JP2013011774A - Manufacturing method of optical film laminate, optical film laminate manufactured by the same, and polarization plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an optical film laminate which hardly generates an excessive curl in edge portions in a direction perpendicular to a mechanical flow direction (TD).SOLUTION: An optical film A the curl amount of which in an edge portion is small is laminated over the surface of an optical film B the curl amount of which in an edge portion in a direction perpendicular to a mechanical flow direction (TD) is relatively large to manufacture an optical film laminate X the curl of which in edge portions in the TD is reduced. The manufacturing method includes: a conveyance step (A) in which the optical films A and B are conveyed in the state where each film is given with a tension in the mechanical flow direction (MD); and a laminating step (B) in which the optical film A is laminated over the surface of the optical film B at the side on which a concave curl is formed. In the laminating step (B), defining the tension given to the optical film B in the mechanical flow direction (MD) as Tand the tension given to the optical film A in the mechanical flow direction (MD) as T, the optical films A and B are laminated each other in the state where a tension of the tension ratio (T/T)<1 is given.

Description

  TECHNICAL FIELD The present invention relates to a method for producing an optical film laminate, an optical film laminate produced by the method, and a polarizing plate, and in particular, a method for producing an optical film laminate in which a plurality of optical films are laminated and the method. The present invention relates to a laminated optical film and a polarizing plate.

  A liquid crystal display device has features such as low power consumption, operation at a low voltage, and light weight and thinness. Therefore, the liquid crystal display device is used in various display devices by taking advantage of these features. The liquid crystal display device is composed of many members such as a liquid crystal cell, a polarizing plate, a retardation film, a light collecting sheet, a diffusion film, a light guide plate, and a light reflecting sheet. For this reason, the improvement aiming at productivity, weight reduction, the improvement of the brightness, etc. is performed actively by reducing the number of sheets of a constituent film, or reducing the thickness of a film or a sheet | seat.

  On the other hand, a liquid crystal display device is required to have a product that can withstand severe durability conditions depending on applications. For example, a liquid crystal display device for a car navigation system may have a high temperature and humidity in a vehicle in which the liquid crystal display device is placed, and the temperature and humidity conditions are severe as compared with a monitor for a normal television or personal computer. For such applications, the polarizing plate is also required to have high durability.

  The polarizing plate has a layer structure in which optical films such as a polarizing film, a retardation film, and a protective film are laminated. In general, these optical films are obtained by winding up a resin composition formed into a sheet shape into a roll-shaped raw material, and feeding it out in the machine flow direction (referred to as MD) as necessary with other optical films. Often manufactured by bonding.

  In recent years, various uses and performances are required for polarizing plates, and various functions are also added to optical films. For example, various functional layers such as a hard coat layer and an antiglare layer are often provided on the surface of a retardation film or a protective film. In such a surface-treated optical film, a phenomenon in which an end portion of the optical film excessively curls (warps) on one surface side is likely to occur due to a difference in stress between the surface-treated layer and the optical film.

  In addition, when two types of optical films manufactured by different materials and manufacturing methods are laminated, a phenomenon in which the end portion curls excessively on one surface side is likely to occur as described above. This is because the front and back sides are asymmetrical with respect to one optical film, so the optical film tends to curl to one side due to the difference in stress between the optical film on the front side and the optical film on the back side. It is.

  Such an optical film with excessively curled edges may be folded when the optical film is handled, or bubbles may enter the bonded area when stacked on other optical films or liquid crystal cells. Inconveniences such as deterioration of the property and visibility, and insufficient application treatment to the end of the optical film during the coating process such as surface coating are likely to occur.

  As a technique for suppressing such excessive curling of an optical film, a method of applying tension to the optical film and bonding it to another optical film has been conventionally known (for example, see Patent Document 1). In the technique described in this document, when a synthetic resin film having an adhesive layer on one side is bonded to a protective layer of a polarizing film, a tensile strength of 0.01 to 0.5 is applied to the synthetic resin film. Then, the tension direction and the orientation direction of the polarizing film are bonded in parallel. Thereby, a certain amount of residual shrinkage stress is added to the polarizing plate after bonding, and the curvature (curl) in the orientation direction of a polarizing film can be prevented. In addition, since a polarizing film is normally manufactured by extending | stretching a polyvinyl alcohol-type resin uniaxially along a machine flow direction (MD), the orientation direction corresponds with a extending direction (namely, machine flow direction: MD). To do.

Further, as another technique for suppressing excessive curling of the optical film, there is known a method in which another optical film that is highly rigid and difficult to curl is bonded to the surface of the optical film that is easily curled (for example, Patent Document 2). reference). In the technique described in this document, when a polarizing plate in which a polarizer protective layer (optical film) is bonded to one side of a polarizer (also referred to as a polarizing film) is manufactured in a roll shape, A protective film (another optical film) having a shear adhesive force of 80 N / 625 mm ² or less is bonded to the polarizer protective layer, and the protective film is wound inside. By manufacturing in this way, the stress generated when the protective film is bonded to the polarizer protective layer is relaxed, and curling is suppressed.

JP-A-10-186133 (Claim 3, paragraphs 0004, 0011) JP 2009-251213 (Claim 1, paragraph 0030)

  According to the technique described in Patent Document 1 described above, it is described that curling can be suppressed by applying tension to the synthetic resin film (optical film). There is no mention of curling suppression effect in a direction perpendicular to the alignment direction of the polarizing film (direction perpendicular to the machine flow direction: TD). In addition, in this technology, tension is applied only to the synthetic resin film, and the protective layer and the polarizing film on the side to be bonded are applied with tension, or the specific value when tension is applied. Is not described at all.

  On the other hand, according to the technique described in Patent Document 2, it is described that curling is suppressed by bonding a protective film to the polarizer protective layer, but the direction perpendicular to the machine flow direction (TD). There is no description about the point of suppressing curling in the case of applying tension in the pasting.

  An object of the present invention is to provide a method for producing an optical film laminate in which excessive curling hardly occurs at the end of the optical film in a direction (TD) perpendicular to the machine flow direction, and an optical film laminate and a polarizing plate produced by the method. Is to provide.

  In the manufacturing process of an optical film laminate in which two kinds of films are laminated, the present inventors pay attention to curling at an end portion in a direction (TD) perpendicular to the machine flow direction, and various methods are used to suppress this. Manufacturing conditions were examined. As a result, when two types of optical films are bonded, the optical film lamination at the end in the direction (TD) perpendicular to the machine flow direction is made by setting the tension ratio in the machine flow direction (MD) as a predetermined condition. The present inventors have found that curling of the body can be greatly suppressed and have completed the present invention.

That is, according to the method for producing an optical film laminate of the present invention, the above problem is caused by the surface of the first optical film having a relatively large curl amount at the end in the direction (TD) perpendicular to the machine flow direction. By laminating a second optical film having a relatively small amount of curl at an end in a direction (TD) perpendicular to the machine flow direction than the first optical film, a direction perpendicular to the machine flow direction (TD) ) Of the optical film laminate in which curling at the end is suppressed, wherein the first optical film and the second optical film are each given tension along the machine flow direction (MD). And a bonding step of bonding the second optical film on the surface side where the curl is concave in the first optical film, and the bonding step includes: 1's Tension T _B applied to the machine flow direction (MD) in Manabu _film, when the tension applied to the machine flow direction (MD) in the second optical film was T _A, the tension ratio (T _B / T _A ) It is solved by laminating the first optical film and the second optical film in a state where tension is applied so as to be <1.

Further, the tension ratio _{(T B / T A) x} , the curl amount at the end of the first direction perpendicular to the machine direction of flow in the optical film _(TD) y _(TD), the curl amount is minimum Where b ₁ is the value of x and a is the value of x when the curl amount is minimum,
y _(TD) = (x−a ₁ ) ² −b ₁
(Where 0 <a ₁ <1, b ₁ ≧ 0)
Satisfy the relationship
In the pasting step (B), the tension ratio (T _B / T _A )
_{a 1 -0.24 ≦ T B / T} A ≦ a 1 +0.24
It is preferable to apply tension so as to satisfy the relationship.

Furthermore, in this case, the tension ratio (T _B / T _A ) is
_{a 1 ≦ T B / T A} ≦ a 1 +0.24
It is preferable to apply tension so as to satisfy this relationship.

In addition in the above case, the _{a 1} is preferably If it is 0.57.

  In addition, the first optical film is preferably one of a single film, a laminated film in which a plurality of films are laminated, or a surface-treated film in which any one of these films is surface-treated. .

  The first optical film is preferably an acrylic resin.

  Furthermore, it is preferable that the second optical film is a protective film made of a polyester resin.

  According to the optical film laminate of the present invention, the above problem is solved by being manufactured by any one of the above manufacturing methods.

  Moreover, according to the polarizing plate of this invention, the said subject is solved by providing said optical film laminated body and the polarizing film which consists of a polyvinyl alcohol-type resin in which the dichroic dye is carrying out adsorption orientation. .

According to the method for producing an optical film laminate of the present invention, when the first optical film and the second optical film are bonded, both optical films are set so that the tension ratio (T _B / T _A ) <1. Is bonded in a state where tension is applied. Thereby, a difference in shrinkage stress is generated between the two optical films, and curling at the end in the direction (TD) perpendicular to the machine flow direction can be suppressed. As a result, the handleability of the optical film laminate is improved, and problems such as folding of the end and entry of bubbles are less likely to occur when bonding to other optical films or liquid crystal cells.

It is the cross-sectional schematic diagram which showed an example of the manufacturing process of an optical film laminated body. It is the perspective view which showed typically the state which conveys an optical film, and the state after bonding. It is the perspective view which showed typically the method of measuring the curl amount of an optical film laminated body. It is the graph which showed the relationship between tension ratio and curl amount. It is the cross-sectional schematic diagram which showed an example of the polarizing plate. It is the top view which showed the state which cuts out the sample of an Example. It is the graph which showed the result of the Example.

  Hereinafter, some embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited by the member, arrangement | positioning, etc. which are demonstrated below, These members etc. can be suitably changed in accordance with the meaning of this invention.

  Hereinafter, the manufacturing method of an optical film laminated body is demonstrated in detail. In addition, in this specification, an optical film is a film used in the member which comprises optical apparatuses, such as a liquid crystal display device, and its manufacture. Specifically, as an optical film, a functional film having various functional layers such as a polarizing film, a retardation film, a protective film, a liquid crystal alignment film, a hard coat layer, an antiglare layer, an antireflection layer, and a low reflection layer. In addition to these, there can be mentioned a protective film, a separate film, etc. used in the production of these films and liquid crystal cells.

  Further, the optical film B (first optical film) may be a single film or a laminated film in which a plurality of films are laminated. Further, the first optical film may be a surface-treated film in which any of these films (film alone, laminated film) is surface-treated.

  The optical film B is a film having a relatively large curl amount at the end in the direction (TD) perpendicular to the machine flow direction, but such a film having a large curl amount is likely to occur in the following situation. First, in the case of a single film, when a shrinking stress acts on one surface due to a stretching process and curls on one side, or when the film is wound up as a result of being rolled and stored for a long time, etc. Tends to curl. In the case of a laminated film, when two or more kinds of films having different materials and manufacturing methods are laminated, the film tends to curl to one side due to a difference in stress between the films. In the case of a surface-treated film, it tends to curl to the treated surface side due to the difference in stress between the treated surface and the non-treated surface.

  The optical film A (second optical film) is an optical film in which the curl amount at the end in the direction (TD) perpendicular to the machine flow direction is relatively smaller than that of the optical film B. The optical film A has a role of correcting the curl of the optical film B and suppressing the curl at the TD end by being laminated with the optical film B having a large curl amount.

  From the viewpoint of correcting and suppressing curling of the optical film B, the optical film A preferably has a small initial curl before being bonded to the optical film B and is flat. Moreover, a thing with rigidity higher than the optical film A is preferable, for example, a thing with a high tensile elasticity modulus is suitable.

  In the following embodiments, an optical film B (first optical film) that is a surface-treated protective film and an optical film A (second optical film) that is a protective film provided with an adhesive layer are bonded. The method for manufacturing the optical film laminate X is described. A surface-treated coated surface is formed on one surface of the protective film, and the one that is curled so that the coated surface side is concave is used as the optical film B. In addition, as optical film A and B, it is not limited to the combination of a protective film and a protective film in this way, A combination can be suitably selected and employ | adopted from the various optical film mentioned above.

  FIG. 1 is a schematic cross-sectional view schematically showing a manufacturing process of an optical film laminate. The manufacturing method of the optical film laminated body X in this embodiment performs the conveyance process (A) which conveys a raw material film, the bonding process (B), and a winding process (C).

[Conveying process (A)]
In a conveyance process (A), the elongate optical film A is drawn | fed out from the optical film A wound by roll shape. On the other hand, the long optical film B is unwound from the optical film B wound in a roll shape. The optical film A is conveyed in a certain direction, and the optical film B is supplied to one surface thereof.

  FIG. 2 is a perspective view schematically showing a process of transporting the optical film A and the optical film B and a state after bonding. As shown to Fig.2 (a), the optical film B is conveyed toward the optical film A side the surface side from which a cross-sectional shape becomes concave. On the other hand, the optical film A is conveyed with an adhesive layer (not shown) facing the optical film B side. That is, it conveys so that the surface (surface treatment coating surface) which becomes concave shape in the optical film B and the adhesive layer of a protect film may face each other, and it is bonded by the bonding process (B) mentioned later.

  The transport speed of each film may be set to a value suitable for the manufacturing apparatus, and is not particularly limited. Usually, however, it is matched with the transport speed of each of the optical films A and B manufactured and transported in the previous process. Speed. In addition, unless the optical film laminate X is restricted by the type or quality used, a higher conveying speed is preferable from the viewpoint of productivity because the tact time becomes faster. As a conveyance speed, it can set to about 1-30 m / min, for example.

  The direction in which each of the optical films A and B is conveyed is not particularly limited as long as the optical films A and B are laminated at the end of the conveying step (A). In the middle of the process, there may be a part where each optical film A, B is conveyed in the vertical direction as shown in the figure, or there may be a part which is conveyed in parallel although not shown. Further, when there is a restriction on the arrangement of the manufacturing apparatus, the optical films A and B may be temporarily fed out in a direction different from the transport direction, and the direction may be changed by an appropriate roll and transported.

The optical film A to be paid out by the transporting step (A), the tension (T _A) is applied in the machine flow direction (MD). In this embodiment, the tension (T _A ) is wound in a winding step (C), which will be described later, with respect to the feeding roll 11 for feeding the raw material film wound in a roll shape and the optical film laminate X after bonding, which will be described later. Tension is applied by making a difference in the peripheral speed of the roll with the take-up roll 13 for taking. That is, the peripheral speed is increased in the take-up roll 13 than the peripheral speed of the feed rolls 11 and 12, and applies tension (T _A) by pulling the machine flow direction (MD) relative to the optical film A.

Similarly, tension (T _B ) is applied in the machine flow direction (MD) to the optical film B fed out in the transport step (A). Similarly to the tension (T _A ), the tension (T _B ) in this case is applied by providing a difference in peripheral speed between the feeding roll 12 and the winding roll.

[Bonding process (B)]
The optical films A and B transported in the transport process (A) are supplied to the subsequent bonding process (B). The laminating step (B) includes the laminating roll 15 in contact with the outside of the optical film A and the laminating roll 16 in contact with the outside of the optical film B, while sandwiching the laminate of the optical film A / optical film B. It is the process of pasting. The laminating roll 15 and the laminating roll 16 are rotating in the conveying direction of the optical film that is in contact with each other, and the curved arrow in the figure indicates the rotating direction. Thereby, the adhesive layer of the optical film A and the concave surface of the optical film B are bonded to form an optical film laminate X as shown in FIG.

  Surface materials constituting the bonding rolls 15 and 16 are metals such as stainless steel, copper alloy, and chrome-plated products; rubbers such as polyurethane, polyfluoroethylene, and silicone; chromium oxide, silicon oxide, and oxidation. And ceramics obtained by thermal spraying one or more of zirconium and aluminum oxide.

Here, when the normal bonding conditions, that is, the tension (T _A ) of the optical film _A and the tension (T _B ) of the optical film B are the same (T _A = T _B , that is, T _B / T _A = 1). ), The resulting optical film laminate X tends to have a large curl at the end in the direction (TD) perpendicular to the machine flow direction. Therefore, in the present invention, when the tension (T _A ) applied in the machine flow direction (MD) in the optical film _A and the tension (T _B ) applied in the machine flow direction (MD) in the optical film B, The optical film A and the optical film B are bonded in a state where tension is applied so that the following tension ratio is obtained.
Tension ratio (T _B / T _A ) <1

Thus, by laminating the optical film A and the optical film B while applying a tension such that the tension ratio _{(T B / T A) <} 1, an optical film laminate X resulting machine flow direction Curling at the end in the direction (TD) perpendicular to is suppressed.

  Here, the relationship between the machine flow direction (MD) and the direction perpendicular to the machine flow direction (TD) and curl will be described. FIG. 3 is a perspective view showing a state in which the end of the optical film laminate X in the direction (TD) perpendicular to the machine flow direction is curled.

  The curl amount of the optical film laminate X can be measured as follows. First, as shown by a dotted line in FIG. 2B, the optical film laminate X is cut into a square shape or a rectangular shape so that the machine flow direction (MD) substantially coincides with one of the diagonal lines. The angle formed by the machine flow direction (MD) and the diagonal line can be appropriately set within a range of about 0 ° to 5 °. The size to be cut can be cut to any size such as 250 mm × 250 mm, 300 mm × 300 mm, 400 mm × 400 mm, 700 mm × 700 mm, 250 mm × 300 mm, 350 mm × 450 mm. In addition, when showing the curl amount, it is necessary to specify the size of the cut.

  Next, as shown in FIG. 3, when the curl is generated in the optical film laminate X, the convex side is directed downward, and when the curl is not generated, either side Is placed on a reference surface P (for example, on a horizontal table) and left to stand in an environment of a temperature of 22 ° C. and a relative humidity of 60% for 1 hour. In this figure, the surface when it is assumed that there is no curl in the optical film laminate X is displayed as a virtual surface P (surface indicated by a dotted line in the drawing).

  If no curl is observed for the first time, the curl amount is measured by the following method as it is if the bottom is convex after standing for 1 hour in an environment of temperature 22 ° C. and relative humidity 60%. If the top is convex after standing for a while, the front and back of the optical film laminate X are reversed, and the curl amount is measured by the method described below. On the other hand, if curl is not observed in the first place after standing for 1 hour, the front and back of the optical film laminate X are reversed. If no curl is observed even when the front and back are reversed, the curl amount is determined to be zero. If curl is observed in a state where the front and back sides are reversed, the curl amount is measured by the method described below in that state. When curl is observed, the curl amount is measured with the convex side facing down as shown in the figure.

  Hereinafter, a curl amount measuring method will be described with reference to the drawings. This figure shows a so-called “positive curl” state in which the optical film B side of the optical film laminate X is convex. The end in the direction (TD) perpendicular to the machine flow direction is the end of the optical film laminate X on the side (TD) side perpendicular to the machine flow direction. The corner C2 or C4 corresponds. The curl amount at the end in the direction (TD) perpendicular to the machine flow direction is any of the measured values of the height H between the corner C2 or C4 of the optical film laminate X and the virtual plane P. Means the larger one (maximum value). This curl at the TD end is referred to as “TD curl”.

  Similarly, the end portion in the machine flow direction (MD) is the end portion on the machine flow direction (MD) side of the optical film laminate X, and in this figure, the corner C1 or C3 of the optical film laminate X is Applicable. The curl amount at the end in the machine flow direction (MD) is the larger one of the measured values of the height between the corner C1 or C3 of the optical film laminate X and the virtual plane P (maximum value). ). This curl at the end of the MD is called “MD curl”. In the case of so-called “reverse curl” in which the optical film A side is convex in the optical film laminate X, the amount of curl is measured in the same manner as described above with the convex side facing down.

The tension (T _A , T _B ) applied to the optical films A and B can be measured and controlled by a known tension controller. The types of tension controllers include torque control type and speed control type according to the classification based on the control method. Examples of the torque control type include a closed loop method that is a slight displacement method, and an open loop method that is an integrated thickness method or a proportional calculation method. An example of the speed control type is a closed loop system. In addition, classification by actuator (mechanical device) includes a powder clutch / brake system and a motor system. As a powder clutch / brake system, a torque control type can be mentioned. Further, examples of the motor system include a torque control type and a speed control type. In the present invention, any method can be adopted, but it is preferable to measure and control the tension of the optical film A and the optical film B by the same method.

(1) About Tension Ratio Next, the relationship between the tension ratio (T _B / T _A ) and the curl amount will be described. The inventors set the tension ratio (T _B / T _A ) under various conditions and measured the curl amount. As a result, the tension ratio (T _B / T _A ) in the bonding step (B) and the curl amount (TD curl) at the end in the direction (TD) perpendicular to the machine flow direction of the obtained optical film laminate X The second-order correlation (that is, the quadratic function) is obtained when the tension ratio (T _B / T _A ) is the horizontal axis x and the TD curl amount is the vertical axis y _(TD). I understood it.
This quadratic function can be expressed by the following equation (1).
y _(TD) = α (x−a ₁ ) ² + b ₁ (1)
(Where 0 <a ₁ <1, b ₁ ≧ 0)

On the other hand, between the tension ratio (T _B / T _A ) in the bonding step (B) and the curl amount (MD curl amount) at the end in the machine flow direction (MD) of the obtained optical film laminate X Similarly in was found to be the tension ratio _(T B / T _a) horizontal axis x, a quadratic function in the case of the vertical axis _{y (MD)} and MD curl amount. This quadratic function can be expressed by the following equation (2).
y _(MD) = α (x−a ₂ ) ² + b ₂ (2)
(Where 0 <a ₂ <1, and a ₁ <a ₂ , b ₂ ≧ 0)

FIG. 4 is a graph showing the above equations (1) and (2). As shown in this figure, regarding the TD curl, when the tension ratio (T _B / T _A ) is the value a ₁ , the TD curl amount becomes the minimum value b ₁ . Further, as the tension ratio (T _B / T _A ) increases or decreases with the value a ₁ as a reference, the TD curl amount increases literally in a quadratic function. That is, from the viewpoint of suppressing the amount of TD curl, the tension ratio (T _B / T _A ) is preferably within a predetermined range (k in the figure), for example, within the range represented by the following formula (3) It can be.
a ₁ -k ≦ tension ratio _{(T B / T A) ≦} a 1 + k ··· (3)
(Where 0 <k <1)

The value of k can be appropriately set according to the curl amount allowable for the product. Specifically, it can be, for example, 0.24 or less, preferably 0.15 or less, and more preferably 0.10 or less. When k is 0.24, the tension ratio (T _B / T _A ) is in a range represented by the following formula (4).
a ₁ -0.24 ≦ tension ratio _{(T B / T A) ≦} a 1 +0.24 ··· (4)

If the tension ratio (T _B / T _A ) is out of the above range, the TD curl amount becomes too large, which is not preferable. If the optical film laminate X has a slight positive curl, when it is bonded to another optical film, a liquid crystal cell or the like, it becomes difficult for air bubbles to be caught by making the convex side the bonding surface. Therefore, it is preferable. However, if the amount of TD curl becomes too large, there is a disadvantage that the polarizing plate is easily peeled off from the end of the polarizing plate after being bonded to the liquid crystal cell. When the positive curl is plus (+) and the reverse curl is minus (−), the TD curl amount is preferably in the range of about 0 mm to +25 mm. As shown in an example described later, when k is 0.24, the TD curl amount is 25 mm.

On the other hand, regarding the MD curl, when the tension ratio (T _B / T _A ) is the value a ₂ , the MD curl amount becomes the minimum value b ₂ . Further, as the tension ratio (T _B / T _A ) increases or decreases based on the value a ₂ , the MD curl amount increases rapidly in a quadratic function. Further, since a ₁ <a ₂ , the MD curl amount is smaller when the tension ratio (T _B / T _A ) is larger than a ₁ .

From the viewpoint of suppressing not only the TD curl amount but also the MD curl amount, the range in which the tension ratio (T _B / T _A ) is a ₁ or more in the range of the above formula (3), that is, the following formula: The range represented by (5) is preferred.
a ₁ ≦ tension ratio (T _B / T _A ) ≦ a ₁ + k (5)
(Where 0 <k <1)

When k is 0.24, the tension ratio (T _B / T _A ) in equation (5) is in the range of equation (6) below.
a ₁ ≦ tension ratio (T _B / T _A ) ≦ a ₁ +0.24 (6)

Here, the mechanism by which TD curl is suppressed as described above is not clear, but is estimated as follows.
( _A ) Reason why TD curl is suppressed by applying a tension ratio (T _B / T _A ) Due to the tension applied to the optical film A and the optical film B, the optical films A and B are in the region of elastic deformation. Respectively, it deforms in the machine flow direction (MD). At this time, due to the necking phenomenon, the optical films A and B are also elastically deformed in the direction (TD) perpendicular to the machine flow direction, and the length in the width direction is reduced. It is estimated that TD curl is suppressed by this deformation to TD.

(B) The reason why the relationship between the tension ratio (T _B / T _A ) and the amount of TD curl is a quadratic function Due to the difference between the amount of deformation of the optical film A into TD and the amount of deformation of the optical film B into TD Presumed to be. The optical film elastically deformed to TD exerts a force (residual stress) to return to the original state, but due to differences in the materials, film thickness, manufacturing history, etc. of the optical film A and optical film B, the respective optical films There is a difference in residual stress. The difference between the residual stress of the optical film A and the residual stress of the optical film B is the smallest, and as a result, the tension ratio (T _B / T _A ) where the total TD curl amount of the optical film laminate X is the smallest is ₁ is considered. On the other hand, as the tension ratio (T _B / T _A ) increases or decreases from the value a ₁ , the difference in residual stress between the two optical films increases, so it is estimated that the amount of TD curl increases.

When the value of (c) tension ratio _(T B / T _A) why tension ratio MD curl amount decreases approaches to 1 _(T B / T _A) is greater than _{a 1,} but TD curl amount is increased, MD curl amount decreases. In general, when a sheet-like material such as the optical film laminate X is bent into a cylindrical shape, one end portion is greatly curled, but the end portion in a direction perpendicular to the end portion is curled. That is, TD curl and MD curl tend to decrease when one increases. For this reason, even if the value of the tension ratio (T _B / T _A ) is greater than a ₁ and the TD curl amount increases, it is presumed that MD curl has decreased.

(2) Regarding the tension difference The condition of the tension ratio (T _B / T _A ) <1 described above can be expressed by using another expression.
T _A -T _B > 0
Can also be expressed. Here, T _A -T _B indicates a value obtained by subtracting the tension (T _B ) of the optical film B from the tension (T _A ) of the optical film _A , that is, the tension difference, and the tension ratio (T _B / T condition _a) can also be expressed as a condition of tension difference _(T a -T _B). Tension difference (T A _{-T B)} on the horizontal axis, even when the longitudinal axis of the curl amount, the same related quadratic function in the case of tension ratio _(T B _/ T _A). Since the relationship between the quadratic functions has already been described, the details are omitted here.

[Winding process (C)]
A winding process (C) is a process of winding the optical film laminated body X obtained at the bonding process (B) in roll shape. In the drawing, the optical film laminate X is wound with the optical film A on the inner side, but the winding direction is not limited thereto, and the optical film B may be wound with the optical film B on the inner side.

(Polarizing plate 20)
Next, a polarizing plate using the optical film laminate X will be described. The optical film laminated body X manufactured with the manufacturing method mentioned above can be used for a polarizing plate. FIG. 5 is a schematic cross-sectional view showing a laminated structure of polarizing plates. As shown in this figure, the polarizing plate 20 has a layer structure in which a transparent resin film 23, a polarizing film 21, a protective film 25, and a protective film 29 are laminated in this order. The optical film B is used as a protective film 25, and the optical film A is used as a protective film 29. Hereinafter, each layer constituting the polarizing plate 20 will be described.

(1) Polarizing film 21
The polarizing film 21 is a member having a function of converting natural light into linearly polarized light. As the polarizing film 21, a film obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol resin film can be used. As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. As the polyvinyl acetate resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, polyvinyl acetate and Examples thereof include copolymers with other copolymerizable monomers. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can also be used. The degree of polymerization of the polyvinyl alcohol resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

  A film obtained by forming such a polyvinyl alcohol resin is used as a raw film of the polarizing film 21. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. Although the thickness of a polyvinyl alcohol-type raw film is not specifically limited, For example, it is about 3-150 micrometers.

  The polarizing film 21 usually has a step of uniaxially stretching such a polyvinyl alcohol resin film, a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol resin film with a dichroic dye, and a dichroic dye It is manufactured through a step of treating the adsorbed polyvinyl alcohol-based resin film with a boric acid aqueous solution and a step of washing with water after the treatment with the boric acid aqueous solution.

  Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing with the dichroic dye, simultaneously with dyeing, or after dyeing. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, uniaxial stretching can also be performed in several steps. For uniaxial stretching, a method of stretching uniaxially between rolls having different peripheral speeds, a method of stretching uniaxially using a hot roll, or the like can be adopted. Further, the uniaxial stretching may be dry stretching in which stretching is performed in the air, or may be wet stretching in which stretching is performed in a state where a polyvinyl alcohol-based resin film is swollen using a solvent such as water. The draw ratio is usually about 3 to 8 times.

  The polyvinyl alcohol resin film can be dyed with a dichroic dye by, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic dye is used as the dichroic dye. In addition, it is preferable to perform the process which a polyvinyl alcohol-type resin film swells by immersing in water before a dyeing process.

  When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. It is. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 20 to 1,800 seconds.

On the other hand, when a dichroic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic dye is usually employed. The content of the dichroic dye in this aqueous solution is usually about 1 × 10 ⁻⁴ to 10 parts by weight, preferably about 1 × 10 ⁻³ to 1 part by weight per 100 parts by weight of water. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the aqueous dichroic dye solution used for dyeing is usually about 20 to 80 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 10 to 1,800 seconds.

  The boric acid treatment after dyeing with a dichroic dye can be performed by immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution. The boric acid content in the boric acid-containing aqueous solution is usually about 2 to 15 parts by weight, preferably about 5 to 12 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The content of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight, preferably about 5 to 12 parts by weight per 100 parts by weight of water. The immersion time in the boric acid-containing aqueous solution is usually about 60 to 1,200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C., more preferably 60 to 80 ° C.

  The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. The temperature of water in the water washing treatment is usually about 5 to 40 ° C., and the immersion time is usually about 1 to 120 seconds.

  After washing with water, a drying process is performed to obtain the polarizing film 21. The drying process can be performed using a hot air dryer or a far infrared heater. The temperature of a drying process is about 30-100 degreeC normally, Preferably it is 50-80 degreeC. The drying time is usually about 60 to 600 seconds, preferably 120 to 600 seconds.

  In this way, the polyvinyl alcohol-based resin film is subjected to uniaxial stretching, dyeing with a dichroic dye, and boric acid treatment, and the polarizing film 21 is obtained. The thickness of the polarizing film 21 can be about 2-40 micrometers, for example.

  Thus, it is preferable that the polarizing film 21 obtained is bonded to the optical film laminated body X by the flow as it is. Thereby, it can produce continuously from the raw film of a polyvinyl alcohol-type resin until the polarizing plate 20 is manufactured.

(2) Protective film 25
The protective film 25 is a member having functions such as preventing wear and reinforcing the surface of the polarizing film 21. The protective film 25 is preferably made of a transparent resin. Examples of the transparent resin include acrylic resin such as methyl methacrylate resin, olefin resin, polyvinyl chloride resin, cellulose resin, styrene resin, acrylonitrile / butadiene / styrene copolymer resin, acrylonitrile / styrene. Copolymer resins, polyvinyl acetate resins, polyvinylidene chloride resins, polyamide resins, polyacetal resins, polycarbonate resins, modified polyphenylene ether resins, polyester resins (for example, polybutylene terephthalate resins, polyethylene terephthalate resins) Resin), polysulfone resin, polyethersulfone resin, polyarylate resin, polyamideimide resin, polyimide resin, epoxy resin, and oxetane resin. These resins can contain additives as long as transparency and adhesiveness with the polarizing film 21 are not impaired.

  Of these, acrylic resins that are relatively inexpensive and excellent in flexibility and capable of being thinned are preferable. Here, acrylic resin means (meth) acrylic resin and is a concept including both acrylic resin and methacrylic resin. In the acrylic resin, rubber elastic particles may be blended in order to improve flexibility and handleability. Hereinafter, the acrylic resin will be described.

(2-1) Acrylic Resin The acrylic resin is a (meth) acrylic resin as described above, and means a polymer of acrylic acid ester or methacrylic acid ester. As the polymer of the methacrylic acid ester, for example, a polymer composed mainly of an alkyl methacrylate is preferable. The monomer composition of the alkyl methacrylate is preferably 70% by weight or more, more preferably 80% by weight or more, and still more preferably 90% by weight or more, based on the total 100% by weight of all monomers. And alkyl methacrylate is 99% by weight or less. The acrylic resin may be a homopolymer of alkyl methacrylate, or a copolymer of 50% by weight or more of alkyl methacrylate and 50% by weight or less of a monomer other than alkyl methacrylate. Also good. As the alkyl methacrylate, those having 1 to 4 carbon atoms of the alkyl group are usually used, and among them, methyl methacrylate is preferably used.

  The monomer other than alkyl methacrylate may be a monofunctional monomer having one polymerizable carbon-carbon double bond in the molecule, or two or more polymerizable carbons in the molecule. -A polyfunctional monomer having a carbon double bond may be used. In particular, monofunctional monomers are preferably used. Examples thereof include alkyl acrylates such as methyl acrylate and ethyl acrylate, styrene monomers such as styrene and alkyl styrene, acrylonitrile and methacrylonitrile. Such unsaturated nitriles. When using alkyl acrylate as a copolymerization component, the carbon number is 1-8 normally.

  The acrylic resin preferably does not have a glutarimide derivative, a glutaric anhydride derivative, a lactone ring structure, or the like. These acrylic resins may not provide sufficient mechanical strength and moist heat resistance as the protective film 25 in some cases.

(2-2) Rubber elastic particle The rubber elastic particle is a particle containing a rubber elastic body, and may be a particle composed only of a rubber elastic body or a particle having a multilayer structure having a rubber elastic body layer. It may be. Examples of rubber elastic bodies include olefin-based elastic polymers, diene-based elastic polymers, styrene-diene-based elastic copolymers, and acrylic-based elastic polymers. Among these, an acrylic elastic polymer is preferably used from the viewpoint of the surface hardness, light resistance, and transparency of the protective film 25.

  The acrylic elastic polymer is preferably a polymer mainly composed of alkyl acrylate, and may be a homopolymer of alkyl acrylate, or may be a single polymer other than alkyl acrylate of 50% by weight or more and alkyl acrylate. A copolymer with 50% by weight or less of the monomer may be used. As the alkyl acrylate, those having 4 to 8 carbon atoms in the alkyl group are usually used. Examples of monomers other than alkyl acrylate include alkyl methacrylates such as methyl methacrylate and ethyl methacrylate, styrene monomers such as styrene and alkyl styrene, acrylonitrile and methacrylonitrile. Monofunctional monomers such as unsaturated nitriles, alkenyl esters of unsaturated carboxylic acids such as allyl (meth) acrylate and methallyl (meth) acrylate, dialkenyl esters of dibasic acids such as diallyl maleate, And polyfunctional monomers such as unsaturated carboxylic acid diesters of glycols such as alkylene glycol di (meth) acrylate.

  The rubber elastic particle containing the acrylic elastic polymer is preferably a multi-layered particle having an acrylic elastic polymer layer, and a polymer mainly composed of alkyl methacrylate outside the acrylic elastic polymer. It may be a two-layer structure having the above-mentioned layer, or a three-layer structure having a polymer layer mainly composed of alkyl methacrylate inside the acrylic elastic polymer. In addition, the example of the monomer composition of the polymer mainly composed of alkyl methacrylate constituting the layer formed on the outside or inside of the acrylic elastic polymer is the alkyl methacrylate mentioned above as an example of the acrylic resin. It is the same as that of the example of the monomer composition of the polymer which has mainly. Such acrylic rubber elastic particles having a multilayer structure can be produced, for example, by the method described in Japanese Patent Publication No. 55-27576.

  As the rubber elastic particles, those having a number average particle diameter of 10 to 300 nm of rubber elastic bodies contained therein are used. Thereby, when the protective film 25 is laminated | stacked on the polarizing film 21 using an adhesive agent, the protective film 25 can be made hard to peel from an adhesive bond layer. The number average particle diameter of the rubber elastic body is preferably 50 nm or more and 250 nm or less.

  In the case of rubber elastic particles in which the outermost layer is a polymer mainly composed of methyl methacrylate and the acrylic elastic polymer is encapsulated therein, the rubber elastic particles are mixed with the base acrylic resin. Since the outermost layer of the resin is mixed with the base acrylic resin, the rubber elastic particles are excluded from the outermost layer when the acrylic elastic polymer is dyed with ruthenium oxide in the cross section and observed with an electron microscope. It is observed as particles in a wet state.

  Specifically, in the case of using rubber elastic particles having a two-layer structure in which the inner layer is an acrylic elastic polymer and the outer layer is a polymer mainly composed of methyl methacrylate, the inner layer is an acrylic elastic polymer. The portion is dyed and observed as particles having a single layer structure. Further, the rubber elastic particles having a three-layer structure in which the innermost layer is a polymer mainly composed of methyl methacrylate, the intermediate layer is an acrylic elastic polymer, and the outermost layer is a polymer mainly composed of methyl methacrylate. When is used, the center part of the innermost layer particle is not dyed, and only the acrylic elastic polymer part of the intermediate layer is dyed and observed as a two-layered particle.

  In the present specification, the number average particle diameter of the rubber elastic particles is, as described above, when the rubber elastic particles are mixed with the base resin and the cross section is dyed with ruthenium oxide, and is dyed in a substantially circular shape. It is the number average value of the diameters of the parts observed in FIG.

  In the acrylic resin composition forming the protective film 25, 25 to 45% by weight of rubber elastic body particles having a number average particle diameter of 10 to 300 nm is blended in a transparent acrylic resin.

  The acrylic resin composition is produced, for example, by obtaining rubber elastic particles and then polymerizing a monomer as a raw material of the acrylic resin in the presence thereof to produce a base acrylic resin. Alternatively, after obtaining rubber elastic particles and an acrylic resin, they may be produced by mixing them by melt kneading or the like.

  As necessary, the acrylic resin composition includes a colorant such as a pigment or a dye, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an infrared absorber, an ultraviolet absorber, an antistatic agent, You may contain compounding agents, such as antioxidant, a lubricant, and a solvent.

  The ultraviolet absorber is added to improve durability by absorbing ultraviolet rays of 400 nm or less. As the ultraviolet absorber, known ones such as a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, and an acrylonitrile ultraviolet absorber can be used. Among them, 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 are preferably used. Among these, 2,2′-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol) is particularly preferable.

  The blending amount of the ultraviolet absorber can be selected in such a range that the transmittance of the optical film at a wavelength of 370 nm or less is preferably 10% or less, more preferably 5% or less, and further preferably 2% or less. Moreover, it is also preferable to mix | blend an ultraviolet absorber so that the transmittance | permeability in wavelength 380nm of an optical film may be 25% or less, Furthermore, 15% or less, Especially 7% or less. What is necessary is just to determine the compounding quantity of a ultraviolet absorber so that the transmittance | permeability of an optical film may satisfy | fill the conditions shown here. On the other hand, it is preferable to determine the blending amount of the ultraviolet absorber so as to satisfy the above-described transmittance from the range of about 0.1 to 2.5 parts by weight, particularly about 0.5 to 2 parts by weight. As a method of containing an ultraviolet absorber, the ultraviolet absorber is premixed in an acrylic resin and pelletized, and this is formed into a film by melt extrusion or the like, or the ultraviolet absorber is directly added during melt extrusion molding. Any method can be used.

  Infrared absorbers include nitroso compounds, metal complexes thereof, cyanine compounds, squarylium compounds, thiol nickel complex compounds, phthalocyanine compounds, naphthalocyanine compounds, triallylmethane compounds, imonium compounds, diimonium compounds, Infrared absorption of naphthoquinone compounds, anthraquinone compounds, amino compounds, aminium salt compounds, carbon black, indium tin oxide, antimony tin oxide, oxides of metals belonging to Group 4A, 5A or 6A, carbides, borides, etc. An agent etc. can be mentioned.

  These infrared absorbers are preferably selected so as to be able to absorb the entire infrared ray (light having a wavelength in the range of about 800 nm to 1100 nm), and two or more types may be used in combination. The amount of the infrared absorber can be appropriately adjusted so that, for example, the light transmittance of the protective film 25 at a wavelength of 800 nm or more is 10% or less.

  The glass transition temperature Tg of the acrylic resin composition is preferably in the range of 80 to 120 ° C. Furthermore, the acrylic resin composition preferably has a high surface hardness when formed into a film, specifically, a pencil hardness (with a load of 500 g, conforming to JIS K5600-5-4) of B or higher. .

  In addition, the acrylic resin composition preferably has a flexural modulus (JIS K7171) of 1500 MPa or less from the viewpoint of the flexibility of the protective film 25. The flexural modulus is more preferably 1300 MPa or less, and still more preferably 1200 MPa or less. This flexural modulus varies depending on the type and amount of acrylic resin and rubber elastic particles in the acrylic resin composition. For example, as the content of rubber elastic particles increases, the flexural modulus generally decreases. . In addition, the use of a copolymer of an alkyl methacrylate and an alkyl acrylate as an acrylic resin generally has a lower flexural modulus than using an alkyl methacrylate homopolymer.

  In addition, the elastic elastic polymer particles having the two-layer structure are generally used as the elastic rubber particles, rather than the acrylic elastic polymer particles having the two-layer structure. In general, the flexural modulus is smaller when the acrylic elastic polymer particles having a layer structure are used. Further, in the rubber elastic body particles, as the average particle diameter of the rubber elastic body is smaller or the amount of the rubber elastic body is larger, the bending elastic modulus is generally smaller. Therefore, it is preferable to adjust the kind and amount of the acrylic resin and the rubber elastic body particles within the predetermined range so that the flexural modulus is 1500 MPa or less.

  When the protective film 25 has a multilayer structure, the layer that can exist other than the layer of the acrylic resin composition is not particularly limited in its composition, for example, an acrylic resin that does not contain rubber elastic particles or a composition thereof. It may be a layer, or may be a layer made of an acrylic resin composition in which the content of the rubber elastic body particles and the average particle diameter of the rubber elastic body in the rubber elastic body particles are outside the above definition.

  Typically, it has a two-layer or three-layer structure, and may be a two-layer structure including, for example, an acrylic resin composition layer / an acrylic resin not containing rubber elastic particles or a layer of the composition. Further, it may have a three-layer structure comprising an acrylic resin composition layer / an acrylic resin not containing rubber elastic particles or a layer of the composition / an acrylic resin composition layer. The protective film 25 having a multilayer structure may have a surface of the acrylic resin composition layer as a bonding surface with the polarizing film 21.

  When the protective film 25 has a multilayer structure, the contents of the rubber elastic particles and the layers of the compounding agent may be different from each other. For example, a layer containing an ultraviolet absorber and / or an infrared absorber and a layer not containing an ultraviolet absorber and / or an infrared absorber may be laminated with this layer interposed therebetween. Further, the content of the ultraviolet absorber in the layer of the acrylic resin composition may be higher than the content of the ultraviolet absorber in the layer of the acrylic resin not containing rubber elastic particles or the composition thereof. Well, specifically, the former is preferably 0.5 to 10% by weight, more preferably 1 to 5% by weight, and the latter is preferably 0 to 1% by weight, more preferably 0 to 0.5% by weight. Also good. Thereby, without deteriorating the color tone of the polarizing plate 20, it is possible to efficiently block ultraviolet rays and prevent a decrease in the degree of polarization during long-term use.

  The protective film 25 may be a non-oriented film that has not been stretched or may be stretched. When the stretching treatment is not performed, the thickness of the polarizing plate 20 is likely to increase because the thickness is increased. On the other hand, the handling property of the protective film 25 is improved because the thickness is large. Such a protective film 25 can be obtained from an unstretched film (raw film) obtained by forming an acrylic resin composition. On the other hand, when stretched, it is easy to develop a phase difference, but stretching has the advantage that the film thickness of the protective film 25 is reduced and the rigidity is improved. The stretched film can be produced by stretching an unstretched film by an arbitrary method.

  The acrylic resin can be formed into an unstretched film by any method. This unstretched film is preferably transparent and substantially free of in-plane retardation. Examples of the film forming method include an extrusion method in which a molten resin is extruded to form a film, and a solvent cast method in which a solvent dissolved in an organic solvent is cast on a flat plate and then the solvent is removed to form a film. Etc. can be adopted.

  As a specific example of the extrusion molding method, for example, there is a method of forming a film in a state where an acrylic resin composition is sandwiched between two metal rolls. In this case, the metal roll is preferably a mirror roll. Thereby, the unstretched film excellent in surface smoothness can be obtained. In addition, when obtaining the thing of a multilayer structure as the protective film 25, what is necessary is just to film-form an acrylic resin composition after multilayer extrusion with another acrylic resin composition. The thickness of the unstretched film thus obtained is preferably 5 to 200 μm, more preferably 10 μm to 85 μm.

  An unstretched film made of an acrylic resin can be stretched by a known method such as uniaxial stretching or biaxial stretching. Examples of the stretching method include a tenter method using a tenter stretching machine. Biaxial stretching may be simultaneous biaxial stretching in which stretching is performed simultaneously in two stretching directions, or sequential biaxial stretching in which stretching is performed in a predetermined direction and then stretching in another direction.

  Next, the haze value of the protective film 25 will be described. The haze value is a ratio of the diffused light transmittance to the total light transmittance when the film is irradiated with visible light, and it is recognized that the smaller the haze value is, the better the film is. Moreover, an internal haze value shows the value which deducted the haze value (external haze value) resulting from the surface shape of a film from the haze value of a film.

  As described above, the haze value of the protective film 25 has an internal haze value of 1.0% or less, more preferably 0.5% or less, and an external haze value of 5% or less. When the internal haze value exceeds 1.0% and the external haze value exceeds 5%, the light transmitted through the film is scattered, and the display characteristics may be deteriorated when the liquid crystal display device 1 is bonded.

  In addition, by performing a surface treatment on the protective film 25, it is possible to impart a function that the protective film 25 alone did not have. For example, the protective film 25 can be subjected to a hard coat treatment from the viewpoint of preventing surface scratches in the assembly process of the liquid crystal module. In addition, surface treatment such as antistatic treatment can be performed. However, when the protective film 25 is used as the protective film of the polarizing film 21 and the polarizing plate 20 is formed, the antistatic function can be imparted by subjecting the protective film 25 to surface treatment, and an adhesive layer. It can also be applied to other portions of the polarizing plate 20 in which the base film is incorporated. Other examples of surface treatment on the protective film 25 include antireflection treatment and antifouling treatment. Furthermore, an antiglare treatment can be performed from the viewpoints of improving visibility, preventing reflection of external light, and reducing moire due to interference between the prism sheet and the color filter. When such a surface treatment is performed, the protective film 25 is easily curled to the treatment surface side, and thus the TD curl suppression technique based on the tension ratio described above is particularly effective.

(3) Protect film 29
The protective film 29 is a peelable film and is a member for protecting the surface of the protective film 25 from damage, abrasion, and the like. The protective film 29 includes a base film made of a transparent resin, and a pressure-sensitive adhesive layer having a weak adhesive property laminated on the surface of the base film. The protective film 29 is bonded to the protective film 25 until the polarizing plate 20 is used, and is peeled off from the protective film 25 when used.

  The protect film 29 can be easily obtained as a commercial product. Examples of commercially available products include “Mastack” sold by Fujimori Kogyo Co., Ltd., “Sanitect” sold by Sanei Kaken Co., Ltd., and “Emask” sold by Nitto Denko Co., Ltd. And “Tretec” sold by Toray Film Processing Co., Ltd.

(3-1) Base film A base film will not be specifically limited if it consists of transparent resin. Examples of such transparent resins include acrylic resins typified by polymethyl methacrylate, olefin resins typified by polypropylene and polyethylene, and polyester resins typified by polybutylene terephthalate and polyethylene terephthalate. Can be mentioned. In particular, polyethylene terephthalate is preferable because it is excellent in transparency and homogeneity, and has a strong and inexpensive cocoon.

  Further, the base film may be blended with a nucleating agent in order to increase rigidity and strengthen the stiffness. A nucleating agent is a substance that becomes a crystal nucleus in a polymer molecule, and has the effect of increasing the crystallinity of the polymer and increasing the elastic modulus of the base film by being blended with the base film. As the nucleating agent, either an inorganic nucleating agent or an organic nucleating agent can be used. Examples of the inorganic nucleating agent include talc, clay, calcium carbonate and the like. Examples of organic nucleating agents include metal salts such as aromatic carboxylic acid metal salts and aromatic phosphoric acid metal salts, high density polyethylene, poly-3-methylbutene-1, polycyclopentene, and polyvinylcyclohexane. And high molecular compounds. Among these, organic nucleating agents are preferable, and the above metal salts and high density polyethylene are more preferable. Moreover, 0.01 to 3 weight% is preferable and, as for content of the nucleating agent in a base film, 0.05 to 1.5 weight% is more preferable. Only one type of nucleating agent may be used, or a plurality of types may be used in combination.

  The thickness of the base film is preferably 15 to 75 μm. If this thickness is less than 15 μm, the handleability may be inferior or the originally required surface protection performance may be reduced. On the other hand, if the thickness exceeds 75 μm, the rigidity is too strong, and the handleability may be inferior or the peel strength may be increased.

  From the viewpoint of suppressing the curling of the protective film 25, the base film preferably has a high rigidity, and more specifically, the base film has a high tensile elastic modulus. The tensile modulus of the base film is preferably 1,000 MPa or more, more preferably 3,000 MPa or more in the longitudinal direction (MD). If the tensile modulus is too small, the rigidity of the base film will be too low, so the curl suppression effect will be low, the handleability will be inferior, and the tension when bonding to the protective film 25 will not be able to endure. There is. The surface of the base film may be subjected to antifouling treatment, antireflection treatment, hard coat treatment, antistatic treatment and the like.

  Similarly, from the viewpoint of suppressing curling of the protective film 25, the base film is preferably flat. The initial TD curl amount of the base film before being bonded to the protective film 25 is preferably small, and specifically about 0 to 10 mm is suitable. If the initial TD curl amount of the base film is too large, the entire polarizing plate 20 is curled due to the curling of the base film itself, and the polarizing plate 20 is difficult to flatten.

(3-2) Pressure-sensitive adhesive layer As the pressure-sensitive adhesive layer, a known re-peeling pressure-sensitive adhesive such as an acrylic pressure-sensitive adhesive can be used. Among these, an acrylic resin having a high elastic modulus and hardness is preferable from the viewpoint of the strength of the protective film. From the standpoint of strength, the pressure-sensitive adhesive layer should be thicker. The pressure-sensitive adhesive layer may contain an antistatic agent or the like in order not to generate static electricity at the time of peeling.

  The acrylic adhesive is based on one or more acrylic esters such as butyl acrylate, ethyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, and a polar monomer is copolymerized therewith. The thing comprised with a polymer is mentioned. Examples of polar monomers include (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, and glycidyl. Mention may be made of monomers having a carboxyl group, a hydroxyl group, an amino group, an epoxy group and the like, such as (meth) acrylate. In addition, crosslinking agents, such as a polyisocyanate compound, an epoxy compound, and an aziridine compound, may be mix | blended with the adhesive.

(4) Transparent resin film 23
The transparent resin film 23 is an optical film that is bonded to the opposite side of the surface of the polarizing film 21 to which the protective film 25 is bonded. Various optical films can be employed depending on the application of the polarizing plate 20, and examples thereof include a protective film and a retardation film.

  The transparent resin film 23 is preferably made of a resin having excellent transparency. Examples of such resins include polycarbonate resins, polyvinyl alcohol resins, polystyrene resins, (meth) acrylate resins, olefin resins including cyclic olefin resins and polypropylene resins, polyarylate resins, and polyimide resins. Examples thereof include resins and polyamide resins. The transparent resin film 23 is preferably an unstretched film that has not been stretched, or a stretched film that has been uniaxially or biaxially stretched.

  When the transparent resin film 23 is a stretched film, an appropriate phase difference is imparted by stretching. The film provided with the retardation may be a wave plate such as a quarter wave plate or a half wave plate, or a viewing angle compensation film. The thickness of the retardation film is usually about 10 to 200 μm, preferably 20 to 120 μm.

When a viewing angle compensation film is used as the retardation film, it is necessary to consider the mode employed in the liquid crystal cell 40. For example, vertical alignment: If (Vertical Alignment VA) mode liquid crystal cell 40, as a viewing angle compensation film, a polymer film having a positive intrinsic birefringence is uniaxially stretched, the refractive index ellipsoid _n x> _{n y} positive a plate having a relationship ≒ _{n z,} transverse stretching and sequential biaxial stretching is _performed, biaxial having a relation of _{n x>} n _y> n _z film, or _{n x} ≒ _n y> _{n z} A negative C plate with a relationship can be used. Here, n _x plane slow axis (x-axis) of the film refractive index in the direction of, n _y in-plane fast axis (y-axis: Axis perpendicular in slow axis in-plane) direction of the refractive index, _Nz is the refractive index in the thickness (z-axis) direction.

As the transparent resin film 23, in particular, a biaxially stretched biaxial film is preferably used. When a biaxial viewing angle compensation film is used, the _Nz coefficient that is a measure of the biaxiality is defined by the following equation (7). Further, the in-plane retardation value _Ro and the thickness direction retardation value _Rth when the film thickness is d are defined by the following equations (8) and (9), respectively.
_{N z = (n x -n z} ) / (n x -n y) ··· (7)
_{R o = (n x -n y} ) × d ··· (8)
R _th = [(n _x + _ny ) / 2−n _z ] × d (9)

Further, from the equation (7) to (9), and _{N z} coefficient, the relationship between the retardation value _{R th} retardation value _{R o} and the thickness direction in the plane, is expressed by the following equation (10) it can.
N _z = R _th / R _o +0.5 (10)

When using a viewing angle compensation film as the transparent resin film 23, the retardation value _{R o} in the plane is in the range of 30 to 300 nm, especially preferably in the range of 50～260Nm. The _{N z} coefficient is in the range of 1.1 to 7, especially preferably in the range of 1.4 to 5. From these ranges, the value of the optical characteristic may be appropriately selected according to the viewing angle characteristic required for the applied liquid crystal display device.

  When the transparent resin film 23 is a retardation film, when the polarizing film 21 and the retardation film are bonded, the angle formed by the absorption axis of the polarizing film 21 and the slow axis of the retardation film is used for the purpose. It may be appropriately selected depending on the situation. For example, when the retardation film is a viewing angle compensation film, the angle formed by the absorption axis of the polarizing film 21 and the slow axis of the viewing angle compensation film is substantially 0 ° or 90 °.

  On the other hand, in the case where the transparent resin film 23 is an unstretched film, the retardation hardly appears and functions as a protective film for the polarizing film 21. The transparent resin film 23 as an unstretched film can be suitably used for the liquid crystal cell 40 in an IPS (In Plane Switching) mode among the modes employed in the liquid crystal cell 40, for example.

(5) Adhesive layer (not shown)
The transparent resin film 23 and the protective film 25 are bonded to the polarizing film 21 usually through an adhesive layer. The adhesive that forms the adhesive layer provided on both surfaces of the polarizing film 21 may be the same or different.

  As the adhesive, an adhesive having an epoxy resin, oxetane resin, urethane resin, cyanoacrylate resin, acrylamide resin, or the like as an adhesive component can be used. One of the adhesives preferably used is a solventless type adhesive. Solventless adhesives do not contain a significant amount of solvent, and are curable compounds (monomers or oligomers) that are reactively cured by heating or irradiation with active energy rays (for example, ultraviolet rays, visible light, electron beams, X-rays, etc.) ), And an adhesive layer is formed by curing of the curable compound, and typically includes a curable compound that is reactively cured by heating or irradiation of active energy rays, and a polymerization initiator. In particular, when the transparent resin film 23 and the protective film 25 are made of a polypropylene resin, the polypropylene resin film has a low moisture permeability. Therefore, when a water-based adhesive is used, drainage is poor, and the polarizing film 21 is caused by moisture in the adhesive. Damage or deterioration of polarization performance may occur. Therefore, when bonding such a resin film with low moisture permeability, a solventless adhesive is preferable.

  From the viewpoint of rapid curing and productivity improvement of the polarizing plate 20 associated therewith, as an example of a preferable adhesive for forming the adhesive layer, an active energy ray-curable adhesive that is cured by irradiation with active energy rays can be mentioned. it can. As an example of such an active energy ray-curable adhesive, for example, a photo-curable adhesive that is cured by light energy such as ultraviolet light and visible light can be cited. As the photocurable adhesive, those that are cured by cationic polymerization are preferable from the viewpoint of reactivity, and in particular, the solventless epoxy adhesive using an epoxy compound as a curable compound includes the polarizing film 21 and the transparent resin film. 23 and the protective film 25 are more preferable because of excellent adhesion.

  Although it does not restrict | limit especially as an epoxy compound which is a sclerosing | hardenable compound contained in the said solventless type epoxy adhesive, The thing hardened | cured by cationic polymerization is preferable. In particular, from the viewpoint of weather resistance and refractive index, it is more preferable to use an epoxy compound that does not contain an aromatic ring in the molecule. Examples of such epoxy compounds that do not contain an aromatic ring in the molecule include hydrides of aromatic epoxy compounds, alicyclic epoxy compounds, and aliphatic epoxy compounds. In addition, the epoxy compound that is a curable compound usually has two or more epoxy groups in the molecule.

  After the transparent resin film 23 and the protective film 25 are bonded to the polarizing film 21 through an adhesive layer made of an uncured epoxy adhesive, the adhesive is irradiated with active energy rays or heated. The layer is cured, and the transparent resin film 23 and the protective film 25 are fixed on the polarizing film 21. In the case of curing by irradiation with active energy rays, ultraviolet rays are preferably used. Specific examples of the ultraviolet light source include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a black light lamp, and a metal halide lamp. The irradiation intensity and irradiation amount of active energy rays such as ultraviolet rays are appropriately selected so as to sufficiently activate the cationic polymerization initiator and not adversely affect the cured adhesive layer, the polarizing film 21 and the like. . In addition, when cured by heating, it can be heated by a generally known method, and the temperature and time at that time can sufficiently activate the cationic polymerization initiator, and the cured adhesive layer or It is appropriately selected so as not to adversely affect the film such as the polarizing film 21.

  The thickness of the adhesive layer comprising the cured epoxy adhesive obtained as described above is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less, and usually 1 μm or more.

  Further, from the viewpoint of thinning the adhesive layer, an aqueous adhesive, that is, an adhesive in which an adhesive component is dissolved in water or an adhesive component is dispersed in water can also be used as the adhesive. For example, an aqueous composition using a polyvinyl alcohol resin or a urethane resin as a main component can be mentioned as a preferred aqueous adhesive.

  As a method of bonding the transparent resin film 23 and the protective film 25 to the surface of the polarizing film 21 using an adhesive, a conventionally known method can be used. For example, the polarizing film 21 and / or the film to be bonded to it by the casting method, Meyer bar coating method, gravure coating method, comma coater method, doctor blade method, die coating method, dip coating method, spraying method, etc. The method of apply | coating an adhesive agent to a surface and superimposing both is mentioned. The casting method is a method of spreading and spreading an adhesive on the surface of a film to be coated while moving the film in a substantially vertical direction, a substantially horizontal direction, or an oblique direction between the two.

  In order to improve the adhesiveness, the polarizing film 21 and / or the adhesive surface of the film bonded thereto are subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, saponification treatment, etc. You may give suitably. Examples of the saponification treatment include a method of immersing in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

  The laminated body joined through the water-based adhesive is usually subjected to a drying treatment, and the adhesive layer is dried and cured. The drying process can be performed, for example, by blowing hot air. A drying temperature is normally selected from the range of about 40-100 degreeC, Preferably it is 60-100 degreeC. The drying time is, for example, about 20 to 1,200 seconds. The thickness of the adhesive layer after drying is usually about 0.001 to 5 μm, preferably 0.01 μm or more, preferably 2 μm or less, more preferably 1 μm or less. If the thickness of the adhesive layer becomes too large, the appearance of the polarizing plate 20 tends to be poor.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the following examples, the part representing the amount used is based on weight unless otherwise specified. The physical property values in each example were measured by the following methods.

[Measurement of curl amount of optical film and laminate]
The amount of curl was measured by a method according to the explanation made earlier with reference to FIG. 3 with the convex surface of the optical film or optical film laminate facing downward. The case where the acrylic resin film (optical film B) side is convex is defined as normal curl, and the case where it is concave is defined as reverse curl.

(A) Production of acrylic resin film (optical film B) (acrylic resin and acrylic elastic polymer particles)
A copolymer having a weight ratio of methyl methacrylate / methyl acrylate of 96/4 was used as an acrylic resin. The innermost layer is a hard polymer polymerized with methyl methacrylate using a small amount of allyl methacrylate, and the intermediate layer is polymerized with butyl acrylate as the main component, and further using styrene and a small amount of allyl methacrylate. Soft elastic body, the outermost layer is a three-layered elastic particle made of a hard polymer obtained by polymerizing methyl methacrylate with a small amount of ethyl acrylate, up to an elastic body that is an intermediate layer Acrylic elastic polymer particles having an average particle size of 240 nm were used.

(Preparation of acrylic resin film)
While melting and kneading a pellet in which the above acrylic resin and the above acrylic elastic polymer particles are blended in a weight ratio of the former / the latter = 70/30 with a twin screw extruder, did. This pellet is put into a 65 mmφ single screw extruder, extruded through a T die having a set temperature of 275 ° C., and two polishings having mirror surfaces whose temperatures are set to 45 ° C. on both sides of the extruded film-like molten resin. Acrylic resin film was prepared by sandwiching between rolls and cooling.

(Preparation of coating solution for antiglare layer formation)
It contains pentaerythritol triacrylate and polyfunctional urethanized acrylate (reaction product of hexamethylene diisocyanate and pentaerythritol triacrylate), the former / latter weight ratio is 60/40, and the total concentration of both is 60%. Thus, a photocurable resin composition dissolved in ethyl acetate and further containing a leveling agent was prepared. The pentaerythritol triacrylate and the polyfunctional urethanized acrylate constituting the photocurable resin composition are collectively referred to as “curable acrylate”.

  To 100 parts of the curable acrylate of this photocurable resin composition, 5 parts of methyl methacrylate / styrene copolymer resin particles having an average particle size of 2.7 μm are added and dispersed, and the curable acrylate and the resin particles are dispersed. Diluted with ethyl acetate to a total concentration of 30%. Thereafter, 1 part of “Irgacure 184” (manufactured by Ciba) as a photopolymerization initiator was added to 100 parts of the curable acrylate in the liquid to prepare a coating liquid for forming an antiglare layer.

  The photo-curing resin composition used here was formed into a film by adding the above-mentioned photopolymerization initiator, and the refractive index of the resin cured by UV irradiation was 1.53, whereas the above-mentioned methyl methacrylate / The refractive index of the styrene copolymer resin particles was 1.49. Therefore, the refractive index difference between them was 0.04.

(Preparation of antiglare film)
In the dryer set to 60 degreeC, apply | coat the coating liquid for anti-glare layer formation prepared above on the surface of the produced acrylic resin film so that the coating-film thickness after drying may be set to 10.0 micrometers. The coating was dried for 3 minutes. After drying, the coating film layer of the photocurable resin composition is cured by irradiating light from a high-pressure mercury lamp with an intensity of 20 mW / cm ² from the coating film side of the film so that the amount of light converted to h-ray is 200 mJ / cm ^2. Thus, an antiglare film was produced in which an antiglare layer having irregularities was formed on the surface of the acrylic resin film.

(Curl measurement of acrylic resin film)
The film thickness of the antiglare layer in the antiglare film obtained above was 10 μm, the total film thickness of the antiglare film including the antiglare layer was 90 μm, the total film width was 1330 mm, and the coating width was 1330 mm. Further, the acrylic resin film was curled toward the antiglare layer by the antiglare layer forming treatment, and the TD curl amount was 80 mm.

(B) Preparation of Protect Film (Optical Film A) “Mastuck” (manufactured by Fujimori Kogyo Co., Ltd.), which is a polyester film having a weakly adhesive acrylic adhesive layer on one side, was prepared. It was. The film thickness of the pressure-sensitive adhesive layer was 24 μm, the total film thickness of the protective film including the pressure-sensitive adhesive layer was 62 μm, and the total film width was 1300 mm. Moreover, the adhesive force with respect to an acrylic resin film (optical film B) was 0.11 N / 25mm.

(C) Bonding of acrylic resin film and protect film The surface treatment layer of the acrylic resin film and the adhesive layer of the protect film face each other and are conveyed in the machine flow direction (MD) by a roll type laminator. An optical film was bonded. As the roll type laminator, a type in which a protective film and an antiglare film are narrowly pressed with two bonding rolls was used. A rubber roll whose surface is made of rubber was used for the bonding roll in contact with the protective film, and a rubber roll whose surface was made of rubber was also used for the bonding roll in contact with the acrylic resin film. The tension of each optical film at the time of bonding was measured and controlled by a speed control type tension controller (manufactured by Eiko Sokki Co., Ltd.). The tension (T _A ) of the protective film was fixed at 200 N / full width, and the tension (T _B ) of the acrylic resin film was arbitrarily set.

From the protective film-bonded acrylic resin film (optical film laminate X) obtained after bonding, as shown in FIG. 6, cut out 250 mm × 300 mm so that one of the diagonals forms an angle of 5 ° with MD, The curl amount at the ends of TD and MD was measured. Similarly, the amount of curl was measured by variously changing the tension (T _B ) of the acrylic resin film. The results are shown in Table 1.

(D) Extrapolation of data FIG. 7 is a graph plotting the above results, with the vertical axis representing the curl amount and the horizontal axis representing the tension (T _B ) or tension ratio (T _B / T _A ) of the acrylic resin film. is there. A curl amount plus (+) indicates a positive curl. Based on this result, a regression curve was calculated between the curl amount and the tension ratio. As a result, it was found that the relationship between the TD curl amount and the tension ratio (T _B / T _A ) is a quadratic function and can be expressed by the following equation (11). Further, the correlation coefficient R ^{2 at} this time was 0.8748.
y _(TD) = 188.32x ² -214.87x + 75.382 (11)
When this equation (11) is modified, it can be expressed by the following equation (12).
y _(TD) = 188.32 (x−0.57) ² +14 (12)

Further, it was found that the relationship between the MD curl amount and the tension ratio (T _B / T _A ) is also a quadratic function and can be expressed by the following equation (13). Further, the correlation coefficient R ^{2 at} this time was 0.96777.
y _(MD) = 61.178x ² -155.75x + 56.708 (13)
When this equation (13) is modified, it can be expressed by the following equation (14).
y _(MD) = 61.178 (x−0.95) ² +2 (14)

From the equation (12), when the tension ratio (T _B / T _A ) is 0.57, the TD curl amount is minimum, and the value is about 14 mm. Further, according to the equation (14), when the tension ratio (T _B / T _A ) is 0.95, the MD curl amount is minimum, and the value is about 2 mm.

Next, the regression curve is extrapolated, and the tension ratio (T _B / T _A ) = 1.0, that is, the tension applied to the acrylic resin film (T _B ) and the tension applied to the protective film (T _A ) are the same. The curl amount was calculated. As a result, when the tension ratio (T _B / T _A ) = 1.0, the TD curl amount was 48.3 mm from the equation (11). The results shown in Table 1 are both TD curl amount in the tension ratio _{(T B / T A) <} 1 Scope, when the both values are tension ratio _{(T B / T A) =} 1 The TD curl amount is smaller than 48.3 mm. From this, it was found that TD curl can be suppressed by applying tension to both optical films so that the tension ratio (T _B / T _A ) <1.

Further, the TD curl amount becomes the minimum when the tension ratio (T _B / T _A ) = 0.57. Therefore, from the viewpoint of reducing the TD curl amount, the tension ratio (T _B / T _A ) = 0.57 is most preferable. On the other hand, from the viewpoint of allowing a certain amount of TD curl, for example, when the amount of TD curl is allowed to be up to 25 mm, 0.33 ≦ tension ratio (T _B / T _A ) ≦ 0.81. It is preferable to set the tension ratio.

Furthermore, in the range of 0.57 ≦ tension ratio (T _B / T _A ) ≧ 0.81, not only can the TD curl amount be 25 mm or less, but also the MD curl amount can be suppressed. The MD curl amount can be 3.1 mm or less.

  A optical film (second optical film), B optical film (first optical film), X optical film laminate, P virtual surface, C1-C4 angle, H height, 11 feeding rolls, 12 feeding rolls, 13 Winding roll, 15 laminating roll, 16 laminating roll, 20 polarizing plate, 21 polarizing film, 23 transparent resin film, 25 protective film (optical film B), 29 protective film (optical film A)

Claims (9)

An end in the direction (TD) perpendicular to the machine flow direction than the first optical film is placed on the surface of the first optical film having a relatively large curl amount at the end in the direction (TD) perpendicular to the machine flow direction. A method of manufacturing an optical film laminate in which curling at an end in a direction (TD) perpendicular to the machine flow direction is suppressed by laminating a second optical film having a relatively small curl amount at the portion. ,
A conveying step of conveying the first optical film and the second optical film in a state where tension is applied along the machine flow direction (MD), respectively;
A bonding step of bonding the second optical film on the surface side of the first optical film where the curl is concave,
In the bonding step, the tension applied in the machine flow direction (MD) in the first optical film is T _B , and the tension applied in the machine flow direction (MD) in the second optical film is T _{When A}
Tension ratio (T _B / T _A ) <1
The method for producing an optical film laminate, wherein the first optical film and the second optical film are bonded in a state where tension is applied so that The tension ratio (T _B / T _A ) is x,
The amount of curl at the end of the first optical film in the direction (TD) perpendicular to the machine flow direction is represented by y _(TD) ,
The value that minimizes the curl amount is b ₁ ,
When the value of x when the curl amount is minimum is a,
y _(TD) = (x−a ₁ ) ² −b ₁
(Where 0 <a ₁ <1, b ₁ ≧ 0)
Satisfy the relationship
In the pasting step (B), the tension ratio (T _B / T _A )
_{a 1 -0.24 ≦ T B / T} A ≦ a 1 +0.24
The manufacturing method of the optical film laminated body of Claim 1 which provides tension | tensile_strength so that these relationships may be satisfy | filled. The tension ratio (T _B / T _A ) is
_{a 1 ≦ T B / T A} ≦ a 1 +0.24
The manufacturing method of the optical film laminated body of Claim 2 which provides tension | tensile_strength so that these relationships may be satisfy | filled. Wherein a ₁ is 0.57, a manufacturing method of an optical film laminate according to claim 2 or 3.   The first optical film is any one of a single film, a laminated film in which a plurality of films are laminated, or a surface-treated film in which any one of these films is surface-treated. The manufacturing method of the optical film laminated body in any one of.   The method for producing an optical film laminate according to claim 1, wherein the first optical film is an acrylic resin.   The method for producing an optical film laminate according to any one of claims 1 to 6, wherein the second optical film is a protective film made of a polyester resin.   It manufactures with the manufacturing method in any one of Claims 1-7, The optical film laminated body characterized by the above-mentioned. An optical film laminate according to claim 8,
A polarizing film comprising: a polarizing film made of a polyvinyl alcohol-based resin on which a dichroic dye is adsorbed and oriented.

Images