JP2000231016A - Production of phase difference plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously provide a phase difference plate having good heat resistance and capable of satisfying refractive index characteristics of the inequality nz>nx>ny when the main refractive indexes in the surface are represented by nx and ny, the main refractive index in the thickness direction is represented by nz and nx>ny. SOLUTION: When a heat shrinkable film is bonded to one face or both faces of a long-sized light transmissive film and the light transmissive film is shrunk under the action of the shrinking force of the heat shrinkable film by heat treatment, the light transmissive film is shrunk in the longitudinal direction using a heat shrinkable film in which the ratio of shrinkage percentage in the longitudinal direction to that in the transverse direction in heating is >=10 and the light transmissive film is shrunk in the transverse direction using a heat shrinkable film in which the ratio of shrinkage percentage in the longitudinal direction to that in the transverse direction in heating is 0-0.1 or 0.5-2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously manufacturing a retardation plate suitable for forming a liquid crystal display.

[0002]

2. Description of the Related Art Conventionally, when the in-plane main refractive index is nx and ny and the main refractive index in the thickness direction is nz and nx> ny (the same applies hereinafter), a retardation plate satisfying nx <nz is known. As a production method, a method of biaxially stretching a film made of a polymer having a negative birefringence characteristic such as polystyrene has been known. The refractive index characteristics of nz>nx> ny are required, for example, in order to compensate for birefringence of liquid crystal to prevent a change in display color or contrast due to a viewing angle.

However, the obtained biaxially stretched film has poor heat resistance, and has a problem that it is difficult to use it for forming a liquid crystal display device due to a problem such as a change in retardation.

[0004]

The present invention relates to the above-mentioned nz>nx> n
It is an object of the present invention to obtain a highly heat-resistant retardation plate that can satisfy the refractive index characteristic of y in a continuous state.

[0005]

According to the present invention, a heat-shrinkable film is adhered to one or both sides of a long light-transmitting film, and the heat-shrinkable film is subjected to a heat-treating action of the heat-shrinkable film. When shrinking, the length direction during heating /
Using a heat-shrinkable film having a shrinkage ratio of 10 or more in the width direction to shrink the length direction of the translucent film,
The shrinkage ratio in the length direction / width direction during heating is 0 to 0.1
Another object of the present invention is to provide a method for manufacturing a retardation plate, wherein a width direction of a light-transmitting film is shrunk using a heat-shrinkable film of 0.5 to 2.

[0006]

According to the present invention, the above-mentioned nz>nx> n
Various phase difference characteristics such as a highly heat-resistant phase difference plate that satisfies the refractive index characteristics of y can be obtained in a continuous state, and the display characteristics change due to the viewing angle based on the birefringence of the liquid crystal cell can be highly compensated. Can easily be obtained.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The manufacturing method according to the present invention is characterized in that a heat-shrinkable film is adhered to one or both sides of a long light-transmitting film and the heat-shrinkable film is subjected to the heat-shrinkage force of the heat treatment. In shrinking the light-transmitting film, the heat-shrinkable film having a shrinkage ratio in the length direction / width direction at the time of heating of 10 or more is used to shrink the length direction of the light-transmitting film and the length at the time of heating. A retardation plate is obtained by using a heat-shrinkable film having a shrinkage ratio in the direction / width direction of 0 to 0.1 or 0.5 to 2 to shrink the light-transmitting film in the width direction.

[0008] As a light-transmitting film to be subjected to shrinkage treatment,
An appropriate light-transmitting film can be used, and there is no particular limitation. A film which is excellent in light transmittance and has a light transmittance of 75% or more, particularly 85% or more, and little alignment unevenness can be preferably used. There is no particular limitation on the polymer forming the light-transmitting film, and an appropriate polymer can be used. Polymers can be classified into positive and negative according to the birefringence characteristics depending on the relationship between the stretching direction and the refractive index when the film is stretched, and any of them can be used in the present invention.

Above all, a translucent film made of a polymer exhibiting a positive birefringence property, which increases the refractive index in the stretching direction, can be preferably used from the viewpoint of processing efficiency, heat resistance and the like. Incidentally, examples of the polymer include polycarbonate, polyvinyl alcohol, cellulose-based polymer, polyester such as polyethylene terephthalate and polyethylene naphthalate, polyarylate, polyimide, norbornene-based polymer, polysulfone, ponoether sulfone,
Examples include polyolefins such as polyethylene and polypropylene. In particular, an amorphous polymer having excellent heat resistance can be preferably used.

The light-transmitting film may be formed by an appropriate method such as a casting method such as a casting method or an extrusion method. A solution casting method such as a casting method is more preferred from the viewpoint of obtaining a light-transmitting film with less thickness unevenness and orientation distortion unevenness. The thickness of the translucent film can be appropriately determined depending on the intended retardation and the like, but is generally 10 to 5
00 μm, especially 20 to 300 μm. As the translucent film, an elongated body such as a wound body is used for the purpose of continuous production, but its length and width are arbitrary.

A heat-shrinkable film adhered to one or both sides of a light-transmitting film shrinks the light-transmitting film by transmission of a contraction force due to its heating to control its retardation characteristics, particularly the refractive index in the thickness direction. And so on. In the present invention, the shrinkage in the length direction of the light-transmitting film has a shrinkage ratio in the length direction / width direction upon heating in view of achieving the above-mentioned refractive index characteristics of nz>nx> ny. For heat-shrinkable films of 10 or more, heat-shrinkable films having a shrinkage ratio of 0 to 0.1 or 0.5 to 2 are used for shrinking the translucent film in the width direction.

The shrinkage ratio is based on the shrinkage ratio in the length direction / shrinkage ratio in the width direction depending on the processing temperature when shrinking the translucent film. The upper limit of the shrinkage ratio of the heat-shrinkable film used for the shrinkage treatment in the length direction of the light-transmitting film is not particularly limited. Therefore, the contraction ratio in the width direction may be 0, and the contraction ratio may be Δ. Further, the heat-shrinkable film having a shrinkage ratio of 0 used for the shrinkage treatment in the width direction of the light-transmitting film has a shrinkage ratio in the length direction of 0, that is, does not shrink in the length direction. .

The heat-shrinkable film can be obtained, for example, as a stretched product of a polymer film. A heat-shrinkable film exhibiting a heat-shrinkage property near the glass transition temperature of the light-transmitting film can be preferably used from the viewpoint of imparting a shrinkage force. The shrinkage force of the heat-shrinkable film can be controlled by, for example, the type of polymer, stretching conditions such as stretching ratio, and film thickness. A heat-shrinkable film having a heat-shrinking force as uniform as possible over the entire surface of the film can be preferably used because it imparts a uniform orientation to the translucent film.

In the heat-shrinkable film, one or two or more layers having the same or different shrinkage ratio or the like can be bonded to one or both surfaces of the light-transmitting film. When two or more layers are bonded, the number of superimposed layers is generally 10 or less, but may be more. In the case of bonding to both surfaces of the translucent film, the number of adhesive layers of the heat-shrinkable film on both surfaces may be the same or different.

For bonding the heat-shrinkable film and the light-transmitting film, it is preferable to use an adhesive from the viewpoint of the propagation of shrinkage force due to good adhesion. As the adhesive, the shrinking force of the heat-shrinkable film is transmitted to the light-transmitting film at the time of the heat-shrinking treatment, and after the treatment, the optical properties of the heat-shrinkable film are not deteriorated as much as the processed material of the light-transmitting film. What can separate the heat-shrinkable film after the process is preferably used.

From the above point, an adhesive layer or the like is preferably used. As the adhesive layer, for example, an acrylic or silicone type, a polyester type or a polyurethane type, a suitable material such as a polyether type or a rubber type can be used.
There is no particular limitation on the type.

With respect to the heat-shrinkable film adhered to the light-transmitting film, the heat-shrinkable film is subjected to a heat treatment to develop a shrinkage force,
The translucent film is contracted under the action of the contraction force to control the refractive index. In that case, in the present invention, shrinkage is applied in two directions orthogonal to the length direction (MD) and the width direction (TD) of the translucent film. Thereby, the above-mentioned nz>nx> n
The refractive index characteristics of y can be achieved.

In the above, the shrinkage treatment in the length direction of the light-transmitting film is performed by bonding a heat-shrinkable film having a shrinkage ratio of 10 or more in the length direction / width direction during heating and heat-treating the film. This is performed by applying a contraction force of the film. The processing can be performed by an appropriate method such as a method using a roll stretching machine including a nip roll or the like capable of controlling a speed ratio, which can continuously process a long film.

On the other hand, in the shrinking treatment in the width direction of the light-transmitting film, the shrinkage ratio in the length direction / width direction at the time of heating is 0 to 0.
The heat-shrinkable film of 0.1 or 0.5 to 2 is bonded and heat-treated to apply a shrinkage force of the heat-shrinkable film.

The processing in the width direction can be performed, for example, by using a heat-shrinkable film having a shrinkage ratio of 0 to 0.1 by the above-described roll stretching machine at the same speed. Also, a long film can be processed in a series by using a heat-shrinkable film having a shrinkage ratio of 0.5 to 2 using a tenter stretching machine.

The shrinkage treatment in the length direction and the width direction of the translucent film is usually performed in a separate step because of the difference in shrinkage characteristics of the heat-shrinkable film used as described above. In that case, each step may be continuous in a series or may be separately and independently. Therefore, the retardation plate may not be manufactured continuously, but in any case, in the present invention, the shrinkage treatment in the length direction and the width direction of the translucent film can be performed in the state of a series of long films, and There is an advantage that the phase difference plate can be manufactured with good mass productivity.

The retardation characteristics such as the refractive index of the obtained retardation plate depend on the type and thickness of the light-transmitting film, the contraction rate of the heat-shrinkable film, the processing conditions such as the processing temperature, and the like. It can be controlled by the degree of contraction in the length and width directions. Either of the shrinkage treatment in the length direction and the width direction of the translucent film may be performed first.

Rather than controlling the retardation characteristics of the retardation plate, a method of shrinking the other while fixing the other in the length direction or the width direction (preventing dimensional change), particularly at least first the shrinking process It is preferable to use a method of shrinking the remaining direction so that the changed direction does not change its dimensions. The above-mentioned method using a roll stretching machine or a tenter stretching machine can satisfy this point. In the shrinking treatment in the direction of the post-treatment, the heat shrinkable film used in the previous shrinking treatment can be peeled off and removed from the translucent film, if necessary.

In the above, the heat treatment for shrinking the heat-shrinkable film can be performed by a suitable heating method according to a conventional stretching treatment such as a roll heating method, an atmosphere heating method, or a combination thereof. There is no particular limitation.
In this case, it is generally preferable to perform the heat treatment in a temperature range of Tg ± 20 ° C. based on the glass transition temperature (Tg) of the polymer forming the light-transmitting film, from the viewpoint of controllability of the shrinking operation.

The retardation plate according to the present invention can be used as a single layer or a laminate of the same or different types, for example, for compensating for the retardation by birefringence for the purpose of expanding the viewing angle of the liquid crystal cell and improving the contrast. Can be preferably used for various purposes. In practical use, for example, a polarizing plate or a protective layer,
The present invention can also be applied as an optical member of an appropriate form according to the related art, which is composed of a laminate of two or three or more layers, such as one obtained by bonding and laminating another type of retardation plate.

[0026]

Example 1 A polycarbonate film having a thickness of 50 μm and a phase difference of almost 0 has a shrinkage ratio (MD / TD) of 2 at 160 ° C. on both sides.
A polypropylene film having a thickness of 0 μm and a thickness of 60 μm is adhered via an acrylic pressure-sensitive adhesive layer, and the TD is subjected to TD with a roll stretching machine.
After the polycarbonate film was shrunk by 2% in the MD direction by heating to 160 ° C. in a direction-free state, the polypropylene film was peeled off, and then both sides of the polycarbonate film had a shrinkage ratio at 160 ° C. of 0.7 and a thickness of 0.7. Is 6
A polypropylene film of 0 μm is adhered via an acrylic pressure-sensitive adhesive layer, and is heated to 160 ° C. with a tenter stretching machine while fixing in the MD direction (magnification 1: no dimensional change) to shrink the polycarbonate film by 4% in the TD direction. Then, the polypropylene film was peeled off, and (nx−ny) d = 100
nm, (nx−nz) d = −60 nm to obtain a long retardation plate. Note that d is the film thickness (the same applies hereinafter).

Example 2 The same procedure as in Example 1 was carried out except that the treatment in the MD direction was performed with a roll stretching machine under the adhesion of a polypropylene film having a shrinkage ratio of 25 to reduce the shrinkage by 4% and the shrinkage in the TD direction by 10%. Accordingly, (nx−ny) d = 110 nm and (nx−nz) d =
A long retardation plate of -173 nm was obtained.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) B29L 11:00 (72) Inventor Hiroyuki Yoshimi 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation In-house (72) Inventor Seiji Kondo 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nippon Denko Corporation F-term (reference) 2H049 BA06 BA25 BA42 BB42 BB43 BB44 BB46 BB49 BB51 BC02 BC03 BC09 4F100 AK01A AK07 AK25G AK45 BA02 BA42 CB05 CB05G EC182 EG002 EH012 EJ37 EJ422 EJ91 GB41 JA03B JN01A JN18 JN18A 4F210 AA11 AA28 AC03 AD05 AE10 AG01 AH33 AH73 RA01 RC02 RG02 RG04 RG43 RG62

Claims (3)

[Claims] At the time of bonding a heat-shrinkable film to one or both sides of a long light-transmitting film and shrinking the light-transmitting film under the action of the heat-shrinkable force of the heat-shrinkable film by heat treatment, Using a heat-shrinkable film having a shrinkage ratio of 10 or more in the length direction / width direction during heating, the length direction of the light-transmitting film is shrunk, and the shrinkage ratio in the length direction / width direction during heating. Is 0 to 0.1 or 0.5 to 2
Using the heat-shrinkable film of (1) to shrink the width direction of the light-transmitting film. 2. The method according to claim 1, wherein the in-plane principal refractive index is n.
A method for producing a retardation plate that satisfies nx <nz when x, ny, and the main refractive index in the thickness direction are nz and nx> ny. 3. The method according to claim 1, wherein the translucent film is made of a polymer having a positive birefringence characteristic.