Adhesive optical film, manufacturing method for the same and image display device using the same

Abstract

A pressure-sensitive adhesive optical film of the invention comprises an optical film and a pressure-sensitive adhesive layer provided on the optical film, wherein the pressure-sensitive adhesive layer has a thickness (μm) standard deviation of 0.12 μm or less. The pressure-sensitive adhesive optical film makes it possible to reduce the problem of visible unevenness caused by a pressure-sensitive adhesive layer.

Description

CROSS-REFERENCE OF RELATED APPLICATIONS[0001]This is a Divisional of application Ser. No. 13 / 820, 606, filed Mar. 4, 2013, which is a 371 of International Application No. PCT / JP2011 / 067337 filed on Jul. 28, 2011, and which claims priority of Japnaese Patent Application Nos. 2010-198126, 2010-268471 and 2011-118362, the entire contents of which are incorporated herein by reference.TECHNICAL FIELD[0002]The invention relates to a pressure-sensitive adhesive optical film and a producing method thereof. The invention also relates to an image display such as a liquid crystal display, an organic electroluminescence (EL) display, a cathode-ray tube (CRT), or a plasma display panel (PDP) produced using the pressure-sensitive adhesive optical film and to a part used together with an image display, such as a front face plate, produced using the pressure-sensitive adhesive optical film. Examples of the optical film that may be used include a polarizing plate, a retardation plate, an optical com...

AI Technical Summary

Benefits of technology

[0053]In the pressure-sensitive adhesive optical film (or the laminated pressure-sensitive adhesive optical film) of the invention, the thickness (μm) of the pressure-sensitive adhesive layer is controlled to have a standard deviation of 0.12 μm or less. Thus, the pressure-sensitive adhesive layer is highly smooth and has a very low level of irregularities in thickness. Surface irregularities of a pressure-sensitive adhesive optical film are caused by variations in the thickness of its pressure-sensitive adhesive layer and its optical film. The pressure-sensitive adhesive optical film of the invention makes it possible to reduce unevenness caused by irregularities on the optical film and the pressure-sensitive adhesive layer.

[0054]The invention is based on the finding that irregularities in the thickness of a pressure-sensitive adhesive layer are caused by flowing of a pressure-sensitive adhesive coating liquid during drying. Thus, increasing the viscosity Y of a pressure-sensitive adhesive coating liquid or decreasing the coating thickness X of the pressure-sensitive adhesive coating liquid makes it possible to reduce flowing of the pressure-sensitive adhesive coating liquid, and forming a pressure-sensitive adhesive layer in such a manner that the thickness X and the viscosity Y satisfy the specified relation enables irregularities in the thickness of the pressure-sensitive adhesive layer to be controlled to a low level.

[0055]The pressure-sensitive adhesive optical film (or the laminated pressure-sensitive adhesive optical film) may be a pressure-sensitive adhesive polarizing plate (or a laminated pressure-sensitive adhesive polarizing plate). In this case, the pressure-sensitive adhesive polarizing plate (or laminated pressure-sensitive adhesive polarizing plate) may have a transparent protective film with a haze value of 15% or less for forming the uppermost surface of an image display such as a liquid crystal display or an organic EL display (a transparent protective film for forming the uppermost surface of an upper-side polarizing plate in a liquid crystal display), so that an image display, such as a liquid crystal display or an organic EL display, having a clear high-grade appearance can be provided without using any front face plate. In the pressure-sensitive adhesive polarizing plate, the thickness (μm) of the pressure-sensitive adhesive layer is controlled to have a standard deviation of 0.12 μm or less. Thus, the pressure-sensitive adhesive layer is highly smooth and has a very low level of irregularities in thickness. The use of the pressure-sensitive adhesive polarizing plate of the invention makes it possible to prevent visible unevenness, which would otherwise be caused by irregularities on a pressure-sensitive adhesive polarizing plate, and to impart a clear high-grade appearance to an image display such as a liquid crystal display.

[0056]The optical film (e.g., a surface treatment film) used in the pressure-sensitive adhesive optical film may have a haze of 15% or less. In this case, the pressure-sensitive adhesive optical film may be bonded to a front face plate, so that the front face plate can provide a clear high-grade appearance, while the pressure-sensitive adhesive layer with a controlled standard deviation of 0.12 μm or less provides no visible irregularities-induced unevenness, which makes it possible to impart a clear high-grade appearance to an image display such as a liquid crystal display or an organic EL display.

Problems solved by technology

Unfortunately, Patent Document 1 does not disclose any specific process for forming a pressure-sensitive adhesive layer, although it discloses that a solvent casting method can be used to form a pressure-sensitive adhesive layer with a small standard deviation.

The disclosure in Patent Document 1 cannot make it possible to form a pressure-sensitive adhesive layer with a substantially small standard deviation.

Unfortunately, the use of the front face plate undesirably increases cost and weight.

However, when such a transparent protective film having undergone no antiglare treatment or a low-haze-value antiglare treatment is used, irregularities on the polarizing plate or the pressure-sensitive adhesive layer are made visible by reflection, which would otherwise be invisible if a conventional transparent protective film with a high haze value is used.

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