JP2011248015A - Hologram sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel hologram sheet using a hologram that reproduces a hologram reproduction image having a wavelength different from an illumination light in contrast with a hologram that reproduces a hologram reproduction image having the same wavelength as the illumination light in order to improve the authenticity thereof.SOLUTION: A photochromic thin film layer is provided on a hologram formation layer, and the photochromic thin film layer is irradiated with an exciting light. A hologram reproduction image caused by the color tone of the light emission in the visible light region is made visually determinable, and thereby an improved forgery prevention effect is achieved.

Description

The present invention relates to a novel hologram sheet, and more particularly to a coloring type hologram sheet in which a photochromic thin film is arranged at the relief position of a relief hologram exhibiting a phase hologram.
In the present specification, “part” indicating the formulation is based on mass. The “hologram” includes a hologram and a hologram having a light diffractive function such as a diffraction grating. “Diffraction gratings” include those formed optically such as optical interference fringes and those formed by a direct drawing method such as an electron beam drawing method.

(Main applications)
The main use of the hologram sheet of the present invention is in the art / craft field and commercial field using the hologram itself for decoration, but is not limited to this, and is a hologram sheet used in the counterfeit prevention field. In particular, credit cards and other counterfeited products that can damage cardholders and card companies, driver's licenses, employee ID cards, ID cards such as membership cards, and entrance examinations For tickets, passports, banknotes, gift certificates, point cards, stock certificates, securities, lottery tickets, horse tickets, bank passbooks, boarding tickets, toll tickets, air tickets, tickets for various events, play tickets, transportation and public telephones There are prepaid cards.
Each of these is an information recording body that holds information having economic or social value, and it is desirable to have a function that can identify the authenticity of the recording body for the purpose of preventing damage caused by forgery. .

In addition to these information recording media, expensive products such as luxury watches, luxury leather products, precious metal products, jewelry, etc., often referred to as luxury brand products, or storage of such expensive products. Boxes and cases can also be forged. In addition, mass-produced products of famous brands, such as audio products, electrical appliances, etc., or tags that are hung on them are also subject to forgery.
Furthermore, a storage body in which music software, video software, computer software, game software, or the like, which is a copyrighted work, or cases thereof can also be forged. In addition, it is desirable that products such as printer toner, paper, and the like in which supplies to be replaced are limited to genuine materials have a function of identifying their authenticity for the purpose of preventing damage caused by forgery.

(Background technology)
Conventionally, for the purpose of preventing counterfeiting of information recording bodies and various articles described above (collectively referred to as authenticity identification objects), it is said that they have manufacturing difficulties due to the precision of their structures. In many cases, holograms are applied as authenticity distinguishable. However, since the hologram manufacturing method itself is known and can be precisely processed by that method, when the hologram is merely for visual judgment, there is no difference between a genuine hologram and a forged hologram. It is difficult to distinguish.
These authentic identification objects, in particular, articles that have been subjected to hologram images in a label form or transfer form, are not only used for authentic identification of visual confirmation of hologram images, but also by using a new authenticity identification method. There is a need to identify the authenticity of.

(Prior art)
In order to meet these requirements, there has been proposed a hologram sheet having a light selective reflection layer that is laminated on a hologram and reflects only one of the left-handed polarized light and the right-handed polarized light among the incident light. (For example, refer to Patent Document 1.)
As this light selective reflection layer, cholesteric liquid crystal is used, and the anti-counterfeiting property is enhanced by a method of confirming using a polarizing plate or the like.
However, as described in Patent Document 1, since the reflectance of the reflective thin film layer on the hologram forming layer is high, the light that is transmitted without being reflected by the cholesteric liquid crystal layer (complementary light of selective reflected light) Reflecting on the reflective thin film layer and returning to the cholesteric liquid crystal layer again (hereinafter referred to as return light), this return light becomes a noise component when observing the cholesteric liquid crystal and is added to and mixed with the selectively reflected light. However, the color tone was not the original color of the liquid crystal, and it was even difficult to see and identify.

In addition, the cholesteric liquid crystal material itself is expensive, and in order to bring out the liquid crystal performance, it is indispensable to form an alignment film in contact with the liquid crystal layer. Furthermore, due to the light scattering property of the cholesteric liquid crystal, the hologram There have been problems such as blurring and distortion of the image when light for reproducing the image passes through the liquid crystal layer.
For this reason, it has been devised to suppress the light scattering property of the cholesteric liquid crystal layer or to make the cholesteric liquid crystal layer itself thin. However, in order to suppress the light scattering property of the cholesteric liquid crystal layer, the refractive index difference is reduced, When the liquid crystal layer is made thin, the function as the light selective reflection layer described above is deteriorated, and it has a drawback that it is difficult to obtain optimum conditions for ensuring the clarity and anti-counterfeit performance of the hologram image. .
Furthermore, a forgery prevention method is proposed in which the hologram forming layer is made of a photochromic material, and a hologram relief and a reflective thin film layer are formed on one surface of the photochromic layer, thereby concealing the presence of the hologram relief. However, the photochromic layer in this stack only serves as a layer that “changes the unexpected color tone”, and is insufficient as an anti-counterfeit effect. (For example, see Patent Document 2.)

JP 2007-90538 A JP-A-3-248188

  Accordingly, the present invention has been made to solve such problems. The purpose is to provide a phase hologram hologram forming layer, that is, a photochromic thin film layer so as to be in contact with the hologram relief, or to form a part of the photochromic thin film layer in synchronization with the hologram relief, and only under predetermined conditions. It is an object of the present invention to provide a novel hologram sheet capable of visually recognizing a hologram having a different color tone or visually recognizing a hologram having a changed color tone under a predetermined condition. Furthermore, since such a hologram sheet has not existed so far, it is to provide a novel decorative property and an anti-counterfeit property to which this is applied.

To solve the above problem,
The first aspect of the hologram sheet of the present invention is:
A transparent resin layer having a hologram relief including a diffraction grating group corresponding to a two-step rainbow hologram image on one surface of the transparent substrate, and following the unevenness forming the hologram relief, with a uniform thickness A photochromic thin film layer is provided.
According to the hologram sheet of the first aspect,
A transparent resin layer having a hologram relief including a diffraction grating group corresponding to a two-step rainbow hologram image on one surface of the transparent substrate, and following the unevenness forming the hologram relief, with a uniform thickness A hologram sheet characterized in that a photochromic thin film layer is provided can be provided.
In the hologram sheet of the present invention, a diffraction grating group for reproducing a two-step rainbow hologram image is formed as a hologram relief as a substantially flat surface on the surface of the transparent resin layer, and on this relief or following this relief. Thus, the photochromic thin film layer is provided with a uniform thickness.
That is, the hologram relief shows the phase difference as a phase hologram in a relief shape, and the photochromic thin film layer is provided by providing (along) a photochromic thin film layer following the relief shape having the phase difference. The color tone will be observed with (including) the phase difference. In other words, “light” having a “color tone” that the photochromic thin film exhibits under a predetermined condition “emits” from the photochromic thin film layer.

This corresponds to the Huygens secondary wave that is generated when the relief hologram is reproduced (the source of hologram reproduction). In the case of the hologram sheet of the present invention, what corresponds to this secondary wave is applied to the hologram relief surface. The color tone exhibited by the arranged photochromic thin film (hereinafter referred to as “colored” as emitted color, or “colored light” or “emitted light” as colored light). The colored light is emitted to the observer side including the phase difference of the hologram relief including the diffraction grating group corresponding to the hologram image.
This colored light causes an interference phenomenon in the space on the hologram relief surface, and as a result, a predetermined hologram reproduction image appears in a predetermined direction.

The present invention reproduces a hologram with one specific color tone different from the wavelength of the illumination light source of the hologram. For example, it can be illuminated with ultraviolet rays and a blue hologram can be visually recognized. As if there is no blue illumination light source that is usually used, only the hologram shines and appears to be floating in the air, and the design is excellent.
The light emission of the photochromic thin film is spontaneous light emission by the photochromic molecule, and the light emission direction is, for example, “omnidirectional” from “one photochromic molecule”. That is, light diverges so that the spherical surface centering on one point in the space is gradually separated from that point and becomes larger.
Such photochromic molecules are confined in a very thin curved surface (the hologram relief curved surface is separated into two curved surfaces separated by a very short distance, and the photochromic molecules are packed between them), and irradiated with excitation light. When emitting light, the emission wavelength itself is converged to almost one emission curve, but the divergence “direction” has continuous and uniform intensity at all angles, that is, , Go all the way.
However, by confining the photochromic molecule in its very thin curved surface, divergent light with (including) the "spatial phase difference of the curved surface" is emitted into the space in the vicinity of the curved surface. Only those that cause an interference phenomenon and strengthen each other remain and appear to the viewer's eyes as being visible, and this becomes a hologram reproduction image.
However, since the divergence direction is omnidirectional, a hologram reproduction image is formed in each direction, and the hologram reproduction images directed in the respective directions are overlapped (image formation distances are slightly different), thereby reducing the visibility. Let
This is because, for example, a relief hologram is illuminated by a planar light source in which single-wavelength point light sources are arranged in an infinite number of vertical and horizontal directions (nearly innumerable). Are reproduced at the respective image forming positions and observed, the innumerable reproduced images are visually recognized with their positions slightly shifted vertically and horizontally.
Therefore, in this situation, it is difficult to grasp the three-dimensional image of the hologram. However, in reality, as described above, the three-dimensional effect is achieved by the effect of selection due to the interference phenomenon and the “effect of restricting (squeezing) the direction from the recording surface” caused by observation from a position somewhat away from the recording surface. It is possible to recognize the image.
The present invention limits the multiplex reproduction of the hologram reproduction image described above and obtains a clearer hologram reproduction image.

In order to separate this overlap, the concept of the “two-step rainbow hologram method” is introduced, and the hologram image recorded in the first step (recording medium 1) is used as object light, and a predetermined amount is placed in front of the recording medium 1. A slit provided with an opening, an object beam generated by passing through the slit and recorded by interference with a predetermined reference beam (recording medium 2) is used as a hologram relief.
When this recording medium 2 is illuminated with “white light” having various continuous wavelengths, slit images of each wavelength are reproduced in different directions, and each (in the back) of each slit image is reproduced. The hologram reproduction image of the wavelength can be seen through. (See Figure 1)
Usually, in the “two-step rainbow hologram method”, the purpose is to separate “white light” into “seven colors”, and the spectrum of a general indoor fluorescent lamp is “three-wave tube”. Since it is not continuous over all wavelengths and is limited to “three wavelengths”, it is not necessary to make the slit width so narrow, the slit width is set to 30 mm to 50 mm, and the slit length (both at the time of observation) There are no restrictions on the eye direction.
In the case of the present invention, although the light source has one emission curve, in order to assume illumination from a collection of point light sources laid vertically and horizontally on one plane, the slit width is made narrower. The diameter of the “human pupil” or 1/2 to 1/10 thereof. If it is less than 1/10, the size of the individual reproduced images in the vertical direction is small, and it is difficult to visually recognize them.
Furthermore, the length of the slit also needs to be limited for the above reasons, but if the distance is smaller than the “distance between both eyes of the human”, the “stereoscopic effect” itself is greatly reduced. 1/2 to 2/1.

When the hologram relief for reproducing such a two-step hologram image has the above-mentioned very thin curved surface shape, and the photochromic molecules confined in the curved surface emit light, the fluorescent light emitted in each direction emits the above-mentioned slit It is possible to reproduce the opening and look into the hologram reproduction image therein, thereby reducing the overlap (disturbance) of the reproduction images.
Since the divergence direction of the fluorescence emission is a spherical object, the width of the slit needs to be very narrow. When observing at a position about 30 cm away from the hologram relief surface, the width is 0.5 mm to 5 mm. To do.
If it is smaller than 0.5 mm, the entire image of the reproduced hologram is difficult to read.
Furthermore, the said disturbance of the top and bottom can be suppressed by setting the length to 20-100 mm for the same reason.
Such a hologram relief is conceptually defined as a “two-step rainbow hologram”, but in order to achieve the effect, a one-step optical imaging method or an electronically controlled spatial modulation element (liquid crystal element or the like). ) As well as a computer-generated hologram (also referred to as CGH) set to limit the hologram reproduction area to a predetermined opening.

There are roughly two methods for creating a computer-generated hologram capable of reproducing a three-dimensional image, one of which is a non-patent document “Image Lab” (April 1997, Vol. 8, No. 4.34 to 37). Page) or “3D Image Conference '99 -3D Image Conference '99-” Lecture Collection CD-ROM (June 30-July 1, Kogakuin University Shinjuku Campus) etc. Is replaced with a set of point light sources. The other is a holographic stereogram method.
In the present invention, a method of replacing the former object surface with a set of point light sources can be employed (see FIG. 2). This is a binary hologram in which the intensity distribution of interference fringes is recorded, and the outline of the case where the reproduced image has only a parallax in the horizontal direction and is observed with white light from above is shown in FIG. Thus, in step ST1, the shape of the object to be converted to CGH is defined. Next, in step ST2, the spatial arrangement of the object, the CGH surface, and the reference light is defined. Next, in step ST3, the object is vertically divided by slicing on a horizontal plane, and further replaced with a set of point light sources on the slice plane. Then, in step ST4, based on these spatial arrangements, the intensity of interference fringes between the light reaching from each point light source constituting the object and the reference light is obtained by calculation at each sample point defined on the CGH plane. Interference fringe data is obtained. Next, in step ST5, the obtained interference fringe data is quantized, and then converted into EB drawing rectangular data in step ST6. In step ST7, the data is recorded on the medium by the EB drawing apparatus to obtain CGH. .

More specifically, the surface of the “three-dimensional structure M” is obtained as a “three-dimensional structure M” that is an original image of a three-dimensional pattern by the method described in the patent application “Japanese Patent Application Laid-Open No. 2008-77042”. The “normal vector N” at the position of the “sample point Q” above is applied to the “object light” that travels from the recording medium 1 through the opening of a predetermined size and is projected onto the projection surface Syz. A pixel located at a point P on the projection plane Syz corresponding to “sample point Q” by obtaining an intersection angle ξ between the projected vector N * and the reference axis R, defining an orientation nucleus θ of θ = ξ / 2 A pixel pattern having a diffraction grating formed by arranging diffraction grating lines oriented in the direction forming an azimuth angle θ with respect to the X axis is assigned to the physical recording medium (corresponding to the recording medium 2 described above). In addition, drawing on an electron beam resist by an electron beam drawing apparatus and The hologram relief of the present invention is obtained through development processing.
Since the recording medium 2 has a desired size, for example, a size of 100 mm × 100 m, when the recording medium 2 is observed, the observation position (the position of the eye to be visually recognized) is In many cases, the observation angle is changed toward the uppermost part and the lowermost part of the recording medium. In this case, since the viewing angle changes (is different), assuming this, a plurality of the slit openings described above can be set at a predetermined distance in consideration of this angular difference, The “visibility” of the hologram reproduction image can be improved.

Furthermore, when the wavelength range of the excitation light for reproducing the hologram is very narrow (meaning that the light source wavelength for exciting the photochromic thin film is limited), the specific wavelength range is known. Only a person who can obtain the hologram can perform hologram reproduction, which is useful for authenticity determination. In addition, only those who can know the color tone that has developed or changed color after excitation can predict the color tone of the hologram reproduction image and only look through the bandpass filter adjusted to the reproduction wavelength and pass through the bandpass filter. Can be determined to be authentic.
Further, the angle (diffraction angle) that passes through the band-pass filter also depends on the wavelength of the colored or changed color, and only those who can know the value can make the determination at the predetermined angle.
Furthermore, if multiple photochromic molecules that can be excited at the same wavelength and have different color tone after excitation are included, this reconstructed image will appear in different color tones at different angles. It will be even better.
The manner in which the photochromic thin film changes its color tone will be described below using a photochromic molecular potential curve (see FIG. 1).
The photochromic molecule A obtains energy by irradiation with light having a certain wavelength λ and becomes a molecule A * in an excited state. (STEP1)
At this time, the excited photochromic molecule A * undergoes an intramolecular reaction, for example, cis-trans isomerization reaction, ring-closing / ring-opening reaction, oxidation / reduction reaction, tautomerization by hydrogen transfer, etc. Changes the molecular geometry and electronic structure.

By this change, the photochromic molecule A * changes to a photochromic molecule B that absorbs light λ ′ having a wavelength different from that of the photochromic molecule A.
Then, the photochromic molecule B 1 absorbs light having the absorption wavelength λ ′ (STEP 2) or absorbs thermal energy (STEP 3), and returns to the photochromic molecule A again.
Then, STEP 1 to STEP 3 can be repeated.
At this time, the ease of heat return from the photochromic molecule B 1 to the photochromic molecule A is based on the ground state potential energy ΔE (FIG. 1: STEP 3
).
If it is difficult for heat to return, that is, if ΔE is extremely large, if it is stored in a dark place, the colored body will be maintained as it is. (Such photochromic molecules are called P-type in the sense that they depend only on light.)
On the other hand, ΔE is relatively small when the light is lost and the color is quickly removed or the original tone is restored. (Such photochromic molecules are called T-type in the sense that they are thermally dependent.)

That is, the photochromic thin film is composed of photochromic molecules A in some cases, and is composed of photochromic molecules B in some cases.
Each of the photochromic molecules A or B has a characteristic light absorption curve. The photochromic molecule A has a large absorption (curved) portion at the wavelength λ and the photochromic molecule B has a large absorption (curved) portion at the wavelength λ ′.
As an example, when the wavelength λ of the photochromic molecule A is in the ultraviolet region, the photochromic molecule A is colorless and transparent, and only after it has changed to the photochromic molecule B through the excited state A *, is in the visible light region. A specific color tone is exhibited by absorption of light centered on the wavelength (which may be the wavelength λ ′).
This "color tone" situation is that the photochromic molecule B has a predetermined light absorption curve in the visible light region, and when the photochromic molecule B is irradiated with white light, a predetermined wavelength including a specific wavelength is included. The light in the wavelength region that absorbs the light in the region and is not absorbed is emitted as divergent light from the holographic film layer made of the photochromic molecule B.
In the hologram sheet according to this example, the divergent light emitted from the photochromic molecule B plays the role of the Huygens secondary wave described above.
Therefore, when the photochromic thin film layer is composed of photochromic molecules A, this photochromic thin film layer is colorless and transparent, and it cannot be recognized that there is a hologram at that position, and what is behind the photochromic thin film layer is visible. However, by applying illumination light of wavelength λ to the photochromic thin film layer, the photochromic thin film layer diverges light in the above-mentioned wavelength region, and due to interference of the divergent light, a hologram based on the “color tone” of the divergent light is in the air. It will appear to float.

When the photochromic thin film layer is the above-described P-type, the hologram reproduction image by the “color tone” of the diverging light is maintained in the “color tone” for a while and is gradually decolored, and the photochromic thin film layer is In the case of the above-described T type, the “color tone” disappears relatively quickly and becomes colorless and transparent again.
In addition, when both the photochromic molecules A and B exhibit a color tone in the visible region, a phenomenon in which the color tone of the hologram reproduction image changes appears.
Such an effect of the hologram sheet of the present invention may be regarded as a design property and employed for appreciation.
Also, among T-types, the decoloring speed is very fast, and the design is such that the illumination of wavelength λ is removed and the color is erased at the same time. (Kimono) The holder holds the hologram sheet (or hologram sheet attachment) and quickly irradiates it with a light of wavelength λ for a short time. It is possible to confirm that there is, and then immediately return the hologram sheet (or hologram sheet attachment) to the holder, so that the authenticity can be determined without the holder's knowledge. You can also
In this case, it is necessary to design the decoloring speed as a half-life of the color development intensity (color density) and to have a half-life of 0.1 to several seconds. In this way, when the light with the wavelength λ is irradiated, the above-described change occurs quickly, and a “color tone” hologram reproduction image of the photochromic molecule B appears. When the irradiation with the light with the wavelength λ is stopped, Thus, a hologram sheet excellent in authenticity determination can be provided.
Of course, it is also preferable to use a determination system that confirms color development after irradiating light of wavelength λ and quickly irradiates light of wavelength λ ′.

Next, the principle of holography will be described.
When an object is illuminated with coherent light and light diffracted from the object illuminates a recording medium (photoresist, etc.), the object wave diffracted from the object and reaches the recording surface is
F (x, y) = A (x, y) EXP [φ (x, y)]
It is expressed. here,
A (x, y) is the amplitude distribution of the object wave,
φ (x, y) is a phase distribution.
At this time, the intensity distribution of the light wave reaching the recording medium is recorded on the recording medium. Its intensity distribution is
I (x, y) = | F (x, y) | ² = A ² (x, y) (1)
Thus, the phase distribution is not recorded.
Here, when an object wave and a coherent light wave (referred to as a reference wave) are superimposed, the intensity distribution of the recorded light wave is
I (x, y) = | F (x, y) + R (x, y) | ²
= | F (x, y) | ² + | R (x, y) | ²
+ F (x, y) R ^* (x, y) + F ^* (x, y) R (x, y) (2)
It becomes. (* Represents a complex conjugate term.)

However, if the reference light is a plane wave incident on the recording surface at an angle θ,
R (x, y) = r (x, y) EXP (2πiαx) (3)
Write,
α = SIN (θ) / λ (4)
It is. In the first and second terms of (2), the phase information is missing for both the intensity of the object wave and the intensity of the reference wave. The third term and the fourth term are interference terms. F (x, y) R * (x, y) =
A (x, y) r (x, y) EXP [i [φ (x, y) -2παx]] (5)
F * (x, y) R (x, y) =
A (x, y) r (x, y) EXP [-i [[phi] (x, y) -2 [pi] [alpha] x]] (6)
The phase term φ (x, y) of the object remains. (5) and (6) are complex conjugates of each other, and the third term in (4.2) includes the complex amplitude distribution of the object. Substituting (5) and (6) into (2),
I (x, y) = | F (x, y) | ² + | R (x, y) | ²
+ 2A (x, y) r (x, y) COS [2παx−φ (x, y)] (7)
It becomes. It can be seen that the object wave and the reference wave interfere to form an interference fringe.

In this way, holography is a method in which a reference wave is superimposed on an object wave and interference recording is performed, and the phase information of the object is recorded without being lost. A recording of (7) is called a “hologram”. The amplitude transmission or reflection of the hologram is proportional to the recorded intensity distribution I (x, y)
T (x, y) = τI (x, y) (8)
Let's call it. When the reference wave used when recording on this hologram is at a predetermined angle, the wavefront transmitted or reflected by the hologram is
T (x, y) R (x, y) = τ (| F (x, y) | ² + | R (x, y) | ² )
+ ΤF (x, y) | R (x, y) | ²
+ ΤF ^* (x, y) R ² (x, y) (9)
Can be expressed. This second term is τF (x, y) | R (x, y) | ² =
τA (x, y) r ² (x, y) EXP [iφ (x, y)]] (10)
The third term is
τF * (x, y) R ² (x, y) =
τA (x, y) r ² (x, y) EXP [−iφ (x, y) + 2πiα] (11)
Call it.

Therefore, the first term of (9) is a light beam penetrating the hologram in the same direction as the illumination light or a specularly reflected light beam, and the second term is a light wave having an amplitude proportional to the object light from (10). From (11), it can be seen that the third term is a light wave having a phase distribution conjugate with the object wave and propagating in the direction of 2θ.
In this way, the complex amplitude distribution can be recorded and reproduced using the holographic technique.
In the case of the present invention, the amplitude transmittance or reflectance of the hologram is proportional to the recorded intensity distribution and is expressed by the equation (8), but the reference wave used when recording on this hologram. Is not a predetermined angle, but a light-emitting wave having a spatial distribution similar to the amplitude transmittance or amplitude reflectance of (8) is emitted from this hologram.
Therefore, the emission wave is emitted while maintaining the phase term already recorded in the hologram, regardless of the conventional principle of hologram reproduction in which the phase term recorded in the hologram is given to the reference light. Therefore, theoretically, it has a three-dimensional continuous curved light emitting surface having a spatial function including the phase difference of an object, and light is emitted from the one curved surface.

To simplify the conventional hologram reproduction principle for the transmission type, when parallel light as reference light is applied to the hologram, the parallel light is shielded in the shielding part, and the parallel light is transmitted only from the transmission part. Diffraction occurs at the boundary between the transmission part and the shielding part, receives the phase term of the object, and the entire component transmitted through the hologram is superimposed, which becomes the hologram reproduction light and reaches the observer's eyes.
In the case of the present invention, there is no parallel light as the reference light described above, and the emitted light retains the phase term of the object when emitting light on the light emitting surface provided in contact with the hologram relief. Hologram reproduction is performed by an interference phenomenon between radiated lights.
The interference effect between synchrotron radiation that does not have temporal and spatial coherence does not cause sufficient interference like laser light, but hologram reproduction is performed at the same level as when a hologram is illuminated with low coherent light. . For example, “natural light generated artificially” such as “fluorescent lamps” used in ordinary homes and general offices without using special light sources such as laser light. Also, it is possible to reproduce the hologram sufficiently. However, whether “natural light generated artificially” is “point light source” or “linear”. Alternatively, depending on whether it is “planar”, whether the emission wavelength is “monochromatic light”, and whether the half-value width of the emission curve is narrow, etc. "Clarity" will be greatly affected.
Since hologram reproduction is based on the principle as described above, it is preferable that reference light at the time of hologram photographing is parallel light (because complex reference light cannot be reproduced), or “hologram represented by a diffraction grating” ( The diffraction grating is preferably parallel light for both the object light and the reference light.) Further, the diffraction grating formed by electron beam drawing, such as a computer generated hologram, is precise and suitable.

Further, for the above reason, in order to make the hologram reproduction image clearer, it is necessary to give the radiation light a characteristic similar to temporal or spatial coherence, for example, the thickness of the light emitting layer. It is desirable to make the thickness thin or to narrow the emission wavelength width. Further, the excitation light source is also preferably a small shape, and a spot shape or the like is particularly suitable.
In addition, it is desirable that the wavelength difference between the excitation light that excites the light-emitting layer and the emission wavelength after the change is large. Further, when observing, the excitation light is filtered to extract only the colored light or further amplify it. It is also effective to do.
As an excitation light source, energy such as ultraviolet rays, visible rays, electron beams, X-rays and the like, and in some cases, a light source capable of emitting infrared energy can be used to emit light, etc. In order to use it for hologram authentication, it is necessary to use a light source corresponding to the photochromic thin film, and use an ultraviolet light source, a visible light source having a predetermined intensity, wavelength, and size of an illumination spot, and an infrared light source in some cases. Is preferred.
From the photochromic thin film layer provided so as to be in contact with the hologram relief surface by illumination with these light sources, more specifically, from the photochromic molecules contained in the photochromic thin film layer, the wavelength of the light source different from that of the illumination light source Luminescence and the like appear. Since the emitted light has the same spatial phase as the hologram relief and has a wavelength (emission wavelength) different from that of the illumination light source, the direction of the specularly reflected light (0th order diffracted light) by the hologram relief and the illumination light The hologram image is reproduced in a direction different from the diffraction direction by the wavelength (excitation light wavelength), that is, in the diffraction direction by the emission wavelength.

However, when the thickness of the photochromic thin film layer is distributed on the hologram surface irrespective of the hologram relief, the emission intensity distribution resulting from the thickness distribution may be reproduced in some cases. Unnecessary interference with light can occur, which can be a cause of blurring of the hologram reproduction image.
In order to eliminate this factor, the photochromic thin film layer is formed with a uniform thickness following the unevenness forming the hologram relief so that light emission of the same intensity occurs from any position on the hologram relief surface, A clear hologram reproduction image is intended.
When ultraviolet light or infrared light other than visible light is used as the illumination light (excitation light) of the hologram sheet of the present invention, the light is not visible to the observer, and the hologram reproduction image is seen from the place where there is no illumination light. However, even if the illumination light is temporally and spatially coherent, as a result, the hologram reconstructed image emits light through a process of excitation and light emission. Therefore, although the spatial phase of the hologram at the time of emission is included, the temporal and spatial coherence between the colored lights is small, and the hologram reproduction image is a normal laser reproduction relief hologram. It is weaker than the reproduced image by the laser beam and is unclear.
Of course, if only observing the beam-shaped diffracted light, it is easy to check its color tone and diffraction direction, and it can be used as it is to determine the authenticity, but this weak and unclear hologram reproduction. In order to enable the observer to recognize the image and accurately determine its presence, the light emission performance of the photochromic thin film is improved, and the diffraction angle is increased to increase the wavelength-diffraction angle dependency. It is necessary to increase the difference in the diffracted light diffraction angle and further reduce the thickness of the photochromic thin film layer to suppress variation in the photochromic thin film layer thickness direction and make it uniform. (Since the light emitting surface contains phase information, its spatial shape is accurately reproduced.)

Furthermore, in order to express temporal coherency, the light source is excited by a pulse laser having a light emission time of 10 ^-15 sec or less, and the time interval between pulses is set longer than the AB intermolecular transition time. It is also suitable to do. As a result, the light emitting surface of one light emission generated by one excitation pulse does not disturb the light emitting surface generated by the next excitation pulse, and the hologram generated by one light emitting surface expressed by one pulse. A clear hologram reproduction image can be observed by the graphic interference phenomenon. Of course, even if a strobe light source that is simply turned on and off in seconds is used, the viewer seems to emit light continuously. When confirming with the above, the above-described effects can be sufficiently obtained.
The photochromic thin film layer is a photochromic molecule-containing ink in which photochromic molecules are mixed into a resin or dispersed in a solvent (or water), a hologram using a gravure method, an offset method, a silk screen method, a nozzle coating method, or an inkjet method. It can be formed on the relief.
At this time, the formed photochromic thin film layer can be formed with a uniform thickness following the unevenness forming the hologram relief by adjusting the content ratio of the photochromic molecules in the ink.
The unevenness of the hologram relief is, for example, a gentle curve having an unevenness of a depth of 0.01 μm with a period of 1 μm level and can be regarded as a substantially flat surface. 1 to 10 pascals / second), exhibiting the leveling effect due to the weight of the ink, and the solid content in the ink is 10% or less, further 5% or less, for example, for a thickness of 1 μm The variation can be suppressed to 1/10 or less, and further to 1/20 or less.

Here, the photochromic thin film layer is set to the order of 1 μm. However, in order to improve the definition of the hologram reproduction image, it is also preferable to provide the photochromic thin film layer discretely. (Size) is about 1.0 μm or less, for example, 0.01 μm to 0.5 μm, more preferably 0.01 to 0.05 μm, and it is also preferable that the size is uniformly scattered in the hologram relief surface. . In the photochromic thin film layer thickness direction, 1 to 10 molecules or 1 to 10 particles are preferably arranged in units of photochromic molecules or fine particles adsorbed with photochromic molecules.
Above all, the nozzle coating method, ink jet method, and physical vapor deposition methods such as chemical vapor deposition can form a thin film only with a solvent and photochromic molecules and particles without using a resin, and are very thin as a photochromic thin film layer. It is preferable because it can be formed (photochromic molecules, particles 1 to 10 molecules, etc.). An appropriate transparent resin layer may be formed as a protective layer in order to fix the photochromic thin film thereon.
By the way, the photochromic material can be used as a hologram recording material or an optical memory recording material itself, and such applications are already known. However, these are used for holographic recording (interference fringe recording) directly on the photochromic material. Recording), and recording fine brightness and darkness on the photochromic material.
This recording is read out using a technique that does not change the photochromic molecules in the recorded area (such as irradiation with light having a wavelength that does not change).
On the other hand, the hologram sheet of the present invention only illuminates the uniformly formed photochromic thin film layer in the same manner (uniformly), and generates a uniform color. The photochromic thin film layer does not require a complicated process of exposing it, and the photochromic thin film layer itself carries the hologram information in the concavo-convex shape that it “holds as its shape”, making the photochromic thin film layer uniform The hologram information can be “acquired” (meaning that “hologram reproduction information” is “acquired”) simply by forming.

The second aspect of the hologram sheet of the present invention is
The photochromic thin film layer is formed only in concave and convex recesses forming the hologram relief.
According to the hologram sheet of the second aspect,
The hologram sheet according to claim 1, wherein the photochromic thin film layer is formed only in the concave and convex portions forming the hologram relief.
The hologram relief has a period of about 1 μm, a depth of 0.01 μm, and a maximum of 0.5 μm, and by forming a photochromic thin film layer only in this recess, it can be synchronized with the period of the hologram relief. Thus, the presence or absence of a photochromic thin film layer, that is, the presence or absence of light emission can be provided.
The concave portion of the hologram relief is a concave portion when the photochromic thin film layer is formed on the hologram relief, and is the convex portion side when observed from the normal observation method, that is, from the hologram forming layer side. In order to form the light emission intensity distribution using the presence or absence of the photochromic thin film layer, it is only necessary to partially form the unevenness, and the entire recess may be filled with the photochromic thin film layer, or You may form only in a part of bottom part. However, since it is necessary to synchronize the phase distribution and the distribution to be formed, when forming a part, it is necessary to always form the same photochromic thin film “amount” at the same position. (Because this “amount” is proportional to the emission intensity.)
As a method for selectively forming the photochromic thin film layer in the concave portion, fine particles (particle diameter of 0.01 μm, etc., containing a photochromic molecule having a very small particle diameter dispersed in a solvent or the like, or adsorbed on the surface thereof are used. Ink may be used to form an ink layer on the hologram relief, and the fine particles may move from the convex portion to the concave portion under its own weight while the solvent volatilizes.

In addition, the photochromic thin film layer uniformly provided on the regular diffraction grating is provided by photolithographic exposure, development and etching in synchronism with the regular diffraction grating. Can be provided synchronously. According to this method, it is possible to control the thickness and size of the photochromic thin film layers scattered in the respective recesses, and the so-called “uniformly” can be formed on the entire relief surface.
What is formed by the above method is to include the phase information of the hologram relief in the emitted light (radiated light) described in the principle of the hologram above, and further include amplitude information synchronized with the phase information. It is.
Therefore, the hologram light information of both the phase hologram and the amplitude hologram can be included in the emitted light, and a clearer hologram can be obtained.
Thereby, the designability and authenticity determination property can be improved.
The third aspect of the hologram sheet of the present invention is:
The photochromic thin film layer has a thickness of 0.01 μm or more and 0.5 μm or less.
According to the hologram sheet of the third aspect,
The hologram sheet according to claim 1 or 2, wherein a thickness of the photochromic thin film layer is 0.01 µm or more and 0.5 µm or less.
From the above-mentioned hologram principle, it is desirable that the thickness of the photochromic thin film layer is thin in order to increase the clarity of the hologram reproduction image. However, the thinner the photochromic thin film layer, the weaker the emission intensity during hologram reproduction. The thickness of the thin film layer needs to be 0.01 μm or more and 1.0 μm or less, and more preferably 0.01 μm or more and 0.5 μm or less.
If it is less than 0.01 μm (one particle of the minimum particle size), the emission intensity is too weak to be distinguished from noise such as stray light even if amplified using a photomultiplier tube, and exceeds 1.0 μm. The emission intensity can be sufficient for the purpose of the present invention, but the position of the curved surface carrying the phase information of the hologram relief by the emission from a plurality of particles in the thickness direction is the thickness direction. As a result, the reproduced hologram image becomes unclear.
On the other hand, the emission intensity is secured at 0.01 μm or more, and the position of the curved surface carrying the phase information is clarified by making the emission intensity 0.5 μm or less, and the hologram reproduction image becomes clear.

According to the hologram sheet of the present invention,
A transparent resin layer having a hologram relief including a diffraction grating group corresponding to a two-step rainbow hologram image and a photochromic thin film layer are provided on one surface of the transparent substrate so as to be in contact with the hologram relief. And a hologram sheet having a hologram reproduction image with a wavelength different from the wavelength of illumination light and excellent in design and authenticity determination.
Moreover, according to another hologram sheet of the present invention,
There is provided a hologram sheet that has amplitude information in addition to phase information, or that has a thin light emitting layer and enables clearer hologram reproduction.

These are explanatory drawings of a two-step rainbow hologram system. These are explanatory drawings of the computer-generated hologram creation method. These are figures explaining a photochromic molecular potential curve. These are sectional drawings of hologram sheet A showing one example of the present invention. (Example in which the photochromic thin film layer is “formed with a uniform thickness following the irregularities that form the hologram relief”.) These are sectional drawings of hologram sheet A 'showing other 1 examples of the present invention. (Example in which the photochromic thin film layer is formed only in the concave and convex portions forming the hologram relief.) Is the process of determining one embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Transparent substrate) The transparent substrate 1 used in the present invention can be reduced in thickness, and can withstand mechanical strength and solvent resistance and heat resistance that can withstand processing when manufacturing the hologram sheet A. Those having the following are preferred. Since it depends on the purpose of use, it is not limited, but a film-like or sheet-like plastic is preferable.
For example, various plastic films such as polyethylene terephthalate (PET), polycarbonate, polyvinyl alcohol, polysulfone, polyethylene, polypropylene, polystyrene, polyarylate, triacetyl cellulose (TAC), diacetyl cellulose, and polyethylene / vinyl alcohol can be exemplified. .
Among them, those having resistance to excitation light such as ultraviolet rays, for example, those containing ultraviolet absorbers may be used. Those containing an ultraviolet absorber also have the effect of preventing unscheduled hologram reproduction, although faint due to ultraviolet rays contained in natural light or the like.
The thickness of the transparent substrate 1 is usually 5 to 100 μm, but in view of the visibility of the hologram reproduction image, it is preferably 5 to 50 μm, particularly 5 to 25 μm.

(Transparent resin layer having a two-step rainbow hologram relief: also called a hologram forming layer.)
As the transparent resin material for constituting the hologram forming layer 2 of the present invention, various thermoplastic resins, thermosetting resins, or ionizing radiation curable resins can be used. Thermoplastic resins include acrylic ester resins, acrylamide resins, nitrocellulose resins, or polystyrene resins. Thermosetting resins include unsaturated polyester resins, acrylic urethane resins, epoxy-modified acrylic resins, and epoxy-modified unsaturated resins. A polyester resin, an alkyd resin, a phenol resin, etc. are mentioned.
These thermoplastic resins and thermosetting resins can be used alone or in combination of two or more. One or more of these resins may be cross-linked using various isocyanate resins, or various curing catalysts, for example, metal soap such as cobalt naphthenate or zinc naphthenate may be blended. Or peroxide such as benzoyl peroxide and methyl ethyl ketone peroxide for initiating polymerization with heat or ultraviolet light, benzophenone, acetophenone, anthraquinone, naphthoquinone, azobisisobutyronitrile, or diphenyl sulfide good.

Examples of the ionizing radiation curable resin include epoxy acrylate, urethane acrylate, acrylic-modified polyester, etc., for the purpose of introducing a crosslinked structure into such an ionizing radiation curable resin or adjusting the viscosity, A monofunctional monomer, a polyfunctional monomer, or an oligomer may be blended and used.
In order to form the hologram forming layer 2 using the above resin material, it can be directly formed by developing the photosensitive resin material by performing interference exposure of the hologram. It is preferable to perform molding by using a replica or a plating mold thereof as a replica mold and pressing the mold surface against the layer of the resin material.
When thermosetting resin or ionizing radiation curable resin is used, curing is performed by heating or ionizing radiation irradiation while keeping the uncured resin in close contact with the mold surface, and then cured by peeling after curing. The fine irregularities of the relief hologram can be formed on one side of the layer made of a transparent resin material. A diffraction grating forming layer having a diffraction grating formed in a pattern by a similar method can also be used as the optical diffraction structure.

In order to precisely create fine irregularities, not only optical methods, but also electron beam lithography equipment can be used to create precisely designed relief structures that produce more precise and complex reproduction light. Good. The relief shape is designed to have a pitch, depth, or specific periodic shape of the unevenness according to the wavelength (range) of the light or light source for reproducing or reproducing the hologram, the direction and the intensity of reproduction or reproduction.
In addition, a color hologram image (a two-step rainbow hologram method is employed, but since the emitted light is monochromatic, it is possible to add a colorization technique) to a diffraction grating pixel composed of diffraction grating lines. (A minimum unit of a single diffraction grating area composed of the same diffraction grating lines. A set of light emitted from these pixels as diffracted light forms one color hologram image.) It is also possible to form by using an image processing method in which a lattice line pitch and a lattice line angle are assigned to each element and reproduced.
The pitch (period) of the unevenness depends on the reproduction or reproduction angle, but is usually 0.1 μm to several μm, and the depth of the unevenness is a factor that greatly affects the reproduction or reproduction intensity, but is usually 0.01 μm. ˜0.5 μm.
As in the case of a single diffraction grating, when the unevenness of exactly the same shape is repeated, as the adjacent unevenness is the same shape, the degree of interference of reflected light increases and the intensity increases, and the maximum value is reached. Converge. Diffraction in the diffraction direction is also minimized. When a single point of an image converges to a focal point, such as a stereoscopic image, the convergence accuracy to the focal point is improved, and a reproduced or reproduced image becomes clear.

The method of shaping (also called duplicating) the hologram relief shape is as follows. A master plate on which diffraction gratings and interference fringes are recorded in a concavo-convex shape is used as a press die (referred to as a stamper), and the master plate is placed on the transparent substrate 1. The concavo-convex pattern of the original plate can be duplicated by stacking and pressing them together by an appropriate means such as a heating roll. The hologram pattern to be formed may be single or plural.
In order to accurately reproduce the above-mentioned extremely fine shape and to minimize distortion and deformation such as heat shrinkage after replication, the original plate is made of metal and replicated at low temperature and high pressure.
For the original plate, a metal having high hardness such as Ni is used. After a Cr or Ni thin film layer is formed on the surface of a glass master or the like formed by optical imaging or electron beam drawing or the like by vacuum deposition or sputtering, Ni or the like is electrodeposited (electroplating, electroless plating) Further, it can be made by peeling the metal after forming 50 to 1000 μm by composite plating or the like.
The duplication method uses a flat plate type or a rotary type, the linear pressure is 0.1 ton / m to 10 ton / m, and the duplication temperature is usually 60 ° C. to 200 ° C.

(Photochromic thin film layer)
In the present invention, the photochromic thin film layer 3 is formed on the hologram relief surface of the hologram forming layer 2.
As the photochromic molecule (photochromic material) used for this photochromic thin film layer, there are an organic compound type and an inorganic compound type,
As an organic compound system,
Azobenzenes (cis-trans isomerism): dimethylaminoazobenzenes, etc.
Spiropyrans (intramolecular ring-opening): spirobenzothiopyran, spiroselenazolinobenzopyran, spirobenzoselenazolinonaphthoxazine, etc. More specifically, 1,3,3-trimethylindolino-6 ′ -Nitrobenzopyrospirane, 1 ', 3'-dihydro-8-methoxy-1', 3 ', 3'-trimethyl-6-nitrospiro [2H-1-benzopyran-2', 2 '-(2H)- Indole], 1,3,3-trimethylindolinobenzopyrospirane, 1,3,3-trimethylindolino-6'-bromobenzopyrrirospirane, 1,3,3-trimethylindolino-8'-methoxy Benzopyrospirane, 1,3,3-trimethylindolino-β-naphthopyrilospirane, etc.
Spirooxazines (intramolecular ring-opening): Spiroquinoxazines, spironaphthoxazines, spirophenanthrooxazines, spirobipyridoxazines, etc., compounds having a heterocyclic structure containing a nitrogen atom in the molecule Etc. (red purple to blue. “Coloring” quickly disappears)
Spiroperimidines: 2,3-dihydro-2-spiro-4 '-[8'-aminonaphthalen-1'(4'H) -one] perimidine, 2,3-dihydro-2-spiro-7 '-[8 '-Imino-7', 8'-dihydronaphthalene-1'-amine] perimidine, etc.

Arylethenes: symmetrical diarylethene, asymmetrical 2,3-diarylmaleic anhydride, asymmetrical diarylperfluorocyclopentene, etc.
1,2-bis (2,4-dimethyl-5-phenyl-3-thienyl) -3,3,4,4,5,5-hexafluoro-1-cyclopentene, 1,2-bis [2-methylbenzo [ b] thiophen-3-yl] -3,3,4,4,5,5-hexafluoro-1-cyclopentene, 2,3-bis (2,4,5-trimethyl-3-thienyl) maleic anhydride 2,3-bis (2,4,5-trimethyl-3-thienyl) maleimide, cis-1,2-dicyano-1,2-bis (2,4,5-trimethyl-3-thienyl) ethene, etc. More specifically, color development wavelengths: 425 nm, 469 nm, 526 nm, 534 nm, 550 nm, 562 nm, 578 nm, 583 nm, 611 nm, 620 nm, 628 nm, 665 nm, 680 nm, 828 nm, etc. (depending on the structure, blue, green, yellow, red, etc. Color development)
Frugides: Diphenyl fulgide, triphenyl fulgide, etc.
Chromenes: 6-morpholino-3,3-bis (3-fluoro-4-methoxyphenyl) -3H-benzo (f) chromene, 6-morpholino-3- (4-methoxyphenyl) -3- (4-tri Fluoromethoxyphenyl) -3H-benzo (f) chromene, 6-piperidino-3-methyl-3- (2-naphthyl) -3H-benzo (f) chromene, 6-piperidino-3-methyl-3-phenyl-3H -Benzo (f) chromene, 6-morpholino-3,3-bis (4-methoxyphenyl) -3H-benzo (f) chromene, 6-hexamethyleneimino-3-methyl-3- (4-methoxyphenyl)- 3H-benzo (f) chromene, 6-morpholino-3- (2-furyl) -3-methyl-3H-benzo (f) chromene, 6-morpholino-3- (2-thienyl) -3 Methyl -3H- benzo (f) chromene, 6- morpholino-3- (2-benzofuryl) -3-methyl -3H- benzo (f) chromene, etc. (colored orange-yellow.),

Cyclophanes: Anthracene-containing cyclophanes such as anthracenophanes, anthracenonaphthalenophanes, anthracenoparacyclophanes, metacyclophanes, etc.
Chalcone (1,3-diphenyl-2-propen-1-one) -flavylium, etc.
Fulgimide compounds: N- cyanomethyl-6,7-dihydro-4-methyl-2-phenyl-spiro (5,6-benzo [b] thiophene-dicarboximide -7,2- tricyclo [3.3.1.1 ^{3 , 7} ] decane), N-cyanomethyl-6,7-dihydro-2- (4′-methoxyphenyl) -4-methylspiro (5,6-benzo [b] thiophenedicarboximide-7,2-tricyclo [3 3.1.1 ^3,7 ] decane), N-cyano-6,7-dihydro-4-methyl-2-phenylspiro (5,6-benzo [b] thiophenedicarboximide-7,2-tricyclo [3.3.1.1 ^3,7 ] decane), N-cyano-6,7-dihydro-4-methylruspiro (5,6-benzo [b] furandcarboximide-7,2-tricyclo [3.3 .1.1 ^3,7 Decane), N- cyano-4-cyclopropyl-6,7-dihydro-spiro (5,6-benzo [b] flange carboximidoyl -7,2- tricyclo [3.3.1.1 ^{3, 7]} decane) N-cyano-6,7-dihydro-4-methylspiro (5,6-benzo [b] thiophenedicarboximide-7,2-tricyclo [3.3.1.1 ^3,7 ] decane), N- Cyanomethyl-4-cyclopropyl-6,7-dihydrospiro (5,6-benzo [b] thiophenedicarboximide-7,2-tricyclo [3.3.1.1 ^3,7 ] decane), N-cyanomethyl -4-cyclopropyl-6,7-dihydro-2- (4'-methoxyphenylspiro (5,6-benzo [b] thiophenedicarboximide-7,2-tricyclo [3.3.1.1 ^{3, 7]} decane), N- Anomechiru 4-cyclopropyl-6,7-dihydro-2-phenyl-spiro (5,6-benzo [b] thiophene-dicarboximide -7,2- tricyclo [3.3.1.1 ^{3, 7]} decane) N- (3′-cyanophenyl) -6,7-dihydro-4-methyl-2- (4′-methoxyphenyl) spirobenzothiophenecarboximide-7,2′-tricyclo [3.3.1.1 ^3,7 ] Decane (colored orange to blue),

Thioindigos (cis-trans isomerism), salicylidene anilines (intramolecular hydrogen transfer: crystal type), nitrobenzylpyridines (intramolecular hydrogen transfer: crystal type), tetrachloro-α-ketodihydronaphthalene, bis (Triphenylimidazolyl) s, tetraphenylhydrazines, beanthrones, pyridylside nonones, anthracene derivatives (photodimerization), methylene blue (photoredox), triphenylmethanes (ion dissociation), hexaphenylbiimidazole (radicals) Dissociation), polycyclic aromatic compounds (oxygenation), etc.
Can be used.

In particular, a product obtained by dispersing diarylethenes in a transparent resin and a crystallized product of diarylethenes are excellent in physical properties and weather resistance.
As an inorganic compound system,
Ternary compounds selected from AgBr, AgCl, AgI, CuBr2, CuCl2, CuCl, CuI2, CuI, Ag alone, Cu alone, etc.
Silver nanoparticles-titanium oxide, etc.
Can be used.
Furthermore, among these photochromic molecules (materials), it is preferable that the emission intensity curve (wavelength as a horizontal axis) as the photochromic molecule B has only one peak in the visible region, A half-width of the peak of 10 to 50 nm is preferable because it gives a clearer hologram reproduction image.

As a forming method, it is possible to use a general printing method, a coating method, etc., but as a method for forming a more precise thin film, a spin coating method, a casting method, a screen printing method, a blade coating method, a roll coating method. , Water surface development method, LB (Langmuir-Blodget) method and the like, and dry process include vacuum deposition method, sputtering method, chemical vapor deposition method and the like.
In particular, chemical vapor deposition is suitable for forming a thin film of an organic compound system uniformly and at the molecular level.
More specifically, a resin-dispersed ink in which photochromic molecules are uniformly dispersed in a transparent resin or a solvent-dispersed ink in which photochromic molecules are dispersed in water or a solvent are prepared, and using them, a printing method or The photochromic thin film layer is formed by using various forming methods such as a coating method and an ink jet method so that the hologram forming layer 2 is in contact with the hologram relief and is uniformly tracked or partially in the recess. 3 can be formed. (Hologram sheet A)
In addition, it is preferable to form the photochromic thin film layer 3 directly on the hologram relief surface of the hologram forming layer 2 by a chemical vapor deposition method from the viewpoint of the hologram relief followability and the uniformity thereof. This is preferable because there is no collision of a high-temperature electron beam in the heating vacuum deposition method and argon atoms in the sputtering method, and the molecular structure is easily maintained.
In addition, after the photochromic thin film layer 3 is formed on the hologram forming layer 2, it is aligned with the diffraction grating pattern by photolithography using a photoresist, exposed to light, developed, and unnecessary patterns are removed to remove the photoresist pattern. The photochromic thin film layer can be removed by etching in synchronization with the concave portion of the pattern, and the photochromic thin film layer can be left only in the concave portion. (Hologram sheet A ')
On the contrary, a photoresist layer is formed on the hologram forming layer 2, aligned with the diffraction grating pattern, exposed to light, developed, and removed unnecessary portions to leave the photoresist on the convex portions and expose the concave portions. After the photochromic thin film layer is formed, the photochromic thin film layer 3 can be left only in the concave portion by removing the photoresist on the convex portion and at the same time partially removing the photochromic thin film layer immediately above the photochromic thin film layer. (Hologram sheet A ')

Resin-dispersed ink includes the above-described photochromic molecule, a transparent resin, for example, an acrylic ester resin, an acrylamide resin, a nitrocellulose resin, or a polystyrene resin as a thermoplastic resin, and as a thermosetting resin, Ball mill using glass beads or steel beads to reduce secondary aggregation by mixing with unsaturated polyester resin, acrylic urethane resin, epoxy-modified acrylic resin, epoxy-modified unsaturated polyester resin, alkyd resin, phenol resin, etc. , Kneading with a kneader, roll mill, etc., adjusting the viscosity with a solvent, etc., and using a gravure method, offset method, silk screen method, curtain coating method, nozzle coating method, and even an inkjet method as appropriate. Form to thickness Rukoto can.
However, in order to make the thickness of the photochromic thin film layer 3 0.003 μm or more and 1.0 μm or less, and further 0.01 μm or more and 0.5 μm or less, the solid content of the resin dispersed ink is 1 to 10%. When the coating film using a solvent or water as a solvent is, for example, 5 μm, the thickness after evaporation of the solvent (the thickness of the photochromic thin film layer) is 1/10 to 1/100. Thus, the thickness is set to 0.5 μm to 0.05 μm.

Since the solvent-dispersed ink does not include a resin component and includes only photochromic molecules and a solvent, the photochromic thin film layer 3 can be made thinner than the resin-dispersed ink.
As the solvent, water or an alcohol solvent, or a cellsolve or paraffin solvent is used in accordance with the polarity of the photochromic molecule to be used, and the photochromic molecule is dissolved and retained, and the hologram is applied by curtain coating, nozzle coating or the like while stirring. It can be provided on the formation layer 2.
Furthermore, several μm of a slow volatile solvent having solubility is applied to the resin forming the hologram relief surface (a ketone solvent such as cyclohexanone for acrylic, vinyl chloride, vinyl acetate resin, polyester resin, etc.). It is also possible to dilute this solvent with a non-soluble solvent and use it to make the remaining components 0.1 μm or less.) Dissolve only the outermost surface of the hologram relief surface, A method of forming a photochromic thin film layer is also preferred in which the surface is given tackiness, and photochromic molecules are sprayed as a mist on the surface so that only the photochromic molecules in contact with the sticky surface remain on the hologram relief surface. .
According to this method, the photochromic thin film layer 3 becomes a film at a molecular level like an LB film, is formed uniformly on the hologram relief surface (compared to the size of the hologram relief), and excitation light from the hologram forming layer 2 side. The light emitting surface when applied is “same” as the hologram relief surface.
In any case, since the unevenness of the hologram relief is very small, the photochromic thin film layer 3 has a uniform thickness and the photochromic molecules therein have a uniform density, or evenly on the hologram relief surface. In order to form (in the case of partial formation, the formed parts are uniform), it is necessary to prevent photochromic molecules from aggregating into secondary particles, and a method of dissolving in a solvent (solvent) Alternatively, it is preferable to form a thin film as a nanoparticle pigment by adsorbing to the surface of the nanoparticle.
Furthermore, in order to physically protect such a very thin photochromic thin film layer 3, the above-described transparent resin may be provided with a thickness of 1.0 μm to 3.0 μm using an appropriate formation method. .
In addition, the hologram forming layer 2, the photochromic thin film layer 3, and the protective layer have a refractive index difference of 0.3 or less, or 0.03 or less, so that unnecessary holograms before excitation can be obtained. It is possible to prevent the appearance of a reconstructed image and further improve the forgery prevention property.

Excitation light suitable for the photochromic molecule used, for example, ultraviolet light (wavelength 365 nm, wavelength 245 nm, etc.) is applied to the hologram sheet thus prepared at an intensity of 10 μW / cm 2 to 10 mW / cm 2 for 1.0 second. For those that irradiate for ~ 100 seconds or change color tone in the visible region, irradiate LED light or semiconductor laser light close to a predetermined wavelength to develop color or change the color tone. The authenticity can be determined by visually recognizing the hologram reproduction image in the color tone.
At this time, the visibility may be improved or a mechanical determination may be performed using a predetermined filter, a reproduction light amplification device, or the like.
Further, the existence of a hologram reproduction image of a predetermined color tone may not be realized by a person who possesses a hologram sheet, that is, a person who possesses an authenticity identification object that is formed by transferring or pasting a hologram sheet. It is also suitable to devise so that the color tone disappears or returns to the original color tone promptly (within several seconds to several tens of seconds) after authenticity confirmation.

Example 1
As a three-dimensional original image, a three-dimensional character image (see FIG. 6) of “Luminescence” with a character size of 30 mm × 30 mm and a thickness of 10 mm is used, the method of FIG. 1 is adopted, and the opening is used as a slit. A 2 step rainbow hologram relief was obtained by photographing a 2 step rainbow hologram using an argon laser light source (wavelength 488 nm: blue) using a 3 mm × 50 mm one.
As a transparent base material 1, a melamine resin composition is applied to the surface of a 12 μm PET film, and a hologram image position detection pattern is added to the two-step rainbow hologram relief. Relief holograms were formed by heating and curing while in contact with each other, and a hologram forming layer 2 having a thickness of 3 μm was obtained.
On this hologram forming layer 2, a resin dispersed photochromic molecule-containing ink having the following composition is coated by a gravure coating method and dried to form a photochromic thin film layer 3 having a thickness of 10 μm so as to be in contact with the hologram relief, Dry to a thickness of 0.1 μm,
・ <Ink composition>
1,2-bis [2-methylbenzo [b] thiophen-3-yl]-
3,3,4,4,5,5-Hexafluoro-1-cyclopentene Crystalline material B2629 manufactured by Tokyo Chemical Industry Co., Ltd. 0.1 part by weight PVC resin 1 part by weight Methyl ethyl ketone 29 parts by weight Toluene 70 parts by weight Hologram of the present invention Sheet A was produced.
When this hologram sheet A is illuminated using a 365 nm wavelength light source (UV-LED module LC-L2 manufactured by Hamamatsu Photonics), as shown in FIG. 4, this ultraviolet light is not visible and has a blue three-dimensional effect. The step rainbow hologram reconstructed image “light emission” can be confirmed, and only the blue reconstructed image appears to float in the space, and the design is excellent.
When the illumination was removed, the light emission reproduction image disappeared quickly and the original state was restored.
This hologram sheet A is cut into a 3 cm square, pasted on a passport, and illuminated with a black light arc tube 40W (with a cover having a 3 mmφ hole in order to reduce the illumination shape), a blue hologram reproduction image is recognized. When the black light illumination was removed, the image disappeared quickly, and it seemed possible to judge the authenticity sufficiently without being noticed by the passport holder.

(Example 2)
The method for forming the photochromic molecule-containing ink on the hologram relief is a spin coating method, the uniform coating thickness is 2 μm, and the dried photochromic thin film layer 3 is formed with a thickness of 0.02 μm. In the same manner as in Example 1, the hologram sheet A of the present invention of Example 2 was produced.
When this hologram sheet A was observed in the same manner as in Example 1, it was possible to more clearly confirm the blue two-step rainbow hologram reproduction image “light emission”, and only the blue reproduction image appeared to be floating in the space. It was excellent in design.
This hologram sheet A is cut into a 3 cm square, pasted on a passport, and illuminated with a black light arc tube 40W (with a cover having a 3 mmφ hole in order to reduce the illumination shape), a blue hologram reproduction image is recognized. When the black light illumination was removed, the image disappeared quickly, and it seemed possible to judge the authenticity sufficiently without being noticed by the passport holder.

(Example 3)
Except that the photochromic molecule-containing ink was a solvent-dispersed ink having the following composition, a curtain coat method was used, and the drying speed was slow (the amount of drying energy was 1/5).
・ <Ink composition>
Crystalline material B2629 manufactured by Tokyo Chemical Industry Co., Ltd. 0.1 part by mass Methyl ethyl ketone 30 parts by mass Toluene 70 parts by mass The hologram sheet A ′ of the present invention was produced.
Since the photochromic molecule-containing ink is biased to the concave portion from the convex portion of the hologram relief, the dried photochromic thin film layer 3 is also biased to the concave portion.
When observed in the same manner as in Example 2, a clearer 2-step rainbow hologram reproduced image than in Example 2 could be confirmed.
Example 4
Except that 2,3-dihydro-2-spiro-4 ′-[8′-aminonaphthalene-1 ′ (4′H) -one] perimidine D3618 manufactured by Tokyo Chemical Industry Co., Ltd. was used as the photochromic molecule. A hologram sheet A of Example 4 was produced in the same manner as Example 1.
Except that a UV-LED manufactured by OMRON Corporation was used as the excitation light, the color tone changed from yellow to blue when observed in the same manner as in Example 1, which was clearer and stronger in intensity than Example 2. A step rainbow hologram reproduction image could be confirmed.

(Comparative example)
A hologram sheet was formed without forming a photochromic thin film layer, and was used as a comparative example.
When observed in the same manner as in Example 1, there was no change even when irradiated with excitation light, and a hologram reproduction image that could be reliably recognized visually could not be confirmed.
From this, it was possible to determine that the hologram sheet was not genuine and the passport was fake.

A, A ′ Hologram sheet 1 Transparent substrate 2 Transparent resin layer having hologram relief (hologram forming layer)
3 Photochromic thin film layer (continuous or partial formation)
4 Example of observation state: Visible ray (illumination light)
5 Same as above: No reconstructed image (in the case of ultraviolet light excitation)
6 Same as above: Ultraviolet light (illumination light)
7 Same as above: Blue reproduction image

Claims (3)

A transparent resin layer having a hologram relief including a diffraction grating group corresponding to a two-step rainbow hologram image on one surface of the transparent substrate, and following the unevenness forming the hologram relief, and having a uniform thickness A hologram sheet, wherein a photochromic thin film layer is provided.
The hologram sheet according to claim 1, wherein the photochromic thin film layer is formed only in the concave and convex portions forming the hologram relief.
  The hologram sheet according to claim 1 or 2, wherein the photochromic thin film layer has a thickness of 0.01 µm to 0.5 µm.

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