JP2008268277A - Infrared ray transmitting structure and infrared ray sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an infrared-transparent structure excellent in shock resistance, peeling resistance and transmittance. <P>SOLUTION: The infrared-transparent structure is characterized in that a first Y<SB>2</SB>O<SB>3</SB>layer, a YF<SB>3</SB>layer, a second Y<SB>2</SB>O<SB>3</SB>layer and a diamond-like carbon layer are laminated in the order from a substrate surface on the surface side of a substrate made of ZnS. The infrared-transparent structure is characterized in that the first Y<SB>2</SB>O<SB>3</SB>layer has a thickness of 10 to 200 nm, the YF<SB>3</SB>layer has a thickness of 400 to 800 nm, the second Y<SB>2</SB>O<SB>3</SB>layer has a thickness of 10 to 200 nm and the diamond-like carbon layer has a thickness of 100 to 500 nm. The infrared-transparent structure is characterized in that a Ge layer is further laminated between the second Y<SB>2</SB>O<SB>3</SB>layer and the diamond-like carbon layer. The infrared-transparent structure is characterized in that a Y<SB>2</SB>O<SB>3</SB>layer, a YF<SB>3</SB>layer and an MgF<SB>2</SB>layer is laminated in the order from the surface on the back surface side of the substrate made of ZnS. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an infrared transmission structure, and more particularly to an infrared transmission structure having an antireflection film and further having a diamond-like carbon layer formed as an outermost layer.

In recent years, infrared sensors such as infrared radiation temperature measuring devices and human intrusion detection sensors have been actively developed. Usually, a substrate made of zinc sulfide (hereinafter referred to as “ZnS”) is used for an infrared transmission structure used for an optical window of an infrared sensor, but ZnS has a large refractive index of 2.2, and remains as it is. Then, the reflection loss of the surface is large. For example, if the substrate is made of ZnS having a thickness of 5 mm, the maximum linear transmittance is about 70%, which is problematic in terms of improving the sensitivity of the infrared sensor.
In addition, since infrared sensors are often used not only in on-vehicle devices and home appliances but also outdoors such as security cameras, the infrared transmission structure is required to have water resistance and environmental resistance.

Therefore, if the surface of the substrate made of ZnS, Y ₂ O ₃ layer as the innermost layer, YF ₃ layer as an intermediate layer, by the anti-reflection film to form a MgF ₂ layer as the outermost layer further line transmittance only In addition, an infrared transmission structure having improved water resistance and environmental resistance is disclosed (Patent Document 1).

This is because the innermost Y ₂ O ₃ layer plays the role of an adhesive layer between the ZnS substrate and the YF ₃ layer, and the intermediate YF ₃ layer and the outermost MgF ₂ layer are the wavelengths to be measured. role not play a role as an anti-reflection film of infrared rays or visible light, and furthermore, since the MgF ₂ layer of the outermost layer is stable even in strongly elevated temperatures MgF ₂ is in the water, to improve water resistance, environmental resistance It is also something that bears.

Further, in order to play these roles, the innermost Y ₂ O ₃ layer has a thickness of about 10 to 200 nm that does not significantly affect the transmittance in the infrared region to be measured, and the intermediate layer YF ₃ The layer has a thickness of about 100 to 2,200 nm, and the outermost MgF ₂ layer has a thickness of about 20 to 800 nm.

Recently, infrared sensors are also installed in automobiles and trains as infrared scanners (detectors).
When used in automobiles, trains, etc., it is not only exposed to moisture and encounters changes in temperature and pressure, but also collides with dust and raindrops in the air and other objects. There are not a few things. For this reason, in the conventional infrared transmission structure, the impact resistance and the peel resistance are insufficient, and as a result, the surface of the antireflection film may be damaged or the antireflection film may be peeled off. As a result, the life of the infrared sensor is shortened and the reliability may be impaired.

For this reason, as the infrared transmission structure, not only the outermost water resistance and environmental resistance are high, but also the hardness and strength are extremely high, that is, because it has excellent impact resistance, the surface is hardly scratched, A diamond-like carbon (hereinafter, referred to as “DLC” as a general rule, which is an abbreviation of “Diamond Like Carbon”) that is not easily damaged is provided.
Japanese Patent No. 3704393

However, generally, as the DLC layer becomes thicker, the film stress increases and the film tends to peel off, absorbs light, and decreases the transmittance. On the other hand, when the thickness is reduced, the impact resistance is reduced, and the DLC layer is worn away in a short period of time, and the layer immediately below it is exposed.
For this reason, it has been desired to develop an infrared transmitting structure having excellent impact resistance and durability, and having excellent peel resistance and transmittance.

  The present invention has been made for the purpose of solving the above-described problems, and has been devised for materials used for each layer constituting the infrared transmission structure and the thickness of the layer. The invention of each claim will be described below.

The invention described in claim 1
An infrared ray characterized in that a first Y ₂ O ₃ layer, a YF ₃ layer, a second Y ₂ O ₃ layer, and a diamond-like carbon layer are laminated in this order from the substrate surface on the surface side of a ZnS substrate. A transmissive structure.

In the present invention, the first Y ₂ O ₃ layer, the YF ₃ layer, the second Y ₂ O ₃ layer, and the DLC layer are laminated in this order from the substrate surface on the surface side of the ZnS substrate. Therefore, an infrared transmission structure having excellent impact resistance and excellent peeling resistance and transmittance is obtained.

Specifically, the outermost DLC layer provides excellent impact resistance as the surface of the infrared transmission structure. The second Y ₂ O ₃ layer and the YF ₃ layer that are formed immediately below (inner side) have an elastic modulus of 100 GPa or more because both Y ₂ O ₃ and YF ₃ have other objects. Acts as a relaxation layer at the time of impact.

Also, two Y ₂ O ₃ layer performs good adhesion between the layer located on their upper and lower, which contributes to the improvement of peel resistance.
In particular, the DLC layer and the YF ₃ layer greatly contribute to the prevention of reflection, and as a result, the transmittance is greatly improved.

The two Y ₂ O ₃ layers, the YF ₃ layer, and the DLC layer all contain impurities that inevitably intrude due to film formation (formation), or have slightly different composition ratios. Even in such a case, it is included in the present invention. Moreover, even when another layer is laminated | stacked between each said layer, it is included in this invention.
In addition, the “surface side of the substrate” refers to the side on which the infrared light to be measured enters.

The invention according to claim 2 is the infrared transmission structure,
Each of the layers has a thickness of 10 to 200 nm for the first Y ₂ O ₃ layer, 400 to 800 nm for the YF ₃ layer, 10 to 200 nm for the second Y ₂ O ₃ layer, and 100 to 500 nm for the diamond-like carbon layer. It is an infrared transmission structure characterized by being.

  In the invention of this claim, since the thickness of each layer is appropriate, an infrared transmission structure having excellent transmittance, peel resistance, and impact resistance is obtained. In addition, the thickness of each said layer employ | adopts a suitable value suitably in the said range according to the wavelength of the infrared rays of a measuring object.

  If the DLC layer is less than 100 nm, the DLC layer is insufficient for exhibiting the impact resistance and the function as a component of the antireflection film, whereas if it exceeds 500 nm, the DLC layer tends to peel off. Although it depends on the wavelength of the infrared ray to be measured, the more preferable thickness is about 300 nm (± 20%).

The YF ₃ layer is preferably set to about 600 nm (± 20%) in consideration of the function and economy as an impact relaxation layer and the antireflection function in combination with the DLC layer.

The first Y ₂ O ₃ layer and the second Y ₂ O ₃ layer are layers for adhering the layers above and below each layer. If the thickness is less than 10 nm, the adhesive strength is insufficient, and the layer cannot exceed 200 nm. If so, the transmittance may be adversely affected. A more preferable thickness is about 30 nm (± 20%).

Invention of Claim 3 is the said infrared rays transmissive structure, Comprising:
The infrared transmission structure is characterized in that a Ge layer is further laminated between the second Y ₂ O ₃ layer and the diamond-like carbon layer.

In the invention of this claim, since there is a Ge layer that is particularly compatible (adhesive) with the DLC between the second Y ₂ O ₃ layer and the DLC layer, the DLC layer has excellent peeling resistance. Further improve. Since the Ge layer is used as an adhesive layer, if it is less than 10 nm, the adhesive force is insufficient, and if it exceeds 200 nm, the transmittance is adversely affected. Further, the Ge layer also serves as an impact relaxation layer.

Invention of Claim 4 is the said infrared rays transmissive structure, Comprising:
An infrared transmission structure characterized in that a Y ₂ O ₃ layer, a YF ₃ layer, and an MgF ₂ layer are laminated in this order from the substrate surface on the back side of the ZnS substrate.

  In the present invention, since an antireflection film is also formed on the back side of the ZnS substrate, an infrared ZnS substrate that passes through the ZnS substrate and exits from the back side toward the light receiving element. Reflection on the back side of is prevented. For this reason, the transmittance of the infrared transmission structure is further improved.

The invention according to claim 5 is the infrared transmission structure,
An infrared transmission structure having a transmittance of 80% or more for infrared rays having a wavelength of 6,000 to 10,700 nm.

  In the invention of this claim, the transmittance is 80% or more in the wavelength range of 6,000 to 10,700 nm, and 70% or more in the range of 4,900 to 11,900 nm. It becomes an excellent infrared transmission structure that can cover a wide area.

  The present inventor has further found out that an infrared transmission structure having the following structure is an infrared transmission structure having excellent impact resistance, wear resistance, and durability.

That is, the invention described in claim 6
On the surface side of the ZnS-made substrate, in order from the substrate surface, 10 to 200 nm thickness of _{ZnS, Al} 2 O _3, any one layer of Y 2 _{O 3,} 100~750nm thickness Ge layer, 500～2,000Nm An infrared transmission structure characterized in that a diamond-like carbon layer having a thickness is laminated.

In the invention of this claim, on the surface side of the substrate made of ZnS, in order from the substrate surface, any one layer of ZnS, Al ₂ O ₃ , Y ₂ O _{3 having} a thickness of 10 to 200 nm, having a thickness of 100 to 750 nm Since a Ge layer, a DLC layer having a thickness of 500 to 2,000 nm, and each layer having an appropriate thickness are laminated thereon, not only the infrared transmittance is excellent, but also excellent impact resistance, It becomes an infrared transmitting structure having wear and durability.

  In addition, the thickness of the DLC layer can be set to 500 to 2,000 nm as an economical thickness that can provide sufficient strength, and is selected according to the strength required for use. Further, the thickness of the Ge layer is selected from 100 to 750 nm so that the optimum transmittance can be obtained depending on the required thickness of the DLC layer.

The invention according to claim 7 is the infrared transmission structure,
An infrared transmission structure characterized in that a Y ₂ O ₃ layer, a YF ₃ layer, and an MgF ₂ layer are laminated in this order from the substrate surface on the back side of the ZnS substrate.

  In the present invention, since an antireflection film is also formed on the back side of the ZnS substrate, an infrared ZnS substrate that passes through the ZnS substrate and exits from the back side toward the light receiving element. Reflection on the back side of is prevented. For this reason, the transmittance of the infrared transmission structure is further improved.

The invention according to claim 8 is the infrared transmission structure,
An infrared transmission structure having a transmittance of 80% or more for infrared rays having wavelengths of 7,600 to 10,500 nm.

  In the present invention, the transmittance is 80% or more in the wavelength range of 7,600 to 10,500 nm, 70% or more in the range of 7,300 to 10,900 nm, and the far-infrared low wavelength region. It is an excellent infrared transmission structure that can cover a wide area.

The invention according to claim 9 is:
An infrared ray sensor comprising the infrared transmission structure according to any one of claims 1 to 8 as an optical window.

In the invention of this claim, since the infrared transmission structure excellent in transmittance, peel resistance, and impact resistance is used for the optical window, the sensitivity is excellent, and even if it is used for an automobile or a train, It is difficult to cause scratches on the surface, and peeling of each layer of the infrared transmitting structure is unlikely to occur. As a result, the infrared sensor has a long life and high reliability.
Here, as long as the “infrared sensor” is a sensor that detects infrared rays, the use of an infrared measuring device, an infrared detector, or the like is not limited.

  According to the present invention, an infrared transmission structure having excellent impact resistance, excellent peel resistance and transmittance, and excellent sensitivity, and further, scratches on the surface are difficult to occur. Therefore, it is possible to provide an infrared sensor having a long life and high reliability.

  Hereinafter, the present invention will be described based on the best mode. Note that the present invention is not limited to the following embodiments. Various modifications can be made to the following embodiments within the same and equivalent scope as the present invention.

(First embodiment)
The structure, the film forming method of each layer, the optical performance, the peel resistance, and the impact resistance of the infrared transmission structure according to the first embodiment will be described in order.

(Construction)
FIG. 1 conceptually shows a cross section of the infrared transmission structure according to the first embodiment. In FIG. 1, 10 is a DLC layer, 31 is a first Y ₂ O ₃ layer, 32 is a second Y ₂ O ₃ layer, 33 is a Y ₂ O ₃ layer on the back side of the substrate, and 41 is a surface side of the substrate. YF ₃ layer, 42 is a YF ₃ layer on the back side of the substrate, 50 is a ZnS substrate, and 60 is a MgF ₂ layer.
As shown in FIG. 1, this infrared transmission structure has a multilayer antireflection film formed on both front and back surfaces of a ZnS substrate 50, and a DLC layer 10 on the outermost layer (uppermost layer) on the front side. Is formed.

(Deposition method for each layer)
The DLC layer was formed by sputtering. The film formation temperature is about 100 ° C., and the film formation pressure is 1.3 × 10 ⁻¹ Pa or less.
All other layers were formed by vacuum deposition. Deposition temperature is about 350 to 380 ° C., during film formation pressure, MgF ₂ layers or less _{^{6.7 × 10 -3 Pa, Y 2}} O 3 layer and YF ₃ layers 2.7 × 10 ^{- 3} Pa or less.

The thickness of each layer formed is 300 nm for the DLC layer 10, 30 nm for the first Y ₂ O ₃ layer 31 and the second Y ₂ O ₃ layer 32, and 80 nm for the Y ₂ O ₃ layer 33 on the back side of the substrate. The YF ₃ layer 41 on the front side of the substrate is 600 nm, the YF ₃ layer 42 on the back side of the substrate is 1,300 nm, and the MgF ₂ layer 60 is 400 nm.

(Optical performance)
FIG. 2 shows measured values of transmittance in the infrared region measured by the spectrometer of the infrared transmission structure having the DLC layer according to the first embodiment. From FIG. 2, it has a transmittance of 70% or more over a wide wavelength region of 5,000 to 12,000 nm, and a transmittance of 80% or more for infrared rays having a wavelength of 6,000 to 10,700 nm. In particular, the transmittance is 90% or more for infrared rays in the region of 6,500 to 10,000 nm, and it can be seen that the film has very excellent transmittance.

(Peeling resistance and impact resistance)
The infrared transmission structure having the DLC layer of the first embodiment was subjected to a humidity test at 60 ° C. × 95% RH (relative humidity) using a constant temperature and humidity chamber. No abnormalities were observed, and it was found that the film had excellent adhesion.

(Second Embodiment)
FIG. 3 conceptually shows a cross section of the infrared transmitting structure according to the second embodiment. The infrared transmission structure of the second embodiment has the same structure as the infrared transmission structure of the first embodiment shown in FIG. 1 except that the infrared transmission structure of FIG.

  The Ge layer 20 was formed by vacuum deposition using an electron beam. The deposition temperature is room temperature, the deposition pressure is 0.2 Pa, and the thickness of the deposited Ge layer is 30 nm. The other layers are formed in the same manner as in the first embodiment.

(Test results)
Since the Ge layer is excellent in adhesiveness and also serves as an impact relaxation layer, the infrared transmitting structure of the second embodiment exhibits particularly excellent peel resistance and impact resistance.
Moreover, since the thickness of the Ge layer was appropriate, the optical performance was as good as that of the infrared transmission structure according to the first embodiment.

(Third embodiment)
In this embodiment, on the surface of a ZnS substrate, an Al ₂ O ₃ layer is formed as a first layer to a thickness of 30 nm, a Ge layer is formed as a second layer to a thickness of 240 nm, and a DLC layer is thick as a third layer. The thickness is 1300 nm. The formation method of each layer is the same as the previous two embodiments.

(Test results)
No abnormalities were found in the film even after 300 hours passed in the weather resistance test with ultraviolet rays and water, and it was found that the film had excellent adhesion.
Further, since the DLC layer was as thick as 1,300 nm, the impact resistance, wear resistance, and durability were very excellent.

Furthermore, the optical performance test of the infrared transmission structure of the third embodiment was performed. The test results are shown in FIG.
As shown in FIG. 4, since the infrared transmission structure according to the present embodiment has an appropriate combination of materials and thicknesses of the respective layers, although the Ge layer and the DLC layer are relatively thick, the wavelengths of 7,600 to 10, It can be seen that the transmittance is 80% or more in the range of 500 nm, 70% or more in the range of 7,300 to 10,900 nm, and covers the low wavelength region of far infrared rays widely.

(Fourth embodiment)
An infrared transmission structure was obtained in the same manner as in the third embodiment except that the ZnS layer was formed to 30 nm as the first layer. The ZnS layer is deposited by vacuum deposition, the deposition temperature is about 200 ° C., and the deposition pressure is 2.0 × 10 ⁻² Pa or less.

  The infrared transmission structure obtained in the present embodiment has excellent adhesion as in the infrared transmission structure obtained in the third embodiment, and has impact resistance, wear resistance, durability. It was excellent in nature.

(Fifth embodiment)
An infrared transmission structure was obtained in the same manner as in the third embodiment except that the Y ₂ O ₃ layer was formed to 30 nm as the first layer.

  The infrared transmission structure obtained in the present embodiment has excellent adhesion as in the infrared transmission structure obtained in the third embodiment, and has impact resistance, wear resistance, durability. It was excellent in nature.

It is a figure which shows notionally the cross section of the infrared rays transmission structure which has a DLC layer of the 1st Embodiment of this invention. It is a figure which shows the measured value of the transmittance | permeability in an infrared region of the infrared rays transmission structure which has a DLC layer of the 1st Embodiment of this invention. It is a figure which shows notionally the cross section of the infrared rays transparent structure which has Ge layer under the DLC layer of 2nd Embodiment of this invention. It is a figure which shows the measured value of the transmittance | permeability in an infrared region of the infrared transmission structure which has a DLC layer of the 3rd Embodiment of this invention.

Explanation of symbols

10 DLC layer 20 Ge layer 31 1st Y ₂ O ₃ layer 32 2nd Y ₂ O ₃ layer 33 Y ₂ O ₃ layer 41 on the back side of the substrate 41 YF ₃ layer 42 on the front side of the substrate 42 on the back side of the substrate YF ₃ layer 50 ZnS substrate 60 MgF ₂ layer

Claims (9)

An infrared ray characterized in that a first Y ₂ O ₃ layer, a YF ₃ layer, a second Y ₂ O ₃ layer, and a diamond-like carbon layer are laminated in this order from the substrate surface on the surface side of a ZnS substrate. Transparent structure. Each of the layers has a thickness of 10 to 200 nm for the first Y ₂ O ₃ layer, 400 to 800 nm for the YF ₃ layer, 10 to 200 nm for the second Y ₂ O ₃ layer, and 100 to 500 nm for the diamond-like carbon layer. The infrared transmission structure according to claim 1, wherein the infrared transmission structure is provided. The infrared transmission structure according to claim 1, wherein a Ge layer is further laminated between the second Y ₂ O ₃ layer and the diamond-like carbon layer. 4. The Y ₂ O ₃ layer, the YF ₃ layer, and the MgF ₂ layer are laminated on the back surface side of the ZnS substrate in order from the substrate surface. 5. Infrared transmission structure.   The infrared transmission structure according to any one of claims 1 to 4, wherein a transmittance for infrared rays having a wavelength of 6,000 to 10,700 nm is 80% or more. On the surface side of the ZnS-made substrate, in order from the substrate surface, 10 to 200 nm thickness of _{ZnS, Al} 2 O _3, any one layer of Y 2 _{O 3,} 100~750nm thickness Ge layer, 500～2,000Nm An infrared transmitting structure characterized in that a diamond-like carbon layer having a thickness is laminated. The infrared transmission structure according to claim 6, wherein a Y ₂ O ₃ layer, a YF ₃ layer, and an MgF ₂ layer are laminated in this order from the substrate surface on the back surface side of the ZnS substrate.   The infrared transmission structure according to claim 6 or 7, wherein the transmittance for infrared rays having a wavelength of 7,600 to 10,500 nm is 80% or more.   An infrared sensor, wherein the infrared transmission structure according to any one of claims 1 to 8 is used for an optical window.

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