JP2010082985A - Solution film forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a multilayer film product, which needs both step of a manufacturing method of a substrate and a coating step, by a solution film forming method without increasing the quantity of waste. <P>SOLUTION: A diffusion film 23 provided with a diffusion layer for scattering, diffusing and exiting incident light to the outside is manufactured by a film manufacturing facility. A first dope 45 forming the diffusion layer and a second dope 46 forming the support are casted to be overlapped. Both end parts held by a clip 68 of a tenter 66 are cut by a cutting device 71. The first dope 45 is joined inside a feed block 61 with the flow of the second dope 46 at the width directional center part to form the side end part to be cut from the second dope 46. The cut side end part is formed into a fine chips 68 to be recycled to a fresh first dope 45 and second dope 46. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a solution casting method for producing a multilayer film.

  The liquid crystal display device includes a liquid crystal display panel and a backlight unit, and the backlight unit includes a light source, a diffusion film that diffuses light from the light source, and a brightness enhancement film that improves front luminance.

  The diffusion film is provided in order to make the light emitted from the light source as uniform as possible in the entire area of the screen. The diffusion film is overlapped with the brightness enhancement film and is disposed closer to the light source than the brightness enhancement film. As a diffusion film, many proposals have been made so far. For example, a diffusion film in which particles as a light diffusing agent, preferably spherical particles, are arranged in a polymer binder is proposed (see Patent Document 1). Has been.

  In addition to the diffusion film as described above, a conductive film has been manufactured by forming a diffusion layer or a conductive layer on a thin and long support by coating, and cutting it into a predetermined size. It was. That is, both the process of manufacturing a support and the process of forming a coating layer on this support and forming a coating film of a diffusion layer or a conductive layer are performed.

  As a method for producing a long support, either a solution casting method or a melt casting method may be used, but in any method, a step of cutting off the side end portion is required in the production process. This is because the side end portion is deformed in a wave shape, or a retention mark by the holding member that has been attached in the manufacturing process remains on the side end portion. In the case of manufacturing a support having a single layer structure, the cut-off side end portion is reused.

  By the way, a polymer film used for a liquid crystal display is particularly required to have optical isotropy and surface smoothness. In order to meet this demand, production by solution casting may be preferable to melt casting. The solution casting method has an advantage that not only a single layer structure but also a multilayer film can be produced. Therefore, according to the solution casting, a film having a multilayer structure can be formed without a post-process such as coating depending on the type of film to be manufactured.

When a film having a multilayer structure, that is, a multilayer film is produced by a solution casting method, a plurality of dopes having different formulations are cast to form a multilayer cast film and dried. In the case of making a long film, the cast film is formed on a traveling support, peeled off, and dried to form a multilayer film. In the case of forming a multi-layer casting film, dopes of different blends are allowed to flow out of the casting die so that the thickness is uniform in the product portion excluding the side edges to be cut. For example, a plurality of dope flows are merged in a feed block provided on a casting die, and distribution pins having a predetermined shape are arranged on the feed block so that the flows are merged in a predetermined cross-sectional shape at the merge portion. A method of co-casting a plurality of dopes has been proposed (see Patent Document 2). And the method of manufacturing the film which is a multilayer and contains microparticles | fine-particles in at least one layer exposed is proposed by the solution casting method (for example, patent document 3).
JP 2002-323700 A JP 2005-279986 A Japanese Patent No. 4036014

  However, even if a multilayer film is manufactured by solution casting as in Patent Document 2, if the side end portion is excised as described above, the side end portion is formed from a plurality of dopes with different blending. Cannot be reused. Therefore, the side edge part cut off in the manufacturing process of a multilayer film must be discarded.

  On the other hand, if a diffusion film and a conductive film are manufactured in one manufacturing process without a coating process, the manufacturing equipment can be downsized and the manufacturing efficiency can be improved. However, even if a diffusion film or a conductive film is manufactured using co-casting in the solution casting method as in Patent Document 3, the amount of waste generated in the manufacturing process is further increased. There's a problem.

  Therefore, the present invention provides a method for producing a multilayer film product that requires both the production process and the coating process of the support by a solution casting method without increasing the amount of waste. Objective.

  In order to solve the above problems, the solution casting method of the present invention includes a first layer containing a polymer, particles, and a solvent that dissolves the polymer, and containing the polymer and the solvent and not containing the particles. A drying step of drying with a drying means while holding a side end portion of a multilayer film having a second layer with a holding means, and a cutting step of excising the side end portion including the holding position held by the holding means; The side end portion excised in the excision step is mixed with the same liquid as the solvent, and the dissolution step in which the polymer contained in the side end portion is dissolved, and the first layer is formed. The first liquid to be formed and the second liquid to form the second layer overlap at the center in the width direction, so that the side end portion excised in the excision step is formed only from the second liquid. Casting the first and second liquids on the support to form a cast film A casting step of peeling the casting film from the support as the multilayer film, and a mixing step of mixing the solution with at least one of the first liquid and the second liquid to be cast. It is characterized by having.

  The solution casting method is particularly effective when the multilayer film with the side edges cut off is a diffusion film that scatters incident light inside and emits it to the outside.

  By the solution casting method of the present invention, it is possible to produce a multilayer film product that requires both the support production process and the coating process without increasing the amount of waste.

  The diffusion film produced by the production method of the present invention can be used for a liquid crystal display device. An outline of a liquid crystal display device using a diffusion film according to the present invention is shown in FIG. However, the liquid crystal display device 10 is not limited to this configuration. The liquid crystal display device 10 includes a liquid crystal panel 11 and a light source unit 12. The liquid crystal panel 11 includes a liquid crystal cell 13 and a pair of polarizing plates 14 and 15 disposed so as to be in close contact with both surfaces thereof. The liquid crystal cell 13 has a liquid crystal sealed between transparent glass substrates, and changes the polarization state of transmitted light by applying a voltage between transparent electrodes formed on the inner surface of each glass substrate. .

  The polarizing plate 14 is composed of a polarizing film 14a and a pair of protective films 14b and 14c adhered to both surfaces thereof. The polarizing plate 15 has the same configuration as that of the polarizing plate 14 and includes a polarizing film 15a and a pair of protective films 15b and 15c. The polarizing plates 14 and 15 are disposed so as to be crossed Nicols, and the liquid crystal cell 13 is disposed therebetween.

  The light source unit 12 includes a light source lamp (not shown), a light guide plate 22, a diffusion film 23, and a brightness enhancement film 26. The light source unit 12 illuminates the liquid crystal panel 11 from behind. The light source unit 12 is an edge light type in which a light source lamp, which is a rod-like fluorescent tube, for example, is arranged along the edge (edge) of the wedge-shaped light guide plate 22. Illumination light emitted from the light source lamp is reflected directly or by a reflector and enters the light guide plate 22 from the end thereof. In FIG. 1, the direction in which light enters the light guide plate 22 is indicated by an arrow line (A). The light guide plate 22 emits light incident from the end portion from one surface of the diffusion film 23 by reflecting the light internally.

  A diffusion film 23 is superimposed on the liquid crystal panel 11 side of the light guide plate 22. The diffusing film 23 scatters and diffuses light emitted from one surface of the light guide plate 22 inside and on the surface in order to uniformly illuminate the entire surface of the liquid crystal panel 11.

  The brightness enhancement film 26 is disposed between the diffusion film 23 and the liquid crystal panel 12, and the size thereof is substantially the same as the back surface of the liquid crystal panel 12. Light diffused by the diffusion film 23 enters the brightness enhancement film 26, and light emitted from the brightness enhancement film 26 enters the liquid crystal panel 12. The brightness enhancement film 26 improves the front brightness in the liquid crystal display device 10.

  FIG. 2 is an example of the diffusion film 23 manufactured by the manufacturing method of the present invention, and is a cross-sectional view in the thickness direction of the diffusion film 23. 3 is a cross-sectional view taken along line III-III in FIG. The diffusion film 23 includes a diffusion layer 31 that reflects and diffuses light inside, and a support 32 that supports the diffusion layer 31. The diffusion film 23 is used in such a manner that the brightness enhancement film 26 and the diffusion layer 31 are in close contact with each other, and diffuses light through the diffusion layer 31 to enter the brightness enhancement film 26. In the following description, one surface of the diffusion film 23 on the brightness enhancement film 26 side is referred to as a first surface 23a, and the other surface on the light guide plate 22 side is referred to as a second surface 23b.

  The diffusion layer 31 includes a plurality of particles 33 and a binder 34 that serves as a connection between the particles 33. The binder 34 is made of a transparent polymer. The particles 33 and the binder 34 have different refractive indexes, so that light is refracted at the interface between the particles 33 and the binder 34. Any particle 33 is arranged so as not to protrude from the diffusion layer 31. “Do not protrude from the diffusion layer 31” means that the particles 33 may be arranged inside the diffusion layer 31 so that the first surface 23 a is smooth, and the surface of the particles 33 is partially covered by the binder 34. It may be exposed from inside. The particles 33 are arranged in the vicinity of the first surface 23a.

  With the above configuration, the light from the light guide plate 22 is reflected at the interface between the binder and the particles, is scattered inside the diffusion film 23, and increases the amount of illumination light emitted in the normal direction of the liquid crystal panel 11. Thus, the light quantity distribution of the irradiation light is controlled. That is, with the above configuration, the diffusion film 23 has a function of scattering and diffusing light, and also has a higher front luminance improving function than a conventional diffusion film. Furthermore, since the first surface 23a is smooth, the diffusion film 23 has good adhesion to the brightness enhancement film 36 and can prevent light leakage in the direction along the film surface.

  In terms of further enhancing the light diffusion effect, it is preferable to use particles 33 having a higher refractive index than the binder 34. The particles 33 having a refractive index higher than that of the binder 34 may be either solid or liquid. When the binder 34 is cellulose triacetate (TAC, refractive index = 1.48), the solid having a higher refractive index is polystyrene (PS, refractive index = 1.6), polyethylene (PE, refractive index = 1). .53), glass beads (refractive index = 1.5), silica (refractive index = 1.54), mica (refractive index = 1.58), etc., the liquid is silicone oil (refractive index = 1.50), Benzene (refractive index = 1.50). Furthermore, it is preferable that the difference dN1 obtained by subtracting the refractive index NB of the binder 34 from the refractive index NP of the particles 33 is at least 0.02, in order to improve the scattering effect inside the particles 33 more reliably.

On the other hand, in terms of increasing the effect of improving the front luminance of the liquid crystal panel 11, it is preferable to use particles having a refractive index lower than that of the binder 34 as the particles 33. The particles 33 having a refractive index lower than that of the binder may be solid, liquid, or gas. When the binder 34 is TAC, the solid having a lower refractive index is polymethyl methacrylate (PMMA, refractive index = 1.50), quartz SiO ₂ (refractive index = 1.45), or the like, and the liquid is water. Examples of gases such as (refractive index = 1.33) and ethyl alcohol (refractive index = 1.36) include air, nitrogen N ₂ , and carbon dioxide CO ₂ . Further, the difference dN2 obtained by subtracting the refractive index NP of the particles 33 from the refractive index NB of the binder 34 is preferably at least 0.02, from the viewpoint of more reliably improving the light collection effect due to refraction inside the particles 33. .

  Further, by selecting the particles 33 based on the refractive index and controlling the volume ratio between the particles 33 and the binder 34, the balance between the diffusion effect and the front luminance improvement effect can be controlled.

  Moreover, the balance between the effect of diffusion and the effect of improving the front luminance can be controlled by selecting the particles 33 based on the refractive index and controlling the volume ratio between the particles 33 and the binder 34.

  When the volume of the binder 34 is VB and the volume of the particles 33 is VP, the diffusion layer 31 does not have a volume ratio obtained by VP / VB of 0.15 or less, that is, larger than 0.15. Has been. Thereby, while being able to express the function of light diffusion reliably, a brightness | luminance can be improved. The volume ratio VP / VB is more preferably in the range of more than 0.15 and not more than 2.0, more preferably in the range of not less than 0.2 and not more than 1.5, and not less than 0.6 and not more than 1.0. It is especially more preferable that it is the range of these.

(Shape of particle 33)
The particle 33 is most preferably a sphere whose shape is a perfect circle in a cross section in any direction, but the shape of the particle 33 is not limited to this.

(Particle size)
When the particle 33 is a sphere having a perfectly circular cross section, the particle 33 has a particle size in the range of 2 μm to 15 μm. Thereby, both the effects of light diffusion and brightness improvement can be expressed in a balanced and effective manner. When the particle diameter is smaller than 2 μm, the brightness enhancement effect may be impaired. Therefore, when making a film by solution casting, particles such as a so-called matting agent that has been contained in the film in order to improve the sliding of the film is too small in particle size, and both effects of light diffusion and brightness improvement are achieved. Hard to get. When the particle diameter is larger than 15 μm, the effect of light diffusion may not be obtained. In the case where the particle 33 is a sphere having a perfectly circular section, a more preferable particle size is in the range of 5 μm to 10 μm, and a more preferable particle size is in the range of 6 μm to 9 μm. Furthermore, it is preferable that all the particle diameters are substantially the same.

(Particle distribution)
The particles 33 are randomly distributed in the diffusion layer 31. Thereby, moire due to the light source and the particles 33 in the diffusion layer 31 can be eliminated. It is preferable that the particles 33 and the particles 33 are arranged at intervals, that is, not in contact with each other in a direction parallel to the film surface.

  The particles 33 are most preferably distributed so as not to overlap in the thickness direction. Thereby, in addition to the light diffusing effect, the effect of improving the brightness can be expressed more reliably.

  The haze of the diffusion film 23 is preferably at least 20%, that is, 20% or more. Thereby, both light diffusion and brightness improvement are expressed more reliably. If the haze is less than 20%, the effect of light diffusion may be insufficient.

  The binder 34 is made of TAC. As described above, the binder 34 may be made of a known polymer that is transparent, that is, has high light transmittance and can be formed into a thin film like a sheet. Further, the polymer is more preferably one having no optical anisotropy, that is, one having optical isotropy. A preferred polymer that satisfies these conditions is cellulose acylate.

Among cellulose acylates, the ratio of esterifying the hydroxyl group of cellulose with carboxylic acid, that is, the substitution degree of acyl group (hereinafter referred to as acyl group substitution degree) satisfies all the conditions of the following formulas (1) to (3). Satisfactory TAC is particularly preferred. In (1) to (3), A and B are both acyl group substitution degrees, the acyl group in A is an acetyl group, and the acyl group in B has 3 to 22 carbon atoms.
2.5 ≦ A + B ≦ 3.0 (1)
0 ≦ A ≦ 3.0 (2)
0 ≦ B ≦ 2.9 (3)

  Glucose units constituting cellulose and having β-1,4 bonds have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer in which some or all of the hydroxyl groups of cellulose are esterified, and the hydrogen of the hydroxyl group is substituted with an acyl group having 2 or more carbon atoms. Since the degree of substitution is 1 when esterification of one hydroxyl group in the glucose unit is 100%, in the case of cellulose acylate, the hydroxyl groups at the 2nd, 3rd and 6th positions are each 100% ester. The degree of substitution is 3.

  Here, the total acyl group substitution degree obtained by “DS2 + DS3 + DS6”, where the acyl group substitution degree at the 2-position in the glucose unit is DS2, the acyl substitution degree at the 3-position is DS3, and the acyl substitution degree at the 6-position is DS6 is 2. It is preferably from 00 to 3.00, more preferably from 2.22 to 2.90, and even more preferably from 2.40 to 2.88. Furthermore, “DS6 / (DS2 + DS3 + DS6)” is preferably 0.32 or more, more preferably 0.322 or more, and further preferably 0.324 to 0.340.

  There may be only one kind of acyl group, or two or more kinds. When there are two or more acyl groups, it is preferable that one of them is an acetyl group. The sum of the substitution degrees of the hydrogen at the 2-, 3- and 6-position hydroxyl groups with acetyl groups is DSA, and the sum of the substitution degrees with acyl groups other than the acetyl groups at the 2-, 3- and 6-positions is DSB. In this case, the value of “DSA + DSB” is preferably 2.2 to 2.86, and particularly preferably 2.40 to 2.80. DSB is preferably 1.50 or more, and particularly preferably 1.7 or more. In DSB, 28% or more is preferably 6-position hydroxyl group substitution, more preferably 30% or more, further preferably 31% or more, particularly preferably 32% or more substitution of 6-position hydroxyl group. It is preferable. In addition, the value of “DSA + DSB” at the 6-position of cellulose acylate is preferably 0.75 or more, more preferably 0.80 or more, and particularly preferably 0.85 or more. By using the cellulose acylate as described above, preferable solubility for obtaining a polymer solution used for solution casting can be obtained, and a polymer solution having a low filterability and a preferable viscosity can be produced. In particular, when a non-chlorine organic solvent is used, the above cellulose acylate is preferable.

  The acyl group having 2 or more carbon atoms may be an aliphatic group or an aryl group, and is not particularly limited. For example, there are cellulose alkylcarbonyl ester, alkenylcarbonyl ester, aromatic carbonyl ester, aromatic alkylcarbonyl ester, etc., and these may each further have a substituted group. Propionyl group, butanoyl group, pentanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, iso-butanoyl group, t-butanoyl group, cyclohexane Examples thereof include a carbonyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, and a cinnamoyl group. Among these, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a t-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and a propionyl group and a butanoyl group are particularly preferable.

  The details of cellulose acylate are described in paragraphs [0140] to [0195] of JP-A-2005-104148, and these descriptions can also be applied to the present invention.

  The binder 34 may appropriately contain various additives such as a plasticizer, a deterioration inhibitor, an ultraviolet absorber, an optical anisotropy control agent, a dye, a matting agent, and a release agent. These are described in detail in paragraphs [0196] to [0516] of JP-A-2005-104148, and can be applied to the present invention.

  The thickness of the diffusion layer 31 is preferably in the range of 2 μm to 15 μm. This is the case where the particles 33 having a true circular section with a diameter in the range of 2 μm or more and 15 μm or less are used, as described above. This is for accommodating in the diffusion layer 31 so as not to overlap. Therefore, when the particle 33 is indefinite or is a sphere having an elliptical cross section, the largest diameter is the upper limit value of the thickness of the diffusion layer 31, and the smallest diameter is the thickness of the diffusion layer 31. Lower limit value.

  The support 32 is for the purpose of improving the handleability and strength of the diffusion film 23 and adjusting the thickness, and is not necessarily a necessary layer. However, it is preferably provided from the viewpoint of improving the strength of the diffusion film 23 and the handleability at the time of bonding with another film.

  The support 32 is made of a transparent polymer like the binder 34. As the polymer constituting the support 32, as in the case of the binder 34, a known polymer that has a high light transmittance and can be formed into a thin film shape may be used. The binder 34 may be made of a different polymer or the same polymer. When the support body 32 is made of the same polymer as the binder 34, the support body 32 and the binder 34 may be integrated with each other and the boundary may disappear during the manufacturing process.

  As shown in FIG. 4, the film production facility 40 includes a dope production unit 41 that produces a plurality of dopes to be cast, and a solution film production unit 42 that creates a diffusion film 23 from the dope by solution film production. In the dope manufacturing section 41, a first dope 45 for forming the diffusion layer 31 (see FIG. 1) and a second dope 46 for forming the support 32 (see FIG. 1) are respectively formed. The solution casting part 42 forms a casting film 47 composed of the first dope 45 and the second dope 46 and peels off the casting film 51 as a wet film 48 containing a solvent, and the wet film 48 is dried. It consists of a drying area 52 that serves as a diffusion film 23 and a winding area 53 that winds the diffusion film 23 into a roll.

  In the casting area 51, a casting die 56 that flows out of the first dope 45 and the second dope 46, a band 57 that is disposed below the casting die 56 and continuously runs, and a band 57 Are wound around the circumferential surface and at least one of them is driven to rotate to drive the band 57, and a roller 59 for supporting the wet film 48 when the casting film 47 is peeled off from the band 57. It has been. In addition, a feed block 61 is provided on the upstream end face of the casting die 56 to join the flows of the first dope 45 and the second dope 46 and guide them to the casting die 56. On the upstream side of the die 56, a decompression chamber 62 that sucks and decompresses air in an area upstream of the bead formed from the casting die 56 to the band 57 is provided.

  Both the first dope 45 and the second dope 46 are cast from one casting die 56 to the band 57, whereby a layer formed from the first dope 45 and a layer formed from the second dope 46 are provided. A casting film 47 having a multilayer structure consisting of two layers is formed. It should be noted that both end portions of the casting film 47 are not a two-layer structure but a single-layer structure composed of only the second dope 46. Details of the overlapping manner of the first dope 45 and the second dope 46 in the casting film 47 will be described later with reference to another drawing. When the casting film 47 becomes hard enough to be conveyed by a roller, that is, when it becomes self-supporting, it is peeled off from the band 57 and the wet film 48 is guided to a tenter 66 in the drying area 52. In the vicinity of the conveyance path from the band 57 to the tenter 66, an air duct 67 for blowing dry air onto the wet film 48 is provided in order to advance the drying of the wet film 48.

  The tenter 66 is provided with a plurality of clips 68 as holding means for holding the side end of the wet film 48 on both sides of the transport path of the wet film 48. The clip 68 grips the side end portion of the wet film 48 that has a single-layer structure. As the holding means, instead of the clip 68 that holds the wet film 48, a pin that pierces and holds the wet film 48 may be used. The plurality of clips 68 are provided in an endless chain (not shown) that continuously travels, and the travel path of the clips 68 can be changed by displacing the travel path of the chain. The width of the wet film 48 can be expanded by setting the chain travel path so that the distance between the clip 68 and the clip 68 disposed on both sides of the wet film 48 gradually increases toward the downstream side. .

  The tenter 66 is provided with a blower duct 66a that blows the temperature-adjusted dry air onto the wet film 48, and by this blow, the wet film 48 is dried while being held by the clip 68 and conveyed.

  The wet film 48 released from the grip by the clip 68 is guided to a cutting device 71 provided downstream of the tenter 66. A grip mark remains at the grip position gripped by the clip 68 of the wet film 48. The excision device 71 continuously cuts the side end portion of the wet film 48 so that the grip mark is separated from the central portion that becomes the diffusion film 23. At this time, the cut position to be cut is in an area having a single layer structure.

  Downstream of the cutting device 71, there is a drying chamber 74 that includes a plurality of rollers 73 that support the wet film 48 with both side ends cut off on the peripheral surface, and a blower duct (not shown) that blows dry air. The roller 73 includes a drive roller that conveys the wet film 48 by being rotationally driven in the circumferential direction. In the air duct, a plurality of slits (not shown) extending in the width direction of the wet film 48 are provided in the transport direction, and the wet film 48 is dried and diffused by dry air of a predetermined temperature that is discharged from these slits. Film 23 is obtained. The diffusion film 23 is wound in a roll shape by a winding device 77 in the winding area 53.

  Each side end portion separated from the central portion of the wet film 48 by the cutting device 71 is cut into a fine chip shape when sent to a crusher 72 having a rotary cutter (not shown). The chip 78 is reused as a raw material of at least one of the first dope 45 and the second dope 46 in the dope manufacturing unit 41.

  In addition to the chip 78, the dope manufacturing unit 41 includes a new polymer, that is, an unused polymer, a solvent 81 that is a solvent component of the first dope 45 and the second dope 46, and particles 33. A particle-containing liquid 82 is used. In order to distinguish the unused polymer from the polymer to be reused contained in the chip 78, in the following description, the former will be referred to as V polymer and the latter will be referred to as R polymer. In FIG. .

  The dope manufacturing unit 41 includes a first dissolving device 86 for mixing the chip 78 and the solvent 81 and dissolving the R polymer in the solvent 81, and a second dissolving device 87 for dissolving the V polymer 83 in the solvent 81. With.

  The chip 78 is mixed with the solvent 81 by the first dissolving device 86. In this mixing, in order to dissolve the R polymer contained in the chip 78 in the solvent 81, the mixture of the chip 78 and the solvent 81 is appropriately heated, pressurized, stirred, and the like. A liquid obtained by mixing in the first dissolution apparatus 86 is referred to as a first dissolution liquid 88. The R polymer is a polymer that has been subjected to casting to constitute the binder 34 (see FIG. 2) and the support 32 (see FIG. 2). Since the side end portion of the tip 78 has a single layer structure formed from the second dope 46, the tip 78 does not include the particles 33 used for the first dope 45, that is, the particles 33. Is not contained. Therefore, the obtained first solution 88 can be used as a part of the first dope 45 or as a part of the second dope 46.

  The solvent 81 mixed with the chip 78 in order to dissolve the R polymer is the same as the solvent of the first dope 45 used for casting in the solution casting part 42. Thereby, the 1st solution 88 becomes easier to mix with the below-mentioned 2nd solution 89. When this solvent consists of a plurality of compounds, the R polymer may be dissolved with the same compound as at least one of them.

  In the second dissolving device 87, the V polymer 83 is dissolved in the solvent 81 to obtain a second dissolving solution 89. In order to dissolve the V polymer 83 more effectively and efficiently, the mixture of the V polymer 83 and the solvent 81 is appropriately heated, pressurized, stirred, and the like.

  The first liquid feeding line L1 for guiding the first dissolving liquid 88 downstream from the first dissolving apparatus 86 and the second liquid feeding line L2 for guiding the second dissolving liquid 89 downstream from the second dissolving apparatus 87 are branched. To do. In one liquid supply line (hereinafter referred to as the third liquid supply line) L3 from which the second liquid supply line L2 is branched, the first dope 45 is formed, and the other liquid supply line (hereinafter referred to as the fourth liquid supply line). ) At L4, a second dope 46 is created. One liquid supply line (hereinafter referred to as the fifth liquid supply line) L5 from which the first liquid supply line L1 is branched is connected to the third liquid supply line L3, and the other liquid supply line (hereinafter referred to as the sixth liquid supply line). L6) is connected to the fourth liquid feeding line L4.

  A valve is provided at a branch position where the first liquid feeding line L1 branches into the fifth liquid feeding line L5 and the sixth liquid feeding line L6, and by this valve, the third liquid feeding line L3 and the fourth liquid feeding line are provided. The on / off of the feeding of the first solution 88 to the line L4 and the feeding amount are independently controlled. Accordingly, the first dissolving liquid 88 is appropriately fed into at least one of the third liquid feeding line L3 and the fourth liquid feeding line L4.

  The fourth liquid supply line L4 is provided with a concentration adjusting means (not shown) downstream from the connection position with the sixth liquid supply line L6, and the mass ratio of the solvent 81 is adjusted by the concentration adjusting means. Thus, the second solution 89 becomes the second dope 46. In addition, the first solution 88 and the second solution 89 that are guided between the connection position where the sixth liquid supply line L6 is connected and the concentration adjusting means are uniformly distributed to the fourth liquid supply line L4. A mixer that mixes to form a liquid is provided, but the illustration is omitted.

  An addition line LA through which the particle-containing liquid 82 is guided is connected to the third liquid feeding line L3, whereby the particle-containing liquid 82 is added to the second solution 89. When adding the 1st solution 88 to the 2nd solution 89 which flows through the 3rd liquid sending line L3, particle-containing solution 82 is added to the 2nd solution 89 after the 1st solution 88 was mixed. It is preferable. Therefore, it is preferable that the connection position of the addition line LA with respect to the third liquid supply line L3 is on the downstream side of the connection position to which the fifth liquid supply line L5 is connected.

  The particle-containing liquid 82 is added from the addition line LA to the second solution 88 so that the ratio of the mass of the particles 33 to the sum of the masses of the V polymer 83 and the R polymer becomes a predetermined value in the first dope 45 to be cast. Add against. In this way, the particles 33 are mixed with the second solution 89 of the third liquid feeding line L3, and the first dope 45 to be newly cast is created. Therefore, the amount of the particles 33 to be mixed is determined according to the mass sum of the V polymer and the R polymer contained in the third solution 89, and the amount of the particle-containing liquid 82 is determined based on the amount of the particles 33. . In addition, it is good to determine the content rate of the particle | grains 33 in the 1st dope 45 which should be newly cast | casted with the target value of the haze value of the diffusion film 23 which is going to manufacture. That is, the haze value of the diffusion film 23 to be manufactured can be controlled by controlling the content ratio of the particles 33 in the particle-containing liquid 82 and the content ratio of the polymer component in the second solution 88 of the third liquid feeding line L3. .

  The particle-containing liquid 82 is a dispersion liquid dispersed in the same liquid compound as the solvent of the first dope 45 used for casting in the solution casting part 42. Thereby, the affinity between the particle-containing liquid 82 and the second solution 89 is improved, so that the particle-containing solution 82 and the second solution 89 are mixed uniformly and effectively so that the particles 33 are in the liquid. Will be dispersed evenly. When the solvent used in the first dope 45 is composed of a plurality of compounds, the particles may be dispersed with the same compound as at least one of them.

  The first solution 88 and the second solution 89 guided between the connection position to which the fifth liquid supply line L5 is connected and the connection position to which the addition line LA is connected are connected to the third liquid supply line L3. A mixer that mixes the mixture so as to form a uniform liquid is provided, but the illustration is omitted.

  The third liquid feed line L3 is provided with a concentration adjusting means (not shown) downstream from the connection position with the addition line LA, and the mass ratio of the solvent 81 is adjusted by the concentration adjusting means to adjust the mass ratio of the solvent 81. One dope 45 is obtained.

  In the solution casting part 42, the production of the diffusion film 23 having different properties of the diffusion layer 31 can be started without stopping the operation by switching the prescription of the first dope 45 to be cast. For example, when the prescription of the first dope 45 is switched so as to increase the mass ratio of the binder 34 in the diffusion layer 31, the first solution 88 is produced from the chip 88 in the pre-switching prescription. Is added to the second solution 89 of the third liquid feeding line L3. As a result, the R polymer is added to the V polymer 83 and the R polymer is reused, and the first dope 45 of a new formulation is created.

  The first dope 45 and the second dope 46 newly produced as described above are cast by the solution casting part 42 to form the diffusion film 23.

  According to the above method, (1) the coating step for applying the diffusion layer 31 to the support 32 is not required, and (2) the side end portion to be excised does not include the particles 33. It can be reused for both the new first dope and the second dope 46 without being discarded. (3) The side end to be reused is either the first dope 45 or the second dope 46. Therefore, there is an effect that any property of the new first dope 45 and the second dope 46 is not changed even when reused.

  FIG. 5 is a schematic view of the casting die 56 and the feed block 61. The first dope 45 and the second dope 46 are sent to the feed block 61. The feed block 61 has a rectangular parallelepiped shape, and two flow paths 103 and 104 are formed therein. The flow path 103 extends in the vertical direction from the opening 103a on the upper surface of the feed block toward the opening 103b on the lower surface. The opening 103 a on the upper surface is an entrance for the second dope 46. The flow path 104 is formed from the opening 104 a on the side surface of the feed block 61 toward the flow path 103, and the opening 104 a serves as an inlet for the first dope 45. The flow path 103 and the flow path 104 are connected so as to form a merge portion 105 so that the first dope 45 and the second dope 46 merge.

  The junction 105 is provided with distribution pins 107 and vanes 108. The distribution pin 107 and the vane 108 are provided on the flow path 104 immediately before the flow path 104 joins the flow path 103. The distribution pin 107 has a cylindrical shape with a notch groove formed in the peripheral surface, and is arranged so that the longitudinal direction thereof coincides with the width direction of the casting die 56 and the feed block 61.

  The distribution pin 107 is rotatable, and the first dope 45 flows with its flow width and depth regulated by the notch groove of the distribution pin 107 and reaches the junction 105. The flow width of the first dope 45 is regulated by the distribution pin 107 so that the flow width is smaller than that of the second dope 46, and the flow of the first dope 45 joins the central portion in the width direction of the flow of the second dope 46. Then, the first dope 45 is made not to overlap the both end portions of the second dope 46, and both the dopes 45 and 46 are sent out from the opening 103 b to the casting die 56. Details of the distribution pin 107 will be described later with reference to another drawing.

  In the casting die 56, one flow path 109 is formed inside. The channel 109 gradually becomes wider from the middle toward the lower side. In addition, an inclined surface 109a is formed in a region in the middle of the flow path 109 so that the depth is narrowed. The first dope 45 and the second dope 46, which are joined at the feed block 61 and whose side ends are made into the second dope 46 and in which the flows are overlapped at the center in the width direction, are widened by the flow path 109, and flow It flows out from the die lip 110 provided at the tip of the extending die 56.

  FIG. 6 is a schematic view of the distribution pins and vanes, FIG. 7 is a cross section in the longitudinal direction of the distribution pins, and FIG. 8 is a radial cross section in the central portion in the longitudinal direction of the distribution pins. The distribution pin 107 has a cylindrical shape with a notch 111 formed in the peripheral surface, and is arranged so that the longitudinal direction thereof coincides with the width direction of the casting die 56 and the feed block 61. The first dope 45 flows with its width and depth regulated by the notch groove 111.

  The flow width of the first dope 45 changes when the distribution pin 107 is rotationally driven. The vane 108 is provided on the upstream side of the distribution pin 107 and has a wedge shape. The vane 108 adjusts the flow rate of the first dope 45 by rotating. The first dope 45 merges with the second dope 46 with a flow width and depth regulated by the notch groove 111 of the distribution pin 107.

  As shown in FIGS. 7 and 8, the cutout groove 111 includes a first groove 111a and a second groove 111b formed on the bottom surface of the first groove 111a. The first groove 111a has a trapezoidal shape as shown in FIG. Thus, the groove width of the first groove portion 111a changes according to the region of the peripheral surface. Further, the groove depth of the first groove portion 111a is constant except for the region where the second groove portion 111b is formed. In addition, you may form a 1st groove part so that the groove depth of the 1st groove part 111a may change according to the area | region of a surrounding surface.

  The second groove portion 111 b is formed at the center of the bottom surface of the notch groove 111. As shown in FIG. 7, the second groove portion 111b is formed in a trapezoidal shape, and the groove width of the second groove portion 111b is adjusted according to the change of the groove width of the first groove portion 111a, that is, according to the area of the peripheral surface. Change. Specifically, the groove width of the second groove portion 111b is increased as the groove width of the first groove portion 111a is increased. The groove depth of the second groove portion 111b is constant regardless of the peripheral area. In addition, you may form a 2nd groove part so that the groove depth of the 2nd groove part 111b may change according to the area | region of a surrounding surface.

  An allowable range is provided for the size of the cutout groove 111 of the distribution pin 107, and the cutout groove 111 is formed within this allowable range. This allowable range is preferably the range described in paragraphs [0033] to [0046] of JP-A-2005-279986.

  FIG. 10A is a cross-sectional view of the flow of the first dope 45 and the second dope 46 in the merge portion 105 (see FIG. 5) of the feed block 61, and FIG. 5 is a cross-sectional view of the flow of the first dope 45 and the second dope 46 when in contact with 57. FIG.

  As shown in FIG. 10A, the first dope 45 has a narrower flow width at the junction than the second dope 46 due to the notch groove 111 (see FIGS. 6 to 9) of the distribution pin. . The second dope 46 exists on both sides of the first dope 45, and both sides of the second dope 46 are convex toward the first dope 45 side. The central portion in the width direction of the first dope 45 is convex toward the second dope 46 side. Therefore, the central portion in the width direction of the second dope 46 is concave. In this way, the first dope 45 and the second dope join together, so that the first dope and the second dope 46 form the casting film 47 (see FIG. 4) as shown in FIG. When the formation is started, the first dope 45 layer and the second dope 46 layer having a uniform thickness overlap each other at the center in the width direction, and both sides have a single layer structure of the second dope 46. The thickness is the same as the thickness of the central portion.

  In FIG. 10B, the position of the side edge of the first dope 45 in the casting film 47 (hereinafter referred to as the first dope side edge position) is denoted by EL and the wet film 48 and then cut by the cutting device 71. The position CL (cut position) is denoted by reference sign CL. The distribution pin 107 controls the flow width of the first dope 45 so that the first dope side edge position EL is outside the cut position CL. The holding position (not shown) by the clip 68 is outside the cutting position CL.

  Although this embodiment is a case where the diffusion film 23 comprised by the diffusion layer 31 and the support body 32 is manufactured, this invention is not limited to this. For example, instead of the particles 33, a conductive substance, such as particles or fillers, is used. The conductive layer made of such a conductive substance and the binder 34 is replaced with the diffusion layer 31, and the conductive layer and the support 32 overlap. It can also be applied to the production of conductive films.

  In addition, the present invention is not limited to the above-described embodiment in which the second dope 46 does not include particles, and can also be applied to the case where the particles 33 are included in the second dope 46 at a lower content than the first dope 45. .

  In the present embodiment, as a method of making the side end portion of the wet film 48 guided to the cutting device 71 have a single layer structure, a method in which the first dope 45 and the second dope 46 are merged using the distribution pin 107 is used. Although used, the present invention is not limited to this method. For example, instead of this method, there is the following method. Dope supply means for flowing out the second dope 46 is provided on each side of the die lip 110 (see FIG. 5) of the casting die 56. From the die lip 110, the first dope 45 and the second dope 46 flow out from one side edge to the other side edge. In this way, the second dope is supplied from the dope supply means to each side edge of the so-called bead where the first dope 45 and the second dope overlap, and the second dope from the dope supply means is integrated with the bead. Thus, a cast film is formed. In this way, each side end of the casting film is formed from the second dope, and is reused after being gripped by the clip and cut by the cutting device.

  The diffusion film 23 was produced by the film production equipment 40 using TAC as the binder 34 and the support 32 and using polymethylmethacrylate beads (MX150H3CF, manufactured by Soken Chemical) as the fine particles 33. Both side ends including the holding position held by the clip 68 of the tenter 66 were excised, and this side end was used as a tip 78 so that a predetermined amount was included in the second dope 46. And the particle | grain containing liquid 82 was added suitably. The ratio of the weight of the support body 32 to the unit weight of the cut-out side end, that is, the side end formed as the tip 78 is 100 wt%. This weight ratio is a value obtained by 100 × y / x, where x is the unit weight of the side end and y is the weight of the support 32.

  And about the obtained long diffusion film 23, as a sample for measuring a haze value, it arbitrarily sampled multiple in the longitudinal direction. When haze value was calculated | required about each sample, all haze was 40% suitable for using as a diffusion film of a liquid crystal display. The haze value is a value Th (unit:%) obtained by irradiating the obtained diffusion film 23 with light and measuring the light transmittance, and 100 × scattered light transmittance Td / total light transmittance Tt.

[Comparative example]
The weight ratio of the support at the side end portion was 50 wt%, and the cut side end portion was a tip 78. This chip was not used for the first dope 45 but was reused as a raw material for the second dope 46. That is, the chip 78 was reused so as to be included in the support. When the haze value of the obtained film was measured in the same manner as in Example 1, the haze was 90%, which was a level that could not be used as a diffusion film.

It is a perspective view which shows an example of the glossing processing apparatus of this invention. It is a schematic sectional drawing of a diffusion film. It is sectional drawing which follows the III-III line of FIG. It is the schematic of the film manufacturing equipment which enforces the manufacturing method of this invention. It is a schematic sectional drawing of a casting die. It is the schematic of a distribution pin and a vane. It is the schematic of a distribution pin. It is sectional drawing which follows the VIII-VIII line of FIG. It is sectional drawing which follows the IX-IX line of FIG. (A) is sectional drawing which shows the overlap of the 1st dope and the 2nd dope in the confluence | merging part of a feed block, (B) is sectional drawing which shows the overlap of the 1st dope and the 2nd dope when contacting the band 57 It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 23 Diffusion film 31 Diffusion layer 32 Support body 33 Particle | grain 34 Binder 40 Film manufacturing equipment 45 1st dope 46 2nd dope 51 Casting area 52 Drying area 66 Tenta 66a Air duct 68 Clip 71 Cutting device 82 Particle-containing liquid

Claims (2)

Means for holding a side end portion of a multilayer film having a first layer containing a polymer, particles and a solvent for dissolving the polymer, and a second layer containing the polymer and the solvent and not containing the particles. A drying step of drying with a drying means while being held in
An excision step of excising the side end including the holding position held by the holding means;
The dissolution step of mixing the side end portion excised in the excision step with the same liquid as the solvent and dissolving the polymer contained in the side end portion;
The first liquid that forms the first layer and the second liquid that forms the second layer overlap at the center in the width direction, and the side end portion excised in the excision step is only the second liquid. To form a casting film by casting the first liquid and the second liquid on a traveling support, and forming the casting film from the support as the multilayer film. Casting process to peel off,
A solution casting method, comprising: a mixing step of mixing the solution with at least one of the first liquid and the second liquid to be cast.   2. The solution casting method according to claim 1, wherein the multilayer film from which the side edges are cut is a diffusion film that scatters incident light inside and emits the light to the outside.

Images