Display device
Provided is a display device, including: a pair of light transmissive substrates disposed to be opposed to each other at an interval; a sealing member which bonds the pair of light transmissive substrates together and defines an encapsulation space between the pair of light transmissive substrates; a plurality of shutters disposed in the encapsulation space so as to optically display an image; liquid having optical isotropy filled in the encapsulation space; and an optical film disposed between the liquid and at least one of the pair of light transmissive substrates. A refractive index of the optical film is different from a refractive index of the pair of light transmissive substrates.
1. A display device, comprising:
a pair of light transmissive substrates disposed to be opposed to each other at an interval;
a sealing member which bonds the pair of light transmissive substrates together and defines an encapsulation space between the pair of light transmissive substrates;
a plurality of shutters disposed in the encapsulation space so as to optically display an image;
liquid having optical isotropy filled in the encapsulation space; and
an optical film disposed between the liquid and at least one of the pair of light transmissive substrates, wherein:
one surface of the optical film is provided in contact with the liquid;
another surface of the optical film is provided in contact with one of the pair of light transmissive substrates; and
a refractive index of the optical film is different from a refractive index of the one of the pair of light transmissive substrates provided in contact with the optical film.
2. The display device according to claim 1 , wherein the optical film is formed of a single layer.
3. The display device according to claim 1 , wherein the optical film is formed of a plurality of layers.
4. The display device according to claim 1 , wherein the refractive index of the optical film is larger than the refractive index of the one of the pair of light transmissive substrates provided in contact with the optical film and is larger than refractive indices of air and the liquid.
5. The display device according to claim 1 , wherein:
the optical film is disposed so that a lower surface thereof is adjacent to the one of the pair of light transmissive substrates; and
when natural light irradiates an upper surface of the optical film, reflection light that is reflected by the upper surface and propagates interferes with reflection light that enters the optical film and is reflected by the lower surface so as to exit from the upper surface.
6. The display device according to claim 5 , wherein:
the following expressions hold:
n 0 <n 1 and n 2 <n 1 ,
where n 0 represents a refractive index of a substance adjacent to the upper surface of the optical film, n 1 represents the refractive index of the optical film, and n 2 represents the refractive index of the one of the pair of light transmissive substrates provided in contact with the optical film;
the natural light comprises a light ray group including light rays having different wavelengths and different incident angles to the optical film;
a light ray group having a wavelength λ 0 included in the natural light comprises a first light ray reflected by the upper surface and a second light ray reflected by the lower surface so as to exit from the upper surface;
when an optical path difference between the first light ray and the second light ray is an odd multiple of half the wavelength λ 0 , a reflection factor of the first light ray and the second light ray becomes a maximum value determined by Rmax=((n 0 n 2 −n 1 2 )/(n 0 n 2 +n 1 2 )) 2 ;
when the optical path difference between the first light ray and the second light ray is an integral multiple of the wavelength λ 0 , the reflection factor of the first light ray and the second light ray becomes a minimum value determined by Rmin=((n 0 −n 2 )/(n 0 +n 2 )) 2 ;
a reflection factor of the natural light when the natural light passes through the liquid is in a range from a minimum reflection factor R LIQUID min to a maximum reflection factor R LIQUID max obtained by substituting a refractive index of the liquid into n 0 in equations for determining the minimum value and the maximum value;
a reflection factor of the natural light when the liquid includes an air bubble on the optical film and the natural light passes through the air bubble is in a range from a minimum reflection factor R Air min to a maximum reflection factor R Air max obtained by substituting a refractive index of air into n 0 in the equations for determining the minimum value and the maximum value; and
one of an average value of the minimum reflection factor R Air min and the maximum reflection factor R Air max and an average value of the minimum reflection factor R LIQUID min and the maximum reflection factor R LIQUID max is larger than twice another thereof.
7. The display device according to claim 1 , wherein:
the optical film is disposed so that an upper surface thereof is adjacent to the one of the pair of light transmissive substrates; and
when natural light irradiates the upper surface, reflection light that is reflected by the upper surface and propagates interferes with reflection light that enters the optical film and is reflected by a lower surface of the optical film so as to exit from the upper surface.
8. The display device according to claim 7 , wherein:
the following expressions hold:
n 0 <n 1 and n 2 <n 1 ,
where n 0 represents a refractive index of a substance adjacent to the lower surface of the optical film, n 1 represents the refractive index of the optical film, and n 2 represents the refractive index of the one of the pair of light transmissive substrates provided in contact with the optical film;
the natural light comprises a light ray group including light rays having different wavelengths and different incident angles to the optical film;
a light ray group having a wavelength λ 0 included in the natural light comprises a first light ray reflected by the upper surface and a second light ray reflected by the lower surface so as to exit from the upper surface;
when an optical path difference between the first light ray and the second light ray is an odd multiple of half the wavelength λ 0 , a reflection factor of the first light ray and the second light ray becomes a maximum value determined by Rmax=((n 2 n 0 −n 1 2 )/(n 2 n 0 +n 1 2 )) 2 ;
when the optical path difference between the first light ray and the second light ray is an integral multiple of the wavelength λ 0 , the reflection factor of the first light ray and the second light ray becomes a minimum value determined by Rmin=((n 2 −n 0 )/(n 2 +n 0 )) 2 ;
a reflection factor of the natural light when the natural light is reflected by the upper surface and the lower surface above the liquid is in a range from a minimum reflection factor R LIQUID min to a maximum reflection factor R LIQUID max obtained by substituting a refractive index of the liquid into n 0 in equations for determining the minimum value and the maximum value;
a reflection factor of the natural light when the liquid includes an air bubble on the optical film and the natural light is reflected by the upper surface and the lower surface above the air bubble is in a range from a minimum reflection factor R Air min to a maximum reflection factor R Air max obtained by substituting a refractive index of air into n 0 in the equations for determining the minimum value and the maximum value; and
one of an average value of the minimum reflection factor R Air min and the maximum reflection factor R Air max and an average value of the minimum reflection factor R LIQUID min and the maximum reflection factor R LIQUID max is larger than twice another thereof.
9. The display device according to claim 1 , wherein:
the optical film comprises a first optical film and a second optical film;
each of the first optical film and the second optical film has an upper surface and a lower surface;
the lower surface of the first optical film is adjacent to one of the pair of light transmissive substrates;
the upper surface of the second optical film is adjacent to another of the pair of light transmissive substrates; and
when natural light irradiates each of the upper surface of the first optical film and the upper surface of the second optical film, reflection light that is reflected by the upper surface of the first optical film and propagates interferes with reflection light that enters the first optical film and is reflected by the lower surface of the first optical film so as to exit from the upper surface of the first optical film, while reflection light that is reflected by the upper surface of the second optical film and propagates interferes with reflection light that enters the second optical film and is reflected by the lower surface of the second optical film so as to exit from the upper surface of the second optical film.
10. The display device according to claim 9 , wherein:
the following expressions hold:
n 0 <n 1 and n 2 <n 1 ,
where n 0 represents a refractive index of a substance adjacent to the upper surface of the first optical film and the lower surface of the second optical film, n 1 represents a refractive index of the first optical film, and n 2 represents a refractive index of the one of the pair of light transmissive substrates provided in contact with the first optical film;
the following expressions hold:
n 0 <n 12 and n 22 <n 12 ,
where n 12 represents a refractive index of the second optical film, and n 22 represents a refractive index of the another of the pair of light transmissive substrates provided in contact with the second optical film;
the natural light comprises a light ray group including light rays having different wavelengths and different incident angles to the first optical film and the second optical film;
a light ray group having a wavelength λ 0 included in the natural light comprises a first light ray reflected by the upper surface of the first optical film, a second light ray reflected by the lower surface of the first optical film so as to exit from the upper surface of the first optical film, a third light ray reflected by the upper surface of the second optical film, and a fourth light ray reflected by the lower surface of the second optical film so as to exit from the upper surface of the second optical film;
when an optical path difference between the first light ray and the second light ray is an odd multiple of half the wavelength λ 0 , a reflection factor of the first light ray and the second light ray on the upper surface and the lower surface of the first optical film becomes a first maximum value determined by Rmax=((n 0 n 2 −n 1 2 )/(n 0 n 2 +n 1 2 )) 2 ;
when the optical path difference between the first light ray and the second light ray is an integral multiple of the wavelength λ 0 , the reflection factor of the first light ray and the second light ray on the upper surface and the lower surface of the first optical film becomes a first minimum value determined by Rmin=((n 0 −n 2 )/(n 0 +n 2 )) 2 ;
a reflection factor of the natural light on the upper surface and the lower surface of the first optical film when the natural light passes through the liquid is in a range from a minimum reflection factor R LIQUID min to a maximum reflection factor R LIQUID max obtained by substituting a refractive index of the liquid into n 0 in equations for determining the first minimum value and the first maximum value;
a reflection factor of the natural light on the upper surface and the lower surface of the first optical film when the liquid includes an air bubble on the first optical film and the natural light passes through the air bubble is in a range from a minimum reflection factor R Air min to a maximum reflection factor R Air max obtained by substituting a refractive index of air into n 0 in the equations for determining the first minimum value and the first maximum value;
an average value of the minimum reflection factor R Air min and the maximum reflection factor R Air max is larger than twice an average value of the minimum reflection factor R LIQUID min and the maximum reflection factor R LIQUID max;
when an optical path difference between the third light ray and the fourth light ray is an odd multiple of half the wavelength λ 0 , a reflection factor of the third light ray and the fourth light ray on the upper surface and the lower surface of the second optical film becomes a second maximum value determined by Rmax 2 =((n 22 n 0 −n 12 2 )/(n 22 n 0 +n 12 2 )) 2 ;
when the optical path difference between the third light ray and the fourth light ray is an integral multiple of the wavelength λ 0 , the reflection factor of the third light ray and the fourth light ray on the upper surface and the lower surface of the second optical film becomes a second minimum value determined by Rmin 2 =((n 22 −n 0 )/(n 22 +n 0 )) 2 ; a reflection factor of the natural light on the upper surface and the lower surface of the second optical film when the natural light is reflected above the liquid is in a range from a minimum reflection factor R LIQUID min 2 to a maximum reflection factor R LIQUID max 2 obtained by substituting the refractive index of the air into n 0 in equations for determining the second minimum value and the second maximum value;
a reflection factor of the natural light on the upper surface and the lower surface of the second optical film when the natural light is reflected above the air bubble is in a range from a minimum reflection factor R Air min 2 to a maximum reflection factor R Air max 2 obtained by substituting the refractive index of the air into n 0 in the equations for determining the second minimum value and the second maximum value; and
one of an average value of the minimum reflection factor R Air min 2 and the maximum reflection factor R Air max 2 and an average value of the minimum reflection factor R LIQUID min 2 and the maximum reflection factor R LIQUID max 2 is larger than twice another thereof.
11. The display device according to claim 1 , wherein:
the sealing member is disposed so as to avoid a periphery of the pair of light transmissive substrates; and
the periphery of the pair of light transmissive substrates extends outward from the sealing member.
12. The display device according to claim 11 , wherein:
the sealing member is disposed so as to avoid an entirety of the periphery of the pair of light transmissive substrates, and
the entirety of the periphery of the pair of light transmissive substrates extends outward from the sealing member.
13. The display device according to claim 11 , wherein:
the sealing member is disposed so as to avoid a first part in the periphery of the pair of light transmissive substrates, and so as to pass a second part in the periphery of the pair of light transmissive substrates; and
the first part in the periphery of the pair of light transmissive substrates extends outward from the sealing member.
14. The display device according to claim 1 , wherein:
each of the pair of light transmissive substrates has a rectangular shape in plan view;
the sealing member is disposed so as to avoid a corner of the pair of light transmissive substrates; and
the corner of the pair of light transmissive substrates extends outward from the sealing member.
15. The display device according to claim 1 , wherein the optical film is disposed at least in a part adjacent to the sealing member in a region surrounded by the sealing member.
16. The display device according to claim 15 , wherein the optical film is disposed in an entire region surrounded by the sealing member.
17. The display device according to claim 15 , wherein the optical film is disposed so as to reach an outside of the region surrounded by the sealing member.
18. The display device according to claim 1 , wherein the optical film is made of a material selected from the group consisting of ZnO, ZnCrO 4 , and Al 2 O 3 .
19. The display device according to claim 1 , further comprising a backlight unit, wherein:
the plurality of shutters each have at least one aperture; and
the plurality of shutters are mechanically movable and control transmission and blocking of light from the backlight unit.