JP6299747B2 - Die and method for producing multilayer film - Google Patents

Description

  The present invention relates to a die and a method for producing a multilayer film using the die.

  For example, various optical films are usually used for image display devices such as liquid crystal display devices. An example of the optical film is a retardation film. As such a retardation film, a multilayer film including a plurality of layers formed of different types of resins may be used.

  In general, when thickness unevenness occurs in a layer included in a multilayer film, the optical characteristics of the multilayer film are not uniform in the plane. Therefore, the thickness unevenness of the layer included in the multilayer film may cause, for example, display unevenness and light leakage. Therefore, in the multilayer film, it is required to increase the thickness accuracy by making the layer thickness uniform in the plane.

  One method for producing a multilayer film is a melt extrusion method. In the multilayer film produced by this melt extrusion method, the thickness unevenness tends to occur in the width direction of the film. On the other hand, Patent Documents 1 and 2 propose a technique for increasing the thickness accuracy of the layers included in the multilayer film in the width direction of the film.

Japanese Patent No. 3564623 JP 2006-231763 A

  In recent years, however, the level of demand for liquid crystal display devices has become high. For this reason, it has become difficult for conventional techniques such as those described in Patent Documents 1 and 2 to increase the thickness accuracy of the layers included in the multilayer film to the extent that recent high demands can be met. Especially, in the multilayer film provided with the several layer from which thickness differs, it is especially difficult to raise the thickness precision of a thin layer in the width direction of a film. Therefore, development of the technique which can raise the thickness precision of a layer in the width direction in the multilayer film provided with the several resin layer was calculated | required.

  The present invention was devised in view of the above-described problems, and is a die that can produce a multilayer film having a layer having excellent thickness accuracy in the width direction, and a multilayer film having a layer having excellent thickness accuracy in the width direction. It aims to provide a method.

As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that the flow path portion (see FIG. 1) has a gap in a predetermined range between the die manifold and the merging portion based on the gap size of the lip portion. It has been found that the thickness accuracy of the multilayer film layer can be improved by providing the adjustment flow path portion), and the present invention has been completed.
That is, the present invention is as follows.

[1] A die for producing a multilayer film comprising a first layer and a second layer,
The die is
A first manifold that can be supplied with a molten resin for forming the first layer;
A first flow path extending downstream from the first manifold;
A second manifold that can be supplied with a molten resin for forming the second layer;
A second flow path extending downstream from the second manifold;
A merge portion where the first flow path and the second flow path merge;
A merge channel extending downstream from the merge section;
A lip portion formed downstream of the merging channel and capable of continuously discharging the molten resin for forming the first layer and the molten resin for forming the second layer merged at the merging portion;
The first channel includes an adjustment channel part,
The dice | dies whose ratio of the magnitude | size of the clearance gap of the said adjustment flow path part with respect to the magnitude | size of the clearance gap of the said lip | rip part is 3.0 or less.
[2] The die according to [1], comprising a heater capable of adjusting the temperature of the adjustment flow path section.
[3] The die according to [1] or [2], wherein a size of the gap of the adjustment channel portion is smaller than a size of a gap of the first channel immediately upstream of the adjustment channel portion.
[4] The die according to any one of [1] to [3], further including a flow path gap control unit capable of adjusting a size of the gap of the adjustment flow path unit.
[5] The first flow path includes a preland at a connection portion with the first manifold,
The size of the gap of the preland is smaller than the size of the gap of the first flow path immediately downstream of the preland,
The die according to any one of [1] to [4], wherein a size of the gap of the adjustment flow path portion is smaller than a size of the gap of the preland.
[6] The die according to any one of [1] to [5], wherein the first layer is an outermost layer of the multilayer film.
[7] The die includes a third manifold capable of supplying a molten resin for forming a third layer, and a third flow path extending downstream from the third manifold,
The third flow path joins the joining portion,
The die according to any one of [1] to [6], wherein the lip portion can continuously discharge the molten resin for forming the third layer.
[8] A method for producing a multilayer film using the die according to any one of [1] to [7], wherein a multilayer film comprising a first layer and a second layer is produced,
Supplying molten resin for forming the first layer to the first manifold;
Supplying molten resin for forming the second layer to the second manifold; and
A method for producing a multilayer film, comprising continuously discharging the molten resin for forming the first layer and the molten resin for forming the second layer from the lip portion.
[9] A method for producing a multilayer film comprising a multilayer film comprising the first layer, the second layer, and the third layer, using the die according to [7],
Supplying molten resin for forming the first layer to the first manifold;
Supplying molten resin for forming the second layer to the second manifold;
Supplying molten resin for forming the third layer to the third manifold; and
Continuously discharging the molten resin for forming the first layer, the molten resin for forming the second layer, and the molten resin for forming the third layer from the lip portion, a method for producing a multilayer film .
[10] The method according to [8] or [9], wherein the ratio of the thickness of the first layer to the thickness of the second layer is from 1/25 to 1/10.

According to the die of the present invention, it is possible to produce a multilayer film including a layer having excellent thickness accuracy in the width direction.
According to the method for producing a multilayer film of the present invention, a multilayer film having excellent layer thickness accuracy can be produced.

FIG. 1 is a cross-sectional view schematically showing a cross section of a die according to an embodiment of the present invention cut by a plane perpendicular to the width direction of the first flow path. FIG. 2 is a cross-sectional view schematically showing a cross section of a die according to an embodiment of the present invention cut along a plane indicated by a line II-II in FIG. 3 is a cross-sectional view schematically showing a cross section of a die according to an embodiment of the present invention cut along a plane indicated by line III-III in FIG. FIG. 4 is a cross-sectional view schematically showing a cross section of the adjustment bolt according to one embodiment of the present invention cut by a plane parallel to the axial direction of the adjustment bolt. FIG. 5 is a cross-sectional view schematically showing a cross section of a multilayer film manufactured using a die according to an embodiment of the present invention.

  Hereinafter, the present invention will be described in detail with reference to examples and embodiments. However, the present invention is not limited to the examples and embodiments described below, and the scope of the claims of the present invention and its equivalents are described below. Any change can be made without departing from the scope.

  In the following description, positive intrinsic birefringence means that the refractive index in the stretching direction is larger than the refractive index in the direction orthogonal thereto. In addition, negative intrinsic birefringence means that the refractive index in the stretching direction is smaller than the refractive index in the direction orthogonal thereto. The value of intrinsic birefringence can be calculated from the dielectric constant distribution.

  Further, the term “long” means that the film has a length of at least 5 times the width, preferably 10 times or more, specifically in a roll shape. It has a length that can be wound and stored or transported.

  Furthermore, the MD direction (machine direction) is a film flow direction in the production line, and is usually parallel to the longitudinal direction and the longitudinal direction of the film. Further, the TD direction (traverse direction) is a direction parallel to the film surface and perpendicular to the MD direction, and is usually parallel to the width direction and the lateral direction of the film.

[1. Embodiment]
FIG. 1 is a cross-sectional view schematically showing a cross section of a die 10 according to an embodiment of the present invention cut along a plane perpendicular to the width direction of the first flow path.
As shown in FIG. 1, a die 10 according to the first embodiment of the present invention includes a die body 100. The die body 100 can be made of, for example, die steel, stainless steel (SUS), or the like. As the die steel, for example, SKD hot die steel (thermal conductivity: about 30 W / m ° C.) or the like can be used. Moreover, as stainless steel, SUS420J2 (thermal conductivity: about 25 W / m ° C.) or the like can be used, for example.

  The die body 100 has a first supply path 110, a first manifold 120, a first flow path 130, a second supply path 210, a second manifold 220, a second flow path 230, and a third flow path through which molten resin can flow. A supply path 310, a third manifold 320, a third flow path 330, a merging portion 410, a merging flow path 420, and a lip portion 430 are formed. Among these, the first supply passage 110, the first manifold 120, and the first flow passage 130 are flow passage portions through which the molten resin for forming the first layer can flow, and the second supply passage 210, the second manifold 220, and the second flow passage. The passage 230 is a flow path portion through which the molten resin for forming the second layer can flow, and the third supply path 310, the third manifold 320, and the third flow path 330 are flow paths through which the molten resin for forming the third layer can flow. Part. In addition, the merging portion 410, the merging channel 420, and the lip portion 430 flow in the form of a layered molten resin for forming the first layer, a molten resin for forming the second layer, and a molten resin for forming the third layer. It is a flow path portion that can be obtained.

(Flow path through which molten resin for forming the first layer can flow)
The first supply path 110 is a flow path portion that opens to the outside of the die body 100. The first supply path 110 can be supplied with a molten resin for forming a first layer by a resin supply device such as an extruder. The first supply path 110 takes in the molten resin supplied from the outside of the die 10 and sends the taken molten resin to the first manifold 120.

  The first manifold 120 is a flow path portion connected downstream of the first supply path 110. The first manifold 120 can be supplied with molten resin for forming the first layer through the first supply path 110.

FIG. 2 is a cross-sectional view schematically showing a cross section of the die 10 according to an embodiment of the present invention taken along the plane indicated by the line II-II in FIG. As shown in FIG. 2, the first manifold 120 is formed so as to extend from the first supply path 110 in the flow path width direction. Thereby, the molten resin supplied to the first manifold 120 is sent to the whole of the flow path width direction. Here, the flow path width direction indicates the normal direction of the paper surface in FIG. 1 and the horizontal direction in FIG.
In addition, as shown in FIG. 2, the first manifold 120 is formed so that the position closer to the end in the flow path width direction is lowered downstream. Thereby, the molten resin supplied to the first manifold 120 can be efficiently distributed to the end in the flow path width direction.

  As shown in FIG. 1, a first flow path 130 is connected downstream of the first manifold 120 so as to extend downstream from the first manifold 120. As a result, the molten resin supplied to the first manifold 120 can flow into the first flow path 130.

A first preland 131 is formed at a connection portion of the first flow path 130 with the first manifold 120. The gap size A _P1 of the first preland 131 is smaller than the gap size A ₁₃₂ of the portion 132 immediately downstream of the first preland 131 of the first flow path 130. Here, “the size of the gap” of the flow path refers to the size in the depth direction of the flow path unless otherwise specified, and corresponds to the thickness direction of the film or layer. The flow path depth direction indicates the horizontal direction in FIG. 1, and the normal direction of the paper surface in FIG. As described above, since the flow passage cross-sectional area is small in the first preland 131, a large resistance is applied to the molten resin flowing through the first preland 131.

  As shown in FIG. 2, the first pre-land 131 protrudes upstream with the central portion of the first flow passage 130 in the flow passage width direction as a top portion. Therefore, the molten resin flowing through the first preland 131 circulates in the first preland 131 at a long distance in the central portion in the flow path width direction, and in the first preland 131 as the position is closer to the end portion in the flow path width direction. It comes to circulate in a short distance.

  Since the central portion in the width direction of the first flow path 130 is directly below the first supply path 110, the pressure of the supplied molten resin is large. Moreover, since the width direction edge part of the 1st flow path 130 is far from the 1st supply path 110, the pressure of the molten resin supplied is small. Therefore, since the molten resin tends to flow in the center portion in the width direction of the first flow path 130, the center portion in the width direction tends to be thick in the first layer of the obtained multilayer film when no countermeasure is taken. There is. On the other hand, by providing the first preland 131 as described above, a large resistance is applied to the molten resin flowing in the center portion in the width direction of the first preland 131 by a long distance, and the end portion in the width direction of the first preland 131 is obtained. A large resistance can be applied to the molten resin flowing through the tube only for a short distance. Thereby, the amount of molten resin flowing into the first flow path 130 from the first manifold 120 can be made uniform in the flow path width direction, and the thickness accuracy of the first layer can be improved in the width direction in the obtained multilayer film. It has become.

As shown in FIG. 1, the first flow path 130 includes a first adjustment flow path portion 133. The first adjustment channel portion 133 is a portion having a gap in a predetermined range in the first channel 130. The specific gap size A _C1 of the first adjustment flow path portion 133 is a ratio A _C1 / A of the gap size A _C1 of the first adjustment flow path portion 133 to the gap size A _L of the lip portion 430. _L can be set to fall within a predetermined range. Specific range of the ratio _A C1 / _{A L} of the usually 3.0 or less, preferably 2.0 or less. By providing such a first adjustment channel portion 133 downstream from the first manifold 120 and upstream from the merge portion 410, the thickness accuracy of the first layer can be increased in the width direction in the resulting multilayer film. it can. Also There is no lower limit value of the ratio _A C1 / _{A L,} and preferably 1.0 or more.

The reason why the thickness accuracy of the first layer of the multilayer film can be improved by keeping the size A _C1 of the gap of the first adjustment flow path portion 133 within the above range is not clear, but according to the study of the present inventors. The following is inferred. That is, generally, in which position in the TD direction of the lip portion the molten resin flows in a large amount and in which position the molten resin flows in a small amount, the molten resin at all positions in the TD direction from the supply to the manifold to the discharge from the lip portion. The pressure loss is determined to be constant. In general, the pressure loss related to the die equipment strongly depends on the flow path gap. For this reason, in order to increase the adjustment amount in the first adjustment channel portion 133, it is preferable to narrow the gap of the first adjustment channel portion 133. Usually, in the die design, the gap of the flow path is the narrowest at the lip portion. Therefore, by setting A _C1 / _AL to 3 or less, the influence of the first adjustment flow path part 133 in the entire die 10 is large. Thus, it can be inferred that the thickness accuracy of the first layer can be improved.

Further, in the present embodiment, the first adjustment channel portion 133 is a portion where the size of the gap is partially reduced in the first channel 130. Therefore, the gap size A _C1 of the first adjustment channel portion 133 is smaller than the gap size A ₁₃₄ of the portion 134 immediately upstream of the first adjustment channel portion 133 of the first channel 130. As a result, the first adjustment flow path portion 133 can function as a throttle whose flow path cross-sectional area is partially reduced in the first flow path 130. For this reason, the pressure of the molten resin in the portion 135 downstream of the first adjustment flow path portion 133 of the first flow path 130 can be stabilized by the action of the restriction. Therefore, in the obtained multilayer film, the thickness accuracy of the first layer can be further increased in the width direction.

Moreover, the gap size A _C1 of the first adjustment channel 133 is preferably smaller than the gap size A _P1 of the first Purirando 131. Thereby, in the obtained multilayer film, the thickness accuracy of the first layer can be further increased in the width direction.

  The first flow path 130 is connected to the merging portion 410 at the downstream end thereof. Therefore, the molten resin that has flowed through the first flow path 130 is sent to the merge portion 410.

(Flow path through which molten resin for forming the second layer can flow)
The second supply path 210 is a flow path portion that opens to the outside of the die body 100. The second supply path 210 can be supplied with a molten resin for forming a second layer by a resin supply device such as an extruder. The second supply path 210 takes in the molten resin supplied from the outside of the die 10 and sends the taken molten resin to the second manifold 220.

  The second manifold 220 is a flow path portion connected downstream of the second supply path 210. The second manifold 220 can be supplied with molten resin for forming the second layer through the second supply path 210.

  FIG. 3 is a cross-sectional view schematically showing a cross section of the die 10 according to an embodiment of the present invention taken along the plane indicated by the line III-III in FIG. As shown in FIG. 3, like the first manifold 120, the second manifold 220 is formed wider than the second supply path 210 in the flow path width direction. In addition, the second manifold 220 is formed so that the position closer to the end in the flow path width direction is lowered downstream. Thereby, the molten resin supplied to the second manifold 220 is sent to the whole in the flow path width direction and can be efficiently distributed to the end in the flow path width direction.

  As shown in FIG. 1, a second flow path 230 is connected downstream of the second manifold 220 so as to extend downstream from the second manifold 220. Thereby, the molten resin supplied to the second manifold 220 can flow into the second flow path 230.

A second preland 231 is formed at a connection portion of the second flow path 230 with the second manifold 220. Gap size _{A P2} of the second Purirando 231 is smaller than the gap size _{A 232} immediately downstream of the portion 232 of the second Purirando 231 of the second flow path 230. As shown in FIG. 3, the second pre-land 231 projects upstream with the central portion of the second flow passage 230 in the flow passage width direction as the top. For this reason, like the first preland 131, the second preland 231 can improve the thickness accuracy of the second layer in the width direction in the obtained multilayer film.

  The second flow path 230 is connected to the merge part 410 at the downstream end thereof. Therefore, the molten resin that has flowed through the second flow path 230 is sent to the merging portion 410.

(Flow path through which molten resin for forming the third layer can flow)
The third supply path 310 is a flow path portion that opens to the outside of the die body 100. The third supply path 310 can be supplied with a molten resin for forming a third layer by a resin supply device such as an extruder. The third supply path 310 takes in the molten resin supplied from the outside of the die 10 and sends the taken molten resin to the third manifold 320.

  The third manifold 320 is a flow path portion connected downstream of the third supply path 310. The third manifold 320 can be supplied with molten resin for forming the third layer through the third supply path 310.

  Similar to the first manifold 120 and the second manifold 220, the third manifold 320 is formed to extend from the third supply path 310 in the flow path width direction. Further, the third manifold 320 is formed so as to be lowered downstream as the position is closer to the end in the flow path width direction. Thereby, the molten resin supplied to the third manifold 320 is sent to the whole in the flow path width direction and can be efficiently distributed to the end in the flow path width direction.

  As shown in FIG. 1, a third flow path 330 is connected downstream of the third manifold 320 so as to extend downstream from the third manifold 320. As a result, the molten resin supplied to the third manifold 320 can flow into the third flow path 330.

A third preland 331 is formed at a connection portion of the third flow path 330 with the third manifold 320. Size _{A P3} gap of the third Purirando 331 is smaller than the gap size _{A 332} immediately downstream of the portion 332 of the third Purirando 331 of third flow channel 330. Further, the third preland 331 protrudes upstream with the central portion of the third channel 330 in the channel width direction as the top. For this reason, similarly to the first preland 131 and the second preland 231, the third preland 331 can improve the thickness accuracy of the third layer in the width direction in the obtained multilayer film.

The third flow path 330 includes a third adjustment flow path portion 333. The third adjustment channel portion 333 is a portion having a gap in a predetermined range in the third channel 330. A specific gap size A _C3 of the third adjustment flow path portion 333 is set to fall within a range defined in the same manner as the gap size A _{C1 of} the first adjustment flow path portion 133. By providing such a third adjustment flow path portion 333 downstream from the third manifold 320 and upstream from the merge portion 410, the thickness accuracy of the third layer can be increased in the width direction in the obtained multilayer film. it can.

The third adjustment flow path portion 333 is a portion where the size of the gap is partially reduced in the third flow path 330, similarly to the first adjustment flow path portion 133. Therefore, the gap size A _C3 of the third adjustment channel portion 333 is smaller than the gap size A ₃₃₄ of the portion 334 immediately upstream of the third adjustment channel portion 333 of the third channel 330. Thereby, in the obtained multilayer film, the thickness accuracy of the third layer can be further increased in the width direction.

Further, the gap size A _C3 of the third adjustment channel 333 is preferably smaller than the gap size A _P3 of the third Purirando 331. Thereby, in the obtained multilayer film, the thickness accuracy of the third layer can be further increased in the width direction.

  The third flow path 330 is connected to the merge part 410 at the downstream end thereof. Therefore, the molten resin that has flowed through the third flow path 330 is sent to the merging portion 410.

(Flow path through which the molten resin for forming the first to third layers can flow)
As shown in FIG. 1, the first flow path 130, the second flow path 230, and the third flow path 330 described above merge at a merge portion 410. Further, a merging channel 420 is connected downstream of the merging portion 410 so as to extend downstream from the merging portion 410. Thereby, the molten resin for forming the first layer that has flowed through the first flow path 130, the molten resin for forming the second layer that has flowed through the second flow path 230, and the resin for forming the third layer that has flowed through the third flow path 330 These molten resins are merged at the merge section 410, and both are layered to flow through the merge flow path 420. Moreover, in this embodiment, as shown in FIG. 1, the 1st flow path 130, the 2nd flow path 230, and the 3rd flow path 330 are provided along with this order from the right side in the figure. Therefore, when flowing through the merge flow path 420, the molten resin for forming the first layer, the molten resin for forming the second layer, and the molten resin for forming the third layer are arranged in this order in the flow path depth direction. It flows in the state.

  A lip portion 430 is formed downstream of the merge channel 420. The lip portion 430 opens to the outside of the die body 100 at the downstream end thereof. As a result, the molten resin for forming the first layer, the molten resin for forming the second layer, and the molten resin for forming the third layer that merged at the merging portion 410 can be continuously discharged from the lip portion 430. It has become.

Size A _L of the gap between the lip portion 430 is set smaller than the confluent channel 420 provided upstream of the lip portion 430. Size A specific range _L of the gap between the lip 430 can be arbitrarily set according to the thickness of the multilayer film to be produced.

(Adjustment mechanism for the size of the gap in the adjustment channel)
The die 10 according to the present embodiment includes a flow path gap control unit 500 that can adjust the size of the gap of the first adjustment flow path unit 133. The flow path gap control unit 500 includes a choke bar 510 and an adjustment bolt 520.

  The choke bar 510 is a bar-like member that is movably provided. The choke bar 510 has a substantially trapezoidal cross section cut by a plane perpendicular to the channel width direction. In addition, the choke bar 510 continuously extends from one end of the first adjustment channel portion 133 in the channel width direction to the other end. Further, the end portion of the choke bar 510 on the flow path side faces the first adjustment flow path portion 133 so that the choke bar 510 can function as a movable weir. Thereby, by adjusting the position of the choke bar 510, the size of the gap of the first adjustment channel portion 133 can be adjusted.

  The adjustment bolt 520 is provided on the opposite side of the choke bar 510 from the first adjustment flow path portion 133. A plurality of adjustment bolts 520 are provided at predetermined intervals in the longitudinal direction of the choke bar 510 (that is, in the flow channel width direction of the first adjustment flow channel portion 133). The tip of each adjustment bolt 520 is supported by the choke bar 510 so as to freely advance and retract. Accordingly, the choke bar 510 can be moved by moving the adjustment bolt 520 in the axial direction, and the size of the gap of the first adjustment flow path portion 133 can be adjusted.

  Specifically, the size of the gap of the first adjustment channel portion 133 can be adjusted by the following operation. For example, when it is desired to reduce the size of a gap in a portion of the first adjustment flow path portion 133 in the width direction, the adjustment bolt 520 corresponding to the portion is advanced and the choke bar 510 is pushed. Further, when it is desired to increase the size of a gap in a certain portion in the width direction of the first adjustment flow path portion 133, the adjustment bolt 520 corresponding to that portion is retracted and the choke bar 510 is pulled. By performing this operation for each adjustment bolt 520, the size of the gap of the first adjustment channel portion 133 can be adjusted for each position in the channel width direction, and as a result, the first adjustment channel in the channel width direction. The distribution of the size of the gaps of the part 133 can be adjusted. Thereby, it is possible to adjust the flow rate of the molten resin flowing through the first adjustment channel portion 133 for each position in the channel width direction, and to suppress the thickness unevenness of the first layer in the width direction.

  The interval between the adjustment bolts 520 is preferably 40 mm or more and 50 mm or less. By setting the distance between the adjustment bolts 520 to be equal to or greater than the lower limit value of the above range, it is possible to suppress the strength reduction of the choke bar 510 due to the bolt holes formed in the choke bar 510. Further, since the number of adjustment bolts 520 can be increased by setting the upper limit value or less, the choke bar 510 can be partially moved in many portions. The size can be adjusted precisely.

FIG. 4 is a cross-sectional view schematically showing a cross section obtained by cutting the adjustment bolt 520 according to the embodiment of the present invention along a plane parallel to the axial direction of the adjustment bolt 520.
As shown in FIG. 4, the outer diameter D ₅₂₀ of the adjusting bolt 520 is preferably 10 mm or more, more preferably 14 mm or more, preferably 30 mm or less, more preferably 24 mm or less. The outer shape D ₅₂₀ of the adjustment bolt 520 by more than the lower limit of the range, can be increased bolt strength. Moreover, the intensity | strength of the chalk bar 510 with which the adjustment bolt 520 is screwed can be made high by making it below an upper limit.

  Each adjustment bolt 520 includes a rod-shaped electric heater 530 as a heater that can adjust the temperature of the first adjustment flow path portion 133. The electric heater 530 is embedded in the shaft portion of the adjustment bolt 520. Further, the electric heater 530 can adjust the amount of heat generated by the electric heater 530 by energizing or interrupting the electric heater. Thereby, the choke bar 510 can be heated at a desired temperature. Therefore, the choke bar 510 can be adjusted to a desired temperature for each position in the longitudinal direction, and as a result, the temperature distribution can be precisely adjusted in the flow path width direction of the first adjustment flow path portion 133.

  Since the temperature distribution can be precisely adjusted in the flow path width direction of the first adjustment flow path portion 133 in this way, in the die 10, the temperature of the molten resin flowing through the first adjustment flow path portion 133 is changed for each position in the flow width direction. Can be adjusted precisely. Here, the resin viscosity generally changes as the temperature changes. Further, the molten resin tends to flow through the flow path when the viscosity is low, and tends to be difficult to flow through the flow path when the viscosity is high. Therefore, by performing the temperature adjustment as described above, the flow rate of the molten resin flowing through the first adjustment channel portion 133 can be adjusted for each position in the channel width direction, so that the thickness of the first layer of the multilayer film can be further increased. It is possible to adjust precisely.

  In particular, since the size of the gap of the first adjustment channel portion 133 is small, the temperature adjustment by the electric heater 530 can be performed particularly precisely. Therefore, the thickness accuracy of the first layer of the multilayer film can be remarkably increased by adjusting the temperature in the first adjustment channel portion 133 in the first channel 130 in particular.

  Furthermore, since the size of the gap of the first adjustment flow path portion 133 is small, the temperature of the molten resin in the first adjustment flow path portion 133 can be adjusted precisely and in a wide temperature range by the electric heater 530. Thus, since the temperature of molten resin can be adjusted precisely and within a wide temperature range, the thickness of the first layer can be adjusted precisely and within a wide thickness range. Therefore, by adjusting the temperature in the first adjustment flow path portion 133, the thickness of the first layer can be adjusted precisely in a particularly wide thickness range.

The diameter D ₅₃₀ of the electric heater 530 is preferably 75% or less, more preferably 50% or less, with respect to the outer diameter D ₅₂₀ of the adjusting bolt 520. Thereby, the strength of the adjustment bolt 520 can be increased. Further, There is no limitation on the lower limit of the diameter _{D 530} of the electric heater 530, typically is at least 30% of the outer diameter _{D 520} of the adjustment bolt 520.

  Further, as shown in FIG. 1, the die 10 includes a channel gap control unit 600 that can adjust the size of the gap of the third adjustment channel unit 333. Similar to the channel clearance control unit 500, the channel clearance control unit 600 includes a choke bar 610 and an adjustment bolt 620. Thereby, in the same manner as the first adjustment channel portion 133, the size of the gap of the third adjustment channel portion 333 can be adjusted for each position in the channel width direction. It is possible to suppress thickness unevenness.

  Each adjustment bolt 620 includes a rod-shaped electric heater 630 similar to the electric heater 530 as a heater that can adjust the temperature of the third adjustment flow path portion 333. As a result, the choke bar 610 can be adjusted to a desired temperature for each position in the longitudinal direction, and as a result, the temperature distribution can be precisely adjusted in the flow passage width direction of the third adjustment flow passage portion 333. Therefore, since the flow rate of the molten resin flowing through the third adjustment channel portion 333 can be adjusted for each position in the channel width direction, the thickness of the third layer of the multilayer film can be adjusted more precisely. .

  Furthermore, as shown in FIG. 1, the die 10 includes a lip adjustment bolt 700 as a flow path gap control unit that can adjust the size of the gap of the lip part 430. The lip adjustment bolt 700 is movably provided. The tip of the lip adjusting bolt 700 is disposed in the vicinity of the lip portion 430. Further, a plurality of lip adjustment bolts 700 are provided at predetermined intervals in the flow path width direction of the lip portion 430. Accordingly, by moving the lip adjusting bolt 700, the size of the gap of the lip portion 430 can be adjusted for each position in the flow path width direction, and consequently the distribution of the size of the gap of the lip portion 430 in the flow path width direction can be adjusted. It can be adjusted.

  Thus, by adjusting the distribution of the size of the gap between the lip portions 430, the resistance of the molten resin flowing through the lip portion 430 can be adjusted for each position in the flow path width direction. Therefore, in the lip portion 430, by adjusting the distribution of the size of the gap, the flow rate of the molten resin can be adjusted for each position, so the thickness of the molten resin discharged from the lip portion 430 can be adjusted, and consequently The total thickness of the multilayer film can be adjusted.

(Manufacturing method of multilayer film)
The die 10 according to the embodiment of the present invention is configured as described above. When manufacturing a multilayer film using this die | dye 10, the manufacturing method by a melt extrusion method can be implemented as follows.

  When trying to produce a multilayer film, using an extruder (not shown), the molten resin for forming the first layer, the molten resin for forming the second layer, and the molten resin for forming the third layer, The first manifold 120, the second manifold 220 and the third manifold 320 are supplied via the first supply path 110, the second supply path 210 and the third supply path 310.

The molten resin supplied to the first manifold 120 is expanded in the flow path width direction in the first manifold 120 and then sent to the first flow path 130. The molten resin sent to the first flow path 130 passes through the first flow path 130 including the first preland 131 and the first adjustment flow path portion 133 and is sent to the merge portion 410.
The molten resin supplied to the second manifold 220 is expanded in the flow path width direction in the second manifold 220 and then sent to the second flow path 230. The molten resin sent to the second flow path 230 passes through the second flow path 230 including the second preland 231 and is sent to the junction 410.
Furthermore, the molten resin supplied to the third manifold 320 is expanded in the flow path width direction in the third manifold 320 and then sent to the third flow path 330. The molten resin sent to the third flow path 330 passes through the third flow path 330 including the third pre-land 331 and the third adjustment flow path portion 333 and is sent to the merge portion 410.

The molten resin for forming the first layer, the molten resin for forming the second layer, and the molten resin for forming the third layer that are sent to the merging portion 410 merge at the merging portion 410. The joined molten resin is superposed in layers. Thereafter, these molten resins flow through the merge channel 420 while maintaining the layer state.
The molten resin that has flowed through the merging channel 420 is continuously discharged from the lip portion 430 while maintaining the layer state.
Then, the discharged molten resin is cooled and cured to obtain a multilayer film.

In the manufacturing method described above, the adjustment bolts 520 and 620 allow the gap size A _{C1 of} the first adjustment channel portion 133 and the gap size A _C3 of the third adjustment channel portion 333 to fall within the above ranges. Adjust as follows. Thereby, in the multilayer film manufactured, the thickness precision of a 1st layer and a 3rd layer can be improved in the width direction.

  Moreover, in the manufacturing method mentioned above, the magnitude | size of the clearance gap in each point of the width direction of the 1st adjustment flow path part 133 and the 3rd adjustment flow path part 333 is adjusted with the some adjustment bolt 520 and 620. FIG. Specifically, in the multilayer film to be manufactured, adjustment is performed so that thickness unevenness in the width direction of the first layer and the third layer is reduced. Thereby, the thickness accuracy of the first layer and the third layer can be further increased in the width direction.

  Furthermore, in the manufacturing method described above, the electric heaters 530 and 630 adjust the temperature at each point in the width direction of the first adjustment channel portion 133 and the third adjustment channel portion 333. Thereby, the thickness precision of the 1st layer and 3rd layer of a multilayer film can be raised especially effectively in the width direction.

  At this time, the rough adjustment of the thicknesses of the first layer and the third layer is preferably performed by adjusting the size of the gap between the first adjustment channel portion 133 and the third adjustment channel portion 333. Moreover, it is preferable to perform fine adjustment of the thicknesses of the first layer and the third layer by adjusting the temperatures of the first adjustment channel portion 133 and the third adjustment channel portion 333. This is because precise adjustment is easy for precise adjustment of the gap between the channels, whereas precise adjustment is easy.

  In the manufacturing method described above, the size of the gap at each point in the width direction of the lip portion 430 is adjusted by the lip adjusting bolt 700. Specifically, adjustment is performed so that the total thickness of the multilayer film to be manufactured becomes a desired size. Thereby, the multilayer film of desired thickness can be obtained.

FIG. 5 is a cross-sectional view schematically showing a cross section of a multilayer film 800 manufactured using the die 10 according to an embodiment of the present invention.
As shown in FIG. 5, the multilayer film 800 provided with the 1st layer 810, the 2nd layer 820, and the 3rd layer 830 which were formed with resin with the manufacturing method mentioned above is obtained. In this multilayer film 800, as described above, the thickness accuracy of the first layer 810 and the third layer 830 which are the outermost layers is high. Further, since the thickness accuracy of the first layer 810 and the third layer 830 is high, the thickness unevenness caused by the thickness unevenness of the first layer 810 and the third layer 830 is suppressed in the second layer 820. The thickness accuracy of the second layer 820 sandwiched between the first layer 810 and the third layer 830 is also high. Therefore, according to the above-described embodiment, the multilayer film 800 excellent in thickness accuracy can be obtained in any of the first layer 810, the second layer 820, and the third layer 830.

  Moreover, in the multilayer film 800 mentioned above, since the thickness precision of the 1st layer 810, the 2nd layer 820, and the 3rd layer 830 which are included in the multilayer film 800 can be improved, the 1st layer 810, The thickness unevenness in the width direction of the second layer 820 and the third layer 830 can be reduced. Specifically, the thickness unevenness of at least one layer (first layer 810, second layer 820, or third layer 830) included in the multilayer film 800 is preferably ± 5 with respect to the average thickness of the layer. %, More preferably within ± 3%, particularly preferably within ± 1%. Here, “thickness unevenness” is obtained by dividing the difference between the maximum value and the minimum value of the thickness of the layer in the region of the central portion 75% excluding the end in the width direction of the film by the average thickness of the layer. Value.

In general, the thinner the layer, the more difficult it is to increase the thickness accuracy. Especially, in the multilayer film provided with the several layer from which thickness differs, when the difference of the thickness of a layer is large, it is especially difficult to raise the thickness precision of a layer with small thickness. Therefore, from the viewpoint of effectively utilizing the above-described advantages, the die 10 according to the present embodiment is preferably used for manufacturing a multilayer film including at least two layers having greatly different thicknesses. For example, in the multilayer film 800 described above, when the thickness T ₈₁₀ of the first layer 810 and the thickness T 830 of the third layer ₈₃₀ are small and the thickness T ₈₂₀ of the second layer ₈₂₀ is large, the ratio T _{810 of} these thicknesses. At least one of / T ₈₂₀ and ratio T ₈₃₀ / T ₈₂₀ is preferably in the range of 1/25 or more and 1/10 or less.

  The total thickness of the multilayer film 800 can be arbitrarily set according to the use of the multilayer film 800. The total thickness range of the specific multilayer film 800 is preferably 10 μm or more, more preferably 20 μm or more, particularly preferably 30 μm or more, preferably 500 μm or less, more preferably 400 μm or less, particularly preferably 300 μm or less. is there.

  The total light transmittance of the multilayer film 800 is preferably 85% or more. Here, the light transmittance can be measured using a spectrophotometer (manufactured by JASCO Corporation, ultraviolet-visible near-infrared spectrophotometer “V-570”) in accordance with JIS K0115.

  The haze of the multilayer film 800 is preferably 5% or less, more preferably 3% or less, and particularly preferably 1% or less. Here, according to JIS K7361-1997, haze can measure five places using the Nippon Denshoku Industries Co., Ltd. "turbidimeter NDH-300A", and can employ | adopt the average value calculated | required from it.

[2. Modified example]
The present invention is not limited to the above-described embodiment, and may be further modified.
For example, an electric heater provided as a heater along the first supply path 110, the first manifold 120, and the first flow path 130 inside the die body 100; the second supply path 210, the second manifold 220, and the second flow An electric heater provided along the path 230; an electric heater provided along the third supply path 310, the third manifold 320, and the third flow path 330 may be provided. The shape of these electric heaters is not particularly limited, and examples thereof include a plate shape and a columnar shape. When a cylindrical electric heater is used, the diameter of the electric heater is preferably 15 mm to 25 mm. Moreover, when using a plate-shaped electric heater, the thickness of the electric heater is preferably 15 mm to 25 mm.

  Further, for example, in addition to the electric heater described above, an electric heater that can adjust the temperature of the entire die body 100 may be provided on the outer periphery of the die body 100.

  Further, for example, an electric heater may be provided in the lip adjustment bolt 700 in the same manner as the electric heater 530. Thereby, the temperature of the molten resin in the lip part 430 can be adjusted. Further, by adjusting the temperature of the lip adjusting bolt 700 with an electric heater, the lip adjusting bolt 700 may be expanded and contracted, and the size of the gap of the lip portion 430 may be adjusted by this expansion and contraction.

  For example, a heater other than an electric heater may be used as the heater. Examples of such a heater include a heat transfer device using oil circulation.

  In addition, for example, surface treatment such as H—Cr plating may be performed on the surfaces of the first flow path 130, the second flow path 230, the third flow path 330, the merge portion 410, and the merge flow path 420. By applying H—Cr plating, the lip portion 430 can be made smooth when the shape of the lip portion 430 is formed by polishing. Therefore, die line can be effectively prevented. Moreover, adhesion of the molten resin to the surfaces of the first flow path 130, the second flow path 230, the third flow path 330, the merging portion 410, and the merging flow path 420 can be suppressed. Thereby, reduction of die line and further reduction of thickness unevenness can be expected. Here, the die line refers to irregularly formed linear recesses and linear projections extending in the MD direction of the manufactured multilayer film.

  Further, for example, the surface of the lip portion 430 may be subjected to a surface treatment such as a ceramic coat. By applying the ceramic coat, adhesion of the molten resin to the surface of the lip portion 430 can be suppressed. Thereby, reduction of die line and further reduction of thickness unevenness can be expected.

  Further, for example, two or more first adjustment flow path portions 133 may be provided in the first flow path 130, and two or more third adjustment flow path portions 333 may be provided in the third flow path 330.

  Further, for example, an adjustment channel portion may be provided in the second channel 230 in the same manner as the first adjustment channel portion 133 and the third adjustment channel portion 333.

  Moreover, although the dice | dies 10 for manufacture of the multilayer film which has three layers were illustrated and demonstrated in embodiment mentioned above, you may use the dice | dies concerning this invention for the use of the multilayer film which has two layers. You may use for the manufacture use of a multilayer film provided with the layer of 4 layers or more.

  Moreover, you may give an arbitrary process further to the multilayer film mentioned above. For example, you may perform the process of extending | stretching a multilayer film. Since the retardation can be expressed in the multilayer film by performing the stretching treatment, the multilayer film can be used as a retardation film. In this case, as a stretching method, for example, a uniaxial stretching method such as a method of uniaxial stretching in the longitudinal direction using a difference in peripheral speed of a roll, a method of uniaxial stretching in a transverse direction using a tenter stretching machine; Examples thereof include a biaxial stretching method such as a stretching method and a sequential biaxial stretching method; a method of stretching obliquely using a tenter stretching machine. Here, the diagonal direction represents a direction not parallel to both the vertical direction and the horizontal direction.

  Moreover, for example, a step of providing an arbitrary layer on the surface of the multilayer film may be performed. Examples of the optional layer include a mat layer, a hard coat layer, an antireflection layer, and an antifouling layer.

[3. Description of resin]
Any of the layers included in the multilayer film described above is formed of a resin. As such a resin, a thermoplastic resin is usually used.
As the thermoplastic resin, a resin having a positive intrinsic birefringence may be used, a resin having a negative intrinsic birefringence may be used, and a resin having a positive intrinsic birefringence and a resin having a negative intrinsic birefringence are combined. May be used. Among them, from the viewpoint of obtaining various optical characteristics by combining a plurality of layers, one of the first layer and the second layer of the multilayer film is formed of a resin having a positive intrinsic birefringence, and the other has a negative intrinsic birefringence. It is preferable to form with resin. In general, a resin having a positive intrinsic birefringence has a higher mechanical strength than a resin having a negative intrinsic birefringence. Therefore, a thin layer of the first layer and the second layer has a positive intrinsic birefringence. It is preferable to form with resin.

  The resin having a positive intrinsic birefringence usually contains a polymer having a positive intrinsic birefringence. Examples of this polymer include olefin polymers such as polyethylene and polypropylene; polyester polymers such as polyethylene terephthalate and polybutylene terephthalate; polyarylene sulfide polymers such as polyphenylene sulfide; polyvinyl alcohol polymers, polycarbonate polymers, poly Examples include arylate polymers, cellulose ester polymers, polyethersulfone polymers, polysulfone polymers, polyallyl sulfone polymers, polyvinyl chloride polymers, norbornene polymers, and rod-like liquid crystal polymers. These polymers may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. The polymer may be a homopolymer or a copolymer.

  Among these, a polycarbonate polymer is preferable from the viewpoints of retardation development, low-temperature stretchability, and adhesion between a resin layer having positive intrinsic birefringence and other layers. As the polycarbonate polymer, any polymer having a structural unit containing a carbonate bond (—O—C (═O) —O—) can be used. Examples of the polycarbonate polymer include bisphenol A polycarbonate, branched bisphenol A polycarbonate, o, o, o ', o'-tetramethylbisphenol A polycarbonate, and the like.

  The resin having a negative intrinsic birefringence usually includes a polymer having a negative intrinsic birefringence. Examples of this polymer include an aromatic vinyl polymer including a homopolymer of styrene or a styrene derivative, and a copolymer of styrene or a styrene derivative and any other monomer; a polyacrylonitrile polymer; a polymethyl A methacrylate polymer; or a multi-component copolymer thereof. Moreover, as said arbitrary monomer which can be copolymerized with styrene or a styrene derivative, acrylonitrile, maleic anhydride, methyl methacrylate, and butadiene are mentioned as a preferable thing, for example. Moreover, these polymers may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Among these, an aromatic vinyl polymer is preferable from the viewpoint of high retardation development, and a copolymer of styrene or a styrene derivative and maleic anhydride is particularly preferable from the viewpoint of high heat resistance. In this case, the amount of the structural unit (maleic anhydride unit) having a structure formed by polymerizing maleic anhydride is preferably 5 parts by weight or more, more preferably 100 parts by weight of the aromatic vinyl polymer. It is 10 parts by weight or more, particularly preferably 15 parts by weight or more, preferably 30 parts by weight or less, more preferably 28 parts by weight or less, and particularly preferably 26 parts by weight or less.

  The resin may contain a compounding agent. Examples of compounding agents include: lubricants; layered crystal compounds; inorganic fine particles; antioxidants, heat stabilizers, light stabilizers, weathering stabilizers, UV absorbers, near infrared absorbers, and other stabilizers; plasticizers; dyes and And coloring agents such as pigments; antistatic agents; and the like. Among these, a lubricant and an ultraviolet absorber are preferable because they can improve flexibility and weather resistance. Moreover, a compounding agent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Examples of the lubricant include inorganic particles such as silicon dioxide, titanium dioxide, magnesium oxide, calcium carbonate, magnesium carbonate, barium sulfate, strontium sulfate; polymethyl acrylate, polymethyl methacrylate, polyacrylonitrile, polystyrene, cellulose acetate, cellulose acetate pro Organic particles such as pionate; Among these, organic particles are preferable as the lubricant.

  Examples of ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone ultraviolet absorbers, benzotriazole ultraviolet absorbers, acrylonitrile ultraviolet absorbers, triazine compounds, nickel complex compounds. And inorganic powders. Specific examples of suitable UV absorbers include 2,2′-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) ) Phenol, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone and the like. Particularly suitable is 2,2'-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol).

  The amount of the compounding agent can be appropriately determined as long as the effects of the present invention are not significantly impaired. For example, the amount of the compounding agent may be within a range in which the total light transmittance in terms of 1 mm thickness of the multilayer film can maintain 80% or more.

  The weight average molecular weight of the resin is preferably adjusted to a range in which the melt extrusion method can be performed with the resin.

  The glass transition temperature Tg of the resin is preferably 80 ° C. or higher, more preferably 90 ° C. or higher, still more preferably 100 ° C. or higher, particularly preferably 110 ° C. or higher, and particularly preferably 120 ° C. or higher. When the glass transition temperature Tg of the resin is thus high, the orientation relaxation of the resin can be reduced when the multilayer film is stretched. Moreover, although there is no restriction | limiting in particular in the upper limit of glass transition temperature Tg, Usually, it is 200 degrees C or less.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof.
In the following description, “%” and “part” representing amounts are based on weight unless otherwise specified. In addition, the operations described below were performed under normal temperature and normal pressure conditions unless otherwise specified.

[Evaluation method]
(Measuring method of average thickness of layers contained in multilayer film)
The multilayer film was placed in a flat state, and the thickness of each layer included in the multilayer film was measured by scanning an interference film thickness meter (FE-2900 manufactured by Otsuka Electronics Co., Ltd.) in the TD direction. The measurement interval in the TD direction was 5 mm. And the average value of the thickness of the layer in each measurement point was made into the average thickness of the layer.

(Evaluation method of layer thickness accuracy)
The maximum value and the minimum value were selected from the thicknesses measured at the plurality of measurement points of each layer as described above, and the difference between the maximum value and the minimum value was calculated. The difference between the obtained maximum value and the minimum value was divided by the average thickness of the layer to determine the thickness unevenness in the width direction. The smaller the thickness unevenness, the better the thickness accuracy of the layer.

(Evaluation method of thickness range adjustable by temperature adjustment)
Each implementation except that the temperature of the first adjustment flow path part and the third adjustment flow path part is increased by 30 ° C. in an area of 30% of the central part with respect to the entire area in the TD direction using an electric heater embedded in the adjustment bolt. The same operations as in Examples and Comparative Examples were performed.
The average thickness of the layers contained in the multilayer film thus obtained was measured. From the obtained value, the increase rate I of the average thickness in the region of 30% of the central part due to the temperature of the first adjustment channel part and the third adjustment channel part being increased by 30 ° C. was calculated by the following formula. Here, T ₀ represents the average thickness of the layers in the region of 30% of the central portion in each example and comparative example. Further, T ₃₀ represents an average thickness of each of the Examples and also Comparative Example in the case where the temperature of the first adjustment channel portion and the third adjustment channel unit higher 30 ° C., the layers at the center 30% of the area .
I = (T ₀ −T ₃₀ ) / T ₀ × 100 (%)

  The larger the increase rate I of the average thickness, the larger the thickness of the layer can be changed by adjusting the temperature. That is, the larger the average thickness increase rate I is, the wider the range can be adjusted by adjusting the temperature.

[Example 1]
As the thermoplastic resin for forming the first layer and the thermoplastic resin for forming the third layer, pellets of polycarbonate resin (“Wonderlite PC-115” manufactured by Chi Mei, glass transition temperature 140 ° C.) were prepared.
Further, as the thermoplastic resin for forming the second layer, pellets of styrene-maleic anhydride copolymer resin (Nova Chemicals “Dylark D332”, glass transition temperature 135 ° C.) and polymethyl methacrylate resin (Asahi Kasei “Dell”) are used. Pellets prepared by mixing pellets of “pet 80NH” and glass transition temperature 110 ° C. at a weight ratio of 85:15 were prepared.

  A film forming apparatus for three-layer / three-layer coextrusion molding was prepared. This film forming apparatus is a type of apparatus that forms a film composed of three layers with resin extruded by three different extruders. In this film molding apparatus, a die having the same configuration as that described in the above-described embodiment was attached as a die. The surface roughness Ra of the lip portion of this die was 0.1 μm.

For formation of the first layer, the polycarbonate resin pellets were put into a first single screw extruder equipped with a double flight type screw and melted.
In addition, for forming the second layer, the pellet obtained by mixing the pellet of the styrene-maleic anhydride copolymer resin and the pellet of the polymethyl methacrylate resin is put into a second single-screw extruder equipped with a double flight type screw. It was charged and melted.
Further, for forming the third layer, the pellets of the polycarbonate resin were put into a third single screw extruder equipped with a double flight type screw and melted.

  The melted polycarbonate resin for forming the first layer at 260 ° C. was supplied to the first manifold of the die through a leaf filter-shaped polymer filter having an opening of 10 μm. Further, a molten mixed resin of styrene-maleic anhydride copolymer resin and polymethyl methacrylate resin at 260 ° C. was supplied to the second manifold of the die through a leaf disk-shaped polymer filter having an opening of 10 μm. Further, the molten polycarbonate resin for forming the third layer at 260 ° C. was supplied to the third manifold of the die through the leaf disk-shaped polymer filter having an opening of 10 μm.

A mixed resin of a styrene-maleic anhydride copolymer resin and a polymethyl methacrylate resin and a polycarbonate resin were simultaneously extruded from the aforementioned die at 260 ° C. to obtain “a first layer made of a polycarbonate resin” / “styrene-maleic anhydride malee”. A film-like molten resin having a three-layer structure including a “second layer made of a mixed resin of an acid copolymer resin and a polymethyl methacrylate resin” / “a third layer made of a polycarbonate resin” was obtained. At this time, in the die, the ratio A _C1 / A _L of the gap size A _C1 of the first adjustment flow path portion to the gap size A _L of the lip portion was set to 1.2. The ratio _A C3 / _{A L} of the gap size _{A C3} of the third adjustment channel unit to the size _{A L} of the gap between the lip was set to 1.76.

The film-like molten resin was cast on a cooling roll adjusted to a surface temperature of 130 ° C., and then passed between two cooling rolls adjusted to a surface temperature of 120 ° C. to obtain a long multilayer film. The width direction both ends of this multilayer film were removed, and the width was 1400 mm.
The average thickness of the layers contained in the obtained multilayer film and the thickness unevenness in the width direction were measured as described above. Moreover, the increase rate I of the average thickness of the layer when the temperature of the 1st adjustment flow path part and the 3rd adjustment flow path part was made 30 degreeC high according to the point mentioned above was measured.

[Example 2]
In the die, the ratio A _C1 / A _L of the gap size A _C1 of the first adjustment flow path portion with respect to the gap size A _L of the lip portion was changed to 1.4. Further, the ratio _A C3 / _{A L} of the gap size _{A C3} of the third adjustment channel unit to the size _{A L} of the gap of the lip portion was changed to 1.6.
A multilayer film was produced and evaluated in the same manner as in Example 1 except for the above items.

[Example 3]
The extrusion amount of the polycarbonate resin forming the first layer and the third layer was changed.
A multilayer film was produced and evaluated in the same manner as in Example 1 except for the above items.

[Comparative Example 1]
In the die, the ratio A _C1 / A _L of the gap size A _C1 of the first adjustment flow path portion to the gap size A _L of the lip portion was changed to 3.2. Further, the ratio _A C3 / _{A L} of the gap size _{A C3} of the third adjustment channel unit to the size _{A L} of the gap of the lip portion was changed to 3.2.
A multilayer film was produced and evaluated in the same manner as in Example 1 except for the above items.

[Comparative Example 2]
In the die, the ratio A _C1 / A _L of the gap size A _C1 of the first adjustment flow path portion to the gap size A _L of the lip portion was changed to 6. Further, the ratio A _{C3 /} A _L of the gap size A _C3 of the third adjustment channel unit to the size A _L of the gap of the lip portion was changed to 6.
A multilayer film was produced and evaluated in the same manner as in Example 1 except for the above items.

[result]
The results of the examples and comparative examples are shown in Table 1. In Table 1, PC indicates a polycarbonate resin, and St-Ma indicates a mixed resin of a styrene-maleic anhydride copolymer resin and a polymethyl methacrylate resin.

[Consideration]
In the production of a multilayer film by the melt extrusion method, it is generally required to precisely control the thickness of each layer. In the conventional extrusion technique, it has been common to try to make the thickness of each layer uniform by designing a die manifold and a preland according to the flow rate and viscosity of each resin. However, in actual industrial production, the resin rarely flows as designed. Further, if there is a slight variation in the temperature of the resin, the layer thickness is often not uniform.

  Moreover, if it is a single layer film which consists of a single layer, it is also considered that adjustment is attempted with the lip portion of the die. However, in a multilayer film having two or more layers, it is possible to increase the accuracy of the total thickness of the multilayer film by adjusting the lip portion, but increase the thickness accuracy of each layer included in the multilayer film. It ’s difficult. In particular, in a multilayer film including a plurality of layers having different thicknesses, it is particularly difficult to increase the thickness accuracy of a thin layer even when the techniques such as Patent Documents 1 and 2 are used.

  On the other hand, it can be seen from Table 1 that the thickness unevenness of each layer of the multilayer film can be reduced if the ratio of the gap size of the adjustment flow path portion to the gap size of the lip portion in the die is set to a predetermined value or less. . Therefore, in a die for manufacturing a multilayer film, the thickness accuracy of each layer is effectively improved by setting the ratio of the gap size of the adjustment flow path portion to the gap size of the lip portion to a predetermined value or less. It was confirmed that it was possible.

  Furthermore, in Examples 1-3, when the temperature of the 1st adjustment flow path part and the 3rd adjustment flow path part is changed, the average thickness of each layer is also changing greatly. From this, it can be seen that the thickness of each layer can be effectively changed by adjusting the temperature of the adjustment flow path portion of the die. Therefore, in a die in which the ratio of the gap size of the adjustment channel portion to the gap size of the lip portion is a predetermined value or less, the thickness accuracy of each layer is further improved by appropriately adjusting the temperature of the adjustment channel portion. It was confirmed that it could be improved.

DESCRIPTION OF SYMBOLS 10 Die 100 Die main body 110 1st supply path 120 1st manifold 130 1st flow path 131 1st preland 132 The part immediately downstream of the 1st preland of 1st flow path 133 1st adjustment flow path part 134 1st adjustment of 1st flow path Portion immediately upstream of channel portion 135 Portion of first channel downstream of first adjustment channel portion 210 Second supply channel 220 Second manifold 230 Second channel 231 Second preland 232 Second channel second channel Portion immediately downstream of preland 310 Third supply channel 320 Third manifold 330 Third channel 331 Third preland 332 Portion of third channel immediately downstream of third preland 333 Third adjustment channel 334 Third channel A portion immediately upstream of the third adjustment flow path portion 410 merging portion 420 merging flow passage 430 lip portion 500,600 flow passage clearance control portion 510 , 610 Choke bar 520, 620 Adjustment bolt 530, 630 Electric heater 700 Lip adjustment bolt 800 Multi-layer film 810 First layer 820 Second layer 830 Third layer

Claims (9)

A die for producing a multilayer film comprising a first layer and a second layer,
The die is
A first manifold that can be supplied with a molten resin for forming the first layer;
A first flow path extending downstream from the first manifold;
A second manifold that can be supplied with a molten resin for forming the second layer;
A second flow path extending downstream from the second manifold;
A merge portion where the first flow path and the second flow path merge;
A merge channel extending downstream from the merge section;
A lip portion formed downstream of the merging channel and capable of continuously discharging the molten resin for forming the first layer and the molten resin for forming the second layer merged at the merging portion;
The first flow path includes a pre-land formed in a connection portion with the first manifold, and an adjustment flow path portion,
The size of the gap of the preland is smaller than the size of the gap of the first flow path immediately downstream of the preland,
The size of the gap of the adjustment flow path portion is smaller than the size of the gap of the preland,
The dice | dies whose ratio of the magnitude | size of the clearance gap of the said adjustment flow path part with respect to the magnitude | size of the clearance gap of the said lip | rip part is 3.0 or less.   The dice | dies of Claim 1 provided with the heater which can adjust the temperature of the said adjustment flow path part.   The die according to claim 1 or 2, wherein a size of the gap of the adjustment channel portion is smaller than a size of a gap of a portion of the first channel immediately upstream of the adjustment channel portion.   The die according to any one of claims 1 to 3, further comprising a flow path gap control unit capable of adjusting a size of the gap of the adjustment flow path unit. The die according to any one of claims 1 to 4 , wherein the first layer is an outermost layer of the multilayer film. The die includes a third manifold that can be supplied with a molten resin for forming a third layer, and a third flow path that extends downstream from the third manifold,
The third flow path joins the joining portion,
The die according to any one of claims 1 to 5 , wherein the lip portion can continuously discharge the molten resin for forming the third layer. It is a manufacturing method of the multilayer film which manufactures the multilayer film provided with the 1st layer and the 2nd layer using the dice according to any one of claims 1 to 6 ,
Supplying molten resin for forming the first layer to the first manifold;
Supplying molten resin for forming the second layer to the second manifold; and
A method for producing a multilayer film, comprising continuously discharging the molten resin for forming the first layer and the molten resin for forming the second layer from the lip portion. A method for producing a multilayer film comprising a multilayer film comprising a first layer, a second layer and a third layer, using the die according to claim 6 ,
Supplying molten resin for forming the first layer to the first manifold;
Supplying molten resin for forming the second layer to the second manifold;
Supplying molten resin for forming the third layer to the third manifold; and
Continuously discharging the molten resin for forming the first layer, the molten resin for forming the second layer, and the molten resin for forming the third layer from the lip portion, a method for producing a multilayer film . The method according to claim 7 or 8 , wherein a ratio of the thickness of the first layer to the thickness of the second layer is 1/25 or more and 1/10 or less.

Images