JPH01112134A - Stiffness measurement method - Google Patents

Abstract

PURPOSE:To find the stiffness of only a coating layer by measuring film thickness, stiffness, and a Young's modulus as to a sample tape where a coating film is formed and a base film from a coating film is separated. CONSTITUTION:The sample tape 1 is set on sample chuck parts 2 and 3 and then the chuck parts 2 and 3 are put together to round the tape 1 and a load cell 4 is pressed against it and the stiffness St of the tape 1 is measured. Then the chuck part 3 is drawn by constant length DELTAl and the current force is detected by the load cell 5 to find the Young's modulus Et. The stiffness Sb and Young's modulus Eb of the base tape from which the coating film is separated are found similarly. Then the stiffness Sm of the coating film is found from an equation based upon the film thickness values dt and db of the tape, the thickness dm=dt-db of the coating film, and the Young's modulus of the coating film.

Description

[Detailed Description of the Invention] Go to 3-7 Industrial Application Field The present invention relates to a method for measuring stiffness (stiffness), and in particular to a coating layer of a tape, such as a magnetic tape, in which a coating film is formed on a base film. This relates to a method for determining the stiffness of a material.

Conventional technology Conventionally, stiffness measuring instruments (for example, the Lube Stiffness Tester from Toff Co., Ltd.) have been used to measure the stiffness of tapes, etc., but this is a device that measures the value of the entire tape. Therefore, in the case of a magnetic tape in which a coating film is formed on a base film, it is impossible to measure the stiffness of only the coating film.

For example, when considering magnetic tape, the issue of the interface between the head and the media is extremely important, and the mechanical properties of the media in the running system are extremely important. Among these, so-called stiffness is a particularly important physical property for video tapes.
Electromagnetic conversion characteristics (S/N.

etc.) and durability (head wear, etc.), and when considering the delicate interface between the head and the media, or considering the constituent components of the magnetic layer (
In order to analyze the factors involved in each process such as material/composition), dispersion, coating, calendaring, and curing, detailed measurement and analysis of the physical property called stiffness was necessary. Furthermore, when discussing the mechanical properties of the magnetic layer, the question of stiffness of the magnetic layer alone has always been a central point of discussion. Of course, the stiffness of the magnetic layer alone is not a physical property that can be easily measured directly. This is because the current method of measuring stiffness is to compress and deform a sample into a loop and measure its deformation recovery force, but samples with only a magnetic layer easily break when bent, resulting in loops and other problems. Because you can't.

Problems to be Solved by the Invention As described above, with the conventional techniques, the stiffness of the magnetic layer alone cannot be measured or known. Therefore,
In the evaluation of video tapes, the concept of stiffness of only the magnetic layer did not exist in the first place.

As described above, with the conventional technology, although it is possible to measure the stiffness of the entire videotape and the stiffness of the base film alone, it is not possible to determine the (virtual) stiffness of the magnetic layer alone, the back coat layer alone, etc. could not.

Means for Solving the Problem In order to solve this problem, the stiffness measuring method of the present invention measures the film thickness (dt), stiffness (St), and young The film thickness (db) was measured in the same way for the base film from which the coating film of the sample tape was peeled off.
, stiffness (Sb) and Young's modulus (Eb) are measured, and the stiffness (sm) of the coating film alone is determined from these measured values by the following formula; Sm = St -3b- Bdmdb (2E
mdm + Emdb + Ebdm + 2 Ebdb
) Here, B is a constant, dm is the thickness of the coating film, and dllll=dj
;-clb, Km is the Young's modulus of the coating film: 61-/ This method makes it possible to measure the stiffness of only the magnetic layer of a magnetic tape, for example, and is effective in elucidating its physical properties. Furthermore, the stiffness of the anchor coat layer+magnetic layer and back coat layer can be determined in the same way, and is extremely useful as a value that has not been previously obtained when examining the electromagnetic conversion characteristics and durability of magnetic tapes.

The actual measuring device is a commercially available stiffness tester that has been modified to be able to measure both stiffness and Young's modulus, as described below.The device also has a built-in memory and arithmetic circuit, so that it can be used to measure film thickness in advance. By inputting the above values, the stiffness value can be easily obtained.

Example How to determine the stiffness of a single layer
First, we must begin with a mechanical consideration of the physical property value called stiffness.

71,- First, consider a two-layer videotape consisting of only a magnetic layer and a base film, and define the necessary variables as follows.

E: Young's modulus d: film thickness l: Tape sample length (circumference length) (radius r = l/2π) L: Tape width H: Gap after compression (see Figure 2) Engineering: Second moment of area Subscripts m, b, and t indicate the magnetic layer and base film, respectively.

The entire tape (represents the meaning of tota7ri).

A commercially available lube stiffness tester measures the sample tape by rolling it, and FIG. 2 shows the deformation of the sample tape. It is assumed that a sample tape 1 having a length β is first rolled up as shown in FIG. 2 1, and then compressed and deformed as shown in FIG. 2, and a recovery force S (stiffness) is generated. Minute displacement δBB'δ. .

Considering, the following relational expression can be obtained using the basic formula of material mechanics.

becomes.

That is, the stiffness St is assumed to be proportional to Ei-dt, and will be abbreviated as 5t=B-Et-dt below.

Here, the stiffness of the base film alone is 9, -
7Sb2B-Ebdb, and the stiffness Sm of only the Young's modulus magnetic layer of the entire tape is as follows (1) to (6
) is obtained from the relational expression.

Si == B-Et-dt5...
... (1) Sm== B-Em-dm
・=-(2)Sb=B-Ebdb3 ・
・・・・・・・・・ (3) dt = dIn+ db river−
(5) (4) , (Putting the four equations into equation (1) and transforming it, (2)
, If we convert the equation to include equation (3), = B(Emdm+lEbdb)(dm2+2dmdb
+db )=: B (Emdm' +Ebdb3+
dmdb(2Kmam+Emdb+Ebdm+2Ebd
b ) ) , °, St = Sm + Sb + Bdmdb (2Emdm
+ Emdb+ Ebdm +2 Eb db)・-
-(6)10,<-,-.

Therefore, Sm'=St-sb. That is, the stiffness of only the magnetic layer is not a simple value such as the value obtained by subtracting the stiffness of the base film from the stiffness of the entire tape.

From equation (6), the stiffness (Sm) of only the magnetic layer is S
m = St-3b-Bdm db (2Emdm +
Emd1)+xbdm+2gbab)・−・−(7). The lube stiffness tester can actually measure only two things, st and sb, but the remaining Em
, Eb, dm, dl) can be easily determined by other measurements. dm and db can be measured in advance using a commercially available film thickness meter.

Next, Young's modulus is usually measured using a tensile tester.
Although it is determined from an SS curve (5tress-5train curve), the gist of the present invention is to mount a load cell on this lube stiffness tester and perform measurement very easily. The value of Em can be easily calculated using the above formula. That is, Etat-Ebdb Em=□ (4) is obtained by modifying equation (4).

m 11, - Figure 3 shows the measuring method of a commercially available lube stiffness tester. Set the tape 1 to the sample chuck part 2°3 (Fig. 3 ■), roll the sample tape with the chuck parts together (Fig. 3 ■), and press the load cell 4 onto it (Fig. 3 ■).
), the stiffness of the sample tape 1 is measured. Also, by wiping the magnetic layer of the tape with a penkotsuton etc. impregnated with DMF (dimethylformamide) and setting the base film alone, the stiffness of only the base film of the tape can be measured, and those values ( s
t, sb) are displayed as digital numbers.

In the present invention, the Young's modulus (Et, ICb) can be determined by pulling the sample a little extra at times shown in (■) in FIG. 3, and Em can be determined by calculation.

That is, as shown in FIG. 1, one of the chuck parts 2 of the pair of samples is connected to the load cell 6, and the other chuck part 3 is set back by a certain length (Δl) as the backlash length. put.

The force detected by the load cell 5 for a constant displacement Δl (elongation) and the film thickness (dt, d
The desired Em can be calculated using the built-in arithmetic circuit according to equations (4) from b). In Fig. 1, 6 is a glue mint switch for setting the sample length before measurement, 7 is a limit switch for micro-stretching after measurement, 8 is a stopper for connecting the load cell and sample chuck jig, and 9 is a chuck part 3. It is a rotating screw gear that moves the In actual measurement, the stiffness Sm of only the magnetic layer can be determined by the following procedure.

(1) Measure the total thickness (dt) of the sample tape in advance with a film thickness meter and input it.

(11) Set the sample tape, measure its stiffness (St), and store the value in memory.

Then, when the state returns to the state shown in Figure 3 ■ (Figure 1 ■), the load cell detects the tension due to the constant bank crash displacement (Figure 1 ■), and the Young's modulus Et is measured.
stored in memory.

ω1) Base fill 13 from which the magnetic layer of the sample tape was peeled off
・Measure and input the film thickness for the film. Next, measurements similar to (11) are performed to measure Sb and Eb, and these values are stored in memory.

6VI Et , ]lCb , dt , and db, Em is calculated by the formula (4) 7, and Sm is obtained by the formula ('r).

Now, regarding the value of B, the stiffness value changes depending on the conditions shown in Fig. 3 @, or the B value can be determined once the geometric form of state 3 is determined.

In reality, many samples are measured and an average and reasonable value is determined from equation (1). In addition, Xt at this time was determined using a tensile tester and was determined to be 5-8 (5tvess -
3tvain) It is better to use the Et value determined more strictly than the curve. From the 30 data of (St, Et, dt) obtained from the number of measurements of N:
A value of B=4.82×107 was determined as St)/(Etdt) (- indicates the average value). The units of numerical values are µm for film thickness, #/rtrm for Young's modulus, and \ for stiffness, which are treated as input and output.

Hereinafter, explanation will be given by giving specific examples. To sample 14-
The videotape 2 was produced by a conventional and well-known method, and its composition and process will be omitted. The tape thickness of the sample videotape (V2 inch width) and the base film thickness were determined using a commercially available film thickness meter.

The sample length β of the tape is 80.0M, and the backlash displacement length for measuring Young's modulus is Δβ=0.40 mm (elongation rate 0.5%). In addition, the short axis length (H in Figure 2, ■) of the sample tape, which had become an ellipse after being compressed and deformed, was set to H = 19 mm. For the load cell, we selected a product manufactured by NMB Co., Ltd., which is small and lightweight.

The results are shown in the table below.

(Margins below) 15...- (at 23°C - 60% RH) As shown in the table above, the stiffness of only the magnetic layer is required, but even if the total thickness of the tape and the base thickness do not change, the stiffness of the tape It can be seen that the stiffness value of only the magnetic layer changes greatly depending on changes in the overall Young's modulus, tape stiffness, and base stiffness.

Effects of the Invention As described in detail above, by the method of the present invention, it is possible to determine the virtual stiffness value of only the magnetic layer, which is an important physical property value that cannot be measured in reality. This method can be widely applied to boat fishing for composite ribbon samples.

Although the above description has been made regarding the case where only a magnetic layer is provided, actual magnetic tapes are often provided with a back coat layer and an anchor coat layer, and may also be provided with a top coat. It is clear that the stiffness of these composite layers and back coat layers can be similarly determined.

Furthermore, the method of the present invention improves the stiffness measuring instruments that are generally available on the market, so that the same device can be used to measure stiffness.

It is also possible to measure the puffer ratio, which is very useful because it allows you to easily determine the stiffness of only the coating film.

[Brief explanation of the drawing]

Fig. 1 is a diagram schematically showing the measuring section of the improved loop stiffness tester used in the present invention, Fig. 2 is a diagram showing the relationship between the displacement and stiffness of a sample tape deformed from a rolled state, and FIG. 3 is a diagram showing a measurement procedure using a conventional lube stiffness tester. 1... Sample tape, 2, 3... Sample chuck section, 4.6... Load cell, 6, 7-...
...Limit switch, 8...Stopper, 9.
...Rotating screw gear. Name of agent: Patent attorney Toshio Nakao and 1 other M1
Figure ■ Figure 2 Figure 3

Claims (5)

[Claims] (1) Measure the film thickness (dt), stiffness (St), and Young's modulus (Et) of the sample tape with the coating film formed on the base film, and then similarly measure the base film from which the coating film of the sample tape was peeled off. The film thickness (db), stiffness (Sb) and Young's modulus (Eb) were measured,
A stiffness measuring method characterized by determining the stiffness (Sm) of only the coating film from these measured values using the following formula: Sm=St-Sb-Bdmdb(2Emdm+Embd
+Ebdm+2Ebdb) Here, B is a constant, dm is the thickness of the coating film, and dm=dt-db
, Em is Young's modulus of the coating film, and Em=(Etdt-Ebdb)/dm. (2) A tension detector is connected to one chuck part of a pair of sample chuck parts of the stiffness tester, and the other chuck part is moved back by a certain length so that both stiffness and Young's modulus can be measured. Claim 1, characterized in that a stiffness tester is used.
Stiffness measurement method described in section. (3) The stiffness measuring method according to claim 1, wherein the coating film is a magnetic coating film. (4) The stiffness measuring method according to claim 1, wherein the coating film comprises an anchor coat layer and a magnetic layer. (5) The sample tape has a coating film formed on both sides of a base film, and the stiffness of only the second coating film is measured considering the first coating film and the base film as the base film, and then the stiffness of only the second coating film is measured. 2. The stiffness measuring method according to claim 1, wherein the stiffness of only the coating film is measured to obtain the stiffness of each coating film on both sides.