KR102150209B1 - Device and method for evaluating dry crack of colloid film - Google Patents

Abstract

The present invention provides a device and method for evaluating a dry crack of a colloid film. According to the present invention, the device for evaluating the dry crack of the colloid film comprises: a processor; and a memory connected to the processor, wherein the memory stores program commands executable by the processor to determine a termination point of a constant drying speed section of the colloid film which is in a drying process, to receive one or more optical microscope images for an uppermost layer of the colloid film at the termination point of the constant drying speed section, and to calculate crack occurrence possibility from the one or more optical microscope images by using an average radius of colloid particles, positions of the colloid particles, and a neighboring particle list of each colloid particle. According to the present invention, the efficiency of process can be improved.

Description

A colloidal film dry crack evaluation apparatus and method TECHNICAL FIELD [DEVICE AND METHOD FOR EVALUATING DRY CRACK OF COLLOID FILM}

The present invention relates to a colloidal film dry crack evaluation apparatus and method.

With the recent development of the industry, with the movement of miniaturization and precision of products, the level of precision required for materials and the demand level of films having specific functions are greatly increasing.

Accordingly, particularly in the case of a large-area coating containing functional particles, dry cracks generated during the drying process, which is an intermediate step of the product, are potentially present and worsen after additional heat treatment, which adversely affects cost and processing time.

In particular, in the case of photonic crystal using colloidal crystallization, it appears severely in a film filled with a high density.

In order to make a film using a complex fluid in which colloid particles are evenly dispersed in a solvent, a coating process in which the complex fluid solution is evenly applied on the substrate as an intermediate process and a drying process in which only the liquid portion is removed from the applied wet film is required. .

During the liquid removal process, shrinkage caused by a decrease in volume and a decrease in physical properties of the product due to the accumulation of stress caused by it is easy to occur, and when this becomes severe, cracks that can be seen in appearance also occur, which is a product defect. Will lead to.

Therefore, it is difficult to return the product after drying completely proceeds or after an additional densification process. Therefore, it is necessary to predict the occurrence of cracks before the drying proceeds completely and develops into cracks.

Japanese Published Patent Publication 2014-079983

In order to solve the problems of the prior art, the present invention is an apparatus for evaluating dry cracks of a colloidal film capable of predicting in advance the possibility of occurrence of dry cracks before final drying in the drying process in a colloidal film made by applying a colloidal dispersion on a substrate. And a method.

In order to achieve the above object, according to an embodiment of the present invention, a colloidal film dry crack evaluation apparatus, comprising: a processor; And a memory connected to the processor, wherein the memory determines the end point of a constant drying speed section of the colloidal film in the drying process, and at least one uppermost layer of the colloidal film at the end of the constant dry speed section A program executable by the processor to receive an optical microscope image and calculate the probability of occurrence of a crack using the average radius of colloid particles, the position of the colloid particles, and a list of neighboring particles of each colloid particle in the one or more optical microscope images. A dry crack evaluation device storing instructions is provided.

The determination of the end point of the constant drying speed section may be performed using the weight or thickness of the colloidal film in the drying process.

The one or more optical microscope images may be acquired in plurality at different positions of the colloidal film.

The program instructions count the total number of particles of colloidal particles included in the first optical microscope image, determine the positional coordinates of each colloidal particle included in the first optical microscope image, and include in the first optical microscope image. For each of the colloidal particles, a list of neighboring particles for one or more neighboring particles can be generated.

The program instructions use the neighboring particle list to calculate a distance and a direction vector for each of one or more neighboring particles adjacent to the first colloidal particle, and use the calculated distance and direction vector to determine the first colloidal particle. And it is possible to calculate the dimensionless force generated by the capillary phenomenon with the one or more neighboring particles.

The program instructions compare the average value of the dimensionless force calculated for all colloidal particles included in the plurality of optical microscope images and the distribution value of the dimensionless force of each of the plurality of optical microscope images with a preset threshold, and the colloidal film The possibility of cracking can be calculated.

The dimensionless force can be calculated through the following equation.

[Equation]

는 입자 m과 n과의 방향벡터의 크기임Here, N _m,neighbor is the total number of particles located adjacent to the particle m, r _mn is the direction vector between the particles m and n,

Is the size of the direction vector between particles m and n

According to another aspect of the present invention, a method of evaluating a drying crack of a colloidal film in a device including a processor and a memory, comprising: determining an end point of a predetermined drying speed section of the colloidal film in a drying process; Receiving at least one optical microscope image of the uppermost layer of the colloidal film at the end of the constant drying speed section; And calculating the probability of occurrence of cracks using an average radius of colloidal particles in the one or more optical microscope images, position coordinates of the colloidal particles, and a list of neighboring particles of one colloidal particle.

According to the present invention, there is an advantage in that the process efficiency is improved because the possibility of occurrence of cracks can be predicted before drying is completed.

1 shows a conceptual diagram of a capillary force generated by a liquid bridge occurring between pairs of identical spherical particles.
2 is a flow chart of a method for evaluating dry cracks of a colloidal film according to an embodiment of the present invention.
3 is an exemplary view of an optical microscope image of an uppermost layer of a colloidal film according to the present embodiment.
4 is a flowchart of a process of calculating the probability of occurrence of cracks using an optical microscope image according to the present embodiment.
5 is a planar image of a particle reconstructed by a computer from an optical microscope image, and shows a planar image of the particle under different conditions (I to III).
6 shows the crack frequency obtained under each condition.

In the present invention, various modifications may be made and various embodiments may be provided, and specific embodiments will be illustrated in the drawings and described in detail.

However, this is not intended to limit the present invention to a specific embodiment, it is to be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

The present invention relates to a method capable of predicting in advance the possibility of occurrence of dry cracks upon completion of final drying from an optical image of colloid particles during a drying process of a colloidal film formed by coating a colloidal dispersion on a substrate.

The present invention takes advantage of the fact that the colloidal film drying process is largely divided into two sections according to the change in the evaporation rate of the solvent.

Depending on the change in the evaporation rate of the solvent, the evaporation rate is significantly reduced after the constant drying rate section (hereinafter referred to as the'first section') and the evaporation of the solvent are significantly reduced. It is divided into a drying speed deceleration section (hereinafter referred to as'second section') in which drying is performed.

In the first section, the colloidal particle dispersion is gradually increased in concentration due to the continuous evaporation of the solvent, forming a particle network.

The particle network maintains its overall shape while contracting at a constant rate throughout.

At the end of the first section, the particle network finally touches the substrate, and then enters the second section.

In the second section, the gas-liquid interface does not have a certain shape, and additional drying is performed while forming a liquid bridge between particles between empty spaces between particles.

1 shows a conceptual diagram of a capillary force generated by a liquid bridge occurring between pairs of identical spherical particles.

Referring to FIG. 1, the force generated by the liquid bridge is a force that pulls each other to generate a strong tension in the entire dry film. At this time, when the magnitude of the generated force exceeds the allowable range of the particle network, it develops into a crack.

If the colloidal particle arrangement information is known during drying, the magnitude of the capillary force can be predicted.

However, in reality, it is difficult to obtain arrangement information of all colloidal particles.

In consideration of this point, according to an embodiment of the present invention, the end point of the first section is determined through weight measurement, and the probability of occurrence of cracks is calculated by using the top layer particle distribution of the colloid film at that point.

2 is a flow chart of a method for evaluating dry cracks of a colloidal film according to an embodiment of the present invention.

The process of FIG. 2 is performed in a crack evaluation apparatus including a processor and a memory.

Here, the processor may include a central processing unit (CPU) capable of executing a computer program or a virtual machine.

The memory may include a nonvolatile storage device such as a fixed hard drive or a removable storage device. The removable storage device may include a compact flash unit, a USB memory stick, or the like. The memory may also include volatile memories such as various random access memories.

Program instructions executable by the processor are stored in such a memory.

Program commands according to an embodiment of the present invention calculate the probability of occurrence of cracks in the colloidal film before final drying by performing the process shown in FIG. 2.

Hereinafter, a process performed by the crack evaluation apparatus will be described.

Referring to FIG. 2, the crack evaluation device receives the weight of the colloidal film during the drying process (step 200).

The weight of the colloidal film is constantly reduced by evaporation of the solvent, and the crack evaluation device determines the end point of the first section (constant drying rate section) in which the weight decreases at a constant rate (step 202).

The end point of the first section may be determined based on whether or not the weight decrease occurs below a preset speed.

As described above, after the end of the first section in the drying process, the drying speed is changed to a second section where the drying speed is greatly reduced.

At the end of the first section, the crack evaluation apparatus receives an optical microscope image of the top layer of the colloid film (step 204).

3 is an exemplary view of an optical microscope image of an uppermost layer of a colloidal film according to the present embodiment.

3 is an example of an optical image obtained during the drying process of spherical polystyrene particles having a diameter of 1 μm, where the scale bar is 10 μm.

Next, the input optical microscope image is analyzed to calculate the probability of occurrence of cracks (step 206).

4 is a flowchart of a process of calculating the probability of occurrence of cracks using an optical microscope image according to the present embodiment.

Referring to FIG. 4, the average radius of colloidal particles is previously input to the crack evaluation device (step 400).

For the colloidal dispersion, the average particle diameter can be obtained using a general particle size measuring device, and 1/2 of the average particle diameter is called the average radius (a).

A point displayed relatively brightly in the optical microscope image of FIG. 3 is the position of the center point of the particle.

According to this embodiment, the total number of particles included in the optical microscope image is counted and position coordinates are determined (step 402).

5 is a planar image of a particle reconstructed by a computer from an optical microscope image, and shows a planar image of the particle under different conditions (I to III).

The crack evaluation apparatus counts the total number of particles by using the planar image of the particles as shown in FIG. 5 and determines the position coordinates of each particle.

The crack evaluation apparatus checks the number of neighboring particles for each particle, and generates a list of neighboring particles (step 404).

When the total number of particles is N and the index of each particle is m, m is a natural number that is 1 or more and N or less.

, 예를 들어,

) 내에 위치하는 입자의 총 수(N_m,neighbor)를 확인하여 이웃 입자 리스트를 생성한다. In step 404, a list of particles adjacent to the particle with index m is created, starting from m=1 and a preset radius around it (

, For example,

), a list of neighboring particles is created by checking the total number of particles (N _m,neighbor ) located in ).

The above process is repeated for all the number of particles N.

Next, a distance (s _mn ) and a direction vector (r _mn ) between n (n≤N _m,neighbor ) _neighboring particles around a particle having m=1 starting from m=1 are calculated (step 406). .

Here, the distance and direction vectors are shown in FIG. 1.

Steps 402 to 406 can be made individually for optical microscope images obtained at different locations.

Hereinafter, each of a plurality of optical microscope images is defined as a set.

)을 계산한다(단계 408). Next, the crack evaluation apparatus uses the following equations 1 and 2 to obtain a dimensionless force of each particle (

) Is calculated (step 408).

Here, s _mn is the distance between the particles m and n, a is the average radius of the particles, and s ^* _mn is the dimensionless distance between the particles m and n.

C. D. Willett, M. J. Adams, S. A. Johnson, and J. P. K. Seville. Capillary bridges between two spherical bodies. Langmuir, 16(24):9396-9405, (2000) describes an equation (Eq. 5) relating to the capillary force between two particles, and in the present invention, it is dimensionless to derive Equation 2 below. In this way, the total sum of the dimensionless forces created by the capillary action with neighboring particles around the colloid particle m is calculated.

For all particles in one set (m = 1 to N), it is a process of calculating the force applied during the drying process, and dimensionless force calculations are made for particles in all sets.

는 입자 m과 n과의 방향벡터의 크기이다. Here, N _m,neighbor is the total number of particles located adjacent to the particle m, r _mn is the direction vector between the particles m and n,

Is the magnitude of the direction vector between particles m and n.

)과 각 세트간 산포값(

)을 계산한다(단계 410). Finally, for the dimensionless forces calculated as above, the average value of the dimensionless forces for all particles in all sets (

) And the spread between each set (

) Is calculated (step 410).

Here, <> means ensemble average.

If both the average value and the spread value exceed a preset threshold, it is determined that the possibility of occurrence of dry cracking is high (step 412).

Here, the threshold value is experimentally determined as different values depending on the type, size, size distribution, or thickness of the dried film of the colloid particles in the process.

Example

A total of three drying conditions were evaluated for a solution in which polystyrene colloidal spherical particles (a=0.5 μm) having an average particle diameter of 1 μm were dispersed.

After a few drops of the colloidal dispersion are dropped on a slide glass, the height of the liquid is made uniform using a coater equipped with a blade at a certain height, and the initial weight is measured.

The drying speed control is controlled by changing the humidity inside the experimental apparatus, and the drying speed is measured as the weight decrease of the film, and the weight decrease from the initial film thickness can be converted into a decrease in the thickness of the wet film. The drying speed and drying section can be confirmed from the weight reduction curve.

Here, the above three drying conditions are the same, but the sample is made by varying the drying speed.

Condition I corresponds to a relatively slow drying rate, condition II to a medium rate, and condition III to a fast drying rate.

The film thickness and drying speed in this experiment are as follows.

The initial thickness in the wet film state was the same as 60 μm, and the reduction rate of each film thickness was adjusted to 0.022, 0.44, and 2.2 μm/sec.

From the distribution of the particles of the uppermost layer observed in the drying process, the average value and the dispersion value of the dimensionless force expected at the completion of drying were calculated according to the calculation method shown in FIGS. 2 and 4.

One of the images obtained during the drying process is illustrated in FIG. 3.

The optical microscope image was measured with a microscope micros MC500 model. It is possible to obtain 10 sample sets in which 1 set of particles present in an area of arbitrary 16 μm x 16 μm is obtained, one of which is illustrated in FIG. 5.

The crack frequency was identified as a large/medium/small average value of the frequency of cracks present at any five points on the film after complete drying, where each point has an area of 45 μm x 45 μm.

The results obtained under each condition are shown in Fig. 6 and Table 1.

Condition I II III Drying speed Slow middle speed Dimensionless force average value 46.4 52.7 85.6 Dimensionless force spread 19.9 17.8 26.8 Crack frequency (large/medium/small) 0/0/0 0/0/0 5.2/8.5/10.1

Looking at the crack frequency, in the case of polystyrene colloidal spherical particles having an average particle diameter of 1 μm, it can be determined that dry cracking is likely to occur when the average value of the dimensionless force is 60 or more and the dispersion value is 25 or more.

The above-described embodiments of the present invention are disclosed for the purpose of illustration, and those skilled in the art who have ordinary knowledge of the present invention will be able to make various modifications, changes, and additions within the spirit and scope of the present invention, and such modifications, changes and additions It should be seen as belonging to the following claims.

Claims (8)

As a dry crack evaluation device of colloidal film,
Processor; And
Including a memory connected to the processor,
The memory,
To determine the end point of the constant drying speed section of the colloidal film in the drying process,
At least one optical microscope image of the top layer of the colloidal film is input at the end of the constant drying speed section,
To calculate the probability of occurrence of cracks using the average radius of colloidal particles, the position of the colloidal particles, and a list of neighboring particles of each colloidal particle in the at least one optical microscope image,
Dry crack evaluation apparatus for storing program instructions executable by the processor. The method of claim 1,
The determination of the end point of the constant drying speed section is performed using the weight or thickness of the colloidal film in the drying process. The method of claim 1,
The apparatus for evaluating dry cracks in which the at least one optical microscope image is obtained in plural at different positions of the colloidal film. The method of claim 3,
The program instructions,
Counting the total number of particles of colloidal particles included in the first optical microscope image,
Determine the positional coordinates of each colloidal particle included in the first optical microscope image,
Dry crack evaluation apparatus for generating a list of neighboring particles for one or more neighboring particles for each colloidal particle included in the first optical microscope image. The method of claim 4,
The program instructions,
Using the neighboring particle list, a distance and a direction vector for each of one or more neighboring particles adjacent to the first colloidal particle are calculated,
Dry crack evaluation apparatus for calculating a dimensionless force generated by a capillary phenomenon between the first colloidal particle and the one or more neighboring particles using the calculated distance and direction vector. The method of claim 5,
The program instructions,
The probability of occurrence of cracks in the colloidal film is determined by comparing the average value of the dimensionless force calculated for all colloidal particles included in the plurality of optical microscope images and the distribution value of the dimensionless force of each of the plurality of optical microscope images with a preset threshold. Dry crack evaluation device to calculate. The method of claim 5,
The dimensionless force is a dry crack evaluation device that is calculated through the following equation.
[Equation]

Here, N _m,neighbor is the total number of particles located adjacent to the particle m, r _mn is the direction vector between the particles m and n,

Is the size of the direction vector between particles m and n A method for evaluating dry cracks of colloidal films in a device including a processor and a memory,
Determining an end point of a predetermined drying speed section of the colloidal film in the drying process;
Receiving at least one optical microscope image of the uppermost layer of the colloidal film at the end of the constant drying speed section; And
Dry crack evaluation method comprising the step of calculating a crack occurrence probability using the average radius of the colloidal particles in the one or more optical microscope images, the position coordinates of the colloidal particles, and a list of neighboring particles of one colloidal particle.

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