JP5604664B2 - Half mirror substrate manufacturing method and half mirror substrate - Google Patents

Description

  The present invention relates to a method for manufacturing a half mirror substrate having light transmissivity and reflectivity, and a half mirror substrate.

  The half mirror substrate has a function as a mirror that reflects incident light, and has transparency that allows the back side to be seen through from the front side, and is used for display panels of various electronic devices.

  In general, a half mirror substrate is manufactured by forming a metal thin film on a base substrate by sputtering or vapor deposition. In addition, a technique for improving the continuity of a metal thin film by oxidizing the formed metal thin film has been proposed (see Patent Document 1).

  Note that the half mirror widely refers to a light transmissive and reflective light, and is not limited to the one in which the intensity of reflected light and transmitted light is 1: 1.

JP-A 64-47845

  When the Sn film is formed as the metal thin film of the half mirror substrate, when the oxidation proceeds, the transmittance increases and the reflectance decreases, and the function as a mirror is impaired. Therefore, it is necessary to prevent the progress of oxidation of Sn.

  By using a material having a high water vapor barrier property (hereinafter also simply referred to as barrier property) as a protective film covering the Sn film in order to protect the Sn film, it is possible to suppress contact of water and oxygen with the Sn film, The progress of oxidation can be suppressed. However, if a highly hygroscopic resin such as PMMA (polymethylmethacrylate) is used for the base substrate serving as the base of the half mirror substrate, the base substrate may be warped.

  The reason for this will be described with reference to FIG. In FIG. 8A, an Sn film (particulate metal) 102 is formed on a PMMA substrate 101, and a high barrier TEOS film (SiO film) 103 is formed so as to cover it. The water molecules 104 absorbed by the PMMA substrate 101 in a high humidity environment are discharged from the PMMA substrate 101 when the surrounding humidity decreases, but since water molecules cannot pass through the high barrier TEOS film 103, the water molecules 104 are on the surface. Water molecules remain. As a result, the surface side of the base substrate from which water molecules are discharged contracts and warpage occurs.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method for manufacturing a half mirror substrate and a half mirror substrate that can suppress the occurrence of warp without reducing the reflectance of light. It is.

The invention according to claim 1, which has been made to solve the above-described problem, includes a first step of forming an Sn film formed by island-like growth on the surface of a base substrate made of polymethyl methacrylate or polycarbonate, and the first step. A second step of forming an oxidized Sn layer by irradiating the surface of the Sn film formed in step 1 with a chemical species containing atomic oxygen, so as to cover the oxidized Sn layer And a third step of forming a SiO film having a water vapor transmission rate equal to or higher than the water vapor transmission rate of the base substrate .

  As described above, a highly hygroscopic resin substrate such as polymethyl methacrylate (polymethyl methacrylate, PMMA) or polycarbonate is warped when a protective film having a high water vapor barrier property is used. Therefore, when a low water vapor barrier SiO film is used as the protective film, water molecules permeate through the SiO film (low barrier TEOS film 105) as shown in FIG. Is suppressed.

  However, in that case, the oxidation of the Sn film proceeds. Therefore, if an oxidized Sn layer is formed on the surface of the Sn film by irradiating chemical species including atomic oxygen (FIG. 3C), the barrier property (humidity resistance) of the oxidized Sn layer is increased. The progress of the oxidation of the Sn film is suppressed inside the oxidized Sn layer.

  That is, according to the method for manufacturing a half mirror substrate of the present invention, it is possible to suppress the occurrence of warpage of the base substrate (that is, warpage of the half mirror substrate) without causing a decrease in reflectance due to oxidation of the Sn film. .

The oxidized Sn layer exhibits a high water vapor barrier property by becoming a passive film by irradiation with chemical species including atomic oxygen. The irradiation of the chemical species including atomic oxygen is selected from the group consisting of an oxygen plasma irradiation step or O ₂ , O ₃ , CO, NO, NO ₂ , N ₂ O, for example, as described in claim 2. It can be set as the process of performing the vacuum ultraviolet light irradiation in 1 or more types of gas atmosphere.

With such a method of manufacturing a half mirror substrate, since the oxidized Sn layer can be used as a passive film, the oxidation of the Sn film can be appropriately suppressed.
It is preferable to manufacture the oxidized Sn layer so that the main component is SnO ₂ by irradiation with atomic oxygen as in the method of manufacturing a half mirror substrate according to claim 3. There are SnO and SnO ₂ as stable oxides of metal Sn, and there is a difference in the denseness of each oxide in the crystalline state. Since SnO ₂ is dense and has higher barrier properties than SnO ₂ , the main component of the oxidized Sn layer is SnO ₂ , so that the moisture resistance can be improved.

By the way, the SiO film is desired to have a low water vapor barrier property in order to suppress warpage of the base substrate, but in the present invention, as described above , the water vapor transmission rate is manufactured to be a value higher than that of the substrate material. If it is such a value, since a SiO film can permeate | transmit a water molecule enough, the curvature of a half mirror board | substrate will be suppressed. In addition, since the water vapor permeability of the PMMA substrate is 41 [g / m ² · 24 h], the warp can be sufficiently suppressed if the water vapor permeability of the SiO film is larger than the value.

In order to make the SiO film have a low water vapor barrier property, a rare gas is added to the TEOS gas as a film material gas in the third step as in the method of manufacturing a half mirror substrate according to claim 4. Alternatively, the SiO film may be formed by plasma CVD without adding any gas.

  With such a half mirror substrate manufacturing method, it is possible to manufacture a half mirror substrate using TEOS (tetraethoxysilane) as a film material and having a water vapor barrier property of the SiO film lowered.

  Incidentally, the SiO film is a film mainly formed by Si—O bonds, and its film structure is schematically shown in FIG. As shown in the figure, it may be a SiOC film containing Si—C or a film not containing Si—C.

  The SiO film can be formed by plasma CVD, for example. As the film material at that time, as shown in FIGS. 7A to 7G, TMMOS, DMDS, HMDSO or HMDS, OMSO or OMTS, TMCTS, OMCTS, etc. can be used in addition to TEOS. Any induction silicone system capable of forming a bond of —O is not limited thereto.

The invention according to claim 5 is the method of manufacturing a half mirror substrate according to any one of claims 1 to 4 , wherein the first step forms the Sn film on the base substrate by vacuum deposition. It is a process to perform.

  With such a method of manufacturing a half mirror substrate, a good half mirror substrate can be manufactured by the transparency and reflectivity of the Sn film. In addition, since an island-grown Sn film can be formed, moisture permeation from the base substrate is possible, and warpage of the half mirror substrate can be suppressed.

According to a sixth aspect of the present invention, there is provided a base substrate made of polymethyl methacrylate or polycarbonate, an island-like Sn film formed on the surface of the base substrate , and water vapor formed so as to cover the Sn film. It has a SiO film whose transmittance is equal to or higher than the water vapor permeability of the base substrate, and an oxide Sn layer whose main component formed at the interface between the Sn film and the SiO film is SnO _2. It is a half mirror substrate.

In the half mirror substrate configured as described above, water molecules absorbed by the base substrate pass through the SiO film having a low water vapor barrier property and are discharged to the outside, so that the occurrence of warping of the base substrate is suppressed. In addition, since the progress of the oxidation of the Sn film is suppressed by the Sn oxide Sn layer that is SnO _2, it is possible to suppress a decrease in reflectance due to the oxidation of the Sn film.

In order to produce an oxidized Sn layer that is SnO ₂ , an oxidized Sn layer is formed as described in claim 7 .
The Sn film may be formed by a process of irradiating chemical species including atomic oxygen.

If such a half mirror substrate configured, since the oxide Sn layer is SnO ₂ by irradiating the atomic oxygen to Sn film is formed, the oxidation of the Sn film is suppressed.
Note that the process of irradiating chemical species including atomic oxygen includes, for example, oxygen plasma irradiation or O ₂ , O ₃ , CO, NO, NO ₂ , N ₂ O as described in claim 8. It may be a process of performing vacuum ultraviolet light irradiation in one or more gas atmospheres selected from the group.

As described above, the half mirror substrate according to claim 6 is characterized in that the water vapor transmission rate of the SiO film is equal to or higher than the water vapor transmission rate of the substrate.

In the half mirror substrate configured as described above, the SiO film can sufficiently transmit water molecules, so that the warp of the half mirror substrate can be sufficiently suppressed.
The invention according to claim 9 is the half mirror substrate according to any one of claims 6 to 8 , wherein the SiO film is obtained by adding a rare gas to a TEOS gas as a film material gas, Alternatively, the SiO film is formed by plasma CVD without adding any gas.

  In the half mirror substrate configured as described above, the water vapor barrier property of the SiO film can be lowered by using TEOS as a film material, thereby suppressing the warp of the base substrate.

According to an eleventh aspect of the present invention, in the half mirror substrate according to any one of the sixth to ninth aspects, the Sn film is formed by vacuum deposition.

  In the case of the half mirror substrate configured as described above, the function of the half mirror can be imparted by the Sn film having transparency and reflectivity. Further, since an island-like grown Sn film can be formed, moisture permeation from the PMMA substrate or the polycarbonate substrate becomes possible, and the warpage of the substrate can be suppressed.

Side sectional view showing schematic configuration of half mirror substrate SEM photo of Sn film surface It is the figure which modeled the cross section of Sn film | membrane on a PMMA board | substrate, Comprising: After 1st process (A), 2nd process (B), and 3rd process (C) Schematic diagram of film forming equipment Graph showing results of moisture resistance evaluation test Schematic diagram showing the film structure of the SiO film Structure diagram showing an example of film material of SiO film The figure which modeled the section of Sn film on the conventional PMMA substrate

Embodiments of the present invention will be described below with reference to the drawings. However, the embodiment described below is merely an example, and it goes without saying that the present invention can be implemented in various forms other than the following examples.
<1. Configuration of half mirror substrate>
FIG. 1 is a side sectional view showing a schematic configuration of the half mirror substrate of this embodiment. The half mirror substrate 1 includes a PMMA substrate 10 made of polymethyl methacrylate (hereinafter referred to as PMMA), an antifouling film (Anti-Fingerprint function film) 20 formed on the front side surface of the PMMA substrate 10, and a PMMA substrate 10. And a reflective film layer 30 formed on the back surface.

The PMMA substrate 10 has a hard coat whose surface is UV-cured of an acrylic resin.
The reflective film layer 30 includes a metal reflective film (Sn film 31) formed on the surface of the PMMA substrate 10 and a protective film (SiO film 32) formed so as to cover the Sn film 31. The Sn film 31 has light transmission and reflection properties, thereby realizing a function as a half mirror. An Sn oxide layer 33 containing SnO ₂ as a main component is formed on the surface of the Sn film 31. The SiO film 32 has a low water vapor barrier property.

In addition, FIG. 1 shows the outline | summary about the arrangement | positioning of each film | membrane, and the ratio of the magnitude | size and shape of each film | membrane may not be accurate.
In the following examples, the production of the reflective film layer 30 will be described. The production of the antifouling film 20 will be described later.
<2. Production of reflective film layer>
[Example 1]
(1) First Step: Formation of Sn Film An Sn film was formed on a PMMA substrate by vacuum deposition. Metal tin wire was used as the evaporation material. The evaporation power was 0.5 KVA, and the degree of vacuum during evaporation was 5 × 10 ⁻³ Pa (3.75 × 10 ⁻⁵ Torr).

An SEM photograph of the surface of the formed Sn film is shown in FIG. Further, FIG. 3A shows a model in which the cross section of the Sn film on the PMMA substrate is modeled.
Although the thickness of the formed Sn film cannot be measured directly, it can be estimated as 20 nm to 30 nm based on the reflectance. With such a film thickness, the Sn vapor deposition film grows (island growth) while the film maintains a particulate structure. The size of the particulate metal is about 100 nm as judged from the scale of the SEM photograph.

Since Sn in the Sn film is particulate, the Sn vapor deposition film has a surface resistance value (10 ¹³ to 10 ¹⁵ Ω / sq.) Close to that of an insulator. Therefore, it is considered that the particulate metals are not in contact with each other.
(2) Second step: Formation of oxidized Sn layer An oxide film (oxidized Sn layer) was formed on the surface of the Sn film formed in the first step by oxygen plasma irradiation treatment. The treatment conditions were an oxygen gas pressure of 5 Pa (0.0375 Torr), an RF output of 100 W, and an oxygen plasma irradiation time of 180 seconds.

FIG. 3B shows a model of the cross section of the Sn oxide layer formed in this way. An oxidized Sn layer 33 is formed on the surface of the Sn film 31. Thus, the main component of the oxidized Sn layer formed by oxygen plasma irradiation is SnO _2, and high barrier properties and high moisture resistance can be obtained due to high density.
(3) Third Step: Formation of Protective Film A film forming apparatus 50 used for forming the protective film is shown in FIG.

This film forming apparatus 50 forms a SiO film on a substrate 60 by plasma CVD. The chamber 51 of the film forming apparatus 50 is supplied with TEOS (tetraethoxysilane) gas as the SiO film material gas. The chamber 51 is connected so that Ar gas or O ₂ gas can be supplied. A high-frequency plasma can be generated by applying high frequency power of 13.56 MHz to the electrodes 52 and 53 in the chamber 51, and a SiO film can be formed on the substrate.

  In this example, the PMMA substrate on which the oxidized Sn layer was formed in the second step was disposed at the position of the substrate 60, and the SiO film was formed so as to cover the Sn film (FIG. 3C). As a result, the Sn oxide layer is located at the interface between the Sn film and the SiO film.

  In the film forming operation, the total pressure in the chamber 51 was set to 10 Pa (0.075 Torr). The breakdown is Ar partial pressure of 3.4 Pa (0.0255 Torr) and TEOS partial pressure of 6.6 Pa (0.0495 Torr). The RF power was 80 W, and the film formation time (plasma irradiation time) was 10 minutes.

In addition, since discharge cannot be performed if the RF power is too small, and discharge is unstable if the RF power is too large, it may be set in the range of 10 W to 80 W.
Further, if the Ar partial pressure is too low, the discharge cannot be performed, and if it is too high, the discharge becomes unstable. Therefore, the Ar partial pressure is preferably in the range of 0.4 to 10 Pa.

  Further, if the TEOS partial pressure is too low, film formation cannot be confirmed. If the partial pressure is high, the film formation rate increases, but if it is too high, a large amount of powder is generated. Therefore, the TEOS partial pressure is preferably in the range of 0.6 to 10 Pa.

The reflective film layer was produced on the PMMA board | substrate by the above process.
[Example 2]
A reflective film layer was produced in the same manner as in Example 1 except that the oxygen plasma irradiation time in the second step was 60 seconds.
[Comparative Example 1]
A reflective film layer was produced by the same first and third steps as in Example 1. That is, the oxidized Sn layer is not formed on the reflective film layer of Comparative Example 1.
[Comparative Example 2]
Perform the same first and second steps as in Example 1, and then change to the third step so that the urethane resin transparent paint is dried as a protective film by a curtain flow coater and the film thickness is about 15 μm after drying. It was applied and dried at 70 ° C. for 1 hour.
[Comparative Example 3]
In the third step, a reflective film layer was formed by the same method as in Example 1 except that O 2 gas was supplied into the chamber. The total pressure in the chamber was adjusted to 10 Pa. The breakdown is that the Ar partial pressure is 3.4 Pa, the TEOS partial pressure is 5.6 Pa, and the O 2 partial pressure is 1.0 Pa. Note that the SiO film (TEOS film) configured in this way has a high water vapor barrier property.
<3. Evaluation of Reflective Film Layer>
The following evaluation tests were performed on the half mirror substrate (without the antifouling film) on which the reflective film layer was produced in Examples 1 and 2.
(1) Humidity resistance evaluation test The prepared half mirror substrate was placed in a constant temperature and humidity chamber of 60 ° C. and 90% RH for 48 hours, and the transmittance change rate before and after humidification (change in transmittance before and after humidification at a wavelength of 550 nm ( %)). The rate of change was set to 10% as a reference value and allowed to be within 10%, while exceeding 10% was unacceptable.

FIG. 5A shows a graph showing the relationship between the transmittance and wavelength before and after humidification for the half mirror substrate of Example 1.
At a wavelength of 550 nm, the transmittance before humidification was 10.85% and the transmittance after humidification was 11.26%, so the rate of change was (11.26-10.85) /10.85=3.8. %, Which was below 10%.

  Note that substantially the same results were obtained for the half mirror substrate of Example 2. That is, under the oxygen plasma irradiation conditions of Examples 1 and 2, it can be said that a good Sn oxide film has already been formed at the time of irradiation for 60 seconds.

In addition, FIGS. 5B and 5C show the results of the above test performed on the half mirror substrates of Comparative Examples 1 and 2. FIG. In Comparative Example 1, the rate of change was 12.3%, and in Comparative Example 2, the rate of change was 27.4%. Thus, both Comparative Examples 1 and 2 had a rate of change exceeding 10%.
(2) Substrate warpage resistance evaluation test First, the prepared half mirror substrate (50 mm × 50 mm) was placed in a constant temperature and humidity chamber of 60 ° C. and 90% RH for 48 hours, and then indoors (room temperature 20 ° C., humidity 40). %) For 24 hours, and the lifting of the end face of the substrate was measured. In addition, with a reference value of 0.2 mm, a value of 0.2 mm or less was acceptable, and a value exceeding 0.2 mm was not acceptable. The measurement of lifting was performed by placing the half mirror substrate after humidification drying on a glass plate, and comparing the clearance between the 0.2 mm thick thickness gauge and the end face.

As a result of the above test, in Examples 1 and 2, warpage was 0.2 mm or less. On the other hand, when a similar test was performed on Comparative Example 3, the warpage exceeded 0.2 mm.
<4. Preparation of antifouling film>
An anti-fingerprint functional film (antifouling film) is formed on the surface of the PMMA substrate opposite to the surface on which the above-described reflective film layer is formed, a fluorocarbon film by plasma CVD, or a self-assembled monolayer film by FAS ( SAM).
<5. Advantages of the invention>
In the half mirror substrate of this example, the Sn film is oxidized by oxygen plasma irradiation, and has a reflective film layer that covers the Sn film with an SiO film having a low barrier property (water vapor transmission rate equal to or higher than the water vapor transmission rate of the substrate). As a result, the occurrence of warpage of the half mirror substrate could be suppressed without causing a decrease in reflectance due to the oxidation of the Sn film.

In addition, a high-fouling fingerprint dirt wiping performance could be achieved by using a fluorocarbon film by plasma CVD and an antifouling film comprising a self-assembled monomolecular film.
<6. Modification>
As mentioned above, although the Example of this invention was described, it cannot be overemphasized that this invention can take a various form, as long as it belongs to the technical scope of this invention, without being limited to the said Example at all.

For example, in the first embodiment, the configuration in which the oxidized Sn layer is formed by performing oxygen plasma irradiation on the surface of the Sn film in the second step is exemplified, but the oxidized Sn layer may be formed by other methods. . In that case, when the oxidized Sn layer is formed by irradiating chemical species including atomic oxygen, as in the case of oxygen plasma irradiation, an oxidized Sn layer containing SnO ₂ as a main component is formed, resulting in high moisture resistance. Can be obtained. Specifically, the Sn film is irradiated with vacuum ultraviolet light in one or more gas atmospheres selected from the group consisting of O ₂ , O ₃ , CO, NO, NO ₂ and N ₂ O to form the oxidized Sn layer. It is conceivable to form.

  In the first embodiment, in the third step, the Ar film is added to the TEOS gas as the film material to form the SiO film, but the rare gas other than Ar (He, Ne, Kr, Xe) is exemplified. Etc.) may be added to form an SiO film, or an additive gas may not be added, and an SiO film may be formed using only TEOS gas.

  In addition to TEOS, various materials including those shown in FIG. 7 can be used as the material for the SiO film. In order to form a low water vapor barrier SiO film, the type of additive gas in plasma CVD may be appropriately changed according to the film material.

  Moreover, in the said Example 1, although the structure which forms a Sn film | membrane by vacuum evaporation in the 1st process was illustrated, methods other than vacuum evaporation may be sufficient as long as Sn can be island-like grown. For example, the Sn film may be formed by a method such as plasma CVD, sputtering, ion plating, or cluster ion beam deposition.

  Moreover, in the said Example, although the structure which used PMMA as a base substrate was illustrated, it is good also considering a polycarbonate as a base substrate.

DESCRIPTION OF SYMBOLS 1 ... Half mirror board | substrate, 10 ... PMMA board | substrate, 20 ... Antifouling film, 30 ... Reflective film layer, 31 ... Sn film, 32 ... SiO film, 33 ... Sn oxide layer, 50 ... Film-forming apparatus, 51 ... Chamber, 52 , 53 ... Electrodes, 60 ... Substrate, 101 ... PMMA substrate, 103 ... High barrier TEOS film, 104 ... Water molecule, 105 ... Low barrier TEOS film

Claims (10)

A first step of forming an Sn film grown on islands on the surface of a base substrate made of polymethyl methacrylate or polycarbonate;
A second step of forming an oxidized Sn layer by irradiating the surface of the Sn film formed in the first step with a chemical species containing atomic oxygen;
A third step of forming a SiO film having a water vapor transmission rate equal to or higher than the water vapor transmission rate of the base substrate so as to cover the Sn oxide layer. In the second step, the surface of the Sn film is irradiated with oxygen plasma, or vacuum ultraviolet light in one or more gas atmospheres selected from the group consisting of O ₂ , O ₃ , CO, NO, NO ₂ , and N ₂ O It is a process of performing irradiation. The manufacturing method of the half mirror substrate of Claim 1 characterized by the above-mentioned. The method for producing a half mirror substrate according to claim 1, wherein the main component of the oxidized Sn layer is SnO ₂ . The third step is a step of forming the SiO film by plasma CVD with or without adding a rare gas to a TEOS gas as a film material gas. The manufacturing method of the half mirror board | substrate of any one of Claim 3 . 5. The method of manufacturing a half mirror substrate according to claim 1 , wherein the first step is a step of forming the Sn film on the base substrate by vacuum vapor deposition. A base substrate made of polymethyl methacrylate or polycarbonate;
An island-shaped Sn film formed on the surface of the base substrate;
A SiO film formed to cover the Sn film and having a water vapor transmission rate equal to or higher than the water vapor transmission rate of the base substrate ;
A half-mirror substrate, comprising: an oxide Sn layer whose main component is SnO ₂ formed at an interface between the Sn film and the SiO film. The half mirror substrate according to claim 6 , wherein the Sn oxide layer is formed by a process of irradiating the Sn film with chemical species including atomic oxygen. The process of irradiating the chemical species including atomic oxygen is oxygen plasma irradiation or vacuum in one or more gas atmospheres selected from the group consisting of O ₂ , O ₃ , CO, NO, NO ₂ , and N ₂ O. The half mirror substrate according to claim 7 , wherein the half mirror substrate is a process of performing ultraviolet light irradiation. The SiO film, the TEOS gas as film material gas, the claim 6, wherein the noble gas is added, or not be added any gas in which the formation of the SiO film by plasma CVD The half mirror substrate according to claim 8 . The half mirror substrate according to any one of claims 6 to 9 , wherein the Sn film is formed by vacuum deposition.