JP2004031876A - Transparent electromagnetic wave shield member and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent electromagnetic wave shield member with the compatibility between an excellent electromagnetic wave shield effect and transparency and to provide a manufacturing method thereof. <P>SOLUTION: The manufacturing method includes the steps of providing a photosensitive resist layer to one side of a transparent substrate; removing a photosensitive resist layer of a part on which a conductive pattern is to be formed through exposure / development by using a mesh mask with the photolithograph method to form a pattern with a concaved cross section; coating conductive ink to the entire pattern to fill the concaved cross section with the conductive ink; removing a remaining projection photosensitive resist layer to obtain the mesh conductive pattern; and baking the conductive pattern. The transparent electromagnetic wave shield member employs the mesh conductive pattern with dimensions within a range of 5 to 30μm in the line width, 0.5 to 5.0μm in the average film thickness, and 72 to 95% in the aperture rate, and has an electromagnetic wave shield effect of 40 dB or over against electromagnetic waves with 10 to 200MHz or over. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
In particular, the present invention is installed on the front of a plasma display panel (hereinafter referred to as a PDP) to effectively shield electromagnetic waves emitted from a display screen, and to transmit light with excellent display transparency on the display screen. TECHNICAL FIELD The present invention relates to a conductive electromagnetic wave shielding member and a method for manufacturing the same.
[0002]
[Prior art]
A PDP using discharge development has a discharge gap of 0.1 to 0.3 mm, which is (1) self-luminous, using discharge light, compared to a liquid crystal display (LCI) or a cathode ray tube (CRT). In recent years, OA such as TV, PC, word processor, etc. has various advantages such as (3) color emission using phosphors, (4) easy to make large screen panel. Research and development and commercialization of display panels for equipment, transportation equipment, signboards, and other display boards have been promoted.
[0003]
The basic display mechanism of a PDP is to display characters and graphics by selectively discharging and emitting phosphors in a large number of discharge cells separated between two glass plates.
Unnecessary electromagnetic wave radiation is large from the front surface of the PDP, and an electromagnetic wave having a frequency of about several kHz to several GHz is generated by voltage application, discharge, and light emission. In order to improve display contrast, it is necessary to prevent reflection of external light on the front surface.
[0004]
For this reason, conventionally, in order to shield electromagnetic waves and the like from the PDP, a type in which a transparent plate with an electromagnetic wave shielding layer is provided on the front surface of the PDP has been known. For example, (1) a mesh made of fibers mixed with a highly conductive metal filament, and (2) a transparent substrate in which fibers of a conductive material such as stainless steel or tungsten are embedded (Japanese Patent Application Laid-Open Nos. Hei 3-35284 and Hei 5-35). (JP-A-269912, JP-A-5-327274), (3) a transparent substrate having a metal or metal oxide deposited film formed on the surface thereof (JP-A-1-278800, JP-A-5-323101), etc. Is mentioned.
[0005]
However, when the mesh (1) is used, there is a problem that the display screen becomes dark and the contrast and the resolution are reduced. Further, since the transparent member of (2) has fibers embedded therein, the manufacturing method is complicated and the cost is high. In addition, the display screen is dark and the contrast and resolution are reduced. . Further, in the case of (3), if the deposited film is made thin enough to maintain a sufficient translucency, the surface resistance of the film is reduced and the attenuation characteristics of electromagnetic waves are reduced. There is a problem that it cannot be compatible with the shielding effect.
[0006]
As a member that covers a display screen of a CRT or the like and shields electromagnetic waves, in addition to the above examples, for example, an ink obtained by mixing highly conductive metal powder on the surface of a transparent substrate is grid-like or striped by screen printing. Printed and formed in the shape of a pattern (Japanese Patent Application Laid-Open Nos. 62-57297 and 9-283977) and a network-like pattern made of conductive ink by screen printing and then vacuum forming A baked product (Japanese Unexamined Patent Publication No. 2-52499) or an ink obtained by mixing a metal powder with an ultraviolet-curable epoxy acrylate resin is used. A material cured by irradiation (Japanese Patent Publication No. 2-48159) is known, but even if these members are used, a sufficient electromagnetic wave It is impossible to achieve both de effect and translucent.
[0007]
In other words, in order to achieve both excellent electromagnetic wave shielding effect and translucency, it is necessary to optimize the line width of the pattern and the gap (pitch) of the pattern and further reduce the electrical resistance of the pattern. It is considered that no consideration is given to any of the techniques described in each of the above publications, and that the consideration for the pattern creation method is also insufficient. For example, in order to obtain sufficient translucency, it is preferable to make the line width of the pattern extremely thin and to increase the interval between them, but in this case, the electromagnetic wave shielding effect becomes insufficient. The electromagnetic wave shielding effect is represented by the decibel (dB) of the attenuation, which is the logarithm of the ratio of the energy transmitted through the shielding material to the incident electromagnetic wave. It is said that the greater the attenuation, the better the shielding effect.
[0008]
Further, in the case of the screen printing method, it is difficult to form a pattern having a small line width, and problems such as variations in the line width of the pattern and occurrence of a large number of portions where the pattern is interrupted are likely to occur. In particular, it is difficult to form a pattern with an extremely thin line width of several tens μm or less. Also in the above-mentioned Japanese Patent Publication No. 2-48159, since the line width of the pattern is 100 μm in the embodiment, it is also assumed that printing is performed by a conventional method such as a screen printing method. It is presumed that it is difficult to form a pattern with an extremely thin line width of several tens of μm or less. As described above, there are problems that the line width of the pattern varies and that a large number of portions where the pattern is interrupted occur. is there.
[0009]
JP-A-3-35284 describes that a metal thin film is formed on a surface of a transparent plastic substrate by vapor deposition and the like and then patterned by a chemical etching process. JP-A-10-41682 discloses that There is a description that a geometric pattern made of a metal thin film is also provided on the surface of a transparent substrate by a chemical etching process. Similarly, Japanese Patent Application Laid-Open No. 10-163673 discloses that a transparent resin film containing a plating catalyst is formed on the surface of a transparent substrate, and a metal thin film such as copper is formed thereon by electroless plating. There is a statement that patterning is performed by a process.
[0010]
[Problems to be solved by the invention]
According to these methods, a very fine pattern can be formed with high accuracy, and the strict electromagnetic wave shielding performance particularly required for PDP applications can be achieved. However, in these chemical etching processes, it is necessary to use a photolithographic method in order to form a fine pattern, and the yield and manufacturing cost are extremely high in the process of the process, which is disadvantageous in cost. Under such circumstances, it is an object of the present invention to provide a light-transmitting electromagnetic wave shielding member that achieves both an excellent electromagnetic wave shielding effect and a light-transmitting property while minimizing manufacturing costs and a method of manufacturing the same.
[0011]
[Means for Solving the Problems]
The present inventors have conducted various studies in order to solve the above-mentioned problems, and as a result, have completed the present invention in which a fine line of a conductive pattern is formed using a photolithographic method.
That is, the method for producing a light-transmitting electromagnetic wave shielding member according to claim 1 of the present invention includes a step of providing a photosensitive resist layer on one surface of a sheet-shaped or plate-shaped transparent base material, and a mesh-like pattern formed by photolithography. Exposing and developing using a mask to remove a portion of the photosensitive resist layer where a conductive pattern is to be formed, thereby forming a concave cross-sectional pattern; and applying a conductive ink over the entire pattern to form a concave cross-sectional pattern. Filling the pattern with conductive ink, removing the remaining convex photosensitive resist layer together with the conductive ink applied on the upper surface thereof to obtain a mesh-shaped conductive pattern, and baking the conductive pattern. And a process.
[0012]
The method for manufacturing a light-transmitting electromagnetic wave shielding member according to claim 2 of the present invention is characterized in that a heat treatment is performed at a temperature of 100 to 130 ° C. after the step of filling the conductive ink into the concave pattern in cross section. .
[0013]
According to a third aspect of the present invention, there is provided a method for manufacturing a light-transmitting electromagnetic wave shielding member, comprising silver as a conductive material constituting a conductive pattern obtained by the manufacturing method according to the first or second aspect. Features.
[0014]
In the light-transmitting electromagnetic wave shielding member according to the fourth aspect of the present invention, the conductive pattern has a line width of 5 to 30 μm, an average film thickness of 0.5 to 5.0 μm, and an aperture ratio of 72 to 95%. And has an electromagnetic wave shielding effect of 40 dB or more with respect to an electromagnetic wave of 10 to 200 MHz.
[0015]
As an effect of the present invention, the formation of a concave cross-sectional pattern by a photolithographic method using a mesh-like mask and the application and filling of the conductive ink into the cross-sectional concave pattern, and the shrinkage hardening by heat treatment of the filled ink, etc. A conductive pattern having a line width smaller than that of the prepared mesh-shaped mask and having a thickness filled with metal particles at a high density can be easily formed. Therefore, problems such as variations in the conductive pattern and breakage of the pattern are solved, and a translucent electromagnetic wave shielding member having both excellent electromagnetic wave shielding effect and light transmissivity can be obtained.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a partial plan view of a transparent electromagnetic wave shielding member of the present invention in which a conductive pattern is formed in a square mesh on one surface of a transparent substrate. 2A to 2E are cross-sectional views schematically showing a manufacturing process of the present invention for forming a conductive pattern on one surface of a transparent substrate. Here, the photolithographic method used in the present invention is a photographic image forming technology in which a resist (film of a photosensitive polymer material) applied to a substrate surface is exposed and developed using a mask to form a photoresist image. It is.
[0017]
First, FIG. 2A shows that after a photosensitive resist layer 2 having a predetermined thickness is provided on one surface of a sheet-shaped or plate-shaped transparent substrate 1, a mesh-shaped mask is brought into close contact with the photosensitive resist layer 2 and exposed by a photolithographic method. This shows a state in which a pattern 3 having a concave cross section in which a photosensitive resist layer is removed from a portion where a conductive pattern is to be formed by development (liquid treatment).
[0018]
Here, examples of the plate-shaped transparent base material 1 include glass base materials such as soda lime glass, non-alkali glass, quartz glass, low alkali glass, and low expansion glass having sufficient translucency to visible light. . From the viewpoint of maintaining the translucency of the electromagnetic wave shielding member, the thinner the better, the better. Usually, the thickness is appropriately set in the range of 0.05 to 5 mm depending on the form at the time of use and the required mechanical strength.
The photosensitive resist layer 2 provided on one surface of the transparent substrate can be selected from known negative or positive wet resists, dry resists, and lift-off photoresists.
[0019]
Here, the negative type hardly dissolves in the developing solution due to the light irradiation by exposure, and the positive type easily conversely dissolves in the developer, and can be selectively used depending on the application by utilizing its characteristics. In the case of using a mask in which a mesh is opened by using a negative resist in FIG. 2A, the resist layer portion of the mesh irradiated with light by exposure is hardly dissolved in a developing solution and remains as a convex shape by development. The resist layer in the portion of the mesh frame that has not been irradiated with light is removed with a developing solution to form a pattern of grooves 3 having a concave cross section. Note that the thickness of the photosensitive resist layer 2 is set to 10 to 10 in consideration of the fact that the conductive ink 4 to the pattern of the concave groove 3 in a later step contracts due to solvent evaporation due to heat treatment and the thickness of the conductive pattern decreases. It is preferably 30 μm, particularly preferably 15 to 25 μm.
[0020]
The mask for forming the pattern of the concave groove 3 in the photosensitive resist layer 2 by the photolithographic method is not particularly limited as long as it is a mesh shape, and is arbitrary. The remaining convex resist layer portion surrounded by the pattern of the cross-sectional concave grooves 3 is a mesh, and the opposite side can be seen through the transparent base material 1 to ensure transparency in this portion. Examples of the shape of the mesh pattern include a circular pattern, a rhombic pattern, a regular hexagonal pattern, and a geometric pattern such as a brick-like arrangement with a rectangular mesh. Further, in order to prevent moire fringes (interference fringes) from being generated in the image in relation to the dot pitch of the display screen in a square lattice pattern and a mesh pattern, a pattern having a bias of 15 degrees is preferably employed. .
[0021]
FIG. 2B shows that the conductive ink 4 is applied to the entire surface including the pattern of the concave groove 3 and the convex resist layer portion 2 ′ formed by the photolithographic method, and particularly the concave groove 3 is formed. 3 shows a state where the conductive ink 4 is filled in the pattern 3. Here, as the method for applying the conductive ink 4, a contact coating method using a squeegee, a printing coating method using a screen, a roll coater, a bar coater, a spin coater, or the like can be suitably used. Considering the amount of ink used and the filling of the ink, the contact coating method using a squeegee is more preferable.
[0022]
The composition of the conductive ink 4 includes a solvent, a dispersion stabilizer (binder), and metal particles having high conductivity. Silver, gold, copper, aluminum, or the like can be used as the metal particles having high conductivity. Particularly, in the present invention, silver having an average particle diameter of 5 to 20 nm can be suitably used in consideration of conductivity and cost. The conductivity of the electromagnetic wave shield is not determined only by the volume specific resistance of the metal itself, but the state in which the metal particles are densely filled inside the conductive metal pattern makes the electromagnetic wave shielding effect after firing even better. From the viewpoint that the concentration is higher, the higher the concentration, the better.
[0023]
FIG. 2C shows a state in which after the conductive ink 4 is filled in the pattern of the concave grooves 3 in a cross section, the heat treatment is performed to reduce the thickness of the ink due to the evaporation of the solvent of the conductive ink. Here, the conductive ink 4 filled in the pattern of the concave grooves 3 is cured by heat treatment at 100 to 130 ° C. for 10 to 30 minutes, so that the solvent component of the conductive ink evaporates and the thickness of the conductive ink decreases. As a result, the metal particles are filled at a high density, and the convex resist layer 2 ′ located on the side surface of the pattern of the concave groove 3 is exposed, so that the peeling liquid can penetrate.
[0024]
During the heat treatment at 100 to 130 ° C., it is preferable to gradually increase the temperature from 60 ° C. over 5 to 15 minutes in order to prevent disconnection of the conductive metal pattern due to foaming of the conductive ink 4. The conductive ink 4 filled in the pattern of the concave grooves 3 increases the mechanical strength of the conductive pattern due to the densification of the metal particles and the fixation to the transparent base material by the binder, and the peeling of the pattern by spraying the peeling liquid. The disconnection resulting from is suppressed.
[0025]
FIG. 2 (d) shows that the remaining convex photosensitive resist layer 2 ′ is removed by a stripping solution together with the conductive ink 4 applied on the upper surface thereof, thereby forming a network-like conductive material having a high density of metal particles. This shows a state where a pattern 4 'is obtained. Here, the convex resist layer 2 'remaining in FIG. 2 (c) is exposed on the side surface, so that the peeling liquid permeates and is easily removed together with the conductive ink 4 applied on the upper surface thereof. As a result, the transparent substrate 1 is exposed, and the transparency at this portion is ensured. Acetone, ketones, alcohols and the like can be suitably used as the stripping solution.
[0026]
After removing the convex resist layer 2 ', a baking treatment is performed to impart conductivity to the conductive pattern 4' provided on the transparent substrate surface. This baking treatment is performed at a temperature of 150 to 270 ° C., preferably 180 to 250 ° C. for 10 to 30 minutes, so that the line width is 10 to 30 μm, the film thickness is 0.5 to 5.0 μm, and the aperture ratio is 80% or more. The transparent electromagnetic wave shielding member of (1) is obtained. The translucent electromagnetic wave shielding member obtained in this manner is cut out into a 100 × 100 mm square by the electromagnetic wave shielding advantest method, and is installed so that the cell made of the aluminum plate can be grounded. Can be confirmed by measuring the attenuation rate (dB) of electromagnetic waves in the frequency range of 10 to 1000 MHz.
[0027]
FIG. 2 (e) shows that the anti-reflection film 5 with an adhesive coated with a near-infrared ray blocking member on the surface of the obtained translucent electromagnetic wave shielding member on which the conductive metal pattern 4 'is not formed is adhered by a roll. A state in which a front panel for PDP is obtained by attaching an anti-reflection film 6 with an adhesive to a surface on which the other conductive metal pattern is formed by a roll. The PDP front panel thus obtained has a shielding effect of at least 40 dB with respect to electromagnetic waves of 10 to 200 MHz.
[0028]
【Example】
Hereinafter, examples of the present invention will be described.
[0029]
Example 1
As a transparent base material, Nichigo Morton resist (NIT215) is laminated on a surface-cleaned 42-inch (980 mm x 580 mm x 2.5 mm) soda lime glass using a dry rifle laminator under the manufacturer's recommended conditions. A mask having a square grid pattern network having a line width of 18 to 20 μm and a pitch of 200 μm with a bias applied by 15 degrees is brought into close contact with a vacuum, exposed by a Fresnel lens type high pressure mercury lamp exposure apparatus, and developed to form a grid resist pattern. did. A conductive ink (aqueous silver nano-dispersion having an average particle diameter of 5 to 20 nm, solid content of 34 wt%) was applied thereon by contact coating with a squeegee, and the conductive ink was filled in the grooves of the square lattice pattern. Heated for minutes. Subsequently, the remaining resist and the conductive ink applied on the resist were removed in acetone.
[0030]
Next, a baking treatment was performed at 200 ° C. for 30 minutes to obtain a translucent electromagnetic wave shielding member having a conductive metal pattern having a line width of 15 to 19 μm, an average film thickness of 0.6 μm, and an aperture ratio of about 85%. An anti-reflection film 5 with an adhesive coated with a near-infrared blocking member is adhered by a roll to the surface of the translucent electromagnetic wave shield member on which the conductive metal pattern is not formed, and another conductive metal pattern is formed. A front panel for PDP was obtained by bonding an anti-reflection film 4 with an adhesive on a roll by a roll. This PDP front panel has an electromagnetic wave shielding effect of 50 dB or more with respect to an electromagnetic wave having a frequency emission of 10 to 200 MHz, and has an average transmittance of 70% or more in a pure range of visible light having a wavelength of 400 to 700 nm over the entire wavelength range. And the transmittance at a wavelength of 850 to 1000 nm was 10% or less.
[0031]
Example 2
As a transparent substrate, wet-resist of Tokyo Ohka Co., Ltd. was applied to a 42-inch (980 mm x 580 mm x 2.5 mm) soda lime glass whose surface was cleaned using a spin coater under the manufacturer's recommended conditions, and the film thickness of the resist was 15 µm. A mask having a square grid pattern with a line width of 18 to 20 μm and a pitch of 200 μm with a bias applied by 15 degrees is brought into close contact with a vacuum, exposed by a Fresnel lens type high-pressure mercury lamp exposure apparatus, and developed. A lattice resist pattern was formed. A conductive ink (aqueous silver nano-dispersion liquid having an average particle diameter of 5 to 20 nm, solid content of 34 wt%) is applied thereon by contact coating with a squeegee, and the grooves of the square lattice pattern are filled with the conductive ink. Heated for minutes. Subsequently, the remaining resist and the conductive ink applied on the resist were removed in acetone. Next, firing was performed at 200 ° C. for 30 minutes to obtain a conductive metal pattern having a line width of 15 to 19 μm, an average film thickness of 0.6 μm, and an aperture ratio of about 85%. The front panel for PDP formed in the same manner as in Example 1 has an electromagnetic wave shielding effect of 50 dB or more against electromagnetic waves with a frequency emission of 10 to 200 MHz, and has an average wavelength over a pure wavelength range of 400 to 700 nm over the entire visible light wavelength range. The transmittance was 70% or more, and the transmittance at a wavelength of 850 to 1000 nm was 10% or less.
[0032]
Comparative Example 1
Using the same transparent base material as in Example 2, a surface-washed 42-inch (980 mm x 580 mm x 2.5 mm) soda-lime glass was coated with a wet resist from Tokyo Ohka Co., Ltd. using a spin coater under the manufacturer's recommended conditions. The resist is coated so as to have a film thickness of 5 μm, and a mask having a square lattice pattern with a line width of 18 to 20 μm and a pitch of 200 μm with a bias of 15 degrees is brought into close contact with a vacuum, and exposed with a Fresnel lens type high pressure mercury lamp exposure apparatus. The pattern was developed to form a lattice resist pattern. A conductive ink (aqueous silver nano-dispersion liquid having an average particle diameter of 5 to 20 nm, solid content of 34 wt%) is applied thereon by contact coating with a squeegee, and the grooves of the square lattice pattern are filled with the conductive ink. Heated for minutes. Subsequently, the remaining resist and the conductive ink applied on the resist were removed in acetone. Next, a baking treatment was performed at 200 ° C. for 30 minutes to obtain a conductive metal pattern having a line width of 15 to 19 μm, an average film thickness of 0.15 μm or less, and an aperture ratio of about 85%. It was found that the PDP front panel formed in the same manner as in Example 1 had an electromagnetic wave shielding effect of about 20 dB against electromagnetic waves having a frequency of 10 to 200 MHz, which was insufficient.
[0033]
【The invention's effect】
According to the method for manufacturing a light-transmitting electromagnetic wave shielding member of the present invention, the number of steps can be simplified as compared with the chemical etching process, and distortion of the mesh such as when a metal-plated mesh is attached to a substrate by hot press fusion is reduced. Does not crack.
In particular, by forming a concave cross-sectional pattern by photolithographic method, applying and filling conductive ink to the cross-sectional concave pattern, and further contracting and curing by heat treatment of the filled ink, with a line width smaller than the line width of the mesh mask prepared first. In addition, a conductive pattern having a sufficiently high concentration film thickness can be easily formed. Therefore, problems such as variations in the conductive pattern and breakage of the pattern are solved, and a translucent electromagnetic wave shielding member having both excellent electromagnetic wave shielding effect and light transmissivity can be obtained.
Further, by using silver having an average particle diameter of 5 to 20 nm for the conductive ink, the firing range is suppressed to 250 ° C. or less, and a metal plating net has a sufficient electromagnetic wave shielding effect and has a very narrow line width of several tens μm or less. Since a pattern can be formed, a high visible light transmittance can be obtained.
[Brief description of the drawings]
FIG. 1 is a partial plan view showing a translucent electromagnetic wave shielding member of the present invention.
FIG. 2 is a cross-sectional view schematically showing a manufacturing process of the electromagnetic wave shielding member of the present invention.
(A) A state in which the photosensitive resist layer in the portion where the conductive pattern is to be formed by photolithography has been removed to form a pattern of concave grooves in cross section.
(B) A state in which the conductive ink is applied to the entire surface including the pattern of the concave grooves in cross section.
(C) A state in which the thickness of the ink is reduced by heat treatment and the solvent of the conductive ink is evaporated.
(D) A state in which the convex photosensitive resist layer is removed to obtain a mesh-shaped conductive pattern in which metal particles are densified.
(E) A state in which a front panel for PDP using a translucent electromagnetic wave shielding member is obtained.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 transparent substrate 2 photosensitive resist layer 2 ′ convex photosensitive resist layer 3 concave groove pattern 4 conductive ink 4 ′ mesh conductive pattern 5 anti-reflection with adhesive coated with near infrared blocking member ( AR) Film 6 Anti-reflection film with adhesive (NIR)

Claims (4)

A step of providing a photosensitive resist layer on one surface of a sheet-shaped or plate-shaped transparent substrate, and exposing and developing a photosensitive resist layer by photolithography using a mesh-shaped mask to form a portion of the photosensitive resist layer where a conductive pattern is to be formed. A step of forming a pattern having a concave cross section by removing, and a step of filling the conductive ink into a pattern having a concave cross section by applying a conductive ink on the entire surface of the pattern; A method for producing a light-transmitting electromagnetic wave shielding member, comprising: a step of obtaining a mesh-like conductive pattern by removing the conductive pattern together with the conductive ink applied on the upper surface; and a step of firing the conductive pattern. 2. The method according to claim 1, wherein a heat treatment is performed at a temperature of 100 to 130 [deg.] C. after the step of filling the conductive ink into the pattern having a concave cross section. The method according to claim 1 or 2, wherein the conductive material forming the mesh-shaped conductive pattern contains silver. The mesh-shaped conductive pattern has a line width of 5 to 30 μm, an average film thickness of 0.5 to 5.0 μm, an aperture ratio of 72 to 95%, and an electromagnetic wave shield of 40 dB or more with respect to an electromagnetic wave of 10 to 200 MHz. The translucent electromagnetic wave shielding member obtained in any one of claims 1 to 3, which has an effect.

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