Optical modulator and display device
The present invention provides an optical modulator that prevents aggregation of shape-anisotropic particles. The optical modulator of the present invention includes: ( 1 ) a first substrate and a second substrate that are disposed to face each other; ( 2 ) an optical modulation layer disposed between the first substrate and the second substrate; and ( 3 ) a vertical alignment film. The optical modulation layer ( 2 ) contains: ( 2 A) liquid crystal molecules that have a positive anisotropy of dielectric constant with a value of the anisotropy Δε of 10 or more; and ( 2 B) shape-anisotropic particles each including a core material and a coating layer that is formed of a material containing a fluorine atom and constitutes an outer surface of the shape-anisotropic particles. The first substrate includes a pair of electrodes. The liquid crystal molecules and the shape-anisotropic particles are aligned perpendicular to the first substrate with no voltage applied to the electrodes and are tilted parallel to the first substrate by a transverse electric field generated by application of voltage to the electrodes. The liquid crystal molecules have a surface energy in the range of 27 to 35 mN/m. The vertical alignment film has a surface energy in the range of 30 to 40 mN/m.
1. An optical modulator, comprising:
a first substrate and a second substrate that are disposed to face each other;
an optical modulation layer disposed between the first substrate and the second substrate; and
a vertical alignment film disposed on an optical modulation layer side surface of at least one of the first substrate and the second substrate,
the optical modulation layer containing shape-anisotropic particles and liquid crystal molecules that have a positive anisotropy of dielectric constant with a value of the anisotropy Δε of 10 or more,
the shape-anisotropic particles each including a core material and a coating layer that is formed of a material containing a fluorine atom and constitutes an outer surface of the shape-anisotropic particles,
the first substrate including a pair of electrodes,
the liquid crystal molecules and the shape-anisotropic particles being aligned perpendicular to the first substrate with no voltage applied to the electrodes and being tilted parallel to the first substrate by a transverse electric field generated by application of voltage to the electrodes,
the liquid crystal molecules having a surface energy in the range of 27 to 35 mN/m,
the vertical alignment film having a surface energy in the range of 30 to 40 mN/m
wherein in a projected image on a surface of the first substrate, the shape-anisotropic particles are dispersed in the optical modulation layer at a density of 500 particles/4 mm 2 or higher.
2. The optical modulator according to claim 1 ,
wherein the shape-anisotropic particles each include an inorganic oxide layer between the core material and the coating layer.
3. The optical modulator according to claim 1 ,
wherein the coating layer contains a functional group containing fluorine.
4. The optical modulator according to claim 1 ,
wherein the pair of electrodes is a pair of comb electrodes whose comb teeth fit each other.
5. The optical modulator according to claim 1 ,
wherein the pair of electrodes is a combination of a planar electrode and an electrode including slits.
6. A display device comprising the optical modulator according to claim 1 .
7. The display device according to claim 6 ,
wherein the display device, with the transverse electric field generated, provides display by utilizing the shape-anisotropic particles to reflect external light.
8. The display device according to claim 7 ,
wherein one of the first substrate and the second substrate disposed on the back surface side includes a light-absorbing layer.