JP6101590B2 - Fine processing method - Google Patents

Description

  The present invention relates to a fine processing method for forming a fine periodic structure on a surface.

  Conventionally, as a nanostructure processing method, nanostructures are formed on a metal surface (see Patent Documents 1 and 2 and Non-Patent Document 1) or a semiconductor surface (see Patent Document 3 and Non-Patent Document 2) by irradiation with a short pulse laser. A method of processing has been reported. In this method, a surface wave is generated on an object irradiated with laser light, and the surface wave and the laser light are made to interfere with each other, thereby making it possible to process a periodic structure having a size approximately equal to the wavelength of the light.

  11 to 13 are cross-sectional views for explaining a method for forming a periodic structure on a metal surface by irradiation with a short pulse laser. As shown in FIG. 11, when the metal material 101 is irradiated with a short pulse laser, the surface absorbs the laser beam, so that an electron density distribution occurs as shown in FIG. 12, and surface plasmons having a period of about the wavelength are generated. To do. Then, as shown in FIG. 13, a Coulomb explosion occurs at a location where the electron density is high, and a fine periodic structure is formed in the metal material 101.

  Although such a processing method can easily obtain a periodic structure and enables fine processing of a large area, fine processing to a material that transmits laser light such as glass is performed because surface waves are not generated. I can't.

  As a nanostructure processing method for glass, it has been reported that it can be processed by lithography (for example, see Patent Document 4). However, it is necessary to maintain accuracy in resist film formation and exposure processes. Moreover, since it is necessary for a processing target object to be a plane which does not have a curvature, the use of a processing target object will be limited. Furthermore, when the workpiece is enlarged, the apparatus becomes very expensive.

  Further, Patent Document 5 describes that a pigment is attached to the surface and a hole is formed in the glass, but the pigment must be removed.

JP 2006-235195 A JP 2010-152296 A JP 2003-211400 A JP 2006-346748 A JP 2002-028799 A

K.okamuro et.al.PhysRevB 82 165417 2010 G.Miyagi, ApplPhysA 80 17 2005

  The present invention has been proposed in view of such a conventional situation, and provides a fine processing method capable of easily forming a fine periodic structure on the surface of any substrate.

  As a result of intensive studies, the present inventor can easily form a fine periodic structure on the surface of any substrate by applying a glass precursor that absorbs light on the substrate. Found that is possible. Furthermore, it has been found that the surface color can be improved in a state where the fine periodic structure is maintained by forming a fine periodic structure on the substrate and then oxidizing it.

That is, the microfabrication method according to the present invention includes an irradiation step of irradiating a glass precursor, which is polysilazane coated on a substrate, with a short pulse laser having a pulse length of 0.01 picosecond to 5 picoseconds , And an oxidation treatment step of oxidizing the fine periodic structure formed by the irradiation step.

  According to the present invention, a fine periodic structure can be formed on the surface of any substrate by a simple process such as irradiation with a short pulse laser instead of a complicated process such as lithography. Furthermore, after forming a fine periodic structure on a base material, the surface color can be improved in the state which maintained the fine periodic structure by oxidizing.

It is sectional drawing which shows the outline of an application | coating process. It is sectional drawing which shows the outline of an irradiation process. It is sectional drawing which shows the outline of fine processing. It is a figure which shows the outline of the optical apparatus which inject | emits a short pulse laser. It is a photograph which shows Si distribution of the cross section of the colored molding by TEM-EDS. It is a photograph which shows O distribution of the cross section of the colored molding by TEM-EDS. FIG. 4 is a diagram showing a temperature profile of heat treatment in Example 1. It is a photograph when the sample before and after heat treatment of Example 3 is placed on a white paper. It is a photograph when the sample before and after heat treatment of Example 3 is placed on black paper. It is a photograph when the sample before and after heat processing of the comparative example 1 is mounted on black paper. It is sectional drawing which shows the outline of the laser irradiation to the metal surface. It is sectional drawing which shows the outline of absorption of the laser beam of a metal surface. It is sectional drawing which shows the outline of the fine processing of a metal surface.

Hereinafter, embodiments of the present invention will be described in detail in the following order with reference to the drawings.
1. 1. Microfabrication method Structure 3. Example

<1. Microfabrication method>
The microfabrication method shown as an embodiment of the present invention includes a coating process for coating a glass precursor on a substrate, an irradiation process for irradiating the glass precursor with a short pulse laser, and a fine process formed by the irradiation process. An oxidation treatment process for oxidizing the periodic structure. Hereinafter, each step will be described.

  FIG. 1 is a cross-sectional view schematically showing the coating process. In this coating step, the glass precursor 12 is coated on the substrate 11.

  The substrate 11 is not particularly limited, and either a transparent material or an opaque material can be used. In the present embodiment, a transparent material that transmits laser light is used, and in particular, glass that is the same quality as the glass to which the glass precursor 12 is converted is preferably used.

As the glass precursor 12, one having a molecular structure having a light absorption ability and having a lone pair such as an amine group is used. Specific examples of the glass precursor 12 include polysilazanes having a basic unit of — (SiH ₂ NH) — such as perhydropolysilazane (PHPS) and methylhydropolysilazane (MHPS). In the present embodiment, perhydropolysilazane that is converted into silica (SiO ₂ ) having excellent optical properties is particularly preferably used.

  Further, the glass precursor 12 may be one to which a catalyst such as palladium or amine is added. Moreover, as a solvent of the glass precursor 12, xylene, dibutyl ether, etc. can be used. Moreover, as a coating method of the glass precursor 12, a roll coater, a flow coat, spray coating, painting, etc. can be used suitably. Moreover, it is preferable that the coating thickness of the glass precursor 12 is about 100 nm-about 5 micrometers. When the coating thickness of the glass precursor 12 is less than 100 nm, it becomes difficult to form a fine periodic structure on the surface, and when the coating thickness of the glass precursor 12 exceeds 5 μm, the surface may be cracked. is there.

  FIG. 2 is a cross-sectional view schematically showing the irradiation process. In this irradiation step, the glass precursor 12 is irradiated with a short pulse laser. By irradiating the short pulse laser, the unshared electron pair of the glass precursor 12 is activated, leading to a thermal reaction, and a fine periodic structure 13 can be easily formed on the surface as shown in FIG. Moreover, since the glass precursor 12 remaining on the substrate 11 is converted into glass by irradiation with a short pulse laser, it can function as a glass film.

  FIG. 4 is a diagram showing an outline of an optical device for emitting a short pulse laser. For example, the laser body 20 emits laser light linearly polarized in the vertical direction and rotates the polarization direction using a wave plate 21 (λ / 2 wave plate), thereby obtaining linearly polarized light in a desired direction. it can. Further, circularly polarized light can be obtained by using a λ / 4 wavelength plate instead of the λ / 2 wavelength plate. Further, in the present apparatus, a part of the laser light is taken out using the aperture 22 having a square opening. This is because the intensity distribution of the laser beam is a Gaussian distribution, and only the vicinity of the center is used to obtain a laser beam having a uniform in-plane intensity distribution. Moreover, in this apparatus, it is possible to obtain a desired beam size by narrowing the laser beam using two orthogonal cylindrical lenses 23.

  By using such an apparatus to irradiate the glass precursor 12 with an ultrashort pulse laser having a predetermined wavelength at a predetermined fluence, a periodic structure having a size smaller than the predetermined wavelength can be formed in the laser irradiation region.

The fluence is energy density E / S (J / cm ² ) obtained by dividing the energy E (J) per pulse of the laser by the irradiation sectional area S (cm ² ). Range of predetermined fluence varies depending on the ^material, and more that is preferably 0.01J / cm ² ~1.0J / cm 2 about ^a 0.05J / cm ² ~0.5J / cm 2 preferable. The number of irradiation pulses depends on the fluence and the processing depth of the periodic structure, but is preferably 50 or more. The pulse length (width) is preferably shorter, preferably about 0.01 picoseconds to 100 picoseconds, and more preferably 0.01 picoseconds to 5 picoseconds. The pulse frequency is preferably 1 kHz or more in consideration of processing time. The wavelength can be selected according to a desired periodic structure such as 800 nm, 400 nm, and 266 nm.

  Moreover, it is preferable that the beam spot has a quadrangular shape. The shaping of the beam spot can be performed by, for example, the aperture 22 or the cylindrical lens 23. Further, the intensity distribution of the beam spot is preferably as uniform as possible. Thereby, in-plane distribution, such as the depth of the unevenness | corrugation to form, can be equalize | homogenized. The size of the beam spot is Lx and Ly in the x-axis direction and y-axis direction of the square, the y-axis direction is the laser scanning direction, and the size of Lx is 1 / N of the periodic structure formation region (N is a natural number) In this case, the periodic structure can be formed by scanning N times. The size of Ly can be appropriately determined according to the stage speed, laser intensity, pulse frequency, and the like, and is, for example, about 30 to 500 μm.

  In the oxidation treatment step, the molded body having a periodic structure formed on the surface is oxidized. Thereby, the color of the colored part of the fine periodic structure formed by irradiation of the short pulse laser can be improved. Examples of the oxidation treatment include annealing treatment, ultraviolet irradiation, plasma treatment, corona treatment, and oxidant application.

  Here, the colored portion of the fine periodic structure will be described. A colored periodic part may occur in a fine periodic structure produced by irradiating a glass precursor with a short pulse laser. The present researchers have found that this colored portion is Si or SiO by cross-sectional elemental analysis.

FIG. 5 is a photograph showing the Si distribution in the cross section of the colored molded body by TEM-EDS (transmission electron microscope), and FIG. 6 is a photograph showing the O distribution in the cross section of the colored molded body by TEM-EDS. From the Si distribution and the O distribution of the colored molded body, it can be seen that in the colored portion of the fine periodic structure, Si precipitates and O or missing Si or SiO portions exist. This is a result of PHPS (perhydropolysilazane) is, when converted to SiO ₂ by reaction with _{H 2} O, by rapid energy reactions due to processing in a short pulse laser, O from _{H 2} O is insufficient, Si And SiO are considered to have precipitated. The following chemical formula (1) shows a conversion reaction in which PHPS is converted to SiO ₂ by reaction with H ₂ O. In the following chemical formula (2) and chemical formula (3), PHPS is converted into Si and SiO by a short pulse laser, respectively. Shows the conversion reaction to convert to.
-(SiH ₂ NH)-+ 2H ₂ O → SiO ₂ + NH ₃ + 2H ₂ (1)
-(SiH ₂ NH)-+ E → Si + NH ₃ (2)
_{- (SiH 2 NH) - +} E + H 2 O → SiO + NH 3 + H 2 (3)

In the present embodiment, colored portions of Si or SiO are reacted with SiO ₂ by oxidation treatment to make the colored portions colorless. The following chemical formula (4) and chemical formula (5) show the oxidation reaction of Si and SiO, respectively.
Si + O ₂ → SiO ₂ (4)
2SiO + O ₂ → 2SiO ₂ (5)

In the present embodiment, simple annealing treatment is preferably used among the above-described oxidation treatments. The temperature of the annealing treatment may be a condition that converts to SiO ₂ , and is preferably 200 ° C. or higher and 1600 ° C. or lower, more preferably 300 ° C. or higher and 550 ° C. or lower. An excessively high temperature will cause cracks. Moreover, it is preferable to perform slow cooling when cooling. Cracks may occur if the cooling is performed rapidly.

  Further, the annealing treatment is preferably performed in an oxygen atmosphere. Thereby, a colored part can be made colorless. Note that the colored portion may become transparent even in an atmosphere in which oxygen does not exist, because oxygen atoms and oxygen molecules may exist independently in the processed fine periodic structure.

  The colored portion can be made colorless by annealing the fine periodic structure produced by irradiating the glass precursor with a short pulse laser. Moreover, the compactness of the molded body having a fine periodic structure can be improved, and heat resistance and translucency can be improved.

  According to the microfabrication method in the present embodiment, a nano-periodic structure can be formed on the surface by a simple process such as irradiation with a short pulse laser instead of a complicated process such as lithography. Moreover, since it can process under normal temperature and normal pressure, it can process into a large area target object and a free-form surface target object. Furthermore, since the transparency of a structure having a fine periodic structure is improved, it can be applied to various fields.

<2. Structure>
Next, a structure in which a periodic structure is formed by the fine processing method described above will be described. The structure body in this embodiment periodically has linear protrusions or dot-like protrusions with a pitch width of 50 to 1000 nm and a depth of 10 to 1000 nm on the surface. Also. Since such a concavo-convex shape has moderate fluctuations in both pitch and angle, for example, generation of interference light can be suppressed.

Particularly preferably, by using silica (SiO ₂ ) as the base material 11 and perhydropolysilazane converted to silica as the glass precursor 12, a periodic structure can be formed on the glass surface more easily than in the past. In addition, the structure in which the periodic structure is formed can realize a reflectance of 1% or less over a range of 300 nm to 800 nm corresponding to the wavelength range of visible light. Therefore, the present invention can be applied to a windshield of an automobile, a surface glass of a heat absorption tube of solar thermal power generation, an optical component having an antireflection function, and the like.

  For example, when applied to a windshield of an automobile, the contact angle with water can be improved by forming a periodic structure on the surface, and it is excellent by being 90 degrees or more, more preferably 110 degrees or more and 130 degrees or less. High water repellency can be obtained. Further, by appropriately changing the depth of the periodic structure, the contact angle with water or oil can be reduced, and excellent hydrophilicity can be obtained by setting it to 30 degrees or less, more preferably 15 degrees or less. Can do. Further, by setting the pitch width of the periodic structure to 350 nm or less, an antireflection function can be imparted to visible light.

  For example, when applying to a substrate glass of a thin film type photovoltaic power generation, by forming a periodic structure having a fine grating with a pitch of about 0.5 μm, light near 0.5 μm which is the peak wavelength of sunlight is efficiently used. Can absorb well.

  In addition, for example, when applied to an optical component having an antireflection function, an antireflection function can be imparted by forming a structure having a period shorter than the wavelength of incident light, and an appropriate fluctuation of the period, Generation of interference colors can be suppressed.

  For example, when applied to the surface glass of a heat absorption tube of solar thermal power generation, an excellent heat absorption performance can be obtained because the reflectance in the visible light wavelength region is low. Moreover, the outstanding heat resistance can be acquired with respect to the surface shape formation method by UV imprint weak to a heat | fever.

<3. Example>
Examples of the present invention will be described in detail below. In this example, a glass precursor was applied on a substrate, a sample was prepared by irradiating a short pulse laser to form a microstructure, and heat treatment (annealing) was performed as an oxidation treatment of the sample. The present invention is not limited to these examples.

[Evaluation of each sample]
The total light transmittance of each sample was measured according to JIS K 7136 using a haze meter (Murakami Color Research Laboratory Co., Ltd., HM-150). Moreover, the reflectance of each sample was measured using a reflection measurement system (manufactured by JASCO Corporation, V-670) when the wavelength was 550 nm. The color of each sample and the presence or absence of cracks were evaluated by visually observing the sample surface.

[Example 1]
Glass was used as the substrate, and perhydropolysilazane was used as the glass precursor. Perhydropolysilazane was coated on glass and irradiated with a short pulse laser from the perhydrosilazane side to prepare a sample in which a fine structure was formed on the substrate. The irradiation conditions were a fluence of 0.2 J / cm ² , an irradiation pulse number of 70, a pulse width of ²⁰⁰ fs, a frequency of 1 kHz, a wavelength of 390 nm, and a beam spot of 300 μm × 120 μm.

  The sample of Example 1 was dried at room temperature for 24 hours, and then heat-treated in an air atmosphere at 600 ° C. for 1 hour under annealing conditions. FIG. 7 is a view showing a temperature profile of the heat treatment of Example 1. FIG. In an air atmosphere, the temperature was raised from room temperature to 600 ° C. over 60 minutes, maintained at 600 ° C. for 1 hour, and then allowed to cool to room temperature by cooling. The total light transmittance of the sample after the heat treatment was 92.1%, and the reflectance (550 nm) was 0.5%. Moreover, the color of the sample was transparent, and cracks were confirmed on the surface of the sample.

[Example 2]
Sample treatment was performed in the same manner as in Example 1 except that the heat treatment was performed under the annealing conditions at 550 ° C. for 2 hours in the air atmosphere. The total light transmittance of the sample after the heat treatment was 92.0%, and the reflectance (550 nm) was 0.5%. Moreover, the color of the sample was transparent, and cracks were confirmed on the surface of the sample.

[Example 3]
Sample treatment was performed in the same manner as in Example 1 except that the heat treatment was performed under annealing conditions at 550 ° C. for 1 hour in an air atmosphere. The total light transmittance of the sample after the heat treatment was 92.1%, and the reflectance (550 nm) was 0.5%. Moreover, the color of the sample was transparent and no cracks were observed on the surface of the sample.

  FIG. 8 is a photograph when the sample before and after heat treatment of Example 3 is placed on a white paper, and FIG. 9 is a photograph when the sample before and after heat treatment of Example 3 is placed on a black paper. It is a photograph. As shown in FIGS. 8 and 9, the brown color before the heat treatment became transparent by the heat treatment.

[Example 4]
Sample treatment was performed in the same manner as in Example 1 except that the heat treatment was performed under the annealing conditions at 500 ° C. for 2 hours in the air atmosphere. The total light transmittance of the sample after the heat treatment was 92.1%, and the reflectance (550 nm) was 0.5%. Moreover, the color of the sample was transparent and no cracks were observed on the surface of the sample.

[Example 5]
Sample treatment was performed in the same manner as in Example 1 except that heat treatment was performed under the annealing conditions at 500 ° C. for 1 hour in the air atmosphere. The total light transmittance of the sample after the heat treatment was 92.1%, and the reflectance (550 nm) was 0.5%. Moreover, the color of the sample was transparent and no cracks were observed on the surface of the sample.

[Example 6]
The sample treatment was performed in the same manner as in Example 1 except that the heat treatment was performed under the annealing conditions at 400 ° C. for 2 hours in the air atmosphere. The total light transmittance of the sample after the heat treatment was 90.5%, and the reflectance (550 nm) was 0.5%. Further, the sample had a light brown color, and no cracks were observed on the surface of the sample.

[Example 7]
Sample treatment was performed in the same manner as in Example 1 except that heat treatment was performed under the annealing conditions at 300 ° C. for 2 hours in the air atmosphere. The total light transmittance of the sample after the heat treatment was 89.4%, and the reflectance (550 nm) was 0.7%. Further, the sample had a light brown color, and no cracks were observed on the surface of the sample.

[Comparative Example 1]
Sample treatment was performed in the same manner as in Example 1 except that heat treatment was performed under annealing conditions at 500 ° C. for 1 hour in a nitrogen atmosphere. The total light transmittance of the sample after the heat treatment was 88.5%, and the reflectance (550 nm) was 0.7%. Further, the sample had a light brown color, and no cracks were observed on the surface of the sample.

  FIG. 10 is a photograph of the sample of Comparative Example 1 before and after heat treatment placed on black paper. As shown in FIG. 10, the oxygen before the heat treatment did not become transparent due to the heat treatment because oxygen was insufficient in the atmosphere.

[Comparative Example 2]
Sample processing was performed in the same manner as in Example 1 except that heat treatment was not performed. The total light transmittance of the sample was 87.5%, and the reflectance (550 nm) was 0.8%. Further, the sample had a brown color, and no cracks were observed on the surface of the sample.

  Table 1 shows the evaluation results of Examples 1 to 6 and Comparative Examples 1 and 2.

  As shown in Examples 1 to 6, it was found that the surface transparency can be improved by performing the oxidation treatment while maintaining the fine periodic structure. Moreover, it turned out that the crack of a surface can be suppressed by making annealing temperature into 300 to 550 degreeC like Examples 4-7.

DESCRIPTION OF SYMBOLS 11 Base material, 12 Glass precursor, 13 Periodic structure, 20 Laser body, 21 Wavelength plate, 22 Aperture, 23 Cylindrical lens, 24 Linear stage, 30 Sample, 101 Metal material

Claims (6)

An irradiation step of irradiating a glass precursor that is polysilazane coated on a substrate with a short pulse laser having a pulse length of 0.01 picosecond to 5 picoseconds ;
Microfabrication method comprising an oxidation treatment step of oxidizing the fine periodic structure formed by the irradiation step. Wherein the substrate, the fine processing method according to claim 1 wherein the glass. The oxidation treatment, fine processing method according to claim 1 or 2 wherein the heat treatment. The fine processing method according to claim 3 , wherein a temperature of the heat treatment is 300 ° C. to 550 ° C. The heat treatment, according to claim 3 or 4 microfabrication methods described are carried out in an oxygen atmosphere. An irradiation step of irradiating a glass precursor that is polysilazane coated on a substrate with a short pulse laser having a pulse length of 0.01 picosecond to 5 picoseconds;
An oxidation treatment step of oxidizing the fine periodic structure formed by the irradiation step;
The manufacturing method of the periodic structure which has these.