JP2003279741A - Optical film and manufacturing method thereof - Google Patents

Abstract

[57] [Summary] [PROBLEMS] To provide a film having a thickness of 100 μm or less, a small retardation value, no residual solvent, less wrinkles when stored in a roll shape, and less different from other films. To provide an optical film excellent in adhesiveness. An optical film obtained from a thermoplastic resin film obtained by a melt extrusion method, having an average thickness D _ave of 100 μm or less, and a difference D between the maximum value and the minimum value of the thickness over the entire surface of the film. the ratio _D r _{/ D ave} of the average thickness _{D ave} and _r is 7% or less, retardation Re is 4nm or less, and the ratio _{Re 40} of the phase difference Re ₀ in the field of view angle of 0 ° and the phase difference _{Re 40} in viewing angle 40 ° Use an optical film characterized in that the average value of / Re ₀ is 0.8 or more and 1.3 or less. The present invention also provides a method for producing such an optical film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical film, and more specifically, it has various retardation values and is uniform, has excellent adhesiveness to other substrates, and is used in various films such as flat panel displays. And an optical film suitable as a raw material film thereof. Furthermore, the present invention relates to a method for producing such an optical film.

[0002]

2. Description of the Related Art For a flat panel display such as a liquid crystal display, a thermoplastic resin phase plate, a polarizing plate,
A liquid crystal cell substrate or the like is used. As the phase plate, a raw material film such as polycarbonate is stretched so as to have a certain retardation (also referred to as a phase difference).
As a polarizing plate, a laminate of protective films laminated on the upper and lower surfaces of a polarizer made of polyvinyl alcohol is used as a polarizing plate, and as a protective film, a film formed by a solution casting method of triacetyl cellulose is a liquid crystal cell substrate. Polyethylene terephthalate (PE
Films made from T) are mainly used. With the recent increase in size, thickness and contrast of flat panel displays, the above-mentioned various thermoplastic resin films are required to have higher quality than ever before. For example, a protective film for a polarizer is
It is required that the retardation be small and constant over the entire surface of the film. Further, there is a demand for a film having a thickness of 100 μm or less, for example, about 60 μm or 40 μm, which satisfies desired performance such as strength and optical characteristics.

Conventionally, an optical film made of a thermoplastic resin, which has a small retardation and is constant, has been proposed. As a protective film for the polarizer,
Conventionally, a film formed by a solution casting method of triacetyl cellulose (TAC) has been mainly used. TAC solution cast film has a relatively small retardation and is relatively constant in the film surface, but it is inferior in productivity, and it is impossible to completely remove the solvent during drying after solution casting. However, due to the solvent remaining in the film, the solvent that volatilizes adversely affects the electronic circuits and other parts of the flat panel display, causing malfunctions and display defects. Therefore, recently, as a protective film, TA
In place of the solution casting method of C, a film obtained by a melt extrusion method of a thermoplastic resin is being studied. For example, in JP-A-2000-273204, a sheet thickness of 150 to 1000 μm, a sheet in-plane thickness tolerance (Rmax) of 15 μ, and a sheet surface roughness are obtained by melt-extruding a specific thermoplastic resin under specific conditions. 0.0
6 μm, surface retardation of sheet (maximum value) is 1
A technique is disclosed in which a sheet having a thickness of 5 nm and a relatively constant retardation can be obtained. However, the technique disclosed in this publication has a sheet thickness of 150 μm.
This is a technology for thick sheets of m or more. Generally, as the thickness becomes thinner, the variation in the thickness tends to be larger than the thickness, and the optical distortion becomes severe, so it corresponds to the recent demand for thinner flat displays. Can not.

A film produced by melt extrusion of a thermoplastic resin is usually wound into a roll and stored for use in the subsequent steps. The present inventors have studied and found that the film is as thin as 100 μm or less. In the case of a film, it was found that winding wrinkles are likely to occur when wound in a roll shape, and if there are winding wrinkles, scratches or defects are likely to occur on the film surface, which leads to display defects. Furthermore, as a result of the study by the present inventors, a film obtained by the melt extrusion method of a thermoplastic resin shows that when the thickness is 100 μm or less,
It has been found that there is a problem that adhesion failure with the polarizer is likely to occur after the durability test.

[0005]

DISCLOSURE OF THE INVENTION The object of the present invention is to have a thickness of 100 μm or less, a small retardation value and a constant value, no residual solvent, and less wrinkling when stored in a roll. Another object of the present invention is to provide an optical film having excellent adhesiveness with other films.

[0006]

Means for Solving the Problems
As a result of diligent study to solve
Average thickness D obtained from the thermoplastic resin film
_aveIs a film of 100 μm or less,
The difference between the maximum and minimum thickness D over the entire surface _rAnd before
Average thickness D_aveRatio D_r/ D_aveIs less than 7%,
Retardation Re of 4 nm or less and viewing angle of 40 °
Phase difference Re₄₀And the phase difference Re at a viewing angle of 0 °
₀Ratio Re₄₀/ Re₀Is 0.8 or more on average and 1.3 or more
If the lower one is used, the retardation value is small.
It is stable and has no residual solvent.
There are few wrinkles when wound, and adhesion to other films
It has been found to be an excellent optical film. Also,
The inventors of the present invention have found that the thermoplastic used as a raw material for the optical film is a thermoplastic.
The alicyclic structure-containing polymer is preferable as the hydrophilic resin.
I found it. Further, the present inventors have found that the above-mentioned thermoplastic resin
As a method of manufacturing film, a transfer process with a specific configuration
Having a certain cooling drum peripheral speed condition and a certain temperature condition
It has been found that the manufacturing method used is suitable. The present invention
Has been completed based on these findings.
It

Thus, according to the present invention, "a film for optics obtained from a thermoplastic resin film obtained by a melt extrusion method, having an average thickness D _ave of 100 μm or less, and having the maximum thickness over the entire surface of the film. Ratio of the difference D _r between the minimum value and the average thickness D _ave and the average thickness D _ave D _r / D
_{av e} 7% or less, retardation Re is 4nm or less, and the ratio _Re 40 / Re ₀ of retardation Re ₀ in the phase difference _{Re 40} and the viewing angle of 0 ° in the viewing angle 40 ° on average at least 0.8 1 An optical film having a thickness of 0.3 or less. ], As a preferred example of the optical film "the optical film described above in which the thermoplastic resin is an alicyclic structure-containing polymer.", And as a preferred method for producing the optical film "extruded from an extruder And a peripheral speed of the third cooling drum, in which the melted thermoplastic resin is transferred to the three cooling drums of the first cooling drum, the second cooling drum, and the third cooling drum in order to circulate. of R _3, the ratio to the circumferential velocity _{R 2} of the second cooling drum R
₃ / R ₂ is less than 0.999 and 0.990 or more, the resin contact time in the first cooling drum is t ₁ (seconds), and the thermoplastic resin in the molten state when leaving the first cooling drum Is T ₁ (° C.), the glass transition temperature of the thermoplastic resin is T g
(℃) and then _{t 1} × _{(T 1} -Tg) at the time it was (in seconds · d
The method for producing any of the optical films described above, characterized in that the thermoplastic resin film is obtained by setting eg) to −50 or more and +20 or less. Is provided.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The thermoplastic resin used in the production of the optical film of the present invention is not particularly limited as long as it is a film used in the production of ordinary optical films.
Specific examples include polyethylene, polypropylene, ethylene-propylene copolymer, polystyrene, polyacrylonitrile, acrylonitrile-styrene copolymer, polyvinyl chloride, polymethylmethacrylate, polyethylene terephthalate, polybutylene terephthalate, polycarbonate and alicyclic structure-containing. Examples thereof include polymers. Among these thermoplastic resins, polyethylene terephthalate, polybutylene terephthalate and alicyclic structure-containing polymers are preferable because of high transparency and excellent film strength, and further alicyclic structure-containing because the retardation can be made smaller. Polymers are particularly preferred.

The alicyclic structure-containing polymer has a ring structure composed of a carbon-carbon saturated bond in the repeating unit (in the present invention,
It is called "alicyclic structure". ), And specific examples thereof include ring-opening polymers of monomers having a norbornene ring structure (hereinafter referred to as “norbornenes”) and hydrogenated products thereof, addition polymers of norbornenes and hydrogens thereof. Additives, addition copolymers of norbornenes and vinyl compounds and hydrogenated products thereof; polymers obtained by hydrogenating an aromatic ring of a polymer of an aromatic vinyl hydrocarbon compound such as polystyrene, an alicyclic structure and a vinyl group. And an addition polymer of a monomer having one or more unsaturated bonds in a carbon-carbon ring structure, and a hydrogenated product thereof.

The above-mentioned thermoplastic resin is usually blended with various compounding agents as required and is supplied to an extruder in the form of pellets suitable for extrusion molding. The compounding agent is not particularly limited, but it is a stabilizer such as an antioxidant, a heat stabilizer, a light stabilizer, a weather resistance stabilizer, an ultraviolet absorber or a near infrared absorber; a resin modifier such as a lubricant or a plasticizer. Colorants such as dyes and pigments; antistatic agents and the like. These combination agents alone
Alternatively, two or more kinds may be used in combination, and the blending amount thereof is appropriately selected within a range that does not impair the object of the present invention.

Examples of the antioxidants include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants and the like. Among them, phenolic antioxidants, particularly alkyl-substituted phenolic antioxidants are preferable. . By compounding these antioxidants, it is possible to prevent the coloring and strength of the molded product from being deteriorated due to oxidative deterioration during molding without deteriorating transparency, low water absorption and the like. These antioxidants can be used alone or in combination of two or more, and the compounding amount thereof is appropriately selected within a range not impairing the object of the present invention.
It is usually 0.001 to 5 parts by weight, preferably 0.01 to 1 part by weight, relative to 00 parts by weight.

In the present invention, a film obtained by processing the above thermoplastic resin into a film by a melt extrusion method is used.
The melt extrusion method is a method in which a thermoplastic resin is heated and melted in a cylinder, pressed by a screw, and extruded from a die such as a T die. Usually, a thermoplastic resin in a molten state extruded from a die is transferred to a plurality of cooling drums by sequentially circumscribing it, cooled in the meantime, and then subjected to necessary steps to form a thermoplastic resin film. Compared with the width of the thermoplastic resin in the molten state immediately after being extruded from the die (the same as the width of the lip of the die), the width of the thermoplastic resin film after passing through the cooling drum is 2 to 2 due to neck-in.
It becomes about 10% narrower. The widthwise end of the thermoplastic resin film (hereinafter, also simply referred to as “edge”) has a larger thickness and a larger retardation than other parts of the film. When used for optical applications like the present invention, usually before winding on a winding drum,
Cut off the appropriate part of the edge. In the present invention, the part that is cut off is called "Mimi". In the present invention, a portion of the unstretched thermoplastic resin film excluding the portion that becomes a stain is referred to as an "optical film". When used in a state where the retardation is close to zero, such as in a protective film or liquid crystal substrate, take out the Mimi from the unstretched thermoplastic resin film, take out the optical film, and wind it with a take-up drum. . The optical film is wound into a roll by a winding drum, and then subjected to the next step, which is a stretching step and a step of laminating with another film.

The optical film of the present invention has an average thickness D
_ave is 100 μm or less. The average thickness Dave is
It can be arbitrarily set by changing the charging speed of the raw material pellets charged into the melt extruder, the rotation speed of the cooling drum, and both of them. The optical film of the present invention is suitable for thin flat panel displays and the like, and is also suitable for use in a thickness of 100 μm or less, 80 μm or less, and particularly 60 μm or less.

[0014] The optical film of the present invention, over the film over the entire surface, necessary that the ratio _D r _{/ D ave} of the difference _{D r} of the maximum value and the minimum value of the thickness said average thickness _{D ave} is not more than 7% Is. The average thickness D _ave and the difference D _r between the maximum value and the minimum value of the thickness are, for example, the length of the extrusion direction (hereinafter, also referred to as “length”) in the extrusion direction with a contact-type continuous thickness meter. (Hereinafter, also simply referred to as "length") by measuring over an appropriate length, and by measuring at least several points including a portion near the edge of the optical film in the width direction, The value that can be obtained can be used as a substitute value. The smaller the value of D _r / D _ave is, the more preferable it is, but it is usually 7% or less. When the value of D _r / D _ave is in this range, there are few winding wrinkles when wound in a roll and stored, and the optical film has excellent adhesiveness to other films.

The optical film of the present invention is required to have a retardation Re of 4 nm or less over the entire surface of the film. The value of Re can be measured by an optical method such as an ellipsometer, and the maximum value is measured over an appropriate length, and several points including a portion near the edge of the optical film in the width direction are included. By measuring the above, the value that can be obtained can be adopted as the substitute value. The smaller the maximum value of Re, the better, but
It is usually 4 nm or less, preferably 3 nm or less, and particularly preferably 2.5 nm. When Re is in this range,
Not only the color unevenness in a flat panel display is small, but there are also few winding wrinkles when wound in a roll and stored, and the optical film has excellent adhesiveness to other films.

The optical film of the present invention has a viewing angle of 40 °.
Phase difference R in the phase difference _{Re 40} and the viewing angle of 0 ° in
If the ratio Re ₄₀ / Re _{0 of} e ₀ is 0.8 or more on average, 1.3
It must be: The values of Re ₄₀ and Re ₀ are obtained by measuring the retardation with the angle of the film surface being 40 ° and 0 °, respectively, and the maximum value and the minimum value thereof are measured over an appropriate length. A value that can be obtained by measuring several points including the portion near the edge of the optical film in the width direction can be used as a substitute value. Re ₄₀ / Re ₀ shows the viewing angle dependence of retardation, and ideally 1.
Although it is 0, it is usually 0.8 or more and 1.3 or less, preferably 0.9 or more and 1.25 or less, and more preferably 0.95 or more and 1.20 or less. Re ₄₀ / Re ₀
When the average value of is within this range, the resulting flat panel display is excellent in color unevenness and contrast.

The method for producing an optical film satisfying the ranges of the maximum value of D _r / D _ave , the maximum value of Re and the average value of Re ₄₀ / Re ₀ is not particularly limited. For example,
There is a method of increasing the proportion of the spots in the entire film as compared with the conventional case so that the above condition is satisfied over the entire surface of the film. In this case, the proportion of the Mimi part is
Usually, it is 3% or more for each of the left and right sides, preferably 5% or more for each of the left and right sides, particularly preferably 7% or more for each of the left and right sides, preferably 40% or less for each of the left and right sides, and particularly preferably 20% or less for each of the left and right sides.

As a preferred method for producing a thermoplastic resin film used for producing the optical film of the present invention, a molten thermoplastic resin extruded from an extruder is used as a first cooling drum and a second cooling. And a step of transferring the three cooling drums, that is, a drum and a third cooling drum, sequentially in contact with each other, and the ratio R ₃ of the peripheral speed R ₃ of the _third cooling drum to the peripheral speed R ₂ of the second cooling drum. / R ₂ is 0.99
If it is less than 9, it is 0.990 or more, the resin contact time in the first cooling drum is t ₁ (second), and the temperature of the thermoplastic resin in the molten state when leaving the first cooling drum is T ₁ (° C. ), When the glass transition temperature of the thermoplastic resin is Tg (° C.), t ₁ × (T ₁ −Tg) (unit: second · deg) is −50.
There is a method characterized in that the value is not less than +20 and not more than +20. This method will be described below.

In this manufacturing method, the material is extruded from the extruder.
In addition, a thermoplastic resin melted into a sheet (hereinafter, "sheet
Also referred to as a thermoplastic resin. ) To the first cooling drum,
2 cooling drums and 3 cooling drums
The method has a step of sequentially circumscribing and transferring. The third cooling door
Ram speed R_ThreeOf the peripheral speed R of the second cooling drum _Two
Ratio to_Three/ R_TwoLess than 0.999, 0.990 or more
Above, preferably less than 0.998, set to 0.995 or more
To do. R_Three/ R_TwoIf the value of is too large, the sheet thermoplastic
Stretching of the flexible resin causes retardation value and its variation
It is not preferable because the wood becomes large. On the other hand, R_Three/ R_TwoThe value of the
If the sheet is too small,
Dripping, the weight becomes tension and becomes a sheet thermoplastic resin
Due to stretching, the retardation value and its variation are large.
It's getting harder, which is also not desirable. R_Three/ R_TwoSet value of
To determine the sheet thermoplastics the second cooling drum
From the second cooling drum to the third cooling drum.
Lowering from around the temperature of the third cooling drum to around the temperature of the third cooling drum
Set the resin temperature to match the shrinkage rate of the resin due to
It By adopting the above peripheral speed ratio, sheet-like thermoplasticity
Do not pull the resin with appropriate tension without sagging
And thermoplastic resin with a small retardation value
The fat sheet can be manufactured.

The ratio R ₂ / R ₁ of the peripheral speed R ₂ of the second cooling drum to the peripheral speed R ₁ of the first cooling drum is 1.
It is preferable to set to less than 01 and 0.990 or more,
It is more preferable to set it to less than 1.000 and 0.995 or more. When the value of R ₂ / R ₁ is in this range, the retardation unevenness of the obtained optical film is particularly small and winding wrinkles are less likely to occur, which is preferable.

Further, the sheet-shaped thermoplastic resin is cooled by the third cooling.
When leaving the drum, the resin temperature T _ThreeThe thermoplastic resin
50-100 ° C lower than the glass transition temperature (Tg) of
It is preferable to set the temperature to 60 ° C. to 80 ° C., especially Tg
More preferably, the temperature is low. T_ThreeIs in this range
At some point, the letter print of the optical film obtained
The unevenness is particularly small and winding wrinkles are less likely to occur.
Is preferred. Temperature T_ThreeTo be within the above range,
3 Control the temperature of the cooling drum and the second cooling drum.

It is preferable that the temperature T ₂ of the sheet-shaped thermoplastic resin when the sheet-shaped thermoplastic resin leaves the second cooling drum is set to a temperature 0 to 60 ° C. lower than its Tg.
More preferably, the temperature is 20 to 40 ° C. lower. T ₂
When the value is within this range, the retardation unevenness of the resulting optical film is particularly small, and winding wrinkles are less likely to occur, which is preferable.

It is preferable that the temperature difference between the first cooling drum and the second cooling drum is less than 10 ° C.

The contact time of the sheet-shaped thermoplastic resin on the first cooling drum is t ₁ (seconds), the resin temperature when leaving the first cooling drum is T ₁ (° C.), and the glass transition temperature of the thermoplastic resin is tg (° C.) and then when _{the, t 1 × (T 1 -Tg} )
(Unit: seconds / deg) is usually -50 or more and +20 or less,
It is preferably −40 or more and +15 or less. When in this range, the thickness uniformity D of the optical film obtained is
_{Since r} / D _ave becomes small and the maximum value of Re becomes small, the optical film of the present invention can be easily obtained, which is preferable.

[0025]

EXAMPLES The present invention will be described more specifically below with reference to Examples and Comparative Examples. “Part” in these examples
And "%" are based on mass unless otherwise specified.
Various sample preparations and tests were performed according to the following.

(1) Average thickness D _{ave of} film and variation D _{r Using a} contact type film thickness meter, the length direction of the film is 500 mm.
The thickness of the film is measured at 5 points at equal intervals in the width direction over 10 m each (20 points), and the average value D
_{The ave} and the difference D _r between the maximum value and the minimum value were obtained.

(2) Retardation value Re and its maximum value phase difference measuring device [manufactured by Oji Scientific Instruments: KOBRA-21A
DH] and the length direction of the film is 1 every 500 mm.
Retardation value Re was measured at 5 locations at equal intervals in the width direction over 0 m (20 locations), and the maximum value was obtained. The measurement wavelength was 550 nm and the incident angle was 0 °.

(3) Retardation Re ₄₀ at a viewing angle of 40 ° and retardation R at a viewing angle of 0 °
average ratio _Re 40 / Re ₀ of e ₀ for the same measuring point (2), _{Re 40} measurement method varying the incident angle of Re ₀ and the measuring light 40 ° in the same measurement method and (2) Was measured to calculate Re ₄₀ / Re ₀ , and the average value thereof was calculated.

(4) Roll winding property The optical film in the form of a roll wound up by a winding drum is visually observed. When no wrinkle is observed, it is indicated by ○, when slight wrinkle is observed, it is indicated by Δ, The one in which wrinkles were clearly observed was marked with x.

(5) Color unevenness Color unevenness and color loss, which are problems when used as a protective film for a polarizer, were simply tested. In the actual configuration of a liquid crystal display, a structure in which both sides of a polarizer are sandwiched between two protective films to form a polarizing plate, and further both sides of a liquid crystal are sandwiched between two polarizing plates (via other layers required) Has become.
If the protective film has optical distortion, it causes color unevenness and color loss in the entire liquid crystal display. It was decided to simply test the optical strain of the optical film to be each protective film as follows. Prepare two commercially available polarizers in which liquid crystal polyvinyl alcohol is doped with iodine, align the two polarizers so that their polarization axes are perpendicular to each other, and sandwich the optical film obtained in the experiment between them. As a three-layer structure consisting of a polarizer / optical film / polarizer, the degree of transmission of non-polarized light (natural light) was visually observed. ○: no leakage of light was observed, △: slightly observed Those clearly recognized were marked with x. The measurement points were measured every 500 mm in the length direction over 10 m (20 locations), and in the width direction at five locations at equal intervals.

(6) 30 ° inclined transmittance ratio Furthermore, the 30 ° inclined transmittance ratio was measured as one index of color unevenness and color loss. Sample pieces were cut out at 5 positions at equal intervals in the width direction of the optical film obtained in the experiment, and these sample pieces were manufactured by NDH manufactured by Nippon Denshoku Industries Co., Ltd.
Using a 300A type turbidimeter, the orthogonal transmittance and the 30 ° inclined transmittance were measured in accordance with JIS K7105, and the 30 ° inclined transmittance / orthogonal transmittance was calculated to obtain the 30 ° inclined transmittance ratio, which was the average. The value was calculated. It is preferable that this value is large, and if it is 1000 or more, it is good without causing problems such as color unevenness and color loss in the obtained flat panel display.

(7) Adhesiveness The optical film is often used by adhering it to other film-like members, and in particular, the adhesiveness after the durability test often becomes a problem. The same polarizer as used in (5) and a sample piece having the same area cut out from the optical film obtained in the experiment were stuck together with a 10% by mass aqueous solution of polyvinyl alcohol. The obtained laminate was heated at 80 ° C., 90% RH, 10
A durability test was performed under the condition of 0 hours, and the state of the laminate after that was visually observed.
What caused slight swelling (peeling of the interface) ×
And

(8) Re unevenness after stretching The optical film obtained in the present invention can be made into a retardation film by subsequent stretching. The retardation film is required to have a predetermined retardation (retardation value) and have a uniform value. The following tests were conducted in order to investigate the performance of the optical film of the present invention as a raw material film for a retardation film. The optical film obtained in the experiment is (width 100 m
m, length 150 mm) to make a test piece, and the test piece is stretched 1.1 to 2 times in the longitudinal direction at 140 ° C., 100 mm /
It was stretched at a speed of a minute. The stretching ratio was adjusted so that the average retardation was 275 ± 10 nm. (2)
Retardation is measured by the same measurement method as described above, and the variation (difference between the maximum value and the minimum value) is divided by the average value to give Re.
It was uneven. The measurement points were at the center in the width direction, and 10 points were set at intervals of 10 mm near the center in the length direction.

[0034]Example 1 ZEONOR 1420 (of ring-opening polymers of norbornenes)
Pellets of hydride, manufactured by Zeon Corporation, Tg 140 ° C)
Was used. The pellet has a cylinder inner diameter of 50 mm and a
Ryu L / D single screw extruder with 28 (made by Japan Steel Works)
Melt extrusion at a barrel temperature of 260 ℃, die temperature of 260 ℃
650mm wide sheet-like melt from the coat hanger die
The resin is extruded and the first cooling drum (diameter 200 mm, temperature
Degree T₁: 135 ℃, peripheral speed R₁To 12.50 m / sec)
Closely contact and immediately use the knife coater to cool the first cooling drum.
Then the second cooling drum (diameter 350 mm, temperature
T_Two: 125 ℃, peripheral speed R_Two: 14.46 m / sec), next
3rd cooling drum (350mm diameter, temperature T_Three: 80
℃, peripheral speed R_Three: 14.40 m / sec)
Transfer, sequential, cooling and surface transfer by cooling drum surface
The back side is smoothed to a width of 550 mm (the neck-in is left and right).
50 mm) of thermoplastic resin film is obtained and adjusted
After passing through the drum, 30m from each end with a cutter
Remove m as a Mimi and roll with a winding drum
It was wound into a roll and a roll-shaped optical film was obtained. this
At the time of contact with the sheet-shaped thermoplastic resin on the first cooling drum
Interval t₁3.1 (sec), when leaving the first cooling drum
Resin temperature is T₁Is 132 (° C), t ₁× (T₁-Tg) is
It was −12 (unit: second · deg). Obtained for optics
The results of each of the above test items for the film are displayed.
Note 1.

Example 2 In Example 1, R ₁ was 7.10 m / sec and R ₂ was 7.
An optical film was produced in the same manner as in Example 1 except that 07 m / sec and R ₃ were changed to 7.04 m / sec. Table 1 shows the test results of the obtained optical film.

Comparative Example 1 An optical film was manufactured in the same manner as in Example 1 except that T ₁ was changed to 120 ° C. Table 1 shows the test results of the obtained optical film.

Comparative Example 2 An optical film was produced in the same manner as in Example 1 except that T ₁ was changed to 120 ° C. and T ₂ was changed to 110 ° C. Table 1 shows the test results of the obtained optical film.

Comparative Example 3 An optical film was manufactured in the same manner as in Example 1 except that T ₁ was changed to 110 ° C. and T ₂ was changed to 100 ° C. Table 1 shows the test results of the obtained optical film.

[0039]

[Table 1]

As shown in Table 1, the optical films of the examples of the present invention were _dr / _r lower than those of the comparative examples.
Since the average values of D _ave , Re and Re ₄₀ / Re ₀ are in the predetermined ranges, the roll winding property, the color unevenness, the 30 inclination ° transmittance ratio, and the adhesiveness are excellent. Comparative Example 1 is D _r / D
The maximum values of _ave and Re are within a predetermined range, but Re ₀ /
Since the average value of Re ₀ is deviated, the roll winding property, the color unevenness, the 30 inclination ° transmittance ratio, and the adhesiveness are all inferior. In Comparative Example 2, the average values of D _r / D _ave and Re ₀ / Re ₀ are within the predetermined range, but since the maximum value of Re is out of the range, roll winding property, color unevenness, 30 inclination ° transmittance ratio, The adhesiveness is poor, and the color unevenness and the adhesiveness are extremely poor.
In Comparative Example 3, since the value of D _r / D _ave is out of the range, the roll winding property is remarkably poor.

Table 2 shows the R after stretching for each experimental example.
The result of measuring the unevenness is shown.

[0042]

[Table 2]

As shown in Table 2, the optical films of the examples of the present invention were dr / dav as compared with the comparative examples.
Since the average value of e, Re and Re ₄₀ / Re ₀ is within a predetermined range, retardation unevenness after stretching is small and excellent, and the optical film of the present invention is suitable as a raw material film for a retardation film. There is.

[0044]

According to the present invention, the thickness is 100 μm or less, the retardation value is small and constant, there is no residual solvent, and there are few wrinkles when wound in a roll and preserved, and the film has a small difference from other films. An optical film having excellent adhesiveness and a method for producing the same are provided. INDUSTRIAL APPLICABILITY The optical film of the present invention is useful as various optical films for flat panel displays such as a polarizer protective film and a liquid crystal cell substrate film. Further, although the optical film of the present invention has a small retardation and is uniform, it can be a retardation film having a predetermined retardation and having a uniform value by being stretched thereafter. Therefore, the optical film of the present invention is also useful as a raw material film such as a retardation film.

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Claims (3)

[Claims] 1. An optical film obtained from a thermoplastic resin film obtained by a melt extrusion method, having an average thickness D _ave of 100 μm or less, and a difference between the maximum value and the minimum value of the thickness over the entire surface of the film. D _r and the ratio _D r _{/ D ave} of the average thickness _{D ave} is 7% or less, retardation Re is 4nm or less, and the ratio Re of the retardation Re ₀ in the field of view angle of 0 ° and the phase difference _{Re 40} in viewing angle 40 ° optical film the average value of _{4 0} / Re ₀ is equal to or more than 1.3 at 0.8 or more. 2. The optical film according to claim 1, wherein the thermoplastic resin is an alicyclic structure-containing polymer. 3. A first cooling drum, a second cooling drum, and a third cooling drum, wherein the molten thermoplastic resin extruded from the extruder is used.
There is a step of sequentially contacting three cooling drums of the cooling drums and transferring them, and a ratio R ₃ / R ₂ of a peripheral speed R ₃ of the _third cooling drum to a peripheral speed R ₂ of the second cooling drum is set. If it is less than 0.999 and is 0.990 or more, the resin contact time in the first cooling drum is t ₁ (second), and the temperature of the thermoplastic resin in the molten state when leaving the first cooling drum is T ₁ (second).
₁ (° C), the glass transition temperature of the thermoplastic resin is Tg (° C)
T ₁ × (T ₁ −Tg) (unit: second · deg)
The thermoplastic resin film is obtained by adjusting the value of -50 to +20.
A method for producing the optical film according to any one of 1.