JP2000206327A - Protective film stuck linear polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute oblique observation for foreign matter of an article to be inspected by sticking a specific protective film to both surfaces of a linear polarizing plate. SOLUTION: A linear polarizing plate 1 is an ordinary linear polarizing plate, and for example, cited is the polarizing plate in which a protective film 13 is laminated on one or both of a polarizing film 12. Protective films 2, 3 are affixed to both surfaces of the linear polarizing plate 1, and in-plane retardation should be 30 nm or less. When the in-plane retardation exceeds 30 nm, coloring in the case of oblique observation by a cross nicol can not be eliminated. The in-plane retardation is preferably 15 nm or less, and substantially it is further preferably 0. The material quality of the protective films 2, 3 is not restrictive, and cited are ester resin such as PET or the like, polyolefin resin such as polyethylene or the like and acrylic resin or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear polarizing plate having a protective film adhered to both sides of a linear polarizing plate.

[0002]

2. Description of the Related Art A linear polarizing plate (1) is useful as one of optical components constituting a liquid crystal display device. If such a linear polarizing plate is contaminated with foreign matter, it will cause a display defect of the liquid crystal display device. Therefore, inspection is indispensable when shipping or assembling the liquid crystal display device. Inspection is performed, for example, by arranging a linear polarizer (1) to be inspected on a linear polarizer (7) for inspection in crossed Nicols and visually illuminating from the back side of the linear polarizer (7) for inspection. The observation is carried out according to Since the two linear polarizers (7, 1) are crossed Nicols, the light transmitted through the linear polarizer for inspection (7) is completely blocked by the linear polarizer (1) to be inspected. Linear polarizing plate to be inspected (1)
If there is a foreign substance on the side of the inspection linear polarizing plate, the foreign substance is observed as a bright spot, whereby inspection can be performed (FIG. 4). The foreign substance on the opposite side is inspected in the same manner by turning over the linear polarizing plate to be inspected. The observation direction in the inspection is usually
This is the normal direction (L0) of the linear polarizing plate to be inspected, and the position of the eye (6) of the worker is on this normal line (L0).

On the other hand, a linear polarizing plate is a protective film-attached linear polarizing plate (4) in which protective films (2, 3) for preventing scratches and the like are respectively attached to both surfaces thereof.
Inspection, transportation, storage, etc. are performed. The protective films (2, 3) are peeled off from the linear polarizing plate when being incorporated in a liquid crystal display device, and are discarded. In addition, the linear polarizing plate is often provided with an adhesive layer on one or both surfaces for incorporation into a liquid crystal display device,
Therefore, a protective film for preventing foreign substances such as dust and dirt from adhering to the adhesive layer is often attached on the adhesive layer. Here, the protective film stuck on the adhesive layer is also called a release film, a separate film, or the like.

However, when visually inspecting a linear polarizing plate with a protective film attached on both sides as described above, coloration due to interference caused by retardation of the protective film is observed, and foreign matter is observed. Tended to be difficult to confirm. This tendency is
This was particularly noticeable when inspecting minute foreign substances of m or less.
The presence of such minute foreign matter is particularly problematic in recent high-resolution and high-definition liquid crystal display devices.

In order to solve this problem, a method is considered in which a biaxially oriented protective film is attached so that the direction of its slow axis and the direction of the absorption axis of the linear polarizing plate are at a specific angle. Can be In the linear polarizing plate on which the protective film having the biaxial orientation is stuck, no coloration is observed when inspecting by observing from the normal direction (L0) of the linear polarizing plate, and the inspection is easy. Becomes

However, in this method, if the inspection is performed by observing even a slight angle from the oblique direction, coloring appears, and the position and posture of the operator's eyes at the time of inspection, the arrangement of the linear polarizing plate for inspection, etc. Is limited. Also, for example, 1
If you try to inspect a large linear polarizer with a size of 0 inches or more, when you look at the whole, the peripheral part of the linear polarizer will be seen from the oblique direction (L1, L2) and will be colored and observed. Thus, there is a problem that it is still not easy to confirm the foreign matter in this portion (FIG. 4).

[0007]

The present inventors have conducted intensive studies to develop a protective film-attached linear polarizing plate which is easy to inspect even when observed from an oblique direction as crossed nicols. It has been found that such a problem can be solved by using a protective film, and the present invention has been accomplished.

[0008]

That is, according to the present invention, protective films (2, 3) are provided on both surfaces of a linear polarizing plate (1).
A protective film-attached linearly polarizing plate (4), wherein both of the protective films attached to both surfaces have an in-plane retardation of 30 nm or less. A linear polarizing plate (4) is provided. An example of the protective film-attached linear polarizing plate of the present invention is shown in FIGS.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The linear polarizing plate (1) applied to the protective film-attached linear polarizing plate of the present invention is an ordinary linear polarizing plate, for example, on one or both sides of a polarizer film (12). One in which a protective film (13) is laminated (FIG. 1). As the polarizer film (12), for example, a vinyl alcohol resin film such as polyvinyl alcohol (PVA) dyed with iodine or a dichroic dye is used, and its thickness is usually about 10 to 30 μm. As the protective film (13), for example, triacetyl cellulose (TAC), diacetyl cellulose (DAC)
Cellulose resin, acrylic resin, and ester resin such as polyethylene terephthalate (PET) are used, and their thickness is usually about 10 to 180 μm. The polarizer film and the protective film are adhered by an adhesive layer. As the adhesive in the adhesive layer, for example, a polyvinyl alcohol-based adhesive or the like is used.

Protective films (2, 3) are adhered to both sides of the linear polarizing plate (FIG. 1). Protective film (2, 3) in the protective film-attached linear polarizing plate of the present invention
Need to have an in-plane retardation of 30 nm or less. If the in-plane retardation exceeds 30 nm, the coloring tends to be unable to be eliminated when observed from an oblique direction with crossed Nicols. The in-plane retardation is preferably about 15 nm or less.
Is more preferable.

The material of such a protective film is not particularly limited as long as it can be used as the protective film. For example, ester resins such as PET, and polyolefins such as polyethylene (PE) and polypropylene (PP) Resin, acrylic resin, cellulose resin such as TAC and DAC, and the like. The thickness of the protective film is usually about 10 to 100 μm, preferably about 30 to 50 μm. Further, antistatic performance can be imparted.

In the linear polarizing plate with a protective film of the present invention, such a protective film is bonded on both sides, and the adhesive layer (5) is formed on one or both sides of the linear polarizing plate (1). May be provided, and either one of the protective films (3) may be attached on the adhesive layer (FIG. 2). As described above, the protective film attached to one or both surfaces of the linear polarizing plate via the adhesive layer is also called a release film or a separate film.

[0013] The adhesive constituting the adhesive layer (5) is not particularly limited as long as it is a transparent and isotropic adhesive. However, incorporation into a liquid crystal display device is simple. Usually, a pressure-sensitive adhesive (adhesive) is used. Examples of such a pressure-sensitive adhesive include an acrylic pressure-sensitive adhesive and a urethane-based pressure-sensitive adhesive. When a protective film (13) is laminated on only one side of the polarizer film (12) as the linear polarizer (1), such an adhesive layer (5) is usually used as the polarizer film (12). (FIG. 3).

[0014]

According to the linear polarizing plate with a protective film of the present invention, no coloring occurs even when obliquely observed with crossed Nicols. The inspection can be performed by observing the inspection from an oblique direction, and the workability of the inspection can be improved. In addition, since the protective films adhered to both sides are non-oriented, the inspection can be easily performed when inspecting the product by turning the linear polarizing plate upside down.

[0015]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 Adhesive layer [acrylic pressure-sensitive adhesive] on one surface (5)
[TAC film (80 μm thick)
/ Iodine-stained PVA film (20 μm thickness) /
TAC film (thickness: 80 μm)] (1), protective film (separate film) [TAC film, R0 = 5 nm, thickness: 50 μm] on adhesive layer (2), slow axis (21) of linear polarizing plate 0 for the absorption axis (11) of
° and form a protective film (TAC film, R0 film) on the surface opposite to the side on which the adhesive layer is provided.
= 5 nm, thickness 50 μm] (3) with its slow axis (31)
Is attached at an angle of 0 ° to the absorption axis (11) of the linear polarizing plate to obtain a protective film-attached linear polarizing plate [size 210 mm × 300 mm] (4) (FIG. 6). .

The linear polarizing plate (4) with the protective film adhered thereto was disposed above the linear polarizing plate (7) for inspection, and crossed Nicols were visually inspected from a position 200 mm above the center to inspect. Inspection of this protective film-attached linear polarizing plate can be performed satisfactorily over the entire surface of the linear polarizing plate without changing the position of the eyes, and the time required to inspect both surfaces is about 20 seconds per sheet. Met.

With the adhesive layer (5) side of the protective film-attached linear polarizing plate (4) facing down (the linear polarizing plate side for inspection),
30 ° from normal direction with normal direction and long side direction as axes
FIG. 6 shows the transmittance spectrum of the transmitted light measured from the inclined direction (oblique direction). When measured not only in the normal direction but also in the tilted direction, it can be seen that the transmittance is 1.0% or less over almost the entire visible light range, and the color is black.
The transmittance spectrum when the protective film-attached linear polarizing plate is turned upside down and the adhesive layer side is measured upward is almost the same.

Comparative Example 1 Protective film (separate film)
Axis oriented protective film (separate film)
[PET film produced by biaxial stretching, R0 = 1
380 nm, thickness 38 μm], so that the slow axis (21) forms an angle of 90 ° with the absorption axis (11) of the linear polarizing plate, and is oriented biaxially in place of the protective film (3). Protective film [PE manufactured by biaxial stretching
T film, R0 = 1380 nm, thickness 38 μm] in the same manner as in Example 1 except that the slow axis (31) is at an angle of 90 ° to the absorption axis (11) of the linear polarizing plate. By operation, a protective film-attached linear polarizing plate [size 210 mm × 300 mm] was obtained.

The protective film-attached linear polarizing plate (4) was placed above the inspection linear polarizing plate (7), and crossed Nicols were visually inspected from a position 200 mm above the center to inspect the product. Inspection of the protective film-attached linear polarizing plate could be carried out without changing the position of the eyes in the central portion, but the surrounding four sides, particularly the four corners, were colored by interference, and It was not easy to carry out inspection without changing the position, and it was not possible to carry out inspection satisfactorily over the entire surface of the linear polarizing plate. Therefore, the time required to inspect both sides is about 35 per sheet.
Seconds.

With the adhesive layer (5) side of the protective film-attached linear polarizing plate (4) facing down (the linear polarizing plate side for inspection),
30 ° from normal direction with normal direction and long side direction as axes
FIG. 7 shows the transmittance spectrum of the transmitted light measured from the inclined direction (oblique direction). In the normal direction, the transmittance becomes almost completely black at a transmittance of about 1% or less over substantially the entire visible light range. However, when measured from an inclined direction, there is a wavelength at which the transmittance is 3% or more. It can be seen that coloring due to interference colors has occurred.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating an example of a linear polarizing plate having a protective film adhered thereto according to the present invention.

FIG. 2 is a schematic cross-sectional view showing another example of the linear polarizing plate with a protective film adhered thereto according to the present invention.

FIG. 3 is a schematic sectional view showing still another example of the linear polarizing plate with a protective film adhered thereto according to the present invention.

FIG. 4 is a schematic diagram showing an observation state in inspection of a linear polarizing plate.

FIG. 5 is a schematic diagram showing the relationship between the direction of the slow axis of the protective film and the direction of the absorption axis of the linear polarizing plate in an example of the linear polarizing plate with the protective film adhered thereto of the present invention.

FIG. 6 is a diagram showing a transmittance spectrum of the linear polarizing plate with a protective film adhered thereto obtained in Example 1, wherein the horizontal axis represents wavelength and the vertical axis represents transmittance.

FIG. 7 is a diagram showing a transmittance spectrum of the linear polarizing plate with a protective film attached thereto obtained in Comparative Example 1, wherein the horizontal axis represents wavelength and the vertical axis represents transmittance.

[Explanation of symbols]

 1: linear polarizing plate 11: absorption axis of linear polarizing plate 2: one protective film 21: slow axis of one protective film 3: other protective film 31: slow axis of the other protective film 4: protective film pasting Attached linear polarizing plate 12: Polarizer film 13: Protective film 5: Adhesive layer 6: Eye position in inspection 7: Linear polarizing plate for inspection L0: Normal direction L1: Oblique direction in inspection L2: Oblique in inspection direction

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H049 BA02 BA26 BB16 BB23 BB28 BB33 BB54 BC22 4F100 AK21 AK25G AT00B AT00C BA03 BA10B BA10C CB00 CB05G EC18 EJ91 GB41 JN01B JN01C JN10A YY00B YY00C

Claims (2)

[Claims] 1. A protective film-attached linear polarizing plate wherein protective films are attached to both surfaces of a linear polarizing plate, wherein both of the protective films attached to both surfaces have an in-plane retardation of 30 nm or less. A protective film-attached linear polarizing plate, characterized in that the protective film is: 2. The protective film according to claim 1, wherein a protective film having an in-plane retardation of 30 nm or less is adhered to one or both surfaces of the linear polarizing plate via an adhesive layer. Polarizer.