Display device and e-book reader provided therewith

A display device comprising:

• a display portion including a plurality of transistors;
• and
• a display controller configured to make the display portion perform display by switching a first still image display period and a second still image display period, wherein the first still image display period comprises a writing period in which a first image signal is written and a holding period in which the first image signal is held,
• wherein the second still image display period comprises a writing period in which a second image signal is written and a holding period in which the second image signal is held,
• wherein the display controller is configured to make a length of the writing period of the first still image display period and a length of the writing period of the second still image display period different from each other, wherein the display controller comprises a switching circuit and a display mode control circuit,
• wherein the switching circuit is configured to switch a first clock signal and a second clock signal and output the first clock signal or the second clock signal, and wherein the display mode control circuit is configured to control the switching circuit.

A display device comprising:

• a display portion including a plurality of transistors;
• and
• a display controller configured to make the display portion perform display by switching a first still image display period and a second still image display period, wherein the first still image display period comprises a writing period in which a first image signal is written and a holding period in which the first image signal is held,
• wherein the second still image display period comprises a writing period in which a second image signal is written and a holding period in which the second image signal is held,
• wherein the display controller is configured to make a length of the writing period of the first still image display period and a length of the writing period of the second still image display period different from each other, wherein the display controller comprises a reference clock generation circuit, a dividing circuit, a switching circuit and a display mode control circuit, wherein the reference clock generation circuit is configured to output a first clock signal,
• wherein the dividing circuit is configured to divide the first clock signal and output a second clock signal,
• wherein the switching circuit is configured to switch the first clock signal and the second clock signal and output the first clock signal or the second clock signal, and wherein the display mode control circuit is configured to control the switching circuit.

A method for driving a display device comprising the steps of:

• displaying a first still image during a first still image display period;
• and
• switching from the first still image display period to a second still image display period, thereby displaying a second still image during the second still image display period,
• wherein the first still image display period comprises a writing period in which a first image signal is written and a holding period in which the first image signal is held,
• wherein the second still image display period comprises a writing period in which a second image signal is written and a holding period in which the second image signal is held, and
• wherein a length of the writing period of the first still image display period is different from a length of the writing period of the second still image display period.