CN105424321B - A kind of detection method of UV curing light sources emittance attenuation rate - Google Patents

Abstract

The invention relates to a method for detecting the attenuation rate of radiation energy of a UV curing light source, belonging to the technical field of printing. Determine the wavelength band that can represent the attenuation degree of the radiation energy of the curing band in the spectral radiant energy of the UV curing light source to be detected as the detection light; prepare the detection pieces V ₀ and V _m from the medium gray light-transmitting material, and prepare the light reduction from the medium-gray light-transmitting material The film group and two light-reducing films T ₀ and T _m overlap the light source screening part, the detection film and the light-reducing film, and put them in a cylindrical device to form a detector that can visually observe the light-transmitting state; After the initial use of the light source and after a period of use, the detector uses the detection film V ₀ , V _m and the light reduction film T ₀ , T _m respectively, and adds a suitable light reduction film T _i to observe the UV light source. Whether the field reaches the luminance difference is just distinguishable to determine whether the attenuation rate of the radiant energy of the light source reaches m times of the design. The method requires simple devices and is suitable for use in production environments.

Description

A detection method for radiation energy decay rate of UV curing light source

technical field

The invention relates to a method for detecting the attenuation rate of radiation energy of a UV (Ultraviolet-UV, ultraviolet) curing light source, which is suitable for use in a printing production environment. The evaluation of the attenuation degree of the radiation energy of a UV light source for curing can instruct production managers to clearly understand the UV light source. Availability, belonging to the field of printing technology.

Background technique

UV curing refers to the process in which a material absorbs a certain band of ultraviolet light to undergo a cross-linking polymerization reaction after being irradiated by ultraviolet light, and instantly changes from liquid to solid. It is widely used in printing, circuit board printing and other industries.

UV light sources for printing ink curing are divided into traditional mercury lamp light sources and LED UV light sources, which are called traditional UV light sources and LED UV light sources respectively. Commonly used traditional UV light sources include medium-pressure mercury lamps (international standards) and metal halide lamps, and LED UV light sources include narrow-band LED lamps with center wavelengths of 365nm, 375nm, 385nm, 395nm and 405nm.

No matter what kind of UV light source is used, a certain amount of radiation energy is required, and if the energy is not enough, the ink cannot be completely cured.

The UV light source will age during use, and the radiant energy will gradually attenuate. In production, the service life of the UV light source is based on the radiation energy decay rate. For example, in the printing industry, when the energy of the radiation peak wavelength drops to 80% of the design radiation peak wavelength energy of the lamp tube, it is considered to have reached its life span and is no longer used.

At the same time, most of the UV radiation energy testing methods used are test strips or professional testing instruments. The method of using a test strip is a German color changing ink test strip. When in use, the test strip needs to be pasted on the moving production product, and the degree of discoloration after UV light is compared with the standard sample, and the UV light is judged by the same color as the standard sample and the light intensity attenuation degree represented. Radiation level. However, it is found in the application that the color of the test sample on the test strip and the color on the standard sample are different in hue, and it is difficult to determine which standard sample color matches. In addition, the use of this method is also troublesome. In the case of using a professional testing instrument, it is necessary to place an instrument with a certain volume and the printed matter together and move it under UV light for testing. In practice, it is found that the thickness of the instrument makes it difficult to fix the printed matter on the instrument; at the same time, direct high-energy UV light is also easy to damage the instrument.

In view of the problems existing in the above-mentioned UV light irradiance test, new detection techniques are expected. The development of a convenient, fast and low-cost detection technology for the radiation attenuation of UV light sources has become an actual demand in printing production.

Contents of the invention

The purpose of the present invention is to provide a method for detecting the attenuation rate of radiation energy of a UV curing light source, so that it can be conveniently used in printing production.

A method for detecting the attenuation rate of radiation energy of a UV curing light source provided by the invention comprises the following steps:

(1) For the UV curing light source used, determine the representative band in the spectral radiant energy of the UV curing light source to be detected as the detection light; that is, select the band that can represent the attenuation degree of the radiant energy of the curing band. For example, the selected wave band is the wavelength range from λ ₁ to λ ₂ , and the radiant energy distribution is S _c (λ).

(2) The test piece is prepared from a medium gray light-transmitting material, and the test piece contains two adjacent areas with different light transmittance; A transmission sheet with a square or circular area is called a detection sheet. The spectral light transmittances of the two regions of the detection sheet are respectively denoted as τ ₁ (λ)=τ ₁ and τ ₂ (λ)=τ ₂ .

(3) Prepare two detection sheets V ₀ and V _m , the transmittances of the two regions of V ₀ are τ ₁ and τ ₂ respectively, and τ ₂ = (1+n ₁ )τ ₁ ; the transmittances of the two regions of V _m The transmittances are τ' ₁ and τ' ₂ respectively, and τ' ₂ = (1+n ₂ )τ'₁; n ₁ and n ₂ are the visual brightness of the light source in the two areas of the detection sheet V ₀ and V _m respectively The ratio of just discernable difference to brightness ΔY/Y, ΔY′/Y′, Y and Y′ are the brightness corresponding to the values of n ₁ and n ₂ respectively, n ₁ and n ₂ are selected as the visual brightness difference and brightness of the light source Different ΔY/Y values in the middle of the curve of the ratio ΔY/Y versus brightness Y and in the range where the curvature changes quickly.

Prepare two test pieces with different τ ₁ and τ ₂ as described in step (2), which are denoted as V ₀ and V _m respectively. V ₀ and V _m are designed to represent the initial use of the light source and the attenuation of the radiant energy to m times the initial value (m is used to represent the attenuation rate of the radiant energy of the light source - the ratio of the radiant energy of the light source after use to the radiant energy of the initial light source, The radiant energy of the light source when 0<m<1). The light transmittances of the two parts of V ₀ are respectively τ ₁ and τ ₂ , and the light transmittances of the two parts of V _m are respectively τ' ₁ and τ' ₂ . It is required that τ ₂ =( ₁ +n ₁ )τ ₁ and τ' ₂ =( ₁ +n ₂ )τ' ₁ . The value of ΔY/Y in the middle of the luminance Y change curve and in the range of rapid curvature change has n ₂ >n ₁ , and the luminance corresponding to the values of n ₁ and n ₂ are Y and Y′ respectively.

(4) The light-reducing film group is prepared from medium-gray light-transmitting materials, including a plurality of light-reducing films with gradually changing light transmittance. The shape and area of each light-reducing film are the same as that of the detection film. The rate is consistent. The light reduction film group requires a sufficient number of sheets, a sufficiently small minimum light transmittance, a large light transmittance variation range, and a small light transmittance difference. For example, the maximum light transmittance in the λ ₁ to λ ₂ band is about 0.4, and the minimum is about 0.05. When the light transmittance of the light-reducing films is arranged in order, the difference in light transmittance between adjacent light-reducing films is about 0.007.

Sort the light-reducing film groups from large to small according to light transmittance, and mark them as T ₁ , T ₂ , ..., T _i , ..., T _N , i=1, 2, ..., N, denoted as T _i , and transmittance The light rate is also denoted as T _i .

(5) Prepare two light-reducing films T ₀ and T _m , and the light transmittance T _m is consistent with T ₀ : The meanings of m, τ ₁ , τ′ ₁ , Y, and Y′ in the formula are the same as in step (3). Among T ₀ and T _m , the light transmittance of T ₀ is relatively high (preferably above 0.3), and the size is between T ₁ and T ₁₀ ; the two light-reducing films are used to represent the initial use of the light source and the attenuation of radiation energy to the initial value respectively The radiant energy of the light source at m times.

(6) Overlay the light source screening components (such as optical filters), detection sheets and light reduction sheets (one or more sheets), and place them in a device such as a lens barrel to form a visually observable light-transmissive state. device, called a detector. Among them, the light reduction film and the detection film can be easily replaced.

(7) At the initial use of the UV light source, place the detection film V ₀ and the light reduction film T ₀ in the detector, observe the UV light source at a position where the UV light source light scatters, and add a suitable light reduction film T _i , so that the brightness difference between the two parts of the light field observed in the detector is just discernible.

(8) After the UV light source has been used for a period of time, place the detection film V _m and the light reduction film T _m in the detector, and at the same position in step (7), observe the UV light source, and the light reduction film T _i remains unchanged , whether the attenuation rate of the radiant energy of the light source reaches m times of the design is determined by whether the two parts of the light field observed in the detector reach the brightness difference just discernible.

In step (1), a band-pass filter can be used to select a band that can represent the degree of attenuation of radiant energy in the band that plays a role in curing. At this time, the spectral radiant energy S _c (λ) for detection is S(λ)·L(λ). S(λ) and L(λ) are the spectral radiant energy and spectral transmittance of the UV light source and the bandpass filter, respectively. The bandpass wavelength range λ ₁ to λ ₂ of L(λ) needs to be aimed at the representative light band for curing. The shape of the filter is square or circular, and the side length or diameter is between 40mm and 50mm.

In the printing industry, for the metal halide UV curing light source, the wavelength band of 380nm to 400nm can be used as the detection light; for the LED UV curing light source, the wavelength range of the light source itself can be used as the detection light.

In step (2), the detection sheet is a medium-gray transmission sheet, that is, the light transmittance does not change with the wavelength, and the light transmittance τ(λ)=τ. In practice, it is only required to satisfy τ(λ)=τ in the λ ₁ -λ ₂ band to be detected. The shape and size of the detection sheet are the same as that of the band-pass filter, that is, the shape is square or circular, and the side length or diameter is between 40 mm and 50 mm.

In step (3), when the detection sheet V ₀ is irradiated by the detection light S _c (λ), the light intensities Y and Y+ΔY of the two parts of the light field in the detection sheet can be expressed as:

In the formula, V(λ) is the spectral light efficiency function of human vision, km is a constant, and the unit is lumen/watt (lm/W), which is _683lm /W under photopic conditions. Y and Y+ΔY are the light intensity of the transmitted light in the two regions of the detection sheet V ₀ , and the unit is cd/m ² . τ ₁ and τ ₂ are the light transmittances of the two light-transmitting regions of the detection sheet V ₀ , respectively.

From (1), (2) and τ ₂ =(1+n ₁ )τ ₁ , we have:

Similarly, when the detection sheet V _m is irradiated by the detection light S _c (λ), the light intensities Y' and Y'+ΔY' of the two parts of the light field in the detection sheet can be expressed as:

From formulas (4), (5) and τ' ₂ =(1+n ₂ )τ' ₁ , we have:

Formulas (3) and (6) show that when the transmittance of the two regions of the detection sheet satisfies the condition τ ₂ =(1+n)τ ₁ (n is a certain value), the value of ΔY/Y is only related to the value of n , and has nothing to do with the radiant energy of the UV detection light and the light transmittance of the detection sheet.

The variation curve of the just-discernible difference in brightness and brightness ratio ΔY/Y with brightness Y is the law of brightness difference threshold value of human vision in the theory of chromaticity, as shown in FIG. 1 . It is characterized by the relationship between the ratio ΔY/Y of the just discernable difference of brightness and the brightness with the brightness Y, which is divided into monocular and binocular cases. All have the characteristics that ΔY/Y decreases gradually with the increase of Y value in the low brightness area, and does not change after decreasing to a certain extent. When the (Y, ΔY/Y) point falls above the threshold curve, the brightness difference is clearly discernible; and when the (Y, ΔY/Y) point falls below the threshold curve, the brightness difference is completely indiscernible.

Taking the binocular regularity curve as an example, the curvature change range in the middle part of the curve is agreed to be the range from point A to point B on the curve, as shown in the partial enlarged view in FIG. 1 and FIG. 2 . It is required that the angle between the tangent of points A and B and the negative direction of the Y axis be between 30° and 70°. The Y and ΔY/Y coordinate values of points A and B are recorded as (Y ₁ , y ₁ ) and (Y ₂ , y ₂ ), respectively.

The values of n ₁ and n ₂ are within the range of ΔY/Y values on curves A and B, that is, between y ₁ and y ₂ .

In step (4), the light-reducing sheet is a near-middle gray transmission sheet, which also has a characteristic that light transmittance is independent of wavelength, expressed as T(λ)=T. In use, it is required to satisfy T(λ)=T in the λ ₁ -λ ₂ band to be detected.

When the light reduction sheet and the detection sheet _V0 in step (3) are superimposed together to transmit UV detection light, the transmitted light intensity of the _τ1 area in _V0 is:

Comparing Equation (7) with Equation (1), it can be seen that the effect of the light reduction film is to reduce the radiation intensity of the detection light S _c (λ), and also reduce the transmitted light intensity.

Therefore, it is not difficult to export:

Formula (8) shows that the addition of the light-reducing film does not change the ΔY/Y value of the transmitted light intensity in the two regions of the test film, but only changes the Y value of the transmitted light intensity of the test film.

The shape and size of the light-reducing sheet are the same as those of the bandpass filter in step (1) and the detection sheet in step (2).

In step (6), the detector is a combination of light source radiant energy screening filter, light reduction sheet and detection sheet, and its transmission light path structure diagram is shown in FIG. 3 . In the figure, S(λ), L(λ), T and τ ₁ , τ ₂ represent the spectral power distribution of the UV curing light source, the spectral light transmittance of the screening filter, the light transmittance of the light-reducing film and the detection film. The light transmittance and the transmitted light intensity Y of the two adjacent areas conform to (7) formula. Wherein, the light-reducing film T can represent a combination of one or more than two light-reducing films, and its light transmittance is the product of the light transmittance of all light-reducing films.

In step (7), when the UV light source is initially used, the light transmittance relationship between the two areas in the detection sheet V ₀ used is τ ₂ =(1+n ₁ )n ₁ in τ ₁ is designed to be greater than y ₁ and close to y ₁ A certain value of , corresponds to a definite value Y on the brightness difference threshold curve.

For a certain S _c (λ) and τ ₁ , the realization of the Y value determined by (7) can be guaranteed by selecting the appropriate light-reducing film T _i , and when using V ₀ in combination with T ₀ , the Y value at this time for:

After the radiation energy of the UV light source is reduced from S(λ) to mS(λ), the detection light S _c (λ) is also reduced to mS _c (λ) when the filter filter L(λ) remains unchanged. When the detection sheet V _m represents this radiant energy, the value of ΔY/Y on the brightness difference threshold curve corresponds to n ₂ , and the corresponding transmitted light brightness is Y′. In order to ensure that the transmitted light intensity conforming to formula (7) reaches the value Y′, if the light reduction film T _i is still configured (similarly, T _{m is used in combination with V m )} , then:

So, there are:

Therefore, it is required that the light-reducing film T ₀ and T _m in the step (5) conform to the relationship of formula (11).

To sum up, it can be seen that the function of the detection sheet is to determine the ΔY/Y value of the two transmitted light fields, and the function of the light reduction sheet is to adjust the final Y value of the transmitted light intensity, and there is no mutual influence between the two.

In addition, the position where the light from the UV light source scatters in step (7) may be the position where the light source cover is opened, which is determined according to the actual situation of the printing equipment.

In steps (7)-(8), the detector prepared by step (6) is used to detect the radiation energy decay rate of the UV curing light source, including:

i) When the UV light source is used initially, the detector uses the detection film V ₀ and the light reduction film T ₀ . At a certain distance from the UV light source, observe the UV light source. At this time, the brightness difference between the two parts of the light field in the detector must be clearly seen. Add a light-reducing film, and replace the light-reducing film sequentially starting from T ₁ with the maximum light transmittance, until a suitable light-reducing film T _i is selected, so that the brightness difference between the two parts of the light field in the detector can just be distinguished.

ii) After the UV light source has been used for a period of time, the detection film V ₀ in step i) is replaced with V _m , the light reduction film T ₀ is replaced with T _m , and T _i remains unchanged. Place the detector at the same position as in step i), and observe the transmitted light field in the detector in the same way. If the brightness difference between the two parts of the light field is visually discernible, it indicates that the attenuation rate of the radiant energy of the light source has not yet reached the design value m; and if there is no brightness difference between the two parts of the light field, it indicates that the attenuation rate of the radiant energy of the light source has reached or exceeded m .

The approximate degree of attenuation of the radiant energy of the light source can be further estimated.

In the former case, the light-reducing film T _i needs to be replaced, and the light-reducing film T _i+1 , T _i+2 , ..., Ti _+n , etc. with smaller light transmittances should be selected successively. When the brightness difference between the two parts of the light field is just felt, the farther the corresponding T _i+n is from T _i , the smaller the attenuation rate of the radiant energy of the light source is than the design value m.

In the latter case, it is necessary to replace the light reduction films T _i-1 , T _i-2 , . . . , T _in with higher transmittance in sequence. When the brightness difference between the two parts of the light field is just felt, the farther the corresponding T _in and T _i are, the greater the attenuation rate of the light source energy is than the design value m.

In this way, the detection of the attenuation rate of the radiant energy of the UV curing light source is realized through the perception of the brightness difference.

So far, the principle of this detection method can be summarized as: determine two characteristic points on the brightness difference threshold curve, the initial UV curing detection light radiation and after the energy is reduced to a certain extent; the ΔY/Y value corresponding to the two points determines the two points. τ ₂ =(1+n ₁ )τ ₁ and τ' ₂ =(1+n ₂ )τ' ₁ of the two detection slices V ₀ and V _m are n ₁ and n ₂ values; on the brightness difference threshold curve , the value of n ₁ , n ₂ corresponding to the value of Y, Y′ is achieved by using V ₀ , T ₀ , T _i and V _m , T _m , T _i respectively in the transmitted light path, as long as the relationship between T _m and T ₀ is consistent with relation An appropriate light reduction film T _i can be selected. In this way, the attenuation rate of the UV detection light radiation energy can be characterized by just distinguishing the brightness difference.

The detection method of the radiation energy decay rate of the UV curing light source provided by the present invention only needs to place the detector on the side illumination part suitable for human eye observation in the UV light field, and use the brightness difference resolution law of human vision to detect UV The decay rate of the curing light source energy. The device required by the method is simple, does not require power supply, is low in cost, and does not need to place the detection instrument on the substrate in the printing line, avoids the inconvenience of use, and does not have the problem of being damaged by strong UV light. Used in production environment.

Description of drawings

Figure 1 is a curve of the brightness difference threshold law of human vision.

FIG. 2 is a partial enlarged view of the human eye visual brightness difference threshold curve.

Fig. 3 is a schematic diagram of the detection optical path principle of the method of the present invention.

Fig. 4 is the radiation spectrum power variation curve of the metal halide lamp UV light source.

Fig. 5 is a radiant energy spectral power distribution curve of the LED light source used in the embodiment of the present invention.

Fig. 6 is a distribution curve of spectral light transmittance of film films with different light transmittance according to the embodiment of the present invention.

FIG. 7 is a just-discernible curve of apparent brightness difference of an LED light source with a center wavelength of 385 nm established in an embodiment of the present invention.

FIG. 8 is an enlarged view of a region with a large curvature change in the just-discernible curve of the apparent brightness difference of the light source used in the embodiment of the present invention.

detailed description

Below in conjunction with specific embodiment, further illustrate the present invention. After reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope of protection claimed by the present application.

In this embodiment, the spectral energy characteristics of the commonly used metal halide lamps, which are traditional mercury lamp UV light sources, are analyzed first. Metal halide lamps are installed in the UV curing experimental equipment.

Use the AvaSpec-2048FT-SPU spectrometer to measure the different working voltages of the metal halide lamp at the initial use, and after 2 months, 4 months, and 6 months, at the outlet of the printed matter of the equipment (with scattered UV light) The radiant energy spectral power distribution function is measured, and the results are shown in Figure 4. There are 5 curves in the figure, the 1st, 3rd and 5th curves where the power value changes from high to low are the maximum working voltage at the initial use and the radiation power distribution when the working voltage is gradually reduced to 60% of the maximum value. It can be seen that the radiation power distribution changes significantly with the decrease of the working voltage. When the working voltage drops to 60% of the maximum value, the overall radiation power is reduced by about half. The second curve in the figure where the power distribution value changes from high to low is the power distribution of radiant energy under the maximum working voltage after 6 months of experiment. The opening time of each working day is 3 to 5 hours, about 500 hours in 6 months, and the total radiated optical power is reduced by about 15%. It is found that the radiation power distribution change of the UV lamp's natural attenuation is very similar to the radiation power distribution change of the working voltage change during the initial use, both showing that the energy of some peaks decreases little or almost unchanged, while the energy of some peaks is regular reduce.

Most ink curing photoinitiators used in the printing industry are mainly sensitive to ultraviolet light between 300nm and 400nm. Within this band, the UV lamp radiation can reduce little or almost constant peaks only at two wavelengths of 314nm and 366nm. The energy of the 366nm peak is also reduced when the natural attenuation is about 15% and the operating voltage is reduced to 70%, and the reduction is not obvious after the operating voltage is further reduced. The energies of other peaks between 300nm and 400nm all decrease with the use of time or the decrease of working voltage.

The light transmission windows of cyan pigments commonly used in the printing industry are around 350nm-370nm, the light transmission windows of magenta pigments are around 300nm-315nm and 345nm-365nm, the light transmission windows of yellow pigments are around 305nm-315nm and 325nm-340nm, black The light transmission window of the pigment is around 315nm-325nm and 355nm-365nm, and the radiation energy in the UV light source that acts on ink curing is the radiation in these light transmission windows. Therefore, the above light transmission windows are classified into four ranges of 300nm-315nm, 315nm-325nm, 325nm-340nm and 345nm-370nm. Table 1 shows the relationship between the four wavelength ranges of concern and the light energy change between 380nm and 400nm when the radiant power of the UV light source shown in Figure 4 changes. The rate of change of radiant energy reflected by the ratio of energy is characterized.

Table 1: Variation rate of radiant energy in different bands of UV light source

If the radiant energy of each wavelength band has the same effect on ink curing, the average radiant energy change rate of the light window for curing ink of each color is shown in Table 2.

Table 2: The change rate of radiant energy in the common UV light band for curing inks of various colors

Analyzing the data in Table 2, only the rate of change of the radiant energy between 380nm and 400nm in the sixth column is smaller than the rate of change of the radiant energy provided by the UV light source for the curing of inks of various colors, and the rate of change of the radiant energy in the sixth column is less than 70%. ~5 columns of data indicate that the rate of change of radiant energy between 380nm and 400nm is equivalent to the rate of change of radiant energy provided by the UV light source to the inks of various colors for curing.

The above analysis shows that for this metal halide UV curing light source, the change rate of radiant energy between 380nm and 400nm can be used to reflect the change of radiant energy in other effective curing bands. The radiant energy between 380nm and 400nm can be extracted as detection light by adopting a band-pass filter that transmits in the 380nm～400nm band.

Another type of LED UV curing light source includes narrow-band LED lamps with center wavelengths of 365nm, 375nm, 385nm, 395nm and 405nm. Since the wavelength range of this type of light source itself is narrow, it can be used as detection light itself.

This embodiment uses an LED light source with a central wavelength of 385nm as the detection light, which on the one hand represents the visible LED curing light source, and on the other hand represents the detection light extracted by the metal halide UV curing light source.

The radiant energy spectral power distribution curve of the LED light is shown in FIG. 5 .

The following are specific implementation steps for realizing the detection of the attenuation rate of radiation energy of the light source by using the method of the present invention, including:

1. Determine the detection light

It is determined that the LED light is the detection light, and no filter is used for screening. Since the perceived wavelength range of human vision is between 380nm and 780nm, and the light energy distribution of the LED is almost cut off at 420nm, the effective wavelength range of the detected light is determined to be 380nm to 420nm.

2. Preparation of test pieces

The preparation material is selected from the film film used in the printing industry. The film is imaged with black metallic silver grains and has ideal neutral gray characteristics. Figure 6 shows the distribution curves of the spectral light transmittance after imaging with different energies of light.

It can be seen from Figure 6 that its light transmittance does not change much between 380nm and 420nm, and it can be approximated that its spectral light transmittance has nothing to do with wavelength.

The preparation process of the test piece is: arrange a series of imaging sub-areas with a size of 50mm × 50mm on a plate-making digital file with a size of 580mm × 860mm, and two adjacent areas of 25mm × 50mm in each sub-area The imaging control values of N% and (N+n)% are respectively set in , and the N value varies from 40 to 100 at intervals of n%, forming several sub-regions with different control parameters. Set n = 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 six conditions, prepare six image files, after exposure, development and fixation by the film output device, several transmission film samples are formed, and the ultraviolet-visible spectroscopic A photometer measures its spectral transmittance. This series of samples is used for experiment and testing.

3. Preparation of light reduction film

Also use film film to prepare light reduction film. Same as the method in step 2, prepare film transmission samples with consistent light transmittance in sub-areas of 50mm×50mm, and the numerical control values of each sub-area range from 40% to 100%, with an interval of 1%, a total of 51 samples. After the output, the spectral light transmittance is also measured by a UV-visible spectrophotometer, and they are sorted according to the light transmittance from large to small, and used as a light reduction film group.

4. For the LED color light with a center wavelength of 385nm, establish the law curve of just discernable difference in apparent brightness

This embodiment intends to use the binocular curve of the law of brightness difference threshold value, but it is seen that the binocular curve of the document shown in Figure 1 is not complete, and it is not clear whether there is a difference between different colors of light. Therefore, the experiment first established the binocular brightness difference threshold curve of the light source.

The method adopted is: in the darkroom environment, place the LED light source horizontally (the light source is a rod-shaped point light source with a small divergence angle), let its central light be along the horizontal direction, and its light emit at different positions in the horizontal direction, then Have different light radiation energy; measure the spectral radiation power distribution at different positions, and obtain the relationship between the spectral radiation energy and the position, so as to obtain the spectral radiation energy of any position that has not been measured; in 43 positions with different radiation energy At the position, use the prepared several test pieces to visually select the sample piece corresponding to the position where the brightness difference is just discernible. During this process, the position of the sample can be moved slightly to achieve the best judgment of the brightness difference threshold; for each position The light transmittance of the two areas is measured by the average light transmittance between 380nm and 420nm, and the transmitted light intensity of the two areas is calculated according to the two formulas (1) and (2) to obtain its Y and △Y/Y value; Y and △Y/Y values are calculated from all 43 position points, and the brightness difference threshold curve is drawn, and the results are shown in Figure 7. It is consistent with the law of the brightness difference resolution curve given in the literature in Figure 1.

5. Determine the V ₀ and V _m of the test piece

According to the requirements in step (3) of the aforementioned detection method, it is necessary to select n 1 in τ ₂ =(1+n ₁ )τ ₁ required by the test piece V ₀ and τ' ₂ =(1+n ₁ ) required by the test piece V _{m 2} ) The value of _n2 in _τ'1 .

FIG. 8 is an enlarged view of the region with a large curvature change in the curve of FIG. 7 . Determine that the two points D ₁ (0.30, 0.08) and D ₂ (0.17, 0.12) in the region with large curvature changes in the curve correspond to the initial detection of the UV light source and the corresponding n ₁ of the detection piece V ₀ after the radiation energy has decayed by 20%. and the value of n ₂ of the test piece V _m , ie n ₁ =0.08, n ₂ =0.12, it is required that τ ₂ of the test piece V ₀ =1.08τ ₁ , and τ' ₂ of the test piece V _m =1.12τ' ₁ .

After measuring the light transmittance of each control value output film film, the test pieces that meet τ ₂ =1.08τ ₁ are selected to have control values of 45% and 40.5% respectively, and the test pieces that meet τ' ₂ =1.12τ' ₁ have respectively 47.5% and 41% control values. See the data in columns 1 and 2 in Table 3 for the corresponding light transmittance.

Table 3: Characteristic parameter (m=0.8) of embodiment UV light radiation energy attenuation rate detector part

6. Determine the T ₀ and T _m of the light reduction film

According to the principle in step (4 ₎ , T needs higher light transmittance (preferably more than 0.3), is selected as the film film of control value 48% output, and light transmittance is _0.3406 ; The selection of T needs to meet formula (11 ), that is, T _m = T ₀ τ ₁ Y′/mτ’ ₁ Y=0.3406×0.3604×0.1719/(0.8×0.3467×0.3013)=0.2525, the film film output by 60% of the control value basically meets this requirement, and the measured light transmission The rate is 0.2536. This data is included in column 3 of Table 3.

7. Preparation of the detector

A cylinder with a diameter of about 40mm and a length of about 100mm was made with black cardboard. Three openings with a thickness of 1 mm were cut at the middle part of its length at intervals of about 5 mm, and the cuts accounted for about 90% of the cross-section of the cylinder. The three cutouts are respectively used for placing the detection sheet V ₀ or V _m , the light reduction film T ₀ or T _m , and the light reduction film T _i . Thereafter, a horn mouth made of the same kind of black hard cardboard is connected to one side of the cylinder. The side length of the horn mouth is about 200mm, and the outer diameter is about 150mm. During use, the eyes are observed against the outside of the bell mouth.

The purpose of using black material is to avoid the influence of internal reflected light; three cutouts are made in the middle of the straight tube to reduce the entry of external stray light; the function of the horn is to make the eyes close to the observation to avoid the influence of external light and meet the dark environment conditions.

8. Marking of initial radiant energy

In practice, for the marking of the light source when it is first used, it is necessary to follow step i) to place the detector where the light source cover is opened, or somewhere on the equipment where the UV light source light or scattered light can be seen.

In this embodiment, the optical radiation at a certain position in the radiation light field in the horizontal direction of the horizontally placed LED light source is selected to represent the detection position of the practical light source. Afterwards, place V ₀ and T ₀ selected in steps 5 and 6 in the detector made in step 7, and observe the brightness of two adjacent light fields in V ₀ at the selected position, and they are clearly distinguishable at this time. According to the method of step i), the label of this energy needs to add a light reduction film T _i in the optical path where V ₀ and T ₀ overlap, and at this time, the brightness difference between the two adjacent light fields in V ₀ should be just enough distinguish. After trials one by one, the light-reducing film with a control value of 66% output was selected to meet the requirements, and its light transmittance T _i test was 0.2151 (listed in the fourth column in Table 1).

9. Marking of radiation energy after attenuation

According to the method of step ii), replace the V ₀ and T ₀ in the detector with V _m , T _m , but keep the light reduction film T _i unchanged, and move the observation position to reduce the radiation energy to the initial radiation in step 8 80% of the position (determined by the relationship between the position and the radiant energy established in step 4), at this time, the brightness difference between two adjacent light fields in V _m needs to be just distinguishable. Experimental results show that T _i selected in step 8 can meet this requirement.

In addition, the dimming film T _i used in steps 8 and 9 should be combined with V ₀ and T ₀ to reach the brightness value of 0.30 corresponding to point D ₁ determined by formula (9), while it needs to be combined with V _m and T _m Reach the brightness value 0.17 corresponding to the D ₂ point determined by the formula (10). After calculation, the two luminance values are 0.3013 and 0.1719 (listed in column 5 in Table 3) respectively, reaching the design goal.

The above process shows that based on the luminance difference threshold curve, by designing reasonable characterization points D ₁ and D ₂ , and further determining the detection slices V ₀ and V _m and the dimming slices T ₀ and T _m , the light source radiation can be In the detection of the energy attenuation rate, an appropriate light-reducing film T _i is selected to jointly characterize the attenuation rate of the radiant energy of the light source.

In practice, there is a problem of how much light transmittance difference between adjacent light-reducing film series T _i is appropriate. If the difference is too small, the application effect will not reflect the difference; if the difference is too large, it may be difficult to find the exact state where the brightness difference is just discernible. will make it difficult to judge. In this embodiment, it is found that the difference in light transmittance of adjacent light-reducing sheets is about 0.007 when the light-reducing sheets are produced at intervals of 1% of the control value. When applied, there is not only a difference that is easy to judge visually, but also can reflect the The brightness difference threshold under different radiant energies is the appropriate light transmittance difference of the light reduction film group.

In practice, there is also the problem of individual differences among observers. Different personnel have different choices of T _i corresponding to when the luminance difference is just discernible. In our experiments, we found that this difference almost only occurs on the adjacent light reduction film, that is, most people choose T _i , and some people choose T _i-1 or T _i+1 . As illustrated by the situation in the embodiment, if T _i-1 (65% control value) is selected instead of T _i (66% control value), the light transmittances are 0.2208 and 0.2151 respectively. The latter corresponds to the correct m=0.8, while the former corresponds to the effect of m=0.771. That is to say, T _i-1 should objectively correspond to the attenuation of radiant energy to 77.1% of the initial value, but it is mistakenly regarded as the case of m=0.8 which meets the design. This is the error that may occur in practical applications, and it also shows that the detection method of this embodiment has an accuracy of about ±3%.

It can be seen from the above embodiments that the present invention uses the law of brightness difference resolution of human vision, rationally designs the light transmittance characteristics of the two light fields of the light-transmitting material, and combines applications with different light transmittance transmission sheets to convert the light source radiation energy The rate of change of is reflected in the way that the brightness difference between the two light fields is just discernible. This method provides a new method for detecting the energy decay rate of UV curing light source in printing production.

Those of ordinary skill in the art should understand that: the above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention etc., should be included within the protection scope of the present invention.

Claims (10)

1. a kind of detection method of UV curing light sources emittance attenuation rate, comprises the following steps：

(1) determine that in UV curing light sources spectral radiant energy to be detected solidification wave band radiation energy attenuation degree can have been represented Wave band is used as detection light；

(2) detection lug V is prepared by middle grey light transmissive material₀And V_m, detection lug includes two adjacent and different areas of light transmittance Domain；V₀The light transmittance in two regions is respectively τ₁And τ₂, and τ₂=(1+n₁)τ₁；V_mThe light transmittance in two regions is respectively τ '₁With τ'₂, and τ '₂=(1+n₂)τ'₁；n₁、n₂Respectively detection lug V₀、V_mTwo regions light source visual brightness just it is distinguishable it is poor with it is bright Ratios delta Y/Y, the Δ Y '/Y ' of degree, and n₂>n₁, Y and Y ' are respectively n₁、n₂It is worth corresponding brightness；

(3) light damping plate group, including the light damping plate that multiple light transmittances are gradually changed, the shape of light damping plate are prepared by middle grey light transmissive material Shape and area are identical with detection lug；

(4) two light damping plate T are prepared₀And T_m, light transmittance T_mWith T₀Meet：Wherein m represents radiation of light source energy Amount decays to the multiple of initial value；

(5) light source screening part, detection lug and light damping plate are overlaped, are placed in a tubular device, composition can vision Observe the detector of light transmission state；

(6) when UV light sources use initial, detection lug V is used in detector₀With light damping plate T₀, against the observation of UV light sources, addition is closed Suitable light damping plate T_i, make in detector observe two parts light field luminance difference it is just distinguishable；

(7) UV light sources were used after a period of time, and detection lug V is used in detector_mWith light damping plate T_m, light damping plate T_iIt is constant, away from UV The same position of light source, against the observation of UV light sources, whether two parts light field observed in detector reaches that luminance difference just may be used Whether the attenuation rate for distinguishing to determine radiation of light source energy reaches m times of design.

2. the detection method of UV curing light sources emittance attenuation rate according to claim 1, it is characterised in that：Described Detection light is the wave band that representative plays solidification wave band radiation energy attenuation degree, can be obtained by using bandpass filter.

3. the detection method of UV curing light sources emittance attenuation rate according to claim 2, it is characterised in that：In printing In industry, for metal halogen UV curing light sources, detection light is used as using 380nm~400nm wave band；Solidify light for LED UV Source, detection light is used as using the wave-length coverage of light source in itself.

4. the detection method of UV curing light sources emittance attenuation rate according to claim 2, it is characterised in that：The band Pass filter, detection lug are identical with the shapes and sizes of light damping plate.

5. the detection method of UV curing light sources emittance attenuation rate according to claim 4, it is characterised in that：Described Bandpass filter, detection lug and light damping plate are shaped as square or circular, and the length of side or diameter are between 40mm~50mm.

6. the detection method of UV curing light sources emittance attenuation rate according to claim 1, it is characterised in that：n₁And n₂ The just distinguishable poor and brightness ratio Δ Y/Y of light source visual brightness is chosen for brightness Y change curves middle part, the very fast model of Curvature varying Interior Δ Y/Y values are enclosed, and have n₂>n₁。

7. the detection method of UV curing light sources emittance attenuation rate according to claim 1, it is characterised in that：Described In light damping plate group, the transmissivity difference between adjacent light damping plate is 0.007, and light transmittance is 0.4, minimum 0.05 to the maximum.

8. the detection method of UV curing light sources emittance attenuation rate according to claim 1, it is characterised in that：UV light sources After a period of time, if the luminance difference vision for two parts light field observed in detector is distinguishable, show light source spoke The attenuation rate for penetrating energy not yet reaches design load m；And if two parts light field shows radiation of light source energy without luminance difference Attenuation rate met or exceeded m.

9. the detection method of UV curing light sources emittance attenuation rate according to claim 8, it is characterised in that：If by examining The luminance difference vision for surveying two parts light field observed in device is distinguishable, then changes light damping plate T_i, it is smaller from light transmittance successively Light damping plate；When just feeling the luminance difference of two parts light field, corresponding light damping plate T_i+nWith T_iIt is separated by more remote, then shows The attenuation rate of radiation of light source energy is more less than design load m.

10. the detection method of UV curing light sources emittance attenuation rate according to claim 8, it is characterised in that：If by Two parts light field observed in detector without luminance difference, then changes the bigger light damping plate of light transmittance successively；When just When feeling the luminance difference of two parts light field, corresponding light damping plate T_i-nWith T_iIt is separated by more remote, then shows the attenuation rate of energy of light source More it is more than design load m.