JPS6258201A - Antireflection filter - Google Patents

Abstract

PURPOSE:To prevent the generation of cracks in multi-layered coating films and to improve the antireflection effect thereof by using yttria (Y2O3) to form a layer which contacts with a base material among said films. CONSTITUTION:The coating films 2 are formed on the plastic base material 1. The films 2 consist of the yttria layer 3 directly formed on the material 1, the 2nd coating layer 4 formed on the yttria layer 3 and the 3rd coating layer 5 formed on the 2nd coating layer 4. The yttria layer 3 is formed by using a thin film forming method such as vacuum deposition or sputtering method. Since the layer which contacts with the plastic base material is formed by using the yttria (Y2O3), the generation of the cracks in the coating films is suppressed even if the plastic base material elongates or contracts with a temp. change and at the same time the adhesiveness of the coating films and the plastic base material is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to filters for CRTs in computer terminals and word processors, and antireflection filters used in optical components and the like.

``Prior Art'' In recent years, office automation has become extremely popular, and as a result, eye fatigue caused by viewing CRTs for display for long periods of time has begun to be seen as a problem.

Such eye fatigue is largely due to indoor light reflecting off the surface of the CRT and entering the eyes, so a general measure to prevent eye fatigue is to install a device near the surface of the CRT to suppress the reflection of indoor light. The method used is to attach an anti-reflection filter.

Initially, anti-reflection filters such as those described above were prototyped by coating a plastic substrate directly with coating agents such as several types of metal oxides. For example, the most common three-layer coating film is one in which alumina, zirconium oxide, and magnesium fluoride are sequentially deposited on a plastic substrate.

However, the above-mentioned plastic base material has a large coefficient of thermal expansion and is easy to bend, while the above-mentioned coating film has poor elasticity, so the surface of the plastic base material expands and contracts due to heating during coating by vacuum evaporation method and cooling after coating. However, there was a problem in that cracks were likely to occur in the coating film, especially in the alumina layer that was in contact with the plastic substrate.

Therefore, an antireflection filter as shown in FIG. 3 was devised. This anti-reflection filter is provided with a buffer layer 6 made of silicon dioxide or the like between the coating film 2 and the plastic base material l, and this buffer layer 6 prevents the coating film from expanding or contracting when the plastic base material l expands or contracts. In addition to relaxing the stress generated in 2 and preventing the occurrence of cracks,
It became possible to improve the adhesiveness between the plastic base material 1 and the coating film 2.

"Problems to be Solved by the Invention" However, in the above conventional antireflection filter, the refractive index of silicon dioxide constituting the buffer layer 6 is 1.46.
Since this is close to the refractive index of the plastic base material (around 1.52), it is impossible to obtain an antireflection effect by the buffer layer 6. Therefore, in the above-mentioned conventional antireflection filter, the buffer layer 6 must be formed in addition to the coating film 2 for antireflection, resulting in a problem that the number of steps is large and the manufacturing cost of the filter is high.

In addition, in a conventional antireflection filter in which a buffer layer 6 made of silicon dioxide is formed, the first coating layer deposited on the buffer layer 6 is made of alumina (refractive index 1.63). The antireflection effect of the filter will be highest when zirconium oxide is selected as the second coating layer and magnesium fluoride is selected as the third coating layer (outermost layer), but magnesium fluoride as the outermost layer is particularly effective against plastic substrates. When sufficient heating cannot be carried out during vapor deposition, as in the case of using a carbon fiber, there is a problem that the physical properties are unstable and the durability against friction and the like is poor. If silicon dioxide, which has stable physical properties, is tried to be used as the third coating layer, the anti-reflection properties of the coating film 2 will be unbalanced, and as a result, by forming the buffer layer 6, the third coating layer There was a dissatisfaction that silicon dioxide, which has excellent durability, could no longer be used.

"Means for Solving the Problems" The anti-reflection filter of the present invention has a multilayer coating film applied on a plastic base material, in which the layer in contact with the base material is formed of Y to S. be.

"Function" In the antireflection filter of the present invention, the coating layer made of yttoria formed in contact with the plastic substrate prevents cracks from occurring in the coating film and enhances the antireflection effect.

"Specific Configuration of the Invention" Hereinafter, the specific configuration of the present invention will be explained with reference to the drawings.

FIG. 1 shows a first embodiment of the antireflection filter of the present invention, and in this figure, reference numeral 1 indicates a plastic base material. A coating film 2 is formed on this plastic base material l, and this coating film 2 includes an ittria layer 3 formed directly on the plastic base material 1,
It consists of a second coating layer 4 formed on this itria layer 3, and a third coating layer 5 further formed on this second coating layer 4.

The plastic base material 1 is made of acrylic resin, polycarbonate resin (PC), or polystyrene resin (PS).
It is made of plastic such as

The above-mentioned ittria layer 3 is formed using a thin film forming method such as a vacuum evaporation method or a sputtering method. The optical thickness (nd) of this ittria layer 3 is 1/4λ. where is the refractive index of the layer, d is the layer thickness, λ
is the center wavelength (hereinafter the same).

The second coating layer 4 is formed in the same manner as the ittria layer 3 using a conventionally used high refractive index coating agent such as titanium dioxide or zirconium dioxide, and its optical thickness is It is assumed to be 1/2λ.

The third coating layer 5 is made of silicon dioxide or magnesium fluoride, which is relatively strong among low refractive index coating agents and has excellent abrasion resistance, and is formed by the same method as that for the ittria layer 3. Its optical thickness is 1/4λ.

Next, the effect of this antireflection filter will be explained.

The following table shows the properties of Ittria, other coating agents that are generally used as intermediate refractive index materials, and silicon dioxide, which has traditionally been used as a buffer layer. rate 1
．． 52. 2j+x) was vacuum-deposited to a predetermined thickness, and various properties of the coating layer thus obtained were compared.

Seatape test 1; Cellotape adhesion residual rate test 9it'
)": The coating film was magnified 400 times and examined clearly using a microscope, and the degree of cracks was determined in 5 of 1.2.3.4.5.
It is evaluated in stages, and the higher the value, the less cracks occur.

Hardness 3: Pencil hardness test Hot water immersion test 4: After immersing the sample in 50°C hot water, perform the cellophane tape test at predetermined intervals, and the time it takes until the adhesion of the coating film is found to be poor.

As shown by the table, the coating layer formed by Ittria exhibits high adhesion to the acrylic substrate and less cracking. Although silicon oxide in the table is excellent in durability, it has a low refractive index, so it is difficult to obtain a sufficient antireflection effect as an intermediate refractive index layer.

In the anti-reflection filter having such a structure, since the ittria layer 3 is a layer in contact with the plastic base material 1, even if the plastic base material 1 expands or contracts due to temperature changes,
It is possible to suppress the occurrence of cracks in the coating film 2, and at the same time, it is possible to improve the adhesion between the coating film 2 and the plastic base material 1. Therefore, unlike conventional anti-reflection filters, this anti-reflection filter does not require a buffer layer made of silicon dioxide or the like in addition to the anti-reflection layer, which simplifies the filter manufacturing process and reduces manufacturing costs. It is.

Moreover, in this anti-reflection filter, the ittria layer 3 is
It has a higher refractive index (1,7
9) For the third coating layer (outermost layer), select silicon dioxide, which is highly durable and easy to deposit, since it cannot be used in filters with conventional silicon dioxide buffer layers. be able to. Therefore, the coating film 2 of this anti-reflection filter is
By selecting silicon dioxide for the coating layer 5, excellent durability can be achieved.

Note that the antireflection filter of the present invention is not limited to the above embodiments, and various other modifications are possible. For example, as shown in FIG. 2, a coating film 2.3 is coated on both sides of a plastic substrate 1 with an ittria layer 3.3 as the innermost layer.
2 can also be formed, and in this case, a higher antireflection effect can be obtained.

"Effects of the Invention" The antireflection filter of the present invention has a multilayer coating film in which the layer in contact with the plastic base material is
*Os), it is possible to suppress the occurrence of cracks in the coating film even when the plastic base material expands and contracts due to temperature changes, and at the same time, it improves the adhesion between the coating film and the plastic base material. can be increased. Therefore, unlike conventional plastic anti-reflection filters, this anti-reflection filter does not require a buffer layer made of silicon dioxide or the like in addition to a coating layer for anti-reflection, which simplifies the filter manufacturing process. It is possible to reduce manufacturing costs.

In addition, in this antireflection filter, the ittria layer has a higher refractive index (1,79
) could not be used in filters with a conventional silicon dioxide buffer layer as the outermost layer,
Silicon dioxide, which is highly durable and easy to vapor deposit, can be selected. Therefore, the coating film of this anti-reflection filter can be made to have excellent durability by selecting silicon dioxide as the outermost layer. I can do it.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a first embodiment of the anti-reflection filter of the present invention, and FIG. 2 is a cross-sectional view showing a second embodiment of the anti-reflection filter of the present invention.
FIG. 3 is a cross-sectional view showing a conventional anti-reflection filter. l...Plastic base material 2...Coating film 3...Ittria layer

Claims (1)

[Claims] An antireflection filter comprising a multilayer coating film formed on one or both sides of a plastic base material, wherein a layer of the multilayer coating film that contacts the base material is formed of yttria (Y_2O_3). filter.