JP2008217907A - Method of forming image on label surface of optical recording medium and optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a color image on the label surface of an optical recording medium using a laser beam. <P>SOLUTION: The image is formed on the label surface 6a of the optical recording medium having a reflection layer 4, a recording surface 2a provided on one side of the reflection layer 4, and an image recording layer 5 provided on a side of the reflection layer 4 opposite to the recording surface 2a. On the image recording layer 5 being the label surface 6a side, a plurality of columns of dots which form columns arranged in one or more directions with the laser beam are arranged. Moreover, the pitch of the plurality of columns is set to be 0.05 to 20 μm and changed according to a color to express. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for forming an image on a label surface of an optical recording medium and an optical recording medium.

In recent years, CD-R and DVD-R in which pits are formed on the recording surface by changing the refractive index, and holographic recording media using holography are known as techniques for optically recording information including music. It has been.
These optical recording media for optical recording are used to identify the title of music data recorded on the recording surface and the recorded data on the surface opposite to the recording surface on which music data is recorded. A label printed with visible information such as a title may be attached. Such a label is usually printed in advance on a circular label sheet by a printer or the like.

  By the way, in order to perform such printing, a printer separate from the optical disk drive is required, and since it takes time and effort to print on the label sheet, an image is directly applied to the label surface using laser light. The technique to form is disclosed (for example, refer patent documents 1-4).

JP 2005-285167 A JP 2006-260750 A JP 2005-317192 A JP 2006-527097 A

  However, conventional image formation on the label surface using laser light can only express the presence or absence of contrast, for example, by forming a hole in the colored dye layer so that the reflective layer under the dye layer can be seen. could not. In short, only a monochrome image could be formed.

  The present invention has been made in view of the background as described above, and an object thereof is to form a color image on a label surface of an optical recording medium with a laser beam.

  The present invention for solving the above-described problems includes a reflective layer, a recording surface provided on one side of the reflective layer, and an image recording layer provided on the opposite side of the reflective layer from the recording surface. A method of forming an image on a label surface of an optical recording medium having dots extending in one direction or a row forming rows in at least one direction by a laser beam on the image recording layer corresponding to the label surface side A plurality of lines are arranged, and a pitch of the plurality of lines is set to 0.05 to 20 μm, and the pitch is changed according to a color to be expressed.

  In this way, by arranging dots or lines in a plurality of rows in at least one direction, a structure similar to a light interference fringe can be formed. Since the arrangement of dots or lines can be viewed as a diffraction grating, when looking at the label surface, light is diffracted by the fringes according to the pitch of the fringes comprising this arrangement, and the color of the intensifying wavelength is particularly strong. appear. In other words, by changing the pitch of the stripes, any of the colors included in the rainbow color can be strongly reflected, and various expressions using a plurality of colors can be made.

  The image recording layer is made of a dye material, and when the peak wavelength of light absorption of the dye material is λa and the wavelength of the laser beam when forming the dot or line is λw, λa <λw. Is desirable.

  When changing the dye material by applying laser light, considering the thickness of the dye material, changing the light with a wavelength slightly shifted from the light absorption peak wavelength of the dye material creates an optical contrast. Efficient on top. In order to realize diffraction and reflection of light in a plurality of colors in the visible light range, it is preferable to be able to form small dots or thin lines. For this reason, the wavelength λw of the laser light is a short wavelength within the visible wavelength range. It is desirable to be close to the side. Then, since the dye material has an absorption peak in a range shorter than the wavelength λw of the laser light, the absorption wavelength of the dye material does not enter the visible wavelength range, and the color expression by the diffraction grating is not hindered.

  For this reason, it is desirable that the wavelength λw of the laser light be shorter than the visual recognition center wavelength λc, for example, λw <580 nm.

  The present invention for solving the above-described problems is a light having a reflective layer, a recording surface provided on one side of the reflective layer, and an image recording layer provided on the opposite side of the reflective layer from the recording surface. A recording medium, wherein the image recording layer includes a plurality of dots arranged in a row aligned in at least one direction or a line extending in one direction, and the pitch of the plurality of rows is 0.05 to 20 μm. Yes, this pitch is changed according to the color to be expressed.

  With such an optical recording medium, the arrangement of dots or lines can be viewed as a diffraction grating, and when the label surface is viewed, light is diffracted by the stripes according to the pitch of the stripes comprising this arrangement, Intensifying wavelengths appear particularly strong. In other words, by changing the pitch of the stripes, any of the colors included in the rainbow color can be strongly reflected, and a variety of expressions using a plurality of colors can be achieved.

A cover layer is preferably provided on the image recording layer.
By providing the cover layer, the formed image can be protected without directly touching the image recording layer.

  The thickness of the image recording layer is desirably 0.01 to 2 times the wavelength of the laser beam forming the dots or lines. By setting it as such a range, the arrangement | sequence of a dot or a line can be functioned as a diffraction grating, and a desired color can be reflected efficiently.

  The dots or lines can be formed by a change in refractive index of the material constituting the image recording layer, a concave shape or a gap.

The image recording layer is made of a dye material, and λa <λw, where λa is the peak wavelength of light absorption of the dye material, and λw is the wavelength of laser light when forming the dots or lines. Is desirable.
By using such a dye material, the color of the dye material does not enter the visible wavelength range, and the color expression by the diffraction grating is not hindered.

  According to the image forming method and the optical recording medium on the label surface of the optical recording medium of the present invention, a plurality of colors can be obtained by changing the pitch of the arrangement of dots or lines formed on the image forming layer according to the color to be expressed. Various expressions using can be made possible.

  Next, an image forming method and an optical recording medium on the label surface of the optical recording medium of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an optical recording medium according to an embodiment, and FIGS. 2A, 2B, and 2C are diagrams illustrating examples of dot arrangements.

  As shown in FIG. 1, an optical recording medium 1 according to an embodiment of the present invention is provided with a recording layer 3, a reflective layer 4, an image recording layer 5, and a cover layer 6 in this order on a substrate 2. . The surface on the substrate 2 side is the recording surface 2a, and the surface on the cover layer 6 side which is the back of the recording surface 2a is the label surface 6a.

  The layer structure of the optical recording medium of the present invention is not limited to the example shown in FIG. 1, and the recording layer 3 is provided on one side of the reflective layer 4 and the recording layer 3 on the other side, that is, the reflective layer 4. The image forming layer 5 only needs to be provided on the opposite side, and in addition to these layers, an adhesive layer, a servo layer on which servo signals are recorded, a selective reflection film, a dummy substrate, or the like may be provided as appropriate. .

  The type of the optical recording medium of the present invention may be any of a read-only type, a write-once type, a rewritable type, and the like. The recording format is not particularly limited, such as a phase change type, a magneto-optical type, and a dye type, but is preferably a dye type.

[Recording layer]
The recording layer 3 is a layer on which code information (encoded information) such as digital information is recorded, and includes a dye type, a write-once type, a phase change type, a magneto-optical type, and the like. It is preferable that

  Specific examples of the dye contained in the dye-type recording layer 3 include a cyanine dye, an oxonol dye, a metal complex dye, an azo dye, and a phthalocyanine dye. JP-A-4-74690, JP-A-8-127174, 11-53758, 11-334204, 11-334205, 11-334206, 11-334207 No. 2000-43423, JP-A 2000-108513, JP-A 2000-158818, and the like are preferably used. Furthermore, the recording material is not limited to a dye, but a triazole compound, triazine compound, cyanine compound, merocyanine compound, aminobutadiene compound, phthalocyanine compound, cinnamic acid compound, viologen compound, azo compound, oxonol benzoxazole compound, benzotriazole compound Organic compounds such as these are also preferably used. Among these compounds, cyanine compounds, aminobutadiene compounds, benzotriazole compounds, and phthalocyanine compounds are particularly preferable.

[substrate]
The substrate 2 can be arbitrarily selected from various materials used as a substrate of a conventional optical recording medium. Examples of substrate materials include acrylic resins such as glass, polycarbonate, and polymethyl methacrylate, vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers, epoxy resins, amorphous polyolefins, and polyesters. You may use them together. These materials can be used as a film or as a rigid substrate. Among the above materials, polycarbonate is preferable from the viewpoint of moisture resistance, dimensional stability, price, and the like.

  The thickness of the substrate 2 is preferably 0.1 to 1.2 mm, and more preferably 0.2 to 1.1 mm. In order to achieve a higher recording density, it is preferable to use a substrate on which grooves having a narrower track pitch are formed as compared with conventional CD-R and DVD-R. In this case, the track pitch of the groove is preferably in the range of 200 to 400 μm, and more preferably in the range of 250 to 350 nm. Further, the depth of the groove (groove depth) is preferably in the range of 20 to 150 nm, and more preferably in the range of 50 to 100 nm.

  Further, the groove width of the groove is preferably in the range of 50 to 250 nm, and more preferably in the range of 100 to 200 nm. The groove inclination angle of the groove is preferably in the range of 20 to 80 °, and more preferably in the range of 30 to 70 °.

  An undercoat layer is provided on the substrate surface side (surface side on which the groove is formed) on which the recording layer 3 is provided for the purpose of improving flatness, improving adhesive force, and preventing alteration of the recording layer 3. Also good. Examples of the material for the undercoat layer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylol acrylamide, styrene / vinyl toluene copolymer, chlorosulfonated. High molecular substances such as polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate; and silane coupling agents And the like. The undercoat layer is formed by dissolving or dispersing the above substances in an appropriate solvent to prepare a coating solution, and then applying this coating solution to the substrate surface by a coating method such as spin coating, dip coating, or extrusion coating. can do. The thickness of the undercoat layer is generally in the range of 0.005 to 20 μm, preferably in the range of 0.01 to 10 μm.

[Reflective layer]
A reflective layer 4 is provided adjacent to the recording layer 3 for the purpose of improving the reflectance during information reproduction. The light-reflective substance that is the material of the reflective layer 4 is a substance that has a high reflectance with respect to laser light. Examples thereof include Mg, Se, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Ru, Rh, Pd, Ir, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Si, Ge, Te, Pb, Po, Sn, Mention may be made of metals such as Bi and metalloids or stainless steel. These substances may be used alone or in combination of two or more or as an alloy. Among these, Cr, Ni, Pt, Cu, Ag, Au, Al, and stainless steel are preferable. Particularly preferred are Au metal, Ag metal, Al metal or alloys thereof, and most preferred are Ag metal, Al metal or alloys thereof. The reflective layer 4 can be formed on the substrate 2 or the recording layer 3, for example, by vapor deposition, sputtering or ion plating of the light reflective material. The thickness of the reflective layer 4 is generally in the range of 10 to 300 nm, and preferably in the range of 50 to 200 nm.

[Dummy substrate]
When using a dummy substrate (protective substrate), the same material as that of the substrate 2 described above can be used.

[Image recording layer]
As described above, the optical recording medium 1 of the present invention has the image recording layer 5 on the opposite side of the recording layer 2 from the recording surface 2a with the reflective layer 4 interposed therebetween. The image recording layer 5 records visible images (visible information) desired by the user, such as characters, graphics, and patterns. Examples of visible images include disc titles, content information, content thumbnails, related patterns, design patterns, copyright information, recording date, recording method, recording format, and the like.

  The visible image recorded in the image recording layer 5 means a visually recognizable image, and includes all visually recognizable information such as characters (rows), pictures, and figures. Also, as character information, usable person designation information, use period designation information, usable number designation information, rental information, resolution designation information, layer designation information, user designation information, copyright holder information, copyright number information, manufacturing Information, manufacturer date information, sales date information, dealer or seller information, use set number information, region designation information, language designation information, application designation information, product user information, use number information, and the like.

  The image recording layer 5 only needs to have optical characteristics that change with respect to visible light by laser irradiation and can record the change. As the constituent material, the dye described in the recording layer 3 described above is preferably used. Can do.

Further, in the optical recording medium 1 of the present embodiment, the constituent components (dye or phase change recording material) of the recording layer 3 described above and the constituent components of the image recording layer 5 may be the same or different. Since the recording layer 3 and the image recording layer 5 have different required characteristics, it is preferable to make the constituent components different.
Specifically, the constituent components of the recording layer 3 are preferably excellent in recording / reproducing characteristics, and the constituent components of the image recording layer 5 are preferably those in which the refractive index modulation of the recorded image is high. In particular, when a dye is used, a cyanine dye, a phthalocyanine dye, an azo dye, an azo metal complex, or an oxonol dye is used in the image recording layer 5 from the viewpoint of improving the contrast of a recorded image, among the dyes described above. preferable. Also, one of the recording layer 3 and the image recording layer 5 may be a phase change type and the other may be a dye type. In this case, it is preferable that the recording layer 3 is a phase change type and the image recording layer 5 is a dye type.

When a dye material is used for the image recording layer 5, the dye absorption wavelength (the peak wavelength at which the dye absorbs light most) λa is preferably shorter than the wavelength λw of the laser used to form the image.
The reason for this is that when the dye material is changed by applying laser light, considering the thickness of the dye material, the optical contrast can be changed with light having a wavelength slightly shifted from the light absorption peak wavelength of the dye material. It is efficient in making. In order to realize diffraction and reflection of light in a plurality of colors in the visible light range, it is preferable to be able to form small dots. For this reason, the wavelength λw of the laser light is closer to the short wavelength side in the visible wavelength range. It is desirable. Then, since the dye material has an absorption peak in a range shorter than the wavelength λw of the laser beam, the absorption wavelength of the dye material does not enter the visible wavelength range, and the color expression by the diffraction grating is not hindered. It is.
Then, in relation to the visual recognition center wavelength (the central wavelength in the visible light wavelength range) λc, by setting λw <λc, the dye of the image recording layer 5 affects the color of the image while forming small dots. It is desirable because there is nothing. That is, it is most preferable that λa <λw <λc.
Since the visible wavelength range is usually about 380 to 780 nm, it can be said that it is preferable that λw <580 nm.

  The image recording layer 5 can be formed by preparing a coating solution by dissolving the aforementioned dye in a solvent and coating the coating solution. As the solvent, the same solvent as that used for preparing the coating solution for the recording layer 3 described later can be used. Other additives and coating methods can be performed in the same manner as the recording layer 3 described above.

  The thickness of the image recording layer 5 is preferably 0.01 to 200 μm, more preferably 0.05 to 100 μm, and further preferably 0.1 to 50 μm.

The layer thickness of the image recording layer 5 is useful for defining the depth of the dots by changing the image recording layer 5 over the entire thickness by irradiation with laser light. The depth of the dots, that is, the thickness of the image recording layer 5, is preferably 0.1 to 2 times the wavelength λw of the laser beam forming the image, more preferably 0.05 to 1 time. More preferably, it is 0.1 to 0.5 times, and most preferably 0.2 to 0.5 times.
If the phase difference between the light that reaches and reflects around the dot (the non-dot portion) and the light that reaches and reflects inside the dot is not determined only by the thickness of the image recording layer 5, the phase difference Is preferably in the above range. That is, the phase difference is preferably 0.1 to 2 times the wavelength λw of the laser beam forming the image, more preferably 0.05 to 1 time, and still more preferably 0.1 to 0. 5 times, most preferably 0.2 to 0.5 times.

  The depth of the dot is determined by the optical path difference between the surface (the surface on the cover layer 6 side) and the bottom surface (the surface on the image recording layer 5 side of the reflective layer 4) when viewing the label surface 6a. It is desirable for the diffraction at the time of observation to be efficient, so that, for example, n is set to, for example, 1/4 or 3/4 of the wavelength λw of the laser beam used for image formation. As an odd number, it is desirable to be n times a quarter. In this way, a deep color can be expressed by efficiently diffracting light.

  This phase difference can be created by changing the refractive index by irradiating the image recording layer 5 with laser light and changing the optical path length by this refractive index change. The optical path length can also be changed by erasing the material of the image recording layer 5 with laser light and forming a concave shape or a gap.

The optical recording medium 1 of this embodiment may have a tracking groove in the image recording area on the image recording layer 5 side. For example, by providing a dummy substrate instead of the cover layer 6 and providing a groove in the dummy substrate, the groove can be easily provided in the image recording area.
By providing the tracking groove in this way, the position of the optical pickup can be precisely controlled, so that a precise image can be recorded. The shape of the groove on the image recording layer 5 side is preferably a spiral shape or a concentric shape since tracking is performed while the optical recording medium 1 is rotated.

(Cover layer)
The cover layer 6 is formed to prevent the inside of the optical recording medium 1 from impact and the like, and is not particularly limited as long as it is a transparent material, but is preferably polycarbonate, cellulose triacetate, and more preferably 23 ° C. and 50%. A material having a moisture absorption rate of 5% or less at RH. Note that “transparent” means that the recording light and the reproduction light are so transparent that the light is transmitted (transmittance: 90% or more).

The cover layer 6 is prepared by dissolving a photocurable resin constituting the adhesive layer in an appropriate solvent to prepare a coating solution, and then coating the coating solution on the recording layer 3 at a predetermined temperature to form a coating film. For example, a cellulose triacetate film (TAC film) obtained by, for example, plastic extrusion is laminated on the coating film, and light is irradiated from above the laminated TAC film to cure the coating film. The TAC film preferably contains an ultraviolet absorber. The thickness of the cover layer 6 is in the range of 0.01 to 0.2 mm, preferably in the range of 0.03 to 0.1 mm, and more preferably in the range of 0.05 to 0.095 mm.
Moreover, a polycarbonate sheet etc. can also be used as a cover sheet.

The cover layer 6 can be provided as follows, for example. After a photocurable resin is dissolved in a suitable solvent to prepare a coating solution, this coating solution is applied onto the recording layer 3 at a predetermined temperature to form a coating film. It is formed by laminating a cellulose triacetate film (TAC film) obtained by extrusion, and irradiating light on the laminated TAC film to cure the coating film. The TAC film preferably contains an ultraviolet absorber.
The thickness of the transparent sheet is in the range of 0.01 to 0.2 mm, preferably in the range of 0.03 to 0.1 mm, and more preferably in the range of 0.05 to 0.095 mm.

  Note that a polycarbonate sheet or the like can be used as the cover layer 6. In the case where a pressure-sensitive adhesive is applied to the bonding surface of the transparent sheet, no adhesive is necessary. Further, instead of the cover layer 6, a light transmission layer made of an ultraviolet curable resin or the like may be formed.

  A hard coat layer may be formed on the cover layer 6. The hard coat layer can be formed by means such as coating on the cover layer 6 after the reflective layer 4 and the recording layer 3 are formed on the substrate 2 and the cover layer 6 is formed thereon. In the case where the cover layer 6 is a transparent sheet, before the transparent sheet is bonded onto the recording layer 3, a hard coat layer is formed on the transparent sheet so that the hard coat layer is the outermost surface. An optical recording medium according to this embodiment may be manufactured by laminating a ridge on the recording layer 3.

  The optical recording medium 1 of the present embodiment can be applied to the so-called read-only optical recording medium 1 having a recording portion (pit) in which information reproducible by laser light is recorded. It is as follows.

[Image forming method]
The image formation on the image recording layer 5 of the optical recording medium 1 of the present embodiment includes the optical recording medium 1 of the present invention and a recording apparatus capable of recording image information on at least the image recording layer 5 of the optical recording medium 1. And using.
Hereinafter, a recording apparatus used for recording on the optical recording medium 1 of the present invention will be described first.

(Recording device)
In the optical recording medium 1 of the present embodiment, recording of an image on the image recording layer 5 and recording of optical information on the recording layer 3 are performed by one optical disc drive (recording apparatus) having a recording function for both layers. be able to. When one optical disk drive is used as described above, after recording on one of the image recording layer 5 and the recording layer 3, it can be reversed and recording can be performed on the other layer. Examples of the optical disc drive having a function of recording a visible image on the image recording layer 5 are described in JP 2003-203348 A, JP 2003-242750 A, and the like.

  When recording a visible image on the image recording layer 5, the recording device tracks the optical recording medium 1 and the laser pickup by a tracking groove formed in the image recording layer 5, and the surface of the optical recording medium 1 is recorded. The laser beam is modulated in accordance with image data such as characters and pictures to be imaged and irradiated toward the image recording layer 5 to record a visible image in synchronization with the relative movement. To do. Such a configuration is described in, for example, Japanese Patent Application Laid-Open No. 2002-203321.

  The recording apparatus for recording optical information on the recording layer 3 has at least a laser pickup that emits laser light and a rotating mechanism that rotates the optical recording medium 1, and recording / reproduction on the recording layer 3 is in a rotated state. The recording layer 3 of the optical recording medium 1 is irradiated with laser light from a laser pickup. The configuration of such a recording apparatus itself is well known.

  Next, recording of information (digital information) on the recording layer 3 will be described. When the recording layer 3 is a dye type, first, laser light is irradiated from a laser pickup while rotating the above-mentioned optical recording medium 1 which has not been recorded at a predetermined recording linear velocity. By this irradiation light, the dye of the recording layer 3 absorbs the light and the temperature rises locally, a desired void (pit) is generated and its optical characteristics are changed to record information.

The power of the laser beam varies depending on the recording linear velocity, but when the recording linear velocity is 3.5 m / s, the range of 1 to 100 mW is preferable, the range of 3 to 50 mW is more preferable, and the range of 5 to 20 mW is further increased. preferable. When the recording linear velocity is doubled, the preferable range of the laser beam power is ^21/2 times, respectively.

  In order to increase the recording density, the NA of the objective lens used for the pickup is preferably 0.55 or more, and more preferably 0.60 or more.

In the present embodiment, a semiconductor laser having an oscillation wavelength in the range of 350 to 850 nm can be used as recording light for recording information.
The laser beam for performing image formation according to the present embodiment preferably has a short wavelength, and a blue laser having a wavelength of 500 nm or less is preferably used. For example, it is preferable to use a blue-violet semiconductor laser having a center wavelength of 405 nm.
The upper limit of the wavelength of the laser beam is preferably 500 nm or less, more preferably 450 nm or less, and further preferably 430 nm or less. Further, the lower limit of the wavelength of the laser beam is preferably 200 nm or more, more preferably 300 nm or more, and further preferably 350 nm or more.

  On the other hand, the case where the recording layer 3 is a phase change type will be described. In the case of the phase change type, it is made of the above-described material, and the phase change between the crystalline phase and the amorphous phase can be repeated by laser light irradiation. At the time of information recording, a concentrated laser light pulse is irradiated for a short time to partially melt the phase change recording layer. The melted portion is rapidly cooled by thermal diffusion and solidified to form an amorphous recording mark. At the time of erasing, the recording mark portion is irradiated with laser light, heated to a temperature not higher than the melting point of the recording layer 3 and not lower than the crystallization temperature, and cooled to crystallize the amorphous recording mark. Return to the unrecorded state.

Only one optical recording system for the recording layer 3 and one optical recording system for the image recording layer 5 are provided from the viewpoint of cost, and information or images on both sides can be obtained by turning the optical recording medium 1 upside down. However, the optical recording system for the recording layer 3 and the optical recording system for the image recording layer 5 are provided separately, and the recording surface 2a side and the label surface 6a of the optical recording medium 1 are respectively provided. It may be provided separately on the side.
In this case, it is not necessary to turn the optical recording medium 1 over. Further, the wavelength of the laser beam of each optical recording system may be varied.

Next, image formation on the image recording layer 5 will be described.
In the image forming method according to the present embodiment, a plurality of rows of dots are formed on the image recording layer 5 by laser light. For example, by irradiating laser light while rotating the disk-shaped optical recording medium 1, the laser light emitted in a pulsed manner is irradiated while changing the relative position in the circumferential direction, and the image recording layer 5 is spirally dotted. Form.

  This dot array must be arranged in a line in at least one direction. For example, as shown in FIG. 2A, the dots are arranged at a pitch P in both the circumferential direction and the diameter direction. As shown in FIG. 2B, a grid-like form, a form in which rows formed in the circumferential direction are arranged at a pitch P in the diameter direction, and a dense form as shown in FIG. There may be a form in which dots are arranged at the vertices of equilateral triangles arranged in a row and arranged in a plurality of rows at a pitch P in three directions. As shown in FIG. 2A and the like, the dots are somewhat elliptical because there is a relative speed between the optical recording medium 1 and the laser light at the time of formation.

  The pitch P of the dot array is, for example, 0.05 to 20 μm. The lower limit of the pitch P is preferably 0.1 μm, and more preferably 0.2 μm. The upper limit of the pitch P is preferably 2 μm, more preferably 1 μm, and most preferably 0.7 μm. If the pitch P is too large, the interference effect cannot be obtained, and the color is not vivid. Further, if the pitch P is too small, it is connected to the adjacent column, and the original light interference effect is not obtained.

When this average pitch is defined in relation to the wavelength λw of the laser beam, it is 0.01 to 50 times, preferably 0.05 to 20 times, more preferably 0.1 to 5 times, Most preferably, it is 0.5 to 2 times.
Further, the dot diameter is 0.005 to 25 times, preferably 0.025 to 10 times, and more preferably 0.05 to 2.times. Λw when defined in relation to the wavelength λw of the laser beam. 5 times, most preferably 0.25 to 1 times.

Since the wavelength of light that is easily diffracted / reflected is determined according to the pitch P of the dot arrangement, the control unit in the recording apparatus stores the relationship between the pitch P and the color. For example, when the pitch P is 1 μm, blue is stored, and when the pitch P is 2 μm, green is stored.
Then, the pitch P of dots to be formed is determined according to the color data of the color image to be printed sent from the host computer, and input to the laser light source in order to form an array of a plurality of rows at this pitch P. The speed / pattern of the pulse signal and the feed speed in the radial direction of the laser light source are determined and driven.
Note that, by controlling the movement in the radial direction at a high speed by a conventionally known method, it is sufficiently possible to finely position the irradiation position of the laser beam in the radial direction even while the optical recording medium 1 makes one round.

  As described above, the image recording layer 5 of the optical recording medium 1 has a label surface by changing the dot arrangement pitch P in accordance with the color information at each position of the image data sent from the host computer. When observing 6a, a plurality of colors can be expressed.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be appropriately modified and implemented.
For example, although the cover layer 6 is provided in the present embodiment, the cover layer 6 is not necessarily required and may be provided arbitrarily. In addition, other layers may be appropriately added as long as the color expression according to the present invention is not hindered.
In the embodiment, only an example in which dots are arranged in at least one direction to form a row has been described, but lines extending in one direction may be arranged at a pitch P as shown in FIG. Also in this case, since the line functions as a diffraction grating, it is possible to express various colors by changing the pitch P according to the color to be expressed.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited to a following example.

[Example 1]
As shown in FIG. 3, an optical recording medium 1 ′ in which a reflective layer 4, an image recording layer 5, and a cover layer 6 were formed in order on a disc-shaped substrate 2 was prepared. The detailed configuration of each layer is as follows.

・ Substrate material Polycarbonate Thickness 0.6mm
120mm outside diameter
Inner diameter 15mm

-Reflective layer A thin film of ABN (Ag 99.48 wt%, Bi 0.32 wt%, Nd 0.20 wt%) was formed by DC magnetron sputtering.
Thickness about 120nm
Output 2kW
Film formation time 5.5 seconds Atmosphere Ar (flow rate 50 sccm)

・ Image recording layer (dye layer)
2 g of a dye material having the following chemical formula was dissolved in 100 ml of a TFP (tetrafluoropropanol) solvent and spin-coated. At the time of spin coating, the coating liquid was dispensed on the inner peripheral portion of the substrate 2 at a coating start rotation speed of 500 rpm and a coating end rotation speed of 1000 rpm, and the rotation was gradually increased to 2200 rpm. The refractive index n of the dye material is 1.986, and the extinction coefficient k is 0.0418.

Cover layer A thin film of ZnO—Ga ₂ 0 ₃ (ZnO 95 wt%, Ga ₂ 0 ₃ 5 wt%) was formed by DC magnetron sputtering.
Thickness about 5nm
Output 1kW
Film formation time 2 seconds Atmosphere Ar (flow rate 50sccm)

An array of dots was recorded on the optical recording medium from the surface on the cover layer 6 side using DDU1000 (pulse wavelength: 405 nm, NA: 0.65) manufactured by Pulstec. The dots were formed in the arrangement as shown in FIG. 2 (a), and the arrangement pitch was a 1 μm region and a 2 μm region.
The image forming conditions are as follows.
Laser power 2mW
Line speed 5m / s
Recording signal 5 MHz rectangular wave

[Example 2]
The difference from Example 1 is that an optical recording medium without the cover layer 6 is used, and the other points are shared, and two types of regions are formed in which dots are formed with an arrangement of 1 μm pitch and 2 μm pitch. did.

As a result of visual observation of the recording media of Example 1 and Example 2 under white light, before the formation of the pits, only silver, that is, reflection of white light from the reflective layer 4 was visible. On the other hand, the 1 μm and 2 μm pitch portions looked like rainbow colors whose colors change depending on the viewing angle. That is, it was confirmed that light diffraction occurred.
At the angle at which the 1 μm pitch region can be seen in blue, the adjacent 2 μm pitch portion appeared in green. That is, it was confirmed that a plurality of colors can be expressed by changing the dot pitch.

1 is a cross-sectional view of an optical recording medium according to an embodiment. (A), (b), (c) is a figure which shows the example of the arrangement | sequence of a dot. It is sectional drawing of the optical recording medium of an Example. It is a figure which shows the dot arrangement | sequence formed in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical recording medium 2 Board | substrate 2a Recording surface 3 Recording layer 4 Reflective layer 5 Image recording layer 6 Cover layer 6a Label surface

Claims (9)

Image forming method on label surface of optical recording medium having a reflective layer, a recording surface provided on one side of the reflective layer, and an image recording layer provided on the opposite side of the reflective layer from the recording surface Because
In the image recording layer corresponding to the label surface side, a plurality of rows of dots or lines extending in one direction are arranged side by side in at least one direction by a laser beam, and the pitch of the plurality of rows is set to 0. A method of forming an image on a label surface of an optical recording medium, characterized in that the pitch is changed according to the color to be expressed, and the pitch is set to 05 to 20 μm.   The image recording layer is made of a dye material, and λa <λw, where λa is the peak wavelength of light absorption of the dye material, and λw is the wavelength of laser light when forming the dots or lines. The image forming method on the label surface of the optical recording medium according to claim 1.   3. The method of forming an image on the label surface of the optical recording medium according to claim 2, wherein [lambda] w <580 nm. An optical recording medium having a reflective layer, a recording surface provided on one side of the reflective layer, and an image recording layer provided on the opposite side of the recording surface of the reflective layer,
In the image recording layer, a plurality of dots forming a line aligned in at least one direction or a line extending in one direction are arranged, and the pitch of the plurality of lines is 0.05 to 20 μm, and the color to be expressed An optical recording medium characterized in that the pitch is changed accordingly.   The optical recording medium according to claim 4, wherein a cover layer is provided on the image recording layer.   6. The optical recording medium according to claim 4, wherein the thickness of the image recording layer is 0.01 to 2 times the wavelength of the laser beam forming the dots or lines.   The optical recording medium according to any one of claims 4 to 6, wherein the dots or lines are formed by a change in refractive index of a material constituting the image recording layer.   The optical recording medium according to claim 4, wherein the dots or lines are formed by forming the image recording layer into a concave shape or a gap.   The image recording layer is made of a dye material, and λa <λw, where λa is the peak wavelength of light absorption of the dye material, and λw is the wavelength of laser light when forming the dots or lines. The optical recording medium according to claim 4, wherein the optical recording medium is an optical recording medium.

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