Doctor device and gravure coating device

Abstract

To provide a doctor device and a gravure coating device that can press a doctor blade in the width direction against a gravure roll with a uniform force, without causing the doctor blade to bend.SOLUTION: A doctor device comprises: a flat plate-shaped doctor blade; a doctor holder that holds the doctor blade in a flat state; and a backup blade interposed between at least one surface of the doctor blade and the doctor holder, wherein a blade edge of the backup blade in the width direction is formed along a convex curve.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a doctor device and a gravure coating device. [Background technology]

[0002] Gravure coating is a widely used method for applying a coating liquid to a web. In gravure coating, the coating liquid is supplied to the surface of a rotating gravure roll (gravure plate), and a doctor blade is pressed against the surface of the gravure roll to scrape off excess coating liquid from the gravure roll surface. The coating liquid held in the cells of the gravure roll is then transferred onto the web, forming a web-like coating film of the coating liquid. The doctor blade is pressed against the surface of the gravure roll between the position where the coating liquid is supplied onto the gravure roll and the position where the gravure roll contacts the web.

[0003] The gravure roll rotates while being supported by bearings at both ends. The length of the gravure roll is, for example, 300 to 2000 mm, and the diameter is, for example, 20 to 500 mm. A small-diameter, long gravure roll, known as a microgravure roll, bends at its center, using the bearings as a fulcrum, resulting in a downwardly convex arc shape. When the tip of a straight doctor blade is brought into contact with a bent gravure roll, if the force pressing the doctor blade against the gravure roll is too small, a gap will form in the center of the width direction. If the force pressing the doctor blade against the gravure roll is uniformly increased in the width direction to prevent a gap from forming in the center, the portions of the gravure roll that contact both ends in the width direction will be pressed against the gravure roll with a greater force than the portion that contacts the center of the bent gravure roll in the width direction. If the force pressing the doctor blade against the gravure roll is uneven in the width direction, the wear of the tip edge (cutting edge) of the doctor blade and the gravure roll will be uneven in the width direction. As a result, the amount of coating liquid supplied and the amount of coating liquid scraped off also become non-uniform in the width direction, and the amount of coating liquid applied to the web also becomes non-uniform in the width direction.

[0004] The non-uniformity of the coating amount described above is particularly noticeable when the amount of coating liquid applied to the web is small. For example, when applying a coating liquid constituting an anti-reflection film for a liquid crystal display to a film substrate, if the amount of coating is 10 mL / m 2 Since the thickness is as low as or less, the requirement for uniformity in the distribution of the coating amount (film thickness) is particularly strict, and measures to uniformize the coating amount are essential.

[0005] For example, Patent Documents 1 and 2 describe a technique in which the doctor blade is bent in accordance with the bending of the roll, thereby pressing the doctor blade uniformly against the gravure roll. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-260393 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-73926 Summary of the Invention [Problem to be solved by the invention]

[0007] As described in Patent Documents 1 and 2, when bending a doctor blade, it is necessary to measure the amount of bending of the gravure roll and, based on the measured amount of bending, form a curved surface on the doctor blade that has the same shape as the bent shape of the gravure roll. To achieve this, it is necessary to form a curved shape corresponding to the curved surface to be formed on the doctor blade on a holder or backing plate that fixes the doctor blade, for example, by polishing. Depending on the length and material of the gravure roll, the amount of bending may be on the order of several hundred μm, and forming the curved shape requires effort, time, and cost.

[0008] SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a doctor device and a gravure coating device that can press a doctor blade against a gravure roll with a uniform force in the width direction without bending the doctor blade. [Means for solving the problem]

[0009] The doctor device of the present invention comprises a flat doctor blade, a doctor holder that holds the doctor blade in a flat state, and a backup blade that is sandwiched between at least one surface of the doctor blade and the doctor holder, and is characterized in that the cutting edge of the backup blade is formed on a convex curve.

[0010] The gravure coating device according to the present invention comprises a gravure roll, a coating liquid supply section that supplies a coating liquid to the gravure roll, a flat doctor blade, a doctor holder that holds the doctor blade in a flat state, and a backup blade that is sandwiched between at least one surface of the doctor blade and the doctor holder, and is characterized in that the cutting edge of the backup blade is formed in a convex curve. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a doctor device and a gravure coating device that can press a doctor blade against a gravure roll with a uniform force in the width direction without bending the doctor blade. [Brief explanation of the drawings]

[0012] [Figure 1] Schematic diagram showing a gravure coating device according to an embodiment. [Figure 2] Plan view of the doctor device according to the embodiment [Figure 3] Enlarged cross-sectional view taken along line III-III in Figure 2 [Figure 4] FIG. 1 is a diagram showing definitions of values used in the description of the embodiment. [Figure 5] Schematic diagram for explaining a method for measuring the thickness of a coating film coated using a conventional backup blade. [Figure 6] Scatter plot of the film thickness ratio t / tave at each measurement point measured using the backup blade shown in Figure 5(a). [Figure 7]Schematic diagram showing the method for measuring the contact pressure of the doctor blade against the gravure roll [Figure 8] Scatter plot of the contact pressure ratio T / Tave at each measurement point measured using the backup blade shown in Figure 7(a) and Figure 7(b). [Figure 9] Scatter plot of α value and measured contact pressure ratio T / Tave [Figure 10] Scatter plot of film thickness ratio t / tave and contact pressure ratio T / Tave for each measurement position [Figure 11] Scatter plot of the film thickness ratio t / tave and contact pressure ratio T / Tave for each measurement position shown in Figure 10. [Figure 12] Scatter plot of α at each measurement position shown in FIG. 7(b) and the membrane pressure ratio t / tave corresponding to each measurement position shown in FIG. 10. [Figure 13] Scatter plot of the α value at each measurement point of the prototype backup blade and the (t / tave-tref / trefave) value at the same measurement point. [Figure 14] A scatter plot in which the vertical and horizontal axes of Figure 13 are swapped and the curve expressed by Equation (5) is also shown as a dashed line. [Figure 15] FIG. 10 is a diagram showing the ratio of lengths of the divided blades that make up the backup blade according to the embodiment. [Figure 16] Scatter diagram showing the film thickness ratio of low refractive index layers formed by applying a coating liquid for forming a low refractive index layer using a backup blade according to the embodiment and a conventional backup blade. DETAILED DESCRIPTION OF THE INVENTION

[0013] FIG. 1 is a schematic diagram showing a gravure coating device according to an embodiment.

[0014] The gravure coating device 1 includes a gravure roll 2, a coating liquid supply unit 5 that supplies a coating liquid to the gravure roll 2, and a doctor unit 6. The gravure roll 2 is rotated by a mechanism not shown, and the coating liquid is supplied to its surface from the coating liquid supply unit 5. Excess coating liquid on the gravure roll 2 is scraped off by the doctor unit 6. The coating liquid held in the cells of the gravure roll 2 is transferred to the surface of the web 10, which is being transported while being guided by guide rolls 3 and 4. In this specification, the term "width direction" refers to the direction corresponding to the width direction (TD direction) of the web being transported. The widths of the doctor blade and backup blade refer to the dimensions corresponding to the width direction of the web, and the length of the backup blade refers to the dimension of the portion of the backup blade exposed from the holder in the direction perpendicular to the width direction.

[0015] FIG. 2 is a plan view of the doctor device according to the first embodiment, and FIG. 3 is an enlarged cross-sectional view taken along the line III-III shown in FIG.

[0016] The doctor unit 6 includes a doctor blade 11, an upper holder 12, a lower holder 13, an upper backup blade 15, and a lower backup blade 16. The upper holder 12 and the lower holder 13 form a doctor holder that holds the flat doctor blade 11 in a flat state. The upper backup blade 15 is sandwiched and held between the upper holder 12 and the side of the doctor blade 11 that does not face the gravure roll 2 (the upper side in FIG. 1 ). The lower backup blade 16 is sandwiched and held between the lower holder 13 and the side of the doctor blade 11 that faces the gravure roll 2 (the lower side in FIG. 1 ). The upper holders 12 and 13 are fastened to each other with bolts 17, with the upper backup blade 15, doctor blade 11, and lower backup blade 16 sandwiched between them, and the doctor blade 11 is fixed to the upper holder 12 and lower holder 13. The lower backup blade 16 may be omitted.

[0017] The lengths L1a and L1b of the upper backup blade 15 at both widthwise ends are shorter than the length L2 of the widthwise center of the upper backup blade 15. In this embodiment, the length of the upper backup blade 15 decreases monotonically from the widthwise center to both widthwise ends. The upper backup blade 15 has a convex curved edge on the cutting edge side of the doctor blade 11. The curved shape of the cutting edge side of the doctor blade 11 of the upper backup blade 15 is not particularly limited as long as it can uniformly apply the pressing force of the doctor blade 11 against the gravure roll across the widthwise direction, but it can be, for example, a circular arc or an elliptical arc.

[0018] The contact pressure of the doctor blade 11 against the gravure roll 2 varies depending on the distance from the tip of the upper backup blade 15 to the cutting edge of the doctor blade 11, and the contact pressure increases as the distance decreases. The contact pressure of the tip of the doctor blade 11 against the gravure roll is proportional to the stress generated by the deflection of the doctor blade 11. The stress generated in the doctor blade 11 is proportional to the square of the distance between the fixed point of the doctor blade 11 and the load point on the gravure roll. The upper backup blade 15 according to this embodiment is configured so that the length L2 of its widthwise center is longer than the lengths L1a and L1b of its widthwise end ends. Since the length from the cutting edge (load point) of the doctor blade 11 (load point) to the leading edge (fixed point) of the upper backup blade 15 at the widthwise center of the doctor blade 11 is relatively short, the stress generated in the widthwise center of the doctor blade 11 becomes relatively large. As a result, the contact pressure of the doctor blade 11 against the center of the gravure roll, which is largely deflected by its own weight, becomes greater than the contact pressure of the doctor blade 11 against both ends of the gravure roll, which are less deflected by their own weight. By making the contact pressure of the doctor blade 11 against the deflected gravure roll uniform across the width, the amount of coating liquid scraped off from the gravure roll can be made uniform across the width, and the distribution of the coating film thickness of the coating liquid can be made closer to uniform across the width.

[0019] As described above, the upper backup blade 15 according to this embodiment has a convex, curved cutting edge, and is configured so that the length of both widthwise ends (the length of the portion exposed from the holder) is shorter than the length of the widthwise center portion. This allows the doctor blade 11 to be pressed firmly against the center portion of the gravure roll, which is subject to significant deflection due to its own weight. This allows the scraped amount of coating liquid to be uniform across the width, thereby achieving a uniform coating film thickness distribution across the width. Furthermore, when using the upper backup blade 15 according to this embodiment, the doctor blade 11 can be used in a flat state without being curved, eliminating the need to form curved surfaces on the upper backup blade 15, upper holder 12, or lower holder 13 by grinding or other methods. Therefore, by using the upper backup blade 15 according to this embodiment, a doctor device and a gravure coating device can be easily realized that can press the doctor blade 11 against the gravure roll with uniform force across the width without bending the doctor blade 11.

[0020] Furthermore, by monotonically increasing the length of the upper backup blade 15 from both ends in the width direction to the center, the contact pressure of the doctor blade 11 against the gravure roll can be increased from both ends in the width direction to the center, and the contact pressure can be adjusted according to the amount of deflection of the gravure roll.

[0021] Furthermore, by making the edge of the upper backup blade 15 on the cutting edge side of the doctor blade 11 curved, for example, in the shape of a circular arc or an elliptical arc, the contact pressure can be continuously reduced in accordance with the change in the amount of deflection of the gravure roll. [Example]

[0022] Examples of specific implementations of the present invention will be described below.

[0023] FIG. 4 is a diagram showing definitions of values used in the description of the embodiment.

[0024] In the following description, the length of the backup blade protruding from the upper blade holder is l, the length of the doctor blade protruding from the blade holder is L, and the ratio α of the difference between the length of the doctor blade and the length of the backup blade to the length of the doctor blade is (Ll) / L. Also, the contact pressure of the tip of the backup blade against the gravure roll is T.

[0025] First, when a cured film was formed by applying a coating liquid to a transparent substrate using a backup blade with a constant protruding length from the doctor holder, it was confirmed that the film thickness tended to vary depending on the position in the longitudinal direction of the gravure roll (the width direction of the transparent substrate).

[0026] Figure 5 is a diagram illustrating a method for measuring the thickness of a coating film applied using a conventional backup blade. More specifically, Figure 5(a) is a schematic diagram showing the general configuration of a gravure coater equipped with a conventional backup blade, and Figure 5(b) is a diagram illustrating measurement points P1 to P30 for the thickness of a cured coating film.

[0027] The gravure roll used was a microgravure roll with a diameter of 50 mm and a length of 1500 mm, with a hard chrome-plated iron core. The doctor blade was a rectangular metal plate with a thickness of 70 μm and a Vickers hardness of 650 Hv. The backup blade was a rectangular metal plate with a thickness of 0.8 mm. Using a microgravure coater (see FIG. 5(a)) equipped with the microgravure roll, doctor blade, and backup blade, a low refractive index layer-forming coating liquid containing a UV-curable acrylic resin, hollow silica microparticles, a photopolymerization initiator, and a solvent was applied to a film thickness of 100 nm after curing. The coating was then cured by UV irradiation to form a low refractive index layer.

[0028] After forming the low refractive index layer, the reflectance spectrum of the low refractive index layer (cured film) at 30 measurement points P1 to P30 (see Figure 5(b)) on the film was measured using a Filmetrics spectral film measurement system. The film thickness of the low refractive index layer at measurement points P1 to P30 was calculated from the refractive index of the cured film (known value) and the wavelength at which the reflectance of the reflection spectrum was minimized. Measurement points P1 to P30 were aligned at 50 mm intervals in the width direction (TD) of the film, and measurement point P1 was located 50 mm away in the width direction of the film from point P0, which corresponds to one end of the tip edge of the doctor blade during coating (origin O shown in Figure 5(a)).

[0029] Figure 6 is a scatter plot of the film thickness ratio t / tave at each measurement point measured using the backup blade shown in Figure 5(a). In Figure 6, the horizontal axis represents the distance from point P0, which corresponds to the origin O of the backup blade, to each measurement point, and the vertical axis represents the film thickness t at each measurement point relative to the average film thickness t of all measurement points. ave Film thickness ratio t / t ave Represents.

[0030] Because the gravure roll is bent downward, the contact pressure of the doctor blade with the gravure roll is smaller at the center of the gravure roll than at both ends of the gravure roll, and as a result, it was confirmed that the thickness of the cured film tends to be thicker at the center of the gravure roll than at both ends of the gravure roll, as shown in Figure 6.

[0031] Next, to verify the effect of making the cutting edge of the backup blade curved, the relationship between the contact pressure against the gravure roll, film thickness, and the protrusion amount of the segment blade (ratio α) was investigated using a conventional backup blade and a prototype backup blade in which the cutting edge was made closer to a curve by combining multiple segment blades.

[0032] Figure 7 is a schematic diagram showing a method for measuring the contact pressure of a doctor blade against a gravure roll. More specifically, Figure 7(a) shows the method for measuring the contact pressure using a conventional backup blade, and Figure 7(b) shows the method for measuring the contact pressure using a prototype backup blade consisting of multiple split blades.

[0033] In both measurements shown in Figures 7(a) and 7(b), a microgravure roll with a diameter of 50 mm and a length of 1500 mm and a hard chrome-plated iron core was used as the gravure roll. A rectangular metal plate (1500 mm wide) with a thickness of 70 μm and a Vickers hardness of 650 Hv was used as the doctor blade. The contact pressure of the doctor blade tip against the gravure roll was measured using a pressure sensor (a squeegee balance measuring instrument manufactured by NewLuon Instrument Precision Industry Co., Ltd.).

[0034] The backup blade shown in Figure 7(a) is a single rectangular metal plate with a thickness of 0.8 mm, and the length of the backup blade protruding from the doctor holder is constant. A pressure sensor was placed between the gravure roll and the doctor blade, and the cutting edge of the doctor blade was pressed against the pressure sensor with a predetermined pressure. The contact pressure was measured at 30 measurement points Q1 to Q30 on the pressure sensor. Measurement points Q1 to Q30 were aligned at 50 mm intervals along the cutting edge of the doctor blade, and measurement point Q1 was located 50 mm away from one end of the cutting edge of the doctor blade (origin O shown in Figure 7(a)) toward the other end of the cutting edge of the doctor blade.

[0035] The prototype backup blade shown in Figure 7(b) consists of 10 split blades (150 mm wide) obtained by dividing the conventional backup blade shown in Figure 7(a) evenly across the width. The position of the cutting edge of each split blade was adjusted so that the protruding length l of each split blade from the doctor holder increased from both ends of the gravure roll to the center, resulting in the value of α (= (Ll) / L) for each split blade shown in Figure 7(b). By gradually increasing the protruding length of each split blade from both ends to the center, the cutting edge of each split blade resembles a convex curve. As with the measurements using the conventional backup blade, a pressure sensor was placed between the gravure roll and the doctor blade. The doctor blade cutting edge was pressed against the pressure sensor with the same pressure as in the measurements using the conventional backup blade. The contact pressure was measured at 30 measurement points Q1 to Q30 on the pressure sensor.

[0036] Figure 8 shows the contact pressure distribution at each measurement point measured using the backup blade shown in Figures 7(a) and 7(b). In Figure 8, the horizontal axis represents the distance from the origin O of the backup blade to each measurement point, and the vertical axis represents the contact pressure T at each measurement point as the average contact pressure T of all measurement points. ave When a conventional backup blade is used, the contact pressure of the doctor blade against the gravure roll (white circles) is smaller at the center of the gravure roll than at both ends of the gravure roll. However, when the prototype backup blade shown in Figure 7(b) is used, the contact pressure of the doctor blade against the gravure roll (black circles) can be made larger at the center of the gravure roll than at both ends of the gravure roll.

[0037] Next, using the prototype backup blade shown in Figure 7(b), the doctor blade contact pressure T was measured multiple times at measurement points Q1 to Q30 using the method described above. Figure 9 shows the relationship between the value of α and the contact pressure ratio T / T ave The following formula (1) was obtained by power approximation from the data of the scatter diagram. T / T ave =0.0911α -1.446 ···(1)

[0038] Next, the relationship between the doctor blade contact pressure and the thickness of the cured film was investigated using the prototype backup blade shown in Figure 7(b).

[0039] Using the prototype backup blade shown in Figure 7(b), a pressure sensor was placed between the gravure roll and the doctor blade, and the backup blade was pressed against the gravure roll with a predetermined pressure to measure the contact pressure of the doctor blade at measurement points Q1 to Q30. The pressure sensor was then removed, and the doctor blade was pressed against the gravure roll with the same pressure to coat the transparent substrate with the above-described low-refractive-index layer-forming coating liquid, and the coating was cured to form a low-refractive-index layer. The film thickness of the low-refractive-index layer was measured at measurement points P1 to P30 using the method described above.

[0040] Figure 10 shows the film thickness ratio t / t ave and contact pressure ratio T / T ave As shown in Figure 10, the contact pressure ratio T / T ave When the thickness ratio of the cured film decreases, the thickness ratio of the cured film decreases. ave The contact pressure ratio T / T ave As the thickness ratio of the cured film increases, ave There was a tendency for this to decrease.

[0041] Figure 11 shows the film thickness ratio t / t ave and contact pressure ratio T / T ave As shown in Figure 12, the film thickness ratio t / t ave and contact pressure ratio T / T ave There is a negative correlation between the two, and the following equation (2) was obtained by linear approximation. T / T ave =-0.1103(T / T ave )+1.1113 (2)

[0042] From the above formulas (1) and (2), the film thickness ratio t / tave The relationship between the ratio α and the temperature is expressed by the following equation (3). T / T ave =-0.010048α -1.446 +1.1113 (3)

[0043] FIG. 12 shows the relationship between α at each measurement position shown in FIG. 7(b) and the membrane pressure ratio t / t corresponding to each measurement position shown in FIG. 10. ave 12 shows a scatter diagram in which α and t / t are plotted. In addition, the curve expressed by the above formula (3) is also shown by a dashed line in Fig. 12. From Fig. 12, it can be seen that formula (3) is a function of α and the membrane pressure ratio t / t ave It can be seen that this is an approximate expression of the relationship between

[0044] From the above, it was confirmed that the film thickness can be adjusted by making the cutting edge of the split blade closer to a convex curve, as in the prototype backup blade.

[0045] Next, we investigated the relationship between the difference in thickness between the coating film formed using the prototype backup blade (Fig. 7(b)) and the coating film formed under the same conditions using the conventional backup blade (Fig. 7(a)), and the value of α for the segmented blade.

[0046] A low refractive index layer was applied to the film under the same conditions using the prototype backup blade (Fig. 7(b)) and the conventional backup blade (Fig. 7(a)). The coating was cured by UV irradiation, and the thickness of the cured film was measured at each measurement point Q1 to Q30. From the measurements, the thickness ratio t / t when the prototype backup blade was used was ave and the film thickness ratio tref / tref when using a conventional backup blade. ave difference (T / T ave -tref / tref ave ) was calculated.

[0047] Figure 13 shows the values of α at each measurement point of the prototype backup blade and the (t / t ave -tref / tref ave) is plotted. From the data of the scatter diagram obtained, the following equation (4) was obtained by polynomial approximation (third order). t / ave -tref / tref ave =-25.584α 3 +24.474α 2 -8.0398α+0.8319 (4)

[0048] The real solution α of equation (4) is expressed by the following equation (5) using the formula for solving a cubic equation. α=e+[f / g+(3h) 1 / 2 / i)] 1 / 3 +[f / g-(3h) 1 / 2 / i)] 1 / 3 ···(5) When the coefficients of each term in equation (4) are a=-25.584, b=24.474, c=-8.0398, and d=0.8319, e to i in equation (5) above are expressed by the following equations. e=-b / 3a f=-2b 3 +9abc-27a 2 ×[d-(t / t ave -tref / tref ave )] g=54a 3 h=27a 2 d 2 -18abcd+4b 3 ×[d-(t / t ave -tref / tref ave )]+4ac 3 -b 2 c 2 i=18a 2

[0049] FIG. 14 shows a scatter diagram in which the vertical and horizontal axes of FIG. 13 are interchanged and the curve expressed by equation (5) is also shown by a dashed line.

[0050] The derived equation (5) represents the value of α corresponding to the difference between the film thickness ratio when the prototype backup blade shown in Figure 7(b) is used and the film thickness ratio when the conventional backup blade shown in Figure 7(a) is used. Therefore, we will explain how to calculate the optimal ratio α (the ratio of the difference between the doctor blade L and the segment blade length l to the doctor blade length L) using the derived equation (5). When calculating the value of the ratio α using equation (5), t / t ave The ideal film thickness (design film thickness) is substituted into . In addition, a single backup blade shown in Figure 7(a) is used to apply and cure the coating liquid, and the film thickness of the cured film at each measurement point is measured. The film thickness of the cured film at each measurement point is calculated as tref / tref ave By substituting the above, the ideal value of α at each measurement point can be calculated from equation (5).

[0051] FIG. 15 is a diagram showing a backup blade according to an embodiment, and FIG. 16 is a scatter plot showing the film thickness ratio of low refractive index layers formed by applying a coating liquid for forming a low refractive index layer using a backup blade according to an embodiment and a conventional backup blade.

[0052] The backup blade according to the example had a cutting edge formed in a convex curve. The convex shape of the cutting edge of the backup blade was determined using the following method. First, the backup blade was divided into 30 50-mm sections in the width direction, and a model backup blade was created whose cutting edge shape more easily approximated a curve than the prototype backup blade shown in Figure 7(b). Specifically, using the backup blade shown in Figure 7(a), a coating liquid for forming a low-refractive-index layer was applied to a transparent substrate, the coating was cured to form a low-refractive-index layer, and the film thickness of the low-refractive-index layer was then measured at measurement points Q1 to Q30. Using the obtained measured values and the designed film thickness of the low-refractive-index layer, the value of α for each segmented blade portion (corresponding to measurement points Q1 to Q30) was calculated using Equation (5). Next, the convex shape of the cutting edge of the backup blade according to the example was obtained as a curve encompassing all of the cutting edges of each segmented blade portion determined by the calculated α value. Figure 15 shows the convex shape of the cutting edge of the backup blade according to the example.

[0053] A backup blade having the obtained cutting edge shape was prepared and fixed to a doctor holder. A low refractive index forming coating liquid was applied to a transparent substrate, the coating film was cured, and the film thickness of the low refractive index layer was measured at measurement points Q1 to Q30. Also, a conventional backup blade was used to apply a low refractive index forming coating liquid to a transparent substrate under the same conditions, the coating film was cured, and the film thickness of the low refractive index layer was measured at measurement points Q1 to Q30.

[0054] When coating was performed using one backup blade, the thickness of the cured film was thicker at the center of the gravure roll than at both ends of the gravure roll, as shown by the white circles in Figure 16. In contrast, when coating was performed using the backup blade according to the example (Figure 15), the film thickness ratio t / t ave By using the backup blade according to the embodiment, it is possible to make the distribution of the coating amount of the coating liquid uniform in the width direction and reduce unevenness in the coating of the coating liquid. [Industrial Applicability]

[0055] The present invention can be used in a doctor device used for gravure coating and a gravure coating device equipped with the doctor device. [Explanation of symbols]

[0056] 1 Gravure coating device 2 Gravure Roll 5 Coating fluid supply section 6 Doctor equipment 11 Doctor Blade 12 Upper holder 13 Lower holder 15 Upper backup blade

Claims

1. A flat doctor blade, a doctor holder for holding the doctor blade in a flat state; a backup blade sandwiched between at least one surface of the doctor blade and the doctor holder, A doctor device characterized in that the cutting edge of the backup blade is formed on a convex curve.

2. 2. The doctor device according to claim 1, wherein the length of the backup blade projecting from the doctor holder increases monotonically from both ends toward the center in the width direction.

3. 3. The doctor device according to claim 2, wherein the edge of the backup blade on the cutting edge side of the doctor blade is arc-shaped or elliptical arc-shaped.

4. Gravure roll and a coating liquid supply unit that supplies a coating liquid to the gravure roll; A flat doctor blade, a doctor holder for holding the doctor blade in a flat state; a backup blade sandwiched between at least one surface of the doctor blade and the doctor holder, A gravure coating device, characterized in that the cutting edge of the backup blade is formed in a convex curve.

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