JPH0495989A - Copying preventing paper and printed matter using it - Google Patents

Abstract

PURPOSE:To make a copied substance indistinct to such an extent that it can be read without hindrance by providing one or more layers which are constituted of transparent layers having different refractive indexes and reflect a visible light beam between an absorption layer and the surface of a paper. CONSTITUTION:One or more layers which are constituted of the transparent layers having different refractive indexes and reflect the visible light beam are provided on at least one absorption layer between the absorption layer and the surface of the paper. Supposing that the refractive index of the layer which is close to the surface is n1 and the refractive index of the layer which is close to the absorption layer is n2, most of the light is transmitted when an incident angle theta is smaller than theta1, which is expressed by sintheta1=n2/n1, and the light is totally reflected on the reflection layer when theta is larger than theta1. In the case that ordinary transparent resin such as polymethyl methacrylate or polystyrene is used as the layer close to the surface and air is used as the layer close to the absorption layer respectively, the light made incident at the incident angle >=50.3 deg. is totally reflected. By forming such a reflection film, the copied substance is made indistinct to such an extent that a document and a printed matter can be read without hindrance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a copy-preventing paper that does not hinder reading but makes copies made by a copying machine unclear, and to printed matter using the same.

[Conventional technology 1] It is said that the amount of damage caused by copying confidential documents and publications reaches tens of billions of yen or more in Japan alone.

In order to prevent publications from being copied, dyes or pigments (black, green, blue, etc.) that absorb some or all of the light that is detected by the light receiving part of the copying machine are printed in a mesh or dot pattern. Means such as printing characters on the top are used. However, with these methods, the printed text itself is difficult to read,
Moreover, copying has not been completely prevented [Examples of publications using this method, supervised by Yoshiaki Tegoshi and Yoshiharu Asano,
Software Security, El Planning (1985)].

(Problems to be Solved by the Invention) The present invention provides a copy-preventing paper that solves the drawbacks of the above-mentioned printed matter that it is difficult to read and that the prevention of copying is incomplete, and a printed matter using the same. The purpose is to provide.

[Means for solving the problem 1] The present invention is directed to light (usually 400
An absorbing layer consisting of at least one layer that absorbs part or all of the wavelengths (~900 nm), and one or more transparent layers that reflect visible light and having a different refractive index between the absorbing layer and the surface of the paper. It was discovered that the layer is provided on at least one of the absorbent layers, thereby making documents or printed matter easier to read and difficult to copy, leading to the invention.

The layer that absorbs some or all of the light that is sensitive to the light-receiving part of the copying machine is formed from pigments such as black, green, blue, and near-infrared absorbers, single pigments or mixtures, or mixtures of these and resins. Ru.

The optimal thickness of the absorption layer varies depending on the dye, the light absorption rate of the pigment, the concentration of the dye and pigment, etc., but is usually 0.5 to 20
μm is preferred. This range is preferably 0.5 μm
It is difficult to form a film with a thickness of 20 μm or more, and it is not economical to form a film with a thickness of 20 μm or more.

This adsorption layer may be a uniform layer, but may also be in the form of a mesh, dots, character pattern, or graphic pattern. One type of dye or pigment may be used, but different colors may be used in a mixed state, in multiple layers, in a dotted form, or the like.

Black dyes and pigments such as carbon black are used for black, green dyes and pigments such as ferrocyanine green are used for green, and blue dyes and pigments such as ferrocyanine blue are used for blue pigments. Ru.

Examples of carbon black include channel black, furnace black, acetylene black, and thermal black. Specific examples of commercially available carbon blacks include Black Pearl 700, Mogul L, ELFTEX pellets-1], 5, Regal 3001, Palcan XC-72, and Sterling N manufactured by Cabot Corporation in the United States.
S, Stirling R, Columbian Carbon's Raben 5ooo, Raben 5250, Raben 890
, Laben 450, Lachen 410, Lachen NITP
Beads, Raven Sebacarb MT-CI, H3500, 360H1 manufactured by Asahi Carbon Co., Ltd. Geast 5H manufactured by Tokai Riki-Hon Co., Ltd., Ketchen Black E manufactured by Agzo Company of the Netherlands
C1 Mitsubishi Kasei = 4040, # 4330 B S
, 34350 BS, #4010, etc. In addition, black dyes and pigments include I manufactured by Mitsui Toatsu Chemical Co., Ltd.
J Black EX-73, IJBlack EX-
85, IJ Black EX-305, Kayaset Black 008 (N) pur manufactured by Nippon Kayaku Co., Ltd.
e etc.

For example, ferrocyanine green such as Heristral Fast Green G manufactured by 13AsF and Monastral Fast Green G manufactured by ICA and Du Pant is used as the green pigment.

Examples of blue pigments include Victoria Blue Lake, metal-free ferrocyanine blue, ferrocyanine blue, Fast Sky Blue, Victoria Blue triphenylmethane dye, and anthraquinone-based Disperse Blue.
Dyes such as e26 are used.

In addition, MS Blue EX-9 manufactured by Mitsui Toatsu Chemical Co., Ltd.
, IJ Blue EX-87, Kay manufactured by Nippon Kayaku Co., Ltd.
aset Blue FR,Kayaset Cyan
There is something like J-301.

Near-infrared absorbers include dyes and pigments such as polymethine dyes (cyanine dyes), phthalocyanine dyes, dithiol metal complex naphthoquinones, anthraquinones, triphenylmethane (similar), aminium, and cyinmonium dyes. Commercially available dyes and pigments include PA1006, PA1005, and PAloo manufactured by Mitsui Toatsu Chemical Co., Ltd.
l, IRG-750 (aminium type) manufactured by Nippon Kayaku Co., Ltd.
IRG-002 (anthraquinone), IRG-003
(Anthraquinone type), IR-820 (Polymethine type)
, IRG-022 (cyinmonium type), IRG-02
3 (diimmonium type), CY-2 (cyanine type), C
There are Y-4 (cyanine type), CY-9 (cyanine type), etc.

Such an absorbing layer is made by: ■ melting dyes or pigments;
A dye or pigment with a predetermined composition and a wax are dispersed in a ball mill or a sand mill and then melted.■ A dye or pigment with a predetermined composition, a resin, and a solvent are dispersed in a ball mill or a sand mill to form a paint and applied onto a film. Created by Depending on the dye or pigment, an absorbing layer can also be formed by vapor deposition on the film.

An antistatic agent such as a quaternary ammonium salt such as polyoxyethylene alkylamine, and a molten resin flow agent such as ethylene bisstearamide may also be included.

The main effect of providing a reflective layer between the adsorption layer and the surface of the paper is to make the document or print difficult to copy while keeping it legible. The effect of the reflective layer will be explained using a case where transparent layers having different refractive indexes are laminated.

Assuming that the refractive index of the layer near the surface is n3 and the refractive index of the layer near the absorption layer is nl, as shown in Figure 1, θ is sin θ+
When the incident angle is smaller than θ1, expressed as =nh/n+, most of the light is transmitted, whereas when θ is larger than 01, the light is totally reflected by this reflective layer. When ordinary transparent resins such as PMMA (polymethyl methacrylate) and PS (polystyrene) are used in the layer near the surface, and air is used in the layer near the absorption layer, nl is approximately 1.3,
Since n is 1.0, 01 becomes 50°3°. In addition, when Tie (rutile) is used in the layer near the surface and air is used in the layer near the absorption layer, nl is 2.55, nl is
Since l is 1.0, 01 becomes 23.1°. Therefore, the light incident on the former reflective layer at an incident angle of 50.3° or more and the latter reflective layer at an incident angle of 23.1° or more will be totally reflected,
．． In the case of light incident at an incident angle of 3° or less and 23.1'' or less, it is mostly transmitted and absorbed by the absorption layer.

When such a reflective film is formed, there is no problem in reading documents and printed matter, but copies become unclear.

The reason why there is no problem in reading documents and printed materials is as follows. In a normal room or outdoors, light strikes the surface of documents and printed matter from all angles.

Among these lights, the light incident at a low angle is absorbed,
Since the light incident at a high angle is totally reflected by the reflective film, the non-printed area becomes white. The intensity of this reflected light increases as the difference in the refractive index of the reflective layers increases, and the non-printed area becomes whiter. On the other hand, in a copying machine, the light is incident on the surface of a document or printed matter at a fixed angle, and at a small angle (the angle varies slightly depending on the copying machine, but is at most 10 degrees). Therefore, the incident light is not reflected by the reflective layer, but is transmitted and almost absorbed by the absorbing layer. Therefore, the non-printed areas of the copy also become black, making the copy unclear. In addition, since the structure is such that it only receives light reflected at a reflection angle that is approximately equal to the incident angle, even if the interface of the reflective layer is rough and there is a surface that satisfies the conditions for total reflection (a rough surface is composed of a composite of various reflective surfaces), and as shown in Figure 2, almost no light reflected from such a surface enters the light-receiving surface of the copying machine. Therefore, even if the interface of the reflective layer is rough, the non-printed areas of the copy will also become black, making the copy unclear.

The reflective layer may have one layer, or two or more layers.

Any material can be used for the reflective layer as long as transparent layers with different refractive indexes are laminated so that the refractive index is higher on the surface side of the paper, but since paper is required to have a certain degree of flexibility, Preferably, each layer is made of a material with a certain degree of flexibility.

Materials used for the high refractive index layer include SnO, A12
Although crystalline transparent inorganic materials such as 01.5iO6, T101, ZrO, and amorphous transparent inorganic materials such as glass may be used, plastic materials are more preferable because of their high flexibility.

As the plastic material, any material may be used as long as it has high light transmittance. Examples of materials used for this include polyethylene terephthalate, polyethylene-2,
Commercially available films such as polyesters such as 6-naphthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, and polycarbonate are used as they are. It's okay.

Also 1, ps (polystyrene), PMMA (polymethyl methacrylate), vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-acrylic acid ester copolymer, vinyl chloride-vinyl chloride Vinylidene copolymer, vinyl chloride-agrylonitrile copolymer, vinyl chloride-vinyl acetate-inic acid copolymer and other vinyl chloride resins, thermoplastic polyurethane resins,
A thermosetting polyurethane resin, a polyester resin, a phenoxy resin, a polyvinyl butyral resin, a cellulose derivative, an epoxy resin, or a mixture thereof may be dissolved in a solvent and applied onto the above film. Further, if necessary, a polyfunctional isocyanate or the like may be mixed with the resin and heat treated to make it insoluble in a solvent. Furthermore, by introducing polar groups such as carboxylic acid, sulfonic acid, sulfonate, phosphoric acid, phosphate, amine, and ammonium salt into these resins, and by introducing acrylic double bonds, UV rays and electron beams can be removed. It may be hardened by irradiation. Solvents used to create paints to form these coatings include alcohols such as ethanol, propatool, butanol, esters such as methyl acetate, ethyl acetate, and butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Ketones, ethers such as tetrahydrofuran and dioxane, aromatic hydrocarbons such as benzene, toluene and xylene, aliphatic hydrocarbons such as heptane, hexane and cyclohexane, chlorinated hydrocarbons such as methylene chloride, ethylene chloride and chloroform, etc. can be mentioned.

Any material may be used for the low refractive index layer as long as it has a lower refractive index than the high refractive index layer, but gases such as air, nitrogen, argon, and oxygen are preferred because they have a low refractive index and are inexpensive. Furthermore, the use of vacuum instead of gas is not excluded. To provide an air layer as a low refractive index layer, adhesive may be applied to a portion between two films and the film may be pressed between rollers or the like.

When a gas such as air is used for the low refractive index layer, white additives such as SiO, TiO, AI, O, and fine particles are added to the adhesive. In addition, the reason why white additives (S i O, fine particles, etc.) are added to the adhesive is that there is no air layer with a low refractive index in the adhesive area, so light is not reflected, and without the white additive, the paper surface will be black. This is to become. The amount of the white additive is determined so that the adhesive layer and the non-adhesive layer have approximately the same visual whiteness.

Although the adhesive part to which a white additive has been added does not have a copying pressure-proofing effect, if the adhesive part is placed at the edge of the paper, no printing will occur in this area, so there is no practical problem.

Furthermore, if the adhesive part is made into a thin line of about 1 mm or less, the thin line will be copied, but the copy will not be readable, so this will not impede the copy prevention effect.

Although the thickness of the low refractive index layer and the high refractive index layer does not control the performance as a reflective layer, 0.05 to 30 μm is usually used. When a gas is used as the low refractive index layer, the film thickness is usually 0.05 to 3 μm.

[Examples] Hereinafter, the present invention will be specifically explained with reference to Examples, but the Examples do not impose any limitations on the present invention.

Example I A. Preparation of absorption layer Cyst 5H manufactured by Tokai Carbon Co., Ltd. was used as carbon black.
15 parts by weight of thermoplastic polyurethane resin, 45 parts by weight of thermoplastic polyurethane resin, and 40 parts by weight of nitrocellulose were blended with 130 parts by weight of cyclohexanone and toluene, and this composition was cross-dispersed in a hole mill for 96 hours to prepare a paint. did. This was placed on a 3.5 μm polyester base to a thickness of 4 mm.
．． It was coated to a thickness of 0 μm and dried. This is called the A film.

Preparation of B9 reflective layer Average surface roughness (Ra) is 0.01 μm, film thickness is 20 μm
, one side of a PET (polyethylene terephthalate) film with a refractive index of 1.3 was subjected to matte processing (surface roughening treatment), and the average surface roughness (Ra) was set to 0.15 μm. This is called the B film.

Preparation of C3 paper Cut A film and B film to A4 size, overlap them on both sides of A film so that the matte surface of B film becomes the surface of the paper, and use an acrylate-based paper containing 10% Sin. A 5 mm edge portion was bonded with adhesive (adhesive film thickness: approximately 2 μm).

In addition, for areas other than the edges, the spacing is approximately 2 cm, and the width is 0.2 cm.
It was glued in a lattice shape with mm.

D. Evaluation: Characters were written with a pencil on the paper of the present invention prepared by the method of C, and the legibility and sharpness of the copies were evaluated.

The results are shown in Table 1.

Table] Readability book Clarity of copy This book Example 1 2 5 Example 2 1 4 Example 3 1 4 Comparative example 1 3 3 Comparative example 25 1. Very easy to read Wooden: l; Very clear 2 : Easy to read 2. Clear 3: Difficult to read 3; Blurred 4: Very difficult to read 4: Very unclear 5: Extremely difficult to read
5; Extremely indistinct Example 2 Paper was produced in the same manner as in Example 1, except that ferrocyanine was used instead of carbon black.

The evaluation results are shown in Table 1.

Example 3 Paper was produced in the same manner as in Example 1, except that ferrocyanate was used instead of carbon black. The evaluation results are shown in Table 1.

Comparative Example I Paper was produced in the same manner as in Example 1, except that the entire surface of the paper was adhered with an acrylate adhesive containing 10% by weight of SiC2. The evaluation results are shown in Table 1.

Comparative Example 2 Paper was produced in the same manner as in Example 1, except that the entire surface of the paper was adhered with an acrylate transparent adhesive that did not contain S103. The evaluation results are shown in Table 1 [Effects of the Invention] As is clear from Table 1, the absorption layer consists of at least one layer that absorbs part or all of the wavelength of the light that is sensitive to the light receiving section of the copying machine; By providing at least one of the absorbing layers with one or more layers that reflect visible light, which are made of transparent layers with different refractive indexes, between the surface of the paper and the surface of the paper, there is no problem with reading, but it is possible to make copies unclear. Become.

[Brief explanation of the drawing]

Figure 1 shows a total reflection film when light is incident on a film with a refractive index n1 to n2 at an angle of 0, 0=Arc [s i
An explanatory diagram showing the behavior of light at forward and backward angles. FIG. 2 is an explanatory diagram showing that even if the reflective layer includes a surface that satisfies the conditions for total reflection, light does not enter the light-receiving surface of the copying machine. Patent applicant: Hitachi Maxell, Ltd. Representative: Hiroshi Watanabe Figure 1 Figure 2

Claims (1)

[Scope of Claims] (1) An absorbing layer consisting of at least one layer that absorbs part or all of the wavelengths of light that is sensitive to the light receiving section of a copying machine, and a layer with a refractive index between the absorbing layer and the surface of the paper. A copy-preventing paper characterized in that at least one of the absorbing layers is provided with one or more visible light-reflecting layers composed of different transparent layers. (2) The wavelength of the light that is sensitive to the light receiving part of the copying machine is 400 to 1
The copy-preventing paper printed material according to claim 1, characterized in that the wavelength is 000 nm. (2) The reflective layer is composed of laminated transparent layers having a refractive index n_1 and a refractive index n_2 when viewed from the surface of the paper, and n_1>n_2, according to claims (1) and (2). Anti-copying paper. (4) The copy according to claims (1), (2) or (3), wherein the surface of the paper is roughened to an average surface roughness (Ra) of 0.1 μm or more so that it can be printed with a pencil. Prevention paper. (5) A printed matter characterized by using the copy-preventing paper according to claims (1), (2), (3) or (4).