JPH11237377A - Paper and sheet quality measuring equipment - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] A paper or sheet that can simultaneously measure the basis weight, moisture, coating amount, ash, etc. of paper with a single measuring device using highly safe light in the near infrared region. To provide a quality measuring device. SOLUTION: A light source 10 that emits near-infrared light, a condensing unit 12 that condenses near-infrared light emitted from the light source and irradiates the light onto a measurement target 30, and a light transmitted through the measurement target A condensing unit 14; a unit 16 for dispersing the light condensed by the condensing unit; a detector 20 for performing spectrum analysis of a frequency or a wavelength of the light dispersed by the dispersing unit; The signal processing unit 22 is configured to calculate at least one of the basis weight, moisture, coating amount, or ash content of the measurement target using spectrum analysis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper or sheet quality measuring device for measuring basis weight, moisture content, coating amount, ash content, film thickness, etc., and more particularly to a single measuring device for measuring a plurality of qualities. Related to measurable structures.

[0002]

2. Description of the Related Art In the papermaking industry, a gravimeter for measuring the weight per unit area of paper, a moisture meter for measuring the moisture of paper, and a paper meter per unit area when the paper surface is coated. And an ash meter for measuring the weight of ash per unit area of paper. In the synthetic organic chemical industry, the thickness of a film or a sheet or the thickness of a multilayer film is measured.

Such a measuring device is disclosed in, for example, Yokogawa Technical Report, Vol. 24, p. 107 (1980) and Vol. 33, p. 193 (1989). Next, the measurement principle of each measurement device will be described. The gravimeter performs stable measurement with high accuracy by the β-ray transmission method. Moisture analyzers use the phenomenon that microwaves are absorbed by water,
Utilizing the transmission and absorption of various types of near-infrared light, water in paper is accurately measured. The ash meter measures the ash content of clay, talc, titanium oxide, calcium carbonate and the like by transmitting and absorbing low energy X-rays.

The film thickness gauge measures an absorption peak in a near infrared to infrared region by a filter method. In addition,
2. Description of the Related Art In a paper thickness gauge for measuring the thickness of paper, a paper thickness gauge is used in which a measuring device is floated at a predetermined interval from the paper surface and the paper thickness is measured from the displacement of the paper thickness gauge.

[0005]

However, in order to measure the basis weight, moisture, coating amount and ash content of paper, four types of sensors are required. Such a sensor has a structure in which the sensor reciprocates along a frame provided in the paper width direction, and measures the entire paper width direction with a small number of sensors. By the way, when sensors are loaded on four types of frames,
There is a problem that a frame having high rigidity that can withstand the weight is required, and the manufacturing cost of the frame increases. In addition, since the measurement position is managed by the position in the paper width direction,
Originally, it is desirable that the measurement position of each measurement value be the same.
However, each sensor has a physical size, and there is a problem that the individual measurement positions do not exactly match.

[0006] Further, since radiation and X-rays are used in the gravimeter, the ash meter, and the coating meter, there is a problem that the use environment and the total use amount are limited, and the maintenance work is difficult. there were. In addition, since the moisture meter employs a filter rotation method, there is a problem that high-speed measurement cannot be performed. Furthermore, since the film thickness meter uses light in the infrared region, expensive parts that do not absorb in the infrared region are required, and are not affected by moisture or carbon dioxide gas in the air. There has been a problem that such structural measures are required.

The present invention solves the above-mentioned problems, and simultaneously measures the basis weight, moisture, coating amount, ash content, etc. of paper using a single measuring device using highly safe light in the near infrared region. An object of the present invention is to provide a paper or sheet quality measuring device that can be measured.

[0008]

In order to achieve the above object, a paper or sheet quality measuring apparatus according to claim 1 of the present invention comprises a light source 10 for emitting near-infrared light and a light source 10 for emitting near infrared light. A condensing means 12 for condensing the near-infrared light and irradiating the measurement target 30 with light; a means 14 for condensing light transmitted through the measurement target; Means 1
6, a detector 20 for performing spectrum analysis of the frequency or wavelength of light separated by the spectroscopic means, and at least the basis weight, moisture, coating amount, or ash content of the measurement object using the spectrum analysis of the detector. The configuration includes a signal processing unit 22 that calculates one type.

According to such a configuration, since a plurality of qualities such as the basis weight, moisture, coating amount, and ash content of the measurement object can be measured by a single optical system, the same portion of the measurement object can be simultaneously measured at high speed. . Further, since a plurality of qualities can be measured by a single measuring device unit, the weight of the measuring device can be reduced as compared with a conventional type in which a measuring device unit is mounted on a frame for each individual quality. With respect to the frame on which the measuring device is mounted, the weight of the frame can be reduced.

In order to achieve the above object, a paper or sheet quality measuring apparatus according to claim 10 of the present invention comprises a light source 10 that emits near-infrared light, and a near-infrared light emitted from this light source. A light projecting means 32 for converging and irradiating the object 30 to be measured, a means 34 for condensing reflected light of the object to be measured, a means 36 for dispersing the light condensed by the light condensing means, Detector 40 that performs spectral analysis of the frequency or wavelength of the light that has been spectrally separated, and at least one type of the thickness, basis weight, moisture, coating amount, or ash of the measurement target using the spectral analysis of the detector. The configuration includes a signal processing unit 42 for calculating.

According to such a configuration, a single optical system can measure a plurality of qualities such as thickness, basis weight, moisture, coating amount, and ash content of the object to be measured. High-speed measurement is possible. By using a detector for spectrum analysis instead of the conventional filter rotation type, it is not necessary to rotate the filter, and high-speed measurement can be performed.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a transmission type configuration showing an embodiment of the present invention. In the figure, the light source 10 emits near-infrared light, and preferably includes near-infrared light in a wavelength region of at least 1.8 μm to 2.5 μm, and 0.8 μm to 2.6 μm to deal with chemometric analysis. It is desirable to include near-infrared light in the above wavelength range.

The light condensing means 12 is an optical system for converging and irradiating near-infrared light emitted from the light source 10 at one point at the position of the measurement object 30, and uses a convex lens here. here,
The measurement object 30 is a paper, a film, a multilayer film, a paper coated with a film, or the like. The light condensing means 14 is an optical system that condenses the light transmitted through the measurement target 30 and converts the light into parallel light.
Here, a convex lens is used. The light separating element 16 separates the light condensed by the light condensing means 14 and is a spectroscope such as a diffraction grating. The condensing optical system 18 separates the light separated by the light separating element 16 for each wavelength band and sends the light to the array detector 20.

The array detector 20 is made of, for example, InGaAs.
In this case, the wavelength band is 1.8
Five channels of μm, 1.9 μm, 2.1 μm, 2.3 μm, and 2.4 μm are prepared and spectral analysis is performed. Wavelength 1.
8 μm is selected as a wavelength band that does not cause absorption in the quality index of paper or sheet, and obtains the light intensity that is a reference when determining the absorbance in other wavelength bands. Wavelength 1.
9 μm is the wavelength at which moisture causes absorption. Wavelength 2.1μm
Is the wavelength at which cellulose absorbs, and the basis weight corresponds to paper quality. The wavelength of 2.3 μm is the wavelength at which ash causes absorption. The wavelength of 2.4 μm is a wavelength at which the coating material causes absorption. Since the absorption wavelength band differs depending on the components of the ash and the coating material, it is preferable to select a wavelength at which absorption occurs instead of the wavelength of 2.3 μm or 2.4 μm.

The signal processing section 22 calculates at least one of basis weight, moisture, coating amount, or ash based on the absorption amount of near-infrared light in each wavelength region obtained by the array detector 20. Note that a multivariable analysis technique called chemometrics may be used to measure the ash content having a small signal component and the coating amount causing much interference.

FIG. 2 illustrates an example of the relationship between paper having different basis weights and absorbance. In this case, a wave number [cm ^-1 ] is used instead of a wavelength.
Is used. As the measurement sample, eight kinds of tracing papers 1 to 8 were used, and the basis weight was 45, 50, 50, 6 from the lightest.
0, 75, 120, 170, 180 [g / m ² ].

FIG. 3 shows the first derivative of the absorbance of FIG. 2 with respect to the wave number. The wave number 5200 [cm ^-1 ] corresponds to a wavelength of 1.9 μm at which moisture causes absorption, and the first derivative is zero. The wave number 4800 [cm ^-1 ] corresponds to a wavelength of 2.1 μm at which cellulose absorbs, and the first derivative is zero. Ash has a wavelength of about 2,600 [cm ^-1 ] with a wavelength of 2.
Although it corresponds to 3 μm, the first derivative is not affected by other absorption in the near-infrared coupled sound region, and the interference component remains only with the absorption of a single wavelength, so that the first derivative does not become zero. The coating amount corresponds to a wavelength of 2.4 μm near the wave number of 4350 [cm ^-1 ], but the first derivative is affected by the absorption of other coupled sound regions in the near infrared. Because the ingredients remain,
The first derivative does not become zero.

FIG. 4 is a calibration diagram showing the relationship between the absorbance and the basis weight in FIG. A calibration curve can be obtained from the relationship between the basis weight and the absorbance in FIGS. The signal processing unit 22 stores this calibration curve, and applies the calibration curve to the absorbance measured this time to measure the measured basis weight and the like of the paper. The basis weight calculated in this way and the actual basis weight of the paper match with an error of, for example, about 2 [g / m ² ].

FIG. 5 is a view for explaining the relationship between the polyester film thickness and the absorbance. Here, 350,250,188,125,100,75,50μm as polyester film thickness
The absorbance was measured using the above seven types. In the case of polyester film, the peak of the absorbance is wave number 4400-4000,
It is in the band of 3700-3400, 3100-2800 [cm ^-1 ]. Therefore, a calibration curve is created by chemometric analysis using the absorbance in these wavenumber bands. Then, when the film thickness was determined by the signal processing unit 42, reproducibility and linearity were obtained with an error of 2 μm over a measurement range of 350 μm.

In the case of a multilayer film, an absorption peak appears at a different wavelength depending on the material, so that the thickness of each layer can be measured simultaneously. Even when paper is coated with a film, simultaneous measurement is possible by removing the interference component by chemometrics using the spectrum change of the wavelength which is an individual characteristic of the paper.

FIG. 6 is a block diagram showing a configuration of a reflection type according to another embodiment of the present invention. The light projecting unit 32 condenses near-infrared light emitted from the light source 10 and irradiates the measurement object 30 with the light. The condensing means 34 condenses the reflected light of the measurement target 30 into parallel light and sends it to the spectroscope 36. The array detector 40 performs spectrum analysis of the frequency or wavelength of the light split by the spectroscope 36. The signal processing unit 42 calculates at least one type of the thickness, the basis weight, the moisture, the coating amount, or the ash of the measurement target 30 using the spectrum analysis of the detector 40.

The use of the reflection type as described above has an effect that the structure of the measuring apparatus can be simplified since access from one side is possible. Further, the measurement accuracy for the coating amount on the surface is superior to that of the transmission type, but the measurement accuracy for other qualities is reduced.

In the above embodiment, the detector 20
However, the present invention is not limited to this, and may be a two-dimensional detector array. Then, the X axis can be used as the position of the measurement target 30 and the Y axis can be used as spectrum information, and there is an advantage that a plurality of spatial distributions of quality can be measured simultaneously. If a microlens array is added before the detector 20, the amount of light focused on each channel of the detector increases, the S / N ratio is improved, and a stable measurement signal can be obtained.

[0024]

As described above, according to the paper or sheet quality measuring apparatus of the first aspect, a plurality of qualities such as basis weight, moisture, coating amount or ash content of a measurement object can be measured by a single optical system. Can be measured at the same time, so that the same portion of the object to be measured can be measured at high speed. Further, since a plurality of qualities can be measured by a single measuring device unit, the weight of the measuring device can be reduced as compared with a conventional type in which a measuring device unit is mounted on a frame for each individual quality. With respect to the frame on which the measuring device is mounted, the weight of the frame can be reduced. In addition, compared to conventional gravimeters, ash meters, and coating weight meters,
It is safer than X-rays and X-rays, and has no restrictions on the use environment. Furthermore, compared to the conventional moisture meter and filter thickness meter, high-speed measurement can be performed because a solid-state array detector is used instead of the conventional filter rotation method. Compared to a filter thickness meter that uses infrared light, near-infrared light is less affected by moisture and carbon dioxide in the air, and optical components need only be inexpensive with absorption in the infrared region. Good and inexpensive to manufacture.

Here, it is desirable that the light source includes near-infrared light in a wavelength region of at least 1.8 μm to 2.5 μm. Then, as in claim 3, the signal processing unit has a basis weight of 2.1 μm and a moisture of 1.9 μm.
m, coating amount: 2.4 μm, ash content: 2.3 μm
The light source required for the single-wavelength type, which calculates based on the absorption amount of near-infrared light in the above wavelength range, is obtained. Further, as in claim 4, the signal processing unit uses a multivariate analysis method based on the absorption amounts of the near-infrared light at a plurality of wavelengths, and uses a multivariate analysis method to obtain at least one of the basis weight, moisture, coating amount, or ash content. If the type is calculated, accurate measurement can be performed even if there is a wavelength region where interference occurs.

Here, if the composition component is InGaAs, it is easy for the detector to convert near-infrared light into an electric signal. Further, when the detector is a two-dimensional detector, the measurement of the spectrum can be performed simultaneously with the measurement of the spectrum. Preferably, when the detector has a microlens array, the S / N ratio is improved.

When the object to be measured is a multilayer film, the signal processing section may calculate the thickness of each layer of the multilayer film. Also,
When the object to be measured is paper coated with a film as in claim 9, the signal processing unit calculates at least one type of the thickness, basis weight, moisture, coating amount, or ash of the film. Good to do.

According to the paper or sheet quality measuring apparatus of the tenth aspect, since the apparatus is of the reflection type, the structure of the measuring apparatus is simpler than that of the transmission type. Further, when it is necessary to measure the quality of one side of the paper as in the case of the amount of coating, the measurement can be performed more easily than in a configuration in which information including the quality of both sides of the paper is obtained as in the transmission type.

[Brief description of the drawings]

FIG. 1 is a block diagram of a transmission type configuration showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a relationship between paper having different basis weights and absorbance.

FIG. 3 shows the first derivative of the absorbance of FIG.

FIG. 4 is a calibration curve diagram showing a relationship between absorbance and basis weight.

FIG. 5 is a diagram illustrating a relationship between a polyester film thickness and absorbance.

FIG. 6 is a structural block diagram of a reflection type showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Light source 12, 14, 18 Condensing optical system 16 Spectral element 20 Array detector 22 Signal processing part 30 Measurement object (paper, film)

Claims (10)

[Claims] A light source for emitting near-infrared light; a near-infrared light emitted from the light source being condensed;
0), a means (14) for condensing light transmitted through the object to be measured, a means (16) for dispersing the light condensed by the condensing means, A detector (20) for analyzing the spectrum of the frequency or wavelength of the light separated by the spectroscopic means, and at least one of the basis weight, moisture, coating amount, or ash of the object to be measured using the spectrum analysis of the detector; A paper or sheet quality measuring device, comprising a signal processing unit (22) for calculating the following. 2. The light source according to claim 1, wherein said light source is at least 1.8 μm to 2.5 μm.
The paper or sheet quality measuring apparatus according to claim 1, wherein the apparatus includes near-infrared light in a wavelength region of m. 3. The signal processing section according to claim 1, wherein the basis weight is 2.1 μm.
m, moisture is 1.9μm, coating amount is 2.4μm
2. The paper or sheet quality measuring apparatus according to claim 1, wherein the m and ash are calculated based on the absorption amount of near-infrared light in a wavelength region of 2.3 [mu] m. 4. The signal processing unit calculates at least one type of basis weight, moisture, coating amount, or ash using a multivariate analysis method based on absorption amounts of a plurality of wavelengths of near-infrared light. The paper or sheet quality measuring device according to claim 1, wherein: 5. The apparatus according to claim 1, wherein the detector has a composition component of InGaAs. 6. An apparatus according to claim 1, wherein said detector is a two-dimensional detector. 7. An apparatus according to claim 1, wherein said detector has a microlens array. 8. The paper or sheet quality measurement according to claim 1, wherein when the object to be measured is a multilayer film, the signal processing unit calculates the thickness of each layer of the multilayer film. apparatus. 9. When the object to be measured is paper coated with a film, the signal processing unit includes at least one of a thickness, a basis weight, a moisture, a coating amount, and an ash content of the film.
The paper or sheet quality measuring device according to claim 1, wherein the type is calculated. 10. A light source (10) for emitting near-infrared light, and a near-infrared light emitted from the light source is condensed to be measured (3).
0), a means (34) for condensing the reflected light of the object to be measured, a means (36) for dispersing the light condensed by the condensing means, A detector (40) for performing spectral analysis of the frequency or wavelength of light separated by the means, and at least the thickness, basis weight, moisture, coating amount, or ash content of the measurement object using the spectral analysis of the detector. A paper or sheet quality measuring device comprising a signal processing unit (42) for calculating one type.