Latent image forming body

Abstract

To provide a latent image forming body capable of precisely reproducing a semi-cylindrical streak, having no difficulty of combined printing, and capable of being manufactured by a simple process.SOLUTION: The latent image forming body comprises: a base material layer made of a thermoplastic resin; an optically variable layer made of the thermoplastic resin laminated on the base material; and a laser coloring layer made of the thermoplastic resin having optical transparency, laminated on the optically variable layer. The base material layer includes a protruding structural element group formed by arranging a plurality of protruding structural elements having a protruding curved cross section at a predetermined regularity. The optically variable layer and the laser coloring layer are formed of a protruding curved shape following the protruding structural element group. The laser coloring layer includes a latent image element group having a laser-colored hue.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a latent image forming body used in the field of security printed matter such as banknotes, passports, securities, identity certificates, cards, tickets, etc., which require anti-counterfeiting effects, and in which an image appears to move at an angle where reflected light or diffracted light is generated.

Background Art

[0002] For security printed matter represented by banknotes, passports, securities, identity certificates, etc., anti-counterfeiting techniques are required to prevent duplication and counterfeiting. Among anti-counterfeiting techniques, there is a particular need for anti-counterfeiting techniques that do not require tools, such as watermarks and holograms, and can be used by anyone who has the printed matter to determine authenticity.

[0003] Among these, anti-counterfeiting techniques with a so-called "video-like visual effect" where an image appears to move have attracted particular attention. A video-like visual effect where an image appears to move (hereinafter referred to as "video effect") is eye-catching and difficult to counterfeit, and in recent years, it has been increasingly used as an element for determining the authenticity of security printed matter. As known techniques capable of realizing the video effect, there are techniques using holograms, parallax barriers, lenticulars, etc. Taking advantage of the feature that an image can be changed with a slight change in angle provided by these techniques, security printed matter with an effect where an image can be visually recognized three-dimensionally or with a video effect already widely exists.

[0004] As an example, the applicant has disclosed a technique in a form that realizes a special three-dimensional visual effect and a video-like visual effect by using a phenomenon (moire magnification phenomenon) in which a collection of fine patterns is magnified and visually recognized by being sampled as moire, and a line configuration of the integral photography method (see, for example, Patent Document 1 and Patent Document 2).

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent No. 5200284 [Patent Document 2] Japanese Patent No. 6399359 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] The technologies described in Patent Document 1 and Patent Document 2 are technologies in which a latent image line is laminated on a katamari-shaped drawn line formed by a glossy ink, and the latent image exhibits a moving image effect under regular reflected light. However, since the katamari-shaped drawn line is formed by printing, not all of them have exactly the same shape, and there are problems in precisely reproducing the katamari-shaped drawn line, such as shape changes due to ink dripping and missing parts of the drawn line due to ink bleeding.

[0007] Also, in the technologies described in Patent Document 1 and Patent Document 2, since a latent image is formed by ink on a katamari-shaped drawn line, it is difficult to register the printing of the katamari-shaped drawn line and the latent image line. If it is not printed at the appropriate position, there is a problem that the latent image does not appear correctly.

[0008] Furthermore, when applying the technologies described in Patent Document 1 and Patent Document 2 to printed matter such as identity certificates, ID information such as names is often formed by laser drawing after the printing process. However, since the process becomes complicated, it has been required to perform manufacturing efficiently.

[0009] The present invention aims to solve the above problems, and provides a latent image forming body capable of precisely reproducing a katamari-shaped drawn line, having no difficulty in registration, and being manufacturable by a simple process. [Means for Solving the Problems]

[0010] The present invention has a base material layer made of a thermoplastic resin, an optical change layer made of a thermoplastic resin laminated on the base material layer, and a laser coloring layer made of a thermoplastic resin having light permeability laminated on the optical change layer. The base material layer includes a convex structure element group formed by arranging a plurality of convex structure elements having a convex shape with a convex curved surface in a cross-sectional shape with a predetermined regularity. The optical change layer and the laser coloring layer each have a convex curved surface having the same shape as the convex structure element group. The laser coloring layer includes a latent image element group of laser-colored colors. The latent image element group is formed by arranging (i) latent image elements in which a plurality of divided elements obtained by dividing a plurality of base images in a predetermined direction are sequentially arranged so as not to overlap each other, having the same regularity as the regularity of the convex structure element group, or (ii) latent image elements obtained by dividing and compressing a base image in a predetermined direction, having the same regularity as the regularity of the convex structure element group and arranged in a plurality, or (iii) latent image elements obtained by compressing a base image at a predetermined compression rate, having a regularity different from the regularity of the convex structure element group and arranged in a plurality, or (iv) latent image elements in which a part of each of a plurality of base images obtained by observing one base image from a plurality of directions is compressed at a predetermined compression rate, and the positions where the plurality of base images are compressed are evenly shifted for each of the plurality of base images, having the same regularity as the regularity of the convex structure element group and arranged in a plurality. It is a latent image forming body characterized by this.

[0011] The present invention is a laminate characterized in that the cross-sectional structure of the convex structure element group is a Fresnel lens structure or a blazed structure.

Effects of the Invention

[0012] In the latent image forming body of the present invention, by forming a convex structure element group in the shape of a clam by embossing, the structure of the convex structure element group in the shape of a clam is made uniform, so that a delicate reproduction of the latent image can be achieved.

[0013] Further, in the latent image forming body of the present invention, since a latent image line is formed on a clam-shaped ruled line by a laser, it is easier to register than printing. Also, a clear moving image effect can be obtained for the latent image that appears thereby.

[0014] Furthermore, since ID information such as names is formed by laser drawing through laser processing after embossing without using a printing process, it can be manufactured by a simple process.

Brief Description of the Drawings

[0015]

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Embodiments for Carrying Out the Invention

[0016] Embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments described below, and other various embodiments are included as long as they are within the scope of the technical idea described in the claims.

[0017] (First Embodiment) The latent image forming body (A1) of the present invention will be described. This embodiment is an example in which the convex structure elements constituting the convex structure element group are formed linearly.

[0018] As shown in FIGS. 1(a) and 1(b), the latent image forming body (A1) is laminated in the order of a base material layer (1) made of a thermoplastic resin, an optical change layer (22) made of a thermoplastic resin, and a laser coloring layer (23) made of a light-transmissive thermoplastic resin. The base material layer (1) has a first convex structure element group (3) composed of first convex structure elements (7) formed by embossing.

[0019] Furthermore, since the optical change layer (22) and the laser coloring layer (23) follow the first convex structure element group (3), the surface shape also naturally has a shape following the first convex structure element group (3). Furthermore, the laser coloring layer (23) has a first latent image element group (6) in which a plurality of first latent image elements (10) composed of laser-colored colors are arranged with a predetermined regularity (first rule) in a first direction (S1) and at a first pitch (P1) with respect to the convex curved surface.

[0020] Note that, since the optical change layer (22) and the laser color-forming layer (23) follow the first convex structure element group (3), they have the same shape. For convenience of explanation, the shape following the first convex structure element group (3) formed in the optical change layer (22) is referred to as the second convex structure element group (4), and the shape following the first convex structure element group (3) formed in the laser color-forming layer (23) is referred to as the third convex structure element group (5).

[0021] (Base material layer) In the present invention, the base material layer (1) is not particularly limited as long as it is a thermoplastic resin, and is preferably a material having light reflectivity. A thermoplastic resin sheet made of a known thermoplastic resin layer such as polycarbonate (PC), polyethylene terephthalate glycol (PETG), polyvinyl chloride (PVC), acrylonitrile-butadiene-styrene copolymer resin (ABS resin), etc. can be used. Note that it is preferable for the base material layer (1) to have light reflectivity because the polarization of the optical change layer (22) described later due to the reflection of incident light or the structural color exhibiting interference by visible light becomes clear, and the latent image that appears becomes clearer.

[0022] Further, the thermoplastic resin sheet forming the base material layer (1) may have a single-layer structure or a multilayer structure. The two surfaces may be made of the same series of materials such as polycarbonate (PC) and polyethylene terephthalate glycol (PETG), or a mixture of the same series of materials, preferably the same material on both surfaces, and the same series of materials may be formed in a plurality of layers such as two layers or three layers.

[0023] The thickness of the base material layer (1) is not particularly limited. When making it into a card shape, according to the JIS standard (JIS X 6301:2005) of the identification card, the thickness is defined as 0.76 mm. Therefore, it is sufficient that the total thickness of the final product is within this range. Next, the first convex structure element group (3) will be described.

[0024] (First convex structure element group) As shown in FIGS. 2(a) and 2(b), the first convex structure element group (3) is composed of first convex structure elements (7) each having a first line width (W1) with a convex cross-sectional shape that is a convex surface, arranged in a first pitch (P1) and in a first direction (S1) according to a predetermined regularity (first regularity). In this example, the first line width (W1) and the first pitch (P1) are of the same size, but they may be of different sizes.

[0025] The height (H1) of the first convex structure element (7) is not particularly limited, but is preferably 20 μm or more and 50 μm or less. If the height is less than 20 μm, the development of the latent image described later becomes unclear, and if it exceeds 50 μm, there is a lack of convenience when using the latent image forming body (A1) as a card.

[0026] In the present embodiment, the cross-sectional shape of the first convex structure element (7) is a clam shape, but it is not particularly limited as long as it has a convex shape with a convex surface, and known convex shapes with convex surfaces such as an elliptical shape, a semi-circular shape, a Fresnel lens shape, or a blazed shape can be used. When the Fresnel lens shape or the blazed shape is used, by reducing the height of the first convex structure element (7), the thickness of the latent image forming body (A1) can be made thinner, and the convenience of the card in the aforementioned JIS standard (JIS X 6301:2005) is enhanced. In addition, since the reflected light with respect to the incident light can be concentrated at one point, a high-brightness latent image can be formed.

[0027] (Optical change layer) In the present invention, the optical change layer (22) is a thermoplastic resin layer formed by laminating a plurality of single-layer thin films made of a material that transmits light in the entire visible region, such as a liquid crystal layer composed of cholesteric liquid crystal or smectic liquid crystal, a metal oxide, a metal nitride, and a metal oxynitride, or a thermoplastic resin layer in which the aforementioned materials are mixed, and is a light-transmissive thermoplastic resin sheet having polarization or a structural color (for example, one hue, structural color, multicolor structural color, peacock color structural color, etc.) that exhibits interference by visible light.

[0028] The thermoplastic resin sheet for forming the optical change layer (22) is not particularly limited as long as it is a thermoplastic resin, and preferably has a light-transmitting property. For example, known liquid crystal sheets, interference sheets, or multilayer interference sheets such as polycarbonate (PC), polyethylene terephthalate glycol (PETG), polyvinyl chloride (PVC), acrylonitrile-butadiene-styrene copolymer resin (ABS resin), etc. may be mentioned. Note that it is preferable for the optical change layer (22) to have light-transmitting property because the transmitted incident light causes the polarization of the optical change layer (22) due to the reflection of the aforementioned base material layer (1), or the structural color caused by the interference of visible light becomes distinct, and thus the latent image that further appears becomes clearer.

[0029] The thermoplastic resin sheet for forming the optical change layer (22) may have a single-layer structure or a multilayer structure. Both sides are preferably made of the same series of materials, more preferably the same material on both sides, and a plurality of layers such as two layers or three layers of the same series of materials may be formed. Note that the thickness of the thermoplastic resin layer for forming the optical change layer (22) is omitted because it is the same as that of the aforementioned base material layer (1). Next, the second convex structure element group (4) will be described.

[0030] (Second convex structure element group) As shown in FIGS. 3(a) and 3(b), the second convex structure element group (4) formed on the optical change layer (22) is composed of a plurality of second convex structure elements (8) each having a first line width (W1) with a convex curved surface arranged at a first pitch (P1) and in a first direction (S1) according to a predetermined regularity (first regularity). Note that the second convex structure element group (4) has a cross-sectional shape following the convex curved surface of the convex shape of the first convex structure element group (3) indicated by the dotted line.

[0031] (Laser color-developing layer) In the present invention, the laser color-developing layer (23) is a laser color-developing sheet having light-transmitting property and composed of a transparent thermoplastic resin layer containing a color-developing agent that absorbs laser light and develops color.

[0032] The laser color - forming sheet for forming the laser color - forming layer (23) can use, for example, known thermoplastic resin sheets such as polycarbonate (PC), polyethylene terephthalate glycol (PETG), polyvinyl chloride (PVC), acrylonitrile - butadiene - styrene copolymer resin (ABS resin), etc. A single material can be used as the thermoplastic resin sheet, or different materials can be combined and used.

[0033] The laser color - forming sheet for forming the laser color - forming layer (23) may have a single - layer structure or a multi - layer structure. Both sides have the same series of materials, preferably the same material on both sides, and the same series of materials can be formed in multiple layers such as two layers or three layers. Note that the thickness of the laser color - forming sheet is the same as that of the aforementioned base material layer (1), so it is omitted.

[0034] As the color - forming agent added to the laser color - forming sheet, metal oxides that absorb a predetermined laser beam and generate heat are used. For example, as the metals that form black - colored oxides, copper, iron, nickel, manganese, titanium, lead, chromium, cobalt, tin, thallium, vanadium, niobium, molybdenum, ruthenium, rhodium, tantalum, tungsten, rhenium, osmium, iridium, bismuth, palladium, silver, platinum, gold, etc. can be mentioned. In addition to these color - forming agents, carbon black with high heat absorption or a light - absorbing agent that absorbs laser light of a predetermined wavelength may be contained. With such a configuration, carbonization can occur around the member, and a more visible color - forming property may be obtained. Examples of the light - absorbing agent include cyanine - based dyes, polymethine - based dyes, anthraquinone - based dyes, phthalocyanine - based dyes, naphthalocyanine - based dyes, etc., which have an absorption peak in the wavelength range of the laser used.

[0035] (Third convex structural element group) As shown in FIGS. 4(a) and 4(b), the third convex structure element group (5) formed in the laser color forming layer (23) is composed of a third convex structure element (9) having a first line width (W1) with a convex curved surface, which is arranged in a first pitch (P1) and in a first direction (direction S1 in the figure) according to a predetermined regularity (first regularity). Note that the third convex structure element group (5) has a cross-sectional shape following the convex curved surface of the convex shape of the first convex structure element group (3) shown by a dotted line, similar to the second convex structure element group (4).

[0036] Next, the first latent image element group (6) formed in the third convex structure element group (5) will be described with reference to FIG. 5. Note that the first latent image element group (6) in this embodiment has an annular shape formed by arranging a plurality of first latent image elements (10) in which divided elements (11) having a second line width (W2) composed of the laser-colored color are adjacent to each other in the first direction (S1).

[0037] (First latent image element group) As shown in FIG. 5, the third convex structure element group (5) has a first latent image element group (6) in which a plurality of first latent image elements (10) formed by arranging a plurality of divided elements (11) having a second line width (W2) composed of the laser-colored color adjacent to each other in the first direction (S1) are arranged in a predetermined regularity (first regularity) in the first direction (S1) and with the first pitch (P1) with respect to the convex curved surface.

[0038] Next, the first latent image element group (6) will be described in detail with reference to FIGS. 6 and 7. First, the divided elements (11) forming the first latent image element group (6) will be described with reference to FIG. 6.

[0039] FIG. 6 shows three base images (12-1, 12-2, 12-n) representing an annular shape from different angles as the basis of the first latent image element group (6). As shown in FIG. 6, the first latent image elements (10) forming the first latent image element group (6) divide the first base image (12-1), the second base image (12-2), ···, the first-n base image (n is an integer of 3 or more) (12-n) in the first direction (S1) and the second line width (W2) (second line width (W2) = first line width (W1) / n), respectively, to form the first-1-1 divided element (11-1-1), the first-1-2 divided element (11-1-2), ··· the first-1-n divided element (11-1-n), the first-2-1 divided element (11-2-1), the first-2-2 divided element (11-2-2), ··· the first-2-n divided element (11-2-n), the first-n-1 divided element (11-n-1), the first-n-2 divided element (11-n-2), ··· the first-n-n divided element (11-n-n) with different shapes.

[0040] Next, as shown in FIG. 7, the first-1-1 divided element (11-1-1), the first-2-1 divided element (11-2-1), ··· the first-n-1 divided element (11-n-1) are arranged adjacent to each other in the first direction (S1) so that the respective divided elements do not overlap, thereby forming the first-1 latent image element (10-1) with the first line width (W1).

[0041] Also, similar to the first-1 latent image element (10-1), the first-2 latent image element (10-2) is formed by the first-1-2 divided element (11-1-2), the first-2-2 divided element (11-2-2), ··· the first-n-2 divided element (11-n-2), and the first-n latent image element (10-n) is also formed by the first-1-n divided element (11-1-n), the first-2-n divided element (11-2-n), ··· the first-n-n divided element (11-n-n).

[0042] Next, as shown in FIG. 8, the first latent image elements (10-1), (10-2),..., (10-n) of the first line width (W1) are sequentially arranged with respect to the third convex structure element group (5) in the first direction (S1) and at the first pitch (P1) so that the respective latent image elements do not overlap, thereby forming the first latent image element group (6).

[0043] In this embodiment, an example is shown in which the first latent image element group (6) is formed by three latent image elements of the first latent image element (10-1), the second latent image element (10-2),..., the nth latent image element (10-n) from three base images of the first base image (12-1), the second base image (12-2),..., the nth base image (12-n) (n is an integer of 3 or more), and the latent image forming body (A1) is produced. However, the present invention is not limited thereto, and the number of base images and latent image elements can be any number, not limited to three.

[0044] Next, the effects of the present invention will be described with reference to FIG. 9. FIG. 9(a) shows the case where the latent image forming body (A1) is observed at a first observation angle (D1) (an angle where the incident angle and the light receiving angle are greatly different) where diffuse reflection is dominant with respect to the light source (B). FIGS. 9(b) and 9(c) show the respective latent images when the latent image forming body (A1) is observed at a second observation angle (D2) and an nth observation angle (Dn) (angles where the incident angle and the light receiving angle are close) where specular reflection is dominant with respect to the light source (B). In the observation from the first observation angle (D1), only the first latent image (C1) in the form of an "annulus" is visible in the latent image forming body (A1). When observed while tilting to the second observation angle (D2) shown in FIG. 9(b), the second latent image (C2) can be continuously visually recognized. When observed while tilting to the nth observation angle (Dn), the nth latent image (Cn) shown in FIG. 9(c) can be continuously visually recognized.

[0045] Next, the principle of the present invention will be described with reference to FIG. 10. As shown in FIG. 10, in an environment where diffuse reflection is dominant, when observed at the first observation angle (D1), the divided elements of the 1-2-1 divided element (11-2-1), the 1-2-2 divided element (11-2-2), and the 1-2-n divided element (11-2-n) are combined to visually recognize the first latent image (C1). At the second observation angle (D2), the divided elements of the 1-1-1 divided element (11-1-1), the 1-1-2 divided element (11-1-2), and the 1-1-n divided element (11-1-n) are combined to visually recognize the second latent image (C2). At the nth observation angle (Dn), the divided elements of the 1-n-1 divided element (11-n-1), the 1-n-2 divided element (11-n-2), and the 1-n-n divided element (11-n-n) are combined to visually recognize the nth latent image (Cn). Therefore, different latent images can be visually recognized depending on the observation angle.

[0046] (Manufacturing method) As shown in FIG. 13(a), the latent image forming body (A1) of the present invention is formed by laminating, on the upper layer, a laser coloring layer (23) made of a thermoplastic resin that forms a third convex structure element group (5), an optical change layer (22) made of a thermoplastic resin on an intermediate layer that forms a second convex structure element group (4), and a base material layer (1) made of a thermoplastic resin that forms a first convex structure element group (3) on the lower layer. Then, it is sandwiched by a molding press plate (2) using a known processing machine capable of performing embossing, and thermocompression bonded in the vertical direction to impart a convex shape in accordance with the shape of the first convex structure element group (3) to integrate the three layers. Further, after integration, as shown in FIG. 13(b), laser light (18) from a laser marker (19) such as a known UV laser or IR laser is irradiated to form a first latent image element group (6).

[0047] By setting the heating temperature to a temperature equal to or higher than the softening point temperature of each thermoplastic resin layer constituting the latent image forming body (A1) and performing thermocompression bonding, each thermoplastic resin layer is firmly adhered to each other. Since the first to third convex structure elements are formed by embossing, compared with the prior art where a herringbone-shaped line is applied by printing, the structure of the convex structure elements can be made uniform.

[0048] In addition, since the first latent image element group (6) is formed by a laser, latent image elements can be formed on the convex curved surface with high precision as compared with printing registration. Further, a clear moving image effect can be obtained for the latent image thereby appearing.

[0049] Furthermore, after forming the first to third convex structural elements by embossing, the first latent image element group (6) can be formed by a known laser marker (19). Therefore, latent image elements can be formed by a simpler process as compared with the printing process.

[0050] Also, by using the laser marker (19), different information can be imparted to each latent image forming body (A1). Therefore, ID information such as an identity card can be formed as the latent image elements.

[0051] (Second Embodiment) Next, a latent image forming body (A2) in which a second latent image element group (14) is formed by applying a method for recording / viewing a three-dimensional image called integral photography will be described. Note that the first convex structural element group (3), the second convex structural element group (4), and the third convex structural element group (5) are linear as in the first embodiment, and thus description thereof will be omitted. The second latent image element group (14) having a different configuration will be described.

[0052] As shown in FIG. 11, for the base image (12) of "cherry blossom", a frame (13) with a first line width (W1) is applied, the base image (12) contained within the frame is divided and extracted, and compressed at the same compression rate in the first direction (S1 direction), so that all the second latent image elements (15) with respect to the base image (12) have the same size of the first line width (W1). In the present invention, as described above, dividing and extracting the base image (12) contained within the frame and compressing it at the same compression rate in the first direction (S1 direction) is referred to as "divided compression". Next, for the third convex structure element group (5), a second latent image element group (14) in which the second latent image elements (15) are arranged according to a predetermined regularity (first rule) in the first direction (S1) and with a first pitch (P1) is formed by laser irradiation.

[0053] Note that the first line width (W1) in the present embodiment refers to the width including the image portion of the "cherry blossom" which is the base image and the blank portion where the image portion is not provided, and is the width formed by compressing the image within the frame.

[0054] The effects of the latent image forming body (A2) in the second embodiment are shown in FIG. 12. FIG. 12(a) shows the case where the latent image forming body (A2) is observed at a first observation angle (D1) (an angle where the incident angle and the light receiving angle are significantly different) where diffuse reflection is dominant with respect to the light source (B). FIGS. 12(b) and 12(c) show the respective latent images when the latent image forming body (A2) is observed at a second observation angle (D2) and an n-th observation angle (Dn) (angles where the incident angle and the light receiving angle are close) where specular reflection is dominant with respect to the light source (B). In the observation from the first observation angle (D1), only the first latent image (C1) of "cherry blossom" is visible in the latent image forming body (A2). When observed at an inclination to the second angle (D2) or the n-th angle (Dn), as shown in FIGS. 12(b) and 12(c), the position of "cherry blossom" moves according to the observation angle.

[0055] Next, an example of a video effect using an effect called moire magnification will be described, in which two periodic images interfere with each other instead of integral photography, and a specific image appears enlarged.

[0056] As shown in FIG. 14, a third latent image element group (16) of vertically long "cherry blossoms" formed by compressing a base image (12) of "cherry blossoms" in a horizontal direction as a first direction (S1) at the same compression ratio to a first line width (W1) is formed by laser irradiation, with a plurality of third latent image elements (17) arranged according to a predetermined regularity (second rule) that is different from a first pitch (P1) in the first direction (S1) and a third pitch (P3).

[0057] In this embodiment, the third latent image element group (16) and each convex structure element group (3, 4, 5) with a slightly different arrangement pitch interfere with each other, and a plurality of enlarged moirés, which are enlarged images of the third latent image element (17) generated from the interference, appear with a certain periodicity, and all the appeared enlarged moirés move in a specific direction, thereby achieving an effect equivalent to integral photography shown in FIG. 12. In FIG. 14, the third pitch (P3) of the third latent image element (17) and the first pitch (P1) of the third convex structure element group (5), which are predetermined regularities (second rule), are made different. However, the predetermined regularity (second rule) also includes making the arrangement angle of the third latent image element (17) different from the arrangement angle of the third convex structure element (9). Therefore, the second rule only needs to be different from either the predetermined regularity (first rule) or the arrangement angle of the first convex structure element group (3).

[0058] (Third Embodiment) Next, as shown in FIG. 15, an example of a latent image forming body (A3) will be described in which the first to third convex structure elements are formed by dots with a hemispherical cross-sectional shape, and the visible latent image is a cube, and the cube is a three-dimensional image with a three-dimensional effect. The convex structure element of this embodiment has a hemispherical cross-sectional shape, but is not particularly limited as long as it is a dot, and may be a Fresnel lens shape, a blazed shape, or the like.

[0059] First, the first convex structure element group (3´) will be described. Note that the second convex structure element group (4´) and the third convex structure element group (5´) (not shown) are omitted because they follow the configuration of the first convex structure element group (3´).

[0060] As shown in FIGS. 16(a) and 16(b), the first convex structure element group (3´) is composed of a set of hemispherical and dot-shaped first convex structure elements (7´). The first convex structure elements (7´) are arranged with a predetermined regularity (third rule) that is a first pitch (P1) in a first direction (S1 direction) and a second pitch (P2) in a second direction (S2 direction). Also, the first pitch (P1) and the second pitch (P2) may have different values or the same value.

[0061] Subsequently, in the third embodiment, the fourth latent image element group (20) formed in the laser coloring layer (23) will be described. In this embodiment, in order to make the visible latent image a three-dimensional image, as shown in FIG. 17, the base image (12´) is configured such that the base image (12´) is an image obtained by observing a cube, which is a three-dimensional structure, from a plurality of directions such as vertically, horizontally, and diagonally. Each base image (12´-1, 12´-2, 12´-3, 12´-4, 12´-5, ···, 12´-n) observed from a plurality of directions will be described.

[0062] As shown in Fig. 18, for each of the base images (12'-1, 12'-2, 12'-3, 12'-4, 12'-5, ···, 12'-n) observed from a plurality of directions, a frame (13) with a frame width (W3) and a frame width (W4) of a certain size is applied according to a predetermined regularity, and the base images (12'-1, 12'-2, 12'-3, 12'-4, 12'-5, ···, 12'-n) contained within the frame (13) are extracted and compressed at the same compression ratio in the first direction (S1 direction) and the second direction (S2 direction) to form fourth latent image elements (21-1, ···, 21―n). A fourth latent image element group (20) in which a plurality of the fourth latent image elements are arranged with the same predetermined regularity (third regularity) as the first convex structure element group (3) is formed by laser irradiation on the third convex structure element group (5') as shown in Fig. 19. At this time, the aspect ratio of the frame (13) and the compression ratio between the first direction (S1 direction) and the second direction (S2 direction) of the base images (12'-1, 12'-2, 12'-3, 12'-4, 12'-5, ···, 12'-n) are set to values according to the ratio of P1:P2.

[0063] Next, an example of a method for forming the fourth latent image element group (20) will be described in detail. Fig. 20 shows an example in which the base images (12'-1, 12'-2, 12'-3, 12'-4, 12'-5, ···, 12'-n) are arranged in a matrix, and the auxiliary line (J) is provided for convenience to clarify the positions where the base images (12'-1, 12'-2, 12'-3, 12'-4, 12'-5, ···, 12'-n) are arranged.

[0064] In Fig. 20, since five base images are arranged in the first direction (S1 direction), the frame (13) is applied to the left end of the base image (12'-1), and then the frame (13) is applied to the right end of the base image (12'-5). For the base images (12'-2, 12'-3, 12'-4), the frame (13) is applied while being evenly shifted from the base image (12'-1) toward the base image (12'-5). Since five base images are also arranged in the second direction (S2) in the same manner, the frame (13) is applied while being evenly shifted from the base image (12'-5) toward the base image (12'-n).

[0065] As described above, for the base images (12'-1, 12'-2, 12'-3, 12'-4, 12'-5, ···, 12'-n) arranged in a matrix, the frame (13) is gradually shifted to extract and compress the images, thereby forming the fourth latent image elements (21-1, ···, 21-n) in the third embodiment.

[0066] Next, the effects of the latent image forming body (A3) will be described with reference to FIGS. 21(a) to 21(e). As shown in FIG. 21(a), when the latent image forming body (A3) is observed from the first observation angle (D1), the first latent image (C1) in the form of a cube viewed from the front is visible. As shown in FIG. 21(b), when the latent image forming body (A3) is observed from the lower right as the second observation angle (D2), a second latent image (C2) of the cube viewed from the lower right is visible as a three-dimensional image inside the latent image forming body (A3). As shown in FIG. 21(c), when the latent image forming body (A3) is observed from the upper right as the third observation angle (D3), a third latent image (C3) of the cube viewed from the upper right is visible as a three-dimensional image inside the latent image forming body (A3). As shown in FIG. 21(d), when the latent image forming body (A3) is observed from the upper left as the fourth observation angle (D4), a fourth latent image (C4) of the cube viewed from the upper left is visible as a three-dimensional image. As shown in FIG. 21(e), when the latent image forming body (A3) is observed from the lower left as the nth observation angle (Dn), the nth latent image (Cn) of the cube viewed from the lower left is visible as a three-dimensional image.

[0067] Next, the embodiments of the present invention will be described in the same manner as the above-described embodiments with reference to FIGS. 11 and 12. Note that the content of the present invention is not limited to the scope of these embodiments.

[0068] (Example) To form the latent image forming body (A2) shown in Fig. 11, a white polycarbonate sheet ("I-1048W" manufactured by Taihei Chemical Products Co., Ltd., thickness: 0.40 mm) was used as the thermoplastic resin sheet for the base material layer (1). Also, as the optical change layer (22), a multilayer interference sheet (REVI-SD900 manufactured by Lintec Co., Ltd., thickness: 0.10 mm) was used, and as the laser coloring layer (23), a laser coloring sheet made of transparent polycarbonate ("I-1005" manufactured by Taihei Chemical Products Co., Ltd., thickness: 0.30 mm) was used.

[0069] The above-mentioned white polycarbonate sheet, multilayer interference sheet, and laser coloring sheet were laminated in this order, and embossing was performed by thermocompression bonding with a mechanical setting of 185°C, 30 seconds, and 2.5 MPa using an SD type molding press machine ("SDOP-1042-2HC-AT-WC1V-PG3" manufactured by Danbell Co., Ltd.).

[0070] The first convex structural element (7) had a cross-sectional shape in the form of a straight line with a first line width (W1) of 0.3 mm in the shape of a wasabi root, and was continuously arranged in the first direction (S1 direction) with a first pitch (P1) of 0.4 mm. The line height (H1) was set to 20 μm. The first line widths (W1) of the second convex structural element (8) and the third convex structural element (9) were the same as those of the first convex structural element (7), and the first pitch (P1) in the first direction (S1 direction) was also 0.4 mm and continuously arranged.

[0071] Next, for the second latent image element group (14), a frame (13) having the same size (W1) as the first line width (W1) is applied to the base image (12) of "sakura", and the base image (12) contained within the frame is divided and extracted. All of them are compressed at the same ratio in the first direction (S1 direction) to obtain second latent image elements (15) with respect to the base image (12), all having the same size with the first line width (W1) set to 0.3 mm. Next, for the third convex structure element group (5), an IR laser with a wavelength of 1064 nm as the laser light (Keyence laser marker (3Axis YVO4LaserMarker MD-V9900)) is used, and the second latent image elements (15) are arranged in the first direction (S1) with a first pitch (P1) of 0.4 mm to form the second latent image element group (14), thereby fabricating the latent image forming body (A2).

[0072] Next, the effects of the latent image forming body (A2) of the example are shown in FIG. 12. When observed from the first observation angle (D1) shown in FIG. 12(a), only the first latent image of "sakura" (C1) is visible. When observed while tilted at the second angle (D2) or the nth angle (D2), as shown in FIGS. 12(b) and 12(c), it was confirmed that the position of "sakura" clearly moves according to the observation angle.

Explanation of Reference Numerals

[0073] 1 Base material layer 2 Molding press plate 3 First convex structure element group 4 Second convex structure element group 5 Third convex structure element group 6 First latent image element group 7 First convex structure element 8 Second convex structure element 9 Third convex structure element 10 First latent image element 11 Division element 12 Base image 13 Frame 14 Second latent image element group 15 Second latent image element 16 Third latent image element group 17 Third latent image element 18 Laser light 19 Laser marker 20 Fourth latent image element group 21 Fourth latent image element 22 Optical change layer 23 Laser color developing layer A Latent image forming body B Light source C Latent image D Observation angle J Auxiliary line

Claims

【Claim 1】 It has a base material layer made of a thermoplastic resin, an optical change layer made of a thermoplastic resin laminated on the base material layer, and a laser coloring layer made of a thermoplastic resin having light transmissibility laminated on the optical change layer. The base material layer includes a convex structure element group formed by arranging a plurality of convex structure elements having a convex shape with a convex curved surface in cross-sectional shape with a predetermined regularity. The optical change layer and the laser coloring layer each have a convex curved surface having the same shape as the convex structure element group. The laser coloring layer includes a latent image element group of a color latent image formed by laser coloring. The latent image element group is i) Latent image elements in which a plurality of divided elements obtained by dividing a plurality of base images in a predetermined direction are sequentially arranged so as not to overlap each other are sequentially arranged with the same regularity as the regularity of the convex structure element group, or ii) Latent image elements obtained by dividing and compressing a base image in a predetermined direction are arranged in a plurality with the same regularity as the regularity of the convex structure element group, or iii) Latent image elements obtained by compressing a base image at a predetermined compression rate are arranged in a plurality with a regularity different from the regularity of the convex structure element group, or iv) For a plurality of base images obtained by observing one base image from a plurality of directions, a part of each base image is compressed at a predetermined compression rate, and the positions where the plurality of base images are compressed are evenly shifted for each of the plurality of base images. The latent image elements are arranged in a plurality with the same regularity as the regularity of the convex structure element group. A latent image forming body characterized by this.

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