JPH0746570B2 - Light transmission plate having electromagnetic wave shielding property - Google Patents

Description

The present invention relates to a plastic light transmitting plate having an electromagnetic wave shielding property. More specifically, the present invention relates to a light transmitting plate capable of effectively blocking harmful electromagnetic waves generated from a display or a cathode ray tube of a television and having a durable antireflection function.

[Prior Art] Large amounts of harmful electromagnetic waves are emitted from office automation devices, such as displays of word processors and various computers, game consoles, and cathode ray tubes of televisions, which may cause health problems and other problems. Is a problem with the equipment. For example, it is often found that a computer has an erroneous signal, or noise is heard from the stereo when the TV and the stereo are turned on at the same time.

Therefore, various improvements have been made in the past to remove such obstacles. An effective means is to cover it with a conductor such as metal. For example, there is one in which carbon is adhered to the surface of a thin fiber to form a mesh structure, or a thin glass wire is introduced into the laminated glass, such as the product name "Isaber" of Chori Co., Ltd.

However, these methods have a drawback in that it is difficult for a user such as a word processor to see because a portion that does not transmit the light generated from the display is generated.
As another publicly known example, there has been proposed a technique in which a conductive material is vapor-deposited on a glass substrate at a high temperature (Japanese Patent Publication No. 49-18).
In this method, many plastic base materials are softened or melted by this method, and the drawback that the surface is easily scratched cannot be improved and cannot be used.

Therefore, there is no effective technique for the transparent plate made of plastic, and no improvement has been made at present.

Further, regarding the antireflection technology, JP-A-59-48702, JP-A-59-78301, and JP-A-59-78304 disclose that a polyorganosilane-based hard coat film or a surface of a plastic substrate is used. A method of coating an epoxy resin cured film and then coating an antireflection film made of an inorganic material is disclosed.

Further, the technology disclosed in JP-A-56-113101,
Although it has high hardness and antireflection property, it has a serious problem of lowering adhesion, heat resistance, impact resistance, hot water resistance, weather resistance and the like.

In addition, Japanese Examined Patent Publication No. 45-6193, Japanese Laid-Open Patent Publication No. 59-48702,
The techniques disclosed in JP-A-59-78301 and JP-A-59-78304 have antireflection properties, but on the other hand, they have insufficient adhesion to the base material and are deeply scratched and thick, and thus are used. It has a major drawback above. Further, it is easily dipped in water, alcohol, etc., and there is a big problem in the adhesion after hot water immersion, weather resistance adhesion, and the like.

The conventional technologies have been reviewed above, but all of these technologies have problems in adhesion between the hard coat layer on the substrate and the vapor deposition film (antireflection layer) on the surface of the hard coat layer. It had a defect that the antireflection layer) peeled off like a scale.

[Problems to be Solved by the Invention] The present invention provides a technique for remedying the above-mentioned drawbacks of the conventional techniques. That is, even with a transparent plastic plate, electromagnetic waves can be shielded by coating the surface with a conductive layer, and even with a plastic material having a low surface hardness, a silica layer is provided on the surface to increase hardness and prevent scratches. By providing a property and by providing a layer having a low refractive index on the surface layer of the conductive layer, an antireflection function is imparted and, at the same time, particularly excellent adhesion strength and durability, scratch resistance, abrasion resistance, and resistance to abrasion are provided. It is intended to provide an optical article having a multilayer antireflection film excellent in impact resistance, chemical resistance, flexibility, heat resistance, light resistance, weather resistance, antistatic property and the like.

[Means for Solving Problems] In order to achieve the above object, the present invention has the following configuration.

"A hard coat layer having abrasion resistance is provided on the surface of the plastic transparent substrate facing the image generation surface, a conductive layer is provided on the surface layer, and a layer having a refractive index lower than the refractive index of the conductive layer is further provided on the surface layer. A light transmitting plate having an electromagnetic wave shielding property, which is provided with a multilayer antireflection film on the other surface of the plastic transparent substrate. ”FIG. 1 shows the preferable electromagnetic wave shielding property and static electricity removal of the present invention. 1 shows a cross section of one embodiment of a light transmitting plate having a property. A hard coat layer 2 having scratch resistance is provided on a plastic transparent substrate 1, a conductive layer 3 is provided on the surface layer thereof, and a layer 4 having a refractive index lower than that of the conductive layer is provided on the surface layer thereof. It is a thing. The hard coat layer 2'having scratch resistance and the antireflection layer 20 are provided on the opposite surface. Reference numeral 5 is a portion where the conductive layer is exposed. The surface having the conductive layer 3 is an image generating surface, that is, a cathode ray tube (CRT).
Install so that it faces the surface such as (CRT).

FIG. 2 is a plan view seen from the surface having the conductive layer 3 of FIG. The portion 5 where the conductive layer is exposed may be provided on the entire surface of the portion hidden by the outer frame or may be a part thereof. Then, for shielding electromagnetic waves and / or for removing static electricity, a metal frame is provided around the conductive layer or the ground wire 6 is drawn out. The ground wire 6 preferably extends from a corner portion.

3 to 7 show examples of taking out the preferred ground wire of the present invention. In FIG. 3, holes 9 are provided in the light transmitting plate itself,
The ground wire 15 is connected using the metal fitting 6a. Metal packing is preferably used in this connection. As the fixture, it is preferable to use a set screw 10a and a nut 10b, a crimping eyelet, or the like. FIG. 4 shows a fixing method using a crimping eyelet. Then, for the sake of aesthetics, the entire connection portion is covered with a plastic cover 11. FIG. 5 shows an example in which the metal fitting 6a is attached inside the cover 11 substantially parallel to the light transmitting plate.

Next, in FIG. 6, a nut helisert 12 is used for the hole 6, and the metal fitting 6a is used.
This is an example in which the ground wire 15 is attached via. in this case,
If the hole 11a is opened in the cover 11 in advance, the screw 13 can be easily removed, which is convenient when removing or cleaning the light transmitting plate. Fig. 7: Adjust the shield removal 14
This is an example performed using a and 14b.

FIG. 8 shows a cross section of one embodiment of an optical article having a preferred multilayer antireflection coating of the present invention. A hard coat layer 2'having scratch resistance is provided on the other surface of the plastic transparent substrate 1, and the above is provided in order on the surface layer thereof.

In the present invention, it is first necessary to provide a hard coat layer having scratch resistance on a plastic transparent substrate. Here, the plastic may be any known material. Further, the transparent substrate may be any as long as it can transmit light. For those used in front of displays such as word processors, visible light transmittance is 25 to 70% by dyeing or dyeing.
Are preferred. This is to reduce eye fatigue. The hard coat layer having scratch resistance refers to a coating layer having high hardness such as polyorganosiloxane, silica, and alumina, or a layer containing an acrylic component.
The surface of a plastic product is generally easily scratched, so that it is for improving it and for enhancing the adhesion as an undercoat of the electromagnetic wave shield layer coated on the surface layer. And particularly preferably, the hard coat layer is methyltrimethoxysilane, and vinyltriethoxysilane,
Alternatively, it is a polyorganosiloxane obtained by coating these hydrolyzates and then heat-condensing them.

The preferable film thickness of the hard coat layer is about 1 to 10 microns.

The acrylic hard coat layer refers to a layer obtained by crosslinking an acrylic compound such as methacrylic acid with an ester compound of a polyfunctional glycol such as pentaerythritol or glycerin.

Next, in the present invention, a conductive layer is provided on the surface layer of the hard coat layer. This is to effectively block electromagnetic waves.
The conductive layer may be any as long as it can transmit visible light, but is preferably a mixture of In ₂ O ₃ (indium oxide) and SnO ₂ (tin oxide) (hereinafter IT
It is called O). This is because it has high conductivity, can effectively block electromagnetic waves, and can transmit visible light. ITO
The film thickness of the layer may be any thickness as long as such an effect is exhibited, but it is preferably 100 to 3000Å. 3000Å
With the above, crack defects are likely to occur. Such an ITO layer can be coated by a sputtering method. As another method, it is also possible to employ a technique in which vapor deposition is performed using plasma by high-frequency discharge in an oxygen atmosphere at 150 ° C. or lower, and at the same time, assist is performed using an ion gun.

Next, in the present invention, it is necessary to provide a layer having a refractive index of the conductive layer on the surface layer of the conductive layer. Since the conductive layer is generally made of a metal layer, it has a high refractive index. For example, the ITO layer has a refractive index of about 2.0. However, this causes the reflection to be too high and tires the eyes of the user. Therefore, it is necessary to provide an antireflection function by providing a low refractive index layer on the surface of the high refractive index conductive layer.

The layer having such a low refractive index may be any known layer, but is preferably a layer containing inorganic silica. Such an inorganic silica layer can be obtained by sputtering or vacuum depositing silica. The film thickness may be any thickness as long as it can prevent reflection of visible light.

In the present invention, the above-mentioned lamination is a plastic substrate.
Provided on one side or two sides

Next, in the present invention, a multilayer antireflection film is provided on the surface opposite to the surface of the conductive layer of the first invention.

A layer containing zirconium oxide as a main component is first provided as a first layer on the surface layer of the hard coat layer. The layer containing zirconium oxide as a main component exerts an effect of improving adhesion strength as a binder for both the lower hard coat layer and the upper layer containing silicon dioxide as a main component, and at the same time,
This is because the second layer has a medium refractive index as compared with the third layer and the fourth layer by forming an equivalent film by combining with the layer containing silicon dioxide as a main component.

Next, in the present invention, a layer containing silicon dioxide as a main component is provided as a second layer on the surface layer of the first layer. The third layer is obtained by combining the first layer and the third layer with the effect of improving the adhesion strength, and at the same time combining the first layer with zirconium oxide as a main component to form an equivalent film. This is because it has a medium refractive index as compared with the fourth layer. As described above, the first layer and the second layer are layers having a medium refractive index as a whole.

Next, a layer containing titanium oxide as a main component is provided as a third layer, and a layer containing silicon dioxide as a main component is provided thereon as a fourth layer. If a high refractive index layer is provided as the third layer and a low refractive index layer is provided as the fourth layer, a film having an excellent antireflection function is achieved in combination with the first and second medium refractive index layers. This is because that.

In the present invention, the first to fourth layers can be provided by vacuum vapor deposition or sputtering. More preferably, it is vacuum deposition. A method such as ion beam assist may be applied as appropriate. Further, titanium oxide or the like may be added to the first layer of zirconium oxide within a range that does not impair the effects of the present invention, and similarly, the second layer of titanium oxide may be mixed with Ta ₂ O ₅ or the like. Good.

The film thickness may be any thickness as long as it can prevent reflection of visible light. Preferred optical film thickness is, when a design wavelength lambda _0, the first layer in the range of 450~550nm; 0.05~0.15λ ₀ second layer; 0.05~0.15λ ₀ third layer; 0.36~0.49λ ₀ 4 Layer; 0.15-0.35λ ₀ . Of these, the fourth layer preferably has a thickness of 0.25λ ₀ .

A ground may be attached to the product of the present invention to remove static electricity. In this case, when the ITO film is present, the ground is preferably taken directly from the ITO film or is in a conductive state. As another means, a metal frame may be attached around the product of the present invention to discharge static electricity.
Also in this case, when the ITO film is present, the metal frame is preferably in direct contact with the ITO film or is in a conductive state.

The conductive film or multilayer film of the present invention can be analyzed by “Auger electron spectroscopy”. This method
The sample surface placed in a high vacuum is irradiated with an electron beam, and Auger electrons emitted from the surface are detected by energy division with an analyzer.

The measurement conditions are as follows.

Measuring device: "JAMP-10S" manufactured by JEOL Ltd. When analyzing the outermost surface: 1 x 10 ^-7 Pa When analyzing in the depth direction: 6 x 10 ^-6 Pa (Ar atmosphere) Sampling: Hold the edge of the sample with a copper plate Fix on the sample table.

Accelerating voltage: 3.0KV Specimen current: 1 × 10 ^-8 A Beam diameter: 1 μm Slit: No.5 Specimen tilt angle: 40-70 degrees Ar ion etching conditions Accelerating voltage: 3.0KV Specimen current: 3 × 10 ^-7 A Etching Speed: 200 Å / min (in the case of SiO ₂ ) The use of the light transmitting plate having an electromagnetic wave shielding property of the present invention is as follows.
It is particularly effective as a screen filter for TVs and displays (so-called optical filter). Other uses such as lenses for eyeglasses, films, and molded products can also be expected.

[Example] Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 A commercially available polymethacrylate plate (trademark "Aqualite" LN-084, gray original, thickness about 2 mm, manufactured by Mitsubishi Rayon Co., Ltd.) was used as a substrate. As the coating material for hard coat, as described in Example 1 of JP-A-59-114501, a coating obtained by hydrolyzing vinyltriethoxysilane with glacial acetic acid and a coating obtained by hydrolyzing methyltriethoxysilane with glacial acetic acid. The mixture was used. Sodium acetate, which is a curing agent, was added to this mixed solution, and a silicone-based surface smoothing agent was further added to obtain a coating material.

This coating material was applied on the surface of the base material to a thickness of 2 μm and cured by heating.

Then, as a conductive layer on one surface of the substrate and on the hard coat layer, a sputtering method was used to form In ₂ O ₃
A mixture of (indium oxide) and SnO ₂ (tin oxide) was coated to a film thickness of 700Å. As for the conditions of the sputtering method, as described in Examples 7 to 9 of JP-A-60-32053, an indium-tin alloy (tin; 10% by weight) is used as a target and a magnetron sputtering apparatus is used to perform argon. It was carried out at a pressure of 1 × 10 ⁻³ Torr while introducing a mixed gas of gas and oxygen (oxygen 30% by volume).

Then, as the antireflection film, a silicon dioxide film was formed by the EB method using a vacuum vapor deposition device (BMC-800T type manufactured by Vacuum Machine Industry Co., Ltd.). The film thickness was 940Å.

The above hard coat layer was provided on the surface of the substrate opposite to the conductive layer, and then the following antireflection layer was provided.

(1) First layer; layer containing zirconium oxide as a main component, optical film thickness (nd) about 45 nm, vacuum degree 3 × 10 ^-5 TORR (introduction of oxygen) (2) Second layer: silicon dioxide as a main component Layer, optical film thickness (nd) about 40 nm, vacuum degree 1 × 10 ^-5 TORR (3) 3rd layer; layer mainly containing titanium oxide, optical film thickness (nd) about 196 nm, vacuum degree 4 × 10 ^-5 TORR (introduction of oxygen) (4) Fourth layer; layer mainly composed of silicon dioxide, optical film thickness (nd) about 110 nm, vacuum degree 1 × 10 ^-5 TORR (however, (1) above) In (4), the optical film thickness uses a design wavelength of 480 nm.) The product of the present invention obtained by the above method and conditions has a blue-violet reflection interference color, and the surface reflectance at 550 nm is about 0.3%. It had an extremely excellent antireflection property.

Further, a test was conducted by placing a square polyester knitted fabric having a hard surface and a side of 2 cm on which tap water was poured, and applying a load of 2 kg and rubbing it 2,000 times back and forth, but no damage was observed.

Further, an exposure test was carried out by leaving it outdoors for one month, but there was no surface damage such as peeling of the antireflection film.

The resulting plastic coated light transmitting plate is
The amount of electromagnetic waves transmitted at a frequency of 10 GHz could be attenuated to about 1 / 10th. Further, when it was used as an optical filter of a word processor, it had an excellent antireflection function and had a remarkable effect in that the user's eyes were not tired.

Further, the surface had a high hardness and was not easily scratched.

Example 2 In Example 1, the steps up to the step of forming a hard coat layer on the surface of the substrate were the same, and then an undercoat of about 10 was used.
A 0Å silicon dioxide film is formed by a sputtering method, and then an ITO layer (140
A film thickness of 0Å), and a silicon dioxide film was formed thereon by the vacuum deposition method.

Further, on the opposite surface of the base material, a hard coat layer was provided in the same manner as in Example 1, and then Y ₂ O ₃ (λ / 4) and TiO ₂ were formed by vacuum deposition.
₂ (λ / 2) and SIO ₂ (λ / 4) layers were provided, respectively.

The resulting coated light transmitting plate has a frequency of 10 GHz.
The transmission amount of the electromagnetic wave in was able to be attenuated to about 1/22. Furthermore, when this was used as an optical filter of a word processor, the antireflection function and the scratch resistance due to the hardness of the surface were the same as in Example 1.

Example 3 In Example 1, as a substrate having a hard coat,
Commercially available gray polymethacrylate board (trade name "Aqualite" AR, manufactured by Mitsubishi Rayon Co., Ltd., thickness about 2
mm) was used, and an ITO layer was provided on the surface and an antireflection film was further formed by the same formulation. This was also excellent as was the transmission plate of Example 1.

Example 4 A commercially available polymethacrylate plate (trade name "Aqualite" LN-084, manufactured by Mitsubishi Rayon Co., Ltd., gray original coating, thickness: about 2 mm) was used as a substrate. As the coating material for hard coat, as described in Example 1 of JP-A-59-114501, a coating obtained by hydrolyzing vinyltriethoxysilane with glacial acetic acid and a coating obtained by hydrolyzing methyltriethoxysilane with glacial acetic acid. The mixture was used. Sodium acetate, which is a curing agent, was added to this mixed solution, and a silicone-based surface smoothing agent was further added to obtain a coating material.

This coating material was applied on the front surface (front and back surfaces) of the substrate to a thickness of 2 μm, and heated and cured at 90 ° C. for 3 hours.

Then, an ITO film was formed on one surface of this hard-coated plastic substrate in the same manner as in Example 1, silicon dioxide was vacuum-deposited on the ITO film, and the surface opposite to this surface was set in a vacuum evaporation tank. , Setting temperature 60 ℃, 1 × 10 ^-5 TORR
After evacuating to, the Kaofman-type ion beam generator generates an argon ion beam to accelerate the voltage.
The substrate was cleaned at 500V. Subsequently, a four-layer film was formed on the front and back surfaces under the following conditions by the electron beam method in order from the substrate side.

(1) First layer; layer containing zirconium oxide as a main component, optical film thickness (nd) of about 42 nm, vacuum degree 3 × 10 ^-5 TORR (oxygen introduction) (2) Second layer: silicon dioxide as a main component Layer, optical film thickness (nd) about 42 nm, vacuum degree 1 × 10 ^-5 TORR (3) Third layer; layer mainly containing titanium oxide, optical film thickness (nd) about 216 nm, vacuum degree 4 × 10 ^-5 TORR (introduction of oxygen) (4) Fourth layer; layer containing silicon dioxide as a main component, optical film thickness (nd) of about 120 nm, vacuum degree of 1 × 10 ^-5 TORR (however, above (1) In (4), the optical film thickness uses a design wavelength of 480 nm.) The product of the present invention obtained by the above method and conditions has a blue-violet reflection interference color, and the surface reflectance at 550 nm is about 0.2%. It had an extremely excellent antireflection property.

Further, a test was conducted by placing a square polyester knitted fabric having a hard surface and a side of 2 cm on which tap water was poured, and applying a load of 2 kg and rubbing it 2,000 times back and forth, but no damage was observed.

Further, an exposure test was carried out by leaving it outdoors for one month, but there was no surface damage such as peeling of the antireflection film.

Further, when it was used as an optical filter of a word processor, it was excellent in antireflection function and had a remarkable effect in that the user's eyes were not tired.

It was also highly durable.

Further, the antistatic performance was measured as follows. In other words, the CRT (N
EC-KD551K) was measured with a static electricity measuring device (Shidishi Static Electricity Co., Ltd. "Statilon M") at a position 53 mm in front, and the electrostatic potential when the switch of the personal computer was turned on was measured and the blank was 9 KV or more. . Next, between the CRT and "Statiron M", at a distance of 30 mm from "Statiron M",
The product of the present invention to which a ground was attached was installed, and the electrostatic potential when the switch was turned on was measured. As a result, the voltage was 0 KV or less from the beginning, and the antistatic effect was extremely excellent.

[Advantages of the Invention] Since the present invention is the technique as described above, a hard coat layer is provided on the surface layer of a plastic transparent plate to increase hardness, and a conductive layer is provided thereon by vacuum vapor deposition or sputtering to further improve the conductivity. By providing a layer having a low refractive index on the surface of the layer, electromagnetic waves can be shielded, and even a plastic material having a low surface hardness can be provided with a property that is unlikely to be scratched. In addition, an antireflection function can be added, and the invention has a remarkable effect as a whole.

Further, the present invention, on the surface opposite to the surface of the conductive layer side of the first invention, excellent adhesion strength, and excellent durability, scratch resistance, abrasion resistance, impact resistance, chemical resistance, Flexibility, heat resistance,
Since the multilayer antireflection film excellent in light resistance, weather resistance, antistatic property, etc. is provided, the optical article as a whole is excellent in electromagnetic wave shielding property, static electricity removal and antireflection property.

[Brief description of drawings]

FIG. 1 shows a cross section of one embodiment of a light transmitting plate having a preferable electromagnetic wave shielding property of the present invention. FIG. 2 is a plan view seen from the surface having the conductive layer 3 of FIG. 3 to 7 show examples of taking out the preferred ground wire of the present invention. FIG. 8 shows a cross section of one embodiment of an optical article having a preferred multilayer antireflection coating of the present invention. 1; Plastic transparent substrate, 2 and 2 '; Hard coat layer having scratch resistance, 3; Conductive layer, 4; Layer having refractive index lower than that of conductive layer, 11; Cover, 15; Ground wire, 20, 21-24;
Multi-layer antireflection film

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04N 5/65 7205-5C H05K 9/00 V

Claims (16)

[Claims] 1. A hard coat layer having scratch resistance is provided on a surface of a plastic transparent substrate facing an image generating surface, a conductive layer is provided on the surface layer, and a refractive index lower than the refractive index of the conductive layer is provided on the surface layer. A transparent plate having an electromagnetic wave shielding property, characterized in that a multi-layer antireflection film is provided on the other surface of the plastic transparent base material in addition to a transparent layer. 2. A multilayer antireflection film, wherein a hard coat layer having scratch resistance is provided on a plastic transparent substrate, and the surface layer thereof has a first layer: zirconium oxide in order from the substrate side to the surface. A layer containing a main component Second layer: a layer containing silicon dioxide as a main component Third layer: a layer containing titanium oxide as a main component Fourth layer: a layer containing silicon dioxide as a main component The light transmitting plate having an electromagnetic wave shielding property according to claim (1), characterized in that the second layer and the second layer are equivalent films. 3. When the optical thickness of the first layer to the fourth layer is a design wavelength λ ₀ , in the range of 450 to 550 nm the first layer: 0.05 to 0.15λ ₀ the second layer: 0.05 to 0.15λ ₀ third layer: 0.36～0.49Ramuda ₀ 4th layer: claims, characterized in that 0.15~0.35λ ₀ second (2) light transmissive plate having electromagnetic shielding property according to claim. 4. The light transmitting plate having an electromagnetic wave shielding property according to claim (2), wherein the first to fourth layers are vapor deposition films or sputtering films. 5. The light transmitting plate having an electromagnetic wave shielding property according to claim 1, wherein the conductive layer is a layer containing indium oxide and tin oxide (ITO layer). 6. A light transmitting plate having an electromagnetic wave shielding property according to claim 1, wherein the ITO layer is provided by a sputtering method. 7. An ITO layer is deposited at a temperature of 150.degree. C. or lower in an oxygen atmosphere by using plasma by high frequency discharge, and at the same time is provided by a method of assisting with an ion gun. A light transmitting plate having an electromagnetic wave shielding property according to the item. 8. A light transmitting plate having an electromagnetic wave shielding property as set forth in claim 1, wherein the conductive layer has a film thickness in the range of 100 to 3000Å. 9. The light transmitting plate having an electromagnetic wave shielding property according to claim 1, wherein the hard coat layer is a layer containing an organic polysiloxane. 10. The hard coat layer is obtained by coating a curable paint, and the hard coat layer is obtained.
A light transmitting plate having a shielding property according to the item. 11. A light transmitting plate having an electromagnetic wave shielding property as set forth in claim 1, wherein the transparent substrate is colored. 12. The light transmitting plate having electromagnetic wave shielding property according to claim 1, wherein the outermost layer having a low refractive index is a silica layer. 13. A light transmitting plate having an electromagnetic wave shielding property according to claim 1, wherein the inorganic silica layer is provided by a vacuum vapor deposition method. 14. A light transmitting plate having an electromagnetic wave shielding property according to claim 1, wherein a ground wire is drawn from the conductive layer. 15. The electromagnetic wave shielding property according to claim 1, wherein a metal frame is provided as an outer frame of the light transmitting plate, and the metal frame is provided so as to contact the conductive layer. A light transmitting plate having. 16. The light having an electromagnetic wave shielding property according to claim 1, wherein the light transmitting plate having a multilayer antireflection film is an optical filter for a cathode ray tube. Transparent plate.