JPH11263861A - Preparation of phase difference film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously obtain a phase difference film which has a large area, is lightweight, and is excellent in mass-productivity and durability by diagonally vapor depositing an inorg. dielectric on at least one side of a continuous film while continuously changing the vapor deposition angle in a specified range. SOLUTION: A continuous clear polymer film 37 having a thickness of 50-500 μm is led from a winding-off section 31 through a guide roll 33 to a drum 34; and simultaneously the vapor deposition starting angle and the vapor deposition ending angle, both obtd. from a vapor deposition angle width by using a deposition prevention plate 35 installed between a vapor deposition source 36 and the film 37, are set so as to cut an inorg. dielectric which comes flying at unnecessary angles. The vapor deposition starting angle 41 is set at 60-85 deg., pref. 70-85 deg.; the vapor deposition ending angle 42, at smaller than the starting angle; the vapor deposition angle width, at 10 deg. or larger; and the vapor deposition center angle 43, at 50-80 deg.. Thus, the inorg. dielectric is diagonally vapor deposited on at least one side of the film 31 while the vapor deposition angle is being continuously changed.

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 A liquid crystal display (hereinafter, referred to as LCD) most frequently used at present is a pair of linearly polarizing films arranged so that absorption axes are orthogonal to each other. A liquid crystal sandwiching a nematic liquid crystal having a helical axis in the normal direction of the glass substrate between a pair of glass substrates on which a transparent electrode is formed, and having a twisted angle of about 90 degrees. Twisted nematic LCD (hereinafter, referred to as TN-LCD) in a normally white (hereinafter, referred to as NW) mode with cells interposed therebetween
). In a 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, resulting in a white state. When a voltage is applied, the liquid crystal molecules are deposited on the glass substrate. On the other hand, it rises up, the optical rotatory power disappears, and 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 a large refractive index in the direction of the molecular axis, exhibiting a positive refractive index anisotropy. The change in the polarization state is different 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 contrast is reduced,
The viewing angle characteristic shows that a phenomenon such as grayscale inversion in which grayscale display is reversed occurs.

Since this viewing angle characteristic is caused by the refractive index anisotropy of the liquid crystal molecules, the 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.

The viewing angle characteristics can be greatly improved 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. JP-A-2-015239 and JP-A-3-103823 disclose methods for using a retardation film having an optical axis in the film normal direction and having a negative refractive index anisotropy as the retardation film. ing. 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 film normal direction and which has a negative refractive index anisotropy is also disclosed in JP-A-63-23942.
No. 1 and JP-A-6-214116. 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, It is described in JP-A-5-080323, JP-A-7-306406 and WO96 / 10773.

[0006] Recently, TN-LCDs have been used for various applications such as personal computers, and there is a strong demand for large-sized, high-definition, wide-viewing-angle, light-weight, and low-cost products.

When a retardation film having an optical axis in the normal direction of the film and having a negative refractive index anisotropy is used, the effect of improving the viewing angle is not always sufficient. Also,
In 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, the effect of improving the viewing angle is large, but the film is disclosed in JP-A-63-239421.
In the method in which the optical axis is cut out from a polymer block oriented so as to exhibit a negative refractive index anisotropy as disclosed in Japanese Patent Publication No. It is difficult to efficiently obtain the retardation film of (1), and the method using a discotic liquid crystal compound as disclosed in JP-A-6-214116 makes it difficult to manufacture the liquid crystal compound and to uniformly align the liquid crystal, which is disadvantageous in cost. It is.

[0008] 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 by 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, a retardation film satisfying the demands of the market including properties other than the performance of improving the viewing angle characteristics has been found. In addition, the production method was not found.

In view of this situation, the inventors of the present invention have conducted an oblique deposition while continuously changing the deposition angle of an inorganic dielectric material on at least one side of a continuous film, wherein the deposition start angle is 85 to 60 degrees, A method of continuously producing a retardation film having a large area, light weight, excellent mass productivity, and excellent durability, in which the optical axis is inclined from the normal direction of the film by setting the deposition angle range to 10 degrees or more. Have been developed, and the present invention has been completed.

[0011]

That is, the present invention relates to a method for producing a retardation film by oblique vapor deposition in which an inorganic dielectric is continuously changed on at least one side of a continuous film while changing a vapor deposition angle. An object of the present invention is to provide a method for producing a retardation film in which the angle is 60 to 85 degrees, the vapor deposition end angle is smaller than the vapor deposition start angle, and the vapor deposition angle width is 10 degrees or more.

[0012]

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 following calculation formula (1) Rb = (nbx-nby) × db (1) [wherein nbx is the refractive index in the slow axis direction in the film plane of the transparent polymer film, and nby is transparent. The refractive index in the fast axis direction in the film plane of the polymer film, and db indicates the thickness of the transparent polymer film. ], The in-plane retardation value (R
For applications in which b) is small, cellulose-based polymer films and acrylic polymer films having small intrinsic birefringence are particularly preferably used, and when a retardation value (Rb) of several tens nm is required. Polycarbonate polymer films, polyester polymer films, polysulfone films, polyethersulfone films, etc., having a large intrinsic birefringence are preferably used. Further, when the inorganic dielectric is obliquely vapor-deposited on the continuous film, a triacetyl cellulose film or a polyethersulfone film, which is less likely to deform the film due to heat generated during vapor deposition and stress generated during film transport, is preferably used.

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 in-plane retardation 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, this transparent polymer film has the following formula (2) R′b = (nbp−nbt) × db (2) (where nbt is the thickness of the transparent polymer film) due to the birefringence in the film thickness direction. In which the retardation value (R'b) in the thickness direction is not 0, which is the refractive index in the direction of the film, nbp is the average refractive index in the film plane, and db is the thickness of the transparent polymer film. When R′b has a value other than 0, the transparent polymer film is not a substrate for simple vapor deposition, but has a negative refractive index anisotropy in which the optical axis is in the normal direction of the film. It becomes a retardation film having a property, and constitutes a layer having optical characteristics different from a layer formed by oblique deposition on at least one surface thereof. The R'b value of this transparent polymer film is used in a range of about 0 nm to 250 nm.

When R'b of the transparent polymer film is insufficient with respect to a predetermined value, a layer containing an inorganic layered compound described in JP-A-5-196819 is formed on the transparent polymer film. Can be formed to adjust the size of R′b.

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 for a uniaxially oriented film is usually set in the range of 100 nm or less. Further, the uniaxial orientation in the present invention includes not only perfect uniaxial orientation but also biaxial orientation having Rb.

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

In the present invention, an oblique vapor deposition of an inorganic dielectric is formed on at least one surface of the transparent polymer film by oblique vapor deposition. When providing the obliquely deposited layer, the obliquely deposited inorganic dielectric layer exhibits a predetermined retardation value for use as a retardation film. Since the thickness of the deposited layer is considerably larger than the thickness of the deposited layer, it is preferable to provide an intermediate layer for improving the adhesion and preventing the deposited layer from cracking.

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

As a method for forming these polymer films, a method of dissolving a polymerized product in a solvent and applying it 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.

For the cellulose-based polymer film, the polycarbonate-based polymer film, and the polyester-based polymer film, an ultraviolet-curable acrylic resin film is preferably used, and a high heat-resistant polymer film such as polysulfone or polyethersulfone is used. 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.

As the inorganic dielectric used in the present invention, a thin film can be formed by vacuum evaporation, a positive refractive index anisotropy is exhibited when oblique evaporation is performed, and the optical principal axis is in the normal direction of the film. It is preferable to use a metal oxide exhibiting optical characteristics inclined from 20 ° to 70 ° from the above, and having excellent transparency and hard film quality. Further, from the viewpoint of productivity, it is preferable that anisotropic refractive index is easily exhibited when the film is obliquely vapor-deposited and the necessary optical characteristics can be obtained with a film thickness as small as possible. As an inorganic dielectric having such characteristics, metal oxides containing Ta ₂ O ₅ [tantalum oxide (V)], TiO ₂ [titanium oxide (IV)] or ZrO ₂ [zirconium oxide (IV)] as a main component And the like. Here, the metal oxide containing Ta ₂ O ₅ , TiO ₂ or ZrO ₂ as a main component refers to a metal oxide containing 50 to 100% by weight of Ta ₂ O ₅ , TiO ₂ or ZrO ₂ .

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 (43). The specific deposition center angle is appropriately set because it depends on the combination of the transparent polymer film and the deposition material to be used and the required optical characteristics, but the angle formed by the optical principal axis of the inorganic dielectric layer and the film normal direction is set. In order to obtain a predetermined angle of about 20 to 70 degrees, the deposition center angle should be about 5 degrees.
It is preferable to set the angle in the range of 0 to 85 degrees. Also,
The distance from the perpendicular 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 varies 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, it is preferably set to 40 cm or less because the property may be deteriorated.

The thickness of the oblique deposition layer of the inorganic dielectric formed by the oblique deposition is not particularly limited as long as it is not less than a film thickness which causes anisotropy in the growth of the deposition material and exhibits birefringence. The following formula (3): Ra = (max−nay) × da (3) [where, nax is the refractive index of the obliquely deposited layer in the slow axis direction in the film plane, and nay is the film of the obliquely deposited layer. The in-plane refractive index in the fast axis direction and da indicate the thickness of the oblique deposition layer, respectively. The in-plane retardation value (Ra) of the obliquely deposited inorganic dielectric layer represented by
The thickness is set so as to obtain a predetermined retardation value in the range of 00 nm. This thickness varies depending on the birefringence of the substance (inorganic dielectric) used and the angle of inclination of the main optical axis from the normal direction of the film, but is usually in the range of about 0.2 μm to 5 μm, preferably about 0.2 μm. It is set in the range of 4 μm to 1 μm.

For the oblique vapor deposition on the continuous film, for example, an inorganic dielectric which is flying 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. Then, it is possible to use a method of selectively depositing only the inorganic dielectric that comes at a predetermined deposition angle on the film on the can roll (34). 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 the deposition start angle (41) and the deposition angle width are determined. The obtained deposition end angle (42) is set. In order to generate birefringence efficiently by causing anisotropy in the growth of the vapor deposition material and to prevent the optical characteristics from significantly deteriorating when subjected to a durability test under conditions of high temperature and high humidity, the vapor deposition start angle Is 8
It is necessary to be 5 degrees to 60 degrees, preferably 85 degrees
Degrees to 70 degrees. If the vapor deposition start angle is larger than 85 degrees, the durability of the optical fiber deteriorates greatly in a durability test, which is not preferable. Further, the vapor deposition angle width is set to 10 degrees or more in a direction in which the vapor deposition end angle is smaller than the vapor deposition start angle. Although oblique deposition is possible even if the deposition angle width is less than 10 degrees, it is preferably 10 degrees or more, more preferably 20 degrees or more, in order to obtain a sufficient inorganic dielectric layer thickness. At this time, a vertical line (4) drawn from a deposition source was used so that the inorganic dielectric was efficiently deposited on the film.
4) is the center angle of vapor deposition formed at the intersection with the film surface (43)
Is disposed between the deposition start angle and the deposition end angle so that the deposition center angle is 8 mm.
It is preferable that it is 0 degree to 50 degrees. On the other hand, if the vapor deposition start angle is smaller than the vapor deposition end angle, the oblique vapor deposition effect is not sufficiently exhibited, and disadvantages such as no Ra value are likely to occur. Note that each vapor deposition angle defined here is an angle formed with the normal direction of the film surface.

When an obliquely deposited film is continuously produced by such an apparatus, the deposition angle changes from the deposition start angle to the deposition end angle. When oblique deposition is performed continuously in accordance with 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. 2 and does not become a single layer. It is presumed that a density difference has occurred at this interface, causing unnecessary interference colors, durability tests,
In particular, in a durability test under conditions of high temperature and high humidity such as 60 ° C. and 90% RH, optical characteristics may be significantly reduced. For this reason, when forming an oblique vapor deposition layer continuously on a continuous film, it is preferable to form the oblique vapor deposition layer as a single layer by one vapor deposition.

The optical property referred to here means that when applied to a liquid crystal display device, it is used by being laminated on a polarizing film. JIS-Z87 based on the spectral transmittance under crossed Nicols measured by the optical system shown in FIG. 5 in the case of bonding at 45 degrees to the absorption axis.
22 means the Y value calculated on the basis of S.22. This optical property is determined by the Ra value resulting from the refractive index anisotropy that is exhibited when the optical principal axis is inclined by 20 to 70 degrees from the normal direction of the film. The change represents a change in the refractive index anisotropy.

In the present invention, the residual ratio of the optical characteristics after leaving for 96 hours at a high temperature and a high humidity of 60 ° C. and 90% RH is 7%.
Although a retardation film having 0% or more can be obtained,
Preferably, the residual ratio is 80%, more preferably, the residual ratio is 90%.
That is all.

As described above, in order to obtain the optical characteristics required by one oblique deposition, it is necessary to reduce the film transport speed, so that the temperature of the polymer film increases during the deposition. However, there is a danger that a defect such as deformation of the film is caused. In order to avoid this, it is preferable to provide a plurality of radiant heat shielding plates and cooling plates so as not to add extra radiant heat.

Although it is a problem that the film is deformed, the characteristics of the formed dielectric layer change depending on the film temperature at the time of oblique vapor deposition. It is preferable that not only 34) but also the film guide roll (32) and the deposition-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 the oblique evaporation method used in the present invention, an electron beam evaporation method, an ion plating method, or a known method can be used. From the viewpoint of productivity, an electron beam evaporation method is preferably used.

As a vapor deposition material, when forming an oblique vapor deposition layer of an inorganic dielectric composed of a metal oxide containing Ta ₂ O ₅ as a main component, a metal oxide containing 50% by weight or more of Ta ₂ O ₅ is used. And mixtures thereof. TiO ₂
When forming an obliquely deposited inorganic dielectric layer composed of a metal oxide whose main component is TiO ₂ , a metal oxide containing TiO ₂ at 50% by weight or more and a mixture thereof can be used. When forming an obliquely deposited inorganic dielectric layer composed of a metal oxide containing ZrO ₂ as a main component, a metal oxide containing 50 wt% or more of ZrO ₂ and a mixture thereof can be used.

When a substance such as Ta ₂ O ₅ is used, which may cause the composition ratio of tantalum and oxygen to collapse at the time of vapor deposition and cause oxygen deficiency to cause coloring, the substance may be installed in the vapor deposition machine as necessary. A method of introducing oxygen gas to adjust the composition ratio of oxygen in the deposition layer to increase transparency may be used.

The amount of oxygen gas to be introduced is appropriately selected because it varies depending on the volume of the vapor deposition apparatus and the exhaust capacity. If the amount is too small, the effect of oxygen introduction is not sufficient, and if the amount is too large, the pressure increases and the deposition rate may decrease. Generally, the introduction amount is adjusted so that the pressure in the apparatus does not become worse than 10 ⁻³ Torr.

In the present invention, when the obliquely deposited inorganic dielectric layer is provided on at least one surface 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 substrate 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.

[0037]

The retardation film of the present invention has a TN-LC
A method for producing a retardation film having an optical principal axis suitable for improving the viewing angle characteristics of D in a direction inclined from the normal direction of the film and having a positive refractive index anisotropy. It is possible to easily and inexpensively manufacture a large-area product excellent in quality.

[0038]

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 carried out 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, From the dependency of the inclination angle on the value obtained by subtracting the retardation value, the refractive index structure was determined by a conventional method on the assumption that the refractive index structure was uniaxial.

In the durability test, the slow axis in the film plane of the retardation film according to the present invention was measured using a polarizing film (SQ-1).
852AP7, manufactured by Sumitomo Chemical Co., Ltd.), a polarizing film is stuck on the transparent polymer film side of the retardation film, and optically isotropic on the oblique evaporation layer side so as to be at 45 degrees with respect to the absorption axis of Sumitomo Chemical Co. 1.1mm thick through a transparent acrylic adhesive
A sample having a size of 30 mm × 30 mm to which a glass plate was bonded was used.

The spectral transmittance for obtaining the optical characteristics was determined by using a spectroscope (MCPD-2000, manufactured by Otsuka Electronics Co., Ltd.) using the optical system shown in FIG. Measured with the absorption axis of
The Y value was calculated based on JIS-Z8722. The ratio of the Y value after standing at 60 ° C. and 90% RH for 96 hours with respect to the initial value of the Y value was defined as the residual ratio of the optical characteristics. In addition, the reference of the spectral transmittance was measured with the absorption axis of the polarizing prism being parallel, and after the reference measurement, the sample was measured with the absorption axis of the polarizing prism being orthogonal.

Example 1 Triacetyl cellulose film (trade name: Fuji TAC)
SH-80 Fuji Photo Film Co., Ltd., Rb is about 1
1 nm) is coated with a UV-curable acrylic resin using a comma coater, and then cured by UV irradiation.
A transparent polymer film having an acrylic resin film having a thickness of about 5 μm as an intermediate layer was obtained. 130m of this film
A continuous film slit to m width was obtained. Further, the surface of the intermediate layer of the transparent polymer continuous film having the intermediate layer formed thereon was subjected to Ar ion bombardment at an atmosphere of 0.05 Torr or less at an electrode pressure of 1.2 KV and a transport speed of 0.5 m / min. . The transparent polymer film subjected to this surface treatment is set in the continuous vacuum vapor deposition machine shown in FIG.
Atmospheric pressure (degree of vacuum) is evacuated to 5 × 10 ⁻⁵ Torr, and a deposition start angle of 80 degrees, a deposition end angle of 60 degrees, a deposition center angle of 72 degrees, and a distance between the deposition center of the film and the substrate of about 300 mm by an electron beam deposition method. The EB gun output is 7 KW, the conveying speed is 0.1 m / min, the cooling temperature of the can roll is 0 ° C., and the oxygen introduction amount is 45 sccm.
Using a mixture of Ta (metal) containing Ta ₂ O ₅ as a main component as a vapor deposition material (trade name: OA-100, manufactured by Optron), a single oblique vapor deposition layer having a thickness of 3320 ° is continuously formed. To obtain a retardation film.

When the external appearance of the retardation film was visually evaluated, no deformation of the substrate due to radiant heat during vapor deposition was observed, and no peeling of the vapor-deposited layer such as cracks was observed. This retardation film has an in-plane retardation value of 18 nm, and the optical principal axis continuously changes in the film thickness direction corresponding to the change in the deposition angle during continuous deposition, but does not change. The value obtained on the assumption that the film was inclined at about 33 degrees from the normal direction of the film. When this retardation film was subjected to a durability test,
The residual ratio of the optical characteristics was 79%.

Example 2 A transparent polymer film on which an intermediate layer obtained in the same manner as in Example 1 was formed and subjected to surface treatment was set in a continuous vacuum vapor deposition machine shown in FIG. 5, and exhausted to a pressure of 5 × 10 ^-5 Torr. Then, a deposition start angle of 80 degrees and a deposition end angle of 4 degrees by an electron beam deposition method.
5 degrees, the deposition center angle is 72 degrees, the deposition prevention plate is arranged so that the distance between the film deposition center and the substrate is about 300 mm,
An EB gun output of 11 KW, a conveying speed of 0.3 m / min, a cooling temperature of the can roll of 0 ° C., an oxygen introduction amount of 45 sccm, and a mixture with Ta (metal) containing Ta ₂ O ₅ as a main component as an evaporation material (manufactured by Optron Corporation) (Trade name: OA-100), an oblique vapor deposition layer having a single layer of 8000 mm in thickness was continuously formed to obtain a retardation film.

When the appearance of the retardation film was visually evaluated, there was no deformation of the substrate due to radiant heat at the time of vapor deposition, and no peeling of the vapor deposited layer such as cracks was observed. This retardation film has a retardation value in the film plane of 45 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 does not change. The value obtained on the assumption that the film was inclined at about 33 degrees from the normal direction of the film. When this retardation film was subjected to a durability test,
The residual ratio of the optical characteristics was 85%.

Comparative Example 1 A transparent polymer film on which an intermediate layer obtained in the same manner as in Example 1 was formed and subjected to surface treatment was set in the continuous vacuum vapor deposition machine shown in FIG. 5, and exhausted to a pressure of 5 × 10 ^-5 Torr. Then, the deposition start angle is 90 degrees and the deposition end angle is 6 by the electron beam deposition method.
0 degree, the deposition center angle is 72 degrees, the deposition prevention plate is arranged so that the distance between the film deposition center and the substrate is about 300 mm,
An EB gun output of 7 KW, a conveyance speed of 0.1 m / min, a cooling temperature of the can roll of 0 ° C., an oxygen introduction amount of 45 sccm, and a mixture with Ta (metal) containing Ta ₂ O ₅ as a main component as a vapor deposition material (Optron Corporation) (Trade name: OA-100) to form a single layer of obliquely vapor-deposited layer having a thickness of 3900 ° continuously to obtain a retardation film.

When the appearance of the retardation film was visually evaluated, there was no deformation of the substrate due to radiant heat at the time of vapor deposition, and no peeling of the vapor deposited layer such as cracks was observed. This retardation film has a retardation value in the film plane of 28 nm, and the optical principal axis continuously changes in the film thickness direction corresponding to the change of the deposition angle during continuous deposition, but does not change. The value obtained on the assumption that the film was inclined at about 35 degrees from the normal direction of the film. However, when this retardation film was subjected to a durability test, the residual ratio of the optical characteristics was 40%, which was inferior to that having a deposition start angle of 80 degrees.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a cross section of a retardation film in which a single oblique vapor deposition layer is formed on a continuous transparent polymer film using a continuous vacuum vapor deposition apparatus.

FIG. 2 is a schematic diagram 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. 3 is a schematic view of an apparatus for forming an oblique evaporation layer by a batch type vacuum evaporation apparatus.

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

FIG. 5 is a schematic diagram of an optical system for measuring optical characteristics.

[Explanation of symbols]

2 Oblique evaporation layer by continuous evaporation method 3 Intermediate layer 4 Transparent polymer film 11 Holder 12 Transparent polymer film 13 Deposition plate 14 Evaporation source 21 Evaporation center angle 22 Vertical line from evaporation 31 Continuous film unwinding part 32 Continuous film writing Part 33 Guide roll 34 Can roll 35 Deposition 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 deposition source 45 Continuous film traveling direction 51 Incident light 52 Incident light Side polarizing prism 53 polarizing film of measurement sample 54 retardation film of measurement sample 55 glass plate on which measurement sample is bonded 56 outgoing light side polarizing prism 57 outgoing light 61 absorption axis direction of incoming side polarizing prism 62 Absorption axis direction of polarizing film of sample for measurement 6 Slow axis direction in the film plane of the retardation film of the measurement sample 64 Angle between the absorption axis direction of the polarizing film of the measurement sample and the slow axis direction of the retardation film (45 degrees) 65 Polarizing prism on the emission light side Absorption axis direction

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G02F 1/1335 610 G02F 1/1335 610 // B32B 9/00 B32B 9/00 A

Claims (6)

[Claims] 1. A method for producing a retardation film by oblique vapor deposition in which an inorganic dielectric is continuously changed on at least one side of a continuous film while changing a vapor deposition angle, wherein a vapor deposition start angle is 60 to 85 degrees. A method for producing a retardation film, wherein the vapor deposition end angle is smaller than the vapor deposition start angle and the vapor deposition angle width is 10 degrees or more. 2. The oblique vapor deposition in which an inorganic dielectric is continuously changed on at least one surface of a continuous film while changing the vapor deposition angle, wherein the vapor deposition center angle is 50 to 80 degrees.
The manufacturing method as described. 3. The method for producing a retardation film according to claim 1, wherein the continuous film is a transparent polymer film. 4. The retardation according to claim 1, wherein the obliquely deposited layer of the inorganic dielectric has a positive refractive index anisotropy and the main optical axis is inclined by 20 to 70 degrees from the normal direction of the film. Film production method. 5. The method for producing a retardation film according to claim 1, wherein an intermediate layer is formed on at least one surface of the continuous film, and an oblique deposition layer is formed on the intermediate layer. 6. The method for producing a retardation film according to claim 1, wherein a main component of the inorganic dielectric is Ta ₂ O ₅ .