conversion layer and a thermosensitive color developing layer.

Example

[0035] In Example 1 above, three color developing layers are laminated in the color information recording section 2, while in the color information recording section 2b according to this example, two color developing layers are laminated. Among the two color developing layers, the upper upper color developing layer is configured to develop color in a red hue, and the lower lower color developing layer is configured to develop color in a green hue. Thus, the color information recording section according to the present invention can be composed of two color developing layers. With such a configuration, the color information recording section 2b can be made thinner than in Example 1, and the manufacturing cost can also be reduced. In addition, since only two types of recording laser light are required for recording on the color information recording section 2b, recording can be performed with a simpler laser recording apparatus, and the time required for recording can also be shortened.

[0036] The embodiments of the present invention have been described above. However, the embodiments of the present invention are not limited to the configurations of the above embodiments, and can be appropriately changed within the scope not departing from the gist of the present invention. For example, although the laser recording medium in the above embodiment is a card-type identity certificate, it may be a booklet-type identity certificate. Further, the present invention is not limited to identity certificates, and is applicable to all laser recording media provided with a color information recording section.

[0037] Also, the layer configurations of the color information recording section 2 and the monochrome information recording section 3 can be appropriately changed within the scope not departing from the gist of the present invention. For example, a layer such as a lenticular lens can be further disposed on the protective layer according to the above embodiment. Further, a base layer for enhancing the adhesion to the color developing layer or the black developing layer, or a background printing layer can be disposed on the surface of the base material layer.

[0038] Also, in the laser recording medium 1 of the above embodiment, the color information recording section 2 and the monochrome information recording section 3 are disposed only on the front side, but a color information recording section or a monochrome information recording section may also be disposed on the back side of the laser recording medium 1.

[0039] Also, in the laser recording medium 1 of the above embodiment, laser light in the near-infrared region is used as the recording laser light, but the recording laser light according to the present invention may be partially or entirely laser light in the ultraviolet region or the visible light region.

Explanation of Reference Numerals

[0040] 1 Laser recording medium 2, 2a, 2b Color information recording section 3 Monochrome information recording section 4 Color developing layer 10 Laser recording apparatus 11a, 11b, 11c Laser oscillator 12 Condensing section 13 Optical fiber 14 Stage 15 Stage moving mechanism 16 Output control section 17 Position control unit 18 Calculation unit 19 Condensing lens F Facial image

Claims

【Claim 1】 A laser recording medium comprising a color information recording section capable of recording a color image by irradiating laser light, wherein a plurality of color developing layers capable of developing with chromatic colors having different hues are laminated on a base material layer in the color information recording section, the plurality of color developing layers have different wavelength ranges of laser light that can be absorbed, each of the color developing layers is capable of transmitting the color developing layer laminated thereon and uses laser light in a wavelength range that can be absorbed by the color developing layer as recording laser light, and the plurality of color developing layers are characterized in that the wavelength range of the recording laser light becomes shorter as the layer is located closer to the upper layer.

Images