Film thickness estimation device and film forming device

Abstract

To provide a technique for determining the thickness of a film.SOLUTION: A film thickness estimation device is used for a film molding apparatus. The film molding apparatus 10 includes a first measuring instrument 50 that measures a frost line position of a film 12 conveyed from a die 14 in a flow direction. The film thickness estimation device includes a film thickness estimation part that estimates the thickness of the film 12 on the basis of the frost line position measured by the first measuring instrument 50.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a film thickness estimation device and a film forming device. [Background technology]

[0002] Patent Document 1 discloses a film forming device that forms a film. This film forming device adjusts the die lip width, the cooling device air speed, air temperature, etc. to keep the film thickness within a target range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-163768 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to keep the film thickness within a target range, it is important to grasp the film thickness. As described in Patent Document 1, the film thickness is usually grasped by sequentially measuring the film thickness using a measuring instrument while changing the measurement position in the transverse direction of the film. The inventors of the present application have discovered a new idea for grasping the film thickness using a different method.

[0005] One of the objects of the present disclosure is to provide a technique for determining the film thickness. [Means for solving the problem]

[0006] One aspect of the present disclosure is a film thickness estimation device used in a film forming apparatus, comprising: a first measuring instrument that measures the frost line position of a film fed in a flow direction from a die; and a film thickness estimation unit that estimates the film thickness of the film based on the frost line position measured by the first measuring instrument. [Effects of the Invention]

[0007] According to the present disclosure, the film thickness can be determined. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a configuration diagram schematically illustrating a film forming apparatus according to an embodiment. [Figure 2] 2 is a block diagram showing the functions of the film forming apparatus according to the embodiment; FIG. [Figure 3] FIG. 10 is an explanatory diagram of film thickness measurement points on a film. [Figure 4] FIG. 10 is an explanatory diagram relating to film thickness measurement points on a film and predicted positions of frost lines. [Figure 5] FIG. 10 is an explanatory diagram regarding a relationship estimation process. [Figure 6] FIG. 10 is an explanatory diagram relating to the location on the film through which the frost line passes and the arrival time. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes the embodiments. Identical components are designated by the same reference numerals, and redundant explanations will be omitted. In each drawing, components are omitted, enlarged, or reduced as appropriate for the sake of convenience. The drawings should be viewed in accordance with the orientation of the reference numerals.

[0010] Referring to FIG. 1, the film forming apparatus 10 of this embodiment is an inflation molding apparatus. The film forming apparatus 10 includes a die 14 that forms a resin film 12 by forcing molten resin extruded from an extruder (not shown) through a die lip 28, and a winder 16 that winds up the film 12 at the most downstream side of the flow path of the film 12. The film forming apparatus 10 also includes a take-up machine 20 that takes up the film 12 discharged from the die 14 using a pair of pinch rolls 18 while folding it flat, and a pair of stabilizers 22 that guide the film 12 as it is taken up by the take-up machine 20. The film forming apparatus 10 also includes a cooling device 24 that cools the film 12 and a control device 26 that controls the various components of the film forming apparatus 10. The control device 26 also functions as a film thickness estimation device 48 that estimates the film thickness distribution of the film 12.

[0011] The die 14 of this embodiment is a round die used in the inflation method, and ejects molten resin from a ring-shaped die lip 28. This die 14 ejects air from air ejection holes 30 onto the inside of the film 12, thereby forming an inflated tubular film 12 (also called a bubble).

[0012] The die 14 is capable of adjusting the lip width (spacing) of the die lip 28 at multiple circumferential positions. It can also be said that the die 14 is capable of adjusting the lip width distribution of the die lip 28 in the circumferential direction. To achieve this, the die 14 may have a deformable flexible portion as part of the die lip 28, and the lip width at multiple circumferential positions may be adjusted by deforming the flexible portion using a drive source. This drive source may be a linear actuator, a heat bolt, or the like.

[0013] The die 14 can adjust the circumferential thickness distribution of the film 12 by adjusting the lip width distribution of the die lip 28 in the circumferential direction. For example, by narrowing the lip width at a certain circumferential position, the thickness of the film 12 emerging from that position can be locally thinned. Conversely, by widening the lip width at a certain circumferential position, the thickness of the film 12 emerging from that position can be locally thickened. In this way, the die 14 constitutes a thickness adjustment section 32 that can adjust the circumferential thickness distribution of the film 12.

[0014] Please refer to Figures 1 and 2. Each block shown in Figure 2 can be realized in terms of hardware by electronic components, circuits, mechanical devices, etc., including a computer's CPU (Central Processing Unit), and in terms of software by a computer program, etc. Here, functional blocks realized by the cooperation of these components are depicted. Those skilled in the art will understand that these functional blocks can be realized in various ways by combining hardware and software.

[0015] The control device 26 includes a communication unit 56 that executes communication processing with other components of the film forming apparatus 10 (e.g., the die 14 and the cooling device 24) in accordance with a predetermined communication protocol, an input unit 58 that accepts user input operations, and a display unit 60 that displays various information. The control device 26 also includes a data processing unit 62 that executes data processing using data acquired from the other components of the film forming apparatus 10 and the input unit 58, and a memory unit 64 that stores data used by the data processing unit 62. The data processing unit 62 includes an operation control unit 70 that controls the operation of the die 14, the cooling device 24, etc., a film thickness estimation unit 72 that estimates the film thickness distribution of the film 12, and a relationship estimation unit 74 that estimates correlation information indicating the correlation between the frost line position and the film thickness. The film thickness estimation unit 72 and the relationship estimation unit 74 will be described in detail below.

[0016] The operation control unit 70 controls the operation of the film thickness adjustment unit 32 based on the film thickness distribution estimated by the film thickness estimation unit 72. The operation control unit 70 controls the operation of the film thickness adjustment unit 32 by transmitting a control command for operating an operation variable that can be adjusted by the film thickness adjustment unit 32. The operation variable here refers to the lip width in the case of the die 14, and the air volume and air temperature in the case of the cooling device 24 described below. The film thickness adjustment unit 32 adjusts the film thickness by adjusting the operation variable (here, the lip width) in accordance with the control command transmitted from the operation control unit 70.

[0017] The operation control unit 70 controls the film thickness adjustment unit 32 so that the film thickness distribution estimated by the film thickness estimating unit 72 falls within a predetermined target range. For example, consider a case where the film thickness at a specific circumferential position on the film 12 exceeds the target range (i.e., is excessively thick). In this case, the operation control unit 70 sends a control command to the die 14 to reduce the lip width at the circumferential position of the die lip 28 corresponding to the specific circumferential position on the film 12, thereby keeping the film thickness at the specific circumferential position within the target range. Consider a case where the film thickness at a specific circumferential position on the film 12 falls below the target range (i.e., is excessively thin). In this case, the operation control unit 70 sends a control command to the die 14 to increase the lip width at the circumferential position of the die lip 28 corresponding to the specific circumferential position on the film 12, thereby keeping the film thickness at the specific circumferential position within the target range. In other words, the operation control unit 70 performs feedback control to control the film thickness adjustment unit 32 so that the film thickness distribution estimated by the film thickness estimating unit 72 falls within the target range.

[0018] Here, a frost line FL occurs during the molding process of the film 12. The frost line FL generally refers to the boundary between the molten portion 12a and the solidified portion 12b of the film 12, which occurs when the molten portion 12a of the film 12 solidifies during the cooling process. In this specification, the frost line FL refers to this commonly known boundary between the molten portion 12a and the solidified portion 12b of the film 12, but is not limited to this. The position of this frost line FL in the flow direction Da is referred to as the frost line position. Here, the flow direction Da refers to the direction in which the entire film advances when molding the film 12 using the film molding apparatus 10 (the so-called machine direction). When using the inflation method, the frost line position can be determined, for example, as the height from the top surface of the die 14 to the frost line FL in the film flow direction Da.

[0019] There is a correlation between the position of the frost line and the film thickness of the film 12. This correlation indicates that the higher the frost line position, the thicker the film thickness, and the lower the frost line position, the thinner the film thickness (see also Figure 5 described below). In other words, this correlation indicates that the farther the frost line position is from the die 14, the thicker the film thickness is, and the closer the frost line position is to the die 14, the thinner the film thickness is. This is because, under constant cooling conditions, the thicker the film, the longer it takes to solidify, and therefore the farther the solidification position of the film 12 is from the die 14, and therefore the farther (higher) the frost line position is from the die 14. This correlation varies depending on the material of the film 12, the blow ratio, and molding conditions such as temperature and air pressure in the environment in which the film molding apparatus 10 is used.

[0020] One feature of the film thickness estimation device 48 of this embodiment is that it estimates the correlation between frost line position and film thickness by measuring the frost line position and film thickness. As a result, by determining the frost line position, it is possible to determine the film thickness of the film 12 according to this correlation. Another feature of the film thickness estimation device 48 of this embodiment is that it estimates the film thickness distribution using the correlation between frost line position and film thickness and the measured values ​​of the frost line position distribution. It can also be said that the film thickness estimation device 48 is characterized by estimating the film thickness using this correlation and the measured values ​​of the frost line position. Details of this will be explained below.

[0021] The film forming apparatus 10 is equipped with a first measuring device 50 that measures the frost line position distribution of the film 12 fed in the flow direction Da from the die 14. The frost line position distribution refers to the distribution of frost line positions in the circumferential direction of the film 12.

[0022] The first measuring instrument 50 includes at least one camera 52 that captures images of the film 12 and a measurement processor 54 that processes the images output by the camera 52 to measure the frost line position distribution. The camera 52 may be, for example, a visible light camera, a thermal camera, or the like. The measurement processor 54 processes the images output by the camera 52 to measure the frost line positions at multiple circumferential positions, and uses the results as the measurement results of the frost line position distribution. The method for measuring the frost line positions using image processing is not particularly limited, and various methods, including well-known methods, may be used. For example, the measurement processor 54 may measure the frost line positions using three-dimensional image processing, two-dimensional image processing, or the like, using images output by multiple cameras 52. Alternatively, a mirror may be placed within the field of view of the camera 52, and the frost line positions may be measured using image processing that uses the image output by a single camera 52 and the image inside the mirror in that image as a pseudo image. Image processing using such images makes it easy to simultaneously measure the frost line positions at multiple circumferential positions, i.e., the frost line position distribution.

[0023] The first measuring instrument 50 simultaneously measures the frost line position distribution in a predetermined measurement range in the circumferential direction for each first measurement cycle. This measurement range is, for example, the entire circumferential range of the film 12. The first measuring instrument 50 sequentially transmits the measurement results of the frost line position distribution to the control device 26.

[0024] The storage unit 64 includes a correlation storage unit 66 that stores correlation information indicating the correlation between the frost line position and the film thickness. The correlation information is, for example, a relational expression, a table, or the like that uses the frost line position as an input and the film thickness as an output.

[0025] The data processing unit 62 includes a film thickness estimation unit 72 that estimates the film thickness distribution in the circumferential direction of the film 12 based on the frost line position distribution measured by the first measuring instrument 50. This process of estimating the film thickness distribution is called a film thickness estimation process. The film thickness estimation unit 72 performs a film thickness estimation process based on the frost line position distribution and correlation information stored in the correlation storage unit 66. In this film thickness estimation process, a measurement value of the frost line position measured at a certain circumferential position is input into a relational expression or the like serving as correlation information, and a film thickness calculation process is performed to calculate the film thickness at that circumferential position. In this film thickness estimation process, a film thickness calculation process is performed for each measurement value of the frost line position at multiple circumferential positions measured simultaneously by the first measuring instrument 50, thereby calculating the film thickness distribution, which is the film thickness at each circumferential position, and this is used as the estimation result.

[0026] The above-described film thickness estimation process may be performed periodically during the formation of the film 12 by the film forming apparatus 10, or may be performed when a predetermined execution condition is satisfied. The execution condition here may be, for example, that a predetermined command is input via the input unit 58.

[0027] The effects of the above-described film thickness estimation device 48 will now be described.

[0028] The film thickness estimation device 48 includes a film thickness estimation unit 72 that estimates the film thickness based on the frost line position measured by the first measuring instrument 50. Therefore, the film thickness of the film 12 can be determined using the film thickness estimation result by the film thickness estimation unit 72.

[0029] Fluctuations in the thickness of the film 12 occur mainly in the melted portion 12a of the film 12, which is located upstream of the frost line FL of the film 12. The frost line FL is located closer to the location of the thickness fluctuations in the film 12 than the measurement position of the thickness by the second measuring instrument 80, which will be described later. By estimating the thickness based on the frost line position identified using such a frost line FL, it is possible to identify thickness fluctuations in the film 12 earlier than when using the thickness measurement value by the second measuring instrument 80, which will be described later.

[0030] If the thickness of the film 12 is measured successively while changing the measurement position, as with the second measuring instrument 80 described below, the cycle for repeatedly determining the thickness distribution becomes long. Therefore, if the thickness fluctuates between measurements of the thickness at a certain circumferential position and the next measurement, a reflection delay occurs, meaning that it takes a while for the fluctuation to be reflected in the measurement value.

[0031] In this regard, according to the present embodiment, the film thickness distribution is determined by the film thickness estimation unit 72 using the frost line position distribution of the film 12 measured simultaneously by the first measuring instrument 50. Therefore, compared to sequentially measuring the film thickness of the film 12 while changing the measurement position, the cycle for repeatedly determining the film thickness distribution can be shortened. Therefore, when the film thickness fluctuates after the film thickness at a certain circumferential position is estimated, the delay until the influence of the fluctuation is reflected in the estimated value can be suppressed. Consequently, the decrease in the accuracy of determining the film thickness due to the delay in reflection can be suppressed.

[0032] The operation control unit 70 controls the film thickness adjustment unit 32 so that the highly accurate estimated film thickness distribution, which suppresses the influence of such a delay in reflection, falls within the target range. Therefore, the actual film thickness distribution of the film 12 can be accurately adjusted by controlling the film thickness adjustment unit 32.

[0033] The film thickness estimation unit 72 estimates the film thickness of the film 12 based on the correlation information stored in the memory unit 64 and the frost line position measured by the first measuring instrument 50. Therefore, by storing the correlation information in the memory unit 64 in advance, the film thickness can be easily estimated from the frost line position.

[0034] According to this embodiment, the frost line position distribution is simultaneously measured by image processing using images taken by the first measuring instrument 50, and the film thickness distribution is estimated based on the frost line position distribution. Therefore, the film thickness distribution can be determined earlier than when the film thickness distribution is determined by sequentially measuring the film thickness of the film 12, as with the second measuring instrument 80 described below.

[0035] Next, we will explain other features of the film thickness estimation device 48. Here, we will explain the features for estimating correlation information used in the film thickness estimation process.

[0036] Please refer to Figures 1 and 3. Figure 3 is a schematic diagram of a portion of the film 12 developed on a plane. The film forming apparatus 10 is equipped with a second measuring device 80 that sequentially measures the film thickness of the film 12 while changing the measurement position Pa in the circumferential direction of the film 12. The second measuring device 80 may be, for example, a capacitance-type film thickness meter. In this embodiment, the second measuring device 80 sequentially measures the film thickness of the film 12 while moving around the film 12. Here, the "measurement position Pa" refers to the position on the film 12 where the film thickness is to be measured by the second measuring device 80. Here, the trajectory Pb of the measurement position Pa of the second measuring device 80 is also shown. Also shown here is a state in which one film thickness measurement point Pc on the film 12 and the measurement position Pa are in the same position. Here, the "film thickness measurement point Pc" refers to the position on the film 12 where the film thickness is measured by the second measuring device 80.

[0037] The second measuring instrument 80 moves the measurement position Pa on the film 12 in the traveling direction Db as the film 12 moves in the flow direction Da. As a result, the film thickness measurement point Pc on the film 12 in this embodiment moves in a spiral shape moving in the traveling direction Db toward the upstream side of the flow path of the film 12. The second measuring instrument 80 sequentially measures the film thickness of the film 12, thereby measuring the film thickness distribution in the measurement range every second measurement period (e.g., 2 minutes) that is longer than the first measurement period. The second measuring instrument 80 sequentially transmits the measurement results to the control device 26.

[0038] The relationship estimation unit 74 (see FIG. 2) described above estimates correlation information indicating the correlation between the frost line position and the film thickness based on the frost line position measured by the first measuring instrument 50 and the film thickness measured by the second measuring instrument 80. The process of estimating this correlation information is called a relationship estimation process. The relationship estimation process will be described in detail below.

[0039] See Fig. 4. The relationship estimation unit 74 performs a correspondence process to associate the film thickness measurement value obtained by the second measuring instrument 80 with the measurement value of the frost line position obtained by the first measuring instrument 50. In this correspondence process, the measurement value of the frost line position to be associated with a certain film thickness measurement value is called a target measurement value. In this embodiment, a measurement value that satisfies the following two conditions is used as the target measurement value of the frost line position.

[0040] The first condition is that the frost line position measurement value is obtained at the same circumferential position as the film thickness measurement value. Here, "same" includes not only completely identical but also nearly identical. The second condition is that the film thickness measurement value is obtained when the film thickness measurement point Pc, where the film thickness measurement value is obtained, passes through the predicted position Pd of the frost line FL. As the frost line position measurement value serving as an index of the film thickness at the film thickness measurement point Pc, the frost line position measurement value measured when the film thickness measurement point Pc passes through the predicted position Pd of the frost line FL is associated with the film thickness measurement value at that film thickness measurement point Pc. The predicted position Pd of the frost line FL refers to the position where the frost line FL is predicted to exist. Assume a passing time s0 at which the film thickness measurement point Pc, whose film thickness is measured at position Pe by the second measuring instrument 80 at measurement time s1, passes through the predicted position Pd of the frost line FL. In this case, the second condition can also be said to be that the frost line position measurement value is obtained at a time immediately prior to the passing time s0. The relationship estimation unit 74 identifies the target measurement value of the frost line position to be associated with the film thickness measurement value so as to satisfy the second condition, in the following manner.

[0041] First, the relationship estimation unit 74 calculates the length ΔL from the measurement position Pa of the second measuring instrument 80 to the predicted position Pd of the frost line FL. The relationship estimation unit 74 calculates this length ΔL based on the length L1 in the flow direction Da from the die 14 to the measurement position Pa of the second measuring instrument 80 and the length L0 in the flow direction Da from the die 14 to the predicted position Pd of the frost line FL. The length ΔL can be calculated, for example, by subtracting the length L0 from the length L1. For example, a value stored in advance in the memory unit 64 is used as the length L1. For example, the length L0 is the measurement value of the frost line position measured by the first measuring instrument 50 at the same circumferential position as the film thickness measurement point Pc at the measurement time s1 when the film thickness at the film thickness measurement point Pc is measured. Alternatively, a fixed value stored in advance in the memory unit 64 may be used as the length L0.

[0042] Next, based on the calculated length ΔL and the winding speed v of the film 12, the relationship estimation unit 74 calculates the required time Δs required for the film thickness measurement point Pc on the film 12 to pass the aforementioned length ΔL. The winding speed v [m / sec] here refers to the speed at which the film 12 is wound by the winder 16. The film 12 flows at a substantially constant winding speed v [m / sec] between the frost line FL and the measurement position Pa measured by the second measuring instrument 80. Therefore, the required time Δs can be calculated, for example, by dividing the length ΔL by the winding speed v. For example, a set value stored in the memory unit 64 is used as the winding speed v.

[0043] Next, the relationship estimation unit 74 calculates the passage time s0 when the film thickness measurement point Pc passes through the predicted position Pd of the frost line FL, based on the measurement time s1 when the film thickness at the film thickness measurement point Pc is measured by the second measuring instrument 80 and the calculated required time Δs. The relationship estimation unit 74 calculates the passage time s0 as, for example, the time that is earlier than the measurement time s1 by the required time Δs.

[0044] Next, the relationship estimation unit 74 identifies a target measurement value to be associated with the film thickness measurement value based on the measurement value of the frost line position measured by the first measuring instrument 50 immediately before the calculated passage time s0. In this case, the relationship estimation unit 74 may, for example, identify the measurement value of the frost line position measured by the first measuring instrument 50 immediately before the passage time s0 as the target measurement value. Alternatively, to reduce the influence of errors, the relationship estimation unit 74 may identify a representative value (e.g., an average value) calculated from multiple measurement values ​​measured within a predetermined time span including the passage time s0 as the target measurement value. This time span is set, for example, to a time span shorter than the second measurement period. As described above, the target measurement value is identified as a measurement value measured at the same circumferential position as the film thickness measurement value.

[0045] Thereafter, the relationship estimation unit 74 performs a correlation process to correlate the film thickness measurement value measured by the second measuring device 80 at the film thickness measurement point Pc on the film 12 with the target measurement value at the identified frost line position.

[0046] See Figure 5. By performing the above-mentioned association process, the relationship estimation unit 74 acquires a set of measurement values, each pairing a film thickness measurement value and a frost line position measurement value that are associated with each other. Figure 5 shows a graph in which the acquired set of measurement values ​​is plotted, with the film thickness on the X axis and the frost line position on the Y axis. Here, the average value and standard deviation σ are calculated from multiple measurement values ​​measured within a time span that includes the passage time s0, and the average value is plotted, with the range of the average value ± the standard deviation σ indicated by error bars.

[0047] The relationship estimation unit 74 acquires multiple sets of measurement values ​​by repeatedly performing the above-described association process. To achieve this, the above-described association process may be performed for each of the film thickness measurement values ​​at multiple circumferential positions measured sequentially by the second measuring instrument 80. Alternatively, the above-described association process may be performed for each of the film thickness measurement values ​​at the same circumferential position measured by the second measuring instrument 80 at each second measurement cycle.

[0048] The relationship estimation unit 74 uses multiple sets of measurement values ​​to calculate an approximation equation as a relational expression showing the correlation between the frost line position and the film thickness, and uses this as the estimated result of the correlation. Here, an approximation line 82 obtained using a linear approximation equation is shown as this approximation equation. Specific examples of this approximation equation are not particularly limited, and various approximation equations, such as a polynomial curve approximation equation, may be used. Alternatively, multiple sets of measurement values ​​may be used to generate a table, such as a look-up table, showing the correlation between the frost line position and the film thickness, and this may be used as the estimated result of the correlation. The relationship estimation unit 74 stores the estimated correlation information in the correlation storage unit 66.

[0049] The relationship estimation process may be executed when a predetermined execution condition is met, such as when the film forming apparatus 10 starts forming the film 12 for the first time. Alternatively, the process may be executed when an update condition, which will be described later, is met.

[0050] As described above, the film thickness estimation device 48 of this embodiment includes a relationship estimation unit 74 that estimates correlation information based on the frost line position measured by the first measuring instrument 50 and the film thickness measured by the second measuring instrument 80. Therefore, even if correlation information showing the correlation between the frost line position and the film thickness is not stored in advance, the correlation information can be estimated using the measurement results of the first measuring instrument 50 and the second measuring instrument 80.

[0051] When a predetermined update condition is satisfied, the relationship estimation unit 74 may update the correlation information stored in the storage unit 64 with newly estimated correlation information by performing the above-described relationship estimation process. By updating the correlation information when the update condition is satisfied, it becomes possible to estimate the film thickness distribution using correlation information that reflects the latest molding conditions.

[0052] The update conditions here may be, for example, (1) that the molding conditions have been changed, (2) that a predetermined time interval has elapsed since the previous relationship estimation process was performed during the molding of the film 12, or (3) that a command for updating has been input to the input unit 58.

[0053] Alternatively, during the formation of the film 12, it may be determined whether or not the estimated film thickness value estimated by the film thickness estimating unit 72 is reliable according to a predetermined determination condition, and the update condition may be determined by determining that the estimated film thickness value is unreliable. To achieve this, for example, a coefficient of determination (R 2 ) may be calculated. In this case, a judgment condition may be that the calculated coefficient of determination is lower than a predetermined reference value, and if the judgment condition is met, it may be judged that the estimated film thickness value is unreliable. In this case, a film thickness value set may be used, which is a combination of a film thickness estimated value calculated from a measurement value of the frost line position measured when the film thickness measurement point Pc passes through the predicted position Pd of the frost line FL, and a film thickness measurement value measured at the film thickness measurement point Pc.

[0054] Although the example in which the film thickness adjusting unit 32 is the die 14 has been described so far, the specific example is not particularly limited. The film thickness adjusting unit 32 may be the cooling device 24 described next. Alternatively, the cooling device 24 and the die 14 may be used as separate film thickness adjusting units 32.

[0055] Referring to FIG. 1 , the cooling device 24 includes an air ring 154 that blows cooling air, sent from a blower (not shown) through an air passage 150, toward the film 12 from a ring-shaped outlet 152. The cooling device 24 also includes multiple valve devices 156 and multiple heaters 158 disposed within the air passage 150. The multiple valve devices 156 are arranged circumferentially to divide the air passage 150 of the air ring 154 into an upstream air passage 150a and a downstream air passage 150b. The valve devices 156 can direct air from the upstream air passage 150a to the downstream air passage 150b via locations whose opening degrees can be adjusted. By adjusting the opening degree of the valve devices 156, the volume of cooling air supplied to the outlet 152 via the valve devices 156 can be adjusted. By adjusting the opening degree of each of the multiple valve devices 156, the circumferential flow distribution of the cooling air can be adjusted.

[0056] The multiple heaters 158 are, for example, heating rods, and are arranged in the circumferential direction within the ventilation path 150. The heaters 158 are capable of heating the air flowing within the ventilation path 150. By adjusting the heating temperature of the heaters 158, it is possible to adjust the temperature of the cooling air that passes around the heaters 158 and is supplied to the air outlet 152. By adjusting the heating temperature of each of the multiple heaters 158, it is possible to adjust the air temperature distribution of the cooling air in the circumferential direction.

[0057] By adjusting at least one of the volume distribution and temperature distribution of the cooling air from the cooling device 24, it is possible to adjust the film thickness distribution in the circumferential direction of the film 12. The molten portion 12a of the film 12 is pulled downstream as it progresses in the flow direction, gradually thinning. Therefore, the molten portion 12a of the film 12 solidifies faster as the cooling rate of the film 12 increases, resulting in a thicker film thickness. The molten portion 12a solidifies slower as the cooling rate of the film 12 decreases, resulting in a thinner film thickness. For example, by increasing the volume of the cooling air at a certain circumferential position, the cooling rate of the film 12 exposed to the cooling air can be locally increased, thereby locally thickening the film 12. The same applies when the temperature of the cooling air at a certain circumferential position (when the heating temperature of the heater 158 is brought closer to zero) is reduced. On the other hand, by decreasing the volume of the cooling air at a certain circumferential position, the cooling rate of the film 12 exposed to the cooling air can be locally slowed, thereby locally thinning the film 12. The same applies when the temperature of the cooling air at a certain circumferential position is increased (when the heating temperature of the heater 158 is increased).

[0058] Next, variations of the components described above will be described.

[0059] The film forming apparatus 10 does not have to include the second measuring device 80. The film thickness estimation device 48 does not have to include the input unit 58, the display unit 60, the operation control unit 70, the relationship estimation unit 74, etc. The film thickness estimation device 48 may include at least one of the first measuring device 50 and the second measuring device 80.

[0060] The first measuring instrument 50 may measure the frost line position or the circumferential distribution of frost line positions on the film 12, and specific examples are not limited to those described in the embodiment. As an example, the first measuring instrument 50 may measure the frost line position using ink applied to the molten portion 12a of the film 12. When ink is applied to the molten portion 12a of the film 12, there is a correlation between the length of the ink in the flow direction Da observed downstream of the frost line FL and the frost line position. This correlation indicates that the longer the ink length, the lower the frost line position, and the shorter the ink length, the higher the frost line position. Therefore, a relational expression, table, or the like showing this correlation may be stored, and the frost line position may be determined by inputting the length of the ink applied to the film 12 into the relational expression, or the like. In this case, the ink length may be determined by image processing using an image captured by the camera 52. The length of the ink in the flow direction may be determined by the length of the ink extending linearly in the flow direction itself, or by the spacing between multiple ink dots.

[0061] The specific method for film thickness estimation unit 72 is not limited to that described in the embodiment, as long as it can estimate the film thickness of film 12 based on the frost line positions measured by first measuring instrument 50. It can also be said that the method for estimating the film thickness distribution of film 12 by film thickness estimation unit 72 based on the measurement values ​​of the frost line position distribution is not particularly limited.

[0062] The relationship estimation unit 74 does not need to update the correlation information stored in the correlation storage unit 66. In this case, a plurality of pieces of correlation information corresponding to a plurality of molding conditions may be stored in advance in the correlation storage unit 66. In this case, when performing the film thickness estimation process, the film thickness estimation unit 72 may select the correlation information corresponding to the actual molding conditions from the plurality of pieces of correlation information.

[0063] In the correlation process by the relationship estimation unit 74, specific examples of the target measurement value at the frost line position to be correlated with the film thickness measurement value are not limited to those described in the embodiment. For example, when a film thickness measurement value is measured at measurement time s1, a representative value (e.g., average value) of multiple measurement values ​​at the frost line position measured within a predetermined time span including the measurement time s1 may be used as the target measurement value. In this case, the representative value (here, average value) of the frost line position as the target measurement value may be correlated with the film thickness measurement value measured at the measurement time s1. Alternatively, film thickness measurement values ​​may be measured multiple times at the same film thickness measurement point Pc, and the representative value (here, average value) of the multiple measurement values ​​at the frost line position measured at each film thickness measurement value measurement time may be used as the target measurement value. In this case, the representative value (here, average value) of the frost line position as the target measurement value may be correlated with the representative value (e.g., average value) of the film thickness measurement values ​​measured multiple times. In either case, in the correlation process by the relationship estimation unit 74, as explained in the first condition above, the measurement value of the frost line position measured at the same circumferential position as the film thickness measurement value is used.

[0064] Alternatively, the target measurement value of the frost line position to be associated with the film thickness measurement value may be specified as follows.

[0065] Referring to Figure 6, when the frost line position is measured at a certain measurement time s1, the portion of the film 12 that passes through the frost line FL at the circumferential position where the frost line position is measured is referred to as the frost line passing portion Pf. Assume that there is an arrival time s2 at which this frost line passing portion Pf reaches the flow direction position Pg that is the same as the measurement position of the second measuring instrument 80. Below, a method will be described for identifying the target measurement value of the frost line position that should be associated with the film thickness measurement value, based on the arrival time s2 of the frost line passing portion Pf of the film 12 at the position Pg and the measurement time s3 of the film thickness measurement value by the second measuring instrument 80.

[0066] First, when the relationship estimation unit 74 measures the frost line position at a certain circumferential position at measurement time s1, it calculates the length ΔL' from the frost line FL to position Pg at that circumferential position. This length ΔL' is calculated by subtracting the length L0' from the die 14 to the frost line FL (the frost line passing portion Pf) from the length L1 in the flow direction Da from the die 14 to the measurement position (position Pg) of the second measuring device 80. As described above, the length L1 is calculated using a value stored in advance in the memory unit 64. For the circumferential position for which the length ΔL' is to be calculated, the measurement value of the frost line position measured by the first measuring device 50 at measurement time s1 is used for the length L0'. Next, based on the length ΔL' calculated for a certain circumferential position and the winding speed v of the film 12, the relationship estimation unit 74 calculates the required time Δs' required for the frost line passing portion Pf on the film 12 at that circumferential position to pass through the aforementioned length ΔL'. As with the aforementioned required time Δs, the required time Δs' can be calculated by dividing the length ΔL' by the winding speed v. Then, the relationship estimation unit 74 calculates the arrival time s2 as a time that is earlier than the measurement time s1 by the required time Δs'. This arrival time s2 represents the time at which the frost line passing portion Pf, which passes through the frost line FL at a certain circumferential position at measurement time s1, reaches position Pg, and is treated as corresponding to the measurement value of the frost line position measured at that circumferential position at measurement time s1.

[0067] When the relationship estimation unit 74 measures the frost line position distribution at a certain measurement time s1, it calculates, for each circumferential position at which the frost line position is measured, the arrival time s2 corresponding to the measurement value of each frost line position, using the procedure described above. Furthermore, the relationship estimation unit 74 performs a linking process to generate measurement value information linking the measurement value of the frost line position with the arrival time s2 corresponding to that measurement value for each circumferential position at which the frost line position is measured. The relationship estimation unit 74 performs the linking process each time the frost line position distribution is measured, and generates a measurement value information group by storing multiple pieces of measurement value information generated for the same circumferential position in the storage unit 64. The measurement value information group is generated for each circumferential position at which the frost line position is measured. The measurement value information group is generated, for example, as time-series data in which multiple pieces of measurement value information are arranged in the order of the measurement times of the frost line positions at a certain circumferential position at which the frost line position is measured.

[0068] When a film thickness is measured at a certain circumferential position at measurement time s3, the relationship estimation unit 74 references a group of measurement value information generated for the same circumferential position as the film thickness measurement position. From the referenced group of measurement value information, the relationship estimation unit 74 identifies measurement value information having an arrival time s2 that is closest to measurement time s3. The relationship estimation unit 74 identifies the measurement value at the frost line position associated with the arrival time s2 of the identified measurement value information as the target measurement value to be associated with the film thickness measurement value measured at measurement time s3. This allows for accurate association between the film thickness measurement value at the frost line passing portion Pf on the film 12 and the measurement value at the frost line position measured when the frost line passing portion Pf passed through the frost line FL.

[0069] As described above, the correlation process correlates film thickness measurements and frost line position measurements that satisfy predetermined conditions. The film thickness measurement value to be correlated may be a single film thickness measurement value or a representative value of multiple film thickness measurement values. Similarly, the frost line position measurement value to be correlated may be a single frost line position measurement value or a representative value of multiple frost line position measurement values.

[0070] So far, an example has been described in which the first measuring instrument 50 measures the frost line position distribution in the circumferential direction of the film 12, and the film thickness estimation unit 72 estimates the film thickness distribution in the circumferential direction of the film 12 based on the measured frost line position distribution. However, this is not limiting, and the first measuring instrument 50 may measure the frost line positions at specific circumferential positions of the film 12, and the film thickness estimation unit 72 may estimate the film thickness at the specific circumferential position of the film 12 based on the measured frost line positions.

[0071] The above description has been given taking as an example a case where the present disclosure is applied to a film forming apparatus 10 using an inflation method in which a tubular film 12 is fed from a round die. However, the present disclosure is not limited to this, and may also be applied to a film forming apparatus 10 using a T-die method in which a sheet-shaped film 12 is fed from a T-die.

[0072] To understand the disclosure so far as it applies to both the inflation method and the T-die method, the disclosure so far can be understood by replacing the term "circumferential direction" with "transverse direction." The "transverse direction" here can also be understood as the in-plane direction of the film 12 in a cross section perpendicular to the film flow direction Da. In the case of a tubular film used in the inflation method, this "transverse direction" refers to the circumferential direction of the film 12 described above. Furthermore, in the case of a sheet-like film 12 used in the T-die method, this "transverse direction" refers to the width direction of the film 12. For example, the first measuring device 50 may measure the frost line position distribution in the transverse direction of the film 12, and the film thickness estimation unit 72 may estimate the film thickness distribution in the transverse direction of the film 12 based on the frost line position distribution. Even when a sheet-like film 12 is the target, the frost line position at a specific transverse position of the film 12 may be measured, and the film thickness of the film 12 at that specific transverse position may be estimated based on the measurement value of the frost line position.

[0073] The above-described embodiments and variations are merely examples. The abstract technical concepts should not be interpreted as being limited to the contents of the embodiments and variations. Many design changes are possible in the contents of the embodiments and variations, such as changes, additions, and deletions of components. In the above-described embodiments, the term "embodiment" is used to emphasize the contents in which such design changes are possible. However, design changes are also permitted even in contents without such notation. Hatching on cross sections in the drawings does not limit the material of the hatched objects. The positional relationships referred to in the embodiments and variations naturally include those that can be considered identical when manufacturing errors, etc. are taken into account.

[0074] Any combination of the above components is also valid. For example, any description of another embodiment may be combined with an embodiment, or any description of an embodiment and another variation may be combined with a variation. Furthermore, any of the components and expressions of the present disclosure may be substituted for methods, devices, systems, etc., and are also valid aspects of the present disclosure. [Explanation of symbols]

[0075] 10...film forming device, 12...film, 14...die, 48...film thickness estimating device, 64...storage unit, 72...film thickness estimating unit, 74...relationship estimating unit.

Claims

1. A film thickness estimation device used in a film forming device, The film forming device a first measuring device for measuring a frost line position of the film fed from the die in the machine direction; a second measuring device that sequentially measures the film thickness while changing the measurement position in the transverse direction of the film, The film thickness estimation device includes: a relationship estimation unit that estimates correlation information indicating a correlation between the frost line position and the film thickness of the film based on the frost line position measured by the first measuring instrument and the film thickness measured by the second measuring instrument; a film thickness estimation unit that estimates a film thickness at at least one transverse position of the film based on the correlation information estimated by the relationship estimation unit and the frost line position measured by the first measuring instrument.

2. a correlation storage unit that stores the correlation information estimated by the relationship estimation unit, 2. The film thickness estimation device according to claim 1, wherein the film thickness estimation unit estimates the film thickness based on the correlation information stored in the correlation storage unit and the frost line position measured by the first measuring instrument.

3. 3. The film thickness estimation device according to claim 2, wherein the relationship estimation unit updates the correlation information stored in the storage unit with newly estimated correlation information when a predetermined update condition is satisfied.

4. A film forming apparatus comprising the film thickness estimation device according to any one of claims 1 to 3.

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