JP2014211395A - Density estimation method of solvent accompanying drying of paint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology which can contactlessly measure a temporal change in the density of paint whose surface dynamically changes by volatilization or the like, can review a painting process, can grasp a curing state, and can evaluate further paint development.SOLUTION: A density change measurement method of volatile paint includes: a phase change measurement process for measuring a temporal phase change of the surface of a specimen coated with objective volatile paint by using digital holography; a volume change calculation process for calculating a volume decrease of the objective volatile paint on the basis of the phase change which is measured in the phase change measurement process; a weight measurement process for measuring a temporal weight decrease of the specimen; a calculation process for calculating a temporal density change of the objective volatile paint on the basis of the volume decrease which is calculated in the volume change calculation process and the weight decrease which is measured in the weight measurement process; and an output process for outputting the temporal density change which is calculated in the calculation process.

Description

  The present invention relates to a method for measuring density change of a volatile paint, and more particularly, to a density change measurement method that can contribute to drying evaluation or volatilization evaluation of a new paint or the like with new characteristics and functions added.

  Conventionally, many industrial products have been painted for the purpose of improving appearance and glazing, improving strength and water resistance, and preventing rust. In recent years, new paints have been developed in many fields for the purpose of high quality, low cost and environmental measures.

  Therefore, it is very important to obtain information on the drying and volatilization of paints from the viewpoint of studying the painting process, grasping the cured state, and further developing paints. In particular, recent paints are not a single solvent component, but are generally added with a function by blending a plurality of types of solvents. Therefore, evaluation of drying and volatilization is important.

  Several methods are known for examining the drying and volatilization of paints. However, for example, the stylus type method scratches the painted surface, and the gravimetric method for examining the change in the weight of the paint has a problem that the sensitivity is low and variation in drying and volatilization cannot be measured. In addition, when there is a solvent component having a high volatilization rate, there are many cases where the surface does not settle uniformly and changes dynamically.

  In recent years, research has also been conducted on methods such as measuring dryness from the attenuation of infrared radiation generated when an ultraviolet pulsed laser beam is applied to a paint surface, and methods for measuring the thickness of a paint surface using terahertz light. However, at this stage, light sources and light receiving elements are special and impractical. In addition, a method of observing the drying process and volatilization process using changes in the speckle pattern generated in the laser reflected light from the rough surface is also known, but this method has a dry (volatile) distribution and depth 3 There is a problem that it is difficult to apply to a case where a three-dimensional object and a surface change dynamically.

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  The present invention has been made in view of the above, and even with a paint whose surface dynamically changes due to volatilization or the like, it is possible to measure a change in density with time without contact, and to examine a coating process and grasp a cured state. It aims to provide a technology that enables evaluation that contributes to further paint development.

  The density change measurement method for a volatile paint according to claim 1 is measured by a phase change measurement process for measuring a phase change over time of a sample surface coated with the target volatile paint using digital holography, and a phase change measurement process. The volume change calculation step for calculating the volume reduction of the target volatile paint based on the phase change, the weight measurement step for measuring the weight loss over time of the sample, and the volume reduction and weight measurement step calculated by the volume change calculation step. A calculation step for calculating a change in density of the target volatile paint over time based on the measured weight loss, and an output step for outputting the change in density over time calculated by the calculation step. And

  That is, according to claim 1, density measurement can be performed based on phase change measurement using digital holography that has not been used for paint evaluation so far, and volatilization evaluation under a plurality of solvents and paint dry evaluation can be performed. Can be done.

  As an output mode by the output process, for example, the horizontal axis represents the drying time and the vertical axis represents the density of the volatile paint, which makes it easy to grasp which component is mainly volatilizing at which time. It becomes possible to do. In addition, the time transition such as weight reduction may be plotted as necessary.

  In addition, phase skip does not occur by shortening the measurement time interval, and more accurate density measurement is realized. When the time interval is large to some extent, it can be corrected by phase connection described later.

  The method for measuring a change in density of a volatile paint according to claim 2 is the method for measuring a change in density of a volatile paint according to claim 1, wherein the phase change is measured at predetermined time intervals in the phase change measurement step. And a correction step for correcting the volume reduction.

  That is, the invention according to claim 2 enables more accurate density measurement by phase connection. In addition, depending on the pigment of the colored paint, the laser may be scattered at the initial stage of volatilization and a relatively inaccurate value may be output. This can be corrected.

  The phase connection method is not particularly limited, and general-purpose software can be used.

  A method for measuring a density change of a volatile paint according to claim 3 is the method for measuring a density change of a volatile paint according to claim 1 or 2, wherein the paint is a transparent paint.

  That is, the invention according to claim 3 can evaluate and measure the density change of the transparent paint, which is extremely difficult to evaluate due to the error derived from the multiple reflections between the paint bottom surface and the paint surface inner side in the conventional method.

  The density change measuring method for volatile paint according to claim 4 is the method for measuring density change of volatile paint according to claim 1, 2 or 3, wherein the output step is controlled to output the density of the solvent. And

  That is, the invention according to claim 4 makes it easy to evaluate and measure which solvent is responsible for the main volatilization when the time has elapsed since the application.

  Note that, for example, when evaluating a paint of another company whose composition is not necessarily clear, it may be used as a reference when the density of a representative solvent is drawn and back-estimated.

  According to the density change measurement method of the volatile paint of the present invention, the time change of the density can be measured in a non-contact manner even if the surface of the paint dynamically changes due to volatilization, etc. Further, it is possible to provide a technology that enables evaluation that contributes to further paint development.

It is the schematic which showed an example of the measurement system which evaluates the density change of a coating material. It is the figure which showed the example of the time change of the phase difference image (DELTA) phit of a transparent paint. It is the output figure which plotted the time change of the weight reduction and volume reduction of a transparent coating material. It is the figure which output the time change of the density of a transparent paint.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, an embodiment using a phase shift digital holography device and an electronic balance will be described, and an example in which a change in the density of the paint is measured by simultaneously measuring the phase difference of the paint surface and the time transition of weight loss will be described. Here, an example in which a transparent paint, which is difficult to measure the density change with the prior art, is used as a sample.

  FIG. 1 is a conceptual diagram of a measurement system for evaluating the density change of a paint. In the figure, a system for imaging a sample with a microscope is also drawn. About a sample, the water-based volatile paint shall be apply | coated to the copper plane board | substrate which roughened the surface. This sample is placed on the electronic balance (EB) of the measurement system.

  A phase shift digital holography apparatus will be outlined. After the light emitted from the semiconductor laser (LD), which is a light source, is converted into parallel light by a lens (Lens), it is divided into sample illumination light by a beam splitter (BS) and reference light reflected by a piezo mirror (PZT-mirror). To do. The coating surface is irradiated with the sample illumination light, and interference fringes (holograms) generated by causing the object light, which is reflected light from the coating surface, to interfere with the reference light are recorded by the CCD.

At this time, the phase of the reference light is recorded as a phase shift hologram shifted by p / 2 radians from the voltage applied to the piezo mirror. Using a four-step phase shift method, the complex amplitude U _o (x, y; t) of the object light on the CCD surface is obtained from four holograms recorded at time t after coating. Specifically, it is expressed as equation (1).

X, y are the coordinates of the sample plane, U _r is the amplitude of the reference light, I ₀ , I _π , I _{π / 2} , and I _{3π / 2} are for each reference light phase-shifted in four stages by a piezo mirror. It is four holograms (interference fringe image) recorded by CCD. j represents a conjugate complex number.

Further, the complex amplitude of the reproduced image U (X, Y; t) of the object light on the plane at a distance Z from the CCD surface is obtained by calculating the Fresnel diffraction integral expressed by the following equation (2).
Here, k = 2p / λ is the wave number, λ is the wavelength of the light source, and (X, Y) is the coordinates on the image plane.

The complex amplitude U (X, Y; t) of the reproduced image obtained as a calculation result is obtained as a discrete value because the hologram is discretely recorded by the CCD. Here, it is assumed that the CCD used for hologram recording is composed of pixels of N × N pixels and vertical and horizontal sizes of Δx and Δy, respectively. When the calculation of the Fresnel diffraction integral is performed by the 1-FFT method, the size of one pixel of the obtained reproduced image depends on the wavelength λ and the reproduction distance Z as shown in the following equation (3).

  In the paint drying process, the coating surface changes due to solvent volatilization, and the phase of object light changes drastically due to multiple reflection and scattering by particles in the coating film. Since capturing this change is an index for evaluating the drying of the paint, in this method, a phase shift hologram is recorded at every fixed time interval T, and this is repeated for a certain period of time until the coated surface is dried to calculate the density change. .

A phase difference Δφ between times t and t + T of the reproduced image is expressed by Expression (4).

As for the transparent paint, the illumination light passes through the coating film, is reflected by the substrate surface below it, and returns to the CCD. In this case, fluctuations in the refractive index distribution, multiple reflections due to the boundary between the substrate surface and the coating film-air, etc. can be virtually ignored, and the phase difference Df _t (X, Y) of the adjacent reproduced image is expressed by the following equation (5). It is expressed in
Here, n _t and h _t coating and the coating film refractive index at each time t the thickness, [Delta] n _t and [Delta] [epsilon] _t is the refractive index change and the coating film thickness change between the T respectively time.

In the formula (5), the actual solvent and pigments in the transparent coating, the refractive index change [Delta] n _t since it is not different things significantly refractive index can be ignored, the change amount [Delta] [epsilon] _t of coating thickness by the phase change [Delta] [phi _t It can be calculated. Thus, the coating volume reduction Δv _loss (t) is calculated by the following equation.

Therefore, using the simultaneously measured decrease amount ΔM _p (t) of the coating film, the change in density d _est of the paint over time can be calculated by the following equation (7).

<Example>
Next, the density measurement experiment of the transparent paint was actually conducted. The laser light source for holography uses a semiconductor laser (LD) having an oscillation wavelength of 657.95 nm, and is converted into parallel light by a lens (Lens) and then has a beam diameter of 30 mm and a size of 40 × 40 mm ² via a beam splitter (BS). The paint applied on the copper substrate was irradiated.

The transparent paint used was Creos Water Hobby Color: H30. Table 1 shows the composition table according to the product safety data sheet (MSDS).

In addition, a monochrome CCD of 512 × 512 pixels, a pixel size of 12.87 × 12.92 μm ² , an 8-bit gray scale (manufactured by Sony Corporation: XC-66) is used for hologram recording. Data was recorded by a frame memory (manufactured by Cybertek: CT-3000A) attached to a PC, and processing such as reproduction calculation was performed in the PC.

  The weight change of the paint was simultaneously measured with an electronic scale having a resolution of 0.1 mg, and the data was sent to a PC. In order to evaluate the drying of the paint, hologram recording, microscopic image, and weight data acquisition were all performed at intervals of 5 seconds (T = 5 sec) and repeated 500 times (2500 seconds). The experiment was performed at room temperature.

  FIG. 2 shows a time change of the phase difference image Δφt. FIG. 3 shows an output diagram of changes over time in weight reduction and volume reduction.

FIG. 4 is a diagram in which changes with time in density are output. Here, d _ex is a plot of density change calculated directly from the original experimental results, and d _ex2 is a plot of density change calculated by estimation from a curve indicating the deformation after 320 seconds. Original d _ex obtained directly from the experimental results, a result of the particular application early volatilization many, phase jumps volume is underestimated occurs, the density is increased, 1 beyond the respective density of the finally solvent component That's it. However, d _ex2 estimated from the deformation amount and calculated using the volume value obtained on the approximate straight line is a more accurate density value as a result of correction. Note that this is because the measurement interval T = 5 sec. In particular, the initial measurement time interval can be shortened to, for example, 0.5 sec. This can be eliminated, and an accurate numerical value can be measured without using an estimated value of deformation. It becomes. In FIG. 4, the change in the phase difference with time and the density of each solvent component are also drawn.

FIG. 4 shows basic data relating to the density of the paint, and various evaluations can be performed based on this data. For example, since the value of _dex2 has reached nearly 0.85 after t = 300 _sec from the change in the composition table and density, the ethanol, isopropyl alcohol, and isobutyl alcohol in the paint are almost volatilized at this stage. It can be judged.

  In addition, the following new solvents or new paints can be evaluated. First, the time change of the density of the basic composition in which plural kinds of solvents are mixed is measured in advance. Next, a new solvent is added to and mixed with this basic composition, and the density change is measured. By monitoring the difference in density change, it becomes possible to know when the newly added solvent volatilizes. Therefore, for example, when a new additive solvent is a solvent that should be handled with care (for example, when it consists of harmful volatile components), it is possible to grasp at which point the solvent is volatilized.

  Moreover, since the change with time of the density is measured based on the phase change, it is possible to evaluate the drying of the paint on the object to be coated with unevenness. Specifically, for example, when coating an object that has been textured or sandblasted, the paint accumulates in the concave portion, and thus the drying process becomes complicated. Even in such a case, drying evaluation, volatilization evaluation, and curing evaluation can be specifically performed using the present invention.

  In addition, although approximation was used in each of the above formulas, whether using colored pigments or using solvents with a large difference in refractive index, the density can be adjusted by optimizing the calculation formula, shortening the measurement time interval, etc. Can be estimated. When colored pigments are used, there is a large amount of deformation error due to multiple reflections at the beginning of coating. Therefore, the time of deformation obtained when the solvent is reduced to some extent and the reflected light from the surface becomes the main component. The density can be estimated by using a method for estimating the entire deformation.

  According to the present invention, it is possible to quantitatively evaluate not only the paint but also the drying and curing processes of ink and thin film, and it is possible to acquire important basic data for improving their performance and functionality.

Claims (4)

A phase change measurement process for measuring the phase change over time of the sample surface coated with the target volatile paint using digital holography;
A volume change calculating step for calculating a volume reduction of the target volatile paint based on the phase change measured by the phase change measuring step;
A weight measurement step for measuring weight loss of the sample over time;
Based on the volume reduction calculated by the volume change calculation step and the weight reduction measured by the weight measurement step, a calculation step for calculating a change in density over time of the target volatile paint,
An output step for outputting a change in density over time calculated by the calculation step;
A method for measuring a change in density of a volatile paint characterized by comprising: In the phase change measurement process, phase change is measured at predetermined time intervals,
The method for measuring a change in density of a volatile paint according to claim 1, further comprising a correction step of correcting the volume loss by performing phase connection.   The method for measuring a density change of a volatile paint according to claim 1 or 2, wherein the paint is a transparent paint. 4. The method for measuring a change in density of a volatile paint according to claim 1, wherein the density of the solvent is also outputted by controlling the output step.