Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2002-08-27
2004-02-10
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of silicon containing
44, 44, 44, 44
Reexamination Certificate
active
06689479
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an anti-reflection film, and a silica layer which can be suitably used for this.
2. Related Art
Transparent substrates such as glasses and plastics are used in various displays used in liquid crystal displays, plasma displays, CRT displays of computers, word processors, televisions, display plates and the like, indicators such as instruments and the like, rearview mirrors, goggles, window glasses and the like. Since letters and figures and other information are read out through those transparent substrates, there is a drawback that, when the light is reflected on the surfaces of the transparent substrates, it becomes difficult to read out the information.
Currently, in order to solve the above drawbacks, light reflection is prevented by using an anti-reflection film comprising a substrate, a hard coated layer, and a layer stack formed by depositing a plurality of thin layers having different refractive indices (e.g. low refractive index layer, intermediate refractive index layer, high refractive index layer), and applying the anti-reflection film on the surface of the above transparent substrate.
In this case, it is known that provision of a layer having a small refractive index for effectively preventing light reflection, so-called a low refractive index layer on an outermost layer in the anti-reflective film with a layer stack provided thereon (surface opposite to a substrate of the anti-reflection film) is preferable and, as the layer having a small refractive index, a silica layer is suitably used.
In addition, as a method of forming a layer stack, a method of formation by a sputtering method or a evaporation method has been previously known.
However, when a layer stack is formed by a sputtering method, there is a problem that precision in layer formation is better, but since a formation rate is very small, the productivity is deteriorated. In addition, when a layer stack is formed by a evaporation method, there is no problem in a rate of layer formation, but formation precision is bad and, therefore, yield is deteriorated, and this may lead to the high cost of the anti-reflection film, being problematic.
In order to solve the aforementioned problems, currently, a method of forming a layer stack by a plasma CVD method is developed. By forming a layer stack by a plasma CVD method, a formation rate can be dramatically heightened as compared with formation by a sputtering method or the like.
SUMMARY OF THE INVENTION
However, when a layer stack is formed by a plasma CVD method, the following problems arise newly.
The first problem is that the adherability between respective thin layers forming a layer stack is deteriorated as compared with the case where a layer stack is formed by a sputtering method or a evaporation method.
In addition, the second problem is that, when a titanium oxide layer functioning as a high refractive index layer among thin layers forming a layer stack is formed by a plasma CVD method, the titanium oxide layer is bad in the resistance to wet heat, and a refractive index is not stable in some cases.
A main object of the present invention is to provide, in an anti-reflection film having a layer stack, an anti-reflection film in which each thin layer constituting a layer stack has the better resistance to wet heat and, therefore, the optical properties are excellent due to stable refractive index in each thin layer and, further, a formation rate is high, and the adherability of each thin layer is also excellent.
In addition, apart from the above problems, there is a new problem that a layer stack of an anti-reflection film prepared by a plasma CVD method is inferior in the resistance to chemicals. For example, in a process of preparing an anti-reflection film, there is a process of treating a layer stack with an alkali in some cases and, upon this, a thin layer formed by a plasma CVD method is dissolved in an alkali solution in some cases.
In particular, a low refractive index layer in a layer stack in an anti-reflection film is used as an outermost layer of a layer stack in many cases and, therefore, since the layer is directly contacted with an alkali solution upon the alkali-treatment, the layer is dissolved in many cases.
In order to solve such the problem, a protecting film is adhered on an outermost layer of a layer stack upon the alkali-treatment, but this can not be said to be a fundamental resolution strategy. In addition, since it is necessary to detach the protecting film, there is a problem that a preparation process becomes complicated.
The present invention has been achieved in order to solve the above problems. It is an object of this invention to provide an anti-reflection film which is excellent in the resistance to chemicals even when formed by a plasma CVD method, and a silica layer.
The present invention for attaining the aforementioned object, firstly, an anti-reflection film having a substrate, a hard coated layer situated on the substrate, and a layer stack which is situated on the hard coated layer and in which a plurality of thin films are deposited, wherein the layer stack is formed by depositing a thin layer formed by a plasma CVD method, and a thin layer formed by a sputtering method or a evaporation method.
According to this invention, since a layer stack constituting an anti-reflection film is formed by depositing a thin layer formed by a plasma CVD method and a thin layer formed by a sputtering method or a evaporation method, the productivity can be improved as compared with formation of all thin layers constituting a layer stack by a sputtering method or a evaporation method and, on the other hand, the resistance to wet heat of each thin layer can be improved and, at the same time, the adherability between respective layers can be improved.
In addition, in the first invention, it is preferable that, among the aforementioned thin layers forming a layer stack, a thin layer formed by a plasma CVD method is a low refractive index layer having a refractive index of not less than 1.40 and not greater than 1.46 (&lgr;=550 nm), or an intermediate refractive index layer having a refractive index of not less than 1.55 and less than 1.80 (&lgr;=550 nm), and a thin layer formed by a sputtering method or a deposition layer is a high refractive index layer having a refractive index of not less than 1.80 (&lgr;=550 nm).
According to this aspect, a formation rate can be heightened by forming a low refractive index layer or an intermediate refractive index layer which dose not give rise to a problem when formed by a plasma CVD method (that is, dose not give rise to a problem in the resistance to wet heat) by a plasma CVD method and, on the other hand, a refractive index of a high refractive index layer can be stabilized by forming only a high refractive index layer in which a refractive index is not stabilized in some cases due to bad resistance to wet heat when formed by a plasma method, by a sputtering method.
In addition, in the first invention, the layer construction of the layer stack may be an intermediate refractive index layer, a high refractive index layer and a low refractive index layer from a hard coated layer side.
Further, in the first invention, the layer construction of the layer stack may be a high refractive index layer, a low refractive index layer, a high refractive index layer and a low refractive index layer from a hard coated layer side.
In addition, in the first invention, a low refractive index layer or an intermediate refractive index layer formed by the plasma CVD method may be a silicon layer, and a high refractive index layer formed by a sputtering method or a evaporation method may be a titanium oxide layer or an ITO layer exhibiting a high resistance.
The present invention for attaining the aforementioned object is, secondly, an anti-reflection film having a substrate, a hard coated layer situated on the substrate, and a layer stack which is situated on the hard coated layer and in which a plurality of t
Nakajima Tatsuji
Sakakura Osamu
Dai Nippon Printing Co. Ltd.
Jones Deborah
Ladas & Parry
Xu Ling
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