JP4459016B2 - Electromagnetic wave shielding material and manufacturing method thereof - Google Patents

Description

  The present invention relates to an electromagnetic wave shielding material for shielding electromagnetic waves generated from electric devices such as CRT and PDP, and a method for manufacturing the same.

  2. Description of the Related Art Conventionally, various articles have been manufactured by forming a pattern having conductivity or magnetism on a base material and utilizing the electrical properties, magnetic properties, and the like. Among them, the electromagnetic wave shield plate is widely used as a front plate attached to the front surface of the display in order to shield electromagnetic waves leaking from the front side of the display unit such as CRT and PDP. The electromagnetic shielding plate used as the front plate is required not to lower the transparency of the display screen of the display in addition to the function of shielding electromagnetic waves.

  Examples of the electromagnetic shielding material having both transparency and electromagnetic shielding properties include the following.

  Patent Documents 1 and 2 report an electromagnetic shielding material having a conductive portion formed by screen printing on the surface of a transparent resin base material using conductive powder and a binder. However, in general, when screen shielding is used to form a shield layer with a lattice pattern, printing defects such as moiré, fine line breakage, and line thickening are likely to occur due to interference with the reed mesh of the printing plate. Printing was not easy. Therefore, the problem that electromagnetic wave shielding performance declines or transparency falls easily occurs.

  Further, in Patent Document 3, a photosensitive resist layer is provided on one side of a transparent substrate, a mesh-like cross-sectional concave pattern is formed by a photolithographic method, and a conductive ink is applied to the entire surface of the pattern to form a concave cross-section. A method for producing a light-transmitting electromagnetic wave shielding member is described, wherein a conductive ink is filled in a pattern, a photosensitive resist layer having a convex cross section is removed to obtain a net-like conductive pattern, and firing is performed. Has been.

However, in this manufacturing method, (1) a conductive ink is applied to the entire surface of the pattern, the conductive ink is filled in the pattern having a concave section, and heat treatment is performed, and the photosensitive resist layer having a convex section is further removed. It requires a two-step heating process to be fired later, and (2) uses a conductive ink containing a solvent and a dispersion stabilizer (binder) in the composition, so it has a resistance value as low as that of a pure metal. (3) The conductive ink contains noble metal particles such as silver, gold, and copper, and is expensive. (4) The transparent substrate is limited to a glass substrate. There was room for further improvement.
Japanese Patent Laid-Open No. 11-26984 JP 2001-196784 A JP 2004-31876 A

  An object of the present invention is to provide a high-quality electromagnetic shielding material having a high electromagnetic shielding effect and excellent in transparency and transparency, and a simple and inexpensive method for producing the electromagnetic shielding material.

  As a result of earnest research to solve the above problems, the present inventor applied (a) a liquid or dry film-like transparent photosensitive resist to the transparent receiving layer surface of a transparent substrate, and A step of forming a resin layer, (b) a step of forming a recess corresponding to the shape of a network-like conductive layer in the transparent resin layer by a photolithography method, and (c) injecting a conductive paste into the recess and transparent A step of removing excess conductive paste on the resin layer, (d) a step of heat-treating the conductive paste to form a network-like conductive layer, and (e) steps (c) and (d) above. It has been found that a method for producing an electromagnetic shielding material comprising a step of repeating the process once more or more, and an electromagnetic shielding material produced by the production method can solve the above problems.

  Based on this knowledge, the present inventor has further studied and completed the present invention.

  That is, this invention provides the following electromagnetic wave shielding materials and its manufacturing method.

Item 1. Production of an electromagnetic shielding material in which a network-like conductive layer and a transparent resin layer are provided on the transparent receiving layer surface of a transparent base material provided with a transparent receiving layer on at least one surface so as to form substantially the same plane. A manufacturing method comprising the following steps (a) to (e):
(A) a step of applying or sticking a liquid or dry film-like transparent photosensitive resist to a transparent receiving layer surface of a transparent substrate to form a transparent resin layer;
(B) a step of forming a recess corresponding to the shape of the mesh-like conductive layer in the transparent resin layer by a photolithography method;
(C) A step of injecting a conductive paste into the concave portion to remove excess conductive paste on the transparent resin layer;
(D) a step of heat-treating the conductive paste to form a mesh-like conductive layer, and (e) a step of repeating the steps (c) and (d) one or more times.

  Item 2. The transparent receiving layer is composed of an aggregate of fine particles mainly containing at least one selected from titania and alumina, and the average particle diameter of the fine particles is about 10 to 100 nm, and the fine particles are about 10 to 100 nm between the fine particles. Item 2. The method according to Item 1, wherein the method has pores and the thickness of the transparent receiving layer is about 0.05 to 20 μm.

  Item 3. The conductive paste is a particulate silver oxide having an average particle diameter of 2 μm or less, a silver salt of a tertiary fatty acid having a total carbon number of 5 to 30, an aromatic hydrocarbon, an ether ester of ethylene glycol, an ether ester of propylene glycol Item 3. The production method according to Item 1 or 2, which is a conductive paste containing a solvent mainly comprising at least one selected from the group consisting of terpineol and terpineol.

  Item 4. The manufacturing method of the electromagnetic wave shielding material in any one of claim | item 1 -3 whose temperature of the said heat processing is about 150-200 degreeC.

  Item 5. Item 5. The production method according to any one of Items 1 to 4, wherein the transparent substrate has a hard coat layer on the surface opposite to the surface having the transparent receiving layer.

  Item 6. The electromagnetic wave shielding material manufactured by the manufacturing method in any one of claim | item 1 -5.

Item 7. A method for producing an electromagnetic wave shielding material having a network-like conductive layer on a surface of a transparent substrate provided with a transparent receiving layer on at least one surface, the following steps (a) to (f): A manufacturing method comprising:
(A) a step of applying or sticking a liquid or dry film-like photosensitive resist to the transparent receiving layer surface of a transparent substrate to form a resin layer;
(B) forming a recess corresponding to the shape of the network-like conductive layer in the resin layer by a photolithography method;
(C) A step of injecting a conductive paste into the concave portion to remove excess conductive paste on the transparent resin layer;
(D) a step of heat-treating the conductive paste to form a network-like conductive layer;
(E) a step of repeating the steps (c) and (d) one or more times, and (f) a step of removing the resin layer from the transparent receiving layer surface of the transparent substrate.

  Item 8. The transparent receiving layer is composed of an aggregate of fine particles mainly containing at least one selected from titania and alumina, and the average particle diameter of the fine particles is about 10 to 100 nm, and the fine particles are about 10 to 100 nm between the fine particles. Item 8. The production method according to Item 7, which has pores and the thickness of the transparent receiving layer is about 0.05 to 20 μm.

  Item 9. The conductive paste is a particulate silver oxide having an average particle size of 2 μm or less, a silver salt of a tertiary fatty acid having a total carbon number of 5 to 30, an aromatic hydrocarbon, an ether ester of ethylene glycol, an ether ester of propylene glycol Item 9. The production method according to Item 7 or 8, which is a conductive paste containing a solvent mainly comprising at least one selected from the group consisting of terpineol and terpineol.

  Item 10. Item 10. The method for producing an electromagnetic shielding material according to any one of Items 7 to 9, wherein the temperature of the heat treatment is about 150 to 200 ° C.

  Item 11. Item 11. The method according to any one of Items 7 to 10, wherein the transparent substrate has a hard coat layer on the surface opposite to the surface having the transparent receiving layer.

  Item 12. The electromagnetic wave shielding material manufactured by the manufacturing method in any one of claim | item 7 -11.

  Item 13. Item 13. The electromagnetic wave shielding material according to Item 6 or 12, wherein the line-like conductive layer has a line width of about 10 to 30 μm and an aperture ratio of about 80 to 95%.

  Item 14. Item 14. The electromagnetic wave shielding material according to Item 13, having a total light transmittance of 72 to 91%, a haze value of 0.5 to 6%, and a surface resistance value of 5Ω / □ or less. Shield material.

  Item 15. Item 15. An electromagnetic wave shielding filter for plasma display comprising the electromagnetic wave shielding material according to Item 6, 12, 13, or 14.

Hereinafter, the present invention will be described in detail.
I. Electromagnetic wave shielding material In the electromagnetic wave shielding material of the present invention, a network-like conductive layer and a transparent resin layer form substantially the same plane on the transparent receiving layer surface of a transparent substrate provided with a transparent receiving layer on at least one surface. Or an electromagnetic shielding material having a network-like conductive layer on the transparent receiving layer surface of a transparent base material provided with a transparent receiving layer on at least one surface. The electromagnetic shielding material of the present invention has a high electromagnetic shielding effect and excellent transparency and transparency.

Transparent substrate The transparent substrate used in the present invention is transparent enough to allow at least a plasma display (PDP) to be seen through, heat resistance, weather resistance, non-shrinkage, mechanical strength, chemical resistance There is no particular limitation as long as the resin is excellent in properties and the like.

  Specific examples of the transparent base material include polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polycarbonate resins; poly (meth) acrylate resins; silicone resins; cyclic polyolefin resins; Resin; polyether sulfone resin and the like are exemplified. Of the above, polyester resins, particularly PET or PEN, are preferably employed from the viewpoint of transparency, cost, durability, heat resistance, and the like. The thickness is usually about 25 μm to 5 mm.

  The transparency of the transparent substrate is not particularly limited as long as it is of a degree that can be used for display applications such as PDP and CRT. Usually, the total light transmittance measured by JIS K7105 is about 85 to 90%, and the haze value measured by JIS K7105 is about 0.1 to 3%.

  As the form of the transparent substrate, a form that can be used for a display unit such as PDP or CRT, that is, a film form, a sheet form, a flat form or the like is adopted. Such a form can be produced from the above base resin by a known method. In the case of a film or sheet, the thickness of the transparent substrate is usually about 25 to 200 μm, preferably about 40 to 188 μm. In particular, when used as an electromagnetic shielding material on the front surface of a display such as a PDP, about 50 to 125 μm is preferable. Moreover, in the case of plate shape, the thickness should just be about 0.5-5 mm normally, Preferably it is about 1-3 mm.

  The transparent substrate used in the present invention is provided with a transparent receiving layer on at least one surface thereof. The transparent receiving layer is composed of an aggregate of fine particles mainly composed of at least one selected from titania and alumina, and the average particle diameter of the fine particles is about 10 to 100 nm, and about 10 to 100 nm between the fine particles. Have pores. The thickness of the transparent receiving layer is about 0.05 to 20 μm.

  By providing the transparent receptive layer on the transparent substrate, the adhesion of the conductive paste to the transparent substrate is greatly improved, and the resulting conductive pattern is firmly bonded on the transparent substrate. Has the advantage. And if it is said transparent receiving layer, it will hardly affect the transparency of a base material.

  The method for forming the transparent receiving layer on the transparent substrate may be either a wet process or a dry process, and is not particularly limited, but a wet process is preferable from the viewpoint of productivity and cost. In the wet process, a predetermined raw material may be coated (applied) on a substrate by a known method. Examples of the raw material include tetraalkoxysilane, tetraalkyl titanate, and a hydrolyzate thereof. You may add suitably other components, such as resin and surfactant, to the said raw material as needed. Examples of the coating method include gravure coating, offset coating, comma coating, die coating, slit coating, spray coating, plating method, sol-gel method, LB film method and the like. A sol-gel method is particularly preferable. As the dry process, for example, silicon oxide, titanium oxide or the like may be used as a raw material, and the substrate may be coated by CVD, vapor deposition, sputtering, ion plating, or the like.

Hard coat layer Moreover, you may provide a hard-coat layer in the surface opposite to the surface which has said transparent receiving layer in the transparent base material used by this invention.

  What is necessary is just to form a hard-coat layer using the hard-coat agent of a general material, and if a transparency is not impaired, there will be no restriction | limiting in particular. Of these, ultraviolet curable acrylate resins are preferred. The main component is not particularly limited as long as it is an ultraviolet curable acrylate having two or more functional groups such as polyester acrylate, urethane acrylate, and epoxy acrylate. 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, tetraethylene glycol acrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, neopentyl glycol PO modified diacrylate, EO modified bisphenol A di Bifunctional acrylate such as acrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol hexaacrylate, trimethylolpropane EO modified triacrylate, PO modified glycerin triacrylate, trishydroxyethyl isocyanate Use of polyfunctional acrylates such as nurate triacrylate is preferred.

  In addition, a photopolymerization initiator is usually added to the ultraviolet curable acrylate resin. As a photopolymerization initiator, 1-hydroxycyclohexyl phenyl ketone (Irgacure 184 manufactured by Ciba Specialty Chemicals Co., Ltd.), 2-hydroxy-2-methyl-1-phenyl-propan-1-one, and the like are added. Thus, a sufficient cured film can be obtained. Others, benzoin, benzoin derivative, benzophenone, benzophenone derivative, thioxanthone, thioxanthone derivative, benzyldimethyl ketal, α-aminoalkylphenone, monoacylphosphine oxide, bisacylphosphine oxide, alkylphenylglyoxylate, diethoxyacetophenone, titanocene compound A photopolymerization initiator such as can also be used.

  The blending ratio of these photopolymerization initiators is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the ultraviolet curable acrylate resin. When the amount is less than 1 part by weight, the polymerization does not start sufficiently, and when the amount exceeds 10 parts by weight, the durability is lowered in some cases.

  The ultraviolet curable acrylate resin may contain a third component (UV absorber, filler, etc.) as long as the transparency is not impaired, and there is no limitation on the yield.

  As a method for forming a hard coat layer on a transparent substrate, a known method can be adopted and there is no particular limitation. For example, the hard coat agent may be applied on a transparent substrate using a Mayer bar or the like, dried, and irradiated with ultraviolet rays. The thickness of the hard coat layer after curing is preferably about 0.1 to 20 μm, particularly preferably about 1 to 10 μm.

  By providing a hard coat layer on a transparent substrate, whitening and yellowing due to precipitation of oligomers from the substrate resin can be suppressed during firing, which will be described later, whereby the electromagnetic shielding material of the present invention has high transparency. Is secured. In addition, it is possible to prevent scratches during the manufacturing process of the electromagnetic shielding material.

Conductive layer The conductive layer formed on a transparent substrate can be formed using a conductive paste. In particular, a conductive paste containing particulate silver oxide, tertiary fatty acid silver and a solvent stably exhibits low resistance, and thus is preferably used. The average particle size of the particulate silver oxide is 2 μm or less, and when silver oxide having a particle size larger than this is used, the average particle size is set in the manufacturing process (kneading step, synthesis step, etc.) of the conductive paste. What is necessary is just to be 2 micrometers or less. The average particle size is more preferably 200 to 500 nm.

  The tertiary fatty acid silver salt is a silver salt of a tertiary fatty acid having a total carbon number of 5 to 30, preferably 10 to 30, and can be dissolved or homogeneously dispersed in a dispersion medium used during paste preparation. This tertiary fatty acid silver salt plays the role of a lubricant. When kneading silver oxide and tertiary fatty acid silver salt into a paste, the silver oxide is pulverized to promote micronization and silver oxide. It exists around the grains to suppress reaggregation of silver oxide grains and improve dispersibility. For this reason, it can be made into a paste without adding a binder. Further, this tertiary fatty acid silver salt has a function of precipitating silver during heating and fusing together silver particles produced by reduction from silver oxide.

  Specific examples of such tertiary fatty acid silver salts include silver pivalate, silver neoheptanoate, silver neononanoate, and silver neodecanoate. The production of the tertiary fatty acid silver salt is carried out, for example, by neutralizing the tertiary fatty acid with an alkali compound in water and reacting this with silver nitrate.

  The blending ratio of the particulate silver oxide and the tertiary fatty acid silver salt in the conductive paste is such that the weight ratio (A / B) is when the weight of the silver oxide is A and the weight of the tertiary fatty acid silver salt is B. It is preferable that it is 1 / 4-3 / 1.

  In the conductive paste, a solvent is contained in addition to silver oxide and tertiary fatty acid silver salt. The solvent is not particularly limited as long as it does not react with silver oxide and the tertiary fatty acid silver salt and can disperse them satisfactorily. For example, aromatic hydrocarbons such as toluene, ether esters of ethylene glycol such as triethylene glycol monobutyl ether, ether esters of propylene glycol such as tripropylene glycol normal butyl ether, and organic solvents such as terpineol are used. The usage-amount of a solvent should just be about 1-100 weight part with respect to 100 weight part of particulate silver oxide.

  Further, if necessary, a dispersing agent can be added to disperse the particulate silver oxide well, thereby preventing secondary aggregation of the particulate silver oxide. As the dispersant, a fiber-based polymer such as hydroxypropylcellulose, a water-soluble polymer such as polyvinylpyrrolidone, polyvinyl alcohol, or the like is used. The amount used may be 0 to 20 parts by weight with respect to 100 parts by weight of the particulate silver oxide.

  The conductive paste of the present invention is produced by, for example, a method in which particulate silver oxide, tertiary fatty acid silver salt and a solvent are mixed and then kneaded with a roll mill or the like to form a paste. Since this conductive paste has particulate silver oxide having an average particle diameter of 2 μm or less, it is easy to form metallic silver particles even under relatively low temperature heating conditions and fuse them together to continuously apply metallic silver. It becomes a film or a lump.

  In addition, the conductive paste is prepared to have a viscosity and thixotropy suitable for the formation of the conductive layer, and is provided for the formation of the conductive layer. The viscosity and thixotropic properties can be appropriately selected according to the particle size of the particulate silver oxide, the type of tertiary fatty acid silver salt, the type of solvent, and the like. For example, the viscosity of the conductive paste may be about 10 to 10000 dPa · s, and the thixotropy index may be appropriately selected within the range of about 0.1 to 0.9.

  Examples of such conductive paste include “Doutite XA-9080” and “Doutite XA-9083” manufactured by Fujikura Kasei Co., Ltd.

  Note that these conductive pastes may exhibit volume shrinkage due to heat treatment, and in that case, the mesh-like conductive layer and the transparent resin layer cannot form substantially the same plane, and the mesh-like The conductive layer may not exhibit a sufficiently low resistance value. Therefore, it is preferable not only to perform the conductive paste injection step and the heat treatment step once, but also to repeat at least twice, preferably about 2 to 5 times.

Transparent resin layer As a resin for forming the transparent resin layer, a transparent photosensitive resist used in a general photolithography method is used.

  The photosensitive resist includes a negative type and a positive type. In the negative type, when exposed to ultraviolet rays, only the portion is photocured. The positive type has a light characteristic opposite to that of the negative type, and a portion that receives ultraviolet light undergoes photolysis. If both development processes are performed, the unexposed portion is dissolved and removed in the negative type, and the exposed portion is dissolved and removed in the positive type. Accordingly, a positive mask (black mesh pattern is black) is used for the negative type (exposure original plate), and a negative mask (mesh pattern is transparent) is used for the positive type.

  The resist is not particularly limited, but in general, an acrylic type can be used for a negative type, and a diazo type can be used for a body type. In addition, since the resist is generally in a liquid state, it is applied by a coating method. However, the resist may be in the form of a film in advance like a dry film.

  Here, the transparency in the transparent resin is not particularly limited as long as it is transparent to the extent that it can be used for applications of display units such as PDP and CRT. Usually, the total light transmittance (Tt) measured by JIS K7105 is 70% or more, preferably about 80 to 90%, and the haze value measured by JIS K7105 may be about 0.1 to 5%.

In addition, as mentioned above, when removing a resin layer from the transparent receiving layer surface of a transparent base material finally at a process (f), the photosensitive resist does not need to be transparent.
II. Manufacturing Method of Electromagnetic Shielding Material Next, a manufacturing method of the transparent sheet heating element of the present invention will be described with reference to FIG.
(1) Embodiment 1
In the method for producing an electromagnetic wave shielding material of the present invention, the network-like conductive layer and the transparent resin layer form substantially the same plane on the transparent receiving layer surface of the transparent base material provided with the transparent receiving layer on at least one surface. A method for producing an electromagnetic shielding material provided as described above, wherein (a) a liquid or dry film-like transparent photosensitive resist is applied or pasted to a transparent receiving layer surface of a transparent substrate, and a transparent resin layer is formed. (B) forming a recess corresponding to the shape of the network-like conductive layer in the transparent resin layer by photolithography, (c) injecting a conductive paste into the recess, (D) the step of removing the excess conductive paste, (d) the step of heat-treating the conductive paste to form a mesh-like conductive layer, and (e) the steps (c) and (d) above. Repeating the process more than once And wherein the door.

  These steps will be described with reference to FIG. In this example, first, as shown in FIG. 1 (a), a liquid or dry film photosensitive resist is applied or adhered to the surface of the transparent receiving layer 4 of the transparent substrate 2, and the transparent substrate 2 is coated. The transparent resin layer 1 is formed. In addition, the film thickness of the formed transparent resin layer 1 can be prepared according to the film thickness of the target electromagnetic wave shielding material.

  Next, the transparent resin layer 1 made of the photosensitive resist of FIG. 1A is removed by photolithography, and the shape of the mesh-like conductive layer shown in FIG. A recess having a cross-section corresponding to is formed. The concave portion is formed between the exposed surface of the transparent receiving layer 4 and the transparent resin layer. The photosensitive resist may be either a negative type or a positive type, and is not particularly limited.

  Here, the mesh shape which is the shape of the conductive layer is not only that the opening portion is a right-sided quadrilateral, but also a state where the opening portion obliquely intersects at a certain angle, that is, the opening portion is a rhombus, or 5-10. It includes a polygonal shape of about a square shape, that is, a case where the opening is a 5-10 polygonal shape. In particular, from the viewpoint of electromagnetic wave shielding properties, a mesh-like conductive layer having a uniform line width and a right-angled quadrilateral (particularly square) opening is preferable.

  Next, a conductive paste is applied to the side where the transparent resin layer 1A shown in FIG. 1B is formed, and the conductive paste is injected into the recesses in the cross section (FIG. 1C). Thereafter, excess conductive paste present on the transparent resin layer 1A is removed with a rubber or resin squeegee, and then the conductive paste is heated (for example, 150 to 200 ° C.) to form the conductive layer 3A. To do. Thereby, the transparent resin layer 1A and the net-like conductive layer 3A are formed on the transparent receiving layer surface of the transparent substrate 2 (FIG. 1D). Since the conductive paste may exhibit volume shrinkage due to heat treatment, the conductive paste injection step and the heat treatment step are not only performed once, but may be repeated at least twice, preferably about 2 to 5 times. preferable.

Thus, the electromagnetic wave shielding material of the present invention is produced, in which the network-like conductive layer and the transparent resin layer are provided on at least one surface of the transparent receiving layer of the transparent substrate so as to form substantially the same plane.
(2) Embodiment 2
Another method for producing the electromagnetic wave shielding material of the present invention is a method for producing an electromagnetic wave shielding material having a network-like conductive layer on the transparent receiving layer surface of a transparent substrate provided with a transparent receiving layer on at least one surface. (A) a liquid or dry film photosensitive resist is applied or pasted to the transparent receiving layer surface of a transparent substrate to form a resin layer; (b) a mesh is formed on the resin layer by photolithography. A step of forming a concave portion corresponding to the shape of the conductive layer, (c) a step of injecting a conductive paste into the concave portion and removing excess conductive paste on the transparent resin layer, (d) a conductive paste (E) a step of further repeating the steps (c) and (d) one or more times, and (f) from the transparent receiving layer surface of the transparent substrate. Removing the resin layer. The features.

  In this case, the liquid or dry film photosensitive resist used in the step (a) does not necessarily need to be transparent, and the formed resin layer does not necessarily have to be transparent. This is because it is finally removed in the step (f).

  Steps (b) to (e) are performed in the same manner as steps (b) to (e) in the above (1) Embodiment 1.

  Further, in the step (f), the method for removing the resin layer from the transparent substrate may be a known method such as peeling in an aqueous sodium hydroxide solution or dissolving in an organic solvent such as acetone. it can.

  Thus, the electromagnetic wave shielding material of the present invention having a network-like conductive layer on the transparent receiving layer surface of the transparent substrate provided with the transparent receiving layer on at least one surface is produced.

Since the manufacturing method of the electromagnetic shielding material shown in these Embodiments 1 and 2 can be carried out simply and with good reproducibility, it is suitable for mass production of the electromagnetic shielding material.
III. Features of Electromagnetic Shielding Material The electromagnetic shielding material of the present invention is produced as described above. The electromagnetic wave shielding material of the present invention has a high aperture ratio, for example, 75% or more, particularly about 80 to 95%. Therefore, high transparency is achieved. In the present specification, the aperture ratio means the ratio of the area of the portion not covered with the conductive layer in the total area of the electromagnetic wave shielding region, specifically, the electromagnetic shielding material shown in FIG. In one pattern of the mesh-like conductive layer, when (area B / area A) × 100 (%) or the line width (W) of the pattern and the pattern line interval (pitch) (P), (P−W) ² / P ² × 100 means.

  The line width (W) of the mesh pattern of the conductive part is usually about 10 to 30 μm, preferably about 15 to 20 μm. A geometric pattern having a line width of less than about 10 μm tends to be difficult to produce, and if it exceeds 30 μm, the pattern tends to be noticeable, which is not preferable.

  In addition, the space | interval (pitch) (P) of the line | wire of a mesh shaped pattern can be suitably selected in the range with which said aperture ratio and line width are satisfy | filled. Usually, it may be in the range of about 200 to 400 μm.

  The thickness of the conductive layer (the average height of fine lines in the vertical direction from the surface of the transparent substrate) changes the thickness of the transparent resin layer (that is, the photosensitive resist layer) used in the photolithography method in the manufacturing method. Can be adjusted. For example, it is about 1 μm or more, particularly about 1 to 30 μm.

  In addition, as in the first embodiment, the electromagnetic wave shielding material produced by the steps (a) to (d) has a mesh-like conductive layer and a transparent resin layer that are substantially in the same plane. It has a feature that the adhesiveness is high and bubbles do not easily remain when bonded, and there is an advantage that an electromagnetic wave shielding material excellent in transparency can be obtained (FIG. 1 (d)).

  The electromagnetic shielding material of the present invention has a high electromagnetic shielding effect and is excellent in transparency and transparency. In addition, since the conductive portion is not disconnected and a uniform mesh pattern can be formed, the resistance is low. The surface resistance value of the electromagnetic wave shielding material of the present invention is 5Ω / □ or less, preferably 3Ω / □ or less, more preferably 2Ω / □ or less. When the surface resistance value is too large, it is not preferable in terms of shielding characteristics.

Here, from the following formula, the surface resistance value (or volume resistance value) of the electromagnetic wave shielding material can be designed by arbitrarily setting the line width and pitch of the conductive layer.
R = Rs × (P / W)
Rs = ρv / t
R: Surface resistance value of electromagnetic shielding material (Ω / □)
Rs: Surface resistance value of conductive layer (Ω · cm)
ρv: Volume resistivity of the conductive layer t: Thickness of the conductive layer P: Spacing (pitch) of the network conductive layer
W: Line width of network conductive layer The total light transmittance (JIS K7105) of the electromagnetic wave shielding material of the present invention can achieve a high value of about 72 to 91%. The haze value (measured according to JIS K7105) is as low as about 0.5 to 6%.

  In the electromagnetic wave shielding material of the present invention, a protective film may be laminated on a mesh-like conductive layer. As the protective film, commonly used known resins are used. These resins are laminated by a known method such as dry lamination or wet lamination.

  The electromagnetic wave shielding material of the present invention may be further laminated with a functional film or the like. The functional film includes an antireflection film provided with an antireflection layer for preventing light reflection on the film surface, a colored film colored by coloring or additives, a near infrared shielding film that absorbs or reflects near infrared rays, and a fingerprint. An antifouling film that prevents the contaminants from adhering to the surface.

  The electromagnetic shielding material of the present invention has a high electromagnetic shielding effect and is excellent in transparency and transparency. Therefore, even an electromagnetic wave shield front plate applied to a display having a large display area can be easily manufactured. Therefore, it is useful as an electromagnetic wave shielding filter used for a display having a large display screen such as a plasma display panel (PDP) in addition to a cathode ray tube (CRT).

  The method for producing an electromagnetic wave shielding material of the present invention is characterized by using a transparent base material provided with a transparent receiving layer, whereby a conductive pattern and a transparent base material are firmly bonded to form a high-quality electromagnetic shielding material. Can be manufactured.

  According to the production method of the present invention, the number of steps is small, simple and advantageous in terms of cost, and mass production and continuous productivity of the electromagnetic shielding material are high.

  In addition, the electromagnetic shielding material of the present invention produced by the above production method exhibits a high electromagnetic wave shielding effect with a low resistance value because a homogeneous conductive pattern is formed on the transparent receiving layer surface, and has a high aperture ratio and fluoroscopy. Sex is secured.

  Therefore, it is particularly useful as an electromagnetic wave shielding filter used for a display having a large display screen such as a cathode ray tube (CRT), a plasma display panel (PDP) or the like.

  Next, the present invention will be described in more detail by way of examples together with comparative examples.

The electromagnetic wave shielding effect, total light transmittance, haze value, sheet resistance, line width, aperture ratio, and line thickness shown in Examples and Comparative Examples were measured by the following measuring methods.
1. Electromagnetic wave shielding effect It measured with the measuring apparatus in the Kansai electronics industry promotion center method (generally called KEC method).
2. Total light transmittance Measured with a turbidimeter NDH-20D type (manufactured by Nippon Denshoku Industries Co., Ltd.) according to JIS K7105.
3. Haze value According to JIS K7105, it measured with the turbidimeter NDH-20D type (made by Nippon Denshoku Industries Co., Ltd.).
4). Sheet resistance was measured using Loresta EP (Dia Instruments).
5). Line width Measured using an optical microscope.
6). Aperture ratio The aperture ratio is obtained by measuring the line width and the line interval of one mesh pattern of the electromagnetic wave shielding material using an optical microscope, calculating the area A and the area B shown in FIG. It was calculated by fitting.

Opening ratio (%) = (area B / area A) × 100 (%)
Alternatively, it can be calculated by setting the line width (W) of the pattern and the interval (pitch) (P) of the line of the pattern and applying this to the following equation.

Opening ratio (%) = (P−W) ² / P ² × 100 (%)
7). Line thickness It measured using the surface roughness meter.

As a transparent substrate having a transparent receiving layer on at least one surface, a polyethylene terephthalate film having a transparent receiving layer (layer thickness: 20 μm) of alumina film (thickness including a transparent receiving layer is 120 μm, manufactured by Pictorico, trade name “ TPX ") was used. On the side of the transparent substrate opposite to the transparent receiving layer, an ultraviolet curable acrylate hard coat agent (manufactured by Dainippon Paint Co., Ltd., trade name “UV clear” solid content concentration 50% by weight) is applied. After coating with a Meyer bar so as to be 2 μm and drying at 80 ° C. for 2 minutes, ultraviolet rays were irradiated at an irradiation amount of 300 mJ / cm ² to form a hard coat layer on the transparent substrate.

Photosensitive resist PMER-N HC600Y (manufactured by Tokyo Ohka Kogyo Co., Ltd.) was coated on the surface opposite to the hard coat layer of the film with a bar coater, dried at 80 ° C. for 10 minutes, and then a glass mask (line width 17 μm, pitch 200 μm). the grid pattern) through and exposed to ultraviolet rays irradiation dose 60 mJ / cm ^2, through development, water washing and drying, the film thickness on the transparent base material to form a transparent resin layer of 13 .mu.m.

  As the conductive paste, conductive paste Doutite XA-9080 (manufactured by Fujikura Kasei Co., Ltd.) was used.

  After injecting the conductive paste and removing the excess, the conductive paste was baked at 170 ° C. together with the film. This was repeated three times (one-second firing for 30 seconds each and third firing for 30 minutes) to form a conductive layer depicting a lattice pattern, and an electromagnetic shielding material was produced.

  The grid pattern of the conductive layer of the obtained electromagnetic wave shielding material had a line width of 19.9 μm, a pitch of 200 μm, and an aperture ratio of 81.1%.

  In Example 1, a single-sided easily-adhesive polyethylene naphthalate film (thickness including a transparent receiving layer 100 μm, manufactured by Teijin Ltd., trade name “Q65”) is used as a transparent substrate having a transparent receiving layer provided on at least one surface. The procedure was the same as in Example 1 except that.

  The grid pattern of the conductive layer of the obtained electromagnetic wave shielding material had a line width of 22 μm, a pitch of 200 μm, and an aperture ratio of 79%.

  The electromagnetic wave shielding material obtained in Example 2 was treated with a 5% aqueous sodium hydroxide solution at 40 ° C. to peel off the photosensitive resist to obtain an electromagnetic wave shielding material.

  The grid pattern of the conductive layer of the obtained electromagnetic wave shielding material had a line width of 22 μm, a pitch of 200 μm, and an aperture ratio of 79.2%.

Comparative Example 1

  In Example 3, it carried out similarly to Example 3 except having used the polyethylene terephthalate film (Thickness 100 micrometer, the Toray company make, brand name "T60") as a transparent base material in which the transparent receiving layer is not provided. .

  However, due to poor adhesion between the electrical conductivity and the transparent substrate, a part of the lattice pattern was missing when the photosensitive resist was peeled off. As a result, an electromagnetic shielding material could not be obtained, and the subsequent measurement work could not be performed.

Comparative Example 2

  In Example 3, it carried out similarly to Example 3 except having used the conductive paste DW-117H-42 (made by Toyobo Co., Ltd.) containing the resin binder as the conductive paste.

  The grid pattern of the conductive layer of the obtained electromagnetic wave shielding material had a line width of 20 μm, a pitch of 200 μm, and an aperture ratio of 81%.

It is sectional drawing which showed typically the manufacturing method of the electromagnetic wave shielding material of this invention. It is the figure which showed typically the measuring method of an aperture ratio.

Claims (9)

The transparent receiving layer surface of at least a transparent substrate transparent receiving layer provided on one surface, the manufacture of reticulated electromagnetic shielding material conductive layer and the transparent resin layer and is provided so as to form a same plane A method,
The transparent receiving layer comprises an aggregate of fine particles mainly comprising at least one selected from titania and alumina;
A production method comprising the following steps (a) to (e):
(A) a step of applying or sticking a liquid or dry film-like transparent photosensitive resist to a transparent receiving layer surface of a transparent substrate to form a transparent resin layer;
(B) a step of forming a recess corresponding to the shape of the mesh-like conductive layer in the transparent resin layer by a photolithography method;
(C) A step of injecting a conductive paste into the concave portion to remove excess conductive paste on the transparent resin layer;
(D) a step of heat-treating the conductive paste to form a mesh-like conductive layer, and (e) a step of repeating the steps (c) and (d) one or more times. A method for producing an electromagnetic wave shielding material having a network-like conductive layer on the transparent receiving layer surface of a transparent substrate provided with a transparent receiving layer on at least one surface,
The transparent receiving layer comprises an aggregate of fine particles mainly comprising at least one selected from titania and alumina;
A production method comprising the following steps (a) to (f):
(A) a step of applying or sticking a liquid or dry film-like photosensitive resist to the transparent receiving layer surface of a transparent substrate to form a resin layer;
(B) forming a recess corresponding to the shape of the network-like conductive layer in the resin layer by a photolithography method;
(C) A step of injecting a conductive paste into the concave portion to remove excess conductive paste on the transparent resin layer;
(D) a step of heat-treating the conductive paste to form a network-like conductive layer;
(E) a step of repeating the steps (c) and (d) one or more times, and (f) a step of removing the resin layer from the transparent receiving layer surface of the transparent substrate. The average particle diameter of the fine particles is 10 to 100 N m, have pores of 10 to 100 N m between the microparticles, to claim 1 or 2 thickness of the transparent receptive layer is 0.05～20Myu m The manufacturing method as described. The conductive paste is a particulate silver oxide having an average particle size of 2 μm or less, a silver salt of a tertiary fatty acid having a total carbon number of 5 to 30, an aromatic hydrocarbon, an ether ester of ethylene glycol, an ether ester of propylene glycol The production method according to any one of claims 1 to 3, which is a conductive paste containing a solvent mainly comprising at least one selected from the group consisting of terpineol and terpineol. The manufacturing method according to any one of claims 1 to 4, wherein the transparent substrate has a hard coat layer on the surface opposite to the surface having the transparent receiving layer. The electromagnetic wave shielding material manufactured by the manufacturing method in any one of Claims 1-5. The line width of the mesh-shaped conductive layer is 10~30μ m, electromagnetic wave shielding material according to claim 6 opening ratio is 80 to 95%. The electromagnetic shielding material according to claim 7 , wherein the total light transmittance is 72 to 91%, the haze value is 0.5 to 6%, and the surface resistance value is 5Ω / □ or less. Electromagnetic shielding material. The electromagnetic wave shielding filter for plasma displays containing the electromagnetic shielding material of Claim 6, 7 or 8 .

Images