JPH11295525A - Method for producing retardation film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a retardation film suitable for improving a viewing angle characteristic of a TN type liquid crystal display device and capable of easily obtaining a large-area one at low cost. SOLUTION: At least one surface of a transparent polymer film has at least one inorganic dielectric monolayer having a positive refractive index anisotropy and an optical principal axis inclined by 20 to 70 degrees from the normal direction of the film. A retardation film formed by forming an oblique evaporation layer made of metal by a reactive evaporation method using a metal as an evaporation material and introducing oxygen gas during film formation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a retardation film.

[0002]

2. Description of the Related Art Liquid crystal display devices (hereinafter referred to as LCDs)
Currently, the one most frequently used is a spiral in a normal direction of a glass substrate between a pair of glass substrates on which transparent electrodes are formed, between a pair of linear polarizing films arranged so that absorption axes are orthogonal to each other. A shaft having a twist angle of about 90
Normally white (hereinafter, NW) sandwiching a liquid crystal cell sandwiching a nematic liquid crystal having an alignment structure of
Mode) twisted nematic LCD
(Hereinafter, referred to as TN-LCD). In the NW mode TN-LCD, when no voltage is applied, the incident linearly polarized light is rotated by 90 degrees due to the optical rotation of the liquid crystal cell and is emitted, so that a white state is obtained. When the voltage is applied, the liquid crystal molecules are deposited on the glass substrate. Rise up, the optical rotation disappears,
The incident linearly polarized light is emitted while maintaining that state, and becomes a black state. Further, gradation display is performed by utilizing the white state, the black state, and the intermediate state. However, nematic liquid crystals used in LCDs have a rod-like molecular structure and exhibit a large positive refractive index anisotropy in the molecular axis direction. The change differs from the normal direction of the LCD due to the phase difference due to the refractive index anisotropy of the liquid crystal.
For this reason, when the display is viewed from an angle deviating from the normal direction of the LCD, the viewing angle characteristic is such that phenomena such as a decrease in contrast and a grayscale inversion in which grayscale display is reversed occur.

Since this viewing angle characteristic is caused by the refractive index anisotropy of the liquid crystal molecules, the liquid crystal molecules have a refractive index anisotropy opposite to that of the liquid crystal for compensating for the phase difference due to the refractive index anisotropy of the liquid crystal molecules. Improvement using the retardation film shown is being studied. A great effect can be obtained by improving the viewing angle characteristics by improving the viewing angle characteristics in black display, that is, in a voltage applied state. Since the liquid crystal molecules are oriented nearly perpendicular to the glass substrate when voltage is applied, this state is regarded as a positive refractive index anisotropic substance having an optical axis in the normal direction of the glass substrate, and this is compensated for. As a retardation film, a method using a retardation film having an optical axis in a film normal direction and having a negative refractive index anisotropy is disclosed in JP-A-2-015239 and JP-A-3-015.
No. 103823 and the like. Also, in an actual LCD, even when a voltage is applied, the liquid crystal near the glass substrate remains inclined at a portion near the glass substrate due to the binding force of the alignment film of the substrate. A method using a retardation film whose axis is in a direction inclined from the normal direction of the film and which has a negative refractive index anisotropy is also described in JP-A-63-239421 and JP-A-6-214116. I have. As another method, while having the same positive refractive index anisotropy as the liquid crystal, it is possible to improve the viewing angle characteristics even by using a retardation plate in which the optical axis is inclined from the film normal direction, JP-A-5-080323, JP-A-7-306
No. 406 and WO 96/10773.

Recently, TN-LCDs have been used for a variety of applications, including personal computers, and have been improved in durability as well as in size, definition, wide viewing angle, weight and cost. Is strongly required. However, when a retardation film having an optical axis in the normal direction of the film and having negative refractive index anisotropy is used, the effect of improving the viewing angle is not always sufficient. A retardation film having an optical axis in a direction inclined from the normal direction of the film and having a negative refractive index anisotropy has a great effect of improving the viewing angle, but is disclosed in JP-A-63-239421. In the method of cutting out the polymer block oriented so as to show negative refractive index anisotropy such that the optical axis is in a direction inclined from the film normal direction, a uniform and large-area retardation film is obtained. It is difficult to get it efficiently,
In the method using a discotic liquid crystal compound as disclosed in Japanese Patent Application Laid-Open No. 6-214116, it is difficult to manufacture the liquid crystal compound and to uniformly align the liquid crystal, which is disadvantageous in cost.

[0005] Even when a retardation film having an optical axis in a direction inclined from the film normal direction and having a positive refractive index anisotropy is used, the effect of improving the viewing angle is large,
In the method disclosed in Japanese Patent Application Laid-Open No. 5-080323, a method of cutting out a polymer block oriented so as to exhibit a positive refractive index anisotropy so that the optical axis is inclined from the normal direction of the film is uniform. It is difficult to efficiently obtain a large-area and large-area retardation film.
Applied O disclosed in JP-A-06406
ptics 28 (1989), pp. 2466-24
A method by oblique vapor deposition of an inorganic dielectric on a glass substrate as described on page 82 or Ta ₂ O ₅ on a glass substrate as disclosed in WO96 / 10773.
In the method using oblique vapor deposition, it is possible to obtain a retardation plate in which the optical axis is in a direction inclined from the normal direction and has a positive refractive index anisotropy. Since it is used, only a retarder which is heavy, lacks flexibility, and is inferior in mass productivity can be obtained.

As for the retardation film used for improving the viewing angle characteristics of the TN-LCD as described above, no retardation film satisfying the needs of the market including properties other than the performance of improving the viewing angle characteristics has not been found. Was in the situation.

[0007]

In view of such a situation, the present inventors have proposed that at least one surface of a transparent polymer film is formed on at least one side of an inorganic dielectric material by an oxygen reactive deposition method using a specific metal. By providing a vapor deposition layer, it was possible to develop a large-area, lightweight, retardation film excellent in mass productivity and uniformity, in which the optical axis was inclined from the film normal direction, and completed the present invention. .

[0008]

That is, according to the present invention, at least one surface of a transparent polymer film has a positive refractive index anisotropy and has an optical principal axis of 20 to 7 degrees from the normal direction of the film.
This is a method for producing a retardation film in which at least one obliquely deposited layer made of a specific inorganic dielectric material inclined at 0 degrees is formed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The transparent polymer film used in the present invention is not particularly limited as long as it is excellent in transparency and uniform, but a thermoplastic polymer film is preferred in view of ease of film production. What consists of is preferably used. Examples of the thermoplastic polymer include a cellulosic polymer, a polycarbonate polymer, a polyarylate polymer, a polyester polymer, an acrylic polymer, polysulfone, and polyethersulfone. Among them, polysulfone, a polymer having excellent heat resistance such as polyethersulfone is advantageous for vapor deposition, but a cellulose-based polymer film, a polycarbonate-based polymer film from which a uniform film can be obtained at a low cost, is also preferable. Used. Further, the in-plane retardation value of the transparent polymer film (Rb = (nbx
-Nby) × db, nbx: refractive index in the slow axis direction in the film plane of the transparent polymer film, nby: refractive index in the fast axis direction in the film plane of the transparent polymer film, db: transparent polymer film (Thickness) is suitable for applications in which cellulose-based polymer film and acrylic polymer film with small intrinsic birefringence are particularly preferably used, and when a retardation value of several tens nm is required, Polycarbonate polymer films, polyester polymer films, polysulfone films, polyethersulfone films, etc. having large birefringence are preferably used. In particular, when an oblique evaporation layer of an inorganic dielectric is provided on a continuous film, a triacetyl cellulose film or a polyethersulfone film, which is less likely to be deformed by heat generated during evaporation and a stress generated for transporting the film, is preferably used. Can be

As a method for forming a transparent polymer film,
A solvent casting method or a precision extrusion method capable of reducing the residual stress of the film can be used, but a solvent casting method is preferably used in terms of uniformity. In particular, a solvent casting method is preferable for producing a film having a small Rb value.
Films formed in this manner, especially films formed by the solvent casting method, have a small Rb value, but have a refractive index (nbt) in the film thickness direction due to the in-plane orientation of the polymer during film formation. It has a refractive index structure that is smaller than the in-plane average refractive index (nbp). Therefore, the transparent polymer film has a retardation value (R'b) in the thickness direction due to the birefringence in the film thickness direction.
= (Nbp-nbt) × db), not a substrate for simple vapor deposition, but having a positive refractive index anisotropy according to the present invention and an optical principal axis inclined from the film normal direction. The optical axis used in combination with the obliquely deposited layer made of an inorganic dielectric can be used as a retardation film having a negative refractive index anisotropy in the normal direction of the film. The R'b value of this transparent polymer film is used in the range of about 0 nm to 250 nm. Also,
If the R'b value of the transparent polymer film is insufficient with respect to a predetermined value, the transparent polymer film is coated with a light-emitting device as disclosed in
It is also possible to form a layer containing an inorganic layered compound described in JP-A-6819 to adjust the R'b value.

On the other hand, a transparent polymer film can be used as a uniaxially oriented film having an Rb value. In this case, a film formed by a solvent casting method or a precision extrusion method is used. It can be obtained by stretching using such as. The Rb value in the case of a uniaxially oriented film is usually set in the range of 100 nm or less, but can be arbitrarily adjusted as needed. Further, the uniaxial orientation in the present invention includes not only perfect uniaxial orientation but also biaxial orientation having an R value in the film plane.

The thickness of these transparent polymer films is not particularly limited, but is usually about 50 μm to 500 μm.

In the present invention, when the oblique vapor deposition layer made of an inorganic dielectric is provided on at least one surface of the transparent polymer film, the predetermined retardation for using the oblique vapor deposition layer made of the inorganic dielectric as a retardation film is provided. In order to express the value, the thickness of the vapor deposition layer becomes considerably thicker than the film thickness when the antireflection layer etc. are formed by a dielectric multilayer vapor deposition film, so the adhesion is increased and the vapor deposition layer is cracked. It is preferable to provide an intermediate layer for preventing the occurrence.

As the intermediate layer used in the present invention, a polymer film made of acrylic resin, urethane resin, silicon resin, cardo resin or polysilazane is exemplified.

As a method for forming these polymer films, a method of dissolving a polymerized material in a solvent and applying the solution to a transparent polymer film, or a method of forming a composition containing a low-molecular monomer or oligomer and a polymerization initiator on a transparent polymer film can be used. A method of applying a polymer to the polymer film by photocuring or heat curing and then polymerizing the polymer film is used. There is no particular limitation on the method for coating the transparent polymer film, and known coating methods such as a comma coating method, a die coating method, a direct gravure method, and a bar coating method can be used.

An ultraviolet-curable acrylic resin film is preferably used for the cellulose-based polymer film, the polycarbonate-based polymer film, and the polyester-based polymer film, and a high heat-resistant polymer film such as polysulfone or polyethersulfone. For this, a thermosetting polysilazane film can also be used.

The thickness of the polymer film as the intermediate layer is not particularly limited as long as the adhesion can be improved.
It is set in the range of μm to 10 μm. When the thickness is less than about 0.2 μm, it is difficult to obtain a uniform film by coating, and when the thickness is more than about 10 μm, the adhesion between the transparent polymer film and the intermediate layer is undesirably reduced.

Inorganic dielectric of the obliquely deposited layer formed in the present invention
The body is formed into a thin film by reactive vapor deposition with oxygen introduced.
Positive refractive index anisotropy when oblique deposition is performed
And its main optical axis is 20 degrees from the normal direction of the film.
It expresses optical characteristics inclined to 70 degrees and is transparent.
A metal oxide having excellent properties and a hard film quality is preferable. Further
In addition, in terms of productivity, the refractive index differs when oblique deposition is performed.
The optical characteristics that are easy to express
Those which can obtain the property are preferable. Having such properties
Ta as an inorganic dielectric_TwoO_Five[Tantalum oxide (V)]
Or TiO_Two[Titanium oxide (IV)] as a main component
Metal oxides can be mentioned. Ta here_TwoO_Five
Or TiO_TwoIs a metal oxide containing Ta as a main component._Two
O _FiveOr TiO_Two80% by weight or more and 100% by weight or less
Points to include.

The angle of oblique deposition is defined by the angle between a line connecting the deposition points on the film from the deposition source and the normal to the film surface, as shown in FIGS. At this time,
The angle between the perpendicular drawn from the deposition source and the normal to the film surface at the intersection of the perpendicular (22, 44) drawn from the deposition source and the film surface is defined as the deposition center angle. The specific deposition center angle is appropriately set because it differs depending on the combination of the transparent polymer film and the deposition material to be used and the required optical characteristics, but the optical principal axis of the oblique deposition layer made of an inorganic dielectric and the film normal are set. In order to make the angle between the directions a predetermined angle of about 20 to 70 degrees, it is preferable to set the deposition center angle in a range of about 50 to 85 degrees. Further, the distance from the vertical line drawn from the vapor deposition source to the intersection of the film surface is defined as the vapor deposition distance. The specific deposition distance is appropriately set because it differs depending on the heat resistance of the transparent polymer film to be used, the cooling capacity of the vapor deposition device, the transport speed of the film, and the like. Usually 80
Preferably, it is set to 0 mm or less.

The thickness of the obliquely deposited layer made of an obliquely deposited inorganic dielectric material is not particularly limited as long as it is not less than a film thickness which gives rise to anisotropy in the growth of the deposited material and exhibits birefringence. In-plane retardation value of the obliquely deposited layer made of a dielectric material (Ra = (nax-nay) × da, nax:
Refractive index in the slow axis direction in the film plane of the oblique deposition layer, na
y: refractive index in the fast axis direction in the film plane of the obliquely deposited layer,
da (thickness of the obliquely deposited layer) is within a range of about 10 nm to 200 nm to obtain a predetermined retardation value. This thickness varies depending on the birefringence of the substance used and the inclination angle of the optical principal axis from the film normal direction, but is usually in the range of about 0.2 μm to 5 μm, preferably in the range of about 0.4 μm to 1 μm. Is set by

In the formation of a dielectric layer by oblique evaporation, a longer time of evaporation is required to reduce the evaporation efficiency as compared with ordinary evaporation from the direction perpendicular to the film surface. In order to suppress the temperature rise, it is conceivable to adopt a method of laminating the vapor-deposited layers in a plurality of times at the same inclination angle. When using a batch type evaporation apparatus,
Since the inclination angle of the vapor deposition layer is kept constant, the oblique vapor deposition layer can be formed as a single layer even if it is actually a multilayer as shown in FIG.

For the oblique vapor deposition on the continuous film, for example, an inorganic dielectric which comes at an unnecessary vapor deposition angle is cut by using a vapor deposition device capable of continuously oblique vapor deposition on the film shown in FIG. Alternatively, a method can be used in which only the inorganic dielectric that comes at a predetermined vapor deposition angle on the film on the can roll (34) is selectively vapor-deposited. In order to cut the inorganic dielectric coming at an unnecessary deposition angle, a deposition prevention plate (35) or a slit is provided between the deposition source (36) and the film, and a deposition start angle (41) and a deposition end angle ( 4
Set 2). In order to efficiently produce birefringence by causing anisotropy in the growth of the deposition material, the deposition start angle is 85 degrees or more.
Preferably, the deposition angle is 60 degrees.
It is preferable that the angle is 30 degrees and smaller than the deposition start angle. At this time, the vapor deposition center angle (43) formed at the intersection of the perpendicular line (44) drawn from the vapor deposition source with the film surface is such that the inorganic dielectric is efficiently vapor-deposited on the film. An evaporation source, a deposition-preventing plate and a film are arranged so as to be between them. Note that each vapor deposition angle defined here is an angle formed with the normal direction of the film surface.
When an oblique vapor deposition film is continuously formed by such an apparatus, the vapor deposition angle changes from the vapor deposition start angle to the vapor deposition end angle. When oblique deposition is performed continuously according to this,
The growth direction of the deposition material also changes, and the growth direction of the deposition material becomes curved as illustrated in FIG. For this reason,
When the oblique deposition layers are stacked by continuous deposition, the interface becomes a discontinuous surface as illustrated in FIG. 3 and cannot be a single layer. It is presumed that a density difference has occurred at this interface, and unnecessary interference colors may occur. For this reason,
When the oblique deposition layer is formed continuously on the continuous film, it is preferable to form the oblique deposition layer as a single layer by one vapor deposition. As described above, in order to obtain the optical characteristics required by one oblique deposition, it is necessary to reduce the transport speed of the film, so that the temperature of the polymer film increases during the deposition, and There is a risk of causing a defect such as inducing deformation. In order to avoid this, it is preferable to provide a plurality of radiation heat shielding plates so as not to add extra radiation heat.

[0023] Deformation of the film is a problem, but the characteristics of the formed dielectric layer change depending on the film temperature during oblique deposition, so that only the can roll is used so that the film temperature in the deposition section can be appropriately controlled. Instead, it is preferable that the film guide roll and the adhesion preventing plate can be controlled in temperature. The temperature control range is lower than the glass transition temperature of the polymer, and preferably lower than the heat distortion temperature, but it is more preferable that the temperature can be cooled to room temperature or lower.

As a method for forming the oblique evaporation layer used in the present invention, a metal is used as an evaporation material, and oxygen gas is introduced into a vacuum chamber while evaporating the metal by a known vacuum evaporation method such as a resistance heating method or an electron beam evaporation method. It is preferable to use a reactive vapor deposition method in which a metal oxide layer is formed by introducing an oxidation reaction. When forming an oblique deposition layer of a semi-fusible metal oxide such as Ta ₂ O _5, if the oxide is used as a deposition material, only the periphery of the portion irradiated with the electron beam is melted without melting the whole. Since the evaporation surface of the evaporation material is not smooth in the crucible because of evaporation and it is difficult to uniformly evaporate, there is a problem that a uniform oblique evaporation layer cannot be stably obtained. However, in the case of reactive vapor deposition using metal Ta as a vapor deposition material, a smooth molten surface is formed in the crucible of the vapor deposition source because metal Ta has a property of completely melting, and the vapor deposition material is vaporized stably. Therefore, a vapor deposition layer having excellent uniformity can be stably obtained. In the case of forming the oblique deposition layer by the molten metal oxide such as TiO _2, even if a Ti oxide such as TiO ₂ or Ti ₃ O ₅ as the vapor deposition material of these oxides meltable Therefore, a smooth molten surface can be obtained in the crucible, but in the case of reactive evaporation using metal Ti, it is melted at a lower temperature than these oxides, and evaporation can be performed. An oblique deposition layer having excellent uniformity can be formed without causing damage.

As an evaporation material, when forming an oblique evaporation layer of an inorganic dielectric made of a metal oxide containing Ta ₂ O ₅ as a main component by a reactive evaporation method by introducing oxygen, Ta is added at 80% by weight. The metal material contained above can be used. Similarly, when forming an oblique evaporation layer of an inorganic dielectric composed of a metal oxide containing TiO ₂ as a main component by a reactive evaporation method by introducing oxygen, a metal material containing 80% by weight or more of Ti is used. be able to. These metals may, if desired, contain less than 20% of minor components.

The amount of oxygen gas to be introduced into the evaporator to react with the evaporated metal is appropriately selected according to the volume of the evaporator, the exhaust capacity, and the like. When the amount is too small, the effect of oxidizing the metal is not sufficient. On the other hand, when the amount is too large, the pressure may increase and the deposition rate may decrease. Generally, the introduction amount is adjusted so that the air pressure in the vacuum chamber does not become higher than 10 ⁻³ Torr. At this time, the oxygen gas to be introduced may be one containing some subcomponents in some cases. Regarding the introduction of oxygen gas, for example, the oxygen inlet is installed at the position shown in FIGS. 4 (15) and 5 (46) and is introduced in the direction of spraying on the film surface. ) Or (17), or a method of installing at the position shown in FIG. 5 (47) or (48) and introducing the gas in a direction in which gas flows along the film surface.

Further, in order to increase the reactivity between the evaporated metal and oxygen, it is possible to use an ion plating method in which oxygen plasma is generated by plasma beam irradiation, a high-frequency electric field, arc discharge, or the like.

In the present invention, when the obliquely deposited inorganic dielectric layer is provided on at least one side of the transparent polymer film, the transparent polymer film having the obliquely deposited inorganic dielectric layer and the transparent polymer film or the intermediate layer as the base material is provided. In order to improve the adhesion to the polymer film, it is also possible to perform the vapor deposition after subjecting the transparent polymer film and the surface of the intermediate layer on the side to be vapor deposited to some sort of surface treatment. The surface treatment method is not particularly limited, but examples of commonly used heat treatment in a vacuum, corona treatment, ion bombardment treatment, plasma treatment, ultraviolet irradiation, acid / alkali treatment, and the like are given. it can. The surface treatment method and the degree of treatment, the transparent polymer film and the intermediate layer to be used, the vapor deposition material, and the mechanical strength required for the finally obtained retardation film,
It is appropriately selected depending on durability and optical characteristics.

The retardation film of the present invention is a TN-LCD
Is used as a retardation film for improving the viewing angle of super twisted nematic (STN)
Can also be used as a retardation film for improving the viewing angle of a liquid crystal display. In this case, the inclination angle of the optical principal axis of the obliquely deposited inorganic dielectric layer with respect to the film normal, the magnitude of the Ra value, the Rb value of the transparent polymer film, and the like are appropriately changed and set.

[0030]

The retardation film of the present invention has a TN-LC
A retardation film having an optical principal axis suitable for improving the viewing angle characteristics of D in a direction inclined from the film normal direction and having a positive refractive index anisotropy, and having excellent uniformity according to the present invention. A large-area product can be easily obtained at low cost.

[0031]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The measurement of the Ra value and the Rb value in the examples was performed by a conventional method using a polarizing microscope with monochromatic light having a wavelength of 546 nm. Also, the tilt angle of the optical principal axis from the film normal direction is the retardation value when the fast axis in the film plane is the tilt axis (when the transparent polymer film has birefringence, The value obtained by subtracting the retardation value) was determined by an ordinary method from the inclination angle dependency.

Example 1 Triacetyl cellulose film (trade name: Fuji TAC)
UV-80 Fuji Photo Film Co., Ltd., Rb # 11
nm) was coated with an ultraviolet curable acrylic resin using a comma coater, and then cured by irradiation with ultraviolet light to obtain a transparent polymer film having an acrylic resin film having a thickness of about 5 μm as an intermediate layer. The transparent polymer film on which the intermediate layer was formed was set in a holder in a vacuum vapor deposition machine shown in FIG. 4, evacuated to a pressure of 2 × 10 ⁻⁵ Torr, and the film was vapor-deposited at a central angle of 75 ° by electron beam vapor deposition. 400mm distance between center and substrate, 9KW electron gun output,
Ta (metal) is used as a vapor deposition material, and oxygen gas is
The film was introduced until the pressure reached × 10 ⁻⁴ Torr, and a single-layer obliquely evaporated Ta oxide layer having a thickness of 5450 ° was formed to obtain a retardation film. At this time, the entire surface of the deposition material was melted in the crucible, and a smooth molten surface was formed in the crucible. When the appearance of the retardation film was visually evaluated, there was no deformation of the substrate due to radiant heat during vapor deposition, and no peeling of the vapor-deposited film such as cracks was observed. This retardation film has a retardation value of 4 in the film plane.
7 nm, and the main optical axis is about 33
It was inclined at a degree.

Example 2 A transparent polymer film having an intermediate layer obtained in the same manner as in Example 1 was set in a holder in a vacuum vapor deposition machine shown in FIG. 4, and evacuated to a pressure of 2 × 10 ^-5 Torr. Using a beam deposition method, a deposition center angle of 75 degrees, a distance between the deposition center of the film and the substrate of 300 mm, an electron gun output of 4 KW, and using Ti (metal) as a deposition material, oxygen gas at a pressure of 1 ×
The film was introduced until the pressure reached 10 ^-4 Torr, and an oblique vapor deposition layer consisting of a single layer having a thickness of 8300 ° was formed to obtain a retardation film. At this time, the entire surface of the deposition material was melted in the crucible, and a smooth molten surface was formed in the crucible. When the appearance of the retardation film was visually evaluated, there was no deformation of the substrate due to radiant heat during vapor deposition, and no peeling of the vapor-deposited film such as cracks was observed. This retardation film had an in-plane retardation value of 44 nm, and the main optical axis was inclined by about 28 degrees from the normal direction of the film.

Example 3 Triacetyl cellulose film (trade name: Fuji TAC)
UV-80 Fuji Photo Film Co., Ltd., Rb # 11
nm) on a continuous film of a UV-curable acrylic resin with a comma coater, and then cured by UV irradiation to obtain a transparent polymer film having an acrylic resin film having a thickness of about 5 μm as an intermediate layer. . A continuous film obtained by slitting this film into a width of 125 mm was obtained.
The surface-treated transparent polymer film was set in the continuous vacuum evaporator shown in FIG. 5, evacuated to a pressure of 5 × 10 ⁻⁵ Torr, and deposited by an electron beam evaporation method at an evaporation start angle of 80 °.
, A deposition end angle of 45 degrees, a deposition center angle of 60 degrees, a distance between the deposition center of the film and the substrate of about 340 mm, the proof plate is arranged, the EB gun output is 8 KW, and the transport speed is 0.
25 m / min, Can roll cooling temperature -10 ° C., Ti (metal) as vapor deposition material, oxygen gas at 7 × 1
The film was introduced until the pressure reached 0 ^-4 Torr, and a single layer of oblique vapor deposition having a thickness of 8500 ° was continuously formed to obtain a retardation film. When the appearance of this retardation film was visually evaluated, there was no deformation of the substrate due to radiant heat during vapor deposition,
In addition, peeling of the deposited film such as cracks was not observed. This retardation film has an in-plane retardation value of 38 nm, and the optical main axis continuously changes in the film thickness direction corresponding to the change in the deposition angle during continuous deposition, but has not changed. The value obtained on the assumption that the film was inclined at about 33 degrees from the normal direction of the film.

Comparative Example 1 A transparent polymer film having an intermediate layer obtained in the same manner as in Example 1 was set in a vacuum evaporation machine shown in FIG.
After evacuation to × 10 ⁻⁵ Torr, Ta ₂ O ₅ was used as a main component of the vapor deposition material at an evaporation center angle of 75 °, a distance between the film deposition center and the substrate of 300 mm, an electron gun output of 3.5 KW by an electron beam vapor deposition method. Using a mixture with Ta (trade name: OA-100, manufactured by Optron) having a thickness of 15
An oblique deposition layer consisting of a single layer of 300 ° was formed to obtain a retardation film. During evaporation, only the part irradiated with the electron beam melts and evaporates in the crucible, and the remaining part remains as it is, so a step occurs in the crucible as the evaporation proceeds, and a uniform evaporation surface is obtained I couldn't do that. When the appearance of this retardation film was visually evaluated, there was no deformation of the substrate due to radiant heat during vapor deposition, and no peeling of the vapor-deposited film such as cracks was observed, but the thickness of the vapor-deposited layer and the in-plane retardation There was a slight distribution in the direction of the optical principal axis. The retardation film had an average in-plane retardation value of 79 nm and an optical main axis inclined by about 33 degrees from the normal direction of the film.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a cross section of a retardation film in which a single-layer oblique evaporation layer is formed on a transparent polymer film using a batch type vacuum evaporation apparatus.

FIG. 2 is a schematic diagram of a cross section of a retardation film in which a single-layer oblique vapor deposition layer is formed on a continuous transparent polymer film using a continuous vacuum vapor deposition apparatus.

FIG. 3 is a schematic view of a cross section of a retardation film in which a multilayer oblique deposition layer is formed on a continuous transparent polymer film using a continuous vacuum deposition apparatus.

FIG. 4 is a schematic view of an apparatus for forming an oblique evaporation layer by a batch type vacuum evaporation apparatus.

FIG. 5 is a schematic view of an apparatus for forming an oblique evaporation layer by a continuous vacuum evaporation apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oblique deposition layer by batch method 2 Oblique deposition layer by continuous evaporation method 3 Intermediate layer 4 Transparent polymer film 11 Holder 12 Transparent polymer film 13 Protective plate 14 Deposition source 15 Oxygen inlet 16 Oxygen inlet 17 Oxygen introduction Port 21 Deposition center angle 22 Perpendicular line from deposition 31 Continuous film unwinding part 32 Continuous film writing part 33 Guide roll 34 Can roll 35 Prevention plate 36 Deposition source 37 Transparent polymer continuous film 41 Deposition start angle 42 Deposition end angle 43 Deposition Center angle 44 Perpendicular line drawn from evaporation source 45 Continuous film traveling direction 46 Oxygen inlet 47 Oxygen inlet 48 Oxygen inlet

Claims (4)

[Claims] 1. The method according to claim 1, wherein at least one side of the transparent polymer film has
A retardation film having a positive refractive index anisotropy and having at least one obliquely deposited inorganic dielectric layer having an optical principal axis inclined at 20 to 70 degrees from the film normal direction; Manufacturing method, using metal as a deposition material,
A method for producing a retardation film, comprising forming a metal oxide layer by a reactive evaporation method in which oxygen gas is introduced during film formation. 2. The method according to claim 1, wherein at least one side of the transparent polymer film has
At least one layer of T having a positive refractive index anisotropy and having an optical principal axis inclined at 20 to 70 degrees from the film normal direction.
A method for producing a retardation film, comprising forming an oblique evaporation layer composed of an inorganic dielectric mainly composed of a ₂ O ₅ , wherein a metal containing 80% by weight or more of Ta is used as an evaporation material,
A method for producing a retardation film, wherein a Ta oxide layer is formed by a reactive vapor deposition method in which oxygen gas is introduced during film formation. 3. A transparent polymer film on at least one side of
Positive refractive index anisotropy and optical axis is normal to film
At least one layer of T inclined at 20 to 70 degrees from the direction
iO _TwoAn obliquely deposited layer composed of an inorganic dielectric mainly composed of
A method for producing a retardation film formed by vapor deposition
Using a metal containing 80% by weight or more of Ti as a material,
Ti acid by reactive vapor deposition that introduces oxygen gas during film formation
Of a retardation film characterized by forming a compound layer
Construction method. 4. The transparent polymer film has a positive refractive index anisotropy on at least one surface thereof with an intermediate layer interposed therebetween, and the main optical axis is inclined by 20 to 70 degrees from the normal direction of the film. 4. An oblique vapor deposition layer comprising at least one layer of an inorganic dielectric is formed.
A method for producing the retardation film according to the above.