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US 7,247,356 B2Granted
Privacy screen for a display
AssigneeE. I. Du Pont de Nemours and Company
InventorSteven William MacMaster
Life of this patent
Estimating the term…
Abstract
A privacy screen for a display (e.g., a LCD) includes having a polarizing film and a birefringent film is described. The privacy screen transmits substantial amounts of light emanating from the display in an orthogonal (or near-orthogonal) direction while not transmitting substantial amounts of horizontal, non-orthogonal light emanating from the display. In this manner, a privacy effect results in that the display is viewable by someone only when that someone is essentially directly in front of the display.
Claims37
A privacy screen for a display comprising:
- a) a first uniaxially birefringent film for transmitting light received from the display that is linearly polarized along a display polarizing axis, the first birefringent film having a thickness d1 and a retardation value R:
- R=(ne−no)d1/cosθ
- θ being the angle of light incident upon the screen from the display, and no and ne being the refractive indices, respectively, along the ordinary and extraordinary axes of the first birefringent film,
- wherein d1 is greater than 25 micrometers so that R is responsive to changes in θ;
- b) a first polarizing film having a polarizing axis positioned to receive linear polarized light transmitted from the first birefringent film;
- and wherein:
- the privacy screen exhibits the following relationship
- (ne−no)d1=(2n−1)λ/2
- where λ is a wavelength of light incident upon the screen from the display, (ne−no)d1 is the retardation value R of the first birefringent film for light incident upon the screen normal to the display and n is an integer.
6 more elements
A privacy screen for a display comprising:
- a) a first uniaxially birefringent film for transmitting light received from the display that is linearly polarized along a display polarizing axis, the first birefringement film having a thickness d1 and a retardation value R:
- R=(ne−no)d1/cosθ
- θ being the angle of light incident upon the screen from the display, and no and ne being the refractive indices, respectively, along the ordinary and extraordinary axes of the first birefringent film,
- and wherein the privacy screen exhibits the following relationship:
- (ne−no)d1=nλ
- where λ is a wavelength of light incident upon the screen from the display, (ne−no)d1 is the retardation value R of the first birefringent film for light incident upon the screen normal to the display, and n is an integer.
3 more elements
A privacy screen for a display comprising:
- a) a first biaxially birefringent film for transmitting light received from the display that is linearly polarized along a display polarizing axis, the first birefringent film having a thickness d1 and a retardation value Rθ for light incident on the film at an angle θ measured with respect to normal that is approximated by the relationship below:
- Rθ˜=Ro[1+sin2 θ/2ninavg];
- wherein the first biaxially birefringent film is characterized as having unit vectors a and b that define its film plane and a unit vector c that defines its normal;
- Ro=[nb−na]d1 and is retardation of normal incident light;
- navg=(na+nb+nc)/3=average index for the biaxially birefringent film;
- ni is selected from the group consisting of na, nb, and nc to correspond to the unit vector (a, b, or c) that describes the vertical direction of the display;
- and
- d1 is greater than 25 micrometers so that R is responsive to changes in θ;
- b) a first polarizing film having a polarizing axis positioned to receive the linear polarized light transmitted from the first birefringent film;
- and wherein the privacy screen exhibits the following relationship:
- Δnxyd=(2n−1)λ/2
- where λ is a wavelength of light incident upon the screen from the display, n is an integer, d is the film thickness of the first biaxially birefringent film and Δnxy is the in-lane birefringence.
9 more elements
A privacy screen for a display comprising:
- a) a first biaxially birefringent film for transmitting light received from the display that is linearly polarized along a display polarizing axis, the first birefringent film having a thickness d1 and a retardation value Rθ for light incident on the film at an angle θ measured with respect to normal that is approximated by the relationship below:
- Rθ˜=Ro[1+sin2 θ/2ninavg];
- wherein the first biaxially birefringent film is characterized as having unit vectors a and b that define its film plane and a unit vector c that defines its normal;
- Ro=[nb−na]d1 and is retardation of normal incident light;
- navg=(na+nb+nc)/3 average index for the biaxially birefringent film;
- ni is selected from the group consisting of na, nb, and nc to correspond to the unit vector (a, b, or c) that describes the vertical direction of the display;
- and
- d1 is greater than 25 micrometers so that R is responsive to changes in θ;
- and
- b) a first polarizing film having a polarizing axis positioned to receive linear polarized light transmitted from the first birefringent film;
- and wherein the privacy screen exhibits the following relationship:
- Δnxyd=nλ
- where λ is a wavelength of light incident upon the screen from the display, n is an integer, d is the film thickness of the first biaxially birefringent film and Δnxyd is the in-plane birefringence.
10 more elements
Dependencies are inferred from the claim text.