JP2013001804A - A plurality of porous films and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plurality of porous films that has the same porous pattern (micropore pattern) and cannot be substantially duplicated, and to provide a method for producing the porous films.SOLUTION: The plurality of porous films are obtained by irradiating polymer films with heavy ions and then performing chemical etching. The porous pattern formed by a plurality of pores in each of the plurality of porous films is the same, and the number of orientation directions of the plurality of pores is one, or two or more.

Description

  The present invention relates to a plurality of porous films and a method for producing the same, and more particularly to a plurality of porous films in which the same porous pattern (micropore pattern) is formed and which is substantially impossible to replicate and a method for producing the same.

Conventionally, a fine processing tag such as a hologram has been attached to a recording medium or the like on which products, banknotes, credit cards, and software are recorded in order to confirm their authenticity or check their counterfeiting.
However, in recent years, there is a problem that the tag itself can be duplicated due to improvements in performance of scanners, copiers and printers, improvement in processing performance of personal computers, and availability of laser devices.

In order to solve such a problem, a hologram recording body that records a stereoscopic image and a pupil image consisting of a minute repetitive pattern that cannot be normally seen on a volume hologram, and determines the authenticity of the hologram based on the reproduction pattern of the pupil image There has been proposed a technique for improving the security level by using (see, for example, Patent Document 1).
However, in the above technique, although the security level is improved, it is not possible to make the copy substantially impossible, and it is not possible to determine the complete authenticity of the tag itself.

  In recent years, it has been studied to use a fine pattern, which is virtually impossible to replicate, as a tag. Examples of the fine pattern include a moth surface structure, an insect wing structure, a marble pattern of paint floating on the water surface, and a porous film produced by sandblasting or heavy ion irradiation. However, these fine patterns have a problem that it is impossible to industrially produce a plurality of completely identical patterns.

  The porous film is formed by, for example, a method in which a polymer film is irradiated with heavy ions, and the film irradiated with the heavy ions is chemically etched to form a large number of nano-sized cylindrical holes. Manufactured (for example, see Patent Documents 2 and 3).

  More specifically, as shown in FIG. 1 (a), the polymer film 1 is irradiated with heavy ions 2 to damage the path through which the heavy ions 2 have passed and the vicinity thereof (the arrows in the figure are heavy) It represents the direction of ion 2 travel). Next, as shown in FIG. 1 (b), the polymer film 1 irradiated with heavy ions 2 is immersed in a chemical solution (etching chemical solution) 3 such as an alkaline solution, and the damaged portion is removed. Selective erosion. Thereby, as shown in FIG.1 (c), the porous film 4 in which many fine holes 5 were formed in the polymer film 1 is obtained.

The detailed principle about hole formation is demonstrated using FIG. 2 (a) (b).
As shown in FIG. 2 (a), the heavy ions 2 enter the polymer film 1 in an accelerated state, damage the path through which the heavy ions 2 have passed and the periphery of the path, The process proceeds while losing the mechanical energy, and finally stops in the polymer film 1 or exits the polymer film 1. As a result, a damaged portion B is formed in the vicinity of the heavy ion passage in the polymer film 1, but when the damaged portion B and the undamaged portion A are compared, the damaged portion B is less resistant to chemicals. Therefore, as shown in FIG. 2 (b), the damaged portion B is selectively decomposed when immersed in a chemical solution (etching chemical solution), and as shown in FIG. 1 is formed with fine holes 5 having a uniform hole diameter.

Here, each pore diameter can be determined by controlling the speed of heavy ions to be used and the chemical etching conditions. Further, the hole density can be determined by the number of heavy ions to be irradiated (about 10 ⁹ / cm ² ). However, it is impossible to artificially control a porous pattern (arrangement of holes) formed by a large number of holes. Therefore, there is a problem that a plurality of porous films having the same porous pattern cannot be manufactured.

As described above, in order to increase the security level, there are many things that make it difficult to copy by combining a plurality of means, but none of them can make copying virtually impossible. In addition, with respect to things using biological phenomena and natural phenomena such as multi-particle development, it can be reproduced macroscopically, but it cannot be reproduced artificially microscopically, making reproduction virtually impossible. Although it is possible, a plurality of industrially cannot be manufactured.
Thus, there is a need for a tag that can be manufactured industrially and that cannot be replicated after manufacturing. However, at present, there is no tag that satisfies such a requirement, and development is strongly desired. ing.

JP 2004-94202 A JP 59-117546 A Japanese Patent No. 2518881

  An object of the present invention is to solve the above problems in the prior art and achieve the following objects. That is, an object of the present invention is to provide a plurality of porous films in which the same porous pattern (micropore pattern) is formed and replication is substantially impossible, and a method for producing the same.

  In order to solve the above-mentioned problems, the present inventor irradiates the laminated polymer film with heavy ions, whereby the same porous pattern (micropore pattern) is formed, and a plurality of porous materials that are substantially impossible to replicate. The present inventors have found that a film can be obtained and have completed the present invention.

  That is, the plurality of porous films of the present invention are a plurality of porous films obtained by chemical etching after irradiating a polymer film with heavy ions. The porous patterns formed by the holes are the same, and the orientation direction of the plurality of holes is one direction.

  Moreover, the plurality of porous films of the present invention are a plurality of porous films obtained by chemical etching after irradiating a polymer film with heavy ions. The porous patterns formed by the holes are the same, and the orientation directions of the plurality of holes are two or more.

In the method for producing a plurality of porous films in which a plurality of porous films of the present invention are chemically etched after irradiating a polymer film with heavy ions, the polymer films are laminated and irradiated with heavy ions. It is characterized by.
The laminated polymer film may be irradiated with the heavy ions from a plurality of incident angles.

ADVANTAGE OF THE INVENTION According to this invention, the same porous pattern (micropore pattern) is formed, and the several porous film which cannot be replicated substantially, and its manufacturing method can be provided.
That is, according to the present invention, it is possible to obtain a plurality of polymer films formed with a porous pattern (micropore pattern) that can be produced industrially and cannot be replicated after production, It can be used as a tag with a very high security level.

It is a figure which shows the outline | summary of the manufacturing method of the porous film using the conventional heavy ion. It is a figure which shows the principle of the manufacturing method of the porous film using the conventional heavy ion. It is an electron micrograph of the surface of the porous film obtained by the manufacturing method using the conventional heavy ion. It is a manufacturing method of the porous film of this invention, Comprising: It is a figure for demonstrating making normal incidence on the film which laminated | stacked the heavy ion. It is a manufacturing method of the porous film of this invention, Comprising: It is a figure for demonstrating making it inject into the film which laminated | stacked heavy ion diagonally. It is a manufacturing method of the porous film of this invention, Comprising: It is a figure for demonstrating making it incident obliquely on the film which laminated | stacked the heavy ion after making it perpendicularly incident on the film which laminated | stacked the heavy ion.

  Hereinafter, the present invention will be specifically described with reference to the drawings as necessary.

(Method for producing porous film)
The method for producing a porous film of the present invention includes at least an irradiation step and a chemical etching step, and further includes other steps appropriately selected as necessary.
Specifically, for example, the laminated polymer film to be processed is irradiated with heavy ions (FIGS. 4 to 6) and subjected to chemical etching (FIG. 1B).

<Irradiation process>
The irradiation step is a step of irradiating the laminated polymer film (polymer film laminate) with heavy ions.

-Polymer film laminate-
The polymer film laminate is not particularly limited as long as a plurality of polymer films are laminated so that the film surfaces are parallel to each other, and can be appropriately selected according to the purpose.
The number of polymer films laminated in the polymer film laminate is not particularly limited as long as it is 2 or more, and can be appropriately selected according to the purpose.

-Polymer film-
There is no restriction | limiting in particular as thickness of the said polymer film, Although it can select suitably according to the objective, From a viewpoint of the possibility of hole formation, it is preferable that it is 1 mm or less, and it is 25 micrometers-300 micrometers. More preferred.
There is no restriction | limiting in particular as a material of the said polymer film, According to the objective, it can select suitably, For example, polymer resins, such as a polycarbonate, polyester, a polyimide, a polyacetal, are mentioned. These may be used individually by 1 type and may use 2 or more types together.
Among these, polycarbonate is preferable because it is amorphous, so that the film surface and the inner diameter of the hole become smooth.

-Heavy ion species-
The ion species of the heavy ions are not particularly limited and can be appropriately selected according to the purpose. For example, rare gas ions (ion population) such as helium ions, neon ions, argon ions, krypton ions, and xenon ions. Are preferably used.

-Heavy ion irradiation-
There is no restriction | limiting in particular as said heavy ion irradiation, According to the objective, it can select suitably, For example, a predetermined amount of energy is given per one nucleon of the said heavy ion with heavy ion accelerators, such as a well-known synchrotron. In addition, the heavy ions may be irradiated in a substantially vertical direction or an oblique direction with respect to the polymer film surface. For example, the range (the distance that heavy ions travel through the medium) of xenon ions having a mass number of 131.904 is about 20 μm at an acceleration energy of 1 MeV / u per nucleon, about 70 μm at 5 MeV / u, and 10 MeV. / U is about 130 μm, and 100 MeV / u is about 3400 μm (u in a unit means an atomic mass unit). In short, it is sufficient to select an acceleration energy that exceeds the heavy ions penetrating the polymer film laminate, depending on the ion species to be used and the polymer species in the polymer film to be irradiated. Range calculation in the medium of accelerated heavy ions can be calculated by the well-known calculation software SRIM (The Stopping and Range of Ions in Matter) code.
The pore density can be arbitrarily determined depending on the ion type of heavy ions, acceleration energy, and irradiation dose. When the acceleration energy is a low LET (LET is an abbreviation for Linear Energy Transfer, meaning energy given per unit length), the beam can be controlled by the irradiation dose. For example, when a xenon ion having an acceleration energy of 184 MeV / u passes through a polycarbonate medium, the LET is 15.6 GeV / cm, and a dose of 250 Gy is necessary to obtain a hole density of 10 ⁸ / cm ^2. is there. On the other hand, since a dosimeter cannot be used in the case of a high LET beam with a small acceleration energy, the hole density according to the irradiation time is measured in advance using a thin plastic scintillator and controlled by the irradiation time. Furthermore, in the case of a high LET beam, the rate of change at the location of the energy applied to the film laminate is increased, and the subsequent chemical etching causes the subsequent stage to be larger than the hole diameter of the previous stage film (film on the irradiation means side). The high LET beam in the vicinity of the Bragg peak is not preferable because there is a problem that the hole diameter of the film (film opposite to the irradiation means) becomes large.

-Irradiation direction-
There is no restriction | limiting in particular as an irradiation direction of the said heavy ion irradiation, According to the objective, it can select suitably, A perpendicular | vertical direction (FIG. 4, incident angle = 0 degree) with respect to a polymer film laminated body surface, a polymer film It may be in an oblique direction (FIG. 5, 0 ° <incident angle <90 °) with respect to the laminate surface.
If the irradiation direction of the heavy ions is oblique to the polymer film laminate surface (0 ° <incident angle <90 °), even if the stamper mold for injection molding is copied, This is because the orientation of the film is oblique with respect to the film surface, so that the duplicate cannot be removed from the stamper mold (anchor effect), and duplication can be prevented.
There is no restriction | limiting in particular as said incident angle, According to the objective, it can select suitably.
The irradiation direction of the heavy ion irradiation may be one direction (FIGS. 4 and 5) or two or more directions (multiple directions) (FIG. 6).

<Chemical etching process>
The chemical etching step is a step of chemically etching the polymer film irradiated with heavy ions.

-Chemical etching-
There is no restriction | limiting in particular as the method of the said chemical etching, According to the objective, it can select suitably, For example, the well-known chemical etching method of immersing in a well-known etching chemical | medical solution for a predetermined time etc. are mentioned. In the chemical etching, uniform etching can be performed by stirring the etching chemical.
There is no restriction | limiting in particular as said etching chemical | medical solution, According to the objective, it can select suitably, For example, alkaline aqueous solution (1N sodium hydroxide aqueous solution which contains 30 vol% of methanol) etc. are mentioned. The etching chemical may further contain an additive such as a surfactant.
As content of alcohol in the said etching chemical | medical solution, as long as it is 1 mass%-95 mass%, there is no restriction | limiting in particular, According to the objective, it can select suitably.
There is no restriction | limiting in particular as alcohol in the said etching chemical | medical solution, According to the objective, it can select suitably, For example, methanol, ethanol, isopropanol, etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together.
Among these, methanol is preferable from the viewpoints of affinity with a polymer (resin) and improvement in activity of a decomposition reaction.
There is no restriction | limiting in particular as a density | concentration of the alkali in the said etching chemical | medical solution, Although it can select suitably according to the objective, It is preferable that it is 0.1N-5N.
There is no restriction | limiting in particular as an alkali in the said etching chemical | medical solution, According to the objective, it can select suitably, For example, sodium hydroxide etc. are mentioned.
There is no restriction | limiting in particular as pH of the said etching chemical | medical solution, Although it can select suitably according to the objective, 13-14 are preferable.
There is no restriction | limiting in particular as pKa (acid dissociation constant) of alcohol in the said etching chemical | medical solution, Although it can select suitably according to the objective, 2-9 are preferable.
There is no restriction | limiting in particular as temperature of the said etching chemical | medical solution, Although it can select suitably according to the objective, 0 to 80 degreeC is preferable and 20 to 40 degreeC is further more preferable.
There is no restriction | limiting in particular as immersion time of the said etching chemical | medical solution, Although it can select suitably according to the objective, 1 minute-24 hours are preferable, and 5 minutes-2 hours are further more preferable.

As described above, a porous film is produced by a method for producing a porous film including an irradiation step and a chemical etching step, thereby forming a porous (micropore) in a portion penetrated by irradiation with a heavy ion group. A plurality of porous films having the same porous pattern can be produced.
Here, “the same porous pattern” indicates that not only the pattern on the film surface is the same, but also the pattern of the film cross section.

(Porous film)
In the porous film of the present invention, pores (micropores) penetrating in the film thickness direction are formed.
There is no restriction | limiting in particular as a porous orientation direction in the said porous film, According to the objective, it can select suitably, Any of a perpendicular direction with respect to a film surface and an oblique direction with respect to a film surface may be sufficient. However, it is preferable that it is a diagonal direction with respect to a film surface.
If the orientation direction of the porous film in the porous film is oblique with respect to the film surface, even if the stamper mold for injection molding is copied, the duplicate cannot be removed from the stamper mold. This is because it is possible to prevent duplication (anchor effect).
The porous orientation direction in the porous film may be one direction or two or more directions (multiple directions).
There is no restriction | limiting in particular as a hole diameter of the hole formed in the porous film of this invention, Although it can select suitably according to the objective, 500 nm or less is preferable, 300 nm or less is more preferable, It replicates with another processing method As small as possible, it is preferred that it be as small as possible. For example, the hole diameter of 200 nm shown in Example 1 described later is merely an example.
There is no restriction | limiting in particular as an aspect-ratio of the hole formed in the porous film of this invention, Although it can select suitably according to the objective, 1-3000 are preferable and 5-1000 are more preferable.

  Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples.

Example 1
As described below, a porous film was obtained through an irradiation process and a chemical etching process.

<Irradiation process>
As shown in FIG. 4, 10 sheets of polycarbonate film (trade name: Iupilon Film FE-2000, manufactured by Mitsubishi Gas Chemical Co., Ltd.) as a polymer film 1 having a thickness of 100 μm are stacked and accelerated by a synchrotron accelerator. Xenon ions as ions 2 were irradiated perpendicularly to the film surface. The irradiation beam was a low LET beam with an acceleration energy of 184 MeV / u. Since the range of the heavy ions 2 in the polycarbonate medium is 9.45 mm, the traces to the 1 mm-thick laminate will penetrate. The irradiation dose was set to 896 Gy so that the hole density was 3.6 × 10 ⁸ . Irradiation was terminated after confirming that the dose reached 896 Gy with a dosimeter.

<Chemical etching process>
A plurality of polycarbonate films irradiated with xenon ions were immediately immersed in an etching chemical. As the etching chemical, a 1N sodium hydroxide aqueous solution containing 30 vol% of methanol was used. The etching time (immersion time in the chemical solution for etching) was 10 minutes, the polycarbonate film was lifted from the etching chemical solution, washed with water, and dried to obtain a porous film.

<Observation and evaluation of porous film>
The surface and cross section of each porous film obtained were observed with a scanning electron microscope. The hole diameter was almost uniform at 200 nm, and the hole depth by etching from one side was 50 μm. That is, erosion progressed from both surfaces of the polycarbonate film, and through holes were formed in the polycarbonate film having a thickness of 100 μm. In addition, the porous patterns of the five laminated films were all the same. As a feature of irradiation with heavy ions by synchrotron, many heavy ions are intermittently irradiated at intervals of several seconds like a shotgun, so heavy ions may collide slightly at the same location. Therefore, there was a part where the hole was connected like a snowman.
Since the porous film produced as described above has each hole formed perpendicular to the film surface, it is substantially possible to duplicate the porous film based on the electroformed mold copied. However, it is impossible to completely deny the possibility that the porous film is duplicated.

(Example 2)
In Example 1, instead of irradiating the xenon ions perpendicularly to the polycarbonate film laminate, as shown in FIG. 5, the xenon ions are oblique to the polycarbonate film laminate (incident angle (angle with respect to the vertical direction) 20. Except for irradiating, the porous film was obtained in the same manner as in Example 1, and the obtained porous films were observed and evaluated. In each of the obtained porous films, the pore diameter was almost uniform at 200 nm, and the pore depth by etching from one side was 53.2089 μm. That is, erosion progressed from both surfaces of the polycarbonate film, and through holes were formed in the polycarbonate film having a thickness of 100 μm. In addition, the porous patterns of the five laminated films were all the same.
As in Example 2, even if the stamper mold for injection molding is copied by irradiating the polycarbonate film laminate with xenon ions from an oblique direction, the orientation direction of the porosity is relative to the film surface. Due to the oblique direction, the duplicate cannot be removed from the stamper mold (anchor effect), and duplication can be prevented.

(Example 3)
In Example 1, instead of irradiating the xenon ions perpendicularly to the polycarbonate film laminate, first, as shown in FIG. 4, the xenon ions were irradiated perpendicularly to the polycarbonate film laminate, and then FIG. As shown in FIG. 5, a plurality of porous films were obtained in the same manner as in Example 1 except that xenon ions were irradiated obliquely (incident angle θ (angle with respect to the vertical direction) 20 °) to the polycarbonate film laminate. Each of the obtained porous films was observed and evaluated. In FIG. 6, a gap is provided between the films for convenience of drawing, but in an actual experiment, the films were laminated without providing a gap between the films (d = 100 μm). When the xenon ions are irradiated obliquely onto the polycarbonate film laminate, as shown in FIG. 6, the films in the polycarbonate film laminate are in a state of being shifted by w (36.397 μm) in the film surface direction. (Tan 20 ° = w / d = 36.397 / 100 = 0.36397). In each of the obtained porous films, the hole diameter was 200 nm, and the depth of the holes by etching from one side was 50 μm (vertical hole) and 53.2089 μm (oblique hole). That is, erosion progressed from both surfaces of the polycarbonate film, and through-holes were formed in the polycarbonate film having a thickness of 100 μm in two directions perpendicular and oblique to the film surface. In addition, the porous patterns of the five laminated films were all the same.
As in Example 3, even if the stamper mold for injection molding is copied by irradiating heavy ions from two directions perpendicular and oblique to the film laminate, the orientation direction of the porous film is Due to the oblique direction with respect to the surface, the duplicate cannot be removed from the stamper mold (anchor effect), and duplication can be prevented.
In Example 3, the xenon ions are irradiated from two directions that are perpendicular and oblique to the polycarbonate film laminate, but a plurality of xenon ions may be irradiated in an oblique direction.

  The porous film of the present invention is effective for use in, for example, an authentication field where a very high security level is required.

DESCRIPTION OF SYMBOLS 1 Polymer film 2 Heavy ion 3 Etching chemical | medical solution 4 Porous film 5 Micropore

Claims (4)

In a plurality of porous films obtained by chemical etching after irradiating the polymer film with heavy ions,
The plurality of porous films, wherein the porous patterns formed by the plurality of holes in each porous film of the plurality of porous films are the same, and the orientation direction of the plurality of holes is one direction the film. In a plurality of porous films obtained by chemical etching after irradiating the polymer film with heavy ions,
A plurality of pores characterized in that the porous patterns formed by a plurality of holes in each porous film of the plurality of porous films are the same, and the orientation directions of the plurality of holes are two or more directions. Sex film.   A method for producing a plurality of porous films, wherein the polymer films are laminated and irradiated with heavy ions in a method for producing a plurality of porous films that are chemically etched after irradiating the polymer films with heavy ions. .   The method for producing a plurality of porous films according to claim 3, wherein the laminated polymer film is irradiated with the heavy ions from a plurality of incident angles.