KR20000017060A - Electromagnetic wave filter - Google Patents

Abstract

PURPOSE: An electromagnetic wave filter is provided to intercept the same infrared rays as lights used in a remote controller and electromagnetic waves outputted from a front plane of a plasma display panel while maintaining an endurance sufficient to a real use and a high visible ray transmissivity. CONSTITUTION: The electromagnetic wave filter for a plasma display panel comprises an electromagnetic wave intercepting plate and a protective film. The electromagnetic wave intercepting plate has a transparent substrate at one side of the plate, and an electromagnetic wave intercepting film is coated on the transparent substrate. The protective film is formed on the intercepting film so as to cover a surface of the electromagnetic wave intercepting film. The electromagnetic intercepting film has a nine-layer structure which is formed by sequentially depositing a dielectric layer and a silver base layer on the transparent substrate. The dielectric layer has a reflectivity of 1.7 to 2.7 in a wavelength 550 nm. The electromagnetic wave intercepting film has a sheet resistance below 2 ohm and a transparent rate of a far infrared ray below 15% in a wavelength of 850nm.

Description

Electromagnetic wave filter

The present invention relates to an electromagnetic wave filter suitably used in front of a plasma display panel to remove electromagnetic waves generated by plasma discharge. In particular, the present invention relates to an electromagnetic wave filter that has high visible light transmission and low near infrared transmission as well as the performance required for blocking electromagnetic waves and has sufficient durability in practical use. Electromagnetic filters can also be used to remove electromagnetic waves emitted from cathode ray tubes (CRTs) or field emission displays (FEDs).

A known transparent electromagnetic wave filter in the visible light region including a transparent plate such as a glass plate and an electromagnetic wave shielding film formed on a main surface includes an electromagnetic wave filter having a multilayer film and a transparent substrate formed thereon by alternately depositing a dielectric layer and a metal layer. The electromagnetic wave shielding film used for this purpose is a film obtained by depositing on a conductive material (having a low sheet resistance) to protect from electromagnetic waves. Multilayer films including thin dielectric layers such as transparent metal oxides and thin silver layers are known as conductor films having high visible light transmittance and low resistance.

JP-A-5-42624 (the term " JP-A " as used herein means Japanese Patent Application Laid-Open) has a glass plate coated with a heat ray shield having a structure including a silver layer sandwiched between dielectric layers. Is disclosed. In the blocking film, the dielectric layer protecting the silver layer has a multilayer structure composed of two or more layers including a zinc oxide layer and a tin oxide layer. A description has been given of the effect that a heat ray shield can be applied to an electronic component or window as an electromagnetic wave shield.

JP-A-9-85893 discloses a glass plate coated with a multilayer film composed of a silver layer containing at least 0.3 atomic% palladium as the metal layer and a zinc oxide layer containing a metal such as aluminum as the dielectric layer. The effect of the addition of metal to the zinc oxide layer to reduce the internal stress to improve the adhesion to the silver layer is disclosed. The film is composed of a five-layer structure (containing two silver layers) to improve the heat and humidity resistance.

JP-A-8-104547 discloses a hot wire shield for an insulated painted double-glazed unit. The barrier film has a five-layer structure consisting of two silver layers as the metal layer, and a tin oxide layer and a zinc oxide layer as the dielectric layer. A description is given of the effect of adjusting the thickness of the dielectric layer so that the light transmitted or reflected by the window glass having the blocking film formed thereon is colorless.

Plasma display panels are known as large image displays, but strong plasma exposure is required to achieve high brightness displays. The plasma display panel emits electromagnetic waves and near infrared rays from the exposed area to the front of the panel. Radiated electromagnetic waves are likely to have a detrimental effect on the human body. On the other hand, the emitted near infrared rays have a problem in that the near infrared rays are detected in the remote control receivers of the devices near the plasma display panel, thereby causing the switch to malfunction.

In order to solve the above problem, it is proposed to deposit a transparent object capable of blocking electromagnetic waves on the front of the plasma display panel. The technique of attaching the electromagnetic filter of the multilayered structure in which a dielectric layer and a silver layer are alternately attached to the front surface of a plasma display is researched. The electromagnetic wave filter must satisfy all the performances described below.

(1) electromagnetic wave shielding performance.

(2) Low electromagnetic transmission performance in the wavelength of the near infrared region (800-900 nm) used for preventing malfunction of equipment near the plasma display panel and remote control of the remote control switch of the equipment.

(3) High visible light transmittance performance to maintain bright image display.

(4) Durability such as moisture and heat resistance due to the use of the filter in the state exposed to air.

In order to obtain the electromagnetic wave shielding film which satisfies the above (2) and (3) simultaneously, it should be designed to have high light transmittance in the visible light region and low light transmittance in the near infrared region. That is, it should have a transmittance characteristic in which the transmittance suddenly drops at the boundary between the visible light region and the near infrared region. Accordingly, the present invention seeks to solve these problems.

In the heat ray shielding film on the glass plate disclosed in JP-A-5-42625, the dielectric layer used as the protective layer is composed of two or more multilayers including a zinc oxide layer and a tin oxide layer. Due to the configuration, the barrier film is excellent in durability, such as moisture and heat resistance. However, since the blocking film has only one silver layer, it is not sufficient to block electromagnetic waves. Moreover, when the conventional blocking film is used on the front of the plasma display, it has a high light transmittance in the near infrared region, and thus is ineffective in preventing false remote control.

As disclosed in JP-A-9-85893, the multilayered film formed on the glass plate has a silver layer containing at least 0.3 atomic% palladium as the metal layer, and contains a metal such as aluminum to reduce internal stress and improve adhesion to the silver layer. Since the zinc oxide layer is used as the dielectric layer, the moisture resistance heat is improved. However, the conventional film containing two silver layers (of all five layers) does not have the performance of (2) and (3) required for the blocking film of the plasma display panel.

Furthermore, the heat ray shielding film disclosed in JP-A-8-104547 has a five-layer structure containing two silver layers, so that there is no performance of (2) and (3) for the same phenomenon.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electromagnetic wave filter having a function of blocking the same infrared rays emitted from the front of the plasma display panel and the light rays used in the remote controller, while maintaining high visible light transmittance and sufficient durability in practical use. will be.

As a result of the study to solve the above problems, the resistance value required for the electromagnetic filter disposed on the front of the plasma display panel to have electromagnetic shielding properties, low light transmittance in the near infrared region, and actual moisture and heat resistance is four separate silver. It was found that the base layer was formed and obtained by adding palladium to each of the silver layers. The present invention has been accomplished based on this fact.

The present invention provides an electromagnetic wave filter for a plasma display panel,

An electromagnetic wave shielding plate having a transparent substrate coated with an electromagnetic wave shielding film on one side thereof, and a protective film formed on the shielding plate to cover the surface of the electromagnetic wave shielding film;

The electromagnetic shielding film has a nine-layer structure formed by alternately depositing a dielectric layer having a reflection coefficient of 1.7 to 2.7 and a silver base layer on a transparent substrate in order at a wavelength of 550 nm, and each of the silver base layers. Has a thickness of 5 nm to 20 nm, so that near infrared transmittance of less than 15% and 2 at a wavelength of 850 nm An electromagnetic wave filter having a sheet resistance of less than / square is provided.

1 is a cross-sectional view of one embodiment of an electromagnetic wave filter in accordance with the present invention.

Fig. 2 is a sectional view showing the layer structure of the electromagnetic wave blocking filter according to the present invention.

3 is a sectional view showing a practical electromagnetic wave filter according to the present invention;

4 is a spectral transmittance characteristic curve of a sample obtained in Example (1).

5 is a spectral reflectance characteristic curve of a sample obtained in Example (1).

<Description of Symbols in Drawings>

1: electromagnetic wave filter

2: electromagnetic wave shielding film

3: pressure-sensitive adhesive layer

4: PET membrane

5: glass plate

6: plasma display panel

7: frame

8: bus-bar

9: black ceramic pattern

10: dielectric layer

11: silver base layer (silver based layer)

The dielectric layer is composed of one or more transparent metal oxides having a reflection coefficient of 1.7 to 2.7 at a wavelength of 550 nm. If a dielectric with a reflection coefficient of less than 1.7 is used, the resulting electromagnetic filter has too high reflectivity, and if a metal oxide with a reflection coefficient of more than 2.7 is used, the deposition of the layer requires high temperature heating of the transparent substrate. The heating oxidatively degrades the silver base layer. In conclusion, the reflection coefficient of the dielectric layer should be 1.7 to 2.7.

When composed of only a silver layer, the silver base layer has insufficient actual weather resistance such as moisture and heat resistance. Thus, metals such as palladium, gold, nickel or titanium may be added to silver within a range that does not significantly reduce the resistivity of silver. In particular, palladium is more preferred among the metals because a small amount of addition improves the heat and moisture resistance of the electromagnetic wave shielding film on a practical level.

Each thickness of the silver base layer is 5 nm to 20 nm. The reason is that if the thickness is less than 5 nm, it is difficult to secure a low sheet resistance that guarantees the electromagnetic wave blocking performance, and if it exceeds 20 nm, the obtained electromagnetic filter has too high a reflection coefficient and a too low transmittance.

In one preferred embodiment, the electromagnetic wave filter of the present invention is a filter having a silver base layer each containing palladium in an amount of at least 0.1 atomic% and less than 0.5 atomic% as an additive metal based on the amount of silver. The lower limit of the palladium content is determined so that the electromagnetic wave shielding film can have sufficient moist heat resistance in practical use. The upper limit is determined to ensure near-infrared blocking performance and to prevent false remote errors.

The inventors of the present invention, through practical experiments, find that false remote control can be prevented when more than 85% of the near infrared rays emitted from the high brightness plasma display panel are blocked (e.g., when the light transmittance is 15 or less). It became. It has also been found that increasing the palladium content reduces the blocking performance of the silver layer.

If there is much palladium content in an electromagnetic wave shielding film | membrane, the relationship between the improvement of moisture-and-moisture resistance and the improvement of a near-infrared cut off performance is established. In securing a practical balanced combination of the two performances, the lower limit of palladium containing is preferably 0.10 atomic%, more preferably 0.3 atomic%. On the other hand, the upper limit is preferably 0.45 atomic%, more preferably 0.4 atomic%.

In another preferred embodiment of the electromagnetic filter, the silver base layer and the dielectric layer each have a controlled thickness such that the filter has a light transmittance of 50% or more at a wavelength of 550 nm. To achieve this, four separate silver base layers are formed such that each silver base layer is sandwiched between dielectric layers having a reflection coefficient of 1.7 to 2.7 at a wavelength of 550 nm, adjusting the thickness of each of the layers. . If a silver base layer thickness smaller than the above range is selected, higher visible light transmittance is obtained. Increased visible light transmittance can be obtained by adjusting the thickness of the silver base layer to have an optimal and close thickness to each other.

In another preferred embodiment, each of the dielectric layer and the silver base layer has the values of the electromagnetic wave filter chromaticity coordinates a ^★ and b ^★ satisfying −1 〈a ^★ 〈4 and −8 〈b ^★ 〈1 when viewed from the side of the transparent substrate. It is an electromagnetic wave filter having a controlled thickness in order to have a reflective hue. In the above relation, a ^★ and b ^★ denote two axes of the Sealab color coordinate system.

The thickness of each dielectric, the thickness ratio of each dielectric, and the thickness of each silver base layer are selected to produce low reflectance over a wide range of visible light regions, to adjust the center wavelength for reflectance at the center of the visible region. Therefore, the filter is adjusted to have an inconspicuous reflection hue, which satisfies the relationship to the color coordinate system. In particular, it is desirable to adjust these factors so that no pronounced red tone occurs.

In another preferred embodiment, the electromagnetic filter is a silver base layer filter having a thickness of 7 nm to 17 nm. In order to sufficiently obtain high visible light transmittance of 50% or more, the thickness of each silver base layer is preferably 17 nm or less. Visible light transmittance of 60% or more is obtained by adjusting the thickness of 14 nm or less. On the other hand, in order to obtain the electromagnetic wave shielding performance by sufficient reduction of sufficient near-infrared transmittance and sheet resistance, if the thickness of a silver base layer is 7 nm or more, it is more preferable if it is 9 nm or more.

In another embodiment, the electromagnetic filter is a filter having a total thickness of the silver base layer of 30 nm to 70 nm. The silver base layer having a total thickness of less than 30 nm is not preferable because the electromagnetic wave blocking performance and the infrared blocking performance gradually decrease as the overall thickness decreases. If the total thickness of the silver base layer exceeds 70 nm, it is not preferable because the visible light transmittance decreases as the total thickness increases due to light absorption by the silver base layer, and thus a bright image is difficult to be obtained.

In another embodiment, the electromagnetic filter is a filter of a silver base layer having a thickness ratio of (9-10) :( 10-13) :( 10-13) :( 9-11) in the layer arrangement order as viewed from the side of the transparent substrate. to be. In order to increase the visible light transmittance and reduce the visible light reflection, the silver base layer preferably has a thickness ratio within the above range.

In another embodiment, the electromagnetic filter has a thickness of 42 nm ± 10 nm closest to the transparent substrate and a thickness ratio of (44 ± 4): (82 ± 8) according to the layer arrangement order as viewed from the side of the transparent substrate. It is a filter containing a dielectric layer of (79 ± 8) :( 82 ± 8) :( 42 ± 4).

The thickness ratio of each dielectric layer and the thickness of the dielectric layer not only affect the transmittance and reflectance of visible light as in the case of the silver base layer, but also have a significant influence on the reflection color. By adjusting respective values of the thickness of the dielectric layer closest to the transparent substrate and the thickness ratio of the dielectric layer within the above-mentioned ranges, it is possible to increase the light transmittance at a wavelength of 550 nm (the visible light transmittance is also increased in the present invention), and It is possible to reduce the reflectance at the wavelength. At the same time, the light reflected by the electromagnetic filter shown in the actual range of use it is possible to 8 <b ^★ have a hue that is noticeable in a range of ^{<1 - 1 <a ★ <} 4 and.

The thickness selection is most important for the dielectric layer closest to the transparent substrate because the thickness of the other dielectric layer is determined based on the thickness of the dielectric layer. In order to obtain a useful electromagnetic filter having a high light transmittance, a low reflectance, and a reflection tone required by the electromagnetic wave filter, the thickness of the dielectric layer closest to the transparent substrate should preferably be adjusted to 42 nm ± 10 nm.

If the thickness of the dielectric layer closest to the transparent substrate increases beyond the upper limit of the above range, the center wavelength is shifted to the long wavelength side in the transmittance region and the reflectance region. On the other hand, if the thickness of the dielectric layer is reduced below the lower limit of the above range, the center wavelength is shifted to the short wavelength side in the transmittance region and the reflectance region. In this case, it is difficult to satisfy high light transmittance and near infrared ray blocking performance in the visible light region; One of the objectives of the present invention is to satisfy both performances.

In order to maintain an undamaged bright image display, the electromagnetic filter preferably has a light transmittance of at least 50% at a wavelength of 550 nm. To achieve this, four separate silver base layers are formed such that each silver base layer is sandwiched between dielectric layers having a reflection coefficient of 1.7 to 2.7 at a wavelength of 550 nm, adjusting the thickness of each layer.

In another embodiment, the electromagnetic filter is a filter having an additional dielectric layer and a silver base layer superimposed on the dielectric layer furthest from the transparent substrate. By appropriately selecting the thickness of the added silver base layer and the dielectric layer, the electromagnetic filter can be composed of five separate silver layers and six separate dielectric layers. Therefore, the filter has a high electromagnetic wave blocking performance and 1 ( / □) can have a sheet resistance of less than.

The dielectric layer used in the present invention is composed of one or more dielectrics having a reflection coefficient of 1.7 to 2.7 at a wavelength of 550 nm. Examples of the dielectrics include metal oxides such as zinc oxide, tin oxide, indium oxide, titanium oxide, zirconium oxide and tantalum pentoxide. The metal oxides may be used in combination. For example, zinc oxide / indium oxide mixtures or indium oxide-tin (ITO) can be used. Two or more transparent metal oxides may be deposited separately to form a multilayered dielectric layer.

Of the metal oxides listed above, the electrically conductive zinc oxide is preferred. The reason is that the deposition of zinc oxide as an undercoat on the silver base layer is the growth of a silver film having a low resistivity (high crystallinity) because the pitch of the zinc oxide crystal lattice is very similar to that of silver. Because it is suitable for. Zinc oxide adsorbs sulfur and other components contained in the silver-corrosive gas in the atmosphere to prevent the sulfur component from directly reaching the silver layer, thereby protecting the layer. Zinc oxide base layers comprising zinc oxide containing small amounts of other metals such as aluminum or gallium increase the electrical conductivity and are advantageous in the film forming step described below. The tin oxide and indium-zinc oxide composites are electrically conductive and deposited as an amorphous film that reliably prevents corrosive gases, thereby improving the moisture and heat resistance of the electromagnetic wave shielding film. The oxide is good from the viewpoint of protecting the silver layer from corrosive gases such as H ₂ O, SO ₂ , NO _x , and HCl in the atmosphere.

For this reason, in the present invention, the outermost dielectric layer or each dielectric layer has two layers composed of a tin oxide layer and a zinc oxide layer, or a zinc oxide layer and a zinc oxide layer containing aluminum (hereinafter referred to as ZAO). In this case, the zinc oxide layer or zinc oxide base layer is deposited as an undercoat to come into contact with the silver layer, from the above-mentioned viewpoint of the crystal lattice. The protective film used in the present invention is deposited for the purpose of chemically and physically protecting the electromagnetic shielding film from the atmosphere such as air. The protective film is a resin film. The resin film has a reflection coefficient of 1.58 to 1.7 at a wavelength of 550 nm from the viewpoint of controlling the light reflected at the interface between the electromagnetic wave blocking film and the resin film. The reflection coefficient of the resin film exceeding 1.7 is undesirable because of the large difference in the reflection coefficient between the resin film and the electromagnetic wave shielding film, the light reflectance occurring between the interface surfaces increases, and the light transmittance of the electromagnetic wave filter decreases considerably. The reflection coefficient of the resin film less than 1.58 is undesirable from the visual point of view because the color of the reflected light seen by the user is far from the natural color.

The resin film may have a wide thickness of 5 μm to 5 mm. Examples of the membrane material that can be used in the present invention include polyethylene terephthalate (PET), polyester (PE), triacetyl cellulose (TAC), and polyurethane (PW).

In the present invention, the resin film is adhered to the electromagnetic wave blocking film with adhesive force. Preferably, it sticks through a pressure-sensitive adhesive layer. The pressure sensitive acrylic resin layer is good for durability improvement.

The pressure-sensitive adhesive layer has a thickness of 20 μm to 500 μm. The reason is described later. If the thickness is less than 20 μm, the particles added at the interface between the electromagnetic wave shielding film and the adhesive layer while the resin film device is not completely removed tend to change levels and produce visually discernible defects, and the thickness is 500 μm. It is because it is difficult to prevent the moisture which permeates from an ambient environment as mentioned above, and will reduce the durability of an electromagnetic wave shielding film.

Another type of protective film that can be used in the present invention is a transparent metal oxide layer. In this case, the metal oxide is deposited directly on the surface of the electromagnetic wave shielding film. Examples of metal oxides that can be used include silicon dioxide and aluminum oxide. The metal oxide protective film preferably has a thickness of about 1 μm or more from the viewpoint of ensuring sufficient performance with respect to moist heat resistance and wear resistance.

Examples of transparent substrates that can be used in the present invention include known glass plates such as soda-lime silicate glass, borosilicate glass and alkali-free glass plates, and PET, acrylic (PMMA) and TAC plates.

In the present invention, the dielectric layer, silver base layer and protective metal oxide film are formed by known vacuum film deposition techniques. Sputtering is very good. Among the dielectric layers, a zinc oxide layer containing aluminum is preferred because the oxide layer is stable by direct current sputtering using a target obtained by sintering an excellent zinc oxide powder containing a predetermined percentage of aluminum oxide. This is because a discharge can be formed. In order to form a thick protective film such as silicon dioxide, known twin-mag sputtering methods are more suitable because they can deposit the film at high speed.

The formation of the film is generally at room temperature. For the purpose of depositing silver with excellently improved crystals, the substrate is suitably heated at temperatures below about 300 ° C. during film formation. The electromagnetic wave shielding film obtained by the film deposition at room temperature may use a method of heating to 300 ° C. or lower in air or nitrogen to remove light absorption by the dielectric layer and reduce specific resistance of the silver layer.

In the present invention, anti-reflective treatment is possible on the surface of the electromagnetic wave shielding film, the outer and inner surfaces of the resin film, or the side of the transparent substrate not covered with the electromagnetic wave shielding film, so that the visible light transmittance is improved.

Tint films for collecting visible light can be used to make transmitted light more similar to colorless light.

Figure 1 shows a cross-sectional view of one embodiment of an electromagnetic wave filter 1 according to the present invention.

The filter 1 adheres to the blocking film 2 through the pressure-sensitive adhesive layer 3 so as to protect the blocking film 2 from the glass plate 5, the electromagnetic wave blocking film 2 formed on the surface of the glass plate 5, and the atmosphere from the atmosphere. The resin film 4 thus prepared. A bus-bar 8 for grounding made from silver paste is supplied to the periphery of the glass plate 5, that is, at the periphery of the boundary between the glass plate 5 and the electromagnetic wave shielding film 2. Furthermore, a black ceramic pattern 9 is supplied to the surface of the glass plate 5 so that the bus-bar 8 is not exposed from the side of the glass plate 5.

Figure 2 shows a cross-sectional view of the layer structure of the electromagnetic wave shielding film according to the present invention.

The electromagnetic wave shielding film 2 formed on the glass plate 5 has a multilayer structure in which the dielectric layer 10 and the silver base layer 11 are alternately deposited. Each of the dielectric layers has a single layer structure composed of a transparent metal oxide having a reflection coefficient within the above-described range, a mixture of the transparent metal oxides, or a multilayer structure composed of two or more layers of the metal oxides, respectively. In the present invention, a silver layer such as titanium and a different metal layer are appropriately interposed between the dielectric layer and the silver base layer to improve durability or color tone control, unless the optical layer significantly reduces the visible light transmittance.

Fig. 3 shows a schematic cross sectional view of the configuration of the electromagnetic wave filter 1 of the present invention in practical use.

The electromagnetic wave filter 1 is supported by the frame 7 and attached to the front surface of the plasma display panel 6.

Fig. 4 shows the spectral transmittance characteristic curve of the sample obtained in Example (1).

5 shows the spectral reflectance characteristic curves of the specimen obtained in Example (1).

The present invention will be described in more detail by reference to the following Examples and Comparative Examples, but the present invention should not be construed as being limited by these Examples.

Explanation of Tables 1-4.

Glass plate: A 2 mm thick flat glass plate with a soda-lime silicate composition.

ZAO: Zinc oxide layer containing 6 weight percent aluminum.

AgPd 0.4: Silver base layer containing 0.4 atomic percent palladium based on silver.

The numerical value in-() indicates the thickness, which is nm in the electromagnetic wave shielding film and μm in the adhesive and protective layers.

Each layer structure of the first, third, fifth, seventh, and ninth layers, which are dielectric layers, shows an order according to an increase in distance from the transparent substrate, for example, the composition layer closest to the transparent substrate First shown.

Description of the table (5)

Sheet resistance: Measurements are made with a four-terminal ohmmeter. 2 Sheet resistance values less than or equal to Values exceeding / □ are indicated by x.

Near-infrared transmittance: The transmittance is measured at a wavelength of 850 nm. A transmittance value of 15% or less is indicated by o, and a value exceeding 15% is indicated by x.

Moisture and heat resistance: The electromagnetic filter is placed in an environment at a temperature of 60 ° C. and 90% humidity, and to improve visually discernible defects such as hillocks, pinholes, or fogging, The time required for the filter is determined as a measurement of heat and humidity resistance.

Time periods of 500 hours or more are indicated by o, and time periods exceeding 500 hours are indicated by x.

Description of the table (6).

Light transmittance: The transmittance is measured with a spectrometer at 450 nm, 550 nm and 650 nm, respectively. A filter having a transmittance of 50% or more at each wavelength is indicated by o, and the others by x.

Hue: The transmitted light and the light entering the glass side are measured to determine the values of a ^★ and b ^★ , the two axes of the Silab color coordinate system. Samples with -1 <a ^★ <4 and-8 <b ^★ <1 are represented by ○, and samples outside the above range are represented by x.

Example (1)

The multilayer structure described in Example (1) in the column of the table 1 is deposited on a 2 mm thick transparent glass plate by an in-line sputtering system. The SnO ₂ layer is deposited by tin metal target and reactive sputtering using oxygen as the reactive gas. The ZAO layer is deposited by Zn (94% by weight) / Al (6% by weight) metal target and reactive sputtering using oxygen as the reactive gas. The silver base layer is deposited by sputtering using Ag (99.6 wt.%) / Pd (0.4 wt.%) Metal targets and argon gas. Each layer is deposited to a thickness given to the table 1 at room temperature. The formed multilayer film is heat-treated at 200 ° C. for 30 minutes in air to remove light absorption by the dielectric layer and to improve crystals of the silver layer. An antireflection PET film having a pressure-sensitive adhesive layer is applied to the surface of the barrier film for the purpose of protecting the resultant electromagnetic wave blocking film and preventing glass breakage. Therefore, an electromagnetic wave filter having four separated silver base layers and five separated dielectric layers (mentioned in the form 4 · 5) is produced. The characteristics of the filter are described in tables 5, 6.

In these specimens, the heat resistance of the sheet resistance and near infrared transmittance is satisfactorily evaluated for use as an electromagnetic filter. In addition, optical characteristics such as transmittance, reflectance, and color tone are satisfactorily evaluated when used as an electromagnetic wave filter. The spectral transmittance characteristic curve and the spectral reflectance characteristic curve of the specimen are shown in Figs. 4 and 5, respectively. It is shown that the reflectance curve is low in most visible light regions.

Example (2,3)

The electromagnetic filter sample (4 · 5 form) is calculated by the same method as in Example (1) except that the palladium content of the silver base layer, the layer structure of each dielectric layer, and the thickness of each layer are different. Each layered structure of the specimen is shown in table 1 and the features are described in tables 5 and 6. Sheet resistance, near-infrared transmittance, and moisture heat resistance of each sample were satisfactorily evaluated when used as an electromagnetic wave filter, and optical characteristics such as transmittance and color tone were satisfactorily evaluated when used as an electromagnetic wave filter. The electromagnetic wave filters obtained in Examples (1 to 3) are filter samples having the most appropriate characteristics for the purpose of the present invention among the filter samples of the multilayer electromagnetic wave shielding film formed based on the calculation of the computer calculation program for the multilayer optical film. These three filters meet the practical requirements for durability known by sheet resistance and heat and moisture resistance, and show satisfactory optical characteristics in the visible range. That is, the filters do not significantly reduce the brightness of the image in the plasma display, but also satisfy the color tone for the reflected light.

Example (4)

The electromagnetic wave filter specimens (4 · 5 forms) each having a layer structure of a relatively thin thickness silver base layer, shown in the table 1, are calculated in the same manner as specified in Example (1). As shown in the tables 5 and 6, the infrared transmittance and the heat and moisture resistance of the specimen are satisfactorily evaluated when used as an electromagnetic filter. As for the optical properties such as transmittance and color tone, the specimen has the characteristics practically required in the electromagnetic filter.

Example (5)

The electromagnetic filter sample (4 · 5 form) having the layer structure shown in the table 2 is calculated in the same manner as specified in Example (1). The silver base layer of the specimen is deposited relatively thick. The sheet resistance, near-infrared transmittance, and moist heat resistance of the specimen are satisfactorily evaluated when used as an electromagnetic filter. As for the optical characteristics such as transmittance, reflectance and color tone, the specimen has the characteristics practically required in the electromagnetic filter.

Example (6)

The electromagnetic filter sample (4 · 5 form) having the layer structure shown in the table 2 is calculated in the same manner as specified in Example (1). The dielectric layer of the sample is deposited relatively thick. As shown in the tables 5 and 6, the sheet resistance, near-infrared transmittance, and moist heat resistance of the specimen are satisfactorily evaluated when used as an electromagnetic filter. As for the optical characteristics such as transmittance, reflectance and color tone, the specimen has the characteristics practically required in the electromagnetic filter.

Example (7)

The electromagnetic filter sample (4 · 5 form) having the layer structure shown in the table 2 is calculated in the same manner as specified in Example (1). The dielectric layer of the sample is deposited relatively thick. As shown in the tables 5 and 6, the sheet resistance, near-infrared transmittance, and moist heat resistance of the specimen are satisfactorily evaluated when used as an electromagnetic filter. As for the optical characteristics such as transmittance, reflectance and color tone, the specimen has the characteristics practically required in the electromagnetic filter.

Example (8)

An electromagnetic wave filter sample (5 · 6 form) having the layer structure shown in the table 2 is calculated by the same method specified in Example (1), and has an electromagnetic wave shielding film of (11) layer. The dielectric layer of the sample is deposited relatively thick. As shown in the tables 5 and 6, the sheet resistance, near-infrared transmittance, and moist heat resistance of the specimen are satisfactorily evaluated when used as an electromagnetic filter. As for the optical characteristics such as transmittance, reflectance and color tone, the specimen has the characteristics practically required in the electromagnetic filter.

Example (9)

Except that the palladium content of the silver base layer is different, an electromagnetic wave shielding film having the same multilayer structure composed of a dielectric layer and a silver base layer (layer thickness is the same) is formed by the same method of Example (1). This barrier is measured for transmittance at 850 nm wavelength and the results are shown in table 7. Table 7 specifies that as the palladium content increases, the increase in transmittance at the 850 nm wavelength, i.e., the near infrared blocking performance, decreases. Otherwise, the moist heat resistance becomes better with the increase of the palladium content.

From the above results, it can be seen that the palladium content is a balance between the ability to block near infrared rays and moisture and heat resistance. In particular, from the viewpoint of ensuring a balanced combination of the two performances, the palladium contained in the silver base layer is preferably 0.10 atomic% or more, and more preferably 0.3 atomic% or more, based on silver. The upper limit is preferably 0.45 atomic% on the basis of silver, and better than 0.4 atomic%.

Comparative Example (1)

A comparative sample (4 · 5 form) of the electromagnetic wave filter having the multilayer structure shown in the table 3 is calculated by the same method as described in Example (1), and the characteristics of the calculated comparative sample are shown in the tables 5 and 6 It is detailed in. The silver base layer of the sample contained 1 atomic% palladium. The sample is 1.8 Even with sheet resistance as low as /, it has a transmittance as high as 22% at 850 nm wavelength (the smaller the transmittance value, the better the near-infrared cut off performance). The comparative sample does not have all the features required for practical use. As described above, the near-infrared cut-off performance is reduced because the palladium content is high in the silver layer even though the electromagnetic shielding performance is satisfied.

Comparative Example (2)

Comparative samples of the electromagnetic wave filters having the multilayer structure shown in the table 3 are calculated by the same method specified in Example (1), and the characteristics of the calculated comparison samples are detailed in the tables 5 and 6. The silver base layer of the sample contained 0.05 atomic% palladium. The specimen satisfies sheet resistance and near infrared transmittance. However, since the amount of palladium used to improve the durability of the silver layer is small, the moisture barrier test deteriorates the electromagnetic wave shielding film within 384 hours. Therefore, the sample does not have the practical performance required by the electromagnetic filter.

Comparative Example (3)

Comparative samples of the electromagnetic wave filters having the multilayer structure shown in the table 3 are calculated by the same method specified in Example (1), and the characteristics of the calculated comparison samples are detailed in the tables 5 and 6. The multilayered structure of the sample is 3 · 4 shape. The sample has a near infrared transmission of 12% and a practically required near infrared cut-off performance, but the sheet resistance is 2.5. / □. That is, the electromagnetic wave blocking performance of the sample is insufficient. Therefore, the electromagnetic wave filter of the comparison does not have all the necessary features in practical use.

Comparative Example (4)

Comparative samples of the electromagnetic wave filters having the multilayer structure shown in the table 3 are calculated by the same method specified in Example (1), and the characteristics of the calculated comparison samples are detailed in the tables 5 and 6. Since the silver base layer of the specimen is as small as 4 nm, the specimen has a high near infrared transmittance and 4.2 It has sheet resistance as high as /. Therefore, the comparative sample does not have the near infrared ray shielding performance and the electromagnetic wave shielding performance required in actual use.

Comparative Example (5)

A comparative sample of the electromagnetic wave filter having the multilayer structure shown in the table 3 is calculated in the same manner as specified in Example (1), and the characteristics of the calculated sample are detailed in the tables 5 and 6. Since the silver base layer of the specimen is as thick as 22 nm to 24 nm, the specimen has high near-infrared blocking performance (transmission as low as 2%) and satisfactory electromagnetic wave blocking performance (0.8 Sheet resistance as low as / ?, but having a transmittance lower than 50% at a wavelength of 550 nm, the comparative sample does not have both the near infrared shielding performance and the electromagnetic shielding performance required in practical use.

Comparative Example (6)

Comparative samples of the electromagnetic wave filters having the multilayer structure shown in the table 3 are calculated by the same method specified in Example (1), and the characteristics of the calculated comparison samples are detailed in the tables 5 and 6. Since the silver base layers of the sample each have a thickness within a good range, the sample has satisfactory electromagnetic shielding performance (1.4 Sheet resistance as low as /?), But because the dielectric layer is too thick, a balance is broken between the transmittances in the visible light region. That is, the specimen has a high transmittance at a wavelength of 650 nm (longer wavelength in the visible light region; a wavelength corresponding to red color) and a low transmittance at a lower wavelength (wavelength corresponding to blue color). Because of the influence of the transmittance distribution in the visible range, the transmittance at a wavelength of 850 nm is not as low as high as 17%. That is, the sample does not have the near infrared blocking ability required in actual use. Moreover, the specimen has a distinct reflection hue, as can be seen from the values for reflection hue.

Comparative Example (7)

Comparative samples of the electromagnetic wave filters having the multilayer structure shown in the table 3 are calculated in the same manner as specified in Example (1), and the calculated samples are detailed in the tables 5 and 6. Since the silver base layers of the specimen each have a thickness within a good range, the specimen has satisfactory electromagnetic shielding performance (1.4 Sheet resistance as low as /). However, since the dielectric layers of the specimen are too thin in thickness compared with the layers of the comparative example 6, the specimen is broken in balance between the transmittances in the visible region. That is, it has a high transmittance characteristic at a wavelength of 450 nm (low wavelength in the visible light region; a wavelength corresponding to blue) and a low transmittance characteristic at a higher wavelength (wavelength corresponding to red). As a result, the specimen has a distinct hue, as can be seen from the value relating to the reflected hue.

As described above in the above embodiments and comparative examples, the filter sample calculated in the embodiment according to the present invention satisfies the near-infrared blocking performance and the optical characteristics in the visible region, respectively, required for the electromagnetic wave filter to be deposited on the front of the plasma display. Was evaluated. It can be seen that electromagnetic waves that have a detrimental effect on the human body are blocked by electrically conductive materials, and the material can be used to block electromagnetic waves. It should have a sheet resistance as low as / square. The filter samples calculated in the example are each 2 It has a sheet resistance of less than / □, and thus has electromagnetic shielding performance in practical use.

The electromagnetic wave filter of the present invention is arranged on a transparent substrate while an electromagnetic wave shielding film at a wavelength of 850 nm, a dielectric layer having a reflection coefficient within a given range at a wavelength of 550 nm, and each silver base layer are adjusted to a thickness of 5 nm to 20 nm. By the structure of the electromagnetic wave shielding film of the 9-layered structure in which the silver base layer which was formed by being deposited alternately is 2, It is adjusted to have sheet resistance of / □ and near infrared transmittance of 15%.

Due to the above features, when the electromagnetic wave filter of the present invention is installed on the front surface of the plasma display panel, the filter can prevent the electromagnetic wave and near infrared rays generated by the plasma discharge from radiating forward from the panel. Therefore, the filter can prevent erroneous remote control of the electronic device in proximity to the plasma display panel.

Since the silver base layer in the filter of the present invention contains a predetermined palladium, the filter may have a practical moist heat resistance while maintaining without deteriorating the infrared blocking performance.

Moreover, when having a predetermined reflection coefficient, that is, when the silver base layer and the dielectric layer have a thickness within a given range, the electromagnetic wave filter of the present invention does not have a distinct reflection color tone and high visible light transmittance. The filter does not degrade the brightness in the picture display.

Although specific embodiments have been described with reference to the present invention, various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention.

Claims (16)

An electromagnetic wave filter for a plasma display panel, An electromagnetic wave shielding plate having a transparent substrate coated with an electromagnetic wave shielding film on one side thereof, and a protective film formed on the shielding plate to cover the surface of the electromagnetic wave shielding film; The electromagnetic shielding film has a nine-layer structure formed by alternately depositing a dielectric layer having a reflection coefficient of 1.7 to 2.7 and a silver base layer on a transparent substrate in order at a wavelength of 550 nm, and each of the silver base layers. Has a thickness of 5 nm to 20 nm, so that near infrared transmittance of less than 15% and 2 at a wavelength of 850 nm Electromagnetic filter having sheet resistance of less than / square. The electromagnetic wave filter of claim 1, wherein each of the silver base layers contains at least 0.1 atomic% and less than 0.5 atomic% palladium based on silver. The electromagnetic wave filter of claim 1, wherein each of the silver base layer and the dielectric layer has a light transmittance of 50% or more at a wavelength of 550 nm. The method of claim 1, wherein the silver base layer and the dielectric layer, respectively, when viewed from the side of the transparent substrate, the electromagnetic wave filter has a value of the chromaticity coordinates a ^★ and b ^★ -1 <a ^★ <4 and-8 <b ^★ An electromagnetic wave filter having a thickness controlled to have a reflection color tone satisfying &lt; The electromagnetic wave filter of claim 4, wherein each of the silver base layers has a thickness of about 7 nm to about 17 nm. The electromagnetic wave filter of claim 4, wherein the silver base layer has a total thickness of 30 nm to 70 nm. The electromagnetic wave according to claim 6, wherein the silver base layer has a thickness ratio of (9-11) :( 10-13) :( 10-13) :( 9-11) in the arrangement order from the side of the transparent substrate. filter. 8. The dielectric layer of claim 7, wherein the dielectric layer closest to the transparent substrate has a thickness of 42 nm ± 10 nm, and the dielectric layer is arranged in the order of (44 ± 4): (82 ± 8): Electromagnetic filter having thickness ratio of (79 ± 8) :( 82 ± 8) :( 42 ± 4). 9. The electromagnetic wave filter of claim 8, further comprising the silver base layer and the transparent dielectric layer sequentially stacked on the dielectric layer furthest away from the transparent substrate. The electromagnetic wave filter according to claim 7, 8 or 9, wherein each of the dielectric layers has a zinc oxide base layer composed mainly of zinc oxide. 11. An electromagnetic wave filter according to claim 10, wherein each of said dielectric layers comprises a tin oxide base layer and at least one zinc oxide base layer in contact with an adjacent silver base layer. The electromagnetic wave filter according to claim 11, wherein said dielectric layer has a tin oxide layer as an outermost layer. The electromagnetic wave filter according to any one of claims 1 to 9, wherein the protective film is a resin film having a reflection coefficient of 1.59 to 1.69 at a wavelength of 550 nm. The electromagnetic wave filter of claim 13, wherein the passivation layer is attached to the electromagnetic wave blocking layer through a pressure-sensitive adhesive layer having a thickness of 20 μm to 500 μm. 15. The electromagnetic wave filter according to claim 14, wherein the electromagnetic wave filter has a ground electrode disposed in the periphery of the transparent substrate between the transparent substrate and the electromagnetic wave blocking film and formed of silver paste through sintering. 16. The electromagnetic wave filter of claim 15, wherein the black ceramic pattern is formed between the ground electrode and the transparent substrate so that the ground electrode is hidden by the black ceramic pattern from the side of the transparent substrate.