Phase difference film, circular polarization plate and organic EL display manufactured using phase difference film

Abstract

A phase difference film according to the present invention has an in-plane phase difference (Ro550) of 100 to 155nm in a wavelength of 550nm, and the ratio of an in-plane phase difference (Ro450) to Ro550 in a wavelength of 450nm is 0.72 to 0.95. The ratio of Ro550 to an in-plane phase difference (Ro650) in a wavelength of 650nm is 0.83 to 0.97. The phase difference film has a slow axis of 10° to 80° with reference to the longitudinal direction, and contains a resin having a positive intrinsic birefringence, an additive that functions to increase retardation and adjust wavelength dispersion, and an additive having a negative intrinsic birefringence.

Description

technical field [0001] The invention relates to a retardation film, a circular polarizing plate made by using the retardation film and an organic EL display. Background technique [0002] In recent years, research and development of organic electroluminescence elements (hereinafter, sometimes simply referred to as organic EL elements) have been actively conducted. Organic EL elements emit light by applying a voltage to a light-emitting layer provided between electrodes. Organic EL elements have excellent characteristics such as high-efficiency light emission, low-voltage drive, light weight, and low cost. Therefore, they are used in various fields such as planar lighting, light sources for optical fibers, backlights for liquid crystal displays, backlights for liquid crystal projectors, and displays. A light source has received widespread attention. [0003] In the organic EL element, electrons are injected from the cathode, holes are injected from the anode, and the two are...

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Problems solved by technology

[0006] However, in an organic EL element having such a structure, since the cathode becomes a mirror surface with strong light reflectivity, external light reflection is particularly remarkable in a non-light-emitting state.

That is, there are problems in that the reflection of indoor lighting etc. is severe during observation, black cannot be displayed under bright conditions, and when used as a light source for displays, the contrast in bright rooms is extremely low.

However, if additives are used to adjust both the required retardation and wavelength dispersion characteristics, a large amount of additives is required, which tends to cause white turbidity

In addition, such additives have the following problems: the major axis direction of the molecule is oriented along the stretching direction, thereby exhibiting the function of improving retardation development, but it is difficult to adjust the additive so that it can exhibit retardation development and the desired effect in a balanced manner. Reverse wavelength dispersion characteristics, and in order to obtain sufficient reverse wavelength dispersion characteristics, it is necessary to give a larger molecular structure in the direction perpendicular to the long axis direction of the molecule, and the compatibility with the resin is reduced, resulting in white turbidity of the film and lower display. contrast

However, in order to display the phase difference obliquely, the slow axis is oriented in the oblique direction, so a high-magnification stretching process is inevitably required, and cloudiness tends to occur. Therefore, a technology for suppressing cloudiness of the retardation film is required

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