JP2019199391A - Glass substrate and manufacturing method of glass substrate - Google Patents

Abstract

To provide a glass substrate with easy handling by improving strength of fluorophosphate-based glass-made glass substrate low in hardness, and a manufacturing method therefor.SOLUTION: There are provided a glass substrate consisting of a fluorophosphate glass, and having surface properties of the glass substrate, including surface strain (S), surface kurtosis (S), maximum valley depth (S), valley solution holding index (S), or core solution holding index (S), satisfying prescribed property values, and a manufacturing method therefor.SELECTED DRAWING: None

Description

  The present invention relates to a glass substrate made of fluorophosphate glass and a method for producing the same.

  In recent years, optical filters that sufficiently transmit light in the visible wavelength region but shield light in the near infrared wavelength region have been used for various applications.

  For example, solid-state imaging devices (CCD, CMOS, etc.) are used in imaging devices such as digital still cameras and digital video. An optical filter is disposed between the imaging lens and the solid-state imaging device in order to bring the sensitivity of the solid-state imaging device close to human visibility.

  Among these, as an optical filter for an imaging device, a near infrared absorbing glass in which CuO or the like is added to a fluorophosphate glass or a phosphate glass so as to selectively absorb light in the near infrared wavelength region, A glass filter using the same is known (see Patent Document 1).

  By the way, fluorophosphate-based glass has a low hardness as a material characteristic in the first place and is easily damaged. And as a use of the plate-shaped glass substrate as described above (especially, an application such as an infrared cut filter as an optical member), since the requirement of thickness accuracy is severe, the thickness of the glass substrate is reduced and the strength is lowered. There was a problem.

  In order to improve the strength of the glass substrate made of fluorophosphate glass as described above, a plate-like optical glass whose strength is improved by performing an etching process after chamfering or polishing (lapping) and its manufacture A method is known (see, for example, Patent Document 2).

Japanese Patent No. 4169545 JP 2010-168262 A

  However, in such an optical glass, after the etching process and the polishing process, a mirror finish is finally performed by a polishing process using fine abrasive grains called polishing. It has been found by the study of the present inventors that the strength of the steel is reduced.

  After this polishing, the abrasive was usually washed away by washing with an alkaline cleaning solution, but the present inventors also discovered that the surface of the glass substrate was etched by this alkaline cleaning solution, resulting in deep irregularities on the surface of the glass substrate. .

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a glass substrate that is easy to handle and a method for producing the same, with improved strength, even if the glass substrate is made of a fluorophosphate glass having low hardness.

  The present invention provides a glass substrate having the following configuration and a method for producing the same.

[1] A glass substrate made of fluorophosphate glass, wherein the surface distortion of the glass substrate satisfies the following formula (1) as a surface distortion ( _Ssk ).
S _sk ≧ −1.0 (1)
[2] A glass substrate made of fluorophosphate glass, wherein the surface kurtosis (S _ku ) satisfies the following formula (2) as the surface characteristics of the glass substrate.
S _ku ≦ 10 (2)
[3] A glass substrate made of fluorophosphate glass, wherein the maximum valley depth (S _v ) satisfies the following formula (3) as the surface characteristics of the glass substrate.
S _v ≦ 9 (3)
[4] A glass substrate made of a fluorophosphate glass, wherein a valley solution retention index (S _vi ) satisfies the following formula (4) as a surface property of the glass substrate.
S _vi ≦ 0.14 (4)
[5] A glass substrate made of fluorophosphate glass, wherein the core solution retention index (S _ci ) satisfies the following formula (5) as the surface characteristics of the glass substrate.
S _ci ≧ 1.40 (5)

[6] The ratio of the average hydrogen concentration (A) in the region having a depth of 5 nm to 55 nm from the outermost surface of the glass substrate to the average hydrogen concentration (B) in the region having a depth of 500 nm to 550 nm that is a bulk portion of the glass substrate is The glass substrate according to any one of [1] to [5], wherein the following formula (6) is satisfied.
(A) / (B) ≦ 10 (6)

[7] A step of preparing a plate glass made of fluorophosphate glass, a polishing step of precisely polishing the main surface of the plate glass, and an acid for acid-cleaning the polishing surface of the plate glass after the polishing step A method for producing a glass substrate, comprising: a cleaning step.
[8] In the acid cleaning step, the plate glass is immersed in an acidic aqueous solution containing either hydrochloric acid or nitric acid having a pH of 0.5 to 3.0 or 20 to 45 ° C. for 1 to 30 minutes. 7] The manufacturing method of the glass substrate of description.

  According to the glass substrate and the manufacturing method thereof of the present invention, it is possible to provide a glass substrate having improved substrate strength by satisfying a predetermined range of the surface characteristics of a glass substrate made of fluorophosphate glass. it can.

It is the figure which showed the surface bearing area ratio curve for demonstrating a parameter. It is a figure for demonstrating the measuring method of a ball-on-ring (BoR) test. It is a diagram showing the relationship between the surface skewness (S _sk) and BoR strength of the glass substrate obtained in Example. Is a graph showing the relationship between the surface kurtosis of the glass substrate obtained in Example and (S _ku) and BoR strength. Is a diagram showing the relationship between the maximum valley depth (S _v) and BoR strength of the glass substrate obtained in Example. It is a diagram illustrating a relationship between the Valley solution holding index (S _vi) and BoR strength of the glass substrate obtained in Example. It is a diagram showing the relationship between the core solution holding index (S _ci) and BoR strength of the glass substrate obtained in Example. It is the figure which showed the relationship between the surface roughness (Ra) of the glass substrate obtained in the Example, and BoR intensity | strength.

  Hereinafter, the present invention will be described with reference to embodiments. In addition, this invention is limited to the following description and is not interpreted.

  The glass substrate which is one embodiment of the present invention is a glass substrate made of fluorophosphate glass whose surface characteristics are predetermined. This glass substrate shall satisfy predetermined conditions as described below for its surface characteristics, and the strength of the glass substrate can be improved by such a configuration.

<Glass substrate>
The glass substrate used in the present embodiment is a substrate formed of fluorophosphate glass. As the fluorophosphate glass used as the material of the glass substrate, a known fluorophosphate glass can be used, and is not particularly limited.

  This glass substrate made of fluorophosphate glass is characterized by its surface characteristics and has surface characteristics that satisfy the following predetermined relationship. By satisfying such a relationship, the strength of the glass substrate made of fluorophosphate glass can be improved, and the same effect can be obtained when an optical film is provided on the glass substrate.

The surface characteristics used in the present embodiment are parameters related to the surface shape. Specifically, the surface distortion (S _sk ), the surface kurtosis (S _ku ), the maximum valley depth (S _v ), _Examples include a valley solution retention index (S _vi ) and a core solution retention index (S _ci ). For these parameters, surface analysis data measured with an atomic force microscope (AFM) is subjected to leveling processing using image analysis software (for example, SPIP 6.2.6 manufactured by Image Metrology), and roughness analysis is performed. It is a parameter calculated by this.

  At least one of these surface characteristics preferably satisfies the following relational expression, preferably satisfies two or more, more preferably satisfies three or more, particularly preferably satisfies four or more, and satisfies all Most preferred.

When two or more surface characteristics are satisfied, at least one of the surface skewness (S _sk ) and the surface kurtosis (S _ku ), the valley solution retention index (S _vi ), and the core solution retention index (S _ci ) It is preferable to satisfy one.

In this embodiment, the surface skewness (S _sk ) is obtained by performing leveling processing on surface analysis data using an atomic force microscope using image analysis software (for example, SPIP 6.2.6 manufactured by Image Metrology). This is an index that represents the distortion of the histogram of the distribution of the height data of each coordinate. This surface skewness (S _sk ) is expressed by the following formula (I)

（式中、ＭはＸ軸方向の測定点数を、ＮはＹ軸方向の測定点数を、Ｓ_ｑは二乗平均平方根粗さを、ｚ（ｘ_ｋ，ｙ_ｌ）は座標（ｘ_ｋ，ｙ_ｌ）における高さ（ここで、ｘ_ｋはｋ番目のｘ座標、ｙ_ｌはｌ番目のｙ座標を表す）を、μは平均高さを表す。）で定義される。

(Wherein M is the number of measurement points in the X-axis direction, N is the number of measurement points in the Y-axis direction, S _q is the root mean square roughness, and z (x _k , y _l ) is the coordinate (x _k , y _l ) (Where x _k represents the k th x coordinate, y _l represents the l th y coordinate), and μ represents the average height).

（式中、Ｍ，Ｎ，ｚ（ｘ_ｋ，ｙ_ｌ）およびμは上記と同一である。）

（式中、Ｍ，Ｎおよびｚ（ｘ_ｋ，ｙ_ｌ）は上記と同一である。）で定義される。 Here, S _q is the following formula (II), and μ is the following formula (III).

(In the formula, M, N, z (x _k , y _l ) and μ are the same as above.)

(Wherein M, N and z (x _k , y ₁ ) are the same as above).

Here, if S _sk = 0, surface analysis data using an atomic force microscope is leveled using image analysis software (for example, SPIP 6.2.6 manufactured by Image Metrology), for example, Gaussian distribution. It shows that the distribution of the height data of each coordinate of the processed data is desirable. When S _sk <0, the height distribution histogram indicates that the left tail is a long curve. For example, an image in which deep holes are scattered on a flat surface is obtained. When S _sk > 0, the height distribution histogram is high. The height distribution histogram shows that the tail is a long curve to the right, and for example, a flat image with a peak is obtained. In other words, when S _sk > 0, the surface has many fine peaks, and when S _sk <0, the surface has many fine valleys. Further, when | S _sk |> 1.0, it is suggested that extreme holes and peaks exist on the surface.

In the present embodiment, it is preferable that the surface distortion (S _sk ) satisfies the following formula (1).
S _sk ≧ −1.0 (1)

By satisfying this relational expression, the strength of the glass substrate can be improved. Furthermore, _Ssk is more preferably −0.7 or more, further preferably −0.5 or more, and particularly preferably −0.3 or more.

Moreover, as an upper limit of _Ssk , 1.0 or less is preferable, 0.7 or less is more preferable, 0.5 or less is further more preferable, and 0.3 or less is especially preferable.

（式中、ＭはＸ軸方向の測定点数を、ＮはＹ軸方向の測定点数を、Ｓ_ｑは二乗平均平方根高さを、ｚ（ｘ_ｋ，ｙ_ｌ）は座標（ｘ_ｋ，ｙ_ｌ）における高さ（ここで、ｘ_ｋはｋ番目のｘ座標、ｙ_ｌはｌ番目のｙ座標を表す）を、μは平均高さを、表す。）で定義される。 In the present embodiment, the surface kurtosis (S _ku ) is an index representing the sharpness of the height distribution histogram. This surface kurtosis (S _ku ) is expressed by the following formula (IV)

(Where, M is the number of measurement points in the X-axis direction, N is the number of measurement points in the Y-axis direction, S _q is the root mean square height, and z (x _k, y _l ) is the coordinate (x _k, y _l). ) (Where x _k represents the k th x coordinate and y _l represents the l th y coordinate), and μ represents the average height).

Here, in the case of the Gaussian distribution, S _ku approaches 3.0 as the number of pixels increases, and when S _ku <3.0, the distribution is a gentle curve, and S _ku > 3.0. And a sharp distribution. In other words, if S _ku <3.0, it means that the surface is flat, and if S _ku > 3.0, it means that the surface has many irregularities.

In the present embodiment, it is preferable that the surface kurtosis (S _ku ) satisfy the following formula (2).
S _ku ≦ 10 (2)

When this relational expression is satisfied, the strength of the glass substrate can be improved. Furthermore, _Sku is more preferably 8 or less, further preferably 6 or less, particularly preferably 5 or less, and most preferably 4 or less.

In the present embodiment, the maximum valley depth (S _v ) is an index of the maximum value of the concave portion formed by polishing scratches or indentation scratches generated on the substrate. As the maximum valley depth (S _v ), the absolute value of the smallest Z value of the measurement data is selected.

In the present embodiment, it is preferable that the maximum valley depth (S _v ) satisfies the following expression (3).
S _v ≦ 9 (3)

When this relational expression is satisfied, the strength of the glass substrate can be improved. Furthermore, _Sv is more preferably 7 or less, further preferably 5 or less, and particularly preferably 4 or less.

In the present embodiment, the valley solution retention index (S _vi ) is an index indicating the volume of the portion close to the bottom of the concave portion. This valley solution retention index (S _vi ) represents the frequency of the deep concave portion that dominates the surface strength. The valley solution retention index (S _vi ) is expressed by the following equation (V)

（式中、ＭはＸ軸方向の測定点数を、ＮはＹ軸方向の測定点数を、Ｓ_ｑは二乗平均平方根高さを、Ｖ_ｖ（ｈ_０．８０）は表面ベアリング面積比曲線より上で水平線ｈ_０．８０より下の領域を表す。）で定義される。

(Where M is the number of measurement points in the X-axis direction, N is the number of measurement points in the Y-axis direction, S _q is the root mean square height, and V _v (h _0.80 ) is above the surface bearing area ratio curve. Represents the area below the horizontal line h _0.80 .

FIG. 1 is a diagram for explaining a surface bearing area ratio curve, a horizontal line h _0.80 , and a horizontal line h _0.05 . The surface bearing area ratio curve is also called an Abbott curve and represents a value obtained by integrating a height distribution histogram. The horizontal line h _0.80 is a horizontal line at a value of 80% of the bearing area ratio curve, the height at this time is Z _0.80 , and the horizontal line h _0.05 is 5% of the bearing area ratio curve. The height at this time is Z _0.05 . That is, V _v (h _0.80 ) in the above formula (V) indicates the region of “Air in valley zone” in FIG.

In the present embodiment, it is preferable that this valley solution retention index (S _vi ) satisfies the following formula (4).
S _vi ≦ 0.14 (4)

When this relational expression is satisfied, the strength of the glass substrate can be improved. Furthermore, S _vi is more preferably 0.13 or less, and further preferably 0.12 or less.

Moreover, since this S _vi is a function that approaches 0, 11, its lower limit value is preferably more than 0.11, more preferably closer to 0.11.

In the present embodiment, the core solution retention index (S _ci ) is an index indicating in-plane uniformity. The core solution retention index (S _ci ) is a value approaching 1.56 if the height distribution is a Gaussian distribution. The core solution retention index (S _ci ) is expressed by the following formula (VI)

（式中、ＭはＸ軸方向の測定点数を、ＮはＹ軸方向の測定点数を、Ｓ_ｑは二乗平均平方根高さを、Ｖ_ｖ（ｈ_０．０５）は表面ベアリング面積比曲線より上で水平線ｈ_０．０５より下の領域を、Ｖ_ｖ（ｈ_０．８０）は表面ベアリング面積比曲線より上で水平線ｈ_０．８０より下の領域を表す。）を、表す。）で定義される。

(Where M is the number of measurement points in the X-axis direction, N is the number of measurement points in the Y-axis direction, S _q is the root mean square height, and V _v (h _0.05 ) is above the surface bearing area ratio curve. in the region below the horizontal line _{h 0.05,} V _v and _{(h 0.80)} represents a region below the horizontal line _{h 0.80} above the surface bearing area ratio curve.) represents. ).

This parameter is also explained by the surface bearing area ratio curve shown in FIG. 1, and V _v (h _0.05 ) −V _v (h _0.80 ) in the above formula (VI) is expressed as “Air in” in FIG. It refers to the area of “core zone”.

In this embodiment, it is preferable that the core solution retention index (S _ci ) satisfies the following formula (5).
S _ci ≧ 1.40 (5)

When this relational expression is satisfied, the strength of the glass substrate can be improved. Further, S _ci is more preferably 1.45 or more, further preferably 1.50 or more, and particularly preferably 1.53 or more.

  In addition, about the surface roughness (Ra) generally used well, a clear correlation was not able to be confirmed between the numerical value of the surface roughness (Ra) and the intensity | strength of a glass substrate. In addition, the surface roughness (Ra) in this specification is based on JIS B 0601: 2001.

  The parameters related to the surface shape as described above are determined based on data obtained by measuring the surface shape of the glass substrate with a scanning probe microscope, for example, an atomic force microscope (AFM). It is obtained by processing.

  More specifically, this surface shape parameter is obtained by using, for example, Cipher S (trade name, manufactured by Oxford Instruments Co., Ltd.) as an atomic force microscope (AFM), 256 points in the X direction, Y in a range of 1 μm × 1 μm. After acquiring the surface shape data of the glass substrate from the data of 256 points in the direction and 65536 points in total, it can be acquired by image analysis software (for example, product name: SPIP manufactured by Image Metrology Co., Ltd.). By performing leveling processing in image analysis software and performing roughness analysis, it is possible to obtain various data indicating the characteristics of the surface shape.

[Hydrogen concentration]
The glass substrate according to this embodiment has an average hydrogen concentration (A) in a region having a depth of 5 nm to 55 nm from the outermost surface of the glass substrate and an average hydrogen concentration (B) in a region having a depth of 500 nm to 550 nm that is a bulk portion of the glass. It is preferable that the ratio satisfies the following formula (6). By satisfying such a range, the surface strength of the glass substrate can be improved.
(A) / (B) ≦ 10 (6)

  Regarding the surface strength of the glass substrate, it is known that the surface strength of the glass decreases due to the presence of hydrogen (water) in the surface layer of the glass substrate. As a result of various investigations, it is presumed that the main cause is that chemical defects are generated by moisture in the atmosphere entering the inside of the glass substrate.

  That is, when the hydrogen concentration in the surface layer of the glass substrate is high, hydrogen may enter the P-O-P bond network of the glass in the form of P-OH, and the P-O-P bond may be broken. If the concentration is high, the portion where the P—O—P bond is broken increases, so that chemical defects are likely to be generated, and the surface strength is considered to decrease.

  The average hydrogen concentration is specified in a region where the depth from the outermost surface of the glass substrate is 5 nm to 55 nm. The hydrogen concentration is highest on the outermost surface and gradually decreases toward the deep part (bulk part). In the glass substrate of the present embodiment, etching is performed by acid cleaning after precision polishing, and a relatively large amount of moisture is removed from the surface of the plate glass before precision polishing and acid cleaning treatment, and the surface strength is removed. Can be maintained well.

Here, the ratio of the average hydrogen concentration (A) in a region having a depth of 5 nm to 55 nm from the outermost surface of the glass substrate and the average hydrogen concentration (B) in a region having a depth of 500 nm to 550 nm that is a bulk portion of the glass is, for example, secondary ion mass spectrometry: obtained from the depth profile of the hydrogen strength of the glass substrate obtained by using the (secondary ion mass Spectrometory SIMS) ( H / F 2). The calculation procedure is described below.

First, a glass substrate to be measured is transported into a SIMS apparatus, measurement is performed, and depth profiles of H and F ₂ intensities (counts / sec) in a predetermined depth region are simultaneously acquired.
Thereafter, the F ₂ depth profile is divided from the H depth profile to create a depth profile with the vertical axis representing the H / F ₂ intensity ratio. Here, this depth profile is referred to as a hydrogen intensity (H / F ₂ ) depth profile. From the depth profile of the hydrogen strength (H / F ₂ ), the average hydrogen strength (I _A ) in the region having a depth of 5 nm to 55 nm and the average hydrogen strength (I _B ) in the region having a depth of 500 nm to 550 nm from the outermost surface of the glass substrate. Ask for. Here, the average hydrogen intensity obtained by SIMS can be converted into an average hydrogen concentration by introducing a relative sensitivity coefficient (K). That is, the following relationships are established between (A) and (I _A ), and (B) and (I _B ).

(A) = (K) × (I _A )
(B) = (K) × (I _B )

Further, if (I _B ) is removed from (I _A ) and (K) is deleted, the following relationship is established.

(A) / (B) = (I _A ) / (I _B )

That is, by determining the ratio of the average hydrogen intensity (I _A ) in the region having a depth of 5 nm to 55 nm and the average hydrogen intensity (I _B ) in the region having a depth of 500 nm to 550 nm from the outermost surface of the glass substrate, It becomes possible to determine the ratio of the average hydrogen concentration (A) in the region having a depth of 5 nm to 55 nm and the average hydrogen concentration (B) in the region having a depth of 500 nm to 550 nm from the outermost surface of the glass substrate.

The SIMS measurement conditions are as follows.
[SIMS measurement conditions]
Apparatus: ADEPT1010 manufactured by ULVAC-PHI
Primary ion species: Cs ⁺
Primary ion incident angle: 60 ° with respect to the normal of the sample surface
Secondary ion polarity: Use of minus neutralization gun: Ultimate vacuum in the measuring chamber: 5 × 10 ⁻⁹ Torr or less

Method of converting horizontal axis of depth profile of hydrogen strength (H / F ₂ ) from sputtering time to depth: Depth of analytical crater formed on glass substrate by SIMS is measured by stylus type surface shape measuring instrument (Veeco) Dektak 150 etc.) to determine the primary ion sputtering rate. Using this sputtering rate, the horizontal axis of the depth profile of hydrogen strength (H / F ₂ ) is converted from sputtering time to depth.

H ^- when detecting Field Axis Potential: could optimum value for each device is changed. The value is set with care by the measurer so that the background is sufficiently cut.

Moreover, when obtaining the depth profile of the hydrogen strength (H / F ₂ ) of the glass substrate to be measured with a film, the back surface of the glass substrate is polished, and the SIMS is performed from the polished surface toward the glass surface under the film. Measurement and analysis are performed to obtain depth profiles of H and F ₂ intensities (counts / sec).
Thereafter, the F ₂ depth profile is divided from the H depth profile to obtain a hydrogen intensity (H / F ₂ ) depth profile. From the surface of the glass substrate under the film, an average hydrogen intensity (I _A ) in a region having a depth of 5 nm to 55 nm and an average hydrogen intensity (I _B ) in a region having a depth of 500 nm to 550 nm are calculated. When SIMS measurement is performed from the polished surface toward the glass surface under the film, the strength of the obtained F ₂ depth profile decreases near the surface of the glass substrate under the film. Here, the surface of the glass substrate under the film refers to a point where the intensity of the F ₂ profile starts to decrease. A method of measuring and analyzing from the polished surface by SIMS is referred to as backside SIMS.

  In order to perform backside SIMS, it is necessary to polish a glass substrate. Polishing is performed from the back side to the depth where the target layer on the measurement surface remains appropriately.

Backside SIMS requires measurements at two different locations. At one place, measurement is performed until the glass surface under the film is exceeded, and a depth profile of hydrogen strength (H / F ₂ ) is obtained. The other point stops the measurement before reaching the glass surface under the membrane. For the analytical crater formed by stopping the measurement before reaching the glass surface under the film, the depth is measured by a stylus type surface shape measuring instrument (such as Deaktak 150 manufactured by Veeco) and sputtered primary ions. Ask for a rate. Using this sputtering rate, the horizontal axis of the depth profile of hydrogen strength (H / F ₂ ) is converted from sputtering time to depth.

  Here, the thickness of the glass substrate of the present embodiment is preferably in the range of 0.03 to 5 mm from the viewpoint of reducing the size and thickness of the apparatus and preventing damage during handling, and is 0 from the viewpoint of weight reduction and strength. The range of 0.05-1 mm is more preferable, and the range of 0.07-0.5 mm is more preferable.

  Moreover, as a fluorophosphate glass used by this embodiment, if the composition is illustrated, the thing of the following compositions will be mentioned. These fluorophosphate glasses contain CuO and are particularly useful as near-infrared cut glass.

(1) P ₂ O ₅ 46 to 70%, AlF ₃ 0.2 to 20%, LiF + NaF + KF 0 to 25%, MgF ₂ + CaF ₂ + SrF ₂ + BaF ₂ + PbF ₂ 1 to 50% in terms of mass%, provided that F The glass which contains 0.5-7 mass parts of CuO by the outer split with respect to 100 mass parts of the basic glass containing 0.5-32% and O 26-54%.

(2) represented by _{mass%, P 2 O 5 25~60%,} Al 2 OF 3 1~13%, MgO 1~10%, CaO 1~16%, BaO 1~26%, SrO 0~16%, _{ZnO 0~16%, Li 2 O 0~13} %, Na 2 O 0~10%, K 2 O 0~11%, CuO 1~7%, ΣRO (R = Mg, Ca, Sr, Ba) 15~ _{40%, ΣR '2 O (} R' = Li, Na, K) 3~18% ( however, ^{O 2-ions} to 39% molar amount F ^- ions is substituted with) glass consisting of.

(3) By mass%, P ₂ O ₅ 5 to 45%, AlF _{3 1 to} 35%, RF (R is Li, Na, K) 0 to 40%, R′F ₂ (R ′ is Mg, Ca , Sr, Ba, Pb, Zn) 10 to 75%, R ″ F _m (R ″ is La, Y, Cd, Si, B, Zr, Ta, m is a number corresponding to the valence of R ″) 0 Glass containing 15% (but up to 70% of the total fluoride weight can be replaced by oxide), and 0.2-15% CuO.

(4) In terms of cation%, P ⁵⁺ 11 to 43%, Al ³⁺ 1 to 29%, R cation (total amount of Mg, Ca, Sr, Ba, Pb, Zn ion) 14 to 50%, R ′ cation ( Total amount of Li, Na, K ions) 0 to 43%, R ″ cation (Total amount of La, Y, Gd, Si, B, Zr, Ta ions) 0 to 8%, and Cu ²⁺ 0.5 to 13 %, And further contains F ^- 17 to 80% in terms of anion%.

(5) In terms of cation%, P ⁵⁺ 23 to 41%, Al ³⁺ 4 to 16%, Li ⁺ 11 to 40%, Na ⁺ 3 to 13%, R ²⁺ (Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Zn ²⁺ ) 12 to 53% and Cu ²⁺ 2.6 to 4.7%, and further anion% F ⁻ 25 to 48% and O ² 52 to 75%.

  When a commercial item is illustrated as the above glass, for example, as glass of (1), NF50-E, NF50-EX (made by Asahi Glass Co., Ltd., trade name) etc., and as glass of (2), BG-60 As a glass of (5) such as BG-61 (manufactured by Shot Corporation, trade name), CD5000 (made by HOYA, trade name) and the like can be mentioned.

Further, the above-mentioned fluorophosphate glass may further contain a metal oxide. Examples of the metal oxide include Fe ₂ O ₃ , MoO ₃ , WO ₃ , CeO ₂ , Sb ₂ O ₃ , V ₂ O _{5 and the} like. When one or more of these are contained, ultraviolet absorption It can have characteristics. The content of the metal oxide, relative to the fluorophosphate glass 100 parts by _weight, the _{Fe 2 O 3, MoO 3,} WO 3 and at least one selected from the group consisting of CeO _{2, Fe} 2 _{O 3} 0.6-5 parts by mass, MoO ₃ 0.5-5 parts by mass, WO ₃ 1-6 parts by mass, CeO ₂ 2.5-6 parts by mass, or Fe ₂ O ₃ and Sb ₂ O ₃ Fe ₂ O ₃ 0.6 to 5 parts by ₊ Sb ₂ O 3 0.1 to 5 parts by weight, or _V 2 _{O 5} two and CeO _{2 V} 2 _O 5 0.01 to 0.5 parts by + CeO ₂ It is preferable to set it as 1-6 mass parts.

[Ball-on-ring test]
FIG. 2 shows a schematic diagram for explaining the ball-on-ring test. In the ball on ring (BoR) test, the glass substrate 1 is added using a pressure jig (hardened steel, diameter 10 mm, mirror finish) made of SUS304 with the glass substrate 1 placed horizontally. The surface strength of the glass substrate 1 is measured.

  In FIG. 1, a glass substrate 1 as a sample is horizontally installed on a receiving jig 2 made of SUS304 (diameter 30 mm, contact portion curvature R2.5 mm, contact portion is hardened steel, mirror finish). A pressurizing jig 3 for pressurizing the glass substrate 1 is installed above the glass substrate 1.

The central region of the glass substrate 1 is pressurized from above the glass substrate 1. The test conditions are as follows.
Lowering speed of the pressure jig 3: 0.5 (mm / min)

  At this time, the breaking load (unit N) when the glass substrate is broken is defined as the BoR surface strength, and the average value of nine or more measurements is defined as the BoR average surface strength. However, when the break starting point of the glass substrate is 2 mm or more away from the ball pressing position, it is excluded from the data for calculating the average value.

<Glass substrate manufacturing method>
The manufacturing method of the glass substrate of this embodiment performs precision grinding | polishing with respect to the plate-shaped glass formed in plate shape in manufacturing operation of the glass substrate made from a well-known fluorophosphate glass, and performs predetermined surface treatment after that. It is characterized by that. The surface treatment performed here is a treatment including acid cleaning. Hereinafter, each step will be described in detail.

[Preparation process]
First, plate glass on which the basic shape of the glass substrate is formed is prepared.

  The preparatory process in the present embodiment is a process for obtaining a plate-like glass to be subjected to precision polishing described below, and the plate-like glass obtained here includes all steps preceding the polishing process described later. That is, the conventional method for manufacturing a glass substrate may include steps such as molding, outer shape processing, lapping, etching, and strengthening treatment.

  More specifically, for example, the prepared plate-like glass is formed into a desired size and shape to be finally finished through processes such as cutting, drilling, notching, polishing, and thread chamfering. At this time, in order to improve the handling of the subsequent process and reduce the process cost, it is cut into a size larger than the desired size to be finally finished, and after all the processing steps are completed, the desired size is obtained. It may be formed into a shape.

  Let the glass shape | molded as mentioned above be the plate-shaped glass attached | subjected to the grinding | polishing process of this embodiment.

[Polishing process]
In the manufacturing method of the glass substrate which concerns on this embodiment, after forming plate-like glass as mentioned above using fluorophosphate glass as a material, the grinding | polishing process (polishing process) which grind | polishes the glass surface is performed. This polishing step is a step of polishing glass with a polishing pad while supplying polishing slurry. The polishing conditions can be performed without any particular limitation as long as the conditions are such that a desired surface roughness is obtained. By polishing the surface of the glass sheet, macro scratches on the surface are removed. At this time, the desired surface roughness is such that the surface roughness (Ra) is 1 nm or less.

The operation of this polishing step may be performed by a known method, for example, a slurry having a specific gravity of 0.9 is prepared by dispersing cerium oxide having an average particle size of about 0.7 μm in water, and polishing of a nonwoven fabric type or a suede type is performed. Using a pad, it can be performed by a general method such as polishing a surface of 0.5 μm or more per side under a polishing pressure of 50 to 100 g / cm ² .

  The glass substrate surface may be polished using abrasive grains having an average particle diameter (d50) of cerium oxide of usually 0.5 to 1.5 μm, and the strength of the glass substrate is increased when polishing scratches from the polishing remain on the glass substrate surface. Although there is a risk of lowering, by performing a surface treatment step described later after the polishing step, the polishing flaws can be thinned and the strength can be improved.

[Acid cleaning process]
In the manufacturing method of the glass substrate which concerns on this embodiment, an acid cleaning process is performed after the said grinding | polishing process.

  The acid cleaning process performed here etches the surface of the polished glass sheet with acid. The acid used here may be an acidic solution, and examples of the acid include organic acids and inorganic acids. Examples of the organic acid include acetic acid, citric acid, oxalic acid, succinic acid, malic acid, and maleic acid, and examples of the inorganic acid include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and carbonic acid. Is preferred. As this acid, an inorganic acid is preferable, and hydrochloric acid and nitric acid are particularly preferable. It is also possible to use a mixture of two or more of these acids.

  The acid used for this acid cleaning does not include fluorine compounds such as hydrofluoric acid. In general, since a fluorine compound is rich in glass solubility, it is difficult to make polishing scratches shallow and make the surface shape of the glass substrate in the above-described range as in this embodiment.

  The acidic solution used here has a pH of preferably 4 or less, more preferably 3 or less, and even more preferably 2 or less.

  In this acid cleaning step, the surface of the plate-like glass may be etched by 500 nm or more, the etching amount is preferably 500 to 3000 nm, more preferably 500 to 2000 nm, and further preferably 1000 to 2000 nm.

  By setting the etching amount to 500 nm or more, irregularities due to polishing flaws generated by the polishing step can be reduced, and a glass substrate with high surface strength can be produced. The etching amount can be adjusted by appropriately adjusting the glass composition of the glass substrate, the temperature or concentration of the solution used for the surface treatment, and the like.

  In order to perform the acid cleaning as described above, an acid cleaning tank in which an acid solution is stored may be prepared, and the glass sheet to be cleaned may be immersed in the acid cleaning tank.

  At this time, the concentration, temperature, immersion time, and the like of the acid solution may be adjusted as appropriate so as to achieve the above etching amount. As for the density | concentration of an acid solution, 0.1-4 are preferable, for example, 0.5-3 are more preferable, and 0.5-1 are more preferable. Moreover, 20-80 degreeC is preferable, as for the temperature of an acid solution, 30-60 degreeC is more preferable, and 30-50 degreeC is especially preferable. The immersion time in the acid solution is preferably 1 to 30 minutes, more preferably 1 to 20 minutes, and further preferably 1 to 10 minutes.

  Moreover, when using nitric acid aqueous solution, it is preferable to set it as pH 0.5-2.5 and 30-50 degreeC, for example, and the immersion time of sheet glass shall be 3 to 30 minutes, and pH 0.5-1 and 30. More preferably, the immersion time of the plate glass is 3 to 10 minutes, the pH is 0.5 to 1, 30 to 50 ° C., and the immersion time of the plate glass is 3 to 5 minutes. Is more preferable.

  In performing the acid cleaning step, the surface of the sheet glass is washed with water or an alkaline solution before the acid cleaning step in order to remove the slurry remaining on the surface polished in the polishing step. Is preferred.

  Moreover, even after this acid cleaning step is performed, it is preferable to clean the glass substrate with water or an alkaline solution in order to remove the acid solution remaining on the surface.

  In particular, care is taken so that the properties of the surface of the glass substrate are not changed as much as possible in the washing with the water or the alkali solution in the washing after the acid washing. For example, in the case of water cleaning, the increase in moisture on the glass substrate surface is not unnecessarily large so that the cleaning time is 30 minutes or less at room temperature, and in the case of alkaline solution cleaning, In order not to unnecessarily increase the etching amount on the surface of the glass substrate, an alkaline aqueous solution having a pH of about 9 to 13 is used at room temperature so that the cleaning time is 15 minutes or less.

  In addition, as an alkali (base) used here, bases, such as lithium hydroxide, sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, ammonia, or an organic amine, are mentioned, for example, These bases are used independently. Alternatively, a plurality of them may be used in combination. An organic acid salt or the like may be added as a chelating agent. Further, an anionic surfactant such as polyacrylate, a cationic surfactant such as alkylamine hydrochloride, and a nonionic surfactant such as alkylphenyl polyoxyethylene ether may be added as the surfactant. Moreover, you may add a zeolite etc. as a builder.

  The glass substrate thus obtained is further subjected to surface treatment, for example, printing, antireflection coating, bonding of a functional film, and the like, whereby a glass substrate having a predetermined function can be obtained. The glass substrate of this embodiment can be suitably used as a blue filter for an image sensor such as a mobile phone or a digital camera. Moreover, when using as a blue filter, you may form the antireflection film and near-infrared cut film for suppressing the reflection loss of incident light by a vacuum evaporation method or sputtering method.

Examples of the present invention will be specifically described below, but the present invention is not limited to these.
<Evaluation method>
Various evaluations in this example were performed by the following analysis methods.

[Surface skewness ( _Ssk )]
First, an atomic force microscope (Oxford Instruments, Cipher S), measurement probe: Si-DF40Plus, measurement area: 1 μm × 1 μm, number of measurement points: X: 256 points, Y: 256 points, scan speed: 2 Hz, shape Acquired a statue. Thereafter, leveling processing of the shape image was performed using image analysis software (SPIP image analysis software version 6.4.3 manufactured by Image Metrology Co., Ltd.), and the surface distortion (S _sk ) was obtained by roughness analysis.

[Surface kurtosis (S _ku )]
First, an atomic force microscope (Oxford Instruments, Cipher S), measurement probe: Si-DF40Plus, measurement area: 1 μm × 1 μm, number of measurement points: X: 256 points, Y: 256 points, scan speed: 2 Hz, shape Acquired a statue. Thereafter, leveling processing of the shape image was performed using image analysis software (SPIP image analysis software version 6.4.3 manufactured by Image Metrology Co., Ltd.), and surface kurtosis (S _ku ) was obtained by roughness analysis.

[Maximum valley depth (S _v )]
First, an atomic force microscope (Oxford Instruments, Cipher S), measurement probe: Si-DF40Plus, measurement area: 1 μm × 1 μm, number of measurement points: X: 256 points, Y: 256 points, scan speed: 2 Hz, shape Acquired a statue. Then, using image analysis software (SPIP image analysis software version 6.4.3 manufactured by Image Metrology Co., Ltd.), the shape image was leveled, and the maximum valley depth (S _v ) was obtained by roughness analysis. .

[Valley Solution Retention Index (S _vi )]
First, an atomic force microscope (Oxford Instruments, Cipher S), measurement probe: Si-DF40Plus, measurement area: 1 μm × 1 μm, number of measurement points: X: 256 points, Y: 256 points, scan speed: 2 Hz, shape Acquired a statue. Then, using image analysis software (SPIP image analysis software version 6.4.3 manufactured by Image Metrology Co., Ltd.), the shape image was leveled, and the valley solution retention index (S _vi ) was obtained from the bearing curve. .

[Core solution retention index (S _ci )]
First, an atomic force microscope (Oxford Instruments, Cipher S), measurement probe: Si-DF40Plus, measurement area: 1 μm × 1 μm, number of measurement points: X: 256 points, Y: 256 points, scan speed: 2 Hz, shape Acquired a statue. Thereafter, leveling processing of the shape image was performed using image analysis software (SPIP image analysis software version 6.4.3 manufactured by Image Metrology Co., Ltd.), and the core solution retention index (S _ci ) was obtained from the bearing curve. .

[Surface roughness (Ra)]
Surface roughness (Ra) is Atomic Force Microscope (manufactured by Oxford Instruments, Cipher S), measurement probe: Si-DF40Plus, measurement area: 1 μm × 1 μm, number of measurement points: X: 256 points, Y: 256 points, scan speed : A shape image was acquired at 2 Hz. Thereafter, using an image analysis software (SPIP image analysis software version 6.4.3 manufactured by Image Metrology Co., Ltd.), the shape image was leveled to obtain Ra.

[Surface strength]
The surface strength of the glass substrate was measured by a ball-on-ring (BoR) test. FIG. 2 shows a schematic diagram for explaining the ball-on-ring test used in this example. SUS304 pressurization with glass substrate 1 placed horizontally on receiving jig 2 made of SUS304 (diameter 30 mm, curvature R2.5 mm of contact part, contact part is hardened steel, mirror finish) The glass substrate 1 was pressurized using the jig 3 (hardened steel, diameter 10 mm, mirror finish), and the surface strength of the glass substrate 1 was measured.

In this Embodiment, the center area | region of the glass substrate 1 was pressurized from the upper direction of the glass substrate 1 obtained after the Example and the comparative example. The test conditions are as follows.
Lowering speed of the pressure jig 2: 0.5 (mm / min)

  At this time, the breaking load (unit: N) when the glass substrate 1 was broken was defined as the BoR surface strength, and the average value of nine measurements was defined as the BoR average surface strength. However, when the fracture starting point of the glass substrate was 2 mm or more away from the ball pressing position, it was excluded from the data for calculating the average value.

[Hydrogen concentration ratio]
According to the method described in [Hydrogen concentration] above, the average hydrogen concentration (A) and the average hydrogen concentration (B) were measured, and the ratio thereof was calculated.

[Example 1]
A glass raw material was melted so as to have the following composition, and a molding and a Lap polishing step were performed to prepare a 0.7 mm plate glass. The composition is expressed in mass% on the basis of oxide, P ₂ O ₅ 46.2%, MgF ₂ 1.9%, CaF ₂ 8.4%, SrF ₂ 18.3%, NaF ₂ 9.0%, AlF ₃ 9.9%, MgO 2.2%, CuO 6.2%.

  As a polishing slurry, cerium oxide having an average particle diameter (d50) of 0.8 μm was dispersed in water to prepare a slurry, and the surface of the obtained glass sheet was polished at a polishing rate (single side) of 0. Polishing was performed with a polishing pad (suede type) at 2 μm / min.

  Next, the polished plate glass was immersed in an aqueous sodium hydroxide solution having a pH of 13 for 5 minutes to clean the polished surface (first cleaning). Then, after wash | cleaning several times with a pure water, it dried by the air blow and the glass substrate 1 was obtained.

[Examples 2 to 6]
An acid cleaning tank storing a pH 2 nitric acid aqueous solution or a pH 2 hydrochloric acid solution is prepared, and the surface of the glass substrate 1 is cleaned by immersing the glass substrate 1 obtained in Example 1 in the acid solution for a predetermined time. (Second wash). Then, after washing several times with pure water, it was dried by air blow.

  The types of chemicals used for the acid cleaning and the acid cleaning time were set as shown in Table 1, and glass substrates 2 to 6 were obtained, respectively.

[Examples 7 to 8]
An acid cleaning tank storing a nitric acid aqueous solution of pH 2 was prepared, and the glass substrate 1 obtained in Example 1 was immersed in the acid solution for 20 minutes to clean the surface of the glass substrate 1 (second cleaning). . Then, after washing several times with pure water, it was dried by air blow.

  Furthermore, an alkaline cleaning tank storing a pH 9 sodium hydroxide aqueous solution was prepared, and the acid-cleaned glass substrate was immersed for 5 minutes or 10 minutes to clean the surface of the glass substrate (third cleaning). Then, after wash | cleaning several times with a pure water, it dried by the air blow and obtained the glass substrates 7-8.

[Examples 9 to 11]
An acid cleaning tank storing a pH 0.77 nitric acid aqueous solution was prepared, and the glass substrate 1 obtained in Example 1 was immersed in the acid solution for a predetermined time to clean the surface of the glass substrate 1 (second Washing). Then, after washing several times with pure water, it was dried by air blow.

  The acid cleaning time was set as shown in Table 1, and glass substrates 9 to 11 were obtained, respectively.

[Surface characteristics]
Table 2 shows the results obtained by measuring the surface shape parameters S _sk , S _ku , S _v , S _vi , and S _ci as the BoR intensity and surface characteristics for the glass substrates 1 to 11 obtained by the above method. Example 1 is a comparative example and Examples 2-11 are examples. Moreover, the graph which plotted the relationship with the BoR intensity | strength about the surface shape parameter shown in Table 2 was shown to FIGS.

  As shown in Table 2 and FIGS. 3 to 8, there is a correlation between the above-described surface shape parameter and the surface strength.

  On the other hand, a clear correlation with the surface strength was not recognized from the measured value of Ra generally used as an index representing the surface shape.

Table 3 shows the measured hydrogen concentration ratio for the glass substrates 1 to 4 obtained in Examples 1 to 4 above.
As the hydrogen concentration ratio, H / F ₂ is based on the hydrogen strength with respect to fluorine as a glass component at a depth of 5 nm to 55 nm from the outermost layer of the glass substrate and the hydrogen strength with respect to fluorine as a glass component at a depth of 500 nm to 550 nm. The ratio of the average hydrogen concentration (A) and the average hydrogen concentration (B) calculated in the above. In addition, each average hydrogen concentration calculated | required the arithmetic average from the value measured for every sample, and computed it as those average values.

  As shown in Table 3, it is considered that there is also a correlation between the above-described hydrogen concentration and surface strength.

  1 ... Glass substrate, 2 ... Receiving jig, 3 ... Pressure jig

Claims (8)

A glass substrate made of fluorophosphate glass,
As a surface characteristic of the glass substrate, a surface distortion (S _sk ) satisfies the following formula (1).
S _sk ≧ −1.0 (1) A glass substrate made of fluorophosphate glass,
As a surface characteristic of the glass substrate, a surface kurtosis (S _ku ) satisfies the following formula (2).
S _ku ≦ 10 (2) A glass substrate made of fluorophosphate glass,
As a surface characteristic of the glass substrate, the maximum valley depth (S _v ) satisfies the following formula (3).
S _v ≦ 9 (3) A glass substrate made of fluorophosphate glass,
As a surface characteristic of the glass substrate, a valley solution retention index (S _vi ) satisfies the following formula (4):
S _vi ≦ 0.14 (4) A glass substrate made of fluorophosphate glass,
As a surface characteristic of the glass substrate, a core solution retention index (S _ci ) satisfies the following formula (5).
S _ci ≧ 1.40 (5) The ratio of the average hydrogen concentration (A) in the region having a depth of 5 nm to 55 nm from the outermost surface of the glass substrate to the average hydrogen concentration (B) in the region having a depth of 500 nm to 550 nm, which is the bulk portion of the glass substrate, is Formula (6) is satisfy | filled, The glass substrate of any one of Claims 1-5 characterized by the above-mentioned.
(A) / (B) ≦ 10 (6) Preparing a sheet glass made of fluorophosphate glass;
A polishing step of precisely polishing the principal surface of the plate glass;
After the polishing step, an acid cleaning step for acid cleaning the polishing surface of the sheet glass,
A method for producing a glass substrate, comprising:   The said acid washing process is a manufacturing method of the glass substrate of Claim 7 which immerses the said plate glass in the nitric acid aqueous solution of pH 0.5-3, 20-50 degreeC for 0.5 to 30 minutes.

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