KR20130106719A - Prism using a liquid crystal - Google Patents

Abstract

PURPOSE: A liquid crystal prism is provided to reduce the thickness, weight, and manufacturing costs of a device by using a plastic substrate. CONSTITUTION: A liquid crystal cell (LC) is formed between a first substrate (110) and a second substrate (120). A first electrode (113) and a second electrode (121) form an electric field that rotates liquid crystal molecules in a liquid crystal cell. A transparent protection layer (123) protects the second electrode. The first substrate is made of a plastic substrate and has a first thickness (d1). The second substrate is made of a glass substrate and has a second thickness (d2) that is thicker than the first thickness.

Description

Liquid prism {Prism using a liquid crystal}

The present invention relates to a prism (hereinafter, referred to as a liquid crystal prism) implemented by using a liquid crystal usefully used to implement a stereoscopic image or a hologram.

Since both eyes are about 6.5cm apart, there is a difference in the image seen by the left and right eyes, and in the process of automatically synthesizing two images in the head and recognizing them as a three-dimensional feeling. Today's stereo-scopic stereoscopic images use such a difference and express a stereoscopic feeling by showing an image having a difference in left and right eyes.

The method of displaying a stereoscopic image can be largely divided into a glasses method and a glasses-free method. The spectacle method displays the image by changing the polarization direction of the left and right parallax image on the direct-view display device or the projector or by time division, and realizes a stereoscopic image using polarized glasses or liquid crystal shutter glasses. In the autostereoscopic method, an optical component such as a parallax barrier and a lenticular lens for separating a polarization axis of a left and right parallax image is generally installed in front of or behind a display screen to realize a stereoscopic image.

In the case of the eyeglass method, eyeglasses using a polarizing film or a liquid crystal shutter as a lens are generally used. However, since the viewer must see the image while wearing the glasses, there is a problem in that it is inconvenient in the field of view or the feeling of wearing / moving.

For this reason, the glasses-free method of viewing a stereoscopic image without wearing glasses may be closer to the user, but there is a limitation that the viewpoint is limited. That is, all of the autostereoscopic display devices use a lens that collects light at a specific point in time, and the light passing through the lens is collected at a specific point. Therefore, the viewer can see the stereoscopic image only when it is located at this point, and there is a limitation that the stereoscopic image cannot be seen elsewhere.

However, the liquid crystal prism can refract light in a desired direction, and when the light is refracted to the viewer's position, the viewer can watch a stereoscopic image anywhere in the autostereoscopic manner.

The present invention was devised in such a background, and provides a liquid crystal prism capable of refracting light in a desired direction.

In addition, the present invention is to provide a liquid crystal prism that can reduce the thickness and weight of the display, when applied to the conventional stereoscopic display device.

In addition, the present invention is to provide an ideal liquid crystal prism in the form of a right triangle.

In an embodiment of the present invention, a liquid crystal cell sandwiched between a first substrate and a second substrate, a first electrode and a second electrode generating an electric field for rotating the liquid crystal molecules constituting the liquid crystal cell, and the liquid crystal molecules may be prisms. The arrangement gradually changes in accordance with the electric field within one pitch corresponding to the bottom length of, and at least one of the first substrate and the second substrate discloses a liquid crystal prism made of a plastic substrate.

The plastic substrate may be made of either polycarbonate or polyimide.

The liquid crystal cell is an ECB mode liquid crystal cell, the first electrode is formed to form a stripe arrangement on the first substrate, and the second electrode is entirely formed on the second substrate.

Within one pitch, the liquid crystal molecules may be linearly arranged in a direction of increasing refractive index.

In the first pitch, n (n = natural numbers) are arranged in the first electrode, and a driving voltage consisting of voltages of which the voltage decreases linearly from maximum to minimum is applied to the n first electrodes. The common voltage may be applied to the two electrodes.

In another embodiment of the present invention, a liquid crystal cell sandwiched between a first substrate and a second substrate, a first electrode and a second electrode generating a fringe field for rotating the liquid crystal molecules constituting the liquid crystal cell, and the liquid crystal molecules The arrangement gradually changes in accordance with the fringe field within one pitch corresponding to the bottom length of the prism, and the liquid crystal cell is composed of a HAN mode liquid crystal cell, and some of the liquid crystal molecules constituting the liquid crystal cell are formed in the fringe field. Disclosed is a liquid crystal prism which is arranged in a state rotated in the clockwise direction in the same plane along the direction, and the rest is arranged in a state rotated in the counterclockwise direction.

And a linear polarizer for linearly polarizing the light incident on the liquid crystal prism, and a circular polarizer for supplying the light transmitted through the linear polarizer to the liquid crystal prism.

Within the 1 pitch, the liquid crystal molecules are arranged in a state rotated clockwise from 0 degrees to 90 degrees according to the positive voltage (potential difference is +), and counterclockwise according to the negative voltage (potential difference is-). It can be arranged rotated from 0 degrees to 90 degrees.

The liquid crystal molecules are linearly rotated from 0 degrees to 360 degrees in the same plane, of which a first prism is achieved by an array of liquid crystal molecules ranging from 0 degrees to 180 degrees, and the liquid crystals of 180 degrees to 360 degrees. The second prism may be formed adjacent to the first prism by the molecular arrangement.

In one embodiment of the present invention, since the liquid crystal prism is formed using the plastic substrate without using the glass substrate, the thickness and weight of the apparatus and the manufacturing cost can be reduced.

In addition, in another embodiment of the present invention, by implementing the liquid crystal prism with the liquid crystal molecules linearly rotated from 0 degrees to 360 degrees in the same plane, it is possible to implement the ideal prism of the right triangle shape.

1 is a view showing a cross-sectional view of a liquid crystal prism according to an embodiment of the present invention.
2 is a diagram illustrating an arrangement relationship between a liquid crystal prism and a display panel.
3 is a diagram illustrating a path in which light travels in a state where a liquid crystal prism is inactivated.
4 is a diagram illustrating a path in which light travels in a state where a liquid crystal prism is activated.
5 to 9 are diagrams illustrating a manufacturing process of the liquid crystal prism shown in FIG. 1.
FIG. 10 is a diagram illustrating an arrangement of liquid crystal molecules in a liquid crystal prism implemented with an ECB mode liquid crystal cell.
11 to 14 are diagrams for explaining the Jones matrix.
FIG. 15 is a view illustrating a state in which liquid crystal molecules are arranged from 0 degrees to 180 degrees in a HAN mode liquid crystal cell and driving voltages thereof accordingly.
16 to 17 illustrate a liquid crystal prism implemented as a HAN mode liquid crystal cell.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Like reference numerals throughout the specification denote substantially identical components. In the following description, when it is determined that a detailed description of known functions or configurations related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 shows a cross-sectional view of a liquid crystal prism 100 according to an embodiment of the present invention. In this embodiment, the liquid crystal prism 100 has a structure in which the liquid crystal is sandwiched between the two electrodes, but like the IPS mode or the FFS mode, the two electrodes may be formed on the same substrate to form a horizontal electric field. The liquid crystal prism 100 adjusts the alignment direction of the liquid crystal to form a line grating, thereby allowing the light to be refracted in a desired direction.

In FIG. 1, the liquid crystal prism 100 has a structure in which a liquid crystal LC is injected between the first substrate 110 and the second substrate 120.

The first substrate 110 is composed of a plastic substrate made of a material such as polycarbonate. Polycarbonate has a low heat resistance range of 150 degrees to 180 degrees Celsius compared to glass, but a thin film can be made in a film form, and it is also lighter and flexible than glass. Therefore, when the first substrate is formed of a plastic substrate, the thickness and weight of the liquid crystal prism 100 can be reduced.

The first electrode 113 is formed on the first substrate 110. The first electrode 113 may be formed on the lower substrate 110 by using a transparent conductive material, for example, a transparent conductive oxide such as ITO or IZO through a photolithography process. The first electrode 113 extends long in one direction, is spaced apart from the neighboring by a predetermined distance, and is disposed side by side to form a lattice. 1 illustrates a form in which the first electrodes 113 are arranged parallel to each other in a direction penetrating the drawing. The first electrode 113 is protected by being covered with a transparent protective layer 115. The transparent protective layer 115 is made of an inorganic material such as silicon oxide (SiOx) or silicon nitride (SiNx).

The second substrate 120 is made of a glass substrate and is configured to maintain the mechanical strength of the liquid crystal prism 100. As such, since the second substrate 120 is formed of a glass substrate, the second substrate 120 is relatively thicker than the first substrate 110. As illustrated in the drawing, the first substrate 110 is made of a plastic substrate to form a first thickness d1, but the second substrate 120 is made of a glass substrate and is thicker than the first thickness d1. 2 thickness (d2). Therefore, as compared with the case where both the first and second substrates 110 and 120 are made of glass substrates, the amount corresponding to the difference d2-d1 between the second thickness d2 and the first thickness d1 is increased. The thickness can be reduced. In addition, since the first substrate 110 uses a plastic that is relatively lighter than the second substrate 120, the weight can also be reduced.

The second electrode 121 is formed on the second substrate 120. Unlike the first electrode 113, the second electrode 121 is formed in common on the entire upper substrate 120. The second electrode 121 may be formed of a transparent material such as transparent conductive oxide such as ITO or IZO to allow light to pass therethrough. The second electrode 121 is covered with a transparent protective layer 123 and protected. The transparent protective layer 123 is made of an inorganic material such as silicon oxide (SiOx) or silicon nitride (SiNx).

As illustrated in FIG. 2, the liquid crystal prism 100 configured as described above is disposed in alignment with pixel columns of the display panel 11 displaying a stereoscopic image. In FIG. 2, the illustrated liquid crystal prism 100 illustrates that the first to tenth units TC1 to TC10 are configured. The units TC1-TC10 are the smallest units in which the liquid crystal prism 100 is driven, and the liquid crystal LC forms a prism in units of units to refract light in a desired direction to provide the viewer. For example, light lines are refracted at a predetermined angle under the influence of a prism formed by the first unit TC1 in the pixel columns (dotted lines in the drawing) disposed corresponding to the first unit TC1.

Hereinafter, the operation of the liquid crystal prism made in units TC1 to TC10 will be described. FIG. 3 is a diagram illustrating a path in which light travels when a potential difference does not occur between the first electrode 113 and the second electrode 121, that is, when the liquid crystal prism is inactivated.

If no electric field is applied between the two electrodes 113 and 121, the liquid crystal LC maintains its initial arrangement. For example, the ECB mode liquid crystals LC are arranged in the horizontal direction. As such, since the liquid crystal cells LC all maintain the state arranged in the horizontal state, there is no change in the refractive index of the liquid crystals depending on the position. Accordingly, the liquid crystal prism 100 has no influence on the transmitted light, so that the light passes through the liquid crystal prism 100 without any change.

4 is a diagram illustrating a path in which light travels when a potential difference occurs between the first electrode 113 and the second electrode 121. In the following description, the liquid crystal prism will be described as an example in which four first electrodes 113a to 113d are formed, and the first electrode constituting the liquid crystal prism 100 may have a provisional electrode 113a in a direction from left to right. It is referred to as a bare electrode 113b, a multi-electrode 113c, and a la electrode 113d.

In FIG. 4, the common voltage Vcom is applied to the second electrode 121, the first electrode V1 is applied to the provisional electrode 113a, and the second voltage V2 is applied to the bare electrode 113b. The third voltage V3 is applied to the multi-electrode 113c and the fourth voltage V4 is applied to the R-electrode 113d. The magnitude of the voltage satisfies the order of 'first voltage V1 <second voltage V2 <third voltage V3 <fourth voltage V4'.

Therefore, the first liquid crystal disposed between the provisional electrode 113a and the second electrode 121 rotates in proportion to the applied voltage, and the second liquid crystal disposed between the bare electrode 113b and the second electrode 121 It rotates more than a 1st liquid crystal in proportion to a lag voltage. Similarly, since the third liquid crystal and the fourth liquid crystal rotate in proportion to the voltage applied between the two liquid crystals, the degree of rotation of the liquid crystal increases from the first liquid crystal to the fourth liquid crystal. Therefore, as illustrated in FIG. 4, a difference in refractive index occurs according to the position, and a right triangular prism is formed in the liquid crystal cell LC. In this state, the light entering through the lower substrate 110 is refracted by an angle equal to the oblique slope angle α of the liquid crystal prism to pass through the liquid crystal prism 100.

Here, the refractive angle α is determined by the wavelength λ of the light and the pitch width Wp of the prism as shown in Equation 1 below.

[Equation 1]

sin α = λ / Wp

As such, the liquid crystal prism 100 forms a prism by adjusting the arrangement of the liquid crystals arranged in the unit. When the light is refracted according to the position of the viewer, the liquid crystal prism 100 can view a stereoscopic image without being limited to the viewing angle even in an autostereoscopic method. have. For example, while the stereoscopic display device displays the left eye, the liquid crystal prism 100 refracts light in accordance with the viewer's left eye position. And while displaying the right eye, the liquid crystal prism 100 refracts the light in accordance with the viewer's right eye position. As such, the liquid crystal prism 100 supplies the left eye image and the right eye image according to the viewer's position, respectively, so that the viewer can watch a stereoscopic image in a non-glasses state.

Meanwhile, the liquid crystal prism 100 described above has described the case in which the first substrate 110 is formed of a plastic substrate, but the first substrate 110 is formed of a glass substrate, and the second substrate 120 is formed of a glass substrate. It is also possible to comprise a plastic substrate. Further, both the first substrate 110 and the second substrate 120 may be formed of a plastic substrate.

Hereinafter, a manufacturing process of a liquid crystal prism consisting of a plastic substrate and a second substrate made of a glass substrate will be described as in the above-described embodiment with reference to the accompanying drawings.

First, FIGS. 5 and 6 show a manufacturing process based on a second substrate made of a glass substrate.

5 and 6, after cleaning the glass substrate 120, the ITO is processed into a sputtering target to sputter the entire glass substrate 120 or the ITO is deposited on the glass substrate 120. The second electrode 121 can be formed.

As such, after depositing ITO on the glass substrate 120, annealing is performed in the range of 230 ° C. to 250 ° C. such that the sheet resistance of the second electrode 121 is 40 (Ω / square).

After the annealing is finished, an inorganic material such as silicon oxide (SiOx) or silicon nitride (SiNx) is deposited on the second electrode 121 to form a transparent protective layer 123. The transparent protective layer 123 prevents the second electrode 121 from being damaged.

Next, a manufacturing process based on a first substrate made of a plastic substrate will be described with reference to FIGS. 7 to 9.

7 and 9, ITO is deposited on the plastic substrate 110 to form the first electrode pattern 113A on the entire surface.

As such, after the first electrode pattern 113A is formed on the plastic substrate 110, a mask MA for patterning the first electrode pattern 113A is prepared thereon. In FIG. 8, a method of patterning the first electrode pattern 113A by a photolithography method is illustrated, and a case in which the mask MA is formed of a photoresist is shown as an example. As is well known, the photolithography method transfers a pattern to the photoresist MA, and then patterns the first electrode pattern 113A as a barrier.

As shown in FIG. 8, when the first electrode pattern 113A is patterned using the mask MA, as described above, the first electrode 113 having a stripe shape and disposed in parallel with the neighboring portion is a plastic substrate ( 110). The mask MA layer is then removed.

As such, after the first electrode 113 is formed on the plastic substrate 110, the first electrode 113 is annealed. However, as described above, since the first electrode 113 is formed on the plastic substrate 110 made of polycarbonate, in view of the heat resistance of the polycarbonate, the sheet resistance value of the first electrode 113 is 47 (Ω). / square) to 120 degrees Celsius to 130 degrees.

After the annealing is finished, an inorganic material such as silicon oxide (SiOx) or silicon nitride (SiNx) is deposited on the first electrode 113 to form a transparent protective layer 115. The transparent protective layer 115 prevents the first electrode 113 from being damaged.

As such, after the manufacturing of the first substrate and the second substrate is finished, the liquid crystal prism 100 is completed by filling a liquid crystal between the two substrates. In one embodiment, the liquid crystal cell LC may be configured in an electrically controlled birefringence (ECB) mode, as described below.

As is known, in the ECB mode, the rubbing directions of the alignment films (not shown) formed inside the first and second substrates are the same, and the pretilt angle is 0 degrees. The liquid crystals present therebetween are horizontally aligned such that their major axes are parallel to the substrate. In this ECB mode, all the liquid crystal molecules in the liquid crystal cell are arranged in parallel with the long axis with respect to the substrate before applying the voltage, and when the voltage is applied, the liquid crystal molecules rotate to form the long axis in the same direction as the electric field. . That is, in the ECB mode, the liquid crystal molecules rotate 90 degrees between the horizontal direction and the vertical direction.

FIG. 10 is a view showing the rotating liquid crystal array of the ECB mode in accordance with the above-described liquid crystal prism.

As shown, in the ECB mode, the liquid crystal prism is implemented by adjusting the alignment direction of the liquid crystal. That is, in the ECB mode, the liquid crystal forms an arrangement state between the state horizontal to the substrate (the x-axis direction of the drawing) and the state perpendicular to the substrate (the y-axis direction of the figure). In the ECB mode, the liquid crystal has a minimum refractive index no when the liquid crystal has a direction perpendicular to the substrate, and a maximum refractive index (ne) when the liquid crystal has a horizontal direction with respect to the substrate. Therefore, when the alignment direction of the liquid crystal is adjusted so that the alignment direction of the liquid crystal contained in one pitch P of the prism becomes gradually horizontal from the vertical state, the liquid crystal prism having the inclination? Can be formed.

However, in the flyback region, that is, the portion A in which the refractive index of the liquid crystal molecules changes rapidly from maximum (ne) to minimum (no), the two consecutive electrodes are successively formed to form a new liquid crystal prism. The minimum voltage Vn and the maximum voltage Vo are applied. The ideal liquid crystal prism should form a right triangle, but in the flyback region the liquid crystals are horizontally arranged by the minimum voltage, vertically by the maximum voltage, and also gradually by vertically in the horizontal array as shown by the dotted line. A plurality of liquid crystals that make up are mixed. Thus, due to this flyback region, the liquid crystal prism of the ECB mode has a triangular shape rather than an ideal right triangle. As such, when the liquid crystal prism is formed, light entering the flyback region may not be folded at the refraction angle θ of the liquid crystal prism and may be refracted in an undesired direction.

In contrast, when the liquid crystal cell LC is configured in the HAN (Hybrid Alignment Nematic) mode as described below, the above-described phenomenon can be solved.

As is well known, in the HAN mode, the long axis of the liquid crystal is pretilted in a direction horizontal to the substrate in accordance with the rubbing direction of the alignment film (not shown) formed inside the first substrate, and the alignment film (not shown) formed inside the second substrate The long axis of the liquid crystal is pretilted in a direction perpendicular to the substrate in accordance with the rubbing direction of. The liquid crystals present therebetween rotate in the same plane in a horizontally oriented state by the fringe field.

How the light incident on the liquid crystal cell is phase-modulated in accordance with the rotation angle θ of the liquid crystal molecules in the HAN mode can be modeled through the Jones matrix, which will be described below.

In the HAN mode, since the liquid crystal rotates in the same plane as described above, it can be regarded as the same as the half-wave plate (HWP). Therefore, this expression is expressed using Equation 1 below using the Jones matrix.

[Equation 1]

In addition, according to the polarization state of the light input to the liquid crystal cell, the right circularly polarized light is expressed by Equation 2 below, and the left circularly polarized light is expressed by Equation 3 below.

&Quot; (2) &quot;

&Quot; (3) &quot;

Meanwhile, when the circularly polarizing plate 320 and the linear polarizing plate 330 are sequentially disposed in front of the HAN mode liquid crystal cell 310 as shown in FIG. 11, the polarization state of light incident to the liquid crystal cell 310 is circularly polarized light. In more detail, the light passing through the linear polarizing plate 330 is linearly polarized, and in the circular polarizing plate 320, a phase delay of λ (wavelength) / 4 is generated and circularly polarized. Therefore, the left circularly flat or right circularly polarized light is incident on the liquid crystal cell 310 according to the polarization control direction of the circular flat plate 320.

Accordingly, when light incident on the HAN mode liquid crystal cell is incident on the liquid crystal cell in a right circularly polarized state, when the long axis of the liquid crystal is rotated by θ in the HAN mode liquid crystal cell, the phase modulation of the output light is Since it is defined as in Equation 4, it can be seen that in this case, the light is output in a left circularly polarized state and phase modulated by 2θ.

&Quot; (4) &quot;

In addition, when light is incident on the liquid crystal cell 310 in a left circularly polarized state as illustrated in FIG. 12, when the long axis of the liquid crystal is rotated by θ in the HAN mode liquid crystal cell, the phase modulation of the output light is Since it is defined as Equation 5, it can be seen that in this case, light is output in a right polarized state and phase modulated by -2θ.

&Quot; (5) &quot;

In addition, when light is incident on the HAN mode liquid crystal cell in a right circularly polarized state as shown in FIG. 13, when the long axis of the liquid crystal is rotated by -θ in the liquid crystal cell, the phase modulation of the output light is expressed by Same as 6. Thus, it can be seen that in this case the light is output in a left circularly polarized state and phase modulated by -2θ.

&Quot; (6) &quot;

Finally, when light is incident on the HAN mode liquid crystal cell in a left circularly polarized state as shown in FIG. 14, when the long axis of the liquid crystal is rotated by -θ in the liquid crystal cell, the phase modulation of the output light is Equation 7 Thus, it can be seen that in this case the light is output in a right circularly polarized state and phase modulated by + 2θ.

[Equation 7]

As can be seen from the above modeling, the light incident on the HAN mode liquid crystal cell in a circularly polarized state is output in a phase delayed state corresponding to twice the rotation angle θ of the liquid crystal. In addition, it can be seen that light incident in a circularly polarized state into the HAN mode liquid crystal cell is output in a circularly polarized state rotating in a direction opposite to the circularly polarized light.

Through the above modeling results, it can be seen that when the rotation angle θ of the liquid crystal is adjusted in the range of 0 to 180 degrees, 2π phase modulation is possible when the HAN mode liquid crystal cell is implemented by the liquid crystal prism.

15 is a view showing an arrangement direction of liquid crystals according to an applied voltage in a HAN mode liquid crystal cell.

In Fig. 15, the liquid crystal shows rotation in the range of 0 to 180 degrees in the same plane (xy plane of the drawing). As illustrated in FIG. 15, in the HAN mode liquid crystal cell, the liquid crystal molecules rotate in accordance with the direction of the applied voltage. That is, when a positive voltage (potential difference is +) is applied, the liquid crystal rotates in a clockwise direction, and a counterclockwise rotation with respect to a negative voltage (potential difference is-).

Accordingly, as illustrated in FIG. 15, the voltage is sequentially applied in the negative direction to rotate the liquid crystal 90 degrees in the counterclockwise direction, and the voltage is applied in the positive polarity direction to sequentially rotate the liquid crystal 90 degrees in the clockwise direction. In this case, the liquid crystal as a whole can rotate in a 180 degree range. In FIG. 15, a bar is displayed at one end of the liquid crystal molecules so that the rotation direction of the liquid crystal can be easily known.

FIG. 16 shows a phase delay value according to an alignment direction of a liquid crystal prism and a liquid crystal implemented in a HAN mode according to the background described above. 16 illustrates that two liquid crystal prisms are formed in succession.

In FIG. 16, light incident on the liquid crystal cell 310 is left circularly polarized light or right circularly polarized light. As confirmed through the Jones matrix modeling described above, when the polarized light is incident on the HAN mode liquid crystal cell, 2π phase modulation can be performed. The light transmitted through the HAN mode liquid crystal cell is output as right circularly polarized light when the left circularly polarized light is incident on the liquid crystal cell, and is output by the left circularly polarized light when the right circularly polarized light is incident on the liquid crystal cell.

In FIG. 16, the liquid crystal of the liquid crystal cell is rotated 360 degrees counterclockwise in the xy plane. In order to understand the rotation direction of a liquid crystal easily, in the figure, the bar was shown at one end of the liquid crystal.

As confirmed through the modeling process described above, if the rotation angle θ of the liquid crystal is adjusted within the range of 0 to 180 degrees, 2π phase modulation is possible. Here, the phase modulation value ranges from 0 radians (rad) to 2π radians (rad). In the case of FIG. 16, two liquid crystal prisms are continuously formed by the characteristics of the phase modulation. Hereinafter, the liquid crystal prism implemented as the liquid crystal rotates from 0 degrees to 180 degrees is referred to as a first liquid crystal prism 1LP, and the liquid crystal prism implemented as rotating from 180 degrees to 360 degrees is referred to as the second liquid crystal prism 2LP. This is called. In this case, the first liquid crystal prism 1LP is formed to have a length of the first pitch 1P, and the second liquid crystal prism 2LP is formed to have a length of the second pitch 2P. Here, the lengths of the first pitch 1P and the second pitch 2P are the same.

In FIG. 16, when looking at the first liquid crystal prism 1LP, one unit liquid crystal prism is rotated 180 degrees in the counterclockwise direction (+ θ) with respect to the initial state in which the liquid crystal is arranged in a direction parallel to the + y axis. Shows the implementation along the direction. The arrangement direction of the liquid crystal shown in FIG. 16 is a view seen from the bottom of the liquid crystal cell 310.

In this case, when the right circularly polarized light enters the liquid crystal cell, the light is output in a state of being phase-modulated according to Equation 4 while passing through the liquid crystal cell at a given position. That is, as the rotation angle (+ θ) of the liquid crystal molecules increases, the phase modulation also increases in proportion to them. Therefore, the phase modulation value increases in the positive direction of the x-axis, resulting in a maximum of 2π radians (rad) at 180 degrees. As a result, since the phase modulation values of the liquid crystals belonging to one pitch 1P have a linear value gradually increasing in the + x-axis direction, the first liquid crystal prism 1LP having a tan (+ α) is formed.

The second liquid crystal prism 2LP is also implemented as the first liquid crystal prism 1LP, except that the second liquid crystal prism 2LP is arranged in a direction parallel to the y-axis (180 degrees) as the x-axis moves in the positive direction. By further rotating (360 degrees) 180 degrees counterclockwise, the phase modulation value increases from 0 radians to 2 pi radians. As a result, since the phase modulation values of the liquid crystals belonging to the two pitches 2P have a linear value gradually increasing, a second liquid crystal prism 2LP having a tan (+ α) is formed.

The case of FIG. 17 shows that two prisms are formed continuously with the inclination tan (−α) opposite to that of FIG. 16 due to the characteristics of the above-described phase modulation. The arrangement direction of the liquid crystal shown in FIG. 16 is a view seen from the bottom of the liquid crystal cell 310.

Hereinafter, the liquid crystal prism implemented as the liquid crystal rotates from 0 degrees to 180 degrees is referred to as a first liquid crystal prism 1LP, and the liquid crystal prism implemented as rotating from 180 degrees to 360 degrees is referred to as the second liquid crystal prism 2LP. This is called. In this case, the first liquid crystal prism 1LP is formed to have a length of the first pitch 1P, and the second liquid crystal prism 2LP is also formed to have a length of the second pitch 2P. Here, the first pitch 1P and the second pitch 2P are the same.

Referring to FIG. 17, first, the first liquid crystal prism 1LP is rotated 180 degrees clockwise with respect to an initial state in which liquid crystals are arranged in a direction parallel to the + y axis. Show the implementation. In this case, when the right circularly polarized light enters the liquid crystal cell, the right circular polarized light passes through the liquid crystal cell at a given position and is output in a phase modulated state according to Equation 6 above. That is, as the rotation angle θ of the liquid crystal molecules increases, the phase modulation also decreases in proportion to them.

Therefore, the phase modulation value becomes smaller toward the x-axis positive direction, resulting in a maximum 2π line at 0 degrees, and a minimum of 0 radians at 180 degrees. As a result, since the phase modulation values of the liquid crystals belonging to one pitch 1P have a linear value gradually decreasing in the + axis direction, a first liquid crystal prism 1LP having a tan (−α) is formed.

The second liquid crystal prism 2LP is also implemented as the first liquid crystal prism 1LP, except that the second liquid crystal prism 2LP is arranged in a direction parallel to the y-axis (180 degrees) as the x-axis moves in the positive direction. The only difference is that it rotates clockwise by 180 degrees (360 degrees).

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

Claims (10)

A liquid crystal cell sandwiched between the first substrate and the second substrate,
A first electrode and a second electrode generating an electric field for rotating the liquid crystal molecules constituting the liquid crystal cell;
The liquid crystal molecules are gradually changed in alignment with the electric field within one pitch corresponding to the bottom length of the prism,
And at least one of the first and second substrates is a plastic substrate. The method of claim 1,
The plastic substrate is a liquid crystal prism made of one of polycarbonate or polyimide. The method of claim 1,
The liquid crystal cell is an ECB mode liquid crystal cell,
The first electrode is formed to form a stripe arrangement on the first substrate, the second electrode is a liquid crystal prism formed entirely on the second substrate. The method of claim 3,
Within 1 pitch, the liquid crystal molecules are linearly arranged in a direction of increasing refractive index. The method of claim 3,
And n (n = natural numbers) of the first electrodes in the first pitch. The method of claim 5, wherein
And a driving voltage consisting of voltages of which voltages decrease linearly from maximum to minimum directions to the n first electrodes, and a common voltage to the second electrodes. A liquid crystal cell sandwiched between the first substrate and the second substrate,
A first electrode and a second electrode generating a fringe field for rotating the liquid crystal molecules of the liquid crystal cell;
The liquid crystal molecules are gradually changed in alignment with the fringe field within one pitch corresponding to the bottom length of the prism,
The liquid crystal cell is composed of a HAN mode liquid crystal cell,
Some of the liquid crystal molecules constituting the liquid crystal cell are arranged in a state rotated in the clockwise direction in the same plane according to the direction of the fringe field, the rest are arranged in a state rotated in the counterclockwise direction. The method of claim 7, wherein
A linear polarizing plate for linearly polarizing the light incident on the liquid crystal prism by retarding the light by 90 degrees;
A circularly polarizing plate for supplying the light transmitted through the linearly polarizing plate to the liquid crystal prism by performing left circularly polarized or right circularly polarized light,
A liquid crystal prism in which a linear polarizer and a circular polarizer are sequentially disposed in front of a direction in which light is incident on a liquid crystal prism. 9. The method of claim 8,
Within the 1 pitch, the liquid crystal molecules are arranged in a state rotated clockwise from 0 degrees to 90 degrees according to the positive voltage (potential difference is +), and counterclockwise according to the negative voltage (potential difference is-). Liquid crystal prism arranged in a state rotated from 0 degrees to 90 degrees. The method of claim 7, wherein
The liquid crystal molecules are linearly rotated from 0 degrees to 360 degrees in the same plane, of which a first prism is achieved by an array of liquid crystal molecules ranging from 0 degrees to 180 degrees, and the liquid crystals of 180 degrees to 360 degrees. A liquid crystal prism in which a second prism is formed adjacent to the first prism by a molecular arrangement.

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